JP5754278B2 - Laminated cellulose acylate film and method for producing the same - Google Patents

Description

  The present invention relates to a laminated cellulose acylate film and a method for producing the same.

  Among cellulose esters, cellulose acylate is known to be applicable to optical films having a wide range of retardation by changing the degree of acyl group substitution. Generally, triacetyl cellulose (TAC) having a high degree of acetyl group substitution is suitably used for a protective film for a polarizing plate because of its low retardation development performance.

  In contrast, cellulose acylates having a low degree of acetyl group substitution (for example, diacetyl cellulose (DAC)) have high retardation development performance, so that an optical compensation film (viewing angle) can be obtained without adding a retardation developer. It is expected that the function as an enlarged film) can be exhibited. In general, cellulose acylate differs from cycloolefin copolymer (COC) and the like in that it has the best surface coatability (ease of compatibility when an antireflection layer or the like is laminated on its surface). It is a promising candidate for a constituent material of a retardation film (λ / 4 plate; also having a function as a polarizing plate protective film) disposed on the viewing side.

  However, when a film is produced by a solution casting method using cellulose acylate having a low degree of acetyl group substitution, the film peels off because of poor peelability from the casting belt (in other words, high adhesion to the casting belt). There is a problem that sometimes horizontal rows are likely to occur. This is thought to be due to the high polarity of the low substituted cellulose acylate. The occurrence of such a horizontal step causes a decrease in surface coatability and a decrease in optical characteristics.

  Here, in Patent Document 1, when a polymer film made of a polymer such as cellulose acylate is produced, the concentration of the Ca ion contained in the dope or a substance that reacts with this to produce a salt is below a predetermined value. Thus, a technique for suppressing the formation of Ca salt and improving the peelability of the film from the support is disclosed. In addition, the cellulose acylate specifically disclosed in Patent Document 1 has only an acyl group substitution degree of 2.5 to 3.0.

  In Patent Document 2, co-casting is performed by sandwiching a low-substituted cellulose acylate with a high-substituted cellulose acylate, and a retardation enhancer is added at that time, resulting in film thickness unevenness. A technique for mitigating adverse effects on the phase difference performance is disclosed. In addition, although the acyl group substitution degree of what is disclosed as low substituted cellulose acylate in patent document 2 exceeds 2.0, it is 2.7.

European Patent No. 91656 JP 2009-235377 A JP 2009-98674 A JP 2010-66348 A

  In general, cellulose acetate having a low degree of acetyl group substitution is prepared by subjecting a highly substituted vinegar to a treatment to remove the acetyl group, and thus has a problem that the molecular weight tends to decrease. In particular, when preparing an ultra-low-substituted vinegar having an acyl group substitution degree of less than 2.0, such a decrease in molecular weight is significant, and the rigidity of the web containing a large amount of residual solvent is lowered. As a result, it becomes difficult to control the film thickness uniformly. Therefore, for the purpose of improving the peelability from the casting belt, for example, even if co-casting of high-substituted cellulose acetate and ultra-low-substituted cellulose acetate is performed, the problem of film thickness unevenness accompanying the decrease in molecular weight is It remains unresolved.

  According to the inventor's study, the problem of film thickness unevenness due to such a decrease in molecular weight in the case of using an ultra-low-substituted cellulose acylate is based on the technique described in Patent Document 1 and Patent Document 2 described above. It became clear that even if applied, it could not be solved. That is, as described in Patent Document 1, even if the concentration of Ca ions in the dope during production of the film and the substance that reacts with this to produce a salt is controlled below a predetermined value, the residual solvent is increased. It was found that the decrease in the rigidity of the web including the film could not be compensated, and the film thickness unevenness still occurred. In addition, it was also found that the adverse effect on the retardation development performance caused by the film thickness unevenness caused by the above mechanism is not sufficiently mitigated by the addition of a retardation developer as described in Patent Document 2. is there.

  The cellulose acylate film used as a retardation film is also required to have high transparency, and in improving the film, a means that does not deteriorate the physical properties such as internal haze, and preferably can improve such physical properties is developed. It is requested to do.

  Accordingly, the present invention provides a means capable of minimizing the occurrence of film thickness unevenness while ensuring high transparency in a cellulose acylate film composed of an ultra-low-substituted cellulose acylate. Objective.

  The present inventor has conducted extensive research in view of the above-described object. As a result, the content of the alkaline earth metal in the film made of ultra-low-substituted cellulose acylate is controlled to a predetermined value or less, and a film made of high-substituted cellulose acylate is formed on both sides of the film. It has been found that the above problem can be solved by laminating with a thickness to form a laminated film, and the present invention has been completed.

  That is, the above object of the present invention is achieved by the following configuration.

1. A cellulose acylate having an acyl group substitution degree DS of 1.0 ≦ DS <2.0 (hereinafter also referred to as “low substitution cellulose acylate”), and an alkaline earth metal content of less than 30 ppm by mass A core layer,
A cellulose acylate having an acyl group substitution degree DS of 2.7 ≦ DS ≦ 3.0 (hereinafter, also referred to as “high substitution cellulose acylate”) disposed on both surfaces of the core layer; A surface layer having a smaller thickness than the layer;
I have a,
The following formula (1) and the following formula (2):
(In the formula, nx represents the refractive index in the slow axis direction in the film plane, ny represents the refractive index in the fast axis direction in the film plane, nz represents the refractive index in the film thickness direction, and d represents the film. The refractive index is measured at a wavelength of 590 nm under an environment of 23 ° C. and 55% RH)
And Ro and Rth respectively represented by
A laminated cellulose acylate film satisfying
2. 1. A value (T _S / T _C ) of a ratio of the thickness (T _S ) of the surface layer to the thickness (T _C ) of the core layer is 0.001 to 0.15. A laminated cellulose acylate film according to claim 1;
3. 1. The thickness (T _C ) of the core layer is 20 to 80 μm, and the thickness (T _S ) of the surface layer is 10 μm or less. Or 2. A laminated cellulose acylate film according to claim 1;
4). 2. The thickness (T _C ) of the core layer is 40 to 60 μm, and the thickness (T _S ) of the surface layer is 0.02 to 2 μm. A laminated cellulose acylate film according to claim 1;

5. It is a manufacturing method of the lamination cellulose acylate film given in any 1 paragraph of the above-mentioned 1-4,
Cellulose acylate having an acyl group substitution degree DS of 1.0 ≦ DS <2.0 (low substitution degree cellulose acylate) and an organic solvent, and the content of alkaline earth metal in the solid content is less than 30 ppm by mass Preparing a dope A, and a dope B containing cellulose acylate having a degree of acyl substitution DS of 2.7 ≦ DS ≦ 3.0 (highly substituted cellulose acylate);
Forming the web by co-casting the dope A and the dope B on a support so that the dope A becomes a core layer and the dope B becomes a surface layer;
Evaporating the organic solvent until the web is peelable from the support, and then peeling the web from the support;
A process for producing a laminated cellulose acylate film comprising:
6 . Above 1. ~ 4 . 4. The laminated cellulose acylate film according to any one of 5) or 5 above. A polarizing plate formed by laminating a laminated cellulose acylate film obtained by the production method described in the above and at least one surface of a polarizer; and
7 . 6. above. A liquid crystal display device comprising the polarizing plate described in 1.

  In the cellulose acylate film constituted using the ultra-low-substituted cellulose acylate, a means capable of minimizing the occurrence of film thickness unevenness while ensuring high transparency can be provided.

1 shows an example of an apparatus for producing a laminated cellulose acylate film according to the present invention. It is the figure which showed an example of sectional drawing of the co-casting die used for manufacture of the laminated cellulose acylate film which concerns on this invention.

  Hereinafter, embodiments of the present invention will be described in detail.

One embodiment of the present invention includes a cellulose acylate having an acyl group substitution degree DS of 1.0 ≦ DS <2.0 (low substitution degree cellulose acylate) and an alkaline earth metal content of less than 30 ppm by mass. A core layer,
Surfaces including cellulose acylate (highly substituted cellulose acylate) having an acyl group substitution degree of 2.7 ≦ DS ≦ 3.0, disposed on both surfaces of the core layer, and having a thickness smaller than that of the core layer Layers,
Is a laminated cellulose acylate film.

<Core layer>
The laminated cellulose acylate film according to one embodiment of the present invention has a “core layer” at the center in the thickness direction. This “core layer” is a main member that contributes to the retardation development performance of the laminated cellulose acylate film according to this embodiment.

(Low substituted cellulose acylate)
The core layer includes cellulose acylate having an acyl group substitution degree DS of 1.0 ≦ DS <2.0 (low substitution degree cellulose acylate). By adopting cellulose acylate having a low acyl group substitution degree in the core layer as described above, high retardation development is exhibited, and even when a retardation film having a high retardation is obtained, a thin film can be formed. Even when a high phase difference is developed, the stretch ratio can be kept low, and failures such as breakage can be avoided.

