JP2012018341A - Polarizing plate and liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate which prevents degradation of a polarizer due to insufficient drying in the process of manufacturing the polarizing plate and which has high adhesion property and durability in a high temperature and high humidity environment and little changes in the optical characteristics, and to provide a liquid crystal display device using the polarizing plate.SOLUTION: The polarizing plate comprises a film (A) containing an acrylic resin and a cellulose ester resin, a polarizer, and a cellulose ester film (B). The cellulose ester resin constituting the cellulose ester film (B) has an acyl group average substitution degree ranging from 2.0 to 2.5.

Description

  The present invention relates to a polarizing plate having high durability under high temperature and high humidity and little fluctuation in optical characteristics, and a liquid crystal display device using the same.

  Liquid crystal display devices are widely used in monitors for personal computers and portable devices, and for television applications because of their various advantages, such as low voltage and low power consumption, enabling miniaturization and thinning. In particular, recently, with the progress of larger TVs and wall-mounted TVs, there is a demand for thinner polarizing plates used in liquid crystal display devices for TV applications.

  In the polarizing plate, a resin film is used as an optical film such as a polarizer protective film or a retardation film. Conventionally, cellulose ester films such as triacetyl cellulose (TAC) and cellulose acetate propionate (CAP) are used. The polarizing plate by the combination of has been used. However, these polarizing plates have drawbacks such as poor durability such as dimensional stability at high temperature and high humidity.

  On the other hand, mixed films of acrylic resin and cellulose resin have advantages such as low cost, excellent durability at high temperature and high humidity, and high transparency. The

  However, when the polarizer protective film made of triacetyl cellulose is replaced with a mixed film of the acrylic resin and cellulose resin as an alternative, the moisture of the polarizer is difficult to escape due to its low hygroscopicity, and the polarizer Coloring, unevenness of the polarizing plate, adhesion, and productivity have been problems. In addition, a polarizing plate was prepared in which triacetyl cellulose (TAC) was easily disposed in the mixed film / polarizer / TAC configuration of acrylic resin and cellulose ester resin, but water leakage after the drying process was still unsatisfactory. It was sufficient and further improvement was necessary (for example, see Patent Document 1).

  On the other hand, a polarizing plate using diacetylcellulose (DAC) has good drainage and good productivity, but has a problem such as light leakage because of large dimensional fluctuation and poor durability (see, for example, Patent Document 2). .

International Publication No. 2009/047924 JP 2009-269970 A

  The present invention has been made in view of the above-mentioned problems and situations, and the solution is to prevent the deterioration of the polarizer due to insufficient drying in the manufacturing process of the polarizing plate, and to prevent adhesion and high temperature and high humidity. An object of the present invention is to provide a polarizing plate having high durability and little variation in optical characteristics. Moreover, it is providing the liquid crystal display device using the same.

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

  1. A polarizing plate comprising a film (A) containing an acrylic resin and a cellulose ester resin, a polarizer, and a cellulose ester film (B), and an acyl group of the cellulose ester resin constituting the cellulose ester film (B) An average substitution degree is in the range of 2.0 to 2.5.

2. The film (A) containing the acrylic resin and the cellulose ester resin satisfies all of the following requirements (1) to (3).
(1) The content ratio (molar ratio) between the acrylic resin and the cellulose ester resin is in the range of 95: 5 to 30:70.
(2) The acrylic resin has a weight average molecular weight of 80000 or more.
(3) The substitution degree of the acyl group of the cellulose ester resin is in the range of 2.0 to 3.0, and the weight average molecular weight Mw of the cellulose ester resin is 75,000 or more.

  3. A liquid crystal display device having at least one polarizing plate according to item 1 or item 2 and a liquid crystal cell, wherein the film (A) containing the acrylic resin and cellulose ester resin of the polarizing plate includes: The liquid crystal display device is provided at a position farther from the liquid crystal cell than the cellulose ester film (B).

  By the above means of the present invention, it is possible to prevent the deterioration of the polarizer due to insufficient drying in the manufacturing process of the polarizing plate, and to provide a polarizing plate having high adhesion and durability under high temperature and high humidity, and less fluctuation in optical properties. can do. In addition, a liquid crystal display device using the same can be provided.

  That is, in this invention, since it has the characteristics that the acyl group average substitution degree of the cellulose ester which comprises a cellulose-ester film (B) exists in the range of 2.0-2.5, in the drying process of a polarizing plate. Even under mild conditions or at high speeds, the effect of sucking in water allows quick drainage and improves the production speed and efficiency of the drying process.

  Moreover, cellulose is provided by providing a film (A) containing an acrylic resin and a cellulose ester resin having low moisture permeability and excellent dimensional stability on the side facing the cellulose ester film (B) across the polarizer. The dimensional change of the ester film (B) can be suppressed. As a result, unevenness in optical characteristics such as the polarization degree of the polarizing plate can be prevented, and productivity and durability can be improved.

  Furthermore, when using the polarizing plate of this invention for a liquid crystal display device, the film (A) containing the said acrylic resin and cellulose-ester resin of the said polarizing plate is a position far from a liquid crystal cell from the said cellulose-ester film (B). In order to prevent moisture from the outside from passing through, it becomes possible to prevent unevenness in the optical characteristics of the polarizer at high temperature and high humidity and variation in the dimensions of the cellulose ester film (B).

  The polarizing plate of the present invention is a polarizing plate comprising a film (A) containing an acrylic resin and a cellulose ester resin, a polarizer, and a cellulose ester film (B), and constitutes the cellulose ester film (B). The acyl group average substitution degree of the cellulose ester resin is in the range of 2.0 to 2.5. This feature is a technical feature common to the inventions according to claims 1 to 3.

  As an embodiment of this invention, it is preferable that the film (A) containing the said acrylic resin and cellulose-ester resin satisfy | fills all the said requirements (1)-(3) from a viewpoint of the effect expression of this invention.

  Moreover, the polarizing plate of this invention can be used suitably for a liquid crystal display device. In that case, the film (A) containing the acrylic resin and cellulose ester resin of the polarizing plate is a liquid crystal display device in an embodiment provided at a position farther from the liquid crystal cell than the cellulose ester film (B). It is preferable.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail.

  In addition, in this application, "-" is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

(Film containing acrylic resin and cellulose ester resin (A))
The polarizing plate of the present invention includes a film (A) containing an acrylic resin and a cellulose ester resin (hereinafter, also referred to as “acrylic resin-containing film”).

As an embodiment of the polarizing plate of the present invention, it is preferable that the film (A) containing the acrylic resin and the cellulose ester resin satisfies all of the following requirements (1) to (3).
(1) The content ratio (molar ratio) between the acrylic resin and the cellulose ester resin is in the range of 95: 5 to 30:70.
(2) The acrylic resin has a weight average molecular weight of 80000 or more.
(3) The substitution degree of the acyl group of the cellulose ester resin is in the range of 2.0 to 3.0, and the weight average molecular weight Mw of the cellulose ester resin is 75,000 or more.

  Hereinafter, the constituent elements of the film (A) will be described in detail.

<acrylic resin>
The acrylic resin used in the present invention includes a methacrylic resin. Although it does not restrict | limit especially as resin, What consists of 50-99 mass% of methyl methacrylate units and 1-50 mass% of other monomer units copolymerizable with this is preferable.

  Other monomers that can be copolymerized include alkyl methacrylates having 2 to 18 carbon atoms, alkyl acrylates having 1 to 18 carbon atoms, acrylic acid, methacrylic acid, and the like. Saturated acids, maleic acids, fumaric acids, unsaturated divalent carboxylic acids such as itaconic acid, aromatic vinyl compounds such as styrene, α-methylstyrene, and nucleus-substituted styrene, α, β- such as acrylonitrile, methacrylonitrile, etc. Examples thereof include unsaturated nitrile, maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride, and the like. These can be used alone or in combination of two or more.

  Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer. n-Butyl acrylate is particularly preferably used.

  The acrylic resin used in the acrylic resin-containing film according to the present invention preferably has a weight average molecular weight (Mw) of 80,000 to 1,000,000 from the viewpoint of mechanical strength as a film and fluidity when producing the film.

  The weight average molecular weight of the acrylic resin according to the present invention can be measured by 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 = 2,800,000-500 calibration curves with 13 samples were used. The 13 samples are preferably used at approximately equal intervals.

