JP2013099958A - Method of manufacturing long oriented film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a wide and long oriented film, free from the thickness unevenness in the width direction and the variation of the oriented direction, having excellent precision of optical characteristics and having an orientation axis inclined in a predetermined angle range to the winding direction.SOLUTION: The long oriented film is manufactured. The long oriented film comprises a material having negative intrinsic birefringence value, has the orientation angel θ of 30-80° to the width direction, through at least a 1,300 mm width direction and the variation thereof is ≤1.0°, and has Nz coefficient of (-1.2 to -0.3) and the variation thereof is ≤0.10.

Description

  The present invention relates to a method for producing a long stretched film.

  Various retardation films are used in liquid crystal display devices in order to improve performance. This phase difference film is designed so that its slow axis is inclined at various specific angles with respect to the polarization transmission axis of the polarizer, the polarization transmission axis of the liquid crystal cell, etc. Installed on the display device. The tilt angle of the slow axis is an angle that is neither parallel nor perpendicular to the side of the display device.

As a method for obtaining a retardation film oriented at an angle that is neither parallel nor perpendicular to the side as described above, a transparent resin film is oriented by longitudinal stretching or lateral stretching to obtain a long stretched film. Thereafter, a method of cutting a rectangular shape obliquely at a predetermined angle with respect to the side of the stretched film is widely known. However, in this method, even if the maximum area is obtained, a large amount of cutting loss occurs, and the utilization efficiency of the stretched film is low.
On the other hand, in the case of a long stretched film oriented obliquely at a predetermined angle, it can be cut parallel to the side edges, and the utilization efficiency of the stretched film is increased. Various methods for obtaining such a film oriented obliquely with respect to the side by stretching have been proposed.

  For example, Patent Document 1 discloses that an optical polymer film is stretched by holding both ends of a continuously supplied polymer film by holding means, and stretching the holding means while moving the holding means in the longitudinal direction of the film. In the method, the trajectory L1 of the holding means from the substantial holding start point to the substantial holding release point at one end of the polymer film and the substantial holding start point to the substantial holding release point at the other end of the polymer film. The distance L between the holding means locus L2 and the two substantial holding release points satisfies the relationship of | L2-L1 |> 0.4W, and the support of the polymer film is maintained, and the volatile content is 5%. There is disclosed a method for stretching an optical polymer film, characterized in that, after stretching in the presence of the above-described state, the volatile content rate is reduced while shrinking.

  Patent Document 2 discloses a long shape obtained by stretching a long film made of a thermoplastic resin and having an orientation axis that is neither parallel nor perpendicular to the winding direction of the long film. A method for producing an optical film, wherein in the region where the film is substantially stretched, the moving speeds at the opposite ends in the width direction are equal and the moving distances are different, and the opposite ends of the film in the width direction A method for producing a long optical film is disclosed, in which at least one of a pair of jigs holding the film moves on a rail having a wave shape with respect to the film surface. ing. Further, Patent Document 2 states that this stretching step may be repeated several times, or the stretching step may be performed after stretching in the longitudinal direction or the transverse direction in advance.

  However, in these oblique stretching methods, wrinkles and twists occur obliquely, and thickness unevenness tends to occur. For this reason, it has been substantially impossible to obtain a wide film of 1300 mm or more in which the thickness in the width direction is uniform and the film is uniformly oriented without variation at an orientation angle of 40 ° or more in the winding direction. Therefore, it was impossible to industrially mass-produce a long and wide optical film in which the orientation axis was oblique (a direction greatly deviating from the width direction or longitudinal direction of the film).

Further, Patent Document 3 discloses a width direction obtained by stretching an unstretched laminate obtained by laminating a resin having a positive intrinsic birefringence value on both sides of a layer made of a resin having a negative intrinsic birefringence value. In contrast, an elongated body of a quarter-wave plate having an orientation axis (slow axis) in the direction of 105 ° ± 7 ° or 75 ° ± 7 ° is disclosed.
However, according to the study by the present inventors, the elongated body described in the above-mentioned patent document is prone to breakage during the film-forming process and breaks easily, and a liquid crystal display device using the same It was found that the display image quality improvement effect may be insufficient.

JP 2002-86554 A JP 2003-232929 A JP 2005-284024 A

  In view of the above circumstances, the object of the present invention is that there is no variation in thickness in the width direction and variation in the orientation direction, excellent optical characteristics, and the orientation axis is tilted within a predetermined angle range with respect to the winding direction. Another object of the present invention is to provide a wide and long stretched film and a method for producing the same.

The present inventors have obtained a first stretched film orientation angle theta ₁ is within ± 1 ° with respect to the width direction and longitudinal stretching an unstretched film of a long intrinsic birefringence value is a negative material, the first By stretching the stretched film at a specific angle with respect to the winding direction of the second stretched film and stretching the tenter, the thickness unevenness in the width direction and the variation in the orientation angle are very small, and the accuracy of the optical characteristics is excellent. It has been found that a wide and long stretched film can be obtained in which the orientation axis is inclined at a relatively large angle with respect to the direction.

  Further, the inventor is made of a material having a negative intrinsic birefringence value, the orientation angle θ is in a specific angle range with respect to the width direction over at least the width direction of 1300 mm, and the variation in the orientation angle is 1.0. An elongated stretched film having an average Nz coefficient in the range of -1.0 to -0.3 and a variation in Nz coefficient of 0.10 or less over the width direction of at least 1300 mm. It has been found that the productivity of polarizing plates and liquid crystal display devices can be improved by using them. The present invention has been completed based on these findings.

That is, the present invention includes the following aspects.
(1) It is made of a material having a negative intrinsic birefringence value and spans at least a width direction of 1300 mm.
The orientation angle θ with respect to the width direction has a value in the range of 30 ° to 80 °, and the variation is 1.0 ° or less,
A long stretched film having a value of Nz coefficient in the range of -1.2 to -0.3 and variation of 0.10 or less.

(2) The above long stretched film having an in-plane retardation Re of 100 to 300 nm.
(3) The stretched film described above, wherein the variation in retardation Re in the in-plane direction is within 10 nm.
(4) The stretched film as described above, wherein the retardation Rth in the thickness direction is -350 nm to -20 nm.
(5) The above stretched film having an average thickness of 30 to 80 μm and a thickness unevenness of 3 μm or less.

(6) intrinsic birefringence is a long film made of a negative and a material with longitudinal stretching, to obtain a first stretched film orientation angle theta ₁ is within ± 1.0 ° with respect to the width direction,
The first stretched film is tenter-stretched while being fed so that the feed angle θ _S with respect to the winding direction of the second stretched film is 15 ° <θ _S <60 °, and the orientation angle θ with respect to the width direction is 30 ° to 30 °. The manufacturing method of a elongate stretched film including the process of obtaining the 2nd stretched film which exists in the range of 80 degrees.

(7) stretching magnification _{R 1} in the step of obtaining the first stretched film is 1.1 to 2.0, the draw ratio _{R 2} in the step of obtaining a second stretched film is 1.3 to 2.0, A method for producing the stretched film.
(8) A long circularly polarizing plate formed by laminating the long stretched film and a long polarizer.
(9) A liquid crystal display device comprising a single-wafer stretched film formed by cutting the long stretched film or a single-wafer circularly-polarized plate formed by cutting the long circular polarizing plate.
(10) The liquid crystal display device including an IPS mode liquid crystal panel.
(11) The liquid crystal display device including a reflective display type liquid crystal panel.
(12) The liquid crystal display device including a transflective display type liquid crystal panel.

  Since the long stretched film of the present invention can be trimmed parallel to the longitudinal direction or the width direction, there are few discarded portions of the film, and the productivity is excellent. In addition, when the circularly polarizing plate of the present invention is used in a liquid crystal display device, particularly in an IPS mode liquid crystal display device, the viewing angle of the display screen is widened, and it is possible to prevent a decrease in contrast and coloring of the display screen. it can.

  According to the production method of the present invention, it is possible to easily form a wide stretched film having a uniform thickness in the width direction and a uniform orientation axis in a direction of 30 ° to 80 ° with respect to the width direction. Can be obtained. A long stretched film whose orientation axis is obliquely oriented is suitable as a retardation plate for a liquid crystal display device or the like. Specifically, when the orientation axis is tilted and overlapped with a certain long angle with another long optical element used in a liquid crystal display device such as a polarizing plate, the orientation axis is inclined with respect to the longitudinal direction. If a film is used, it can be overlapped with other long optical elements by roll-to-roll.

