JP2011162769A - Cellulose acylate film, polarization plate, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cellulose acylate film that has flat dispersion properties or reverse dispersion properties, low haze, and high optical expression and that uses an inexpensive film material. <P>SOLUTION: The cellulose acylate film contains a cellulose acylate having the total degree of acyl substitution of 2.00-2.70 and at least one polycondensated ester including an aromatic dicarboxylic acid residue and an aliphatic diol residue. The ratio of the aromatic dicarboxylic acid residue to the total dicarboxylic acid residues in the polycondensated ester is 60 mol% or more, and both terminals of the polycondensated ester are each independently any one selected from the group consisting of -OH group, -O-C(=O)-R<SP>1</SP>group, -C(=O)-O-R<SP>2</SP>group, -O-R<SP>3</SP>group, and -COOH group (wherein the R<SP>1</SP>to R<SP>3</SP>are each independently an aliphatic group). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  Polymer films represented by cellulose acylate, polyester, polycarbonate, cycloolefin polymer, vinyl polymer, polyimide, and the like are used for silver halide photographic light-sensitive materials, retardation films, polarizing plates, and image display devices. . From these polymers, films that are more excellent in terms of flatness and uniformity can be produced, and are therefore widely used as films for optical applications. For example, a cellulose acylate film having an appropriate moisture permeability can be directly bonded on-line with a most common polyvinyl alcohol (PVA) / iodine polarizer. For this reason, cellulose acylate, particularly cellulose acetate, has been widely adopted as a protective film for polarizing plates.

  When the cellulose acylate film is used for an optical application such as a retardation film, a support for the retardation film, a protective film for a polarizing plate, and a liquid crystal display device, the control of the optical anisotropy is performed in the liquid crystal display device. This is a very important factor in determining performance. In a liquid crystal display device, it is a well-known technique to use an optical compensation film for widening the viewing angle, improving image coloring, and improving contrast. In the most widespread VA (Vertically Aligned) mode (vertical alignment mode), TN (Twisted Nematic) mode, etc., a retardation film capable of controlling optical characteristics (for example, Re value and Rth value) to a desired value is required. Yes.

  When a cellulose acylate film is applied to such an optical application, in recent years, a cellulose acylate film to which a polyester plasticizer is added has been used from the viewpoint of improving various properties of the cellulose acylate film. For example, Patent Document 1 discloses a cellulose acylate film using, as an additive, a polyester whose both ends are aromatic ends (specifically, a polycondensed ester in which hydroxyl groups at both ends are substituted with aromatic acyl groups). Has been. Although it is described that the cellulose acylate film described in the same document can improve the humidity dependency by such a configuration, there is no mention of optical developability and wavelength dispersion, and the purpose is to improve optical developability in the first place. In addition, the haze was not examined. As the structure of the polycondensed ester, an embodiment in which an aromatic carboxylic acid residue is partly disclosed is disclosed, but a preferred ratio of the aromatic carboxylic acid residue in the polycondensed ester has not been studied. There was no description about the effect which group carboxylic acid residue shows. In addition, polycondensation esters other than aromatic acyl group substitution at both ends of the polycondensation ester have not been studied, and there has been no description regarding the effects exhibited when both ends of the polycondensation ester are other than aromatic acyl group substitution. .

  On the other hand, Patent Document 2 discloses a cellulose acylate film using an ester oligomer (polycondensation ester) containing an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid as a high molecular weight plasticizer. It is described that the cellulose acylate film described in this document can adjust the expression of retardation, reduce moisture permeability, and has excellent environmental durability. However, this document does not discuss chromatic dispersion, and the examples have not disclosed any examples in which the retardation is largely expressed. As for the structure of the polycondensed ester, although an embodiment containing a large amount of aromatic carboxylic acid is slightly disclosed as the plasticizer PP-18 or the like, the preferred ratio of the aromatic carboxylic acid residue in the polycondensed ester has been studied. According to the same document [0033], there was no mention of the influence of the ratio of aromatic carboxylic acid residues. Further, in the examples, a mode in which a cellulose acylate having a high acyl substitution degree and a polycondensed ester containing a large amount of aromatic carboxylic acid are used in combination is disclosed, but the evaluation was comparable to the other examples. . In addition, both ends of the polycondensed ester are preferably sealed with monocarboxylic acids or phenols so as not to contain free carboxylic acids, according to the documents [0039] and [0041]. In particular, there is no description on which aspect of sealing with an aromatic group and other sealing aspects is preferable, and the effect obtained by the difference between these aspects.

  In recent years, VA mode films are required to have flat dispersion or reverse dispersion and low haze from the viewpoints of improving the tint and contrast when incorporated in a liquid crystal display device. At the same time, it is required to use an inexpensive film material from the viewpoint of achieving high optical expression from the viewpoint of achieving cost reduction by thinning the film and from the viewpoint of achieving cost reduction of the film itself. However, the actual situation is that a film that has achieved these requirements at the same time, including the cellulose acylate films described in Patent Documents 1 and 2, is still unknown.

International Publication WO2006 / 121026 JP 2009-155454 A

  Using the polycondensed esters described in Patent Documents 1 and 2, the present inventors examined the characteristics of the cellulose acylate films described in these documents. However, none of the cellulose acylate films can simultaneously achieve flat dispersion or reverse dispersibility, low haze, high optical expression and inexpensive film materials, especially reverse dispersibility and low haze. It was found that there was a dissatisfaction in terms of enhancing optical expression while maintaining the above, and further detailed examination was required.

  An object of the present invention is to provide a cellulose acylate film that satisfies all of the above requirements. That is, the problem to be solved by the present invention is to provide a cellulose acylate film using a film material having flat dispersion or reverse dispersion, low haze, high optical expression, and low cost. There is to do.

  In order to solve the above-mentioned problems, the present inventors diligently studied to control in detail the structure of the polycondensation ester added to the cellulose acylate. As a result, the ratio of each residue in the polycondensed ester and the structure of both ends are controlled, and the specific polycondensed ester is used in combination with a cellulose acylate having a specific range of total acyl substitution degree. Thus, it has been found that an inexpensive cellulose acylate film can be obtained which can reduce haze and exhibit high optical expression while maintaining flat dispersion or reverse dispersion. As a result of intensive studies, the present inventors have found that the above problem can be solved by the following configuration.

[1] A cellulose acylate having a total acyl substitution degree of 2.00 to 2.70, and at least one polycondensed ester containing an aromatic dicarboxylic acid residue and an aliphatic diol residue, the polycondensed ester The ratio of aromatic dicarboxylic acid residues to all dicarboxylic acid residues in the solvent is 60 mol% or more, and both ends of the polycondensed ester are independently —OH group, —O—C (═O). -R ¹ group, -C (= O) -O-R ² group, -O-R ³ group and -COOH group (provided that R ^{1 to} R ³ each independently represents an aliphatic group) A cellulose acylate film, which is any one selected from the group consisting of:
[2] The polycondensation ester according to [1], wherein the ratio of aliphatic diol residues having 3 or more carbon atoms to all diol residues is 30 mol% or more. Cellulose acylate film.
[3] The cellulose acylate film of [1] or [2], wherein the polycondensed ester has a number average molecular weight of 500 to 2,000.
[4] The cellulose acylate according to any one of [1] to [3], wherein the content of the polycondensed ester is 5 to 30 parts by mass with respect to 100 parts by mass of the cellulose acylate. the film.
[5] Both ends of the polycondensed ester are each independently —OH group or —O—C (═O) —R ¹ group (provided that when a plurality of R ¹ are present, each independently represents an aliphatic group. The cellulose acylate film according to any one of [1] to [4], wherein
[6] The cellulose acylate film according to any one of [1] to [5], wherein the cellulose acylate film is obtained by film formation by solution casting and further stretching.
[7] The cellulose acylate film according to [6], wherein the solution casting film is a simultaneous multilayer casting film by co-casting or a sequential multilayer casting film.
[8] The cellulose acylate film according to [6], wherein the solution casting film is a single layer casting film.
[9] The cellulose acylate film according to any one of [6] to [8], wherein the stretching is stretching at a magnification of 5% to 100% in a direction orthogonal to the conveyance direction. .
[10] The stretching is simultaneous or sequential stretching in a direction orthogonal to a direction parallel to the transport direction, and is stretching at a magnification of 5% to 100% in a direction orthogonal to the transport direction. The cellulose acylate film according to any one of [6] to [8], which is characterized.
[11] The cellulose acylate film according to any one of [1] to [10], wherein the following formula (1) and formula (2) are satisfied.
Formula (1): 30 nm ≦ | Re (590) | ≦ 100 nm
Formula (2): 80 nm ≦ | Rth (590) | ≦ 280 nm
(In the formulas (1) and (2), Re (590) and Rth (590) are the retardation value and thickness in the in-plane direction measured with light having a wavelength of 590 nm in an environment of 25 ° C. and a relative humidity of 60%, respectively. Represents the direction retardation value.)
[12] The cellulose acylate film according to any one of [1] to [11], wherein the following expressions (3) and (4) are satisfied.
Formula (3): 0 nm ≦ Re (630) −Re (440) ≦ 15 nm
Formula (4): 0 nm ≦ Rth (630) −Re (440) ≦ 30 nm
(In the formulas (3) and (4), Re (440) and Rth (440) are the retardation value and thickness in the in-plane direction measured with light having a wavelength of 440 nm in an environment of 25 ° C. and a relative humidity of 60%, respectively. Re (630) and Rth (630) represent the retardation value in the in-plane direction and the thickness direction letter measured with light having a wavelength of 630 nm in an environment of 25 ° C. and a relative humidity of 60%, respectively. Represents the foundation value.)
[13] The cellulose acylate film according to any one of [1] to [12], wherein the total haze is 0.5% or less and the internal haze is 0.1% or less. .
[14] The cellulose acylate film according to any one of [1] to [13], wherein the film thickness is 30 to 70 μm.
[15] The cellulose acylate film according to any one of [1] to [14], wherein the following formula (5) is satisfied.
Formula (5): 2.5 × 10 ⁻³ ≦ | Rth (590) | / d
(In Formula (5), Rth (590) represents a retardation value in the thickness direction measured with light having a wavelength of 590 nm in an environment of 25 ° C. and a relative humidity of 60%, and d represents the film thickness of the film.)
[16] A polarizing plate comprising a polarizer and at least one cellulose acylate film according to any one of [1] to [15].
[17] A liquid crystal cell and at least one cellulose acylate film according to any one of [1] to [15] or at least one polarizing plate according to [16] are included. Liquid crystal display device.
[18] The liquid crystal display device according to [17], wherein the liquid crystal cell is a VA mode liquid crystal cell.

  According to the present invention, it is possible to provide a cellulose acylate film using a film material having flat dispersion or reverse dispersion, low haze, high optical expression, and low cost. Further, by using the cellulose acylate film of the present invention, it is possible to provide an inexpensive liquid crystal display device with improved color tone and good contrast and a polarizing plate used in the liquid crystal display device.

It is sectional drawing for demonstrating an example of the manufacturing method of the retardation film of this invention.

