KR20100039277A - Optical film, and polarizing plate and liquid crystal display device each using the optical film - Google Patents

Abstract

Disclosed is an optical film which can be melt-casted, rarely causes retardation, and has excellent surface quality and physical properties. Disclosed is an optical film which comprises a cellulose ester film having a residual solvent content of 0.01 mass% or less, an in-plane retardation (Ro) of 0 to 10 nm (inclusive), and a thicknesswise retardation (Rth) of-20 to 20 nm (inclusive). In the cellulose ester contained in the cellulose ester film, the types of substituents and the degree of substitution per one glucose unit of the cellulose ester meet all of the requirements represented by the following formulae (1) to (3). 6.7 <= 2×X+3×Y <= 7.4 Formula (1) 2.86 <= X+Y <= 3.00 Formula (2) 1.0 <= Y <= 1.4 Formula (3) wherein X represents the degree of substitution of an acetyl group; and Y represents the degree of substitution of a propionyl group.

Description

Optical film, polarizing plate and liquid crystal display using the same {OPTICAL FILM, AND POLARIZING PLATE AND LIQUID CRYSTAL DISPLAY DEVICE EACH USING THE OPTICAL FILM}

The present invention relates to an optical film comprising a cellulose ester formed by the melt casting method, a polarizing plate using the same, and a liquid crystal display device.

BACKGROUND ART A liquid crystal display device widely used as a display element is composed of a liquid crystal cell comprising a pair of substrates sandwiching a liquid crystal layer, a pair of polarizing plates or the like arranged on both sides of the liquid crystal cell in an orthogonal state, and an IPS (In-Plane). Various display modes such as switching, TN (twisted nematic), and VA (vertically aligned) have been proposed.

In the case of the IPS mode, since the liquid crystal molecules mainly rotate in the plane parallel to the substrate, it is known that the difference in the degree of birefringence between the application of the electric field and the application of the oblique view is small and the viewing angle is wide.

IPS mode uses liquid crystal molecules oriented homogeneous in the horizontal direction, and two polarizing plates arranged so that the transmission axis is perpendicular to the front, vertical, and horizontal directions with respect to the front of the screen. When the screen is viewed at an angle from the camera, sufficient contrast can be obtained.

On the other hand, when the screen is viewed obliquely from the direction of 45 degrees of azimuth, since the angle formed by the transmission axes of the two polarizing plates appears to be shifted from 90 degrees, the transmitted light generates birefringence and the light leaks, thereby sufficient black. Cannot be obtained, resulting in a decrease in contrast.

That is, in the polarizing plate which uses the cellulose ester film generally used as a protective film, there exists a problem that a viewing angle becomes narrow by birefringence which a film has, and in order to improve this, the retardation value of in-plane and thickness direction is close to zero. Film was required.

In solution casting film formation, the technique of obtaining the optical film whose retardation value of in-plane and thickness direction is close to zero by adding to a cellulose ester the cellulose triacetate film with small retardation originally, or the specific polymer which cancels the retardation which a film has. (See, for example, Patent Documents 1 and 2 below).

However, when this technique is applied to the melt casting method of an environmentally useful cellulose ester film, it is very difficult to apply it as it is because of the difficulty of decomposition | disassembly of the said specific polymer and manufacture of the viscosity at the time of film forming.

On the other hand, in following patent document 3, the retardation value of the in-plane and thickness direction of the unstretched film after film forming is close to 0 by adjustment of the temperature at the time of film forming by a melt casting method (slow cooling film at the time of film forming). Techniques for obtaining are disclosed.

However, this technique is very low in productivity because it slows down the cooling temperature during film formation, and is used as an unstretched film because retardation occurs when the film is stretched. It was a distant thing.

Patent Document 1: Japanese Patent Application Laid-Open No. 11-5851

Patent Document 2: Japanese Patent Application Laid-Open No. 2007-65184

Patent Document 3: Japanese Patent Laid-Open No. 2006-348269

The technique disclosed in patent document 1 and patent document 2 is a technique with respect to the solution casting film | membrane using all the cellulose triacetate.

Cellulose triacetate film is widely used as a polarizing plate protective film from the point that the retardation of an in-plane direction is very small originally, and the adhesiveness with a polarizer is excellent.

Therefore, Patent Literature 1 and Patent Literature 2 are techniques that further reduce not only the in-plane direction of the cellulose triacetate film but also the retardation in the thickness direction.

By the way, since cellulose triacetate has high melting temperature, it is difficult to melt-cast, and the cellulose ester which introduce | transduced the substituent by propionyl group etc. instead of acetate is examined for melt casting.

However, the introduction of substituents such as propionyl groups causes retardation of both the in-plane and thickness directions of the cellulose ester film to occur in the cellulose triacetate film, and as disclosed in Patent Document 3, it must be used as an unstretched film. I did.

For the unstretched film, the physical properties, especially the retardation value, fluctuate greatly depending on the moist heat, and the display quality of the liquid crystal display, i.e., a characteristic nonuniformity not seen in the VA (vertical orientation) and TN (twisted nematic) methods The graininess resulting from the black matrix of a pixel called this and a fine transparent electrode shape arises.

An object of the present invention is to provide a cellulose ester film having a small retardation made of a melt-castable cellulose ester and having excellent surface quality and physical properties.

The inventors have found that in any very narrow substituent composition region of the cellulose ester, the occurrence of retardation is particularly small, and the stretching treatment is also possible.

In other words, the present inventors have studied cellulose esters in which the second, third and sixth hydroxyl groups of the 1 glucose unit constituting the cellulose ester are substituted with acetyl group and propionyl group in the course of earnestly examining for solving the above problems. As a result, when the substitution state (average degree of substitution) of an acetyl group and a propionyl group is specific, it discovered that all the said subjects could be solved and came to complete this invention.

An object of the present invention is to provide an optical film capable of melt casting, very low generation of retardation, and excellent surface quality and physical properties.

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

1. Optical containing cellulose ester film whose amount of residual solvent is 0.01 mass% or less, in-plane retardation Ro is 0 <= <= <= 10 nm, and retardation (Rth) of thickness direction is -20 <= Rth <= 20nm. It is a film, The optical film characterized by the type of substituent per 1 glucose unit of cellulose ester contained in the said cellulose ester film, and its substitution degree being a cellulose ester which satisfy | fills the conditions of following formula (1)-(3) simultaneously.

6.7≤2 × X + 3 × Y≤7.4

2.86≤X + Y≤3.00

1.0≤Y≤1.4

In the formula, X represents the degree of substitution of the acetyl group, and Y represents the degree of substitution of the propionyl group.

