JP6460977B2 - Photocurable adhesive, and polarizing plate, laminated optical member and liquid crystal display device using the same - Google Patents

Description

  The present invention relates to a photocurable adhesive for bonding a polarizer composed of a polyvinyl alcohol-based resin film on which a dichroic dye is adsorbed and oriented and a protective film composed of a transparent resin film, and polarized light using the same The present invention relates to a plate, a laminated optical member, and a liquid crystal display device.

  The polarizing plate is useful as one of the optical components constituting the liquid crystal display device. A polarizing plate usually has a structure in which protective films are laminated on both sides of a polarizer, and is incorporated in a liquid crystal display device. It is also known that a protective film is provided only on one side of a polarizer, but in many cases, a layer having another optical function is attached to the other side as a protective film instead of a simple protective film. Combined. Further, as a method for producing a polarizer, a method in which a uniaxially stretched polyvinyl alcohol-based resin film dyed with a dichroic dye is treated with boric acid, washed with water, and dried is widely adopted.

  Usually, a protective film is bonded to the polarizer immediately after washing with water and drying. This is because the dried polarizer has a weak physical strength, and once it is wound, there is a problem that it is easily broken in the processing direction. Therefore, usually, a water-based adhesive that is an aqueous solution of a polyvinyl alcohol resin is immediately applied to the polarizer after drying, and protective films are simultaneously bonded to both sides of the polarizer via this adhesive. Usually, a triacetyl cellulose film having a thickness of 30 to 100 μm is used as the protective film.

  Triacetyl cellulose is excellent in transparency, easily forms various surface treatment layers and optical functional layers, has high moisture permeability, and can be dried after being bonded to a polarizer using an aqueous adhesive as described above. While having an excellent advantage as a protective film such that it can be performed smoothly, the polarizing plate bonded as a protective film due to its high moisture permeability is, for example, at a temperature of 70 ° C. and a relative humidity of 90 under wet heat. %, There was a problem such as easy to cause deterioration. Therefore, it is also known to use an amorphous polyolefin resin having a lower moisture permeability than that of triacetyl cellulose, for example, an amorphous polyolefin resin represented by a norbornene resin as a protective film. Specifically, JP-A-6-511117 (Patent Document 1) describes that a thermoplastic saturated norbornene resin sheet is laminated as a protective film on at least one surface of a polarizer.

  When bonding a protective film made of a resin with low moisture permeability to a polyvinyl alcohol polarizer, an aqueous solution of a polyvinyl alcohol resin generally used for bonding a polyvinyl alcohol polarizer and a triacetyl cellulose film is conventionally used. When the adhesive is used, there are problems that the adhesive strength is not sufficient or the appearance of the obtained polarizing plate becomes poor. This is because a resin film having low moisture permeability is generally hydrophobic, and water that is a solvent cannot be sufficiently dried due to low moisture permeability. On the other hand, it is also known to bond different types of protective films on both sides of the polarizer. For example, in JP-A-2002-174729 (Patent Document 2), a protective film made of a resin having low moisture permeability such as an amorphous polyolefin-based resin is bonded to one surface of a polarizer. There is also a proposal to paste a protective film made of a highly moisture-permeable resin such as cellulose resin including triacetyl cellulose on the other surface.

  Therefore, a high adhesion force is provided between the protective film made of a resin having a low moisture permeability and the polyvinyl alcohol polarizer, and a high adhesion between a highly moisture permeable resin such as a cellulose resin and the polyvinyl alcohol polarizer. There is an attempt to use a photo-curable adhesive as an adhesive that gives force. For example, JP-A-2004-245925 (Patent Document 3) discloses an adhesive mainly composed of an epoxy compound not containing an aromatic ring, and irradiation with active energy rays, specifically irradiation with ultraviolet rays. It has been proposed that this adhesive is cured by cationic polymerization by, thereby bonding the polarizer and the protective film. JP-A-2008-257199 (Patent Document 4) discloses a photocurable adhesive comprising a combination of an alicyclic epoxy compound and an epoxy compound having no alicyclic epoxy group, and further containing a photocationic polymerization initiator. A technique using an agent for bonding a polarizer and a protective film is disclosed.

  JP-A-2004-245925 (Patent Document 3) discloses an adhesive mainly composed of an epoxy resin that does not contain an aromatic ring. The adhesive is irradiated with active energy rays to be cationically polymerized. A method for adhering a polarizer and a protective film is proposed. The epoxy-based adhesive disclosed herein is particularly effective for bonding various transparent resin films including amorphous polyolefin-based resins and cellulose-based resins to polarizers. In the case of a protective film, it has become clear that the adhesive force is not always sufficient.

  Japanese Patent Application Laid-Open No. 2012-172026 (Patent Document 5) has an epoxy group or an oxetanyl group in 100% by weight of the active energy ray-curable compound (A) and does not have an active energy ray radically polymerizable functional group. An active energy ray-curable compound (5) containing 5 to 100% by weight of an active energy ray cationic curable compound (a1) having a weight average molecular weight of less than 5000 and an active energy ray radically curable compound (a2) (0 to 95% by weight). A) An adhesive for optical films containing 0.0001 to 2 parts by weight of an acrylic resin (B) having a weight average molecular weight of 5000 to 150,000 having an epoxy group or an oxetanyl group with respect to 100 parts by weight is disclosed. However, when the content of the acrylic resin (B) exceeds 2 parts by weight, the viscosity of the adhesive increases, and on the contrary, the smoothness of the coated surface may be deteriorated (see paragraph [0079]). The acrylic resin (B) content is set to 2 parts by weight or less.

JP-A-6-511117 JP 2002-174729 A JP 2004-245925 A JP 2008-257199 A JP 2012-172026 A

  An object of the present invention is to provide a polarizing plate having a sufficiently low viscosity that enables coating at room temperature when bonding a protective film to a polarizer, and also having improved adhesion between the polarizer and the protective film. It is to provide a photocurable adhesive. Another object of the present invention is to provide a laminated optical member suitably used for a liquid crystal display device by laminating another optical layer such as a retardation plate on the polarizing plate.

  As a result of intensive studies to solve such problems, the present inventors have completed the present invention. Specifically, in a photocurable adhesive comprising a predetermined amount of a photocationic curable component and a photocationic polymerization initiator, a specific alicyclic diepoxy compound as a main component as the photocationic curable component And a composition comprising a diglycidyl compound having two epoxy groups not bonded to an alicyclic ring in the molecule and not having an aromatic ring, and a polymer composed of a specific ethylenically unsaturated monomer. Was found to be effective. That is, the photocurable adhesive having such a specific composition exhibits a low viscosity at room temperature and gives good coating suitability, expresses a high storage elastic modulus after curing, and strengthens the polarizer and the protective film. Found to adhere.

That is, the present invention is a photocurable adhesive for bonding a protective film made of a transparent resin film to a polarizer made of a polyvinyl alcohol-based resin film on which a dichroic dye is adsorbed and oriented,
(A) 100 parts by weight of a photocationic curable component;
(B) containing 1 to 10 parts by weight of a cationic photopolymerization initiator,
The photocationic curable component (A) contains the following predetermined amounts of (A1), (A2) and (A3).

  (A1) 10 to 60% by weight of an alicyclic diepoxy compound represented by the following formula (I) (based on the total amount of the photocationic curable component (A))

In the formula, R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and may have an alicyclic structure when the alkyl group has 3 or more carbon atoms. X represents an oxygen atom, an alkanediyl group having 1 to 6 carbon atoms, or a divalent group represented by any of the following formulas (Ia) to (Id).

In the formula, Y ^{1 to} Y ⁴ each independently represent an alkanediyl group having 1 to 20 carbon atoms, and may have an alicyclic structure in the case of 3 or more carbon atoms. a and b each independently represents an integer of 0 to 20;

  (A2) 20 to 75% by weight of diglycidyl compound represented by the following formula (II) (based on the total amount of the photocationic curable component (A))

In the formula, Z represents an alkylene group having 1 to 9 carbon atoms, an alkylidene group having 3 or 4 carbon atoms, or a divalent alicyclic hydrocarbon group, and the methylene group in the alkylene group is an oxygen atom, It may be interrupted by a divalent group represented by —CO—O—, —O—CO—, —SO ₂ —, —SO— or —CO—.

  (A3) 5 to 50% by weight of a polymer having a weight average molecular weight of 5,000 to 100,000 (photocation) comprising at least one ethylenically unsaturated monomer selected from the monomers represented by the following formula (III) or (IV) (Based on the total amount of curable component (A))

  In the formula, X is an alkyl group having 1 to 7 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alicyclic hydrocarbon group having 6 to 10 carbon atoms, or a part of these functional groups. It is substituted with one or more groups selected from the group consisting of epoxy groups, oxetane groups, hydroxyl groups and carboxyl groups.

In the formula, R ₃ represents a hydrogen atom, a methyl group or a halogen atom, and X is the same as in the above formula (III).

In the polymer (A3), the ethylenically unsaturated monomer is
X is a methyl group partially substituted with one or more groups selected from the group consisting of an epoxy group, an oxetane group and a hydroxyl group, a branched alkyl group having 2 to 7 carbon atoms, and 6 to 12 carbon atoms. And an ethylenically unsaturated monomer represented by the above formula (III) or (IV) in the case of the aryl group or the alicyclic hydrocarbon group having 6 to 10 carbon atoms.

In the above (A3), the ethylenically unsaturated monomer is
(I) In the case where X is a methyl group, a branched alkyl group having 2 to 7 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alicyclic hydrocarbon group having 6 to 10 carbon atoms And 20 to 90% by weight of the ethylenically unsaturated monomer represented by the formula (III) or (IV), and (ii) one selected from the group consisting of the epoxy group, oxetane group and hydroxyl group A methyl group partially substituted with the above groups, a branched alkyl group having 2 to 7 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alicyclic hydrocarbon group having 6 to 10 carbon atoms. In a certain case, it is preferable to contain 10 to 80% by weight of the ethylenically unsaturated monomer represented by the formula (III) or (IV).

  The photocurable adhesive preferably has a viscosity at 25 ° C. of 2 to 300 mPa · sec or less.

  In the formula (II) representing the diglycidyl compound (A2), Z is preferably a branched alkyl group having 3 to 10 carbon atoms.

The above-mentioned photocurable adhesive also preferably contains 0.5 to 4 parts by weight of moisture.
The photocurable adhesive also preferably contains 0.5 to 8 parts by weight of a diol compound having two hydroxyl groups in the molecule.

  The above-mentioned photocurable adhesive preferably has a solubility of 15 to 70% by weight when the protective film is immersed for 2 days at 23 ° C.

