JP7380225B2 - Polarizer - Google Patents

Description

The present invention relates to a polarizing plate.

A polarizing plate usually has a structure in which a polarizer and a protective film are laminated on at least one surface of the polarizer. A polarizer and a protective film are usually attached via an adhesive layer, but depending on the type of protective film (for example, a protective film with low moisture permeability formed from a norbornene resin film), the surface of the protective film may It is known to provide an easily adhesive layer. For example, in Patent Document 1, a polarizer, an adhesive layer formed from a water-based adhesive containing a polyvinyl alcohol resin, an easy-adhesion layer formed from a composition containing a urethane resin, and a protective film are laminated in this order. A polarizing plate is described.
Furthermore, Patent Document 2 discloses that, without using an easy-adhesion layer, a polarizer and a protective film with low moisture permeability are bonded to each other using an adhesive formed from an adhesive composition containing an epoxy compound as a main component that does not contain an aromatic ring. Polarizing plates bonded together via layers are described.

Japanese Patent Application Publication No. 2013-10853 Japanese Patent Application Publication No. 2004-245925

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

The present invention includes the following inventions.
[1] A polarizing plate in which a polarizer, an adhesive layer, an easily adhesive layer, and a protective film are laminated in this order,
The easy-adhesion layer contains a basic component, and the atomic concentration ratio (N/C) of nitrogen atoms to 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 material layer of a composition containing a photocationic curable compound (A) and a photocationic polymerization initiator (B),
Containing 30 to 80% by mass of an alicyclic epoxy compound in the total mass of the photocationic curable compound (A),
A polarizing plate characterized in that the photocationic polymerization initiator (B) is contained in an amount of 2.5 to 15 parts by mass based on 100 parts by mass of the photocationic curable 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 under a moist heat environment.

The polarizer, adhesive layer, adhesive layer, and protective film in the polarizing plate of the present invention will be explained in order.

(polarizer)
The polarizer is composed of a polyvinyl alcohol resin film on which a dichroic dye is adsorbed and oriented. The polyvinyl alcohol resin constituting the polarizer can be obtained by saponifying polyvinyl acetate resin. In addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, the polyvinyl acetate resin may be a copolymer of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The degree of saponification of the polyvinyl alcohol resin is usually in the range of 85 to 100 mol%, preferably 98 to 100 mol%. The polyvinyl alcohol resin may be further modified; for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may also 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.

Polarizers are produced through a process of uniaxially stretching such a polyvinyl alcohol resin film, a process of dyeing the polyvinyl alcohol resin film with a dichroic dye, and a process of adsorbing the dichroic dye. It is manufactured through a process of treating a polyvinyl alcohol-based 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 uniaxial stretching is performed after dyeing with a dichroic dye, this uniaxial stretching may be performed before or during the boric acid treatment. Of course, it is also possible to carry out uniaxial stretching in these plural steps. For uniaxial stretching, stretching may be performed uniaxially between rolls having different circumferential speeds, or uniaxially stretching may be performed using hot rolls. Further, dry stretching may be performed in the atmosphere, or wet stretching may be performed in a state swollen with a solvent. The stretching ratio is usually about 4 to 8 times.

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

When using iodine as a dichroic dye, a method is usually employed in which a polyvinyl alcohol resin film is immersed in an aqueous solution containing iodine and potassium iodide for dyeing.
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 (dying time) in this aqueous solution is usually 30 to 300 seconds.

On the other hand, when using a dichroic organic dye as the dichroic dye, a method of dyeing the polyvinyl alcohol resin film by immersing it in an aqueous solution containing a water-soluble dichroic organic dye is usually employed. The content of the dichroic organic dye in this aqueous solution is usually 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 (dying time) in this aqueous solution is usually 30 to 300 seconds.

The boric acid treatment after dyeing with a dichroic dye is performed by immersing the dyed polyvinyl alcohol resin film in an aqueous boric acid solution. The content of boric acid in the boric acid aqueous solution is usually about 2 to 15 parts by weight, preferably about 5 to 12 parts by weight per 100 parts by weight of water. When using iodine as the dichroic dye, the boric acid aqueous solution preferably contains potassium iodide. The content of potassium iodide in the boric acid aqueous solution is usually 2 to 20 parts by weight, preferably 5 to 15 parts by weight per 100 parts by weight of water. The immersion time in the boric acid aqueous solution is usually 100 to 1,200 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 resin film treated with boric acid is usually washed with water. The water washing treatment is performed, for example, by immersing the boric acid-treated polyvinyl alcohol resin film in water. After washing with water, a drying process is performed to obtain a polarizer. The temperature of water in the washing process is usually about 5 to 40°C, and the immersion time is usually about 2 to 120 seconds. The subsequent drying process is usually performed using a hot air dryer or a far-infrared heater.
The drying temperature is usually 40 to 100°C. Further, the drying treatment time is usually about 120 to 600 seconds.

The thickness of the polarizer made of a polyvinyl alcohol 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 (hereinafter sometimes referred to as photocurable adhesive composition (1)) containing a photocationic curable compound (A) and a photocationic polymerization initiator (B). It is.

(Photocationic 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 modulus of the adhesive layer can be increased. When the storage modulus of the adhesive layer becomes high, cracking of the polarizing film can be prevented even in an environment where the temperature is repeatedly high and low. On the other hand, if the content of the alicyclic epoxy compound exceeds 80% by mass based on the total mass of the photocationic curable compound (A), the polarizing film tends to lose color in a humid heat environment, and the optical durability of the polarizing plate increases. There is a tendency for the quality 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 photocationically curable compound (A).

