WO2011136014A1

WO2011136014A1 - Phase difference film, polarization plate using the same, and liquid crystal display unit

Info

Publication number: WO2011136014A1
Application number: PCT/JP2011/059062
Authority: WO
Inventors: 和樹赤阪
Original assignee: コニカミノルタオプト株式会社
Priority date: 2010-04-28
Filing date: 2011-04-12
Publication date: 2011-11-03
Also published as: KR20120139837A; TW201204778A; JP5737287B2; KR101361251B1; TWI518125B; JPWO2011136014A1

Abstract

Provided is a phase difference film having excellent phase difference performance and moisture permeability and few changes in the phase difference value with respect to environmental humidity, and also provided are a polarization plate comprising the phase difference film, and a liquid crystal display unit. The phase difference film prevents polarizer irregularities between the core of a roll and the outside of the roll when a polarization plate roll is fabricated, and the phase difference film has excellent adhesion with the polarizer. The phase difference film comprises: a cellulose ester that satisfies a predetermined relational expression; and a vinyl compound polymer or oligomer having substituent groups selected from specific substituent groups and a weight-average molecular weight within a range of 500 to 200,000, in which the mass ratio of the cellulose ester and the polymer or oligomer content is within a range of 95:5 to 50:50.

Description

Retardation film, polarizing plate using the same, and liquid crystal display device

The present invention relates to a retardation film, a polarizing plate using the same, and a liquid crystal display device.

The retardation film is used for expanding the viewing angle in the liquid crystal display device. However, with the development of liquid crystal display devices, higher performance is required for the retardation film, and even when the film is thin, it is required to have a large retardation performance. It has become to.

Among the retardation films, the cellulose ester film is excellent in moisture permeability required for producing a polarizing plate. Triacetyl cellulose having an acyl group substitution degree close to 3 and diacetyl cellulose having an acyl group substitution degree of around 2.5 are well studied. However, the case where the acyl group substitution degree is less than 2 is hardly studied.

As a result of various studies on the cellulose ester retardation film, the present inventor has found that the retardation performance is particularly large when the acyl group substitution degree of the cellulose ester is smaller than 2.0. Furthermore, as a result of repeated studies, the cellulose ester having an acyl group substitution degree of less than 2.0 has a large retardation performance and good moisture permeability, but the fluctuation of the retardation value with respect to the environmental humidity shows that the acyl group substitution degree is 2 A problem was found that it was particularly large compared to cellulose esters of 0.0 or more.

The moisture permeability in manufacturing the above polarizing plate will be described in more detail. In a liquid crystal display device, a polarizing plate is used as a component for taking out linearly polarized light from light emitted from a light source and making it incident on a liquid crystal cell and detecting linearly polarized light emitted from the liquid crystal cell.

The polarizing plate is usually constituted by laminating a polarizer protective film on at least one surface of a polarizer made of a polyvinyl alcohol resin to which a dichroic dye is adsorbed and oriented. In addition, an adhesive layer is provided on one side of the polarizing plate for bonding to a liquid crystal cell or other optical member, and the surface is covered with a separate film to protect it until use. It circulates with the structure provided with the peelable protective film which has an agent layer. Furthermore, since a manufacturing speed and efficiency will increase if a polarizing plate is manufactured in the state wound by the elongate roll shape, manufacturing a polarizing plate product from a polarizing plate roll is desired.

In the present invention, the protective film is thus bonded to the surface of the polarizer protective film, the separate film is bonded to the surface of the pressure-sensitive adhesive layer on the other side, and the polarized light produced in a rolled state. The plate is referred to as a “polarizing plate roll”, and a sheet cut from the plate to a predetermined size is referred to as a “polarizing plate product”.

When the polarizing plate is manufactured, the polarizer is manufactured in a state containing moisture. For this reason, the polarizer protective film is required to have high moisture permeability in order to release moisture to the outside. When the moisture permeability of the polarizer protective film is low, it causes unevenness of the polarizing plate, and when the moisture permeability is low, the drying becomes insufficient, so that the adhesion between the polarizer and the polarizing plate protective film is lowered. was there.

As described above, it is known that the cellulose ester film has high moisture permeability and is excellent as a protective film.

However, in the case of the conventional cellulose ester film, particularly when the polarizing plate roll as described above is produced, there is a difference in moisture removal between the winding core and the unwinding of the polarizing plate wound in a roll shape. This causes a problem of unevenness of the polarizer.

Moreover, in the winding core, the polarizer is slow to dry, and the polarizer is peeled off when the separated film is peeled and removed just before the product cut into a predetermined size from the polarizing plate roll is bonded to a liquid crystal cell or another optical member. It was found that the adhesion between the polarizer and the polarizer protective film was weak and the polarizer and the polarizer protective film were peeled off.

Furthermore, since the cellulose ester film has a high photoelastic coefficient and the fluctuation of the retardation value with respect to the environmental humidity is large, when the liquid crystal television is used as a retardation film, the corner unevenness that changes the color of the corner of the screen. In addition, since the phase difference value is changed from the value set at the time of manufacture, there is a problem that the viewing angle fluctuates and the color changes.

Such a change in viewing angle and color tone has a problem that the fluctuation is large especially in a film having a large retardation value.

Therefore, there is a demand for a polarizing plate that achieves both improvement in unevenness of the polarizing plate and adhesion as described above. As a retardation film, a film having a low photoelastic coefficient, a large retardation value, and a small fluctuation of the retardation value with respect to environmental humidity is desired.

Therefore, for example, a protective film for a cyclic polyolefin mixed resin (cycloolefin polymer: COP) film as described in Patent Document 1 has been proposed. This protective film has a low photoelastic coefficient and a small fluctuation of the retardation value with respect to the environmental humidity, but since the moisture permeability is low, and furthermore, the adhesiveness with the polarizer is low, it is not suitable for use as a protective film for a polarizing plate. It was unsuitable.

Moreover, although the cellulose ester film with high moisture permeability is proposed by patent document 2, on the other hand, since the photoelastic coefficient is high and the fluctuation | variation with respect to environmental humidity of a phase difference value is large, it is used for a polarizing plate protective film. Was unsuitable.

In addition, Patent Document 3 proposes a retardation film mainly composed of an acrylic resin and containing a cellulose ester, but when the acyl group substitution degree of the cellulose ester is smaller than 2.0 as in the present invention, In particular, the invention is completely different from the invention utilizing the features of large phase difference performance and high moisture permeability, and it does not improve the heat resistance and brittleness of acrylic resin by containing cellulose ester. There is no description that it contains a phase difference control agent.

JP 2009-157352 A JP 2009-198666 A International Publication No. 09/081607

The present invention has been made in view of the above problems and situations, and a first problem to be solved is a retardation film having excellent retardation performance and moisture permeability and having a small fluctuation of the retardation value with respect to environmental humidity. It is to provide a polarizing plate and a liquid crystal display device provided with a phase difference film.

The second problem to be solved by the present invention is to provide a retardation film that suppresses unevenness of the polarizer on the roll core and outside of the roll and has excellent adhesion to the polarizer in producing a polarizing plate roll. It is to be.

Further, the photoelastic coefficient is low, the fluctuation of the retardation value with respect to the environmental humidity is small, and when used as a retardation film in a liquid crystal display device, the effect of widening the viewing angle is large and corner unevenness, and further, the retardation value is small. The object of the present invention is to provide a retardation film with little change in viewing angle and color due to a change from the initially set value. Another object of the present invention is to provide a polarizing plate and a liquid crystal display device provided with the retardation film.

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

1. A cellulose ester satisfying the following relational formula (I) and a substituent selected from a carboxy group, an alkoxycarbonyl group, a hydroxy group, an amino group, an amide group, and a sulfo group, and having a weight average molecular weight of 500 to 200,000 A polymer or oligomer of a vinyl compound within a range, and the mass ratio of the content of the cellulose ester and the polymer or oligomer is within a range of 95: 5 to 50:50. A retardation film. Relational expression (I): 1.0 ≦ X + Y <2.0
(In the formula, X represents the degree of substitution of the acetyl group, and Y represents the degree of substitution of the acyl group having 3 or more carbon atoms.)
2. 2. The retardation film according to claim 1, wherein the substitution degree Y of the acyl group having 3 or more carbon atoms of the cellulose ester is 0.9 or more.

3. 3. The retardation film according to item 1 or 2, wherein the photoelastic coefficient is in the range of −1.0 × 10 ⁻¹² to 1.0 × 10 ⁻¹² cm ² / dyn.

4). The fluctuation range ΔRo with respect to the temperature and humidity change of the retardation defined by the following relational expression (II) is 10% or less, the rank according to any one of the first to third terms, Phase difference film.
Relational formula (II): ΔRo = {[Ro (23 ° C. 10% RH) −Ro (23 ° C. 80% RH)] / Ro (23 ° C. 55% RH)} × 100 (%)
Wherein Ro (23 ° C. 10% RH), Ro (23 ° C. 80% RH), and Ro (23 ° C. 55% RH) are 23 ° C. 10% RH, 23 ° C. 80% RH, and 23 ° C. 55, respectively. Represents in-plane retardation Ro measured at a measurement light wavelength of 590 nm after conditioning the retardation film for 36 hours in an environment of% RH.)
5. A polarizing plate, wherein the retardation film according to any one of items 1 to 4 is provided on at least one surface of a polarizer.

6. 6. The polarizing plate according to item 5, wherein the polarizing plate is wound in a roll shape in the longitudinal direction.

7. A liquid crystal display device comprising the liquid crystal cell comprising the retardation film according to any one of items 1 to 4.

By the above means of the present invention, it is possible to provide a retardation film having excellent retardation performance and moisture permeability and having a small variation in retardation value with respect to environmental humidity, a polarizing plate provided with the retardation film, and a liquid crystal display device. . Moreover, when manufacturing a polarizing plate roll, the retardation film which suppressed the nonuniformity of the polarizer in the roll core and unwinding, and was excellent in adhesiveness with a polarizer can be provided. Furthermore, the photoelastic coefficient is low, the fluctuation of the retardation value with respect to the environmental humidity is small, and when used as a retardation film in a liquid crystal display device, the effect of widening the viewing angle is large and corner unevenness and also the retardation value are produced. It is possible to provide a retardation film with little change in viewing angle and color due to a change from the initially set value. In addition, a polarizing plate and a liquid crystal display device provided with the retardation film can be provided.

That is, in the present invention, it is possible to use a cellulose ester having an acyl group substitution degree of less than 2.0, which could not be used for the following reason 3). Since it has high moisture permeability, moisture is easily removed even when it is processed into a polarizing plate roll. 2) In addition, the cellulose ester having an acyl group substitution degree of less than 2.0 has a large number of hydroxy groups (hydroxyl groups) which are the controlling factors of adhesion to the polarizer. Moreover, since it has many hydroxy groups (hydroxyl groups) not only on the surface but also on the inside, it forms high hydrogen bonds and has higher adhesion than conventional cellulose esters. 3) The cellulose ester having a degree of acyl group substitution smaller than 2.0 is inferior to the conventional cellulose ester in the fluctuation of the retardation value with respect to the environmental humidity, but is improved by containing the specific polymer or oligomer according to the present invention. is doing. Furthermore, it is further improved by containing a large proportion of the degree of substitution of the acyl group having 3 or more carbon atoms of the cellulose ester. The photoelastic coefficient deteriorates as the ratio of the degree of substitution of the acyl group having 3 or more carbon atoms of the cellulose ester increases, but is improved by making the degree of acyl group substitution of the cellulose ester lower than 2.0. Furthermore, it improves also by containing the specific polymer or oligomer which concerns on this invention.

In the present invention, the optimum range of the acyl group substitution degree of the cellulose ester is found, and by containing a specific polymer or oligomer, the photoelastic coefficient and the phase difference variation under high temperature and high humidity can be improved. . Moreover, when manufacturing a polarizing plate roll, the retardation film which suppressed the nonuniformity of a polarizer and was excellent in adhesiveness with a polarizer can be provided.