The present invention also includes a polarizer comprising a polyvinyl alcohol-based resin film on which a dichroic dye is adsorbed and oriented,
The present invention also relates to a polarizing plate having a protective film made of a transparent resin film bonded to at least one surface of the polarizer via a cured product of any one of the above photocurable adhesives.

  The main component of the transparent resin film is preferably at least one resin selected from the group consisting of cellulose resins, acrylic resins, amorphous polyolefin resins, polyester resins, and polycarbonate resins. Moreover, it is preferable that the said transparent resin film contains a ultraviolet absorber.

  The polarizing plate preferably has an adhesive strength between the polarizer and the protective film measured by a 180 degree peeling test of 0.5 N / 25 mm or more.

  The present invention also relates to a laminated optical member comprising a laminate of the above polarizing plate and one or more other optical layers. The other optical layer preferably includes a retardation plate.

  The present invention also relates to a liquid crystal display device including a liquid crystal cell and the above laminated optical member disposed on one side or both sides of the liquid crystal cell.

  The photocurable adhesive of the present invention includes a specific alicyclic diepoxy compound (A1), a specific diglycidyl compound (A2), and a specific ethylenically unsaturated monomer as the photocationic curable component (A). By blending a predetermined amount of each of the polymers (A3) having a weight average molecular weight of 5000 to 100,000, the adhesive strength between the polarizer and the protective film can be increased with a low viscosity. A laminated optical member obtained by laminating another optical layer on this polarizing plate also sufficiently exhibits the function of the polarizing plate.

  Hereinafter, embodiments of the present invention will be described in detail. The present invention provides a photocurable adhesive for adhering a protective film made of a transparent resin to a polarizer made of a polyvinyl alcohol-based resin film. The present invention also provides a polarizing plate in which a protective film made of a transparent resin is bonded to the polarizer using the photocurable adhesive, and a laminated optical member in which another optical layer is laminated on the polarizing plate. Is also provided. These photocurable adhesives, polarizing plates, and laminated optical members will be described in order.

[Photocurable adhesive]
In the present invention, a photocurable adhesive for adhering a protective film made of a transparent resin to a polarizer made of a polyvinyl alcohol-based resin film includes (A) a photocationic curable component and (B) photocationic polymerization initiation. Contains agents.

(A) Photocationic curable component The photocationic curable component (A), which is the main component of the photocurable adhesive and provides adhesive strength by polymerization and curing, contains the following three types of compounds.
(A1) An alicyclic diepoxy compound represented by the above formula (I),
(A2) Weight comprising at least one ethylenically unsaturated monomer selected from the diglycidyl compound represented by the formula (II) and (A3) the monomer represented by the formula (III) or (IV). Polymer having an average molecular weight of 5,000 to 100,000.

(A1) Alicyclic diepoxy compound The amount of the alicyclic diepoxy compound (A1) in the photocationic curable component (A) is 10 to 60% by weight based on the total amount of the photocationic curable component (A). . By containing 10% by weight or more of the alicyclic diepoxy compound (A1) in the photocationic curable component (A), the reactivity of the cationic polymerization becomes high and the curability is excellent. On the other hand, when the amount exceeds 60% by weight, the amount of the polymer (A3) composed of the diglycidyl compound (A2) and the ethylenically unsaturated monomer described below becomes relatively small, which is contemplated by the present invention. It becomes difficult to reduce the viscosity of the photocurable adhesive and improve the adhesion between the polarizer and the protective film.

In the above formula (I) representing the alicyclic diepoxy compound (A1), R ¹ and R ² are each independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, but the alkyl group has 3 or more carbon atoms. In some cases, it may have an alicyclic structure. This alkyl group has a 1-position on the position of the cyclohexane ring bonded to X in formula (I) (therefore, the positions of the epoxy groups in the two cyclohexane rings are 3,4-positions). It can be bonded to any position of the -6-position. Of course, this alkyl group may be a straight chain or may be branched when it has 3 or more carbon atoms. Moreover, as above-mentioned, in C3 or more, you may have an alicyclic structure. Typical examples of the alkyl group having an alicyclic structure include cyclopentyl and cyclohexyl.

  Similarly, in the formula (I), X connecting two 3,4-epoxycyclohexane rings is an oxygen atom, an alkanediyl group having 1 to 6 carbon atoms, or 2 represented by any of the above formulas (Ia) to (Id). Is a valent group. Here, the alkanediyl group is a concept including alkylene and alkylidene, and the alkylene may be a straight chain or may be branched when it has 3 or more carbon atoms.

In addition, when X is a divalent group represented by any one of the above formulas (Ia) to (Id), the linking groups Y ¹ , Y ² , Y ³ and Y ⁴ in each formula each have 1 to 1 carbon atoms. When the alkanediyl group has 3 or more carbon atoms, it may have an alicyclic structure. Of course, these alkanediyl groups may be linear, or may be branched when having 3 or more carbon atoms. Moreover, as above-mentioned, in C3 or more, you may have an alicyclic structure. Typical examples of alkanediyl groups having an alicyclic structure include cyclopentylene and cyclohexylene.

The alicyclic diepoxy compound (A1) represented by the formula (I) will be specifically described. X in the formula (I) is a divalent group represented by the above formula (Ia), and a in the formula is The compound which is 0 includes 3,4-epoxycyclohexylmethanol (an alkyl group having 1 to 6 carbon atoms may be bonded to the cyclohexane ring) and 3,4-epoxycyclohexanecarboxylic acid (carbon is added to the cyclohexane ring). The esterified product with an alkyl group of 1 to 6 may be bonded. Specific examples thereof include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (formula (I) (wherein X is a divalent group represented by formula (Ia) where a = 0)). A compound of R ¹ = R ² = H], 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate [in the formula (I) having the same X as above, R ¹ = 6-methyl, R ² = 6-methyl compound], 3,4-epoxy-1-methylcyclohexylmethyl-3,4-epoxy-1-methylcyclohexanecarboxylate [formula having the same X as above ( in ^I), R 1 = 1- ^methyl, R 2 = 1-methyl compound], 3,4-epoxy-3-methyl-cyclohexylmethyl-3,4-epoxy [In the formula (I) having the same X as ^above, R 1 = ^3-methyl, R 2 = 3-methyl compound 3- methylcyclohexane carboxylate and the like.

  The compound in which X in the formula (I) is a divalent group represented by the above formula (Ib) is an alkylene glycol and 3,4-epoxycyclohexanecarboxylic acid (an alkyl group may be bonded to the cyclohexane ring) ) And an esterified product. The compound in which X in the formula (I) is a divalent group represented by the above formula (Ic) is an aliphatic dicarboxylic acid and 3,4-epoxycyclohexylmethanol (an alkyl group may be bonded to the cyclohexane ring). ) And an esterified product. The compound in which X in the formula (I) is a divalent group represented by the above formula (Id) is an ether of 3,4-epoxycyclohexylmethanol (an alkyl group may be bonded to the cyclohexane ring). (When b = 0), or etherified product of alkylene glycols or polyalkylene glycols and 3,4-epoxycyclohexylmethanol (an alkyl group may be bonded to the cyclohexane ring) (b> 0) In the case of

(A2) Diglycidyl Compound The amount of the diglycidyl compound (A2) in the photocationic curable component (A) is 20 to 75% by weight based on the total amount of the photocationic curable component (A). By mix | blending 20 weight% or more of diglycidyl compounds (A2) in a photocationic curable component (A), the viscosity in 25 degreeC of a photocurable adhesive agent can be adjusted to 2-300 mPa * s. On the other hand, when the amount exceeds 75% by weight, the adhesion between the polarizer and the protective film is not sufficient.

  From the viewpoint of adjusting the viscosity, it is preferable that the amount of the diglycidyl compound (A2) exceeds 50% by weight with respect to the total amount of the alicyclic diepoxy compound (A1) and the diglycidyl compound (A2).

In the above formula (II) representing the diglycidyl compound (A2), Z is an alkylene group having 1 to 9 carbon atoms, an alkylidene group having 3 or 4 carbon atoms, a divalent alicyclic hydrocarbon group, SO ₂ , SO or CO. Typical examples of the divalent alicyclic hydrocarbon group include cyclopentylene and cyclohexylene.

  The compound in which Z is an alkylene group in formula (II) is a diglycidyl ether of alkylene glycol. Specific examples thereof include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,3-propanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and the like. is there.

(A3) Polymer composed of ethylenically unsaturated monomer The amount of the polymer (A3) composed of at least one ethylenically unsaturated monomer is 5 to 50 based on the total amount of the photocationically curable component (A). % By weight, preferably 7-30% by weight. The effect which improves the adhesive force between a polarizer and a protective film can be expressed by mix | blending 5 weight% or more of polymers (A3) in a photocationic curable component (A). On the other hand, when the amount exceeds 50% by weight, the viscosity increases, which is not preferable. If it is less than 5%, the adhesion to the acrylic protective film is low, such being undesirable.

  The polymer (A3) comprising at least one ethylenically unsaturated monomer is obtained by polymerizing at least one ethylenically unsaturated monomer selected from the monomers represented by the formula (III) or (IV). Can be obtained. Moreover, the weight average molecular weight is 5000-100000.

X in the above formulas (III) and (IV) is
(I) an alkyl group having 1 to 7 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alicyclic hydrocarbon group having 6 to 10 carbon atoms, or
(Ii) an alkyl group having 1 to 7 carbon atoms and an aryl having 6 to 12 carbon atoms partially substituted with one or more groups selected from the group consisting of an epoxy group, an oxetane group, a hydroxyl group and a carboxyl group Represents a group or an alicyclic hydrocarbon group having 6 to 10 carbon atoms.

  Examples of the alkyl group having 1 to 7 carbon atoms (preferably 1 to 4) include methyl, ethyl, propyl, iso-propyl, butyl, sec-butyl, tert-butyl, iso-butyl, amyl, iso-amyl, tert -Amyl, hexyl, 2-hexyl, 3-hexyl, cyclohexyl, 4-methylcyclohexyl, heptyl, 2-heptyl, 3-heptyl, iso-heptyl, tert-heptyl and the like. Among these, a methyl group or a methyl group partially substituted with one or more groups selected from the group consisting of an epoxy group, an oxetane group, a hydroxyl group and a carboxyl group, or a branched alkyl group having 2 to 4 carbon atoms Alternatively, a branched alkyl group having 2 to 4 carbon atoms is preferable from the viewpoint of the durability of the film.

