JPWO2008044452A1 - Horizontal electric field switching mode type liquid crystal display device - Google Patents

Abstract

An object of the present invention is to provide a lateral electric field switching mode type liquid crystal display device that simultaneously satisfies color shift, corner unevenness, and front contrast. In the transverse electric field switching mode type liquid crystal display device of the present invention, the polarizing plate protective film used between the liquid crystal cell on the backlight light source side and the polarizer has retardation values Ro and Rt of 0 nm ≦ Ro ≦ 2 nm and − The cellulose ester film is in the range of 10 nm ≦ Rt ≦ 10 nm, and the cellulose ester film is characterized in that the following Rt temperature fluctuation is 7 nm or less and the following Rt humidity fluctuation is 20 nm or less. Rt temperature fluctuation; ΔRt value Rt humidity fluctuation of difference between Rt values measured in a state of standing at 23 ° C. relative humidity 55% environment and 35 ° C. relative humidity 27% environment for 24 hours; 23 ° C. relative humidity 20% ΔRt value of the difference between the Rt value measured in the environment and in a state of standing for 24 hours at 23 ° C. and 80% relative humidity

Description

  The present invention relates to a horizontal electric field switching mode type liquid crystal display device, and more particularly to a horizontal electric field switching mode type liquid crystal display device having excellent color shift, corner unevenness, and front contrast characteristics.

  The horizontal electric field switching mode type liquid crystal display device is a so-called IPS (In Plane) liquid crystal mode of the liquid crystal display device because of excellent effects such as a small change in luminance depending on a viewing angle and a small drop in response speed in a halftone. It is offered to the market as a switching type liquid crystal display device. Examples of the IPS liquid crystal display device include an FFS (fringe field switching) mode and an FLC (ferroelectric liquid crystal) mode in addition to the so-called IPS mode.

  In this IPS type liquid crystal display device, the retardation film and polarizing plate protective film disposed between the liquid crystal cell and the polarizer are TN (twisted nematic) type liquid crystal, VA for the purpose of improving the viewing angle, color shift, etc. (Vertical alignment, vertical alignment) type liquid crystal has a characteristic configuration that is greatly different.

  In this IPS type liquid crystal display device, the retardation value Rt value is in the range of −70 to 70 nm and the Ro value is in the range of 70 to 390 nm (for example, the Rt value is −30 nm, the Ro value is 130 nm). In addition, in Patent Document 1 and Non-Patent Document 1, the retardation value (Ro value is 0 to 2 nm) substantially zero for the polarizing plate protective film used between the liquid crystal cell and the polarizer. It has been proposed to improve color shift and corner unevenness by using a cellulose ester film having an Rt value of −10 to 10 nm.

  In the method of Patent Document 1, in addition to making Ro and Rt substantially zero, physical properties of the film in the machine direction and the direction perpendicular thereto, especially tensile elastic modulus, storage elastic modulus, photoelastic coefficient, dimensional stability It is claimed that by making the properties equivalent to the three directions, it is particularly effective for corner irregularities that are affected by the temperature and humidity of the environment. In Patent Document 2, the humidity dependency of the light leakage rate during black display is improved by using a cellulose acylate film having an Rt value of 40 nm or less and an Rt humidity fluctuation of 40 nm or less for an IPS liquid crystal display device. It is claimed. However, these techniques have little improvement effect on performance such as front contrast, and are not sufficient for color shift and corner unevenness.

  On the other hand, the retardation film for IPS is expensive, color shift, and corner unevenness improvement effect may be insufficient, and there is little change in luminance due to viewing angle, which is a characteristic of IPS, and response speed in halftone Excellent effects such as a small drop of the IPS can be obtained even without the retardation film for IPS. For this reason, there are many IPS liquid crystal display devices that use a polarizing plate protective film having a retardation value close to zero between the polarizers on both sides of the liquid crystal cell without a retardation film.

However, it has not been a sufficient improvement for the desire to satisfy color shift, corner unevenness, and front contrast at the same time.
JP 2006-18245 A JP 2005-139304 A Hajime Nakayama et al. (FUJI PHOTO FILM Co., Ltd) IDW / AD '05 p1317-1320

  An object of the present invention is to provide a technique that simultaneously satisfies color shift, corner unevenness, and front contrast in a horizontal electric field switching mode type liquid crystal display device.

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

1. In the transverse electric field switching mode type liquid crystal display device having polarizing plates on both sides of the liquid crystal cell, the polarizing plate protective film used between the liquid crystal cell on the backlight source side and the polarizer is represented by the following formulas (1) and (2). Ro and Rt represented are cellulose ester films each having a range of 0 nm ≦ Ro ≦ 2 nm and −10 nm ≦ Rt ≦ 10 nm. The cellulose ester film has the following Rt temperature fluctuation of 7 nm or less, A lateral electric field switching mode type liquid crystal display device characterized in that the Rt humidity fluctuation is 20 nm or less.
Ro, Rt measurement conditions: Measured after standing the film for 24 hours in an environment of 23 ° C. and 55% relative humidity. Rt temperature fluctuation; static for 24 hours in an environment of 23 ° C. relative humidity of 55% and 35 ° C. relative humidity of 27%. ΔRt value Rt humidity fluctuation of the difference in Rt value measured in a standing state; difference in Rt value measured in a 24 hour relative environment under a 23 ° C. relative humidity 20% environment and a 23 ° C. relative humidity 80% environment ΔRt value formula (1) Ro = (nx−ny) × d
Formula (2) Rt = {(nx + ny) / 2−nz} × d
(Here, the refractive index in the slow axis direction in the plane of the cellulose ester film is nx, the refractive index in the direction perpendicular to the slow axis in the plane is ny, the refractive index in the thickness direction of the film is nz, d is Represents the thickness (nm) of the film.)
2. 2. The transverse electric field switching mode type liquid crystal display device according to 1 above, wherein the cellulose ester film contains a compound having negative orientation birefringence.

  3. 3. The horizontal electric field switching mode type liquid crystal display device according to 1 or 2 above, wherein the horizontal electric field switching mode type liquid crystal display device is an IPS (In Plane Switching) mode type liquid crystal display device.

  4). 4. The transverse electric field switching mode type liquid crystal display device according to any one of 1 to 3, wherein the Rt temperature variation is in a range of 1 to 5 nm, and the Rt humidity variation is in a range of 4 to 12 nm. .

  5. The polarizing plate protective film used between the polarizer on the viewing side and the liquid crystal cell is the same as the polarizing plate protective film used between the liquid crystal cell on the backlight light source side and the polarizer. 5. A horizontal electric field switching mode type liquid crystal display device according to any one of.

  6). 6. The transverse electric field switching mode liquid crystal display device according to any one of 1 to 5, wherein the IPS retardation film is not provided between the polarizer and the liquid crystal cell.

  In order to solve the above-mentioned problems, the present inventor only needs that Ro and Rt of the polarizing plate protective film on the backlight side are practically zero in a region where both Ro and Rt are substantially zero. However, it was found that if the fluctuation of Rt due to temperature and humidity is below a certain level, it does not necessarily depend on the change of Ro.

  That is, in an 80 μ-thick cellulose ester film having a retardation value substantially close to zero, even if, for example, Ro is 0.5 nm and Rt is −2 nm, the Rt temperature fluctuation is 11 nm. It has been found that the Rt humidity fluctuation is not numerically as small as 23 nm and can be improved by suppressing this to a certain level or less.

  Patent Document 2 describes that “Rt humidity fluctuation” is preferably small, and that the dimensional change rate is preferably small with respect to temperature. However, the retardation value region of the present application is substantially close to zero. Then, it has been found that it is necessary to keep the Rt value below a certain level not only when the humidity varies but also when the temperature varies. In particular, it has been found that for corner unevenness, it is not necessary for the polarizing plate protective film to be physically fluctuated by temperature and humidity, and the problem can be solved only by a small rate of change in Rt.

  Furthermore, the present inventor found that in the region where Ro and Rt are practically zero, the influence of the film thickness terms of Ro and Rt defined by the formulas (1) and (2) differs between Ro and Rt. That is, it was found that the term of film thickness has a stronger influence on Rt than on Ro. Due to this property, the present invention has been achieved by making the most of the effect of Rt. Therefore, in the present invention, the mechanical properties in the film surface direction and the film thickness direction are not necessarily equivalent.

  Conventionally, in order to realize the retardation value region of the present application substantially close to zero, it is known that it can be realized by incorporating a compound having negative orientation birefringence into a cellulose ester film. Adjustment of ester acyl substituent, degree of substitution, selection of compound having negative orientation birefringence and adjustment of addition amount, manufacturing conditions (solvent casting, solvent type, stripping conditions, stretching conditions, melt casting The Rt value and Ro value can be adjusted according to the stretching conditions. However, the Rt humidity fluctuation and the Rt temperature fluctuation are the consequences. In the case of an 80 μm film having a normal film thickness, when the ranges of 0 nm ≦ Ro ≦ 2 nm and −10 nm ≦ Rt ≦ 10 nm of the present application are set, the Rt humidity fluctuation is 16 The Rt temperature variation was in the range of about 11 to 21 nm. In the study, it was found that the Rt temperature / humidity fluctuation is substantially proportional to the film thickness, and when the Rt temperature fluctuation and Rt humidity fluctuation are within a certain range by changing the film thickness, the color shift is performed. It has been found that corner unevenness and front contrast can be improved.

  That is, the present invention has found that the preferable ranges of the Rt temperature fluctuation and the Rt humidity fluctuation of the polarizing plate protective film between the liquid crystal cell on the backlight side and the polarizer are in a region that has not been realized in the past.

  Therefore, according to the present invention, in the horizontal electric field switching mode type liquid crystal display device, it is possible to provide a technique that simultaneously satisfies the color shift, the corner unevenness, and the front contrast.

1 is a schematic view of a liquid crystal display device according to a preferred embodiment of the present invention.

