The ultimate guide for Sunlight Readable Display

When the displays are used in outdoor, have you struggled to read the instructions on the display under sunlight? We could see a display that looked good in the outdoor, but the display image wash out in outdoor environment with high ambient sunlight. So for outdoor environment, we need sunlight readable displays. In this article, we would introduce technologies of sunlight readable displays and some tips for improving sunlight readable displays.

What is sunlight readable display?

Sunlight readable display means the display that could be read under sunlight, we also call it daylight readable display. the sunlight readable display technologies are including traditional sunlight readable LED display, sunlight readable lcd display, and sunlight readable oled display technology. Different to usual displays, sunlight readable displays could be clearly viewed under the strong sunlight without blur or color fade.

The best sunlight readable display has the properties of high contrast under directly sunlight without blur, wide temperature range, lower heat emission and power saving, long life time.

Which is the best of sunlight readable display technology:

OLED Displays: OLED displays offer high contrast and excellent image quality in direct sunlight. OLED displays are ideal for outdoor applications such as meters,smart phones,kiosks. However, the cost of sunlight readable OLED screen is much expensive than lcd display,the lifetime of common OLED displays are shorter than LCD displays.

E-Paper Displays: E-paper displays use a reflective technology that mimics the appearance of ink on paper. These displays can be used for outdoor applications such as electronic shelf labels and outdoor digital signage. E-paper displays are power saving displays, but the reflesh time of E-paper display is much longer than LCD display, it is only fit for the displays that no need to reflesh content frequently,  E-paper displays are also costly than lcd displays.

LED Displays: LED displays can be used for outdoor digital signage applications. The displays use light emitting diode technology to provide bright and clear images in direct sunlight. Traditional LED display can be in higher brightness when in outdoor working, beside micro-LED technology, traditional LED screens are hard to be made in high resolution(PPI). So it is hard to get a high quality display effect. The power consumption of LED displays are much higher than sunlight readable LCD displays.

Sunlight readable LCD displays: Lcd displays are the most suitable technology using for sunlight readable displays, by using sunlight readable LCD displays, we can get the best balance in display effect of sunlight readable, power saving, high resolution, colorful, fast response time, temperature range, touch panel optional, and cost.

There are several technologies for sunlight readable LCD displays, the technologies are included high brightness LCD in transmissive type, transflective lcd and reflective LCD.

High brightness LCD display: High-brightness LCD displays use advanced backlighting technology on transmissive LCD panel, it provide clear and bright images in direct sunlight. By using high brightness backlight on the transmissive LCD, high brightness light from backlight transmit through LCD panel, the high brightness light compete the strong sunlight in human's eyes visual system, make the LCD display clearly viewable in sunlight. High brightness lcd is a good choice for outdoor displays, such as used for the LCD in transmissive negative display mode, or transmissive TFT LCD panel. the high brightness TFT LCD displays is a good choice for color display in outdoor application, it is high resolution, full colors, fast response time, economy.

Reflective lcd: Reflective lcd could reflect the ambient light on the screen, but it is without backlight system, the reflective light would increase the brightness of lcd screen and reduce the ambient light on the screen. Reflective monochrome lcds are the economy solutions for sunlight readable displays, but the reflective LCD technology is only used for monochrome LCD panel, due to the color filter inside tft panel,  the transmissive rate of TFT panel is much lower than monochrome LCD panel, the reflective light brightness would be too low to use for reflective TFT. Therefore, reflective LCD is only used for monochrome LCD technology.

Another disadvantage of reflective LCD: Reflective LCD is only used for outdoor with strong ambient light, if it is used in dark environment, because LCD is passive display, LCD can not emit light by itself, without the backlight and other light on reflective LCD, we can not see the display content from reflective LCD.