  Examples of the aryl group having 6 to 12 (preferably 6 to 10) carbon atoms include phenyl, methylphenyl, naphthyl and the like.

  Examples of the alicyclic hydrocarbon group having 6 to 10 carbon atoms include cyclohexyl, methylcyclohexyl, norbornyl, bicyclopentyl, bicyclooctyl, trimethylbicycloheptyl, tricyclooctyl, tricyclodecanyl, spirooctyl, spirobicyclopentyl. , Adamantyl, isobornyl and the like.

  In the above formula (III), the ethylenically unsaturated monomer represented by the formula (III) when a part of X is substituted with an epoxy group or an oxetane group includes, for example, the following formulas (1) to The monomer represented by (3) is mentioned.

(In the formula, R ₄ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and m is an integer of 1 to 6).

(Wherein R ₅ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n is an integer of 1 to 6)

(In the formula, R ₆ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and s is an integer of 1 to 6)

In the above formula (IV), examples of the halogen atom that can be R ₃ include fluorine, chlorine, bromine, and iodine.

  In the above formula (IV), the ethylenically unsaturated monomer represented by the formula (IV) when a part of X is substituted with an epoxy group or an oxetane group includes the following formulas (4) to (6) ).

(In the formula, R ₃ is the same as the above formula (IV), R ₇ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and t is an integer of 1 to 6).

(In the formula, R ₃ is the same as the above formula (IV), R ₈ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and x is an integer of 1 to 6).

(In the formula, R ₃ is the same as the above formula (IV), R ₉ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and y is an integer of 1 to 6).

The ethylenically unsaturated monomer is
X is a methyl group partially substituted with one or more groups selected from the group consisting of an epoxy group, an oxetane group and a hydroxyl group, a branched alkyl group having 2 to 7 carbon atoms, and 6 to 12 carbon atoms. And an ethylenically unsaturated monomer represented by the above formula (III) or (IV) in the case of the aryl group or the alicyclic hydrocarbon group having 6 to 10 carbon atoms.

The ethylenically unsaturated monomer is
(I) In the case where X is a methyl group, a branched alkyl group having 2 to 7 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alicyclic hydrocarbon group having 6 to 10 carbon atoms 20 to 90% by weight of the ethylenically unsaturated monomer represented by the above formula (III) or (IV),
(Ii) X is a methyl group partially substituted with one or more groups selected from the group consisting of an epoxy group, an oxetane group and a hydroxyl group, a branched alkyl group having 2 to 7 carbon atoms, and the number of carbon atoms 10 to 80 weight of ethylenically unsaturated monomer represented by the above formula (III) or (IV) in the case of 6-12 aryl group or alicyclic hydrocarbon group having 6-10 carbon atoms % Is preferably included.

  The polymer (A3) has a weight average molecular weight of 5,000 to 100,000, preferably 7,000 to 70,000.

  The glass transition temperature (Tg) of the polymer (A3) is preferably 40 ° C. or higher from the viewpoint of film durability.

  The photocationic curable component (A) constituting the photocurable adhesive is a polymer (A3) comprising the above-described alicyclic diepoxy compound (A1), diglycidyl compound (A2), and an ethylenically unsaturated monomer. In the proportions described above. In order to more effectively reduce the viscosity of the photocurable adhesive before curing and improve the adhesion between the polarizer and the protective film, the alicyclic type is based on the total amount of the photocurable adhesive. It is preferable that the total amount of the diepoxy compound (A1) and the polymer (A3) composed of the ethylenically unsaturated monomer is 25% by weight or more.

(Other photocationic curable components)
If the photocationic curable component (A) is an alicyclic diepoxy compound (A1), a diglycidyl compound (A2) and a polymer (A3) composed of an ethylenically unsaturated monomer in the above amounts, The photocation curable component may be contained in an amount of 1 to 30 parts by weight with respect to 100 parts by weight of the photo cation curable component.

  Examples of other photocationic curable components include epoxy compounds other than (A1) to (A3), oxetane compounds, cyclic lactone compounds, cyclic acetal compounds, cyclic thioether compounds, spiroorthoester compounds, vinyl compounds, and the like.

  Examples of the vinyl compound include aliphatic or alicyclic vinyl ether compounds, such as n-amyl vinyl ether, i-amyl vinyl ether, n-hexyl vinyl ether, n-octyl vinyl ether, 2-ethylhexyl vinyl ether, and n-dodecyl vinyl ether. , Vinyl ethers of 5 to 20 alkyl or alkenyl alcohols such as stearyl vinyl ether and oleyl vinyl ether, hydroxyl-containing vinyl ethers such as 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, cyclohexyl vinyl ether, 2- Aliphatic rings such as methyl cyclohexyl vinyl ether, cyclohexyl methyl vinyl ether, and benzyl vinyl ether Are monoalcohol vinyl ethers having an aromatic ring, glycerol monovinyl ether, 1,4-butanediol monovinyl ether, 1,4-butanediol divinyl ether, 1,6-hexanediol divinyl ether, neopentyl glycol divinyl ether, penta Erythritol divinyl ether, pentaerythritol tetravinyl ether, trimethylolpropane divinyl ether, trimethylolpropane trivinyl ether, 1,4-dihydroxycyclohexane monovinyl ether, 1,4-dihydroxycyclohexane divinyl ether, 1,4-dihydroxymethylcyclohexane monovinyl ether, 1 Mono-polyvinyl of polyhydric alcohols such as 1,4-dihydroxymethylcyclohexanedivinyl ether Ethers, diethylene glycol divinyl ether, polyalkylene glycol mono-divinyl ethers such as triethylene glycol divinyl ether, diethylene glycol monobutyl monovinyl ether, glycidyl vinyl ether, and other vinyl ethers such as ethylene glycol vinyl methacrylate.

(B) Photocationic polymerization initiator In the present invention, since the above cationically polymerizable compound is cured by cationic polymerization by irradiation of active energy rays to form an adhesive layer, the photocurable adhesive includes: A photocationic polymerization initiator (B) is blended. The cationic polymerization initiator generates a cationic species or a Lewis acid upon irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams, and starts a polymerization reaction of the cationic polymerizable compound (A). . Since the cationic photopolymerization initiator acts catalytically by light, it is excellent in storage stability and workability even when mixed with the cationically polymerizable compound (A). Examples of the compound that generates a cationic species or a Lewis acid upon irradiation with active energy rays include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; iron-allene complexes.

As an aromatic diazonium salt, for example,
Benzenediazonium hexafluoroantimonate,
Benzenediazonium hexafluorophosphate,
Examples thereof include benzenediazonium hexafluoroborate.

As an aromatic iodonium salt, for example,
Diphenyliodonium tetrakis (pentafluorophenyl) borate,
Diphenyliodonium hexafluorophosphate,
Diphenyliodonium hexafluoroantimonate,
Di (4-nonylphenyl) iodonium hexafluorophosphate is mentioned.

As an aromatic sulfonium salt, for example,
Triphenylsulfonium hexafluorophosphate,
Triphenylsulfonium hexafluoroantimonate,
Triphenylsulfonium tetrakis (pentafluorophenyl) borate,
4,4′-bis [diphenylsulfonio] diphenyl sulfide bishexafluorophosphate,
4,4′-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide bishexafluoroantimonate,
4,4′-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide bishexafluorophosphate,
7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone hexafluoroantimonate,
7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone tetrakis (pentafluorophenyl) borate,
4-phenylcarbonyl-4′-diphenylsulfonio-diphenyl sulfide hexafluorophosphate,
4- (p-tert-butylphenylcarbonyl) -4′-diphenylsulfonio-diphenyl sulfide hexafluoroantimonate,
4- (p-tert-butylphenylcarbonyl) -4′-di (p-toluyl) sulfonio-diphenyl sulfide tetrakis (pentafluorophenyl) borate and the like.

As an iron-allene complex, for example,
Xylene-cyclopentadienyl iron (II) hexafluoroantimonate,
Cumene-cyclopentadienyl iron (II) hexafluorophosphate,
Xylene-cyclopentadienyl iron (II) tris (trifluoromethylsulfonyl) methanide.

  These cationic photopolymerization initiators may be used alone or in combination of two or more. Among these, aromatic sulfonium salts are particularly preferably used because they have ultraviolet absorption characteristics even in a wavelength region near 300 nm, and therefore can provide a cured product having excellent curability and good mechanical strength and adhesive strength. It is done.

  The compounding quantity of a photocationic polymerization initiator (B) shall be 1-10 weight part with respect to 100 weight part of the whole cationic polymerizable compound (A). By blending 1 part by weight or more of the cationic photopolymerization initiator per 100 parts by weight of the cationically polymerizable compound (A), the cationically polymerizable compound (A) can be sufficiently cured, and the resulting polarizing plate has high mechanical strength. And give adhesive strength. On the other hand, when the amount increases, the ionic substance in the cured product increases, so that the hygroscopic property of the cured product increases and the durability performance of the polarizing plate may be lowered. ) In an amount of 10 parts by weight or less per 100 parts by weight of the cationically polymerizable compound (A). The amount of the cationic photopolymerization initiator (B) is preferably 2 parts by weight or more and preferably 6 parts by weight or less per 100 parts by weight of the cationic polymerizable compound (A).

(Photosensitizer)
The photocurable adhesive of the present invention may contain a photosensitizer in addition to the cationic polymerizable compound (A) and the photo cationic polymerization initiator (B) containing the epoxy compound as described above. The above-mentioned photocationic polymerization initiator (B) exhibits maximum absorption at a wavelength near or shorter than 300 nm, generates a cationic species or a Lewis acid in response to light having a wavelength in the vicinity of the photocationic polymerization initiator (A). ) Is initiated, but the photosensitizer is preferably a photosensitizer that exhibits maximum absorption in light having a wavelength longer than 380 nm so as to be sensitive to light having a longer wavelength. As such a photosensitizer, an anthracene compound is preferably used.

Specific examples of anthracene compounds include
9,10-dimethoxyanthracene,
9,10-diethoxyanthracene,
9,10-dipropoxyanthracene,
9,10-diisopropoxyanthracene,
9,10-dibutoxyanthracene,
9,10-dipentyloxyanthracene,
9,10-dihexyloxyanthracene,
9,10-bis (2-methoxyethoxy) anthracene,
9,10-bis (2-ethoxyethoxy) anthracene,
9,10-bis (2-butoxyethoxy) anthracene,
9,10-bis (3-butoxypropoxy) anthracene,
2-methyl or 2-ethyl-9,10-dimethoxyanthracene,
2-methyl or 2-ethyl-9,10-diethoxyanthracene,
2-methyl or 2-ethyl-9,10-dipropoxyanthracene,
2-methyl or 2-ethyl-9,10-diisopropoxyanthracene,
2-methyl or 2-ethyl-9,10-dibutoxyanthracene,
2-methyl or 2-ethyl-9,10-dipentyloxyanthracene,
Examples include 2-methyl or 2-ethyl-9,10-dihexyloxyanthracene.

