TWI583762B - Polarizing plate using photo-curable adhesive and laminated optical member - Google Patents

Description

Polarizing plate and laminated optical member using photocurable adhesive

The present invention relates to a polarizing plate in which a protective film containing a transparent resin is bonded to a polarizer containing a polyvinyl alcohol-based resin film having a dichroic dye adsorbed thereon via a photocurable adhesive. And a laminated optical member in which another optical layer such as a retardation film is laminated on the polarizing plate.

The polarizing plate is used as one of optical parts constituting a liquid crystal display device. The polarizing plate usually has a structure in which a protective film is provided on two areas of the polarizing member, and is assembled in a liquid crystal display device. It is also known that a protective film is provided only on one surface of a polarizing member. However, in most cases, a simple protective film is not attached to the other surface, but a layer having other optical functions is bonded to serve as a protective film. Further, in the method of 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 used.

Usually, after the above washing and drying, the protective film is directly bonded to the polarizing member. This is because the physical strength of the polarizer after drying is weak, and once it is taken up, there is a problem that it is easily broken in the processing direction. Therefore, a water-based adhesive which is an aqueous solution of a polyvinyl alcohol-based resin is usually applied directly to the polarizing member after drying, and a protective film is bonded to both surfaces of the polarizing member via the adhesive. For the general case, the protective film is a cellulose triacetate film having a thickness of 30 to 100 μm.

Triacetyl cellulose is excellent in transparency and is easy to form various surface treatments. The layer and the optical functional layer have a high moisture permeability, and have an excellent advantage that the drying can be carried out by adhering to the polarizing material using the water-based adhesive, and the like, but on the other hand, the moisture permeability Therefore, the polarizing plate which is bonded as a protective film is subjected to moist heat, for example, at a temperature of 70 ° C and a relative humidity of 90%, which may cause deterioration or the like. Here, an amorphous polyolefin-based resin having, for example, a norbornene-based resin having a lower moisture permeability than cellulose triacetate as a representative example is known as a protective film.

When a protective film containing a resin having a low moisture permeability is bonded to a polyvinyl alcohol-based polarizer, a polyvinyl alcohol-based resin which is generally used when a polyvinyl alcohol-based polarizer and a cellulose triacetate film are conventionally bonded together is used. When the aqueous solution is used as an adhesive, the strength is insufficient or the appearance of the obtained polarizing plate may be poor. The reason is that the resin film having a low moisture permeability is generally water-repellent, and water which is a solvent cannot be sufficiently dried due to low moisture permeability. On the other hand, it is known that different types of protective films are bonded to both sides of a polarizing member. For example, it is also proposed to bond a protective film containing a resin having a low moisture permeability such as an amorphous polyolefin resin to one surface of a polarizing member, and to laminate a fiber containing cellulose triacetate on the other surface of the polarizing member. A protective film of a resin having a high moisture permeability such as a resin.

Then, it is attempted to use a photocurable adhesive to achieve a high adhesion between a protective film containing a resin having a low moisture permeability and a polyvinyl alcohol-based polarizer, and also a resin having a high moisture permeability such as a cellulose resin. A high adhesion force is imparted to the polyvinyl alcohol-based polarizer. For example, Japanese Laid-Open Patent Publication No. 2004-245925 (Patent Document 1) discloses epoxidation without an aromatic ring. As a binder of the main component, it is proposed to cure the adhesive by irradiation with an active energy ray, specifically, cationic polymerization by irradiation of ultraviolet rays, and to carry out the polarizer and the protective film. . In addition, Japanese Laid-Open Patent Publication No. 2008-257199 (Patent Document 2) discloses the combination of an alicyclic epoxy compound and an epoxy compound containing no alicyclic epoxy group, and a light compounded with a photocationic polymerization initiator. A sclerosing adhesive is used in the subsequent technique of a polarizer and a protective film.

(previous technical literature) (Patent Literature)

Patent Document 1: Japanese Laid-Open Patent Publication No. 2004-245925

Patent Document 2: Japanese Laid-Open Patent Publication No. 2008-257199

However, the adhesives of the compositions specifically disclosed in Patent Document 1 and Patent Document 2 are not necessarily low in viscosity, and may not be easily applied to a polarizing member or a protective film to which the polarizing member is attached. It is a film and a uniform adhesive layer. In addition, among the above-mentioned adhesives, there are also those which dissolve the protective film, and also cause bubble defects due to the dissolution.

An object of the present invention is to provide a polarizing plate which is a photocurable adhesive which can be applied at room temperature when a protective film is bonded to a polarizing member and which has a sufficiently low viscosity and does not dissolve a protective film. The polarizer is attached to the protective film. Another object of the present invention is to provide a laminated optical member in which another optical layer such as a retardation film is laminated on the polarizing plate, and is suitable for use in a liquid crystal display device.

The present inventors conducted intensive studies in order to solve the related problems, and as a result, completed the present invention. Specifically, in the photocurable adhesive in which a predetermined amount of the photocationic polymerization initiator is blended in the photocationic curable component, a composition doped with the following components is used as the photocationic curable component. It is effective: it is compounded with a specific alicyclic diepoxide compound, in which there are two epoxy groups in the molecule which are not bonded to the alicyclic ring and the linking group is a branched alkyl group. A divalent diglycidyl compound having a branched structure; and a small amount of a monofunctional epoxy compound having no epoxy group bonded to the alicyclic ring in the molecule. That is, it has been found that the photocurable adhesive of the specific composition has a small ability to dissolve the protective film, and exhibits low viscosity at room temperature and can impart good coating suitability, and can be firmly followed by a polarizing member after hardening. With a protective film. The present invention includes the following.

[1] A polarizing plate comprising a polarizing material comprising a polyvinyl alcohol-based resin film which adsorbs a dichroic dye, and a protective film containing a transparent resin which is bonded to at least one surface of the polarizer via an adhesive. The adhesive is formed of a photocurable adhesive containing 100 parts by weight of the photocationic curable component (A) and 1 to 10 parts by weight of the photocationic polymerization initiator (B). The photocationic curable component (A) contains the following amounts (A1), (A2), and (A3) based on the total amount thereof; and the protective film is immersed in the photocurable adhesive at 23 ° C 2 days, the weight of the protective film is reduced by 0 to 30% by weight; the alicyclic diepoxide (A1) represented by the following formula (I) is 30 to 85 wt%;

In the formula, R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, but when the alkyl group has a carbon number of 3 or more, it may have an alicyclic structure; X represents an oxygen atom and has a carbon number of 1 to 6 An alkanoyl group, or a divalent group represented by any one of the following formulae (Ia) to (Id), wherein each of Y ¹ to Y ⁴ represents an alkanediyl group having 1 to 20 carbon atoms, but When the carbon number is 3 or more, it may have an alicyclic structure; a and b each represent an integer of 0 to 20;

1 to 69% by weight of the diepoxypropyl compound (A2) represented by the following formula (II);

Wherein Z represents a branched alkyl group having a carbon number of 2 to 8, or a divalent group represented by the formula -C _m H _2m -Z ¹ -C _n H _2n -, wherein -Z ¹ - represents -O- , -CO-O- or -O-CO-; one of m and n represents an integer of 1 or more, and the other represents an integer of 2 or more, but the total of the two is 8 or less; and, C _m H _2m and C _{One of n} H _2n represents a branched divalent saturated hydrocarbon group; the monofunctional epoxy compound (A3) represented by the following formula (III) is from 1 to 69% by weight;

In the formula, R ³ represents an alkyl group having 1 to 15 carbon atoms.

