TW202017988A - Polarizing plate with phase difference layer and image display device using the same wherein the polarizing plate is thin, excellent in handling capability, and excellent in optical characteristics - Google Patents

Abstract

The present invention provides a polarizing plate with a phase difference layer, which is thin, excellent in handling capability, and excellent in optical characteristics. The polarizing plate with a phase difference layer of the present invention is provided with a polarizing plate and a phase difference layer, wherein the polarizing plate includes a polarizing film and a protective layer arranged at least on one side of the polarizing film. The polarizing film is composed of a polyvinyl alcohol-based resin film containing a dichroic material, which has a thickness of 8 <mu>m or less, a single transmittance of 43.0% or more, and a polarization degree of 99.980% or more. The phase difference layer is an alignment cured layer of a liquid crystal compound.

Description

Polarizing plate with phase difference layer and image display device using the polarizing plate with phase difference layer

Field of invention The present invention relates to a polarizing plate with a phase difference layer and an image display device using the polarizing plate with a phase difference layer.

Background of the invention In recent years, image display devices represented by liquid crystal display devices and electroluminescence (EL) display devices (for example, organic EL display devices, inorganic EL display devices) are rapidly spreading. In image display devices, polarizing plates and retardation plates are typically used. In practical use, a polarizing plate with a phase difference layer integrated with a polarizing plate and a phase difference plate is widely used (for example, Patent Document 1). Recently, as the expectation of thinner image display devices has increased, The expectation of the thinning of the polarizing plate of the phase difference layer is also increasing. In addition, in recent years, expectations for curved image display devices and/or flexible or bendable image display devices are increasing, and further thinning and softening of polarizing plates and polarizing plates with retardation layers are also required . For the purpose of reducing the thickness of the polarizing plate with a retardation layer, the protective layer of the polarizing film and the retardation film that contribute greatly to the thickness have been thinned. However, if the protective layer and the retardation film are thinned, the influence of shrinkage of the polarizing film becomes relatively large, and problems such as warpage of the image display device and reduced operability of the polarizing plate with a retardation layer occur.

In order to solve the above-mentioned problems, it is necessary to thin the polarizing film together. However, if the thickness of the polarizing film is simply reduced, the optical characteristics are reduced. More specifically, one or both of the degree of polarization and the transmittance of the monomer having a trade-off relationship may be reduced to a level that is not practically acceptable. As a result, the optical characteristics of the polarizing plate with a retardation layer also become insufficient. Existing technical literature Patent Literature

Patent Document 1: Japanese Patent No. 3325560

Problems to be solved by the invention The present invention is made to solve the above-mentioned conventional problems, and its main object is to provide a polarizing plate with a retardation layer which is thin, excellent in handleability, and excellent in optical characteristics. way of solving the problem

The polarizing plate with a phase difference layer of the present invention includes a polarizing plate and a phase difference layer. The polarizing plate includes a polarizing film and a protective layer provided on at least one side of the polarizing film. The polarizing film is composed of a polyvinyl alcohol-based resin film containing a dichroic substance, the thickness thereof is 8 μm or less, the monomer transmittance is 43.0% or more, and the degree of polarization is 99.980% or more. The retardation layer is an oriented cured layer of a liquid crystal compound. In one embodiment, the unit weight of the polarizing plate with a phase difference layer is 6.5 mg/cm ² or less. In one embodiment, the polarizing plate with a phase difference layer has a total thickness of 60 μm or less. In one embodiment, the phase difference layer is a single layer of an orientation curing layer of a liquid crystal compound, Re (550) of the phase difference layer is 100 nm to 190 nm, the slow axis of the phase difference layer is related to the absorption axis of the polarizing film The angle formed is 40°~50°. In one embodiment, the phase difference layer has a laminated structure of an alignment cured layer of a first liquid crystal compound and an alignment cured layer of a second liquid crystal compound; Re (550) of the alignment cured layer of the first liquid crystal compound is 200 nm to 300 nm , The angle formed by the slow axis and the absorption axis of the polarizing film is 10°~20°; the Re(550) of the alignment cured layer of the second liquid crystal compound is 100nm~190nm, and the absorption of the slow axis and the polarizing film The angle formed by the shaft is 70°~80°. In one embodiment, the difference between the maximum value and the minimum value of the unit transmittance of the polarizing film in the 50 cm ² region is 0.2% or less. In one embodiment, the width of the polarizing plate with a phase difference layer is 1000 mm or more, and the difference between the maximum value and the minimum value of the cell transmittance at the position of the polarizing film in the width direction is 0.3% or less. In one embodiment, the polarizing film has a single transmittance of 43.5% or less and a degree of polarization of 99.998% or less. In one embodiment, the polarizing plate with a phase difference layer further has another phase difference layer outside the phase difference layer, and the refractive index characteristics of the other phase difference layer show a relationship of nz>nx=ny. In one embodiment, the polarizing plate with a phase difference layer further has a conductive layer or an isotropic base material with a conductive layer outside the phase difference layer. According to other aspects of the present invention, an image display device is provided. This video display device includes the above-mentioned polarizing plate with a phase difference layer. In one embodiment, the image display device is an organic electroluminescence display device or an inorganic electroluminescence display device. Effect of invention

According to the present invention, a combination of adding a halide (typically potassium iodide) to a polyvinyl alcohol (PVA)-based resin, two-stage stretching including air-assisted stretching and underwater stretching, and drying and heating using a heating roller By shrinking, a thin polarizing film with very excellent optical characteristics can be obtained. By using such a polarizing film, a polarizing plate with a retardation layer that is thin, excellent in handleability, and excellent in optical characteristics can be realized.

Detailed description of the preferred embodiment Hereinafter, the embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

(Definition of terms and symbols) The definitions of terms and symbols in this specification are as follows. (1) Refractive index (nx, ny, nz) "Nx" is the refractive index in the direction in which the in-plane refractive index reaches the maximum (ie, slow axis direction), "ny" is the refractive index in the direction orthogonal to the slow axis (ie, fast axis direction) in the plane, "nz" Is the refractive index in the thickness direction. (2) In-plane phase difference (Re) "Re(λ)" is an in-plane phase difference measured at 23°C with light having a wavelength of λnm. For example, "Re(550)" is an in-plane phase difference measured at 23°C with light having a wavelength of 550 nm. When the thickness of the layer (thin film) is d (nm), Re(λ) can be obtained by the formula: Re(λ)=(nx-ny)×d. (3) Phase difference in thickness direction (Rth) "Rth(λ)" is the phase difference in the thickness direction measured at 23°C with light having a wavelength of λnm. For example, “Rth(550)” is the phase difference in the thickness direction measured at 23° C. with light having a wavelength of 550 nm. When the thickness of the layer (thin film) is d (nm), Rth(λ) can be obtained by the formula: Rth(λ)=(nx-nz)×d. (4) Nz coefficient The Nz coefficient is obtained by Nz=Rth/Re. (5) Angle In this specification, when referring to an angle, the angle includes both clockwise and counterclockwise relative to the reference direction. Therefore, for example, "45°" means ±45°.

A. Overall configuration of polarizing plate with retardation layer FIG. 1 is a schematic cross-sectional view of a polarizing plate with a phase difference layer according to an embodiment of the present invention. The polarizing plate with retardation layer 100 of this embodiment includes the polarizing plate 10 and the retardation layer 20. The polarizing plate 10 includes a polarizing film 11, a first protective layer 12 disposed on one side of the polarizing film 11, and a second protective layer 13 disposed on the other side of the polarizing film 11. Depending on the purpose, one of the first protective layer 12 and the second protective layer 13 may be omitted. For example, when the retardation layer 20 can also function as a protective layer of the polarizing film 11, the second protective layer 13 may be omitted. In the embodiment of the present invention, the polarizing film is composed of a polyvinyl alcohol-based resin film containing a dichroic substance. The thickness of the polarizing film is 8 μm or less, the single transmittance is 43.0% or more, and the degree of polarization is 99.980% or more.

As shown in FIG. 2, in the polarizing plate with a phase difference layer 101 of another embodiment, another phase difference layer 50 and/or a conductive layer or an isotropic base material 60 with a conductive layer may be provided. The other retardation layer 50 and the conductive layer or the isotropic base material 60 with the conductive layer are typically provided outside the retardation layer 20 (the side opposite to the polarizing plate 10 ). The refractive index characteristics of other retardation layers typically show the relationship nz>nx=ny. Typically, another phase difference layer 50 and a conductive layer or an isotropic base material 60 with a conductive layer are provided in order from the phase difference layer 20 side. Typically, the other retardation layer 50 and the conductive layer or the isotropic substrate 60 with the conductive layer are any layers provided as needed, and either or both of them may be omitted. It should be noted that, for convenience, the phase difference layer 20 may be referred to as a first phase difference layer, and the other phase difference layer 50 may be referred to as a second phase difference layer. It should be noted that when a conductive layer or an isotropic substrate with a conductive layer is provided, the polarizing plate with a phase difference layer can be applied between the image display unit (such as an organic EL unit) and the polarizing plate. The so-called touch panel type input display device of the touch sensor.

In the embodiment of the present invention, the first retardation layer 20 is an oriented cured layer of a liquid crystal compound. The first retardation layer 20 may be a single layer of the orientation-cured layer shown in FIGS. 1 and 2, or may have a laminated structure of the first orientation-cured layer 21 and the second orientation-cured layer 22 shown in FIG. 3.

The above-mentioned embodiments can be combined as appropriate, and those skilled in the art can obviously change the constituent elements in the above-mentioned embodiments. For example, the second retardation layer 50 and/or the conductive layer or the isotropic base material 60 with a conductive layer may be provided on the polarizing plate 102 with a phase difference layer in FIG. 3. In addition, for example, the configuration in which the isotropic base material 60 with a conductive layer is provided outside the second retardation layer 50 may be replaced with an optically equivalent configuration (for example, a laminate of the second retardation layer and the conductive layer) .

The polarizing plate with a retardation layer according to an embodiment of the present invention may further include other retardation layers. The optical characteristics (for example, refractive index characteristics, in-plane retardation, Nz coefficient, photoelastic coefficient), thickness, arrangement position, etc. of other retardation layers can be appropriately set according to purposes.

The polarizing plate with a phase difference layer of the present invention may be monolithic or long. In this specification, the "long shape" refers to an elongated shape having a sufficiently long length relative to a width, and includes, for example, an elongated shape with a length of 10 times or more, preferably 20 times or more. A long polarizing plate with a phase difference layer can be wound into a roll shape.

In actual use, an adhesive layer (not shown) may be provided on the opposite side of the phase difference layer from the polarizing plate, so that the polarizing plate with the phase difference layer can be adhered to the image display unit. In addition, it is preferable to temporarily stick a release film on the surface of the adhesive layer until the polarizing plate with the phase difference layer is ready for use. By temporarily sticking the peeling film, the adhesive layer can be protected and a coil can be formed.