[Long stretched film]
The elongated stretched film of the present invention is
Made of a material with a negative intrinsic birefringence value,
Over the width direction of at least 1300 mm,
The orientation angle θ with respect to the width direction has a value in the range of 30 ° to 80 °, and the variation is 1.0 ° or less,
The value of the Nz coefficient is in the range of -1.2 to -0.3, and the variation is 0.10 or less.

  In the present invention, “long” means one having a length of about 5 times or more, preferably 10 times or more, in the width direction of the film or laminate. Specifically, it has a length that can be stored in a roll and stored or transported.

  The material having a negative intrinsic birefringence value used for the stretched film of the present invention has an in-plane slow axis in the direction perpendicular to the stretching direction in the plane when the plate-like material (non-oriented material) is uniaxially stretched. Material. The material having a negative intrinsic birefringence value is not particularly limited, and examples thereof include aromatic vinyl polymer resins, acrylonitrile polymer resins, methyl methacrylate polymer resins, and cellulose ester polymer resins. These materials having a negative intrinsic birefringence value can be used singly or in combination of two or more. Among these, aromatic vinyl polymer resins, acrylonitrile polymer resins, and methyl methacrylate polymer resins can be preferably used, and aromatic vinyl polymer resins are particularly preferably used because they exhibit high birefringence. Can do.

The aromatic vinyl polymer resin is a polymer resin containing an aromatic vinyl monomer as a main monomer unit.
Aromatic vinyl polymer resins include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-chlorostyrene, p-nitrostyrene, p-aminostyrene, p-carboxystyrene. , Homopolymers of aromatic vinyl monomers such as p-phenylstyrene, p-methoxystyrene, pt-butoxystyrene; or aromatic vinyl monomers and ethylene, propylene, butene, butadiene, isoprene, Aromatic vinyl such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, acrylic acid, methacrylic acid, maleic anhydride, maleimide, vinyl acetate, vinyl chloride Ethylenically unsaturated monomers other than the monomer and Can be mentioned. These can be used individually by 1 type or in combination of 2 or more types. Of these, styrene homopolymers and copolymers of styrene and maleic anhydride are preferred.

The material having a negative intrinsic birefringence value is not particularly limited by the molecular weight, but the weight average molecular weight is usually 10,000 to 300,000, preferably 15,000 to 250,000, more preferably 20,000 to 200. , 000.
The material having a negative intrinsic birefringence value used in the present invention preferably has _a melting point or glass transition temperature Tga of 120 ° C. or higher, more preferably 120 to 200 ° C., and particularly preferably 120 to 140 ° C.

  The material having a negative intrinsic birefringence value is not particularly limited depending on the production method. For example, in the case of a resin having a negative intrinsic birefringence value, a material having a negative intrinsic birefringence value can be obtained by a suspension polymerization method, an emulsion polymerization method, a bulk polymerization method, or the like. Can do.

  Antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, infrared absorbers, antistatic agents, etc. are added to the material having a negative intrinsic birefringence value in order to provide durability. May be.

The stretched film of the present invention is a plate-like product of layer A made of a material having a negative intrinsic birefringence value. In order to improve the mechanical strength of the stretched film, a material transparent on at least one side of the layer A A layered product C can be obtained by providing the layer B made of In particular, the laminate C is preferably a layer B ₂ consisting of a layer B ₁ and transparent material made of a transparent material on both surfaces of the layer A is a structure in which respectively laminated. At this time, the transparent material forming the transparent material and a layer B ₂ constituting the layer B ₁ represents, be the same type, or a different type.
In the case where the stretched film of the present invention has a laminated structure like the laminate C, when the non-oriented product is uniaxially stretched, the direction orthogonal to the stretching direction in the plane becomes the in-plane slow axis. Thus, it is preferable to select a transparent material.

  The transparent material may have a total light transmittance of 70% or more measured by forming a test piece having a thickness of 1 mm, more preferably 80% or more, particularly 90% or more. preferable. Examples of the transparent material include alicyclic olefin polymer, methacrylic resin, polycarbonate, acrylic ester-vinyl aromatic compound copolymer resin, methacrylic ester-vinyl aromatic compound copolymer resin, and polyethersulfone. A thermoplastic resin, a discotic liquid crystal, etc. can be mentioned. Among these, alicyclic olefin polymers and methacrylic resins are preferable, and methacrylic resins are particularly preferable.

The alicyclic olefin polymer is an amorphous polymer having a cycloalkane structure or a cycloalkene structure in the main chain and / or side chain. From the viewpoint of mechanical strength and heat resistance, a polymer containing a cycloalkane structure in the main chain is preferred. In addition, examples of the cycloalkane structure include monocyclic rings and polycyclic rings (condensed polycyclic rings, bridged rings, etc.). The number of carbon atoms constituting one unit of the cycloalkane structure is not particularly limited, but is usually 4 to 30, preferably 5 to 20, more preferably 5 to 15 when the resin film is used. The mechanical strength, heat resistance, and moldability of these are highly balanced and suitable.
Examples of the alicyclic olefin polymer include those described in JP-A No. 05-310845, JP-A No. 05-097978, and US Pat. No. 6,511,756.

  The ratio of the repeating unit having an alicyclic structure constituting the alicyclic olefin polymer is preferably 55% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight or more. It is preferable from a viewpoint of transparency and heat resistance that the ratio of the repeating unit which has an alicyclic structure in an alicyclic olefin polymer exists in this range.

  Examples of the alicyclic olefin polymer include norbornene resins, monocyclic cyclic olefin resins, cyclic conjugated diene resins, vinyl alicyclic hydrocarbon resins, and hydrides thereof. Among these, norbornene-based resins can be suitably used because of their good transparency and moldability.

  Examples of the norbornene-based resin include a ring-opening polymer of a monomer having a norbornene structure, a ring-opening copolymer of a monomer having a norbornene structure and another monomer, or a hydride thereof; norbornene structure The addition polymer of the monomer which has this, the addition copolymer of the monomer which has a norbornene structure, and another monomer, those hydrides, etc. can be mentioned. Among these, a ring-opening (co) polymer hydride of a monomer having a norbornene structure is particularly suitable from the viewpoints of transparency, moldability, heat resistance, low hygroscopicity, dimensional stability, lightness, and the like. Can be used.

Examples of the monomer having a norbornene structure include bicyclo [2.2.1] hept-2-ene (common name: norbornene) and tricyclo [4.3.0.1 ^2,5 ] deca-3,7-diene. (Common name: dicyclopentadiene), 7,8-benzotricyclo [4.3.0.1 ^2,5 ] dec-3-ene (common name: methanotetrahydrofluorene), tetracyclo [4.4.0. 1 ^2,5 . ^{17, 10} ] dodec-3-ene (common name: tetracyclododecene), and derivatives of these compounds (for example, those having a substituent in the ring). Here, examples of the substituent include an alkyl group, an alkylene group, and a polar group. Moreover, these substituents may be the same or different and a plurality may be bonded to the ring. Monomers having a norbornene structure can be used singly or in combination of two or more.

  Examples of the polar group include a hetero atom or an atomic group having a hetero atom. Examples of the hetero atom include an oxygen atom, a nitrogen atom, a sulfur atom, a silicon atom, and a halogen atom. Specific examples of the polar group include a carboxyl group, a carbonyloxycarbonyl group, an epoxy group, a hydroxyl group, an oxy group, an ester group, a silanol group, a silyl group, an amino group, a nitrile group, and a sulfone group. To obtain a film with a small saturated water absorption rate. It is preferable that the amount of polar groups is small, and it is more preferable that there are no polar groups.

Other monomers capable of ring-opening copolymerization with monomers having a norbornene structure include monocyclic olefins such as cyclohexene, cycloheptene, and cyclooctene and derivatives thereof; cyclic conjugated dienes such as cyclohexadiene and cycloheptadiene; Derivatives thereof; and the like.
A ring-opening polymer of a monomer having a norbornene structure and a ring-opening copolymer of a monomer having a norbornene structure and another monomer copolymerizable with the monomer have a known ring-opening polymerization catalyst. It can be obtained by (co) polymerization in the presence.