[2] The polarizing plate according to [1], wherein, in the formula (III) representing the monofunctional epoxy compound (A3), R ³ is an alkyl group having 6 to 10 carbon atoms.

[3] The polarizing plate according to [1], wherein the photocurable adhesive has a viscosity at 25 ° C of 100 mPa ‧ sec or less.

[4] The polarizing plate according to any one of [1] to [3] wherein the photocurable adhesive is cured.

[5] The polarizing plate according to any one of [1] to [4] wherein the protective film to be bonded to at least one surface of the polarizing member comprises a cellulose acetate-based resin to which a UV absorber is blended.

[6] The polarizing plate according to any one of [1] to [4] wherein the protective film bonded to at least one surface of the polarizer comprises an amorphous polyolefin resin, a polyester resin, and The transparent resin selected in the group of the chain polyolefin resin.

[7] A laminated optical member comprising the laminate of the polarizing plate and the other optical layer according to any one of [1] to [6].

[8] The laminated optical member according to [7], wherein the other optical layer contains a retardation film.

In the present invention, the photocationic curable component (A) which is a main component of the photocurable adhesive which bonds the polarizer and the protective film is blended with a predetermined amount of the alicyclic diepoxide (A1), The photo-curable adhesive is a di-epoxy propyl compound (A2) having a bivalent group (typically a branched alkyl group) having a branched structure, and a monofunctional epoxy compound (A3). It has a low viscosity and is difficult to dissolve the protective film. Further, the viscosity is also low at room temperature, and the coating suitability is excellent. Therefore, when a protective film containing a transparent resin is bonded to at least one surface of the polarizer via the photocurable adhesive, bubble defects caused by dissolution of the protective film can be greatly reduced, and a polarizing member and a protective film can be produced. A polarizing plate with good adhesion. Further, the laminated optical member in which the other optical layer is laminated on the polarizing plate is similarly less defective.

Hereinafter, embodiments of the present invention will be described in detail. The present invention is provided on a polarizing material comprising a polyvinyl alcohol resin film, and a polarizing plate comprising a protective film of a transparent resin is bonded via a photocurable adhesive. In addition, the present invention also provides a laminated optical member in which other optical layers are laminated on the polarizing plate. Hereinafter, the photocurable adhesive used in the production of the polarizing plate, the polarizing plate using the photocurable adhesive, and the laminated optical member will be described in order.

[Photocurable adhesive]

In the present invention, a photocurable adhesive for bonding a protective film containing a transparent resin to a polarizer comprising a polyvinyl alcohol resin film contains the following two components (A) and (B): (A) light Cationic hardening component, and (B) Photocationic polymerization initiator.

(photocation hardening component)

The photocationic curable component (A) which is a main component of the photocurable adhesive and which imparts an adhesive force by polymerization hardening contains the following three compounds.

(A1) an alicyclic diepoxy compound represented by the above formula (I), (A2) a diepoxypropyl compound represented by the above formula (II), and (A3) a single represented by the above formula (III) Functional epoxy compound.

In the above formula (I) representing the alicyclic diepoxy compound (A1), R ¹ and R ² each independently represent a hydrogen atom or a C 1 to 6 alkyl group, but when the alkyl group has a carbon number of 3 or more, Has an alicyclic structure. In the formula (I), when the position of the cyclohexane ring bonded to X is 1-position (hence, the positions of the epoxy groups in the two cyclohexane rings are all 3, 4-position), the alkane The base can be bonded to any of the 1-position to the 6-position. The alkyl group may of course be a straight chain, and may be branched at a carbon number of 3 or more. Further, as described above, when the carbon number is 3 or more, it may have an alicyclic structure. Typical examples of the alkyl group having an alicyclic structure are a cyclopentyl group and a cyclohexyl group.

Similarly, in the formula (I), X which is a link of two 3,4-epoxycyclohexane rings is an oxygen atom, an alkanediyl group having 1 to 6 carbon atoms or the above formulas (Ia) to (Id). The divalent group represented by either. Here, the alkanediyl group includes the concept of an alkylene group and an alkylidene group, and the alkyl group may be a straight chain, and may be a branch at a carbon number of 3 or more.

Further, 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 are each a carbon number of 1 to The alkanediyl group may have an alicyclic structure when the carbon number of the alkanediyl group is 3 or more. The alkanediyl group may of course be a straight chain, and may also be a branch at a carbon number of 3 or more. Further, as described above, when the carbon number is 3 or more, it may have an alicyclic structure. Typical examples of the alkanediyl group having an alicyclic structure are a cyclopentyl group and a cyclohexyl group.

To specifically describe the alicyclic diepoxy compound (A1) represented by the formula (I), the compound of the formula (I) wherein X is a divalent group represented by the above formula (Ia) and a is 0 in the formula 3,4-epoxycyclohexylmethanol (alkyl groups having 1 to 6 carbon atoms may be bonded to the cyclohexane ring) and 3,4-epoxycyclohexanecarboxylic acid (alkyl groups having 1 to 6 carbon atoms) An esterate that can be bonded to the cyclohexane ring). This specific example may, for example, be 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylic acid [in the formula (I) (only X is represented by the formula (Ia) of a=0) In the valence group, a compound of R ¹ =R ² =H], 3,4-epoxy-6-methylcyclohexanecarboxylic acid 3,4-epoxy-6-methylcyclohexylmethyl ester [in having In the formula (I) wherein X is the same as the above, R ¹ = 6-methyl, R ² = 6-methyl compound], 3,4-epoxy-1-methylcyclohexanecarboxylic acid 3, 4-epoxy-1-methylcyclohexylmethyl ester [in the formula (I) having the same X as above, R ¹ = 1 -methyl, R ² = 1 -methyl compound], 3, 4 - epoxy-3-methylcyclohexanecarboxylic acid 3,4-epoxy-3-methylcyclohexylmethyl ester [in the formula (I) having the same X as above, R ¹ = 3-methyl , R ² = 3-methyl compound] and the like.

