JP6357447B2 - Cellulose acylate film, polarizing plate and liquid crystal display device - Google Patents

Description

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

  A cellulose acylate film typified by a cellulose acetate film has high transparency and has been conventionally used as an optical film in various applications. For example, it is used as a polarizing plate protective film in a liquid crystal display device because it can easily ensure adhesion with polyvinyl alcohol used in a polarizer.

  In recent years, thinning of liquid crystal display devices, particularly liquid crystal display devices for small and medium-sized applications, has been progressing rapidly, and there is a demand for thinning of the members used, in particular, thinning of polarizing plate protective films and the like. In addition, medium- and small-sized liquid crystal display devices are often exposed to severe environmental changes due to use as digital signage and other outdoor use, and durability under high-temperature and high-humidity environments is also an important performance. If the polarizing plate protective film is made thinner, the polarizer protection function required per thickness will increase, and it will be possible to guarantee better UV absorption ability and higher durability in high temperature and high humidity environments. The optical film is required.

  Patent Document 1 describes a cellulose ester film containing a polyester resin having a cyclohexane ring in the main chain skeleton and polymerized by an ester bond at the 1-position and the 2-position of the cyclohexane ring.

  Patent Document 2 describes a cellulose ester film containing an ester plasticizer having a benzenecarboxylic acid or a phenol residue at both ends and having an aliphatic cyclic glycol and an aliphatic cyclic dibasic acid.

International Publication No. 2014/027594 JP 2007-84692 A

  However, if a conventional cellulose acylate film is thinned and a high-concentration UV absorber is added for the purpose of enhancing the protective function of a polarizer / liquid crystal against UV rays, bleeding out (deposition of the UV absorber after film formation) may occur. There is a problem of getting up.

  The problem to be solved by the present invention is a thin film with high hardness, bleed out is suppressed, and when used as a polarizing plate protective film, the durability of the polarizer in a high temperature and high humidity environment is good, An object of the present invention is to provide a cellulose acylate film excellent in the function of protecting a polarizer / liquid crystal against ultraviolet rays, a polarizing plate having the cellulose acylate film, and a liquid crystal display device.

  As a result of intensive studies by the present inventors in order to solve the above problems, a unit derived from a diol, a unit derived from 1,2-cyclohexyl dicarboxylic acid, and a unit derived from 1,4-cyclohexyl dicarboxylic acid In the oligomer containing at least one, when the terminal is sealed with a group derived from a monocarboxylic acid having an alicyclic structure, the cellulose acylate film containing this oligomer can be used even when a high-concentration ultraviolet absorber is added. It turns out that no bleed out occurs.

  That is, the above problem can be solved by the following means.

<1>
A cellulose acylate film containing a cellulose acylate, a benzotriazole-based ultraviolet absorber, and an ester oligomer,
The film thickness of the cellulose acylate film is 10 μm or more and 40 μm or less,
Containing 4 to 20 parts by mass of the benzotriazole-based ultraviolet absorber with respect to 100 parts by mass of the cellulose acylate,
The ester oligomer includes a unit derived from a diol, at least one of a unit derived from 1,2-cyclohexanedicarboxylic acid and a unit derived from 1,4-cyclohexanedicarboxylic acid, and a terminal having an alicyclic structure Sealed with a group derived from a carboxylic acid and having a hydroxyl value of 30 mgKOH / g or less,
Cellulose acylate film.
<2>
The cellulose acylate film according to <1>, wherein the monocarboxylic acid having the alicyclic structure is a cycloalkane monocarboxylic acid having 6 to 12 carbon atoms.
<3>
The cellulose acylate film according to <2>, wherein the monocarboxylic acid having an alicyclic structure is cyclohexanecarboxylic acid.
<4>
The cellulose acylate film according to any one of <1> to <3>, wherein the ester oligomer has a number average molecular weight of 500 to 3000.
<5>
The cellulose acylate film according to <4>, wherein the ester oligomer has a number average molecular weight of 750 to 1500.
<6>
The cellulose acylate film according to any one of <1> to <5>, wherein the diol is ethylene glycol, propanediol, or butanediol.
<7>
The cellulose acylate film according to <6>, wherein the diol is propanediol or butanediol.
<8>
The cellulose acylate film according to <7>, wherein the diol has a branched structure.
<9>
The cellulose acylate film according to any one of <1> to <8>, wherein a content of the ester oligomer is 4 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the cellulose acylate.
<10>
The cellulose acylate film according to <9>, wherein the content of the ester oligomer is 10 parts by mass or more and 13 parts by mass or less with respect to 100 parts by mass of the cellulose acylate.
<11>
The cellulose acylate film according to any one of <1> to <10>, wherein the content of the benzotriazole-based ultraviolet absorber is 5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the cellulose acylate. .
<12>
The polarizing plate which has a polarizer and the cellulose acylate film in any one of <1>-<11>.
<13>
A liquid crystal display device comprising a liquid crystal cell and at least one polarizing plate according to <12>.

  According to the present invention, although it is a thin film, it has high hardness, bleed-out is suppressed, and when used as a polarizing plate protective film, it has good polarizer durability under a high temperature and high humidity environment, and is a polarizer against ultraviolet rays. -The cellulose acylate film excellent in the protective function of a liquid crystal, the polarizing plate which has this cellulose acylate film, and a liquid crystal display device can be provided.

  Hereinafter, the contents of the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

[Cellulose acylate film]
The cellulose acylate film of the present invention contains cellulose acylate, a benzotriazole-based ultraviolet absorber, and an ester oligomer.
The film thickness of the cellulose acylate film is 10 μm or more and 40 μm or less,
Containing 4 to 20 parts by mass of the benzotriazole-based ultraviolet absorber with respect to 100 parts by mass of the cellulose acylate,
The ester oligomer includes a unit derived from a diol, at least one of a unit derived from 1,2-cyclohexanedicarboxylic acid and a unit derived from 1,4-cyclohexanedicarboxylic acid, and a terminal having an alicyclic structure Sealed with a group derived from a carboxylic acid and having a hydroxyl value of 30 mgKOH / g or less,
It is a cellulose acylate film.

<Cellulose acylate>
The cellulose acylate film of the present invention contains cellulose acylate. The cellulose acylate film of the present invention preferably contains one or more cellulose acylates as a main component. Here, “main component” means a polymer when a single polymer is included as a raw material, and a polymer with the highest mass fraction when two or more polymers are included as a raw material. Means that.

  Examples of the cellulose acylate raw material cellulose include cotton linter and wood pulp (hardwood pulp, softwood pulp), and any cellulose acylate obtained from any raw material cellulose may be used, and may be used in some cases. . Detailed descriptions of these raw material celluloses can be found in, for example, “Plastic Materials Course (17) Fibrous Resin” (Marusawa, Uda, Nikkan Kogyo Shimbun, published in 1970) and Invention Association Publication Technical Report 2001-1745 ( The cellulose described in pages 7 to 8) can be used.

  In the cellulose acylate used in the present invention, a hydrogen atom of a hydroxyl group of cellulose is substituted with an acyl group. The number of carbon atoms in the acyl group is preferably 2-22. The acyl group may be an aliphatic acyl group or an aromatic acyl group, and may be single or substituted with two or more types of acyl groups. Specifically, examples of the cellulose acylate include cellulose alkylcarbonyl esters, alkenylcarbonyl esters, aromatic carbonyl esters, and aromatic alkylcarbonyl esters. Each of the alkyl moiety, the alkenyl moiety, the aromatic moiety, and the aromatic alkyl moiety may further have a substituent. Examples of preferred acyl groups include acetyl, propionyl, butanoyl, heptanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl, i-butanoyl, t-butanoyl, cyclohexanecarbonyl, Oleoyl, benzoyl, naphthylcarbonyl, cinnamoyl groups and the like are included. Among these, acetyl, propionyl, butanoyl, dodecanoyl, octadecanoyl, t-butanoyl, oleoyl, benzoyl, naphthylcarbonyl, and cinnamoyl are preferable, acetyl, propionyl, and butanoyl are more preferable, and acetyl is most preferable.

The acyl substitution degree of the cellulose acylate to be used is not particularly limited, but when cellulose acylate having an acyl substitution degree of 2.00 to 2.95 is used, film forming properties and various characteristics of the produced film are considered. Is preferable. The acyl substitution degree can be obtained by measuring the degree of binding of fatty acid such as acetic acid and calculating it. The measurement method is ASTM
It can be carried out according to D-817-91.

In the embodiment of the cellulose acylate having at least two kinds of acyl groups of acetyl group / propionyl group / butanoyl group, the total substitution degree is preferably 2.50 to 2.95, and more preferably the acyl substitution degree is 2. It is 60-2.95, More preferably, it is 2.65-2.95.
In the cellulose acylate having only an acetyl group, ie, cellulose acetate, the total substitution degree is preferably 2.00 to 2.95. Furthermore, the substitution degree is more preferably 2.40 to 2.95, and further preferably 2.85 to 2.95.

