WO2015111435A1

WO2015111435A1 - Phase difference film, polarizing plate, and va-type liquid crystal display

Info

Publication number: WO2015111435A1
Application number: PCT/JP2015/050323
Authority: WO
Inventors: 佐々木　達也; 貴史世良; 由紀金子
Original assignee: コニカミノルタ株式会社
Priority date: 2014-01-24
Filing date: 2015-01-08
Publication date: 2015-07-30
Also published as: TW201541161A; KR20160101159A; JPWO2015111435A1

Abstract

The present invention addresses the problem of providing a cellulose-ester phase difference film that is provided to a VA-type liquid crystal display, the phase difference film being a thin film and having a high phase difference value, and also, under high temperatures, having excellent phase-difference-value-fluctuation resistivity and being highly suitable for saponification. The phase-difference film according to the present invention is characterized in that the film contains a retardation enhancer and at least two types of cellulose esters, in that the at least two types of cellulose esters are a cellulose acetate (resin A) that has a degree of acetylation in the range of 2.40-2.60 and a cellulose ester (resin B) that has a total degree of acylation in the range of 2.40-2.60 and that has acyl groups that have 3-6 carbons, and in that the mass ratio of the resin A and the resin B is in the range of resin A:resin B=1:9-9:1.

Description

Retardation film, polarizing plate and VA liquid crystal display device

The present invention relates to a retardation film, and more specifically, a cellulose ester-based retardation film provided in a VA liquid crystal display device, which is a thin film and has a high retardation value, and further under high humidity. The present invention relates to a retardation film excellent in resistance to fluctuation of retardation value and suitability for saponification treatment.

Cellulose ester-based retardation films are conventionally used as retardation films for VA liquid crystal display devices. However, as the polarizing plates and liquid crystal display devices become thinner, the retardation films also become thinner and lower in cost. Is required. In general, as the retardation film becomes thinner, the retardation tends to be less likely to occur. Therefore, the cellulose ester resin itself has a high retardation and low cost diacetylcellulose resin (in this application, diacetylcellulose or DAC). However, the desired retardation value cannot be achieved with the resin alone, and a retardation increasing agent must be used in combination.

Further, since DAC is more hydrophilic than triacetyl cellulose resin (also referred to as triacetyl cellulose or TAC in the present application), a retardation film using DAC penetrates a saponified solution as the film is made thinner. There was a problem that the amount increased and the resin component eluted during saponification to contaminate the saponification solution. With respect to such a problem, Patent Documents 1 to 3 disclose techniques for improving saponification suitability.

However, in an ultra-thin film containing DAC as a main component (for example, a retardation film having a film thickness of 10 to 36 μm), the amount of retardation increasing agent required for optical compensation of a VA liquid crystal display device is used together with DAC. In the film, the retardation value fluctuates greatly under high humidity depending on the type of the retardation increasing agent, and the retardation increasing agent elutes in the saponification solution to contaminate the saponification solution. Or the eluted retardation elevating agent precipitates on the film surface and becomes foreign matter.

JP 2013-83706 A JP 2013-44856 A International Publication No. 2013/051176

The present invention has been made in view of the above-described problems and situations, and a solution to the problem is a cellulose ester phase difference film provided in a VA liquid crystal display device, which is a thin film and has a high phase difference value. Furthermore, it is to provide a retardation film having excellent retardation value fluctuation under high humidity and suitability for saponification treatment.

In order to solve the above-mentioned problems, the present inventor is a retardation film containing at least two types of cellulose esters and a retardation increasing agent in the course of examining the cause of the above-mentioned problems, and the cellulose ester is specified. A retardation film in which the above-mentioned problems are solved by a retardation film characterized by comprising two kinds of cellulose esters having a degree of substitution and a substituent, and containing the two kinds of cellulose esters in a specific mass ratio. It was found that it can be obtained.

That is, the above-mentioned problem according to the present invention is solved by the following means.

1. A retardation film containing at least two cellulose esters and a retardation increasing agent,
The two types of cellulose esters are cellulose acetate (resin A) having an acetyl group substitution degree in the range of 2.40 to 2.60, and a total acyl group substitution degree in the range of 2.40 to 2.60. And a cellulose ester (resin B) having an acyl group having 3 to 6 carbon atoms, and containing the resin A and the resin B in a mass ratio of resin A: resin B = 1: 9 to 9: 1 A retardation film characterized by comprising:

2. The resin B is a cellulose acetate propionate having a propionyl group substitution degree in the range of 0.5 to 2.2, or a cellulose acetate butyrate having a butyryl group substitution degree in the range of 0.5 to 2.2. The retardation film as described in item 1, wherein

3. The retardation film according to

Item

1 or 2, wherein the retardation increasing agent is a nitrogen-containing heterocyclic compound and is a compound having a pyrrole ring, a pyrazole ring, a triazole ring, or an imidazole ring.

4. 4. The retardation film according to item 3, wherein the nitrogen-containing heterocyclic compound is a compound having a structure represented by the following general formula (3).

(In the formula, A represents a pyrazole ring. Ar ₁ and Ar ₂ each represent an aromatic hydrocarbon ring or an aromatic heterocyclic ring and may have a substituent. R ₁ represents a hydrogen atom, an alkyl group, or an acyl group. A sulfonyl group, an alkyloxycarbonyl group, or an aryloxycarbonyl group, q represents 1 or 2, and n and m represent an integer of 1 to 3.
5. 5. The retardation film according to any one of items 1 to 4, wherein the film thickness is in the range of 10 to 36 μm.

6. Furthermore, it contains the polycondensation ester containing the repeating unit obtained by making sugar ester or dicarboxylic acid and diol react, The retardation film as described in any one of 1st term | claim to 5th term | claim characterized by the above-mentioned. .

7. A polarizing plate comprising the retardation film according to any one of items 1 to 6.

8. A VA liquid crystal display device comprising the polarizing plate according to item 7.

By the above means of the present invention, a cellulose ester phase difference film provided in a VA liquid crystal display device, which is a thin film and a film having a high phase difference value, and further excellent in saponification suitability, A retardation film containing a cellulose ester can be provided.

The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.

Retardation film using DAC, which is more hydrophilic than TAC alone, increases the penetration of the saponification liquid as the film is thinned, and the resin components are eluted during saponification to contaminate the saponification liquid. There was a problem to do. In addition, when a retardation increasing agent is included in the film together with the DAC in the amount used for optical compensation of the VA liquid crystal display device, the retardation value fluctuation under high humidity may be caused depending on the type of the retardation increasing agent. There was a problem that it could not be sufficiently suppressed, and that the retardation increasing agent was eluted in the saponification solution to contaminate the saponification solution, or deposited on the film surface to form foreign matter.

As a result of repeated studies on the above problems, the present inventors have found that the problem of phase difference fluctuation and saponification suitability under high humidity is due to the use of a more hydrophilic DAC alone as a resin. As a result of reviewing the use conditions of the resin, a combination of a DAC having a specific degree of acetyl group substitution and a cellulose ester having an acyl group having 3 to 6 carbon atoms with a specific degree of acyl group substitution, It was found that the fluctuation of the retardation value under humidity can be reduced and the saponification suitability can be improved. Further, by using cellulose acetate propionate (also referred to as CAP in the present application) or cellulose acetate butyrate (also referred to as CAB in the present application) in combination with the DAC, the phase difference variation under high humidity is further increased. It was found that the saponification suitability can be further improved by reducing the saponification value.

This is because CAP and CAB are moderately hydrophobic compared to DAC, and by using in combination with DAC, it is possible to suppress the movement of moisture under high humidity and reduce phase difference value fluctuations, and further to film It is presumed that the penetration of the saponification solution can be controlled to prevent the elution of the retardation increasing agent and to improve the saponification suitability.

On the other hand, CAP and CAB are resins that are more likely to exhibit retardation than TAC, but are inferior in retardation development and brittleness compared to DAC, respectively, so that they are ultrathin films such as the retardation film of the present invention. It is difficult to use it alone for the retardation film.

Therefore, the retardation film of the present invention combines a DAC having a specific substitution degree as a resin with a specific amount of CAP or CAB in a specific amount range, and contains a retardation increasing agent. Although it is a thin film, it is speculated that a retardation film having a high retardation value can be obtained which is free from brittleness problems and excellent in retardation value fluctuation and saponification suitability under high humidity.

The figure which showed typically an example of the dope preparation process, casting process, and drying process of the solution casting film forming method preferable for this invention

The present invention is a retardation film containing at least two types of cellulose esters and a retardation increasing agent, wherein one of the two types of cellulose esters is a cellulose acetate (resin A) having a specific degree of substitution. The other is a cellulose ester (resin B) having a specific substitution degree and having an acyl group in the range of 3 to 6 carbon atoms, and contains the resin A and the resin B in a specific mass ratio. It is characterized by. This feature is a technical feature common to the inventions according to claims 1 to 8.

The resin B is a cellulose acetate propionate having a propionyl group substitution degree in the range of 0.5 to 2.2, or a cellulose acetate having a butyryl group substitution degree in the range of 0.5 to 2.2. From the viewpoint of providing a retardation film excellent in suitability for saponification treatment by imparting appropriate hydrophobic properties to the film, being butyrate, suppressing elution of DAC and retardation increasing agent into the saponification solution ,preferable.

The retardation increasing agent is a nitrogen-containing heterocyclic compound, and is a compound having a pyrrole ring, a pyrazole ring, a triazole ring or an imidazole ring, and exhibits retardation development when combined with DAC, and dew condensation during transportation. From the viewpoint of imparting excellent retardation value fluctuation resistance even under severe high humidity conditions where the film is directly exposed to water. Among these, the nitrogen-containing heterocyclic compound is preferably a compound having a pyrazole ring having a structure represented by the general formula (3) because of excellent retardation development and retardation value fluctuation resistance.

The film thickness of the retardation film of the present invention is in the range of 10 to 36 μm, and has a sufficient film strength and retardation value, and is a preferable film thickness even in thinning the polarizing plate and the liquid crystal display device. is there.

Further, the retardation film of the present invention contains a polycondensation ester containing a repeating unit obtained by reacting a sugar ester or a dicarboxylic acid with a diol, so that elution of a DAC and a retardation increasing agent into a saponification solution can be achieved. It is preferable from the viewpoint of suppressing and providing a retardation film excellent in saponification suitability.

The retardation film of the present invention is suitably provided for thin polarizing plates and liquid crystal display devices.

<< Outline of retardation film of the present invention >>
The retardation film of the present invention is a retardation film containing at least two types of cellulose esters and a retardation increasing agent, and the two types of cellulose esters have a degree of acetyl group substitution of 2.40 to 2.60. Cellulose acetate (resin A) having a total acyl group substitution degree in the range of 2.40 to 2.60 and having an acyl group of 3 to 6 carbon atoms (resin B), The resin A and the resin B are contained in a mass ratio of resin A: resin B = 1: 9 to 9: 1.

In the case of a thin phase difference film, when diacetyl cellulose (DAC) having a high phase difference is used alone as the resin A, the hydrophilicity of the film is increased. Since the permeation increased, there were problems of fluctuations in the retardation value under high humidity and elution of the resin and the retardation increasing agent into the saponification solution. In the present invention, cellulose acetate propionate (CAP) or cellulose acetate butyrate (CAB) is preferably used as the cellulose ester having a relatively hydrophobic acyl group having 3 to 6 carbon atoms in the DAC. The hydrophilicity is controlled by the retardation film contained at a specific ratio, and the retardation value fluctuation under high humidity and the saponification suitability are greatly improved.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In the present application, “˜” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

≪Cellulose ester≫
[Cellulose acetate (resin A)]
The resin A according to the present invention is a cellulose acetate having an acetyl group substitution degree in the range of 2.40 to 2.60.

When the degree of acetyl group substitution of cellulose acetate is less than 2.40, the resin becomes more hydrophilic and the amount of moisture and saponification solution penetrated increases, causing phase difference fluctuations and saponification under high humidity. The aptitude deteriorates. Further, the film surface quality may be deteriorated due to an increase in the dope viscosity.

In addition, when the degree of acetyl group substitution is greater than 2.60, it is difficult to obtain a necessary retardation value, and if excessive stretching is performed for the expression of the retardation, haze is increased and transparency is deteriorated. In order to obtain a retardation value, a large amount of addition of a retardation increasing agent is required, and haze increases due to precipitation, and elution into a saponification solution increases.

The total substitution degree of the acyl group of the resin A is more preferably in the range of 2.45 to 2.55, and further preferably in the range of 2.45 to 2.50.

Here, the “degree of acetyl group substitution” represents the total of the ratios of esterification of hydroxy groups by acetyl groups at the 2nd, 3rd and 6th positions of glucose in the cellulose ester. Specifically, when the hydroxy groups at the 2nd, 3rd and 6th positions of cellulose are all 100% esterified, the degree of substitution is 3 at the maximum.

Therefore, in the present application, “acetyl group substitution degree” refers to a substitution degree in which the total degree of acetyl group substitution of a plurality of glucose units constituting the cellulose ester is expressed as an average value per unit. The same applies to the degree of substitution of propionyl group or butyryl group described later.

The retardation film of the present invention has a cellulose acetate (resin A) having an acetyl group substitution degree in the range of 2.40 to 2.60 and a total acyl group substitution degree described later in the range of 2.40 to 2.60. The cellulose ester (resin B) having an acyl group having 3 to 6 carbon atoms is contained in a mass ratio of resin A: resin B = 1: 9 to 9: 1.

By containing the resin A and the resin B in combination in the mass ratio, the hydrophilicity of the DAC, which is the subject of the present invention, is controlled to improve the phase difference fluctuation under high humidity and the suitability for saponification treatment, In addition, by improving the brittleness of the resin B, it is possible to provide a retardation film that is excellent in the productivity of a thin film and the handleability of the film by customers.

Further, by matching the range of the acetyl group substitution degree of the resin A and the range of the total acyl group substitution degree of the resin B, the compatibility of the resin A and the resin B is improved, in addition to the manifestation of the effect of the present invention. In addition, it suppresses generation of bright spot foreign matter, precipitation of additives, and the like, and improves the productivity of thin film.

The use ratio of the resin A and the resin B is preferably within a range of resin A: resin B = 3: 7 to 7: 3, and within a range of resin A: resin B = 4: 6 to 6: 4. More preferably. The range of the use ratio is preferably adjusted as appropriate from the viewpoints of optical properties, physical properties, and production suitability of the retardation film.

The average degree of substitution of acetyl groups in cellulose acetate can be determined by measurement according to ASTM-D817-96.

The number average molecular weight (Mn) of the cellulose acetate according to the present invention is preferably in the range of 125000 to 155000, and more preferably in the range of 129000 to 152000. The weight average molecular weight (Mw) is preferably in the range of 265,000 to 310000. The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is preferably in the range of 1.4 to 2.5, more preferably in the range of 1.5 to 2.0. .