  Here, the cellulose molecule consists of many glucose units connected, and the glucose unit has three hydroxyl groups. The number of acyl groups derived from these three hydroxyl groups is called the degree of substitution. For example, diacetylcellulose (DAC) has an acetyl group bonded to an average of 2 to 2.5 of the three hydroxyl groups of the glucose unit.

  Examples of the cellulose acylate used in the present invention include esters of carboxylic acids having about 2 to 22 carbon atoms, and may be esters of aromatic carboxylic acids, but are particularly preferably lower fatty acid esters of cellulose. The lower fatty acid in the lower fatty acid ester of cellulose means a fatty acid having 6 or less carbon atoms. The acyl group bonded to the hydroxyl group may be linear or branched or may form a ring. Furthermore, another substituent may be substituted. When the degree of substitution is the same, birefringence decreases when the number of carbon atoms is large, and therefore, it is preferably selected from acyl groups having 2 to 6 carbon atoms. The acyl group preferably has 2 to 4 carbon atoms, more preferably 2 to 3 carbon atoms.

  For example, cellulose acetate, cellulose propionate, cellulose butyrate and the like, cellulose acetate propio as described in JP-A Nos. 10-45804, 8-231761, US Pat. No. 2,319,052, etc. It is preferable to use mixed fatty acid esters such as nate, cellulose acetate butyrate, and cellulose acetate phthalate.

  The acyl group substitution degree of cellulose acylate can be measured in accordance with ASTM D-817-91, and the preferred acyl group substitution degree of the low substitution cellulose acetate is 1.7 to 1.9. It is.

  When the acyl group substitution degree of the low-substituted cellulose acylate contained in the core layer is less than 1.0, deterioration of film surface quality due to increase in dope viscosity, haze-up due to increase in stretching tension, etc. may occur. is there. Moreover, when the acyl group substitution degree is 2.0 or more, it is difficult to obtain a necessary phase difference, and there is a possibility that sufficient interfacial adhesion with a surface layer described later may not be ensured. The core layer may contain a cellulose acylate other than the low-substituted cellulose acylate and a polymer other than the cellulose acylate as long as the retardation development performance is not affected. However, from the viewpoint of exhibiting sufficient retardation development performance, the content of the low-substituted cellulose acylate with respect to 100% by mass of the total amount of the core layer is preferably 40% by mass or more, more preferably 50% by mass. Or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more.

  The number average molecular weight (Mn) of the cellulose acylate is preferable because the mechanical strength of the film from which a range of 30000 to 300000 is obtained is strong. Furthermore, the thing of 50000-150,000 is used preferably.

  The ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the cellulose acylate is preferably 1.4 to 3.0. In addition, the value measured using a gel permeation chromatography (GPC) shall be employ | adopted as a value of the number average molecular weight (Mn) and weight average molecular weight (Mw) of a cellulose acylate. At this time, the measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three products manufactured by Showa Denko KK)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) Mw = 100000 to 500 calibration curves with 13 samples are used. Thirteen samples are used at approximately equal intervals.

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

  Cellulose as a raw material for cellulose acylate is not particularly limited, and examples thereof include cotton linter, wood pulp (derived from coniferous tree, derived from broadleaf tree), kenaf and the like. Moreover, you may mix and use the cellulose acylate obtained from them in arbitrary ratios, respectively.

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

There is no particular limitation on the thickness of the core layer (T _C), the value of retardation with the film, the relationship between the phase difference which is required when used as a retardation film can be set appropriately. As an example, the thickness (T _C ) of the core layer is preferably about 20 to 80 μm, more preferably 40 to 60 μm.

(Alkaline earth metal content)
In the present invention, the content of alkaline earth metals (calcium (Ca), strontium (Sr), barium (Ba)) in the core layer is defined. Specifically, the content of alkaline earth metal in the core layer is less than 30 ppm by mass. The content of the alkaline earth metal in the core layer is preferably less than 20 ppm by mass, more preferably less than 10 ppm by mass, and particularly preferably less than 5 ppm by mass. In addition, as a content of the alkaline earth metal in the core layer, a value measured using an atomic absorption analyzer is adopted as described in Examples described later. When the core layer includes a plurality of alkaline earth metals, the “alkaline earth metal content” means the total value of the contents of the plurality of alkaline earth metals included in the core layer. When the alkaline earth metal content in the core layer is within the above-mentioned range, it is possible to prevent the occurrence of lateral steps during the production of the film, and to provide a laminated cellulose acylate film excellent in surface coatability and optical characteristics. There is an advantage of being. Further, there is an advantage that an increase in internal haze is suppressed and a film having excellent transparency can be provided.

<Surface layer>
The laminated cellulose acylate film according to one embodiment of the present invention has “surface layers” on both surfaces of the “core layer” located in the center in the thickness direction.

(Highly substituted cellulose acylate)
The surface layer includes cellulose acylate having an acyl group substitution degree DS of 2.7 ≦ DS ≦ 3.0 (high substitution cellulose acylate). By adopting cellulose acylate having a large acyl group substitution degree in the surface layer as described above, a laminated cellulose acylate film having a uniform film thickness can be provided. One reason for this is thought to be a reduction in the rigidity of the web peeled off from the support during the production of the film and the resulting occurrence of film thickness unevenness.

  The specific form of the acyl group constituting the highly substituted cellulose acylate, the number average molecular weight of the cellulose acylate, the value of Mw / Mn, the method for preparing the cellulose acylate, the method for measuring the degree of substitution, etc. Since it is as having mentioned above about the low substitution degree cellulose acylate, detailed description is abbreviate | omitted here.

When the degree of acyl group substitution of the highly substituted cellulose acylate contained in the surface layer is less than 2.7, the above-described effect (ie, uniform film thickness) is sufficiently obtained by providing the surface layer. It may not be possible. On the other hand, the upper limit 3.0 of the acyl substitution degree of the highly substituted cellulose acylate is a theoretical upper limit. The surface layer may contain a cellulose acylate other than the highly substituted cellulose acylate and a polymer other than the cellulose acylate as long as the above-described effects are not affected. However, from the viewpoint of sufficiently exerting the above effects, the content of the highly substituted cellulose acylate with respect to the total amount of the surface layer of 100% by mass is preferably 40% by mass or more, more preferably 50% by mass or more. More preferably, it is 60% by mass or more, and particularly preferably 70% by mass or more.
In addition, the surface layer is disposed on both surfaces of the core layer, but the form and content of the highly substituted cellulose acylate in each surface layer may be the same or different from each other. .

There is no particular limitation on the thickness of the surface layer (T _S), the value of retardation with the film, the relationship between the phase difference which is required when used as a retardation film can be set appropriately. However, as described above, since the core layer mainly contributes to the retardation development performance and the surface layer hardly contributes to this, in the laminated cellulose acylate film according to this embodiment, the thickness of the surface layer (T It is essential that _{S 1} ) is smaller than the thickness (T _C ) of the core layer. As an example, the thickness (T _S ) of the surface layer (one side) is preferably about 10 μm or less, more preferably 0.02 to 2 μm. Moreover, the value (T _S / T _C ) of the ratio of the thickness (T _S ) of the surface layer to the thickness (T _C ) of the core layer is preferably 0.001 to 0.15, more preferably 0.005. It is -0.1, Most preferably, it is 0.01-0.03. If the value of this ratio is 0.001 or more, the function and effect obtained by providing the surface layer can be sufficiently exhibited. On the other hand, if the value of this ratio is 0.15 or less, the retardation development performance as the whole laminated cellulose acylate film is sufficiently ensured. In addition, the thickness (T _S ) of each surface layer located on both surfaces of the core layer may be the same or different.

<Additives>
The core layer and the surface layer may contain various additives in addition to the above-described cellulose acylate. Hereinafter, typical additives that can be contained in the core layer and the surface layer will be described, but the present invention is not limited to the following forms.

(Tg lowering agent)
The core layer and / or the surface layer may contain a Tg reducing agent. Thus, when the laminated cellulose acylate film contains a Tg reducing agent, the glass transition temperature (Tg) of the cellulose acylate having hard and brittle properties is lowered, and the workability and mechanical properties can be improved. As a result, the cellulose acylate film has a high retardation value despite being a thin film, suppresses an increase in internal haze even when stretched at a high magnification, reduces retardation unevenness, and suppresses an increase in haze even in a humid heat environment. Can be provided.

  The “Tg lowering agent” used in the present invention means an additive in which the value of the glass transition temperature (Tg) of “cellulose acylate” alone, which does not contain it, decreases by adding it. Any substance may be used as the “Tg lowering agent” as long as such a definition is satisfied.

  The Tg lowering ability of the Tg lowering agent is not particularly limited, but is preferably 3.5 ° C./part by mass or more, more preferably 3.8 ° C./part by mass or more, and further preferably 4.0. ° C / part by mass or more. When the Tg reducing ability of the Tg reducing agent is within such a range, an excellent Tg reducing effect can be exhibited even with a small addition amount. For this reason, it is possible to prevent the occurrence of problems such as bleed out that occurs when a large amount of additive must be added. On the other hand, the upper limit of the Tg lowering ability of the Tg lowering agent is not particularly limited, but is actually about 5.0 ° C./part by mass or less. Here, “Tg reducing ability” means the ability to reduce Tg per unit mass of a certain substance. And in this specification, Tg reduction ability of a certain substance is defined by following Numerical formula (3).

