JP5478900B2 - Light diffusable pressure-sensitive adhesive composition, light diffusable pressure-sensitive adhesive layer, and light diffusable pressure-sensitive adhesive sheet - Google Patents

Description

  The present invention relates to a light diffusing pressure-sensitive adhesive composition. Moreover, this invention relates to the light diffusable adhesive layer formed with the said adhesive composition, and a light diffusable adhesive sheet using the same.

  As a backlight light source of a liquid crystal display, a cold cathode fluorescent lamp (CCFL) is used, or recently a light emitting diode (LED) is used. However, CCFL has a linear shape and an LED has a dot shape. The transmitted light is not uniform. Therefore, a light diffusing (adhesive) sheet is used to make the light emitted from the light source uniform and flat and take out the transmitted light.

  When a non-adhesive light diffusing sheet is used, light loss due to the air layer increases due to a gap with the optical member. Therefore, it is desirable to provide an adhesive layer. However, an increase in the number of processes causes an increase in cost. Therefore, it is preferable to provide a light diffusion function to the pressure-sensitive adhesive.

  As a method for imparting light diffusivity, a method of applying a paint mixed with a light-transmitting diffusing material has also been proposed (Patent Document 1). There is a problem because it requires materials.

  As a method for obtaining a light diffusing sheet having adhesiveness, a method of adding various fine particles to an adhesive is generally employed.

  That is, the adoption of a light diffusing adhesive (Patent Document 2) in which the difference in refractive index between the pressure-sensitive adhesive matrix and the organic polymer fine particles is 0.01 to 0.2, and a filler having a different refractive index is used as the adhesive. And a method of adding (Patent Document 3).

  There is also a description that it is important to control the tensile modulus of elasticity in a light-transmitting diffusion pressure-sensitive adhesive in which transparent uncolored particles are added to the pressure-sensitive adhesive (Patent Document 4).

  In addition, a method of adding silicone resin fine particles to an acrylic pressure-sensitive adhesive (Patent Document 5), a method of adding needle-like fillers having different refractive indices to the pressure-sensitive adhesive (Patent Document 6), and an acrylic copolymer made of a fluororesin There is a method of adding fine particles (Patent Document 7).

  As described above, a method for obtaining a light diffusion adhesive by adding fine particles to an adhesive is widely used. However, in order to uniformly disperse the particles in the adhesive, it is necessary to combine the adhesive with the adhesive. The balance of adhesion is important. If the addition amount of the fine particles is simply increased in order to increase the haze, the adhesiveness is deteriorated and peeling from the adherend is caused, resulting in a problem.

JP-A-11-160505 Japanese National Patent Publication No. 11-508622 JP-A-11-223712 Japanese Patent No. 3908934 JP 2002-122714 A JP 2004-258105 A JP 2006-348208 A

  An object of this invention is to provide the light diffusable adhesive composition which has a light diffusibility, without an additive.

  Moreover, an object of this invention is to provide the light diffusable adhesive sheet which has the light diffusable adhesive layer formed with the said light diffusable adhesive composition, and the said light diffusable adhesive layer.

  In order to achieve the above-mentioned object, the present inventors diligently studied the constitution of the pressure-sensitive adhesive composition. As a result, the following light-diffusible pressure-sensitive adhesive composition, light-diffusible pressure-sensitive adhesive layer, and light-diffusible pressure-sensitive adhesive sheet As a result, the present invention has been completed.

The present invention is, with respect to (meth) acrylic polymer (A), radical polymerization refractive index n _b when the homopolymer is larger than the refractive index n _a of the (meth) acrylic polymer (A) A light diffusable pressure-sensitive adhesive composition comprising a modified (meth) acrylate copolymer (B) obtained by blending and polymerizing a polymerizable monomer; and a crosslinking agent,
Provided is a light diffusable pressure-sensitive adhesive composition having a haze value of 30% or more when a pressure-sensitive adhesive layer having a thickness of 20 μm is formed.

In the light diffusing pressure-sensitive adhesive composition, the difference between the _{n b} and _{n a (n} b -n _a) is preferably in the range of 0.02 to 0.2.

  In the light diffusible pressure-sensitive adhesive composition, the modified (meth) acrylate copolymer (B) is used in an amount of 5 to 100 radical polymerizable monomers based on 100 parts by weight of the (meth) acrylic polymer (A). It is preferably obtained by blending parts by weight and polymerizing.

  In the light diffusing pressure-sensitive adhesive composition, the (meth) acrylic polymer (A) preferably contains a monomer having a hydroxyl group as a monomer unit.

  The present invention also provides a light diffusable pressure-sensitive adhesive layer obtained by crosslinking one of the above light diffusable pressure-sensitive adhesive compositions.

  In the light diffusable pressure-sensitive adhesive layer, the gel fraction is preferably 30 to 95% by weight.

  The present invention also provides a light diffusable pressure-sensitive adhesive sheet in which any one of the above light diffusable pressure-sensitive adhesive layers is formed on one side or both sides of an optical member.

  The light diffusable pressure-sensitive adhesive composition of the present invention has a balanced property that is excellent in both light diffusibility and adhesiveness required to make the light emitted from the light source uniform and flat and take out the transmitted light. It can be demonstrated. Further, even when no particles are added, a high haze value and stickiness can be maintained.

  Hereinafter, embodiments of the present invention will be described in detail.

The pressure-sensitive adhesive composition of the present invention, (meth) acrylic polymer to (A), the refractive index n _b when the homopolymer than the refractive index n _a of the (meth) acrylic polymer (A) A light diffusable pressure-sensitive adhesive composition comprising a modified (meth) acrylate copolymer (B) obtained by blending and polymerizing a radically polymerizable monomer that is also large, and a crosslinking agent. And
The haze value when a pressure-sensitive adhesive layer having a thickness of 20 μm is 30% or more.

Here, as a monomer unit constituting the (meth) acrylic polymer (A), a general formula CH ₂ = C (R ¹ ) COOR ² (where R ¹ is hydrogen or a methyl group, and R ² is optionally substituted) A monomer having 2 to 14 carbon atoms which may be present) can be used.

  Specific examples of such (meth) acrylic monomers include, for example, ethyl (meth) acrylate, n-butyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, and isobutyl. (Meth) acrylate, n-pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, isoamyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl ( (Meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-dodecyl (meth) acrylate, isomyristi (Meth) acrylate, n- tridecyl (meth) acrylate, n- tetradecyl (meth) acrylate, etc. phenoxyethyl (meth) acrylate. Of these, one type may be used alone, or two or more types may be used in combination.

  In addition to such a (meth) acrylic monomer, a modifying monomer that can be copolymerized therewith and that improves adhesive properties and heat resistance may be used in combination. In this case, in order to obtain good adhesive properties, the above-mentioned modifying monomer is 50% by weight or less, preferably 30% by weight or less, more preferably 20% by weight or less of the entire (meth) acrylic monomer. Like that.

  Examples of such adhesive and heat resistance modifying monomers include monomers containing unsaturated carboxylic acids such as (meth) acrylic acid, itaconic acid, maleic acid, (meth) acrylamide, mono- or diesters of maleic acid, N, N -Dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N-vinylpyrrolidone, acrylonitrile, (meth) acryloylmorpholine and the like. In the above polymer preparation, it is also possible to copolymerize styrene monomers such as styrene, α-methylstyrene, and 2,4-dimethylstyrene.