2. A polarizing plate having a structure in which both surfaces of a polarizer are sandwiched between two polarizing plate protective films, wherein at least one of the polarizing plate protective films is the optical film according to 1 above.

3. The polarizing plate of 2 is used for at least one surface of a liquid crystal cell, The liquid crystal display device characterized by the above-mentioned.

Effect of the Invention

Industrial Applicability According to the present invention, a cellulose ester film having a low retardation containing a melt-castable cellulose ester and excellent in surface quality and physical properties can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic diagram of the manufacturing process of the optical film which concerns on this invention.

2 is an enlarged view of the flexible die portion during the manufacturing process of the optical film according to the present invention.

<Description of the code>

1: extruder

2: filter

3: static mixer

4: flexible die

5: rotating support (first cooling roll)

6: sandwich presser (touch roll)

7: rotating support (second cooling roll)

8: rotating support (third cooling roll)

9, 11, 13, 14, 15: conveying roll

10: optical film

16: winding device

Best Mode for Carrying Out the Invention

EMBODIMENT OF THE INVENTION Although the best form for implementing this invention below is demonstrated in detail, this invention is not limited to these.

<< retardation >>

In-plane retardation Ro of the cellulose ester film of this invention is 0 <= R <= 10nm, and retardation Rth of thickness direction is -20 <= Rth <= 20nm.

Moreover, when the refractive index Nx of the slow axis direction of a film, the refractive index Ny of a fast axis direction, the refractive index Nz of a thickness direction, and the film thickness of a film are set to d (nm),

Ro = (Nx-Ny) × d

Rt = {(Nx + Ny) / 2-Nz} × d

Represented as

In addition, retardation Ro and Rth are the film samples which were left to stand in the environment of 23 degreeC and 55% RH for 24 hours using the automatic birefringence system KOBRA-21ADH (made by Oji Keisukuki Co., Ltd.), under the same environment, The retardation measurement of the film in wavelength 590nm was performed. It obtained by inputting the above-mentioned average refractive index and the film film thickness measured using the commercially available micrometer.

The smaller the deviation in the film plane of the retardation is, the more preferable, usually within ± 5 nm, preferably ± 2 nm or less.

Uniformity in the slow axis direction is also important, preferably an angle of -5 to + 5 ° with respect to the film width direction, further preferably in the range of -1 to + 1 °, particularly of -0.5 to + 0.5 °. It is preferable to exist in a range, and it is especially preferable to exist in the range of -0.1 to +0.1 degrees. These deviations can be achieved by optimizing the stretching conditions.

In order to achieve the said retardation, the optical film of this invention has the following cellulose ester as a main component, and has the structure which contains additives, such as a plasticizer, a ultraviolet absorber, and a particle | grain.

<< cellulose ester >>

The cellulose has three hydroxyl groups in total, one each at the 2nd, 3rd, and 6th positions in 1 glucose unit, and the degree of substitution is a value indicating how much acyl groups are bound to which position in average on 1 glucose unit.

Therefore, the maximum substitution degree is 3.00 and the part which is not substituted by the said acyl group exists normally as a hydroxyl group.

A part or all of the hydroxyl groups of such cellulose is substituted by the acyl group is called cellulose ester.

The cellulose ester used for the melt casting method of this invention makes X the sum of the average substitution degree by the acetyl group of 2nd, 3rd, and 6th positions, and averages it by the propionyl group of 2nd, 3rd, and 6th positions. When the sum of substitution degree is Y, it is a cellulose ester which satisfy | fills following formula (1)-(3) simultaneously (henceforth average substitution degree is only called substitution degree).

Equation 1 shows the total carbon number of the substituted acyl group. The acetyl group has 2 carbon atoms and the propionyl group 3 carbon atoms.

Such cellulose esters are commonly referred to as highly substituted cellulose acetate propionate.

In addition, it is important to satisfy all three at the same time only by satisfying any one or two of the following formulas.

<Equation 1>

6.7≤2 × X + 3 × Y≤7.4

<Equation 2>

2.86≤X + Y≤3.00

<Equation 3>

1.0≤Y≤1.4

Especially, it is preferable to set it as 6.9 <= 2 * X + 3 * Y <= 7.3 in the formula (1) from the point which further demonstrates the effect of this invention.

In Equation 2, it is preferable to set 2.9 ≤ X + Y ≤ 3.0 in order to further exhibit the effect of the present invention.

In Equation 3, it is preferable to set 1.0 ≦ Y ≦ 1.3 in order to further exhibit the effect of the present invention.

In addition, the information about substitution degree and substitution position of an acetyl group and a propionyl group can be calculated | required by the method demonstrated below.

Next, the substitution degree of the acyl group (acetyl group and propionyl group) of the cellulose ester used for this invention is demonstrated.

The method for measuring the degree of substitution at each position of the glucose unit of the acyl group of the present invention is described in Y. Tezuka & Y. Tsuchiya's paper [Carbohydrate Research, Vol. 273, pages 83 to 91 (1995)]. By the 13 C-NMR method.

Using this method, the signal of 13C-NMR of acetyl group and the signal of propionyl group are clearly divided, and the signals of 2nd, 3rd, and 6th positions are also divided into three adjacent peaks. The degree of substitution can be known from the height of.

In addition, the substitution degree of an acetyl group and a propionyl group can also be calculated | required by the method of the prescription | regulation to ASTMD817-96, and is consistent with the said method.

Next, the necessity of satisfying all of the above three equations (1) to (3) will be described.

Regarding the retardation value change in the in-plane and thickness directions due to the stretching of the film formed by melting, the total substitution degree of substituted acyl groups per glucose unit of the cellulose ester (X + Y or less, simply referred to as total substitution degree) is largely related. The higher the total substitution degree, the smaller the change in retardation value due to stretching.

Although it is not clear about this reason, it is thought that the hydrogen bond by the hydroxyl group which remain | survives in a cellulose ester reduces, and even if it is extended | stretched, the orientation and refractive index of a molecule | numerator do not change.

In Patent Document 1, this phenomenon has been suggested in the cellulose triacetate film. However, in cellulose triacetate, the deterioration of the physical properties due to the decrease in the elastic modulus and the solubility in the solvent due to the decrease in the elasticity from the vicinity of the substitution degree exceeding 2.86. Deterioration has arisen, and it is used in the range of practical substitution degree, and the examination which raises substitution degree and the influence of introduction of propionyl group etc. are hardly examined.

The present invention suppresses deterioration of film physical properties and enables melt casting by introducing a specific amount of propionyl group.

In this invention, in order to obtain the optical film whose retardation value of in-plane and thickness direction is close to 0, even if it extends by 1.3 times the draw ratio in a width direction (horizontal direction), without adding a retardation reducing agent in melt film forming, We found that total substitution was needed above 2.86.

