JP2020064280A - Polarizing plate with phase difference layer and image display device using the same - Google Patents

Abstract

To provide a polarizing plate with a phase difference layer which is thin, and is excellent in handling property and optical characteristics.SOLUTION: A polarizing plate with a phase difference layer according to the present invention includes: a polarizing plate having a polarizing film and a protective layer on at least one side of the polarizing film; and a phase difference layer. The polarizing film is formed of a polyvinyl alcohol-based resin film containing a dichroic substance, and has a thickness of not larger than 8 μm, a single layer transmittance of 48% or more, and a polarization degree of 85% or more. The phase difference layer is an alignment fixed layer of a liquid crystal compound.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polarizing plate with a retardation layer and an image display device using the same.

  2. Description of the Related Art 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) have rapidly spread. A polarizing plate and a retardation plate are typically used for the image display device. Practically, a polarizing plate with a retardation layer in which a polarizing plate and a retardation plate are integrated is widely used (for example, Patent Document 1), and recently, there is a strong demand for thinner image display devices. Accordingly, there is an increasing demand for thinner polarizing plates with retardation layers. Further, in recent years, there has been an increasing demand for a curved image display device and / or an image display device that can be bent or bent, and thus a polarizing plate and a polarizing plate with a retardation layer are required to be thinner and more flexible. ing. For the purpose of reducing the thickness of the polarizing plate with a retardation layer, the thickness of the protective layer of the polarizing film and the retardation film, which make a large contribution to the thickness, has been reduced. However, when the protective layer and the retardation film are made thin, the influence of the shrinkage of the polarizing film becomes relatively large, which causes the problems of warpage of the image display device and deterioration of the operability of the polarizing plate with the retardation layer.

  In order to solve the above problems, it is necessary to thin the polarizing film as well. However, if the thickness of the polarizing film is simply reduced, the optical characteristics will deteriorate. More specifically, one or both of the polarization degree and the single-body transmittance, which are in a trade-off relationship, are reduced to a practically unacceptable level. As a result, the optical characteristics of the polarizing plate with the retardation layer are also insufficient.

Japanese Patent No. 3325560

  The present invention has been made to solve the above-mentioned conventional problems, and a main object thereof is to provide a polarizing plate with a retardation layer, which is thin, excellent in handleability, and excellent in optical characteristics. .

The polarizing plate with a retardation layer of the present invention has a polarizing plate including a polarizing film, 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 a thickness of 8 μm or less, a single transmittance of 48% or more, and a polarization degree of 85% or more. The retardation layer is an alignment solidified layer of a liquid crystal compound.
In one embodiment, the polarizing plate with a retardation layer has a unit weight of 6.5 mg / cm ² or less.
In one embodiment, the polarizing plate with a retardation layer has a total thickness of 60 μm or less.
In one embodiment, the retardation layer is a single layer of an alignment-fixed layer of a liquid crystal compound, Re (550) of the retardation layer is 100 nm to 190 nm, and the retardation axis of the retardation layer is The angle formed by the absorption axis of the polarizing film is 40 ° to 50 °.
In one embodiment, the retardation layer has a laminated structure of an alignment fixed layer of a first liquid crystal compound and an alignment fixed layer of a second liquid crystal compound; the alignment fixed layer of the first liquid crystal compound. Re (550) is 200 nm to 300 nm, and the angle formed by the slow axis and the absorption axis of the polarizing film is 10 ° to 20 °; Re (550) of the alignment solidified 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 °.
In one embodiment, the difference between the maximum value and the minimum value of the single-piece transmittance in the area of 50 cm ² of the polarizing film is 0.5% or less.
In one embodiment, the polarizing plate with the retardation layer has a width of 1000 mm or more, and the difference between the maximum value and the minimum value of the single transmittance at the position along the width direction of the polarizing film is 1% or less. is there.
In one embodiment, the single transmittance of the polarizing film is 50% or less, and the polarization degree is 92% 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 characteristic of the another retardation layer is nz> nx = ny. Show the relationship.
In one embodiment, the above-mentioned polarizing plate with a retardation layer further has a conductive layer or an isotropic substrate with a conductive layer outside the above-mentioned retardation layer.
According to another aspect of the present invention, an image display device is provided. This image display device includes the above polarizing plate with a retardation layer.
In one embodiment, the image display device is an organic electroluminescence display device or an inorganic electroluminescence display device.

  According to the present invention, addition of a halide (typically potassium iodide) to a polyvinyl alcohol (PVA) -based resin, two-stage stretching including auxiliary stretching in air and stretching in water, and drying and shrinking with a heating roll. By adopting in combination, it is possible to obtain a polarizing film that is thin and has extremely excellent optical characteristics. By using such a polarizing film, it is possible to realize a polarizing plate with a retardation layer, which is thin, has excellent handleability, and has excellent optical characteristics.

1 is a schematic sectional view of a polarizing plate with a retardation layer according to one embodiment of the present invention. FIG. 6 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to another embodiment of the present invention. It is a schematic sectional drawing of the polarizing plate with a retardation layer by another embodiment of this invention. It is a schematic diagram showing an example of dry shrinkage processing using a heating roll in a manufacturing method of a polarizing film used for a polarizing plate with a phase contrast layer of the present invention.

  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 the present specification are as follows.
(1) Refractive index (nx, ny, nz)
“Nx” is the refractive index in the direction in which the in-plane refractive index is maximum (that is, the slow axis direction), and “ny” is the direction in the plane that is orthogonal to the slow axis (that is, the fast axis direction). , And "nz" is the refractive index in the thickness direction.
(2) In-plane retardation (Re)
“Re (λ)” is an in-plane retardation measured with light having a wavelength of λ nm at 23 ° C. For example, “Re (550)” is an in-plane retardation measured with light having a wavelength of 550 nm at 23 ° C. Re (λ) is calculated by the formula: Re (λ) = (nx−ny) × d when the thickness of the layer (film) is d (nm).
(3) Phase difference in the thickness direction (Rth)
“Rth (λ)” is a phase difference in the thickness direction measured with light having a wavelength of λ nm at 23 ° C. For example, “Rth (550)” is a phase difference in the thickness direction measured with light having a wavelength of 550 nm at 23 ° C. Rth (λ) is calculated by the formula: Rth (λ) = (nx−nz) × d when the thickness of the layer (film) is d (nm).
(4) Nz coefficient The Nz coefficient is calculated by Nz = Rth / Re.
(5) Angle When an angle is referred to in this specification, the angle includes both clockwise and counterclockwise rotations with respect to the reference direction. Therefore, for example, “45 °” means ± 45 °.

A. Overall Configuration of Polarizing Plate with Retardation Layer FIG. 1 is a schematic 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 includes 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 for 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 polarizing film has a thickness of 8 μm or less, a single transmittance of 48% or more, and a polarization degree of 85% or more.

  As shown in FIG. 2, in the polarizing plate 101 with a retardation layer according to another embodiment, another retardation layer 50 and / or a conductive layer or an isotropic substrate 60 with a conductive layer may be provided. Another retardation layer 50 and the conductive layer or the isotropic substrate 60 with a conductive layer are typically provided outside the retardation layer 20 (on the side opposite to the polarizing plate 10). Another retardation layer typically has a refractive index characteristic of nz> nx = ny. Another retardation layer 50 and the conductive layer or the isotropic substrate 60 with a conductive layer are typically provided in this order from the retardation layer 20 side. The different retardation layer 50 and the conductive layer or the isotropic substrate 60 with a conductive layer are typically arbitrary layers provided as needed, and either one or both may be omitted. Note that, for convenience, the retardation layer 20 may be referred to as a first retardation layer, and another retardation layer 50 may be referred to as a second retardation layer. When a conductive layer or an isotropic base material with a conductive layer is provided, the polarizing plate with a retardation layer is a so-called inner layer in which a touch sensor is incorporated between an image display cell (for example, an organic EL cell) and the polarizing plate. It can be applied to a touch panel type input display device.

  In the embodiment of the present invention, the first retardation layer 20 is an alignment solidified layer of a liquid crystal compound. The first retardation layer 20 may be a single layer of the alignment solidification layer as shown in FIGS. 1 and 2, and the first alignment solidification layer 21 and the second alignment solidification layer 22 as shown in FIG. It may have a laminated structure of.