Outline flow sheet showing an example of an embodiment of production of retardation film Cross-sectional schematic diagram showing an example of a layer structure of a polarizing plate roll or a polarizing plate product to be manufactured A cross-sectional schematic diagram showing a state where a polarizing plate roll is wound up in an enlarged manner.

In the retardation film of the present invention, a cellulose ester satisfying the relational formula (I), a carboxy group (also referred to as “carboxyl group”), an alkoxycarbonyl group, a hydroxy group (also referred to as “hydroxyl group”), and an amino group. And a vinyl compound polymer or oligomer having a substituent selected from an amide group and a sulfo group (also referred to as “sulfonic acid group”) and having a weight average molecular weight in the range of 500 to 200,000. And the mass ratio of the content of the cellulose ester and the polymer or oligomer is in the range of 95: 5 to 50:50. This feature is a technical feature common to the inventions according to claims 1 to 7.

As an embodiment of the present invention, it is preferable that the substitution degree Y of the acyl group having 3 or more carbon atoms of the cellulose ester is 0.9 or more from the viewpoint of the effect of the present invention. The photoelastic coefficient is preferably in the range of −1.0 × 10 ⁻¹² to 1.0 × 10 ⁻¹² cm ² / dyn. Furthermore, it is preferable that the fluctuation range ΔRo with respect to the temperature and humidity change of the retardation defined by the relational expression (II) is 10% or less.

The retardation film of the present invention can be suitably used for a polarizing plate in an aspect in which the retardation film is provided on at least one surface of a polarizer. In this case, in particular, it can be suitably used for a polarizing plate in a form wound in a roll shape in the longitudinal direction. Therefore, the retardation film of this invention can be used suitably for the liquid crystal display device of the aspect with which the said retardation film is equipped with the liquid crystal cell.

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>
The cellulose ester according to the present invention satisfies the following relational expression (I).
Relational expression (1): 1.0 ≦ X + Y <2.0
In the above formula, X represents the degree of substitution of the acetyl group, and Y represents the degree of substitution of the acyl group having 3 or more carbon atoms.

The cellulose ester according to the present invention has a total acyl group substitution degree of 1.0 or more and less than 2.0.

Here, the total acyl group substitution degree represents an average value of the number of esterified hydroxy groups (hydroxyl groups) among the three hydroxy groups (hydroxyl groups) of anhydroglucose constituting cellulose. When the substitution degree Y of the acyl group having 3 or more carbon atoms of the cellulose ester according to the present invention is 0.9 or more, the hydrophobicity of the cellulose ester is improved, and the fluctuation of the retardation value with respect to the environmental humidity becomes smaller.

When the total acyl group substitution degree of the cellulose ester is less than 1.0, the film surface quality is deteriorated due to an increase in the dope viscosity, and the water resistance may be extremely lowered. Moreover, when the total acyl group substitution degree is 2.0 or more, the water resistance is improved, but sufficient moisture permeability that allows the polarizing plate to dry cannot be obtained. Furthermore, by adding a vinyl compound polymer or oligomer according to the present invention, the retardation performance is greatly reduced, but by using a cellulose ester having an acyl group substitution degree of less than 2.0, Phase difference performance can be improved.

In the present invention, the acyl group is preferably an aliphatic acyl group. The portion not substituted with an acyl group usually exists as a hydroxy group (hydroxyl group). These can be synthesized by known methods.

The cellulose ester according to the present invention is particularly preferably a cellulose ester containing at least one selected from cellulose acetate, cellulose diacetate, cellulose acetate propionate, and cellulose acetate butyrate. Among these, a particularly preferable cellulose ester is cellulose acetate propionate.

The degree of substitution of acetyl groups and the degree of substitution of other acyl groups were determined by the methods prescribed in ASTM-D817-96 (test method for cellulose acetate etc.).

The number average molecular weight (Mn) of the cellulose ester according to the present invention is preferably in the range of 30,000 to 300,000, since the mechanical strength of the resulting film is strong. Further, 50,000 to 200,000 are preferably used.

The ratio Mw / Mn of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the cellulose ester is preferably 1.4 to 3.0.

The weight average molecular weight Mw and number average molecular weight Mn of the cellulose ester were 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 = 1,000,000 to 500 13 calibration curves were used. Thirteen samples are used at approximately equal intervals.

The cellulose as a raw material of the cellulose ester according to the present invention is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively.

The cellulose ester according to the present invention can be produced by a known method. Generally, cellulose is esterified by mixing cellulose as a raw material, a predetermined organic acid (such as acetic acid or propionic acid), an acid anhydride (such as acetic anhydride or propionic anhydride), and a catalyst (such as sulfuric acid). The reaction proceeds until the triester form of In the triester, three hydroxy groups (hydroxyl groups) of the glucose unit are substituted with an acyl acid of an organic acid. When two kinds of organic acids are used at the same time, a mixed ester type cellulose ester such as cellulose acetate propionate or 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, the cellulose ester is completed 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.

Commercially available products include L20, L30, L40, and L50 manufactured by Daicel Chemical Industries, Ltd., and Ca398-3, Ca398-6, Ca398-10, Ca398-30, and Ca394-60S manufactured by Eastman Chemical Co., Ltd.

The total amount of calcium and magnesium and the amount of acetic acid contained in the cellulose ester film according to the present invention preferably satisfy the following relational expression (a).

Relational expression (a): 1 ≦ (acetic acid amount) / (total amount of calcium and magnesium) ≦ 30
Calcium and magnesium are contained in the cellulose ester used as the raw material for the cellulose ester film, but metal oxides and metal hydroxides are used to neutralize and stabilize the acid catalyst (especially sulfuric acid) added to the cellulose ester production process. , And may be added as a metal salt (inorganic acid salt, organic acid salt). Moreover, you may add as a metal oxide, a metal hydroxide, and a metal salt (inorganic acid salt, organic acid salt) at the time of film forming of a cellulose ester film. The total amount of calcium and magnesium contained in the cellulose ester film referred to in the present invention refers to the total amount thereof.

In the production process of cellulose ester, acetic anhydride and acetic acid are used as reaction solvents and esterifying agents. Unreacted acetic anhydride is hydrolyzed by a reaction stopper (water, alcohol, acetic acid, etc.) to produce acetic acid. The amount of acetic acid contained in the cellulose ester film in the present invention refers to the total amount of residual acetic acid and free acetic acid.

In the above relational expression (a), when the amount of acetic acid / (total amount of calcium and magnesium) is less than 1, light scattering due to calcium and magnesium metal salts occurs, which is not preferable. On the other hand, when the value is larger than 30, the deterioration of the polarizer is accelerated by acetic acid after the cellulose ester is bonded to the polarizer.

The total amount of calcium and magnesium contained in the cellulose ester film is preferably 5 to 130 ppm, more preferably 5 to 80 ppm, and still more preferably 5 to 50 ppm.

For the determination of calcium and magnesium contained in the cellulose ester film, a known method can be used. For example, after the dried cellulose ester is completely burned, the ash is dissolved in hydrochloric acid and pretreated. It can be measured by atomic absorption method. The measured value is obtained in units of ppm as the calcium and magnesium contents in 1 g of the completely dry cellulose ester.

The amount of acetic acid contained in the cellulose ester film is preferably 20 to 500 ppm, more preferably 25 to 250 ppm, and still more preferably 30 to 150 ppm.

For quantification of acetic acid contained in the cellulose ester film, a known method can be used. For example, the following method can be used. The film is dissolved in methylene chloride, and methanol is added to perform reprecipitation. The amount of acetic acid can be obtained by filtering the supernatant and measuring the supernatant with gas chromatography.

<Polymer or oligomer>
The retardation film of the present invention has a cellulose ester satisfying the relational formula (I) and a substituent selected from a carboxy group, an alkoxycarbonyl group, a hydroxy group, an amino group, an amide group, and a sulfo group, and has a weight average. A polymer or oligomer of a vinyl compound having a molecular weight in the range of 500 to 200,000 (hereinafter also referred to as vinyl polymer or oligomer), and the content of the cellulose ester and the polymer or oligomer The mass ratio is in the range of 95: 5 to 50:50.

Hereinafter, the polymer or oligomer of the vinyl compound according to the present invention will be described.

The carboxy group is a group having a structure of —COO—. The alkoxycarbonyl group is a group having a structure of —COOR, such as a methoxycarbonyl group or an ethoxycarbonyl group.

The amino group is a group having a structure of —NR1, R2, and R3, and R1, R2, and R3 each represent a substituent such as a hydrogen atom, an alkyl group, or a phenyl group. The amide group is a group having a structure of —NHCO—, and a substituent such as an alkyl group or a phenyl group may be linked thereto.

Examples of the polymer and oligomer according to the present invention include the following vinyl polymers and oligomers.

These compounds are preferably used in the range of 5 to 50% by mass with respect to the cellulose ester and are excellent in compatibility. The transmittance is 80% over the entire visible range (400 to 800 nm) when formed into a film. Thus, 90% or more, more preferably 92% or more is obtained.

<Polymers and oligomers of vinyl compounds>
The polymer and oligomer of the vinyl compound used in the present invention are not particularly limited in structure, but the weight average molecular weight obtained by polymerizing an ethylenically unsaturated monomer is in the range of 500 to 200,000. It is preferable that it is a polymer which is.

The vinyl polymer and oligomer according to the present invention may be composed of a single monomer or a plurality of types of monomers. The monomer is preferably selected from acrylic acid ester or methacrylic acid ester, but appropriately contains other monomers such as maleic anhydride, styrene, etc. depending on the retardation characteristics, wavelength dispersion characteristics, and heat resistance of the film to be produced. It does not matter.

Hereinafter, the vinyl polymer and oligomer according to the present invention will be described as polymer X.

<Polymer X>
The polymer X according to the present invention is obtained by copolymerizing an ethylenically unsaturated monomer Xa having no aromatic ring in the molecule and an ethylenically unsaturated monomer Xb having no aromatic ring in the molecule and having a polar group. A polymer represented by the following general formula (1) having a weight average molecular weight of 500 to 200,000 is preferred. Further, it is preferably solid at 30 ° C. or glass transition temperature of 35 ° C. or higher.

When the weight average molecular weight is 500 or more, the effect of improving corner unevenness is large, and when it is 200,000 or less, the compatibility with the cellulose ester and the transparency are excellent.

General formula (1)
-[Xa] m- [Xb] n-
(M and n represent molar composition ratios, and m + n = 100.)
Although the monomer as a monomer unit which comprises the polymer X based on this invention is mentioned below, it is not limited to this.

Examples of the ethylenically unsaturated monomer Xa having no aromatic ring in the molecule include methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-) , Nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-Ethoxyethyl) and the like, or those obtained by replacing the acrylic ester with a methacrylic ester. Of these, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, and propyl methacrylate (i-, n-) are preferable.

The ethylenically unsaturated monomer Xb having no aromatic ring in the molecule and having a polar group is preferably acrylic acid or methacrylic acid as a monomer unit having a hydroxy group (hydroxyl group), for example, (meth) acrylic acid 2- Hydroxyethyl, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10- (meth) acrylic acid Hydroxydecyl, hydroxy group-containing monomers such as (meth) acrylic acid 12-hydroxylauryl and (4-hydroxymethylcyclohexyl) -methyl acrylate; (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, Itaconic acid, male Carboxy group-containing monomers such as acid, fumaric acid and crotonic acid; acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; caprolactone adducts of acrylic acid; styrene sulfonic acid and allyl sulfonic acid, 2- (meth) Sulfo group-containing monomers such as acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxynaphthalene sulfonic acid; phosphoric acid group such as 2-hydroxyethyl acryloyl phosphate And monomers.

Also, (N-substituted) amides such as (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylolpropane (meth) acrylamide, etc. Monomer; (meth) acrylic acid aminoethyl, (meth) acrylic acid N, N-dimethylaminoethyl, (meth) acrylic acid t-butylaminoethyl and other (meth) acrylic alkylaminoalkyl monomers; (meth) acrylic (Meth) acrylic acid alkoxyalkyl monomers such as methoxyethyl acid and ethoxyethyl (meth) acrylate; N- (meth) acryloyloxymethylenesuccinimide, N- (meth) acryloyl-6-oxyhexamethylenesuccinimide, N- ( (Meta) acryloyl 8 oxy octamethylene succinimide, also including succinimide-based monomers such as N- acryloyl morpholine and the like as a monomer Examples of the reforming purposes.