Examples of other monomers that can be addition copolymerized with a monomer having a norbornene structure include α-olefins having 2 to 20 carbon atoms such as ethylene, propylene, and 1-butene, and derivatives thereof; cyclobutene, cyclopentene, And cycloolefins such as cyclohexene and derivatives thereof; non-conjugated dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, and the like. These monomers can be used alone or in combination of two or more. Among these, α-olefin is preferable and ethylene is more preferable.
An addition polymer of a monomer having a norbornene structure and an addition copolymer of a monomer having a norbornene structure with another monomer copolymerizable with a monomer having a norbornene structure are prepared in the presence of a known addition polymerization catalyst. It can be obtained by polymerization.

  Hydrogenated product of ring-opening polymer of monomer having norbornene structure, hydrogenated product of ring-opening copolymer of monomer having norbornene structure and other monomer capable of ring-opening copolymerization, norbornene structure The hydride of an addition polymer of a monomer having a monomer, and the hydride of an addition copolymer of a monomer having a norbornene structure and another monomer capable of addition copolymerization with these ring-opening (copolymerization) ) A known hydrogenation catalyst containing a transition metal such as nickel or palladium is added to a polymer or addition (co) polymer solution, and brought into contact with hydrogen, so that the carbon-carbon unsaturated bond is preferably 90% or more. It can be obtained by hydrogenation.

Among norbornene-based resins, as repeating units, X: bicyclo [3.3.0] octane-2,4-diyl-ethylene structure and Y: tricyclo [4.3.0.1 ^2,5 ] decane-7 , 9-diyl-ethylene structure, the content of these repeating units is 90% by weight or more based on the entire repeating units of the norbornene-based resin, and the content ratio of X and the content ratio of Y Is preferably 100: 0 to 40:60 by weight ratio of X: Y. By using such a resin, it is possible to obtain an optical film that has no dimensional change in the long term and is excellent in stability of optical characteristics.

  The molecular weight of the alicyclic olefin polymer used in the present invention is appropriately selected according to the purpose of use, but it is determined by gel permeation chromatography using cyclohexane (toluene when the polymer resin does not dissolve) as a solvent. The weight average molecular weight (Mw) of isoprene (in terms of polystyrene when the solvent is toluene) is usually 10,000 to 100,000, preferably 15,000 to 80,000, more preferably 20,000 to 50,000. It is. When the weight average molecular weight is in such a range, the mechanical strength and formability of the film are highly balanced and suitable.

  The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the alicyclic olefin polymer is not particularly limited, but is usually 1.0 to 10.0, preferably 1.1 to 4.0, more preferably. Is in the range of 1.2 to 3.5.

The methacrylic resin is a polymer resin containing a methacrylic acid alkyl ester as a main monomer unit.
As the methacrylic resin, a homopolymer of an alkyl ester having 1 to 4 carbon atoms such as methyl methacrylate or ethyl methacrylate; a hydrogen of the alkyl group is a functional group such as OH group, COOH group or NH ₂ group. A homopolymer of a methacrylic acid alkyl ester having a C 1-4 alkyl group substituted by a group; or a methacrylic acid alkyl ester and styrene, vinyl acetate, α, β-monoethylenically unsaturated carboxylic acid, vinyltoluene , Α-methylstyrene, acrylonitrile, copolymers with ethylenically unsaturated monomers other than methacrylic acid alkyl esters such as alkyl acrylate. These can be used individually by 1 type or in combination of 2 or more types. Among these, acrylic acid alkyl esters are suitable for copolymerization with methacrylic acid alkyl esters. In a suitable methacrylic resin, the methacrylic acid alkyl ester having an alkyl group having 1 to 4 carbon atoms which may be substituted with a functional group is preferably 50 to 100% by weight, more preferably 50 to 99.9% by weight, Preferably it contains 50-99.5 weight%, Preferably it is 0-50 weight% of acrylic acid alkylester, More preferably, it contains 0.1-50 weight%, More preferably, it contains 0.5-50 weight%.

The transparent material constituting the layer B (the layer B ₁ and the layer B ₂ ) preferably has a melting point or a glass transition temperature Tg _b (Tg _b1 or Tg _b2 when the type of the transparent material is different), preferably 40 ° C. or higher. More preferably, it is 60 degreeC or more, Most preferably, it is 90 degreeC or more. Further melting point or glass transition temperature Tg _b of the transparent material constituting the transparent material and a layer B ₂ constituting the layer B ₁ represents, than the melting point or glass transition temperature Tg _a of the material having a negative intrinsic birefringence value low it is preferable, it is more preferably less 15 ℃ or higher than Tg _a, it is particularly preferably lower 20 ° C. or higher than Tg _a. By setting it as such a structure, it becomes possible to improve the mechanical strength of the said laminated body C more.

Transparent material constituting the transparent material and a layer B ₂ constituting the layer B ₁ represents, in accordance with this manufacturing method is not particularly limited, suspension polymerization method, emulsion polymerization method, can be obtained in such bulk polymerization. Have suitable glass transition temperatures, in order to obtain a transparent resin constituting the superior layers B ₁ and / or layer B ₂ on the film formability, it is preferable to use a chain transfer agent during polymerization. The amount of the chain transfer agent is appropriately determined according to the type and composition of the monomer.

The transparent material forming the transparent material and a layer B ₂ constituting the layer B _1, light resistance, in order to provide heat resistance, antioxidants, heat stabilizers, light stabilizers, UV absorbers, An infrared absorber, an antistatic agent, a surfactant, rubber particles and the like may be added.

  The ultraviolet absorber is added to improve durability by absorbing ultraviolet rays of 400 nm or less. As the ultraviolet absorber, known ones such as a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, and an acrylonitrile ultraviolet absorber can be used. Among them, 2,2′-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (5-methyl-2-hydroxy Phenyl) -2H-benzotriazole, 2- (2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl) -2H-benzotriazole, 2- (3,5-di-tert-butyl-2) -Hydroxyphenyl) -2H-benzotriazole, 2- (3-tert-butyl-5-methyl-2-hydroxyphenyl) -5-chloro-2H-benzotriazole, 2- (3,5-di-tert-butyl -2-hydroxyphenyl) -5-chloro-2H-benzotriazole, 2- (3,5-di-tert-amyl-2-hydroxyphenyl) -5-chloro- 2H-benzotriazole, 2- (2′-hydroxy-5′-tert-octylphenyl) -2H-benzotriazole; 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2,4- Dihydroxybenzophenone, 2-hydroxy-4-methoxy-4′-chlorobenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2- (2′-hydroxy-3′-tert-butyl-5′-methylphenyl) -5-chlorobenzotriazole, 2,4-di-tert-butyl-6- (5-chlorobenzotriazol-2-yl) phenol, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone; p-tert Butylphenyl salicylate, etc. p- octylphenyl salicylate is preferably used. Among these, 2,2'-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol) is particularly preferable. The concentration of the ultraviolet absorber can be selected within a range where the transmittance at a wavelength of 370 nm or less is preferably 10% or less, more preferably 5% or less, and still more preferably 2% or less. Examples of the method of containing the ultraviolet absorber include a method of previously blending the ultraviolet absorber into the transparent material; a method of directly supplying at the time of melt extrusion molding, and any method may be employed.

  The effect of the amount of the ultraviolet absorber varies depending on the type of the ultraviolet absorber, and may be appropriately adjusted to an amount that can effectively block ultraviolet rays without deteriorating the color tone of the film.

  The stretched film of the present invention has an orientation angle θ in the range of 30 ° to 80 ° when the film width direction (direction perpendicular to the film winding direction (longitudinal direction) in the film plane) is 0 °. The optimum value within this range is selected depending on the design of the display device used. In particular, when the orientation angle θ is in the range of 40 ° to 50 °, the mechanical properties of the stretched film of the present invention Strength is improved. Although the detailed reason for obtaining a film in which the mechanical strength is improved when the orientation angle θ is in the above-mentioned angle range with respect to the width direction of the film is not known, it is Since the tension in the direction or the longitudinal direction is dispersed and the tension does not concentrate in the slow axis or the direction perpendicular thereto, it is considered that the film is difficult to break in the winding process or the like.