  The above embodiments may be combined as appropriate, and modifications obvious to those skilled in the art may be made to the components in the above embodiments. For example, the second retardation layer 50 and / or the conductive layer or the isotropic substrate 60 with the conductive layer may be provided on the polarizing plate 102 with the retardation layer in FIG. Further, for example, the configuration in which the conductive layer-equipped isotropic substrate 60 is provided outside the second retardation layer 50 is replaced with an optically equivalent configuration (for example, a laminate of the second retardation layer and the conductive layer). May be.

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

  The polarizing plate with a retardation layer of the present invention may have a sheet-like shape or a long shape. In the present specification, "long shape" means an elongated shape having a length sufficiently longer than the width, and for example, an elongated shape having a length 10 times or more, preferably 20 times or more the width. Including. The long polarizing plate with a retardation layer can be wound into a roll.

  Practically, an adhesive layer (not shown) is provided on the side of the retardation layer opposite to the polarizing plate, and the polarizing plate with the retardation layer can be attached to the image display cell. Further, it is preferable that a release film is temporarily attached to the surface of the pressure-sensitive adhesive layer until the polarizing plate with a retardation layer is used. By temporarily attaching the release film, the pressure-sensitive adhesive layer can be protected and the roll can be formed.

  The total thickness of the polarizing plate with a retardation layer is preferably 60 μm or less, more preferably 55 μm or less, further preferably 50 μm or less, and particularly preferably 40 μm or less. The lower limit of the total thickness can be, for example, 28 μm. According to the embodiment of the present invention, an extremely thin polarizing plate with a retardation layer can be realized in this way. Such a polarizing plate with a retardation layer can have extremely excellent flexibility and bending durability. Such a polarizing plate with a retardation layer can be particularly suitably applied to a curved image display device and / or a bendable or bendable image display device. Incidentally, the total thickness of the polarizing plate with a retardation layer means all layers constituting the polarizing plate with a retardation layer except for an adhesive layer for adhering the polarizing plate to an external adherend such as a panel or glass. Refers to the total thickness (that is, the total thickness of the polarizing plate with a retardation layer is the pressure-sensitive adhesive layer for sticking the polarizing plate with a retardation layer to an adjacent member such as an image display cell and peeling that can be temporarily attached to the surface thereof. Does not include film thickness).

The unit weight of the polarizing plate with a retardation layer according to 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 , and more preferably 3 mg / cm ^{2. .0mg / cm 2 ~5.5mg / cm 2} , more preferably from ^{3.5mg / cm 2 ~5.0mg / cm 2} . When the display panel is thin, the panel may be slightly deformed due to the weight of the polarizing plate with a retardation layer and display defects may occur. Therefore, a polarizing plate with a retardation layer having a unit weight of 6.5 mg / cm ² or less may be used. The plate can prevent such deformation of the panel. Further, the polarizing plate with a retardation layer having the above unit weight has good handleability even when it is made thin, and can exhibit extremely excellent flexibility and bending durability.

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

B. Polarizing plate B-1. Polarizing Film As described above, the polarizing film 11 has a thickness of 8 μm or less, a single transmittance of 48% or more, and a polarization degree of 85% or more. In general, the single-body transmittance and the polarization degree are in a trade-off relationship with each other, and increasing the single-body transmittance may decrease the polarization degree, and increasing the polarization degree may decrease the single-body transmittance. For this reason, conventionally, it has been difficult to practically use a thin polarizing film that satisfies the optical characteristics of a single transmittance of 48% or more and a polarization degree of 85% or more. It is a feature of the present invention to use a thin polarizing film having excellent optical characteristics such that the single-piece transmittance is 48% or more and the polarization degree is 85% or more, and variation in optical characteristics is suppressed. There is one.

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

The polarizing film preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizing film is preferably 50% or less. The polarization degree of the polarizing film is preferably 86% or more, more preferably 87% or more, and further preferably 88% or more. On the other hand, the polarization degree is preferably 92% or less. The single-piece transmittance is typically a Y value measured using an ultraviolet-visible spectrophotometer and subjected to luminosity correction. The polarization degree is typically obtained by the following formula based on the parallel transmittance Tp and the orthogonal transmittance Tc measured by using an ultraviolet-visible spectrophotometer and subjected to the visibility correction.
Polarization degree (%) = {(Tp-Tc) / (Tp + Tc)} ^1/2 × 100

In one embodiment, the transmittance of a thin polarizing film having a thickness of 8 μm or less is typically obtained by laminating a polarizing film (refractive index of surface: 1.53) and a protective film (refractive index: 1.50). It is measured using an ultraviolet-visible spectrophotometer with the body as the measurement target. Depending on the refractive index of the surface of the polarizing film and / or the refractive index of the surface of the protective film in contact with the air interface, the reflectance at the interface of each layer may change, and as a result, the measured transmittance may change. . Therefore, for example, when using a protective film whose refractive index is not 1.50, the measured value of the transmittance may be corrected according to the refractive index of the surface of the protective film in contact with the air interface. Specifically, the transmittance correction value C is expressed by the following equation using the reflectance R ₁ (transmission axis reflectance) of polarized light parallel to the transmission axis at the interface between the protective film and the air layer.
C = R ₁ -R _{0
^{R 0 = ((1.50-1) 2}} /(1.50+1) 2) × (T 1/100)
^{_{R 1 = ((n 1 -1}} ) 2 / (n 1 +1) 2) × (T 1/100)
Here, R ₀ is the transmission axis reflectance when a protective film having 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. Is. For example, when a substrate having a surface refractive index of 1.53 (such as a cycloolefin film and a film with a hard coat layer) is used as a protective film, the correction amount C is about 0.2%. In this case, by adding 0.2% to the transmittance obtained by the measurement, it is possible to convert it to the transmittance when a protective film having a surface refractive index of 1.50 is used. According to the calculation based on the above formula, the change amount of 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 the correction value C. The effect on the value of is limited. When the protective film has absorption other than surface reflection, appropriate correction can be performed according to the amount of absorption.

In one embodiment, the polarizing plate with a retardation layer has a width of 1000 mm or more, and therefore the polarizing film also has a width of 1000 mm or more. In this case, the difference (D1) between the maximum value and the minimum value of the single transmittance at the position along the width direction of the polarizing film is preferably 1% or less, more preferably 0.8% or less, and It is preferably 0.6% or less. The smaller D1 is, the more preferable, and the lower limit of D1 can be, for example, 0.01%. When D1 is within the above range, a polarizing plate with a retardation layer having excellent optical characteristics can be industrially produced. In another embodiment, in the polarizing film, the difference (D2) between the maximum value and the minimum value of the single transmittance in the region of 50 cm ² is preferably 0.5% or less, more preferably 0.25%. It is below, and more preferably 0.15% or below. The smaller D2 is, the more preferable, and the lower limit of D2 can be, for example, 0.01%. When D2 is within the above range, it is possible to suppress variations in luminance on the display screen when the polarizing plate with a retardation layer is used in an image display device.

  Any appropriate polarizing film can be adopted as the polarizing film. The polarizing film can be typically manufactured by using a laminate of two or more layers.

  Specific examples of the polarizing film obtained by using the laminate include a polarizing film obtained by using a laminate of a resin base material and a PVA-based resin layer formed by coating on the resin base material. A polarizing film obtained by using a laminate of a resin base material and a PVA-based resin layer applied and formed on the resin base material is, for example, a resin base material obtained by applying a PVA-based resin solution to the resin base material and drying it. A PVA-based resin layer is formed thereon to obtain a laminate of a resin substrate and a PVA-based resin layer; the laminate is stretched and dyed to form the PVA-based resin layer as a polarizing film. obtain. In the present embodiment, the stretching typically includes dipping the laminate in a boric acid aqueous solution and stretching. Further, the stretching may further include optionally stretching the laminate in air at a high temperature (for example, 95 ° C. or higher) before stretching in the aqueous boric acid solution. The obtained resin base material / polarizing film laminate may be used as it is (that is, the resin base material may be used as a protective layer of the polarizing film), or the resin base material is peeled from the resin base material / polarizing film laminate. However, any appropriate protective layer may be laminated and used on the peeled surface depending on the purpose. Details of the method for manufacturing such a polarizing film are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580. The entire description of the publication is incorporated herein by reference.