  There is no restriction | limiting in particular as a manufacturing method of the acrylic resin in this invention, You may use any well-known methods, such as suspension polymerization, emulsion polymerization, block polymerization, or solution polymerization. Here, as a polymerization initiator, a normal peroxide type and an azo type can be used, and a redox type can also be used. Regarding the polymerization temperature, suspension or emulsion polymerization may be performed at 30 to 100 ° C, and bulk or solution polymerization may be performed at 80 to 160 ° C. Furthermore, in order to control the reduced viscosity of the produced copolymer, polymerization can be carried out using alkyl mercaptan or the like as a chain transfer agent.

  With this molecular weight, both heat resistance and brittleness can be achieved.

  A commercially available thing can also be used as an acrylic resin which concerns on this invention. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dianal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd.), KT75 (Denki Kagaku Kogyo Co., Ltd.) and the like can be mentioned. .

<Cellulose ester resin>
The cellulose ester resin contained in the film (A) according to the present invention may be substituted with either an aliphatic acyl group or an aromatic acyl group, but is preferably substituted with an acetyl group.

  When the cellulose ester resin according to the present invention is an ester with an aliphatic acyl group, the aliphatic acyl group has 2 to 20 carbon atoms, specifically acetyl, propionyl, butyryl, isobutyryl, valeryl, pivaloyl, hexanoyl , Octanoyl, lauroyl, stearoyl and the like.

  In the present invention, the “aliphatic acyl group” is meant to include those further having a substituent, and the substituent is a benzene ring when the aromatic ring is a benzene ring in the above-mentioned aromatic acyl group. What was illustrated as a substituent of a ring is mentioned.

  When the cellulose ester resin is an ester with an aromatic acyl group, the number of substituents substituted on the aromatic ring is 0 or 1 to 5, preferably 1 to 3, and particularly preferably 1 Or two.

  Further, when the number of substituents substituted on the aromatic ring is 2 or more, they may be the same or different from each other, but they may be linked together to form a condensed polycyclic compound (for example, naphthalene, indene, indane, phenanthrene, quinoline). , Isoquinoline, chromene, chroman, phthalazine, acridine, indole, indoline, etc.).

  As the structure used for the cellulose resin according to the present invention, the cellulose ester resin has a structure having a structure selected from at least one of a substituted or unsubstituted aliphatic acyl group and a substituted or unsubstituted aromatic acyl group. Used, these may be single or mixed acid esters of cellulose.

  The substitution degree of the cellulose ester resin according to the present invention is preferably such that the total substitution degree (T) of the acyl group is 2.00 to 3.00 and the substitution degree of acetyl group (ac) is 0 to 1.89. It is preferable. More preferably, the acyl group substitution degree (r) other than the acetyl group is 2.00 to 2.89. The acyl group other than the acetyl group preferably has 3 to 7 carbon atoms.

  In the cellulose ester resin according to the present invention, those having an acyl group having 2 to 7 carbon atoms as a substituent, that is, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose It is preferably at least one selected from acetate benzoate and cellulose benzoate.

  Among these, particularly preferable cellulose ester resins include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate.

  More preferably, the mixed fatty acid is a lower fatty acid ester of cellulose acetate propionate or cellulose acetate butyrate and having an acyl group having 2 to 4 carbon atoms as a substituent.

  The portion not substituted with an acyl group usually exists as a hydroxyl group (hydroxyl group). These can be synthesized by known methods.

  In addition, the substitution degree of an acetyl group and the substitution degree of other acyl groups are obtained by a method prescribed in ASTM-D817-96.

  If the weight average molecular weight (Mw) of the cellulose ester resin according to the present invention is 75,000 or more, the object of the present invention can be achieved even if the weight average molecular weight is about 1,000,000. The thing of 100000-2400 is still more preferable.

<Acrylic particles>
In the present invention, the acrylic resin-containing film may contain acrylic particles.

  The acrylic particles according to the present invention are preferably present in the state of particles (also referred to as “incompatible state”) in the acrylic resin, cellulose ester resin and acrylic resin-containing film. Specifically, the acrylic particles (C) described in paragraphs [0065] to [0102] of JP 2010-122340 A are preferably used for the acrylic particles.

<Other additives>
In the acrylic resin containing film which concerns on this invention, in order to improve the fluidity | liquidity and softness | flexibility of a composition, it is also possible to use a plasticizer together. Examples of the plasticizer include phthalate ester, fatty acid ester, trimellitic ester, phosphate ester, polyester, and epoxy.

  Of these, polyester and phthalate plasticizers are preferably used. Polyester plasticizers are superior in non-migration and extraction resistance compared to phthalate ester plasticizers such as dioctyl phthalate, but are slightly inferior in plasticizing effect and compatibility.

  Therefore, it can be applied to a wide range of uses by selecting or using these plasticizers according to the use.

  The polyester plasticizer is a reaction product of a monovalent or tetravalent carboxylic acid and a monovalent or hexavalent alcohol, and is mainly obtained by reacting a divalent carboxylic acid with a glycol. . Representative divalent carboxylic acids include glutaric acid, itaconic acid, adipic acid, phthalic acid, azelaic acid, sebacic acid and the like.

  In particular, when adipic acid, phthalic acid or the like is used, those having excellent plasticizing properties can be obtained. Examples of the glycol include glycols such as ethylene, propylene, 1,3-butylene, 1,4-butylene, 1,6-hexamethylene, neopentylene, diethylene, triethylene, and dipropylene. These divalent carboxylic acids and glycols may be used alone or in combination.

  The ester plasticizer may be any of ester, oligoester and polyester types, and the molecular weight is preferably in the range of 100 to 10000, but preferably in the range of 600 to 3000, the plasticizing effect is large.

  The viscosity of the plasticizer has a correlation with the molecular structure and molecular weight. In the case of an adipic acid plasticizer, the viscosity is preferably in the range of 200 to 5000 mPa · s (25 ° C.) in view of compatibility and plasticization efficiency. Furthermore, some polyester plasticizers may be used in combination.

  The plasticizer is preferably added in an amount of 0.5 to 30 parts by mass with respect to 100 parts by mass of the composition containing an acrylic resin. If the added amount of the plasticizer exceeds 30 parts by mass, the surface becomes sticky, which is not preferable for practical use.

  The composition containing the acrylic resin according to the present invention preferably contains an ultraviolet absorber, and examples of the ultraviolet absorber used include benzotriazole, 2-hydroxybenzophenone, or salicylic acid phenyl ester. . For example, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3 Triazoles such as 5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone And benzophenones.

  Here, among ultraviolet absorbers, ultraviolet absorbers having a molecular weight of 400 or more are less likely to volatilize at a high boiling point and are difficult to disperse even during high-temperature molding, so that the weather resistance is effectively improved with a relatively small amount of addition. be able to.

  In addition, since the transition from the thin coating layer to the substrate layer is particularly small and hardly precipitates on the surface of the laminate, the amount of contained UV absorber is maintained for a long time, and the durability of the weather resistance improvement effect is excellent. From the point of view, it is preferable.

  Examples of the ultraviolet absorber having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- (1, 1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol], bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis ( Hindered amines such as 1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonic acid Bis (1,2,2,6,6-pentamethyl-4-piperidyl), 1- [2- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] ethyl L] -4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine and the like, hindered phenol and hindered amine Examples include hybrid systems having both structures, and these can be used alone or in combination of two or more. Among these, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole and 2,2-methylenebis [4- (1,1,3,3- Tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] is particularly preferred.

  Furthermore, various antioxidants can also be added to the acrylic resin used for the acrylic resin-containing film according to the present invention in order to improve the thermal decomposability and thermal colorability during molding. In addition, an antistatic agent can be added to impart antistatic performance to the acrylic resin-containing film.

  As the acrylic resin composition according to the present invention, a flame retardant acrylic resin composition containing a phosphorus flame retardant may be used.

  Phosphorus flame retardants used here include red phosphorus, triaryl phosphate ester, diaryl phosphate ester, monoaryl phosphate ester, aryl phosphonate compound, aryl phosphine oxide compound, condensed aryl phosphate ester, halogenated alkyl phosphorus. Examples thereof include one or a mixture of two or more selected from acid esters, halogen-containing condensed phosphate esters, halogen-containing condensed phosphonate esters, halogen-containing phosphite esters, and the like.

  Specific examples include triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris (β-chloroethyl) phosphate, tris (dichloropropyl). Examples thereof include phosphate and tris (tribromoneopentyl) phosphate.

<Formation of acrylic resin-containing film (film (A))>
Although the example of the film forming method of an acrylic resin containing film (film (A)) is demonstrated, this invention is not limited to this.

  Production methods such as inflation method, T-die method, calendar method, cutting method, casting method, emulsion method, hot press method, etc. can be used as a method for producing an acrylic resin-containing film according to the present invention, but coloring suppression is also possible. From the viewpoints of suppressing foreign matter defects and optical defects such as die lines, solution casting by casting is preferred.