Explanation of symbols

1: Polarizing plate protective film 2: Polarizer 3: Polarizing plate protective film 4: Non-electrode side cell glass substrate 5: IPS type liquid crystal layer 6: Electrode side cell glass substrate (electrodes are formed on the substrate)
7: Polarizing plate protective film 8: Polarizer 9: Polarizing plate protective film 10: Viewing-side polarizing plate 11: IPS liquid crystal cell 12: Backlight polarizing plate 13: Prism sheet 14: Light guide plate 15: Backlight

  The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.

The polarizing plate protective film used between the liquid crystal cell on the backlight light source side and the polarizer used in the lateral electric field switching mode type liquid crystal display device of the present invention is represented by the following formulas (1) and (2). , Rt is a cellulose ester film in the range of 0 nm ≦ Ro ≦ 2 nm and −10 nm ≦ Rt ≦ 10 nm, respectively. The cellulose ester film has the following Rt temperature fluctuation of 7 nm or less, and the following Rt humidity fluctuation: A transverse electric field switching mode type liquid crystal display device characterized by being 20 nm or less.
Ro, Rt measurement conditions: Measured after standing the film for 24 hours in an environment of 23 ° C. and 55% relative humidity. Rt temperature fluctuation; static for 24 hours in an environment of 23 ° C. relative humidity of 55% and 35 ° C. relative humidity of 27%. ΔRt value Rt humidity fluctuation of the difference in Rt value measured in a standing state; difference in Rt value measured in a 24 hour relative environment under a 23 ° C. relative humidity 20% environment and a 23 ° C. relative humidity 80% environment ΔRt value formula (1) Ro = (nx−ny) × d
Formula (2) Rt = {(nx + ny) / 2−nz} × d
(Here, the refractive index in the slow axis direction in the plane of the cellulose ester film is nx, the refractive index in the direction perpendicular to the slow axis in the plane is ny, the refractive index in the thickness direction of the film is nz, d is Represents the thickness (nm) of the film.)
The birefringence and retardation value of the film can be measured using an automatic birefringence measuring apparatus (trade name KOBRA-21ADH manufactured by Oji Scientific Instruments), but is not limited thereto.

  The above Ro and Rt are those in which Ro is in the range of 0 to 2 nm and Rt is in the range of −10 to 10 nm, more preferably Ro is 0 to 2 nm, Rt is −5 to 5 nm, and particularly preferably Ro is The range is 0 to 1 nm and Rt is -3 to 3 nm.

As a method for achieving the present invention, for example, reducing the thickness of the polarizing plate protective film can be mentioned.

  The film thickness of the preferred polarizing plate protective film in which the range of Rt temperature fluctuation and Rt humidity fluctuation is within the present invention is determined and different depending on the film material, but the particularly preferred range is from 20 to 50 μm, more preferably from the examples. Is in the range of 20-40 μm.

  That is, it is essential that Ro and Rt are within the scope of the present invention, and the substantial film thickness is 20 to 50 μm, which is smaller than the normal film thickness, and preferably 20 to 40 μm. In this region, the influence of the film thickness term on Rt is larger than that of Ro. When the thickness exceeds 50 μm, the influence of the film thickness on Ro and Rt becomes gradually equal.

  Although the thickness of the polarizer must be constant due to the requirement of the degree of polarization, reducing the thickness of the polarizing plate protective film on the backlight side is from the point of dimensional stability of the entire polarizing plate. Although it acts in a seemingly disadvantageous direction as an effect of suppressing the dimensional change of the polarizer, it becomes an advantageous direction as a variation rate of temperature and humidity of Ro and Rt, and as a result, optical performance such as corner unevenness is improved. It was.

  The polarizing plate protective film of the present invention is more effective when there is an electrode for generating a transverse electric field on the backlight side liquid crystal cell substrate.

<Ro, Rt achievement means: backlight side>
The polarizing plate protective film used between the liquid crystal cell on the backlight light source side of the present invention and the polarizer has practically zero Ro and Rt. The means for setting Ro and Rt to desired values is not limited as long as the film is a single sheet, but is preferably a cellulose ester film containing a compound having negative orientation birefringence and having a film thickness. 20 to 50 μm.

  The polarizing plate protective film at this position is preferably uniform as a film. For example, even if a plurality of films are overlapped or a coating layer is provided to have the same Ro and Rt, one film The performance improvement effect is greater in the case of.

(Cellulose ester)
Examples of the cellulose ester forming the cellulose ester film of the present invention include triacetyl cellulose (TAC), diacetyl cellulose (DAC), cellulose acetate propionate (CAP), cellulose acetate butyrate (CAB), cellulose acetate phthalate, and cellulose acetate. Examples thereof include cellulose esters such as trimellitate and cellulose nitrate.

  The cellulose used as a raw material for the cellulose ester used in the present invention is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf. Moreover, although the cellulose ester obtained from these can be used individually or in mixture of arbitrary ratios, it is preferable to use 50 mass% or more of cotton linters.

  When the molecular weight of the cellulose ester film is large, the elastic modulus is increased. However, when the molecular weight is excessively increased, the viscosity of the cellulose ester solution becomes too high, and the productivity is lowered. The molecular weight of the cellulose ester is preferably 30000-200000 in terms of number average molecular weight (Mn), more preferably 500000-200000.

  The cellulose ester used in the present invention preferably has an Mw / Mn ratio of 1 to 5, more preferably 1 to 3, and particularly preferably 1.4 to 2.3.

  Since the average molecular weight and molecular weight distribution of the cellulose ester can be measured using high performance liquid chromatography, the number average molecular weight (Mn) and the mass average molecular weight (Mw) can be calculated using this, and the ratio can be calculated.

  The measurement conditions are as follows.

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

  A particularly preferred cellulose ester has an acyl group having 2 to 4 carbon atoms as a substituent, the substitution degree of acetyl group is Xac, and the substitution degree of propionyl group or butyryl group is Ypb. And (II) at the same time.

Formula (I) 2.2 ≦ (Xac + Ypb) ≦ 2.55
Formula (II) 0 ≦ Xac ≦ 2.1
Among them, cellulose acetate propionate (total acyl group substitution degree = Xac + Ypb) satisfying 1.0 ≦ Xac ≦ 2.1 and 0.1 ≦ Ypb ≦ 1.55 is preferable. The degree of substitution of these acyl groups can be measured according to the method prescribed in ASTM-D817-96. The portion not substituted with an acyl group usually exists as a hydroxyl group. These cellulose esters can be synthesized by a known method.

<Compound with negative orientation birefringence>
The compound having negative orientation birefringence preferably used in the present invention means a material exhibiting negative birefringence in the direction of stretching of the cellulose ester film, and is an acrylic polymer, polyester, furanose. Examples thereof include compounds having a structure or a pyranose structure, sulfone compounds and the like.

  Whether or not the film has negative orientation birefringence can be determined by measuring the birefringence of the film in a system not added with the compound with a birefringence meter and comparing the difference.

(Acrylic polymer, polyester, compound having furanose structure or pyranose structure)
Next, the acrylic polymer, polyester, and compound having a furanose structure or a pyranose structure used in the present invention will be described.

<Acrylic polymer>
The cellulose ester film of the present invention preferably contains an acrylic polymer having a negative average birefringence in the stretching direction and having a weight average molecular weight of 500 or more and 30000 or less, and the acrylic polymer has an aromatic ring as a side chain. An acrylic polymer having a cyclohexyl group in the side chain is preferable.

  By controlling the composition of the polymer so that the weight average molecular weight of the polymer is 500 or more and 30000 or less, the compatibility between the cellulose ester and the polymer can be improved.

  In particular, for an acrylic polymer, an acrylic polymer having an aromatic ring in the side chain, or an acrylic polymer having a cyclohexyl group in the side chain, if the weight average molecular weight is preferably 500 or more and 10,000 or less, in addition to the above, The cellulose ester film has excellent transparency and extremely low moisture permeability, and exhibits excellent performance as a protective film for polarizing plates.

  Since the polymer has a weight average molecular weight of 500 or more and 30000 or less, it is considered to be between the oligomer and the low molecular weight polymer. In order to synthesize such a polymer, it is difficult to control the molecular weight in normal polymerization, and it is desirable to use a method that can align the molecular weight as much as possible by a method that does not increase the molecular weight too much.

  Such polymerization methods include a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than normal polymerization, and a mercapto compound in addition to the polymerization initiator. And a method of using a chain transfer agent such as carbon tetrachloride, a method of using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and further, Japanese Patent Application Laid-Open No. 2000-128911 or 2000-344823. Examples thereof include a compound having one thiol group and a secondary hydroxyl group, or a bulk polymerization method using a polymerization catalyst in which the compound and an organometallic compound are used in combination. Although used, the method described in the publication is particularly preferable.

  Although the monomer as a monomer unit which comprises the polymer useful for this invention is mentioned below, it is not limited to this.

  The ethylenically unsaturated monomer unit constituting the polymer obtained by polymerizing the ethylenically unsaturated monomer is as a vinyl ester, for example, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl pivalate, caproic acid. Vinyl, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl benzoate, vinyl cinnamate Etc .; As acrylate ester, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n -, I-, s-), hexyl acrylate (n I-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic Cyclohexyl acid, acrylic acid (2-ethylhexyl), benzyl acrylate, phenethyl acrylate, acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3- Hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid-p-hydroxymethylphenyl, acrylic acid-p- (2-hydroxyethyl) phenyl, etc .; The above acrylic acid ester is changed to methacrylic acid ester; Examples thereof include acrylic acid, methacrylic acid, maleic anhydride, crotonic acid, itaconic acid and the like. The polymer composed of the above monomers may be a copolymer or a homopolymer, and is preferably a vinyl ester homopolymer, a vinyl ester copolymer, or a copolymer of vinyl ester and acrylic acid or methacrylic acid ester.

  In the present invention, an acrylic polymer (simply referred to as an acrylic polymer) refers to a homopolymer or copolymer of acrylic acid or methacrylic acid alkyl ester having no monomer unit having an aromatic ring or a cyclohexyl group. An acrylic polymer having an aromatic ring in the side chain is an acrylic polymer that always contains an acrylic acid or methacrylic acid ester monomer unit having an aromatic ring.

