JP2010122445A - Twist nematic liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively provide a liquid crystal display device by which problems of the inversion of a half tone, black crush and a color shift at a visual angle needed for practical performance are solved and front contrast is also enhanced. <P>SOLUTION: In the twist nematic liquid crystal display device, each of first and second retardation films 7 and 19 contains a thermoplastic resin and has 5 to 35 nm Ro in a formula (i), 70 to 150 nm Rth in a formula (ii) and a 10 to 50 μm film thickness. A scattering film 5 formed by dispersing a scattering body in a transparent resin is provided at a viewer side of a first polarizer 6, the scattering body comprises particles having a 5 to 30 μm volume average particle diameter, and the scattering film has a 20 to 120 μm thickness. The scattering film contains a 5 to 50 pts.mass scattering body to a 100 pts.mass scattering film and has a thickness 2.0 times as thick as the particle diameter and a difference between refractive indices of the scattering body and the transparent resin is 0.01 or larger, and the formula (i) is Ro=(nx-ny)×d, formula (ii) Rth=((nx+ny)/2-nz)×d. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a twisted nematic type liquid crystal display device, and in particular, the performance relating to the visibility such as halftone inversion, blackout, and color shift, and the vertical viewing angle which is a particular problem in the TN type liquid crystal display device are greatly improved. The present invention relates to a twisted nematic type liquid crystal display device excellent in front contrast.

Twist nematics (hereinafter referred to as optical rotation mode) are used for notebook PCs and desktop monitors because low power consumption, thinning, and price reduction are more important than video performance and ultra-wide viewing angle characteristics like LCD TVs. Many devices adopt the type drive system.
However, since the viewing angle is very narrow as it is with the TN type driving system, it is necessary to enlarge the viewing angle, and a retardation film coated, oriented and polymerized as shown in Patent Document 1 is used. ing. In recent years, the response speed of the TN system has also increased, and since it has been adopted in some liquid crystal TVs, there is an increasing demand for viewing angle expansion.
However, in the TN type display device using the retardation film, the contrast viewing angle indicated by the light quantity ratio of white and black is widened, but the halftone inversion, blackout, or color shift, which are important for practical performance, are large. In addition to remaining problems, there is a problem that light leakage occurs around the screen in black display, which is called frame unevenness. In addition, since it is a retardation film coated with a discotic liquid crystal, it is difficult to manufacture, and there is a problem in that the manufacturing cost increases. The problem of performance related to visibility is that the liquid crystal component in the TN cell has both tilt and twist, so there is a limit that can be compensated by the optical compensation sheet, and the improvement of the viewing angle in the vertical direction is not sufficient. It was a typical issue.

On the other hand, Patent Document 2 describes a technique for providing a diffusion film containing fine particles having an average particle diameter of about 0.1 to 3 μm and exhibiting different scattering abilities depending on the wavelength in order to correct a gradation change depending on a viewing angle. However, according to this technology, light having a short wavelength such as blue light is diffused by the diffusion film even if it is light from the front. There was a problem that the image was poor in contrast.
JP 2002-156527 A JP 2007-188618 A

  Accordingly, an object of the present invention is to provide a low-cost TN liquid crystal display device that solves halftone inversion and blackout due to viewing angles required for practical performance, has a wide viewing angle, and has high front contrast. is there.

The above-described object of the present invention can be achieved by the following configuration.
1. Twisted nematic liquid crystal cell, first polarizer provided on the viewing side of the liquid crystal cell, twisted nematic liquid crystal display having a second polarizer and a backlight unit provided on the backlight side of the liquid crystal cell In the device
A first retardation film and a second retardation film are provided between the liquid crystal cell and the first polarizer and between the liquid crystal cell and the second polarizer, respectively.
Each of the first retardation film and the second retardation film contains a thermoplastic resin, and Ro represented by the following formula (i) is in the range of 5 to 35 nm, and the following formula (ii) The Rth represented is in the range of 70 to 150 nm, and the film thickness is in the range of 10 to 50 μm.
On the viewing side of the first polarizer, a scattering film in which scatterers are dispersed in a transparent resin is provided,
The scatterer is a particle having a volume average particle diameter of 5 to 30 μm,
The scattering film has a thickness of 20 to 120 μm,
The scattering film contains 5 to 50 parts by mass of the scatterer with respect to 100 parts by mass of the scattering film,
The thickness of the scattering film is at least 2.0 times the particle size,
A twisted nematic liquid crystal display device, wherein the difference in refractive index between the scatterer and the transparent resin is 0.01 or more.
(I) Ro = (nx−ny) × d
(Ii) Rth = ((nx + ny) / 2−nz) × d
Where nx is the maximum refractive index in the plane, ny is the refractive index in the direction perpendicular to nx in the plane, nz is the refractive index in the film thickness direction, each refractive index is a value for light having a wavelength of 590 nm, and d is Represents the film thickness (nm).

  2. The first retardation film is provided adjacent to the first polarizer, contains a cellulose ester resin, and serves also as a protective film on the liquid crystal cell side of the first polarizer. The liquid crystal display device according to 1 above.

  3. The second retardation film is provided adjacent to the second polarizer, contains a cellulose ester resin, and serves also as a protective film on the liquid crystal cell side of the second polarizer. 3. The liquid crystal display device according to item 1 or 2.

4). 4. The polarizing plate-integrated retardation film according to the above item 2 or 3, wherein the cellulose ester satisfies the following formula when the acetyl group substitution degree is X and the propionyl group substitution degree is Y. A liquid crystal display device.
(Iii) 2.0 ≦ (X + Y) ≦ 2.6
(Iv) 0.1 ≦ Y ≦ 1.2

  5. The retardation film is a film obtained by stretching 1.05 to 1.3 times in the transport direction or the direction orthogonal to the transport direction, and the in-plane slow axis is substantially perpendicular to the transport direction. 5. The liquid crystal display device according to any one of items 1 to 4, wherein:

  6). The scattering film is provided adjacent to the viewing side of the first polarizer, and serves also as a protective film on the viewing side of the first polarizer. The liquid crystal display device described.

  7). 7. The liquid crystal display device according to any one of 1 to 6, wherein the scatterer has a volume average particle diameter of 5 to 15 μm.

  8). The liquid crystal display device according to any one of 1 to 7, wherein the scattering film contains 5 to 30 parts by mass of the scatterer with respect to 100 parts by mass of the scattering film.

  9. 9. The liquid crystal display device according to any one of 1 to 8, wherein the scattering film has a thickness of 30 to 90 μm.

  10. 10. The liquid crystal display device according to any one of items 1 to 9, wherein in the scattering film, a difference in refractive index between the transparent resin and the scatterer is 0.01 or more.

The present invention combines retardation film and surface-side scattering to suppress halftone inversion, suppress blackout, suppress color shift, increase viewing angle, and increase front contrast, which are practical performances of a TN liquid crystal display device. To achieve.
As a result of the study by the present inventors, the thickness obtained by dispersing scatterer particles having a volume average particle diameter of 5 to 30 μm in a transparent resin is 20 to 120 μm, and the film thickness is 2.0 times or more that of the scatterer particles. By using a scattering film, by giving a sufficient scattering effect to light in all wavelength regions, it is possible to scatter light with excellent gradation incident on the liquid crystal cell in a wide range to a certain extent. It became possible to enlarge the viewing angle.
However, in the TN liquid crystal display device, particularly when light is incident on the liquid crystal cell from an oblique direction, light that should be blocked leaks from the polarizing plate on the viewing side, and the light is scattered to the front. As a result, it became clear that the front contrast of the liquid crystal display device was greatly reduced. In addition, in the TN liquid crystal display device, in particular, the light incident on the liquid crystal cell from obliquely in the vertical direction is diffused by the scattering film, so that the contrast in the oblique direction is lowered and the viewing angle characteristic in the vertical direction is also deteriorated. It became clear.