Next, the synthesis method of the cellulose ester used by this invention is demonstrated.

Although the raw material cellulose of the cellulose ester used by this invention may be a wood pulp, a cotton linter, and a wood pulp may be coniferous or a hardwood, conifers are more preferable. In view of peelability at the time of film forming, a cotton printer is preferably used. The cellulose esters made from these may be appropriately mixed or used alone.

For example, the ratio of cellulose ester derived from cotton linter: cellulose ester derived from wood pulp (softwood): cellulose ester derived from wood pulp (softwood) is 100: 0: 0, 90: 10: 0, 85: 15: 0, 50: 50: 0, 20: 80: 0, 10: 90: 0, 0: 100: 0, 0: 0: 100, 80:10:10, 85: 0: 15, and 40:30:30.

The cellulose ester of this invention can be synthesize | combined with reference to a well-known method. For example, the hydroxyl group of the starting cellulose can be acetylated and propionylated by a conventional method using acetic anhydride and propionic anhydride, and the acetyl group, propionyl group can be substituted, and acetic anhydride to be used, and anhydrous By appropriately changing the amount of propionic acid used, it is possible to adjust the degree of substitution of the acetyl group, the degree of substitution of the propionyl group, and the total degree of substitution.

In addition to an acetyl group and a propionyl group, you may contain acyl groups, such as a butyryl group, with 0.15 or less substitution degree.

By using the above method, the cellulose ester of the present invention satisfying the above Equations 1 to 3 can be synthesized.

Although the cellulose ester of this invention does not have limitation in particular, It is preferable to have a weight average molecular weight (Mw) of 150,000-250,000, It is more preferable to have a weight average molecular weight of 180,000-230,000, The weight average of 190,000-220,000 Most preferred is to have a molecular weight.

When the weight average molecular weight is in the above preferable range, problems such as excessively high melt viscosity or lowering of the strength of the resulting film are preferable, which is preferable.

In addition, the cellulose ester used in the present invention preferably has a weight average molecular weight (Mw) / number average molecular weight (Mn) ratio of 1.3 to 5.5, particularly preferably 1.5 to 5.0, more preferably 1.7 to 4.0 More preferably, the cellulose ester of 2.0-3.5 is used preferably. When Mw / Mn exceeds 5.5, a viscosity will become high and melt filterability will fall and it is unpreferable. On the other hand, it is preferable that it is 1.3 or more from the point of industrial manufacturing characteristics.

In addition, Mw and Mw / Mn can be computed by gel permeation chromatography (GPC) by the following method.

Measurement conditions are as follows.

Solvent: Methylene Chloride

Apparatus: HLC-8220 [manufactured by Tosoh Corporation]

Column: TSKgel SuperHM-M [manufactured by Tosoh Corporation]

Column temperature: 40 ℃

Sample temperature: 0.1% by mass

Injection volume: 10 μl

Flow rate: 0.6ml / min

Calibration curve: Standard polystyrene: PS-1 (manufactured by Polymer Laboratories) Mw = 2,560,000 to 580 A calibration curve with 9 samples was used.

It is preferable that the alkaline earth metal content of the cellulose ester of this invention is 1-50 ppm.

If the alkaline earth metal content of the cellulose ester is in the range of 1 to 50 ppm, there is no increase in lip adhesion contamination, and no breakage occurs in the slitting portion during thermal stretching or after thermal stretching, whereby the effect of the present invention is further exhibited.

Moreover, in this invention, the range whose alkali earth metal content of a cellulose ester is 1-30 ppm is preferable.

The alkaline earth metal referred to here is the total content of Ca and Mg, and can be measured using an X-ray photoelectron spectroscopy apparatus (XPS).

The residual sulfuric acid content in the cellulose ester of the present invention is preferably in the range of 0.1 to 45 ppm in terms of sulfur element. It can be considered that they are contained in the form of a salt.

If the residual sulfuric acid content exceeds 45 ppm, the adhesion of the die lip portion at the time of hot melting increases, which is not preferable.

Moreover, since it becomes easy to fracture | rupture at the time of thermal stretching or the slitting after thermal stretching, it is not preferable. Moreover, the range of 1-30 ppm is preferable.

Residual sulfuric acid content can be measured by the method of the prescription | regulation to ASTM D817-96.

It is preferable that the free acid content in the cellulose ester of this invention is 1-500 ppm.

If it is the said range, the deposit | attachment of a die lip part will not increase and it is hard to break.

Moreover, in this invention, it is preferable that it is the range of 1-100 ppm, and it becomes difficult to fracture. In particular, the range of 1-70 ppm is preferable.

Free acid content can be measured by the method of the prescription | regulation to ASTM D817-96.

By carrying out the washing | cleaning of the synthesized cellulose ester more fully compared with the case used for the solution casting method, it is preferable because the residual alkaline earth metal content, residual sulfuric acid content, and residual acid content can be made into the said range.

In addition, in addition to water, the cellulose ester can be washed with a poor solvent such as methanol or ethanol, or consequently a poor solvent and a mixed solvent of a poor solvent and a good solvent. Can be removed

Moreover, washing | cleaning of a cellulose ester is also performed in presence of a deterioration inhibitor, and the heat resistance and film forming stability of a cellulose ester improve.

The deterioration inhibitor to be used can be used without limitation as long as it is a compound which inactivates radicals generated in cellulose esters or suppresses deterioration of cellulose esters due to addition of oxygen to radicals generated in cellulose esters. , Hindered amine compounds and phosphorous acid ester compounds are preferable.

In order to improve the heat resistance, mechanical properties, optical properties, etc. of the cellulose ester, after dissolving in a good solvent of the cellulose ester, reprecipitation and filtration in a poor solvent, or stirring and suspending and filtering in a poor solvent, The molecular weight component and other impurities can be removed.

Under the present circumstances, it is preferable to carry out in presence of a deterioration inhibitor similarly to washing of the cellulose ester mentioned above.

The deterioration inhibitor used for washing | cleaning a cellulose ester may remain in the cellulose ester after washing | cleaning. The residual amount is preferably 0.01 to 2000 ppm, more preferably 0.05 to 1000 ppm. More preferably, it is 0.1-100 ppm.

Moreover, you may add another polymer or a low molecular weight compound after the reprecipitation process of a cellulose ester.

The optical film of this invention WHEREIN: The cellulose ester contained in a cellulose ester film is 60-99 mass%.

`` Antioxidants, thermal degradation inhibitors. ''

In this invention, what is normally known can be used as antioxidant and a thermal deterioration inhibitor. In particular, those of a lactone-based, sulfur-based, phenol-based, double-bond-based, hindered amine-based and phosphorus-based compounds can be preferably used.

