JP2013076872A - Cellulose acylate film, polarizing plate and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cellulose acylate film that can develop predetermined optical properties and significantly improve a contrast in a frontal direction and changes in a hue in a viewing angle direction when the film is incorporated in a liquid crystal display device.SOLUTION: The cellulose acylate film comprises cellulose acylate having a total substitution degree of 2.0 to 2.5, a polymerization condensation ester including at least one kind of aliphatic dicarboxylic acid residue and an aliphatic diol residue (however, the polymerization condensation ester contains neither aromatic dicarboxylic acid residue nor aromatic diol residue), and at least one kind of nitrogen-containing aromatic compound. The film is an oriented film satisfying (1):40 nm≤Re(550)≤80 nm, (2):100 nm≤Rth(550)≤300 nm and (3):0 nm≤ΔRe(λ)≤30 nm, and having a film thickness of 45 to 70 μm.

Description

  The present invention relates to a cellulose acylate film, and a polarizing plate and a liquid crystal display device using the cellulose acylate film. In particular, the present invention relates to a cellulose acylate film that can be preferably used as an optical film such as a polarizing plate protective film or an optical compensation film.

  In recent years, TV applications of liquid crystal display devices have progressed, and there has been an increasing demand for higher image quality and lower price as the screen size increases. In particular, a VA mode liquid crystal display device is the most common liquid crystal display device for TV because it has a relatively high contrast and a relatively high manufacturing yield.

However, when the VA mode liquid crystal display device displays black, a black image can be displayed to a certain degree in the normal direction of the liquid crystal display screen, but is displayed black from the viewing angle direction (diagonal direction) of the liquid crystal display screen. , There is a problem that the viewing angle becomes narrow because light leakage occurs and the background cannot be displayed in black. Therefore, there has been a demand for a retardation film that exhibits retardation to such an extent that viewing angle compensation can be performed.
Further, in recent years, in order to improve the yellow tint in the halftone of the liquid crystal display screen, a multi-gap (MG) cell in which the thickness of the liquid crystal layer, that is, the cell gap is changed for each color has been used. . However, the multi-gap cell has a larger color change when viewing black in the viewing angle direction than conventional liquid crystal display screens, and there is an increasing need to improve the blackness change in the viewing angle direction of the liquid crystal display screen. Yes.

  In order to satisfy these requirements, it is possible to use a retardation film having reverse dispersion (reverse wavelength dispersion), that is, a retardation film having an optical characteristic that the retardation Re in the in-plane direction increases as the wavelength becomes longer. It is known to be effective as a method for improving the blackness change in the viewing angle direction of the display screen (see Patent Document 1).

  However, reverse dispersion films that have been studied so far have been manufactured by using an additive having negative intrinsic birefringence in combination with a resin film (see, for example, Patent Documents 1 and 2). Patent Document 1 discloses a film using an acrylic polymer as an additive having negative intrinsic birefringence and further used in combination with a sugar ester compound. Patent Document 2 discloses a film using a polystyrene compound having an absorption maximum in a wavelength range of 250 nm to 400 nm as an additive having negative intrinsic birefringence. However, the additive having negative intrinsic birefringence is expensive, and the retardation Rth in the film thickness direction is lowered by the additive having negative intrinsic birefringence, so that a desired phase difference is expressed. Therefore, it is necessary to increase the film thickness or increase the retardation increasing agent, resulting in dissatisfaction from the viewpoint of material cost.

On the other hand, Patent Document 3 discloses a liquid crystal display device by using a cellulose acylate laminated film in which a cellulose acylate layer having a low substitution degree is used as a core layer and a cellulose acylate layer having a high substitution degree is provided on both surfaces thereof. It is described that contrast and color change can be improved when it is incorporated.
Patent Document 4 describes that by adding a specific high molecular weight additive to a cellulose acylate layer having a low degree of substitution, a film having reverse wavelength dispersion and a small haze can be provided.

JP 2009-1696 A JP 2010-170128 A US Publication No. 2010-0271574A1 JP 2011-118222 A

When the inventors incorporated the film described in Patent Document 1 into a liquid crystal display device, the color fluctuation u′v ′ could not be controlled to 0.06 or less, which is practically required in recent years. I found out that there was still dissatisfaction. In addition, film No. According to Comparative Example 201, it is described that when only a sugar ester compound is used without using a negative intrinsic birefringent resin, the haze is significantly increased. From the viewpoint of manufacturing cost, it was found that the dissatisfaction remains because the basic resin is essential.
Similarly, when the present inventors examined the film described in Patent Document 2 by incorporating it in a liquid crystal display device, the document described that the front contrast is high and the color change due to viewing angle is small, but in recent years, It turns out that dissatisfaction remains from the required level.
In addition, when the present inventors examined the film described in Patent Document 3 by incorporating it in a liquid crystal display device, the document discloses that the front contrast is high and the change in color depending on the viewing angle is small. It was found that dissatisfaction remained from the level that was given.
Furthermore, when the film described in Patent Document 4 was incorporated into a liquid crystal display device and examined, it was found that although the document described that the haze of the film was low, the front contrast was lowered.

  The problem to be solved by the present invention is cellulose that can obtain a predetermined optical expression and can remarkably improve the contrast in the front direction and the color change in the viewing angle direction when incorporated in a liquid crystal display device. It is to provide an acylate film.

  As a result of intensive studies by the present inventors based on the above problems, a cellulose acylate having a total acyl substitution degree within a specific range contains at least one aliphatic dicarboxylic acid residue and an aliphatic diol residue. Condensation ester (however, the polycondensation ester does not contain an aromatic dicarboxylic acid residue and does not contain an aromatic diol residue) and at least one nitrogen-containing aromatic compound, and specifies the film thickness It was found that the above-mentioned problems can be solved by a cellulose acylate film that is controlled in this range and whose optical characteristics are controlled in a specific range, and the present invention has been completed.

Specifically, the above problem has been solved by the following means.
[1] A polycondensation ester comprising a cellulose acylate having a total substitution degree of 2.0 to 2.5, at least one aliphatic dicarboxylic acid residue and an aliphatic diol residue (provided that the polycondensation ester is aromatic) Including no dicarboxylic acid residue and no aromatic diol residue) and at least one nitrogen-containing aromatic compound, satisfying the following formulas (1) to (3), and having a film thickness of 45 to 45 A cellulose acylate film which is 70 μm and is stretched.
Formula (1) 40nm <= Re (550) <= 80nm
(In formula (1), Re (550) represents in-plane retardation at a wavelength of 550 nm.)
Formula (2) 100 nm ≦ Rth (550) ≦ 300 nm
(In Formula (2), Rth (550) represents retardation in the film thickness direction at a wavelength of 550 nm.)
Formula (3) 0 nm ≦ ΔRe (λ) ≦ 30 nm
(In the formula (3), ΔRe (λ) represents Re (650) -Re (480), Re (650) represents in-plane retardation at a wavelength of 650 nm, and Re (480) represents a surface at a wavelength of 480 nm. Represents inward retardation.)
[2] In the cellulose acylate film according to [1], the polycondensed ester is preferably composed of an aliphatic dicarboxylic acid residue and an aliphatic diol residue.
[3] The cellulose acylate film according to [1] or [2] is preferably formed by stretching the cellulose acylate film at Tg−20 ° C. or more and Tg or less (where Tg is a cellulose acylate film). Of glass transition temperature).
[4] The cellulose acylate film according to any one of [1] to [3] preferably has a humidity dependency satisfying the following formulas (5) and (6).
Formula (5) (DELTA) Re (10-80) <= 13nm
Formula (6) ΔRe (10−80) = Re (10% RH) −Re (80% RH)
(In the formulas (5) and (6), Re (10% RH) represents the retardation value in the in-plane direction of the film at a relative humidity of 10%, and Re (80% RH) represents the in-plane of the film at a relative humidity of 80%. Represents the direction retardation value.)
[5] The cellulose acylate film according to any one of [1] to [4] preferably has an internal haze of less than 0.08%.
[6] The cellulose acylate film according to any one of [1] to [5] is preferably a single layer.
[7] The cellulose acylate film according to any one of [1] to [6] has a dimensional change rate of about ± 0.5% or less in an environment of 60 ° C. and a relative humidity of 90% around 24 hours. It is preferable.
[8] In the cellulose acylate film according to any one of [1] to [7], the content of the cellulose acylate in the film is 84% by mass or more based on the mass of the film. preferable.
[9] In the cellulose acylate film according to any one of [1] to [8], the cellulose acylate is preferably cellulose acetate.
[10] The cellulose acylate film according to any one of [1] to [9] preferably has a thickness of 48 μm to 65 μm.
[11] A polarizing plate comprising a polarizer and the cellulose acylate film according to any one of [1] to [10] on at least one side of the polarizer.
[12] A liquid crystal display device comprising at least one polarizing plate according to [11].

  According to the present invention, there is provided a cellulose acylate film which can obtain a predetermined optical expression and can remarkably improve the contrast in the front direction and the color change in the viewing angle direction when incorporated in a liquid crystal display device. Can be provided.

It is a cross-sectional schematic diagram of an example of the VA-type liquid crystal display device of the present invention.

  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. In this specification, “front side” means the display surface side, and “rear side” means the backlight side. In this specification, “front” means a normal direction to the display surface, and “front contrast (hereinafter, contrast is also referred to as CR)” means white luminance measured in the normal direction of the display surface and The contrast calculated from the black luminance is assumed.

