JP2008058893A - Cellulose ester film, polarizing plate protection film, polarizing plate, manufacturing method of cellulose ester film and liquid crystal display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate which is used for a large-sized liquid crystal display and is excellent in a rework nature. <P>SOLUTION: The required polarizing plate can be obtained by using a roll-like cellulose ester film as a polarizing plate protection film. The roll-like cellulose ester film has 1,500 to 4,000 mm width, contains a compound having negative birefringence, elastic modulus in a width direction is larger than elastic modulus in a longitudinal direction, Rt is 15 to 70 nm and Ro is 0 to 15 nm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polarizing plate protective film for a large-sized liquid crystal display device, a polarizing plate and a method for producing the same.

  In the liquid crystal display device, the display area is increasing in size, and the polarizing plate bonded to the liquid crystal panel is also increased in size. And, for example, in a large polarizing plate exceeding 40 inches, the polarizing plate has been easily broken when it is peeled off due to some failure after being bonded to a liquid crystal cell (at the time of rework), and even during normal handling. It is a problem.

  That is, the large polarizing plate is required to have a characteristic that the tear strength is strong, although the optical characteristics are not different from those of the conventional polarizing plate.

  By the way, the polarizing plate is configured such that a polarizer composed of a normally stretched polyvinyl alcohol film is sandwiched between cellulose acetate type or cycloolefin type polarizing plate protective films.

  These polarizing plate protective films are generally produced as a long roll film using a solution or a melt casting method, and in the production process, they are generally stretched as appropriate in order to improve the flatness.

  In a process of manufacturing a polarizing plate by sandwiching a polarizer between polarizing plate protective films, a so-called bonding step, a roll-shaped polyvinyl alcohol film stretched in the longitudinal direction and a polarizing plate protective film that is also manufactured in a roll shape are rolled up. Since the lamination is performed by a roll, the long direction of the polyvinyl alcohol film and the long direction of the polarizing plate protective film are usually bonded in a form that coincides.

  At this time, a polarizer composed of a polyvinyl alcohol film to be bonded is generally produced with anisotropy by being stretched in the longitudinal direction, while the polarizing plate protective film is stretched in the longitudinal direction and in the width direction. Although it is manufactured by being held or stretched, the elastic modulus of the polarizing plate produced by combining both of them by roll-to-roll is higher in the longitudinal direction.

  This is because when the polarizing plate protective film is manufactured in a roll shape, the film extends in the transport direction, the molecules are easily aligned in the transport direction (coincident with the long direction), and are oriented by width retention and width direction stretching. It comes from being much larger than that. Usually, it is known that the elastic modulus of the film in the direction of a large degree of stretching becomes high.

Then, in order to improve tear strength in a large polarizing plate, it was also proposed to use a polarizing plate protective film having a greater degree of stretching in the width direction (Patent Document 1). Since originally required optical properties exist, it has not been possible to propose a polarizing plate protective film capable of stretching conditions that can achieve both optical properties as a polarizing plate protective film and tear strength.
JP 2006-58437 A

  An object of the present invention is to provide a polarizing plate protective film for a large-sized liquid crystal display device, a polarizing plate, and a liquid crystal display device using the polarizing plate without fear of breakage and without impairing the optical properties of a conventional film.

The above object of the present invention is achieved by the following configurations.
1. A roll-shaped cellulose ester film having a width of 1500 to 4000 mm, the film containing a compound having negative birefringence, an elastic modulus in the width direction being larger than an elastic modulus in the longitudinal direction, and Rt being 15 A roll-like cellulose ester film having a thickness of ˜70 nm and Ro of 0 to 15 nm.
2. A polarizing plate protective film comprising the cellulose ester film as described in 1 above.
3. A polarizing plate comprising a polarizer and two polarizing plate protective films sandwiching the polarizer, wherein at least one of the polarizing plate protective films is the polarizing plate protective film according to claim 2, and the polarizing plate protective film A polarizing plate characterized in that an elastic modulus in a direction perpendicular to the absorption axis direction of the polarizer is larger than an elastic modulus in the same direction as the absorption axis direction of the polarizer.
4). 2. The method for producing a cellulose ester film according to 1 above, wherein the film is obtained by stretching a cellulose ester film containing a compound having negative birefringence by 15 to 50% in the width direction. A method for producing a cellulose ester film.
5. 4. A liquid crystal display device using the polarizing plate described in 3 above.

  With the above configuration, a polarizing plate used in a large-sized liquid crystal display device, which has excellent optical characteristics and physical characteristics, can be provided.

The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.
(Rolled cellulose ester film)
The rolled cellulose ester film of the present invention has a width of 1500 to 4000 mm. Conventionally, the effective width of the polarizer is limited to the liquid crystal display device of 60 inch type (film width 1328 mm × flow direction 784 mm). However, according to the present invention, the effective width is 68 inch type (film width 1505 mm × flow direction 889 mm). Became possible.