In the present invention, a mixture of two or more cellulose acetates having different degrees of substitution and molecular weights may be used.

The weight average molecular weight Mw and the number average molecular weight Mn of cellulose acetate can be measured using gel permeation chromatography (GPC).

The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 500 to 1,000,000 13 calibration curves were used. Thirteen samples are used at approximately equal intervals.

The cellulose acetate according to the present invention can be produced by a conventional method such as a sulfuric acid catalyst method, an acetic acid method, a methylene chloride method, and the raw materials are not particularly limited, but cotton linter, wood pulp (derived from coniferous trees, derived from broadleaf trees) ), Kenaf and the like. Moreover, the cellulose acetate obtained from them can be mixed and used in arbitrary ratios, respectively. The cellulose acetate according to the present invention can be synthesized with reference to the methods described in JP-A Nos. 10-45804 and 2005-281645, for example.

Commercially available products of cellulose acetate (cellulose diacetate) according to the present invention include L20, L30, L40, and L50 manufactured by Daicel Corporation, Ca398-3, Ca398-6, and Ca398- manufactured by Eastman Chemical Japan Co., Ltd. 10, Ca398-30, Ca394-60S.

[Cellulose ester (resin B)]
The retardation film of the present invention contains, as the resin B, a cellulose ester having an acyl group having 3 to 6 carbon atoms and a total acyl group substitution degree in the range of 2.40 to 2.60.

When the carbon number of the acyl group is large, the hydrophobicity of the film is improved and the phase difference fluctuation and saponification suitability at high humidity are improved. On the other hand, the larger the carbon number of the acyl group, the more easily the brittleness resistance is lowered. It is necessary for the retardation film of the present invention to be a cellulose ester having an acyl group having a number in the range of 3-6. Among them, the cellulose ester having an acyl group having 3 or 4 carbon atoms controls the hydrophilicity of the DAC, improves the phase difference value fluctuation under high humidity and the suitability for saponification treatment. By adjusting the brittleness, it is possible to provide a retardation film that is excellent in the productivity of a thin film and the handleability of the film by a customer, which is preferable.

The cellulose ester as the resin B according to the present invention is a compound obtained by esterifying cellulose and at least one of an aliphatic carboxylic acid or an aromatic carboxylic acid having about 2 to 22 carbon atoms.

Specific examples of the cellulose ester having an acyl group having 3 to 6 carbon atoms include cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, and cellulose acetate propionate butyrate. Etc. The butyryl group that can be contained in the cellulose ester may be linear or branched.

Among them, the cellulose mixed fatty acid ester in which the resin B is cellulose acetate propionate or cellulose acetate butyrate is excellent in compatibility with DAC, for improving the retardation value fluctuation and saponification suitability under high humidity. In addition, it is preferable from the viewpoints of brittleness and production suitability.

The retardation film of the present invention may be used by mixing a plurality of cellulose esters having an acyl group having 3 to 6 carbon atoms.

The total substitution degree of the acyl group of the cellulose ester as the resin B is in the range of 2.40 to 2.60. The total substitution degree of the acyl group is preferably smaller from the viewpoint of enhancing the retardation development. On the other hand, the smaller the degree of substitution, the stronger the hydrophilicity of the resin B. Therefore, the problem when the DAC is used alone is likely to occur even when the resin B is used in combination. is required.

In addition, since the compatibility deteriorates when the total substitution degree of the acyl groups of the resin A and the resin B is separated, the precipitation of the resin, the retardation increasing agent, and the like easily aggregate. Therefore, the total substitution degree of the acyl group of the resin B is more preferably in the range of 2.45 to 2.55, similarly to the resin A, and further preferably in the range of 2.45 to 2.50. preferable.

Resin B according to the present invention includes cellulose acetate propionate having a propionyl group substitution degree in the range of 0.5 to 2.2, or cellulose having a butyryl group substitution degree in the range of 0.5 to 2.2. Acetate butyrate is preferred from the viewpoint of brittleness and saponification suitability because of its high compatibility with resin A, which is DAC. Both the propionyl group substitution degree and the butyryl group substitution degree are preferably within the range of 0.8 to 1.9.

The substitution degree of the acyl group of the cellulose ester according to the present invention can be measured by a method prescribed in ASTM-D817-96.

The number average molecular weight (Mn) of the cellulose ester is preferably in the range of 6 × 10 ⁴ to 3 × 10 ^{5 in} order to increase the mechanical strength of the obtained film, and 7 × 10 ⁴ to 2 × 10 ^5. It is more preferable to be within the range.

The weight average molecular weight Mw and the number average molecular weight Mn of the cellulose ester are measured using the gel permeation chromatography (GPC).

The content of residual sulfuric acid in the cellulose ester according to the present invention is preferably in the range of 0.1 to 45.0 mass ppm in terms of elemental sulfur, and more preferably in the range of 1 to 30 mass ppm. preferable. Sulfuric acid is considered to remain in the film in a salt state. If the content of residual sulfuric acid is within 45.0 ppm by mass, it will be difficult to break during the heat stretching of the film or during the cutting after the heat stretching.

The content of residual sulfuric acid can be measured by the method prescribed in ASTM D817-96.

The content of free acid in the cellulose ester is preferably in the range of 1 to 500 ppm by mass, more preferably 1 to 100 ppm by mass, and further preferably in the range of 1 to 70 ppm by mass. preferable. When the content of the free acid is within the above range, as described above, the film is not easily broken during the heat stretching of the film or during the cutting after the heat stretching.

The free acid content can be measured by the method prescribed in ASTM D817-96.

Cellulose ester may contain a trace amount of metal components. It is thought that a trace amount metal component originates in the water used in the cellulose ester synthesis process. Like these metal components, the content of components that can become insoluble nuclei is preferably as small as possible. In particular, metal ions such as iron, calcium, and magnesium may form an insoluble matter by forming a salt with a resin decomposition product or the like that may contain an organic acidic group. In addition, the calcium (Ca) component easily forms a coordination compound (that is, a complex) with an acidic component such as a carboxylic acid or a sulfonic acid, and many ligands. May form insoluble starch, turbidity).

Specifically, the content of the iron (Fe) component in the cellulose ester is preferably 1 mass ppm or less. The content of the calcium (Ca) component in the cellulose ester is preferably 60 ppm by mass or less, and more preferably in the range of 0 to 30 ppm by mass. The content of the magnesium (Mg) component in the cellulose ester is preferably in the range of 0 to 70 ppm by mass, and particularly preferably in the range of 0 to 20 ppm by mass.

The content of metal components such as iron (Fe) component, calcium (Ca) component, magnesium (Mg) component, etc. can be either by treating the completely dried cellulose ester with a micro digest wet cracking device (sulfuric acid decomposition) or by alkali melting. After the pretreatment, the measurement can be performed using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometer).

The contents of residual alkaline earth metal, residual sulfuric acid and residual acid can be adjusted by thoroughly washing the cellulose ester obtained by synthesis.

The cellulose ester according to the present invention can be produced by a known method. Generally, cellulose is esterified by mixing raw material cellulose, aliphatic carboxylic acid or aromatic carboxylic acid with carboxylic anhydride, catalyst (sulfuric acid, etc.) and the like. The raw material cellulose is not particularly limited, and may be cotton linter, wood pulp, kenaf or the like. You may mix and use the cellulose ester from which a raw material differs. The esterification reaction proceeds until a cellulose triester is formed. In the triester, the three hydroxy groups of the glucose unit are substituted with an acyl acid of an aliphatic or aromatic carboxylic acid. When two types of aliphatic carboxylic acids or aromatic carboxylic acids are used at the same time, mixed cellulose esters such as cellulose acetate propionate and cellulose acetate butyrate can be produced. Next, a cellulose ester having a desired acyl group substitution degree is synthesized by hydrolyzing the cellulose triester. Thereafter, a cellulose ester is obtained through steps such as filtration, precipitation, washing with water, dehydration, and drying.

Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

The retardation film of the present invention is a range in which the resin A is cellulose acetate and the cellulose ester is a resin B having an acyl group having 3 to 6 carbon atoms, and other resins do not inhibit the effects of the present invention. You may use together.

As other resins, cellulose derivatives other than the above-described cellulose esters (for example, cellulose ester resins, cellulose ether resins, etc.), polycarbonate resins, polystyrene resins, polysulfone resins, polyester resins, polyarylate resins, (Meth) acrylic resins, olefin resins (for example, norbornene resins, cyclic olefin resins, cyclic conjugated diene resins, vinyl alicyclic hydrocarbon resins) and the like. Of these, cellulose derivatives, (meth) acrylic resins, polycarbonate resins, and cyclic olefin resins are preferable.

For example, the cellulose derivative is a compound using cellulose as a raw material (compound having a cellulose skeleton). Examples of the cellulose derivative include cellulose ethers (for example, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, cyanoethyl cellulose, etc.), Cellulose ether esters (for example, acetyl methyl cellulose, acetyl ethyl cellulose, acetyl hydroxyethyl cellulose, benzoyl hydroxypropyl cellulose and the like), cellulose carbonate (for example, cellulose ethyl carbonate and the like), cellulose carbamate (for example, cellulose phenyl carbamate and the like) and the like are included.

≪Retardation raising agent≫
The retardation increasing agent as used herein refers to a retardation value Rth (wavelength 590 nm measurement) in a thickness direction of a retardation film containing 3 parts by mass of the compound with respect to 100 parts by mass of a cellulose ester, and an unadded retardation. The compound which has a function which shows a value 1.1 times or more compared with a film.

The retardation increasing agent according to the present invention is not particularly limited. For example, a well-known disk having an aromatic ring described in paragraphs [0143] to [0179] of JP-A-2006-113239. -Like compounds (1,3,5-triazine compounds, etc.), rod-like compounds described in paragraphs [0106] to [0112] of JP-A-2006-113239, paragraphs [0118] to [0133] of JP-A-2012-214682 Pyrimidine compounds described in JP-A-2011-140637, epoxy ester compounds described in paragraphs [0022] to [0028], polyester compounds described in paragraphs [0044] to [0058] of international publication 2012/014571, etc. Can do.

The properties required for the retardation increasing agent according to the present invention are excellent in compatibility with the resin DAC, CAP or CAB, excellent in retardation expression when the film is thinned, and precipitation resistance. The following nitrogen-containing heterocyclic compound is preferably used as a retardation increasing agent from such a viewpoint.

[Nitrogen-containing heterocyclic compounds]
The retardation increasing agent according to the present invention is preferably a nitrogen-containing heterocyclic compound having a structure represented by the following general formula (1).

The nitrogen-containing heterocyclic compound is characterized by controlling the hydrogen bonding property of cellulose ester by CH / π interaction with cellulose ester and having both functions of a phase difference increasing agent and a wavelength dispersion adjusting agent with one compound. It has excellent compatibility when combined with a cellulose ester, and there is little generation of fine foreign matters and precipitates during the production process. For example, 1,3,5-triazine-based phase difference increasing agents tend to be slightly inferior in compatibility and easily generate foreign matter, etc. due to weak CH / π interaction, and have a high elution property in a saponification solution. It is in.

CH / π interaction refers to the compatibility of hydrogen bond donating sites such as cellulose esters (for example, hydrogen atoms of hydroxy groups) and hydrogen bond accepting sites (for example, carbonyl oxygen atoms of ester groups) with additives. It is a bond interaction between the hydrogen bonding site present in the main chain or side chain of the resin and the π electrons of the additive aromatic compound. Due to this CH / π interaction, the compatibility is excellent.

When forming the CH / π interaction using the hydrogen bonding site of the resin (CH of cellulose ester) and π of the additive, it is naturally better that the π property of the additive is stronger. There is an index called NICS (nucleus-independent chemical shift) value as an example that directly represents the strength of the π property.

This NICS value is an index used for quantification of aromaticity by magnetic properties. If the ring is aromatic, the ring current effect strongly shields the center of the ring, and conversely if it is antiaromatic. Anti-shielding (J. Am. Chem. Soc. 1996, 118, 6317). Depending on the magnitude of the NICS value, it is possible to determine the strength of the ring current, that is, the degree of contribution of π electrons to the aromaticity of the ring. Specifically, it represents the chemical shift (calculated value) of a virtual lithium ion arranged directly in the center of the ring, and the larger the value, the stronger the π property.

Some reports have been made on the measured NICS values. For example, Canadian Journal of Chemistry. , 2004, 82, 50-69 (Reference A) and The Journal of Organic Chemistry. , 2000, 67, 1333-1338 (Document B).

Specifically, a pyrrole ring (-14.87), a thiophene ring (-14.09) furan rather than an aromatic hydrocarbon such as a benzene ring (-7.98) or a naphthalene ring (-8.11). 5-membered aromatic heterocycles such as ring (-12.42), pyrazole ring (-13.82), or imidazole ring (-13.28), triazole ring (-13.18), oxadiazole ring ( 6-12 membered aromatic hydrocarbon rings such as -12.44) or thiazole ring (-12.82) have larger NICS values, and such aromatic 5-membered rings or aromatic 6-membered rings It is predicted that the CH / π interaction can be strengthened by using the compound having the above (the NICS value is shown in parentheses). Among these, a pyrrole ring, a pyrazole ring, a triazole ring or an imidazole ring is preferable because of excellent compatibility with a cellulose ester.

The nitrogen-containing heterocyclic compound according to the present invention is preferably a nitrogen-containing heterocyclic compound having a pyrrole ring, a pyrazole ring, a triazole ring, or an imidazole ring, and has a structure represented by the following general formula (1). Of the nitrogen heterocyclic compounds, nitrogen-containing heterocyclic compounds having the specific ring structure are preferred. The compound having the structure represented by the following general formula (1) is used together with cellulose acetate, so that when a polarizing plate is used in a liquid crystal display device, the occurrence of retardation fluctuation due to environmental humidity fluctuation is suppressed, and contrast reduction or Occurrence of color unevenness can be suppressed. Furthermore, it functions as a phase difference increasing agent showing forward wavelength dispersibility by appropriately adjusting the type and addition amount of the nitrogen-containing heterocyclic compound.

The molecular weight is preferably in the range of 100 to 800, from the viewpoint of controlling the affinity with the casting belt, and more preferably in the range of 250 to 450.

In the general formula (1), A ₁ , A ₂ and B are each independently an alkyl group (methyl group, ethyl group, n-propyl group, isopropyl group, tert-butyl group, n-octyl group, 2- An ethenyl group), a cycloalkyl group (cyclohexyl group, cyclopentyl group, 4-n-dodecylcyclohexyl group, etc.), an aromatic hydrocarbon ring or an aromatic heterocycle. Among these, an aromatic hydrocarbon ring or an aromatic heterocycle is preferable, and a 5-membered or 6-membered aromatic hydrocarbon ring or an aromatic heterocycle is particularly preferable.