[Cellulose acylate film]
The cellulose acylate film of the present invention (hereinafter also referred to as the film of the present invention) comprises a cellulose acylate having a total substitution degree of 2.0 to 2.5, at least one aliphatic dicarboxylic acid residue and an aliphatic diol residue. (Wherein the polycondensation ester does not contain an aromatic dicarboxylic acid residue and does not contain an aromatic diol residue) and at least one nitrogen-containing aromatic compound, (1) to (3) are satisfied, the film thickness is 45 to 70 μm, and the film is stretched.
Formula (1) 40nm <= Re (550) <= 80nm
(In formula (1), Re (550) represents in-plane retardation at a wavelength of 550 nm.)
Formula (2) 100 nm ≦ Rth (550) ≦ 300 nm
(In Formula (2), Rth (550) represents retardation in the film thickness direction at a wavelength of 550 nm.)
Formula (3) 0 nm ≦ ΔRe (λ) ≦ 30 nm
(In the formula (3), ΔRe (λ) represents Re (650) −Re (480))
The film of the present invention having such a configuration uses a polycondensation ester A containing an aliphatic dicarboxylic acid residue and an aliphatic diol residue described in Example 1 of JP2011-118222A. The cellulose acylate film having a low degree of substitution is greatly different in that it does not contain a nitrogen-containing aromatic compound. The film of the present invention has a predetermined optical expression by selecting a film having a specific structure from polycondensation esters and combining it with a nitrogen-containing aromatic compound with respect to a low-substituted cellulose acylate film. Thus, when incorporated in a liquid crystal display device, the contrast in the front direction and the color change in the viewing angle direction can be remarkably improved.
The cellulose acylate film of the present invention may be a single layer or a laminate obtained by co-casting.
Hereinafter, the film of the present invention will be described.

<Cellulose acylate>
The film of the present invention contains cellulose acylate having a total substitution degree of 2.0 to 2.5. Hereinafter, the cellulose acylate used in the present invention will be described.

  Cellulose acylate raw material cellulose used in the present invention includes cotton linter and wood pulp (hardwood pulp, conifer pulp), and any cellulose acylate obtained from any raw material cellulose can be used. May be used. Detailed descriptions of these raw material celluloses can be found in, for example, Marusawa and Uda, “Plastic Materials Course (17) Fibrous Resin”, published by Nikkan Kogyo Shimbun (published in 1970), and the Japan Society of Invention and Innovation Technical Bulletin No. 2001. The cellulose described in No.-1745 (pages 7 to 8) can be used, and is not particularly limited to the cellulose acylate laminated film of the present invention.

  First, the cellulose acylate preferably used in the present invention will be described in detail. Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by acylating part or all of these hydroxyl groups with an acyl group. The degree of acyl substitution means the sum of the ratios of acylation of the hydroxyl groups of cellulose located at the 2-position, 3-position and 6-position (100% acylation at each position is substitution degree 1).

Only one type of acyl group may be used in the cellulose acylate of the present invention, or two or more types of acyl groups may be used.
The acyl group of cellulose acylate in the present invention may be an aliphatic group or an allyl group and is not particularly limited. 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. Preferred examples of these are acetyl group, propionyl group, butanoyl group, heptanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group, isobutanoyl group. Group, ter
Examples thereof include a t-butanoyl group, a cyclohexanecarbonyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, and a cinnamoyl group. Among these, an acetyl group, a propionyl group, a butanoyl group, a dodecanoyl group, an octadecanoyl group, a tert-butanoyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, a cinnamoyl group, and the like are more preferable, and an acetyl group is particularly preferable. A propionyl group and a butanoyl group (when the acyl group has 2 to 4 carbon atoms), more preferably an acetyl group (when the cellulose acylate is cellulose acetate).

  That is, examples of the cellulose acylate include triacetyl cellulose (TAC), diacetyl cellulose (DAC), cellulose acetate propionate (CAP), cellulose acetate butyrate (CAB), and cellulose acetate phthalate. In the cellulose acylate film of the present invention, it is preferable from the viewpoint of retardation development and cost that all the acyl groups of the cellulose acylate are acetyl groups.

The film of the present invention contains cellulose acylate having a total substitution degree of 2.0 to 2.5. The total acyl substitution degree of the cellulose acylate preferably satisfies 2.1 to 2.5, and more preferably 2.2 to 2.45.
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.

  In a preferred embodiment of the present invention, even in a cellulose acylate film containing a cellulose acylate having a low acyl substitution degree, the retardation change under wet heat conditions is improved, and chromatic dispersion is converted to reverse wavelength dispersion (ΔRe is positive). Improvement can be improved at the same time, and a cellulose acylate film containing cellulose acylate having a low acyl substitution degree can be produced.

  These cellulose acylates can be synthesized by a known method, for example, by the method described in JP-A-10-45804.

In the acylation of cellulose, when an acid anhydride or acid chloride is used as an acylating agent, an organic acid such as acetic acid or methylene chloride is used as an organic solvent as a reaction solvent.
As the catalyst, when the acylating agent is an acid anhydride, a protic catalyst such as sulfuric acid is preferably used, and when the acylating agent is an acid chloride (for example, CH ₃ CH ₂ COCl), Basic compounds are used.

  The most common industrial synthesis method of cellulose mixed fatty acid ester is to use cellulose corresponding to fatty acid corresponding to acetyl group and other acyl groups (acetic acid, propionic acid, valeric acid, etc.) or their anhydrides. This is a method of acylating with a mixed organic acid component.

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.

  In the film of the present invention, the content of the cellulose acylate in the film is preferably 85% by mass or more, more preferably more than 85% by mass, and 86% by mass or more with respect to the mass of the film. It is particularly preferred. Moreover, the cellulose acylate content in the film can be decreased as the total substitution degree of cellulose acylate is higher, and the cellulose acylate content in the film can be increased as the total substitution degree is lower.

<Additives>
The film of the present invention contains a polycondensed ester containing at least one aliphatic dicarboxylic acid residue and an aliphatic diol residue, and at least one nitrogen-containing aromatic compound.
The polycondensed ester containing an aliphatic dicarboxylic acid residue and an aliphatic diol residue used in the film of the present invention and the nitrogen-containing aromatic compound used in the film of the present invention will be described in order.

(Polycondensed ester containing aliphatic dicarboxylic acid residue and aliphatic diol residue)
The polycondensation ester containing an aliphatic dicarboxylic acid residue and an aliphatic diol residue used in the film of the present invention has a repeating unit in the compound, and preferably has a number average molecular weight of 700 to 10,000. . The high molecular weight additive has a function of increasing the volatilization rate of the solvent and a function of reducing the residual solvent amount in the solution casting method. Furthermore, it exhibits useful effects from the viewpoint of film modification such as improvement in mechanical properties, imparting flexibility, imparting water absorption resistance, and reducing moisture permeability.

Here, the number average molecular weight of the polycondensed ester containing an aliphatic dicarboxylic acid residue and an aliphatic diol residue in the present invention is more preferably a number average molecular weight of 700 to 8000, and still more preferably a number average molecular weight of 700 to 8000. 5000, particularly preferably a number average molecular weight of 1000 to 5000.
Hereinafter, the polycondensation ester containing an aliphatic dicarboxylic acid residue and an aliphatic diol residue used in the present invention will be described in detail with specific examples, but the aliphatic dicarboxylic acid residue used in the present invention will be described. Needless to say, the polycondensed ester containing a diol residue and an aliphatic diol residue is not limited to these.

  Examples of the polycondensation ester containing an aliphatic dicarboxylic acid residue and an aliphatic diol residue include polyester polymers (aliphatic polyester polymers and the like), copolymers of polyester components and other components, and the like. Of these, aliphatic polyester polymers, copolymers of polyester polymers (such as aliphatic polyester polymers) and acrylic polymers, and copolymers of polyester polymers (aliphatic polyester polymers) and styrene polymers are preferred. However, the polycondensed ester does not contain an aromatic dicarboxylic acid residue and does not contain an aromatic diol residue.

  As a polycondensation ester containing an aliphatic dicarboxylic acid residue and an aliphatic diol residue used in the present invention, from the viewpoint of not generating haze in the film, bleeding out or volatilizing from the film, It is preferable to use a polycondensed ester compound having a smaller number average molecular weight than the above range, and it is particularly preferable to use a polyester plasticizer having a number average molecular weight of 300 or more and less than 2000.

The aliphatic diol residue refers to a structure derived from an alkylene glycol component contained in a polyester obtained by polycondensation of an alkylene glycol component. Specifically, when the alkylene glycol component is represented by HO—R—OH, the aliphatic diol residue means an —O—R—O— structure (R represents an arbitrary alkylene group).
Examples of the alkylene glycol component of the polycondensation ester containing an aliphatic dicarboxylic acid residue and an aliphatic diol residue preferably used in the present invention include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1, 2-butanediol, 1,3-butanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1 , 3-propanediol (neopentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3 , 3-dimethylolheptane), 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2,2,4-tri Methyl 1,3-pentanediol, 2-ethyl 1,3-hexanediol, 2-methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, etc. Yes, these glycols are used as one or a mixture of two or more.
In particular, the aliphatic diol residue preferably has a structure derived from an alkylene glycol component having 2 to 12 carbon atoms because of excellent compatibility with cellulose acylate.

  More preferable alkylene glycols include ethylene glycol (1,2-ethanediol), propylene glycol (1,2-propanediol, 1,3-propanediol), 1,2-butanediol, 1,3-butanediol. 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol 1,4-cyclohexanedimethanol, particularly preferably ethylene glycol (1,2-ethanediol), propylene glycol (1,2-propanediol, 1,3-propanediol), 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentane All, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, more preferably ethylene glycol (1,2-ethanediol) and propylene glycol (1,2-propanediol) 1,3-propanediol).

