CN112840249B - Polarizing plate with retardation layer and image display device using the same - Google Patents

Polarizing plate with retardation layer and image display device using the same Download PDF

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Publication number
CN112840249B
CN112840249B CN201980067858.0A CN201980067858A CN112840249B CN 112840249 B CN112840249 B CN 112840249B CN 201980067858 A CN201980067858 A CN 201980067858A CN 112840249 B CN112840249 B CN 112840249B
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Prior art keywords
retardation layer
layer
polarizing plate
film
stretching
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CN112840249A (en
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后藤周作
柳沼宽教
友久宽
清水享
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Nitto Denko Corp
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Nitto Denko Corp
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Priority claimed from PCT/JP2019/039636 external-priority patent/WO2020080184A1/en
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3083—Birefringent or phase retarding elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
    • G02B1/14—Protective coatings, e.g. hard coatings
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
    • G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
    • G02B5/3058—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state comprising electrically conductive elements, e.g. wire grids, conductive particles
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • H10K59/50—OLEDs integrated with light modulating elements, e.g. with electrochromic elements, photochromic elements or liquid crystal elements

Abstract

Provided is a polarizing plate with a retardation layer, which is thin, has excellent handleability, and has excellent optical properties. The polarizing plate with the phase difference layer comprises a polarizing film and a protective layer positioned on at least one side of the polarizing film. The polarizing film is composed of a polyvinyl alcohol resin film containing a dichroic material, and has a thickness of 8 [ mu ] m or less, a monomer transmittance of 44.0% or more, and a polarization degree of 99.50% or more. Re (550) of the retardation layer is 100nm to 190nm, and Re (450)/Re (550) is 0.8 or more and less than 1. The slow axis of the retardation layer forms an angle of 40 DEG to 50 DEG with the absorption axis of the polarizing film.

Description

Polarizing plate with retardation layer and image display device using the same
Technical Field
The present invention relates to a polarizing plate with a retardation layer and an image display device using the same.
Background
In recent years, image display devices typified by liquid crystal display devices and Electroluminescent (EL) display devices (for example, organic EL display devices and inorganic EL display devices) have been rapidly spreading. In an image display device, a polarizing plate and a phase difference plate are typically used. In practical use, a polarizing plate with a retardation layer, which is formed by integrating a polarizing plate and a retardation plate, is widely used (for example, patent document 1), and in this case, as the recent demand for thinning of an image display device has increased, the demand for thinning of a polarizing plate with a retardation layer has also increased. In addition, in recent years, there has been an increasing demand for curved image display devices and/or flexible or bendable image display devices, and in this case, there has been a demand for further thinning and further softening of polarizing plates and polarizing plates with retardation layers. For the purpose of thinning a polarizing plate with a retardation layer, thinning of a protective layer of a polarizing film and a retardation film, which contribute greatly to the thickness, is advancing. However, when the protective layer and the retardation film are thinned, the influence of shrinkage of the polarizing film becomes relatively large, and there are problems that the image display device is warped and operability of the polarizing plate with the retardation layer is lowered.
In order to solve the above-described problems, the polarizing film needs to be thinned at the same time. However, if the thickness of the polarizing film is reduced only, the optical characteristics are degraded. More specifically, one or both of the polarization degree and the monomer transmittance in a trade-off relationship may be reduced to a degree that is practically unacceptable. As a result, the optical characteristics of the polarizing plate with the retardation layer are also insufficient.
Prior art literature
Patent literature
Patent document 1: japanese patent No. 3325560
Disclosure of Invention
Problems to be solved by the invention
The present invention has been made to solve the above-described conventional problems, and a main object of the present invention is to provide a polarizing plate with a retardation layer, which is thin, has excellent handleability, and has excellent optical characteristics.
Solution for solving the problem
The polarizing plate with the phase difference layer comprises a polarizing plate and a phase difference layer, wherein the polarizing plate comprises a polarizing film and a protective layer positioned on at least one side of the polarizing film. The polarizing film is composed of a polyvinyl alcohol resin film containing a dichroic material, and has a thickness of 8 [ mu ] m or less, a monomer transmittance of 44.0% or more, and a polarization degree of 99.50% or more. Re (550) of the retardation layer is 100-190 nm, re (450)/Re (550) is 0.8-1, and the angle formed by the slow axis of the retardation layer and the absorption axis of the polarizing film is 40-50 degrees.
In one embodiment, the protective layer is composed of a base material having an elastic modulus of 3000MPa or more.
In one embodiment, the polarizing plate with a retardation layer has a total thickness of 90 μm or less, a front reflection color of 3.5 or less, and the protective layer is formed of a resin film having an elastic modulus of 3000MPa or more.
In one embodiment, the protective layer is made of a triacetyl cellulose resin film.
In one embodiment, the polarizing plate includes the polarizing film and the protective layer disposed only on one side of the polarizing film, and the retardation layer is bonded to the polarizing film via an adhesive layer.
In one embodiment, the retardation layer is made of a polycarbonate resin film.
In one embodiment, the retardation layer is formed of a polycarbonate resin film having a thickness of 40 μm or less.
In one embodiment, the polarizing film is 50cm 2 The difference between the maximum value and the minimum value of the monomer transmittance in the region (a) is 0.2% or less.
In one embodiment, the polarizing plate with the retardation layer has a width of 1000mm or more, and a difference between a maximum value and a minimum value of the individual transmittance at a position in the width direction of the polarizing film is 0.3% or less.
In one embodiment, the polarizing film has a monomer transmittance of 44.5% or less and a polarization degree of 99.95% or less.
In one embodiment, the polarizing plate with a retardation layer further includes a different retardation layer outside the retardation layer, and the refractive index characteristics of the different retardation layer show a relationship of nz > nx=ny.
In one embodiment, the polarizing plate with a retardation layer further includes a conductive layer or an isotropic substrate with a conductive layer on the outer side of the retardation layer.
In one embodiment, the polarizing plate with the retardation layer is elongated, the polarizing film has an absorption axis in a longitudinal direction, and the retardation layer is a diagonally stretched film having a slow axis in a direction at an angle of 40 ° to 50 ° with respect to the longitudinal direction. In one embodiment, the polarizing plate with a retardation layer is wound in a roll.
According to another aspect of the present invention, there is provided an image display apparatus. The image display device includes the polarizing plate with the retardation layer.
In one embodiment, the image display device is an organic electroluminescent display device or an inorganic electroluminescent display device.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, a polarizing film having extremely excellent optical characteristics although thin can be obtained by using a combination of two-stage stretching including air-assisted stretching and water stretching, and drying and shrinkage by a heated roller, in which a halide (typically potassium iodide) is added to a polyvinyl alcohol (PVA) resin. By using such a polarizing film, a polarizing plate with a retardation layer having a thin shape, excellent handleability, and excellent optical characteristics can be realized.
Drawings
Fig. 1 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to an embodiment of the present invention.
Fig. 2 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to another embodiment of the present invention.
Fig. 3 is a schematic diagram showing an example of a drying shrinkage process using a heating roller in the method for producing a polarizing film used in a polarizing plate with a retardation layer according to the present invention.
Detailed Description
Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.
(definition of terms and symbols)
The terms and symbols in the present specification are defined as follows.
(1) Refractive index (nx, ny, nz)
"nx" is the refractive index in the direction in which the in-plane refractive index becomes maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction orthogonal to the slow axis (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction.
(2) In-plane phase difference (Re)
"Re (λ)" is the in-plane retardation measured at 23℃with light of wavelength λnm. For example, "Re (550)" is the in-plane retardation measured at 23℃with light having a wavelength of 550 nm. Re (lambda) is represented by the formula: re (λ) = (nx-ny) ×d.
(3) Retardation in thickness direction (Rth)
"Rth (λ)" is a phase difference in the thickness direction measured at 23℃with light having a wavelength of λnm. For example, "Rth (550)" is a phase difference in the thickness direction measured at 23 ℃ with light having a wavelength of 550 nm. Rth (λ) is represented by the formula: rth (λ) = (nx-nz) ×d.
(4) Nz coefficient
The Nz coefficient can be obtained by nz=rth/Re.
(5) Angle of
In the present specification, when referring to an angle, the angle includes an angle in both a clockwise direction and a counterclockwise direction with respect to a reference direction. Thus, for example, "45" means ± 45 °.
A. Integral structure of polarizing plate with phase difference layer
Fig. 1 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to an embodiment of the present invention. The polarizing plate 100 with a retardation layer of the present embodiment includes a polarizing plate 10 and a retardation layer 20. The polarizing plate 10 includes: a polarizing film 11, a 1 st protective layer 12 disposed on one side of the polarizing film 11, and a 2 nd protective layer 13 disposed on the other side of the polarizing film 11. One of the 1 st protective layer 12 and the 2 nd protective layer 13 may be omitted according to purposes. For example, when the retardation layer 20 can function as a protective layer for the polarizing film 11, the 2 nd protective layer 13 may be omitted. In an embodiment of the present invention, the polarizing film is composed of a polyvinyl alcohol resin film containing a dichroic material. The polarizing film has a thickness of 8 μm or less, a monomer transmittance of 44.0% or more, and a polarization degree of 99.50% or more.
As shown in fig. 2, another retardation layer 50 and/or a conductive layer or an isotropic substrate 60 with a conductive layer may be provided in the polarizing plate 101 with a retardation layer according to another embodiment. The retardation layer 50 and the conductive layer or the isotropic substrate 60 with a conductive layer are typically disposed outside the retardation layer 20 (on the opposite side of the polarizing plate 10). The other retardation layer typically has refractive index characteristics showing a relationship of nz > nx=ny. The retardation layer 50 and the conductive layer or the conductive-layer-attached isotropic base material 60 are typically provided in this order from the retardation layer 20 side. The retardation layer 50 and the conductive layer or the conductive-layer-attached isotropic substrate 60 are typically any layers provided as needed, and either or both of them may be omitted. For convenience, the phase difference layer 20 may be referred to as a 1 st phase difference layer, and the other phase difference layer 50 may be referred to as a 2 nd phase difference layer. In the case of providing a conductive layer or an isotropic substrate with a conductive layer, the polarizing plate with a retardation layer can be applied to a so-called internal touch panel type input display device in which a touch sensor is incorporated between an image display unit (for example, an organic EL unit) and the polarizing plate.
In the embodiment of the present invention, re (550) of the 1 st retardation layer 20 is 100nm to 190nm, and Re (450)/Re (550) is 0.8 or more and less than 1. The angle formed between the slow axis of the 1 st retardation layer 20 and the absorption axis of the polarizing film 11 is 40 DEG to 50 deg.
The above embodiments may be appropriately combined, or variations obvious in the art may be applied to the constituent elements of the above embodiments. For example, the structure of the isotropic base material 60 having a conductive layer provided on the outer side of the 2 nd retardation layer 50 may be replaced with an optically equivalent structure (for example, a laminate of the 2 nd retardation layer and the conductive layer).
The polarizing plate with a retardation layer according to the embodiment of the present invention may further include another retardation layer. The optical characteristics (for example, refractive index characteristics, in-plane retardation, nz coefficient, photoelastic coefficient), thickness, arrangement position, and the like of the other retardation layer can be appropriately set according to the purpose.
The polarizing plate with a retardation layer of the present invention may be in the form of a sheet or a long sheet. In the present specification, "elongated" means an elongated shape having a length long enough to the width, and includes, for example, an elongated shape having a length 10 times or more, preferably 20 times or more, the width. The elongated polarizing plate with the retardation layer may be wound into a roll. When the polarizing plate with the retardation layer is elongated, the polarizing plate and the retardation layer are elongated. In this case, the polarizing film preferably has an absorption axis in the longitudinal direction. The 1 st retardation layer is preferably a stretched film having a slow axis in a direction at an angle of 40 ° to 50 ° with respect to the longitudinal direction. When the polarizing film and the 1 st retardation layer are configured as described above, a polarizing plate with a retardation layer can be manufactured by roll-to-roll.
