Polarizer is a key component of liquid crystal display. Its main function is to make the light vibrating in all directions pass through only one direction, while the light vibrating in other directions will be blocked or absorbed. The polarizer controls the polarization direction of the light...More

Polarizer is a key component of liquid crystal display. Its main function is to make the light vibrating in all directions pass through only one direction, while the light vibrating in other directions will be blocked or absorbed. The polarizer controls the polarization direction of the light, so that the liquid crystal display can change the light and dark display by applying an external electric field. Depending on the characteristics of the polarizer, it can be used alone or in combination with different optical compensation films and surface treatments to make the liquid crystal display display performance with higher contrast and viewing angle.

A polarizer is a material that can produce polarized light, which is light with only one simple transverse vibration mode (Figure 1). Polarized light can be roughly divided into linear polarized light, circular polarized light, and elliptical polarized light. Film) can convert the polarized light type.

When the transmission axes of the polarizers are parallel, the overlapping light can pass through (as shown in Figure 2). When the transmission axes of the polarizing plates are perpendicular, the overlapping light is blocked and cannot pass through (as shown in Figure 3).

The most commonly used polarizer is the linear polarizer. The structure is shown in Figure 4, including six layers of protective film, TAC (Tri-acetate cellulose), PVA (Polyvinyl alcohol), TAC, pressure-sensitive adhesive (PSA), and release film. structure. ...More

The most commonly used polarizer is linear polarizer, the structure is shown in Figure 4, including protective film, TAC (Tri-acetate cellulose), PVA (Polyvinyl alcohol), TAC, pressure sensitive adhesive (PSA), release film and other six-layer structure. The protective film is used to protect the surface of the polarizer, and consumers need to tear it off when using it; TAC is used to protect PVA, so that PVA is not easy to be brittle, not easy to shrink, and prevents optics from being affected by moisture, and can provide different surface treatment functions; PVA is Make the main body of polarized light; the lower TAC can be used to protect PVA or replace it with a compensation film with phase difference to compensate for the liquid crystal; PSA is used to adhere to the glass substrate of the LCD.

Manufacturing method

The most common polarizing plate nowadays is the H film invented by Edwin H. Land in 1938. The general process is shown in Figure 5. First, a film with polarizing properties is produced, and the hydrophilic PVA (Polyvinyl alcohol) After the film is soaked in water and swells,...More

The most common polarizer nowadays is the H film invented by Edwin H. Land in 1938. The general process is as follows Figure 5, the first is to manufacture a film with polarizing properties. After the hydrophilic PVA (Polyvinyl alcohol) film is soaked in water and swollen, it is soaked in a dichroic dye solution to dye it. The dichroic dye is usually iodine and potassium iodide solution. Afterwards, the dyed film is stretched, and the stretching endows the order of the dichroic dyes. The higher the order, the better the optical properties of the prepared polarizing film. After the stretched film is dried, it is easy to be brittle along the stretching direction, and its raw material is a hydrophilic polymer film, which is easily affected by moisture. Therefore, it needs to be laminated with a protective film material with support and moisture barrier.

The selected protective film material is generally TAC (Tri-acetate cellulose) film, which is soaked in an alkaline aqueous solution to convert the carboxylic acid groups on the surface into hydroxyl groups, and then laminate it with the polarizing film using a water-based adhesive. For the TAC film close to the panel, products with specific retardation compensation values can be used to match the optical characteristics of different panels. For the outermost TAC film, products with additional functional coatings with anti-glare and anti-scratch functions can be used on the surface. Finally, a pressure-sensitive adhesive with adhesive properties is added so that the polarizer can be adhered to the panel glass. During the polarizer manufacturing process, the pressure-sensitive adhesive is usually pre-coated on the PET (Polyethylene terephthalate) release film and aligned with the polarizer roll. Roll fit. The protective film made of PET is used to protect the surface of the polarizer before the polarizer is attached to the panel.

Panel application principle

Taking TN (Twisted Nematic) LCD as an example, Figure 6 (left side): The upper and lower glass substrates are coated with an alignment layer vertical to the alignment groove, and the liquid crystal molecules will rotate 90° with the alignment layer. ...More

Take TN (Twisted Nematic) LCD as an example, Figure 6 (left side): Alignment grooves are applied vertically on the upper and lower glass substrates layer, the liquid crystal molecules will rotate 90° with the alignment layer. A polarizing plate with a vertical polarizing direction is pasted on the outside of the upper and lower glass. When the incident light enters the upper polarizing plate and turns into polarized light, its polarizing direction rotates 90° with the arrangement of the liquid crystal, so that the light can pass through the lower polarizing plate to achieve a bright state. . Figure 6 (right side): After applying a voltage to the liquid crystal cell, the alignment direction of the liquid crystal molecules is parallel to the direction of the applied electric field and no longer twists. At this time, the polarized light of the incident light is not affected by the liquid crystal, maintains the original direction and passes through the liquid crystal layer, and is absorbed (shielded) by the polarizer just vertically below to become a dark state. In this way, black and white display can be achieved with or without voltage application.