  Moreover, the polycondensed ester containing an aliphatic dicarboxylic acid residue and an aliphatic diol residue used in the present invention may contain a group derived from an oxyalkylene glycol component. The oxyalkylene glycol component is preferably an oxyalkylene glycol component having 4 to 12 carbon atoms. Examples of the oxyalkylene glycol component having 4 to 12 carbon atoms include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. These glycols are used alone or as a mixture of two or more. Can be used as

The aliphatic dicarboxylic acid residue refers to a structure derived from an alkylene dicarboxylic acid component contained in a polyester obtained by polycondensation of an alkylene dicarboxylic acid component. Specifically, when the alkylenedicarboxylic acid component is represented by HOOC-R′—COOH, the aliphatic diol residue means a —OOC—R′—COO— structure (R ′ represents an arbitrary alkylene group). Represent).
Examples of the alkylene dicarboxylic acid component of the polycondensed ester containing an aliphatic dicarboxylic acid residue and an aliphatic diol residue used in the present invention include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, and azelaic acid. , Sebacic acid, dodecanedicarboxylic acid and the like, and these are used as one kind or a mixture of two or more kinds, respectively.
Among these, the aliphatic dicarboxylic acid residue preferably has a structure derived from an alkylene dicarboxylic acid component having 2 to 12 carbon atoms. The alkylene dicarboxylic acid component having 2 to 12 carbon atoms is more preferably malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, or 1,4-cyclohexanedicarboxylic acid. Particularly preferred are succinic acid, glutaric acid and adipic acid, and particularly preferred are succinic acid and adipic acid.

The polycondensed ester containing an aliphatic dicarboxylic acid residue and an aliphatic diol residue used in the present invention does not contain an aromatic dicarboxylic acid residue and does not contain an aromatic diol residue. That is, in the polycondensation ester containing an aliphatic dicarboxylic acid residue and an aliphatic diol residue used in the present invention, all dicarboxylic acid residues are aliphatic dicarboxylic acid residues, and all diol residues are aliphatic diols. Residue.
Furthermore, the polycondensation ester containing an aliphatic dicarboxylic acid residue and an aliphatic diol residue used in the present invention is preferably composed of an aliphatic dicarboxylic acid residue and an aliphatic diol residue.

The polycondensation ester containing an aliphatic dicarboxylic acid residue and an aliphatic diol residue used in the present invention has a number average molecular weight of preferably 300 to 1500, more preferably 400 to 1000.
The acid value is preferably 0.5 mgKOH / g or less, the hydroxyl value is 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxyl value is 15 mgKOH / g or less.

  In addition, the polycondensation ester containing the aliphatic dicarboxylic acid residue and the aliphatic diol residue used in the present invention is [0141] of JP 2010-46834 A, unless it is contrary to the gist of the present invention. To [0156] can also be preferably used.

The polycondensation of the polycondensed ester containing the aliphatic dicarboxylic acid residue and the aliphatic diol residue is performed by a conventional method. For example, (I) heat melting and shrinkage by direct reaction of the dibasic acid and glycol, polyesterification reaction or transesterification reaction of the dibasic acid or alkyl esters thereof such as methyl ester of dibasic acid and glycols. The aliphatic dicarboxylic acid residue and the aliphatic diol residue used in the present invention can be easily synthesized by any method of (II) dehydrohalogenation reaction between acid chlorides of these acids and glycols. The polycondensation ester containing a group is preferably by direct reaction.
A polycondensation ester having a high distribution on the low molecular weight side has very good compatibility with cellulose acylate, and after formation of the film, a moisture permeability is small, and a cellulose acylate film rich in transparency can be obtained.

A conventional method can be used as a method for adjusting the molecular weight without particular limitation. For example, depending on the polymerization conditions, the amount of these monovalent compounds can be controlled by a method of blocking the molecular ends with a monovalent acid or monovalent alcohol.
In this case, a monovalent acid is preferable from the viewpoint of polymer stability. For example, acetic acid, propionic acid, butyric acid and the like can be mentioned, but during the polycondensation reaction, they are not distilled out of the system, but are stopped and such monovalent acids are removed out of the reaction system. Those that are easily removed are sometimes selected, but these may be mixed and used.
In the case of direct reaction, the number average molecular weight can also be adjusted by measuring the timing at which the reaction is stopped by the amount of water distilled off during the reaction. In addition, it can be adjusted by biasing the number of moles of glycol or dibasic acid to be charged or by controlling the reaction temperature.
The molecular weight of the polycondensed ester containing an aliphatic dicarboxylic acid residue and an aliphatic diol residue used in the present invention can be measured using the GPC measurement method and the terminal group determination method (hydroxyl value) described above. it can.

  The polycondensation ester containing an aliphatic dicarboxylic acid residue and an aliphatic diol residue used in the present invention is preferably contained in an amount of 1 to 40% by mass based on cellulose acylate. It is preferable to contain 5-15 mass% especially.

(Nitrogen-containing aromatic compounds)
The film of the present invention contains at least one nitrogen-containing aromatic compound.

  The nitrogen-containing aromatic compound has any one of pyridine, pyrimidine, triazine, and purine as a mother nucleus, and an alkyl group, an alkenyl group, an alkynyl group, an amino group, an amide group ( This means a structure in which an arbitrary acyl group is bonded via an amide bond), an aryl group, an alkoxy group, a thioalkoxy group, an alkyl or an arylthio group (an alkyl group or an aryl group is linked via a sulfur atom) Group) or a heterocyclic group as a substituent. However, the substituent of the mother nucleus of these nitrogen-containing aromatic compounds may be further substituted with another substituent, and the other substituent is not particularly limited. For example, when the mother nucleus is substituted with an amino group, the amino group may be an alkyl group (further, the alkyl groups may be linked to form a ring) or -SO2R '(R' is an optional substituent). May be substituted).

  In the film of the present invention, the content of the nitrogen-containing aromatic compound is preferably less than 7% by mass, more preferably 2 to 5% by mass with respect to the cellulose acylate. It is especially preferable that it is 4.5 mass%.

The film of the present invention may contain a conventionally known so-called retardation enhancer as the nitrogen-containing aromatic compound. By adopting a retardation developer, high retardation expression can be obtained at a low draw ratio. On the other hand, the film of the present invention is produced by the method for producing a cellulose acylate film, which will be described later, and thus has good retardation development properties even when these retardation developing agents are not included.
The retardation developer is not particularly limited, but includes a rod-shaped compound, a compound having a cyclic structure such as a cycloalkane or an aromatic ring, and a retardation among the non-phosphate ester compounds. The compound which shows expression property can be mentioned. As the compound having a cyclic structure, a discotic compound is preferable. As the rod-like compound or discotic compound, a compound having at least two aromatic rings can be preferably used as a retardation developer.
Two or more types of retardation developing agents may be used in combination.
It is preferable that the retardation developer has substantially no absorption in the visible region.

As the retardation developing material, for example, compounds described in JP 2004-50516 A, JP 2007-86748 A, and compounds described in JP 2010-46834 A can be used. The present invention is not limited to these.
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 a method described in 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.

  Although the specific example of a nitrogen-containing aromatic compound is given to the following, this invention is not limited by the following specific examples.

（上記式中におけるＲ¹〜Ｒ³はそれぞれ下記化合物Ｃ−１０１〜Ｃ−１８０におけるＲ¹〜Ｒ³を表す）

(Representing R ¹ to R ³ in R ¹ to R ³ each is the following compound C-101~C-180 in the above formula)

（上記式中におけるＲ²〜Ｒ³はそれぞれ下記化合物Ｃ−１８１〜Ｃ−１９０におけるＲ²〜Ｒ³を表す）

(Representing R ² to R ³ each R ² to R ³ in the following compound C-181~C-190 in the above formula)

（上記式中におけるＲ³は下記化合物Ｄ−１０１〜Ｄ−１１０におけるＲ³を表す）

(R ³ in the above formula represents a R ³ in the following compound D-101~D-110)

(Other additives)
In addition to the polycondensation ester and nitrogen-containing aromatic compound containing the aliphatic dicarboxylic acid residue and the aliphatic diol residue, the cellulose acylate film used in the present invention is added to a normal cellulose acylate film. Can be added.
Examples of these additives include additives having a negative intrinsic birefringence, fine particles, retardation developing agents, antioxidants, thermal deterioration inhibitors, colorants, ultraviolet absorbers, and the like.
About the said other additive, the compound described in international publication WO2008-126535 can be used preferably.

(1) Additive with negative intrinsic birefringence The film of the present invention may contain an additive with negative intrinsic birefringence. The compound having negative intrinsic birefringence that can be used as an additive having negative intrinsic birefringence will be described below.

  The compound having negative intrinsic birefringence means a material exhibiting negative intrinsic birefringence in a specific direction of the film in the cellulose acylate film. In the present specification, the negative intrinsic birefringence refers to a property having a negative birefringence. Whether or not it has negative intrinsic birefringence can be determined, for example, by measuring the birefringence of the film in a system not added with the compound with a birefringence meter and comparing the difference. be able to.

The compound having negative intrinsic birefringence of the present invention is not particularly limited, and a known compound exhibiting negative intrinsic birefringence can be used. For example, JP-A 2010-46834 discloses [0036] to [0036] The compounds disclosed in [0092] can be preferably used.
Examples of the compound having negative intrinsic birefringence include a polymer having negative intrinsic birefringence, and acicular fine particles having negative intrinsic birefringence (including acicular fine particles of a polymer having negative intrinsic birefringence). And so on. Hereinafter, a polymer having negative intrinsic birefringence that can be used in the present invention will be described.

  The polymer having negative intrinsic birefringence means that when light is incident on a layer in which molecules have a uniaxial orientation, the refractive index of light in the orientation direction is perpendicular to the orientation direction. A polymer smaller than the refractive index of light.