  The method for manufacturing a polarizing film is typically a laminate of a polyvinyl alcohol resin layer containing a halide and a polyvinyl alcohol resin on one side of a long thermoplastic resin substrate. And subjecting the laminate to an in-air auxiliary stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment of shrinking 2% or more in the width direction by heating while conveying in the longitudinal direction in this order. including. As a result, a polarizing film having a thickness of 8 μm or less, a single transmittance of 48% or more, and a polarization degree of 85% or more, having excellent optical characteristics and suppressing variations in optical characteristics can be provided. . That is, by introducing the auxiliary stretching, the crystallinity of PVA can be increased and high optical characteristics can be achieved even when PVA is applied onto the thermoplastic resin. At the same time, by preliminarily enhancing the orientation of PVA, it is possible to prevent problems such as reduction in orientation and dissolution of PVA when immersed in water in the subsequent dyeing step or stretching step, and high optical characteristics. Can be achieved. Furthermore, when the PVA-based resin layer is dipped in a liquid, the disorder of the alignment of the polyvinyl alcohol molecules and the deterioration of the orientation can be suppressed as compared with the case where the PVA-based resin layer does not contain a halide. This can improve the optical characteristics of the polarizing film obtained through a treatment process such as a dyeing treatment and an underwater stretching treatment performed by immersing the laminate in a liquid. Further, the optical characteristics can be improved by shrinking the laminate in the width direction by the dry shrinking treatment.

B-2. Protective Layer The first protective layer 12 and the second protective layer 13 are each formed of any suitable film that can be used as a protective layer of a polarizing film. Specific examples of the material serving as the main component of the film include cellulose resins such as triacetyl cellulose (TAC), polyester resins, polyvinyl alcohol resins, polycarbonate resins, polyamide resins, polyimide resins, polyether sulfone resins, and polysulfone resins. , Polystyrene-based, polynorbornene-based, polyolefin-based, (meth) acrylic-based, acetate-based transparent resins and the like. Further, a thermosetting resin such as a (meth) acrylic resin, a urethane resin, a (meth) acrylic urethane resin, an epoxy resin, a silicone resin, or an ultraviolet curable resin can also be used. In addition to these, for example, a glassy polymer such as a siloxane polymer may be used. Further, the polymer film described in JP 2001-343529 A (WO 01/37007) can also be used. Examples of the material for this film include a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain. Can be used, and examples thereof include a resin composition having an alternating copolymer of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer. The polymer film can be, for example, an extruded product of the resin composition.

  The polarizing plate with a retardation layer of the present invention is typically disposed on the viewing side of the image display device, and the first protective layer 12 is typically disposed on the viewing side thereof, as described below. Therefore, the first protective layer 12 may be subjected to surface treatment such as hard coat treatment, antireflection treatment, sticking prevention treatment, and antiglare treatment, if necessary. Further / or, if necessary, the first protective layer 12 is processed to improve the visibility when viewed through polarized sunglasses (typically, a (elliptical) circular polarization function is added, (Giving an ultrahigh phase difference) may be applied. By performing such a process, excellent visibility can be realized even when the display screen is viewed through a polarizing lens such as polarized sunglasses. Therefore, the polarizing plate with a retardation layer can be suitably 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 further preferably 10 μm to 30 μm. When the surface treatment is applied, the thickness of the outer protective layer is the thickness including the thickness of the surface treated layer.

  The second protective layer 13 is preferably optically isotropic in one embodiment. In the present 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. Say. The second protective layer 13 may be a retardation layer having any appropriate retardation value in one embodiment. In this case, the in-plane retardation Re (550) of the retardation layer is, for example, 110 nm to 150 nm. The thickness of the second protective layer is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, and further preferably 10 μm to 30 μm. From the viewpoint of reduction in thickness and weight, the second protective layer can be preferably omitted.

B-3. Method for manufacturing polarizing film The polarizing film is, for example, a polyvinyl alcohol resin layer (PVA resin layer) containing a halide and a polyvinyl alcohol resin (PVA resin) on one side of a long thermoplastic resin substrate. To form a laminated body, and the laminated body is subjected to an in-air auxiliary stretching treatment, a dyeing treatment, an underwater stretching treatment, and drying for shrinking 2% or more in the width direction by heating while conveying in the longitudinal direction. The shrinkage treatment and the shrinkage treatment may be performed in this order. The content of the halide in the PVA-based resin layer is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin. The drying shrinkage treatment is preferably performed using a heating roll, and the temperature of the heating roll is preferably 60 ° C to 120 ° C. The shrinkage ratio in the width direction of the laminate by the dry 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 including a PVA-based resin layer containing a halide is prepared, and the laminate is stretched in multiple stages including in-air auxiliary stretching and underwater stretching, and the laminated laminate is heated with a heating roll. It is possible to obtain a polarizing film having excellent optical characteristics (typically, single-body transmittance and polarization degree) and suppressing variations in optical characteristics. Specifically, by using a heating roll in the drying shrinkage treatment step, the laminate can be uniformly shrunk while being conveyed. As a result, not only can the optical characteristics of the obtained polarizing film be improved, but also a polarizing film with excellent optical characteristics can be stably produced, and variations in optical characteristics (particularly, single transmittance) of the polarizing film can be suppressed. can do.

B-3-1. Preparation of Laminate As a method of preparing a laminate of the thermoplastic resin substrate and the PVA-based resin layer, any suitable method can be adopted. Preferably, a PVA-based resin layer is formed on the thermoplastic resin substrate by applying a coating liquid containing a halide and a PVA-based resin on the surface of the thermoplastic resin substrate and drying the coating liquid. As described above, the content of the halide in the PVA-based resin layer is preferably 5 to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.

  Any appropriate method can be adopted as a method for applying the application liquid. For example, a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method, a knife coating method (a comma coating method, etc.) and the like can be mentioned. The coating / drying temperature of the coating liquid is preferably 50 ° C. or higher.

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

  Prior to forming the PVA-based resin layer, the thermoplastic resin substrate may be subjected to surface treatment (for example, corona treatment), or the easily adhesive layer may be formed on the thermoplastic resin substrate. By performing such a treatment, the adhesion between the thermoplastic resin base material and the PVA-based resin layer can be improved.

B-3-1-1. Thermoplastic resin substrate The thickness of the thermoplastic resin substrate is preferably 20 μm to 300 μm, more preferably 50 μm to 200 μm. If it is less than 20 μm, it may be difficult to form the PVA-based resin layer. If it exceeds 300 μm, it may take a long time for the thermoplastic resin substrate to absorb water in the below-described underwater stretching treatment, and an excessive load may be required for stretching.

  The thermoplastic resin substrate preferably has a water absorption of 0.2% or more, more preferably 0.3% or more. The thermoplastic resin base material absorbs water, and the water acts as a plasticizer and can be plasticized. As a result, the stretching stress can be significantly reduced, and stretching can be performed at a high ratio. On the other hand, the water absorption of the thermoplastic resin substrate is preferably 3.0% or less, more preferably 1.0% or less. By using such a thermoplastic resin base material, it is possible to prevent problems such as the dimensional stability of the thermoplastic resin base material being significantly reduced during production, and the appearance of the polarizing film obtained being deteriorated. In addition, it is possible to prevent the base material from breaking during the underwater stretching and the PVA-based resin layer from peeling off from the thermoplastic resin base material. The water absorption of the thermoplastic resin substrate can be adjusted, for example, by introducing a modifying group into the constituent material. The water absorption rate is a value determined according to JIS K 7209.

  The glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 120 ° C. or lower. By using such a thermoplastic resin substrate, it is possible to sufficiently secure the stretchability of the laminate while suppressing the crystallization of the PVA-based resin layer. Further, in consideration of good plasticization of the thermoplastic resin substrate with water and favorable underwater stretching, the temperature is preferably 100 ° C. or lower, and 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 base material, the thermoplastic resin base material is deformed (for example, unevenness, wrinkles, or wrinkles are generated) when the coating liquid containing the PVA-based resin is applied and dried. It is possible to satisfactorily produce a laminated body by preventing the above problems. Moreover, the PVA-based resin layer can be stretched well at a suitable temperature (for example, about 60 ° C.). The glass transition temperature of the thermoplastic resin substrate can be adjusted, for example, by introducing a modifying group into the constituent material and heating it with a crystallization material. The glass transition temperature (Tg) is a value determined according to JIS K 7121.

