JP2020115207A - Polarizing plate - Google Patents

Abstract

To provide a polarizing plate which exhibits good optical durability in hot and humid environments.SOLUTION: A polarizing plate is provided, comprising a polarizer, an adhesive layer, an easy-adhesion layer, and a protective film laminated in the described order. The easy-adhesion layer contains a basic component, and features an atomic concentration ratio (N/C) of nitrogen and carbon atoms that is equal to or greater than 0.05 and less than 1.0 on a surface in contact with the adhesive layer. The adhesive layer is a photocured product layer of a composition containing a photo-cation curable compound (A) and a photo-cationic polymerization initiator (B), where the photo-cation curable compound (A) contains 30-80 mass% of an alicyclic epoxy compound with respect to the total mass thereof, and content of the photo-cationic polymerization initiator (B) is 2.5-15 pts.mass with respect to 100 pts.mass of the photo-cation curable compound (A).SELECTED DRAWING: None

Description

The present invention relates to a polarizing plate.

The polarizing plate usually has a structure in which a polarizer and a protective film are laminated on at least one surface of the polarizer. The polarizer and the protective film are usually attached via an adhesive layer, but depending on the type of the protective film (for example, a protective film having low moisture permeability formed from a norbornene resin film), the surface of the protective film may be adhered. It is known to provide an easy adhesion layer. For example, in Patent Document 1, a polarizer, an adhesive layer formed of a water-based adhesive containing a polyvinyl alcohol-based resin, an easy-adhesion layer formed of a composition containing a urethane resin, and a protective film are laminated in this order. A polarizing plate is described.
Further, in Patent Document 2, an adhesive formed by using a polarizer and a protective film having low moisture permeability from an adhesive composition containing an epoxy compound containing no aromatic ring as a main component, without using an easily adhesive layer. A polarizing plate laminated via layers is described.

JP, 2013-10853, A JP, 2004-245925, A

However, the polarizing plates described in Patent Document 1 and Patent Document 2 may not have sufficient optical durability in a wet heat environment.

The present invention includes the following inventions.
[1] A polarizing plate in which a polarizer, an adhesive layer, an easy-adhesion layer and a protective film are laminated in this order,
The easy-adhesion layer contains a base component, and the atomic concentration ratio (N/C) of nitrogen atoms and carbon atoms on the surface in contact with the adhesive layer is 0.05 or more and less than 1.0,
The adhesive layer is a photocured product layer of a composition containing the photocationic curable compound (A) and the photocationic polymerization initiator (B),
30-80 mass% of alicyclic epoxy compounds are contained in the total mass of the cationic photocurable compound (A),
The polarizing plate characterized by containing 2.5 to 15 parts by mass of the cationic photopolymerization initiator (B) with respect to 100 parts by mass of the cationic photocurable compound (A).
[2] The polarizing plate according to [1], wherein the easily adhesive layer has a thickness of 1 to 200 nm.
[3] The polarizing plate according to [1] or [2], wherein the adhesive layer has a thickness of 0.5 to 5 μm.

An object of the present invention is to provide a polarizing plate having good optical durability in a humid heat environment.

The polarizer, the adhesive layer, the easy-adhesion layer, and the protective film in the polarizing plate of the present invention will be described in order.

(Polarizer)
The polarizer is composed of a polyvinyl alcohol-based resin film in which a dichroic dye is adsorbed and oriented. The polyvinyl alcohol-based resin forming the polarizer is obtained by saponifying a polyvinyl acetate-based resin. The polyvinyl acetate-based resin may be polyvinyl acetate, which is a homopolymer of vinyl acetate, or may be a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers and unsaturated sulfonic acids. The saponification degree of the polyvinyl alcohol resin is usually in the range of 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 in the range of 1,000 to 10,000, preferably 1,500 to 5,000.

The polarizer is a step 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 the dichroic dye is adsorbed. It is manufactured through a process of treating the polyvinyl alcohol resin film with a boric acid aqueous solution.

Uniaxial stretching may be performed before dyeing with a dichroic dye, simultaneously with dyeing with a dichroic dye, or after dyeing with a dichroic dye. When the uniaxial stretching is performed after dyeing with the dichroic dye, the uniaxial stretching may be performed before the boric acid treatment or during the boric acid treatment. Of course, it is also possible to carry out uniaxial stretching in these plural stages. For uniaxial stretching, stretching may be uniaxial between rolls having different peripheral speeds, or uniaxial stretching may be performed using hot rolls. Further, it may be dry stretching in which stretching is performed in the atmosphere, or wet stretching in which stretching is performed in a state of being swollen by a solvent. The draw ratio is usually about 4 to 8 times.

To dye the polyvinyl alcohol-based resin film with the dichroic dye, for example, the polyvinyl alcohol-based resin film may be dipped in an aqueous solution containing the dichroic dye. Specifically, iodine or a dichroic organic dye is used as the dichroic pigment.

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

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

The boric acid treatment after dyeing with the dichroic dye is performed by immersing the dyed polyvinyl alcohol resin film in an aqueous boric acid solution. The content of boric acid in the aqueous boric acid solution is usually 2 to 15 parts by mass, preferably 5 to 12 parts by mass, per 100 parts by mass of water. When iodine is used as the dichroic dye, this aqueous boric acid solution preferably contains potassium iodide. The content of potassium iodide in the aqueous boric acid solution is usually 2 to 20 parts by mass, preferably 5 to 15 parts by mass, per 100 parts by weight of water. The immersion time in the aqueous boric acid solution is usually 100 to 1200 seconds, preferably 150 to 600 seconds, and more preferably 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-based resin film after the boric acid treatment is usually washed with water. The water washing treatment is performed, for example, by immersing the boric acid-treated polyvinyl alcohol-based 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 subsequent drying treatment is usually performed using a hot air dryer or a far infrared heater.
The drying temperature is usually 40 to 100°C. The time for the drying process is usually about 120 to 600 seconds.

The thickness of the polarizer made of a polyvinyl alcohol-based resin film can be about 10 to 50 μm.

(Adhesive layer)
The adhesive layer of the present invention is a cured product of a composition containing a cationic photocurable compound (A) and a cationic photopolymerization initiator (B) (hereinafter sometimes referred to as photocurable adhesive composition (1)). Is.

(Cationic photo-curable compound (A))
The photocationic curable component (A) contains an alicyclic epoxy compound, and the alicyclic epoxy compound is contained in an amount of 30 to 80% by mass based on the total mass of the photocationic curable compound (A).
By containing the alicyclic epoxy compound in an amount of 30% by mass or more based on the total mass of the photocationic curable compound (A), the storage elastic modulus of the adhesive layer can be increased. When the storage elastic modulus of the adhesive layer becomes high, cracking of the polarizing film can be prevented even in an environment where high temperature and low temperature are repeated. On the other hand, when the alicyclic epoxy compound exceeds 80% by mass based on the total mass of the photocationic curable compound (A), color loss of the polarizing film is likely to occur in a humid heat environment, and the optical durability of the polarizing plate is increased. The property tends to deteriorate.
The content of the alicyclic epoxy compound is preferably 30 to 75% by mass, more preferably 50 to 70% by mass, based on the total mass of the photocationic curable compound (A).

