JP5682517B2 - Polarizing plate protective film and polarizing plate - Google Patents

Description

  The present invention relates to a polarizing plate protective film and a polarizing plate.

Cellulose acetate films using triacetyl cellulose or diacetyl cellulose are excellent in transparency and optical isotropy, and thus are applied to various optical films.
The cellulose acetate film can hydrophilize the film surface by alkali saponification treatment, and can be adhered to the polarizer with an inexpensive aqueous adhesive. Therefore, the cellulose acetate film is particularly suitable as a polarizing plate protective film, and is an indispensable member for liquid crystal display devices.

  By the way, in recent years, a cellulose acetate film has been produced using a photocurable adhesive so that a polarizing plate can be produced at high speed without performing the alkali saponification treatment as described above. However, it has been found that the photocurable adhesive has a higher viscosity than the conventional water-based adhesive, and when it is bonded to the polarizer at a high speed, air is engulfed at the adhesive interface and a bright spot foreign matter is generated.

  In order to solve the above problems, various diluting solvents for reducing the viscosity of the photocurable adhesive were studied. However, the use of the solvent caused poor curing of the photocurable adhesive. Furthermore, it turned out that a part of polarizing plate protective film melt | dissolves with a solvent and a haze arises when manufacturing a polarizing plate. Thus, it was very difficult to use a photocurable adhesive under high speed conditions.

  On the other hand, as a result of various studies on high-speed adhesiveness between the polarizing plate protective film and the photo-curing adhesive, cellulose acetate propionate described in Patent Document 1, in particular, having a high degree of substitution of propionyl groups, By using it as a protective film, a polarizing plate could be produced without involving air. However, when a photocurable adhesive is used, a large amount of heat is generated when the photocurable adhesive is cured in the manufacturing process of the polarizing plate. Since the polarizing plate protective film described in Patent Document 1 has low heat resistance, another problem that the polarizing plate curls occurred.

  To solve this problem, cellulose acetate propionate, which has high heat resistance and is highly suitable for bonding with a photocurable adhesive, is mixed with triacetyl cellulose and diacetyl cellulose, which have been used as polarizing plate protective films. An attempt was made to solve the problem of air entrainment that occurs during the manufacture of polarizing plates.

  However, triacetyl cellulose and diacetyl cellulose cannot be compatible with cellulose acetate propionate, and it has been difficult to solve the problem of air entrainment that occurs during the production of polarizing plates.

International Publication No. 2006/106639 Pamphlet

  The present invention has been made in view of the above-described problems and circumstances, and a solution to the problem is that it can be bonded to a polarizer at high speed without involving air using a photocurable adhesive, and has heat resistance and a polarizer. It is providing a polarizing plate protective film with high adhesiveness. Moreover, it is providing the polarizing plate provided with the said polarizing plate protective film.

As a result of various studies on cellulose ester resins to solve the above-mentioned problems, the present inventors include two kinds of cellulose ester resins containing a specific substituent at a specific substitution degree or more in a polarizing plate protective film at a specific ratio. Thus, the present inventors have found that the heat resistance of the polarizing plate protective film can be increased, thereby eliminating the entrainment of air caused by the use of the photocurable adhesive.
That is, the subject concerning this invention is solved by the following means.
1. A polarizing plate protective film containing a cellulose ester (A) satisfying the following formulas (1a) to (1d) and a cellulose ester (B) satisfying the following formulas (2a) to (2c):
The mass ratio of the cellulose ester (A) and the cellulose ester (B) is in the range of 1:99 to 30:70, and the glass transition temperature Tg of the polarizing plate protective film is in the range of 148 to 190 ° C. A polarizing plate protective film characterized by being inside.
Formula (1a) 2.00 ≦ DSac (A) + DSay (A) ≦ 2.90
Formula (1b) 1.50 ≦ DSay (A) ≦ 2.80
Formula (1c) 1000 ≦ Mw (A) ≦ 80000
Formula (1d) 120 ° C. ≦ Tg (A) ≦ 147 ° C.
Formula (2a) 2.00 ≦ DSac (B) ≦ 2.90
Formula (2b) 100000 ≦ Mw (B) ≦ 300000
Formula (2c) 150 ≦ Tg (B) ≦ 190
[In the formula, DSac (A) represents the degree of acetyl group substitution of the cellulose ester (A), and DSay (A) represents the total degree of substitution of the acyl group having 3 or 4 carbon atoms of the cellulose ester (A). . DSac (B) represents the degree of acetyl group substitution of cellulose ester (B). Mw (A) represents the weight average molecular weight of the cellulose ester (A), and Mw (B) represents the weight average molecular weight of the cellulose ester (B). Tg (A) represents the glass transition temperature (° C.) of the cellulose ester (A), and Tg (B) represents the glass transition temperature (° C.) of the cellulose ester (B). ]
2. A polarizing plate, wherein the polarizing plate protective film according to item 1 is bonded to at least one surface of a polarizer with a photocurable adhesive containing an epoxy compound and a cationic polymerization initiator.
3. The dispersion force component of the surface free energy (mJ / m ² ) after the easy adhesion treatment of the surface of the polarizing plate protective film that adheres to the polarizer satisfies the following formula (3a), and the polar component satisfies the following formula (3b). 3. The polarizing plate according to item 2, wherein
Formula (3a) 24.5 ≦ dispersing force component (mJ / m ² ) ≦ 40.0
Formula (3b) 10.0 ≦ polar component (mJ / m ² ) ≦ 33.0
4). The easy-adhesion treatment, corona treatment, plasma treatment, flame treatment, ITRO treatment, glow treatment, a polarizing plate according to paragraph 3 you, characterized in that at least one ozone treatment or primer coating treatment.

  According to the present invention, there is provided a polarizing plate protective film that can be bonded to a polarizer at high speed without involving air by using a photocurable adhesive and that has excellent heat resistance and adhesion to the polarizer. That is. Moreover, it is providing the polarizing plate provided with the said polarizing plate protective film.

The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.
The present invention is exhibited by containing two kinds of cellulose esters containing an acyl group at a specific substitution degree or more. The surface free energy of the cellulose ester film containing many acyl groups having 3 or more carbon atoms is closely related to the surface free energy of the photocurable adhesive. For this reason, the cellulose ester film has a high leveling property (uniform coating property) of the photo-curable adhesive, and can produce a polarizing plate at a high speed without causing air entrainment when adhering to the polarizer. It is guessed that has become possible.
On the other hand, the cellulose ester containing many acyl groups having 3 or more carbon atoms has a low glass transition temperature. When a photocurable adhesive is used, the polarizing plate curls due to heat generation during curing.
However, the surface free energy of the polarizing plate protective film surface can be obtained by using the cellulose ester containing an acyl group having 2 carbon atoms having a high glass transition temperature together with the cellulose ester containing an acyl group having 3 or more carbon atoms. Provides a polarizing plate protective film having a high glass transition temperature while maintaining a state close to that of the photocurable adhesive. Thereby, the heat resistance of the polarizing plate protective film can be improved, and it is presumed that no curling occurs in the polarizing plate even when a photocurable adhesive is used.

  Moreover, the adhesive agent containing an epoxy compound and a cationic polymerization initiator contains a large amount of a low molecular weight epoxy compound. Since the epoxy compound before polymerization is hydrophobic in polarity, it has a behavior different from the surface free energy of the film surface made of cellulose diacetate and cellulose triacetate. On the other hand, when there are many acyl groups like the cellulose ester which concerns on this invention, it has the surface free energy close | similar to the epoxy resin before the said superposition | polymerization. For this reason, it is guessed that the effect of this invention is acquired by making a polarizing plate protective film contain the said 2 types of cellulose ester by a specific ratio.

It is a figure explaining the measuring method of surface free energy.

The polarizing plate protective film of this invention contains the cellulose ester (A) which satisfy | fills said Formula (1a)-(1d), and the cellulose ester (B) which fills said Formula (2a)-(2c), The said cellulose The mass ratio of the ester (A) and the cellulose ester (B) is in the range of 1:99 to 30:70, and the glass transition temperature Tg of the polarizing plate protective film is in the range of 148 to 190 ° C. .
This feature is a technical feature common to the inventions according to claims 2 to 4.

  The polarizing plate of the present invention is characterized in that the polarizing plate protective film is bonded to at least one surface of a polarizer with a photocurable adhesive containing an epoxy compound and a cationic polymerization initiator.

As an embodiment of the polarizing plate of the present invention, from the viewpoint of manifesting the effect of the present invention, the surface free energy (mJ / m ² ) dispersibility after the easy adhesion treatment of the surface of the polarizing plate protective film to be bonded to the polarizer. satisfy the component (mJ / ^{m 2)} is the formula (3a), it is preferable to satisfy the polar component (mJ / ^{m 2)} is the formula (3b).
The easy adhesion treatment is preferably at least one of corona treatment, plasma treatment, flame treatment, itro treatment, glow treatment, ozone treatment or primer coating treatment.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

<Polarizing plate protective film>
The polarizing plate protective film which concerns on one form of this invention contains 2 types of cellulose esters (A) and (B).

(Cellulose ester (A), (B))
The cellulose ester (A) satisfies the following formulas (1a) to (1d), and the cellulose ester (B) satisfies the following formulas (2a) to (2c).
Formula (1a) 2.00 ≦ DSac (A) + DSay (A) ≦ 2.90
Formula (1b) 1.50 ≦ DSay (A) ≦ 2.80
Formula (1c) 1000 ≦ Mw (A) ≦ 80000
Formula (1d) 120 ° C. ≦ Tg (A) ≦ 147 ° C.
Formula (2a) 2.00 ≦ DSac (B) ≦ 2.90
Formula (2b) 100000 ≦ Mw (B) ≦ 300000
Formula (2c) 150 ≦ Tg (B) ≦ 190
[In the formula, DSac (A) represents the degree of acetyl group substitution of the cellulose ester (A), and DSay (A) represents the total degree of substitution of the acyl group having 3 or 4 carbon atoms of the cellulose ester (A). Represent. DSac (B) represents the degree of acetyl group substitution of cellulose ester (B). Mw (A) represents the weight average molecular weight of the cellulose ester (A), and Mw (B) represents the weight average molecular weight of the cellulose ester (B). Tg (A) represents the glass transition temperature (° C.) of the cellulose ester (A), and Tg (B) represents the glass transition temperature (° C.) of the cellulose ester (B). ]

  Cellulose esters (A) and (B) can be produced by known methods. For example, when cellulose acetate propionate is produced as a cellulose ester, cellulose is treated with a strong caustic soda solution to obtain alkali cellulose, which is acylated with a mixture of acetic anhydride and propionic anhydride. The obtained cellulose acetate propionate has a total acetyl group substitution degree Dsac and substitution degree Dsay of 3 or 4 carbon acyl groups of about 3, but by partially hydrolyzing the acyl group The cellulose acetate propionate having the desired degree of acetyl group substitution can be produced. Moreover, the target propionyl substitution degree can be obtained by changing the ratio of acetic anhydride and propionic anhydride during acylation.

  In addition, as disclosed in JP2009-19123A, by adjusting the type and amount of carboxylic acid and the amount of catalyst, the reaction rate of the acylation reaction is changed, the degree of substitution and the like are adjusted, A cellulose ester having the desired type of acyl group, degree of substitution, and molecular weight can be synthesized.

The mass ratio of the cellulose ester (A) and the cellulose ester (B) (cellulose ester (A): cellulose ester (B)) is in the range of 1:99 to 30:70.
When the content mass ratio of the cellulose ester (A) is smaller than 1%, the effect of the present invention is not exhibited. Moreover, when cellulose ester (A) is added exceeding 30%, the effect of this invention will be large, but since the molecular weight of cellulose ester (A) is small, the brittleness of a film falls and it is not preferable.

  When the substitution degree DSay (A) of the cellulose ester (A) is less than 1.50, the effect of the present invention is not exhibited. If the substitution degree DSay (A) is greater than 2.80, the effect of the present invention is exhibited, but the glass transition temperature Tg of the entire polarizing plate protective film is lowered, the elastic modulus is lowered, and the photoelasticity is reduced. There are problems such as an increase in coefficient. For this reason, the substitution degree DSay (A) is preferably 2.80 or less.

  With respect to the cellulose ester (B), when the acetyl group substitution degree DSac (B) of the cellulose ester (B) is smaller than 2.00, the water resistance decreases. When the degree of acetyl group substitution DSac (B) is greater than 2.90, solubility in a solvent decreases.

  When the weight average molecular weight Mw (A) of the cellulose ester (A) is smaller than 1000, the compatibility with the cellulose ester (B) is improved, but the brittleness is remarkably lowered. In addition, problems such as bleeding out occur. On the other hand, when the weight average molecular weight Mw (A) is larger than 80000, the compatibility with the cellulose ester (B) decreases, which is not preferable.

  When the weight average molecular weight Mw (B) of the cellulose ester (B) is smaller than 100,000, the brittleness is lowered when the low molecular weight cellulose ester (A) is added. In order to maintain brittleness, the weight average molecular weight Mw (B) is preferably 100,000 or more. On the other hand, when the weight average molecular weight Mw (B) is larger than 300,000, the viscosity increases when dissolved in a solvent, which is not preferable from the viewpoint of productivity.

When the glass transition temperature Tg (A) of the cellulose ester (A) is 120 ° C. or lower, the heat resistance when the cellulose ester (B) is dissolved is lowered. Further, since the cellulose ester (A) has a large acyl group substitution degree DSay (A), the glass transition temperature Tg (A) cannot be 147 ° C. or higher.
On the other hand, the glass transition temperature Tg (B) of the cellulose ester (B) is preferably high in order to improve the heat resistance of the polarizing plate protective film, and the glass transition temperature Tg (B) is preferably 150 ° C. or higher. . Moreover, since the acetyl group substitution degree DSac (B) of the cellulose ester (B) is larger than 2.00, it cannot be made 190 ° C. or higher.

(Hydrolysis inhibitor)
The polarizing plate protective film can contain a hydrolysis inhibitor.
When the polarizing plate protective film contains a hydrolysis inhibitor, hydrolysis of the cellulose esters (A) and (B) is prevented, so that the water resistance of the polarizing plate protective film can be improved.

  The hydrolysis inhibitor that can be used in the present invention is not particularly limited, but a hydrolysis inhibitor having an octanol-water partition coefficient log P of 7 or more and less than 11 is preferred. When the octanol-water partition coefficient logP is less than 7, the hydrolysis-preventing effect is small, and when the logP (A) is 11 or more, the compatibility with the cellulose ester is low, and bleeding out due to wet heat is not preferable.

As the hydrolysis inhibitor, for example, a mixture of ester compounds having at least one pyranose structure or at least one furanose structure and at least one OH group of the structure being esterified can be preferably used. . The esterification ratio of such an ester compound is preferably 70% or more of the OH groups present in the pyranose structure or furanose structure.
In the present invention, the above ester compounds are collectively referred to as sugar ester compounds.

  Examples of the ester compound include, for example, glucose, galactose, mannose, fructose, xylose, arabinose, lactose, sucrose, nystose, 1F-fructosyl nystose, stachyose, maltitol, lactitol, lactulose, cellobiose, maltose, cellotriose, malto Examples include triose, raffinose, and kestose. In addition, gentiobiose, gentiotriose, gentiotetraose, xylotriose, galactosyl sucrose and the like can be mentioned, but the present invention is not limited to these.

  Among these ester compounds, ester compounds having both a pyranose structure and a furanose structure are particularly preferable. As examples, sucrose, kestose, nystose, 1F-fructosyl nystose, stachyose and the like are preferable, and sucrose is more preferable.

  The monocarboxylic acid used for esterifying all or part of the OH group in the pyranose structure or furanose structure is not particularly limited, and is a known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic A monocarboxylic acid or the like can be used. The carboxylic acid used may be one type or a mixture of two or more types.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid , Saturated fatty acids such as tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid, Examples include unsaturated fatty acids such as undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid and octenoic acid.