  In the following, the cellulose acylate film of the present invention, the production method thereof, the additives used therein and the like 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, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

[Cellulose acylate film]
The cellulose acylate film of the present invention (hereinafter also referred to as the film of the present invention) comprises a cellulose acylate having a total acyl substitution degree of 2.00 to 2.70, an aromatic dicarboxylic acid residue and an aliphatic diol residue. Containing at least one polycondensed ester, the ratio of aromatic dicarboxylic acid residues to all dicarboxylic acid residues in the polycondensed ester is 60 mol% or more, and both ends of the polycondensed ester Are each independently a group consisting of —OH group, —O—C (═O) —R ¹ group, —C (═O) —O—R ² group, —O—R ³ group and —COOH group (wherein Wherein R ^{1 to} R ³ each independently represents an aliphatic group).
Hereinafter, the film of the present invention will be described.

[Polycondensed ester]
The film of the present invention contains at least one polycondensed ester containing an aromatic dicarboxylic acid residue and an aliphatic diol residue. In addition, the ratio of aromatic dicarboxylic acid residues to all dicarboxylic acid residues in the polycondensed ester used in the present invention is 60 mol% or more, and both ends of the polycondensed ester are independently- OH group, —O—C (═O) —R ¹ group, —C (═O) —O—R ² group, —O—R ³ group and —COOH group (provided that R ^{1 to} R ³ each independently represents an aliphatic group).

  In the present specification, the residue of the polycondensed ester is a partial structure of the polycondensed ester and represents a partial structure having the characteristics of the monomer forming the polycondensed ester. For example, the dicarboxylic acid residue formed from the dicarboxylic acid HOOC-R—COOH is —OC—R—CO—, and the diol residue formed from the diol HO—R′—OH is —O—R′—O—. It is.

(Dicarboxylic acid residue)
In the polycondensed ester, an aromatic dicarboxylic acid residue and an aliphatic dicarboxylic acid residue can be used as the dicarboxylic acid residue.
The polycondensed ester used in the present invention contains at least one aromatic dicarboxylic acid residue.
Moreover, the ratio of the aromatic dicarboxylic acid residue with respect to all the dicarboxylic acid residues in the polycondensation ester used for this invention is 60 mol% or more.
The ratio of aromatic dicarboxylic acid residues to all dicarboxylic acid residues in the polycondensed ester used in the present invention (hereinafter also referred to as aromatic dicarboxylic acid residue ratio or aromatic dicarboxylic acid ratio) is 60 mol% or more. 70 mol% or more, preferably 80 mol% to 100 mol%, more preferably 90 mol% to 100 mol%.
By making the aromatic dicarboxylic acid residue ratio 60 mol% or more, sufficient optical expression is exhibited even when the film thickness is thin (particularly, the value of Rth per film thickness is large), and the wavelength dispersion is flat dispersion. Or it exists in the tendency which can obtain the cellulose acylate film which is reverse dispersion.

In the present specification, the aromatic dicarboxylic acid residue refers to a dicarboxylic acid residue containing at least one arylene group. That is, in the present specification, the aromatic dicarboxylic acid residue includes, for example, -OC-Ar'-L-CO- and -OC-L'- in addition to -OC-Ar-CO- residue. Dicarboxylic acid residues having a structure such as Ar ″ —CO— or —OC—L ″ —Ar ′ ″ — L ″ —CO— (Ar, Ar ′, Ar ″ and Ar ′ ″ described above) Each independently represents an arylene group, and L, L ′ and L ″ each independently represents a divalent linking group other than an arylene group). Examples of the divalent linking group other than the arylene group include an aliphatic group and an atom linking group, and specific examples include an alkylene group, an alkyleneoxy group, an oxygen atom, and a sulfur atom. it can.
Among these, the aromatic dicarboxylic acid residue preferably has a structure of —OC—Ar—CO— residue from the viewpoint of compatibility with cellulose acylate.

  Ar is preferably an arylene group having 6 to 16 carbon atoms, more preferably an arylene group having 6 to 12 carbon atoms, particularly preferably a phenylene group or a naphthylene group, and a phenylene group. Is more particularly preferred. The Ar may or may not further have a substituent, but preferably does not have a substituent. Examples of the substituent include a hydroxyl group, an acyl group, and a carbonyl group. Examples include groups.

Specific examples of the aromatic dicarboxylic acid residue include phthalic acid residue, terephthalic acid residue, isophthalic acid residue, 1,5-naphthalenedicarboxylic acid residue, 1,4-naphthalenedicarboxylic acid residue, 1, Examples thereof include an 8-naphthalenedicarboxylic acid residue, a 2,8-naphthalenedicarboxylic acid residue, and a 2,6-naphthalenedicarboxylic acid residue. Among these examples, phthalic acid residues, terephthalic acid residues, and 2,6-naphthalenedicarboxylic acid residues are preferable, phthalic acid residues and terephthalic acid residues are more preferable, and terephthalic acid residues are more preferable.
In the polycondensed ester, an aromatic dicarboxylic acid residue is formed by the aromatic dicarboxylic acid used for mixing.
When the polycondensed ester contains a terephthalic acid residue as an aromatic dicarboxylic acid residue, it is more compatible with cellulose acylate and causes bleed-out during film formation and heat stretching of the cellulose acylate film. It can be set as a difficult cellulose acylate film.

  Further, the polycondensed ester may contain only one kind of aromatic dicarboxylic acid residue or two or more kinds thereof. When two types of aromatic dicarboxylic acid residues are included in the polycondensed ester, it is preferable that a phthalic acid residue and a terephthalic acid residue are included.

The polycondensed ester may contain an aliphatic dicarboxylic acid residue as the dicarboxylic acid residue in addition to the aromatic dicarboxylic acid residue.
Specific examples of the aliphatic dicarboxylic acid residue include, for example, oxalic acid residue, malonic acid residue, succinic acid residue, maleic acid residue, fumaric acid residue, glutaric acid residue, adipic acid residue, Examples thereof include a pimelic acid residue, a suberic acid residue, an azelaic acid residue, a sebacic acid residue, a dodecanedicarboxylic acid residue, or a 1,4-cyclohexanedicarboxylic acid residue.
In the polycondensed ester, an aliphatic dicarboxylic acid residue is formed from the aliphatic dicarboxylic acid used for mixing.
The aliphatic dicarboxylic acid residue preferably has an average carbon number of 5.5 to 10.0, more preferably 5.5 to 8.0, and 5.5 to 7.0. Is more preferable. If the average carbon number of the aliphatic diol is 7.0 or less, the heat loss of the compound can be reduced, and the occurrence of planar failure that may be caused by process contamination due to bleed-out when the cellulose acylate web is dried can be prevented. . Moreover, it is preferable that the aliphatic diol has an average carbon number of 2.5 or more because the compatibility is excellent and precipitation of the polycondensed ester hardly occurs.
Specifically, when the polymerizable ester includes the aliphatic dicarboxylic acid residue, the polymerizable ester preferably includes a succinic acid residue or an adipic acid residue, and more preferably includes a succinic acid residue.
The polycondensed ester may contain only one type of aliphatic dicarboxylic acid residue or two or more types. When two types of aliphatic dicarboxylic acid residues are contained in the polycondensed ester, it is preferable that a succinic acid residue and an adipic acid residue are contained. When one kind of aliphatic dicarboxylic acid residue is contained in the polycondensed ester, it is preferable that a succinic acid residue is contained. By setting it as such an aspect, the average carbon number of a diol residue can be adjusted to the said preferable range, and compatibility with a cellulose acylate becomes favorable.

(Diol residue)
In the polycondensed ester, an aromatic diol residue and an aliphatic diol residue can be used as the diol residue.
The polycondensed ester used in the present invention contains at least one aliphatic diol residue as a diol residue.

  Examples of the aliphatic diol used in the present invention include alkyl diols and alicyclic diols, such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3- Methyl-1,5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl -1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, diethylene glycol, cyclohexanedimethanol, etc. Is preferably used together with ethylene glycol as one or a mixture of two or more.

Among them, in the present invention, the ratio of the aliphatic diol residue having 3 or more carbon atoms to all diol residues (hereinafter also referred to as the ratio of aliphatic diol having 3 or more carbon atoms) is 30 mol. % Or more of the polycondensation ester is preferable from the viewpoint of improving the compatibility between the cellulose acylate and the polycondensation ester and improving the solubility of the polycondensation ester in the solvent.
The ratio of the aliphatic diol having 3 or more carbon atoms is more preferably 30 mol% or more, and particularly preferably 50 to 80 mol%.

Examples of the aliphatic diol residue having 3 or more carbon atoms include 1,2-propanediol residue, 1,3-propanediol residue, 1,2-butanediol residue, 1,3-butanediol residue, 2-methyl-1,3-propanediol residue, 1,4-butanediol residue, 1,5-pentanediol residue, 2,2-dimethyl-1,3-propanediol (neopentyl glycol) residue, Examples include 1,4-hexanediol residue, 1,4-cyclohexanediol residue and the like. Among them, the aliphatic diol residue having 3 or more carbon atoms preferably used in the present invention includes 1,2-propanediol residue, 1,3-propanediol residue, 1,2-butanediol residue, 1, 3-butanediol residue, 2-methyl-1,3-propanediol residue, 1,4-butanediol residue, 1,5-pentanediol residue, 2,2-dimethyl-1,3-propanediol ( Neopentyl glycol) residue, more preferably 1,2-propanediol residue, 1,3-propanediol residue residue, 1,2-butanediol, 1,3-butanediol residue. Group, 2-methyl-1,3-propanediol residue, 1,4-butanediol residue, particularly preferably 1,2-propanediol residue.
By using a 1,2-propanediol residue or a 1,3-propanediol residue, crystallization of the polycondensed ester can be prevented.

When an aliphatic diol residue is used as a diol residue other than the aliphatic diol having 3 or more carbon atoms, an ethylene glycol residue or the like can be used.
In the polycondensed ester, an aliphatic diol residue is formed by the aliphatic diol used for mixing.

The polycondensed ester may contain an aromatic diol residue as the diol residue in addition to the aliphatic diol residue.
Specific examples of the aromatic diol residue include, for example, bisphenol A residue, 1,2-hydroxybenzene residue, 1,3-hydroxybenzene residue, 1,4-hydroxybenzene residue, 1,4- Examples thereof include benzenedimethanol residues.

The polycondensed ester may contain only one type of aliphatic diol residue or two or more types. When two types of aliphatic diol residues are included in the polycondensed ester, it is preferable that 1,2-propanediol residues and ethylene glycol residues are included.
In the polycondensed ester, an aromatic diol acid residue is formed from the aromatic diol used for mixing.

(Both ends of polycondensation ester)
In the present invention, both ends of the polycondensed ester are independently —OH group, —O—C (═O) —R ¹ group, —C (═O) —O—R ² group, —O—R. ^It is any one selected from the group consisting of ³ groups and —COOH groups (wherein R ^{1 to} R ³ each independently represents an aliphatic group).

That is, the end of the polycondensed ester satisfies the above-mentioned definition and remains a —diol group derived from a diol or a —COOH group derived from a dicarboxylic acid without being sealed unless it is contrary to the spirit of the present invention. In addition, by reacting monocarboxylic acids or monoalcohols, etc., so-called terminal blocking is carried out to form —O—C (═O) —R ¹ group, —C (═O) —O—R ² group and — O-R ³ group (wherein, the R ¹ to R ³ each independently represents an aliphatic group) may be.

