JP2011039343A - Method for manufacturing retardation plate, retardation plate and polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wide, thin and long retardation plate which is effective for compensating viewing angle of a liquid crystal display apparatus. <P>SOLUTION: The long retardation plate is formed by obliquely stretching a laminate comprising a layer A containing a material of positive intrinsic birefringence value and a layer B containing a material of negative intrinsic birefringence value. The slow axis of the retardation plate is in a direction of 40 to 50° relative to a width direction of the retardation plate. When nx denotes an average value of refractive indexes in an in-plane slow axis direction, ny denotes an average value of refractive indexes in an in-plane fast axis direction, and nz denotes an average value of refractive indexes in a thickness direction, an Nz value expressed by (nx-nz)/(nx-ny) is >0 and <1, variation in the Nz values which is difference between the maximum value and the minimum value of the Nz value in the width direction is -0.1 to 0.1, the width of the retardation plate is 1,000 mm or more and the thickness thereof is 15 o 70 μm. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a retardation plate manufacturing method, a retardation plate, and a polarizing plate, and more particularly to a retardation plate manufacturing method suitable for viewing angle compensation of a liquid crystal display device, a retardation plate, and a polarizing plate including the retardation plate. Regarding the board.

A liquid crystal display device is generally provided with a phase difference plate in order to play a role of compensating the viewing angle of the liquid crystal display device. As such a phase difference plate, in order to reduce the angle dependency of the color tone of the liquid crystal display device, the retardation Re at an incident angle of 0 degrees and the retardation R _{40 at} an incident angle of 40 degrees are 0.92 ≦ R ₄₀ / Retardation plate satisfying the relationship of Re ≦ 1.08 (relation 1), in-plane slow axis direction refractive index nx, in-plane orthogonal refractive index ny, and thickness direction refractive index nz And a phase difference plate satisfying the relationship (relation 2) of nx>nz> ny, a relationship in which the coefficient Nz value expressed by (nx−nz) / (nx−ny) exceeds 0 and less than 1 (relation 3) The ones in are proposed. Note that these relationships 1 to 3 are all indicators that are generally equivalent in terms of optical properties.

  As such a phase difference plate, for example, in Patent Document 1, a norbornene-based resin film is stretched in an oblique direction within a range of a predetermined stretch ratio, thereby being inclined in a direction inclined by 10 ° to 80 ° from the width direction of the film. A stretched film having a slow axis and having a coefficient Nz value represented by (nx−nz) / (nx−ny) exceeding 0 and less than 1 is obtained, and this is a long film in the longitudinal direction of the polarization absorption axis. It is disclosed that a circularly polarizing plate is obtained by laminating with a polarizing film of the above and roll-to-roll.

JP 2007-233198 A

  In recent years, with the increase in size, thickness, and definition of liquid crystal display devices, there has been a demand for a retardation plate that is wide and thin and has a higher viewing angle compensation effect. However, in the method described in Patent Document 1, since the above-described Nz value is not within a predetermined range and the optical performance cannot be sufficiently exhibited, the deformation magnification in the width direction is limited. In addition, there is a problem that a thin retardation plate cannot be manufactured. In order to obtain a thin and wide phase difference plate while adjusting the deformation magnification to be within a predetermined range, it is possible to prepare a thin and wide pre-stretch film in advance. In this case, since the strength of the thin pre-stretch film is very low, there is a high possibility that breakage or the like will occur during film formation of the pre-stretch film. It is considered that the productivity of the phase difference plate cannot be improved and the practical implementation is not possible.

  An object of the present invention is to provide a manufacturing method capable of efficiently manufacturing a wide and thin long retardation plate that is effective for viewing angle compensation of a liquid crystal display device, and effective for viewing angle compensation of a liquid crystal display device. An object of the present invention is to provide a wide and thin retardation plate, and a polarizing plate including the retardation plate.

  The inventors of the present invention stretch a multilayer laminate having a predetermined configuration under predetermined conditions, so that the Nz value is in the range of more than 0 and less than 1, and the slow axis is 40 to 40 in the width direction. The inventors have found that a long and thin retardation plate having a width of 50 ° and a small amount of phase difference unevenness can be efficiently produced, and the present invention has been completed based on this finding.

According to the present invention, the following inventions are disclosed.
(1) A method for producing a long retardation plate, wherein the intrinsic birefringence value is positive and the A layer containing a material having a glass transition temperature Tg (A), the intrinsic birefringence value is negative, And the process of obtaining the elongate laminated body which has B layer containing the material which is glass transition temperature Tg (B), The said laminated body is the lower one of said Tg (A) and said Tg (B) At a temperature T1 (° C.) that is 5 ° C. or more higher than the temperature of the first, a first stretch is performed in the direction of an angle θ of 40 to 50 ° with respect to the width direction of the laminate to obtain a stretched film for a retardation plate The stretched film for retardation plate obtained in one stretching step and the first stretching step is lower than the higher one of Tg (A) and Tg (B) and is different from T1. At a temperature T2 (° C.), θ + 80 ° to θ + 1 from the width direction of the stretched film for retardation film. A second stretching step in which a retardation plate is obtained by performing a second stretching in the direction of 0 °, and the retardation plate has a slow axis of 40 to the width direction of the retardation plate. The average refractive index in the slow axis direction in the plane is nx, the average refractive index in the fast axis direction in the plane is ny, and the average refractive index in the thickness direction is nz. The Nz value represented by (nx−nz) / (nx−ny) is greater than 0 and less than 1, and the width dimension is 1.5 to 5.0 times the width dimension of the laminate. The manufacturing method of the long phase difference plate whose width dimension is 1000 mm or more and whose thickness is 15 micrometers-70 micrometers.
(2) The method for producing the long retardation plate satisfying 0.15 <d / d ₀ <0.70, where d ₀ is the thickness of the laminate and d is the thickness of the retardation plate.
(3) The manufacturing method of the said long phase difference plate which satisfy | fills the relationship of Tg (A)> Tg (B) +5 (degreeC).
(4) The process of obtaining the said laminated body is a manufacturing method of the said long phase difference plate which implements the said A layer and the said B layer by a coextrusion method.
(5) A long retardation plate obtained by obliquely stretching a laminate having an A layer containing a material having a positive intrinsic birefringence value and a B layer containing a material having a negative intrinsic birefringence value The slow axis is a direction of 40 to 50 ° with respect to the width direction of the retardation plate, the average value of the refractive index in the slow axis direction in the plane is nx, and the fast phase in the plane is When the average value of the refractive index in the axial direction is ny and the average value of the refractive index in the thickness direction is nz, the Nz value represented by (nx−nz) / (nx−ny) is greater than 0 and less than 1. The variation of the Nz value which is the difference between the maximum value and the minimum value of the Nz value in the width direction is −0.1 to 0.1, the width dimension is 1000 mm or more, and the thickness is 15 μm to A long retardation plate of 70 μm.
(6) A long polarizing plate obtained by laminating the long retardation plate and a long polarizing film with their longitudinal directions aligned.

