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The ST7789 TFT module contains a display controller with the same name: ST7789. It’s a color display that uses SPI interface protocol and requires 3, 4 or 5 control pins, it’s low cost and easy to use. This display is an IPS display, it comes in different sizes (1.3″, 1.54″ …) but all of them should have the same resolution of 240×240 pixel, this means it has 57600 pixels. This module works with 3.3V only and it doesn’t support 5V (not 5V tolerant).

As mentioned above, the ST7789 TFT display controller works with 3.3V only (power supply and control lines). The display module is supplied with 3.3V (between VCC and GND) which comes from the Arduino board.

The first library is a driver for the ST7789 TFT display which can be installed from Arduino IDE library manager (Sketch —> Include Library —> Manage Libraries …, in the search box write “st7789” and install the one from Adafruit).

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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 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.

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.

In market, LCD means passive matrix LCDs which increase TN (Twisted Nematic), STN (Super Twisted Nematic), or FSTN (Film Compensated STN) LCD Displays. It is a kind of earliest and lowest cost display technology.

LCD screens are still found in the market of low cost watches, calculators, clocks, utility meters etc. because of its advantages of low cost, fast response time (speed), wide temperature range,  low power consumption, sunlight readable with transflective or reflective polarizers etc.  Most of them are monochrome LCD display and belong to passive-matrix LCDs.

TFT LCDs have capacitors and transistors. These are the two elements that play a key part in ensuring that the TFT display monitor functions by using a very small amount of energy without running out of operation.

Normally, we say TFT LCD panels or TFT screens, we mean they are TN (Twisted Nematic) Type TFT displays or TN panels, or TN screen technology. TFT is active-matrix LCDs, it is a kind of LCD technologies.

TFT has wider viewing angles, better contrast ratio than TN displays. TFT display technologies have been widely used for computer monitors, laptops, medical monitors, industrial monitors, ATM, point of sales etc.

Actually, IPS technology is a kind of TFT display with thin film transistors for individual pixels. But IPS displays have superior high contrast, wide viewing angle, color reproduction, image quality etc. IPS screens have been found in high-end applications, like Apple iPhones, iPads, Samsung mobile phones, more expensive LCD monitors etc.

Both TFT LCD displays and IPS LCD displays are active matrix displays, neither of them can produce color, there is a layer of RGB (red, green, blue) color filter in each LCD pixels to make LCD showing colors. If you use a magnifier to see your monitor, you will see RGB color. With switch on/off and different level of brightness RGB, we can get many colors.

Neither of them can’t release color themselves, they have relied on extra light source in order to display. LED backlights are usually be together with them in the display modules as the light sources. Besides, both TFT screens and IPS screens are transmissive, it will need more power or more expensive than passive matrix LCD screens to be seen under sunlight.  IPS screens transmittance is lower than TFT screens, more power is needed for IPS LCD display.

Do you need a display with beautiful graphics and touch capabilities in a tough environment? This resistive touch IPS EVE TFT module is a fantastic choice. The BT817 EVE chip helps simplify sending complex graphics to the display and also handles the touchscreen sensing and communication to the host. Read more about the benefits of an EVE module.

We have over two dozen TFT LCD display modules to choose from. All of them are full-color graphic displays. Unlike standard monochrome character displays, you can create complex images for imaginative user experiences. Thin and light, these are ideal for handheld devices, communications equipment, information displays, and test and measurement equipment.

Listed by the diagonal size of the active area (the usable area for lit pixels), our TFT display sizes range from 1.3 inches to 10.1 inches. Choose from six different interfaces, many of our TFT modules have more than one interface available. Arduino users should select modules with SPI for fast and easy communications to add color graphics to their projects.

Contrast ratio is the difference between a pixel that is lit or dark. Standard STN LCD displays typically have a 10:1 contrast ratio while TFT displays are 300:1 and up, so details stand out and text looks extra sharp. For standard STN displays, you must choose a display limited to a specific viewing angle (12, 3, 6 or 9 o"clock) while TFTs can have a viewing cone greater than 160 degrees.