  When both ends of the polycondensed ester are unsealed, it is preferable from the viewpoint of inhibiting hydrolysis of the ester group that both ends are —OH groups than both ends are —COOH. That is, when both ends of the polycondensed ester are unsealed, the polycondensed ester is preferably a polyester polyol.

When both ends of the polycondensed ester are sealed, both ends are —O—C (═O) —R ¹ group, —C (═O) —O—R ² group or —O—R ³ group. It is preferable that More preferably, both ends are —O—C (═O) —R ¹ groups, that is, both ends of the polycondensed ester are more preferably sealed by reacting with an aliphatic monocarboxylic acid. .
At this time, both ends of the polycondensed ester are aliphatic monocarboxylic acid residues.

Here, said R < ¹ > -R < ³ > represents an aliphatic group each independently. The aliphatic group represented by R ^{1 to} R ³ may be saturated or unsaturated as long as the aliphatic group does not contain an aromatic ring. The aliphatic group represented by R ^{1 to} R ³ may be either a chain aliphatic group or a cyclic aliphatic group (for example, a cycloalkyl group), and a chain aliphatic group. If it is, it may be linear or branched. The aliphatic group represented by R ^{1 to} R ³ may further have a substituent unless it is contrary to the spirit of the present invention, and the substituent is not particularly limited as long as it does not contain an aromatic ring. An aliphatic group having no substituent is preferred. Moreover, it is preferable that carbon number of the aliphatic group which said R < ¹ > -R < ³ > represents is 1-21, It is more preferable that it is 1-5, It is especially preferable that it is 1-3, 1 or 2 More preferably, it is more preferably 1.
Among them, the aliphatic group represented by R ^{1 to} R ³ is preferably a chain saturated aliphatic group, more preferably a chain alkyl group, and particularly preferably a linear alkyl group. .

That is, when both ends of the polycondensed ester are sealed, both ends of the polycondensed ester are preferably acyl groups having 2 to 22 carbon atoms, and are acyl groups having 2 to 6 carbon atoms. More preferably, it is particularly preferably an acyl group having 2 to 4 carbon atoms (that is, an acetyl group, a propionyl group or a butyryl group), and an acyl group having 2 or 3 carbon atoms (that is, an acetyl group or a propionyl group) More preferably, it is more preferably an acyl group having 2 carbon atoms (that is, an acetyl group). The acyl group here includes an aromatic acyl group (a so-called aroyl group) in addition to an aliphatic acyl group, and is preferably an aliphatic acyl group. When the carbon number of the acyl group at both ends of the polycondensed ester is 3 or less, the volatility is lowered, the weight loss due to heating of the polycondensed ester is not increased, and the occurrence of process contamination and surface failure is reduced. Is possible.
In this case, the monocarboxylic acid used for sealing is preferably an aliphatic monocarboxylic acid having 2 to 22 carbon atoms, more preferably an aliphatic monocarboxylic acid having 2 to 6 carbon atoms, and 2 carbon atoms. It is particularly preferably an aliphatic monocarboxylic acid having 4 to 4, more preferably an aliphatic monocarboxylic acid having 2 or 3 carbon atoms, and more preferably an aliphatic monocarboxylic acid residue having 2 carbon atoms. Even more preferable.

On the other hand, when both ends of the polycondensed ester are sealed, both ends of the polycondensed ester may be a —C (═O) —O—R ² group or a —O—R ³ group.
In this case, methanol, ethanol, propanol, isopropanol, butanol, isobutanol and the like are preferable as monoalcohols used for sealing, and methanol is most preferable.

Both ends of the polycondensed ester are each independently an —OH group or —O—C (═O) —R ¹ group (provided that a plurality of R ¹ are present from the viewpoint of controlling compatibility with cellulose acylate). In some cases, each independently represents an aliphatic group). The both ends may be the same group or different groups, but both are preferably the same group from the viewpoint of ease of synthesis.
More preferably, both ends of the polycondensed ester are —OH groups or are sealed with acetic acid or propionic acid.

  Both ends of the polycondensed ester of the present invention are sealed with acetic acid so that both ends become acetyl ester residues (sometimes referred to as acetyl residues). The cellulose acylate film is preferable from the viewpoint that the handling of the cellulose acylate film is improved and the cellulose acylate film excellent in humidity stability and polarizing plate durability can be obtained.

(Molecular weight of polycondensed ester)
The number average molecular weight of the polycondensed ester is preferably 500 to 2000, more preferably 700 to 1500, and particularly preferably 700 to 1200. The number average molecular weight of the polycondensed ester is preferably 500 or more from the viewpoint of improving optical expression. Moreover, if it is 2000 or less, compatibility with a cellulose acylate will become high and it will become difficult to produce the bleed-out at the time of film forming and a heat-stretching.
The number average molecular weight of the polycondensed ester of the present invention can be measured and evaluated by gel permeation chromatography. Further, in the case of a polyester polyol having an unsealed terminal, it can also be calculated from the amount of hydroxyl group per weight (hereinafter referred to as hydroxyl value). The hydroxyl value is determined by measuring the amount (mg) of potassium hydroxide required for neutralizing excess acetic acid after acetylating the polyester polyol.
The polycondensed ester according to the present invention can be used as a plasticizer.

(Content of polycondensation ester)
In the cellulose acylate film of the present invention, the content of the polycondensed ester with respect to 100 parts by mass of the cellulose acylate is preferably 5 to 30 parts by mass, more preferably 8 to 30% by mass, Most preferably, it is 25 mass%.

The dicarboxylic acid residue, the diol residue, and the type and ratio of each residue contained in the polycondensed ester used in the present invention can be measured by an ordinary method using H-NMR. Usually, deuterated chloroform can be used as a solvent.
The number average molecular weight of the polycondensed ester can be measured by a usual method using GPC (Gel Permeation Chromatography), and polystyrene can be usually used as a standard material.
For measurement of the hydroxyl value of the polycondensed ester, the acetic anhydride method described in Japanese Industrial Standards JIS K3342 (discontinued) can be applied. When the polycondensate is a polyester polyol, the hydroxyl value is preferably 50 to 190, and more preferably 50 to 130.

  Table 1 below shows specific examples of the polycondensation ester according to the present invention and specific examples of the polycondensation ester outside the scope of the present invention, but the present invention is not limited to the following specific examples.

(Method for synthesizing polycondensed ester)
The polycondensation ester used in the present invention can be synthesized by a conventional method such as a hot melt condensation method using a polyesterification reaction or transesterification reaction between a diol and a dicarboxylic acid, or an interfacial condensation method between an acid chloride of these acids and a glycol. It can be easily synthesized by either method. In addition, the polycondensed ester according to the present invention is described in detail in Koichi Murai, “Plasticizer Theory and Application” (Kokai Shobo Co., Ltd., first edition issued on March 1, 1973). In addition, Japanese Patent Laid-Open Nos. 05-155809, 05-155810, Japanese Patent Laid-Open Nos. 05-97073, 2006-259494, 07-330670, 2006-342227, 2007-003679. The materials described in each publication can also be used.

[Cellulose acylate]
The cellulose acylate film of the present invention contains cellulose acylate having a total acyl substitution degree of 2.00 to 2.70.
Examples of the film material contained in the cellulose acylate film of the present invention include cellulose esters, and ester substitution obtained by introducing a functional group biologically or chemically from the cellulose acylate and other cellulose as raw materials. Examples thereof include compounds having a cellulose skeleton. In addition, it is preferable that the cellulose acylate film of this invention contains the said cellulose acylate as a main component. Here, “as the main component” indicates a polymer when it is composed of a single polymer, and when it is composed of a plurality of polymers, the polymer having the highest mass fraction among the constituent polymers. It shows that.

  The cellulose acylate is an ester of cellulose and carboxylic acid, and the carboxylic acid is more preferably a fatty acid having 2 to 22 carbon atoms, and cellulose acylate being a lower fatty acid having 2 to 4 carbon atoms. Most preferred.

(Cellulose acylate raw material)
Cellulose acylate raw material cellulose used in the present invention includes cotton linter and wood pulp (hardwood pulp, softwood pulp), etc., and any cellulose acylate obtained from any raw material cellulose can be used. May be. Detailed descriptions of these raw material celluloses can be found in, for example, “Plastic Materials Course (17) Fibrous Resin” (Marusawa, Uda, Nikkan Kogyo Shimbun, published in 1970) and Invention Association Publication Technical Report 2001-1745 ( 7 to 8) can be used, and the cellulose acylate film of the present invention is not particularly limited.

(Degree of substitution of cellulose acylate)
Next, the cellulose acylate suitable for the present invention produced from the above-mentioned cellulose will be described.

  The cellulose acylate used in the present invention is one in which the hydroxyl group of cellulose is acylated, and the substituent can be any acetyl group having 2 carbon atoms to 22 carbon atoms. In the present invention, there is no particular limitation on the measurement of the degree of substitution of cellulose with a hydroxyl group in cellulose acylate, but the degree of binding of acetic acid and / or a fatty acid having 3 to 22 carbon atoms substituted with a hydroxyl group of cellulose is measured and calculated. The degree of substitution can be obtained. As a measuring method, it can carry out according to ASTM D-817-91.

The cellulose acylate film of the present invention is preferably composed of cellulose acylate. In the cellulose acylate film of the present invention, the total acyl substitution degree of the cellulose acylate is preferably 2.00 to 2.70, and the total acyl substitution degree is preferably 2.1 to 2.70.
It is more preferably 2.1 to 2.60, and particularly preferably 2.2 to 2.5.
In the present invention, a cellulose acylate having a total acyl substitution degree of 2.00 to 2.70 is combined with the polycondensed ester to have flat dispersion or reverse dispersion, low haze, and high optical expression. And a cellulose acylate film using a cheap and inexpensive film material is preferable. Further, if the total acyl substitution degree of the cellulose acylate film is within the above preferable range, it is more preferable in terms of optical characteristics and humidity stability of the optical characteristics, and if it is 2.60 or less, it is preferable from the viewpoint of lowering haze. .

  Among the acetic acid substituted for the hydroxyl group of cellulose and / or the fatty acid having 3 to 22 carbon atoms, the acyl group having 2 to 22 carbon atoms may be an aliphatic group or an aryl group, and is not particularly limited. A mixture of They are, for example, alkyl carbonyl esters, alkenyl carbonyl esters, aromatic carbonyl esters, or aromatic alkyl carbonyl esters of cellulose, each of which may further have a substituted group. These preferred acyl groups include acetyl, propionyl, butanoyl, heptanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl I-butanoyl group, t-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like. Among these, acetyl group, propionyl group, butanoyl group, dodecanoyl group, octadecanoyl group, t-butanoyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like are preferable, and acetyl group, propionyl group, butanoyl group are preferable. Groups are more preferred. Further preferred groups are an acetyl group and propionyl, and the most preferred group is an acetyl group.

On the other hand, as said C3-C22 acyl group, a propionyl group and a butyryl group are preferable, and a propionyl group is more preferable.
When the cellulose acylate has both a propionyl group as a substituent, the acetyl group and the propionyl group preferably have a value of X + Y when the substitution degree of the acetyl group is X and the substitution degree of the propionyl group is Y. Is the same as the preferred range of the total acyl substitution degree of the cellulose acylate. The value of Y is preferably 0 to 1.0, more preferably 0.2 to 1.0, and particularly preferably 0.5 to 1.0.