  As a monomer for introducing a crosslinkable functional group, a hydroxyl group-containing monomer, that is, a hydroxyl group-containing (meth) acrylate is preferably included. As such a monomer, those having a polymerizable functional group having an unsaturated double bond of a (meth) acryloyl group and having a hydroxyl group can be used without particular limitation. Examples of the hydroxyl group-containing (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxy. Hexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, hydroxyalkyl (meth) acrylate such as 12-hydroxylauryl (meth) acrylate; hydroxyethyl (meth) acrylamide, etc. (4-hydroxymethylcyclohexyl) methyl acrylate, N-methylol (meth) acrylamide, N-hydroxy (meth) acrylamide; polyoxypropylene (meth) acrylate, cap Lactone-modified (meth) acrylate and the like. Of these, preferably hydroxyalkyl acrylate, more preferably 4-hydroxybutyl acrylate.

  The hydroxyl group-containing (meth) acrylate is 3% by weight or less, preferably 0.01 to less than the total amount of monomer components forming the (meth) acrylic copolymer (A) in order to obtain good adhesive properties. It is preferably used at a ratio of 2% by weight, more preferably 0.02 to 1.8% by weight. When the content is 3% by weight or less, the crosslinking density is not excessively increased and is appropriately maintained, and the stress relaxation property is also maintained. Moreover, if content is 0.01 weight% or more, the reactivity with a crosslinking agent will be hold | maintained and durability will also become favorable.

  The (meth) acrylic polymer (A) is an acrylic ester having an alkyl group having 4 to 12 carbon atoms such as butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, and isononyl acrylate. The refractive index is usually in the range of 1.46 to 1.47, and by copolymerizing the modifying monomer, the refractive index of the (meth) acrylic polymer (A) depends on the copolymerization ratio. fluctuate. Preferred na is in the range of 1.46 to 1.48.

  The weight average molecular weight of the (meth) acrylic polymer (A) is preferably 500,000 or more, more preferably 600,000 to 3,000,000, and further preferably 700,000 to 2,500,000. When the weight average molecular weight is less than 500,000, durability may be poor. On the other hand, from the viewpoint of workability, the weight average molecular weight is preferably 3 million or less. The weight average molecular weight is a value measured by GPC (gel permeation chromatography) and calculated in terms of polystyrene.

  For the production of such a (meth) acrylic polymer (A), known production methods such as solution polymerization, bulk polymerization, emulsion polymerization, and various radical polymerizations can be appropriately selected. Further, the (meth) acrylic polymer (A) to be obtained may be any of a random copolymer, a block copolymer, a graft copolymer and the like.

  In solution polymerization, for example, ethyl acetate, toluene or the like is used as a polymerization solvent. As a specific example of solution polymerization, the reaction is carried out under an inert gas stream such as nitrogen, as a polymerization initiator, for example, azobisisobutyronitrile 0.01 to 0.2 parts per 100 parts by weight of the total amount of monomers. Addition of parts by weight is usually performed at about 50 to 70 ° C. for about 8 to 30 hours.

  The polymerization initiator, chain transfer agent, emulsifier and the like used for radical polymerization are not particularly limited and can be appropriately selected and used.

  Examples of the polymerization initiator used in the present invention include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis [2- ( 5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis (2-methylpropionamidine) disulfate, 2,2′-azobis (N, N′-dimethyleneisobutylamidine) ), 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate (manufactured by Wako Pure Chemical Industries, Ltd., VA-057), azo initiators, potassium persulfate, ammonium persulfate Persulfate such as di (2-ethylhexyl) peroxydicarbonate, di (4-t-butylcyclohexyl) peroxydicarbonate Di-sec-butylperoxydicarbonate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t-butylperoxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di (4-methylbenzoyl) peroxide, dibenzoyl peroxide, t-butylperoxyisobutyrate, 1,1-di ( t-hexylperoxy) peroxide such as cyclohexane, t-butyl hydroperoxide, hydrogen peroxide and other peroxide initiators, a combination of persulfate and sodium bisulfite, a combination of peroxide and sodium ascorbate Redox initiators that combine products and reducing agents Kill, but is not limited to these.

  The polymerization initiator may be used alone or in combination of two or more, but the total content is 0.005 to 1 part by weight with respect to 100 parts by weight of the monomer. Is preferably about 0.02 to 0.5 parts by weight.

  In addition, when a peroxide is used as a polymerization initiator, it is possible to use the remaining peroxide for the crosslinking reaction without being used in the polymerization reaction. If necessary, it can be added again and used in a predetermined amount of peroxide.

  In the present invention, a chain transfer agent may be used in the polymerization. By using a chain transfer agent, the molecular weight of the (meth) acrylic polymer (A) can be appropriately adjusted.

  Examples of the chain transfer agent include lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol.

  These chain transfer agents may be used alone or in admixture of two or more, but the total content is 0.01-0. About 1 part by weight.

  Examples of the emulsifier used in emulsion polymerization include anionic emulsifiers such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, ammonium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, and polyoxy Nonionic emulsifiers such as ethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, and polyoxyethylene-polyoxypropylene block polymer are listed. These emulsifiers may be used alone or in combination of two or more.

  Furthermore, as reactive emulsifiers, as emulsifiers into which radical polymerizable functional groups such as propenyl groups and allyl ether groups are introduced, specifically, for example, Aqualon HS-10, HS-20, KH-10, BC-05 BC-10, BC-20 (all of which are manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Adekaria soap SE10N (manufactured by Asahi Denka Kogyo Co., Ltd.), and the like. Reactive emulsifiers are preferable because they are incorporated into the polymer chain after polymerization and thus have improved water resistance. The amount of the emulsifier used is more preferably 0.3 to 5 parts by weight and 0.5 to 1 part by weight with respect to 100 parts by weight of the monomer in view of polymerization stability and mechanical stability.

Further, the modified (meth) acrylic polymer (B) of the present invention, the (meth) acrylic polymer to (A), the refractive index n _b of the homopolymer (meth) acrylic polymer (A ) is obtained by polymerizing by blending a radical polymerizable monomer such as larger than the refractive index n _a of.

The radical polymerizable monomer is a main chain (meth) than the refractive index n _a of the acrylic polymer (A) domain, be used as appropriate as long as the monomer, such as refractive index n _b of the homopolymer is higher it can. Among these, a monomer having an aromatic group is preferable because it has a high refractive index of 1.51 to 1.6. These may be used singly or in combination of two or more.

  Examples of the (meth) acrylic monomer having an aromatic group include styrene monomers such as styrene and α-methylstyrene, vinyltoluene monomers such as vinyltoluene and αvinyltoluene, benzyl (meth) acrylate, Examples include naphthyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxybutyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl acrylate, phenoxypolyethylene glycol acrylate, and the like. In order to increase the refractive index, a monomer substituted with bromine can be used.

  Here, the radical polymerizable monomer is added in an amount of 5 to 100 parts by weight, more preferably 5 to 90 parts by weight with respect to 100 parts by weight of the (meth) acrylic polymer (A). A modified (meth) acrylate copolymer can be obtained by adjusting the product and medium and further conducting a polymerization reaction.

  As a polymerization method of the radical polymerizable monomer, in the case of solution polymerization, after adding a necessary monomer and a solvent whose viscosity is adjusted to a solution of the (meth) acrylic polymer (A), and substituting with nitrogen. And a method of adding a polymerization initiator such as 2,2′-azobisisobutyronitrile and dibenzoyl peroxide and heating at 50 ° C. to 80 ° C. for 4 to 15 hours to terminate the reaction. it can. If it is emulsion polymerization, water for adjusting the solid content is added to the aqueous dispersion of the (meth) acrylic polymer (A), the necessary monomer is further added, and nitrogen substitution is performed while stirring. Then, after the monomer is absorbed into the (meth) acrylic polymer particles, an aqueous solution such as a water-soluble azo compound or ammonium persulfate is added, and the reaction is performed by heating at 50 to 80 ° C. for 4 to 15 hours. The method of ending can be given.