IPS (In-Plane Switching) lcd is still a type of TFT LCD, IPS TFT is also called SFT LCD (supper fine tft ),different to regular tft in TN (Twisted Nematic) mode, theIPS LCD liquid crystal elements inside the tft lcd cell, they are arrayed in plane inside the lcd cell when power off, so the light can not transmit it via theIPS lcdwhen power off, When power on, the liquid crystal elements inside the IPS tft would switch in a small angle, then the light would go through the IPS lcd display, then the display on since light go through the IPS display, the switching angle is related to the input power, the switch angle is related to the input power value of IPS LCD, the more switch angle, the more light would transmit the IPS LCD, we call it negative display mode.

The regular tft lcd, it is a-si TN (Twisted Nematic) tft lcd, its liquid crystal elements are arrayed in vertical type, the light could transmit the regularTFT LCDwhen power off. When power on, the liquid crystal twist in some angle, then it block the light transmit the tft lcd, then make the display elements display on by this way, the liquid crystal twist angle is also related to the input power, the more twist angle, the more light would be blocked by the tft lcd, it is tft lcd working mode.

A TFT lcd display is vivid and colorful than a common monochrome lcd display. TFT refreshes more quickly response than a monochrome LCD display and shows motion more smoothly. TFT displays use more electricity in driving than monochrome LCD screens, so they not only cost more in the first place, but they are also more expensive to drive tft lcd screen.The two most common types of TFT LCDs are IPS and TN displays.

Super AMOLED (S-AMOLED) and Super LCD (IPS-LCD) are two display types used in different kinds of electronics. The former is an improvement on OLED, while Super LCD is an advanced form of LCD.

All things considered, Super AMOLED is probably the better choice over Super LCD, assuming you have a choice, but it"s not quite as simple as that in every situation. Keep reading for more on how these display technologies differ and how to decide which is best for you.

Super LCD is the same as IPS LCD, which stands forin-plane switching liquid crystal display. It"s the name given to an LCD screen that utilizes in-plane switching (IPS) panels. LCD screens use a backlight to produce light for all the pixels, and each pixel shutter can be turned off to affect its brightness.

There isn"t an easy answer as to which display is better when comparing Super AMOLED and IPS LCD. The two are similar in some ways but different in others, and it often comes down to opinion as to how one performs over the other in real-world scenarios.

For example, one quick consideration is that you should choose S-AMOLED if you prefer deeper blacks and brighter colors because those areas are what makes AMOLED screens stand out. However, you might instead opt for Super LCD if you want sharper images and like to use your device outdoors.

S-AMOLED displays are much better at revealing dark black because each pixel that needs to be black can be true black since the light can be shut off for each pixel. This isn"t true with Super LCD screens since the backlight is still on even if some pixels need to be black, and this can affect the darkness of those areas of the screen.

However, since LCD screens have backlights, it sometimes appears as though the pixels are closer together, producing an overall sharper and more natural effect. AMOLED screens, when compared to LCD, might look over-saturated or unrealistic, and the whites might appear slightly yellow.

When using the screen outdoors in bright light, Super LCD is sometimes said to be easier to use, but S-AMOLED screens have fewer layers of glass and so reflect less light, so there isn"t really a clear-cut answer to how they compare in direct light.

Another consideration when comparing the color quality of a Super LCD screen with a Super AMOLED screen is that the AMOLED display slowly loses its vibrant color and saturation as the organic compounds break down, although this usually takes a very long time and even then might not be noticeable.

Without backlight hardware, and with the added bonus of only one screen carrying the touch and display components, the overall size of an S-AMOLED screen tends to be smaller than that of an IPS LCD screen.

This is one advantage that S-AMOLED displays have when it comes to smartphones in particular, since this technology can make them thinner than those that use IPS LCD.

Since IPS-LCD displays have a backlight that requires more power than a traditional LCD screen, devices that utilize those screens need more power than those that use S-AMOLED, which doesn"t need a backlight.

That said, since each pixel of a Super AMOLED display can be fine-tuned for each color requirement, power consumption can, in some situations, be higher than with Super LCD.