Therefore, as a result of further studies, Ro represented by the above formula (i) is in the range of 5 to 35 nm, Rth represented by the above formula (ii) is in the range of 70 to 150 nm, and the film thickness is 10 It has been found that when a retardation film having a thickness of ˜50 μm is provided on both surfaces of a liquid crystal cell, the front contrast can be remarkably improved and halftone inversion, blackout, and color shift can be suppressed.
Such a retardation film is weaker than the retardation film using the discotic liquid crystal described in Patent Document 1 described above as an optical compensation function for the liquid crystal cell. By compensating for part of the phase difference given to the light incident from the oblique direction and suppressing the light leakage in the oblique direction to some extent, the light emitted obliquely from the display device surface is incident on the liquid crystal cell from the front. It is presumed that the viewing angle characteristics in the vertical direction are improved as a result of an increase in the proportion of light components scattered by the diffusion film. In addition, it is presumed that the light leakage in the vertical and oblique directions, which was a problem in particular, was suppressed, so that the scattering in the front direction was reduced and the front contrast was improved at the same time.

  According to the present invention, it is possible to provide a TN liquid crystal display device in which halftone inversion, blackout, and color shift are suppressed, the viewing angle is wide, and the front contrast is greatly improved without increasing the cost. Can do. Further, the effect of the present invention can greatly suppress the frame unevenness seen in the TN type liquid crystal surface device.

The present invention is described in further detail below.
(Retardation film)
The retardation film used in the present invention contains a thermoplastic resin, the retardation value Ro is 5 to 35 nm or less, the retardation value Rt is 70 to 150 nm or less, and the film thickness is 10 to 50 μm. It is a certain resin film.
The 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 using KOBRA-21ADH (Oji Scientific Instruments) under an environment of 23 ° C. and 55% RH.
Further, the in-plane maximum refractive index of the retardation film used in the present invention is substantially parallel to or substantially orthogonal to the film transport direction, both of which are directions perpendicular to the film transport direction ± 1 ° or the film transport direction. It is preferable to be within ± 1 °.
Moreover, it is a preferable structure that the retardation film used in the present invention also serves as a protective film on the liquid crystal cell side of the polarizer by being provided adjacent to the liquid crystal cell side of the polarizer.
The retardation film used in the present invention preferably has a light transmittance (of visible light) of 90% or more, more preferably 94% or more, and more preferably 95% or more even after saponification treatment. The haze is preferably less than 1.4%, more preferably less than 1.0%, and further preferably less than 0.5%. In particular, 0% is most preferable.

(Thermoplastic resin)
Preferred examples of the thermoplastic resin constituting the retardation film used on both sides of the liquid crystal cell in the present invention include cellulose esters, polycarbonates, acrylic resins, cycloolefin polymers, polyesters, and the like. is not.
Among these resins, the polarizing plate-integrated retardation film of the present invention preferably contains a cellulose ester, and is preferably a cellulose ester film (hereinafter, the retardation film used in the present invention is referred to as the retardation film of the present invention). Sometimes referred to as cellulose ester film).

Hereinafter, the cellulose ester used in the present invention will be described.
The cellulose ester film constituting the retardation film preferably uses a lower fatty acid ester of cellulose. The lower fatty acid in the lower fatty acid ester of cellulose means a fatty acid having 6 or less carbon atoms. For example, cellulose acetate, cellulose propionate, cellulose butyrate and the like are preferable as the lower fatty acid ester of cellulose. In addition, mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate can be used. The most preferable lower fatty acid ester of cellulose has an acyl group having 2 to 4 carbon atoms as a substituent, and preferably satisfies the following formula when the substitution degree of acetyl group is X and the substitution degree of propionyl group is Y.
(Iii) 2.0 ≦ (X + Y) ≦ 2.6
(Iv) 0.1 ≦ Y ≦ 1.2
The portion that is not substituted with an acyl group usually exists as a hydroxyl group. These can be synthesized by known methods.
These acyl group substitution degrees can be measured according to the method prescribed in ASTM-D817-96.

The molecular weight of the cellulose ester used in the present invention is preferably a number average molecular weight (Mn) of 80,000 to 200,000. More preferred are 100,000 to 200,000, particularly preferably 150,000 to 200,000.
In the cellulose ester used in the present invention, the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), Mw / Mn is preferably 1.4 to 3.0 as described above, and more preferably 1.7. It is the range of -2.2.
The average molecular weight and molecular weight distribution of the cellulose ester can be measured by a known method using high performance liquid chromatography. Using this, the number average molecular weight and the weight average molecular weight can be calculated, and the ratio (Mw / Mn) can be calculated.

The measurement conditions are as follows.
Solvent: Methylene chloride column: Shodex K806, K805, K803G (used by connecting 3 products manufactured by Showa Denko KK)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 100000-500 calibration curves with 13 samples were used. It is preferable to obtain 13 samples at approximately equal intervals.

As the cellulose ester, cellulose ester synthesized from cotton linter, wood pulp, kenaf or the like as a raw material can be used alone or in combination. In particular, it is preferable to use a cotton linter (hereinafter sometimes simply referred to as a linter) or a cellulose ester synthesized from wood pulp alone or in combination.
Moreover, the cellulose ester obtained from these can be mixed and used in arbitrary ratios, respectively. These cellulose esters are prepared by using an organic acid such as acetic acid or an organic solvent such as methylene chloride when sulfuric acid is used as the acylating agent (acetic anhydride, propionic anhydride, butyric anhydride). It can obtain by making it react by a conventional method using a protic catalyst like.
In the case of acetylcellulose, it is necessary to extend the time for the acetylation reaction in order to increase the acetylation rate. However, if the reaction time is too long, the decomposition proceeds at the same time, and the polymer chain is broken and the acetyl group is decomposed, resulting in undesirable results. Therefore, it is necessary to set the reaction time within a certain range in order to increase the degree of acetylation and suppress decomposition to some extent. It is not appropriate to define the reaction time because the reaction conditions are various and greatly change depending on the reaction apparatus, equipment and other conditions. As the decomposition of the polymer progresses, the molecular weight distribution becomes wider. Therefore, in the case of cellulose ester, the degree of decomposition can be defined by the value of weight average molecular weight (Mw) / number average molecular weight (Mn) that is usually used. That is, in the process of acetylation of cellulose triacetate, the weight average molecular weight is used as one index of the reaction degree for allowing the acetylation reaction to be carried out for a sufficient time for acetylation without being too long and being decomposed too much. The value of (Mw) / number average molecular weight (Mn) can be used.

