adjusting backlight on lcd panel made in china

There are more and more TFT displays used in outdoor applications, such as automobile display, digital signage and kiosks. High ambient light in outdoor environment often causes wash-out image and renders the screen not readable. Readability & sustainability of TFT  display under direct sunlight is becoming vital. Topway Display has been developing sunlight readable LCD display solution for years. The company understands the ins and outs of sunlight readable TFT LCD.

Visibility is the ease with which a viewer can detect an object, or in more scientific term: the relationship between luminance contrast and human eye’s threshold. Therefore, the higher an object’s contrast is, the better is its visibility.

For an LCD to be readable in outdoor environment with very bright ambient light, the LCD screen’s brightness needs to exceed the intensity of light that is reflected from the display surface. To be comfortably viewed by human eyes, the LCD’s brightness needs to exceed its reflected light by a factor of 2.5 at minimum. Naturally, to make an LCD sunlight readable, we can work on two areas, increasing brightness or reducing reflectance.

On a clear day in direct sunlight, the ambient brightness is about 6000 cd/m2. And a typical TFT LCD with touch screen reflects about 14% of ambient light, which is around 840 cd/m2. These days, most LCD displays use LED backlight as light source. It is not too difficult to increase an LCD’s brightness to 800 ~ 1000 Nits, to overpower the bright reflected sunlight. Thus, you have a sunlight readable TFT LCD.

However, this method requires more backlight LEDs and/or higher driving current. The drawbacks are high power consumption, more heat dissipation, increased product size and shorter LED backlight lifespan. Apparently, increasing backlight to make TFT LCD sunlight-readable is not a very good solution.

Transflective TFT LCD is a TFT LCD with both transmissive and reflective characteristics. A partially reflective mirror layer is added between LCD and backlight. This change turns part of the reflected ambient light into LCD’s light source, increasing the TFT display’s brightness. However, transflective TFT LCD is more expensive than transmissive one. At the same time, the partially reflective mirror layer will block some of the backlight, making it not ideal in indoor or low ambient light environment.

What causes light reflection? When light traveling in one transparent medium encounters a boundary with another transparent medium, a portion of the light bounces off the border. Through the simplest version of Fresnel’s equation, we can calculate the amount of reflected light.

The total reflectance on a TFT LCD with touch panel is the sum of reflected light on any interface where two materials meet. As an example, between polarizer and display glass, the difference in index of refractions for the two materials is very small, around 0.1. So the reflected light on this interface is only 0.1%. As Fresnel’s equation points out, we should focus reflection reduction on air interfaces. For air, its index of refraction is 1; for glass, it is 1.5. And that results in a reflectance of 4.5%. Therefore, the three air interfaces contribute majority of TFT LCD’s reflectance, at about 13%.

The quick and easiest thing we can do to reduce air-glass interface reflectance is to use an Anti-Reflection and Anti-Glare film or apply AR coating. An external film with AR properties not only reduces reflected light, but also brings other benefits.

For food industry application, shattered glass is a serious problem. An LCD screen with external film solves this issue nicely. As for automotive applications, in an accident, broken LCD with top AR film won’t produce sharp edge glass that could harms auto occupant. Nevertheless, 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 tag.

Another quick and easy way to tackle reflectance is to affix a linear polarizer on the top of TFT screen. When ambient light gets to the top polarizer, only half of the light passes through. Which results in reflection light cutting to half. This is a very low cost way to increase TFT LCD’s contrast, such that making it more sunlight readable.

Laminating a circular polarizer in TFT LCD will get rid of a lot of reflectance. That is because 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.

This method is very effective for an LCD display with resistive touch panel. We know resistive touch LCD has two air gaps: air gap between two ITO layers and air gap between touch panel and LCD display. Reflectance caused by the two air gaps is very high. Applying circular polarizer blocks off most of the reflected light, and makes the LCD display sunlight readable.