  Any appropriate thermoplastic resin can be adopted as a constituent material of the thermoplastic resin substrate. Examples of the thermoplastic resin include ester-based resins such as polyethylene terephthalate-based resins, cycloolefin-based resins such as norbornene-based resins, olefin-based resins such as polypropylene, polyamide-based resins, polycarbonate-based resins, and copolymer resins thereof. Is mentioned. Among these, norbornene-based resins and amorphous polyethylene terephthalate-based resins are preferable.

  In one embodiment, an amorphous (non-crystallized) polyethylene terephthalate resin is preferably used. Among them, an amorphous (hard to crystallize) polyethylene terephthalate resin is particularly preferably used. Specific examples of the amorphous polyethylene terephthalate resin include a copolymer further containing isophthalic acid and / or cyclohexanedicarboxylic acid as a dicarboxylic acid, and a copolymer further containing cyclohexanedimethanol or diethylene glycol as a glycol.

  In a preferred embodiment, the thermoplastic resin base material is composed of a polyethylene terephthalate resin having an isophthalic acid unit. This is because such a thermoplastic resin substrate has extremely excellent stretchability and can suppress crystallization during stretching. It is considered that this is because the main chain is largely bent by introducing the isophthalic acid unit. 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, more preferably 1.0 mol% or more based on the total of all repeating units. This is because a thermoplastic resin substrate having extremely excellent stretchability can be obtained. On the other hand, the content ratio of the isophthalic acid unit is preferably 20 mol% or less, more preferably 10 mol% or less, based on the total of all repeating units. By setting such a content ratio, the crystallinity can be favorably increased in the drying shrinkage treatment described below.

  The thermoplastic resin substrate may be stretched in advance (before forming the PVA-based resin layer). In one embodiment, the elongated thermoplastic resin substrate is stretched in the lateral direction. The lateral direction is preferably a direction orthogonal to the stretching direction of the laminate described below. In addition, in this specification, the term "orthogonal" includes the case of being substantially orthogonal. Here, “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 substrate is preferably Tg-10 ° C to Tg + 50 ° C with respect to the glass transition temperature (Tg). The stretch ratio of the thermoplastic resin substrate is preferably 1.5 times to 3.0 times.

  Any appropriate method can be adopted as a method for stretching the thermoplastic resin substrate. Specifically, it may be fixed-end stretching or free-end stretching. The stretching method may be dry or wet. Stretching of the thermoplastic resin substrate may be performed in one stage or in multiple stages. When performing in multiple stages, the above-mentioned draw ratio is a product of the draw ratio 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 prepared by dissolving the halide and the PVA resin in a solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These can be used alone or in combination of two or more. Of these, water is preferable. The PVA-based resin concentration of the solution is preferably 3 to 20 parts by weight with respect to 100 parts by weight of the solvent. With 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 to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.

  Additives may be added to the coating liquid. Examples of the additive include a plasticizer and a surfactant. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. Examples of the surfactant include nonionic surfactants. These can be used for the purpose of further improving the uniformity, dyeability and stretchability of the obtained PVA-based resin layer.

  Any appropriate resin can be adopted as the PVA-based resin. For example, polyvinyl alcohol and ethylene-vinyl alcohol copolymer are mentioned. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer. The saponification degree of the PVA-based resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, more preferably 99.0 mol% to 99.93 mol%. . The saponification degree can be determined according to JIS K 6726-1994. By using a PVA-based resin having such a saponification degree, a polarizing film having excellent durability can be obtained. If the degree of saponification is too high, gelation may occur.

  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 1000 to 10000, preferably 1200 to 4500, and more preferably 1500 to 4300. The average degree of polymerization can be determined according to JIS K 6726-1994.

  Any appropriate halide can be adopted as the above-mentioned halide. Examples include iodide and sodium chloride. Examples of iodides include potassium iodide, sodium iodide, and lithium iodide. Among these, potassium iodide is preferable.

  The amount of the halide in the coating solution is preferably 5 to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin, and more preferably 10 to 15 parts by weight with respect to 100 parts by weight of the PVA-based resin. It is a department. If 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 polarizing film finally obtained may become cloudy.

  Generally, when the PVA-based resin layer is stretched, the orientation of the polyvinyl alcohol molecules in the PVA-based resin increases, but when the stretched PVA-based resin layer is immersed in a liquid containing water, the polyvinyl alcohol molecules The orientation may be disturbed and the orientation may be deteriorated. In particular, when a laminate of a thermoplastic resin base material and a PVA-based resin layer is stretched in boric acid water, the laminate is heated in boric acid water at a relatively high temperature in order to stabilize the stretching of the thermoplastic resin base material. In the case of stretching, the above-mentioned tendency of decreasing the degree of orientation is remarkable. For example, while stretching of a PVA film alone in boric acid water is generally performed at 60 ° C., stretching of a laminate of A-PET (thermoplastic resin substrate) and PVA-based resin layer is performed. It is carried out at a high temperature of around 70 ° C. In this case, the orientation of PVA in the initial stage of stretching may be lowered in a stage before being raised by the underwater stretching. On the other hand, by forming a laminate of a PVA-based resin layer containing a halide and a thermoplastic resin substrate, and stretching the laminate at high temperature in air (auxiliary stretching) before stretching in boric acid water. The crystallization of the PVA-based resin in the PVA-based resin layer of the laminate after the auxiliary stretching can be promoted. As a result, when the PVA-based resin layer is immersed in the liquid, the disorder of the alignment of the polyvinyl alcohol molecules and the deterioration of the orientation can be suppressed as compared with the case where the PVA-based resin layer does not contain a halide. This can improve the optical characteristics of the polarizing film obtained through a treatment process such as a dyeing treatment and an underwater stretching treatment performed by immersing the laminate in a liquid.

B-3-2. In-air auxiliary stretching treatment In order to obtain particularly high optical characteristics, a two-stage stretching method is selected in which dry stretching (auxiliary stretching) and boric acid in-water stretching are combined. By introducing auxiliary stretching like two-stage stretching, it is possible to perform stretching while suppressing crystallization of the thermoplastic resin substrate, and excessive crystallization of the thermoplastic resin substrate in subsequent boric acid underwater stretching. Thereby, the problem that the stretchability is lowered can be solved, and the laminate can be stretched at a higher ratio. Furthermore, in the case of applying the PVA-based resin on the thermoplastic resin base material, in order to suppress the influence of the glass transition temperature of the thermoplastic resin base material, compared with the case of applying the PVA-based resin on a normal metal drum. Therefore, it is necessary to lower the coating temperature, and as a result, the crystallization of the PVA-based resin becomes relatively low, which may cause a problem that sufficient optical characteristics cannot be obtained. On the other hand, by introducing the auxiliary stretching, the crystallinity of the PVA-based resin can be increased even when the PVA-based resin is applied on the thermoplastic resin, and high optical characteristics can be achieved. Become. Further, at the same time, by preliminarily enhancing the orientation of the PVA-based resin, it is possible to prevent problems such as deterioration of the orientation of the PVA-based resin and dissolution when the PVA-based resin is immersed in water in the subsequent dyeing step or stretching step. It becomes possible to achieve high optical characteristics.

The stretching method for the in-air auxiliary stretching may be fixed-end stretching (for example, a stretching method using a tenter stretching machine) or free-end stretching (for example, a uniaxial stretching method in which a laminate is passed between rolls having different peripheral speeds). Although good, free-end stretching can be positively adopted in order to obtain high optical characteristics. In one embodiment, the in-air stretching treatment includes a heating roll stretching step of stretching the laminate by the difference in peripheral speed between the heating rolls while conveying the laminate in the longitudinal direction. The in-air stretching treatment typically includes a zone stretching step and a heating roll stretching step. 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 zone stretching step may be omitted. In one embodiment, the zone stretching step and the heated roll stretching step are performed in this order. Further, in another embodiment, in the tenter stretching machine, stretching is performed by gripping the film end portion and widening the distance between the tenter in the flow direction (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 flow direction) is set to be arbitrarily close. Preferably, it can be set so as to be closer to the free end stretching with respect to the stretching ratio in the machine direction. In the case of free end drawing, the shrinkage ratio in the width direction is calculated by (1/1 / drawing ratio) ^1/2 .