Transflective lcd display:

Transflecive LCD display could reflect the ambient light on the screen, it could use the transmited light from its backlight as well, it combine the functions of transmissive LCD and reflective LCD displays. it is popular display mode for sunlight readable displays. When the ambient light is dark, we could use its transmissive function. When in outdoor environment, transflective LCD could use the reflective light from ambient. Therefore, transflective LCD display is suit for varienty applications, both indoor and outdoor.

Transflective lcd displays are available in monochrome lcd and transflective color tft lcd, they can be used for outdoor displays that required low power consumption.

Both transflective tfts and high brightness TFT LCDs are suitable for sunlight readable color displays, you could check more to find which is better sunlight readable displays in the link: ==> https://www.szmaclight.com/new/How-to-choose-Sunlight-readable-tft.html

What makes display sunlight readable and how it works?

Challenges of sunlight readability: Overcoming Environmental Obstacles

The challenges of sunlight readable displays are involved in making displays visible in bright outdoor environments, such as glare, reflections, and extreme temperatures.

There are three ways to make displays sunlight readability:

a.  Increase display's brightness -- High brightness display

b.  Reuse the ambient light inside the screen -- Transflective lcd or reflective lcd

c.  Reducing light reflectance on the surface of screen -- Antiglare surface treatment on the screen.

How sunlight readable display works:

To make sunlight readable displays(sunlight viewable displays), we have to know the definition of visibility. The visibility means an object is detected by a viewer’s eyes. In scientific words, it means an object’s brightness and contrast is higher than its ambient light, and the different ratio must be higher than human being eyes’ viewing threshold.

So for a display that under the strong sunlight, a display with higher brightness light to complete the ambient light, it would be the key point for making the sunlight readable displays.

There is the way to get sunlight readability:  High brightness compete to the strong sunlight

a) From the test data, the display ambient contrast is declined as the ambient illumination increased, they are inverse relationship

b) The display with lower brightness, the contrast declined faster than higher brightness display

Principle for making sunlight readable display:

The principle for making sunlight readable display clearly be viewable : The brightness on top surface of screen higher than ambient illumination on the screen (the ambient illumination means the screen’s reflective light from ambient light).

In the mean time, as the research result, for comfortably viewed by eyes, the display brightness needs to 2.5 multiple than its reflective light.

So we have three directions to create sunlight readable display,

a)     Increasing the brightness on top surface from the screen.

b)     Reduce the reflective light from ambient light on the screen surface.

c）  Reuse the ambient light to the screen.

Factors we need to concern in designing sunlight readable lcd display:

Screen size: Choose the suitable screen size for your project.

Resolution: Choose the resolution (PPI ) based on the application

Brightness: If it is transmissive display, choose the high brightness display refer to ambient illumination.

Raflective: For transflective display or reflective lcd, the higher reflective ratio would be benefit to sunlight readability.

Power consumption: We have to consider power consumption for sunlight readable displays, especially for the devices with battery charge, such as hand held devices

Temperature range: Choose wide temperature displays to stand outdoor environment, the high brightness displays also intensify the temperature of sunlight readable displays.

Life time: Choose the long life time sunlight displays for outdoor application. The LED backlight lifetime would be affected by long working in high brightness.

Some tips for improving the performance of sunlight readable displays:

Tip 1: Surface treatments for the sunlight readable display

The surface treatment could reduce reflectance on the screen surface. the display are made by many materials layers, such as a Sunlight readable tft lcd display with capacitive touch, from the top layer to bottom layer, it is made by top cover lens -->  touch sensors layer-->OCA layer or air gap layer --> top polarizer --> top glass -->  bottom glass-->bottom polarizer-->backlight films.

When the ambient light go through the display, the refraction and reflection happened in each layer. The refraction and reflection light combine to diffuse lights inside the display, it leads to display blur to the screen,  the situation would be worse under the sunlight that with strong incident light to the screen.

The solutions for reducing reflection would be:

Tip 2. Reduce the reflection of screen surface by AR and AG treatment.

We could add the surface treatments such as Anti-Reflection and Anti-Glare film or apply AR coating. It could reduce 2%~3% surface reflectance on the top surface of sunlight readable display. The surface treatment could be made by additional materials coating on the screen's surface or an external film on the screen.