An example of a method for producing a cellulose ester is shown below: 100 parts by mass of a flocculent linter was crushed as a cellulose raw material, 40 parts by mass of acetic acid was added, and pretreatment activation was performed at 36 ° C. for 20 minutes. Thereafter, 8 parts by mass of sulfuric acid, 260 parts by mass of acetic anhydride and 350 parts by mass of acetic acid were added, and esterification was performed at 36 ° C. for 120 minutes. After neutralization with 11 parts by mass of a 24% magnesium acetate aqueous solution, saponification aging was carried out at 63 ° C. for 35 minutes to obtain acetylcellulose. This was stirred for 160 minutes at room temperature using a 10-fold acetic acid aqueous solution (acetic acid: water = 1: 1 (mass ratio)), then filtered and dried to obtain purified acetylcellulose having an acetyl substitution degree of 2.75. . This acetylcellulose had Mn of 92000, Mw of 156000, and Mw / Mn of 1.7. Similarly, cellulose esters having different degrees of substitution and Mw / Mn ratios can be synthesized by adjusting the esterification conditions (temperature, time, stirring) and hydrolysis conditions of the cellulose ester.
The synthesized cellulose ester is preferably purified to remove low molecular weight components or to remove unacetylated or low acetylated components by filtration.
In the case of mixed acid cellulose ester, it can be obtained by the method described in JP-A-10-45804. The measuring method of the substitution degree of an acyl group can be measured according to the provisions of ASTM-D817-96.

Cellulose esters are also affected by trace metal components in cellulose esters. These are considered to be related to water used in the production process, but it is preferable that there are few components that can become insoluble nuclei, and metal ions such as iron, calcium, and magnesium contain organic acidic groups. Insoluble matter may be formed by salt formation with a polymer degradation product or the like that may be present, and it is preferable that the amount is small. The iron (Fe) component is preferably 1 ppm or less. About calcium (Ca) component, it is contained in a lot of ground water and river water, etc., and it becomes hard water, and it is unsuitable as drinking water. Coordination compounds with ligands, that is, complexes are easily formed, and scum (insoluble starch, turbidity) derived from many insoluble calcium is formed.
The calcium (Ca) component is 60 ppm or less, preferably 0 to 30 ppm. The magnesium (Mg) component is preferably in the range of 0 to 70 ppm, particularly preferably 0 to 20 ppm, since too much will cause insoluble matter. Metal components such as iron (Fe) content, calcium (Ca) content, magnesium (Mg) content, etc. are pre-processed by completely digesting cellulose ester with micro digest wet cracking equipment (sulfuric acid decomposition) and alkali melting. After performing, it can obtain | require by performing an analysis using ICP-AES (inductively coupled plasma emission spectroscopy analyzer).

<Plasticizer>
The plasticizer is not particularly limited, but preferably at least a plasticizer selected from a polyhydric alcohol ester plasticizer, a phthalate ester, a citrate ester, a fatty acid ester, a glycolate plasticizer, a polycarboxylic acid ester, and the like. It is preferable to include 1 type. Of these, at least one is preferably a polyhydric alcohol ester plasticizer.
The polyhydric alcohol ester plasticizer is a plasticizer comprising an ester of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule. Preferably it is a 2-20 valent aliphatic polyhydric alcohol ester.
The polyhydric alcohol used in the present invention is represented by the following general formula (1).
Formula (1) R1- (OH) n
However, R1 represents an n-valent organic group, n represents a positive integer of 2 or more, and the OH group represents an alcoholic and / or phenolic hydroxyl group.

  Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these. Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane- Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, and xylitol. In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

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

Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.
As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-10. When acetic acid is contained, the compatibility with the cellulose ester is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.
Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanoic acid, undecylic acid, lauric acid, tridecylic acid, Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, laccelic acid, undecylenic acid, olein Examples thereof include unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.
Examples of preferable alicyclic monocarboxylic acids include cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, and derivatives thereof.
Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenylcarboxylic acid, naphthalenecarboxylic acid, and tetralincarboxylic acid. The aromatic monocarboxylic acid which has, or those derivatives can be mentioned. Benzoic acid is particularly preferable.

The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably 300 to 1500, and more preferably 350 to 750. A higher molecular weight is 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 carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

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

  The glycolate plasticizer is not particularly limited, but alkylphthalylalkyl glycolates can be preferably used. Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl Glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl glycol Butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl phthalate Ethyl glycolate, and the like.

Examples of the phthalate ester plasticizer include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, and dicyclohexyl terephthalate.
Examples of the citrate plasticizer include acetyl trimethyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate.
Examples of fatty acid ester plasticizers include butyl oleate, methylacetyl ricinoleate, and dibutyl sebacate.
Polycarboxylic acid ester plasticizers can also be preferably used. Specifically, it is preferable to add the polyvalent carboxylic acid ester described in paragraphs [0015] to [0020] of JP-A No. 2002-265639 as one of the plasticizers.
Examples of the phosphate ester plasticizer include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate and the like.

The polyester plasticizer is not particularly limited, but a polyester plasticizer having an aromatic ring or a cycloalkyl ring in the molecule can be preferably used. Although it does not specifically limit as a preferable polyester plasticizer, For example, the aromatic terminal ester plasticizer represented by following General formula (2) is preferable.
General formula (2) B- (GA) n-GB
(In the formula, B is a benzene monocarboxylic 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 (2), a benzene monocarboxylic acid residue represented by B and an alkylene glycol residue, oxyalkylene glycol residue or aryl glycol residue represented by G, an alkylene dicarboxylic acid residue or aryl dicarboxylic group represented by A It is composed of an acid residue and can be obtained by a reaction similar to that of a normal polyester plasticizer.

Examples of the benzene monocarboxylic acid component of the polyester plasticizer used in the present invention include benzoic acid, para-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, and normalpropyl. There exist benzoic acid, aminobenzoic acid, acetoxybenzoic acid, etc., and these can be used as 1 type, or 2 or more types of mixtures, respectively.
Examples of the alkylene glycol component having 2 to 12 carbon atoms of the polyester plasticizer include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1, 2-propanediol, 2-methyl 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2 -Diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3propanediol (3,3-dimethylolheptane), 3-methyl-1, 5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl 1,3-pentanediol, 2-ethyl 1, -Hexanediol, 2-methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, etc., and these glycols are one kind or two kinds or more Used as a mixture. In particular, an alkylene glycol having 2 to 12 carbon atoms is particularly preferable because of excellent compatibility with a cellulose ester.

Examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the aromatic terminal ester include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. Or it can be used as a mixture of two or more.
Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the aromatic terminal ester include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. These are used as one kind or a mixture of two or more kinds. 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 polyester plasticizer that can be used in the present invention has a number average molecular weight of preferably 300 to 1500, more preferably 400 to 1000. The acid value is preferably 0.5 mgKOH / g or less, the hydroxyl value is 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxyl value is 15 mgKOH / g or less.

Hereinafter, synthesis examples of the aromatic terminal ester plasticizer will be shown.
<Sample No. 1 (Aromatic terminal ester sample)>
A reaction vessel was charged with 410 parts of phthalic acid, 610 parts of benzoic acid, 737 parts of dipropylene glycol, and 0.40 part of tetraisopropyl titanate as a catalyst. While refluxing the monohydric alcohol, heating was continued at 130 to 250 ° C. until the acid value became 2 or less, and water produced was continuously removed. Subsequently, the distillate was removed at 200 to 230 ° C. under a reduced pressure of 100 to finally 4 × 10 2 Pa or less, followed by filtration to obtain an aromatic terminal ester plasticizer having the following properties.
Viscosity (25 ° C., mPa · s); 43400
Acid value: 0.2

<Sample No. 2 (Aromatic terminal ester sample)>
Sample No. 1 was used except that 410 parts of phthalic acid, 610 parts of benzoic acid, 341 parts of ethylene glycol, and 0.35 part of tetraisopropyl titanate as a catalyst were used in the reaction vessel. In the same manner as in No. 1, an aromatic terminal ester having the following properties was obtained.
Viscosity (25 ° C., mPa · s); 31000
Acid value: 0.1

<Sample No. 3 (Aromatic terminal ester sample)>
Sample No. 1 was used except that 410 parts of phthalic acid, 610 parts of benzoic acid, 418 parts of 1,2-propanediol, and 0.35 part of tetraisopropyl titanate as the catalyst were used in the reaction vessel. In the same manner as in No. 1, an aromatic terminal ester having the following properties was obtained.
Viscosity (25 ° C., mPa · s); 38000
Acid value: 0.05

<Sample No. 4 (Aromatic terminal ester sample)>
Sample No. 4 was used except that 410 parts of phthalic acid, 610 parts of benzoic acid, 418 parts of 1,3-propanediol, and 0.35 part of tetraisopropyl titanate as a catalyst were used in the reaction vessel. In the same manner as in No. 1, an aromatic terminal ester having the following properties was obtained.
Viscosity (25 ° C., mPa · s); 37000
Acid value: 0.05

Although the specific compound of an aromatic terminal ester plasticizer is shown below, this invention is not limited to this.

