JPS638704A - Polarizing plate - Google Patents

Abstract

PURPOSE:To obtain the titled plate which does not generates a color shade on the surface of a liquid crystal display plate, without generating strain to the liquid crystal cell by forming great number of irregularities on the outer surface of an adhesive thermoplastic resin film, and making the outer surfaces of a pressure-sensitive adhesive layer smooth. CONSTITUTION:The resin usable to the adhesive thermoplastic resin film is exemplified by polyvinylbutyral, etc., and the great number of irregularities are formed on an protective glass so as to be sufficiently degassed at the time of laminating the protective glass to said film. the pressure-sensitive adhesive layer mounted on an another surface of the polarizing film is exemplified by an acrylic resin such as acrylic acid-(2-ethylhexyl)-methacrylic acid copolymer, etc. The outer surface of the pressure sensitive adhesive layer is made smooth so that the strain of the liquid crystal cell is reduced. The liquid crystal display plate used to said polarizing plate is formed for example, by laminating a front polarizing plate 1 on the liquid crystal cell 2, and by mounting a protective glass 3 on said plate 1, and by laminating a back polarizing plate 1' on the downward of the liquid crystal cell 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a polarizing plate suitable for use in liquid crystal display panels, and particularly to a polarizing plate that can provide a liquid crystal display panel with excellent display performance.

(Prior art) A polarizing film is formed by laminating a protective film such as a cellulose triacetate film on both sides of a polyvinyl alcohol film that has been imparted with polarizing properties using, for example, iodine or a dichroic dye. There is. Generally, a liquid crystal display board is provided with a pressure-sensitive adhesive layer on the polarizing film,
It is manufactured by pressing this onto a liquid crystal cell.

In recent years, as liquid crystal display panels have become larger, protective glass (AR glass) with anti-reflection treatment has been placed on top of the polarizing film in order to protect the polarizing film and improve visibility during use. There is. but.

There is a gap between the protective glass and the polarizing film, which makes the liquid crystal display panel easily damaged. Furthermore, these voids are the reason why the layers of the liquid crystal display panel are thick.

For this reason, attempts have been made to eliminate gaps and make the liquid crystal display panel thinner, while also providing a resin film between the polarizing film and the protective glass.

Thereby, the liquid crystal display panel can be made thinner, and damage to the liquid crystal display panel caused by voids can be avoided.

As the resin film, an adhesive thermoplastic resin film such as polyvinyl butyral has been proposed. but,
When the protective glass is placed on the resin film, since the protective glass lacks flexibility, air removal between the resin film and the protective glass is insufficient, and air bubbles remain on the adhesive surface. In order to eliminate these air bubbles, attempts have been made to provide unevenness on the surface of the resin film to ensure complete degassing. Since these irregularities are formed randomly, when a resin film is provided on both sides of a polarizing film, the resin film, such as polyvinyl butyral, on which these irregularities are provided will be distorted as a whole, and the glass surface of the liquid crystal cell will be distorted. It will be attached to. The unevenness of this resin film causes
The display quality of the liquid crystal deteriorates, such as color unevenness occurring on the display surface of the liquid crystal display board. Moreover, since it is necessary to provide unevenness on the resin film, it becomes impossible to make the pressure-sensitive adhesive layer or the resin film thinner than a certain layer thickness. Therefore, the liquid crystal display panel cannot be made thinner, and one display panel becomes expensive. Plasticized polyvinyl butyral as a resin film is soft and highly adhesive at room temperature. Therefore, when stacking this on a liquid crystal cell,
It cannot be automated and operations are complicated. Further, when manufacturing a liquid crystal display panel having a protective glass using the polyvinyl butyral film described above, a pressure-sensitive adhesive layer is first provided on one side of the polarizing film, and this is pressure-bonded to the liquid crystal cell. Next, a polyvinyl butyral film is placed on the other side of the polarizing film, and a protective glass is placed on top of it and heated.
It was necessary to apply pressure.