  Examples of preferable alicyclic monocarboxylic acids include acetic acid, cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid and derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include aromatic monocarboxylic acids having an alkyl group or alkoxy group introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, cinnamic acid, benzylic acid, biphenylcarboxylic acid, and naphthalene. Aromatic monocarboxylic acids having two or more benzene rings such as carboxylic acid and tetralin carboxylic acid or derivatives thereof can be mentioned. More specifically, xylic acid, hemelic acid, mesitylene acid, prenicylic acid, γ-isoduric acid, duryl acid, mesitonic acid, α-isoduryl acid, cumic acid, α-toluic acid, hydroatropic acid, atropic acid, hydrocinnamic Acid, salicylic acid, o-anisic acid, m-anisic acid, p-anisic acid, creosote acid, o-homosalicylic acid, m-homosalicylic acid, p-homosalicylic acid, o-pyrocatechuic acid, β-resorcylic acid, vanillic acid , Isovanillic acid, veratrumic acid, o-veratrumic acid, gallic acid, asaronic acid, mandelic acid, homoanisic acid, homovanillic acid, homoveratrumic acid, o-homoveratric acid, phthalonic acid, p-coumaric acid, etc. Benzoic acid and naphthylic acid are particularly preferable.

An oligosaccharide ester compound may be applied as a compound having 1 to 12 at least one of a pyranose structure or a furanose structure.
Oligosaccharides are produced by causing an enzyme such as amylase to act on starch, sucrose or the like. Examples of oligosaccharides include maltooligosaccharide, isomaltooligosaccharide, fructooligosaccharide, galactooligosaccharide, and xylo-oligosaccharide.

〔式中、Ｒ_１１〜Ｒ_１５、Ｒ_２１〜Ｒ_２５は、炭素数２〜２２のアシル基又は水素原子を表す。ｍ、ｎはそれぞれ０〜１２の整数、ｍ＋ｎは１〜１２の整数を表す。〕 Moreover, the said ester compound is a compound which condensed 1 or more and 12 or less of the pyranose structure or furanose structure represented by the following general formula (SE).

[In formula, R < ₁₁ > -R < ₁₅ >, R < ₂₁ > -R < ₂₅ > represents a C2-C22 acyl group or a hydrogen atom. m and n each represents an integer of 0 to 12, and m + n represents an integer of 1 to 12. ]

R _{11 to} R ₁₅ and R _{21 to} R ₂₅ are preferably a benzoyl group or a hydrogen atom. Benzoyl group may further have a substituent R _26. Examples of the substituent R ₂₆ include an alkyl group, an alkenyl group, an alkoxyl group, and a phenyl group, and these alkyl group, alkenyl group, and phenyl group may have a substituent.

Although the specific example of the said ester compound is given to the following, this invention is not limited to this.

  The polarizing plate protective film of the present invention preferably contains a hydrolysis inhibitor in the range of 0.5 to 30% by mass of the polarizing plate protective film, particularly preferably in the range of 2 to 15% by mass.

(Phase difference adjusting agent)
The polarizing plate protective film which concerns on this invention can also contain a phase difference adjusting agent.
The phase difference adjusting agent of the present invention is not particularly limited, but a phase difference adjusting agent having an octanol-water partition coefficient log P of 0 or more and less than 7 is preferable. The phase difference adjusting agent needs to have an appropriate solubility corresponding to the cellulose ester contained in the polarizing plate protective film, but when the octanol-water partition coefficient logP of the phase difference adjusting agent is smaller than 0, the phase difference adjusting agent. Due to its high water solubility, alignment disorder occurs. Further, if the octanol-water partition coefficient logP is 7 or more, the orientation of the retardation adjusting agent is low, so that a desired retardation cannot be obtained, which is not preferable.

As the phase difference adjusting agent, for example, an ester compound represented by the following general formula (4) can be preferably used.
General formula (4) Y- (GX) _n -G-Y
[Wherein, X represents an alkylenedicarboxylic acid residue having 4 to 12 carbon atoms or an aryldicarboxylic acid residue having 6 to 12 carbon atoms. Y represents a hydroxy group or a carboxylic acid residue. G represents an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms. n represents an integer of 1 or more. ]
The ester compound represented by the general formula (4) can be obtained by the same reaction as a normal ester compound.

  Examples of the carboxylic acid component of the ester compound represented by the general formula (4) include acetic acid, propionic acid, butyric acid, benzoic acid, p-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, and dimethylbenzoic acid. , Ethyl benzoic acid, normal propyl benzoic acid, aminobenzoic acid, acetoxybenzoic acid, aliphatic acid and the like, and these can be used as one kind or a mixture of two or more kinds, respectively.

In the general formula (4), the alkylene glycol component having 2 to 12 carbon atoms of the ester compound represented by G includes ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butane. Diol, 1,3-butanediol, 1,2-propanediol, 2-methyl 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3- Propanediol (neopentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3propanediol (3,3- Dimethylolheptane), 3-methyl-1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl 1,3-pentane Ol, 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, there are 1,12-octadecanediol like. These glycols are used as one kind or a mixture of two or more kinds.
Especially as G, C2-C12 alkylene glycol is especially preferable since it is excellent in compatibility with a cellulose ester.

  In the general formula (4), examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the ester compound represented by G include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. Etc. These glycols can be used as one kind or a mixture of two or more kinds.

  Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the ester compound represented by X in the general formula (4) include, for example, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, and sebacin. There are acid, dodecanedicarboxylic acid, and the like, and these are used as one kind or a mixture of two or more kinds, respectively. Examples of the arylene dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5 naphthalene dicarboxylic acid, and 1,4 naphthalene dicarboxylic acid.

  The number average molecular weight of the ester compound represented by the general formula (4) is preferably 300 to 1500, and more preferably 400 to 1000. The acid value is preferably 0.5 mgKOH / g or less, the hydroxy value (also referred to as hydroxyl value or hydroxyl value) is preferably 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxy value is 15 mgKOH. / G or less.

  In addition, an acid value means the milligram number of potassium hydroxide required in order to neutralize the acid (carboxy group which exists in a sample) contained in 1g of samples. The acid value is measured according to JIS K0070.

Hereinafter, specific compounds (ar-1) to (ar-19) of the ester compound represented by the general formula (4) are shown, but the present invention is not limited thereto.

  The polarizing plate protective film of the present invention preferably contains a retardation adjusting agent in a range of 0.1 to 30% by mass, particularly in a range of 0.5 to 10% by mass with respect to the polarizing plate protective film. Is preferred.

(Other additives)
(Plasticizer)
The polarizing plate protective film according to the present invention can contain a plasticizer as necessary in obtaining the effects of the present invention.

The plasticizer is not particularly limited, but preferably a polyhydric alcohol ester plasticizer, glycolate plasticizer, phthalate ester plasticizer, citrate ester plasticizer, fatty acid ester plasticizer, phosphate ester plasticizer. , Polycarboxylic acid ester plasticizers, polyester plasticizers, acrylic plasticizers, and the like.
Of these, when two or more plasticizers are used, at least one plasticizer is preferably a polyhydric alcohol ester plasticizer.

  The polyhydric alcohol ester plasticizer is a plasticizer comprising an ester of a divalent or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule. Preferably, it is a 2-20 valent aliphatic polyhydric alcohol ester.

The polyhydric alcohol preferably used in the present invention is represented by the following general formula (5).
Formula (5) R _1- (OH) _n
[Wherein, R ₁ represents an n-valent organic group, n represents a positive integer of 2 or more, and the OH group represents an alcoholic hydroxy group (hydroxyl group) or a phenolic hydroxy group (hydroxyl group). ]

Preferred polyhydric alcohols include adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2- Butanediol, 1,3-butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, Mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol and the like can be mentioned, but the present invention is not limited to these. No.
Of these, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

  There is no restriction | limiting in particular as monocarboxylic acid used for polyhydric alcohol ester, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred in terms of improving moisture permeability and retention.

Preferred examples of the monocarboxylic acid include the following examples, but the present invention is not limited thereto.
As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is preferably 1-20, and more preferably 1-10. When acetic acid is contained, the compatibility with the cellulose ester is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanoic acid, undecylic acid, lauric acid, tridecylic acid, Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, laccelic acid, undecylenic acid, olein Examples thereof include unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which 1 to 3 alkoxy groups such as alkyl group, methoxy group or ethoxy group are introduced into the benzene ring of benzoic acid such as benzoic acid or toluic acid, biphenylcarboxylic acid, Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as naphthalenecarboxylic acid and tetralincarboxylic acid, or derivatives thereof. Benzoic acid is particularly preferable.

  The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably 300 to 1500, and more preferably 350 to 750. A higher molecular weight is preferable because it is less likely to volatilize, and a lower molecular weight is preferable in terms of moisture permeability and compatibility with cellulose ester.

  The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

Specific examples of the polyhydric alcohol ester compounds (ae-1) to (ae-35) are shown below.

  The glycolate plasticizer is not particularly limited, but alkylphthalylalkyl glycolates can be preferably used.

  Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl Glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl glycol Butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl phthalate Ethyl glycolate, and the like.

  Examples of the phthalate ester plasticizer include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, and dicyclohexyl terephthalate.

  Examples of the citrate plasticizer include acetyl trimethyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate.

  Examples of fatty acid ester plasticizers include butyl oleate, methylacetyl ricinoleate, and dibutyl sebacate.

  Examples of the phosphate ester plasticizer include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate and the like.

  Examples of the polyvalent carboxylic acid ester compound include ester compounds composed of a divalent or higher, preferably a divalent to a 20-valent polyvalent carboxylic acid and an alcohol. The aliphatic polyvalent carboxylic acid is preferably 2 to 20 valent, and in the case of an aromatic polyvalent carboxylic acid or an alicyclic polyvalent carboxylic acid, it is preferably 3 to 20 valent.

The polyvalent carboxylic acid used for the polyvalent carboxylic acid ester compound is represented by the following general formula (6).
Formula (6) R ₂ (COOH) _m (OH) _n
[Wherein R ₂ is an (m + n) -valent organic group, m is an integer of 2 or more, n is an integer of 0 or more, a COOH group is a carboxy group, an OH group is an alcoholic hydroxy group (hydroxyl group) or a phenolic hydroxy group (Hydroxyl group). ]

  Preferred polyvalent carboxylic acids include trivalent or higher aromatic polyvalent carboxylic acids such as trimellitic acid, trimesic acid and pyromellitic acid or derivatives thereof, succinic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid, Aliphatic polycarboxylic acids such as fumaric acid, maleic acid and tetrahydrophthalic acid, oxypolycarboxylic acids such as tartaric acid, tartronic acid, malic acid and citric acid can be preferably used. It is not limited to. In particular, it is preferable to use an oxypolycarboxylic acid from the viewpoint of improving the retention.

  When an oxypolycarboxylic acid is used as the polycarboxylic acid, the alcoholic or phenolic hydroxy group (hydroxyl group) of the oxypolycarboxylic acid may be esterified with a monocarboxylic acid. Preferred examples of the monocarboxylic acid include the following examples, but the present invention is not limited thereto.

There is no restriction | limiting in particular as alcohol used for a polyhydric carboxylic acid ester compound, Well-known alcohol and phenols can be used.
For example, an aliphatic saturated alcohol or aliphatic unsaturated alcohol having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is preferable that it is C1-C20, and it is more preferable that it is C1-C10.

In addition, alicyclic alcohols such as cyclopentanol and cyclohexanol or derivatives thereof, aromatic alcohols such as benzyl alcohol and cinnamyl alcohol, or derivatives thereof can also be preferably used.
The alcohol used for the polyvalent carboxylic acid ester may be one kind or a mixture of two or more kinds.

  Although there is no restriction | limiting in particular in the molecular weight of a polyhydric carboxylic acid ester compound, It is preferable that it is the range of molecular weight 300-1000, and it is more preferable that it is the range of 350-750. The larger one is preferable in terms of improvement in retention, and the smaller one is preferable in terms of moisture permeability and compatibility with cellulose ester.

  The acid value of the polyvalent carboxylic acid ester compound is preferably 1 mgKOH / g or less, and more preferably 0.2 mgKOH / g or less. By setting the acid value within the above range, the environmental fluctuation of the retardation is also suppressed, which is preferable.

  Particularly preferred polyvalent carboxylic acid ester compounds include, for example, triethyl citrate, tributyl citrate, acetyl triethyl citrate (ATEC), acetyl tributyl citrate (ATBC), benzoyl tributyl citrate, acetyl triphenyl citrate, acetyl tribenzyl citrate Examples include, but are not limited to, rate, dibutyl tartrate, diacetyl dibutyl tartrate, tributyl trimellitic acid, tetrabutyl pyromellitic acid, and the like.

(UV absorber)
The polarizing plate protective film which concerns on this invention can also contain a ultraviolet absorber.
The ultraviolet absorber is added for the purpose of improving the durability of the polarizing plate protective film by absorbing ultraviolet rays of 400 nm or less. It is preferable that the transmittance | permeability of the ultraviolet-ray of wavelength 370nm in a polarizing plate protective film is 10% or less, More preferably, it is 5% or less, More preferably, it is 2% or less.

Although the ultraviolet absorber used in the present invention is not particularly limited, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex compounds, inorganic powders Examples include the body. Of these, benzotriazole ultraviolet absorbers and benzophenone ultraviolet absorbers are preferred.
The polarizing plate protective film according to the present invention preferably contains two or more ultraviolet absorbers.

  Examples of the ultraviolet absorber include 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -2H-benzotriazole, (2-2H-benzotriazol-2-yl) -6- (Linear and side chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone and the like. In addition, tinuvins such as tinuvin 109, tinuvin 171, tinuvin 234, tinuvin 326, tinuvin 327, and tinuvin 328 are also included. All the chinuvins listed here are commercially available from BASF Japan, and can be preferably used.

A discotic compound such as a compound having a 1,3,5 triazine ring is also preferably used as the ultraviolet absorber.
Polymer ultraviolet absorbers can also be preferably used, and polymer type ultraviolet absorbers described in JP-A-6-148430 are particularly preferably used.

As for the method of adding the ultraviolet absorber, the ultraviolet absorber is dissolved in an alcohol such as methanol, ethanol, butanol, an organic solvent such as methylene chloride, methyl acetate, acetone, dioxolane, or a mixed solvent thereof, and then added to the dope. Or may be added directly into the dope composition.
For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and cellulose ester to disperse and then added to the dope.

  The content of the UV absorber is not uniform depending on the type of UV absorber, use conditions, etc., but when the dry film thickness of the polarizing plate protective film is 30 to 200 μm, it is 0.5 with respect to the polarizing plate protective film. It is preferable that it is the range of -10 mass%, and it is further more preferable that it is the range of 0.6-4 mass%.

(Antioxidant)
The polarizing plate protective film may be decomposed by a residual solvent amount of halogen in the polarizing plate protective film, phosphoric acid of a phosphoric acid plasticizer contained in the polarizing plate protective film, or the like. The antioxidant is preferably contained in the polarizing plate protective film for the purpose of delaying or preventing the polarizing plate protective film from decomposing.
Antioxidants are also referred to as deterioration inhibitors. This is because when the image display device is placed in a high humidity and high temperature state, the polarizing plate protective film provided in the image display device may be deteriorated, and the antioxidant has a function of preventing such deterioration. .

  As such an antioxidant, a hindered phenol compound is preferably used. For example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di- t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1 , 3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octade Ru-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-tert-butyl-4-hydroxy-hydrocinnamamide) 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxy Benzyl) -isocyanurate and the like.

In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred.
Further, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine, tris (2,4-di-t- A phosphorus processing stabilizer such as (butylphenyl) phosphite may be used in combination.

