KR101605978B1 - Polarizer and liquid-crystal display device - Google Patents

Abstract

Provided is a polarizing plate which improves adhesion between a cellulose acylate film constituting a polarizing plate and a polarizer when a photocurable adhesive is used, and reduces a decrease in polarization degree. A liquid crystal display device provided with the polarizing plate is also provided. The polarizing plate is a polarizing plate obtained by bonding a cellulose acylate film containing a cellulose acylate having an acyl group substitution degree within the range of 2.0 to 2.5 and a glass transition temperature lowering agent to one side of a polarizer using a photocurable adhesive, The detection value of the glass transition temperature-reducing agent on the bonding surface of the cellulose acylate film detected by using the time-of-flight secondary ion mass spectrometry (TOF-SIMS) is d _A , and the detection value of the other side is d _B , The r value represented by the following formula (1) is 1.1 or more.
(1) r = d _A / d _B

Description

POLARIZER AND LIQUID-CRYSTAL DISPLAY DEVICE [0002]

The present invention relates to a polarizing plate and a liquid crystal display device using cellulose acylate.

Among cellulose esters, cellulose acylate is known to be applicable to an optical film having a wide retardation by changing the substitution degree of an acyl group. Generally, triacetyl cellulose (TAC) having a high acetyl group substitution degree is suitably used for a protective film of a polarizing plate because of low retardation. On the other hand, in order to use triacetyl cellulose as an optical compensation film for various liquid crystal modes such as VA type and TN type, it is necessary to add a retardation increasing agent because it lacks the expression of retardation (see, for example, 1).

On the other hand, diacetyl cellulose (DAC) having a small degree of acetyl group substitution is expected to exert its function as an optical compensation film without adding a retardation enhancer because of its high retardation manifestation.

When a film containing a cellulose acylate having a low acyl group substitution degree is used as an optical compensation film, it is common that a polarizing plate is produced by bonding with a polarizer. In consideration of the durability as a polarizing plate, the higher the adhesion between the cellulose acylate film and the polarizer is, the better.

Further, when bonding the cellulose acylate film and the polarizer, a step of superimposing the slow axis of the cellulose acylate film and the absorption axis of the polarizer in a strictly parallel or orthogonal manner is required. This is because the polarizability of the polarizing plate is deteriorated if a phenomenon referred to as a shaft misalignment occurs because these two axes are slightly shifted. The higher the phase difference developing performance of the cellulose acylate film is, the lower the degree of polarization becomes, the more remarkable it is. Therefore, it has been desired to develop a means capable of mitigating a decrease in the polarization degree due to the axis deviation.

Heretofore, polyvinyl alcohol-based adhesives have been widely used for bonding polarizer protective films containing a polarizer and cellulose acylate. At this time, it was necessary to hydrophilize the surface of the cellulose acylate film with an alkali saponified liquid or the like in advance. However, a cellulose acylate film having a low acyl group substitution degree has a problem in that, in the alkali saponification process, a part of the film is eluted into an alkali saponified liquid, thereby contaminating the process. Therefore, an adhesive that does not require an alkali saponification process has been desired.

Recently, a photo-curable adhesive has attracted attention as an adhesive when a polarizer and a polarizing plate protective film are bonded (see, for example, Patent Documents 2 to 4). It is expected that the photo-curable adhesive can be applied to a cellulose acylate having a small acyl group substitution degree because it can be bonded to a polarizer without going through an alkali saponification process.

However, the present inventors have found that when the optical compensation film and the polarizer comprising a cellulose acylate having a small acyl group substitution degree are bonded to each other using a photocurable adhesive, the adhesiveness to the polarizer is not sufficient and the polarization degree of the polarizing plate is greatly reduced . It is presumed that this is caused by misalignment of the minute alignment angle of the optical compensation film due to heat generation or curing shrinkage upon curing of the photo-curable adhesive and causing axis misalignment.

European Patent No. 911656 specification Japanese Patent Application Laid-Open No. 2010-39298 Japanese Patent Application Laid-Open No. 2009-244860 Japanese Patent Application Laid-Open No. 2009-211057

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems and it is an object of the present invention to provide a cellulose acylate film which improves the adhesion between a cellulose acylate film constituting a polarizing plate and a polarizer, And to provide a polarizing plate. The present invention also provides a liquid crystal display device provided with the polarizing plate.

The present inventors have found that by adopting a cellulose acylate film containing a cellulose acylate having a small degree of acyl group substitution and a glass transition temperature lowering agent in the course of examining the cause of the above problems, A retardation value, and a high retardation manifestation are exhibited. Further, when the polarizer and the cellulose acylate film are bonded to each other by using a photocurable adhesive, the inventors have found that the adhesiveness of the bonding surface is improved by decreasing the distribution of the glass transition temperature- And the present invention has been accomplished.

That is, the above object of the present invention is solved by the following means.

1. A polarizing plate obtained by bonding a cellulose acylate film comprising a cellulose acylate having an acyl group substitution degree within a range of 2.0 to 2.5 and a glass transition temperature lowering agent to one side of a polarizer using a photocurable adhesive,

The detected value of the glass transition temperature-reducing agent on the bonding surface of the cellulose acylate film detected by using the time-of-flight secondary ion mass spectrometry (TOF-SIMS) is d _A , the detected value of the other side is d _B , The value of r represented by the following formula (1) is 1.1 or more.

(1) r = d _A / d _B

2. The polarizer of claim 1, wherein the cellulose acylate is diacetyl cellulose having an acyl group substitution degree in the range of 2.0 to 2.5.

3. The polarizing plate according to any one of the preceding claims, wherein the glass transition temperature lowering agent has a glass transition temperature lowering capability of 3.5 占 폚 / mass part or more.

4. The cellulose acylate film according to claim 1, further comprising a hydrolysis inhibitor,

The polarizer according to any one of claims 1 to 3, wherein an average log P value of the hydrolysis inhibitor is at least 7.5.

5. The polarizing plate according to any one of claims 1 to 4, wherein the arithmetic average roughness of the bonding surface is larger than that of the other side.

6. The polarizing plate according to any one of claims 1 to 5, wherein the polarizing plate has a degree of polarization of 99.99% or more.

7. A liquid crystal display device comprising the polarizing plate according to any one of claims 1 to 6.

By the means of the present invention, the adhesion between the cellulose acylate film and the polarizer can be improved, and the decrease in the degree of polarization of the polarizing plate can be mitigated.

The mechanism or mechanism for manifesting the effect of the present invention is not disclosed, but is estimated as follows.

That is, when the cellulose acylate film is bonded to the polarizer using the photocurable adhesive, the glass transition temperature-lowering agent is abundant on the bonding surface, so that the bonding surface has a lot of minute irregularities than the other surface and has a rough surface structure. It is considered that this surface structure contributes to the improvement of the adhesion with the polarizer.

Further, the amount of cellulose acylate present decreases with an increase in the amount of the glass transition temperature-reducing agent present on the joint surface. Therefore, it is considered that the value of the retardation of the cellulose acylate film in the vicinity of the bonding surface is smaller than that of the entire cellulose acylate film. The higher the value of the retardation of the cellulose acylate film is, the lower the degree of polarization due to the off-axis shift at the time of bonding is significant. Therefore, it is considered that the lowering of the degree of polarization is alleviated by bonding the polarizing surface with the junction surface having a relatively small retardation.

The polarizing plate of the present invention comprises a cellulose acylate film containing a cellulose acylate having an acyl group substitution degree in the range of 2.0 to 2.5 and a glass transition temperature lowering agent and a polarizer attached to one side of the polarizer using a photocurable adhesive , D _{A A} is the detection value of the glass transition temperature-lowering agent on the bonding surface of the cellulose acylate film, and d is the detection value of the other side, which is detected using the time-of-flight secondary ion mass spectrometry (TOF-SIMS) _B , the r value represented by the formula (1) is 1.1 or more. This feature is a technical feature that is common to the invention according to claims 1 to 7.

As an embodiment of the present invention, it is preferable that the cellulose acylate is diacetyl cellulose having an acyl group substitution degree in the range of 2.0 to 2.5 from the viewpoint of manifesting the effect of the present invention. The glass transition temperature lowering agent of the glass transition temperature lowering agent is preferably at least 3.5 ° C / mass part. In addition, the cellulose acylate film preferably further comprises a hydrolysis inhibitor, and the average logP value of the hydrolysis inhibitor is preferably 7.5 or more. In addition, it is preferable that the arithmetic average roughness of the joining surface is larger than that of the other side. The polarizing plate preferably has a degree of polarization of 99.99% or more.

The polarizing plate of the present invention can be suitably provided in a liquid crystal display device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention, its constituent elements, and specific details and modes for carrying out the present invention will be described in detail. In the present application, " to " is used to mean that the numerical values described before and after the lower limit and the upper limit are included.

<Polarizer>

The polarizing plate according to the present invention is characterized in that a cellulose acylate film having an acyl group substitution degree in the range of 2.0 to 2.5 and a cellulose acylate film containing a glass transition temperature lowering agent are bonded to one side of a polarizer using a photo- .

<Cellulose Acylate Film>

The cellulose acylate film used in the present invention includes a cellulose acylate having an acyl group substitution degree in the range of 2.0 to 2.5. By employing the cellulose acylate having a small acyl group substitution degree as described above, high phase difference manifestation is exhibited, and even when the phase difference film has a high retardation, it is possible to reduce the thickness. In addition, even when a high phase difference is expressed, the draw magnification can be suppressed to a low level, and a failure such as breakage can be avoided.

Here, the cellulose molecule includes a plurality of glucose units linked together, and the glucose unit has three hydroxyl groups (hydroxyl groups). The number of acyl groups derived from these three hydroxyl groups is referred to as an acyl group substitution degree. For example, diacetyl cellulose (DAC) has an acetyl group bonded to an average of 2.0 to 2.5 hydroxyl groups out of the three hydroxyl groups of the glucose unit.

As the cellulose acylate used in the present invention, a carboxylic acid ester having about 2 to 22 carbon atoms can be enumerated, and an ester of an aromatic carboxylic acid may be used, but it is particularly preferable to be a low fatty acid ester of cellulose. The lower fatty acid in the lower fatty acid ester of cellulose means a fatty acid having 6 or less carbon atoms. The acyl group bonded to the hydroxy group may be linear or branched or may form a ring. Other substituents may also be substituted. The carbon number is preferably selected from an acyl group having 2 to 6 carbon atoms. The acyl group preferably has 2 to 4 carbon atoms, more preferably 2 to 3 carbon atoms.

For example, cellulose acetate, cellulose propionate, and cellulose butyrate; cellulose acetate propionate described in Japanese Patent Application Laid-Open Nos. 10-45804, 8-231761, and 2,319,052; It is preferable to use a mixed fatty acid ester such as cellulose acetate butyrate, cellulose acetate phthalate and the like.

The degree of substitution of the acyl group of the cellulose acylate can be measured in accordance with ASTM D-817-91, and the preferred degree of acyl group substitution is 2.18 to 2.45.

When the substitution degree of the acyl group of the cellulose acylate is 2.0 or more, deterioration of the film surface quality due to an increase in the doped viscosity and occurrence of haze due to an increase in stretching tension can be prevented. When the substitution degree of the acyl group is 2.5 or less, a required retardation is easily obtained.

The number-average molecular weight (Mn) of the cellulose acylate is preferably in the range of 30,000 to 300,000, because the obtained cellulose acylate film has a strong mechanical strength. Further, cellulose acylate having a number average molecular weight of 50000 to 200000 is preferably used.

The value of the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the cellulose acylate is preferably within the range of 1.4 to 3.0.

The number average molecular weight (Mn) and the weight average molecular weight (Mw) of the cellulose acylate are measured using gel permeation chromatography (GPC).

The measurement conditions are as follows.

Solvent: methylene chloride

Column: Shodex K806, K805, K803G (used by connecting three manufactured by Showa Denko K.K.)

Column temperature: 25 ° C

Sample concentration: 0.1 mass%

Detector: RI Model 504 (manufactured by GL Science)

Pump: L6000 (manufactured by Hitachi Seisakusho Co., Ltd.)

Flow rate: 1.0 ml / min

Calibration curve: standard polystyrene STK standard A calibration curve of 13 samples of polystyrene (manufactured by Tosoh Corporation) Mw = 1000000 to 500 is used. 13 samples are used at almost equal intervals.

The cellulose acylate used in the present invention can be synthesized by a known method. Specifically, it can be synthesized by referring to the method described in JP-A-10-45804.

The cellulose of the raw material of the cellulose acylate is not particularly limited, and examples thereof include cotton linter, wood pulp (derived from softwood, broad-leafed water), kenaf and the like. Further, the cellulose acylate obtained therefrom may be mixed in an arbitrary ratio.

On the other hand, a commercially available product of cellulose acylate may be used. Examples of commercially available products of cellulose acylate include L20, L30, L40 and L50 of Daicel, Ca398-3, Ca398-6, Ca398-10, Ca398-30 and Ca394-60S of Eastman Chemical Company.

<Glass transition temperature lowering agent>

The cellulose acylate film used in the present invention includes a glass transition temperature lowering agent (hereinafter referred to as a Tg reducing agent). As described above, when the cellulose acylate film contains a Tg reducing agent, the glass transition temperature (Tg) of the hard and brittle cellulose acylate decreases, and the processability and mechanical properties thereof can be improved. As a result, it is possible to provide a cellulose acylate film having a thin film and a high retardation value, suppressing an increase in internal haze even at a high magnification, suppressing phase difference nonuniformity, and suppressing an increase in haze even under a humid environment have.

The Tg reducing agent used in the present invention means an additive whose glass transition temperature (Tg) in the cellulose acylate alone having an acyl group substitution degree of from 2.0 to 2.5, which does not contain it, is lowered by adding it. Any substance may be used as the Tg reducing agent as long as the definition is satisfied.

The value of the glass transition temperature (Tg) of the cellulose acylate film is a value measured by differential scanning calorimetry (DSC).

In addition, depending on the kind of the cellulose acylate having an acyl group substitution degree of 2.0 to 2.5, when a substance corresponds to the definition of the Tg reducing agent and a case does not exist, the substance corresponds to the definition of the Tg reducing agent Is used in combination with a cellulose acylate having an acyl group substitution degree of from 2.0 to 2.5, it can be used as a Tg reducing agent in the present invention.

There is no particular limitation on the glass transition temperature lowering ability of the Tg reducing agent (hereinafter referred to as Tg lowering ability), but it is preferably at least 3.5 deg. C / mass part, more preferably at least 3.8 deg. C / Lt; 0 &gt; C / mass part or more.

Here, the Tg lowering ability refers to the ability to lower the glass transition temperature (Tg) per unit mass of a substance, and is defined by the following equation (3).

Equation (3)

(Wherein X represents the glass transition temperature (Tg) of the cellulose acylate film obtained by film-forming the cellulose acylate alone, Y is 5 mass parts of the Tg reducing agent per 100 mass parts of the cellulose acylate, Represents the glass transition temperature (Tg) of the cellulose acylate film obtained by film formation.

If the Tg reducing ability of the Tg reducing agent is within the above range, an excellent Tg lowering effect can be exhibited even with a small addition amount. This can prevent bleeding or the like which may occur when a large amount of additive should be added. On the other hand, the upper limit value of the Tg lowering ability is not particularly limited, but it is actually 5.0 占 폚 / mass part or less.

As for the Tg lowering ability, depending on the kind of the cellulose acylate having an acyl group substitution degree of 2.0 to 2.5, the case where the substance used as the Tg lowering agent is included in the preferable range of the above-mentioned Tg lowering ability, May occur. In this case, only when the substance is used in combination with the cellulose acylate having an acyl group substitution degree of 2.0 to 2.5 in the case where it falls within the above-mentioned preferable range of the Tg lowering ability, the range of the preferable Tg lowering ability is satisfied Is considered to be interpreted as a Tg reducing agent.

The specific form of the Tg reducing agent used in the present invention is not particularly limited so long as it satisfies the definition of the Tg reducing agent as long as it satisfies the preferable range of the Tg reducing ability described above. An example of the Tg reducing agent is a polyester compound represented by the following formula (I).

(I) XOB- {OC (= O) -AC (= O) -OB} _n- OX

Wherein B represents a linear or branched alkylene group having 2 to 6 carbon atoms, or a linear or branched cycloalkylene group. A represents an aromatic ring having 6 to 14 carbon atoms, a straight-chain or branched alkylene group having 2 to 6 carbon atoms, or a straight-chain or branched cycloalkylene group having 2 to 6 carbon atoms. X represents a hydrogen atom or a monocarboxylic acid residue containing an aromatic ring having 6 to 14 carbon atoms. n represents a natural number of 1 or more.]

The polyester compound represented by the formula (I) can be produced by reacting a dicarboxylic acid having an aromatic ring (having 6 to 14 carbon atoms), a straight chain or branched alkylene group, or a straight chain or branched cycloalkylene group (both having 2 to 6 carbon atoms) An alkylene diol having 2 to 6 carbon atoms and a linear or branched alkylene diol or cycloalkylene diol having 2 to 6 carbon atoms.

The aromatic dicarboxylic acid and the dicarboxylic acid having a straight chain or branched alkylene group or cycloalkylene group may be used singly or as a mixture, but from the viewpoint of compatibility with cellulose acylate, at least an aromatic dicarboxylic acid It is preferable that the content of the carboxylic acid is 10% or more. Further, both ends may be sealed with a monocarboxylic acid having an aromatic ring (carbon number of 6 to 14).