According to the production method of the present invention, a laminate having a predetermined layer structure is formed at a temperature T1 (° C.) higher by 5 ° C. or more than the lower one of Tg (A) and Tg (B). The stretched laminate is stretched at an angle θ of 40 to 50 ° with respect to its width direction, and the stretched laminate is lower than the higher one of Tg (A) and Tg (B), and T1 Is stretched again in the direction of θ + 80 ° to θ + 100 ° with respect to the width direction at a different temperature T2 (° C.), and the deformation ratio in the width direction is 1.5 to 5.0 times, that is, the unstretched film By stretching so that the width becomes 1.5 to 5.0 times, a retardation plate having a predetermined coefficient Nz value relationship, wide and thin can be efficiently manufactured with increased productivity. effective.
According to the retardation plate of the present invention, the slow axis is a direction of 40 to 50 ° with respect to the width direction of the retardation plate, the Nz value is more than 0 and less than 1, and Nz in the width direction. The difference in Nz value, which is the difference between the maximum value and the minimum value, is −0.1 to 0.1, the width dimension is 1000 mm or more, and the thickness is 15 μm to 70 μm. When the plate is used in a liquid crystal display device, the viewing angle of the display screen is widened, and a reduction in contrast and coloring can be prevented. As described above, a wide and thin retardation film having specific optical performance Therefore, the liquid crystal display device can contribute to an increase in screen size, weight reduction, and thickness reduction.

Hereinafter, embodiments of the present invention will be described in detail.
<Method for producing retardation plate>
The method for producing a retardation plate according to the present invention includes an A layer containing a material having a positive intrinsic birefringence value and a glass transition temperature Tg (A), a negative intrinsic birefringence value, and a glass transition temperature. A step of obtaining a long laminate having a B layer containing a material that is Tg (B) (laminate formation step), and a temperature that is lower than the lower one of Tg (A) and Tg (B). A first stretching step of obtaining a stretched film for a retardation film by performing a first stretching in a direction of an angle θ of 40 to 50 ° with respect to the width direction of the laminate at a temperature T1 (° C) higher than or equal to ° C; The stretched film for retardation plate obtained in the first stretching step is at a temperature T2 (° C.) lower than Tg (A) and Tg (B), whichever is higher, and different from T1. The second extension in the direction of θ + 80 ° to θ + 100 ° from the width direction of the stretched film for retardation film. And a second stretching step of obtaining the retardation performed. Here, the positive intrinsic birefringence value means that the refractive index in the stretching direction is larger than the refractive index in the direction orthogonal thereto, and the negative intrinsic birefringence value is in the stretching direction. It means that the refractive index is smaller than the refractive index in the direction perpendicular thereto.

<Laminated body formation process>
The laminate is a long film having an A layer made of a material having a positive intrinsic birefringence and a B layer made of a material having a negative intrinsic birefringence.

  As a material having a positive intrinsic birefringence value used for the A layer, a thermoplastic resin a can be used. Examples of the thermoplastic resin a include olefin resins such as polyethylene and polypropylene; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polyarylene sulfide resins such as polyphenylene sulfide; polyvinyl alcohol resins, polycarbonate resins, polyarylate resins, cellulose ester resins, Examples thereof include polyethersulfone resins, polysulfone resins, polyallyl sulfone resins, polyvinyl chloride resins, norbornene resins, and rod-like liquid crystal polymers. These resins may be used alone or in combination of two or more. In the present invention, among these, a polycarbonate resin is preferable from the viewpoint of retardation development, stretchability at low temperature, and adhesion to other layers.

  The glass transition temperature of the thermoplastic resin a is Tg (A). Tg (A) is usually 80 ° C. or higher, preferably 90 ° C. or higher, more preferably 100 ° C. or higher, still more preferably 110 ° C. or higher, and particularly preferably 120 ° C. or higher. With such a high glass transition temperature Tg (A), the relaxation of orientation of the resin A can be reduced. In addition, although there is no restriction | limiting in particular in the upper limit of glass transition temperature Tg (A), Usually, it is 200 degrees C or less.

  As a material having a negative intrinsic birefringence value used for the B layer, a thermoplastic resin b can be used. Examples of the thermoplastic resin b include a polystyrene resin containing a homopolymer of styrene or a styrene derivative or a copolymer with another monomer; a polyacrylonitrile resin, a polymethyl methacrylate resin, or a multi-component copolymer thereof. These may be used singly or in combination of two or more. Preferred examples of the other monomer to be copolymerized with styrene or a styrene derivative include acrylonitrile, maleic anhydride, methyl methacrylate, and butadiene. In the present invention, among these, a polystyrene resin is preferable from the viewpoint of high retardation development, and a copolymer of styrene or a styrene derivative and maleic anhydride is particularly preferable from the viewpoint of high heat resistance.

  Let the glass transition temperature of the thermoplastic resin b be Tg (B). Tg (B) is usually 80 ° C. or higher, preferably 90 ° C. or higher, more preferably 100 ° C. or higher, still more preferably 110 ° C. or higher, and particularly preferably 120 ° C. or higher. With such a high glass transition temperature Tg (B), the relaxation of orientation of the thermoplastic resin a can be reduced. In addition, although there is no restriction | limiting in particular in the upper limit of glass transition temperature Tg (B), Usually, it is 200 degrees C or less.

  The absolute value of the difference between the glass transition temperature Tg (A) of the thermoplastic resin a and the glass transition temperature Tg (B) of the thermoplastic resin b is preferably greater than 5 ° C, more preferably 8 ° C or more, Preferably it is 40 degrees C or less, More preferably, it is 20 degrees C or less. If the absolute value of the difference between the glass transition temperatures is too small, the temperature dependence of the retardation development tends to be small. On the other hand, if the absolute value of the difference between the glass transition temperatures is too large, it becomes difficult to stretch a resin having a high glass transition temperature, and the flatness of the retardation plate may be easily lowered. The glass transition temperature Tg (A) is preferably higher than the glass transition temperature Tg (B). Therefore, it is preferable that the thermoplastic resin a and the thermoplastic resin b normally satisfy the relationship of Tg (A)> Tg (B) + 5 ° C.