For example, playing a video with lots of black areas on an S-AMOLED display will save power compared to an IPS LCD screen since the pixels can be effectively shut off and then no light needs to be produced. On the other hand, displaying lots of color all day would most likely affect the Super AMOLED battery more than it would the device using the Super LCD screen.

An IPS LCD screen includes a backlight while S-AMOLED screens don"t, but they also have an additional layer that supports touch, whereas Super AMOLED displays have that built right into the screen.

For these reasons and others (like color quality and battery performance), it"s probably safe to say that S-AMOLED screens are more expensive to build, and so devices that use them are also more expensive than their LCD counterparts.

As the mainstream display mode of LCD, IPS is overwhelmingly used in many fields of flat displays. However, due to the stress sensitivity of glass, the stressed light leakage is a bottleneck for achieving perfect dark state performance. The conventional scheme of using a compensation polarizer outside the cell has no effect on this light leakage. Although many studies have been conducted to overcome this limitation, the proposed methods have limited effects. Our research team has proposed a novel light leakage compensation mechanism by introducing a positive A plate that is sandwiched between the glass and the LC layer, therefore the light leakage which is caused by the combined effect of the phase retardations from the stressed glasses and the LC layer can be eliminated. In addition to theoretically analyzing the compensation principles of the novel light leakage compensation mechanism, we also use the developed positive A material to prepare light leakage compensation demos. And then the electric-optical characteristics and light leakage compensation effects of the demos are evaluated. While maintaining excellent optical and electrical characteristics, this technology effectively solves the problem of stressed light leakage of glass-based IPS, improves the dark-state image quality, and breaks the application of IPS in products such as curve products.

After decades of development, IPS (In-Plane Switching) LCD (Liquid Crystal Display) occupies a dominant position in the display field. Due to its excellent display performance, IPS is widely used in all sizes of display products, such as mobile phones, tablet computers, notebook computers, monitors, and TVs

Due to the manufacturing process of CF/TFT glass and panel, and even the using process of IPS panel, it is difficult to completely avoid the stress birefringence of glass. Although some studies have proposed solutions, such as slimming of glass thickness

where σ is the stress from bending, E is Young’s modulus of glass (73,000 MPa for LCD display used glass), t is the thickness of the glass sheet and r is the radius to which the sheet is bent. In an ideal case, as the light passes through the bent glass, the in-plane retardation can be calculated by the stress-optic law shown in formula (

In this article, referring to the fundamental reason for light leakage, we have proposed a novel light leakage compensation mechanism, and a new LCD structure with an in-cell phase retarder as a solution. The basic idea of phase compensation is to introduce a positive A (+A) plate to compensate for the retardation of LC, make the stress birefringence of CF and TFT glass offset each other, and effectively eliminate light leakage. We have explained the compensation mechanisms, analyzed the electric-optical characteristics, and studied the effects of LL compensation. It is a very important point to note that, different from studies of compensation layers on improving the viewing angle

As mentioned above, our research focuses on stressed LL caused by mechanical deformation stress. When the panel is under force, due to the fixing effect of the sealant, the panel as a whole, it experiences tension on the TFT glass and compression on the CF glass as bending 1, under pure bending, these tensile and compressive stresses are equal in magnitude but opposite in direction. At the neutral axis where the transition between tensile and compressive zones occurs, the stress is zero.

In order to analyze the stress leakage mechanism of IPS and the leakage compensation mechanism proposed in this paper, we calculated the stress value and the stressed retardation of the glass and carried out the relevant simulation and analysis. According to formula (

And as shown in Fig. 2a, the angle between the optical axis of TFT glass and LC is θ, and the angle between the optical axis of CF glass and LC is θ + 90°. The residual stress of the glass or the uneven stress caused by the frame during the IPS manufacturing process will cause the glass to produce retardation. And the brightness of the LL is proportional to the square of phase retardation (δ). After the stressed retardation of glass is got, the LL can be confirmed by simulation software.

