JP2012234094A - Cellulose acylate film, polarizing plate and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cellulose acylate film developing desired optical properties, showing inverse dispersion and giving good frontal contrast and changes in the hue depending on a viewing angle when the film is assembled in a liquid crystal display device.SOLUTION: The cellulose acylate film comprises cellulose acylate and a short wavelength maximum absorption compound having an absorption maximum λmax at 180 to 250 nm, in which an average of the total substitution degree of all cellulose acylates included in the film is 2.7 to 3.0. The film satisfies the following expressions: 40 nm≤Re(550)≤80 nm; 100 nm≤Rth(550)≤250 nm; 1 nm≤ΔRe(λ)≤30 nm; ΔRe(λ)=Re(630)-Re(440). In the expressions, Re(550) represents a retardation in a plane direction at a wavelength of 550 nm; Rth(550) represents a retardation in a film thickness direction at a wavelength of 550 nm; Re(630) represents a retardation in the plane direction at a wavelength of 630 nm; and Re(440) represents a retardation in the plane direction at a wavelength of 440 nm.

Description

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

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

  However, when the VA mode liquid crystal display device displays black, a black image can be displayed to a certain degree in the normal direction of the liquid crystal display screen, but is displayed black from the viewing angle direction (diagonal direction) of the liquid crystal display screen. , There is a problem that the viewing angle becomes narrow because light leakage occurs and the background cannot be displayed in black. Therefore, there has been a demand for a retardation film that exhibits retardation to such an extent that viewing angle compensation can be performed. As such a retardation film, a film obtained by adding a specific additive to a cellulose acylate film widely used as a polarizing plate protective film is preferably used. Specifically, it has been found that a retardation film for compensating the viewing angle of a VA mode liquid crystal display device requires high Re and high Rth (in the vicinity of 50 nm and 120 nm, respectively), and the total substitution degree. In order to develop such a high retardation using a cellulose acylate (so-called triacetyl acetate etc.) film having a high viscosity, a 1,3,5-triazine-based additive having a high maximum wavelength λmax is added to the cellulose acylate layer. Added films have been known (see, for example, Patent Document 1). Patent Document 2 discloses a cellulose triacetate film having an acetyl substitution degree of 2.9 in which a 1,3,5-triazine compound substituted with a substituent having a specific structure is added as an additive having a high maximum wavelength λmax. It is described that a high retardation can be expressed with a small amount of the additive described in Document 1 and the like, and the front contrast when incorporated in a liquid crystal display device can be improved.

On the other hand, in recent years, in order to improve the yellow tint in the halftone of the liquid crystal display screen, multi-gap (MG) cells in which the thickness of the liquid crystal layer, that is, the cell gap is changed for each color, have been used. ing. However, the multi-gap cell has a larger color change when viewing black in the viewing angle direction than conventional liquid crystal display screens, and there is an increasing need to improve the blackness change in the viewing angle direction of the liquid crystal display screen. Yes.
In addition, there is still a need for further improvement in the display performance of liquid crystal display devices and reduction in manufacturing cost, and even when the film thickness is thin, the viewing angle can be sufficiently compensated, and an inexpensive phase difference that can further increase the contrast. There is a need for films.
In order to satisfy these requirements, it is possible to use a retardation film having reverse dispersion (reverse wavelength dispersion), that is, a retardation film having an optical characteristic that the retardation Re in the in-plane direction increases as the wavelength becomes longer. It is known to be effective as a method of improving the blackness change in the viewing angle direction of the display screen (see Patent Document 3).

Here, additives that have a high λmax and are advantageous for high retardation tend to reduce reverse dispersibility. Conversely, additives that have a low λmax and are advantageous for developing reverse dispersibility reduce the expression of retardation. It has been found that there is a tendency to let them. Therefore, it is possible to improve both the color change in the viewing angle direction by using an additive having a low λmax, which is advantageous for the development of reverse dispersion, and to develop a desired phase difference suitable for a VA mode liquid crystal display device. Was a very important and difficult task. In addition, the reverse dispersion film examined so far, such as the film of patent document 3, was manufactured mainly using the additive with negative intrinsic birefringence together with the resin film.
Patent Document 4 is known as an example of imparting reverse dispersion using an additive other than an additive having negative intrinsic birefringence. In this document, a cellulose acylate layer having a low substitution degree is used as a core layer, and a cellulose acylate laminated film having a cellulose acylate layer having a high substitution degree provided on both sides thereof is used to incorporate it into a liquid crystal display device. It describes that front contrast and color change can be improved.

JP 2003-344655 A International Publication WO2010 / 146891 JP 2009-1696 A US Publication No. 2010-0271574A1

The present inventors examined the film described in Patent Document 2 by incorporating it in a liquid crystal display device, and as a result, dissatisfaction remains from the viewpoint of reverse dispersion, and the color change due to the viewing angle when incorporated in the liquid crystal display device. Was unsatisfactory. Moreover, it was found that the front contrast at that time remained unsatisfactory.
When the present inventors examined the film described in Patent Document 3, the reverse dispersibility is small and the color change due to the viewing angle when incorporated in a liquid crystal display device has not been controlled to a level that is practically required in recent years. Furthermore, it was found that the front contrast was unsatisfactory.
In addition, when the present inventors examined the film described in Patent Document 4 by incorporating it in a liquid crystal display device, the document discloses that the front contrast is high and the change in color depending on the viewing angle is small. It was found that dissatisfaction remained from the level that was given.

  The problem to be solved by the present invention is a cellulose acylate film having a desired optical expression, reverse dispersion, and favorable front contrast and viewing angle color change when incorporated in a liquid crystal display device. Is to provide.

Based on the above problems, as a result of intensive studies by the present inventors, the addition of a compound having a short maximum wavelength λmax to the cellulose acylate having a high total substitution degree has a desired optical expression, In addition, it was found that a cellulose acylate film having reverse dispersion and good front contrast and viewing angle color change when incorporated in a liquid crystal display device can be produced.
That is, the present inventors have found that the above problem can be solved by a cellulose acylate film having a specific total substitution degree range and a cellulose acylate film containing an additive having a specific maximum wavelength λmax. The present invention has been completed.
Specifically, the above problem has been solved by the following means.