The stretched film of the present invention has an orientation angle variation of 1.0 ° or less, preferably 0.8 ° or less, more preferably 0.6 ° or less over a width direction of at least 1300 mm. A stretched film with a variation in orientation angle exceeding 1.0 ° is bonded to a polarizing plate to obtain a circularly polarizing plate, and when this is installed on a liquid crystal display device, light leakage may occur and the contrast may be lowered. .
In addition, orientation angle | corner (theta) is an average value of the value which measured the stretched film at 50 mm intervals in the width direction using the commercially available polarizing microscope. The variation in the orientation angle θ is a value obtained by subtracting the minimum value from the maximum value of each measurement value.

Stretched film of the present invention, the slow axis direction of the refractive indices n _x in the plane of the _film, the refractive index in a direction perpendicular to the slow axis in the film plane n _y, the refractive index in the thickness direction of the film when was a _{n z, (n x -n z} ) / (n x -n y) range Nz coefficient of -1.2～-0.3, represented by, preferably -1.2～-0 .5, more preferably in the range of -1.2 to -0.7. When the Nz coefficient is within this range, the display quality can be improved when used as a retardation film for a liquid crystal display device.

The stretched film of the present invention has an Nz coefficient variation of 0.10 or less, preferably 0.08 or less over the width direction of at least 1300 mm. If the variation of the Nz coefficient exceeds 0.10, it causes deterioration in display quality such as color unevenness when incorporated in a liquid crystal display device.
In addition, Nz coefficient is the average value of the value which measured the stretched film at 50 mm intervals in the width direction using the commercially available phase difference measuring apparatus. Further, the variation in the Nz coefficient is a value obtained by subtracting the minimum value from the maximum value of each measurement value.

In the present invention, the retardation Re in the in-plane direction of the stretched film is optimally selected depending on the design of the display device used, but is preferably 100 to 300 nm. Incidentally, Re is an average thickness d of the film to the difference between the refractive index n _y in the direction perpendicular to the slow axis in the refractive indices n _x and plane-plane slow axis direction (the difference in refractive index [Delta] n) a multiplication value _{(Re = (n x -n y} ) × d = Δn × d).

  In the present invention, the variation in retardation Re in the in-plane direction of the stretched film is preferably within 10 nm, more preferably within 5 nm, and particularly preferably within 2 nm over the width direction of at least 1300 mm. By setting the variation of the retardation Re in the in-plane direction within the above range, the display quality can be improved when used as a retardation film for a liquid crystal display device.

In the stretched film of the present invention, the retardation Rth in the thickness direction represented by the formula [1] is preferably less than 0 nm, more preferably −350 nm to −20 nm, and particularly preferably −250 nm to −120 nm.
Rth = {(n _x + _ny ) / 2−n _z } × d [1]
Incidentally, the n _x-plane slow axis direction of the refractive index, the n _y refractive index in a direction perpendicular to the plane slow axis, n _z is the thickness direction of the refractive index, d is the average thickness.
When a stretched film having such a retardation Rth in the thickness direction is used in a liquid crystal display device in combination with a circularly polarized light separating element including a layer having cholesteric regularity, the display screen is also observed from an oblique direction. The color is the same as that observed from the front and the screen is less likely to be colored. This refractive index can be measured by an automatic birefringence meter (for example, “KOBRA series” manufactured by Oji Scientific Instruments).

When the stretched film of the present invention has a laminated structure like the laminate C, the orientation degree ΔP of the layer B ₁ and / or the layer B ₂ is 0.1 × 10 ⁻⁴ or more and 9.0 × 10 ^−. It is preferably ⁴ or less, and more preferably 0.3 × 10 ⁻⁴ or more and 0.6 × 10 ⁻⁴ or less. When the ΔP is in the above range, the adhesiveness with the polarizing plate becomes better. The degree of orientation is a value defined by the formula [2].
ΔP = (n _x + n _y ) / 2−n _z [2]

In the laminate C, the in-plane retardation Re of the layer B ₁ and / or the layer B ₂ is preferably 0 nm or more and 15 nm or less, more preferably more than 1 nm and less than 10 nm, and the layer B ₁ and it is more preferred in-plane direction retardation Re of the layer _{B 2} are both less than 1nm super 10 nm. When the retardation Re in the in-plane direction satisfies the above range, good optical characteristics can be obtained.

  The retardation Rth in the thickness direction and the retardation Re in the in-plane direction are measured at a light incident angle of 0 ° (incident light is perpendicular to the surface of the stretched film of the present invention) at intervals of 50 mm in the width direction. An automatic birefringence meter is used at intervals of 50 mm within a length of 1000 mm in the direction. And what averaged all the measurement results is made into retardation Rth of the thickness direction of each layer, and retardation Re of an in-plane direction. Further, the variation in retardation Re in the in-plane direction is a value obtained by subtracting the minimum value from the maximum value of each measurement value.

When the stretched film of the present invention is used as a quarter-wave plate combined with a circularly polarized light separating element including a layer having cholesteric regularity, the in-plane retardation Re of the stretched film is in the range of 100 to 155 nm. It is preferable to adjust so that it becomes. Incidentally, Re is a value defined by _{(n x -n y) × d} . The circularly polarized light separated by the circularly polarized light separating element can be efficiently converted into linearly polarized light by adjusting the in-plane retardation Re to the above range.

The stretched film of the present invention has an average thickness (total thickness) of preferably 20 μm or more and 200 μm or less, more preferably 40 μm or more and 180 μm or less from the viewpoint of mechanical strength and the like.
When the stretched film of the present invention has a laminated structure like the laminate C, the average thickness of the layer A is preferably 10 to 150 μm, more preferably 20 to 100 μm, and the layer B ₁ and the average thickness of the layer _{B 2} is preferably 20～180Myuemu, more preferably 30 to 150 [mu] m. Furthermore, the ratio of the average thickness of the average thickness / layer A layer _{B 1} represents 3 / 1-1 / 3, preferably 2 / 1-1 / 2. The ratio of the average thickness / layer average thickness of _{B 2} layer A is 1 / 3-3 / 1, preferably from 1/2 / to 2/1. Note that the layer B ₁ and the layer B ₂ do not have to have the same average thickness, but preferably have substantially the same average thickness in order to prevent warping and the like.
In addition, the thickness unevenness in the width direction of the stretched film of the present invention affects whether or not the film can be wound. Therefore, it is preferably 3 μm or less, particularly preferably 2 μm or less over the width direction of at least 1300 mm. preferable.
The average thickness and the total thickness are measured by the following procedure. First, the reflection spectral film thickness meter is scanned at 50 mm intervals in the width direction of the stretched film to measure the thickness (of each layer) of the stretched film. Next, this measurement is performed over a length of 1000 mm at intervals of 50 mm in the flow direction of the stretched film. All the measurement results are averaged to obtain the thickness (of each layer). The total thickness is the sum of the average thickness of each layer. The thickness unevenness is a value obtained by subtracting the minimum value from the maximum value of each measurement value.

  The elongated stretched film of the present invention has a width of at least 1300 mm, preferably at least 1500 mm. In the production process, the elongated stretched film of the present invention is optionally created by cutting off both ends in the width direction after stretching, but in this case, the width of the film referred to above is the result of cutting off both ends. It can be a dimension.

In the stretched film of the present invention, the content of residual volatile components is preferably 0.1% by weight or less, more preferably 0.05% by weight or less, and further preferably 0.02% by weight or less. If the content of residual volatile components is large, the optical characteristics may change over time. By making the content of the volatile component in the above range, the dimensional stability is improved, the temporal change of the in-plane direction retardation Re and the thickness direction retardation Rth can be reduced, and the circularly polarized light of the present invention Deterioration of the plate and the liquid crystal display device can be suppressed, and the display image can be kept in a good state for a long time.
The volatile component is a substance having a molecular weight of 200 or less, and examples thereof include residual monomers and solvents. The content of the volatile component can be quantified by dissolving the film in chloroform and analyzing it by gas chromatography as the total of substances having a molecular weight of 200 or less contained in the film.