As said phenol type compound, what has a structure of 2, 6- dialkyl phenol is preferable, and what is marketed under the brand names of "Irganox1076", "Irganox1010", for example is Shiva Japan.

The phosphorus-based compound is, for example, "SumilizerGP" from Sumitomo Chemical Co., Ltd., "ADK STAB PEP-24G", "ADK STAB PEP-36" and "ADK STAB 3010" from SADE Japan Japan. It is preferable that it is marketed under the brand names "GSY-P101" from "IrgafosXP40", "IrgafosXP60", "IRGAFOS P-EPQ", and Sakai Kagaku Kogyo Co., Ltd. from Shiki Kaisha.

It is preferable that the said hindered amine type compound is marketed by the brand name "ADK STAB LA-52" from Shiva Japan Co., Ltd. by "Tinuvin144" and "Tinuvin770", and ADEKA, for example.

It is preferable that the said sulfur type compound is marketed under the brand names "Sumilizer TPL-R" and "Sumilizer TP-D", for example from Sumitomo Chemical Co., Ltd ..

It is preferable that the said double bond type compound is marketed by Sumitomo Chemical Co., Ltd. under the brand names "Sumilizer GM" and "Sumilizer GS."

It is also possible to contain a compound having an epoxy group as described in US Pat. No. 4,137,201 as an acid trapping agent.

These antioxidants and the like are appropriately added in accordance with the process at the time of regeneration, but are generally added in the range of 0.05 to 20 mass% based on the cellulose ester which is the main raw material of the film.

These antioxidants and thermal deterioration inhibitors can obtain synergistic effects by using several different types of compounds in combination than using only one type. For example, combined use of a lactone system (manufactured by HP136 Ciba Japan Co., Ltd.), phosphorus, phenol and double bond compounds is preferable.

<< plasticizer >>

In manufacture of the cellulose ester film which concerns on this invention, it is preferable to contain 1-30 mass% of 1 or more types of plasticizers in a cellulose ester film.

The plasticizer is generally an additive which has an effect of improving fragility or imparting flexibility by adding it to a polymer. However, in the present invention, the same heating is performed in order to lower the melting temperature than the melting temperature of the cellulose ester alone. A plasticizer is added in order to reduce the melt viscosity of the film structural material containing a plasticizer rather than a cellulose resin alone in temperature.

Moreover, since it is added also in order to improve the hydrophilicity of a cellulose ester and to improve the water vapor transmission rate of a cellulose ester film, it has a function as a moisture absorption inhibitor.

Here, the melting temperature of the film constituent material means a temperature of a state in which the material is heated to express fluidity. In order to melt-flow a cellulose ester, it is necessary to heat at least higher than glass transition temperature.

Above the glass transition temperature, the elastic modulus or the viscosity decreases due to absorption of the amount of heat, and fluidity is expressed. However, in the cellulose ester, the molecular weight of the cellulose ester may decrease due to thermal decomposition at the same time as melting under high temperature, and may adversely affect the mechanical properties of the resulting film. Therefore, it is necessary to melt the cellulose ester at the lowest possible temperature. have.

In order to reduce the melting temperature of a film component material, it can achieve by adding the plasticizer which has melting | fusing point or glass transition temperature lower than the glass transition temperature of a cellulose ester.

It is preferable that the cellulose ester film of this invention contains 1-25 mass% of ester compounds which have a structure which the organic acid and the trivalent or more alcohol condensed.

By addition of 1 mass% or more, the effect of planarity improvement is confirmed, and when it is less than 25 mass%, it is difficult to bleed out and it is preferable because it is excellent in the aging stability of a film.

More preferably, it is a cellulose ester film containing 3-20 mass% of said plasticizers, More preferably, it is a cellulose ester film containing 5-15 mass%.

Although it does not specifically limit as other plasticizer which can be used for this invention, Preferably it is a sugar ester compound, an acrylic polymer, a polyhydric carboxylic acid ester plasticizer, a glycolate plasticizer, a phthalic acid ester plasticizer, a fatty acid ester plasticizer, and a polyhydric alcohol Ester plasticizer, polyester plasticizer and the like.

Among these, when using 2 or more types of plasticizers, it is preferable that 1 or more types are polyhydric alcohol ester plasticizers.

<< plasticizer-sugar ester compound >>

It is preferable that the optical film of this invention melt-film-forms the molten composition containing the sugar ester compound which esterified the hydroxyl group of the sugar compound which 1-1 or more types of structures chosen from the furanose structure and the pyranose structure have couple | bonded 1-12. Do.

Examples of the sugar compound of the present invention include glucose, galactose, mannose, fructose, xylose, arabinose, lactose, sucrose, cellobiose, cellulose trios, martotriose and raffinose. It is preferable to have both a furanose structure and a pyranose structure. An example is sucrose.

The sugar ester compound of this invention is a thing in which one part or all part of the hydroxyl group which a sugar compound has esterified, or its mixture.

<< plasticizer-acrylic polymer >>

In this invention, it is preferable to melt-film-form the melt composition containing the acryl-type polymer whose weight average molecular weights are 500 or more and 30000 or less.

As the acrylic polymer of the present invention, a polymer having a weight average molecular weight of 5000 or more and 30000 or less obtained by copolymerizing an ethylenically unsaturated monomer Xa which does not have an aromatic ring and a hydrophilic group in a molecule and an ethylenically unsaturated monomer Xb which does not have an aromatic ring in a molecule and having a hydrophilic group X is an example.

And more preferably, it is preferable to use together the polymer Y of the weight average molecular weights 500 or more and 3000 or less obtained by superposing | polymerizing the ethylenically unsaturated monomer Ya which does not have an aromatic ring.

Polymer X of the present invention is a polymer having a weight average molecular weight of 5000 to 30000, obtained by copolymerizing an ethylenically unsaturated monomer Xa having no aromatic ring and a hydrophilic group in a molecule and an ethylenically unsaturated monomer Xb having a hydrophilic group without an aromatic ring in a molecule. .

Preferably, Xa is an acrylic or methacrylic monomer which does not have an aromatic ring and a hydrophilic group in the molecule, and Xb is an acrylic or methacrylic monomer which does not have an aromatic ring in the molecule and has a hydrophilic group.

<< retardation adjustment agent >>

In the cellulose ester film of this invention, you may contain the compound for adjusting retardation.

As the compound added to adjust the retardation, an aromatic compound having two or more aromatic rings, as described in European Patent No. 911,656A2, may be used.