In the formula, X represents Tg of a film obtained by independently forming the cellulose acylate constituting the cellulose acylate film, and Y represents 5 parts by mass of a substance with respect to 100 parts by mass of the cellulose acylate. The Tg of the film obtained by forming the film in the same manner after the addition is represented.

  Here, the value measured by the differential scanning calorimetry (DSC) shall be adopted as the Tg value of the film containing cellulose ester.

  The specific form of the Tg reducing agent used in the present invention is not particularly limited as long as the definition of the Tg reducing agent described above (and preferably the preferable range of the Tg reducing ability described above) is satisfied. As an example of the Tg lowering agent, the following general formula (I):

The polyester compound represented by these is mentioned.

  In the general formula (I), B represents a linear or branched alkylene group or cycloalkylene group having 2 to 6 carbon atoms, and A represents an aromatic ring having 6 to 14 carbon atoms, or 2 to 6 carbon atoms. A linear or branched alkylene group or a cycloalkylene group is represented, X represents a monocarboxylic acid residue containing a hydrogen atom or an aromatic ring having 6 to 14 carbon atoms, and n represents a natural number of 1 or more.

  The polyester compound represented by the general formula (I) includes an aromatic ring (6 to 14 carbon atoms), a dicarboxylic acid having a linear or branched alkylene group or a cycloalkylene group (both having 2 to 6 carbon atoms), and a carbon number. It is an alternating copolymer obtained by alternating copolymerization with 2-6 linear or branched alkylene diols or cycloalkylene diols. The aromatic dicarboxylic acid and the dicarboxylic acid having a linear or branched alkylene group or cycloalkylene group may be used alone or as a mixture, but from the viewpoint of compatibility with cellulose acylate. It is preferable that at least 10% or more of the aromatic dicarboxylic acid is contained. Moreover, you may seal both ends with the monocarboxylic acid which has an aromatic ring (C6-C14).

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

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

  Examples of the linear or branched alkylene diol or cycloalkylene diol having 2 to 6 carbon atoms include ethanediol (ethylene glycol), 1,2-propanediol, 1,3-propanediol, 1,2- Butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6- Examples include hexanediol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol. Among these, ethanediol (ethylene glycol), 1,2-propanediol, 1,3-propanediol, and 1,3-butanediol are preferable.

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

  Examples of the monocarboxylic acid having an aromatic ring (having 6 to 14 carbon atoms) that seals both ends of the polyester compound include benzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, p-tert-butylbenzoic acid, and dimethylbenzoic acid. Examples include acids and paramethoxybenzoic acid. Of these, benzoic acid, p-toluic acid, and p-tert-butylbenzoic acid are preferred.

  Aromatic polyester compounds can be prepared by the conventional methods, such as the above-mentioned hot-melt condensation method by the polyesterification reaction or transesterification reaction between the dicarboxylic acid and alkylene diol or cycloalkylene diol, or the interfacial condensation method between acid chlorides of these acids and glycols. It can be easily synthesized by either method. Furthermore, by adding the above-described aromatic monocarboxylic acid, a polyester compound in which both ends are sealed can be synthesized.

  Below, the aromatic polyester compound which can be used in this invention is illustrated.

  As described above, the aromatic polyester compound represented by the general formula (I) has been described in detail as a specific example of the Tg reducing agent, but other Tg reducing agents may be used as a matter of course.

  In the cellulose acylate film according to one embodiment of the present invention, only one Tg reducing agent may be used alone, or two or more Tg reducing agents may be used in combination. Further, there is no particular limitation on the amount of the Tg-lowering agent added in the laminated cellulose acylate film according to one embodiment of the present invention, but it is preferably based on 100% by mass of the cellulose acylate contained in the entire laminated cellulose acylate film. It is 1-5 mass%, More preferably, it is 1.5-3.5 mass%. If the addition amount of the Tg reducing agent is 1% by mass or more, the Tg reducing performance which is the original purpose of the Tg reducing agent can be sufficiently exhibited. On the other hand, if the addition amount of the Tg reducing agent is 5% by mass or less, the retardation development performance of the laminated cellulose acylate film accompanying the increase in the addition amount of the T reducing agent can be prevented.

(Hydrolysis inhibitor)
The core layer and / or the surface layer may contain a hydrolysis inhibitor. Thus, since the hydrolysis of a cellulose acylate is prevented because a laminated cellulose acylate film contains a hydrolysis inhibitor, the water resistance of the film can be improved. In addition, the film surface is saponified at the time of bonding with a polarizer when constituting a polarizing plate, but hydrolysis of cellulose acylate during the saponification treatment and accompanying elution into an alkaline saponification solution are also possible. Can be prevented.

  “Hydrolysis inhibitor” that can be used in the present invention means an additive in which the hydrolysis resistance of “cellulose acylate” alone, which does not contain it, is lowered by the addition thereof. Any substance may be used as the “hydrolysis inhibitor” as long as the definition is satisfied. As an index of hydrolysis resistance of cellulose acylate (film) for determining whether a substance is included in the concept of “hydrolysis inhibitor”, the weight loss rate before and after saponification is used. Can be used. Specifically, for example, the film is immersed in a 2.0 M KOH aqueous solution at 50 ° C. for 90 seconds, and the rate of change in the weight of the film before and after that is calculated (in the alkaline solution, cellulose acylate is hydrolyzed, To dissolve in the chemical). The weight reduction rate of a film formed only with cellulose acylate is A%, and the weight reduction rate of a film added with 5 parts by weight of the additive with respect to 100 parts by weight of cellulose acylate is B%. When | B | is satisfied, it can be determined that the additive is a “hydrolysis inhibitor” for cellulose acylate.

  Although there is no restriction | limiting in particular about the hydrolysis inhibitory ability of a hydrolysis inhibitor, The regulation | regulation by an average logP value is effective as a hydrophobic parameter | index of a hydrolysis inhibitor. That is, it can be said that the higher the average log P value, the better the performance as a hydrolysis inhibitor.

  Here, the “log P value” is also referred to as “octanol-water partition coefficient” or “log Pow”, and is a value of the ratio of the distribution concentration of a substance to each phase of a two-phase solvent system composed of n-octanol and water. Defined as the common logarithm of The “average log P value” is taken into consideration when the hydrolysis inhibitor is used as a mixture of a plurality of compounds. In such a case, the “average log P value” constitutes the mixture. The specific log P value of each compound is first calculated and then calculated by weighting with the mixing ratio (mass ratio) of each compound in the mixture. In the present specification, the value of the logP value can be measured by a flask shaking method described in JIS Z-7260-107: 2000. Further, the logP value can be estimated by a computational chemical method or an empirical method instead of the actual measurement.

  As a calculation method, Crippen's fragmentation method ("J. Chem. Inf. Comput. Sci.", 27, p21 (1987)), Viswanadhan's fragmentation method ("J. Chem. Inf. Comput. Sci."). , 29, p163 (1989)), Broto's fragmentation method (“Eur. J. Med. Chem.-Chim. Theor.”, 19, p71 (1984)), CLogP method (references) Leo, A., Jow, PYC, Silipo, C., Hansch, C., J. Med. Chem., 18, 865 1975) and the like are preferably used, but the Crippen's fragmentation method ( “J.Chem Inf.Comput.Sci. ", 27, p21 (1987)). However, when the measurement value by the flask shaking method mentioned above and the value estimated by the calculation chemical method or the empirical method are significantly different, the measurement value by the flask shaking method has priority.

  The log P value of the hydrolysis inhibitor used in the present invention is preferably 7.5 or more, more preferably 8.0 or more, still more preferably 9.0 or more, and particularly preferably 9.5 or more. It is. If the log P value of the hydrolysis inhibitor is within such a range, an excellent hydrolysis prevention effect can be exhibited even with a small addition amount. For this reason, it is possible to prevent the occurrence of problems such as bleed out that occurs when a large amount of additive must be added. On the other hand, the upper limit value of the log P value of the hydrolysis inhibitor is not particularly limited, but it is usually preferably about 13.0 or less from the viewpoint of compatibility with cellulose acylate.

  The specific form of the hydrolysis inhibitor that can be used in the present invention is not particularly limited as long as it satisfies the definition of the hydrolysis inhibitor described above (and preferably the preferred range of the log P value described above). As an example of the hydrolysis inhibitor, the following general formula (II):

The sugar ester compound represented by these is mentioned.

In the general formula (II), G represents a monosaccharide or disaccharide residue, R ² represents an aliphatic group or an aromatic group, and m is directly bonded to the monosaccharide or disaccharide residue. 1 is the total number of — (O—C (═O) —R ² ) groups directly bonded to the monosaccharide or disaccharide residue, and 3 ≦ m + l ≦ 8 and l ≠ 0.

