TW202026157A - Polarizing plate with retardation layer and image display device using the same - Google Patents

Abstract

Provided is a polarizing plate with a retardation layer which is thin, has excellent handling properties, and has excellent optical characteristics. The polarizing plate with a retardation layer of the present invention has a polarizing plate including a polarizing film and a protective layer on at least one side of the polarizing film, and a retardation layer. The polarizing film is composed of a polyvinyl alcohol-based resin film containing a dichroic material, has the thickness of 8 [mu]m or less, has the simple substance transmittance of 43.5% or more, and has the polarization degree of 99.940% or more. The retardation layer is an alignment-solidified layer of a liquid crystal compound.

Description

Polarizing plate with retardation layer and image display device using the polarizing plate with retardation layer

Invention field The present invention relates to a polarizing plate with a retardation layer and an image display device using the polarizing plate with a retardation 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 and inorganic EL display devices) are rapidly spreading. In image display devices, polarizing plates and retardation plates are typically used. In actual use, a polarizing plate with a retardation layer formed by integrating a polarizing plate and a retardation plate is widely used (for example, Patent Document 1). Recently, as the desire for thinning of image display devices has increased, the The expectation for the thickness reduction of the polarizing plate of the retardation 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 polarizers and polarizers with retardation layers are also required to be thinner and more flexible. . For the purpose of reducing the thickness of the polarizing plate with a retardation layer, the protective layer and the retardation film of the polarizing film that contribute a large amount to the thickness are reduced. However, if the protective layer and retardation film are made thinner, the influence of the shrinkage of the polarizing film will be relatively large, and problems such as warpage of the image display device and deterioration of the workability of the polarizing plate with the retardation layer may occur.

In order to solve the above-mentioned problems, it is necessary to reduce the thickness of the polarizing film together. However, if the thickness of the polarizing film is simply reduced, the optical characteristics will decrease. More specifically, one or both of the degree of polarization and the transmittance of the monomer in a trade-off relationship may be reduced to a degree that is not allowed in actual use. As a result, the optical properties of the polarizing plate with retardation layer also become insufficient. Prior art literature Patent literature

Patent Document 1: Japanese Patent No. 3325560

Summary of the invention The problem to be solved by the invention The present invention was made in order to solve the above-mentioned conventional problems, and its main object is to provide a polarizing plate with a retardation layer that is thin, has excellent handling properties, and excellent optical properties. way of solving the problem

The polarizing plate with a retardation layer of the present invention has a polarizing plate and a retardation layer, and 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, and has a thickness of 8 μm or less, a monomer transmittance of 43.5% or more, and a polarization degree of 99.940% or more. The retardation layer is an orientation cured layer of a liquid crystal compound. In one embodiment, the unit weight of the polarizing plate with retardation layer is 6.5 mg/cm ² or less. In one embodiment, the total thickness of the polarizing plate with retardation layer is 60 μm or less. In one embodiment, the retardation layer is a single layer of an orientation cured layer of a liquid crystal compound, the Re (550) of the retardation layer is 100 nm to 190 nm, and the slow axis of the retardation layer is aligned with the absorption axis of the polarizing film. The angle formed is 40°~50°. In one embodiment, the retardation layer has a laminated structure of an orientation cured layer of a first liquid crystal compound and an orientation cured layer of a second liquid crystal compound; Re (550) of the orientation cured layer of the first liquid crystal compound is 200 nm to 300 nm The angle between the slow axis and the absorption axis of the polarizing film is 10°~20°; the Re(550) of the orientation curing layer of the second liquid crystal compound is 100nm~190nm, and its slow axis is in relation to the absorption axis of 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 single transmittance of the polarizing film in a 50 cm ² region is 0.15% or less. In one embodiment, the width of the polarizing plate with retardation layer is 1000 mm or more, and the difference between the maximum value and the minimum value of the monomer transmittance in the position along the width direction of the polarizing film is 0.3% or less. In one embodiment, the monomer transmittance of the polarizing film is 44.0% or less, and the polarization degree is 99.990% or less. In one embodiment, the polarizing plate with a retardation layer further has another retardation layer outside the retardation layer, and the refractive index characteristics of the other retardation layer show the relationship of nz>nx=ny. In one embodiment, the polarizing plate with a retardation layer further has a conductive layer or an isotropic substrate with a conductive layer outside the retardation layer. According to another aspect of the present invention, an image display device is provided. This image display device includes the above-mentioned polarizing plate with a retardation layer. In one embodiment, the above-mentioned image display device is an organic electroluminescence display device or an inorganic electroluminescence display device. Effect of invention

According to the present invention, the addition of halide (representatively potassium iodide) to polyvinyl alcohol (PVA)-based resins, two-stage stretching including aerial auxiliary stretching and underwater stretching, and drying and heating rollers By shrinking, a thin polarizing film with very excellent optical characteristics can be obtained. By using such a polarizing film, it is possible to realize a polarizing plate with a retardation layer that is thin, has excellent handling properties, and has excellent optical properties.

detailed description Hereinafter, 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 where the in-plane refractive index reaches the maximum (ie the slow axis direction), "ny" is the refractive index in the direction orthogonal to the slow axis (ie the fast axis direction) in the plane, "nz" Is the refractive index in the thickness direction. (2) In-plane phase difference (Re) "Re(λ)" is the in-plane phase difference measured with light of wavelength λnm at 23°C. For example, "Re(550)" is the in-plane phase difference measured with light with a wavelength of 550 nm at 23°C. 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 thickness direction retardation measured with light of wavelength λnm at 23°C. For example, "Rth(550)" is the thickness direction retardation measured by light with a wavelength of 550 nm at 23°C. 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 with respect to the reference direction. Therefore, for example, "45°" means ±45°.

A. Overall structure of polarizer with retardation layer Fig. 1 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to an embodiment of the present invention. The polarizing plate 100 with a retardation layer of this embodiment has a polarizing plate 10 and a retardation layer 20. The polarizing plate 10 includes a polarizing film 11, a first protective layer 12 arranged on one side of the polarizing film 11, and a second protective layer 13 arranged 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 43.5% or more, and the polarization degree is 99.940% or more.

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

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

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

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

The polarizing plate with a retardation layer of the present invention may be a single sheet or a long strip. In the present specification, the “long strip” refers to an elongated shape having a length sufficiently long relative to a width, and includes, for example, an elongated shape having a length of 10 times or more, preferably 20 times or more, with respect to the width. The long polarizing plate with retardation layer can be wound into a roll.

In actual use, an adhesive layer (not shown) can be provided on the side of the retardation layer opposite to the polarizing plate, so that the polarizing plate with the retardation layer can be stuck 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 a retardation layer is used. By temporarily sticking the release film, the adhesive layer can be protected and a roll can be formed.

The total thickness of the polarizing plate with 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 embodiment of the present invention, a very thin polarizing plate with a retardation 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 retardation layer can be particularly suitable for use in 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 retardation layer refers to the thickness of the polarizing plate with retardation layer, except for the adhesive layer used to adhere the polarizing plate to external adherends such as panels and glass. The total thickness of all layers (that is, the total thickness of the polarizing plate with retardation layer does not include the adhesive layer used to stick the polarizing plate with retardation layer to adjacent components such as image display units, and can be temporarily pasted on its surface The thickness of the release film).

The unit weight of the polarizing plate with retardation layer of the 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 , 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 polarizer with retardation layer, which may cause display failure. According to the polarizer with retardation layer having a unit weight of 6.5 mg/cm ² or less, Prevent such panel deformation. In addition, even when the polarizing plate with a retardation layer having the above-mentioned unit weight is thinned, it has good handling properties, and can exhibit very excellent flexibility and bending durability.