The alicyclic epoxy compound is a compound having at least one epoxy group (hereinafter also referred to as alicyclic epoxy group) bonded to an alicyclic ring in the molecule. Examples of the alicyclic epoxy group include an oxabicyclohexyl group and an oxabicycloheptyl group.
The alicyclic epoxy compound may be a compound containing one alicyclic epoxy group, or may contain two or more alicyclic epoxy groups.

［式（Ｉ）中、Ｒ^１及びＲ^２は、それぞれ独立して、水素原子、炭素数１〜６のアルキル基又は炭素数３〜６のシクロアルキル基を表す。
Ｘは、−Ｏ−、炭素数１〜６のアルカンジイル基又は下記式（Ｉａ）〜（Ｉｄ）で表される２価の基を表す。

Ｙ^１、Ｙ^２、Ｙ^３及びＹ^４は、それぞれ独立して、炭素数１〜２０のアルカンジイル基又は炭素数３〜２０の２価の脂環式炭化水素基を表す。］ The alicyclic epoxy compound is preferably an alicyclic diepoxy compound containing two alicyclic epoxy groups, and more preferably a compound represented by the following formula (I).

[In the formula (I), R ¹ and R ² each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
X represents -O-, an alkanediyl group having 1 to 6 carbon atoms, or a divalent group represented by the following formulas (Ia) to (Id).

Y ¹ , Y ² , Y ³ and Y ⁴ each independently represent an alkanediyl group having 1 to 20 carbon atoms or a divalent alicyclic hydrocarbon group having 3 to 20 carbon atoms. ]

In the formula (I), the position of the cyclohexane ring bonded to X is the 1-position (therefore, the positions of the epoxy groups in the two cyclohexane rings are the 3,4-positions), R ¹ and R ² are respectively , 1-position to 6-position.
Examples of the alkyl group represented by R ¹ and R ² include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group and a hexyl group. Examples of the cycloalkyl group represented by R ¹ and R ² include a cyclopentyl group and a cyclohexyl group.

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

The compound in which X in the formula (I) is a divalent group represented by the formula (Ib) includes alkylene glycols and 3,4-epoxycyclohexanecarboxylic acid (wherein an alkyl group having 1 to 6 carbon atoms is bonded to the cyclohexane ring). May be present). The compound in which X in the formula (I) is a divalent group represented by the formula (Ic) includes aliphatic dicarboxylic acids and 3,4-epoxycyclohexylmethanol (wherein an alkyl group having 1 to 6 carbon atoms is bonded to the cyclohexane ring). May be present). The compound in which X in the formula (I) is a divalent group represented by the formula (Id) is 3,4-epoxycyclohexylmethanol (wherein the cyclohexane ring has an alkyl group having 1 to 6 carbon atoms bonded thereto). Or an alkylene glycol or polyalkylene glycol and 3,4-epoxycyclohexylmethanol (wherein a cyclohexane ring has an alkyl group having 1 to 6 carbon atoms bonded thereto) It may be an etherified compound (when b>0).

（式（ＩＩ）中、Ｚ^２は炭素数３〜８の直鎖又は分岐のアルキレン基、炭素数３もしくは４のアルキリデン基、２価の脂環式炭化水素基、または式−Ｃ_mＨ_2m−Ｚ¹−Ｃ_nＨ_2n−で示される２価の基を表す。−Ｚ¹−は、−Ｏ−、−ＣＯ−Ｏ−、−Ｏ−ＣＯ−、−ＳＯ₂−、−ＳＯ−、または−ＣＯ−であり、ｍおよびｎは各々独立に１以上の整数であるが、両者の合計は９以下である。） The photocationic curable component (A) may contain a curable component other than the alicyclic epoxy compound, and is represented by, for example, a monofunctional aliphatic epoxy compound, an oxetane compound, a vinyl ether compound and the following formula (II). Diglycidyl compound.

(In the formula (II), Z ² is a linear or branched alkylene group having 3 to 8 carbon atoms, an alkylidene group having 3 or 4 carbon atoms, a divalent alicyclic hydrocarbon group, or a formula —C _m H _2m -Z ¹ -C _n H _2n - represents a divalent group represented by-Z. ¹ - is, -O -, - CO-O -, - O-CO -, - SO 2 -, - SO-, Or -CO-, and m and n are each independently an integer of 1 or more, but the sum of both is 9 or less.)

The compound in which Z ² is an alkylene group in the 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, neo. Examples include pentyl glycol diglycidyl ether.

Further, in the formula (II), when Z is a divalent group represented by the formula —C _m H _2m —Z ¹ —C _n H _2n —, Z is an alkylene group having 2 or more carbon atoms, and C-C bonds of the group, -O -, - CO-O -, - O-CO -, - SO 2 -, - SO-, or equivalent to be interrupted by -CO-.

Examples of the monofunctional aliphatic epoxy compound include glycidyl ether compounds of aliphatic alcohols and glycidyl esters of alkylcarboxylic acids. Specific examples thereof include allyl glycidyl ether, butyl glycidyl ether, sec-butylphenyl glycidyl ether, 2-ethylhexyl glycidyl ether, C12 and C13 mixed alkyl glycidyl ether, alcohol glycidyl ether, aliphatic higher alcohol monoglycidyl ether. , Glycidyl esters of higher fatty acids, and the like.

The oxetane compound is a compound having an oxetanyl group, and specific examples thereof include 3,7-bis(3-oxetanyl)-5-oxa-nonane and 1,4-bis[(3-ethyl-3-oxetanylmethoxy). ) Methyl]benzene, 1,2-bis[(3-ethyl-3-oxetanylmethoxy)methyl]ethane, 1,3-bis[(3-ethyl-3-oxetanylmethoxy)methyl]propane, ethylene glycol bis(3 -Ethyl-3-oxetanylmethyl) ether, triethylene glycol bis(3-ethyl-3-oxetanylmethyl) ether, tetraethylene glycol bis(3-ethyl-3-oxetanylmethyl) ether, 1,4-bis(3- Ethyl-3-oxetanylmethoxy)butane, 1,6-bis(3-ethyl-3-oxetanylmethoxy)hexane, 3-ethyl-3-[(phenoxy)methyl]oxetane, 3-ethyl-3-(hexyloxymethyl) ) Oxetane, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, 3-ethyl-3-(hydroxymethyl)oxetane, 3-ethyl-3-(chloromethyl)oxetane and the like.

