JP2010243821A - Method of manufacturing retardation compensation film, retardation compensation film, composite polarizing plate, polarizing plate, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a retardation compensation film having sufficient frontal retardation and biaxial property as an optical compensation member and having high durability under heating conditions. <P>SOLUTION: The method of manufacturing the retardation compensation film includes: a preheat step of preheating a film obtained by using an amorphous resin and a thermoplastic elastomer resin that substantially has a phase separation form with respect to the amorphous resin, a heat-drawing step of heat-drawing the film; and a heat treatment step of heat-treating the stretched film. In the heat-drawing step, the heat-drawing process is carried out at least twice, and the following expressions are satisfied: (1) Ts1<Tg+15<Tp≤Tg+35 and (2) Tg<Tsn<Ts1, wherein Tp(°C) represents the heating temperature in the preheat step, Ts1(°C) represents the heating temperature in the first heat-drawing process, Tsn(°C) represents the heating temperature in the n-th (the second or subsequent) heat-drawing process, and Tg(°C) represents the glass transition temperature of the amorphous resin. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  INDUSTRIAL APPLICABILITY The present invention can be used for a liquid crystal display device, and a method for producing a retardation compensation film, a retardation compensation film, a composite polarizing plate, a polarizing plate, which can maintain a display image of the liquid crystal display device with high quality over a long period of time. The present invention relates to a plate and a liquid crystal display device.

  A liquid crystal display device is configured by laminating a retardation film and a polarizing plate in a liquid crystal cell in which liquid crystal molecules are sealed and an electrode is incorporated. In a liquid crystal display device, optical films having various functions are used to improve the image quality of a display viewed through a polarizing plate. Optical films are required not only to be excellent in transparency and optical compensation properties, but also to be excellent in various optical properties depending on applications.

  In order to eliminate the optical distortion inherent in liquid crystals due to birefringence and the viewing angle dependence such as the coloration of the display depending on the visual direction, the optical film is used as a retardation compensation using optical anisotropy. Film is widely used.

  An IPS (In-Plane Switching) type and OCB (Optically Compensated Bend) type liquid crystal display device has a structure in which liquid crystal molecules are aligned horizontally or inclined with respect to a panel substrate. For this reason, a negative retardation compensation plate in which the refractive index ellipsoid has a major axis in the panel normal direction and the intrinsic birefringence is a negative value is suitably used as the retardation compensation film. The material of the negative retardation compensator is required to have a property that the refractive index increases in a direction orthogonal to the orientation direction of the molecular main chain. As a thermoplastic resin material exhibiting negative intrinsic birefringence, an acrylic resin, a styrene resin, or a fluorene resin is used. Since the light transmittance and optical characteristics can be improved, acrylic resins are generally used for various applications as optical members. By stretching a sheet obtained from these resins, excellent optical anisotropy is exhibited, and the sheet can be used as the negative retardation compensation plate.

  In addition, in a large screen application such as a liquid crystal television or a monitor, a VA (Vertical Alignment) method (vertical alignment type liquid crystal) is becoming mainstream because of excellent wide viewing angle and contrast ratio. A VA liquid crystal display device has a structure in which liquid crystal molecules are vertically aligned. For this reason, a positive phase difference compensation plate in which the refractive index ellipsoid has a long axis in the horizontal direction of the panel, is flat, and the intrinsic birefringence has a positive value is preferably used as the retardation compensation film. This retardation compensation film is generally produced by stretching a resin film in at least one direction.

  In order to highly adjust the retardation (phase difference) or optical axis (slow axis) of the retardation compensation film as described above, a stretching method and a stretching condition control technique have been studied.

  For example, Patent Document 1 below discloses a method of stretching at a specific stretching temperature, and a method of removing a residual strain by heat-treating a film after stretching under low tension.

JP 2006-341393 A

  When the film is stretched at the stretching temperature described in Patent Document 1, a predetermined retardation value may not be designed. For this reason, the original value as a retardation compensation film may be impaired. In addition, when the heat treatment is performed under low tension after the end of stretching, the retardation value may decrease. Further, in the case of tenter clip type stretching, it may be difficult to simultaneously satisfy the slow axis accuracy and durability by promoting the bowing phenomenon in which the molecular orientation angle is curved and oriented in the width direction.

  In addition, in order to increase durability, the annealing treatment after the end of stretching, especially in the case of tenter clip type stretching, promotes the bowing phenomenon, and either of the slow axis accuracy and the durability has a practical quality. It is easy to deviate, and it is difficult to achieve both the optical axis control and the durability of optical properties. Accordingly, a factor that degrades the slow axis accuracy is controlled, and a change in optical properties with time is suppressed while ensuring uniformity of optical properties, and a retardation compensation film having stable and high optical compensation performance is obtained. It is difficult. Conventionally, a technique for realizing high optical axis control has not been sufficiently established.

  The object of the present invention is to have front retardation and biaxiality suitable as an optical compensation member in the production and quality control of retardation compensation films, and to have higher retardation slow axis uniformity and optical compensation physical properties at high temperatures. A method for producing a retardation compensation film, a retardation compensation film, a composite polarizing plate, and a polarizing plate, which can suppress deterioration of the liquid crystal and have high durability and can maintain a high-quality display image of a liquid crystal display device over a long period of time. And a liquid crystal display device.

  According to a wide aspect of the present invention, retardation compensation using a film obtained by using an amorphous resin and a thermoplastic elastomer-based resin substantially exhibiting a phase separation form with respect to the amorphous resin. A method for producing a film, comprising: a preheating step for preheating the film before the heat stretching; a heat stretching step for stretching the film while heating the film in at least one of a longitudinal direction and a width direction; A heat treatment step for heat-treating the formed film, and in the heat drawing step, the heat drawing is performed at least twice, the heating temperature in the preheating step is Tp (° C.), and the heating temperature in the first heat drawing is Ts1 ( ° C), the heating temperature in the second and subsequent n-th heating stretches is Tsn (° C), and the glass transition temperature of the amorphous resin is Tg (° C). Satisfies the equation (2), a manufacturing method of the retardation film.

Ts1 <Tg + 15 <Tp ≦ Tg + 35 (1)
Tg <Tsn <Ts1 (2)

  In a specific aspect of the method for producing a retardation compensation film according to the present invention, at least one selected from the group consisting of an acrylic resin, a cyclic olefin resin, and a maleimide resin is used as the amorphous resin.

  Moreover, according to the present invention, the retardation compensation film obtained by the method for producing a retardation compensation film, wherein the front retardation R0 (nm) defined by the following formula (3) is in the range of 20 to 300 nm. And a retardation compensation film having a thickness direction retardation Rth defined by the following formula (4) in the range of −200 to 300 nm.

R0 (nm) = (nx−ny) × d (3)
Rth (nm) = ((nx + ny) / 2−nz) × d (4)
nx: maximum refractive index in the film plane ny: refractive index in the direction orthogonal to the nx direction in the film plane nz: refractive index in the film thickness direction orthogonal to the refractive index direction of nx and ny d: average thickness of the retardation compensation film (Nm)

  In a specific aspect of the retardation compensation film according to the present invention, a differential value with respect to the measurement position Ln (mm) in the width direction defined by the following formula (5) at the slow axis angle θ (°) in the film width direction. Δθ is in the range of −0.03 to +0.03, and the standard deviation of the slow axis angle θ is 0.15 ° or less.

Δθ = (θ [n + 1] −θ [n]) / (L [n + 1] −L [n]) (5)
n: Slow axis angle measurement order in the film width direction (natural number)
θ [n]: nth slow axis angle measured value (°)
L [n]: Distance (mm) from the end of the film at the nth measurement position where the slow axis angle is measured

  In another specific aspect of the retardation compensation film according to the present invention, in the front retardation in the film width direction, the absolute value of the differential value ΔR0 with respect to the measurement position Ln (mm) in the width direction defined by the following formula (6) Is a maximum value of 0.3 or less.

ΔR0 = | (R0 [n + 1] −R0 [n]) / (L [n + 1] −L [n]) | Expression (6)
n: Front retardation measurement order in the film width direction (natural number)
R0 [n]: n-th front retardation measurement (nm)
L [n]: Distance (mm) from the film end of the nth measurement position where the measurement order of front retardation is

  The composite polarizing plate according to the present invention includes a retardation compensation film configured according to the present invention and a polarizing plate laminated on one surface of the retardation compensation film.

  A liquid crystal display device according to the present invention includes a pair of substrates constituting a liquid crystal cell, and a composite polarizing plate laminated on at least one outer surface of the pair of substrates and configured according to the present invention. .

  The polarizing plate according to the present invention includes a retardation compensation film configured according to the present invention, an adhesive layer laminated on one surface of the retardation compensation film, and the retardation compensation film of the adhesive layer. And a polarizer laminated on a surface opposite to the formed surface.

  The liquid crystal display device according to the present invention comprises a pair of substrates constituting a liquid crystal cell, and a polarizing plate laminated on at least one outer surface of the pair of substrates and configured according to the present invention. Prepare.