An alicyclic epoxy compound is a compound having at least one epoxy group (hereinafter sometimes referred to as an alicyclic epoxy group) bonded to an alicyclic ring in its molecule. Examples of the alicyclic epoxy group include oxabicyclohexyl group and 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 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 formula (I), assuming that 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 both the 3- and 4-positions), R ¹ and R ² are each , can be bonded to any position from the 1-position to the 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.

To specifically explain the alicyclic diepoxy compound represented by formula (I), X in formula (I) is a divalent group represented by the above formula (Ia), and a in the formula is 0. The compounds include 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 (which has 1 to 6 carbon atoms bonded to its cyclohexane ring). It is an esterified product of 6, which may have an alkyl group bonded thereto. To give a specific example, in 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate [a divalent group represented by formula (I) (however, X is a divalent group represented by formula (Ia) where a=0)] , R ¹ =R ² =H], 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate [in formula (I) having the same X as above, R ¹ =6-methyl, R ² =6-methyl], 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 [formula having the same X as above ( In I), examples include compounds in which R ¹ =3-methyl and R ² =3-methyl.

Compounds in which X in formula (I) is a divalent group represented by formula (Ib) include alkylene glycols and 3,4-epoxycyclohexanecarboxylic acid (an alkyl group having 1 to 6 carbon atoms is bonded to the cyclohexane ring). It is an esterified product with Compounds in which X in formula (I) is a divalent group represented by formula (Ic) include aliphatic dicarboxylic acids and 3,4-epoxycyclohexylmethanol (an alkyl group having 1 to 6 carbon atoms is bonded to the cyclohexane ring). It is an esterified product with In addition, a compound in which X in formula (I) is a divalent group represented by formula (Id) is 3,4-epoxycyclohexylmethanol (an alkyl group having 1 to 6 carbon atoms is bonded to the cyclohexane ring). (b=0), or alkylene glycols or polyalkylene glycols and 3,4-epoxycyclohexylmethanol (an alkyl group having 1 to 6 carbon atoms is bonded to the cyclohexane ring); (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, for example, a monofunctional aliphatic epoxy compound, an oxetane compound, a vinyl ether compound, and a compound represented by the following formula (II). Examples include diglycidyl compounds.

(In 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 group of the formula -C _m H _2m -Z ¹ -C _n H _2n - represents a divalent group represented by -Z ¹ -, -O-, -CO-O-, -O-CO-, -SO ₂ -, -SO-, or -CO-, where m and n are each independently an integer of 1 or more, but the sum of both is 9 or less.)

A compound in which Z ² is an alkylene group in formula (II) is a diglycidyl ether of alkylene glycol. Specific examples 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.

Furthermore, when Z in formula (II) 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 the alkylene This corresponds to the C-C bond of the group being interrupted by -O-, -CO-O-, -O-CO-, -SO ₂ -, -SO-, or -CO-.

Examples of the monofunctional aliphatic epoxy compound include glycidyl etherified products of aliphatic alcohols, glycidyl esters of alkyl carboxylic acids, and the like. Specific examples thereof include allyl glycidyl ether, butyl glycidyl ether, sec-butylphenyl glycidyl ether, 2-ethylhexyl glycidyl ether, mixed alkyl glycidyl ether with 12 and 13 carbon atoms, glycidyl ether of alcohol, and monoglycidyl ether of aliphatic higher alcohol. , 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-oxanonan, 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, n- - Vinyl ethers of alkyl or alkenyl alcohols with 5 to 20 carbon atoms such as dodecyl vinyl ether, stearyl vinyl ether, and oleyl vinyl ether; hydroxyl group-containing vinyl ethers such as 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, and 4-hydroxybutyl vinyl ether; cyclohexyl vinyl ether , 2-methyl cyclohexyl vinyl ether, cyclohexyl methyl vinyl ether, benzyl vinyl ether and other monoalcohol vinyl ethers having aliphatic or aromatic rings; glycerol monovinyl ether, 1,4-butanediol divinyl ether, 1,6-hexanediol divinyl ether Vinyl ether, neopentyl glycol divinyl ether, pentaerythritol divinyl ether, pentaerythritol tetravinyl ether, limethylolpropane divinyl ether, trimethylolpropane divinyl ether, 1,4-dihydroxycyclohexane monovinyl ether, 1,4-dihydroxycyclohexane divinyl ether, 1, Mono- or polyvinyl ethers of polyhydric alcohols such as 4-dihydroxymethylcyclohexane monovinyl ether and 1,4-dihydroxymethylcyclohexane divinyl ether; polyalkylene glycol mono such as diethylene glycol divinyl ether, triethylene glycol divinyl ether, diethylene glycol monobutyl monovinyl ether, etc. or divinyl ethers; other vinyl ethers such as glycidyl vinyl ether and ethylene glycol vinyl ether methacrylate;