The disadvantage of such solution is its cost. Since we need not only a circular polarizer, but also a retarder film on the top of LCD display, making sure light originates from within LCD is not blocked by external circular polarizer.

Add AR films on both interfaces of internal air gap. The add-ons can reduce this area’s reflection from 8.5% to 2%. And since the AR films are not outside facing, they are much cheaper than the one used outside. Keeping the air gap also retains the ease of service, in case either touch panel or LCD display needs to be repaired.

The most effective way is to eliminate air gap totally, by using optical bonding. In plain language, we fill air gap with special optical adhesive, to smooth out the area’s refraction index differences. Such that reflectance caused by internal air gap drops from 8.5% to 0.5%. Optical bonding is expensive but effective way to improve TFT LCD sunlight readability. It enhances durability and resistance to impact. Moreover, no air gap means no moisture condensation and fogging.

There are many ways to make TFT LCDsunlight readable. They all have their own pros and cons. With 20+ years" LCD design and manufacturing experience, Topway knows how to create the best sunlight readable TFT LCD for challenging environments. Leave us a message and let"s start the conversation of creating suitable sunlight readable TFT LCD for your project.

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Introduction: Global LCD industry shift and automotive intelligence together to promote the rapid development of China’s LCD panel industry, which will bring a continuous increase in demand for backlight modules, China’s backlight module industry has greater potential for development.

LCD panel backlight module consists of a backlight light source, light guide, optical film, and a plastic frame, which is an important component of LCD display panel. As the backlight module has technology-intensive and labor-intensive attributes, with abundant high-skilled labor advantage China is attracting the global LCD panel industry to the domestic rapid transfer.

From LCD application to the present, the global LCD panel industry capacity transfer has gone through three periods, 2000 Japan dominated the global LCD industry; 2000 – 2010, Japan’s production capacity to South Korea and Taiwan; 2010 to the present, Japanese manufacturers gradually withdraw from the LCD panel industry, production capacity began to transfer to mainland China, so far, mainland China LCD production capacity has occupied the global half of the world.

In recent years, South Korea’s Samsung and LG display will shift their business focus to OLED, and will gradually shut down their LCD production lines and withdraw from the LCD panel industry; at the time of South Korean manufacturers’ withdrawal, domestic enterprises are stepping up new construction to expand LCD production capacity.

BOE, Huaxing photoelectric, Huike, CEC in 2020 – 2021, a total of eight 7 generation LCD production lines completed and put into operation, and domestic panel manufacturers have further expansion plans, the next few years domestic LCD production capacity will continue to increase.

LCD panel manufacturers tend to choose the nearby supporting module suppliers for the safety of the key component supply chain and cost reduction considerations. LCD panel production capacity transfer to China will bring opportunities to domestic backlight module manufacturers and drive the development of the domestic backlight module industry.

The future of the car will pay more attention to the human driving experience, to the intelligent development, which will bring the increasing demand for car display. On the one hand, the number of car displays gradually increased, for example, the instrument panel, rearview mirror, central control platform more to display the way, the passenger and rear position with entertainment display. On the other hand, the car display is constantly to a large screen, multi-screen development, especially in high-end models, the large display has become standard, for example, Tesla Model S screen size of 17 inches, Mercedes-Benz A-class car configuration of two 10.5-inch display.

At the same time, there is also a huge demand for new cars in China. Although China’s car sales have reached 25 million, the current per capita car ownership in China is only a quarter of the developed countries, the future potential for new car demand is still very large. Therefore, China’s car display market growth potential is large, which will directly drive the domestic backlight module demand continues to increase.

According to the terminal application size, backlight module can be divided into large, medium, and small size, of which small size backlight module is mainly used in smartphones, wearable devices, and other terminals, the medium size used in notebook computers, tablet PCs, car screens and other terminals, the large size is mainly used in LCD TV.

