22 Nov
Control Board, Displays

Unique Requirements for Touch Controllers in Two-Wheeled Electric Vehicle Touch Screens

Although countless articles about the future of transportation focus on four-wheeled electric vehicles, more and more mobility rely more heavily on economical two-wheeled electric vehicles, including scooters, heavy motorcycles, electric motorcycles, e-mopeds, and e-bikes. These two-wheeled electric vehicles are following the design trends of four-wheeled electric vehicles by incorporating touchscreens for control, replacing physical knobs, buttons, and mechanical dials.

The adoption of touchscreens enables designers of two-wheeled electric vehicles to create models with a modern appearance, flexible layouts, and stylish designs. It also allows for easy customization according to different models or even individual vehicles. User-friendly menu systems can meet the more complex control, display, and functionality requirements of two-wheeled electric vehicles while also enabling value-added features such as navigation, infotainment systems, remote payments, and vehicle security.

The touchscreens on two-wheeled electric vehicles are often exposed to harsh outdoor environments, making them vulnerable to rain, snow, dust, or sand. In hot climates, these vehicles may sometimes be parked under direct sunlight, subjected to intense UV and infrared radiation. Additionally, they are prone to accidents or deliberate damage.

Considering these factors, touchscreens for two-wheeled electric vehicles should ideally have an IP65/68 protection rating and thick cover glass to safeguard the underlying touch sensors and LCD or OLED display components. To prevent damage from sunlight and UV radiation, UV/IR filters are required, and anti-reflective/anti-glare coatings should be applied to enhance screen visibility under all lighting conditions.

Consequently, the display stack needs a thick, multi-layered design. However, each additional layer increases the distance between the finger and the capacitive touch sensor, making it more challenging to accurately detect touch inputs on the screen surface.

In cold regions, touchscreens are often operated by riders wearing thick gloves, which further increases the distance between the fingers and the touch sensor. Additionally, rain or snow on the screen in wet weather can lead to false touches or missed inputs.

A high-quality touchscreen must not only reliably track the path of a finger moving across the screen but also accurately detect multi-finger gestures made with thick gloves in wet conditions, enabling functions like navigation on maps. Touchscreens need to meet a wide range of environmental demands, placing stringent requirements on the touchscreen controller IC, which must address the following design challenges:

Thicker Display Stacks

Touchscreen controllers must support significant flexibility to accommodate various layers above the touch sensor in the display stack. Advanced technology with an equivalent thickness of 10 mm or more is required, enabling the use of anti-reflective and anti-glare coatings, along with 4 mm thick cover glass and operation with 3 mm thick gloves. Alternatively, touchscreen designers may include an air gap between the screen and glass, allowing the top glass layer to be replaced without swapping the entire display in case of damage. However, the increased thickness makes it more challenging for the touchscreen controller to accurately detect and decode touch inputs. Controllers must rise to this challenge.

Reliable Touch Performance

Two-wheeled electric vehicles are typically used outdoors for most of their lifespan. Touchscreen controller algorithms must prevent water droplets from being misinterpreted as touches, detecting only inputs from fingers or gloved hands. Capacitive sensing must also distinguish between conductive cleaning solutions (like bleach) and their mixtures with water, ensuring no false touches occur.

Functional Safety

Two-wheeled electric vehicles worldwide require functional safety features to protect riders while using the touchscreen. Features like navigation and hands-free calls during riding could pose distractions. Screens may need to comply with safety standards such as ISO 26262 (ASIL-B). Controllers must provide self-testing functions, documentation, and guidelines to support certification.

Security

In rental scenarios, touchscreens may be used to input PINs, granting vehicle access to renters. They also support contactless payments via credit cards or smartphones. Touchscreen controllers must include encryption and firmware authentication to ensure data privacy.

Noise Immunity

Powertrain circuits that drive electric motors generate radiated and conducted electromagnetic noise. Switching power supply-based chargers introduce noise into vehicle power lines, and lighting systems may cause conducted noise. Even LCD or OLED panels can emit electromagnetic interference. Without proper noise control, these sources can degrade touchscreen functionality. Controllers must include noise filtering algorithms to avoid false activations, especially during operation.

Microchip’s maXTouch® Touchscreen Controllers

Microchip’s maXTouch® series is equipped with features to meet these stringent requirements and enhance the touchscreen experience. Key capabilities include:

  • Support for screens from 2 to 34 inches with various aspect ratios.
  • Compatibility with thick cover glass up to 10 mm and air gaps of 0.2 mm or more.
  • Accurate touch detection through 5 mm thick gloves (e.g., ski or motorcycle gloves).
  • Moisture resistance, preventing false touches caused by water droplets, flows, 3.5% saline, or cleaning solutions.
  • Encrypted messages and hidden PIN configurations.
  • Interoperability with NFC( Near Field Communication) technology.
  • High conducted noise immunity (certified to Class A IEC 61000-4-6).
  • Self-diagnostic and reporting functionality.
  • Support for Linux®/Android™ operating systems.

Conclusion

Two-wheeled electric vehicle designs are complex, much like four-wheeled vehicles. Designers continuously add new features to meet evolving consumer expectations. Enhanced touchscreens, supported by capable touchscreen controllers, offer the flexibility required to integrate these features into vehicle designs. By addressing unique requirements and carefully selecting touchscreen controllers, the demands of two-wheeled electric vehicle designs can be effectively met.

22 Nov
Control Board, Displays

What If a Display Screen Can’t be Light Up?

Summary of Steps to Resolve Issues When the Display Screen Won’t Turn On

Step 1:
Provide the schematic diagram and testing program. Generally, 95% of customers can light up the display screen with the information.

Step 2:
If the display still doesn’t turn on, the customer needs to determine whether the issue lies in the hardware or software. At this point, it’s best to provide the customer with a demo unit. This helps the customer confirm that the display itself is not damaged and significantly aids their troubleshooting process.

Step 3:
If the issue persists, the customer can share their schematic design and software with the factory engineers for review to identify any potential problems. This step should resolve 99% of issues.

Step 4:
If the display still doesn’t turn on after the previous steps, the customer can send their designed board to the factory engineers for further troubleshooting assistance.

Note: Some customers send us the MCU or evaluation kit (e.g., development board) they are using and ask us to provide design suggestions. However, this is highly challenging. The market has a vast variety of MCUs, and it is unrealistic for or engineers to be familiar with all of them.

For example, it’s similar to a scenario where our engineers are skilled at repairing Toyota cars, but a customer brings in a Tesla and asks for diagnostics. The engineers would need to spend a significant amount of time studying and understanding the new system.

Here is a detailed description of the issue:

We often receive customer emails like this:
“I have issues with getting the display to work. How can I do?”

When it comes to troubleshooting display screens that won’t turn on, the problem typically falls into two categories: hardware or software.

Hardware:

Configuration Issues

LCD screens often have many pins, and factories may have implemented specific configurations. Simply relying on the datasheet to troubleshoot can sometimes be very challenging. Customers not only need to be familiar with the LCD driver but also deal with component configurations or failures, which can sometimes drive them to frustration.

Proper documentation and detailed schematics are crucial for helping customers overcome these hardware challenges.

Since our engineers already successfully lit up the display, the simplest solution is to provide the schematic diagram of the our testing setup for the display to the customer. This makes the our approach to configuring the display and components clear at a glance.

While the customer’s MCU might differ from the one used by the factory in testing, they are often similar in functionality. Sharing this schematic helps the customer avoid unnecessary detours during troubleshooting.

The schematic typically looks like this:

When Everything Seems Correct, But the Display Still Won’t Light Up:

Sometimes, even when all configurations appear correct, the display still doesn’t turn on. This could be due to common physical issues such as:

  • Display damage (e.g., from handling or manufacturing defects).
  • FPC (Flexible Printed Circuit) tearing, which disrupts the electrical connection.
  • Electrostatic discharge (ESD) damage, which can destroy sensitive components.

For delicate and high-precision displays, it’s recommended to keep at least two spare units on hand to avoid downtime caused by damage.