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

  The draw ratio in the in-air auxiliary drawing is preferably 2.0 to 3.5 times. The maximum draw ratio when the in-air auxiliary drawing and the underwater drawing are combined is preferably 5.0 times or more, more preferably 5.5 times or more, and further preferably 6.0 times, with respect to the original length of the laminate. That is all. In the present specification, the "maximum stretch ratio" means a stretch ratio immediately before the laminated body breaks, and separately confirms the stretch ratio at which the laminated body breaks, and means a value 0.2 lower than the value.

The stretching temperature of the in-air auxiliary stretching can be set to any appropriate value depending on the forming material of the thermoplastic resin substrate, the stretching method and the like. The stretching temperature is preferably the glass transition temperature (Tg) or higher of the thermoplastic resin substrate, more preferably the glass transition temperature (Tg) + 10 ° C. or higher of the thermoplastic resin substrate, 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 rapid crystallization of the PVA-based resin and suppress defects due to the crystallization (for example, to prevent orientation of the PVA-based resin layer due to stretching). it can. The crystallization index of the PVA-based resin after the in-air auxiliary stretching is preferably 1.3 to 1.8, more preferably 1.4 to 1.7. The crystallization index of the PVA-based resin can be measured by the ATR method using a Fourier transform infrared spectrophotometer. Specifically, measurement is performed using polarized light as the measurement light, and the crystallization index is calculated according to the following formula using the intensities of 1141 cm ⁻¹ and 1440 cm ⁻¹ of the obtained spectrum.
Crystallization index = (I _C / I _R ).
However,
I _C: intensity _{I R} of 1141cm ^-1 when measured by the incident measurement light: the intensity of 1440cm ^-1 when measured by the incident measurement light.

B-3-3. Insolubilization treatment If necessary, an insolubilization treatment is performed after the in-air auxiliary stretching treatment and before the underwater stretching treatment or the dyeing treatment. The insolubilization treatment is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. By applying the insolubilization treatment, it is possible to impart water resistance to the PVA-based resin layer and prevent the orientation of PVA from being lowered 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 insolubilizing bath (boric acid aqueous solution) is preferably 20 ° C to 50 ° C.

B-3-4. Dyeing Treatment The above dyeing treatment is typically performed by dyeing the PVA-based resin layer with a dichroic material (typically iodine). Specifically, it is performed by adsorbing iodine on the PVA resin layer. Examples of the adsorption method include a method of immersing the PVA-based resin layer (laminate) in a dyeing solution containing iodine, a method of applying the dyeing solution to the PVA-based resin layer, and a method of applying the dyeing solution to the PVA-based resin layer. Examples include a method of spraying. A preferred method is to immerse the laminate in a dyeing solution (dyeing bath). This is because iodine can be favorably adsorbed.

  The dyeing solution is preferably an aqueous iodine solution. The blending amount of iodine is preferably 0.05 parts by weight to 0.5 parts by weight with respect to 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to add iodide to the aqueous iodine solution. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Etc. Among these, potassium iodide is preferable. The iodide content 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. The liquid temperature during dyeing of the dyeing liquid is preferably 20 ° C to 50 ° C in order to suppress dissolution of the PVA-based resin. When the PVA-based resin layer is immersed in the dyeing solution, the immersion time is preferably 5 seconds to 5 minutes, more preferably 30 seconds to 90 seconds in order to secure the transmittance of the PVA-based resin layer.

  The dyeing conditions (concentration, liquid temperature, immersion time) can be set such that the final transmittance of the polarizing film obtained is 48% or more and the polarization degree is 85% or more. As such a dyeing condition, preferably, an iodine aqueous solution is used as the dyeing solution, and the ratio of the contents of iodine and potassium iodide in the iodine aqueous solution is 1: 5 to 1:20. The ratio of the contents of iodine and potassium iodide in the aqueous iodine solution is preferably 1: 5 to 1:10. As a result, a polarizing film having the above optical characteristics can be obtained.

  When the dyeing treatment is continuously performed after the treatment of dipping the laminate in a treatment bath containing boric acid (typically, the insolubilization treatment), the boric acid contained in the treatment bath is mixed in the dyeing bath. The concentration of boric acid in the dyeing bath may change with time, resulting in unstable dyeability. In order to suppress the destabilization of the dyeability as described above, the upper limit of the boric acid concentration in the dyeing bath is preferably 4 parts by weight, more preferably 2 parts by weight, relative to 100 parts by weight of water. Adjusted. On the other hand, the lower limit of the concentration of boric acid in the dyeing bath is preferably 0.1 part by weight, more preferably 0.2 part by weight, still more preferably 0.5 part by weight, relative to 100 parts by weight of water. Is. In one embodiment, the dyeing process is performed using a dyeing bath in which boric acid is preliminarily blended. This can reduce the rate of change in boric acid concentration when boric acid in the treatment bath is mixed in the dyeing bath. The amount of boric acid blended in the dyeing bath in advance (that is, the content of boric acid not derived from the treatment bath) is preferably 0.1 to 2 parts by weight with respect to 100 parts by weight of water. , And more preferably 0.5 to 1.5 parts by weight.

B-3-5. Crosslinking Treatment If necessary, a crosslinking treatment is performed after the dyeing treatment and before the underwater stretching treatment. The cross-linking treatment is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. By performing the cross-linking treatment, it is possible to impart water resistance to the PVA-based resin layer and prevent the PVA from being lowered in orientation when it is immersed in high-temperature water in the subsequent underwater stretching. The concentration of the boric acid aqueous solution is preferably 1 part by weight to 5 parts by weight with respect to 100 parts by weight of water. Further, when the crosslinking treatment is performed after the dyeing treatment, it is preferable to further add iodide. By blending iodide, elution of iodine adsorbed on the PVA-based resin layer can be suppressed. The iodide content is preferably 1 part by weight to 5 parts by weight with respect to 100 parts by weight of water. Specific examples of iodide are as described above. The liquid temperature of the crosslinking bath (boric acid aqueous solution) is preferably 20 ° C to 50 ° C.

B-3-6. Underwater Stretching Treatment The underwater stretching treatment is performed by immersing the laminate in a stretching bath. According to the underwater stretching treatment, stretching can be performed at a temperature lower than the glass transition temperature (typically about 80 ° C.) of the thermoplastic resin substrate or the PVA-based resin layer, and the PVA-based resin layer is crystallized. It is possible to stretch at a high magnification while suppressing the above. As a result, a polarizing film having excellent optical properties can be manufactured.

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

  The underwater stretching is preferably performed by immersing the laminate in a boric acid aqueous solution (boric acid underwater stretching). By using an aqueous boric acid solution as the stretching bath, the PVA-based resin layer can be provided with rigidity that can withstand the tension applied during stretching and water resistance that does not dissolve in water. Specifically, boric acid can generate a tetrahydroxyborate anion in an aqueous solution to crosslink with a PVA-based resin by hydrogen bond. As a result, the PVA-based resin layer can be imparted with rigidity and water resistance, can be favorably stretched, and a polarizing film having excellent optical characteristics can be manufactured.

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

  Preferably, iodide is added to the stretching bath (boric acid aqueous solution). By blending iodide, elution of iodine adsorbed on the PVA-based resin layer can be suppressed. Specific examples of iodide are as described above. The concentration of iodide is preferably 0.05 to 15 parts by weight, 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. At such a temperature, the PVA-based resin layer can be stretched at a high magnification while suppressing the dissolution. Specifically, as described above, the glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 60 ° C. or higher in relation to the formation of the PVA-based resin layer. In this case, if the stretching temperature is lower than 40 ° C., it may not be possible to stretch well even if the plasticization of the thermoplastic resin substrate by water is taken into consideration. On the other hand, the higher the temperature of the stretching bath, the higher the solubility of the PVA-based resin layer, and there is a possibility that excellent optical characteristics may not be obtained. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.

  The draw ratio by underwater stretching is preferably 1.5 times or more, more preferably 3.0 times or more. The total draw ratio of the laminated body is preferably 5.0 times or more, more preferably 5.5 times or more, with respect to the original length of the laminated body. By achieving such a high draw ratio, a polarizing film having extremely excellent optical characteristics can be manufactured. Such a high draw ratio can be achieved by adopting an underwater drawing method (boric acid underwater drawing).