Moreover, you may use together 2 or more types of aromatic compounds. The aromatic ring of the said aromatic compound contains an aromatic heterocyclic ring in addition to an aromatic hydrocarbon ring. It is especially preferable that it is an aromatic hetero ring, and an aromatic hetero ring is generally an unsaturated hetero ring. Among them, compounds having a 1,3,5-triazine ring are particularly preferred.

As a cellulose ester film which concerns on this invention, since a haze value exceeds 1.0%, it affects as an optical material, Preferably haze value is less than 1.0%, More preferably, it is less than 0.5%. The haze value can be measured based on JIS-K7136.

"coloring agent"

In this invention, it is preferable to use a coloring agent. The colorant means a dye or a pigment, but in the present invention, it refers to an effect of making the color tone of the liquid crystal screen blue, or adjusting the yellow index and reducing the haze.

Although various dyes and pigments can be used as a coloring agent, anthraquinone dye, an azo dye, a phthalocyanine pigment, etc. are effective. Although the specific example of a preferable coloring agent is given to the following, it is not limited to these.

<< other additives >>

The cellulose ester film of this invention can be made to contain the additive which can be added to a normal cellulose ester film other than the said compound.

As these additives, a plasticizer, an ultraviolet absorber, microparticles | fine-particles, etc. are mentioned.

Although the ultraviolet absorber used for this invention is not specifically limited, For example, an oxybenzo phenone type compound, a benzotriazole type compound, a salicylic acid ester type compound, a benzophenone type compound, the cyanoacrylate type compound, a triazine type compound, nickel Complex salt compounds, inorganic powders, and the like. It is good also as a polymer type ultraviolet absorber.

As the fine particles used in the present invention, examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and Calcium phosphate. It is preferable that microparticles | fine-particles contain silicon from the point which becomes turbidity low, and silicon dioxide is especially preferable.

5-50 nm is preferable and, as for the average particle diameter of the primary particle of microparticles | fine-particles, 7-20 nm is preferable. It is preferable to contain these mainly as a secondary aggregate of 0.05-0.3 micrometer in particle size. It is preferable that content of these microparticles | fine-particles in a cellulose ester film is 0.05-1 mass%, and 0.1-0.5 mass% is especially preferable. In the case of the cellulose-ester film of the multilayered constitution by a covalent smoke method, it is preferable to contain this addition amount microparticles on the surface.

The fine particles of silicon dioxide are commercially available, for example, under the trade names of Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600, NAX50 (manufactured by Nippon Aerosol Co., Ltd.). It becomes and can use it.

The fine particles of zirconium oxide are commercially available under the trade names of Aerosil R976 and R811 (above Nippon Aerosil Co., Ltd. product), and can be used, for example.

Examples of the polymer include silicone resins, fluororesins and acrylic resins. A silicone resin is preferable, and it is especially preferable to have a three-dimensional network structure, for example, tospul 103, tospul 105, tospul 108, tospul 120, tospul 145, tospul 3120 and tospul 240 [more than It is marketed under the brand name of Toshiba Silicone Co., Ltd., and can be used.

Among these, aerosil 200V and aerosil R972V are particularly preferably used because the effect of lowering the coefficient of friction is great while keeping the turbidity of the cellulose ester film low.

<Flexible film forming of a cellulose ester film>

The cellulose ester of the present invention is usually obtained in powder form. In the manufacturing method of the cellulose-ester film of this invention, although a powdery cellulose ester may be used, it is preferable from a viewpoint of handling to use powder shape | molding in pellet form.

When molding powder into pellets, a known single screw extruder or a twin screw extruder can be used. For example, a powdered cellulose ester is introduced from a hopper of an extruder, melt-kneaded at a temperature of about (Tg + 100) ° C. of the cellulose ester to extrude a stranded product from a die, and the stranded product is cooled by a method such as water cooling. After that, the pellet can be obtained by cutting with a pelletizer.

When putting a powdered cellulose ester into a hopper, you may pelletize by adding various antioxidants, such as a phenolic antioxidant and phosphorus antioxidant, and lubricating agents, such as a higher fatty acid amide and a higher fatty acid metal salt, as needed.

The powder is preferably dried at a temperature near Tg in advance. Moreover, when shape | molding in a pellet form, it is preferable to shape | mold while sucking the inside of an extruder using the extruder which has a vent.

It is preferable to dry the pellet which consists of cellulose esters to the temperature of Tg vicinity, and to use. In order to suppress that a polymer oxidizes and deteriorates at the time of drying, drying under nitrogen is preferable.

The cellulose esters are melt kneaded in a single screw or twin screw extruder and extruded into a sheet form from the flexible die. Usually, the temperature of an extruder is set so that resin temperature may become the range of (Tg + 100) degreeC-(Tg + 200) degreeC.

It is also possible to nitrogen seal the extruder hopper portion to suppress deterioration of the cellulose ester in the extruder, to use leaf disc filters to suppress the generation of foreign substances such as fisheye, or to use a gear pump to suppress extrusion fluctuations. You may also

It is preferable to use a die having a shape in which the tip is processed to a sharp edge (curvature radius R = 0.1 µm or less) from the viewpoint of suppressing the occurrence of viscous impurities.

The molten cellulose ester extruded from the casting die into a sheet shape is a cold casting roll which is the rotary support of the present invention, and an elastic touch roll made of metal, which is a clamping press rotating body according to the present invention, installed to be pressed against the casting roll along the circumferential direction, or By forming the nip by the endless belt, and passing the sheet-like molten cellulose ester through the nip, the cellulose ester film is sandwiched and pressed by the casting roll, the elastic touch roll or the endless belt to have a desired surface shape, thickness and optical performance. Is formed.

As an elastic touch roll of this invention, Unexamined-Japanese-Patent No. 03-124425, Unexamined-Japanese-Patent No. 08-224772, Unexamined-Japanese-Patent No. 07-100960, Unexamined-Japanese-Patent No. 10-272676, WO97-028950, Japanese patent Although the surfaces described in Japanese Patent Laid-Open No. 11-235747, Japanese Patent Laid-Open No. 2002-36332, Japanese Patent Laid-Open No. 2005-172940 or Japanese Patent Laid-Open No. 2005-280217 can be used a thin-film metal sleeve-covered silicone rubber roll, It is preferable that it is a touch roll which has elasticity.

The endless belt of the present invention is a flexible metal sleeve belt which is held by a plurality of rolls arranged in parallel with the casting roll in the circumferential direction of the casting roll, and the thickness thereof is preferably 100 to 1500 µm. .

If the thickness of the endless belt is too thin, the strength of the belt is weak and the belt may deform when the molten state cellulose ester is pressed. If the endless belt is too thick, the pressure for clamping the molten cellulose ester may be too strong and a bank may be formed.