  The cellulose ester film of the present invention is produced into a roll by a continuous solution casting and melting method. Thereafter, the polarizer and the roll-to-roll which are similarly manufactured in a roll shape are bonded together and cut to produce a desired polarizing plate.

<Cellulose ester>
Examples of the cellulose ester of the present invention include triacetyl cellulose (TAC), diacetyl cellulose (DAC), cellulose acetate propionate (CAP), cellulose acetate butyrate (CAB), cellulose acetate phthalate, cellulose acetate trimellitate, cellulose nitrate. And the like.

  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, the cellulose ester obtained from these can be used individually or in mixture in arbitrary ratios, However, 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 having negative birefringence)
The compound having negative birefringence of the present invention means a material exhibiting negative birefringence in the direction of stretching of the cellulose ester film. Needle-like fine particles, acrylic polymer, polyester, furanose Examples thereof include compounds having a structure or a pyranose structure. Negative birefringence refers to the property of negative birefringence.

<Acicular fine particles>
The cellulose film of the present invention is characterized by containing at least one kind of acicular fine particles exhibiting negative birefringence in the stretching direction.

  As the acicular fine particles having negative birefringence with respect to the stretching direction (hereinafter also referred to as birefringent fine particles), birefringent fine particles described in JP-A-2004-109355 can be used. Examples thereof include various carbonates such as calcium carbonate, strontium carbonate, magnesium carbonate, manganese carbonate, cobalt carbonate, zinc carbonate, and barium carbonate.

  For example, tetragonal, hexagonal and rhombohedral crystals are preferably uniaxial birefringent crystals, orthorhombic, monoclinic and triclinic crystals. These may be single crystals or polycrystals.

  Further, polystyrene or acrylic resin rod-like particles are also preferably used. For example, it may be a short fiber needle-shaped fine particle having a polystyrene resin or an acrylic resin and manufactured by finely cutting an ultrafine fiber. These fibers are preferably stretched during the production process because they easily develop birefringence. These resins are preferably cross-linked.

  These birefringent fine particles preferably have an aspect ratio of a major axis of 10 to 500 nm and a minor axis perpendicular thereto of 1: 1.1 or more, particularly preferably an aspect ratio of 1: 2 to 1: 100. 1 to 3:30 is preferable.

  However, the present invention is not limited to these, and various types can be used as long as the above-described requirements such as size, shape, and aspect ratio are satisfied.

  The birefringent fine particles are preferably surface-treated with a silane coupling agent, a titanate coupling agent, or the like.

  The birefringence of the birefringent fine particles is defined as follows. The refractive index for light polarized in the major axis direction of the birefringent fine particles is npr, and the average refractive index for light polarized in the direction orthogonal to the major axis direction is nvt. The birefringence Δn of the birefringent fine particles is defined by the following formula.

Δn = npr−nvt
That is, if the refractive index in the major axis direction of the birefringent fine particles is larger than the average refractive index in the direction orthogonal thereto, positive birefringence is obtained, and negative birefringence is obtained in the opposite case.

  The absolute value of the negative birefringence of the birefringent fine particles used in the present invention is not particularly limited, but is preferably 0.01 to 0.3, and is preferably 0.05 to 0.3. More preferably. In the case of acicular crystals, it means a material whose refractive index in the long direction of the crystal is smaller than the refractive index in the direction perpendicular thereto.

  The carbonate fine particles can be produced by a uniform precipitation method or a carbon dioxide compounding method.

  For example, it can be produced by methods such as JP-A-3-88714, JP-B-55-51852, JP-A-59-223225, and the like.

  The strontium carbonate crystal can be obtained by bringing strontium ions dissolved in water into contact with carbonate ions. Carbonate ions can be obtained by adding carbon dioxide gas to a solution containing a strontium compound by a method such as bubbling carbon dioxide, or by adding a substance that generates carbonate ions to react or decompose.

  For example, strontium carbonate crystal fine particles can be produced by the method described in JP-A-2004-35347, and strontium carbonate fine particles obtained by this method can be preferably used as birefringent fine particles. A substance that generates carbon dioxide includes urea, and strontium carbonate fine particles can be obtained by reacting carbon dioxide ions and strontium ions generated in combination with a hydrolyzing enzyme of urea. In order to obtain fine crystals, it is preferable to lower the temperature as much as possible. Cooling below the freezing point is preferable because fine crystal particles can be obtained.

  For example, it is also preferable to add an organic solvent such as ethylene glycol as a freezing point depressing substance, and it is preferable to add so that the freezing point is below 5 ° C below freezing point. Thereby, fine particles of strontium carbonate having an average particle size in the major axis direction of 500 nm or less can be obtained.

  Strontium carbonate is a biaxial birefringent crystal, and according to Japanese Patent Application Laid-Open No. 2004-35347, the refractive index in each optical axis direction is n (na, nb, nc) = (1.520, 1.666, 1.669), and it is reported that the major axis direction of the needle-like crystal substantially coincides with the optical axis direction having a refractive index of 1.520.

