JP5525464B2 - 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 using the cellulose acylate film, and a liquid crystal display device. Specifically, the present invention relates to a cellulose acylate film used as a polarizing plate protective film capable of improving the durability of a polarizing plate under high temperature and high humidity when combined with a polarizer, a polarizing plate using the cellulose acylate film, and a liquid crystal display device. .

  Liquid crystal display devices are increasingly used year by year as space-saving image display devices with low power consumption. Conventionally, a liquid crystal display device has a major drawback that the viewing angle dependency of a display image is large. However, a wide viewing angle liquid crystal mode such as a VA mode has been put into practical use, and thereby, a high-quality image such as a television can be obtained. The demand for liquid crystal display devices is rapidly expanding even in the required market and the market where outdoor installation is required.

  The basic configuration of a liquid crystal display device is one in which polarizing plates are provided on both sides of a liquid crystal cell. The polarizing plate plays a role of allowing only light having a polarization plane in a certain direction to pass through, and the performance of the liquid crystal display device is greatly influenced by the performance of the polarizing plate. The polarizing plate is generally composed of a polarizer made of a polyvinyl alcohol film or the like on which iodine or dye is adsorbed and oriented, and a transparent protective film bonded to both the front and back sides of the polarizer. A cellulose acylate film typified by cellulose acetate has been widely used as a polarizing plate protective film because it has high transparency and can easily ensure adhesion with polyvinyl alcohol used in a polarizer. In recent years, the reality is that high-quality images are required even when the liquid crystal display device is installed outdoors under high temperature and high humidity. The polarizing plate protective film has a high temperature and high temperature when combined with a polarizer. There is a demand for improvement in durability of polarizing plates under humidity.

  First, the cellulose acylate film generally used as a protective film for a polarizing plate has high transparency (low haze), good moisture permeability (not too high and not too low), good from the above viewpoint. Optical performance is required, and conventionally, adjustment was made to satisfy the performance by adding a specific plasticizer. However, phosphate esters such as triphenyl phosphate (TPP), which are typical plasticizers, are volatilized during the drying process when a cellulose acylate film is formed, and dirt adhering to the production line is deposited on the film. It dropped and caused problems such as surface failure. In addition to this problem, from the viewpoint of providing an environmentally friendly polarizing plate protective film and a method for producing the same, it is required not to use a phosphate ester as a plasticizer for a cellulose acylate film.

  On the other hand, various compounds are known as plasticizers that can be added to other modified cellulose other than cellulose acylate, and it has been known that sugars and derivatives thereof can be added as plasticizers. For example, Patent Document 1 discloses a plastic composition for an environmentally friendly film excellent in biodegradability and mechanical properties by adding galactose as a plasticizer in a plastic composition containing starch and carboxymethyl cellulose. It is described that it can be provided.

  It has been known that saccharides and derivatives thereof are also suitable for the use of plasticizers used in cellulose films for optical films, and examples using sugar ester compounds among saccharides and derivatives thereof are known. For example, in Patent Document 2, at least five hydroxyl groups of a sugar alcohol derived from hexose with respect to cellulose acylate having an acetylation degree of 59.5% (total acyl substitution degree of about 2.8). An esterified plasticizer of a sugar alcohol in which is substituted. In Patent Document 3, a plasticizer in which 80 to 99% of hydroxyl groups of saccharides are esterified is used for cellulose acetate having a total degree of acetyl substitution of 2.5 (the same document [0032], [0115], [0134]). Patent Document 4 describes that a cellulose acylate having a total acyl substitution degree of 2.1 to 2.7 uses a plasticizer obtained by esterifying all or part of hydroxyl groups of saccharides. It can be read that the sugar ester compound used in the above is a plasticizer in which the hydroxyl group is 100% esterified (see Example Compounds 1 to 10 etc. in the same document). In Patent Document 5, several types of sugar ester compounds in which the hydroxyl groups of monosaccharides to trisaccharides are partially esterified with respect to cellulose acylate having a total acyl substitution degree of 2.7 to 2.95 have different substitution degrees. Are mixed and used as a plasticizer (see [0393], Exemplified Compounds 3-6, 9, 18, [Table 3] to [Table 6], etc.).

  However, in these documents, only examples of use of sugar ester compounds having a relatively high degree of ester substitution are shown, and in particular, Patent Document 5, which uses a mixture of several types having different degrees of substitution, is also low. Only an embodiment in which the addition ratio of the sugar ester compound with a degree of substitution was very small was shown. Furthermore, none of the documents describes an example in which the relationship between the range of the total acyl substitution degree of cellulose acylate (particularly the acetyl substitution degree) and the ester substitution degree of the sugar ester compound is examined. That is, the optimum combination of the acetyl substitution degree of cellulose acylate (particularly cellulose acetate) and the ester substitution degree of the sugar ester compound has not been shown.

  Moreover, in these literatures, when the obtained polarizing plate protective film was combined with the polarizer, the polarizing plate durability under high temperature and high humidity was not examined.

JP-A-5-320418 JP 2001-247717 A JP 2005-515285 A WO2007 / 125564 WO2009 / 031464

  Under such circumstances, the compounds described in Patent Documents 2 to 5 described above are substituted with acetyl substitution from the viewpoint of replacing or improving a conventionally used plasticizer such as triphenyl phosphate (TPP). The physical properties of the film obtained when combined with a cellulose acylate film having a degree of 2.7 or more and less than 2.95 were examined. However, when the high-substitution sugar ester compounds described in Patent Documents 2 to 5 are used, desired film properties such as transparency, moisture permeability and optical performance cannot be obtained, and combined with a polarizer. It was found that the polarizing plate durability under high temperature and high humidity was insufficient, and further improvement was required.

  An object of the present invention is to provide a cellulose acetate film that has good transparency, moisture permeability and optical performance, and can improve the durability of a polarizing plate under high temperature and high humidity when combined with a polarizer. . Moreover, it is providing the polarizing plate using this cellulose acylate film, and a liquid crystal display device using the same.

  As a result of diligent research conducted by the present inventors for the purpose of solving the above-mentioned problems, a mixture of different substitution degrees for a sugar ester compound having a specific ester substitution range as a plasticizer and a specific substitution degree of acetyl are used. When used in combination with cellulose acylate in the range, transparency, moisture permeability and optical performance are good, and durability of polarizing plate under high temperature and high humidity when combined with a polarizer can be improved. It has been found that a cellulose acylate film can be obtained.

That is, the said subject is solved by this invention of the following structures.
[1] and the ester substitution degree different sugar ester compound, a including cellulose acylate film and the cellulose acylate, acetyl substitution degree of the cellulose acylate is less than 2.70 or more 2.95, and The sugar constituting the sugar ester compound is disaccharide to tetrasaccharide, and the average ester substitution degree of the plurality of sugar ester compounds having different ester substitution degrees is 62% to 94%, in the cellulose acylate film Among a plurality of sugar ester compounds having different degrees of ester substitution, the content of a sugar ester compound having an ester substitution degree of 75% or more is 80% or less, and the sugar ester compound having an ester substitution degree of 35% to 50% A cellulose acylate film having a rate of 5% to 30%.
[2] The cellulose acylate film of [1], wherein the sugar ester compound contains at least a furanose ring or a pyranose ring.
[3] The cellulose acylate film according to [1] or [2], wherein a sugar serving as a mother nucleus of the sugar ester compound is a disaccharide.
[4] The cellulose acylate film according to any one of [1] to [3], wherein the sugar ester compound has at least one of a benzoyl group and an acetyl group as an ester group.
[5] The cellulose acylate film according to any one of [1] to [4], wherein the cellulose acylate is cellulose acetate.
[6] The cellulose acylate film according to any one of [1] to [5], which has a phase difference.
[7] The cellulose acylate film according to any one of [1] to [6], wherein a functional layer is further laminated.
[8] The cellulose acylate film according to [7], wherein the functional layer is a hard coat layer.
[9] A polarizing plate comprising a polarizer and the cellulose acylate film according to any one of [1] to [8].
[10] A liquid crystal display device comprising at least one of the cellulose acylate film according to any one of [1] to [8] or the polarizing plate according to [9].

  According to the present invention, it is possible to provide a cellulose acylate film that has good transparency, moisture permeability, and optical performance, and can improve the durability of a polarizing plate under high temperature and high humidity when combined with a polarizer. it can. Further, by using the cellulose acylate film of the present invention, the polarizing plate of the present invention capable of obtaining a high-quality image even when installed outdoors at high temperature and high humidity, and the liquid crystal display device of the present invention using the same. 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 (hereinafter also referred to as the film of the present invention) includes a plurality of sugar ester compounds having different degrees of ester substitution and cellulose acylate, and the degree of acetyl substitution of the cellulose acylate is 2.70. The sugar ester compound is less than 2.95 and the sugar constituting the sugar ester compound is disaccharide to tetrasaccharide, and the average ester substitution degree of the plurality of sugar ester compounds having different ester substitution degrees is 62% to 94%. Yes, among the plurality of sugar ester compounds having different ester substitution degrees contained in the cellulose acylate film, the content of the sugar ester compound having an ester substitution degree of 75% or more is 80% or less, and the ester substitution degree is 35%. The content of the sugar ester compound of ˜50% is 5% to 30%.
Hereinafter, the film of the present invention will be described.