The stretched film of the present invention has a saturated water absorption rate of preferably 0.03% by weight or less, more preferably 0.02% by weight or less, and particularly preferably 0.01% by weight or less. When the saturated water absorption is in the above range, the temporal change of the in-plane direction retardation Re and the thickness direction retardation Rth can be reduced, and further the deterioration of the circularly polarizing plate and the liquid crystal display device of the present invention can be suppressed. The displayed image can be kept in a good state for a long time.
The saturated water absorption is determined by immersing a film specimen in water at 23 ° C. for 24 hours in accordance with JIS K7209, and measuring the change in mass of the specimen, that is, the difference in mass before and after immersion. , A value expressed as a percentage of the mass before immersion.

[Production method of long stretched film]
In the production method of the present invention, first, a long film made of a material having a negative intrinsic birefringence value is longitudinally stretched, and the first stretching in which the orientation angle θ ₁ with respect to the width direction is within ± 1.0 °. A film is obtained (first stretching step).

The material which comprises the elongate film (henceforth a "raw film" may be described hereafter) used for the manufacturing method of this invention can mention the thing similar to what was demonstrated with the stretched film of this invention.
The long original film can be obtained by a known method, for example, a cast molding method, an extrusion molding method, an inflation molding method, or the like. Of these, the extrusion molding method is preferable because a film having a small amount of the residual volatile component, a small saturated water absorption, and excellent dimensional stability can be obtained. The original film may be a single layer or a laminated film having two or more layers. The laminated film can be obtained by a known method such as a coextrusion molding method, a film lamination method, or a coating method. Of these, the extrusion method is preferred.

If the melting temperature of the material which comprises the said raw film is a temperature which can be extrusion-molded, it will not restrict | limit, Usually, it is 200-300 degreeC.
The molten material supplied to the die passes through the die slip and is extruded as a molten film. The molten film extruded from the die is taken up by a first cooling roll (also referred to as a cast roll), cooled, and becomes a raw film.
In order to make the optical properties uniform after stretching, the thickness unevenness of the original film needs to be as small as possible. The maximum value-minimum value is 3 μm or less, preferably 2 μm or less.

Incidentally, the stretched film of the present invention, when having a laminated structure as the laminate C are, for example, a material having a negative intrinsic birefringence value constituting the layer A, the layer B ₁ and the layer the material constituting the B ₂ coextruding, give a melt film is passed through the die lip to obtain a raw film take back the molten film in the first cooling roll, followed by stretching the raw fabric film Easy to get.
The material having the negative intrinsic birefringence value constituting the layer A and the material constituting the layer B ₁ and the layer B ₂ are first removed by removing excess moisture and organic volatile components by vacuum drying or the like. In addition, it is melted by a single screw extruder, a twin screw extruder or the like and supplied to a die for coextrusion molding. As the die, there are a feed block method, a multi-manifold method, and the like, which can be appropriately selected.

  The width of the long original film used in the production method of the present invention may be determined by the material constituting the stretched film, the width of the stretched film, and the stretch ratio, but is preferably at least 1000 mm.

  In the first stretching step, a known longitudinal stretching method is used. For example, it is possible to use a technique in which a heated film is stretched in the flow direction using a peripheral speed difference between rolls. Examples of the heating means include a method of heating the roll itself by heating a heat medium circulated in the roll, a method of installing an infrared heater between the rolls, and a method of installing a float type oven between the rolls. Among these, a float method capable of performing uniform stretching is preferable.

Stretch ratio _{R 1} in the first stretching step is preferably 1.1 to 2.0, more preferably 1.2 to 1.8. When the stretching ratio R ₁ is in this range, it is possible to suppress the thickness unevenness in the width direction of the first stretched film, the variation in the orientation angle.

The stretching temperature in the first stretching step is Tg _a (° C.) or higher and Tg _a +30 (° C.) with respect to the melting point or glass transition temperature Tg _a (° C.) of the material having a negative intrinsic birefringence value constituting the raw film. It is suitably selected from the following ranges. If the stretching temperature is less than Tg _a (° C.), moldability may be insufficient and defects such as craze may occur. On the other hand, if Tg _a +30 (° C.) is exceeded, flow stretching occurs and it is difficult to obtain an effective refractive index difference Δn. Further, the stretched film of the present invention, when having a laminated structure as the laminate C is the stretching temperature, melting point or glass transition temperature Tg of the material constituting the material and the layer B ₂ constituting the layer B _{1 b} (Tg _b1 , Tg _b2 when the material is different) 15 ° C. to 60 ° C., preferably 20 ° C. to 50 ° C. higher, and Tg _{a to} Tg _a + 30 ° C. It is preferable. When stretching is performed under such conditions, the degree of orientation and in-plane retardation of the layers B ₁ and B ₂ can be adjusted to the above-described ranges.

The first stretched film has an orientation angle θ ₁ with respect to the width direction within a range of ± 1.0 °. Moreover, it is preferable that refractive index difference (DELTA) n of a 1st stretched film exists in the range of 0.001-0.003. The orientation angle θ ₁ is the smaller of the angles formed by the film width direction and the orientation axis.

  The first stretched film may be wound around a core and formed into a wound body, and then supplied to the second stretching step described later, or may be supplied to the second stretching step without being wound around the core. .

  Next, the first stretched film is obliquely stretched to obtain a second stretched film having an orientation angle θ of 30 ° to 80 ° with respect to the width direction (second stretch step) (sometimes referred to as an oblique stretch step).

In the second stretching step, the angle θ _S of the first stretched film in the feeding direction with respect to the winding direction of the second stretched film is 15 ° <θ _S <60 °, preferably 25 ° <θ. Tenter stretching is carried out while drawing out so that _S <55 °, and a second stretched film having an orientation angle θ in the range of 30 ° to 80 °, preferably 40 ° to 50 ° with respect to the width direction is produced. In this specification, the angle of the film feeding direction with respect to the film winding direction is referred to as a feeding angle. By setting the feeding angle θ _S within this range, it is possible to obtain a wide and uniform physical property even in an obliquely stretched film having a large orientation angle as in the present invention.

Draw ratio _{R 2} in _the second stretching step is preferably 1.3 to 2.0, more preferably 1.5 to 1.9. Can draw ratio R ₂ is wider on that it is possible to reduce the width direction of the thickness unevenness is within this range. When the draw ratio R ₂ is greater than 2.0, there is a possibility that the orientation of the film by the first stretching step is almost disappeared, there is a possibility that the orientation angle of the stretched film of the present invention θ is not within the above range. When the draw ratio R ₂ is smaller than 1.3, there is a possibility that the orientation of the film by the first stretching step is left strong, there is a possibility that the orientation angle of the stretched film of the present invention θ is not within the above range.
In addition, the draw ratio in a 2nd extending process can be calculated | required from the amount of length change of the width direction. Specifically, the width of the unstretched film W _0, and the width of the stretched film after the W _1, the draw ratio can be obtained by W _{1 /} W _0.

  In the second stretching step, if the stretching temperature is differentiated in the width direction in the stretching zone of the tenter stretching machine, the thickness unevenness in the width direction can be further improved. As a method of making a difference in the stretching temperature in the width direction, a method of adjusting the opening degree of the nozzle that sends warm air into the temperature-controlled room so as to make a difference in the width direction, and controlling the heating by arranging the heaters in the width direction are known. Can be used.

The stretching temperature in the second stretching step is Tg _a (° C.) or higher and Tg _a +30 (° C.) or lower with respect to the melting point or glass transition temperature Tg _a (° C.) of the material having a negative intrinsic birefringence value constituting the film. It is appropriately selected from the range. If the stretching temperature is less than Tg _a (° C.), moldability may be insufficient and defects such as craze may occur, and if the temperature exceeds Tg _a +30 (° C.), flow stretching occurs and the intended retardation (Re or Rth). It is not possible to obtain a sufficient molecular orientation to express Further, the stretched film of the present invention, when having a laminated structure as the laminate C is the stretching temperature, melting point or glass transition temperature Tg of the material constituting the material and the layer B ₂ constituting the layer B _{1 b} (Tg _b1 , Tg _b2 when the material is different) 15 ° C. to 60 ° C., preferably 20 ° C. to 50 ° C. higher, and Tg _{a to} Tg _a + 30 ° C. It is preferable. When subjected to the stretching under such conditions, the degree of orientation of the layers B ₁ and the layer B ₂ and the in-plane direction retardation Re can be adjusted to the above-described range.