(Organic solvent)
The organic solvent useful for forming the dope when the acrylic resin-containing film according to the present invention is produced by the solution casting method is limited as long as it dissolves acrylic resin, cellulose ester resin, and other additives simultaneously. Can be used.

  For example, as the chlorinated organic solvent, methylene chloride, as the non-chlorinated organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro- Examples include 2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, and nitroethane. Methylene chloride, methyl acetate, ethyl acetate and acetone can be preferably used.

  In addition to the organic solvent, the dope preferably contains 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. When the proportion of alcohol in the dope increases, the web gels and peeling from the metal support becomes easy, and when the proportion of alcohol is small, the acrylic resin and cellulose ester resin dissolve in a non-chlorine organic solvent system. There is also a role to promote.

  In particular, in a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms, at least 15 to 45 mass in total of three types of acrylic resin, cellulose ester resin, and acrylic particles. It is preferable that the dope composition is dissolved in%.

  Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Ethanol is preferred because of the stability of these dopes, the relatively low boiling point, and good drying properties.

  Hereinafter, the preferable film-forming method of the acrylic resin containing film which concerns on this invention is demonstrated.

1) Dissolution process In an organic solution mainly composed of a good solvent for acrylic resin and cellulose ester resin, the acrylic resin, cellulose ester resin, and in some cases acrylic particles, and other additives are dissolved in a dissolution vessel while stirring. The step of forming, or the step of forming a dope which is a main solution by mixing the acrylic resin or cellulose ester resin solution with an acrylic particle solution or other additive solution as the case may be.

  For dissolution of acrylic resin and cellulose ester resin, a method performed at normal pressure, a method performed below the boiling point of the main solvent, a method performed under pressure above the boiling point of the main solvent, JP-A-9-95544, JP-A-9- Various dissolution methods such as a method of performing a cooling dissolution method as described in JP-A-95557 or JP-A-9-95538, a method of performing at high pressure as described in JP-A No. 11-21379 can be used, In particular, a method of pressurizing at a temperature equal to or higher than the boiling point of the main solvent is preferable.

  The total amount of the acrylic resin and the cellulose ester resin in the dope is preferably 15 to 45% by mass. An additive is added to the dope during or after dissolution to dissolve and disperse, then filtered through a filter medium, defoamed, and sent to the next step with a liquid feed pump.

  Filtration is preferably performed using a filter medium having a collected particle size of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml.

  In this method, the aggregate remaining at the time of particle dispersion and the aggregate generated when the main dope is added are only aggregated by using a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml. Can be removed. In the main dope, the concentration of particles is sufficiently thinner than that of the additive solution, so that aggregates do not stick together at the time of filtration and the filtration pressure does not increase suddenly.

  FIG. 1 is a diagram schematically showing a dope preparation step, a casting step, and a drying step of a solution casting film forming method preferable for the present invention.

  If necessary, large agglomerates are removed from the acrylic particle charging kettle 41 by the filter 44 and fed to the stock kettle 42. Thereafter, the acrylic particle additive solution is added from the stock kettle 42 to the main dope dissolving kettle 1.

  Thereafter, the main dope solution is filtered by the main filter 3, and an ultraviolet absorbent additive solution is added in-line from 16 to this.

  In many cases, the main dope may contain about 10 to 50% by mass of the recycled material. The return material may contain acrylic particles. In that case, it is preferable to control the addition amount of the acrylic particle addition liquid in accordance with the addition amount of the return material.

  The additive solution containing acrylic particles preferably contains 0.5 to 10% by mass of acrylic particles, more preferably 1 to 10% by mass, and 1 to 5% by mass. Most preferably.

  The above range is preferable because the smaller the acrylic particle content, the lower the viscosity and the easier the handling, and the higher the acrylic particle content, the smaller the addition amount and the easier the addition to the main dope.

  Recycled material is a finely pulverized acrylic resin-containing film that is generated when an acrylic resin-containing film is formed. The original fabric is used.

  In addition, an acrylic resin, a cellulose ester resin, and, in some cases, acrylic particles kneaded into pellets can be preferably used.

2) Casting process An endless metal belt 31, such as a stainless steel belt or a rotating metal drum, which feeds the dope through a liquid feed pump (for example, a pressurized metering gear pump) to the pressure die 30 and transfers it infinitely. This is a step of casting the dope from the pressure die slit to the casting position on the support.

  A pressure die that can adjust the slit shape of the die base portion and can easily make the film thickness uniform is preferable. The pressure die includes a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface. In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and stacked. Or it is also preferable to obtain the film of a laminated structure by the co-casting method which casts several dope simultaneously.

3) Solvent evaporation step In this step, the web (the dope is cast on the casting support and the formed dope film is called a web) is heated on the casting support to evaporate the solvent.

  To evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat from the back side of the support by a liquid, a method of transferring heat from the front and back by radiant heat, and the like. High efficiency and preferable. A method of combining them is also preferably used. The web on the support after casting is preferably dried on the support in an atmosphere of 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C., it is preferable to apply hot air at this temperature to the upper surface of the web or to heat by means such as infrared rays.

  From the viewpoint of surface quality, moisture permeability, and peelability, it is preferable to peel the web from the support within 30 to 120 seconds.

4) Peeling process It is the process of peeling the web which the solvent evaporated on the metal support body in a peeling position. The peeled web is sent to the next process.

  The temperature at the peeling position on the metal support is preferably 10 to 40 ° C, more preferably 11 to 30 ° C.

  The residual solvent amount at the time of peeling of the web on the metal support at the time of peeling is preferably peeled in the range of 50 to 120% by mass depending on the strength of drying conditions, the length of the metal support, and the like. When peeling off at a time when the amount of residual solvent is larger, if the web is too soft, the flatness at the time of peeling will be impaired, and slippage and vertical stripes are likely to occur due to peeling tension, so the balance between economic speed and quality The amount of residual solvent is determined.

  The residual solvent amount of the web is defined by the following formula.

Residual solvent amount (%) = (mass before web heat treatment−mass after web heat treatment) / (mass after web heat treatment) × 100
Note that the heat treatment for measuring the residual solvent amount represents performing heat treatment at 115 ° C. for 1 hour.

  The peeling tension at the time of peeling the metal support and the film is usually 196 to 245 N / m. However, when wrinkles easily occur at the time of peeling, it is preferable to peel with a tension of 190 N / m or less. It is preferable to peel at a minimum tension that can be peeled to 166.6 N / m, and then peel at a minimum tension to 137.2 N / m, and particularly preferably peel at a minimum tension to 100 N / m.

  In the present invention, the temperature at the peeling position on the metal support is preferably -50 to 40 ° C, more preferably 10 to 40 ° C, and most preferably 15 to 30 ° C.

5) Drying and stretching step After peeling, a drying device 35 that transports the web alternately through rolls arranged in the drying device and / or a tenter stretching device 34 that clips and transports both ends of the web with clips. And dry the web.

  Generally, the drying means blows hot air on both sides of the web, but there is also a means for heating by applying microwaves instead of the wind. Too rapid drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed from about 8% by mass or less of the residual solvent. Throughout the drying is generally carried out at 40-250 ° C. It is particularly preferable to dry at 40 to 160 ° C.

  When using a tenter stretching apparatus, it is preferable to use an apparatus that can independently control the film gripping length (distance from the start of gripping to the end of gripping) left and right by the left and right gripping means of the tenter. In the tenter process, it is also preferable to intentionally create sections having different temperatures in order to improve planarity.

  It is also preferable to provide a neutral zone between different temperature zones so that the zones do not interfere with each other.

  The stretching operation may be performed in multiple stages, and it is also preferable to perform biaxial stretching in the casting direction and the width direction. When biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise.

  In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible. That is, for example, the following stretching steps are possible.

-Stretch in the casting direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction-Stretch in the width direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction Simultaneous biaxial stretching includes stretching in one direction and contracting the other while relaxing the tension. The preferable draw ratio of simultaneous biaxial stretching can be taken in the range of x1.01 to x1.5 times in both the width direction and the longitudinal direction.

  When the tenter is used, the residual solvent amount of the web is preferably 20 to 100% by mass at the start of the tenter, and it is preferable to perform drying while applying the tenter until the residual solvent amount of the web becomes 10% by mass or less. More preferably, it is 5% by mass or less.

  30-150 degreeC is preferable, as for the drying temperature in the case of performing a tenter, 50-120 degreeC is more preferable, and 70-100 degreeC is the most preferable.