In other words, the manufacturing process was complicated.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned conventional problems, and its purpose is to prevent distortion of the liquid crystal cell (for this purpose, the liquid crystal display panel It is an object of the present invention to provide a polarizing plate that does not cause color unevenness on a display surface.Another object of the present invention is to provide a polarizing plate that can be sufficiently degassed when laminated with a protective glass. Yet another object of the present invention.

An object of the present invention is to provide a polarizing plate that can be easily laminated with a liquid crystal cell or a protective glass.

(Means for solving problems) In the present invention, the outer surface of the pressure-sensitive adhesive layer is smooth.

By providing a resin film with an uneven outer surface on the opposite side of the polarizing film from the pressure-sensitive adhesive layer, the distortion of the liquid crystal cell is reduced and the air between the polarizing plate and the protective glass is sufficiently removed. Because it can be done.

The display performance of the liquid crystal display board can be improved. It was completed based on the inventor's knowledge.

The polarizing plate of the present invention is a polarizing plate comprising an adhesive thermoplastic resin film provided on one side of the polarizing film and a pressure-sensitive adhesive layer provided on the other side of the polarizing film,
A large number of irregularities are formed on the outer surface of the adhesive thermoplastic resin film, and the outer surface of the pressure-sensitive adhesive layer is smooth, thereby achieving the above object.

The polarizing film used in the present invention is not particularly limited,
Any conventionally known film can be used.

This is a polarizing film that has been given polarizing properties, and on one or both sides is a cellulose film such as cellulose triacetate, or a polycarbonate film.

Obtained by laminating protective films such as polyether sulfone films. Polarizing film 2 For example, a film of polyvinyl alcohol resin such as polyvinyl alcohol, polyvinyl formal, polyvinyl acecool, or saponified product of ethylene-vinyl acetate copolymer is impregnated with a polarizing element such as iodine or dichroic dye. It is produced by stretching.

The adhesive thermoplastic resin film provided on one surface of the polarizing film is firmly adhered and laminated to the protective glass (AR glass) by heating and pressurizing. This is preferably transparent, has appropriate adhesiveness and toughness, and the surface in contact with the polarizing film is formed into a mirror surface.

Examples of resins used for adhesive thermoplastic resin films include polyvinyl acetal such as polyvinyl butyral, polyurethane, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-vinyl alcohol copolymer, and ethylene-methyl methacrylate copolymer. Polyvinyl butyral containing a plasticizer is particularly preferred.

The polarizing plate of the present invention using plasticized polyvinyl butyral has a well-balanced cohesive force and adhesive force, and can form an adhesive layer with stable quality. Liquid crystal display panels made using this polarizing plate can be used at high temperatures.

No bubbles or interfacial peeling occurs under high humidity conditions. Further, the cellulose triacetate film constituting the polarizing plate will not decompose and deteriorate, and the reflective metal foil used for Wl and crystal display plates will not deteriorate due to corrosion. Furthermore, polyvinyl butyral has excellent weather resistance and light resistance. Therefore, plasticized polyvinyl butyral is suitable as the adhesive thermoplastic resin film.

If the degree of polymerization of the polyvinyl butyral used in the plasticized polyvinyl butyral is too low, blocking is likely to occur when a film is formed and wound, making peeling difficult. On the other hand, if the temperature is too high, high temperature conditions are required when laminating with a polarizing film or glass after film formation, making the operation complicated and expensive. The degree of polymerization of polyvinyl butyral is 500 to 2,000. Further, the degree of butyralization is preferably 55 to 80 mol%.

As the plasticizer to be added and mixed with polyvinyl butyral, conventionally known plasticizers can be used, such as triethylene glycol di-2-ethyl butyrate.

triethylene glycol di-2-ethylhexoate,
Dibutyl sebacate is mentioned. If the amount of these plasticizers used is too small, the polyvinyl butyral layer will not exhibit plasticity, and if the amount is too large.

A so-called bleed phenomenon occurs in which the plasticizer seeps out onto the surface of the polyvinyl butyral layer. The amount of plasticizer used is 20 to 60 parts by weight per 100 parts by weight of polyvinyl butyral.
Preferably it is 30 to 50 parts by weight.