In the formula (I), X is a divalent group compound represented by the formula (Ib), and the alkylene glycol and the 3,4-epoxycyclohexanecarboxylic acid (the alkyl group having 1 to 6 carbon atoms may be bonded to each other). An ester of the cyclohexane ring). In the formula (I), X is a divalent group compound represented by the formula (Ic), and an aliphatic dicarboxylic acid and 3,4-epoxycyclohexylmethanol (the alkyl group having 1 to 6 carbon atoms may be bonded thereto). Ester of cyclohexane ring). Further, in the formula (I), X is a compound of a divalent group represented by the formula (Id), which is a 3,4-epoxycyclohexylmethanol (the alkyl group having 1 to 6 carbon atoms may be bonded to the cyclohexane ring). )of Ethers (b = 0), or alkanediols or polyalkylene glycols and 3,4-epoxycyclohexylmethanol (alkyl groups having 1 to 6 carbon atoms may be bonded to the cyclohexane ring) Ether ether (b>0).

In the above formula (II) representing the diepoxypropyl compound (A2), Z is a branched alkyl group having a carbon number of 3 to 8, or a formula represented by the formula -C _m H _2m -Z ¹ -C _n H _2n - The 2 price base. Here, -Z ¹ - is -O-, -CO-O- or -O-CO-; one of m and n is an integer of 1 or more, and the other is an integer of 2 or more, and the total of 8 is 8 Hereinafter, one of C _m H _2m and C _n H _2n is a branched divalent saturated hydrocarbon group.

The compound of the formula (II) wherein Z is a branched alkyl group is a di-epoxypropyl ether of a branched alkanediol. Specific examples thereof include propylene glycol diepoxypropyl ether, 1,3-butylene glycol diepoxypropyl ether, 1,2-butanediol diepoxypropyl ether, and neopentyl glycol diepoxypropyl ester. Ether, 3-methyl-1,5-pentanediol diepoxypropyl ether, 2-methyl-1,8-octanediol diepoxypropyl ether, 1,4-cyclohexanedimethanol Wait.

Further, in the formula (II), Z is a compound of the above formula -C _m H _2m -Z ¹ -C _n H _2n -, which is a divalent group, and is equivalent to Z being a branched alkyl group and the alkyl group of the alkyl group. The case where the bond is interrupted by -O-, -CO-O- or -O-CO-.

In the above formula (III) representing a monofunctional epoxy compound, R ³ is an alkyl group having 1 to 15 carbon atoms. The alkyl group may of course be a straight chain, and may also be branched at a carbon number of 3 or more. The alkyl group is preferably a carbon number, and is, for example, a carbon number of 6 or more, more preferably a carbon number of 6 to 10. Among them, a branched alkyl group is preferred. A typical example of the monofunctional epoxy compound represented by the formula (III) is, for example, 2-ethylhexylepoxypropyl ether.

The amount of the alicyclic diepoxide (A1) in the photocationic curable component (A) is 30 to 10 based on the total amount of the photocationic curable component (A). 85 wt%. The amount is preferably from 40 to 80% by weight, more preferably from 60 to 75% by weight. When the amount of the alicyclic diepoxide (A1) in the photocationic curable component (A) is too small, the hardening is insufficient and the adhesion between the polarizer/protective film is lowered. On the other hand, when the amount is too large, the amount of the diepoxy propyl compound (A2) and the monofunctional epoxy compound (A3) described below will be relatively small, and it is difficult to achieve the photocurability of the present invention. The low viscosity of the subsequent agent.

Further, in the photocationic curable component (A), the amount of the diepoxypropyl compound (A2) having a branched structure at the linking group is from 1 to 69% by weight. The amount is preferably from 5 to 50% by weight, more preferably from 5 to 30% by weight. In the photocationic curable component (A), when the amount of the diepoxy propyl compound (A2) is more than 69% by weight, the curing is insufficient and the adhesion between the polarizer/protective film is lowered.

Further, in the photocationic curable component (A), the amount of the monofunctional epoxy compound (A3) is from 1 to 69% by weight. The amount is preferably from 2 to 50% by weight, more preferably from 2 to 15% by weight. When the amount of the monofunctional epoxy compound (A3) in the photocationic curable component (A) is more than 69% by weight, the curing is insufficient and the adhesion between the polarizer/protective film is lowered.

The photocationic curable component (A) constituting the photocurable adhesive contains the above-described alicyclic diepoxy compound (A1) in the ratio described above and the diepoxypropyl compound having a branched structure at the linking group. (A2) and a monofunctional epoxy compound (A3). In order to more effectively achieve the low viscosity of the photocurable adhesive before curing and to increase the adhesion between the polarizer and the protective film by the cured product, it is preferred to use the entire amount of the photocurable adhesive. The total amount of the diepoxypropyl compound (A2) and the monofunctional epoxy compound (A3) is 25% by weight or more based on the standard.

Photo-cationic hardening of the alicyclic diepoxy compound (A1), the diepoxypropyl compound (A2) having a branched structure at the linking group, and the monofunctional epoxy compound (A3) within the range of the amounts described above The sexual component (A) may contain other cationically polymerizable compounds.

(Photocationic polymerization initiator)

In the present invention, since the photocationic curable component is cured by cationic polymerization by irradiation with an active energy ray to form an adhesive layer, the photocurable adhesive composition is doped with photocationic polymerization. Starting agent (B). The photocationic polymerization initiator is a polymerization reactor which initiates a photocationic hardening component (A) by irradiation with an active energy ray such as visible light, ultraviolet light, X-ray or electron beam to generate a cationic species or a Lewis acid. . Since the photocationic polymerization initiator is catalyzed by light, it is excellent in storage stability and workability even when it is mixed into the photocationic curable component (A). A compound of a cationic species or a Lewis acid is produced by irradiating an active energy ray, and examples thereof include an diazonium salt, an iodonium salt, and a sulfonium salt. Onium salt; iron-propadiene complex and the like.

Examples of the aromatic diazonium salt include the following compounds: benzene diazonium hexafluoroantimonate, benzene diazonium hexafluorophosphate, and benzene diazonium hexafluoroborate.

Examples of the aromatic onium salt include the following compounds: diphenylphosphonium tetrakis(pentafluorophenyl)borate, diphenylphosphonium hexafluorophosphate, Diphenylphosphonium hexafluoroantimonate, bis(4-mercaptophenyl)phosphonium hexafluorophosphate, and the like.

Examples of the aromatic onium salt include the following compounds: triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis(pentafluorophenyl)borate, and bishexafluorophosphate 4,4. '-Bis[diphenylsulfonio]diphenyl sulfide bishexafluorophosphate, 4,4'-bis[bis(β-hydroxyethoxy) bis(hexafluoroantimonate) Phenylfluorenyl]diphenyl sulfide, 4,4'-bis[bis(β-hydroxyethoxy)phenylindenyl]diphenyl sulfide, hexafluoroantimonic acid 7-[ ((p-toluylsulfonio)-2-isopropylthioxanthone hexafluoroantimonate), tetrakis(pentafluorophenyl)borate 7-[ Di(p-tolylmethyl) fluorenyl]-2-isopropylthioxanthone, 4-phenylcarbonyl-4'-diphenylindenyl-diphenyl sulfide, hexafluoroantimonic acid 4 -(p-tert-butylphenylcarbonyl)-4'-diphenylindenyl-diphenyl sulfide, tetrakis(pentafluorophenyl)borate 4-(p-tert-butylphenylcarbonyl)-4' - bis(p-tolylmethyl) fluorenyl-diphenyl sulfide or the like.

