I. The manufacturing process of TFT-LCD has the following parts
①、Formation of TFT array on TFT substrate.
②, forming the color filter pattern and ITO conductive layer on the color filter substrate.
③、Formation of liquid crystal cassette with two substrates.
④. Module assembly for installing peripheral circuits, assembling backlight, etc.
Second, the process of forming TFT arrays on TFT substrates
The types of TFTs that have been industrialized include: amorphous silicon TFT (a-Si TFT), polycrystalline silicon TFT (p-Si TFT), and monocrystalline silicon TFT (c-Si TFT). Currently, a-Si TFTs are still used.
The manufacturing process of a-Si TFT is as follows.
①. The gate material film is first sputtered on the borosilicate glass substrate, and the gate wiring pattern is formed after mask exposure, development, and dry etching. General mask exposure with step exposure machine.
②. Continuous film formation by PECVD method to form SiNx film, non-doped a-Si film, phosphorus doped n+a-Si film. Then mask exposure and dry etching are performed to form the a-Si pattern of the TFT part.
(iii) Transparent electrode (ITO film) is formed by the sputtering film formation method, followed by mask exposure and wet etching to form the display electrode pattern.
(4) The contact hole pattern of the insulating film at the gate terminal is formed by mask exposure and dry etching.
⑤. The source, drain, and signal line patterns of TFTs are formed by sputtering AL, etc., mask exposure, and etching. The protective insulating film is formed by PECVD method, and the insulating film is etched by mask exposure and dry etching (the protective film is used to protect the gate, signal line electrode and display electrode).
The TFT array process is the key to the TFT-LCD manufacturing process, and is also the part with a lot of investment in equipment, and the whole process requires high purification conditions (e.g. class 10).
The process of forming the color filter pattern on the color filter (CF) substrate
The color filter coloring part of the formation method are dye method, pigment dispersion method, printing method, electrolytic deposition method, ink jet method. Currently, the pigment dispersion method is the main method.
The pigment dispersion method is to disperse uniform micro-pigments (average particle size less than 0.1 μm) (R, G, and B colors) in a transparent photopolymer. They are then sequentially coated, exposed and developed to form the R.G.B. pattern. Photo-etching technology is used in the manufacturing process, and the equipment used is mainly coating, exposure, and development equipment.
In order to prevent light leakage, a black matrix (BM) is generally added at the junction of the RGB three colors. In the past, a single layer of metallic chromium film was formed by sputtering, but now there is also a switch to a BM film with a combination of metallic chromium and chromium oxide or a resin BM with resin mixed with carbon.
In addition, it is necessary to make a protective film on the BM and form IT0 electrodes, because the substrate with color filter is used as the front substrate of the LCD and the back substrate with TFT to form the LCD box. Therefore, it is necessary to pay attention to the positioning problem, so that each cell of the color filter corresponds to each pixel of the TFT substrate.
IV. Preparation process of liquid crystal box
A polyimide film is applied to the top and bottom substrate surfaces respectively, and an orientation film is formed by a friction process to induce molecules to align as required. After that, the sealant material is laid around the TFT array substrate and the liner is sprayed on the substrate. At the same time, a silver paste is applied to the transparent electrode end of the CF substrate. The two substrates are then bonded in alignment so that the CF pattern is aligned with the TFT pixel pattern, and then the sealing material is cured by heat treatment. When printing the sealing material, the injection port needs to be left for vacuum infusion of liquid crystal.
In recent years, with the technological progress and the increasing size of the substrate, there has been a great improvement in the production process of the box, which is representative of the change in the way of crystal infusion, from the original box after the infusion to the ODF method, that is, the crystal infusion and box synchronization. In addition . Matting method is no longer the traditional spray method, but directly on the array with photolithography production.
V. Module assembly process of peripheral circuits and backlight assembly
After the completion of the LCD box production process, the peripheral driver circuit needs to be installed on the panel, and then paste the polarizer on the surface of the two substrates. In case of transmissive LCD. backlight is also installed.
Material and process are the two main factors affecting the performance of the product, TFT-LCD after the above four major processes, a large number of complicated production processes to form the products we see.