The second stretching process will be described with reference to the drawings.
FIG. 1 is a conceptual diagram showing an example of a tenter stretching machine that can suitably carry out the production method of the present invention. FIG. 2 is a view showing a grip means for the rail portion in the stretching machine of FIG. FIG. 3 is a view for explaining a rail pattern in the stretching machine of FIG. The angle θ _S is a feeding angle with respect to the film winding direction.

  The tenter stretching machine shown in FIG. 1 includes a feed roll (first stretched film B roll) 21, a take-up roll 22, a constant temperature chamber 10 composed of a preheating zone A, a stretching zone B, and a fixed zone C, and a film. At least a rail 11 on which a gripping means for transporting and a gripping means 12 (the gripping means is not shown in FIGS. 1 and 3) are provided.

  The gripping means 12 grips both ends of the first stretched film B drawn from the feed roll 21, and guides the first stretched film B into the temperature-controlled room composed of the preheating zone A, the stretching zone B, and the fixed zone C, and obliquely stretches the first stretched film B. And the 2nd stretched film B extended diagonally in front of the winding roll 22 is open | released. The second stretched film B released from the gripping means is taken up by the take-up roll 22. The pair of left and right rails 11 have a continuous endless track without a terminal, and return the gripping means that has traveled as described above from the exit side of the temperature-controlled room to the entrance side.

The first stretched film B (denoted as 1 in FIG. 1) is stretched by tension from the gripping means while passing through the temperature-controlled room composed of the preheating zone, the stretching zone, and the fixing zone.
The preheating zone, the stretching zone, and the fixed zone can be independently set in temperature, and the temperature is normally kept constant in each zone. Although the temperature of each zone can be selected as appropriate, the preheating zone is Tg to Tg + 30 (° C.) with respect to the glass transition temperature Tg (° C.) of the material having a negative intrinsic birefringence constituting the unstretched film, and the stretching zone is Tg to Tg + 20 (° C.), and the fixing zone is Tg to Tg + 15 (° C.).

  In the present invention, in order to control thickness unevenness in the width direction, a temperature difference may be given in the width direction in the stretching zone. In particular, in the present invention, it is preferable that the temperature in the vicinity of the gripping means is higher than that at the center of the film. In order to create a temperature difference in the width direction in the stretching zone, a method of adjusting the opening degree of the nozzle for sending warm air into the temperature-controlled room so as to make a difference in the width direction, or controlling the heating by arranging the heaters in the width direction is known. Can be used. The length of the preheating zone, the stretching zone and the fixed zone can be appropriately selected. Usually, the length of the preheating zone is usually 100 to 150% and the length of the fixing zone is usually 50 to 100% with respect to the length of the stretching zone. It is.

  The gripping means 12 travels on the rail 11 whose arrangement can be changed, for example. The rails 11 are arranged so that the film is stretched at a desired angle. In FIG. 1, the arrangement of the rails is set so that the film traveling direction is the direction described below. In the present invention, the film running direction is a tangential direction of a line connecting the midpoints in the film width direction from the film drawing roll to the film winding roll.

  At the boundary 13 between the preheating zone and the stretching zone and at the boundary 14 between the stretching zone and the fixing zone, a partition plate having a slit through which the film can pass is installed. It is preferable that the boundary between the preheating zone and the stretching zone and the boundary between the stretching zone and the fixing zone, that is, the partition plate is perpendicular to the film running direction 49 of the fixing zone.

  The preheating zone A is a zone in which the film is conveyed while warming the film without substantially changing the film length in the direction perpendicular to the film running direction 47 of the preheating zone. The film running direction in the preheating zone is a direction parallel to the film feeding direction, and is usually perpendicular to the rotation axis of the drawing roll.

  The stretching zone B is a zone for transporting a film while increasing the film length in a direction perpendicular to the film running direction of the stretching zone. The film running direction in the stretching zone is as follows. In the rail arrangement in which the stretching zone spreads at a constant angle without changing the inclination as shown in FIG. 1, the stretching zone and the fixed zone are from the middle point of the film at the boundary between the preheating zone and the stretching zone. This is the direction of the straight line connected to the midpoint of the film at the border.

  In FIG. 1, the film running direction in the stretching zone is the same as the film running direction 47 in the preheating zone, but may be shifted. In the case of shifting, it is preferable to shift upward in the film running direction of the preheating zone in FIG.

  The fixing zone C is a zone for transporting the film while cooling the film without substantially changing the film length in the direction perpendicular to the film running direction 49 of the fixing zone. The film running direction 49 in the fixed zone is a direction parallel to the film winding direction, and is generally orthogonal to the rotation axis of the winding roll.

  In the production method of the present invention, the film surfaces in the preheating zone, the stretching zone, and the fixing zone are preferably substantially parallel to each other. That is, it is preferable that the film coming out of the drawing roll passes through the preheating zone, the stretching zone and the fixing zone without being twisted, and is wound around the winding roll.

In the manufacturing method of the present invention, it is preferable that the traveling speed of the gripping means is substantially equal at both ends of the film. In FIG. 2, a broken line is drawn between a pair of gripping means facing each other. Stretching starts near the stretching start point and ends near the stretching end point. The stretching start point is a point where the distance between the pair of gripping means starts to widen, and is S1 and S2 in FIG. The stretching end point is a point where the distance between the pair of gripping means starts to become constant, and is E1 and E2 in FIG. In the present specification, the direction connecting E1 and E2 may be referred to as a stretching direction in the oblique stretching step. In addition, the extending | stretching direction in this diagonal extending process is a direction substantially orthogonal to the drawing | feeding-out direction of a 1st stretched film.
The traveling speed of the gripping means can be selected as appropriate, but is usually 10 to 100 m / min. The difference in travel speed between the pair of left and right gripping means is preferably 1% or less, more preferably 0.5% or less, and particularly preferably 0.1% or less of the travel speed.

As shown in FIG. 3, the traveling direction (film feeding direction) 47 in the preheating zone is inclined by an angle θ _{S with} respect to the film traveling direction (film winding direction) 49 in the fixed zone. In FIG. 3, the rail is bent downward, but it may be bent upward by making the line in the film running direction of the preheating zone of FIG. The feeding angle θ _S is in the range of 15 ° <θ _S <(θ−90 °) + 5 °, preferably 25 ° <θ _S <55 °, with respect to the orientation angle θ of the obtained second stretched film. To.

  The stretching zone may be linear without changing the film running direction, or the film running direction may be changed stepwise or continuously. The opening angle of the rail can be appropriately selected according to the draw ratio.

Running direction of the fixing zone (film take-up direction) is inclined at an angle of the theta _S as shown in FIG. 3 from the running direction of the preheating zone (film feeding direction). For this reason, the upper gripping means in the figure goes farther than the lower gripping means. Therefore, in FIG. 2, when the upper gripping means reaches E1, the corresponding lower gripping means reaches E2. When viewed from the film width direction of the fixed zone, E2 has advanced to a position ahead of E1.

  The stretched film that has passed through the temperature-controlled room as described above is released from the gripping means before the take-up roll and is taken up by the take-up roll. Moreover, you may trim the both ends of the film currently hold | gripped with the holding means of a tenter stretching machine before winding up to a winding roll as needed. In addition, before winding, for the purpose of preventing blocking between the films, the masking film may be overlapped and wound up at the same time, or at least one of the stretched films, preferably wound up with tape or the like attached to both ends. Also good. The masking film is not particularly limited as long as it can protect the film, and examples thereof include a polyethylene terephthalate film, a polyethylene film, and a polypropylene film.

  The stretched film of the present invention can be easily obtained by the above-described production method and can highly compensate birefringence, so that it can be used alone or in combination with other members as a retardation plate or a viewing angle compensation film. The present invention can be widely applied to liquid crystal display devices, organic EL display devices, plasma display devices, FED (field emission) display devices, SED (surface electric field) display devices, and the like.

For example, as described above, when the stretched film of the present invention is used as a quarter wavelength plate, it can be bonded to a circularly polarized light separating element and used in a liquid crystal display device.
As the circularly polarized light separating element, a layer having cholesteric regularity disclosed in JP-A-6-235900, JP-A-8-271731, JP-A-11-231130, JP-A-2005-91825 and the like There are known circularly polarized light separation membranes and the like.