Hereinafter, the components of the polarizing plate with retardation layer will be described in more detail.

B. Polarizing plate B-1. Polarizing film As described above, the thickness of the polarizing film 11 is 8 μm or less, the single transmittance is 43.5% or more, and the polarization degree is 99.940% or more. Generally speaking, there is a trade-off relationship between monomer transmittance and polarization degree. If the monomer transmittance is increased, the polarization degree will decrease, and if the polarization degree is increased, the monomer transmittance will decrease. Therefore, it has been difficult to provide a thin polarizing film that satisfies the optical characteristics of a monomer transmittance of 43.5% or more and a polarization degree of 99.940% or more in practical use. It is one of the characteristics of the present invention to use a thin polarizing film that has excellent optical characteristics such as a monomer transmittance of 43.5% or more and a degree of polarization of 99.940% or more, and the deviation of the optical characteristics is suppressed.

The thickness of the polarizing film is preferably 1 μm to 8 μm, more preferably 1 μm to 7 μm, and even more preferably 2 μm to 5 μm.

The polarizing film preferably exhibits absorption dichroism at any wavelength from 380 nm to 780 nm. The monomer transmittance of the polarizing film is preferably 44.0% or less. The degree of polarization of the polarizing film is preferably 99.950% or more, more preferably 99.960% or more. On the other hand, the degree of polarization is preferably 99.990% or less. The above-mentioned monomer transmittance is typically the Y value obtained by measuring with an ultraviolet-visible spectrophotometer and performing visibility correction. The above-mentioned degree of polarization is typically based on the parallel transmittance Tp and the orthogonal transmittance Tc obtained by measuring with an ultraviolet-visible spectrophotometer and performing visibility correction, 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 is typically measured using a laminate of a polarizing film (refractive index of the surface: 1.53) and a protective film (refractive index: 1.50), and ultraviolet-visible spectroscopy is used. Measured with a photometer. Depending on the refractive index of the surface of the polarizing film and/or the refractive index of the surface of the protective film contacting the air interface, the reflectance of 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 with a refractive index of not 1.50 is used, the measured value of transmittance can be corrected based on the refractive index of the surface of the protective film contacting the air interface. Specifically, the correction value C of the transmittance is the reflectance R ₁ (transmission axis reflectance) of polarized light parallel to the transmission axis in the interface between the protective film and the air layer and is expressed by the following formula. 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 base material (cycloolefin-based film, hard coat film, etc.) having a surface refractive index of 1.53 is used as a protective film, the correction amount C becomes approximately 0.2%. In this case, by adding 0.2% to the transmittance obtained by the measurement, it can be converted into the transmittance when a protective film with a surface refractive index of 1.50 is used. It should be noted that, 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 is brought to the value of the correction value C The impact is limited. In addition, when the protective film has absorption other than surface reflection, appropriate correction can be made according to the amount of absorption.

In one embodiment, the width of the polarizing plate with retardation 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 in the position along the width direction of the polarizing film is preferably 0.3% or less, more preferably 0.25% or less, and even more preferably 0.2% or less. The smaller D1 is, the more preferable, and the lower limit of D1 may be, for example, 0.01%. When D1 is in the above range, a polarizing plate with a retardation layer having excellent optical characteristics can be manufactured industrially. In another embodiment, the difference (D2) between the maximum value and the minimum value of the monomer transmittance in the 50 cm ² region of the polarizing film is preferably 0.15% or less, more preferably 0.1% or less, and even more preferably 0.08% or less. The smaller D2 is, the more preferable, and the lower limit of D2 may be, for example, 0.01%. When D2 is in the above-mentioned range, it is possible to suppress uneven brightness in the display screen when the polarizing plate with a retardation layer is used in an image display device.

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

As a specific example of the polarizing film obtained using the laminated body, the polarizing film obtained using the laminated body of the resin base material and the PVA-type resin layer formed on this resin base material by coating is mentioned. A polarizing film obtained by using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced by the following method: for example, a PVA-based resin solution is applied to the resin substrate and dried to form 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 form the PVA-based resin layer into a polarizing film. In this embodiment, stretching typically includes stretching the laminate by immersing the laminate in an aqueous boric acid solution. In addition, the stretching may further include in-air stretching of the laminate at a high temperature (for example, 95° C. or higher) before stretching in an aqueous boric acid solution, as necessary. The obtained resin substrate/polarizing film laminate can be used as it is (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 used Any appropriate protective layer according to the purpose is laminated on the peeling surface and used. The details of the manufacturing method of such a polarizing film are described in, for example, JP 2012-73580 A. The entire description of this publication can be cited in this specification as a 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-shaped thermoplastic resin substrate to form a laminate; Sequentially, air-assisted stretching treatment, dyeing treatment, underwater stretching treatment, and drying shrinkage treatment in which heating is performed while being transported in the longitudinal direction to shrink by 2% or more in the width direction are performed. Thereby, it is possible to provide a polarizing film having a thickness of 8 μm or less, a single transmittance of 43.5% or more, and a polarization degree of 99.940% or more, having excellent optical characteristics and suppressing variations in optical characteristics. 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 properties can be realized. In addition, by improving the orientation of PVA in advance, it is possible to prevent problems such as decrease in orientation and dissolution of PVA when immersed in water in the subsequent dyeing step and stretching step, and to achieve high optical properties. 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 orientation disorder of the polyvinyl alcohol molecule and the decrease in orientation. Thereby, the optical characteristics of the polarizing film obtained by the process of immersing the laminated body in a liquid, such as a dyeing process and an underwater stretching process, can be improved. In addition, by shrinking the laminate in the width direction by the dry shrinking treatment, the optical characteristics can be improved.

B-2. Protection layer The first protective layer 12 and the second protective layer 13 can 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, polyamides, and polyimides. Transparent resins such as polyether-based, polyether-based, poly-based, polystyrene, polynorbornene, polyolefin, (meth)acrylic, and acetate, etc. In addition, thermosetting resins such as (meth)acrylic resins, urethanes, (meth)acrylate urethanes, epoxy resins, and silicone resins, or ultraviolet curing resins, etc., can also be cited. In addition to these, for example, glassy polymers such as silicone polymers can be cited. In addition, the polymer film described in JP 2001-343529 A (WO01/37007) can also be used. As the material of the film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted amide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain can be used. For example, a resin composition having an alternating copolymer of isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer can be cited. The polymer film may be, for example, an extrusion molded product of the above-mentioned resin composition.

As described later, the polarizing plate with a retardation layer of the present invention is typically arranged on the visible side of an image display device, and the first protective layer 12 is typically arranged on the visible side. Therefore, if necessary, surface treatments such as hard coating treatment, anti-reflection treatment, anti-adhesion treatment, and anti-glare treatment may be performed on the first protective layer 12. In addition/or, if necessary, the first protective layer 12 may be subjected to processing to improve the visibility when it is visually recognized through polarized sunglasses (representatively, imparting (elliptical) circular polarization function and imparting ultra-high 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 retardation 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 the surface treatment is performed, the thickness of the outer protective layer is the thickness including the thickness of the surface treatment layer.