The compound having the structure represented by the general formula (II) is a single kind of compound in which the number of hydroxyl groups (m) and the number of-(O—C (═O) —R ² ) groups (1) are fixed. It is difficult to isolate, and it is known that a compound in which several different components of m and l in the formula are mixed is obtained. Therefore, the performance as a mixture in which the number of hydroxyl groups (m) and the number of-(O—C (═O) —R ² ) groups (1) are important is important, and the laminated cellulose acylate film of the present invention In this case, a compound having a structure represented by the general formula (II) with respect to haze characteristics and a mixing ratio of the component m = 0 and the component m> 0 is 45:55 to 0: 100 is preferable. More preferably, in terms of performance and cost, the mixing ratio of the component m = 0 and the component m> 0 is in the range of 10:90 to 0.1: 99.9. In addition, the component of said m = 0 and the component of m> 0 can be measured by a high performance liquid chromatography by a conventional method.

  In the general formula (II), G represents a monosaccharide or disaccharide residue. Specific examples of monosaccharides include allose, altrose, glucose, mannose, gulose, idose, galactose, talose, ribose, arabinose, xylose, lyxose, and the like.

  Although the structural example of the compound which has a monosaccharide residue represented by general formula (II) below is shown, this invention is not limited to these specific examples.

  Specific examples of the disaccharide include trehalose, sucrose, maltose, cellobiose, gentiobiose, lactose, and isotrehalose.

  Although the structural example of the compound which has a disaccharide residue represented by general formula (II) below is shown, this invention is not limited to these specific examples.

In the general formula (II), R ² represents an aliphatic group or an aromatic group. Here, the aliphatic group and the aromatic group may each independently have a substituent.

In the general formula (II), m is the total number of hydroxyl groups directly bonded to the monosaccharide or disaccharide residue, and l is directly bonded to the monosaccharide or disaccharide residue. The total number of — (O—C (═O) —R ² ) groups. And it is necessary that 3 ≦ m + 1 ≦ 8, and it is preferable that 4 ≦ m + 1 ≦ 8. Also, l ≠ 0. In addition, when l is 2 or more, the — (O—C (═O) —R ² ) groups may be the same or different.

The aliphatic group in the definition of R ² may be linear, branched or cyclic, and preferably has 1 to 25 carbon atoms, more preferably 1 to 20 carbon atoms. Those of ˜15 are particularly preferred. Specific examples of the aliphatic group include, for example, methyl, ethyl, n-propyl, iso-propyl, cyclopropyl, n-butyl, iso-butyl, tert-butyl, amyl, iso-amyl, tert-amyl, n- Examples include hexyl, cyclohexyl, n-heptyl, n-octyl, bicyclooctyl, adamantyl, n-decyl, tert-octyl, dodecyl, hexadecyl, octadecyl, didecyl and the like.

The aromatic group in the definition of R ² may be an aromatic hydrocarbon group or an aromatic heterocyclic group, and more preferably an aromatic hydrocarbon group. The aromatic hydrocarbon group preferably has 6 to 24 carbon atoms, and more preferably 6 to 12 carbon atoms. Specific examples of the aromatic hydrocarbon group include benzene, naphthalene, anthracene, biphenyl, terphenyl and the like. As the aromatic hydrocarbon group, benzene, naphthalene, and biphenyl are particularly preferable. As the aromatic heterocyclic group, those containing at least one of an oxygen atom, a nitrogen atom or a sulfur atom are preferable. Specific examples of the heterocyclic ring include, for example, furan, pyrrole, thiophene, imidazole, pyrazole, pyridine, pyrazine, pyridazine, triazole, triazine, indole, indazole, purine, thiazoline, thiadiazole, oxazoline, oxazole, oxadiazole, quinoline, Examples include isoquinoline, phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline, pteridine, acridine, phenanthroline, phenazine, tetrazole, benzimidazole, benzoxazole, benzthiazole, benzotriazole, and tetrazaindene. As the aromatic heterocyclic group, pyridine, triazine, and quinoline are particularly preferable.

  Next, although the preferable example of a compound represented by general formula (II) is shown below, this invention is not limited to these specific examples.

  (Synthesis Example: Synthesis Example of Compound Represented by General Formula (II))

Four-headed Kolben equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen gas inlet tube was charged with 34.2 g (0.1 mol) of sucrose, 180.8 g (0.8 mol) of benzoic anhydride, 379. 7 g (4.8 mol) was charged, the temperature was raised while bubbling nitrogen gas from a nitrogen gas introduction tube with stirring, and an esterification reaction was carried out at 70 ° C. for 5 hours. Next, the inside of the Kolben was depressurized to 4 × 10 ² Pa or less, and after excess pyridine was distilled off at 60 ° C., the inside of the Kolben was depressurized to 1.3 × 10 Pa or less and the temperature was raised to 120 ° C. Most of the acid and benzoic acid formed were distilled off. Then, 1 L of toluene and 300 g of a 0.5% by mass aqueous sodium carbonate solution were added, and the mixture was stirred at 50 ° C. for 30 minutes and then allowed to stand to separate a toluene layer. Finally, 100 g of water is added to the collected toluene layer, and after washing with water at room temperature for 30 minutes, the toluene layer is separated, and toluene is distilled off at 60 ° C. under reduced pressure (4 × 10 ² Pa or less). A mixture of A-1, A-2, A-3, A-4 and A-5 was obtained. When the obtained mixture was analyzed by HPLC and LC-MASS, A-1 was 7% by mass, A-2 was 58% by mass, A-3 was 23% by mass, A-4 was 9% by mass, A-5. Was 3% by mass. A part of the obtained mixture was purified by silica gel column chromatography to obtain A-1, A-2, A-3, A-4 and A-5 having a purity of 100%, respectively.

(Plasticizer)
In order to obtain the effects of the present invention, the laminated cellulose acylate film of the present invention contains a plasticizer other than the compounds represented by the general formula (I) and the general formula (II) described above, if necessary. Also good.

  The specific form of such a plasticizer is not particularly limited, but preferably a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a fatty acid ester plasticizer, and a polyhydric alcohol. It is selected from ester plasticizers, ester plasticizers, acrylic plasticizers and the like. Of these, when two or more plasticizers are used, at least one of them is preferably a polyhydric alcohol ester plasticizer.

  The polyhydric alcohol ester plasticizer is a plasticizer comprising a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid ester, and preferably has an aromatic ring or a cycloalkyl ring in the molecule. Preferably it is a 2-20 valent aliphatic polyhydric alcohol ester.

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

In the formula, R ₁₁ represents an n-valent organic group, n represents a positive integer of 2 or more, and the OH group represents an alcoholic and / or phenolic hydroxyl group.

  Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these.

  Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane- Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol and the like. In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

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

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

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

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanoic acid, undecylic acid, lauric acid, tridecylic acid, Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, laccelic acid, undecylenic acid, olein Examples thereof include unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which 1 to 3 alkoxy groups such as an alkyl group, a methoxy group or an ethoxy group are introduced into the benzene ring of benzoic acid such as benzoic acid or toluic acid, biphenylcarboxylic acid, Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as naphthalenecarboxylic acid and tetralincarboxylic acid, or derivatives thereof. Benzoic acid is particularly preferable.

  The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably 300 to 1500, and more preferably 350 to 750. A higher molecular weight is preferable because it is less likely to volatilize, and a lower molecular weight is preferable in terms of moisture permeability and compatibility with cellulose acylate.

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

  Below, the specific compound of a polyhydric alcohol ester is illustrated.

  The glycolate plasticizer is not particularly limited, but alkylphthalylalkyl glycolates can be preferably used.

  Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl Glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl glycol Butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl phthalate Ethyl glycolate, and the like.

  Examples of the phthalate ester plasticizer include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, and dicyclohexyl terephthalate.

  Examples of the citrate plasticizer include acetyl trimethyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate.

  Examples of fatty acid ester plasticizers include butyl oleate, methylacetyl ricinoleate, and dibutyl sebacate.

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

  The polyvalent carboxylic acid ester compound is composed of an ester of divalent or higher, preferably divalent to 20 valent polyvalent carboxylic acid and alcohol. The aliphatic polyvalent carboxylic acid is preferably 2 to 20 valent, and in the case of an aromatic polyvalent carboxylic acid or an alicyclic polyvalent carboxylic acid, it is preferably 3 to 20 valent.

  The polyvalent carboxylic acid is represented by the following general formula (b).

In the formula, R ₁₂ represents an (m1 + n1) -valent organic group, m1 represents a positive integer of 2 or more, n1 represents an integer of 0 or more, a COOH group represents a carboxy group, an OH group is alcoholic and / Or represents a phenolic hydroxyl group.

  Examples of preferred polyvalent carboxylic acids include the following, but the present invention is not limited to these.