In addition to the alicyclic epoxy compound, the photocationic curable component (A) preferably contains at least one member selected from the group consisting of a diglycidyl compound represented by formula (II) and a monofunctional aliphatic epoxy compound. .
The content of the diglycidyl compound represented by formula (II) is usually 15 to 70% by mass based on the total mass of the photocationically curable component (A). By containing 15% by mass or more of the diglycidyl compound based on the total mass of the photocationically curable component (A), the storage modulus after curing the photocurable adhesive composition (1) can be maintained at a high value. , it is possible to increase the adhesion between the polarizer and the protective film. On the other hand, if the amount exceeds 70% by mass, the storage modulus after curing the photocurable adhesive composition (1) also tends to be low. The content of the diglycidyl compound is preferably 20 to 70% by mass, more preferably 20 to 60% by mass, and 20 to 50% by mass, based on the total mass of the photocationic curable compound (A). It is more preferable that
The content of the monofunctional aliphatic epoxy compound is usually 1 to 30% by weight, preferably 5 to 20% by weight, and 7 to 15% by weight based on the total weight of the photocationically curable component (A). It is more preferable that When the content of the monofunctional aliphatic epoxy compound exceeds 30% by mass, the glass transition temperature of the cured layer of the photocurable adhesive composition (1) tends to decrease, and the heat resistance tends to deteriorate. Moreover, 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.

(Photocationic polymerization initiator (B))
In the present invention, since the adhesive layer is formed by curing the photocationic curable component as described above through cationic polymerization by irradiation with active energy rays, the photocurable adhesive composition contains a photocationic polymerization initiator. (B) is blended. The photocationic polymerization initiator (B) generates cationic species or Lewis acids upon irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, or electron beams, and initiates the polymerization reaction of the photocationic curable component (A). This is the start of the process. Since the photocationic polymerization initiator acts catalytically with light, it has excellent storage stability and workability even when mixed with the photocationic curable component (A). Examples of compounds that generate cationic species or Lewis acids upon irradiation with active energy rays include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; and iron-alene complexes.

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

Examples of aromatic iodonium salts include the following compounds.
diphenyliodonium tetrakis(pentafluorophenyl)borate,
diphenyliodonium hexafluorophosphate,
diphenyliodonium hexafluoroantimonate,
Di(4-nonylphenyl)iodonium hexafluorophosphate, etc.

Examples of aromatic sulfonium salts include the following compounds.
triphenylsulfonium hexafluorophosphate,
triphenylsulfonium hexafluoroantimonate,
triphenylsulfonium tetrakis(pentafluorophenyl)borate,
4,4'-bis[diphenylsulfonio]diphenylsulfide bishexafluorophosphate,
4,4'-bis[di(β-hydroxyethoxy)phenylsulfonio]diphenylsulfide bishexafluoroantimonate,
4,4'-bis[di(β-hydroxyethoxy)phenylsulfonio]diphenylsulfide bishexafluorophosphate,
7-[di(p-tolyl)sulfonio]-2-isopropylthioxanthone hexafluoroantimonate,
7-[di(p-tolyl)sulfonio]-2-isopropylthioxanthone tetrakis(pentafluorophenyl)borate,
4-phenylcarbonyl-4'-diphenylsulfonio-diphenylsulfide hexafluorophosphate,
4-(p-tert-butylphenylcarbonyl)-4'-diphenylsulfonio-diphenylsulfide hexafluoroantimonate,
4-(p-tert-butylphenylcarbonyl)-4'-di(p-tolyl)sulfonio-diphenyl sulfide tetrakis(pentafluorophenyl)borate, etc.

Examples of iron-alene complexes include the following compounds.
Xylene-cyclopentadienyl iron(II) hexafluoroantimonate,
Cumene-cyclopentadienyl iron (II) hexafluorophosphate,
Xylene-cyclopentadienyl iron(II) tris(trifluoromethylsulfonyl) methanide, etc.

These photocationic polymerization initiators (B) may be used alone or in combination of two or more. Among these, aromatic sulfonium salts in particular have ultraviolet absorbing properties even in the wavelength region around 300 nm, so they are useful for photocurable adhesive compositions (1) that have excellent curability and good mechanical and adhesive strength. It is preferably used because it can give a cured product.

The amount of the photocationic polymerization initiator (B) is usually 2.5 to 15 parts by weight, preferably 2.5 to 10 parts by weight, based on 100 parts by weight of the entire photocationic curable component (A). The amount is more preferably 2.5 to 4 parts by mass. By blending 2.5 parts by mass or more of the photocationic polymerization initiator (B) per 100 parts by mass of the photocationic curable component (A), the nitrogen atom to carbon atomic ratio ( Even if N/C) is 0.05 or more, the photocationic curable component (A) can be sufficiently cured, and the color fading of the polarizer after storing the resulting polarizing plate in a humid heat environment can be prevented. At the same time, it is possible to provide high mechanical strength and adhesive strength. On the other hand, when the amount of the photocationic polymerization initiator (B) increases, the amount of ionic substances in the cured product of the photocurable adhesive composition (1) increases, which increases the hygroscopicity of the cured product and It is preferable that the amount is 15 parts by mass or less because it may reduce the durability performance of.

(Reaction accelerator for photocurable adhesive)
The photocurable adhesive composition (1) of the present invention is blended into 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 present may also be included. Suitable examples of other components include photosensitizers and photosensitizers. The photosensitizer is a compound that exhibits maximum absorption at a wavelength longer than the maximum absorption wavelength of the cationic photopolymerization initiator (B) and promotes the polymerization initiation reaction by the cationic photopolymerization initiator (B). A photosensitizer is a compound that further promotes the action of a photosensitizer. Depending on the type of protective film, it may be preferable to include such a photosensitizer or even a photosensitizer.