The iron-propadiene complex compound may, for example, be the following compounds: Xylene hexafluoroantimonate-cyclopentadienyl iron (II), cumene-cyclopentadienyl iron (II), xylene-cyclopentadienyl iron (II) (trimethyl-cyclopentadienyliron (II) tris (trifluoromethylsulfonyl) methanate).

These photocationic polymerization initiators may be used singly or in combination of two or more kinds. Among these, the aromatic sulfonium salt is particularly suitable for use because it has ultraviolet absorbing properties in the wavelength range of around 300 nm, and thus can be provided with a cured product having excellent curability and good mechanical strength and adhesion strength.

The photocationic polymerization initiator (B) is blended in an amount of from 1 to 10 parts by weight based on 100 parts by weight of the total of the photocationic curable component (A). By blending 1 part by weight or more of the photocationic polymerization initiator per 100 parts by weight of the photocationic curable component (A), the photocationic curable component (A) can be sufficiently cured to impart high mechanical strength to the obtained polarizing plate. With the strength of the next. On the other hand, if the amount is too large, the ionic substance in the hardened material increases, so that the hygroscopicity of the cured product may be improved and the durability of the polarizing plate may be lowered, so that each 100 parts by weight of the photocationic hardening component is contained. In (A), the amount of the photocationic polymerization initiator (B) is 10 parts by weight or less. The blending amount of the photocationic polymerization initiator (B) per 100 parts by weight of the photocationic curable component (A) is preferably 2 parts by weight or more and 6 parts by weight or less.

(Other ingredients that can be blended in the photocurable adhesive)

In the photocurable adhesive of the present invention, in addition to the above-mentioned photocationic curable component (A) containing an epoxy compound and a photocationic polymerization initiator (B) In addition, other components generally known to be blended in a photocurable resin or an adhesive may be contained. Suitable examples of the other components include, for example, a photosensitizer and a photosensitizer. The photosensitizer exhibits maximum absorption at a wavelength longer than the maximum absorption wavelength shown by the photocationic polymerization initiator (B), and is a compound which promotes the polymerization initiation reaction of the photocationic polymerization initiator (B). Further, the photosensitizer is a compound which further promotes the action of the photosensitizer. The photosensitizer is preferably a complex doped photo-sensing agent depending on the type of the protective film.

The photosensitizer is preferably a compound which exhibits maximum absorption at light having a longer wavelength than 380 nm. The photocationic polymerization initiator (B) exhibits maximum absorption at a wavelength of around 300 nm or shorter, and induces light of the nearby wavelength to generate a cationic species or a Lewis acid to initiate photocationic hardening component (A). Cationic polymerization, but if the above photosensitizer is blended, it will also induce longer wavelengths, especially for wavelengths longer than 380 nm. The photosensitizer is advantageous in the use of an onion compound. Specific examples of the onion-based photosensitizer include the following compounds: 9,10-dimethoxy onion, 9,10-diethoxy onion, 9,10-dipropoxy onion, 9,10-diisopropyl Oxygen onion, 9,10-dibutoxy onion, 9,10-dipentoxy onion, 9,10-dihexyloxy onion, 9,10-bis(2-methoxyethoxy) onion 9,10-bis(2-ethoxyethoxy) onion, 9,10-bis(2-butoxyethoxy) onion, 9,10-bis(3-butoxypropoxy) onion, 2-methyl- or 2-ethyl-9,10-di Methoxy onion, 2-methyl- or 2-ethyl-9,10-diethoxy onion, 2-methyl- or 2-ethyl-9,10-dipropoxy onion, 2-A Base- or 2-ethyl-9,10-diisopropoxy onion, 2-methyl- or 2-ethyl-9,10-dibutoxy onion, 2-methyl- or 2-ethyl -9,10-dipentyloxy onion, 2-methyl- or 2-ethyl-9,10-dihexyloxy onion, and the like.

When the above photosensitizer is blended in the photocurable adhesive, the hardenability of the adhesive is improved as compared with the case where the photosensitizer is not blended. This effect is exhibited by adding 0.1 part by weight or more of the photosensitizer to 100 parts by weight of the photocationic curable component (A). On the other hand, when the amount of the photosensitizer is increased, the problem of precipitation or the like occurs during storage at a low temperature. Therefore, the amount is preferably 2 parts by weight or less based on 100 parts by weight of the photocationic curable component (A). . From the viewpoint of maintaining neutral gray in the polarizing plate, it is advantageous to keep the bonding amount of the photosensing agent to be less in the range in which the bonding force between the polarizing member and the protective film is kept to a moderate extent. For example, the amount of the photosensitizer is set to be 0.1 to 0.5 part by weight, more preferably 0.1 to 0.3 part by weight, based on 100 parts by weight of the photocationic curable component (A).

Next, the photosensitizer will be explained. Although there are various types of photosensitizers, it is advantageous to use naphthalene compounds. Specific examples of the naphthalene-based photosensitizer include the following compounds: 4-methoxy-1-naphthol, 4-Ethoxy-1-naphthol, 4-propoxy-1-naphthol, 4-butoxy-1-naphthol, 4-hexyloxy-1-naphthol, 1,4-dimethyl Oxynaphthalene, 1-ethoxy-4-methoxynaphthalene, 1,4-diethoxynaphthalene, 1,4-dipropoxynaphthalene, 1,4-dibutoxynaphthalene, and the like.

When a naphthalene-based photosensitive auxiliary agent is blended in the photocurable adhesive, the hardenability of the adhesive is improved as compared with the case where the naphthalene-based photosensitive auxiliary agent is not blended. This effect is exhibited by adding 0.1 part by weight or more of the naphthalene-based photosensitive auxiliary agent to 100 parts by weight of the photocationic curable component (A). On the other hand, when the blending amount of the naphthalene-based photosensitizer is increased, problems such as precipitation occur during storage at a low temperature. Therefore, the amount is preferably 5 based on 100 parts by weight of the photocationic curable component (A). It is preferably 3% by weight or less, more preferably 3 parts by weight or less.

