JP2000171634A - Adhesive optical member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an adhesive optical member that does not generate any optical abnormality such as uneven brightness. SOLUTION: The adhesive optical member comprises an adhesive layer 3, which is located on the front surface of one or both sides of an optical member 2, temporally covered with a separator 4 composed of a polyester film containing low molecular weight oligomers, with <=1,000 molecular weight, equal to or less than 1.5 wt.%. Thereby generation of transparent crystals at the adhesive layer 3 due to migration of components of the separator 4, and generation of luminescent points or the like due to abnormality of refractive index are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive optical member having excellent stability of optical characteristics.

[0002]

BACKGROUND ART Optical members used in a liquid crystal display (LCD), such as a polarizing plate, a retardation plate, and an elliptically polarizing plate obtained by laminating them, are key devices of the LCD and prevent variations in quality and increase the efficiency of LCD assembly. For the purpose, etc., it is used for transportation and assembling work as an adhesive type optical member in which an adhesive layer made of an acrylic adhesive or the like for bonding to another member such as a liquid crystal cell is attached to the outermost surface in advance. . In this case, if the adhesive layer provided on the outermost surface is left exposed, contaminants which cause a decrease in adhesive strength or impaired visibility are likely to adhere to the adhesive layer. Measures have been taken.

Heretofore, as the separator, a separator obtained by subjecting a polyester film to a surface treatment with a release agent has been known. However, when it is temporarily attached to an adhesive layer provided on an optical member, transported or stored, and then the separator is peeled off and adhered to a liquid crystal cell or the like, optical abnormalities such as uneven brightness due to bright spots occur. There was a problem to do.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to develop an adhesive optical member which does not cause optical abnormalities such as uneven brightness.

[0005]

According to the present invention, an adhesive layer provided on one or both outermost surfaces of an optical member comprises a polyester film in which the content of a low molecular oligomer having a molecular weight of 1,000 or less is 1.5% by weight or less. An object of the present invention is to provide a pressure-sensitive adhesive optical member which is temporarily covered with a separator.

[0006]

According to the present invention, even if the separator is peeled off and adhered to a liquid crystal cell or the like after being temporarily attached to the adhesive layer provided on the optical member and transported or stored, luminance unevenness due to a luminescent spot or the like is obtained. And an adhesive optical member exhibiting stable optical characteristics without causing optical abnormality. This is due to the use of the separator having the features described above.

That is, the inventors of the present invention have conducted intensive studies on the members forming the adhesive optical member in order to overcome the above-mentioned problem of optical abnormalities such as bright spots. The present inventors have clarified that this is a problem peculiar to the optical application caused by the transparent crystal generated in the above, and furthermore, that the transparent crystal is based on the components forming the separator, and have reached the above-mentioned present invention.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The pressure-sensitive adhesive optical member according to the present invention is characterized in that the pressure-sensitive adhesive layer provided on the outermost surface on one or both sides of the optical member is prepared by reducing the content of low molecular oligomers having a molecular weight of 1,000 or less to 1.5.
It is made by temporarily covering with a separator made of a polyester film having a weight percent or less. An example is shown in FIG. 2 is an optical member, 3 is an adhesive layer, 4 is a separator, and 1 is a protective film as required.

As the optical member, for example, a polarizing plate, a retardation plate, an elliptically polarizing plate obtained by laminating the polarizing plate, an appropriate member used for forming a liquid crystal display device or the like can be used, and the type thereof is not particularly limited. Therefore, the polarizing plate may be a reflection type or the like. Also, the phase difference plate is や or ４
It may have an appropriate purpose, such as a wave plate such as that described above, and viewing angle compensation. In the case of a laminated optical member such as the above-mentioned elliptically polarizing plate, the lamination may be performed through an appropriate bonding means such as an adhesive layer.