Examples of the vinyl ether compound include aliphatic or alicyclic vinyl ether compounds, and specific examples thereof include n-amyl vinyl ether, i-amyl vinyl ether, n-hexyl vinyl ether, n-octyl vinyl ether, 2-ethylhexyl vinyl ether, and n. -Vinyl ethers of C5-20 alkyl or alkenyl alcohols such as dodecyl vinyl ether, stearyl vinyl ether, oleyl vinyl ether; hydroxyl group-containing vinyl ethers such as 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether; cyclohexyl vinyl ether , Vinyl ethers of monoalcohols having an aliphatic ring or an aromatic ring such as 2-methylcyclohexyl vinyl ether, cyclohexyl methyl vinyl ether and benzyl vinyl ether; glycerol monovinyl ether, 1,4-butanediol divinyl ether, 1,6-hexanediol di Vinyl ether, neopentyl glycol divinyl ether, pentaerythritol divinyl ether, pentaerythritol tetravinyl ether, trimethylolpropane divinyl ether, trimethylolpropane trivinyl ether, 1,4-dihydroxycyclohexane monovinyl ether, 1,4-dihydroxycyclohexane divinyl ether, 1, Mono- or polyvinyl ethers of polyhydric alcohols such as 4-dihydroxymethyl cyclohexane monovinyl ether and 1,4-dihydroxymethyl cyclohexane divinyl ether; polyalkylene glycol mono such as diethylene glycol divinyl ether, triethylene glycol divinyl ether and diethylene glycol monobutyl monovinyl ether Or divinyl ethers; other vinyl ethers such as glycidyl vinyl ether, ethylene glycol vinyl ether methacrylate and the like.

The cationic photocurable component (A) preferably contains, in addition to the alicyclic epoxy compound, at least one selected from the group consisting of a diglycidyl compound represented by the formula (II) and a monofunctional aliphatic epoxy compound. ..
The content of the diglycidyl compound represented by the formula (II) is usually 15 to 70 mass% with respect to the total mass of the photocationic curable component (A). While containing the diglycidyl compound in an amount of 15% by mass or more based on the total mass of the photocationic curable component (A), the storage elastic modulus after curing the photocurable adhesive composition (1) is kept at a high value. The adhesion between the polarizer and the protective film can be increased. On the other hand, when the amount exceeds 70 mass %, the storage elastic modulus after curing the photocurable adhesive composition (1) tends to decrease. The content of the diglycidyl compound is preferably 20 to 70% by mass, more preferably 20 to 60% by mass, and more preferably 20 to 50% by mass, based on the total mass of the photocationic curable compound (A). Is more preferable.
The content of the monofunctional aliphatic epoxy compound is usually 1 to 30% by mass, preferably 5 to 20% by mass, and 7 to 15% by mass with respect to the total mass of the photocationic curable component (A). Is more preferable. When the content of the monofunctional aliphatic epoxy compound is more than 30% by mass, the glass transition temperature of the cured product layer of the photocurable adhesive composition (1) is lowered and the heat resistance tends to be deteriorated. Further, if it is less than 1% by mass, the viscosity of the photocurable adhesive composition (1) increases, which is not preferable from the viewpoint of coatability.

(Cationic photopolymerization initiator (B))
In the present invention, the photocationic curable component as described above is cured by cationic polymerization by irradiation with active energy rays to form an adhesive layer. Therefore, the photocurable adhesive composition contains a photocationic polymerization initiator. (B) is blended. The cationic photopolymerization initiator (B) generates a cationic species or a Lewis acid upon irradiation with an active energy ray such as visible light, ultraviolet rays, X-rays, or electron beams, and causes a polymerization reaction of the cationic photocurable component (A). Is what starts. Since the cationic photopolymerization initiator acts catalytically with light, it is excellent in storage stability and workability even when mixed with the cationic photocurable component (A). Examples of the compound that produces 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, and the like.

Examples of the aromatic diazonium salt include the following compounds.
Benzenediazonium hexafluoroantimonate,
Benzenediazonium hexafluorophosphate,
Benzenediazonium hexafluoroborate, etc.

Examples of the aromatic iodonium salt include the following compounds.
Diphenyliodonium tetrakis(pentafluorophenyl)borate,
Diphenyliodonium hexafluorophosphate,
Diphenyliodonium hexafluoroantimonate,
Di(4-nonylphenyl)iodonium hexafluorophosphate and the like.

Examples of the aromatic sulfonium salt include the following compounds.
Triphenylsulfonium hexafluorophosphate,
Triphenylsulfonium hexafluoroantimonate,
Triphenylsulfonium tetrakis(pentafluorophenyl)borate,
4,4′-bis[diphenylsulfonio]diphenyl sulfide bishexafluorophosphate,
4,4′-bis[di(β-hydroxyethoxy)phenylsulfonio]diphenylsulfide bishexafluoroantimonate,
4,4′-bis[di(β-hydroxyethoxy)phenylsulfonio]diphenylsulfide 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-diphenylsulfide hexafluoroantimonate,
4-(p-tert-butylphenylcarbonyl)-4′-di(p-toluyl)sulfonio-diphenyl sulfide tetrakis(pentafluorophenyl)borate and the like.

Examples of the iron-allene complex include the following compounds.
Xylene-cyclopentadienyl iron(II) hexafluoroantimonate,
Cumene-cyclopentadienyl iron(II) hexafluorophosphate,
Xylene-cyclopentadienyl iron(II) tris(trifluoromethylsulfonyl)methanide and the like.

These cationic photopolymerization initiators (B) may be used alone or in combination of two or more. Among them, the aromatic sulfonium salt has an ultraviolet absorbing property even in a wavelength region of around 300 nm, and therefore has excellent curability and is excellent in the photocurable adhesive composition (1) having good mechanical strength and adhesive strength. It is preferably used because it can give a cured product.

The content of the photocationic polymerization initiator (B) is usually 2.5 to 15 parts by mass, preferably 2.5 to 10 parts by mass, based on 100 parts by mass of the entire photocationic curable component (A). Yes, and more preferably 2.5 to 4 parts by mass. By mixing 2.5 parts by mass or more of the cationic photopolymerization initiator (B) with 100 parts by mass of the cationic photocurable component (A), the ratio of nitrogen atom to carbon atom on the surface of the easily adhesive layer in contact with the adhesive layer ( Even if (N/C) is 0.05 or more, the photocationic curable component (A) can be sufficiently cured, and color loss of the polarizer after storing the obtained polarizing plate in a humid heat environment can be prevented. In addition to suppressing, high mechanical strength and high adhesive strength can be provided. On the other hand, when the amount of the cationic photopolymerization initiator (B) is increased, the ionic substance in the cured product of the photocurable adhesive composition (1) is increased, and the hygroscopic property of the cured product is increased, resulting in a polarizing plate. Therefore, it is preferable that the amount be 15 parts by mass or less.