The total thickness of the polarizing plate with a retardation layer is preferably 60 μm or less, more preferably 55 μm or less, still more preferably 50 μm or less, and particularly preferably 40 μm or less. The lower limit of the total thickness may be 28 μm, for example. According to the embodiments of the present invention, a very thin polarizing plate with a phase difference layer can be realized in this way. Such a polarizing plate with a retardation layer can have very excellent flexibility and bending durability. Such a polarizing plate with a phase difference layer may be particularly suitable for a curved image display device and/or a flexible or bendable image display device. It should be noted that the total thickness of the polarizing plate with a retardation layer refers to a polarizing plate with a retardation layer other than an adhesive layer for adhering the polarizing plate to an external adherend such as a panel and glass. Total thickness of all layers (that is, the total thickness of the polarizing plate with a phase difference layer does not include the adhesive layer for adhering the polarizing plate with a phase difference layer to adjacent components such as an image display unit and can be temporarily adhered to the surface Thickness of the release film).

The unit weight of the polarizing plate with a retardation layer according to an embodiment of the present invention is, for example, 6.5 mg/cm ² or less, preferably 2.0 mg/cm ² to 6.0 mg/cm ² , and more preferably 3.0 mg/cm ² to 5.5 mg /cm ² , more preferably 3.5 mg/cm ² to 5.0 mg/cm ² . When the display panel is thin, the panel is slightly deformed due to the weight of the polarizing plate with a retardation layer, which may cause display defects. According to the polarizing plate with a retardation layer having a unit weight of 6.5 mg/cm ² or less, Prevent deformation of such panels. In addition, the polarizing plate with a phase difference layer having the above unit weight has good handling properties even when it is thinned, and can exhibit very excellent flexibility and bending durability.

Hereinafter, the constituent elements of the polarizing plate with a phase difference layer will be described in more detail.

B. Polarizer B-1. Polarizing film As described above, the thickness of the polarizing film 11 is 8 μm or less, the single transmittance is 43.0% or more, and the degree of polarization is 99.980% or more. Generally speaking, there is a trade-off relationship between the monomer transmittance and the degree of polarization. If the monomer transmittance is increased, the polarization degree will decrease, and if the polarization degree is increased, the monomer transmittance will decrease. Therefore, in the past, it has always been difficult to provide a thin polarizing film that satisfies the optical characteristics of the monomer transmittance of 43.0% or more and the degree of polarization of 99.980% or more in practical use. It is one of the characteristics of the present invention to use a thin polarizing film having a single transmittance of 43.0% or more and a polarization degree of 99.980% or more, which is excellent in optical characteristics and in which variations in optical characteristics are suppressed.

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 380 nm to 780 nm. The monomer transmittance of the polarizing film is preferably 43.5% or less. The polarization degree of the polarizing film is preferably 99.990% or more, and more preferably 99.998% or less. The above-mentioned monomer transmittance is typically a Y value obtained by measuring with an ultraviolet-visible spectrophotometer and performing visibility correction. The above-mentioned polarization degree is typically based on the parallel transmittance Tp and the orthogonal transmittance Tc measured by using an ultraviolet-visible spectrophotometer and corrected for visibility, and is obtained by the following formula. Polarization (%) = {(Tp－Tc)/(Tp＋Tc)} ^1/2 × 100

In one embodiment, the transmittance of a thin polarizing film of 8 μm or less typically uses a laminate of a polarizing film (refractive index on the surface: 1.53) and a protective film (refractive index: 1.50) as the measurement object, and uses ultraviolet-visible spectroscopy Photometric measurement. Depending on the refractive index of the surface of the polarizing film and/or the refractive index of the surface of the protective film that contacts the air interface, the reflectance at the interface of each layer changes, and as a result, the measured value of the transmittance may change. Therefore, for example, when a protective film having a refractive index other than 1.50 is used, the measured value of transmittance can be corrected based on the refractive index of the surface of the protective film that contacts the air interface. Specifically, the correction value C of the transmittance is represented by the following formula using the reflectance R ₁ (transmission axis reflectance) of polarized light parallel to the transmission axis at the interface between the protective film and the air layer. 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) where R ₀ is the transmission axis reflectance when a protective film with a refractive index of 1.50 is used, n ₁ is the refractive index of the protective film used, and T ₁ is the transmittance of the polarizing film. For example, when a substrate having a surface refractive index of 1.53 (cycloolefin-based film, hard-coated film, etc.) is used as the protective film, the correction amount C becomes about 0.2%. In this case, by adding 0.2% to the transmittance obtained by the measurement, it can be converted into the transmittance when the protective film having a surface refractive index of 1.50 is used. In addition, according to the calculation based on the above formula, the amount of change in the correction value C when the transmittance T _{1 of the} polarizing film is changed by 2% is 0.03% or less, and the transmittance of the polarizing film contributes to the value of the correction value C The impact is limited. In addition, in the case where the protective film has absorption other than surface reflection, it can be corrected appropriately according to the absorption amount.

In one embodiment, the width of the polarizing plate with a phase difference layer is 1000 mm or more, so the width of the polarizing film is also 1000 mm or more. In this case, the difference (D1) between the maximum value and the minimum value of the monomer transmittance at the position along the width direction of the polarizing film is preferably 0.3% or less, more preferably 0.25% or less, and still more preferably 0.2% or less, It is particularly preferably 0.17% or less. The smaller D1 is, the more preferable, and the lower limit of D1 may be 0.01%, for example. When D1 is within the above range, a polarizing plate with a retardation layer having excellent optical characteristics can be industrially manufactured. In another embodiment, the difference (D2) between the maximum value and the minimum value of the monomer transmittance of the polarizing film in the 50 cm ² region is preferably 0.2% or less, more preferably 0.15% or less, and still more preferably 0.1% or less. The smaller D2 is, the more preferable. The lower limit of D2 may be, for example, 0.01%. When D2 is within the above range, it is possible to suppress uneven brightness in the display screen when a polarizing plate with a phase difference layer is used in an image display device.

As the polarizing film, any appropriate polarizing film can be used. The polarizing film can typically be produced using a laminate of two or more layers.

Specific examples of the polarizing film obtained using the laminate include a polarizing film obtained by using a laminate of a resin substrate and a PVA-based resin layer formed on the resin substrate. A polarizing film obtained by using a laminate of a resin substrate and a PVA-based resin layer formed on the resin substrate can be produced by, for example, applying a PVA-based resin solution to the resin substrate and drying it. A PVA-based resin layer is formed on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; the laminate is stretched and dyed to make the PVA-based resin layer into a polarizing film. In the present embodiment, stretching typically includes immersing the laminate in a boric acid aqueous solution to perform stretching. In addition, the stretching may further include aerial stretching at a high temperature (for example, 95° C. or higher) before stretching in the boric acid aqueous solution as necessary. The obtained resin substrate/polarizing film laminate can be used directly (that is, the resin substrate can be used as a protective layer of the polarizing film), or the resin substrate can be peeled from the resin substrate/polarizing film laminate and the Any appropriate protective layer according to the purpose is laminated and used on the peeling surface. Details of the manufacturing method of such a polarizing film are described in, for example, Japanese Patent Laid-Open No. 2012-73580. The entire description of this publication can be incorporated into this specification by reference.

The manufacturing method of the polarizing film typically includes: forming a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin on one side of a long thermoplastic resin substrate to form a laminate; The air-assisted stretching treatment, dyeing treatment, underwater stretching treatment, and drying shrinkage treatment by heating in the longitudinal direction to shrink it by 2% or more in the width direction are sequentially performed. Thereby, a polarizing film having a thickness of 8 μm or less, a single transmittance of 43.0% or more, and a polarization degree of 99.980% or more, having excellent optical characteristics and suppressing variations in optical characteristics can be provided. That is, by introducing auxiliary stretching, even when PVA is coated on a thermoplastic resin, the crystallinity of PVA can be improved, and high optical characteristics can be achieved. In addition, by improving the orientation of PVA in advance, it is possible to prevent problems such as a decrease in orientation of PVA and dissolution when immersed in water in the subsequent dyeing step and drawing step, and high optical characteristics can be achieved. In addition, when the PVA-based resin layer is immersed in a liquid, compared with the case where the PVA-based resin layer does not contain a halide, it is possible to suppress the disorder of the orientation of the polyvinyl alcohol molecules and the decrease in the orientation. Thereby, the optical characteristics of the polarizing film obtained by the treatment step of immersing the laminate in the liquid through dyeing treatment, water stretching treatment, etc. can be improved. In addition, the shrinkage of the laminate in the width direction by the drying shrinkage treatment can improve the optical characteristics.

B-2. Protective layer The first protective layer 12 and the second protective layer 13 may each be formed of any appropriate thin film that can be used as a protective layer of a polarizing film. Specific examples of the material that becomes the main component of the film include cellulose resins such as cellulose triacetate (TAC) and polyesters, polyvinyl alcohols, polycarbonates, polycarbonates, polyamides, and polyimides. Transparent resins such as polyethers, polyethers, polystyrenes, polystyrenes, polynorcamenes, polyolefins, (meth)acrylics, acetates, etc. In addition, thermosetting resins such as (meth)acrylics, urethanes, (meth)acrylics urethanes, epoxys, and polysiloxanes, ultraviolet curing resins, and the like can also be mentioned. In addition to this, glassy polymers such as siloxane-based polymers can also be mentioned. In addition, the polymer film described in Japanese Patent Laid-Open No. 2001-343529 (WO01/37007) may also be used. As the material of the film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted amide imide group in the side chain, and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain, For example, a resin composition having an alternating copolymer formed of isobutylene and N-methylmaleimide, and an acrylonitrile-styrene copolymer. The polymer film may be, for example, an extruded product of the resin composition described above.

As described later, the polarizing plate with a phase difference layer of the present invention is typically arranged on the visible side of the image display device, and the first protective layer 12 is typically arranged on the visible side. Therefore, if necessary, the first protective layer 12 may be subjected to surface treatments such as hard coating treatment, anti-reflection treatment, anti-adhesion treatment, and anti-glare treatment. In addition/or, if necessary, the first protective layer 12 may be subjected to a process for improving the visibility of the polarizing sunglasses when it is visually recognized (typically, it is given an (elliptical) circular polarized light function and an ultrahigh phase difference) . By performing such processing, even when the display screen is visually recognized through polarized lenses such as polarized sunglasses, excellent visibility can be achieved. Therefore, the polarizing plate with a phase difference layer can also be applied to an image display device that can be used outdoors.

The thickness of the first protective layer is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, and still more preferably 10 μm to 30 μm. It should be noted that when surface treatment is performed, the thickness of the outer protective layer includes the thickness of the surface treatment layer.

In one embodiment, the second protective layer 13 is preferably optically isotropic. In this specification, "is optically isotropic" means that the in-plane retardation Re (550) is 0 nm to 10 nm, and the thickness direction retardation Rth (550) is -10 nm to +10 nm. In one embodiment, the second protective layer 13 may be a phase difference layer having any appropriate phase difference value. In this case, the in-plane phase difference Re(550) of the phase difference layer is, for example, 110 nm to 150 nm. The thickness of the second protective layer is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, and still more preferably 10 μm to 30 μm. From the viewpoint of thinning and weight reduction, it is preferable that the second protective layer can be omitted.