The endless belt is preferably held by two or more rolls having a diameter of 100 to 300 mm. By holding the endless belt with the roll as described above, the molten state cellulose ester can be clamped at a stable pressure.

Moreover, it is preferable from a viewpoint of peeling failure that the surface temperature of an endless belt is 50 degreeC or more (Tg-5) degrees C or less.

In the manufacturing apparatus of the present invention, the length (air gap) until the molten state cellulose ester extruded from the lip of the flexible die contacts the elastic touch roll endless belt or the casting roll is 30 to 300 mm, preferably 70 To 200 mm.

By producing on such conditions, an unoriented and optically uniform film can be obtained. The air gap is the shortest length from the lip of the casting die until the molten state cellulose ester contacts either the endless belt or the casting roll.

For example, when the molten cellulose ester is first contacted with the endless belt, it is the shortest length from the flexible die lip to the point where the endless belt and the molten cellulose ester have started contacting.

The air gap in the case where the molten state cellulose ester is in contact with the casting roll first is similarly determined. The air gap can be determined by the size of the endless belt and casting roll, the shape of the flexible die tip, and the positional relationship of the casting roll, the endless belt and the flexible die.

In order to make an air gap 150 mm or less, it is preferable to use the casting roll of 200-400 mm (phi). It is preferable that the surface of the casting roll is mirror-finished with high smoothness.

It is preferable that the lower limit of the surface temperature of the casting roll is more than the surface temperature of an elastic touch roll or an endless belt from a viewpoint of suppressing generation | occurrence | production of a corrugation of a wave, and peeling, and is also 50 degreeC or more, and an upper limit is (Tg-5) degrees C or less. It is preferable.

Moreover, in the manufacturing method of this invention, the distance which clamps a molten state cellulose ester between a casting roll, an elastic touch roll, or an endless belt is 50-150 mm from the point of the effect of improving the appearance defects, such as a die line. Preferably it is 70-130 mm.

It is also preferable that the cellulose ester film held by pressing and cooling solidified by an elastic touch roll or an endless belt and a casting roll is further stretched at least 1.01 to 5.0 times in at least one direction. By stretching, the sharpness of the string is gentle and can be highly corrected.

Preferably, it is preferably stretched 1.1 to 3.0 times in both the longitudinal (film conveyance direction) and the transverse (width direction) directions.

As a method of extending | stretching, a well-known roll stretching machine, a tenter, etc. can be used preferably. Especially when a polarizing plate protective film is a retardation film, since lamination | stacking with a polarizing film is possible in roll form by making an extending | stretching direction into a width direction, it is preferable.

Then, it is taken out with a take-out machine, and it winds up in roll shape with a winder after slitting and removing the edge part of a film.

A protective film can also be bonded using the nip roll of a drawer. As a protective film, the film etc. which consist of a commercially available ethylene-vinyl acetate copolymer can be used, and can be bonded to one side or both sides of a cellulose ester film.

The film made of the cellulose ester obtained in the present invention may be a multilayer film. In the case of a multilayer film, it is good to have one or more layers which consist of cellulose esters.

When using the film obtained by this invention for an optical product, it is preferable that all the layers are multilayer films which consist of cellulose esters. When manufacturing a multilayer film by this invention, a multi-manifold type casting die or a feed block type casting die can be used. Since it is easy to control the thickness of each layer accurately, it is preferable to use the multi-manifold type casting die.

In addition, the measuring method of the glass transition temperature of a cellulose ester was performed using Seiko Denshi Kogyo Co., Ltd. differential scanning calorimeter DSC220 according to JISK7121.

About 10 mg of sample was set, and it heated up from room temperature to 250 degreeC at 20 degree-C / min, hold | maintained for 10 minutes under the conditions of nitrogen flow volume 50 ml / min (the 1st scan), and then to 30 degreeC at the speed of 20 degree-C / min. The temperature was lowered and maintained for 10 minutes (second scan), and the temperature was further increased to 250 ° C. at 20 ° C./min (third scan) to obtain a DSC curve. The glass transition temperature of the cellulose ester was calculated | required from the DSC curve of the obtained 3rd scan.

<Belt cleaning equipment>

It is preferable to add the apparatus which automatically cleans a belt and a roll to the manufacturing apparatus of this invention. Although there is no limitation in particular about a cleaning apparatus, For example, the method of nipping a brush roll, an absorption roll, an adhesive roll, a wiping roll, etc., the air blow system which injects clean air, the incineration apparatus by a laser, these combinations, etc. There is this.

In the case of nipping the cleaning roll, the cleaning effect is large when the belt line speed and the roller line speed are changed.

<Optical film>

The optical film which concerns on this invention can be used for a polarizing plate as a polarizing plate protective film.

<< polarizing plate >>

As for the thickness of the polarizing plate protective film which is the optical film of this invention, 10-500 micrometers is preferable. 20-150 micrometers is especially preferable, and its preferable range is 25-90 micrometers. When the polarizing plate protective film is thick, the polarizing plate after polarizing plate processing becomes too thick, and is not particularly suitable for the purpose of thin and light in liquid crystal display used in notebook computers and mobile electronic devices.

On the other hand, when a polarizing plate protective film is thin, the moisture permeability of a film will become high and the ability to protect a polarizer from humidity may fall.

When the slow axis or fast axis of a polarizing plate protective film exists in a film plane, and the angle which forms the film forming direction is (theta) 1, it is preferable to make (theta) 1 become -1 to +1 degree, Preferably it is -0.5 to +0.5 degree. . In particular, in the case of imparting a phase difference function, it is preferably from -0.1 to + 0.1 °.

This (theta) 1 can be defined as an orientation angle, and measurement of (theta) 1 can be performed using automatic birefringence system KOBRA-21ADH (made by Oji Keisukuki Co., Ltd.).

θ1 satisfying the above relationship contributes to obtaining high luminance in the display image, suppressing or preventing light leakage, and contributing to faithful color reproduction in the color liquid crystal display device.

When using the cellulose ester film which concerns on this invention as a polarizing plate protective film, the manufacturing method of a polarizing plate is not specifically limited, It can manufacture by a general method, for example, a roll to roll.

There exists a method of bonding a polarizing plate protective film to both surfaces of a polarizer using the fully saponified polyvinyl alcohol aqueous solution on both surfaces of the polarizer which alkali-processed the obtained cellulose-ester film, and immersed and stretched the polyvinyl alcohol film in the iodine solution, The polarizing plate protective film of this invention directly bonds to a polarizer on at least one surface.