  By mix | blending the above photosensitizers with a photocurable adhesive, the sclerosis | hardenability of an adhesive improves compared with the case where it is not mix | blended. Such an effect is exhibited by setting the blending amount of the photosensitizer to 100 parts by weight of the cationic polymerizable compound (A) constituting the photocurable adhesive to 0.1 parts by weight or more. On the other hand, when the blending amount of the photosensitizer increases, problems such as precipitation during low-temperature storage occur. Therefore, the amount is set to 2 parts by weight or less with respect to 100 parts by weight of the cationic polymerizable compound (A). From the viewpoint of maintaining the neutral gray of the polarizing plate, it is more advantageous to reduce the amount of the photosensitizer in the range in which the adhesive force between the polarizer and the protective film is appropriately maintained. The amount of the photosensitizer is preferably 0.1 to 0.5 parts by weight, more preferably 0.1 to 0.3 parts by weight with respect to 100 parts by weight of the compound (A).

(Photosensitizer)
The photocurable adhesive of the present invention contains a photosensitizing assistant in addition to the cationic polymerizable compound (A) containing the epoxy compound as described above, the photocationic polymerization initiator (B), and the photosensitizer. May be. The photosensitizer is preferably a naphthalene photosensitizer.

As a specific example of a naphthalene photosensitizing aid,
4-methoxy-1-naphthol,
4-ethoxy-1-naphthol,
4-propoxy-1-naphthol,
4-butoxy-1-naphthol,
4-hexyloxy-1-naphthol,
1,4-dimethoxynaphthalene,
1-ethoxy-4-methoxynaphthalene,
1,4-diethoxynaphthalene,
1,4-dipropoxynaphthalene,
1,4-dibutoxynaphthalene is mentioned.

  By blending a naphthalene photosensitizer with the photocurable adhesive, the curability of the adhesive is improved as compared with the case where it is not blended. Such an effect is exhibited by setting the blending amount of the naphthalene photosensitizer to 100 parts by weight of the cationic polymerizable compound (A) constituting the photocurable adhesive to 0.1 parts by weight or more. On the other hand, if the blending amount of the naphthalene photosensitizer is increased, problems such as precipitation during low-temperature storage occur, so the amount is 5 parts by weight or less with respect to 100 parts by weight of the cationic polymerizable compound (A). And The blending amount of the naphthalene photosensitizing assistant is preferably 3 parts by weight or less with respect to 100 parts by weight of the cationic polymerizable compound (A).

  Furthermore, an additive component can be contained in the photocurable adhesive of the present invention as an optional component as long as the effects of the present invention are not impaired. Additive components include thermal cationic polymerization initiators, polyols, ion trapping agents, antioxidants, light stabilizers, chain transfer agents, tackifiers, thermoplastic resins, fillers, flow regulators, plasticizers, quenchers. Foaming agents, leveling agents, pigments, organic solvents and the like can be blended.

  When the additive component is contained, the amount of the additive component used is preferably 1000 parts by weight or less with respect to 100 parts by weight of the above-mentioned photocationic curable component (A). When the amount used is 1000 parts by weight or less, the storage stability of the combination of the photocationic curable component (A) and the photocationic polymerization initiator (B), which are essential components of the photocurable adhesive of the present invention, is improved. The effects of improving, preventing discoloration, improving the curing rate, and ensuring good adhesion can be exhibited well.

(moisture)
The photocurable adhesive of the present invention may contain moisture in addition to the cationic polymerizable compound (A) containing the epoxy compound as described above and the photo cationic polymerization initiator (B). By blending moisture, the adhesive force between the polarizer and the protective film is further improved. By making the blending amount of the water with respect to 100 parts by weight of the cationic polymerizable compound (A) constituting the photocurable adhesive 0.5 parts by weight or more, more preferably 1 part by weight or more, the effect of improving the adhesive strength is obtained. To express. On the other hand, when the amount of moisture increases, the photocurable adhesive and the moisture are separated, making it impossible to uniformly apply the photocurable adhesive to the surface of the polarizer or the protective film. Since the curability of the adhesive is deteriorated, the blending amount of water with respect to 100 parts by weight of the cationic polymerizable compound (A) constituting the photocurable adhesive is preferably 4 parts by weight or less, more preferably 3 parts by weight. Less than. Although the kind of moisture is not particularly limited, for example, purified water such as distilled water or pure water is used.

(Diol compound)
The photocurable adhesive of the present invention may contain a diol compound in addition to the cationic polymerizable compound (A) containing the epoxy compound as described above and the photo cationic polymerization initiator (B). By blending the diol compound, the adhesive strength, particularly the adhesive strength between the polarizer and the protective film is improved.

  The diol compound is a compound having two hydroxyl groups in the molecule, and can typically be a compound represented by the following formula (V).

HO-A-OH (V)
A in the formula can be an alkylene group having 2 to 8 carbon atoms which may be interrupted by an oxygen atom.

  Specific examples of the diol compound include oligoalkylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,4 -Butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol and the like.

  The oligoalkylene glycol is preferably an oligoalkylene glycol represented by the following formula (Va).

_{HO- (C m H 2m -O)} n -H (Va)
M in the formula is 2 or 3, and n is an integer of 1 or more, but m × n is 8 or less.

  Examples of the oligoalkylene glycol represented by the formula (Va) include ethylene glycol, diethylene glycol, and triethylene glycol. Among them, it is easy to obtain and has a high affinity for a polyvinyl alcohol-based resin. Ethylene glycol is preferred.

  The effect of improving adhesive strength by setting the blending amount of the diol compound to 100 parts by weight of the cationic polymerizable compound (A) constituting the photocurable adhesive is 0.5 parts by weight or more, more preferably 1 part by weight or more. Is expressed. On the other hand, when the amount of the diol compound is increased, the photocurable adhesive and the diol compound are separated, and the photocurable adhesive cannot be uniformly applied to the surface of the polarizer or the protective film. The blending amount of the diol compound with respect to 100 parts by weight of the cationic polymerizable compound (A) constituting the curable adhesive is preferably 8 parts by weight or less, more preferably 6 parts by weight or less.

[Polarizer]
The polarizer is composed of a polyvinyl alcohol-based resin film on which a dichroic dye is adsorbed and oriented. The polyvinyl alcohol resin constituting the polarizer can be obtained by saponifying a polyvinyl acetate resin. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The degree of saponification of the polyvinyl alcohol resin is usually 85 to 100 mol%, preferably 98 to 100 mol%. The polyvinyl alcohol-based resin may be further modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The degree of polymerization of the polyvinyl alcohol resin is usually 1,000 to 10,000, preferably 1,500 to 5,000.

  The polarizer is a process of uniaxially stretching such a polyvinyl alcohol-based resin film, a step of dyeing the polyvinyl alcohol-based resin film with a dichroic dye and adsorbing the dichroic dye, and a dichroic dye being adsorbed It is manufactured through a step of treating the polyvinyl alcohol resin film with a boric acid aqueous solution.

  Uniaxial stretching may be performed before dyeing with a dichroic dye, may be performed simultaneously with dyeing with a dichroic dye, or may be performed after dyeing with a dichroic dye. When uniaxial stretching is performed after dyeing with a dichroic dye, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Of course, it is also possible to perform uniaxial stretching in these plural stages. For uniaxial stretching, rolls having different peripheral speeds may be uniaxially stretched or uniaxially stretched using a hot roll. Moreover, the dry-type extending | stretching which extends | stretches in air | atmosphere may be sufficient, and the wet extending | stretching which extends | stretches in the state swollen with the solvent may be sufficient. The draw ratio is usually about 4 to 8 times.

  In order to dye the polyvinyl alcohol resin film with the dichroic dye, for example, the polyvinyl alcohol resin film may be immersed in an aqueous solution containing the dichroic dye. Specifically, iodine or a dichroic organic dye is used as the dichroic dye.

  When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol resin film by dipping it in an aqueous solution containing iodine and potassium iodide is usually employed. The content of iodine in this aqueous solution is usually about 0.01 to 0.5 parts by weight per 100 parts by weight of water, and the content of potassium iodide is usually about 0.5 to 10 parts by weight per 100 parts by weight of water. It is. The temperature of this aqueous solution is usually about 20 to 40 ° C., and the immersion time (dyeing time) in this aqueous solution is usually about 30 to 300 seconds.

On the other hand, when a dichroic organic dye is used as the dichroic dye, a method of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic organic dye is usually employed. The content of the dichroic organic dye in this aqueous solution is usually about 1 × 10 ⁻³ to 1 × 10 ⁻² parts by weight per 100 parts by weight of water. This aqueous solution may contain an inorganic salt such as sodium sulfate. The temperature of this aqueous solution is usually about 20 to 80 ° C., and the immersion time (dyeing time) in this aqueous solution is usually about 30 to 300 seconds.

  The boric acid treatment after dyeing with a dichroic dye is performed by immersing the dyed polyvinyl alcohol resin film in an aqueous boric acid solution. The boric acid content in the boric acid aqueous solution is usually about 2 to 15 parts by weight, preferably about 5 to 12 parts by weight per 100 parts by weight of water. When iodine is used as the dichroic dye, the aqueous boric acid solution preferably contains potassium iodide. The content of potassium iodide in the boric acid aqueous solution is usually about 2 to 20 parts by weight, preferably 5 to 15 parts by weight per 100 parts by weight of water. The immersion time in the boric acid aqueous solution is usually about 100 to 1,200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the boric acid aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C.

  The polyvinyl alcohol resin film after the boric acid treatment is usually washed with water. The water washing treatment is performed, for example, by immersing a boric acid-treated polyvinyl alcohol resin film in water. After washing with water, a drying process is performed to obtain a polarizer. The temperature of water in the water washing treatment is usually about 5 to 40 ° C., and the immersion time is usually about 2 to 120 seconds. The drying process performed thereafter is usually performed using a hot air dryer or a far infrared heater. The drying temperature is usually 40 to 100 ° C. Moreover, the time of a drying process is about 120 to 600 seconds normally.

  Thus, the thickness of the polarizer which consists of a polyvinyl alcohol-type resin film can be about 10-50 micrometers.

