TWI568579B - Polarizing plate - Google Patents

Description

Polarizer

The present invention relates to a polarizing plate, and more particularly to an iodine polarizing plate.

Nowadays, liquid crystal displays are becoming more and more widely used, for example, mobile phones, wearable devices, etc., and the requirements for the transmittance, polarization, and color reproducibility of polarizing plates are becoming higher and higher.

The polarizer is the most important component of the polarizing plate, and the polarizer is generally formed by adsorbing a dichroic dye in a polyvinyl alcohol film, for example, an iodine-based polarizer using iodine as a dichroic dye. The formation of the polarizer usually has the following steps: a swelling treatment, a dyeing treatment, a stretching treatment, a crosslinking treatment, a washing treatment, and a drying treatment. Among them, the stretching treatment causes the polyvinyl alcohol to have a polarizing effect.

The present invention relates to a polarizing plate. The polarizing plate of the invention has good high temperature weather resistance, that is, good optical stability, and can improve yellowing at high temperatures.

According to an aspect of the invention, a polarizing plate comprising an iodine polarizer, an adhesive layer, and a protective layer is provided. The protective layer is attached by an adhesive layer At least one side of the iodine polarizer. The zinc ion content of the polarizing plate is 100 ppm to 800 ppm.

In order to better understand the above and other aspects of the present invention, the preferred embodiments are described below in detail as follows:

100, 200‧‧‧ polarizing plate

101‧‧‧ polarizer

102, 102A‧‧‧ adhesive layer

103, 103A‧‧‧ protective layer

304‧‧‧ display panel

305‧‧‧Adhesive layer

306‧‧‧Optical adhesive layer

307‧‧‧glass cover

FIG. 1 is a cross-sectional view of a polarizing plate according to an embodiment.

2 is a cross-sectional view of a polarizing plate according to an embodiment.

3 is a cross-sectional view of a display device in accordance with an embodiment.

Compared with the dye-based polarizing plate, the iodine-based polarizing plate is widely used because of its high light transmittance and polarizing property. However, the iodine type polarizing plate is inferior in durability at a high temperature. That is, under high temperature conditions, the optical properties of the iodine type polarizing plate such as the transmittance may be lowered or yellowed, and it is difficult to pass the high temperature environment requirement of the mobile product. The polarizing plate of the invention has good high temperature weather resistance, that is, good optical stability, and can improve yellowing at high temperatures.

According to an embodiment, the polarizing plate comprises a polarizer, an adhesive layer, and a protective layer. The protective layer is attached to at least one side of the polarizer or the opposite sides by an adhesive layer.

For example, referring to FIG. 1 , the protective layer 103 of the polarizing plate 100 of the three-layer structure is attached to one side of the polarizer 101 by the adhesive layer 102 .

Referring to FIG. 2, the protective layer 103 of the five-layer structure polarizing plate 200 The protective layer 103A is attached to the opposite sides of the polarizer 101 by the adhesive layer 102 and the adhesive layer 102A, respectively.

In one embodiment, the polarizer 101 is an iodine polarizer. The iodine polarizer comprises a polyvinyl Vinyl Alcohol (PVA) resin film and iodine adsorbed thereon and directed thereto. The polyvinyl alcohol resin can be obtained by saponifying a polyvinyl acetate resin. Examples of the polyvinyl acetate resin include a single polymer of vinyl acetate, that is, polyvinyl acetate, and a copolymer of vinyl acetate and other monomers copolymerizable with vinyl acetate. Other examples of monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids (e.g., acrylic acid, methacrylic acid, ethyl acrylate, n-propyl acrylate, methyl methacrylate), olefins (e.g., ethylene, propylene, 1). -butene, 2-propene), vinyl ether (such as ethyl vinyl ether, methyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether), unsaturated sulfonic acid (such as vinyl sulfonic acid, vinyl) Sodium sulfonate) and so on.

The protective layer 103, 103A may be selected from the group consisting of polymethylmethacrylate (PMMA), Triacetyl Cellulose (TAC), acrylic resin film, polyaromatic resin film, and polyether resin film. , a cyclic polyolefin resin film (for example, a polyferrene resin film), a polyester (Polyethylene Terephthalate, PET), a polypropylene (PP), a cycloolefin polymer (COP), a polycarbonate (Polycarbonate, PC) and a group of any combination of the above. In an embodiment, the protective layer is a TAC film.

The adhesive layer 102, 102A is a transparent adhesive layer made of an aqueous adhesive, wherein the material of the adhesive comprises polyvinyl alcohol powder.

In one embodiment, a water soluble zinc salt is optionally added to the adhesive of an adhesive layer 102, 102A. In one embodiment, the weight ratio of the polyvinyl alcohol powder to the water-soluble zinc salt in the adhesive is from 100:25 to 125, preferably from 100:50 to 100, and the adhesive layer remains transparent. In one embodiment, a water-soluble zinc salt may also be added to the adhesive of the two adhesive layers 102, 102A.

The water soluble zinc salt may include zinc chloride, or other suitable inorganic zinc salt such as zinc nitrate, or zinc iodide. Among them, zinc chloride is preferred.

In one embodiment, the polarizing plate has a zinc ion content of 100 ppm to 800 ppm, or 100 ppm to 700 ppm, or 100 ppm to 600 ppm, or 100 ppm to 500 ppm, or 100 ppm to 400 ppm, or 100 ppm to 300 ppm, or 200 ppm. ~500ppm, or 200ppm~400ppm. The aforementioned unit ppm represents the number of milligrams of zinc ions contained per 1 kg of the polarizing plate.