  Both the breaking elongation of the thermoplastic resin a in Tg (B) and the breaking elongation of the thermoplastic resin b in Tg (A) are both preferably 50% or more, and particularly preferably 80% or more. If it is a thermoplastic resin whose breaking elongation is in this range, a retardation film can be stably produced by stretching. The elongation at break is determined at a tensile speed of 100 mm / min using a type 1B test piece described in JIS K7127. The upper limit of the breaking elongation of the thermoplastic resin a and the upper limit of the breaking elongation of the thermoplastic resin b are not particularly limited, but are usually 200% or less.

  A compounding agent may be added to the thermoplastic resin a and / or the thermoplastic resin b as long as the total light transmittance at 1 mm thickness can be maintained at 80% or more. The compounding agent to be added is not particularly limited. For example, lubricants; layered crystal compounds; inorganic fine particles; stabilizers such as antioxidants, heat stabilizers, light stabilizers, weathering stabilizers, ultraviolet absorbers, and near infrared absorbers. Plasticizers; colorants such as dyes and pigments; antistatic agents; The amount of the compounding agent can be appropriately determined within a range not impairing the object of the present invention. In particular, it is preferable to add a lubricant or an ultraviolet absorber since flexibility and weather resistance can be improved.

  As the lubricant, inorganic particles such as silicon dioxide, titanium dioxide, magnesium oxide, calcium carbonate, magnesium carbonate, barium sulfate, strontium sulfate; polymethyl acrylate, polymethyl methacrylate, polyacrylonitrile, polystyrene, cellulose acetate, cellulose acetate propionate Organic particles such as In the present invention, organic particles are preferred as the lubricant.

  UV absorbers include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone UV absorbers, benzotriazole UV absorbers, acrylonitrile UV absorbers, triazine compounds, nickel complex compounds, inorganic Examples include powder. Suitable ultraviolet absorbers include 2,2′-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2 '-Hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2,4-di-tert-butyl-6- (5-chlorobenzotriazol-2-yl) phenol, 2 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, and particularly preferred is 2,2′-methylenebis (4- (1, 1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol).

The laminate is a long film.
Here, the long length means one having a length of at least about 5 times the width of the film, preferably 10 times or more, and specifically wound in a roll shape. It has a length enough to be stored or transported. The long laminate has a width of 200 mm or more, preferably 500 mm or more, more preferably 1000 mm or more.

  As a method for obtaining such a laminate, for example, a co-extrusion molding method such as a co-extrusion T-die method, a co-extrusion inflation method, a co-extrusion lamination method, a film lamination molding method such as dry lamination, and a resin on the resin film surface Well-known methods, such as coating molding methods, such as coating a solution, or a co-casting method, are mentioned. Among these, the coextrusion molding method is preferable from the viewpoint of manufacturing efficiency and not leaving a volatile component such as a solvent in the unstretched film. Among the coextrusion molding methods, the coextrusion T-die method is preferable. The coextrusion T-die method includes a feed block method and a multi-manifold method, and the multi-manifold method is particularly preferable in that variation in the thickness of the A layer can be reduced.

  When the co-extrusion T-die method is employed as a method for obtaining the laminate, the melting temperature of the resin material in the extruder having the T-die is 80 to 180 ° C. than the glass transition temperature (Tg) of the thermoplastic resins a and b. It is preferable that the temperature is high, and it is more preferable that the temperature is 100 to 150 ° C. higher than the glass transition temperature. If the melting temperature in the extruder is excessively low, the fluidity of the resin material may be insufficient. Conversely, if the melting temperature is excessively high, the resin may be deteriorated.

  In the extrusion molding method, the sheet-like molten resin material extruded from the opening of the die is brought into close contact with the cooling drum. The method for bringing the molten resin material into close contact with the cooling drum is not particularly limited, and examples thereof include an air knife method, a vacuum box method, and an electrostatic contact method. The number of cooling drums is not particularly limited, but is usually two or more. Examples of the arrangement method of the cooling drum include, but are not limited to, a linear type, a Z type, and an L type. Further, the way of passing the molten resin extruded from the opening of the die through the cooling drum is not particularly limited.

  In the present invention, the degree of adhesion of the extruded sheet-shaped resin material to the cooling drum changes according to the temperature of the cooling drum. If the temperature of the cooling drum is raised, the adhesion will be improved, but if the temperature is raised too much, the sheet-like resin material may not be peeled off from the cooling drum, and there is a possibility that a problem of winding around the drum may occur. Therefore, the cooling drum temperature is preferably (Tg + 30) ° C. or less, more preferably (Tg-5), where Tg is the glass transition temperature of the resin in the layer that contacts the drum out of the resin extruded from the die. ) C. to (Tg-45) C. By doing so, problems such as slipping and scratches can be prevented.

  Moreover, it is preferable to reduce content of the residual solvent in a laminated body. Means for that purpose include (1) reducing the residual solvent of the thermoplastic resin as a raw material; and (2) pre-drying the material before forming the laminate. The preliminary drying is performed with a hot air dryer or the like, for example, in the form of pellets or the like. The drying temperature is preferably 100 ° C. or more, and the drying time is preferably 2 hours or more. By performing preliminary drying, the residual solvent in the laminate can be reduced, and foaming of the extruded sheet-like material can be prevented.

  The laminate is perpendicularly incident on the main surface when the first stretching direction described later is the X axis, the direction perpendicular to the X axis in the plane is the Y axis, and the thickness direction is the Z axis. When the phase of the linearly polarized light whose vector plane of vibration is perpendicularly incident on the principal plane with respect to the linearly polarized light in the YZ plane and the plane of polarization of the electric vector is in the XZ plane is delayed at the temperature T1 in the X-axis direction, the temperature T2 When the film is stretched in the X-axis direction, it is preferable to proceed.

  Such a film having a temperature dependency in the retardation development includes an A layer made of a thermoplastic resin a having a positive intrinsic birefringence and a B layer made of a thermoplastic resin b having a negative intrinsic birefringence. It can be obtained by appropriately adjusting the relationship between the intrinsic birefringence of the thermoplastic resin and the thickness ratio of each resin layer.