If the display still doesn’t work, the customer should consider purchasing our demo board or evaluation board. These provide a pre-tested and reliable reference design, significantly shortening the customer’s development cycle and helping them identify whether the issue lies in their setup or the display itself.

 

Software (Firmware)

For some displays, the configuration can be highly complex, especially with settings like register configurations. These settings often require meticulous understanding and programming, and even factory engineers may occasionally make mistakes.

The good news is that IC manufacturers typically provide example code and library files, which handle the most intricate tasks. By including the library files, engineers can streamline their workflow:

c

Copy code

#include <LibraryFile>

This allows the IC manufacturer’s pre-defined settings to be imported into the program. Afterward, engineers only need to define the interface and desired functions.

For customers unfamiliar with the ICs we use, it’s best to provide the sample code from our product testing. This helps them avoid unnecessary detours and significantly simplifies their development process.

Sample code can be provided in formats such as .txt files, .h (hexadecimal files), or other formats, all of which are useful references for the customer.

Sample code typically looks like this:

Alternatively (when using a compiler IDE)

With the above hardware and software support, 95% of customers can resolve their issues. However, some customers may still be unable to light up the display. This could indicate a problem with the customer’s motherboard.

Supporting the customer’s motherboard is challenging for the factory, mainly because of the vast variety of controllers they use. Factory engineers would need to invest significant time in thoroughly studying the customer’s controller and PCB wiring.

That said, if the factory engineers are familiar with commonly used controllers, such as the 51 series, STM32 series, or Arduino series, they may be able to assist.

If the factory engineers have knowledge of the customer’s MCU, they can provide targeted support by offering:

  • The connection method between the MCU and the LCD (as shown in the diagram below).
  • Corresponding sample code for the specific setup.

Note:

  1. Difference Between Demo Board and Evaluation Board (Evaluation Kit):
    • Demo Board:
      Designed specifically for demonstrating display functionality by the factory. Customers cannot, or find it difficult to, modify the images or display configurations.
    • Evaluation Board:
      More flexible as it allows customers to program and upload their own images, or even modify display settings. Currently, we offer two affordable evaluation boards:

      • JAZZ-MCU-01:
        Designed to drive displays with SPI, I2C, 8-bit, or 16-bit MCU/TTL interfaces. The factory can pre-load images provided by the customer, or if the customer is familiar with AGU’s products, they can upload their own images.
      • JAZZ-HDMI-01:
        Designed to drive displays with RGB, LVDS, or MIPI interfaces. Since it uses HDMI, customers can connect it to a computer to view their desired images and videos directly.
  2. Difference Between Software (Code) and Firmware:
    • Firmware:
      Firmware is also code but is used at the hardware’s lower levels. It typically involves fundamental hardware settings that are rarely changed. For example, in touch control ICs, factory-set firmware often includes settings like touch sensitivity and temperature curves.
    • Code (Software):
      Built on top of the firmware, software enhances the hardware’s functionality by implementing advanced features. It allows for user-specific customization and higher-level operations.
11 Nov
Control Board, Displays

Introduction to Embedded Touch Display Driver Chip (TDDI)

TDDI (Touch and Display Driver Integration) technology combines touch functionality with the display driver in a single chip, simplifying the display structure and enhancing performance. In TDDI technology, the touch sensor is typically integrated directly into the glass substrate of the display panel, creating an all-in-one touch and display solution.

Specifically, TDDI technology embeds the touch sensor between the color filter substrate and the polarizer of the display screen, positioning the touch sensor within the glass layer of the display. This high level of integration enables both display and touch functionality in a streamlined form. This design makes the display thinner, reduces bezel width, improves the screen-to-body ratio, and simplifies the supply chain. The structure is as follows:

  1. The GFF (Glass-Film-Film) solution uses a separate structure for display and touch, where display and touch are independent modules.
  2. The On-cell solution embeds the touch sensor between the color filter substrate and the polarizer of the display screen, positioning the touch sensor on the display glass. This merges the display and touch modules into one, but the IC and FPC remain separate with two distinct designs.
  3. The TDDI solution fully integrates the touch sensor into the display’s TFT panel, unifying the display and touch modules, IC, and FPC into a single design. This is a highly integrated solution for display and touch functionality.

Due to its high level of integration, the TDDI solution offers benefits such as a thinner display, cost reduction, and a simplified supply chain. It has become the mainstream solution for LCD screens in smartphones. As of 2020, the LCD TDDI solution has accounted for over 50% of applications in smartphone display and touch functionality.

The development trends in smartphone TDDI display technology include high refresh rates, narrow bezels, and high functional integration.

(1) Advantages of High Refresh Rates

  1. Reduces flickering and jitter in image display, which helps alleviate eye strain.
  2. Enhances dynamic scenes in gaming applications, reducing blur and screen tearing during fast movements.
  3. Improves smoothness during screen transitions or scrolling, minimizing blurriness and ghosting in images and videos.

Requirements for TDDI IC: To support high refresh rates, TDDI ICs need faster MIPI data reception, higher oscillation frequencies (OSC), stronger drive capabilities, and faster response and processing speeds.

FHD LTPS TDDI: Production for 144Hz displays has been achieved, but 160Hz is still in the initial RFI (Request for Information) stage, with no corresponding products yet. Additionally, demand for LCD TDDI at 160Hz remains unclear, so most manufacturers are adopting a wait-and-see approach.

HD a-Si TDDI: Production has reached 90Hz, and a new recessed bump IC now supports 120Hz. For HD 120Hz displays, there are no technical bottlenecks or additional costs. Once cost-compatible motherboard configurations become available, manufacturers plan to launch projects, potentially upgrading HD displays to 120Hz.

(2) Narrow Bezels and Ultra-Narrow Bottom Bezels for Full-Screen Design

Manufacturers are also pursuing ultra-narrow bezels, especially at the bottom, to achieve a truly full-screen experience.

Narrow Bezel Technology Solutions:

  1. Pad Arrangement:
    The interlace arrangement, compared to the no-interlace design, can reduce the bottom bezel by about 1mm without additional cost or performance impact. Thus, since 2017, interlace has replaced no-interlace as the mainstream choice.
  2. Bonding Type:
    The COF (Chip on Film) solution offers an advantage over COG (Chip on Glass) in terms of achieving narrower bezels. However, COF increases costs, making it less suitable for mid-to-low-end LCD models. Therefore, COG remains the primary bonding type for LCD TDDI solutions.
  3. Gate Design:
    Between 2018 and 2019, display and IC manufacturers introduced the dual gate design for HD a-Si displays to achieve narrower bottom bezels. However, as the dual gate design had performance issues and conflicted with the high refresh rate trend that emerged in late 2019, the market quickly abandoned it. Currently, the traditional single gate design dominates TDDI for smartphones.
  4. Bump Design:
    Following the discontinuation of the dual gate approach, glass manufacturers proposed a new recessed bump design to achieve narrower bezels. This design adds no extra cost and has no impact on other performance areas. It is expected to gradually replace the standard normal bump design, becoming the mainstream approach.

FHD LTPS: With a source demux design, the bottom bezel in the traditional normal bump configuration is already around 3.1mm. The reduction achieved by switching to recessed bump is minimal, so the demand for this change is not strong, and it remains in pre-research.

HD a-Si: The traditional normal bump design has a bottom bezel of 4.0-4.2mm, while the recessed bump design can reduce it to 3.0-3.2mm, achieving approximately a 1mm reduction. This approach is prioritized for HD products and is already in production for some smartphone models. Large-scale production is anticipated in the second half of 2022, with recessed bump expected to gradually replace normal bump as the mainstream solution.