  The content of these antioxidants is preferably in the range of 1 to 1.0% by mass and more preferably in the range of 10 to 1000% by mass with respect to the polarizing plate protective film.

(Fine particles)
In order to impart slipperiness to the polarizing plate protective film of the present invention, it is preferable to add fine particles.
The primary average particle diameter of the fine particles is preferably 20 nm or less, more preferably 5 to 16 nm, and still more preferably 5 to 12 nm.

  These fine particles are preferably contained in the polarizing plate protective film by forming secondary particles having a particle diameter of 0.1 to 5 μm. The preferable average particle diameter of the secondary particles is 0.1 to 2 μm, and more preferably 0.2 to 0.6 μm. Thereby, the unevenness | corrugation about 0.1-1.0 micrometer high is formed in the surface of a polarizing plate protective film, and appropriate slipperiness can be given to the surface of a polarizing plate protective film.

  About the measuring method of the primary average particle diameter of microparticles | fine-particles, it observes a particle | grain with a transmission electron microscope (magnification 500,000-2 million times), observes 100 particle | grains, measures a particle diameter, and has the average value, The primary average particle diameter was used.

  The apparent specific gravity of the fine particles is preferably 70 g / liter or more, more preferably 90 to 200 g / liter, still more preferably 100 to 200 g / liter. A larger apparent specific gravity is preferable because a high-concentration dispersion can be produced, and haze and aggregates are improved. It is particularly preferably used when preparing a dope having a high solid content concentration.

  The fine particles of silicon dioxide having an average primary particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more include, for example, a vaporized mixture of silicon tetrachloride and hydrogen at a temperature of 1000 to 1200 ° C. It is obtained by burning in. For example, Aerosil 200V and Aerosil R972V (both manufactured by Nippon Aerosil Co., Ltd.) are commercially available and can be used.

The apparent specific gravity is a value calculated by the following formula from the measured mass and volume after taking silicon dioxide fine particles in a measuring cylinder and measuring the mass and volume.
Apparent specific gravity (g / liter) = silicon dioxide mass (g) / volume of silicon dioxide (liter)

Examples of the method for preparing the fine particle dispersion include the following three types.
(Preparation method 1)
After stirring and mixing the solvent and fine particles, dispersion is performed with a disperser. This is a fine particle dispersion. The fine particle dispersion is added to the dope solution and stirred.

(Preparation method 2)
After stirring and mixing the solvent and the fine particles, the fine particles are dispersed by dispersing with a disperser. Separately, a small amount of cellulose acylate is added to the solvent and dissolved by stirring. To this, the obtained fine particle dispersion is added and stirred to obtain a fine particle addition solution. Using an in-line mixer, thoroughly mix the fine particle additive solution and the dope solution.

(Preparation method 3)
Add a small amount of cellulose acylate to the solvent and stir to dissolve. Fine particles are added to this and dispersed with a disperser to obtain a fine particle addition liquid. The fine particle addition solution is thoroughly mixed with the dope solution using an in-line mixer.

  Preparation method 1 is excellent in dispersibility of silicon dioxide fine particles, and preparation method 3 is excellent in that the silicon dioxide fine particles are difficult to re-aggregate. Preparation method 2 is preferable because the dispersibility of the silicon dioxide fine particles is excellent, and the silicon dioxide fine particles are difficult to re-aggregate and are excellent in both.

(Distribution method)
The concentration range of silicon dioxide when the silicon dioxide fine particles are mixed and dispersed with a solvent or the like is preferably 5% by mass to 30% by mass, more preferably 10% by mass to 25% by mass, and most preferably 15% to 20% by mass. . When the concentration of silicon dioxide at the time of dispersion is high, the liquid turbidity tends to be low with respect to the amount of silicon dioxide added, and haze and aggregates are reduced, which is preferable.

  Examples of the solvent used include lower alcohols. Preferable lower alcohols include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like. Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film forming of a cellulose ester.

  The amount of silicon dioxide fine particles added is preferably in the range of 0.01 to 5.0 parts by mass, and 0.05 to 1.0 parts by mass with respect to 100 parts by mass of the cellulose ester. More preferably, it is the range of 0.1 part by mass to 0.5 part by mass. The larger the amount added, the better the dynamic friction coefficient, and the smaller the amount added, the less aggregate.

A normal disperser can be used as the disperser. Dispersers are broadly divided into media dispersers and medialess dispersers.
Examples of the media disperser include a ball mill, a sand mill, and a dyno mill.
Examples of the medialess disperser include an ultrasonic type, a centrifugal type, and a high pressure type. In the present invention, a high pressure disperser is preferable. The high-pressure dispersion device is a device that creates special conditions such as high shear and high-pressure conditions by passing a composition in which fine particles and a solvent are mixed at high speed through a narrow tube.
It is preferable to use a medialess disperser for dispersing the silicon dioxide fine particles because the haze is low.

  When processing with a high-pressure dispersion apparatus, for example, the maximum pressure condition inside the apparatus is preferably 9.807 MPa or more in a thin tube having a tube diameter of 1 to 2000 μm. More preferably, it is 19.613 MPa or more. Further, a high-pressure dispersion device in which the maximum arrival speed reaches 100 m / second or more and the heat transfer speed reaches 420 kJ / hour or more is preferable.

  Examples of the high-pressure dispersing device as described above include an ultra-high pressure homogenizer (trade name: Microfluidizer) manufactured by Microfluidics Corporation and a nanomizer manufactured by Nanomizer. In addition, a Menton Gorin type high-pressure dispersion device such as a homogenizer manufactured by Izumi Food Machinery Co., Ltd., UHN-01 manufactured by Sanwa Machinery Co., Ltd., or the like can be given.

When producing a polarizing plate protective film, casting a dope containing fine particles so as to be in direct contact with the casting support is preferable because a polarizing plate protective film having high slip properties and low haze can be obtained.
Moreover, after peeling and drying after casting, and winding up in roll shape, functional thin films, such as a hard-coat layer and an antireflection layer, may be provided. Until processing or shipping, packaging is usually performed to protect the product from dirt or dust adhering due to static electricity.

  The packaging material is not particularly limited as long as the above purpose can be achieved, but a material that does not hinder volatilization of the residual solvent of the polarizing plate protective film is preferable. Specific examples include polyethylene, polyester, polypropylene, nylon, polystyrene, paper, various non-woven fabrics, and the like. Those in which the fibers are mesh cloth are more preferably used.

<Method for producing polarizing plate protective film>
Next, the manufacturing method of the said polarizing plate protective film is demonstrated.
The polarizing plate protective film according to the present invention can be preferably used regardless of whether it is produced by a solution casting method or a melt casting method.

  In the solution casting method, the polarizing plate protective film of the present invention is produced by dissolving a cellulose ester and an additive in a solvent to prepare a dope, and casting the dope onto an endless metal support that moves indefinitely. It is carried out by a step, a step of drying the cast dope as a web, a step of peeling from the metal support, a step of stretching or maintaining the width, a step of further drying, and a step of winding up the finished film.

Hereinafter, the manufacturing process by the solution casting method will be specifically described.
A higher concentration of cellulose ester in the dope is preferable because the drying load after casting on a metal support can be reduced, but if the concentration of cellulose ester is too large, the load during filtration increases and the filtration accuracy decreases. To do. As a concentration range in which these are compatible, 10 to 35% by mass is preferable, and 15 to 25% by mass is more preferable.

Although the solvent used by dope may be used independently or may use 2 or more types together, it is preferable from the point of production efficiency to mix and use the good solvent and poor solvent of a cellulose ester. A good solvent refers to a solvent that dissolves the cellulose ester used alone, and a poor solvent refers to a solvent that swells alone or does not dissolve.
A more good solvent than a poor solvent is preferred in terms of the solubility of the cellulose ester. The preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass for the good solvent and 2 to 30% by mass for the poor solvent.

  Depending on the average degree of acetylation (also referred to as acetyl group substitution degree) of the cellulose ester, the good solvent and the poor solvent change. For example, when acetone is used as the solvent, the cellulose ester is acetate ester (acetyl group substitution degree 2.4) or cellulose. If acetate propionate is used, acetone becomes a good solvent, and if cellulose ester is acetate (acetyl group substitution degree 2.8), it becomes a poor solvent.

  Although the good solvent used for this invention is not specifically limited, Organic halogen compounds, such as a methylene chloride, dioxolanes, acetone, methyl acetate, methyl acetoacetate, etc. are mentioned. Preferably, methylene chloride or methyl acetate is used.

  Although the poor solvent used for this invention is not specifically limited, For example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone etc. are used preferably. Moreover, it is preferable that 0.01-2 mass% water is contained in dope.

The solvent used to dissolve the cellulose ester can be reused. The solvent removed from the film by drying in the film forming process can be recovered and reused.
The recovered solvent may contain trace amounts of additives such as plasticizers, UV absorbers, polymers, and monomer components added to the cellulose ester, but they are preferably reused even if they are included. Can be purified and reused if necessary.

As a method for dissolving the cellulose ester at the time of preparing the dope, a general method can be used.
Moreover, when heating and pressurization are combined, it is possible to heat above the boiling point at normal pressure. It is preferable to stir and dissolve while heating at a temperature that is equal to or higher than the boiling point of the solvent at normal pressure and that the solvent does not boil under pressure, in order to prevent the formation of massive undissolved material called gel or mamako.

The pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or a method of increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.
The heating temperature with the addition of a solvent is preferably higher from the viewpoint of the solubility of the cellulose ester, but if the heating temperature is too high, the required pressure increases and the productivity deteriorates.
The range of preferable heating temperature is 45-120 degreeC, 60-110 degreeC is more preferable, and 70 degreeC-105 degreeC is further more preferable. The pressure is adjusted so that the solvent does not boil at the set temperature.

In addition, a method in which a cellulose ester is mixed with a poor solvent and wetted or swollen, and then a good solvent is added and dissolved is also preferably used.
Alternatively, a cooling dissolution method is also preferably used, whereby the cellulose ester can be dissolved in a solvent such as methyl acetate.

Next, the prepared dope is filtered using a suitable filter medium such as filter paper.
The absolute filtration accuracy of the filter medium is preferably small in order to remove insoluble matters and the like, but if the absolute filtration accuracy is too small, there is a problem that the filter medium is easily clogged. Therefore, a filter medium having an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium having a filtration accuracy in the range of 0.001 to 0.008 mm is more preferable, and a filter medium having a filtration accuracy in the range of 0.003 to 0.006 mm. Is more preferable.

There are no particular restrictions on the material of the filter medium, and ordinary filter media can be used. However, plastic filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel do not drop off fibers. preferable.
It is preferable to remove and reduce impurities, particularly bright spot foreign matter, contained in the raw material cellulose ester by filtration.

Bright spot foreign matter means that when two polarizing plates are placed in a crossed Nicol state, an optical film or the like is placed between them, light is applied from one polarizing plate side, and observation is performed from the other polarizing plate side. The point (foreign matter) that the light from the opposite side appears to leak.
The number of bright spot foreign matters having a diameter of 0.01 mm or more is preferably 200 pieces / cm ² or less. More preferably, it is 100 pieces / cm < ² > or less, More preferably, it is 50 pieces / m < ² > or less, More preferably, it is 0-10 pieces / cm < ² > or less. Moreover, it is preferable that there are few bright spot foreign materials of 0.01 mm or less.

The dope can be filtered by a normal method, but the method of filtering while heating at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil under pressure is the filtration pressure before and after filtration. The increase in the difference is small and preferable.
A preferable temperature range is 45 to 120 ° C, more preferably 45 to 70 ° C, and further preferably 45 to 55 ° C.

  A smaller filtration pressure is preferred. The filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and further preferably 1.0 MPa or less.

  The metal support in the casting process is preferably a mirror finished surface. For example, a stainless steel belt or a drum whose surface is plated with a casting can be used as the metal support.

  The width of casting can be 1 to 4 m. The surface temperature of the metal support in the casting step is preferably within a temperature range of −50 ° C. to less than the boiling point of the solvent, and a higher temperature is preferable because the web can be dried faster. Or flatness may deteriorate.

  The temperature range of a preferable metal support is 0 to 55 ° C, more preferably 25 to 50 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent.

  The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing warm air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short. When warm air is used, wind at a temperature higher than the target temperature may be used.

  In order for the polarizing plate protective film to exhibit good flatness, the range of the residual solvent amount when peeling the web from the metal support is preferably 10 to 150% by mass, more preferably 20 to 40% by mass. % Or 60 to 130% by mass, more preferably 20 to 30% by mass or 70 to 120% by mass.

In the present invention, the amount of residual solvent is defined by the following formula.
Residual solvent amount (% by mass) = {(MN) / N} × 100
[In the formula, M represents the mass of a sample collected at any time during or after the production of the web or film, and N represents the mass after heating M at 115 ° C. for 1 hour. ]

  In the drying step, the web is preferably peeled off from the metal support and further dried to make the residual solvent amount 1% by mass or less, more preferably 0.1% by mass or less, and particularly preferably 0 to 0%. 0.01% by mass or less.

  As a drying method, generally, a roll drying method (a method in which webs are alternately passed through a large number of upper and lower rolls) and a method in which the web is dried while being conveyed by a tenter method are employed.

  In order to produce the polarizing plate protective film of the present invention, it is preferable to stretch in the width direction (lateral direction) of the polarizing plate protective film by a tenter method in which both ends of the web are held with clips or the like. Peeling is preferably performed at a peeling tension of 300 N / m or less.

The means for drying the web is not particularly limited, and can be generally performed with hot air, infrared rays, a heating roll, microwave, or the like, but it is preferably performed with hot air from the viewpoint of simplicity.
The drying temperature in the web drying step is preferably increased stepwise within a range of 40 to 200 ° C.

In order to give the following desired retardation values Ro and Rt to the polarizing plate protective film, it is preferable that the polarizing plate protective film has the configuration of the present invention, and further the refractive index is controlled by controlling the transport tension and stretching operations.
For example, the retardation value can be changed by lowering or increasing the tension in the longitudinal direction.
Moreover, it is preferable to carry out biaxial stretching or uniaxial stretching sequentially or simultaneously with respect to the longitudinal direction (film forming direction) of the film and the width direction perpendicular to the longitudinal direction.

  It is preferable that the draw ratios in the biaxial directions perpendicular to each other are finally in the range of 0.8 to 1.5 times in the casting direction and 1.1 to 2.5 times in the width direction. More preferably, the range is 0.8 to 1.0 times in the extending direction and 1.2 to 2.0 times in the width direction.

It is preferable that the temperature range at the time of extending | stretching is 120 to 200 degreeC, More preferably, it is 150 to 200 degreeC, More preferably, it exceeds 150 degreeC and is 190 degrees C or less.
The range of the residual solvent amount in the polarizing plate protective film is preferably 20 to 0%, more preferably 15 to 0%.
Specifically, the stretching temperature is preferably 155 ° C. and the residual solvent amount is 11%, or the stretching temperature is preferably 155 ° C. and the residual solvent amount is 2%. Further, it is preferable that the temperature during stretching is 160 ° C. and the residual solvent amount is 11%, or the temperature during stretching is 160 ° C. and the residual solvent amount is less than 1%.

  There is no particular limitation on the method of stretching the web. For example, a method in which a difference in peripheral speed is applied to a plurality of rolls, and the roll peripheral speed difference is used to stretch in the longitudinal direction, the both ends of the web are fixed with clips and pins, and the interval between the clips and pins is increased in the traveling direction. And a method of stretching in the longitudinal direction, a method of stretching in the width direction and stretching in the width direction, a method of stretching simultaneously in the longitudinal direction and the width direction, and a method of stretching in both the longitudinal direction and the width direction. Of course, these methods may be used in combination.

In the case of the so-called tenter method, it is preferable to drive the clip portion by the linear drive method because smooth stretching can be performed and the risk of breakage and the like can be reduced.
These width maintenance or width direction stretching in the film forming step is preferably performed by a tenter, and may be a pin tenter or a clip tenter.