[Protective film]
The polarizing plate of the present invention is formed by laminating a protective film made of a transparent resin film on the polarizer made of the polyvinyl alcohol-based resin film described above via the photo-curable adhesive described above, and photocurable adhesive. It is obtained by curing the agent.

  The transparent resin film constituting the protective film may be either an unstretched film or a uniaxially or biaxially stretched film.

  The main component of the transparent resin film is preferably at least one resin selected from the group consisting of a cellulose resin, an acrylic resin, an amorphous polyolefin resin, a polyester resin, and a polycarbonate resin.

  The polyester resin is not particularly limited, but polyethylene terephthalate is particularly preferable in terms of mechanical properties, solvent resistance, scratch resistance, cost, and the like. Polyethylene terephthalate means a resin in which 80 mol% or more of repeating units are composed of ethylene terephthalate, and may contain structural units derived from other copolymerization components.

  Examples of other copolymer components include a dicarboxylic acid component and a diol component. Dicarboxylic acid components include isophthalic acid, p-β-hydroxyethoxybenzoic acid, 4,4′-dicarboxydiphenyl, 4,4′-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid, sebacic acid , 5-sodium sulfoisophthalic acid, 1,4-dicarboxycyclohexane, and the like. Examples of the diol component include propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. These dicarboxylic acid components and diol components can also be used in combination of two or more as required. In addition, a hydroxycarboxylic acid such as p-hydroxybenzoic acid can be used in combination with the dicarboxylic acid component and the diol component. As other copolymer components, a small amount of a dicarboxylic acid component and / or a diol component having an amide bond, a urethane bond, an ether bond, a carbonate bond or the like may be used.

  The polyethylene terephthalate-based resin means a resin in which 80 mol% or more of repeating units are composed of ethylene terephthalate, and may include structural units derived from other copolymerization components. Other copolymer components include isophthalic acid, 4,4′-dicarboxydiphenyl, 4,4′-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid, sebacic acid, 5-sodium sulfoisophthalate. Acid, dicarboxylic acid components such as 1,4-dicarboxycyclohexane; propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. A diol component is mentioned. These dicarboxylic acid components and diol components can be used in combination of two or more if necessary. It is also possible to use a hydroxycarboxylic acid such as p-hydroxybenzoic acid or p-β-hydroxyethoxybenzoic acid together with the carboxylic acid component or diol component. As other copolymerization component, a dicarboxylic acid component and / or a diol component containing a small amount of an amide bond, a urethane bond, an ether bond, a carbonate bond or the like may be used.

  After filming the above polyethylene terephthalate resin, it is excellent in mechanical properties, solvent resistance, scratch resistance, cost, etc., and reduced in thickness by using the film subjected to the above-mentioned stretching treatment as a protective film. Thus, a rolled polarizing plate can be obtained.

  The polycarbonate resin used for the protective film is a polyester formed from carbonic acid and glycol or bisphenol. Among these, an aromatic polycarbonate having a diphenylalkane in the molecular chain is preferably used because it is excellent in heat resistance, weather resistance and acid resistance. Such polycarbonates include 2,2-bis (4-hydroxyphenyl) propane (also known as bisphenol A), 2,2-bis (4-hydroxyphenyl) butane, 1,1-bis (4-hydroxyphenyl) cyclohexane, Illustrative are polycarbonates derived from bisphenols, such as 1,1-bis (4-hydroxyphenyl) isobutane or 1,1-bis (4-hydroxyphenyl) ethane.

  As a method for producing a polycarbonate resin film, any method such as a casting film forming method or a melt extrusion method may be used. As an example of a specific production method, a polycarbonate resin is dissolved in an appropriate organic solvent to form a polycarbonate resin solution, which is cast on a metal support to form a web, and the web is formed on the metal support. After peeling off from the film, a method of obtaining a film by drying the peeled web with hot air can be mentioned.

  The acrylic resin used for the protective film is not particularly limited, but is generally a polymer having a methacrylic acid ester as the main monomer, and a copolymer in which a small amount of other comonomer components are copolymerized. Is preferred. This copolymer can be usually obtained by polymerizing a monofunctional monomer containing methyl methacrylate and methyl acrylate in the presence of a radical polymerization initiator and a chain transfer agent. The acrylic resin can be copolymerized with a third monofunctional monomer.

  Examples of the third monofunctional monomer that can be copolymerized with methyl methacrylate and methyl acrylate include, for example, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate. , And methacrylates other than methyl methacrylate, such as 2-hydroxyethyl methacrylate; ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, and acrylic acid 2 Acrylic esters such as hydroxyethyl; methyl 2- (hydroxymethyl) acrylate, methyl 2- (1-hydroxyethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, and 2- Hydroxyalkyl acrylates such as (hydroxymethyl) butyl acrylate; unsaturated acids such as methacrylic acid and acrylic acid; halogenated styrenes such as chlorostyrene and bromostyrene; substituted styrenes such as vinyltoluene and α-methylstyrene And unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated acid anhydrides such as maleic anhydride and citraconic anhydride; unsaturated imides such as phenylmaleimide and cyclohexylmaleimide. Each of these may be used alone, or a plurality of different types may be used in combination.

  When copolymerizing polyfunctional monomers, examples of polyfunctional monomers that can be copolymerized with methyl methacrylate and methyl acrylate include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, and triethylene. Glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, nonaethylene glycol di (meth) acrylate, tetradecaethylene glycol di (meth) acrylate, etc. Esterified with methacrylic acid; Propylene glycol or its oligomers hydroxylated at both terminal hydroxyl groups with acrylic acid or methacrylic acid; Neopentyl glycol di (meth) acrylate, One obtained by esterifying a hydroxyl group of a dihydric alcohol such as xanthdiol di (meth) acrylate and butanediol di (meth) acrylate with acrylic acid or methacrylic acid; bisphenol A, alkylene oxide adduct of bisphenol A, or halogens thereof Those obtained by esterifying the hydroxyl groups at both ends of the substituent with acrylic acid or methacrylic acid; those obtained by esterifying polyhydric alcohols such as trimethylolpropane and pentaerythritol with acrylic acid or methacrylic acid, and glycidyl acrylate or glycidyl at these terminal hydroxyl groups Ring-opening addition of an epoxy group of methacrylate; dibasic acids such as succinic acid, adipic acid, terephthalic acid, phthalic acid, and halogen-substituted products thereof, and alkylene oxy Id adducts as epoxy group of glycidyl acrylate or glycidyl methacrylate was ring-opening addition to the like; aryl (meth) acrylate; and aromatic divinyl compounds such as divinylbenzene. Among these, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and neopentyl glycol dimethacrylate are preferably used.

  The acrylic resin having such a composition may be further modified by a reaction between functional groups of the copolymer. As the reaction, for example, demethanol condensation reaction in a polymer chain between a methyl ester group of methyl acrylate and a hydroxyl group of methyl 2- (hydroxymethyl) acrylate, a carboxyl group of acrylic acid and 2- (hydroxymethyl) acrylic Examples thereof include a dehydration condensation reaction in a polymer chain with a hydroxyl group of methyl acid.

  The glass transition temperature of the acrylic resin is preferably in the range of 80 to 120 ° C. In order to adjust the glass transition temperature of the acrylic resin to the above range, the polymerization ratio of the methacrylic acid ester monomer and the acrylic acid ester monomer, the carbon chain length of each ester group, and the functional group possessed by the polymerization ratio And a method of appropriately selecting the polymerization ratio of the polyfunctional acrylic monomer with respect to the whole monomer.

  The acrylic resin may contain a known additive as required. Known additives include, for example, lubricants, anti-blocking agents, heat stabilizers, antioxidants, antistatic agents, light resistance agents, impact resistance improvers, surfactants and the like. However, since transparency is required as a protective film laminated on the polarizing film, it is preferable to keep the amount of these additives to a minimum.

  As a method for producing the acrylic resin film, any method such as a melt casting method, a melt extrusion method such as a T-die method or an inflation method, or a calendar method may be used. Among these, a method of forming a film by melting and extruding a raw material resin from, for example, a T die and bringing at least one surface of the obtained film-like material into contact with a roll or a belt is preferable in that a film having good surface properties can be obtained.

  The acrylic resin may contain acrylic rubber particles that are impact modifiers from the viewpoint of film-forming properties on the film and impact resistance of the film. The acrylic rubber particles here are particles having an elastic polymer mainly composed of an acrylate ester as an essential component, and those having a single layer structure consisting essentially of this elastic polymer, or this elastic polymer. Can be a multi-layer structure having a single layer. An example of such an elastic polymer is a cross-linked elastic copolymer obtained by copolymerizing an alkyl acrylate as a main component with another vinyl monomer and a cross-linkable monomer copolymerizable therewith. Examples of the alkyl acrylate that is the main component of the elastic polymer include those having an alkyl group of about 1 to 8 carbon atoms, such as methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate. An acrylate having an alkyl group of several 4 or more is preferably used. Examples of the other vinyl monomer copolymerizable with the alkyl acrylate include compounds having one polymerizable carbon-carbon double bond in the molecule, and more specifically, methacrylic acid such as methyl methacrylate. Examples thereof include aromatic vinyl compounds such as esters and styrene and vinylcyan compounds such as acrylonitrile. Examples of the crosslinkable monomer include a crosslinkable compound having at least two polymerizable carbon-carbon double bonds in the molecule, and more specifically, ethylene glycol di (meth) acrylate and butanediol. Examples include (meth) acrylates of polyhydric alcohols such as di (meth) acrylate, alkenyl esters of (meth) acrylic acid such as allyl (meth) acrylate, and divinylbenzene.

  Furthermore, a laminate of a film made of an acrylic resin not containing rubber particles and a film made of an acrylic resin containing rubber particles can be used as a protective film. Commercially available acrylic resins can be easily obtained. For example, Sumipex (manufactured by Sumitomo Chemical Co., Ltd.), Acrypet (manufactured by Mitsubishi Rayon Co., Ltd.), Delpet (Asahi Kasei Co., Ltd.) Product), parapet (manufactured by Kuraray Co., Ltd.), acryl viewer (manufactured by Nippon Shokubai Co., Ltd.), and the like.