Here are some major manufacturers of TDDI (Touch and Display Driver Integration) chips and examples of their products:

  1. Novatek:
    • NT36525: Supports high-resolution displays, suitable for smartphones and tablets.
    • NT36523: Designed for mid-to-high-end smartphones, featuring high refresh rates.
  2. FocalTech:
    • FT8756: Supports Full HD (FHD) resolution, suitable for smartphones.
    • FT8751: A cost-effective option for mid-to-low-end devices.
  3. Himax:
    • HX8399: Supports high-resolution displays, suitable for smartphones and tablets.
    • HX8394: Suitable for mid-range smartphones with good display performance.
  4. Solomon Systech:
    • SSD2010: Supports a 454RGBx454 resolution, ideal for wearable devices.
  5. Chipone:
    • ICNL9911C: Supports HD/HD+ resolution, suitable for smartphones.
  6. TDYTech:
    • TD4160: Supports high refresh rates and multi-finger touch, suitable for smartphones and tablets.
  7. Synaptics:
    • TD4303: Supports hybrid in-cell panel technology, suitable for smartphones.

These TDDI chips are widely used in smartphones, tablets, and wearable devices, offering high integration and excellent display and touch performance.

If you have any questions about Display and Touch Waterproofing Requirements, please contact Orient Display support engineers

11 Nov
Displays, Control Board

Introduction to Cover Glass for Displays

Cover Glass (Cover Lens) is primarily used as the outermost layer of touch screens. The main raw material for these products is ultra-thin flat glass, which offers features such as impact resistance, scratch resistance, oil and fingerprint resistance, and enhanced light transmittance. It is currently widely used in various electronic consumer products with touch and display functionalities.

1. Classification of Glass

a. Soda-lime glass: Primarily composed of SiO₂, with additional content of 15% Na₂O and 16% CaO.
b. Aluminosilicate glass: Mainly composed of SiO₂ and Al₂O₃.
c. Quartz glass: Contains more than 99.5% SiO₂.
d. High-silica glass: Contains approximately 96% SiO₂.
e. Lead-silicate glass: Mainly composed of SiO₂ and PbO.
f. Borosilicate glass: Primarily made up of SiO₂ and B₂O₃.
g. Phosphate glass: Mainly composed of phosphorus pentoxide (P₂O₅).

Types c through g are rarely used in displays, so they will not be discussed here.

2. Processing Techniques for Glass Raw Materials

a. Float Glass

Float glass is produced using raw materials such as sea sand, quartz sandstone powder, soda ash, and dolomite. These materials are mixed and melted at high temperatures in a furnace. The molten glass continuously flows from the furnace and floats on the surface of a molten metal bath, forming a uniformly thick, flat glass ribbon that is flame-polished. After cooling and hardening, the glass separates from the molten metal, and it is then annealed and cut to create transparent, colorless flat glass. The forming process of float glass is completed in a tin bath with protective gas, resulting in a distinction between the tin side and the air side of the glass.

b. Overflow Process:

In the overflow process, molten glass enters the overflow channel from the feeder section and flows downward along the surface of a long overflow trough. The glass converges at the bottom tip of a wedge-shaped body under the overflow trough, forming a glass ribbon. After annealing, this process creates flat glass. This method is currently a popular technique for manufacturing ultra-thin cover glass, offering high processing yield, good quality, and overall excellent performance. Unlike float glass, overflow glass does not have a tin side or an air side.

3. Introduction to Soda-Lime Glass

a. Also known as soda glass (English: soda-lime glass), it is processed using the float method, hence also called float glass. Due to the presence of a small amount of iron ions, the glass appears green when viewed from the side, and is therefore also referred to as green glass.

b. Thickness of Soda-Lime Glass: 0.3–10.0 mm

c. Brands of Soda-Lime Glass:

  • Japanese brands: Asahi Glass Co. (AGC), Nippon Sheet Glass Co. (NSG), Central Glass (CENTRAL), etc.
  • Chinese brands: CSG Holding, Xinyi Glass, Luoyang Glass, AVIC Sanxin, Jinjing Group, etc.
  • Taiwanese brand: Taiwan Glass (TGC).

4. Introduction to High Aluminosilicate Glass (High Alumina Glass)

a. Brands of High Alumina GlassUnited States: Corning Gorilla Glass, an eco-friendly aluminosilicate glass produced by Corning Incorporated.Japan: Dragontrail Glass, produced by AGC Inc. This glass is commonly referred to as “Dragontrail Glass.”China: Panda Glass, produced by Xuhong Company, is a high alumina glass. Other manufacturers include CSG Holding and Kibing Group.

b. Cover Glass ProcessingCompanies involved in processing cover glass include Lens Technology, Boen Optics, Shenzhen Xinhao, G-Tech Optoelectronics, Jiangxi Firstar , BYD, and others.

5. Chemical Strengthening of Glass

a. Principle:

The glass is immersed in a molten salt bath (KNO₃). The high concentration of K⁺ ions penetrates the glass surface and replaces the Na⁺ ions within the glass. Since the ionic radius of K⁺ is larger than that of Na⁺, this substitution increases the surface density of the glass, generating compressive stress on the surface. This process enhances the glass’s strength through chemical reinforcement.

 

b. Test Items for Chemical Strengthening

Depth of Layer (DOL): Indicates the depth of the stress layer after the glass has been strengthened.

Compressive Stress (CS): Represents the surface compressive stress of the chemically strengthened glass.

Surface Hardness: Evaluated using a pencil hardness test.

Drop Ball Test: A destructive test to assess the glass’s impact resistance.

Note:

  1. Based on our project experience, we recommend the following:

    a. Use 1.1 mm thick glass for IK04.

    b. Use 1.8 mm thick glass for IK06.

    c. Use 3.0 mm thick glass for IK08.

    d. Use 6.0 mm thick glass for IK10.

  2. Physically tempered glass is mainly recommended when safety is a priority for the customer. This is because, when broken, physically tempered glass shatters into small granular pieces, unlike chemically tempered glass, which can break into sharp shards, posing a safety hazard.
  3. For chemically strengthened glass, to enhance safety, optical bonding or applying an anti-shatter film to the surface can prevent glass fragments from scattering upon breakage.

6. Production Process Flow for Glass Cover Lens

Cutting → CNC (shaping, drilling, edging, and chamfering) → Ultrasonic Cleaning → Chemical Strengthening → Ultrasonic Cleaning → Full Inspection of Blank Glass → Screen Printing → Baking → Full Inspection of Glass → Ultrasonic Cleaning → Surface AR Coating → AF Anti-Fingerprint Coating → Full Inspection of Glass → Film Coating and Packaging.

Key steps are explained as follows:

a. Cutting

The original glass sheet is cut with a diamond wheel cutter and then snapped into rectangular pieces that are 20-30 mm larger on each side than the final product dimensions.

b. CNC (Shaping, Drilling, Edging, and Chamfering)

Using high-hardness diamond grinding wheels rotating at high speed, the glass substrate undergoes mechanical grinding under excellent cooling and lubrication conditions to achieve the desired structural dimensions. Different tool shapes and grit sizes are designed to meet various processing requirements.

c. Chemical Strengthening

At high temperatures, an ion exchange occurs between the glass and KNO₃, where ions from KNO₃ replace the ions in the glass. Due to the larger atomic radius of the replacement ions, the surface of the glass undergoes compressive stress after tempering. When the glass is subjected to external force, this compressive layer can offset some of the tensile stress, preventing the glass from breaking. This compressive stress increases the glass’s resistance to bending and impact. Factors affecting the strength performance of chemically tempered glass (such as drop ball tests and four-point bending tests) include: 1) Tempering performance indicators of the glass (DOL, CS); 2) Internal and surface defects of the glass (micro-cracks and scratches); 3) Edge chipping and hidden damage formed during CNC processing; 4) Inherent defects in the glass raw material (impurities in the raw material, uneven areas, air bubbles, and inclusions, which are uncontrollable factors).

d. Polishing

The glass material is ground and polished using a double-sided grinder equipped with polishing pads and polishing powder. This process removes surface impurities and micro-cracks, enhancing the glass’s surface smoothness and reducing roughness. The main component of the polishing powder is cerium oxide. Cerium oxide polishing powder particles are polygonal with distinct edges, having an average diameter of about 2 microns and a hardness of Mohs 7-8. The particle size and purity of cerium oxide polishing powder directly affect the polishing outcome.