  The degree of polymerization of cellulose acylate preferably used in the present invention is 180 to 700 in terms of viscosity average polymerization degree, and in cellulose acetate, 180 to 550 is more preferable, 180 to 400 is more preferable, and 180 to 350 is particularly preferable. . If the degree of polymerization is less than or equal to this upper limit value, the viscosity of the cellulose acylate dope solution does not become too high, and a film can be easily produced by casting. If the degree of polymerization is equal to or greater than this lower limit, it is preferable because there is no inconvenience such as a decrease in strength of the produced film. The viscosity average degree of polymerization can be measured by Uda et al.'S intrinsic viscosity method {Kazuo Uda, Hideo Saito, "Journal of the Textile Society," Vol. 18, No. 1, pages 105-120 (1962)}. This method is also described in detail in JP-A-9-95538.

  The molecular weight distribution of cellulose acylate preferably used in the present invention is evaluated by gel permeation chromatography, and its polydispersity index Mw / Mn (Mw is a mass average molecular weight, Mn is a number average molecular weight) is small, and the molecular weight A narrow distribution is preferred. The specific value of Mw / Mn is preferably 1.0 to 4.0, more preferably 2.0 to 4.0, and more preferably 2.3 to 3.4. Further preferred.

<Ester oligomer>
The ester oligomer used in the present invention will be described.
The ester oligomer used in the present invention includes a unit derived from a diol and at least one of a unit derived from 1,2-cyclohexanedicarboxylic acid and a unit derived from 1,4-cyclohexanedicarboxylic acid, and the terminal is an alicyclic ring. The oligomer is sealed with a group derived from a monocarboxylic acid having a structure and has a hydroxyl value of 30 mgKOH / g or less.

Here, the ester oligomer used in the present invention is an ester oligomer obtained by synthesis of at least one of a unit derived from 1,2-cyclohexanedicarboxylic acid and a unit derived from 1,4-cyclohexanedicarboxylic acid and a diol. Preferably there is.
Hereinafter, the dicarboxylic acid and diol that can be preferably used for the synthesis of the ester oligomer in the present invention will be described.

  The ester oligomer used in the present invention is synthesized from an aliphatic diol having 2 to 10 carbon atoms and at least one of a unit derived from 1,2-cyclohexanedicarboxylic acid and a unit derived from 1,4-cyclohexanedicarboxylic acid. It is preferable to synthesize from an acyclic aliphatic diol having 2 to 10 carbon atoms and at least one of a unit derived from 1,2-cyclohexanedicarboxylic acid and a unit derived from 1,4-cyclohexanedicarboxylic acid. preferable.

(Dicarboxylic acid)
As the dicarboxylic acid, it is preferable to use at least one of a unit derived from 1,2-cyclohexanedicarboxylic acid and a unit derived from 1,4-cyclohexanedicarboxylic acid, and a unit derived from 1,2-cyclohexanedicarboxylic acid or It is more preferable to use at least a unit derived from 1,4-cyclohexanedicarboxylic acid.
Here, in 1,2-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid, the hydrogen atom of the cyclohexane ring in the structure may be substituted by the substituent (R).

R represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkynyl group having 2 to 8 carbon atoms, or an aryl group having 6 carbon atoms, which may form a ring structure, The definition of the carbon number of the group represented by R does not include the carbon number of the substituent that the group represented by R may further have.
Examples of the alkyl group having 1 to 8 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group, a pentyl group, a hexyl group, an octyl group, and a 2-ethylhexyl group. An alkyl group is preferable, and a methyl group and an ethyl group are more preferable.
Examples of the alkenyl group having 2 to 8 carbon atoms include ethenyl group, 1-methylethenyl group, 1-propenyl group, 2-propenyl group, 2-methyl-1-propenyl group, 2-methyl-2-propenyl group, and 2-methylene. A butyl group etc. are mentioned. Examples of the alkynyl group having 2 to 8 carbon atoms include ethynyl group, 1-methylethynyl group, 1-propyne group, 2-propyne group, 2-methyl-1-propyne group, 2-methyl-2-propyne group, 2- And a methylene butyne group.
Examples of the aryl group having 6 carbon atoms include a phenyl group and a 4-methylphenyl group. R may form a ring structure, and examples of the ring structure include a cyclohexyl group, a cyclooctyl group, a boronyl group, an isobornyl group, and a norbornyl group.
R may have a substituent, and examples of the substituent include an alkyl group, an alkoxy group, a hydroxyl group, an alkoxy-substituted alkyl group, a carboxyl group, an alkyl group is preferable, and a methyl group or an ethyl group is more preferable. . However, the definition of the number of carbon atoms of the group represented by R does not include the number of carbon atoms of the substituent that the group represented by R may further include, for example, a phenyl group substituted with a methyl group is a methyl group as a substituent. And is included in R (that is, a phenyl group substituted with a methyl group is not an aryl group having 7 carbon atoms).

The number of hydrogen atoms of the cyclohexane ring in the dicarboxylic acid structure optionally substituted by R is preferably 0 to 8, more preferably 6 to 8, and still more preferably 8, ie, unsubstituted. It is preferable from the viewpoint of hardness.
When 1,2-cyclohexanedicarboxylic acid is substituted with R, it is preferable that R is substituted at the 4-position of the cyclohexane ring in 1,2-cyclohexanedicarboxylic acid from the viewpoint of reactivity and raw material procurement.

  Specific examples of the dicarboxylic acid substituted by R include 3-methyl-1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, and 4-ethyl-1,2-cyclohexanedicarboxylic acid. 4,5-dimethyl-1,2-cyclohexanedicarboxylic acid, 4-isoboronyl-1,2-cyclohexanedicarboxylic acid, 4-phenyl-1,2-cyclohexanedicarboxylic acid, 3-methyl-1,4-cyclohexanedicarboxylic acid Examples include 2,3-norbornene dicarboxylic acid, decahydro-1,4-naphthalenedicarboxylic acid, decahydro-1,2-naphthalenedicarboxylic acid, and the like. Of these, 4-methyl-1,2-cyclohexyldicarboxylic acid is preferable from the viewpoint of availability.

The ester oligomer used in the present invention is an effect of the present invention, in addition to at least one of a unit derived from a diol, a unit derived from 1,2-cyclohexanedicarboxylic acid, and a unit derived from 1,4-cyclohexanedicarboxylic acid. Other units may be used in combination as the ester oligomer constituent unit as long as the above is not impaired. In that case, the other units are preferably synthesized from an acyclic aliphatic diol having 2 to 10 carbon atoms and a dicarboxylic acid other than 1,2-cyclohexyldicarboxylic acid and 1,4-cyclohexyldicarboxylic acid. Examples of dicarboxylic acids other than 1,2-cyclohexyl dicarboxylic acid and 1,4-cyclohexyl dicarboxylic acid include, for example, oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, and adipic acid as aliphatic dicarboxylic acids. And pimelic acid.
However, in the ester oligomer used in the present invention, the total molar ratio of at least one of a unit derived from a diol, a unit derived from 1,2-cyclohexanedicarboxylic acid, and a unit derived from 1,4-cyclohexanedicarboxylic acid. Is preferably 80% or more, and more preferably 90% or more.

(Diol)
The diol is preferably an aliphatic diol having 2 to 10 carbon atoms.
Examples of the aliphatic diol having an alicyclic structure include 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol and the like.
Examples of the acyclic aliphatic diol include alkyl diols such as ethylene glycol, 1,2-propanediol (propylene glycol), 1,3-propanediol, 1,2-butanediol, 1,3. -Butanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2 -Diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3-methyl-1 , 5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl- , 3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, diethylene glycol, and the like.

The diol is preferably ethylene glycol, propanediol, or butanediol from the viewpoint of hardness, and more preferably ethylene glycol from the viewpoint of hardness. In addition, the hydrophobicity of the cellulose acylate film resulting from the increase in the number of carbon atoms in the diol improves the durability of the polarizer when the film of the present invention is used for a polarizing plate. Therefore, from the viewpoint of the durability of the polarizer, propanediol Or it is more preferable that it is a butanediol. Furthermore, it is particularly preferable that the diol has a branched structure (for example, propylene glycol) from the viewpoint of lowering the viscosity of the ester oligomer (ensuring handling suitability).
The diol has more preferably 2 to 6 carbon atoms, and particularly preferably 2 to 4 carbon atoms. When using 2 or more types of diol, it is preferable that 2 or more types of average carbon number becomes the said range. When the diol has a carbon number within the above range, it is preferable because the compatibility with the cellulose acylate and the ultraviolet absorber is excellent, and bleed-out hardly occurs during film formation and heat stretching.