The photosensitizer is preferably a compound that exhibits maximum absorption of light with a wavelength longer than 380 nm. The photocationic polymerization initiator (B) exhibits maximum absorption at a wavelength around 300 nm or shorter than that, generates a cationic species or a Lewis acid in response to light at a wavelength around 300nm, and generates a photocationic curable component. The cationic polymerization of (A) is initiated, but if a photosensitizer such as the one described above is added, the product becomes sensitive to light of longer wavelengths, particularly wavelengths longer than 380 nm. Anthracene compounds are advantageously used as such photosensitizers. Specific examples of anthracene photosensitizers 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 blending the above photosensitizer into the photocurable adhesive composition, the curability of the photocurable adhesive composition (1) is improved compared to the case where no photosensitizer is blended. By blending 0.1 part by mass or more of a photosensitizer with 100 parts by mass of the photocation-curable component (A), such an effect is exhibited. On the other hand, if the amount of the photosensitizer is increased, problems such as precipitation may occur during low-temperature storage, so the amount should be 2 parts by mass or less per 100 parts by mass of the photocationic curable component (A). is preferable. From the viewpoint of maintaining the neutral gray color of the polarizing plate, it is advantageous to reduce the amount of photosensitizer to the extent that the adhesive strength between the polarizer and the protective film is maintained appropriately. It is more preferable that the amount of the photosensitizer is in the range of 0.1 to 0.5 parts by weight, more preferably 0.1 to 0.3 parts by weight, based on 100 parts by weight of the sexual component (A).

Next, the photosensitizer will be explained. Although there are various types of photosensitizing aids, naphthalene compounds are advantageously used. Specific examples of naphthalene photosensitizers 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 blending the naphthalene-based photosensitizing aid into the photocurable adhesive composition (1), the curability of the adhesive is improved compared to the case where the naphthalene-based photosensitizing aid is not blended. By blending 0.1 part by mass or more of the naphthalene photosensitizer with respect to 100 parts by mass of the photocationic curable component (A), such an effect is exhibited. On the other hand, if the amount of the naphthalene-based photosensitizing agent increases, problems such as precipitation may occur during low-temperature storage. It is preferably at most 3 parts by mass, and even more preferably at most 3 parts by mass.

(Leveling agent)
When the photocurable adhesive composition (1) contains a leveling agent, the coating properties of the photocurable adhesive composition (1) are 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, such as KF-640, 642, 643, KP341, X-70-092, ), SH-28PA, SH-190, SH-193, SZ-6032, SF-8428, DC-57, DC-190 (all product names, manufactured by Toray Dow Corning Silicone Company), SILWET L-77 , L-7001, FZ-2105, FZ-2120, FZ-2154, FZ-2164, FZ-2166, L-7604 (all product names, 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 (trade name, manufactured by BIC Chemie Japan), Granol (trade name, manufactured by Kyoeisha Kagaku Co., Ltd.), KRM-230 (trade name, manufactured by ADEKA Co., Ltd.), 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 based on 100 parts by mass of the photocationic curable component (A), It is preferably 0.01 to 3 parts by mass.

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

Ether polyurethane or ester/ether polyurethane is used as the polyurethane resin. Ether polyurethane is a polyurethane having an ether bond in its molecular main chain, and ester/ether polyurethane is a polyurethane having an ester bond and an ether bond in its molecular main chain. The polyurethane resin may have an acid structure within the molecule. The acid structure may be present in the side chain or at the end of the polyurethane. Examples of the acid structure include acid groups such as carboxyl group (-COOH) and 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 usually the polyurethane and other components included as necessary are dispersed in water. Commercially available water-based urethane resins include, for example, the "ADEKA BONTITER" series manufactured by Asahi Denka Industries, the "OLESTAR" series manufactured by Mitsui Toatsu Chemical Co., Ltd., and the "BONDIC" series manufactured by Dainippon Ink and Chemicals. , "Hydran" series, "Implanyl" series manufactured by Bayer, "Sofranate" series manufactured by Nippon Sofran, "Poise" series manufactured by Kao, "Samplen" series manufactured by Sanyo Chemical Industries, Ltd., Hodogaya Chemical Co., Ltd. Examples include the "Izerax" series manufactured by Daiichi Kogyo Seiyaku Co., Ltd., the "Superflex" series manufactured by Daiichi Kogyo Seiyaku, the "Neoretz" series manufactured by Zeneca, and the "Sancure" series manufactured by Lubrizol.

Epoxy compounds include 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. A diepoxy compound obtained by etherification with 2 moles of polyhydric alcohol such as glycerin, polyglycerin, trimethylolpropane, pentaerythritol, sorbitol, etc. and a polyepoxy compound obtained by etherification with 2 moles or more of epichlorohydrin; Epoxy compounds such as diepoxy compounds obtained by esterifying 1 mole of dicarboxylic acid such as phthalic acid, terephthalic acid, oxalic acid, adipic acid, etc. with 2 moles of epichlorohydrin; and the like. One type of epoxy compound may be used alone, or two or more types may be used in combination in any 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, per 100 parts by mass of the polyurethane. It is. By setting the amount of the epoxy compound at or above the lower limit of the above range, the reaction between the epoxy compound and polyurethane will proceed sufficiently, so that the mechanical strength of the easy-adhesive layer can be appropriately improved, and the amount should be at or below the upper limit. As a result, the amount of unreacted epoxy compound remaining can be reduced, and the mechanical strength of the easily adhesive layer can be appropriately improved.