  The slow axis or the fast axis of the polarizing plate protective film of the present invention is present in the film plane, and θ1 is preferably −1 ° or more and + 1 ° or less when the angle formed with the longitudinal direction is θ1. It is more preferably 0.5 ° or more and + 0.5 ° or less, and further preferably −0.1 ° or more and + 0.1 ° or less.

  This θ1 can be defined as an orientation angle, and θ1 can be measured using an automatic birefringence meter KOBRA-21ADH (Oji Scientific Instruments). When each θ1 satisfies the above relationship, it is possible to contribute to obtaining high luminance in a display image, suppressing or preventing light leakage, and obtaining faithful color reproduction in a color liquid crystal image display device.

<Physical properties of polarizing plate protective film>
The glass transition temperature Tg of the polarizing plate protective film is in the range of 148 ° C to 190 ° C.
When the glass transition temperature Tg of the polarizing plate protective film is 148 ° C. or lower, when an adhesive containing an epoxy compound and a cationic polymerization initiator is used, heat is generated when the adhesive is cured, which is not preferable from the viewpoint of heat resistance. . The polarizing plate protective film is deformed by heat, and the polarizing plate is curled during the manufacturing process of the polarizing plate. For this reason, it is preferable that the glass transition temperature Tg of a polarizing plate protective film is 148 degreeC or more.

The range of moisture permeability of the polarizing plate protective film according to the present invention is preferably 300 to 1800 g / m ² · 24 h, more preferably 400 to 1500 g / m ² · 24 h in an environment of 40 ° C. and 90% RH, 40 ˜1300 g / m ² · 24 h is particularly preferred. The moisture permeability can be measured according to the method described in JIS Z 0208.

  The polarizing plate protective film according to the present invention preferably has a breaking elongation range of 5 to 80%, and more preferably 10 to 50%.

  The polarizing plate protective film according to the present invention preferably has a visible light transmittance range of 90% or more, and more preferably 93% or more.

  The polarizing plate protective film according to the present invention preferably has a haze of less than 1%, more preferably 0 to 0.1%.

By applying a liquid crystal layer on the polarizing plate protective film according to the present invention, retardation values over a wider range can be obtained.
In the polarizing plate protective film according to the present invention, the in-plane retardation value Ro is preferably 0 ≦ Ro ≦ 70 nm, and the retardation value Rt in the thickness direction is preferably 0 ≦ Rt ≦ 70 nm. More preferably, 0 ≦ Ro ≦ 30 nm and 0 ≦ Rt ≦ 50 nm, and still more preferably 0 ≦ Ro ≦ 10 nm and 0 ≦ Rt ≦ 30 nm.

  The polarizing plate protective film according to the present invention is preferably used as a retardation film. In that case, 30 ≦ Ro ≦ 100 nm and 70 ≦ Rt ≦ 400 nm, more preferably 35 ≦ Ro ≦ 65 nm and 90 ≦. Rt ≦ 180 nm. Further, the variation of the retardation value Rt in the thickness direction and the width of the distribution are preferably less than ± 50%, more preferably less than ± 30%, and even more preferably less than ± 20%. Further, it is preferably less than ± 15%, preferably less than ± 10%, preferably less than ± 5%, particularly preferably less than ± 1%. Most preferably, there is no variation in Rt.

The retardation values Ro and Rt are obtained by the following formula.
_{Ro = (n x -n y)} × d
Rt = ((n _x + n _y ) / 2−n _z ) × d
[Wherein, d represents the thickness (nm) of the film. n _x represents the maximum refractive index in the film plane of the polarizing plate protective film (also referred to as a slow axis direction of the refractive index). n _y represents a refractive index in the direction perpendicular to the slow axis in the film plane. _nz represents the refractive index of the polarizing plate protective film in the thickness direction. ]

  The retardation values Ro and Rt can be measured using an automatic birefringence meter. For example, it can be obtained at a wavelength of 590 nm using KOBRA-21ADH (Oji Scientific Instruments) under an environment of 23 ° C. and 55% RH.

  Although the film thickness of a polarizing plate protective film is not specifically limited, 10-200 micrometers is used. In particular, the film thickness is particularly preferably 10 to 100 μm. More preferably, it is 20-60 micrometers.

The polarizing plate protective film of the present invention has a width of 1 to 4 m. Particularly those having a width of 1.4 to 4 m are preferably used, and particularly preferably 1.6 to 3 m. If it exceeds 4 m, conveyance becomes difficult.
The polarizing plate protective film may be a film or layer having other optical functions such as an antireflection layer.

<Polarizing plate>
In the polarizing plate of the present invention, the polarizing plate protective film according to the present invention is bonded to at least one surface of a polarizer with an adhesive containing an epoxy compound and a cationic polymerization initiator.

(Production method of polarizing plate)
The polarizing plate which concerns on one form of this invention can be manufactured by adhere | attaching the surface which carried out the adhesion process of the above-mentioned polarizing plate protective film, and the surface of a polarizer, and bonding together. For example, one of two polarizing plate protective films is bonded to one surface of a polarizer using the above adhesive, and the other polarizing plate protective film is similarly attached to the other side of the polarizer using an adhesive. A polarizing plate is manufactured by laminating to the surface.

(Easy adhesion treatment)
The easy adhesion treatment is performed in order to improve the hydrophilicity on the surface of the polarizing plate protective film that adheres to the polarizer and to improve the adhesion of the polarizing plate protective film to the polarizer. The easy adhesion treatment is performed on the adhesive surface of the polarizing plate protective film with the polarizer, but may be performed on both surfaces of the polarizing plate protective film.

  Examples of the easy adhesion treatment include corona (discharge) treatment, plasma treatment, flame treatment, itro treatment, glow treatment, ozone treatment, primer coating treatment, and the like, and at least one of them is performed. Of these easy adhesion treatments, corona treatment and plasma treatment are preferred from the viewpoint of productivity.

Corona discharge treatment is a method of treating the surface of a sample by generating a corona by applying a high frequency / high voltage between an electrode insulated from a dielectric and passing the sample between the dielectric and the electrode. . Depending on the type of electrode, electrode spacing, voltage, humidity, and the type of polarizing plate protective film to be treated, generally, the surface of the film subjected to corona discharge treatment is imparted with adhesiveness.
As a material of the electrode, for example, ceramics, aluminum and the like are preferable. The distance between the electrode and the dielectric is preferably in the range of 1 to 5 mm, and more preferably in the range of 1 to 3 mm. The line speed (moving speed) is preferably about 3 to 70 m / min, and more preferably about 3 to 50 m / min.
Further, the corona output intensity is preferably set within a range of 0.2 kW to 3 kW, and more preferably within a range of 0.5 kW to 1.5 kW. When the corona output intensity is less than 0.2 kW, corona discharge becomes unstable, and it may be difficult to give a stable adhesive force to the polarizing plate protective film surface. On the other hand, when the corona output intensity is larger than 2.0 kW, there may be a problem that the polarizing plate protective film is easily damaged.

  The plasma treatment is a treatment for activating the surface of the polarizing plate protective film by performing plasma discharge in a gas atmosphere such as an inert gas or oxygen gas generated under reduced pressure or atmospheric pressure. In order to produce efficiently under conveyance using a roll, plasma treatment under atmospheric pressure is preferable.

In the plasma treatment, the surface of the object to be treated can be variously modified by changing the type of the gas described above, so that the type of gas can be arbitrarily selected when activating the polarizing plate protective film surface. Can do. Examples of the gas used include fluorine compounds such as nitrogen, oxygen, argon, helium, acrylic acid, hydroxyalkyl, CF ₄ , CHF ₃ , and C ₂ F ₆ . These may be used alone or in combination of two or more.
The plasma output is preferably set in the range of 0.2 kW to 3 kW. The line speed (moving speed) is preferably about 3 to 70 m / min, more preferably about 3 to 50 m / min. The frequency range is preferably 3 to 30 kH, more preferably 5 to 20 kH.

The surface free energy (mJ / m ² ) on the adhesive surface of the polarizing plate protective film after the easy-adhesion treatment is such that the dispersion component satisfies the following formula (3a) and the polar component satisfies the following formula (3b). It is preferable to satisfy.
Formula (3a) 24.5 ≦ dispersion force component ≦ 40.0
Formula (3b) 10.0 ≦ polar component ≦ 33.0

The surface free energy of the polarizing plate protective film according to the present invention is measured according to the Kitazaki-Hata theory. According to the Kitazaki-Hata theory, the contact angle θ with respect to several kinds of liquids whose surface free energies are known is expressed by the following formula.
γ _S = γ _SL + γ _L cos θ
In the formula, γ _S represents the surface free energy of the polarizing plate protective film, γ _SL represents the surface free energy between the polarizing plate protective film and the liquid, and γ _L represents the surface free energy of the liquid.
The surface free energy γ _S can also be expressed as γ _S = γ ^d + γ ^p + γ ^h by three components, that is, a dispersion force component γ ^d , a polar component γ ^p , and a hydrogen bond component γ ^h .

Specifically, the surface free energy is measured by the following measuring method.
For measurement, an average contact angle of the probe liquid is obtained by a droplet method using a solid-liquid interface analyzer (DropMaster 500) manufactured by Kyowa Interface Science Co., Ltd. Water, ethylene glycol, or diiodomethane is used as the probe liquid. Specifically, about 30 μl of the probe liquid is dropped on the polarizing plate protective film, and the contact angle θ of the droplet T is measured as shown in FIG. An average value of the contact angles θ measured 10 times is calculated to obtain an average contact angle θ _av for each probe liquid. After this, by analyzing with the Kitazaki-Hata method using the FAMAS surface free energy analysis add-in software, which is an accessory software, the dispersion force component, polar component, hydrogen bonding component of the surface free energy of the polarizing plate protective film 3 components are obtained.

The adhesive used for bonding is preferably an adhesive having a storage elastic modulus at a temperature of 25 ° C. in the range of 1.0 × 10 ^{4 to} 1.0 × 10 ⁹ Pa when used as an adhesive layer. Moreover, after apply | coating and bonding an adhesive agent, the curable adhesive agent which forms a high molecular weight body or a crosslinked structure by various chemical reaction is used suitably.

  Specific examples of adhesives include urethane adhesives, epoxy adhesives, aqueous polymer-isocyanate adhesives, curable adhesives such as thermosetting acrylic adhesives, moisture-curing urethane adhesives, and polyether methacrylate types. Anaerobic adhesives such as ester methacrylate type and oxidized polyether methacrylate, cyanoacrylate instant adhesives, acrylate and peroxide type two-component instant adhesives, among which photocurable adhesives are preferred . The pressure-sensitive adhesive may be a one-component type or a two-component type in which two or more components are mixed before use.

  The adhesive may be a solvent system using an organic solvent as a medium, or an aqueous system such as an emulsion type, a colloidal dispersion type, or an aqueous solution type that is a medium containing water as a main component. It may be a solvent type. The concentration of the adhesive liquid may be appropriately determined depending on the film thickness after bonding, the coating method, the coating conditions, and the like, and is usually 0.1 to 50% by mass.

(Photo curable adhesive)
Preferred examples of the photocurable adhesive for laminating the polarizer and the polarizing plate protective film include a photocurable adhesive composition containing the following components (α) to (δ). .

(Α) a cationically polymerizable compound,
(Β) a cationic photopolymerization initiator,
(Γ) Photosensitizer exhibiting maximum absorption in light having a wavelength longer than 380 nm (δ) Naphthalene photosensitizer

(Cationically polymerizable compound (α))
The cationically polymerizable compound (α), which is a main component of the photocurable adhesive composition and serves as a component that gives adhesive force by polymerization and curing, may be any compound that can be cured by cationic polymerization. It is preferable to include an epoxy compound having one epoxy group. The epoxy compound includes an aromatic epoxy compound having an aromatic ring in the molecule, an alicyclic epoxy compound having at least two epoxy groups in the molecule, and at least one of which is bonded to the alicyclic ring. A fatty acid that does not have an aromatic ring in the molecule and one carbon atom of the ring containing the two carbon atoms to which it is bonded (usually an oxirane ring) is bonded to another aliphatic carbon atom Group epoxy compounds. The photocurable adhesive composition used in the present invention is preferably a cation polymerizable compound (α) having, as a main component, an epoxy resin not containing an aromatic ring or an alicyclic epoxy compound. If a cationically polymerizable compound having an alicyclic epoxy compound as a main component is used, a cured product having a high storage elastic modulus is given, and the polarizing plate protective film and the polarizer are bonded via the cured product (adhesive layer). In the polarizing plate, the polarizer is difficult to break.

As described above, the alicyclic epoxy compound has at least two epoxy groups in the molecule, and at least one of them is bonded to the alicyclic ring. Here, the epoxy group bonded to the alicyclic ring is, as shown in the following formula (ep), two bonds in which two bonds of the epoxy group (—O—) constitute the alicyclic ring. Each of the carbon atoms (usually adjacent carbon atoms). In the following general formula (ep), m represents an integer of 2 to 5.

A compound in which one or a plurality of hydrogen atoms in (CH ₂ ) _m in the formula (ep) are removed and bonded to another chemical structure can be an alicyclic epoxy compound. Hydrogen constituting the alicyclic ring may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Of these, compounds having an epoxycyclopentane ring (m = 3 in the above formula (ep)) or an epoxycyclohexane ring (m = 4 in the above formula (ep)) are preferable.

Among the alicyclic epoxy compounds, any of the following compounds (ep-1) to (ep-11) is more preferable because they are easily available and have a large effect of increasing the storage elastic modulus of the cured product.

In said formula, R < ³ > -R < ²⁴ > represents a hydrogen atom or a C1-C6 alkyl group each independently, and when R < ³ > -R < ²⁴ > is an alkyl group, the position couple | bonded with an alicyclic ring is 1. It is an arbitrary number of the first to sixth positions. The alkyl group having 1 to 6 carbon atoms may be a straight chain, may have a branch, or may have an alicyclic ring. Y ⁸ represents an oxygen atom or an alkanediyl group having 1 to 20 carbon atoms. Y ^{1 to} Y ⁷ each independently represents a straight chain, may have a branch, and represents an alkanediyl group having 1 to 20 carbon atoms which may have an alicyclic ring. n, p, q and r each independently represents a number of 0 to 20.

Among the compounds represented by the above formulas (ep-1) to (ep-11), the alicyclic diepoxy compound represented by the formula (ep-2) is preferable because it is easily available. The alicyclic diepoxy compound of the formula (ep-2) is composed of 3,4-epoxycyclohexylmethanol (an alkyl group having 1 to 6 carbon atoms may be bonded to the cyclohexane ring) and 3,4-epoxycyclohexane. An ester compound with a carboxylic acid (an alkyl group having 1 to 6 carbon atoms may be bonded to the cyclohexane ring). Specific examples of such ester compounds include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (a compound in which R ⁵ = R ⁶ = H and n = 0 in the formula (ep-2)) 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate (in the formula (ep-2), R ⁵ = 6-methyl, R ⁶ = 6-methyl, n = Compound which is 0) and the like.

〔一般式（ｇｅ）中、Ｘは直接結合、メチレン基、炭素原子数１〜４のアルキリデン基、脂環式炭化水素基、Ｏ、Ｓ、ＳＯ_２、ＳＳ、ＳＯ、ＣＯ、ＯＣＯ又は下記式（ｇｅ−１）〜（ｇｅ−３）で表される３種の置換基からなる群から選ばれる置換基を表し、アルキリデン基はハロゲン原子で置換されていてもよい。〕

In addition, it is effective to use an alicyclic epoxy compound in combination with an epoxy resin having substantially no alicyclic epoxy group. If a cation-polymerizable compound containing an alicyclic epoxy compound as the main component and an epoxy resin substantially free of an alicyclic epoxy group is used as a cationically polymerizable compound, the cured product has a high storage elastic modulus. However, the adhesion between the polarizer and the polarizing plate protective film can be further enhanced. As used herein, an epoxy resin having substantially no alicyclic epoxy group means that one carbon atom of a ring (usually an oxirane ring) containing an epoxy group and two carbon atoms to which the epoxy group is bonded in the molecule. A compound bonded to another aliphatic carbon atom. Examples thereof include polyglycidyl ether of polyhydric alcohol (phenol). Among these, a diglycidyl ether compound represented by the following general formula (ge) is preferable because it is easily available and has a large effect of improving the adhesion between the polarizer and the polarizing plate protective film.