Furthermore, vinyl acetate, vinyl propionate, N-vinyl pyrrolidone, methyl vinyl pyrrolidone, vinyl pyridine, vinyl piperidone, vinyl pyrimidine, vinyl piperazine, vinyl pyrazine, vinyl pyrrole, vinyl imidazole, vinyl oxazole, vinyl morpholine, N-vinyl carboxylic acid amide , Vinyl monomers such as styrene, α-methylstyrene, N-vinylcaprolactam; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; acrylic monomers containing epoxy groups such as glycidyl (meth) acrylate; (meth) acrylic Polyethylene glycol acid, polypropylene glycol (meth) acrylate, methoxyethylene glycol (meth) acrylate, methoxypropyl methacrylate (meth) acrylate Glycol acrylic ester monomers such as glycol; (meth) acrylic acid tetrahydrofurfuryl, fluorine (meth) acrylate, silicone (meth) acrylate and acrylic acid ester monomers such as 2-methoxyethyl acrylate, etc. may also be used.

In the present invention, the polymer X is synthesized by copolymerization using the hydrophobic monomer Xa and the polar monomer Xb. Further, the above-described hydrophobic monomer or polar monomer can be used as the monomer Xc to form a terpolymer.

The use ratio during the synthesis of the hydrophobic monomer Xa and the polar monomer Xb is preferably in the range of 99: 1 to 50:50, more preferably in the range of 95: 5 to 60:40. When the use ratio of the hydrophobic monomer Xa is large, the compatibility with the cellulose ester is lowered, but the effect of reducing the fluctuation of the retardation value with respect to the environmental humidity is high. When the use ratio of the polar monomer Xb is large, the compatibility with the cellulose ester is improved, but the fluctuation of the retardation value with respect to the environmental humidity is increased. Moreover, since the haze comes out at the time of film forming when the usage-amount of polar monomer Xb exceeds the said range, it is unpreferable.

In order to synthesize such a polymer, it is difficult to control the molecular weight in normal polymerization, and it is desirable to use a method that can align the molecular weight as much as possible by a method that does not increase the molecular weight too much. Examples of such a polymerization method include a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than usual polymerization, and a mercapto compound in addition to the polymerization initiator. And a method using a chain transfer agent such as carbon tetrachloride, a method using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and further disclosed in JP 2000-128911 or 2000-344823. Examples include a compound having one thiol group and a secondary hydroxy group (hydroxyl group), or a bulk polymerization method using a polymerization catalyst in which the compound and an organometallic compound are used in combination. It is preferably used in the present invention.

The weight average molecular weight of the polymer X according to the present invention can be adjusted by a known molecular weight adjusting method. Examples of such a molecular weight adjusting method include a method of adding a chain transfer agent such as carbon tetrachloride, lauryl mercaptan, octyl thioglycolate, and the like. The polymerization temperature is usually from room temperature to 130 ° C., preferably from 50 ° C. to 100 ° C., but this temperature or the polymerization reaction time can be adjusted.

The measuring method of the weight average molecular weight can be based on the molecular weight measuring method.

The amount of polymer X added is appropriately adjusted so that the film has desired performance. Addition to reduce fluctuation of photoelastic coefficient and retardation value with respect to environmental humidity. Addition of small amount to increase retardation performance. , Corner irregularities that change the color of the corners of the screen, and even if the phase difference value changes from the initially set value, the viewing angle fluctuates and the color changes. Since phase difference performance cannot be obtained, 5 mass% or more and 50 mass% or less are preferable.

The retardation film of the present invention may be a single layer film or a laminated structure film in which a plurality of layers are laminated.

<Hydrolysis inhibitor>
You may add a hydrolysis inhibiting agent to the retardation film of this invention as needed. The hydrolysis inhibitor is not particularly limited, but the octanol-water partition coefficient (hereinafter sometimes referred to as logP) is preferably 7 or more and less than 11 from the viewpoint of hydrolysis prevention effect, compatibility with cellulose ester, and the like.

The logP value can be measured by a flask soaking method described in JIS Z-7260-107 (2000). In addition, logP can be estimated by a computational chemical method or an empirical method instead of actual measurement.

As a calculation method, Crippen's fragmentation method ("J. Chem. Inf. Comput. Sci.", 27, p21 (1987)), Viswanadhan's fragmentation method ("J. Chem. Inf. Comput. Sci."). ", 29, p163 (1989)), Broto's fragmentation method (" Eur. J. Med. Chem.-Chim. Theor. ", 19, p71 (1984)), CLogP method (references) Leo, A., Jow, PYC, Silipo, C., Hansch, C., J. Med. Chem., 18, 865, 1975) are preferably used, but the Crippen's fragmentation method ( “JC em.Inf.Comput.Sci. ", 27 volumes, p21 (1987 years)) is more preferable.

As the hydrolysis inhibitor, for example, an ester compound having at least one pyranose structure or at least one furanose structure and 12 or less OH groups in the structure can be preferably used. The proportion of esterification is preferably 70% or more.

In the present invention, the above ester compounds are collectively referred to as sugar ester compounds.

Examples of ester compounds used in the present invention include the following saccharide ester compounds, but the present invention is not limited to these.

Glucose, galactose, mannose, fructose, xylose, arabinose, lactose, sucrose, nystose, 1F-fructosyl nystose, stachyose, maltitol, lactitol, lactulose, cellobiose, maltose, cellotriose, maltotriose, raffinose or kestose.

Other examples include gentiobiose, gentiotriose, gentiotetraose, xylotriose, and galactosyl sucrose.

Among these compounds, compounds having both a pyranose structure and a furanose structure are particularly preferable. Preferred examples include sucrose, kestose, nystose, 1F-fructosyl nystose, stachyose, and more preferably sucrose.

The monocarboxylic acid used for esterifying all or part of the OH group in the pyranose structure or furanose structure is not particularly limited, and is a known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic A monocarboxylic acid or the like can be used. The carboxylic acid used may be one kind or a mixture of two or more kinds.

Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid , Saturated fatty acids such as tridecylic acid, 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, Examples include unsaturated fatty acids such as undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid and octenoic acid.

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

Examples of preferred aromatic monocarboxylic acids include aromatic monocarboxylic acids having an alkyl group or alkoxy group introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, cinnamic acid, benzylic acid, biphenylcarboxylic acid, and naphthalene. Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as carboxylic acid and tetralincarboxylic acid, or derivatives thereof. For example, xylic acid, hemelic acid, mesitylene acid, prenylic acid, γ-isoduric acid, duryl acid, mesitonic acid, α-isoduryl acid, cumic acid, α-toluic acid, hydroatropic acid, atropaic acid, hydrocinnamic acid, salicylic acid o-anisic acid, m-anisic acid, p-anisic acid, creosote acid, o-homosalicylic acid, m-homosalicylic acid, p-homosalicylic acid, o-pyrocatechuic acid, β-resorcylic acid, vanillic acid, isovanillic acid, Examples include veratric acid, o-veratrumic acid, gallic acid, asaronic acid, mandelic acid, homoanisic acid, homovanillic acid, homoveratrumic acid, o-homoberatrumic acid, phthalonic acid, and p-coumaric acid, particularly benzoic acid, naphthyl Acid is preferred.

Oligosaccharide ester compounds can be applied as compounds having 1 to 12 of at least one of the pyranose structure or furanose structure according to the present invention.

Oligosaccharides are produced by allowing an enzyme such as amylase to act on starch, sucrose, etc. Examples of oligosaccharides that can be applied to the present invention include maltooligosaccharides, isomaltoligosaccharides, fructooligosaccharides, galactooligosaccharides, xylooligos. Sugar.

Moreover, the said ester compound is a compound which condensed 1 or more and 12 or less of at least 1 type of the pyranose structure or furanose structure represented with the following general formula (A). R ₁₁ to R ₁₅ and R ₂₁ to R _{25 each} represents an acyl group having 2 to 22 carbon atoms or a hydrogen atom, m and n each represents an integer of 0 to 12, and m + n represents an integer of 1 to 12.

R ₁₁ to R ₁₅ and R ₂₁ to R ₂₅ are preferably a benzoyl group or a hydrogen atom.

The benzoyl group may further have a substituent R ₂₆ , and examples thereof include an alkyl group, an alkenyl group, an alkoxyl group, and a phenyl group, and these alkyl group, alkenyl group, and phenyl group have a substituent. May be. Oligosaccharides can also be produced in the same manner as the ester compound according to the present invention.

Specific examples of the ester compound according to the present invention will be given below, but the present invention is not limited thereto.

The cellulose ester film according to the present invention preferably contains a hydrolysis inhibitor in an amount of 0.5 to 30% by mass, particularly 2 to 15% by mass of the cellulose ester film.

<Phase difference adjusting agent>
A retardation adjusting agent (also referred to as “retardation adjusting agent”) may be added to the retardation film of the present invention.

Although the phase difference adjusting agent is not particularly limited, a compound having a log P of 0 or more and less than 7 is preferable. The phase difference adjusting agent needs to have an appropriate solubility corresponding to the resin. However, in the cellulose ester according to the present invention, when the log P is smaller than 0, the compound is highly water-soluble, causing orientation disorder. When it is 7 or more, the desired phase difference cannot be obtained because the orientation of the compound is low, which is not preferable.

As the phase difference adjusting agent, for example, an ester compound represented by the following general formula (B) can be preferably used.

Formula (B): B- (GA) _n -GB
Wherein B is a hydroxy group or carboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms. A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.)
In the general formula (B), a hydroxy group or a carboxylic acid residue represented by B, an alkylene glycol residue, an oxyalkylene glycol residue or an aryl glycol residue represented by G, an alkylene dicarboxylic acid residue represented by A or It is composed of an aryl dicarboxylic acid residue and can be obtained by the same reaction as that of a normal ester compound.

In the general formula (B), as the carboxylic acid component represented by B, for example, acetic acid, propionic acid, butyric acid, benzoic acid, p-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, There are ethyl benzoic acid, normal propyl benzoic acid, aminobenzoic acid, acetoxybenzoic acid, aliphatic acid, and the like, and these can be used as one kind or a mixture of two or more kinds, respectively.

In the general formula (B), the alkylene glycol component having 2 to 12 carbon atoms represented by G includes 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 (neo Pentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane) 3-methyl-1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl 1,3-pentanediol, 1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, etc., and oxyalkylene having 4 to 12 carbon atoms Examples of the glycol component include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. These glycols are used as one kind or a mixture of two or more kinds. In particular, alkylene glycols having 2 to 12 carbon atoms are particularly preferable because of excellent compatibility with cellulose esters.

In the general formula (B), examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms represented by A include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. There are acids and the like, and these are used as one kind or a mixture of two or more kinds, respectively. Examples of the arylene dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5 naphthalene dicarboxylic acid, and 1,4 naphthalene dicarboxylic acid.

The ester compound represented by the general formula (B) has a number average molecular weight of preferably 300 to 2000, more preferably 400 to 1500. The acid value is 0.5 mgKOH / g or less, the hydroxyl value (hydroxyl value) is 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxyl value (hydroxyl value) is 15 mgKOH / g or less. It is.

Hereinafter, specific compounds of the ester compound represented by the general formula (B) that can be used in the present invention are shown, but the present invention is not limited thereto.

The retardation film according to the present invention preferably contains a retardation adjusting agent in an amount of 0.1 to 30% by mass of the cellulose ester film, and particularly preferably 0.5 to 10% by mass.

<Plasticizer>
You may make the retardation film of this invention contain a plasticizer as needed. Although it does not specifically limit as a plasticizer which can be contained, For example, a polyhydric alcohol ester plasticizer, a polyhydric carboxylic ester plasticizer, a glycolate plasticizer, a phosphate ester plasticizer, a phthalate ester A plasticizer, a fatty acid ester plasticizer, an acrylic polymer, or the like can be used. Moreover, it is preferable that the addition amount of a phosphoric ester plasticizer shall be 6 mass% or less from a durable viewpoint of a polarization degree.