e. Ultrasonic Cleaning

When high-frequency vibrations (28–40 kHz) are transmitted to the cleaning medium, the liquid medium generates nearly vacuum-like cavitation bubbles. As these bubbles collide, merge, and dissipate, they create localized pressure bursts of several thousand atmospheres within the liquid. Such high pressure causes surrounding materials to undergo various physical and chemical changes, a process known as “cavitation.” Cavitation can break chemical bonds in material molecules, leading to physical changes (dissolution, adsorption, emulsification, dispersion) and chemical changes (oxidation, reduction, decomposition, synthesis), effectively removing contaminants and cleaning the product.

f. Printing

The principle of printing involves creating a stencil using photosensitive materials. Ink is placed in the screen frame, and a squeegee applies pressure to push the ink through the screen mesh openings onto the substrate, forming patterns and text identical to the original design.

g. Coating

Under vacuum conditions (10⁻³ Pa), an electron gun emits a high-speed electron beam to bombard and heat the coating material, causing it to evaporate and deposit onto the substrate surface, forming a thin film. Coating equipment primarily consists of a vacuum system, an evaporation system, and a film thickness monitoring system. Common coatings include functional films like AF (anti-fingerprint), AR (anti-reflective), AG (anti-glare), high-hardness films, decorative films such as NCVM (Non-Conductive Vacuum Metallization), and iridescent films.

7. IK Rating

IK ratings are an international classification that indicate the degree of protection provided by electrical enclosures against external mechanical impacts.

IK ratings are defined as IK00 to IK10. The IK rating scale identifies the ability of an enclosure to resist impact energy levels measured in joules (J) in accordance with IEC 62262 (2002).

IEC 62262 specifies how the enclosure must be mounted for testing, the atmospheric conditions required, the quantity and distribution of the test impacts and the impact hammer to be used for each level of IK rating. The test is carried out by a Charpy pendulum impact tester.

IK00 Not protected

IK01 Protected against 0.14 joules impact.
Equivalent to impact of 0.25 kg mass dropped from 56 mm above impacted surface.

IK02 Protected against 0.2 joules impact.
Equivalent to impact of 0.25 kg mass dropped from 80 mm above impacted surface.

IK03 Protected against 0.35 joules impact.
Equivalent to impact of 0.25 kg mass dropped from 140 mm above impacted surface.

IK04 Protected against 0.5 joules impact.
Equivalent to impact of 0.25 kg mass dropped from 200 mm above impacted surface.

IK05 Protected against 0.7 joules impact.
Equivalent to impact of 0.25 kg mass dropped from 280 mm above impacted surface.

IK06 Protected against 1 joules impact.
Equivalent to impact of 0.25 kg mass dropped from 400 mm above impacted surface.

IK07 Protected against 2 joules impact.
Equivalent to impact of 0.5 kg mass dropped from 400 mm above impacted surface.

IK08 Protected against 5 joules impact.
Equivalent to impact of 1.7 kg mass dropped from 300 mm above impacted surface.

IK09 Protected against 10 joules impact.
Equivalent to impact of 5 kg mass dropped from 200 mm above impacted surface.

IK10 Protected against 20 joules impact.
Equivalent to impact of 5 kg mass dropped from 400 mm above impacted surface.

 

If you have any questions about Display Cover Glass, please contact Orient Display support engineers

 

08 Aug
Displays

The analysis of Waterproof Requirements for Touch and Displays

Normally, for our display screens, when a customer mentions waterproofing, we need to clarify which part of the display needs to be waterproof.

The product needs to be waterproof. This requirement is generally for products with touchscreens. The waterproofing of the back of the display relies on the customer’s housing. We mainly focus on the sealing between the cover plate and the customer’s housing, as well as the sealing at the junction between the touchscreen and the display.

  • The touchscreen cover plate needs to be waterproof when assembled into the customer’s product. This requirement is quite common, and customers often have specific data requirements for sealing, such as an IP rating – grading the resistance of an enclosure against the intrusion of dust or liquids. In this case, we only need to choose the appropriate 3M double-sided tape to achieve the desired result. If no touch panel in the design, the polarizer will not resist long term water corrosion. Apply an acrylic protective layer on top of the display screen and securely adhere it with glue.
  • The area between the display screen and the touchscreen needs to be waterproof. Although some of our touchscreens are bonded to the display with OCA, the sensor part is still exposed. Therefore, it is necessary to use RTV sealant to seal the perimeter around the bonding area between the touchscreen and the TFT.
  • Waterproof Touchscreen Functionality. In some cases, customers may use the touchscreen while water droplets are present. The touchscreen needs to function properly in the presence of water droplets (normal touch function with water/no false touches from falling water droplets). For this situation, it is necessary to select an appropriate touch IC and special sensor design to ensure better reliability.
  • Waterproof PCB. Sometimes customers require the PCB to be waterproof. In this case, it is necessary to add a layer of Conformal Coating on the PCB. This involves applying a transparent polymer film over the PCB, which maintains the shape of the printed circuit board and protects the electronic components on the PCB from environmental damage, thereby improving and extending their lifespan. For more severe weatherproofing requirements, the entire circuit board is fully encapsulated in glue, effectively immersing the board in the adhesive. It is essential that this glue is neutral, without any acidic or alkaline properties, to prevent corrosion of the components.
  • Housing Assembly. After assembling the casing, apply sealant to the seams of the casing to ensure that the entire hardware part is airtight. However, even with these measures, it cannot be guaranteed that no water vapor will penetrate, as water molecules are very pervasive. The goal is to minimize the ingress as much as possible. Incorporate breathable vents like Gore vents that allow air to pass through but block water and moisture. Sometimes, utilizing laser welding for creating precise and strong seals in the device’s casing.
  • Other Waterproofing Ideas
    • Potting: Apply potting compounds around connectors and cables to seal any potential entry points.
    • Sealed Connectors: Use waterproof connectors and cables to prevent moisture ingress at connection points.
    • Incorporation of Desiccants: Place desiccants inside the device to absorb any residual moisture.

 

IP Rating — IP XX

The two digits following IP indicate the level of protection that the device’s enclosure provides against the ingress of solid objects and water. The first digit represents the level of protection against dust and foreign objects, while the second digit indicates the level of moisture and water resistance. The higher the number, the greater the level of protection.

For example, an IP rating of IP54:

  • IP: Designates the protection marking.
  • 5: The first digit indicates the level of protection against contact and foreign objects.
  • 4: The second digit indicates the level of protection against water.

The first digit (5) signifies a level of protection against dust and limited ingress of particles. The second digit (4) signifies a level of protection against water splashes from any direction.

Dust Protection Level

The first digit in the IP rating system represents the level of protection against solid objects, including dust. Here are the possible levels:

  • 0: No protection against contact and ingress of objects.
  • 1: Protection against solid objects over 50 mm (e.g., accidental touch by hands).
  • 2: Protection against solid objects over 12.5 mm (e.g., fingers).
  • 3: Protection against solid objects over 2.5 mm (e.g., tools, thick wires).
  • 4: Protection against solid objects over 1 mm (e.g., most wires, screws).
  • 5: Limited protection against dust ingress (no harmful deposits).
  • 6: Complete protection against dust ingress.

Water Protection Level

The second digit in the IP rating system indicates the level of protection against the ingress of water. Here are the possible levels:

  • 0: No protection.
  • 1: Protection against vertically dripping water.
  • 2: Protection against dripping water when tilted up to 15 degrees.
  • 3: Protection against spraying water at an angle up to 60 degrees.
  • 4: Protection against splashing water from any direction.
  • 5: Protection against water jets from any direction.
  • 6: Protection against powerful water jets.
  • 7: Protection against immersion in water up to 1 meter depth.
  • 8: Protection against continuous immersion in water beyond 1 meter.

IP Rating Explanation for Immersion

  • 7: The device can be immersed in water under specified pressure for a specified time, ensuring that the amount of water ingress does not reach harmful levels.
  • 8: The device can be continuously immersed in water under conditions agreed upon by the manufacturer and the user, typically more stringent than those of IP67.

