JPH10301105A - Liquid crystal display polarizing plate and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the warpage of a liquid crystal display device as much as possible by laminating plastic barrier film which is transparent and has moisture barrier performance and whose glass transition temperature is equal to or above a specified value on the surface of a polarizing plate. SOLUTION: The polarizing plate 10 is constituted by laminating the plastic barrier film 14 on either protective film 11a of polarizing film 12 coated and protected with/by the protective films 11a and 11b through an adhesive layer 13. Then, the plastic barrier film 14 laminated is transparent and has the moisture barrier performance, and for instance polyester film and polystyrene film or the like whose glass transition temperature is >=60 deg.C are used. Also, the plastic barrier film 14 whose moisture permeability is <=500 g/m<2> .24 hours and is specially desirably <=10 g/m<2> .24 hours may be used. Thus, the polarizing plate 10 is restricted, and is made moisture-proof, so that the warpage of a cell substrate and a whole liquid crystal display device caused by the expansion and shrinkage of the polarizing film 12 is prevented as much as possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polarizing plate for a liquid crystal display device and a liquid crystal display device, and more particularly to a polarizing plate for a liquid crystal display device in which a liquid crystal cell substrate is a plastic substrate and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art A liquid crystal cell substrate constituting a liquid crystal display device has conventionally been formed of glass. Recently, however, a plastic liquid crystal cell substrate has been used to reduce the weight. It has become

On the other hand, a polarizing plate adhered to the front and back of such a liquid crystal cell is formed by using a plastic polarizing film which has been given a polarizing property by stretching. It expands and contracts greatly.

For this reason, when such a polarizing plate is adhered to a liquid crystal cell substrate made of plastic, there arises a problem that not only the cell substrate but also the entire liquid crystal display device is considerably warped due to environmental changes.

[0005] In this case, improvements have been made to reduce the expansion and contraction of the polarizing plate. However, it is impossible to completely eliminate the expansion and contraction of a polarizing plate having a polarizing property by stretching. However, the warpage of the entire liquid crystal display device cannot be completely eliminated.

SUMMARY OF THE INVENTION The present invention has been made in order to improve the above circumstances, and provides a polarizing plate for a liquid crystal display device which can prevent the warpage of the liquid crystal display device as much as possible, and a liquid crystal display device using the same. The purpose is to:

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a polarizing plate adhered to a liquid crystal cell of a liquid crystal display device, wherein a transparent water vapor barrier is provided on the surface of the polarizing plate. A polarizing plate for a liquid crystal display device, comprising a laminated plastic barrier film having a glass transition temperature of 60 ° C. or higher, and a liquid crystal layer on one surface of a substrate via a transparent electrode and an alignment layer. A liquid crystal display device comprising a liquid crystal cell provided with a polarizing plate and a polarizing plate adhered to the other surface of the substrate is provided. In this case, the plastic barrier film preferably has a water vapor permeability of 500 g / m ² · 24 hours or less.

According to the present invention, the polarizing plate and the liquid crystal cell substrate are restrained and moisture-proof by the lamination of the plastic barrier film and the expansion and contraction of the polarizing film as shown in the embodiments described later. As a result, warpage of the cell substrate and the entire liquid crystal display device is prevented as much as possible.

Hereinafter, the present invention will be described in more detail. The polarizing plate for a liquid crystal display device of the present invention is, for example, a polarizing plate whose both surfaces are covered and protected with protective films, and where necessary, transparent on both front and back surfaces. It is obtained by laminating plastic barrier films.

In this case, the polarizing film may be a known film obtained by adsorbing and orienting iodine or a dichroic dye on a hydrophilic polymer film such as a polyvinyl alcohol-based film or a saponified ethylene-vinyl acetate copolymer film. The thickness is usually 5 to 250 μm, particularly 10 to 180
μm.

As a protective film for covering and protecting the polarizing film, a cellulose film, a polyester film, a polyacryl film, a polycarbonate film, a polyether sulfone, or the like is used.
This thickness is usually 5 to 150 μm, especially 10 to 100 μm
It is.

The plastic barrier film to be laminated on the polarizing plate is transparent and has a water vapor barrier property, and has a glass transition temperature of 60 ° C. or higher. Specifically, a polyester film, a polystyrene film, a polyacrylonitrile film, Examples include a polycarbonate film and a polyacryl film.

In the present invention, the transparency of such a plastic barrier film is preferably 70% or more, particularly 90% or more, from the viewpoint of maintaining the performance of the liquid crystal display device. Is 20 in terms of visibility.
% Or less is preferable.

The water vapor permeability is 500 g / m ² · 2
The time is preferably 4 hours or less, particularly preferably 10 g / m ² · 24 hours or less. If the water vapor permeability is high, moisture transmitted through the film during the rainy season or the like reaches the polarizing plate and warps.