Adhesive films such as plasticized polyvinyl butyral film contain UV absorbers and antioxidants.

A coloring agent, an adhesion modifier such as a metal salt of carboxylic acid, etc. may be contained. In particular, when an ultraviolet absorber is blended, harmful ultraviolet rays are blocked for polarizing films and liquid crystals, thereby improving weather resistance.

The outer surface (the surface not in contact with the polarizing film) of the adhesive thermoplastic resin film used in the present invention has many irregularities formed to ensure sufficient deaeration during lamination onto the protective glass. There is. This unevenness.

The average distance between adjacent recesses or adjacent projections is 1
It is preferable to set the roughness to about twice or more than the zero point average roughness from the viewpoint of improving deaeration performance, and to set it to about 10 times or less.

This is preferable in that the adhesiveness can be reduced when a highly adhesive resin is used. And the average interval of unevenness is 100 to 500
μm, preferably 200 to 300 μm.

The 10-point average roughness is 20 to 100 μm, preferably 25 to 100 μm.
It is assumed to be 70 μm. If the thickness is less than 25 μm, when a protective glass is laminated on a polarizing plate, the peripheral portion of the glass is sealed first, resulting in insufficient degassing of the central portion. Therefore, the protective glass becomes opaque. Since there is a large amount of residual air even with a diameter of 70 μm or more, foaming occurs during heat and moisture resistance tests. Here, the 10-point average roughness means RZ measured in accordance with 15O-R468.

The pressure-sensitive adhesive layer provided on the other side of the polarizing film has 1
For example, an acrylic resin such as acrylic acid (2-ethylhexyl)-methacrylic acid copolymer is used. The outer surface of the pressure sensitive adhesive layer is smooth. By doing so, distortion of the liquid crystal cell is reduced. Furthermore, in the lamination of the pressure-sensitive adhesive layer and the liquid crystal cell, sufficient deaeration can be achieved even if the outer surface of the pressure-sensitive adhesive layer is smooth.

If necessary, a separator is provided on the surfaces of the adhesive thermoplastic resin film and the pressure-sensitive adhesive layer laminated on the polarizing film. This separator has the function of maintaining the adhesiveness of the resin film and the pressure-sensitive adhesive layer and preventing the adhesion of foreign matter. In particular, when polyvinyl butyral is used as the adhesive thermoplastic resin film, it must be stored at a temperature of 510° C. or lower, which requires equipment such as a refrigerator, which is expensive. Therefore.

Preferably, a separator is provided. Examples of the separator include a release film such as a polyethylene film coated with silicone on two surfaces.

Examples of methods for forming irregularities on the adhesive thermoplastic resin film include an embossing roll method, a calendar roll method, a profile extrusion method, a mechanical etching method, and a method using male and female press plates.

Particularly preferred is the embossing roll method. The embossing roll method is a method in which an embossing roll on which irregularities corresponding to the irregularities to be imparted to the surface of a thermoplastic resin film are formed is used as a forming press roll during resin film production.

One example of a liquid crystal display plate using the polarizing plate of the present invention is as follows.

As shown in FIG. 1, an upper polarizing plate 1 is laminated on a liquid crystal cell 2, a protective glass (AR glass) 3 is provided on the upper polarizing plate 1, and a lower polarizing plate is provided below the liquid crystal cell 2. The plates 1' are laminated, and a reflective layer 4 made of aluminum foil or the like is provided below them. The upper polarizing plate 1 consists of an adhesive thermoplastic resin film 11 provided on one side of the polarizing film 10 and a pressure-sensitive adhesive layer 12 provided on the other side of the polarizing film 10. The liquid crystal cell 2 includes a liquid crystal cell glass 20 and a liquid crystal 21 housed within the glass 20. The pressure sensitive adhesive layer 12 is a liquid crystal cell glass 20
The adhesive thermoplastic resin film 11 is adhered to the protective glass 3. Note that the reflective layer 4 provided on the lower polarizing plate 1' is generally extremely thin.