<Cellulose acylate>
In the present invention, cellulose acylate having an acetyl substitution degree of 2.70 or more and less than 2.95 is used. It is preferable that the degree of acetyl substitution is 2.7 or more because the compatibility with a sugar ester compound (for example, sucrose benzoate having a specific degree of substitution) that satisfies the conditions described later is good and the film is not easily whitened. Furthermore, in addition to transparency, moisture permeability and water content are favorable, which is preferable. Further, the polarizing plate durability and the wet heat durability of the film itself are also favorable, which is preferable. On the other hand, it is preferable that the degree of substitution is less than 2.95 because the optical performance is remarkably improved.

The degree of acetyl substitution of the cellulose acylate is more preferably 2.75 to 2.90, and particularly preferably 2.82 to 2.87.
The preferred range of the total acyl substitution degree is the same as the preferred range of the acetyl substitution degree.
In addition, the substitution degree of an acyl group can be measured according to the method prescribed | regulated to ASTM-D817-96. The portion not substituted with an acyl group usually exists as a hydroxyl group.

Among the acyl groups having 2 to 22 carbon atoms to be substituted for the hydroxyl group of cellulose, the acyl group having 2 to 22 carbon atoms may be an aliphatic group or an allyl group, and is not particularly limited. A single or a mixture of two or more types But you can. These are, for example, cellulose alkylcarbonyl esters, alkenylcarbonyl esters, aromatic carbonyl esters, aromatic alkylcarbonyl esters, and the like, each of which may further have a substituted group. These preferred acyl groups include acetyl, propionyl, butanoyl, heptanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl, iso-butanoyl, t-butanoyl, cyclohexanecarbonyl, Examples include oleoyl, benzoyl, naphthylcarbonyl, and cinnamoyl groups. Among these, acetyl, propionyl, butanoyl, dodecanoyl, octadecanoyl, t-butanoyl, oleoyl, benzoyl, naphthylcarbonyl, cinnamoyl and the like are preferable, and acetyl, propionyl and butanoyl are more preferable.
The cellulose acylate film used in the present invention preferably has a substituent composed of an acetyl group in order to impart hydrophilicity from the viewpoint of moisture permeability and moisture content adjustment.

  Further, mixed fatty acid cellulose acylate may be used, and specific examples of the mixed fatty acid cellulose acylate include cellulose acetate propionate and cellulose acetate butyrate.

The basic principle of the cellulose acylate synthesis method is described in Mita et al., Wood Chemistry pages 180-190 (Kyoritsu Shuppan, 1968). A typical synthesis method is a liquid phase acetylation method using a carboxylic acid anhydride-acetic acid-sulfuric acid catalyst.
In order to obtain the cellulose acylate, specifically, a cellulose raw material such as cotton linter or wood pulp is pretreated with an appropriate amount of acetic acid, and then esterified by introducing it into a pre-cooled carboxylated mixed solution. Synthesize the rate (total of acyl substitution at the 2nd, 3rd and 6th positions is approximately 3.00). The carboxylated mixed solution generally contains acetic acid as a solvent, carboxylic anhydride as an esterifying agent, and sulfuric acid as a catalyst. The carboxylic anhydride is usually used in a stoichiometric excess over the sum of the cellulose that reacts with it and the water present in the system. After completion of the esterification reaction, a neutralizing agent (for example, calcium, magnesium, iron, aluminum or zinc) is used for hydrolysis of excess carboxylic anhydride remaining in the system and neutralization of a part of the esterification catalyst. Of carbonate, acetate or oxide). Next, the obtained complete cellulose acylate is saponified and aged by maintaining it at 50 to 90 ° C. in the presence of a small amount of an acetylation reaction catalyst (generally, remaining sulfuric acid) to obtain the desired degree of acyl substitution and polymerization. The cellulose acylate having a degree is changed. When the desired cellulose acylate is obtained, the catalyst remaining in the system is completely neutralized with a neutralizing agent as described above, or in water or dilute sulfuric acid without neutralization. The cellulose acylate solution is added (or water or dilute sulfuric acid is added to the cellulose acylate solution), the cellulose acylate is separated, washed and stabilized, etc. Can be obtained.

The cellulose acylate preferably has a number average molecular weight (Mn) of 40,000 to 200,000, more preferably 100,000 to 200,000. The cellulose acylate used in the present invention preferably has an Mw / Mn ratio of 4.0 or less, more preferably 1.4 to 2.3.
In the present invention, the average molecular weight and molecular weight distribution of cellulose acylate, etc. are calculated by calculating the number average molecular weight (Mn) and the weight average molecular weight (Mw) using gel permeation chromatography (GPC). International Publication WO 2008-126535 The ratio can be calculated by the method described in the publication.

<Sugar ester compound>
The film of the present invention contains a plurality of sugar ester compounds having different ester substitution degrees, the sugars constituting the sugar ester compound are disaccharides to tetrasaccharides, and an average of the plurality of sugar ester compounds having different ester substitution degrees Among the plurality of sugar ester compounds having an ester substitution degree of 62% to 94% and different ester substitution degrees contained in the cellulose acylate film, the content of the sugar ester compound having an ester substitution degree of 75% or more is 80% or less. And the content of the sugar ester compound having an ester substitution degree of 35% to 50% is 5% to 30%.
By adding the sugar ester compound to the cellulose acylate film, it is possible to reduce the total haze and internal haze without deteriorating the expression of optical properties and without performing heat treatment before the stretching step. Furthermore, the front contrast can be greatly improved by using the cellulose acylate film of the present invention in a liquid crystal display device.

-Sugar residue-
The sugar ester compound refers to a compound in which at least one substitutable group (for example, a hydroxyl group or a carboxyl group) in the polysaccharide constituting the compound and at least one substituent are ester-bonded. . That is, the sugar ester compound referred to here includes a wide range of sugar derivatives, for example, a compound containing a sugar residue such as gluconic acid as a structure. That is, the sugar ester compound includes an ester of glucose and carboxylic acid and an ester of gluconic acid and alcohol.
The substitutable group in the polysaccharide constituting the sugar ester compound is preferably a hydroxyl group.

  The sugar ester compound includes a structure derived from a polysaccharide constituting the sugar ester compound (hereinafter also referred to as a sugar residue). The structure of the sugar residue per monosaccharide is referred to as the structural unit of the sugar ester compound. The structural unit of the sugar ester compound preferably includes a pyranose structural unit or a furanose structural unit, and more preferably all sugar residues are a pyranose structural unit or a furanose structural unit. Further, when the sugar ester is composed of a polysaccharide, it preferably contains both a pyranose structural unit or a furanose structural unit.

  The sugar residue of the sugar ester compound may be derived from 5 monosaccharides or 6 monosaccharides, but is preferably derived from 6 monosaccharides.

  The number of structural units contained in the sugar ester compound is preferably 2 to 4, more preferably 2 to 3, and particularly preferably 2. That is, the sugar constituting the sugar ester compound is preferably a disaccharide to a tetrasaccharide, more preferably a disaccharide to a trisaccharide, and particularly preferably a disaccharide.

  In the present invention, the sugar ester compound is more preferably a sugar ester compound containing 2 to 4 pyranose structural units or furanose structural units in which at least one hydroxyl group is esterified, and at least one of the hydroxyl groups is esterified. More preferably, the sugar ester compound contains two pyranose structural units or furanose structural units.

  Examples of the monosaccharides or saccharides containing 2 to 4 monosaccharide units include, for example, erythrose, threose, ribose, arabinose, xylose, lyxose, allose, altrose, glucose, fructose, mannose, gulose, idose, galactose , Talose, trehalose, isotrehalose, neotrehalose, trehalosamine, caudibiose, nigerose, maltose, maltitol, isomaltose, sophorose, laminaribiose, cellobiose, gentiobiose, lactose, lactosamine, lactitol, lactulose, melibiose, primebelloose, rutiose , Sucrose, sucralose, turanose, vicyanose, cellotriose, cacotriose, gentianose, isomaltori , Isopanose, maltotriose, manninotriose, melenotriose, panose, planteose, raffinose, solatriose, umbelliferose, lycotetraose, maltotetraose, stachyose, baltopentaose, velval course, maltohexaose , Xylitol, sorbitol and the like.

  Preferably, ribose, arabinose, xylose, lyxose, glucose, fructose, mannose, galactose, trehalose, maltose, cellobiose, lactose, sucrose, sucralose, xylitol, sorbitol, more preferably arabinose, xylose, glucose, fructose, mannose , Galactose, maltose, cellobiose and sucrose, particularly preferably xylose, glucose, fructose, mannose, galactose, maltose, cellobiose, sucrose, xylitol and sorbitol.

-Substituent structure-
It is more preferable that the sugar ester compound used in the present invention has a structure represented by the following general formula (1) including the substituent used.
Formula _{(1) (OH) p -G-} (L 1 -R 11) q (O-R 12) r
In general formula (1), G represents a sugar residue, L ¹ represents any ^one of —O—, —CO—, and —NR ¹³ —, and R ¹¹ represents a hydrogen atom or a monovalent substituent. R ¹² represents a monovalent substituent bonded by an ester bond. p, q, and r each independently represent an integer of 0 or more, and p + q + r is equal to the number of hydroxyl groups on the assumption that G is an unsubstituted saccharide having a cyclic acetal structure.

  The preferable range of G is the same as the preferable range of the sugar residue.

L ¹ is preferably —O— or —CO—, and more preferably —O—. When L ¹ is —O—, it is particularly preferably a linking group derived from an ether bond or an ester bond, and more preferably a linking group derived from an ester bond.
Further, when there are a plurality of L ^{1 s} , they may be the same or different.