B-3. Manufacturing method of polarizing film The polarizing film can be produced by a method including the steps of, for example, forming a polyvinyl alcohol-based resin layer (PVA-based) containing a halide and a polyvinyl alcohol-based resin (PVA-based resin) on one side of a long thermoplastic resin substrate Resin layer), a laminate is made; and the laminate is sequentially subjected to air assisted stretching treatment, dyeing treatment, underwater stretching treatment, and heated while being transported in the longitudinal direction to shrink it by 2% or more in the width direction The drying shrinkage treatment. 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 heating roller, and the temperature of the heating roller is preferably 60°C to 120°C. The shrinkage rate of the laminate in the width direction due to the drying shrinkage treatment is preferably 2% or more. According to such a manufacturing method, the polarizing film described in the above item B-1 can be obtained. In particular, a laminate including a halide-containing PVA-based resin layer is prepared, and the laminate is stretched to perform multi-stage stretching including air-assisted stretching and underwater stretching, and the stretched laminate is heated with a heating roller By heating, it is possible to obtain a polarizing film having excellent optical characteristics (typically, the transmittance and polarization degree of the monomer), and the variation of the optical characteristics is suppressed. Specifically, by using a heating roller in the drying and shrinking treatment step, it is possible to uniformly shrink the entire laminated body while transporting the laminated body. Thereby, not only can the optical characteristics of the obtained polarizing film be improved, but also a polarizing film excellent in optical characteristics can be stably produced, and variations in the optical characteristics (particularly the transmittance of the monomer) of the polarizing film can be suppressed.

B-3-1. Production of laminated body As a method for producing a laminate of a thermoplastic resin base material and a PVA-based resin layer, any appropriate method can be adopted. It is preferable to apply a coating liquid containing a halide and a PVA-based resin to the surface of the thermoplastic resin substrate and dry, thereby forming a PVA-based resin layer on the thermoplastic resin substrate. As described above, 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.

As a coating method of the coating liquid, any appropriate method can be adopted. For example, a roll coating method, a spin coating method, a wire-wound bar coating method, a dip coating method, a die coating method, a shower coating method, a spray coating method, a blade coating method (angular wheel coating method, etc.), etc. are mentioned. The coating/drying temperature of the coating liquid is preferably 50°C or higher.

The thickness of the PVA-based resin layer is preferably 3 μm to 40 μm, and more preferably 3 μm to 20 μm.

Before forming the PVA-based resin layer, the thermoplastic resin substrate may be subjected to surface treatment (for example, corona treatment, etc.), or an easy adhesion 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 substrate is preferably 20 μm to 300 μm, and more preferably 50 μm to 200 μm. If it is less than 20 μm, it may be difficult to form a PVA-based resin layer. When it exceeds 300 μm, for example, in the water stretching process to be described later, it may take a long time for the thermoplastic resin substrate to absorb water, and an excessive load may be required for stretching.

The water absorption rate of the thermoplastic resin substrate is preferably 0.2% or more, and more preferably 0.3% or more. The thermoplastic resin base material absorbs water, and the water acts like a plasticizer and can be plasticized. As a result, the tensile stress can be greatly reduced, and stretching can be performed at a high rate. On the other hand, the water absorption rate of the thermoplastic resin substrate is preferably 3.0% or less, and more preferably 1.0% or less. By using such a thermoplastic resin base material, it is possible to prevent defects such as a significant decrease in the dimensional stability of the thermoplastic resin base material at the time of manufacture and deterioration of the appearance of the obtained polarizing film. In addition, it is possible to prevent the base material from breaking during water stretching, and the PVA-based resin layer peeling off from the thermoplastic resin base material. In addition, the water absorption rate of the thermoplastic resin base material can be adjusted, for example, by introducing a modifying group into the constituent material. The water absorption rate is a value determined in accordance with JIS K 7209.

The glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 120° C. or lower. By using such a thermoplastic resin base material, the crystallization of the PVA-based resin layer can be suppressed, and the stretchability of the laminate can be sufficiently ensured. In addition, in consideration of plasticization of the thermoplastic resin substrate by water and good water stretching, it is more preferably 100°C or lower, and still more preferably 90°C or lower. On the other hand, the glass transition temperature of the thermoplastic resin substrate is preferably 60° C. or higher. By using such a thermoplastic resin substrate, it is possible to prevent defects such as deformation (for example, unevenness, slack, wrinkles, etc.) of the thermoplastic resin substrate when coating/drying with the coating solution containing the PVA-based resin described above, and it is possible to satisfactorily Production of a laminate. In addition, the PVA-based resin layer can be stretched satisfactorily at an appropriate temperature (for example, about 60°C). The glass transition temperature of the thermoplastic resin base material can be adjusted by, for example, using a crystallization material that introduces modified groups into the constituent material and heating. The glass transition temperature (Tg) is a value determined in accordance with JIS K 7121.

As a constituent material of the thermoplastic resin base material, any appropriate thermoplastic resin can be used. Examples of the thermoplastic resins include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, and polycarbonate Ester resins, their copolymer resins, etc. Among these, norbornene-based resins and amorphous polyethylene terephthalate-based resins are preferred.

In one embodiment, an amorphous (uncrystallized) polyethylene terephthalate-based resin is preferably used. Among them, it is particularly preferable to use an amorphous (not easily crystallized) polyethylene terephthalate resin. Specific examples of the amorphous polyethylene terephthalate resin include copolymers further containing isophthalic acid and/or cyclohexane dicarboxylic acid as the dicarboxylic acid, and further containing cyclohexane Dimethanol and diethylene glycol are copolymers of diol.

In a preferred embodiment, the thermoplastic resin substrate is composed of a polyethylene terephthalate-based resin having isophthalic acid units. This is because such a thermoplastic resin substrate is very excellent in stretchability, and can suppress crystallization during stretching. It is considered that this is because the introduction of isophthalic acid units gives large deflection to the main chain. The polyethylene terephthalate-based resin has terephthalic acid units and ethylene glycol units. The content ratio of isophthalic acid units relative to the total of all repeating units is preferably 0.1 mol% or more, and more preferably 1.0 mol% or more. This is because a thermoplastic resin base material having excellent stretchability can be obtained. On the other hand, the content ratio of isophthalic acid units relative to the total of all repeating units is preferably 20 mol% or less, and more preferably 10 mol% or less. By setting to such a content ratio, the crystallinity can be improved satisfactorily in the drying shrinkage treatment described later.

The thermoplastic resin substrate may be stretched in advance (before the PVA-based resin layer is formed). In one embodiment, the elongated thermoplastic resin substrate can be stretched in the lateral direction. The lateral direction is preferably a direction orthogonal to the stretching direction of the laminate to be described later. In addition, in this specification, "orthogonal" also includes the case where it is substantially orthogonal. Here, "substantially orthogonal" includes the case of 90°±5.0°, preferably 90°±3.0°, and more preferably 90°±1.0°.

With respect to the glass transition temperature (Tg), the stretching temperature of the thermoplastic resin substrate is preferably Tg-10°C to Tg+50°C. The stretching ratio of the thermoplastic resin substrate is preferably 1.5 times to 3.0 times.

As a method of stretching the thermoplastic resin substrate, any appropriate method can be adopted. Specifically, it may be fixed-end stretching or free-end stretching. The stretching method may be dry or wet. The stretching of the thermoplastic resin substrate may be performed in one step or in multiple steps. When performing in multiple stages, the above-mentioned stretching magnification is the product of the stretching magnifications in each stage.

B-3-1-2. Coating liquid The coating liquid contains halide and PVA resin as described above. 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 polyhydric alcohols such as water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various diols, and trimethylolpropane. Amines, ethylenediamine, diethylenetriamine and other amines. They can be used alone 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. With such a resin concentration, a uniform coating film that is in close contact with the thermoplastic resin substrate can be formed. The content 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.

Additives can be blended in the coating liquid. Examples of additives include plasticizers and surfactants. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. Examples of the surfactant include nonionic surfactants. These additives are used for the purpose of further improving the uniformity, dyeability, and stretchability of the obtained PVA-based resin layer.

As the PVA-based resin, any appropriate resin can be used. For example, polyvinyl alcohol and ethylene-vinyl alcohol copolymer can be mentioned. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer can be obtained by saponifying the 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%, and further preferably 99.0 mol% to 99.93 mol%. The degree of saponification can be determined in accordance with JIS K 6726-1994. By using such a saponification degree PVA resin, a polarizing film excellent in durability can be obtained. When the degree of saponification is too high, there is a fear of gelation.

The average degree of polymerization of the PVA-based resin can be appropriately selected according to the purpose. The average degree of polymerization is usually 1,000 to 10,000, preferably 1,200 to 4,500, and more preferably 1,500 to 4,300. In addition, the average degree of polymerization can be determined in accordance with JIS K 6726-1994.

As the above halide, any suitable halide can be used. Examples 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 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. When the amount of halide exceeds 20 parts by weight with respect to 100 parts by weight of the PVA-based resin, the halide may bleed out, and the polarizing film finally obtained may become cloudy.

In general, by stretching the PVA-based resin layer, the orientation of the polyvinyl alcohol molecules in the PVA-based resin is improved. However, if the stretched PVA-based resin layer is immersed in a liquid containing water, there is polymerization. The orientation of vinyl alcohol molecules is disordered and the orientation is reduced. In particular, when the laminate of the thermoplastic resin substrate and the PVA-based resin layer is stretched in boric acid water, the laminate is stretched in boric acid water at a relatively high temperature in order to stabilize the stretching of the thermoplastic resin substrate. At this time, the tendency of the above-mentioned orientation degree to decrease is remarkable. For example, the stretching of the PVA film monomer in boric acid water is usually carried out at 60°C, while the stretching of the laminate of A-PET (thermoplastic resin substrate) and PVA-based resin layer is at a temperature of about 70°C. Such a high temperature process is performed. In this case, the orientation of the PVA in the initial stage of stretching decreases before it is increased by underwater stretching. In contrast, by preparing a laminate of a halide-containing PVA-based resin layer and a thermoplastic resin base material, and before stretching the laminate in boric acid water, high-temperature stretching (auxiliary stretching) is performed in the air by This can promote crystallization of the PVA-based resin in the PVA-based resin layer of the laminate after auxiliary stretching. As a result, in the case where the PVA-based resin layer is immersed in liquid, compared with the case where the PVA-based resin layer does not contain a halide, the orientation disorder of the polyvinyl alcohol molecule and the decrease in the orientation can be more suppressed. Thereby, the optical characteristics of the polarizing film obtained by the treatment step of immersing the laminate in the liquid through dyeing treatment, water stretching treatment, etc. can be improved.

B-3-2. Air-assisted stretching treatment In order to obtain high optical characteristics, a two-stage stretching method combining dry stretching (auxiliary stretching) and boric acid underwater stretching is particularly selected. By introducing auxiliary stretching like two-stage stretching, it is possible to perform stretching while suppressing the crystallization of the thermoplastic resin substrate, which can be solved by excessive crystallization of the thermoplastic resin substrate during subsequent boric acid water stretching There is a problem of reduced stretchability, and the laminate can be stretched at a higher magnification. In addition, when coating a PVA-based resin on a 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 compared to the case where a PVA-based resin is generally coated on a metal drum, as a result The problem is that the crystallization of the PVA-based resin relatively decreases, and sufficient optical characteristics cannot be obtained. On the other hand, by introducing auxiliary stretching, even when a PVA-based resin is coated on a thermoplastic resin, the crystallinity of the PVA-based resin can be improved, and high optical characteristics can be achieved. In addition, by improving the orientation of the PVA-based resin in advance, when immersed in water in the subsequent dyeing step and stretching step, problems such as reduced orientation and dissolution of the PVA-based resin can be prevented, and high optical characteristics can be achieved.