In one embodiment, the second protective layer 13 is preferably optically isotropic. In this specification, “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 retardation layer having any appropriate retardation value. In this case, the in-plane retardation Re (550) of the retardation layer is 110 nm to 150 nm, for example. 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 thickness reduction 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 following steps: for example, a polyvinyl alcohol resin layer (PVA resin) containing a halide and a polyvinyl alcohol resin (PVA resin) is formed on one side of a long thermoplastic resin substrate. Resin layer) to form a laminate; and sequentially perform aerial auxiliary stretching treatment, dyeing treatment, underwater stretching treatment on the laminate, and heating while conveying it 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 with 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 section B-1 can be obtained. In particular, a laminate containing a PVA-based resin layer containing a halide is produced, the above-mentioned laminate is stretched by multi-stage stretching including air-assisted stretching and underwater stretching, and the stretched laminate is subjected to heating rollers. By heating, it is possible to obtain a polarizing film having excellent optical properties (typically, monomer transmittance and polarization degree) and with suppressed variations in optical properties. Specifically, by using a heating roller in the drying and shrinking treatment step, it is possible to uniformly shrink the entire laminate while conveying the laminate. As a result, not only can the optical properties of the obtained polarizing film be improved, a polarizing film with excellent optical properties can be stably produced, and the deviation of the optical properties (especially monomer transmittance) of the polarizing film can be suppressed.

B-3-1. Production of laminated body As a method of producing a laminate of a thermoplastic resin substrate and a PVA-based resin layer, any appropriate method can be adopted. Preferably, a coating solution containing a halide and a PVA-based resin is applied to the surface of the thermoplastic resin substrate and dried to form 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 parts by weight to 20 parts by weight relative to 100 parts by weight of the PVA-based resin.

As the 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 curtain coating method, a spray coating method, a blade coating method (a missing corner wheel coating method, 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.), and an easily adhesive layer may be formed on the thermoplastic resin substrate. By performing such treatment, the adhesion between the thermoplastic resin substrate 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 the thickness exceeds 300 μm, for example, in the underwater stretching treatment described later, it may take a long time for the thermoplastic resin substrate to absorb water, and the stretching may require an excessive load.

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

The glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 120°C or less. By using such a thermoplastic resin base material, 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 excellent underwater stretching, the temperature is more preferably 100°C or lower, and even 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, occurrence of unevenness, slack, wrinkles, etc.) of the thermoplastic resin substrate during coating/drying with the above-mentioned coating solution containing PVA-based resin, and can be used well. Make a laminate. In addition, the PVA-based resin layer can be stretched well at a suitable temperature (for example, about 60°C). It should be noted that the glass transition temperature of the thermoplastic resin substrate can be adjusted by, for example, using a crystallization material in which a modifying group is introduced into the constituent material and heating it. The glass transition temperature (Tg) is a value determined in accordance with JIS K7121.

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

In one embodiment, it is preferable to use an amorphous (non-crystallized) polyethylene terephthalate resin. Among them, it is particularly preferable to use an amorphous (not easily crystallized) polyethylene terephthalate resin. As a specific example of the amorphous polyethylene terephthalate resin, a copolymer that further contains isophthalic acid and/or cyclohexanedicarboxylic acid as a dicarboxylic acid, and further contains cyclohexane Dimethanol and diethylene glycol are copolymers of diols.

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

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

The stretching temperature of the thermoplastic resin base material is preferably Tg-10°C to Tg+50°C relative to the glass transition temperature (Tg). The stretch ratio of the thermoplastic resin substrate is preferably 1.5 times to 3.0 times.

As the stretching method of the thermoplastic resin substrate, any appropriate method can be adopted. Specifically, it can 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 stage or in multiple stages. When it is performed in multiple stages, the above-mentioned stretch magnification is the product of the stretch magnifications of each stage.

B-3-1-2. Coating liquid The coating liquid contains a halide and a PVA-based 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 solvents include water, dimethyl sulfide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, and polyhydric alcohols such as trimethylolpropane. Amines such as ethylenediamine and diethylenetriamine. These can be used alone or in combination of two or more kinds. Among these, water is preferable. The PVA-based resin concentration of the solution is preferably 3 parts by weight to 20 parts by weight relative to 100 parts by weight of the solvent. If it is such a resin concentration, it is possible to form a uniform coating film in close contact with the thermoplastic resin substrate. The content of the halide in the coating liquid is preferably 5 parts by weight to 20 parts by weight with respect 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 plasticizers include polyhydric alcohols such as ethylene glycol and glycerol. 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 above-mentioned PVA-based resin, any appropriate resin can be adopted. 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 an ethylene-vinyl acetate copolymer. The degree of saponification of the PVA-based resin is generally 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. The degree of saponification can be determined in accordance with JIS K 6726-1994. By using a PVA-based resin with such a degree of saponification, a polarizing film excellent in durability can be obtained. When the saponification is too high, there is a risk 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. It should be noted that the average degree of polymerization can be determined in accordance with JIS K 6726-1994.

As the above-mentioned halide, any appropriate 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 parts by weight to 20 parts by weight relative to 100 parts by weight of PVA-based resin, and more preferably 10 parts by weight to 15 parts by weight relative to 100 parts by weight of PVA-based resin. When the amount of the 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 resulting polarizing film may become cloudy.

Generally speaking, by stretching the PVA-based resin layer, the orientation of the polyvinyl alcohol molecules in the PVA-based resin is improved, but if the stretched PVA-based resin layer is immersed in a liquid containing water, polyvinyl alcohol is present. The orientation of vinyl alcohol molecules is disordered and the orientation is reduced. Especially when the laminate of the thermoplastic resin substrate and the PVA-based resin layer is stretched in boric acid water, in order to stabilize the stretching of the thermoplastic resin substrate, the laminate is stretched in boric acid water at a relatively high temperature At this time, the tendency of the above-mentioned orientation degree to decrease is remarkable. For example, the stretching of a PVA film monomer in boric acid water is usually carried out at 60°C. In contrast, the stretching of a laminate of A-PET (thermoplastic resin substrate) and PVA-based resin layer is at a temperature of about 70°C. It is carried out at such a high temperature. In this case, the orientation of the PVA in the initial stage of stretching is lowered in the stage before it rises by stretching in water. In contrast, by making a laminate of a halide-containing PVA-based resin layer and a thermoplastic resin substrate, and before stretching the laminate in boric acid water, it is stretched at high temperature in the air (assisted stretching). This can promote the crystallization of the PVA-based resin in the PVA-based resin layer of the laminate after the auxiliary stretching. As a result, when the PVA-based resin layer is immersed in a liquid, compared to a case where the PVA-based resin layer does not contain a halide, it is possible to suppress the orientation disorder of the polyvinyl alcohol molecules and the decrease in orientation. Thereby, the optical characteristics of the polarizing film obtained by the process of immersing the laminated body in a liquid, such as a dyeing process and an underwater stretching process, can be improved.

B-3-2. Aerial auxiliary stretch processing In order to obtain high optical properties, a two-stage stretching method combining dry stretching (assisted stretching) and boric acid water stretching is particularly selected. By introducing auxiliary stretching like two-stage stretching, stretching can be performed while suppressing the crystallization of the thermoplastic resin substrate, which can solve the problem of excessive crystallization of the thermoplastic resin substrate in the subsequent boric acid water stretching Because of the problem of reduced stretchability, the laminate can be stretched at a higher magnification. In addition, when PVA-based resin is coated 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 PVA-based resin is generally coated on a metal drum. As a result , The crystallization of the PVA-based resin is relatively low, and sufficient optical properties cannot be obtained. In contrast, 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 properties can be achieved. In addition, by increasing the orientation of the PVA-based resin in advance, when it is immersed in water in the subsequent dyeing step and stretching step, problems such as the decrease in orientation and dissolution of the PVA-based resin can be prevented, and high optical properties can be achieved.