  In the present invention, in the heat stretching step, the heat stretching is performed at least twice, the heating temperature Tp in the preheating step, the heating temperature Ts1 in the first heating stretching, and the heating temperature Tsn in the second and subsequent nth heating stretching. Satisfies the above formulas (1) and (2), so that the optical compensation performance hardly deteriorates with respect to heat exposure in the liquid crystal display panel, and a retardation compensation film having high slow axis accuracy and durability is obtained. Can do. Further, when the retardation compensation film is used in a liquid crystal display device, the display unevenness can be eliminated by compensating the birefringence of the liquid crystal substance. Furthermore, the contrast of the liquid crystal display device can be improved and the viewing angle characteristics can be improved, and the image display of the liquid crystal panel can be stabilized over a long period of time.

  The inventors of the present application have found that the deterioration of slow axis angle accuracy or retardation unevenness that varies greatly in the local part of the film is mainly caused by internal stress generated in the film such as stretching stress or shrinkage stress in the first half of the preheating step and the stretching step. , Found to be due to excessive concentration or sparseness in the film local area. Furthermore, in order to make the stress applied to very small parts in the film uniform, the resin composition constituting the film is studied, and in particular, a composite material film having a certain amount of a flexible component as a sub-component is used, In addition, the film preheating conditions during the stretching process and the stretching conditions are set to a specific heating temperature history to control the molecular orientation behavior in the width direction, and it is found that high slow axis accuracy and extremely low front retardation change can be obtained. The present invention has been completed.

  Details of the present invention will be described below.

  The method for producing a retardation compensation film according to the present invention includes a preheating step for preheating the film and a heat stretching for stretching the film while heating the film in at least one of the longitudinal direction and the width direction before the heat stretching. A step and a heat treatment step of heat-treating the stretched film.

  In the heat stretching step, heat stretching is performed at least twice. In the present invention, the heating temperature in the preheating step is Tp (° C.), the heating temperature in the first heating stretching is Ts1 (° C.), the heating temperature in the second and subsequent n-th heating stretching is Tsn (° C.), When the glass transition temperature of the amorphous resin is Tg (° C.), the following formula (1) and the following formula (2) are satisfied.

Ts1 <Tg + 15 <Tp ≦ Tg + 35 (1)
Tg <Tsn <Ts1 (2)

  Further, in the present invention, as the film to be stretched by heating, a film obtained by using an amorphous resin and a thermoplastic elastomer resin substantially exhibiting a phase separation form with respect to the amorphous resin is used. It is done.

(Amorphous resin)
The amorphous resin is not particularly limited. As the above amorphous resin, transparency, heat resistance and matching with liquid crystal are high, intrinsic birefringence is low, photoelastic coefficient is small, suitable properties as an optical member, and substantially no crystallinity. Resins are preferably used. Since it exhibits such properties, the amorphous resin is preferably at least one selected from the group consisting of acrylic resins, cyclic olefin resins, and maleimide resins. Specific examples of the amorphous resin include an acrylic resin having a (meth) acryl group or a (meth) acryl group-derived group in the molecular side chain, and an alicyclic hydrocarbon structure in the molecular main chain or side chain. And a maleimide resin having a maleimide structure.

The acrylic resin is used for films for optical applications. The acrylic resin can be obtained by homopolymerizing or copolymerizing an acrylate monomer. The acrylate monomer is preferably a resin represented by the following formula (21).
CH ₂ = C (R1) COOR2 (Formula (21))

  In the above formula (21), R1 represents a hydrogen atom or a methyl group, and R2 represents an aliphatic hydrocarbon group, an aromatic hydrocarbon group, a hydrocarbon group containing a halogen atom, a hydrocarbon group containing an amine structure, and an ether. A monovalent group selected from the group consisting of a hydrocarbon group containing a structure is shown.

  The acrylic ester monomer is not particularly limited. Examples of the acrylic ester monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, Isobutyl methacrylate, sec-butyl (meth) acrylate, t-butyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth ) 2-ethylhexyl acrylate, n-octyl (meth) acrylate, lauryl (meth) acrylate, n-tridecyl (meth) acrylate, myristyl (meth) acrylate, cetyl (meth) acrylate, (meth) acrylic Stearyl acid, allyl (meth) acrylate, vinyl (meth) acrylate, benzyl (meth) acrylate (Meth) acrylic acid phenyl, (meth) acrylic acid 2-naphthyl, (meth) acrylic acid 2,4,6-trichlorophenyl, (meth) acrylic acid 2,4,6-tribromophenyl, (meth) acrylic acid Isobornyl, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, diethylene glycol monomethyl ether (meth) acrylate, polyethylene glycol monomethyl ether (meth) acrylate, polypropylene glycol monomethyl ether (meth) acrylate , Tetrahydrofluoryl (meth) acrylate, 2,3-dibromopropyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2,2,2-trifluoroethyl (meth) acrylate, (meth) acryl Acid hexafluoroisopropyl Glycidyl (meth) acrylate, 3-trimethoxysilylpropyl (meth) acrylate, 2-diethylaminoethyl (meth) acrylate, 2-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate , 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, (meth) acrylic acid, itaconic acid, crotonic acid, (anhydrous) maleic acid, fumaric acid, 2 -(Meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, neopentyl di (meth) acrylate, dimethylol tricyclodecane di (meth) acrylate, bifunctional epoxy (meth) acrylate, caprolactone modified (Meta) Acrylate, dipentaerythritol hexa (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, trimethylolpropane triacrylate, trimethylolpropane tetraacrylate, (meth) acrylonitrile, N-vinylpyrrolidone, N -Vinyl caprolactam, N-vinyllaurylactam, (meth) acrylamide, dimethyl (meth) acrylamide, diethylaminoethyl (meth) acrylate, PEG # 200 di (meth) acrylate, PEG # 400 di (meth) acrylate, PEG # 600 di (meth) acrylate, polyfunctional urethane acrylate, etc. are mentioned. When obtaining the said acrylic resin, only 1 type may be used for the said acrylic ester-type monomer, and 2 or more types may be used together. The (meth) acryl means acryl or methacryl.

  When obtaining the acrylic resin, a radical polymerizable monomer copolymerizable with the acrylic ester monomer may be used together with the acrylic ester monomer. For example, a vinyl monomer having a polar group may be used. Examples of the radical polymerizable monomer include maleic anhydride and styrene. As for the said radically polymerizable monomer, only 1 type may be used and 2 or more types may be used together.

  Abrasion resistance and heat resistance of the acrylic resin can be enhanced by crosslinking and modifying by various methods. The crosslinking method is not particularly limited. Examples of the crosslinking method include a method in which a crosslinking assistant is added to a (meth) acrylic acid ester monomer and polymerized.

  The said crosslinking adjuvant is not specifically limited. Examples of the crosslinking aid include radical generators such as benzoyl peroxide, divinylbenzene, trimethylolpropane tri (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and 1,9-nonanediol di (meta). And polyfunctional monomers such as acrylate and 1,2,4-benzenetricarboxylic acid triallyl ester. As for the said crosslinking adjuvant, only 1 type may be used and 2 or more types may be used together.

  The content of the acrylate ester monomer is preferably in the range of 5 to 99 mol% of the whole polymer, and more preferably in the range of 30 to 90 mol%.

  As a method for polymerizing the acrylic resin, any of known radical polymerization methods such as bulk polymerization method, solution polymerization method, suspension polymerization method and emulsion polymerization method can be selected. From the viewpoint of the polymerization process, and from the viewpoint of improving the quality of the film, the solution polymerization method and the bulk polymerization method are preferable.

  The glass transition temperature of the acrylic resin is an important factor that affects optical properties or durability. Considering the thermal environment to which the retardation compensation film used in the liquid crystal display device is exposed, the glass transition temperature of the acrylic resin is preferably 80 ° C. or higher, and more preferably 100 ° C. or higher.

  The glass transition temperature indicates a glass transition temperature at the time of final temperature rise measured under the following temperature program conditions using a differential scanning calorimeter (trade name “DSC2920 Modulated DSC” manufactured by TA Instruments).

Temperature program conditions:
The temperature is raised from room temperature to 50 ° C. at a rate of 10 ° C./min, and held at 100 ° C. for 5 minutes. Next, the temperature is raised from 50 ° C. to 200 ° C. at a rate of 10 ° C./min and held at 200 ° C. for 5 minutes. Next, the temperature is lowered from 200 ° C. to −50 ° C. at a rate of 10 ° C./min, and held at −50 ° C. for 5 minutes. Next, the temperature is raised from −50 ° C. to 200 ° C. at a rate of 10 ° C./min, and held at 200 ° C. for 5 minutes.

  From the viewpoint of improving sheet formability and stretchability and the quality of the retardation compensation film, the weight average molecular weight of the acrylic resin is preferably in the range of 10,000 to 1,000,000. The minimum with a more preferable weight average molecular weight of the said acrylic resin is 50,000, and a more preferable upper limit is 500,000.

