JP2001323238A - Pressure sensitive adhesive for optical member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pressure sensitive adhesive for optical members having an adhesive strength required in use and capable of easily releasing from the partner members in unnecessary cases. SOLUTION: This adhesive formed on the optical members to laminate the partner members therewith comprises, as a main component, a copolymer of a first 3-10C alkylactylate and a second >=12C alkylacrylate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an adhesive for an optical member.

[0002]

2. Description of the Related Art A panel of a liquid crystal display device is formed by bonding an optical member such as a polarizing plate or a wave plate to a transparent base material such as a glass substrate which encloses liquid crystal via an adhesive. For this reason, in the step of bonding to the transparent base material, the bonding position is likely to shift or a foreign substance is likely to be caught. When the displacement or the inclusion of foreign matter occurs as described above, the liquid crystal is not normally displayed, so that the optical member is peeled off and a new optical member of the same shape and the same quality is bonded to the transparent substrate.

[0003]

However, since the size of the liquid crystal display device has been increased and the thickness of the transparent substrate has been reduced,
When the above optical member such as a polarizing plate is peeled off, the adhesive force is so strong that a large force is required to peel it off, which may cause inconveniences such as poor workability. Further, when the force required for peeling is extremely large, there is a problem that the cell gap of the liquid crystal cell is changed, the display quality is reduced, and the liquid crystal cell is damaged.
Therefore, an object of the present invention is to steadily bond an optical member to a mating member, and to easily separate the optical member without damaging the mating member bonded to the optical member when peeling is necessary. To provide a pressure-sensitive adhesive that can be used.

[0004]

In order to solve the problem, the present invention relates to a pressure-sensitive adhesive formed on an optical member for laminating the optical member to another member. A first acrylic acid alkyl ester having 3 to 10 carbon atoms and an alkyl group having 1 carbon atom
It is a copolymer with two or more second acrylic acid alkyl esters.

In the present invention, since a long-chain alkyl group having 12 or more carbon atoms is introduced as a side chain of the main component polymer of the pressure-sensitive adhesive, the surface energy of the whole pressure-sensitive adhesive is reduced, and the peeling is reduced. A preferable monomer fraction of the second acrylic acid-based alkyl ester is 5% by weight or more. 5
If the amount is less than the percentage by weight, the effect of facilitating peeling is poor. Similarly, the preferred monomer fraction of the second acrylic acid-based alkyl ester is 60% by weight or less. If the content exceeds 60% by weight, the adhesive strength becomes poor. A suitable range of adhesion is 5-8 N / 25 mm.
Examples of the optical member include various polarizing plates such as a reflective polarizing plate, a transflective polarizing plate, and a polarization separating polarizing plate, a wave plate, and a laminate thereof.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Among the monomers constituting the main component polymer of the pressure-sensitive adhesive, an appropriate one can be used as the first acrylic acid-based alkyl ester, and is not particularly limited. Ester of acrylic acid or methacrylic acid having a linear alkyl group having 3 to 10 carbon atoms such as a group, butyl group, heptyl group, hexyl group, cyclohexyl group, 2-ethylhexyl group, octyl group, nonyl group, decyl group, etc. One or two of
More than one species is used.

The second alkyl ester is an acrylic or methacrylic acid ester having an alkyl group having 12 to 20 carbon atoms, such as a lauryl group, tridecyl group, tetradecyl group, stearyl group, octadecyl group and the like. One or two or more of these are used. The preferred content of the second acrylic acid-based alkyl ester is as described above.

[0008] Further, such as improvement of tackiness by introducing a functional group or a polar group, improvement of cohesive force and heat resistance by controlling the glass transition temperature of the formed copolymer, and increase of molecular weight by imparting crosslinking reactivity. Adhesive properties can be modified. Examples of such modifying means include acrylic acid and methacrylic acid, carboxyethyl acrylate and carboxypentyl acrylate, carboxyl group-containing monomers such as itaconic acid and maleic acid, fumaric acid and crotonic acid, and maleic anhydride and itaconic anhydride. Acid anhydride monomers,
Hydroxy group-containing monomers such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate and hydroxyhexyl (meth) acrylate can be used.