(Reaction accelerator of photocurable adhesive)
The photocurable adhesive composition (1) of the present invention is blended with a general photocurable resin composition or adhesive in addition to the photocationic curable component (A) and the photocationic polymerization initiator (B). Other ingredients known to be included may also be included. Suitable examples of other components include photosensitizers and photosensitization aids. The photosensitizer is a compound that exhibits maximum absorption at a wavelength longer than the maximum absorption wavelength of the photocationic polymerization initiator (B) and accelerates the polymerization initiation reaction by the photocationic polymerization initiator (B). Further, the photosensitizer aid is a compound that further promotes the action of the photosensitizer. Depending on the type of protective film, it may be preferable to blend such a photosensitizer and further a photosensitization aid.

The photosensitizer is preferably a compound that exhibits maximum absorption for light having a wavelength longer than 380 nm. The above-mentioned photocationic polymerization initiator (B) has a maximum absorption at a wavelength of around 300 nm or shorter, and generates a cationic species or a Lewis acid in response to light having a wavelength near that wavelength, thereby generating a cationic photocurable component. The cationic polymerization of (A) is initiated, but when the photosensitizer as described above is blended, it becomes sensitive to light having a longer wavelength, particularly longer than 380 nm. Anthracene compounds are advantageously used as the photosensitizer. Specific examples of the anthracene-based photosensitizer include the following compounds.

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,
2-Methyl- or 2-ethyl-9,10-dihexyloxyanthracene and the like.

By adding the photosensitizer as described above to the photocurable adhesive composition, the curability of the photocurable adhesive composition (1) is improved as compared with the case where the photosensitizer is not added. Such an effect is exhibited by adding 0.1 parts by mass or more of the photosensitizer to 100 parts by mass of the photocationic curable component (A). On the other hand, when the blending amount of the photosensitizer increases, problems such as precipitation during low temperature storage occur, so the amount is set to 2 parts by mass or less based on 100 parts by mass of the photocationic curable component (A). Is preferred. From the viewpoint of maintaining the neutral gray of the polarizing plate, it is advantageous to reduce the compounding amount of the photosensitizer within a range in which the adhesive force between the polarizer and the protective film is appropriately maintained. The amount of the photosensitizer is more preferably 0.1 to 0.5 parts by mass, further preferably 0.1 to 0.3 parts by mass with respect to 100 parts by mass of the sexual component (A).

Next, the photosensitizing aid will be described. There are various types of photosensitization aids, but naphthalene compounds are advantageously used. Specific examples of the naphthalene photosensitization aid 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-dimethoxynaphthalene,
1-ethoxy-4-methoxynaphthalene,
1,4-diethoxynaphthalene,
1,4-dipropoxynaphthalene,
1,4-dibutoxynaphthalene, etc.

By adding a naphthalene-based photosensitization aid to the photocurable adhesive composition (1), the curability of the adhesive is improved as compared with the case where the naphthalene-based photosensitization aid is not added. Such an effect is exhibited by adding 0.1 part by mass or more of the naphthalene-based photosensitization aid to 100 parts by mass of the photocationic curable component (A). On the other hand, if the compounding amount of the naphthalene photosensitizer is large, problems such as precipitation during low temperature storage occur. The amount is preferably the following, and more preferably 3 parts by mass or less.

(Leveling agent)
When the photocurable adhesive composition (1) contains a leveling agent, the coatability of the photocurable adhesive composition (1) is improved, and the generation of streaks after coating can be prevented.
Examples of the leveling agent include organosiloxane polymer compounds. As the leveling agent, commercially available products may be used, for example, KF-640, 642, 643, KP341, X-70-092, X-70-093, KBM303, KBM403, KBM803 (trade names, Shin-Etsu Chemical Co., Ltd.). SH-28PA, SH-190, SH-193, SZ-6032, SF-8428, DC-57, DC-190 (trade name, manufactured by Toray Dow Corning Silicone Co., Ltd.), SILWET L-77. , L-7001, FZ-2105, FZ-2120, FZ-2154, FZ-2164, FZ-2166, L-7604 (above, trade name, manufactured by Nippon Unicar Co., Ltd.), DBE-814, DBE-224, DBE-. 621, CMS-626, CMS-222, KF-352A, KF-354L, KF-355A, KF-6020, DBE-821, DBE-712 (Gelest), BYK-307, BYK-310, BYK-378, BYK. -333 (above, brand name, manufactured by Big Chemie Japan), granol (brand name, manufactured by Kyoeisha Chemical Co., Ltd.) KRM-230 (ADEKA Corporation, trade name) and the like.

When the photocurable adhesive composition (1) contains a leveling agent, the content of the leveling agent is usually 0.001 to 5 parts by mass relative to 100 parts by mass of the photocationic curable component (A), It is preferably 0.01 to 3 parts by mass.

[Easy adhesion layer]
The easy-adhesion layer is formed by curing a composition containing a polyurethane resin, a water-soluble epoxy, a base component and the like (hereinafter, sometimes referred to as easy-adhesive composition (1)).

As the polyurethane resin, ether polyurethane or ester/ether polyurethane is used. The ether polyurethane is a polyurethane having an ether bond in the molecular main chain, and the ester/ether polyurethane is a polyurethane having an ester bond and an ether bond in the molecular main chain. The polyurethane resin may have an acid structure in the molecule. In the polyurethane, the acid structure may be present at the side chain or at the terminal. The acid structure, for example, a carboxyl group (-COOH), a acid group such as a sulfonic acid group (-SO ₃ H).

As the polyurethane resin, a commercially available water-based urethane resin may be used. The water-based urethane resin is a composition containing polyurethane and water, and is usually one in which polyurethane and other optional components are dispersed in water. As commercial products of water-based urethane resin, for example, "Adeka Bontiter" series manufactured by Asahi Denka Kogyo Co., Ltd., "Orestar" series manufactured by Mitsui Toatsu Kagaku Co., Ltd., "Bondick" series manufactured by Dainippon Ink and Chemicals Co., Ltd. , "Hydran" series, "Implaneil" series manufactured by Bayer, "Sofranate" series manufactured by Japan Soflan, "Poise" series manufactured by Kao, "Samplen" series manufactured by Sanyo Chemical Industry, Hodogaya Chemical Co., Ltd. The "Izelax" series manufactured by the same company, the "Superflex" series manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., the "Neorets" series manufactured by Zeneca, and the "Sancure" series manufactured by Lubrizol.

As the epoxy compound, 1 mol of glycols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexane glycol, neopentyl glycol and epichlorohydrin are used. A diepoxy compound obtained by etherification with 2 mols; a polyepoxy compound obtained by etherification with 1 mol of polyhydric alcohols such as glycerin, polyglycerin, trimethylolpropane, pentaerythritol, sorbitol and 2 mol or more of epichlorohydrin; Examples thereof include epoxy compounds such as diepoxy compounds obtained by esterification of 1 mol of a dicarboxylic acid such as phthalic acid, terephthalic acid, oxalic acid and adipic acid with 2 mol of epichlorohydrin. As the epoxy compound, one type may be used alone, or two or more types may be used in combination at an arbitrary ratio.