  In the tenter process, it is preferable that the temperature distribution in the width direction of the atmosphere is small from the viewpoint of improving the uniformity of the film. The temperature distribution in the width direction in the tenter process is preferably within ± 5 ° C, and within ± 2 ° C Is more preferable, and within ± 1 ° C. is most preferable.

6) Winding step This is a step of winding up the acrylic resin-containing film by the winder 37 after the residual solvent amount in the web is 2% by mass or less, and by setting the residual solvent amount to 0.4% by mass or less. A film having good dimensional stability can be obtained.

  As a winding method, a generally used method may be used. There are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, and the like.

  The acrylic resin-containing film according to the present invention is preferably a long film. Specifically, the acrylic resin-containing film is about 100 m to 5000 m, and is usually in the form of a roll. Moreover, it is preferable that the width | variety of a film is 1.3-4m, and it is more preferable that it is 1.4-2m.

  Although there is no restriction | limiting in particular in the film thickness of the acrylic resin containing film which concerns on this invention, When using for the polarizing plate protective film mentioned later, it is preferable that it is 20-200 micrometers, and it is more preferable that it is 25-100 micrometers, 30- It is especially preferable that it is 80 micrometers.

(Cellulose ester film (B))
The polarizing plate of the present invention comprises a cellulose ester film (B), and the cellulose ester constituting the cellulose ester film film (B) has an acyl group average substitution degree in the range of 2.0 to 2.5. It is characterized by that.

  Since the polarizing plate of the present invention has this characteristic, in the drying process of the polarizing plate, the drainage is quick due to the effect of sucking water even under mild conditions or high speed conditions, and the production speed of the drying process is high. Can be improved.

<Cellulose ester resin>
The cellulose ester film (B) according to the present invention contains a cellulose ester resin having an acyl group average substitution degree in the range of 2.0 to 2.5.

  The cellulose ester resin according to the present invention has an acyl group average substitution degree in the range of 2.0 to 2.5, but more preferably in the range of 2.2 to 2.5.

  The “acyl group average substitution degree” as used herein refers to an esterified (acylated) hydroxyl group (hydroxyl group) among the three hydroxyl groups (hydroxyl groups) of anhydroglucose (per basic unit) constituting cellulose. The average value of the number of is shown, and the value within the range of 0-3 is shown.

  When the average acyl substitution degree of the cellulose ester resin is less than 2.0, deterioration of film surface quality due to an increase in dope viscosity, haze increase due to an increase in stretching tension, and the like may occur. Further, when the total acyl substitution degree is larger than 2.5, a necessary phase difference cannot be obtained.

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

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

  In addition, the substitution degree of an acetyl group and the substitution degree of other acyl groups are obtained by a method prescribed in ASTM-D817-96 (testing method for cellulose acetate and the like).

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

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

  The weight average molecular weight Mw and the number average molecular weight Mn of the cellulose ester resin were measured using gel permeation chromatography (GPC).

  The measurement conditions are as follows.

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

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

  The cellulose ester resin according to the present invention can be produced by a known method. Generally, cellulose is esterified by mixing cellulose as a raw material, a predetermined organic acid (such as acetic acid or propionic acid), an acid anhydride (such as acetic anhydride or propionic anhydride), and a catalyst (such as sulfuric acid). The reaction proceeds until the triester is formed. In the triester, three hydroxyl groups (hydroxyl groups) of the glucose unit are substituted with an acyl acid of an organic acid. When two kinds of organic acids are used at the same time, a mixed ester type cellulose ester such as cellulose acetate propionate or cellulose acetate butyrate can be produced. Next, a cellulose ester resin having a desired degree of acyl substitution is synthesized by hydrolyzing the cellulose triester. Thereafter, a cellulose ester resin is completed through steps such as filtration, precipitation, washing with water, dehydration, and drying.

  Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

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

  In this invention, it is preferable that melting | fusing point of the cellulose-ester film which concerns on this invention shall be in the range of 200-290 degreeC. Methods for adjusting the melting point within the above range include controlling the degree of substitution of the cellulose ester resin or adding a plasticizer.

  In addition, as long as the effect of this invention is not impaired, thermoplastic resins other than the said cellulose ester resin can also be used together for the cellulose-ester film which concerns on this invention.

  Here, the “thermoplastic resin” refers to a resin that becomes soft when heated to the glass transition temperature or melting point and can be molded into a desired shape.

  General thermoplastic resins include polyethylene (PE), high density polyethylene, medium density polyethylene, low density polyethylene, polypropylene (PP), polyvinyl chloride (PVC), polyvinylidene chloride, polystyrene (PS). Polyvinyl acetate (PVAc), Teflon (registered trademark) (polytetrafluoroethylene, PTFE), ABS resin (acrylonitrile butadiene styrene resin), AS resin, and the like can be used.

  When strength and resistance to breakage are particularly required, polyamide (PA), nylon, polyacetal (POM), polycarbonate (PC), modified polyphenylene ether (m-PPE, modified PPE, PPO), polybutylene terephthalate (PBT) ), Polyethylene terephthalate (PET), glass fiber reinforced polyethylene terephthalate (GF-PET), cyclic polyolefin (COP), and the like.

  Furthermore, when high heat distortion temperature and long-term use characteristics are required, polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), polysulfone, polyethersulfone, amorphous polyarylate, liquid crystal polymer, polyether Ether ketone, thermoplastic polyimide (PI), polyamideimide (PAI), or the like can be used.

  In addition, it is possible to perform the kind of resin and the combination of molecular weight according to the use of this invention.

(Hydrolysis inhibitor)
In the present invention, as the hydrolysis inhibitor, for example, a mixture of ester compounds in which 1 to 12 of at least one pyranose structure or furanose structure and a part of the OH group of the structure is esterified is preferably used. it can.

  The ratio of esterification of an ester compound in which at least one of the pyranose structure or furanose structure is 1 to 12 and all or part of the OH groups of the structure is esterified is present in the pyranose structure or furanose structure. It is preferably 70% or more of the OH group.

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

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

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

  In addition, gentiobiose, gentiotriose, gentiotetraose, xylotriose, galactosyl sucrose, and the like are also included.

  Among these compounds, compounds having both a pyranose structure and a furanose structure are particularly preferable.

  Examples include sucrose, kestose, nystose, 1F-fructosyl nystose, stachyose, and more preferably sucrose.

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

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

  Examples of preferable alicyclic monocarboxylic acids include acetic acid, cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, and derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include aromatic monocarboxylic acids having an alkyl group or alkoxy group introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, cinnamic acid, benzylic acid, biphenylcarboxylic acid, and naphthalene. Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as carboxylic acid and tetralincarboxylic acid, or derivatives thereof. More specifically, xylyl acid, hemelic acid, mesitylene acid, prenylic acid, γ-isoduric acid, jurylic acid, mesitic acid, α-isoduric acid, cumic acid, α-toluic acid, hydroatropic acid, atropic acid, hydrocinnamic acid, salicylic acid, o-anisic acid, m-anisic acid, p-anisic acid , Creosote acid, o-homosalicylic acid, m-homosalicylic acid, p-homosalicylic acid, o-pyrocate Acid, β-resorcylic acid, vanillic acid, isovanillic acid, veratromic acid, o-veratrumic acid, gallic acid, asaronic acid, mandelic acid, homoanisic acid, homovanillic acid, homoveratrumic acid, o-homoveratrumic acid, phthalonic acid, p-coumaric Examples of the acid include benzoic acid and naphthylic acid.

  The oligosaccharide ester compound can be applied as a compound having 1 to 12 at least one of the pyranose structure or the furanose structure according to the present invention.

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

Moreover, the said ester compound is a compound which condensed 1 or more and 12 or less of at least 1 type of the pyranose structure or furanose structure represented with the following general formula (A). However, R < ₁₁ > -R < ₁₅ >, R < ₂₁ > -R < ₂₅ > represents a C2-C22 acyl group or a hydrogen atom, m and n represent the integer of 0-12, respectively, and m + n represents the integer of 1-12.

R _{11 to} R ₁₅ and R _{21 to} R ₂₅ are preferably a benzoyl group or a hydrogen atom. The benzoyl group may further have a substituent R ₂₆ , and examples thereof include an alkyl group, an alkenyl group, an alkoxyl group, and a phenyl group, and these alkyl group, alkenyl group, and phenyl group further have a substituent. May be. Oligosaccharides can also be produced in the same manner as the ester compound according to the present invention.

  Although the specific example of the ester compound which concerns on this invention is given to the following, this invention is not limited to this.