In actual use, an adhesive layer (not shown) is provided on the opposite side of the retardation layer from the polarizing plate, so that the polarizing plate with the retardation layer can be attached to the image display unit. Further, it is preferable to temporarily adhere the release film to the surface of the pressure-sensitive adhesive layer until the polarizing plate with the retardation layer is used. By temporarily bonding the release film, a roll can be formed while protecting the adhesive layer.
Front reflection hue of polarizing plate with phase difference layerPreferably 3.5 or less, more preferably 3.0 or less. When the front reflection hue is within the above range, undesired coloring or the like can be suppressed, and as a result, a polarizing plate with a retardation layer excellent in reflection characteristics can be obtained.
The total thickness of the polarizing plate with the retardation layer is preferably 140 μm or less, more preferably 120 μm or less, further preferably 100 μm or less, further preferably 90 μm or less, further preferably 85 μm or less. The lower limit of the total thickness may be, for example, 30 μm. According to the embodiment of the present invention, such an extremely thin polarizing plate with a retardation layer can be realized. Such a polarizing plate with a retardation layer can have extremely excellent flexibility and bending durability. Such a polarizing plate with a retardation layer can be particularly suitably applied to a curved image display device and/or a flexible or bendable image display device. The total thickness of the polarizing plate with a retardation layer is the sum of the thicknesses of all layers constituting the polarizing plate with a retardation layer excluding an adhesive layer for adhering the polarizing plate with a retardation layer to an external adherend such as a panel or glass (that is, the total thickness of the polarizing plate with a retardation layer excluding an adhesive layer for adhering the polarizing plate with a retardation layer to an adjacent member such as an image display unit and a thickness of a release film temporarily adhering to the surface thereof).
The constituent elements of the polarizing plate with a retardation layer will be described in more detail below.
B. Polarizing plate
B-1 polarizing film
The polarizing film 11 has a thickness of 8 μm or less, a monomer transmittance of 44.0% or more, and a polarization degree of 99.50% or more as described above. In general, the monomer transmittance and the polarization degree are in a trade-off relationship with each other, and when the monomer transmittance is increased, the polarization degree is decreased, and when the polarization degree is increased, the monomer transmittance is decreased. Therefore, conventionally, it has been difficult to put a thin polarizing film satisfying optical characteristics of 44.0% or more of the monomer transmittance and 99.50% or more of the polarization degree into practical use. The use of a thin polarizing film having excellent optical characteristics with a monomer transmittance of 44.0% or more and a polarization degree of 99.50% or more, and suppressing unevenness in optical characteristics, is one of the features of the present invention.
The thickness of the polarizing film is preferably 1 μm to 8 μm, more preferably 1 μm to 7 μm, and still more preferably 2 μm to 5 μm.
The polarizing film preferably exhibits absorption dichroism at any wavelength of 380nm to 780 nm. The monomer transmittance of the polarizing film is preferably 44.5% or less. The polarization degree of the polarizing film is preferably 99.70% or more, more preferably 99.80% or more. On the other hand, the degree of polarization is preferably 99.95% or less. The above-mentioned monomer transmittance is typically a Y value obtained by measuring and correcting the visibility by using an ultraviolet-visible spectrophotometer. The polarization degree is typically obtained by the following equation based on the parallel transmittance Tp and the orthogonal transmittance Tc measured by an ultraviolet-visible spectrophotometer and corrected for visibility.
Polarization (%) = { (Tp-Tc)/(tp+tc) } 1/2 ×100
In one embodiment, the transmittance of a thin polarizing film of 8 μm or less is typically measured by using an ultraviolet-visible spectrophotometer with a laminate of a polarizing film (refractive index of surface: 1.53) and a protective film (refractive index: 1.50) as a measurement object. Depending on the refractive index of the surface of the polarizing film and/or the refractive index of the surface of the protective film in contact with the air interface, the reflectance at the interface of each layer may change, and as a result, the measured value of the transmittance may change. Thus, for example, when a protective film having a refractive index other than 1.50 is used, the correction can be made based on the refractive index of the surface of the protective film in contact with the air interfaceMeasurement of transmittance. Specifically, the correction value C of the transmittance uses the reflectance R of polarized light parallel to the transmission axis at the interface of the protective film and the air layer 1 (transmission axis reflectivity) is expressed by the following equation.
C＝R 1 -R 0
R 0 ＝((1.50-1) 2 /(1.50+1) 2 )×(T 1 /100)
R 1 ＝((n 1 -1) 2 /(n 1 +1) 2 )×(T 1 /100)
Here, R is 0 In order to obtain a transmission axis reflectivity n when a protective film having a refractive index of 1.50 is used 1 For the refractive index of the protective film used, T 1 Is the transmittance of the polarizing film. For example, when a base material (cycloolefin film, hard-coated film, or the like) having a surface refractive index of 1.53 is used as the protective film, the correction amount C is about 0.2%. In this case, the transmittance obtained by the measurement can be converted into the transmittance when a protective film having a refractive index of 1.50 is used by adding 0.2%. The transmittance T of the polarizing film was calculated based on the above formula 1 The change amount of the correction value C at the change of 2% is 0.03% or less, and the influence of the transmittance of the polarizing film on the value of the correction value C is limited. In addition, when the protective film has absorption other than surface reflection, appropriate correction can be performed according to the absorption amount.
In 1 embodiment, the width of the polarizing plate with the retardation layer is 1000mm or more, and therefore the width of the polarizing film is also 1000mm or more. In this case, the difference (D1) between the maximum value and the minimum value of the monomer transmittance at the position in the width direction of the polarizing film is preferably 0.3% or less, more preferably 0.29% or less, and still more preferably 0.28% or less. The smaller D1 is, the more preferable, and the lower limit of D1 may be, for example, 0.01%. D1 in the above range, a polarizing plate with a retardation layer having excellent optical characteristics can be industrially produced. In other embodiments, 50cm of the polarizing film 2 The difference (D2) between the maximum value and the minimum value of the monomer transmittance in the region (C) is preferably 0.2% or less, more preferably 0.15% or less,More preferably 0.1% or less. The smaller D2 is, the more preferable, and the lower limit of D2 may be, for example, 0.01%. When D2 is within the above range, uneven brightness in the display screen can be suppressed when the polarizing plate with the retardation layer is used in an image display device.
As the polarizing film, any suitable polarizing film may be used. The polarizing film can be typically produced using a laminate of two or more layers.
Specific examples of the polarizing film obtained by using the laminate include a polarizing film obtained by using a laminate of a resin substrate and a PVA-based resin layer formed by coating the resin substrate. A polarizing film obtained by using a laminate of a resin substrate and a PVA-based resin layer formed by coating the resin substrate can be produced, for example, by: coating a PVA-based resin solution on a resin substrate, drying the resin substrate to form a PVA-based resin layer on the resin substrate, and obtaining a laminate of the resin substrate and the PVA-based resin layer; the laminate was stretched and dyed to prepare a polarizing film from the PVA-based resin layer. In this embodiment, the stretching typically includes: the laminate was immersed in an aqueous boric acid solution and stretched. Further, the stretching may further include, as required: the laminate is air-stretched at a high temperature (e.g., 95 ℃ or higher) before stretching in an aqueous boric acid solution. The obtained laminate of the resin substrate and the polarizing film (that is, the resin substrate may be used as a protective layer for the polarizing film) may be used as it is, or the resin substrate may be peeled from the laminate of the resin substrate and the polarizing film and any appropriate protective layer suitable for the purpose may be laminated on the peeled surface. Details of such a method for producing a polarizing film are described in, for example, japanese patent application laid-open No. 2012-73580. The entire disclosure of this publication is incorporated by reference in this specification.
The method for producing a polarizing film typically includes: forming a polyvinyl alcohol resin layer containing a halide and a polyvinyl alcohol resin on one side of a long thermoplastic resin substrate to form a laminate; and sequentially performing an air-assisted stretching treatment, a dyeing treatment, an in-water stretching treatment, and a drying shrinkage treatment for shrinking the laminate by 2% or more in the width direction by heating the laminate while conveying the laminate in the longitudinal direction. Thus, a polarizing film having excellent optical characteristics and suppressed unevenness in optical characteristics, which has a thickness of 8 μm or less, a monomer transmittance of 44.0% or more, and a polarization degree of 99.50% or more, can be provided. That is, by introducing the auxiliary stretching, crystallinity of PVA can be improved even when PVA is coated on a thermoplastic resin, and high optical characteristics can be achieved. Further, by simultaneously improving the orientation of PVA in advance, problems such as lowering of the orientation of PVA or dissolution when immersed in water in a subsequent dyeing step or stretching step can be prevented, and high optical characteristics can be achieved. Further, when the PVA-based resin layer is immersed in a liquid, disturbance of orientation and decrease of orientation of polyvinyl alcohol molecules can be suppressed as compared with the case where the PVA-based resin layer does not contain a halide. This can improve the optical characteristics of the polarizing film obtained by the treatment step of immersing the laminate in a liquid, such as dyeing treatment or underwater stretching treatment. Further, the laminate is shrunk in the width direction by the drying shrinkage treatment, whereby the optical characteristics can be improved.
B-2. Protective layer
The 1 st protective layer 12 and the 2 nd protective layer 13 are each formed of any appropriate thin film that can be used as a protective layer of a polarizing film. Specific examples of the material that is the main component of the film include cellulose resins such as Triacetylcellulose (TAC), polyester resins, polyvinyl alcohol resins, polycarbonate resins, polyamide resins, polyimide resins, polyether sulfone resins, polysulfone resins, polystyrene resins, polynorbornene resins, polyolefin resins, (meth) acrylic resins, acetate resins, and the like. Further, there may be mentioned a thermosetting resin such as a (meth) acrylic resin, a urethane resin, a (meth) acrylic urethane resin, an epoxy resin, or a silicone resin, an ultraviolet curable resin, or the like. Other examples include glass polymers such as silicone polymers. In addition, a polymer film described in Japanese patent application laid-open No. 2001-343529 (WO 01/37007) may also be used. Examples of the material of the film include a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in a side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in a side chain, and examples thereof include a resin composition containing an alternating copolymer of isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer. The polymer film may be, for example, an extrusion molded product of the above resin composition. In one embodiment, the protective layer (particularly, the protective layer on the visual recognition side) contains TAC-based resin. By using a TAC-based resin film as the protective layer, bending durability can be improved.
The polarizing plate with a retardation layer of the present invention is typically disposed on the visual recognition side of an image display device as described later, and the 1 st protective layer 12 is typically disposed on the visual recognition side thereof. Accordingly, the 1 st protective layer 12 may be subjected to surface treatments such as hard coat treatment, antireflection treatment, anti-blocking treatment, and antiglare treatment, if necessary. Further, the 1 st protective layer 12 may be subjected to a treatment (typically, an (elliptical) polarization function, or an ultra-high retardation) for improving the visibility when the user performs visual recognition through polarized sunglasses, if necessary. By performing such a process, even when the display screen is visually recognized through a polarized lens such as polarized sunglasses, excellent visual recognition can be achieved. Therefore, the polarizing plate with the retardation layer can be suitably used for an image display device which can be used outdoors.
The 1 st protective layer preferably has a thickness of 5 μm to 80. Mu.m, more preferably 10 μm to 40. Mu.m, still more preferably 10 μm to 35. Mu.m. When the surface treatment is performed, the thickness of the outer protective layer includes the thickness of the surface treatment layer.
In one embodiment, the 2 nd protective layer 13 is preferably optically isotropic. In the present specification, "optically isotropic" means that the in-plane retardation Re (550) is 0nm to 10nm, and the retardation Rth (550) in the thickness direction is-10 nm to +10nm. In one embodiment, the 2 nd protective layer 13 may be a phase difference layer having any suitable phase difference value. In this case, the in-plane retardation Re (550) of the retardation layer is, for example, 110nm to 150nm. The thickness of the 2 nd protective layer is preferably 5 μm to 80. Mu.m, more preferably 10 μm to 40. Mu.m, still more preferably 10 μm to 30. Mu.m. From the viewpoint of thickness reduction and weight reduction, the 2 nd protective layer is preferably omitted.