[In general formula (ge), X is a direct bond, a methylene group, an alkylidene group having 1 to 4 carbon atoms, an alicyclic hydrocarbon group, O, S, SO ₂ , SS, SO, CO, OCO, or the following formula: It represents a substituent selected from the group consisting of three substituents represented by (ge-1) to (ge-3), and the alkylidene group may be substituted with a halogen atom. ]

In the formula (ge-1), R ²⁵ and R ²⁶ may each independently be substituted with a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 10 carbon atoms, or an alkoxy group. Represents a cycloalkyl group having 3 to 10 carbon atoms which may be substituted by a phenyl group, an alkyl group having 1 to 10 carbon atoms or an alkoxy group, and R ²⁵ and R ²⁶ may be linked to each other to form a ring. Good.
In the formula (ge-2), A and D are each independently an alkyl group having 1 to 10 carbon atoms which may be substituted with a halogen atom, or 6 carbon atoms which may be substituted with a halogen atom. Represents an aryl group having ˜20, an arylalkyl group having 7 to 20 carbon atoms which may be substituted with a halogen atom, a heterocyclic group having 2 to 20 carbon atoms which may be substituted with a halogen atom, or a halogen atom; The methylene group in the alkyl group, aryl group or arylalkyl group may be interrupted by an unsaturated bond, -O- or -S-. a represents a number of 0 to 4, and d represents a number of 0 to 4.

  Examples of the diglycidyl ether compound of the general formula (ge) include bisphenol-type epoxy resins such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, diglycidyl ether of bisphenol S; glycidyl ether of tetrahydroxyphenylmethane , Glycidyl ether of tetrahydroxybenzophenone, polyfunctional epoxy resin such as epoxidized polyvinylphenol; polyglycidyl ether of aliphatic polyhydric alcohol; polyglycidyl ether of alkylene oxide adduct of aliphatic polyhydric alcohol; Examples thereof include diglycidyl ether, and among them, polyglycidyl ether of aliphatic polyhydric alcohol is preferable because it is easily available.

  Examples of the aliphatic polyhydric alcohol include those having 2 to 20 carbon atoms. More specifically, for example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,4-butanediol, neopentyl glycol, 3-methyl-2,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2-methyl -2,4-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 3,5-heptanediol, 1,8-octanediol, 2 -Aliphatic diols such as methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol; cyclohexanedi Cycloaliphatic diols such as butanol, cyclohexanediol, hydrogenated bisphenol A, hydrogenated bisphenol F; trimethylolethane, trimethylolpropane, hexitols, pentitols, glycerin, polyglycerin, pentaerythritol, dipentaerythritol, tetramethylol Examples include trivalent or higher polyols such as propane.

  When using together an alicyclic epoxy compound and an epoxy resin substantially free of an alicyclic epoxy group, the blending ratio of both is 50 to 50 based on the total amount of the cationically polymerizable compound. It is preferable that 95% by mass and an epoxy resin substantially not having an alicyclic epoxy group be 5% by mass or more. By blending 50% by mass or more of the alicyclic epoxy compound in the whole cationic polymerizable compound, the storage elastic modulus at 80 ° C. of the cured product becomes 1,000 MPa or more, and such a cured product (adhesive layer) is obtained. In the polarizing plate in which the polarizer and the polarizing plate protective film are bonded to each other, the polarizer is hardly broken. Moreover, the adhesiveness of a polarizer and a polarizing plate protective film improves by mix | blending 5 mass% or more of epoxy resins which do not have an alicyclic epoxy group substantially with respect to the whole cationically polymerizable compound. The amount of the epoxy resin having substantially no alicyclic epoxy group is 50 based on the total amount of the cation polymerizable compound when the cation polymerizable compound is a two-component system with the alicyclic epoxy compound. However, if the amount is too large, the storage elastic modulus of the cured product is lowered and the polarizer is easily cracked. Therefore, the amount of the cationically polymerizable compound as a whole is 45% by mass or less. Is preferred.

  As the cationically polymerizable compound (α) constituting the photocurable adhesive composition, when using an alicyclic epoxy compound and an epoxy resin substantially free of an alicyclic epoxy group as described above, In the range where becomes the above-mentioned amount, in addition to these, other cationically polymerizable compounds may be included. Examples of other cationic polymerizable compounds include epoxy compounds other than formulas (ep-1) to (ep-11) and general formula (ge), oxetane compounds, and the like.

  Epoxy compounds other than formulas (ep-1) to (ep-11) and formula (ge) include at least one alicyclic ring in a molecule other than formulas (ep-1) to (ep-11). An alicyclic epoxy compound having an epoxy group to be bonded, an aliphatic epoxy compound having an oxirane ring bonded to an aliphatic carbon atom other than the formula (ge), an aromatic epoxy compound having an aromatic ring and an epoxy group in the molecule, aromatic There are hydrogenated epoxy compounds in which aromatic rings in group epoxy compounds are hydrogenated.

  Examples of alicyclic epoxy compounds having an epoxy group bonded to at least one alicyclic ring in a molecule other than those represented by formulas (ep-1) to (ep-11) include 4-vinylcyclohexene diepoxide, 2: diepoxides of vinylcyclohexenes such as 8,8,9-diepoxy limonene.

  Examples of the aliphatic epoxy compound having an oxirane ring bonded to an aliphatic carbon atom other than the general formula (ge) include triglycidyl ether of glycerin, triglycidyl ether of trimethylolpropane, and diglycidyl ether of polyethylene glycol.

  The aromatic epoxy compound having an aromatic ring and an epoxy group in the molecule can be a glycidyl ether of an aromatic polyhydroxy compound having at least two phenolic hydroxy groups (hydroxyl groups) in the molecule. Bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, phenol novolac resin glycidyl ether, and the like.

  A hydrogenated epoxy compound in which an aromatic ring in an aromatic epoxy compound is hydrogenated is an aromatic polyhydroxy compound having at least two phenolic hydroxy groups (hydroxyl groups) in a molecule as a raw material of the aromatic epoxy compound. Can be obtained by performing a hydrogenation reaction selectively under pressure in the presence of a catalyst and glycidyl etherifying the resulting hydrogenated polyhydroxy compound. Specific examples include diglycidyl ether of hydrogenated bisphenol A, diglycidyl ether of hydrogenated bisphenol F, diglycidyl ether of hydrogenated bisphenol S, and the like.

  Among the epoxy compounds other than these formulas (ep-1) to (ep-11) and the general formula (ge), they have an epoxy group bonded to an alicyclic ring and are classified as the alicyclic epoxy compounds defined above. When the compound to be blended is added, the sum of the alicyclic epoxy compounds represented by the formulas (ep-1) to (ep-11) does not exceed 95% by mass based on the total amount of the cationically polymerizable compounds. Used in a range.

  An oxetane compound that can be any cationically polymerizable compound is a compound having a 4-membered ring ether (oxetanyl group) in the molecule. Specific examples thereof include 3-ethyl-3-hydroxymethyloxetane, 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene, 3-ethyl-3- (phenoxymethyl) oxetane, di [ (3-ethyl-3-oxetanyl) methyl] ether, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, 3-ethyl-3- (cyclohexyloxymethyl) oxetane, phenol novolak oxetane, 1,3-bis [(3-Ethyloxetane-3-yl) methoxy] benzene, oxetanylsilsesquioxane, oxetanyl silicate and the like.

  By blending the oxetane compound at a ratio of 30% by mass or less based on the total amount of the cationic polymerizable compound, an effect of improving curability is expected compared to the case where only the epoxy compound is used as the cationic polymerizable compound. There are things you can do.

(Photocationic polymerization initiator (β))
In the present invention, the cationically polymerizable compound as described above is cationically polymerized by irradiation with active energy rays and cured to form an adhesive layer. Therefore, the photocurable adhesive composition has photocationic polymerization initiation. It is preferable to blend the agent (β).

  The cationic photopolymerization initiator generates a cationic species or a Lewis acid upon irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams, and initiates a polymerization reaction of the cationic polymerizable compound (α). It is. Since the cationic photopolymerization initiator acts catalytically by light, it is excellent in storage stability and workability even when mixed with the cationically polymerizable compound (α). Examples of compounds that generate cation species and Lewis acids 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 benzenediazonium hexafluoroantimonate, benzenediazonium hexafluorophosphate, and benzenediazonium hexafluoroborate.

  Examples of the aromatic iodonium salt include diphenyliodonium tetrakis (pentafluorophenyl) borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, di (4-nonylphenyl) iodonium hexafluorophosphate, and the like.

  Examples of aromatic sulfonium salts include triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis (pentafluorophenyl) borate, 4,4'-bis [diphenylsulfonio] diphenyl sulfide bishexafluoro. 4,4'-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide bishexafluoroantimonate, 4,4'-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide bishexa Fluorophosphate, 7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone hexafluoroantimonate, 7- [di (p-toluyl) sulfonio ] -2-Isopropylthioxanthone tetrakis (pentafluorophenyl) borate, 4-phenylcarbonyl-4'-diphenylsulfonio-diphenylsulfide hexafluorophosphate, 4- (p-tert-butylphenylcarbonyl) -4'-diphenylsulfonio -Diphenyl sulfide hexafluoroantimonate, 4- (p-tert-butylphenylcarbonyl) -4'-di (p-toluyl) sulfonio-diphenyl sulfide tetrakis (pentafluorophenyl) borate and the like.

  Examples of iron-allene complexes include xylene-cyclopentadienyl iron (II) hexafluoroantimonate, cumene-cyclopentadienyl iron (II) hexafluorophosphate, xylene-cyclopentadienyl iron (II) tris (tri Fluoromethylsulfonyl) methanide and the like.

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

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

〔式中、Ｒ^５及びＲ^６は、それぞれ独立に炭素数１〜６のアルキル基又は炭素数２〜１２のアルコキシアルキル基を表す。Ｒ^７は、水素原子又は炭素数１〜６のアルキル基を表す。〕 (Photosensitizer (γ))
The photocurable adhesive composition that can be used in the present invention is suitable for light having a wavelength longer than 380 nm in addition to the cationic polymerizable compound (α) and the cationic photopolymerization initiator (β) including the epoxy compound as described above. Contains a photosensitizer (γ) exhibiting maximum absorption. The cationic photopolymerization initiator (β) exhibits maximum absorption at a wavelength near or shorter than 300 nm, generates a cationic species or a Lewis acid in response to light having a wavelength near the wavelength, and generates a cationic polymerizable compound (α ) Is initiated, but a photosensitizer (γ) that exhibits maximum absorption in light having a wavelength longer than 380 nm is blended so as to be sensitive to light having a longer wavelength than that.
As such a photosensitizer (γ), an anthracene compound represented by the following general formula (nf) is advantageously used.

[Wherein, R ⁵ and R ⁶ each independently represent an alkyl group having 1 to 6 carbon atoms or an alkoxyalkyl group having 2 to 12 carbon atoms. R ⁷ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. ]

  Specific examples of the anthracene compound represented by the general formula (nf) include 9,10-dimethoxyanthracene, 9,10-diethoxyanthracene, 9,10-dipropoxyanthracene, 9,10-diisopropoxyanthracene, 9 , 10-dibutoxyanthracene, 9,10-dipentyloxyanthracene, 9,10-dihexyloxyanthracene, 9,10-bis (2-methoxyethoxy) anthracene, 9,10-bis (2-ethoxyethoxy) anthracene, 9 , 10-bis (2-butoxyethoxy) anthracene, 9,10-bis (3-butoxypropoxy) anthracene, 2-methyl or 2-ethyl-9,10-dimethoxyanthracene, 2-methyl or 2-ethyl-9, 10-diethoxyanthracene, 2-methyl or 2 Ethyl-9,10-dipropoxyanthracene, 2-methyl or 2-ethyl-9,10-diisopropoxyanthracene, 2-methyl or 2-ethyl-9,10-dibutoxyanthracene, 2-methyl or 2-ethyl Examples include -9,10-dipentyloxyanthracene, 2-methyl or 2-ethyl-9,10-dihexyloxyanthracene.

  By mix | blending the above photosensitizers ((gamma)) with a photocurable adhesive composition, the sclerosis | hardenability of a photocurable adhesive composition improves compared with the case where it is not mix | blended. Curability is improved by setting the blending amount of the photosensitizer (γ) to 100 parts by mass of the cationic polymerizable compound (α) constituting the photocurable adhesive composition to be 0.1 parts by mass or more. The effect is manifested. On the other hand, when the blending amount of the photosensitizer (γ) increases, problems such as precipitation during low-temperature storage occur, so the blending amount of 2 parts by weight or less with respect to 100 parts by weight of the cationic polymerizable compound (α) To do. From the viewpoint of maintaining the neutral gray of the polarizing plate, it is advantageous to reduce the blending amount of the photosensitizer (γ) within a range in which the adhesiveness between the polarizer and the polarizing plate protective film is appropriately maintained. For example, with respect to 100 parts by mass of the cationically polymerizable compound (α), the amount of the photosensitizer (γ) is 0.1 to 0.5 parts by mass, and further 0.1 to 0.3 parts by mass. Is preferred.

〔式中、Ｒ^１及びＲ^２はそれぞれ、炭素数１〜６のアルキル基である。〕 (Photosensitizer (δ))
The photocurable adhesive composition that can be used in the present invention includes the following cationic polymerizable compound (α) containing an epoxy compound, a cationic photopolymerization initiator (β), and a photosensitizer (γ). It contains a naphthalene photosensitizer (δ) represented by the general formula (at).

[Wherein, R ¹ and R ² are each an alkyl group having 1 to 6 carbon atoms. ]

  Specific examples of the naphthalene photosensitizing aid (δ) include 1,4-dimethoxynaphthalene, 1-ethoxy-4-methoxynaphthalene, 1,4-diethoxynaphthalene, 1,4-dipropoxynaphthalene, 1, 4-dibutoxynaphthalene etc. are mentioned.

  By mix | blending a naphthalene type photosensitization adjuvant ((delta)) with a photocurable adhesive composition, the sclerosis | hardenability of a photocurable adhesive composition improves compared with the case where it is not mix | blended. By setting the blending amount of the naphthalene photosensitizer (δ) to 100 parts by mass of the cationic polymerizable compound (α) constituting the photocurable adhesive composition to be 0.1 parts by mass or more, curability is improved. The improvement effect is manifested. On the other hand, if the amount of the naphthalene-based photosensitization aid (δ) increases, problems such as precipitation during low-temperature storage occur, and therefore the amount is 10 parts by mass or less with respect to 100 parts by mass of the cationic polymerizable compound (α). The blending amount. Preferably, the blending amount is 5 parts by mass or less with respect to 100 parts by mass of the cationic polymerizable compound (α).

  Furthermore, the photocurable adhesive composition that can be used in the present invention can contain an additive component as an optional component as long as the effects of the present invention are not impaired. As additive components, in addition to the above-mentioned photocationic polymerization initiator and photosensitizer (γ), photosensitizers other than the photosensitizer (γ), thermal cationic polymerization initiators, polyols, ion trapping agents , Antioxidants, light stabilizers, chain transfer agents, tackifiers, thermoplastic resins, fillers, flow regulators, plasticizers, antifoaming agents, leveling agents, dyes, organic solvents, and the like.