The stretching method for air-assisted stretching may be fixed-end stretching (for example, a method using a tenter stretching machine) or free-end stretching (for example, passing the laminate between rolls with different peripheral speeds) The unidirectional stretching method) can actively use free-end stretching in order to obtain high optical characteristics. In one embodiment, the aerial stretching process includes a heating roller stretching step, which is to perform stretching using the circumferential speed difference between the heating rollers while transporting the laminate in its longitudinal direction. The aerial drawing process typically includes a zone drawing step and a heating roll drawing step. It should be noted that the order of the area stretching step and the heating roller stretching step is not limited, and the area stretching step may be performed first, or the heating roller stretching step may be performed first. The area stretching step can also be omitted. In one embodiment, the zone stretching step and the heating roller stretching step are performed sequentially. In addition, in another embodiment, the end of the film is held in a tenter stretching machine, and the distance between the tenter stretches in the conveying direction and stretches (the extension of the distance between the tenter stretches becomes the stretching ratio) . At this time, the distance of the tenter in the width direction (a direction perpendicular to the conveying direction) is set to be arbitrarily close. Preferably, it can be set to be drawn closer to the free end with respect to the drawing magnification in the conveying direction. In the case of free-end stretching, it is calculated by shrinkage ratio in the width direction = (1/stretch ratio) ^1/2 .

The air-assisted stretching can be performed in one stage or in multiple stages. When performing in multiple stages, the draw ratio is the product of the draw ratios in each stage. The stretching direction in the air-assisted stretching is preferably substantially the same as the stretching direction in the underwater stretching.

The stretching ratio in the air-assisted stretching is preferably 2.0 times to 3.5 times. In the case of combining air-assisted stretching and underwater stretching, the maximum stretching ratio relative to the original length of the laminate is preferably 5.0 times or more, more preferably 5.5 times or more, and still more preferably 6.0 times or more. In this specification, the "maximum stretch ratio" refers to the stretch ratio immediately before the laminate is broken, and also refers to a value that is 0.2 smaller than the stretch ratio at which the laminate is broken.

The stretching temperature of the air-assisted stretching can be set to any appropriate value according to the forming material of the thermoplastic resin base material, the stretching method, and the like. The stretching temperature is preferably equal to or higher than the glass transition temperature (Tg) of the thermoplastic resin substrate, more preferably equal to or higher than the glass transition temperature (Tg) of the thermoplastic resin substrate + 10°C, and particularly preferably equal to or higher than Tg + 15°C. On the other hand, the upper limit of the stretching temperature is preferably 170°C. By stretching at such a temperature, rapid crystallization of the PVA-based resin can be suppressed, and defects caused by the crystallization can be suppressed (for example, hindering the orientation of the PVA-based resin layer by stretching). The crystallization index of the PVA-based resin after air-assisted stretching is preferably 1.3 to 1.8, and more preferably 1.4 to 1.7. The crystallization index of the PVA-based resin can be measured by the ATR method using a Fourier transform infrared spectrophotometer. Specifically, the measurement was performed using polarized light as measurement light, and using the intensities of 1141 cm ^-1 and 1440 cm ^-1 in the obtained spectrum, the crystallization index was calculated by the following formula. Crystallinity index = (I _C / I _R) wherein, I _C: so that when the measured intensity of the measurement light incident on the I _R 1141cm ^-1: 1440cm ^-1 in the strength of measured light incidence measured.

B-3-3. Insoluble treatment If necessary, the insolubilization treatment is performed after the air-assisted stretching treatment and before the water stretching treatment and the dyeing treatment. The above-mentioned insolubilization treatment is typically performed by immersing the PVA-based resin layer in an aqueous solution of boric acid. By performing the insolubilization treatment, the PVA-based resin layer can be provided with water resistance, and the orientation of PVA can be prevented from decreasing when immersed in water. The concentration of the boric acid aqueous solution is preferably 1 part by weight to 4 parts by weight with respect to 100 parts by weight of water. The liquid temperature of the insolubilization bath (boric acid aqueous solution) is preferably 20°C to 50°C.

B-3-4. Dyeing treatment The above dyeing treatment is typically performed by dyeing the PVA-based resin layer with a dichroic substance (typically iodine). Specifically, it is performed by adsorbing iodine on the PVA-based resin layer. Examples of the adsorption method include: a method of immersing a PVA-based resin layer (laminate) in a dyeing solution containing iodine; a method of applying the dyeing solution to the PVA-based resin layer; and spraying the dyeing to the PVA-based resin layer Liquid methods, etc. The method of immersing the laminate in a dyeing liquid (dyeing bath) is preferred. This is because iodine can be adsorbed well.

The dyeing solution is preferably an aqueous iodine solution. The blending amount of iodine is preferably 0.05 parts by weight to 0.5 parts by weight with respect to 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to mix iodide in 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 blending amount of the iodide is preferably 0.1 to 10 parts by weight, and more preferably 0.3 to 5 parts by weight with respect to 100 parts by weight of water. In order to suppress the dissolution of the PVA-based resin, the liquid temperature during dyeing with the dyeing liquid is preferably 20°C to 50°C. When the PVA-based resin layer is immersed in the dyeing solution, in order to ensure the transmittance of the PVA-based resin layer, the immersion time is preferably 5 seconds to 5 minutes, and more preferably 30 seconds to 90 seconds.

The dyeing conditions (concentration, liquid temperature, immersion time) can be set so that the monomer transmittance of the polarizing film finally obtained is 43.0% or more, and the degree of polarization is 99.980% or more. As such dyeing conditions, an iodine aqueous solution is preferably used as the dyeing solution, and the ratio of the content of iodine and potassium iodide in the iodine aqueous solution is set to 1:5 to 1:20. The ratio of the content of iodine and potassium iodide in the iodine aqueous solution is preferably 1:5 to 1:10. Thus, a polarizing film having the optical characteristics as described above can be obtained.

When the laminate is immersed in a treatment bath containing boric acid (typically an insolubilization treatment) and the dyeing treatment is continuously performed, the boric acid concentration in the dyeing bath changes over time because the boric acid contained in the treatment bath is mixed into the dyeing bath As a result, the dyeability sometimes becomes unstable. In order to suppress the above-mentioned destabilization of the dyeing property, the upper limit of the boric acid concentration of the dyeing bath is adjusted so that it is preferably 4 parts by weight and more preferably 2 parts by weight with respect to 100 parts by weight of water. On the other hand, the lower limit of the boric acid concentration of the dyeing bath is preferably 0.1 part by weight relative to 100 parts by weight of water, more preferably 0.2 part by weight, and still more preferably 0.5 part by weight. In one embodiment, a dyeing bath in which boric acid is premixed is used for dyeing treatment. Thereby, the change ratio of the boric acid concentration when the boric acid in the treatment bath is mixed into the dyeing bath can be reduced. The blending amount of boric acid preliminarily blended in the dyeing bath (that is, the content of boric acid not derived 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 Parts by weight.

B-3-5. Cross-linking treatment If necessary, the cross-linking treatment is performed after the dyeing treatment and before the water stretching treatment. The above-mentioned cross-linking treatment is typically performed by immersing the PVA-based resin layer in an aqueous solution of boric acid. By performing the cross-linking treatment, water resistance can be provided to the PVA-based resin layer, and the subsequent orientation of PVA can be prevented from decreasing when immersed in high-temperature water during the subsequent water stretching. The concentration of the boric acid aqueous solution is preferably 1 part by weight to 5 parts by weight with respect to 100 parts by weight of water. In addition, when the cross-linking treatment is performed after the above-mentioned dyeing treatment, it is preferable to further mix the iodide. By blending iodide, elution of iodine adsorbed on the PVA-based resin layer can be suppressed. The blending amount of the iodide is preferably 1 part by weight to 5 parts by weight with respect to 100 parts by weight of water. Specific examples of iodide are as described above. The liquid temperature of the cross-linking bath (boric acid aqueous solution) is preferably 20°C to 50°C.

B-3-6. Stretching in water The underwater stretching treatment is performed by immersing the laminate in a stretching bath. According to the underwater stretching process, it is possible to perform stretching at a temperature lower than the glass transition temperature of the thermoplastic resin base material and the PVA-based resin layer (typically around 80°C), which can suppress the PVA-based resin layer’s It is stretched at a high rate while crystallizing. As a result, a polarizing film having excellent optical characteristics can be manufactured.

Any appropriate method can be adopted as the stretching method of the laminate. Specifically, it may be a fixed-end stretching or a free-end stretching (for example, a method of unidirectionally stretching a laminate between rollers having different peripheral speeds). Preferably, the free end stretch is selected. The stretching of the laminate may be performed in one step or in multiple steps. When performing in multiple stages, the stretching magnification (maximum stretching magnification) of the laminate to be described later is the product of the stretching magnifications in each stage.

The underwater stretching is preferably carried out by immersing the laminate in a boric acid aqueous solution (boric acid underwater stretching). By using a boric acid aqueous solution as a stretching bath, the PVA-based resin layer can be given rigidity that can withstand the tension applied during stretching and water resistance that is insoluble in water. Specifically, boric acid can generate tetrahydroxyboric acid anions in an aqueous solution and cross-link with PVA-based resins through hydrogen bonding. As a result, it is possible to impart rigidity and water resistance to the PVA-based resin layer, to stretch it well, and to produce a polarizing film having excellent optical characteristics.

The boric acid aqueous solution is preferably obtained by dissolving boric acid and/or borate in water as a solvent. The boric acid concentration is preferably 1 part by weight to 10 parts by weight with respect to 100 parts by weight of water, more preferably 2.5 parts by weight to 6 parts by weight, and particularly preferably 3 parts by weight to 5 parts by weight. By setting the concentration of boric acid to 1 part by weight or more, the dissolution of the PVA-based resin layer can be effectively suppressed, and a polarizing film with higher characteristics can be manufactured. In addition, an aqueous solution obtained by dissolving boron compounds such as borax other than boric acid or borate, glyoxal, glutaraldehyde and the like in a solvent can also be used.

It is preferable to mix iodide in the above stretching bath (boric acid aqueous solution). By blending iodide, elution of iodine adsorbed on the PVA-based resin layer can be suppressed. Specific examples of iodide are as described above. The concentration of the iodide is preferably 0.05 to 15 parts by weight with respect to 100 parts by weight of water, and more preferably 0.5 to 8 parts by weight.

The stretching temperature (liquid temperature of the stretching bath) is preferably 40°C to 85°C, and more preferably 60°C to 75°C. With such a temperature, it is possible to suppress the dissolution of the PVA-based resin layer while stretching at a high magnification. Specifically, as described above, the glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 60° C. or higher in consideration of the relationship with the formation of the PVA-based resin layer. In this case, if the stretching temperature is lower than 40°C, even if the plasticization of the thermoplastic resin substrate by water is considered, it may not be stretched well. On the other hand, the higher the temperature of the stretching bath, the higher the solubility of the PVA-based resin layer, 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 by stretching in water is preferably 1.5 times or more, and more preferably 3.0 times or more. The total stretching ratio of the laminate relative to the original length of the laminate is preferably 5.0 times or more, and more preferably 5.5 times or more. By achieving such a high stretching ratio, a polarizing film with very excellent optical characteristics can be manufactured. Such a high stretching ratio can be achieved by using an underwater stretching method (boric acid underwater stretching).