The structure of the 5-membered or 6-membered aromatic hydrocarbon ring or aromatic heterocyclic ring is not limited, but for example, benzene ring, pyrrole ring, pyrazole ring, imidazole ring, 1,2,3-triazole ring, 1,2 , 4-triazole ring, tetrazole ring, furan ring, oxazole ring, isoxazole ring, oxadiazole ring, isoxadiazole ring, thiophene ring, thiazole ring, isothiazole ring, thiadiazole ring, isothiadiazole ring, etc. .

The 5-membered or 6-membered aromatic hydrocarbon ring or aromatic heterocyclic ring represented by A ₁ , A ₂ and B may have a substituent. Examples of the substituent include a halogen atom ( Fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), alkyl group (methyl group, ethyl group, n-propyl group, isopropyl group, tert-butyl group, n-octyl group, 2-ethylhexyl group, etc.), cycloalkyl Groups (cyclohexyl group, cyclopentyl group, 4-n-dodecylcyclohexyl group, etc.), alkenyl groups (vinyl group, allyl group, etc.), cycloalkenyl groups (2-cyclopenten-1-yl, 2-cyclohexen-1-yl group, etc.) ), Alkynyl groups (ethynyl group, propargyl group, etc.), aromatic hydrocarbon ring groups (phenyl group, p-tolyl group, naphthyl group, etc.), aromatic heterocyclic groups (2 Pyrrole group, 2-furyl group, 2-thienyl group, pyrrole group, imidazolyl group, oxazolyl group, thiazolyl group, benzimidazolyl group, benzoxazolyl group, 2-benzothiazolyl group, pyrazolinone group, pyridinyl group, pyridinone group, 2- Pyrimidinyl group, triazine group, pyrazole group, 1,2,3-triazole group, 1,2,4-triazole group, oxazole group, isoxazole group, 1,2,4-oxadiazole group, 1,3,4 -Oxadiazole group, thiazole group, isothiazole group, 1,2,4-thiodiazole group, 1,3,4-thiadiazole group, etc.), cyano group, hydroxy group, nitro group, carboxy group, alkoxy group (methoxy group) Ethoxy group, isopropoxy group, tert-butoxy group, n-octyloxy group, 2-methyl Xyloxy group, etc.), aryloxy groups (phenoxy group, 2-methylphenoxy group, 4-tert-butylphenoxy group, 3-nitrophenoxy group, 2-tetradecanoylaminophenoxy group, etc.), acyloxy groups (formyloxy group, Acetyloxy group, pivaloyloxy group, stearoyloxy group, benzoyloxy group, p-methoxyphenylcarbonyloxy group, etc.), amino group (amino group, methylamino group, dimethylamino group, anilino group, N-methyl-anilino group, diphenyl) Amino groups, etc.), acylamino groups (formylamino group, acetylamino group, pivaloylamino group, lauroylamino group, benzoylamino group, etc.), alkyl and arylsulfonylamino groups (methylsulfonylamino group, butylsulfonylamino group, phenyl) Sulfonylamino group, 2,3,5-trichlorophenylsulfonylamino group, p-methylphenylsulfonylamino group, etc.), mercapto group, alkylthio group (methylthio group, ethylthio group, n-hexadecylthio group, etc.), arylthio group (phenylthio group) P-chlorophenylthio group, m-methoxyphenylthio group, etc.), sulfamoyl group (N-ethylsulfamoyl group, N- (3-dodecyloxypropyl) sulfamoyl group, N, N-dimethylsulfamoyl group, N -Acetylsulfamoyl group, N-benzoylsulfamoyl group, N- (N'-phenylcarbamoyl) sulfamoyl group, etc.), sulfo group, acyl group (acetyl group, pivaloylbenzoyl group, etc.), carbamoyl group (carbamoyl group) Group, N-methylcarbamoyl group, N, N-di Chi-carbamoyl, N, N-di -n- octylcarbamoyl group, and each group such as N- (methylsulfonyl) carbamoyl group).

In the general formula (1), A ₁ , A ₂ and B represent a benzene ring, a pyrrole ring, a pyrazole ring, an imidazole ring, a 1,2,3-triazole ring or a 1,2,4-triazole ring. It is preferable because a retardation film having excellent optical property variation effects and excellent durability can be obtained.

In the general formula (1), T ₁ and T ₂ each independently represents a pyrrole ring, a pyrazole ring, an imidazole ring, a 1,2,3-triazole ring or a 1,2,4-triazole ring. Among these, a pyrazole ring, a triazole ring, or an imidazole ring is preferable because a resin composition that is particularly excellent in retardation fluctuation suppressing effect against humidity fluctuation and excellent in durability is obtained. It is particularly preferred. The pyrazole ring, 1,2,3-triazole ring, 1,2,4-triazole ring and imidazole ring represented by T ₁ and T2 may be tautomers. Specific structures of the pyrrole ring, pyrazole ring, imidazole ring, 1,2,3-triazole ring or 1,2,4-triazole ring are shown below.

In the formula, * represents a bonding position with L ₁ , L ₂ , L ₃ or L ₄ in the general formula (1). R ⁵ represents a hydrogen atom or a non-aromatic substituent. Examples of the non-aromatic substituent represented by R ⁵ include the same groups as the non-aromatic substituent among the substituents that A ₁ in the general formula (1) may have. In the case where the substituent represented by R ⁵ is a substituent having an aromatic group, A ₁ and T ₁ or B and T ₁ are easily twisted, and A ₁ , B and T ₁ are resin A, cellulose acetate or resin Since it becomes impossible to form an interaction with the cellulose ester which is B, it is difficult to suppress fluctuations in optical characteristics. In order to enhance the effect of suppressing fluctuations in optical properties, R ⁵ is preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or an acyl group having 1 to 5 carbon atoms, and particularly preferably a hydrogen atom. .

In the general formula (1), T ₁ and T ₂ may have a substituent, and examples of the substituent include a substituent that A ₁ and A ₂ in the general formula (1) may have Similar groups can be mentioned.

In the general formula (1), L ₁ , L ₂ , L ₃ and L ₄ each independently represent a single bond or a divalent linking group, and are 5 or 6 via 2 or less atoms. Membered aromatic hydrocarbon rings or aromatic heterocycles are linked. The term “via two or less atoms” refers to the minimum number of atoms existing between the connected substituents among the atoms constituting the linking group. The divalent linking group having 2 or less linking atoms is not particularly limited, but includes an alkylene group, an alkenylene group, an alkynylene group, O, (C═O), NR, S, and (O═S═O). It is a divalent linking group selected from the group consisting of or a linking group in which two of them are combined. R represents a hydrogen atom or a substituent. Examples of the substituent represented by R include an alkyl group (methyl group, ethyl group, n-propyl group, isopropyl group, tert-butyl group, n-octyl group, 2-ethylhexyl group, etc.), cycloalkyl group ( Cyclohexyl group, cyclopentyl group, 4-n-dodecylcyclohexyl group, etc.), aromatic hydrocarbon ring group (phenyl group, p-tolyl group, naphthyl group, etc.), aromatic heterocyclic group (2-furyl group, 2-thienyl group, etc.) Group, 2-pyrimidinyl group, 2-benzothiazolyl group, 2-pyridyl group, etc.), cyano group and the like. The divalent linking group represented by L ₁ , L ₂ , L ₃ and L ₄ may have a substituent, and the substituent is not particularly limited. For example, A in the general formula (1) and ₁ and a ₂ have include the same groups as also substituents.

In the general formula (1), L ₁ , L ₂ , L ₃ and L ₄ are a resin that adsorbs water by increasing the planarity of the compound having the structure represented by the general formula (1). And the fluctuation of optical properties is suppressed, so that a single bond or O, (C═O) —O, O— (C═O), (C═O) —NR or NR— (C═O) is preferable, and a single bond is more preferable.

In the general formula (1), n represents an integer of 0 to 5. When n represents an integer of 2 or more, the plurality of A ₂ , T ₂ , L ₃ , and L ₄ in the general formula (1) may be the same or different. The larger n is, the stronger the interaction between the compound having the structure represented by the general formula (1) and the resin that adsorbs water is, so that the effect of suppressing fluctuations in optical properties is excellent. Excellent compatibility with resin that adsorbs. For this reason, n is preferably an integer of 1 to 3, more preferably an integer of 1 or 2.

<Compound having a structure represented by the general formula (2)>
The compound having a structure represented by the general formula (1) is preferably a compound having a structure represented by the general formula (2).

(In the formula, A ₁ , A ₂ , T ₁ , T ₂ , L ₁ , L ₂ , L ₃ and L ₄ are respectively A ₁ , A ₂ , T ₁ , T ₂ , L in the general formula (1). _1, _L 2, _{L 3} and .A ₃ and _{T 3} _{L 4} as synonymous, the .L ₅ and _{L 6} represent the same group as _{a 1} and _{T 1,} respectively, in the general formula (1), the general And represents the same group as L ₁ in Formula (1), m represents an integer of 0 to 4.)
A smaller m is more compatible with cellulose acetate, and therefore m is preferably an integer from 0 to 2, more preferably an integer from 0 to 1.

<Compound having structure represented by general formula (1.1)>
The compound having a structure represented by the general formula (1) is preferably a triazole compound having a structure represented by the following general formula (1.1).

_(Wherein, A 1, B, _{L 1} and _{L 2,} .k representing the _A 1, B, the same group as _{L 1} and _{L 2} in formula (1) represents an integer of 1-4 T ₁ represents a 1,2,4-triazole ring.)
Furthermore, the triazole compound having a structure represented by the general formula (1.1) is preferably a triazole compound having a structure represented by the following general formula (1.2).

(In the formula, Z represents the structure of the following general formula (1.2a). Q represents an integer of 2 to 3. At least two Zs represent at least one Z substituted on a benzene ring. Bonded to ortho or meta position.)

(In the formula, R ¹⁰ represents a hydrogen atom, an alkyl group or an alkoxy group. P represents an integer of 1 to 5. * represents a bonding position with a benzene ring. T ₁ represents a 1,2,4-triazole ring. Represents.)
The compound having the structure represented by the general formula (1), (2), (1.1) or (1.2) may form a hydrate, a solvate or a salt. In the present invention, the hydrate may contain an organic solvent, and the solvate may contain water. That is, “hydrate” and “solvate” include mixed solvates containing both water and organic solvents. Salts include acid addition salts formed with inorganic or organic acids. Examples of inorganic acids include, but are not limited to, hydrohalic acids (hydrochloric acid, hydrobromic acid, etc.), sulfuric acid, phosphoric acid, and the like. Examples of organic acids include acetic acid, trifluoroacetic acid, propionic acid, butyric acid, oxalic acid, citric acid, benzoic acid, alkylsulfonic acid (methanesulfonic acid, etc.), allylsulfonic acid (benzenesulfonic acid, 4-toluene) Sulfonic acid, 1,5-naphthalenedisulfonic acid, and the like), but are not limited thereto. Of these, hydrochloride, acetate, propionate and butyrate are preferable.

Examples of salts are those in which the acidic moiety present in the parent compound is a metal ion (eg, an alkali metal salt, such as sodium or potassium salt, an alkaline earth metal salt, such as calcium or magnesium salt, an ammonium salt, an alkali metal ion, alkaline earth And salts formed when substituted with organic bases (ethanolamine, diethanolamine, triethanolamine, morpholine, piperidine, etc.) It is not limited. Of these, sodium salts and potassium salts are preferred.

Examples of the solvent contained in the solvate include any common organic solvent. Specifically, alcohol (eg, methanol, ethanol, 2-propanol, 1-butanol, 1-methoxy-2-propanol, t-butanol), ester (eg, ethyl acetate), hydrocarbon (eg, toluene, hexane) , Heptane), ether (eg, tetrahydrofuran), nitrile (eg, acetonitrile), ketone (acetone) and the like. Preferred are solvates of alcohols (eg, methanol, ethanol, 2-propanol, 1-butanol, 1-methoxy-2-propanol, t-butanol). These solvents may be a reaction solvent used at the time of synthesizing the compound, a solvent used at the time of crystallization purification after synthesis, or a mixture thereof.

Further, two or more kinds of solvents may be included at the same time, or a form containing water and a solvent (for example, water and alcohol (for example, methanol, ethanol, t-butanol, etc.)) may be used.

Even if the compound having the structure represented by the general formula (1), (2), (1.1) or (1.2) is added in a form not containing water, solvent or salt, In the retardation film in the invention, a hydrate, a solvate or a salt may be formed.

The molecular weight of the compound having the structure represented by the general formula (1), (2), (1.1) or (1.2) is not particularly limited, but the smaller the compound, the better the compatibility with the resin and the greater Since the effect of suppressing fluctuations in the optical value with respect to changes in environmental humidity is higher, it is preferably 150 to 2000, more preferably 200 to 1500, and more preferably 300 to 1000.

Furthermore, the nitrogen-containing heterocyclic compound according to the present invention is particularly preferably a compound having a structure represented by the following general formula (3).

(In the formula, A represents a pyrazole ring. Ar ₁ and Ar ₂ each represent an aromatic hydrocarbon ring or an aromatic heterocyclic ring and may have a substituent. R ₁ represents a hydrogen atom, an alkyl group, or an acyl group. A sulfonyl group, an alkyloxycarbonyl group, or an aryloxycarbonyl group, q represents 1 or 2, and n and m represent an integer of 1 to 3.
The aromatic hydrocarbon ring or aromatic heterocyclic ring represented by Ar ₁ and Ar ₂ may be the 5-membered or 6-membered aromatic hydrocarbon ring or aromatic heterocyclic ring mentioned in the general formula (1), respectively. preferable. Examples of the substituent for Ar ₁ and Ar ₂ include the same substituents as those shown for the compound having the structure represented by the general formula (1).

Specific examples of R ₁ include halogen atoms (fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), alkyl groups (methyl group, ethyl group, n-propyl group, isopropyl group, tert-butyl group, n-octyl group). Group, 2-ethylhexyl group etc.), acyl group (acetyl group, pivaloylbenzoyl group etc.), sulfonyl group (eg methylsulfonyl group, ethylsulfonyl group etc.), alkyloxycarbonyl group (eg methoxycarbonyl group), An aryloxycarbonyl group (for example, phenoxycarbonyl group etc.) etc. are mentioned.

Q represents 1 or 2, and n and m represent integers of 1 to 3.

