In 2007, the touch screen market was at a level of 200 billion yen. It is understood that resistive touch screens account for 75% of the entire touch screen market, and are growing at a rate of 15% to 20% every year. More than 90% of the touch screens with integrated liquid crystal display are resistive touch screens. The market and technical trends of resistive touch screen materials are summarized based on the author's speculation.
The recently expanding rro film market has attracted much attention. Not only the existing ito film manufacturers have increased production, but also many new manufacturers have emerged to study alternative ito materials. It can be seen from Table 5-1 that the material composition of the touch screen is divided into top (movable) electrode ITO film substrate, bottom (fixed) electrode ITO glass substrate, FPC, optical film, and peripheral bonding materials.
Almost all transparent conductive materials used in flat panel displays are ITO. Although researchers have been studying materials that can replace ITO for a long time, so far, there is still no material that can replace ITO in terms of practicality. ITO glass substrate is a necessary raw material for liquid crystal display panels and has a huge market.
LCD manufacturers also put it into internal production. More than 95% of ITO film substrates are used in touch screens. In contrast, electroluminescent devices (EL) and liquid crystal display substrates (including electronic paper) are rarely used, and the occupancy rate is less than 1/100.
According to statistics, the market size of IT0 film substrates in 2007 was 4 million m2, of which more than 90% were used for resistive touch screens. However, recently, ITO film has begun to be applied to projection-type capacitive touch screens, which is a new growth area for ITO film substrates. With the continuous expansion of the projection type capacitive touch screen market, it is likely to grow at a rate of 1 million square meters per year, reaching a market of 50 billion yen.
The crystallization level of the ITO film structure directly affects the characteristics of the touch screen. The film quality of ITO is closely related to the coating technology of the manufacturer. Due to the requirements of the optical performance of the product, the ITO film is not directly formed on the thin film substrate, but after functional treatments such as reducing interference fringes, preventing reflection, improving surface hardness, improving viscosity, and antifouling treatment, the ITO film is formed on the thin film substrate. . In fact, only using the ITO film as the top electrode is sufficient to meet the characteristic requirements of touch.
One of the characteristics of the touch screen with integrated liquid crystal display is that it requires high transmittance. The transmittance of the resistive touch screen is determined by the transmittance of the top electrode material and the bottom electrode material. Generally, the transmittance of the upper ITO film substrate of the touch screen is about 88%, and the transmittance of the lower ITO glass substrate is about 90%, so the transmittance of the touch screen is about 78%. Although the transmittance of ITO glass has reached 97%, the 92% transmittance of ITO film substrates on the market is relatively good, and people are looking forward to the emergence of ITO film substrates with a transmittance of more than 95%.