  Therefore, it has a negative birefringence effect with respect to the orientation direction of the acicular crystal. Since the strontium carbonate crystal particles are in a needle-like (rod-like) form, they can be statistically oriented in a predetermined direction by applying a stress in a state of being dispersed in a viscous medium.

  When mixing acicular fine particles and a cellulose ester solution, it is possible to produce a cellulose ester film using a dope produced using an acicular fine particle dispersion in which acicular fine particles are dispersed in a resin for dispersing acicular fine particles and an organic solvent. preferable.

  The resin for dispersing the acicular fine particles preferably has a weight average molecular weight of 3000 to 200000, and preferably 3000 to 90000.

  Specifically, the resin for dispersing the acicular fine particles is a homopolymer or copolymer having an ethylenically unsaturated monomer unit, an acrylic acid or methacrylic acid ester homopolymer or copolymer, or a methacrylic acid methyl ester homopolymer. It is preferably at least one selected from a coalescence or copolymer, cellulose ester, cellulose ether polyurethane resin, polycarbonate resin, polyester resin, epoxy resin and ketone resin.

  Even if these resins are contained in a dope (cellulose concentration: 10 to 30% by mass), which is a high concentration cellulose ester solution used for solution casting, there is little increase in haze and a uniform film can be formed. It is a resin that can be used. The concentration of these acicular fine particle dispersion resins contained in the acicular fine particle dispersion is preferably less than 0.1 to 10% by mass, and the concentration in the fine particle dispersion varies depending on the resin to be added. It is preferable that 2-5 mass% is contained.

  In the present invention, the viscosity of the fine particle dispersion is preferably controlled in the range of 100 to 500 mPa · s.

<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 according to the present invention will be described.

<Acrylic polymer>
The cellulose ester film of the present invention preferably contains an acrylic polymer having a negative 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 in the side chain. An acrylic polymer or an acrylic polymer having a cyclohexyl group in the side chain is preferred.

  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 so 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) acrylate (2-ethoxyethyl), etc., or the acrylic acid ester can be exemplified those obtained by changing the methacrylic acid 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, Examples include benzyl methacrylate, phenethyl acrylate, phenethyl methacrylate, and acrylic acid (2-naphthyl), 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 preferably 50 to 80% 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 acrylic acid-2-hydroxyethyl and methacrylic acid-2-hydroxyethyl. 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 disclosed in JP 2000-128911 A or 2000-344823, or a polymerization catalyst using the compound and an organometallic compound in combination It can be obtained by a method of bulk polymerization using, 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 birefringence in 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 of the present invention is a copolymer of 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. The polymer having a weight average molecular weight of 5,000 to 30,000. 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 of 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 (-R 1} ) (- CO 2 R 2)] m- [CH 2 -C (-R 3) (- CO 2 R 4 -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 —, —C ₂ H ₄ — or —C ₃ H ₆ —, Xc represents a monomer unit that can be polymerized to Xa and Xb, m, n, and p represent a molar composition ratio, provided that m ≠ 0, n ≠ 0, k ≠ 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. Preferred are acrylic acid (2-hydroxyethyl) and methacrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), and acrylic acid (3-hydroxypropyl).

  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 of 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 (-R 5} ) (- CO 2 R 6)] k- [Yb] q-
(In the formula, R ₅ represents H or CH _3. R ₆ represents an alkyl group or a cycloalkyl group having 1 to 12 carbon atoms. Yb represents a monomer unit copolymerizable with Ya. K and q Represents a 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 , 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 align the molecular weight as much as possible by a method that does not increase the molecular weight so 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. In particular, polymerization using a compound having a thiol group and a secondary hydroxyl group in the molecule as a chain transfer agent The law is preferable.

  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 and 1 ml of purified water is added from an air cooling tube to decompose acetic anhydride 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, laccelic acid, etc., 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 chloride of these acids and glycol, but polyester having a weight average molecular weight not so large is preferably by direct reaction.

  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 at least one furanose structure or pyranose structure, and a compound obtained by esterifying all or part of OH groups in a compound having 1 to 12 furanose structures or pyranose structures bonded thereto. It is characterized by that.

  Examples of preferable “compounds having at least one furanose structure or pyranose structure, and having 1 to 12 furanose structures or pyranose structures bound thereto” 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 having at least one furanose structure or pyranose structure and esterifying all or part of the OH groups in the compound having 1 to 12 furanose structures or pyranose structures bonded thereto” of 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.

<Other additives>
In addition to the compound having negative 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.

  As fine particles used in the present invention, examples of inorganic compounds include 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.). I can do it.

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

  Examples of the polymer include silicone resin, fluorine resin, 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.
(Rt, Ro)
In the present invention, Rt and Ro are represented by formula (i) and formula (ii) at a wavelength of 590 nm under 23 ° C. and 55% RH.

Formula (i) Ro = (nx−ny) × d
Formula (ii) Rt = {(nx + ny) / 2−nz} × d
(Here, the refractive index in the slow axis direction in the film is nx, the refractive index in the direction perpendicular to the slow axis is ny, the refractive index in the film thickness direction is nz, and d is the film thickness (nm) of the film. Represent each.)
The retardation value and birefringence can be measured using an automatic birefringence measuring apparatus (trade name KOBRA-21ADH manufactured by Oji Scientific Instruments), but are not limited thereto.