The compounds having a 5-membered or 6-membered aromatic hydrocarbon ring or aromatic heterocycle used in the present invention are, among others, those represented by the general formulas (1), (2), (1.1) and (1.2). A compound having a structure represented is preferable, and a compound having a structure represented by the general formula (3) is more preferable. The compound having a 5-membered or 6-membered aromatic hydrocarbon ring or aromatic heterocyclic ring that can be used in the present invention is a compound described in paragraphs [0140] to [0214] of International Publication No. 2014/109350. Can be given as a specific example. In addition, this invention is not limited at all by the said specific example. Further, as described above, specific examples may be tautomers, and may form hydrates, solvates or salts.

For the synthesis methods of the compounds mentioned in the specific examples, paragraphs [0215] to [0239] of International Publication No. 2014/109350 can be similarly referred.

<About the method of using the compound having the structure represented by the general formulas (1) to (3)>
The compound having the structure represented by the general formulas (1) to (3) according to the present invention can be contained in the retardation film by adjusting the amount as appropriate. 0.1 to 10% by mass, preferably 1 to 5% by mass, particularly preferably 2 to 5% by mass. The amount of addition varies depending on the type of cellulose acetate and the type of the compound, but the optimum value can be determined by the amount of addition that the retardation film of the present invention exhibits a desired retardation value. If it is in this range, the fluctuation | variation of the retardation depending on the change of environmental humidity can be reduced, without impairing the mechanical strength of the retardation film of this invention.

As a method for adding the compound having the structure represented by the general formulas (1) to (3), it may be added as a powder to the resin forming the retardation film. You may add to resin which forms a phase difference film.

≪Other additives≫
The retardation film of the present invention preferably contains other additives, and examples thereof include a plasticizer, an antioxidant, an ultraviolet absorber, a light stabilizer, an antistatic agent, and a release agent. . The compound used more effectively is preferably containing a plasticizer, and among them, a sugar ester described below, or a polycondensed ester containing a repeating unit obtained by reacting a dicarboxylic acid and a diol is used, From the viewpoint of excellent compatibility with cellulose ester, reducing the fluctuation of the retardation value by controlling the moisture in and out at high humidity, and also improving the saponification suitability by controlling the penetration of the saponification liquid into the film ,preferable.

[Plasticizer]
<Sugar ester>
The sugar ester according to the present invention is preferably a sugar ester in which at least one pyranose ring or furanose ring is 1 to 12 and all or part of the OH groups in the structure are esterified. The sugar ester according to the present invention is preferably added for the purpose of preventing hydrolysis.

The sugar ester according to the present invention is a compound containing at least one of a furanose ring and a pyranose ring, and may be a monosaccharide or a polysaccharide having 2 to 12 sugar structures linked together. The sugar ester is preferably a compound in which at least one OH group of the sugar structure is esterified. In the sugar ester according to the present invention, the average ester substitution degree is preferably within the range of 4.0 to 8.0, and more preferably within the range of 5.0 to 7.5.

Particularly preferred sugar esters in the present invention include sugar esters represented by the following general formula (A).

Formula (A)
(HO) _m -G- (OC (= O) -R ² ) _n
In the general formula (A), G represents a monosaccharide or disaccharide residue, R ² represents an aliphatic group or an aromatic group, and m is directly bonded to the monosaccharide or disaccharide residue. N is the total number of — (O—C (═O) —R ² ) groups directly bonded to the monosaccharide or disaccharide residue, 3 ≦ m + n ≦ 8, and n ≠ 0.

The sugar ester having the structure represented by the general formula (A) is a single kind of hydroxy group (m) and-(O—C (═O) —R ² ) groups in which the number (n) is fixed. It is difficult to isolate as a compound, and it is known that a compound in which several components different in m and n in the formula are mixed is obtained. Accordingly, the performance as a mixture in which the number (m) of hydroxy groups and the number (n) of — (O—C (═O) —R ² ) groups are changed is important. In the case of the retardation film of the present invention, A sugar ester having an average degree of ester substitution within the range of 5.0 to 7.5 is preferred.

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

Specific examples of the compound having a monosaccharide residue of the sugar ester represented by the general formula (A) are shown below, but the present invention is not limited to these exemplified compounds.

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

Specific examples of the compound having a disaccharide residue of the sugar ester represented by the general formula (A) are shown below, but the present invention is not limited to these exemplified compounds.

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

In general formula (A), m is the total number of hydroxy groups directly bonded to the monosaccharide or disaccharide residue, and n is directly bonded to the monosaccharide or disaccharide residue. And the total number of — (O—C (═O) —R ² ) groups. Further, it is necessary that 3 ≦ m + n ≦ 8, and it is preferable that 4 ≦ m + n ≦ 8. Further, n ≠ 0. When n is 2 or more, the — (O—C (═O) —R ² ) groups may be the same as or different from each other.

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

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

Next, preferred examples of the sugar ester represented by the general formula (A) are shown below, but the present invention is not limited to these exemplified compounds.

A sugar ester may contain two or more different substituents in one molecule, contains an aromatic substituent and an aliphatic substituent in one molecule, and contains two or more different aromatic substituents. Two or more different aliphatic substituents contained in one molecule can be contained in one molecule.

It is also preferable to contain a mixture of two or more sugar esters. It is also preferable to simultaneously contain a sugar ester containing an aromatic substituent and a sugar ester containing an aliphatic substituent.

<Synthesis Example: Synthesis Example of Sugar Ester Represented by Formula (A)>
Below, an example of the synthesis | combination of the sugar ester which can be used suitably for this invention is shown.

Four-headed Kolben equipped with a stirrer, reflux condenser, thermometer and nitrogen gas inlet tube, 34.2 g (0.1 mol) of sucrose, 180.8 g (0.8 mol) of benzoic anhydride, pyridine 379.7 g (4.8 mol) of each were charged, and the temperature was raised while bubbling nitrogen gas from a nitrogen gas inlet tube under stirring, and esterification was carried out at 70 ° C. for 5 hours. Next, the inside of the Kolben was depressurized to 4 × 10 ² Pa or less, and after excess pyridine was distilled off at 60 ° C., the inside of the Kolben was depressurized to 1.3 × 10 Pa or less and the temperature was raised to 120 ° C. Most of the acid and benzoic acid formed were distilled off. Then, 1 L of toluene and 300 g of a 0.5% by mass sodium carbonate aqueous solution were added, and the mixture was stirred at 50 ° C. for 30 minutes, and then allowed to stand to separate a toluene layer. Finally, 100 g of water was added to the separated toluene layer, and after washing with water at room temperature for 30 minutes, the toluene layer was separated, and toluene was distilled off at 60 ° C. under reduced pressure (4 × 10 ² Pa or less). A mixture of compounds A-1, A-2, A-3, A-4 and A-5 was obtained. Analysis of the resulting mixture by HPLC and LC-MASS revealed that A-1 was 7% by mass, A-2 was 58% by mass, A-3 was 23% by mass, A-4 was 9% by mass, A-5 Was 3% by mass, and the average ester substitution degree of the sugar ester was 6.57. A part of the obtained mixture was purified by silica gel column chromatography to obtain 100% pure A-1, A-2, A-3, A-4 and A-5, respectively.

The addition amount of the sugar ester is preferably in the range of 0.1 to 20% by mass and more preferably in the range of 1 to 15% by mass with respect to the cellulose ester.

<Polycondensed ester>
A preferable plasticizer for the retardation film of the present invention includes a polycondensed ester containing a repeating unit obtained by reacting a dicarboxylic acid and a diol.

The dicarboxylic acid constituting the polycondensed ester is an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid or an alicyclic dicarboxylic acid, preferably an aromatic dicarboxylic acid. The dicarboxylic acid may be one type or a mixture of two or more types.

The diol constituting the polycondensed ester is an aromatic diol, an aliphatic diol or an alicyclic diol, preferably an aliphatic diol, more preferably a diol having 1 to 4 carbon atoms. The diol may be one type or a mixture of two or more types.

Among them, the polycondensed ester preferably contains a repeating unit obtained by reacting at least a dicarboxylic acid containing an aromatic dicarboxylic acid and a diol having 1 to 4 carbon atoms. The aromatic dicarboxylic acid and the aliphatic dicarboxylic acid are preferably used. More preferably, it contains a repeating unit obtained by reacting a dicarboxylic acid containing an acid with a diol having 1 to 4 carbon atoms.

The both ends of the molecule of the polycondensed ester may or may not be sealed, but are preferably sealed from the viewpoint of reducing the moisture permeability of the film.

The polycondensed ester is preferably a compound having a structure represented by the following general formula (4) or (5). In the following formula, n is an integer of 1 or more.

Formula (4) B- (GA) _n -GB
Formula (5) C- (AG) _n -AC
A in the general formulas (4) and (5) is a divalent group derived from an alkylene dicarboxylic acid having 3 to 20 carbon atoms (preferably 4 to 12 carbon atoms), and has 4 to 20 carbon atoms (preferably 4 to 4 carbon atoms). 12) a divalent group derived from an alkenylene dicarboxylic acid or a divalent group derived from an aryl dicarboxylic acid having 8 to 20 carbon atoms (preferably 8 to 12).

Examples of the divalent group derived from an alkylenedicarboxylic acid having 3 to 20 carbon atoms in A include 1,2-ethanedicarboxylic acid (succinic acid), 1,3-propanedicarboxylic acid (glutaric acid), 1 Divalent groups derived from 1,4-butanedicarboxylic acid (adipic acid), 1,5-pentanedicarboxylic acid (pimelic acid), 1,8-octanedicarboxylic acid (sebacic acid) and the like are included. Examples of the divalent group derived from alkenylene dicarboxylic acid having 4 to 20 carbon atoms in A include a divalent group derived from maleic acid, fumaric acid and the like. Examples of divalent groups derived from aryl dicarboxylic acids having 8 to 20 carbon atoms in A include 1,2-benzenedicarboxylic acid (phthalic acid), 1,3-benzenedicarboxylic acid, 1,4-benzene. Divalent groups derived from naphthalenedicarboxylic acid such as dicarboxylic acid and 1,5-naphthalenedicarboxylic acid are included.

A may be one type or two or more types may be combined. Among these, A is preferably a combination of an alkylene dicarboxylic acid having 4 to 12 carbon atoms and an aryl dicarboxylic acid having 8 to 12 carbon atoms.

G in the general formulas (4) and (5) is a divalent group derived from an alkylene glycol having 2 to 20 (preferably 2 to 12) carbon atoms, and has 6 to 20 (preferably 6 to 12) carbon atoms. ) Or a divalent group derived from an oxyalkylene glycol having 4 to 20 (preferably 4 to 12) carbon atoms.

Examples of the divalent group derived from an alkylene glycol having 2 to 20 carbon atoms in G include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1, 3-butanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol ( Neopentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylol) Heptane), 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanedio , 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, etc. Divalent groups are included.

Examples of divalent groups derived from aryl glycols having 6 to 20 carbon atoms in G include 1,2-dihydroxybenzene (catechol), 1,3-dihydroxybenzene (resorcinol), 1,4-dihydroxybenzene Divalent groups derived from (hydroquinone) and the like are included. Examples of the divalent group derived from oxyalkylene glycol having 4 to 12 carbon atoms in G are derived from diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol and the like. Divalent groups are included.

G may be one type or two or more types may be combined. Among these, G is preferably an alkylene glycol having 2 to 12 carbon atoms.

B in the general formula (4) is a monovalent group derived from an aromatic ring-containing monocarboxylic acid or an aliphatic monocarboxylic acid.

The aromatic ring-containing monocarboxylic acid in the monovalent group derived from the aromatic ring-containing monocarboxylic acid is a carboxylic acid containing an aromatic ring in the molecule, and not only those in which the aromatic ring is directly bonded to a carboxy group, Also included are those in which an aromatic ring is bonded to a carboxy group via an alkylene group or the like. Examples of monovalent groups derived from aromatic ring-containing monocarboxylic acids include benzoic acid, para-tert-butyl benzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethyl benzoic acid, ethyl benzoic acid, and normal propyl benzoic acid. , Monovalent groups derived from aminobenzoic acid, acetoxybenzoic acid, phenylacetic acid, 3-phenylpropionic acid and the like.

Examples of monovalent groups derived from aliphatic monocarboxylic acids include monovalent groups derived from acetic acid, propionic acid, butanoic acid, caprylic acid, caproic acid, decanoic acid, dodecanoic acid, stearic acid, oleic acid and the like. Is included. Among these, a monovalent group derived from an alkyl monocarboxylic acid having 1 to 3 carbon atoms in the alkyl portion is preferable, and an acetyl group (a monovalent group derived from acetic acid) is more preferable.

C in the general formula (5) is a monovalent group derived from an aromatic ring-containing monoalcohol or an aliphatic monoalcohol.

An aromatic ring-containing monoalcohol is an alcohol containing an aromatic ring in the molecule, and includes not only those in which an aromatic ring is directly bonded to an OH group, but also those in which an aromatic ring is bonded to an OH group via an alkylene group or the like. . Examples of the monovalent group derived from an aromatic ring-containing monoalcohol include a monovalent group derived from benzyl alcohol, 3-phenylpropanol and the like.

Examples of monovalent groups derived from aliphatic monoalcohols include methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, isopentanol, hexanol, isohexanol, cyclohexyl alcohol, octanol, isooctanol, Monovalent groups derived from 2-ethylhexyl alcohol, nonyl alcohol, isononyl alcohol, tert-nonyl alcohol, decanol, dodecanol, dodecahexanol, dodecaoctanol, allyl alcohol, oleyl alcohol and the like are included. Of these, monovalent groups derived from alcohols having 1 to 3 carbon atoms such as methanol, ethanol, propanol and isopropanol are preferred.

The weight average molecular weight of the polycondensed ester is preferably in the range of 350 to 3000, and more preferably in the range of 400 to 1500. If the weight average molecular weight is within the above range, the precipitation from the retardation film of the polycondensed ester used in the present invention is satisfied, and the intended effect can be obtained. The weight average molecular weight can be measured by the gel permeation chromatography (GPC).

Specific examples of the polycondensation ester are shown below. First, a specific example of a polycondensed ester in which both ends are sealed with an “aromatic group” is shown.

Next, specific examples of the polycondensed ester having both ends sealed with an “aliphatic group” are shown below.