(physical properties of photocurable adhesive)

The photocurable adhesive agent described above is used to produce a polarizing plate by laminating a protective film on a polarizer including a polyvinyl alcohol resin film as described above. At this time, if the adhesive dissolves the protective film, as described above, bubble defects are generated in the polarizing plate due to the dissolution. In the present invention, a photocurable adhesive agent (A) containing a photocatalytic component (A) containing a specific three kinds of compounds described above in a predetermined ratio is used, and in particular, a branching structure is used (for example, a linker is used) a compound which is a branched alkyl group) As the di-epoxypropyl compound (A2), an adhesive which is difficult to dissolve the protective film is prepared. That is, when the protective film constituting the polarizing plate was immersed in the adhesive at 23 ° C for 2 days, the weight of the protective film was reduced by 0 to 30% by weight.

Here, the weight loss when the protective film was immersed in the adhesive was determined in the following manner. That is, the transparent resin film constituting the protective film is first cut into an appropriate size, and the weight is obtained. Next, the cut film was immersed in a photocurable adhesive prepared in a liquid state and maintained at a temperature of 23 ° C, and then taken out for 2 days, taken out, and the adhesive adhering to the surface was wiped off to obtain the weight. . Then, the weight reduction after the immersion was determined according to the following formula.

Weight loss (%) = (1 - film weight after immersion / film weight before immersion) × 100

Further, after applying the adhesive to the bonding surface of at least one of the polarizer and the protective film, the adhesive layer is laminated via the adhesive layer to cure the adhesive. Then, in order to improve the coating suitability for the polarizer and/or the protective film, the viscosity of the adhesive is preferably lower. In the present invention, by blending a specific three kinds of compounds described above as a photocationic curable component (A) in a predetermined ratio, the viscosity of the photocurable adhesive is lowered, and the coating suitability is improved. Specifically, the photocurable adhesive can have a viscosity at 25 ° C of 100 mPa ‧ sec or less.

[Polarizer]

In the present invention, a protective film containing a transparent resin is bonded to at least one surface of a polarizing material including a polyvinyl alcohol resin film via the photocurable adhesive described above, and the photocurable adhesive is cured. Biased Light board. In the present invention, as described above, the storage modulus of the adhesive layer which is a cured product of the photocurable adhesive can be improved, and the adhesion between the polarizer and the protective film can be improved. Therefore, the bonding strength of the 180-degree peeling test between the polarizer and the protective film can be made 0.6 N/25 mm or more. Here, the 180-degree peeling test was carried out in accordance with JIS K 6854-2:1999 "Adhesive-peeling strength test method - Part 2: 180 degree peeling".

Hereinafter, a polarizing member and a protective film constituting the polarizing plate of the present invention will be described, and a method of manufacturing the polarizing plate will be briefly described.

(polarizer)

The polarizer is composed of a polyvinyl alcohol-based resin film which is adsorbed and has a dichroic dye. The polyvinyl alcohol-based resin constituting the polarizing material is obtained by saponification of a polyvinyl acetate-based resin. The vinyl acetate-based resin may be a polyvinyl acetate which is a homopolymer of vinyl acetate, and may be a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of the other monomer copolymerized with vinyl acetate include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The degree of saponification of the polyvinyl alcohol-based resin is usually from 85 to 100 mol%, preferably from 98 to 100 mol%. The polyvinyl alcohol-based resin may be further modified. For example, polyvinyl formal and polyvinyl acetal modified with an aldehyde may also be used. The degree of polymerization of the polyvinyl alcohol-based resin is usually from 1,000 to 10,000, preferably from 1,500 to 5,000.

The polarizing member is produced by the following steps: a step of uniaxially stretching such a polyvinyl alcohol-based resin film; and a polyvinyl alcohol by a dichroic dye The step of dyeing the resin film and adsorbing the dichroic dye; and treating the polyvinyl alcohol-based resin film having the dichroic dye adsorbed thereto with a boric acid aqueous solution.

The uniaxial stretching can be carried out before the dyeing of the dichroic dye, or simultaneously with the dyeing of the dichroic dye, or after the dyeing of the dichroic dye. When uniaxial stretching is performed after dyeing of the dichroic dye, the uniaxial stretching may be carried out before the boric acid treatment or in the boric acid treatment. Furthermore, it is of course also possible to carry out a uniaxial extension in these plurality of stages. If uniaxial stretching is desired, it may be uniaxially stretched between rolls having different circumferential speeds, or may be uniaxially extended using a heat roll. Further, it may be a dry stretching which is extended in the atmosphere, or may be a wet stretching which is extended in a state of being swollen by a solvent. The stretching ratio is usually about 4 to 8 times.

When the polyvinyl alcohol-based resin film is to be dyed with a dichroic dye, for example, a polyvinyl alcohol-based resin film can be immersed in an aqueous solution containing a dichroic dye. Specifically, the dichroic dye system uses iodine or a dichroic organic dye.

When iodine is used as the dichroic dye, a method in which a polyvinyl alcohol resin film is immersed in an aqueous solution containing iodine and potassium iodide and dyed is usually used. In the aqueous solution, the content of iodine 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. The temperature of the aqueous solution is usually about 20 to 40 ° C, and in addition, the immersion time (dyeing time) in the aqueous solution is usually about 30 to 300 seconds.

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

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

The polyvinyl alcohol-based resin film after boric acid treatment is usually subjected to water washing treatment. The water washing treatment is carried out, for example, by immersing a boric acid-treated polyvinyl alcohol-based resin film in water. After washing with water, drying treatment was carried out to obtain a polarizing member. The temperature of the 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 treatment performed thereafter is usually carried out using a hot air dryer or a far infrared heater. The drying temperature is usually from 40 to 100 °C. Further, the drying treatment time is usually about 120 to 600 seconds.

The thickness of the polarizing member comprising the polyvinyl alcohol-based resin film thus obtained The degree can be about 10 to 50 μm.

(protective film)

In the polarizing material including the polyvinyl alcohol-based resin film described above, the protective film is bonded to the photocurable adhesive described above, and the photocurable adhesive is cured to form a polarizing plate. The protective film may be composed of a cellulose acetate-based resin film such as cellulose triacetate which is most widely used as a protective film for a polarizing plate, or a resin film having a lower moisture permeability than cellulose triacetate. The trans-humidity of cellulose triacetate is about 400 g/m ² /24 hr.

In a preferred embodiment, the protective film attached to at least one surface of the polarizer is made of a cellulose acetate resin. In particular, the protective film to be bonded to one surface of the polarizing member may be composed of a cellulose acetate resin blended with a UV absorber. In another preferred embodiment, the protective film attached to at least one side of the polarizing member is a resin film having a lower moisture permeability than cellulose triacetate, for example, a resin having a moisture permeability of 300 g/m ² /24 hr or less. The film is composed of. Examples of the resin constituting the resin film having a low moisture permeability include an amorphous polyolefin resin, a polyester resin, an acrylic resin, a polycarbonate resin, and a chain polyolefin resin. Among these, an amorphous polyolefin resin, a polyester resin, and a chain polyolefin resin are preferably used. In another preferred embodiment, a protective film comprising a cellulose acetate resin is bonded to one surface of the polarizer via the adhesive layer, and the other layer of the polarizer is similarly passed through the adhesive layer. A protective film containing the above transparent resin having a low moisture permeability is bonded.