  The amorphous polyolefin resin used for the protective film is a resin obtained by performing ring-opening metathesis polymerization from cyclopentadiene and olefins using norbornene obtained by Diels-Alder reaction or a derivative thereof as a monomer, followed by hydrogenation; Resins obtained by ring-opening metathesis polymerization from dicyclopentadiene and olefins or methacrylic esters using tetracyclododecene or its derivatives obtained by Diels-Alder reaction, followed by hydrogenation; norbornene, tetracyclo A resin obtained by carrying out ring-opening metathesis copolymerization using two or more selected from dodecene and derivatives thereof, and other cyclic polyolefin monomers in the same manner, followed by hydrogenation; norbornene, Tiger cyclododecene or their derivatives, resins obtained by addition copolymerization of aromatic compounds and the like having a vinyl group. Examples of commercially available amorphous polyolefin resins include “Arton” from JSR Corporation, “ZEONEX” and “ZEONOR” from ZEON Corporation, “APO” and “APO” from Mitsui Chemicals, Inc. Appel ”. When the amorphous polyolefin-based resin is formed into a film, a known method such as a solvent casting method or a melt extrusion method is appropriately used for forming the film.

  The cellulose-based resin is a resin in which at least a part of hydroxyl groups in cellulose is acetate esterified, and may be a mixed ester in which part is acetated and partly esterified with another acid. . The cellulose resin is preferably a cellulose ester resin, and more preferably an acetyl cellulose resin. Specific examples of the acetyl cellulose resin include triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate. Commercially available films made of such acetylcellulose-based resins include, for example, “Fujitac TD80”, “Fujitac TD80UF” and “Fujitac TD80UZ” manufactured by Fuji Film Co., Ltd., and “KC8UX2M” manufactured by Konica Minolta Opto Co., Ltd. "And" KC8UY ".

  A cellulose resin film provided with an optical compensation function can also be used. As such an optical compensation film, for example, a film in which a compound having a retardation adjusting function is contained in a cellulose resin, a film in which a compound having a retardation adjusting function is applied to the surface of the cellulose resin, a cellulose resin is uniaxial or biaxial. Examples thereof include a film obtained by stretching on a shaft. Examples of commercially available optical compensation films for cellulose resins include “Wide View Film WV BZ 438” and “Wide View Film WV EA” manufactured by Fujifilm Corporation, manufactured by Konica Minolta Opto Corporation. There are “KC4FR-1” and “KC4HR-1”.

  The protective film (transparent resin film) bonded to one surface of the polarizer may contain an ultraviolet absorber. This is because the liquid crystal cell can be protected from deterioration due to ultraviolet rays by disposing a protective film containing an ultraviolet absorber on the viewing side of the liquid crystal cell.

  In this invention, the protective film which consists of the above-mentioned transparent resin film is bonded on the at least one surface of a polarizer using the above-mentioned photocurable adhesive agent. When bonding a protective film only to one side of a polarizer, for example, it may take a form such as directly providing an adhesive layer for bonding to another member such as a liquid crystal cell on the other side of the polarizer. it can.

  On the other hand, when a protective film is bonded to both surfaces of the polarizer, the respective protective films may be the same type or different types.

  The protective film bonded to one surface of the polarizer is bonded using the above-described photocurable adhesive, but the protective film bonded to the other surface of the polarizer is bonded to the other adhesive. May be used and bonded.

  Prior to bonding to the polarizer, the protective film may be subjected to easy adhesion treatment such as saponification treatment, corona treatment, primer treatment, and anchor coating treatment on the bonding surface. Moreover, you may have various process layers, such as a hard-coat layer, an antireflection layer, and a glare-proof layer, on the surface on the opposite side to the bonding surface to the polarizer of a protective film. The thickness of the protective film is usually in the range of about 5 to 200 μm, preferably 10 to 120 μm, and more preferably 10 to 85 μm.

[Adhesion of polarizer and protective film]
In bonding the polarizer and the protective film, the photocurable adhesive coating layer described above is formed on one or both of the bonding surfaces of the polarizer and the protective film, and the polarizer and the protective film are interposed through the coating layer. A protective film is bonded, the uncured photocurable adhesive coating layer thus formed is cured by irradiation with active energy rays, and the protective film is fixed on the polarizer. The application layer of a photocurable adhesive may be formed on the bonding surface of the polarizer, or may be formed on the bonding surface of the protective film. For forming the coating layer, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Moreover, it is also possible to employ a method in which an adhesive is cast while a polarizer and a protective film are continuously supplied so that the bonding surfaces of both are inside. Since each coating system has an optimum viscosity range, it is also a useful technique to adjust the viscosity using a solvent. As the solvent for this purpose, a solvent that dissolves the photocurable adhesive satisfactorily without reducing the optical performance of the polarizer is used, but there is no particular limitation on the type thereof. For example, organic solvents such as hydrocarbons typified by toluene and esters typified by ethyl acetate can be used. The film thickness can be arbitrarily set depending on the characteristic design of the polarizing plate, but is preferably smaller from the viewpoint of reducing the adhesive material cost, and is large from the viewpoint of suppressing defects such as bubbles and foreign matters during bonding. From the viewpoint of adhesion and durability, it is preferable to carry out within the optimum range determined for each combination of the adherend and the adhesive. Generally, it is 0.01-20 micrometers, Preferably, it is 0.1-10 micrometers, More preferably, it is 0.5-5 micrometers.

  When bonding the polarizer and the protective film, before forming the coating layer of the adhesive on one or both of the bonding surfaces of both, corona discharge treatment, plasma treatment, flame treatment, primer treatment, anchor coating treatment Such an easy adhesion treatment may be performed.

  The light source used for irradiating active energy rays to the coating layer of the photocurable adhesive may be any one that generates ultraviolet rays, electron beams, X-rays, and the like. In particular, for example, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp, a metal halide lamp or the like having a light emission distribution at a wavelength of 400 nm or less is preferably used.

The active energy ray irradiation intensity to the photocurable adhesive is determined for each adhesive to be cured and is not particularly limited, but the irradiation intensity in the wavelength region effective for activation of the initiator is It is preferable that it is 0.1-3000 mW / cm < ² >. When the light irradiation intensity to the photocurable adhesive is less than 0.1 mW / cm ² , the reaction time becomes too long, and when it exceeds 3000 mW / cm ² , the heat radiated from the lamp and the photocurable adhesive The heat generated during the polymerization may cause yellowing of the photocurable adhesive and deterioration of the polarizer.

The light irradiation time to the photocurable adhesive is controlled for each adhesive to be cured and is not particularly limited. However, the integrated light amount expressed as the product of the irradiation intensity and the irradiation time is 10 It is preferably set to be ˜5,000 mJ / cm ² . If the cumulative amount of light to the photocurable adhesive is less than 10 mJ / cm ² , active species derived from the initiator are not sufficiently generated, and the resulting adhesive layer may be insufficiently cured, When the integrated light quantity exceeds 5,000 mJ / cm ² , the irradiation time becomes very long, which is disadvantageous for improving productivity.

  When a protective film is bonded to both sides of the polarizer, active energy rays may be irradiated from either protective film side. For example, one protective film contains an ultraviolet absorber and the other protective film When the ultraviolet absorber is not contained, it is preferable to irradiate the active energy ray from the protective film side not containing the ultraviolet absorber in order to effectively utilize the irradiated active energy ray and increase the curing rate.

[Laminated optical member]
The polarizing plate of the present invention can be made into a laminated optical member by laminating optical layers having optical functions other than the polarizing plate. Typically, a laminated optical member is obtained by laminating and attaching an optical layer to a protective film of a polarizing plate via an adhesive or a pressure-sensitive adhesive. According to the invention, a protective film may be bonded via a photocurable adhesive, and an optical layer may be laminated and bonded to the other surface of the polarizer via an adhesive or a pressure-sensitive adhesive. In the latter case, if the photocurable adhesive defined in the present invention is used as an adhesive for adhering the polarizer and the optical layer, the optical layer can simultaneously be a protective film defined in the present invention.

  As an example of the optical layer laminated on the polarizing plate, a reflective layer laminated on the side opposite to the side facing the liquid crystal cell of the polarizing plate with respect to the polarizing plate arranged on the back side of the liquid crystal cell, Examples thereof include a transflective layer, a light diffusion layer, a light collector, and a brightness enhancement film. In addition, with respect to the polarizing plate disposed on the front side of the liquid crystal cell and / or the polarizing plate disposed on the back side of the liquid crystal cell, a retardation plate or the like laminated on the side of the polarizing plate facing the liquid crystal cell Can be mentioned.

  The reflective layer, transflective layer, or light diffusion layer is a reflective polarizing plate (optical member), a transflective polarizing plate (optical member), or a diffusing polarizing plate (optical member), respectively. Provided for. The reflective polarizing plate is used in a liquid crystal display device of a type that reflects and displays incident light from the viewing side. Since a light source such as a backlight can be omitted, the liquid crystal display device can be easily thinned. The transflective polarizing plate is used as a reflection type in a bright place and used in a liquid crystal display device that displays light from a backlight in a dark place. An optical member as a reflective polarizing plate can form a reflective layer by attaching a foil or a vapor deposition film made of a metal such as aluminum to a protective film on a polarizer, for example. The optical member as a transflective polarizing plate can be formed by using the reflective layer as a half mirror, or by adhering a reflective plate containing a pearl pigment or the like and exhibiting light transmittance to the polarizing plate. On the other hand, an optical member as a diffusion type polarizing plate can be obtained by various methods such as a method of performing a mat treatment on a protective film on a polarizing plate, a method of applying a resin containing fine particles, and a method of adhering a film containing fine particles. Use to form a fine relief structure on the surface.

  Furthermore, an optical member can be formed as a polarizing plate for both reflection and diffusion. In that case, for example, a method of providing a reflective layer reflecting the concavo-convex structure on the fine concavo-convex structure surface of the diffusion polarizing plate is adopted. it can. The reflective layer having a fine concavo-convex structure has advantages such that incident light is diffused by irregular reflection, directivity and glare can be prevented, and uneven brightness can be suppressed. In addition, the resin layer or film containing fine particles also has an advantage that incident light and its reflected light are diffused when passing through the fine particle-containing layer, and brightness unevenness can be suppressed. The reflective layer reflecting the surface fine concavo-convex structure can be formed by directly attaching a metal to the surface of the fine concavo-convex structure by a method such as vapor deposition such as vacuum deposition, ion plating, sputtering, or plating. The fine particles to be blended to form the surface fine concavo-convex structure are, for example, silica, aluminum oxide, titanium oxide, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide having an average particle diameter of 0.1 to 30 μm. It may be inorganic fine particles, organic fine particles such as a crosslinked or non-crosslinked polymer, and the like.

  The light collector is used for the purpose of optical path control and can be formed as a prism array sheet, a lens array sheet, or a dot-attached sheet.