The plasticizer preferably has a 1% weight loss temperature (Td1) of 250 ° C. or higher, more preferably 280 ° C. or higher, and particularly preferably 300 ° C. or higher. When the 1% weight loss temperature is within this range, it is possible to suppress surface quality deterioration and physical property variations caused by volatilization in the production process.

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

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

Formula (a): R _1- (OH) _n
However, R ₁ represents an n-valent organic group, n represents a positive integer of 2 or more, and the OH group represents an alcoholic hydroxy group (hydroxyl group) or a phenolic hydroxy group (hydroxyl group).

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

Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, glycerin, diglycerin, galactitol, inositol, Mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, pentaerythritol, dipentaerythritol, xylitol It can be mentioned.

In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, and xylitol are preferable.

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

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

As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. More preferably, it has 1 to 20 carbon atoms, and particularly preferably 1 to 10 carbon atoms. The use of acetic acid is preferred because the compatibility with the cellulose ester increases, and it is also preferred to use a mixture of acetic acid and another monocarboxylic acid.

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

Preferred alicyclic monocarboxylic acids are preferably cycloalkyl groups having 3 to 8 carbon atoms, and specific examples include cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, and derivatives thereof.

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

The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably in the range of 300 to 1500, and more preferably in the range of 400 to 1000. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose ester.

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

The polyhydric alcohol ester can be synthesized by a known method. For example, a method of condensing and esterifying the monocarboxylic acid and the polyhydric alcohol in the presence of an acid, a method of previously reacting an organic acid with an acid chloride or acid anhydride and reacting with the polyhydric alcohol, There is a method of reacting a phenyl ester and a polyhydric alcohol, and it is preferable to select a method with a good yield appropriately depending on the target ester compound.

The following are specific compounds of polyhydric alcohol esters.

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

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

Formula (c): R ₂ (COOH) _m (OH) _n
(However, R ₂ is an (m + n) -valent organic group, m is a positive integer of 2 or more, n is an integer of 0 or more, a COOH group is a carboxy group, an OH group is an alcoholic or phenolic hydroxy group (hydroxyl group). To express.)
Examples of preferred polyvalent carboxylic acids include the following, but the present invention is not limited to these.

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

The alcohol used in the polyvalent carboxylic acid ester compound that can be used in the present invention is not particularly limited, and known alcohols and phenols can be used.

For example, an aliphatic saturated alcohol or aliphatic unsaturated alcohol having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. More preferably, it has 1 to 20 carbon atoms, and particularly preferably 1 to 10 carbon atoms.

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

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

As the aliphatic monocarboxylic acid, a straight-chain or side-chain fatty acid having 1 to 32 carbon atoms can be preferably used. More preferably, it has 1 to 20 carbon atoms, and particularly preferably 1 to 10 carbon atoms.

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

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

The molecular weight of the polyvalent carboxylic acid ester compound is not particularly limited, but is preferably in the range of 300 to 1000, and more preferably in the range of 350 to 750. The larger one is preferable in terms of improvement in retention, and the smaller one is preferable in terms of moisture permeability and compatibility with cellulose ester.

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

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

For example, dibutyl tartrate, diacetyl dibutyl tartrate, triethyl citrate, tributyl citrate, acetyl triethyl citrate (ATEC), acetyl tributyl citrate (ATBC), benzoyl tributyl citrate, acetyl triphenyl citrate, acetyl tribenzyl citrate, Tributyl trimesate, trihexyl trimesate, tri-2-ethyl-hexyl trimesate, tricyclohexyl trimesate, tributyl trimellitic acid, trihexyl trimellitic acid, tri-2-ethyl-hexyl trimellitic acid, tricyclohexyl trimellitic acid, pyromellitic Examples include tetrabutyl acid, pyromellitic acid tetrahexyl, pyromellitic acid tetra-2-ethylhexyl, pyromellitic acid tetracyclohexyl, and the like. That.

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

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

Phosphate ester plasticizers include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, 1,3-phenylenebis (dixylenyl phosphate), 1,3-phenylenebis (diphenyl phosphate) and the like.

As the phthalate ester plasticizer, diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, butyl benzyl phthalate, di-2-ethylhexyl phthalate, dicyclohexyl phthalate, dicyclohexyl terephthalate and the like can be used.

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

In addition, epoxidized oil plasticizers can also be used.

<Ultraviolet absorber>
The retardation film of the present invention can also contain an ultraviolet absorber. The ultraviolet absorber is intended to improve durability by absorbing ultraviolet light having a wavelength of 400 nm or less, and the transmittance at a wavelength of 370 nm is particularly preferably 10% or less, more preferably 5% or less. Preferably it is 2% or less.

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

Specific examples of ultraviolet absorbers include, for example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -2H-benzotriazole, (2-2H-benzotriazol-2-yl) -6- (straight and side chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, discoidal compounds such as compounds having 1,3,5 triazine ring In addition, commercially available ultraviolet absorbers such as TINUVIN109, TINUVIN171, TINUVIN326, TINUVIN327, TINUVIN328, TINUVIN900, and TINUVIN928 manufactured by BASF Japan Ltd., and LA-31 manufactured by ADEKA can also be preferably used.

UV absorbers preferably used in the present invention are benzotriazole-based UV absorbers, benzophenone-based UV absorbers, and triazine-based UV absorbers.

Also, as the ultraviolet absorber, a polymeric ultraviolet absorber can be preferably used, and in particular, a polymer type ultraviolet absorber described in JP-A-6-148430 is preferably used.

The ultraviolet absorber may be used alone or as a mixture of two or more.

The amount of UV absorber used is not uniform depending on the type of UV absorber, usage conditions, etc., but when the dry film thickness of the film is 30 to 200 μm, it is preferably 0.5 to 10% by mass relative to the film. 0.6 to 4% by mass is more preferable.

<Antioxidants, thermal degradation inhibitors>
When a liquid crystal image display device or the like is placed in a high humidity and high temperature state, the cellulose ester film may be deteriorated. Antioxidants and thermal degradation inhibitors have a role of delaying or preventing the cellulose ester film from being decomposed by, for example, the residual solvent amount of halogen in the cellulose ester film or phosphoric acid of a phosphoric acid plasticizer. Therefore, it is preferable to make it contain in the said cellulose-ester film.

In the present invention, as an antioxidant and a thermal degradation inhibitor, generally known degradation inhibitors (antioxidants, peroxide decomposition agents, radical inhibitors, metal deactivators, acid scavengers, amines, etc.) ) Can be used. In particular, lactone, sulfur, phenol, double bond, hindered amine, and phosphorus compounds can be preferably used. The deterioration preventing agents are described in JP-A-3-199201, JP-A-5-194789, JP-A-5-194789, JP-A-5-271471, and JP-A-6-107854.

As the phenolic compound, those having a 2,6-dialkylphenol structure are preferable, for example, those commercially available from BASF Japan under the trade names Irganox 1076 and Irganox 1010 are preferable.

Examples of the phosphorus compounds include Sumitizer Chemical Co., Ltd., Sumilizer-GP, ADEKA Co., Ltd., ADK STAB PEP-24G, ADK STAB PEP-36 and ADK STAB 3010, and BASF Japan Co., Ltd. IRGAFOS P-EPQ. A product commercially available from Sakai Chemical Co., Ltd. under the trade name GSY-P101 is preferred.

The hindered amine compound is preferably commercially available from BASF Japan, Inc. under the trade names of Tinuvin 144 and Tinuvin 770, and ADEKA, Inc., ADK STAB LA-52.

The above sulfur compounds are preferably those commercially available from Sumitomo Chemical Co., Ltd. under the trade names Sumilizer TPL-R and Sumilizer TP-D.

The above-mentioned double bond compounds are preferably those commercially available from Sumitomo Chemical Co., Ltd. under the trade names Sumilizer-GM and Sumilizer-GS.

Furthermore, it is possible to contain a compound having an epoxy group as described in US Pat. No. 4,137,201 as an acid scavenger.

The amount of these antioxidants and the like to be added is appropriately determined in accordance with the process at the time of recycling. Generally, the range of 0.05 to 5% by mass with respect to the resin as the main raw material of the film. Is added.

These antioxidants and thermal deterioration inhibitors can obtain a synergistic effect by using several different types of compounds in combination rather than using only one kind. For example, the combined use of lactone, phosphorus, phenol and double bond compounds is preferred.

<Colorant>
In the present invention, a colorant may be used. Usually, the colorant means a dye or a pigment, but in the present invention, it means a material having an effect of adjusting the yellow index (yellowness) of the film and reducing haze.

Various dyes and pigments can be used as the colorant, but anthraquinone dyes, azo dyes, phthalocyanine pigments and the like are effective.

<Matting agent>
In the present invention, inorganic fine particles may be added as a matting agent in order to impart slipperiness to the film. Examples of inorganic compounds 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, silica Mention may be made of magnesium and calcium phosphates. Among these, silicon dioxide is preferable in terms of reducing haze.

Further, it is preferable that the matting agent fine particles are surface-treated with an organic substance because the haze of the film can be reduced. Preferred organic materials for the surface treatment include halosilanes, alkoxysilanes, silazanes, siloxanes, and the like.

The larger the average diameter of the fine particles, the greater the mat effect, but if the particle size is too large, the transparency deteriorates. Therefore, in the present invention, the average particle diameter of the primary particles of the fine particles is preferably 5 to 20 nm, and more preferably 5 to 12 nm.

These fine particles preferably form secondary particles having a particle diameter of 0.1 to 5 μm and are contained in the retardation film, and a preferable average particle diameter is 0.1 to 2 μm, more preferably 0.2. ~ 0.6 μm. Thereby, irregularities having a height of about 0.1 to 1.0 μm can be formed on the film surface, and appropriate slipperiness can be given to the film surface.

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

The content of these fine particles in the cellulose ester film is preferably 0.05 to 1% by mass, particularly preferably 0.1 to 0.8% by mass. In the case of a cellulose ester film having a multilayer structure by a co-casting method, it is preferable that the surface layer contains fine particles of this addition amount.

The fine particles of silicon dioxide are, for example, trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, R812V, 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 can be used.

Zirconium oxide fine particles are commercially available under the trade names of Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used.

Examples of the polymer include silicone resin, fluororesin and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.) It is marketed by name and can be used.

Among these, Aerosil 200V, R812V, R972V, NAX50, and Seahoster KE-P30 are particularly preferably used because they have a large effect of reducing the friction coefficient while keeping the turbidity of the cellulose ester film low.

The apparent specific gravity of the fine particles is preferably 70 g / liter or more, more preferably 90 to 200 g / liter, and particularly preferably 100 to 200 g / liter. A larger apparent specific gravity makes it possible to make a high-concentration dispersion, which improves haze and agglomerates, and is preferable when preparing a dope having a high solid content concentration as in the present invention. Are particularly preferably used.

The dispersion of the matting agent can be prepared by putting the matting agent in a solvent and then applying it to a dispersing machine. The disperser is preferably a medialess disperser in order to prevent foreign matter from entering.

As the medialess disperser, there are an ultrasonic type, a centrifugal type, a high pressure type, and the like. In the present invention, a high pressure disperser is preferable. The high pressure dispersion device is a device that creates special conditions such as high shear and high pressure by passing a composition in which fine particles and a solvent are mixed at high speed through a narrow tube.

When processing with a high-pressure dispersion apparatus, for example, the maximum pressure condition inside the apparatus is preferably 9.807 MPa or more in a thin tube having a tube diameter of 1 to 2000 μm.

More preferably, it is 19.613 MPa or more. Further, at that time, those having a maximum reaching speed of 100 m / second or more and those having a heat transfer speed of 420 kJ / hour or more are preferable.

Examples of the high-pressure dispersing apparatus include an ultra-high pressure homogenizer (trade name: Microfluidizer) manufactured by Microfluidics Corporation or a nanomizer manufactured by Nanomizer, and other manton gorin type high-pressure dispersing apparatuses such as homogenizer manufactured by Izumi Food Machinery. And UHN-01 manufactured by Sanwa Machinery Co., Ltd.