  In the case of using a radically polymerizable monomer having an aromatic group, if the amount of the monomer having an aromatic group is decreased, the compatibility with the tackifier is lowered, and when the tackifier is blended, it becomes cloudy, which is not preferable. On the other hand, if the amount of the monomer having an aromatic group is too large, the adhesive property is lowered, which is not preferable.

  The pressure-sensitive adhesive composition of the present invention comprises the modified (meth) acrylic copolymer (B) as described above as a base polymer.

In the present invention, (meth) than the refractive index n _a of the acrylic polymer, a large refractive index n _b of the homopolymer. Preferably, (n _b −n _a ) is in the range of 0.02 to 0.2, more preferably in the range of 0.03 to 0.18. When (n _b −n _a ) is in the range of 0.02 to 0.2, the light diffusibility of the obtained pressure-sensitive adhesive composition is surely ensured, and unevenness of transmitted light hardly occurs.

  The light diffusive mechanism is that the domain of the polymer of the radical polymerizable monomer formed in the modified (meth) acrylic polymer (B) has a difference in refractive index from the main chain, so that the light diffusibility is expressed. It is guessed that it will do.

  The refractive index in the present invention is a value measured with an Abbe refractometer (DR-M2 manufactured by ATAGO) by irradiating sodium D-line in an atmosphere at 25 ° C.

  The pressure-sensitive adhesive composition of the present invention is characterized by containing a crosslinking agent.

  A peroxide can be illustrated as a crosslinking agent of this invention. As the peroxide, any radical active species can be used as long as it generates radical active species by heating or light irradiation to advance the crosslinking of the base polymer of the pressure-sensitive adhesive composition. However, in consideration of workability and stability. It is preferable to use a peroxide having a one-minute half-life temperature of 80 ° C. to 160 ° C., and more preferable to use a peroxide having a 90 ° C. to 140 ° C. If the half-life temperature for 1 minute is too low, the reaction proceeds at the time of storage before coating and drying, and the viscosity may become high and the coating may become impossible. On the other hand, if the half-life temperature is too high, Since the temperature becomes high, side reactions occur, and a large amount of unreacted peroxide remains, which may cause cross-linking over time.

  Examples of the peroxide used in the present invention include di (2-ethylhexyl) peroxydicarbonate (1 minute half-life temperature: 90.6 ° C.), di (4-t-butylcyclohexyl) peroxydicarbonate ( 1 minute half-life temperature: 92.1 ° C.), di-sec-butyl peroxydicarbonate (1 minute half-life temperature: 92.4 ° C.), t-butyl peroxyneodecanoate (1 minute half-life temperature: 103.5 ° C.), t-hexyl peroxypivalate (half-life temperature for 1 minute: 109.1 ° C.), t-butyl peroxypivalate (half-life temperature for 1 minute: 110.3 ° C.), dilauroyl peroxide (1 minute half-life temperature: 116.4 ° C.), di-n-octanoyl peroxide (1 minute half-life temperature: 117.4 ° C.), 1,1,3,3-tetramethylbutyl Oxy-2-ethylhexanoate (1 minute half-life temperature: 124.3 ° C), di (4-methylbenzoyl) peroxide (1 minute half-life temperature: 128.2 ° C), dibenzoyl peroxide (half-minute for 1 minute) Period temperature: 130.0 ° C.), t-butyl peroxyisobutyrate (1 minute half-life temperature: 136.1 ° C.), 1,1-di (t-hexylperoxy) cyclohexane (1 minute half-life temperature: 149.2 ° C.). Especially, since the crosslinking reaction efficiency is excellent, di (4-t-butylcyclohexyl) peroxydicarbonate (1 minute half-life temperature: 92.1 ° C.), dilauroyl peroxide (1 minute half-life temperature: 116. 4 ° C), dibenzoyl peroxide (1 minute half-life temperature: 130.0 ° C) and the like are preferably used.

  The peroxide half-life is an index representing the decomposition rate of the peroxide, and means the time until the remaining amount of peroxide is reduced to half. The decomposition temperature for obtaining a half-life at an arbitrary time and the half-life time at an arbitrary temperature are described in the manufacturer catalog, for example, “Organic peroxide catalog 9th edition by Nippon Oil & Fats Co., Ltd.” (May 2003) ".

  The peroxide may be used alone, or two or more kinds may be mixed and used, but the total content is 0.1% of the peroxide with respect to 100 parts by weight of the base polymer. The content is preferably 02 to 2 parts by weight, more preferably 0.04 to 1.5 parts by weight, and even more preferably 0.05 to 1 part by weight. If the amount is less than 0.02 parts by weight, the cross-linking may be insufficient and the durability may be poor. On the other hand, if the amount exceeds 2 parts by weight, the cross-linking may be excessive and the adhesiveness may be poor.

  In addition, as a measuring method of the peroxide decomposition amount which remained after the reaction process, it can measure by HPLC (high performance liquid chromatography), for example.

  More specifically, for example, about 0.2 g of the pressure-sensitive adhesive composition after the reaction treatment is taken out, immersed in 10 ml of ethyl acetate, extracted by shaking at 25 ° C. and 120 rpm for 3 hours with a shaker, and then at room temperature. Leave for 3 days. Next, 10 ml of acetonitrile was added, shaken at 120 rpm at 25 ° C. for 30 minutes, and about 10 μl of the extract obtained by filtration through a membrane filter (0.45 μm) was injected into the HPLC for analysis. The amount of peroxide can be set.

  In addition, the pressure-sensitive adhesive composition of the present invention preferably contains an isocyanate-based crosslinking agent for the purpose of further improving adhesive strength and durability.

  Examples of the isocyanate-based crosslinking agent include aromatic isocyanates such as tolylene diisocyanate and xylene diisocyanate, alicyclic isocyanates such as isophorone diisocyanate, and aliphatic isocyanates such as hexamethylene diisocyanate. Of these, aliphatic isocyanates and alicyclic isocyanates are particularly preferably used since the crosslinked product becomes transparent.

  More specifically, for example, lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate, alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate, 2,4-tolylene diisocyanate, Aromatic diisocyanates such as 4,4′-diphenylmethane diisocyanate, xylylene diisocyanate, polymethylene polyphenyl isocyanate, trimethylolpropane / tolylene diisocyanate trimer adduct (trade name Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd.), tri Methylolpropane / hexamethylene diisocyanate trimer adduct (trade name Coronate HL, manufactured by Nippon Polyurethane Industry Co., Ltd.), hexamethylene dii Isocyanurate of cyanate (product name: Coronate HX, manufactured by Nippon Polyurethane Industry Co., Ltd.), polyether polyisocyanate, polyester polyisocyanate, and adducts of these with various polyols, isocyanurate bond, burette bond And polyisocyanates polyfunctionalized with allophanate bonds.

  The isocyanate-based crosslinking agent may be used alone or in combination of two or more, but the total content is 100 parts by weight of the base polymer with respect to the isocyanate-based crosslinking agent. It is preferable to contain 0.02 to 2 parts by weight, more preferably 0.04 to 1.5 parts by weight, and even more preferably 0.05 to 1 part by weight. By using an isocyanate-based crosslinking agent in the above range, the cohesive strength and durability can be more reliably improved. On the other hand, when the amount exceeds 2 parts by weight, crosslinking is excessive and the adhesiveness is poor. There is a case.

  In addition, when an isocyanate crosslinking agent is used in an aqueous dispersion of a modified (meth) acrylic polymer (B) produced by emulsion polymerization, an isocyanate group that is blocked because the isocyanate group easily reacts with water. A cross-linking agent may be used.