At least one of R ¹¹ and R ¹² preferably has an aromatic ring.

In particular, when L ¹ is —O— (that is, when R ¹¹ and R ¹² are substituted on the hydroxyl group in the sugar ester compound), R ¹¹ , R ¹² and R ¹³ are substituted or unsubstituted. Are preferably selected from the group consisting of acyl groups, substituted or unsubstituted aryl groups, substituted or unsubstituted alkyl groups, substituted or unsubstituted amino groups, substituted or unsubstituted acyl groups, substituted or unsubstituted A substituted alkyl group or a substituted or unsubstituted aryl group is more preferable, and an unsubstituted acyl group, a substituted or unsubstituted alkyl group, or an unsubstituted aryl group is particularly preferable.
When there are a plurality of R ¹¹ , R ¹² and R ¹³ , they may be the same as or different from each other.

Said p represents an integer greater than or equal to 0, and its preferable range is the same as the preferable range of the number of hydroxyl groups per monosaccharide unit mentioned later.
The r preferably represents a number larger than the number of pyranose structural units or furanose structural units contained in the G.
Q is preferably 0.
Moreover, since p + q + r is equal to the number of hydroxyl groups assuming that G is an unsubstituted saccharide having a cyclic acetal structure, the upper limit values of p, q and r are uniquely determined according to the structure of G. Is done.

  Preferred examples of the substituent of the sugar ester compound include an alkyl group (preferably an alkyl group having 1 to 22 carbon atoms, more preferably 1 to 12 carbon atoms, and particularly preferably an alkyl group having 1 to 8 carbon atoms, such as a methyl group, An ethyl group, a propyl group, a hydroxyethyl group, a hydroxypropyl group, a 2-cyanoethyl group, a benzyl group, etc.), an aryl group (preferably having a carbon number of 6 to 24, more preferably 6 to 18 and particularly preferably 6 to 12). A group such as a phenyl group or a naphthyl group, an acyl group (preferably having a carbon number of 1 to 22, more preferably a carbon number of 2 to 12, particularly preferably a carbon number of 2 to 8, such as an acetyl group or a propionyl group, Butyryl group, pentanoyl group, hexanoyl group, octanoyl group, benzoyl group, toluyl group, phthalyl group), amide group (preferred) Or an amide group (preferably 4 to 22 carbon atoms, more preferably an amide having 2 to 12 carbon atoms, particularly preferably an amide having 2 to 8 carbon atoms, such as a formamide group or an acetamide group). May include amide groups having 4 to 12 carbon atoms, particularly preferably 4 to 8 carbon atoms (for example, succinimide group, phthalimide group, etc.). Among them, an alkyl group or an acyl group is more preferable, a methyl group, an acetyl group, or a benzoyl group is more preferable, and at least one of a benzoyl group and an acetyl group is particularly preferable, and a benzoyl group is more particularly preferable.

  As the method for obtaining the sugar ester compound, commercially available products such as those manufactured by Tokyo Chemical Industry Co., Ltd., Aldrich, etc., or known ester derivatization methods for commercially available carbohydrates (for example, Japanese Patent Laid-Open No. Hei. Can be synthesized by carrying out the method described in JP-A-8-245678.

  The sugar ester compound has a number average molecular weight of preferably 200 to 3500, more preferably 200 to 3000, and particularly preferably 250 to 2000.

  Specific examples of the sugar ester compound that can be preferably used in the present invention are listed below, but the present invention is not limited to the following embodiments.

  In the following structural formulae, R each independently represents an arbitrary substituent, and a plurality of R may be the same or different. The ClogP value is a value obtained by calculating the common logarithm logP of the distribution coefficient P between 1-octanol and water. For calculation of ClogP value, the CLOGP program incorporated in the system: PCModels of Daylight Chemical Information Systems was used.

It is preferable to contain 2-30 mass% of said sugar ester compounds with respect to a cellulose acylate, It is more preferable to contain 5-20 mass%, It is especially preferable to contain 5-15 mass%.
Moreover, when using together the polyester plasticizer mentioned later with the said sugar ester compound, the addition amount (mass part) of the said sugar ester compound with respect to the addition amount (mass part) of a polyester plasticizer is 2-10 times (mass). Ratio) is preferably added, more preferably 3 to 8 times (mass ratio).

(Content ratio of sugar ester compounds with different degrees of ester substitution)
In the present invention, a plurality of sugar ester compounds having different ester substitution degrees are included, and the average ester substitution degree of the plurality of sugar ester compounds having different ester substitution degrees is 62% to 94%. By controlling the average ester substitution degree of the sugar ester compound within such a range, the moisture content and moisture permeability of the film of the present invention can be reduced, and the durability of the polarizing plate and the wet heat durability of the film itself are good. Tend to be. Furthermore, a film in which the average ester substitution degree of the sugar ester compound is controlled within such a range is preferable because of its large optical expression (Rth).

In the present invention, among a plurality of sugar ester compounds having different ester substitution degrees contained in the cellulose acylate film, the content of the sugar ester compound having an ester substitution degree of 75% or more is 80% or less, and the ester substitution degree is 35. The content of the sugar ester compound of 5% to 50% is 5% to 30%. By controlling the content of each substitution product of the sugar ester compound within such a range, the transparency of the film of the present invention can be maintained.
The present inventors provide a sugar ester compound which is a highly substituted product having a degree of ester substitution of 75% or more with respect to a plurality of sugar ester compounds having different degrees of ester substitution contained in a cellulose acylate film having a high degree of acetyl substitution. It has been found that when the content of is 80% or more, it tends to bleed out without being compatible with cellulose acylate.
Further, although not bound by any theory, the present inventors have a low substitution with an ester substitution degree of 35% to 50% in a plurality of sugar ester compounds having an average ester substitution degree in the above-mentioned range and different ester substitution degrees. When a certain amount of the sugar ester compound is contained, the compatibility with the cellulose acylate having a high degree of acetyl substitution is improved by the compatibilizing ability of the low substitution product, and the sugar ester compound is formed when the film is formed. It was found that bleeding out can be prevented.

  In addition, when the sugar ester compound is a disaccharide, the average value of the number of esterified substituents is 5 to 7.5, and the esterified substituent has 6 to 8 highly substituted products. The content rate is 80% or less, and the content rate of the substituent having 3 to 4 esterified substituents is 5 to 30%.

  The average ester substitution degree of a plurality of sugar ester compounds having different ester substitution degrees is preferably 60 to 95%, and more preferably 65 to 85%. Controlling the average ester substitution degree of a plurality of sugar ester compounds having different ester substitution degrees within the above range corresponds to the average number of hydroxyl groups per structural unit in the plurality of sugar ester compounds having different ester substitution degrees. It means to control to the range. By controlling the average number of hydroxyl groups per structural unit in the sugar ester compound, migration of the sugar ester compound to the polarizer layer and destruction of the PVA-iodine complex during high temperature and high humidity are suppressed, Degradation of the polarizer performance during wet aging can be suppressed, which is preferable.

  In this invention, it is preferable that the content rate of the sugar ester compound 75 degree or more of ester substitution degree is 40-80% among several sugar ester compounds from which the ester substitution degree contained in a cellulose acylate film differs 55-55. More preferably, it is 75%. In particular, among a plurality of sugar ester compounds having different ester substitution degrees contained in the cellulose acylate film, the content of the sugar ester compound having an ester substitution degree of 75% or more has higher optical performance, moisture content and moisture permeability. It is preferable from the viewpoint.

  In the present invention, among the plurality of sugar ester compounds having different ester substitution degrees contained in the cellulose acylate film, the content of the sugar ester compound having an ester substitution degree of 35% to 50% is preferably 5 to 40%, More preferably, it is 10 to 30%.

  By using a plurality of sugar ester compounds having different degrees of ester substitution satisfying the above conditions and combining with cellulose acylate satisfying the range of the degree of acetyl substitution, the physical properties and optical performance of the film can be obtained, and the durability of the polarizing plate can be obtained. The properties can also be improved over known phosphate ester plasticizers such as so-called TPP / BDP. Moreover, when laminated | stacked with a hard-coat layer, it is also excellent in adhesiveness and can also obtain a film with favorable pencil hardness.

(Method for preparing a plurality of sugar ester compounds having different ester substitution degrees)
There is no restriction | limiting in particular as a method of mixing the some sugar ester compound from which the said ester substitution degree differs, A well-known method can be used. The timing of mixing a plurality of sugar ester compounds having different ester substitution degrees may be, for example, before adding to the cellulose acylate dope when a solution film forming method is adopted, It may be after adding the sugar ester compound individually.

<Other additives other than sugar ester compounds>
(1) Plasticizers other than sugar ester compounds The cellulose acylate film of the present invention has, as plasticizers other than the sugar ester compounds, polyhydric alcohol ester hydrophobizing agents, polycondensation ester hydrophobizing agents, and carbohydrate derivative hydrophobes. It is preferable to include at least one hydrophobizing agent selected from among the agents. The hydrophobizing agent is preferably one that can reduce the water content without reducing the glass transition temperature of the film as much as possible. By using such a hydrophobizing agent, the phenomenon that the additive in the cellulose acylate film diffuses into the polarizer layer under high temperature and high humidity can be suppressed, and deterioration of the polarizer performance can be improved.

(Polyhydric alcohol ester hydrophobizing agent)
The polyhydric alcohol is represented by the following general formula (A).