As a base component, inorganic bases such as sodium hydroxide and 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 dihydrazide, 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 ethylenediamine, N,N-dimethylbenzylamine, diethylaminopropylamine, N-(2-aminoethyl)piperazine, 2,4,6-tris(dimethylaminomethyl)phenol, N,N-bis(trimethylsilyl)urea, etc. class amine;
Imidazole, 2-methylimidazole, 1-(2-aminoethyl)-2-methylimidazole, 1-(2-aminoethyl)-2-ethylimidazole, 2-aminoimidazole sulfate, 2-(2-aminoethyl)- Imidazole compounds such as benzimidazole;
Examples include imidazoline compounds such as imidazoline and 2-methyl-2-imidazoline.

Among these, hydrazide compounds having a hydrazino group (-NHNH ₂ groups) are preferred. Moreover, one type of base component may be used alone, or two or more types may be used in combination.
The content of the base component is usually 3 to 25 parts by weight, preferably 3 to 10 parts by weight, and more preferably 5 to 10 parts by weight based on 100 parts by weight of the polyurethane resin.
By appropriately setting the content of the base component, the atomic concentration ratio (N/C) of nitrogen atoms to carbon atoms on the surface in contact with the adhesive layer in the adhesive layer formed from the adhesive composition (1) can be adjusted. can be adjusted to a range of 0.05 to less than 1.0. Note that the atomic concentration ratio (N/C) between nitrogen atoms and carbon atoms on the surface of the easily bonding layer in contact with the adhesive layer can be measured by the method described in Examples.

The easily 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 water-soluble solvents include methanol, ethanol, isopropyl alcohol, acetone, tetrahydrofuran, N-methylpyrrolidone, dimethyl sulfoxide, ethylene glycol monomethyl ether, and ethylene glycol monobutyl ether. Among these, it is preferable to use water as the solvent. In addition, one type of solvent may be used alone, or two or more types may be used in combination in any ratio.

It is preferable that the easily adhesive composition (1) further contains fine particles. The easily adhesive layer formed from the easily adhesive composition (1) contains fine particles, so that irregularities can be formed on the surface of the easily adhesive layer. When irregularities are formed on the surface of the easy-adhesive layer, the area in which the easy-adhesive layer comes into contact with other layers during winding becomes smaller, and the slipperiness of the surface of the easy-adhesive layer is improved by that much, making the book more durable. The generation of wrinkles when winding the multilayer film of the invention can be suppressed.

The average particle diameter 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 equal to or greater than the lower limit of the above range, the slipperiness of the urethane resin layer can be effectively increased, and by setting the average particle diameter to be equal to or less than the upper limit of the range, haze can be suppressed to a low level. The average particle diameter of the fine particles is determined by measuring the particle size distribution using a laser diffraction method, and determining the particle diameter at which the cumulative volume calculated from the small diameter side in the measured particle size distribution is 50% (50% volume cumulative diameter D50). Adopt.

As the fine particles, either inorganic fine particles or organic fine particles may be used, but it is preferable to use water-dispersible fine particles. Examples of 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, etc. It will be done. Furthermore, examples of the organic fine particles include silicone resins, fluororesins, acrylic resins, and the like. Among these, silica is preferred. This is because fine silica particles have excellent ability to suppress the generation of wrinkles and excellent transparency, are less likely to cause haze, and are not colored, so they have less influence on the optical properties of the polarizing plate of the present invention. Among the fine silica particles, amorphous colloidal silica particles are particularly preferred.
Note that one type of fine particles may be used alone, or two or more types of fine particles may be used in combination in any ratio.

The easily adhesive composition (1) may contain other components, such as a surfactant.

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 adhesive layer of the present invention, the atomic concentration ratio (N/C) of nitrogen atoms to carbon atoms on the surface in contact with the adhesive layer is from 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 easily adhesive layer is preferably 1.0×10 ⁻¹⁴ mol/m ² to 1.0×10 ⁻⁷ mol/m ² . The content of the base component contained in the easy-adhesive layer can be adjusted to a desired range by appropriately setting the content of the base component contained in the easy-adhesive composition (1) and the thickness of the easy-adhesive layer. . The thickness of the adhesive layer is preferably 1 to 200 nm, more preferably 10 to 200 nm.

(Protective film)
The protective film is made of acetyl cellulose resin film including triacetyl cellulose; more transparent than triacetyl cellulose such as amorphous polyolefin resin, polyester resin, acrylic resin, polycarbonate resin, chain polyolefin resin, etc. Examples include resin films with low humidity. The moisture permeability of triacetyl cellulose is approximately 400 g/m ² /24 hr.

Acetyl cellulose resin is a resin in which at least some of the hydroxyl groups in cellulose are acetate-esterified, and even if it is a mixed ester in which some are acetate-esterified and some are esterified with other acids. good. Specific examples of cellulose acetate resins include cellulose triacetate, cellulose diacetate, cellulose acetate propionate, cellulose acetate butyrate, and the like.

Amorphous polyolefin resins are polymers that have polymerized units of cyclic olefins, such as norbornene, tetracyclododecene (also known as dimetanooctahydronaphthalene), or compounds with substituents bonded to them. It may also be a copolymer obtained by copolymerizing a chain olefin and/or an aromatic vinyl compound. In the case of homopolymers of cyclic olefins or copolymers of two or more types of cyclic olefins, double bonds remain after ring-opening polymerization, so the hydrogenated product is commonly used as amorphous polyolefin resin. used in many ways. Among these, thermoplastic norbornene resins are representative.