  In the present invention, the addition amount of a crosslinking agent (peroxide and isocyanate crosslinking agent when combined with an isocyanate crosslinking agent) so that the gel fraction of the crosslinked pressure-sensitive adhesive layer is 30 to 95% by weight. In the modified (meth) acrylate copolymer, it is more preferable to adjust the addition amount of the crosslinking agent so as to be 35 to 90% by weight, and to be 40 to 90% by weight. In addition to adjusting the amount of the reactive functional group and the crosslinking agent, it is necessary to sufficiently consider the influence of the crosslinking treatment temperature and the crosslinking treatment time. If the gel fraction is less than 30% by weight, the durability is inferior, and if it is more than 95% by weight, crosslinking is excessive and stress relaxation is inferior. The amount of such a crosslinking agent varies depending on the material used, but is usually in the range of 0.01 to 5 parts by weight with respect to 100 parts by weight of the modified (meth) acrylic copolymer.

  In order to adjust to a predetermined gel fraction, it is necessary to fully consider the influence of the crosslinking treatment temperature and the crosslinking treatment time as well as adjusting the addition amount of the peroxide and the isocyanate crosslinking agent.

  The adjustment of the crosslinking treatment temperature and the crosslinking treatment time is, for example, preferably set so that the decomposition amount of the peroxide contained in the pressure-sensitive adhesive composition is 50% by weight or more, and is set to be 60% by weight or more. It is more preferable to set it to 70% by weight or more. When the peroxide decomposition amount is less than 50% by weight, the amount of peroxide remaining in the pressure-sensitive adhesive composition increases, and a crosslinking reaction over time may occur even after the crosslinking treatment.

  More specifically, for example, at a crosslinking treatment temperature of 1 minute half-life temperature, the decomposition amount of peroxide is 50% by weight in 1 minute, and the decomposition amount of peroxide is 75% by weight in 2 minutes. A crosslinking treatment time of 1 minute or more is required. Further, for example, if the peroxide half-life (half-life time) at the crosslinking treatment temperature is 30 seconds, a crosslinking treatment time of 30 seconds or more is required, and for example, the peroxide half-life at the crosslinking treatment temperature. If the (half time) is 5 minutes, a crosslinking treatment time of 5 minutes or more is required.

  Thus, the crosslinking treatment temperature and crosslinking treatment time can be calculated by theoretical calculation from the half-life (half-life time) assuming that the peroxide is linearly proportional to the peroxide used. It can be adjusted as appropriate. On the other hand, the higher the temperature, the higher the possibility of side reactions, so the crosslinking treatment temperature is preferably 170 ° C. or lower.

  Moreover, this crosslinking process may be performed at the temperature at the time of the drying process of an adhesive layer, and you may carry out by providing a crosslinking process process separately after a drying process.

  The crosslinking treatment time can be set in consideration of productivity and workability, but is usually about 0.2 to 20 minutes, preferably about 0.5 to 10 minutes.

  In the pressure-sensitive adhesive composition of the present invention, a silane coupling agent can be used for the purpose of further improving adhesive strength and durability. As the silane coupling agent, known ones can be appropriately used without particular limitation.

  Specifically, for example, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltri Epoxy group-containing silane coupling agents such as methoxysilane, 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N- (1,3- Amino group-containing silane coupling agents such as dimethylbutylidene) propylamine, (meth) acryl group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-isocyanatopropyl Triethoxysilane etc. Such Inshianeto group-containing silane coupling agent. Use of such a silane coupling agent is preferable for improving durability.

  The silane coupling agent may be used alone or in combination of two or more, but the total content is 100 parts by weight of the (meth) acrylic polymer (A). On the other hand, it is preferable to contain 0.01-1 weight part of the said silane coupling agent, It is more preferable to contain 0.02-0.6 weight part, It is 0.05-0.3 weight part containing. Further preferred. By using the silane coupling agent in the above range, it can be more reliably improved cohesive strength and durability, but if less than 0.01 parts by weight, the durability may be inferior, On the other hand, if the amount exceeds 1 part by weight, the adhesive force to an optical member such as a liquid crystal cell may increase excessively.

  In addition, a tackifier can be used in the pressure-sensitive adhesive composition of the present invention for the purpose of further improving adhesive strength, durability, and refractive index.

  As the tackifier, known ones can be appropriately used without particular limitation, but it is preferable to use a tackifier having an aromatic ring or a hydrogenated product thereof and having a refractive index of 1.51 to 1.75. The refractive index is more preferably 1.53 to 1.65, and further preferably 1.54 to 1.63. In addition, since a colored tackifier colors an adhesive composition, a transparent tackifier is preferably used. As a standard of the transparent tackifier, those having a Gardner hue of 1 or less in a 50 wt% toluene solution of the tackifier are preferably used.

  Moreover, when using a tackifier, it is preferable that the modified (meth) acrylic copolymer (B) has a refractive index of 1.49 to 1.54 because the compatibility with the tackifier is improved. More preferably, it is 49 to 1.53. The refractive index of the acrylic copolymer can be controlled to be in the above range by adjusting the copolymerization ratio of the monomer having an aromatic group. In addition, the modified (meth) acrylic polymer (B) having the refractive index has good compatibility with the tackifier, so that the refractive index can be improved by the addition of the tackifier, and the adhesive property is also good. Become good.

  Specific examples of the tackifier include, for example, a styrene oligomer, a phenoxyethyl acrylate oligomer, a copolymer of styrene and α-methylstyrene, a copolymer of vinyltoluene and α-methylstyrene, a hydrogenated product of C9 petroleum resin, and a terpene. Examples thereof include phenols and hydrogenated products thereof, rosin phenols and hydrogenated products thereof, aromatic petroleum resins and hydrogenated products thereof. Among these, a styrene oligomer and a copolymer of styrene and α-methylstyrene are preferable.

  Moreover, it is preferable to contain the tackifier whose softening point is 40 degrees C or less. Furthermore, it is preferable that it is 60 degreeC or more and 70-160 degreeC. When using a tackifier with a softening point of less than 40 ° C., the amount used is less than 20 parts by weight and used in combination with a tackifier with a softening point of 50 ° C. or more. It is preferable from the viewpoint of heat resistance that the temperature is 40 ° C or higher.

  Further, the tackifier preferably has a weight average molecular weight of 300 to 7000, more preferably 400 to 6000, and still more preferably 420 to 6000.

  Moreover, it is preferable to contain 10-100 weight part of the said tackifier with respect to 100 weight part of said base polymers, It is more preferable to contain 20-80 weight part, It is more preferable to contain 30-50 weight part. The pressure-sensitive adhesive composition is adjusted to a predetermined refractive index by such a blending amount. That is, the refractive index of the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive layer is preferably adjusted to be 1.51 to 1.75, preferably 1.52 to 1.66. If the amount of the tackifier is too small, the refractive index is not sufficiently increased. On the other hand, if the amount is too large, the pressure-sensitive adhesive layer becomes hard and the adhesive properties are deteriorated, which is not preferable.

  Furthermore, the pressure-sensitive adhesive composition of the present invention may contain other known additives, such as powders such as colorants and pigments, dyes, surfactants, plasticizers, surface lubricants, and leveling. As appropriate depending on the use of the agent, softener, antioxidant, anti-aging agent, light stabilizer, ultraviolet absorber, polymerization inhibitor, inorganic or organic filler, metal powder, particles, foil, etc. Can be added. Moreover, you may employ | adopt the redox system which added a reducing agent within the controllable range.

  The pressure-sensitive adhesive composition of the present invention has the above-described configuration.

  On the other hand, the pressure-sensitive adhesive layer of the present invention is obtained by crosslinking the pressure-sensitive adhesive composition as described above. At that time, the pressure-sensitive adhesive composition is generally crosslinked after application of the pressure-sensitive adhesive composition, but it is also possible to transfer the pressure-sensitive adhesive layer comprising the crosslinked pressure-sensitive adhesive composition to a support or the like. is there.

