1. High technical barriers for polarizers
Polarizers are called polarizers, which can control the polarization direction of a specific light beam. When natural light passes through a polarizer, light whose vibration direction is perpendicular to the transmission axis of the polarizer will be absorbed, and only polarized light whose vibration direction is parallel to the transmission axis of the polarizer will be left. There are two polarizers in the liquid crystal display module, which are attached to both sides of the glass substrate. The lower polarizer is used to convert the light beam generated by the backlight source into polarized light, and the upper polarizer is used to analyze the polarized light after being electrically modulated by the liquid crystal to produce light and dark contrast, thereby producing a display screen.
The imaging of the liquid crystal display module must rely on polarized light. Without any polarizer, the liquid crystal display module cannot display an image. Organic light-emitting diode displays OLED also need a polarizer to prevent the light-emitting electrode from reflecting light to improve the contrast of ambient light. The structure of this type of polarizer requires a phase difference compensation layer to be attached to the inner side of the linear polarizer. Its function is to convert the linear polarized light of the ambient light absorbed by the polarizer into circular polarized light.
Therefore, the polarizer for OLED is also called a circular polarizer.
2. Main film materials of polarizer
Polarizer is made of a variety of materials, and PVA film plays a core role. Polarizer is mainly made of PVA film, TAC film, protective film, release film and pressure-sensitive adhesive.
PVA film
Polyvinyl alcohol has the characteristics of high transparency, high ductility, good iodine adsorption, good film-forming properties, etc. The thickness before extension is 75 microns, 60 microns, 45 microns and other specifications. After the film absorbs the two-dimensional absorption molecules of iodine, it is stretched and aligned to play a polarizing role. It is the core part of the polarizer and determines the key optical indicators of the polarizer such as polarization performance, transmittance, and color.
AC film
Cellulose triacetate film has excellent support, optical uniformity and high transparency, acid and alkali resistance, and UV resistance. The thickness is mainly 80 microns, 60 microns, 40 microns, 25 microns and other specifications. On the one hand, as the support of the PVA film, it ensures that the stretched PVA film will not shrink. On the other hand, it protects the PVA film from damage by water vapor, ultraviolet rays and other external substances, ensuring the environmental weather resistance of the polarizer.
Protective film
It has the characteristics of high strength, good transparency, acid and alkali resistance, anti-static, etc., and its general thickness is 58 microns. One side is coated with pressure-sensitive adhesive, which can protect the polarizer body from external damage when attached to the polarizer.
Pressure-sensitive adhesive
Also known as pressure-sensitive adhesive, it has good adhesion with TAC, good transparency, and less residual adhesive. The thickness of pressure-sensitive adhesive for polarizer is generally about 20 microns. It is the adhesive material for polarizer to be attached to LCD panel, which determines the adhesion performance of polarizer and patch processing performance.
Release film
The PET (polyethylene terephthalate) film with silicon coating on one side has the characteristics of high strength, not easy to deform, good transparency, high surface flatness, etc. Different applications have different peel strengths. Before the polarizer is attached to the LCD, protect the pressure-sensitive adhesive layer from damage and avoid the generation of bonding bubbles.
Reflective film
It is a PET film with single-sided aluminum vaporization, with high reflectivity. Mainly used for reflective LCDs that do not have their own light source, reflecting external light back as the light source for display
Phase difference film
Also known as compensation film, different applications have different optical anisotropy and compensation amount. It is used to compensate for the phase difference of liquid crystal materials inside liquid crystal displays, and plays a role in improving the contrast, viewing angle, and correcting display colors of liquid crystal displays.
3. Low localization rate of polarizers
TAC and PVA films account for the main cost of polarizers, and domestic materials only cover release films and protective films, and technical barriers need to be broken through. According to the data, the upstream raw material cost of domestic polarizers accounts for more than 70% of the total cost, of which TAC film and PVA film account for about 56% and 16% of the material cost. At the same time, only the import dependence of release films is relatively low, and core materials such as PVA and TAC still rely on Japanese and Korean manufacturers.
4. There is a broad space for domestic substitution
Benefiting from the recovery of TV panels, LCD TV panels are the largest downstream of LCD polarizers, and the high shipment base serves as a demand ballast to ensure the scale of the industry.
The market space for OLED polarizers is smaller than that for LCDs, but with the increase in OLED penetration in TV and mobile terminals, the market space is growing at a higher rate. However, it should also be noted that compared with LCD polarizers, OLED polarizers have higher technical barriers. In addition, new processes for OLED polarizers are constantly emerging, and the technical barriers for miniaturization and high precision requirements of mobile phone OLED polarizers are extremely high.