 

ISO 16750 and Other International Standards:

  1. Scope

The waterproof tests include the second characteristic digits from 1 to 8, corresponding to protection levels IPX1 to IPX8.

  1. Waterproof Test Content for Various Levels

(1) IPX1

  • Method Name: Vertical Drip Test
  • Test Equipment: Drip test device and its test method
  • Sample Placement: Place the sample in its normal working position on a rotating sample table at 1 rotation per minute (r/min). The distance from the top of the sample to the drip outlet should not exceed 200mm.
  • Test Conditions:
    • Drip rate: 1.0 +0.5 mm/min
    • Test duration: 10 minutes

(2) IPX2

  • Method Name: Tilted Drip Test
  • Test Equipment: Drip test device and its test method
  • Sample Placement: Tilt the sample 15 degrees from its normal working position, in four fixed positions, one for each tilted direction.
  • Test Conditions:
    • Drip rate: 3.0 +0.5 mm/min
    • Test duration: 2.5 minutes per tilt direction (total 10 minutes)

(3) IPX3

  • Method Name: Spraying Water Test
  • Test Equipment: Oscillating spray test device or spray nozzle
  • Sample Placement: Place the sample in its normal working position.
  • Test Conditions:
    • Spray water at an angle up to 60 degrees from vertical.
    • Water flow rate: 10 liters per minute.
    • Test duration: 5 minutes.

(4) IPX4

  • Method Name: Splashing Water Test
  • Test Equipment: Oscillating spray test device or spray nozzle
  • Sample Placement: Place the sample in its normal working position.
  • Test Conditions:
    • Splash water from all directions.
    • Water flow rate: 10 liters per minute.
    • Test duration: 5 minutes.

(5) IPX5

  • Method Name: Water Jet Test
  • Test Equipment: Nozzle with a 6.3mm diameter
  • Sample Placement: Place the sample in its normal working position.
  • Test Conditions:
    • Water jet flow rate: 12.5 liters per minute.
    • Distance: 2.5 to 3 meters.
    • Test duration: 3 minutes per square meter for at least 3 minutes.

(6) IPX6

  • Method Name: Powerful Water Jet Test
  • Test Equipment: Nozzle with a 12.5mm diameter
  • Sample Placement: Place the sample in its normal working position.
  • Test Conditions:
    • Water jet flow rate: 100 liters per minute.
    • Distance: 2.5 to 3 meters.
    • Test duration: 3 minutes per square meter for at least 3 minutes.

(7) IPX7

  • Method Name: Immersion Test
  • Test Equipment: Water tank
  • Sample Placement: Submerge the sample in water.
  • Test Conditions:
    • Depth: 1 meter.
    • Test duration: 30 minutes.

(8) IPX8

  • Method Name: Continuous Immersion Test
  • Test Equipment: Water tank
  • Sample Placement: Submerge the sample in water under conditions agreed upon by the manufacturer and user.
  • Test Conditions:
    • Depth: Generally deeper than IPX7, specific conditions defined by agreement.
    • Test duration: Typically longer than IPX7, as agreed upon.

These tests ensure that the devices meet specific standards for waterproofing based on their intended use and environmental conditions.

 

If you have any questions about Display and Touch Waterproofing Requirements, please contact Orient Display support engineers

29 May
Displays

Analysis of Display and Touch Waterproofing Requirements

For our display screens, when customers mention waterproofing, it’s important for us to understand which specific parts they require to be waterproof.

  • The product needs to be waterproof. This usually applies to products with touch screens, where the backside waterproofing of the display screen relies on the customer’s external casing to ensure. Our main considerations lie in sealing the cover plate and the customer’s casing, as well as sealing the interface between the touch screen and the display screen.
    • The touch screen cover assembly onto the customer’s product needs to be waterproof. This requirement is quite common, and customers often have specific data requirements for sealing, such as an IP rating, which grades the resistance of an enclosure against the intrusion of dust or liquids. In this case, we only need to select the appropriate 3M double-sided adhesive to achieve the desired waterproofing.
    • Waterproofing is required between the display screen and the touch screen. Although some of our touch screens are optically clear adhesive (OCA) bonded to the display screen, the sensor part remains exposed. Therefore, it is necessary to use RTV sealant to seal the periphery of the bond between the touch screen and TFT (thin-film transistor) display.
  • Waterproofing for touch screen functionality:

In some cases, customers may use the touch screen in environments where water droplets are present. In such situations, the touch screen should be able to function normally even with water droplets present (ensuring normal touch functionality with water present and preventing accidental touches from falling water droplets). In this scenario, it’s necessary to select appropriate ICs for better water or salt water stability.

  • Waterproofing for PCBs:

Sometimes, customers request waterproofing for PCBs. In such cases, the solution typically involves adding a layer of conformal coating (also known as three-proof paint) onto the PCB. This coating is a transparent polymer film applied to the PCB, maintaining the shape of the printed circuit board while protecting the electronic components from environmental damage. This process enhances and prolongs their usability.

IP Rating — IP XX

The two digits following “IP” indicate the device’s enclosure’s protection against solid foreign objects and water ingress. The first digit represents the degree of protection against dust and ingress of solid foreign objects, while the second digit represents the degree of protection against moisture and water ingress. A higher number indicates a higher level of protection.

For example, in the IP54 rating, “IP” is the designation letter, “5” is the first digit indicating protection against contact and ingress of solid foreign objects, and “4” is the second digit indicating protection against water ingress.

1st digit Intrusion protection 2nd digit Moisture protection
0 No protection. 0 No protection.
1 Protected against solid objects over 50mm, e.g. accidental touch by hands. 1 Protected against vertically falling drops of water, e.g. condensation.
2 Protected against solid objects over 12mm, e.g. fingers. 2 Protected against direct sprays of water up to 15 degrees from the vertical.
3 Protected against solid objects over 2.5mm, e.g. tools & wires. 3 Protected against direct sprays of water up to 60 degrees from the vertical.
4 Protected against solid objects over 1mm, e.g. wires & nails. 4 Protected against water splashed from all directions, limited ingress permitted.
5 Protected against dust limited ingress, no harmful deposits. 5 Protected against low pressure jets of water from all directions, limited ingress permitted.
6 Totally protected against dust. 6 Protected against strong jets of water, e.g. on ships deck, limited ingress permitted.
/ / 7 Ability to withstand immersion in water under specified pressure for a set duration without allowing water ingress to a level that would cause harm.
/ / 8 Under conditions agreed upon by the manufacturer and user, the product should be able to be submerged in water without reaching a harmful level of water ingress.

 

ISO 16750 Standard

ISO 16750 is an international standard that specifies environmental conditions and testing for electrical and electronic equipment in road vehicles. It covers various aspects such as mechanical loads, vibrations, temperature, and humidity, among others, to ensure the reliability and durability of automotive electronic components and systems.

1. Scope
Waterproof testing includes second characteristic digits ranging from 1 to 8, corresponding to protection level codes from IPX1 to IPX8.

2. Waterproof Test Content for Various Levels:
(1) IPX1
Test Method: Vertical Drip Test
Test Equipment: Drip test device and its test method
Sample Placement: The sample is placed in its normal operating position on a rotating sample table at 1 revolution per minute (1r/min), with the distance from the sample top to the drip nozzle not exceeding 200mm.
Test Conditions: Drip rate of 1.0 ± 0.5 mm/min; Test duration: 10 minutes

 

(2) IPX2
Test Method: 15° Tilt Drip Test
Test Equipment: Drip test device and its test method
Sample Placement: Tilt the sample at a 15° angle from the vertical, with the distance from the sample top to the drip nozzle not exceeding 200mm. After testing one side, rotate to another side, repeating this process four times.
Test Conditions: Drip rate of 3.0 ± 0.5 mm/min; Test duration: 4 cycles of 2.5 minutes each, totaling 10 minutes.