  As a method for forming the pressure-sensitive adhesive layer, for example, a method in which the pressure-sensitive adhesive composition is applied to a release-treated separator, and the polymerization solvent is dried and removed to form a pressure-sensitive adhesive layer, and then transferred to an optical film, or The pressure-sensitive adhesive composition is prepared by applying the pressure-sensitive adhesive composition to an optical film, drying and removing a polymerization solvent, and the like to form a pressure-sensitive adhesive layer on the optical film. In applying the pressure-sensitive adhesive, one or more solvents other than the polymerization solvent may be added as appropriate.

  A silicone release liner is preferably used as the release-treated separator. In the step of applying the adhesive composition of the present invention on such a liner and drying to form a pressure-sensitive adhesive layer, a method for drying the pressure-sensitive adhesive is appropriately employed depending on the purpose. obtain. Preferably, a method of heating and drying the coating film is used. The heat drying temperature is preferably 40 ° C to 200 ° C, more preferably 50 ° C to 180 ° C, and particularly preferably 70 ° C to 170 ° C. By setting the heating temperature within the above range, an adhesive having excellent adhesive properties can be obtained.

  As the drying time, an appropriate time can be adopted as appropriate. The drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 10 minutes, and particularly preferably 10 seconds to 5 minutes.

  Moreover, an adhesive layer can be formed after forming an anchor layer on the surface of an optical film, or performing various easy-adhesion treatments, such as a corona treatment and a plasma treatment. Moreover, you may perform an easily bonding process on the surface of an adhesive layer.

  Various methods are used as a method of forming the pressure-sensitive adhesive layer. Specifically, for example, roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat, lip coat, die coater, etc. Examples thereof include an extrusion coating method.

  The thickness in particular of an adhesive layer is not restrict | limited, For example, it is about 1-100 micrometers. Preferably, it is 2-50 micrometers, More preferably, it is 2-40 micrometers, More preferably, it is 5-35 micrometers.

  The gel fraction after 1 hour of application of the pressure-sensitive adhesive layer of the present invention thus obtained is 30% to 95%, preferably 35 to 90%, more preferably 40 to 90. %. Such a gel fraction means that the crosslinking speed is high, the occurrence of dents is small, and no dent is generated in the obtained pressure-sensitive adhesive layer.

  In general, if the gel fraction is too large or too small, defects in durability tend to occur. If it is too large, it is difficult to withstand dimensional changes due to shrinkage / expansion of the optical film, particularly under humidified conditions, and problems such as peeling from the liquid crystal cell are likely to occur. On the other hand, if it is too small, problems such as foaming generated between the liquid crystal cell and the pressure-sensitive adhesive layer under heating conditions tend to occur.

  Further, the haze value when the pressure-sensitive adhesive layer is 20 μm thick is preferably 30% or more, more preferably 32%, and further preferably 35% or more. When the haze value is less than 30%, it is not preferable because the transmittance becomes too large when laminated on the optical member. In the modified (meth) acrylic polymer (B) obtained by polymerizing other monomers in the presence of the (meth) acrylic polymer (A) as in the present invention, the homopolymers of the monomers are A uniform pressure-sensitive adhesive layer can be obtained even if it is hardly compatible. For this reason, what uses the range of the said haze value can be easily obtained by using the adhesive composition and adhesive layer of this invention.

  Furthermore, the pressure-sensitive adhesive composition and pressure-sensitive adhesive layer of the present invention are particularly suitable for use as an optical member because they exhibit the above-described effects.

  When the pressure-sensitive adhesive layer is exposed, the pressure-sensitive adhesive layer may be protected with a sheet (separator) that has been subjected to a release treatment until practical use.

  Examples of the constituent material of the separator include, for example, plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films, porous materials such as paper, cloth, and nonwoven fabric, nets, foam sheets, metal foils, and laminates thereof. A thin film can be used, but a plastic film is preferably used because of its excellent surface smoothness.

  The plastic film is not particularly limited as long as it can protect the pressure-sensitive adhesive layer. For example, a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, and a vinyl chloride co-polymer are used. Examples thereof include a polymer film, a polyethylene terephthalate film, a polybutylene terephthalate film, a polyurethane film, and an ethylene-vinyl acetate copolymer film.

  The thickness of the separator is usually about 5 to 200 μm, preferably about 5 to 100 μm. For the separator, if necessary, mold release and antifouling treatment with a silicone type, fluorine type, long chain alkyl type or fatty acid amide type release agent, silica powder, etc., coating type, kneading type, vapor deposition type It is also possible to perform antistatic treatment such as. In particular, when the surface of the separator is appropriately subjected to a release treatment such as silicone treatment, long-chain alkyl treatment, or fluorine treatment, the peelability from the pressure-sensitive adhesive layer can be further improved.

  In addition, the sheet | seat which carried out the peeling process used in preparation of said adhesive type optical film can be used as a separator of an adhesive type optical film as it is, and can simplify in the surface of a process.

  As an optical film, what is used for formation of image display apparatuses, such as a liquid crystal display device, is used, and the kind in particular is not restrict | limited. For example, the optical film includes a polarizing plate. A polarizing plate having a transparent protective film on one or both sides of a polarizer is generally used.

  The polarizer is not particularly limited, and various types can be used. Examples of polarizers include dichroic iodine and dichroic dyes on hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films. Examples thereof include polyene-based oriented films such as those obtained by adsorbing substances and uniaxially stretched, polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products. Among these, a polarizer composed of a polyvinyl alcohol film and a dichroic material such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 μm.

  A polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching it can be prepared, for example, by immersing polyvinyl alcohol in an aqueous solution of iodine and stretching it 3 to 7 times the original length. If necessary, it can be immersed in an aqueous solution such as potassium iodide which may contain boric acid, zinc sulfate, zinc chloride or the like. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing. In addition to washing the polyvinyl alcohol film surface with dirt and anti-blocking agents by washing the polyvinyl alcohol film with water, it also has the effect of preventing unevenness such as uneven coloring by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be dyed with iodine after stretching. The film can be stretched even in an aqueous solution such as boric acid or potassium iodide or in a water bath.

  The transparent protective film may be subjected to surface modification treatment in order to improve adhesiveness with the polarizer before applying the adhesive. Specific examples of the treatment include corona treatment, plasma treatment, flame treatment, ozone treatment, primer treatment, glow treatment, saponification treatment, and treatment with a coupling agent. Further, an antistatic layer can be appropriately formed.

  The surface of the transparent protective film to which the polarizer is not adhered may be subjected to a hard coat layer, an antireflection treatment, an antisticking treatment, or a treatment for diffusion or antiglare.

  In addition, as an optical film, for example, for formation of a liquid crystal display device such as a reflection plate, an anti-transmission plate, the retardation plate (including wavelength plates such as 1/2 and 1/4), a visual compensation film, and a brightness enhancement film. The optical layer which may be used is mentioned. These can be used alone as an optical film, or can be laminated on the polarizing plate for practical use and used as one layer or two or more layers.

  The pressure-sensitive adhesive optical film of the present invention can be preferably used for forming various image display devices such as liquid crystal display devices. The liquid crystal display device can be formed according to the conventional method. That is, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, an adhesive optical film, and an illumination system as necessary, and incorporating a drive circuit. There is no particular limitation except that an adhesive optical film is used. As the liquid crystal cell, an arbitrary type such as an arbitrary type such as a TN type, STN type, π type, VA type, or IPS type can be used.

  An appropriate liquid crystal display device such as a liquid crystal display device in which an adhesive optical film is disposed on one side or both sides of a liquid crystal cell, or a backlight or a reflector used in an illumination system can be formed. In that case, the optical film according to the present invention can be installed on one side or both sides of the liquid crystal cell. When optical films are provided on both sides, they may be the same or different. Further, when forming a liquid crystal display device, for example, a single layer or a suitable part such as a diffusing plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusing plate, a backlight, etc. Two or more layers can be arranged.