Polyester resins are polymers obtained by condensation polymerization of dibasic acids and dihydric alcohols, and polyethylene terephthalate is a typical example. Acrylic resin is a polymer whose main monomer is methyl methacrylate, and in addition to homopolymers of methyl methacrylate, acrylic resins include methyl methacrylate, acrylic esters such as methyl acrylate, and aromatic vinyl compounds. It may also be a copolymer with. Polycarbonate 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 whose main monomer is a chain olefin such as ethylene or propylene, and can be a homopolymer or a copolymer. Among these, propylene homopolymers and copolymers in which propylene is copolymerized with a small amount of ethylene are representative.

The protective film may have a phase difference.
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 when 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. be.

(Manufacturing method of polarizing plate)
The polarizing plate of the present invention can be manufactured by first preparing a protective film with an easily adhesive layer, and bonding the obtained protective film with an easily adhesive layer and a polarizer via an adhesive layer.
A protective film with an easily adhesive layer can be obtained by forming a coating layer of the easily adhesive composition (1) on a protective film, curing the coating layer by applying heat, and forming an easily adhesive layer on the protective film. It will be done. Various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used to form the coating layer of the 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 an easy-to-adhesion layer, and the polarizer and the protective film with an easy-to-adhesion layer are bonded through the coating layer. A polarizing plate can be manufactured by laminating the photocurable adhesive composition (1) and curing the coating layer by irradiating 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 an easily adhesive layer. The same method as for forming the coating layer of the easily adhesive composition (1) can be used to form the coating layer of the photocurable adhesive composition (1). In addition, a method is adopted in which the photocurable adhesive composition (1) is cast while continuously supplying the polarizer and the protective film with an easy-to-adhesive layer so that the bonding surfaces of both are facing inside. You can also do that. Since each coating method has its own optimum viscosity range, the viscosity may be adjusted using a solvent. The solvent used for this purpose is one that can dissolve the photocurable adhesive composition (1) well without reducing the optical performance of the polarizer, but there is no particular limitation on the type. For example, organic solvents such as hydrocarbons such as toluene and esters such as ethyl acetate can be used. The thickness of the adhesive layer is usually 20 μm or less, preferably 10 μm or less, and more preferably 5 μm or less. When the adhesive layer becomes thick, the reaction rate of the adhesive decreases, and the heat and humidity resistance of the polarizing plate tends to deteriorate.

The light source used to irradiate the coating layer of the photocurable adhesive composition (1) with active energy rays may be any light source that generates ultraviolet rays, electron beams, X-rays, or the like. In particular, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, metal halide lamps, and the like, which have an emission distribution at a wavelength of 400 nm or less, are preferably used. The intensity of active energy ray irradiation to the photocurable adhesive is determined for each target composition, and is not particularly limited, but the irradiation intensity in the wavelength range effective for activating the photocationic polymerization initiator is It is preferable to set it to 5 to 3000 mW/cm ² .
If the light irradiation intensity to the photocurable adhesive composition (1) is too low, the reaction time will be too long; on the other hand, if the light irradiation intensity is too high, the heat radiated from the lamp and the photocurable adhesive will decrease. 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 may be an integrated value expressed as the product of the irradiation intensity and the irradiation time. It is preferable to set the light amount to 10 to 5,000 mJ/cm ² .
If the cumulative amount of light applied to the photocurable adhesive composition (1) is too small, the generation of active species derived from the photocationic polymerization initiator may not be sufficient, and the resulting adhesive layer may be insufficiently cured. On the other hand, if an attempt is made to increase the cumulative amount of light, 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 polarizer surface opposite to the surface to which the protective film with an easily adhesive layer is laminated. . The protective film A and the polarizer may be bonded together via an adhesive layer formed from the above-mentioned photocurable adhesive composition (1), or an adhesive layer formed from a known adhesive. The protective film A and the polarizer may be bonded together via. Moreover, 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 made into a laminated optical member by laminating optical layers having optical functions other than the polarizing plate.

To give an example of an optical layer, for a polarizing plate placed on the back side of a liquid crystal cell, a reflective layer or a semi-transparent reflective layer is laminated on the opposite side of the polarizing plate from the side facing the liquid crystal cell. , light diffusion layers, light condensing plates, brightness enhancement films, etc. In addition, for both the polarizing plate placed on the front side of the liquid crystal cell and the polarizing plate placed on the back side of the liquid crystal cell, retardation films etc. are laminated on the side of the polarizing plate facing the liquid crystal cell. There is.

The reflective layer, semi-transparent reflective layer, or 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. established in A reflective polarizing plate is used in a type of liquid crystal display device that displays by reflecting incident light from the viewing side, and since a light source such as a backlight can be omitted, it is easy to make the liquid crystal display device thinner. In addition, a semi-transmissive polarizing plate is used in a liquid crystal display device that uses light from a backlight to display information in a dark place and as a reflective type in a bright place. In the optical member as a reflective polarizing plate, for example, a reflective layer can be formed by attaching a foil or vapor-deposited film made of a metal such as aluminum to a protective film on a polarizer. The optical member as a semi-transmissive polarizing plate can be formed by using a half mirror as the above-mentioned reflective layer, or by adhering a reflective plate containing pearl pigment or the like and exhibiting light transmittance to the polarizing plate. On the other hand, optical components such as diffusive polarizing plates can be produced using various methods, such as applying a matte treatment to the protective film on the polarizing plate, applying a resin containing fine particles, and bonding a film containing fine particles. to form a fine uneven structure on the surface.