<Photoelastic coefficient>
The photoelastic coefficient is measured for retardation Ro in the film plane while applying a load to the produced retardation film. Then, Ro was obtained while changing the load, a load-Ro curve was created, and the slope was taken as the photoelastic coefficient.

Retardation Ro in the film plane measured the value in wavelength 589nm using the retardation measuring apparatus (KOBRA31PR, Oji Scientific Instruments company make).

The retardation film of the present invention is preferably adjusted so that the photoelastic coefficient is −1.0 × 10 ⁻¹³ to 1.0 × 10 ⁻¹² cm ² / dyn.

In the present invention, in order to adjust the photoelastic coefficient within the above range, the ratio of each resin of the acrylic resin and the cellulose ester resin is adjusted within a mass ratio range of 95: 5 to 50:50. Accordingly, the composition is optimized by adjusting the combination of the phase difference controlling agent and the amount to be added.

Even if stress is applied to the retardation film when the liquid crystal display device is turned on for a long time by adjusting the photoelastic coefficient to such a range and the panel becomes high temperature or the surrounding atmosphere becomes high temperature and high humidity. The phase difference is less likely to occur and image unevenness can be reduced. Furthermore, image unevenness that occurs when used for a long time can also be reduced.

Further, the thickness of the retardation film of the present invention is preferably 20 μm or more. More preferably, it is 30 μm or more.

The retardation film of the present invention can be particularly preferably used as a polarizing plate protective film for a large-sized liquid crystal display device or a liquid crystal display device for outdoor use as long as the above physical properties are satisfied.

<Method for producing retardation film>
The cellulose ester film according to the present invention can be preferably used regardless of whether it is a film produced by a solution casting method or a film produced by a melt casting method.

In the solution casting method, the retardation film of the present invention is produced by dissolving a cellulose ester and an additive in a solvent to prepare a dope, casting a dope onto an endless metal support that moves infinitely It is performed by a step of drying the cast dope as a web, a step of peeling from the metal support, a step of stretching or maintaining the width, a step of further drying, and a step of winding up the finished film.

(Dope preparation process)
The concentration of cellulose ester in the dope is preferably higher because the drying load after casting on the metal support can be reduced. However, if the concentration of cellulose ester is too high, the load during filtration increases and the filtration accuracy is poor. Become. The concentration that achieves both of these is preferably 10 to 35% by mass, and more preferably 15 to 25% by mass.

The solvent used in the dope may be used alone or in combination of two or more, but it is preferable to use a mixture of a good solvent and a poor solvent of cellulose ester in terms of production efficiency, and there are many good solvents. This is preferable from the viewpoint of the solubility of the cellulose ester.

A preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass for the good solvent and 2 to 30% by mass for the poor solvent. With a good solvent and a poor solvent, what dissolve | melts the cellulose ester to be used independently is defined as a good solvent, and what poorly swells or does not melt | dissolve is defined as a poor solvent. Therefore, the good solvent and the poor solvent change depending on the total acyl group substitution degree of the cellulose ester.

The good solvent used in the present invention is not particularly limited, and examples thereof include organic halogen compounds such as methylene chloride, dioxolanes, acetone, methyl acetate, and methyl acetoacetate. Particularly preferred is methylene chloride or methyl acetate.

The poor solvent used in the present invention is not particularly limited, but for example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone and the like are preferably used. The dope preferably contains 0.01 to 2% by mass of water.

Also, the solvent used for dissolving the cellulose ester is used by collecting the solvent removed from the film by drying in the film-forming process and reusing it.

The recovery solvent may contain trace amounts of additives added to the cellulose ester, such as plasticizers, UV absorbers, polymers, monomer components, etc., but even if these are included, they are preferably reused. Can be purified and reused if necessary.

As a method for dissolving the cellulose ester when preparing the dope described above, a general method can be used. When heating and pressurization are combined, it is possible to heat above the boiling point at normal pressure.

It is preferable to stir and dissolve while heating at a temperature that is higher than the boiling point of the solvent at normal pressure and that the solvent does not boil under pressure, in order to prevent the formation of massive undissolved material called gel or mamako.

In addition, a method in which a cellulose ester is mixed with a poor solvent and wetted or swollen, and then a good solvent is added and dissolved is also preferably used.

Pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or a method of increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

The heating temperature with the addition of the solvent is preferably higher from the viewpoint of the solubility of the cellulose ester, but if the heating temperature is too high, the required pressure increases and the productivity deteriorates.

The preferred heating temperature is 45 to 120 ° C, more preferably 60 to 110 ° C, and still more preferably 70 ° C to 105 ° C. The pressure is adjusted so that the solvent does not boil at the set temperature.

Further, a cooling dissolution method is also preferably used, whereby the cellulose ester can be dissolved in a solvent such as methyl acetate.

Next, the cellulose ester solution is filtered using an appropriate filter medium such as filter paper. As the filter medium, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matters and the like, but there is a problem that the filter medium is likely to be clogged if the absolute filtration accuracy is too small.

For this reason, a filter medium with an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium with 0.001 to 0.008 mm is more preferable, and a filter medium with 0.003 to 0.006 mm is still more preferable.

There are no particular restrictions on the material of the filter medium, and ordinary filter media can be used. However, plastic filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel do not drop off fibers. preferable.

It is preferable to remove and reduce impurities, particularly bright spot foreign matter, contained in the raw material cellulose ester by filtration.

A bright spot foreign material is an arrangement in which two polarizing plates are placed in a crossed Nicols state, an optical film (retardation film) or the like is placed between them, and light is applied from one polarizing plate side. It is a point (foreign matter) that light from the opposite side appears to leak when observed from the side, and the number of bright spots having a diameter of 0.01 mm or more is preferably 200 pieces / cm ² or less.

More preferably, it is 100 pieces / cm ² or less, still more preferably 50 pieces / m ² or less, still more preferably 0 to 10 pieces / cm ² . Further, it is preferable that the number of bright spots of 0.01 mm or less is small.

The dope can be filtered by a normal method, but the method of filtering while heating at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil under pressure is the filtration pressure before and after filtration. The increase in the difference (referred to as differential pressure) is small and preferable.

The preferred temperature is 45 to 120 ° C, more preferably 45 to 70 ° C, and still more preferably 45 to 55 ° C.

A smaller filtration pressure is preferable. The filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and further preferably 1.0 MPa or less.

(Dope casting process)
The metal support in the casting (casting) step preferably has a mirror-finished surface. As the metal support, a stainless steel belt or a drum whose surface is plated with a casting is preferably used.

The cast width can be 1 ~ 4m. The surface temperature of the metal support in the casting step is −50 ° C. to less than the boiling point of the solvent, and a higher temperature is preferable because the web drying speed can be increased. May deteriorate.

The preferred support temperature is 0 to 55 ° C, more preferably 25 to 50 ° 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, but there are a method of blowing hot 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 warm air is used, wind at a temperature higher than the target temperature may be used.

The peeling tension when peeling the film from the support is preferably 300 N / m or less.

In order for the cellulose ester film to exhibit good flatness, the amount of residual solvent when peeling the web from the metal support is preferably 10 to 150% by mass, more preferably 20 to 40% by mass or 60 to 130% by mass. Particularly preferred is 20 to 30% by mass or 70 to 120% by mass.

In the present invention, the amount of residual solvent is defined by the following formula.

Residual solvent amount (% by mass) = {(MN) / N} × 100
M is the mass of a sample collected during or after the production of the web or film, and N is the mass after heating M at 115 ° C. for 1 hour.

Further, in the drying step of the cellulose ester film, the web is peeled off from the metal support, and further dried, and the residual solvent amount is preferably 1% by mass or less, more preferably 0.1% by mass or less, Particularly preferred is 0 to 0.01% by mass or less.

In the film drying process, generally, a roll drying method (a method in which webs are alternately passed through a plurality of rolls arranged above and below) and a method in which the web is dried while being conveyed by a tenter method are employed.

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

It is preferable that the drying temperature in the web drying process is increased stepwise from 40 to 200 ° C.

(Co-casting process)
In the case of producing a laminated structure film, a method of casting a plurality of cellulose ester solutions of two or more layers on a smooth belt or drum as a metal support is preferable.

When casting a plurality of cellulose ester solutions, a film may be produced while casting and laminating the cellulose ester solutions from a plurality of casting openings provided at intervals in the traveling direction of the metal support ( (Sequential multi-layering) Alternatively, two or more casting ports may be provided in one die, and the cellulose ester solution may be simultaneously cast to produce a multilayer structure film (simultaneous multi-layering). Examples of the method for producing the successive layers include the methods described in JP-B-60-27562, JP-A-61-104413, JP-A-61-158414, JP-A-1-122419, and the like. It is done. Examples of the method for producing the simultaneous multilayer include the methods described in JP-A-61-94724, JP-A-61-158413, JP-A-6-134933, and the like.

The film thickness of the cellulose ester film is not particularly limited, but 10 to 200 μm is used. In particular, the film thickness is particularly preferably 10 to 100 μm. More preferably, it is 20 to 60 μm.

The cellulose ester film according to the present invention is formed with a width of 1 to 4 m, particularly preferably with a width of 1.4 to 4 m, particularly preferably 1.9 to 3 m. If it exceeds 4 m, conveyance becomes difficult.

(Stretching process)
In order to give the following desired retardation values Ro and Rt to the cellulose ester film, it is preferable that the cellulose ester film has the configuration of the present invention, and the refractive index is controlled by controlling the transport tension and stretching.

For example, the retardation value can be changed by lowering or increasing the tension in the longitudinal direction.

Further, it is preferable to perform biaxial stretching or uniaxial stretching sequentially or simultaneously with respect to the longitudinal direction (film forming direction) of the film and the direction orthogonal to the longitudinal direction of the film, that is, the width direction.

In the present invention, it is preferable that the film obtained as described above is stretched 1.01 to 3.0 times in at least one direction after passing through the step of contacting the cooling roll. Stretching can improve surface quality, such as streaking, and adjust retardation.

As a stretching method, a known roll stretching machine or tenter can be used. For example, a method in which a circumferential speed difference is applied to a plurality of rolls, and the roll circumferential speed difference is used to stretch the rolls in the longitudinal direction. And a method of stretching in the vertical direction, a method of stretching in the horizontal direction and stretching in the horizontal direction, or a method of stretching in the vertical and horizontal directions and stretching in both the vertical and horizontal directions. Of course, these methods may be used in combination.

Also, in the case of the so-called tenter method, driving the clip portion by the linear drive method is preferable because smooth stretching can be performed and the risk of breakage and the like can be reduced.

It is preferable to carry out the width maintenance or lateral stretching in the film forming step by a tenter, and it may be a pin tenter or a clip tenter.

The draw ratios in the biaxial directions perpendicular to each other are preferably in the range of 0.8 to 1.5 times in the casting direction and 1.1 to 2.5 times in the width direction, respectively. It is preferable to carry out in the range of 0.8 to 1.0 times in the direction and 1.2 to 2.0 times in the width direction.

The stretching temperature is preferably 120 ° C. to 200 ° C., more preferably 150 ° C. to 200 ° C., more preferably more than 150 ° C. and 190 ° C. or less.

The residual solvent in the film is preferably 20 to 0%, more preferably 15 to 0%.

Specifically, it is preferable that the residual solvent is stretched by 11% at 155 ° C., or the residual solvent is stretched by 2% at 155 ° C. Alternatively, it is preferable that the residual solvent is stretched at 11% at 160 ° C, or the residual solvent is stretched at less than 1% at 160 ° C.

The stretching is preferably performed under a uniform temperature distribution controlled in the width direction. The temperature is preferably within ± 2 ° C, more preferably within ± 1 ° C, and particularly preferably within ± 0.5 ° C.

In the stretching step, known heat setting conditions, cooling, and relaxation treatment may be performed, and adjustment can be made as appropriate so as to have characteristics required for the target film.

For the purpose of reducing the retardation of the optical film (retardation film) produced by the above method and reducing the dimensional change rate, the film may be contracted in the longitudinal direction or the lateral direction.