B-3-7. Dry shrinkage treatment The above-mentioned drying shrinkage treatment may be performed by area heating by heating the entire area, or by heating the transport roller (using a so-called heating roller) (heating roller drying method). It is preferable to use both. By using a heating roller for drying, it is possible to efficiently suppress the heating curl of the laminate, and to manufacture a polarizing film having an excellent appearance. Specifically, by drying the laminate in a state of being close to the heating roller, the crystallization of the above thermoplastic resin substrate can be efficiently promoted and the crystallinity can be increased, and the thermoplastic resin can be favorably increased even at a relatively low drying temperature The crystallinity of the substrate. As a result, the rigidity of the thermoplastic resin base material is increased, and it can withstand the shrinkage of the PVA-based resin layer due to drying, and curling can be suppressed. In addition, by using a heating roller, the laminate can be dried while being kept flat, and therefore, not only the curl but also the generation of wrinkles can be suppressed. At this time, the optical properties can be improved by shrinking the laminate in the width direction through the drying shrinkage process. This is because the orientation of PVA and PVA/iodine complex can be effectively improved. The shrinkage rate of the laminate in the width direction due to the drying shrinkage treatment is preferably 1% to 10%, more preferably 2% to 8%, and particularly preferably 4% to 6%. By using a heating roller, the laminate can be continuously contracted in the width direction while being transported, and high productivity can be achieved.

4 is a schematic diagram showing an example of drying shrinkage treatment. In the drying shrinkage process, the transport rollers R1 to R6 heated to a predetermined temperature and the guide rollers G1 to G4 are dried while transporting the laminated body 200. In the example shown in the figure, the conveying rollers R1 to R6 are arranged so as to alternately heat the surface of the PVA resin layer and the surface of the thermoplastic resin base material alternately. However, for example, only one surface of the laminated body 200 (for example, a thermoplastic resin base) may be used. (Material surface) The rollers R1 to R6 are arranged in a continuous heating manner.

By adjusting the heating temperature (temperature of the heating roller) of the conveying roller, the number of heating rollers, the contact time with the heating roller, etc., the drying conditions can be controlled. The temperature of the heating roller is preferably 60°C to 120°C, more preferably 65°C to 100°C, and particularly preferably 70°C to 80°C. The crystallinity of the thermoplastic resin can be increased satisfactorily, curling can be suppressed satisfactorily, and an optical laminate with very excellent durability can be produced. In addition, the temperature of a heating roller can be measured with a contact thermometer. In the example shown in the figure, six transport rollers are provided, but as long as there are a plurality of transport rollers, there is no particular limitation. The conveying rollers are usually provided from 2 to 40, preferably from 4 to 30. The contact time (total contact time) between the laminate and the heating roller is preferably 1 second to 300 seconds, more preferably 1 to 20 seconds, and still more preferably 1 to 10 seconds.

The heating roller may be installed in a heating furnace (for example, an oven), or may be installed in a general manufacturing line (room temperature environment). It is preferably installed in a heating furnace equipped with a blower mechanism. By combining the use of heating roller drying and hot air drying, the rapid temperature change between the heating rollers can be suppressed, and the shrinkage in the width direction can be easily controlled. The temperature of hot air drying is preferably 30°C to 100°C. In addition, the hot air drying time is preferably 1 second to 300 seconds. The wind speed of the hot air is preferably about 10 m/s to 30 m/s. It should be noted that this wind speed is the wind speed in the heating furnace, and can be measured by a mini-blade digital anemometer.

B-3-8. Other processing It is preferable to perform the cleaning treatment after the water stretching treatment and before the drying shrinkage treatment. The aforementioned cleaning treatment is typically performed by immersing the PVA-based resin layer in an aqueous potassium iodide solution.

C. The first phase difference layer As described above, the first retardation layer 20 is an orientation-cured layer of a liquid crystal compound. By using a liquid crystal compound, the difference between nx and ny of the obtained retardation layer can be greatly increased compared to the non-liquid crystal material, and therefore, the thickness of the retardation layer for obtaining a desired in-plane retardation can be significantly reduced. As a result, the polarizing plate with the phase difference layer can be further reduced in thickness and weight. In this specification, the "orientation cured layer" refers to a layer in which a liquid crystal compound is oriented in a predetermined direction within a layer and its orientation state is fixed. It should be noted that the “orientation cured layer”, as described later, includes the concept of an orientation hardened layer obtained by curing liquid crystal monomers. In this embodiment, the rod-shaped liquid crystal compound is typically aligned in the state of being aligned along the slow axis direction of the first retardation layer (alignment along the plane).

As the liquid crystal compound, for example, a liquid crystal compound in which the liquid crystal phase is a nematic phase (nematic liquid crystal). As such a liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The development mechanism of the liquid crystallinity of the liquid crystal compound may be lyotropic or thermal. The liquid crystal polymer and the liquid crystal monomer may be used alone or in combination.

When the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer and a crosslinkable monomer. This is because, by polymerizing or crosslinking (ie, hardening) the liquid crystal monomer, the alignment state of the liquid crystal monomer can be fixed. After the liquid crystal monomers are aligned, for example, if the liquid crystal monomers are polymerized or crosslinked with each other, the alignment state can be fixed thereby. Here, a polymer is formed by polymerization, and a three-dimensional network structure is formed by crosslinking, but they are non-liquid crystalline. Therefore, the formed first retardation layer does not cause transition to the liquid crystal phase, the glass phase, or the crystal phase due to, for example, a temperature change unique to the liquid crystal compound. As a result, the first retardation layer becomes a retardation layer that is not affected by temperature changes and has excellent stability.

The temperature range in which the liquid crystal monomer exhibits liquid crystallinity differs depending on the type. Specifically, the temperature range is preferably 40°C to 120°C, more preferably 50°C to 100°C, and most preferably 60°C to 90°C.

As the liquid crystal monomer, any appropriate liquid crystal monomer can be used. For example, the polymerizable mesogen compounds described in Japanese Patent Table 2002-533742 (WO00/37585), EP358208 (US5211877), EP66137 (US4388453), WO93/22397, EP0261712, DE19504224, DE4408171, and GB2280445 can be used. Specific examples of such a polymerizable mesogenic compound include, for example, the trade name LC242 of BASF, the trade name E7 of Merck, and the trade name LC-Sillicon-CC3767 of Wacker-Chem. As the liquid crystal monomer, for example, a nematic liquid crystal monomer is preferable.

The alignment cured layer of the liquid crystal compound can be formed by performing an alignment treatment on the surface of a predetermined substrate, applying a coating liquid containing a liquid crystal compound on the surface, and orienting the liquid crystal compound in a direction corresponding to the above alignment treatment To fix the orientation state. In one embodiment, the substrate is any suitable resin film, and the orientation-cured layer formed on the substrate can be transferred to the surface of the polarizing plate 10. In another embodiment, the base material may be the second protective layer 13. In this case, the transfer step can be omitted, and after the formation of the orientation-cured layer (first phase difference layer), the roll-to-roll layering can be continuously performed. Therefore, the productivity can be further improved.

As the above-mentioned orientation processing, any appropriate orientation processing may be adopted. Specifically, mechanical orientation treatment, physical orientation treatment, and chemical orientation treatment can be cited. Specific examples of the mechanical orientation treatment include friction treatment and stretching treatment. Specific examples of physical orientation processing include magnetic field orientation processing and electric field orientation processing. Specific examples of the chemical orientation treatment include oblique vapor deposition method and light orientation treatment. The processing conditions of various directional treatments can adopt any suitable conditions according to the purpose.

The alignment of the liquid crystal compound can be performed as follows: according to the type of the liquid crystal compound, the treatment is performed at a temperature at which the liquid crystal phase is displayed. By performing such temperature treatment, the liquid crystal compound becomes a liquid crystal state, and the liquid crystal compound is aligned in accordance with the alignment treatment direction on the surface of the substrate.

In one embodiment, the alignment state is fixed by cooling the liquid crystal compound that has been aligned as described above. When the liquid crystal compound is a polymerizable monomer or a crosslinkable monomer, the alignment state can be fixed by performing a polymerization treatment or a crosslinking treatment on the liquid crystal compound that has been aligned as described above.

Specific examples of the liquid crystal compound and the method of forming the alignment-cured layer are described in Japanese Patent Application Laid-Open No. 2006-163343. The description of this publication is incorporated into this specification by reference.

、杯芳烴等這樣的環狀母核配置於分子的中心，並將直鏈的烷基、烷氧基、取代苯甲醯氧基等作為其側鏈放射狀地取代而成的結構。作為盤狀液晶的代表例，可列舉在C.Destrade等的研究報告、Mol.Cryst.Liq.Cryst.71卷、111頁(1981年)中記載的苯衍生物、聯伸三苯衍生物、參茚并苯衍生物、酞菁衍生物、B.Kohne等的研究報告、Angew.Chem.96卷、70頁(1984年)中記載的環己烷衍生物、以及J.M.Lehn等的研究報告、J.Chem.Soc.Chem.Commun.，1794頁(1985年)、J.Zhang等的研究報告、J.Am.Chem.Soc.116卷、2655頁(1994年)中記載的氮冠類、苯基乙炔類的大環。作為盤狀液晶化合物的其它具體例，可列舉例如：日本特開2006-133652號公報、日本特開2007-108732號公報、日本特開2010-244038號公報中記載的化合物。將上述文獻及公報的記載作為參考引用至本說明書。As another example of the alignment-cured layer, a form in which the discotic liquid crystal compound is aligned in any of vertical alignment, mixed alignment, and oblique alignment can be cited. Regarding the discotic liquid crystal compound, typically, the disc surface of the discotic liquid crystal compound is oriented substantially perpendicular to the film surface of the first retardation layer. The discotic liquid crystal compound being substantially perpendicular means that the average value of the angle formed by the film surface and the disc surface of the discotic liquid crystal compound is preferably 70° to 90°, more preferably 80° to 90°, and still more preferably 85° ~90°. The discotic liquid crystal compound generally refers to a liquid crystal compound having a discoid molecular structure, the discotic molecular structure is composed of benzene, 1,3,5-tri

Such as calixarene, etc. are arranged at the center of the molecule, and linear alkyl groups, alkoxy groups, substituted benzoyloxy groups, etc. are radially substituted as side chains. Representative examples of discotic liquid crystals include benzene derivatives, triphenylene derivatives described in C. Destrade’s research report, Mol. Cryst. Liq. Cryst. 71, page 111 (1981), and Research reports of indenobenzene derivatives, phthalocyanine derivatives, B. Kohne, etc., cyclohexane derivatives described in Angew. Chem. Volume 96, page 70 (1984), and research reports of JMLehn, etc. Chem. Soc. Chem. Commun., page 1794 (1985), J. Zhang et al. research report, J. Am. Chem. Soc. 116, page 2655 (1994) nitrogen crowns, phenyl Macrocycle of acetylene. As other specific examples of the discotic liquid crystal compound, for example, the compounds described in JP 2006-133652, JP 2007-108732, and JP 2010-244038 can be cited. The descriptions of the above documents and gazettes are cited as references in this specification.