(Terminal structure)
The terminal of the ester oligomer used in the present invention is sealed with a group derived from a monocarboxylic acid having an alicyclic structure. That is, the ester oligomer has a terminal structure (monocarboxylic acid residue having an alicyclic structure) obtained by reacting a terminal hydroxyl group with a monocarboxylic acid having an alicyclic structure.
Although the detailed mechanism of action is unknown, ester oligomers obtained by sealing with a group derived from a monocarboxylic acid having an alicyclic structure in this way are cellulose acylates and benzotriazole-based ultraviolet absorbers (“UV” It is presumed that it is possible to provide a cellulose acylate film that does not bleed out even when a high concentration of UV absorber is added.
In addition, protecting the terminal with a hydrophobic functional group is effective in improving the durability of the polarizer and the surface of the film in a high-temperature and high-humidity environment of the polarizing plate, and delays the hydrolysis of the ester group. Is a factor.
Here, the residue is a partial structure of the ester oligomer and represents a partial structure having the characteristics of the monomer forming the ester oligomer. The monocarboxylic acid residue formed from the monocarboxylic acid R′—COOH is R′—CO—.

The monocarboxylic acid having an alicyclic structure is preferably a monocarboxylic acid having an alicyclic structure having 4 to 12 carbon atoms, more preferably a cycloalkane monocarboxylic acid having 4 to 12 carbon atoms, A cycloalkane monocarboxylic acid having a number of 6 to 12 is particularly preferred. The monocarboxylic acid having an alicyclic structure is most preferably a cycloalkane monocarboxylic acid having 6 to 12 carbon atoms, and the cycloalkane monocarboxylic acid having 6 to 12 carbon atoms includes at least one cyclohexane ring. .
Specifically, cyclopropanecarboxylic acid, cyclobutanecarboxylic acid, cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, 4-methylcyclohexanecarboxylic acid, 4-ethylcyclohexanecarboxylic acid, 4-propylcyclohexanecarboxylic acid, 4-tert-butylcyclohexanecarboxylic acid An acid etc. are mentioned. Among these, cyclohexanecarboxylic acid and 4-methylcyclohexanecarboxylic acid are more preferable, and cyclohexanecarboxylic acid is most preferable. In addition, the cycloalkane monocarboxylic acid having 6 to 12 carbon atoms and the cycloalkane monocarboxylic acid having 6 to 12 carbon atoms including at least one cyclohexane ring are linked to substituents on the cyclohexane ring. A C6-C12 cycloalkane monocarboxylic acid containing a condensed ring is also included.

Two or more monocarboxylic acids having an alicyclic structure used for sealing may be mixed. At this time, it is preferable that both ends of the ester oligomer are monocarboxylic acid residues having an alicyclic structure. By protecting the terminal with a functional group having a hydrophobic and bulky alicyclic structure, compatibility with cellulose acylate and UV absorber is enhanced, and polarizer durability in a high-temperature and high-humidity environment of the polarizing plate It is effective in improving the rigidity of the film, and the rigidity of the film can be improved.
The acid value of the ester oligomer is preferably 10 mgKOH / g or less, more preferably 5 mgKOH / g or less, and particularly preferably 1 mgKOH / g or less. The hydroxyl value of the ester oligomer is required to be 30 mgKOH / g or less from the viewpoint of suppressing bleeding out of the ultraviolet absorber, more preferably 5 mgKOH / g or less, and particularly preferably 1 mgKOH / g or less. .
The hydroxyl value of the ester oligomer can be measured as follows.
The film is immersed in methanol to extract the ester oligomer. The extract is analyzed by NMR (Nuclear Magnetic Resonance, nuclear magnetic resonance), HPLC (High performance liquid chromatography, high performance liquid chromatography), etc., and the molecular structure and addition amount of the ester oligomer are determined. The extract is evaporated to collect 1 g of the added component, and the hydroxyl value is measured by the method described in JIS K0700. From the hydroxyl value of the extract, the hydroxyl value of the ester oligomer is determined in consideration of the determined addition amount of the ester oligomer and the presence or absence of the hydroxyl group.

(Synthesis method)
As a method for synthesizing the ester oligomer used in the present invention, a known method such as a dehydration condensation reaction of a dicarboxylic acid and a diol or an addition of a dicarboxylic anhydride to a diol and a dehydration condensation reaction can be used.
Furthermore, the synthesis of the ester oligomer is a hot melt condensation method by a polyesterification reaction or a transesterification reaction between the dicarboxylic acid, the diol, and a monocarboxylic acid having an alicyclic structure for terminal blocking, according to a conventional method. Alternatively, it can be easily synthesized by any of the interfacial condensation methods of acid chlorides of these acids and diols.

The number average molecular weight (Mn) of the ester oligomer used in the present invention is preferably 500 to 3000, more preferably 600 to 1500, and further preferably 750 to 1500. If the number average molecular weight of the ester oligomer is 500 or more, the volatility is low, and film failure or process contamination due to volatilization under high temperature conditions during stretching of the optical film is less likely to occur. If the number average molecular weight of the ester oligomer is 3000 or less, the compatibility with the cellulose acylate and the UV absorber is increased, and bleeding out during film formation and heat stretching is less likely to occur.
The number average molecular weight of the ester oligomer used in the present invention can be measured and evaluated by gel permeation chromatography (GPC). Specifically, the value measured by the following method is adopted. The ester oligomer was dissolved in THF (tetrahydrofuran), and this was performed using high-speed GPC manufactured by Tosoh Corporation. The number average molecular weight Mn was calculated in terms of polystyrene. More detailed conditions are shown below.
Solvent: THF (tetrahydrofuran)
Column: TOSOH TSKgel Super HZM-H, HZ4000, HZ2000 (manufactured by Tosoh Corporation) are used;
Column temperature: 40 ° C .;
Sample concentration: 0.1% by mass;
Detector: EcoSEC HLC-8320GPC (manufactured by Tosoh Corporation);
Flow rate: 0.01 mL / min
Calibration curve: A calibration curve with 6 samples of standard polystyrene (TSK standard polystyrene, manufactured by Tosoh Corporation, Mw = 7000000 to 1000) is used.

(Addition amount (content))
In the cellulose acylate film of the present invention, the content of the ester oligomer is preferably 4 to 30 parts by mass, more preferably 5 to 15 parts by mass with respect to 100 parts by mass of the cellulose acylate. It is especially preferable that it is 10-13 mass parts. By setting it as the said range, the hardness of a film becomes especially favorable. The ester oligomer may contain only 1 type and may contain 2 or more types. When two or more types are included, the total amount is preferably within the above range.

<Benzotriazole UV absorber>
The cellulose acylate film of the present invention contains a benzotriazole-based ultraviolet absorber (also referred to as “UV absorber”). The UV absorber prevents the liquid crystal or the like of the liquid crystal display from being deteriorated by ultraviolet rays, and contributes to improvement of the durability of the polarizer in a high temperature and high humidity environment. In particular, the addition of a UV absorber is effective in a mode in which the cellulose acylate film of the present invention is used as a polarizing plate protective film for protecting the polarizer of the polarizing plate or a surface protective film for a liquid crystal display device.

  The benzotriazole-based ultraviolet absorber that can be used in the present invention is not particularly limited, but is not limited to a compound having the following structure or 2,2-methylenebis [4- (1,1,3,3-tetramethylbutyl)- 6- (2H-benzotriazol-2-yl) phenol], (2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3, 5-triazine, triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], N, N′-hexamethylenebis (3,5-di-tert-butyl- 4-hydroxy-hydrocinnamide), 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, -(2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3', 5'-di-tert-amylphenyl) -5 -Chlorobenzotriazole, 2,6-di-tert-butyl-p-cresol, or pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate]. From the viewpoint of compatibility with the oligomer to be used and halogen-free, it is preferable to use a compound having the following structure.

  The said benzotriazole type ultraviolet absorber may be used individually by 1 type, or may use 2 or more types together.

The amount of the benzotriazole-based ultraviolet absorber used is 4 to 20 parts by mass, preferably 4 to 15 parts by mass, more preferably 5 to 10 parts by mass with respect to 100 parts by mass of the cellulose acylate. preferable. When it is 4 parts by mass or more, a sufficient ultraviolet protection function is obtained at a thickness of 25 μm or more, and when it is 20 parts by mass or less, bleeding out can be suppressed.
When two or more kinds of benzotriazole ultraviolet absorbers are used in combination, the total amount used is preferably within the above range.

  Other than the benzotriazole ultraviolet absorber, there is no particular limitation on the UV absorber that can be used in the present invention. Any of the UV absorbers conventionally used in cellulose acylate films can be used. As said ultraviolet absorber, the compound as described in Unexamined-Japanese-Patent No. 2006-184874 can be mentioned. Polymer ultraviolet absorbers can also be preferably used. In particular, polymer type ultraviolet absorbers described in JP-A-6-148430 are preferably used.