The laminate may have one layer or two or more layers, respectively, A layer and B layer.
The phase difference is obtained by multiplying the thickness d by the difference (= nx−ny) between the refractive index nx in the X-axis direction and the refractive index ny in the Y-axis direction which is a direction orthogonal to the X-axis direction (the stretching direction). This is the required value. The phase difference when the A layer and the B layer are laminated is synthesized from the phase difference of the A layer and the phase difference of the B layer. In order to reverse the sign of the phase difference of the laminate composed of the A layer and the B layer by stretching at the high temperature T _H and the low temperature T _L, the stretching at the low temperature T _L is performed at the glass transition temperature. The absolute value of the phase difference expressed by the high resin is smaller than the absolute value of the phase difference expressed by the resin having a low glass transition temperature, and the phase difference expressed by the resin having a low glass transition temperature by stretching at a high temperature T _H. It is preferable to adjust the thicknesses of the A layer and the B layer so that the absolute value of is smaller than the absolute value of the phase difference developed by the resin having a high glass transition temperature. As described above, the difference between the refractive index nx in the X-axis direction and the refractive index ny in the Y-axis direction, which is expressed in each of the A layer and the B layer by stretching, the total thickness of the A layer, and the thickness of the B layer. Is adjusted so that the plane of incidence of the electric vector is perpendicular to the main surface of the laminate and the plane of vibration of the electric vector is linearly polarized in the XZ plane. Can be obtained in which the phase with respect to the linearly polarized light in the YZ plane is delayed when it is obliquely stretched in the X-axis direction at the temperature T1, and advanced when it is stretched in the X-axis direction at a temperature T2 different from the temperature T1. The temperature T1 is one of T _{H and} T _L , and the temperature T2 is the other temperature of T _{H and} T _L different from T1.

  FIG. 1 shows the temperature of retardation when the layer A (a layer of a thermoplastic resin a having a high glass transition temperature) and a layer B (a layer of a thermoplastic resin b having a low glass transition temperature) are individually stretched. It shows the dependency and the temperature dependency of the retardation when the laminate (A layer + B layer) is stretched. In the stretching at the temperature Tb, the negative phase difference expressed by the stretching of the B layer is larger than the positive retardation expressed by the stretching of the A layer. Therefore, in the stretching of the laminate (A layer + B layer), a negative phase difference is exhibited. Δ will be expressed. On the other hand, in the stretching at the temperature Ta, the negative phase difference expressed by the stretching of the B layer is smaller than the positive retardation expressed by the stretching of the A layer. Therefore, in the stretching of the laminate (A layer + B layer) A phase difference Δ is developed.

  For example, when the material constituting the A layer is a polycarbonate resin and the material constituting the B layer is a styrene-maleic anhydride copolymer, the total thickness of the A layer and the total thickness of the B layer The ratio is preferably 1: 5 to 1:15, and more preferably 1: 5 to 1:10. If the A layer becomes too thick or the B layer becomes too thick, the temperature dependence of the phase difference expression becomes small.

<First stretching step>
In the first stretching step, the laminate is heated at a temperature T1 (° C.) of 5 ° C. or more higher than the lower one of Tg (A) and Tg (B) with respect to the width direction of the laminate. In this step, stretching is performed in the direction of angle θ of ˜50 ° (preferably 42-48 °, more preferably 44-46 °) to obtain a stretched film for a retardation plate. In this case, in the first stretching step, the width of the laminate is co stretched so that the magnification N ₁ × 1.0 to 5.0 times.

  The temperature T1 is preferably higher than Tg (B) based on Tg (A) and Tg (B), more preferably higher than Tg (B) + 5 ° C., and lower than Tg (A) + 20 ° C. It is preferable that the temperature is lower than Tg (A) + 15 ° C. Outside the above range, variations in thickness in the width direction and variations in the slow axis become large, and a wide and thin retardation plate cannot be obtained.

  A 1st extending | stretching process can be performed by using the diagonal extending | stretching method described, for example in international publication WO2007 / 111313 pamphlet. In addition, the 2nd extending process mentioned later can also be performed using the diagonal extending | stretching method similar to the above.

  In order to reduce stretching unevenness and thickness unevenness (thickness variation), it is possible to make a temperature difference in the film width direction in the stretching zone. In order to create a temperature difference in the film width direction in the stretching zone, a known method such as adjusting the opening degree of the hot air nozzle in the width direction or controlling the heating by arranging IR heaters in the width direction can be used.

<Second stretching step>
In the second stretching step, the stretched film for a retardation film obtained in the first stretching step is lower than the higher temperature of Tg (A) and Tg (B) and is different from T1. At T2 (° C.), θ + 80 ° to θ + 100 ° (preferably θ + 85 ° to θ + 95 °, more preferably θ + 87 ° to θ + 93 °, more preferably θ + 89 ° to θ + 91) from the width direction of the stretched film for retardation plate. This is a step of obtaining a retardation plate by performing the second stretching in the direction of °). At this time, in the second stretching step, the width of the phase difference plate for stretching the film is co-stretched so as to be _twice as large as 1.0 to 5.0 times magnification N, to produce a retardation plate. And the magnification N ₁ times the width direction in the first stretching step, the product N ₁ × N ₂ with magnification N ₂ times the width direction in the second stretching step, so that 1.5 to 5.0 times adjust.

  The temperature T2 is preferably higher than Tg (B) −20 ° C., more preferably higher than Tg (B) −10 ° C., based on the glass transition temperature Tg (B) of the thermoplastic resin B, and Tg (B) It is preferably lower than + 5 ° C, more preferably lower than Tg (B).

  The difference between the temperature T1 and the temperature T2 is usually 5 ° C. or higher, preferably 10 ° C. or higher, more preferably 15 ° C. or higher. By increasing the difference between the temperature T1 and the temperature T2 as described above, the polarizing plate compensation function can be stably exhibited in the retardation plate. In addition, although there is no restriction | limiting in particular in the upper limit of the difference of temperature T1 and temperature T2, it is preferable that it is 100 degrees C or less from a viewpoint of industrial productivity.

  For the oblique stretching in the second stretching step, a method similar to the method that can be adopted in the oblique stretching in the first stretching step can be applied. However, the oblique stretching in the second stretching step is preferably performed at a stretching ratio that is equal to or slightly smaller than the oblique stretching in the first stretching step.

<Other processes>
In the method for producing a retardation plate of the present invention, other steps may be performed in addition to the first stretching step and the second stretching step. For example, you may provide the process (preheating process) of heating a laminated body before extending | stretching a laminated body. Examples of the means for heating the laminate include an oven-type heating device, a radiation heating device, or immersion in a liquid. Among these, an oven-type heating device is preferable. The heating temperature in this step is usually a stretching temperature of −40 ° C. to a stretching temperature of + 20 ° C., preferably a stretching temperature of −30 ° C. to a stretching temperature of + 15 ° C., which will be described later. The stretching temperature means the set temperature of the heating device.