  When an adhesive (including an adhesive) is used for bonding the stretched film of the present invention and the circularly polarized light separating element, the average thickness of the adhesive layer made of the adhesive is usually 0.01 μm to 30 μm, preferably 0.00. 1 μm to 15 μm. The adhesive constituting this adhesive layer includes acrylic adhesive, urethane adhesive, polyester adhesive, polyvinyl alcohol adhesive, polyolefin adhesive, modified polyolefin adhesive, polyvinyl alkyl ether adhesive, rubber adhesive, vinyl chloride, Vinyl acetate adhesive, styrene / butadiene / styrene copolymer (SBS copolymer) adhesive, hydrogenated product (SEBS copolymer) adhesive, ethylene / vinyl acetate copolymer, ethylene-styrene copolymer, etc. Ethylene adhesives and acrylic ester adhesives such as ethylene / methyl methacrylate copolymers, ethylene / methyl acrylate copolymers, ethylene / ethyl methacrylate copolymers, and ethylene / ethyl acrylate copolymers And so on.

  Further, a linear polarizer can be further combined with the combination of the quarter wavelength plate and the circularly polarized light separating element. A linear polarizer is arrange | positioned in the direction which permeate | transmits the linearly polarized light converted by the stretched film of this invention in which the circularly polarized light isolate | separated with the circularly polarized light separation element has 1/4 wavelength Re.

The long circularly polarizing plate of the present invention is formed by laminating the long stretched film of the present invention and a long polarizer.
The polarizer used in the present invention transmits one of two linearly polarized light intersecting at right angles. For example, a hydrophilic polymer film such as a polyvinyl alcohol film or an ethylene vinyl acetate partially saponified film adsorbed a dichroic substance such as iodine or a dichroic dye and uniaxially stretched, the hydrophilic polymer film Examples include uniaxially stretched and dichroic substances adsorbed, and polyene oriented films such as polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products. Other examples include reflective polarizers such as grid polarizers and anisotropic multilayer films. The thickness of the polarizer is usually 5 to 80 μm.

  As a lamination | stacking form, the stretched film of this invention may be laminated | stacked on both surfaces of a polarizer, or may be laminated | stacked on one side, and there is no limitation in particular in the number of lamination | stacking, You may laminate | stack two or more sheets. When the stretched film of the present invention is laminated only on one side of the polarizer, a conventional protective film may be laminated on the remaining side for the purpose of protecting the polarizer.

  As a conventional protective film, an appropriate transparent film can be used. Among them, a film having a resin excellent in transparency, mechanical strength, thermal stability, moisture shielding property, etc. is preferably used. Examples of the resin include acetate polymers such as triacetyl cellulose, alicyclic olefin polymers, chain polyolefins, polycarbonates, polyesters such as polyethylene terephthalate, polyvinyl chloride, polystyrene, polyacrylonitrile, polysulfones, polyethersulfones, polyamides. , Polyimide, acrylic polymer and the like.

  A preferred production method for obtaining the long circularly polarizing plate of the present invention is that the stretched film and the polarizer are drawn simultaneously from the wound film and polarizer rolls of the stretched film of the present invention, respectively. It is a method including closely attaching a polarizer. An adhesive can be interposed between the contact surfaces of the obliquely stretched film and the polarizer. As a method for bringing the stretched film and the polarizer into close contact with each other, there is a method in which the stretched film and the polarizer are passed and pressed together through the nip between two parallel rolls.

  The long stretched film or the long circularly polarizing plate of the present invention is cut into a desired size according to the usage pattern and used as a phase difference plate or a polarizing plate. In this case, it is preferable to cut out along a direction perpendicular or parallel to the winding direction of the long film.

The liquid crystal display device of the present invention includes the cut out circularly polarizing plate.
An example of the liquid crystal display device of the present invention includes a liquid crystal cell that can change the polarization transmission axis by adjusting the voltage and the above-described circularly polarizing plate that is disposed so as to sandwich the liquid crystal cell. . The stretched film described above is used as a retardation plate in a liquid crystal display device for optical compensation, polarization conversion, and the like. In order to send light to the liquid crystal cell, the liquid crystal display device is usually provided with a backlight device in the transmissive liquid crystal display device and a reflector in the reflective liquid crystal display device on the back side of the display surface. Examples of the backlight device include a cold cathode tube, a mercury flat lamp, a light emitting diode, and an EL.

  The display mode of the liquid crystal cell included in the liquid crystal display device is not particularly limited. For example, in-plane switching (IPS) mode, vertical alignment (VA) mode, multi-domain vertical alignment (MVA) mode, continuous spin wheel alignment ( CPA) mode, hybrid alignment nematic (HAN) mode, twisted nematic (TN) mode, super twisted nematic (STN) mode, and optically compensated bend (OCB) mode. Among these, the IPS mode is preferable.

Liquid crystal display devices are roughly classified into a reflection type, a transmission type, and a semi-transmission type depending on how light is taken. In the transmissive type, a backlight serving as a light source is disposed behind the liquid crystal panel, and light from the backlight is transmitted through the liquid crystal panel so that an observer can visually recognize it. On the other hand, the reflective type takes external light from the front of the liquid crystal display device. The light is reflected by a reflection plate behind the liquid crystal panel, and the reflected light is transmitted through the liquid crystal panel so that an observer can visually recognize it. The transflective type operates as a reflection type when there is external light, and operates as a transmission type when there is no external light.
The stretched film or the circularly polarizing plate of the present invention can be used in any of a reflective type, a transmissive type, and a semi-transmissive type. However, in a transflective or reflective liquid crystal display device, the viewing angle of the display screen is wide. This is preferable because it can prevent a decrease in contrast and coloring of the display screen.

  The liquid crystal display device of the present invention may include other members. For example, a member such as a prism array sheet, a lens array sheet, a light diffusing plate, a light guide plate, a diffusing sheet, and a brightness enhancement film can be arranged in one or more layers at appropriate positions.

The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.
Evaluation in this example is performed by the following method.

(1) Thickness The thickness of the stretched film (of each layer) is measured by scanning a reflective spectral film thickness meter (FE-3000 manufactured by Otsuka Electronics Co., Ltd.) at intervals of 50 mm in the width direction of the stretched film. This measurement is performed over a length of 1000 mm at intervals of 50 mm in the flow direction of the stretched film. All the measurement results were averaged to obtain the thickness (of each layer). The thickness unevenness was a value obtained by subtracting the minimum value from the maximum value of each measurement value.

(2) Orientation angle Using a phase difference meter (KOBRA-WIST, manufactured by Oji Scientific Co., Ltd.) at an interval of 50 mm in the width direction of the stretched film, the direction of the in-plane slow axis of the film (the angle formed with the width direction of the film) ). This measurement is performed over a length of 1000 mm at intervals of 50 mm in the flow direction of the stretched film. All measurement results were averaged to obtain an orientation angle θ. The difference between the maximum value of the orientation angle and the minimum value of the orientation angle was defined as the variation in the orientation angle.

(3) Re, Rth, and Nz coefficients Using a phase difference meter (manufactured by Oji Scientific Co., Ltd., KOBRA-21ADH), the retardation Re in the in-plane direction, the retardation Rth in the thickness direction at intervals of 50 mm in the width direction of the film, and Nz coefficients were measured, and their average values were taken as Re, Rth and Nz coefficients, respectively. The difference between the maximum value of the Nz coefficient and the minimum value of the Nz coefficient was defined as the variation of the Nz coefficient.

(4) Glass transition temperature Based on JIS K7121, it measured by the differential scanning calorimetry (DSC method).