B-3-7. Drying Shrinkage Treatment The drying shrinkage treatment may be performed by zone heating performed by heating the entire zone, or may be performed by heating the transport roll (using a so-called heating roll) (heating roll drying method). Both are preferably used. By drying using a heating roll, it is possible to efficiently suppress the curling of the laminate by heating and to produce a polarizing film having an excellent appearance. Specifically, by drying the laminate along a heating roll, the crystallization of the thermoplastic resin substrate can be efficiently promoted to increase the crystallinity, which is relatively low. Even at the drying temperature, the crystallinity of the thermoplastic resin substrate can be satisfactorily increased. As a result, the rigidity of the thermoplastic resin base material increases, and the thermoplastic resin base material can withstand the shrinkage of the PVA-based resin layer due to drying, and curling is suppressed. Further, by using the heating roll, the laminate can be dried while being kept flat, so that not only curling but also wrinkling can be suppressed. At this time, the laminated body can be improved in optical characteristics by shrinking in the width direction by a drying shrinkage treatment. This is because the orientation of PVA and the PVA / iodine complex can be effectively enhanced. The shrinkage ratio in the width direction of the laminate by the dry shrinkage treatment is preferably 1% to 10%, more preferably 2% to 8%, and particularly preferably 4% to 6%. By using the heating roll, the laminate can be continuously contracted in the width direction while being conveyed, and high productivity can be realized.

  FIG. 4 is a schematic diagram showing an example of the drying shrinkage treatment. In the drying shrinkage treatment, the laminate 200 is dried while being transported by the transport rolls R1 to R6 heated to a predetermined temperature and the guide rolls G1 to G4. In the illustrated example, the transport rolls R1 to R6 are arranged so as to alternately and continuously heat the surface of the PVA resin layer and the surface of the thermoplastic resin substrate, but for example, one surface of the laminate 200 (for example, thermoplastic The transport rolls R1 to R6 may be arranged so that only the resin substrate surface) is continuously heated.

  The drying conditions can be controlled by adjusting the heating temperature of the transport roll (temperature of the heating roll), the number of heating rolls, the contact time with the heating roll, and the like. The temperature of the heating roll 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 favorably increased, curling can be favorably suppressed, and an optical laminate having extremely excellent durability can be manufactured. The temperature of the heating roll can be measured with a contact thermometer. In the illustrated example, six transport rolls are provided, but there is no particular limitation as long as there are multiple transport rolls. The number of transport rolls is usually 2 to 40, preferably 4 to 30. The contact time (total contact time) between the laminate and the heating roll is preferably 1 second to 300 seconds, more preferably 1 to 20 seconds, and further preferably 1 to 10 seconds.

  The heating roll may be provided in a heating furnace (for example, an oven) or may be provided in a normal production line (under room temperature environment). Preferably, it is provided in a heating furnace equipped with a blowing means. By using the drying with the heating roll and the hot air drying together, a sharp temperature change between the heating rolls 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. 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. The wind speed is the wind speed in the heating furnace, and can be measured by a mini vane type digital anemometer.

B-3-8. Other Treatments Preferably, a washing treatment is performed after the underwater stretching treatment and before the drying shrinkage treatment. The cleaning treatment is typically performed by immersing the PVA-based resin layer in an aqueous potassium iodide solution.

C. First Retardation Layer As described above, the first retardation layer 20 is an alignment-solidified 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 made significantly larger than that of a non-liquid crystal material. Therefore, the thickness of the retardation layer for obtaining a desired in-plane retardation. Can be significantly reduced. As a result, it is possible to further reduce the thickness and weight of the polarizing plate with a retardation layer. In the present specification, the “alignment solidified layer” means a layer in which the liquid crystal compound is aligned in a predetermined direction in the layer and the alignment state is fixed. The “alignment solidified layer” is a concept including an alignment cured layer obtained by curing a liquid crystal monomer as described later. In the present embodiment, typically, rod-shaped liquid crystal compounds are aligned in a state of being aligned in the slow axis direction of the first retardation layer (homogeneous alignment).

  Examples of the liquid crystal compound include a liquid crystal compound in which the liquid crystal phase is a nematic phase (nematic liquid crystal). As such a liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The 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 (that is, curing) the liquid crystal monomer. After aligning the liquid crystal monomers, for example, by polymerizing or cross-linking the liquid crystal monomers, the alignment state can be fixed. Here, a polymer is formed by polymerization and a three-dimensional network structure is formed by crosslinking, but these are non-liquid crystalline. Therefore, in the formed first retardation layer, for example, the transition to the liquid crystal phase, the glass phase, or the crystal phase due to the temperature change peculiar to the liquid crystal compound does not occur. As a result, the first retardation layer becomes an extremely stable retardation layer that is not affected by temperature changes.

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

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

  The alignment-fixed layer of the liquid crystal compound is subjected to an alignment treatment on the surface of a predetermined base material, and a coating liquid containing a liquid crystal compound is applied to the surface to align the liquid crystal compound in a direction corresponding to the alignment treatment, It can be formed by fixing the orientation state. In one embodiment, the substrate is any suitable resin film, and the alignment-solidified layer formed on the substrate can be transferred to the surface of the polarizing plate 10. In another embodiment, the substrate can be the second protective layer 13. In this case, the transfer step is omitted, and the roll-to-roll lamination can be performed continuously from the formation of the orientation solidified layer (first retardation layer), so that the productivity is further improved.

  Any appropriate alignment treatment can be adopted as the alignment treatment. Specifically, mechanical orientation treatment, physical orientation treatment, and chemical orientation treatment can be mentioned. Specific examples of the mechanical orientation treatment include rubbing treatment and stretching treatment. Specific examples of the physical orientation treatment include magnetic field orientation treatment and electric field orientation treatment. Specific examples of the chemical alignment treatment include an oblique vapor deposition method and a photo-alignment treatment. As the processing conditions for various alignment treatments, any appropriate conditions can be adopted depending on the purpose.

  Alignment of the liquid crystal compound is performed by processing at a temperature at which a liquid crystal phase is exhibited depending on the type of the liquid crystal compound. By performing such temperature treatment, the liquid crystal compound takes a liquid crystal state, and the liquid crystal compound is aligned according to the alignment treatment direction on the surface of the base material.

  In one embodiment, fixing the alignment state is performed by cooling the liquid crystal compound aligned as described above. When the liquid crystal compound is a polymerizable monomer or a crosslinkable monomer, the alignment state is fixed by subjecting the liquid crystal compound oriented as described above to a polymerization treatment or a crosslinking treatment.

  Specific examples of the liquid crystal compound and details of the method for forming the alignment solidified layer are described in JP-A-2006-163343. The description of the publication is incorporated herein by reference.

  As another example of the alignment fixed layer, there is a form in which the discotic liquid crystal compound is aligned in any of vertical alignment, hybrid alignment and tilt alignment. In 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. When the discotic liquid crystal compound is substantially vertical, the average value of the angles 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 more preferably 85 ° to 90 °. The discotic liquid crystal compound generally has a cyclic mother nucleus such as benzene, 1,3,5-triazine, and calixarene arranged at the center of the molecule, and has a linear alkyl group, an alkoxy group, or a substituted benzoyl group. It refers to a liquid crystal compound having a disk-shaped molecular structure in which an oxy group or the like is radially substituted as a side chain. Typical examples of discotic liquid crystals include C.I. Report of Destrade et al., Mol. Cryst. Liq. Cryst. 71, 111 (1981), benzene derivatives, triphenylene derivatives, truxene derivatives, phthalocyanine derivatives and B.I. Kohne et al., Angew. Chem. 96, 70 (1984), and cyclohexane derivatives described in J. M. Lehn et al., J. Chem. Soc. Chem. Commun. , Pp. 1794 (1985), J. Research report by Zhang et al. Am. Chem. Soc. 116, 2655 (1994) and azacrown-type and phenylacetylene-type macrocycles. Further specific examples of the discotic liquid crystal compound include the compounds described in JP-A-2006-133652, JP-A-2007-108732, and JP-A-2010-244038. The descriptions in the above documents and publications are incorporated herein by reference.

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

  The first retardation layer typically has a refractive index characteristic of nx> ny = nz. The first retardation layer is typically provided for imparting antireflection properties to the polarizing plate, and functions as a λ / 4 plate when the first retardation layer is a single layer of the orientation solidification layer. You can 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, still more preferably 130 nm to 160 nm. 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, ny> nz or ny <nz may occur as long as the effect of the present invention is not impaired.