  The said weight average molecular weight shows the polystyrene conversion molecular weight measured by gel permeation chromatography (GPC) using the tetrahydrofuran solvent.

  Conventionally, use of a norbornene resin, which is a kind of the cyclic olefin resin, as an optical material has been studied. Examples of the cyclic olefin resins include ring-opening (co) polymers of norbornene monomers, addition copolymers of norbornene monomers and olefin monomers, addition copolymers of norbornene monomers, and derivatives thereof. It is done. As for the said norbornene-type resin, only 1 type may be used and 2 or more types may be used together. In order to reduce the amount of carbon-carbon unsaturated double bonds and improve the weather resistance, the norbornene-based resin may be saturated by hydrogenation.

  The norbornene monomer constituting the norbornene resin is not particularly limited as long as it is a monomer having a norbornene ring. Examples of the norbornene-based monomer include bicyclic compounds such as norbornene and norbornadiene, tricyclic compounds such as dicyclopentadiene and dihydroxypentadiene, tetracyclic compounds such as tetracyclododecene, pentacyclic compounds such as cyclopentadiene trimer, tetra 7-rings such as cyclopentadiene, alkyl substitutions such as methyl, ethyl, propyl and butyl, alkenyl substitutions such as vinyl, alkylidene substitutions such as ethylidene, phenyls, tolyl and naphthyl Aryl substituents, and ester groups, ether groups, cyano groups, halogen groups, alkoxycarbonyl groups, pyridyl groups, hydroxyl groups, carboxylic acid groups, amino groups, hydroxyl-free groups, silyl groups, epoxy groups, and (meth) acrylic groups Polar groups containing elements other than carbon and hydrogen, such as Substitution products of the like. As for the said norbornene-type monomer, only 1 type may be used and 2 or more types may be used together.

  Since it is easily available, has excellent reactivity, and can improve the heat resistance of the retardation compensation film, a polycyclic norbornene-based monomer having three or more rings is preferable, and tricyclic, tetracyclic and pentacyclic monomers. Norbornene monomers are more preferred.

  Examples of the olefin monomer constituting the norbornene resin include, for example, ethylene, propylene, 1-butene, 3-methyl-1-butene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1- Examples include pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene and 1-hexadecene. Since the copolymerizability is high, an α-olefin monomer having 2 to 10 carbon atoms is preferable, and ethylene is more preferable.

  The glass transition temperature of the cyclic olefin resin is an important factor that affects optical properties and durability. Considering the thermal environment to which the retardation compensation film used in the liquid crystal display device is exposed, the glass transition temperature of the cyclic olefin resin is preferably 80 ° C. or higher, more preferably 100 ° C. or higher. .

  The norbornene-based resin preferably has a weight average molecular weight in the range of 5,000 to 100,000. The minimum with a more preferable weight average molecular weight of the said norbornene-type resin is 10,000, and a more preferable upper limit is 70,000. If the weight average molecular weight of the norbornene-based resin is too small, the mechanical strength of the retardation compensation film tends to decrease. If the weight average molecular weight of the norbornene resin is too large, the moldability of the film may be hindered.

  As a polymerization method of the cyclic olefin resin, a conventionally known method such as ring-opening metathesis polymerization or addition polymerization can be used.

  Conventionally, use of the maleimide resin as an optical application material has been studied. As said maleimide-type resin, the maleimide-olefin copolymer which has the following structural component (1) and structural component (2) as a structural component is mentioned. The maleimide resin can be obtained, for example, by radical copolymerization reaction of maleimides and olefins.

  Examples of the compound that gives the component (1) include N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, Ni-propylmaleimide, Nn-butylmaleimide, Ni-butylmaleimide, Ns-butylmaleimide, Nt-butylmaleimide, Nn-pentylmaleimide, Nn-hexylmaleimide, Nn-heptylmaleimide, Nn-octylmaleimide, N-laurylmaleimide, N-stearyl Maleimide, N-cyclopropylmaleimide, N-cyclobutylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N- (2-methylphenyl) maleimide, N- (2-ethylphenyl) maleimide, N- (2-isopropyl) Phenyl) maleimide, N- (3-methylphenyl) Reimide, N- (3-ethylphenyl) maleimide, N- (4-methylphenyl) maleimide, N- (4-ethylphenyl) maleimide, N- (2,6-dimethylphenyl) maleimide, N- (2,6 -Diethylphenyl) maleimide, N- (2,6-diisopropylphenyl) maleimide, N- (2,4,6-trimethylphenyl) maleimide, N-carboxyphenylmaleimide, N- (2-chlorophenyl) maleimide, N- ( N-substituted maleimides such as 2,6-dichlorophenyl) maleimide, N- (2-bromophenyl) maleimide, N- (perbromophenyl) maleimide, N- (2,4-dimethylphenyl) maleimide and p-tolylmaleimide Can be mentioned. Among these, N-methylmaleimide, N-ethylmaleimide, N-isopropylmaleimide or N-cyclohexylmaleimide is preferable. As for the compound which gives the said structural component (1), only 1 type may be used and 2 or more types may be used together.

  Examples of the compound that gives the component (2) include isobutene, 2-methyl-1-butene, 2-methyl-1-pentene, 2-methyl-1-hexene, 1-methyl-1-heptene, 1-isooctene, Examples include olefins such as 2-methyl-1-octene, 2-ethyl-1-pentene, 2-methyl-2-butene, 2-methyl-2-pentene, and 2-methyl-2-hexene. Isobutene is preferable from the viewpoint of improving heat resistance, mechanical properties, and transparency. As for the compound which gives the said structural component (2), only 1 type may be used and 2 or more types may be used together.

  The content of the component (1) is preferably in the range of 30 to 70 mol% of the whole copolymer, and more preferably in the range of 40 to 60 mol%. If the content of the component (1) is too small, sufficient heat resistance or transparency may not be obtained. When there is too much content of the said structural component (1), moldability may fall.

  As the polymerization method of the maleimide resin, any of known polymerization methods such as bulk polymerization method, solution polymerization method, suspension polymerization method and emulsion polymerization method can be selected. From the viewpoint of enhancing the transparency and color tone of the film, the precipitation polymerization method is more preferable.

  The maleimide-olefin copolymer can also be obtained by post-amidating a resin obtained by copolymerization of maleic anhydride and olefins with ammonia or alkylamine.

  Similar to the acrylic resin, the glass transition temperature of the maleimide resin is an important factor that affects optical properties and durability. The glass transition temperature of the maleimide resin is preferably 80 ° C. or higher, and more preferably 100 ° C. or higher.

  From the viewpoint of improving sheet formability and stretchability, and the quality of the film as a retardation compensation film, the maleimide resin preferably has a weight average molecular weight in the range of 1,000 to 500,000.

The photoelastic coefficient of the amorphous resin is preferably 2.0 × 10 ⁻¹¹ Pa ⁻¹ or less. When the retardation compensation film is used as a polarizing plate protective film, various external forces such as shrinkage stress of the polarizing plate, distortion at the time of bonding to the polarizing plate, and stress due to distortion at the time of incorporation into the display are applied. Stress is generated inside the phase difference compensation film. In a high temperature and high humidity environment, the contraction stress of the polarizing plate is large. The photoelastic coefficient is defined by the following formula (11) and is a value representing a change in birefringence with respect to a stress generated in the film.

C = Δn / σ Expression (11)
C: Photoelastic coefficient (Pa ⁻¹ )
Δn: expressed birefringence σ: film internal stress (Pa)

The smaller the photoelastic coefficient, the smaller the amount of change in birefringence due to external force. If the photoelastic coefficient exceeds 2.0 × 10 ⁻¹¹ Pa ⁻¹ , the optical performance largely changes due to deformation by an external force, so that it is difficult to use for optical film applications. The photoelastic coefficient of the amorphous resin is more preferably 1.0 × 10 ⁻¹¹ Pa ⁻¹ or less.

  In 100% by weight of the polymer composition constituting the film, the content of the amorphous resin is preferably in the range of 60 to 95% by weight. When there is too little content of the said amorphous resin, transparency and heat resistance of a film will fall easily.

(Thermoplastic elastomer resin)
The thermoplastic elastomer-based resin is selected from, for example, a polymer composed of a hard segment and a soft segment, and is a generic term for polymer materials having flexibility at room temperature.

  The thermoplastic elastomer resin is not particularly limited. Examples of the thermoplastic elastomer-based resin include ethylene- (meth) acrylate copolymer (EA), methyl methacrylate-styrene-butadiene copolymer (MBS), and acrylonitrile-butadiene copolymer (NBR). Styrene-butadiene block copolymer (SB), styrene-ethylene-butylene copolymer (SEBS), styrene-ethylene-propylene copolymer, styrene-isoprene-styrene copolymer (SIS), hydrogenated styrene-butadiene Block copolymer, styrene-isoprene block copolymer, hydrogenated styrene-isoprene block copolymer, ethylene-vinyl acetate copolymer (EVA), low crystalline polybutadiene resin, ethylene-propylene elastomer, styrene-grafted ethylene-propylene Ella Tomah, chlorinated polyethylene (CPE), chlorosulfonated polyethylene (CSPE), polyurethanes, thermoplastic polyester elastomers, thermoplastic polyamide elastomers and ethylene ionomer resins. The thermoplastic elastomer resin may be modified with a functional group such as an epoxy group, a carboxyl group, a hydroxyl group, an amino group, an acid anhydride group, or an oxazoline group. As for the said thermoplastic elastomer resin, only 1 type may be used and 2 or more types may be used together.