  As a material constituting the transparent protective film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like is used. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth) acrylic resins, cyclic Examples thereof include polyolefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. A transparent protective film is bonded to one side of the polarizer by an adhesive layer. On the other side, as a transparent protective film, (meth) acrylic, urethane-based, acrylurethane-based, epoxy-based, silicone A thermosetting resin such as a system or an ultraviolet curable resin can be used. One or more kinds of arbitrary appropriate additives may be contained in the transparent protective film. Examples of the additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a coloring agent. The content of the thermoplastic resin in the transparent protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. . When content of the said thermoplastic resin in a transparent protective film is 50 weight% or less, there exists a possibility that the high transparency etc. which a thermoplastic resin originally has cannot fully be expressed.

  Moreover, as a transparent protective film, the polymer film as described in Unexamined-Japanese-Patent No. 2001-343529 (WO01 / 37007), for example, (A) thermoplastic resin which has a substituted and / or unsubstituted imide group in a side chain, ( B) Resin compositions containing thermoplastic resins having substituted and / or unsubstituted phenyl and nitrile groups in the side chains. A specific example is a film of a resin composition containing an alternating copolymer composed of isobutylene and N-methylmaleimide and an acrylonitrile / styrene copolymer. As the film, a film made of a mixed extruded product of the resin composition or the like can be used. Since these films have a small phase difference and a small photoelastic coefficient, problems such as unevenness due to the distortion of the polarizing plate can be eliminated, and since the moisture permeability is small, the humidification durability is excellent.

  Although the thickness of a transparent protective film can be determined suitably, generally it is about 1-500 micrometers from points, such as workability | operativity, such as intensity | strength and handleability, and thin layer property. 1-300 micrometers is especially preferable, and 5-200 micrometers is more preferable. The transparent protective film is particularly suitable when the thickness is 5 to 150 μm.

  In addition, when providing a transparent protective film on both sides of a polarizer, the protective film which consists of the same polymer material may be used by the front and back, and the protective film which consists of a different polymer material etc. may be used.

  As the transparent protective film of the present invention, it is preferable to use at least one selected from cellulose resin, polycarbonate resin, cyclic polyolefin resin, and (meth) acrylic resin.

  Cellulose resin is an ester of cellulose and fatty acid. Specific examples of the cellulose ester resin include triacetyl cellulose, diacetyl cellulose, tripropionyl cellulose, dipropionyl cellulose and the like. Among these, triacetyl cellulose is particularly preferable. Many products of triacetylcellulose are commercially available, which is advantageous in terms of availability and cost. Examples of commercial products of triacetyl cellulose include trade names “UV-50”, “UV-80”, “SH-80”, “TD-80U”, “TD-TAC”, “UZ” manufactured by Fuji Film Co., Ltd. -TAC "and" KC series "manufactured by Konica. In general, these triacetyl celluloses have an in-plane retardation (Re) of almost zero, but a thickness direction retardation (Rth) of about 60 nm.

  In addition, the cellulose resin film with a small thickness direction phase difference is obtained by processing the said cellulose resin, for example. For example, a base film such as polyethylene terephthalate, polypropylene, and stainless steel coated with a solvent such as cyclopentanone and methyl ethyl ketone is bonded to a general cellulose film and dried by heating (for example, at 80 to 150 ° C. for about 3 to 10 minutes). ) And then peeling the base film; a solution obtained by dissolving norbornene resin, (meth) acrylic resin, etc. in a solvent such as cyclopentanone, methyl ethyl ketone, etc. is applied to a general cellulose resin film and dried by heating ( For example, a method of peeling the coated film after 80 to 150 ° C. for about 3 to 10 minutes is mentioned.

  Moreover, as a cellulose resin film with a small thickness direction retardation, the fatty acid cellulose resin film which controlled the fat substitution degree can be used. Generally used triacetyl cellulose has an acetic acid substitution degree of about 2.8. Preferably, the Rth can be reduced by controlling the acetic acid substitution degree to 1.8 to 2.7. Rth can be controlled to be small by adding a plasticizer such as dibutyl phthalate, p-toluenesulfonanilide, acetyltriethyl citrate to the fatty acid-substituted cellulose resin. The addition amount of the plasticizer is preferably 40 parts by weight or less, more preferably 1 to 20 parts by weight, and still more preferably 1 to 15 parts by weight with respect to 100 parts by weight of the fatty acid cellulose resin.

  Specific examples of the cyclic polyolefin resin are preferably norbornene resins. The cyclic olefin-based resin is a general term for resins that are polymerized using a cyclic olefin as a polymerization unit, and is described in, for example, JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, and the like. Resin. Specific examples include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, cyclic olefins and α-olefins such as ethylene and propylene (typically random copolymers), And graft polymers obtained by modifying them with an unsaturated carboxylic acid or a derivative thereof, and hydrides thereof. Specific examples of the cyclic olefin include norbornene monomers.

  Various products are commercially available as the cyclic polyolefin resin. As specific examples, trade names “ZEONEX” and “ZEONOR” manufactured by ZEON CORPORATION, product names “ARTON” manufactured by JSR Corporation, “TOPAS” manufactured by TICONA, and product names manufactured by Mitsui Chemicals, Inc. “APEL”.

  The (meth) acrylic resin preferably has a Tg (glass transition temperature) of 115 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 125 ° C. or higher, and particularly preferably 130 ° C. or higher. When Tg is 115 ° C. or higher, the polarizing plate can be excellent in durability. Although the upper limit of Tg of the (meth) acrylic resin is not particularly limited, it is preferably 170 ° C. or less from the viewpoint of moldability. From (meth) acrylic resin, a film having in-plane retardation (Re) and thickness direction retardation (Rth) of almost zero can be obtained.

  As the (meth) acrylic resin, any appropriate (meth) acrylic resin can be adopted as long as the effects of the present invention are not impaired. For example, poly (meth) acrylic acid ester such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester- (Meth) acrylic acid copolymer, (meth) methyl acrylate-styrene copolymer (MS resin, etc.), polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, Methyl methacrylate- (meth) acrylate norbornyl copolymer, etc.). Preferably, poly (meth) acrylate C1-6 alkyl such as poly (meth) acrylate methyl is used. More preferred is a methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight).

  Specific examples of (meth) acrylic resins include (meth) acrylic resins having a ring structure in the molecule described in, for example, Acrypet VH and Acrypet VRL20A manufactured by Mitsubishi Rayon Co., Ltd., and JP-A-2004-70296. And a high Tg (meth) acrylic resin system obtained by intramolecular crosslinking or intramolecular cyclization reaction.

  As the (meth) acrylic resin, a (meth) acrylic resin having a lactone ring structure can also be used. It is because it has high mechanical strength by high heat resistance, high transparency, and biaxial stretching.

  Examples of the (meth) acrylic resin having a lactone ring structure include JP 2000-230016, JP 2001-151814, JP 2002-120326, JP 2002-254544, and JP 2005. Examples thereof include (meth) acrylic resins having a lactone ring structure described in Japanese Patent No. 146084.

  The (meth) acrylic resin having a lactone ring structure preferably has a ring pseudo structure represented by the following general formula (Formula 1).

^Wherein, R 1, ^{R 2} and ^{R 3} each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom.

  The content ratio of the lactone ring structure represented by the general formula (Formula 1) in the structure of the (meth) acrylic resin having a lactone ring structure is preferably 5 to 90% by weight, more preferably 10 to 70% by weight, More preferably, it is 10 to 60% by weight, and particularly preferably 10 to 50% by weight. When the content of the lactone ring structure represented by the general formula (Chemical Formula 1) in the structure of the (meth) acrylic resin having a lactone ring structure is less than 5% by weight, the heat resistance, solvent resistance, and surface hardness are low. May be insufficient. If the content of the lactone ring structure represented by the general formula (Chemical Formula 1) in the structure of the (meth) acrylic resin having a lactone ring structure is more than 90% by weight, molding processability may be poor.