Formula (A) R ³¹ — (OH) _n
(However, R ³¹ represents an n-valent organic group, and n represents a positive integer of 2 or more.)
Examples of the preferred polyhydric alcohol hydrophobizing agent include the following, but are not limited thereto. Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane- Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, and xylitol. In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

  Among them, the polyhydric alcohol hydrophobizing agent is preferably a polyhydric alcohol ester using a polyhydric alcohol having 5 or more carbon atoms. Most preferably, it is C5-C20.

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

  Examples of preferable monocarboxylic acid used in the polyhydric alcohol ester include the following, but are not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-10. When acetic acid is contained, the compatibility with the cellulose derivative is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

  Preferred examples of the aliphatic monocarboxylic acid include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecyl Acids, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid, undecylenic acid And unsaturated fatty acids such as oleic acid, sorbic acid, linoleic acid, linolenic acid and arachidonic acid.

  Preferred examples of the alicyclic monocarboxylic acid include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, and derivatives thereof.

  Preferred examples of the aromatic monocarboxylic acid include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two benzene rings such as biphenylcarboxylic acid, naphthalenecarboxylic acid, and tetralincarboxylic acid. Although the aromatic monocarboxylic acid which has the above, or those derivatives can be mentioned, benzoic acid is especially preferable.

  The molecular weight of the polyhydric alcohol hydrophobizing agent is not particularly limited, but is preferably 300 to 3000, and more preferably 350 to 1500. A higher molecular weight is preferable because it is less likely to volatilize, and a lower molecular weight is preferable in terms of moisture permeability and compatibility with cellulose derivatives.

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

  Specific compounds of the polyhydric alcohol ester are shown below.

(Polycondensed ester hydrophobizing agent)
The polycondensation ester hydrophobizing agent is obtained from at least one dicarboxylic acid having an aromatic ring (also referred to as aromatic dicarboxylic acid) and at least one aliphatic diol having an average carbon number of 2.5 to 8.0. It is preferable. Moreover, it is also preferable to obtain from the mixture of aromatic dicarboxylic acid and at least 1 type of aliphatic dicarboxylic acid, and at least 1 type of aliphatic diol whose average carbon number is 2.5-8.0.

Calculation of the average carbon number of the dicarboxylic acid residue is performed separately for the dicarboxylic acid residue and the diol residue.
The value calculated by multiplying the constituent carbon number by the composition ratio (molar fraction) of the dicarboxylic acid residue is defined as the average carbon number. For example, when the adipic acid residue and the phthalic acid residue are composed of 50 mol% each, the average carbon number is 7.0.
The same applies to the diol residue, and the average carbon number of the diol residue is a value calculated by multiplying the constituent carbon number by the composition ratio (molar fraction) of the diol residue. For example, when it is composed of 50 mol% of ethylene glycol residues and 50 mol% of 1,2-propanediol residues, the average carbon number is 2.5.

The number average molecular weight of the polycondensed ester is preferably 500 to 2000, more preferably 600 to 1500, and still more preferably 700 to 1200. If the number average molecular weight of the polycondensed ester is 600 or more, the volatility is low, and film failure and process contamination due to volatilization under high temperature conditions during stretching of the cellulose acylate film are less likely to occur. Moreover, if it is 2000 or less, compatibility with a cellulose acylate will become high and it will become difficult to produce the bleed-out at the time of film forming and a heat-stretching.
The number average molecular weight of the polycondensed ester can be measured and evaluated by gel permeation chromatography. Further, in the case of a polyester polyol having an unsealed terminal, it can also be calculated from the amount of hydroxyl groups per weight (hereinafter also referred to as hydroxyl value). In the present specification, the hydroxyl value is determined by measuring the amount (mg) of potassium hydroxide necessary for neutralizing excess acetic acid after acetylating the polyester polyol.

When a mixture of an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid is used as the dicarboxylic acid component, the dicarboxylic acid component is preferably a dicarboxylic acid having an average carbon number of 5.5 to 10.0, more preferably 5 .6-8.
If the average carbon number is 5.5 or more, a polarizing plate having excellent durability can be obtained. If the average number of carbon atoms is 10 or less, the compatibility with cellulose acylate is excellent, and the occurrence of bleed-out can be suppressed during the process of forming a cellulose acylate film.

The polycondensation ester obtained from a diol and a dicarboxylic acid containing an aromatic dicarboxylic acid contains an aromatic dicarboxylic acid residue.
In the present specification, a residue is a partial structure of a polycondensed ester and represents a partial structure having the characteristics of a monomer forming the polycondensed ester. For example, the dicarboxylic acid residue formed from dicarboxylic acid HOOC-R-COOH is -OC-R-CO-.
The aromatic dicarboxylic acid residue ratio of the polycondensed ester is preferably 40 mol% or more, and more preferably 40 mol% to 95 mol%.
By setting the aromatic dicarboxylic acid residue ratio to 40 mol% or more, a cellulose acylate film exhibiting sufficient optical anisotropy can be obtained, and a polarizing plate excellent in durability can be obtained. Moreover, if it is 95 mol% or less, it is excellent in compatibility with a cellulose ester, and it can make it hard to produce a bleed-out also at the time of film forming of a cellulose acylate film, and the time of heat-stretching.

Examples of the aromatic dicarboxylic acid that can be used to form the polycondensation ester hydrophobizing agent include phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1 , 8-naphthalenedicarboxylic acid, 2,8-naphthalenedicarboxylic acid or 2,6-naphthalenedicarboxylic acid. Of these, phthalic acid, terephthalic acid, and 2,6-naphthalenedicarboxylic acid are preferable, phthalic acid and terephthalic acid are more preferable, and terephthalic acid is more preferable.
An aromatic dicarboxylic acid residue derived from the aromatic dicarboxylic acid used for mixing is formed in the polycondensed ester.
That is, the aromatic dicarboxylic acid residue preferably includes at least one of a phthalic acid residue, a terephthalic acid residue, and an isophthalic acid residue, more preferably at least one of a phthalic acid residue and a terephthalic acid residue. A seed, more preferably a terephthalic acid residue.
By using terephthalic acid as the aromatic dicarboxylic acid for mixing in the formation of the polycondensed ester, it is more compatible with cellulose acylate and bleeds out when forming a cellulose acylate film and during heat stretching. It can be set as the cellulose acylate film which is hard to produce. The aromatic dicarboxylic acid may be used alone or in combination of two or more. When two types are used, it is preferable to use phthalic acid and terephthalic acid.
By using together two kinds of aromatic dicarboxylic acids of phthalic acid and terephthalic acid, the polycondensation ester at normal temperature can be softened, which is preferable in terms of easy handling.
The content of the terephthalic acid residue in the dicarboxylic acid residue of the polycondensed ester is preferably 40 mol% to 100 mol%.
By setting the terephthalic acid residue ratio to 40 mol% or more, a cellulose acylate film exhibiting sufficient optical anisotropy can be obtained.

A polycondensation ester obtained from a diol and a dicarboxylic acid containing an aliphatic dicarboxylic acid contains an aliphatic dicarboxylic acid residue.
Examples of the aliphatic dicarboxylic acid capable of forming the polycondensed ester hydrophobizing agent include oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, pimelic acid, suberic acid, Examples include azelaic acid, sebacic acid, dodecanedicarboxylic acid, or 1,4-cyclohexanedicarboxylic acid.
In the polycondensed ester, an aliphatic dicarboxylic acid residue derived from the aliphatic dicarboxylic acid used for mixing is formed.
The aliphatic dicarboxylic acid residue preferably has an average carbon number of 5.5 to 10.0, more preferably 5.5 to 8.0, and preferably 5.5 to 7.0. Further preferred. If the average carbon number of the aliphatic dicarboxylic acid residue is 10.0 or less, the heat loss of the compound can be reduced, and the occurrence of surface failure that may be caused by process contamination due to bleed-out during drying of the cellulose acylate web is prevented. be able to. Moreover, it is preferable that the aliphatic dicarboxylic acid residue has an average carbon number of 5.5 or more because it is excellent in compatibility and precipitation of the polycondensed ester hardly occurs.
Specifically, the aliphatic dicarboxylic acid residue preferably includes a succinic acid residue, and when two types are used, it preferably includes a succinic acid residue and an adipic acid residue.
That is, one kind of aliphatic dicarboxylic acid or two or more kinds may be used for mixing in the formation of the polycondensed ester. When two kinds are used, it is preferable to use succinic acid and adipic acid. When one kind of aliphatic dicarboxylic acid is used for mixing in the formation of the polycondensed ester, it is preferable to use succinic acid. The average carbon number of the aliphatic dicarboxylic acid residue can be adjusted to a desired value, which is preferable in terms of compatibility with cellulose acylate.

  For mixing in the formation of the polycondensed ester, it is preferable to use two or three dicarboxylic acids. When using two kinds, it is preferable to use one kind of aliphatic dicarboxylic acid and one kind of aromatic dicarboxylic acid. When using three kinds, one kind of aliphatic dicarboxylic acid and two kinds of aromatic dicarboxylic acid or aliphatic dicarboxylic acid are used. Two kinds of acids and one kind of aromatic dicarboxylic acid can be used. This is because the average carbon number value of the dicarboxylic acid residue can be easily adjusted, the content of the aromatic dicarboxylic acid residue can be within a preferable range, and the durability of the polarizer can be improved.