P-1: acetyl esterified product of both ends of a condensate (weight average molecular weight 950) comprising adipic acid / phthalic acid / ethanediol (1/1/2 molar ratio) P-2: succinic acid / phthalic acid / ethane Acetyl esterified compound at both ends of a condensate (weight average molecular weight 2500) consisting of diol / (1/1/2 molar ratio) P-3: glutaric acid / isophthalic acid / 1,3-propanediol (1/1 / Acetyl esterified product at both ends of a condensate (weight average molecular weight 1300) consisting of 2 mole ratio) P-4: Succinic acid / glutaric acid / adipic acid / terephthalic acid / isophthalic acid / ethanediol / 1,2-propanediol Propyl ester of both ends of a condensate (number average molecular weight 3000) consisting of (1/1/1/1/1/3/2 molar ratio) P-5: Succinic acid / phthalic acid / ethane Butyl esterified product at both ends of a condensate (weight average molecular weight 2100) consisting of diol / (1/1/2 molar ratio) P-6: adipic acid / terephthalic acid / 1,2-propanediol (1/1 / 2-ethylhexyl esterified product of both ends of a condensate (number average molecular weight 2500) consisting of 2 mole ratio P-7: Succinic acid / terephthalic acid / poly (average polymerization degree 5) propylene ether glycol / 1,2-propane 2-ethylhexyl esterified product of both ends of a condensate (weight average molecular weight 3500) comprising a diol (2/1/1/2 molar ratio) P-8: adipic acid / phthalic acid / 1,2-propanediol (3 / 1/3 molar ratio) of the condensate (weight average molecular weight 490) at both ends is a benzoate ester. The amount of the polycondensation ester added to the cellulose ester Preferably added in an amount of 0.1 to 20 wt% Te, it is more preferably in the range of 1 to 15 wt%.

<Other plasticizers>
Examples of other plasticizers include polyhydric alcohol esters, polyhydric carboxylic acid esters (including phthalic acid esters), glycolate compounds, and fatty acid esters and phosphoric acid esters. These may be used alone or in combination of two or more.

The polyhydric alcohol ester is an ester (alcohol ester) of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, preferably a divalent to 20-valent aliphatic polyhydric alcohol ester. The polyhydric alcohol ester preferably has an aromatic ring or a cycloalkyl ring in the molecule.

Preferred examples of the aliphatic polyhydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2- Butanediol, 1,3-butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, trimethylolpropane , Pentaerythritol, trimethylolethane, xylitol and the like. Of these, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, xylitol and the like are preferable.

The monocarboxylic acid is not particularly limited, and may be an aliphatic monocarboxylic acid, an alicyclic monocarboxylic acid, an aromatic monocarboxylic acid, or the like. In order to increase the moisture permeability of the film and make it less likely to volatilize, alicyclic monocarboxylic acids or aromatic monocarboxylic acids are preferred. One type of monocarboxylic acid may be sufficient and a 2 or more types of mixture may be sufficient as it. Further, all of the OH groups contained in the aliphatic polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

The aliphatic monocarboxylic acid is preferably a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms. The number of carbon atoms of the aliphatic monocarboxylic acid is more preferably 1-20, and still more preferably 1-10. Examples of aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanoic acid, undecylic acid, lauric acid, tridecylic acid , Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid; undecylenic acid, Examples include unsaturated fatty acids such as oleic acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid. Of these, acetic acid or a mixture of acetic acid and other monocarboxylic acid is preferable in order to enhance the compatibility with cellulose acetate.

Examples of the alicyclic monocarboxylic acid include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid and the like.

Examples of aromatic monocarboxylic acids include benzoic acid; one having 1 to 3 alkyl or alkoxy groups (for example, methoxy group or ethoxy group) introduced into the benzene ring of benzoic acid (for example, toluic acid); benzene ring Aromatic monocarboxylic acids having two or more (for example, biphenyl carboxylic acid, naphthalene carboxylic acid, tetralin carboxylic acid, etc.) are included, and benzoic acid is preferred.

Specific examples of the polyhydric alcohol ester include compounds described in paragraphs [0058] to [0061] of JP-A-2006-113239.

The polyvalent carboxylic acid ester is an ester of a divalent or higher, preferably 2 to 20 valent polycarboxylic acid and an alcohol compound. The polyvalent carboxylic acid is preferably a divalent to 20-valent aliphatic polyvalent carboxylic acid, a 3- to 20-valent aromatic polyvalent carboxylic acid, or a 3- to 20-valent alicyclic polyvalent carboxylic acid. .

Examples of polyvalent carboxylic acids include trivalent or higher aromatic polyvalent carboxylic acids or derivatives such as trimellitic acid, trimesic acid, pyromellitic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid Contains aliphatic polycarboxylic acids such as fumaric acid, maleic acid, and tetrahydrophthalic acid, and oxypolycarboxylic acids such as tartaric acid, tartronic acid, malic acid, and citric acid, and suppresses volatilization from the film. For this, oxypolycarboxylic acids are preferred.

Examples of the alcohol compound include an aliphatic saturated alcohol compound having a straight chain or a side chain, an aliphatic unsaturated alcohol compound having a straight chain or a side chain, an alicyclic alcohol compound, or an aromatic alcohol compound. The carbon number of the aliphatic saturated alcohol compound or the aliphatic unsaturated alcohol compound is preferably 1 to 32, more preferably 1 to 20, and further preferably 1 to 10. Examples of the alicyclic alcohol compound include cyclopentanol, cyclohexanol and the like. Examples of the aromatic alcohol compound include benzyl alcohol and cinnamyl alcohol.

The molecular weight of the polyvalent carboxylic acid ester is not particularly limited, but is preferably in the range of 300 to 1000, more preferably in the range of 350 to 750. The molecular weight of the polyvalent carboxylic acid ester plasticizer is preferably larger from the viewpoint of suppressing bleeding out; it is preferably smaller from the viewpoint of moisture permeability and compatibility with cellulose acetate.

Examples of polycarboxylic acid esters include triethyl citrate, tributyl citrate, acetyl triethyl citrate (ATEC), acetyl tributyl citrate (ATBC), benzoyl tributyl citrate, acetyl triphenyl citrate, acetyl tribenzyl citrate , Dibutyl tartrate, diacetyl dibutyl tartrate, tributyl trimellitic acid, tetrabutyl pyromellitic acid and the like.

The polyvalent carboxylic acid ester may be a phthalic acid ester. Examples of the phthalic acid ester include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, dicyclohexyl terephthalate and the like.

Examples of glycolate compounds include alkylphthalyl alkyl glycolates. Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl Ethyl glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl Glycolate, butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl phthalyl ethyl Glycolate and the like, preferably ethyl phthalyl ethyl glycolate.

Esters include fatty acid esters, citrate esters and phosphate esters.

Examples of fatty acid esters include butyl oleate, methylacetyl ricinoleate, and dibutyl sebacate. Examples of the citrate ester include acetyltrimethyl citrate, acetyltriethyl citrate, and acetyltributyl citrate. Examples of the phosphate ester include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, biphenyl diphenyl phosphate, trioctyl phosphate, tributyl phosphate, and the like, and preferably triphenyl phosphate.

Of these, polyester, glycolate compound, and phosphate ester are preferable, and polyester is particularly preferable.

The content of the plasticizer is preferably in the range of 1 to 20% by mass, more preferably in the range of 1.5 to 15% by mass with respect to the cellulose ester. When the content of the plasticizer is within the above range, the effect of imparting plasticity can be exhibited, and the plasticizer is also excellent in resistance to bleeding.

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

The antioxidant has a role of delaying or preventing the retardation film from being decomposed by, for example, the residual solvent amount of halogen in the retardation film or phosphoric acid of the phosphoric acid plasticizer. It is preferable to make it contain in.

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

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

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

<Ultraviolet absorber>
The retardation film of the present invention can contain an ultraviolet absorber for the purpose of imparting an ultraviolet absorbing function.

The ultraviolet absorber is not particularly limited, and examples thereof include an ultraviolet absorber such as benzotriazole, 2-hydroxybenzophenone, or salicylic acid phenyl ester. For example, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3 Triazoles such as 5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone And benzophenones.

Among UV absorbers, UV absorbers with a molecular weight of 400 or more are difficult to sublimate or volatilize at a high boiling point, and are difficult to disperse when dried at high temperatures. From the viewpoint of improving weather resistance, it is preferable.

Examples of the ultraviolet absorber having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- ( Benzotriazoles such as 1,1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol], bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, Hindered amines such as bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butyl Bis (1,2,2,6,6-pentamethyl-4-piperidyl) malonate, 1- [2- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionylo Xyl] ethyl] -4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine The thing of the hybrid type | system | group which has the structure of a hindered amine is mentioned, These can be used individually or in combination of 2 or more types. Among these, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole and 2,2-methylenebis [4- (1,1,3,3- Tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] is particularly preferred.

As these ultraviolet absorbers, commercially available products may be used. For example, Tinuvin 109, Tinuvin 171, Tinuvin 234, Tinuvin 326, Tinuvin 327, Tinuvin 328, Tinuvin 928, etc. manufactured by BASF Japan, or 2, 2'-methylenebis [6- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol] (molecular weight 659; examples of commercially available products are manufactured by ADEKA Corporation LA31) can be preferably used.

The ultraviolet absorbers can be used singly or in combination of two or more.

The amount of the UV absorber used is not uniform depending on the type of UV absorber and the use conditions, but generally 0.05 to 10% by weight, preferably 0.1 to 5% by weight, based on cellulose acetate. It is added in the range of.

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

For inorganic powders that do not dissolve in organic solvents, use a dissolver or sand mill in the organic solvent and cellulose acetate to disperse them before adding them to the dope.

<Fine particles (matting agent)>
The retardation film of the present invention may further contain fine particles (matting agent) as necessary in order to enhance the slipperiness of the surface.

The fine particles may be inorganic fine particles or organic fine particles. Examples of inorganic fine particles include silicon dioxide (silica), titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, Examples include magnesium silicate and calcium phosphate. Among these, silicon dioxide and zirconium oxide are preferable, and silicon dioxide is more preferable in order to reduce the increase in haze of the obtained film.

Examples of the fine particles of silicon dioxide include Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600, NAX50 (manufactured by Nippon Aerosil Co., Ltd.), Seahoster KE-P10, KE-P30, KE-P50, KE-P100 (manufactured by Nippon Shokubai Co., Ltd.) and the like are included. Of these, Aerosil R972V, NAX50, Seahoster KE-P30 and the like are particularly preferable because they reduce the coefficient of friction while keeping the turbidity of the resulting film low.

The primary particle diameter of the fine particles is preferably in the range of 5 to 50 nm, more preferably in the range of 7 to 20 nm. A larger primary particle size has a greater effect of increasing the slipperiness of the resulting film, but transparency tends to decrease. Therefore, the fine particles may be contained as secondary aggregates having a particle diameter in the range of 0.05 to 0.3 μm. The size of the primary particles or the secondary aggregates of the fine particles was determined by observing the primary particles or secondary aggregates with a transmission electron microscope at a magnification of 500,000 to 2,000,000 times, and measuring 100 primary particles or secondary aggregates. It can be determined as an average value of the particle diameter.

The content of fine particles is preferably in the range of 0.05 to 1.0% by mass, more preferably in the range of 0.1 to 0.8% by mass with respect to the cellulose ester.

≪Method for producing retardation film≫
As the method for producing the retardation film of the present invention, the usual inflation method, T-die method, calendar method, cutting method, casting method, emulsion method, hot press method and the like can be used. From the viewpoint of suppression of foreign matter defects, suppression of optical defects such as die lines, etc., a film casting method can be selected from a solution casting film forming method and a melt casting film forming method, and in particular, a solution casting film forming method, It is preferable from the viewpoint that a uniform and smooth surface can be obtained.

Hereinafter, production examples for producing the retardation film of the present invention by the solution casting method will be described.

The phase difference film of the present invention was prepared by preparing a dope by dissolving at least cellulose acetate as resin A and cellulose ester as resin B, a retardation increasing agent and an additive in a solvent, and preparing a filtration. Casting the dope on a belt-shaped or drum-shaped metal support to form a web, peeling the formed web from the metal support to form a film, stretching and drying the film, and drying The film is cooled and wound into a roll. The retardation film of the present invention preferably contains a cellulose ester specified by Resin A and Resin B in the solid content in the range of 60 to 95% by mass.

Hereinafter, each process will be described.

(1) Dissolution process The organic ester mainly composed of a good solvent for the cellulose ester, the cellulose ester in a dissolution vessel, and in some cases, the retardation increasing agent, sugar ester, polycondensation ester, or other compound according to the present invention. In the step of dissolving with stirring to form a dope, or in the step of forming a dope which is a main solution by mixing the retardation increasing agent, sugar ester, polycondensation ester or other compound solution with the cellulose ester solution. is there.

When the retardation film of the present invention is produced by a solution casting method, an organic solvent useful for forming a dope is used without limitation as long as it dissolves a cellulose ester, a retardation increasing agent and other compounds at the same time. be able to.

For example, as a chlorinated organic solvent, methylene chloride, as a non-chlorinated organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro- 2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, etc. For example, methylene chloride, methyl acetate, ethyl acetate, and acetone can be preferably used as the main solvent. Particularly preferably ethyl acetate.

In addition to the above organic solvent, the dope preferably contains a linear or branched aliphatic alcohol having 1 to 4 carbon atoms in the range of 1 to 40% by mass. When the proportion of alcohol in the dope increases, the web gels and peeling from the metal support becomes easy. When the proportion of alcohol is small, cellulose ester and other compounds dissolve in non-chlorine organic solvents. There is also a role to promote. In the film formation of the retardation film of the present invention, a method of forming a film using a dope having an alcohol concentration in the range of 0.5 to 15.0% by mass from the viewpoint of improving the flatness of the obtained retardation film. Can be applied.

In particular, a dope composition in which cellulose ester and other compounds are dissolved in a total amount of 15 to 45% by mass in a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. It is preferable that it is a thing.

Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Methanol and ethanol are preferred because of the stability, boiling point of these inner dopes, and good drying properties.

For dissolution of cellulose ester, retardation increasing agent, sugar ester, polycondensation ester or other compound, a method performed at normal pressure, a method performed below the boiling point of the main solvent, a method performed under pressure above the boiling point of the main solvent, A method using a cooling dissolution method as described in JP-A-9-95544, JP-A-9-95557, or JP-A-9-95538, and a high pressure described in JP-A-11-21379 Although various dissolution methods such as a method can be used, a method of pressurizing at a temperature equal to or higher than the boiling point of the main solvent is particularly preferable.

The concentration of the cellulose ester in the dope is preferably in the range of 10 to 40% by mass. After the compound is added to the dope during or after dissolution and dissolved and dispersed, it is filtered through a filter medium, defoamed, and sent to the next step with a liquid feed pump.

Regarding the filtration of the dope, it is preferable to filter the dope with, for example, a filter medium having a 90% collection particle diameter of 10 to 100 times the average particle diameter of the fine particles in the main filter 3 having a leaf disk filter.

In the present invention, the filter medium used for filtration preferably has a low absolute filtration accuracy. However, if the absolute filtration accuracy is too small, the filter medium is likely to be clogged, and the filter medium must be frequently replaced. There is a problem of lowering productivity.