  The (meth) acrylic resin having a lactone ring structure has a mass average molecular weight (sometimes referred to as a weight average molecular weight) of preferably 1,000 to 2,000,000, more preferably 5,000 to 1,000,000, still more preferably 10,000 to 500,000, and particularly preferably. Is 50,000 to 500,000. If the mass average molecular weight is out of the above range, it is not preferable from the viewpoint of molding processability.

  The (meth) acrylic resin having a lactone ring structure preferably has a Tg of 115 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 125 ° C. or higher, and particularly preferably 130 ° C. or higher. Since Tg is 115 ° C. or higher, for example, when incorporated into a polarizing plate as a transparent protective film, it has excellent durability. Although the upper limit of Tg of the (meth) acrylic resin having the lactone ring structure is not particularly limited, it is preferably 170 ° C. or less from the viewpoint of moldability and the like.

  The (meth) acrylic resin having a lactone ring structure is preferably as the total light transmittance of a molded product obtained by injection molding measured by a method according to ASTM-D-1003 is higher, preferably 85. % Or more, more preferably 88% or more, and still more preferably 90% or more. The total light transmittance is a measure of transparency. If the total light transmittance is less than 85%, the transparency may be lowered.

  The transparent protective film may be subjected to surface modification treatment in order to improve adhesiveness with the polarizer before applying the adhesive. Specific examples of the treatment include corona treatment, plasma treatment, flame treatment, ozone treatment, primer treatment, glow treatment, saponification treatment, and treatment with a coupling agent. Further, an antistatic layer can be appropriately formed.

  The surface of the transparent protective film to which the polarizer is not adhered may be subjected to a hard coat layer, an antireflection treatment, an antisticking treatment, or a treatment for diffusion or antiglare.

  In addition, as an optical film, for example, for formation of a liquid crystal display device such as a reflection plate, an anti-transmission plate, the retardation plate (including wavelength plates such as 1/2 and 1/4), a visual compensation film, and a brightness enhancement film. The optical layer which may be used is mentioned. These can be used alone as an optical film, or can be laminated on the polarizing plate for practical use and used as one layer or two or more layers.

  The pressure-sensitive adhesive optical film of the present invention can be preferably used for forming various image display devices such as liquid crystal display devices. The liquid crystal display device can be formed according to the conventional method. That is, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, an adhesive optical film, and an illumination system as necessary, and incorporating a drive circuit. There is no particular limitation except that an adhesive optical film is used. As the liquid crystal cell, an arbitrary type such as an arbitrary type such as a TN type, STN type, π type, VA type, or IPS type can be used.

  An appropriate liquid crystal display device such as a liquid crystal display device in which an adhesive optical film is disposed on one side or both sides of a liquid crystal cell, or a backlight or a reflector used in an illumination system can be formed. In that case, the optical film according to the present invention can be installed on one side or both sides of the liquid crystal cell. When optical films are provided on both sides, they may be the same or different. Further, when forming a liquid crystal display device, for example, a single layer or a suitable part such as a diffusing plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusing plate, a backlight, etc. Two or more layers can be arranged.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. In addition, the evaluation item in an Example etc. measured as follows.

<Measurement of molecular weight>
The weight average molecular weight of the obtained (meth) acrylic polymer was measured by GPC (gel permeation chromatography).
・ Analyzer: HLC-8120GPC manufactured by Tosoh Corporation
Column: manufactured by Tosoh Corporation, G7000H _XL + GMH _XL + GMH _XL
Column size: 7.8mmφ x 30cm each (total 90cm)
-Column temperature: 40 ° C
・ Flow rate: 0.8ml / min
・ Injection volume: 100 μl
・ Eluent: Tetrahydrofuran ・ Detector: Differential refractometer (RI)
The molecular weight was calculated in terms of polystyrene.

<Measurement of gel fraction>
About 0.1 g of the adhesive layer after aging produced in each Example / Comparative Example was taken and weighed to determine the weight (W ₁ ). This was then wrapped in a microporous tetrafluoroethylene membrane (membrane weight W ₂ ), immersed in about 50 ml of ethyl acetate at room temperature (about 23 ° C.) for 2 days, and then the soluble content of the pressure-sensitive adhesive layer subjected to the immersion treatment Extracted. Then removed the adhesive layer with the film, which was dried for 2 hours at 120 ° C., was measured total weight (W _3). From these measured values, the gel fraction (% by weight) of the pressure-sensitive adhesive layer was determined according to the following formula.
The value calculated as ((W ₃ −W ₂ ) / W ₁ ) × 100 was taken as the gel fraction (% by weight).

<Measurement of adhesive strength>
The light diffusion adhesive sheet affixed to the 20-mm-wide polyethylene terephthalate film (S-10: thickness 25 micrometers) obtained in the Example and the comparative example was used for alkali free glass (Corning, # 1737, thickness). The thickness was 0.7 mm, and the roll was reciprocated with a 2 kg roller for pasting. Thereafter, the film was treated in an autoclave at 50 ° C. and 0.5 Mpa for 15 minutes, and then allowed to stand for 3 hours in an atmosphere of 23 ° C. × 50% RH, and then peel strength was measured at a peel angle of 90 ° and a peel rate of 300 mm / min.

<Measurement of refractive index>
Under an atmosphere of 25 ° C., sodium D line was irradiated, and the refractive index was measured using an appe refractometer (manufactured by ATAGO, DR-M4).

<Measurement of haze value>
Based on JIS-K7361-1 and JIS-K7136, the haze value of the light-diffusion adhesive sheet affixed to the polyethylene terephthalate film (Toray Industries, Inc., S-10: thickness 25micrometer) obtained by the Example and the comparative example was used. Measured with the following apparatus.
Device name: REFECTANCE TRANSMITTANCE METER
Manufacturer: Murakami Color Research Laboratory Model: HR-100
Total light transmittance and haze value compensation haze value = (τd / τt) × 100
τd: diffuse transmittance (%)
τt: Total light transmittance (%)

<Preparation of (meth) acrylic polymer>
[Acrylic polymer (A)]
In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser, 98.5 parts by weight of n-butyl acrylate, 1 part by weight of acrylic acid, 0.5 part by weight of 4-hydroxybutyl acrylate, polymerization 2,2′-Azobisisobutyronitrile 0.1 part by weight (manufactured by Wako Pure Chemical Industries, Ltd.) as an initiator and 200 parts by weight of ethyl acetate as a polymerization solvent were sufficiently purged with nitrogen, and then stirred under a nitrogen stream. Then, a polymerization reaction was performed at about 60 ° C. for 9 hours to prepare an acrylic polymer solution. The refractive index of the acrylic polymer (A) was 1.466.

[Modified acrylic copolymer (B1)]
To a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler, 400 parts by weight of the above acrylic polymer (A) solution diluted with ethyl acetate to 25% by weight was added to the homopolymer. 100 parts by weight of a styrene monomer having a refractive index of 1.591 (manufactured by Wako Pure Chemical Industries, Ltd.) and 0.5 parts by weight of dibenzoyl peroxide (manufactured by Wako Pure Chemical Industries, Ltd.) as an agent for initiating polymerization are added, and the nitrogen substitution is performed. Then, a graft polymerization reaction was performed at 60 ° C. for 5 hours and at 70 ° C. for 8 hours to obtain a modified acrylic copolymer (B1).

