OLED Polarizers are So Expensive, See How Strong Laser Can Protect the Display Industry "Price" Escort!

Release Date:2020.05.10 Views:2891 Source:盛雄激光

What is a polarizer?

Polarizers are all called polarizers, and can control the polarization direction of a specific light beam. When natural light passes through the polarizer, the light whose vibration direction is perpendicular to the transmission axis of the polarizer will be absorbed, and only the polarization direction parallel to the transmission axis and the vibration direction will remain in the transmitted light.

The basic structure of a conventional polarizer is a sandwich-like structure, which is formed by laminating various film materials. The main body layer is generally supported by a double-sided anti-stretch protection support layer, sandwiching a layer of polarizing mechanism functional layer. The functions are as follows:

  • TAC film: polarizer support, protection and prevention of retraction, general thickness 25~40um

  • PVA film: Polarization mechanism functional layer, general thickness 12um

  • PSA film: pressure sensitive adhesive layer, used to attach the polarizer to the display screen, the general thickness is 25um

In practical applications, according to different applications, there will be additional functions such as HC (Hard Coating anti-scratch), AR (Anti-Reflection anti-glare), AF (Anti-Fingerprint anti-fingerprint) on the TAC layer on the upper surface of the light entrance Coating or coating.

Schematic diagram of polarizer structure (Source: Sanli Spectrum)

The composition of the polarizer raw material is slightly different according to different product requirements, mainly including TAC film, PVA film, protective film, incremental film, pressure sensitive adhesive, retardation film and TAC film alternative materials (PET/PMMA/COP), etc.

In fact, the main PVA optical film is polyvinyl alcohol, which is the core part of the polarizer, which determines the key optical indicators such as polarizing performance, transmittance, and color tone of the polarizer.

The TAC optical film is an optical protective film. Because the polarizing layer made of PVA film is easy to absorb water and fade and lose polarizing performance, a TAC (Triacetyl Cellulose) film with uniform optical transparency and good transparency should be used on both sides of the PVA film to isolate moisture and Air, protect the polarizing layer.

The characteristics and functions of various main film materials constituting the polarizer are shown in the following table:

Application of polarizer in OLED screen

OLED display panels usually use polarizers to change the characteristics of the light polarization mode, and are made into circular polarizers through the wavelength compensation mechanism of special optical films to effectively resist the interference of ambient light on the brightness and contrast of OLED displays.

Schematic diagram of the principle of OLED polarizer (source: network)

In the current common OLED display functional film layer structure, the cathode material is metal materials such as Mg-Ag magnesium silver alloy. After the coating process is completed, there is basically a mirror effect, which is easy to reflect the external ambient light, thereby interfering with the normal OLED display. The light coming out causes the display contrast to be greatly reduced. In order to eliminate the influence of ambient light, the industry has designed a circular polarizer with a phase difference film for the OLED display through the principle of optical rotation control of the original LCD display.

Schematic diagram of 1/4λ phase difference film OLED polarizer

(Source: Internet)

The polarizer used in the OLED display combines linear and circular polarization. As shown in the figure above, external natural light first passes through a 90° linear polarizer and then a 45° circular polarizer. The circular polarizer is a combination of a linear polarizing film and a phase retardation film, and the light (90°) passing through the polarizer becomes 135° circularly polarized light after a 45° optical phase delay, and then is reflected by the metal electrode of the OLED .

The reflected light passes through the optical phase retardation film again and becomes 180° linearly polarized light, and finally reaches the outermost 90° linear polarizer. Since the polarization direction of the reflected light is perpendicular to the linear polarizer, the reflected light cannot pass through , Was eventually wiped out on the screen. Therefore, the use of OLED polarizer can make the external light no longer emitted, to achieve the role of eliminating ambient reflected light.

In fact, the wavelength range of ambient light in nature covers a wide range. Conventional 1/4λ phase retardation films can generally only correspond to a single wavelength. To achieve the ideal wide wavelength compensation effect, generally more than two layers of phase difference films must be used Addition and subtraction, for example, use materials with little difference in refractive index distribution to make a 1/2λ phase retardation film, and then stack it with a 1/4λ phase difference film normally distributed in a narrow band, according to a certain direction, to achieve the formation of visible light band Wide band coverage, the effect is that the display is darker after the screen is turned off, and the contrast is higher when displayed.

Schematic diagram of the principle of OLED polarizer (source: network)

At present, OLED polarizers optimized by Apple and the supply chain have adopted an updated process to replace the traditional 1/4λ+1/2λ dual-wavelength dual-phase retardation film composite process. The new process can coat the 1/4λ wavelength liquid crystal layer on one side and the 1/2λ wavelength liquid crystal layer on the other side of the TAC film or other optical film materials, so as to reduce the number of optical film layers and reduce the thickness of the polarizer .

Therefore, polarizers for OLED displays are not only harder to manufacture than conventional LCD polarizers, but also use much more expensive raw materials. The relative price is also a lot higher than LCD polarizers. If you want to use a 1/4λ+1/2λ dual-wavelength liquid crystal coating compensation circular polarizer similar to the effect of an Apple mobile phone OLED display, the processing is more difficult, the production yield is lower, and the use cost is more expensive.

How to process OLED polarizer?

In order to minimize unnecessary losses in the process of processing OLED circular polarizers, the OLED display industry introduced a non-contact laser processing method to organize production to reduce wear and waste and retain profits. In fact, it is equivalent to retaining OLED manufacturers’ profits at the same profit. Price competitiveness.

Dongguan Stronglaser Advanced Equipment Co., Ltd. (hereinafter referred to as Stronglaser) has used more than ten years of technology precipitation and experience accumulation to launch an OLED full-screen automated laser processing production line at the request of industry customers, which includes polarized light for OLED displays The cutting and digging process can provide different cutting materials and cutting parameters according to different polarizer materials of the OLED panel factory, and selectively cut special-shaped OLED circular polarizers, which greatly accelerates the production capacity of the OLED industry. Ramp speed.

OLED laser cutting and drilling machine

Stronglaser actively promotes the application of laser processing technology in the production process of OLED, such as laser marking, laser terminal cutting/etching, laser line repair, laser screen cutting/digging, laser polarizer cutting/digging, etc. Laser processing is to use the energy of light to focus on the lens to achieve a high energy density at the focal point and process by photothermal effect. Laser processing does not require tools, the processing speed is fast, the surface deformation is small, and various materials can be processed. The laser beam is used to process various materials, such as drilling, cutting, dicing, welding, and heat treatment.

In fact, Stronglaser has accumulated a lot of laser processing technology and experience in the consumer electronics field including smart phones for more than ten years. The flexibility, stability, and high efficiency of laser processing technology have been used to meet the needs of the mobile phone industry. The demand for precision machining. Stronglaser products and services cover almost all aspects of the entire consumer electronics manufacturing industry.

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