  The brightness enhancement film is used for the purpose of improving the brightness in a liquid crystal display device. For example, a plurality of thin film films having different refractive index anisotropies are laminated to produce anisotropy in reflectance. Examples thereof include a reflective polarization separation sheet designed as described above, an oriented film of a cholesteric liquid crystal polymer, and a circularly polarized light separation sheet in which the oriented liquid crystal layer is supported on a film substrate.

  On the other hand, the above-described retardation plate as an optical layer is used for the purpose of compensation of retardation by a liquid crystal cell. Examples thereof include a birefringent film made of a stretched film of various plastics, a film in which a discotic liquid crystal or a nematic liquid crystal is oriented and fixed, and a film substrate on which the above liquid crystal layer is formed. When the liquid crystal layer is formed on the film substrate, a cellulose resin film such as triacetyl cellulose is preferably used as the film substrate.

  Examples of the plastic forming the birefringent film include amorphous polyolefin resins, polycarbonate resins, acrylic resins, chain polyolefin resins such as polypropylene, polyvinyl alcohol, polystyrene, polyarylate, polyamide, and the like. It is done. The stretched film can be processed by an appropriate method such as uniaxial or biaxial. Note that two or more retardation plates may be used in combination for the purpose of controlling optical characteristics such as broadening the bandwidth.

  Of the laminated optical members, those including a retardation plate as an optical layer other than the polarizing plate are preferably used because they can effectively ensure optical security when applied to a liquid crystal display device. The optimum retardation value (in-plane and thickness direction) of the retardation plate may be selected in accordance with the applied liquid crystal cell.

  The laminated optical member can be a laminated body of two layers or three or more layers by combining a polarizing plate and one layer or two or more layers selected according to the purpose of use from the various optical layers described above. In that case, the various optical layers forming the laminated optical member are integrated with the polarizing plate using an adhesive or pressure-sensitive adhesive, but the adhesive or pressure-sensitive adhesive layer used for this purpose is good. As long as it is formed, there is no particular limitation. It is preferable to use a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive) from the viewpoint of easy bonding work and prevention of optical distortion. As the pressure-sensitive adhesive, those having an acrylic polymer, a silicone polymer, polyester, polyurethane, polyether, or the like as a base polymer can be used. Among them, like acrylic adhesives, it has excellent optical transparency, retains appropriate wettability and cohesion, has excellent adhesion to substrates, and has weather resistance and heat resistance. However, it is preferable to select and use a material that does not cause peeling problems such as floating and peeling under the conditions of heating and humidification. In acrylic adhesives, alkyl esters of (meth) acrylic acid having an alkyl group having 20 or less carbon atoms such as methyl, ethyl and butyl groups, and (meth) acrylic acid and hydroxyethyl (meth) acrylate An acrylic copolymer having a weight average molecular weight of 100,000 or more, in which a glass transition temperature is preferably 25 ° C. or less, more preferably 0 ° C. or less, and a functional group-containing acrylic monomer comprising Useful as a base polymer.

  The pressure-sensitive adhesive layer is formed on the polarizing plate by, for example, dissolving or dispersing the pressure-sensitive adhesive composition in an organic solvent such as toluene or ethyl acetate to prepare a 10 to 40% by weight solution, which is directly on the polarizing plate. It can be carried out by a coating method, a method in which an adhesive layer is previously formed on a protective film, and transferred onto a polarizing plate. Although the thickness of an adhesive layer is determined according to the adhesive force etc., the range of about 1-50 micrometers is suitable.

  In addition, the pressure-sensitive adhesive layer is blended with fillers made of glass fibers, glass beads, resin beads, metal powders and other inorganic powders, pigments, colorants, antioxidants, UV absorbers, etc. as necessary. It may be. Examples of ultraviolet absorbers include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, and nickel complex compounds.

  The laminated optical member can be disposed on one side or both sides of the liquid crystal cell. The liquid crystal cell to be used is arbitrary. For example, a liquid crystal display device using various liquid crystal cells such as an active matrix drive type typified by a thin film transistor type and a simple matrix drive type typified by a super twisted nematic type. Can be formed. A pressure-sensitive adhesive is usually used for bonding the laminated optical member and the liquid crystal cell.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. In the examples, “%” and “part” representing the content or amount used are based on weight unless otherwise specified. Moreover, the (A) photocationic curable component and the (B) photocationic polymerization initiator used in the following examples are as follows.

(A) Photocationic curable component:
(A1) Alicyclic diepoxy compound:
(A1) 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate [compound of the above formula (I), R ¹ = R ² = H, X = —COOCH ₂ —].

(A2) Diglycidyl compound:
(A2) Neopentyl diglycidyl ether [compound of the above formula (II), Z = —CH ₂ C (CH ₃ ) ₂ CH ₂ —]
(A2 ′) 2-ethylhexyl glycidyl ether.

(A3) Polymer composed of ethylenically unsaturated monomer:
(A3-I) Polymer having a weight average molecular weight of 15000 (GMA-PS (polystyrene) copolymer) obtained by radical polymerization of a monomer comprising 25 parts of glycidyl methacrylate (GMA) and 75 parts of styrene.
(A3-II) Polymer having a weight average molecular weight of 15000 (GMA-PMMA (polymethyl methacrylate) copolymer) obtained by radical polymerization of a monomer comprising 25 parts of glycidyl methacrylate and 75 parts of methyl methacrylate.
(A3-III) Polymer having a weight average molecular weight of 30000 (GMA-PMMA copolymer having a molecular weight of 30000) obtained by radical polymerization of a monomer comprising 25 parts of glycidyl methacrylate and 75 parts of methyl methacrylate.
(A4-I) 2-ethylhexyl vinyl ether (a4-II) hydroxybutyl vinyl ether (B) photocationic polymerization initiator (b1) triarylsulfonium hexafluorophosphate [Examples 1 to 14 and Comparative Example 1]
(1) Preparation of photocurable adhesive After mixing each said component, it degas | foamed and the photocurable adhesive (liquid form) of Examples 1-14 and Comparative Example 1 was prepared. Table 1 shows the blending ratio (unit is part) of each component using symbols. The photocationic polymerization initiator (b1) was actually blended as a 50% propylene carbonate solution, but Table 1 shows the blending ratio based on the solid content.

(2) Viscosity measurement of photocurable adhesive at 25 ° C. For each photocurable adhesive (adhesive liquid) prepared above, E-type viscometer “TVE-25L” manufactured by Toki Sangyo Co., Ltd. was used. The viscosity at a temperature of 25 ° C. was measured. The results are shown in Table 2.

(3) Solubility of protective film As a protective film, 20 g of 10 mm × 40 mm 80 μm thick acrylic resin (PMMA) [trade name “Technoloy S001”, manufactured by Sumitomo Chemical Co., Ltd.] was prepared. This protective film was immersed in the photocurable adhesives (adhesive solutions) of each Example and Comparative Example prepared in (1) above at room temperature (23 ° C.) for 2 days. Thereafter, the protective film was taken out from the adhesive liquid, and after the adhesive liquid adhering to the protective film was wiped off with Ben cotton, the weight of the protective film was measured.

The dissolution rate was determined from the following formula.
Dissolution rate (% by weight) = (1−weight of protective film after immersion / weight of protective film before immersion (20 g)) × 100
If the dissolution rate is large to some extent, the adhesion to the protective film is improved. On the other hand, if the dissolution rate is too large, the protective film is remarkably dissolved, and there is a high possibility of causing defects such as bubbles in the bonded portion. Become. Therefore, it is preferable that the dissolution rate be in an appropriate range, and the range is, for example, about 15 to 70% by weight.

(4) Production of polarizing plate containing acrylic resin The surface of an acrylic resin (PMMA) [trade name “Technoloy S001”, manufactured by Sumitomo Chemical Co., Ltd.] having a thickness of 80 μm containing an ultraviolet absorber was subjected to corona discharge treatment. Each of the adhesive liquids prepared above was applied to the corona discharge treated surface using a bar coater so that the film thickness after curing was about 3 μm. A polyvinyl alcohol (PVA) -iodine polarizer having a thickness of 25 μm was bonded to the adhesive layer.

  Further, a corona discharge treatment is applied to the surface of a 50 μm-thick retardation film made of norbornene resin (COP: cycloolefin polymer) (trade name “ZEONOR”, manufactured by Nippon Zeon Co., Ltd.). The same adhesive solution as above was applied using a bar coater so that the film thickness after curing was about 3 μm. The adhesive layer was bonded to the polarizer side of the polarizer with the acrylic resin prepared above bonded to one side, and a laminate was prepared.

From the phase difference film side of this laminate, using a UV irradiation device with a belt conveyor (the lamp is a “D bulb” manufactured by Fusion UV Systems Co., Ltd.), UV light is applied so that the integrated light quantity becomes 250 mJ / cm ² (UVB). Irradiated to cure the adhesive. In this way, a polarizing plate (acrylic resin / polarizer / norbornene resin) containing an acrylic resin was produced.

(5) Production of polarizing plate containing triacetyl cellulose-based resin Corona discharge on the surface of 80 μm-thick triacetyl cellulose-based resin [trade name “Konica Katak KC8UX2MW”, manufactured by Konica Minolta Opto Co., Ltd.] containing an ultraviolet absorber. The treatment was applied, and the adhesive solution prepared above was applied onto the corona discharge treated surface using a bar coater so that the film thickness after curing was about 3 μm. A polyvinyl alcohol-iodine polarizer having a thickness of 25 μm was bonded to the adhesive layer.

  Further, a corona discharge treatment is applied to the surface of a 50 μm-thick retardation film made of norbornene resin (COP: cycloolefin polymer) (trade name “ZEONOR”, manufactured by Nippon Zeon Co., Ltd.). The same adhesive solution as above was applied using a bar coater so that the film thickness after curing was about 3 μm. The adhesive layer was bonded to the polarizer side of the polarizer having the triacetylcellulose film prepared above bonded on one side, to prepare a laminate.

From the norbornene phase difference film side of this laminate, the integrated light quantity is 250 mJ / cm ² (UVB) using an ultraviolet irradiation device with a belt conveyor (the lamp is a “D bulb” manufactured by Fusion UV Systems). The adhesive was cured by irradiating with ultraviolet rays. Thus, a polarizing plate (triacetyl cellulose resin / polarizer / norbornene resin) containing a triacetyl cellulose resin was produced.

(6) 180 degree peeling test of polarizing plate containing acrylic resin The polarizing plate produced in the above (4) was cut into a size of 200 mm length × 25 mm width. Then, an acrylic pressure-sensitive adhesive layer was provided on the acrylic resin side having a thickness of 80 μm to obtain a test piece for measuring the peel strength between the acrylic resin and the polarizer. Separately from this, an acrylic pressure-sensitive adhesive layer was provided on the 50 μm-thick norbornene phase difference film side to obtain a test piece for measuring the peel strength between the acrylic resin and the polarizer.

