Basic knowledge of polarizers

Basic knowledge of polarizers

Composition of polarizer
The earliest polarizer was mainly composed of a PVA film in the middle that can produce polarized light, and then a TAV protective film on both sides. In order to facilitate use and obtain different optical effects, polarizer suppliers, at the request of LCD manufacturers, coated both sides with pressure-sensitive adhesive and then covered with a release film. This type of polarizer is the most common TN ordinary full-transmission polarizer we see. If a layer of release film is removed and a layer of reflective film is compounded, it is the most common reflective polarizer.

The pressure-sensitive adhesive used is a high-temperature and moisture-proof pressure-sensitive adhesive, and the PVA is specially dipped (dye series products), and the polarizer made is a wide-temperature type polarizer; adding ingredients that prevent ultraviolet rays from passing through the pressure-sensitive adhesive can make an anti-ultraviolet polarizer; compounding a birefringent optical compensation film on the transmission original film can make a polarizer for STN; compounding a light-redirecting film on the transmission original film can make a wide-viewing angle polarizer or a narrow-viewing angle polarizer; coloring the pressure-sensitive adhesive, PVA film or TAC film used is a color polarizer. In fact, with the continuous development of new liquid crystal display products, there are more and more types of polarizers.

1. Characteristics of polarized PVA film
Polarized PVA film, as a product made by stretching method, has the following unique characteristics:
 Light selectivity: selects light with the same polarization direction as the stretching direction to pass through;
 Temperature and humidity sensitivity: after absorbing moisture or heating, the stretched linear molecular chain will automatically return to the clustered molecular chain and lose light selectivity.
 Fragility: It is easy to lose light selectivity under the action of external force.

Classification of polarizers:
 According to temperature, they can be divided into ordinary polarizers and wide temperature polarizers;
 According to transmittance, they can be divided into ordinary transmittance films and high transmittance films;
 According to background color, they can be divided into gray-white polarizers and color polarizers;
 According to the optical films with different composite functions, they can be divided into full transmittance films, semi-transmittance and semi-reflection films, full reflection films, optical compensation films, and viewing angle control films.

2. The main parameters affecting the performance of polarizers:
thickness; transmittance (single transmittance, parallel transmittance, vertical transmittance); polarization efficiency; color coordinates (NBS); composite film type; UV resistance

3. Factory adaptive test method and judgment standard of polarizer:
Size:
A. Test method: Use a ruler, micrometer or caliper to measure the length, width and thickness of the original polarizer to be tested.
B. Judgment standard: The measurement result is qualified if it is within the parameter range provided by the supplier.

Photoelectric performance:
A. Test method: Put the polarizer on the product and test and compare its photoelectric performance with the same model product with the same polarizer in use.
B. Judgment standard: The Voff value of the test sample is equivalent to the Voff value of the production product; the contrast of the test sample is greater than the contrast of the production product; the background color of the test sample is consistent with the required background color.

Reliability:
A. Test method: Stick the polarizer to be tested on the glass and test it together with the product with the same polarizer to compare its reliability performance.
B. Judgment standard: After the reliability test, the optical and electrical performance and reliability test results are equivalent to the results of the same polarizer and are within the range required by the test product model.

Paste and peel performance:
A. Test method: Paste the polarizer to be tested on the glass, and repeat pasting and peeling for many times.
B. Judgment standard: It can be pasted and peeled for more than three times, there is no residual glue on the glass after peeling three times, the bonding is firm after pasting, the defoaming is complete according to the parameters set by production, and it passes the high temperature and high humidity test.

4. Rules for the selection of polarizers:
 For the surface films of A+ products, in principle, the original whole polarizers are used. For some products, TFT non-optical triangle materials can be used; for the negative films, in principle, the original whole polarizers are used.
 For the surface films of A-level products, the original whole polarizers, TFT non-optical triangle materials, or TFT scrap polarizers with a large inventory are generally used; or TFT scrap polarizers from suppliers of major channels in the future are used; the negative films are original whole polarizers or composite negative films.
 For the surface films of B-level products, try to use TFT scrap polarizers and scraps with a small inventory, or TFT scrap polarizers from suppliers that are no longer the main channels for procurement in the future; the negative films are composite negative films.
When customers have special requirements, special polarizers are selected according to customer requirements.

5. How to use polarizer:
 Handle with care, and do not push or scratch the surface with hard objects.
 Do not fold when taking or placing.
 Color screening should be performed on graded sheets and scrap sheets before putting them into production.
 When attaching the sheets, make sure that the cleaning liquid remaining on the LCD surface is completely evaporated before attaching the polarizer.
 When slitting the ultra-wide temperature polarizer, be sure to place it with the glue side facing down.

6. Storage and handling methods of polarizers:
Storage methods of polarizers:
Polarizers should be stored at room temperature and kept in a dark place with humidity below 75%. They should be stored flat. Polarizers that are fully packaged by the supplier should be stacked at the stacking height and position marked by the supplier. Polarizers in express packaging and bulk stacks should be stacked with separate isolation supports for every 300 sheets.

How to transport polarizers:
When transporting polarizers, they should be placed on the top layer of the objects being transported. The height should not exceed the stacking height. They should be handled with care and should not be placed vertically or bumped or pressed.

Appendix 2: Common specifications of polarizers
Appendix 3: Some special classification methods of polarizers used in our factory according to the purchase method:
original whole sheet; original grade processed sheet; outsourced whole composite sheet; TFT scraps; outsourced TFT scrap composite sheet; scrap sheet

Appendix 4: How to use the composite film currently used in the factory:
 It is recommended that all composite polarizers be color-separated in the factory before being sent out for composite processing by external processors; then they are divided into batches according to color or fixed in one color before being processed and composited to ensure that the color of the polarizers before composite is roughly consistent.
 After the polarizers are color-separated and re-warehoused by quality control, the production department is recommended to have a general understanding of the product's base color before slicing. If the base color is green or has a slight green rainbow, a slightly yellowish polarizer should be selected; conversely, if the product base color is yellow or has a slight yellow rainbow, a slightly greenish polarizer should be selected.
 When producing polarizers, it is recommended to use them in batches according to color. Generally, do not store too many colors online to avoid confusion.
 After color separation, unless the color of the existing polarizers in the warehouse cannot meet the customer's base color requirements, it is not recommended to make large adjustments to the polarizer angle to avoid losing the photoelectric performance required by the product.