<Polarizer durability improver>
The cellulose acylate film of the present invention may contain a polarizer durability improving agent as an additive in order to improve the durability of the polarizer in a high temperature and high humidity environment.
As the polarizer durability improver, known organic acids can be used. For example, organic acid monoglycerides such as monoglycerides of polyvalent carboxylic acids, compounds described in JP 2012-72348 A, barbituric acid derivatives And so on.
The content of the polarizer durability improving agent contained in the cellulose acylate film of the present invention is preferably 6% by mass or less and more preferably 4% by mass or less with respect to the cellulose acylate.

<Other additives>
The cellulose acylate film of the present invention may further contain at least one other additive as long as the effects of the present invention are not impaired. Examples of other additives include polymer plasticizers other than the above ester oligomers (for example, phosphate ester plasticizers, carboxylic ester plasticizers, polycondensation oligomer plasticizers), antioxidants, etc. And a matting agent described later.
As content of the said other additive contained in the cellulose acylate film of this invention, 3 mass parts or less are preferable with respect to 100 mass parts of cellulose acylates, 1 mass part or less is more preferable, and substantially contains More preferably not.
Further, the content of the retardation enhancer (including the retardation reducing agent) contained in the cellulose acylate film of the present invention is preferably 3 parts by mass or less with respect to 100 parts by mass of the cellulose acylate. The following is more preferable, and it is further preferable that the following is not substantially included.

(Other polymer plasticizers)
The cellulose acylate film of the present invention can be added with other polymer plasticizers in addition to the ester oligomer as long as the effects of the present invention are not impaired. Other polymer plasticizers include polyester polyurethane plasticizers, aliphatic hydrocarbon polymers, alicyclic hydrocarbon polymers, acrylic polymers such as polyacrylates and polymethacrylates (as ester groups , Methyl group, ethyl group, propyl group, butyl group, isobutyl group, pentyl group, hexyl group, cyclohexyl group, octyl group, 2-ethylhexyl group, nonyl group, isononyl group, tert-nonyl group, dodecyl group, tridecyl group, Stearyl group, oleyl group, benzyl group, phenyl group, etc.), polyvinyl isobutyl ether, vinyl polymers such as poly N-vinyl pyrrolidone, styrene polymers such as polystyrene and poly 4-hydroxystyrene, poly, such as polyethylene oxide and polypropylene oxide. ether, Polyamide, polyurethane, polyurea, phenol - formaldehyde condensates, urea - formaldehyde condensate, vinyl acetate, and the like.

Among these, it is particularly preferable to use an acrylic polymer in combination. In the present invention, the acrylic polymer is preferably a homopolymer or copolymer synthesized from monomers such as acrylic acid or alkyl methacrylate.
Examples of the acrylate monomer having no aromatic ring include, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i, s-, t-), acrylic Pentyl acid (n-, i-, s-), hexyl acrylate (n, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-), nonyl acrylate (n -, I-), myristyl acrylate (n-, i-), acrylic acid (2-ethyl hesyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl) Acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid (2-methoxyethyl), Acrylic acid (2-ethoxyethyl), etc., or the acrylic acid ester may include those obtained by changing the methacrylic acid ester. Examples of the acrylic monomer used for the acrylic polymer having an aromatic ring include styrene, methylstyrene, and hydroxystyrene.

  When the acrylic polymer is a copolymer, it is composed of X ′ (a monomer component having a hydrophilic group) and Y ′ (a monomer component having no hydrophilic group), and X ′: Y ′ (molar ratio) is 1: 1. ~ 1: 99 is preferred. The content of the acrylic polymer is preferably 1 to 20% by mass with respect to the cellulose acylate. These acrylic polymers can be synthesized with reference to the method described in JP-A-2003-12859.

(Antioxidant)
The cellulose acylate film of the present invention is a known antioxidant such as 2,6-di-tert-butyl-4-methylphenol, 4,4′-thiobis- (6-tert-butyl-3-methylphenol). ), 1,1′-bis (4-hydroxyphenyl) cyclohexane, 2,2′-methylenebis (4-ethyl-6-tert-butylphenol), 2,5-di-tert-butylhydroquinone, pentaerythrityl-tetrakis Phenolic or hydroquinone antioxidants such as [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] can be included. Further, tris (4-methoxy-3,5-diphenyl) phosphite, tris (nonylphenyl) phosphite, tris (2,4-di-tert-butylphenyl) phosphite, bis (2,6-di-tert) It is preferable to include phosphorus antioxidants such as -butyl-4-methylphenyl) pentaerythritol diphosphite and bis (2,4-di-tert-butylphenyl) pentaerythritol diphosphite. The content of the antioxidant in the cellulose acylate film of the present invention is preferably 0.05 to 5.0 parts by mass with respect to 100 parts by mass of the cellulose acylate.

<Method for producing cellulose acylate film>
There is no restriction | limiting in particular in the method of manufacturing the cellulose acylate film of this invention, It can form into a film using a well-known method. For example, the film may be formed using either a solution casting film forming method or a melt film forming method. From the viewpoint of improving the surface shape of the film, the cellulose acylate film of the present invention is preferably produced using a solution casting film forming method. Hereinafter, although the case where the solution casting film forming method is used will be described as an example, the method for producing the cellulose acylate film of the present invention is not limited to the solution casting film forming method. In addition, about the case where a melt film forming method is used, a well-known method can be used.

-Solution-
In the solution casting film forming method, a web is formed using a solution containing cellulose acylate, UV absorber, ester oligomer, and various additives as required. Hereinafter, a solution that may be used in the solution casting film forming method (hereinafter, also referred to as “cellulose acylate solution” or “dope”) will be described.

-Solvent-
The cellulose acylate used in the present invention is dissolved in a solvent to form a dope, which is cast on a substrate (for example, a metal support) to form a film. At this time, since it is necessary to evaporate the solvent after extrusion or casting, it is preferable to use a volatile solvent.
Furthermore, it does not react with a reactive metal compound or a catalyst, and does not dissolve the casting base material. Two or more solvents may be mixed and used.
Alternatively, cellulose acylate and a reactive metal compound capable of hydrolysis polycondensation may be dissolved in different solvents and then mixed.
Here, an organic solvent having good solubility in the cellulose acylate is referred to as a good solvent, and has a main effect on dissolution, and an organic solvent used in a large amount among them is a main (organic) solvent or a main solvent ( Organic) solvent.

  Examples of the good solvent include ketones such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, ethers such as tetrahydrofuran (THF), 1,4-dioxane, 1,3-dioxolane, 1,2-dimethoxyethane, and the like. In addition to esters such as methyl acid, ethyl formate, methyl acetate, ethyl acetate, amyl acetate, γ-butyrolactone, methyl cellosolve, dimethylimidazolinone, dimethylformamide, dimethylacetamide, acetonitrile, dimethylsulfoxide, sulfolane, nitroethane, Examples include methylene chloride and methyl acetoacetate, and 1,3-dioxolane, THF, methyl ethyl ketone, acetone, methyl acetate and methylene chloride are preferred.

The dope preferably contains 1 to 40% by mass of an alcohol having 1 to 4 carbon atoms in addition to the organic solvent.
After casting the dope on the metal support, the solvent starts to evaporate and the ratio of alcohol increases so that the web (referred to as the dope film after casting the cellulose acylate dope on the support) Used as a gelling solvent that makes it easy to gel and peel off from the metal support, or when these ratios are small, promote the dissolution of cellulose acylate, a non-chlorine organic solvent There is also a role to suppress gelation, precipitation, and viscosity increase of the reactive metal compound.

Examples of the alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol, and propylene glycol monomethyl ether.
Of these, methanol and ethanol are preferred because they are excellent in dope stability, have a relatively low boiling point, good drying properties, and no toxicity. Ethanol is most preferred. These organic solvents alone are not soluble in cellulose esters and are referred to as poor solvents.

In the present invention, since the cellulose acylate contains a hydrogen bonding functional group such as a hydroxyl group, an ester or a ketone, it is 5 to 30% by mass in the total solvent, more preferably 7 to 25% by mass, and still more preferably 10 to 20%. From the viewpoint of reducing the peeling load from the casting support, it is preferable to contain a mass% of alcohol.
Further, in the present invention, it is effective to contain a small amount of water to increase the solution viscosity and the film strength in the wet film state at the time of drying, or to increase the dope strength at the time of casting the drum method. It may be contained in an amount of 0.1 to 5% by mass, more preferably 0.1 to 3% by mass, and particularly 0.2 to 2% by mass.

  Examples of combinations of organic solvents preferably used as the solvent for the cellulose acylate solution in the present invention are described in JP-A-2009-262551.

  In addition, if necessary, a non-halogen organic solvent can be used as a main solvent, and detailed description can be found in the Japan Institute of Invention Publication (Publication No. 2001-1745, published on March 15, 2001, Invention Association). There is a description.