In one embodiment, as shown in FIGS. 1 and 2, the first retardation layer 20 is a single layer of an orientation-cured layer of a liquid crystal compound. When the first retardation layer 20 is composed of a single layer of an orientation-cured layer of a liquid crystal compound, its thickness is preferably 0.5 μm to 7 μm, and more preferably 1 μm to 5 μm. By using the liquid crystal compound, the in-plane retardation equivalent to that of the resin film can be achieved with a thickness that is significantly thinner than the resin film.

Typically, the refractive index characteristic of the first retardation layer shows a relationship of nx>ny=nz. The first phase difference layer is typically provided to impart anti-reflection properties to the polarizing plate, and when the first phase difference layer is a single layer of a directional curing layer, it can function as a λ/4 plate. In this case, the in-plane retardation Re(550) of the first retardation layer is preferably 100 nm to 190 nm, more preferably 110 nm to 170 nm, and still more preferably 130 nm to 160 nm. It should be noted that “ny=nz” includes not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, it may be ny>nz or ny<nz within a range that does not impair the effects of the present invention.

The Nz coefficient of the first retardation layer is preferably 0.9 to 1.5, and more preferably 0.9 to 1.3. By satisfying such a relationship, when the obtained polarizing plate with a phase difference layer is used for an image display device, a very excellent reflection hue can be realized.

The first retardation layer can show the inverse dispersion wavelength characteristic in which the phase difference value increases according to the wavelength of the measurement light, or the positive wavelength dispersion characteristic in which the phase difference value decreases according to the measurement light wavelength, and can also display It shows a flat wavelength dispersion characteristic in which the phase difference value hardly changes with the wavelength of the measurement light. In one embodiment, the first retardation layer exhibits 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, and more preferably 0.8 or more and 0.95 or less. With such a configuration, very excellent anti-reflection characteristics can be achieved.

The angle θ formed by the slow axis of the first retardation layer 20 and the absorption axis of the polarizing film 11 is preferably 40° to 50°, more preferably 42° to 48°, and still more preferably about 45°. When the angle θ is in such a range, as described above, by using the first retardation layer as a λ/4 plate, it is possible to obtain a retardation with a very excellent circularly polarized characteristic (the result is a very excellent anti-reflection characteristic) Layer of polarizer.

In another embodiment, as shown in FIG. 3, the first retardation layer 20 may have a layered structure of the first orientation cured layer 21 and the second orientation cured layer 22. In this case, either of the first orientated cured layer 21 and the second orientated cured layer 22 can function as a λ/4 plate, and the other can function as a λ/2 plate. Therefore, the thicknesses of the first orientated cured layer 21 and the second orientated cured layer 22 can be adjusted so as to obtain the desired in-plane phase difference of the λ/4 plate or the λ/2 plate. For example, when the first oriented cured layer 21 functions as a λ/2 plate and the second oriented cured layer 22 functions as a λ/4 plate, the thickness of the first oriented cured layer 21 is, for example, 2.0 μm to 3.0 μm, and the second orientation The thickness of the cured layer 22 is, for example, 1.0 μm to 2.0 μm. In this case, the in-plane retardation Re(550) of the first oriented cured layer is preferably 200 nm to 300 nm, more preferably 230 nm to 290 nm, and still more preferably 250 nm to 280 nm. The in-plane retardation Re(550) of the second orientation-cured layer is as described above for the orientation-cured layer of a single layer. The angle formed by the slow axis of the first oriented cured layer and the absorption axis of the polarizing film is preferably 10° to 20°, more preferably 12° to 18°, and still more preferably about 15°. The angle formed by the slow axis of the second oriented cured layer and the absorption axis of the polarizing film is preferably 70° to 80°, more preferably 72° to 78°, and still more preferably about 75°. With such a configuration, characteristics close to the ideal reverse wavelength dispersion characteristics can be obtained, and as a result, very excellent anti-reflection characteristics can be achieved. The liquid crystal compound constituting the first orientated cured layer and the second orientated cured layer, the formation method of the first orientated cured layer, and the second orientated cured layer, and optical characteristics are as described above for the single-layer oriented cured layer.

D. 2nd phase difference layer As described above, the second retardation layer may be a so-called negative C-plate having a refractive index characteristic showing the relationship nz>nx=ny. By using a negative-type C plate as the second retardation layer, reflection in the oblique direction can be well prevented, and a wide viewing angle of the anti-reflection function can be realized. In this case, the thickness direction retardation Rth(550) of the second retardation layer is preferably -50 nm to -300 nm, more preferably -70 nm to -250 nm, still more preferably -90 nm to -200 nm, and particularly preferably- 100nm~-180nm. Here, "nx=ny" is not only a case where nx and ny are strictly equal, but also a case where nx and ny are substantially equal. That is, the in-plane retardation Re (550) of the second retardation layer may be less than 10 nm.

The second retardation layer having a refractive index characteristic of nz>nx=ny may be formed of any appropriate material. The second retardation layer is preferably formed of a thin film containing a liquid crystal material fixed in a vertical alignment. The liquid crystal material (liquid crystal compound) that can be aligned vertically can 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 the liquid crystal compounds described in [0020] to [0028] of JP 2002-333642A and the method for forming the retardation layer. In this case, the thickness of the second retardation layer is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 8 μm, and still more preferably 0.5 μm to 5 μm.

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 method, sputtering method, CVD method, ion plating method, spraying method, etc.). Examples of metal oxides 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 preferred.

When the conductive layer contains a metal oxide, the thickness of the conductive layer is preferably 50 nm or less, and more preferably 35 nm or less. The lower limit of the thickness of the conductive layer is preferably 10 nm.

The conductive layer can be transferred from the above-mentioned base material to the first phase difference layer (or the second phase difference layer when the second phase difference layer is present), and the conductive layer alone is used as the polarizer with a phase difference layer The constituent layer may be a laminate with a substrate (substrate with conductive layer) and laminated on the first retardation layer (or, in the case where the second retardation layer is present, the second retardation layer). Preferably, the substrate is optically isotropic. 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 appropriate isotropic substrate can be used. Examples of the material that constitutes the isotropic base material include, for example, materials that do not have conjugated resins as the main skeleton, such as norbornene-based resins and olefin-based resins; the main chain of the acrylic resin has a lactone ring, Materials such as glutarimide rings and other ring structures. If such a material is used, when an isotropic base material is formed, the phenomenon that the phase difference is exhibited along with the orientation of the molecular chain can be suppressed to a small level. The thickness of the isotropic substrate is preferably 50 μm or less, and more preferably 35 μm or less. The lower limit of the thickness of the isotropic base material is, for example, 20 μm.

The conductive layer and/or the conductive layer of the isotropic substrate with a conductive layer may be patterned as needed. By patterning, the conduction part and the insulation part can be formed. As a result, an electrode can be formed. The electrode can function as a touch sensor electrode that senses contact with the touch panel. As a pattern forming method, any appropriate method can be adopted. Specific examples of the pattern forming method include a wet etching method and a screen printing method.

F. Image display device The polarizing plate with a phase difference layer described in the above items A to E can be applied to an image display device. Therefore, the present invention includes an image display device using such a polarizing plate with a phase difference layer. Representative examples of image display devices include liquid crystal display devices and electroluminescence (EL) display devices (for example, organic EL display devices and inorganic EL display devices). An image display device according to an embodiment of the present invention includes a polarizing plate with a phase difference layer described in items A to E on the visible side. The polarizing plate with a phase difference layer is laminated in such a manner that the phase difference layer becomes the side of the image display unit (for example, liquid crystal cell, organic EL unit, and inorganic EL unit) (the mode in which the polarizing film becomes the viewing side). In one embodiment, the image display device may have a curved shape (essentially a curved display screen), and/or be flexible or bendable. In such an image display device, the effect of the polarizing plate with a phase difference layer of the present invention becomes remarkable.

需要說明的是，例如在將經過防眩(AG)表面處理並具有擴散性能的具備黏著劑的偏光板作為測定物件的情況下，依賴分光光度計可得到不同的測定結果，在該情況下，基於用各個分光光度計測定同一偏光板時的測定值進行數值換算，由此可對依賴分光光度計的測定值之差進行補償。 (3)長條狀偏光膜的光學特性的偏差 從用於實施例及比較例的偏光板中，沿著寬度方向等間隔地在5個位置分別切出測定樣品，以與上述(2)同樣方式測定了5個測定樣品各自的中央部分的單體透射率。接著，計算出在各測定位置測得的單體透射率中最大值與最小值之差，將該值設為長條狀偏光膜的光學特性的偏差。 (4)單片狀偏光膜的光學特性的偏差 從用於實施例及比較例的偏光板中，切出100mm×100mm的測定樣品，求出單片狀偏光板(50cm² )的光學特性的偏差。具體而言，以與上述(2)同樣方式測定了從測定樣品的4條邊各邊的中點向內側約1.5cm~2.0cm附近的位置及中央部分、共計5個位置的單體透射率。接下來，計算出在各測定位置測得的單體透射率中最大值與最小值之差，將該值設為單片狀偏光膜的光學特性的偏差。 (5)翹曲 將實施例及比較例中得到的帶相位差層的偏光板切出110mm×60mm尺寸。此時，以偏光膜的吸收軸方向成為長邊方向的方式切出。將切出的帶相位差層的偏光板透過黏著劑貼合於尺寸120mm×70mm、厚度0.2mm的玻璃板，作為試驗樣品。將試驗樣品投入保持為85℃的加熱烘箱中24小時，測定取出後的翹曲量。將玻璃板朝下來將試驗樣品靜置於平面上時，將從該平面起算最高的部分的高度作為翹曲量。 (6)單位重量 將實施例及比較例中得到的帶相位差層的偏光板切出預定的尺寸，用重量(mg)除以面積(cm² )，由此算出帶相位差層的偏光板的每單位面積的重量(單位重量)。 (7)耐彎折性 將實施例及比較例中得到的帶相位差層的偏光板切出50mm×100mm尺寸。此時，以偏光膜的吸收軸方向成為短邊方向的方式切出。使用帶有恆溫恆濕室的耐折試驗機(YUASA公司製、CL09 type-D01)，在20℃、50%RH的條件下，將切出的帶相位差層的偏光板供於彎折試驗。具體而言，將帶相位差層的偏光板以相位差層側成為外側的方式朝與吸收軸方向平行的方向重複彎折，測定直到產生成為顯示不良那樣的裂紋、剝離、薄膜的斷裂等為止的彎折次數，按照以下的基準進行了評價(彎折直徑：2mmφ)。 >評價基準＞ 小於1萬次：不良 1萬次以上且小於3萬次：良 3萬次以上：優EXAMPLES Hereinafter, the present invention will be specifically described by examples, but the present invention is not limited to these examples. The measuring method of each characteristic is as follows. In addition, unless otherwise stated, the "part" and "%" in an Example and a comparative example are based on weight. (1) The thickness of 10 μm or less was measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name “MCPD-3000”). The thickness greater than 10 μm is measured using a digital micrometer (manufactured by Anritsu Corporation, product name “KC-351C”). (2) Monomer transmittance and polarizing degree For the polarizing film/protective layer laminate (polarizing plate) used in the examples and comparative examples, each was measured using an ultraviolet-visible spectrophotometer (V-7100 manufactured by Japan Spectroscopy Co., Ltd.) The obtained single transmittance Ts, parallel transmittance Tp, and orthogonal transmittance Tc are Ts, Tp, and Tc of the polarizing film. These Ts, Tp, and Tc are Y values obtained by measuring the visibility of 2 degrees (C light source) of JIS Z8701 and correcting the visibility. The refractive index of the protective layer is 1.50, and the refractive index of the surface of the polarizing film on the side opposite to the protective layer is 1.53. From the obtained Tp and Tc, the polarization degree P is obtained by the following formula. Polarization P(%)={(Tp-Tc)/(Tp+Tc)} ^1/2 ×100 Note that the spectrophotometer can be measured equivalently using LPF-200 manufactured by Otsuka Electronics Co., Ltd. As an example, for the samples 1 to 3 of the polarizing plate configured in the same manner as in the following examples, the monomer transmittance Ts and the degree of polarization P were obtained by measurement using V-7100 and LPF-200. The measured value is shown in Table 1. As shown in Table 1, it can be seen that the difference between the measured value of the monomer transmittance of V-7100 and the measured value of the monomer transmittance of LPF-200 is 0.1% or less, and any spectrophotometer will give the same measurement result. [Table 1]