[1] A cellulose acylate and a short maximum absorption compound having an absorption maximum λmax of 180 to 250 nm are contained, and the average total substitution degree of all cellulose acylates contained in the film is 2.7 to 3.0. The cellulose acylate film characterized by satisfying the following formula (1), formula (2) and formula (3).
Formula (1) 40nm <= Re (550) <= 80nm
(In formula (1), Re (550) represents in-plane retardation at a wavelength of 550 nm.)
Formula (2) 100 nm ≦ Rth (550) ≦ 250 nm
(In Formula (2), Rth (550) represents retardation in the film thickness direction at a wavelength of 550 nm.)
Formula (3) 1 nm ≦ ΔRe (λ) ≦ 30 nm
Formula (4) ΔRe (λ) = Re (630) −Re (440)
(In formulas (3) and (4), Re (630) represents in-plane retardation at a wavelength of 630 nm, and Re (440) represents in-plane retardation at a wavelength of 440 nm.)
[2] The cellulose acylate film as described in [1], wherein the short maximum absorption compound is a layered compound.
[3] The cellulose acylate film according to [1], wherein the short maximum absorption compound is an inorganic layered compound.
[4] The cellulose acylate film according to any one of [1] to [3], wherein the following formula (5) is satisfied.
Formula (5) 5 nm ≦ ΔRe (λ) ≦ 30 nm
Formula (4) ΔRe (λ) = Re (630) −Re (440)
(In formulas (4) and (5), Re (630) represents in-plane retardation at a wavelength of 630 nm, and Re (440) represents in-plane retardation at a wavelength of 440 nm.)
[5] The cellulose acylate film according to any one of [1] to [4], wherein the cellulose acylate is cellulose acetate.
[6] The average total substitution degree of all cellulose acylates contained in the film is 2.75 to 2.85, according to any one of [1] to [5], Cellulose acylate film.
[7] The cellulose acylate film according to any one of [1] to [6], which contains at least 1 to 7 parts by mass of a nitrogen-containing compound with respect to the cellulose acylate.
[8] The cellulose acylate film according to any one of [1] to [7], wherein the absorption maximum λmax of all the optical developing agents contained in the film is 180 to 250 nm.
[9] The cellulose acylate film according to any one of [1] to [8], wherein the short maximum absorption compound is contained in a layer mainly composed of cellulose acylate.
[10] Any one of [1] to [9], wherein the short maximum absorption compound is contained in a layer mainly composed of cellulose acylate having a total substitution degree of 2.7 to 3.0. The cellulose acylate film according to item.
[11] The thickness of the layer containing the short maximum absorption compound and mainly composed of cellulose acylate having a total substitution degree of 2.7 to 3.0 is 50% or more of the total film thickness. The cellulose acylate film according to [10].
[12] Any one of [1] to [11], wherein the cellulose acylate contained in the film is only one type of cellulose acylate having a total substitution degree of 2.7 to 3.0. The cellulose acylate film described in 1.
[13] The cellulose acylate film according to any one of [1] to [12], which is a single layer.
[14] A polarizing plate having a polarizer and the cellulose acylate film according to any one of [1] to [13] on at least one side of the polarizer.
[15] A liquid crystal display device comprising at least one polarizing plate according to [14].

  According to the present invention, there is provided a cellulose acylate film which has desired optical development properties, is reversely dispersed, and has a good front contrast and good viewing angle color change when incorporated in a liquid crystal display device. Can do.

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

  Hereinafter, the contents of the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value. In this specification, “front side” means the display surface side, and “rear side” means the backlight side. In this specification, “front” means a normal direction to the display surface, and “front contrast (hereinafter, contrast is also referred to as CR)” means white luminance measured in the normal direction of the display surface and The contrast calculated from the black luminance is assumed.

[Cellulose acylate film]
The cellulose acylate film of the present invention (hereinafter also referred to as the film of the present invention) contains cellulose acylate and a short maximum absorption compound having an absorption maximum λmax of 180 to 250 nm, and all the cellulose acylates contained in the film The average total substitution degree is 2.7 to 3.0, and satisfies the following formula.
Formula (1) 40nm <= Re (550) <= 80nm
(In formula (1), Re (550) represents in-plane retardation at a wavelength of 550 nm.)
Formula (2) 100 nm ≦ Rth (550) ≦ 250 nm
(In Formula (2), Rth (550) represents retardation in the film thickness direction at a wavelength of 550 nm.)
Formula (3) 1 nm ≦ ΔRe (λ) ≦ 30 nm
Formula (4) ΔRe (λ) = Re (630) −Re (440)
(In formulas (3) and (4), Re (630) represents in-plane retardation at a wavelength of 630 nm, and Re (440) represents in-plane retardation at a wavelength of 440 nm.)
Hereinafter, the film of the present invention will be described.

<Cellulose acylate>
The film of this invention contains a cellulose acylate, and the average of the total substitution degree of all the cellulose acylates contained in a film is 2.7-3.0. Hereinafter, the cellulose acylate used in the present invention will be described.

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

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

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

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

The film of the present invention has an average total substitution degree of all cellulose acylates contained in the film of 2.7 to 3.0, and a cellulose acylate having a total substitution degree of 2.7 to 3.0. It is preferable to include. The average total degree of substitution of all the cellulose acylates contained in the film is preferably 2.75 to 2.9, and more preferably 2.70 to 2.9.
Here, the average of the total substitution degree of all the cellulose acylates contained in the film is the abundance ratio (mass ratio) of the cellulose acylate of each total substitution degree when plural kinds of cellulose acylates are contained in the film. Can be obtained by multiplying
Moreover, the average of the total substitution degree of all the cellulose acylates contained in a film means the average of the total substitution degree of the cellulose acylate contained in the layer, when the film of this invention is a single layer film. On the other hand, when the film of the present invention is a laminated film of two or more layers, the average total substitution degree of all cellulose acylates contained in the film is the total substitution of cellulose acylates contained in all layers. Mean average degree. In the case of a laminated film, the cellulose acylate is obtained by calculating the content of cellulose acylate in each layer from the solid content concentration of each layer, and determining the mass of the cellulose acylate in each layer by multiplying the content concentration and the film thickness of each layer. The abundance ratio (mass ratio) can be determined.
The cellulose acylate contained in the film of the present invention is preferably only one cellulose acylate having a total substitution degree of 2.7 to 3.0, and one total substitution degree of 2.75 to 2. More preferably, it is only cellulose acylate of 85, and particularly preferably only cellulose acylate having one total substitution degree of 2.75 to 2.83.
In addition, the substitution degree of an acyl group can be measured according to the method prescribed | regulated to ASTM-D817-96. The portion not substituted with an acyl group usually exists as a hydroxyl group.

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

  In the acylation of cellulose, when an acid anhydride or acid chloride is used as an acylating agent, an organic acid such as acetic acid or methylene chloride is used as an organic solvent as a reaction solvent.

As the catalyst, when the acylating agent is an acid anhydride, a protic catalyst such as sulfuric acid is preferably used, and when the acylating agent is an acid chloride (for example, CH ₃ CH ₂ COCl), Basic compounds are used.

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

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

<Short maximum absorption compound>
The film of the present invention contains a short maximum absorption compound having an absorption maximum λmax of 180 to 250 nm. By adding such a short maximum absorption compound to cellulose acylate in the range of the total substitution degree, it is possible to obtain a film having desired optical expression and reverse dispersion.
That is, the short maximum absorbing compound is preferably an optical enhancer that can increase at least one of Re or Rth by adding to the cellulose acylate film.

(Absorption maximum)
When the short maximum absorption compound is a layered compound described later, the absorption maximum λmax is preferably 200 nm or more and less than 250 nm, more preferably 200 to 240 nm, and more preferably 200 to 230 nm. It is particularly preferable that it is 200 to 220 nm, more preferably 200 to 210 nm.
On the other hand, when the short maximum absorption compound is another compound other than the layered compound, the absorption maximum λmax is preferably 200 to 250 nm, more preferably 210 to 250 nm, and more than 240 nm to 250 nm or less. It is particularly preferred.

(Distribution of short maximum absorption compounds)
In the film of the present invention, the short maximum absorbing compound is preferably contained in a layer mainly composed of cellulose acylate. That is, when the cellulose acylate film of the present invention includes, as a layer other than cellulose acylate as a main component, for example, an alignment film layer mainly composed of another resin or a liquid crystal layer mainly composed of a liquid crystal compound, The short maximum absorption compound is preferably contained in a layer mainly composed of cellulose acylate from the viewpoint of imparting reverse dispersibility to the cellulose acylate film while expressing desired optical properties.
In the present specification, “a layer containing a resin as a main component” means that the resin is contained in an amount of 50% by mass or more based on the mass of the entire layer. Further, the “layer mainly composed of a certain resin” preferably contains 70% by mass or more, and particularly preferably contains 80% by mass or more of the resin with respect to the mass of the entire layer.