Furthermore, it is also possible to form an optical member that acts as a polarizing plate for both reflection and diffusion. In this case, for example, a method such as providing a reflective layer whose uneven structure is reflected on the finely uneven structure surface of the diffusive polarizing plate is possible. Can be adopted. A reflective layer having a fine uneven structure has advantages such as being able to diffuse incident light through diffuse reflection, preventing directivity and glare, and suppressing unevenness in brightness and darkness. Further, a resin layer or film containing fine particles has the advantage that incident light and its reflected light are diffused when passing through the fine particle-containing layer, thereby suppressing unevenness in brightness and darkness. The reflective layer that reflects the fine unevenness structure on the surface can be formed by directly attaching metal to the surface of the fine unevenness structure, for example, by vacuum deposition, ion plating, or vapor deposition such as sputtering, plating, or the like. The fine particles blended to form a fine surface unevenness structure include, for example, silica, aluminum oxide, titanium oxide, zirconia, tin oxide, indium oxide, cadmium oxide, and antimony oxide, each having an average particle size of 0.1 to 30 μm. They may be inorganic fine particles or organic fine particles such as crosslinked or non-crosslinked polymers.

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

Brightness enhancement films are used for the purpose of improving the brightness in liquid crystal display devices.An example of this is a film made by laminating multiple thin films with different anisotropy of refractive index to create anisotropy in reflectance. Examples include reflective polarized light separating sheets designed as shown in FIG.

On the other hand, the above-mentioned retardation film that acts as an optical layer is used for the purpose of compensating for the retardation caused by the liquid crystal cell. Examples include birefringent films made of stretched films of various plastics, films with fixed alignment of discotic liquid crystals or nematic liquid crystals, and films in which the above-mentioned liquid crystal layer is formed on a film base material. When forming a liquid crystal layer on a film base material, a cellulose resin film such as triacetyl cellulose is preferably used as the film base material.

Examples of plastics forming the birefringent film include amorphous polyolefin resins, polycarbonate resins, acrylic resins, chain polyolefin resins such as polypropylene, polyvinyl alcohol, polystyrene, polyarylates, and polyamides. It will be done. The stretched film can be one that has been processed using an appropriate method such as uniaxial or biaxial processing. Note that two or more retardation films may be used in combination for the purpose of controlling optical properties such as widening the band.

In the laminated optical member, one containing a retardation film as an optical layer other than a polarizing plate is preferably used because optical security can be effectively ensured when applied to a liquid crystal display device. The optimum retardation value (in-plane and thickness direction) of the retardation film may be selected depending on the liquid crystal cell to which it is applied.

The laminated optical member can be a laminate of two or three or more layers by combining a polarizing plate and one or more layers selected from the various optical layers described above depending on the purpose of use. In that case, the various optical layers forming the laminated optical member are integrated with the polarizing plate using an adhesive or pressure-sensitive adhesive, but the adhesive or pressure-sensitive adhesive used for this purpose has a good adhesive layer or pressure-sensitive adhesive layer. There is no particular limitation as long as it is formed. From the viewpoint of ease of bonding work and prevention of optical distortion, it is preferable to use an adhesive (also called a pressure sensitive adhesive). As the adhesive, one having a base polymer such as an acrylic polymer, a silicone polymer, polyester, polyurethane, or polyether can be used. Among these, acrylic adhesives have excellent optical transparency, maintain appropriate wettability and cohesive strength, and have excellent adhesion to substrates, as well as weather resistance and heat resistance. However, it is preferable to select and use a material that does not cause peeling problems such as lifting or peeling under conditions of heating or humidification. In acrylic adhesives, alkyl esters of (meth)acrylic acid having an alkyl group having 20 or less carbon atoms such as methyl, ethyl, or butyl groups, and hydroxyethyl (meth)acrylic acid or (meth)acrylate are used. An acrylic copolymer with a weight average molecular weight of 100,000 or more, which is blended with a functional group-containing acrylic monomer such as Useful as a base polymer.

To form an adhesive layer on a polarizing plate, for example, the adhesive composition is dissolved or dispersed in an organic solvent such as toluene or ethyl acetate to prepare a 10 to 40% by mass solution, and this is directly applied onto the polarizing plate. This can be done by a method of coating, or a method of forming an adhesive layer on a protect film in advance and transferring it onto a polarizing plate. The thickness of the adhesive layer is determined depending on its adhesive strength, etc., but is suitably in the range of about 1 to 50 μm.

In addition, fillers such as glass fibers, glass beads, resin beads, metal powders, and other inorganic powders, pigments, colorants, antioxidants, and ultraviolet absorbers may be added to the adhesive layer as necessary. You can leave it there. Examples of ultraviolet absorbers include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, and nickel complex salt compounds.

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

The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples. In the examples, % and parts indicating content or amount used are based on mass unless otherwise specified. Further, the photocationic curable components and photocationic polymerization initiators used in the following examples are as follows, and are indicated by respective symbols below.

(1) Preparation of cycloolefin film with easily adhesive layer Preparation example 1: Preparation of aqueous dispersion of urethane resin (1) Solid content of urethane resin aqueous solution (“Superflex 170” manufactured by Dai-ichi 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), and 100 mg of isopropyl alcohol were mixed and stirred at room temperature for 24 hours to form an aqueous dispersion of urethane resin. A body (1) was prepared.

Preparation Example 2-4: Preparation of urethane resin water dispersion (2) to urethane resin water dispersion (4) Same as Preparation Example 1 except that various components and contents were changed as shown in Table 1. In the same manner, urethane resin water dispersion (2) to urethane resin water dispersion (4) were prepared.