Examples of the dicarboxylic acid having an aromatic ring (carbon number of 6 to 14), that is, the aromatic dicarboxylic acid having 6 to 16 carbon atoms include phthalic acid, isophthalic acid, terephthalic acid, 1,5-naphthalenedicarboxylic acid, Naphthalene dicarboxylic acid, 2,8-naphthalene dicarboxylic acid, 2,8-naphthalene dicarboxylic acid, 2,3-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 2'-biphenyldicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and the like. Among them, terephthalic acid, 2,6-naphthalene dicarboxylic acid and 4,4'-biphenyldicarboxylic acid are preferable.

Examples of the dicarboxylic acid having a linear or branched alkylene group or a cycloalkylene group (having 2 to 6 carbon atoms) include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, -Cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and the like. Among them, succinic acid, adipic acid and 1,4-cyclohexanedicarboxylic acid are preferable.

Examples of the straight chain or branched alkylene diol or cycloalkylene diol having 2 to 6 carbon atoms include ethanediol (ethylene glycol), 1,2-propanediol, 1,3-propanediol, 1,2- Butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and the like. Among them, ethanediol (ethylene glycol), 1,2-propanediol, 1,3-propanediol and 1,3-butanediol are preferable.

Among them, it is preferable that A is a benzene ring, naphthalene ring or biphenyl ring which may have a substituent from the viewpoint of excellent Tg lowering ability. Here, the substituent that the benzene ring, naphthalene ring or biphenyl ring may have is an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

Examples of the monocarboxylic acid having an aromatic ring (having 6 to 14 carbon atoms) for sealing both ends of the polyester compound include benzoic acid, orthotoluic acid, meta-toluic acid, para-toluic acid, para- Benzoic acid, and para-methoxybenzoic acid. Among them, benzoic acid, para-toluic acid and para-tert-butylbenzoic acid are preferable.

The aromatic polyester compound may be produced by a conventional method such as a polyesterification reaction of a dicarboxylic acid and an alkylene diol or a cycloalkylene diol, a thermal fusion condensation reaction by transesterification reaction, or a combination of an acid chloride and a glycol Can be easily synthesized by any one of the interfacial condensation methods. By adding the above-mentioned aromatic monocarboxylic acid, a polyester compound having both ends sealed can be synthesized.

Examples of the aromatic polyester compounds (PES-1) to (PES-14), (ar-1) to (ar-20) which can be used in the present invention are illustrated below.

As specific examples of the Tg reducing agent, the aromatic polyester compound represented by the formula (I) has been described in detail. However, other Tg reducing agents may be used.

In the cellulose acylate film according to one embodiment of the present invention, only one Tg reducing agent may be used alone, or two or more Tg reducing agents may be used in combination. The addition amount of the Tg reducing agent in the cellulose acylate film according to one embodiment of the present invention is not particularly limited, but is preferably from 1 to 5% by mass, more preferably from 1.5 to 5% by mass based on 100% by mass of the cellulose acylate. 3.5% by mass. If the addition amount of the Tg reducing agent is 1% by mass or more, the Tg reducing agent can sufficiently exhibit the Tg lowering performance as its original purpose. On the other hand, when the addition amount of the Tg reducing agent is 5 mass% or less, deterioration of the phase difference developing performance of the cellulose acylate film accompanying increase of the addition amount of the Tg reducing agent can be prevented.

The cellulose acylate film according to one embodiment of the present invention has a Tg (Tg) by a time-of-flight secondary ion mass spectrometry (TOF-SIMS) at a bonding surface with a polarizer and other surfaces And the detection value of the degrading agent has a certain degree of bias.

If this is expressed quantitatively, the detection value of the Tg reducing agent on the bonding surface of the cellulose acylate film with the polarizer is d _A and the detection value of the other side is d _B , which is detected using the time-of-flight secondary ion mass spectrometry , The r value represented by the following formula (1) is at least 1.1.

(1) r = d _A / d _B

Here, the time-of-flight secondary ion mass spectrometry can measure the chemical information of an atom or molecule on a solid sample with a sensitivity of not more than one molecule layer, and the distribution of a specific atom or molecule can be observed with a spatial resolution of 100 nm or less Method. Time-of-flight secondary ion mass spectrometry is a kind of secondary ion mass spectrometry (SIMS), in which a primary ion beam is irradiated to a solid sample, and ions (secondary ions) emitted from the outermost surface of the sample Analysis is performed. It is called TOF-SIMS in that a time-of-flight mass spectrometer (TOF-MS) is used as a mass spectrometer.

According to the time-of-flight secondary ion mass spectrometry, a non-destructive sample can be substantially measured by irradiating an ion beam to a sample in a pulsed manner, and it is now widely used for analysis of organic materials and polymer materials.

The r value may be 1.1 or more, preferably 1.2 or more, more preferably 1.3 or more, and further preferably 1.4 or more. On the other hand, in the production of the polarizing plate, the occurrence of curling can be easily suppressed.

As a preferred embodiment based on another aspect of the cellulose acylate film according to the present invention, it is preferable that the r value and the preferable form of the rg value, which are indispensable constituent elements in the present invention, And a concentration gradient is present. For example, as a simplest example, when the cellulose acylate film according to the present invention is cut so as to be bisected by a plane perpendicular to the thickness direction (parallel to the plane direction of the film), the bonding surface with the polarizer Is preferably larger than the amount of the Tg reducing agent present in the other fragment (the fragment including the other surface) is preferably exemplified. When this is generalized, when the cellulose acylate film according to the present invention is cut so as to be k-divided into a plane perpendicular to the thickness direction (parallel to the surface direction of the film), the amount of the Tg reducing agent present in each fragment , An embodiment in which the angle is gradually reduced from a fragment including a bonding surface with a polarizer to a fragment including the other surface is also preferably exemplified. In the present embodiment, the case where k = 2 has been separately described above. However, k is preferably 3 or more, more preferably 5 or more, further preferably 10 or more, and particularly preferably 20 or more to be.

According to the cellulose acylate film of one embodiment of the present invention, the r value is set to be 1.1 or more, whereby the adhesion with the polarizer constituting the polarizing plate can be further improved. When a cellulose acylate having a small acyl group substitution degree, for example, DAC, is used not only as a retardation film but also as an optical compensation film for widening a viewing angle, it is common to form a polarizing plate by bonding with a polarizer. In consideration of the durability as a polarizing plate, the higher the adhesion between the cellulose acylate film and the polarizer, the better.

Although the mechanism for improving the adhesion is not completely clear, according to the study by the present inventor, the following mechanism is presumed.

As described later, the cellulose acylate film is produced through a process of drying a film obtained by softening a dope containing a cellulose acylate and an additive on a support, drying the film, and then drawing the film. When the production method in which the r value of the obtained cellulose acylate film is 1.1 or more is employed, it is found that one surface of the obtained cellulose acylate film exhibits a rough surface irregularity as compared with the other surface, .

This is because the Tg reducing agent having a Tg lowering ability which lowers the glass transition temperature (Tg) of the cellulose acylate is abundantly present on one surface, which is a result of allowing the cellulose acylate to move smoothly at the time of stretching It is being considered. It is believed that a roughened surface structure having many such minute unevenness contributes to improvement of adhesion with a polarizer.

Normally, when the polarizer and the cellulose acylate film are bonded, the bonding surface of the cellulose acylate film is alkali saponified for the purpose of improving the adhesion. However, according to the cellulose acylate film provided by the present invention, since the adhesion between the cellulose acylate film and the polarizer is improved by the mechanism as described above, it is expected that such alkali saponification treatment becomes unnecessary, The cost reduction effect can be achieved.

In addition, when the alkali saponification treatment is performed, there is a possibility that a part of the cellulose acylate present on the saponified surface (joint surface) of the cellulose acylate film is hydrolyzed. However, the alkali saponification treatment is unnecessarily , There is no possibility of hydrolysis of the cellulose acylate at the time of the alkali saponification treatment, and a highly advantageous technique is provided.

A preferred embodiment of the cellulose acylate film according to one embodiment of the present invention is a quantitative representation of the existence of a surface structure including minute concavities and convexities contributing to improvement of adhesion with a polarizer by the mechanism described above. That is, in the cellulose acylate film according to one aspect of the present invention, the value of the arithmetic average roughness (Ra) measured by JIS B0601: 2001 of the surface of the film bonded to the polarizer is different from that of the other surface Is preferably larger than the value in At this time, the value of the arithmetic mean roughness (Ra) on the joint surface is preferably 1.05 times or more, more preferably 1.1 times or more, more preferably 1.1 times or more, Is at least 1.2 times, particularly preferably at least 1.3 times, particularly preferably at least 1.4 times.

Further, conventionally, when a polarizing plate is manufactured by bonding a cellulose acylate film and a polarizer, a step of strictly overlapping the slow axis of the cellulose acylate film as the retardation film and the absorption axis of the polarizer has been required. When these two axes are slightly shifted at the time of bonding, when the so-called axis deviation occurs, there is a problem that the polarization degree of the polarizing plate is lowered. The higher the phase difference developing performance of the cellulose acylate film constituting the polarizing plate, the lower the degree of polarization becomes remarkable. Therefore, development of a means capable of mitigating the decrease in the degree of polarization caused by the above-described axis shift is also It was strongly demanded.

The cellulose acylate film according to one aspect of the present invention also provides a certain solution to such a demand. That is, according to the cellulose acylate film according to one aspect of the present invention, even when slight axial misalignment occurs at the time of bonding with the polarizer, the decrease in the degree of polarization of the polarizing plate resulting therefrom can be alleviated. Although the mechanism is not completely clear, according to the study of the present inventor, the following mechanism is estimated.

The Tg reducing agent included in the cellulose acylate film according to one embodiment of the present invention reduces the relative abundance of cellulose acylate contributing to the phase difference development with an increase in the amount existing in the film. In the cellulose acylate film of the present invention, since the Tg reducing agent is present on the bonding surface with the polarizer more than the other surface, microscopic observation of the vicinity of the bonding surface reveals that the retardation value Ro of the cellulose acylate film , Rth) is considered to be smaller than the macroscopic value for the entire cellulose acylate film. On the other hand, when microscopically observed in the vicinity of the other surface, it is considered that the retardation values (Ro, Rth) are larger than the macroscopic values for the entire cellulose acylate film.

Even in such a case, when the amount of the Tg reducing agent and the thickness of the cellulose acylate film contained in the film are constant, the retardation values Ro and Rth of the film as a whole are unchanged. As described above, the higher the retardation performance (retardation value Ro and Rth) of the cellulose acylate film as the retardation film, the greater the decrease in the degree of polarization due to the axis misalignment with the polarizer. In addition, on the bonding surface with the polarizer, axial displacement of the cellulose acylate film is liable to occur due to external factors such as shrinkage of the adhesive and heat generation upon curing. Therefore, in the case of joining the bonding surfaces constituted so that the retardation values (Ro, Rth) are microscopically small to the polarizers, as compared with the case where the surface where the Tg reducing agent uniformly exists on the entire film is bonded to the polarizer, Even if an axial misalignment occurs, the degree of decrease in the degree of polarization of the polarizing plate is small. As a result, the lowering of the polarization degree of the polarizing plate due to the axial misalignment is alleviated.

Conventionally, additives designed to constitute cellulose acylate films have been variously designed so as to be distributed as uniformly as possible in a film. That is, those skilled in the art who examine the addition of various additives to the cellulose acylate film will not attempt to have a distribution in the formulation of additives, although a more homogeneous blend may be noted. Therefore, the present invention, which can exhibit the above-mentioned excellent action and effect by having a distribution in the combination of the Tg lowering agent even under such technical knowledge, can provide a technique having a very high advantage over the prior art.

<Other additives>

The cellulose acylate film according to one embodiment of the present invention may contain other additives in addition to the above-mentioned Tg reducing agent. Hereinafter, the additives usable in the present invention will be described.

(Hydrolysis inhibitor)

The cellulose acylate film according to one embodiment of the present invention may include a hydrolysis inhibitor. As described above, since the cellulose acylate film contains the hydrolysis inhibitor, the hydrolysis of the cellulose acylate is prevented, and the water resistance of the cellulose acylate film can be improved.

The hydrolysis inhibitor which can be used in the present invention refers to an additive which is degraded by hydrolysis of cellulose acylate alone and having an acyl group substitution degree of 2.0 to 2.5 which does not contain it and is deteriorated by adding it. Any material may be used as the hydrolysis inhibitor.

As the hydrolysis-resistant index of the cellulose acylate film for judging which substance is included in the concept of the hydrolysis inhibitor, the rate of mass change before and after saponification can be used. Specifically, the film is immersed in a 2.0M aqueous KOH solution at 50 占 폚 for 90 seconds, and the rate of mass change of the film before and after the film is calculated. According to the mass change rate, the ratio of the cellulose acylate that has been hydrolyzed in the alkaline solution and started to melt in the saponified solution can be grasped. When the mass change rate of the film formed only by cellulose acylate is d1% and the mass change rate of the film to which 5 parts by mass of the additive is added to 100 parts by mass of the cellulose acylate satisfies | d1 |> | d2 | , It can be judged that the additive is a hydrolysis inhibitor for cellulose acylate.

In addition, depending on the kind of the cellulose acylate having an acyl group substitution degree of 2.0 to 2.5, when a substance corresponds to the definition of the hydrolysis inhibitor or does not correspond to the definition of the hydrolysis inhibitor, the substance corresponds to the definition of the hydrolysis inhibitor Is used in combination with a cellulose acylate having an acyl group substitution degree of from 2.0 to 2.5, it can be used as a hydrolysis inhibitor in the present invention.

The hydrolysis inhibiting ability of the hydrolysis inhibitor is not particularly limited, but can be represented by an average log P value which is an index of the hydrophobicity of the hydrolysis inhibitor. The higher the average log P value, the better the performance as a hydrolysis inhibitor.

Here, the log P value is also referred to as the octanol-water partition coefficient, or logPow, and is defined as the logarithm of the value of the ratio of the distribution concentration of a substance to each phase of a two-phase solvent system comprising n-octanol and water . The average log P value is obtained by first obtaining the log P value inherent to each compound constituting the mixture in consideration of the case where the hydrolysis inhibitor is used as a mixture of plural kinds of compounds, Weight ratio).

The log P value is a value measured by the flask shaking method described in JIS Z-7260-107: 2000. Further, the logP value may be a value estimated by a computational chemical method or an empirical method instead of the actual measurement.

When the log P value is obtained by the calculation chemical method, the calculation method is Crippen's fragmentation method (J. Chem. Inf. Comput. Sci., Vol. 27, p21 (1987)), Viswanadhan's fragmentation method , Broto's fragmentation method (Eur. J. Med. Chem.-Chim. Theor., 19 vol., P71 (1984)), CLogP method (reference Leo , A., Jow, PYC, Silipo, C., Hansch, C., J. Med. Chem., 18, 865 1975) are preferably used, but Crippen's fragmentation method (J. Chem. Sci., Vol. 27, p21 (1987)). However, when the measured value by the above-described flask shaking method is significantly different from the value calculated by the calculation chemical method or empirical method, the measured value by the flask shaking method has priority.

The average log P value of the hydrolysis inhibitor used in the present invention is preferably 7.5 or more, more preferably 8.0 or more, further preferably 9.0 or more, and particularly preferably 9.5 or more. If the average log P value of the hydrolysis inhibitor is within this range, an excellent hydrolysis preventing effect can be exhibited even with a small addition amount. This can prevent occurrence of bleed-out or the like which may occur when a large amount of additive is to be added. On the other hand, there is no particular limitation on the upper limit of the average logP value of the hydrolysis inhibitor, but from the viewpoint of compatibility with the cellulose acylate, it is usually preferably about 13.0 or less.

The specific form of the hydrolysis inhibitor which can be used in the present invention is not particularly limited as long as the above-mentioned preferable range of the logP value is also satisfied as long as the definition of the hydrolysis inhibitor described above is satisfied. Examples of the hydrolysis inhibitor include sugar ester compounds represented by the following formula (II).

Formula _{(II) (HO) m -G-} (OC (= O) -R 2) l

Wherein G represents a residue of a monosaccharide or a disaccharide. R ² represents an aliphatic group or an aromatic group. and m represents the total number of hydroxy groups directly bonded to the monosaccharide or disaccharide moiety. 1 represents the total number of - (OC (= O) -R ² ) groups directly bonded to a residue of a monosaccharide or a disaccharide, 3? m + l? 8, and l?

The compound having the structure represented by the general formula (II) is a compound in which the total number (m) of hydroxyl groups and the total number (l) of - (OC (= O) -R ² ) And it is known that it becomes a compound in which several kinds of different components of m and l are mixed in the formula. Therefore, the performance as a mixture in which the number (m) of hydroxyl groups and the number (l) of - (OC (= O) -R ² ) groups are respectively changed is important.

In the case of the cellulose acylate film of the present invention, the mixing ratio of the component represented by the formula (II) to the haze characteristic and the component with m = 0 and the component with m> 0 is 45:55 to 0: 100 Are preferred. In terms of performance and cost, more preferably, the mixing ratio of the component of m = 0 to the component of m > 0 is in the range of 10:90 to 0.1: 99.9. In addition, the component of m = 0 and the component of m > 0 can be measured by high performance liquid chromatography by a conventional method.

Specific examples of monosaccharide residues represented by G in the above formula (II) include, for example, alooses, altroose, glucose, mannose, gulose, idose, galactose, talose, ribose, arabinose, xylose , Rick Source, and the like.

Examples of the structure of the compound having a monosaccharide residue represented by the formula (II) are shown below, but the present invention is not limited to these specific examples.

Specific examples of the disaccharide of the residue represented by G include, for example, trehalose, sucrose, maltose, cellobiose, gentiobiose, lactose, isotrehalose and the like.