  For example, the stretched film may be fixed after the first stretching step and / or the second stretching step. The temperature in the fixing treatment is usually room temperature or higher, preferably stretching temperature −40 ° C. or higher, and usually stretching temperature + 30 ° C. or lower, preferably stretching temperature + 20 ° C. or lower.

<Phase difference plate>
The retardation plate of the present invention is obtained by obliquely stretching a laminate having an A layer containing a material having a positive intrinsic birefringence value and a B layer containing a material having a negative intrinsic birefringence value, The slow axis is a direction of 40 to 50 ° with respect to the width direction of the retardation plate, the average value of the refractive index in the slow axis direction in the plane is nx, and the refraction in the fast axis direction is in the plane. When the average value of the refractive index is ny and the average value of the refractive index in the thickness direction is nz, the Nz value represented by (nx−nz) / (nx−ny) is more than 0 and less than 1, and its width dimension Is 1000 mm or more, and the thickness is 15 μm to 50 μm. Here, in the present invention, a layer formed by obliquely stretching the A layer constituting the laminate is referred to as α layer, and a layer formed by obliquely stretching the B layer constituting the laminate is referred to as β layer.

  The retardation plate has an in-plane slow axis in the direction of 40 to 50 ° (preferably 42 to 48 °, more preferably 44 to 46 °) from the width direction. In this case, the in-plane slow axis preferably has a variation in direction within ± 1.0 °, and within ± 0.5 °, over the entire width in the width direction of the retardation plate. More preferably, it is more preferably within ± 0.2 °. The variation in the direction of the slow axis is the angle between the slow axis and the width direction of the film (hereinafter referred to as orientation) when the slow axis is arbitrarily measured at several points across the width direction of the retardation plate. It is the difference between the maximum value and the minimum value.

  The retardation plate has an Nz value exceeding 0 and less than 1, preferably exceeding 0.15 and less than 0.85, particularly preferably exceeding 0.30 and less than 0.70. Since the Nz value is in this range and the slow axis has the above characteristics, when the retardation plate is used for a display device, the brightness and front contrast of the display device are improved and the variation in viewing angle is reduced. I can do it. Here, the average value of the refractive index nx is arbitrarily set at several points using a phase difference meter (“KOBRA21-ADH” manufactured by Oji Scientific Co., Ltd.) over the width direction of the retardation plate of the present invention. It is the arithmetic average value when measured. Further, the refractive indexes ny and nz can be obtained in the same manner.

The retardation of the retardation plate is preferably within ± 0.10, and more preferably within ± 0.05. Here, the variation of the Nz value is obtained by measuring the Nz value according to the following formula at a predetermined interval in the width direction of the phase difference plate, and obtaining an average value. Further, the difference between the maximum value and the minimum value of the Nz value is defined as the variation of the Nz value.
Nz = (nx-nz) / (nx-ny)

In the retardation plate, in-plane retardation Re (nm) and thickness direction retardation Rth (nm) vary depending on the design of the display device, but usually Re is in the range of 50 to 1000 nm and Rth is in the range of about -500 to 500 nm. Is appropriately selected. Note that Re in the present invention is a value defined by (nx−ny) × T _ave when the average thickness T _{ave of the} film is used, and Rth in the present invention is (((nx + ny) / 2) −. nz) × T _ave .

  The retardation of the retardation plate is usually within 10 nm, preferably within 5 nm, and more preferably within 2 nm. By setting the unevenness of Re within the above range, it is possible to improve the display quality when used for a display device. Here, the dispersion of Re is arbitrarily selected at several points over the width direction of the phase difference plate of the present invention when the light incident angle is 0 ° (the incident light beam and the surface of the phase difference plate of the present invention are orthogonal). It is the difference between the maximum value and the minimum value of Re when measured.

  The retardation plate usually has a variation of Rth within 10 nm, preferably within 5 nm, and more preferably within 2 nm. By setting the unevenness of Rth within the above range, it is possible to improve the display quality when used for a display device. Here, the variation of Rth is obtained by shifting Rth obtained by slightly shifting from the light incident angle of 0 ° (the state where the incident light beam and the retardation plate surface of the present invention are orthogonal) across the width direction of the retardation plate of the present invention. This is the difference between the maximum value and the minimum value of Rth when several points are arbitrarily measured.

  The retardation plate can be obtained by deforming the laminate in the width direction in a range of 1.5 to 5 times, preferably 2 to 5 times, particularly preferably 2 to 4 times. When the deformation ratio in the width direction is less than 1.5, a wide and thin retardation plate cannot be obtained efficiently. Further, if the deformation ratio in the width direction is more than 5 times, peeling at the interface of the laminate or cracking of the surface may occur, and phase difference unevenness may occur.

  The width dimension of the phase difference plate is 1000 mm or more, preferably 1500 mm or more, and more preferably 2000 mm or more.

  The thickness of the retardation plate is preferably 15 μm to 70 μm, more preferably 20 to 60 μm, and even more preferably 25 to 50 μm. When the thickness of the retardation plate is less than 15 μm, the mechanical strength may be weakened. When it is thicker than 70 μm, the productivity of the retardation film may be deteriorated. Moreover, it is preferable that the thickness of each of the α layer and β layer constituting the retardation plate is 1 μm or more.

  The variation in the thickness of the retardation film is 1.0 μm or less, preferably 0.5 μm or less over the entire surface, whereby the variation in color tone can be reduced. Moreover, the color tone change after long-term use becomes uniform. In addition, when the thickness variation is in such a range, the retardation plate of the present invention can be wound up at a high speed and in a longer length, and display quality when the retardation plate is used in a display device. Can be improved.

  The phase difference plate can be configured to have one or two or more α and β layers. The ratio of the total thickness of the α layer / the total thickness of the β layer is preferably 1/5 to 1/10, more preferably 1/6 to 1/9. Even if the α layer becomes too thick or the β layer becomes too thick, the temperature dependence of the phase difference expression becomes small. Here, the thicknesses of the α layer and the β layer are measured by measuring the total thickness of the film using a commercially available contact thickness meter, then cutting the thickness measurement portion and observing the cross section with an optical microscope. The thickness ratio is obtained, and the thicknesses of the α layer and the β layer are calculated from the ratio. The above operation is performed at regular intervals in the MD direction and TD direction of the film, and the average value and variation of the thickness can be obtained.