Example 1
Rubber particles were produced by the method described in Example 3 of JP-B-55-27576. The rubber particles have a spherical three-layer structure, the core layer is a crosslinked polymer consisting of methyl methacrylate and a small amount of allyl methacrylate, and the intermediate layer is composed of butyl acrylate, styrene and a small amount of allyl methacrylate. It is a crosslinked polymer, and the shell layer is a polymer composed of methyl methacrylate and a small amount of ethyl acrylate. The number average particle diameter of the rubber particles was 0.19 μm.
70 parts of alkyl methacrylate polymer resin (methyl methacrylate / methyl acrylate (mass ratio) = 97.8 / 2.2 copolymer resin, glass transition temperature 105 ° C.) and 30 parts of the rubber particles By kneading, a methacrylic acid alkyl ester polymer resin composition (hereinafter referred to as PMMA; containing 30% rubber particles) was obtained.
The methacrylic acid alkyl ester polymer resin composition and a styrene polymer resin having a negative intrinsic birefringence value (Dilark D332, manufactured by Nova Chemical Japan, styrene-maleic anhydride copolymer, glass transition temperature 125 ° C., below PST) and the methacrylic acid alkyl ester polymer resin composition were respectively melted by an extruder and supplied to a die for coextrusion. The supplied molten resin passed through a die slip and formed into a PMMA / PST / PMMA three-layered molten film. The molten film was taken up on a first cooling roll to obtain a raw film (width 1350 mm, average thickness of PMMA layer 60 μm / average thickness of PST layer 40 μm / average thickness of PMMA layer 60 μm).
This raw film is continuously supplied to a float-type longitudinal stretching machine as it is, and is subjected to first stretching under the conditions shown in Table 1. The orientation angle θ ₁ is 0 with respect to the direction perpendicular to the winding direction (width direction). A first stretched film oriented at 1 ° was obtained.

Next, the first stretched film is supplied to the tenter stretching machine shown in FIGS. 1 to 3 at a feed angle θ _S = 40 ° with respect to the winding direction of the second stretched film, and the second stretch is performed under the conditions shown in Table 1. The film was trimmed at 300 mm from both ends to obtain a long second stretched film having a width of 1530 mm. The obtained long second stretched film was uniform in the width direction, and neither wrinkles nor breakage occurred.
Table 1 shows the stretching conditions, and the properties of the first stretched film and the second stretched film.

  A long polarizing plate with a transmission axis in the width direction (manufactured by Sanlitz, HLC2-5618S, thickness 180 μm, width 1340 mm) and a second stretched film are bonded together by a roll-to-roll, and a circle having a width of 1340 mm A roll of polarizing plate was obtained. The circularly polarizing plate cut out from this wound body is replaced with the polarizing plate on the backlight side of the reflective liquid crystal display device in IPS (in-plane switching) mode, and the side on which the second stretched film is bonded is arranged on the liquid crystal cell side. Thus, a reflection type liquid crystal display device was prepared. When the display characteristics of the prepared liquid crystal display device were visually confirmed from the front direction or the oblique direction, color unevenness was not observed over the entire width, and the display was good. Further, even when observed from an oblique direction, the color was the same as that observed from the front direction, and no discoloration of the screen was observed.

Comparative Example 1
The raw film is continuously supplied to a tenter stretching machine as it is, and obliquely stretched under the conditions shown in Table 1 to obtain a stretched film having an orientation angle θ of 45 ° with respect to the winding direction. It was. The properties of this stretched film are shown in Table 1. The stretched film obtained by only one stretching treatment had a large variation in the orientation angle and a large variation in the Nz coefficient, and the uniformity was insufficient.
Further, a circularly polarizing plate and a reflective liquid crystal display device were prepared in the same manner as in Example 1 except that the obtained stretched film was used. When the display characteristics of the reflective liquid crystal display device provided with the circularly polarizing plate using the stretched film were visually confirmed from the front, some color unevenness was observed in the screen. Moreover, when it observed from the diagonal direction, it was a different hue | tone from the case where it observed from the front direction.

Comparative Example 2
A first stretched film and a second stretched film were obtained in the same manner as in Example 1 except that the first stretching and the second stretching were performed under the conditions shown in Table 1. (However, since the thickness of the second stretched film is large, the winding deviation becomes extremely large and deformation due to the winding deviation was partially observed.) Further, the retardation film cut out from the second stretched film The circularly polarizing plate was obtained by pasting so that the in-plane slow axis of the polarizing plate and the absorption axis of the polarizing film cut out from the polarizing plate were at an angle of 45 °. A reflective liquid crystal display device having a plate was obtained. Table 1 shows the characteristics of the first stretched film and the second stretched film. This second stretched film had a large variation in the orientation angle and was insufficient in uniformity. In the reflective liquid crystal display device including the circularly polarizing plate using the second stretched film, color unevenness was observed in the screen. Further, when observed from an oblique direction, color unevenness was observed in the screen.

Comparative Example 3
A first stretched film, a second stretched film, a circularly polarizing plate and a reflective liquid crystal display device were obtained in the same manner as in Comparative Example 2 except that the first stretching and the second stretching were performed under the conditions shown in Table 1. . (However, since the thickness of the second stretched film was large, the winding deviation was extremely large and deformation due to the winding deviation was seen.) Table 1 shows the characteristics of the first stretched film and the second stretched film. Show. This second stretched film had a large variation in the orientation angle and was insufficient in uniformity. In the reflective liquid crystal display device including the circularly polarizing plate using the second stretched film, color unevenness was observed in the screen. Further, when observed from an oblique direction, color unevenness was observed in the screen.

Comparative Example 4
A stretched film was obtained in the same manner as Comparative Example 1 except that the oblique stretching was performed under the conditions shown in Table 1. The properties of this stretched film are shown in Table 1. In addition, when this stretched film was wound up continuously, wrinkles were formed, and there were occasions where broken (cracked) portions were observed.

  From the results of Comparative Example 1, it can be seen that, when uniaxial stretching is performed at an angle of 45 °, the obtained stretched film has a large variation in physical properties and the effect of improving the display image quality of the liquid crystal display device is insufficient. Further, from the results of Comparative Examples 2 and 3, in the two-stage stretching in which the oblique stretching is performed after the longitudinal stretching, the stretched film obtained when the feeding angle is too large or the variation in the orientation angle of the first stretched film is too large. It can be seen that the variation in the physical properties of the liquid crystal display becomes large and the effect of improving the display image quality of the liquid crystal display device is insufficient. Furthermore, it can be seen from the results of Comparative Example 4 that if uniaxial stretching is performed at an angle of 15 °, wrinkles or the like may occur in the obtained stretched film.

On the other hand, when the method of the present invention is used, it can be seen that an obliquely stretched film having a large orientation angle can be produced without causing wrinkles. Further, even if the feeding angle θ _S in the oblique stretching process is small, the orientation angle of the obtained stretched film can be increased, and the direction orthogonal to the stretching direction in the first stretching process (first stretched film) The in-plane slow axis of the stretched film can be accurately expressed in a direction between the direction of the in-plane slow axis) and the direction perpendicular to the stretch direction in the oblique stretching step. The resulting stretched film of the present invention is wide, has little thickness unevenness and excellent optical characteristics, and can improve the display image quality of a liquid crystal display device.

FIG. 1 is a conceptual diagram showing an example of a tenter stretching machine that can suitably carry out the production method of the present invention. FIG. 2 is a view showing a means for gripping the rail portion in the stretching machine of FIG. FIG. 3 is a view for explaining rail arrangement in the stretching machine of FIG.

1: Film 10: Temperature-controlled room 11: Rail 12: Grasping means 13: Boundary between preheating zone and stretching zone 14: Boundary between stretching zone and fixing zone 21: Feeding roll 22: Winding roll 47: Film feeding direction 49: Film winding direction S1, S2: Stretch start point E1, E2: Stretch end point

Claims (2)

A method for producing a long stretched film,
The long film is
Made of a material with a negative intrinsic birefringence value,
Over the width direction of at least 1300 mm,
Of the orientation angle θ with respect to the width direction,
The value is in the range of 30 ° -80 °,
Variation is 1.0 ° or less,
Of the Nz coefficient
The value is in the range of -1.2 to -0.3,
The variation is 0.10 or less,
A long stretched film,
The manufacturing method includes:
The long film of intrinsic birefringence value is negative at a material with longitudinal stretching, to obtain a first stretched film orientation angle theta ₁ is within ± 1.0 ° with respect to the width direction,
The first stretched film is tenter-stretched while being fed so that the feed angle θ _S with respect to the winding direction of the second stretched film is 15 ° <θ _S <60 °, and the orientation angle θ with respect to the width direction is 30 ° to 30 °. The manufacturing method of a elongate stretched film including the process of obtaining the 2nd stretched film which exists in the range of 80 degrees. Stretch ratio _{R 1} in the step of obtaining the first stretched film is 1.1 to 2.0, the draw ratio _{R 2} in the step of obtaining a second stretched film is 1.3 to 2.0, in claim 1 The manufacturing method of the stretched film of description.

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