JPH08136731A - Polarizing plate - Google Patents

Abstract

PURPOSE: To decrease color voids around a film caused by the heat treatment in the production process of a liquid crystal display device or caused during checking discontinuity in a high temp. environment or in a durability test, by cutting a polarizing plate into chips in such a manner that the absorption axis of the chip is in a specified range of angle from the longer side of the chip after cutting. CONSTITUTION: This polarizing plate is used by sticking to a liquid crystal display device. The polarizing plate is cut into chips in such a manner that the absorption axis of the chip is in the angle range of 0±10 deg. or 90±10 deg. from the longer side of the chip after cutting. The polarizer used for the polarizing plate is not limited, and for example, a polarizing plate is used in which a protective film having excellent transparency such as a triacetylecellulose film is adhered to a polarizer prepared by absorbing and orienting iodine and/or a dichroic dye to a hydrophilic polymer film such as polyvinyl alcohol film with a polyvinyl alcohol adhesive. Since color voids significantly appear with the larger size of the chip, this method is effective for a chip product having >=7cm diagonal length.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polarizing plate. Specifically, it relates to a polarizing plate having no color drop phenomenon.

[0002]

2. Description of the Related Art Liquid crystal display devices are widely used in portable televisions, personal computers, personal word processors, etc., but normally use a polarizing plate and display using polarized light. There are many.

These liquid crystal display devices are often subjected to heat treatment at 60 ° C. or higher and circuit disconnection check in a high temperature environment during manufacture, and also in actual use, such as in-vehicle use and outdoor use. It may be used under harsh conditions.

When a conventional polarizing plate or an elliptically polarizing plate is used, a lighting test is performed after the processing or circuit check in such a high temperature environment, a high temperature durability test of 80 ° C. or more, and a 60 ° C.- In a 90% RH high temperature and high humidity durability test, there is a problem that a defective phenomenon due to a polarizing plate, that is, a so-called color drop phenomenon in which the surrounding becomes brighter than the central portion or darker on the contrary is generated. there were.

[0005]

Means for Solving the Problems As a result of intensive investigations by the present inventors in order to solve such a problem, as a result, a chip has a specific relationship between the absorption axis direction of a polarizing plate and the long side after chip cutting. They have found that the above problems can be solved by using a cut polarizing plate, and reached the present invention.

That is, according to the present invention, a polarizing plate used by being attached to a liquid crystal display device is chip-cut so that its absorption axis is 0 ± 10 ° or 90 ± 10 ° with respect to the long side after chip-cutting. Polarizing plate, which is characterized by
The present invention also relates to an elliptically polarizing plate obtained by laminating a retardation plate on the above polarizing plate, and a liquid crystal display device using the above polarizing plate or the above elliptically polarizing plate.

The polarizer used in the polarizing plate of the present invention is not particularly limited, and examples thereof include polyvinyl alcohol film, polyvinyl formal film, polyvinyl acetal film, poly (ethylene-vinyl acetate) copolymer saponified film. Polyvinyl alcohol-based adhesives, urethane-based adhesives are used for polarizers in which iodine and / or dichroic dyes are adsorbed and oriented on hydrophilic polymer films such as , A polarizing plate adhered using a vinyl acetate adhesive or the like. Preferred is a polarizing plate comprising a polarizer in which iodine and / or a dichroic dye is adsorbed and oriented on a polyvinyl alcohol film, and a protective film of a triacetyl cellulose film. The thickness of the polarizer and the thickness of the protective film are not particularly limited. For example, the polarizer has a thickness of about 15 to 25 μm, and the protective film has a thickness of about 50 to 400 μm.

Normally, the polarizing plate is used by cutting it into chips of a predetermined size. However, since the color gap becomes noticeable as the size of the chip increases, the present invention is effective for chip-cut products with a diagonal of 7 cm or more. Is.

The chip cut of the polarizing plate has an absorption axis of 0 ± 10 ° or 90 ± 1 with respect to the long side after the chip cut.
It should be 0 °, preferably 0 ± 5 ° or 90 ± 5 °. By doing so, for example, when using a polarizing plate chip-cut so as to be 45 ° or 135 ° with respect to the long side, heat treatment or high temperature environment performed when manufacturing a liquid crystal display device is performed. It is possible to significantly reduce the occurrence of color loss around the film that occurs during the disconnection check and durability test.

The retardation plate laminated on the polarizing plate of the present invention is not particularly limited, and is usually a retardation plate made of a thermoplastic resin having excellent transparency, such as uniaxial stretching. It is possible to use a retardation plate or the like made of the above polycarbonate film.

The method of laminating the polarizing plate of the present invention and the retardation plate into an elliptically polarizing plate is not particularly limited, and ordinary methods such as laminating with an adhesive may be used.
In this case, the optical axis angle of the retardation plate is appropriately set so that the display characteristics of the liquid crystal display device using this elliptically polarizing plate are optimized.