In order to shrink in the longitudinal direction, for example, there is a method in which the film is shrunk by temporarily clipping out the width stretching and relaxing in the longitudinal direction, or by gradually narrowing the interval between adjacent clips of the transverse stretching machine.

The latter method can be performed by using a general simultaneous biaxial stretching machine, and by gradually and gradually narrowing the interval between adjacent clips in the longitudinal direction by driving the clip portion by, for example, a pantograph method or a linear drive method. it can. You may combine with extending | stretching of arbitrary directions (diagonal direction) as needed. The dimensional change rate of the optical film (retardation film) can be reduced by shrinking 0.5% to 10% in both the longitudinal direction and the lateral direction.

Stretching can be performed, for example, sequentially or simultaneously in the longitudinal direction of the optical film (retardation film) and the direction orthogonal to the longitudinal direction of the optical film (retardation film), that is, the width direction.

The film thickness variation of the obtained optical film (retardation film) can be reduced by stretching in biaxial directions perpendicular to each other. If the film thickness variation of the optical film (retardation film) is too large, the retardation will become uneven, and unevenness such as coloring may be a problem when used in a liquid crystal display.

The film thickness variation of the optical film (retardation film) is preferably ± 3%, and more preferably ± 1%.

When the slow axis or the fast axis of the retardation film of the present invention exists in the film plane and the angle formed with the film forming direction is θ1, θ1 is preferably −1 ° or more and + 1 ° or less, −0 It is more preferably from 5 ° to + 0.5 °, and further preferably from −0.1 ° to + 0.1 °.

This θ1 can be defined as an orientation angle, and θ1 can be measured using an automatic birefringence meter KOBRA-21ADH (Oji Scientific Instruments). Each of θ1 satisfying the above relationship can contribute to obtaining high luminance in a display image, suppressing or preventing light leakage, and contributing to obtaining faithful color reproduction in a color liquid crystal display device.

The in-plane retardation value (Ro) and the retardation value (Rt) in the thickness direction of the retardation film of the present invention are 30 to 100 nm when used as a polarizer protective film. And the retardation value (Rt) in the thickness direction needs to be in the range of 100 to 300 nm, but the in-plane retardation value (Ro) is in the range of 35 to 65 nm, and The retardation value (Rt) in the thickness direction is preferably in the range of 100 to 180 nm.

Further, the variation of Rt and the width of distribution are preferably less than ± 50%, preferably less than ± 30%, and preferably less than ± 20%. Further, it is preferably less than ± 15%, preferably less than ± 10%, preferably less than ± 5%, particularly preferably less than ± 1%. Most preferably, there is no variation in Rt.

The retardation values Ro and Rt can be obtained by the following equations.

Ro = (nx−ny) × d
Rt = ((nx + ny) / 2−nz) × d
Here, d is the film thickness (nm), nx is the maximum refractive index in the plane of the film (also referred to as the refractive index in the slow axis direction), and ny is in the direction perpendicular to the slow axis in the film plane. The refractive index, nz, is the refractive index of the film in the thickness direction.

Retardation values Ro and Rt can be measured using an automatic birefringence meter. For example, it can be obtained at a wavelength of 590 nm under an environment of 23 ° C. and 55% RH using KOBRA-21ADH (Oji Scientific Instruments).

It is known that the physical properties of the film vary greatly depending on the stretching temperature. This tendency is prominent around the glass transition temperature (Tg) of the film.

As a result of the study by the present inventors, it was found that the adhesiveness between the retardation film and the polarizer was the best when the stretching temperature was Tg to Tg + 20 (° C.) of the resin. On the other hand, it was found that if the film was stretched at a temperature higher than Tg, the expression of retardation (retardation) was insufficient. It is better to stretch the phase difference at a temperature lower than Tg. However, if the stretching temperature is too low, it becomes difficult to stretch, so that the film becomes cloudy or breaks during stretching. The film is preferably stretched at Tg-20 to Tg (° C.).

For this reason, the range of the stretching temperature that achieves both polarizer adhesion and retardation development is extremely narrow, and unless the Tg is the same, the desired performance cannot be obtained, but it is found that the performance is not stable due to the pinpoint. It was.

As a result of studying to solve this problem, the retardation film has a three-layer structure, the glass transition temperature (Tgs) of the surface layer (hereinafter sometimes referred to as skin layer), and the inner layer (hereinafter referred to as core). When the glass transition temperature (Tgc) of the composition (which may be a layer) is adjusted to satisfy the relationship of the following relational expression (1), it has been found that the film can be stretched at a temperature at which both the polarizer adhesion and the phase difference are compatible.

Relational expression (1): Tgc-30 (° C.) ≦ Tgs (° C.) ≦ Tgc-10 (° C.)
The draw ratio is preferably 30 to 60 (%), and more preferably 35 to 50 (%). Increasing the value improves the adhesion of the polarizer and the phase difference is good, but if the stretch ratio is too large, the film becomes cloudy or breaks during stretching.

The method of changing the glass transition temperature includes a method of changing the substitution degree of the cellulose ester and a method of adding additives such as a plasticizer and a resin. In the method of changing the substitution degree of the cellulose ester, light scattering at the interface of the laminated layers, generation of bright spot foreign matters when recycled, and the like are preferable.

When two or more kinds of resins are mixed, if the glass transition temperatures of the two resins are different, there are two or more glass transition temperatures of each mixture because there is a glass transition temperature of each resin. When melted, the glass transition temperature peculiar to each resin disappears and becomes one glass transition temperature, which becomes the glass transition temperature of the compatible resin.

The glass transition temperature was measured at a rate of temperature increase of 20 ° C./min using a differential scanning calorimeter (DSC-7 manufactured by Perkin Elmer) and determined according to JIS K7121 (1987).

(Subsequent steps)
After stretching, the end of the optical film (retardation film) is slit to a product width by a slitter and cut off, and then the knurling (embossing processing) is performed by a knurling apparatus comprising an embossing ring and a back roll. Retardation film) It is applied to both ends and taken up by a winder, thereby preventing sticking and scratching in the optical film (retardation film) (original winding). The knurling method can process a metal ring having an uneven pattern on its side surface by heating or pressing.

In addition, you may reuse the both ends of the optical film (retardation film) cut out with the slitter as a raw material.

Next, in the winding process of the optical film (retardation film), the shortest distance between the outer peripheral surface of the cylindrically wound optical film (retardation film) and the outer peripheral surface of the mobile transport roll immediately before this is constant. The optical film (retardation film) is wound on a winding roll while being held. In front of the take-up roll, means such as a static elimination blower for removing or reducing the surface potential of the optical film (retardation film) is provided.

The winder related to the production of the optical film (retardation film) of the present invention may be generally used, such as a constant tension method, a constant torque method, a taper tension method, a program tension control method with a constant internal stress, etc. It can be wound up by the winding method. The initial winding tension when winding the optical film (retardation film) is preferably 90.2 to 300.8 N / m.

In the winding process of the optical film (retardation film) in the method of the present invention, the optical film (retardation film) is preferably wound under environmental conditions of a temperature of 20 to 30 ° C. and a humidity of 20 to 60% RH. If the temperature in the winding process is in the range of 20 to 30 ° C., there will be no wrinkling, and there will be no deterioration in the winding quality of the optical film (retardation film). Also, if the humidity in the winding process of the optical film (retardation film) is 20 to 60% RH, the deterioration of the optical film (retardation film) winding quality due to moisture absorption is reduced, the winding quality is excellent, and there is also a sticking failure. There is no deterioration in transportability.

The winding core for winding the optical film (retardation film) into a roll may be any material as long as it is a cylindrical core, but is preferably a hollow plastic core. The plastic material may be any heat-resistant plastic that can withstand the heat treatment temperature, and examples thereof include phenol resins, xylene resins, melamine resins, polyester resins, and epoxy resins.

Further, a thermosetting resin reinforced with a filler such as glass fiber is preferable. For example, a hollow plastic core: a wound core made of FRP having an outer diameter of 6 inches (hereinafter, 1 inch is 2.54 cm) and an inner diameter of 5 inches is used.

In the production of the optical film (retardation film) of the present invention, the roll length is preferably 10 to 5000 m, more preferably 50 to 4500 m in consideration of productivity and transportability.

The width of the optical film (retardation film) at this time can be selected from the width of the polarizer and the width suitable for the production line, but it is 0.5 to 4.0 m, preferably 1.0 to 3.0 m. It is preferable to produce an optical film (retardation film) with a width of 5 mm and wind it into a roll.

Haze value (turbidity) is used as an index for judging the transparency of the optical film (retardation film) in the present invention. In particular, liquid crystal display devices used outdoors are required to have sufficient brightness and high contrast even in a bright place. Therefore, the haze value is required to be 0.5% or less, and 0.35% or less. More preferably.

The optical film (retardation film) of the present invention preferably has a total light transmittance of 90% or more, more preferably 92% or more. In order to achieve excellent transparency expressed by such total light transmittance, it is necessary not to introduce additives and copolymerization components that absorb visible light, or to remove foreign substances in the polymer by high-precision filtration. It is effective to reduce the diffusion and absorption of light inside the film.

Also, reduce the surface roughness of the film surface by reducing the surface roughness of the film contact part (cooling roll, calender roll, drum, belt, coating substrate in solution casting, transport roll, etc.) during film formation. It is also effective to reduce the diffusion and reflection of light on the film surface by reducing the refractive index of the acrylic resin.

Further, the optical film (retardation film) of the present invention has an elongation at break in at least one direction of 30% or more, more preferably 50% or more, in the measurement based on JIS-K7127-1999. In the present invention, the elongation at break is used as a measure of brittleness. Other measures of brittleness are known, such as tear strength and ease of cracking by bending, but the tear strength is better as the film thickness is larger, and the ease of cracking by bending is better as the film thickness is smaller. In the present invention, the elongation at break which is not affected by the film thickness is used as an index. The upper limit of the elongation at break is not particularly limited, but is practically about 250%. In order to increase the elongation at break, it is effective to suppress defects in the film caused by foreign matter and foaming.

The film thickness of the optical film (retardation film) of the present invention is not particularly limited, but when used for a polarizing plate protective film described later, it is preferably 20 to 200 μm, more preferably 25 to 100 μm, A thickness of 30 to 80 μm is particularly preferable.

In addition, it is preferable that the film width after extending | stretching of the optical film (retardation film) of this invention is 1900 mm or more.

Moreover, after peeling off after casting and drying and winding up in a roll shape, a functional thin film such as a hard coat layer or an antireflection layer may be provided. Until processing or shipment, packaging is usually performed in order to protect the product from dirt, static electricity, and the like.

The packaging material is not particularly limited as long as the above purpose can be achieved, but preferably does not hinder volatilization of the residual solvent from the film. Specific examples include polyethylene, polyester, polypropylene, nylon, polystyrene, paper, various non-woven fabrics, and the like. Those in which the fibers are mesh cloth are more preferably used.

<Polarizing plate>
The polarizing plate using the retardation film of the present invention can be produced by a general method. An adhesive layer is provided on the back side of the retardation film of the present invention, and it is preferably 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. It is preferable. On the other side, the retardation film of the present invention may be used, or another polarizer protective film may be used.

For example, commercially available cellulose ester films (for example, Konica Minoltack KC8UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UY, KC4UE, KC8UE, KC8UY-HA, KC8UX-RHA, KC8UX-RHA, KC8UX KC4UXW-RHA-NC, manufactured by Konica Minolta Opto Co., Ltd.) is also preferably used.

Further, the polarizer protective film used on the surface side of the liquid crystal display device preferably has an antireflection layer, an antistatic layer, an antifouling layer, and a backcoat layer in addition to the antiglare layer or the clear hard coat layer.

When manufacturing a polarizing plate roll, it is preferable that a separate film is bonded to the surface of the outermost pressure-sensitive adhesive layer, and a peelable protective film is bonded to the surface of the polarizer protective film.