A polycondensation ester obtained from a diol and a dicarboxylic acid containing a dicarboxylic acid contains a diol residue.
In the present specification, the diol residue formed from the diol HO—R—OH is —O—R—O—.
Examples of the diol that forms the polycondensed ester include aromatic diols and aliphatic diols, and the polycondensed ester used in the hydrophobizing agent is preferably formed from at least an aliphatic diol.
The polycondensed ester preferably contains an aliphatic diol residue having an average carbon number of 2.5 to 7.0, more preferably an aliphatic diol residue having an average carbon number of 2.5 to 4.0. Including. When the average carbon number of the aliphatic diol residue is less than 7.0, the compatibility with cellulose acylate is improved, bleed-out is less likely to occur, and the loss on heating of the compound is less likely to increase. It is difficult for a sheet-like failure to be caused by process contamination during web drying. Further, the synthesis is easy if the average carbon number of the aliphatic diol residue is 2.5 or more.
Preferred examples of the aliphatic diol that can form the polycondensed ester hydrophobizing agent include alkyl diols and alicyclic diols, such as ethylene glycol, 1,2-propanediol, 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-1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecane Diol, diethylene glycol, cyclohexanedimethanol and the like are preferable. These are preferably used together with ethylene glycol as one or a mixture of two or more.

More preferably, the aliphatic diol is at least one of ethylene glycol, 1,2-propanediol, and 1,3-propanediol, and particularly preferably at least one of ethylene glycol and 1,2-propanediol. It is. In the case where the polycondensation ester is formed using two kinds of the aliphatic diol, it is preferable to use ethylene glycol and 1,2-propanediol. By using 1,2-propanediol or 1,3-propanediol, crystallization of the polycondensed ester can be prevented.
In the polycondensed ester, a diol residue is formed by the diol used for mixing.
That is, the polycondensation ester preferably contains at least one of an ethylene glycol residue, a 1,2-propanediol residue, and a 1,3-propanediol residue as a diol residue. More preferably, it is a 1,2-propanediol residue.
The aliphatic diol residue contained in the polycondensed ester preferably contains 10 mol% to 100 mol%, more preferably 20 mol% to 100 mol% of ethylene glycol residue.

The terminal of the polycondensed ester may be left as it is without being blocked, and may be left as a diol or carboxylic acid, or may be further blocked with a so-called terminal by reacting with a monocarboxylic acid or monoalcohol.
As monocarboxylic acids used for sealing, acetic acid, propionic acid, butanoic acid, benzoic acid and the like are preferable. As monoalcohols used for sealing, methanol, ethanol, propanol, isopropanol, butanol, isobutanol and the like are preferable, and methanol is most preferable. When the number of carbon atoms of the monocarboxylic acid used at the terminal of the polycondensed ester is 7 or less, the loss on heating of the compound does not increase, and no surface failure occurs.
More preferably, the end of the polycondensed ester remains as a diol residue without being sealed, or is sealed with acetic acid, propionic acid or benzoic acid.
It does not matter whether both ends of the polycondensed ester have the same sealing performance.
When both ends of the condensate are unsealed, the polycondensed ester is preferably a polyester polyol.
One aspect of the polycondensed ester is a polycondensed ester in which the aliphatic diol residue has 2.5 to 8.0 carbon atoms, and both ends of the polycondensed ester are unblocked.
When both ends of the polycondensed ester are sealed, it is preferably sealed by reacting with a monocarboxylic acid. At this time, both ends of the polycondensed ester are monocarboxylic acid residues. In the present specification, the monocarboxylic acid residue formed from the monocarboxylic acid R-COOH is R-CO-. When both ends of the polycondensed ester are sealed with a monocarboxylic acid, the monocarboxylic acid is preferably an aliphatic monocarboxylic acid residue, and the monocarboxylic acid residue is an aliphatic monocarboxylic acid having 22 or less carbon atoms. It is more preferably a carboxylic acid residue, and even more preferably an aliphatic monocarboxylic acid residue having 3 or less carbon atoms. In addition, an aliphatic monocarboxylic acid residue having 2 or more carbon atoms is preferable, and an aliphatic monocarboxylic acid residue having 2 carbon atoms is particularly preferable.
In one embodiment of the polycondensation ester, the aliphatic diol residue has a carbon number of more than 2.5 and 7.0 or less, and both ends of the polycondensation ester are capped with monocarboxylic acid residues. Mention may be made of condensed esters.
When the carbon number of the monocarboxylic acid residue sealing both ends of the polycondensed ester is 3 or less, the volatility is lowered, the weight loss due to heating of the polycondensed ester is not increased, and the occurrence of process contamination It is possible to reduce the occurrence of planar failures.
That is, the monocarboxylic acid used for sealing is preferably an aliphatic monocarboxylic acid, more preferably an aliphatic monocarboxylic acid having 2 to 22 carbon atoms, and an aliphatic monocarboxylic acid having 2 to 3 carbon atoms. A carboxylic acid is more preferable, and an aliphatic monocarboxylic acid residue having 2 carbon atoms is particularly preferable.
For example, acetic acid, propionic acid, butanoic acid, benzoic acid and derivatives thereof are preferable, acetic acid or propionic acid is more preferable, and acetic acid is most preferable.
Two or more monocarboxylic acids used for sealing may be mixed.
Both ends of the polycondensed ester are preferably sealed with acetic acid or propionic acid, and most preferably both ends are acetyl ester residues (sometimes referred to as acetyl residues).
When both ends of the polycondensed ester are sealed, the cellulose acylate film can be obtained in which the state at normal temperature is unlikely to be in a solid form, handling is good, and humidity stability and polarizing plate durability are excellent. .

  Specific examples A-1 to A-34 of the polycondensed ester are shown in Table 4 below, but are not limited thereto.

  The abbreviations in Table 4 above represent the following compounds, respectively. PA: phthalic acid, TPA: terephthalic acid, AA: adipic acid, SA: succinic acid, 2,6-NPA: 2,6-naphthalenedicarboxylic acid.

  The synthesis of the polycondensed ester is performed either by a conventional method, a hot melt condensation method by a polyesterification reaction or transesterification reaction between a diol and a dicarboxylic acid, or an interfacial condensation method between an acid chloride of these acids and a glycol. Can be easily synthesized. The polycondensation ester is described in detail in Koichi Murai, “Plasticizers, Theory and Application” (Kobo Publishing Co., Ltd., first published on March 1, 1973). In addition, Japanese Patent Laid-Open Nos. 05-155809, 05-155810, Japanese Patent Laid-Open Nos. 05-97073, 2006-259494, 07-330670, 2006-342227, 2007-003679. The materials described in each publication can also be used.

  The addition amount of these hydrophobizing agents is preferably 1 to 20% by mass with respect to cellulose acylate. If the content is 1% by mass or more, the effect of improving the durability of the polarizer can be easily obtained, and if the content is 20% by mass or less, bleeding out hardly occurs. A more preferable addition amount is 2 to 15% by mass, and particularly preferably 5 to 15% by mass.

  The timing for adding these hydrophobizing agents to the cellulose acylate film is not particularly limited as long as it is added at the time of film formation. For example, it may be added at the time of cellulose acylate synthesis, or may be mixed with cellulose acylate during dope preparation.

(2) Retardation developer The film of the present invention may contain a retardation developer. By adopting a retardation developer, high Re developability can be obtained at a low draw ratio. The type of the retardation developing agent is not particularly defined, and examples thereof include those composed of a rod-like or discotic compound and compounds exhibiting retardation development among the non-phosphate ester compounds. As the rod-like or discotic compound, a compound having at least two aromatic rings can be preferably used as a retardation developer.
Two or more retardation developing agents may be used in combination.
The retardation developer preferably has a maximum absorption in the wavelength region of 250 to 400 nm, and preferably has substantially no absorption in the visible region.

As the retardation developing material, for example, compounds described in JP-A-2004-50516 and JP-A-2007-86748 can be used, but are not limited thereto.
Examples of the discotic compound include a compound described in European Patent Application No. 0911656A2, a triazine compound described in Japanese Patent Application Laid-Open No. 2003-344655, and Japanese Patent Application Laid-Open No. 2008-150592 [0097] to [0108]. The triphenylene compound to be used can also be preferably used.

  The discotic compound can be synthesized by a known method such as a method described in JP-A No. 2003-344655 and a method described in JP-A No. 2005-134484.

  In addition to the aforementioned discotic compound, a rod-shaped compound having a linear molecular structure can also be preferably used. For example, the rod-shaped compounds described in JP 2008-150592 A [0110] to [0127] are preferably used. it can.

(3) Acrylic polymer An acrylic polymer having a weight average molecular weight of 500 to 10,000 may be further added to the cellulose acylate film of the invention. Preferably, the weight average molecular weight is 500 to 5,000.
When the acrylic polymer is added, the cellulose acylate film after film formation is excellent in transparency, moisture permeability is extremely low, and exhibits excellent performance as a protective film for a polarizing plate. As the acrylic polymer, compounds described in International Publication WO2008-126535 can be preferably used.

(4) Antioxidant, thermal degradation inhibitor In this invention, what is generally known can be used as an antioxidant and a thermal degradation inhibitor. In particular, lactone, sulfur, phenol, double bond, hindered amine, and phosphorus compounds can be preferably used. As the antioxidant and the thermal degradation inhibitor, compounds described in International Publication WO2008-126535 can be preferably used.

(5) Colorant In the present invention, a colorant may be used. The colorant means a dye or a pigment. In the present invention, the colorant means an effect of making the color tone of a liquid crystal screen blue, adjusting the yellow index, and reducing haze. As the colorant, compounds described in International Publication WO2008-126535 can be preferably used.