The compensation principle of the new IPS. (a) The structure of normal IPS. (a") The stressed LL principle of normal IPS. (b) The structure of compensation mode 1. (b") The compensation mechanism of compensation mode 1. (c) The structure of compensation mode 2. (c") The compensation mechanism of compensation mode 2.

The stressed LL mechanism of normal IPS is illustrated by using the Poincaré sphere2a", PI (Point 1), P2 (Point 2), P3 (Point 3), and P4 (Point 4) respectively represent the polarization state of light after passing through the polarizer, the TFT glass, the LC layer, and the CF glass. Due to the effect of phase retardation of LC, a certain level of LL occurs. When the angle between the optical axis of LC and the glass with stress birefringence is 0° or 90°, the phase retardation of the LC is invalid, and there is no light leakage. But when the angle between the optical axis of LC and the optical axis of the glass with stress birefringence is not 0° or 90°, the vertically incident light becomes linearly polarized light after passing through the TFT polarizer, due to the effect of the LC phase retardation, the polarization state after passing through the TFT glass, the LC layer, and the CF glass is changed. When passing through the CF polarizer, it cannot be completely absorbed and LL occurs. As shown in Fig. 2a", the distance from P1 (Point 1) to P4 (Point 4) is proportional to LL brightness.

Due to the combined effect of the phase retardations from the stressed glass and the LC layer, the existing IPS structure cannot eliminate the influence of glass stress. The key to solving this problem is to ensure that the light is located at P2 (as shown in Fig. 2a") before the light reaches the CF glass. We have proposed two compensation structures based on IPS mode. These compensation structures with an additional optical layer that can be matched with LC, and effectively eliminate light leakage. Although both schemes introduce a  +A plate and effectively eliminate LL at a dark state, they have different structures and mechanisms.

As shown in Fig. 2b, the first new LCD structure called compensation mode 1, introduces the  +A plate, which is sandwiched between the glass and LC. More specifically, the optical axis of the  +A plate is perpendicular to the initial optical axis of LC, and the phase retardation of the  +A plate is 350 nm, which is equal to that of the LC.Fig. 2b" illustrates the compensation principle of compensation mode 1. When receives external stress, the light from the backlight unit traverses the TFT polarizer, the effective optical axis position on the Poincaré sphere is P1, when the light (P1) successively passes through the stressed TFT glass, its polarization state is rotated from P1 to P2. And when the light (P2) passes through LC, its polarization state is rotated from P2 to P3. Then, the light (P3) successively passes through the  +A plate and the stressed CF glass, whose effective optical axis positions on the Poincaré sphere are P4 and P5, respectively. The intermediate polarization state (P2) in general, is an elliptical polarization state. Due to the role of the  +A plate, the polarization state (P5) on the Poincaré sphere is very near to the polarization state (P1), so the light almost can be absorbed by the CF polarizer, and the elimination of LL is achieved.

The second new LCD structure called compensation mode 2, also introduces a  +A plate, but the optical axis of the  +A plate is parallel to the initial optical axis of LC, the sum of the phase retardation of  +A and LC is an integer multiple of a specific wavelength. Considering that the human eye has the strongest sensitivity to green light, the retardation value of  +A is designed to be 200 nm, and the sum of phase retardation of  +A and LC is 550 nm, that is the specific wavelength is 550 nm.

The compensation structure of mode 2 is shown in Fig. 2c. The main difference between mode 1 and mode 2 is reflected in the role of the  +A plate. For mode 1,  +A plate realizes that the light follows the same path as LC, and returns back in the opposite direction to the same polarization state as the light before the incident LC. For mode 2, the  +A plate realizes that the light continues along the same direction as the LC and moves forward with a certain optical path to the same polarization state as the light before the incident LC. So for mode 2, as shown in Fig. 2c", due to the role of  +A plate, the polarization state (P5) on the Poincaré sphere is very near to the polarization state (P1) of the light passed through the TFT polarizer, so the light almost can be absorbed by CF polarizer and the LL compensation is realized.

The electro-optical characteristics of IPS, such as the dark state brightness and V-T curve, are usually studied by the TechWiz (Korea Sanayi System Company) software which is based on Extended Jones.