Examples of the structure of the compound having a disaccharide residue represented by the formula (II) are shown below, but the present invention is not limited to these specific examples.

In the formula (II), the aliphatic group or aromatic group represented by R ² may each independently have a substituent.

In the formula (II), m and l are required to satisfy 3? M + l? 8 and 4? M + l? 8. L &lt; / RTI &gt; When l is 2 or more, the - (OC (= O) -R ² ) groups may be the same or different.

The aliphatic group in the definition of R ^{2 in} the formula (II) may be linear, branched or cyclic. The number of carbon atoms in the aliphatic group is preferably from 1 to 25, more preferably from 1 to 20, and still more preferably from 2 to 15, carbon atoms. Specific examples of the aliphatic group include linear or branched aliphatic groups such as methyl, ethyl, n-propyl, iso-propyl, cyclopropyl, n-butyl, iso-butyl, Cyclohexyl, n-heptyl, n-octyl, bicyclooctyl, adamantyl, n-decyl, tert-octyl, dodecyl, hexadecyl, octadecyl and didecyl.

The aromatic group in the definition of R ^{2 in} the formula (II) may be an aromatic hydrocarbon group or an aromatic heterocyclic group, and more preferably an aromatic hydrocarbon group. The aromatic hydrocarbon group preferably has 6 to 24 carbon atoms, more preferably 6 to 12 carbon atoms. Specific examples of the aromatic hydrocarbon group include benzene, naphthalene, anthracene, biphenyl, terphenyl, and the like. As the aromatic hydrocarbon group, benzene, naphthalene and biphenyl are particularly preferable. The aromatic heterocyclic group preferably contains at least one of an oxygen atom, a nitrogen atom and a sulfur atom. Specific examples of the heterocycle include, for example, furan, pyrrole, thiophene, imidazole, pyrazole, pyridine, pyrazine, pyridazine, triazole, triazine, indole, indazole, purine, thiazoline, thiadiazole, Wherein the benzene ring is selected from the group consisting of benzene ring, benzene ring, benzene ring, benzene ring, benzene ring, benzene ring, benzene ring, benzene ring, phenylene ring, Benzoxazole, benzothiazole, benzotriazole, tetrazaine, and the like. As the aromatic heterocyclic group, pyridine, triazine, and quinoline are particularly preferable.

Next, preferred examples of the compound represented by the formula (II) are shown below, but the present invention is not limited to these specific examples.

Hereinafter, synthesis examples of the compound represented by the formula (II) are shown.

34.2 g (0.1 mol) of sucrose, 180.8 g (0.8 mol) of anhydrous benzoic acid and 379.7 g (4.8 mol) of pyridine were fed into a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen gas introducing tube, The temperature was elevated while nitrogen gas was bubbled through the nitrogen gas introduction tube, and the esterification reaction was carried out at 70 DEG C for 5 hours. Subsequently, the inside of the flask was reduced to 4 × 10 ² Pa or less, excess pyridine was distilled off at 60 ° C., the pressure in the flask was reduced to 1.3 × 10 5 Pa or less, and the temperature was raised to 120 ° C. to obtain an anhydrous benzoic acid Most were distilled off. Subsequently, 300 g of an aqueous solution of sodium carbonate of 0.5% by mass and 1 L of toluene was added, stirred at 50 캜 for 30 minutes, and then allowed to stand to separate the toluene layer. Finally, 100 g of water was added to the separated toluene layer, and the mixture was washed with water at room temperature for 30 minutes. Then, the toluene layer was collected, and toluene was distilled off at 60 캜 under reduced pressure (4 × 10 ² Pa or less) A mixture of the compounds (C-1), (C-2), (C-3), (C-4) and (C-5) was obtained. The resulting mixture was analyzed by HPLC and LC-MASS to find that 7 mass% of (C-1), 58 mass% of (C-2), 23 mass% of (C-3) Mass%, and (C-5) was 3 mass%. (C-1), (C-2), (C-3), (C-4) and (C-5) having a purity of 100% were obtained by purifying a part of the obtained mixture by silica gel column chromatography ).

The hydrolysis inhibitor which can be added to the cellulose acylate film according to one embodiment of the present invention exerts the action and effect of imparting water resistance to the film as described above. Therefore, unlike the aforementioned Tg reducing agent, it is preferable that the hydrolysis inhibitor is uniformly distributed throughout the film as much as possible.

Quantitatively, this can be expressed by the following equation (2) when d _C and d _D are the detection values of the hydrolysis inhibitor on both sides of the film, which are detected using the time-of-flight secondary ion mass spectrometry The value of s is preferably less than 1.1.

Equation (2)

[Wherein, max {d _C , d _D } represents the larger of d _C or d _D , and min {d _C , d _D } represents the smaller of d _C or d _D.

As can be understood from the above description of the deviation of the detected value of the Tg reducing agent, this preferred embodiment of the deviation of the detection value of the hydrolysis inhibitor is, in short, Means that there is almost no deviation in the detection value of the hydrolysis inhibitor by ion mass spectrometry, specifically, only in a degree that the ratio is less than 1.1.

Further, in the preferred embodiment, the s value is a theoretical number of 1 or more in theory. The s value may be less than 1.1, but the s value is preferably 1.05 or less, more preferably 1.03 or less, still more preferably 1.02 or less, particularly preferably 1.01 or less, and most preferably 1.005 or less.

(Plasticizer)

The cellulose acylate film of the present invention may contain conventionally known plasticizers as needed in obtaining the effects of the present invention. The compounds represented by the above-mentioned formulas (I) and (II) are also used as plasticizers, but may contain other plasticizers.

The specific form of the other plasticizer is not particularly limited, but is preferably a polyvalent carboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a fatty acid ester plasticizer, a polyhydric alcohol ester plasticizer, an ester plasticizer, Is selected. When two or more plasticizers are used, at least one of them is preferably a polyhydric alcohol ester plasticizer.

The polyhydric alcohol ester plasticizer is preferably a plasticizer containing an ester of a divalent or higher aliphatic polyhydric alcohol and a monocarboxylic acid and having an aromatic ring or a cycloalkyl ring in the molecule. Preferably 2 to 20, aliphatic polyhydric alcohol esters.

The polyhydric alcohol preferably used in the present invention is represented by the following formula (III).

(III) R &lt; ₁₁ &gt; - (OH) _n

Wherein R &lt; ₁₁ &gt; represents an n-valent organic group. n represents an integer of 2 or more. OH group represents an alcoholic and / or phenolic hydroxy group.

Preferable examples of the polyhydric alcohol include adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexane Triol, galactitol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylol propane, trimethylol ethane and xylitol. Particularly preferred are triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylol propane and xylitol.

The monocarboxylic acid used in the polyhydric alcohol ester is not particularly limited and known aliphatic monocarboxylic acids, alicyclic monocarboxylic acids, aromatic monocarboxylic acids and the like can be used. The use of an alicyclic monocarboxylic acid or an aromatic monocarboxylic acid is preferable because it improves the moisture permeability and retention.

Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

As the aliphatic monocarboxylic acid, a linear or branched chain fatty acid having 1 to 32 carbon atoms can be preferably used. More preferably 1 to 20 carbon atoms, and particularly preferably 1 to 10 carbon atoms. Incorporation of acetic acid increases the compatibility with cellulose acylate. Therefore, it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

Preferred aliphatic monocarboxylic acids are acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2- ethylhexanoic acid, undecanoic acid, But are not limited to, trimellitic acid, trimellitic acid, decyl acid, myristic acid, pentadecyl acid, palmitic acid, heptadecyl acid, stearic acid, nonadecanoic acid, arachic acid, behenic acid, lignoceric acid, , Saturated fatty acids such as lactic acid, undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid and arachidonic acid.

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

Examples of preferable aromatic monocarboxylic acids include those obtained by introducing one to three alkoxy groups such as alkyl groups, methoxy groups or ethoxy groups into benzene rings of benzoic acids such as benzoic acid and toluic acid, those having biphenylcarboxylic acid and naphthalenecarboxylic acid , Tetralin carboxylic acid, and the like, or derivatives thereof. The term &quot; aromatic monocarboxylic acid &quot; Particularly preferred is benzoic acid.

The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably 300 to 1500, more preferably 350 to 750. [ A larger molecular weight is preferable because it is less likely to be volatilized, and a smaller molecular weight is preferable from the viewpoint of water vapor permeability and compatibility with cellulose acylate.

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

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

The glycolate-based plasticizer is not particularly limited, but alkyl phthalyl alkyl glycolates can be preferably used.

The alkyl phthalyl alkyl glycolates include, for example, methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octylphthalyl octyl 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 Glycolate, butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octylphthalyl methyl glycolate, and octylphthalyl ethyl glycolate.

Examples of the phthalate ester plasticizers include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, dicyclohexylterephthalate, .

Examples of the citrate ester plasticizer include acetyltrimethyl citrate, acetyltriethyl citrate, and acetyl tributyl citrate.

Examples of the fatty acid ester plasticizer include butyl oleate, methyl acetyl ricinolate, dibutyl sebacate, and the like.

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

The polycarboxylic acid ester compound includes an ester of a polyvalent carboxylic acid and an alcohol having a valence of 2 or more, preferably 2 to 20, The aliphatic polycarboxylic acid is preferably 2 to 20 carbon atoms, and in the case of an aromatic polycarboxylic acid and an alicyclic polycarboxylic acid, it is preferably 3 to 20 carbon atoms.

The polycarboxylic acid is represented by the following formula (IV).

(IV) ???????? R ₁₂ (COOH) _m1 (OH) _n1 ?????

[Wherein, R ₁₂ is (m1 + n1) valent represents an organic group, m1 represents an integer of 2 or more, n1 denotes an integer of 0 or more, COOH group shows the carboxyl group, OH group represents an alcoholic and / or phenolic hydroxy groups .]

Examples of preferred polyvalent carboxylic acids include, but are not limited to, the following.

Aromatic polycarboxylic acids or derivatives thereof having three or more valences such as trimellitic acid, trimesic acid and pyromellitic acid, aliphatic polycarboxylic acids or derivatives thereof such as succinic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid, fumaric acid, maleic acid and tetrahydrophthalic acid Oxycarboxylic acids such as polycarboxylic acids, tartaric acid, tartronic acid, malic acid and citric acid may be preferably used. Particularly, it is preferable to use an oxydarboxylic acid in view of improvement in retention property and the like.

The alcohol used in the polycarboxylic acid ester compound is not particularly limited, and known alcohols and phenols can be used.

For example, aliphatic saturated alcohols or aliphatic unsaturated alcohols having 1 to 32 carbon atoms may be preferably used. More preferably from 1 to 20 carbon atoms, and particularly preferably from 1 to 10 carbon atoms.

In addition, alicyclic alcohols such as cyclopentanol and cyclohexanol or derivatives thereof, aromatic alcohols such as benzyl alcohol and cinnamyl alcohol, and derivatives thereof may also be preferably used.

When an oxydarboxylic acid is used as the polycarboxylic acid, the alcoholic or phenolic hydroxyl group of the oxydarboxylic acid may be esterified using a monocarboxylic acid.

Although the molecular weight of the polycarboxylic acid ester compound is not particularly limited, it is preferably in the range of 300 to 1000, more preferably in the range of 350 to 750. In view of improving the retention property, a large one is preferable, and in view of the compatibility with the cellulose acylate, the smaller one is preferable.

The alcohols used in the polyvalent carboxylic acid ester which can be used in the present invention may be one kind or a mixture of two or more kinds.

The acid value of the polyvalent carboxylic acid ester compound usable in the present invention is preferably 1 mgKOH / g or less, more preferably 0.2 mgKOH / g or less. By setting the acid value in the above range, fluctuation of the environment of retardation is suppressed, which is preferable.

Further, it means the number of milligrams of potassium hydroxide necessary to neutralize the acid cloud, the acid contained in 1 g of the sample (the carboxyl group present in the sample). As the value of the acid value, a value measured in accordance with JIS K0070 shall be employed.

Examples of particularly preferable polyvalent carboxylic acid ester compounds are shown below, but the present invention is not limited thereto.

For example, there may be mentioned triethyl citrate, tributyl citrate, acetyl triethyl citrate (ATEC), acetyl tributyl citrate (ATBC), benzoyl tributyl citrate, acetyltriphenyl citrate, acetyl tribenzyl citrate, Dibutyl tartarate, diacetyl dibutyl tartrate, tributyl trimellitate, tetrabutyl pyromellitate, and the like.

(Ultraviolet absorber)

The cellulose acylate film of the present invention may contain an ultraviolet absorber. The ultraviolet absorber is added for the purpose of improving the durability of the cellulose acylate film by absorbing ultraviolet rays of 400 nm or less. The transmittance at a wavelength of 370 nm in the cellulose acylate film is preferably 10% or less, more preferably 5% or less, further preferably 2% or less.

The ultraviolet absorber to be used in the present invention is not particularly limited, and examples thereof include oxybenzophenone compounds, benzotriazole compounds, salicylic ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, Based compounds, inorganic powders, and the like.

Benzotriazole, (2-2H-benzotriazol-2-yl) -6- (3,5-di-sec- (Straight chain and branched dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone and the like, and also Tinuvin 109, Tinuvin 171, Tinuvin 234 , Tinuvin 326, Tinuvin 327 and Tinuvin 328, all of which are commercially available from BASF Japan, and can be preferably used.

The ultraviolet absorber preferably used in the present invention is a benzotriazole ultraviolet absorber, a benzophenone ultraviolet absorber, a triazine ultraviolet absorber, and particularly preferably a benzotriazole ultraviolet absorber and a benzophenone ultraviolet absorber.

In addition, a discotic compound such as a compound having 1,3,5-triazine ring is also preferably used as an ultraviolet absorber.

As the ultraviolet absorber, a polymer ultraviolet absorber can be preferably used. In particular, a polymer-type ultraviolet absorber described in JP-A-6-148430 is preferably used.

The ultraviolet absorber may be added by dissolving the ultraviolet absorber in an alcohol such as methanol, ethanol or butanol, or an organic solvent such as methylene chloride, methyl acetate, acetone, or dioxolane, or a mixed solvent thereof, May be added during the composition.

In the case of not dissolving in an organic solvent such as an inorganic powder, it is dispersed in an organic solvent and a cellulose acylate using a dissolver or a sand mill, and then added to the dope.

The amount of the ultraviolet absorber to be used is not uniform depending on the kind of the ultraviolet absorber and the conditions of use, but when the dry film thickness of the cellulose acylate film is 30 to 200 탆, it is preferably 0.5 to 10.0% by mass relative to the total mass of the film , And more preferably 0.6 to 4.0 mass%.

(Antioxidant)

Antioxidants are also called deterioration inhibitors. When a liquid crystal image display device is placed in a state of high humidity and high temperature, deterioration of the cellulose acylate film may occur.

The antioxidant has a role of retarding or preventing the degradation of the cellulose acylate film by, for example, halogen in the residual solvent amount in the cellulose acylate film or phosphoric acid in the phosphoric acid plasticizer, etc. Therefore, .

As such an antioxidant, a hindered phenol-based compound is preferably used, and for example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexane Di-tert-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4- Di-t-butyl anilino) -1,3,5-triazine, 2,2-thio-diethylene bis [3- (3,5- Propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5- (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5 Di-t-butyl-4-hydroxybenzyl) -isocyanurate.

Particularly preferred are 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t- Glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferable. Further, a hydrazine-based metal inactive agent such as N, N'-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine, -t-butylphenyl) phosphite may be used in combination.

The amount of these compounds to be added is preferably 1 to 5000 ppm, more preferably 10 to 1000 ppm, in mass ratio with respect to the cellulose acylate film.

(Acid scavenger)

Since the cellulose acylate accelerates decomposition even at an elevated temperature by an acid, it is preferable that the cellulose acylate contains an acid scavenger when used in the cellulose acylate film of the present invention.

As the useful acid capturing agent, any compound capable of reacting with an acid to inactivate an acid can be used without limitation, and among them, a compound having an epoxy group described in USP 4,137,201 is preferable.

Epoxy compounds as such acid scavengers are known in the art and include diglycidyl ethers of various polyglycols, especially polyglycols derived from condensation of about 8 to 40 moles of ethylene oxide per mole of polyglycol , Diglycidyl ether of glycerol, and the like. Further, in the vinyl chloride polymer composition or in combination with the vinyl chloride polymer composition, a conventionally used metal epoxy compound, epoxidized ether condensation product, diglycidyl ether of bisphenol A (i.e., 4,4'-dihydro Epoxidized unsaturated fatty acid esters, and the like. The epoxidized unsaturated fatty acid ester is preferably an ester of a fatty acid having 2 to 22 carbon atoms and an alcohol having 2 to 4 carbon atoms, for example, butyl epoxystearate. In addition, epoxidized vegetable oils and other unsaturated natural oils, which may be exemplified and represented by compositions such as various epoxidized long chain fatty acid triglycerides such as epoxidized soybean oil and the like, are included. These fats are also referred to as epoxidized natural glycerides or unsaturated fatty acids, and the fatty acids of these fats generally contain 12 to 22 carbon atoms. EPON 815C is also preferably used as a commercially available epoxy group-containing epoxide resin compound.

Examples of the acid capturing agent which can be used in addition to the above include oxetane compounds and oxazoline compounds, organic acid salts of alkaline earth metals, acetylacetonate complexes, compounds described in paragraphs 0068 to 0105 of JP-A No. 5-194788 .

The acid scavenger is sometimes referred to as an acid scavenger, an acid scavenger, or an acid catcher. In the present invention, the acid scavenger can be used without any difference depending on their designations.