The polarizing plate protective film of this invention can also be used for the other surface. Alternatively, a commercially available cellulose ester film manufactured by the solution casting method {KONICA MINOLTA TACK KC8UX2M, KC4UX, KC5UX, KC4UY, KC8UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC4CR, KC4UE, KC8UE, KC8UE, Film thicknesses such as HA, KC8UX-RHA [above, manufactured by Konica Minolta Opto Co., Ltd.], or a polyester film, a cycloolefin resin film [Zenoa Film (manufactured by Nippon Zeon), Aton Film (manufactured by JSR Corporation)] You may use the film of 150 micrometers.

Instead of the alkali treatment, the adhesive bonding described in Japanese Patent Application Laid-Open No. Hei 6-94915 and Japanese Patent Application Laid-open No. Hei 6-118232 may be performed to perform polarizing plate processing, and corona discharge treatment or plasma treatment may be performed. You may.

A polarizing plate is comprised from the polarizer and the protective film which protects both surfaces, Moreover, a protective film can be bonded to one side of the said polarizing plate, and a separate film can be bonded to the opposite side. A protective film and a separate film are used for the purpose of protecting a polarizing plate at the time of a polarizing plate shipment, a product inspection, etc.

In this case, a protective film is bonded in order to protect the surface of a polarizing plate, and is used for the opposite surface side of the surface which bonds a polarizing plate to a liquid crystal plate. In addition, a separator film is used for the purpose of covering the contact bonding layer bonded to a liquid crystal plate, and is used for the surface side which bonds a polarizing plate to a liquid crystal cell.

In addition, the polarizer which is a main component of a polarizing plate is an element which passes only the light of the polarization plane of a fixed direction, and the representative polarizer currently known is a polyvinyl alcohol-type polarizing film suitably used.

This is dyed with iodine or dichroic dye in polyvinyl alcohol-based films such as ethylene-modified polyvinyl alcohol having 1 to 4 mol% of polyvinyl alcohol or ethylene units, a polymerization degree of 2000 to 4000, and a saponification degree of 99.0 to 99.99 mol%. have.

The polarizer is preferably uniaxially stretched and dyed a polyvinyl alcohol-based film, or after uniaxially stretched after dyeing, preferably one that is subjected to durability treatment with a boron compound is preferably used.

One side of the polarizing plate protective film of this invention is bonded on the surface of the said polarizer, and a polarizing plate is formed. Preferably, it joins with the water-based adhesive agent which has fully saponified polyvinyl alcohol etc. as a main component. As film thickness of a polarizer, the thing of 5-30 micrometers is used preferably.

The manufacturing effect obtained by this invention becomes more remarkable especially in the long roll of 100 m or more, The longer it is 1500 m, 2500 m, 5000 m, and 10000 m, the more the manufacturing effect of polarizing plate manufacture is acquired.

<Liquid crystal display device>

The polarizing plate containing the optical film of this invention can express high display quality compared with a normal polarizing plate.

The polarizer of the present invention can be used in a multi-domein vertical alignment (MVA) mode, a patterned vertical alignment (PVA) mode, a continuous pinwheel alignment (CPA) mode, an optically compensated bend (OCB) mode, an IPS mode, and the like. The use of is valid.

The liquid crystal display device is also applied as a device for colorization and moving image display, and the present invention improves display quality and improves contrast and durability of the polarizing plate, thereby making it possible to faithfully display a moving image so that eyes are hardly tired.

In the liquid crystal display device which contains the polarizing plate containing retardation film at least, one polarizing plate of this invention is arrange | positioned with respect to a liquid crystal cell, or two sheets are arrange | positioned at both sides of a liquid crystal cell.

At this time, it can contribute to the improvement of display quality by using so that the optical film side of this invention contained in a polarizing plate may face the liquid crystal cell of a liquid crystal display device.

When using the polarizing plate of this invention for a liquid crystal display device, what is necessary is just to make one or more polarizing plates of the polarizing plate of a liquid crystal display device as the polarizing plate of this invention. By using the polarizing plate of this invention, display quality improves and the liquid crystal display device excellent in viewing angle characteristic can be provided.

<Example 1>

[Production of Optical Film 1-1 Containing Cellulose Ester]

As follows, the optical film 1-1 of this invention was produced by melt casting using the cellulose ester which has a substitution degree and polymerization degree shown in Table 1, and various additives.

Cellulose ester 1 92 parts by mass

Plasticizer-A 8 parts by mass

IRGANOX1010 [Shiba Japan Co., Ltd. product] 0.50 mass part

0.25 parts by mass of GSY-P101 (manufactured by Sakai Chemical Industries, Ltd.)

0.25 parts by mass of Sumilizer GS (manufactured by Sumitomo Chemical Industries, Ltd.)

TINUVIN928 [Shiba Japan Co., Ltd. product] 1.5 mass parts

The cellulose ester 1 was dried under reduced pressure at 130 degreeC for 4 hours, cooled to room temperature, and the additive was mixed. The above mixture was melt mixed at 230 ° C. using a twin screw extruder to produce pellet 1-1.

In addition, the glass transition temperature Tg of this pellet was 132 degreeC.

It melts at 250 degreeC in nitrogen atmosphere using this pellet 1-1, and after passing the filter 2 from the extruder 1, it extrudes on the 1st cooling roll 5 from the casting die 4, The film was clamped and molded between the first cooling roll 5 and the touch roll 6.

From the hopper opening of the middle part of the extruder 1, 0.2 parts by mass of silica particles, aerosil NAX50 (manufactured by Nippon Aerosil Co., Ltd.), and KE-P100 (manufactured by Nippon Shokubai Co., Ltd.) were used as lubricants. It added so that it might be 0.02 mass part.

The heat bolt was adjusted so that the width | variety of the gap of the casting die 4 might be set to 0.5 mm and 1 mm in 30 mm from the width direction edge part of the film in other places. As the touch roll, an elastic touch roll A was used, and 120 degreeC oil was made to flow inside as cooling water.

1st cooling roll 5 upstream direction of the nip of the nip of the 1st cooling roll 5 and the elastic touch roll 6 from the position P1 which resin extruded from the casting die 4 contact | connects the 1st cooling roll 5 The length L along the peripheral surface of the 1st cooling roller 5 to the position P2 of an edge part was set to 20 mm.

Then, the elastic touch roll 6 was spaced apart from the 1st cooling roll 5, and the temperature T of the melting part just before clamping by the nip of the 1st cooling roll 5 and the elastic touch roll 6 was measured. .

In the present embodiment, the temperature T of the melted portion immediately before being clamped to the nip of the first cooling roll 5 and the elastic touch roll 6 is 1 mm upstream from the nip upstream end P2. It measured by Tsu-Geki Co., Ltd. HA-200E).