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

(Phase difference adjusting agent)
In the present invention, it is also preferable to add a retardation adjusting agent to the cellulose ester film or the like according to the present invention.

  The retardation adjusting agent used in the present invention needs to have an appropriate solubility corresponding to the resin. From the viewpoint of the orientation of the compound, for example, an ester compound represented by the following general formula (R1) is preferably used. be able to.

Formula (R1): B- (GA) n-GB
(In the formula, B is a hydroxyl group or carboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms. A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.)
In the general formula (R1), a hydroxyl group or a carboxylic acid residue represented by B, an alkylene glycol residue, an oxyalkylene glycol residue or an aryl glycol residue represented by G, an alkylene dicarboxylic acid residue represented by A or It is composed of an aryl dicarboxylic acid residue and can be obtained by the same reaction as that of a normal ester compound.

  Examples of the carboxylic acid component of the ester compound represented by the general formula (R1) include acetic acid, propionic acid, butyric acid, benzoic acid, p-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, and dimethylbenzoic acid. , Ethyl benzoic acid, normal propyl benzoic acid, aminobenzoic acid, acetoxybenzoic acid, aliphatic acid and the like, and these can be used as one kind or a mixture of two or more kinds.

  Examples of the alkylene glycol component having 2 to 12 carbon atoms of the ester compound represented by the general formula (R1) include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, , 3-butanediol, 1,2-propanediol, 2-methyl 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol ( Neopentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane) ), 3-methyl-1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl 1,3-pentanedio 2, 2-ethyl 1,3-hexanediol, 2-methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, and the like. , One or a mixture of two or more.

  In particular, an alkylene glycol having 2 to 12 carbon atoms is particularly preferable because of excellent compatibility with a cellulose ester.

  Examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the ester compound represented by the general formula (R1) include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. Yes, these glycols can be used as one or a mixture of two or more.

  Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the ester compound represented by the general formula (1) include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecane. There exist dicarboxylic acid etc., and these are each used as a 1 type, or 2 or more types of mixture. Examples of the arylene dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5 naphthalene dicarboxylic acid, and 1,4 naphthalene dicarboxylic acid.

  The number average molecular weight of the ester compound represented by the general formula (R1) is preferably 300 to 1500, and more preferably 400 to 1000. The acid value is 0.5 mgKOH / g or less, the hydroxyl (hydroxyl) value is 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxyl (hydroxyl) value is 15 mgKOH / g or less. is there.

  Although the specific compound of the ester-type compound represented with general formula (R1) which can be used for this invention below is shown, this invention is not limited to this.

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

  Moreover, the phase difference adjusting agent used for the film which concerns on this invention is used in order to speed up the volatilization rate of a solvent or to reduce the amount of residual solvents in a solution casting method. Moreover, also in the film by a melt film-forming method, a phase difference adjusting agent is a useful material in order to prevent coloring and film strength deterioration. Further, the addition of the retardation adjusting agent to the film according to the present invention has a useful effect in terms of film modification such as improvement of mechanical properties, flexibility, water absorption resistance, and moisture permeability reduction. Show.

  The content of the additive is 1 to 35% by mass and 4 to 30% by mass with respect to the cellulosic resin from the viewpoint of compatibility with temperature and humidity changes, prevention of whitening of the film, physical properties, and the like. It is more preferably 10 to 25% by mass.

  Here, the number average molecular weight of the retardation adjusting agent in the present invention is more preferably a number average molecular weight of 700 or more and less than 10,000, still more preferably a number average molecular weight of 800 to 8000, and still more preferably a number average molecular weight of 800 to 8000. 5000, particularly preferably a number average molecular weight of 1000 to 5000. By setting it as such a range, it is more excellent in compatibility.

(Phase difference agent)
In the present invention, a conventionally known retardation (also referred to as “retardation”) developing agent may be included. For example, the discotic compounds and rod-like compounds described in paragraphs [0087] to [0202] of JP2009-265295A, and the paragraphs [0037] to [0060] of JP2010-054736A are described. A triazine compound or the like can be used as a phase difference developing agent.

  The retardation (retardation) developing agent can be contained in the cellulose ester film or the like, for example, at a rate of 0.5 to 10% by mass, and more preferably 2 to 6% by mass. . By adopting a retardation developing agent, high Re developability can be obtained at a low draw ratio.

(Plasticizer)
The cellulose ester film according to the present invention can contain a plasticizer as necessary to obtain the effects of the present invention.

  The plasticizer is not particularly limited, but is preferably a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a fatty acid ester plasticizer, a polyhydric alcohol ester plasticizer, or a polyester plasticizer. Agent, acrylic plasticizer 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 polyhydric alcohol preferably used in the present invention is represented by the following general formula (a).

Formula (a): R1- (OH) n
However, R1 represents an n-valent organic group, n represents a positive integer of 2 or more, and the OH group represents an alcoholic and / or phenolic hydroxyl group (hydroxyl group).

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

  Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane- Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol and the like.

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

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

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

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-10. When acetic acid is contained, the compatibility with the cellulose ester is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

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

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

  The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably 300 to 1500, and more preferably 350 to 750. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose ester.

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

(Antioxidant)
In the present invention, known antioxidants for cellulose ester solutions such as 2,6-di-tert-butyl-4-methylphenol, 4,4'-thiobis- (6-tert-butyl-3-methylphenol) ), 1,1′-bis (4-hydroxyphenyl) cyclohexane, 2,2′-methylenebis (4-ethyl-6-tert-butylphenol), 2,5-di-tert-butylhydroquinone, pentaerythrityl-tetrakis A phenolic or hydroquinone antioxidant such as [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] can be added. Further, tris (4-methoxy-3,5-diphenyl) phosphite, tris (nonylphenyl) phosphite, tris (2,4-di-tert-butylphenyl) phosphite, bis (2,6-di-tert) It is preferable to use a phosphorus-based antioxidant such as -butyl-4-methylphenyl) pentaerythritol diphosphite and bis (2,4-di-tert-butylphenyl) pentaerythritol diphosphite. The added amount of the antioxidant is 0.05 to 5.0 parts by mass with respect to 100 parts by mass of the cellulose resin.

(UV absorber)
In the present invention, an ultraviolet absorber is preferably used for the cellulose ester solution from the viewpoint of preventing deterioration of a polarizing plate or liquid crystal. As the ultraviolet absorber, those excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less and having little absorption of visible light having a wavelength of 400 nm or more are preferably used from the viewpoint of good liquid crystal display properties. Specific examples of ultraviolet absorbers preferably used in the present invention include, for example, hindered phenol compounds, hydroxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds Etc. Examples of hindered phenol compounds include 2,6-di-tert-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate]. N, N'-hexamethylenebis (3,5-di-tert-butyl-4-hydroxy-hydrocinnamide), 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert) -Butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-tert-butyl-4-hydroxybenzyl) -isocyanurate and the like. Examples of benzotriazole compounds include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2,2-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), (2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5- Triazine, triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], N, N′-hexamethylenebis (3,5-di-tert-butyl-4- Hydroxy-hydrocinnamide), 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, (2- (2'-hydroxy-3', 5'-di-tert-amylphenyl) -5-chlorobenzotriazole, 2,6-di-tert-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] The addition amount of these ultraviolet light inhibitors is preferably 1 ppm to 1.0% by mass ratio, more preferably 10 to 1000 ppm, in the whole cellulose ester film.

(Matting agent)
It is preferable to add fine particles as a matting agent to the cellulose ester film according to the present invention. The fine particles used in the present invention include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, silica Mention may be made of magnesium and calcium phosphates. Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable. The fine particles of silicon dioxide preferably have a primary average particle size of 20 nm or less and an apparent specific gravity of 70 g / liter or more. Those having an average primary particle size as small as 5 to 16 nm are more preferred because they can reduce the haze of the film. The apparent specific gravity is preferably 90 to 200 g / liter or more, and more preferably 100 to 200 g / liter or more. A larger apparent specific gravity is preferable because a high-concentration dispersion can be produced, and haze and aggregates are improved.

  These fine particles usually form secondary particles having an average particle size of 0.1 to 3.0 μm, and these fine particles exist in the film as aggregates of primary particles, and 0.1 to 0.1 μm on the film surface. An unevenness of 3.0 μm is formed. The secondary average particle size is preferably 0.2 to 1.5 μm, more preferably 0.4 to 1.2 μm, and most preferably 0.6 to 1.1 μm. For the primary and secondary particle sizes, the particles in the film were observed with a scanning electron microscope, and the diameter of a circle circumscribing the particles was defined as the particle size. In addition, 200 particles were observed at different locations, and the average value was taken as the average particle size.