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

Aerial auxiliary stretching can be carried out in one stage or in multiple stages. When it is performed in multiple stages, the stretch magnification is the product of the stretch magnifications of each stage. The stretching direction in the aerial auxiliary stretching is preferably approximately the same as the stretching direction in the underwater stretching.

The stretching ratio in the aerial 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 draw ratio" refers to the draw ratio immediately before the laminate is broken, and also refers to the draw ratio at which the laminate is confirmed to be broken and a value smaller than this value by 0.2.

The stretching temperature of the air-assisted stretching can be set to any appropriate value according to the forming material of the thermoplastic resin substrate, 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 Tg + 15° C. or higher. On the other hand, the upper limit of the stretching temperature is preferably 170°C. By stretching at such a temperature, it is possible to suppress the rapid progress of crystallization of the PVA-based resin, and it is possible to suppress defects caused by the crystallization (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 PVA-based resins can be measured by the ATR method using a Fourier transform infrared spectrophotometer. Specifically, measurement is performed using polarized light as measurement light, and the intensities at 1141 cm ^-1 and 1440 cm ^-1 in the obtained spectrum are used to calculate the crystallization index 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, an insolubilization treatment is performed after the aerial auxiliary stretching treatment and before the underwater stretching treatment and the dyeing treatment. The above-mentioned insolubilization treatment is typically performed by immersing the PVA-based resin layer in a boric acid aqueous solution. By performing the insolubilization treatment, water resistance can be imparted to the PVA-based resin layer, and the orientation of the PVA can be prevented from decreasing when immersed in water. The concentration of the boric acid aqueous solution is preferably 1 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 aforementioned 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 to 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 coating the PVA-based resin layer with the dyeing solution; and spraying the dyeing on the PVA-based resin layer Liquid method, etc. The method of immersing the laminated body in a dyeing liquid (dyeing bath) is preferable. This is because iodine can be adsorbed well.

The above-mentioned dyeing liquid is preferably an iodine aqueous solution. The blending amount of iodine is preferably 0.05 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 blend iodide in the iodine aqueous solution. Examples of iodides include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, etc. . Among these, potassium iodide is preferable. The blending amount of the iodide is preferably 0.1 parts by weight to 10 parts by weight, and more preferably 0.3 parts by weight 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 when 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 such that the monomer transmittance of the finally obtained polarizing film is 43.5% or more, and the polarization degree is 99.940% or more. As such dyeing conditions, it is preferable to use an iodine aqueous solution as the dyeing solution, and to set the ratio of the content of iodine to potassium iodide in the iodine aqueous solution to 1:5 to 1:20. The ratio of the content of iodine to potassium iodide in the iodine aqueous solution is preferably 1:5 to 1:10. Thus, a polarizing film having the above-mentioned optical characteristics can be obtained.

When the laminate is immersed in a treatment bath containing boric acid (typically an insolubilization treatment) followed by dyeing treatment, the boric acid contained in the treatment bath is mixed into the dyeing bath, and the concentration of boric acid in the dyeing bath changes with time As a result, the dyeability may become unstable. In order to suppress the destabilization of the dyeability as described above, the upper limit of the boric acid concentration of the dyeing bath is adjusted so that it is preferably 4 parts by weight, more preferably 2 parts by weight with respect to 100 parts by weight of water. On the other hand, the lower limit of the concentration of boric acid in the dye bath is preferably 0.1 parts by weight, more preferably 0.2 parts by weight, and even more preferably 0.5 parts by weight with respect to 100 parts by weight of water. In one embodiment, the dyeing process is performed using a dyeing bath pre-blended with boric acid. Thereby, the ratio of the change in the concentration of boric acid in the case where the boric acid of the treatment bath is mixed into the dyeing bath can be reduced. The blending amount of boric acid pre-blended in the dyeing bath (ie, the content of boric acid not derived from the above-mentioned treatment bath) is preferably 0.1 parts by weight to 2 parts by weight, and more preferably 0.5 parts by weight to 1.5 with respect to 100 parts by weight of water Parts by weight.

B-3-5. Cross-linking treatment If necessary, a crosslinking treatment is performed after the dyeing treatment and before the underwater stretching treatment. The above-mentioned crosslinking treatment is typically performed by immersing the PVA-based resin layer in a boric acid aqueous solution. By performing the crosslinking treatment, water resistance can be imparted to the PVA-based resin layer, and during subsequent underwater stretching, the orientation of the PVA can be prevented from being reduced when immersed in high-temperature water. The concentration of the boric acid aqueous solution is preferably 1 to 5 parts by weight with respect to 100 parts by weight of water. In addition, when the crosslinking treatment is performed after the dyeing treatment, it is preferable to further blend an iodide. By blending iodide, it is possible to suppress the elution of iodine adsorbed on the PVA-based resin layer. The blending amount of the iodide is preferably 1 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 crosslinking 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 treatment, it can be stretched at a temperature lower than the glass transition temperature (typically about 80°C) of the thermoplastic resin substrate and the PVA-based resin layer. Stretching at high magnification while crystallization. As a result, a polarizing film having excellent optical characteristics can be manufactured.

Any appropriate method can be adopted for the stretching method of the laminate. Specifically, it may be fixed-end stretching or free-end stretching (for example, a method of uniaxial stretching by passing the laminated body between rolls with different peripheral speeds). Preferably, free end stretching is selected. The stretching of the laminate may be performed in one stage or in multiple stages. When it is performed in multiple stages, the stretching ratio (maximum stretching ratio) of the laminate described later is the product of the stretching ratios in each step.

The underwater stretching is preferably performed by immersing the laminate in an aqueous boric acid solution (boric acid underwater stretching). By using a boric acid aqueous solution as a stretching bath, it is possible to impart rigidity that can withstand the tension applied during stretching and water resistance that is insoluble in water to the PVA-based resin layer. Specifically, boric acid can generate tetrahydroxyborate anions in an aqueous solution and crosslink with PVA-based resins through hydrogen bonds. As a result, rigidity and water resistance can be imparted to the PVA-based resin layer, and it can be stretched well, and a polarizing film having excellent optical properties can be manufactured.

The boric acid aqueous solution is preferably obtained by dissolving boric acid and/or borate in water as a solvent. The concentration of boric acid relative to 100 parts by weight of water is preferably 1 part by weight to 10 parts by weight, 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 boric acid concentration 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. It should be noted that an aqueous solution obtained by dissolving boron compounds such as borax other than boric acid or borate, glyoxal, glutaraldehyde, etc. in a solvent can also be used.

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

The stretching temperature (liquid temperature of the stretching bath) is preferably 40°C to 85°C, more preferably 60°C to 75°C. If it is such a temperature, it is possible to suppress the dissolution of the PVA-based resin layer and simultaneously stretch at a high magnification. Specifically, as described above, in view of the relationship with the formation of the PVA-based resin layer, the glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 60°C or higher. In this case, if the stretching temperature is lower than 40°C, it may not be stretched well even if the plasticization of the thermoplastic resin base material due to water is considered. On the other hand, the higher the temperature of the stretching bath, the higher the solubility of the PVA-based resin layer and the possibility that excellent optical properties may not be obtained. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.

The stretching ratio by underwater stretching is preferably 1.5 times or more, and more preferably 3.0 times or more. The total stretch ratio of the laminate is preferably 5.0 times or more with respect to the original length of the laminate, and more preferably 5.5 times or more. By achieving such a high stretching ratio, a polarizing film with very excellent optical properties can be manufactured. Such a high stretching ratio can be achieved by adopting an underwater stretching method (boric acid underwater stretching).

