JPS5891408A - Polarizing plate - Google Patents

Abstract

PURPOSE:To improve the thermal stability (dimensional stability) and mechanical strength by sticking a longitudinally and laterally stretched plastic film, a polarizing film and a nondirectional film or a unidirectionally stretched film together. CONSTITUTION:A longitudinally and laterally stretched plastic film 1 is obtd. by stretching a polyester film about 1.5-7 times in the longitudinal and lateral directions and by heat-setting (annealing) the stretched film. In place of the polyester film a film of polyether sulfone, polysulfone, polymethylpentene, polystyrene, polyolefin, polyamide, polymethyl methacrylate, polyvinyl chloride or acetate may be used. A unidirectionally stretched plastic film is stuck so that the stretching direction is made parallel or perpendicular to the direction of the absorption axis. A nondirectional film may be laminated by dissolving a plastic substance in a solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel polarizing plate.
2. It provides a polarizing plate with excellent thermal stability (dimensional stability) and mechanical strength. In recent years, desktop computers,
Liquid crystal display devices are used in electronic watches, instruments, etc., and the demand for polarizing plates*41 is increasing accordingly.

In particular, instruments are used under harsh conditions, and the use of self-delivered vehicles is also being considered, and the polarizing plates used in these instruments are now more durable and heat-resistant than ever before. Something with excellent stability! ! being sought after.

In general, a polarizing plate is a polarizing film made by adsorbing and aligning iodine and/or dichroic dye, or aligning polyene, and a di- or triacetate film (or sheet), cellulose butyl acetate film (or sheet), etc. It is commonly used to provide a surface protection layer by laminating films of 1 to 3 or by applying and curing polyacrylic resin.

However, these polarizing plates can be used without burning problems when used under relatively gentle conditions such as in desktop electronic computers, but when used under harsh conditions such as in instruments, they are often used with secondary crystal displays. When used for electrical equipment, there are problems with its durability and thermal stability, and improvement is desired, and the actual situation is %A.

Recently, as a means to solve the problems of durability and thermal stability, a film with excellent heat resistance such as a polyester film, which is stretched in only one direction on both sides of a polarizing film, is used in the direction of its absorption axis. A polarizing plate has been proposed in which the polarizing plates are laminated with the stretching direction substantially parallel to each other.

Although the durability of such tip plates is considerably improved compared to conventional ones, the stretched film still lacks thermal stability because it has the property of shrinking under heating under the stretching force IRj. In addition, if the absorption axis direction and the stretching direction are bonded parallel to each other, the polarizing plate may easily tear in the absorption axis (or stretching) direction, and cracks often occur. It has the disadvantage that defects occur during manufacturing, punching, or on the mounting line, resulting in a decrease in product yield.

The invention is that a polarizing plate using such a stretched film as a surface protective layer has good thermal stability and mechanical strength, and the polarizing properties are 1Ii1 or better than conventional polarizing plates. The purpose of this project is to provide a product having the following characteristics: a plastic film (or sheet) stretched along the vertical and horizontal axes; a polarizing film; and a plastic film (or sheet) stretched in no direction or in only one direction. sheets) are pasted together in this order, and 0
In order to specifically explain using drawings below, in drawing 0, 1
is l [axially stretched plastic film or sheet (thickness is preferably 10 to 8004 m), 2 is a polarizing film, 3
is a plastic film or sheet (thickness preferably ranges from 10 to 100 mm) stretched in no direction or only in one direction.

tm & transversely stretched plastic film or sheet is a film or sheet made of polyester such as polyethylene terephthalate, polyethylene isophthalate, polyethylene terephthalate, etc., with a width of about 1.5 to 100% in the longitudinal and transverse directions. 7@Stretched and heat-set C annealed) vertically and horizontally stretched polyester film or sheet is preferably used, but polyethersulfone, polysulfone polymethylpentene, polystyrene, polyolefin, polyamide V, polymethyl methacrylate, polychloride Since vertically and horizontally stretched films or sheets made of vinyl, acetate, etc. can also be used, the surface of these films or sheets (the surface that is not pasted with the polarizing film) K is the surface of the film or sheet, such as hard carbon. For the purpose of improving visibility, scratch-resistant treatments such as coating silicone resin are applied, and for the purpose of improving transmittance, well-known antireflection layers such as magnesium fluoride are formed by vapor deposition. Because of that.

The polarizing film 2 is a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or an ethylene-vinyl acetate saponified iris film, in which iodine and/or a dichroic dye is added. iodine and/or dichroic dye-based polarizing film that has been adsorbed and oriented, a polyene-based polarizing film that has been oriented by dehydrating a polyvinyl alcohol film to form polyene, and a polyene polarizing film that has been oriented by dehydrating a polyvinyl chloride film to form a polyene. Examples include polyene-based polarizing films formed and oriented with a polyene polarizing film, and these films generally have a film size of 10 to 80. III
This is because a material with a thickness of I is used.

In addition, the plastic film or sheet stretched in no direction or only in one direction is made of the same plastic material as the above-mentioned longitudinally and transversely stretched plastic film or sheet and stretched in either no direction (non-stretched) or only in one direction. Where a film or sheet is used, the polyester film or sheet is stretched at least 5 times, preferably 50-800%, only in the longitudinal or transverse axis and heated at 100°C for 60 minutes to 230°C for 5 minutes. The use of a polyester film or sheet that is set and not stretched in the force direction is particularly preferred from the viewpoint of chemical resistance.

The plastic film or sheet stretched only in one direction and the polarizing film are bonded together so that the direction of the stretching force and the direction of the absorption axis are parallel or perpendicular to each other.

In addition, the non-directional plastic film or sheet formed on the surface of the polarizing film can be made by forming a plastic material into a film in advance and laminating it with heat, or by dissolving the plastic material in an appropriate solvent and then laminating it. It can be formed by

The polarizing plates configured in this manner are incorporated into a liquid crystal display device, either singly or in pairs. In the case of a single sheet, the vertical and horizontal axes stretched film is positioned on the visible side, and in the case of a pair, the plastic 74 A or sheets are stretched in no direction or only in one direction through a liquid crystal display cell, and The polarizing film phases are assembled so that their absorption axes are perpendicular to each other.

As described above, the polarizing plate of the present invention is characterized by excellent thermal stability (dimensional stability) and mechanical strength because a vertically and horizontally stretched plastic film or sheet is laminated on one surface of the polarizing film. .

In addition, especially when polyester film is used, it has good gas permeation resistance and has excellent long-term durability compared to polarizing plates using conventional di- or triacetate films due to the permeation resistance. Deaaa.

[Brief explanation of the drawing]

The drawing is a side view showing an example of the present invention. l...Plastic film (or sheet) stretched along the vertical and horizontal axes 2...Polarizing film 3...Plastic film (or sheet) stretched in no direction or only in one direction Patent applicant Mizo Hijikata, representative of Nitto Electric Industry Co., Ltd. Department

Claims (1)

[Claims] l) A plastic film (or sheet) stretched in the vertical and horizontal axes, a polarizing film, and a plastic film (or sheet) stretched in no direction or in only one direction [7] are bonded together in this order. polarizing plate. 2) Claim W11 in which the plastic film (or sheet) is a polyester film (or sheet)
Polarizing plate/