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

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

〔Additive〕
In this invention, well-known additives other than the said polycondensation ester can be widely employ | adopted as an additive of a cellulose acylate film. The content of the additive is preferably 1 to 35% by mass, more preferably 4 to 30% by mass, and particularly preferably 10 to 25% by mass with respect to the cellulose acylate. If the amount of the additive added to the cellulose acylate is 1% by mass or more, it is possible to cope with changes in temperature and humidity, and if it is 30% by mass or less, the film is hardly whitened, and physical properties are also preferable.
Here, the additive in the present invention is a component added for the purpose of improving various functions of the optical film of the present invention, and a component contained in a range of 1% by mass or more with respect to cellulose acylate. Say. That is, impurities and residual solvents are not additives in the present invention.
In the present invention, two or more kinds of additives can be used. By using two or more types, each additive has the merit that both optical properties, film elastic modulus, film brittleness, and web handling suitability can be achieved.

(Low molecular weight additive)
Examples of the low molecular weight additive include an Rth control agent / regulator, a deterioration preventing agent, an ultraviolet ray preventing agent, a peeling accelerator, another plasticizer, and an infrared absorber. These may be solid or oily. That is, the melting point and boiling point are not particularly limited. For example, mixing of an ultraviolet absorbing material at 20 ° C. or lower and 20 ° C. or higher, and a mixture of deterioration preventing agents are also possible. Furthermore, infrared absorbing dyes are described, for example, in JP-A No. 2001-194522. Moreover, the addition time may be added at any time in the cellulose acylate solution (dope) preparation step, but may be added by adding a step of adding an additive to the final preparation step of the dope preparation step. Furthermore, the amount of each material added is not particularly limited as long as the function is manifested.

  Degradation inhibitors (for example, antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid scavengers, amines) may be added to the cellulose acylate film of the present invention. The deterioration inhibitors are described in JP-A-3-199201, JP-A-597073, JP-A-5-194789, JP-A-5-271471, and JP-A-6-107854. The amount of the deterioration inhibitor added is 0.01 of the solution (dope) to be prepared from the viewpoint that the effect of the addition of the deterioration inhibitor is manifested and that the deterioration inhibitor is prevented from bleeding out on the film surface. It is preferably ˜1% by mass, more preferably 0.01-0.2% by mass. Particularly preferable examples of the deterioration inhibitor include butylated hydroxytoluene (BHT) and tribenzylamine (TBA).

  In order to improve the mechanical properties or improve the drying speed, a known plasticizer other than the polycondensation ester can be added to the cellulose acylate film of the present invention. As the plasticizer, phosphoric acid ester or carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP). Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethyl hexyl phthalate (DEHP). Examples of citrate esters include triethyl O-acetylcitrate (OACTE) and tributyl O-acetylcitrate (OACTB). Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Phthalate plasticizers (DMP, DEP, DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred. The addition amount of the plasticizer is preferably 0.1 to 25% by mass of the amount of cellulose acylate, more preferably 1 to 20% by mass, and most preferably 3 to 15% by mass.

(Compound having at least two aromatic rings)
The cellulose acylate film of the present invention preferably further contains a compound having at least two aromatic rings.
The compound having at least two or more aromatic rings will be described below.
The compound having at least two or more aromatic rings preferably exhibits optically positive uniaxiality when uniformly oriented.
The molecular weight of the compound having at least two or more aromatic rings is preferably 300 to 1200, and more preferably 400 to 1000.
When the cellulose acylate film of the present invention is used as an optical compensation film, stretching is effective for controlling optical characteristics, particularly Re, to a preferable value. To increase Re, it is necessary to increase the refractive index anisotropy in the film plane, and one method is to improve the main chain orientation of the polymer film by stretching. Further, by using a compound having a large refractive index anisotropy as an additive, the refractive index anisotropy of the film can be further increased. For example, in the compound having at least two aromatic rings, the orientation of the polymer main chain is transmitted by stretching, so that the orientation of the compound is improved and it becomes easy to control the desired optical characteristics.

Examples of the compound having at least two aromatic rings include triazine compounds described in JP-A No. 2003-344655, rod-like compounds described in JP-A No. 2002-363343, JP-A Nos. 2005-134848 and 2007-119737. Liquid crystalline compounds described in Japanese Patent Publication No. Gazette. More preferably, the triazine compound or the rod-like compound.
Two or more compounds having at least two aromatic rings can be used in combination.

  The addition amount of the compound having at least two aromatic rings is preferably 0.05% to 10%, more preferably 0.5% to 8%, and more preferably 1% to 5% in terms of mass ratio with respect to cellulose acylate. Further preferred.

(Matting agent fine particles)
The cellulose acylate film of the present invention preferably contains fine particles as a matting agent. Examples of fine particles that can be used in the present invention include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. Can do. Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable. The fine particles of silicon dioxide preferably have a primary average particle size of 20 nm or less and an apparent specific gravity of 70 g / L or more. Those having an average primary particle size as small as 5 to 16 nm are more preferred because they can reduce the haze of the film. The apparent specific gravity is preferably 90 to 200 g / L, more preferably 100 to 200 g / L. A larger apparent specific gravity is preferable because a high-concentration dispersion can be produced, and haze and aggregates are improved. A desirable embodiment is described in detail in pages 35 to 36 of the Japan Institute of Invention and Technology (Publication No. 2001-1745, published on March 15, 2001, Japan Society of Invention), and in the cellulose acylate film of the present invention. Can also be preferably used.

[Method for producing cellulose acylate film]
The production method of the film of the present invention is not particularly limited, but is preferably obtained by solution casting and further stretching. As a preferred example of the method for producing a film of the present invention, a method comprising a film forming step of casting a dope on a support and evaporating the solvent to form a cellulose acylate film, and then a stretching step of stretching the film. Can be mentioned. Further, it is preferable to have a drying step for drying the film obtained thereafter, and it is preferable to have a step of heat-treating at a temperature of 150 to 200 ° C. for 1 minute or longer after the drying step.

(Film forming process)
As a method for producing the film of the present invention, a known method for producing a cellulose acylate film or the like can be widely adopted, and it is preferably produced by a solvent cast method. In the solvent cast method, a film can be produced using a solution (dope) in which cellulose acylate is dissolved in an organic solvent.
The organic solvent is a solvent selected from ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, esters having 3 to 12 carbon atoms, and halogenated hydrocarbons having 1 to 6 carbon atoms. It is preferable to contain. The ether, ketone and ester may have a cyclic structure. A compound having two or more functional groups of ether, ketone and ester (that is, —O—, —CO— and COO—) can also be used as the organic solvent. The organic solvent may have another functional group such as an alcoholic hydroxyl group. In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group.

Examples of the ether having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole.
Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone.
Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate.
Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.
The number of carbon atoms of the halogenated hydrocarbon is preferably 1 or 2, and most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. The proportion of halogen atoms substituted by halogen in the halogenated hydrocarbon is preferably 25 to 75 mol%, more preferably 30 to 70 mol%, and more preferably 35 to 65 mol%. More preferably, it is most preferable that it is 40-60 mol%. Methylene chloride is a representative halogenated hydrocarbon.
Two or more organic solvents may be mixed and used.

A cellulose acylate solution can be prepared by a general method. A general method means processing at a temperature of 0 ° C. or higher (ordinary temperature or high temperature). The solution can be prepared by using a dope preparation method and apparatus in a normal solvent cast method. In the case of a general method, it is preferable to use a halogenated hydrocarbon (particularly, methylene chloride) as the organic solvent.
The amount of cellulose acylate is adjusted so as to be contained in the obtained solution in an amount of 10 to 40% by mass. The amount of cellulose acylate is more preferably 10 to 30% by mass. Arbitrary additives described later may be added to the organic solvent (main solvent).
The solution can be prepared by stirring the cellulose acylate and the organic solvent at room temperature (0 to 40 ° C.). The high concentration solution may be stirred under pressure and heating conditions. Specifically, the cellulose acylate and the organic solvent are placed in a pressure vessel and sealed, and stirred while being heated to a temperature equal to or higher than the boiling point of the solvent at normal temperature and in a range where the solvent does not boil. The heating temperature is usually 40 ° C. or higher, preferably 60 to 200 ° C., and more preferably 80 to 110 ° C.

Each component may be roughly mixed in advance and then placed in a container. Moreover, you may put into a container sequentially. The container needs to be configured so that it can be stirred. The container can be pressurized by injecting an inert gas such as nitrogen gas. Moreover, you may utilize the raise of the vapor pressure of the solvent by heating. Or after sealing a container, you may add each component under pressure.
When heating, it is preferable to heat from the outside of the container. For example, a jacket type heating device can be used. The entire container can also be heated by providing a plate heater outside the container and piping to circulate the liquid.
It is preferable to provide a stirring blade inside the container and stir using this. The stirring blade preferably has a length that reaches the vicinity of the wall of the container. A scraping blade is preferably provided at the end of the stirring blade in order to renew the liquid film on the vessel wall.
Instruments such as a pressure gauge and a thermometer may be installed in the container. Each component is dissolved in a solvent in a container. The prepared dope is taken out of the container after cooling, or taken out and then cooled using a heat exchanger or the like.

From the prepared cellulose acylate solution (dope), a cellulose acylate film can be produced by a solvent cast method.
The dope is cast on a drum or band and the solvent is evaporated to form a film. The concentration of the dope before casting is preferably adjusted so that the solid content is 18 to 35% by mass. The surface of the drum or band is preferably finished in a mirror state. For casting and drying methods in the solvent casting method, U.S. Pat. No. 736892, JP-B Nos. 45-4554, 49-5614, JP-A-60-176834, No. 60-203430, and No. 62-1115035.

  The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less. After casting, it is preferable to dry it by applying air for 2 seconds or more. The obtained film can be peeled off from the drum or band and further dried with high-temperature air whose temperature is successively changed from 100 ° C. to 160 ° C. to evaporate the residual solvent. The above method is described in Japanese Patent Publication No. 5-17844. According to this method, it is possible to shorten the time from casting to stripping. In order to carry out this method, it is necessary for the dope to gel at the surface temperature of the drum or band during casting.

(Co-casting)
The cellulose acylate film of the present invention is preferably produced by stretching after film formation by a solution casting film formation method.
In the cellulose acylate film of the present invention, the solution casting film is preferably a simultaneous multilayer casting film by co-casting or a sequential multilayer casting film. It is because it can be set as the film which has a desired retardation value. On the other hand, in some cases, it is also preferable from the viewpoint of thinning the solution casting film to be a single layer casting film.
That is, in the present invention, the obtained cellulose acylate solution may be cast as a single layer liquid on a smooth band or drum as a metal support, or a plurality of cellulose acylate liquids of two or more layers may be cast. You may cast. When casting a plurality of cellulose acylate solutions, produce a film while casting and laminating a solution containing cellulose acylate from a plurality of casting openings provided at intervals in the traveling direction of the metal support. For example, the methods described in JP-A-61-158414, JP-A-1-122419, JP-A-11-198285 and the like can be applied. Further, it may be formed into a film by casting a cellulose acylate solution from two casting ports. For example, JP-B-60-27562, JP-A-61-94724, JP-A-61-947245, It can be carried out by the methods described in JP-A Nos. 61-104813, 61-158413, and 6-134933. Further, a cellulose acylate film in which a flow of a high-viscosity cellulose acylate solution described in JP-A-56-162617 is wrapped with a low-viscosity cellulose acylate solution and the high- and low-viscosity cellulose acylate solutions are simultaneously extruded. A casting method may be used. Furthermore, it is also a preferred embodiment that the outer solution described in JP-A-61-94724 and JP-A-61-94725 contains a larger amount of an alcohol component which is a poor solvent than the inner solution.