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

  The first retardation layer may exhibit an inverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, and a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light. It may be shown, or may exhibit a flat wavelength dispersion characteristic in which the phase difference value hardly changes even with the wavelength of the measurement light. In one embodiment, the first retardation layer exhibits an inverse dispersion wavelength characteristic. In this case, Re (450) / Re (550) of the retardation layer is preferably 0.8 or more and less than 1, and more preferably 0.8 or more and 0.95 or less. With such a configuration, it is possible to realize a very excellent antireflection characteristic.

  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 further preferably about. It is 45 °. When the angle θ is in such a range, by using the λ / 4 plate as the first retardation layer as described above, very excellent circular polarization characteristics (as a result, very excellent antireflection characteristics) are obtained. A polarizing plate with a retardation layer having is obtained.

  In another embodiment, the first retardation layer 20 may have a laminated structure of a first alignment fixed layer 21 and a second alignment fixed layer 22 as shown in FIG. In this case, one of the first alignment solidified layer 21 and the second alignment solidified layer 22 can function as a λ / 4 plate, and the other can function as a λ / 2 plate. Therefore, the thicknesses of the first alignment solidified layer 21 and the second alignment solidified layer 22 can be adjusted so as to obtain a desired in-plane retardation of a λ / 4 plate or a λ / 2 plate. For example, when the first alignment solidification layer 21 functions as a λ / 2 plate and the second alignment solidification layer 22 functions as a λ / 4 plate, the thickness of the first alignment solidification layer 21 is, for example, 2.0 μm to The thickness of the second alignment fixed layer 22 is, for example, 1.0 μm to 2.0 μm. In this case, the in-plane retardation Re (550) of the first alignment solidified layer is preferably 200 nm to 300 nm, more preferably 230 nm to 290 nm, and further preferably 250 nm to 280 nm. The in-plane retardation Re (550) of the second alignment fixed layer is as described above for the single-layer alignment fixed layer. The angle formed by the slow axis of the first alignment solidified layer and the absorption axis of the polarizing film is preferably 10 ° to 20 °, more preferably 12 ° to 18 °, and further preferably about 15 °. is there. The angle formed by the slow axis of the second alignment solidified layer and the absorption axis of the polarizing film is preferably 70 ° to 80 °, more preferably 72 ° to 78 °, and further preferably about 75 °. is there. With such a configuration, it is possible to obtain a characteristic close to an ideal reverse wavelength dispersion characteristic, and as a result, it is possible to realize a very excellent antireflection characteristic. Regarding the liquid crystal compounds constituting the first alignment solidified layer and the second alignment solidified layer, the method for forming the first alignment solidified layer and the second alignment solidified layer, the optical characteristics, etc., with respect to the single layer alignment solidified layer, As described in.

D. Second Retardation Layer As described above, the second retardation layer may be a so-called positive C plate whose refractive index characteristics show a relationship of nz> nx = ny. By using the positive C plate as the second retardation layer, it is possible to favorably prevent reflection in an oblique direction, and it is possible to widen the viewing angle of the antireflection function. 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, further preferably −90 nm to −200 nm, particularly preferably -100 nm to -180 nm. Here, “nx = ny” includes not only the case where nx and ny are exactly equal but also the case where nx and ny are substantially equal. That is, the in-plane retardation Re (550) of the 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 preferably comprises a film containing a liquid crystal material fixed in homeotropic alignment. The liquid crystal material (liquid crystal compound) capable of homeotropic alignment may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the method for forming the liquid crystal compound and the retardation layer include the liquid crystal compounds and the method for forming the retardation layer described in [0020] to [0028] of JP-A-2002-333642. 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 further preferably 0.5 μm to 5 μm.

E. Conductive Layer or Isotropic Substrate with Conductive Layer The conductive layer is formed by any appropriate film formation method (eg, vacuum deposition method, sputtering method, CVD method, ion plating method, spray method, etc.). It may be formed by depositing a metal oxide film thereon. Examples of the metal oxide include indium oxide, tin oxide, zinc oxide, indium-tin complex oxide, tin-antimony complex oxide, zinc-aluminum complex oxide, and indium-zinc complex oxide. Of these, indium-tin composite oxide (ITO) is preferable.

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

  The conductive layer may be transferred from the above-mentioned base material to the first retardation layer (or the second retardation layer, if present), and the conductive layer alone may serve as the constituent layer of the polarizing plate with the retardation layer. Of course, it may be laminated on the first retardation layer (or the second retardation layer, if present) as a laminate with the substrate (substrate with conductive layer). Preferably, the above-mentioned substrate is optically isotropic, so that the conductive layer can be used as a isotropic substrate with a conductive layer in a polarizing plate with a retardation layer.

  As the optically isotropic substrate (isotropic substrate), any suitable isotropic substrate can be adopted. Examples of the material forming the isotropic substrate include, for example, a material having a resin having no conjugated system such as norbornene-based resin or olefin-based resin as a main skeleton, and a cyclic structure such as a lactone ring or a glutarimide ring of an acrylic resin. Materials included in the main chain are included. When such a material is used, it is possible to suppress the development of retardation due to the orientation of the molecular chains when forming the isotropic substrate. The thickness of the isotropic substrate is preferably 50 μm or less, more preferably 35 μm or less. The lower limit of the thickness of the isotropic substrate is, for example, 20 μm.

  The conductive layer and / or the conductive layer of the isotropic substrate with the conductive layer may be patterned as required. By patterning, conductive parts and insulating parts can be formed. As a result, electrodes can be formed. The electrodes may function as touch sensor electrodes that sense a touch on the touch panel. Any appropriate method can be adopted as the patterning method. Specific examples of the patterning method include a wet etching method and a screen printing method.

F. Image Display Device The polarizing plate with a retardation layer described in the above items A to E can be applied to an image display device. Therefore, the present invention includes an image display device using such a polarizing plate with a retardation layer. Typical examples of the image display device include a liquid crystal display device and an electroluminescence (EL) display device (for example, an organic EL display device and an inorganic EL display device). The image display device according to the embodiment of the present invention includes the polarizing plate with a retardation layer described in the above items A to E on the viewing side. The polarizing plate with a retardation layer is laminated such that the retardation layer is on the image display cell (for example, liquid crystal cell, organic EL cell, inorganic EL cell) side (the polarizing film is on the viewing side). In one embodiment, the image display device has a curved shape (substantially a curved display screen) and / or is bendable or foldable. In such an image display device, the effect of the polarizing plate with a retardation layer of the present invention becomes remarkable.