In the film of the present invention, the short maximum absorption compound is more preferably contained in a layer mainly composed of cellulose acylate having a total substitution degree of 2.7 to 3.0. That is, as a layer other than the cellulose acylate film of the present invention having a cellulose acylate having a total substitution degree of 2.7 to 3.0 as a main component, for example, a cellulose acylate having a total substitution degree of less than 2.7 is a main component. The short maximum absorption compound is contained in a layer mainly composed of cellulose acylate having a total substitution degree of 2.7 to 3.0, the cellulose acylate film has desired optical characteristics. It is preferable from the viewpoint of imparting reverse dispersibility while expressing the.
The film of the present invention contains the short maximum absorption compound, and the thickness of the layer mainly composed of cellulose acylate having a total substitution degree of 2.7 to 3.0 is 50% or more of the total film thickness. Preferably, it is 80% or more of the total film thickness, more preferably 90% or more of the total film thickness, and 100% of the total film thickness (that is, the film of the present invention is More preferably, it is a single layer comprising only a cellulose acylate having a short maximum absorption compound and having a total substitution degree of 2.7 to 3.0 as a main component.

In the present invention, there is no particular limitation on the type of the short maximum absorption compound having the absorption maximum λmax of 180 to 250 nm. For example, among the layered compounds; hydrophobizing agents such as nitrogen-containing compounds, sugar ester compounds and polycondensed ester compounds; and other compounds known as additives for cellulose acylate films, the absorption maximum λmax is an arbitrary value of 180 to 250 nm Can be mentioned. Among these, among the hydrophobizing agents such as layered compounds; nitrogen-containing compounds, sugar ester compounds, and polycondensed ester compounds, any compound having an absorption maximum λmax of 180 to 250 nm is preferable. Further, among the layered compound and the nitrogen-containing compound, an arbitrary compound having the absorption maximum λmax of 180 to 250 nm is more preferable.
Hereinafter, the low absorption maximum compound preferably used in the present invention will be described.
For the polycondensed ester compound and the like, details of their structure and the like will be described for convenience in the column of compounds other than the absorption maximum λmax of 180 to 250 nm described later. A compound having a wavelength of 180 to 250 nm can naturally be used as a short maximum absorption compound having an absorption maximum λmax of 180 to 250 nm.

(Layered compound)
In the present invention, the short maximum absorption compound having the absorption maximum λmax of 180 to 250 nm is preferably a layered compound.
In this specification, a layered compound has a structure in which atoms are strongly bonded by a covalent bond or the like and densely arranged, and the sheets are stacked almost in parallel by weak forces such as van der Waals force and electrostatic force. A compound that exhibits the property of swelling or cleaving by coordinating or absorbing a solvent.
Although not bound by any theory, such a layered compound exhibits a desired optical expression in a VA mode liquid crystal display device by the following mechanism, although λmax is small, which has heretofore been difficult. Expected to be able to.

  As long as the layered compound is not contrary to the gist of the present invention, its structure and shape are not particularly limited, but is preferably a flat compound.

The layered compound is not particularly limited as long as it is not contrary to the gist of the present invention, and may be an organic compound, an inorganic compound, or an organic-inorganic composite material.
Hereinafter, preferred embodiments of the layered compound will be described.

  In the present invention, the short maximum absorption compound having an absorption maximum λmax of 180 to 250 nm is preferably an inorganic layered compound from the viewpoint of imparting optical expression. Hereinafter, preferable examples of the inorganic layered compound will be described.

Examples of such inorganic layered compounds include swellable hydrous silicates such as smectite group clay minerals (montmorillonite, beidellite, nontronite, saponite, hectorite, soconite, stevensite, etc.), vermiculite group clay minerals (vermiculite, etc.) ), Kaolin-type minerals (such as halloysite, kaolinite, enderite, dickite), phyllosilicates (such as talc, pyrophyllite, mica, margarite, muscovite, phlogopite, tetracyllic mica, teniolite), jamonite Examples include group minerals (such as antigolite), chlorite group minerals (such as chlorite, cookite, and nanthite). These swellable inorganic layered compounds may be natural products or synthetic products.
Further, the inorganic layered compound may be one obtained by subjecting the inorganic layered compound as described above to an organic treatment. The organic treatment can be organicized by adding a compound having an onium ion to the inorganic layered compound. Specifically, an organic agent comprising an organic onium ion is added to the inorganic layered compound and processed. It is done.
The organic onium ion is not particularly limited, but monoalkyl primary to quaternary ammonium ions, dialkyl secondary to tertiary ammonium ions, trialkyl tertiary to quaternary ammonium ions, Examples thereof include tetraalkylammonium ions. The alkyl chain length is preferably 4 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, and particularly preferably 8 to 18 carbon atoms.
In addition to the alkyl chain, primary to quaternary ammonium ions having a polyethylene glycol chain and having ethylene oxide as a structural unit (monoethylene glycol, diethylene glycol, triethylene glycol, or tetraethylene glycol may be used) may also be used. Alternatively, it may be a primary to quaternary ammonium ion of a higher fatty acid, a primary to quaternary ammonium ion of a higher fatty acid ester, or a primary to quaternary ammonium ion of a higher alcohol. Moreover, you may have these multiple types of molecular chains. Further, it may be a secondary to quaternary ammonium ion obtained by adding these molecular chains to a fatty acid amide.
These inorganic layered compounds can be used alone or in combination of two or more.

The inorganic layered compound is preferably finely divided from the viewpoint of achieving both gas barrier properties and adhesion between the substrate and the gas barrier layer. The swellable inorganic layered compound subjected to the fine particle treatment is usually plate-shaped or flat, and the planar shape is not particularly limited, and may be an amorphous shape.
The average particle size of the planar shape of the swellable inorganic layered compound that has been microparticulated is, for example, preferably from 0.1 to 10 μm, more preferably from 0.5 to 8 μm, still more preferably from 0.8 to 6 μm. When the particle size is smaller than 0.1 μm, the moisture permeability reduction effect is not sufficient, and when the particle size is larger than 10 μm, an increase in haze value, an increase in surface roughness, and the like occur, which is not preferable.
The average particle size of the planar shape referred to here is the average particle size of the planar shape measured by a general particle size distribution meter, for example, a light scattering type particle size distribution meter (“MICROTRACK UPA” manufactured by Nikkiso Co., Ltd.). This is the average value of the distribution values.
The concentration of the inorganic layered compound is preferably 2 to 20% by mass and more preferably 3 to 10% by mass with respect to the vinyl alcohol resin. When the concentration of the inorganic layered compound is less than 2% by mass, the moisture permeability reduction effect is not sufficient, and when the concentration of the inorganic layered compound is more than 20% by mass, an increase in haze value and deterioration of brittleness are caused.

The inorganic layered compound is dispersed in the binder in a state where the interlayer is surely cleaved, thereby increasing the moisture transmission path length and decreasing the moisture permeability.
Therefore, a dispersion treatment for obtaining a state where each layer of the inorganic layered compound is appropriately cleaved is very important.
Therefore, the value obtained by dividing the average particle size of particles (average particle size in the plane direction when the particles are plate-like) by the interval between the sheets of inorganic layered compound (which can be determined by X-ray diffraction method). It is preferably in the range of 100 to 10,000, more preferably in the range of 500 to 9,000, and particularly preferably in the range of 1,000 to 8,000.
The dispersion treatment is preferably carried out by high-pressure dispersion treatment a plurality of times in the solution. The treatment pressure is preferably 10 MPa or more, more preferably 20 MPa or more. Distributed materials are also available on the market and can be used.
There is no restriction | limiting in particular as a solvent, According to the objective, it can select suitably, About the inorganic layered compound which is not organically-treated, water or water-soluble solvent (lower alcohols such as methanol, ethanol, isopropyl alcohol, acetone) Etc.), and water is particularly preferable.
Moreover, in order to provide defoaming property, the mixed solvent of water and a lower alcohol can also be used preferably.
Examples of the high-pressure dispersion treatment method include a method in which a swellable inorganic layered compound is swollen in a solvent and then stirred by a high-pressure homogenizer to perform high-pressure dispersion.
The method for preparing the coating solution is not particularly limited, but a method of dissolving the binder component of the coating layer described above uniformly in a solvent and then mixing with a solvent in which layered particles are uniformly dispersed is effectively used.
Moreover, in order to remove an insoluble matter after solution preparation, it is preferable to filter using the filter which has a mesh larger than the largest particle size of an inorganic layered compound.