  Alternatively, by using two casting ports, the film cast on the metal support is peeled off by the first casting port, and the second casting is performed on the side in contact with the metal support surface. Further, a film may be prepared, for example, a method described in Japanese Patent Publication No. 44-20235. The cellulose acylate solutions to be cast may be the same solution or different cellulose acylate solutions, and are not particularly limited. In order to give a function to a plurality of cellulose acylate layers, a cellulose acylate solution corresponding to the function may be extruded from each casting port. Further, the cellulose acylate solution of the present invention may be cast simultaneously with other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, a UV absorbing layer, a polarizing layer). .

  In the case of single layer casting, it is easy to recover the material produced by casting, and productivity can be improved. On the other hand, in the case of single layer casting, it is necessary to extrude a cellulose acylate solution having a high concentration and a high viscosity in order to obtain the required film thickness. In many cases, this causes a problem such as a fault or flatness. As a solution to this, by casting a plurality of cellulose acylate solutions from a casting port, a highly viscous solution can be extruded onto a metal support at the same time. Not only can it be produced, but also a concentrated cellulose acylate solution can be used to reduce the drying load and increase the film production speed.

  In the case of co-casting, the inner and outer thicknesses are not particularly limited, but preferably the outer side is preferably 1 to 50% of the total film thickness, and more preferably 2 to 30%. Here, in the case of co-casting with three or more layers, the total thickness of the layer in contact with the metal support and the layer in contact with the air side is defined as the outer thickness.

  In the case of co-casting, a cellulose acylate film having a laminated structure can be produced by co-casting cellulose acylate solutions having different degrees of substitution. For example, a cellulose acylate film having a configuration of TAC layer / DAC layer / TAC layer can be produced, or a cellulose acylate film having a configuration of DAC layer / TAC layer / DAC layer can be produced. In addition, a cellulose acylate film having a laminated structure can be produced by co-casting cellulose acylate acylate solutions having different additive concentrations such as the plasticizer, ultraviolet absorber, and matting agent. For example, the matting agent can be contained in the surface layer in a large amount or only in the surface layer. The plasticizer and the ultraviolet absorber can be contained in the inner layer more than the surface layer, and may be contained only in the inner layer. Also, the type of plasticizer and UV absorber can be changed between the inner layer and the surface layer. For example, the surface layer contains a low-volatile plasticizer and / or UV absorber, and the inner layer has excellent plasticity. It is also possible to add a plasticizer or an ultraviolet absorber excellent in ultraviolet absorption. Moreover, it is also a preferable aspect that a release agent is included only in the surface layer on the metal support side. Moreover, in order to cool a metal support body by a cooling drum method and to gelatinize a solution, it is also preferable to add more alcohol which is a poor solvent to a surface layer than an internal layer. The Tg of the surface layer and the inner layer may be different, and the Tg of the inner layer is preferably lower than the Tg of the surface layer. Further, the viscosity of the solution containing cellulose acylate during casting may be different between the surface layer and the inner layer, and the viscosity of the surface layer is preferably smaller than the viscosity of the inner layer. It may be smaller than the viscosity.

(Drying process, stretching process)
A method for drying a web that has been dried on a drum or belt and peeled off will be described. The web peeled at the peeling position just before the drum or belt makes one round is conveyed by alternately passing through a group of rolls arranged in a staggered manner, or the both ends of the peeled web are gripped by clips or the like and are not contacted. It is conveyed by the method of conveying it automatically. Drying is performed by a method of applying wind at a predetermined temperature to both sides of the web (film) being conveyed or a method using a heating means such as a microwave. Since rapid drying may impair the flatness of the film to be formed, it is preferable to dry at a temperature at which the solvent does not foam in the initial stage of drying, and to dry at a high temperature after the drying proceeds. In the drying process after peeling from the support, the film tends to shrink in the longitudinal direction or the width direction by evaporation of the solvent. Shrinkage increases with drying at higher temperatures. Drying while suppressing this shrinkage as much as possible is preferable for improving the flatness of the finished film. From this point, for example, as shown in Japanese Patent Laid-Open No. 62-46625, a method in which all or part of the drying process is performed while holding the width at both ends of the web with clips or pins in the width direction. (Tenter method) is preferable. It is preferable that the drying temperature in the said drying process is 100-145 degreeC. The drying temperature, the amount of drying air, and the drying time vary depending on the solvent used, but may be appropriately selected according to the type and combination of the solvents used.

  In the production of the film of the present invention, the web (film) peeled from the support is preferably stretched when the amount of residual solvent in the web is less than 120% by mass.

The residual solvent amount can be expressed 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 web of which M is measured is dried at 110 ° C. for 3 hours. If the amount of residual solvent in the web is too large, the effect of stretching cannot be obtained, and if it is too small, stretching becomes extremely difficult and the web may break. The more preferable range of the residual solvent amount in the web is 70% by mass or less, more preferably 10% by mass to 50% by mass, and particularly preferably 12% by mass to 35% by mass. Further, if the stretching ratio is too small, a sufficient phase difference cannot be obtained, and if it is too large, stretching may become difficult and breakage may occur.

The draw ratio is preferably 5% to 100%, more preferably 15% to 40%, and particularly preferably 20% to 35%. Here, extending from 5% to 100% in one direction means that the distance between clips and pins supporting the film is in the range of 1.05 to 2.00 times the distance before stretching. Means.
Stretching may be performed in the film transport direction (longitudinal direction), in the direction orthogonal to the film transport direction (transverse direction), or in both directions, but the cellulose acylate film of the present invention is transported in the film. It is obtained by stretching in a direction orthogonal to the direction, and the stretching ratio is preferably 5% to 100% in the direction orthogonal to the transport direction. A more preferable range of the draw ratio in the direction orthogonal to the transport direction is the same as the above range. By setting the draw ratio to 5% or more, Re can be expressed more appropriately, and the bowing can be improved. Moreover, haze can be reduced by making a draw ratio into 50% or less.

In the present invention, the solution cast film can be stretched without being heated to a high temperature as long as the residual solvent amount is in a specific range, but it is preferable because drying and stretching can shorten the process. . In this invention, it is preferable that the extending | stretching temperature in the said extending process is 110-190 degreeC, and it is more preferable that it is 120-150 degreeC. The stretching temperature is preferably 120 ° C. or higher from the viewpoint of lowering haze, and 150 ° C. or lower is preferable from the viewpoint of enhancing optical expression (thin film forming).
On the other hand, since the plasticizer volatilizes when the temperature of the web is too high, the range of room temperature (15 ° C.) to 145 ° C. or lower is preferable when using a low molecular plasticizer that easily volatilizes as a plasticizer.

  In addition, stretching in biaxial directions perpendicular to each other is an effective method from the viewpoint of improving the optical expression of the film, particularly from the viewpoint of increasing the Rth value of the film. The cellulose acylate film of the present invention is obtained by simultaneous or sequential stretching in a direction perpendicular to the direction parallel to the transport direction, and the stretch ratio in the direction parallel to the transport direction is 1. % To 30% is preferable, 3% to 20% is more preferable, and 5% to 10% is particularly preferable. On the other hand, the draw ratio in the direction orthogonal to the transport direction is preferably 5% to 100%, more preferably 20% to 50%, and particularly preferably 25% to 45%. A more preferable range of the draw ratio in the direction orthogonal to the transport direction is the same as the above range.

In general, when the film is stretched 5% to 100% in a direction (width direction) perpendicular to the film conveyance direction using a biaxial stretching tenter, the film shrinks in a direction (longitudinal direction) parallel to the film conveyance direction which is the orthogonal direction. Power works.
Therefore, if the force is applied in only one direction and the stretching is continued, the width in the perpendicular direction is reduced, but this means that the amount of shrinkage is suppressed with respect to the amount that shrinks without restricting the width. This means that the interval between the clip or pin whose width is restricted is restricted to a range of 1.05 to 2.00 times that before stretching. At this time, in the longitudinal direction, a force is exerted to shrink the film by stretching in the width direction. By taking the interval between the clips or pins in the longitudinal direction, an excessive tension is not applied in the longitudinal direction. There is no particular limitation on the method of stretching the web. For example, a method in which a difference in peripheral speed is applied to a plurality of rolls, and the roll peripheral speed difference is used to stretch in the longitudinal direction, the both ends of the web are fixed with clips and pins, and the interval between the clips and pins is increased in the traveling direction. And a method of stretching in the width direction, a method of extending in the width direction and stretching in the width direction, a method of extending the length of the width at the same time and stretching in the both directions of the width of the width. Of course, these methods may be used in combination. In the case of the so-called tenter method, driving the clip portion by a linear drive method is preferable because smooth stretching can be performed and the risk of breakage and the like can be reduced.

In this invention, you may extend | stretch to a biaxial direction simultaneously in a extending | stretching process, and may extend | stretch to a biaxial direction sequentially. When extending | stretching to a biaxial direction sequentially, you may change extending | stretching temperature for every extending | stretching in each direction.
In the case of simultaneous biaxial stretching, the film of the present invention can be obtained even when the stretching temperature is 110 ° C. to 190 ° C., and the stretching temperature in the case of simultaneous biaxial stretching is 120 ° C. to 150 ° C. More preferably, it is 130 to 150 degreeC. Further, by simultaneous biaxial stretching, the haze is increased to some extent, but the optical expression can be further enhanced.
On the other hand, when sequentially biaxially stretching, it is preferable to first stretch in a direction parallel to the film transport direction and then stretch in a direction orthogonal to the film transport direction. A more preferable range of the stretching temperature at which the successive stretching is performed is the same as the stretching temperature range at which the simultaneous biaxial stretching is performed.

(Heat treatment process)
The film production method of the present invention is preferably provided with a heat treatment step after the drying step. The heat treatment in the heat treatment step may be performed after completion of the drying step, and may be performed immediately after the stretching / drying step, or may be separately provided only after the winding process is performed by a method described later after the completion of the drying step. . In the present invention, it is preferable to provide the heat treatment step again after the drying step is once cooled to room temperature to 100 ° C. or less. This is because a film having better thermal dimensional stability can be obtained. For the same reason, it is preferable that the amount of residual solvent is dried to less than 2% by mass, preferably less than 0.4% by mass immediately before the heat treatment step.
Although the reason why the shrinkage rate of the film can be reduced by such treatment is not clear, in the film that has undergone 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 heat treatment is preferably performed at a temperature of 150 to 200 ° C., more preferably 160 to 180 ° C. The heat treatment is preferably performed for 1 to 20 minutes, more preferably 5 to 10 minutes.
When the heat treatment temperature exceeds 200 ° C. for a long time, it may cause a problem because the amount of the plasticizer scattered in the film increases.

  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.