The content of the epoxy compound is usually 2 parts by mass or more, preferably 5 parts by mass or more, more preferably 8 parts by mass or more, and usually 20 parts by mass or less, preferably 15 parts by mass or less, relative to 100 parts by mass of the polyurethane. Is. By setting the amount of the epoxy compound to the lower limit or more of the above range, the reaction between the epoxy compound and the polyurethane sufficiently proceeds, so that the mechanical strength of the easy-adhesion layer can be appropriately improved, and the upper limit or less is set. As a result, the amount of unreacted epoxy compound remaining can be reduced, and the mechanical strength of the easy-adhesion layer can be appropriately improved.

As the base component, an inorganic base such as sodium hydroxide or potassium hydroxide; 2-amino-2-methyl-1-propanol (AMP), monoethanolamine, 2-amino-2-methyl-1,3-propanediol (AMPD), 2-amino-2-hydroxymethyl-1,3-propane potassium hydroxide, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropyl Trimethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethyldimethoxysilane, 3-ureidopropyltrimethoxysilane, 3-aminopropyl-tris(2-methoxy-ethoxy-ethoxy)silane, cyclohexylamine, hexa Methylenediamine, ethylenediamine, diethylenetriamine, tetraethylenepentamine, pentaethylenepentamine, aminoethylethanolamine, 1,2-propanediamine, isophoronediamine, 4,4'-dicyclohexylmethanediamine, 3,3'-dimethyl-dicyclohexylmethane. Diamine, 1,2-cyclohexanediamine, 1,4-cyclohexanediamine, aminoethylethanolamine, aminopropylethanolamine, aminohexylethanolamine, aminoethylpropanolamine, aminopropylpropanolamine, aminohexylpropanolamine, 5-aminopyrazole , 1-methyl-5-aminopyrazole, 1-isopropyl-5-aminopyrazole, 1-benzyl-5-aminopyrazole, 1,3-dimethyl-5-aminopyrazole, 1-isopropyl-3-methyl-5-amino Pyrazole, 1-benzyl-3-methyl-5-aminopyrazole, 1-methyl-4-chloro-5-aminopyrazole, 1-methyl-4-acino-5-aminopyrazole, 1-isopropyl-4-chloro-5. Primary amines such as -aminopyrazole, 3-methyl-4-chloro-5-aminopyrazole, 1-benzyl-4-chloro-5-aminopyrazole;

Secondary amines such as diethanolamine, morpholine, piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, N-phenyl-γ-aminopropyltrimethoxysilane;
N-methyl-3-aminopropyltrimethoxycarboxylic acid dihydrazide, carbodihydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid Hydrazide compounds such as glycolic acid dihydrazide and polyacrylic acid dihydrazide;
Triethanolamine, triisopropanolamine, tri[(2-hydroxy)-1-propyl]amine, N,N-diethylmethanolamine, N,N-dimethylethanolamine, N,N,N′,N′-tetramethyl Three such as ethylenediamine, N,N-dimethylbenzylamine, diethylaminopropylamine, N-(2-aminoethyl)piperazine, 2,4,6-tris(dimethylaminomethyl)phenol, N,N-bis(trimethylsilyl)urea Primary amines;
Imidazole, 2-methylimidazole, 1-(2-aminoethyl)-2-methylimidazole, 1-(2-aminoethyl)-2-ethylimidazole, 2-aminoimidazole sulfate, 2-(2-aminoethyl)- Imidazole compounds such as benzimidazole;
Imidazoline compounds such as imidazoline and 2-methyl-2-imidazoline; and the like.

Among them, a hydrazide compound having a hydrazino group (—NHNH ₂ group) is preferable. Moreover, as the base component, one kind may be used alone, or two or more kinds may be combined.
The content of the base component is usually 3 to 25 parts by mass, preferably 3 to 10 parts by mass, and more preferably 5 to 10 parts by mass with respect to 100 parts by mass of the polyurethane resin.
By appropriately setting the content of the base component, the atomic concentration ratio (N/C) of nitrogen atoms and carbon atoms on the surface of the easy-adhesive layer formed from the easy-adhesive composition (1) in contact with the adhesive layer Can be adjusted in the range of 0.05 to less than 1.0. The atomic concentration ratio (N/C) of nitrogen atoms and carbon atoms on the surface of the easy-adhesion layer that contacts the adhesive layer can be measured by the method described in the examples.

The easy-adhesive composition (1) is usually a composition in which a polyurethane resin, an epoxy compound, a base, and other components used as necessary are dissolved or dispersed in a solvent.

Examples of the solvent include water and water-soluble solvents.
Examples of the water-soluble solvent include methanol, ethanol, isopropyl alcohol, acetone, tetrahydrofuran, N-methylpyrrolidone, dimethyl sulfoxide, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether and the like. Of these, water is preferably used as the solvent. The solvent may be used alone or in combination of two or more kinds at an arbitrary ratio.

The easy-adhesive composition (1) preferably further contains fine particles. Since the easy-adhesion layer formed from the easy-adhesive composition (1) contains fine particles, irregularities can be formed on the surface of the easy-adhesion layer. When unevenness is formed on the surface of the easy-adhesion layer, the area of contact of the easy-adhesion layer with other layers during winding is reduced, and the slipperiness of the surface of the easy-adhesion layer is improved by that much, and It is possible to suppress the generation of wrinkles when winding the multilayer film of the invention.

The average particle size of the fine particles is usually 1 nm or more, preferably 5 nm or more, more preferably 10 nm or more, and usually 500 nm or less, preferably 300 nm or less, more preferably 200 nm or less. By setting the average particle diameter to be the lower limit value or more in the above range, the slipperiness of the urethane resin layer can be effectively enhanced, and by setting it to be the upper limit value or less in the above range, haze can be suppressed low. As the average particle diameter of the fine particles, the particle diameter distribution is measured by a laser diffraction method, and the cumulative volume calculated from the smaller diameter side in the measured particle diameter distribution is 50% (50% volume cumulative diameter D50). To adopt.

As the fine particles, either inorganic fine particles or organic fine particles may be used, but water-dispersible fine particles are preferably used. Examples of the inorganic fine particles include inorganic oxides such as silica, titania, alumina, and zirconia; calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate, and the like. To be Examples of the organic fine particles include silicone resin, fluororesin, acrylic resin and the like. Of these, silica is preferable. This is because fine particles of silica have excellent ability to suppress the generation of wrinkles and transparency, are less likely to cause haze, and have no coloring, and therefore have a smaller effect on the optical characteristics of the polarizing plate of the present invention. Among the silica fine particles, amorphous colloidal silica particles are particularly preferable.
The fine particles may be used alone or in combination of two or more kinds at an arbitrary ratio.

The easy-adhesive composition (1) may contain other components, for example, a surfactant and the like.