  Trivalent or higher aromatic polyvalent carboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid or derivatives thereof, succinic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid, fumaric acid, maleic acid, tetrahydrophthal An aliphatic polyvalent carboxylic acid such as an acid, an oxypolyvalent carboxylic acid such as tartaric acid, tartronic acid, malic acid and citric acid can be preferably used. In particular, it is preferable to use an oxypolycarboxylic acid from the viewpoint of improving retention.

  There is no restriction | limiting in particular as alcohol used for the polyhydric carboxylic acid ester compound which can be used for this invention, Well-known alcohol and phenols can be used.

  For example, an aliphatic saturated alcohol or aliphatic unsaturated alcohol having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

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

  When an oxypolycarboxylic acid is used as the polycarboxylic acid, the alcoholic or phenolic hydroxyl group of the oxypolycarboxylic acid may be esterified with a monocarboxylic acid. Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecylic acid, Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid, undecylenic acid, olein Examples thereof include unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. The aromatic monocarboxylic acid which has, or those derivatives can be mentioned. Particularly preferred are acetic acid, propionic acid, and benzoic acid.

  Although there is no restriction | limiting in particular in the molecular weight of a polyhydric carboxylic acid ester compound, It is preferable that it is the range of molecular weight 300-1000, and it is more preferable that it is the range of 350-750. The larger one is preferable in terms of improvement in retention, and the smaller one is preferable in terms of moisture permeability and compatibility with cellulose acylate.

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

  The acid value of the polyvalent carboxylic acid ester compound that can be used in the present invention is preferably 1 mgKOH / g or less, and more preferably 0.2 mgKOH / g or less. Setting the acid value in the above range is preferable because the environmental fluctuation of retardation is also suppressed.

  In addition, an acid value means the milligram number of potassium hydroxide required in order to neutralize the acid (carboxyl group which exists in a sample) contained in 1g of samples. As the acid value, a value measured in accordance with JIS K0070 is adopted.

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

  For example, triethyl citrate, tributyl citrate, acetyl triethyl citrate (ATEC), acetyl tributyl citrate (ATBC), benzoyl tributyl citrate, acetyl triphenyl citrate, acetyl tribenzyl citrate, dibutyl tartrate, diacetyl dibutyl tartrate, Examples include tributyl trimellitic acid and tetrabutyl pyromellitic acid.

(UV absorber)
The laminated cellulose acylate film of the present invention can also contain an ultraviolet absorber. The ultraviolet absorber is intended to improve durability by absorbing ultraviolet light having a wavelength of 400 nm or less. In particular, the transmittance at a wavelength of 370 nm is preferably 10% or less, more preferably 5% or less, Preferably it is 2% or less.

  Although the ultraviolet absorber used in the present invention is not particularly limited, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex compounds, inorganic powders Examples include the body.

  For example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -2H-benzotriazole, (2-2H-benzotriazol-2-yl) -6- (linear and side Chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc., and tinuvin 109, tinuvin 171, tinuvin 234, tinuvin 326, tinuvin 327, tinuvin 328, etc. These are commercially available products from Ciba Japan and can be preferably used.

  The UV absorbers preferably used in the present invention are benzotriazole UV absorbers, benzophenone UV absorbers, and triazine UV absorbers, particularly preferably benzotriazole UV absorbers and benzophenone UV absorbers. .

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

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

  The method of adding the UV absorber can be added to the dope after dissolving the UV absorber in an alcohol such as methanol, ethanol or butanol, an organic solvent such as methylene chloride, methyl acetate, acetone or dioxolane or a mixed solvent thereof. Or you may add directly in dope composition.

  For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and cellulose acylate to disperse and then added to the dope.

  The amount of the UV absorber used is not uniform depending on the type of UV absorber, the operating conditions, and the like, but when the dry film thickness of the laminated cellulose acylate film is 30 to 200 μm, the amount of the UV absorber is about 0. 5-10 mass% is preferable and 0.6-4 mass% is further more preferable.

(Antioxidant)
Antioxidants are also referred to as deterioration inhibitors. When a liquid crystal image display device or the like is placed in a high humidity and high temperature state, the laminated cellulose acylate film may be deteriorated.

  The antioxidant has a role of delaying or preventing the decomposition of the laminated cellulose acylate film due to, for example, halogen in the residual solvent amount in the laminated cellulose acylate film or phosphoric acid of the phosphoric acid plasticizer. The laminated cellulose acylate film is preferably contained in the laminated cellulose acylate film.

  As such an antioxidant, a hindered phenol compound is preferably used. For example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di- -T-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino)- 1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octa Sil-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxy Benzyl) -isocyanurate and the like.

  In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di- A phosphorus processing stabilizer such as t-butylphenyl) phosphite may be used in combination.

  The amount of these compounds added is preferably 1 ppm to 1.0%, more preferably 10 to 1000 ppm in terms of mass ratio with respect to the cellulose derivative.

(Acid scavenger)
Since cellulose acylate is accelerated by acid at high temperatures, it is preferable to contain an acid scavenger when used in the laminated cellulose acylate film of the present invention.

  Any useful acid scavenger can be used without limitation as long as it is a compound that reacts with an acid to inactivate the acid. Among them, the epoxy group described in US Pat. No. 4,137,201 is particularly useful. A compound having is preferred. Epoxy compounds as such acid scavengers are known in the art and are derived by condensation of various polyglycol diglycidyl ethers, particularly about 8-40 moles of ethylene oxide per mole of polyglycol. Glycol, diglycidyl ether of glycerol, metal epoxy compounds (such as those conventionally used in and together with vinyl chloride polymer compositions), epoxidized ether condensation products, diphenols of bisphenol A Glycidyl ether (i.e., 4,4'-dihydroxydiphenyldimethylmethane), epoxidized unsaturated fatty acid ester (especially an ester of an alkyl of about 4 to 2 carbon atoms of a fatty acid of 2 to 22 carbon atoms (e.g. butyl Epoxy stearate And epoxidized vegetable oils and other unsaturated natural oils (sometimes these are epoxidized natural glycerides, which can be represented and exemplified by compositions of various epoxidized long chain fatty acid triglycerides and the like (eg epoxidized soybean oil and the like) Or unsaturated fatty acids, which generally contain 12 to 22 carbon atoms). Moreover, EPON 815C can also be preferably used as a commercially available epoxy group-containing epoxide resin compound.

  Furthermore, as an acid scavenger that can be used in addition to the above, an oxetane compound, an oxazoline compound, an organic acid salt of an alkaline earth metal, an acetylacetonate complex, or paragraphs 68 to 105 of JP-A-5-194788 Is included.

  In addition, although an acid scavenger may be called an acid scavenger, an acid capture agent, an acid catcher, etc., in this invention, it can use without a difference by these names.

(Fine particles)
The laminated cellulose acylate film of the present invention has, for example, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, It is preferable to contain matting agents such as inorganic fine particles such as aluminum oxide, magnesium silicate, and calcium phosphate, and a crosslinked polymer. Of these, silicon dioxide is preferable because it can reduce the haze of the film.

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

  These fine particles preferably form secondary particles having a particle diameter of 0.1 to 5 μm and are contained in the laminated cellulose acylate film, and the preferable average particle diameter is 0.1 to 2 μm, and more preferably 0.8. 2 to 0.6 μm. Thereby, the unevenness | corrugation about 0.1-1.0 micrometer high can be formed in the film surface, and this can give appropriate slipperiness to the film surface.

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

<Method for producing laminated cellulose acylate film>
According to the other form of this invention, the manufacturing method of a laminated cellulose acylate film is also provided. That is, the method for producing a laminated cellulose acylate film according to this embodiment includes a low-substituted cellulose acylate having an acyl group substitution degree DS of 1.0 ≦ DS <2.0 and an organic solvent, and an alkaline earth in a solid content. A step of preparing a dope A having a metal group content of less than 30 ppm by mass, and a dope B containing a highly substituted cellulose acylate having an acyl group substitution degree DS of 2.7 ≦ DS ≦ 3.0;
Forming the web by co-casting the dope A and the dope B on a support so that the dope A becomes a core layer and the dope B becomes a surface layer;
Evaporating the organic solvent until the web is peelable from the support, and then peeling the web from the support;
Is a method for producing a laminated cellulose acylate film.

(Preparation of dope)
First, a cellulose acylate and an organic solvent are dissolved in a dissolution vessel while stirring to form a dope. The dissolution method is not particularly limited, and various methods such as a method performed at normal pressure, a method performed below the boiling point of the main solvent, a method performed under pressure above the boiling point of the main solvent, a method performed using the cooling dissolution method, a method performed at high pressure, etc. A dissolution method can be employed.

  In the manufacturing method of this embodiment, at least two types of dopes A and B are prepared. The dope A includes a low-substituted cellulose acylate having an acyl group substitution degree DS of 1.0 ≦ DS <2.0 and an organic solvent. And content of the alkaline-earth metal in solid content contained in dope A shall be less than 30 mass ppm. On the other hand, the dope B includes a highly substituted cellulose acylate having an acyl group substitution degree DS of 2.7 ≦ DS ≦ 3.0.