  When the additive component is contained, the amount of the additive component used is preferably 1000 parts by mass or less with respect to 100 parts by mass of the cationic polymerizable compound (α). When the amount used is 1000 parts by mass or less, a cationically polymerizable compound (α), a photocationic polymerization initiator (β), and a photosensitizer, which are essential components of the photocurable adhesive composition that can be used in the present invention. By combining (γ) and the photosensitizing aid (δ), the effects of improving storage stability, preventing discoloration, improving curing speed, and ensuring good adhesion can be exhibited well.

Other preferable examples of the adhesive for laminating the polarizer and the polarizing plate protective film include a photocurable adhesive that essentially contains the following three components (α1), (α2), and (β1). A composition is included.
(Α1) Epoxy compound having at least two epoxy groups in the molecule (α2) Oxetane compound having at least one oxetanyl group in the molecule (β1) Photocationic polymerization initiator

  Hereinafter, the epoxy compound (α1), the oxetane compound (α2), and the photocationic polymerization initiator (β1) are simply referred to as the epoxy compound (α1), the oxetane compound (α2), and the photocationic polymerization initiator, respectively. It is called (β1).

  The mass ratio of the epoxy compound (α1) to the oxetane compound (α2) (epoxy compound (α1): oxetane compound (α2)) is preferably about 90:10 to 10:90. Moreover, it is preferable to mix | blend a photocationic polymerization initiator ((beta) 1) in the composition in the ratio of about 0.5-20 mass%.

  The photo-curable adhesive can optionally contain an unsaturated compound having at least one ethylenically unsaturated bond in the molecule as the (ε) component. When such an unsaturated compound (ε) is contained, it is preferable to contain a radical photopolymerization initiator as the (ζ) component. Furthermore, this photocurable adhesive agent can also contain the other component which does not have polymerizability as ((eta)) component.

  The unsaturated compound (ε), the photoradical polymerization initiator as the (ζ) component, and the other non-polymerizable component as the (η) component are simply referred to as the unsaturated compound (ε) and the photoradical, respectively. It is referred to as a polymerization initiator (ζ) and other component (η) having no polymerizability.

(Epoxy compound (α1))
In the photo-curable adhesive composition that can be used in the present invention, the epoxy compound (α1) is not particularly limited as long as it has at least two epoxy groups in the molecule, and various kinds of generally known curings. A functional epoxy compound can be used. As a preferable epoxy compound (α1), a compound having at least two epoxy groups and at least one aromatic ring in the molecule (hereinafter referred to as an aromatic epoxy compound), or having at least two epoxy groups in the molecule. Examples of the compound include at least one compound formed between two adjacent carbon atoms constituting the alicyclic ring (hereinafter referred to as an alicyclic epoxy compound).

  The aromatic epoxy compound is not particularly limited as long as the effect of the present invention is not hindered. Resin; Novolak type epoxy resin such as phenol novolac type epoxy resin, cresol novolak type epoxy resin; other, biphenyl type epoxy resin, hydroquinone diglycidyl ether, resorcin diglycidyl ether, terephthalic acid diglycidyl ester, phthalic acid diglycidyl ester, Epoxy product of styrene-butadiene copolymer, epoxidized product of styrene-isoprene copolymer, addition reaction of terminal carboxylic acid polybutadiene and bisphenol A type epoxy resin Goods and the like as examples.

  Here, the epoxy resin means a compound or polymer having an average of two or more epoxy groups in the molecule and cured by reaction. In accordance with the practice in this field, a monomer may be referred to as an epoxy resin as long as it has two or more curable epoxy groups in the molecule.

  The alicyclic epoxy compound is not particularly limited as long as the effects of the present invention are not hindered, but dicyclopentadiene dioxide, limonene dioxide, 4-vinylcyclohexene dioxide, 3,4-epoxycyclohexylmethyl-3,4- Examples include compounds having at least one epoxidized cyclohexyl group such as epoxycyclohexanecarboxylate and bis (3,4-epoxycyclohexylmethyl) adipate.

  In addition to the above, aliphatic epoxy compounds such as 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, polytetramethylene glycol diglycidyl ether; dihydrogenated bisphenol A Epoxy compounds such as glycidyl ether in which the aromatic ring is hydrogenated; polybutadienes having both ends of hydroxyl groups (hydroxyl groups) having both ends of glycidyl ether, polybutadiene internal epoxidation products, styrene-butadiene copolymers A compound in which the double bond is partially epoxidized (for example, Epofriend manufactured by Daicel Chemical Industries, Ltd.), a compound in which the isoprene unit of the block copolymer of ethylene-butylene copolymer and polyisoprene is partially epoxidized (E.g., KRATON Co. L-207) polymeric epoxy compounds, such as, may also be an epoxy compound ([alpha] 1).

  Among these, an aromatic epoxy compound is preferable because it is excellent in durability when used in a polarizing plate, and particularly excellent in adhesion to a polarizer and a polarizing plate protective film. Furthermore, preferred examples of the aromatic epoxy compound include glycidyl ethers of aromatic compounds or glycidyl esters of aromatic compounds. Specific examples of glycidyl ethers of aromatic compounds include bisphenol type epoxy resins such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, diglycidyl ether of brominated bisphenol A; phenol novolac type epoxy resin, cresol novolak type Preferred examples include novolak-type epoxy resins such as epoxy resins; biphenyl-type epoxy resins; hydroquinone diglycidyl ether; resorcin diglycidyl ether and the like. Specific examples of glycidyl esters of aromatic compounds include terephthalic acid diglycidyl ester and phthalic acid diglycidyl ester.

  Especially, since the glycidyl ether of an aromatic compound is more excellent in the adhesiveness between a polarizer and a polarizing plate protective film, and durability when used for a polarizing plate, it is particularly preferable. Among the glycidyl ethers of aromatic compounds, particularly preferable compounds include diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, and phenol novolac type epoxy resin.

  As the epoxy compound (α1), one kind can be used alone, or two or more kinds can be mixed and used. For example, two or more aromatic epoxy compounds can be mixed and used, or an aromatic epoxy compound as a main component and an alicyclic epoxy compound can also be mixed.

(Oxetane compound (α2))
In the photocurable adhesive that can be used in the present invention, the oxetane compound (α2) is not particularly limited as long as it has at least one oxetanyl group in the molecule, and various compounds having an oxetanyl group are also used. be able to. Preferred examples of the oxetane compound (α2) include a compound having one oxetanyl group in the molecule (hereinafter referred to as monofunctional oxetane) and a compound having two or more oxetanyl groups in the molecule (hereinafter referred to as polyfunctional oxetane). As mentioned.

  Examples of the monofunctional oxetane include an alkoxyalkyl group-containing monofunctional oxetane such as 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane and an aromatic group-containing monofunctional group such as 3-ethyl-3-phenoxymethyloxetane. Preferred examples include hydroxy group (hydroxyl group) -containing monofunctional oxetane such as oxetane and 3-ethyl-3-hydroxymethyloxetane.

  Examples of the polyfunctional oxetane include 3-ethyl-3-[(3-ethyloxetane-3-yl) methoxymethyl] oxetane, 1,4-bis [(3-ethyloxetane-3-yl) methoxymethyl] benzene, 1,4-bis [(3-ethyloxetane-3-yl) methoxy] benzene, 1,3-bis [(3-ethyloxetane-3-yl) methoxy] benzene, 1,2-bis [(3-ethyl Oxetane-3-yl) methoxy] benzene, 4,4′-bis [(3-ethyloxetane-3-yl) methoxy] biphenyl, 2,2′-bis [(3-ethyloxetane-3-yl) methoxy] Biphenyl, 3,3 ′, 5,5′-tetramethyl-4,4′-bis [(3-ethyloxetane-3-yl) methoxy] biphenyl, 2,7-bis [(3-ethyl Xetane-3-yl) methoxy] naphthalene, bis [4-{(3-ethyloxetane-3-yl) methoxy} phenyl] methane, bis [2-{(3-ethyloxetane-3-yl) methoxy} phenyl] Etherified modification of methane, 2,2-bis [4-{(3-ethyloxetane-3-yl) methoxy} phenyl] propane, novolak type phenol-formaldehyde resin with 3-chloromethyl-3-ethyloxetane, 3 (4), 8 (9) -bis [(3-ethyloxetane-3-yl) methoxymethyl] -tricyclo [5.2.1.02,6] decane, 2,3-bis [(3-ethyloxetane -3-yl) methoxymethyl] norbornane, 1,1,1-tris [(3-ethyloxetane-3-yl) methoxymethyl] propane, 1- Toxi-2,2-bis [(3-ethyloxetane-3-yl) methoxymethyl] butane, 1,2-bis [{2- (3-ethyloxetane-3-yl) methoxy} ethylthio] ethane, bis [ {4- (3-Ethyloxetane-3-yl) methylthio} phenyl] sulfide, 1,6-bis [(3-ethyloxetane-3-yl) methoxy] -2,2,3,3,4,4,4 Hydrolysis condensate of 5,5-octafluorohexane, 3-[(3-ethyloxetane-3-yl) methoxy] propyltriethoxysilane, condensation of tetrakis [(3-ethyloxetane-3-yl) methyl] silicate Thing etc. are mentioned.

The oxetane compound (α2) is preferably liquid at room temperature with a molecular weight of 500 or less from the viewpoint of coating properties and adhesion to a polarizing plate protective film when used for a polarizing plate. Furthermore, in terms of excellent durability of the polarizing plate, a monofunctional oxetane is more preferably an aromatic ring in the molecule or a polyfunctional oxetane. Examples of such preferred oxetane compounds include 3-ethyl-3-phenoxymethyloxetane, 3-ethyl-3-[(3-ethyloxetane-3-yl) methoxymethyl] oxetane, 1,4-bis [(3 -Ethyloxetane-3-yl) methoxymethyl] benzene and the like.
The oxetane compound (α2) can also be used alone or in combination of two or more.

  The mass ratio of the epoxy compound (α1) to the oxetane compound (α2) (epoxy compound (α1): oxetane compound (α2)) is 90:10 to 10:90. If this mass ratio is excessive or insufficient, the effect of curing in a short time, which is one of important characteristics in the photocurable adhesive composition that can be used in the present invention, is not sufficiently exhibited. A preferable mass ratio is about 70:30 to 20:80, more preferably 60:40, because it has a low viscosity before curing, excellent coating properties, and can exhibit sufficient adhesion and flexibility after curing. ~ 25: 75 or so.

(Photocationic polymerization initiator (β1))
The photocurable adhesive composition that can be used in the present invention contains the above-described epoxy compound (α1) and oxetane compound (α2) as curing components, and these are all cured by cationic polymerization. In order to start the cationic polymerization, a photocationic polymerization initiator (β1) is blended. The cationic photopolymerization initiator (β1) generates a cationic species or a Lewis acid by irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams, and initiates a polymerization reaction of an epoxy group or an oxetanyl group.

By blending the cationic photopolymerization initiator (β1), curing at room temperature becomes possible, and there is little need to consider the heat resistance of the polarizer and distortion due to expansion or contraction, and the polarizing plate protective film is adhered well. be able to. In addition, since the cationic photopolymerization initiator (β1) acts catalytically upon irradiation with active energy rays, it is excellent in storage stability and workability even when mixed with the epoxy compound (α1) and the oxetane compound (α2). .
Examples of the photocationic polymerization initiator (β1) that generates cationic species and Lewis acids upon irradiation with such active energy rays include, for example, onium salts such as aromatic diazonium salts, aromatic iodonium salts and aromatic sulfonium salts, iron- An allene complex etc. can be mentioned.

  Examples of the aromatic diazonium salt include benzenediazonium hexafluoroantimonate, benzenediazonium hexafluorophosphate, and benzenediazonium hexafluoroborate.

  Examples of the aromatic iodonium salt include diphenyliodonium tetrakis (pentafluorophenyl) borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, di (4-nonylphenyl) iodonium hexafluorophosphate, and the like.

  Examples of the aromatic sulfonium salt include triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis (pentafluorophenyl) borate, diphenyl [4- (phenylthio) phenyl] sulfonium hexafluorophosphate, diphenyl [ 4- (phenylthio) phenyl] sulfonium hexafluoroantimonate, 4,4′-bis (diphenylsulfonio) diphenyl sulfide bishexafluorophosphate, 4,4′-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl Sulfide bishexafluoroantimonate, 4,4'-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenylsulfi Dobishexafluorophosphate, 7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone hexafluoroantimonate, 7- [di (p-toluyl) 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-toluyl) sulfonio-diphenyl sulfide tetrakis (pentafluorophenyl) borate and the like.

  Examples of iron-allene complexes include xylene-cyclopentadienyl iron (II) hexafluoroantimonate, cumene-cyclopentadienyl iron (II) hexafluorophosphate, xylene-cyclopentadienyl iron (II) -tris ( (Trifluoromethylsulfonyl) methanide and the like.

  Each of these cationic photopolymerization initiators (β1) may be used alone or in combination of two or more. Among these, aromatic sulfonium salts are particularly preferably used because they have ultraviolet absorption characteristics even in a wavelength region of 300 nm or more, and therefore can provide a cured product having excellent curability and good mechanical strength and adhesive strength. It is done.

  As the cationic photopolymerization initiator (β1), commercially available products can be easily obtained. For example, Kayrad PCI-220 and Kayalad PCI-620 (all manufactured by Nippon Kayaku Co., Ltd.) are trade names. UVI-6992 (manufactured by Dow Chemical Co.), Adekaoptomer SP-150, Adekaoptomer SP-170 (above, manufactured by ADEKA), CI-5102, CIT-1370, CIT-1682S, CIP-1866S CIP-2048S, CIP-2064S (manufactured by Nippon Soda Co., Ltd.), DPI-101, DPI-102, DPI-103, DPI-105, MPI-103, MPI-105, BBI-101, BBI-102 , BBI-103, BBI-105, TPS-101, TPS-102, TPS-103, TPS-105, DS-103, MDS-105, DTS-102, DTS-103 (manufactured by Midori Chemical Co., Ltd.), PI-2074 (manufactured by Rhodia), Irgacure 250, Irgacure PAG103, Irgacure PAG108, Irgacure PAG121, Irgacure PAG203 ( As mentioned above, BASF), CPI-100P, CPI-101A, CPI-200K, CPI-210S (above, San Apro Co., Ltd.) and the like can be mentioned. Of these, UVI-6992, CPI-100P, CPI-101A, CPI-200K, and CPI-210S containing diphenyl [4- (phenylthio) phenyl] sulfonium as a cation component are preferable.

  The blending ratio of the photocationic polymerization initiator (β1) is in the range of 0.5 to 20% by mass based on the entire photocurable adhesive. When the blending ratio is less than 0.5% by mass, curing of the photocurable adhesive becomes insufficient, and mechanical strength and adhesive strength are lowered. On the other hand, when the blending ratio exceeds 20% by mass, the ionic substance in the cured product is increased, so that the hygroscopic property of the cured product is increased and the durability may be lowered.

(Unsaturated compound (ε))
The photocurable adhesive may contain an unsaturated compound (ε) having at least one ethylenically unsaturated bond in the molecule, if necessary.
A typical example of such an unsaturated compound (ε) is a (meth) acrylic compound having at least one (meth) acryloyl group in the molecule.

  Although it does not specifically limit as a (meth) acrylic-type compound, For example, (meth) acrylates, (meth) acrylamides, (meth) acrylic acid, (meth) acryloylmorpholine, (meth) acrylaldehyde, etc. are mentioned.