  The acrylic polymer having a cyclohexyl group in the side chain is an acrylic polymer containing an acrylic acid or methacrylic acid ester monomer unit having a cyclohexyl group.

  Examples of the acrylate monomer having no aromatic ring and cyclohexyl group include, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-) , Nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid 2-methoxy-ethyl), acrylic acid (2-ethoxyethyl), or the acrylic acid ester may include those obtained by changing the methacrylic ester.

  The acrylic polymer is a homopolymer or copolymer of the above-mentioned monomers, but the acrylic acid methyl ester monomer unit preferably has 30% by mass or more, and the methacrylic acid methyl ester monomer unit has 40% by mass or more. preferable. In particular, a homopolymer of methyl acrylate or methyl methacrylate is preferred.

  Examples of acrylic acid or methacrylic acid ester monomers having an aromatic ring include phenyl acrylate, phenyl methacrylate, acrylic acid (2 or 4-chlorophenyl), methacrylic acid (2 or 4-chlorophenyl), and acrylic acid (2 or 3 Or 4-ethoxycarbonylphenyl), methacrylic acid (2 or 3 or 4-ethoxycarbonylphenyl), acrylic acid (o or m or p-tolyl), methacrylic acid (o or m or p-tolyl), benzyl acrylate, Benzyl methacrylate, phenethyl acrylate, phenethyl methacrylate, acrylic acid (2-naphthyl) and the like can be mentioned, but benzyl acrylate, benzyl methacrylate, phenethyl acrylate, and phenethyl methacrylate are preferably used. That.

  Among acrylic polymers having an aromatic ring in the side chain, the acrylic acid or methacrylic acid ester monomer unit having an aromatic ring has 20 to 40% by mass, and the acrylic acid or methacrylic acid methyl ester monomer unit is 50 to 80% by mass. % Is preferable. The polymer preferably has 2 to 20% by mass of acrylic acid or methacrylic acid ester monomer units having a hydroxyl group.

  Examples of the acrylate monomer having a cyclohexyl group include cyclohexyl acrylate, cyclohexyl methacrylate, acrylic acid (4-methylcyclohexyl), methacrylic acid (4-methylcyclohexyl), acrylic acid (4-ethylcyclohexyl), and methacrylic acid. (4-ethylcyclohexyl) and the like can be mentioned, but cyclohexyl acrylate and cyclohexyl methacrylate can be preferably used.

In the acrylic polymer having a cyclohexyl group in the side chain, the acrylic acid or methacrylic acid ester monomer unit having a cyclohexyl group has 20 to 40% by mass and 50 to 8
It is preferable to have 0% by mass. Moreover, it is preferable to have 2-20 mass% of acrylic acid or methacrylic acid ester monomer units having a hydroxyl group in the polymer.

  A polymer obtained by polymerizing the above ethylenically unsaturated monomer, an acrylic polymer, an acrylic polymer having an aromatic ring in the side chain, and an acrylic polymer having a cyclohexyl group in the side chain are all excellent in compatibility with the cellulose resin.

  In the case of an acrylic acid or methacrylic acid ester monomer having these hydroxyl groups, it is not a homopolymer but a structural unit of a copolymer. In this case, it is preferable that the acrylic acid or methacrylic acid ester monomer unit having a hydroxyl group is contained in the acrylic polymer in an amount of 2 to 20% by mass.

  In the present invention, a polymer having a hydroxyl group in the side chain can also be preferably used. The monomer unit having a hydroxyl group is the same as the monomer described above, but acrylic acid or methacrylic acid ester is preferable. For example, acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3 -Hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid-p-hydroxymethylphenyl, acrylic acid-p- (2-hydroxyethyl) phenyl, or these acrylic acids. The thing replaced by methacrylic acid can be mentioned, Preferably, it is 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate. The acrylic acid ester or methacrylic acid ester monomer unit having a hydroxyl group in the polymer is preferably contained in the polymer in an amount of 2 to 20% by mass, more preferably 2 to 10% by mass.

  A polymer containing 2 to 20% by mass of the above-mentioned monomer unit having a hydroxyl group, of course, is excellent in compatibility with cellulose ester, retention, dimensional stability, low moisture permeability, and polarized light. It is particularly excellent in adhesiveness with a polarizer as a plate protective film, and has the effect of improving the durability of the polarizing plate.

  The method of having a hydroxyl group at at least one terminal of the main chain of the acrylic polymer is not particularly limited as long as it has a hydroxyl group at the terminal of the main chain, but azobis (2-hydroxyethylbutyrate) A method using a radical polymerization initiator having such a hydroxyl group, a method using a chain transfer agent having a hydroxyl group such as 2-mercaptoethanol, a method using a polymerization terminator having a hydroxyl group, and terminating a hydroxyl group by living ion polymerization. A compound having one thiol group and a secondary hydroxyl group as described in JP-A No. 2000-128911 or 2000-344823, or polymerization using the compound and an organometallic compound in combination It can be obtained by a bulk polymerization method using a catalyst, and the method described in the publication is particularly preferable.

  The polymer produced by the method related to the description in this publication is commercially available as Act Flow Series manufactured by Soken Chemical Co., Ltd., and can be preferably used. In the present invention, the polymer having a hydroxyl group at the terminal and / or the polymer having a hydroxyl group in a side chain has an effect of significantly improving the compatibility and transparency of the polymer.

  Furthermore, a polymer using styrene as an ethylenically unsaturated monomer exhibiting negative orientation birefringence with respect to the stretching direction is preferred in order to develop negative refraction. Examples of styrenes include styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, isopropyl styrene, chloromethyl styrene, methoxy styrene, acetoxy styrene, chloro styrene, dichloro styrene, bromo styrene, and vinyl benzoic acid methyl ester. Although it is mentioned, it is not a thing limited to these.

  It may be copolymerized with the exemplified monomers listed as the unsaturated ethylenic monomer, or may be used by being dissolved in a cellulose ester using two or more kinds of the above polymers for the purpose of controlling birefringence.

  Furthermore, the cellulose ester film according to the present invention includes an ethylenically unsaturated monomer Xa that does not have an aromatic ring and a hydrophilic group in the molecule, and an ethylenically unsaturated monomer that does not have an aromatic ring in the molecule and has a hydrophilic group. A weight average molecular weight of 500 to 3,000 obtained by polymerizing a polymer X having a weight average molecular weight of 5,000 to 30,000 obtained by copolymerization with Xb, and more preferably an ethylenically unsaturated monomer Ya having no aromatic ring. It is preferable to contain the following polymer Y.

(Polymer X, Polymer Y)
The polymer X used in the present invention comprises an ethylenically unsaturated monomer Xa having no aromatic ring and a hydrophilic group in the molecule and an ethylenically unsaturated monomer Xb having no aromatic ring and having a hydrophilic group in the molecule. It is a polymer having a weight average molecular weight of 5,000 to 30,000 obtained by copolymerization. Preferably, Xa is an acrylic or methacrylic monomer that does not have an aromatic ring and a hydrophilic group in the molecule, and Xb is an acrylic or methacrylic monomer that does not have an aromatic ring in the molecule and has a hydrophilic group.

  The polymer X used in the present invention is represented by the following general formula (1).

General formula (1)
-(Xa) m- (Xb) n- (Xc) p-
More preferably, it is a polymer represented by the following general formula (1-1).

General formula (1-1)
_{- [CH 2 -C (-R1)} (- CO 2 R2)] m- [CH 2 -C (-R3) (- CO 2 R4-OH) -] n- [Xc] p-
(In the formula, R 1, R ₃ and R 5 represent H or CH _3. R ₂ represents an alkyl group having 1 to 12 carbon atoms and a cycloalkyl group. R 4 and R 6 represent —CH ₂ — and —C ₂ H ₄ —. Or -C ₃ H _6- , Xc represents a monomer unit polymerizable to Xa and Xb, m, n and p represent molar composition ratios, where m ≠ 0, n ≠ 0, m + n + p = 100 .)
Although the monomer as a monomer unit which comprises the polymer X of this invention is mentioned below, it is not limited to this.

  In X, the hydrophilic group means a group having a hydroxyl group or an ethylene oxide chain.

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

  The ethylenically unsaturated monomer Xb having no aromatic ring in the molecule and having a hydrophilic group is preferably acrylic acid or methacrylic acid ester as a monomer unit having a hydroxyl group. For example, acrylic acid (2-hydroxyethyl), List acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), or those in which these acrylic acids are replaced by methacrylic acid. Acrylic acid (2-hydroxyethyl) and methacrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), and acrylic acid (3-hydroxypropyl) are preferable.

  Xc is not particularly limited as long as it is an ethylenically unsaturated monomer other than Xa and Xb and copolymerizable, but preferably has no aromatic ring.

  The molar composition ratio m: n of Xa, Xb and Xc is preferably in the range of 99: 1 to 65:35, more preferably in the range of 95: 5 to 75:25. P of Xc is 0-10. Xc may be a plurality of monomer units.

  When the molar composition ratio of Xa is large, the compatibility with the cellulose ester is improved, but the retardation value Rt in the film thickness direction is increased. When the molar composition ratio of Xb is large, the compatibility is deteriorated, but the effect of reducing Rt is high. Further, if the molar composition ratio of Xb exceeds the above range, haze tends to occur during film formation, and it is preferable to optimize these and determine the molar composition ratio of Xa and Xb.

  As for the molecular weight of the polymer X, the weight average molecular weight is from 5,000 to 30,000, more preferably from 8,000 to 25,000.

  By setting the weight average molecular weight to 5,000 or more, it is preferable because the cellulose ester film has advantages such as less dimensional change under high temperature and high humidity and less curling as a polarizing plate protective film. When the weight average molecular weight is 30000 or less, the compatibility with the cellulose ester is further improved, and bleeding out under high temperature and high humidity, and further haze generation immediately after film formation is suppressed.

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

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

(Weight average molecular weight measurement method)
The weight average molecular weight Mw was measured using gel permeation chromatography.

  The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 100000-500 calibration curves with 13 samples were used. Thirteen samples are used at approximately equal intervals.

