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ITO technology touch screen
May 22, 2018

The glass itself is not conductive and does not emit light. The secret is all in the thin layer of transparent conductive film behind the coating. This is a film with less than one-hundredth of the diameter of a hair filament and an invisible "target" behind it.

       “We have more than 20 target manufacturers, but we can do more than 32-inch targets. We are still 'zero'!” Professor Zhengzhou University, Henan Province Resources and Materials Industry Research Institute, who has been engaged in R&D for more than 20 years in this industry The former chief engineer of the institute, Sun Benshuang, told the reporter of Science and Technology Daily.


       The problem lies in the size

       In the non-ferrous metal “friend circle”, the indium tin oxide is an excellent combination of electrical conduction and optical transparency.

       As a non-ferrous metal oxide, indium tin oxide, which is abbreviated as ITO, has good conductivity and transparency on a flat plate. It can also cut off harmful electron radiation, ultraviolet rays, and far infrared rays, and is an important raw material for the manufacture of flat panel displays. In the form of a film, it is a slightly brown transparent substance; in the block, it is yellowish gray.

       However, instead of being brushed onto flat glass like paint, it is first made into a standard size solid target, which is continuously “fired” by vapor-sputtering “gunners” and vaporized. An ITO film is formed on a glass substrate or a flexible organic film. The thickness of this film varies depending on the functional requirements, typically from 30 nanometers to 200 nanometers.

       ITO targets are used not only for the production of liquid crystal displays, flat panel displays, plasma displays, touch screens, electronic papers, organic light emitting diodes, but also for solar cells and transparent conductive coatings for antistatic coatings and EMI shielding, and have a wide market worldwide.

       ITO targets are very much like tiles, but they are far more complex than tile firing. People mix indium oxide and tin oxide powders in a strict ratio and then go through a series of production processes to form a floor tile. In a special furnace, it was sintered at a high temperature of 1700 degrees Celsius to form a dark gray ceramic semiconductor. In general, the larger the target size, the less seams are sputtered onto the plate and the higher the value.

       However, as far as size is concerned, domestic ITO target companies have rarely made breakthroughs, and the flat-panel display manufacturing companies at the back end also have to rely on people.

       Technology and craftsmanship are difficult

       The ITO target core technology has long been held by Japanese companies such as Mitsui, Tosoh, Hitachi, Sumitomo, VMC, and South Korea’s Samsung and Corning.

       For domestic companies, technology and craftsmanship are difficult steps. Because the ITO target is made of high-temperature sintering, the sintering technology process determines the quality and quantity of production. If the effort is not enough, the problem of batch quality instability most often occurs. Sputtering on the screen, some ITO film surface "pit"; some easy to appear in the etching of the linear radial type of lack of resistance or high band; and there will be microcrystalline groove.

       When talking about the gap between production equipment and foreign countries, Professor Sun Benshuang sighed and said: "Far far!" Sintering large-size ITO targets requires a large-scale sintering furnace. Foreign countries can make monolithic targets with a width of 1,200 mm and a length of nearly 3,000 mm. Domestically, they can only manufacture no more than 800 mm wide. "It's like people are already firing large floor tiles. We can only burn small tiles," said Sun Benshuang.

       In the "dan furnace" of 1700 degrees Celsius, the target sintering takes 6 to 10 days. Sintering at high temperatures requires the participation of high concentrations of oxygen. This process is also not easily controlled. Burning for a long time can easily lead to uneven product and low yield.

       In terms of output efficiency, the Japanese-style equipment "bull gas" can reach a monthly output of 30 tons to 50 tons, and our annual output is only 30 tons - while the price of imported equipment will cost 10 million yuan, which is for small domestic enterprises. That is no different from the sky price.

       At present, there are also some imitation equipment, but the refractory materials are too close to withstand the fiery test required for the sintering process, and the overall quality of the sintering furnace is unsatisfactory. "This requires the support of major special projects in production technology and equipment localization," said Sun Benshuang.

       The quality of the material is not stable, but it does not matter. All kinds of terminal manufacturers have figured it out or think that buying foreign imports will save time, and as time goes by, relying on imports has become an "addiction."

       Functional Products: Pain in Big Nonferrous Metals

       Each year, the consumption of ITO targets in China exceeds 1,000 tons, and about half of them rely on imports for the production of high-end products. Due to the superposition of non-ferrous metal futures price fluctuations and technical blockades and other factors, prices have been high for a long time, and the finished product prices have reached a maximum of 6,000 to 8,000 yuan per kilogram, which occupies a considerable cost for the company.