When the inorganic layered compound is dispersed in a compound having low hydrophilicity, an inorganic layered compound that can be dispersed in an organic solvent is preferably used, and an inorganic layered compound that has been subjected to an organic treatment is more preferable.
Examples of these inorganic layered compounds are layered compounds subjected to an organic treatment with an organic agent such as alkylamine.
For the purpose of further strengthening the strength of the coating layer and reducing moisture permeability, it is preferable to perform an organic treatment with an organic agent containing a polymerizable group.
Organic layered inorganic layered compounds that can be used as commercial products include Somasif MAE / MTE / MEE / MPE (all synthetic mica manufactured by Coop Chemical Co., Ltd.), Lucentite SAN, STN, SEN, SPN (all corp chemical) Synthetic smectite manufactured by Co., Ltd.) or the like is used.

Further, organic layered inorganic layered compounds such as Lucentite ME-100 Corp. Chemical Co., Ltd. synthetic mica) and Lucentite SWN (Coop Chemical Corp. synthetic smectite) are organically treated. It is also preferable.
The organic agent is preferably a quaternary ammonium salt, and is not particularly limited, but a quaternary ammonium salt represented by the following general formula (3) is more preferable.
In the following general formula (3), Ra is represented by (CH ₂ ) _m H, (CH ₂ ) _m RcH or (CH ₂ Rc) _m H, m is an integer of 2 or more, and Rc is an arbitrary structure. or may be absent, Rb is CH _3, n is 0 or an integer of 1-3. A ^- is Cl ^- or Br ^- represents a.

In the said General formula (3), 0-3 are preferable, 0-2 are more preferable, and 0-1 are still more preferable. When n is large, dispersibility deteriorates, which is not preferable. With respect to Ra, all groups may have the same structure or different structures.
m is 2 or more, and in at least one group of Ra, m is particularly preferably 4 or more, more preferably 8 or more, and further preferably 8 to 30. The larger m is, the better the dispersibility, but it is not preferred, if it is too large, the ratio of the organic matter to the inorganic layered compound becomes too large.

Ra also preferably has a structure in which interaction between molecules is large. Examples of the structure that increases the interaction between molecules include —OH, —CH ₂ CH ₂ O—, —CHO (CH) ₃ —, and the like.
Examples of the quaternary ammonium salt used in the organic treatment include dimethyldioctadecylammonium bromide, trimethyloctadecylammonium chloride, benzyltrimethylammonium chloride, dimethylbenzyloctadecylammonium bromide, trioctylmethylammonium chloride, polyoxypropylenetrimethylammonium chloride, di ( Examples include polyoxypropylene) dimethylammonium chloride, di (polyoxyethylene) dodecylmethylammonium chloride, tri (polyoxypropylene) methylammonium chloride, tri (polyoxypropylene) methylammonium bromide and the like.

As a method of using an organically treated inorganic layered compound, in addition to a method in which the layered compound is sufficiently dispersed in an organic solvent and a solution in which a hydrophobic binder is dissolved and / or dispersed in the solvent is added, A method of adding the dispersed organic layered inorganic layered compound solution to the hydrophobic binder solution is used.
In addition, as a method of directly adding the inorganic layered compound to the hydrophobic binder, a method of adding the inorganic layered compound in a molten state of the hydrophobic binder and adding it while being dispersed in the hydrophobic binder by a method such as kneading may be used. it can.

  Examples of the organic layered compound include graphite, graphite fluoride, boron nitride, melamine cyanurate, and other known polymer compounds having cleavage properties.

(Nitrogen-containing compounds)
The optical film of the present invention preferably contains a nitrogen-containing compound as the second optical developer.
Among the nitrogen-containing compounds, nitrogen-containing aromatic compounds are more preferable.
The nitrogen-containing aromatic compound has any one of pyridine, pyrimidine, triazine, and purine as a mother nucleus, and an alkyl group, an alkenyl group, an alkynyl group, an amino group, an amide group ( This means a structure in which an arbitrary acyl group is bonded via an amide bond), an aryl group, an alkoxy group, a thioalkoxy group, an alkyl or an arylthio group (an alkyl group or an aryl group is linked via a sulfur atom) Group) or a heterocyclic group as a substituent. However, the substituent of the mother nucleus of these nitrogen-containing aromatic compounds may be further substituted with another substituent, and the other substituent is not particularly limited. For example, when the mother nucleus is substituted with an amino group, the amino group may be an alkyl group (further, the alkyl groups may be linked to form a ring) or —SO ₂ R ′ (R ′ is an arbitrary group). (Which represents a substituent).
However, for compounds in which nitrogen atoms are linked to all of the 2,4,6 positions of the 1,3,5-triazine ring, λmax often exceeds 180 to 250 nm. Therefore, when the nitrogen-containing compound contains a 1,3,5-triazine ring, nitrogen atoms are linked to 0 to 2 of the 2,4,6 positions of the 1,3,5-triazine ring. Is preferable as the short absorption maximum compound.
As the nitrogen-containing compound in the present invention, hydrogen bonding compounds described in [0026] to [0113] of WO2011 / 040468 can be preferably used.

  In the film of the present invention, the content of the nitrogen-containing aromatic compound is preferably 1 to 7% by mass, more preferably 2 to 5% by mass with respect to the cellulose acylate. It is especially preferable that it is 4.5 mass%.

  Preferred examples of the nitrogen-containing compound in the present invention are the same as the compounds mentioned as specific examples of [0026] to [0113] hydrogen bonding compounds in WO2011 / 040468.

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

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

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

  The number of structural units contained in the sugar ester compound is preferably 1 to 12, more preferably 1 to 6, and particularly preferably 1 or 2.

  In the present invention, the sugar ester compound is more preferably a sugar ester compound containing 1 to 12 pyranose structural units or furanose structural units in which at least one hydroxyl group is esterified, and at least one of the hydroxyl groups is an ester. More preferably, it is a sugar ester compound containing one or two pyranose structural units or furanose structural units.

  Examples of the monosaccharide or saccharide containing 2 to 12 monosaccharide units include, for example, erythrose, threose, ribose, arabinose, xylose, lyxose, allose, altrose, glucose, fructose, mannose, gulose, idose, galactose , Talose, trehalose, isotrehalose, neotrehalose, trehalosamine, caudibiose, nigerose, maltose, maltitol, isomaltose, sophorose, laminaribiose, cellobiose, gentiobiose, lactose, lactosamine, lactitol, lactulose, melibiose, primebelloose, rutiose , Sucrose, sucralose, turanose, vicyanose, cellotriose, cacotriose, gentianose, isomaltoto Oose, isopanose, maltotriose, manninotriose, melezitose, panose, planteose, raffinose, solatriose, umbelliferose, lycotetraose, maltotetraose, stachyose, baltopentaose, velval course, maltohexaose, Examples include α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, δ-cyclodextrin, xylitol, sorbitol and the like.

  Preferably, ribose, arabinose, xylose, lyxose, glucose, fructose, mannose, galactose, trehalose, maltose, cellobiose, lactose, sucrose, sucralose, α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, δ-cyclodextrin Xylitol, sorbitol, more preferably arabinose, xylose, glucose, fructose, mannose, galactose, maltose, cellobiose, sucrose, β-cyclodextrin, γ-cyclodextrin, particularly preferably xylose, glucose, fructose , Mannose, galactose, maltose, cellobiose, sucrose, xylitol, sorbitol. The sugar ester compound has a glucose skeleton or a sucrose skeleton, and is described in JP-A 2009-1696 [0059] as Compound 5 and has a maltose skeleton used in the examples of the same document. Compared to an ester compound and the like, it is more preferable from the viewpoint of compatibility with a polymer.