B-3 method for producing polarizing film
The polarizing film can be produced, for example, by a method comprising: forming a laminate by forming a polyvinyl alcohol resin layer (PVA resin layer) containing a halide and a polyvinyl alcohol resin (PVA resin) on one side of a long thermoplastic resin substrate; and sequentially performing an air-assisted stretching process, a dyeing process, an in-water stretching process, and a drying shrinkage process for shrinking the laminate by 2% or more in the width direction by heating the laminate while conveying the laminate in the longitudinal direction. The content of the halide in the PVA-based resin layer is preferably 5 to 20 parts by weight relative to 100 parts by weight of the PVA-based resin. The drying shrinkage treatment is preferably performed using a heated roller, and the temperature of the heated roller is preferably 60 to 120 ℃. The shrinkage in the width direction of the laminate by the drying shrinkage treatment is preferably 2% or more. According to such a production method, the polarizing film described in the above item B-1 can be obtained. In particular, by producing a laminate including a PVA-based resin layer containing a halide, stretching the laminate in multiple stages including air-assisted stretching and in-water stretching, and heating the stretched laminate with a heating roller, a polarizing film having excellent optical characteristics (typically, a monomer transmittance and a degree of polarization) and suppressed unevenness in optical characteristics can be obtained. Specifically, by using the heating roller in the drying shrinkage treatment step, the laminate can be uniformly shrunk over the whole laminate while being conveyed. This can not only improve the optical characteristics of the obtained polarizing film, but also stably produce a polarizing film having excellent optical characteristics, and suppress the unevenness of the optical characteristics (particularly, the transmittance of the monomer) of the polarizing film.
B-3-1 production of laminate
As a method for producing the laminate of the thermoplastic resin base material and the PVA-based resin layer, any suitable method can be used. Preferably, it is: the PVA-based resin layer is formed on the thermoplastic resin substrate by coating a coating liquid containing a halide and a PVA-based resin on the surface of the thermoplastic resin substrate and drying. As described above, the content of the halide in the PVA-based resin layer is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.
As a coating method of the coating liquid, any suitable method can be employed. Examples thereof include roll coating, spin coating, bar coating, dip coating, die coating, curtain coating, spray coating, knife coating (comma coating, etc.), and the like. The coating/drying temperature of the coating liquid is preferably 50℃or higher.
The thickness of the PVA based resin layer is preferably 3 to 40. Mu.m, more preferably 3 to 20. Mu.m.
Before forming the PVA-based resin layer, the thermoplastic resin substrate may be subjected to a surface treatment (for example, corona treatment or the like), or an easy-to-adhere layer may be formed on the thermoplastic resin substrate. By performing such treatment, the adhesion between the thermoplastic resin base material and the PVA-based resin layer can be improved.
B-3-1-1. Thermoplastic resin substrate
The thickness of the thermoplastic resin base material is preferably 20 μm to 300. Mu.m, more preferably 50 μm to 200. Mu.m. If the particle size is less than 20. Mu.m, it may be difficult to form a PVA based resin layer. If the particle size exceeds 300. Mu.m, for example, in the in-water stretching treatment described later, the thermoplastic resin substrate may take a long time to absorb water and an excessive load may be required for stretching.
The water absorption rate of the thermoplastic resin base material is preferably 0.2% or more, more preferably 0.3% or more. The thermoplastic resin base material absorbs water, and the water acts as a plasticizer to plasticize. As a result, the tensile stress can be greatly reduced, and the steel sheet can be stretched to a high magnification. On the other hand, the water absorption rate of the thermoplastic resin base material is preferably 3.0% or less, more preferably 1.0% or less. By using such a thermoplastic resin base material, the following problems can be prevented: the dimensional stability of the thermoplastic resin base material is significantly reduced during production, and the appearance of the obtained polarizing film is deteriorated. Further, it is possible to prevent the base material from breaking or the PVA-based resin layer from peeling from the thermoplastic resin base material when stretched in water. The water absorption rate of the thermoplastic resin base material can be adjusted by introducing a modifying group into the constituent material, for example. The water absorption was determined in accordance with JIS K7209.
The glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 120℃or lower. By using such a thermoplastic resin base material, crystallization of the PVA-based resin layer can be suppressed, and stretchability of the laminate can be sufficiently ensured. Further, in view of plasticization of the thermoplastic resin substrate by water, in-water stretching is preferably performed at 100℃or less, more preferably at 90℃or less. On the other hand, the glass transition temperature of the thermoplastic resin substrate is preferably 60℃or higher. By using such a thermoplastic resin base material, when a coating liquid containing the PVA-based resin is applied and dried, it is possible to satisfactorily produce a laminate while preventing the thermoplastic resin base material from being deformed (for example, causing irregularities, looseness, wrinkles, and the like). Further, the PVA-based resin layer can be stretched well at a suitable temperature (for example, about 60 ℃). The glass transition temperature of the thermoplastic resin base material can be adjusted by heating the thermoplastic resin base material using, for example, a crystallization material in which a modifying group is introduced into a constituent material. The glass transition temperature (Tg) is a value obtained in accordance with JIS K7121.
As the constituent material of the thermoplastic resin base material, any suitable thermoplastic resin may be used. Examples of the thermoplastic resin include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymer resins thereof. Of these, norbornene-based resins and amorphous polyethylene terephthalate-based resins are preferable.
In one embodiment, an amorphous (non-crystallized) polyethylene terephthalate-based resin is preferably used. Among them, an amorphous (hardly crystallized) polyethylene terephthalate resin is particularly preferably used. Specific examples of the amorphous polyethylene terephthalate resin include copolymers further containing isophthalic acid and/or cyclohexanedicarboxylic acid as dicarboxylic acid; copolymers of cyclohexanedimethanol, diethylene glycol as diols are also included.
In a preferred embodiment, the thermoplastic resin base material is composed of a polyethylene terephthalate resin having isophthalic acid units. This is because: the thermoplastic resin base material is extremely excellent in stretchability, and crystallization upon stretching is suppressed. This is considered to be because the introduction of isophthalic acid units imparts a large deflection to the main chain. The polyethylene terephthalate resin has terephthalic acid units and ethylene glycol units. The content of isophthalic acid units is preferably 0.1 mol% or more, more preferably 1.0 mol% or more, based on the total of all the repeating units. This is because: a thermoplastic resin substrate extremely excellent in stretchability can be obtained. On the other hand, the content ratio of isophthalic acid units is preferably 20 mol% or less, more preferably 10 mol% or less, based on the total of all the repeating units. By setting the content ratio as described above, the crystallinity can be satisfactorily increased in the drying shrinkage treatment described later.
The thermoplastic resin base material may be stretched in advance (before forming the PVA-based resin layer). In one embodiment, stretching is performed in the transverse direction of the elongated thermoplastic resin substrate. The transverse direction is preferably a direction perpendicular to the stretching direction of the laminate to be described later. In the present specification, "orthogonal" also includes a case of being substantially orthogonal. Here, "substantially orthogonal" includes a case of 90 ° ± 5.0 °, preferably 90 ° ± 3.0 °, further preferably 90 ° ± 1.0 °.
The stretching temperature of the thermoplastic resin substrate is preferably from Tg to 10℃to Tg+50℃, compared with the glass transition temperature (Tg). The stretching ratio of the thermoplastic resin base material is preferably 1.5 to 3.0 times.
As the stretching method of the thermoplastic resin substrate, any suitable method can be employed. Specifically, the stretching may be performed at the fixed end or at the free end. The stretching method may be dry or wet. The stretching of the thermoplastic resin substrate may be performed in one stage or may be performed in a plurality of stages. When the stretching ratio is set to be the product of the stretching ratios of the respective stages.
B-3-1-2. Coating solution
As described above, the coating liquid contains the halide and the PVA-based resin. The coating liquid is typically a solution obtained by dissolving the halide and the PVA-based resin in a solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various diols, polyols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These may be used singly or in combination of two or more. Among these, water is preferable. The PVA-based resin concentration of the solution is preferably 3 to 20 parts by weight relative to 100 parts by weight of the solvent. In the case of such a resin concentration, a uniform coating film can be formed to be adhered to the thermoplastic resin base material. The halide content in the coating liquid is preferably 5 parts by weight to 20 parts by weight relative to 100 parts by weight of the PVA-based resin.
Additives may be compounded into the coating liquid. Examples of the additive include plasticizers and surfactants. Examples of the plasticizer include polyols such as ethylene glycol and glycerin. Examples of the surfactant include nonionic surfactants. They can be used for the purpose of further improving the uniformity, dyeing property, stretchability of the resulting PVA-based resin layer.
As the PVA-based resin, any suitable resin may be used. Examples thereof include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. The polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer may be obtained by saponifying an ethylene-vinyl acetate copolymer. The saponification degree of the PVA-based resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, more preferably 99.0 mol% to 99.93 mol%. The saponification degree can be obtained in accordance with JIS K6726-1994. By using the PVA-based resin having such a saponification degree, a polarizing film excellent in durability can be obtained. If the saponification degree is too high, gelation may occur.
The average polymerization degree of the PVA-based resin may be appropriately selected according to the purpose. The average polymerization degree is usually 1000 to 10000, preferably 1200 to 4500, more preferably 1500 to 4300. The average polymerization degree can be determined in accordance with JIS K6726-1994.
As the above-mentioned halide, any suitable halide may be used. Examples thereof include iodide and sodium chloride. Examples of the iodide include potassium iodide, sodium iodide, and lithium iodide. Among these, potassium iodide is preferable.
The amount of the halide in the coating liquid is preferably 5 to 20 parts by weight relative to 100 parts by weight of the PVA-based resin, and more preferably 10 to 15 parts by weight relative to 100 parts by weight of the PVA-based resin. If the amount of the halide exceeds 20 parts by weight relative to 100 parts by weight of the PVA-based resin, the halide may ooze out, and the finally obtained polarizing film may be clouded.
In general, since the PVA-based resin layer is stretched, the orientation of the polyvinyl alcohol molecules in the PVA-based resin is high, and when the stretched PVA-based resin layer is immersed in an aqueous liquid, the orientation of the polyvinyl alcohol molecules may be disturbed, and the orientation property may be lowered. In particular, when a laminate of a thermoplastic resin substrate and a PVA-based resin layer is stretched in an aqueous boric acid solution, the degree of orientation tends to be significantly reduced when the laminate is stretched in an aqueous boric acid solution at a relatively high temperature in order to stabilize the stretching of the thermoplastic resin substrate. For example, in a case where the stretching of the PVA film itself in an aqueous boric acid solution is usually performed at 60 ℃, whereas the stretching of the laminate of a-PET (thermoplastic resin base) and PVA-based resin layer is performed at a high temperature of about 70 ℃, the orientation of PVA at the initial stage of the stretching may be reduced in a stage before the stretching in water is improved. In contrast, by producing a laminate of a PVA-based resin layer containing a halide and a thermoplastic resin substrate, the laminate is stretched in air at a high temperature (auxiliary stretching) before stretching in an aqueous boric acid solution, and crystallization of the PVA-based resin in the PVA-based resin layer of the laminate after the auxiliary stretching can be promoted. As a result, when the PVA-based resin layer is immersed in a liquid, disorder of alignment and decrease of alignment property of the polyvinyl alcohol molecules can be suppressed as compared with the case where the PVA-based resin layer does not contain a halide. This can improve the optical characteristics of the polarizing film obtained by the treatment step of immersing the laminate in a liquid, such as dyeing treatment or stretching treatment in water.