  The thermoplastic elastomer resin includes at least one selected from the group consisting of an acrylate monomer, an acrylonitrile monomer, and a styrene monomer as a hard segment, and a conjugated diene monomer as a soft segment. It is preferable that it is a copolymer.

  From the viewpoint of improving sheet formability and stretchability and the quality of the retardation compensation film, the weight average molecular weight of the thermoplastic elastomer resin is preferably in the range of 5,000 to 500,000. The minimum with a more preferable weight average molecular weight of the said thermoplastic elastomer-type resin is 10,000, and a more preferable upper limit is 300,000.

  The thermoplastic elastomer resin substantially exhibits a phase separation form with respect to the amorphous resin. The thermoplastic elastomer-based resin is preferably insoluble in the amorphous resin and dispersed in the amorphous resin as the matrix phase while maintaining a certain domain structure. After melt-kneading the amorphous resin and the thermoplastic elastomer resin, the amorphous resin constitutes a matrix as a continuous phase, and the thermoplastic elastomer resin forms an island structure in the continuous phase. It is preferable that the thermoplastic elastomeric resin constituting the domain is dispersed in the matrix as a discontinuous phase.

  As the domain size of the thermoplastic elastomer resin dispersed in the matrix phase of the amorphous resin, the aspect ratio obtained by dividing the domain major axis size by the domain minor axis size is preferably 1-50, The domain major axis size is preferably 0.1 to 5 μm. When the aspect ratio exceeds 50, the tear propagation resistance in the principal axis direction of the molecular orientation decreases, and it becomes easy to cut during film transportation, or the film tends to buckle along the molecular orientation principal axis. When the domain major axis size is less than 0.1 μm, the front retardation R0 and the thickness retardation Rth are unlikely to be in the desired ranges, and the durability under heating tends to decrease. When the domain major axis size exceeds 5 μm, transparency tends to decrease.

  When evaluating the domain dispersion state of the thermoplastic elastomer resin dispersed in the matrix phase of the amorphous resin, the retardation compensation film is dyed with ruthenium tetroxide or the like. Next, using a microtome, the film is cut to a thickness of about 0.05 μm in the longitudinal and width directions during extrusion molding. The cross section of the cut film is observed using a transmission electron microscope (JEM-1200EXII, manufactured by JEOL Ltd.). In the cross-sectional area of 80 μm × 100 μm, the average dispersion diameter and aspect ratio of the domains of the thermoplastic elastomer resin are measured.

  The difference in refractive index between the amorphous resin and the thermoplastic elastomer resin is preferably 0.2 or less. If the difference in refractive index exceeds 0.2, the transparency or residual phase difference of the film may deteriorate, or optical distortion or the like may easily occur. A more preferable upper limit of the difference in refractive index is 0.1, a more preferable upper limit is 0.05, and a more preferable upper limit is 0.03.

  In 100% by weight of the polymer composition constituting the film, the content of the thermoplastic elastomer resin is preferably in the range of 5 to 40% by weight. If the content of the thermoplastic elastomer resin is too small, the effect of improving the friction characteristics is insufficient. When the content of the thermoplastic elastomer-based resin is too large, the product form may be lost due to winding deviation that occurs during film winding, and the appearance may be deteriorated due to film whitening. For this reason, the product form and optical characteristics of the retardation compensation film are likely to deteriorate. Furthermore, a film formation defect or a film thickness defect in the width direction due to the die swell when forming into a sheet is likely to occur.

(Other ingredients)
In the polymer composition constituting the film, 2,6-di-t-butyl-4-methylphenol, 2- (1-methylcyclohexyl) -4 is optionally added within the range not impairing the object of the present invention. , 6-dimethylphenol, 2,2-methylene-bis- (4-ethyl-6-tert-butylphenol) and tris (di-nonylphenyl phosphite), pt-butylphenyl salicylate, 2 UV absorbers such as 2,2'-dihydroxy-4-methoxy-benzophenone and 2- (2'-dihydroxy-4'-m-octoxyphenyl) benzotriazole, lubricants such as paraffin phenos and hydrogenated oil, and stearo An antistatic agent such as aditopropyldimethyl-β-hydroxyethylammonium trate may be added.

(Film used for manufacturing method of retardation compensation film)
The method for producing a film used in the method for producing a retardation compensation film of the present invention is not particularly limited. For example, after the raw material resin in which the amorphous resin and the thermoplastic elastomer resin are mixed is supplied to an extruder, melted, kneaded, and extruded into a film from a die attached to the tip of the extruder A melt extrusion method in which a film is formed on a long film by cooling and solidifying on a cooled rotating drum by an electrostatic imprint casting method, a touch roll method or an air knife casting method, the amorphous resin and the thermoplastic A solution in which an elastomeric resin is dissolved in an organic solvent is cast on a drum or an endless belt, and then a conventionally known method such as a solution casting method in which the organic solvent is evaporated to form a long film. Any molding method can be used. In the case of obtaining a non-oriented film having a thickness of 80 μm or more, it is difficult to sufficiently evaporate and remove the organic solvent by the solution casting method. Therefore, the melt extrusion method is preferable.

  The obtained film is generally a substantially non-oriented amorphous resin film. The film is preferably substantially non-oriented, that is, the retardation values in the film in-plane direction and the film thickness direction of the film are preferably close to zero. More specifically, the retardation value in the in-plane direction of the film is preferably 20 nm or less, and more preferably 10 nm or less.

(Method for producing retardation compensation film)
In the method for producing a retardation compensation film according to the present invention, for example, the film is stretched in at least one of the longitudinal direction and the width direction by a tenter or the like.

  In stretching the film, before stretching, a preheating step of preheating the film, a heating stretching step of stretching the film while heating the film in at least one of the longitudinal direction and the width direction, and stretching And a heat treatment step of heat treating the formed film. Further, when the film is stretched, it is preferable that a cooling step is performed after the heat treatment step.

  Examples of the film heating method in each step include a hot roll contact heating method and an air convection heating method using an air floating heating method. These film heating methods may be used in combination. The film heating method is appropriately selected according to the stretching form.

  The preheating step is a step of heating the film to a film temperature at which the film can be stretched. The preheating step has a function of reducing the curved pattern (so-called bowing) of molecular orientation that occurs particularly in the tenter clip-type stretched form and aligning the orientation.

In the preheating step, the non-oriented film is heated to a temperature near which it can be stretched. In the preheating step, for example, heating is performed to near the stretching temperature in the stretching step. The heating temperature in the preheating step is preferably a temperature equal to or slightly higher than the film temperature in the heating and stretching step that is the next step. Further, the heating temperature in the preheating step is Tp (° C.), the heating temperature in the first heating stretching is Ts1 (° C.), the heating temperature in the second and subsequent n-th heating stretching is Tsn (° C.), When the glass transition temperature of the crystalline resin is Tg (° C.), the heating temperature Tp satisfies the following formula (1).
Ts1 <Tg + 15 <Tp ≦ Tg + 35 (1)

  As shown by the above formula (1), by setting the heating temperature Tp sufficiently higher than the glass transition temperature of the amorphous resin, plasticity is imparted to the film before stretching, and the die line exists in the film flow direction. The effect which suppresses linear or planar defects, such as these, is acquired. As a result, it can be avoided that a film defect generated during film formation leads to an optical defect. When the glass transition temperature of the amorphous resin is Tg (° C.), the heating temperature Tp preferably satisfies Tg + 20 <Tp <Tg + 30. When the heating temperature Tp is too low, film defects are not sufficiently relaxed. If the heating temperature Tp is too high, the fluidity of the film becomes too high, a sufficient transport tension cannot be obtained, the hot air or the film's own weight cannot be endured, and running failure may occur in the preheating process. For this reason, the film may not be transferred to the stretching process.

  By setting the heating temperature Ts1 of the first heating and stretching performed after the preheating step to satisfy the above formula (1), a predetermined retardation value can be secured. Furthermore, since the film is stretched while being cooled immediately after the start of stretching, an extremely short temperature distribution corresponding to the thickness is obtained in the film width direction. For this reason, uniform stretching deformation can be realized.

  The substantially non-oriented amorphous resin film is expanded and deformed by heating, and the sheet width is increased. For this reason, during the passage of the film in the preheating step, the film may be bent by its own weight, and may contact a furnace member such as a hot air nozzle. In the case of the longitudinal uniaxial stretching method based on the inter-roll stretching method, such a traveling trouble can be avoided by providing a mechanism capable of independently adjusting the film tension at the preheating process inlet and the film tension at the process outlet. In the case of the tenter clip type lateral uniaxial stretching method and simultaneous biaxial stretching method, the film may be bent by its own weight during passage of the film in the preheating step, and may contact a furnace member such as a hot air nozzle. Such a traveling trouble can be avoided by widening the clip rail width with respect to the seat width.