The cellulose acylate concentration in the cellulose acylate solution in the present invention is preferably 5 to 40% by mass, more preferably 10 to 30% by mass, and most preferably 15 to 30% by mass.
The cellulose acylate concentration can be adjusted to a predetermined concentration at the stage where cellulose acylate is dissolved in a solvent. Further, after preparing a solution with a low concentration (for example, 4 to 14% by mass) in advance, the solution may be concentrated by evaporating the solvent or the like. Furthermore, after preparing a high concentration solution in advance, it may be diluted. Moreover, the density | concentration of a cellulose acylate can also be reduced by adding an additive.

  The timing of adding the additive can be appropriately determined according to the type of the additive. For example, ester oligomers and UV absorbers are added to the dope after dissolving the UV absorber in alcohols such as methanol, ethanol, butanol, organic solvents such as methylene chloride, methyl acetate, acetone, dioxolane, or mixed solvents thereof. Or may be added directly into the dope composition. For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and cellulose ester to disperse and then added to the dope.

  The most preferable solvent that satisfies such conditions and dissolves cellulose acylate, which is a preferred polymer compound, at a high concentration is a mixed solvent having a ratio of methylene chloride: ethyl alcohol of 95: 5 to 80:20. Alternatively, a mixed solvent of methyl acetate: ethyl alcohol 60:40 to 95: 5 is also preferably used.

(1) Dissolution process In a dissolution vessel, the cellulose acylate and additives are dissolved in an organic solvent mainly in a dissolution solvent while stirring to form a dope, or an additive in a cellulose acylate solution. This is a step of mixing a solution to form a dope.
For dissolving cellulose acylate, a method carried out at normal pressure, a method carried out below the boiling point of the main solvent, a method carried out under pressure above the boiling point of the main solvent, JP-A-9-95544, JP-A-9-95557 Alternatively, various dissolution methods such as a cooling dissolution method as described in JP-A-9-95538 and a high-pressure method as described in JP-A-11-21379 can be used. The method of pressurizing at a boiling point or higher is preferred.
The concentration of cellulose acylate in the dope is preferably 10 to 35% by mass. It is preferable that an additive is added to the dope during or after dissolution to dissolve and disperse, and then filtered through a filter medium, defoamed, and sent to the next step with a liquid feed pump.

(2) Casting process An endless metal belt that feeds the dope to a pressure die through a liquid feed pump (for example, a pressurized metering gear pump) and transfers it infinitely, such as a stainless steel belt, or a metal such as a rotating metal drum This is a step of casting the dope from the pressure die slit to the casting position on the support.
A pressure die that can adjust the slit shape of the die base and facilitates uniform film thickness is preferred. The pressure die includes a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface. In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and stacked. Or it is also preferable to obtain the film of a laminated structure by the co-casting method which casts several dope simultaneously.

(3) Solvent evaporation process The web (the state before the cellulose acylate film is completed, which still contains a lot of solvent) is heated on the metal support, and the web peels from the metal support. This is the process of evaporating the solvent until it becomes possible.
To evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat from the back side of the metal support by a liquid, a method of transferring heat from the front and back by radiant heat, etc. However, drying efficiency is preferable. A method of combining them is also preferable. In the case of backside liquid heat transfer, it is preferable to heat at or below the boiling point of the main solvent of the organic solvent used in the dope or the organic solvent having the lowest boiling point.

(4) Peeling process It is the process of peeling the web which the solvent evaporated on the metal support body in a peeling position. The peeled web is sent to the next process. In addition, if the residual solvent amount (the following formula) of the web at the time of peeling is too large, peeling is difficult, or conversely, if the film is peeled off after being sufficiently dried on the metal support, a part of the web is in the middle. It may come off.
Here, there is a gel casting method (gel casting) as a method for increasing the film forming speed (the film forming speed can be increased by peeling while the residual solvent amount is as large as possible). For example, there are a method in which a poor solvent for cellulose acylate is added to the dope and the dope is cast and then gelled, a method in which the temperature of the metal support is lowered and gelled. By gelling on the metal support and increasing the strength of the film at the time of peeling, the speed of film formation can be increased by speeding up the peeling.
The amount of residual solvent during peeling of the web on the metal support is preferably within a range of 5 to 150% by mass depending on the strength of drying conditions, the length of the metal support, etc., but the amount of residual solvent is larger. In the case of peeling at the time, the amount of residual solvent at the time of peeling is determined in consideration of economic speed and quality. In the present invention, the temperature at the peeling position on the metal support is preferably −50 to 40 ° C., more preferably 10 to 40 ° C., and most preferably 15 to 30 ° C.

The residual solvent amount of the web at the peeling position is preferably 10 to 150% by mass, and more preferably 10 to 120% by mass.
The amount of residual solvent can be represented by the following formula.
Residual solvent amount (% by mass) = [(MN) / N] × 100
Here, M is the mass of the web at an arbitrary point in time, and N is the mass when the mass M is dried at 110 ° C. for 3 hours.

(5) Drying or heat treatment process, stretching process After the peeling process, a drying apparatus that alternately conveys the web through a plurality of rolls arranged in the drying apparatus, and / or a tenter that clips and conveys both ends of the web with clips. It is preferred to dry the web using an apparatus.

When heat treatment is performed in the present invention, the heat treatment temperature is less than Tg (glass transition temperature) −5 ° C., preferably Tg−20 ° C. or more and less than Tg−5 ° C., Tg−15 ° C. or more and Tg−5 ° C. More preferably, it is less.
The heat treatment temperature is preferably 30 minutes or less, more preferably 20 minutes or less, and particularly preferably about 10 minutes.

  As a means for drying and heat treatment, hot air is generally blown on both sides of the web, but there is also a means for heating by applying a microwave instead of the wind. The temperature, air volume, and time vary depending on the solvent used, and the conditions may be appropriately selected according to the type and combination of the solvents used.

  The stretching process may be performed in any one of MD (transport direction) and TD (direction orthogonal to the transport direction), or may be biaxially stretched in both directions. Biaxial stretching is preferred. Stretching may be performed in one stage or in multiple stages. The tensile elastic modulus is adjusted to the above range by adjusting the type of cellulose acylate to be used and the acyl substitution degree, selecting the type of additive, or adjusting the ratio thereof. Can do.

The stretching ratio in stretching in the film transport direction MD is preferably 0 to 20%, more preferably 0 to 15%, and particularly preferably 0 to 10%. The stretch ratio (elongation) of the web during the stretching can be achieved by the difference in peripheral speed between the metal support speed and the stripping speed (stripping roll draw). For example, when an apparatus having two nip rolls is used, the film can be preferably stretched in the conveying direction (longitudinal direction) by increasing the rotational speed of the nip roll on the outlet side rather than the rotational speed of the nip roll on the inlet side. it can. By performing such stretching, the tensile modulus of MD can be adjusted.
Here, the “stretch ratio (%)” means that obtained by the following formula.
Stretch ratio (%) = 100 × {(Length after stretching) − (Length before stretching)} / Length before stretching

The stretching ratio in stretching in the direction TD perpendicular to the film conveying direction is preferably 0 to 30%, more preferably 1 to 20%, and particularly preferably 5 to 15%.
In addition, in this invention, it is preferable to extend | stretch using a tenter apparatus as a method of extending | stretching to the direction TD orthogonal to a film conveyance direction.

  In the biaxial stretching, a desired retardation value can be obtained by relaxing in the longitudinal direction, for example, 0.8 to 1.0 times. The draw ratio is set according to various purposes. When producing the cellulose acylate film of the present invention, it can also be uniaxially stretched in the longitudinal direction.

  It is preferable for the temperature during stretching to be Tg or less because the tensile elastic modulus in the stretching direction increases. The stretching temperature is preferably Tg-50 ° C to Tg, and more preferably Tg-30 ° C to Tg-5 ° C. On the other hand, when stretched under the above temperature conditions, the tensile elastic modulus in the stretching direction increases, while the tensile elastic modulus in the direction orthogonal thereto tends to decrease. Therefore, in order to increase the tensile elastic modulus in both the MD and TD directions by stretching, it is preferable to perform stretching in both directions, that is, biaxial stretching in the above temperature range.

  In addition, you may dry after an extending process. When drying after the stretching step, the drying temperature, the amount of drying air and the drying time differ depending on the solvent used, and the drying conditions may be appropriately selected according to the type and combination of the solvents used. In the present invention, the drying temperature after the stretching step is preferably lower than the stretching temperature in the stretching step from the viewpoint of increasing the front contrast when the film is incorporated into a liquid crystal display device.

(6) Winding The length of the film obtained as described above is preferably wound at 100 to 10000 m per roll, more preferably 500 to 7000 m, and further preferably 1000 to 6000 m. . The width of the film is preferably 0.5 to 5.0 m, more preferably 1.0 to 3.0 m, and still more preferably 1.0 to 2.5 m. When winding, it is preferable to give knurling to at least one end, the knurling width is preferably 3 mm to 50 mm, more preferably 5 mm to 30 mm, and the height is preferably 0.5 to 500 μm, more preferably 1 to 200 μm. is there. This may be a single push or a double push.