The total content of the plasticizer in the cellulose ester film is preferably 5 to 30% by mass with respect to the total solid content. Furthermore, 5-20 mass% is preferable, 6-16 mass% is more preferable, Especially preferably, it is 8-13 mass%. The contents of the two kinds of plasticizers are each at least 1% by mass, preferably 2% by mass or more.
The polyhydric alcohol ester plasticizer is preferably contained in an amount of 1 to 12% by mass, particularly preferably 3 to 11% by mass. If the amount is too small, deterioration of flatness is recognized, and if it is too much, bleeding out tends to occur. The mass ratio between the polyhydric alcohol ester plasticizer and the other plasticizer is preferably in the range of 1: 4 to 4: 1, more preferably 1: 3 to 3: 1. If the amount of the plasticizer added is too large or too small, the film is liable to be deformed, which is not preferable.

<Ultraviolet absorber>
The retardation film according to the present invention may contain an ultraviolet absorber. The ultraviolet absorber is intended to improve durability by absorbing ultraviolet rays of 400 nm or less, and is particularly preferably added so that the transmittance at a wavelength of 370 nm is 10% or less. Is 5% or less, more preferably 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.
Furthermore, ultraviolet absorbers preferably used in the present invention include benzophenone ultraviolet absorbers and triazine ultraviolet absorbers.

<Fine particles>
The retardation film of the present invention preferably contains fine particles.
The fine particles used in the present invention include, as examples of inorganic compounds, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, tin oxide, indium oxide, zinc oxide, ITO, antimony oxide. Alternatively, these composite oxides, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate can be mentioned. Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable.
The average primary particle diameter of the fine particles is preferably 5 nm to 1 μm, and more preferably 5 to 50 nm. These are mainly contained as primary particles or secondary aggregates having a particle size of 0.05 to 1 μm, preferably 0.05 to 0.3 μm. The content of these fine particles in the retardation film is preferably 0.05 to 10% by mass, particularly preferably 0.1 to 1% by mass.

Silicon dioxide fine particles are commercially available, for example, under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (manufactured by Nippon Aerosil Co., Ltd.). I can do it.
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, cross-linked acrylic resin, and cross-linked polystyrene resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.) It is marketed by name and can be used.
Among these, Aerosil 200V and Aerosil R972V are particularly preferably used because they have a large effect of reducing the friction coefficient while keeping the turbidity of the retardation film low.

<dye>
A dye may be added to the retardation film of the present invention for color adjustment. For example, a blue dye may be added to suppress the yellowness of the film. Preferred examples of the dye include anthraquinone dyes.
The anthraquinone dye may have an arbitrary substituent at an arbitrary position from the 1st position to the 8th position of the anthraquinone. Preferred substituents include an anilino group, hydroxyl group, amino group, nitro group, or hydrogen atom. In particular, it is preferable to contain a blue dye described in paragraphs [0034] to [0037] of JP-A No. 2001-154017, particularly an anthraquinone dye. Further, it preferably contains an infrared absorbing dye, and in particular, any one of thiopyrylium squarylium dye, thiopyrylium croconium dye, pyrylium squarylium dye, and pyrylium croconium dye disclosed in JP-A-2001-154017. It is preferable that Specifically, an infrared absorbing dye represented by the general formula (1) or general formula (2) of the publication can be preferably added.

Various additives can be used in the present invention.
For example, it is useful to contain an antioxidant, and the type of antioxidant to be contained is not particularly limited, and various kinds of antioxidants can be used. For example, hindered phenol compounds, phosphite compounds can be used. Examples thereof include antioxidants such as compounds and thioether compounds. Among these, an antioxidant of a hindered phenol compound is preferable in terms of transparency. Content of antioxidant is 0.01-2 mass% normally with respect to polyester, Preferably it is 0.1-0.5 mass%.
In addition, anti-coloring agents, crystal nucleating agents, slip agents, stabilizers, anti-blocking agents, peeling aids, fluorescent whitening agents, viscosity modifiers, antifoaming agents, clearing agents, antistatic agents, pH adjusting agents, etc. You may let them.

Various additives may be batch-added to a dope that is a cellulose ester-containing solution before film formation, or an additive solution may be separately prepared and added in-line. In particular, it is preferable to add a part or all of the fine particles in-line in order to reduce the load on the filter medium.
When the additive solution is added in-line, it is preferable to dissolve a small amount of cellulose ester in order to improve mixing with the dope. The amount of the cellulose ester is preferably 1 to 10 parts by mass, more preferably 3 to 5 parts by mass with respect to 100 parts by mass of the solvent.
In order to perform in-line addition and mixing in the present invention, for example, an in-line mixer such as a static mixer (manufactured by Toray Engineering), SWJ (Toray static type in-tube mixer Hi-Mixer) or the like is preferably used.

<Method for producing retardation film>
Next, the method for producing the retardation film of the present invention will be described by taking cellulose ester as an example of the thermoplastic resin.
The production of the retardation film of the present invention includes the steps of preparing a dope by dissolving a cellulose ester and an additive in a solvent, the step of casting the dope on a belt-like or drum-like metal support, and the cast dope. It is carried out by a step of drying as a web, a step of peeling from a metal support, a step of stretching or maintaining the width, a step of further drying, and a step of winding up the finished film.

The process for preparing the dope will be described. 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 increases. Becomes worse. As a density | concentration which makes these compatible, 10-35 mass% is preferable, More preferably, it is 15-25 mass%.
The solvent used in the dope of the present invention may be used alone or in combination of two or more. However, it is preferable from the viewpoint of production efficiency that a good solvent and a poor solvent of cellulose ester are mixed and used. The more solvent is preferable from the viewpoint of solubility of the cellulose ester. The 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, depending on the acyl group substitution degree of the cellulose ester, the good solvent and the poor solvent change. For example, when acetone is used as the solvent, the cellulose ester acetate ester (acetyl group substitution degree 2.4) and cellulose acetate propionate are good. As a solvent, cellulose acetate (acetyl group substitution degree 2.8) is a poor solvent.
Although the good solvent used for this invention is not specifically limited, Organic halogen compounds, such as a methylene chloride, dioxolanes, acetone, methyl acetate, methyl acetoacetate, etc. are mentioned. Particularly preferred is methylene chloride or methyl acetate.
Moreover, although the poor solvent used for this invention is not specifically limited, For example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone, etc. are used preferably. Moreover, it is preferable that 0.01-2 mass% of water contains in dope.