  The (meth) acrylates having one (meth) acryloyl group in the molecule (hereinafter referred to as monofunctional (meth) acrylate) are not particularly limited, but for example, methyl (meth) acrylate, ethyl (meth) acrylate, Propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, lauryl (meth) acrylate, Alkyl (meth) acrylates such as stearyl (meth) acrylate; hydrides such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate Xyalkyl (meth) acrylates; cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, 1,4-cyclohexanedimethylol mono (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, di Alicyclic monofunctional (meth) acrylates such as cyclopentenyloxyethyl (meth) acrylate; benzyl (meth) acrylate, (meth) acrylate of p-cumylphenol alkylene oxide adduct, o-phenylphenol alkylene oxide addition (Meth) acrylate, phenolalkylene oxide adduct (meth) acrylate, nonylphenol alkylene oxide adduct (meth) acrylate with a single ring (Meth) acrylates (wherein alkylene oxide includes ethylene oxide, propylene oxide, etc.); 2-methoxyethyl (meth) acrylate, ethoxymethyl (meth) acrylate, alkylene oxide adduct of 2-ethylhexyl alcohol Alkoxyalkyl (meth) acrylates such as (meth) acrylates; such as ethylene glycol mono (meth) acrylate, propylene glycol mono (meth) acrylate, pentanediol mono (meth) acrylate, hexanediol mono (meth) acrylate Mono (meth) acrylates of dihydric alcohol; mono (meth) acrylate of diethylene glycol, mono (meth) acrylate of triethylene glycol, tetraethyleneglycol Poly (mono) (meth) acrylate, polyethylene glycol mono (meth) acrylate, dipropylene glycol mono (meth) acrylate, tripropylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate Mono (meth) acrylates of alkylene glycols; glycidyl (meth) acrylates; tetrahydrofurfuryl (meth) acrylates; tetrahydrofurfuryl (meth) acrylates such as caprolactone-modified tetrahydrofurfuryl (meth) acrylates; 3,4-epoxy Examples thereof include cyclohexylmethyl (meth) acrylate; N, N-dimethylaminoethyl (meth) acrylate; 2- (meth) acryloyloxyethyl isocyanate.

  Moreover, although it does not specifically limit as (meth) acrylates which have a 2 or more (meth) acryloyl group in a molecule | numerator, For example, the following compounds are mentioned.

  Alicyclic rings such as tricyclodecane dimethylol di (meth) acrylate, 1,4-cyclohexane dimethylol di (meth) acrylate, norbornane dimethylol di (meth) acrylate, di (meth) acrylate of hydrogenated bisphenol A Di (meth) acrylates having bisphenol A ethylene oxide adduct di (meth) acrylate, bisphenol A propylene oxide adduct di (meth) acrylate containing di (meth) acrylate, bisphenol A Di (meth) acrylates having an aromatic ring such as di (meth) acrylate of A diglycidyl ether; ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, pentane Di (meth) acrylates of alkylene glycols such as all di (meth) acrylate and hexanediol di (meth) acrylate; diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate Di (meth) acrylates of polyalkylene glycols such as polyethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate; Di- or tri (meth) acrylates, di- or tri (meth) acrylates of glycerol such as di- or tri (meth) acrylate of diglycerol; glycerols Di- or tri (meth) acrylates of alkylene oxide adducts; di (meth) acrylates of bisphenol A alkylene oxide adducts, di (meth) acrylates of bisphenol alkylene oxide adducts (Meth) acrylates; trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipenta Polyol poly (meth) acrylates such as erythritol penta (meth) acrylate and dipentaerythritol hexa (meth) acrylate; these Poly (meth) acrylates of polyol alkylene oxide adducts; di- or tri (meth) acrylates of isocyanuric acid alkylene oxide adducts; 1,3,5-tri (meth) acryloylhexahydro-s-triazine and the like It is done.

  (Meth) acrylamides include (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-methylol (meth) acrylamide, N- (3-N, N- Examples thereof include dimethylaminopropyl) (meth) acrylamide, methylene bis (meth) acrylamide, and ethylene bis (meth) acrylamide.

  In addition, oligomers such as urethane (meth) acrylate, polyester (meth) acrylate, and epoxy (meth) acrylate can also be used as the (meth) acrylic compound.

  Furthermore, the compound which has an ethylenically unsaturated bond other than that with a (meth) acryloyl group can also be used as a (meth) acrylic-type compound. Specific examples thereof include allyl (meth) acrylate and N, N-diallyl (meth) acrylamide.

  The unsaturated compound (ε) is not particularly limited, and in addition to the above (meth) acrylic compounds, vinyl compounds such as N-vinyl-2-pyrrolidone, divinyl adipate and divinyl sebacate; triallyl isocyan Allyl compounds such as nurate, triallylamine, tetraallyl pyromellitate, N, N, N ′, N′-tetraallyl-1,4-diaminobutane, tetraallylammonium salt, allylamine; such as maleic acid and itaconic acid Unsaturated carboxylic acids and the like can also be used.

  Of these unsaturated compounds (ε), (meth) acrylic compounds are preferred. Furthermore, when a polarizer and a polarizing plate protective film are bonded via an adhesive containing the same to produce a polarizing plate, at least one alicyclic group is included in the molecule from the viewpoint of enhancing durability such as heat resistance. A (meth) acrylic compound having a skeleton or an aromatic ring skeleton is more preferable. Specific examples of the (meth) acrylic compound having at least one alicyclic skeleton or aromatic ring skeleton in the molecule include the above-described alicyclic monofunctional (meth) acrylates and monofunctional having an aromatic ring. Preferable examples include (meth) acrylates, di (meth) acrylates having an alicyclic ring, or di (meth) acrylates having an aromatic ring. Among these, di (meth) acrylate having a tricyclodecane skeleton is preferable, and specific examples of such (meth) acrylic compounds are tricyclodecane dimethylol di (meth) acrylate and the like. be able to.

  The unsaturated compound (ε) can be used to adjust the curing rate, the adhesion between the polarizer and the polarizing plate protective film, the elastic modulus of the adhesive layer, the durability of the adhesive, and the like. An unsaturated compound ((epsilon)) can be used individually by 1 type or in mixture of 2 or more types.

  When the unsaturated compound (ε) is blended, the blending ratio is preferably 35% by mass or less based on the entire composition. Thereby, the adhesiveness between a polarizer and a polarizing plate protective film becomes excellent. When the amount of the unsaturated compound (ε) exceeds 35% by mass, it is difficult to obtain sufficient adhesive strength with the polarizer. Therefore, the blending ratio of the unsaturated compound (ε) is more preferably 30% by mass or less, more preferably about 5 to 25% by mass, particularly preferably about 10 to 20% by mass.

(Photoradical polymerization initiator (ζ))
When the photocurable adhesive contains an unsaturated compound (ε), it is preferable to add a photoradical polymerization initiator (ζ) in order to promote the radical polymerizability and make the curing rate sufficient.

  Specific examples of the radical photopolymerization initiator (ζ) are not particularly limited. For example, 4′-phenoxy-2,2-dichloroacetophenone, 4′-tert-butyl-2,2-dichloroacetophenone, 2,2- Dimethoxy-2-phenylacetophenone, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, 1-hydroxycyclohexyl phenyl ketone, α, α-diethoxyacetophenone, 2-hydroxy-2 -Methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 1- (4-dodecylphenyl) -2-hydroxy-2-methyl Propan-1-one, 1- [4- (2-hydroxyethoxy) phenyl] -2-hydroxy-2-methyl Acetophenone photopolymerization initiators such as lepropan-1-one and 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butan-1-one; benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin Benzoin ether photopolymerization initiators such as isopropyl ether and benzoin isobutyl ether; benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, 2,4,6-trimethylbenzophenone Benzophenone photopolymerization initiators such as: 2-Isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, thioxanthates such as 1-chloro-4-propoxythioxanthone Photopolymerization initiator; 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) Acylphosphine oxide photoinitiators such as phenylphosphine oxide; 1,2-octanedione, oxime ester systems such as 1- [4- (phenylthiophenyl)]-, 2- (O-benzoyloxime) Photopolymerization initiator; camphorquinone and the like can be mentioned.

  The radical photopolymerization initiator (ζ) can be used alone or in combination of two or more according to the desired performance. When the radical photopolymerization initiator (ζ) is blended, the blending ratio is preferably 10% by mass or less, more preferably about 0.1 to 3% by mass, based on the entire composition. If the amount of the photo radical polymerization initiator (ζ) is too large, sufficient strength may not be obtained. Moreover, when the amount is insufficient, the adhesive may not be sufficiently cured.

(Other components (η))
Furthermore, in the photocurable adhesive composition that can be used in the present invention, other components different from the above (α1) to (ζ) components are arbitrarily blended within a range not impairing the effects of the present invention. Can do.
As one type belonging to such other components, there may be mentioned compounds having cationic polymerizability other than the epoxy compound (α1) and the oxetane compound (α2). Specific examples include, but are not limited to, an epoxy compound having one epoxy group in the molecule, and the like. Further, as another type belonging to the other component, other component (η) having no polymerizability can be exemplified. When the other component (η) having no polymerizability is blended, the blending ratio is preferably about 10% by mass or less based on the entire composition.

  Although it does not specifically limit as an example of the other component ((eta)) which does not have polymerizability, A photosensitizer is mentioned. By blending a photosensitizer, the reactivity is improved and the mechanical strength and adhesive strength of the cured product can be improved. Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, and photoreductive dyes.

  Specific photosensitizers are not particularly limited. For example, benzoin derivatives such as benzoin methyl ether, benzoin isopropyl ether, α, α-dimethoxy-α-phenylacetophenone; benzophenone, 2,4-dichlorobenzophenone, o -Benzophenone derivatives such as methyl benzoylbenzoate, 4,4'-bis (dimethylamino) benzophenone, 4,4'-bis (diethylamino) benzophenone; thioxanthone derivatives such as 2-chlorothioxanthone, 2-isopropylthioxanthone; 2 -Anthraquinone derivatives such as chloroanthraquinone and 2-methylanthraquinone; Acridone derivatives such as N-methylacridone and N-butylacridone; Others, α, α-diethoxyacetophenone, benzyl, full Examples include olenone, xanthone, uranyl compound, halogen compound and the like.

  Among these, there is a compound corresponding to the above-mentioned photo radical polymerization initiator (ζ), but the photo sensitizer here is particularly one that functions as a sensitizer for the photo cationic polymerization initiator (β 1). It is not limited. These may be used alone or in combination of two or more.

  The photosensitizer is a cationically polymerizable monomer (including the above epoxy compound (α1) and oxetane compound (α2) in the photocurable adhesive composition that can be used in the present invention, and has the other cationic polymerization properties described above. It is preferable to contain in the range of 0.1-20 mass parts by making 100 mass parts the total amount of a compound including that when the compound is mix | blended.

  Moreover, a thermal cationic polymerization initiator can also be used as another component ((eta)) which does not have polymerizability. Examples of the thermal cationic polymerization initiator include benzylsulfonium salt, thiophenium salt, thiolanium salt, benzylammonium salt, pyridinium salt, hydrazinium salt, carboxylic acid ester, sulfonic acid ester, and amine imide. These initiators can be easily obtained as commercial products. For example, both of them are indicated by trade names, and ADEKA OPTON CP77 and ADEKA OPTON CP66 (manufactured by ADEKA, Inc.), CI-2639, CI- 2624 (manufactured by Nippon Soda Co., Ltd.), Sun-Aid SI-60L, Sun-Aid SI-80L, Sun-Aid SI-100L (manufactured by Sanshin Chemical Industry Co., Ltd.), and the like.

  Since polyols have the property of promoting cationic polymerization, they can also be used as other components (η) that do not have polymerizability. As the polyols, those having no acidic group other than the phenolic hydroxy group (hydroxyl group) are preferable. For example, a polyol compound having no functional group other than the hydroxy group (hydroxyl group), a polyester polyol compound, a polycaprolactone polyol compound, a phenolic compound. Examples thereof include a polyol compound having a hydroxy group (hydroxyl group) and a polycarbonate polyol compound.

Furthermore, as long as the effects of the present invention are not impaired, other components (η) having no polymerizability include silane coupling agents, ion trapping agents, antioxidants, light stabilizers, chain transfer agents, sensitizers, and tackifiers. An agent, a thermoplastic resin, a filler, a flow regulator, a plasticizer, an antifoaming agent, a leveling agent, a dye, an organic solvent, and the like can also be blended.
It is also effective to add a thermoplastic resin as another component (η) having no polymerizability for the purpose of further improving the adhesion to the polarizing plate protective film. As the thermoplastic resin, those having a glass transition temperature of 70 ° C. or higher are preferable from the viewpoint of enhancing the durability of the polarizer, and particularly preferred examples include a methyl methacrylate polymer.

<Production method of polarizing plate>
Hereinafter, an example of the manufacturing method of the polarizing plate using a photocurable adhesive agent is demonstrated.
The polarizing plate has the following photo-curing adhesive on at least one of the pretreatment step for easily bonding the surface of the polarizing plate protective film to which the polarizer is bonded, and the bonding surface of the polarizer and the polarizing plate protective film. Adhesive application process to be applied, polarizer and polarizing plate protective film are bonded and bonded through an adhesive layer, and the polarizer and polarizing plate protective film are bonded through an adhesive layer. It can manufacture by the manufacturing method including the hardening process which hardens an adhesive bond layer in a state.

(Pretreatment process)
In the pretreatment step, the surface of the polarizing plate protective film that adheres to the polarizer is subjected to easy adhesion treatment. When polarizing plate protective films are bonded to both surfaces of the polarizer, easy adhesion treatment is performed on the respective polarizing plate protective films. In the next adhesive application process, the surface subjected to the easy adhesion treatment is treated as an adhesion surface with the polarizer.

(Adhesive application process)
In the adhesive application step, the photocurable adhesive is applied to at least one of the adhesive surfaces of the polarizer and the polarizing plate protective film. When applying a photocurable adhesive directly on the surface of a polarizer or a polarizing plate protective film, there is no special limitation in the coating method. For example, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Moreover, after casting a photocurable adhesive between a polarizer and a polarizing plate protective film, the method of pressurizing with a roll etc. and spreading it uniformly can also be utilized.

(Bonding process)
Thus, after apply | coating a photocurable adhesive agent, it uses for a bonding process. In this bonding step, for example, when a photocurable adhesive is applied to the surface of the polarizer in the previous application step, a polarizing plate protective film is superimposed thereon. When a photocurable adhesive is applied to the surface of the polarizing plate protective film in the previous application step, a polarizer is superimposed thereon. Moreover, when a photocurable adhesive agent is cast between a polarizer and a polarizing plate protective film, a polarizer and a polarizing plate protective film are piled up in that state. In the case where a polarizing plate protective film is bonded to both sides of a polarizer, and a photocurable adhesive is used on both sides, the polarizing plate protective film is superimposed on both sides of the polarizer via a photocurable adhesive. Is done. Usually, in this state, both sides (when a polarizing plate protective film is overlaid on one side of the polarizer, when the polarizing plate protective film is overlaid on both the polarizer side and the polarizing plate protective film side, or on both sides of the polarizer) Is sandwiched between rolls or the like from the side of the polarizing plate protective film side) and pressed. As the material of the roll, metal, rubber or the like can be used. The rolls arranged on both sides may be the same material or different materials.

(Curing process)
In the curing process, an uncured photocurable adhesive is irradiated with active energy rays to cure the adhesive layer containing an epoxy compound or an oxetane compound, and the polarizer and polarized light superimposed via the photocurable adhesive Adhere to the plate protection film. When bonding a polarizing plate protective film to the single side | surface of a polarizer, you may irradiate an active energy ray from either a polarizer side or a polarizing plate protective film side. Moreover, when bonding a polarizing plate protective film on both surfaces of a polarizer, either polarizing plate protective film in the state which laminated | stacked the polarizing plate protective film on both surfaces of the polarizer through the photocurable adhesive agent, respectively. It is advantageous to irradiate active energy rays from the side and simultaneously cure the photocurable adhesive on both sides. However, when an ultraviolet absorber is blended in one of the polarizing plate protective films and the active energy ray is ultraviolet rays, the side of the other polarizing plate protective film not usually blended with the ultraviolet absorber Is irradiated with ultraviolet rays.