 

(3) IPX3
Test Method: Rainfall Test
a. Oscillating Tube Rain Test
Test Equipment: Oscillating tube rainfall test equipment
Sample Placement: Select an appropriate radius for the oscillating tube so that the height of the sample platform is at the diameter position of the oscillating tube. Place the sample on the platform, ensuring that the distance from the top of the sample to the water spray nozzle is not greater than 200mm. The sample platform does not rotate.
Test Conditions: The water flow rate is calculated based on the number of water spray holes in the oscillating tube, with each hole at 0.07 L/min. During rainfall, water sprays from the water spray holes within a 60° arc segment on each side of the midpoint of the oscillating tube, totaling 120°. The test sample is placed at the center of the oscillating tube’s semi-circle. The oscillating tube swings 60° on each side of the vertical line, totaling 120°. Each swing (2×120°) takes approximately 4 seconds.
Test Pressure: 400 kPa; Test Duration: Continuous rainfall for 10 minutes; After 5 minutes of testing, rotate the sample 90°.

b. Nozzle Type Rain Test
Test Equipment: Handheld rainfall test equipment
Sample Placement: Position the sample so that the parallel distance from the top of the sample to the nozzle of the handheld spray is between 300mm and 500mm.
Test Conditions: During the test, a shield with balance weights should be installed. The water flow rate is set at 10 L/min.
Test Duration: The test duration is calculated based on the surface area of the test sample enclosure, with 1 minute per square meter (excluding the mounting area), and a minimum of 5 minutes.

 

(4) IPX4
Test Method: Water Splash Test
a. Oscillating Tube Water Splash Test
Test Equipment and Sample Placement: Select an appropriate radius for the oscillating tube so that the height of the sample platform is at the diameter position of the oscillating tube. Place the sample on the platform, ensuring that the distance from the top of the sample to the water spray nozzle is not greater than 200mm. The sample platform does not rotate.
Test Conditions: The water flow rate is calculated based on the number of water spray holes in the oscillating tube, with each hole at 0.07 L/min. Water is sprayed from the water spray holes within a 90° arc segment on each side of the midpoint of the oscillating tube, totaling 180°. The test sample is placed at the center of the oscillating tube’s semi-circle. The oscillating tube swings 180° on each side of the vertical line, totaling approximately 360°. Each swing (2×360°) takes about 12 seconds.
Test Duration: Same as the IPX3 test described in section (3) above (i.e., 10 minutes).

b. Nozzle Type Water Splash Test

Test Equipment: Handheld rainfall test equipment
Sample Placement: Remove the shield with balance weights from the equipment. Position the sample so that the parallel distance from the top of the sample to the nozzle of the handheld spray is between 300mm and 500mm.
Test Conditions: During the test, a shield with balance weights should be installed. The water flow rate is set at 10 L/min.
Test Duration: The test duration is calculated based on the surface area of the test sample enclosure, with 1 minute per square meter (excluding the mounting area), and a minimum of 5 minutes.

 

(5) IPX4K
Test Name: Pressurized Oscillating Tube Rain Test
Test Equipment: Oscillating tube rainfall test equipment.
Sample Placement: Select an appropriate radius for the oscillating tube so that the height of the sample platform is at the diameter position of the oscillating tube. Place the sample on the platform, ensuring that the distance from the top of the sample to the water spray nozzle is not greater than 200mm. The sample platform does not rotate.
Test Conditions: The water flow rate is calculated based on the number of water spray holes in the oscillating tube, with each hole at 0.6 ± 0.5 L/min. Water is sprayed from the water spray holes within a 90° arc segment on each side of the midpoint of the oscillating tube, totaling 180°. The test sample is placed at the center of the oscillating tube’s semi-circle. The oscillating tube swings 180° on each side of the vertical line, totaling approximately 360°. Each swing (2×360°) takes about 12 seconds.
Test Pressure: 400 kPa.
Test Duration: Rotate the sample 90° after 5 minutes of testing.
Note: The spray tube has 121 holes with a diameter of 0.5mm:
— 1 hole in the center
— 2 layers in the core area (12 holes per layer, distributed at 30-degree intervals)
— 4 circles in the outer ring (24 holes per circle, distributed at 15-degree intervals)
— Removable cover
The spray tube is made of brass (copper-zinc alloy).

 

(6) IPX5
Test Method: Water Jet Test
Test Equipment: Nozzle with an inner diameter of 6.3mm
Test Conditions: Position the test sample 2.5 to 3 meters away from the nozzle, with a water flow rate of 12.5 L/min (750 L/h).
Test Duration: The test duration is calculated based on the surface area of the test sample enclosure, with 1 minute per square meter (excluding the mounting area), and a minimum of 3 minutes.

 

(7) IPX6
Test Method: Powerful Water Jet Test
Test Equipment: Nozzle with an inner diameter of 12.5mm
Test Conditions: Position the test sample 2.5 to 3 meters away from the nozzle, with a water flow rate of 100 L/min (6000 L/h).
Test Duration: The test duration is calculated based on the surface area of the test sample enclosure, with 1 minute per square meter (excluding the mounting area), and a minimum of 3 minutes. Note: D=6.3mm for IPX5 and IPX6K; D=12.5mm for IPX6.

 

(8) IPX7
Test Method: Immersion Test
Test Equipment: Immersion tank.
Test Conditions: The dimensions of the tank should allow the test sample to be submerged with the distance from the bottom of the sample to the water surface being at least 1 meter. The distance from the top of the sample to the water surface should be at least 0.15 meters.
Test Duration: 30 minutes.

 

(9) IPX8
Test Method: Continuous Immersion Test
Test Equipment, Conditions, and Duration: To be agreed upon by both the supplier and the purchaser. The severity should be higher than IPX7.

 

(10) IPX9K
Test Method: High-Pressure Jetting Test
Test Equipment: Nozzle with an inner diameter of 12.5mm
Test Conditions:

 

Water jet angles: 0°, 30°, 60°, 90° (4 positions)
Number of water spray holes: 4
Sample platform rotation speed: 5 ±1 revolutions per minute (r.p.m)
Distance: 100 to 150mm from the nozzle
Duration: 30 seconds at each position
Water flow rate: 14 to 16 L/min
Water jet pressure: 8000 to 10000 kPa
Water temperature requirement: 80 ±5℃
Test Duration: 30 seconds at each position, totaling 120 seconds.

 

If you have any questions about Display and Touch Waterproofing Requirements, please contact Orient Display support engineers

29 Feb
Displays

Analysis and Common Solutions to LCD Image Sticking Issues

1. What is LCD Display Image Sticking

Image Sticking refers to the persistence of a static image on a display screen even after the content has changed. Image Sticking, Image Retention, Residual Image, and sometimes also referred to as screen aging phenomenon (Burn-In), are terms used to describe the effect of static images on subsequent image displays. This can involve the rapid disappearance of previous static content or temporary lingering of aged images.

Fig.1 Good Display
Fig.2 Image Sticking Display

2.The definitions and causes of Image Sticking Display

In TFT (Thin Film Transistor) displays, liquid crystal (LC) is a material with polar properties. An electric field can cause it to twist correspondingly.

In TFT (Thin Film Transistor) displays, liquid crystal (LC) must be driven by alternating current (AC). If direct current (DC) were used, it would disrupt the polarity of the crystals. In reality, there is no such thing as perfectly symmetrical alternating current. When continuously driving the pixels of a TFT, tiny inherent imbalances attract free ions to the internal electrodes. These ions adsorbed onto the internal electrodes create a drive effect similar to a combination of DC and AC.

In display fabrication, there are 3 main reasons which can cause image sticking.