The thickness variation is calculated from the following equation using the arithmetic average value T _ave of the measured values obtained above as a reference, with the maximum value of the measured thickness T being T _max and the minimum value being T _min. .
Thickness variation (μm) = T _ave −T _min , and
The larger of T _max -T _ave

  The variation in thickness of each of the α layer and the β layer is 0.7 μm or less, preferably 0.4 μm or less over the entire surface, so that the variation in color tone is reduced. Moreover, the color tone change after long-term use becomes uniform. In addition, when the thickness variation is in such a range, the retardation plate of the present invention can be wound up at a high speed at a long length, and the display quality is improved when the retardation plate is used in a display device. Can be improved.

  The retardation plate preferably has a total light transmittance of 85% or more. If it is less than 85%, it is not suitable for a retardation plate. The light transmittance can be measured using a spectrophotometer (manufactured by JASCO Corporation, ultraviolet-visible near-infrared spectrophotometer “V-570”) in accordance with JIS K0115.

  The retardation plate has a haze of preferably 5% or less, more preferably 3% or less, and particularly preferably 1% or less. If the haze is high, the sharpness of the displayed image tends to decrease. Here, the haze is an average value obtained by measuring five points using a “turbidimeter NDH-300A” manufactured by Nippon Denshoku Industries Co., Ltd. according to JIS K7361-1997.

  In the retardation plate, ΔYI is preferably 5 or less, and more preferably 3 or less. When this ΔYI is in the above range, there is no coloring and visibility is improved. ΔYI is measured according to ASTM E313 using a “spectral color difference meter SE2000” manufactured by Nippon Denshoku Industries Co., Ltd., and the same measurement is performed five times to obtain the arithmetic average value.

  The retardation plate preferably has a hardness of H or higher in terms of JIS pencil hardness. The adjustment of the JIS pencil hardness can be performed by changing the type of resin, changing the layer thickness of the resin, or the like. JIS pencil hardness is the hardness of a pencil that begins to scratch, scratching the film surface by tilting a pencil of various hardnesses by 45 degrees and applying a load of 500 g weight from the top in accordance with JIS K5600-5-4. .

  The retardation plate may have a shrinkage ratio of preferably 0.5% or less, more preferably 0.3% or less in the longitudinal direction and the transverse direction by heat treatment at 60 ° C. and 90% RH for 100 hours. Good. If the shrinkage rate exceeds this range, the retardation plate may be deformed or peeled off from the display device due to shrinkage stress when used in a high temperature / high humidity environment.

  The retardation plate may have a layer other than the α layer and the β layer. For example, an adhesive layer that bonds the α layer and the β layer, a mat layer that improves the slipperiness of the film, a hard coat layer such as an impact-resistant polymethacrylate resin layer, an antireflection layer, an antifouling layer, etc. it can. As described above, the α layer and the β layer may be laminated via an adhesive layer, but the α layer and the β layer are laminated so as to be in direct contact with each other. From the viewpoint of sex.

<Polarizing plate>
A long polarizing plate can be obtained by laminating the long retardation plate and the long polarizing film with their longitudinal directions aligned (for example, by a roll-to-roll method). The polarizing film 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 thereof include a film obtained by uniaxial stretching to adsorb a dichroic material, and a polyene oriented film such as a dehydrated polyvinyl alcohol product or a dehydrochlorinated polyvinyl chloride product. In addition, reflective polarizing films, such as a grid polarizing film and an anisotropic multilayer film, can be mentioned. The thickness of the polarizing film is usually 5 to 80 μm.

  A preferred manufacturing method for obtaining a long polarizing plate is to bring the retardation plate and the polarizing film into close contact with each other while simultaneously drawing the film from the winding body of the retardation plate and the winding body of the polarizing film. And laminating them. An adhesive may or may not be interposed on the adhesion surface between the retardation plate and the polarizing film. As a method for bringing the retardation plate and the polarizing film into close contact with each other, there is a method in which the retardation plate and the polarizing film are passed through and pressed together between the nips of two parallelly arranged rolls.

  The long retardation plate and / or the long polarizing plate can be used by being cut into, for example, a rectangular shape (sheet-like shape) for use in a display device such as a liquid crystal display device. At this time, the long retardation plate and / or the long polarizing plate is preferably cut out along a direction perpendicular or parallel to the longitudinal direction from the viewpoint of obtaining a large number of polarizing plates.

  The retardation plate may be laminated on both sides of the polarizing film, or may be laminated on one side. The number of layers to be stacked is not particularly limited, and two or more layers may be stacked. When the retardation film is laminated only on one surface of the polarizing film, a protective film may be laminated on the remaining one surface with an appropriate adhesive layer for the purpose of protecting the polarizing film.

  An appropriate transparent film can be used as the protective film. 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, polyolefin polymers, polycarbonate polymers, polyester polymers such as polyethylene terephthalate, polyvinyl chloride polymers, polystyrene polymers, polyacrylonitrile. Examples thereof include a polymer, a polysulfone polymer, a polyethersulfone polymer, a polyamide polymer, a polyimide polymer, and an acrylic polymer.

<Liquid crystal display device>
The liquid crystal display device of the present invention comprises a polarizing plate obtained by cutting out the long polarizing plate into a rectangular shape (single sheet shape) and a liquid crystal panel. Preferred examples of the liquid crystal display device include a reflective liquid crystal display device and a transflective liquid crystal display device that display using external light. As described above, since the angle formed between the polarization transmission axis of the polarizing plate and the slow axis of the retardation plate is 40 to 50 °, the polarizing plate is a polarizing plate on the viewing side of a liquid crystal display device such as a reflective type ( It can be suitably used as a circularly polarizing plate.

  In addition to the liquid crystal display device, the retardation plate of the present invention can be used alone or in combination with other members to provide a liquid crystal display device, organic EL display device, plasma display device, FED (field emission) display device, SED (surface). It can be applied to electric field display devices.

  Next, the present invention will be described in further detail using examples and comparative examples. However, the present invention is not limited to the following examples.

In this example and comparative example, evaluation was performed by the following method.
(Glass-transition temperature)
The glass transition temperature (Tg) of the present invention was measured using a differential scanning calorimeter (manufactured by Rigaku Denki Co., Ltd., DSC8230 type). Tg is an average value of the temperature at which the baseline starts to deviate and the temperature at which the baseline returns to the baseline. The measurement start temperature was set to a temperature lower by 50 ° C. or more than the measured Tg.