(6) Fine particles As fine particles used in the present invention, examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, and hydrated silica. Mention may be made of calcium acid, aluminum silicate, magnesium silicate and calcium phosphate.
Fine particles containing silicon are preferable in terms of low haze, and silicon dioxide is particularly preferable.
The average primary particle size of the fine particles is preferably 5 to 50 nm, and more preferably 7 to 20 nm. These are preferably contained mainly as secondary aggregates having a particle size of 0.05 to 0.3 μm.
The content of these fine particles in the cellulose derivative film is preferably 0.05 to 1% by mass, particularly preferably 0.1 to 0.5% by mass. In the case of a cellulose derivative film having a multilayer structure by the co-casting method, it is preferable to contain fine particles of this addition amount on the surface.
Silicon dioxide fine particles are commercially available, for example, under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600, NAX50 (Nippon Aerosil Co., Ltd.). be able to.
Zirconium oxide fine particles are commercially available under the trade names of Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used.
Examples of the polymer include silicone resin, fluororesin, and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.) It is marketed by name and can be used.
Among these, Aerosil 200V and Aerosil R972V are particularly preferably used because they have a large effect of reducing the friction coefficient while keeping the haze of the cellulose derivative film low.

(7) Other Additives The cellulose acylate film used in the present invention may contain additives that can be added to a normal cellulose acylate film in addition to the above compounds.
Examples of these additives include ultraviolet absorbers.
About the said other additive, the compound described in international publication WO2008-126535 can be used preferably.

<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. Specifically, the film containing the cellulose acylate can be formed using a solution casting film forming method or a melt film forming method. From the viewpoint of improving the surface shape of the film, the film production method of the present invention preferably includes a step of forming a film containing the cellulose acylate by solution casting.
Hereinafter, although the case where the solution casting film forming method is used is demonstrated to the example for the manufacturing method of the film of this invention, this invention is not limited to the solution casting film forming method. In addition, about the case where the said melt film forming method is used as a manufacturing method of the film of this invention, a well-known method can be used.

(Polymer solution)
In the solution casting film forming method, a web is formed using the cellulose acylate or a polymer solution (cellulose acylate solution) containing various additives as required. Hereinafter, a polymer solution (hereinafter also referred to as a cellulose acylate solution as appropriate) that can be used in the solution casting film forming method 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 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, and 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 (the name of the dope film after casting the cellulose acylate dope on the support is called It is used as a gelling solvent that makes it easy to peel off from the metal support, and when these ratios are small, it promotes dissolution of cellulose acylate of 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, ethanol is preferred because it has excellent dope stability, has a relatively low boiling point, good drying properties, and no toxicity. These organic solvents alone are not soluble in cellulose acylate and are referred to as poor solvents.

In the present invention, the cellulose acylate constituting the cellulose acylate film contains hydrogen bonding functional groups such as hydroxyl groups, esters, and ketones, and therefore 5 to 30% by mass, more preferably 7 to 25% by mass in the total solvent. More preferably, it contains 10 to 20% by mass of alcohol from the viewpoint of reducing the peeling load from the casting support.
By adjusting the alcohol content, it is possible to easily adjust the expression of Re and Rth of the cellulose acylate film produced by the production method of the present invention. Specifically, by increasing the alcohol content or setting the drying temperature (heat treatment temperature) before stretching in the production method of the present invention described later to be relatively low, the reach range of Re and Rth can be further increased. It becomes possible to do.
In the present invention, it is effective to contain a small amount of water to increase the solution viscosity and the film strength of the wet film during drying, or to increase the dope strength during casting by the drum method. 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 polymer 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 polymer 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 of dissolving the cellulose acylate in a solvent. Further, after preparing a low concentration (for example, 4 to 14% by mass) solution in advance, the solution may be concentrated by evaporating the solvent. 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.

  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 step A step of dissolving the cellulose acylate and additives in an organic solvent mainly containing a good solvent for cellulose acylate 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. An additive is added to the dope during or after dissolution to dissolve and disperse, then filtered through a filter medium, defoamed, and sent to the next step with a liquid feed pump.
Used frequently.

(2) Casting process An endless metal belt, such as a stainless steel belt or a rotating metal drum, that feeds the dope to a pressure die through a liquid feed pump (for example, a pressurized metering gear pump) and transfers it indefinitely. 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 (which is in a state before becoming a finished product of cellulose acylate film and still containing a lot of solvent) is heated on a metal support, and the web is peeled off 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 step, stretching step After the peeling step, a drying device that alternately conveys the web through a plurality of rolls arranged in the drying device, 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-5 ° C, preferably Tg-20 ° C or more and less than Tg-5 ° C, and preferably Tg-15 ° C or more and less than Tg-5 ° C. More preferred.
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 film may be stretched in any direction of the film transport direction (hereinafter also referred to as the longitudinal direction) and the direction orthogonal to the film transport direction (hereinafter also referred to as the lateral direction). This is preferable from the viewpoint of developing retardation. More preferably, it is biaxially stretched in the longitudinal and transverse directions. Stretching may be performed in one stage or in multiple stages.

The draw ratio in stretching in the film transport direction is preferably 0 to 20%, more preferably 0 to 15%, and particularly preferably 0 to 10%. The stretch ratio (elongation) of the cellulose acylate 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 cellulose acylate film is preferably stretched in the transport 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. can do. By performing such stretching, the expression of retardation 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 perpendicular to the film conveying direction is preferably 0 to 50%, more preferably 10 to 50%, and particularly preferably 20 to 40%.
In the present invention, it is preferable to stretch using a tenter device as a method of stretching in a direction perpendicular to the film conveying direction.

  In the case of biaxial stretching, a desired retardation value can be obtained by relaxing the length in the longitudinal direction, for example, 0.8 to 1.0 times. The draw ratio is set according to the target optical characteristics. Moreover, when manufacturing the cellulose acylate film of this invention, it can also uniaxially stretch in a elongate direction.

  The temperature during stretching is preferably Tg-5 ° C to Tg + 10 ° C, more preferably Tg-5 ° C to Tg + 5 ° C, and particularly preferably Tg-5 ° C to Tg + 3 ° C. By stretching the film in such a temperature range, the haze of the film of the present invention can be reduced, which is preferable.

  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 of the present invention is incorporated in 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 film of the present invention is particularly suitable for use in a large screen liquid crystal display device. When used as an optical compensation film for a large-screen liquid crystal display device, for example, the film width is preferably set to 1470 mm or more. In addition, the film of the present invention is produced not only in the form of a film piece cut into a size that can be incorporated into a liquid crystal display device as it is, but also in a long form by continuous production and wound up into a roll. Films of the described embodiments are also included. The film of the latter mode is stored and transported in that state, and is cut into a desired size and used when actually incorporated into a liquid crystal display device or bonded to a polarizer or the like. Similarly, it is cut into a desired size when it is actually incorporated into a liquid crystal display device after being bonded to a polarizer or the like made of a polyvinyl alcohol film or the like that has been made into a long shape. Used. As an aspect of the film wound up in a roll shape, an embodiment in which the roll length is rolled up into a roll having a length of 2500 m or more can be mentioned.

  The web thus obtained is wound up to obtain a cellulose acylate film as a final finished product.

<Characteristics of cellulose acylate film>
(Haze)
The cellulose acylate film of the present invention preferably has a haze of 1.0% or less, more preferably 0.4% or less, and particularly preferably 0 to 0.30%. preferable.

(Glass transition temperature Tg of cellulose acylate film)
In the present specification, the glass transition temperature Tg of the cellulose acylate film refers to the glass transition temperature (hereinafter abbreviated as Tg) of the entire film including cellulose acylate, plasticizer, and other additives constituting the film. .

(Retardation)
In the film of the present invention, the retardation value Rth (550) in the film thickness direction at a wavelength of 550 nm is preferably 0 to 50 nm, more preferably 20 to 40 nm, and particularly preferably 25 to 35 nm.

The film of the present invention is preferably a biaxial film, and more preferably a biaxial optical compensation film.
Here, the film is biaxial, nx, ny and nz of the film (nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction perpendicular to nx in the plane, nz represents the refractive index in the direction orthogonal to nx and ny). In the present invention, it is more preferable that nx>ny> nz.
The fact that the film of the present invention exhibits biaxial optical characteristics is a preferable characteristic for reducing the problem of color shift when observed from an oblique direction in a liquid crystal display device, particularly a VA mode liquid crystal display device.

  In this specification, Re (λ) and Rth (λ) represent in-plane retardation and retardation in the thickness direction at the wavelength λ, respectively. In the present specification, the wavelength λ is 590 nm unless otherwise specified. Re (λ) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH (manufactured by Oji Scientific Instruments). Rth (λ) is Re (λ), with the in-plane slow axis (determined by KOBRA 21ADH) as the tilt axis (rotary axis) (in the absence of the slow axis, any direction in the film plane) Is measured in 6 points from the inclined direction in 10 degree steps from the normal direction to 50 degrees on one side with respect to the normal direction of the film. KOBRA 21ADH calculates based on the retardation value, the assumed average refractive index, and the input film thickness value. The retardation value is measured from any two directions with the slow axis as the tilt axis (rotation axis) (in the absence of the slow axis, the arbitrary direction in the film plane is the rotation axis), and the value Rth can also be calculated from the following formula (A) and formula (B) based on the assumed average refractive index and the input film thickness value. Here, as the assumed value of the average refractive index, values in the polymer handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer. The average refractive index values of main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). The KOBRA 21ADH calculates nx, ny, and nz by inputting the assumed value of the average refractive index and the film thickness. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.