Incidentally, specific examples of the above-mentioned polarizing plate include iodine and / or iodine on a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, and an ethylene / vinyl acetate copolymer-based partially saponified film. Examples thereof include a film obtained by adsorbing a dichroic dye and stretching, a polarizing film made of a polyene oriented film such as a dehydrated product of polyvinyl alcohol and a dehydrochlorinated product of polyvinyl chloride. The thickness of the polarizing film is usually 5 to 80 μm, but is not limited thereto. The polarizing film may have a transparent protective layer such as a protective film on one or both sides.

On the other hand, the reflection type polarizing plate is provided with a reflection layer on the polarizing plate, and is used to form a liquid crystal display device or the like of a type that reflects incident light from the viewing side (display side) to display. In addition, there is an advantage that a built-in light source such as a backlight can be omitted, and the thickness of the liquid crystal display device can be easily reduced.

The reflection type polarizing plate can be formed by an appropriate method such as a method in which a reflecting layer made of metal or the like is provided on one side of the polarizing plate via a transparent protective layer or the like, if necessary.
The above-mentioned polarizing plate, in particular, the transparent protective layer provided on one or both sides of the polarizing film as required can also serve as the protective film 1 as shown in the figure.

Specific examples of the reflective polarizing plate include a transparent protective layer that is matted if necessary, and a reflective layer formed by attaching a foil or a vapor-deposited film made of a reflective metal such as aluminum to one surface of the transparent protective layer. can give. Further, there may be mentioned, for example, those in which fine particles are contained in the transparent protective layer to form a fine surface uneven structure, and a reflective layer having a fine uneven structure is provided thereon. The reflective layer is used in a state where the reflective surface is covered with a transparent protective layer, a polarizing plate, or the like, in order to prevent a decrease in reflectance due to oxidation, and to maintain the initial reflectance for a long period of time, and to separately provide a protective layer. Is more preferable.

The reflective layer having the above-mentioned fine uneven structure has an advantage that the incident light is diffused by irregular reflection to prevent directivity and glare, and to suppress uneven brightness.
Further, the transparent protective layer containing fine particles also has an advantage that the incident light and the reflected light thereof are diffused when transmitting the light and the unevenness of light and darkness can be further suppressed. The reflective layer having a fine uneven structure reflecting the fine uneven structure on the surface of the transparent protective layer is formed by, for example, making the metal transparent by an appropriate method such as an evaporation method such as a vacuum evaporation method, an ion plating method, or a sputtering method, or a plating method. It can be performed by a method of directly attaching to the surface of the protective layer.

The formation of the above-mentioned protective film or a transparent protective layer on a polarizing plate, which is disposed as necessary for the purpose of protecting the surface of the optical member, etc., requires transparency, mechanical strength, thermal stability, and moisture shielding. Polymers having excellent properties and the like are preferably used. Examples thereof include polyester resins and acetate resins, polyethersulfone resins and polycarbonate resins, polyamide resins and polyimide resins, polyolefin resins and acrylic resins, or acrylic, urethane and acrylic urethane resins. And thermosetting resins such as epoxy resins and silicone resins, and ultraviolet curing resins.

The transparent protective layer may be formed by an appropriate method such as a method of applying a polymer or a method of laminating a film, and the thickness may be appropriately determined. Generally 500 μm
Hereinafter, the thickness is preferably 1 to 300 μm, particularly 5 to 200 μm. The fine particles to be included in the formation of the transparent protective layer having the fine surface uneven structure include, for example, an average particle size of 0.5 to 5
Transparent inorganic fine particles of 0 μm silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, and the like, and organic fine particles of a crosslinked or uncrosslinked polymer, etc. Fine particles are used. The amount of fine particles used is 1
It is generally 2 to 50 parts by weight, especially 5 to 25 parts by weight, per 100 parts by weight.