In the heat treatment step, stretching can be performed at a high temperature separately from the stretching step. The draw ratio is preferably 5% to 100%, more preferably 15% to 40%, and particularly preferably 20% to 35%.
Stretching may be performed in the film transport direction (longitudinal direction), in the direction orthogonal to the film transport direction (transverse direction), or in both directions, but the cellulose acylate film of the present invention is transported in the film. It is obtained by stretching in a direction orthogonal to the direction, and the stretching ratio is preferably 5% to 100% in the direction orthogonal to the transport direction. A more preferable range of the draw ratio in the direction orthogonal to the transport direction is the same as the above range. By setting the draw ratio to 5% or more, Re can be expressed more appropriately, and the bowing can be improved. Moreover, haze can be reduced by making a draw ratio into 50% or less.

  The stretching temperature in the heat treatment step is the same as the heat treatment temperature range. The stretching temperature is preferably 140 ° C. or higher from the viewpoint of reducing haze, and it is preferably 190 ° C. or lower from the viewpoint of improving optical expression (thin film forming).

  In addition, stretching in biaxial directions perpendicular to each other is an effective method from the viewpoint of improving the optical expression of the film, particularly from the viewpoint of increasing the Rth value of the film. The cellulose acylate film of the present invention is obtained by simultaneous or sequential stretching in a direction perpendicular to the direction parallel to the transport direction, and the stretch ratio in the direction parallel to the transport direction is 1. % To 30% is preferable, 3% to 20% is more preferable, and 5% to 10% is particularly preferable. On the other hand, the draw ratio in the direction orthogonal to the transport direction is preferably 5% to 100%, more preferably 20% to 50%, and particularly preferably 25% to 45%.

In this invention, you may extend | stretch to a biaxial direction simultaneously in a extending | stretching process, and may extend | stretch to a biaxial direction sequentially. When extending | stretching to a biaxial direction sequentially, you may change extending | stretching temperature for every extending | stretching in each direction.
In the case of simultaneous biaxial stretching, a preferred stretching temperature range is the same as the above heat treatment temperature range. Further, by simultaneous biaxial stretching, the haze is increased to some extent, but the optical expression can be further enhanced.
On the other hand, when sequentially biaxially stretching, it is preferable to first stretch in a direction parallel to the film transport direction and then stretch in a direction orthogonal to the film transport direction. A more preferable range of the stretching temperature at which the sequential stretching is performed is the same as the above heat treatment temperature range.

  As the winder for winding the obtained film, a commonly used winder can be used, such as a constant tension method, a constant torque method, a taper tension method, and a program tension control method with a constant internal stress. It can be wound up by a take-up 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.

[Heating steam treatment]
In addition, the stretched film may be manufactured through a process of spraying steam heated to 100 ° C. or higher. By passing through this water vapor spraying step, the residual stress of the cellulose acylate film to be produced is relaxed, and the dimensional change is reduced, which is preferable. The temperature of the water vapor is not particularly limited as long as it is 100 ° C. or higher, but considering the heat resistance of the film, the temperature of the water vapor is 200 ° C. or lower.

  These steps from casting to post-drying may be performed in an air atmosphere or an inert gas atmosphere such as nitrogen gas. The winder used for producing the cellulose acylate film of the present invention may be a commonly used winder such as a constant tension method, a constant torque method, a taper tension method, a program tension control method with a constant internal stress, or the like. It can be wound up by the method.

(surface treatment)
The produced cellulose acylate film is preferably subjected to a surface treatment. Specific examples include corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment, and ultraviolet irradiation treatment. It is also preferable to provide an undercoat layer as described in JP-A-7-333433.
From the viewpoint of maintaining the flatness of the film, in these treatments, the temperature of the cellulose acylate film is preferably Tg (glass transition temperature) or lower, specifically 150 ° C. or lower.
When used as a transparent protective film for a polarizing plate, it is particularly preferable to carry out acid treatment or alkali treatment, that is, saponification treatment for cellulose acylate, from the viewpoint of adhesiveness with a polarizer.
The surface energy is preferably 55 mN / m or more, and more preferably 60 mN / m to 75 mN / m.

Hereinafter, the alkali saponification treatment will be specifically described as an example.
The alkali saponification treatment of the cellulose acylate film is preferably performed in a cycle in which the film surface is immersed in an alkali solution, neutralized with an acidic solution, washed with water and dried.
Examples of the alkaline solution include potassium hydroxide solution and sodium hydroxide solution, and the hydroxide ion concentration is preferably in the range of 0.1 to 3.0 mol / liter, 0.5 to 2.0 mol / liter. More preferably, it is in the range of liters. The alkaline solution temperature is preferably in the range of room temperature to 90 ° C, more preferably in the range of 40 to 70 ° C.

The surface energy of the solid can be determined by the contact angle method, the wet heat method, and the adsorption method as described in “Basics and Applications of Wetting” (issued by Realize Inc. 1989.12.10). In the case of the cellulose acylate film of the present invention, it is preferable to use a contact angle method.
Specifically, two kinds of solutions having known surface energies are dropped on a cellulose acylate film, and at the intersection of the surface of the droplet and the surface of the film, the angle formed between the tangent line drawn on the droplet and the film surface, The surface angle of the film can be calculated by defining the angle containing the droplet as the contact angle.

[Characteristics of cellulose acylate film]
(Film thickness)
The film thickness of the cellulose acylate film of the present invention is preferably 30 to 70 μm, more preferably 35 μm to 70 μm, and still more preferably 40 μm to 60 μm. A film thickness of 20 μm or more is preferable in terms of handling properties when processing into a polarizing plate or the like and curling suppression of the polarizing plate. Further, the film thickness unevenness of the cellulose acylate film of the present invention is preferably 0 to 2% in both the transport direction and the width direction, more preferably 0 to 1.5%, and 0 to 1%. Is particularly preferred.

(Film retardation)
In the present specification, Re (λ) and Rth (λ) respectively represent in-plane retardation and retardation in the thickness direction at a wavelength λ. Re is measured with KOBRA 21ADH (manufactured by Oji Scientific Instruments Co., Ltd.) by making light of wavelength λ nm incident in the normal direction of the film. Rth was measured by making light having a wavelength λ nm incident from a direction inclined + 40 ° with respect to the normal direction of the film with the slow axis in the plane (determined by KOBRA 21ADH) as the tilt axis (rotation axis). A retardation value and a retardation value measured by making light of wavelength λ nm incident from a direction inclined by −40 ° with respect to the film normal direction with the in-plane slow axis as the tilt axis (rotation axis). KOBRA 21ADH is calculated based on the retardation value measured in the direction. 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.

The cellulose acylate film of the present invention is preferably used as a protective film for a polarizing plate, and can be particularly preferably used as a retardation film corresponding to various liquid crystal modes. The retardation film of the present invention includes the cellulose acylate film of the present invention.
When the cellulose acylate film of the present invention is used as a retardation film, the film of the present invention preferably satisfies the following formulas (1) and (2).
Formula (1): 30 nm ≦ | Re (590) | ≦ 100 nm
Formula (2): 80 nm ≦ | Rth (590) | ≦ 280 nm
(In the formulas (1) and (2), Re (590) and Rth (590) are the retardation value and thickness in the in-plane direction measured with light having a wavelength of 590 nm in an environment of 25 ° C. and a relative humidity of 60%, respectively. Represents the direction retardation value.)
It is more preferable to satisfy the following formula (1 ′) and formula (2 ′).
Formula (1 ′): 40 nm ≦ | Re (590) | ≦ 100 nm
Formula (2 ′): 100 nm ≦ | Rth (590) | ≦ 250 nm
When Re (590) and Rth (590) satisfy the above formulas (1) and (2), they can be more preferably used as retardation films.

More preferable optical properties of the cellulose acylate film vary depending on the liquid crystal mode.
For VA mode, Re measured at 590 nm is preferably 30 to 200 nm, more preferably 30 to 150 nm, and even more preferably 40 to 100 nm. Rth is preferably 70 to 400 nm, more preferably 100 to 300 nm, and even more preferably 100 to 250 nm.
For TN mode, Re measured at 590 nm is preferably 0 to 100 nm, more preferably 20 to 90 nm, and even more preferably 50 to 80 nm. Rth is preferably 20 to 200 nm, more preferably 30 to 150 nm, and even more preferably 40 to 120 nm.
For the TN mode, an optically anisotropic layer can be coated on a cellulose acylate film having the retardation value and used as an optical compensation film.
The cellulose acylate film of the present invention is characterized by high optical expression. Specifically, it is preferable that | Re (590) | per film thickness is large, and it is more preferable to satisfy the following formula (5).
Formula (5): 2.5 × 10 ⁻³ ≦ | Rth (590) | / d
(In Formula (5), Rth (590) represents a retardation value in the thickness direction measured with light having a wavelength of 590 nm in an environment of 25 ° C. and a relative humidity of 60%, and d represents the film thickness of the film.)
The cellulose acylate film of the present invention preferably has a value of Rth (unit: nm) / d (μm) of 2.6 × 10 ⁻³ or more.

(Wavelength dispersion)
The film of the present invention is characterized in that the wavelength dispersion is flat dispersion or reverse wavelength dispersion. Thus, when the optical properties of the cellulose acylate film are flat dispersion or reverse wavelength dispersion, the color tone when incorporated in a liquid crystal display device can be improved, which is preferable. In the present specification, “reverse wavelength dispersion” means that Re and Rth satisfy 0 nm <Re (630) −Re (440) and 0 nm <Rth (630) −Re (440), respectively. .
The film of the present invention more preferably satisfies the following formulas (3) and (4).
Formula (3): 0 nm ≦ Re (630) −Re (440) ≦ 15 nm
Formula (4): 0 nm ≦ Rth (630) −Re (440) ≦ 30 nm
(In the formulas (3) and (4), Re (440) and Rth (440) are the retardation value and thickness in the in-plane direction measured with light having a wavelength of 440 nm in an environment of 25 ° C. and a relative humidity of 60%, respectively. Re (630) and Rth (630) represent the retardation value in the in-plane direction and the thickness direction letter measured with light having a wavelength of 630 nm in an environment of 25 ° C. and a relative humidity of 60%, respectively. Represents the foundation value.)

(Haze of film)
The total haze of the cellulose acylate film of the present invention is preferably 0.5% or less, more preferably 0.4% or less, particularly preferably 0.3% or less, More preferably, it is% or less. As an optical film, the transparency of the film is important. The haze can be measured according to JIS K-6714 using a haze meter “HGM-2DP” {manufactured by Suga Test Instruments Co., Ltd.}.
On the other hand, the internal haze of the cellulose acylate film of the present invention is preferably 0.1% or less, more preferably 0.07% or less, and particularly preferably 0.05% or less. In the present invention, the internal haze was measured using the following method.
A few drops of liquid paraffin are added to the front and back surfaces of the film, and two glass plates with a thickness of 1 mm (micro slide glass product number S9111, made by MATAUNAMI) are sandwiched from the front and back to obtain completely two glass plates. The film was optically adhered, the haze was measured in a state where the surface haze was removed, and the value obtained by subtracting the haze measured by sandwiching only liquid paraffin between two separately measured glass plates was used as the internal haze ( Calculated as Hi).
The film of the present invention preferably has a total haze of 0.5% or less and an inner haze of 0.1% or less.