  In the present invention, Rt is 15 to 70 nm, preferably 15 to 50 nm. Ro is 0 to 15 nm.

Rt and Ro of the present invention can be arbitrarily adjusted by appropriately selecting the type and amount of the compound having negative birefringence.
(Method for producing rolled cellulose ester film)
Next, the manufacturing method of the roll-shaped cellulose-ester 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 roll cellulose ester film of the present invention was produced by dissolving a cellulose ester and an additive in a solvent to prepare a dope, casting a dope onto an endless metal support, and casting the dope. It is carried out by a step of drying the dope as a web, a step of peeling from the metal support, a step of stretching or maintaining the width, a step of further drying, and a step of winding up the finished film.

  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 ester (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 method of dissolving the cellulose ester when preparing the dope described above. When heating and pressurization are combined, it is possible to heat above the boiling point at normal pressure. It is preferable to stir and dissolve while heating at a temperature that is equal to or higher than the boiling point of the solvent at normal pressure and that the solvent does not boil under pressure, in order to prevent the generation of massive undissolved materials called gels and mamacos. Moreover, after mixing a cellulose ester with a poor solvent and making it wet or swell, the method of adding a good solvent and melt | dissolving is also used preferably.

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

  The heating temperature with the addition of a solvent is preferably higher from the viewpoint of the solubility of the cellulose ester, but if the heating temperature is too high, the required pressure increases and the productivity deteriorates. A preferable heating temperature is 45 to 120 ° C, more preferably 60 to 110 ° C, and still more preferably 70 ° C to 105 ° C. The pressure is adjusted so that the solvent does not boil at the set temperature.

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

  Next, this cellulose ester solution is filtered using a suitable filter medium such as filter paper. As the filter medium, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matters and the like, but there is a problem that the filter medium is likely to be clogged if the absolute filtration accuracy is too small. For this reason, a filter medium with an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium with 0.001 to 0.008 mm is more preferable, and a filter medium with 0.003 to 0.006 mm is still more preferable.

  There are no particular restrictions on the material of the filter medium, and ordinary filter media can be used. However, plastic filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel do not drop off fibers. preferable. It is preferable to remove and reduce impurities, particularly bright spot foreign matter, contained in the raw material cellulose ester by filtration.

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 an ordinary method, but the method of filtering while heating at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil under pressure is the filtration pressure before and after filtration. The increase in the difference (referred to as differential pressure) is small and preferable. A preferred temperature is 45 to 120 ° C, more preferably 45 to 70 ° C, and still more preferably 45 to 55 ° C.

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

  Here, the dope casting will be described.

  The metal support in the casting (casting) step preferably has a mirror-finished surface, and a stainless steel belt or a drum whose surface is plated with a casting is preferably used as the metal support. The cast width can be 1 to 4 m. The surface temperature of the metal support in the casting step is −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 at a higher speed. 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 rolled 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 immediately after peeling from the metal support is large, and both ends of the web are further clipped. It is particularly preferable to perform stretching in the width direction by a tenter method of gripping with.

<Stretching in the width direction>
A preferred draw ratio in the width direction is 1.15 to 1.50 times (15 to 50%), preferably 1.20 to 1.50 (20 to 50%) times.

  The stretching ratio in the longitudinal direction is preferably smaller than the stretching ratio in the width direction, and is 1.05 to 1.30. It is preferable that the area is 1.12 times to 1.44 times, and preferably 1.15 times to 1.32 times due to stretching in the longitudinal direction and the width direction. This can be determined by the draw ratio in the long direction × the draw ratio in the width direction.

  The stretching ratio here refers to the total stretching ratio in the case where the film is stretched with tension applied to the entire manufacturing process, such as a conveying process, as well as the stretching process. This total draw ratio can be determined from the difference from the ideal film when ideally produced from the dope casting amount, the film thickness of the finished film, the winding length, and the winding width.

  In order to stretch in the longitudinal direction immediately after peeling, it is preferable to peel at a peeling tension of 210 N / m or more, particularly preferably 220 to 300 N / m.

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

  The drying temperature in the web drying step is preferably increased stepwise from 40 to 200 ° C, and more preferably in the range of 50 to 140 ° C in order to improve dimensional stability.

  Although the film thickness of a roll-like cellulose ester is not specifically limited, 10-200 micrometers is used. In particular, the film thickness is particularly preferably 20 to 100 μm. More preferably, it is 25-90 micrometers.

