Resistive touch screens have various top and bottom electrode support components. The basic structure is F/G, which is widely used due to its low cost. F/F/G is also widely used, but due to problems such as low transmittance, its use is decreasing recently. Film/Plas-tic (F/P) structure has advantages in portable game consoles and other aspects such as being thin or not damaged when dropped, and is widely used. The F/F type refers to a method in which optical bonding materials, etc., are directly attached to a liquid crystal display device, and is called an optical bonding method. In terms of reliability, the pure car navigation system (MOP) that enters the production line of an automobile manufacturer has a G/G standard. In order to minimize the reflection of sunlight, car navigation systems attach linear polarizers, but high-end products use circular polarizers with a phase difference of 1/4 above and below.
①Improvement of optical characteristics
One of the shortcomings of resistive touch screens lies in the optical characteristics, especially the low transmittance. There is an air layer between the top electrode and the bottom electrode, and the transmittance will decrease due to internal reflection. In the past, some methods of injecting liquid into the air were developed in order to increase the transmission rate. However, due to lack of reliability or price issues, the company was unable to switch to production and remained in the development state.
Recently, in order to increase the transmittance, it has been proposed to increase the transmittance of ITO glass and ITO film materials. For example, the transmittance of ITO glass is usually 90 percent . By improving each interface, the transmittance can be increased to 97 percent . The transmittance of ITO film is usually 88 percent , and some developed products can reach 95 percent . However, products with high transmittance in the use stage are around 91 percent . Table 2-2 shows the theoretical transmittance of the panel. Using the materials currently in use, the F/G method panel should theoretically increase the transmittance to 88 percent , but the unit price of each material will increase several times, so it is not realistic. The transmittance of the G/G touch screen can also reach 94 percent , but in practice, it is difficult to exceed 90 percent if the film to prevent scattering is not attached.
The touch screen with polarizer attached, there is a layer of unnecessary polarizer in the middle (required for liquid crystal). If the polarizer on the top of the liquid crystal is removed, its optical characteristics will be greatly improved. Because its structure is similar to putting the touch screen inside the liquid crystal, it is called "Inner TP". The picture seems to be relatively simple, but it needs to cooperate with LCD manufacturers. Few manufacturers actually carry out this.
②Improvement of other characteristics
Although resistive touch screens have many requirements in terms of characteristics, most of them are improving the ITO film on the side of the touch surface. Table 2-3 is related content. Although there are many requirements, there are three recent development trends:
(1) Liquid crystal display and Super Glass
(2) Antifouling/fingerprint resistance
(3) Scratch resistance
Recently, the level of LCD display has become high-definition, and the RGB light-emitting phenomenon of the touch screen processed by AG has been highlighted. Moreover, there are more opportunities to watch single-segment broadcast and television with mobile phones or car navigation, so that obvious fingerprints will make consumers feel uncomfortable. Like mobile phones, people often use clothes to wipe off the oil and fingerprints on the phone