  The web thus obtained can be wound up to obtain a cellulose acylate film.

<Layer structure>
The cellulose acylate film may be a single layer film or may have a laminated structure of two or more layers. For example, a laminated structure composed of two layers of a core layer and an outer layer (sometimes referred to as a surface layer or a skin layer) or a laminated structure composed of three layers of an outer layer, a core layer, and an outer layer are also preferable. It is also preferable that the laminated structure be formed by co-casting.
When the cellulose acylate film used in the present invention has a laminated structure of two or more layers, it is preferable to add a matting agent to the outer layer. As the matting agent, for example, those described in JP-A-2011-127045 can be used, and for example, silica particles having an average particle size of 20 nm can be used.

<Characteristics of cellulose acylate film>
(Thickness of cellulose acylate film)
The thickness of the cellulose acylate film of the present invention is 10 to 40 μm, preferably 15 to 35 μm, more preferably 15 to 30 μm, and particularly preferably less than 30 μm from the viewpoint of thinning. . In the said range, the bleed-out suppression effect by ester oligomer addition is acquired highly.
When the cellulose acylate film used in the present invention has a laminated structure of two or more layers, the thickness of each outer layer is preferably 1 to 10 μm, more preferably 1 to 5 μm. The thickness is preferably 1 to 3 μm.

<Uses of cellulose acylate film>
The cellulose acylate film of the present invention is useful for various applications such as a polarizing plate protective film and a surface protective film disposed on an image display surface. In order to show functions suitable for each application, the cellulose acylate film of the present invention has, for example, a hard coat layer, an antiglare layer, a clear hard coat layer, an antireflection layer, an antistatic layer, an antifouling layer, and the like. You may do it.

  The cellulose acylate film of the present invention has good bonding properties with a polarizer and is suitable for use in a liquid crystal display device having a polarizing plate as an essential member.

The polarizing plate protective film used on the surface side of a display device such as a liquid crystal display device preferably has an antireflection layer, an antistatic layer and an antifouling layer in addition to the antiglare layer or the clear hard coat layer.
Further, when the polarizing plate is produced, if the cellulose acylate film of the present invention has an in-plane slow axis, it is bonded so that the in-plane slow axis and the transmission axis of the polarizer are parallel or perpendicular to each other. Is preferred.

[Hard coat layer]
In one preferred embodiment, the cellulose acylate film of the present invention has a hard coat layer having a thickness of 0.1 to 6 μm (preferably 3 to 6 μm). By having a thin hard coat layer in the above range, an optical film including a hard coat layer that has improved physical properties such as brittleness and curl suppression, reduced weight, and reduced manufacturing costs is obtained.
Moreover, it becomes an optical film excellent also in the adhesiveness of a hard-coat layer and a base film by hardening the curable composition of a hard-coat layer on the cellulose acylate film (base material) of this invention.
For the purpose of adding another function, another functional layer may be laminated on the hard coat layer. Specifically, it is an antireflection layer or an antifouling layer.
In addition, by adding fillers and additives to the hard coat layer, chemical properties such as mechanical, electrical and optical physical performance and water and oil repellency can be imparted to the hard coat layer itself. it can.

  The hard coat layer is preferably formed by curing the curable composition. The curable composition is preferably prepared as a liquid coating composition. An example of the coating composition contains a matrix-forming binder monomer or oligomer, polymers, and an organic solvent. A hard coat layer can be formed by curing the coating composition after coating. For curing, a crosslinking reaction or a polymerization reaction can be used.

(Monomer or oligomer for matrix forming binder)
Examples of matrix forming binder monomers or oligomers that can be used include ionizing radiation curable polyfunctional monomers and polyfunctional oligomers. The polyfunctional monomer or polyfunctional oligomer is preferably a monomer capable of crosslinking reaction or polymerization reaction. The functional group of the ionizing radiation-curable polyfunctional monomer or polyfunctional oligomer is preferably a light, electron beam, or radiation polymerizable group, and among them, a photopolymerizable functional group is preferable.

  Examples of the photopolymerizable functional group include unsaturated polymerizable functional groups such as (meth) acryloyl group, vinyl group, styryl group, and allyl group, and ring-opening polymerizable functional groups such as epoxy compounds. Of these, a (meth) acryloyl group is preferred.

  Specific examples of the photopolymerizable polyfunctional monomer having a photopolymerizable functional group include (meth) alkylene glycols such as neopentyl glycol acrylate, 1,6-hexanediol (meth) acrylate, and propylene glycol di (meth) acrylate. Acrylic acid diesters; (Meth) acrylic acid of polyoxyalkylene glycols such as triethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate Diesters; (meth) acrylic acid diesters of polyhydric alcohols such as pentaerythritol di (meth) acrylate; 2,2-bis {4- (acryloxy-diethoxy) phenyl} propane, 2,2-bi {4- (acryloxy · polypropoxy) phenyl} (meth) diesters acrylate of ethylene oxide or propylene oxide adducts such as propane; and the like.

  Furthermore, urethane (meth) acrylates, polyester (meth) acrylates, isocyanuric acid acrylates, and epoxy (meth) acrylates are also preferably used as the photopolymerizable polyfunctional monomer.

Among the above, esters of polyhydric alcohol and (meth) acrylic acid are preferable, and polyfunctional monomers having three or more (meth) acryloyl groups in one molecule are more preferable.
Specifically, (di) pentaerythritol tri (meth) acrylate, (di) pentaerythritol tetra (meth) acrylate, (di) pentaerythritol penta (meth) acrylate, (di) pentaerythritol hexa (meth) acrylate, tri Pentaerythritol triacrylate, tripentaerythritol hexatriacrylate, trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, EO-modified trimethylolpropane tri (meth) acrylate, PO-modified trimethylolpropane tri (meth) acrylate, EO-modified tri (meth) acrylate phosphate, 1,2,4-cyclohexanetetra (meth) acrylate, Printer glycerol triacrylate, 1,2,3-cyclohexane tetramethacrylate, polyester polyacrylate and caprolactone-modified tris (acryloyloxyethyl) isocyanurate, and the like.
In the present specification, “(meth) acrylate”, “(meth) acrylic acid”, and “(meth) acryloyl” represent “acrylate or methacrylate”, “acrylic acid or methacrylic acid”, and “acryloyl or methacryloyl”, respectively. .

Furthermore, resins having three or more (meth) acryloyl groups, such as relatively low molecular weight polyester resins, polyether resins, acrylic resins, epoxy resins, urethane resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiol polyene resins And oligomers or prepolymers such as polyfunctional compounds such as polyhydric alcohols.
As specific compounds of polyfunctional acrylate compounds having three or more (meth) acryloyl groups, reference may be made to [0096] of JP-A No. 2007-256844.

As urethane acrylates, for example, alcohols, polyols, and / or hydroxyl group-containing compounds such as hydroxyl group-containing acrylates are reacted with isocyanates, and if necessary, polyurethane compounds obtained by these reactions (meth) Mention may be made of urethane acrylate compounds obtained by esterification with acrylic acid.
As specific examples of specific compounds, reference can be made to the description of [0017] in JP-A-2007-256844.

  Use of isocyanuric acid acrylates is preferable because curling can be further reduced. Examples thereof include isocyanuric acid diacrylates and isocyanuric acid triacrylates, and examples of specific compounds can be referred to JP-A-2007-256844 [0018] to [0021].

  In the hard coat layer, an epoxy compound can be further used for reducing shrinkage due to curing. As monomers having an epoxy group for constituting this, monomers having two or more epoxy groups in one molecule are used, and examples thereof include JP-A Nos. 2004-264563, 2004-264564, and Examples thereof include epoxy monomers described in 2005-37737, 2005-37738, 2005-140862, 2005-140862, 2005-140863, 2002-322430 and the like. It is also preferable to use a compound having both epoxy and acrylic functional groups such as glycidyl (meth) acrylate.

(Curable composition)
An example of the curable composition that can be used for forming the hard coat layer is a curable composition containing an acrylate compound. The curable composition preferably contains a photoradical polymerization initiator or a thermal radical polymerization initiator together with the acrylate compound, and may further contain a filler, a coating aid, and other additives as desired. . Curing of the curable composition can be carried out by allowing the polymerization reaction to proceed by irradiation with ionizing radiation or heating in the presence of a photo radical polymerization initiator or a thermal radical polymerization initiator. Both ionizing radiation curing and thermal curing can be performed. Commercially available compounds can be used as the photo and thermal polymerization initiators, and they are described in “Latest UV Curing Technology” (p. 159, publisher: Kazuhiro Takahisa, publisher; Technical Information Association, 1991). Issued) and Ciba Specialty Chemicals catalog.