An easy-adhesive layer can be formed by applying the easy-adhesive composition (1) to a protective film described below and then curing the composition. In the easily adhesive layer according to the present invention, the atomic concentration ratio (N/C) of nitrogen atoms and carbon atoms on the surface in contact with the adhesive layer is 0.05 to less than 1.0. The atomic concentration ratio (N/C) is preferably 0.05 to 0.2. The content of the base component contained in the easy-adhesion layer is preferably 1.0×10 ⁻¹⁴ mol/m ^{2 to} 1.0×10 ⁻⁷ mol/m ² . The content of the basic component contained in the easy-adhesion layer can be adjusted to a desired range by appropriately setting the content of the basic component contained in the easy-adhesive composition (1) and the thickness of the easy-adhesion layer. .. The thickness of the easily adhesive layer is preferably 1 to 200 nm, more preferably 10 to 200 nm.

(Protective film)
The protective film is more transparent than triacetyl cellulose such as acetyl cellulose resin film including triacetyl cellulose; amorphous polyolefin resin, polyester resin, acrylic resin, polycarbonate resin and chain polyolefin resin. A resin film having low humidity can be used. The moisture permeability of triacetyl cellulose is about 400 g/m ² /24 hr.

Acetylcellulose-based resin is a resin in which at least a part of the hydroxyl groups in cellulose is acetic acid ester, a part of which is acetic acid ester, and a part of which is esterified with other acid even a mixed ester Good. Specific examples of the acetyl cellulose resin include triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate.

Amorphous polyolefin resins are polymers having polymerized units of cyclic olefins, such as norbornene, tetracyclododecene (also known as dimethanooctahydronaphthalene), or compounds having a substituent bonded to them. It may be a copolymer obtained by copolymerizing a chain olefin and/or an aromatic vinyl compound. In the case of a homopolymer of a cyclic olefin or a copolymer of two or more cyclic olefins, a double bond remains due to ring-opening polymerization. Therefore, hydrogenated one is generally used as an amorphous polyolefin resin. Is used for. Of these, thermoplastic norbornene-based resins are typical.

The polyester resin is a polymer obtained by condensation polymerization of dibasic acid and dihydric alcohol, and polyethylene terephthalate is typical. Acrylic resins are polymers whose main monomer is methyl methacrylate, and include homopolymers of methyl methacrylate, methyl methacrylate, and acrylic acid esters such as methyl acrylate and aromatic vinyl compounds. And the like. The polycarbonate-based resin is a polymer having a carbonate bond (—O—CO—O—) in its main chain, and is typically obtained by condensation polymerization 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 can be a homopolymer or a copolymer. Of these, a propylene homopolymer and a copolymer obtained by copolymerizing propylene with a small amount of ethylene are typical.

The protective film may have a retardation.
The protective film may have various surface treatment layers such as a hard coat layer, an antireflection layer, an antiglare layer, or an antistatic layer on the surface opposite to the easily adhesive layer. The thickness of the protective film, including the case where such a surface treatment layer is formed, is usually 5 to 150 μm, preferably 10 μm or more, and preferably 120 μm or less, more preferably 100 μm or less. is there.

(Production method of polarizing plate)
The polarizing plate of the present invention can be manufactured by first producing a protective film with an easy-adhesion layer, and laminating the obtained protective film with an easily-adhesive layer and a polarizer via an adhesive layer.
The protective film with an easy-adhesion layer is obtained by forming a coating layer of the easy-adhesive composition (1) on the protective film, curing the coating layer by applying heat, and forming the easy-adhesion layer on the protective film. To be Various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used for forming the coating layer of the easy-adhesive composition (1). Further, the surface of the protective film may be subjected to surface treatment such as corona treatment.

A coating layer of the photocurable adhesive composition (1) is formed on one or both of the bonding surfaces of the polarizer and the protective film with the easy-adhesion layer, and the polarizer and the protective film with the easy-adhesion layer are interposed via the coating layer. A polarizing plate can be manufactured by laminating and curing the coating layer of the photocurable adhesive composition (1) by irradiation with active energy rays. The coating layer of the photocurable adhesive composition (1) may be formed on the bonding surface of the polarizer, or may be formed on the bonding surface of the protective film with the easy-adhesion layer. For forming the coating layer of the photocurable adhesive composition (1), the same method as that for forming the coating layer of the easy-adhesive composition (1) can be used. In addition, a method is adopted in which the photocurable adhesive composition (1) is flow-cast while continuously supplying the polarizer and the protective film with the easy-adhesion layer so that the bonding surface of both is inside. You can also Since each coating method has an optimum viscosity range, the viscosity may be adjusted using a solvent. As the solvent for this purpose, a solvent that can satisfactorily dissolve the photocurable adhesive composition (1) without deteriorating the optical performance of the polarizer is used, but the kind thereof is not particularly limited. For example, organic solvents such as hydrocarbons typified by toluene and esters typified by ethyl acetate can be used. The thickness of the adhesive layer is usually 20 μm or less, preferably 10 μm or less, more preferably 5 μm or less. When the adhesive layer is thick, the reaction rate of the adhesive decreases, and the wet heat resistance of the polarizing plate tends to deteriorate.

The light source used for irradiating the coating layer of the photocurable adhesive composition (1) with active energy rays may be any one that emits ultraviolet rays, electron beams, X-rays and the like. Particularly, 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, and the like, which have an emission distribution at a wavelength of 400 nm or less, are preferably used. The irradiation intensity of the active energy ray to the photocurable adhesive is determined for each intended composition and is not particularly limited, but the irradiation intensity in the wavelength region effective for activation of the photocationic polymerization initiator is not limited. It is preferably set to 5 to 3000 mW/cm ² .
If the light irradiation intensity to the photocurable adhesive composition (1) is too low, the reaction time becomes too long, while if the light irradiation intensity is too high, the heat radiated from the lamp and the photocurable adhesive are obtained. The heat generated during polymerization of the composition (1) may cause yellowing of the photocurable adhesive composition (1) and deterioration of the polarizer. The light irradiation time to the photocurable adhesive composition (1) is controlled for each composition to be cured and is not particularly limited, but it is an integrated value represented by the product of irradiation intensity and irradiation time. It is preferable to set the light amount to be 10 to 5,000 mJ/cm ² .
If the integrated light amount to the photocurable adhesive composition (1) is too small, the generation of active species derived from the photocationic polymerization initiator will not be sufficient, and the resulting adhesive layer may be insufficiently cured. However, on the other hand, if an attempt is made to increase the integrated light amount, the irradiation time becomes extremely long, which is disadvantageous for improving productivity.

In the polarizing plate of the present invention, a protective film (hereinafter sometimes referred to as protective film A) may be further laminated on the surface of the polarizer opposite to the surface on which the protective film with the easy-adhesion layer is attached. .. The protective film A and the polarizer may be bonded via the adhesive layer formed of the photocurable adhesive composition (1) described above, or an adhesive layer formed of a known adhesive. The protective film A and the polarizer may be attached via the. Further, the protective film A may be a protective film with an easily adhesive layer, or may be an optical layer described later.

[Laminated optical member]
The polarizing plate of the present invention can be a laminated optical member by laminating optical layers having an optical function other than the polarizing plate.