Further, the barrier film has a glass transition temperature of 60 ° C. or higher, preferably 100 ° C. or higher. When the glass transition temperature is lower than 60 ° C., the binding force to the polarizing plate is inferior, and in some cases, the barrier film is inferior. It can shrink itself and cause warping.

The thickness of the barrier film is preferably 10 μm or more, preferably 25 μm or more, more preferably 50 μm or more, as the thickness is larger, but the upper limit is 500 μm in consideration of practicality. In particular, it is 200 μm.

The lamination of the barrier film and the polarizing plate is usually carried out using an acrylic, urethane or epoxy adhesive. The adhesive used for this purpose is not particularly limited, but has a light transmittance of 70% or more, especially 90%.
As described above, those having a haze value of 20% or less are preferable.

As shown in FIG. 1, the polarizing plate 10 of the present invention comprises a barrier film 14 with an adhesive layer 13 interposed therebetween on the one protective film 11a of the polarizing film 12 covered and protected by the protective films 11a and 11b. Can be laminated. In this case, the barrier film 14 may be laminated on the polarizing film 12 via the adhesive layer 13 without providing the one protective film 11a.

As shown in FIG. 2, the liquid crystal display of the present invention comprises two substrates 2, 2 'each having a transparent electrode 3, 3' and an alignment layer 4, 4 'on one surface. Are disposed so as to face each other, and a liquid crystal cell 1 having a liquid crystal layer 5 interposed therebetween and a polarizing plate 10 laminated on the other surface of one of the substrates 2.
And a transflective / reflective polarizer, a reflective polarizer, or an analyzer plate 6 laminated on the other surface of the other substrate 2 ′. The polarizing plate 10 on which the film 14 is laminated is provided.

[0020]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[Examples] As a polarizing plate, PLN-12432Z manufactured by Nippon Synthetic Chemical Industry Co., Ltd., having a thickness of 120 μm, was used, and an acrylic pressure-sensitive adhesive was used for the films A, B, and C shown in Table 1. Were adhered to obtain a polarizing plate.

This was combined with a liquid crystal cell and a transflective polarizing plate to obtain a film-like liquid crystal display device as shown in FIG. In this case, the specifications of the liquid crystal cell and the transflective polarizing plate were as follows, and an acrylic pressure-sensitive adhesive was used for bonding these.

[0023]

[Table 1] Liquid crystal cell: Substrate Fujimori Kogyo Co., Ltd. Amorex A
M 3015 E thickness 320 μm transflective polarizing plate: PUN manufactured by Nippon Synthetic Chemical Industry Co., Ltd.
-12450 HR Z

COMPARATIVE EXAMPLE Films A,
Except that B and C were not bonded to the polarizing plate, a film-like liquid crystal display device similar to that of the example was produced.

Next, the film-form liquid crystal display device was put into an environmental tester, left under the environmental conditions shown in Table 2, and
When one end of the film-like liquid crystal display device was pressed, the warpage was evaluated by measuring how many mm the other end lifted. Table 2 shows the results.

In this embodiment, a transflective polarizing plate is used. However, a similar effect can be obtained by using a reflective polarizing plate instead.

[0027]

[Table 2]

[0028]

By using the polarizing plate of the present invention, warpage of the liquid crystal display device can be prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view of a polarizing plate according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating an example of a liquid crystal display device to which a polarizing plate according to one embodiment of the present invention is attached.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal cell 2, 2 'substrate 3, 3' transparent electrode 4, 4 'orientation layer 5 Liquid crystal layer 6 Transflective transflective polarizing plate 10 Polarizing plate 11a, 11b Protective film 12 Polarizing film 13 Adhesive layer 14 Barrier film

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takahiro Matsuse 3-1-1, Ogawa-Higashi-cho, Kodaira-shi, Tokyo Inside Bridgestone Corporation (72) Inventor Yasuhiro Morimura 3-1-1, Ogawa-Higashi-cho, Kodaira-shi, Tokyo Inside Bridgestone

Claims (3)

[Claims] 1. A polarizing plate to be bonded to a liquid crystal cell of a liquid crystal display device, wherein a plastic barrier film having a transparent and water vapor barrier property and a glass transition temperature of 60 ° C. or higher is laminated on the surface of the polarizing plate. A polarizing plate for a liquid crystal display device. 2. The polarizing plate for a liquid crystal display device according to claim 1, wherein the water vapor permeability of the plastic barrier film is 500 g / m ² · 24 hours or less. 3. A liquid crystal display device comprising: a liquid crystal cell having a liquid crystal layer provided on one surface of a substrate via a transparent electrode and an alignment layer; and a polarizing plate adhered to the other surface of the substrate.
Or a liquid crystal display device using the polarizing plate according to 2.