(Glass-transition temperature)
The glass transition temperature of the cellulose acylate film of the present invention is preferably 120 ° C. or higher, and more preferably 140 ° C. or higher.
The glass transition temperature is a temperature at which the base line derived from the glass transition of the film starts to change and a temperature at which it returns to the base line again when measured at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC). It can be calculated as an average value.
Moreover, the measurement of a glass transition temperature can also be calculated | required using the following dynamic viscoelasticity measuring apparatuses. After adjusting the cellulose acylate film sample (unstretched) 5 mm × 30 mm of the present invention for 2 hours or more at 25 ° C. and a relative humidity of 60%, a dynamic viscoelasticity measuring apparatus (Vibron: DVA-225 (IT measurement control ( Measured at a gripping distance of 20 mm, a heating rate of 2 ° C./minute, a measurement temperature range of 30 ° C. to 250 ° C., and a frequency of 1 Hz, the vertical axis is the logarithmic axis, the storage elastic modulus, and the horizontal axis is the linear axis When the temperature (° C.) is taken, the straight line 1 is drawn in the solid region and the straight line 2 is drawn in the glass transition region, as the storage elastic modulus shifts from the solid region to the glass transition region. The intersection of the straight line 1 and the straight line 2 when drawn is the temperature at which the storage elastic modulus suddenly decreases and the film begins to soften when the temperature rises, and the temperature at which the film begins to transition to the glass transition region. Dynamic viscoelasticity To.

(Configuration of cellulose acylate film)
The cellulose acylate film of the present invention may have a single layer structure or a plurality of layers, but preferably has a single layer structure. Here, the “single layer structure” film does not mean that a plurality of film materials are bonded together, but means a single cellulose acylate film. When a single cellulose acylate film is produced from a plurality of cellulose acylate solutions using a sequential casting method or a co-casting method, a single layer structure is formed.

When a single cellulose acylate film is produced from a plurality of cellulose acylate solutions using the sequential casting method or the simultaneous co-casting method, the type and amount of additives, the molecular weight distribution of cellulose acylate and the cellulose acylate are used. A cellulose acylate film having a distribution in the thickness direction can be obtained by appropriately adjusting the type of rate. Moreover, what has various functional parts, such as an optical anisotropy part, a glare-proof part, a gas barrier part, and a moisture-resistant part, in those one film is also included.
That is, the cellulose acylate film of the present invention may be obtained by co-casting, and the surface layer may be laminated on both sides of the inner layer. In this case, the preferred range of acyl substitution degree of the cellulose acylate used for the inner layer is the same as the preferred range of acyl substitution degree in the case of a single cellulose acylate composition obtained by single layer casting film formation. It is. On the other hand, the acyl substitution degree of the cellulose acylate used for the surface layer is preferably 2.7 or more in terms of the total acyl substitution degree from the viewpoint of improving the peelability from the support during the fluent film formation. It is more preferably 75 to 2.95, and particularly preferably 2.8 to 2.95. The polycondensed ester may be contained in the inner layer and / or the surface layer, and is preferably contained in at least the inner layer. An embodiment included in the inner layer and the surface layer is also preferable.

[Phase difference film]
The cellulose acylate film of the present invention can be used as a retardation film. The “retardation film” is generally used for a display device such as a liquid crystal display device, and means an optical material having optical anisotropy, and is synonymous with a retardation plate, an optical compensation film, an optical compensation sheet, and the like. It is. In a liquid crystal display device, a retardation film is used for the purpose of improving the contrast of a display screen or improving viewing angle characteristics and color.
By using the transparent cellulose acylate film of the present invention, a retardation film in which the Re value and the Rth value are freely controlled can be easily produced.

  A plurality of the cellulose acylate films of the present invention can be laminated, or the cellulose acylate film of the present invention and a film outside of the present invention can be laminated to adjust Re and Rth as appropriate and used as a retardation film. . Lamination of the film can be performed using a pressure-sensitive adhesive or an adhesive.

  In some cases, the cellulose acylate film of the present invention may be used as a support for a retardation film, and an optically anisotropic layer made of liquid crystal or the like may be provided thereon to be used as a retardation film.

[Polarizer]
The polarizing plate of the present invention has a polarizer and at least one film of the present invention. When the film of the present invention is used as a protective film for polarizing plate, the protective film for polarizing plate / polarizer / protective film for polarizing plate / liquid crystal cell / protective film for polarizing plate of the present invention / polarizer / protective film for polarizing plate. It can preferably be used in the configuration, or a protective film for polarizing plate / polarizer / protective film for polarizing plate of the present invention / liquid crystal cell / protective film for polarizing plate of the present invention / polarizer / protective film for polarizing plate. In particular, by bonding to a liquid crystal cell such as a TN type, a VA type, or an OCB type, it is possible to provide a display device that is further excellent in viewing angle and visibility with little coloring.

The polarizing plate of the present invention is a polarizing plate having protective films on both sides of the polarizer, and at least one of the protective films is preferably the cellulose acylate film of the present invention. That is, the film of the present invention is preferably used for a protective film for a polarizing plate. As described above, the polarizing plate is preferably formed by laminating and laminating a protective film on at least one surface of the polarizer. A conventionally known polarizer can be used. For example, a hydrophilic polymer film such as a polyvinyl alcohol film is treated with a dichroic dye such as iodine and stretched. The bonding of the cellulose acylate film and the polarizer is not particularly limited, but can be performed with an adhesive made of an aqueous solution of a water-soluble polymer. The water-soluble polymer adhesive is preferably a completely saponified polyvinyl alcohol aqueous solution.
In particular, a polarizing plate using the film of the present invention has little deterioration under high temperature and high humidity conditions and can maintain stable performance for a long time.

[Liquid Crystal Display]
The liquid crystal display device of the present invention preferably includes a liquid crystal cell and at least one cellulose acylate film of the present invention or at least one polarizing plate of the present invention. Further, it is a liquid crystal display device including a liquid crystal cell and two polarizing plates disposed on both sides thereof, and at least one of the polarizing plates is more preferably the polarizing plate of the present invention.
In the liquid crystal display device of the present invention, it is preferable that the liquid crystal cell is a VA mode or TN mode liquid crystal cell, and that the film of the present invention expresses Re and Rth within the above preferred ranges. Is particularly preferred.
The cellulose acylate film of the present invention and the polarizing plate using the film can be used for liquid crystal cells and liquid crystal display devices in various display modes. TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-Ferroelectric Liquid Nyst) Various display modes such as HAN (Hybrid Aligned Nematic) have been proposed.

In a VA mode liquid crystal cell, rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied.
The VA mode liquid crystal cell includes (1) a narrowly defined VA mode liquid crystal cell in which rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied, and substantially horizontally when a voltage is applied (Japanese Patent Laid-Open No. Hei 2-). 176625 (in Japanese Patent Publication No. 176625), and (2) a liquid crystal cell (SID97, Digest of tech. Papers (Proceedings) 28 (1997) 845 in which the VA mode is converted into a multi-domain (for MVA mode) in order to enlarge the viewing angle. ), (3) a liquid crystal cell in a mode (n-ASM mode) in which rod-like liquid crystalline molecules are substantially vertically aligned when no voltage is applied and twisted multi-domain alignment is applied when a voltage is applied (Sharp Technical Report No. 80, page 11); (4) A SURVAVAL mode liquid crystal cell (Monthly Display May 14th page (1999)) is included.

  The VA mode liquid crystal display device includes a liquid crystal cell and two polarizing plates disposed on both sides thereof. The liquid crystal cell carries a liquid crystal between two electrode substrates. In one aspect of the transmission type liquid crystal display device of the present invention, the film of the present invention is disposed between the liquid crystal cell and one polarizing plate, or between the liquid crystal cell and both polarizing plates. Arrange two.

  In another aspect of the transmissive liquid crystal display device of the present invention, an optical compensation sheet made of the film of the present invention is used as a transparent protective film for a polarizing plate disposed between a liquid crystal cell and a polarizer. The above optical compensation sheet may be used only for the protective film (between the liquid crystal cell and the polarizer) of one polarizing plate, or two (between the liquid crystal cell and the polarizer) of both polarizing plates. You may use said optical compensation sheet for a sheet of protective film. When the optical compensation sheet is used for only one polarizing plate, it is particularly preferable to use it as a protective film for the liquid crystal cell side of the backlight side polarizing plate of the liquid crystal cell. For the lamination to the liquid crystal cell, the film of the present invention is preferably on the VA cell side. The protective film may be a normal cellulose acylate film, and is preferably thinner than the film of the present invention. For example, it is preferably 40 to 80 μm, and examples thereof include, but are not limited to, commercially available KC4UX2M (40 μm manufactured by Konica Capto), KC5UX (60 μm manufactured by Konica Caputo), TD80 (80 μm manufactured by Fuji Film), and the like.

  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.

(Preparation of cellulose acylate)
Cellulose acylates with different types of acyl groups and different degrees of substitution described in Table 2 were prepared. This was carried out by adding sulfuric acid (7.8 parts by mass with respect to 100 parts by mass of cellulose) as a catalyst, adding carboxylic acid as a raw material for the acyl substituent, and carrying out an acylation reaction at 40 ° C. At this time, the kind and substitution degree of the acyl group were adjusted by adjusting the kind and amount of the carboxylic acid. In addition, aging was performed at 40 ° C. after acylation. Further, the low molecular weight component of the cellulose acylate was removed by washing with acetone.
In the table, Ac in the type of cellulose acylate represents an acetyl substituent, and Pr represents a propionyl group.

[Examples 1 to 43 and Comparative Examples 1 to 8]
[Film formation of cellulose acylate film]
Using the cellulose acylate dope shown below, a film was formed by a solution casting method and used for each of Examples and Comparative Examples.

  In addition, unless otherwise indicated in the following Table 2, cellulose acetate was used as the cellulose acylate. Moreover, about various additives, the addition amount with respect to 100 mass parts of cellulose acylates was described. As the retardation developer A, the following triazine compounds were used.

(Cellulose acylate dope A)
――――――――――――――――――――――――――――――――――――――――
Cellulose acylate resin: Substituents listed in Table 2, those having a degree of substitution 100 parts by mass Additives: those listed in Table 2 Amounts listed in Table 2 (unit: parts by mass)
Retardation expression agent A Amounts shown in Table 2 (unit: parts by mass)
Dichloromethane 406 parts by mass Methanol 61 parts by mass ――――――――――――――――――――――――――――――――――――――――

  Cellulose acylate dope A has a matting agent (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd., secondary average particle size of 1.0 μm or less) as 0.13 parts by mass with respect to 100 parts by mass of cellulose acylate. The matting agent dispersion was mixed and stirred.

(Solution casting in a single layer)
The dope having the above composition was put into a mixing tank and stirred to dissolve each component, and then filtered through a filter paper having an average pore size of 34 μm and a sintered metal filter having an average pore size of 10 μm to prepare a cellulose acylate dope. The dope was cast with a band casting machine. The film peeled off from the band with a residual solvent amount of about 30% by mass was applied with hot air so that the stretching temperature would be the film surface temperature described in Table 2 below with a tenter, and the magnification and direction described in Table 2 below. Stretching was performed. Thereafter, the tenter conveyance was shifted to the roll conveyance, and the film was further dried at 120 to 150 ° C. and wound up. Further, the dried film was stretched by a tenter in the magnifications and directions described in Table 2 below while applying hot air so that the heat treatment temperature became the film surface temperature described in Table 2 below. The film thicknesses at this time are shown in Table 2 with film thicknesses such that Re (590) = 70 nm and Rth (590) = 200 nm based on the results obtained by measuring the retardation value described later. .