B-3-2, auxiliary stretching treatment in air
In particular, in order to obtain high optical characteristics, a two-stage stretching method in which dry stretching (auxiliary stretching) is combined with stretching in an aqueous boric acid solution is selected. By introducing the auxiliary stretching as in the two-stage stretching, the thermoplastic resin base material can be stretched while suppressing crystallization, and the problem of the reduced stretchability due to excessive crystallization of the thermoplastic resin base material in the subsequent stretching in the aqueous boric acid solution can be solved, and the laminate can be stretched to a higher magnification. Further, when the PVA-based resin is coated on the thermoplastic resin substrate, in order to suppress the influence of the glass transition temperature of the thermoplastic resin substrate, it is necessary to lower the coating temperature as compared with the case of coating the PVA-based resin on a usual metal drum, and as a result, there is a possibility that crystallization of the PVA-based resin is relatively low and sufficient optical characteristics are not obtained. In contrast, by introducing the auxiliary stretching, even when the PVA-based resin is coated on the thermoplastic resin, crystallinity of the PVA-based resin can be improved, and high optical characteristics can be realized. Further, by simultaneously improving the orientation of the PVA-based resin in advance, problems such as a decrease in orientation and dissolution of the PVA-based resin when immersed in water in a subsequent dyeing step and stretching step can be prevented, and high optical characteristics can be achieved.
The stretching method of the air-assisted stretching may be fixed-end stretching (for example, stretching using a tenter), or free-end stretching (for example, stretching the laminate unidirectionally between rolls having different circumferential speeds), and free-end stretching may be positively employed in order to obtain high optical characteristics. In one embodiment, the air stretching process includes a heated roll stretching step of stretching the laminate by using a peripheral speed difference between heated rolls while conveying the laminate in a longitudinal direction thereof. Typically, in-air stretchingThe treatment includes a zone stretching process and a heated roll stretching process. The order of the block stretching step and the heat roller stretching step is not limited, and the block stretching step may be performed first, or the heat roller stretching step may be performed first. The zone stretching process may be omitted. In one embodiment, the block stretching process and the heat roller stretching process are sequentially performed. In other embodiments, the stretching is performed by grasping the film end portions and expanding the distance between the tenters in the moving direction in the tenter stretching machine (the expansion of the distance between the tenters becomes the stretching magnification). At this time, the distance of the tenter in the width direction (the direction perpendicular to the moving direction) is set to be arbitrarily close. The stretch ratio in the moving direction can be preferably set so as to be closer to the free end stretch. In the case of free end stretching, the shrinkage in the width direction= (1/stretch ratio) 1/2 To calculate.
The air assist stretching may be performed in one stage or may be performed in a plurality of stages. When the stretching is performed in a plurality of stages, the stretching ratio is a product of stretching ratios in the respective stages. The stretching direction in the air-assisted stretching is preferably substantially the same as the stretching direction in the water stretching.
The stretching ratio in the air-assisted stretching is preferably 2.0 to 3.5 times. The maximum stretching ratio when the air-assist stretching and the in-water stretching are combined is preferably 5.0 times or more, more preferably 5.5 times or more, and still more preferably 6.0 times or more, relative to the original length of the laminate. In the present specification, "maximum stretch ratio" means a stretch ratio immediately before the laminate breaks, and means a stretch ratio at which the laminate breaks is confirmed separately and is lower than this by 0.2.
The stretching temperature of the air-assisted stretching may be set to any appropriate value depending on the material forming the thermoplastic resin base material, the stretching method, and the like. The stretching temperature is preferably not less than the glass transition temperature (Tg) of the thermoplastic resin substrate, more preferably not less than the glass transition temperature (Tg) +10 ℃ of the thermoplastic resin substrate, and particularly preferably not less than tg+15 ℃. On the other hand, the upper limit of the stretching temperature is preferably 170 ℃. By the following steps of By stretching at such a temperature, the rapid progress of crystallization of the PVA-based resin can be suppressed, and defects caused by the crystallization (e.g., the inhibition of orientation of the PVA-based resin layer by stretching) can be suppressed. The crystallization index of the PVA based resin after the air-assisted stretching is preferably 1.3 to 1.8, more preferably 1.4 to 1.7. The crystallization index of the PVA-based resin can be measured by ATR method using a fourier transform infrared spectrometer. Specifically, measurement was performed using polarized light as measurement light, and 1141cm of the obtained spectrum was used -1 1440cm -1 The crystallization index was calculated according to the following formula.
Crystallization index= (I) C /I R )
Wherein, the liquid crystal display device comprises a liquid crystal display device,
I C : 1141cm for measurement by incidence of measurement light -1 Is used for the strength of the steel sheet,
I R : 1440cm when measuring light is incident -1 Is a strength of (a) is a strength of (b).
B-3-3 insolubilization treatment
If necessary, the insolubilization treatment is performed after the air-assisted stretching treatment and before the underwater stretching treatment and dyeing treatment. Typically, the insolubilization treatment is performed by immersing the PVA-based resin layer in an aqueous boric acid solution. By performing the insolubilization treatment, water resistance can be imparted to the PVA-based resin layer, and the decrease in orientation of PVA when immersed in water can be prevented. The concentration of the aqueous boric acid solution is preferably 1 to 4 parts by weight based on 100 parts by weight of water. The temperature of the insoluble bath (boric acid aqueous solution) is preferably 20 to 50 ℃.
B-3-4 dyeing treatment
The dyeing treatment is typically performed by dyeing the PVA-based resin layer with a dichroic substance (typically iodine). Specifically, iodine is adsorbed to the PVA-based resin layer. Examples of the adsorption method include a method of immersing a PVA-based resin layer (laminate) in a dye solution containing iodine, a method of applying the dye solution to the PVA-based resin layer, and a method of spraying the dye solution onto the PVA-based resin layer. A method of immersing the laminate in a dyeing liquid (dyeing bath) is preferable. This is because iodine can be adsorbed well.
The staining solution is preferably an aqueous iodine solution. The amount of iodine to be blended is preferably 0.05 to 0.5 parts by weight based on 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to compound iodide into an aqueous iodine solution. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Among these, potassium iodide is preferable. The amount of iodide to be blended is preferably 0.1 to 10 parts by weight, more preferably 0.3 to 5 parts by weight, based on 100 parts by weight of water. In order to suppress dissolution of the PVA-based resin, the liquid temperature at the time of dyeing of the dyeing liquid is preferably 20 to 50 ℃. When the PVA-based resin layer is immersed in the dyeing liquid, the immersion time is preferably 5 seconds to 5 minutes, more preferably 30 seconds to 90 seconds, in order to ensure the transmittance of the PVA-based resin layer.
The dyeing conditions (concentration, liquid temperature, immersion time) may be set so that the monomer transmittance of the finally obtained polarizing film is 44.0% or more and the polarization degree is 99.50% or more. As such dyeing conditions, preferred are: the iodine aqueous solution is used as the staining solution, and the content ratio of iodine to potassium iodide in the iodine aqueous solution is set to be 1:5-1:20. The content ratio of iodine to potassium iodide in the aqueous iodine solution is preferably 1:5 to 1:10. This can provide a polarizing film having the above-described optical characteristics.
When the dyeing treatment is continuously performed after the laminate is immersed in the treatment bath containing boric acid (typically, the insolubilization treatment), the boric acid concentration in the dyeing bath may change with time due to the mixing of the boric acid contained in the treatment bath into the dyeing bath, and as a result, the dyeing property may be unstable. In order to suppress the above-described instability of dyeing properties, the upper limit of the boric acid concentration in the dyeing bath is adjusted so as to be preferably 4 parts by weight, more preferably 2 parts by weight, relative to 100 parts by weight of water. On the other hand, the lower limit of the boric acid concentration in the dyeing bath is preferably 0.1 part by weight, more preferably 0.2 part by weight, and further preferably 0.5 part by weight, relative to 100 parts by weight of water. In one embodiment, the dyeing process is performed using a dyeing bath pre-compounded with boric acid. This can reduce the ratio of change in boric acid concentration when boric acid in the treatment bath is mixed into the dyeing bath. The compounding amount of boric acid to be compounded in advance into the dyeing bath (i.e., the content of boric acid not originating from the above-mentioned treatment bath) is preferably 0.1 to 2 parts by weight, more preferably 0.5 to 1.5 parts by weight, relative to 100 parts by weight of water.
B-3-5 Cross-linking treatment
If necessary, the crosslinking treatment is performed after the dyeing treatment and before the stretching treatment in water. Typically, the crosslinking treatment is performed by immersing the PVA-based resin layer in an aqueous boric acid solution. By performing the crosslinking treatment, water resistance can be imparted to the PVA-based resin layer, and in the subsequent stretching in water, the decrease in the orientation of PVA when immersed in high temperature water can be prevented. The concentration of the aqueous boric acid solution is preferably 1 to 5 parts by weight based on 100 parts by weight of water. In the case of performing the crosslinking treatment after the dyeing treatment, it is preferable to further compound an iodide. By adding iodide, elution of iodine adsorbed by the PVA-based resin layer can be suppressed. The amount of iodide to be blended is preferably 1 to 5 parts by weight based on 100 parts by weight of water. Specific examples of iodides are described above. The liquid temperature of the crosslinking bath (aqueous boric acid solution) is preferably 20℃to 50 ℃.
B-3-6. In-water stretching treatment
The stretching treatment in water is performed by immersing the laminate in a stretching bath. By the in-water stretching treatment, the PVA-based resin layer can be stretched at a temperature lower than the glass transition temperature (typically about 80 ℃) of the thermoplastic resin substrate and the PVA-based resin layer, and the PVA-based resin layer can be stretched to a high magnification while suppressing crystallization. As a result, a polarizing film having excellent optical characteristics can be produced.
Any suitable method may be used for stretching the laminate. Specifically, the stretching may be performed at a fixed end or at a free end (for example, a method in which a laminate is uniaxially stretched by passing the laminate between rolls having different peripheral speeds). The free end stretch is preferably selected. Stretching of the laminate may be performed in one stage or in a plurality of stages. When the stretching is performed in a plurality of stages, the stretching ratio (maximum stretching ratio) of the laminate to be described later is the product of the stretching ratios of the respective stages.
The stretching in water is preferably performed by immersing the laminate in an aqueous boric acid solution (stretching in an aqueous boric acid solution). By using an aqueous boric acid solution as a stretching bath, rigidity that can withstand tension applied at the time of stretching and water resistance that is insoluble in water can be imparted to the PVA-based resin layer. Specifically, boric acid can be crosslinked with the PVA-based resin by generating a tetrahydroxyborate anion in an aqueous solution and by hydrogen bonding. As a result, rigidity and water resistance can be imparted to the PVA-based resin layer, and stretching can be performed well, and a polarizing film having excellent optical characteristics can be produced.
The aqueous boric acid solution is preferably obtained by dissolving boric acid and/or a borate in water as a solvent. The boric acid concentration is preferably 1 to 10 parts by weight, more preferably 2.5 to 6 parts by weight, and particularly preferably 3 to 5 parts by weight, relative to 100 parts by weight of water. When the boric acid concentration is 1 part by weight or more, dissolution of the PVA-based resin layer can be efficiently suppressed, and a polarizing film having higher characteristics can be produced. In addition to boric acid or a borate, an aqueous solution obtained by dissolving a boron compound such as borax, glyoxal, glutaraldehyde, or the like in a solvent may be used.
The iodide is preferably compounded into the above-mentioned stretching bath (aqueous boric acid solution). By adding iodide, elution of iodine adsorbed by the PVA-based resin layer can be suppressed. Specific examples of iodides are described above. The concentration of iodide is preferably 0.05 to 15 parts by weight, more preferably 0.5 to 8 parts by weight, relative to 100 parts by weight of water.
The stretching temperature (liquid temperature of the stretching bath) is preferably 40 to 85 ℃, more preferably 60 to 75 ℃. If the temperature is such, the PVA-based resin layer can be stretched to a high magnification while suppressing dissolution. Specifically, as described above, the glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 60 ℃ or higher in relation to the formation of the PVA-based resin layer. In this case, if the stretching temperature is less than 40 ℃, there is a possibility that the thermoplastic resin base material may not be stretched well even if plasticization by water is considered. On the other hand, the higher the temperature of the stretching bath is, the higher the solubility of the PVA-based resin layer becomes, and there is a possibility that excellent optical characteristics cannot be obtained. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.
The stretching ratio based on stretching in water is preferably 1.5 times or more, more preferably 3.0 times or more. The total stretch ratio of the laminate is preferably 5.0 times or more, more preferably 5.5 times or more, relative to the original length of the laminate. By realizing such a high stretching ratio, a polarizing film extremely excellent in optical characteristics can be produced. Such a high stretching ratio can be achieved by employing an in-water stretching method (stretching in an aqueous boric acid solution).