It should be noted that, for example, when an anti-glare (AG) surface-treated polarizing plate with an adhesive having diffusion properties is used as the measurement object, different measurement results can be obtained by relying on a spectrophotometer. In this case, The numerical value conversion is performed based on the measured value when the same polarizing plate is measured with each spectrophotometer, and thereby the difference between the measured values depending on the spectrophotometer can be compensated. (3) Variations in the optical characteristics of the long polarizing film From the polarizing plates used in Examples and Comparative Examples, measurement samples were cut out at five positions at equal intervals in the width direction, as in the above (2) Method, the individual transmittance of the central part of each of the five measurement samples was measured. 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 deviation of the optical characteristics of the long polarizing film. (4) Variation in the optical characteristics of the monolithic polarizing film From the polarizing plates used in Examples and Comparative Examples, a measurement sample of 100 mm×100 mm was cut out to obtain the optical properties of the monolithic polarizing plate (50 cm ² ) deviation. Specifically, in the same manner as in the above (2), the cell transmittances at a total of 5 positions from the midpoint of each side of the four sides of the measurement sample to the inner side in the vicinity of approximately 1.5 cm to 2.0 cm and the central portion were measured. 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 deviation of the optical characteristics of the monolithic polarizing film. (5) Warpage The polarizing plates with retardation layers obtained in Examples and Comparative Examples were cut out to a size of 110 mm×60 mm. At this time, the polarizing film is cut out so that the absorption axis direction becomes the longitudinal direction. The cut polarizing plate with a phase difference layer was bonded to a glass plate having a size of 120 mm×70 mm and a thickness of 0.2 mm through an adhesive, and used as a test sample. The test sample was put into a heating oven maintained at 85°C for 24 hours, and the amount of warpage after taking out was measured. When the glass plate is placed down and the test sample is placed on a flat surface, the height of the highest part from the flat surface is regarded as the amount of warpage. (6) Unit weight The polarizing plates with retardation layers obtained in Examples and Comparative Examples were cut to a predetermined size, and the polarizing plates with retardation layers were calculated by dividing the weight (mg) by the area (cm ² ) Weight per unit area (unit weight). (7) Bending resistance The polarizing plates with retardation layers obtained in Examples and Comparative Examples were cut to a size of 50 mm×100 mm. At this time, the polarizing film is cut out so that the absorption axis direction becomes the short side direction. Using a folding endurance testing machine (made by YUASA, CL09 type-D01) with a constant temperature and humidity chamber, the polarizing plate with a phase difference layer cut out was subjected to a bending test under the conditions of 20°C and 50%RH . Specifically, the polarizing plate with a retardation layer is repeatedly bent in a direction parallel to the absorption axis direction so that the retardation layer side is outside, and measurement is performed until cracks such as display failure, peeling, and film breakage occur. The number of bending times was evaluated according to the following criteria (bending diameter: 2 mmφ). >Evaluation criteria> Less than 10,000 times: bad 10,000 times or more and less than 30,000 times: good 30,000 times or more: excellent

[Example 1] 1. Production of polarizing film As the thermoplastic resin substrate, an elongated amorphous isophthalic acid copolymer polyethylene terephthalate film (thickness: 100 μm) having a water absorption rate of 0.75% and a Tg of about 75° C. was used. Corona treatment was applied to one side of the resin substrate. PVA prepared by blending polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z410") at 9:1 To 100 parts by weight of the resin-like substance, 13 parts by weight of potassium iodide was added, and the resulting mixture was dissolved in water to prepare a PVA aqueous solution (coating solution). The PVA aqueous solution was coated on the corona-treated surface of the resin substrate and dried at 60°C, thereby forming a PVA-based resin layer with a thickness of 13 μm, and a laminate was produced. In an oven at 130° C., the resulting laminate was uniaxially stretched 2.4 times in the longitudinal direction (longitudinal direction) free end between rolls with different peripheral speeds (air assisted stretching treatment). Next, the laminate was immersed in an insolubilization bath (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (insolubilization treatment). Next, in a dye bath (liquid solution of iodine obtained by blending 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° C.), the monomer transmittance of the polarizing film finally obtained ( Ts) so as to become 43.0% or more soaked for 60 seconds while adjusting the concentration (dyeing treatment). Next, it was immersed in a crosslinking bath (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide with respect to 100 parts by weight of water and 5 parts by weight of boric acid) at a liquid temperature of 40°C (crosslinking treatment). Then, while immersing the laminate in a boric acid aqueous solution at a liquid temperature of 70° C. (boric acid concentration 4.0% by weight), the rolls with different peripheral speeds were stretched so that the total draw ratio in the longitudinal direction (longitudinal direction) became 5.5 times. Unidirectional stretching (underwater stretching treatment) Then, the laminate was immersed in a cleaning bath (aqueous solution obtained by blending 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 20° C. (washing treatment). Then, while drying in an oven kept at 90°C, it was brought into contact with a SUS heating roller whose surface temperature was kept at 75°C for about 2 seconds (drying shrinkage treatment). The shrinkage rate of the laminate in the width direction due to the drying shrinkage treatment was 5.2%. In this way, a polarizing film with a thickness of 5 μm was formed on the resin substrate.

2. Production of polarizer On the surface (surface opposite to the resin substrate) of the polarizing film obtained above, an acrylic film (surface refractive index 1.50, 40 μm) was bonded as a protective layer through an ultraviolet curing adhesive. Specifically, the coating was applied so that the total thickness of the hardening adhesive was 1.0 μm, and the bonding was performed using a roller machine. Then, UV light is irradiated from the protective layer side to harden the adhesive. Next, after cutting both ends, the resin substrate was peeled off to obtain a long polarizing plate (width: 1300 mm) having a protective layer/polarizing film structure. The polarizing plate (essentially a polarizing film) has a single transmittance of 43.15% and a polarization degree of 99.995%. In addition, the deviation of the optical characteristics of the long polarizing film was 0.14%, and the deviation of the optical characteristics of the monolithic polarizing film was 0.09%.

使用摩擦布(rubbing cloth)對聚對苯二甲酸乙二醇酯(PET)薄膜(厚度38μm)表面進行摩擦，實施了定向處理。定向處理的方向設定成貼合於偏光板時相對於偏光膜的吸收軸方向從可視側觀察成為15°方向。利用棒塗機將上述液晶塗敷液塗敷於該定向處理表面，在90℃下加熱乾燥2分鐘，由此使液晶化合物定向。使用金屬鹵化物燈，對如此形成的液晶層照射1mJ/cm² 的光，使該液晶層硬化，由此，在PET薄膜上形成了液晶定向固化層A。液晶定向固化層A的厚度為2.5μm、面內相位差Re(550)為270nm。此外，液晶定向固化層A具有nx＞ny＝nz的折射率分佈。 變更塗敷厚度，並將定向處理方向設定成相對於偏光膜的吸收軸方向從可視側觀察成為75°方向，除此以外，以與上述同樣方式在PET薄膜上形成了液晶定向固化層B。液晶定向固化層B的厚度為1.5μm、面內相位差Re(550)為140nm。此外，液晶定向固化層B具有nx＞ny＝nz的折射率分佈。3. The preparation of the first orientated cured layer and the second orientated cured layer constituting the retardation layer will display a polymerizable liquid crystal (manufactured by BASF: trade name "Paliocolor LC242", expressed by the following formula) 10g, and 3 g of a photopolymerization initiator (manufactured by BASF: trade name "IRGACURE 907") for this polymerizable liquid crystal compound was dissolved in 40 g of toluene to prepare a liquid crystal composition (coating liquid). [Chemical Formula 1]

The surface of the polyethylene terephthalate (PET) film (thickness 38 μm) was rubbed using rubbing cloth, and orientation treatment was performed. The direction of the orientation process is set so that when it is attached to the polarizing plate, the direction of the absorption axis with respect to the polarizing film becomes a 15° direction when viewed from the viewing side. The liquid crystal coating liquid was applied to the alignment treatment surface using a bar coater and heated and dried at 90°C for 2 minutes, thereby aligning the liquid crystal compound. Using a metal halide lamp, the liquid crystal layer thus formed was irradiated with light of 1 mJ/cm ² to harden the liquid crystal layer, 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 μm, and the in-plane retardation Re(550) was 270 nm. In addition, the liquid crystal alignment cured layer A has a refractive index distribution of nx>ny=nz. The coating thickness was changed, and the orientation treatment direction was set to a 75° direction when viewed from the viewing side with respect to the absorption axis direction of the polarizing film. Except for this, a liquid crystal orientation cured layer B was formed on the PET film in the same manner as described above. The thickness of the liquid crystal alignment cured layer B was 1.5 μm, and the in-plane retardation Re(550) was 140 nm. In addition, the liquid crystal alignment cured layer B has a refractive index distribution of nx>ny=nz.

4. Fabrication of polarizing plate with phase difference layer On the surface of the polarizing film of the polarizing plate obtained in 2. above, the liquid crystal alignment cured layer A and the liquid crystal alignment cured layer B obtained in 3. were sequentially transferred. At this time, the angle between the absorption axis of the polarizing film and the slow axis of the orientation curing layer A became 15°, and the angle between the absorption axis of the polarizing film and the slow axis of the orientation curing layer B became 75°. Seal (fit). In addition, each transfer (lamination) is performed through the ultraviolet-curable adhesive (thickness 1.0 micrometer) used in 2. above. In this way, a polarizing plate with a retardation layer composed of a protective layer/adhesive layer/polarizing film/adhesive layer/retardation layer (first oriented cured layer/adhesive layer/second oriented cured layer) was obtained. The total thickness of the obtained polarizing plate with a phase difference layer was 52 μm. The obtained polarizing plate with a retardation layer was subjected to the above evaluations (5) to (7). The amount of warpage was 1.8 mm.

[Example 2] A polarizing plate with a retardation layer was produced in the same manner as in Example 1 except that an acrylic film with a thickness of 20 μm was used as a protective layer. The total thickness of the obtained polarizing plate with a retardation layer was 32 μm. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1. The amount of warpage is 1.5 mm.

[Example 3] A polarizing plate with a retardation layer was produced in the same manner as in Example 1 except that a cellulose triacetate (TAC) film with a thickness of 25 μm was used as a protective layer. The total thickness of the obtained polarizing plate with a phase difference layer was 37 μm. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1. The amount of warpage was 1.3 mm.