The rolled cellulose ester film of the present invention has a width of 1500 to 4000 mm. And when this roll-shaped cellulose-ester film is cut | judged as it is and used as a sheet-like cellulose-ester film, after bonding with a roll-shaped polarizer and a roll toe roll, when cut | judged as a polarizing plate and used There is. In addition, the thing exceeding 4000 mm is very difficult to manufacture practically.
(Elastic modulus in width direction and long direction)
In this invention, the elastic modulus of the width direction of a roll-shaped cellulose-ester film is larger than the elastic modulus of a elongate direction, It is characterized by the above-mentioned. This feature can be achieved by the fact that the total stretching ratio in the width direction including the transport process and the stretching process is larger than the total stretching ratio in the longitudinal direction.

  In the present invention, the elastic modulus in the width direction is 3.5 to 5.5 Gpa, and the elastic modulus in the longitudinal direction is 3.0 to 4.5 Gpa.

In addition, the elasticity modulus of this invention measured the sample cut out to length 150mm and width 10mm according to the standard of ISO1184-1983 at the initial sample length of 100 mm and the pulling speed of 10 mm / min.
(Polarizer)
In the polarizing plate of this invention, with respect to the polarizer which is a uniaxially stretched film, the cellulose-ester film of this invention is bonded on at least one surface of a polarizer as a polarizing plate protective film.

<Polarizer>
As the polarizer, a uniaxially stretched film containing a dichroic material is used. Examples of the polarizer include hydrophilic polymer films such as polyvinyl alcohol film, partially formalized polyvinyl alcohol film, and ethylene / vinyl acetate copolymer partially saponified film, and two colors such as iodine and dichroic dye. And uniaxially stretched by adsorbing the active substance.

  Further, there may be mentioned those uniaxially stretched with a polyene-based oriented film such as a dehydrated polyvinyl alcohol product or a dehydrochlorinated polyvinyl chloride product. Among these, a polarizer made of a dichroic substance such as a polyvinyl alcohol film and iodine or a dichroic dye is preferable.

  As a polyvinyl alcohol film, a film formed by any method such as a casting method, a casting method or an extrusion method in which a stock solution in which a polyvinyl alcohol resin is dissolved in water or an organic solvent is cast is appropriately used. can do. The degree of polymerization of the polyvinyl alcohol-based resin is preferably about 100 to 5000, and more preferably 1400 to 4000.

  A polarizer obtained by dyeing a polyvinyl alcohol-based film with iodine or the like and uniaxially stretching can be produced, for example, by the following method.

  In the dyeing process, the polyvinyl alcohol film is immersed in a dyeing bath at about 20 to 70 ° C. to which iodine is added for about 1 to 20 minutes to adsorb iodine. The iodine concentration in the dyeing bath is usually about 0.001 to 1 part by mass per 100 parts by mass of water. In the dyeing bath, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, etc. An auxiliary such as iodide may be added in an amount of about 0.02 to 20 parts by mass. These additives are particularly preferable for increasing the dyeing efficiency. In addition to the water solvent, a small amount of an organic solvent compatible with water may be contained.

  The polyvinyl alcohol film may be subjected to a swelling treatment at about 20 to 60 ° C. for about 0.1 to 10 minutes in a water bath or the like before being dyed in an aqueous solution containing iodine or a dichroic dye. In addition to washing the polyvinyl alcohol film surface with dirt and anti-blocking agents by washing the polyvinyl alcohol film with water, it also has the effect of preventing unevenness such as uneven coloring by swelling the polyvinyl alcohol film. is there.

  The dyed polyvinyl alcohol film can be cross-linked as necessary. The composition of the aqueous crosslinking solution used for the crosslinking treatment is usually about 1 to 10 parts by mass with one or a mixture of a crosslinking agent such as boric acid, borax, glyoxal and glutaraldehyde per 100 parts by mass of water. The concentration of the crosslinking agent is determined in consideration of the balance between the optical properties and the contraction of the polarizing plate caused by the stretching force generated in the polyvinyl alcohol film.

  In the crosslinking bath, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, etc. An auxiliary such as iodide may be added in an amount of about 0.05 to 15% by mass. These additives are particularly preferable from the viewpoint of obtaining in-plane uniform characteristics of the polarizer. The temperature of the aqueous solution is usually about 20 to 70 ° C, preferably 40 to 60 ° C. The immersion time is not particularly limited, but is usually about 1 second to 15 minutes, preferably 5 seconds to 10 minutes. In addition to the water solvent, a small amount of an organic solvent compatible with water may be contained.

  The total draw ratio of the polyvinyl alcohol film is about 3 to 7 times, preferably 5 to 7 times the original length. When the total draw ratio exceeds 7 times, the film is easily broken. Stretching may be carried out after a swelling step or after dyeing with iodine, or may be stretched while dyeing or crosslinking, or may be dyed with iodine after stretching. The stretching method and the number of stretching are not particularly limited, and may be performed only in any one step. Moreover, you may perform several times in the same process. The stretching method may be either wet or dry.

  In addition, the polyvinyl alcohol film subjected to iodine adsorption alignment treatment is further added to an aqueous iodide solution such as potassium iodide having a water temperature of about 10 to 60 ° C., preferably about 30 to 40 ° C. and a concentration of 0.1 to 10% by mass. A step of dipping for 1 minute to 1 minute can be provided. In the iodide aqueous solution, auxiliary agents such as zinc sulfate and zinc chloride may be added. The polyvinyl alcohol film subjected to the iodine adsorption alignment treatment can be provided with a water washing step and a drying step of about 20 to 80 ° C. for about 1 minute to 10 minutes.