(1) Insufficient alignment capability
PI (Polyimide) material is responsible for liquid crystal alignment. The liquid crystals in the white grid area rotate, while those in the black grid area do not. The rotation of liquid crystals is influenced by both the external electric field and intermolecular forces. The interaction force between the PI (polyimide) molecules on the surface of the liquid crystal is greater than the external electric field force, so the liquid crystal molecules on the surface do not rotate. The closer to the middle layer, the greater the effect of the external electric field on the liquid crystals, and the rotation angle approaches the theoretical value. During continuous signal output, the liquid crystals in the white grid area affect the surface liquid crystals through intermolecular forces (electrostatic force and dispersion force). If the alignment capability of the PI film is poor, the pre-tilt angle of the surface liquid crystals will change as the liquid crystals rotate. In Figure C, when switching to a grayscale image, because the pre-tilt angle of the liquid crystals in the white grid area has deviated from that of the black grid area, under the same grayscale voltage, the liquid crystals in the region where the angle deviation has occurred are more likely to rotate to the theoretical angle, resulting in an increase in transmittance and thus causing image sticking.

(2) Impurity of Liquid Crystal Material
Asymmetric alternating current (AC) driving occurs in the pixel area, and the part of the voltage that deviates from the center is the direct current (DC) bias. The DC bias attracts impurity ions within the screen, causing ion accumulation and resulting in residual DC bias. When switching display screens, due to the effect of residual DC bias, liquid crystal molecules influenced by ions fail to maintain the state required by the design, causing differences in brightness between areas with ion accumulation and other regions, leading to undesirable image sticking.

(3) Distortion of Driving Waveform
By applying different voltages, the rotation angle of liquid crystal molecules can be controlled to display different images. Here, the concepts of γ value and Vcom need to be introduced.
In simple terms, γ value divides the transition from white to black into 2 to the power of N (6 or 8) equal parts. γ voltage is used to control the gradation of the display, usually divided into G0 to G14. The first γ voltage and the last γ voltage represent the same gray level, but they correspond to positive and negative voltages respectively.
To prevent the formation of inertial deviation in liquid crystal molecules, dynamic voltage control is required. Vcom voltage is the reference voltage at the midpoint of G0 to G14. Specifically, Vcom is usually positioned between the first and last γ voltages. However, in practice, due to differences in peripheral circuits, adjusting the match between Vcom and γ voltages is necessary. When Vcom is adjusted to its optimum value, the positive and negative frame voltages of the pixels are symmetric, resulting in equal brightness for both positive and negative frames. However, when Vcom deviates from the center value, the voltage difference between positive and negative frames of the pixels is no longer the same, leading to a change in brightness between positive and negative frames.
When the Vcom voltage is set incorrectly, it can cause charged ions inside the liquid crystal to adsorb at the upper and lower ends of the glass, forming an inherent electric field. After switching the screen, these ions may not be immediately released, or the liquid crystal molecules may become disordered during state transitions, preventing the liquid crystal molecules from immediately rotating to the desired angle.

3.TFT LCD Image Sticking Testing

The following gives a fast-testing method:
Room temperature; Displaying a black and white checkerboard pattern (each square approximately 60×60 pixels); Static display for 30 minutes. Displaying full-screen 128 (50%) gray; after waiting for 10 seconds, no ghosting visible is deemed as qualified.
(Note: This is a destructive reliability test, not a routine test.)

In a TFT with normal white, the white areas receive the minimum driving voltage, while the black areas receive the maximum driving voltage. Free ions within the TFT are more likely to be attracted to the black areas (those with higher driving voltage). When displaying full-screen 128 (50%) gray, the entire screen will use the same driving voltage, causing ions to quickly leave their previously attracted positions. Additionally, when displaying full-screen 128 (50%) gray, anomalies in the display are more likely to be noticeable.

4. Common Methods to Resolve Image Sticking Issues

1) Screensaver: When the system is idle, the pixels of the TFT display different content, either displaying a moving screensaver or periodically switching content, to avoid displaying static images for more than 20 minutes.

2) If the image sticking occurs already, leaving the TFT powered off for several hours presents an opportunity for recovery; (recovery may take up to 48 hours in some cases). Or creating an all-white image and moving it across the screen for several hours without turning on the backlight. There are many image sticking repair software available online that may also be helpful. Once ghosting occurs, it becomes more likely to recur, so proactive measures are needed to prevent the reappearance of image sticking in TFT LCD displays.

3) Adjusting the Vcom voltage to match the γ voltage helps prevent ghosting caused by residual voltage in liquid crystal molecules.

4) Adjust discharge timing to ensure rapid release of residual voltage in liquid crystal molecules. In circuit design, specialized voltages are typically used to control the first and last γ voltages. Here, VGH and VGL represent G0 and G14, respectively. If the discharge of VGH and VGL is slow during system sleep, it can also result in an excessive residual voltage in the liquid crystal molecules. When the system wakes up, there is a chance of ghosting occurring.

5) Image sticking on LCD screens typically falls under the category of functional defects in LCD displays and requires LCD panel manufacturers to perform adjustments. Generally, reputable LCD display panel manufacturers by using high quality orientation alignment PI material and high purity liquid crystal material will reduce the possibility of image sticking.

• Firstly, it’s important to confirm whether the current settings of VSPR/VSNR meet the glass requirements.
• Verify the optimal VCOM value, which can be determined by measuring the flicker value using CA210. A smaller flicker value indicates a better VCOM value.
• Re-scan the gamma and observe whether ghosting persists.
• Asymmetric Gamma: Typically, tuning symmetric gamma, where the absolute values of positive and negative voltages for each gray level are equal. This approach relies on the LCD glass’s VT curve being symmetric. However, if the VT curve of the glass is asymmetric, asymmetric gamma adjustment is needed.
• VT curve: A curve representing the relationship between liquid crystal voltage and transmittance.
• Asymmetric gamma typically occurs in two scenarios: 1) Overall polarity offset: In this case, one polarity is shifted overall. Adjustments to VSPR/VSNR are required to address this state. 2) Single or multiple order offset: In this scenario, specific points on the gamma curve need voltage adjustments to address the offset.

03 Dec
Displays

TFT Display vs Super AMOLED, which is Better?

Thanks for the display technology development, we have a lot of display choices for our smartphones, media players, TVs, laptops, tablets, digital cameras, and other such gadgets. The most display technologies we hear are LCD, TFT, OLED, LED, QLED, QNED, MicroLED, Mini LED etc. The following, we will focus on two of the most popular display technologies in the market: TFT Displays and Super AMOLED Displays.

TFT Display

TFT means Thin-Film Transistor. TFT is the variant of Liquid Crystal Displays (LCDs). There are several types of TFT displays: TN (Twisted Nematic) based TFT display, IPS (In-Plane Switching) displays. As the former can’t compete with Super AMOLED in display quality, we will mainly focus on using IPS TFT displays.

Super AMOLED

OLED means Organic Light-Emitting Diode. There are also several types of OLED, PMOLED (Passive Matrix Organic Light-Emitting Diode) and AMOLED (Active Matrix Organic Light-Emitting Diode). It is the same reason that PMOLED can’t compete with IPS TFT displays. We pick the best in OLED displays: Super AMOLED to compete with the LCD best: IPS TFT Display.

Super AMOLED vs IPS TFT

  AMOLED IPS TFT
Light Source it emits own light It requires a backlight
Thickness Very slim profile Thicker because of the backlight
Contrast Higher because of dark background Lower because of backlighting
Viewing Angles All around It has color changes at extreme viewing angles
Colors Bright and vibrant colors available Not the same good compared with AMOLED
Super dark color Easily available dark background Difficult because the backlight leakage
Super White Color Difficult to get because color mix difficult which can look yellowish Easily avaible by using white LED backlight
Sunlight Readable Needs to drive hard and difficult Easily and low cost to get by using high brightness backlight, transflective displays, optical bonding and surface treatment
Power Consumption Lower because of selective display area and better battery life Higher because of backlight on
Life time Shorter, especially affected by the presence of water Longer
Cost Very high Very competitive prices
Availability Limited sizes and manufacturers Widely available on different sizes and many manufacturers to choose from

If you have any questions about Orient Display displays and touch panels. Please feel free to contact: Sales Inquiries, Customer Service or Technical Support.

03 Dec
Displays

What is the difference between LED and LCD display?

Although there are big differences between LCD and LED displays, there are a lot of confusion in the market which shouldn’t happen. Part of the confusion comes from the manufacturers. We will clarify as below.