(Fine particles)

In the cellulose acylate film of the present invention, in order to improve the handleability, it is possible to use a film of a metal oxide such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, Magnesium, calcium phosphate and the like or a matting agent such as a crosslinked polymer. Among them, silicon dioxide is preferable because the haze of the cellulose acylate film can be reduced.

The primary average particle diameter of the fine particles is preferably 20 nm or less, more preferably 5 to 16 nm, and particularly preferably 5 to 12 nm.

These fine particles are preferably contained in the cellulose acylate film by forming secondary particles having an average particle diameter of 0.1 to 5.0 占 퐉, more preferably 0.1 to 2.0 占 퐉, and more preferably 0.2 to 0.6 占 퐉. Thus, irregularities having a height of about 0.1 to 1.0 mu m can be formed on the surface of the cellulose acylate film, and appropriate irregularity can be imparted to the surface by the irregularities.

The primary average particle diameter of the fine particles used in the present invention is measured by observing the particles with a transmission electron microscope (magnification: 500,000 to 2,000,000 times), observing 100 particles, measuring the particle diameter, The average primary particle diameter.

&Lt; Process for producing cellulose acylate film >

The method for producing a cellulose acylate film used in the present invention includes a step of drying a film obtained by softening a dope on a metal support, followed by peeling and stretching. Since the dope essentially contains a cellulose acylate having an acyl group substitution degree of 2.0 to 2.5 and a Tg reducing agent, the above steps are carried out such that the amount of the Tg reducing agent present on both surfaces of the obtained cellulose acylate film is somewhat biased.

The method for producing the cellulose acylate film may be a solution casting method or a melt casting method, preferably a solution casting method.

Hereinafter, a method for producing a cellulose acylate film by the solution casting method is described as an example, but the present invention is not limited to the following embodiment.

The preparation of the cellulose acylate film by the solution softening method may be carried out by, for example, a step of dissolving a cellulose acylate having an acyl group substitution degree of 2.0 to 2.5 and a Tg reducing agent and, if necessary, other additives in a solvent to prepare a dope, A step of drying the flexible dope as a web, a step of peeling off the metal support, a step of stretching or width maintaining, a step of further drying, a step of winding the finished film, It goes through.

First, the process of manufacturing the dope will be described.

The concentration of the cellulose acylate in the dope is preferably in view of reducing the drying load after being softened to the metal support, but if the concentration of the cellulose acylate is too high, the load during filtration increases and the filtration accuracy is poor . The concentration at which they are compatible is preferably 10 to 35 mass%, and more preferably 15 to 25 mass%. In addition, for the Tg-lowering agent and other additives, it is preferable to batch-add a specified amount to the dope production kiln.

The solvent used for the preparation of the dope may be used alone or in combination of two or more kinds. However, it is preferable to mix a good solvent of cellulose acylate with a poor solvent in view of production efficiency, and the cellulose acylate Which is preferable in view of the solubility of the rate.

The preferred range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass of the two solvents and 2 to 30% by mass of the poor solvent. Both solvents and poor solvents are defined as solvents in which the solvent to be used alone dissolves the cellulose acylate to be used, and solvents which are not swollen or dissolve singly are defined as poor solvents. As a result, depending on the acyl group substitution degree of the cellulose acylate, the good solvent and the poor solvent are changed.

The two solvents to be used in the present invention are not particularly limited, and examples thereof include organic halogen compounds such as methylene chloride, dioxolanes, acetone, methyl acetate, and methyl acetoacetate. Particularly preferred are methylene chloride or methyl acetate.

The poor solvent used in the present invention is not particularly limited, and for example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone and the like are preferably used. It is also preferable that 0.01 to 2.00 mass% of water is contained in the dope.

The solvent used for the dissolution of the cellulose acylate can be reused by recovering the solvent removed from the film by drying in the film-forming step.

Some of the additives added to the cellulose acylate such as a plasticizer, an ultraviolet absorber, a polymer, a monomer component and the like are contained in the recovery solvent. However, even if they are contained, they can be preferably reused and purified It can also be reused.

As a method for dissolving cellulose acylate at the time of preparing the dope, a general method can be used. When heating and pressurization are combined, heating can be performed at a boiling point or more at normal pressure.

It is preferable to stir and dissolve the solvent while heating at a temperature in the range where the solvent does not boil under a pressure of at least the boiling point of the solvent at normal pressure, thereby preventing the generation of massive solids called a gel or agglomerate.

The heating is preferably performed from the outside, and for example, a jacket type is preferable because temperature control is easy.

The heating temperature in the state in which the solvent is added is preferably from the viewpoint of the solubility of the cellulose acylate, but if the heating temperature is too high, the pressure required becomes large and the productivity becomes poor.

The preferred range of the heating temperature is 45 to 120 占 폚, more preferably 60 to 110 占 폚, and even more preferably 70 to 105 占 폚.

The pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or a method of raising the vapor pressure of the solvent by heating. The pressure is adjusted so that the solvent does not boil at the set temperature.

As a method of dissolving cellulose acylate, a method of mixing cellulose acylate with a poor solvent to wet or swell the cellulose acylate, and then adding a good solvent to dissolve the cellulose acylate is also preferably used.

In addition, a cooling dissolution method is also preferably used, whereby the cellulose acylate can be dissolved in a solvent such as methyl acetate.

This cellulose acylate solution is then filtered using a suitable filter medium such as a filter paper. As the filter medium, it is preferable that the absolute filtration accuracy is small in order to remove insolubles and the like. From the viewpoint of suppressing the occurrence of clogging of the filter medium, a filter medium having an absolute filtration accuracy of 0.008 mm or less is preferable, and a filter medium of 0.001 to 0.008 mm More preferably 0.003 to 0.006 mm, and still more preferably 0.003 to 0.006 mm.

The material of the filter medium is not particularly limited and a usual filter material can be used. However, a plastic filter material such as polypropylene or Teflon (registered trademark) or a metal filter material such as stainless steel is preferable because the fiber does not fall off .

By filtration, it is preferable to remove and reduce impurities contained in cellulose acylate as a raw material, especially foreign matter of spots.

The spot foreign object means a structure in which two polarizing plates are placed in a crossed Nicols state and an optical film or the like is placed therebetween so as to shine light on one polarizing plate side and light leakage from the opposite side when observed on the other polarizing plate side (Foreign body).

The number of spot foreign objects having a diameter of 0.01 mm or more is preferably 200 pieces / cm ² or less, more preferably 100 pieces / cm ² or less, still more preferably 50 pieces / m ² or less, particularly preferably 0 to 10 Cm / ² or less. It is also preferable that the foreign matter having a diameter of 0.01 mm or less is also small.

The filtration of the dope can be carried out by a usual method. However, a method in which the filtration is performed while heating the solvent at a temperature within a range that the solvent does not boil under a pressure of at least the boiling point of the solvent at normal pressure, Is preferable.

The preferred temperature range is 45 to 120 占 폚, more preferably 45 to 70 占 폚, and still more preferably 45 to 55 占 폚.

The filtration pressure is preferably small. 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.

Here, as described above, a series of steps are performed so that the amount of the Tg reducing agent present on both surfaces of the obtained cellulose acylate film is reduced to some extent. Concretely, the above-mentioned series of steps is performed so that the r value determined from the bonding surface of the prepared cellulose acylate film with the polarizer and the detection values d _A and d _B of the Tg reducing agent on the other side is 1.1 or more I do.

The specific method of performing the above process so that the r value is 1.1 or more is not particularly limited, and various methods can be employed. Hereinafter, three representative embodiments (first to third embodiments) will be described, but the present invention is not limited thereto.

(First Embodiment)

The first embodiment makes it possible to carry out the above process by selection of various materials at the time of manufacturing the dope. Concretely, there are three components, that is, cellulose acylate, a Tg reducing agent and a solvent, as essential components of the dope, and a material is selected so that the solubility parameter values of each of these three components satisfy a predetermined relationship. As a result, it was found that the distribution of the Tg reducing agent in the obtained cellulose acylate film can be biased in the thickness direction. More specifically, when the values of the solubility parameters of the cellulose acylate, the Tg reducing agent and the Hansen of the solvent are respectively HSP _C , HSP _G and HSP _S in this order, the respective materials are adjusted so as to satisfy the following equation (4) Select it.

(4) | HSP _{G -} HSP _C |> | HSP _{G -} HSP _S |

Hansen's solubility parameter (HSP) is a parameter developed by Charles Hansen to indicate the solubility of a substance. As the values of the solubility parameters HSP _C , HSP _G and HSP _S of Hansen, Hansen, Charles (2007). Hansen Solubility Parameters: A user's handbook, Second Edition. There may be a form in which a mixture of two or more kinds of cellulose acylate, a Tg reducing agent and a solvent are used respectively, but values measured as a mixture are adopted as the values of HSP _C , HSP _G and HSP _S in such form .

Simply described, the technical significance of the formula _{(4), | HSP G -HSP} C | , the difference between the Tg values of the solubility parameter of the reducing agent (HSP _G) to the value of the solubility parameter of the cellulose acylate (HSP _C) Quot; On the other hand, | HSP _G -HSP _S | represents the absolute value of the difference between the value of the solubility parameter (HSP _G ) of the Tg reducing agent and the value (HSP _S ) of the solubility parameter of the solvent. Then, the equation (4) is not that satisfied, E is large, a value of the solubility parameter of the Tg-lowering agent than the latter (HSP _G) close to the value of the solvent than that of the cellulose acylate (HSP _C) (HSP _S) .

When the material is selected so as to satisfy the formula (4), the mechanism in which the distribution of the Tg reducing agent in the obtained cellulose acylate film is shifted in the film thickness direction is not completely clear, but the closer the solubility parameter is, ) Is higher, the following mechanism is presumed. That is, when the film is dried on the metal support, the solvent is gradually evaporated from the surface not contacting the metal support (the interface with the air), so that a concentration gradient of the solvent occurs in the thickness direction of the cellulose acylate film. At this time, if the affinity of the Tg reducing agent to the solvent is higher than the affinity to the cellulose acylate, it is considered that the Tg reducing agent is biased toward the metal support having a higher solvent concentration.

The value of the solubility parameter HSP _{C, G} HSP, HSP _S, if satisfying the above formula _{(4), | HSP G -HSP} C | is, | _G -HSP HSP _S | of 1.1 times and preferably 1.2 times or more Or more, more preferably 1.5 times or more. By setting the content in such a range, it becomes possible to reliably manifest the unevenness of the distribution in the thickness direction of the Tg reducing agent in the produced cellulose acylate film.

Subsequently, the dope flex (cast) will be described.

The metal support used in the casting (casting) step is preferably a mirror-finished surface, and as the metal support, a stainless steel belt or a casting finish drum is preferably used.

The width of the cast may be 1 to 4 m. The surface temperature of the metal support of the softening process is preferably from -50 占 폚 to less than the boiling point of the solvent, and a high temperature is preferable because the drying speed of the web can be accelerated. However, if the temperature is too high, the web may be foamed or the planarity may deteriorate.

A preferred range of the support temperature is 0 to 55 캜, more preferably 25 to 50 캜.

It is also preferable that the web be gelled by cooling to peel off the drum in a state containing a large amount of residual solvent.

A method of controlling the temperature of the metal support is not particularly limited, but there is a method of spraying warm air or cold air with extreme pressure, or a method of bringing warm water into contact with the metal support. Use of the hot water is preferable because heat is efficiently transferred and the time until the temperature of the metal support becomes constant becomes shorter. In the case of using warm air, a wind of a temperature higher than a desired temperature may be used.

Then, the film obtained by the softening is dried and peeled off.

Here, as a second embodiment in which the distribution of the Tg reducing agent in the cellulose acylate film is shifted in the thickness direction, there is a method of controlling the process conditions after the dope is softened on the metal support.

Concretely, the amount of the residual solvent in the film at the time of peeling the film from the metal support is reduced. That is, it has been found that, by drying under more severe conditions, the distribution of the Tg reducing agent in the obtained cellulose acylate film can be shifted in the thickness direction.

More specifically, the process conditions may be controlled so that the amount of the residual solvent in the film at the time of peeling from the metal support is 90% or less. The amount of the residual solvent in the film at the time of peeling from the metal support is preferably 85% or less, more preferably 80% or less. The control according to the second embodiment and the control according to the first embodiment (selection of the material at the time of the doping) may be performed at the same time. Of course, it is also possible to produce a cellulose acylate film having a deviation of the distribution of the Tg reducing agent by either or both of the controls.

The residual solvent amount is defined by the following equation (5).

(5) Residual solvent amount (mass%) = {(M-N) / N} 100

Wherein M represents the mass of the sample collected at any point in time during or after the production of the web or cellulose acylate film and N represents the mass after heating the sample at 115 ° C for 1 hour.

As the process conditions for controlling the value of the residual solvent amount to a predetermined value or less, drying conditions before the film is peeled off from the metal support may be mentioned. There is no particular limitation on the specific form of the drying condition before the film peeling from the metal support, and controlling the drying condition so that the value of the residual solvent amount of the film at the time of peeling becomes a predetermined value or less is accompanied by a special difficulty It is possible to carry out the present invention. As an example of the drying conditions, the range of the drying temperature is preferably about 25 to 50 占 폚, and more preferably 35 to 45 占 폚. The drying time is preferably about 15 to 150 seconds, more preferably 25 to 120 seconds. It goes without saying that conditions that deviate from these ranges may be employed as far as the value of the residual solvent amount of the film at the time of peeling becomes a predetermined value or less.

There is no particular limitation on the drying means employed in the drying process, and known knowledge can be suitably referred to. Specific examples of the drying means include hot air, infrared ray, heating roller, microwave, and the like, but from the viewpoint of simplicity, it is preferable to perform the drying by hot air.

Then, the peeled film (web) is stretched from the metal support. At this time, it is particularly preferable to perform the stretching in the width direction (the direction perpendicular to the film forming direction in the plane of the film) by a tenter system in which both ends of the peeled film (web) are held by clips or the like. Further, the peeling tension from the metal support is preferably 300 N / m or less.

The film thickness and the retardation value of the obtained cellulose acylate film can be controlled by adjusting the conditions at the time of the stretching treatment.

For example, it is possible to vary the retardation by lowering or increasing the tension in the longitudinal direction. The retardation can be changed by biaxial stretching or monoaxial stretching in the longitudinal direction (also referred to as a film forming direction or the stretching direction) and the width direction of the film in order or simultaneously.

The stretching magnifications in the biaxial directions orthogonal to each other are preferably set in the range of 0.8 to 1.5 times in the longitudinal direction and 1.1 to 2.0 times in the width direction, respectively, and 0.8 to 1.1 times in the longitudinal direction and 1.3 To 1.7 times, and particularly preferably in the range of 1.3 to 1.5 times in the width direction.

The cellulose acylate film of the present invention is easy to stretch, and in some cases, retardation is easy to develop, so that the cellulose acylate film is highly resistant to process failures such as breakage.

The temperature range at the time of stretching is preferably 120 deg. C to 200 deg. C, more preferably 130 deg. C to 170 deg. C, and still more preferably 140 deg. The range of the amount of the residual solvent in the film during the stretching treatment is preferably 20 to 0%, more preferably 15 to 0%. More specifically, for example, it is preferable that the residual solvent amount is 11% at a temperature of 155 캜, or that the residual solvent amount is 2% at a temperature of 155 캜. Alternatively, it is preferable that the elongation is carried out at a temperature of 160 ° C at a residual solvent amount of 11% or at a temperature of 160 ° C at a residual solvent amount of less than 1%.

There is no particular limitation on the method of extending the web. For example, there is a method in which a plurality of rollers are provided with a main speed difference and a longitudinal direction is stretched using the main speed difference, a method in which both ends of the web are fixed with clips or pins, A method of stretching in the transverse direction in the same manner as the stretching method in the transverse direction or a method of stretching in both longitudinal and transverse directions in both longitudinal and transverse directions. Of course, these methods may be used in combination.

In the so-called tenter method, it is preferable to drive the clip portion in the linear drive system because smooth drawing can be performed and the possibility of breakage can be reduced.

This width maintenance or stretching in the transverse direction of the film-forming step is preferably performed by a tenter, and may be a pin tenter or a clip tenter.

After the above-described stretching, the step of drying is further preferably carried out so that the residual solvent amount is preferably 1 mass% or less, more preferably 0.10 mass% or less, further preferably 0.00 to 0.01 mass% or less.

The drying temperature after stretching is preferably 125 캜 or higher, and more preferably 140 캜 or higher. When the temperature exceeds 150 ° C, the glass transition temperature (Tg) of the cellulose acylate film becomes close to the lower limit of the retardation value, and the deviation of the orientation angle sometimes occurs.

The manufacturing method by the solution casting method has been described above as an example, but it may be manufactured by the melt casting method from the viewpoint of the production cost. In this case, the desired cellulose acylate film can be obtained by the control according to the second embodiment.

Molding by melt-blowing in which a solvent (for example, methylene chloride or the like) used in the solution casting method is not used is heated and melted by a melt extrusion molding method, a press molding method, an inflation method, an injection molding method, a blow molding method, Can be classified. Among them, the melt extrusion molding method is excellent in order to obtain a cellulose acylate film excellent in mechanical strength and surface precision. There is no particular limitation on a specific method for obtaining a web of cellulose acylate by the melt softening method, and known knowledge can be appropriately referred to.

In addition to the solution casting method and the melt casting method, a cellulose acylate film having a distribution of the Tg reducing agent in the thickness direction can be produced by the covalent bonding method.