  As the fine particles of silicon dioxide, for example, commercially available products such as Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above Nippon Aerosil Co., Ltd.) can be used. Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used.

  Among them, Aerosil 200V and Aerosil R972V are fine particles of silicon dioxide having a primary average particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more, while keeping the turbidity of the cellulose ester film low. This is particularly preferable because the effect of reducing the friction coefficient is great.

  In the present invention, in order to obtain a film having particles having a small secondary average particle size, several methods are conceivable when preparing a dispersion of fine particles. For example, there is a method in which a fine particle dispersion prepared by stirring and mixing a solvent and fine particles is prepared in advance, and this fine particle dispersion is added to a separately prepared small amount of cellulose ester solution, dissolved by stirring, and further mixed with the main cellulose ester dope solution. . This method is a preferable preparation method in that the dispersibility of the silicon dioxide fine particles is good and the silicon dioxide fine particles are more difficult to reaggregate. In addition, after adding a small amount of cellulose ester to the solvent and dissolving with stirring, add the fine particles to this and disperse with a disperser. This is used as a fine particle additive solution, and this fine particle additive solution is sufficiently mixed with the dope solution using an in-line mixer. There is also a method of mixing. Although this invention is not limited to these methods, 5-30 mass% is preferable, as for the density | concentration of silicon dioxide when silicon dioxide microparticles | fine-particles are mixed and disperse | distributed with a solvent etc., 10-25 mass% is further more preferable, 15-15. Most preferred is 20% by weight. A higher dispersion concentration is preferable because the liquid turbidity with respect to the added amount is lowered, and haze and aggregates are improved. In addition, when the matting agent is added to the cellulose ester film according to the present invention and used, the matting agent content in the film surface layer is 0.05 regardless of spherical or irregular fine particles with respect to 100 parts by mass of the film surface layer. It is -1.00 mass part, Preferably it is 0.07-0.60 mass part, More preferably, it is 0.10-0.40 mass part. When the content of fine particles in the surface layer is less than 0.05 parts by mass, it becomes difficult to ensure the slipperiness and anti-tacking properties of the cellulose ester film surface, and when it exceeds 1.00% by mass, the transparency is poor. Become.

  The solvent used is preferably lower alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like. Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film forming of a cellulose ester.

(Physical properties of cellulose ester film)
Hereinafter, the characteristics of the cellulose ester film according to the present invention as an optical film will be described.

<Phase difference (retardation)>
A retardation (retardation) was obtained by cutting a 35 mm × 35 mm sample from the produced cellulose ester film, adjusting the humidity for 2 hours at 23 ° C. and 55% RH, and using an automatic birefringence meter (KOBRA WR, Oji Scientific Co., Ltd.) at 590 nm. Ro (590) and Rt (590) at each wavelength were calculated from the value measured from the vertical direction at λ and the extrapolated value of the retardation value measured in the same manner while tilting the film surface.

  The cellulose ester film according to the present invention has an in-plane retardation (retardation) value Ro (590) defined by the following formula (I) at a measurement light wavelength of 590 nm within a range of 30 to 70 nm. It is preferable that the retardation value Rt (590) in the thickness direction defined by II) is in the range of 100 to 200 nm and the thickness is in the range of 20 to 50 μm.

In the present application, Ro (590) and Rt (590) are defined by the following formulas (I) to (III), respectively.
Formula (I): Ro (590) = (nx−ny) × d
Formula (II): Rt (590) = ((nx + ny) / 2−nz) × d
In the above formula, Ro (590) represents the in-plane retardation (retardation) value in the film at the measurement light wavelength of 590 nm, and Rt (590) represents the thickness direction retardation (retard) in the film at the measurement light wavelength of 590 nm. Value). D represents the thickness (nm) of the film, nx represents the maximum refractive index in the plane of the film at the measurement light wavelength of 590 nm, and is also referred to as the refractive index in the slow axis direction. ny represents the refractive index in the direction perpendicular to the slow axis in the film plane at the measurement light wavelength of 590 nm, and nz represents the refractive index of the film in the thickness direction at the measurement light wavelength of 590 nm.

  In the present invention, a cellulose ester having an acyl substituent having 2 to 4 carbon atoms and an acyl group substitution degree in the range of 2.0 to 2.5, an amphiphilic additive, By containing a suitable amount of hydrolysis inhibitor and retardation adjusting agent, the retardation (retardation) value is set to a desired value, the stretching temperature (combination of the temperatures of the respective sections), the magnification, the stretching speed, The retardation value can be adjusted to a desired value by adjusting and controlling the stretching order, the residual solvent amount of the film when stretching, and the like.

  By adjusting the retardation (retardation) to such a range, the viewing angle of the liquid crystal display device using the film of the present invention can be widened, and the front contrast can be improved.

Front contrast = (brightness of white display measured from normal direction of display device) / (brightness of black display measured from normal direction of display device)
The viewing angle is an angle at which a certain level of contrast can be maintained when the viewing direction of the liquid crystal display device is tilted from the normal direction.

<Method for producing cellulose ester film>
The cellulose ester film according to the present invention is produced by a solution casting method in which a cellulose ester and an additive are dissolved in a solvent to prepare a dope, and a dope is cast on a metal support such as a belt or a drum. It is performed by a step of drying the cast dope as a web, a step of peeling from the metal support, a step of stretching or maintaining the width, a step of further drying, and a step of winding up the finished film.

<< About the process of preparing dope >>
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 organic solvent is a solvent selected from ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, esters having 3 to 12 carbon atoms, and halogenated hydrocarbons having 1 to 6 carbon atoms. It is preferable to contain. The ether, ketone and ester may have a cyclic structure. A compound having two or more functional groups of ether, ketone, and ester (that is, —O—, —CO—, and COO—) can also be used as the organic solvent. The organic solvent may have another functional group such as an alcoholic hydroxyl group (hydroxyl group).

  In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group.

  Examples of the ether having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole.

  Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone.

  Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate.

  Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.

  The number of carbon atoms of the halogenated hydrocarbon is preferably 1 or 2, and most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. The proportion of halogen atoms substituted by halogen in the halogenated hydrocarbon is preferably 25 to 75 mol%, more preferably 30 to 70 mol%, and more preferably 35 to 65 mol%. More preferably, it is most preferable that it is 40-60 mol%. Methylene chloride is a representative halogenated hydrocarbon. These are called good solvents.

  The dope preferably contains 1 to 40% by mass of an alcohol having 1 to 4 carbon atoms in addition to the organic solvent. After casting the dope on the metal support, the solvent starts to evaporate and the alcohol ratio increases, so that the web (referred to as the dope film after casting the cellulose derivative dope on the support is called web As a gelling solvent that makes it easy to peel off from the metal support, and when these ratios are small, it promotes the dissolution of cellulose derivatives of non-chlorine organic solvents There is also a role to suppress gelation, precipitation, and viscosity increase of the reactive metal compound.

  Examples of the alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol, and propylene glycol monomethyl ether. Of these, ethanol is preferred because of its excellent dope stability, relatively low boiling point, and good drying properties. These are called poor solvents.

  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.

  There may be a trace amount of additives added to the cellulose ester in the recovered solvent, but even if they are contained, they can be reused preferably, and if necessary, purified and reused. You can also

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

  It is preferable to stir and dissolve while heating at a temperature that is 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.

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

  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.

  In the present invention, 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 easily 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 is arranged in a crossed Nicols state with two polarizing plates, a cellulose ester film or the like is placed between them, light is applied from the side of one polarizing plate, and observation is performed from the side of the other polarizing plate. It is a point (foreign matter) where light from the opposite side sometimes leaks, and the number of bright spots having a diameter of 0.01 mm or more is preferably 200 / cm ² or less.

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

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

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

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

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

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

  A preferable support temperature is 0 to 55 ° C, and more preferably 25 to 50 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent.

  The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing warm 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 cellulose ester film to exhibit good flatness, the residual solvent amount when peeling the web from the metal support is preferably 10 to 150% by mass, more preferably 20 to 40% by mass or 60 to 130% by mass. Especially preferably, it is 20-30 mass% or 70-120 mass%.

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

Residual solvent amount (% by mass) = {(MN) / N} × 100
Note that 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.

<< About the drying process >>
In the drying step of the cellulose ester film, the web is peeled off from the metal support and further dried, and the residual solvent amount is preferably 1% by mass or less, more preferably 0.1% by mass or less, and particularly preferably. Is 0 to 0.01% by mass or less.