  The polymer Y of the present invention is a polymer having a weight average molecular weight of 500 or more and 3000 or less obtained by polymerizing an ethylenically unsaturated monomer Ya having no aromatic ring.

  A weight average molecular weight of 500 or more is preferable because the residual monomer of the polymer is reduced. Moreover, it is preferable to set it as 3000 or less in order to maintain retardation value Rt fall performance.

  Ya is preferably an acrylic or methacrylic monomer having no aromatic ring.

  The polymer Y used in the present invention is represented by the following general formula (2).

General formula (2)
-(Ya) k- (Yb) q-
More preferably, it is a polymer represented by the following general formula (2-1).

General formula (2-1)
_{- [CH 2 -C (-R5)} (- CO 2 R6)] k- [Yb] q-
(Wherein, R5 is, .Yb .R6 representing H or CH ₃ is representing an alkyl group or a cycloalkyl group having 1 to 12 carbon atoms, .k and q represents the Ya and copolymerizable monomer units, This represents the molar composition ratio, where k ≠ 0 and k + q = 100.)
Yb is not particularly limited as long as it is an ethylenically unsaturated monomer copolymerizable with Ya. Yb may be plural. k + q = 100, q is preferably 0-30.

  The ethylenically unsaturated monomer Ya constituting the polymer Y obtained by polymerizing an ethylenically unsaturated monomer having no aromatic ring is, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i- , N-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (N-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), cyclohexyl acrylate, acrylic acid (2- Ethyl hexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropiyl) ), Acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), methacrylic acid ester, the above acrylic acid ester changed to methacrylic acid ester; unsaturated acid, for example, acrylic acid, methacrylic acid And maleic anhydride, crotonic acid, itaconic acid and the like.

  Yb is not particularly limited as long as it is an ethylenically unsaturated monomer copolymerizable with Ya. Examples of vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl pivalate, and vinyl caproate. Vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl cinnamate and the like are preferred. Yb may be plural.

In order to synthesize the polymers X and Y, it is difficult to control the molecular weight in normal polymerization, and it is desirable to use a method that can make the molecular weights as uniform as possible without increasing the molecular weight. Such polymerization methods include a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than normal polymerization, and a mercapto compound in addition to the polymerization initiator. And a method of using a chain transfer agent such as carbon tetrachloride, a method of using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and further, Japanese Patent Application Laid-Open No. 2000-128911 or 2000-344823. Examples thereof include a compound having one thiol group and a secondary hydroxyl group, or a bulk polymerization method using a polymerization catalyst in which the compound and an organometallic compound are used in combination. In particular, a polymerization method using a compound having a thiol group and a secondary hydroxyl group in the molecule as a chain transfer agent. It is preferred.

  In this case, the terminal of the polymer X and the polymer Y has a hydroxyl group and a thioether resulting from the polymerization catalyst and the chain transfer agent. By this terminal residue, the compatibility between the polymers X and Y and the cellulose ester can be adjusted.

  The hydroxyl values of the polymers X and Y are preferably 30 to 150 [mg KOH / g].

(Measurement method of hydroxyl value)
This measurement conforms to JIS K 0070 (1992). This hydroxyl value is defined as the number of mg of potassium hydroxide required to neutralize acetic acid bonded to a hydroxyl group when 1 g of a sample is acetylated. Specifically, sample Xg (about 1 g) is precisely weighed in a flask, and 20 ml of an acetylating reagent (a solution obtained by adding pyridine to 20 ml of acetic anhydride to 400 ml) is accurately added thereto. An air cooling tube is attached to the mouth of the flask and heated in a glycerin bath at 95-100 ° C.

  After 1 hour and 30 minutes, the mixture is cooled, 1 ml of purified water is added from an air condenser, and acetic anhydride is decomposed into acetic acid. Next, titration is performed with a 0.5 mol / L potassium hydroxide ethanol solution using a potentiometric titrator, and the inflection point of the obtained titration curve is set as the end point. Further, as a blank test, titration is performed without a sample, and an inflection point of the titration curve is obtained.

  The hydroxyl value is calculated by the following formula.

Hydroxyl value = {(BC) × f × 28.05 / X} + D
(Wherein B is the amount of 0.5 mol / L potassium hydroxide ethanol solution used in the blank test (ml), and C is the amount of 0.5 mol / L potassium hydroxide ethanol solution used in the titration (ml). F is a factor of 0.5 mol / L potassium hydroxide ethanol solution, D is an acid value, and 28.05 is 1/2 of 1 mol amount of potassium hydroxide 56.11)
All of the above-mentioned X polymer polymers Y have excellent compatibility with cellulose esters, excellent productivity without evaporation and volatilization, good retention as a protective film for polarizing plates, low moisture permeability, and excellent dimensional stability. ing.

The content of the polymer X and the polymer Y in the cellulose ester film is preferably in a range satisfying the following formulas (i) and (ii). When the content of the polymer X is Xg (mass% = the mass of the polymer X / the mass of the cellulose ester × 100) and the content of the polymer Y is Yg (mass%),
Formula (i) 5 ≦ Xg + Yg ≦ 35 (mass%)
Formula (ii) 0.05 ≦ Yg / (Xg + Yg) ≦ 0.4
A preferable range of the formula (i) is 10 to 25% by mass.

  If the total amount of the polymer X and the polymer Y is 5% by mass or more, the polymer X and the polymer Y sufficiently act to reduce the retardation value Rt. Moreover, if it is 35 mass% or less as a total amount, adhesiveness with polarizer PVA is favorable.

  The polymer X and the polymer Y can be directly added and dissolved as a material constituting the dope liquid described later, or can be added to the dope liquid after being previously dissolved in an organic solvent for dissolving the cellulose ester.

<polyester>
The cellulose ester film of the present invention preferably contains the following polyester.

(Polyester represented by formula (3) or (4))
The cellulose ester film of the present invention preferably contains a polyester represented by the following general formula (3) or (4).

General formula (3) B1- (GA-) mG-B1
(In the formula, B1 represents a monocarboxylic acid, G represents a divalent alcohol, A represents a dibasic acid, and B1, G, and A do not contain an aromatic ring. M represents the number of repetitions. )
General formula (4) B2- (AG-) nA-B2
(In the formula, B2 represents a monoalcohol, G represents a divalent alcohol, A represents a dibasic acid, and B2, G, and A do not contain an aromatic ring. N represents the number of repetitions.)
In the general formulas (3) and (4), B1 represents a monocarboxylic acid component, B2 represents a monoalcohol component, G represents a divalent alcohol component, A represents a dibasic acid component, and these are synthesized. It represents what has been done. B1, B2, G, and A are all characterized by containing no aromatic ring. m and n represent the number of repetitions.

  There is no restriction | limiting in particular as monocarboxylic acid represented by B1, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, etc. can be used.

  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 1-12. 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 formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecyl Acids, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid, undecylenic acid And unsaturated fatty acids such as oleic acid, sorbic acid, linoleic acid, linolenic acid and arachidonic acid.

  The monoalcohol component represented by B2 is not particularly limited, and known alcohols can be used. For example, an aliphatic saturated alcohol or aliphatic unsaturated alcohol having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-12.

  Examples of the divalent alcohol component represented by G include the following, but the present invention is not limited thereto. For example, ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,5-pentanediol, , 6-hexanediol, 1,5-pentylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, etc., among which ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,6-hexanediol, diethylene glycol and triethylene glycol are preferable, and 1,3-propylene glycol is more preferable. 1,4-butylene glycol 1,6-hexanediol, are used preferably diethylene glycol.

  The dibasic acid (dicarboxylic acid) component represented by A is preferably an aliphatic dibasic acid or an alicyclic dibasic acid. Examples of the aliphatic dibasic acid include malonic acid, succinic acid, glutaric acid, Adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, etc., especially aliphatic dicarboxylic acids having 4 to 12 carbon atoms, at least one selected from these To do. That is, two or more dibasic acids may be used in combination.

  m and n represent the number of repetitions and are preferably 1 or more and 170 or less.

(Polyester represented by formula (5) or (6))
The cellulose ester film of the present invention preferably contains a polyester represented by the following general formula (5) or (6).

General formula (5) B1- (GA-) mG-B1
(In the formula, B1 represents a monocarboxylic acid having 1 to 12 carbon atoms, G represents a divalent alcohol having 2 to 12 carbon atoms, and A represents a dibasic acid having 2 to 12 carbon atoms. B1, G , A does not contain an aromatic ring, and m represents the number of repetitions.)
General formula (6) B2- (AG-) nA-B2
(In the formula, B2 represents a monoalcohol having 1 to 12 carbon atoms, G represents a divalent alcohol having 2 to 12 carbon atoms, and A represents a dibasic acid having 2 to 12 carbon atoms. B2, G, (A does not contain an aromatic ring. N represents the number of repetitions.)
In the general formulas (5) and (6), B1 represents a monocarboxylic acid component, B2 represents a monoalcohol component, G represents a divalent alcohol component having 2 to 12 carbon atoms, and A represents 2 to 2 carbon atoms. Twelve dibasic acid components are represented and synthesized by them. B1, G, and A do not contain an aromatic ring. m and n represent the number of repetitions.

  B1 and B2 are synonymous with B1 and B2 in the general formula (3) or (4).

  G and A are alcohol components or dibasic acid components having 2 to 12 carbon atoms in G and A in the above general formula (3) or (4).

  The weight average molecular weight of the polyester is preferably 20000 or less, and more preferably 10,000 or less. In particular, polyesters having a weight average molecular weight of 500 to 10,000 have good compatibility with cellulose esters and are preferably used.

  Polycondensation of polyester is performed by a conventional method. For example, a direct reaction of the above dibasic acid and glycol, the above dibasic acid or an alkyl ester thereof, for example, a polyesterification reaction or transesterification reaction between a dibasic acid methyl ester and a glycol, or a hot melt condensation method, Alternatively, it can be easily synthesized by any method of dehydrohalogenation reaction between acid chlorides of these acids and glycols, but polyesters having a weight average molecular weight not so large are preferably directly reacted.