Therefore, in the present invention, the filter medium used for the cellulose ester dope preferably has an absolute filtration accuracy of 0.008 mm or less, more preferably in the range of 0.001 to 0.008 mm, and more preferably in the range of 0.003 to 0.006 mm. A range of filter media is more preferred.

There are no particular restrictions on the material of the filter medium, and normal filter media can be used. However, plastic fiber filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel fibers are used to remove fibers. This is preferable.

In the present invention, the flow rate of the dope during filtration is preferably 10 to 80 kg / (h · m ² ), preferably 20 to 60 kg / (h · m ² ). Here, if the flow rate of the dope at the time of filtration is 10 kg / (h · m ² ) or more, it becomes efficient productivity, and the flow rate of the dope at the time of filtration is within 80 kg / (h · m ² ). If so, the pressure applied to the filter medium is appropriate, and the filter medium is not damaged, which is preferable.

The filtration pressure is preferably 3500 kPa or less, more preferably 3000 kPa or less, and even more preferably 2500 kPa or less. The filtration pressure can be controlled by appropriately selecting the filtration flow rate and the filtration area.

FIG. 1 is a diagram schematically showing an example of a dope preparation step, a casting step, and a drying step of a solution casting film forming method preferable for the present invention.

大きな Remove large agglomerates from the charging vessel 41 with the filter 44 and feed the solution to the stock vessel 42. Thereafter, various additive solutions are added from the stock kettle 42 to the main dope dissolving kettle 1.

Thereafter, the main dope is filtered by the main filter 3, and a matting agent dispersion liquid, an ultraviolet absorbent additive liquid, and the like are added thereto inline from 16.

In many cases, the main dope may contain about 10 to 50% by weight of recycled material.

Recycled material is, for example, a product obtained by finely pulverizing a cellulose ester film, which is generated when a cellulose ester film is formed, and has exceeded the specified value of the film due to a material from which both sides of the film are cut off, or due to scratches. A cellulose ester film raw material is used.

Also, as a raw material of the resin used for the dope preparation, those obtained by pelletizing cellulose ester and other compounds in advance can be preferably used.

(2) Casting step (2-1) Dope casting An endless metal support 31 that feeds the dope to a pressure die 30 through a liquid feed pump (for example, a pressurized metering gear pump) and transfers it infinitely, For example, the dope is cast from a pressure die slit at a casting position on a metal support such as a stainless steel belt or a rotating metal drum.

The metal support in the casting process is preferably a mirror-finished surface, and a stainless steel belt or a drum whose surface is plated with a casting is preferably used as the metal support. The cast width can be in the range of 1 to 4 m, preferably in the range of 1.5 to 3 m, more preferably in the range of 2 to 2.8 m. The surface temperature of the metal support in the casting step is set in the range of −50 ° C. to below the temperature at which the solvent boils and does not foam, more preferably in the range of −30 to 0 ° C. A higher temperature is preferred because the web can be dried faster, but if it is too high, the web may foam or the flatness may deteriorate. A preferable support temperature is appropriately determined at 0 to 100 ° C., and more preferably within a range of 5 to 30 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent. The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing warm air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short. When using warm air, considering the temperature drop of the web due to the latent heat of vaporization of the solvent, while using warm air above the boiling point of the solvent, there may be cases where wind at a temperature higher than the target temperature is used while preventing foaming. . In particular, it is preferable to perform drying efficiently by changing the temperature of the support and the temperature of the drying air during the period from casting to peeling.

¡Pressure dies that can adjust the slit shape of the die base and make the film thickness uniform are preferred. Examples of the pressure die include 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 laminated.

(3) Solvent evaporation step The web (the dope is cast on the casting support and the formed dope film is referred to as a web) is heated on the casting support to evaporate the solvent.

To evaporate the solvent, there are a method of blowing air from the web side, a method of transferring heat from the back side of the support, a method of transferring heat from the front and back by radiant heat, etc. Is preferable. A method of combining them is also preferably used. The web on the support after casting is preferably dried on the support in an atmosphere of 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C., it is preferable to apply hot air at this temperature to the upper surface of the web or heat by means such as infrared rays.

From the viewpoint of surface quality, moisture permeability, and peelability, it is preferable to peel the web from the support within 30 to 120 seconds.

(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 as a film.

The temperature at the peeling position on the metal support is preferably in the range of 10 to 40 ° C, more preferably in the range of 11 to 30 ° C.

The amount of residual solvent at the time of peeling of the web on the metal support at the time of peeling is preferably 50 to 120% by mass depending on the strength of drying conditions, the length of the metal support, and the like. When peeling at a higher residual solvent amount, if the web is too soft, the flatness at the time of peeling is impaired, and slippage and vertical stripes are likely to occur due to the peeling tension. The amount of solvent is determined.

The residual solvent amount of the web is defined by the following formula (Z).

Formula (Z)
Residual solvent amount (%) = (mass before web heat treatment−mass after web heat treatment) / (mass after web heat treatment) × 100
Note that the heat treatment for measuring the residual solvent amount represents performing heat treatment at 115 ° C. for 1 hour.

The peeling tension when peeling the metal support from the film is usually in the range of 196 to 245 N / m. However, when wrinkles are likely to occur during peeling, peeling with a tension of 190 N / m or less is preferable. .

In the present invention, the temperature at the peeling position on the metal support is preferably in the range of −50 to 40 ° C., more preferably in the range of 10 to 40 ° C., and in the range of 15 to 30 ° C. Is most preferred.

(5) Drying and stretching step The drying step can be divided into a preliminary drying step and a main drying step.

<Preliminary drying process>
The web obtained by peeling from the metal support is dried. The web may be dried while being conveyed by a large number of rollers arranged above and below, or may be dried while being conveyed while fixing both ends of the web with clips like a tenter dryer. .

The means for drying the web is not particularly limited, and can be generally performed with hot air, infrared rays, a heating roller, microwave, or the like, but it is preferably performed with hot air in terms of simplicity.

The drying temperature in the web drying process is preferably a glass transition point of the film of −5 ° C. or less, and it is effective to perform a heat treatment at a temperature of 100 ° C. or more for 10 minutes or more and 60 minutes or less. Drying is performed at a drying temperature in the range of 100 to 200 ° C, more preferably in the range of 110 to 160 ° C.

<Extension process>
The retardation film of the present invention can be subjected to stretching treatment to control the molecular orientation in the film, and target retardation values Ro and Rth can be obtained.

The retardation film of the present invention is preferably stretched in the casting direction (also referred to as MD direction) and / or in the width direction (also referred to as TD direction), and is stretched in the width direction by at least a tenter stretching device. It is preferable to manufacture.

The stretching operation may be performed in multiple stages. When biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise. In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible.

Thus, for example, the following stretching steps are possible:
-Stretch in the casting direction-> Stretch in the width direction-> Stretch in the casting direction-> Stretch in the casting direction-Stretch in the width direction-> Stretch in the width direction-> Stretch in the casting direction-> Stretch in the casting direction Simultaneous biaxial stretching includes stretching in one direction and contracting the other while relaxing the tension.

The residual solvent amount at the start of stretching is preferably in the range of 2 to 10% by mass.

If the amount of the residual solvent is 2% by mass or more, the film thickness deviation is small and is preferable from the viewpoint of flatness, and if it is within 10% by mass, the unevenness of the surface is reduced and the flatness is improved.

The retardation film of the present invention has (Tg + 15) when the glass transition temperature of the film is defined as Tg in the MD direction and / or TD direction, preferably in the TD direction so that the film thickness after stretching is in a desired range. ) To (Tg + 50) ° C. is preferably stretched. If the stretching is performed within the above temperature range, the retardation can be easily adjusted, and the stretching stress can be reduced, so that the haze is lowered. Moreover, the retardation film which suppressed generation | occurrence | production of a fracture | rupture and was excellent in flatness and the coloring property of the film itself is obtained. The stretching temperature is preferably in the range of (Tg + 20) to (Tg + 40) ° C.

The glass transition temperature Tg referred to here is a midpoint glass transition temperature (Tmg) measured at a rate of temperature increase of 20 ° C./min using a commercially available differential scanning calorimeter and determined according to JIS K7121 (1987). It is. A specific method for measuring the glass transition temperature Tg of the retardation film is measured using a differential scanning calorimeter DSC220 manufactured by Seiko Instruments Inc. according to JIS K7121 (1987).

The retardation film of the present invention preferably stretches the web at least 1.1 times in the TD direction. The range of stretching is preferably 1.1 to 1.5 times the original width, and more preferably 1.2 to 1.4 times. If it is in the said range, the movement of the molecule | numerator in a film will be large and not only a desired phase difference value will be obtained, but a film can be thinned and planarity can be improved.

In order to stretch in the MD direction, peeling is preferably performed at a peeling tension of 130 N / m or more, particularly preferably 150 to 170 N / m. Since the web after peeling is in a high residual solvent state, stretching in the MD direction can be performed by maintaining the same tension as the peeling tension. As the web dries and the residual solvent amount decreases, the draw ratio in the MD direction decreases.

The draw ratio in the MD direction can be calculated from the rotation speed of the belt support and the tenter operation speed.

In order to stretch in the TD direction, for example, the entire drying process or a part of the process as disclosed in Japanese Patent Application Laid-Open No. 62-46625 is performed while holding the width at both ends of the web with clips or pins in the width direction. A drying method (referred to as a tenter method), among them, a tenter method using clips and a pin tenter method using pins are preferably used.

In stretching in the TD direction, stretching in the width direction of the film at a stretching speed of 250 to 500% / min is preferable from the viewpoint of improving the flatness of the film.

If the stretching speed is 250% / min or more, the planarity is improved and the film can be processed at a high speed, which is preferable from the viewpoint of production aptitude, and if it is within 500% / min, the film is broken. Can be processed without any problem.

A preferable stretching speed is in the range of 300 to 400% / min. The stretching speed is defined by the following formula 1.

Formula 1 Stretching speed (% / min) = [(d1 / d2) -1] × 100 (%) / t
(In Formula 1, d1 is the width dimension in the stretching direction of the cellulose ester film after stretching, d2 is the width dimension in the stretching direction of the cellulose ester film before stretching, and t is the time (min) required for stretching. .)
The retardation film of the present invention contains a retardation increasing agent and necessarily has retardation by stretching. In-plane retardation value Ro and thickness direction retardation value Rth were measured using an automatic birefringence meter Axoscan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axometrics) under an environment of 23 ° C. and 55% RH. A three-dimensional refractive index measurement is performed at a wavelength of 590 nm, and the refractive indexes nx, ny, and nz obtained can be calculated.

The retardation film of the present invention is represented by the following formulas (i) and (ii), the retardation value Ro in the in-plane direction of the retardation film is in the range of 45 to 60 nm, and the retardation in the film thickness direction. A value Rth within the range of 110 to 140 nm is preferable from the viewpoint of improving visibility such as viewing angle and contrast when the VA liquid crystal display device is provided. The retardation film can be adjusted within the range of the retardation value by stretching while adjusting the stretching ratio at least in the TD direction.

Formula (i): Ro = (n _x −n _y ) × d (nm)
Formula (ii): Rth = {(n _x + n _y ) / 2−n _z } × d (nm)
In [Equation (i) and Formula (ii), n _x represents a refractive index in the direction x in which the refractive index is maximized in the plane direction of the film. n _y, in-plane direction of the film, the refractive index in the direction y perpendicular to the direction x. _nz represents the refractive index in the thickness direction z of the film. d represents the thickness (nm) of the film. ]
<Knurling>
After a predetermined heat treatment or cooling treatment, it is preferable to provide a slitter and cut off the end portion before winding to obtain a good winding shape. Furthermore, it is preferable to knurling both ends of the width.

The knurling process can be formed by pressing a heated embossing roller. Fine embossing is formed on the embossing roller, and by pressing the embossing roller, unevenness can be formed on the film and the end can be made bulky.

The height of the knurling at both ends of the width of the retardation film of the present invention is preferably 4 to 20 μm and the width is 5 to 20 mm.

In the present invention, the knurling process is preferably provided after the drying in the film forming process and before winding.

(6) Winding step This is a step of winding as a film after the residual solvent amount in the web is 2% by mass or less, and the film having good dimensional stability by making the residual solvent amount 0.4% by mass or less. Can be obtained.

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

≪Physical properties of retardation film≫
<Haze>
The retardation film of the present invention preferably has a haze of less than 1%, more preferably less than 0.5%. By setting the haze to less than 1%, there is an advantage that the transparency of the film becomes higher and it becomes easier to use as a film for optical applications.

<Equilibrium moisture content>
In the retardation film of the present invention, the equilibrium water content at 25 ° C. and 60% relative humidity is preferably 4% or less, more preferably 3% or less. By setting the equilibrium moisture content to 4% or less, it is preferable to easily cope with a change in humidity and to hardly change the optical characteristics and dimensions.

<Film length, width, film thickness>
The retardation film of the present invention is preferably long, specifically, preferably has a length of about 100 to 10,000 m, and is wound up in a roll shape. The width of the retardation film of the present invention is preferably 1 m or more, more preferably 1.4 m or more, and particularly preferably 1.4 to 4 m.

The film thickness is preferably in the range of 10 to 36 μm from the viewpoint of thinning the display device and productivity. If the film thickness is 10 μm or more, a certain level of film strength and retardation can be expressed. If the film thickness is 36 μm or less, the film has a desired retardation and can be applied to make the polarizing plate and the display device thinner. Preferably, it is in the range of 20 to 36 μm.

≪Polarizing plate≫
The retardation film of this invention can be used for a polarizing plate and a liquid crystal display device provided with the same. The retardation film of the present invention is preferably a film serving as both a polarizing plate protective film and a retardation film. In that case, it is not necessary to prepare a retardation film separate from the polarizing plate protective film. Therefore, the thickness of the liquid crystal display device can be reduced and the manufacturing process can be simplified.

The polarizing plate has a polarizer and a polarizing plate protective film bonded to one or both surfaces of the polarizer.

A polarizer is an element that allows only light of a plane of polarization in a certain direction to pass through. A typical polarizer is a polyvinyl alcohol polarizing film, which is dichroic with a polyvinyl alcohol film dyed with iodine. There are dyed dyes.

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

The polarizing plate of the present invention can be produced by a general method. The surface to be attached to the polarizer of the retardation film of the present invention is subjected to alkali saponification treatment. The retardation film of the present invention is bonded to at least one surface of a polarizer produced by immersion and stretching in an iodine solution, using a completely saponified polyvinyl alcohol aqueous solution.

Specifically, the retardation film of the present invention and the polarizer are usually bonded after the saponification treatment is performed by immersing the retardation film of the present invention in a saponification solution. For example, the saponification solution is 2 mol / L sodium hydroxide solution.