The simulated V-T curve is shown in Fig. 3a. The V-T curve of normal IPS and compensation mode 1 and mode 2 are basically the same. As can be seen from the enlarged picture Fig. 3a’, the dark state brightness without the additional stress of normal IPS, compensation mode 1 and mode 2, is basically the same. But when the additional stress is applied, the difference between normal IPS and compensation modes appears. As shown in Fig. 3b, after being subjected to external stress, the V-T curves of normal IPS, compensation mode 1, and mode 2 have a slight shift. The main difference is reflected in the dark state brightness. It can be seen from the enlarged picture Fig. 3b", the transmittance of the dark state rises from 0.067% to 0.987%, which means the LL occurs in normal IPS. And the transmittances of the compensation modes at the dark state remain almost unchanged (0.067%). So we can conclude that the compensation mode can effectively resist the dark state LL caused by external stress.

(a) The V-T curves of normal IPS, compensation mode 1 and mode 2. (a") The partial enlarged V-T curves of (a). (b) The V-T curves of stressed normal IPS, stressed compensation mode 1 and mode 2. (b") The partial enlarged V-T curves of (b).

When the thickness of the glass is not equal, such as the thickness of the CF glass is 0.3t and the thickness of the TFT glass is 0.4t, the panel as a whole still has the same compressive and tensile stresses on the neutral axis, but the neutral axis is not in the middle of the CF and TFT glass. When the neutral layer is located in the TFT glass, the CF glass has compressive stress. But the TFT glass has tensile and compressive stress, as the stress birefringence δ generated by each has different directions, the δcompressive of TFT can be offset by the δtensile of TFT, and finally, the δtensile of TFT will be equal to the δcompressive of CF glass. At this time, the situation is the same as when the thickness of TFT and CF glass is equal. So when the stresses of the CF and TFT glass are not completely equal, the proposed compensation mode can still effectively reduce light leakage.

By comparing the viewing angle results in Fig. 4, the viewing angles of normal IPS and compensation mode 1 and mode 2 in the horizontal and vertical directions are almost equivalent, but for other viewing angles of compensation mode1 and mode 2 are different from the reference. This is mainly due to the effect of the  +A layer. For mode 1, since the optical axis of LC and  +A are perpendicular to each other, it is slightly worse than normal IPS at large viewing angles. For mode 2, the  +A and LC optical axes are parallel, the difference in viewing angle is aggravated, but this has little effect, mode 1and mode 2 can still meet the viewing angle specification of 89°/89°/89°/89°.

Normally, +A film is an anisotropic birefringence film with only one optical axis. The refractive index ellipsoid of the uniaxial  +A film: nx > ny = nz. The shadow plane represents the film’s surface plane, which is parallel to the X–Y plane. From the viewpoint of optical axis orientation, and the  +A film’s optical axis is parallel to the film surface. +A plate is a commonly used uniaxial birefringence film for phase compensation. It can be fabricated by the use of uniaxially stretched polymer films, such as polyvinyl alcohol (PVA), cyclic olefin polymer (COP), cyclic olefin copolymer (COC), or other suitably oriented organic birefringence materials. And +A plate is usually used in combination with a polarizer to achieve viewing angle compensation.

According to the LL principle of the glass-based IPS and the compensation principle of the compensation mode, the  +A film is required to be placed between the two glass substrates to compensate for the LC phase retardation. Integrating the display specification requirements of IPS products, a series of requirements are put forward for  +A materials. Firstly, from the aspect of process manufacturing, it is required that the  +A film should be prepared by IPS’s coating equipment, and the thickness of the  +A film should be as thin as possible. Secondly, in terms of characteristics, the  +A film is required to have excellent optical properties, such as transmittance and CR, and have good process stability and reliability. Therefore, the  +A material is required to be a polymer material with LC characteristics. Although LC polymer materials have been extensively studied due to their good optical properties

As shown in Fig. 5, it is a schematic diagram of the structure of a LC polymerized monomer. In addition to the stiff central core and the flexible spacer required by conventional LC materials, polymerizable end groups are added. Among the end groups, acrylic end groups are widely used due to their higher degree of polymerization with a small amount of initiator. The physical properties of the LC are achieved by adjusting these structural units and their combinationsni) is 100 ~ 140 degrees centigrade, which can meet the optical characteristics and reliability requirements of IPS.