Anti-glare surface treatment with high haze surface, it could reduce the mirror reflectance on the screen surface.
An external film with AR properties not only reduces reflected light, but also brings some other benefits in some application. A top film always reduces TFT LCD’s surface hardness. And it is susceptible to scratches. On the other hand, AR coating retains LCD’s hardness and touch performance. But it comes with a bigger price gap.

For the sunlight readable tft display with PCAP touch,

An additional linear polarizer on the top of tft screen would also decrease the surface reflectance from ambient light. Or a circular polarizer (O-film) to block reflected light. when ambient light passes through circular polarizer it gets circularly polarized. And when it is reflected, the polarization direction flips by 180 degrees. So when reflected light comes back to the circular polarizer, nothing goes through to viewer’s eyes. But the additional polarizers would make the more thickness to the screen, and reducing the brightness of the lcd screen,  a surface coating with AR or AG treatment are more effective and popular for the sunlight readable LCD display.

The brightness will be reduced if the module requires touch panel or O-Film on it). meanwhile, high brightness displays will generate more heat and use more power than a traditional LCD.

Tip 3. OCA bonding to replace air gap bonding to the PCAP touch screen

OCA bonding would help to reduce the reflection light of the LCD display. Air-gap reflection is the main culprit causing worse sunlight readability. We can improve it from two directions. Add AR films or AR surface treatment on both interfaces of internal air gap. it could reduce the reflection ratio from 8.5% to 2%.

·        The most effective way is to eliminate air gap totally, by using OCA bonding (optical bonding). OCA bonding means we fill air gap with special optical adhesive (OCA), to smooth out the area’s refraction index differences. it leads to the reflectance by internal air gap drops from 8.5% to 0.5%. Optical bonding is expensive but effective way to improve TFT LCD sunlight readability. Moreover, no air gap means no moisture condensation and fogging for the sunlight readable TFT display.

Benefits of sunlight readable displays:

There are many benefit for Sunlight-readable displays in outdoor applications. Some of these benefits include:

Visibility: Sunlight-readable displays offer excellent visibility even in direct sunlight. This ensures that the display is visible and readable even in bright outdoor conditions.

Durability: Sunlight-readable displays are designed to withstand harsh outdoor environments. They are built with rugged materials and are often waterproof and dustproof.

Energy Efficiency: Sunlight-readable LCD displays use advanced backlighting techniques to reduce power consumption. This makes them ideal for use in battery-powered outdoor applications.

Cost-effective: Sunlight-readable LCD displays are cost-effective compared to other outdoor display technologies. This makes them an ideal choice for businesses and organizations that require outdoor displays on a budget.

Maintenance of Sunlight Readable Displays:

a) Put sunlight readable displays into the devices with water proof case.

b) Add heat dissipation design for sunlight readable displays.

c) Add a shield for sunlight readable display, such as digital kiosk display in the outdoor.

d) Light off it when sunlight display is no need on working.

e) Keep the sunlight readable display's brightness less than 80% maximum of its design value.

f) Add light sensor for sunlight readable displays, the display brightness could be auto-adjusted following the ambient light.

How can i get best Sunlight readable lcd displays: Choosing the right supplier for your project

Maclight display is profession in sunlight readable displays, Maclight's high brightness TFT LCD panels are featured with brightness up to 1500 nits. our high brightness tft is made by using a very bright backlight to keep the display visible even when the sun is on it. we could upgrade the backlight to dramatically increase brightness with long lifetime LED backlights and wide temperature lcd displays.

Maclight's sunlight readable display models are optional in resistive touch panel and capacitive touch screen.  Maclight Sunlight Readable LCD Modules are including 1.8 "~10.1" sunlight readable TFT LCD, transflective lcd, OLED displays.

Welcome contact Maclight for more information of sunlight readable display, Email: [email protected]