  In the heating and stretching step, the film-constituting molecules that are substantially non-oriented are oriented in a specific direction by stretching in at least one of the longitudinal direction and the width direction of the film while heating the film. Thereby, optical anisotropy including birefringence is imparted, a function as a retardation compensation film is exhibited, and further, mechanical properties and durability as a film can be enhanced by molecular orientation by stretching.

  The film may be uniaxially stretched in only one of the longitudinal direction and the width direction, or may be biaxially stretched in the longitudinal direction and the width direction.

  As the biaxial stretching method, after stretching in the longitudinal direction or the width direction, a sequential biaxial stretching method of stretching in a direction orthogonal to the previous stretching direction, and a simultaneous biaxial stretching method of stretching simultaneously in the longitudinal direction and the width direction are included. Can be mentioned. In consideration of optical compensation performance and productivity, the biaxial stretching method can be appropriately selected. From the viewpoint of reducing the equipment cost and improving the operability and optical compensation performance, the sequential biaxial stretching method is preferable.

  A conventionally known method can be adopted as a longitudinal uniaxial stretching method in the longitudinal direction. Examples of the longitudinal uniaxial stretching method include an inter-roll stretching method and a clip tenter method. From the viewpoint of improving the operability and reducing the equipment cost, the inter-roll stretching method is more preferable. In the inter-roll stretching method, a plurality of rolls rotated at different rotational speeds are arranged at arbitrary intervals in the longitudinal direction, with the upstream installation roll at a low speed and the downstream installation roll at a high speed. It is a method of extending a film according to a roll speed difference by conveying a film under heating. If the stretching distance, which is practically defined by the roll arrangement distance, is shorter than the film width, the molecular orientation in the longitudinal direction becomes insufficient. When the said extending | stretching distance is too long, it will become easy to generate | occur | produce the damage of a film, the wrinkle of a film, the contact damage to a heating furnace part, etc. The stretching distance can be appropriately set according to the running property of the film. The roll preferably includes a nip mechanism for the purpose of enhancing the holding power of the film to the roll, improving the grip, and further preventing the influence of stress in the heating and stretching step from affecting the preceding and following steps.

  Any conventionally known tenter stretching method can be employed as the lateral uniaxial stretching method in the width direction and the simultaneous biaxial stretching method in the longitudinal direction and the width direction. As the horizontal uniaxial stretching method and the simultaneous biaxial stretching method, for example, both end portions in the width direction of the non-oriented film are held by the tenter clips, the intervals in the width direction of the tenter clips are gradually separated, and the film is widened in the width direction. The method of extending | stretching is mentioned. Furthermore, in addition to the width direction stretching method, a method of stretching the film in the longitudinal direction by gradually separating the clips adjacent to each other in the longitudinal direction by using a link mechanism by a pantograph structure or a linear motor system.

In the present invention, the heat stretching is performed at least twice in the heat stretching step. The heating temperature in the first heating stretching is Ts1 (° C.), the heating temperature in the second and subsequent n-th heating stretching is Tsn (° C.), and the glass transition temperature of the amorphous resin is Tg (° C.). When satisfied, the above formula (1) and the following formula (2) are satisfied.
Tg <Tsn <Ts1 (2)

  The heating stretching in the heating stretching step is divided into a plurality of times, the heating temperature Tsn in the first heating stretching step after the preheating step is made relatively lower than the heating temperature Tp in the preheating step, and the film flow By making the heating temperature in the second and subsequent heating stretching installed downstream in the direction relatively and gradually lower than the heating temperature Tsn, uniform plastic deformation of the film is promoted, and the unevenness of the optical axis It is possible to obtain an optically uniform retardation compensation film with extremely small phase difference unevenness.

  The heating temperature Ts1 is preferably substantially higher than the glass transition temperature of the amorphous resin and the heating temperature Tsn. When the glass transition temperature of the amorphous resin is Tg (° C.), the heating temperature Ts1 preferably satisfies Tg + 2 <Ts1 <Tg + 10, and more preferably satisfies Tg + 5 ≦ Ts1 <Tg + 10.

  Moreover, it becomes possible to obtain a high retardation by setting the heating temperature Tsn in the second and subsequent n-th heating and stretching following the first heating and stretching to be within the above temperature range. When the glass transition temperature of the amorphous resin is Tg (° C.), the heating temperature Tsn preferably satisfies Tg + 2 <Tsn <Tg + 5. If the heating temperature Tsn is too high, the stretching stress is insufficient, the molecular alignment effect by stretching cannot be sufficiently obtained, and sufficient relaxation to prioritize the alignment relaxation to compensate for the birefringence when passing through the liquid crystal. The foundation may not be obtained. If the heating temperature Tsn is too low, the durability is lower than the practical performance, and further uneven deformation due to uneven stretching occurs, resulting in uneven retardation in the film surface, and the image display quality of the liquid crystal panel is deteriorated. Sometimes. For this reason, the commercial value as a phase difference compensation film may fall.

  The stretching time from the start to the end of heat stretching in the heat stretching step is preferably in the range of 10 to 100 seconds. A more preferable lower limit of the stretching time is 20 seconds, and a more preferable upper limit is 60 seconds. If the stretching time is too long, the retardation is remarkably lowered by thermal relaxation, and the molecular orientation effect by stretching may not be obtained. If the stretching time is too short, the uneven distribution in the film width direction of the slow axis cannot be corrected due to the remarkable bowing phenomenon, and the film is cut during stretching due to excessive stretching stress, and the tenter clip comes off. The film running stability in the stretching process may be impaired.

  The heating time in the heating and stretching step can be appropriately set according to the film running speed determined mainly based on continuous productivity. The heating time is important in balancing the optical axis accuracy and the durability of optical properties. In particular, the heating time of the first heat stretching greatly affects the durability. The heating time for the first heating and stretching is preferably in the range of 5 to 50 seconds, and more preferably in the range of 10 to 30 seconds. The heating time of the entire heating and stretching step is preferably within a range of 10 to 100 seconds, and more preferably within a range of 20 to 60 seconds. By setting the heating time in the above preferred range, it is possible to achieve both high retardation development performance and excellent durability. If the heating time is too short, film running stability such as film breakage due to excessive stretching stress or clip gripping may be impaired. When the heating time is too long, the stretching stress is insufficient, and it is impossible to obtain a sufficient molecular orientation effect by stretching, and a predetermined retardation may not be obtained.

  The draw ratio in the heating and stretching step can be appropriately determined depending on the compensation retardation amount of the retardation compensation film. If the draw ratio is too low, the orientation direction may not be uniform. When the draw ratio is too high, the central portion of the film is bent, the retardation value, the slow axis, or the thickness direction distribution of the thickness becomes non-uniform. Therefore, the stretching ratio is preferably in the range of 1.10 to 6.00. A more preferable lower limit of the stretching ratio is 1.50 times, and a more preferable upper limit is 5.00 times.

  The preferred lower limit of the stretching strain rate in the heating and stretching step is 50% / minute, the more preferred lower limit is 100% / minute, and the preferred upper limit is 2,000% / minute. If the strain rate is too slow, the expression of retardation may be reduced. If the strain rate is too high, the film may be cut or the tenter clip may come off. In addition, by stretching at a high strain rate, particularly in the stretching by the tenter clip method, the clip rail opening angle can be increased and the furnace length of the stretching zone can be shortened as much as possible.

  The heat treatment step is a step for removing or reducing residual strain of the stretched film and annealing. By the heat treatment step, the molecular orientation can be controlled and the optical characteristics and thickness in the width direction can be made uniform. Moreover, the said heat processing process can reduce the bowing of a stretched film and can align orientation.

  If the heating temperature in the heat treatment step is too high, the retardation value decreases. When the glass transition temperature of the amorphous resin is Tg (° C.), the heating temperature in the heat treatment step is preferably in the range of (Tg-30) to (Tg + 10) ° C. By setting the heating temperature within the preferable range, bowing can be controlled and the molecular alignment accuracy in the film width direction can be increased.

  The heating time in the heat treatment step can be appropriately set according to the film running speed determined mainly based on continuous productivity. The heating time is preferably in the range of 5 to 60 seconds, and more preferably in the range of 10 to 30 seconds. By setting the heating time in the heat treatment step after the heat stretching within the above preferable range, the bowing phenomenon can be suppressed and excellent optical axis accuracy can be obtained. If the heating time is too short, a sufficient annealing effect cannot be obtained, and as a result, the orientation protrudes to the downstream side of the film flow, which may promote reverse bowing. If the heating time is too long, the orientation protrudes to the upstream side of the film flow, which may promote positive bowing. For this reason, the image display quality of a liquid crystal panel may fall, and the commercial value as a phase difference compensation film may fall.