Cellulose acetate resin for at least a portion of hydroxyl groups in cellulose The resin obtained by esterification may also be a mixed ester which is partially esterified by acetic acid esterification and partially acidified. Specific examples of the cellulose acetate-based resin include cellulose triacetate, cellulose diacetate, cellulose acetate propionate, and cellulose acetate butyrate.

The amorphous polyolefin-based resin has a polymerization unit such as norbornene or tetracyclododecene (dimethanooctahydronaphthalene) or a cyclic olefin such as a compound having such a substituent bonded thereto The polymer may also be a copolymer obtained by copolymerizing a cyclic olefin with a chain olefin and/or an aromatic vinyl compound. When it is a homopolymer of a cyclic olefin or a copolymer of two or more kinds of cyclic olefins, since a double bond is left by ring-opening polymerization, it is generally used as an amorphous polyolefin. Resin. Among them, thermoplasticity-reducing terpene-based resins are representative.

The polyester resin is a polymer obtained by condensation polymerization of a dibasic acid and a glycol, and polyethylene terephthalate is representative. The acrylic resin is a polymer containing methyl methacrylate as a main monomer, and may be an acrylate or aromatic ester such as methyl methacrylate or methyl acrylate, in addition to a homopolymer of methyl methacrylate. a copolymer of a vinyl compound or the like. The polycarbonate resin is a polymer having a carbonate bond (-O-CO-O-) in its main chain, and is obtained by polycondensation of bisphenol A and phosgene. The chain polyolefin resin is a polymer having a chain olefin such as ethylene or propylene as a main monomer, and may be a homopolymer or a copolymer. Among them, a copolymer of a homopolymer of propylene or a copolymer of a small amount of ethylene in propylene is representative.

Such a protective film can be on the side opposite to the surface attached to the polarizing member There are various surface treatment layers such as a hard coat layer, an antireflection layer, an antiglare layer or an antistatic layer. In the case where such a surface treatment layer is formed, the thickness of the protective film may be about 5 to 150 μm. The thickness is preferably 10 μm or more, more preferably 120 μm or less, still more preferably 100 μm or less.

(Manufacturing method of polarizing plate)

In the production of the polarizing plate, the coating layer of the photocurable adhesive described above is formed on one or both of the bonding surfaces of the polarizer and the protective film, and the polarizing member and the protective film are provided via the coating layer. The coating layer of the uncured photocurable adhesive thus formed is cured by irradiation with an active energy ray, and the protective film is fixed to the polarizing member. The coating layer of the photocurable adhesive may be formed on the bonding surface of the polarizer or may be formed on the bonding surface of the protective film. The coating layer can be formed by, for example, a doctor blade, a wire bar, a die coater, a comma coater, a gravure coater, or the like. Coating method. Further, a method in which the polarizer and the protective film are continuously supplied and the bonding surfaces of the both are formed inside, and the adhesive is cast therebetween may be employed. Each coating method has a suitable viscosity range, so the use of a solvent for viscosity adjustment is also a usable technique. The solvent used for this purpose is not particularly limited as long as the optical performance of the polarizer is not lowered and the photocurable adhesive is well dissolved. For example, an organic solvent such as a hydrocarbon represented by toluene or an ester represented by ethyl acetate can be used. The thickness of the subsequent layer is usually 20 μm or less, preferably 10 μm or less, more preferably 5 μm or less. When the adhesive layer is too thick, the reaction rate of the adhesive decreases, and the heat and humidity resistance of the polarizing plate tends to deteriorate.

When the polarizer and the protective film are subsequently adhered, one or both of the bonding surfaces of the two may be subjected to corona discharge treatment, plasma treatment, flame treatment, and primer before forming the coating layer of the adhesive ( The primer treatment or anchor coating treatment is easy to proceed.

The light source for irradiating the coating layer of the photocurable adhesive with an active energy ray may be an ultraviolet ray, an electron beam, an X-ray or the like. Particularly suitable for use in a light distribution with a wavelength of 400 nm or less, such as a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excited mercury lamp, a metal halide lamp, etc. . The intensity of the active energy ray of the photocurable adhesive is determined according to the intended composition, and is not particularly limited. However, it is preferred that the irradiation intensity in the wavelength range in which the activation of the photocationic polymerization initiator is effective becomes 0.1 to 100 mW/cm ² . When the light irradiation intensity of the photocurable adhesive is too small, the reaction time is too long. On the other hand, if the light irradiation intensity is too large, heat generated by the lamp and heat generated during polymerization of the photocurable adhesive agent are caused. Yellowing of the photocurable adhesive and deterioration of the polarizer may occur. The light irradiation time of the photocurable adhesive is controlled according to the composition of the hardened composition, and is not particularly limited. However, it is preferably set such that the cumulative light amount represented by the product of the irradiation intensity and the irradiation time is 10 to 5,000 mJ/ Cm ² . When the amount of accumulated light of the photocurable adhesive is too small, the generation of the active species derived from the photocationic polymerization initiator is insufficient, and the resulting adhesive layer may be insufficiently hardened. On the other hand, if the accumulated amount of light is too large, the irradiation is performed. Time is very long, which is not conducive to improving productivity.

When the protective film is attached to both sides of the polarizer, it can be moved from either side of the protective film. When the active energy ray is irradiated, for example, when the protective film on one side contains the ultraviolet absorbing agent and the protective film on the other side does not contain the ultraviolet absorbing agent, it is preferred to irradiate the active energy ray from the side of the protective film containing no ultraviolet absorbing agent. The reason is that the active energy line of the irradiation can be effectively utilized and the hardening speed is increased.

[Laminated optical member]

The polarizing plate of the present invention can form an optical layer having an optical function other than the polarizing plate to form a laminated optical member. In a typical manner, an optical layer is laminated on a protective film of a polarizing plate via an adhesive or an adhesive to form a laminated optical member, and, for example, a photocurable adhesive can also be applied to one surface of the polarizing member according to the present invention. The protective film is attached, and the optical layer is laminated on the other side of the polarizer via an adhesive or an adhesive. In the latter case, if the photocurable adhesive specified in the present invention is used as an adhesive for attaching the polarizer to the optical layer, the optical layer can also serve as a protective film as defined in the present invention.

Examples of the optical layer laminated on the polarizing plate include, for example, a polarizing plate disposed on the back side of the liquid crystal cell, and a reflective layer laminated on the side opposite to the side facing the liquid crystal cell of the polarizing plate. , a semi-transmissive reflective layer, an optical diffusion layer, a light collecting plate, a film for enhancing brightness, and the like. Further, the phase difference of the layer deposited on the side of the polarizing plate facing the liquid crystal cell, for example, with respect to the polarizing plate disposed on the front side of the liquid crystal cell and the polarizing plate disposed on the back side of the liquid crystal cell Membrane and the like.