The electric-optical characteristics of the panel are measured by DMS-1250 (Autronic Melchers Company). Figure 7 shows the V-T curves of 3.54inches demos. Because the light dispersion effect of LC and other materials was not considered in the simulation, the simulated value and the actual value cannot be completely consistent, but the trends and conclusions of the two are consistent. As can be seen from Fig. 7a, the V-T curves of normal IPS, compensation mode 1, and mode 2 basically coincides. Furthermore, it can be seen from the enlarged picture Fig. 7a", the dark state brightness of the sample is basically the same when no external force is applied, and the dark state brightness of compensation mode 1 is somewhat higher. The transmittance of normal IPS, compensation mode 1, and mode 2 are 0.099%, 0.128%, and 0.106% respectively. The transmittance curves are obtained from the brightness of the gray scales. The L0 brightness of normal IPS, compensation mode 1, and mode 2 are 0.5769nit, 0.6774nit, and 0.5526nit, respectively. Because the brightness test accuracy of the equipment is ± 0.01, the device error can be eliminated. It can be seen that the difference in brightness and transmittance is mainly caused by sample differences. The L0 brightness of ordinary IPS and mode 2 is basically the same, while the L0 brightness of mode 1 is higher.

The other test results of electric-optical characteristics are listed in Table ​Table1,1, the transmittance of normal IPS, compensation mode 1, and mode 2 are 5.76%, 5.32%, and 5.39%, respectively. And the lower transmittances of compensation mode 1 and mode 2 are mainly affected by the low transmittance of  +A at 380 ~ 450 nm. The Vop of normal IPS, compensation mode 1 and mode 2 are all 4.4 V, respectively. And the RT of normal IPS, compensation mode 1 and mode 2 are 16.67 ms, 16.38 ms and 16.64 ms, respectively.

The CR of compensation mode 1 is 789, lower than that of normal IPS (1002). The CR of compensation mode 2 is 993, which is basically the same as that of normal IPS. So for compensation mode 2, besides improving the image quality of the dark state, it maintains the original technical advantages of normal IPS in terms of electric-optical characteristics.

Table ​Table22 are the CR of  +A and panels. The retardations of compensation mode 1 and mode 2 are 350 nm and 200 nm, respectively. Due to the effect of light scattering, the CR of mode 1 (4100) is lower than that of mode 2 (6900). For mode 1, the low CR of  +A is the bottleneck CR among the various optical layers of the panel and further reduces the CRpanel to 789. So it is necessary to increase the CR+A for mode 1. For mode 2,  +A has a higher CR of 6900 which is almost equivalent to the color filter CR in IPS, the CRpanel remains the same as normal IPS. Based on the existing compensation materials, compensation mode 2 is recommended.

Therefore, in order to further study the dark state LL compensation effect of compensation technology, we have prepared the 13.3inches (293.76 mm × 165.24 mm, resolution 2160 × 1080) demos of compensation mode 2, and carried out related researches on the effects and influencing factors of light leakage. First, apply additional stress to 13.3inches demos using the pressure gauge, and then use optical equipment CA310 to test the brightness of the sample before and after the extra force. At last, we compared and analyzed the LL results of normal IPS and compensation, and conducted a more in-depth study on the factors that affect the LL compensation.

Figure 10 is the LL compensation result. It can be seen from Fig. 9a that when the additional stress is received, the brightness ratios of light leakage position (0.265nit) to the center position (0.145nit) is 1.81 for normal IPS, and the brightness ratios of LL position (0.179nit) to the center position (0.167nit) is 1.07 for compensation mode.