  The curable composition is preferably prepared as a coating solution. The coating solution can be prepared by dissolving and / or dispersing the above components in an organic solvent.

(Properties of hard coat layer)
The hard coat layer is preferably excellent in scratch resistance. Specifically, when a pencil hardness test as an index of scratch resistance is carried out, it is preferable to achieve 3H or more in both MD and TD directions, and it is more preferable to achieve 4H or more.
Further, it may have an anti-glare function by forming irregularities on the surface of the hard coat layer using a conventionally known method.

  The cellulose acylate film of the present invention is useful for various applications such as a polarizing plate protective film and a surface protective film disposed on an image display surface. In order to exhibit a function suitable for each application, the cellulose acylate film may have other layers in addition to the above-described hard coat layer. For example, you may have an antireflection layer, an antistatic layer, an antifouling layer, etc.

[Polarizer]
The polarizing plate of the present invention includes a polarizer and at least one cellulose acylate film of the present invention.
The polarizing plate of the present invention can be produced by a general method. For example, it can be produced by laminating one surface of the cellulose acylate film of the present invention and a polarizer. The bonding surface of the cellulose acylate film of the present invention is preferably subjected to an alkali saponification treatment. Moreover, complete saponification type polyvinyl alcohol aqueous solution can be used for bonding.

  A conventionally well-known thing can be used as said polarizer. For example, a film made of a hydrophilic polymer such as polyvinyl alcohol or ethylene-modified polyvinyl alcohol having an ethylene unit content of 1 to 4 mol%, a polymerization degree of 2000 to 4000, and a saponification degree of 99.0 to 99.99 mol%, A film stretched by treatment with a dichroic dye such as the above, or a film oriented by treating a plastic film such as vinyl chloride is used.

  The film thickness of the polarizer is preferably 5 to 30 μm. The polarizer thus obtained is bonded to the cellulose acylate film of the present invention. When the thickness of the polarizer is reduced, the durability of the polarizer is likely to deteriorate. However, the cellulose acylate film of the present invention can improve the durability of the polarizer in a high temperature and high humidity environment. It is also suitably used when the film thickness is small. It is particularly preferable to bond with a 5 to 20 μm polarizer, and more preferable to bond with a 5 to 15 μm polarizer.

The cellulose acylate film of the present invention may be further bonded to the surface opposite to the surface where the cellulose acylate film of the present invention is bonded to the polarizer, or a conventionally known optical film is bonded. May be.
The above-described conventionally known optical film is not particularly limited in terms of optical properties and materials, but includes (or has as a main component) an optical material including a cellulose acylate resin, an acrylic resin, and / or a cyclic olefin resin. A film can be preferably used, and an optically isotropic film or an optically anisotropic retardation film may be used.
As for the above-described conventionally known optical films, for example, ZRF25 (manufactured by FUJIFILM Corporation) or the like can be used as the one containing a cellulose acylate resin.
As for the above-mentioned conventionally known optical films, those containing an acrylic resin include an optical film containing a (meth) acrylic resin containing a styrene resin described in Japanese Patent No. 4570042, and described in Japanese Patent No. 5041532. An optical film containing a (meth) acrylic resin having a glutarimide ring structure in the main chain, an optical film containing a (meth) acrylic resin having a lactone ring structure described in JP2009-122664A, and JP2009- An optical film containing a (meth) acrylic resin having a glutaric anhydride unit described in Japanese Patent No. 139754 can be used.
As for the above-mentioned conventionally known optical films, those containing a cyclic olefin resin include cyclic olefin-based resin films described in paragraph [0029] and subsequent paragraphs of JP-A-2009-237376, Japanese Patent No. 4881827, A cyclic olefin resin film containing an additive for reducing Rth described in JP-A-2008-063536 can be used.
In an embodiment in which the polarizing plate of the present invention is used in a liquid crystal display device, the cellulose acylate film of the present invention can be disposed so as to be a polarizing plate protective film on the side close to the liquid crystal cell, or on the side far from the liquid crystal cell. Although it can also arrange | position so that it may become a polarizing plate protective film, it is preferable to arrange | position so that it may become a polarizing plate protective film of the side far from a liquid crystal cell.

[Liquid Crystal Display]
The liquid crystal display device of the present invention is a liquid crystal display device having a liquid crystal cell and two polarizing plates (viewing-side polarizing plate and backlight-side polarizing plate) disposed on both sides of the liquid crystal cell. At least one of the polarizing plates is the polarizing plate of the present invention.
There is no restriction | limiting in particular about the function in the liquid crystal display device of the cellulose acylate film of this invention.
As a preferable example of the arrangement method of the cellulose acylate film of the present invention, the cellulose acylate film is arranged on the viewing side polarizing plate (that is, the side far from the liquid crystal cell) in the viewing side polarizing plate in the state having the hard coat layer.
Another example of the arrangement method of the cellulose acylate film of the present invention is an embodiment in which the cellulose acylate film is arranged on the backlight side (that is, the side far from the liquid crystal cell) in the backlight side polarizing plate without the hard coat layer. .
Thus, in the liquid crystal display device of the present invention, it is preferable that the cellulose acylate film of the present invention is disposed on the far side from the liquid crystal cell in the polarizing plate.
As for other configurations, any configuration of a known liquid crystal display device can be adopted. The mode of the liquid crystal cell is not particularly limited, and a TN (Twisted Nematic) mode type liquid crystal cell, a lateral electric field switching IPS (In-Plane Switching) mode type liquid crystal cell, a FLC (Ferroelectric Liquid Crystal) mode type liquid crystal cell, AFLC (Anti-ferroelectric Liquid Crystal) mode type liquid crystal cell, OCB (Optically Compensatory Bend) mode type liquid crystal cell, STN (Super Twisted Nematic) mode type liquid crystal cell, VA (Vertical mode liquid crystal cell) Various display modes such as (Hybrid Aligned Nematic) mode type liquid crystal cell Can be configured as a liquid crystal display device. Among them, the liquid crystal display device of the present invention is preferably a liquid crystal display device in which the liquid crystal cell is a transverse electric field switching IPS mode type liquid crystal cell.

  The features of the present invention will be described more specifically with reference to examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[Example 1]
(Preparation of core layer cellulose acylate dope)
The following composition was put into a mixing tank and stirred to dissolve each component to prepare a cellulose acetate solution used as a core layer cellulose acylate dope.
―――――――――――――――――――――――――――――――――――
Core layer cellulose acylate dope ――――――――――――――――――――――――――――――――――――
Cellulose acetate having an acetyl substitution degree of 2.88 100 parts by mass ester oligomer (described in Table 1 below) 13 parts by mass The following UV absorber B 5 parts by mass Methylene chloride (first solvent) 430 parts by mass Methanol (second solvent) 64 parts by mass Department ――――――――――――――――――――――――――――――――――――
The structures of the ester oligomers used in Example 1 are shown in Tables 1 and 2 below together with the structures of the ester oligomers used in Examples and Comparative Examples described later.

  The structure of the UV absorber used in Example 1 is shown below together with the structure of the UV absorber used in each Example and Comparative Example described later.

(Preparation of outer layer cellulose acylate dope)
10 parts by mass of the following matting agent solution was added to 90 parts by mass of the core layer cellulose acylate dope to prepare a cellulose acetate solution used as an outer layer cellulose acylate dope.
――――――――――――――――――――――――――――――――
Matting agent solution ――――――――――――――――――――――――――――――――
Silica particles having an average particle size of 20 nm (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd.)
2 parts by mass Methylene chloride (first solvent) 76 parts by mass Methanol (second solvent) 11 parts by mass Core layer Cellulose acylate dope 1 part by mass ――――――――――――――――――― ―――――――――――――

(Preparation of cellulose acylate film)
The core layer cellulose acylate dope and the outer layer cellulose acylate dope are filtered through a filter paper having an average pore size of 34 μm and a sintered metal filter having an average pore size of 10 μm, and then the core layer cellulose acylate dope and the outer layer cellulose acylate dope on both sides thereof. 3 layers were simultaneously cast on a 20 ° C. band from a casting port (band casting machine). The film was peeled off at a solvent content of about 20% by mass, both ends in the width direction of the film were fixed with tenter clips, and dried while being stretched in the transverse direction at a stretch ratio of 1.1. Then, it dried further by conveying between the rolls of a heat processing apparatus, and produced the 40-micrometer-thick cellulose acylate film, and this was made into the cellulose acylate film of Example 1. The core layer of the cellulose acylate film of Example 1 had a thickness of 36 μm, and the outer layers disposed on both sides of the core layer had a thickness of 2 μm.