The reflective layer, the semi-transmissive reflective layer, or the light-diffusing layer are respectively provided for forming a reflective polarizing plate (optical member), a transflective polarizing plate (optical member), or a diffusing polarizing plate (optical member). . Reflective polarizer In a liquid crystal display device of a type that reflects 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 made thinner. Further, the semi-transmissive polarizing plate is a liquid crystal display device of a type which is a reflective type in a bright place and a light-emitting display in a dark place. As the optical member of the reflective polarizing plate, for example, a foil containing a metal such as aluminum or a vapor deposited film may be attached to the protective film on the polarizing member to form a reflective layer. As the optical member of the semi-transmissive polarizing plate, the reflecting layer can be formed as a half mirror, or a reflecting plate containing a pearl pigment or the like to exhibit light transmittance can be formed next to the polarizing plate. On the other hand, as the optical member of the diffusing type polarizing plate, for example, a method of performing matting treatment on a protective film on a polarizing plate, a method of applying a resin containing fine particles, and a film containing fine particles are used. A method such as a method forms a fine uneven structure on the surface.

In addition, an optical member that functions as a polarizing plate for reflection and diffusion can be formed. In this case, for example, a method of reflecting a reflective layer or the like of the uneven structure on the fine uneven structure surface of the diffusing type polarizing plate can be employed. The reflective layer of the fine uneven structure has the advantage that the incident light can be diffused by diffused reflection, and directivity and glare are prevented, and unevenness in brightness and darkness can be suppressed. Further, the resin layer or film containing fine particles also has an advantage of diffusing the incident light and the reflected light while penetrating the layer containing the fine particles, and suppressing unevenness in brightness and the like. The reflective layer reflecting the fine uneven structure on the surface can be formed by directly depositing a metal on the surface of the fine uneven structure by vapor deposition or plating such as vacuum deposition, ion plating or sputtering. The fine particles blended to form the surface fine uneven structure may be, for example, flat Organic fine particles such as cerium oxide, aluminum oxide, titanium oxide, zirconium dioxide, tin oxide, indium oxide, cadmium oxide, or cerium oxide having an average particle diameter of 0.1 to 30 μm, and organic fine particles such as a crosslinked or non-crosslinked polymer Wait.

The light collecting plate is designed for the purpose of controlling an optical path, etc., and may be formed as a prism array sheet and a lens array sheet or a sheet with dots. Wait.

The film for improving the luminance is intended to enhance the luminance in the liquid crystal display device, and examples thereof include a film in which the refractive index of the laminated plurality of films is different from each other, and the reflectance is anisotropic. The reflective polarizing separation sheet is designed; an alignment film of a cholesteric liquid crystal polymer or a circularly polarizing separation sheet supporting the liquid crystal layer on a film substrate.

On the other hand, the retardation film which functions as an optical layer is intended for the purpose of compensating for the phase difference of the liquid crystal cell. In this example, a birefringent film including a stretched film of various plastics, a film in which a discotic liquid crystal or a nematic liquid crystal is fixed, and the above liquid crystal are formed on the film substrate. Layers and so on. When a liquid crystal layer is formed on a film substrate, it is preferable to use a cellulose resin film such as cellulose triacetate as the film substrate.

Examples of the plastic forming the birefringent film include a chain polyolefin resin such as an amorphous polyolefin resin, a polycarbonate resin, an acrylic resin, and a polypropylene, polyvinyl alcohol, polystyrene, and polyaryl. Polyarylate, polyamine, and the like. The stretch film can be uniaxial or biaxial, etc. Appropriate way to handle. Further, for the purpose of controlling optical characteristics such as widening, it is possible to use two or more retardation films in combination.

Among the laminated optical members, the retardation film is included as an optical layer other than the polarizing plate, and is preferably used because it can be optically compensated when applied to a liquid crystal display device. The phase difference (in-plane and thickness direction) of the retardation film can be selected according to the applicable liquid crystal cell.

In the laminated optical member, a polarizing plate and one or two or more layers selected from the above various optical layers depending on the purpose of use can be combined to form a laminated body of two or more layers. In this case, the various optical layers forming the laminated optical member are integrated with the polarizing plate using an adhesive or an adhesive, and the adhesive or the adhesive used for the adhesive layer or the adhesive is preferably formed as an adhesive layer or an adhesive layer. There is no special limit. It is preferable to use an adhesive (also referred to as a pressure-sensitive adhesive) from the viewpoint of ease of handling and prevention of optical distortion. As the adhesive, an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyether or the like can be used as the base polymer. Among them, it is preferred to use an optical adhesive such as an acrylic adhesive, which is excellent in transparency, maintains moderate wettability and cohesive force, and is excellent in adhesion to a substrate, and has weather resistance and heat resistance. Under the conditions of humidification, there is no problem of peeling such as floating and peeling. In the acrylic adhesive, it is useful to use the following acrylic polymer as a base polymer: a (meth) acrylate having an alkyl group having a carbon number of 20 or less, such as a methyl group or an ethyl group or a butyl group. The alkyl ester and the acrylic monomer containing a functional group such as (meth)acrylic acid or hydroxyethyl (meth)acrylate, so that the glass transition temperature is preferably 25 ° C or lower, more preferably 0 ° C An acrylic copolymer having a weight average molecular weight of 100,000 or more produced by blending under the following conditions.

The formation of the adhesive layer on the polarizing plate is carried out, for example, by dissolving or dispersing the adhesive composition in an organic solvent such as toluene or ethyl acetate and preparing a solution of 10 to 40% by weight, which is directly coated thereon. a method on the polarizing plate; and a method of forming an adhesive layer on the protective film in advance and moving it to the polarizing plate. The thickness of the adhesive layer is determined depending on the adhesion force or the like, but is suitably in the range of about 1 to 50 μm.

Further, in the adhesive layer, it may be blended as needed: glass fiber or glass beads, resin beads, a filler containing a metal powder or the like, a pigment or a colorant, an antioxidant, an ultraviolet absorber, or the like. The ultraviolet absorber includes a salicylate-based compound, a benzophenone-based compound, a benzotriazole-based compound, a cyanoacrylate-based compound, and a nickel-salted salt-based compound.

The laminated optical member can be disposed on one side or both sides of the liquid crystal cell. Any one of the liquid crystal cells can be used, and a liquid crystal display device can be formed by using, for example, an active matrix drive type represented by a thin film transistor type and a simple matrix drive type represented by a super twisted nematic type. . The adhesive of the laminated optical member and the liquid crystal cell is usually the same as described above.

(Example)

The present invention is illustrated by the following examples, but the present invention is not limited to the examples. In the examples, the % or the part of the content or the amount used is a weight basis unless otherwise noted. In addition, the light used in the following examples The cationic hardening component and the photocationic polymerization initiator are as follows, and are indicated by the following symbols.

