JPS6340283B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polarizing plate having excellent durability, thermal stability and scratch resistance. Polarizing plates are generally made by forming a transparent plastic layer on the surface of a polarizing film, and their use ranges from small items such as conventional calculators and watches to large items such as automobile meters and instruments. It is being expanded to include products. With the expansion of such fields of use, polarizing plates are required to have higher properties such as durability and thermal stability. On the other hand, with the increase in size, there is a demand for the scratch resistance of the polarizing plate itself. This is because if the surface of the polarizing plate is scratched during the manufacturing process or mounting of the polarizing plate, the product yield will be significantly lowered, and the appearance and optical characteristics of the display device will also be degraded. The polarizing plate of the present invention was developed in accordance with such a request, and its gist is that a polarizing plate is produced by forming a plastic layer on the surface of a polarizing film, either unstretched or stretched only in one direction. A cured film layer made of a composition containing silica sol in an ultraviolet curable acrylic urethane resin is formed on the surface of the plastic layer of the base material. According to the polarizing plate of the present invention, a cured film layer made of a composition containing silica sol in an ultraviolet curable acrylic urethane resin is formed on the plastic layer surface of the polarizing base material, so the surface hardness is large and the scratch resistance is excellent. Moreover, it has the characteristics of good durability and thermal stability. The UV-curable acrylic urethane resin used in the present invention is generally produced by reacting an isocyanate monomer or prepolymer with a polyester polyol, and then adding 2-hydroxyethyl (meth)acrylate or 2-hydroxypropyl (meth)acrylate to this. It is obtained by reacting an acrylate or methacrylate monomer having a hydroxyl group such as the following, and by using such a resin, it is possible to cure the composition with ultraviolet rays, and this also provides a high surface hardness and excellent scratch resistance. It has been found that a cured film layer can be obtained. The silica sol used in the present invention is amorphous, porous, and colloidally dispersed. The particle size is 30 mμ or less, preferably an average particle size of 5 to 25 mμ, and the refractive index is approximately
1.46, and the apparent specific gravity is about 0.836. It is desirable that the proportion of the ultraviolet curable acrylic urethane resin and silica sol is 0.1 to 35 parts by weight based on 100 parts by weight of the resin. If the amount of silica sol is less than 0.1 parts by weight, the surface hardness of the cured film layer will be low, and if it is more than 35 parts by weight, the optical properties will deteriorate, which is not preferable. The composition of ultraviolet curable acrylic urethane resin and silica sol contains ethyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, etc. for the purpose of improving film formation and adjusting viscosity during coating. Alkyl (meta)
Monomers such as acrylates, styrene, (meth)acrylonitrile, vinyl ester monomers such as vinyl acetate, functional monomers such as (meth)acrylates, glycidyl methacrylate, etc. can be added in the range of 1 to 40% by weight. It is something. Furthermore, additives such as dyes, pigments, and antistatic agents may be added to the composition, and a photopolymerization agent for the resin may be added. Examples of the initiator include those selected from the group such as acetophenone, benzophenone, micellar ketone, benzyl, and benzoin; photosensitizers include amines and urea compounds, and thermal polymerization initiators include imidazole compounds and urea compounds. Oxides etc. can also be used in combination. The composition thus formulated may be used alone or diluted with an organic solvent inert to the plastic layer to be coated and cured to a solid content of 20 to 95% by weight, and then applied to a spinner. coat,
It is applied by a general coating method such as a gravure coater, reverse coater, spray coater, or slot orifice coater at a concentration of 1 to 30 g/m ² (solid content), and then cured with ultraviolet light after drying. The polarizing base material on which a cured film layer made of such a composition is formed is a plastic film formed on both or one side of a polarizing film by coating or bonding, and is either non-stretched or stretched only in one direction. It consists of layers. Therefore, the polarizing plate of the present invention may have the shapes shown in FIGS. 1 to 3, for example. In FIG. 1, 1 is a polarizing film, 2 is a plastic layer, and 3 is a cured film layer made of the above composition. Figure 2 shows that layers 2, 2' and 3, 3' are film 1.
are formed on both sides of the . FIG. 3 shows an example of using a polarizing plate as a substrate for a plastic liquid crystal cell, in which a patterned transparent conductive film 4 is formed on the surface of a layer 3' made of a cured film. ' prevents disconnection of the membrane 4 due to scratches or the like. The polarizing film is a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or a saponified ethylene-vinyl acetate copolymer film, on which iodine and/or dichroic dyes are adsorbed and oriented. iodine and/or dichroic dye-based polarizing film,
Examples include polyene polarizing films in which polyenes are oriented by dehydrating a polyvinyl alcohol film or dehydrochlorinating a polyvinyl chloride film, and these films usually have a
A material having a thickness of 80 μm is used. The unstretched or unidirectionally stretched plastic layer (preferably about 10 to 2,000 μm in thickness) formed on one or both sides of the polarizing film is a coating-curable plastic layer such as polyacrylic resin or polyurethane resin. Apply and cure the resin, or use non-directional or unidirectional film with excellent optical transparency such as polyester film, polycarbonate film, polysulfone film, polyether film, trimethylpentene film, polyether ketone film, (meth)acrylonitrile film, etc. The stretched plastic film is pasted using adhesives with excellent optical transparency such as polyester adhesives, polyacrylic adhesives, polyurethane adhesives, polyvinyl acetate adhesives, or adhesive means such as welding. It is composed by combining. If chemical resistance or the like is desired for the plastic layer, at least 5% in the vertical or horizontal direction only.
Preferably 50-800% stretching and 5-800% stretching at 100-230°C.
A polyester film heat-treated for 60 minutes is preferred. In a polarizing base material composed of such a polarizing film and a plastic layer, the surface of the plastic layer on which the composition is applied and cured may be subjected to surface treatment such as alkali treatment, corona treatment, sputtering treatment, etc. depending on the material of the plastic base material. It is preferable to perform a surface modification treatment such as coating with a silane coupling agent or Si vapor deposition from the viewpoint of improving the adhesion between the plastic layer and the cured film layer made of the composition. The polarizing plate obtained in this way has good scratch resistance due to the high hardness of the cured film layer.
Furthermore, since the film is made of acrylic urethane resin, it has excellent durability and thermal stability. Examples of the present invention will be shown below. Example A polarizing substrate was prepared by adhering a 100 μm thick uniaxially stretched (stretching ratio: 300%) polyester film to both sides of a 50 μm thick iodine polarizing film using a polyester adhesive. The composition shown in Table 1 was applied onto one film surface of this substrate using a spinner coater at a line speed of 10.
After drying at 100℃ for 3 minutes, UV irradiation was performed using two ozone-type high-pressure mercury lamps (80W/cm, 15cm condensing type) to create a cured film layer with an average coating thickness of 4μm. Got the board. The surface hardness of the film layer surface of each polarizing plate was measured using a JISK5401 paint film pencil scratch tester, and the surface hardness of the reference example before film formation was H.
Each of the examples had a hardness of 2 to 4H. Table 1 shows the composition (parts by weight) and measurement results. The light transmittance and degree of polarization in Table 1 were measured by conventional methods. 【table】

[Brief explanation of the drawing]

1 to 3 are partially enlarged side views showing examples of the polarizing plate of the present invention. 3...Cured film layer.

Claims (1)

[Claims] 1 A cured film made of a composition containing siligasol in an ultraviolet curable acrylic urethane resin is applied to the surface of the plastic layer of a polarizing base material formed by forming a plastic layer unstretched or stretched only in one direction on the surface of a polarizing film. A polarizing plate characterized by forming layers.