From the market competition pattern, the domestic backlight module enterprises are deeply plowed in their respective competitive advantage in the field of segmentation, including Baoming technology, Longli technology mainly layout small size cell phone display field, Hanbo high-tech, Weishi electronics mainly layout in the size of car display and notebook computer field, Rui Yi photoelectric and photoelectric in each field have layout.

From the industry development trend, smartphone display is transitioning to OLED, LCD TV market is gradually saturated, the future of large size and small size backlight module market potential is relatively small; and the future of the car display market potential is huge, by the backlight module manufacturers are unanimously optimistic, are currently accelerating the layout ( see Table 2 ). Focusing on the traditional medium-sized backlight module field, Hanbo Hi-Tech and Weishi Electronics have significant advantages in core technology patents, downstream customer resources, process experience accumulation, production costs, etc., and have more development advantages in the future.

The current global LCD display panel industry is rapidly moving to China, which brings development opportunities to China’s backlight module industry. In addition, automotive intelligence will also bring a continuous increase in demand for medium-sized car displays, the first to enter the field of medium-sized backlight module manufacturers with its customer resources, core technology, scale efficiency, and other advantages will be more beneficial.

Responsible for performing installations and repairs (motors, starters, fuses, electrical power to machine etc.) for industrial equipment and machines in order to support the achievement of Nelson-Miller’s business goals and objectives:

• Perform highly diversified duties to install and maintain electrical apparatus on production machines and any other facility equipment (Screen Print, Punch Press, Steel Rule Die, Automated Machines, Turret, Laser Cutting Machines, etc.).

• Provide electrical emergency/unscheduled diagnostics, repairs of production equipment during production and performs scheduled electrical maintenance repairs of production equipment during machine service.

Responsible for performing installations and repairs (motors, starters, fuses, electrical power to machine etc.) for industrial equipment and machines in order to support the achievement of Nelson-Miller’s business goals and objectives:

• Perform highly diversified duties to install and maintain electrical apparatus on production machines and any other facility equipment (Screen Print, Punch Press, Steel Rule Die, Automated Machines, Turret, Laser Cutting Machines, etc.).

• Provide electrical emergency/unscheduled diagnostics, repairs of production equipment during production and performs scheduled electrical maintenance repairs of production equipment during machine service.

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Ever had your TV showing nothing but a black screen even if the audio was working? Unfortunately, that’s a common issue with low/middle-end LCD/LED TVs these days… Even more frustrating, this issue often comes from a rather tiny and cheap component that can be easily replaced. Most common issues are:

One of my relatives had this exact symptom happening all of a sudden. This problem on low-end TVs often occurs within the first couple years. As the repair costs for that kind of TV is pretty low, considering repairing it yourself might be a good idea!

The first step into repair is to find the root cause of the issue. As backlight failure is a very common issue, this is the first thing to test. To do so, the easiest way is to power on your screen, put a flashlight very close to it and check if you can see the image through. The image would be very dark, like turning the brightness of the screen very very low.

That implies disassembling the TV to access the backlight which is between the LCD screen in the front and the boards in the rear. In my case, with a Samsung F5000, I had to process as follows:

First we have to remove the back housing to reveal the boards (from left to right: main board, T-CON, power supply) and disconnect the LCD panel from the T-CON board.

Note: Older TVs have neon tubes for backlight, which is thicker and less exposed to this kind of failure. LED backlight is the most common thing these days, but do not mistake an LED TV with an OLED TV. The first one is a classic LCD panel with a LED backlight, whereas the second is an OLED panel that doesn’t need any backlight as it is integrated in each pixels (making the spare parts much more expensive by the way).

As we can see, the backlight system is made of 5 LED strips. First thing to do is look for burnt LEDs. Most LED backlight systems have strips set in series, meaning that if one of the them fails, all the system goes dark…

Using a multimeter, we can confirm that the strips are indeed set in series, so now we have to test each strip individually. Professionals use LED testers such as this one (about 40$ on amazon) but as I didn’t had one at the time, I decided to make one, McGyver style!