Hereinafter, a method for producing a cellulose acylate film by a covalent bonding method will be described as a third embodiment in which the distribution of the Tg reducing agent in the cellulose acylate film is shifted in the thickness direction. Specifically, the manufacturing method according to the third aspect includes a step of swinging a plurality of doughs having different concentrations of the Tg reducing agent on the metal support, a step of drying the film obtained by softening, peeling, and stretching.

(Third Embodiment)

First, a plurality of dope including cellulose acylate, a Tg reducing agent, and other additives are prepared. Dose A, in which the concentration of the Tg reducing agent is low, and Doping B, in which the concentration of the Tg reducing agent is high, is prepared when the dew is two in the shared swelling state, and Dop A is shared on the surface side and Dop B is shared on the metal support That's all. When three or more dopes having different concentrations of the Tg reducing agent are covalently bonded to each other, the doping is performed in the order of increasing the concentration of the Tg reducing agent toward the metal support layer side from the surface layer side, have. The specific value of the concentration of the Tg reducing agent in the dope in the third embodiment is not particularly limited and may be appropriately adjusted in consideration of the retardation value of the entire cellulose acylate film to be obtained.

&Lt; Physical Properties of Cellulose Acylate Film >

The film thickness of the cellulose acylate film used in the present invention is preferably in the range of 10 to 200 mu m, preferably in the range of 10 to 100 mu m, more preferably in the range of 10 to 60 mu m, Lt; / RTI &gt;

The cellulose acylate film used in the present invention has a width of 1.0 to 4.0 m. Particularly preferably 1.4 to 4.0 m, more preferably 1.6 to 3.0 m. When the width is 4.0 m or less, conveyance is easy.

The retardation values (Ro, Rth) of the cellulose acylate film used in the present invention are determined by the following expressions (6) and (7).

Equation _{(6) Ro = (n x} -n y) × d [nm]

Equation (7) Rth = {(n x + n y) / 2-n z} × d [nm]

Wherein n _x represents the refractive index in the direction of the slow axis in the plane of the cellulose acylate film. and n _y represents the refractive index in the fast axis direction in the plane of the cellulose acylate film. and n _z represents the refractive index in the thickness direction of the cellulose acylate film. The refractive index is a value measured at a wavelength of 590 nm under an environment of 23 캜 and 55% RH. and d represents the thickness (nm) of the cellulose acylate film.

The retardation value (Ro, Rth) was obtained by cutting 35 mm x 35 mm of a sample from the obtained cellulose acylate film, humidity-conditioned at 25 DEG C x 55% RH for 2 hours, ), And a value measured from the vertical direction at 590 nm and an extrapolated value of a retardation value similarly measured while tilting the surface of the cellulose acylate film can be calculated.

The cellulose acylate film used in the present invention preferably has a retardation value (Ro, Rth) satisfying the following range from the viewpoint of achieving a high retardation developing ability although the phase difference required is different depending on the obtained optical compensation effect Do.

10? Ro? 100

70? Rth? 300

Here, the retardation value Ro is preferably 30 to 70, more preferably 40 to 60, and still more preferably 45 to 55.

The retardation value (Rth) is preferably 90 to 230, more preferably 100 to 170, still more preferably 110 to 160.

The angle θ1 is preferably -1 ° or more and + 1 ° or less, more preferably -0.5 ° or more and +0 ° or less, more preferably -0.5 ° or more, more preferably -0.5 ° or more, More preferably 0.5 deg. Or less.

This? 1 can be defined as an orientation angle, and the measurement of? 1 can be performed using an automatic birefringence system KOBRA-21ADH (Oji Keisoku Kiki). ? 1 respectively satisfy the above-described range, it is possible to obtain a high luminance in a display image, contribute to suppress or prevent light leakage, and contribute to achieve faithful color reproduction in a color liquid crystal display device.

The moisture permeability of the cellulose acylate film, 40 ℃, and is at 90% RH 300 to 1800g / m ² · 24h preferable, and from 400 to 1500g / m ² · 24h, far preferably from 400 to 1300g / m ² · 24h, especially desirable. The moisture permeability can be measured according to the method described in JIS Z0208.

The range of the elongation at break of the cellulose acylate film is preferably from 10 to 80%, more preferably from 20 to 50%.

The range of the visible light transmittance of the cellulose acylate film is preferably 90% or more, more preferably 93% or more.

The haze of the cellulose acylate film is preferably less than 1.0%, more preferably 0.0 to 0.1%.

<Photocurable adhesive>

Preferable examples of the photocurable adhesive for bonding the polarizer and the cellulose acylate film include a photocurable adhesive composition containing the following components (a) to (delta).

(?) cationic polymerizable compound

(?) Photo cationic polymerization initiator

(?) a photosensitizer exhibiting maximum absorption in light having a wavelength longer than 380 nm

(?) naphthalene-based photo-sensitizers

(Cationic polymerizable compound (?))

The cationic polymerizable compound (?) Which is the main component of the photocurable adhesive composition and which is a component imparting an adhesive force by polymerization and curing may be any compound that can be cured by cationic polymerization, but in particular, an epoxy compound having at least two epoxy groups in the molecule . 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 an alicyclic ring, an epoxy compound having no aromatic ring in the molecule, And an aliphatic epoxy compound in which one carbon atom of a ring (usually an oxirane ring) containing two carbon atoms to which it is bonded is bonded to another aliphatic carbon atom. The photo-curable adhesive composition used in the present invention preferably contains, as a cationic polymerizable compound (a), an epoxy resin not containing an aromatic ring, especially an alicyclic epoxy compound as a main component. The use of a cationic polymerizable compound containing a cycloaliphatic epoxy compound as a main component allows a polarizer to be provided with a cured product having a high storage modulus and to which a cellulose acylate film and a polarizer are bonded via the cured product (adhesive layer) It becomes 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 means that two bonds of the epoxy group (-O-) are bonded to two carbon atoms constituting an alicyclic ring (usually adjacent carbon Atoms) in the molecule. In the following formula (ep), m represents an integer of 2 to 5.

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

Among the alicyclic epoxy compounds, compounds represented by any one of the following formulas (ep-1) to (ep-11) are more preferable since they are easy to obtain and have a large effect of increasing the storage modulus of the cured product.

In the formula, R ³ to R ²⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and when R ³ to R ²⁴ are alkyl groups, the position bonding to the alicyclic ring is preferably from 1 to 6 Any number above. The alkyl group having 1 to 6 carbon atoms may be straight-chain, branched 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 represent a straight-chain, branched or straight-chain alkanediyl group having 1 to 20 carbon atoms which may have an alicyclic ring. n, p, q and r each independently represent a number of 0 to 20;

Of the compounds represented by the above-mentioned formulas (ep-1) to (ep-11), alicyclic diepoxy compounds represented by formula (ep-2) are preferred since they are readily available. The alicyclic diepoxy compound of the formula (ep-2) can be produced by reacting 3,4-epoxycyclohexylmethanol (the cyclohexane ring may have an alkyl group having 1 to 6 carbon atoms) and 3,4-epoxycyclohexanecarboxylic acid (An alkyl group having 1 to 6 carbon atoms may be bonded to the cyclohexane ring). Specific examples of such an ester compound include 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (a compound wherein R ⁵ = R ⁶ = H, n = 0 in the formula (ep-2) 6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate (In the formula (ep-2), R ⁵ = 6-methyl, R ⁶ = = 0), and the like.

Further, it is effective to use an epoxy resin having substantially no alicyclic epoxy group in combination with the alicyclic epoxy compound. When a cationically polymerizable compound is used in which an alicyclic epoxy compound as a main component and an epoxy resin substantially not having an alicyclic epoxy group are used in combination with the alicyclic epoxy compound as the main component and the cured product has a high storage modulus, The adhesion can be further enhanced. Herein, the epoxy resin having substantially no alicyclic epoxy group means a compound in which one carbon atom of a ring (usually an oxirane ring) having two epoxy groups and two carbon atoms to which the epoxy group is bonded is bonded to another aliphatic carbon atom in the molecule to be. Examples thereof include polyglycidyl ethers of polyhydric alcohols (phenols). Of these, a diglycidyl ether compound represented by the following formula (ge) is preferable because it is easy to obtain and has a high effect of enhancing the adhesion between the polarizer and the cellulose acylate film.

Wherein 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, To (ge-3), and the alkylidene group may be substituted with a halogen atom.]

In formula (ge-1), R ²⁵ and R ²⁶ each independently represent a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 10 carbon atoms or a phenyl group which may be substituted by an alkoxy group, A cycloalkyl group having 3 to 10 carbon atoms which may be substituted with an alkyl group or alkoxy group of 1 to 10, and R ²⁵ and R ²⁶ may be connected to each other to form a ring.

In formula (ge-2), A and D each independently represent an alkyl group having 1 to 10 carbon atoms which may be substituted with a halogen atom, an aryl group having 6 to 20 carbon atoms which may be substituted with a halogen atom, An arylalkyl group having 7 to 20 carbon atoms which may be substituted, a heterocyclic group having 2 to 20 carbon atoms which may be substituted with a halogen atom or a halogen atom, and the methylene group in the alkyl group, aryl group or arylalkyl group may be 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 diglycidyl ether compounds of the formula (ge) include bisphenol-type epoxy resins such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F and diglycidyl ether of bisphenol S; A multifunctional epoxy resin such as glycidyl ether of tetrahydroxyphenylmethane, glycidyl ether of tetrahydroxybenzophenone, and epoxidized polyvinyl phenol; Polyglycidyl ethers of aliphatic polyhydric alcohols; Polyglycidyl ethers of alkylene oxide adducts of aliphatic polyhydric alcohols; And diglycidyl ether of an alkylene glycol. Of these, a polyglycidyl ether of an aliphatic polyhydric alcohol is preferable because it is easy to obtain.

As the aliphatic polyhydric alcohol, for example, those having a carbon number of 2 to 20 can be exemplified. More specifically, there may be mentioned, for example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, , 1,4-butanediol, neopentyl glycol, 3-methyl-2,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, Pentanediol, 1,6-hexanediol, 1,7-heptanediol, 3,5-heptanediol, 1,8-octanediol, Aliphatic diols such as 2-methyl-1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol; Alicyclic diols such as cyclohexane dimethanol, cyclohexanediol, hydrogenated bisphenol A and hydrogenated bisphenol F; Trimethylol ethane, trimethylol propane, hexitol, pentitol, glycerin, polyglycerin, pentaerythritol, dipentaerythritol, and tetramethylol propane.

When an alicyclic epoxy compound and an epoxy resin having substantially no alicyclic epoxy group are used in combination, the compounding ratio of the alicyclic epoxy compound and the alicyclic epoxy compound is preferably 50 to 95% by mass, It is preferable that an epoxy resin having no substantial epoxy group is contained in an amount of 5% by mass or more. When the alicyclic epoxy compound is blended in an amount of 50 mass% or more in the entire cationic polymerizable compound, the storage elastic modulus at 80 캜 of the cured product becomes 1,000 MPa or more, and the polarizer and the cellulose acylate film are bonded The polarizer is less likely to be broken. Further, by adding an epoxy resin having substantially no alicyclic epoxy group to the cationic polymerizable compound in an amount of 5% by mass or more, adhesion between the polarizer and the cellulose acylate film is improved. When the cationic polymerizable compound is a two-component system with an alicyclic epoxy compound, the amount of the epoxy resin having substantially no alicyclic epoxy group is allowed up to 50 mass% based on the amount of the cationic polymerizable compound as a whole, It is preferable that the amount of the cationic polymerizable compound is set to 45 mass% or less based on the total amount of the cationic polymerizable compound from the viewpoint of suppressing the lowering of the elastic modulus and preventing breakage of the polarizer.

When an alicyclic epoxy compound as described above and an epoxy resin having substantially no alicyclic epoxy group are used in combination as the cationic polymerizable compound (?) Constituting the photocurable adhesive composition, In addition to these, other cationic polymerizable compounds may be contained. Examples of other cationic polymerizable compounds include epoxy compounds and oxetane compounds other than the formulas (ep-1) to (ep-11) and (ge).

Epoxy compounds other than the formulas (ep-1) to (ep-11) and (ge) include epoxy groups which are bonded to at least one alicyclic ring in the molecule other than the formulas (ep- An alicyclic 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 a molecule, a hydrogenated epoxy having an aromatic ring hydrogenated in an aromatic epoxy compound Compounds.

Examples of the alicyclic epoxy compound having an epoxy group bonded to at least one alicyclic ring in the molecule other than the formulas (ep-1) to (ep-11) include 4-vinylcyclohexene diepoxide, And diepoxide of vinylcyclohexanes such as 9-diepoxy limonene.

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

The aromatic epoxy compound having an aromatic ring and an epoxy group in the molecule may be a glycidyl ether of an aromatic polyhydroxy compound having at least two phenolic hydroxy groups in the molecule. Specific examples thereof include diglycidyl ether of bisphenol A, Diglycidyl ether of bisphenol F, diglycidyl ether of bisphenol S, glycidyl ether of phenol novolac resin, and the like.

The hydrogenated epoxy compound in which the aromatic ring in the aromatic epoxy compound is hydrogenated is obtained by subjecting an aromatic polyhydroxy compound having at least two phenolic hydroxyl groups in a molecule which is a raw material of the above aromatic epoxy compound to hydrogenation To obtain a glycidyl etherified 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 the above-mentioned formulas (ep-1) to (ep-11) and (ge), when a compound having an epoxy group bonded to an alicyclic ring and categorized as the alicyclic epoxy compound defined above is compounded, And the alicyclic epoxy compound represented by the formula (ep-1) to (ep-11) is used in a range not exceeding 95 mass% based on the total amount of the cationic polymerizable compound.

The oxetane compound which can be any cationic 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] Ethyl-3- (cyclohexyloxymethyl) oxetane, 3-ethyl-3- (2-ethylhexyloxymethyl) Cetane, phenol novolak oxetane, 1,3-bis [(3-ethyloxetan-3-yl) methoxy] benzene, oxetanyl silsesquioxane, oxetanil silicate and the like.

By mixing the oxetane compound in a proportion of 30 mass% or less based on the total amount of the cationic polymerizable compound, an effect of improving the curability can be expected as compared with the case where only the epoxy compound is used as the cationic polymerizable compound .

(Photo cationic polymerization initiator (?))

In the present invention, the cationic polymerizable compound as described above is cationically polymerized and cured by irradiation with an active energy ray to form an adhesive layer, so that the photo-curable adhesive composition preferably contains a photo cationic polymerization initiator (?) .

The cationic photopolymerization initiator (?) Generates a cationic species or a Lewis acid by irradiation of an active energy ray such as visible light, ultraviolet ray, X-ray or electron beam to initiate the polymerization reaction of the cationic polymerizable compound (?) . Since the photo cationic polymerization initiator (?) Acts catalytically with light, it is excellent in storage stability and workability even when it is mixed with the cationic polymerizable compound (?). As a compound which generates cationic species or Lewis acid by irradiation with an active energy ray, for example, 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 benzene diazonium hexafluoroantimonate, benzene diazonium hexafluorophosphate, and benzene diazonium hexafluoroborate.

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

Examples of the aromatic sulfonium salt include triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis (pentafluorophenyl) borate, 4,4'-bis [di 4,4'-bis [di (? - hydroxyethoxy) phenylsulfonio] diphenylsulfide bis hexafluoroantimonate, 4,4'-bis [ Di (p-toluyl) sulfonium] -2-isopropylthioquinoxaline, bis (4-hydroxyphenyl) diphenylsulfide bishexafluorophosphate, (Pentafluorophenyl) borate, 4-phenylcarbonyl-4'-di (pentafluorophenyl) borate, and 2-isopropylthioxanthone tetrakis Phenylsulfonio-diphenylsulfide hexafluorophosphate, 4- (p-tert-butylphenylcarbonyl) -4'-diphenylsulfone-diphenylsulfide hex (P-tert-butylphenylcarbonyl) -4'-di (p-toluyl) sulfonio-diphenylsulfide tetrakis (pentafluorophenyl) borate, and the like. have.

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

These photo cationic polymerization initiators (?) May be used alone or in combination of two or more. Among them, the aromatic sulfonium salt is preferably used because it has an ultraviolet ray absorbing property even in a wavelength region around 300 nm, is excellent in curability, can give a cured product having good mechanical strength and adhesive strength.

The blending amount of the cationic photopolymerization initiator (?) Is 1 to 10 parts by mass based on 100 parts by mass of the cationic polymerizable compound (?). By mixing at least 1 part by mass of the cationic photopolymerization initiator (?) Per 100 parts by mass of the cationic polymerizable compound (?), The cationic polymerizable compound (?) Can be sufficiently cured and a high mechanical strength and adhesion strength do. On the other hand, when the amount of the cationic polymerization initiator (b) is increased, the amount of the ionic substance in the cured product increases, and the hygroscopicity of the cured product is increased, which may lower the endurance performance of the polarizing plate. ?) is less than or equal to 10 parts by mass per 100 parts by mass.

The blending amount of the photo cationic polymerization initiator (β) is preferably 2 parts by mass or more, more preferably 6 parts by mass or less, per 100 parts by mass of the cationic polymerizable compound (α).

(Photosensitizer (?))

The photo-curable adhesive composition that can be used in the present invention is a photo-curable adhesive composition which contains, in addition to the cationic polymerizable compound (?) And the photo cationic polymerization initiator (?) Containing an epoxy compound as described above, (?). The photo cationic polymerization initiator (?) Exhibits maximum absorption at a wavelength of around 300 nm or shorter and generates a cationic species or a Lewis acid in response to light of a wavelength in the vicinity thereof to form a cationic polymerizable compound A polymerization initiator is added, but a photosensitizer (gamma) exhibiting maximum absorption in light having a wavelength longer than 380 nm is added so as to respond to light having a wavelength longer than that.