  The dope A is for constituting the core layer, and the dope B is for constituting the surface layer. The dope formulation which comprises both surfaces may be the same as a film structure like B / A / B, for example, dope formula of both surfaces may differ like B / A / C.

  When an additive is added to the dope A and / or dope B, as an addition method, the additive or additive may be added between the dissolving kettle and the co-casting die. The dissolved or dispersed solution may be added to the dope being fed. In the latter case, it is preferable to provide a mixing means such as a static mixer in order to improve the mixing property.

Since the cellulose acylate may contain impurities such as non-acetate, it is preferable to filter the dope with a filter medium after dissolving the cellulose acylate in an organic solvent as described above. For example, it can be carried out by passing the dope from a coarse filter to a fine filter using a filter press type filtration device. The filtration operation may be repeated by circulating the dope. As the filter paper to be used, for example, No. made by Azumi filter paper is used. 142451, no. 244, no. A laminate of 260 grades of filter paper is preferred. The filtration flow rate is preferable because it slowly prevents the passage of gel or the like. Usually, it is preferably 5 L / m ² or less per minute. A smaller filtration pressure is preferable because it prevents passage of gel and the like. Usually, 2 MPa or less is preferable. A metal fiber type leaf disk type filter can also be preferably used. Examples thereof include NF-06D2 and NF12N manufactured by Nippon Seisen. A filter press and a leaf disk type filter may be used in combination.

  The filtered dope is sent to a dope tank, left to stand and degassed by a conventional method. For example, the dope can be degassed by standing at a temperature of 30 ° C. to the boiling point of the solvent for several hours.

  Moreover, there is no restriction | limiting in particular also about the specific method for making content of the alkaline-earth metal in solid content of dope A less than 30 mass ppm. As an example, the dope A may be prepared by dissolving cellulose acylate having a reduced alkaline earth metal content in an organic solvent. As described above, as a technique for reducing the content of the alkaline earth metal contained in the cellulose acylate itself before the dope preparation, for example, cellulose acetate and an acid having a specific acid dissociation index pKa or a metal salt thereof are mixed. And a technique of treating cellulose acetate with a specific acid or a metal salt thereof.

(Casting process)
FIG. 1 shows an example of an apparatus for producing a laminated cellulose acylate film according to the present invention. Moreover, FIG. 2 is the figure which showed an example of sectional drawing of the co-casting die used for manufacture of the laminated cellulose acylate film which concerns on this invention.

  In the dope tank 1, the dope A and the dope B are prepared so as to correspond to the core layer and the surface layer, respectively. If necessary, an additive solution for dope A and an additive solution for dope B containing additives are prepared in additive solution tank 2. The additive liquid containing fine particles is prepared in the fine particle tank 15. The fine particles may be mixed in an additive solution containing an additive. When the fine particles are added to only one of the two surface layers, the liquid feed pump for the additive liquid containing the fine particles to which no fine particles are added may be stopped.

  The dope A and dope B are fed to the co-casting die 5 by the metering pump 3. The additive solution for dope A and the additive solution for dope B are joined to the dope A and dope B by the metering pump 3 and mixed uniformly by the respective static mixers 4. Further, the additive liquid containing fine particles is joined to the dope B by the metering pump 3 and uniformly mixed by the static mixer 4.

  The dope A containing a predetermined amount of additive passes through the slit 22, and the dope B containing a predetermined amount of additive or fine particles passes through the slit 23 and is layered in the co-casting die 5 and continuously moves. It is cast into a sheet on the casting belt 7. The cast three-layer dope film is evaporated from the casting belt 7 by the peeling roll 8 until the organic solvent is evaporated until the belt can be peeled once.

  As the support for casting, an endless metal belt that moves indefinitely or a rotating metal drum (hereinafter also simply referred to as “support”) can be used. The surface of the casting support is preferably a mirror surface. Both end portions (portions that do not become products) when the casting film is grounded are preferably roughened to facilitate peeling of the dope film from the support. The co-casting die 5 is not limited as long as it is a structure capable of co-casting. For example, a coat hanger die or a T die can be preferably used. A multi-manifold type die or a feed block type die may be used.

  To heat the web (the dope film after casting the dope on the casting support) on the casting support and evaporate the solvent until the web can be peeled from the support, There are a method of spraying and / or a method of transferring heat from the back surface of the support by a liquid, a method of transferring heat from the front and back by radiant heat, and the like, but the back surface liquid heat transfer method is preferable from the viewpoint of drying efficiency. A method of combining them is also preferable.

  Next, the web on which the solvent has evaporated on the support is peeled off from the support. However, if the residual solvent amount of the web at the time of peeling is too large, it may be difficult to peel off. On the other hand, if the film is sufficiently dried on the support and then peeled off, a part of the web may be peeled off.

  As a method for increasing the film forming speed (the film forming speed can be increased because the film is peeled off while the amount of residual solvent is as large as possible), there is a gel casting method (gel casting) capable of peeling even if the amount of residual solvent is large. As this method, there are a method of adding a poor solvent for cellulose acylate into the dope and casting the dope and then gelling, a method of reducing the temperature of the support and gelling. There is also a method of adding a metal salt in the dope. By gelling on the support and strengthening the film, peeling can be accelerated and the film forming speed can be increased. When peeling at a time when the amount of residual solvent is higher, if the web is too soft, the flatness at the time of peeling will be lost, or slippage and vertical stripes will easily occur due to peeling tension, and at the time of peeling due to the balance between economic speed and quality The amount of residual solvent is determined.

  Although there is no restriction | limiting in particular about the web temperature at the time of peeling a web from a support body, Preferably it is 10-40 degreeC, More preferably, it is 11-30 degreeC. Moreover, it is preferable to peel the web when the residual solvent amount of the web at the peeling position is 10 to 120% by mass. In order to set the residual solvent amount at the time of peeling of the web within this range, there is a method of controlling the surface temperature of the support after casting so that the organic solvent can be efficiently evaporated from the web. It can be preferably used. In order to control the support temperature, it is preferable to use a heat transfer method with good heat transfer efficiency. For example, a back surface heat transfer method using a liquid is preferable. In the belt (support) machine, the belt temperature can be adjusted with a gentle wind for temperature control at the point where the belt to be transferred comes to the lower side. The temperature of the support can be partially changed by dividing the heating means, and can be set to different temperatures such as a casting position, a drying part, and a peeling position of the casting support.

(Dry)
The web peeled from the support as described above is dried by the dryer 9 until a desired residual solvent amount is obtained, if necessary. The drying method can be carried out, for example, using a drying device that alternately conveys the web through rolls arranged in a staggered manner or a tenter device that clips and conveys both ends of the web with a clip. These may be used in combination.

  As a drying means, hot air is generally blown on both sides of the web, but there is also a means of heating by applying microwaves instead of wind. Excessive drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed from a residual solvent of about 8% by mass or less. Throughout, the drying temperature is usually 40 to 250 ° C, preferably 70 to 180 ° C. The drying temperature, the amount of drying air, and the drying time differ depending on the solvent used, and the drying conditions may be appropriately selected according to the type and combination of the solvents used.

  In the drying step after peeling from the casting support surface, the web tends to shrink in the width direction due to evaporation of the solvent. Shrinkage increases as the drying temperature increases rapidly. Drying while suppressing this shrinkage as much as possible is preferable for improving the flatness of the finished film. From this point of view, for example, a method of drying the whole drying process or a part of the process as shown in Japanese Patent Application Laid-Open No. 62-46625 while holding the both ends of the web with a width in the width direction (tenter method) ) Is preferred. Thereafter, if necessary, both width ends of the web are cut off by the slitter 17 and introduced into the stretching step.

(Stretching)
Next, the obtained film is stretched by the stretching machine 10 in at least one axial direction, preferably 1.1 times to 3.0 times, more preferably 1.1 to 2.0 times. If the stretch ratio is too small, retardation as a retardation film may be insufficient, and if the stretch ratio is too large, the film may become cloudy.

  By setting the amount of residual solvent in the film at the time of stretching in the range of 3 to 50% by mass, the occurrence of delamination phenomenon can be prevented and a retardation film excellent in transparency can be obtained. The stretching direction may be a longitudinal direction (casting direction) or a transverse direction (a direction perpendicular to the casting direction, also referred to as a width direction).

  The stretching temperature can be stretched without heating to a high temperature, but it is preferable to combine drying and stretching because the process can be shortened. However, when the stretching temperature is too high, the plasticizer is volatilized, and therefore a range of room temperature (15 ° C.) to 140 ° C. is preferable. In addition, when extending | stretching and drying are used like this case, it is preferable that the amount of residual solvents in the time of completion | finish of extending | stretching exists in the range of 5-45 mass%, and the range of 10-30 mass% is more preferable.

  There is no particular limitation on the stretching method, but a transverse stretching machine called a tenter can be preferably used. In this method, both ends of the web are fixed with clips and pins, and the gap between the clips and pins is extended in the horizontal direction and stretched in the horizontal direction. Stretching or shrinking in the longitudinal direction can be performed by widening or shrinking the interval in the transport direction of the clip or pin in the transport direction (longitudinal direction) using a simultaneous biaxial stretching machine. Driving the clip portion by the linear drive method is preferable because it can be smoothly stretched and the risk of breakage and the like can be reduced.

