Overview：

I am still quite hesitant to write about phase difference film today, because I have read a lot of information, but I still can’t understand a lot of technical content. I believe that most people can’t understand it either. However, it doesn’t matter. Learning always requires a gradual process. I will collect some information for the time being. I will write as much as I can. If there are industry experts who understand phase difference film, you can leave it. These are all basic popular content, and they may not be correct. Of course, it would be best if experts can give me advice.
First of all, I think we should pay tribute to those domestic companies that invest in the research and development of phase difference film, such as Sichuan Longhua, Yitaiji, etc., and strive to fill the domestic technology gap and challenge cutting-edge products. This is more meaningful than those companies that purchase a large number of machines from Bruckner in Germany, expand production of BOPP and BOPET films, and then crush their domestic counterparts.

What  is PatternedRetarder,MicroRetarder？

What is a phase difference film? Phase difference film, also called phase difference film, is also called optical compensation film. Here we are discussing thin film products used in the display polarizer industry. There are different optical compensation methods for different liquid crystal display modes, such as TN/STN/IPS/TFT, etc. Liquid crystal molecules have a variety of appearances, such as rod-shaped and disc-shaped, but they all have an optical property, which is the birefringence property. Learn about the birefringence property of crystals.

The phenomenon that one incident light ray produces two refracted light rays. One light obeys the ordinary law of refraction and is called ordinary light (or o light); the other light does not obey the ordinary law of refraction and is called extraordinary light (or e light). The two beams of light have different refractive indices and different travel distances. The refractive index of o light is No, and the refractive index of e light is Ne. When the light passes through a wave plate with a thickness of d, the phase difference δ is: and the phase difference value is: As for why there is a phase difference, my understanding is that these polymer materials have a certain directionality in molecular arrangement, and there are processes such as stretching during the production process. From a three-dimensional perspective, the molecular functional groups in the XYZ directions are densely arranged, etc., which causes different optical properties in each direction. The phase difference causes the difference between o light and e light. On the display, different images appear, and there is ghosting, which is definitely not desirable. Therefore, we see that there is a key parameter for the phase difference film, which is the requirement to be less than a certain number of nanometers, such as less than 5nm, etc. Since the molecular arrangement of TAC film in all directions is disordered and similar in all directions, it is a low phase difference film, which can be used on polarizers or low-reflection films as a base film or protective film. However, PET is stretched more during the production process, and the anisotropy difference is large, so it is not suitable for use. Of course, there are exceptions. Japan’s TOYOBO Toyobo does the opposite. The SRF film simply pulls the phase difference to a large extent, more than 8000nm, so that different shadows are farther away, and there will be no interference, and no undesirable phenomena such as rainbow lines will appear. Since there is a difference between o light and e light, rainbow lines and moiré lines will be caused. In order to improve this optical path difference, it is necessary to use an optical compensation film, or a phase difference film, or a phase difference film. At the same time, if optical compensation is not performed at different viewing angles, the display screen will also have whitening or unclear contrast or color grayscale inversion when viewed from the edge or up and down angles. The phase difference is caused by the anisotropy of the material. If optical compensation is to be used to make the directions close to isotropy, n represents the refractive index, which is to adjust the refractive index in each direction. Make △n=ne-no as small as possible, or super large (SRF). If the △n of the liquid crystal is > 0, use △n<0 to adjust it, because the liquid crystal has many forms of structure, and the refractive index of o light and e light is also different, so there are positive and negative points. According to the optical axis of the phase compensation film, the optical axis parallel to the film surface is called A-plate, the vertical surface is called C-plate, and the surface is at an angle called O-plate. Take rod-shaped liquid crystal as an example: A-plate can be made by horizontal alignment to compensate for the upright liquid crystal molecules in the liquid crystal box; O-plate is often made of alignment film with a larger pre-tilt angle or oblique evaporation, mainly to compensate for the reverse tilt of liquid crystal molecules during the driving process of the liquid crystal box; C-plate is an optical film with upright molecules, which is generally obtained by vertical alignment and is used to compensate for the horizontally arranged liquid crystal molecules in the liquid crystal box. In short, the role of using optical compensation film is to eliminate the birefringence effect of the liquid crystal layer, thereby increasing the viewing angle. Then different liquid crystal display modes, such as TN/IPS/VA, require different compensation films, including because of patents and other reasons, each Japanese manufacturer also has its own unique solution. For example, the working principle of the wide-viewing angle film of Fuji Polymer in Japan: TAC film with low optical delay. For example, the various product solutions developed by Japan ZOEN Ruiong stretching technology. (Picture from ZOEN official website) In addition, there are also companies represented by Japan Nitto that use coating to produce compensation films, which also attracts many domestic manufacturers to study. At present, the proportion of OLED screens in the entire market is increasing, and the demand for quarter-phase compensation films is also increasing. The main function is to cover the cathode metal circuit on the OLED screen to prevent the high reflectivity of the metal circuit from affecting the effect of the outside world viewing the display screen. The non-polarized ambient natural light is incident through the linear polarizer, the horizontal polarized light passes through, and the vertical polarized light is absorbed; then it passes through the QWP to become left-handed polarized light, and then after reflection on the cathode circuit, it becomes right-handed polarized light, passes through the QWP again, becomes vertically polarized light, and is finally absorbed by the polarizer, no longer interfering with the observer’s line of sight of the display screen.