(Thickness, thickness variation)
The thickness of the phase difference plate was measured at an interval of 5 cm in the film width direction using a contact-type thickness meter (manufactured by Mitutoyo Corporation, snap gauge ID-C112BS), and an average value was obtained. Further, the difference between the maximum value and the minimum value of the thickness was regarded as the thickness variation.

(Variation in slow axis direction)
The orientation angle was measured at intervals of 5 cm in the width direction of the film using a polarizing microscope (manufactured by Olympus, BX51), and the difference between the maximum value and the minimum value of the orientation angle was defined as the variation in the direction of the slow axis.

(Coefficient Nz value, variation of Nz value)
An Nz value was measured according to the following formula at an interval of 5 cm in the film width direction using a phase difference meter (manufactured by Oji Scientific Co., Ltd., KOBRA21-ADH) to obtain an average value. Further, the difference between the maximum value and the minimum value of the Nz value was defined as the variation of the Nz value.
Nz = (nx-nz) / (nx-ny)
(Nx is the average value of the refractive index in the slow axis direction in the film plane, ny is the average value of the refractive index in the fast axis direction in the film plane, and nz is the average value of the refractive index in the film thickness direction).

(Check for peeling and cracking)
The surface of the retardation plate was visually observed to check for peeling and cracking.

(Effective width)
Variation in thickness within ± 1.0 μm, variation in slow axis direction within ± 1.0 °, and variation in coefficient Nz value within ± 0.1 over the width direction of the retardation plate, which is the entire width L Was obtained, and the effective width (= (T / L) × 100 (%)) was obtained.

(Display unevenness due to oblique observation)
A white image was displayed on the liquid crystal display screen, and was observed from four sides of the liquid crystal display screen at an angle of 70 ° from the direction perpendicular to the liquid crystal display screen, and the presence or absence of unevenness of the display screen was confirmed.

<Production Example 1>
A film forming apparatus for two-type two-layer coextrusion molding was prepared, and a pellet of polycarbonate resin (manufactured by Asahi Kasei Co., Ltd., Wonderlite PC-110, glass transition temperature 145 ° C.) was provided with a double flight type screw. It was put into a single screw extruder and melted. Further, pellets of styrene-maleic anhydride copolymer resin (Nova Chemicals, Dylark 332, glass transition temperature 135 ° C.) were charged into another uniaxial extruder equipped with a double flight type screw and melted. A molten 260 ° C. styrene-anhydrous maleic resin is passed through a molten polycarbonate resin at 260 ° C. through one leaf disk-shaped polymer filter with an opening of 10 μm and into one manifold of a multi-manifold die (die slip surface roughness Ra: 0.1 μm). The acid copolymer resin was supplied to the other manifold through a leaf disk-shaped polymer filter having an opening of 10 μm.

  A polycarbonate resin and a styrene-maleic anhydride copolymer resin were simultaneously extruded from the multi-manifold die at 260 ° C. to form a film. The film-like molten resin was cast on a cooling roll adjusted to a surface temperature of 130 ° C., and then passed between two cooling rolls adjusted to a surface temperature of 50 ° C. to obtain a polycarbonate resin layer (A layer: 10 μm) and styrene A laminate E1 composed of a maleic anhydride copolymer resin layer (B layer: 80 μm) having a thickness of 90 μm and a width of 1000 mm, and a laminate E2 having a width of 300 mm by slitting the end of the laminate E1. Got. The thickness variation of the multilayer body E1 was 0.8 μm. The thickness variation of the multilayer body E2 was 0.8 μm. These results are shown in Table 1.

<Production Example 2>
A polycarbonate resin layer (A layer: 7 μm) and a styrene-maleic anhydride copolymer resin layer (B layer) were prepared in the same manner as in Production Example 1 except that the thickness of the A layer was 7 μm and the thickness of the B layer was 53 μm. : 53 μm), and a laminate E3 having a thickness of 60 μm and a width of 1000 mm was obtained. The thickness variation of the laminate E3 was 0.8 μm. These results are shown in Table 1.

<Production Example 3>
A norbornene resin pellet (manufactured by Nippon Zeon Co., Ltd., ZEONOR1420, glass transition temperature 136 ° C.) was molded with a T-die type film extruder to obtain a laminate E4 having a thickness of 100 μm and a width of 1000 mm. The thickness variation of the multilayer body E4 was 0.8 μm. These results are shown in Table 1.

<Example 1>
The laminate E1 obtained in Production Example 1 is supplied to a predetermined oblique stretching machine, and at a stretching temperature of 150 ° C., an angle of θ = 45 ° with respect to the width direction of the laminate, A first stretched film (corresponding to a stretched film for a retardation film) was obtained by performing the first oblique stretching so as to be 1.4 times. Subsequently, the first stretched film is formed at an angle of 135 ° (45 ° / θ + 90 ° in the reverse direction) with respect to the width direction of the first stretched film at a stretch temperature of 130 ° C. The second oblique stretching was carried out so as to be 1.2 times the width of the film to obtain a retardation film R1 as a second stretched film. The obtained results are shown in Table 2.

<Example 2>
The laminate E2 obtained in Production Example 1 is supplied to a predetermined oblique stretching machine, and at a stretching temperature of 150 ° C., an angle of θ = 45 ° with respect to the width direction of the laminate is set to the width of the laminate. The first stretched film was obtained by performing the first oblique stretching so as to be 2.0 times. Subsequently, the first stretched film is formed at an angle of 135 ° (45 ° / θ + 90 ° in the reverse direction) with respect to the width direction of the first stretched film at a stretch temperature of 130 ° C. The second oblique stretching was carried out so as to be 2.0 times the width of the film to obtain a retardation film R2 as a second stretched film. The obtained results are shown in Table 2.

<Comparative Example 1>
The laminate E2 obtained in Production Example 1 is supplied to a predetermined oblique stretching machine, and at a stretching temperature of 150 ° C., an angle of θ = 45 ° with respect to the width direction of the laminate is set to the width of the laminate. The first stretched film was obtained by performing the first oblique stretching so as to be 3.0 times. Subsequently, the first stretched film is formed at an angle of 135 ° (45 ° / θ + 45 ° in the reverse direction) with respect to the width direction of the first stretched film at a stretch temperature of 130 ° C. The second oblique stretching was carried out so as to be 2.0 times the width of the film to obtain a retardation film R3 as a second stretched film. The obtained results are shown in Table 2.