  The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 μm. When the thickness of the polarizer is reduced, the moisture in the polarizer is likely to be volatilized in the drying process when being bonded to the polarizing plate protective film during the manufacturing process of the polarizing plate.

<Manufacture of polarizing plate>
For bonding the polarizer and the polarizing plate protective film of the present invention, an adhesive is usually used. Examples of the adhesive include isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latexes, and water-based polyesters. The said adhesive agent is normally used as an adhesive agent which consists of aqueous solution, and contains 0.5 to 60 mass% solid content normally. Adhesives include cross-linking agents, silane coupling agents, coupling agents such as titanium coupling agents, various tackifiers, UV absorbers, antioxidants, heat stabilizers, hydrolysis stabilizers and other stabilizers, etc. Can also be blended.

  Moreover, an easily bonding process can be given to the surface which adhere | attaches a polarizing plate protective film and a polarizer. Examples of the easy adhesion treatment include dry treatment such as plasma treatment and corona treatment, chemical treatment such as alkali treatment, and coating treatment for forming an easy adhesive layer. Among these, the coating process which forms an easily adhesive layer is suitable. For the formation of the easy-adhesive layer, various easy-adhesive materials such as polyol resin, polycarboxylic acid resin, and polyester resin can be used. The thickness of the easy-adhesive layer is usually 10 μm or less, preferably about 0.01 to 10 μm.

  Application | coating of an adhesive agent may be performed to any of a polarizing plate bright protection film and a polarizer, and may be performed to both. The application operation is not particularly limited, and various means such as a roll method, a spray method, and an immersion method can be employed. After the bonding, a drying process is performed to form an adhesive layer composed of a coating dry layer. Bonding of a polarizer and a protective film can be performed with a roll laminator or the like. The thickness of the adhesive layer is not particularly limited, but is usually 5 μm or less, preferably about 0.1 to 5 μm.

  In the present invention, the polarizing plate protective film is characterized in that the elastic modulus in the direction orthogonal to the absorption axis direction of the polarizer is larger than the elastic modulus in the same direction as the absorption axis direction of the polarizer. That is, the polarizing plate is manufactured so that the direction of uniaxial stretching of the polarizer and the longitudinal direction of the present invention coincide.

  Since the roll-like cellulose ester film of the present invention is produced such that the stretching ratio in the width direction is larger than the stretching ratio in the longitudinal direction, the stretching direction of the uniaxially stretched polarizer matches the absorption axis. When the roll-shaped polarizer and the roll-shaped cellulose ester film are bonded by roll-to-roll, the polarizing plate of the present invention can be obtained without worrying about the direction of the absorption axis.

<Other polarizing plate protective film>
As a polarizing plate protective film other than the cellulose ester film of the present invention to be bonded to the polarizing plate, an appropriate transparent material can be used, but those having excellent transparency, mechanical strength, thermal stability, moisture barrier properties, etc. are preferable. Used.

  For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as cellulose diacetate and cellulose triacetate, acrylic polymers such as polymethyl methacrylate, styrene such as polystyrene and acrylonitrile / styrene copolymer (AS resin) -Based polymer, polycarbonate-based polymer and the like.

  In addition, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Polymer blends and the like are also examples of polymers that form the transparent protective film.

  The transparent protective film can also be formed as a cured layer of thermosetting or ultraviolet curable resin such as acrylic, urethane, acrylurethane, epoxy, and silicone.

  You may use the cellulose-ester film of this invention for the polarizing plate protective film of both surfaces.

  For the polarizing plate protective film of the present invention, a film having another function used for a liquid crystal display device such as another retardation plate or a brightness enhancement film may be further bonded and used.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
<Prescription 1: Production of samples 1 to 4>
(Dope composition A formulation)
・ Triacetylcellulose (acetylation degree 61.0%) 85 parts by mass ・ 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) bezotriazole 1.5 parts by mass ・ Methyl methacrylate- 2-hydroxyethyl acrylate copolymer 8 parts by mass (80/20 (mass ratio)) Mw; 8000
-Methyl acrylate polymer (*) Mw; 1000 5 parts by mass-Methylene chloride 475 parts by mass-Ethanol 50 parts by mass (*) A methyl acrylate monomer is polymerized by the polymerization method described in Example 3 of JP 2000-128911 A, Polymers of Mw1000 and Mn700 were obtained. The reaction product had a hydroxyl value (OHV; mg / g KOH) of 50.