When the retardation film is continuously saponified in the manufacturing process of the polarizing plate or troubles occur and the retardation film is immersed in the saponification solution for a long time, the retardation film using only the DAC is Since it was hydrophilic, it was eluted in the saponification solution and easily contaminated the saponification solution.

Since the retardation film of the present invention uses CAP or CAB having a relatively hydrophobic property in combination with DAC, for example, even if the retardation film of the present invention is immersed in a saponification solution for a long time, it becomes a saponification solution of DAC. Of the saponification, thus improving the saponification suitability.

Another conventional polarizing plate protective film may be bonded to the other surface of the polarizer.

Examples of conventional polarizing plate protective films include commercially available cellulose ester films (for example, Konica Minoltack KC8UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC6UY, KC4UY, KC4UE, KC8UE-HA-C KC8UXW-RHA-C, KC8UXW-RHA-NC, KC4UXW-RHA-NC, Konica Minolta, Fujitac T40UZ, Fujitac T60UZ, Fujitac T80UZ, Fujitac TD80UL, Fujitac TD40UL Fujitac T25TJ, Fujitac T40TJ, Fujitac R02, Fujitac R06, Fujitac R032, Fuji Click r033, or produced by Fujifilm Corp., etc.) and the like.

≪Liquid crystal display device≫
The liquid crystal display device of the present invention includes a polarizing plate including the retardation film of the present invention. Specifically, the polarizing film disposed in at least one of the liquid crystal cells includes the retardation film of the present invention; the film on the liquid crystal cell side of the polarizing plate is preferably the retardation film of the present invention. .

In the liquid crystal display device of the present invention, it is preferable that a polarizing plate is bonded to one or both surfaces of the liquid crystal cell via an adhesive layer. The direction of bonding of the polarizing plate in the VA mode liquid crystal display device can be performed with reference to JP-A-2005-234431.

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

The retardation film and polarizing plate of the present invention can be used for liquid crystal display devices of various drive systems such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS, OCB. The retardation film of the present invention is suitably used for a VA (MVA, PVA) mode type liquid crystal display device and improves visibility. In particular, even when used in a liquid crystal display device having a large screen of 30 type or more, coloring during black display due to light leakage can be reduced and visibility such as front contrast can be improved. Thus, the VA liquid crystal display device of the present invention is excellent in various visibility.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "mass part" or "mass%" is represented.

The compounds having the structure represented by the general formula (1) according to the present invention used in the examples are shown below.

Example 1
<Production of retardation film>
[Production of Retardation Film 101]
A retardation film 101 was produced according to the following method.

(Preparation of fine particle dispersion)
10 parts by weight Aerosil R812 (manufactured by Nippon Aerosil Co., Ltd., primary average particle size: 7 nm, apparent specific gravity 50 g / L) and 90 parts by weight of ethanol were stirred and mixed with a dissolver for 30 minutes, and then high pressure disperser Manton Gorin Was used to prepare a fine particle dispersion.

Into the obtained fine particle dispersion, 88 parts by mass of dichloromethane was added with stirring, and the mixture was diluted by stirring and mixing with a dissolver for 30 minutes. The obtained solution was filtered through a polypropylene wind cartridge filter TCW-PPS-1N manufactured by Advantech Toyo Co., Ltd. to obtain a fine particle dispersion dilution.

(Preparation of inline additive solution)
To 100 parts by mass of dichloromethane, 36 parts by mass of the prepared fine particle dispersion diluted liquid was added with stirring and further stirred for 30 minutes, and then 6 parts by mass of diacetyl cellulose (acetyl group substitution degree 2.50, weight average molecular weight 27). Was added with stirring and further stirred for 60 minutes. The obtained solution was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. to obtain an in-line additive solution. The filter medium having a nominal filtration accuracy of 20 μm was used.

(Preparation of dope)
The following components were put into a sealed container and completely dissolved with heating and stirring. The obtained solution was filtered at a temperature of 50 ° C. with a filter equipped with a leaf disk filter to obtain a main dope. The filter medium having a nominal filtration accuracy of 20 μm was used.

<Composition of main dope>
Diacetylcellulose (acetyl group substitution degree: 2.50, weight average molecular weight 2
70,000) 100 parts by mass Plasticizer: Sugar ester 1; BzSc (benzyl sucrose: mixture of compounds a1 to a4 described in Chemical formula 11), average ester substitution degree = 5.5 12 parts by mass Dichloromethane 430 parts by mass Methanol 11 parts by mass 100 parts by mass of the main dope 1 and 2.5 parts by mass of the in-line additive solution were sufficiently mixed with an in-line mixer (Toray static in-tube mixer Hi-Mixer, SWJ) to obtain a dope.

(Film forming process)
The obtained dope was uniformly cast on a stainless steel band support using a belt casting apparatus under the conditions of a dope liquid temperature of 35 ° C. and a width of 1.95 m and a final film thickness of 33 μm. . On the stainless steel band support, the organic solvent in the obtained dope film was evaporated until the residual solvent amount reached 100% by mass to form a web, and then the web was peeled from the stainless steel band support. The obtained web was further pre-dried at 110 ° C. for 5 minutes so that the residual solvent amount was 10% by mass, and the web was then increased by a factor of 1.2 to the original width in the TD direction at 160 ° C. Stretched. The stretching speed was 300% / min.

After stretching with a tenter, relaxation was performed at 130 ° C. for 5 minutes, and then drying was completed while the drying zone was being conveyed by a number of rollers. The drying temperature was 130 ° C. and the transport tension was 100 N / m. The obtained film was slit to 2.0 m width, 10 mm wide and 5 μm knurled at both ends of the film, wound on a core of 15.24 cm in inner diameter with an initial tension of 220 N / m and a final tension of 110 N / m. A retardation film 101 having a thickness of 4000 m and a dry film thickness of 33 μm was obtained.

[Production of Retardation Film 102]
In the production of the retardation film 101, a retardation film 102 was produced in the same manner except that 4 parts by mass of a compound having a structure represented by the general formula (1) which is a retardation increasing agent: pyrazole 3 was added. .

[Preparation of retardation film 103]
In the preparation of the retardation film 102, cellulose acetate propionate (acetyl group (Ac group) substitution degree 1.5, propionyl group (Pr group) substitution degree 1.0, total acyl group substitution degree instead of diacetylserose A retardation film 103 was produced in the same manner except that 2.5 and a weight average molecular weight of 270,000 were used.

[Preparation of retardation film 104]
In the production of the retardation film 102, a retardation film 104 was produced in the same manner except that triacetylcellulose (acetyl group substitution degree 2.98, weight average molecular weight 270,000) was used instead of diacetylserose.

[Production of Retardation Film 105]
In the production of the retardation film 102, a retardation film 105 was produced in the same manner except that the dope was prepared with the following main dope composition.

(Preparation of dope)
<Composition of main dope>
Diacetylcellulose (acetyl group substitution degree: 2.50, weight average molecular weight 2
70,000) 50 parts by mass Cellulose acetate propionate (acetyl group substitution degree 1.5, propionyl group substitution degree 1.0, total acyl group substitution degree 2.5, weight average molecular weight 270,000)
50 parts by mass Retardation increasing agent: Compound having structure represented by general formula (1): Pyrazole 3 4 parts by mass Plasticizer: Sugar ester 1; BzSc (benzylsucrose: mixture of compounds a1 to a4 described in Chemical formula 11 ), Average degree of ester substitution = 5.5 12 parts by mass Dichloromethane 430 parts by mass Methanol 11 parts by mass [Production of retardation films 106 to 116]
In the production of the retardation film 105, resin A: diacetyl cellulose having a degree of acetyl group substitution described in Table 1 (weight average molecular weight is adjusted to 270,000), resin B: degree of acetyl group substitution described in Table 1, propionyl group Retardation films 106 to 116 are the same except that cellulose acetate propionate having a substitution degree and a butyryl group (Bt group) substitution degree and cellulose acetate butyrate (both weight average molecular weights are adjusted to 270,000) are used. Was made.

<< Evaluation of retardation film >>
The following evaluations were performed on the produced retardation films 101 to 116.

(1) Retardation value measurement In-plane retardation value Ro and thickness direction retardation value Rth are obtained by arbitrarily cutting 10 sample films from the retardation film, and using an automatic birefringence meter Axoscan (Axo Scan). Using a Mueller Matrix Polarimeter (manufactured by Axometrics), three-dimensional refractive index measurement is performed at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH, and the obtained average refractive indexes nx, ny, and nz Obtained by substituting into (i) and (ii).

Formula (i): Ro = (n _x −n _y ) × d (nm)
Formula (ii): Rth = {(n _x + n _y ) / 2−n _z } × d (nm)
In [Equation (i) and Formula (ii), n _x represents a refractive index in the direction x in which the refractive index is maximized in the plane direction of the film. n _y, in-plane direction of the film, the refractive index in the direction y perpendicular to the direction x. _nz represents the refractive index in the thickness direction z of the film. d represents the thickness (nm) of the film. ]
(2) Brittleness evaluation <Cutting property: Brittleness alternative evaluation in manufacturing process>
The optical film sample was torn using a light load tear tester (manufactured by Toyo Seiki Co., Ltd.) and evaluated visually by the following criteria.

◎: The tear surface is very smooth and is torn straight ○: The tear surface has slight burrs but is torn straight △: The tear surface has burrs but is torn straight × : There are considerable burrs on the tear surface, and it is not torn straight. (3) Suitability for saponification treatment In alkali saponification treatment, a 2 m wide retardation film is subjected to alkaline saponification treatment for 120 hours under the following conditions, followed by saponification. The liquid was sampled and visually confirmed. When white foreign matter was confirmed, visual confirmation of the film after saponification was also performed.

<Saponification process>
Saponification process 2M-KOH 55 ° C. 30 seconds Water washing process Water 30 ° C. 45 seconds Neutralization process 10% HCl 30 ° C. 45 seconds Water washing process Water 30 ° C. 45 seconds <White foreign substance of saponification solution>
◎: No white foreign matter in the saponification liquid or coloring of the saponification liquid can be confirmed. ○: White foreign matter in the saponification liquid or coloring of the saponification liquid can be confirmed slightly, but reattachment to the film cannot be confirmed. Δ: White foreign matter can be confirmed in the saponification solution, but reattachment to the film cannot be confirmed. ×: A large amount of white foreign matter can be confirmed in the saponification solution, and reattachment to the film also occurs. (4) Humidity Retardation value fluctuation due to fluctuations (abbreviated as R value fluctuation in the table)
<Measurement of retardation value by water immersion>
The retardation value variation due to humidity variation was measured as follows. The following operations were all performed in an environment of a temperature of 23 ° C. and a relative humidity of 55%.

1. Ro and Rth were measured in a state where the retardation film was sandwiched between two slide glasses, and these were designated as Ro ₁ and Rth ₁ .

2. After immersing the retardation film in pure water for 24 hours, the retardation film wet with water was quickly sandwiched between two glass slides, and Ro and Rth were measured. These were designated as Ro ₂ and Rth ₂ . At this time, care was taken not to allow air bubbles to enter between the slide glass and the film.

3. Absolute values of the differences ΔRo, ΔRth of the retardation values of the optical film after being immersed in pure water at 23 ° C. for 24 hours from Ro ₁ , Rth ₁ , Ro ₂ , Rth ₂ obtained in 1 and 2 above. As follows.

ΔRo = | Ro ₁ −Ro 2 |
ΔRth = | Rth ₁ −Rth ₂ |
Next, the retardation value fluctuation suppression effect was evaluated as a fluctuation suppression rate (%) obtained by the following formula.

Ro fluctuation suppression rate (%) = ((ΔRo of reference film) − (ΔRo of each sample film)) / (ΔRo of reference film) × 100
Rth fluctuation suppression rate (%) = ((ΔRth of reference film) − (ΔRth of each sample film)) / (ΔRth of reference film) × 100
The retardation value fluctuation suppression effect was evaluated as a fluctuation suppression rate (%) obtained by the following formula.

◎: Both Ro fluctuation rate suppression rate and Rth fluctuation suppression rate are 70% or more. ○: Ro fluctuation rate suppression rate and Rth fluctuation suppression rate are both 50% or more and less than 70%. Δ: Ro fluctuation rate suppression rate and Rth fluctuation suppression rate. Are both 20% or more and less than 50%. X: Ro fluctuation rate suppression rate and Rth fluctuation suppression rate are both less than 20%. The structure of the retardation film and the evaluation results are shown in Table 1 below.

From Table 1, it can be seen that the retardation films 105, 106, 107, and 110 to 112 having the configuration of the present invention are comprehensively superior in brittleness, saponification suitability, and R value fluctuation compared to the comparative example.

Retardation films 101 to 104 using cellulose ester resin alone, acetyl group substitution degree as resin A is retardation film 108, 109 outside the present invention, and total acyl group substitution degree as resin B is retardation outside the present invention. The films 113 to 116 are inferior in brittleness, saponification suitability, and R value fluctuation, and it is clear that a comprehensive retardation film is not obtained.

Example 2
[Production of retardation film 201]
In the production of the retardation film 101 of Example 1, a retardation film 201 was produced in the same manner except that the dope was prepared with the following main dope composition.

(Preparation of dope)
<Composition of main dope>
Diacetylcellulose (acetyl group substitution degree: 2.50, weight average molecular weight 2
70,000) 100 parts by mass Retardation increasing agent described in Table 2 (compound having structure represented by general formula (1): triazole 1) 4 parts by mass plasticizer: sugar ester 1; BzSc (benzyl sucrose: A mixture of the described compounds a1 to a4), average ester substitution degree = 5.5 12 parts by mass dichloromethane 430 parts by mass methanol 11 parts by mass [Preparation of retardation film 202]
In the production of the retardation film 201, a retardation film 202 was produced in the same manner except that the dope was prepared with the following main dope composition.

(Preparation of dope)
<Composition of main dope>
Diacetylcellulose (acetyl group substitution degree: 2.50, weight average molecular weight 2
70,000) 50 parts by mass Cellulose acetate propionate (acetyl group substitution degree 1.5, propionyl group substitution degree 1.0, total acyl group substitution degree 2.5, weight average molecular weight 270,000)
50 parts by mass Retardation increasing agent described in Table 2 (compound having structure represented by general formula (1): triazole 1) 4 parts by mass Plasticizer: sugar ester 1; BzSc (benzyl sucrose: compound described in Chemical formula 11 mixture of a1 to a4), average ester substitution degree = 5.5 12 parts by mass dichloromethane 430 parts by mass methanol 11 parts by mass [Preparation of retardation films 203 to 221]
In the production of the phase difference film 201 and the phase difference film 202, the phase difference films 203 to 221 were produced in the same manner except that the resin A, resin B and the retardation increasing agent according to the present invention shown in Table 2 were used. did. In addition to the compound having the structure represented by the general formula (1) as the retardation increasing agent, 1,3,5-triazine compounds described in paragraphs [0143] to [0179] of JP-A-2006-113239 The following

compounds

1 and 2 were used as pyrimidine compounds described in JP-A-2012-214682, paragraphs [0118] to [0133].