In the present Example, the temperature T was 141 degreeC as a result of the measurement.

The linear pressure with respect to the 1st cooling roll 5 of the elastic touch roll 6 was 14.7 N / cm.

Further, it was introduced into the tenter, stretched at 1.35 times in the width direction at 165 ° C, then cooled to 30 ° C with 1% relaxation in the width direction, and then opened from the clip to cut off the clip grip and removed at both ends of the film. A knurling process having a width of 10 mm and a height of 5 μm was performed, and the wound cores were wound with a winding tension of 220 N / m and a taper of 40%.

Moreover, the extrusion amount and the extraction speed were adjusted so that an optical film might be set to 80 micrometers, and the optical film of the finish was slit and wound so that it might be set to 1430 mm width. The size of the winding core was 152 mm in inner diameter, 165 to 180 mm in outer diameter, and 1550 mm in length.

As this core base material, the prepreg resin in which epoxy resin was impregnated into glass fiber and carbon fiber was used. The core surface was coated with an epoxy conductive resin, the surface was polished, and the surface roughness Ra was finished to 0.3 mu m. In addition, the winding length was 2500 m. Some optical films are cut out from this film original sample of this invention, and let it be the optical film 1-1 of this invention.

[Production of Optical Film 1-2 to Optical Film 1-20]

In preparation of optical film 1-1, except having changed the kind of cellulose ester as Table 1, the optical film 1-2 of this invention, the optical film 1-10, and the comparative optical film 1-11- Optical film 1-20 was produced.

In addition, in 1-18, the butyryl group was introduced instead of the propionyl group. In addition, in 1-19 and 1-20, the cellulose ester film of Unexamined-Japanese-Patent No. 2006-348269 Example 7 and Example 14 was compared. This optical film is not extending | stretching process.

The addition amount of the cellulose ester instead of the used cellulose ester 1 was made into the mass part similar to the cellulose ester 1.

The structures of plasticizer-A, IRGANOX1010, GSY-P101, SumilizerGS, and TINUVIN928 used in Example 1 are as follows.

The change by temperature and humidity of retardation was evaluated about this sample. The results are shown in Table 1 below.

(Evaluation of retardation)

One side is cut out of the obtained optical film into the rectangle of 200 mm, and wavelength is 5 mm pitch in the environment of temperature of 23 degreeC and 55% RH of humidity using automatic birefringence system KOBRA-21-ADH (made by Oji Keisukuki Co., Ltd.). Refractive index Nx, Ny, Nz in 590 nm was calculated | required, and the retardation Ro of the film in-plane direction and the retardation Rt of the thickness direction were calculated according to the following formula.

Ro = (Nx + Ny) × d

Rt = ((Nx + Ny) / 2-Nz) × d

Here, Nx represents the refractive index in the slow axis direction in the film plane, Ny represents the refractive index in the fast axis direction in the film plane, and d represents the thickness (nm) of the film, respectively.

(Evaluation of temperature and humidity change of retardation)

Rt humidity change measures the Rt of the sample subjected to humidity control for 12 hours under the condition of 23 ° C. 20% RH, and then measures the Rt of the sample subjected to humidity control for 12 hours under the environment of 30 ° C. 80% RH, and then measures the change. The calculation evaluated the following classification.

◎: less than 5 nm change

○: less than 10 nm change

△: change less than 15 nm

×: change 15 nm or more

<Example 2>

<< production of polarizing plate >>

The long roll polyvinyl alcohol film with a thickness of 120 µm was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and stretched in the conveyance direction at 5 times at 50 ° C to form a polarizing film. Next, the cellulose ester film subjected to alkali saponification treatment on one side of the polarizing film under the following conditions was attached as a polarizing plate protective film with a fully saponified polyvinyl alcohol 5% aqueous solution as an adhesive, and similarly to the other side of the polarizing film. KC4UX manufactured by Konica Minolta Opto Co., which had been subjected to alkali saponification, was bonded to each other and dried to prepare Polarizing Plate 1-1. In the same manner, polarizing plates 1-2 to polarizing plates 1-20 were produced.

(Alkaline saponification treatment)

Saponification process 2M-NaOH 50 ℃ 90 seconds

Water washing process water 30 degrees Celsius 45 seconds

Neutralization process 10 mass% HCl 30 degrees Celsius 45 seconds

Water washing process water 30 degrees Celsius 45 seconds

After the saponification treatment, water washing, neutralization, and washing with water were performed in order, followed by drying at 80 ° C.

(Characteristic evaluation as a liquid crystal display device)

The liquid crystal panel was taken out from the liquid crystal display device (Panasonic liquid crystal television VIERA TH-26LX60 by Matsushita Denkizan Bridge Co., Ltd.) containing the liquid crystal cell of IPS mode, and the polarizing plate arrange | positioned above and below the liquid crystal cell was removed, and an Example Each polarizing plate produced in 1 was attached to both surfaces of the liquid crystal cell using an acrylic adhesive (thickness 20 µm) such that the slow axis of the polarizer was parallel to the long side of the liquid crystal cell (0 ± 0.2 degrees).

The characteristic as a polarizing plate of an optical film was evaluated. The results are shown in Table 1.

<Evaluation of Unevenness>

Images of white, black, red, green, blue, and color bars were displayed on the liquid crystal display device, and visual sensory evaluation was performed to determine whether there was a non-uniformity of pixels.

○… Does not care about unevenness.

×… There is a sense of unevenness.

This confirmed that it was excellent as a polarizing plate for image display apparatuses, such as a liquid crystal display.

Claims (3)

It is an optical film containing the cellulose-ester film whose amount of residual solvent is 0.01 mass% or less, in-plane retardation Ro is 0 <= <= <= 10nm, and retardation (Rth) of thickness direction is -20 <= Rth <= 20nm. And a type of substituent per 1 glucose unit of the cellulose ester contained in the cellulose ester film and a degree of substitution thereof are cellulose esters satisfying the conditions of the following Equations 1 to 3 simultaneously. <Equation 1> 6.7≤2 × X + 3 × Y≤7.4 <Equation 2> 2.86≤X + Y≤3.00 <Equation 3> 1.0≤Y≤1.4 In the formula, X represents the degree of substitution of the acetyl group, and Y represents the degree of substitution of the propionyl group. A polarizing plate having a structure in which both surfaces of a polarizer are sandwiched between two polarizing plate protective films, wherein at least one of the polarizing plate protective films is the optical film according to claim 1. The polarizing plate of Claim 2 is used for at least one surface of a liquid crystal cell, The liquid crystal display device characterized by the above-mentioned.

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