(Matting agent solution composition)
-Silica particle dispersion with an average particle size of 16 nm 11.0 parts by mass-Methylene chloride (first solvent) 76.1 parts by mass-Ethanol (second solvent) 3.5 parts by mass-Acetylpropionyl cellulose (acetyl substitution degree 2. 06, propionyl substitution degree 0.79) 1.9 parts by mass (Preparation of matting agent solution)
20 parts by mass of silica particles having an average particle diameter of 16 nm (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd.) and 80 parts by mass of methanol were mixed well for 30 minutes to obtain a silica particle dispersion. This dispersion was put into a disperser together with the following composition, and further stirred for 30 minutes or more to dissolve each component to prepare a matting agent solution.

  The dope composition A having the above formulation was put into a sealed container, heated to 70 ° C., and stirred to completely dissolve cellulose triacetate (TAC) to obtain a dope. The time required for dissolution was 4 hours. After the dope composition A is filtered, 6.5 parts by weight of the matting agent solution is mixed, and the mixture is uniformly cast on a stainless steel band support at a dope temperature of 35 ° C. and a temperature of 22 ° C. did. The temperature of the stainless steel band support was 20 ° C.

  Then, after making it dry to the range which can be peeled, dope was peeled from the stainless steel band support body. The residual solvent amount of the dope at this time was 25% by mass. The time required from casting the dope to peeling was 3 minutes. After peeling from the stainless steel band support with a tension of 10 kg / m, stretching 20% in the width direction with a tenter at 140 ° C, and then drying in a drying zone at 120 ° C and 135 ° C while being transported by many rolls Then, a knurling process having a width of 10 mm and a height of 5 μm was applied to both ends of the film to produce a cellulose triacetate film sample 1 having a thickness of 40 μm.

  The film width was 1500 mm and the winding length was 4000 m. The haze (measured with a haze meter HM150 manufactured by Murakami Color Research Laboratory) was 3%, and the single transmittance (measured with a spectrophotometer U-4100 with an integrating sphere manufactured by Hitachi, Ltd.) was 97%. . The winding tension was an initial tension of 10 kg / m and a final winding tension of 8 kg / m.

Sample 2 was manufactured in the same manner as Sample 1 so that the film thickness was 80 μm. Sample 3 had a stretching ratio in the width direction of 50% in the same manner as Sample 1. In the same manner as Sample 1, Sample 4 was not stretched in the width stretching step in the film production process, but was stretched and finished as a film, and then stretched in the width direction (offline process). In this step, while a triacetyl cellulose film or the like was run in the longitudinal direction, the film was stretched in the width direction at 165 ° C. with a stretching machine (manufactured by Hirano Giken Kogyo Co., Ltd.) to obtain a desired film.
<Prescription 2: Production of Sample 5>
(Additive solution composition)
-44.3 parts by mass of cyclohexylsulfonanilide-7.9 parts by mass of 2-hydroxy-4-octanoxybenzophenone-58.8 parts by mass of methylene chloride (first solvent)-8.4 parts by mass of methanol (second solvent) Triacetyl cellulose (acetylation degree 61.0%) 2.2 parts by mass The above dope composition A is 95.6 parts by mass, the matting agent solution is 1.8 parts by mass, and the additive solution is 6.7 parts by mass. After filtration, mixing was performed, and Sample 5 was produced in the same manner as Sample 1.
<Prescription 3: Production of sample 6>
The copolymer mass ratio of the methyl methacrylate-2-hydroxyethyl acrylate copolymer (80/20 (mass ratio)) of the dope composition A is (70/30 (mass ratio) Mw; 8000), and the addition amount is 5 Sample 6 was produced in the same manner as Sample 1 by using a dope composition containing no parts of methyl acrylate polymer.
<Prescription 4: Production of Sample 7>
Sample 7 was produced in the same manner as Sample 1 except that 13 parts by mass of octaacetyl sucrose was used instead of the methyl methacrylate-2-hydroxyethyl acrylate copolymer and methyl acrylate polymer of Dope Composition A.
<Prescription 5: Production of sample 8>
Instead of the triacetyl cellulose of the dope composition A, the same amount of acetyl propionyl cellulose having an acetyl substitution degree of 2.06 and a propionyl substitution degree of 0.79 was used, and further 4 parts by mass of triphenyl phosphate, biphenyl diphenyl phosphate 1 Mass 8 was added and Sample 8 was produced in the same manner as Sample 1.
<Prescription 6: Production of samples 10 to 13>
Instead of the methyl methacrylate-2-hydroxyethyl acrylate copolymer and methyl acrylate polymer of the dope composition A, 4 parts by mass of triphenyl phosphate and 1 part by mass of biphenyl diphenyl phosphate were used. Sample 10 was produced in the same manner as Sample 1 in terms of parts by mass. Sample 11 was manufactured in the same manner as Sample 4 in Sample 10 in an off-line process. Sample 12 had a thickness of 80 μm in sample 11. Sample 13 was manufactured in the same manner as Sample 1 with a stretching ratio in the width direction of 10%.
<Prescription 7: Production of sample 14>
Instead of the triacetyl cellulose of the dope composition A, 100 parts by mass of acetyl propionyl cellulose having an acetyl substitution degree of 1.6 and a propionyl substitution degree of 0.8 is used, and further 5.5 parts by mass of trimethylolpropane tribenzoate, Sample 14 was produced in the same manner as Sample 1 by adding 5.5 parts by mass of Compound A having the structure.