Further, (meth) acrylamide, N, N-
Dimethyl (meth) acrylamide, N-butyl (meth)
(N-substituted) amide monomers such as acrylamide and N-methylol (meth) acrylamide; alkylaminoalkyl (meth) acrylates such as aminoethyl (meth) acrylate and N, N-dimethylaminoethyl (meth) acrylate Monomers, alkoxyalkyl (meth) acrylate monomers such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate, N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide and N-phenylmaleimide A maleimide-based monomer or the like can also be used.

Further, N-methylitaconimide and N-methyl
Ethyl itaconimide, N-butyl itaconimide or N
-Itaconimide monomers such as octylitaconimide; succinimide monomers such as N- (meth) acryloyloxymethylene succinimide and N- (meth) acryloyl-6-oxyhexamethylene methylene succinimide; vinyl acetate and vinyl propionate;
Vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, N-vinylcarboxylic acid amides, styrene, α-methylstyrene, N- Vinyl monomers such as vinyl caprolactam can also be used.

In addition, cyanoacrylate monomers such as acrylonitrile and methacrylonitrile, epoxy group-containing acrylic monomers such as glycidyl (meth) acrylate, polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, (meth) Methoxyethylene glycol acrylate or (meth)
Use of glycol-based acrylic ester monomers such as methoxypropylene glycol acrylate, and acrylate-based monomers such as tetrahydrofurfuryl (meth) acrylate, fluorine (meth) acrylate, silicone (meth) acrylate and 2-methoxyethyl acrylate Can be.

In addition, divinylbenzene, butyl diacrylate, hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate and neopentyl glycol di (meth) acrylate Polyfunctional monomers such as acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, epoxy acrylate, polyester acrylate, urethane acrylate, etc. Can also be used.

The preparation of the acrylic polymer which is a copolymer of the above-mentioned monomers and is a main component of the pressure-sensitive adhesive is carried out, for example, by adding a mixture of the component monomers to a solution polymerization system, an emulsion polymerization system, a bulk polymerization system, a suspension polymerization system or the like. It can be performed by applying an appropriate method. The acrylic polymer that can be preferably used in the present invention has a weight average molecular weight of 100,000 or more, especially 200,000 or more, particularly 300,000 to 2 from the viewpoint of heat resistance and adhesive properties.
One million.

The pressure-sensitive adhesive can be crosslinked by an appropriate method such as an internal crosslinking method or an external crosslinking method. Generally, an external cross-linking method in which an intermolecular cross-linking agent is blended with an adhesive to perform a cross-linking treatment is employed. Examples of the intermolecular crosslinking agent include a polyfunctional isocyanate crosslinking agent and an epoxy crosslinking agent, a melamine resin crosslinking agent and a metal salt crosslinking agent, a metal chelate crosslinking agent and an amino resin crosslinking agent, and a peroxide crosslinking agent. Any suitable agent such as an agent can be used.

As a method for forming an adhesive layer (adhesive layer) on an optical member, for example, a base polymer or the like is dissolved or dispersed in a solvent such as toluene or ethyl acetate to prepare an acrylic adhesive of about 10 to 40% by weight. Prepare a liquid, and attach it directly on the protective substrate with an appropriate developing means such as casting or coating,
Alternatively, there is a method in which an adhesive layer is once formed on a release film and then transferred onto an optical member. The surface of the optical member on which the adhesive layer is provided may be subjected to an appropriate surface treatment such as a corona treatment for the purpose of improving the adhesion to the adhesive layer.

For the purpose of controlling the above-mentioned properties and adhesive strength, appropriate additives such as natural or synthetic resins for imparting tackiness and antioxidants are added to the pressure-sensitive adhesive layer, if necessary. be able to. The thickness of the adhesive layer can be appropriately determined according to the adhesive strength, the surface roughness of the optical member, and the like.
00 μm, especially 5 to 200 μm, especially 10 to 100 μm. On one or both sides of the optical member, an antistatic layer may be provided for the purpose of preventing static electricity during peeling.