  Polyester having a high distribution on the low molecular weight side has very good compatibility with the cellulose ester, and after forming the film, it is possible to obtain a cellulose ester film having low moisture permeability and high transparency. A conventional method can be used as a method for adjusting the molecular weight without particular limitation. For example, although depending on the polymerization conditions, the amount of these monovalent compounds can be controlled by a method of blocking the molecular ends with a monovalent acid or monovalent alcohol.

  In this case, a monovalent acid is preferable from the viewpoint of polymer stability. For example, acetic acid, propionic acid, butyric acid and the like can be mentioned, but during the polycondensation reaction, they are not distilled out of the system, but are stopped and such monovalent acids are removed out of the reaction system. Those that are easily removed are sometimes selected, but these may be mixed and used. In the case of a direct reaction, the weight average molecular weight can also be adjusted by measuring the timing at which the reaction is stopped by the amount of water distilled off during the reaction. In addition, it can be adjusted by biasing the number of moles of glycol or dibasic acid to be charged or by controlling the reaction temperature.

  The polyester according to the present invention is preferably contained in an amount of 1 to 40% by mass relative to the cellulose ester, and the polyester represented by the general formula (5) or (6) is preferably contained in an amount of 2 to 30% by mass. It is preferable to contain 5-15 mass% especially.

<Compound with furanose structure or pyranose structure>
The cellulose ester film of the present invention comprises a compound having at least one furanose structure or pyranose structure and esterifying all or part of OH groups in a compound having 1 to 12 furanose structures or pyranose structures bonded thereto. Is preferred.

  Examples of preferable “compounds having at least one furanose structure or pyranose structure and having 1 to 12 furanose structures or pyranose structures bonded to each other” include, for example, the following. It is not limited to these.

  Examples include glucose, galactose, mannose, fructose, xylose, arabinose, lactose, sucrose, cellobiose, cellotriose, maltotriose, raffinose, and the like, and those having both a furanose structure and a pyranose structure are particularly preferable. An example is sucrose.

  The monocarboxylic acid used in the “compound obtained by esterifying all or part of the OH groups in a compound having at least one furanose structure or pyranose structure and having 1 to 12 furanose structures or pyranose structures bonded” according to the present invention. There is no restriction | limiting in particular as an acid, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. The carboxylic acid used may be one type or a mixture of two or more types.

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

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

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group or alkoxy group is introduced into the benzene ring of benzoic acid such as benzoic acid or toluic acid, cinnamic acid, benzylic acid, biphenylcarboxylic acid, naphthalenecarboxylic acid, tetralin An aromatic monocarboxylic acid having two or more benzene rings such as carboxylic acid, or a derivative thereof can be mentioned, and benzoic acid is particularly preferable.

  Details of the production methods of these compounds are described in JP-A Nos. 62-42996 and 10-237084.

  Specific examples are given below, but the present invention is not limited thereto.

(Sulfone compound)
For the cellulose film of the present invention, the following sulfone compound exhibiting negative orientation birefringence with respect to the stretching direction can also be used.

In the following general formula (7), R ¹ represents an alkyl group or an aryl group, and R ² and R ³ each independently represent a hydrogen atom, an alkyl group, or an aryl group. Moreover, it is particularly preferable that the total number of carbon atoms of R ¹ , R ² and R ³ is 10 or more.

In the general formula (8), R ⁴ and R ⁵ each independently represents an alkyl group or an aryl group. The total number of carbon atoms of R ⁴ and R ⁵ is 10 or more, and each of the alkyl group and aryl group may have a substituent. As the substituent, a fluorine atom, an alkyl group, an aryl group, an alkoxy group, a sulfone group, and a sulfonamide group are preferable, and an alkyl group, an aryl group, an alkoxy group, a sulfone group, and a sulfonamide group are particularly preferable.

  Further, the alkyl group may be linear, branched or cyclic, and preferably has 1 to 25 carbon atoms, more preferably 6 to 25, and more preferably 6 to 20 (E.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, amyl, isoamyl, t-amyl, hexyl, cyclohexyl, heptyl, octyl, bicyclooctyl, nonyl, adamantyl, decyl, t-octyl, undecyl, Dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, didecyl) are particularly preferred. As the aryl group, those having 6 to 30 carbon atoms are preferable, and those having 6 to 24 carbon atoms (for example, phenyl, biphenyl, terphenyl, naphthyl, binaphthyl, triphenylphenyl) are particularly preferable.

  Although the preferable example of a compound represented by General formula (7) or General formula (8) is shown below, this invention is not limited to these specific examples.

<Other additives>
In addition to the compound having negative orientation birefringence, the cellulose ester film of the present invention may contain an additive that can be added to a normal cellulose ester film.

  Examples of these additives include plasticizers, ultraviolet absorbers, and fine particles.

  The plasticizer that can be used in the present invention is not particularly limited, but preferably a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a fatty acid ester plasticizer, and a polyvalent plasticizer. It is selected from alcohol ester plasticizers, polyester plasticizers, acrylic plasticizers and the like. Of these, when two or more plasticizers are used, at least one plasticizer 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 ultraviolet absorber that can be used in the present invention aims to improve durability by absorbing ultraviolet rays of 400 nm or less, and preferably has a transmittance of 10% or less at a wavelength of 370 nm. More preferably, it is 5% or less, and further 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. It is good also as a polymer type ultraviolet absorber.

  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, calcined kaolin, calcined calcium silicate, and hydrated silicic acid. Mention may be made of calcium, aluminum silicate, magnesium silicate and calcium phosphate. Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable.

  The average primary particle size of the fine particles is preferably 5 to 50 nm, and more preferably 7 to 20 nm. These are preferably contained mainly as secondary aggregates having a particle size of 0.05 to 0.3 μm. The content of these fine particles in the cellulose ester film is preferably 0.05 to 1% by mass, particularly preferably 0.1 to 0.5% by mass. In the case of a cellulose ester film having a multilayer structure by the co-casting method, it is preferable to contain fine particles of this addition amount on the surface.

  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.). it can.

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

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

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

<Polarizing plate protective film manufacturing method>
Next, the manufacturing method of the cellulose-ester film which forms the polarizing plate protective film of this invention is demonstrated.

  The cellulose ester film according to the present invention is preferably a cellulose ester film produced by a solution casting method or melt casting.

  The cellulose ester film of the present invention is prepared by dissolving a cellulose ester, a compound having negative orientation birefringence and an additive in a solvent to prepare a dope, flowing on an endless metal support that moves the dope indefinitely. The step of extending, the step of drying the cast dope as a web, the step of peeling from the metal support, the step of stretching or maintaining the width, the step of further drying, and the step of winding up the finished film are performed.

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

  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 average acetylation degree (acetyl 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 (acetyl group substitution degree 2.4), cellulose Acetate propionate is a good solvent, and 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. Moreover, the solvent used for melt | dissolution of a cellulose ester collect | recovers the solvent removed from the film by drying at the film-forming process, and uses this again.

  A general method can be used as a dissolution method of 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 does not boil under pressure, in order to prevent the formation 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.

The bright spot foreign matter was placed in a crossed Nicols state with two polarizing plates, a rolled cellulose ester was placed between them, and light was applied from the side of one polarizing plate, and observed from the side of the other polarizing plate. It is a point (foreign matter) that light from the opposite side appears to leak sometimes, 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 a normal method, but the method of filtering while heating at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil under pressure is the filtration pressure before and after filtration. The increase in the difference (referred to as differential pressure) is small and preferable. 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. As the metal support, a stainless steel belt or a drum whose surface is plated with a casting is preferably used. The cast width can be 1 to 4 m. The surface temperature of the metal support in the casting step is −50 ° C. to a temperature lower than the boiling point of the solvent, and a higher temperature is preferable because the web can be dried faster. May deteriorate. A preferable support body temperature is 0-40 degreeC, and 5-30 degreeC is still more preferable.

  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 warm air is used, wind at a temperature higher than the target temperature may be used.

  In order for the roll cellulose ester 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. %, Particularly preferably 20 to 30% by mass or 70 to 120% by mass.

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

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

  In the drying step of the roll cellulose ester, the web is peeled off from the metal support and further dried, and the residual solvent amount is preferably 1% by mass or less, more preferably 0.1% by mass or less. Particularly preferably, it is 0 to 0.01% by 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 of the present invention, the web is stretched in the conveying direction (= long direction) where the residual solvent amount of the web is large immediately after peeling from the metal support, and both ends of the web are gripped with clips or the like. It is particularly preferable to perform stretching in the width direction by the tenter method.

<Polarizing plate and liquid crystal display device>
Since the polarizing plate protective film of the present invention is a cellulose ester film, there is an advantage that a conventional polarizing plate production process can be utilized. In particular, a generally used polyvinyl alcohol derivative is stretched to form a dichroic dye. Since the polarizing plate protective film according to the present invention can be directly bonded with a water-soluble adhesive material such as water paste to the utilized light-absorbing polarizer, it is greatly excellent in thinning and productivity.

  In addition, since the polarizing plate protective film according to the present invention can be delivered to the manufacturing process of the polarizing plate in the form of a roll as a long film, the roll-shaped film can be prevented from being scratched or adhering to dust. There is also an advantage that it is not necessary to use a protective sheet. In particular, in the case where the polarizing plate has a configuration of polarizing plate protective film / polarizer / polarizing plate protective film, it is preferable that each is a long film, and it is preferable to perform roll-to-roll in order to bond each of them. .

  When used in a liquid crystal display device, the polarizing plate protective film of the present invention is characterized by being used between a liquid crystal cell and a polarizer on the backlight source side.

  FIG. 1 is a schematic view of an IPS mode liquid crystal display device according to the present invention.

  A light guide plate 14, a prism sheet 13, and a backlight side polarizing plate 12 are disposed adjacent to the backlight 15 from below. The polarizer 8 of the backlight side polarizing plate 12 is sandwiched between the polarizing plate protective film 7 and the polarizing plate protective film 9. Next, there is an IPS type liquid crystal cell 11 having a configuration of an electrode side cell glass substrate 6, an IPS type liquid crystal cell 5, and a non-electrode type cell glass substrate 4, a polarizer 2 constituting a viewing side polarizing plate 10, and a polarizing plate protective film 1. There are three.