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

  In order to produce the cellulose ester film according to the present invention, it is particularly preferable to perform stretching in the width direction (lateral direction) by a tenter method in which both ends of the web are held with clips or the like. Peeling is preferably performed at a peeling tension of 300 N / m or less.

  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.

  The thickness (film thickness) of the cellulose ester film is preferably 20 to 50 μm.

  The cellulose ester film according to the present invention has a width of 1 to 4 m. In particular, those having a width of 1.4 to 4 m are preferably used, and particularly preferably 1.9 to 2.5 m. By making it in this range, it is possible to achieve both efficient polarizing plate cutting and handling suitability.

  In addition, the cellulose ester film according to the present invention preferably has a length of 100 m to 10000 m, more preferably 1000 m to 10000 m, and particularly preferably 5000 m to 10000 m per roll. By setting it as this range, it is easy to handle in a roll form, and further, it has an effect of being adapted to a continuous process of polarizing plates and improving the yield.

  In order to impart the following desired retardation values (Ro, Rt) to the cellulose ester film, the cellulose ester film may have the configuration of the present invention, and the refractive index may be controlled by controlling the transport tension and stretching operation. preferable.

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

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

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

  The stretching temperature is preferably 120 ° C to 200 ° C, more preferably 120 ° C to 180 ° C, and further preferably 120 ° C to 160 ° C.

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

  There is no particular limitation on the method of stretching the web. For example, a method in which a difference in peripheral speed is applied to a plurality of rolls, and the roll peripheral speed difference is used to stretch in the longitudinal direction, the both ends of the web are fixed with clips and pins, and the interval between the clips and pins is increased in the traveling direction. And a method of stretching in the vertical direction, a method of stretching in the horizontal direction and stretching in the horizontal direction, a method of stretching in the vertical and horizontal directions and stretching in both the vertical and horizontal directions. Of course, these methods may be used in combination.

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

  These width maintenance or lateral stretching in the film forming step is preferably performed by a tenter, and may be a pin tenter or a clip tenter.

  The slow axis or the fast axis of the cellulose ester film according to the present invention is present in the film plane, and θ1 is preferably −1 ° or more and + 1 ° or less when the angle formed with the film forming direction is θ1. It is more preferably 0.5 ° or more and + 0.5 ° or less, and further preferably −0.1 ° or more and + 0.1 ° or less.

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

(Change in humidity of equilibrium moisture content)
In the present invention, a film (A) and a cellulose ester film (B) containing an acrylic resin and a cellulose ester resin on both sides sandwiching the polarizer are easy to cope with a change in humidity and optical properties and dimensions are more difficult to change. ) The absolute value of the difference ΔH (80% -20%) between the equilibrium water content at each temperature of 23 ° C. and 20% relative humidity and the equilibrium water content at the temperature of 23 ° C. and 80% relative humidity is 3.0. The absolute value of the difference ΔH between the equilibrium moisture content ΔH (80% -20%) of each of the films (A) and (B) on both sides is in the range of ˜5.0%. It is preferable to be within the range of 0.0%.

  Here, the “equilibrium moisture content” is the water content contained in the sample (film) in an equilibrium state as a percentage of the sample mass.

  As a specific method of obtaining the humidity change of the equilibrium moisture content, a sample 7 mm × 35 mm was conditioned at a temperature of 23 ° C. and a relative humidity of 20% RH for 2 hours, and the Karl Fischer method trace moisture meter LE-20S (Hiranuma Sangyo) The water content was calculated by dividing the water content (g) in the sample at a relative humidity of 20% by the sample mass (g). A similar sample was conditioned at a temperature of 23 ° C. and a relative humidity of 80% RH for 2 hours, measured with a Karl Fischer method trace moisture meter LE-20S (manufactured by Hiranuma Sangyo Co., Ltd.), and a sample at a relative humidity of 80%. The moisture content was calculated by dividing the moisture content (g) in the sample by the sample mass (g). The difference between the equilibrium moisture content at 20% relative humidity and the equilibrium moisture content at 80% relative humidity was determined as ΔH (80% -20%).

  Moreover, the difference (DELTA) H (80% -20%) difference of the said equilibrium moisture content of each film (A) and (B) of the said both sides was calculated | required as (DELTA) H.

  As a means for controlling the equilibrium moisture content within the above range, it is carried out by adjusting the total substitution degree of the cellulose ester resin and adjusting the kinds and addition amounts of various additives contained in the films (A) and (B). be able to.

(Polarizer)
The polarizing plate of the present invention is a polarizing plate comprising a film (A) containing an acrylic resin and a cellulose ester resin, a polarizer, and a cellulose ester film (B).

  The polarizing plate using the film according to the present invention can be produced by a general method. An adhesive layer is provided on the back side of the film, and it is preferably bonded to at least one surface of a polarizer produced by immersing and stretching in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution.

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

  In addition, the "polarizer" which is the main component of the polarizing plate is an element that passes only light having a polarization plane in a certain direction, and a currently known typical polarizing film is a polyvinyl alcohol-based polarizing film, There are one in which iodine is dyed on a polyvinyl alcohol film and one in which a dichroic dye is dyed.

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

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

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

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

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

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

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

  The pressure-sensitive adhesive may be a solvent system using an organic solvent as a medium, or an aqueous system such as an emulsion type, a colloidal dispersion type, or an aqueous solution type that is a medium containing water as a main component. It may be a solvent type. The density | concentration of the said adhesive liquid should just be suitably determined with the film thickness after adhesion, the coating method, the coating conditions, etc., and is 0.1-50 mass% normally.

<Liquid crystal display device>
The polarizing plate of this invention can be used for the liquid crystal display device of a various aspect. For example, a liquid crystal display device having at least one polarizing plate of the present invention and a liquid crystal cell, wherein the film (A) containing the acrylic resin and cellulose ester resin of the polarizing plate is the cellulose ester film (B From the viewpoint of manifesting the effects of the present invention, it is preferable to use the liquid crystal display device in a mode provided at a position far from the liquid crystal cell.

  By using the polarizing plate of the present invention for a liquid crystal display device, various liquid crystal display devices with excellent visibility can be produced.

  The polarizing plate of the present invention can be used for liquid crystal display devices of various drive systems such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS, OCB. A VA (MVA, PVA) type liquid crystal display device is preferable.

  In particular, even a large-screen liquid crystal display device with a 30-inch or larger screen can provide a liquid crystal display device with excellent visibility such as uneven coloring and front contrast with little environmental fluctuation and reduced light leakage.

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

Example 1
<Production of Cellulose Ester Film (B) 101-107>
(Production of cellulose ester film (B) 107)
(Fine particle dispersion)
Fine particles (Aerosil R812 manufactured by Nippon Aerosil Co., Ltd.) 11 parts by weight Ethanol 89 parts by weight The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

(Fine particle additive)
Cellulose ester CE-7 (see Table 1) was added to a dissolution tank containing methylene chloride and heated to completely dissolve, then, this was added to Azumi Filter Paper No. Azumi Filter Paper No. Filtered using 244. While sufficiently stirring the cellulose ester solution after filtration, the fine particle dispersion was slowly added thereto. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle addition solution.

Methylene chloride 99 parts by weight Cellulose ester CE-7 4 parts by weight Fine particle dispersion 11 parts by weight Cellulose ester CE-7 was used to prepare a main dope liquid having the following composition.

  First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose ester CE-7 was added to a pressurized dissolution tank containing a solvent while stirring. This is completely dissolved with heating and stirring. This was designated as Azumi Filter Paper No. The main dope solution was prepared by filtration using 244.

(Main dope composition)
Methylene chloride 300 parts by mass Ethanol 30 parts by mass Cellulose ester CE-7 (acetyl substitution degree 2.43) 100 parts by mass Hydrolysis inhibitor (A) 10 parts by mass Phase difference modifier (B) 2.5 parts by mass Main dope solution 2 parts by mass of the fine particle additive solution is added to 100 parts by mass and thoroughly mixed with an in-line mixer (Toray static type in-pipe mixer Hi-Mixer, SWJ), and then the dope solution is heated to a temperature of 33 using an endless belt casting apparatus. The film was uniformly cast on a stainless steel belt support at a temperature of 1500 mm and a width of 1500 mm. The temperature of the stainless steel belt was controlled at 30 ° C.

  On the stainless steel belt support, the solvent was evaporated until the residual solvent amount in the cast (cast) film was 75%, and then peeled off from the stainless steel belt support with a peeling tension of 130 N / m.

  The peeled cellulose ester film 107 was stretched 36% in the width direction using a tenter while applying heat at 160 ° C. The residual solvent at the start of stretching was 15%.