A general method can be used as a method of dissolving the cellulose ester when preparing the dope described above. 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 equal to or 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 generation of massive undissolved materials called gels and mamacos. Moreover, after mixing a cellulose ester with a poor solvent and making it wet or swell, the method of adding a good solvent and melt | dissolving is also used preferably.
The 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 a 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. A preferable 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.
Alternatively, a cooling dissolution method is also preferably used, whereby the cellulose ester can be dissolved in a solvent such as methyl acetate.

Next, this cellulose ester solution is filtered using a suitable 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 substance is when two polarizing plates are placed in a crossed Nicol state, a cellulose ester film is placed between them, light is applied from the side of one polarizing plate, and observed from the side of the other polarizing plate. It is a point (foreign matter) where light from the opposite side appears to leak, and the number of bright spots having a diameter of 0.01 mm or more is preferably 200 / cm ² or less. More preferably, it is 100 pieces / cm < ² > or less, More preferably, it is 50 pieces / m < ² > or less, More preferably, it is 0-10 pieces / cm < ² > or less. Further, it is preferable that the number of bright spots of 0.01 mm or less is small.

The dope can be filtered by an ordinary 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. A 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 preferred. 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.

Here, the dope casting will be described.
The metal support in the casting (casting) step preferably has a mirror-finished surface, and a stainless steel belt or a drum whose surface is plated with a casting is preferably used as the metal support. The cast width can be 1 to 4 m. The surface temperature of the metal support in the casting step is set to −50 ° C. to a temperature at which the solvent boils and does not foam. A higher temperature is preferable because the web can be dried faster, but if it is too high, the web may foam or flatness may deteriorate. The preferable support temperature is appropriately determined at 0 to 100 ° C, and more preferably 5 to 30 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent. The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing 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 using warm air, considering the temperature drop of the web due to the latent heat of vaporization of the solvent, while using warm air above the boiling point of the solvent, there may be cases where wind at a temperature higher than the target temperature is used while preventing foaming. . In particular, it is preferable to perform drying efficiently by changing the temperature of the support and the temperature of the drying air during the period from casting to peeling.

  In order for the cellulose ester film to exhibit good flatness, the residual solvent amount 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. Especially preferably, it is 20-30 mass% or 70-120 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.
The poor solvent ratio in the residual solvent can be measured by the following measuring method.
(Poor solvent amount in residual solvent amount)
The residual solvent is collected from the sample containing the residual solvent, and each solvent is quantified by gas chromatography measurement.
Ratio of poor solvent in residual solvent (%) = {content of poor solvent (g) / total amount of residual solvent (g)} × 100

The amount of residual solvent can be measured for each type of solvent by the method described below.
A film of a certain area is cut out, finely cut to about 5 mm, stored in a dedicated vial, sealed with a septum and an aluminum cap, and then set in a head space sampler HP7694 manufactured by Hewlett-Packard. Gas chromatography (GC) connected to a headspace sampler uses a 5971 model manufactured by Hewlett-Packard Co. equipped with a flame ionization detector (FID) as a detector. The measurement conditions are as follows.
Headspace sampler heating conditions: 120 ° C, 20 minutes GC introduction temperature 150 ° C
Column: DB-624 manufactured by J & W
Temperature rise: 45 ° C, hold for 3 minutes → 100 ° C (8 ° C / min)
A gas chromatogram is obtained using the above measurement conditions. After storing a certain amount of each solvent to be measured diluted with butanol in a vial, each solvent using a calibration curve prepared using the peak area of the chromatogram obtained by measurement in the same manner as above. The amount of residual solvent in the film was obtained, and the poor solvent ratio in the residual solvent was determined from the above formula.
Specifically, the ratio of a good solvent such as methylene chloride or methyl acetate and a poor solvent such as an alcohol having 1 to 4 carbon atoms can be obtained and used as the poor solvent ratio in the residual solvent.
Ratio of poor solvent in residual solvent (%) = {content of poor solvent (C1-C4 alcohol (g)) / total residual solvent amount (C1-C4 alcohol + methylene chloride or methyl acetate (g)] } × 100

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, Especially preferably, it is 0-0.01 mass% or less.
In the film drying process, generally, a roll drying method (a method in which a plurality of rolls arranged on the upper and lower sides are alternately passed through and dried) or a method of drying while transporting the web by a tenter method is adopted.

In order to produce the cellulose ester film for the retardation film of the present invention, it is preferable to stretch 1.05 to 1.3 times in the direction orthogonal to the transport direction after peeling from the metal support.
In that case, you may extend | stretch also to a conveyance direction (it is also called MD direction) simultaneously or sequentially. In that case, it is preferable to extend | stretch by peeling tension and subsequent conveyance tension immediately after peeling. For example, it is preferable to peel at a peeling tension of 210 N / m or more, and particularly preferably 220 to 300 N / m.
The temperature during stretching is effective when the temperature of the film is in the range of a glass transition point of −30 to + 20 ° C., preferably 100 to 160 ° C.

In the tenter process, the heat transfer coefficient may be constant or changed. The heat transfer coefficient preferably has a heat transfer coefficient in the range of 41.9 to 419 × 10 ³ J / m ² hr. More preferably, in the range of ^{41.9~209.5 × 10 3 J / m 2} hr, and most preferably a range of ^{41.9~126 × 10 3 J / m 2} hr.
The stretching speed in the width direction may be constant or may be changed. The stretching speed is preferably 50 to 500% / min, more preferably 100 to 400% / min, and most preferably 200 to 300% / min.

It is preferable to provide a post-drying step (hereinafter, step D1) after the treatment in the tenter step. 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 it is preferably performed with hot air in terms of simplicity.
The drying temperature in the web drying step is preferably increased stepwise from 30 to 150 ° C, and more preferably from 50 to 140 ° C in order to improve dimensional stability.
In order to obtain the effects of the present invention, the thickness of the retardation film needs to be in the range of 10 to 50 μm, and preferably in the range of 20 to 40 μm.
In the present invention, a retardation film having a multilayer structure by a co-casting method may be used as long as the film thickness is within the above range. When the retardation film has a multilayer structure, the plasticizer, ultraviolet absorber and other additives can be appropriately blended in the base layer, the surface layer, or both.
The variation of the film thickness of the retardation film is preferably within ± 3% in both the width direction and the longitudinal direction, more preferably within ± 2%, and particularly preferably within ± 0.5%.
The retardation film of the present invention preferably has a width of 1 to 4 m. Preferably it is 1.4-4m, More preferably, it is the range of 1.5-3m.

<Other physical properties>
The water vapor permeability of the retardation film of the present invention is 1200 g / m ² · 24 h or less at 40 ° C. and 90% RH, preferably 20 to 1000 g / m ² · 24 h, and 20 to 900 g / m ² · 24 h. It is particularly preferred. The moisture permeability can be measured according to the method described in JIS Z 0208.
(Haze value)
According to JIS K-6714, it can be measured using a haze meter (1001DP type, manufactured by Nippon Denshoku Industries Co., Ltd.) and used as an index of transparency.
(Measurement of transmittance)
The transmittance T is 380, 400, 500 nm from the spectral transmittance τ (λ) obtained every 10 nm in the wavelength region of 350-700 nm using a spectral altimeter U-3400 (Hitachi, Ltd.). Transmittance can be calculated.