Protect film is usually composed of an adhesive layer on the surface of a transparent base resin film. The pressure-sensitive adhesive used for the protective film is composed of a polymer such as acrylic, urethane, or rubber. Of these, an acrylic pressure-sensitive adhesive is preferably used because of its excellent transparency. Acrylic adhesives are generally based on one or more acrylate esters such as butyl acrylate, ethyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, and copolymerized with polar monomers. Composed of polymer. Examples of polar monomers include (meth) acrylic acid, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, and glycidyl. Mention may be made of monomers having a carboxy group, a hydroxy group (hydroxyl group), an amino group, an epoxy group and the like, such as (meth) acrylate. Moreover, crosslinking agents, such as a polyisocyanate compound, an epoxy compound, and an aziridine compound, are mix | blended with the adhesive.

The separate film is usually composed of a transparent resin film that has been subjected to a release treatment, and the release treatment surface is bonded to the adhesive layer. As the resin film constituting the protect film or the separate film, for example, a film made of polyester such as polyethylene terephthalate or polyethylene naphthalate can be used.

A polarizer, which is a main component of a polarizing plate, is an element that transmits only light having a plane of polarization in a certain direction. A typical polarizing film known at present is a polyvinyl alcohol polarizing film, which is a polyvinyl alcohol. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed.

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

Further, the ethylene unit content described in JP-A-2003-248123, JP-A-2003-342322, etc. is 1 to 4 mol%, the degree of polymerization is 2000 to 4000, and the degree of saponification is 99.0 to 99.99 mol%. Ethylene-modified polyvinyl alcohol is also preferably used.

Among these, an ethylene-modified polyvinyl alcohol film having a hot water cutting temperature of 66 to 73 ° C. is preferably used.

A polarizer using this ethylene-modified polyvinyl alcohol film is excellent in polarization performance and durability performance and has few color spots, and is particularly preferably used for a large liquid crystal display device.

As the pressure-sensitive adhesive used in the pressure-sensitive adhesive layer, a pressure-sensitive adhesive having a storage elastic modulus at 25 ° C. in the range of 1.0 × 10 ⁴ to 1.0 × 10 ⁹ Pa in at least a part of the pressure-sensitive adhesive layer is used. It is preferable to use a curable pressure-sensitive adhesive that forms a high molecular weight body or a crosslinked structure by various chemical reactions after the pressure-sensitive adhesive is applied and bonded.

Specific examples include, for example, urethane adhesives, epoxy adhesives, aqueous polymer-isocyanate adhesives, curable adhesives such as thermosetting acrylic adhesives, moisture-curing urethane adhesives, polyether methacrylate types, Examples include anaerobic pressure-sensitive adhesives such as ester-based methacrylate type and oxidized polyether methacrylate, cyanoacrylate-based instantaneous pressure-sensitive adhesives, and acrylate-peroxide-based two-component instantaneous pressure-sensitive adhesives.

The above-mentioned pressure-sensitive adhesive may be a one-component type or a type in which two or more components are mixed before use.

The pressure-sensitive adhesive may be a solvent system using an organic solvent as a medium, or may be an aqueous system such as an emulsion type, a colloidal dispersion type, or an aqueous solution type that is a medium containing water as a main component. It may be a solventless type. The concentration of the pressure-sensitive adhesive liquid may be appropriately determined depending on the film thickness after adhesion, the coating method, the coating conditions, and the like, and is usually 0.1 to 50% by mass.

<Liquid crystal display device>
By incorporating the polarizing plate bonded with the optical film (retardation film) of the present invention into a liquid crystal display device, various liquid crystal display devices with excellent visibility can be produced. It is preferably used for a liquid crystal display device for outdoor use such as digital signage. The polarizing plate according to the present invention is bonded to a liquid crystal cell via the adhesive layer or the like.

The polarizing plate according to the present invention is a reflective type, transmissive type, transflective LCD or TN type, STN type, OCB type, HAN type, VA type (PVA type, MVA type), IPS type (including FFS type), etc. It is preferably used in LCDs of various driving methods. In particular, in a large-screen display device having a screen of 30 or more, especially 30 to 54, there is no white spot at the periphery of the screen and the effect is maintained for a long time.

Moreover, the polarizing plate roll according to the present invention can be continuously attached to the glass cell, and has an effect of improving productivity. That is, the polarizing plate shown in claim 5, which is bonded to a glass cell that has been cut into a predetermined size on a long roll-shaped polarizing plate using an adhesive, and then cut into each glass cell. The liquid crystal display device can be manufactured with high productivity by the glass panel manufacturing method characterized by the above. The long roll referred to herein is one having a length of 1000 m or more, more preferably 3000 m or more.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
(Synthesis of vinyl polymers and oligomers A2 to A6)
A glass flask equipped with a stirrer, two dropping funnels, a gas introduction tube and a thermometer was charged with 40 g of the monomer Xa and Xb mixed solution of the types and ratios shown in Table 1, 2 g of mercaptopropionic acid as a chain transfer agent and 30 g of toluene. The temperature was raised to 90 ° C. Thereafter, 60 g of a mixture of monomers Xa and Xb having the types and ratios shown in Table 1 was dropped from one dropping funnel over 3 hours, and at the same time, azobisisobutyronitrile 0 dissolved in 14 g of toluene from the other funnel. .4 g was added dropwise over 3 hours. Thereafter, 0.6 g of azobisisobutyronitrile dissolved in 56 g of toluene was added dropwise over 2 hours, and the reaction was further continued for 2 hours to obtain polymer X. The obtained polymer X was solid at room temperature. Next, polymers X having different molecular weights were prepared by changing the addition amount of the chain transfer agent mercaptopropionic acid and the addition rate of azobisisobutyronitrile. The weight average molecular weight of the polymer X is shown in Table 1 by the following measurement method.

(Weight average molecular weight)
The weight average molecular weight of the polymer was determined by GPC polystyrene conversion described above.

Table 1 shows the monomer composition of the vinyl polymer and oligomers A1 to A6 according to the present invention. A1 is a polymethyl methacrylate resin manufactured by Aldrich. B1 is “Arton” (trade name) manufactured by JSR Corporation, which is a cyclic polyolefin resin.

In addition, the meaning of the abbreviation symbol which shows each monomer described in Table 1 is as follows.
MMA: methyl methacrylate HEMA: 2-hydroxyethyl methacrylate ACMO: acryloylmorpholine VP: N-vinylpyrrolidone

(Preparation of dope solution)
Cellulose ester (cellulose acetate propionate, vacuum dried at 60 ° C. for 24 hours, acetyl group substitution degree 0.12, propionyl group 1.12)
70 parts by mass Vinyl polymer and oligomer (see Table 1) 30 parts by mass Silicon oxide fine particles (Aerosil R972V (produced by Nippon Aerosil Co., Ltd.))
) 0.1 part by mass Methylene chloride 300 parts by mass Ethanol 40 parts by mass The addition amount of the silicon oxide fine particles was an addition amount when the total addition amount of cellulose ester, vinyl polymer and oligomer was 100 parts by mass.

(Preparation of cellulose ester film 1-1)
The dope solution was prepared with Finemet NF manufactured by Nippon Seisen Co., Ltd., then filtered, and uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 2 m using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the amount of residual solvent reached 100%, and peeling was performed from the stainless steel band support with a peeling tension of 162 N / m. The peeled cellulose ester web was evaporated at 35 ° C., slit to 1.6 m width, and then dried at a drying temperature of 135 ° C. while stretching 1.1 times in the width direction with a tenter. At this time, the residual solvent amount when starting stretching with a tenter was 10%. After stretching with a tenter and relaxing at 130 ° C. for 5 minutes, drying was completed while transporting the drying zone at 120 ° C. and 130 ° C. with many rolls, slitting to a width of 1.5 m, and 10 mm wide at both ends of the film. A knurling process having a thickness of 5 μm was performed, and the resultant was wound around a 6-inch inner diameter core with an initial tension of 220 N / m and a final tension of 110 N / m to obtain a cellulose ester film 1-1. The draw ratio in the MD direction calculated from the rotational speed of the stainless steel band support and the operating speed of the tenter was 1.01. The residual solvent amounts of the cellulose ester films listed in Tables 2 and 3 were each 0.1%, the film thickness was 40 μm, and the number of turns was 4000 m.

Next, the same as the cellulose ester film 1-1, except that the cellulose ester type, addition amount, vinyl polymer and oligomer type, addition amount, additive type and addition amount were changed as shown in Tables 2 and 3. Thus, cellulose ester films 1-2 to 1-32 were produced.

(Preparation of cellulose ester film 2-1)
As described below, a cellulose ester film 2-1 was produced by melt casting using a cellulose ester and various additives.

Cellulose ester (cellulose acetate propionate: acetyl group substitution degree 0.15, propionyl group substitution degree 1.47; dried at 60 ° C. for 24 hours) 70 parts by weight Vinyl polymer and oligomer (see Table 1) 30 parts by weight IRGANOX-1010 (manufactured by BASF Japan) 0.5 parts by mass GSY-P101 (manufactured by Sakai Chemical Industry) 0.25 parts by mass Sumilizer GS (manufactured by Sumitomo Chemical) 0.25 parts by mass TINUVIN 928 (manufactured by BASF Japan) 5 parts by mass or more of the mixture was melt-mixed at 230 ° C. using a twin-screw extruder and pelletized. In addition, the glass transition temperature Tg of this pellet was 135 degreeC.

In IRGANOX-1010, GSY-P101, Sumizer GS, and TINUVIN 928, the total addition amount of cellulose ester, vinyl polymer, and oligomer was taken as 100 parts by mass.

The pellets are melted at 250 ° C. in a nitrogen atmosphere and extruded onto the first cooling roll 5 from the casting die 4 in the film production method apparatus shown in FIG. 1, and the first cooling roll 5 and the touch roll 6 A film was sandwiched between them to form. Further, silica particle Aerosil 200V (manufactured by Nippon Aerosil Co., Ltd.) was added as a slip agent from the hopper opening in the middle of the extruder 1 so as to be 0.5 part by mass. The addition amount of the silica fine particles was the addition amount when the total addition amount of the cellulose ester, the vinyl polymer and the oligomer was 100 parts by mass.

The heat bolt was adjusted so that the gap width of the casting die 4 was 0.5 mm within 30 mm from the end in the width direction of the film and 1 mm at other locations. The touch roll A was used as the touch roll, and 80 ° C. water was poured as cooling water therein.

From the position P1 at which the resin extruded from the casting die 4 contacts the first cooling roll 5 to the position P2 at the upstream end in the rotation direction of the first cooling roll 5 in the nip between the first cooling roll 5 and the touch roll 6. 1 The length L along the peripheral surface of the cooling roller 5 was set to 20 mm. Thereafter, the touch roll 6 was separated from the first cooling roll 5, and the temperature T of the melted part immediately before being sandwiched between the first cooling roll 5 and the touch roll 6 was measured. In the present embodiment, the temperature T of the melted part immediately before being sandwiched between the nips of the first cooling roll 5 and the touch roll 6 is 1 mm upstream from the nip upstream end P2, and a thermometer (an independent meter). This was measured by HA-200E). As a result of the measurement in this example, the temperature T was 141 ° C. The linear pressure of the touch roll 6 against the first cooling roll 5 was 14.7 N / cm. Furthermore, after introducing into a tenter and stretching 1.3 times at 160 ° C in the width direction, cooling to 30 ° C while relaxing 3% in the width direction, then releasing from the clip, cutting off the clip gripping part, Was subjected to a knurling process having a width of 10 mm and a height of 5 μm, and wound around a core with a winding tension of 220 N / m and a taper of 40%. The extrusion amount and the take-up speed were adjusted so that the film had a thickness of 40 μm, and the finished film width was slit and wound up so as to have a width of 1430 mm. The winding core had an inner diameter of 152 mm, an outer diameter of 165 to 180 mm, and a length of 1550 mm. A prepreg resin obtained by impregnating glass fibers and carbon fibers with an epoxy resin was used as the core material for the core. The surface of the core was coated with an epoxy conductive resin, the surface was polished, and the surface roughness Ra was finished to 0.3 μm. The winding length was 3500 m. Next, the cellulose ester was the same as the cellulose ester film 2-1, except that the cellulose ester type, addition amount, vinyl polymer and oligomer type, addition amount, additive type, and addition amount were changed as shown in Table 4. Films 2-1 to 2-8 were produced.