  (Compound A)

(Production of polarizer)
A polyvinyl alcohol film having a thickness of 80 μm and a width of 3100 mm (manufactured by Kuraray Co., Ltd., average polymerization degree 2400, saponification degree 99.9 mol%, length 800 m) is immersed in pure water at 30 ° C. for 60 seconds to swell. At the same time, the film was uniaxially stretched in the length direction (flow direction) to a draw ratio of 2.5 times. Next, the film was immersed in an aqueous solution of 0.05% iodine / potassium iodide (mass ratio = 1/10) at 30 ° C. for 60 seconds and stretched so that the total draw ratio was 2.8 times, and then 40 ° C. In an aqueous solution having a boric acid concentration of 3% by mass and a potassium iodide concentration of 2% by mass, the film was stretched until the total stretching ratio was tripled.

Furthermore, it extended | stretched until the total draw ratio became 6 time in 60 degreeC boric acid density | concentration 4 mass% and aqueous solution of potassium iodide density | concentration 3 mass%. Thereafter, the film was immersed in an aqueous solution having a potassium iodide concentration of 5% by mass at 25 ° C. for 30 seconds without stretching. Next, drying was performed for 1 minute at 40 ° C. while maintaining the tension, and a polarizer having a thickness of 20 μm and a width of 1550 mm was obtained. The polarizer was manufactured continuously.
(Preparation of polarizing plate)
While the polarizer and the sample film were run in the longitudinal direction, a polarizing plate was produced by continuously laminating on both surfaces of the polarizer with a roll-to-roll with a polyvinyl alcohol adhesive. The tear strength was evaluated about the polarizing plate (same number as a sample number) from the obtained samples 1-14. In Sample 9, after cutting the sample into a sheet, the bonding direction of the polarizing plate protective film and the polarizer was the cross direction.

  Note that the cross direction refers to bonding so that the transport direction (long direction) of the polarizer and the transport direction (long direction) of the film of the present invention are perpendicular to each other, and the parallel direction is the direction of the polarizer. It refers to pasting together so that a conveyance direction (long direction) and the conveyance direction (long direction) of the film of this invention may become parallel. When a polarizer and a polarizing plate protective film can be bonded by roll-to-roll, it becomes a parallel direction and bonding with extremely high productivity is attained.

<Measurement method of tear strength>
The tear strength of the Elmendorf method was measured with a light load tear device manufactured by Toyo Seiki Co., Ltd. according to JIS K 7128-1991. This is the result of tearing in the direction parallel to the absorption axis of the polarizer.

<Characteristic evaluation as a liquid crystal display device>
Instead of the liquid crystal display device exceeding 68 inches, the optical performance of the polarizing plate was evaluated by substitution using a 32-type TFT color liquid crystal display Vega (manufactured by Sony Corporation).

  The polarizing plate of 32-type TFT color liquid crystal display Vega (manufactured by Sony Corporation) was peeled off, and each of the produced polarizing plates was cut according to the size of the liquid crystal cell. With the liquid crystal cell sandwiched, the two polarizing plates prepared as described above were pasted so that the polarizing axes of the polarizing plates were not perpendicular to each other so as to be orthogonal to each other to produce a 32-type TFT color liquid crystal display. The front contrast was evaluated.

<Front contrast>
In an environment of 23 ° C. and 55% RH, the backlight of the liquid crystal display was turned on and left for 30 minutes before measurement. For measurement, EZ-Contrast 160D manufactured by ELDIM was used to measure the front luminance of white display and black display with a liquid crystal TV, and the ratio was defined as the front contrast. The higher the value, the better the contrast.

  Front contrast = Front brightness of white display / Front brightness of black display

  As is clear from Table 1, the present invention has a tear strength suitable for reworking while having optical performance as a polarizing plate.

Claims (5)

A roll-shaped cellulose ester film having a width of 1500 to 4000 mm, the film containing a compound having negative birefringence, an elastic modulus in the width direction being larger than an elastic modulus in the longitudinal direction, and Rt being 15 A roll-like cellulose ester film having a thickness of ˜70 nm and Ro of 0 to 15 nm. A polarizing plate protective film comprising the cellulose ester film according to claim 1. A polarizing plate comprising a polarizer and two polarizing plate protective films sandwiching the polarizer, wherein at least one of the polarizing plate protective films is the polarizing plate protective film according to claim 2, and the polarizing plate protective film A polarizing plate characterized in that an elastic modulus in a direction perpendicular to the absorption axis direction of the polarizer is larger than an elastic modulus in the same direction as the absorption axis direction of the polarizer. The method for producing a cellulose ester film according to claim 1, wherein the film is obtained by stretching a cellulose ester film containing a compound having negative birefringence by 15 to 50% in the width direction. The manufacturing method of the cellulose-ester film characterized by these. A liquid crystal display device using the polarizing plate according to claim 3.