  The polarizing plate protective film of this invention is shown by the polarizing plate protective film 7 in FIG.

  Other polarizing plate protective films 1, 3, and 9 are not particularly limited. For example, polyester films such as polyethylene terephthalate and polyethylene naphthalate, polyethylene films, polypropylene films, polycycloolefin films, cellophane, and cellulose acetate films. , Cellulose acetate butyrate film, cellulose acetate phthalate film, cellulose acetate propionate film, cellulose triacetate, film made of cellulose esters such as cellulose nitrate or derivatives thereof, polyvinylidene chloride film, polyvinyl alcohol film, ethylene vinyl alcohol Film, syndiotactic polystyrene film, polycarbonate film Cycloolefin polymer film (for example, ARTON (manufactured by JSR), ZEONEX, ZEONOR (manufactured by ZEON)), polymethylpentene film, polyetherketone film, polyethersulfone film, polysulfone film, polyetherketoneimide film, Examples thereof include a polyamide film, an acrylic film, and a polyacrylate film.

  In the present invention, cellulose ester films such as cellulose acetate propionate film and cellulose triacetate film (TAC film) (for example, Konica Minoltap KC8UX, KC4UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5 manufactured by Konica Minolta Opto Co., Ltd., KC8UY, KC4UY, KC12UR, KC16UR, KC4UE, KC8UE, KC4FR-1, KC4FR-2 etc. are preferably used), cycloolefin polymer film, polycarbonate film, polyester film or polyacryl film are transparent, mechanical properties, optical Preferred in that there is no anisotropy, etc., especially cellulose ester film, cycloolefin polymer film is preferred, as described above From the viewpoint of producing a polarizing plate with Lumpur to roll, a cellulose ester film excellent in saponification adaptability is most preferred. These resin films may be films formed by a melt casting method or a solution casting method.

  Further, the polarizing plate protective film 3 used between the polarizer on the viewing side and the liquid crystal cell is the same as the polarizing plate protective film 7 of the present invention used between the liquid crystal cell on the backlight source side and the polarizer. It is also preferable.

  Moreover, it is also preferable that the polarizing plate used for the IPS mode type liquid crystal display device is a polarizing plate protective film that is not a retardation film for IPS. As described above, the retardation film for IPS generally has a retardation value Rt value in the range of −70 to 70 nm and a Ro value in the range of 70 to 390 nm (for example, the Rt value is −30 nm and the Ro value is 130 nm). is there. In the present invention, an ordinary TAC film having a Ro value of 0 to 20 nm and an Rt value of 10 to 50 nm is used without reducing the manufacturing cost and simplifying the members without using an expensive IPS retardation film. The polarizing plate protective films 1, 3, and 9 are preferably used.

<Horizontal electric field switching mode type liquid crystal display device>
By incorporating a polarizing plate using the polarizing plate protective film of the present invention into a commercially available IPS (In Plane Switching) mode type liquid crystal display device, it has excellent visibility, excellent color shift, corner unevenness, and front contrast characteristics. The liquid crystal display device of the present invention can be manufactured.

  The transverse electric field switching mode of the present invention includes a fringe-field switching (FFS) mode in the present invention, and the polarizing plate of the present invention can be incorporated in the same manner as the IPS mode, and has the same effect. The liquid crystal display device of the invention can be manufactured.

(IPS mode liquid crystal cell)
The liquid crystal layer of the liquid crystal panel in the IPS mode type liquid crystal display device is homogeneously aligned parallel to the substrate surface in the initial state, and the director of the liquid crystal layer is parallel to the electrode wiring direction when no voltage is applied. The direction of the director of the liquid crystal layer shifts to a direction perpendicular to the electrode wiring direction when a voltage is applied, and the director direction of the liquid crystal layer is the direction of the director when no voltage is applied. When tilted in the direction of 45 ° electrode wiring, the liquid crystal layer when the voltage is applied rotates the azimuth angle of the polarization by 90 ° like a half-wave plate, and the transmission axis of the output side deflection plate and the polarization The azimuth angles of the two coincide with each other to display white.

  In general, the thickness of the liquid crystal layer is constant, but since it is driven by a lateral electric field, it is considered that a slight unevenness in the thickness of the liquid crystal layer can increase the response speed to switching. Even if the thickness of the layer is not constant, the effect can be maximized.

  In this invention, there is little influence with respect to the change of the thickness of a liquid crystal layer. The thickness of the liquid crystal layer capable of greatly exerting the effect in the present invention is 2 to 6 μm, and preferably 3 to 5.5 μm.

  The liquid crystal display device of the present invention is used for a large liquid crystal television. As a screen size, it can be used for 17 or more types, preferably 26 to 100 types.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1
<Preparation of polarizing plate protective film>
(Polarizing plate protective film A)
[Silicon dioxide dispersion A]
Aerosil 972V (manufactured by Nippon Aerosil Co., Ltd.) 12 parts by mass (average primary particle diameter 16 nm, apparent specific gravity 90 g / liter)
88 parts by mass of ethanol or more was stirred and mixed with a dissolver for 30 minutes, and then dispersed with Manton Gorin. The liquid turbidity after dispersion was 200 ppm. 88 parts by mass of methylene chloride was added to the silicon dioxide dispersion while stirring, and the mixture was stirred and mixed with a dissolver for 30 minutes to prepare a silicon dioxide dispersion dilution A.

[Preparation of inline additive solution A]
Tinuvin 109 (manufactured by Ciba Specialty Chemicals) 11 parts by weight Tinuvin 171 (manufactured by Ciba Specialty Chemicals) 5 parts by weight 100 parts by weight of methylene chloride Dissolved and filtered.

  To this, 36 parts by mass of silicon dioxide dispersion diluent A was added with stirring, and the mixture was further stirred for 30 minutes, and then cellulose acetate propionate (acetyl group substitution degree 1.9, propionyl group substitution degree 0.8) 6 masses. The mixture was added with stirring, and further stirred for 60 minutes, and then filtered through a polypropylene wind cartridge filter TCW-PPS-1N manufactured by Advantech Toyo Co., Ltd. to prepare an in-line additive solution A.

[Preparation of dope solution A]
Cellulose ester (cellulose triacetate synthesized from linter cotton)
100 parts by mass (Mn = 148000, Mw = 310000, Mw / Mn = 2.1, acetyl group substitution degree 2.92)
Trimethylolpropane tribenzoate 5.0 parts by weight Ethylphthalylethyl glycolate 5.5 parts by weight Methylene chloride 440 parts by weight Ethanol 40 parts by weight The above is put into a closed container, heated and stirred, and completely dissolved. Azumi Filter Paper No. manufactured by Azumi Filter Paper Co., Ltd. 24, and the dope liquid A was prepared.

  The dope solution A was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. in the film production line. In-line additive solution line was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. Add 2 parts by mass of the filtered in-line additive A to 100 parts by mass of the filtered dope liquid A, mix well with an in-line mixer (Toray static type in-pipe mixer Hi-Mixer, SWJ), and then cast the belt. Using the apparatus, it was cast uniformly on a stainless steel band support at a temperature of 35 ° C. and a width of 1.8 m. With the stainless steel band support, the solvent was evaporated until the residual solvent amount became 120%, and then peeled off from the stainless steel band support. The peeled cellulose ester web was evaporated at 35 ° C., slit to 1.6 m width, and then stretched 1.1 times in the TD direction (direction perpendicular to the film transport direction) with a tenter, while 135 Drying was performed at a drying temperature of ° C. At this time, the residual solvent amount when starting stretching with a tenter was 30%.

  Then, drying is completed while transporting the drying zone of 110 ° C. and 120 ° C. with many rolls, slitting to a width of 1.4 m, a knurling process of 15 mm in width and 10 μm in average height is applied to both ends of the film, and the initial winding is performed A polarizing plate protective film A was obtained by winding it around a 6-inch inner core with a tension of 220 N / m and a final tension of 110 N / m. The draw ratio in the MD direction (same direction as the film transport direction) immediately after peeling calculated from the rotational speed of the stainless steel band support and the operating speed of the tenter was 1.07. The residual solvent amount of the polarizing plate protective film A was 0.2%, the average film thickness was 80 μm, and the winding number was 4000 m.

(Polarizing plate protective film B)
[Silicon dioxide dispersion B]
Aerosil 972V (manufactured by Nippon Aerosil Co., Ltd.) 12 parts by mass (average primary particle diameter 16 nm, apparent specific gravity 90 g / liter)
88 parts by mass of ethanol or more was stirred and mixed with a dissolver for 30 minutes, and then dispersed with Manton Gorin. The liquid turbidity after dispersion was 200 ppm. 88 parts by mass of methylene chloride was added to the silicon dioxide dispersion while stirring, and the mixture was stirred and mixed for 30 minutes with a dissolver to prepare a silicon dioxide dispersion dilution B.

[Preparation of inline additive solution B]
Tinuvin 109 (manufactured by Ciba Specialty Chemicals) 11 parts by weight Tinuvin 171 (manufactured by Ciba Specialty Chemicals) 5 parts by weight 100 parts by weight of methylene chloride Dissolved and filtered.

  To this, 36 parts by mass of silicon dioxide dispersion diluent B was added with stirring, and the mixture was further stirred for 30 minutes, and then cellulose acetate propionate (acetyl group substitution degree 1.9, propionyl group substitution degree 0.8) 6 masses. The mixture was added with stirring, and further stirred for 60 minutes, and then filtered through a polypropylene wind cartridge filter TCW-PPS-1N manufactured by Advantech Toyo Co., Ltd. to prepare an in-line additive solution B.