An example of the optical layer is a reflective layer or a semi-transmissive reflective layer, which is laminated on the polarizing plate arranged on the back side of the liquid crystal cell on the side opposite to the side of the polarizing plate facing the liquid crystal cell. , A light diffusion layer, a light collector, and a brightness enhancement film. Further, for both the polarizing plate arranged on the front side of the liquid crystal cell and the polarizing plate arranged on the back side of the liquid crystal cell, a retardation film laminated on the side of the polarizing plate facing the liquid crystal cell, etc. There is.

The reflective layer, the semi-transmissive reflective layer, or the light diffusion layer is a reflective polarizing plate (optical member), a semi-transmissive reflective polarizing plate (optical member), or a diffusive polarizing plate (optical member), respectively. It is provided in. The reflective polarizing plate is used in a liquid crystal display device of a type that reflects incident light from the viewing side to display, and a light source such as a backlight can be omitted, so that the liquid crystal display device can be easily thinned. Further, the semi-transmissive polarizing plate is used in a liquid crystal display device of a type which is reflective in a bright place and which is displayed by light from a backlight in a dark place. In the optical member as the reflection type polarizing plate, for example, a foil or a vapor deposition film made of a metal such as aluminum is attached to the protective film on the polarizer to form the reflection layer. The optical member as a semi-transmissive polarizing plate can be formed by using the above-mentioned 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, for the optical member as the diffusion type polarizing plate, various methods such as a method of matting the protective film on the polarizing plate, a method of applying a resin containing fine particles, a method of adhering a film containing fine particles, etc. Then, a fine concavo-convex structure is formed on the surface.

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

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

The brightness enhancement film is used for the purpose of improving the brightness in a liquid crystal display device, and as an example, a plurality of thin film films having different anisotropies in refractive index are laminated to cause 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-mentioned retardation film acting as an optical layer is used for the purpose of compensating the retardation by the liquid crystal cell. Examples thereof include birefringent films made of stretched films of various plastics, films in which discotic liquid crystals and nematic liquid crystals are aligned and fixed, and those in which the above liquid crystal layer is formed on a film substrate. 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 resin, polycarbonate resin, acrylic resin, chain polyolefin resin such as polypropylene, polyvinyl alcohol, polystyrene, polyarylate, and polyamide. To be The stretched film may be processed by an appropriate method such as uniaxial or biaxial. The retardation film may be used in combination of two or more for the purpose of controlling the optical characteristics such as widening the band.

In the laminated optical member, an optical layer including a retardation film as an optical layer other than the polarizing plate is preferably used because it can effectively ensure optical protection when applied to a liquid crystal display device. The retardation value (in-plane and thickness direction) of the retardation film may be optimally selected according to the liquid crystal cell to be applied.

The laminated optical member can be made into a laminated body of two layers or three layers by combining a polarizing plate and one layer or two layers or more selected from the various optical layers described above according to the purpose of use. In that case, various optical layers forming the laminated optical member are integrated with the polarizing plate by using an adhesive or a pressure-sensitive adhesive, and the adhesive or pressure-sensitive adhesive used for that purpose is preferably an adhesive layer or a pressure-sensitive adhesive layer. There is no particular limitation as long as it is formed in the above. It is preferable to use a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive) from the viewpoint of easiness of bonding work and prevention of optical distortion. As the pressure-sensitive adhesive, one 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, maintains appropriate wettability and cohesive strength, has excellent adhesion to base materials, and has weather resistance and heat resistance. However, it is preferable to select and use a material that does not cause a peeling problem such as floating or peeling under the condition of heating or humidifying. In the acrylic pressure-sensitive adhesive, an alkyl ester of (meth)acrylic acid having an alkyl group having a carbon number of 20 or less such as a methyl group, an ethyl group or a butyl group, and (meth)acrylic acid or hydroxyethyl (meth)acrylate An acrylic copolymer having a weight average molecular weight of 100,000 or more, which is prepared by blending a functional group-containing acrylic monomer composed of, for example, a glass transition temperature of 25° C. or lower, more preferably 0° C. or lower, It is 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 mass% solution, which is directly applied to the polarizing plate. It can be carried out by a coating method, a method of forming an adhesive layer on a protect film in advance, and then transferring it onto a polarizing plate. The thickness of the pressure-sensitive adhesive layer is determined according to its adhesive strength and the like, but a range of about 1 to 50 μm is suitable.

If necessary, the adhesive layer may be mixed with glass fibers, glass beads, resin beads, fillers made of metal powder or other inorganic powder, pigments or colorants, antioxidants, ultraviolet absorbers, etc. May be. Examples of the ultraviolet absorber include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds and nickel complex salt compounds.

The laminated optical member can be arranged 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 represented by a thin film transistor type and a simple matrix drive type represented by a super twisted nematic type. Can be formed. Usually, the same pressure-sensitive adhesive as described above is used to bond the laminated optical member and the liquid crystal cell.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. In the examples,% and parts indicating the content or the amount used are based on mass unless otherwise specified. In addition, the photocationic curable component and the photocationic polymerization initiator used in the following examples are as follows, and are represented by respective symbols below.

(1) Preparation of cycloolefin film with easy-adhesion layer Preparation example 1: Preparation of aqueous dispersion of urethane resin (1) Solid content of urethane resin aqueous solution (“Superflex 170” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 0.59 g , 10 g of pure water, 41.2 mg of isophthalic acid dihydrazide, 88.2 mg of an epoxy compound (“Denacol EX-313” manufactured by Nagase Chemtex Corp.) and 100 mg of isopropyl alcohol were mixed and stirred at room temperature for 24 hours to disperse the urethane resin in water. Body (1) was prepared.

Preparation Example 2-4: Preparation of Water Dispersion (2) of Urethane Resin to Water Dispersion (4) of Urethane Resin As described in Table 1, except that the various components and contents were changed, Similarly, a urethane resin aqueous dispersion (2) to a urethane resin aqueous dispersion (4) were prepared.

Each component in Table 1 shows the following.
170: manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. "Superflex 170" (nonvolatile content: 33% by mass)
830HS; "Superflex 830HS" manufactured by Daiichi Kogyo Seiyaku Co., Ltd. (nonvolatile content: 27% by mass)
500M: "Superflex 540M" manufactured by Daiichi Kogyo Seiyaku Co., Ltd. (nonvolatile content: 45% by mass)

[Production of multi-layer film]
Using a corona treatment device (produced by Kasuga Denki Co., Ltd.), a thickness of a norbornene-based resin (COP: cycloolefin polymer) under the conditions of an output of 300 W, an electrode length of 240 mm, a work electrode distance of 3.0 mm, and a transfer speed of 4 m/min. The surface of a 50 μm retardation film [trade name “ZEONOR”, manufactured by Nippon Zeon Co., Ltd.] was subjected to discharge treatment.
The urethane resin water dispersion (1) prepared in Preparation Example 1 was applied to the discharge treated surface of the COP film by a bar coater (D-bar manufactured by OSG System Products Co., Ltd.) so that the film thickness after drying was 125 nm. (P) 0.08 mm (H) 3 μm) was applied, dried at 120° C. for 3 minutes and cured to obtain a COP film (1) with an easy-adhesion layer.