B-3-7. Drying shrinkage treatment The above-mentioned drying and shrinking treatment may be performed by area heating performed by heating the entire area, or may be performed by heating the transport roller (using a so-called heating roller) (heat roller drying method). It is preferable to use both. By using a heating roller for drying, heating curl of the laminate can be efficiently suppressed, and a polarizing film with excellent appearance can be produced. Specifically, by drying the laminate in the state next to the heating roller, the crystallization of the above-mentioned thermoplastic resin substrate can be efficiently promoted, and the crystallinity can be increased. Even at a relatively low drying temperature, the thermoplastic resin can be increased well. The crystallinity of the substrate. As a result, the rigidity of the thermoplastic resin substrate is increased, and the shrinkage of the PVA-based resin layer due to drying can be endured, and curling can be suppressed. In addition, by using a heating roller, the laminated body can be dried while being kept in a flat state. Therefore, it is possible to suppress not only curling but also the generation of wrinkles. At this time, by shrinking the laminate in the width direction by the dry shrinking treatment, the optical characteristics can be improved. This is because it can effectively improve the orientation of PVA and PVA/iodine complexes. 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 laminated body can be continuously shrunk in the width direction while being transported, and high productivity can be achieved.

Fig. 4 is a schematic diagram showing an example of drying shrinkage treatment. In the drying shrinkage treatment, the laminated body 200 is dried while being transported by the transport rollers R1 to R6 and the guide rollers G1 to G4 heated to a predetermined temperature. In the example shown in the figure, the transport rollers R1 to R6 are arranged to alternately continuously heat the surface of the PVA resin layer and the surface of the thermoplastic resin base material. However, for example, it may be applied to only one surface of the laminate 200 (e.g., thermoplastic resin base). Material surface) The conveying rollers R1 to R6 are arranged in a continuous heating method.

The drying conditions can be controlled by adjusting the heating temperature of the transport roller (temperature of the heating roller), the number of heating rollers, the contact time with the heating roller, and the like. 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 well, curling can be well suppressed, and an optical laminate having very excellent durability can be manufactured. It should be noted that the temperature of the heating roller can be measured with a contact thermometer. In the illustrated example, six transport rollers are provided, but as long as there are a plurality of transport rollers, there is no particular limitation. There are usually 2 to 40 transport rollers, preferably 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 (at room temperature). It is preferably installed in a heating furnace equipped with an air blowing mechanism. By combining the drying by the heating roller and the 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 with a mini-blade digital anemometer.

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

C. The first retardation 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 non-liquid crystal materials, and therefore, the thickness of the retardation layer for obtaining a desired in-plane retardation can be greatly reduced. As a result, the thickness and weight of the polarizing plate with retardation layer can be further reduced. In the present specification, the "aligned curing layer" refers to a layer in which the liquid crystal compound is oriented in a predetermined direction in the layer and the orientation state of the layer is fixed. It should be noted that, as described later, the "alignment hardening layer" is a concept including an alignment hardening layer obtained by curing a liquid crystal monomer. In the present embodiment, it is representative that the rod-shaped liquid crystal compound is aligned in a state of being juxtaposed in the slow axis direction of the first retardation layer (alignment along the plane).

As the liquid crystal compound, for example, a liquid crystal compound (nematic liquid crystal) whose liquid crystal phase is a nematic phase. As such a liquid crystal compound, for example, a liquid crystal polymer and a liquid crystal monomer can be used. The development mechanism of the liquid crystallinity of the liquid crystal compound may be lyotropic or thermotropic. 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 the alignment state of the liquid crystal monomer can be fixed by polymerizing or crosslinking (ie, hardening) the liquid crystal monomer. After the liquid crystal monomers are aligned, for example, if the liquid crystal monomers are polymerized or cross-linked with each other, the above-mentioned alignment state can be thereby fixed. 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 undergo transition to a liquid crystal phase, a glass phase, or a crystal phase due to, for example, a temperature change peculiar to a liquid crystal compound. As a result, the first retardation layer becomes a retardation layer that is not affected by temperature changes and is extremely stable.

The temperature range in which the liquid crystal monomer exhibits liquid crystallinity differs according to its kind. 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 above-mentioned liquid crystal monomer, any appropriate liquid crystal monomer can be used. For example, the polymerizable mesogen compounds described in JP 2002-533742 (WO00/37585), EP358208 (US5211877), EP66137 (US4388453), WO93/22397, EP0261712, DE19504224, DE4408171, GB2280445, etc. can be used. Specific examples of such polymerizable mesogen compounds include, for example, BASF's trade name LC242, Merck's trade name E7, and Wacker-Chem's trade name LC-Sillicon-CC3767. As the liquid crystal monomer, for example, a nematic liquid crystal monomer is preferable.

The orientation curing layer of the liquid crystal compound can be formed by the following method: performing orientation treatment on the surface of a predetermined substrate, coating the surface with a coating liquid containing a liquid crystal compound, and aligning the liquid crystal compound in a direction corresponding to the orientation treatment described above To fix the orientation state. In one embodiment, the substrate is any suitable resin film, and the orientation curing layer formed on the substrate can be transferred to the surface of the polarizing plate 10. In another embodiment, the substrate may be the second protective layer 13. In this case, the transfer step can be omitted, and after the orientation curing layer (first retardation layer) is formed, the roll-to-roll lamination can be carried out continuously. Therefore, the productivity can be further improved.

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

The orientation of the liquid crystal compound can be performed as follows: According to the kind of the liquid crystal compound, the treatment is performed at a temperature showing a liquid crystal phase. By performing such a temperature treatment, the liquid crystal compound becomes a liquid crystal state, and the liquid crystal compound is aligned in accordance with the orientation treatment direction of the substrate surface.

In one embodiment, the fixation of the orientation state is performed by cooling the liquid crystal compound that has been oriented as described above. In the case where the liquid crystal compound is a polymerizable monomer or a crosslinkable monomer, the fixation of the alignment state can be performed by subjecting the liquid crystal compound aligned as described above to a polymerization treatment or a crosslinking treatment.

The specific examples of the liquid crystal compound and the details of the method for forming the orientation cured layer are described in Japanese Patent Application Laid-Open No. 2006-163343. The description of this gazette is used as a reference in this specification.

、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 orientation curing layer, a form in which the discotic liquid crystal compound is oriented in any one of vertical orientation, mixed orientation, and oblique orientation can be cited. For 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 is substantially perpendicular to mean 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 disc-shaped molecular structure. The disc-shaped molecular structure is a combination of benzene, 1,3,5-tri

A cyclic core such as calixarene, etc. is arranged in the center of the molecule, and a linear alkyl group, alkoxy group, substituted benzyloxy group, etc. are used as a structure in which side chains are radially substituted. As a representative example of discotic liquid crystals, benzene derivatives, triphenyl derivatives, and benzene derivatives described in research reports by C. Destrade, etc., Mol. Cryst. Liq. Cryst. Vol. 71, page 111 (1981) Indenobenzene derivatives, phthalocyanine derivatives, research reports by B. Kohne et al., cyclohexane derivatives described in Angew.Chem. Vol. 96, page 70 (1984), and research reports by JMLehn et al., J. Chem. Soc. Chem. Commun., 1794 pages (1985), research report by J. Zhang et al., J. Am. Chem. Soc. 116, 2655 pages (1994) described in the nitrogen crowns, phenyl A large ring of acetylenes. As other specific examples of the discotic liquid crystal compound, for example, the compounds described in Japanese Patent Application Publication No. 2006-133652, Japanese Patent Application Publication No. 2007-108732, and Japanese Patent Application Publication No. 2010-244038 may be cited. The descriptions in the above-mentioned 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, the thickness thereof is preferably 0.5 μm to 7 μm, and more preferably 1 μm to 5 μm. By using the liquid crystal compound, it is possible to achieve the same in-plane retardation as the resin film with a thickness significantly thinner than that of the resin film.