       "The data shows that China's semiconductor product imports cost more than oil." The winner of the 2017 Ho Leung Ho Lee Foundation Award, Prof. Yang Bin, Vice President of Kunming University of Science and Technology said.

       In China, the level of smelting and indium for the important raw materials of semiconductors, indium and tin, is already at the top level in the world, and the output and grade are also world-class. Nearly 80% of the world's high-quality indium and tin come from China, and Japanese companies purchase long-term Chinese indium ingots.

       “But we lack the downstream functional products and long enough industrial chain, can only earn the primary profits of raw materials, such as high-quality, large-size ITO target, is the pain of powder metallurgy and the semiconductor industry.” Professor Yang Bin said that domestic The large-size target material is only in the laboratory stage, and the technology is a difficult point, and it is difficult to achieve mass production.

       With the development of the domestic LCD industry and the development of touch input electronic products such as PDAs and e-books in the past ten years, especially with the development of organic light-emitting diodes (OLEDs) and other display devices, ITO targets have been made Processes and equipment have been updated with higher expectations. For some time in the future, this is still a promising industry.

       The small-scale, low-level, domestically-targeted "target" has been "rewarded" because it has not been able to embark on the forefront of the world and has long relied on imports. In recent years, due to the huge Chinese market, the “small target” domestic capacity has risen dramatically. At this time, foreign monopoly companies “scraped” and began to suppress prices, and once lowered the price of ITO target materials to 800 yuan a ton, which was once close to At one-tenth of the highest price point, more than 20 domestic companies suffered huge losses, and some enterprises even waited.

       “But in other words, the low construction costs are also low because of low prices. This is also an opportunity for reshuffling.” Sun Benshuang said that if there is national support, five or six key enterprises will be retained, and technical breakthroughs will be accelerated and the laboratory's technology will be mass-produced. We are expected to break through in the large-scale area and eliminate some foreign companies.

related news

Luoyang builds the "Leading LCD Screen" international leader

■ Project Name: Luoyang Jinglian Photoelectric ITO Target Production Project

■ Project Overview: The project has a total investment of 150 million yuan, and it is located in the Airport Industry Gathering District in Mengjin County. The investor Luoyang Jinglian Photoelectric Material Co., Ltd. is a wholly-owned subsidiary of Luoyang Longhua Heat Transfer Energy Conservation Co., Ltd. The project utilizes the existing plant area of Luoyang Longhua Company and plans to build an ITO target supporting production line with an annual output of 200 tons in three phases within three years.

Dense and rocky, black and black, like coal, touch screens can be indispensable. The Indium Oxide (ITO) target market, previously monopolized by imported products, is being accelerated by a company in our city through independent innovation.

ITO conductive film has been hailed as the "nerve" of touch screens. In the production process of the liquid crystal screen, it is necessary to place the ITO target in a vacuum environment and bombard it with an electron beam. The generated particles are dispersed on the screen substrate to form a transparent conductive film of indium tin oxide. Because of the presence of these conductive films, the liquid crystal display can sense the static electricity of the finger and achieve touch control.

Nowadays, with the acceleration of domestic industry transformation and upgrading, the production technology of high-end LCD screens has become increasingly popular, and the demand for target materials has also increased. “The annual usage of ITO targets for domestic high-end TFT-LCD display panels is more than 600 tons, and the usage volume is increased by 10% to 20% per year,” said the person in charge of the company. In recent years, Luoyang Jinglian Company has been deeply cultivating in the field of ITO target materials, and has increased investment in R&D. Its relative density, purity, resistivity and other performance indicators have reached the international leading level.

The process is more environmentally friendly. In the preparation process of the target powder, the conventional chemical acid dissolution method consumes 100 tons of ultrapure water for every 100 kilograms of target material to be produced. Since the discharged sewage contains chlorine ions, it is subject to environmental constraints and needs to be increased. Sewage treatment can be discharged.

The project adopts the industry's first technology to make zero sewage discharge in the production process, and the production efficiency is increased by 30%. It is a true green environmental protection process.

The higher end of the product. In recent years, tubular targets with higher material usage have become more and more popular in the market. The longer the tube target, the less the seams in the production process and the higher the quality of the touch screen LCD produced. The tube target produced by Luoyang Jinglian Co., Ltd. can reach a maximum length of 600mm, which is about 1 times longer than the market for similar products. It is a rare high-end product.

According to the responsible person, the project is expected to achieve 600,000 tons of production capacity this year. After completion, it will have an annual production capacity of 200 tons and annual sales of 400 million yuan. Luoyang Jinglian will become the largest domestic ITO target with global influence. Business.


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