As such photosensitizer (?), An anthracene-based compound represented by the following formula (at) 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. And 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 formula (at) include 9,10-dimethoxyanthracene, 9,10-diethoxyanthracene, 9,10-dipropoxyanthracene, 9,10-diisopropoxyanthracene, Bis (2-methoxyethoxy) anthracene, 9,10-bis (2-ethoxyphenyl) anthracene, 9,10-dibutoxyanthracene, (3-butoxypropoxy) anthracene, 2-methyl or 2-ethyl-9,10-dimethoxyanthracene, 9,10-bis (2-butoxyethoxy) anthracene, Methyl or 2-ethyl-9,10-diethoxy anthracene, 2-methyl or 2-ethyl-9,10-dipropoxyanthracene, 2- Methyl or 2-ethyl-9,10-dibutoxyanthracene, 2-methyl or 2-ethyl-9,10-dipentyloxyanthracene, 2- And the like.

By compounding the photosensitizer (?) As described above in the photo-curable adhesive composition, the curability of the photo-curable adhesive composition is improved as compared with the case where it is not blended. When the blending amount of the photosensitizer (?) Relative to 100 parts by mass of the cationic polymerizable compound (?) Constituting the photocurable adhesive composition is 0.1 part by mass or more, an effect of improving the curability is exhibited. On the other hand, in order to prevent precipitation during storage at a low temperature, the amount is 2 parts by mass or less based on 100 parts by mass of the cationic polymerizable compound (?). From the viewpoint of maintaining the neutral gray of the polarizing plate, it is advantageous to reduce the blending amount of the photosensitizer (?) Within a range where the adhesiveness between the polarizer and the cellulose acylate film is appropriately maintained. For example, the amount of the photosensitizer (y) is preferably in the range of 0.1 to 0.5 parts by mass, more preferably 0.1 to 0.3 parts by mass, based on 100 parts by mass of the cationic polymerizable compound (?).

(Photosensitivity assisting agent (?))

The photo-curable adhesive composition that can be used in the present invention is a composition comprising a cationic polymerizable compound (a), a photo cationic polymerization initiator (?), And a photosensitizer (?) Comprising the above epoxy compound, And a naphthalene-based photo-sensitization assistant (?).

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

Specific examples of the naphthalene-based photosensitizer (隆) include 1,4-dimethoxynaphthalene, 1-ethoxy-4-methoxynaphthalene, 1,4-diethoxynaphthalene, 4-dibutoxynaphthalene, and the like.

The curing property of the photo-curable adhesive composition is improved by blending the photo-curable adhesive composition with the naphthalene-based photo-sensitization assistant (?), As compared with the case where it is not blended. When the blending amount of the naphthalene-based photo-sensitizers (?) Relative to 100 parts by mass of the cationic polymerizable compound (?) Constituting the photo-curable adhesive composition is 0.1 part by mass or more, an effect of improving the curability is exhibited. On the other hand, the blending amount of the naphthalene-type photo-sensitization assistant (δ) is adjusted to 10 parts by mass or less based on 100 parts by mass of the cationic polymerizable compound (α) in order to prevent precipitation during storage at a low temperature. The amount is preferably 5 parts by mass or less based on 100 parts by mass of the cationic polymerizable compound (?).

Further, the photo-curable adhesive composition that can be used in the present invention may contain an additive component as another component, which is an optional component, so long as the effect of the present invention is not impaired. Examples of the additive component include a photosensitizer other than the photosensitizer (?), A thermal cationic polymerization initiator, a polyol, an ion trapping agent, an antioxidant, a light stabilizer, and a chain transfer agent other than the photo- A lubricant, a flow regulator, a plasticizer, a defoaming agent, a leveling agent, a coloring matter, an organic solvent and the like can be added.

When the additive component is contained, the amount of the additive component used is preferably 1000 parts by mass or less based on 100 parts by mass of the cationic polymerizable compound (a). (?), A photo cationic polymerization initiator (?), A photosensitizer (?) And a photosensitizer (?), Which are essential components of the photocurable adhesive composition that can be used in the present invention, ), It is possible to satisfactorily exhibit the effect of improving storage stability, preventing discoloration, improving the curing rate, and securing good adhesiveness.

Another preferred example of an adhesive for bonding a polarizer and a cellulose acylate film includes a photo-curable adhesive composition containing essentially the following three components (? 1), (? 2) and (? 1).

(? 1) an epoxy compound having at least two epoxy groups in the molecule

(? 2) oxetane compound having at least one oxetanyl group in the molecule

(? 1) photo cationic polymerization initiator

Hereinafter, the epoxy compound (α1), the oxetane compound (α2), and the photocationic polymerization initiator (β1) are respectively referred to as epoxy compound (α1), oxetane compound (α2), photo cationic polymerization initiator beta 1).

It is preferable that the mass ratio (epoxy compound (? 1): oxetane compound (? 2)) of the epoxy compound (? 1) and the oxetane compound (? 2) is about 90:10 to 10:90. The photo cationic polymerization initiator (? 1) is preferably blended at a ratio of about 0.5 to 20.0 mass% in the composition.

The photocurable adhesive may optionally contain an unsaturated compound having at least one ethylenic unsaturated bond in the molecule as the (?) Component. In the case of containing such an unsaturated compound (?), It is preferable to contain a photo radical polymerization initiator as the (?) Component. The photo-curable adhesive may also contain other components that do not have polymerizability as the component (eta).

(Ε), a photo radical polymerization initiator (ζ), a polymerization initiator (ζ), a photo radical polymerization initiator (ζ), and a photo radical polymerization initiator It is called another component (?) Having no property.

(Epoxy compound (? 1))

In the photocurable adhesive composition that can be used in the present invention, the epoxy compound (? 1) is not particularly limited as long as it has at least two epoxy groups in the molecule, and various generally known curable epoxy compounds can be used. The preferable epoxy compound (? 1) is an aromatic epoxy compound having at least two epoxy groups and at least one aromatic ring in the molecule or at least two epoxy groups in the molecule, and at least one of them is adjacent to the alicyclic ring And an alicyclic epoxy compound which is formed between the two carbon atoms.

The aromatic epoxy compound is not particularly limited as long as it does not interfere with the effect of the present invention. However, diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, diglycidyl ether of brominated bisphenol A, The same bisphenol type epoxy resin; Novolak type epoxy resins such as phenol novolak type epoxy resin and cresol novolak type epoxy resin; In addition, there may be mentioned, for example, biphenyl type epoxy resins, hydroquinone diglycidyl ether, resorcin diglycidyl ether, diglycidyl terephthalate, diglycidyl phthalate, epoxides of styrene-butadiene copolymers, styrene- Epoxides of a copolymer, addition reactants of a terminal carboxylic acid polybutadiene and a bisphenol A type epoxy resin, and the like.

The epoxy resin as used herein refers to a compound or polymer having two or more epoxy groups on average in the molecule and curing by reaction. Depending on the custom in the field, even a monomer may be referred to as an epoxy resin if it has two or more curable epoxy groups in the molecule.

The alicyclic epoxy compound is not particularly limited as long as it does not interfere with the effect of the present invention. Examples of the alicyclic epoxy compound include dicyclopentadiene dioxide, limonene dioxide, 4-vinylcyclohexene dioxide, 3,4-epoxycyclohexylmethyl- , 4-epoxycyclohexanecarboxylate, and bis (3,4-epoxycyclohexylmethyl) adipate. Examples of the compound having at least one epoxycyclohexyl group include, for example,

In addition to the above, aliphatic epoxy compounds such as 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether and polytetramethylene glycol diglycidyl ether; An epoxy compound in which an aromatic ring such as diglycidyl ether of hydrogenated bisphenol A is hydrogenated; A compound in which both ends of the polybutadiene of both end hydroxyl groups are glycidyl etherified, an internal epoxide of polybutadiene, a compound in which a double bond of a styrene-butadiene copolymer is partially epoxidized (for example, (For example, L-207 manufactured by KRATON), an epoxy compound of a polymerization system such as a compound in which an isoprene unit of a block copolymer of an ethylene-butylene copolymer and polyisoprene is partially epoxidized May also be an epoxy compound (? 1).

Among them, the aromatic epoxy compound is preferable because it has excellent durability when used in a polarizing plate and is particularly excellent in adhesion to a polarizer and a cellulose acylate film. As the aromatic epoxy compound, a glycidyl ether of an aromatic compound or a glycidyl ester of an aromatic compound may be mentioned as a preferable example. Specific examples of the glycidyl ether of the aromatic compound include bisphenol-type epoxy resins such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, and diglycidyl ether of brominated bisphenol A; Novolak type epoxy resins such as phenol novolak type epoxy resin and cresol novolak type epoxy resin; Biphenyl type epoxy resins; Hydroquinone diglycidyl ether; Resorcine diglycidyl ether, and the like. Specific examples of glycidyl esters of aromatic compounds include diglycidyl ester of terephthalic acid, diglycidyl ester of phthalic acid, and the like.

Among them, the glycidyl ether of the aromatic compound is particularly preferable because it is more excellent in adhesion between the polarizer and the cellulose acylate film and durability when used in a polarizing plate. Among glycidyl ethers of aromatic compounds, particularly preferred compounds are diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, and phenol novolak type epoxy resin.

The epoxy compound (? 1) may be used singly or in combination of two or more kinds. For example, two or more kinds of aromatic epoxy compounds may be used in combination, or alicyclic epoxy compounds may be mixed mainly using an aromatic epoxy compound.

(Oxetane compound (? 2))

In the photocurable adhesive that can be used in the present invention, the oxetane compound (? 2) is not particularly limited as long as it has at least one oxetanyl group in the molecule, and various compounds having an oxetanyl group can also be used. As the oxetane compound (? 2), a compound having one oxetanyl group in the molecule (hereinafter referred to as monofunctional oxetane), a compound having two or more oxetanyl groups in the molecule (hereinafter referred to as polyfunctional oxetane) As a preferable example.

Examples of the monofunctional oxetane include monofunctional oxetane containing an alkoxyalkyl group such as 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, aromatic group-containing monofunctional group such as 3-ethyl- Oxetane, and 3-ethyl-3-hydroxymethyloxetane; and the like.

Examples of the polyfunctional oxetane include 3-ethyl-3 - [(3-ethyloxetan-3-yl) methoxymethyl] oxetane, 1,4-bis [ ) Methoxymethyl] benzene, 1,4-bis [(3-ethyloxetan-3-yl) methoxy] benzene, 1,3-bis [ , Bis [(3-ethyloxetan-3-yl) methoxy] biphenyl, 2,2- 3,3 ', 5,5'-tetramethyl-4,4'-bis [(3-ethyloxetane-3-yl) methoxy] Methoxy] naphthalene, bis [4 - {(3-ethyloxetan-3-yl) methoxy} biphenyl, 2,7- ] Methane, bis [2 - {(3-ethyloxetan-3-yl) methoxy} phenyl] methane, 2,2- ] Propane, 3-chloromethyl-3-ethyloxetane etherified product of novolac phenol-formaldehyde resin, 3 (4), 8 (9) -bis [ Yl) methoxy Methyl] -tricyclo [5.2.1.0 2,6] decane, 2,3-bis [(3-ethyloxetan-3- yl) methoxymethyl] norbornane, 1,1,1- Methoxymethyl] propane, 1-butoxy-2,2-bis [(3-ethyloxetan-3-yl) methoxymethyl] - [(3-ethyloxetan-3-yl) methoxy} ethylthio] ethane, bis [ (3-ethyloxetan-3-yl) methoxy] -2,2,3,3,4,4,5,5-octafluorohexane, 3- [ Methoxy] propyltriethoxysilane, condensates of tetrakis [(3-ethyloxetan-3-yl) methyl] silicate, and the like.

The oxetane compound (? 2) is preferably liquid at room temperature having a molecular weight of 500 or less, from the viewpoints of coating workability and adhesion to a cellulose acylate film when used in a polarizing plate. Further, from the viewpoint that the polarizing plate has excellent durability, monofunctional oxetane is preferable because it has an aromatic ring in the molecule or polyfunctional oxetane. Examples of such preferred oxetane compounds include 3-ethyl-3-phenoxymethyloxetane, 3-ethyl-3 - [(3-ethyloxetan-3- yl) methoxymethyl] oxetane, Bis [(3-ethyloxetan-3-yl) methoxymethyl] benzene and the like.

The oxetane compound (? 2) may be used singly or in a mixture of two or more kinds.

The mass ratio (epoxy compound (? 1): oxetane compound (? 2)) of the epoxy compound (? 1) and the oxetane compound (? 2) is 90:10 to 10:90. If the mass ratio is too large, the effect of curing in a short time, which is one of the important characteristics of the photo-curable adhesive composition that can be used in the present invention, is not sufficiently exhibited. The preferable mass ratio is about 70:30 to 20:80, more preferably about 60:40 to 25:75 in terms of good coatability at a low point before curing and sufficient adhesion and flexibility after curing, And so on.

(Photo cationic polymerization initiator (? 1))

The photo-curable adhesive composition that can be used in the present invention contains the above-mentioned epoxy compound (? 1) and oxetane compound (? 2) as curing components and all of them are cured by cationic polymerization, A cationic photopolymerization initiator (? 1) is blended. The cationic cationic polymerization initiator (? 1) generates a cationic species or a Lewis acid by irradiation of an active energy ray such as visible light, ultraviolet ray, X-ray or electron beam to initiate polymerization reaction of an epoxy group or oxetanyl group.

By blending the photo cationic polymerization initiator (? 1), it becomes possible to cure at room temperature, and there is little need to consider the heat resistance of the polarizer and the distortion caused by the expansion or contraction, so that the cellulose acylate film can be favorably adhered. Further, since the photo cationic polymerization initiator (? 1) acts catalytically by irradiation of an active energy ray, it is excellent in storage stability and workability even when mixed with the epoxy compound (? 1) and the oxetane compound (? 2).

As the photo cationic polymerization initiator (? 1) which generates cationic species or Lewis acid by irradiation with such active energy rays, for example, onium salts such as aromatic diazonium salts, aromatic iodonium salts and aromatic sulfonium salts, iron- .

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

Examples of the aromatic iodonium salt include diphenyl iodonium tetrakis (pentafluorophenyl) borate, diphenyl iodonium hexafluorophosphate, diphenyl iodonium 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) diphenylsulfide bishexafluoro Bis [di (? - hydroxyethoxy) phenylsulfonio] diphenyl sulfide bishexafluoroantimonate, 4,4'-bis [di (? - hydroxy (P-toluyl) sulfonium] -2-isopropylthioxanthone hexafluoroantimonate, 7- [di (p-toluyl) sulfonyl] -2-isopropylthioxanthone hexafluoroantimonate, (p-toluyl) sulfonio] -2-isopropylthioxanthone tetrakis (pentafluorophenyl) borate, 4-phenylcarbonyl- 4'-diphenylsulfone-diphenylsulfide hexafluorophosphate, 4- (p-tert-butylphenylcarbonyl) -4'-diphenylsulfonio-diphenylsulfide hexafluoroantimonate , And 4- (p-tert-butylphenylcarbonyl) -4'-di (p-toluyl) sulfonio-diphenylsulfide tetrakis (pentafluorophenyl) borate.

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

Each of these photo cationic polymerization initiators (? 1) may be used alone or in combination of two or more. Among them, aromatic sulfonium salts are preferably used since they have an ultraviolet ray absorption property even in a wavelength region of 300 nm or more, and are therefore excellent in curability and can give a cured product having good mechanical strength and adhesive strength.

The cationic cationic polymerization initiator (? 1) is commercially available, for example, Kayarad PCI-220, Kayalad PCI-620 (manufactured by Nippon Kayaku Co., Ltd.), UVI (ADEKA), CI-5102, CIT-1370, CIT-1682 (manufactured by Dow Chemical Company), ADEKA OPTOMER SP-150 and ADEKA OPTOMER SP- DPI-101, DPI-102, DPI-103, DPI-105, MPI-103, MPI-105 and BBI-101 (manufactured by NIPPON SODA CO., LTD.), CIP-1866S, CIP- , BBI-102, BBI-103, BBI-105, TPS-101, TPS-102, TPS-103, TPS-105, MDS-103, MDS-105, DTS- (Manufactured by Shiba Co., Ltd.), CPI-100P (manufactured by Shimadzu Corporation), PI-2074 (manufactured by Rhodia), Irgacure 250, Irgacure PAG103, Irgacure PAG108, Irgacure PAG121, Irgacure PAG203 , CPI-101A, CPI-200K and CPI-210S (manufactured by Sanyo-Afro Co., Ltd.). Of these, UVI-6992, CPI-100P, CPI-101A, CPI-200K and CPI-210S, which contain diphenyl [4- (phenylthio) phenyl] sulfonium as a cation component, are preferred.

The blending ratio of the photo cationic polymerization initiator (? 1) is set in the range of 0.5 to 20.0% by mass based on the entire photo-curable adhesive. When the blending ratio is 0.5% by mass or more, the photocurable adhesive sufficiently cures, and mechanical strength and adhesive strength can be maintained. On the other hand, when the compounding ratio is 20% by mass or less, an increase in the hygroscopic property of the cured product due to an increase in the ionic substance in the cured product is suppressed, and the decrease in durability can be prevented.

(Unsaturated compound (?))

The photocurable adhesive may contain an unsaturated compound (?) Having at least one ethylenic unsaturated bond in the molecule, if necessary.