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

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

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

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

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

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

  Preferred examples of the substituent of the sugar ester compound include an alkyl group (preferably an alkyl group having 1 to 22 carbon atoms, more preferably 1 to 12 carbon atoms, and particularly preferably an alkyl group having 1 to 8 carbon atoms, such as a methyl group, An ethyl group, a propyl group, a hydroxyethyl group, a hydroxypropyl group, a 2-cyanoethyl group, a benzyl group, etc.), an aryl group (preferably having a carbon number of 6 to 24, more preferably 6 to 18 and particularly preferably 6 to 12). A group such as a phenyl group or a naphthyl group, an acyl group (preferably having a carbon number of 1 to 22, more preferably a carbon number of 2 to 12, particularly preferably a carbon number of 2 to 8, such as an acetyl group or a propionyl group, Butyryl group, pentanoyl group, hexanoyl group, octanoyl group, benzoyl group, toluyl group, phthalyl group), amide group (preferred) Or an amide group (preferably 4 to 22 carbon atoms, more preferably an amide having 2 to 12 carbon atoms, particularly preferably an amide having 2 to 8 carbon atoms, such as a formamide group or an acetamide group). Is an amide group having 4 to 12 carbon atoms, particularly preferably 4 to 8 carbon atoms, such as a succinimide group and a phthalimide group, and an arylalkyl group (preferably having 7 to 25 carbon atoms, more preferably 7 to 19 carbon atoms, particularly Preferred examples include 7 to 13 aryl groups such as benzyl group. Among these, an alkyl group or an acyl group is more preferable, a methyl group, an acetyl group, a benzoyl group, or a benzyl group is more preferable, and an acetyl group and a benzyl group are particularly preferable. Furthermore, among them, when the constituent sugar of the sugar ester compound has a sucrose skeleton, a sugar ester compound having an acetyl group and a benzyl group as substituents is described as compound 3 in [0058] of JP2009-1696A. Therefore, it is more preferable from the viewpoint of compatibility with the polymer, compared with the sugar ester compound having a benzoyl group used in the examples of the document.

  The number of hydroxyl groups per structural unit in the sugar ester compound (hereinafter also referred to as hydroxyl group content) is preferably 3 or less, more preferably 1 or less, and zero. Particularly preferred. By controlling the hydroxyl group content within the above range, the migration of the sugar ester compound to the polarizer layer and the destruction of the PVA-iodine complex at high temperature and high humidity can be suppressed, and the deterioration of the polarizer performance at high temperature and high humidity can be prevented. It is preferable from the point of suppression.

The sugar ester compound used in the film of the present invention preferably has no unsubstituted hydroxyl group, and the substituent consists only of an acetyl group and / or a benzyl group.
The ratio of acetyl groups to benzyl groups in the sugar ester compound tends to increase the value of wavelength dispersion ΔRe and ΔRe / Re (550) of the cellulose acylate film obtained when the ratio of benzyl groups is somewhat small. The change in blackness when incorporated in a liquid crystal display device is small, which is preferable. Specifically, the ratio of the benzyl group to the sum of all unsubstituted hydroxyl groups and all substituents in the sugar ester compound is preferably 60% or less, and preferably 40% or less.

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

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

Specific examples of the sugar ester compound that can be preferably used in the present invention are listed below, but the present invention is not limited to the following embodiments.
In the following structural formulae, R each independently represents an arbitrary substituent, and a plurality of R may be the same or different.

The sugar ester compound is preferably contained in an amount of 0 to 30% by mass, more preferably 0 to 20% by mass, and particularly preferably 0 to 15% by mass relative to the cellulose acylate.
In addition, the said sugar ester compound may be used independently, or may use 2 or more types together.

<Other optical developing agents :: Optical developing agents whose absorption maximum λmax is outside the range of 180 to 250 nm>
The film of the present invention may contain an optical developer having an absorption maximum λmax outside the range of 180 to 250 nm in combination with a short maximum absorption compound having an absorption maximum λmax of 180 to 250 nm.
There is no restriction | limiting in particular as an optical expression agent outside the range whose said absorption maximum (lambda) max is 180-250 nm, A well-known compound etc. can be used as an optical expression agent of a cellulose acylate film. However, as for the film of this invention, it is more preferable that absorption maximum (lambda) max of all the optical expression agents contained in a film is 180-250 nm.

  In the present invention, there is no particular limitation on the type of the optical developing agent having the absorption maximum λmax outside the range of 180 to 250 nm. For example, among the hydrophobizing agents such as phosphate ester compounds and polycondensed ester compounds; and other compounds known as additives for cellulose acylate films, the absorption maximum λmax is outside the range of 180 to 250 nm. An optical developing agent can be mentioned.

(Other hydrophobizing agents)
In the film of the present invention, a hydrophobizing agent having an absorption maximum λmax outside the range of 180 to 250 nm may be used in combination with a short maximum absorption compound having an absorption maximum λmax of 180 to 250 nm. Examples of the hydrophobizing agent having an absorption maximum λmax outside the range of 180 to 250 nm include other plasticizers other than the nitrogen-containing compound and the sugar ester compound.
Examples of the other plasticizers include phosphate ester plasticizers, phthalate ester plasticizers, trimellitic ester plasticizers, pyromellitic acid plasticizers, polyhydric alcohol plasticizers, and glycolate plasticizers. Agents, citrate plasticizers, polyester plasticizers (fatty acid-terminated polyester plasticizers, aromatic ring-containing polyester plasticizers), carboxylic acid ester plasticizers, acrylic polymers, and the like.

  As the other plasticizer, it is preferable to use a polyester plasticizer having a number average molecular weight of 300 or more and less than 2000 so as not to cause haze in the film, bleed out or volatilize from the film.

Although the said polyester plasticizer is not specifically limited, The polyester plasticizer which has an aromatic ring or a cycloalkyl ring in a molecule | numerator can be used.
For example, an aromatic terminal polyester plasticizer represented by the following general formula (2) is preferable.

Formula ^{(2) B 1 - (G} 1 -A 1) n-G 1 -B 1
(In the formula, B ¹ is a benzene monocarboxylic acid residue, G ¹ is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms. Group A ¹ represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.)

In the general formula (2), a benzene monocarboxylic acid residue represented by B ¹ , an alkylene glycol residue, an oxyalkylene glycol residue or an aryl glycol residue represented by G ¹ , an alkylene dicarboxylic acid residue represented by A ¹ Or it is comprised from an aryl dicarboxylic acid residue.
Examples of the benzene monocarboxylic acid component of the polyester plasticizer used in the present invention include benzoic acid, para-tert-butyl benzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethyl benzoic acid, ethyl benzoic acid, and normal propyl. There exist benzoic acid, aminobenzoic acid, acetoxybenzoic acid, etc., and these can be used as 1 type, or 2 or more types of mixtures, respectively.

Examples of the alkylene glycol component having 2 to 12 carbon atoms of the polyester plasticizer include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1, 2-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2 -Diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3propanediol (3,3-dimethylolheptane), 3-methyl-1, 5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl 1,3-pentanediol, 2-ethyl 1,3-hex There are sun diol, 2-methyl 1,8-octane diol, 1,9-nonane diol, 1,10-decane diol, 1,12-octadecane diol, etc., and these glycols are one kind or a mixture of two or more kinds. Used as.
In particular, an alkylene glycol having 2 to 12 carbon atoms is preferable because of excellent compatibility with cellulose acylate.

Examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the polyester plasticizer include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. These glycols are one kind. Or it can be used as a mixture of two or more.
Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the polyester plasticizer used in the present invention include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. These are each used as one or a mixture of two or more.
Examples of the arylene dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, and 1,4-naphthalenedicarboxylic acid.