On the other hand, as a specific example of the above retardation plate, a film made of an appropriate polymer such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene, other polyolefin, polyarylate, or polyamide is stretched. Birefringent film or liquid crystal polymer oriented film,
Examples thereof include a film in which an alignment layer of a liquid crystal polymer is supported by a film. The retardation plate may have an appropriate retardation according to the purpose of use such as, for example, various wavelength plates or those intended for compensation of a viewing angle or the like due to birefringence of a liquid crystal layer, and may have two or more types. A retardation plate may be laminated to control optical characteristics such as retardation.

The above-mentioned elliptically polarizing plate or reflection type elliptically polarizing plate is obtained by laminating a polarizing plate or a reflection type polarizing plate and a retardation plate in an appropriate combination. Such an elliptically polarizing plate or the like can also be formed by sequentially and separately laminating a (reflection type) polarizing plate and a retardation plate in a manufacturing process of a liquid crystal display device so as to form a combination. An optical member such as a polarizing plate has an advantage that the stability of quality and laminating workability are excellent and the production efficiency of a liquid crystal display device or the like can be improved.

The adhesive layer provided on one or both outermost surfaces of the optical member is for bonding to another member such as a liquid crystal cell. For the formation thereof, for example, an adhesive substance or an adhesive having an appropriate polymer such as an acrylic polymer or a silicone-based polymer, a polyester or a polyurethane, a polyamide or a polyether, a fluorine-based or a rubber-based polymer as a base polymer can be used. There is no particular limitation. In particular, those having excellent optical transparency, such as acrylic pressure-sensitive adhesives, exhibiting appropriate wettability, cohesiveness and adhesiveness and exhibiting excellent weatherability and heat resistance can be preferably used.

In addition, in addition to the above, prevention of foaming and peeling phenomena due to moisture absorption, prevention of deterioration of optical characteristics due to differences in thermal expansion, prevention of liquid crystal cell warpage, and formation of a liquid crystal display device having high quality and excellent durability. In view of the above, an adhesive layer having a low moisture absorption rate and excellent heat resistance is preferable.

The adhesive layer is made of, for example, natural or synthetic resins, especially, tackifier resins, fillers, pigments, coloring agents, oxidizing agents, and the like comprising glass fibers, glass beads, metal powders, and other inorganic powders. It may contain an appropriate additive such as an inhibitor which may be added to the adhesive layer. Further, an adhesive layer containing fine particles and exhibiting light diffusibility may be used.

The attachment of the adhesive layer to one or both sides of the optical member can be performed by an appropriate method. By the way, as an example,
For example, an adhesive substance or a composition thereof is dissolved or dispersed in a solvent composed of an appropriate solvent alone or a mixture of appropriate solvents such as toluene and ethyl acetate to prepare an adhesive liquid of about 10 to 40% by weight, and it is cast. Examples thereof include a method in which the adhesive layer is directly provided on the optical member by an appropriate development method such as a method or a coating method, or a method in which an adhesive layer is formed on a separator and transferred to the optical member in accordance with the above.

The adhesive layer may be provided on one or both sides of the optical member as a superposed layer of different compositions or types. When the optical member is provided on both sides, an adhesive layer having a different composition, type, thickness, and the like may be formed on the front and back surfaces of the optical member. The thickness of the pressure-sensitive adhesive layer can be appropriately determined depending on the purpose of use, adhesive strength, and the like, and is generally 1 to 500 μm, preferably 5 to 20 μm.
0 μm, especially 10 to 100 μm.

The separator 4 is temporarily attached to the exposed surface of the adhesive layer for the purpose of preventing contamination or the like until it is put to practical use as shown in the figure, and covered. In the present invention, as the separator, a separator made of a polyester film in which the content of a low molecular oligomer having a molecular weight of 1,000 or less is 1.5% by weight or less is used. As a result, it is possible to prevent optical abnormalities such as bright spots from occurring.