B-3-7 drying shrinkage treatment
The drying shrinkage treatment may be performed by zone heating in which the whole zone is heated, or may be performed by heating a conveying roller (using a so-called heating roller) (heating roller drying method). Both are preferably used. By drying the laminate using a heating roller, the heating curl of the laminate can be effectively suppressed, and a polarizing film excellent in appearance can be produced. Specifically, by drying the laminate in a state of being brought along the heating roller, the crystallization of the thermoplastic resin base material can be efficiently promoted to increase the crystallinity, and even at a low drying temperature, the crystallinity of the thermoplastic resin base material can be satisfactorily increased. As a result, the rigidity of the thermoplastic resin base material increases, and the PVA-based resin layer is allowed to shrink due to drying, and curling is suppressed. Further, since the laminate can be dried while maintaining a flat state by using the heating roller, not only curling but also occurrence of wrinkles can be suppressed. At this time, the laminate is shrunk in the width direction by the drying shrinkage treatment, and the optical characteristics can be improved. This is because: the orientation of PVA and PVA/iodine complex can be improved efficiently. The shrinkage in the width direction of the laminate by the drying shrinkage treatment is preferably 1% to 10%, more preferably 2% to 8%, and particularly preferably 4% to 6%. By using the heating roller, the laminate can be continuously contracted in the width direction while being conveyed, and high productivity can be achieved.
Fig. 3 is a schematic diagram showing an example of the drying shrinkage treatment. In the drying shrinkage process, the laminate 200 is dried while being conveyed by the conveying rollers R1 to R6 and the guide rollers G1 to G4 heated to a predetermined temperature. In the example shown in the figure, the conveying rollers R1 to R6 are arranged so as to alternately and continuously heat the surface of the PVA resin layer and the surface of the thermoplastic resin substrate, but for example, the conveying rollers R1 to R6 may be arranged so as to continuously heat only one surface (for example, the surface of the thermoplastic resin substrate) of the laminate 200.
The drying condition can be controlled by adjusting the heating temperature of the conveying roller (temperature of the heating roller), the number of heating rollers, the time of contact with the heating roller, and the like. The temperature of the heating roller is preferably 60 to 120 ℃, more preferably 65 to 100 ℃, and particularly preferably 70 to 80 ℃. The crystallinity of the thermoplastic resin can be increased well, curling can be suppressed well, and an optical laminate extremely excellent in durability can be produced. The temperature of the heating roller may be measured by a contact thermometer. In the example shown in the figure, 6 conveying rollers are provided, but there is no particular limitation as long as there are a plurality of conveying rollers. The number of the conveying rollers is usually 2 to 40, preferably 4 to 30. The contact time (total contact time) between the laminate and the heating roller is preferably 1 to 300 seconds, more preferably 1 to 20 seconds, and even more preferably 1 to 10 seconds.
The heating roller may be provided in a heating furnace (for example, an oven) or may be provided in a general production line (in a room temperature environment). Preferably, the air supply device is arranged in a heating furnace provided with an air supply means. By using the drying by the heating roller and the hot air drying in combination, abrupt temperature changes between the heating rollers can be suppressed, and the shrinkage in the width direction can be easily controlled. The temperature of the hot air drying is preferably 30 to 100 ℃. The hot air drying time is preferably 1 to 300 seconds. The wind speed of the hot air is preferably about 10m/s to 30 m/s. The wind speed is the wind speed in the heating furnace, and can be measured by a mini-blade type digital anemometer.
B-3-8. Other treatments
The washing treatment is preferably performed after the stretching treatment in water and before the drying shrinkage treatment. The washing treatment is typically performed by immersing the PVA-based resin layer in an aqueous potassium iodide solution.
C. 1 st phase difference layer
The 1 st phase difference layer 20 may have any suitable optical and/or mechanical properties depending on the purpose. The 1 st retardation layer 20 typically has a slow axis. In one embodiment, the angle θ formed by the slow axis of the 1 st retardation layer 20 and the absorption axis of the polarizing film 11 is 40 ° to 50 °, preferably 42 ° to 48 °, and more preferably about 45 °, as described above. When the angle θ is within such a range, a polarizing plate with a retardation layer having very excellent circular polarization characteristics (as a result, very excellent antireflection characteristics) can be obtained by forming the 1 st retardation layer into a λ/4 plate as described later.
The preferred refractive index characteristics of the 1 st retardation layer show a relationship of nx > ny.gtoreq.nz. The 1 st retardation layer is typically provided to impart anti-reflection properties to the polarizing plate, and in one embodiment, can function as a λ/4 plate. In this case, the in-plane retardation Re (550) of the 1 st retardation layer is preferably 100nm to 190nm, more preferably 110nm to 170nm, and still more preferably 130nm to 160nm. Here, "ny=nz" includes not only the case where ny is completely equal to nz but also the case where ny is substantially equal to nz. Therefore, ny < nz may be present within a range that does not impair the effect of the present invention.
The Nz coefficient of the 1 st retardation layer is preferably 0.9 to 3, more preferably 0.9 to 2.5, still more preferably 0.9 to 1.5, and particularly preferably 0.9 to 1.3. By satisfying such a relationship, when the obtained polarizing plate with a retardation layer is used in an image display device, a very excellent reflection hue can be achieved.
The 1 st phase difference layer may exhibit an inverse dispersion wavelength characteristic in which the phase difference value increases with the wavelength of the measurement light, a positive dispersion wavelength characteristic in which the phase difference value decreases with the wavelength of the measurement light, or a flat dispersion wavelength characteristic in which the phase difference value hardly changes with the wavelength of the measurement light. In one embodiment, the 1 st phase difference layer shows inverse dispersion wavelength characteristics. In this case, re (450)/Re (550) of the retardation layer is preferably 0.8 or more and less than 1, more preferably 0.8 or more and 0.95 or less. With such a configuration, extremely excellent antireflection characteristics can be achieved.
The 1 st phase difference layer preferably has an absolute value of photoelastic coefficient of 2×10 -11 m 2 N or less, more preferably 2.0X10 -13 m 2 /N～1.5×10 -11 m 2 N, further preferably 1.0X10 -12 m 2 /N～1.2×10 -11 m 2 Resin of/N. When the absolute value of the photoelastic coefficient is within such a range, a change in phase difference is less likely to occur when shrinkage stress occurs during heating. As a result, thermal unevenness of the obtained image display device can be prevented well.
The 1 st retardation layer is typically a stretched film of a resin film. In one embodiment, the thickness of the 1 st retardation layer is preferably 70 μm or less, more preferably 45 μm to 60 μm. When the thickness of the 1 st retardation layer is within such a range, the curl at the time of heating can be favorably suppressed, and the curl at the time of bonding can be favorably adjusted. In the embodiment in which the 1 st retardation layer is made of a polycarbonate resin film as described later, the thickness of the 1 st retardation layer is preferably 40 μm or less, more preferably 10 μm to 40 μm, and still more preferably 20 μm to 30 μm. The 1 st retardation layer is formed of a polycarbonate resin film having such a thickness, and thus can suppress occurrence of curling and contribute to improvement of bending durability and reflection hue.
The 1 st retardation layer 20 may be made of any suitable resin film that satisfies the above characteristics. Typical examples of such resins include polycarbonate resins, polyester carbonate resins, polyester resins, polyvinyl acetal resins, polyarylate resins, cycloolefin resins, cellulose resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyether resins, polystyrene resins, and acrylic resins. These resins may be used alone or in combination (e.g., blending, copolymerization). When the 1 st retardation layer is formed of a resin film exhibiting reverse dispersion wavelength characteristics, a polycarbonate resin or a polyester carbonate resin (hereinafter, may be simply referred to as a polycarbonate resin) may be suitably used.
As the polycarbonate resin, any suitable polycarbonate resin may be used as long as the effects of the present invention can be obtained. For example, the polycarbonate resin contains a structural unit derived from a fluorene dihydroxy compound, a structural unit derived from an isosorbide dihydroxy compound, and a structural unit derived from at least 1 dihydroxy compound selected from the group consisting of alicyclic diol, alicyclic dimethanol, di-, tri-, and polyethylene glycol, and alkylene glycol or spiroglycol. Preferably, the polycarbonate-based resin contains a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and contains a structural unit derived from alicyclic dimethanol and/or a structural unit derived from di-, tri-or polyethylene glycol; more preferably, the composition comprises a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and a structural unit derived from a di-, tri-or polyethylene glycol. The polycarbonate resin may contain a structural unit derived from another dihydroxy compound, if necessary. The details of the polycarbonate-based resin that can be suitably used in the present invention are described in, for example, japanese patent application laid-open No. 2014-10291, japanese patent application laid-open No. 2014-26262, japanese patent application laid-open No. 2015-212816, japanese patent application laid-open No. 2015-212817, and Japanese patent application laid-open No. 2015-212818, and the descriptions are incorporated herein by reference.
The glass transition temperature of the polycarbonate resin is preferably 110 ℃ to 150 ℃, more preferably 120 ℃ to 140 ℃. If the glass transition temperature is too low, the heat resistance tends to be poor, and there is a possibility that dimensional change may occur after film formation, or the image quality of the obtained organic EL panel may be degraded. If the glass transition temperature is too high, the film may have poor molding stability during film molding or may have impaired transparency. The glass transition temperature can be obtained in accordance with JIS K7121 (1987).
The molecular weight of the polycarbonate resin can be expressed by reduced viscosity. Reduced viscosity after precisely preparing the polycarbonate concentration to 0.6g/dL using methylene chloride as a solvent, measurement was performed at a temperature of 20.0deg.C.+ -. 0.1 ℃ using a Ubbelohde viscosity tube. The lower limit of reduced viscosity is generally preferably 0.30dL/g, more preferably 0.35dL/g. The upper limit of the reduced viscosity is usually preferably 1.20dL/g, more preferably 1.00dL/g, and further preferably 0.80dL/g. If the reduced viscosity is less than the lower limit, there is a problem that the mechanical strength of the molded article may be reduced. On the other hand, if the reduced viscosity exceeds the upper limit, fluidity during molding may be reduced, and there may be a problem in that productivity and moldability may be reduced.
As the polycarbonate resin film, a commercially available film can be used. Specific examples of the commercial products include "PURE-ACE WR-S", "PURE-ACE WR-W", "PURE-ACE WR-M" manufactured by Di Kagaku Co., ltd., and "NRF" manufactured by Nito Kagaku Co., ltd.
The 1 st retardation layer 20 can be obtained by stretching a film made of the polycarbonate resin. As a method for forming a film from a polycarbonate resin, any suitable molding method can be used. Specific examples include: compression molding, transfer molding, injection molding, extrusion molding, blow molding, powder molding, FRP molding, cast coating (e.g., casting), calendaring, hot pressing, and the like. Extrusion molding or cast coating is preferred. This is because the smoothness of the obtained film can be improved and good optical uniformity can be obtained. The molding conditions may be appropriately set according to the composition and type of the resin used, the desired properties of the retardation layer, and the like. As described above, since a large number of film products are commercially available as polycarbonate-based resins, the commercially available films can be directly subjected to stretching treatment.
The thickness of the resin film (unstretched film) may be set to any appropriate value depending on the desired thickness of the 1 st retardation layer, the desired optical characteristics, stretching conditions to be described later, and the like. Preferably 50 μm to 300. Mu.m.
The stretching may be performed by any suitable stretching method or stretching conditions (for example, stretching temperature, stretching ratio, stretching direction). Specifically, various stretching methods such as free end stretching, fixed end stretching, free end shrinkage, fixed end shrinkage, and the like may be used alone, or may be used simultaneously or sequentially. The stretching direction may be performed in various directions or dimensions such as a longitudinal direction, a width direction, a thickness direction, and an oblique direction. The stretching temperature is preferably from Tg to 30℃to Tg+60℃and more preferably from Tg to 10℃to Tg+50℃relative to the glass transition temperature (Tg) of the resin film.