  The cooling step is a step for fixing the molecular orientation formed in the film by rapidly cooling the film. When the glass transition temperature of the amorphous resin is Tg (° C.), the cooling temperature in the cooling step is preferably in the range of (Tg-50) to (Tg-5) ° C.

(Phase difference compensation film)
The retardation compensation film has a front retardation R0 (nm) defined by the following formula (3) within a range of 20 to 300 nm, and a thickness direction retardation Rth defined by the following formula (4) is − It is preferable to be in the range of 200 to 300 nm.

R0 (nm) = (nx−ny) × d (3)
Rth (nm) = ((nx + ny) / 2−nz) × d (4)
nx: maximum refractive index in the film plane ny: refractive index in the direction orthogonal to the nx direction in the film plane nz: refractive index in the film thickness direction orthogonal to the refractive index direction of nx and ny d: average thickness of the retardation compensation film (Nm)

  When the retardation retardation film is laminated on the liquid crystal panel by controlling the front retardation R0 within the preferred range, a stable and high-quality image display can be obtained. When the value of the retardation R0 is out of the above range, the birefringence when passing through the liquid crystal cannot be fully compensated, and the commercial value as a retardation compensation film may be lowered. By controlling the retardation Rth within the above-mentioned preferable range, when the retardation compensation film is laminated on the liquid crystal panel, the characteristics inherent to the liquid crystal display device such as a wide viewing angle and high contrast can be further enhanced and stabilized. A high-quality image display can be obtained.

  At the slow axis angle θ (°) in the film width direction, the differential value Δθn (hereinafter referred to as optical axis unevenness) with respect to the measurement position Ln (mm) in the width direction is within a range of −0.03 to +0.03. The standard deviation of the slow axis angle θ is preferably 0.15 ° or less. Δθn is defined by the following formula (5).

Δθn = (θ [n + 1] −θ [n]) / (L [n + 1] −L [n]) (5)
n: Slow axis angle measurement order in the film width direction (natural number)
θ [n]: nth slow axis angle measured value (°)
L [n]: Distance (mm) from the end of the film at the nth measurement position where the slow axis angle is measured

  Even if the orientation in the oblique direction other than the reference axis or the curved orientation with respect to the reference axis due to the bowing phenomenon is relaxed or eliminated by the conventional technique, the optical axis unevenness at a short pitch is mainly caused by the material characteristics of the non-oriented film. If this remains, it is difficult to precisely control the slow axis, suppress variations, and maintain stable optical quality. By setting the optical axis unevenness Δθn defined by the above formula (5) within the range of −0.03 to +0.03 and the standard deviation of the slow axis angle θ being 0.15 ° or less, the retardation compensation film Thus, it is possible to maintain the slow axis quality under a high process capability. In particular, by setting the standard deviation of the slow axis angle θ to 0.15 ° or less, it is possible to maintain the slow axis quality of the retardation compensation film under a high process capability. The measurement interval of the slow axis angle is preferably 25 mm. When measuring the retardation in the film width direction, if the measurement interval is larger than 25 mm, the data resolution is lowered due to the decrease in the number of measurements, and it becomes increasingly difficult to detect the optical axis unevenness at a short pitch. If the measurement interval is smaller than 25 mm, the resolution is improved, but the measurement frequency is too high, which is disadvantageous in terms of time or economy.

  In general, a process capability index (hereinafter referred to as Cp) is used to express the process capability. Cp is an index of the capability of a process for a specific quality standard, and is conventionally known and is defined by the following formula (9). Refer to page 251 of “Introduction to Statistical Methods for Quality Control” published by Nikka Giren Publisher.

Cp = θr / 6σ Equation (9)
θr: Slow axis angle quality standard range σ: Slow axis angle standard deviation (°)

  As for the slow axis angle quality standard of retardation compensation films used for large displays such as televisions, the upper limit of the standard is generally + 0.5 °, and the lower limit is preferably −0.5 °. Therefore, if the standard deviation of the slow axis angle is 0.15 ° or less, the process capability is 1.0 or more, and stable slow axis quality can be maintained.

  In the front retardation R0 (nm) in the width direction of the retardation compensation film, the maximum absolute value of the differential value ΔR0 (hereinafter referred to as R0 unevenness) with respect to the measurement position Ln (mm) in the width direction is 0.3 or less. Is preferred. ΔR0 is defined by the following formula (6).

ΔR0 = | (R0 [n + 1] −R0 [n]) / (L [n + 1] −L [n]) | Expression (6)
n: Front retardation measurement order in the film width direction (natural number)
R0 [n]: n-th front retardation measurement (nm)
L [n]: Distance (mm) from the film end of the nth measurement position where the measurement order of front retardation is

  In a liquid crystal display device using a retardation compensation film in which the above R0 unevenness at a short pitch remains, it is difficult to maintain stable display quality. By setting the maximum absolute value of the R0 unevenness to 0.3 or less, it is possible to provide a liquid crystal display device in which the optical compensation performance of the retardation compensation film is kept high and there is no display defect such as color unevenness. Become. In addition, it is preferable that the measurement interval of front retardation is 25 mm. When measuring the retardation in the film width direction, if the measurement interval is larger than 25 mm, the data resolution is lowered due to the decrease in the number of measurements, and it becomes increasingly difficult to detect the optical axis unevenness at a short pitch. If the measurement interval is smaller than 25 mm, the resolution is improved, but the measurement frequency is too high, which is disadvantageous in terms of time or economy.

  The average thickness of the retardation compensation film is not particularly limited. The average thickness of the retardation compensation film is preferably in the range of 20 to 200 μm. The more preferable lower limit of the average thickness of the retardation compensation film is 40 μm, and the more preferable upper limit is 100 μm. When the average thickness of the retardation compensation film is within the above preferred range, it does not impair the predetermined birefringence and has a certain mechanical strength, and is also important when laminated on a liquid crystal display device. The weight of the member can be reduced. Moreover, a retardation compensation film can be suitably used as an optical compensation film.

  The preferable upper limit of the haze value of the retardation compensation film is 8%, the more preferable upper limit is 5%, the still more preferable upper limit is 3%, and the more preferable upper limit is 1%. If the haze value is too high, it may cause light leakage when used for applications such as a polarizing plate protective film.

  The surface of the retardation compensation film may be subjected to surface activation treatment such as corona treatment, plasma treatment, ultraviolet irradiation, and various chemical treatments. Furthermore, various performances can be added to the surface of the retardation compensation film by performing various functional coatings, lamination, etc. by coating or vapor deposition, and the utility value can be further improved.

(Composite polarizing plate, polarizing plate and liquid crystal display device)
The composite polarizing plate according to the present invention includes a retardation compensation film and a polarizing plate laminated on one surface of the retardation compensation film. The retardation compensation film and the polarizing plate are preferably integrated.

  A liquid crystal display device according to the present invention includes a pair of substrates constituting a liquid crystal cell and the composite polarizing plate laminated on at least one outer surface of the pair of substrates.

  The polarizing plate according to the present invention includes the retardation compensation film, an adhesive layer laminated on one surface of the retardation compensation film, and a surface of the adhesive layer on which the retardation compensation film is laminated. And a polarizer laminated on the opposite surface. The retardation compensation film and the polarizer are preferably integrated via the adhesive layer.

  In addition, another liquid crystal device according to the present invention includes a pair of substrates constituting a liquid crystal cell and the polarizing plate laminated on at least one outer surface of the pair of substrates.

  The retardation compensation film is preferably used as a component of a liquid crystal display device. The retardation compensation film may be used alone, or may be laminated with a polarizing plate and used as a composite polarizing plate. Furthermore, the retardation compensation film may be laminated on a polarizer via an adhesive layer and used as a polarizing plate instead of a protective film on the liquid crystal cell side of the polarizing plate. Since the thickness of the liquid crystal display device can be reduced and the manufacturing efficiency can be increased, the retardation compensation film is laminated on the polarizer via an adhesive layer as a polarizing plate instead of the protective film on the liquid crystal cell side of the polarizing plate. It is preferable to be used.

  As a method of manufacturing a liquid crystal display device using the retardation compensation film alone, a polarizing plate is disposed on each outer surface of a pair of substrates constituting the liquid crystal cell, The retardation compensation film is disposed between at least one of the substrate and the polarizing plate facing the substrate, and further on the polarizing plate disposed on the substrate side opposite to the liquid crystal display surface in the liquid crystal cell, For example, a known illumination system of a backlight type or a sidelight type is provided and a driving circuit is incorporated. The retardation compensation film is preferably disposed on the outer surface of the substrate on the liquid crystal display surface side.

  In the liquid crystal display device, the retardation compensation film may be previously laminated on one surface of a polarizing plate via an adhesive or a pressure-sensitive adhesive and used as a composite polarizing plate. The adhesive or pressure-sensitive adhesive is not particularly limited as long as it does not impair optical properties. An acrylic adhesive or a transparent pressure-sensitive adhesive is preferably used.