Typical examples of such unsaturated compounds (?) Include (meth) acrylic compounds having at least one (meth) acryloyl group in the molecule.

Examples of the (meth) acrylic compound include, but are not limited to, (meth) acrylates, (meth) acrylamides, (meth) acrylic acid, (meth) acryloylmorpholines, .

(Meth) acrylates having one (meth) acryloyl group in the molecule (hereinafter referred to as monofunctional (meth) acrylate) are not particularly limited and include, for example, methyl (meth) acrylate, ethyl (Meth) acrylate, isopropyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl Alkyl (meth) acrylates such as isooctyl (meth) acrylate, lauryl (meth) acrylate and stearyl (meth) acrylate; Hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate; (Meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyl (meth) acrylate, Alicyclic monofunctional (meth) acrylates such as dicyclopentenyloxyethyl (meth) acrylate; (Meth) acrylate of benzyl (meth) acrylate, p-cumylphenol alkylene oxide adduct, (meth) acrylate of an o-phenylphenol alkylene oxide adduct, (meth) acrylate of a phenol alkylene oxide adduct, Monofunctional (meth) acrylates having an aromatic ring such as (meth) acrylate of phenol alkylene oxide adducts (here, examples of alkylene oxides include ethylene oxide and propylene oxide); Alkoxyalkyl (meth) acrylates such as 2-methoxyethyl (meth) acrylate, ethoxymethyl (meth) acrylate and alkylene oxide adducts of 2-ethylhexyl alcohol; Mono (meth) acrylates of divalent alcohols such as ethylene glycol mono (meth) acrylate, propylene glycol mono (meth) acrylate, pentanediol mono (meth) acrylate and hexanediol mono (meth) acrylate; Mono (meth) acrylate of diethylene glycol, mono (meth) acrylate of triethylene glycol, mono (meth) acrylate of tetraethylene glycol, mono (meth) acrylate of polyethylene glycol, mono (meth) acrylate of dipropylene glycol Mono (meth) acrylates of polyalkylene glycols such as mono (meth) acrylate of polypropylene glycol, mono (meth) acrylate of tripropylene glycol, and mono (meth) acrylate of polypropylene glycol; Glycidyl (meth) acrylate; Tetrahydrofurfuryl (meth) acrylate; Tetrahydrofurfuryl (meth) acrylates such as caprolactone-modified tetrahydrofurfuryl (meth) acrylate; 3,4-epoxycyclohexylmethyl (meth) acrylate; N, N-dimethylaminoethyl (meth) acrylate; 2- (meth) acryloyloxyethyl isocyanate, and the like.

The (meth) acrylates having two or more (meth) acryloyl groups in the molecule are not particularly limited, and for example, the following compounds may be mentioned.

(Meth) acrylate such as tricyclodecane dimethylol di (meth) acrylate, 1,4-cyclohexanedimethylol di (meth) acrylate, norbornane dimethylol di (meth) acrylate and hydrogenated bisphenol A Di (meth) acrylates having a ring structure; Di (meth) acrylates of bisphenol A ethylene oxide adducts, di (meth) acrylates of bisphenol A alkylene oxide adducts including di (meth) acrylates of bisphenol A propylene oxide adducts, bisphenol A diglycidyl Di (meth) acrylates having an aromatic ring such as di (meth) acrylate of an ether; Di (meth) acrylates of alkylene glycols such as ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, pentanediol di (meth) acrylate and hexanediol di (meth) acrylate; Acrylates such as diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, dipropylene glycol di Di (meth) acrylates of polyalkylene glycols such as propylene glycol di (meth) acrylate and polypropylene glycol di (meth) acrylate; Di- or tri (meth) acrylates of glycerin such as di or tri (meth) acrylate of glycerin, di or tri (meth) acrylate of diglycerin; Di- or tri (meth) acrylates of alkylene oxide adducts of glycerine type; Di (meth) acrylates of bisphenol A alkylene oxide adducts such as di (meth) acrylate and di (meth) acrylate of bisphenol F alkylene oxide adducts; (Meth) acrylate, trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tri (meth) acrylate, ditrimethylolpropane tetra Polyol poly (meth) acrylates such as dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate; Poly (meth) acrylates of alkylene oxide adducts of these polyols; Di or tri (meth) acrylates of isocyanuric acid alkylene oxide adducts; 1,3,5-tri (meth) acryloylhexahydro-s-triazine, and the like.

(Meth) acrylamides include N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-isopropylacrylamide, (Meth) acrylamide, N-methylol (meth) acrylamide, N-methylol (meth) acrylamide, Aminomethyl (meth) acrylamide, aminoethyl (meth) acrylamide, mercaptomethyl (meth) acrylamide, and mercaptoethyl (meth) acrylamide.

Oligomers such as urethane (meth) acrylate, polyester (meth) acrylate and epoxy (meth) acrylate can also be used as (meth) acrylic compounds.

Further, a compound having an ethylenically unsaturated bond other than the (meth) acryloyl group may also be used as the (meth) acrylic compound. Specific examples thereof include allyl (meth) acrylate and N, N-diallyl (meth) acrylamide.

The unsaturated compound (?) 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; Aryl compounds such as triallyl isocyanurate, triallylamine, tetraallyl pyromellitate, N, N, N ', N'-tetraallyl-1,4-diaminobutane, tetraallyl ammonium salt and allylamine; Unsaturated carboxylic acids such as maleic acid and itaconic acid may also be used.

Among these unsaturated compounds (?), (Meth) acrylic compounds are preferable. When a polarizer and a cellulose acylate film are bonded to each other through an adhesive containing the polarizer and a cellulose acylate film, the polarizing plate is preferably made of a (meth) acrylate having at least one alicyclic skeleton or aromatic cyclic skeleton in the molecule from the viewpoint of enhancing durability, An acrylic compound is more preferable. Specific examples of the (meth) acrylic compound having at least one alicyclic skeleton or aromatic ring skeleton in the molecule include alicyclic monofunctional (meth) acrylates, monofunctional (meth) acrylates having aromatic rings , Di (meth) acrylates having an alicyclic ring or di (meth) acrylates having an aromatic ring. Among them, di (meth) acrylate having a tricyclodecane skeleton is particularly preferable, and specific examples of such particularly preferable (meth) acrylic compounds include tricyclodecane dimethylol di (meth) acrylate.

The unsaturated compound (?) Can be used to control the curing rate, the adhesion between the polarizer and the cellulose acylate film, the elastic modulus of the adhesive layer, and the durability of the adhesive. The unsaturated compound (?) Can be used singly or in a mixture of two or more kinds.

When the unsaturated compound (?) Is compounded, the compounding ratio thereof is preferably 35% by mass or less based on the entire composition. As a result, the adhesion between the polarizer and the cellulose acylate film is excellent. When the amount of the unsaturated compound (epsilon) is 35 mass% or less, sufficient adhesion strength with the polarizer is likely to be obtained. Therefore, the blending ratio of the unsaturated compound (?) Is more preferably 30% by mass or less, still more preferably from 5 to 25% by mass, particularly preferably from 10 to 20% by mass.

(Photo radical polymerization initiator (?))

When the photo-curable adhesive contains an unsaturated compound (?), It is preferable to blend the photo radical polymerization initiator (?) In order to accelerate the radical polymerizability and make the curing rate sufficient.

Specific examples of the photo radical polymerization initiator (zeta) include, but are not limited to, 4'-phenoxy-2,2-dichloroacetophenone, 4'-tert-butyl-2,2-dichloroacetophenone, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1-one, 1-hydroxycyclohexyl phenyl ketone, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 1- 2-methylpropan-1-one, 1- [4- (2-hydroxyethoxy) phenyl] -2-hydroxy- An acetophenone-based photopolymerization initiator such as 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butan-1-one; Benzoin ether photopolymerization initiators such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether and benzoin isobutyl ether; Benzophenone based photopolymerization initiators such as benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyldiphenylsulfide and 2,4,6-trimethylbenzophenone; Thioxanthone photopolymerization initiators such as 2-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone and 1-chloro-4-propanedioxanthone; (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, Acylphosphine oxide photopolymerization initiators such as pin oxide; Oxime ester-based photopolymerization initiators such as 1,2-octanedione, 1- [4- (phenylthiophenyl)] -, and 2- (O-benzoyloxime); Camphorquinone and the like.

The photo radical polymerization initiator (?) May be used singly or in combination of two or more depending on the desired performance. When the photo radical polymerization initiator (?) Is blended, from the viewpoint of obtaining sufficient curing and strength, the compounding ratio is preferably 10% by mass or less, more preferably 0.1 to 3.0% by mass or less based on the entire composition .

(Other component (?))

The photo-curable adhesive composition that can be used in the present invention may optionally contain other components that are different from the components (? 1) to (?) Within the range that does not impair the effect of the present invention.

As a type belonging to these other components, a compound having a cationic polymeric property other than the epoxy compound (? 1) or the oxetane compound (? 2) can be mentioned. Specific examples include, but are not limited to, epoxy compounds having one epoxy group in the molecule. Other types (?) That do not have polymerizability include other types belonging to other components. When other component (?) Having no polymerizing property is compounded, the compounding ratio thereof is preferably 10% by mass or less based on the entire composition.

Examples of other components (?) Having no polymerizable property include, but are not limited to, photosensitizers. By incorporating 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 a carbonyl compound, an organic sulfur compound, a persulfate, a redox compound, an azo compound and a diazo compound, a halogen compound and a light reducing pigment.

Specific examples of the photosensitizer include, but are not limited to, benzoin derivatives such as benzoin methyl ether, benzoin isopropyl ether, and?,? -Dimethoxy-? -Phenylacetophenone; Benzophenone derivatives such as benzophenone, 2,4-dichlorobenzophenone, methyl o-benzoylbenzoate, 4,4'-bis (dimethylamino) benzophenone and 4,4'-bis (diethylamino) benzophenone; Thioxanthone derivatives such as 2-chlorothioxanthone and 2-isopropylthioxanthone; Anthraquinone derivatives such as 2-chloro anthraquinone and 2-methyl anthraquinone; Acridone derivatives such as N-methyl acridone, N-butyl acridone; Other examples include?,? -Diethoxyacetophenone, benzyl, fluorenone, xanthone, uranyl compound, halogen compound and the like.

Among these compounds, there are some compounds corresponding to the photo radical polymerization initiator (?), But the photosensitizer referred to herein is not particularly limited as long as it functions as a sensitizer for the photo cationic polymerization initiator (? 1). These may be used alone or in combination of two or more.

The photosensitizer is a compound containing a cationically polymerizable monomer (the above-mentioned epoxy compound (? 1) and oxetane compound (? 2)) in the photocurable adhesive composition that can be used in the present invention and having the above- And, if present, it is also included) in an amount of 0.1 to 20 parts by mass, preferably 100 parts by mass.

As another component (?) Having no polymerizable property, a thermal cationic polymerization initiator may also be used. Examples of the thermal cationic polymerization initiator include a benzylsulfonium salt, a thiophenium salt, a thioranium salt, a benzylammonium salt, a pyridinium salt, a hydrazinium salt, a carboxylic acid ester, a sulfonic acid ester, and an amine imide. These initiators can be easily obtained from commercial products, and examples thereof include ADEKAOFTONE CP77 and ADEKAOFTONE CP66 (manufactured by Adeka), CI-2639 , CI-2624 (manufactured by Nippon Soda Co., Ltd.), Sun Aid SI-60L, Sun Aid SI-80L and Sun Aid SI-100L (manufactured by Sunshine Chemical Industry Co., Ltd.).

Since the polyol has a property of promoting cationic polymerization, it can be used as another component (?) Having no polymerizable property. As the polyol, it is preferable that an acid group other than the phenolic hydroxyl group is not present. For example, a polyol compound, a polyester polyol compound, a polycaprolactone polyol compound, a polyol compound having a phenolic hydroxyl group, Polycarbonate polyol compounds, and the like.

As the other component (?) Not having a polymerizable property, a silane coupling agent, an ion trapping agent, an antioxidant, a light stabilizer, a chain transfer agent, a sensitizer, a tackifier, a thermoplastic resin, A filler, a flow control agent, a plasticizer, a defoaming agent, a leveling agent, a pigment, an organic solvent, and the like.

As another component (?) Having no polymerizing property, it is also effective to blend a thermoplastic resin for the purpose of further improving adhesion with the cellulose acylate film. From the viewpoint of enhancing the durability of the polarizer, the thermoplastic resin preferably has a glass transition temperature of 70 DEG C or higher, and particularly preferable examples thereof include a methyl methacrylate-based polymer.

<Polarizer>

The polarizer, which is a main component of the polarizer, is a device that allows only light of a polarization plane in a certain direction to pass. A currently known polarizer is a polyvinyl alcohol polarizing film. The polyvinyl alcohol polarizing film includes a polyvinyl alcohol film stained with iodine and a dichroic dye stained.

As the polarizer, a polarizer in which a polyvinyl alcohol aqueous solution is formed, uniaxially stretched, dyed, uniaxially stretched, and preferably subjected to a durability treatment with a boron compound can be used. The film thickness of the polarizer is preferably 5 to 30 占 퐉, and more preferably 10 to 20 占 퐉.

Further, an ethylene-modified polyvinyl alcohol having an ethylene unit content of 1 to 4 mol%, a degree of polymerization of 2000 to 4000 and a saponification degree of 99.0 to 99.99 mol% described in JP-A-2003-248123 and JP-A-2003-342322 Alcohol is also preferably used. Among them, an ethylene-modified polyvinyl alcohol film having a hot water cutting temperature of 66 to 73 占 폚 is preferably used. A polarizer using this ethylene-modified polyvinyl alcohol film is excellent in polarization performance and durability, and has less color unevenness and is particularly preferably used in a large-sized liquid crystal display device.

&Lt; Polarizing plate production method >

The polarizing plate can be produced by bonding a cellulose acylate film having a degree of acetyl substitution of 2.0 to 2.5 and a cellulose acylate film containing a Tg reducing agent to one side of the polarizer using a photo-curable adhesive. When the joint, both of the surface of the cellulose acylate film, the value of r that satisfies 1.1 or greater, d _A is the detection surface, it is bonded to the polarizer. That is, of the both surfaces of the cellulose acylate film, the surface having the larger detection value of the Tg reducing agent by the time-of-flight secondary ion mass spectrometry becomes the bonding surface with the polarizer.

The cellulose acylate film according to the present invention may be used for the other side of the polarizer constituting the polarizing plate, and it is also preferable to bond other optical films. Examples of such other optical films include commercially available cellulose ester films (for example, Konica Minolta Tact KC8UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UY, KC4UE, KC8UE, KC8UY-HA, KC8UX- RHA-C, KC8UXW-RHA-NC, KC4UXW-RHA-NC, and more, Konica Minolta Opto).

Hereinafter, an example of a method for producing a polarizing plate using a photo-curable adhesive will be described.

The polarizing plate is characterized by comprising a preprocessing step of facilitating the adhesion of the surface to which the polarizer of the cellulose acylate film is adhered, an adhesive applying step of applying the following photocurable adhesive to at least one of the polarizer and the adhesive surface of the cellulose acylate film, A bonding step of adhering a polarizer and a cellulose acylate film to each other through an adhesive layer and a curing step of curing the adhesive layer in a state in which the polarizer and the cellulose acylate film are adhered via the adhesive layer Can be manufactured.

(Pre-processing step)

In the pretreatment step, the surface of the cellulose acylate film adhered to the polarizer is subjected to an adhesion facilitating treatment. When the cellulose acylate film is adhered to both sides of the polarizer, the cellulose acylate film is subjected to the adhesion facilitating treatment. In the following adhesive application step, the surface subjected to the adhesion facilitating treatment is treated as a bonding surface with the polarizer, so that the surface on which both of the surfaces of the cellulose acylate film satisfy the r value of 1.1 or more and whose d _A is detected is bonded It is facilitated.

(Adhesive application step)

In the adhesive applying step, the photo-curing adhesive is applied to at least one of the bonding surfaces of the polarizer and the cellulose acylate film. When the photocurable adhesive is applied directly to the surface of the polarizer or the cellulose acylate film, there is no particular limitation on the coating method. For example, various application methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Further, a method may be employed in which a photo-curable adhesive is poured between the polarizer and the cellulose acylate film, and then the film is uniformly spread by pressing with a roller or the like.

(Bonding step)

After the photocurable adhesive is applied in this manner, it is provided in the bonding step. In this bonding step, for example, when a photocurable adhesive is applied to the surface of the polarizer in the previous coating step, the cellulose acylate film is superposed thereon. When the photocurable adhesive is applied to the surface of the cellulose acylate film in the previous coating step, the polarizer is superimposed thereon. When the photo-curable adhesive is softened between the polarizer and the cellulose acylate film, the polarizer and the cellulose acylate film are overlapped with each other in this state. When a cellulose acylate film is adhered to both sides of a polarizer, and when a photo-curable adhesive is used on both sides, a cellulose acylate film is superimposed on both sides of a polarizer via a photo-curable adhesive. Normally, when the cellulose acylate film is laminated on one side of the polarizer, the side of the polarizer and the side of the cellulose acylate film are referred to, and when the cellulose acylate film is laminated on both sides of the polarizer, The side of the acylate film) is sandwiched and pressed by a roller or the like. As for the material of the roller, metal or rubber can be used. The rollers disposed on both sides may be the same material or different materials.