The optical member to be used is, for example, a polarizing plate or a retardation plate, an elliptically polarizing plate or a reflective polarizing plate obtained by laminating them, a transflective polarizing plate or a reflective elliptically polarizing plate, or a semi-transmissive elliptically polarizing plate. And the like used for forming a liquid crystal panel, etc., and there is no particular limitation on the type. Therefore, the polarizing plate may be of a reflection type or a transflective type.
Also, the retardation plate may have an appropriate purpose such as a half-wave plate or a quarter-wave plate or 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.

Specific examples of the above 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. Further, the polarizing plate may have a transparent protective layer on one side or both sides of the polarizing film.

The reflection type polarizing plate is provided with a reflection layer on the polarizing plate, and is used to form a liquid crystal panel or the like of a type that reflects incident light from the viewing side (display side) to display. As a result, the incorporation of a light source such as a backlight can be omitted, and the liquid crystal panel can be made thinner. The reflective polarizing plate can be formed by an appropriate means such as providing a reflective layer made of metal or the like on one surface of the polarizing plate via a transparent protective layer or the like as necessary.

Specific examples of the reflective polarizing plate include a transparent protective layer that has been matted as required, 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 a transparent protective layer containing fine particles to form a fine surface uneven structure, and a reflective layer having a fine uneven structure 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. Is more preferable.

For the formation of the transparent protective layer in the above-mentioned polarizing plate, a polymer or the like having excellent transparency, mechanical strength, heat stability, moisture shielding property and the like is preferably used. Examples of such resins include polyester resins and acetate resins, polyethersulfone resins and polycarbonate resins,
Examples of the resin include a polyamide resin, a polyimide resin, a polyolefin resin, an acrylic resin, and a thermosetting resin such as an acrylic resin, a urethane resin, an acrylic urethane resin, an epoxy resin, or a silicone resin, or an ultraviolet curing resin.

On the other hand, as a specific example of the above-mentioned wave plate,
Birefringent film, liquid crystal polymer alignment film, liquid crystal polymer alignment film obtained by stretching a film made of an appropriate polymer such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene and other polyolefins, polyalate and polyamide. Is supported by a film. Examples of the wave plate include those having a phase difference depending on the intended use, such as those for the purpose of compensating for coloring due to birefringence of the liquid crystal layer and for compensating for a viewing angle such as expansion of a viewing angle, and the like. May be an obliquely oriented film in which is controlled. Further, two or more types of wave plates may be laminated to control optical characteristics such as a phase difference.

The above-mentioned inclined orientation film is heated, for example, by bonding a heat-shrinkable film to a polymer film and heating the film.
It can be obtained by a method of stretching or / and shrinking the polymer film by the shrinkage force, a method of obliquely aligning the liquid crystal polymer, or the like. The optical member is made of a material such as a laminate of the above-described elliptically polarizing plate, reflection type polarizing plate, and wavelength plate.
It may be composed of a layer or a laminate of three or more optical layers. Therefore, a reflective elliptically polarizing plate or a transflective elliptically polarizing plate obtained by combining a transflective polarizing plate and a wavelength plate may be used.

The optical member in which two or more optical layers are laminated can be formed by a method of sequentially laminating the optical members in a manufacturing process of a liquid crystal panel or the like. This has the advantage that the stability of quality, the workability of assembling, etc. are excellent and the production efficiency of liquid crystal panels and the like can be improved.

When the adhesive layer provided on the optical member is exposed on the surface, it is preferable to temporarily cover the adhesive layer with a release film for the purpose of preventing contamination and the like until the adhesive layer is put to practical use. The release film can be formed by providing a suitable sheet or film with a release agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide.