As another polarizing plate protective film to be bonded to the other surface different from the retardation film used in the present invention, a commercially available cellulose ester film, for example, Konica Minoltack KC8UX, KC4UX, KC5UX, KC8UCR3, KC8UCR4 KC8UY, KC4UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC8UY-HA, KC8UX-RHA, KC8UX-RHA-N, Konica Minolta Opto Co., Ltd., Fujitac TD80U A prevention film (Fuji Film CV Clear View UA) manufactured by Fuji Photo Film Co., Ltd. is preferably used. With respect to the retardation film of the present invention, the polarizing plate protective film used on the other surface is an optically isotropic polarizing plate protection with in-plane retardation Ro of 0 to 20 nm and Rt of -50 to 50 nm. A film is preferred. The polarizing plate protective film preferably has a hard coat layer or an antiglare layer having a thickness of 8 to 20 μm. For example, JP-A Nos. 2003-114333, 2004-203209, and 2004-354699 are disclosed. , 2004-354828, etc., a polarizing plate protective film having a hard coat layer or an antiglare layer is preferably used. Further, an antireflection layer, an antifouling layer or the like is preferably laminated on the hard coat layer or antiglare layer.
The polarizing plate thus obtained is provided on one side or both sides of the cell side of the liquid crystal cell. In any case, the retardation film of the present invention is disposed closer to the liquid crystal cell than the polarizing film.

(Scattering film)
The scattering film used in the present invention has a scatterer and a transparent resin, and is a film in which the scatterer is dispersed in the transparent resin.
The scattering film used in the present invention is provided at least on the viewing side of the viewing side polarizing plate. You may provide a scattering film in the visual recognition side and liquid crystal cell side of the polarizer of a visual recognition side polarizing plate. More preferably, the scattering film is provided only on the viewing side of the polarizer of the viewing side polarizing plate. When the scattering film is provided on the outermost surface on the viewing side of the polarizer of the viewing side polarizing plate, it can be used together with the antiglare film.
The scattering film is a film having a thickness of 20 μm to 120 μm, and more preferably a film having a thickness of 30 μm to 90 μm. Further, in order to obtain a sufficient scattering effect, the thickness of the scattering film needs to be 2.0 times or more the particle size of the scatterer.
Moreover, it is preferable that a scattering film contains 5 thru | or 30 mass parts of scatterers with respect to 100 mass parts of scattering films.

(Scatterer)
In order to obtain a scattering effect, the scatterer needs to be a particle having a refractive index different from that of the transparent resin, but is preferably a particle having a refractive index difference of 0.01 or more from the transparent resin. More preferably, the particle has a refractive index difference of 0.05 or more with the transparent resin. As the difference in refractive index is larger, the scattering efficiency can be improved. Further, the refractive index of the scatterer may be larger or smaller than the refractive index of the transparent resin. When the refractive index of the scatterer is larger than the refractive index of the transparent resin, the intensity of forward scattering can be increased, and when it is smaller, the scattering spread angle can be increased.
The scatterer is a particle having a volume average particle diameter of 5 μm to 30 μm, and more preferably a particle having a volume average particle diameter of 5 μm to 15 μm. By adjusting the particle diameter, it is possible to obtain an angular distribution of light scattering. However, in order to maintain the front brightness in terms of display quality, it is necessary to increase the transmittance as much as possible. When the particle diameter is less than 5 μm, the effect of scattering is great and the viewing angle characteristics are dramatically improved, but the backscattering becomes large and the brightness is drastically reduced. On the other hand, in the case of more than 30 μm, the scattering effect becomes small and the improvement of the viewing angle characteristic becomes small.
When the particle size of the scatterer is in the range of 5 μm to 30 μm, the particle size of the scatterer is sufficiently large compared to the wavelength of visible light, and therefore individual scattering within the scattering film is well-known Mie scattering theory. As the scatterer that can be described approximately by the above, it is preferable to use translucent fine particles. The translucent fine particles are not particularly limited, but are preferably translucent resin particles with high transparency, and more preferably silicone resins. The shape of the scatterer is preferably spherical.

(Transparent resin)
As a transparent resin used for a scattering film, it is mentioned that it is easy to manufacture, is optically isotropic, and is optically transparent.
The term “transparent” as used in the present invention means that the visible light transmittance is 60% or more, preferably 80% or more, and particularly preferably 90% or more.
Although it does not specifically limit if it has said property, For example, polyesters, such as a cellulose ester, polyester, a polycarbonate, a polyarylate, a polysulfone (a polyether sulfone is also included), a polyethylene terephthalate, a polyethylene naphthalate, polyethylene, a polypropylene, Cellophane, polyvinylidene chloride, polyvinyl alcohol derivative, cycloolefin polymer (Arton (manufactured by JSR), Zeonex, Zeonoor (manufactured by Nippon Zeon)), polymethylpentene, polyether ketone, polyether ketone imide, polyamide, fluorine Examples thereof include acrylic derivatives such as resin, nylon and polymethyl methacrylate, and acrylic. As the transparent resin according to the present invention, it is particularly preferable to use a cellulose ester or a material obtained by blending an acrylic resin and a cellulose ester resin.

Hereinafter, the liquid crystal display device of the present invention will be described with reference to the drawings.
Units such as electrodes, color filters, and backlights are not shown because the drawing becomes complicated and optically important parts of the present invention are difficult to see.
FIG. 1 is a schematic view showing an example of a TN liquid crystal display device.
FIG. 1A is a schematic diagram showing the liquid crystal monitor A. A portion (diamond) of the liquid crystal portion is taken out, the polarizing plate 1 of the partial configuration is shown in FIG. 1B, and the liquid crystal cell 3 is shown in FIG. The other polarizing plate 4 is shown in FIG.
In FIGS. 1B and 1D, reference numerals 5 and 21 denote polarizing plate protective films, reference numerals 6 and 20 denote polarizing films, and adjacent retardation films 7 and 19.
In FIGS. 1B and 1D, arrows 9 and 22 are absorption axes of the polarizing film, and 10 and 18 are in-plane slow axes of the retardation film sheet.
In FIG. 1C, reference numerals 11 and 13 denote substrates, reference numerals 14 and 15 denote rubbing axes, and reference numeral 12 denotes a liquid crystal.
In addition, although a scattering film is not shown in this drawing, the polarizing plate protective film 5 may be a scattering film, or may be separately provided on the viewing side of the polarizing plate protective film 5 or the polarizing film 6 side.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
<< Production of retardation film >>
The cellulose ester and plasticizer used are described below.
Cellulose ester C-1: acetyl substitution degree 0.7, propionyl substitution degree 1.1, total acyl substitution degree 1.8
C-2: Acetyl substitution degree 1.0, propionyl substitution degree 1.0, total acyl substitution degree 2.0
C-3: Acetyl substitution degree 1.7, propionyl substitution degree 0.7, total acyl substitution degree 2.4
C-4: Acetyl substitution degree 2.5, propionyl substitution degree 0.1, total acyl substitution degree 2.6
C-5: acetyl substitution degree 2.8, total acyl substitution degree 2.8
Plasticizer A: aromatic terminal ester plasticizer exemplified compound (1)
B: Trimethylolpropane tribenzoate

<Fine particle dispersion>
Fine particles (Aerosil R972V (produced by Nippon Aerosil Co., Ltd.)) 11 parts by mass (average diameter of primary particles 16 nm, apparent specific gravity 90 g / liter)
89 parts by mass of ethanol or more was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