Retardation Rt, Ro, ΔRo and photoelastic coefficient were determined by the following method using the produced cellulose ester films 1-1 to 1-32 and 2-1 to 2-8, and are shown in Tables 2 to 4.

(Evaluation of retardation)
Using an automatic birefringence meter (manufactured by Oji Scientific Instruments Co., Ltd., KOBRA-21ADH), the cellulose ester films 1-1 to 1-32 and 2-1 to 2-8 are placed in an environment of 23 ° C. and 55% RH. Three-dimensional refractive index measurement was performed at 10 locations at a wavelength of 590 nm, and refractive indexes nx, ny, and nz were obtained. The retardation Rt in the thickness direction was calculated according to the following formula. Each of them was measured at 10 points and the average value was shown.

Rt = {(nx + ny) / 2−nz} × d
Here, the maximum refractive index in the plane of the film is nx, the refractive index in the axial direction perpendicular to the plane is ny, the refractive index in the film thickness direction is nz, and the thickness of the film is d (nm). .

(Evaluation of fluctuation range for changes in humidity of retardation)
The magnitude of the fluctuation range ΔRo with respect to the temperature and humidity change of the retardation defined by the following relational expression (II) was evaluated. Note that the automatic birefringence meter described above was used as a measuring apparatus.
Relational formula (II): ΔRo = {[Ro (23 ° C. 10% RH) −Ro (23 ° C. 80% RH)] / Ro (23 ° C. 55% RH)} × 100 (%)
In the formula, Ro (23 ° C. 10% RH), Ro (23 ° C. 80% RH), and Ro (23 ° C. 55% RH) are 23 ° C. 10% RH, 23 ° C. 80% RH, and 23 ° C. 55%, respectively. An in-plane retardation Ro measured at a measurement light wavelength of 590 nm after humidity conditioning of the retardation film for 36 hours in an RH environment.

Moreover, the fluctuation range ΔRo with respect to the temperature / humidity change of the retardation was ranked into the following levels.

◎: 0% or more and less than 5% ○: 5% or more and less than 10% △: 10% or more and less than 15% ×: 15% or more (Measurement of photoelastic coefficient)
The obtained retardation film sample is sandwiched at both ends in the width direction, the retardation (Ro) in the film surface is measured while applying a load, and this is divided by the thickness (d) of the film to obtain Δn (= Ro / D). Δn was determined while changing the load, the load-Δn curve was measured, and the slope was taken as the photoelastic coefficient. The retardation (Ro) in the film plane was measured at a wavelength of 590 nm under an environment of 25 ° C. and 55% RH using a retardation measuring device (KOBUURA 31PR, manufactured by Oji Scientific Instruments).

The above evaluation results are summarized in Table 2 to Table 4.

As is apparent from the results shown in Tables 2 to 4, it can be seen that the retardation film of the present invention has a low photoelastic coefficient and little retardation fluctuation when used under high temperature and high humidity.

Example 2
A polarizing plate having a layer structure shown in FIG. 2 was produced in a roll shape using the produced cellulose ester film. FIG. 2 is a schematic cross-sectional view showing an example of a layer structure of a polarizing plate roll or a polarizing plate product to be manufactured. Moreover, the cross-sectional schematic diagram which expands and shows the state which winds up a polarizing plate roll in FIG. 3 was shown.

As the protect film 5, a commercially available product “AS3-304” manufactured by Fujimori Kogyo Co., Ltd. was used. ("" Is the product name). The protective film 5 is obtained by forming an acrylic pressure-sensitive adhesive layer on the surface of a polyethylene terephthalate film having a thickness of 38 μm.

In one side of a polarizer 1 having a thickness of 23 μm made of polyvinyl alcohol on which iodine is adsorbed and oriented, an adhesive made of an aqueous solution of a polyvinyl alcohol resin is passed through an aqueous solution of sodium hydroxide having a concentration of 2 mol / l at 60 ° C. After treating for 2 minutes and washing with water, 80 μm thick polarizer protective film 2 (Konica Minolta Tack KC8UX (manufactured by Konica Minolta Opto)) dried at 100 ° C. for 10 minutes is bonded to the other surface of the polarizer 1. Similarly, a thickness of 40 μm was obtained by treating with an aqueous solution of a polyvinyl alcohol resin in an aqueous solution of sodium hydroxide having a concentration of 2 mol / l at 60 ° C. for 2 minutes, washing with water, and drying at 100 ° C. for 10 minutes. The cellulose ester film 3 (cellulose ester film original fabric sample 1-1) was bonded.

Further, on the surface of the cellulose ester film 3, a sheet-like adhesive in which an acrylic adhesive layer 6 having a thickness of 25 μm is formed on a separate film 7 made of polyethylene terephthalate having a thickness of 38 μm is provided on the adhesive layer 6 side. Then, a general protective film 5 was bonded to the polarizer protective layer 2 side to prepare a polarizing plate roll 8 (polarizing plate roll 3-1) having the layer structure shown in FIG. In addition, it bonded so that the transmission axis of a polarizer and the slow axis of the cellulose-ester film 3 might become parallel at this time.

Next, a polarizing plate roll 8 (polarizing plate rolls 3-1 to 3-7) was prepared in the same manner as the polarizing plate roll 3-1, except that the types of the polarizer protective film 2 and the cellulose ester film 3 were changed as shown in Table 5. ) Was produced.

As a comparative example, a ZEONOR film (ZF-14) manufactured by Nippon Zeon Co., Ltd. was used instead of the cellulose ester film 3, and an ultraviolet curable adhesive (( KRX492-25) manufactured by ADEKA Co., Ltd. was applied with a coating device, and then irradiated with ultraviolet rays (irradiation ultraviolet wavelength: 365 nm, adhesive film thickness: 3 μm) with an ultraviolet ray irradiation device at an integrated light quantity of 300 mJ / cm ² for 5 seconds. A polarizing plate roll 8 (polarizing plate roll 3-8) was prepared in the same manner as the polarizing plate roll 3-1, except that the ultraviolet curable adhesive was cured and bonded.

(Evaluation of polarizing plate roll)
A part of the polarizing plate was cut out from the winding core and unwinding of the obtained polarizing plate roll, and evaluated by the following methods. The evaluation results are shown in Table 5. In addition, about the cutout part of a polarizing plate, it cut out as follows.
A: Less than 1000 m from the core part B: 1000 m or more and less than 2000 m from the core part C: 2000 m or more from the core part.

(Evaluation of unevenness at the winding core and unwinding of the polarizing plate roll)
The polarizing plate previously bonded to Sony 30-inch liquid crystal television KDL-32S1000, which is a vertical alignment type liquid crystal display device, is peeled off. A liquid crystal panel was prepared, and a plurality of (10 persons) evaluators visually observed unevenness that looked whitish when viewed from the front and oblique directions. In addition, Table 5 shows the cutout portion of the polarizing plate and the type of each film constituting the polarizing plate.
Evaluation criteria for unevenness of polarizing plate ○: Unevenness is not seen at all Δ: Unevenness is faintly recognized, but it can be used as a product x: Unevenness is recognized by many evaluators (5 or more).

(Evaluation of adhesion)
The polarizing plate cut out from the polarizing plate roll was measured by hand to determine whether it could be peeled off.
Evaluation criteria for adhesion ○: Bonded and cannot be peeled by hand Δ: Only the edge is peeled off, and the member is destroyed when peeled further. ×: Easy peeling by hand.

(Corner unevenness)
The prepared liquid crystal display device was stored at 65 ° C. and humidity for 500 hours, and then the liquid crystal display device was turned on. After 6 hours, a plurality of (10) It was confirmed visually by an evaluator.
Evaluation criteria for corner unevenness ○: No light leakage in the surrounding area is observed △: Light leakage in the surrounding area may be recognized, but it can be used as a product ×: A lot of evaluators (more than 5 people) Leakage is observed.

(Viewing angle fluctuation)
For evaluation of viewing angle characteristics, EZ-contrast manufactured by ELDIM was used to measure the amount of transmitted light during black display and white display. The viewing angle was evaluated by calculating contrast = (transmitted light amount during white display) / (transmitted light amount during black display).

The durability of the viewing angle function was evaluated by measuring the viewing angle characteristics before and after the treatment for 500 hours under the conditions of 60 ° C. and 90% RH, and observing the change in angle indicating the viewing angle of contrast 10.
Evaluation ○: No change in upper, lower, left and right Δ: Change in viewing angle of 2 ° or more and less than 5 ° in either up, down, left or right direction ×: Change in viewing angle of 5 ° or more in either upper, lower, left or right direction

(Change in color)
The produced liquid crystal display device was displayed in black in an environment of 23 ° C. and 55% RH and observed from an oblique angle of 45 °. Subsequently, the polarizing plate treated at 60 ° C. and 90% RH for 1000 hours was similarly observed, and the presence or absence of a color change was visually confirmed by a plurality (10 persons) of evaluators.
○: No color change △: Color change may be slightly recognized, but a level that can be used as a product ×: Many evaluators (5 or more) recognize that the color change is large. Table 5 shows.

As is clear from the results shown in Table 5, the polarizing plate roll produced using the retardation film of the present invention exhibits the characteristics that it suppresses unevenness of the polarizer even in the winding core and unwinding, and has excellent adhesion. It was. In addition, when the retardation film of the present invention is used in a liquid crystal display device, it is excellent in evaluation of variation in viewing angle and change in color tone because corner unevenness and furthermore, the designed retardation changes. I understand that.

DESCRIPTION OF SYMBOLS 1 Extruder 2 Filter 3 Static mixer 4 Casting die 5 Rotating support body (1st cooling roll)
6 Nipping pressure rotating body (touch roll)
7 Rotating support (second cooling roll)
8 Rotating support (3rd cooling roll)
9, 11, 13, 14, 15 Transport roll 10 Cellulose ester film 16 Winding device 1a Polarizer 2a Polarizer protective film 3a Cellulose ester film

4a Polarizing plate

5a Protective film

6a Adhesive layer 7a Separate film 8a Polarizing roll or polarizing Plate products

Claims

A cellulose ester satisfying the following relational formula (I) and a substituent selected from a carboxy group, an alkoxycarbonyl group, a hydroxy group, an amino group, an amide group, and a sulfo group, and having a weight average molecular weight of 500 to 200,000 A polymer or oligomer of a vinyl compound within a range, and the mass ratio of the content of the cellulose ester and the polymer or oligomer is within a range of 95: 5 to 50:50. A retardation film.
Relational expression (I): 1.0 ≦ X + Y <2.0
(In the formula, X represents the degree of substitution of the acetyl group, and Y represents the degree of substitution of the acyl group having 3 or more carbon atoms.)
The retardation film according to claim 1, wherein the substitution degree Y of the acyl group having 3 or more carbon atoms of the cellulose ester is 0.9 or more.
3. The retardation film according to claim 1, wherein the photoelastic coefficient is in the range of −1.0 × 10 −12 to 1.0 × 10 −12 cm 2 / dyn.
4. The phase difference according to claim 1, wherein a fluctuation range ΔRo with respect to temperature and humidity change of the retardation defined by the following relational expression (II) is 10% or less. the film.
Relational formula (II): ΔRo = {[Ro (23 ° C. 10% RH) −Ro (23 ° C. 80% RH)] / Ro (23 ° C. 55% RH)} × 100 (%)
Wherein Ro (23 ° C. 10% RH), Ro (23 ° C. 80% RH), and Ro (23 ° C. 55% RH) are 23 ° C. 10% RH, 23 ° C. 80% RH, and 23 ° C. 55, respectively. Represents in-plane retardation Ro measured at a measurement light wavelength of 590 nm after conditioning the retardation film for 36 hours in an environment of% RH.)
A polarizing plate, wherein the retardation film according to any one of claims 1 to 4 is provided on at least one surface of a polarizer.
The polarizing plate according to claim 5, wherein the polarizing plate is wound in a roll shape in the longitudinal direction.
A liquid crystal display device, wherein the retardation film according to any one of claims 1 to 4 is provided in a liquid crystal cell.