(A) Photocationic hardening component

(a1) 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylic acid [in the above formula (I), a compound of R ¹ =R ² =H, X=-COOCH ₂ -]; (a21) neopentyl glycol diepoxypropyl ether [in the above formula (II), a compound of Z=-CH ₂ C(CH ₃ ) ₂ CH ₂ -]; (a22) 1,4-butanediol II Epoxypropyl ether [Compound of Z=-(CH ₂ ) ₄ - in the above formula (II)] (comparative); (a3) 2-ethylhexylepoxypropyl ether [in the above formula (III) , R ³ = CH ₃ (CH ₂ ) ₃ -CH(CH ₂ CH ₃ )-CH ₂ - compound].

(B) Photocationic polymerization initiator (abbreviated as "starter" in the table)

(b1) Triarylsulfonium hexafluorophosphate.

[Examples 1 to 4 and Comparative Examples 1 to 3] (1) Modulation of photocurable adhesive

The photocationic curable component and the photocationic polymerization initiator were mixed at a mixing ratio (unit: part) shown in Table 1, and then defoamed to prepare a photocurable adhesive liquid. Further, a 50% propylene carbonate solution was blended as a photocationic polymerization initiator (b1), and the solid content thereof is shown in Table 1.

(2) Viscosity measurement of the adhesive solution at 25 ° C

For each of the above-mentioned prepared adhesive liquids, the viscosity at a temperature of 25 ° C was measured using a rotary viscoelasticity measuring apparatus "Physica MCR 301" manufactured by Anton Paar Co., Ltd. The results are shown in Table 1.

(3) Solubility of protective film

A retardation film [trade name "N-TAV KC4FR-1" having a thickness of 40 μm containing a cellulose acetate-based resin, manufactured by Konica Minolta Opto Co., Ltd.] was prepared. This retardation film is bonded to a polyvinyl alcohol-based polarizer to serve as a protective film having an optical compensation function, and is used for the production of a polarizing plate. The retardation film was cut into a size of 10 mm × 40 mm, and then immersed in 20 g of each of the above-mentioned adhesive liquids prepared at the temperature of 23 ° C for 2 days. Two days later, the retardation film was taken out, and the adhesive liquid adhering to the protective film was wiped with the dust-free paper BEMCOT, and the weight was measured. Then, the weight of the film before the immersion in the adhesive liquid and the weight of the film after immersion were determined by the following formula, and the results are shown in Table 1.

Weight loss (%) = (1 - film weight after immersion / film weight before immersion) × 100

A ternary system of a diglycidyl ether (a21) having a branched alkyl group as a linking group and a monofunctional epoxy compound (a3) is blended in the alicyclic diepoxide (a1) as in Comparative Example 1. The subsequent agent, although it has low solubility in the cellulose acetate resin film of the protective film, is alicyclic diepoxide (a1) The blending ratio is large, so the viscosity becomes high, and the coating suitability when applied to the protective film or the polarizing member is not sufficient. On the other hand, when the diepoxypropyl compound (a2) of Comparative Examples 2 and 3 is a diglycidyl ether (a22) having a linear alkylene group having 4 carbon atoms as a linking group, it is protected. The cellulose acetate resin film of the film has a large solubility. On the other hand, in the case of a ternary-based adhesive containing a diglycidyl ether (a21) having a branched alkyl group as a linking group, the blending ratios of Examples 1 to 4 are low. A photocurable adhesive which is viscous and hard to dissolve the protective film.

The retardation film used in Examples 1 to 4 was adhered to one surface of the polarizing member having iodine adsorbed on the polyvinyl alcohol film, and the photocurable adhesive prepared in Examples 1 to 4 was bonded to the polarizing film. On the other surface of the member, a cellulose triacetate film having a thickness of 80 μm was bonded through the same adhesive, and when ultraviolet rays were irradiated from the retardation film side, a polarizing plate which exhibited good adhesion was obtained. In particular, when the amount of the alicyclic diepoxide (a1) is 50% or more in the photocationic curable component as in Examples 1 and 2, a high adhesion can be obtained.

Claims (8)

A polarizing plate comprising: a polarizer comprising a polyvinyl alcohol-based resin film which adsorbs a dichroic dye; and a protective film containing a transparent resin which is bonded to at least one surface of the polarizer via an adhesive; The above-mentioned adhesive agent is formed of a photocurable adhesive; the photocurable adhesive contains 100 parts by weight of the photocationic curable component (A) and 1 to 10 parts by weight of the photocationic polymerization initiator (B); The curable component (A) contains the following (A1), (A2), and (A3) based on the total amount thereof: an alicyclic diepoxide compound (A1) 30 to 85 represented by the following formula (I) weight% In the formula, R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, but the alkyl group may have an alicyclic structure when the carbon number is 3 or more; X represents an oxygen atom and has a carbon number of 1 to 6. An alkanediyl group or a divalent group represented by any one of the following formulae (Ia) to (Id); wherein, each of Y ¹ to Y ⁴ represents an alkanediyl group having 1 to 20 carbon atoms, but a carbon number of 3 or more And may have an alicyclic structure; a and b each represent an integer from 0 to 20; The diepoxypropyl compound (A2) represented by the following formula (II) is 1 to 69% by weight Wherein Z represents a branched alkyl group having a carbon number of 3 to 8 or a divalent group represented by the formula -C _m H _2m -Z ¹ -C _n H _2n -, wherein -Z ¹ - represents -O-, -CO-O- or -O-CO-; one of m and n represents an integer of 1 or more, and the other represents an integer of 2 or more, but the total of the two is 8 or less; and, C _m H _2m and C _n One of H _2n represents a branched divalent saturated hydrocarbon group; and the monofunctional epoxy compound (A3) represented by the following formula (III) is 1 to 69% by weight In the formula, R ³ represents a branched alkyl group having 3 to 15 carbon atoms; and when the protective film is immersed in the photocurable adhesive at 23 ° C for 2 days, the weight of the protective film is reduced by 0 to 30% by weight. The polarizing plate according to claim 1, wherein, in the formula (III) representing the monofunctional epoxy compound (A3), R ³ is a branched alkyl group having 6 to 10 carbon atoms. The polarizing plate according to claim 1, wherein the photocurable adhesive has a viscosity at 25 ° C of 100 mPa ‧ sec or less. The polarizing plate according to claim 1, wherein the photocurable adhesive is cured. The polarizing plate of claim 1, wherein the protective film attached to at least one side of the polarizing member comprises a blended ultraviolet absorber. The cellulose acetate resin. The polarizing plate according to claim 1, wherein the protective film attached to at least one surface of the polarizing member comprises an amorphous polyolefin resin, a polyester resin, and a chain polyolefin resin. The transparent resin selected in the group. A laminated optical member comprising the laminate of the polarizing plate and the other optical layer described in claim 1 of the patent application. The laminated optical member according to claim 7, wherein the optical layer contains a retardation film.