Color filter is an optical filter that represents color. It can accurately select the light wave in a small range to pass through, and reflect other unwanted bands. Color filters are usually installed in front of the light source, so that the human eye can receive saturated light of a certain color. There are infrared filters, green, blue and so on. Compared with UV filter and VD filter, it is the general name of colored filter. Such as contrast filter, color separation filter, LB filter, etc.
Characteristics of color filter products
The purpose of color filter includes enhancing the contrast of monochrome display (such as VF (vacuum fluorescent display), EL (electro luminescent display), LED (light emitting diode display)) through the color selection passband and the maximum output power of the display. Broadband filters are used to improve the contrast and performance of optical scanners and red, yellow and AMBER LED displays. The medium density three slot filter and polarizer enhance the contrast of liquid crystal display (LCD) by reducing internal reflection and producing a large variable between the output power of the display and the background
Contrast enhancement: contrast enhanced medium density filter (gray, bronze)
Broadband filter (yellow, amber, red)
Passband filter (blue, green)
Custom color filter (three slot filter)
Polarizing mirror (linear or circular)
Band rejection: band stop near infrared filter
Infrared thermal reflector
Night vision filter
Dontech color filters are made of optical substrates such as acrylic acid, polycarbonate and glass. Coloring can be carried out by stacking substrate and water absorbent material or thin film coating; These coatings can pass or block special wavelengths of visible, infrared and near-infrared spectra.
Basic structure of color filter
The basic structure of color filter is composed of glass substrate, black matrix, color layer, over coat and ITO conductive film.
Key components of color filter
Color filter is a key component for the colorization of liquid crystal display. Liquid crystal flat panel display is a non active light emitting component. Its color display must provide light source through the internal backlight module (penetrating LCD) or external ambient incident light (reflective or semi penetrating LCD), and then cooperate with the drive IC and liquid crystal to form gray scale display, and then provide hue through the R, G and B color layers of the color filter to form a color display picture.
Manufacturing process of color filter
The color layer of pigment dispersion method forms a yellow light lithography process similar to semiconductor. Firstly, the pigment dispersion color photoresist is coated on the glass substrate with black matrix, and the process is repeated for three times through pre bake, aligned, developed, stripping and post bake to form the three color pattern of R, G and B.
The manufacturing methods of color filters include dyeing method, pigment dispersion method, printing method, electroplating method and inkjet method. The pigment dispersion method has become the mainstream manufacturing method of color filters because of its advantages in color characteristics, quality and commensurability. The so-called pigment dispersion method of color filter manufacturing engineering includes black matrix engineering, RGB engineering, post engineering and shipping engineering.
Firstly, in the black matrix project, the low reflection two-layer film of chromium oxide / chromium is formed by splashing on the alkali free boron glass substrate as the substrate. This low reflection two-layer film is called metal black. Then, the positive photoresist on the metal black side is spin coated, and then the ultraviolet light is irradiated and exposed through the mask pattern of the black matrix. After photoresist imaging, metal black is etched to form a black matrix (BM) pattern. Then, after the pattern of black matrix is formed, it goes to RGB engineering.
The so-called RGB project is the project of forming the r.g.b three color pattern at the opening. Firstly, the color photoresist colored as R is coated with spin, irradiated with ultraviolet light through the R pattern mask and exposed, and then the unexposed part is removed with alkaline developer to form the R pattern for the first color, and then applied to post coating above 200 ℃ to make the pattern have the same property, and then the same project of forming the R pattern is repeated on G and B, Each pattern is separated by an inner color matrix. This function is to increase the contrast during display and avoid the generation of heterochromatic light. Then, in terms of post engineering, it is the ITO transparent electrode layer forming the opposite electrode of TFT array substrate, which is the color filter. Finally, the delivery engineering is the final inspection and packaging.
The key to the process technology of color filter is the segment difference between RGB three colors. The segment difference will affect the performance of liquid crystal. If the segment difference is too large, it will show that there will be faults. In addition, RGB project is a high-temperature process, so the selection of raw materials must have drug resistance and will not decline. In addition, BM is mainly to isolate RGB three colors. In order to improve the key of color pair, BM generally requires low reflection. The lower the reflection, the better the color performance.