  Moreover, as a method of extending | stretching to a vertical direction, the method of giving a circumferential speed difference to several rolls, and extending | stretching to a vertical direction using a roll circumferential speed difference among them can also be used.

  These stretching methods may be used in combination, or the stretching process may be performed in two or more stages, such as longitudinal stretching, lateral stretching, longitudinal stretching or longitudinal stretching, longitudinal stretching.

  Further, the obtained film may be stretched 1.1 times to 3.0 times in at least one axial direction as follows. That is, it is a method of extending | stretching by extending | stretching temperature for 140-200 degreeC. In this case, the amount of residual solvent in the film during stretching is preferably 10% by mass or less, particularly preferably 3% by mass or less, and most preferably 2% by mass or less.

  By setting the conditions at the time of stretching in the above range, a retardation film excellent in transparency that does not cause delamination between layers can be obtained. The stretching direction may be a longitudinal direction (casting direction) or a transverse direction (a direction perpendicular to the casting direction, also referred to as a width direction). As the stretching method, the above-described method is preferably used.

(Take-up)
The retardation film 13 obtained as described above is slit to a predetermined width by the slitter 17 and wound into a roll using the winder 12. The amount of residual solvent in the film during winding is preferably 2% by mass or less, more preferably 0.4% by mass or less. A film with good dimensional stability can be obtained by reducing the amount of residual solvent in the film. When the amount of residual solvent in the film after stretching is too much than the desired range, it is preferable to provide drying 11 before rewinding before the winding process. At the time of winding, embossing (sometimes referred to as knurling) is preferably performed on both ends by the embossing ring 18 and the back roll 19. The height of the emboss (the difference in thickness between the inner part of the emboss and the embossed part) is preferably 5 to 30 μm. If it is too low, the film surfaces may be in close contact with each other and the film may be deformed. If it is too high, film deformation near the emboss may occur. These film deformations become defects during post-processing such as coating. As the embossing method, for example, a known method performed on a thermoplastic resin film such as a polyester film can be preferably used. In particular, it is preferable that embossing is performed only on one surface without deforming the back surface of the film. As such an embossing method, an embossing ring heated near the melting point of the resin constituting the film (in the case of an amorphous resin, near the softening temperature) is used as a back roll 19 having a surface of metal, rubber, ceramic or the like. The processing method of pressing on the film surface is preferable.

  As a winding method, a generally used method may be used, and there are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, and the like.

  In the present specification, the residual solvent amount is represented by the following mathematical formula (4).

In the formula, M is the mass of the web at any point, and N is the mass when the web is dried at 110 ° C. for 3 hours.

  When manufacturing a retardation film, for example, a cut-off portion at both ends before stretching, a cut-off portion of a clip gripping portion after lateral stretching, a cut-off portion to a product width, a defect occurrence portion of a retardation film, etc. cannot be used as a product. . These are pulverized and can be used again as cellulose acylate as a production raw material.

<Physical properties of laminated cellulose acylate film>
The total film thickness of the laminated cellulose acylate film provided by the present invention is preferably a thin film, a range of 10 to 200 μm is used, preferably 10 to 100 μm, more preferably 10 to 60 μm. And particularly preferably 20 to 60 μm.

  A laminated cellulose acylate film having a width of 1 to 4 m is used. In particular, those having a width of 1.4 to 4 m are preferably used, and particularly preferably 1.6 to 3 m. If it exceeds 4 m, there is a possibility that the conveyance becomes difficult.

  The laminated cellulose acylate film has different retardations depending on the required optical compensation effect, but from the viewpoint of taking advantage of high retardation development, the following formulas (1) and (2):

In the formula, nx represents the refractive index in the slow axis direction in the film plane, ny represents the refractive index in the fast axis direction in the film plane, nz represents the refractive index in the film thickness direction, and d represents the film thickness. Represents thickness (nm); refractive index measured at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH)
And Ro and Rth respectively represented by

Is preferably satisfied. Here, Ro is preferably 120 to 160. The measurement of Ro and Rth was performed by cutting a 35 mm × 35 mm sample from the obtained film, adjusting the humidity at 25 ° C. × 55% RH for 2 hours, and measuring 590 nm with an automatic birefringence meter (KOBRA21DH, Oji Scientific Co., Ltd.). It can be calculated from the extrapolated value of the retardation value measured in the same manner while tilting the film surface and the value measured from the vertical direction.

  When the slow axis or the fast axis of the laminated cellulose acylate film exists in the film plane, and θ1 is an angle formed with the film forming direction, θ1 is preferably −1 ° or more and + 1 ° or less, and −0. More preferably, it is 5 ° or more and + 0.5 ° or less.

  This θ1 can be defined as an orientation angle, and the measurement of θ1 can be performed using an automatic birefringence meter KOBRA-WR (Oji Scientific Instruments). Each of θ1 satisfying the above relationship can contribute to obtaining high luminance in a display image, suppressing or preventing light leakage, and contributing to obtaining faithful color reproduction in a color liquid crystal display device.

The moisture permeability of the laminated cellulose acylate film, 40 ° C., preferably 300~1800g ^/ m 2 · 24h at 90% RH, preferably more ^{400~1500g / m 2 · 24h, 40~1300g} / m 2 · 24h is particularly preferable. The moisture permeability can be measured according to the method described in JIS Z0208.

  The breaking elongation of the laminated cellulose acylate film is preferably 10 to 80%, more preferably 20 to 50%. Further, the visible light transmittance of the laminated cellulose acylate film is preferably 90% or more, and more preferably 93% or more. Furthermore, the haze of the laminated cellulose acylate film is preferably less than 1%, particularly preferably 0 to 0.1%.

<Polarizing plate>
The laminated cellulose acylate film provided by the present invention can be used as a polarizing plate and a liquid crystal display device using the same as an optical compensation film (retardation film).

  The polarizing plate provided by still another embodiment of the present invention is a polarizing plate in which the laminated cellulose acylate film provided by the present invention is bonded to at least one surface of a polarizer.

  A polarizer, which is a main component of a polarizing plate, is an element that allows only light of a plane of polarization in a certain direction to pass. A typical polarizer currently known is a polyvinyl alcohol-based polarizing film, which includes polyvinyl alcohol. There are a film in which iodine is dyed on an alcohol film and a film in which a dichroic dye is dyed.

  The polarizer may be formed by forming a polyvinyl alcohol aqueous solution into a film and dyeing it by uniaxial stretching or dyeing and then uniaxially stretching, and then preferably performing a durability treatment with a boron compound. The film thickness of the polarizer is preferably 5 to 30 μm, particularly preferably 10 to 20 μm.

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

  The polarizing plate can be produced by a general method. For example, a completely saponified polyvinyl alcohol aqueous solution is used on at least one surface of a polarizer prepared by subjecting the laminated cellulose acylate film according to the present invention to alkali saponification treatment and immersion drawing in an iodine solution. It is preferable to stick them together. In addition, when the laminated cellulose acylate film contains a hydrolysis inhibitor, hydrolysis of cellulose acylate is prevented, and as a result, alkali saponification of cellulose acylate during saponification treatment at the time of bonding with a polarizer is performed. There is an advantage that elution into the crystallization solution can be prevented.

  In addition, the laminated cellulose acylate film which concerns on this invention may be used for the other surface of the polarizer which comprises a polarizing plate, and it is also preferable to paste another optical film. Examples of such other optical films include commercially available cellulose ester films (for example, Konica Minoltak KC8UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UY, KC4UE, KC8UE, KC8UY-HA, HC8X, -RHA-C, KC8UXW-RHA-NC, KC4UXW-RHA-NC, manufactured by Konica Minolta Opto Co., Ltd.) are preferably used.

  Bonding of the polarizer, the laminated cellulose acylate film according to the present invention and, if necessary, another optical film is usually performed using an adhesive. Examples of the adhesive that can be used in this case include a PVA-based adhesive and a urethane-based adhesive. Among them, a PVA-based adhesive is preferably used.

  In addition to the antiglare layer or the clear hard coat layer, the viewing side protective film of the polarizing plate used on the surface side of the display device preferably has an antireflection layer, an antistatic layer, an antifouling layer, and a backcoat layer.

<Liquid crystal display device>
The polarizing plate provided by the said form can be used for a liquid crystal display device. Since the liquid crystal display device according to this embodiment uses the laminated cellulose acylate film having an excellent optical compensation function provided by the present invention, the liquid crystal display device has excellent visibility.

  There are no particular restrictions on the mode (driving method) of the liquid crystal display device, and liquid crystal display devices in various modes (driving methods) such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS, and OCB can be used. . A VA (MVA, PVA) type liquid crystal display device is preferable. By using the laminated cellulose acylate film provided by the present invention for these liquid crystal display devices, there are few environmental fluctuations even in a large-screen liquid crystal display device with a size of 30 type or more, color unevenness, front contrast, etc. A liquid crystal display device excellent in visibility can be obtained.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

≪Evaluation method≫
Various measurements and evaluations in the examples were performed by the following methods.