Here, Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction, nx, ny, and nz represent refractive indexes in respective principal axis directions of the refractive index ellipsoid, and d represents a film. Represents thickness.
Rth = ((nx + ny) / 2−nz) × d Formula (B)
At this time, an average refractive index n is required as a parameter, and a value measured by an Abbe refractometer (“Abbe refractometer 2-T” manufactured by Atago Co., Ltd.) was used.

(Moisture content)
The film of the present invention has a low equilibrium moisture content at 25 ° C. and a relative humidity of 80%. When the liquid crystal display panel is enlarged, the protective film acts as a buffer to protect against changes in environmental humidity. The internal humidity change can be homogenized at the center and the end, which is preferable.

(Moisture permeability)
The film of the present invention has a polarizing plate durability and a polarizing plate processing of 25 ° C. converted to a film thickness of 40 μm, a relative humidity of 80%, and a moisture permeability after 24 hours of aging of 1500 to 3500 g / m ² · day. from the viewpoint of the drying time, more preferably 1500~3000g / m ² · day, and particularly preferably 2000~2500g / m ² · day.

  If the moisture permeability and moisture content are too high, the wet heat durability of the polarizer tends to be inferior, and this tends to cause light leakage in a high humidity environment. Therefore, it is more preferable to control the moisture permeability and moisture content of the polarizing plate protective film within an optimal range.

(Film thickness)
The film thickness of the cellulose acylate film of the present invention is preferably 20 to 200 μm, more preferably 20 to 85 μm, still more preferably 25 to 65 μm. When the film thickness is less than 20 μm, the mechanical strength is insufficient, failure such as breakage during production tends to occur, and the film surface condition tends to deteriorate.

  The film thickness may be adjusted by adjusting the solid content concentration contained in the dope, the slit gap of the die base, the extrusion pressure from the die, the metal support speed, and the like so as to obtain a desired thickness.

(Film width)
The film of the present invention preferably has a film width of 1000 mm or more, more preferably 1500 mm or more, and particularly preferably 1800 mm or more.

(Functional layer)
The film of the present invention may be a single layer film or may have a laminated structure of two or more layers. Here, the polarizing plate of the present invention described later preferably includes a functional layer, but the film of the present invention is incorporated into the polarizing plate of the present invention even if the film of the present invention has a functional layer. Sometimes other functional films may be stacked.
The functional layer is not particularly limited as long as it is not contrary to the gist of the present invention, and examples thereof include the following functional layers.
Base film / hard coat layer / medium refractive index layer / low refractive index layer Base film / hard coat layer / medium refractive index layer / high refractive index layer / low refractive index layer Base film / hard coat layer / low refractive index Layer Base film / hard coat layer / conductive layer / low refractive index layer Base film / hard coat layer / high refractive index layer (conductive layer) / low refractive index layer Base film / hard coat layer / antiglare Layer / low refractive index layer

[Polarizer]
The polarizing plate of the present invention includes at least one film of the present invention. Hereinafter, the polarizing plate of the present invention will be described.

The polarizing plate of the present invention can be produced by a general method. For example, there is a method in which the cellulose acylate film of the present invention is subjected to alkali saponification treatment and then bonded to both sides of a polarizer using a completely saponified polyvinyl alcohol aqueous solution.
The alkali saponification treatment refers to a treatment in which the cellulose derivative film is immersed in a high-temperature strong alkaline solution in order to improve the wetness of the water-based adhesive and improve the adhesion.

A conventionally well-known thing can be used as a polarizer used for the polarizing plate of this invention. 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 a polarizing plate protective film.
At this time, the film of the present invention is used as at least one of the polarizing plate protective films. Another polarizing plate protective film (preferably a cellulose derivative film) can be used on the other surface.
As the polarizing plate protective film on the other surface, the cellulose acylate film of the present invention may be used, or a commercially available cellulose ester film may be used.
In addition to the antiglare layer or the clear hard coat layer, the polarizing plate protective film used on the surface side of the display device preferably has an antireflection layer, an antistatic layer, and an antifouling layer.
Moreover, at the time of producing the polarizing plate, it is preferable that the in-plane slow axis of the retardation film of the present invention and the transmission axis of the polarizer are bonded so as to be parallel or orthogonal.

[Liquid Crystal Display]
The liquid crystal display device of the present invention includes at least one film of the present invention or the polarizing plate of the present invention.
In the liquid crystal display device of the present invention, the polarizing plate of the present invention obtained as described above can be disposed and bonded on both surfaces of the liquid crystal cell to produce the liquid crystal display device of the present invention.
The liquid crystal display device of the present invention is a liquid crystal display device using at least one polarizing plate of the present invention. The polarizing plate of the present invention can be used for liquid crystal cells in various display modes, such as TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-ferroelectric Liquid Crystal), It can be used in combination with cells of various display modes such as OCB (Optically Compensatory Bend), STN (Supper Twisted Nematic), VA (Vertically Aligned), and HAN (Hybrid Aligned Nematic).

  The features of the present invention will be described more specifically with reference to examples and comparative 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.

[Examples 1 to 3 and Comparative Examples 1 to 7]
(1) Preparation of Raw Material (1-1) Preparation of Cellulose Acylate Resin Cellulose acylate having a degree of acetyl substitution described in the following table was prepared. Sulfuric acid (7.8 parts by mass with respect to 100 parts by mass of cellulose) was added as a catalyst, each carboxylic acid was added, and an acylation reaction was performed at 40 ° C. Thereafter, the total substitution degree and the 6-position substitution degree were adjusted by adjusting the amount of sulfuric acid catalyst, the amount of water and the aging time. The aging temperature was 40 ° C. Further, the low molecular weight component of the cellulose acylate was removed by washing with acetone.

(1-2) Preparation of a plurality of sugar ester compounds having different ester substitution degrees A plurality of sugar ester compounds having different ester substitution degrees described in the following table were prepared by the following method.
First, the compounds 111 to 117 shown in Table 1 were synthesized by the method described in the synthesis of WO2009 / 03164 [0054] Exemplified Compound 3.
Other compounds were synthesized by the same method. Then, it mixed and the sugar ester compound was adjusted.

(2) Dope preparation The following composition is put into a mixing tank, stirred to dissolve each component, heated to 90 ° C. for about 10 minutes, and then filtered with a filter paper having an average pore size of 34 μm and a sintered metal filter having an average pore size of 10 μm. Filtered.
――――――――――――――――――――――――――――――――――――
Cellulose acylate solution of Example 1 ――――――――――――――――――――――――――――――――――――
Cellulose acylate described in the following table 100.0 parts by mass A plurality of sugar ester compounds having different degrees of ester substitution described in the following table
8.0 parts by mass Methylene chloride 365.8 parts by mass Methanol 92.6 parts by mass Butanol 4.6 parts by mass ――――――――――――――――――――――――― ――――――――――
In the following table, Ac represents an acetyl group, and Pr represents a propionyl group.

<1-2> Matting Agent Dispersion Next, the following composition containing the cellulose acylate solution prepared by the above method was charged into a disperser to prepare a matting agent dispersion.
――――――――――――――――――――――――――――――――――――
Matting agent dispersion of Example 1 ――――――――――――――――――――――――――――――――――――
-Matting agent (Aerosil R972) 0.2 parts by weight-Methylene chloride 65.7 parts by weight-Methanol 16.6 parts by weight-Butanol 0.8 parts by weight-Cellulose acylate solution 10.3 parts by weight ――――――――――――――――――――――――――――――
100 parts by mass of the cellulose acylate solution of Example 1 and the matting agent dispersion of Example 1 were mixed in an amount of 0.02 parts by mass of inorganic fine particles with respect to the cellulose acylate resin, and the dope for film formation was mixed. Prepared.
In addition, the sucrose benzoate used in the examples and comparative examples were all subjected to vacuum drying (less than 10 mmHg) of toluene as a reaction solvent and less than 100 ppm.

  As shown in the following table, the dopes of other examples and comparative examples were prepared in the same manner as the dope of Example 1, except that the acetyl substitution degree of cellulose acylate and the type of plasticizer were changed.

(3) Casting The above dope was cast using a drum film forming machine. The drum was made of SUS.

(4) Drying The web (film) obtained by casting was dried at a temperature shown in the following table for 20 minutes on a drum before peeling using a drying apparatus. Moreover, after peeling from a drum as another aspect, it dried for 20 minutes in this tenter apparatus using the tenter apparatus which clips and conveys the both ends of a web with a clip. The results obtained with these two embodiments were similar. In addition, the drying temperature here means the film surface temperature of a film.

(5) Stretching The obtained web (film) is peeled from the drum, sandwiched between clips, and when the amount of residual solvent is 30 to 5% with respect to the mass of the entire film, the conditions shown in the table below are fixed uniaxial stretching conditions. The film was stretched in the direction (lateral direction) perpendicular to the film conveying direction using a tenter at the described stretching temperature and stretch ratio.
Thereafter, the clip was removed from the film and dried at 110 ° C. for 30 minutes. At this time, the cast film thickness was adjusted so that the film thickness after stretching was 40 μm.