[Examples 101 to 122, Comparative Examples 101 and 102]
(Solution casting with co-casting)
In the same manner as the cellulose acylate dope A in Example 1, the inner layer dope (total acyl substitution degree 2.43) and the surface layer dope A using cellulose acylates having the acyl substitution degree shown in Table 3 below and B (all with a total acyl substitution degree of 2.81) was prepared. As shown in FIG. 1, the following three types of dopes were cast from a casting die 89 on a traveling casting band 85. Here, the inner layer is made thickest by adjusting the casting amount of each dope. As a result, the film thickness after stretching is the total film thickness as shown in Table 3 below, the surface layers A and B layers In each example, simultaneous multi-layer co-casting was performed so that the film thickness was 2.5 μm, and the cast film 70 was formed. Stretching process, heat treatment process and heat treatment process in the temperature and direction shown in the following Table 3 while applying hot air of the temperature described in Table 3 below with a tenter on the film peeled off from the band with a residual solvent amount of about 30% by mass Went. Thereafter, the tenter conveyance was shifted to the roll conveyance, and the film was further dried at 120 to 150 ° C. and wound up. The film thicknesses at this time are shown in Table 3 with film thicknesses such that Re (590) = 70 nm and Rth (590) = 200 nm based on the results obtained by measuring the retardation value described later. .

[Evaluation]
(Measurement of retardation value)
The produced cellulose acylate film was conditioned for 2 hours or more at 25 ° C. and a relative humidity of 60%, and was measured at 25 ° C. and a relative humidity of 60% using a birefringence measuring device (KOBRA 21ADH, manufactured by Oji Scientific Instruments). Table 2 and Table 3 show the Re value and Rth value at a wavelength of 590 nm. Further, the value of Rth (nm) per film thickness (μm) was calculated and is shown in Table 2 and Table 3 together.

(Surface, all haze, internal haze)
The surface shape of the obtained film was determined according to the following criteria.
○: The total haze can be measured by the following method, and the surface state is good.
(Triangle | delta): Although all haze can be measured with the following method, some whitening is recognized and surface shape is favorable.
X: Whitening was remarkable, there was no transparency, the surface shape was poor, and the optical film was not formed.
Measurement of total haze and internal haze is JIS K using a haze meter “HGM-2DP” (manufactured by Suga Test Instruments Co., Ltd.) at 25 ° C. and a relative humidity of 60% on a 40 mm × 80 mm cellulose acylate film sample of the present invention. Measured according to -6714 and shown in Table 3.

(Measurement of chromatic dispersion)
Re and Rth at wavelengths of 440 nm and 630 nm are obtained by the same method as the measurement of the retardation value, and the values of Re (630) -Re (440) and Rth (630) -Rth (440) are calculated. The results are shown in Tables 2 and 3.

From Table 2 and Table 3, in each Example, it is possible to obtain a cellulose acylate film using a film material having reverse dispersion, low haze, high optical expression, and inexpensive. I knew it was possible.
Further, when a polycondensation ester outside the scope of the present invention is used (Comparative Examples 1 to 3, 6, 7, 101 and 102), when both ends of the polycondensation ester contain an aromatic ring group, planar failure and haze In the case where the aromatic dicarboxylic acid ratio is 60 mol% or less, the optical developability (particularly, the Rth expression per film thickness) is insufficient. If the film thickness is not increased, Re and Rth Is insufficient in that it cannot be adjusted to a preferred value. On the other hand, Comparative Example 5 using cellulose acylate exceeding the range of the present invention is insufficient in that a planar failure occurs, and Comparative Examples 4 and 8 using cellulose acylate falling below the range of the present invention. However, this is insufficient in that the wavelength dispersion becomes forward dispersion.

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

(Mounting on VA panel)
As the viewing-side polarizing plate and the backlight-side polarizing plate of the liquid crystal display device using the above vertical alignment type liquid crystal cell, both the examples shown in Table 4, the polarizing plate of the comparative example, and the polarizer are commercially available cellulose tria. A polarizing plate of a sylate film (Fujitac TD80UF, manufactured by FUJIFILM Corporation) was installed. The viewing side polarizing plate and the backlight side polarizing plate were attached to the liquid crystal cell via an adhesive. The crossed Nicols were arranged so that the transmission axis of the viewing side polarizing plate was in the vertical direction and the transmission axis of the backlight side polarizing plate was in the left and right direction.

(Evaluation of VA liquid crystal display device)
The following evaluation was performed about each produced liquid crystal display device.

(1) Measurement of front contrast ratio:
Using a measuring instrument (BM5A, manufactured by TOPCON), the luminance values of black display and white display in the normal direction of the panel were measured in a dark room, and the front contrast (white luminance / black luminance) was calculated.
At this time, the distance between the measuring instrument and the panel was set to 700 mm.

(2) Viewing angle contrast (contrast in oblique direction):
Using a measuring instrument (BM5A, manufactured by TOPCON), in a dark room, the luminance values of black display and white display in three directions of polar angle direction 60 degrees from the front of the apparatus and azimuth angle directions 0 degrees, 45 degrees, and 90 degrees And the viewing angle contrast (white luminance / black luminance) was calculated to evaluate the viewing angle characteristics of the liquid crystal display device.
A: The viewing angle contrast is 50 or more, and light leakage cannot be recognized.
Δ: The minimum value of the viewing angle contrast is less than 50 and 25 or more, and a slight leak of light is recognized, but is acceptable.
X: The minimum value of the viewing angle contrast is less than 25, and large light leakage is recognized and is not acceptable.

(3) Color shift:
The prepared liquid crystal display device was subjected to the following sensory evaluation and evaluated according to the following criteria.
In the dark room, the sensory evaluation of the color shift in the oblique direction during black display was performed.
A: Almost no tinting is observed in all polar and azimuthal directions.
○: Slight tint is observed when rotated 360 degrees around the normal line of the liquid crystal cell in the polar angle direction of 60 degrees.
(Triangle | delta): Coloring is observed when it rotates 360 degree | times centering on the normal line of a liquid crystal cell in the polar angle 60 degree direction.

  The results are shown in Table 4 below. When the films of Examples 2, 10, 11, 17, 18, 28, 33, 41 and 43 in which the wavelength dispersion of the film is flat or reverse dispersion are used, compared with the film in which the wavelength dispersion of the film is forward dispersion, It was found that the color shift was excellent and the color was improved.

70 casting film 85 casting band 86a rotating roller 89 casting die 120 inner layer dope 121 surface A layer dope 122 surface B layer dope 120a inner layer 121a surface A layer 122a surface B layer t1 inner layer film thickness t2 surface A layer thickness t3 Surface B layer thickness

Claims (18)

Cellulose acylate having a total acyl substitution degree of 2.00 to 2.70;
Containing at least one polycondensed ester containing an aromatic dicarboxylic acid residue and an aliphatic diol residue,
The ratio of aromatic dicarboxylic acid residues to all dicarboxylic acid residues in the polycondensed ester is 60 mol% or more, and both ends of the polycondensed ester are independently —OH group, —O—C (═O) —R ¹ group, —C (═O) —O—R ² group, —O—R ³ group and —COOH group (provided that R ^{1 to} R ³ are each independently aliphatic. A cellulose acylate film, wherein the cellulose acylate film is any one selected from   The cellulose acylate according to claim 1, wherein the polycondensed ester is a polycondensed ester in which the ratio of the aliphatic diol residue having 3 or more carbon atoms to all diol residues is 30 mol% or more. the film.   The cellulose acylate film according to claim 1 or 2, wherein the polycondensed ester has a number average molecular weight of 500 to 2,000.   Content of the said polycondensation ester with respect to 100 mass parts of said cellulose acylates is 5-30 mass parts, The cellulose acylate film as described in any one of Claims 1-3 characterized by the above-mentioned. Both ends of the polycondensed ester are each independently an —OH group or —O—C (═O) —R ¹ group (provided that when a plurality of R ¹ are present, each independently represents an aliphatic group). The cellulose acylate film according to claim 1, wherein the cellulose acylate film is a film.   The cellulose acylate film according to any one of claims 1 to 5, wherein the cellulose acylate film is obtained by film formation by solution casting and further stretching.   The cellulose acylate film according to claim 6, wherein the solution casting film is a simultaneous multilayer casting film by co-casting or a sequential multilayer casting film.   The cellulose acylate film according to claim 6, wherein the solution casting film is a single-layer casting film.   The cellulose acylate film according to any one of claims 6 to 8, wherein the stretching is stretching at a magnification of 5% to 100% in a direction orthogonal to the transport direction.   The stretching is simultaneous or sequential stretching in a direction orthogonal to a direction parallel to the transport direction, and is stretching at a magnification of 5% to 100% in a direction orthogonal to the transport direction. The cellulose acylate film according to any one of claims 6 to 8. The cellulose acylate film according to claim 1, wherein the following formula (1) and formula (2) are satisfied.
Formula (1): 30 nm ≦ | Re (590) | ≦ 100 nm
Formula (2): 80 nm ≦ | Rth (590) | ≦ 280 nm
(In the formulas (1) and (2), Re (590) and Rth (590) are the retardation value and thickness in the in-plane direction measured with light having a wavelength of 590 nm in an environment of 25 ° C. and a relative humidity of 60%, respectively. Represents the direction retardation value.) The cellulose acylate film according to any one of claims 1 to 11, wherein the following formula (3) and formula (4) are satisfied.
Formula (3): 0 nm ≦ Re (630) −Re (440) ≦ 15 nm
Formula (4): 0 nm ≦ Rth (630) −Re (440) ≦ 30 nm
(In the formulas (3) and (4), Re (440) and Rth (440) are the retardation value and thickness in the in-plane direction measured with light having a wavelength of 440 nm in an environment of 25 ° C. and a relative humidity of 60%, respectively. Re (630) and Rth (630) represent the retardation value in the in-plane direction and the thickness direction letter measured with light having a wavelength of 630 nm in an environment of 25 ° C. and a relative humidity of 60%, respectively. Represents the foundation value.)   The cellulose acylate film according to any one of claims 1 to 12, wherein the total haze is 0.5% or less and the inner haze is 0.1% or less.   14. The cellulose acylate film according to claim 1, wherein the film thickness is 30 to 70 μm. The cellulose acylate film according to claim 1, wherein the following formula (5) is satisfied.
Formula (5): 2.5 × 10 ⁻³ ≦ | Rth (590) | / d
(In Formula (5), Rth (590) represents a retardation value in the thickness direction measured with light having a wavelength of 590 nm in an environment of 25 ° C. and a relative humidity of 60%, and d represents the film thickness of the film.)   A polarizing plate comprising a polarizer and at least one cellulose acylate film according to claim 1.   A liquid crystal display device comprising: a liquid crystal cell; and at least one cellulose acylate film according to claim 1 or at least one polarizing plate according to claim 16.   The liquid crystal display device according to claim 17, wherein the liquid crystal cell is a VA mode liquid crystal cell.

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