Typically, the refractive index characteristics of the first retardation layer show a relationship of nx>ny=nz. The first retardation layer is typically provided to impart anti-reflection properties to the polarizing plate. When the first retardation layer is a single layer of the orientation 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 here, "ny=nz" includes not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, in a range that does not impair the effect of the present invention, it may be ny>nz or ny<nz.

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 retardation layer is used in an image display device, a very excellent reflection hue can be realized.

The first retardation layer can exhibit reverse dispersion wavelength characteristics in which the retardation value increases in accordance with the wavelength of the measurement light, or it can exhibit positive wavelength dispersion characteristics in which the retardation value decreases in accordance with the wavelength of the measurement light, and can also display The retardation value hardly changes with the wavelength of the measurement light and the flat wavelength dispersion characteristics. In one embodiment, the first retardation layer exhibits reverse 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 structure, 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 setting the first retardation layer as a λ/4 plate, it is possible to obtain a band retardation with very excellent circular polarization characteristics (and as a result, very good anti-reflection characteristics). Layer of polarizing plate.

In another embodiment, as shown in FIG. 3, the first retardation layer 20 may have a laminated structure of the first oriented solidified layer 21 and the second oriented solidified layer 22. In this case, any one of the first orientation curing layer 21 and the second orientation curing layer 22 can function as a λ/4 plate, and the other can function as a λ/2 plate. Therefore, the thickness of the first oriented cured layer 21 and the second oriented cured layer 22 can be adjusted so as to obtain a desired in-plane phase difference of the λ/4 plate or the λ/2 plate. For example, when the first orientation curing layer 21 functions as a λ/2 plate and the second orientation curing layer 22 functions as a λ/4 plate, the thickness of the first orientation curing 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 phase difference Re(550) of the first orientation 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 phase difference Re (550) of the second directional solidified layer is as described above for the single-layer directional solidified 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 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 and second orientation curing layers, the formation method and optical properties of the first and second orientation curing layers are as described above for the single layer orientation curing layer.

D. The second retardation layer As described above, the second retardation layer may be a so-called negative C plate whose refractive index characteristic shows the relationship of nz>nx=ny. By using the negative C plate as the second retardation layer, reflection in the oblique direction can be prevented well, and the anti-reflection function can achieve a wide viewing angle. 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 the case where nx and ny are strictly equal, but also the 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 can be formed of any appropriate material. The second retardation layer is preferably formed of a thin film containing a liquid crystal material fixed in the vertical alignment. The liquid crystal material (liquid crystal compound) capable of vertical alignment may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the liquid crystal compound and the method for forming the retardation layer include the liquid crystal compounds described in [0020] to [0028] of JP 2002-333642 A 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 even 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, a vacuum evaporation method, a sputtering method, a CVD method, an ion plating method, a 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 substrate to the first retardation layer (or the second retardation layer when the second retardation layer is present), and the conductive layer alone can be used as the polarizing plate with retardation layer. The constituent layer may be formed as a laminate with a substrate (a substrate with a conductive layer) and laminated on the first retardation layer (or, if the second retardation layer is present, the second retardation layer). It is preferable that the above-mentioned 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 materials constituting the isotropic substrate include materials having a resin that does not have a conjugated system, such as norbornene resins and olefin resins, as the main skeleton; acrylic resins having a lactone ring, Materials with cyclic structure such as glutarimide ring. If such a material is used, when an isotropic substrate is formed, it is possible to suppress the phenomenon of the phase difference accompanying the orientation of the molecular chain 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 substrate is, for example, 20 μm.

The conductive layer and/or the conductive layer of the isotropic substrate with a conductive layer can be patterned as needed. By patterning, conductive parts and insulating parts can be formed. As a result, electrodes can be formed. The electrode can function as a touch sensor electrode that senses contact with the touch panel. As the pattern formation method, any appropriate method can be adopted. As specific examples of the pattern formation method, a wet etching method and a screen printing method can be cited.

F. Image display device The polarizing plate with retardation 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 retardation 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). The image display device according to the embodiment of the present invention is provided with the polarizing plate with a retardation layer described in the above items A to E on the viewing side. The polarizing plate with retardation layer is laminated so that the retardation layer is on the side of the image display unit (for example, liquid crystal cell, organic EL unit, and inorganic EL unit) (the polarizing film is on the visible side). In one embodiment, the image display device may have a curved shape (substantially a curved display screen), and/or be flexible or bendable. In such an image display device, the effect of the polarizing plate with retardation layer of the present invention becomes remarkable. Example

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對象的情況下，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公司制、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Hereinafter, the present invention will be specifically described through 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, "parts" and "%" in the examples and comparative examples are based on weight. (1) The thickness of 10 μm or less is 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, product name "KC-351C"). (2) Monomer transmittance and degree of polarization. The polarizing film/protective layer laminate (polarizing plate) used in the examples and comparative examples will be measured using an ultraviolet-visible spectrophotometer (V-7100 manufactured by JASCO Corporation). The obtained monomer transmittance Ts, parallel transmittance Tp, and orthogonal transmittance Tc are used as Ts, Tp, and Tc of the polarizing film. These Ts, Tp, and Tc are Y values measured by JIS Z8701 2 degree field of view (C light source) and corrected for visibility. It should be noted that the refractive index of the protective layer was 1.50, and the refractive index of the surface of the polarizing film opposite to the protective layer was 1.53. From the obtained Tp and Tc, the degree of polarization P is obtained by the following formula. Polarization degree P(%)={(Tp-Tc)/(Tp+Tc)} ^1/2 ×100 It should be noted that the spectrophotometer can be equivalently measured with LPF-200 manufactured by Otsuka Electronics Corporation. As an example, for samples 1 to 3 of the polarizing plate constructed in the same manner as 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 values are 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 the same measurement result can be obtained with any spectrophotometer.