  As the polarizing plate, those conventionally used in general are used. In the polarizing plate, for example, protective films are laminated and integrated on both surfaces of a polarizer. As this polarizer, a polyvinyl alcohol-iodine polarizing film, a dye-based polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based film, a dehydration reaction is induced from a polyvinyl alcohol-based film, or a polyvinyl chloride film A polyene-based polarizing film in which a polyene is formed by dehydrochlorination reaction, and a polarizing film having a dichroic dye on one of the surface and the inside of a polyvinyl alcohol-based film comprising a modified polyvinyl alcohol containing a cationic group in the molecule Etc.

  The protective film laminated and integrated on the polarizer is not particularly limited as long as the optical properties of the polarizer are not impaired. Examples of the protective film include films made of triacetyl cellulose, alkali-treated triacetyl cellulose, and the like.

  Moreover, instead of the protective film on the liquid crystal cell side of the polarizing plate, as a method of using the retardation compensation film as a polarizing plate laminated on the polarizer via an adhesive layer, a polarizer and a retardation compensation film are used. A method of laminating and integrating a polarizer and a retardation compensation film in a state where an adhesive is interposed, after an adhesive is applied to one of the opposing surfaces almost uniformly. Is mentioned. The adhesive is preferably applied to the retardation compensation film surface. The adhesive may be any adhesive that does not impair the optical properties of the polarizer and the retardation compensation film, and is preferably a water-based urethane adhesive.

  It is preferable that a normal optically isotropic protective film is laminated and integrated with an adhesive on the surface of the polarizer opposite to the surface on which the retardation compensation film is laminated.

  A liquid crystal display device using a polarizing plate using the retardation compensation film as a protective film is at least a liquid crystal display surface among polarizing plates disposed on the outer surface of each of a pair of substrates constituting a liquid crystal cell. As the polarizing plate on the side, the polarizing plate is obtained by disposing the polarizing plate so that the phase difference compensation film surface is on the liquid crystal cell side.

  The liquid crystal cell is not particularly limited. A conventionally known liquid crystal cell can be used. When the retardation compensation film according to the present invention is applied to the VA mode and the IPS mode which are excellent in display performance as a large screen, an excellent effect can be obtained. For these liquid crystal modes, a non-oriented film in which a resin material having positive or negative intrinsic birefringence is appropriately selected according to the display method is stretched in accordance with the present invention, so that it is in the panel parallel plane or in the thickness direction. A retardation compensation film with a controlled refractive index can be provided. Accordingly, it is possible to effectively compensate the refractive index of the liquid crystal cell and greatly improve the contrast change or the viewing angle dependency due to the positive contrast or the expected angle of the liquid crystal display device.

  Examples of the present invention will be described below. The present invention is not limited to the following examples.

(Non-oriented film production example 1)
90 parts by weight of a polymethyl methacrylate resin (methyl methacrylate component content 55 mol%, styrene component content 30 mol%, maleic acid component content 15 mol%, Tg: 120 ° C., weight average molecular weight: 120,000), and Acrylonitrile-styrene-butadiene copolymer (butadiene component content 50 mol%, styrene component content 25 mol%, acrylonitrile component content 18 mol%, methyl methacrylate component content 7 mol%, weight average molecular weight: 48,000 ) 10 parts by weight were mixed and fed to a twin-screw extruder set at a cylinder temperature of 260 ° C. and filled. The extruded strand was cut with a pelletizer to produce a mixed resin (C) pellet.

  The mixed resin (C) is supplied to a single screw extruder, melted and kneaded at a cylinder temperature of 260 ° C., then melt extruded from a T die onto a chrome plating roll at a take-up speed of 10 m / min, cooled and solidified to form a sheet. The film was continuously formed to produce a substantially non-oriented amorphous resin film.

  A non-oriented film (C-1) having a width of 1500 mm and an average thickness in the width direction of 150 μm and a non-oriented film (C-2) having a width of 1500 mm and an average thickness in the width direction of 100 μm were obtained. The domain particle size dispersed in the non-oriented film (C-1) was 0.61 μm. The domain particle size dispersed in the non-oriented film (C-2) was 0.75 μm.

(Non-oriented film production example 2)
The polymethyl methacrylate resin was changed to a norbornene resin (Zeon Corporation, “Zeonor 1420” weight average molecular weight: 50,000, Tg: 135 ° C.), and the pellet production process twin screw extruder and film melt A mixed resin (D) pellet was produced in the same manner as in Production Example 1 except that the cylinder temperature of the single-screw extruder in the membrane process was changed to 270 ° C., and a non-oriented film was produced in the same manner as in Production Example 1. .

  A non-oriented film (D-1) having a width of 1500 mm and a width direction average thickness of 150 μm and a non-oriented film (D-2) having a width of 1500 mm and a width direction average thickness of 100 μm were obtained. The domain particle size dispersed in the non-oriented film (D-1) was 0.43 μm, and the domain particle size dispersed in the non-oriented film (D-2) was 0.54 μm.

(Non-oriented film production example 3)
The polymethyl methacrylate resin was changed to a maleimide copolymer resin (maleimide component content 50 mol%, isobutene component content 50 mol%, Tg: 145 ° C., weight average molecular weight: 250,000), and pellet production A pellet of mixed resin (E) was produced in the same manner as in Production Example 1 except that the cylinder temperature of the twin-screw extruder in the process and the single-screw extruder in the film melting film forming process was changed to 280 ° C. In the same manner as in Example 1, a non-oriented film was produced.

  A non-oriented film (E-1) having a width of 1500 mm and an average thickness in the width direction of 150 μm was obtained. The domain particle size dispersed in the non-oriented film (E-1) was 0.90 μm.

(Non-oriented film production example 4)
Acrylonitrile-styrene-butadiene copolymer is styrene-ethylene-butylene copolymer (styrene component content 30 mol%, ethylene component content 40 mol%, butylene component content 30 mol%, weight average molecular weight: 160,000) A mixed resin (F) pellet was produced in the same manner as in Production Example 1 except that the non-oriented film was produced in the same manner as in Production Example 1.

  A non-oriented film (F-1) having a width of 1500 mm and an average thickness of 150 μm was obtained. The domain particle size dispersed in the non-oriented film (F-1) was 1.57 μm.

(Non-oriented film production example 5)
A pellet of the mixed resin (G) was produced in the same manner as in Production Example 2 except that the acrylonitrile-styrene-butadiene copolymer was changed to the styrene-ethylene-butylene copolymer described in Production Example 4 above. A non-oriented film was produced in the same manner as in Example 2.

  A non-oriented film (G-1) having a width of 1500 mm and an average thickness of 150 μm was obtained. The diameter of the domain particles dispersed in the non-oriented film (G-1) was 1.26 μm.

(Non-oriented film production example 6)
In the production of the non-oriented film, only 100 parts by weight of the polymethyl methacrylate resin described in Preparation Example 1 was used without mixing the acrylonitrile-styrene-butadiene copolymer described in Preparation Example 1 above. In the same manner as in Production Example 1, mixed resin (H) pellets were produced, and a non-oriented film produced in the same manner as in Production Example 1 was produced. A non-oriented film (H-1) having a width of 1500 mm and an average thickness in the width direction of 150 μm was obtained.

(Non-oriented film production example 7)
Manufacture except that only 100 parts by weight of norbornene-based resin described in Preparation Example 2 was used without mixing the acrylonitrile-styrene-butadiene copolymer described in Preparation Example 1 in the production of the non-oriented film. Mixed resin (I) pellets were produced in the same manner as in Example 2, and non-oriented films were produced in the same manner as in Production Example 2. A non-oriented film (I-1) having a width of 1500 mm and an average thickness in the width direction of 150 μm was obtained.

(Non-oriented film production example 8)
Production of the non-oriented film except that only 100 parts by weight of the maleimide resin described in Production Example 3 was used without mixing the acrylonitrile-styrene-butadiene copolymer described in Production Example 1 above. Mixed resin (J) pellets were produced in the same manner as in Example 2, and non-oriented films were produced in the same manner as in Production Example 2. A non-oriented film (J-1) having a width of 1500 mm and an average thickness of 150 μm was obtained.

(Examples 1-6 and Comparative Examples 1-8)
The non-oriented films obtained by the above Production Examples 1 to 8 were continuously unwound and supplied to a horizontal uniaxial tenter stretching machine having a preheating zone, a stretching zone, a heat treatment zone, and a cooling zone. After gripping the end of the non-oriented film with a tenter clip and heating the non-oriented film in the preheating zone, at the first drawing zone immediately after preheating at a draw ratio of 2.0 times and a strain rate of 300% / min. Immediately after the heat stretching in the width direction, the film is further heat-stretched in the width direction in the second stretching zone having a relatively high temperature relative to the heating temperature of the first stretching zone, annealed in the subsequent heat treatment zone, and further the cooling zone. And cooled to 80 ° C. to fix the orientation. At the subsequent outlet of the stretching machine, the film edge was released from the clip gripping. Then, the film edge where the clip grip marks remain in the slitting process is removed by slitting with a shear blade installed symmetrically from the center of the film, and wound into a roll of vinyl chloride resin core at a winding tension of 100 N / m. To obtain a retardation compensation film. In addition, the types of the non-oriented film, the preheating zone, the first stretching zone, the second stretching zone, and the temperature of the heat treatment zone are as shown in Tables 1 and 2 below.