Evaluation similar to Example 1 was performed using the produced retardation film.

Table 2 shows the configuration and evaluation results of the retardation film.

From Table 2, retardation films 202, 204, 206, 208, and 210 to 221 using various retardation increasing agents in the constitution of the present invention reproduce Example 1 and are brittle and saponified with respect to the comparative example. It can be seen that aptitude and R value fluctuation are excellent overall. Among them, the retardation films 213 and 214 using a nitrogen-containing heterocyclic compound having a pyrazole ring as a retardation increasing agent were excellent in brittleness, saponification suitability and R value fluctuation.

Example 3
[Preparation of retardation film 301]
In the production of the retardation film 105 of Example 1, a retardation film 301 was produced in the same manner except that the dope was prepared with the following main dope composition.

(Preparation of dope)
<Composition of main dope>
Diacetylcellulose (acetyl group substitution degree: 2.50, weight average molecular weight 2
70,000) 5 parts by mass Cellulose acetate propionate (acetyl group substitution degree 1.5, propionyl group substitution degree 1.0, total acyl group substitution degree 2.5, weight average molecular weight 270,000)
95 parts by mass Retardation increasing agent: Compound having the structure represented by the general formula (1): Pyrazole 3 4 parts by mass Plasticizer: Sugar ester 1; BzSc (benzylsucrose: mixture of compounds a1 to a4 described in Chemical formula 11 ), Average ester substitution degree = 5.5 12 parts by mass Dichloromethane 430 parts by mass Methanol 11 parts by mass [Production of retardation films 302 to 308]
In the production of the retardation film 301, retardation films 302 to 308 were produced in the same manner except that the mixing ratio of resin A: diacetyl cellulose and resin B: cellulose acetate propionate was changed as shown in Table 3. .

Table 3 shows the configuration and evaluation results of the retardation film.

From Table 3, it can be seen that the retardation films 302 to 307 having the configuration of the present invention reproduce Example 1 and are generally excellent in brittleness, saponification suitability, and R value fluctuation compared to the comparative example. Among them, the retardation film in which the mixing ratio of the resin A and the resin B is in the range of resin A: resin B = 3: 7 to 7: 3 is excellent in brittleness, saponification suitability and R value fluctuation. Met.

Example 4
[Production of Retardation Film 401]
In the production of the retardation film 105 of Example 1, a retardation film 401 was produced in the same manner except that the dope was prepared with the following main dope composition.

(Preparation of dope)
<Composition of main dope>
Diacetylcellulose (acetyl group substitution degree: 2.50, weight average molecular weight 2
50,000 parts by weight Cellulose acetate propionate (acetyl group substitution degree 0.1, propionyl group substitution degree 2.5, total acyl group substitution degree 2.6, weight average molecular weight 27
50 parts by mass Retardation increasing agent: Compound having structure represented by general formula (1): Pyrazole 3 4 parts by mass Plasticizer: Sugar ester 1; BzSc (benzylsucrose: Compounds a1 to a4 described in Chemical formula 11 ), Average ester substitution degree = 5.5 12 parts by mass Dichloromethane 430 parts by mass Methanol 11 parts by mass [Production of retardation films 402 to 416]
In the production of the retardation film 401, as the resin B, cellulose acetate propionate having a degree of acetyl group substitution and propionyl group substitution described in Table 4 (both having a weight average molecular weight of 270,000), or a degree of acetyl group substitution described in Table 4 Retardation films 402 to 416 were prepared in the same manner except that each was replaced with cellulose acetate butyrate having a butyryl group substitution degree (all with a weight average molecular weight of 270,000).

[Production of Retardation Film 417]
In the production of the retardation film 404, a retardation film 417 was produced in the same manner except that the dope was prepared with the following main dope composition.

(Preparation of dope)
<Composition of main dope>
Diacetylcellulose (acetyl group substitution degree: 2.50, weight average molecular weight 2
70 parts by weight Cellulose acetate propionate (acetyl group substitution degree 1.0, propionyl group substitution degree 1.5, total acyl group substitution degree 2.5, weight average molecular weight 27
50 parts by weight Retardation increasing agent: Compound having structure represented by general formula (1): 4 parts by weight of pyrazole 3 Plasticizer: Polycondensation ester having structure represented by general formula (4): P— 8
10 parts by mass Dichloromethane 430 parts by mass Methanol 11 parts by mass [Production of retardation film 418]
In the production of the retardation film 404, a retardation film 418 was produced in the same manner except that the dope was prepared with the following main dope composition.

(Preparation of dope)
<Composition of main dope>
Diacetylcellulose (acetyl group substitution degree: 2.50, weight average molecular weight 2
70,000) 50 parts by weight Cellulose acetate propionate (acetyl group substitution degree 1.0, propionyl group substitution degree 1.5, total acyl group substitution degree 2.5, weight average molecular weight 270,000) 50 parts by weight Retardation increasing agent : Compound having a structure represented by the general formula (1): 4 parts by mass of pyrazole 3 Plasticizer: Sugar ester 1; BzSc (benzyl sucrose: mixture of compounds a1 to a4 described in Chemical formula 11), average ester substitution degree = 5.5 12 parts by mass Dichloromethane 430 parts by mass Methanol 11 parts by mass [Production of retardation films 419 to 421]
In the production of the retardation film 418, retardation films 419 to 421 were produced in the same manner except that the sugar ester 1 was replaced with the following sugar esters 2 to 4.

Sugar ester 2: BzSc (benzyl sucrose: mixture of compounds b1 to b4 described in Chemical formula 11), average degree of ester substitution = 5.8
Sugar ester 3: BzSc (benzyl sucrose: mixture of compounds c1 to c4 described in Chemical formula 11), average degree of ester substitution = 6.1
Sugar ester 4: BzSc (benzyl sucrose: mixture of compounds e1 to e4 described in Chemical formula 11), average degree of ester substitution = 5.7
[Production of Retardation Film 422]
In the production of the retardation film 404, a retardation film 422 was produced in the same manner except that the dope was prepared with the following main dope composition.

(Preparation of dope)
<Composition of main dope>
Diacetylcellulose (acetyl group substitution degree: 2.50, weight average molecular weight 2
70 parts by weight Cellulose acetate propionate (acetyl group substitution degree 1.0, propionyl group substitution degree 1.5, total acyl group substitution degree 2.5, weight average molecular weight 27
50 parts by weight Retardation increasing agent: Compound having the structure represented by the general formula (1): 4 parts by weight of pyrazole 3 Plasticizer: 10 parts by weight of trimethylolpropane tribenzoate Dichloromethane 430 parts by weight Methanol 11 parts by weight Evaluation similar to Example 1 was performed using the retardation film.

Table 4 shows the structure and evaluation results of the retardation film.

From Table 4, it can be seen that the retardation film of the constitution of the present invention reproduces Example 1 and is comprehensively excellent in brittleness, saponification suitability and R value fluctuation. Among them, the retardation films 402 to 407 and 410 to 415 in which the substitution degree of propionyl group and butyryl group of the resin B are in the range of 0.5 to 2.2 have brittleness, saponification suitability, and R value fluctuation. The result was excellent.

Example 5
[Production of Retardation Film 501]
In the production of the retardation film 418 of Example 4, a retardation film 501 was produced in the same manner except that the dope was prepared with the following main dope composition and the film thickness was 9 μm.

(Preparation of dope)
<Composition of main dope>
Diacetylcellulose (acetyl group substitution degree: 2.50, weight average molecular weight 2
70 parts by weight Cellulose acetate propionate (acetyl group substitution degree 1.0, propionyl group substitution degree 1.5, total acyl group substitution degree 2.5, weight average molecular weight 27
50 parts by weight Retardation increasing agent: Compound having structure represented by general formula (1): 4 parts by weight of pyrazole 3 Plasticizer: Polycondensation ester having structure represented by general formula (4): P— 8
5 parts by mass Plasticizer: Sugar ester 1; BzSc (benzyl sucrose: mixture of compounds a1 to a4 described in Chemical formula 11), average ester substitution degree = 5.5 7 parts by mass Dichloromethane 430 parts by mass Methanol 11 parts by mass [Phase difference Preparation of film 502 to 506]
In the production of the retardation film 501, retardation films 501 to 506 were produced in the same manner except that the film thickness was changed to 10 μm, 20 μm, 30 μm, 36 μm, and 40 μm.

For the retardation films 501 to 506 produced above, the same evaluation as in Example 1 was performed.

Further, a polarizing plate and a VA type liquid crystal display device were produced by the following procedure.

[Production of Polarizing Plates 501 to 506]
The surface of each retardation film produced above was subjected to alkali saponification treatment. It was immersed in a 1.5 mol / L 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 iodine aqueous solution and dried to obtain a polarizer 1 having a thickness of 20 μm. Prepared each of the above alkali saponified retardation films and the same alkali saponified Konica Minolta KC6UA (manufactured by Konica Minolta Co., Ltd.) using a 3% aqueous solution of polyvinyl alcohol (Kuraray PVA-117H) as an adhesive. The polarizing plates 501 to 506 are bonded to each other so that the saponified surfaces are on the polarizer side with the polarizer sandwiched therebetween, and the retardation films, the polarizer 1 and the KC6UA are bonded in this order. Obtained. At this time, the retardation films were stuck so that the slow axis of each retardation film and the slow axis of KC6UA were orthogonal to the absorption axis of the polarizer.

<Evaluation of visibility of liquid crystal display device>
[Production of liquid crystal display devices 501 to 506]
Strip the polarizing plates on both sides of the Sony 40-inch display BRAVIA X1 previously bonded, and then paste the polarizing plates 501 to 506 prepared above on both sides of the glass surface of the liquid crystal cell using an acrylic adhesive. did.

At that time, the polarizing plate is bonded so that the surface of the retardation film is on the liquid crystal cell side and the absorption axis is directed in the same direction as the polarizing plate previously bonded. Then, liquid crystal display devices 501 to 506 corresponding to the polarizing plates 501 to 506 were produced, respectively.

[Visibility: Evaluation of contrast]
When a white image was displayed on the liquid crystal display device, the Y value of the XYZ display system in the azimuth angle 45 ° direction and polar angle 60 ° direction of the display screen was measured by a product name “EZ Contrast 160D” manufactured by ELDIM. Similarly, the Y value of the XYZ display system in the azimuth angle 45 ° direction and polar angle 60 ° direction of the display screen when displaying a black image on the liquid crystal display device was measured. Then, the contrast ratio “YW / YB” in the oblique direction was calculated from the Y value (YW) in the white image and the Y value (YB) in the black image. The contrast ratio was measured in a dark room at a temperature of 23 ° C. and a relative humidity of 55%. The azimuth angle of 45 ° represents an azimuth rotated 45 ° counterclockwise when the long side of the display screen is 0 ° in the plane of the display screen. The polar angle of 60 ° represents a direction inclined by 60 ° with respect to the normal line when the normal direction of the display screen is 0 °. The higher the contrast ratio, the higher the contrast and the better.

◎: Contrast ratio is 60 or more ○: Contrast ratio is 55 or more and less than 60 Δ: Contrast ratio is 50 or more and less than 55 ×: Contrast ratio is less than 50 Retardation film The structure and the above evaluation results are shown in Table 5 below.

From Table 5, the retardation films 502 to 505 having the constitution of the present invention and having a film thickness in the range of 10 to 36 μm reproduce Example 1, and are comprehensively excellent in brittleness, saponification suitability, and R value fluctuation. I understand that

Moreover, the polarizing plate and the liquid crystal display device using the retardation film having the structure of the present invention within the thickness range have a high retardation value despite being a retardation film that is a thin film. It can be seen that a polarizing plate and a VA liquid crystal display device excellent in visibility can be provided.

The retardation film of the present invention is a cellulose ester-based retardation film provided in a VA liquid crystal display device, which is a thin film and has a high retardation value, and is resistant to retardation value fluctuation under high humidity. And is suitable for a polarizing plate and a liquid crystal display device.

DESCRIPTION OF SYMBOLS 1

Melting pot

3, 6, 12, 15

Filter

4, 13

Stock pot

5, 14

Liquid feed pump

8, 16 Conduit 10 Ultraviolet absorber preparation pot 20 Merge pipe 21 Mixer 30 Pressure die 31 Metal belt 32 Web 33 Peeling Position 34 Tenter stretching device 35 Drying device 41 Feeding pot 42 Stock pot 43 Pump 44 Filter

Claims

A retardation film containing at least two cellulose esters and a retardation increasing agent,
The two types of cellulose esters are cellulose acetate (resin A) having an acetyl group substitution degree in the range of 2.40 to 2.60, and a total acyl group substitution degree in the range of 2.40 to 2.60. A cellulose ester (resin B) having an acyl group having 3 to 6 carbon atoms, and the resin A and the resin B in a mass ratio of resin A: resin B = 1: 9 to 9: 1 A retardation film containing the same.
The resin B is a cellulose acetate propionate having a propionyl group substitution degree in the range of 0.5 to 2.2, or a cellulose acetate butyrate having a butyryl group substitution degree in the range of 0.5 to 2.2. The retardation film according to claim 1, wherein:
The retardation film according to claim 1 or 2, wherein the retardation increasing agent is a nitrogen-containing heterocyclic compound, and is a compound having a pyrrole ring, a pyrazole ring, a triazole ring or an imidazole ring.
The retardation film according to claim 3, wherein the nitrogen-containing heterocyclic compound is a compound having a structure represented by the following general formula (3).

(In the formula, A represents a pyrazole ring. Ar 1 and Ar 2 each represent an aromatic hydrocarbon ring or an aromatic heterocyclic ring and may have a substituent. R 1 represents a hydrogen atom, an alkyl group, or an acyl group. A sulfonyl group, an alkyloxycarbonyl group, or an aryloxycarbonyl group, q represents 1 or 2, and n and m represent an integer of 1 to 3.
The retardation film according to any one of claims 1 to 4, wherein the film thickness is in the range of 10 to 36 nm.
Furthermore, it contains the polycondensation ester containing the repeating unit obtained by making sugar ester or dicarboxylic acid and diol react, The retardation film as described in any one of Claim 1-5 characterized by the above-mentioned. .
A polarizing plate comprising the retardation film according to any one of claims 1 to 6.
A VA liquid crystal display device comprising the polarizing plate according to claim 7.