The polyester plasticizer has a number average molecular weight of preferably 300 to 1500, more preferably 400 to 1000.
The acid value is preferably 0.5 mgKOH / g or less, the hydroxyl value is 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxyl value is 15 mgKOH / g or less.

  Moreover, as the polyester plasticizer, polymers described in [0141] to [0156] of JP 2010-46834 A can be preferably used.

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

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

  The plasticizer other than the sugar ester compound such as a polyester plasticizer is preferably contained in an amount of 0 to 40% by mass, more preferably 0 to 15% by mass with respect to the cellulose acylate. Particularly preferred.

The known retardation enhancer having an absorption maximum λmax outside the range of 180 to 250 nm is not particularly limited, but is composed of a rod-shaped compound or a compound composed of a compound having a cyclic structure such as a cycloalkane or an aromatic ring. Can be mentioned. As the compound having a cyclic structure, a discotic compound is preferable. As the rod-like compound or discotic compound, a compound having at least two aromatic rings can be used as a retardation developer.
Two or more types of retardation developing agents may be used in combination.
The retardation enhancer, which is an optical enhancer having an absorption maximum λmax outside the range of 180 to 250 nm, preferably has a maximum absorption in a wavelength region of more than 250 and 400 nm or less, and has a substantial absorption in the visible region. Preferably not.

Examples of the retardation developer having an absorption maximum λmax outside the range of 180 to 250 nm include compounds described in JP-A No. 2004-50516 and JP-A No. 2007-86748, and JP-A No. 2010-46834. The compound which has been used can be used.
Examples of the discotic compound include a compound described in European Patent Application No. 0911656A2, a triazine compound described in Japanese Patent Application Laid-Open No. 2003-344655, and Japanese Patent Application Laid-Open No. 2008-150592 [0097] to [0108]. Mention may also be made of triphenylene compounds.

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

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

<Additives other than optical enhancers>
The cellulose acylate film used in the present invention may contain an additive that can be added to an ordinary cellulose acylate film, in addition to the above-described optical enhancer.
Examples of these additives include fine particles, antioxidants, thermal deterioration inhibitors, and colorants.
About the said other additive, the compound described in international publication WO2008-126535 can be used preferably.

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

  The content of these fine particles with respect to the cellulose acylate in the cellulose film of the present invention is preferably 0.05 to 1% by mass, particularly preferably 0.1 to 0.5% by mass. In the case of a cellulose derivative film having a multilayer structure by the co-casting method, it is preferable to contain fine particles of this addition amount on the surface.

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

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

<Characteristics of cellulose acylate film>
(Re, Rth)
The film of the present invention satisfies the following formulas (1) and (2): Formula (1) 40 nm ≦ Re (550) ≦ 80 nm
(In formula (1), Re (550) represents in-plane retardation at a wavelength of 550 nm.)
Formula (2) 100 nm ≦ Rth (550) ≦ 250 nm
(In Formula (2), Rth (550) represents retardation in the film thickness direction at a wavelength of 550 nm.)
It is preferable that retardation is developed in such a range from the viewpoint of improving the contrast and blackness change of the liquid crystal display device.
The Re (550) is preferably 40 to 65 nm, and more preferably 45 to 60 nm.
The Rth (550) is preferably 105 to 240 nm, and more preferably 110 to 140 nm.

(Wavelength dispersion)
The film of the present invention satisfies the formula (3).
Formula (3) 1 nm ≦ ΔRe (λ) ≦ 30 nm
Formula (4) ΔRe (λ) = Re (630) −Re (440)
(In formulas (3) and (4), Re (630) represents in-plane retardation at a wavelength of 630 nm, and Re (440) represents in-plane retardation at a wavelength of 440 nm.)
That is, the reverse dispersion film has a difference ΔRe (λ) between an in-plane retardation Re (630) at a wavelength of 630 nm and an in-plane retardation Re (440) at a wavelength of 450 nm in a specific numerical range. Such a reverse dispersible film can improve the blackness change when incorporated in a liquid crystal display device.

In the film of the present invention, it is more preferable that the ΔRe (λ) satisfies the following formula (5).
Formula (5) 5 nm ≦ ΔRe (λ) ≦ 30 nm
Formula (4) ΔRe (λ) = Re (630) −Re (440)
(In formulas (4) and (5), Re (630) represents in-plane retardation at a wavelength of 630 nm, and Re (440) represents in-plane retardation at a wavelength of 440 nm.)
Furthermore, in the film of the present invention, the ΔRe (λ) is particularly preferably 1 to 20 nm.

(Retardation humidity dependency)
The film of the present invention preferably satisfies the following formulas (6) and (7).
Expression (6) ΔRe (10-80) ≦ 10 nm
Expression (7) ΔRe (10−80) = Re (10% RH) −Re (80% RH)
(In the formulas (6) and (7), Re (10% RH) represents the retardation value in the in-plane direction of the film at a relative humidity of 10%, and Re (80% RH) represents the in-plane of the film at a relative humidity of 80%. Represents the direction retardation value.)
The film of the present invention preferably has a small variation due to the environmental humidity of Re.
The ΔRe (10-80) is more preferably 9 nm or less, particularly preferably 8 nm or less, and particularly preferably 7 nm or less.

(Internal haze)
The cellulose acylate film of the present invention preferably has an internal haze of 0.05% or less.
The haze represents a haze value (%) measured according to JIS K7136.
The internal haze of the film of the present invention is obtained by dropping several drops of glycerin on both sides of the obtained cellulose acylate film and sandwiching it from both sides with two 1.3 mm thick glass plates (MICRO SLIDE GLASS product number S9213, manufactured by MATSUNAMI). The value (%) obtained by subtracting the haze measured in a state where several drops of glycerin were dropped between two sheets of glass from the haze value (%) measured in an open state.
The haze of the cellulose acylate film of the present invention was measured using a turbidimeter (NDH2000, Nippon Denshoku Industries Co., Ltd.) in a film that was allowed to stand for 24 hours in an environment of 23 ° C. and 55% relative humidity. It was measured.

The internal haze of the cellulose acylate film of the present invention is more preferably 0.04% or less.
A lower haze is generally preferred. Further, simply reducing the total haze is not sufficient for improving the front contrast, and adjusting the inner haze to the above range is preferable for improving the front contrast of the liquid crystal display device.

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

  In this specification, Re (λ) and Rth (λ) represent in-plane retardation and retardation in the thickness direction at the wavelength λ, respectively. In the present specification, the wavelength λ is 550 nm unless otherwise specified. Re (λ) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH (manufactured by Oji Scientific Instruments). Rth (λ) is Re (λ), with the in-plane slow axis (determined by KOBRA 21ADH) as the tilt axis (rotary axis) (in the absence of the slow axis, any direction in the film plane) Is measured in 6 points from the inclined direction in 10 degree steps from the normal direction to 50 degrees on one side with respect to the normal direction of the film. KOBRA 21ADH calculates based on the retardation value, the assumed average refractive index, and the input film thickness value. The retardation value is measured from any two directions with the slow axis as the tilt axis (rotation axis) (in the absence of the slow axis, the arbitrary direction in the film plane is the rotation axis), and the value Rth can also be calculated from the following formula (A) and formula (B) based on the assumed average refractive index and the input film thickness value. Here, as the assumed value of the average refractive index, values in the polymer handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer. The average refractive index values of main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). The KOBRA 21ADH calculates nx, ny, and nz by inputting the assumed value of the average refractive index and the film thickness. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.