As a polymer having such a negative intrinsic birefringence, as a negative polymer, a polymer having a specific cyclic structure (a disc-shaped ring such as an aliphatic aromatic ring or a heteroaromatic ring) in a side chain (for example, , Polystyrene, poly (4-hydroxy) styrene, styrene polymers such as styrene-maleic anhydride copolymer, polyvinylpyridine, etc.), (meth) acrylic polymers such as polymethyl methacrylate, cellulose ester polymers (birefringence) Polyester polymers (excluding those with positive birefringence), acrylonitrile polymers, alkoxysilyl polymers, or multi-component (binary, ternary, etc.) copolymer polymers, etc. Is mentioned. These may be used individually by 1 type and may use 2 or more types together. Further, when it is a copolymer, it may be a block copolymer or a random copolymer.
Among these, a polymer having a specific cyclic structure, a (meth) acrylic polymer, and an alkoxysilyl polymer are more preferable, and polystyrene, polyhydroxystyrene, polyvinylpyridine, and a (meth) acrylic polymer are particularly preferable.

The addition of the polymer having the specific cyclic structure is preferable because the Rth expression of the cellulose acylate film after film formation can be increased.
As the polymer having the specific cyclic structure, a polymer having an aliphatic aromatic ring in a side chain described in JP-A-2010-46834 can be preferably used. Among these, polystyrene and poly (4-hydroxy) styrene are preferable, and a copolymer of polystyrene and poly (4-hydroxy) styrene is more preferable. The copolymerization ratio (molar ratio) of the copolymer of polystyrene and poly (4-hydroxy) styrene is preferably 10/90 to 100/0, and more preferably 20/80 to 90/10. .
On the other hand, as the polymer having the specific cyclic structure, a polymer having a heteroaromatic ring such as polyvinylpyridine in the side chain can also be preferably used.

  When the (meth) acrylic polymer is added, the cellulose acylate film after film formation is excellent in transparency and moisture permeability is extremely low, and exhibits excellent performance as a protective film for a polarizing plate. As the (meth) acrylic polymer, compounds described in JP2009-1696A and International Publication WO2008-126535 can be preferably used. The (meth) acrylic polymer may have an aliphatic aromatic ring or a heteroaromatic ring in the side chain.

When the compound having negative intrinsic birefringence is a polymer having negative intrinsic birefringence, the weight average molecular weight is preferably 500 to 100,000, and preferably 700 to 50,000. More preferably, it is particularly preferably 700 to 100,000.
When the molecular weight is 500 or more, the volatility is good, and when the molecular weight is 100,000 or less, the compatibility with the cellulose acylate resin is good, so the film-forming property of the cellulose acylate film is also good. preferable.

In the film of the present invention, the compound having negative intrinsic birefringence is preferably added in an amount of 0 to 20% by mass, more preferably 0 to 15% by mass, more preferably 0 to 15% by mass relative to the cellulose acylate. It is particularly preferable to add 10% by mass.
On the other hand, the film of the present invention is produced by the method for producing the cellulose acylate film described later, so that even if these relatively expensive compounds having negative intrinsic birefringence are not included, the reverse wavelength Dispersibility is large. Therefore, in the film of the present invention, it is preferable that the addition amount of the compound having negative intrinsic birefringence is small from the viewpoint of reducing the manufacturing cost.

(2) 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.
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.

  The content of these fine particles with respect to the cellulose acylate in the cellulose film of the present invention 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.

(3) 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.

(4) 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.

<Peeling accelerator>
(Organic acid that satisfies the requirements of (1) to (3))
The cellulose acylate film of the present invention preferably contains 0.01% by mass to 20% by mass of an organic acid that satisfies the following requirements (1) to (3) with respect to the resin.
(1) Includes a structure in which a polyhydric alcohol and a polycarboxylic acid are bonded by forming an ester bond.
(2) The total number of molecules of the polyhydric alcohol and polycarboxylic acid forming the compound is 3 or more.
(3) It has at least one unsubstituted carboxyl group derived from a polyvalent carboxylic acid.

In the organic acid satisfying the above requirements (1) to (3), the detachability from the solution film-forming equipment (metal support when the dope is fluent) can be improved by an unsubstituted carboxyl group, and the present invention. Then, an organic acid satisfying the requirements (1) to (3) can be used as a peeling accelerator.
Further, the unsubstituted carboxyl group adheres to the metal surface of the support, and the polyhydric alcohol part or the hydrophobic group part substituted therewith blocks the metal surface of the support from an oxidizing agent such as oxygen. Compared to organic acids that do not contain a monohydric alcohol moiety or a hydrophobic group moiety substituted therefor, corrosion of the metal can be prevented.
Hereinafter, the organic acid that satisfies the requirements (1) to (3) that can be used as a peeling accelerator in the cellulose acylate film of the present invention and other peeling accelerators that may be used in combination will be described.

Although it does not specifically limit as polyvalent carboxylic acid used for the organic acid which satisfy | fills the requirements of said (1)-(3), For example, a succinic acid, a citric acid, tartaric acid, diacetyl tartaric acid, malic acid, and adipic acid are preferable.
In the organic acid that satisfies the requirements (1) to (3), the number of polyvalent carboxylic acid molecules is preferably 1 to 20, more preferably 1 to 15, and more preferably 1 to 10. Particularly preferred.

Examples of the polyhydric alcohol used in the organic acid that satisfies the requirements (1) to (3) include adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, , 3-butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3- Examples thereof include methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol, and glycerin. Among these, glycerin is preferable.
Among the organic acids that satisfy the requirements (1) to (3), the number of polyhydric alcohol molecules is preferably 1 to 20, more preferably 1 to 15, and particularly preferably 1 to 10. preferable.

In addition to the polyhydric alcohol and polyvalent carboxylic acid that constitute the organic acid, the organic acid that satisfies the requirements (1) to (3) is a monovalent acid having a substituent having 4 or more carbon atoms. You may have the structure which formed the ester bond with the one part hydroxyl group of this polyhydric alcohol. Specific examples of the monovalent acid having a substituent having 4 or more carbon atoms are given below. The substituent in the monovalent acid having a substituent having 4 or more carbon atoms means R when the monovalent acid having a substituent having 4 or more carbon atoms is represented as RCOOH.
"fatty acid"
Caproic acid, heptylic acid, caprylic acid, pelargonic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, ricinolenic acid, undecanoic acid.
《Alkyl sulfate》
Myristyl sulfate, cetyl sulfate, oleyl sulfate.
《Alkylbenzene sulfonic acid》
Dodecylbenzenesulfonic acid, pentadecylbenzenesulfonic acid.
《Alkyl naphthalene sulfonic acid》
Sesquibutyl naphthalene sulfonic acid, diisobutyl naphthalene sulfonic acid.
Among these, a monovalent acid having a substituent having 4 or more carbon atoms, which is a fatty acid, is preferable, caprylic acid, lauric acid, stearic acid, and oleic acid are more preferable, and oleic acid is particularly preferable.
In the organic acid satisfying the requirements (1) to (3), the number of molecules of the monovalent acid having a substituent having 4 or more carbon atoms is preferably 0 to 4, and preferably 0 to 3. More preferred is 0-2.

  In the organic acid satisfying the requirements (1) to (3), the total number of molecules of the polyhydric alcohol and the polycarboxylic acid forming the compound is 3 or more, preferably 3 to 30. More preferably, it is ~ 20.

In the organic acid satisfying the above requirements (1) to (3), the ratio of the polyvalent carboxylic acid, the polyhydric alcohol, and the monovalent acid having a substituent having 4 or more carbon atoms is not particularly limited. Two or more unsubstituted hydroxyl groups may remain, or an unsubstituted hydroxyl group may remain.
The organic acid that satisfies the requirements (1) to (3) has at least one unsubstituted carboxyl group derived from a polyvalent carboxylic acid, and has 1 to 40 unsubstituted carboxyl groups derived from the polyvalent carboxylic acid. It is preferable to have 1-30.

  The organic acid satisfying the requirements (1) to (3) may be used alone or as a mixture. In addition, the organic acid satisfying the requirements (1) to (3) may be ionized depending on the case, and may form a salt with any metal ion depending on the case.

Examples of preferred organic acid compounds that satisfy the requirements (1) to (3) used in the present invention are shown below.
Organic acids (partial condensates of organic acids) having the following composition are preferred. An organic acid having the following composition can be prepared using, for example, Poem K-37V manufactured by Riken Vitamin.

The addition amount of the organic acid that satisfies the requirements (1) to (3) contained in the cellulose acylate film of the present invention is 0.01% by mass to 20% by mass with respect to the resin. It is particularly preferably from 05% by mass to 10% by mass, and more preferably from 0.1% by mass to 5% by mass. In addition, when the organic acid which satisfy | fills the requirements of said (1)-(3) is a mixture as for the addition amount of the organic acid which satisfy | fills the requirements of said (1)-(3), all said (1)-( It means the total amount of organic acid that satisfies the requirement 3).
If the addition amount is 0.01% or more, the polarizer durability improving effect and the peelability improving effect are sufficient.
In addition, even if the addition amount is about 0.001 to 0.01%, improvement in peelability can be expected by combining with a peelability improvement technique such as peeling site cooling of the casting support.
An addition amount of 20% by mass or less is preferable because the organic acid hardly bleeds out at a high temperature and high humidity, and the orthogonal transmittance of the polarizing plate hardly increases.