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

[Manufacture of multilayer film]
Using a corona treatment device (manufactured by Kasuga Denki Co., Ltd.), the thickness of norbornene resin (COP: cycloolefin polymer) was The surface of a 50 μm retardation film (trade name “ZEONOR”, manufactured by Nippon Zeon Co., Ltd.) was subjected to a discharge treatment.
The urethane resin aqueous dispersion (1) prepared in Preparation Example 1 was applied to the discharge-treated surface of the COP film using 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), and dried and cured at 120° C. for 3 minutes to obtain a COP film (1) with an easily adhesive layer.

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

[Measurement of N/C ratio]
Using the K-Alpha + X-ray photoelectron spectroscopy (XPS) system manufactured by Thermo Fisher Scientific, the resin primer was determined from the area intensity ratio of the N (1s) and C (1s) peaks of the easy-adhesion layer and the sensitivity constant of the device. 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: 400μmφ
X-ray output: 6.0mA/1.2kV
Neutralization gun: 0.15mA/0.2V
Pass energy: 50eV
Number of scans: 5 times Step: 0.1eV
Dwell time: 50ms

[Example 1]
(2) Preparation of photocurable adhesive After mixing each component in the proportions shown in Table 2 (unit: parts), defoaming was performed to prepare a photocurable adhesive. Note that the photocationic polymerization initiator (b1) was blended as a 50% propylene carbonate solution, and Table 2 shows 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 Corporation)
(a3) Monofunctional aliphatic epoxy compound EX-121 (manufactured by Nagase ChemteX Corporation)
(B) Photocationic polymerization initiator (b1) SP-500 (manufactured by ADEKA Co., Ltd.)
(c) Leveling agent KRM-230 (manufactured by ADEKA Co., Ltd.)

(3) Preparation of polarizing plate (1) Corona discharge treatment is applied to the surface of an 80 μm thick triacetyl cellulose film containing an ultraviolet absorber (trade name “Konicatack KC8UX2MW”, manufactured by Konica Minolta Opto Co., Ltd.). 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 bonded to the coating layer. Further, the photocurable adhesive composition (1) was coated on the easily adhesive layer side of the COP film with an easily adhesive layer (1) using a bar coater. The polarizer side of the polarizer, on which the triacetyl cellulose film produced above was bonded on one side, was bonded to the coating layer to produce a laminate. From the COP film side with the easy-adhesive layer of this laminate, an integrated light amount of 150 mJ/cm ² was applied in the UVB wavelength range using an ultraviolet irradiation device equipped with a belt conveyor (the lamp used was "D Bulb" manufactured by Fusion UV Systems). The adhesive was cured by irradiating it with ultraviolet light. In this way, a polarizing plate (1) (triacetyl cellulose film/adhesive layer/polarizer/adhesive layer/adhesive layer/COP film) in which protective films were bonded to both sides of the polarizer was produced.

(4) Measuring the film thickness of the adhesive layer The produced polarizing plate was cut out into a piece of 3 mm (width) x 1 cm, cut in the stretching direction of the polarizer using a microtome [LEICA microtome EM UC7], and the cross section was observed. A sample was prepared. The obtained sample for cross-sectional 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 produced polarizing plate was subjected to corona treatment, and an acrylic adhesive was laminated thereon. The produced polarizing plate with adhesive layer was cut into a size of 30 mm x 30 mm, and the adhesive layer side was laminated to alkali-free glass (trade name "EAGLE XG (registered trademark)" manufactured by Konin Co., Ltd.) to form a laminate. The laminate was left standing in a moist heat environment at a temperature of 80°C and a relative humidity of 90% for 50 hours, and the color of the polarizing plate after 50 hours was visually confirmed.Evaluation was made based on the following evaluation judgment.
○: There is no discoloration of the polarizing plate before and after leaving it in a moist heat environment.
×: After standing in a moist heat environment, a mottled pattern had a mixture of transparent parts and black parts. Or the entire surface of the polarizing plate was transparent.

(6) Adhesion evaluation The produced polarizing plate was cut into a size of 200 mm in length x 25 mm in width. An acrylic adhesive layer was provided on the COP film side of the cut polarizing plate, and the acrylic adhesive layer and the glass plate were bonded together to obtain a laminate. A cutter blade was inserted between the polarizer and the COP film of the obtained laminate, and 30 mm was peeled from the end in the length direction, and the peeled portion was grasped with the grip part of the testing machine. The laminate in this state was tested in an atmosphere at a temperature of 23°C and a relative humidity of 55% in accordance with JIS K 6854-2:1999 "Adhesives - Peeling adhesive strength test method - Part 2: 180 degree peeling". A 180 degree peel test was conducted at a gripping movement speed of 300 mm/min, and the average peeling force over a length of 170 mm excluding 30 mm of the grip portion was determined.

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

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

Claims (3)

A polarizing plate in which a polarizer, an adhesive layer, an easily adhesive layer, and a protective film are laminated in this order,
The easy-adhesion layer contains a basic component, and the atomic concentration ratio (N/C) of nitrogen atoms to 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 material layer of a composition containing a photocationic curable compound (A) and a photocationic polymerization initiator (B),
Containing 30 to 80% by mass of an alicyclic epoxy compound in the total mass of the photocationic curable compound (A),
A polarizing plate characterized in that the photocationic polymerization initiator (B) is contained in an amount of 2.5 to 15 parts by mass based on 100 parts by mass of the photocationic curable 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.