(Preparation of dope solution B)
Cellulose ester (cellulose triacetate synthesized from linter cotton)
100 parts by mass (Mn = 148000, Mw = 310000, Mw / Mn = 2.1, acetyl group substitution degree 2.92)
Trimethylolpropane tribenzoate 5.0 parts by weight Ethylphthalylethyl glycolate 5.5 parts by weight Methylene chloride 440 parts by weight Ethanol 40 parts by weight The above is put into a closed container, heated and stirred, and completely dissolved. Azumi Filter Paper No. manufactured by Azumi Filter Paper Co., Ltd. 24, and the dope liquid B was prepared.

  The dope solution B was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. in the film production line. In-line additive solution line was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. in the in-line additive solution line. Add 3 parts by mass of filtered inline additive B to 100 parts by mass of filtered dope liquid B, mix well with an inline mixer (Toray static type in-pipe mixer Hi-Mixer, SWJ), and then belt cast Using an apparatus, the film was uniformly cast on a stainless steel band support at a temperature of 32 ° C. and a width of 1.8 m. With the stainless steel band support, the solvent was evaporated until the amount of residual solvent reached 100%, and then peeled off from the stainless steel band support. The peeled cellulose ester web was evaporated at 35 ° C., slit to 1.6 m width, and then stretched by 1.05 times in the TD direction (direction perpendicular to the film transport direction) with a tenter. Drying was performed at a drying temperature of ° C. At this time, the residual solvent amount when starting stretching with a tenter was 20%.

  Then, drying was completed while transporting the drying zone at 120 ° C and 110 ° C with many rolls, slitting to 1.4m width, and knurling of width 15mm and average height 10µm was applied to both ends of the film. A polarizing plate protective film B was obtained by winding it around a 6-inch inner diameter core with a tension of 220 N / m and a final tension of 110 N / m. The draw ratio in the MD direction (same direction as the film transport direction) immediately after peeling calculated from the rotational speed of the stainless steel band support and the operating speed of the tenter was 1.07. The residual solvent amount of the polarizing plate protective film B was 0.02%, the average film thickness was 40 μm, and the number of turns was 4000 m.

(Polarizing plate protective film C1)
<Synthesis of Polymer X>
In a glass flask equipped with a stirrer, two dropping funnels, a gas introduction tube and a thermometer, 40 g of the monomer Xa and Xb mixed solution of the types and ratios (molar composition ratio) shown in Table 1, and 2 g of mercaptopropionic acid as a chain transfer agent And 30 g of toluene were charged, and the temperature was raised to 90 ° C. Thereafter, from one dropping funnel, 60 g of a mixture of monomers Xa and Xb having the types and ratios (molar composition ratio) shown in Table 1 was dropped over 3 hours, and at the same time, azobis dissolved in 14 g of toluene from the other funnel. 0.4 g of isobutyronitrile was added dropwise over 3 hours. Thereafter, 0.6 g of azobisisobutyronitrile dissolved in 56 g of toluene was added dropwise over 2 hours, and the reaction was further continued for 2 hours to obtain polymer X. The obtained polymer X was solid at room temperature. The weight average molecular weight of the polymer X is shown in Table 1 by the following measurement method.

  In Table 1, MMA and HEA are abbreviations for the following compounds, respectively.

MMA: methyl methacrylate HEA: 2-hydroxyethyl acrylate (weight average molecular weight measurement)
The weight average molecular weight was measured using gel permeation chromatography.

  The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 100000-500 calibration curves with 13 samples were used. Thirteen samples are used at approximately equal intervals.

<Synthesis of polymer Y>
Bulk polymerization was performed by the polymerization method described in JP-A No. 2000-128911. That is, the following methyl acrylate (MA) as monomer Ya was introduced into a flask equipped with a stirrer, nitrogen gas inlet tube, thermometer, inlet, and reflux condenser, and nitrogen gas was introduced to replace the inside of the flask with nitrogen gas. The following thioglycerol was added with stirring. After the addition of thioglycerol, the temperature of the contents was appropriately changed and polymerization was performed for 4 hours. The contents were returned to room temperature, and 20 parts by mass of a 5% by weight benzoquinone tetrahydrofuran solution was added thereto to stop the polymerization. The contents were transferred to an evaporator, and tetrahydrofuran, residual monomer and residual thioglycerol were removed under reduced pressure at 80 ° C. to obtain Polymer Y shown in Table 1. The obtained polymer Y was liquid at room temperature. The weight average molecular weight of the polymer Y is shown in Table 1 by the above measurement method.

Methyl acrylate 100 parts by weight Thioglycerol 5 parts by weight

[Composition of dope C1]
(Silicon dioxide dispersion diluent C1)
Aerosil 972V (manufactured by Nippon Aerosil Co., Ltd.) 12 parts by mass (average diameter of primary particles 16 nm, apparent specific gravity 90 g / liter)
88 parts by mass of ethanol or more was stirred and mixed with a dissolver for 30 minutes, and then dispersed with Manton Gorin. The liquid turbidity after dispersion was 200 ppm. 88 parts by mass of methylene chloride was added to the silicon dioxide dispersion while stirring, and the mixture was stirred and mixed for 30 minutes with a dissolver to prepare a silicon dioxide dispersion dilution C1.

(Dope additive liquid C1)
Methylene chloride 50 parts by weight Polymer X 12 parts by weight Polymer Y 7 parts by weight Silicon dioxide dispersion diluent C1 10 parts by weight Tinuvin 109 (manufactured by Ciba Specialty Chemicals) 1.2 parts by weight Tinuvin 171 (manufactured by Ciba Specialty Chemicals) ) 0.8 parts by mass After the methylene chloride, the polymer X, and the polymer Y were completely dissolved while stirring, the silicon dioxide dispersion diluted liquid C1 was added and stirred to prepare a dope additive liquid C1.

(Preparation of dope C1)
Cellulose ester (cellulose triacetate synthesized from linter cotton, acetyl group substitution degree 2.92) 100 parts by mass Methylene chloride 380 parts by mass Ethanol 30 parts by mass Dope additive C1 The above preparation part by mass The solution was completely dissolved while stirring, and Azumi Filter Paper No. 24 was used to prepare a dope C1.

  The dope solution was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd., and uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 2 m using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the residual solvent amount became 105%, and the film was peeled from the stainless steel band support with a peeling tension of 162 N / m. The peeled cellulose ester web was evaporated at 35 ° C., slit to 1.6 m width, and then dried at a drying temperature of 135 ° C. while stretching 1.1 times in the width direction with a tenter. At this time, the residual solvent amount when starting stretching with a tenter was 10%. After stretching with a tenter and releasing the width holding at 130 ° C., the width is released, and then the drying is finished while transporting the drying zone at 120 ° C. and 130 ° C. with a number of rolls, slit to a width of 1.4 m, A knurling process having a width of 10 mm and a height of 7 μm was applied to both ends of the film, and the film was wound around a core having an inner diameter of 6 inches with an initial tension of 220 N / m and a final tension of 110 N / m to obtain a polarizing plate protective film C1. The draw ratio in the MD direction calculated from the rotational speed of the stainless steel band support and the operating speed of the tenter was 1.1 times. The residual solvent amount of the polarizing plate protective film C1 was less than 0.1%, respectively, and the film thickness was 80 μm.

(Polarizing plate protective film C2)
A polarizing plate protective film C2 was produced in the same manner as the polarizing plate protective film C1 except that the film thickness was changed to 40 μm.

  The produced polarizing plate protective films A, B, C1, and C2 were cut out and evaluated as follows.

(Measurement of Ro and Rt)
The average refractive index of the film was measured using an Abbe refractometer (4T).

  Retardation of a film at a wavelength of 590 nm in a film sample that was allowed to stand for 24 hours in an environment of 23 ° C. and 55% RH using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments) Measurements were made. The film thickness measured using the above-mentioned average refractive index and a commercially available micrometer was input, and the values of in-plane retardation (Ro) and retardation in the thickness direction (Rt) were obtained according to the following formulas.

Formula (1) Ro = (nx−ny) × d
Formula (2) Rt = {(nx + ny) / 2−nz} × d
(Here, the refractive index in the slow axis direction in the plane of the cellulose ester film is nx, the refractive index in the direction perpendicular to the slow axis in the plane is ny, the refractive index in the thickness direction of the film is nz, d is Represents the thickness (nm) of the film.)
(Rt temperature fluctuation, Rt humidity fluctuation)
Rt temperature fluctuation: The ΔRt value of the difference between the Rt values measured in a state where the film sample was allowed to stand for 24 hours in a 23 ° C. relative humidity 55% environment and a 35 ° C. relative humidity 27% environment was determined.

  Rt humidity fluctuation: ΔRt value of the difference between Rt values measured in a state where the film sample was allowed to stand for 24 hours in a 23 ° C. relative humidity 20% environment and a 23 ° C. relative humidity 80% environment was determined.

(Film modulus)
The measurement was performed in an environment of 23 ° C. and 55% RH according to the method described in JIS K 7127. The sample width was cut to 10 mm and the length was 130 mm, the distance between chucks was set to 100 mm at an arbitrary temperature, and a tensile test was performed at a pulling speed of 100 mm / min. At that time, the elastic modulus in two directions of the longitudinal direction (MD) and the width direction (TD) of the film was determined.

  The above results are shown in Table 2.

  Using the polarizing plate protective films A, B, C1, and C2, a viewing-side polarizing plate and a backlight-side polarizing plate were prepared with the configuration shown in Table 3.

  The polarizing film was a uniaxially stretched polyvinyl alcohol film having a thickness of 120 μm (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.

  Subsequently, according to the following processes 1-5, the polarizing film and the said polarizing plate protective film were bonded together, and the visual recognition side and the backlight side polarizing plate were produced.

  Step 1: Dipped in a 1 mol / L sodium hydroxide solution at 50 ° C. for 60 seconds, then washed with water and dried to obtain a polarizing plate protective film saponified on 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 this was placed on the polarizing plate protective film treated in Step 1 and laminated.

Step 4: The polarizing plate protective film and the polarizing 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.

  Process 5: The sample which bonded together the polarizing film produced at the process 4 and the polarizing plate protective film in the 80 degreeC dryer was dried for 2 minutes, and the polarizing plate was produced.