There is no restriction | limiting in particular about distribution of the organic acid which satisfy | fills the requirements of said (1)-(3) in the cellulose acylate film of this invention.
The cellulose acylate film of the present invention has a concentration of organic acid that satisfies the requirements (1) to (3) in a region having a depth of 5 μm from one film surface, and a region having a depth of 5 μm from the opposite film surface. It is preferable from the viewpoint of improving the decrease in the molecular weight of the resin that the concentration of the organic acid satisfying the requirements (1) to (3) in the above satisfies the relationship of the following formula (4).
Formula (4)
1.2 ≦ (average concentration of organic acid in the region from the surface on the film surface on the higher organic acid side to a depth of 5 μm) / (from surface on the film surface on the lower side of the organic acid to 5 μm in depth) Average concentration of organic acids in the region) ≦ 5.0
The lower limit value of the inequality (4) is more preferably 1.5, and particularly preferably 2.0. The upper limit value of the inequality (4) is more preferably 4.5, and particularly preferably 4.0.

(Other peeling accelerators)
In addition to the organic acid that satisfies the requirements (1) to (3), a known peeling accelerator may be added to the cellulose acylate film of the invention. As the known peeling accelerator, for example, compounds described in paragraph numbers 0048 to 0069 of JP-A-2006-45497 can be preferably used.

The peeling accelerator is preferably an organic acid, a polyvalent carboxylic acid ester, a surfactant or a chelating agent.
As the polyvalent carboxylic acid ester, the compound described in paragraph No. 0049 of JP-A-2006-45497 can be preferably used.
As the surfactant, compounds described in paragraph numbers 0050 to 0051 of JP-A-2006-45497 can be preferably used.
The chelating agent is a compound capable of coordinating (chelating) a metal ion such as an iron ion or an alkaline earth metal ion such as a calcium ion. 11-190892, JP-A-2000-18038, JP-A-2010-158640, JP-A-2006-328203, JP-A-2005-68246, and JP-A-2006-306969 can be used. .
The total addition amount of all peeling accelerators contained in the cellulose acylate film of the present invention is preferably 0.01% by mass (100 ppm) to 20% by mass (200000 ppm) with respect to the resin, and 0.01% by mass. % (100 ppm) to 15% by mass (150,000 ppm), more preferably 0.01% by mass (100 ppm) to 10% by mass (100,000 ppm), and 0.03% by mass (300 ppm) to 10%. More preferably, it is mass% (100,000 ppm), and even more particularly 0.1 mass% (1000 ppm) to 5 mass% (50000 ppm).

<Characteristics of cellulose acylate film>

(Re, Rth)
In the film of the present invention, the retardation in the plane and in the film thickness direction at a wavelength of 550 nm satisfies the following formulas (1) and (2).
Formula (1) 40nm <= Re (550) <= 80nm
(In formula (1), Re (550) represents in-plane retardation at a wavelength of 550 nm.)
Formula (2) 100 nm ≦ Rth (550) ≦ 300 nm
(In Formula (2), Rth (550) represents retardation in the film thickness direction at a wavelength of 550 nm.)
It is preferable that retardation is developed in such a range from the viewpoint of improving the contrast and blackness change of the liquid crystal display device.
The Re (550) is preferably 40 to 65 nm, and more preferably 45 to 60 nm.
The Rth (550) is preferably 100 to 300 nm, and more preferably 110 to 230 nm.

(Wavelength dispersion)
The film of the present invention has a difference ΔRe (λ) between in-plane retardation Re (650) at a wavelength of 630 nm and in-plane retardation Re (480) at a wavelength of 480 nm (that is, ΔRe (λ) = Re ( 650) -Re (480)) is preferably a reverse dispersion film from the viewpoint of improving the blackness change when incorporated in a liquid crystal display device.

The film of the present invention more preferably satisfies the formula (3).
Formula (3) 0 nm ≦ ΔRe (λ) ≦ 30 nm
(In the formula (3), ΔRe (λ) represents Re (650) -Re (480), Re (650) represents in-plane retardation at a wavelength of 650 nm, and Re (480) represents a surface at a wavelength of 480 nm. Represents inward retardation.)

  In the film of the present invention, the ΔRe (λ) is preferably 1 nm or more, more preferably 3 nm or more, and particularly preferably 3 to 5 nm.

(Retardation humidity dependency)
The film of the present invention more preferably satisfies the following formulas (5) and (6).
Formula (5) (DELTA) Re (10-80) <= 13nm
Formula (6) ΔRe (10−80) = Re (10% RH) −Re (80% RH)
(In the formulas (5) and (6), Re (10% RH) represents the retardation value in the in-plane direction of the film at a relative humidity of 10%, and Re (80% RH) represents the in-plane of the film at a relative humidity of 80%. Represents the direction retardation value.)
The film of the present invention preferably has a small variation due to the environmental humidity of Re.
The ΔRe (10-80) is preferably 9 nm or less, and more preferably 7 nm or less.

The film of the present invention is preferably a biaxial optical compensation film.
Here, the optical compensation film is biaxial means nx, ny and nz of the optical compensation film (nx represents the refractive index in the slow axis direction in the plane, and ny is the refraction in the direction perpendicular to nx in the plane. Nz represents the refractive index in the direction orthogonal to nx and ny), and 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 550 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.

(Internal haze)
The cellulose acylate film of the present invention preferably has an internal haze of less than 0.08%.
The haze represents a haze value (%) measured according to JIS K7136.
The internal haze of the film of the present invention was obtained by dropping several drops of glycerin on both sides of the obtained cellulose acylate film, and a glass plate having a thickness of 1.3 mm (MICRO SLIDE GLASS product number S92).
13 (manufactured by MATSANAMI) represents a value (%) obtained by subtracting the haze measured in a state where a few drops of glycerin were dropped between two sheets of glass from a haze value (%) measured between two sheets.
The haze of the cellulose acylate film of the present invention was measured using a turbidimeter (NDH2000, Nippon Denshoku Industries Co., Ltd.) in a film that was allowed to stand for 24 hours in an environment of 23 ° C. and 55% relative humidity. It was measured.

The internal haze of the cellulose acylate film of the present invention is preferably 0.05% or less, and more preferably 0.03% or less.
A lower haze is generally preferred. Further, simply reducing the total haze is insufficient for improving the front contrast, and adjusting the inner haze to the above range is preferable from the viewpoint of improving the front contrast of the liquid crystal display device.

(Dimensional change rate)
The film of the present invention more preferably satisfies the following formula (7) in the direction of film conveyance and the direction orthogonal thereto at a dimensional change rate of about 24 hours at 60 ° C. and 90% relative humidity.
−0.5% ≦ {(L′−L0) / L0} × 100 ≦ 0.5% (7)
The L0 represents the film length after conditioning for 2 hours or more in an atmosphere of 25 ° C. and a relative humidity of 60%, and L ′ is 24 hours at 60 ° C. and 90% relative humidity, and further conditioned for 2 hours. Represents film length.
When the dimensional change rate is within the range of the formula (7), the saponification treatment hardly causes dimensional change of the film, so that wrinkles and air can be prevented from being mixed in the polarizing plate bonding process. The dimensional change rate is more preferably −0.4 to 0.4%, and particularly preferably −0.2 to 0.2%.

(Layer structure of cellulose acylate film)
The film of the present invention may be a single layer film or may have a laminated structure of two or more layers, but is preferably a single layer film.

(Film thickness)
The film of the present invention has a film thickness of 45 to 70 μm. By controlling to such a film thickness, desired optical characteristics tend to be easily obtained. The film thickness of the film of the present invention is preferably 48 to 65 μm, more preferably more than 50 μm and less than 65 μm, and particularly preferably more than 50 μm and 60 μm or less. When the film of the present invention is a laminated film, the range of the total film thickness of the film is preferably within the above-mentioned preferable range.

(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.

[Method for Producing Cellulose Acylate Film of the Present Invention]
The method for producing a cellulose acylate film of the present invention (hereinafter also referred to as the method for producing the cellulose acylate film) is not particularly limited except that it includes a stretching step.

As the method for producing the cellulose acylate film, a 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 method for producing the cellulose acylate film preferably includes a step of forming the film containing the cellulose acylate by solution-flow casting.
Hereinafter, although the manufacturing method of the said cellulose acylate film is demonstrated to the case where the solution casting film forming method is used for an example, the manufacturing method of the said cellulose acylate film 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 said cellulose acylate film, 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 sometimes referred to as a cellulose acylate solution or a dope 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 exhibits a main effect on dissolution, and an organic solvent used in a large amount among them is a main (organic) solvent or a main ( 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 formic acid. Esters such as methyl, ethyl formate, methyl acetate, ethyl acetate, amyl acetate, γ-butyrolactone, methyl cellosolve, dimethylimidazolinone, dimethylformamide, dimethylacetamide, acetonitrile, dimethyl sulfoxide, sulfolane, nitroethane, methylene chloride And 1,3-dioxolane, THF, methyl ethyl ketone, acetone, methyl acetate and methylene chloride are preferable.

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, and Is.
Examples thereof include o-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 method for producing a cellulose acylate film. Specifically, by increasing the alcohol content or setting the drying temperature (heat treatment temperature) before stretching in the method for producing the cellulose acylate film described later, the reach range of Re and Rth can be further increased. It becomes possible to enlarge.
Further, in the present invention, it is effective to contain a small amount of water to increase the solution viscosity and the film strength in the wet film state at the time of drying, or to increase the dope strength at the time of casting the drum method. It may be contained in an amount of 0.1 to 5% by mass, more preferably 0.1 to 3% by mass, and particularly 0.2 to 2% by mass.

  Examples of combinations of organic solvents preferably used as the solvent for the 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 solution with a low concentration (for example, 4 to 14% by mass) in advance, the solution may be concentrated by evaporating the solvent or the like. Furthermore, after preparing a high concentration solution in advance, it may be diluted. Moreover, the density | concentration of a cellulose acylate can also be reduced by adding an additive.