It should be noted that, for example, in the case of an anti-glare (AG) surface treatment and a polarizing plate equipped with an adhesive with diffusing properties as the measurement object, different measurement results can be obtained by relying on a spectrophotometer. In this case, Numerical conversion is performed based on the measured value when the same polarizing plate is measured with each spectrophotometer, so that the difference in the measured value depending on the spectrophotometer can be compensated. (3) The deviation of the optical characteristics of the strip-shaped polarizing film. From the polarizing plates used in the examples and comparative examples, the measurement samples were cut out at 5 positions at equal intervals along the width direction to be the same as the above (2) The method measured the transmittance of the monomer in the central part of each of the five measurement samples. 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 taken as the deviation of the optical characteristics of the long-shaped polarizing film. (4) The deviation of the optical characteristics of the single-piece polarizing film. From the polarizing plates used in the Examples and Comparative Examples, a measurement sample of 100 mm×100 mm was cut out, and the optical characteristics of the single-piece polarizing plate (50 cm ² ) were determined. deviation. Specifically, in the same manner as in (2) above, the cell transmittance was measured at a position approximately 1.5 cm to 2.0 cm inward from the midpoint of each of the four sides of the measurement sample, and the central part, at 5 positions in total. Next, the difference between the maximum value and the minimum value of the monomer transmittance measured at each measurement position is calculated, and this value is used as the deviation of the optical characteristics of the single-piece polarizing film. (5) Warpage The polarizing plates with retardation layer obtained in the examples and comparative examples were cut into a size of 110 mm×60 mm. At this time, it cut out so that the absorption axis direction of a polarizing film might become a longitudinal direction. The cut out polarizing plate with a retardation 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, 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 it out was measured. When the test sample is placed on a flat surface with the glass plate facing down, the height of the highest part from the flat surface is used as the amount of warpage. (6) The polarizing plate with retardation layer obtained in the examples and comparative examples is cut into a predetermined size per unit weight, and the weight (mg) is divided by the area (cm ² ) to calculate the polarizing plate with retardation layer The weight per unit area (unit weight). (7) Flexural resistance The polarizing plates with retardation layers obtained in the examples and comparative examples were cut into a size of 50 mm×100 mm. At this time, it was cut out so that the absorption axis direction of the polarizing film became the short side direction. Using a flexural tester (manufactured by YUASA Corporation, CL09 type-D01) with a constant temperature and humidity chamber, the cut out polarizing plate with retardation layer was subjected to the bending test under the conditions of 20°C and 50% RH . Specifically, a polarizing plate with a retardation layer is repeatedly bent in a direction parallel to the absorption axis direction so that the retardation layer side becomes the outer side, and the measurement is performed until cracks, peeling, and film breaks such as display failures occur. The number of folds was evaluated according to the following criteria (bending diameter: 2mmφ). >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 amorphous isophthalic acid copolymer polyethylene terephthalate film (thickness: 100 μm) with a water absorption rate of 0.75% and a Tg of about 75° C. was used. Corona treatment is applied to one side of the resin substrate. PVA is made by mixing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetyl acetyl modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z410") at 9:1 13 parts by weight of potassium iodide was added to 100 parts by weight of the similar resin, and the obtained mixture was dissolved in water to prepare a PVA aqueous solution (coating liquid). The above-mentioned PVA aqueous solution was applied to the corona-treated surface of the resin substrate and dried at 60° C. to form a PVA-based resin layer with a thickness of 13 μm to produce a laminate. In an oven at 130°C, the obtained laminate was uniaxially stretched 2.4 times to the free end in the longitudinal direction (length direction) 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 mixing 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 dyeing bath with a liquid temperature of 30°C (an iodine aqueous solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with respect to 100 parts by weight of water), the monomer transmittance of the polarizing film finally obtained ( Ts) was immersed for 60 seconds while adjusting the concentration so as to be 43.5% or more (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 and blending 5 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 (crosslinking treatment). Then, while immersing the laminate in a boric acid aqueous solution (boric acid concentration 4.0% by weight) at a liquid temperature of 70°C, it was performed between rolls with different peripheral speeds so that the total stretching ratio in the longitudinal direction (length direction) became 5.5 times The unidirectional stretching (underwater stretching treatment). Then, the laminate was immersed in a cleaning bath (an aqueous solution in which 4 parts by weight of potassium iodide was blended with respect to 100 parts by weight of water) at a liquid temperature of 20°C (washing treatment). Then, while drying in an oven maintained at 90°C, it was brought into contact with a heating roller made of SUS whose surface temperature was maintained 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. Making of polarizing plate On the surface (the 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 curable adhesive. Specifically, the coating was applied so that the total thickness of the curable adhesive became 1.0 μm, and the bonding was performed using a roll machine. Then, UV light is irradiated from the protective layer side to harden the adhesive. Next, after cutting both ends, the resin base material was peeled off, and a strip-shaped polarizing plate (width: 1300 mm) having a protective layer/polarizing film configuration was obtained. The single transmittance of the polarizing plate (essentially a polarizing film) is 43.76% and the degree of polarization is 99.980%. In addition, the deviation of the optical characteristics of the elongated polarizing film was 0.14%, and the deviation of the optical characteristics of the monolithic polarizing film was 0.06%.

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 oriented cured layer and the second oriented cured layer constituting the retardation layer will show a nematic liquid crystal phase polymerizable liquid crystal (made by BASF Corporation: trade name "Paliocolor LC242", represented by the following formula) 10g, and 3 g of a photopolymerization initiator (manufactured by BASF Corporation: 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]

A rubbing cloth was used to rub the surface of a polyethylene terephthalate (PET) film (thickness 38 μm), and the orientation treatment was performed. The direction of the orientation treatment was set to be a 15° direction when viewed from the visible side with respect to the absorption axis direction of the polarizing film when it was bonded to the polarizing plate. The above-mentioned 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 the liquid crystal orientation cured layer A on the PET film. The thickness of the liquid crystal orientation cured layer A was 2.5 μm, and the in-plane phase difference Re (550) was 270 nm. In addition, the liquid crystal orientation 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 direction of 75° when viewed from the visible side with respect to the absorption axis direction of the polarizing film, except that the 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 orientation cured layer B was 1.5 μm, and the in-plane phase difference Re (550) was 140 nm. In addition, the liquid crystal orientation cured layer B has a refractive index distribution of nx>ny=nz.

4. Production of polarizing plate with retardation 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. above are sequentially transferred. At this time, the rotation was carried out so that the angle formed by the absorption axis of the polarizing film and the slow axis of the orientation curing layer A became 15°, and the angle formed by the absorption axis of the polarizing film and the slow axis of the orientation curing layer B became 75°. Printing (fitting). In addition, each transfer (bonding) is performed through the ultraviolet curable adhesive (thickness 1.0 μm) used in 2. above. In this way, a polarizing plate with a retardation layer having a configuration of 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 retardation layer was 52 μm. The obtained polarizing plate with retardation layer was used for the evaluation of (5) to (7) above. The amount of warpage is 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 the protective layer. The total thickness of the obtained polarizing plate with retardation layer was 32 μm. The obtained polarizing plate with retardation layer was used for 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 triacetate cellulose (TAC) film with a thickness of 25 μm was used as the protective layer. The total thickness of the obtained polarizing plate with retardation layer was 37 μm. The obtained polarizing plate with retardation layer was used for the same evaluation as in Example 1. The amount of warpage is 1.3 mm.

[Comparative Example 1] 1. Production of polarizing parts A polyvinyl alcohol resin film with 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, it was stretched 2.4 times in the conveying direction between rollers with different peripheral speeds (swelling step), and then at 30 In a dyeing bath at °C (aqueous solution with an iodine concentration of 0.03% by weight and a potassium iodide concentration of 0.3% by weight), the original polyvinyl alcohol film is dipped and dyed so that the monomer transmittance after the final stretching becomes the desired value (The polyvinyl alcohol film which is not stretched at all in the conveying direction) is stretched to 3.7 times in the conveying direction 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 (an aqueous solution with a boric acid concentration of 3.0% by weight and a potassium iodide concentration of 3.0% by weight) at 40°C, the original polyvinyl alcohol film was used as a reference Stretched to 4.2 times in the conveying direction (crosslinking step). Furthermore, the obtained polyvinyl alcohol film was immersed in a stretching bath (an aqueous solution with a boric acid concentration of 4.0% by weight and a potassium iodide concentration of 5.0% by weight) at 64°C for 50 seconds, and transported on the basis of the original polyvinyl alcohol film. Stretched to 6.0 times in the direction (stretching step), and then immersed in a clean bath (aqueous 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 produce a polarizer (thickness 12 μm).