By appropriately selecting the stretching method and the stretching conditions, a retardation film having the desired optical characteristics (for example, refractive index characteristics, in-plane retardation, nz coefficient) can be obtained.
In one embodiment, the retardation film may be produced by uniaxially stretching or uniaxially stretching the resin film at the fixed end. A specific example of the unidirectional stretching at the fixed end is a method of stretching the resin film in the width direction (transverse direction) while moving the resin film in the longitudinal direction. The stretching ratio is preferably 1.1 to 3.5 times.
In another embodiment, the retardation film may be produced by continuously stretching a long resin film in a direction at the angle θ with respect to the longitudinal direction. By using oblique stretching, a long stretched film having an orientation angle of θ (having a slow axis in the direction of the angle θ) with respect to the longitudinal direction of the film can be obtained, and for example, a roll-to-roll can be used when laminating with a polarizing film, whereby the manufacturing process can be simplified. The angle θ may be an angle formed between an absorption axis of the polarizing film in the polarizing plate with the retardation layer and a slow axis of the retardation layer. The angle θ is preferably 40 ° to 50 °, more preferably 42 ° to 48 °, and still more preferably about 45 °, as described above.
Examples of the stretching machine used for the oblique stretching include a tenter stretching machine that imparts a conveying force or a stretching force or a drawing force at different speeds in the lateral direction and/or the longitudinal direction. The tenter type stretching machine includes a transverse unidirectional stretching machine, a simultaneous bidirectional stretching machine, and the like, and any suitable stretching machine may be used as long as the long resin film can be continuously stretched obliquely.
By appropriately controlling the speeds of the left and right sides of the stretching machine, a retardation layer (substantially long retardation film) having the desired in-plane retardation and having a slow axis in the desired direction can be obtained.
The stretching temperature of the film varies depending on the desired in-plane phase difference value and thickness of the retardation layer, the type of resin used, the thickness of the film used, the stretching ratio, and the like. Specifically, the stretching temperature is preferably from Tg to 30℃to Tg+30℃, more preferably from Tg to 15℃to Tg+15℃, and most preferably from Tg to 10℃to Tg+10℃. By stretching at such a temperature, a 1 st retardation layer having suitable characteristics can be obtained in the present invention. Tg is the glass transition temperature of the constituent material of the film.
D. 2 nd phase difference layer
The 2 nd retardation layer may be a so-called Positive C plate (Positive C-plate) having refractive index characteristics showing a relationship of nz > nx=ny as described above. By using the positive C plate as the 2 nd retardation layer, oblique reflection can be prevented well, and the antireflection function can be made wide viewing angle. In this case, the retardation Rth (550) in the thickness direction of the 2 nd retardation layer is preferably-50 nm to-300 nm, more preferably-70 nm to-250 nm, still more preferably-90 nm to-200 nm, particularly preferably-100 nm to-180 nm. Here, "nx=ny" includes not only the case where nx and ny are exactly equal but also the case where nx and ny are substantially equal. That is, the in-plane retardation Re (550) of the 2 nd retardation layer may be less than 10nm.
The 2 nd retardation layer having refractive index characteristics of nz > nx=ny may be formed of any suitable material. The 2 nd retardation layer is preferably formed of a film containing a liquid crystal material fixed in homeotropic alignment. The liquid crystal material (liquid crystal compound) that can be homeotropic alignment may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the method for forming the liquid crystal compound and the retardation layer include those described in paragraphs [0020] to [0028] of JP-A-2002-333642 and a method for forming the retardation layer. In this case, the thickness of the 2 nd retardation layer is preferably 0.5 μm to 10. Mu.m, more preferably 0.5 μm to 8. Mu.m, still more preferably 0.5 μm to 5. Mu.m.
E. Conductive layer or isotropic substrate with conductive layer
The conductive layer can be formed by forming a metal oxide film on any suitable substrate by any suitable film forming method (for example, vacuum evaporation, sputtering, CVD, ion plating, or spraying). Examples of the metal oxide include indium oxide, tin oxide, zinc oxide, indium tin composite oxide, tin antimony composite oxide, zinc aluminum composite oxide, and indium zinc composite oxide. Among them, indium tin composite oxide (ITO) is preferable.
When the conductive layer contains a metal oxide, the thickness of the conductive layer is preferably 50nm or less, more preferably 35nm or less. The lower limit of the thickness of the conductive layer is preferably 10nm.
The conductive layer may be transferred from the base material to the 1 st retardation layer (or the 2 nd retardation layer if the 2 nd retardation layer is present) and the conductive layer itself may be used as a constituent layer of the polarizing plate with a retardation layer, or may be laminated on the 1 st retardation layer (or the 2 nd retardation layer if the 2 nd retardation layer is present) in the form of a laminate with the base material (base material with a conductive layer). Preferably, the substrate is optically isotropic, and therefore, the conductive layer can be used as an isotropic substrate with a conductive layer for a polarizing plate with a retardation layer.
As the optically isotropic substrate (isotropic substrate), any suitable isotropic substrate may be used. Examples of the material constituting the isotropic substrate include a material having a main skeleton of a resin having no conjugated system such as a norbornene-based resin or an olefin-based resin, a material having a cyclic structure such as a lactone ring or a glutarimide ring in the main chain of an acrylic resin, and the like. When such a material is used, a phase difference caused by molecular chain orientation can be suppressed to be small when an isotropic substrate is formed. The thickness of the isotropic substrate is preferably 50 μm or less, more preferably 35 μm or less. The lower limit of the thickness of the isotropic substrate is, for example, 20 μm.
The conductive layer and/or the conductive layer of the isotropic substrate with conductive layer may be patterned as needed. By patterning, the via portion and the insulating portion can be formed. As a result, an electrode can be formed. The electrodes may function as touch sensor electrodes for sensing contact to the touch panel. As the patterning method, any suitable method may be employed. Specific examples of the patterning method include a wet etching method and a screen printing method.
F. Image display device
The polarizing plate with a retardation layer described in the above items A to E can be applied to an image display device. Accordingly, the present invention includes an image display device using such a polarizing plate with a retardation layer. Typical examples of the image display device include a liquid crystal display device and an Electroluminescence (EL) display device (for example, an organic EL display device and an inorganic EL display device). The image display device according to the embodiment of the present invention includes the polarizing plate with a retardation layer described in the above items a to E on the visual recognition side. The polarizing plate with the retardation layer is laminated such that the retardation layer is on the side of the image display unit (e.g., liquid crystal unit, organic EL unit, inorganic EL unit) (such that the polarizing film is on the side of visual recognition). In one embodiment, the image display device has a curved shape (substantially curved display screen), and/or may be flexed or bent. In such an image display device, the polarizing plate with a retardation layer of the present invention has a remarkable effect.
Examples
Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. The method for measuring each characteristic is as follows. Unless otherwise specified, "parts" and "%" in examples and comparative examples are based on weight.
(1) Thickness of (L)
The thickness of 10 μm or less was measured by an interferometric film thickness meter (product name "MCPD-3000" manufactured by Katsukamu electronic Co., ltd.). Thicknesses of greater than 10 μm were measured using a digital micrometer (product name "KC-351C", manufactured by Anritsu Co.).
(2) Monomer transmittance and polarization degree
The laminate (polarizing plate) of the polarizing film/protective layer used in examples and comparative examples was measured using an ultraviolet-visible spectrophotometer (V-7100 manufactured by japan spectroscopy), and the measured single transmittance Ts, parallel transmittance Tp, and orthogonal transmittance Tc were respectively used as Ts, tp, and Tc of the polarizing film. These Ts, tp, and Tc are Y values obtained by measuring and correcting the visibility using a 2 degree field of view (C light source) of JIS Z8701. The refractive index of the protective layer was 1.50, and the refractive index of the surface of the polarizing film opposite to the protective layer was 1.53.
The polarization degree P was obtained from Tp and Tc obtained by the following equation.
The polarization degree P (%) = { (Tp-Tc)/(tp+tc) } 1/2 ×100
The spectrophotometer may be used for equivalent measurement by using LPF-200 manufactured by Katsukamu electronic Co., ltd. As an example, the measured values of the cell transmittance Ts and the polarization degree P obtained by the measurement using V-7100 and LPF-200 for samples 1 to 3 of the polarizing plate having the same configuration as the following example are shown in table 1. As shown in Table 1, the difference between the measured value of the monomer transmittance of V-7100 and the measured value of the monomer transmittance of LPF-200 was 0.1% or less, and it was found that the same measurement results were obtained in the case of using any spectrophotometer.
TABLE 1
In the case of using a polarizing plate having an adhesive having Antiglare (AG) surface treatment and diffusion properties as a measurement target, for example, different measurement results are obtained by spectrophotometers, but in this case, a difference depending on the measurement values of spectrophotometers can be compensated by performing numerical conversion based on the measurement values obtained when the same polarizing plate is measured by each spectrophotometer.
(3) Uneven optical characteristics of elongated polarizing film
The measurement samples were cut out from the polarizing plates used in examples and comparative examples at 5 positions at equal intervals in the width direction, and the monomer transmittance at the central portion of each of the 5 measurement samples was measured in the same manner as in (2) above. Next, the difference between the maximum value and the minimum value of the monomer transmittance measured at each measurement position was calculated, and this value was used as the unevenness of the optical characteristics of the elongated polarizing film.
(4) Unevenness of optical characteristics of a polarizing film in a sheet form
From the polarizing plates used in examples and comparative examples, measurement samples of 100 mm. Times.100 mm were cut out, and a polarizing plate in the form of a sheet (50 cm) 2 ) Is not uniform in optical characteristics. Specifically, in the same manner as in (2) above, the monomer transmittance was measured at a position approximately 1.5cm to 2.0cm inward from the midpoint of each of the 4 sides of the measurement sample and 5 in total at the central portion. Next, the difference between the maximum value and the minimum value of the monomer transmittance measured at each measurement position was calculated, and this value was regarded as the unevenness of the optical characteristics of the polarizing film in the form of a sheet.
(5) Warp of
The polarizing plates with retardation layers obtained in examples and comparative examples were cut into dimensions of 110mm×60 mm. At this time, the polarizing film is cut so that the absorption axis direction thereof is the longitudinal direction. The cut polarizing plate with the retardation layer was bonded to a glass plate of 120mm×70mm in size and 0.2mm in thickness with an adhesive to prepare a test sample. The test specimen was put into a heating oven maintained at 85℃for 24 hours, and the amount of warpage after removal was measured. The height of the highest portion from the plane when the test sample was left standing on the plane with the glass plate facing down was taken as the warpage amount.
(6) Bending durability
The polarizing plates with retardation layers obtained in examples and comparative examples were cut into dimensions of 50mm×100 mm. At this time, the polarizing film is cut so that the absorption axis direction thereof is the short side direction. The cut polarizing plate with the retardation layer was subjected to a bending test at 20℃and 50% RH using a bending tester (CL 09 type-D01, manufactured by Yuasa Co., ltd.). Specifically, the bias with the phase difference layerThe light sheet was repeatedly bent in a direction parallel to the absorption axis direction so that the retardation layer side was the outer side, and the number of times of bending until cracks, peeling, film breakage, and the like, which caused defects, were generated was measured, and evaluated according to the following criteria (bending diameter:)。
< evaluation criterion >
Less than 1 ten thousand times: failure of
More than 1 ten thousand times and less than 3 ten thousand times: good grade (good)
More than 3 ten thousand times: excellent (excellent)
(7) Front reflection hue
The polarizing plates with retardation layers obtained in examples and comparative examples were bonded to a reflective plate (trade name "DMS-X42", manufactured by TORAY FLIM Co., ltd.; reflectance was 86%, and the reflection hue a in the absence of polarizing plates) using an acrylic adhesive having no ultraviolet absorption function * ＝-0.22、b * =0.32), a measurement sample was prepared. At this time, the retardation plate side of the polarizing plate bonded with the retardation layer is opposed to the reflection plate. The measurement sample was measured by a spectrocolorimeter (CM-2600 d manufactured by Konica Minolta) in SCE method, and a * B * Substitution of the value of (2)And the front reflection hue is obtained.