<Fine particle additive solution>
Cellulose ester C-3 was added to a dissolution tank containing methylene chloride and heated to completely dissolve, and this was then added to Azumi filter paper No. 3 manufactured by Azumi Filter Paper Co., Ltd. Filtered using 244. While finely stirring the filtered cellulose ester solution, the fine particle dispersion was slowly added thereto. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution.
Methylene chloride 99 parts by weight Cellulose ester C-3 (cellulose acetate propionate; acetyl group substitution degree 1.7, propionyl group substitution degree 0.7, total acyl group substitution degree 2.4) 4 parts by weight Fine particle dispersion 11 parts by weight Part <Composition of main dope 101>
Methylene chloride 300 parts by mass Ethanol 40 parts by mass Cellulose ester C-3 (cellulose acetate propionate; acetyl group substitution degree 1.7, propionyl group substitution degree 0.7, total acyl group substitution degree 2.4) 100 parts by mass Plasticity Agent (A) 6.5 parts by weight Plasticizer Ethylphthalylethyl glycolate 5.5 parts by weight

A dope solution 101 having the above composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. The cellulose ester was added to the pressure dissolution tank containing the solvent while stirring. This was heated and stirred to completely dissolve, and a plasticizer and an ultraviolet absorber were further added and dissolved. This was designated as Azumi Filter Paper No. The main dope solution 101 was prepared by filtration using 244.
Add 100 parts by weight of the main dope solution 101 and 5 parts by weight of the fine particle additive solution, mix thoroughly with an in-line mixer (Toray static in-tube mixer Hi-Mixer, SWJ), and then use a belt casting apparatus. And uniformly cast on a stainless steel band support having a width of 2 m. On the stainless steel band support, peeling is performed under the conditions of a peeling tension of 130 N / m, a residual solvent amount of 100% by mass, and a cold air temperature of 20 ° C. Further, a portion (roll) for cutting the tension of the peeling portion and the next transport tension are set. The conveyance was performed with a speed difference from the portion to be applied (roll).

  Next, the both ends of the web are gripped by clips with a tenter device capable of independently controlling the gripping length of the web (distance from the start of gripping to the end of gripping) by the left and right gripping means of FIG. 1, and 1.05 times at 145 ° C. And then holding the width at 145 ° C. and then releasing the holding, and further carrying it in a drying zone set at 145 ° C. for 30 minutes for drying, a width of 1.4 m and a width of 1 cm at the end. A 40 μm-thick retardation film 101 having a knurling height of 8 μm was produced.

Next, as shown in Table 1, the types of cellulose ester and plasticizer, the draw ratio, and the film thickness were changed to prepare retardation films 102 to 124.
Further, a retardation film 125 in which an optically anisotropic layer was formed on a TAC film having a thickness of 120 μm using a liquid crystal compound by the method described in Example 1 of JP-A-2001-100042 was prepared.

The retardation values Ro and Rth of the produced retardation film were measured by the following method and are shown in Table 1.
[Measurement of retardation values Ro and Rth]
The average refractive index of the film sample was measured using an Abbe refractometer (1T) and a spectral light source. Moreover, the thickness of the film was measured using a commercially available micrometer.
Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments Co., Ltd.), in a film that was allowed to stand for 24 hours in an environment of 23 ° C. and 55% RH, the retardation of the film was measured at a wavelength of 589 nm. went. The above-described average refractive index and film thickness are input to the following formula, and the in-plane retardation value Ro and the thickness direction retardation value Rth are obtained. The direction of the slow axis with respect to the width direction of the film is also measured at the same time.
Ro = (nx−ny) × d
Rt = {(nx + ny) / 2−nz} × d
(Where nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the thickness direction of the film, and d is (The thickness of the film (nm).)

Preparation of scattering film <Preparation of scattering film A>
(Dope solution composition)
Cellulose ester (cellulose triacetate (degree of acetylation: 61.5%, Mn: 110000, Mw / Mn = 2.0) 100 parts by mass Trimethylolpropane tribenzoate 4.5 parts by mass Ethylphthalyl ethyl glycolate 5 parts by mass Methylene Chloride 430 parts by mass Ethanol 40 parts by mass Spherical particle S1 10 parts by mass
The composition was sufficiently stirred while heating to dissolve the resin and disperse the particles, thereby preparing a dope solution.

(Making of scattering film)
The produced dope solution was 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 residual solvent amount reached 100%, and the film was peeled off from the stainless steel band support with a peeling tension of 162 N / m.
The web of the peeled scattering film was evaporated at 35 ° C., slit to 1.6 m width, and then dried at a drying temperature of 135 ° C. while being stretched 1.1 times in the width direction by a tenter. At this time, the residual solvent amount when starting stretching with a tenter was 10%.
After stretching with a tenter, relaxation was performed at 130 ° C. for 5 minutes, and then drying was completed while transporting a drying zone at 120 ° C. and 140 ° C. with many rolls, slitting to a width of 1.5 m, and a width of 10 mm at both ends of the film A knurling process having a height of 5 μm was performed, and the film was wound around a core having an initial tension of 220 N / m and a final tension of 110 N / m, and an inner diameter of 15.24 cm.
In the manufacture of the scattering film A, the following spherical particles S1 were used.
Scattering films B to E were prepared using the following particles S2 to S5 instead of the spherical particles S1.
Scattering film (production of silicone resin particles)
The following spherical particles S1-S5 (refractive index 1.43) were prepared by the method described in the reference (Japanese Patent Laid-Open No. 63-77940).
S1: True spherical polymethylsilsesquioxane particles, average particle size 6 μm
S2: Spherical polymethylsilsesquioxane particles, average particle size 11 μm
S3: Spherical polymethylsilsesquioxane particles, average particle size 15 μm
S4: Spherical polymethylsilsesquioxane particles, average particle size 30 μm
S5: Spherical polymethylsilsesquioxane particles, average particle size 40 μm

<< Preparation of polarizing plate for viewing side >>
Subsequently, a polarizing plate was produced using each of the retardation films 101 to 125 and the scattering films A to E.
A polyvinyl alcohol film having a thickness of 120 μm was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times). This was immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. composed of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. This was washed with water and dried to obtain a polarizing film.
Next, the retardation films 101 to 125 are bonded to the polarizing film and the liquid crystal cell side of the polarizing film in accordance with the following steps 1 to 5, and the scattering films A to E are bonded to the viewing side of the liquid crystal cell in combinations as shown in Table 1. A polarizing plate was produced.

The polarizing film, the retardation film, and the scattering film were bonded by the following process.
Step 1: The retardation film and the scattering film were immersed in a 1 mol / L sodium hydroxide solution at 50 ° C. for 60 seconds, then washed with water and dried to saponify the side to be bonded to the polarizing film.
Step 2: The polarizing film was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass for 1 to 2 seconds.
Step 3: Excess adhesive adhered to the polarizing film in Step 2 was lightly wiped off, and the polarizing film was sandwiched between the retardation film and scattering film processed in Step 1 and placed.
Step 4: The retardation film, the polarizing film, and the scattering film laminated in Step 3 were bonded at a pressure of 20 to 30 N / cm ² and a conveyance speed of about 2 m / min.
Step 5: A sample obtained by bonding the polarizing film, the scattering film, and the retardation films 101 to 125 produced in Step 4 in a dryer at 80 ° C. was dried for 2 minutes to produce viewing-side polarizing plates 101 to 125.
In addition, when producing the polarizing plate 105 and using the retardation film 125 to produce the polarizing plate 125, Konica Minolta Tack KC8UX-RHA (manufactured by Konica Minolta Opto Co., Ltd.) is used as the visual protective film. Using. In addition, when laminating the retardation film 125, the liquid crystal coating layer was laminated and adhered so that it was on the outside.