  The timing of adding the additive can be appropriately determined according to the type of the additive.

  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.

<Details of each process>
(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.

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

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

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

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

(5) Drying or heat treatment step, stretching step The method for producing a cellulose acylate film of the present invention is characterized by performing a stretching step on the peeled film. Furthermore, it is preferable to perform the said extending | stretching process at the temperature of Tg-20 degreeC-TgdegreeC from a viewpoint of improving the optical expression with respect to the film thickness of the cellulose acylate film obtained. Tg represents the glass transition temperature (unit: ° C.) of the cellulose acylate film of the present invention, and tan δ has a peak when the dynamic viscoelasticity tan δ of the cellulose acylate film when the residual volatile content is 0% is measured. It means the temperature shown.
After the peeling step, the web is transferred using a drying device that alternately conveys the web through a plurality of rolls arranged in the drying device, and / or a tenter device that conveys the web while clipping both ends with the clip. It is preferable to dry.

In the method for producing a cellulose acylate film, the web may or may not be heat-treated before stretching.
The drying or 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.

  In the method for producing a cellulose acylate film, the cellulose acylate film may be stretched in any direction of a film transport direction (hereinafter also referred to as a longitudinal direction) and a direction orthogonal to the film transport direction (hereinafter also referred to as a lateral direction) Stretching in the transverse direction is preferable from the viewpoint of expressing desired 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 more than 20%, more preferably more than 20% to 60% or less, particularly preferably 25 to 55%, 25 More preferably, it is ˜50%.
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.

  In the method for producing a cellulose acylate film, the stretching temperature is preferably Tg-20 ° C to Tg.

  In a more preferred embodiment of the method for producing a cellulose acylate film, cellulose acetate having a low acetyl substitution degree (particularly cellulose acetate having an acetyl substitution degree of 2.0 to 2.5) is used, and in the range of the stretching temperature. By extending | stretching, the haze resulting from the said extending | stretching can also be suppressed. Without being bound by any theory, when cellulose acetate having a low acetyl substitution degree is used as the cellulose acylate, the cellulose acetate having a low acetyl substitution degree is composed of the aliphatic dicarboxylic acid residue and the aliphatic diol residue. Since the difference in refractive index from the polycondensed ester is high, scattering in the film is unlikely to occur. Moreover, haze can be further suppressed by selecting what has high compatibility with the cellulose acetate of a low acetyl substitution degree as said polycondensation ester. As a result, the internal haze of the film obtained by the method for producing the cellulose acylate film can be easily controlled within the preferable range.

  The stretching temperature is more preferably Tg-17 ° C to Tg ° C.

  In addition, you may dry before the wet heat treatment process mentioned later after an extending process. When drying after the stretching step and before the wet heat treatment step described later, 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 and before the wet heat treatment step, which will be described later, is lower than the stretching temperature in the stretching step, so that the front contrast when the film of the present invention is incorporated in a liquid crystal display device is increased. To preferred.

(6) Wet heat treatment step The cellulose acylate film is produced by wet heat treatment at a wet heat treatment temperature of 80 to 140 ° C. and an absolute humidity of 150 to 500 g / m ³ (hereinafter also referred to as HSV, sometimes referred to as steam treatment). It is preferable to include the process of doing.
Although not bound by any theory, when a film with a large dimensional change rate is incorporated into a liquid crystal display device, the problem is that the film is left for a long time under conditions of, for example, 60 ° C. and 90% relative humidity. This is due to the irreversible change in dimensions. When the obtained cellulose acylate film is mounted on a liquid crystal display device by actively generating an irreversible change during film formation by performing wet heat treatment under the above-mentioned conditions, the corner in the licking direction of the liquid crystal display panel Generation of unevenness (display unevenness that occurs when wet heat treatment is performed) can be further suppressed.

  Moreover, the more preferable aspect of the manufacturing method of the said cellulose acylate film uses a cellulose acetate with a low acetyl substitution degree, and improves optical developability and reverse wavelength dispersibility expressibility. Such cellulose acetates with a low acetyl substitution degree are cellulose acetate propionate (hereinafter also referred to as CAP) having the same degree of acyl substitution, and other acyl groups other than acetyl groups having the same degree of acyl substitution. Is more advantageous than cellulose acylate having a substituent as described above (for example, cellulose acetate phthalate described in JP-A-2009-1696) from the viewpoint of optical developability and reverse wavelength dispersibility. The film of the present invention can be sufficiently reduced in dimensional change by being wet-heat treated under specific conditions. As a result, even when the cellulose acylate film obtained in a more preferred embodiment of the method for producing the cellulose acylate film is mounted on a liquid crystal display device, the liquid crystal display device is further improved in contrast and color change, while the liquid crystal display device is further improved. It is possible to sufficiently suppress the occurrence of corner unevenness in the licking direction of the display panel (display unevenness that occurs when wet heat treatment is performed).

  The wet heat treatment temperature is particularly preferably 90 to 130 ° C. In addition, the wet heat treatment temperature said here means the temperature of the cellulose acylate film after making it contact with contact gas.

The heat-moisture treatment absolute humidity content is preferably 180~480g / m ^3, more preferably from 200~450g / m ^3, particularly preferably 220~450g / m ^3.

  The gas (contact gas) in contact with the cellulose acylate film in the wet heat treatment step is a gas containing water vapor, more preferably a gas containing water vapor as a main component, and further preferably water vapor. Here, the gas included as the main component indicates that gas when it is composed of a single gas, and when it is composed of a plurality of gases, the gas having the highest mass fraction among the constituent gases. It shows that.

  The contact gas is preferably a gas generated by a wet gas supply device. Specifically, the solvent in a liquid state is heated by a boiler to be in a gaseous state, and then sent by a blower. The contact gas may be mixed with air as appropriate, and heated after being sent by a blower. Further heating may be performed via the apparatus. Here, the air is preferably heated. The temperature of the contact gas thus produced is preferably 70 to 200 ° C, more preferably 80 to 160 ° C, and most preferably 100 to 140 ° C. If the temperature is not more than the upper limit temperature, the curl of the film does not become too strong, and if it is not less than the lower limit temperature, a sufficient effect can be obtained.

  The relative humidity of the contact gas is preferably 10% to 100%, more preferably 15 to 100%, and particularly preferably 20 to 100%.

  As a contact method between the cellulose acylate film and the aforementioned contact gas in the wet heat treatment step, a method of applying the contact gas to the cellulose acylate film, a method of disposing the cellulose acylate film in a space filled with the contact gas, or A method of passing through the space filled with the contact gas can be used, and a method of applying the contact gas to the cellulose acylate film or a method of passing through the space filled with the contact gas is preferable. The contact between the cellulose acylate film and the contact gas is preferably carried out while guiding the cellulose acylate film with a plurality of rollers arranged in a staggered manner.

  The contact time with the contact gas is not particularly limited, but is preferably as short as possible from the viewpoint of production efficiency as long as the effect of the present invention is exhibited. As an upper limit of processing time, it is preferred that it is 60 minutes or less, for example, and it is more preferred that it is 10 minutes or less. On the other hand, the lower limit of the processing time is, for example, preferably 10 seconds or more, and more preferably 30 seconds or more. The temperature of the cellulose acylate film before contacting with the contact gas is not particularly limited, but is preferably 80 to 130 ° C.

Further, the residual solvent amount of the cellulose acylate film before the wet heat treatment is not particularly limited, but it is preferable that the fluidity of the cellulose acylate molecule has almost disappeared, and it is preferably 0 to 5% by mass. More preferably, it is -0.3 mass%.
The contact gas in contact with the cellulose acylate film may be sent to a condensing device to which a cooling device is connected, and may be divided into a heated gas and a condensate.

  In the method for producing a cellulose acylate film, the wet heat treatment step may be performed immediately after the stretching step or immediately after the drying step and after the stretching step. You may go after winding up. When the wet heat treatment is performed after being wound into a roll shape, it may be performed in a roll shape or after being unwound into a film shape again.

(7) Drying step after wet heat treatment The cellulose acylate film in contact with the contact gas in this way may be cooled as it is to about room temperature, or in order to adjust the amount of contact gas molecules remaining in the film. Then, you may convey to a drying zone. When transporting to the drying zone, hot or warm air or a low gas concentration is applied to the cellulose acylate film transported by a group of rolls or the cellulose acylate film transported while being clipped at both ends by a tenter. There are a method, a method of irradiating with heat rays, a method of contacting a heated roll, and the like, but a method of applying hot air or warm air or a low gas concentration is preferable. In addition, when a water vapor contact process is implemented before a heat treatment process, a heat treatment process can also be made into a drying process.

(8) Heat treatment step after wet heat treatment It is also preferable to provide the above heat treatment step after the wet heat treatment step of the film production method of the present invention. In the present invention, the heat treatment may be performed after the wet heat treatment step and before the drying step, the heat treatment step may be performed after the wet heat treatment step, or may be performed after the wet heat treatment step and the drying step. After winding up, only the heat treatment step may be provided separately. In the present invention, it is preferable to provide the heat treatment step after the wet heat treatment step and before the drying step. This is because a film having better thermal dimensional stability can be obtained.
The reason why the shrinkage rate of the film can be reduced by such treatment is not clear, but in the film that has been subjected to the treatment to be stretched in the stretching process, the residual stress in the stretching direction is large, so the residual stress is eliminated by heat treatment. Thus, it is presumed that the shrinkage force in the region below the heat treatment temperature is reduced.

The heat treatment is performed by a method of applying a wind at a predetermined temperature to the film being conveyed or a method using a heating means such as a microwave.
The absolute humidity is preferably 0 g / m ³ during heat treatment drying. The heat treatment temperature in the heat treatment step is preferably the same as that in the wet heat treatment step from the viewpoints of prevention of condensation and film shrinkage.