The pressure-sensitive adhesive used in the polarizing plate and the elliptically polarizing plate of the present invention is not particularly limited, and a common pressure-sensitive adhesive such as acrylic can be used.

[0013]

EFFECTS OF THE INVENTION By using the polarizing plate of the present invention, color loss around the film, which is generated during heat treatment, a disconnection check in a high temperature environment, or a durability test, which is performed in manufacturing a liquid crystal display device, is significantly reduced. A liquid crystal display device can be obtained.

[0014]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

EXAMPLE A polarizing plate (trade name: SUMIKARAN SF-1822A, manufactured by Sumitomo Chemical Co., Ltd.) in which a polyvinyl alcohol-based polarizer (thickness: 20 μm) and a triacetyl cellulose film (thickness: 80 μm) as a protective film are laminated on both surfaces. Acrylic adhesive layers P-1 and P-2 (thickness about 2
5 μm) was provided to obtain two types of polarizing plates with an adhesive.

Each of these polarizing plates was 6.6 cm ×
A 8.4 cm rectangle was chip-cut so that its absorption axis was 0 ° with respect to the long side (8.4 cm side) (Sample 1). In addition, the same polarizing plate is used for each 6.6 cm ×
The absorption axis is 90 ° to the long side in a 8.4 cm rectangle.
It was cut into chips (Sample 2). These two types of chip-cut product samples 1 and 2 having the same size but different absorption axis angles were set as a set, and 15 sets of samples were obtained for each polarizing plate with an adhesive.

Next, these polarizing plates were formed into SiO ₂ coated glass plates (H plate manufactured by Nippon Sheet Glass Co., Ltd.) using the respective adhesive layers.
Sample 1 on the front side of the glass and Sample 2 on the back side of the glass, respectively, so that their absorption axes are orthogonal to each other with the glass sandwiched, and the polarizing plates are attached to both the front and back sides. To obtain a glass plate (polarizing plate / adhesive layer / glass plate / adhesive layer / polarizing plate).

15 sets of such glass plates were used for each polarizing plate with an adhesive, and 3 sets of each of the following 5 plates were used.
Color blanking test was conducted by heat treatment and wet heat treatment under various conditions. A: In autoclave (temperature 50 ° C, pressure 5 kg / cm
² ) for 20 minutes, and then 85 ℃ -in a constant temperature and humidity chamber.
It was treated for 48 hours under a dry atmosphere (normal pressure). B: In autoclave (temperature 50 ° C, pressure 5 kg / cm
² ) treatment for 20 minutes, then 100 ℃ in a constant temperature and humidity chamber
Treated in a dry atmosphere (normal pressure) for 48 hours. C: In autoclave (temperature 50 ° C, pressure 5 kg / cm
² ) for 20 minutes, then in a constant temperature and humidity chamber at 60 ° C-
It was treated for 48 hours under an atmosphere (normal pressure) of 95% RH. D: In autoclave (temperature 50 ° C, pressure 5 kg / cm
² ) for 20 minutes, and then in a constant temperature and humidity chamber at 65 ° C-
It was treated for 48 hours under an atmosphere (normal pressure) of 95% RH. E: In autoclave (temperature 50 ° C, pressure 5 kg / cm
² ) treatment for 20 minutes, then in a constant temperature and humidity chamber at 80 ° C-
The treatment was performed for 48 hours under an atmosphere (normal pressure) of 90% RH.

After heat treatment and wet heat treatment, the presence or absence of color unevenness was evaluated by visually observing the glass plate to which the polarizing plate was attached. The results are shown in Table 1. In all of the samples using any of the pressure-sensitive adhesives and under any of the treatment conditions, almost no color loss was observed.

Comparative Example As a polarizing plate to be stuck on both the front side and the back side of a glass plate, a polarizing plate chip-cut so that the absorption axis was 45 ° with respect to the long side (the side of 8.4 cm) was used. The same test as in the example was carried out except that it was used. The results are shown in Table 1. In all the samples using any of the pressure-sensitive adhesives, color loss occurred under all treatment conditions.

[0021]

[Table 1] X: There is a color gap. ○: There is a color loss immediately after the treatment, but it disappears while being left. ⊚: No color loss.

Claims (5)

[Claims] 1. A polarizing plate used by being stuck to a liquid crystal display device, wherein the absorption axis thereof is 0 ± with respect to the long side after chip cutting.
A polarizing plate, which is chip-cut so as to form an angle of 10 ° or 90 ± 10 °. 2. The polarizing plate according to claim 1, wherein the polarizing plate has a diagonal size of 7 cm or more. 3. An elliptically polarizing plate obtained by laminating a retardation plate on the polarizing plate according to claim 1. 4. A liquid crystal display device using the polarizing plate according to claim 1. 5. A liquid crystal display device using the elliptically polarizing plate according to claim 2.