  The width of the obtained retardation compensation film was 1400 mm excluding both ends including the tenter clip grip marks, and the average thickness was as described in Tables 1 and 2 below. Front retardation R0 and thickness retardation value Rth of the obtained retardation compensation film were measured, and front retardation R0 unevenness was calculated. Further, the slow axis angle θ was measured, and the optical axis unevenness Δθ and the standard deviation θσ of the slow axis angle were calculated.

(Examples 7 and 8 and Comparative Examples 9 and 10)
The non-oriented films described in Tables 1 and 2 below obtained by Production Examples 1 and 2 are continuously unwound, and a preheating zone, a first stretching zone, a second stretching zone, a heat treatment zone, and a cooling zone are provided. The roll type stretching machine horizontal uniaxial tenter stretching machine was fed at a film conveyance speed of 10 m / min at the entrance of the preheating zone. After heating the non-oriented film in the preheating zone, the rotation speed ratio is set to the upstream nip roll and the downstream nip roll in the film flow direction arranged before and after the stretching zone, and the rotation of the downstream roll speed relative to the upstream roll speed is performed. The speed ratio was set to 2.0, the draw ratio was set, and the strain sparse rate was 300% / min. First, the film was first heated and stretched in the longitudinal direction in the first stretching zone immediately after preheating, and then immediately with respect to the heating temperature of the first stretching zone. The film was further heated and stretched in the longitudinal direction in the second drawing zone having a relatively high temperature, annealed in the subsequent heat treatment zone, and further cooled to 80 ° C. in the cooling zone to fix the orientation. A part of the film edge is removed by slitting with a shear blade installed symmetrically from the center of the film, and wound into a roll of vinyl chloride resin at a winding speed of 20 m / min and a winding tension of 100 N / m. A retardation compensation film was obtained. In addition, the types of the non-oriented film, the preheating zone, the first stretching zone, the second stretching zone, and the temperature of the heat treatment zone are as shown in Tables 1 and 2 below.

  The width of the obtained retardation compensation film was 1000 mm excluding both ends, and the average thickness was as described in Tables 1 and 2 below. Front retardation R0 and thickness retardation value Rth of the obtained retardation compensation film were measured, and front retardation ΔR0 was calculated. Further, the slow axis angle θ was measured, and the optical axis unevenness Δθ and the standard deviation θσ of the slow axis angle were calculated.

  The average thickness of the retardation compensation film, the hot air treatment method of the retardation compensation film and the evaluation method of the rate of change with time of heating, front retardation value R0, thickness retardation value Rth, front retardation R0 unevenness, slow axis angle θ The measuring method of the optical axis unevenness Δθ is as follows.

[Measurement method of average thickness of retardation compensation film]
The film width direction was taken as a reference axis, and a strip-shaped film piece was sampled with a longitudinal direction of 50 mm with respect to the reference axis and the width direction being full width. Film thickness measuring device (trade name “Millitron 1240” manufactured by Seiko EM Co., Ltd.) was measured at intervals of 10 mm parallel to the width direction of the film piece, the total average of the measured values was calculated, and the average thickness of the film (μm) It was.

[Measurement method of front retardation value R0 and thickness retardation value Rth of retardation compensation film]
Automatic birefringence measurement device (made by Oji Scientific Instruments Co., Ltd., trade name “KOBRA-WR”), the wavelength of the measurement light is set to 550 nm, the axis orthogonal to the longitudinal direction of the phase difference compensation film is used as a reference axis, and phase difference compensation is performed. The film was measured at intervals of 50 mm in the width direction, and the average value was calculated as the front retardation value R0 of the film and the thickness retardation value Rth of the film.

[Measurement method of standard deviation of slow axis angle θ of retardation compensation film and optical axis unevenness Δθ in width direction]
A strip-shaped film piece was sampled with the film width direction as a reference and a longitudinal direction of 50 mm with respect to the reference axis and the width direction being full width. Automatic birefringence measurement device (trade name “RETS” manufactured by Otsuka Electronics Co., Ltd. was used to measure film pieces at 25 mm intervals in the width direction, and the measured slow axis angle at each position was θ, and the standard deviation was calculated. As the slow axis angle, the smaller one of the axis angles obtained with the width direction or the longitudinal direction as the reference axis was adopted as the slow axis angle, and the optical axis based on the above equation (5). Unevenness was calculated, and the maximum absolute value was Δθn.

[Measuring method of front retardation R0 unevenness (ΔR0) of retardation compensation film]
A strip-shaped film piece was sampled with the film width direction as a reference and a longitudinal direction of 50 mm with respect to the reference axis and the width direction being full width. Automatic birefringence measuring device (trade name “RETS” manufactured by Otsuka Electronics Co., Ltd.) Film pieces are measured at 25 mm intervals in the width direction, the front retardation measurement value at each position is R0, and the above formula (6) The front retardation unevenness was calculated based on the above, and the maximum absolute value thereof was taken as ΔR0.

  The results are shown in Tables 1 and 2 below.

Claims (9)

A method for producing a retardation compensation film using an amorphous resin and a film obtained by using a thermoplastic elastomer-based resin substantially exhibiting a phase separation form with respect to the amorphous resin,
A preheating step for preheating the film before heating and stretching;
A heating and stretching step in which the film is stretched while heating in at least one of the longitudinal direction and the width direction; and
A heat treatment step of heat treating the stretched film,
In the heat stretching step, heat stretching is performed at least twice,
The heating temperature in the preheating step is Tp (° C.), the heating temperature in the first heating stretching is Ts1 (° C.), the heating temperature in the second and subsequent n-th heating stretching is Tsn (° C.), and the amorphous The manufacturing method of the phase difference compensation film which satisfy | fills following formula (1) and following formula (2) when the glass transition temperature of an adhesive resin is set to Tg (degreeC).
Ts1 <Tg + 15 <Tp ≦ Tg + 35 (1)
Tg <Tsn <Ts1 (2)   The method for producing a retardation compensation film according to claim 1, wherein at least one selected from the group consisting of an acrylic resin, a cyclic olefin resin, and a maleimide resin is used as the amorphous resin. A retardation compensation film obtained by the method for producing a retardation compensation film according to claim 1 or 2,
The front retardation R0 (nm) defined by the following formula (3) is in the range of 20 to 300 nm, and the thickness direction retardation Rth defined by the following formula (4) is in the range of -200 to 300 nm. A retardation compensation film.
R0 (nm) = (nx−ny) × d (3)
Rth (nm) = ((nx + ny) / 2−nz) × d (4)
nx: maximum refractive index in the film plane ny: refractive index in the direction orthogonal to the nx direction in the film plane nz: refractive index in the film thickness direction orthogonal to the refractive index direction of nx and ny d: average thickness of the retardation compensation film (Nm) At the slow axis angle θ (°) in the film width direction, the differential value Δθ with respect to the measurement position Ln (mm) in the width direction defined by the following formula (5) is in the range of −0.03 to +0.03. The retardation compensation film according to claim 3, wherein the standard deviation of the slow axis angle θ is 0.15 ° or less.
Δθ = (θ [n + 1] −θ [n]) / (L [n + 1] −L [n]) (5)
n: Slow axis angle measurement order in the film width direction (natural number)
θ [n]: nth slow axis angle measured value (°)
L [n]: Distance (mm) from the end of the film at the nth measurement position where the slow axis angle is measured In the front retardation in the film width direction, the maximum absolute value of the differential value ΔR0 with respect to the measurement position Ln (mm) in the width direction defined by the following formula (6) is 0.3 or less. The retardation compensation film described in 1.
ΔR0 = | (R0 [n + 1] −R0 [n]) / (L [n + 1] −L [n]) | Expression (6)
n: Front retardation measurement order in the film width direction (natural number)
R0 [n]: n-th front retardation measurement (nm)
L [n]: Distance (mm) from the film end of the nth measurement position where the measurement order of front retardation is The retardation compensation film according to any one of claims 3 to 5,
A composite polarizing plate comprising: a polarizing plate laminated on one surface of the retardation compensation film.   A liquid crystal display device comprising: a pair of substrates constituting a liquid crystal cell; and the composite polarizing plate according to claim 6 laminated on at least one outer surface of the pair of substrates. The retardation compensation film according to any one of claims 3 to 5,
An adhesive layer laminated on one surface of the retardation compensation film;
A polarizing plate comprising: a polarizer laminated on a surface opposite to a surface on which the retardation compensation film of the adhesive layer is laminated.   A liquid crystal display device comprising: a pair of substrates constituting a liquid crystal cell; and the polarizing plate according to claim 8 laminated on at least one outer surface of the pair of substrates.