  In the heat treatment step, the film tends to shrink in the longitudinal direction or the width direction. It is preferable to heat-treat while suppressing the shrinkage as much as possible in order to improve the flatness of the finished film, and a method in which the width ends of the web are held with clips or pins in the width direction (tenter method). Is preferred. Furthermore, it is preferable to extend | stretch 0.9 to 1.5 times in the width direction and conveyance direction of a film, respectively.

(9) Winding As the winder for winding the obtained film, a commonly used winder can be used. A constant tension method, a constant torque method, a taper tension method, a program tension with a constant internal stress. It can be wound up by a winding method such as a control method. In the optical film roll obtained as described above, the slow axis direction of the film is preferably ± 2 ° with respect to the winding direction (longitudinal direction of the film), and further within the range of ± 1 °. Preferably there is. Alternatively, it is preferably ± 2 degrees with respect to the direction perpendicular to the winding direction (film width direction), and more preferably within a range of ± 1 degree. In particular, the slow axis direction of the film is preferably within ± 0.1 degrees with respect to the winding direction (longitudinal direction of the film). Alternatively, it is preferably within ± 0.1 degrees with respect to the width direction of the film.

  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 optical compensation 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 shape by continuous production, and in a roll shape. The film of the aspect wound up by this is also included. The optical compensation 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 one mode of the optical compensation film wound up in a roll shape, a mode in which the roll length is rolled up to 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.

In the manufacturing method of the said cellulose acylate film, it is preferable to manufacture so that it may become the range of the preferable film thickness of the said cellulose acylate film from a viewpoint of manufacturing cost or optical characteristic expression.

  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.

[Polarizer]
The polarizing plate of the present invention includes a polarizer and at least one cellulose acylate film of the present invention on at least one side of the polarizer. Hereinafter, the polarizing plate of the present invention will be described.

Like the film of the present invention, the polarizing plate of the present invention is not only a polarizing plate 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. The polarizing plate of the aspect (for example, aspects with roll length 2500m or more, 3900m or more) wound up in roll shape is also contained. In order to use for a large-screen liquid crystal display device, the width of the polarizing plate is preferably 1470 mm or more as described above.
The specific configuration of the polarizing plate of the present invention is not particularly limited, and a known configuration can be employed. For example, the configuration described in FIG. 6 of JP-A-2008-262161 can be employed.

[Liquid Crystal Display]
The liquid crystal display device of the present invention includes at least one polarizing plate of the present invention. Since the liquid crystal display device of the present invention includes the polarizing plate of the present invention including the cellulose acylate film of the present invention, the contrast in the front direction and the color change in the viewing angle direction are remarkably improved.
The liquid crystal display device of the present invention is a liquid crystal display device having a liquid crystal cell and a pair of polarizing plates disposed on both sides of the liquid crystal cell, wherein at least one of the polarizing plates is the polarizing plate of the present invention. An IPS, OCB or VA mode liquid crystal display device is preferable.
The specific configuration of the liquid crystal display device of the present invention is not particularly limited, and a known configuration can be adopted. For example, an example having the configuration shown in FIG. 1 can be adopted. Further, the configuration described in FIG. 2 of JP-A-2008-262161 can also be preferably employed.

  The present invention will be described more specifically with reference to the following 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 is not limited to the specific examples shown below.

<Measurement method>
In the present invention, film properties were measured by the following measuring method.

(Optical expression)
Re and Rth were measured at wavelengths of 480 nm, 550 nm, and 650 nm by KOBRA 21ADH (manufactured by Oji Scientific Instruments) by the above method. The obtained Re (650) -Re (480) was calculated to obtain ΔRe (λ). The results are shown in Table 6 below.

(ΔRe (10-80))
After adjusting the sample film for 12 hours at 25 ° C. and 10% relative humidity, in-plane at 25 ° C. and 60% relative humidity using an automatic birefringence meter (KOBRA-21ADH: manufactured by Oji Scientific Instruments) The retardation value (Re) was measured and calculated. Further, Re was measured and calculated in the same manner as described above except that the humidity was adjusted for 12 hours at 25 ° C. and a relative humidity of 80%. The absolute value of the difference between these values was defined as the humidity dependence ΔRe (10-80) of Re.
The results are shown in Table 6 below.

(Internal haze)
A few drops of glycerin were dropped on both sides of the obtained cellulose acylate film sample 40 mm × 80 mm, and a glass plate having a thickness of 1.3 mm (MICRO SLIDE GLASS product number S9213, MA
(Tsunami made) Haze meter (25 ° C, 60% relative humidity)
The value (%) obtained by subtracting the haze measured in a state where several drops of glycerin were dropped between two sheets of glass from the haze value measured according to JIS K-6714 with HGM-2DP (Suga Test Machine) was defined as the internal haze. . The results are shown in Table 6 below.

(Dimensional change rate)
The dimensional change rate of the sample film after 90 hours at 60 ° C. and 90% relative humidity, that is, a value of (L′−L0) / L0} × 100% was determined in the film transport direction and the direction orthogonal thereto. Here, L0 represents the film length (unit: mm) before passing for 24 hours at 60 ° C. and 90% relative humidity, and L ′ is further 2 hours after passing for 24 hours at 60 ° C. and 90% relative humidity. The film length (unit: mm) after conditioning. The sample film used was 30 mm × 120 mm, and other conditions were as follows.
After conditioning for 2 hours or more in an atmosphere of 25 ° C. and relative humidity 60%, automatic pin gauges (manufactured by Shinbun Kagaku Co., Ltd.) are used to open 6 mmφ holes at 100 mm intervals so that they are parallel to the 120 mm side of the film. , The original size (L0) of the interval is measured to a minimum scale of 1/1000 mm. After 24 hours at 60 ° C. and a relative humidity of 90%, after adjusting the humidity for 2 hours in an atmosphere of 25 ° C. and a relative humidity of 60%, the dimension L ′ of the punch interval is measured.
The obtained results are shown in Table 6 below.

[Examples 1 to 12 and Comparative Examples 1 to 10]
(1) Preparation of Cellulose Acylate Resin by Synthesis Cellulose acylate having an acyl substitution degree shown in Table 6 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.

(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 ――――――――――――――――――――――――――――――――――
Cellulose acylate described in the following Table 6 Total 100.0 parts by mass Optical developing agent 1 described in the following Table 6 (Amount described in the following Table 6 Unit: parts by mass)
Optical developing agent 2 described in Table 6 below (Amount described in Table 6 below Unit: part by mass)
Peeling accelerators listed in Table 6 below (Amounts listed in Table 6 below Units: parts by mass)
Methylene chloride 403.0 parts by mass Methanol 60.2 parts by mass ――――――――――――――――――――――――――――――――――

  In Table 6 below, Ac represents an acetyl group, and Pr represents a propionyl group. Moreover, the structure of each additive is described below. In Table 5 below, TPA is terephthalic acid, PA is phthalic acid, AA is adipic acid, SA is succinic acid, EG is ethylene glycol, PG is propylene glycol, and OAc is hydroxyl group terminal acetyl. It shows that it was sealed with a group. In Table 6 below, K-37V represents the condensate A-2 (trade name Poem K-37V, manufactured by Riken Vitamin Co., Ltd.) described in Table 1 above.

<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 ――――――――――――――――――――――――――――――――――――
-Matting agent (Aerosil R972) 0.2 parts by mass-Methylene chloride 72.4 parts by mass-Methanol 10.8 parts by mass-Cellulose acylate solution 10.3 parts by mass ------- ―――――――――――――――――――――――
The cellulose acylate solution was mixed in an amount of 100 parts by mass, and the matting agent dispersion was mixed in an amount of 0.02 parts by mass of inorganic fine particles with respect to the cellulose acylate resin to prepare a dope for film formation.

(3) Casting The above dope was cast using a band casting machine. The band was made of SUS.

(4) Drying The web (film) obtained by casting was peeled from the band, and then dried for 20 minutes in the tenter device using a tenter device that clips and conveys both ends of the web with clips. In addition, the drying temperature here means the film surface temperature of a film.

(5) Stretching The obtained web (film) was peeled from the band, sandwiched between clips, and when the amount of residual solvent relative to the total film mass was 30 to 0% under the conditions of fixed end uniaxial stretching, the following Table 6 The film was stretched in the direction (lateral direction) perpendicular to the film conveying direction using a tenter at the stretching temperature and the stretching ratio described in 1. At this time, the cast film thickness was adjusted so that the film thickness after stretching became the film thickness (unit: μm) shown in Table 6.

(6) Wet heat treatment Each film subjected to the stretching treatment was sequentially subjected to a condensation prevention treatment, a wet heat treatment (water vapor contact treatment) and a heat treatment.
In the anti-condensation treatment, the film temperature Tf0 was adjusted to 120 ° C. by applying dry air to each film. In the wet heat treatment (water vapor contact treatment), the absolute humidity of the wet gas in the wet gas contact chamber (the wet heat treatment absolute humidity) is 400 g / m ^3, and the dew point of the wet gas is higher than the temperature Tf0 of each film. Each film was conveyed while maintaining the temperature (wet heat treatment temperature) of each film at 100 ° C. for only the treatment time (60 seconds).

(7) Drying and (8) Heat treatment after wet heat treatment In heat treatment, the absolute humidity of the gas in the heat treatment chamber (heat treatment absolute humidity) is 0 g / m ^3, and the temperature of each film (heat treatment temperature) is the same temperature as the wet heat treatment temperature. And maintained for the treatment time (2 minutes). The film surface temperature was determined from the average value obtained by attaching a tape-type thermocouple surface temperature sensor (ST series manufactured by Anri Keiki Co., Ltd.) to the film at three points.