In order to verify the LL elimination effect of compensation technology on curved samples, the samples of 13.3 inches with a curvature of 2800R/2500R/2000R/1500R/1000R are prepared. And the glass thickness of normal IPS and compensation samples are 0.5t/0.5t (TFT/CF glass). The L0 brightness at the center of the panel and at the four corners of the panel are tested respectively. And the LL compensation effect of different curvatures samples are compared and analyzed. The ratio of the brightness of the four corners to the center is used to represent the LL level. The larger the ratio, the greater the brightness of the four corners, and the worse the compensation effect of LL.

As shown in Fig. 11a, without compensation, the curved normal IPS has serious light leakage. When the curvatures of demos are 2800R/2500R/2000R/1500R/1000R, the ratios of the four corner brightness to the center brightness are 2.02/4.04/5.38/8.97/10.68, respectively. For the compensation demos, when the retardation of the  +A plate is 200 nm and the curvatures are 2800R/2500R/2000R/1500R/1000R, the LL compensation effects are obvious, the ratios of the four corner brightness to the center brightness are 0.96/1.03/1.20/1.31/1.71, respectively. When the phase retardation of  +A is between 113 and 240 nm, there is a certain effect of LL compensation, and when the retardation value of  +A plate is between 180 and 220 nm, compensation technology can achieve a better LL compensation effect.

In addition, the photos of curved normal IPS and compensation mode 2 at 5000R, 2800R, 2000R are shown in Fig. 11b–g. It can be seen that compensation mode 2 can significantly reduce the brightness of LL compared with normal IPS, it still appears slightly purple and is different from that of the normal IPS. This is also caused by the dispersion characteristics of  +A plate and LC materials, and can be optimized by adjusting the retardation and dispersion characteristics of  +A plate and LC materials.

Consequently, according to the L0 brightness test results of the curved demos above, if the curved demos are prepared with 0.5t/0.5t (TFT/CF) glasses, the four corners of normal IPS demos have serious light leakage, but the compensation mode2 can achieve effective LL elimination. The thickness of 0.5t glass is a commonly used glass thickness in the IPS industry, which can achieve the greatest thickness reduction while meeting the strength of the glass in the manufacturing process. If the glass is thinned, although the stress birefringence of the glass can be reduced, it will also seriously reduce the strength of the glass and Introduce a series of inevitable problems, such as the lower yield rate and the increased cost caused by glass slimming.

In this paper, a compensation structure with excellent dark state image quality is proposed and experimentally analyzed. This technology can fundamentally improve the dark state LL even under deformation. By introducing a  +A plate that is sandwiched between the glass and the homogeneous LC layer, the LL caused by the combined effect of the phase retardations from the stressed glasses and the LC layer can be eliminated. But the compensation layer for glass stressed LL must be placed between the upper and lower glass, inside the cell. The conventional scheme of using compensation polarizer outside the cell cannot achieve the compensation effect of the scheme proposed in this article. We have proposed two light leakage compensation mechanisms and structures, compensation mode 1 and mode 2. Considering the optical characteristics, especially the effect of CR of  +A on the panel, we recommend the mode 2 solution. For mode 1, after the CR of  +A material is improved, it is also a good light leakage improvement solution. This compensation technology is applicable for IPS modes. In addition to theoretical analysis of compensation principles, we have also developed  +A materials that can meet the preparation process of IPS and prepared effective compensation demos. It is proved that the solution proposed in this paper is not only effective for reducing the local stress LL of flat panels but also effective for weakening the curved stress LL.

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The IPS transmissive type color active matrix TFT liquid crystal display. In-Plane Switching (IPS) was one of the first refinements to produce significant gains in the light-transmissive characteristics of TFT panels. It is a technology that addresses the two main issues of a standard twisted nematic (TN) TFT display: colour and viewing angle. If you would like to learn more IPS TFT LCD display, IPS touchscreen display products details, please browse the following categories and feel free to inquire.

The 27B1H comes with an elegant 3-sides borderless design, an ultra slim profile with 13 mm thickness and Full HD resolution on its 27" IPS panel. Enjoy videos, productivity on a larger scale with the 27B1H. It also protects your eyes with Flicker-Free and Low Blue Light technologies.Frameless design

IPS panel ensures an excellent viewing experience with lifelike yet brilliant and accurate colours. Colours look consistent no matter from which angle you look at the display