(8) Modulus of elasticity
The film to be measured was measured according to JIS K6734:2000 into a dumbbell film for a tensile test having a parallel portion width of 10mm and a length of 40mm according to JIS K7161:1994, a tensile test was performed to determine the tensile elastic modulus. Here, the longitudinal direction generally coincides with the stretching direction of the polarizing film.
Example 1
1. Manufacture of polarizing film
As the thermoplastic resin base material, an amorphous isophthalic acid-copolymerized polyethylene terephthalate film (thickness: 100 μm) having a long water absorption of 0.75% and a Tg of about 75℃was used. Corona treatment is performed on one side of the resin base material.
At 9:1 to 100 parts by weight of a PVA-based resin obtained by mixing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (trade name "GOHSEFIMER Z410" manufactured by Japanese synthetic chemical industry Co., ltd.), 13 parts by weight of potassium iodide was added, and then dissolved in water to prepare a PVA aqueous solution (coating liquid).
The PVA aqueous solution was applied to the corona treated surface of the resin substrate and dried at 60 ℃ to form a PVA-based resin layer having a thickness of 13 μm, thereby producing a laminate.
The resulting laminate was uniaxially stretched to 2.4 times in the longitudinal direction (longitudinal direction) between rolls of different peripheral speeds in an oven at 130 c (air-assisted stretching treatment).
Next, the laminate was immersed in an insolubilization bath (an aqueous boric acid solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40 ℃ for 30 seconds (insolubilization treatment).
Next, the resulting polarizing film was immersed in a dyeing bath (aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with respect to 100 parts by weight of water) at a liquid temperature of 30 ℃ for 60 seconds while adjusting the concentration so that the monomer transmittance (Ts) of the resulting polarizing film was 44.0% or more (dyeing treatment).
Then, the resultant solution was immersed in a crosslinking bath (aqueous boric acid solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40℃for 30 seconds (crosslinking treatment).
Then, the laminate was immersed in an aqueous boric acid solution (boric acid concentration: 4.0 wt%) at a liquid temperature of 70 ℃ and uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds so that the total stretching ratio became 5.5 times (in-water stretching treatment).
Thereafter, the laminate was immersed in a washing bath (aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20 ℃ (washing treatment).
Thereafter, while drying in an oven maintained at 90 ℃, a SUS heated roller with a contact surface temperature maintained at 75 ℃ was contacted for about 2 seconds (drying shrinkage treatment). The shrinkage in the width direction of the laminate based on the drying shrinkage treatment was 5.2%.
In the above manner, a polarizing film having a thickness of 5.0 μm was formed on the resin substrate.
2. Manufacture of polarizing plate
The cycloolefin film (thickness: 28 μm, elastic modulus: 2100 MPa) having a hard coat layer (refractive index: 1.53) was laminated on the surface (surface opposite to the resin substrate) of the polarizing film obtained as described above as a protective layer via an ultraviolet curable adhesive. Specifically, the cured adhesive was applied so that the total thickness of the cured adhesive was 1.0 μm, and bonded by using a roll mill. Thereafter, UV light is irradiated from the protective layer side to cure the adhesive. Then, after cutting both ends, the resin base material was peeled off to obtain a long polarizing plate (width: 1300 mm) having a configuration of a protective layer, an adhesive layer and a polarizing film. The single transmittance of the polarizing plate (substantially polarizing film) was 44.12%, and the polarization degree was 99.929%. Further, the unevenness of the optical characteristics of the elongated polarizing film was 0.27%, and the unevenness of the optical characteristics of the single sheet-like polarizing film was 0.10%.
3. Production of retardation film constituting retardation layer
3-1 polymerization of polyester carbonate resin
The polymerization was carried out using a batch polymerization apparatus consisting of 2 vertical reactors equipped with stirring blades and a reflux condenser controlled at 100 ℃. Adding bis [9- (2-phenoxycarbonylethyl) fluoren-9-yl ] ]29.60 parts by mass (0.046 mol) of methane, 29.21 parts by mass (0.200 mol) of Isosorbide (ISB), 42.28 parts by mass (0.139 mol) of Spiroglycol (SPG), 63.77 parts by mass (0.298 mol) of diphenyl carbonate (DPC) and 1.19X10 of calcium acetate monohydrate as a catalyst -2 Parts by mass (6.78X10) -5 mol). After the inside of the reactor was replaced with nitrogen under reduced pressure, the reactor was warmed by a heat medium, and stirring was started at a point in time when the internal temperature reached 100 ℃. The internal temperature was brought to 220℃40 minutes after the start of the temperature increase, and the pressure was reduced so as to be 13.3kPa after 90 minutes from the start of the temperature increase, while the temperature was kept. Introducing phenol vapor by-produced during polymerization reaction into reflux condenser at 100deg.CA small amount of monomer components contained in the phenol vapor was returned to the reactor, and the uncondensed phenol vapor was introduced into a condenser at 45 ℃ and recovered. After nitrogen gas was introduced into the 1 st reactor and once the pressure was returned to the atmospheric pressure, the oligomerization reaction liquid in the 1 st reactor was transferred to the 2 nd reactor. Then, the temperature rise and pressure reduction in the 2 nd reactor were started, and after 50 minutes, the temperature became 240℃and the pressure became 0.2kPa. Thereafter, polymerization was carried out until a predetermined stirring power was reached. At the time point when the predetermined power was reached, nitrogen gas was introduced into the reactor to restore the pressure, and the produced polyester-carbonate resin was extruded into water, and the cut material was cut to obtain pellets.
3-2 preparation of retardation film
The obtained polyester-carbonate resin (pellet) was dried under vacuum at 80℃for 5 hours, and then a film-forming apparatus comprising a single screw extruder (manufactured by Toshiba machine Co., ltd., cylinder set temperature: 250 ℃), a T-die (width: 200mm, set temperature: 250 ℃), a cooling roll (set temperature: 120 to 130 ℃) and a winder was used to prepare a long resin film having a thickness of 130. Mu.m. The obtained long resin film was stretched while being adjusted so as to obtain a predetermined retardation, thereby obtaining a retardation film having a thickness of 48. Mu.m. The stretching condition was a stretching temperature of 143℃in the width direction and a stretching magnification of 2.8 times. The Re (550) of the obtained retardation film was 141nm, re (450)/Re (550) was 0.86, and the Nz coefficient was 1.12.
4. Manufacturing of polarizing plate with phase difference layer
The retardation film obtained in the above 3 was bonded to the polarizing film surface of the polarizing plate obtained in the above 2 via an acrylic adhesive (thickness 5 μm). At this time, the absorption axis of the polarizing film and the slow axis of the retardation film were bonded to each other at an angle of 45 °. In the above-described manner, a polarizing plate with a retardation layer having a structure of a protective layer/an adhesive layer/a polarizing film/an adhesive layer/a retardation layer was obtained. The total thickness of the obtained polarizing plate with a retardation layer was 87. Mu.m. The obtained polarizing plate with a retardation layer was subjected to the evaluation of (5) and (6) above. The warpage amount was 3.4mm. The results are shown in Table 2.
Example 2
1. Manufacture of polarizing film
A polarizing film having a thickness of 5.0 μm was formed on a resin substrate in the same manner as in example 1, except that the concentration of the dyeing bath was adjusted so that the monomer transmittance (Ts) of the polarizing film was 44.0%.
2. Manufacture of polarizing plate
A polarizing plate having a configuration of a protective layer, an adhesive layer, and a polarizing film was produced in the same manner as in example 1, except that the polarizing film obtained in step 1 was used. The single transmittance of the polarizing plate (substantially polarizing film) was 44.0%, and the polarization degree was 99.960%.
3. Production of retardation film constituting retardation layer
A retardation film was obtained in the same manner as in example 1 except that Re (550) of the retardation film was stretched so as to be 144 nm.
4. Manufacturing of polarizing plate with phase difference layer
The retardation film obtained in the above 3 was laminated on the surface of the polarizing film of the polarizing plate obtained in the above 2 in the same manner as in example 1, to produce a polarizing plate with a retardation layer having a constitution of a protective layer, an adhesive layer, a polarizer, an adhesive layer and a retardation layer. The total thickness of the obtained polarizing plate with a retardation layer was 87. Mu.m. The obtained polarizing plate with the retardation layer was subjected to the evaluations of (5) to (7) above. The results are shown in Table 2.
Examples 3 to 1
1. Manufacture of polarizing film
In the same manner as in example 2, a polarizing film having a thickness of 5.0 μm was formed on a resin substrate.
2. Manufacture of polarizing plate
A polarizing plate having a configuration of a protective layer, an adhesive layer, and a polarizing film was produced in the same manner as in example 1, except that a hard-coated cellulose Triacetate (TAC) film (hard-coated thickness 7 μm, TAC thickness 25 μm, elastic modulus: 3600 MPa) was used as the protective layer. The single transmittance of the polarizing plate was 44.0% and the polarization degree was 99.960%.
3. Production of retardation film constituting retardation layer
A polyester carbonate resin (pellet) obtained in the same manner as in example 1 except that 0.7 parts by mass of PMMA was melt-kneaded was dried in vacuo at 80℃for 5 hours, and then a film-forming apparatus comprising a single screw extruder (cylinder set temperature: 250 ℃) and a T-die (width: 200mm, set temperature: 250 ℃) and a cooling roll (set temperature: 120 to 130 ℃) and a coiler was used to prepare a long resin film having a thickness of 105. Mu.m. The obtained long resin film was stretched at 138℃in the width direction 2.8 times while adjusting the film so as to obtain a predetermined retardation, and a retardation film having a thickness of 38. Mu.m was obtained. The Re (550) of the obtained retardation film was 144nm, and Re (450)/Re (550) was 0.86.
4. Manufacturing of polarizing plate with phase difference layer
The retardation film obtained in the above 3 was bonded to the polarizing film surface of the polarizing plate obtained in the above 2 via an acrylic adhesive (thickness 5 μm). At this time, the absorption axis of the polarizing film and the slow axis of the retardation film are bonded to each other at an angle of 45 °. In the above-described manner, a polarizing plate with a retardation layer having a structure of a protective layer/an adhesive layer/a polarizing film/an adhesive layer/a retardation layer was obtained. The total thickness of the obtained polarizing plate with a retardation layer was 81. Mu.m. The obtained polarizing plate with the retardation layer was subjected to the evaluations of (5) to (7) above. The results are shown in Table 2.
Examples 3 to 2
A long polyester carbonate resin film having a thickness of 105 μm obtained in the same manner as in example 3-1 was stretched in the width direction while adjusting to obtain a predetermined retardation, to obtain a retardation film having a thickness of 38. Mu.m. Re (550) of the obtained retardation film was 140nm.
A polarizing plate with a retardation layer having a structure of a protective layer, an adhesive layer, a polarizing film, an adhesive layer, and a retardation layer was obtained in the same manner as in example 3-1, except that the retardation film was used as the retardation layer. The total thickness of the obtained polarizing plate with a retardation layer was 81. Mu.m. The obtained polarizing plate with the retardation layer was subjected to the same evaluation as in example 3-1. The results are shown in Table 2.
Comparative example 1
1. Manufacture of polarizing element
A polyvinyl alcohol resin film having an average polymerization degree of 2,400, a saponification degree of 99.9 mol% and a thickness of 30 μm was prepared. The polyvinyl alcohol film was stretched to 2.4 times in the transport direction while being swollen by immersing it in a swelling bath (water bath) at 20℃for 30 seconds between rolls having different peripheral speed ratios (swelling step), and then was stretched to 3.7 times in the transport direction with respect to the original polyvinyl alcohol film (polyvinyl alcohol film not stretched at all in the transport direction) while being immersed in a dyeing bath (aqueous solution having an iodine concentration of 0.03 wt% and a potassium iodide concentration of 0.3 wt%) at 30℃so that the final stretched monomer transmittance became a desired value and dyed (dyeing step). The immersion time at this time was about 60 seconds. Next, the dyed polyvinyl alcohol film was stretched in the transport direction to 4.2 times based on the original polyvinyl alcohol film while being immersed in a crosslinking bath (aqueous solution having a boric acid concentration of 3.0 wt% and a potassium iodide concentration of 3.0 wt%) at 40 ℃. Further, the obtained polyvinyl alcohol film was immersed in a stretching bath (aqueous solution having a boric acid concentration of 4.0 wt% and a potassium iodide concentration of 5.0 wt%) at 64℃for 50 seconds, and was stretched in the transport direction to 6.0 times based on the original polyvinyl alcohol film (stretching step), and then immersed in a washing bath (aqueous solution having a potassium iodide concentration of 3.0 wt%) at 20℃for 5 seconds (washing step). The washed polyvinyl alcohol film was dried at 30℃for 2 minutes to prepare a polarizing plate (thickness: 12 μm).