That is, the occurrence of a luminescent spot or the like by a conventional polyester film separator is limited to a molecular weight of 1,000.
The following dimer to pentamer, particularly a low molecular oligomer composed of the lower polymer, is heated at a heating temperature, for example, when a pressure-sensitive adhesive is applied to the above-described separator and dried to form a pressure-sensitive adhesive layer, particularly at a high temperature. Bleeds into the surface or inside of the adhesive layer made of acrylic or the like, which precipitates and crystallizes under the satisfaction of saturation conditions and the like, which becomes an abnormal point of the refractive index.

Therefore, by forming the separator from a polyester film in which the content of the low molecular oligomer having a molecular weight of 1000 or less is 1.5% by weight or less, the transfer of the low molecular oligomer to the adhesive layer can be suppressed, and Can be prevented from being precipitated, and crystallization as an abnormal point of the refractive index which causes an optical abnormality such as a bright point can be avoided. The content of the low molecular oligomer in the polyester film can be adjusted by an appropriate method such as a solvent extraction method or a heating method.

As the separator, a polyester film in which the content of a low molecular oligomer having a molecular weight of 1000 or less is 1.5% by weight or less is appropriately peeled off from a silicone-based or long-chain alkyl-based, fluorine-based or molybdenum sulfide as needed. It can be formed by an appropriate method according to the related art, such as a method of performing a surface treatment with an agent. The thickness of the separator is 5 to 30
0 μm is common, but not limited to this.

In the present invention, the respective layers such as a polarizing plate and a retardation plate, a protective film and a transparent protective layer, and an adhesive layer which form the above-mentioned optical member are formed of, for example, a salicylate compound, a benzophenol compound, a benzophenol compound or a benzophenol compound. A compound having an ultraviolet absorbing ability by an appropriate method such as a method of treating with an ultraviolet absorbent such as a triazole compound, a cyanoacrylate compound, or a nickel complex compound may be used.

The adhesive optical member according to the present invention can be preferably used for forming various devices such as a liquid crystal display device.

[0030]

EXAMPLES Example 1 The content of a low molecular oligomer having a molecular weight of 1,000 or less was determined as follows.
A 20% by weight toluene solution of an acrylic pressure-sensitive adhesive is applied to a release coating surface of a separator obtained by providing a surface coating of a silicone-based release agent on a PET film having a thickness of 2% by weight and a thickness of 50 μm, and dried at 180 ° C. for 5 minutes. Processing and thickness 20
Forming an acrylic adhesive layer of μm, bonding it to one side of a polarizing plate of 180 μm thickness provided with a transparent protective layer on both sides of the polarizing film together with its separator, and bonding the protective film to the other side of the polarizing plate An adhesive optical member was obtained.

Comparative Example The content of a low molecular oligomer having a molecular weight of 1,000 or less was 1.
A separator was formed in the same manner as in Example 1 except that a 7 wt% PET film was used, and an adhesive optical member was obtained using the separator.

Evaluation Test The adhesive optical members obtained in Examples and Comparative Examples were adhered to both sides of a glass plate in a crossed Nicols state via an adhesive layer from which the separator was peeled off, and visually observed. As a result, optically abnormal portions such as bright spots were not observed in Example 1, but optically abnormal portions such as bright spots were observed in Comparative Example.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of an optical member.

[Explanation of symbols]

1: protective film 2: optical member 3: adhesive layer
4: Separator

Continued on front page F-term (reference) 2H049 BA02 BA04 BA06 BB44 BB51 BB54 BB63 BC22 4F100 AK25B AK25D AK41C AK41E AK41K AR00B AR00C AR00D AR00E AT00A BA03 BA05 BA06 BA07 BA10C BA10E CC00B CC20D GB51L J90L GBJL J90L YY00E

Claims (2)

[Claims] An adhesive layer provided on one or both outermost surfaces of an optical member is temporarily attached to a separator made of a polyester film in which the content of a low molecular oligomer having a molecular weight of 1,000 or less is 1.5% by weight or less. An adhesive optical member, which is covered. 2. The adhesive optical member according to claim 1, wherein the optical member has at least a polarizing plate or a retardation plate.