(Curing Process)

In the curing step, an uncured light-curable adhesive is irradiated with an active energy ray to cure an adhesive layer containing an epoxy compound or an oxetane compound, and the polarizer and the cellulose acylate film are superimposed via a photo-curing adhesive . When the cellulose acylate film is bonded to one surface of the polarizer, the active energy ray may be irradiated either on the side of the polarizer or on the side of the cellulose acylate film. When a cellulose acylate film is bonded to both sides of a polarizer, an active energy ray is irradiated from either side of the cellulose acylate film in a state in which the cellulose acylate film is superimposed on both sides of the polarizer with a photo-curable adhesive interposed therebetween , It is advantageous to simultaneously cure the photocurable adhesive on both sides. However, when the ultraviolet absorber is blended in either cellulose acylate film, ultraviolet rays are irradiated on the side of the other cellulose acylate film to which the ultraviolet absorber is not added when the active energy ray is ultraviolet ray.

As the active energy ray, visible light, ultraviolet ray, X-ray, electron beam, or the like can be used, but ultraviolet ray is preferably used because it is easy to handle and has a sufficient curing speed. The light source of the active energy ray is not particularly limited, but a light source having a wavelength of 400 nm or less, such as a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, a high pressure mercury lamp, a chemical lamp, LED lamps can be used.

The light irradiation intensity with respect to the photocurable adhesive is determined not only by the intended composition but also by the UV-B (280 to 320 nm long-wave ultraviolet region), which is effective in the activation of the polymerization initiator, To be in the range of 1 to 3,000 mW / cm &lt; ² &gt;. When the irradiation intensity is in the range of 1 to 3,000 mW / cm ² , a suitable reaction time is sufficient, and the heat radiated from the lamp and the heat generated during polymerization of the photocurable adhesive prevent yellowing of the photocurable adhesive and deterioration of the polarizer .

The light irradiation time for the photocurable adhesive is controlled for each composition to be cured and is not particularly limited, but it is preferable that the integrated light quantity expressed by the product of irradiation intensity and irradiation time is set to be in the range of 10 to 5000 mJ / cm ² Do. When the accumulated light quantity is within the range of 10 to 5000 mJ / cm ² , sufficient active paper derived from the polymerization initiator is generated, and the curing of the adhesive layer becomes sufficient. Further, a suitable irradiation time is sufficient, which is suitable for improvement of productivity.

In curing the photocurable adhesive by irradiating an active energy ray, it is preferable to cure under the condition that various functions of the polarizing plate are not deteriorated, such as polarizability, transmittance, hue and transparency of the cellulose acylate film.

In the polarizing plate thus obtained, the thickness of the adhesive layer is not particularly limited, but is usually 50 占 퐉 or less, preferably 20 占 퐉 or less, more preferably 10 占 퐉 or less, further preferably 5 占 퐉 or less.

<Liquid Crystal Display Device>

The polarizing plate according to the present invention can be suitably used for a liquid crystal display device. The liquid crystal display device using the polarizing plate according to the present invention is excellent in visibility because a cellulose acylate film having excellent optical compensation function is used. Such a liquid crystal display device is also excellent in durability because of high adhesion between the polarizer and the cellulose acylate film.

The surface of the polarizing plate on the side of the cellulose acylate film and the surface of at least one of the liquid crystal cells can be bonded by a known method. In some cases, they may be bonded through an adhesive layer.

A liquid crystal display device of various driving modes such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS and OCB can be used for the mode (driving method) of the liquid crystal display device. Preferably, it is a VA (MVA, PVA) type liquid crystal display. By using the polarizing plate according to the present invention in such a liquid crystal display device, even a liquid crystal display device of a large screen of 30 or more in size can obtain a liquid crystal display device with less environmental fluctuation, excellent color visibility, and excellent visibility such as frontal contrast.

Example

Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited thereto. The term "part" or "%" used in the examples indicates "part by mass" or "% by mass", unless otherwise specified.

[Example 1]

<Production of Cellulose Acylate Film 101>

(Preparation of fine particle dispersion 1)

Fine particles (Aerosil R972V, manufactured by Nippon Aerosil Co., Ltd.) 11 parts by mass

Ethanol 89 parts by mass

The resulting mixture was stirred with a dissolver for 50 minutes and dispersed with Manton-Gaulin to prepare a fine particle dispersion 1.

(Production of fine particle addition liquid 1)

The fine particle dispersion 1 was slowly added while sufficiently stirring in a dissolution tank containing methylene chloride. The mass of the methylene chloride and the fine particle dispersion 1 is as follows. Further, the particles were dispersed in the attritor so that the particle diameter of the secondary particles became a predetermined value. This was filtered with Fine Mat NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle addition liquid 1.

99 parts by mass of methylene chloride

Fine particle dispersion 1 5 parts by mass

(Preparation of the main doping solution)

To prepare a main dope solution having the following composition.

Methylene chloride 340 parts by mass

64 parts by mass of ethanol

A mixture of cellulose acylate (cellulose acylate having an acetyl substitution degree of 2.45 and a weight average molecular weight (Mw) of 135,000 and a cellulose acylate having an acetyl substitution degree of 2.45 and a weight average molecular weight (Mw) of 180000 in a mass ratio of 6: 4) 100 Mass part

(A1: a2: a3: a4) of 1: 14: 35: 40, the average logP value of the mixture obtained by mixing the hydrolysis inhibitor (sugar ester compounds a1, a2, a3 and a4) 8.7, Tg lowering ability = 2.1 占 폚 / mass part) 8 mass parts

Fine particle addition liquid 1 1 part by mass

First, methylene chloride and ethanol of the above composition were added to a pressurizing and dissolving tank. A pressurized dissolution tank containing this solvent was charged with a cellulose acylate having an acetyl substitution degree of 2.45 and a weight average molecular weight (Mw) of 135000 and a cellulose acylate having an acetyl substitution degree of 2.45 and a weight average molecular weight (Mw) of 180000 at a mass ratio of 6: And the above-mentioned composition was added with stirring. The solution was heated and completely dissolved with stirring, and then filtered using Azumi Rossi No. 244 manufactured by Azumi Co., Ltd. to prepare a main dope solution. The main dope liquid was put into a closed vessel and dissolved while stirring to adjust the dope liquid.

(Production of cellulose acylate film)

Subsequently, the dope solution was uniformly softened on the stainless steel belt support at a temperature of 33 DEG C and a width of 1500 mm using an endless belt softening apparatus. The temperature of the stainless steel belt was controlled at 30 占 폚.

On the stainless steel belt support, the solvent was evaporated until the amount of the residual solvent in the casted cellulose acylate film reached 88%, and then peeled off on the stainless steel belt support at a peel tension of 130 N / m.

The peeled cellulose acylate film was stretched by 1.15 times in the transverse direction using a tenter while heating at 160 캜. The amount of the residual solvent at the start of the stretching was 10%.

Subsequently, drying was completed while conveying the drying zone to a plurality of rolls. The drying temperature was 130 占 폚 and the conveying tension was 100 N / m.

Thus, a cellulose acylate film 101 having a dried film thickness of 45 탆 and a length of 2000 m was obtained.

&Lt; Preparation of cellulose acylate films 102 to 118 >

Cellulose acylate films 102 to 118 were prepared in the same manner as in the cellulose acylate film 101 except that the dope liquid composition and the preparation conditions were changed as shown in Table 1 below. In the preparation of the cellulose acylate film 101, the Tg reducing agent is not added, but when the Tg reducing agent is added, the composition of the main doping liquid contains the Tg reducing agent.

Table 1 shows the compound of the Tg reducing agent contained in the main dope liquid composition of each of the cellulose acylate films 101 to 118, the addition amount, the value of the Tg lowering ability, the mixing ratio of the compound mixed as the hydrolysis inhibitor, And the value of the residual solvent amount in the cellulose acylate film at the time of peeling are described.

<Evaluation>

With respect to the cellulose acylate films 101 to 118 obtained above, the r value of the distribution of the Tg reducing agent on both surfaces, the s value of the distribution of the hydrolysis inhibitor, and the arithmetic average roughness (Ra) Respectively. The measurement results are shown in Table 1 below. In Table 1, the surface Q1 represents the surface opposite to the surface that was in contact with the metal support during softening of the dope. And the surface Q2 represents the surface which was in contact with the metal support during softening of the dope.

(Method of measuring r value and s value)

The detection value of the Tg reducing agent on each surface of the cellulose acylate films 101 to 118 was obtained using the time-of-flight secondary ion mass spectrometry under the following measurement conditions.

Measurement apparatus: 2100 TRIFT2 (manufactured by Phisical Electronics)

Measurement mode: Cooling measurement (temperature range -95 to -105 ℃)

Primary ion: Ga (15 kV)

Measurement area: 60 탆 square

Accumulation time: 2 minutes

Reference ion m / Z in the case of the Tg reducing agent (aromatic polyester (ar-14)): 119

A reference ion m / Z in the case of the hydrolysis inhibitor (a mixture of the sugar ester compounds (a1), (a2), (a3) and (a4)

The r value was calculated according to the above-mentioned formula (1) with d _{A as the} larger value and d _B as the smaller value among the detected values of the Tg reducing agent on each surface.

In addition, in both of the cellulose acylate films 102 to 107 and 109 to 118, except for the cellulose acylate films 101 and 108 to which the Tg reducing agent was not added, the detection value of the Tg reducing agent was larger on the Q2 side than on the Q1 side.

Based on the same measurement conditions, the detection value of the hydrolysis inhibitor on each surface of the cellulose acylate films 101 to 118 was obtained using the time-of-flight secondary ion mass spectrometry. Among the detection values of the hydrolysis inhibitor on each surface, the value of s was calculated in accordance with the above-mentioned equation (2), with d _C being a larger value and d _D being a smaller value.

(Measurement method of arithmetic mean roughness (Ra)) [

The arithmetic mean roughness (Ra) was measured by an optical interference type surface roughness meter (RST / PLUS, manufactured by WYKO) according to JIS B0601: 2001.

In Table 1, the aromatic polyester compounds of the Tg reducing agent represent the aromatic polyester compounds (ar-5), (ar-14), (ar-16) or (PES-7) exemplified above.

A1 to a4 in the compound No. of the hydrolysis inhibitor show the sugar ester compounds (a1), (a2), (a3) and (a4). Further, PETB represents pentaerythritol tetrabenzoate. The ratio of the compound of the hydrolysis inhibitor indicates the mixing ratio of the compound represented by the compound No..

[Example 2]

&Lt; Production of Polarizers 201 to 221 >

(Production of Polarizer)

A polyvinyl alcohol film having a thickness of 70 탆 was swelled with water at 35 캜. The obtained film was immersed in an aqueous solution containing 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds and immersed in an aqueous solution at 45 캜 containing 3 g of potassium iodide, 7.5 g of boric acid and 100 g of water. The resulting film was uniaxially stretched under the conditions of a stretching temperature of 55 캜 and a draw ratio of 5. The uniaxially stretched film was washed with water and then dried to obtain a polarizer having a thickness of 20 탆.

(Preparation of adhesive)

The following components were mixed and defoamed to prepare a photocurable adhesive liquid. Further, triarylsulfonium hexafluorophosphate was compounded as a 50% propylene carbonate solution, and the solid content of triarylsulfonium hexafluorophosphate was shown below.

(Adhesive liquid composition)

45 parts by mass of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate

40 parts by mass of Polyd GT-301 (alicyclic epoxy resin manufactured by Daicel Chemical Industries, Ltd.)

15 parts by mass of 1,4-butanediol diglycidyl ether

Triarylsulfonium hexafluorophosphate 2.3 parts by mass

9,10-dibutoxyanthracene 0.1 part by weight

2.0 parts by mass of 1,4-diethoxynaphthalene

(Production of polarizing plate)

The polarizing plates each using the cellulose acylate films 101 to 118 were prepared as follows.

First, a film of KC6UY (manufactured by Konica Minolta Opto) was prepared, and its surface was subjected to corona discharge treatment. The conditions of the corona discharge treatment were a corona output power of 2.0 kW and a line speed of 18 m / min. Subsequently, the adhesive liquid prepared above was coated on the corona discharge treated surface of the film with a bar coater so as to have a film thickness after curing of about 3 mu m to form an adhesive layer. To the obtained adhesive layer, a polyvinyl alcohol-iodine polarizer prepared as described above was bonded.

Similarly, the surfaces of the cellulose acylate films 101 to 118 were corona discharge treated. The conditions of the corona discharge treatment were a corona output power of 2.0 kW and a line speed of 18 m / min. Subsequently, on the corona discharge treated surface of the cellulose acylate films 101 to 118, the adhesive liquid prepared above was applied and coated with a bar coater so as to have a film thickness after curing of about 3 mu m to form an adhesive layer. At that time, the cellulose acylate film was bonded so that the slow axis and the absorption axis of the polarizer were orthogonal to each other.

A polarizer of a polarizer bonded to one side of a film made of KC6UY (manufactured by Konica Minolta Opto) was bonded to this adhesive layer, and a film of a cellulose acylate film 101 to 118 / polarizer / KC6UY (manufactured by Konica Minolta Opto) A laminate was obtained. From a laminate of cellulose acylate films 101 to 118 side, using the ultraviolet irradiation apparatus (lamp, using the D valve of Fusion UV Systems, Inc.) equipped with a belt conveyor, UV accumulated light quantity so that 750mJ / cm ² To cure the adhesive layer.

Thus, using the cellulose acylate films 101 to 118, the polarizers 201 to 221 having polarizers sandwiched between the two films were produced.

Which of the cellulose acylate films 101 to 118 used for the production of each of the polarizers 201 to 221 and which of the Q1 surface and the Q2 surface are in contact with the polarizer is shown in Table 2 below.

That is, as shown in Table 2, the polarizers 201 to 218 have the Q2 side of the cellulose acylate films 101 to 118 as the bonding surfaces with the polarizer, and the polarizers 219 to 221 are the cellulose acylate films 102, 104 and 109 Quot; Q1 &lt; / RTI &gt;

<Evaluation of Polarizer>

The polarizers 201 to 221 thus obtained were evaluated for adhesion between the polarizer and the cellulose acylate film and the degree of polarization of the polarizing plate by the following measuring method. The evaluation results are shown in Table 2 below.

(Method for evaluating adhesion between polarizer and cellulose acylate film)

The polarizers 201 to 221 were allowed to stand for 500 hours under a wet heat condition of 60 DEG C and 90% RH. Thereafter, adhesion was evaluated depending on whether or not the polarizer and the cellulose acylate film constituting the polarizing plates 201 to 221 could be peeled by hand.

The evaluation criteria are as follows.

○: It was not possible to peel by hand.

X: It was possible to peel off by hand.

(Method for evaluating the polarization degree of the polarizing plate)

Polarizers of the polarizers 201 to 221 were measured using "V-7100" manufactured by Nippon Bunko Co., Ltd.

Specifically, the parallel transmittance (H0) and the orthogonal transmittance (H90) of the polarizing plate were measured and the degree of polarization was calculated from the formula: polarization degree (%) = {(H0-H90) / (H0 + H90)} ^1/2 100 Respectively. Here, the parallel transmittance H0 is a value of the transmittance of a parallel laminated polarizing plate produced by superimposing two polarizing plates of the same polarizing plate so that their absorption axes become parallel to each other. On the other hand, the orthogonal transmittance (H90) is a value of transmittance of an orthogonal laminated polarizing plate produced by superimposing two identical polarizing plates so that their absorption axes are perpendicular to each other. These transmittances are Y values obtained by performing visibility correction using a 2-degree field of view (C light source) of JIS Z 8701 (1982 edition).

Evaluation standards for the degree of polarization are as follows.

○: The polarization degree is 99.990 or more

?: The degree of polarization is 99.980 or more and less than 99.990

X: The degree of polarization is less than 99.980

As a result of the evaluation, all of the polarizing plates according to the present invention were found to be excellent in adhesion to polarizers, and furthermore, the decrease in the degree of polarization of the polarizing plate due to the axis misalignment at the time of bonding with the polarizer could be suppressed.

On the other hand, all of the polarizing plates using the cellulose acylate film of the comparative example were inferior in adhesiveness to the polarizer, and the decrease in the degree of polarization of the polarizing plate could not be suppressed to a satisfactory level.

&Lt; Industrial applicability >

It can be used in the field of liquid crystal display technology, and can be applied to a polarizing plate and a liquid crystal display device using cellulose acylate.

Claims (7)

A cellulose acylate film comprising a cellulose acylate having an acyl group substitution degree in the range of 2.0 to 2.5 and a glass transition temperature lowering agent bonded to one side of a polarizer using a photocurable adhesive,
The detected value of the glass transition temperature-reducing agent on the bonding surface of the cellulose acylate film detected by using the time-of-flight secondary ion mass spectrometry (TOF-SIMS) is d _A , the detected value of the other side is d _B , The value of r indicated by the following formula (1) is not less than 1.1 and not more than 1.5.
(1) r = d _A / d _B The polarizing plate according to claim 1, wherein the cellulose acylate is diacetyl cellulose having an acyl group substitution degree within a range of 2.0 to 2.5. The polarizing plate according to any one of claims 1 to 5, wherein the glass transition temperature lowering agent has a glass transition temperature lowering capability of 3.5 占 폚 / mass part to 5.0 占 폚 / mass part. The cellulose acylate film according to claim 1 or 2, wherein the cellulose acylate film further comprises a hydrolysis inhibitor,
Wherein the average log P value of the hydrolysis inhibitor is from 7.5 to 13.0. 3. The polarizing plate according to claim 1 or 2, wherein the arithmetic average roughness of the bonding surface is larger than the other side. The polarizer according to claim 1 or 2, wherein the polarization degree of the polarizer is 99.99% or more. A liquid crystal display device comprising the polarizing plate according to claim 1 or 2.