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

(Dimension change rate)
The film of the present invention preferably satisfies the following formula (8) in the direction of film conveyance and the direction perpendicular thereto at a dimensional change rate of about 24 hours at 60 ° C. and 90% relative humidity.
Formula (8) −0.5% ≦ {(L′−L0) / L0} × 100 ≦ 0.5%
(In Formula (8), L0 represents the film length (unit: mm) before passing for 24 hours at 60 ° C. and 90% relative humidity, L ′ is allowed to pass for 24 hours at 60 ° C. and 90% relative humidity, and 2 (Represents the film length (unit: mm) after humidity control.)
The film of the present invention preferably has a dimensional change rate of about 24 hours at 60 ° C. and 90% relative humidity of 0.3% or less in the film transport direction, more preferably 0.2% or less, It is especially preferable that it is 0.1% or less.
The film of the present invention preferably has a dimensional change rate of about 24 hours at 60 ° C. and 90% relative humidity of 0.4% or less in the direction perpendicular to the film conveyance direction, and 0.3% or less. Is more preferable and 0.2% or less is particularly preferable.

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

(Film thickness)
The film of the present invention has a film thickness of 20 to 70 μm, preferably from the viewpoint of reducing production costs, more preferably 35 to 60 μm, particularly preferably 35 to 50 μm, and 40 to 50 μm. More particularly preferred. When the film of the present invention is a laminated film, the range of the total film thickness of the film is preferably within the above-mentioned preferable range. In addition, the thickness of the layer containing the short maximum absorption compound and mainly composed of cellulose acylate having a total substitution degree of 2.7 to 3.0 is preferable with respect to the preferable film thickness range and the total film thickness described above. It may be set by multiplying the ratio range.

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

<Method for producing cellulose acylate film>
The method for producing the cellulose acylate film of the present invention (hereinafter also referred to as the method for producing the cellulose acylate film) is not particularly limited.
Hereinafter, the manufacturing method of the said cellulose acylate film is demonstrated.

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

<Polymer solution>
In the solution casting film forming method, a web is formed using the cellulose acylate or a polymer solution (cellulose acylate solution) containing various additives as required. Hereinafter, a polymer solution (hereinafter sometimes referred to as a cellulose acylate solution or a dope as appropriate) that can be used in the solution casting film forming method will be described.

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

  Examples of the good solvent include ketones such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, ethers such as tetrahydrofuran (THF), 1,4-dioxane, 1,3-dioxolane, 1,2-dimethoxyethane, and formic acid. Esters such as methyl, ethyl formate, methyl acetate, ethyl acetate, amyl acetate, γ-butyrolactone, methyl cellosolve, dimethylimidazolinone, dimethylformamide, dimethylacetamide, acetonitrile, dimethyl sulfoxide, sulfolane, nitroethane, methylene chloride And 1,3-dioxolane, THF, methyl ethyl ketone, acetone, methyl acetate and methylene chloride are preferable.

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

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

In the present invention, the cellulose acylate constituting the cellulose acylate film contains hydrogen bonding functional groups such as hydroxyl groups, esters, and ketones, and therefore 5 to 30% by mass, more preferably 7 to 25% by mass in the total solvent. More preferably, it contains 10 to 20% by mass of alcohol from the viewpoint of reducing the peeling load from the casting support.
By adjusting the alcohol content, it is possible to easily adjust the expression of Re and Rth of the cellulose acylate film produced by the method for producing a cellulose acylate film. Specifically, by increasing the alcohol content or setting the drying temperature (heat treatment temperature) before stretching in the method for producing the cellulose acylate film described later, the reach range of Re and Rth can be further increased. It becomes possible to enlarge.
Further, in the present invention, it is effective to contain a small amount of water to increase the solution viscosity and the film strength in the wet film state at the time of drying, or to increase the dope strength at the time of casting the drum method. It may be contained in an amount of 0.1 to 5% by mass, more preferably 0.1 to 3% by mass, and particularly 0.2 to 2% by mass.

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

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

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

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

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

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

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

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

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

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

(5) Drying or heat treatment step, stretching step In the method for producing a cellulose acylate film, performing the stretching step at a temperature of 130 to 190 ° C., that is, optical expression with respect to the film thickness of the resulting cellulose acylate film, From the viewpoint of increasing Rth (550) / d, it is preferable.
After the peeling step, the web is dried by using a drying device that alternately conveys the web through rolls arranged in a drying device and / or a tenter device that clips and conveys both ends of the web with a clip. Is preferred.

In the method for producing a cellulose acylate film, the web may or may not be heat-treated before stretching.
The drying or heat treatment temperature is preferably 30 minutes or less, more preferably 20 minutes or less, and particularly preferably about 10 minutes.

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

  In the method for producing a cellulose acylate film, the cellulose acylate film may be stretched in any direction of a film transport direction (hereinafter also referred to as a longitudinal direction) and a direction orthogonal to the film transport direction (hereinafter also referred to as a lateral direction) Stretching in the transverse direction is preferable from the viewpoint of expressing desired retardation. More preferably, it is biaxially stretched in the longitudinal and transverse directions. Stretching may be performed in one stage or in multiple stages.

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

The stretching ratio in stretching in the direction perpendicular to the film conveying direction is preferably more than 20%, more preferably more than 20% to 60% or less, particularly preferably 25 to 55%, 25 More preferably, it is ˜50%.
In addition, in this invention, it is preferable to extend | stretch using a tenter apparatus as a method of extending | stretching in the direction orthogonal to a film conveyance direction.

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

  In the method for producing a cellulose acylate film, the stretching temperature is preferably Tg-5 ° C. or lower. Hereinafter, stretching in such a temperature range is also referred to as low temperature stretching. By low-temperature stretching the film formed in a film shape, it is possible to increase Rth expression without increasing the film thickness of the film of the present invention, that is, Rth (550) / d can be further increased, which is preferable. . Although not bound by any theory, Re can be expressed without lowering Rth because the orientation of the polymer or additive during stretching is less likely to occur in the low-temperature stretching than in high-temperature stretching.

  Further, in a more preferred embodiment of the method for producing the cellulose acylate film, by using cellulose acetate having a low acetyl substitution degree (particularly cellulose acetate having an acetyl substitution degree of 2.0 to 2.5) and stretching at a low temperature, Haze resulting from the low temperature stretching can also be suppressed. Although not bound by any theory, when cellulose acetate having a low acetyl substitution degree is used as the cellulose acylate, the cellulose acetate having a low acetyl substitution degree is highly compatible with the sugar ester compound. Are dispersed, and it is expected that the additives are difficult to phase separate during low-temperature stretching. Therefore, it can control so that extending | stretching stress may be applied uniformly to the whole web, and generation | occurrence | production of the said craze which is easy to occur at the time of low temperature extending | stretching can be suppressed. As a result, the internal haze of the film obtained by the method for producing the cellulose acylate film can be controlled within the preferred range.

The stretching temperature is more preferably Tg-50 ° C to Tg-5 ° C, and particularly preferably Tg-40 ° C to Tg-5 ° C.
In addition to the regulation by Tg of the unstretched film, the lower limit value of the stretching temperature is preferably more than 150 ° C., more preferably 160 ° C. or more. The upper limit of the stretching temperature is also preferably 190 ° C. or lower, and more preferably 180 ° C. or lower.

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

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

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

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

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

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

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

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

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

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

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

(Optical expression)
Re and Rth were measured at wavelengths of 450 nm, 550 nm, and 630 nm by KOBRA 21ADH (manufactured by Oji Scientific Instruments) by the above method. The obtained Re (630) -Re (450) was calculated to obtain ΔRe (λ). The results are shown in Table 6 below.