[Comparative Example 1] 1. Production of polarizers A polyvinyl alcohol resin film having an average degree of polymerization of 2,400, a degree of saponification of 99.9 mol%, and a thickness of 30 μm was prepared. While immersing the polyvinyl alcohol film in a swelling bath (water bath) at 20°C for 30 seconds to swell, it was stretched 2.4 times in the conveying direction between rolls with different peripheral speed ratios (swelling step), then, at 30 In a dyeing bath (water solution with an iodine concentration of 0.03% by weight and a potassium iodide concentration of 0.3% by weight) in the temperature of ℃, the original polyvinyl alcohol film was immersed and dyed so that the monomer transmittance after the final stretching became a desired value. (A polyvinyl alcohol film that is completely unstretched in the transport direction) is stretched in the transport direction by 3.7 times as a reference (dyeing step). The immersion time at this time is about 60 seconds. Next, while immersing the dyed polyvinyl alcohol film in a crosslinking bath at 40° C. (aqueous solution with boric acid concentration of 3.0% by weight and potassium iodide concentration of 3.0% by weight), the original polyvinyl alcohol film was used as a reference Stretch in the transport direction to 4.2 times (crosslinking step). Further, the obtained polyvinyl alcohol film was immersed in a stretching bath at 64° C. (aqueous solution with boric acid concentration of 4.0% by weight and potassium iodide concentration of 5.0% by weight) for 50 seconds, and transported toward the original polyvinyl alcohol film as a reference The direction was stretched to 6.0 times (stretching step), and then immersed in a cleaning bath (water solution with a potassium iodide concentration of 3.0% by weight) at 20°C for 5 seconds (washing step). The washed polyvinyl alcohol film was dried at 30° C. for 2 minutes to prepare a polarizer (thickness 12 μm).

2. Production of polarizer As an adhesive, a polyvinyl alcohol resin containing an acetylacetonyl group in a weight ratio of 3:1 (average degree of polymerization of 1,200, saponification degree of 98.5 mol%, and acetylacetonylation rate of 5 mol was used %) and an aqueous solution of methylolmelamine. Using this adhesive agent, a 25 μm-thick hard-coated cellulose triacetate (TAC) film was bonded to one side of the polarizer obtained above using a roller bonding machine, and a thickness of 25 μm was bonded to the other side of the polarizer After the TAC film was heated and dried in an oven (temperature 60°C, time 5 minutes), a protective layer 1 (thickness 25 μm)/adhesive layer/polarizer/adhesive layer/protective layer 2 (thickness 25 μm) was produced The polarizing plate.

3. Fabrication of polarizing plate with phase difference layer On the surface of the protective layer 2 of the polarizing plate obtained in 2. above, the liquid crystal alignment cured layer A and the liquid crystal alignment cured layer B were sequentially transferred in the same manner as in Example 1, to produce a protective layer 1/adhesion layer/polarized light A polarizing plate with a retardation layer composed of a material/adhesive layer/protective layer 2/adhesive layer/retardation layer (first oriented cured layer/adhesive layer/second oriented cured layer). The total thickness of the obtained polarizing plate with a phase difference layer was 68 μm. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1. The amount of warpage was 4.2 mm.

[Comparative Example 2] Potassium iodide was not added to the PVA aqueous solution (coating solution), the stretching ratio in the air assisted stretching process was set to 1.8 times, and the heating roller was not used in the drying shrinkage process, except that it was the same as in Example 1. A polarizing film and polarizing plate were produced. The polarizer (essentially a polarizing film) has a single transmittance of 42.34% and a polarization degree of 99.988%. A polarizing plate with a phase difference layer was produced in the same manner as in Example 1 except that this polarizing plate was used.

[Comparative Example 3] 1. Production of polarizer A long polarizing plate (width: 1300 mm) having a protective layer/polarizing film configuration was obtained in the same manner as in Example 1 except that a TAC film with a thickness of 25 μm was used as the protective layer.

2. Production of retardation film constituting the retardation layer 2-1. Polymerization of polyester carbonate-based resin uses a batch consisting of two vertical reactors equipped with a stirring blade and a reflux cooler controlled at 100°C The polymerization device polymerized. 29.60 parts by mass (0.046mol) of bis[9-(2-phenoxycarbonylethyl)fluorene-9-yl]methane, 29.21 parts by mass (0.200mol) of isosorbide (ISB), spirodiol (SPG) 42.28 parts by mass (0.139 mol), diphenyl carbonate (DPC) 63.77 parts by mass (0.298 mol) and 1.19×10 ⁻² parts by mass (6.78×10 ⁻⁵ mol) of calcium acetate monohydrate as a catalyst. After replacing the inside of the reactor with reduced-pressure nitrogen, heating was performed with a heating medium, and stirring was started when the internal temperature reached 100°C. 40 minutes after the start of the temperature increase, the internal temperature was brought to 220°C, and the pressure was reduced while controlling and maintaining the temperature, and reached 13.3 kPa 90 minutes after reaching 220°C. The phenol vapor produced as a by-product during the polymerization reaction was introduced into a reflux cooler at 100°C, and a certain amount of monomer components contained in the phenol vapor were returned to the reactor, while the uncondensed phenol vapor was introduced to 45°C Was recovered in the condenser. After introducing nitrogen gas into the first reactor and temporarily returning to atmospheric pressure, the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Next, the temperature rise and pressure reduction in the second reactor were started, and the internal temperature was 240° C. and the pressure was 0.2 kPa in 50 minutes. Then, the polymerization is performed until the predetermined stirring power is reached. At the time when the predetermined power was reached, nitrogen gas was introduced into the reactor, the pressure was restored, the resulting polyester carbonate resin was extruded into water, and the strand was cut to obtain pellets.

2-2. Production of retardation film After the obtained polyester carbonate-based resin (pellet) was vacuum-dried at 80°C for 5 hours, a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder set temperature: 250°C), T-die (width 200 mm) was used 1. Set temperature: 250°C), chill roll (set temperature: 120~130°C) and the film-forming device of the winder produced a long resin film with a thickness of 135μm. The obtained long resin film was stretched in the width direction at a stretching temperature of 133° C. and a stretching ratio of 2.8 times to obtain a retardation film with a thickness of 53 μm. Re(550) of the obtained retardation film was 141 nm, Re(450)/Re(550) was 0.82, and Nz coefficient was 1.12.

3. Fabrication of polarizing plate with phase difference layer On the surface of the polarizing film of the polarizing plate obtained in the above 1., the retardation film obtained in the above 2. was bonded through an acrylic adhesive (thickness 5 μm). At this time, the absorption axis of the polarizing film and the slow axis of the phase difference film were bonded so as to form an angle of 45°. In this way, a polarizing plate with a phase difference layer including a protective layer/adhesion layer/polarizing film/adhesive layer/phase difference layer was obtained. The obtained polarizing plate with a phase difference layer had a total thickness of 89 μm. The obtained polarizing plate with a retardation layer was subjected to the above evaluations (6) and (7).

Table 2 shows the configurations and evaluation results of the polarizing plates with retardation layers obtained in Examples 1 to 3 and Comparative Examples 1 and 3. [Table 2]

[Evaluation] As is clear from Table 2 and the comparison between Example 1 and Comparative Example 2, the polarizing plate with a retardation layer according to an example of the present invention is thin, which can suppress warpage after a heating test and has excellent optical characteristics. In addition, by setting the weight per unit area of the polarizing plate with a phase difference layer to a predetermined value or less, bending resistance is improved. Industrial applicability

The polarizing plate with a retardation layer of the present invention can be suitably used as a circular polarizing plate for liquid crystal display devices, organic EL display devices, and inorganic EL display devices.

10: polarizer 11: Polarizing film 12: The first protective layer 13: 2nd protective layer 20: Phase difference layer (1st phase difference layer) 21: The first directional curing layer 22: The second directional curing layer 50: Other retardation layer (second retardation layer) 60: Isotropic substrate with conductive layer 100: polarizing plate with phase difference layer 101: Polarizing plate with phase difference layer 102: Polarizing plate with phase difference layer 200: stack G1~G4: Guide roller R1~R6: conveyor roller

FIG. 1 is a schematic cross-sectional view of a polarizing plate with a phase difference layer according to an embodiment of the present invention. 2 is a schematic cross-sectional view of a polarizing plate with a phase difference layer according to another embodiment of the present invention. 3 is a schematic cross-sectional view of a polarizing plate with a phase difference layer according to still another embodiment of the present invention. 4 is a schematic diagram showing an example of a drying shrinkage process using a heating roller in the method of manufacturing a polarizing film used in the polarizing plate with a phase difference layer of the present invention.

10: polarizer

11: Polarizing film

12: The first protective layer

13: 2nd protective layer

20: Phase difference layer (1st phase difference layer)

100: polarizing plate with phase difference layer

Claims (12)

A polarizing plate with a phase difference layer has a polarizing plate and a phase difference layer, the polarizing plate includes a polarizing film and a protective layer provided on at least one side of the polarizing film, The polarizing film is composed of a polyvinyl alcohol resin film containing a dichroic substance, and its thickness is 8 μm or less, the monomer transmittance is 43.0% or more, and the degree of polarization is 99.980% or more. The retardation layer is an oriented cured layer of a liquid crystal compound. The polarizing plate with a retardation layer according to claim 1 has a unit weight of 6.5 mg/cm ² or less. The polarizing plate with a phase difference layer according to claim 1 has a total thickness of 60 μm or less. The polarizing plate with a phase difference layer as in claim 1, wherein, The phase difference layer is a single layer of the directional curing layer of the liquid crystal compound, The Re(550) of the retardation layer is 100nm~190nm, The angle formed by the slow axis of the phase difference layer and the absorption axis of the polarizing film is 40° to 50°. The polarizing plate with a phase difference layer as in claim 1, wherein, The phase difference layer has a layered structure of an oriented cured layer of a first liquid crystal compound and an oriented cured layer of a second liquid crystal compound, Re (550) of the alignment cured layer of the first liquid crystal compound is 200 nm to 300 nm, and the angle formed by the slow axis and the absorption axis of the polarizing film is 10° to 20°, Re (550) of the alignment cured layer of the second liquid crystal compound is 100 nm to 190 nm, and the angle formed by the slow axis and the absorption axis of the polarizing film is 70° to 80°. The polarizing plate with a phase difference layer according to claim 1, wherein the difference between the maximum value and the minimum value of the unit transmittance of the polarizing film in the region of 50 cm ² is 0.2% or less. The polarizing plate with a retardation layer according to claim 1 has a width of 1000 mm or more, and the difference between the maximum value and the minimum value of the cell transmittance at the position of the polarizing film in the width direction is 0.3% or less. The polarizing plate with a phase difference layer according to claim 1, wherein the single transmittance of the polarizing film is 43.5% or less, and the degree of polarization is 99.998% or less. The polarizing plate with a phase difference layer according to claim 1, further has another phase difference layer outside the phase difference layer, and the refractive index characteristics of the other phase difference layer show a relationship of nz>nx=ny. The polarizing plate with a phase difference layer according to claim 1 further has a conductive layer or an isotropic base material with a conductive layer outside the phase difference layer. An image display device provided with a polarizing plate with a phase difference layer according to any one of claims 1 to 10. The image display device according to claim 11, which is an organic electroluminescence display device or an inorganic electroluminescence display device.

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