<< Preparation of backlight-side polarizing plate >>
A polarizing film and a retardation film similar to the polarizing plate on the viewing side are used, and Konica Minoltack KC8UX-RHA (manufactured by Konica Minolta Opto Co., Ltd.) is bonded as a protective film on the backlight side. Backlight-side polarizing plates 101 to 125 were produced in the same manner as the plate.
Hereinafter, in manufacturing the liquid crystal display device, the viewing-side polarizing plates 101 to 125 and the backlight-side polarizing plates 101 to 125 having the same number are used as a set.

<Production of liquid crystal cell and liquid crystal display device>
A polyimide alignment film was provided on a glass substrate on which an ITO transparent electrode was provided, and a rubbing treatment was performed. The two substrates were stacked with the alignment film facing each other through a 4.3 μm spacer. The two substrates were arranged so that the rubbing directions of the alignment films were orthogonal. Rod-like liquid crystalline molecules (ZLI-4792, manufactured by Merck & Co., Inc.) are injected into the gap between the substrates, and the viewing side polarizing plates 101 to 125 and the backlight side polarizing plates 101 to 125 are formed on both sides of the TN liquid crystal cell produced as described above. Were attached using an adhesive so as to be on the phase difference film liquid crystal cell side, and liquid crystal display devices 101 to 125 were produced. A rectangular wave voltage of 55 Hz is applied to the liquid crystal cell of the liquid crystal display device, and the contrast ratio of 10 at the top, bottom, left, and right is defined as the contrast ratio of white display and black display at 1.6 V for white display and 4.8 V for black display. The viewing angle at which 20 was obtained was measured. In addition, the polarizing plate was bonded to the liquid crystal cell so that the rubbing axis of the substrate on which the polarizing plate was bonded and the absorption axis of the polarizing plate were matched.

<Evaluation>
The viewing angle measurement was performed using EZ-contrast 160R manufactured by ELDIM. The luminance ratio of white and black in the front was used as the front contrast, and the angle of the contrast ratio 10: 1 was used as the viewing angle. Moreover, the practical evaluation evaluated visually by displaying the following.
(1) Halftone inversion of image (2) White display (3) Blur of characters and lines

(Viewing angle)
TN viewing angle evaluation criteria:
A: Improved by 30 ° or more each on the left and right compared with the following commercially available TN ○: Improved 15 ° or more on each of the left and right compared with the following commercially available TN Δ: Improved by 10 ° or more on each of the left and right compared with the following commercially available TN ×: No improvement compared with the following commercially available TN Viewing angle of a commercially available TN type liquid crystal display device:
Viewing angle Up / Down Left / Right Inverted Left / Right TN 27 ° 60 ° 45 ° × 2 40 °

(Front contrast)
◎ No problem for practical use with front contrast of 70% or more for product ○ No problem for practical use with front contrast of 40% or more for product △ No problem for practical use with front contrast of 15% or more for product Less than practical

(Practical evaluation)
(1) Halftone inversion of image ◎: Almost no inversion is recognized ○: Minor inversion is recognized but hardly noticed ×: Inversion is visible and practically problematic (2) White display ◎: No color change is seen ○ : Slight color change is observed but hardly noticed ×: Color shift is clearly understood and practically problematic (3) Blur of characters and lines ○: Blur is not concerned ×: Blur becomes practically problematic

(Frame unevenness)
Each manufactured liquid crystal display device was lit for 1000 hours, and then the presence or absence of light leakage (frame unevenness) around the screen in black display was visually confirmed.
○: No light leakage in the surrounding area is observed △: Light leakage in the surrounding area is recognized ×: Light leakage in the surrounding area is remarkable

The above evaluation results are shown in Table 1.
From Table 1, it is clear that the polarizing plate using the retardation film having the configuration of the present invention has improved viewing angle, color change, and frame unevenness compared to the comparative example.

It is the schematic which shows an example of the TN type | mold liquid crystal display device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 4 Polarizing plate 3 Liquid crystal cell 5, 21 Polarizing plate protective film 6, 20 Polarizing film 7, 19 Retardation film 9, 22 Polarizing film absorption axis 10, 18 In-plane slow axis 11, 13 of retardation film Substrate 12 Liquid crystal 14, 15 Rubbing axis

Claims (10)

Twisted nematic liquid crystal cell, first polarizer provided on the viewing side of the liquid crystal cell, twisted nematic liquid crystal display having a second polarizer and a backlight unit provided on the backlight side of the liquid crystal cell In the device
A first retardation film and a second retardation film are provided between the liquid crystal cell and the first polarizer and between the liquid crystal cell and the second polarizer, respectively.
Each of the first retardation film and the second retardation film contains a thermoplastic resin, and Ro represented by the following formula (i) is in the range of 5 to 35 nm, and the following formula (ii) The Rth represented is in the range of 70 to 150 nm, and the film thickness is in the range of 10 to 50 μm.
On the viewing side of the first polarizer, a scattering film in which scatterers are dispersed in a transparent resin is provided,
The scatterer is a particle having a volume average particle diameter of 5 to 30 μm,
The scattering film has a thickness of 20 to 120 μm,
A twisted nematic type liquid crystal display device, wherein the thickness of the scattering film is 2.0 times or more of the particle size.
(I) Ro = (nx−ny) × d
(Ii) Rth = ((nx + ny) / 2−nz) × d
Where nx is the maximum refractive index in the plane, ny is the refractive index in the direction perpendicular to nx in the plane, nz is the refractive index in the film thickness direction, each refractive index is a value for light having a wavelength of 590 nm, and d is Represents the film thickness (nm).   The first retardation film is provided adjacent to the first polarizer, contains a cellulose ester resin, and serves also as a protective film on the liquid crystal cell side of the first polarizer. The liquid crystal display device according to claim 1.   The second retardation film is provided adjacent to the second polarizer, contains a cellulose ester resin, and serves also as a protective film on the liquid crystal cell side of the second polarizer. The liquid crystal display device according to claim 1 or 2. 4. The polarizing plate-integrated retardation film according to claim 2, wherein when the cellulose ester has an acetyl group substitution degree of X and a propionyl group substitution degree of Y, the following formula is satisfied. 5. A liquid crystal display device.
(Iii) 2.0 ≦ (X + Y) ≦ 2.6
(Iv) 0.1 ≦ Y ≦ 1.2   The retardation film is a film obtained by stretching 1.05 to 1.3 times in the transport direction or the direction orthogonal to the transport direction, and the in-plane slow axis is substantially perpendicular to the transport direction. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a liquid crystal display device.   The said scattering film is provided adjacent to the visual recognition side of the said 1st polarizer, and serves also as the protective film of the visual recognition side of the said 1st polarizer, In any one of Claims 1-5 characterized by the above-mentioned. The liquid crystal display device described.   The liquid crystal display device according to claim 1, wherein the scatterer has a volume average particle diameter of 5 to 15 μm.   The liquid crystal display device according to any one of claims 1 to 7, wherein the scattering film contains 5 to 50 parts by mass of the scatterer with respect to 100 parts by mass of the scattering film.   The liquid crystal display device according to claim 1, wherein the scattering film has a thickness of 30 to 90 μm.   The liquid crystal display device according to claim 1, wherein in the scattering film, a difference in refractive index between the transparent resin and the scatterer is 0.01 or more.

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