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

(Internal haze)
A few drops of glycerin were dropped on both sides of the obtained cellulose acylate film sample 40 mm × 80 mm and sandwiched from two glass sheets (MICRO SLIDE GLASS part number S9213, manufactured by MATSUNAMI) with a thickness of 1.3 mm at 25 ° C. From the haze value measured according to JIS K-6714 with a haze meter (HGM-2DP, Suga test machine) at a relative humidity of 60%, the haze measured with a few drops of glycerin dropped between two glasses was subtracted. The value (%) was defined as internal haze. The results are shown in Table 6 below.

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

[Examples 1 to 7 and Comparative Examples 1 to 4]
(1) Preparation of Cellulose Acylate Resin by Synthesis Cellulose acylate having an acyl substitution degree shown in Table 6 was prepared. Sulfuric acid (7.8 parts by mass with respect to 100 parts by mass of cellulose) was added as a catalyst, each carboxylic acid was added, and an acylation reaction was performed at 40 ° C. Thereafter, the total substitution degree and the 6-position substitution degree were adjusted by adjusting the amount of sulfuric acid catalyst, the amount of water and the aging time. The aging temperature was 40 ° C. Further, the low molecular weight component of the cellulose acylate was removed by washing with acetone.

(2) Dope preparation The following composition is put into a mixing tank, stirred to dissolve each component, further heated to 90 ° C. for about 10 minutes, and then filtered with a filter paper having an average pore size of 34 μm and a sintered metal filter having an average pore size of 10 μm. Filtered.
――――――――――――――――――――――――――――――――――
Cellulose acylate solution of Example 1 ――――――――――――――――――――――――――――――――――
Cellulose acylate described in the following Table 6 Total 100.0 parts by mass Optical developing agent 1 described in the following Table 6 (Amount described in the following Table 6 Unit: parts by mass)
Optical developing agent 2 described in Table 6 below (Amount described in Table 6 below Unit: part by mass)
Methylene chloride 403.0 parts by mass Methanol 60.2 parts by mass ――――――――――――――――――――――――――――――――――

In Table 6 below, Ac represents an acetyl group, and Pr represents a propionyl group. Moreover, the structure of each additive is described below.
Both Lucentite STN and Lucentite SPN are synthetic smectites manufactured by Co-op Chemical Co., Ltd.

<1-2> Matting Agent Dispersion Next, the following composition containing the cellulose acylate solution prepared by the above method was charged into a disperser to prepare a matting agent dispersion.
――――――――――――――――――――――――――――――――――――
Matting agent dispersion ――――――――――――――――――――――――――――――――――――
-Matting agent (Aerosil R972) 0.2 parts by mass-Methylene chloride 72.4 parts by mass-Methanol 10.8 parts by mass-Cellulose acylate solution 10.3 parts by mass ------- ―――――――――――――――――――――――
The dope for film formation was prepared by mixing 100 parts by mass of the cellulose acylate solution of Example 1 and mixing the matting agent dispersion in an amount of 0.02 parts by mass of inorganic fine particles with respect to the cellulose acylate resin.

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

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

(5) Stretching The obtained web (film) was peeled from the band, sandwiched between clips, and when the amount of residual solvent relative to the total mass of the film was in the state of 30 to 5% under the conditions of fixed end uniaxial stretching, The film was stretched in the direction (lateral direction) perpendicular to the film conveying direction using a tenter at the stretching temperature and the stretching ratio described in 1.
Thereafter, the clip was removed from the film and dried at 110 ° C. for 30 minutes. At this time, the cast film thickness was adjusted so that the film thickness after stretching became the film thickness (unit: μm) shown in Table 6.

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

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

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

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

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

From the above, it can be seen that each of the films of each example has a desired optical expression, is reversely dispersed, and has good front contrast and viewing angle color change when incorporated in a liquid crystal display device. It was.
On the other hand, the film of Comparative Example 1 is a film having a small ΔRe (λ) (that is, having a low reverse dispersibility) produced using only cellulose acylate having a total substitution degree lower than the lower limit of the range of the present invention. It was found that the front contrast when incorporated into a display device was inferior. The film of Comparative Example 2 was produced using an optical enhancer having a λmax lower than the lower limit of the range of the present invention, and Re and Rth were lower than the lower limit of the range of the present invention. It was found to be inferior to the viewing angle color change. The film of Comparative Example 3 is a film having a negative ΔRe (λ) (ie, forward dispersibility) produced using an optical enhancer having a λmax lower than the lower limit of the range of the present invention, and incorporated in a liquid crystal display measure. It was found to be inferior to the front contrast and viewing angle color change. The film of Comparative Example 4 is a three-layer laminated film in which the average total substitution degree of cellulose acylate contained in the film described in Example 21 of US Publication 2010-0271574A1 is 2.48, and when incorporated in a liquid crystal display device It was found that the front contrast was inferior.

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

Claims (15)

Cellulose acylate,
A short maximum absorption compound having an absorption maximum λmax of 180 to 250 nm,
The average total substitution degree of all the cellulose acylates contained in the film is 2.7 to 3.0,
A cellulose acylate film characterized by satisfying the following formula (1), formula (2) and formula (3).
Formula (1) 40nm <= Re (550) <= 80nm
(In formula (1), Re (550) represents in-plane retardation at a wavelength of 550 nm.)
Formula (2) 100 nm ≦ Rth (550) ≦ 250 nm
(In Formula (2), Rth (550) represents retardation in the film thickness direction at a wavelength of 550 nm.)
Formula (3) 1 nm ≦ ΔRe (λ) ≦ 30 nm
Formula (4) ΔRe (λ) = Re (630) −Re (440)
(In formulas (3) and (4), Re (630) represents in-plane retardation at a wavelength of 630 nm, and Re (440) represents in-plane retardation at a wavelength of 440 nm.)   The cellulose acylate film according to claim 1, wherein the short maximum absorption compound is a layered compound.   The cellulose acylate film according to claim 1, wherein the short maximum absorption compound is an inorganic layered compound. The cellulose acylate film according to any one of claims 1 to 3, wherein the following formula (5) is satisfied.
Formula (5) 5 nm ≦ ΔRe (λ) ≦ 30 nm
Formula (4) ΔRe (λ) = Re (630) −Re (440)
(In formulas (4) and (5), Re (630) represents in-plane retardation at a wavelength of 630 nm, and Re (440) represents in-plane retardation at a wavelength of 440 nm.)   The cellulose acylate film according to any one of claims 1 to 4, wherein the cellulose acylate is cellulose acetate.   The average of the total substitution degree of all the cellulose acylates contained in the said film is 2.75-2.85, The cellulose acylate film as described in any one of Claims 1-5 characterized by the above-mentioned. .   The cellulose acylate film according to claim 1, wherein the cellulose acylate film contains at least 1 to 7 parts by mass of a nitrogen-containing compound with respect to the cellulose acylate.   The cellulose acylate film according to any one of claims 1 to 7, wherein the absorption maximum λmax of all the optical developing agents contained in the film is 180 to 250 nm.   The cellulose acylate film according to any one of claims 1 to 8, wherein the short maximum absorption compound is contained in a layer mainly composed of cellulose acylate.   The cellulose according to any one of claims 1 to 9, wherein the short maximum absorption compound is contained in a layer mainly composed of cellulose acylate having a total substitution degree of 2.7 to 3.0. Acylate film.   The thickness of the layer containing the short maximum absorption compound and containing cellulose acylate having a total substitution degree of 2.7 to 3.0 as a main component is 50% or more of the total film thickness. Item 11. The cellulose acylate film according to Item 10.   The cellulose acylate contained in the film is only one type of cellulose acylate having a total substitution degree of 2.7 to 3.0, The cellulose acylate according to any one of claims 1 to 11 Rate film.   It is a single layer, The cellulose acylate film as described in any one of Claims 1-12 characterized by the above-mentioned.   A polarizing plate comprising a polarizer and the cellulose acylate film according to claim 1 on at least one side of the polarizer.   A liquid crystal display device comprising at least one polarizing plate according to claim 14.

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