Normally, instead of the resin film 11 of the upper polarizing plate 1, the polarizing film 10' is bonded to the polarizing film 10' by a pressure-sensitive adhesive layer 1da, and the polarizing film 10' is further bonded to the pressure-sensitive adhesive layer 12''.
It is bonded to the liquid crystal cell 2 by.

(Example) The present invention will be described below with reference to examples.

Polyvinyl butyral resin (average polymerization degree 1700° butyralization degree 65 mol%, residual vinyl alcohol 34.5
B) IT O, 2 parts by weight as an antioxidant and 2 parts by weight as an ultraviolet absorber.
-(3-t-butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzotriazole (Chinbin 32
6. Ciba Geigy) 0.2 parts by weight were mixed to prepare a polyvinyl butyral composition.

After kneading this composition with a roll at 70°C.

Pressing was performed using a male and female press plate under the conditions of 150°C and 50 kir/cut, and as shown in Fig. 2, one side was mirror-finished and the other side had irregularities 111, and a thickness of 380 μm was visualized. Polyvinyl butyral film 11
I got it. The unevenness had a 10-point average roughness of 35 μm.

This polyvinyl butyral film 11 and a cellulose triacetate/polyvinyl alcohol/cellulose triacetate trilayer (polarizing film, thickness 18
0 μm) 10 were laminated so that the mirror side of the polyvinyl butyral film was in contact with one of the cellulose triacetate layers. The other cellulose triacetate layer is coated with an adhesive layer 12 using an acrylic pressure-sensitive adhesive prepared separately using a conventional method.
was formed to obtain polarizing plate 1. For acrylic pressure sensitive adhesive layer.

An acrylic acid (2-ethylhexyl)-methacrylic acid copolymer containing polyisocyanate (triepoxypropyl isocyanate) as a crosslinking agent was used.

The obtained polarizing plate was cut into a size of 1QQmm x 250mm, and the pressure-sensitive adhesive layer was placed on the glass plate of the liquid crystal cell.

The adhesive was gradually attached to the glass surface by pushing out the air. Next, a protective glass (AR glass, 100in x 25
0m long, 1.1mm thick) was placed on it.

On the other hand, a pressure-sensitive adhesive layer is formed on the other side of the polarizing film with aluminum foil adhered to the - side, the above-mentioned structure for a liquid crystal display board is placed on this adhesive layer, and this is placed in a rubber bag. Reduce the pressure to below Ryu Hg.

Preliminary pressing was carried out by heating in gear open for 30 minutes (surface temperature 70°C) while degassing. after that.

Heat and pressurize in an air autoclave at 70°C and 5 kg/cot (maintaining time at maximum temperature 20 minutes) to convert the pressure-sensitive adhesive layer to the liquid crystal cell glass and the polyvinyl butyral film to the protective glass. Strongly bonded (
This press). In this case, the space between the polyvinyl butyral film and the protective glass was sufficiently degassed, and no air bubbles remained in the resulting liquid crystal display panel. Furthermore, no color unevenness occurred on the display surface of the liquid crystal display board.

Using the liquid crystal display board obtained in this way as a sample,
A moisture resistance test (60°C, 90% R, H, 500 hours) and a heat resistance test (80°C, 500 hours) were conducted. As a result, the polarizing plate did not peel off not only at the center of the sample but also at the periphery, and no abnormalities such as bubbles or wrinkles were observed.

Moreover, since the above-mentioned polarizing plate is configured by integrating a polarizing film, an adhesive thermoplastic resin film, and a pressure-sensitive adhesive layer, the manufacturing process of the liquid crystal display panel is shortened compared to the conventional method.

A polyvinyl butyral film having a composition similar to that of the comparative spotting example and having unevenness formed on one side was obtained.

This polyvinyl butyral film and a cellulose triacetate/polyvinyl alcohol/cellulose triacetate trilayer (polarizing film, thickness 180 μm) separately prepared by a conventional method.
11) were laminated under pressure, and then a pressure-sensitive adhesive layer was formed on the cellulose triacetate layer on the opposite side of the polyvinyl butyral film to obtain a polarizing plate.