(6) Winding For the purpose of producing a film having the composition shown in the table below and judging its production suitability, 24 rolls having a roll width of 1280 mm and a roll length of 2600 mm were produced under the above conditions. About 1 roll in 24 rolls manufactured continuously, a 1-m long sample (width 1280 mm) was cut out at intervals of 100 m, and each measurement was performed.

(Creation of polarizing plate)
A polarizer was produced by adsorbing iodine to a stretched polyvinyl alcohol film. The produced films of each Example and Comparative Example were attached to one side of a polarizer using a polyvinyl alcohol-based adhesive. The saponification treatment was performed under the following conditions.
A 1.5 mol / L aqueous sodium hydroxide solution was prepared and kept at 55 ° C. A 0.005 mol / L dilute sulfuric acid aqueous solution was prepared and kept at 35 ° C. The film produced in each Example and Comparative Example was immersed in the aqueous sodium hydroxide solution for 2 minutes, and then immersed in water to sufficiently wash away the aqueous sodium hydroxide solution. Subsequently, after being immersed in the above-mentioned dilute sulfuric acid aqueous solution for 1 minute, it was immersed in water to sufficiently wash away the dilute sulfuric acid aqueous solution. Finally, the sample was thoroughly dried at 120 ° C.
A commercially available cellulose triacylate film (Fujitac TD80UF, manufactured by Fuji Film Co., Ltd.) is saponified, and is attached to the opposite side of the polarizer using a polyvinyl alcohol adhesive and dried at 70 ° C. for 10 minutes or more. did.
The transmission axis of the polarizer and the slow axis of the films of the examples and comparative examples were arranged in parallel. The transmission axis of the polarizer and the slow axis of the commercially available film were arranged so as to be orthogonal.

<Measurement method>
(Measuring method of average degree of substitution of sucrose benzoate)
By measurement under the following HPLC conditions, the peak having a retention time of about 31.5 min is 8 substituted, the peak group of 27 to 29 min is 7 substituted, the peak group of 22 to 25 min is 6 substituted, The peak group in the vicinity of 15 to 20 min is 5 substitutions, the peak group in the vicinity of 8.5 to 13 min is 4 substitutions, the peak group in the vicinity of 3 to 6 min is 3 substitutions, and the total area ratio is relative to the total value The average degree of substitution was calculated.
<< HPLC measurement conditions >>
Column: TSK-gel ODS-100Z (Tosoh), 4.6 * 150 mm, lot number (P0014)
Eluent A: H ₂ O = 100, Eluent B: AR = 100. Both A and B contain 0.1% AcOH and NEt ₃ flow rate: 1 ml / min, column temperature: 40 ° C., wavelength: 254 nm, sensitivity: AUX2, injection amount: 10 μl, rinse solution: THF / H ₂ O = 9 / 1 (vol ratio)
Sample concentration: 5 mg / 10 ml (THF)

(Haze)
The haze was measured in accordance with JIS K-6714 using a haze meter (HGM-2DP, Suga Test Instruments) with a film sample of 40 mm × 80 mm at 25 ° C. and a relative humidity of 60%. The results are shown in the following table.

(Optical performance)
The optical performance was comprehensively evaluated. The results are listed in the table below.

(Optical expression)
Re and Rth were measured at a wavelength of 590 nm by KOBRA 21ADH (manufactured by Oji Scientific Instruments) by the above method. The results are listed in the table below.

(Tg)
The glass transition temperature is measured by the following method. A cellulose acylate film sample 24 mm × 36 mm was conditioned at 25 ° C. and a relative humidity of 60% for 2 hours or more and then grasped with a dynamic viscoelasticity measuring device (Vibron: DVA-225 (manufactured by IT Measurement Control Co., Ltd.)) The distance was 20 mm, the temperature rising rate was 2 ° C./min, the measurement temperature range was 30 ° C. to 200 ° C., and the frequency was 1 Hz. Taking the storage elastic modulus on the logarithmic axis on the vertical axis and the temperature on the linear axis on the horizontal axis, the storage elastic modulus suddenly decreases when the storage elastic modulus transitions from the solid region to the glass transition region. The glass transition temperature Tg was determined by the method described in FIG. 3 of K7121-1987.

(Moisture content)
The moisture content was measured by measuring a cellulose acylate film sample 7 mm × 35 mm by a Karl Fischer method using a moisture meter and a sample drying apparatus (CA-03, VA-05, both Mitsubishi Chemical Corporation). It was calculated by dividing the amount of water (g) by the sample weight (g).

(Bleed out)
The bleed-out was evaluated as to whether or not precipitation of the additive occurred when the dope was cast and dried for 1000 hours under wet heat conditions of a temperature of 60 ° C. and a humidity of 90% and a temperature of 80% and a humidity of 10%. The results are shown in Table 5.

(Adhesion evaluation method)
A cross cut test according to JIS K 5600 was conducted. Specifically, a hard coat was applied, and 11 cuts were made vertically and horizontally at 1 mm intervals on the sample surface after UV curing to make 100 1 mm square grids. A cellophane tape and a mylar tape were affixed on this, and the part peeled off quickly was evaluated by adhesion by visual observation.
The result of irradiation with Xe for 24 h before making a notch is referred to as light-resistant adhesion, and the result of non-Xe irradiation as initial adhesion.
Adhesiveness ○: Peeling part 0 to 10 squares.
Adhesiveness (triangle | delta): The peeling location 11-50 mass.
Adhesiveness x: The peeled portion exceeds 50 squares and is 99 squares or less.
Adhesiveness XX: 100 squares peeled off (all taped parts)
Super Xenon weather meter SX75 manufactured by Suga Test Instruments Co., Ltd. is used for Xe irradiation.

(Pencil hardness evaluation method)
After applying a hard coat and conditioning the sample after UV curing at 25 ° C. and a relative humidity of 60% for 2 hours, using a test pencil specified by JIS S 6006, pencil hardness evaluation specified by JIS K 5400 In accordance with the law, a sample obtained by repeating scratching with a pencil of each hardness 5 times using a 500 g weight is put into a 100 ° C. Serco for 5 minutes and then evaluated, and the hardness of the sample is evaluated until there is no scratch more than 4 times. It was. The scratches defined in JIS K 5400 are torn coating films and scratches on the coating film, and are described as not covering the coating dents. Judging. The higher the number, the higher the hardness.

(Polarizing plate durability)
The durability of the obtained polarizing plate under wet heat conditions was examined by the following method.
Observing the change in cross transmittance after 1000 hours of aging under conditions of humidity and heat of 60 ° C humidity 90%, temperature 80% humidity 10%, all sucrose benzoate systems have better polarizing plate durability than TPP systems confirmed.

From Table 5, the cellulose acylate films obtained in the examples have good transparency, moisture permeability and optical performance, and can improve the durability of polarizing plates under high temperature and high humidity when combined with a polarizer. I knew it was possible.
On the other hand, from Comparative Examples 1 and 2, when a mixture of sugar ester compounds having different degrees of substitution was used, the content of sugar ester compounds having an ester substitution degree of 75% or more exceeded the scope of the present invention, and the degree of ester substitution was 35%. It was found that when the content of the sugar ester compound of ˜50% is less than the range of the present invention, the sugar ester compound bleeds out and the transparency and optical performance deteriorate.

Example 4
Even when 25% of sucrose benzoate, which is the sugar ester compound of Example 3 in Table 5, is replaced with sucrose octaacetate, which is the sugar ester compound of the same disaccharide, adhesion performance with the hard coat, pencil hardness, polarizing plate durability Was as good as in Example 3.

(Creation of liquid crystal display device)
When the polarizing plate using the film of the present invention was mounted on a liquid crystal panel and evaluated, it was confirmed that there was no problem in performance without a difference from the TPP film.

  It was found that the obtained liquid crystal display device was excellent in durability under high temperature and high humidity.

Claims (10)

A plurality of sugar ester compounds having different degrees of ester substitution;
And the cellulose acylate is including cellulose acylate film,
The cellulose acylate has an acetyl substitution degree of 2.70 or more and less than 2.95, and
The sugar constituting the sugar ester compound is a disaccharide to a tetrasaccharide,
The average ester substitution degree of the plurality of sugar ester compounds having different ester substitution degrees is 62% to 94%,
Among the plurality of sugar ester compounds having different ester substitution degrees contained in the cellulose acylate film, the content of the sugar ester compound having an ester substitution degree of 75% or more is 80% or less, and the ester substitution degree is 35% to 50%. % Cellulose ester film, wherein the content of the sugar ester compound is 5% to 30%.   The cellulose acylate film according to claim 1, wherein the sugar ester compound contains at least a furanose ring or a pyranose ring.   The cellulose acylate film according to claim 1 or 2, wherein the sugar constituting the sugar ester compound is a disaccharide.   The cellulose acylate film according to any one of claims 1 to 3, wherein the sugar ester compound has at least one of a benzoyl group and an acetyl group as an ester group.   The cellulose acylate film according to any one of claims 1 to 4, wherein the cellulose acylate is cellulose acetate.   It has a phase difference, The cellulose acylate film as described in any one of Claims 1-5 characterized by the above-mentioned.   Furthermore, the functional layer is laminated | stacked, The cellulose acylate film as described in any one of Claims 1-6 characterized by the above-mentioned.   The cellulose acylate film according to claim 7, wherein the functional layer is a hard coat layer.   A polarizing plate comprising a polarizer and at least one cellulose acylate film according to claim 1.   A liquid crystal display device comprising at least one of the cellulose acylate film according to claim 1 or the polarizing plate according to claim 9.