<Comparative Example 2>
The laminate E3 obtained in Production Example 2 is supplied to a predetermined oblique stretching machine, and at a stretching temperature of 150 ° C., an angle of θ = 45 ° from the width direction of the laminate is 1. A first stretched film was obtained by performing the first oblique stretching so as to be 1-fold. Subsequently, the first stretched film is formed at an angle of 135 ° (45 ° / θ + 45 ° in the reverse direction) with respect to the width direction of the first stretched film at a stretch temperature of 130 ° C. The second oblique stretching was performed so as to be 1.2 times the width of the film. However, since the breakage occurred frequently during the second stretching step, the retardation plate R4 could not be obtained. The obtained results are shown in Table 2.

<Comparative Example 3>
The laminate E4 obtained in Production Example 3 is supplied to a predetermined oblique stretching machine, and at a stretching temperature of 145 ° C., an angle of θ = 45 ° with respect to the width direction of the laminate, The first stretched film was obtained by performing the first oblique stretching so as to be 1.4 times. Subsequently, the first stretched film is formed at an angle of 135 ° (45 ° / θ + 45 ° in the reverse direction) with respect to the width direction of the first stretched film at a stretch temperature of 140 ° C. The second oblique stretching was carried out so as to be 1.2 times the width of the film to obtain a retardation film R5 as a second stretched film. The obtained results are shown in Table 2.

<Example 3>
A long polarizing film with a polarizing absorption axis in the longitudinal direction of the film (manufactured by Sanlitz, HLC2-5618S, thickness 180 μm) and the retardation plate R1 obtained in Example 1 are obtained by the roll-to-roll method. By laminating with the directions aligned, a long polarizing plate P1 was obtained.

<Example 4>
A long polarizing plate P2 was obtained in the same manner as in Example 3 except that the retardation plate R2 obtained in Example 2 was used.

<Comparative example 4>
A long polarizing plate P3 was obtained in the same manner as in Example 3 except that the retardation plate R3 obtained in Comparative Example 1 was used.

  Next, the polarizing plates P <b> 1 to P <b> 3 were cut to a panel size and replaced with a polarizing plate on the side close to the viewing side of the display device having the STN mode transflective liquid crystal panel. Table 3 shows the evaluation results of display unevenness by oblique observation.

From the results shown in Tables 1 and 2, the following can be understood.
From the result of Comparative Example 1, when the product of the deformation ratio in the width direction in the first stretching step and the deformation ratio in the width direction in the second stretching step exceeds 5.0 times, the variation in Nz value, the variation in thickness, It can be seen that the variation of the slow axis increases and peeling or cracking occurs in the phase difference plate. From the result of Comparative Example 2, it can be seen that when a thin film is used as the unstretched film, the film is broken in the stretching process, so that a retardation plate cannot be obtained, and the productivity is poor. From the result of Comparative Example 3, it can be seen that when a single-layer film is used as the unstretched film, the Nz value exceeds 0 and falls outside the range of less than 1. From the results of Comparative Example 4, when the variation in the coefficient Nz value, the variation in the thickness, and the variation in the slow axis are large, display unevenness is confirmed by oblique observation when mounted on the liquid crystal display device, and the optical compensation of the liquid crystal display device It turns out that the effect is insufficient.
On the other hand, according to the present invention, the coefficient Nz value is greater than 0 and less than 1, and the wide and thin retardation plate is free from peeling and cracking, thickness variation, slow axis variation, and coefficient Nz value variation. Is small and can be obtained with a wide effective width.

It is a figure which shows the temperature dependence of the phase difference of the laminated body of A layer, B layer, and A layer and B layer.

Claims (6)

A method for producing a long retardation plate,
A layer containing a material having a positive intrinsic birefringence value and a glass transition temperature Tg (A), and a B layer containing a material having a negative intrinsic birefringence value and a glass transition temperature Tg (B) Obtaining a long laminate having:
The laminate is at a temperature T1 (° C.) higher by 5 ° C. or more than the lower temperature of Tg (A) and Tg (B), and 40 to 50 ° with respect to the width direction of the laminate. A first stretching step for obtaining a stretched film for a retardation plate by performing a first stretching in a direction of an angle θ;
The stretched film for retardation plate obtained in the first stretching step has a temperature T2 (° C.) lower than the higher one of Tg (A) and Tg (B) and different from T1. A second stretching step of obtaining a retardation plate by performing a second stretching in the direction of θ + 80 ° to θ + 100 ° from the width direction of the stretched film for the retardation plate,
The retardation plate is
The slow axis is a direction of 40 to 50 ° with respect to the width direction of the retardation plate,
When the average value of the refractive index in the slow axis direction in the plane is nx, the average value of the refractive index in the fast axis direction in the plane is ny, and the average value of the refractive index in the thickness direction is nz, (nx−nz ) / (Nx−ny) Nz value is more than 0 and less than 1,
The width dimension is 1.5 to 5.0 times the width dimension of the laminate,
The width dimension is 1000 mm or more,
The manufacturing method of the long phase difference plate whose thickness is 15 micrometers-70 micrometers. In the manufacturing method of the long phase difference plate according to claim 1,
A method for producing a long retardation plate satisfying 0.15 <d / d ₀ <0.70, where d ₀ is the thickness of the laminate and d is the thickness of the retardation plate. In the manufacturing method of the long phase difference plate according to claim 1 or 2,
A method for producing a long retardation film satisfying a relationship of Tg (A)> Tg (B) +5 (° C.). In the manufacturing method of the long phase difference plate according to any one of claims 1 to 3,
The process of obtaining the said laminated body is a manufacturing method of the elongate phase difference plate which implements the said A layer and the said B layer by a coextrusion method. A long retardation film obtained by obliquely stretching a laminate having an A layer containing a material having a positive intrinsic birefringence value and a B layer containing a material having a negative intrinsic birefringence value. ,
The slow axis is a direction of 40 to 50 ° with respect to the width direction of the retardation plate,
When the average value of the refractive index in the slow axis direction in the plane is nx, the average value of the refractive index in the fast axis direction in the plane is ny, and the average value of the refractive index in the thickness direction is nz, (nx−nz ) / (Nx−ny) Nz value is more than 0 and less than 1,
The variation of the Nz value that is the difference between the maximum value and the minimum value of the Nz value in the width direction is −0.1 to 0.1,
Its width dimension is 1000 mm or more,
The long retardation plate has a thickness of 15 μm to 70 μm.   A long polarizing plate formed by laminating the long retardation plate according to claim 5 and a long polarizing film with their longitudinal directions aligned.

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