2. Making of polarizing plate As the adhesive, a polyvinyl alcohol resin containing acetyl acetyl groups in a weight ratio of 3:1 was used (average degree of polymerization of 1,200, saponification degree of 98.5 mol%, acetylation rate of 5 mol %) and an aqueous solution of methylol melamine. Using this adhesive and using a roll laminator, a 25μm-thick triacetate cellulose (TAC) film with a hard coat layer was laminated on one side of the polarizer obtained above, and a thickness of 25μm was laminated on the other side of the polarizer. After the TAC film, it was heated and dried in an oven (temperature of 60℃, time of 5 minutes) to produce a protective layer 1 (thickness 25μm)/adhesive layer/polarizer/adhesive layer/protective layer 2 (thickness 25μm) The composition of the polarizing plate.

3. Production of polarizing plate with retardation layer On the surface of the protective layer 2 of the polarizing plate obtained in 2. above, the liquid crystal orientation cured layer A and the liquid crystal orientation cured layer B were sequentially transferred in the same manner as in Example 1, to produce a protective layer 1 / adhesive layer / polarizing A polarizing plate with a retardation layer composed of parts/adhesive layer/protective layer2/adhesive layer/phase difference layer (first oriented cured layer/adhesive layer/second oriented cured layer). The total thickness of the obtained polarizing plate with retardation layer was 68 μm. The obtained polarizing plate with retardation layer was used for the same evaluation as in Example 1. The amount of warpage is 4.2 mm.

[Comparative Example 2] The PVA aqueous solution (coating liquid) was not added with potassium iodide, the stretching ratio in the air-assisted stretching treatment was set to 1.8 times, and the heating roller was not used in the drying shrinkage treatment, except that it was the same as in Example 1 Produced polarizing film and polarizing plate. The single transmittance of the polarizing plate (essentially a polarizing film) is 43.13%, and the degree of polarization is 99.881%. Except for using this polarizing plate, a polarizing plate with a retardation layer was produced in the same manner as in Example 1.

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

2. Production of retardation film constituting retardation layer 2-1. Polymerization of polyester carbonate resin used a batch consisting of 2 vertical reactors with stirring blades and reflux coolers controlled to 100°C The polymerization device performed polymerization. Add bis[9-(2-phenoxycarbonylethyl)fluorene-9-yl]methane 29.60 parts by mass (0.046mol), 29.21 parts by mass (0.200mol) of isosorbide (ISB), and spirodiol (SPG) 42.28 parts by mass (0.139 mol), 63.77 parts by mass (0.298 mol) of diphenyl carbonate (DPC), and 1.19×10 ^-2 parts by mass (6.78×10 ^-5 mol) of calcium acetate monohydrate as a catalyst. After the inside of the reactor was replaced with nitrogen under reduced pressure, it was heated 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 started while maintaining the temperature, and it reached 13.3 kPa 90 minutes after reaching 220°C. The phenol vapor produced during the polymerization reaction is introduced into a reflux cooler at 100°C, a certain amount of monomer components contained in the phenol vapor is returned to the reactor, and uncondensed phenol vapor is introduced to 45°C The condenser is recycled. After introducing nitrogen gas into the first reactor to temporarily return to atmospheric pressure, the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Next, the temperature increase 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, polymerization is carried out until it reaches a predetermined stirring power. When the predetermined power is reached, nitrogen is introduced into the reactor, the pressure is restored, the produced polyester carbonate-based resin is extruded into water, the strands are cut, and pellets are obtained.

2-2. Production of retardation film After drying the obtained polyester carbonate resin (pellet) in vacuum at 80°C for 5 hours, a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder set temperature: 250°C) and T-die (width 200mm) were used. , Set temperature: 250°C), chill roll (set temperature: 120~130°C), and the film forming device of the coiler 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. The Re(550) of the obtained retardation film was 141 nm, the Re(450)/Re(550) was 0.82, and the Nz coefficient was 1.12.

3. Production of polarizing plate with retardation layer On the surface of the polarizing film of the polarizing plate obtained in 1. above, the retardation film obtained in 2. above was bonded through an acrylic adhesive (thickness 5 μm). At this time, bonding was performed so that the absorption axis of the polarizing film and the slow axis of the retardation film became an angle of 45°. In this way, a polarizing plate with a retardation layer having a configuration of a protective layer/adhesive layer/polarizing film/adhesive layer/retardation layer was obtained. The total thickness of the obtained polarizing plate with retardation layer was 89 μm. The obtained polarizing plate with a retardation layer was used for the evaluation of (6) and (7) above.

Table 2 shows the structure of the polarizing plate with retardation layer obtained in Examples 1 to 3 and Comparative Examples 1 and 3, and each evaluation result.

[Evaluation] From Table 2 and the comparison between Example 1 and Comparative Example 2, it is clear that the polarizing plate with retardation layer of the example of the present invention is thin, can suppress warpage after the heating test, and has excellent optical characteristics. In addition, by setting the weight per unit area of the polarizing plate with a retardation layer to a predetermined value or less, the 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: Polarizing plate 11: Polarizing film 12: The first protective layer 13: The second protective layer 20: retardation layer (first retardation 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, 101, 102: Polarizing plate with retardation layer 200: laminated body R1~R6: Transport roller G1~G4: guide roller

Fig. 1 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to an embodiment of the present invention. 2 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to another embodiment of the present invention. Fig. 3 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to 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 manufacturing method of the polarizing film of the polarizing plate with retardation layer used in the present invention.

10: Polarizing plate

11: Polarizing film

12: The first protective layer

13: The second protective layer

20: retardation layer (first retardation layer)

100: Polarizing plate with retardation layer

Claims (12)

A polarizing plate with a retardation layer, which has a polarizing plate and a retardation layer, the polarizing plate comprising 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, with a thickness of 8μm or less, a monomer transmittance of 43.5% or more, and a degree of polarization of 99.940% or more. The retardation layer is an orientation cured layer of a liquid crystal compound. For example, the polarizing plate with retardation layer of claim 1 has a unit weight of 6.5 mg/cm ² or less. For example, the polarizing plate with retardation layer of claim 1 has a total thickness of 60 μm or less. Such as the polarizing plate with retardation layer of claim 1, in which, The retardation layer is a single layer of a oriented solidified layer of a liquid crystal compound, The Re(550) of the retardation layer is 100nm~190nm, The angle formed by the slow axis of the retardation layer and the absorption axis of the polarizing film is 40°-50°. Such as the polarizing plate with retardation layer of claim 1, in which, The retardation layer has a laminated structure of an orientation cured layer of a first liquid crystal compound and an orientation cured layer of a second liquid crystal compound, The Re (550) of the orientation cured layer of the first liquid crystal compound is 200 nm to 300 nm, and the angle between its slow axis and the absorption axis of the polarizing film is 10° to 20°, The Re (550) of the orientation 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 retardation layer according to claim 1, wherein the difference between the maximum value and the minimum value of the single transmittance of the polarizing film in a 50 cm ² area is 0.15% or less. The polarizing plate with retardation layer of claim 1 has a width of 1000 mm or more, and the difference between the maximum value and the minimum value of the monomer transmittance in the position along the width direction of the polarizing film is 0.3% or less. The polarizing plate with retardation layer according to claim 1, wherein the single transmittance of the polarizing film is 44.0% or less, and the degree of polarization is 99.990% or less. The polarizing plate with retardation layer according to claim 1, further having another retardation layer outside the retardation layer, and the refractive index characteristics of the other retardation layer show the relationship of nz>nx=ny. The polarizing plate with a retardation layer according to claim 1, which further has a conductive layer or an isotropic substrate with a conductive layer on the outer side of the retardation layer. An image display device provided with a polarizing plate with a retardation layer as in any one of claims 1 to 10. Such as the image display device of claim 11, which is an organic electroluminescence display device or an inorganic electroluminescence display device.

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