The obtained polarizing plate was cut into a size of 10,100t and 250mm, and the pressure-sensitive adhesive layer was placed on a glass plate for a liquid crystal cell.

The adhesive was gradually attached to the glass surface by pushing out the air. Furthermore, on top of that is a protective glass (AR glass, 10
0x250m, thickness 1, 11m) were stacked.

Using this structure, a liquid crystal display board was obtained in the same manner as in the example. In this case, the space between the polyvinyl butyral film and the protective glass was sufficiently degassed, and no air bubbles remained in the resulting liquid crystal display panel. Even in the moisture resistance test and the heat resistance test, no peeling of the polarizing plate occurred and no abnormalities such as foaming or wrinkles were observed. However, color unevenness occurred on the display surface of the liquid crystal display board after one press was completed.

This color unevenness is caused by yellowish spots (10
~151 mψ) were observed. Furthermore, in this method of manufacturing a liquid crystal display plate, after the polarizing film and the liquid crystal cell are bonded together, it is necessary to further place a polyvinyl butyral film on the polarizing plate.

The number of steps is increased by one compared to the method of the embodiment.

As is clear from the Examples and Comparative Examples, 1. According to the polarizing plate of the present invention, the air between the polyvinyl butyral film and the protective glass is sufficiently removed, so that no air bubbles remain in the obtained liquid crystal display panel. do not.

Further, color unevenness does not occur on the display surface of the liquid crystal display panel.

A liquid crystal display panel with excellent moisture resistance and heat resistance can be provided. Moreover, the manufacturing process of the liquid crystal display panel is shortened compared to the conventional method. According to the conventional polarizing plate, color unevenness occurs on the display surface of the obtained liquid crystal display plate, and the display performance deteriorates.

(Effects of the Invention) As described above, the polarizing plate of the present invention has unevenness formed only on one side of the polarizing plate, so compared to a polarizing plate with unevenness on both sides of the 4/4/4 exhibition size polarizing plate. The distortion of the liquid crystal cell caused by this is reduced.

Therefore, color unevenness does not occur in the obtained liquid crystal display panel.

This is because of the unevenness provided on one side of the polarizing plate when manufacturing a liquid crystal display panel using this polarizing plate.

Since air is sufficiently removed between the adhesive thermoplastic resin film and the protective glass, no air bubbles remain in the obtained liquid crystal display panel. As a result, a liquid crystal display panel with excellent display performance can be provided. The polarizing film that makes up the polarizing plate includes:
Since the adhesive thermoplastic resin film and the pressure-sensitive adhesive layer are integrally formed in advance, it is easier to make the LCD panel than the conventional manufacturing method in which the thermoplastic resin film is laminated to the polarizing plate during the manufacturing process. Fabrication becomes easy.

4. Fn of #~゛' of S Fig. 1 is a cross-sectional front view showing one embodiment of a liquid crystal display plate using the polarizing plate of the present invention, and Fig. 2 shows an embodiment of the polarizing plate of the present invention. It is a cross-sectional front view.

1.1゛... Polarizing plate, 2... Liquid crystal cell, 3... Protective glass (AR glass), 4... Reflective layer, 10.
10'...Polarizing film, 11...Adhesive thermoplastic resin film.

12, 12'...Pressure sensitive adhesive layer, 20...; Glass for night cell.

21...Liquid crystal.

that's all

Claims (1)

[Claims] 1. A polarizing plate comprising an adhesive thermoplastic resin film provided on one side of a polarizing film and a pressure-sensitive adhesive layer provided on the other side of the polarizing film, comprising: A polarizing plate, wherein the outer surface of an adhesive thermoplastic resin film has many irregularities formed therein, and the outer surface of the pressure-sensitive adhesive layer is smooth. 2. The polarizing plate according to claim 1, wherein the adhesive thermoplastic resin film is a polyvinyl butyral film containing a plasticizer. 3. The polarizing plate according to claim 1, wherein the 10-point average roughness of the unevenness is in the range of 20 to 100 μm.