  Visible light, ultraviolet rays, X-rays, electron beams, and the like can be used as the active energy rays, but ultraviolet rays are generally preferably used because they are easy to handle and have a sufficient curing rate. The light source of the active energy ray is not particularly limited, but has a light emission distribution at a wavelength of 400 nm or less. An LED lamp or the like can be used.

The light irradiation intensity to the photocurable adhesive is determined for each target composition and is not particularly limited, but the irradiation intensity in the wavelength region effective for activating the polymerization initiator is UV. It is preferable to adjust so that it may become the range of 1-3000 mW / cm < ² > as -B (280-320 nm medium wavelength range ultraviolet-ray). When the irradiation intensity is less than 1 mW / cm ² , the reaction time becomes too long, and when the irradiation intensity exceeds 3,000 mW / cm ² , due to the heat radiated from the lamp and the heat generated during polymerization of the photocurable adhesive, There is a possibility of causing yellowing of the photocurable adhesive and deterioration of the polarizer.

The light irradiation time to the photocurable adhesive is controlled for each composition to be cured and is not particularly limited, but the integrated light amount represented by the product of the irradiation intensity and the irradiation time is 10 to 5000 mJ / cm. It is preferably set to be in the range of ² . When the integrated light quantity is less than 10 mJ / cm ² , active species derived from the polymerization initiator are not sufficiently generated, and the adhesive layer may be insufficiently cured. On the other hand, if the integrated light quantity exceeds 5000 mJ / cm ² , the irradiation time becomes very long, which is disadvantageous for improving productivity.

  When curing the photocurable adhesive by irradiating active energy rays, it is cured under conditions that do not deteriorate the various functions of the polarizing plate, such as the degree of polarization of the polarizer, the transmittance, the hue, and the transparency of the polarizing plate protective film. It is preferable.

  In the polarizing plate obtained as described above, the thickness of the adhesive layer is not particularly limited, but is usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less, and further preferably 5 μm or less.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless there is particular notice, it represents "mass part" or "mass%".

(Synthesis of cellulose esters (A) and (B))
Cellulose esters (A1) to (A12) and (B1) to (B8) having different acyl groups, substitution degrees, and weight average molecular weights described in Table 1 below were synthesized.

That is, sulfuric acid (7.8 parts by mass with respect to 100 parts by mass of cellulose) was added as a catalyst, carboxylic acid serving as a raw material for the acyl group substituent was added, and an acylation reaction was performed at 40 ° C. At this time, the reaction rate of the acylation reaction is changed by adjusting the type and amount of the carboxylic acid and the amount of the catalyst according to the production method described in JP-A-2009-19123. The cellulose ester having the kind of acyl group, the degree of substitution, and the molecular weight described in Table 2 below was synthesized by adjusting the degree and the like. Moreover, it age | cure | ripened at 40 degreeC after acylation.

Furthermore, samples having different average degrees of polymerization were prepared by washing and removing low molecular weight components of the cellulose ester with acetone.
The acyl substitution degree was measured according to the method of Tezuka (Tezuka, Carbohydr. Res., 273, 83 (1995)). That is, a sample (cellulose ester) was dissolved in deuterated chloroform, and a 13C-NMR spectrum was measured. For example, the carbonyl carbon signal of the acetyl group appears in the region of 169 ppm to 171 ppm, the second, third, and sixth positions from the high magnetic field, and the carbonyl carbon signal of the propionyl group appears in the same order in the 172 ppm to 174 ppm region. .
Therefore, the distribution of acyl groups was determined from the abundance ratio of acetyl groups, propionyl groups, etc. at the corresponding positions.

<Preparation of Samples 1 to 26 of Polarizing Plate Protective Film>
(Preparation of sample 2)
(Fine particle dispersion)
Fine particles (Aerosil R812 manufactured by Nippon Aerosil Co., Ltd.) 11 parts by weight Ethanol 89 parts by weight The above composition was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin to prepare a fine particle dispersion.

(Particulate additive solution)
The prepared fine particle dispersion was slowly added to the dissolution tank containing methylene chloride with sufficient stirring. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution having the following composition.
99 parts by mass of methylene chloride 5 parts by mass of fine particle dispersion

A main dope solution having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose ester (A3) and cellulose ester (B3) were added to the pressurized dissolution tank containing the solvent in the combinations shown in Table 2 while stirring. This is completely dissolved with heating and stirring. This was designated as Azumi Filter Paper No. The main dope liquid of the following composition was prepared by filtering using 244.
(Main dope solution)
Cellulose ester (A3) 1 part by weight Cellulose ester (B3) 99 parts by weight Hydrolysis inhibitor; Ester compound (SE-5) 7 parts by weight Retardation adjusting agent; Aromatic ester compound (ar-16) 6 parts by weight Dichloromethane 406 Parts by mass methanol 61 parts by mass

  2 parts by mass of the fine particle additive solution was added to 100 parts by mass of the main dope solution, and the mixture was sufficiently mixed with an in-line mixer (Toray static in-tube mixer Hi-Mixer, SWJ). Next, the mixed liquid was uniformly cast on a stainless steel band support having a width of 2 m using a belt casting apparatus. On the stainless steel band support, the solvent was evaporated until the amount of residual solvent was 110%, and was peeled from the stainless steel band support. Tension is applied during the peeling so that the stretching ratio in the longitudinal direction is 1.02 times, and then both ends of the web are gripped by a tenter so that the stretching ratio in the width direction is 1.25 times. Stretched. The residual solvent at the start of stretching was 30%. After stretching, the width was held for several seconds while maintaining its width, and the width was released after the tension in the width direction was relaxed. Furthermore, it was made to convey for 30 minutes and dried in the 3rd drying zone set to 125 degreeC, and the polarizing plate protective film (sample 2) which concerns on the Example of this invention was produced. The polarizing plate protective film of Sample 2 had a width of 1.5 m, a knurling with a width of 1 cm and a height of 8 μm at the end, and a film thickness of 40 μm.

(Preparation of Samples 1 and 3-25)
In the production of the polarizing plate protective film of Sample 2, the combinations of cellulose esters (A1) to (A12) and cellulose esters (B1) to (B8) shown in Table 1 were changed to the combinations shown in Table 2. In the same manner as above, Samples 1 to 3 to 25 of the polarizing plate protective film were prepared.

(Preparation of sample 26)
In the production of the polarizing plate protective film of Sample 2, a polarizing plate protective film sample 26 was produced in the same manner as above except that the cellulose esters (A) and (B) were changed to the following components (A13) and (B9). did.
Cellulose ester (A13); cellulose acetate propionate (trade name CAP482, manufactured by Eastman Chemical Co., Ltd.), Dsac (A) + Dsay (A) = 2.68, Dsay (A) = 2.50, Mw (A) = 235000, Tg (A) = 143 ° C.
1 part by mass Cellulose ester (B9); cellulose acetate propionate (trade name CAP482-0.5, manufactured by Eastman Chemical Co., Ltd.), Dsac (B) + Dsay (B) = 2.58, Dsay (B) = 2. 40, Mw (B) = 62000, Tg (B) = 145 ° C.
99 parts by mass

<Preparation of polarizing plate>
(Production of polarizer)
A 70 μm thick polyvinyl alcohol film was swollen with water at 35 ° C. The obtained film was immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and further immersed in an aqueous solution at 45 ° C. consisting of 3 g of potassium iodide, 7.5 g of boric acid and 100 g of water. . The obtained film was uniaxially stretched under conditions of a stretching temperature of 55 ° C. and a stretching ratio of 5 times. The uniaxially stretched film was washed with water and dried to obtain a polarizer having a thickness of 20 μm.

(Preparation of photocurable adhesive)
Each of the following components was mixed and then defoamed to prepare a photocurable adhesive liquid. Triarylsulfonium hexafluorophosphate was blended as a 50% propylene carbonate solution, and the solid content of triarylsulfonium hexafluorophosphate was shown below.
(Composition of photocurable adhesive liquid)
3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate 45 parts by mass Epolide GT-301 (alicyclic epoxy resin manufactured by Daicel Chemical Industries) 40 parts by mass 1,4-butanediol diglycidyl ether 15 parts by mass Triarylsulfonium hexafluorophosphate 2.3 parts by mass 9,10-dibutoxyanthracene 0.1 parts by mass 1,4-diethoxynaphthalene 2.0 parts by mass

(Preparation of polarizing plate)
Polarizing plates using the produced polarizing plate protective films of Samples 1 to 26 were prepared as follows.
First, the surface of the polarizing plate protective film was subjected to corona discharge treatment. The conditions for the corona discharge treatment were a corona output intensity of 2.0 kW and a line speed of 18 m / min. Next, the prepared adhesive liquid was applied to the corona discharge-treated surface of the polarizing plate protective film with a bar coater so that the film thickness after curing was about 3 μm to form an adhesive layer. The polyvinyl alcohol-iodine-type polarizer produced as mentioned above was bonded to the obtained adhesive layer.

Similarly, a KC6UY (Konica Minolta Opto Co., Ltd.) film was prepared, and the surface was subjected to corona discharge treatment. The corona discharge treatment was performed at a corona output intensity of 2.0 kW and a line speed of 18 m / min. Next, the adhesive solution prepared above was applied to the corona discharge treated surface of the film with a bar coater so that the film thickness after curing was about 3 μm to form an adhesive layer. A polarizing plate protective film / polarizer / polarizer / KC6UY (Konica Minolta Opto Co., Ltd.) film laminate is bonded to this adhesive layer with a polarizer polarizer bonded to one side of the polarizing plate protective film. Got. Using an ultraviolet irradiation device with a belt conveyor (the lamp uses a D bulb manufactured by Fusion UV Systems), the laminated polarizing plate protective film is irradiated with ultraviolet rays so that the integrated light amount becomes 750 mJ / cm ^2. The adhesive layer was cured.
In this manner, a polarizing plate in which a polarizer was sandwiched between two polarizing plate protective films was prepared using each of the polarizing plate protective films of Samples 1 to 26.

<Evaluation>
Sample No. The following evaluation was performed about each polarizing plate produced using the polarizing plate protective film of 1-26.

(Heat-resistant)
Evaluation of heat resistance was performed using DSC (manufactured by Rigaku Corporation, apparatus name: DSC-8230) under conditions of a sample of about 10 mg, a heating rate of 10 ° C./min, and a nitrogen flow of 50 ml / min. In addition, the glass transition temperature Tg of the polarizing plate was calculated | required by the midpoint method according to the specification of ASTM-D-3418.

(Evaluation of surface free energy)
The surface free energy of the adhesive surface of the polarizing plate protective film with the polarizer was measured under the following measurement conditions.
Measuring device: Solid-liquid interface analyzer (DropMaster 500, manufactured by Kyowa Interface Science Co., Ltd.)
Measuring method: Droplet method Environment: Temperature 23 ° C, 55% RH
Probe liquid: water, ethylene glycol, diiodomethane

Specifically, about 30 μl of each of the three probe liquids was dropped on the adhesive surface of the polarizing plate protective film with the polarizer, and the contact angle θ was measured as shown in FIG. The average value θ _av of the contact angle θ measured 10 times was obtained as the average contact angle for each probe liquid. After this, analysis is performed by the Kitazaki-Hata method using the FAMAS surface free energy analysis add-in software, which is an accessory software, and the surface free energy (mJ / m ² ) dispersion component, polar component, hydrogen of the polarizing plate protective film Three component measurements of the binding component were obtained. Table 2 shows only measured values of the dispersion component and the polar component among the three components.

(Polarizer adhesion)
The produced polarizing plate was cut into a square having a size of 5 cm × 5 cm, left in an atmosphere of 23 ° C. and 55% RH for 24 hours, and then peeled off from the corner portion at the interface between the polarizer and the film. This operation was performed with 100 polarizing plates for one type of sample, and the number of polarizing plates in which peeling was observed between the polarizer and the film was counted and evaluated as follows.
◎: 0 to 2 sheets ○: 3 to 5 sheets △: 6 to 20 sheets ×: 21 sheets or more The polarizer adhesion is preferably evaluated as ◯ or ◎.

(Polarizing plate curl)
The polarizing plate was cut into a width direction of 35 mm and a longitudinal direction of 1 mm to prepare a curl measurement sample. This was allowed to stand for 3 days in an atmosphere of 25 ° C. and 55% RH, and then the degree of curl was measured. The curl degree represents the reciprocal of the radius of curvature. Specifically, the curl degree was measured according to the method A of JIS-K7619-1988. The evaluation for the curl degree is as follows.
○: 0 to 5%
Δ: 5-30%
X: 30% to 100%

(With or without air entrainment)
The number of irregularities of 30 μm or more present per 1 m ^{2 of the} produced polarizing plate was counted. The evaluation of the number of counted irregular defects is as follows.
A: 0 to 1 △: 1 to 20 ×: 20 or more

The evaluation results are as shown in Table 2. In Table 2, the indication that manufacture is impossible indicates that the polarizing plate protective film could not be manufactured as a product.
As shown in Table 2, the polarizing plate according to the example has a dispersion component of surface free energy after easy adhesion treatment in the range of 24.5 to 40.0, and a polar component of 10.0 to 33.0. It was in the range. Moreover, favorable evaluation was obtained about the presence or absence of polarizing plate curl and air entrainment.

Claims (4)

A polarizing plate protective film containing a cellulose ester (A) satisfying the following formulas (1a) to (1d) and a cellulose ester (B) satisfying the following formulas (2a) to (2c):
The mass ratio of the cellulose ester (A) and the cellulose ester (B) is in the range of 1:99 to 30:70,
The polarizing plate protective film, wherein the polarizing plate protective film has a glass transition temperature Tg in the range of 148 to 190 ° C.
Formula (1a) 2.00 ≦ DSac (A) + DSay (A) ≦ 2.90
Formula (1b) 1.50 ≦ DSay (A) ≦ 2.80
Formula (1c) 1000 ≦ Mw (A) ≦ 80000
Formula (1d) 120 ° C. ≦ Tg (A) ≦ 147 ° C.
Formula (2a) 2.00 ≦ DSac (B) ≦ 2.90
Formula (2b) 100000 ≦ Mw (B) ≦ 300000
Formula (2c) 150 ≦ Tg (B) ≦ 190
[In the formula, DSac (A) represents the degree of acetyl group substitution of the cellulose ester (A), and DSay (A) represents the total degree of substitution of the acyl group having 3 or 4 carbon atoms of the cellulose ester (A). . DSac (B) represents the degree of acetyl group substitution of cellulose ester (B). Mw (A) represents the weight average molecular weight of the cellulose ester (A), and Mw (B) represents the weight average molecular weight of the cellulose ester (B). Tg (A) represents the glass transition temperature (° C.) of the cellulose ester (A), and Tg (B) represents the glass transition temperature (° C.) of the cellulose ester (B). ]   The polarizing plate protective film of Claim 1 adhere | attaches at least one surface of a polarizer with the photocurable adhesive agent containing an epoxy compound and a cationic polymerization initiator, The polarizing plate characterized by the above-mentioned. The dispersion force component of the surface free energy (mJ / m ² ) after the easy adhesion treatment of the surface of the polarizing plate protective film that adheres to the polarizer satisfies the following formula (3a), and the polar component satisfies the following formula (3b). The polarizing plate according to claim 2.
Formula (3a) 24.5 ≦ dispersing force component (mJ / m ² ) ≦ 40.0
Formula (3b) 10.0 ≦ polar component (mJ / m ² ) ≦ 33.0 The polarizing plate according to claim 3 , wherein the easy adhesion treatment is at least one of corona treatment, plasma treatment, flame treatment, itro treatment, glow treatment, ozone treatment, and primer coating treatment.

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