LCD Displays vs LED Displays

LCD stands for “liquid crystal display”. LCD can’t emit light itself; it has to use a backlight. In the old days, manufacturers used to use CCFL (cold cathode fluorescent lamps) as backlight, which is bulky and not environment friendly. Then, with the development of LED (light emitting diode ) technology, more and more backlights use LEDs. The manufacturers name them as LED monitors or TV which makes the consumers think they are buying LED displays. But technically, both LED and LCD TVs are liquid crystal displays. The basic technology is the same in that both television types have two layers of polarized glass through which the liquid crystals both block and pass light. So really, LED TVs are a subset of LCD TVs.

Quantum Dot Displays

Quantum-dot TVs are also widely discussed for recent years. It is basically a new type of LED-backlit LCD TV. The image is created just like it is on an LCD screen, but quantum-dot technology enhances the color.

For normal LCD displays, when you light up the display, all the LEDs light up even for unwanted area (for example, some areas need black). Whatever perfect the LCD display made, there is still small percentage of light transmitting through the LCD display which makes it difficult to make the super black background. The contrast decreases.
Quantum-dot TV can have full-array backlit quantum-dot sets with local-dimming technology (good for image uniformity and deeper blacks). There can be edge-lit quantum-dot sets with no local dimming (thinner, but you may see light banding and grayer blacks).

Photo-emissive quantum dot particles are used in RGB filters, replacing traditional colored photoresists with a QD layer. The quantum dots are excited by the blue light from the display panel to emit pure basic colors, which reduces light losses and color crosstalk in RGB filters, improving display brightness and color gamut. Although this technology is primarily used in LED-backlit LCDs, it is applicable to other display technologies which use color filters, such as blue/UV AMOLED(Active Matrix Organic Light Emitting Diodes)/QNED(Quantum nano-emitting diode)/Micro LED display panels. LED-backlit LCDs are the main application of quantum dots, where they are used to offer an alternative to very expensive OLED displays.

Micro LEDs and Mini LEDs

Micro LED is true LED display without hiding at the backside of the LCD display as backlight. It is an emerging flat-panel display technology. Micro LED displays consist of arrays of microscopic LEDs forming the individual pixel elements. When compared with widespread LCD technology, micro-LED displays offer better contrast, response times, and energy efficiency.

Micro LEDs can be used at small, low-energy devices such as AR glasses, VR headsets, smartwatches and smartphones. Micro LED offers greatly reduced energy requirements when compared to conventional LCD systems while has very high contrast ratio. The inorganic nature of micro-LEDs gives them a long lifetime of more than 100,000 hours.

As of 2020, micro LED displays have not been mass-produced, though Sony, Samsung and Konka sell microLED video walls and Luumii mass produces microLED lighting. LG, Tianma, PlayNitride, TCL/CSoT, Jasper Display, Jade Bird Display, Plessey Semiconductors Ltd, and Ostendo Technologies, Inc. have demonstrated prototypes. Sony and Freedeo already sells microLED displays as a replacement for conventional cinema screens. BOE, Epistar and Leyard have plans for microLED mass production. MicroLED can be made flexible and transparent, just like OLEDs.
There are some confusions between mini-LED used in LCD backlight as Quantum dot displays. To our understanding, mini-LED is just bigger size of micro LED which can be used for larger size of cinema screen, advertisement walls, high end home cinema etc. When discussing Mini-LED and Micro-LED, a very common feature to distinguish the two is the LED size. Both Mini-LED and Micro-LED are based on inorganic LEDs. As the names indicate, Mini-LEDs are considered as LEDs in the millimeter range while Micro-LEDs are in the micrometer range. However, in reality, the distinction is not so strict, and the definition may vary from person to person. But it is commonly accepted that micro-LEDs are under 100 µm size, and even under 50 µm, while mini-LEDs are much larger.

When applied in the display industry, size is just one factor when people are talking about Mini-LED and Micro-LED displays. Another feature is the LED thickness and substrate. Mini-LEDs usually have a large thickness of over 100 µm, largely due to the existence of LED substrates. While Micro-LEDs are usually substrate less and therefore the finished LEDs are extremely thin.
A third feature that is used to distinguish the two is the mass transfer techniques that are utilized to handle the LEDs. Mini-LEDs usually adopt conventional pick and place techniques including surface mounting technology. Every time the number of LEDs that can be transferred is limited. For Micro-LEDs, usually millions of LEDs need to be transferred when a heterogenous target substrate is used, therefore the number of LEDs to be transferred at a time is significantly larger, and thus disruptive mass transfer technique should be considered.

It is exciting to see all the kinds of display technologies which make our world colorful. We definitely believe that LCD and/or LED displays will pay very important roles in the future metaverse.
If you have any questions about Orient Display displays and touch panels. Please feel free to contact: Sales Inquiries, Customer Service or Technical Support.

18 Nov
Displays

Difference between resistive and capacitive touch panel

Capacitive Touch Screen

Projected capacitive touch screen contains X and Y electrodes with insulation layer between them. The transparent electrodes are normally made into diamond pattern with ITO and with metal bridge.

Human body is conductive because it contains water. Projected capacitive technology makes use of conductivity of human body. When a bare finger touches the sensor with the pattern of X and Y electrodes, a capacitance coupling happens between the human finger and the electrodes which makes change of the electrostatic capacitance between the X and Y electrodes. The touchscreen controller detects the electrostatic field change and the location.

Resistive Touch Screen

A resistive touch screen is made of a glass substrate as the bottom layer and a film substrate (normally, clear poly-carbonate or PET) as the top layer, each coated with a transparent conductive layer (ITO: Indium Tin Oxide), separated by spacer dots to make a small air gap. The two conducting layers of material (ITO) face each other. When a user touches the part of the screen with finger or a stylus, the conductive ITO thin layers contacted. It changes the resistance. The RTP controller detects the change and calculate the touch position. The point of contact is detected by this change in voltage.

Which Is Better Capacitive or Resistive Touchscreen?

  Resistive Touch Screen Capacitive Touch Screen
Manufacturing Process Simple More complicated
Cost Lower Higher: Depending on size, number of touches
Touch Screen Control Type Requires pressure on the touchscreen. Can sense proximity of finger.
Power Consumption Lower Higher
touch with thick gloves Always good more expensive, need special touch controller
Touch Points Single Touch Only Single, two, gesture or Multi-Touch 
Touch Sensitivity Low High (Adjustable)
Touch Resolution High Relatively low
Touch Material Any type Fingers. Can be designed to use other materials like glove, stylus, pencil etc.
False Touch Rejection False touches can result when two fingers touch the screen at same time. Good Performance
Immunity to EMI Good Need to special design for EMI
Image Clarity Less transparent and smoky looking Very high transparent especially with optical bonding and surface treatment
Sliders or Rotary Knobs Possible, but not easy to use Very good
Cover Glass None Flexible with different shapes, colors, holes etc.
Overlay Can be done No
Curve Surface Difficult Available
Size Small to medium Small to very big size
Immunity to Objects/Contaminants on Screen Good Need to special design to avoid false touch
Resistant to Chemical Cleaners No Good
Durability Good Excellent
Impact Ball Drop Test Surface film protected Need special design for smash
Scratch Resistance As high as 3H As high as 9H
UV Degradation Protection Less protection Very good

What Are Resistive Touch Screens Used For?

Resistive touch screens still reign in cost-sensitive applications. They also prevail in point-of-sale terminals, industrial, automotive, and medical applications.

What Are Capacitive Touch Screens Used For?

Projected Capacitive Touch Panel (PCAP) was actually invented 10 years earlier than the first resistive touchscreen. But it was no popular until Apple first used it in iPhone in 2007. After that, PCAP dominates the touch market, such as mobile phones, IT, automotive, home appliances, industrial, IoT, military, aviation, ATMs, kiosks, Android cell phones etc.

If you have any questions about Orient Display capacitive touch panels. Please feel free to contact: Sales Inquiries, Customer Service or Technical Support.

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