<Evaluation>
<Evaluation of contrast of liquid crystal display device>
It measured in the dark room of 23 degreeC using the following methods, a liquid crystal cell, and a display apparatus.

  A liquid crystal panel including an IPS mode liquid crystal cell [Panasonic liquid crystal television VIERA TH-26LX60 manufactured by Matsushita Electric Industrial Co., Ltd.] is taken out, and the polarizing plates arranged above and below the liquid crystal cell are removed. The glass surfaces (front and back) were washed. Subsequently, an acrylic adhesive (thickness 20 μm) was used on both surfaces of the liquid crystal cell so that the polarizing plate produced as described above was parallel (0 ± 0.2 degrees) with the long axis of the liquid crystal cell. Stuck.

  The configuration of the polarizing plate and the liquid crystal cell is as follows.

(Viewing side) Polarizing plate protective film 1st sheet / polarizing film / polarizing plate protective film 2nd sheet / IPS mode liquid crystal cell / polarizing plate protective film 3rd sheet / polarizing film / polarizing plate protective film 4th sheet (backlight side) )
The viewing angle of this liquid crystal display device was measured using EZ-contrast manufactured by ELDIM. As the measurement method, the contrast of the liquid crystal panel during white display and black display was ranked as follows for the contrast with respect to an inclination angle of 80 ° from the normal direction to the panel surface in all directions.

A: Contrast is 30 or more in all directions. ○: Contrast is in all directions 15 or more. Δ: A region in which the contrast is 5 or more and less than 15 exists. X: There is a region in which the contrast is less than 5 in all directions. Shift evaluation>
The liquid crystal display panel was displayed in black, and the color shift was ranked as follows by visual observation.

◎: Black appears to be clear and clear, no color shift is observed ○: Black appears to be crisp and clear, but slight color shift is observed Low, color shift observed x: No black spots, low sharpness, and color shift concerns <Evaluation of color 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 color unevenness was present.

    A: The color unevenness is not a concern at all.

◯: Partially felt color unevenness but within acceptable range X: Feels color unevenness, not acceptable Allowable results are shown in Table 3.

  It can be seen that the liquid crystal display devices 4 to 7 incorporating the polarizing plate protective film of the present invention are excellent in color shift, color unevenness, and contrast in comparison.

  Moreover, when only the liquid crystal display device in the liquid crystal display device 1 and the liquid crystal display device 6 was evaluated using a Hitachi liquid crystal television W32L-H9000, similar results were obtained.

Example 2
In the same manner as the production of the polarizing plate protective film C1 of Example 1, the polarizing plate protective film produced by changing the film thickness as shown in Table 4 was used. The polarizing plate protective film C1 was used in place of the polarizing plate 3 to prepare a liquid crystal display device.

  Evaluation of Example 1 was performed using the produced polarizing plate protective film and the liquid crystal display device, and the results are shown in Table 4.

  The liquid crystal display devices 13 to 16 using the polarizing plate protective film having a film thickness of 20 to 55 μm in which the Rt temperature fluctuation and the Rt humidity fluctuation are in the range of the present invention reproduce the example 1, and are excellent in color shift, color unevenness, and contrast. I understand that

Example 3
A polarizing plate protective film C3 was prepared using the following compound instead of the polymer X and the polymer Y used in the polarizing plate protective film C1 of Example 1.

(Polarizing plate protective film C3)
[Composition of dope C3]
(Silicon dioxide dispersion dilution C3)
Aerosil 972V (manufactured by Nippon Aerosil Co., Ltd.) 12 parts by mass (average diameter of primary particles 16 nm, apparent specific gravity 90 g / liter)
88 parts by mass of ethanol or more was stirred and mixed with a dissolver for 30 minutes, and then dispersed with Manton Gorin. The liquid turbidity after dispersion was 200 ppm. 88 parts by mass of methylene chloride was added to the silicon dioxide dispersion while stirring, and the mixture was stirred and mixed for 30 minutes with a dissolver to prepare a silicon dioxide dispersion dilution C3.

(Dope additive liquid C3)
Methylene chloride 50 parts by mass General formula (7) Exemplified compound A-19 19 parts by mass Silicon dioxide dispersion diluent C3 10 parts by mass Tinuvin 109 (manufactured by Ciba Specialty Chemicals) 1.2 parts by mass Tinuvin 171 (Ciba Specialty Chemicals ( Co., Ltd.) 0.8 parts by mass Methylene chloride and compound C3 were completely dissolved while stirring, and then a silicon dioxide dispersion diluent C3 was added and stirred and mixed to prepare a dope additive solution C3.

(Preparation of dope C3)
Cellulose ester (cellulose triacetate synthesized from linter cotton, acetyl group substitution degree 2.92) 100 parts by mass Methylene chloride 380 parts by mass Ethanol 30 parts by mass Dope additive liquid C3 The above preparation part by mass The solution was completely dissolved while stirring, and Azumi Filter Paper No. 24 was used to prepare dope C3.

  The dope solution was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd., and uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 2 m using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the residual solvent amount became 105%, and the film was peeled from the stainless steel band support with a peeling tension of 162 N / m. The peeled cellulose ester web was evaporated at 35 ° C., slit to 1.6 m width, and then dried at a drying temperature of 135 ° C. while stretching 1.1 times in the width direction with a tenter. At this time, the residual solvent amount when starting stretching with a tenter was 10%. After stretching with a tenter and releasing the width holding at 130 ° C., the width is released, and then the drying is finished while transporting the drying zone at 120 ° C. and 130 ° C. with a number of rolls, slit to a width of 1.4 m, A knurling process with a width of 10 mm and a height of 7 μm was applied to both ends of the film, and the film was wound around a core having an inner diameter of 6 inches with an initial tension of 220 N / m and a final tension of 110 N / m to obtain a polarizing plate protective film C3. The draw ratio in the MD direction calculated from the rotational speed of the stainless steel band support and the operating speed of the tenter was 1.1 times. The residual solvent amount of the polarizing plate protective film C3 was less than 0.1%, respectively, and the film thickness was 80 μm.

  Subsequently, polarizing plate protective films having film thicknesses of 70, 60, and 40 μm were produced in the same manner.

  About the four types of polarizing plate protective films obtained, the liquid crystal display device No. 1 of Example 1 was used. A polarizing plate was prepared using the polarizing plate protective film C1 of No. 3 to prepare a liquid crystal display device.

  Example 1 was evaluated using the produced polarizing plate protective film and the liquid crystal display device, and the results are shown in Table 5.

  The liquid crystal display devices 22 to 24 using the polarizing plate protective film having a film thickness of 40 to 70 μm in which the Rt temperature fluctuation and the Rt humidity fluctuation are in the range of the present invention reproduce the examples 1 and 2, and perform color shift and color unevenness. It can be seen that the contrast is excellent.

Example 4
In preparation of the polarizing plate protective film 3 of Example 3, instead of general formula (7) exemplary compound A-19 of dope addition liquid C3, following compound C-1, C2 and general formula (7) exemplary compound A- 2, A polarizing plate protective film was produced in the same manner except that A-14 was used, and liquid crystal display devices 25 to 28 were produced in the same manner as in Example 3 using the same, and then evaluation of Example 1 was performed. The results are shown in Table 6.

  In addition, with respect to 19 parts by mass of the exemplary compound A-19 of the general formula (7) in the dope additive liquid C3, the addition amounts of the compounds C-1 and C-2 are each 7 parts by mass, and A-2 is 4.5 parts by mass and A-14 used 9 parts by mass, respectively.

  The liquid crystal display devices 26 and 28 using a polarizing plate protective film having a film thickness of 40 μm whose Rt temperature fluctuation and Rt humidity fluctuation are within the scope of the present invention reproduce Examples 1 to 3 and are excellent in color shift, color unevenness, and contrast. I understand that

Claims (6)

In the transverse electric field switching mode type liquid crystal display device having polarizing plates on both sides of the liquid crystal cell, the polarizing plate protective film used between the liquid crystal cell on the backlight source side and the polarizer is represented by the following formulas (1) and (2). Ro and Rt represented are cellulose ester films each having a range of 0 nm ≦ Ro ≦ 2 nm and −10 nm ≦ Rt ≦ 10 nm. The cellulose ester film has the following Rt temperature fluctuation of 7 nm or less, A lateral electric field switching mode type liquid crystal display device characterized in that the Rt humidity fluctuation is 20 nm or less.
Ro, Rt measurement conditions: Measured after standing the film for 24 hours in an environment of 23 ° C. and 55% relative humidity. Rt temperature fluctuation; ΔRt value Rt humidity fluctuation of the difference in Rt value measured in a standing state; difference in Rt value measured in a 24 hour relative environment under a 23 ° C. relative humidity 20% environment and a 23 ° C. relative humidity 80% environment ΔRt value formula (1) Ro = (nx−ny) × d
Formula (2) Rt = {(nx + ny) / 2−nz} × d
(Here, the refractive index in the slow axis direction in the plane of the cellulose ester film is nx, the refractive index in the direction perpendicular to the slow axis in the plane is ny, the refractive index in the thickness direction of the film is nz, d is Represents the thickness (nm) of the film.) 2. The lateral electric field switching mode liquid crystal display device according to claim 1, wherein the cellulose ester film contains a compound having negative orientation birefringence. The horizontal electric field switching mode type liquid crystal display device according to claim 1 or 2, wherein the horizontal electric field switching mode type liquid crystal display device is an IPS (In Plane Switching) mode type liquid crystal display device. . The transverse electric field according to any one of claims 1 to 3, wherein the Rt temperature variation is in a range of 1 to 5 nm, and the Rt humidity variation is in a range of 4 to 12 nm. Switching mode type liquid crystal display. The polarizing plate protective film used between the viewer-side polarizer and the liquid crystal cell is the same as the polarizing plate protective film used between the backlight light source-side liquid crystal cell and the polarizer. 5. A transverse electric field switching mode type liquid crystal display device according to any one of ranges 1 to 4. 6. The transverse electric field switching mode type liquid crystal display device according to claim 1, wherein the IPS phase difference film is not provided between the polarizer and the liquid crystal cell. .