<Measurement of alkaline earth metal content>
The content of alkaline earth metal in the core layer of the produced laminated cellulose acylate film was measured using an atomic absorption spectrometer.

<Evaluation of horizontal stage when belt is peeled>
When the web was peeled from the support (belt), the web was visually checked for the presence of lateral steps and evaluated according to the following criteria:
○ = No horizontal row occurred;
X = A horizontal stage occurred.

<Coating adhesion>
The coating adhesion of the exposed surface of the surface layer of the produced laminated cellulose acylate film was measured according to JIS K 5600. Specifically, a grid of 100 squares in 1 mm square is put, and a continuous peel test is performed 5 times using an industrial 24 mm cello tape (registered trademark) manufactured by Nichiban Co., Ltd., and the number of remaining squares is measured. The adhesion was evaluated by measuring the degree of adhesion based on the following criteria.

The evaluation criteria are as follows:
○ = Adhesion 90% or more;
Δ: Adhesion degree is less than 90%.

<Thickness unevenness>
The film thickness unevenness of the entire laminated cellulose acylate film produced was evaluated by the following method. That is, the thickness of 100 points in the longitudinal direction and 50 points in the width direction are measured with respect to the sample film. The maximum thickness, the minimum thickness, and the average thickness were obtained from these 150 points, and the difference between the maximum thickness and the minimum thickness was defined as film thickness unevenness. The evaluation criteria are as follows:
○ = Thickness unevenness is less than 2.0 μm;
X = Thickness unevenness is 2.0 μm or more.

<Interfacial adhesion>
The adhesion of the interface between the core layer and the surface layer of the produced laminated cellulose acylate film was evaluated by the following method. That is, under the conditions of 23 ° C. and 20% RH, scratches were made in a grid pattern on the surface of the film at intervals of 1 mm with a single blade, and a cellophane tape was applied, and then peeled off in a vertical direction. A peel test was performed. The evaluation criteria are as follows:
◎ = No peeling;
○ = With less than 10% peeling of the mesh;
X = 10% or more peeling of the mesh.

<Transparency (Haze%)>
Transparency was evaluated by measuring film haze according to JIS-K6714.

Example 1
<Preparation of laminated cellulose acylate film 1>
First, as dope A, 100 parts by mass of cellulose acetate having an acetyl group substitution degree of 1.7 and a number average molecular weight of 150,000, 300 parts by mass of methylene chloride, and 26 parts by mass of ethanol are put into a pressure sealed container and heated to 80 ° C. Then, the inner pressure of the container was set to 2 atm, and the cellulose ester was completely dissolved while stirring to obtain a dope. The solution was Azumi Filter Paper No. 1 manufactured by Azumi Filter Paper Co., Ltd. After filtering using 244, the dope was lowered to 35 ° C. and allowed to stand overnight to degas the dope.

  On the other hand, as dope B, 100 parts by mass of cellulose acetate having a substitution degree of acetyl group of 2.7 and a number average molecular weight of 150,000, 400 parts by mass of methylene chloride, and 80 parts by mass of ethanol were put into a pressure sealed container and heated to 80 ° C. Then, the inner pressure of the container was set to 2 atm, and the cellulose ester was completely dissolved while stirring to obtain a dope. The solution was Azumi Filter Paper No. After filtering using 244, the dope was lowered to 35 ° C. and allowed to stand overnight to degas the dope.

  The dope A and the dope B prepared above were cast on a stainless steel belt from the co-casting die 5 shown in FIG. After contacting with hot water from the back of the stainless steel belt and drying on a stainless steel belt controlled at 35 ° C. for 1 minute, the back of the stainless steel belt was further contacted with cold water of 15 ° C. and held for 10 seconds, and then the stainless steel belt. The dried film was peeled off. In addition, 60 degreeC warm air was flowed in parallel with the conveyance direction from the surface of the stainless steel belt. The amount of residual solvent in the film at the time of peeling was 100% by mass.

  Next, the peeled film was conveyed while being wound around a roll and dried at 60 ° C., and the amount of residual solvent in the film immediately before the tenter was 30% by mass. Next, the film was stretched 1.5 times in the transverse direction (width direction) at 100 ° C. while holding both ends with a tenter clip. Next, it was dried while being conveyed at 120 ° C. for 10 minutes while maintaining the width. At this time, the tenter clip width was adjusted so that the film width contracted by 3%. Furthermore, it dried at 110 degreeC, making it roll convey, and obtained the cellulose-ester film of 1 micrometer of each surface layer, core layer 38 micrometers, and a total film thickness of 40 micrometers. The final film residual solvent amount was 0.2% by mass.

  Various evaluation results for the obtained laminated cellulose acylate film 1 are shown in Table 1 below.

<Preparation of laminated cellulose acylate films 2-14>
Acyl group substitution degree of cellulose acylate (core layer cellulose acylate) contained in dope A and cellulose acylate (surface layer cellulose acylate) contained in dope B, alkaline earth metal content in dope A, and surface The thickness of the layer (single layer) and the core layer (surface layer / core layer) was changed by the same method as described above except that the thickness ratio (surface layer / core layer) was changed as shown in Table 1 below. Rate films 2 to 14 were produced.

  Various evaluation results for the obtained laminated cellulose acylate films 2 to 14 are shown in Table 1 below.

  As a result of the evaluation, the film 4 resulted in a horizontal step due to the high alkaline earth metal content in the core layer. Moreover, in the film 12, it became a result inferior to interface adhesiveness. This is presumably because the hydrogen bondability between celluloses decreased due to the large acyl substitution degree of cellulose acylate contained in the core layer. Furthermore, the film 13 composed of only a single layer of cellulose acylate having a very low degree of substitution required a large peeling force at the time of peeling. As a result, sufficient satisfactory results were not obtained. Moreover, in the film 14 comprised from the single layer only of the highly substituted cellulose acylate, sufficient in-plane phase difference did not express.

  On the other hand, it was confirmed that the laminated cellulose acylate film provided by the present invention is excellent in various physical properties.

1 Dope tank,
2 Additive tank
3 metering pump,
4 Static mixer,
5 Co-casting dies,
6 drums,
7 Casting belt,
8 peeling roll,
9, 11 dryer,
10 Stretching machine,
12 Winder,
13 retardation film,
14 Dancer roll,
15 fine particle tank,
16 vacuum chamber,
17 Slitter,
18 Embossing ring,
19 Backroll,
21 Casting outlet,
22, 23 Slit.

Claims (7)

A core layer containing cellulose acylate having an acyl group substitution degree of 1.0 ≦ DS <2.0, and an alkaline earth metal content of less than 30 ppm by mass;
A surface layer disposed on both surfaces of the core layer, the cellulose acylate having an acyl substitution degree DS of 2.7 ≦ DS ≦ 3.0, and having a thickness smaller than that of the core layer;
I have a,
The following formula (1) and the following formula (2):
(In the formula, nx represents the refractive index in the slow axis direction in the film plane, ny represents the refractive index in the fast axis direction in the film plane, nz represents the refractive index in the film thickness direction, and d represents the film. The refractive index is measured at a wavelength of 590 nm under an environment of 23 ° C. and 55% RH)
And Ro and Rth respectively represented by
A laminated cellulose acylate film that satisfies the above requirements. 2. The laminated cellulose according to claim 1, wherein a value (T _S / T _C ) of a ratio of the thickness (T _S ) of the surface layer to the thickness (T _C ) of the core layer is 0.001 to 0.15. Acylate film. The thickness of the core layer (T _C ) Is 20 to 80 μm, and the thickness of the surface layer (T _S ) Is 10 μm or less. The laminated cellulose acylate film according to claim 1 or 2. The thickness of the core layer (T _C ) Is 40 to 60 μm, and the thickness of the surface layer (T _S 4) The laminated cellulose acylate film according to claim 3, wherein 0.02 to 2 μm. A method for producing a laminated cellulose acylate film according to any one of claims 1 to 4,
Dope A containing a cellulose acylate having an acyl group substitution degree DS of 1.0 ≦ DS <2.0 and an organic solvent, and an alkaline earth metal content in a solid content of less than 30 ppm by mass, and an acyl group Preparing a dope B containing cellulose acylate having a substitution degree DS of 2.7 ≦ DS ≦ 3.0;
Forming the web by co-casting the dope A and the dope B on a support so that the dope A becomes a core layer and the dope B becomes a surface layer;
Evaporating the organic solvent until the web is peelable from the support, and then peeling the web from the support;
A method for producing a laminated cellulose acylate film, comprising: The laminated cellulose acylate film according to any one of claims 1 to 4 or the laminated cellulose acylate film obtained by the production method according to claim 5 and at least one surface of a polarizer are bonded together. A polarizing plate. A liquid crystal display device comprising the polarizing plate according to claim 6 .