In order to make the above description of the present invention more comprehensible, the following specific examples are described in detail below: Table 1 lists the parts by weight of the materials used for the adhesive and the dissolution of the materials in water. In Examples 1 to 5, the adhesive contained zinc chloride, and the weight ratio of the polyvinyl alcohol powder to the zinc chloride was between 100:37.5 and 125. In Comparative Examples 1 to 2, the adhesive contained zinc sulfate. 7 water compounds, and polyvinyl alcohol powder and zinc sulfate. The weight ratio of 7 water compounds is between 100:25 and 37.5. In Comparative Example 3, when the polyvinyl alcohol powder was 100 parts by weight, zinc chloride and zinc sulfate hydrate were not added.

As shown in Table 1, in Examples 1 to 5 and Comparative Example 3, the adhesive The layers remained transparent; in Comparative Examples 1 to 2, the zinc sulfate in the adhesive layer did not dissolve.

In Table 2, the adhesive layer was coated on an iodine polarizer to form an adhesive layer, and the protective layer was attached to the iodine polarizer through an adhesive layer, and the obtained polarized plate product was subjected to property analysis.

Table 2 lists the transmittance of the monomer after the high temperature treatment (ΔT, unit: %) and the degree of change in the degree of polarization (ΔP, unit) of the polarizing plate composed of the adhesive layer, the protective layer and the iodine polarizer. : %), yellow-blueness change (Δb), and Zn content measured by inductively coupled plasma spectrometer (ICP-OES), and surface appearance after heating at 95 ° C for 500 hours. The monomer transmittance was measured by a spectrophotometer (manufactured by JASCO Corporation, model number V-7100) equipped with an integrating sphere. The degree of change in the degree of polarization was measured using a spectrophotometer equipped with an integrating sphere. The yellow-blueness change (Δb) was measured using a luminometer (manufactured by JASCO Corporation, model number V-7100).

According to Table 2, the optical properties of the examples were relatively stable and the amount of change in yellow-blueness was lower than that of the comparative examples. Among them, the results of Examples 2 and 3 are preferred, and the polarizing plate product has almost no color change. While Examples 1, 4, and 5 have slight color changes, the polarizing plate products of Comparative Examples 1, 2, and 3 are all severe yellowish black.

According to the above, adding an appropriate content of zinc ions in the adhesive layer can improve the high temperature weather resistance of the polarizing plate, and has good optical stability, small change in yellow and blueness, and no abnormal appearance, without affecting the polarizing plate product. The function.

Table 1

In some comparative examples, when a panel of a specific model is covered with a layer of pressure sensitive adhesive and glass, the moisture permeability is greatly reduced, resulting in more severe weathering test conditions, which may easily lead to loss of optical performance in the iodine polarizer. A condition of severe yellowing. Therefore, it is extremely important to improve the high temperature weather resistance of the polarizing plate.

For example, FIG. 3 is a cross-sectional view of a display device according to an embodiment, which may include a display panel 304, an adhesive layer 305, a polarizing plate 200, and an Optical Clear Adhesive (OCA) 306, from bottom to top. Transparent glass cover 307. The display panel 304 can be a liquid crystal display panel. The five-layer polarizing plate 200 can be referred to FIG. 2, and the protective layers 103, 103A are attached to opposite sides of the polarizer 101 by the adhesive layers 102, 102A. In other embodiments, a polarizing plate 100 having a three-layer structure as shown in Fig. 1 can also be used. In an embodiment, the display device can also Depending on the application, other components, such as a touch module, may be disposed above the glass cover, or between the polarizer and the display panel, or within the display panel.

Since the iodine-type polarizing plate according to the embodiment has excellent high-temperature weather resistance, good optical stability, small change in yellow-blueness, and no uneven appearance, the display device using the polarizing plate according to the embodiment can also It has excellent optical display properties and long service life.

In conclusion, the present invention has been disclosed in the above preferred embodiments, and is not intended to limit the present invention. A person skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

100‧‧‧Polar plate

101‧‧‧ polarizer

102‧‧‧Adhesive layer

103‧‧‧Protective layer

Claims (10)

A polarizing plate comprising: an iodine type polarizer; an adhesive layer; and a protective layer attached to at least one side of the iodine polarizer by the adhesive layer, wherein the polarizing plate has a zinc ion content of 100 ppm~ 800ppm. The polarizing plate described in claim 1 has a zinc ion content of 200 ppm to 500 ppm. The polarizing plate of claim 1, wherein the material of the iodine polarizer is a polyvinyl alcohol (PVA) film, and/or the material of the protective film is cellulose triacetate. (Triacetate Cellulose Film, TAC). The polarizing plate of claim 1 or 2, wherein the zinc ion is contained in the adhesive layer. The polarizing plate of claim 1, wherein the adhesive layer is made of an adhesive, and the material of the adhesive comprises a polyvinyl alcohol powder. The polarizing plate of claim 5, wherein the adhesive further comprises a water-soluble zinc salt, and wherein the weight ratio of the polyvinyl alcohol powder to the water-soluble zinc salt is between 100:25 and 125. The polarizing plate of claim 5, wherein the adhesive further comprises a water-soluble zinc salt, and wherein the weight ratio of the polyvinyl alcohol powder to the water-soluble zinc salt is between 100:50 and 100. The polarizing plate according to any one of claims 5 to 7, wherein the adhesive is an aqueous clear transparent solution. The polarizing plate of claim 6 or 7, wherein the water-soluble zinc salt comprises zinc chloride, zinc nitrate, or zinc iodide. A liquid crystal display comprising: a display panel; a touch module; and a polarizing plate as described in claim 1, 2, 3, 5, 6 or 7.