(9) Winding Then, after cooling to room temperature, each film was wound up, and a roll having a roll width of 1280 mm and a roll length of 2600 mm was produced at least 24 rolls under the above conditions. About 1 roll in 24 rolls manufactured continuously, a sample (width 1280 mm) having a length of 1 m was cut out at intervals of 100 m to obtain films of Examples and Comparative Examples, and each measurement was performed.

(Preparation of polarizing plate sample)
The surface of the film of each Example and Comparative Example prepared above was subjected to alkali saponification treatment. It was immersed in a 1.5 N aqueous sodium hydroxide solution at 55 ° C. for 2 minutes, washed in a water bath at room temperature, and neutralized with 0.1 N sulfuric acid at 30 ° C. Again, it was washed in a water bath at room temperature and further dried with hot air at 100 ° C. Subsequently, a roll-shaped polyvinyl alcohol film having a thickness of 80 μm was continuously stretched 5 times in an aqueous iodine solution and dried to obtain a polarizer having a thickness of 20 μm. Using the 3% aqueous solution of polyvinyl alcohol (Kuraray PVA-117H) as an adhesive, the alkali saponified films of Examples and Comparative Examples and the same alkali saponified Fujitac TD80UL (Fuji Film Co., Ltd.) were prepared. Then, the saponified surface is bonded to the polarizer so that the polarizer is sandwiched between the polarizers, and the polarizing plates in which the films of the examples and comparative examples, the polarizer, and TD80UL are bonded in this order are obtained. It was. At this time, the films were pasted so that the MD direction of each film and the slow axis of TD80UL were parallel to the absorption axis of the polarizer.

(Production of liquid crystal display device)
The front and back polarizing plates and retardation plates of a VA mode liquid crystal TV (LC-46LX1, manufactured by SHARP) were peeled off and used as a liquid crystal cell. As in the configuration of FIG. 1 (upper side is the front side), an outer protective film (not shown), a polarizer 11, each example and comparative example film 14 (rear side cellulose acylate film) described in the following table, A liquid crystal cell 13 (the above VA liquid crystal cell), a film 15 (a cellulose acylate film on the front side), a polarizer 12 and an outer protective film (not shown) of the examples and comparative examples described in the following table were adhered in this order. The liquid crystal display device of each Example and the comparative example was produced by bonding using the agent. At this time, they were bonded so that the absorption axes of the upper and lower polarizing plates were orthogonal.

(Front contrast)
Using a measuring instrument (BM5A, manufactured by TOPCON), the luminance values of black display and white display in the front direction of the panel were measured in a dark room, and the front contrast (white luminance / black luminance) was calculated.
The observed contrast was evaluated according to the following criteria.
A: 6500 or more.
○: 6000-6500.
Δ: 5000 to 6000.
X: 5000 or less.
The results are shown in Table 6 below.

(Change in color (color shift))
(Color shift in viewing angle (polar angle) direction)
During black display, changes in chromaticity Δxθ and Δyθ when the viewing angle is tilted from the normal direction of the liquid crystal cell to the center line direction of the transmission axis of the pair of polarizing plates (azimuth angle 45 degrees) are polar angles 0 to 80. Measured between degrees. Here, [Delta] x [theta] = x [theta] -x [theta] 0, [Delta] y [theta] = y [theta] -y [theta] 0, (x [theta] 0, y [theta] 0) is the chromaticity measured in the normal direction of the liquid crystal cell in black display, and (x [theta], y [theta]) is the liquid crystal cell in black display. It is chromaticity measured in a direction in which the viewing angle is tilted from the normal direction to the polar angle θ degree in the direction of the center line of the transmission axis of the pair of polarizing plates.
The results were evaluated according to the following criteria. The obtained evaluation is shown in Table 6 below.
A: Δxθ and Δyθ are both 0.03 or less.
○: Δxθ and Δyθ both exceed 0.03 and are 0.05 or less.
Δ: Δxθ and Δyθ are both more than 0.05 and 0.07 or less.
X: Both Δxθ and Δyθ are larger than 0.1.

As mentioned above, it turned out that the liquid crystal display device using the cellulose acylate film of each Example has favorable front contrast and a viewing angle color change.
The cellulose acylate film of Comparative Example 1 does not contain a nitrogen-containing aromatic compound, Rth is lower than the lower limit of the range of the present invention, and the color change in the viewing angle direction when incorporated in a liquid crystal display device and I found that the contrast was inferior.
The cellulose acylate film of Comparative Example 2 had Re lower than the lower limit of the range of the present invention, and it was found that the color change and contrast in the viewing angle direction were poor when incorporated in a liquid crystal display device.
In the cellulose acylate film of Comparative Example 3, Rth exceeds the upper limit of the range of the present invention, and ΔRe (λ) is lower than the lower limit of the range of the present invention, and the viewing angle when incorporated in a liquid crystal display device It was found that the color change in the direction and the contrast were inferior.
The cellulose acylate film of Comparative Example 4 had ΔRe (λ) below the lower limit of the range of the present invention, and it was found that the color change and contrast in the viewing angle direction were poor when incorporated in a liquid crystal display device. .
The cellulose acylate film of Comparative Example 5 has a film thickness, Re and Rth below the lower limit of the range of the present invention, and the color change and contrast in the viewing angle direction when incorporated in a liquid crystal display device may be inferior. all right.
The cellulose acylate film of Comparative Example 6 has a film thickness and Re exceeding the upper limit of the range of the present invention, and it was found that the color change and contrast in the viewing angle direction were poor when incorporated in a liquid crystal display device. .
In the cellulose acylate film of Comparative Example 7, the total acyl substitution degree of the cellulose acylate was lower than the lower limit of the range of the present invention, and could not be peeled from the support.
In the cellulose acylate film of Comparative Example 8, the total acyl substitution degree of the cellulose acylate exceeds the upper limit of the range of the present invention, and Re and Rth are lower than the lower limit of the range of the present invention. It was found that the color change and the contrast in the viewing angle direction were poor when incorporated.
The cellulose acylate film of Comparative Example 9 had ΔRe (λ) below the lower limit of the range of the present invention, and it was found that the front contrast when incorporated in a liquid crystal display device was inferior.
The cellulose acylate film of Comparative Example 10 is a film that does not contain a nitrogen-containing aromatic compound that was subjected to the supplementary test of Example 1 of JP 2011-118222 A, and has a front contrast and humidity when incorporated in a liquid crystal display device. It turns out that the dependency is inferior.

DESCRIPTION OF SYMBOLS 11 Polarizer 12 Polarizer 13 Liquid crystal cell 14 Cellulose acylate film 15 of each Example and Comparative Example Cellulose acylate film of each Example and Comparative Example

Claims (12)

A polycondensation ester comprising cellulose acylate having a total substitution degree of 2.0 to 2.5, at least one aliphatic dicarboxylic acid residue and an aliphatic diol residue (provided that the polycondensation ester is an aromatic dicarboxylic acid residue) No group and no aromatic diol residue), and at least one nitrogen-containing aromatic compound,
The following formulas (1) to (3) are satisfied,
The film thickness is 45 to 70 μm,
A cellulose acylate film characterized by being stretched.
Formula (1) 40nm <= Re (550) <= 80nm
(In formula (1), Re (550) represents in-plane retardation at a wavelength of 550 nm.)
Formula (2) 100 nm ≦ Rth (550) ≦ 300 nm
(In Formula (2), Rth (550) represents retardation in the film thickness direction at a wavelength of 550 nm.)
Formula (3) 0 nm ≦ ΔRe (λ) ≦ 30 nm
(In the formula (3), ΔRe (λ) represents Re (650) -Re (480), Re (650) represents in-plane retardation at a wavelength of 650 nm, and Re (480) represents a surface at a wavelength of 480 nm. Represents inward retardation.)   The cellulose acylate film according to claim 1, wherein the polycondensed ester is composed of an aliphatic dicarboxylic acid residue and an aliphatic diol residue.   3. The cellulose acylate film according to claim 1, wherein the cellulose acylate film is stretched at Tg−20 ° C. or more and Tg or less, wherein Tg is a glass transition temperature of the cellulose acylate film. Represent). The cellulose acylate film according to any one of claims 1 to 3, wherein the humidity dependency satisfies the following formulas (5) and (6).
Formula (5) (DELTA) Re (10-80) <= 13nm
Formula (6) ΔRe (10−80) = Re (10% RH) −Re (80% RH)
(In the formulas (5) and (6), Re (10% RH) represents the retardation value in the in-plane direction of the film at a relative humidity of 10%, and Re (80% RH) represents the in-plane of the film at a relative humidity of 80%. Represents the direction retardation value.)   The cellulose acylate film according to any one of claims 1 to 4, wherein an internal haze is less than 0.08%.   The cellulose acylate film according to claim 1, wherein the cellulose acylate film is a single layer.   The cellulose acylate film according to any one of claims 1 to 6, wherein a dimensional change rate around 24 hours in an environment of 60 ° C and a relative humidity of 90% is ± 0.5% or less.   Content of the said cellulose acylate in a film is 85 mass% or more with respect to the mass of a film, The cellulose acylate film as described in any one of Claims 1-7 characterized by the above-mentioned.   The cellulose acylate film according to claim 1, wherein the cellulose acylate is cellulose acetate.   A film thickness is 48 micrometers-65 micrometers, The cellulose acylate film as described in any one of Claims 1-9 characterized by the above-mentioned.   A polarizing plate comprising a polarizer and the cellulose acylate film according to claim 1 on at least one side of the polarizer.   A liquid crystal display device comprising at least one polarizing plate according to claim 11.

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