A COP with an easy-adhesion layer was prepared in the same manner as above except that the urethane resin water dispersion (1) was changed to the urethane resin water dispersion (2) to the urethane resin water dispersion (4) prepared in Preparation Examples 2 to 4. Film (2) to COP film (4) with an easily adhesive layer were obtained.

[Measurement of N/C ratio]
Using a K-Alpha+X-ray photoelectron spectroscopy (XPS) system manufactured by Thermo Fisher Scientific, a resin primer was prepared from the area intensity ratio of the N(1s) and C(1s) peaks of the easy-adhesion layer and the sensitivity constant of the apparatus. The N/C element ratio on the surface of the layer was calculated. The results are shown in Table 3.
The measurement conditions were as follows.
X-ray light source: Monochrome Al-Kα
X-ray spot size: 400 μmφ
X-ray output: 6.0mA/1.2kV
Neutralizing gun: 0.15mA/0.2V
Pass energy: 50 eV
Number of scans: 5 times Step: 0.1 eV
Dwell time: 50ms

[Example 1]
(2) Preparation of Photocurable Adhesive The components were mixed at the compounding ratio (unit: parts) shown in Table 2 and then defoamed to prepare a photocurable adhesive. The cationic photopolymerization initiator (b1) was blended as a 50% propylene carbonate solution and shown in Table 2 by its solid content.
(A) Photocationic curable component (a1) Alicyclic epoxy compound CEL2021 (manufactured by Daicel Corporation)
(A2) Diglycidyl compound EX-211 (manufactured by Nagase Chemtex Co., Ltd.)
(A3) Monofunctional aliphatic epoxy compound EX-121 (manufactured by Nagase Chemtex Co., Ltd.)
(B) Photocationic polymerization initiator (b1) SP-500 (manufactured by ADEKA Corporation)
(C) Leveling agent KRM-230 (manufactured by ADEKA Corporation)

(3) Preparation of Polarizing Plate (1) A surface of a 80 μm thick triacetyl cellulose film [trade name “Konikatak KC8UX2MW”, manufactured by Konica Minolta Opto Co., Ltd.] containing an ultraviolet absorber was subjected to corona discharge treatment, and The photocurable adhesive composition (1) was applied to the corona discharge treated surface using a bar coater. A polyvinyl alcohol-iodine polarizer having a thickness of 28 μm was attached to the coating layer. Further, the photocurable adhesive composition (1) was coated on the easy adhesive layer side of the COP film (1) with an easy adhesive layer using a bar coater. The triacetyl cellulose film produced above was attached to the coating layer on the polarizer side of the polarizer attached on one side to produce a laminate. From the side of the COP film with the easy-adhesion layer of this laminate, using an ultraviolet irradiation device with a belt conveyor (the lamp uses "D bulb" manufactured by Fusion UV Systems Co., Ltd.), the accumulated light amount is 150 mJ/cm ^{2 in the} UVB wavelength region. The adhesive was cured by irradiating ultraviolet rays so that In this way, a polarizing plate (1) (triacetylcellulose film/adhesive layer/polarizer/adhesive layer/easy-adhesion layer/COP film) having protective films attached to both surfaces of the polarizer was produced.

(4) Measurement of Film Thickness of Adhesive Layer The produced polarizing plate was cut into 3 mm (width)×1 cm, cut in the stretching direction of the polarizer using a microtome [LETOMIC Microtome EM UC7], and a cross-section was observed. A sample was prepared. The obtained sample for cross-section observation was observed with an optical microscope [Digital Microscope manufactured by Keyence Corporation] to determine the thickness of the adhesive layer. The results are shown in Table 3.

(5) Durability Evaluation of Polarizing Plate The COP surface of the prepared polarizing plate was corona-treated and laminated with an acrylic pressure-sensitive adhesive. The prepared polarizing plate with an adhesive layer was cut into a size of 30 mm×30 mm, and the adhesive layer side was laminated to non-alkali glass (trade name “EAGLE XG (registered trademark)” manufactured by Konin Co., Ltd. to form a laminate). The laminate was allowed to stand for 50 hours in a moist heat environment having a temperature of 80° C. and a relative humidity of 90%, and the color of the polarizing plate after 50 hours was visually confirmed, which was evaluated based on the following evaluation judgments.
◯: There is no discoloration in the polarizing plate before and after standing in a humid heat environment.
X: A transparent part and a black part were mixed in a mottled pattern after standing still in a moist heat environment. Alternatively, the entire surface of the polarizing plate was transparent.

(6) Evaluation of Adhesion The produced polarizing plate was cut into a size of length 200 mm×width 25 mm. An acrylic pressure-sensitive adhesive layer was provided on the COP film side of the cut polarizing plate, and the acrylic pressure-sensitive adhesive layer and the glass plate were bonded together to obtain a laminate. A blade of a cutter was put between the polarizer and the COP film of the obtained laminated body, and peeled by 30 mm from the end in the length direction, and the peeled portion was grasped by the grasping portion of the tester. According to JIS K 6854-2:1999 "Adhesive-Peeling Adhesive Strength Test Method-Part 2: 180 Degree Peeling", the laminated body in this state was placed in an atmosphere of a temperature of 23° C. and a relative humidity of 55%. A 180-degree peel test was performed at a grip moving speed of 300 mm/min, and the average peel force over a length of 170 mm excluding 30 mm of the grip was obtained.

Examples 2-4 and Comparative Examples 1-3
Polarizing plates (2) to (7) were obtained in the same manner except that the adhesive composition and the COP film with the easy-adhesion layer are shown in Table 3.

The polarizing plate of the present invention has improved optical durability in a wet heat environment.

Claims (3)

A polarizing plate in which a polarizer, an adhesive layer, an easy-adhesion layer, and a protective film are laminated in this order,
The easy-adhesion layer contains a base component, and the atomic concentration ratio (N/C) of nitrogen atoms and carbon atoms on the surface in contact with the adhesive layer is 0.05 or more and less than 1.0,
The adhesive layer is a photocured product layer of a composition containing the photocationic curable compound (A) and the photocationic polymerization initiator (B),
30-80 mass% of alicyclic epoxy compounds are contained in the total mass of the cationic photocurable compound (A),
The polarizing plate characterized by containing 2.5 to 15 parts by mass of the cationic photopolymerization initiator (B) with respect to 100 parts by mass of the cationic photocurable compound (A). The polarizing plate according to claim 1, wherein the easily adhesive layer has a thickness of 1 to 200 nm. The polarizing plate according to claim 1 or 2, wherein the adhesive layer has a thickness of 0.5 to 5 µm.