  The adhesive layer of each test piece is attached to a glass plate, a cutter blade is inserted between the polarizer and the protective film (acrylic resin or norbornene phase difference film) on the adhesive side, and 30 mm from the end in the length direction. It peeled off and the peeled part was grasped with the grasping part of the testing machine. The test piece in this state was subjected to JIS K 6854-2: 1999 “Adhesive—Peeling peel strength test method—Part 2: 180 degree peeling” in an atmosphere at a temperature of 23 ° C. and a relative humidity of 55%. A 180 degree peeling test was performed at a gripping moving speed of 300 mm / min, and an average peeling force over a length of 170 mm excluding 30 mm of the gripping part was obtained. The measurement is performed 24 hours after the polarizing plate is produced. The results are shown in Table 2.

  In the section of 180 degree peel strength in Table 2, the column “PMMA / PVA” represents the peel strength between the acrylic resin film and the polarizer, and the column “COP / PVA” It represents the peel strength between the norbornene-based retardation film and the polarizer.

(7) 180 degree peeling test of polarizing plate containing triacetyl cellulose resin The polarizing plate produced in the above (5) was cut into a size of 200 mm length × 25 mm width. And the acrylic adhesive layer was provided in the 80-micrometer-thick triacetylcellulose resin side, and it was set as the test piece for measuring the peeling strength between the triacetylcellulose-type resin and a polarizer.

  The pressure-sensitive adhesive layer of each test piece was attached to a glass plate, a cutter blade was inserted between the polarizer and the protective film (acrylic resin) on the pressure-sensitive adhesive side, and peeled off 30 mm from the end in the length direction. I grabbed the part with the grip of the testing machine. Similar to the 180 degree peeling test, the average peeling force was determined. The measurement is performed 24 hours after the polarizing plate is produced. The results are shown in Table 2.

  In the section of 180 degree peel strength in Table 2, the column “TAC / PVA” represents the peel strength between the triacetyl cellulose resin film and the polarizer.

  As can be seen from Tables 1 and 2, in Examples 7 and 8 using an adhesive containing (a3-II) or (a3-III) which is a polymer (A3) composed of an ethylenically unsaturated monomer All peel strengths were 0.5 N / 25 mm or more. On the other hand, the comparative example 1 using the adhesive which does not contain the polymer (A3) and the comparison using the adhesive whose content of the polymer (A3) in the photocationic curable component (A) is less than 5% In Examples 2 to 5, the peel strength of PMMA / PVA was as extremely low as 0.15 to 0.03 N / 25 mm. Further, the solubility of the protective film was 15% or more in Examples 7 and 8, whereas Comparative Examples 1 to 3 were as small as 10 to 11%.

  From the results of Examples 1 and 2, when (a3-I) and (a3-II), both of which are polymers (A3) having a weight average molecular weight of 15000, were used, the peeling force was equivalent. Moreover, from the results of Examples 2 and 3, when the polymer (A3) was a GMA-PMMA copolymer, the peel strength increased when the weight average molecular weight was 30000.

  Further, from the results of Examples 3, 6, 8, 11 and 13, it was found that (a2) further compared with the case where the adhesive made of (a1), (a2) and (a3-III) was used (Example 3). ') Even when an adhesive containing 5% of any of (a4-I) and (a4-II) was used (Examples 6, 8, 11 and 13), the peelability to PMMA did not change. On the other hand, the peeling force with respect to COP and TAC was better when the adhesive containing (a4-II) was used.

[Examples 15 to 25 and Comparative Examples 6 to 7]
Next, Examples 15 to 25 and Comparative Examples 6 to 7 in which polarizing plates were prepared using an adhesive solution in which water or a diol compound was added to (A) a photocationic curable component and (B) a photocationic polymerization initiator. Indicates. In Examples 15 to 25 and Comparative Examples 6 to 7, (A) the photocationic curable component and (B) the photocationic polymerization initiator were the same as those shown above. Moreover, the water | moisture content and diol compound used in Examples 15-25 and Comparative Examples 6-7 are as follows.

<Moisture>
purified water.

<Diol compound>
(C1) ethylene glycol (c2) 1,2-propanediol (c3) 1,4-butanediol.

(1) Preparation of photocurable adhesive After mixing each said component, it degas | foamed and the photocurable adhesive (liquid form) of Examples 15-25 and Comparative Examples 6-7 was prepared. Table 3 shows the blending ratio (unit: parts) of each component using symbols. The photocationic polymerization initiator (b1) was actually blended as a 50% propylene carbonate solution, but Table 3 shows the blending ratio based on the solid content.

(2) Uniformity of adhesive liquid The state of the adhesive liquid prepared in the above (1) was visually confirmed and classified according to the following criteria. The results are shown in Table 3.

<Evaluation criteria for uniformity of adhesive liquid>
A: The adhesive liquid is not separated into layers.

B: The adhesive liquid is separated into layers.
(3) Production of Polarizing Plate Containing Acrylic Resin Using the obtained adhesive liquid, acrylic resin was prepared in the same manner as shown in Examples 1-14 and Comparative Examples 1-5 (4). A polarizing plate was prepared.

(4) 180 degree peeling test of polarizing plate containing acrylic resin About the obtained polarizing plate, it is the same method as shown to (1) of Examples 1-14 and Comparative Examples 1-5, and acrylic resin and The peel strength between the polarizers was measured. The results are shown in Table 3.

  As can be seen from Table 3, in Examples 15 to 18 using an adhesive containing a predetermined amount of moisture, the peel strength was further improved as compared to Example 10 using an adhesive containing no water. Moreover, in Examples 19 to 25 using an adhesive containing a predetermined amount of a diol compound, the peel strength was further improved as compared to Example 10 using an adhesive containing no diol compound.

Claims (13)

A photocurable adhesive for adhering a protective film made of a transparent resin film to a polarizer made of a polyvinyl alcohol resin film in which a dichroic dye is adsorbed and oriented,
(A) 100 parts by weight of a photocationic curable component;
(B) containing 1 to 10 parts by weight of a cationic photopolymerization initiator,
The photocationic curable component (A) is:
(A1) 10 to 60% by weight of an alicyclic diepoxy compound represented by the following formula (I):

(In the formula, R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, if the alkyl group is 3 or more carbon atoms which may have an alicyclic structure .X Represents an oxygen atom, an alkanediyl group having 1 to 6 carbon atoms, or a divalent group represented by any of the following formulas (Ia) to (Id).)

(In the formula, Y ^{1 to} Y ⁴ each independently represents an alkanediyl group having 1 to 20 carbon atoms, and may have an alicyclic structure in the case of 3 or more carbon atoms. Independently represents an integer of 0 to 20.)
(A2) 20 to 75% by weight of a diglycidyl compound represented by the following formula (II):

(In the formula, Z represents an alkylene group having 1 to 9 carbon atoms, an alkylidene group having 3 or 4 carbon atoms, or a divalent alicyclic hydrocarbon group, and the methylene group in the alkylene group is an oxygen atom. , -CO-O -, - O -CO -, - SO 2 -, - SO- or -CO- a divalent radical may be interrupted represented by).
(A3) containing 5 to 50% by weight of a polymer having a weight average molecular weight of 5,000 to 100,000 consisting of at least one ethylenically unsaturated monomer selected from the monomers represented by the following formula (III) or (IV) then you,
In the polymer (A3), the ethylenically unsaturated monomer is
(I) In the case where X is a methyl group, a branched alkyl group having 2 to 7 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alicyclic hydrocarbon group having 6 to 10 carbon atoms 20 to 90% by weight of the ethylenically unsaturated monomer represented by the formula (III) or (IV),
(Ii) X is a methyl group partially substituted with one or more groups selected from the group consisting of an epoxy group, an oxetane group and a hydroxyl group, a branched alkyl group having 2 to 7 carbon atoms, and the number of carbon atoms 10 to 80 weight of ethylenically unsaturated monomer represented by the formula (III) or (IV) in the case of 6 to 12 aryl group or alicyclic hydrocarbon group having 6 to 10 carbon atoms %, A photo-curable adhesive.

(In the formula, X represents (i) an alkyl group having 1 to 7 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alicyclic hydrocarbon group having 6 to 10 carbon atoms, or (ii) an epoxy. An alkyl group having 1 to 7 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a carbon atom partially substituted with one or more groups selected from the group consisting of a group, an oxetane group, a hydroxyl group and a carboxyl group (It is an alicyclic hydrocarbon group of several 6 to 10.)

(In the formula, R ₃ represents a hydrogen atom, a methyl group or a halogen atom, and X is the same as in the above formula (III).) The photocurable adhesive according to claim 1 , wherein the viscosity at 25 ° C. is 2 to 300 mPa · sec or less. The photocurable adhesive according to claim 1 or 2 , wherein in the formula (II) representing the diglycidyl compound (A2), Z is a branched alkyl group having 3 to 10 carbon atoms. Furthermore, moisture comprises 0.5-4 parts by weight, light-curable adhesive according to any one of claims 1-3. Further, the photocurable adhesive according diol compound 0.5-8 containing parts, in any one of claims 1 to 4 having two hydroxyl groups in the molecule. The photocurable adhesive according to any one of claims 1 to 5 , wherein the solubility of the protective film is 15 to 70% by weight when the protective film is immersed for 2 days at 23 ° C. A polarizer comprising a polyvinyl alcohol-based resin film on which a dichroic dye is adsorbed and oriented;
Polarized light having a protective film made of a transparent resin film bonded via a cured product of the photocurable adhesive according to any one of claims 1 to 6 on at least one surface of the polarizer. Board. The main component of the transparent resin film, a cellulose resin, acrylic resin, amorphous polyolefin resin is at least one resin selected from the group consisting of polyester resin and polycarbonate resin, to claim 7 The polarizing plate as described. The polarizing plate according to claim 7 or 8 , wherein the transparent resin film contains an ultraviolet absorber. The polarizing plate according to any one of claims 7 to 9 , wherein an adhesive strength between the polarizer and the protective film measured by a 180 degree peeling test is 0.5 N / 25 mm or more. The laminated optical member which consists of a laminated body of the polarizing plate of any one of Claims 7-10 , and one or more other optical layers. The laminated optical member according to claim 11 , wherein the other optical layer includes a retardation plate. The liquid crystal display device containing a liquid crystal cell and the laminated optical member of Claim 11 or 12 arrange | positioned at the one side or both sides of the said liquid crystal cell.