[Examples 2 to 17, Comparative Examples 1 to 6]
In preparation of the cellulose acylate film of Example 1, the types and addition amounts of ester oligomers used in the cellulose acylate film, the types and addition amounts of UV absorbers, and the film thickness were changed as described in Tables 1 and 2 below. The cellulose acylate film of Examples 2-17 and Comparative Examples 1-6 was produced like Example 1 except having carried out.

[Evaluation]
<Evaluation of cellulose acylate film>
The following evaluation was performed using the cellulose acylate films of the obtained Examples and Comparative Examples.

(Bleed-out evaluation)
The prepared cellulose acylate film was observed to visually evaluate whether there was a white portion. When there was a part that looked white, it was wiped off with a cloth, and it was confirmed whether or not the UV absorber adhered to the cloth, and the presence or absence of precipitation was evaluated. Specifically, after the wiped cloth is extracted with a solvent (methanol, methylene chloride, etc.), the obtained extract is added to the KBr powder and dried to obtain a mixture of the extract and KBr. The obtained mixture was ground with a mortar, made into a thin pellet with a compressor, analyzed by infrared spectroscopy, and confirmed whether or not a signal due to the UV absorber was detected.
A: The whitened part is not visible at all. B: Although there is a whitened part, precipitation of the UV absorber is not confirmed.
C: There are whitened portions, and precipitation of the UV absorber is confirmed.

(Pencil hardness evaluation)
The pencil hardness evaluation described in JIS K 5600-5-4 (1999) was performed. The prepared cellulose acylate film was conditioned for 2 hours at a temperature of 25 ° C. and a relative humidity of 60%, and then 10 times with a load of 4.9 N using a H test pencil specified in JIS S 6006 (2007). A scratch test was conducted.
5: Number of scratches 0 to 1 4: Number of scratches 2 to 3 3: Number of scratches 4 to 5 2: Number of scratches 6 to 7 1: Scratch More than 8 times

<Evaluation of polarizing plate>
(Preparation of polarizing plate)
1) Saponification of film After immersing the prepared sesulose acylate film and ZRF25 (manufactured by FUJIFILM Corporation) in a 4.5 mol / L sodium hydroxide aqueous solution (saponification solution) adjusted to 37 ° C. for 1 minute. The film was washed with water, then immersed in a 0.05 mol / L sulfuric acid aqueous solution for 30 seconds, and then passed through a washing bath. Then, draining with an air knife was repeated three times, and after dropping the water, the film was retained in a drying zone at 70 ° C. for 15 seconds and dried to produce a saponified film.

2) Production of Polarizer According to Example 1 of Japanese Patent Application Laid-Open No. 2001-141926, a peripheral speed difference was given between two pairs of nip rolls and stretched in the longitudinal direction to prepare a polarizer having a thickness of 12 μm.

3) Bonding After selecting the polarizer obtained in this way and the saponified film from two sheets and sandwiching the polarizer between them, PVA (manufactured by Kuraray Co., Ltd., PVA-117H) 3 mass Using a% aqueous solution as an adhesive, a polarizing plate was prepared by laminating with a roll-to-roll so that the polarization axis and the longitudinal direction of the film were orthogonal to each other. Here, the film on one surface side of the polarizer is a saponified film selected from the cellulose acylate film groups of Examples and Comparative Examples described in Tables 1 and 2 below, and the other surface side. This film was a saponified film of ZRF25 (manufactured by FUJIFILM Corporation).

(Durability of polarizer in high temperature and high humidity environment)
About the polarizing plate produced above, two sets of samples (about 5 cm × 5 cm) in which one side of ZRF25 (manufactured by FUJIFILM Corporation) was bonded to a glass plate with an adhesive were produced. This was arranged in a crossed Nicol state, and an orthogonal transmittance (orthogonal transmittance before wet heat aging) was measured at 410 nm using an automatic polarizing film measuring device VAP-7070 manufactured by JASCO Corporation. Thereafter, the orthogonal transmittance (orthogonal transmittance after wet heat aging) after storage for 500 hours in a high temperature and high humidity environment of 60 ° C. and 90% relative humidity was measured by the above method.
The evaluation value of the polarizer durability of the polarizing plate is defined as follows.
Evaluation value of polarizer durability of polarizing plate = [orthogonal transmittance after wet heat aging (%) − orthogonal transmittance before wet heat aging (%)] / orthogonal transmittance before wet heat aging (%)
Less than 5: 7 4: More than 7 and less than 8 3: More than 8 and less than 9 2: More than 9 and less than 10 1:10 or more

<Evaluation of liquid crystal display device>
(Display performance after Xe irradiation (polarizer / liquid crystal protection function against ultraviolet rays))
The polarizing plate of the Example and the comparative example which peeled off the viewing-side polarizing plate from the commercially available liquid crystal television (IPS mode slim type 42 type liquid crystal television) among the polarizing plates sandwiching the liquid crystal cell, and produced by the above method. Are attached to the liquid crystal cell via an adhesive on the ZRF25 surface side so that the cellulose acylate films of Examples and Comparative Examples described in Tables 1 and 2 below are arranged on the side far from the liquid crystal cell (viewing side). Combined. After confirming the display performance (brightness and color from the front and diagonal) on the reassembled LCD TV, irradiate with a xenon lamp (manufactured by Suga Test Instruments Co., Ltd.) for 64 days, and confirm the display performance again. evaluated.
A: Deterioration was not confirmed at all.
B: Deterioration in luminance and color was confirmed only from an oblique direction.
C: Deterioration was confirmed in luminance and color from the front and diagonal.

In Tables 1 and 2, EG represents ethylene glycol, PG represents propylene glycol, and 1,3-BG represents a unit derived from 1,3-butanediol.
Mn represents a number average molecular weight.
In addition, about the terminal structure of ester oligomer, all the terminals are the structures described in Tables 1-2.

Although the cellulose acylate film of the example is a thin film, it can be added with a high-concentration UV absorber without causing bleed-out, so it is excellent in the function of protecting a polarizer and liquid crystal against ultraviolet rays, and in a high-temperature and high-humidity environment. It was found that the polarizer had excellent durability and hardness.
On the other hand, Comparative Example 1 using an ester oligomer whose terminal structure is a hydroxyl group, Comparative Example 3 using an ester oligomer whose end is sealed with a group derived from acetic acid using a dicarboxylic acid not having a cyclohexane ring. In the cellulose acylate film, the bleed-out remarkably appeared. Further, in the cellulose acylate film of Comparative Example 2 having a small amount of UV absorber, although the bleed-out does not occur, the display performance when mounted on a liquid crystal display device is inferior.
In addition, as shown in Comparative Example 4, even when the film is other than the cellulose acylate film of the present invention, when the film thickness is thick, there are cases where good liquid crystal display performance is exhibited without causing bleed out. When the film was thinned, these performances could not be maintained (see Comparative Example 5).

Claims (13)

A cellulose acylate film containing a cellulose acylate, a benzotriazole-based ultraviolet absorber, and an ester oligomer,
The film thickness of the cellulose acylate film is 10 μm or more and 40 μm or less,
Containing 4 to 20 parts by mass of the benzotriazole-based ultraviolet absorber with respect to 100 parts by mass of the cellulose acylate;
The ester oligomer includes a unit derived from a diol, at least one of a unit derived from 1,2-cyclohexanedicarboxylic acid and a unit derived from 1,4-cyclohexanedicarboxylic acid, and a terminal having an alicyclic structure Sealed with a group derived from a carboxylic acid and having a hydroxyl value of 30 mgKOH / g or less,
Cellulose acylate film.   The cellulose acylate film according to claim 1, wherein the monocarboxylic acid having an alicyclic structure is a cycloalkane monocarboxylic acid having 6 to 12 carbon atoms.   The cellulose acylate film according to claim 2, wherein the monocarboxylic acid having an alicyclic structure is cyclohexanecarboxylic acid.   The number average molecular weight of the said ester oligomer is 500-3000, The cellulose acylate film as described in any one of Claims 1-3.   The cellulose acylate film according to claim 4, wherein the ester oligomer has a number average molecular weight of 750 to 1500.   The cellulose acylate film according to any one of claims 1 to 5, wherein the diol is ethylene glycol, propanediol, or butanediol.   The cellulose acylate film according to claim 6, wherein the diol is propanediol or butanediol.   The cellulose acylate film according to claim 7, wherein the diol has a branched structure.   The cellulose acylate film according to any one of claims 1 to 8, wherein a content of the ester oligomer is 4 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the cellulose acylate.   The cellulose acylate film according to claim 9, wherein the content of the ester oligomer is 10 parts by mass or more and 13 parts by mass or less with respect to 100 parts by mass of the cellulose acylate.   The cellulose acylate film according to any one of claims 1 to 10, wherein a content of the benzotriazole ultraviolet absorber is 5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the cellulose acylate. .   The polarizing plate which has a polarizer and the cellulose acylate film as described in any one of Claims 1-11 at least.   A liquid crystal display device comprising a liquid crystal cell and at least one polarizing plate according to claim 12.