2. Manufacture of polarizing plate
As the adhesive, the following aqueous solutions were used: an aqueous solution containing an acetoacetyl group-containing polyvinyl alcohol resin (average polymerization degree: 1,200, saponification degree: 98.5 mol%, acetoacetylation degree: 5 mol%) and methylolmelamine. The adhesive was used so that the thickness of the adhesive layer became 0.1 μm, a TAC film (7 μm in the hard coat layer, 25 μm in the TAC layer, and 3600 MPa) with a hard coat layer was attached to one surface of the obtained polarizer by a roll laminator, and a TAC film having a thickness of 25 μm was attached to the other surface of the polarizer, and then the polarizer was dried by heating in an oven (temperature: 60 ℃ C., time: 5 minutes) to produce a polarizing plate having a configuration of a protective layer 1 (thickness: 32 μm)/adhesive layer/polarizer/adhesive layer/protective layer 2.
3. Manufacturing of polarizing plate with phase difference layer
A retardation film was laminated on the surface of the protective layer 2 of the polarizing plate obtained in the above 2 in the same manner as in example 1 to produce a polarizing plate with a retardation layer having a constitution of protective layer 1/adhesive layer/polarizing material/adhesive layer/protective layer 2/adhesive layer/retardation layer. The total thickness of the obtained polarizing plate with a retardation layer was 122. Mu.m. The obtained polarizing plate with the retardation layer was subjected to the same evaluation as in example 2. The warpage amount was 5.3mm.
Comparative example 2
1. Manufacture of polarizing element
A polarizing plate (thickness: 12 μm) was produced in the same manner as in comparative example 1.
2. Manufacture of polarizing plate
In the same manner as in comparative example 1, a polarizing plate having a constitution of a protective layer 1 (thickness 32 μm)/adhesive layer/polarizer/adhesive layer/protective layer 2 (thickness 25 μm) was produced.
3. Production of 1 st orientation-cured layer and 2 nd orientation-cured layer constituting retardation layer
A liquid crystal composition (coating liquid) was prepared by dissolving 10g of a polymerizable liquid crystal (product name: paliocolor LC242, manufactured by BASF corporation, represented by the following formula) exhibiting a nematic liquid crystal phase and 3g of a photopolymerization initiator (product name: IRGACURE 907, manufactured by BASF corporation) for the polymerizable liquid crystal compound in 40g of toluene.
The surface of a polyethylene terephthalate (PET) film (thickness: 38 μm) was rubbed with a rubbing cloth, and an orientation treatment was performed. The orientation treatment direction was set to be 15 ° with respect to the absorption axis direction of the polarizing material when viewed from the visual recognition side when attached to the polarizing plate. Applying the liquid crystal coating liquid to the alignment-treated surface by a bar coater at 90 DEG CThe liquid crystal compound was aligned by heat-drying for 2 minutes. Using a metal halide lamp at 1mJ/cm 2 The liquid crystal layer thus formed was cured by irradiation with light, thereby forming a liquid crystal alignment cured layer a on the PET film. The thickness of the liquid crystal alignment cured layer A was 2.5. Mu.m, and the in-plane phase difference Re (550) was 270nm. Further, the liquid crystal alignment cured layer a has a refractive index distribution of nx > ny=nz.
The liquid crystal alignment cured layer B was formed on the PET film in the same manner as described above except that the coating thickness was changed and the alignment treatment direction was set to be 75 ° with respect to the absorption axis direction of the polarizing material as seen from the visual recognition side. The thickness of the liquid crystal alignment cured layer B was 1.5. Mu.m, and the in-plane retardation Re (550) was 140nm. Further, the liquid crystal alignment cured layer B has a refractive index distribution of nx > ny=nz. In addition, re (450)/Re (550) of the liquid crystal alignment cured layers A and B was 1.11.
4. Manufacturing of polarizing plate with phase difference layer
The surface of the polarizing plate obtained in the above 2 on the protective layer 2 side was sequentially transferred with the liquid crystal alignment cured layer a and the liquid crystal alignment cured layer B obtained in the above 3. At this time, transfer (bonding) was performed such that the angle formed by the absorption axis of the polarizer and the slow axis of the alignment cured layer a became 15 ° and the angle formed by the absorption axis of the polarizer and the slow axis of the alignment cured layer B became 75 °. The transfer (bonding) was performed with an ultraviolet curable adhesive (thickness 1 μm). In the above manner, a polarizing plate with a retardation layer having a structure of protective layer 1/adhesive layer/polarizing element/adhesive layer/protective layer 2/adhesive layer/retardation layer (1 st orientation cured layer/adhesive layer/2 nd orientation cured layer) was obtained. The total thickness of the obtained polarizing plate with a retardation layer was 75. Mu.m. The obtained polarizing plate with the retardation layer was subjected to the same evaluation as in example 2. The results are shown in Table 2.
Comparative example 3
1. Manufacture of polarizing film
A polarizing film having a thickness of 5.0 μm was formed on a resin substrate in the same manner as in example 1, except that the monomer transmittance (Ts) of the polarizing film was 43.0%.
2. Manufacture of polarizing plate
An acrylic film (surface refractive index 1.50, 20 μm) was laminated on the surface of the polarizing film (the surface opposite to the resin substrate) obtained as described above as a protective layer via an ultraviolet curable adhesive. Specifically, the cured adhesive was applied so that the total thickness of the cured adhesive was 1.0 μm, and bonded by using a roll mill. Thereafter, UV light is irradiated from the protective layer side to cure the adhesive. Then, after cutting both ends, the resin base material was peeled off to obtain a long polarizing plate (width: 1300 mm) having a configuration of a protective layer, an adhesive layer and a polarizing film. The single body transmittance of the polarizing plate (substantially polarizing film) was 43.0%, and the polarization degree was 99.995%.
3. Manufacturing of polarizing plate with phase difference layer
The liquid crystal alignment cured layer a and the liquid crystal alignment cured layer B obtained in the same manner as in comparative example 2 were sequentially transferred onto the polarizing film surface of the polarizing plate obtained in the above 2. In the above manner, a polarizing plate with a retardation layer having a structure of a protective layer/an adhesive layer/a polarizing film/an adhesive layer/a retardation layer (1 st orientation cured layer/adhesive layer/2 nd orientation cured layer) was obtained. The total thickness of the obtained polarizing plate with a retardation layer was 32. Mu.m. The obtained polarizing plate with the retardation layer was subjected to the same evaluation as in example 2. The results are shown in Table 2.
TABLE 2
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Comparative example 4
A polarizing film was attempted to be produced in the same manner as in example 1, except that potassium iodide was not added to the PVA aqueous solution (coating liquid), the stretching ratio in the air assist stretching treatment was set to 1.8 times, and a heating roller was not used in the drying shrinkage treatment, but the PVA-based resin layer was dissolved in the dyeing treatment and the in-water stretching treatment, and the polarizing film could not be produced. Therefore, a polarizing plate with a retardation layer cannot be manufactured.
[ evaluation ]
As is clear from the comparison between examples and comparative examples, the polarizing film of the examples of the present invention is excellent in optical characteristics and can significantly suppress warpage after the heating test. Further, it is found that excellent reflection hue can be obtained by using a phase difference layer composed of a polycarbonate-based resin (including a polyester carbonate-based resin) film in combination. Further, the bending property can be further improved by reducing the thickness of the polycarbonate resin to 40 μm or less and the thickness of the polarizing plate layer to 85 μm or less, and further using a base material having an elastic modulus of 3000MPa or more, preferably a TAC film, as the protective layer. On the other hand, the polarizing plate with the retardation layer of comparative example 3 was thin and the warpage after the heat test was significantly suppressed, but the reflection hue was large, which was unsatisfactory in terms of display characteristics.
Industrial applicability
The polarizing plate with a retardation layer of the present invention can be suitably used as a circularly polarizing plate for liquid crystal display devices, organic EL display devices and inorganic EL display devices.
Description of the reference numerals
10. Polarizing plate
11. Polarizing film
12. 1 st protective layer
13. 2 nd protective layer
20. Phase difference layer
100. Polarizing plate with phase difference layer
101. Polarizing plate with phase difference layer

Claims (10)

1. A method for manufacturing a polarizing plate with a retardation layer, wherein the polarizing plate with a retardation layer comprises a polarizing film and a protective layer on at least one side of the polarizing film,
the polarizing film is composed of a polyvinyl alcohol resin film containing a dichroic material, has a thickness of 8 μm or less, a monomer transmittance of 44.0% or more, and a polarization degree of 99.50% or more,
re (550) of the retardation layer is 100nm to 190nm, re (450)/Re (550) is 0.8 or more and less than 1,
the angle formed by the slow axis of the phase difference layer and the absorption axis of the polarizing film is 40-50 degrees,
the manufacturing method comprises the following steps: forming a polyvinyl alcohol resin layer containing iodide or sodium chloride and a polyvinyl alcohol resin on one side of a long thermoplastic resin substrate to produce a laminate; and sequentially performing an air-assisted stretching treatment, a dyeing treatment, an in-water stretching treatment, and a drying shrinkage treatment for shrinking the laminate in the width direction by using a heating roller in a heating furnace while conveying the laminate in the longitudinal direction to obtain the polarizing film,
The total contact time of the laminate and the heating roller is 1 to 20 seconds,
the temperature of the heating roller is 65-100 ℃.
2. The method for producing a polarizing plate with a retardation layer according to claim 1, wherein the protective layer is composed of a triacetyl cellulose resin film.
3. The method for producing a polarizing plate with a retardation layer according to claim 1, wherein the retardation layer is composed of a polycarbonate-based resin film.
4. The method for producing a polarizing plate with a retardation layer as claimed in claim 1, wherein the polarizing film is 50cm 2 The difference between the maximum value and the minimum value of the monomer transmittance in the region (a) is 0.2% or less.
5. The method for producing a polarizing plate with a retardation layer according to claim 1, wherein the width of the polarizing film is 1000mm or more, and the difference between the maximum value and the minimum value of the single transmittance at the position in the width direction of the polarizing film is 0.3% or less.
6. The method for producing a polarizing plate with a retardation layer according to claim 1, wherein the polarizing film has a single body transmittance of 44.5% or less and a polarization degree of 99.95% or less.
7. The method for manufacturing a polarizing plate with a retardation layer according to claim 1, further comprising: an additional retardation layer is provided on the outside of the retardation layer, and the refractive index characteristics of the additional retardation layer show a relationship of nz > nx=ny.
8. The method for manufacturing a polarizing plate with a retardation layer according to claim 1, further comprising: and a conductive layer or an isotropic base material with a conductive layer is arranged on the outer side of the phase difference layer.
9. The method for producing a polarizing plate with a retardation layer according to claim 1, wherein the polarizing plate with a retardation layer is elongated,
the manufacturing method comprises the following steps: the polarizing film is formed by laminating a long polarizing film having an absorption axis in the longitudinal direction and a long retardation layer, which is an obliquely stretched film having a slow axis in a direction at an angle of 40 DEG to 50 DEG with respect to the longitudinal direction, by means of a roll-to-roll method.
10. The method for manufacturing a polarizing plate with a retardation layer according to claim 9, comprising: the elongated polarizing plate with the retardation layer is wound into a roll.
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