  Next, drying was terminated while the drying zone was conveyed by a number of rolls. The drying temperature was 130 ° C. and the transport tension was 100 N / m.

  As described above, a cellulose acetate film (B) 107 having a dry film thickness of 40 μm was obtained.

  Table 1 shows the contents of cellulose ester CE-7 used above and the cellulose ester used in the following examples. In addition, CE-2 described in Table 1 is cellulose acetate propionate (acetyl group substitution degree = 0.88, propionyl group substitution degree = 1.58).

(Production of cellulose ester film (B) 101-106)
Cellulose esters 101 to 106 were prepared in the same manner as described above except that the cellulose ester, hydrolysis inhibitor (A), and retardation adjusting agent (B) shown in Table 1 were changed as shown in Table 1. It was.

<Production of acrylic resin / cellulose ester resin mixed film (A) 108-112>
(Preparation of acrylic resin / cellulose ester resin mixed film (A) 111)
(Dope composition solution)
Acrylic resin: Dianal BR85 (Mitsubishi Rayon Co., Ltd.) 70 parts by mass Cellulose ester resin: CAP482-20 (acyl group total substitution degree 2.75, acetyl group total substitution degree 0.19, propionyl group total substitution degree 2.56) Mw = 200000, manufactured by Eastman Chemical Co., Ltd.) 30 parts by mass Methylene chloride 300 parts by mass Ethanol 40 parts by mass The above was put into a closed container, stirred and dissolved while heating to prepare a dope solution. Next, an endless belt casting apparatus was used to uniformly cast the dope solution on a stainless steel belt support at a temperature of 22 ° C. and a width of 2000 mm. The temperature of the stainless steel belt was controlled at 30 ° C.

  On the stainless steel belt support, the solvent was evaporated until the amount of residual solvent in the cast (cast) film reached 100%, and then peeled off from the stainless steel belt support with a peeling tension of 162 N / m.

  The peeled cellulose acetate film was stretched 36% in the width direction using a tenter while applying heat at 160 ° C. The residual solvent at the start of stretching was 15%.

  Next, drying was terminated while the drying zone was conveyed by a number of rolls. The drying temperature was 130 ° C. and the transport tension was 100 N / m.

  As described above, an acrylic resin / cellulose ester resin mixed film (A) 111 having a dry film thickness of 40 μm was obtained.

(Production of acrylic resin / cellulose ester resin mixed film (A) 108 to 110, 112)
Acrylic resin / cellulose ester resin mixed films (A) 108 to 110 and 112 were produced in the same manner as described above except that the acrylic resin and cellulose ester resin shown in Table 2 were changed as shown in Table 2.

<Preparation of polarizing plates 1 to 35>
A 120 μm-thick polyvinyl alcohol film was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times). This was immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and then immersed in an aqueous solution at 68 ° C. consisting of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. This was washed with water and dried to obtain a polarizer.

  Subsequently, according to the following processes 1-5, the said cellulose-ester film and the acrylic resin / cellulose-ester resin mixed film were bonded together as a polarizer protective film on the back surface side, and the polarizing plate was produced.

  Step 1: A cellulose ester film and an acrylic resin / cellulose ester resin mixed film were immersed in a 2 mol / L potassium hydroxide solution at 50 ° C. for 30 seconds, then washed with water and dried to obtain a saponified film.

  Step 2: The deflector was immersed in a polyvinyl alcohol adhesive bath having a solid content of 2% by mass for 1 to 2 seconds.

  Step 3: Acrylic resin / cellulose ester resin in which excess adhesive adhering to the deflector in Step 2 is lightly wiped and placed on the cellulose ester film treated in Step 1, and further on the back side on the deflector side The mixed film was placed and placed.

Step 4: Step 3 Cellulose ester film laminated with the polarizers and the backside film pressure 20-30 N / cm ^2, the conveyance speed was laminated at about 2m / min.

  Process 5: The sample which bonded the cellulose-ester film and back surface film produced at process 4 in the 60 degreeC dryer was dried for 2 minutes, and the polarizing plate was produced.

  According to said method, the polarizing plates 1-35 of the combination of various films (A) and films (B) as shown in Table 3 were obtained. These polarizing plates were evaluated as follows.

Evaluation method (Adhesion evaluation)
Each of the produced polarizing plates was cut into a square of 5 cm × 5 cm, left in an atmosphere of 23 ° C. and 55% RH for 24 hours, and then peeled off from the interface of the polarizer and the film from the corner. The state of peeling at the time was visually evaluated according to the following criteria.
A: No peeling at all. B: A little peeled around. ×: Half or more peeled off.

(Evaluation for preventing polarization unevenness)
For each of the produced polarizing plates, two 10 cm × 10 cm polarizing plates were cut out as test pieces, stored for 120 hours in a high temperature and high humidity atmosphere at a temperature of 60 ° C. and a relative humidity of 90% RH, and then on a light box with a color temperature of 5000 K. The test pieces cut out from the same polarizing plate were placed in crossed Nicols, and the degree of polarization was measured in an environment of 23 ° C. and relative humidity 55%, and uneven polarization degree (variation in polarization degree) was visually evaluated. : No occurrence of uneven polarization degree ○: Unevenness of polarization degree cannot be recognized with naked eyes Δ: Although it appears as uneven polarization degree, there is no problem in use ×: There is a problem in display quality.

<Production of liquid crystal display device>
A liquid crystal panel was produced as follows, and the characteristics as a liquid crystal display device were evaluated.

  A film (A) containing the acrylic resin and cellulose ester resin of the produced polarizing plate by peeling off the previously bonded polarizing plates of a VA mode type liquid crystal display device (BRAVIAV1, 40 type manufactured by SONY). However, it bonded on both surfaces so that it might be in the state equipped with the position far from a liquid crystal cell from the said cellulose-ester film (B) so that it may become the glass surface of a liquid crystal cell.

  In that case, it performed so that an absorption axis might turn to the same direction as the polarizing plate previously bonded, and each liquid crystal display device was produced.

  As the polarizing plate, a polarizing plate stored for 120 hours in a high-temperature and high-humidity atmosphere at a temperature of 60 ° C. and a relative humidity of 90% RH was used in the same manner as in the evaluation of prevention of uneven polarization degree.

<Evaluation of liquid crystal display device>
In an environment of 23 ° C. and 55% RH, the backlight was continuously turned on for 12 hours, and the entire black display state was visually observed in a dark room to evaluate the display uniformity of the polarizing plate.

[Display uniformity]
The display uniformity during black display was visually evaluated according to the following criteria.
○: Black luminance is almost the same Δ: Some unevenness is observed in black luminance ×: Large difference in black luminance is observed Note that if it is Δ or more, there is no problem in use.

  The above evaluation results are shown in Table 3.

  As is clear from the results shown in Table 3, the polarizing plate of the present invention has superior adhesion compared to the comparative example, and polarization degree unevenness does not occur or cannot be recognized after long-term storage in a high temperature and high humidity atmosphere. It can be seen that it has a level of durability.

  It can also be seen that the liquid crystal display device using the polarizing plate of the present invention has excellent display uniformity even though the polarizing plate is stored for a long time in a high temperature and high humidity atmosphere.

  As is clear from the above results, the present invention prevents the polarizer from being deteriorated due to insufficient drying in the manufacturing process of the polarizing plate, has high adhesion and durability under high temperature and high humidity, and changes in optical characteristics. Can be provided. In addition, a liquid crystal display device using the same can be provided.

Claims (3)

  A polarizing plate comprising a film (A) containing an acrylic resin and a cellulose ester resin, a polarizer, and a cellulose ester film (B), and an acyl group of the cellulose ester resin constituting the cellulose ester film (B) An average substitution degree is in the range of 2.0 to 2.5. The polarizing plate according to claim 1, wherein the film (A) containing the acrylic resin and the cellulose ester resin satisfies all of the following requirements (1) to (3).
(1) The content ratio (molar ratio) between the acrylic resin and the cellulose ester resin is in the range of 95: 5 to 30:70.
(2) The acrylic resin has a weight average molecular weight of 80000 or more.
(3) The substitution degree of the acyl group of the cellulose ester resin is in the range of 2.0 to 3.0, and the weight average molecular weight Mw of the cellulose ester resin is 75,000 or more.   A liquid crystal display device having at least one polarizing plate according to claim 1 or 2 and a liquid crystal cell, wherein the film (A) containing the acrylic resin and cellulose ester resin of the polarizing plate is A liquid crystal display device provided at a position farther from the liquid crystal cell than the cellulose ester film (B).