[0026]

EXAMPLES-Example-70 parts by weight of butyl acrylate (hereinafter, "weight" is omitted), 10 parts of stearyl acrylate, 20 parts of methyl acrylate and 1 part of acrylic acid were prepared by adding azobisisobutyronitrile 0.2 Parts as an initiator in 100 parts of ethyl acetate in about 6 parts.
By conducting a polymerization reaction at 0 ° C. for 8 hours, a solution of a polymer having a long-chain alkyl group in a side chain was obtained. 0.1 part of a tetrafunctional epoxy cross-linking agent (trade name: Tetrad C, manufactured by Mitsubishi Gas Chemical Co., Ltd.) was added to this acrylic polymer solution per 100 parts of the solid content to prepare an adhesive syrup.

Separately, a polyvinyl alcohol was stretched 5 times in an aqueous iodine solution and then dried, and a triacetyl cellulose film was adhered to both surfaces via an adhesive to produce a polarizing plate. The above adhesive syrup was applied to one surface of the polarizing plate and dried to form an adhesive layer having a thickness of 25 μm.

Comparative Example 80 parts of butyl acrylate, 20 parts of methyl acrylate and 1 part of acrylic acid were used as initiators in 0.2 part of azobisisobutyronitrile in 100 parts of ethyl acetate at about 60 ° C. for 8 hours. A polymer solution was obtained by the polymerization reaction. Others were the same as in Example 1.

[Evaluation Test] The polarizing plate with the above-mentioned adhesive layer was tested for 2
Cut out to a width of 5 mm, bonded to a 0.7 mm thick non-alkali glass plate, and placed in an autoclave at 50 ° C.
It was kept at 0.49 MPa for 15 minutes. Then, using a tensile tester, a tensile speed of 300 mm / min. The polarizing plate was peeled off from the glass plate at a pulling angle of 90 °. The force required for peeling is shown in Table 1 as the adhesive force. Also,
Ten sheets of the polarizing plate with the adhesive layer were cut out to a size of 300 mm × 200 mm, respectively, attached to the glass plate, peeled off from the corners, and the time required for peeling was measured. At this time, it was confirmed whether troubles such as lifting of the glass plate itself occurred during the work. Table 1 shows the results of these evaluations.

[0030]

[Table 1]

As can be seen from the results shown in Table 1, since the main component polymer of the pressure-sensitive adhesive has a long-chain alkyl group in the side chain, the workability when peeling off the polarizing plate is excellent, and the adhesion to the polarizing plate is improved. The glass plate that has been used can be kept clean even after the polarizer is peeled off.

[0032]

As described above, the pressure-sensitive adhesive of the present invention can improve the efficiency of the peeling operation of the optical member and can eliminate the damage to the partner member, thereby reducing the production efficiency and the cost of the liquid crystal display device and the like. Greatly contributes to

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor: Nei Takahashi 1-1-2, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor: Tomomori Masada 1-2-1, Shimohozumi, Ibaraki-shi, Osaka No. Nitto Denko F-term (reference) 2H049 BA02 BA04 BA06 BB51 BB54 BC14 2H091 FA08X FA08Z FA11X FA11Z GA17 LA02 LA07 4J040 DF041 JA05 JA12 JB09 KA23 LA01 LA06 MA02 MA05 MA10 NA17 NA19

Claims (5)

[Claims] 1. A pressure-sensitive adhesive formed on an optical member for bonding an optical member to another member, wherein the main component polymer is a first acrylic acid alkyl ester having an alkyl group having 3 to 10 carbon atoms. And a second acrylic acid-based alkyl ester having 12 or more carbon atoms in the alkyl group. 2. The pressure-sensitive adhesive according to claim 1, wherein the second acrylic acid alkyl ester has a monomer fraction of 5% by weight or more. 3. The pressure-sensitive adhesive according to claim 1, wherein a monomer fraction of the second acrylic acid alkyl ester is 60% by weight or less. 4. The pressure-sensitive adhesive according to claim 1, which has a pressure-sensitive adhesive strength of 5 to 8 N / 25 mm. 5. The optical member according to claim 1, wherein the optical member is any one of various polarizing plates such as a reflective polarizing plate, a semi-transmissive polarizing plate, a polarized light separating polarizing plate, a wave plate, and a laminate thereof. A pressure-sensitive adhesive as described in Crab.