[Modified acrylic copolymer (B2)]
To a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler, 400 parts by weight of the above acrylic polymer (A) solution diluted with ethyl acetate to 25% by weight was added to the homopolymer. 40 parts by weight of benzyl acrylate having a refractive index of 1.511 and 0.25 parts by weight of dibenzoyl peroxide (manufactured by Wako Pure Chemical Industries, Ltd.) as a polymerization initiator were added, and the atmosphere was replaced with nitrogen for 5 hours at 60 ° C., 70 ° C. Then, a graft polymerization reaction was carried out for 8 hours to obtain a modified acrylate copolymer (B2).

[Modified acrylic copolymer (B3)]
To a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler, 400 parts by weight of the above acrylic polymer (A) solution diluted with ethyl acetate to 25% by weight was added to the homopolymer. 50 parts by weight of phenoxyethyl acrylate having a refractive index of 1.519 and 0.25 parts by weight of dibenzoyl peroxide (manufactured by Wako Pure Chemical Industries, Ltd.) as a polymerization initiator were added, and the atmosphere was replaced with nitrogen for 5 hours at 70 ° C. for 70 hours. A graft polymerization reaction was carried out at 0 ° C. for 8 hours to obtain a modified acrylate copolymer (B3).

[Modified acrylic copolymer (B4)]
To a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler, 400 parts by weight of the above acrylic polymer (A) solution diluted with ethyl acetate to 25% by weight was added to the homopolymer. While adding 3 parts by weight of a styrene monomer having a refractive index of 1.591 (manufactured by Wako Pure Chemical Industries, Ltd.) and 0.1 part by weight of dibenzoyl peroxide (manufactured by Wako Pure Chemical Industries, Ltd.) as a polymerization initiator, A graft polymerization reaction was carried out at 60 ° C. for 5 hours and at 70 ° C. for 8 hours to obtain a modified acrylate copolymer (B4).

[Example 1]
To the solid content of 100 parts by weight of the modified acrylic copolymer (B1) solution, 1.5 parts by weight of xylylene diisocyanate and 1.5 parts by weight of a trimethylolpropane adduct (manufactured by Mitsui Takeda Chemical Co., Ltd .: D-110N) were uniformly mixed and stirred. . This solution was applied to one side of a polyethylene terephthalate film (manufactured by Toray Industries Inc., thickness: 25 μm) and a silicone-treated polyethylene terephthalate film (manufactured by Toray Industries Inc., thickness 38 μm), heated at 130 ° C. for 3 minutes, An adhesive layer having a thickness of 20 μm after drying was formed. The gel fraction after this pressure-sensitive adhesive layer was aged at 60 ° C. × 48 H was 86% by weight.
Total light transmittance 81.4%
Haze value 70.9%
Adhesive strength 3N / 20mm
[Example 2]
To 100 parts by weight of the solid content of the modified acrylic copolymer (B2) solution, 1.5 parts by weight of xylylene diisocyanate and 1.5 parts by weight of a trimethylolpropane adduct (manufactured by Mitsui Takeda Chemical Co., Ltd .: D-110N) were uniformly mixed and stirred. . This solution was applied to one side of a polyethylene terephthalate film (manufactured by Toray Industries Inc., thickness: 25 μm) and a silicone-treated polyethylene terephthalate film (manufactured by Toray Industries Inc., thickness 38 μm), heated at 130 ° C. for 3 minutes, An adhesive layer having a thickness of 20 μm after drying was formed. The gel fraction after this pressure-sensitive adhesive layer was aged at 60 ° C. × 48 H was 87% by weight.
Total light transmittance 85.2%
Haze value 33.6%
Adhesive strength 6N / 20mm
Example 3
To 100 parts by weight of the solid content of the modified acrylic copolymer (B3) solution, 1.5 parts by weight of xylylene diisocyanate and 1.5 parts by weight of a trimethylolpropane adduct (Mitsui Takeda Chemical Co., Ltd .: D-110N) were uniformly mixed and stirred. . This solution was applied to one side of a polyethylene terephthalate film (manufactured by Toray Industries Inc., thickness: 25 μm) and a silicone-treated polyethylene terephthalate film (manufactured by Toray Industries Inc., thickness 38 μm), heated at 130 ° C. for 3 minutes, An adhesive layer having a thickness of 20 μm after drying was formed. The gel fraction after this pressure-sensitive adhesive layer was aged at 60 ° C. × 48 H was 87% by weight.
Total light transmittance 85.4%
Haze value 31.4%
Adhesive strength 5N / 20mm

[Comparative Example 1]
To 100 parts by weight of the solid content of the acrylic polymer (A) solution, 1.5 parts by weight of xylylene diisocyanate and 1.5 parts by weight of a trimethylolpropane adduct (manufactured by Mitsui Takeda Chemical Co., Ltd .: D-110N) were uniformly mixed and stirred. This solution was applied to one side of a polyethylene terephthalate film (manufactured by Toray Industries Inc., thickness: 25 μm) and a silicone-treated polyethylene terephthalate film (manufactured by Toray Industries Inc., thickness 38 μm), heated at 130 ° C. for 3 minutes, An adhesive layer having a thickness of 20 μm after drying was formed. The gel fraction after the pressure-sensitive adhesive layer was aged at 60 ° C. × 48 H was 85% by weight.
Total light transmittance 90.9%
Haze value 3.4%
Adhesive strength 5N / 20mm

[Comparative Example 2]
To 100 parts by weight of the solid content of the modified acrylic copolymer (B4) solution, 1.5 parts by weight of xylylene diisocyanate and 1.5 parts by weight of a trimethylolpropane adduct (Mitsui Takeda Chemical Co., Ltd .: D-110N) were uniformly mixed and stirred. . This solution was applied to one side of a polyethylene terephthalate film (manufactured by Toray Industries Inc., thickness: 25 μm) and a silicone-treated polyethylene terephthalate film (manufactured by Toray Industries Inc., thickness 38 μm), heated at 130 ° C. for 3 minutes, An adhesive layer having a thickness of 20 μm after drying was formed. The gel fraction after this pressure-sensitive adhesive layer was aged at 60 ° C. × 48 H was 86% by weight.
Total light transmittance 90.1%
Haze value 5.5%
Adhesive strength 4N / 20mm

Claims (8)

To alkyl (meth) including acrylate and hydroxyl group-containing (meth) acrylate as a constituent unit (meth) acrylic polymer (A), as La radical polymerizable monomer is polymerized by blending benzyl acrylate or phenoxyethyl acrylate A light diffusable pressure-sensitive adhesive composition comprising a modified (meth) acrylate copolymer (B) obtained by
A light diffusive pressure-sensitive adhesive composition having a haze value of 30% or more when a pressure-sensitive adhesive layer having a thickness of 20 μm is formed. The modified (meth) acrylate copolymer (B) is polymerized by blending 5 to 100 parts by weight of the radical polymerizable monomer with respect to 100 parts by weight of the (meth) acrylic polymer (A). light diffusing pressure-sensitive adhesive composition of claim 1 Symbol mounting characterized in that it is obtained. Furthermore, the light diffusable adhesive composition of Claim 1 or 2 which contains an unsaturated carboxylic acid containing monomer as a structural unit. The light diffusable adhesive composition according to any one of claims 1 to 3, wherein the alkyl (meth) acrylate is n-butyl acrylate, and the hydroxyl group-containing (meth) acrylate is a hydroxyalkyl acrylate. . The light diffusable adhesive composition of any one of Claim 1 to 4 whose said crosslinking agent is an isocyanate type crosslinking agent. The light diffusable adhesive layer obtained by bridge | crosslinking the light diffusable adhesive composition in any one of Claim 1-5 . The light diffusable pressure-sensitive adhesive layer according to claim 6 , wherein the light diffusable pressure-sensitive adhesive layer has a gel fraction of 30 to 95% by weight. Light diffusing adhesive sheet characterized by forming the light-diffusing adhesive layer according to one or both sides of the optical member to claim 6 or 7.