なお、例えば、アンチグレア（ＡＧ）の表面処理や拡散性能を有する粘着剤を備える偏光板を測定対象とする場合、分光光度計に依存して異なる測定結果が得られ得るが、この場合、同一の偏光板をそれぞれの分光光度計で測定したときの測定値に基づいて数値換算を行うことにより、分光光度計に依存する測定値の差を補償することが可能である。
（３）長尺状の偏光膜の光学特性のバラつき
実施例および比較例に用いた偏光板から、幅方向に沿って等間隔に５か所の各位置で測定サンプルを切り出し、５つの各測定サンプルの中央部分の単体透過率を上記（２）と同様にして測定した。次いで、各測定位置において測定された単体透過率のうちの最大値と最小値との差を算出し、この値を長尺状の偏光膜の光学特性のバラつきとした。
（４）枚葉状の偏光膜の光学特性のバラつき
実施例および比較例に用いた偏光板から、１００ｍｍ×１００ｍｍの測定サンプルを切り出し、枚葉状の偏光板（５０ｃｍ^２）の光学特性のバラつきを求めた。具体的には、測定サンプルの４辺の各辺の中点から内側に約１．５ｃｍ〜２．０ｃｍ付近の位置および中央部分の計５か所の単体透過率を上記（２）と同様にして測定した。次いで、各測定位置において測定された単体透過率のうちの最大値と最小値との差を算出し、この値を枚葉状の偏光膜の光学特性のバラつきとした。
（５）反り
実施例および比較例で得られた位相差層付偏光板を１１０ｍｍ×６０ｍｍサイズに切り出した。このとき、偏光膜の吸収軸方向が長辺方向となるように切り出した。切り出した位相差層付偏光板を、１２０ｍｍ×７０ｍｍサイズ、厚み０．２ｍｍのガラス板に粘着剤を介して貼り合わせ、試験サンプルとした。試験サンプルを、８５℃に保持された加熱オーブンに２４時間投入し、取り出した後の反り量を測定した。ガラス板を下にして試験サンプルを平面上に静置した時に、当該平面から最も高い部分の高さを反り量とした。
（６）単位重量
実施例および比較例で得られた位相差層付偏光板を所定のサイズに切り出し、重量（ｍｇ）を面積（ｃｍ^２）で除することにより、位相差層付偏光板の単位面積当たりの重量（単位重量）を算出した。
（７）耐折り曲げ性
実施例および比較例で得られた位相差層付偏光板を５０ｍｍ×１００ｍｍサイズに切り出した。このとき、偏光膜の吸収軸方向が短辺方向となるように切り出した。恒温恒湿チャンバー付耐折試験機（ＹＵＡＳＡ社製、ＣＬ０９ ｔｙｐｅ−Ｄ０１）を用いて、２０℃５０％ＲＨの条件下で、切り出した位相差層付偏光板を折り曲げ試験に供した。具体的には、位相差層付偏光板を、位相差層側が外側となるように、吸収軸方向に平行な方向に繰り返し折り曲げて、表示不良となるようなクラック、剥がれやフィルムの破断などが発生するまでの折り曲げ回数を測定し、以下の基準で評価した（折り曲げ径：２ｍｍφ）。
＜評価基準＞
１万回未満：不良
１万回以上３万回未満：良
３万回以上：優 Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples. The measuring method of each characteristic is as follows. Unless otherwise specified, "parts" and "%" in the examples and comparative examples are based on weight.
(1) Thickness The thickness of 10 μm or less was measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name “MCPD-3000”). The thickness exceeding 10 μm was measured using a digital micrometer (manufactured by Anritsu Corporation, product name “KC-351C”).
(2) Single Transmittance and Polarization Degree The layered product (polarizing plate) of the polarizing film / protective layer used in Examples and Comparative Examples was measured using an ultraviolet-visible spectrophotometer (V-7100 manufactured by JASCO Corporation). The single-piece transmittance Ts, the parallel transmittance Tp, and the orthogonal transmittance Tc are defined as Ts, Tp, and Tc of the polarizing film, respectively. These Ts, Tp and Tc are Y values measured by the 2 degree visual field (C light source) of JIS Z8701 and subjected to the luminosity correction. The refractive index of the protective layer was 1.50, and the refractive index of the surface of the polarizing film opposite to the protective layer was 1.53.
The degree of polarization P was calculated from the obtained Tp and Tc by the following formula.
Polarization degree P (%) = {(Tp-Tc) / (Tp + Tc)} ^1/2 × 100
Note that the spectrophotometer can also perform the same measurement by using LPF-200 manufactured by Otsuka Electronics Co., Ltd. As an example, Table 1 shows the measured values of the single transmittance Ts and the polarization degree P obtained by the measurement using V-7100 and LPF-200 for Samples 1 to 3 of the polarizing plate having the same configurations as the following Examples. Show. As shown in Table 1, the difference between the measured value of the single transmittance of V-7100 and the measured value of the single transmittance of LPF-200 was 0.1% or less, and any spectrophotometer was used. It can be seen that the same measurement result can be obtained even in the case.

Note that, for example, when a polarizing plate provided with an adhesive having an anti-glare (AG) surface treatment or a diffusion property is used as a measurement target, different measurement results may be obtained depending on the spectrophotometer, but in this case, the same measurement result is obtained. It is possible to compensate for the difference in the measured values depending on the spectrophotometer by performing the numerical conversion based on the measured values when the polarizing plate is measured by each spectrophotometer.
(3) Variation in optical properties of long polarizing film From the polarizing plates used in Examples and Comparative Examples, measurement samples were cut out at five positions at equal intervals along the width direction, and five measurements were made. The simple substance transmittance of the central portion of the sample was measured in the same manner as in the above (2). Next, the difference between the maximum value and the minimum value of the single-piece transmittance measured at each measurement position was calculated, and this value was used as the variation in the optical characteristics of the elongated polarizing film.
(4) Variation in optical characteristics of sheet-shaped polarizing film A measurement sample of 100 mm × 100 mm was cut out from the polarizing plates used in Examples and Comparative Examples, and variation in optical characteristics of the sheet-shaped polarizing plate (50 cm ² ) was obtained. It was Specifically, the single-piece transmittances at a total of 5 positions in the vicinity of the center of about 1.5 cm to 2.0 cm from the midpoint of each side of the four sides of the measurement sample and the central part are the same as those in (2) above. Measured. Next, the difference between the maximum value and the minimum value of the single-element transmittance measured at each measurement position was calculated, and this value was used as the variation in the optical characteristics of the sheet-shaped polarizing film.
(5) Warpage The polarizing plate with a retardation layer obtained in each of Examples and Comparative Examples was cut out into a size of 110 mm × 60 mm. At this time, the polarizing film was cut out so that the absorption axis direction was the long side direction. The cut out polarizing plate with a retardation layer was attached to a glass plate of 120 mm × 70 mm size and 0.2 mm thickness via an adhesive to give a test sample. The test sample was placed in a heating oven maintained at 85 ° C. for 24 hours, and the amount of warp after taking out was measured. When the test sample was allowed to stand on a flat surface with the glass plate facing down, the height of the highest portion from the flat surface was defined as the amount of warpage.
(6) Unit Weight The polarizing plate with a retardation layer obtained in each of Examples and Comparative Examples was cut into a predetermined size, and the weight (mg) was divided by the area (cm ² ) to obtain a polarizing plate with a retardation layer. The weight per unit area (unit weight) was calculated.
(7) Bending resistance The polarizing plates with retardation layers obtained in Examples and Comparative Examples were cut out into a size of 50 mm x 100 mm. At this time, the polarizing film was cut out so that the absorption axis direction was the short side direction. Using a folding tester with a constant temperature and constant humidity chamber (CL09 type-D01 manufactured by YUASA), the cut out polarizing plate with a retardation layer was subjected to a bending test under conditions of 20 ° C. and 50% RH. Specifically, the polarizing plate with a retardation layer, so that the retardation layer side is the outside, by repeatedly bending in a direction parallel to the absorption axis direction, such as cracks that cause display defects, peeling or film breakage, etc. The number of times of bending before occurrence was measured and evaluated according to the following criteria (bending diameter: 2 mmφ).
<Evaluation criteria>
Less than 10,000 times: Poor 10,000 to less than 30,000 times: Good 30,000 times or more: excellent

[Example 1]
1. Preparation of Polarizing Film As the thermoplastic resin substrate, an amorphous isophthalic copolymer polyethylene terephthalate film (thickness: 100 μm) having a long shape, a water absorption of 0.75% and a Tg of about 75 ° C. was used. Corona treatment was applied to one surface of the resin substrate.
Polyvinyl alcohol (polymerization degree: 4200, saponification degree: 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosephimmer Z410") in a ratio of 9: 1 100 weight of PVA resin. What added 13 parts by weight of potassium iodide to a part was dissolved in water to prepare a PVA aqueous solution (coating solution).
The 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 having a thickness of 13 μm, and a laminate was prepared.
The obtained laminated body was uniaxially stretched 2.4 times in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 130 ° C. (in-air auxiliary stretching treatment).
Next, the laminated body was immersed in an insolubilizing bath having a liquid temperature of 40 ° C. (boric acid aqueous solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insolubilization treatment).
Then, a dyeing bath having 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) was added to the finally obtained polarizing film. Immersion was performed for 60 seconds while adjusting the concentration so that the simple substance transmittance (Ts) was 48% or more (dyeing treatment).
Then, it was immersed for 30 seconds in a crosslinking bath at a liquid temperature of 40 ° C. (boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with 100 parts by weight of water). (Crosslinking treatment).
Then, while the laminate was immersed in an aqueous boric acid solution (boric acid concentration 4.0% by weight) having a liquid temperature of 70 ° C., the total draw ratio was 5.5 in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds. Uniaxial stretching was performed so as to double the length (underwater stretching treatment).
After that, the laminate was immersed in a cleaning bath having a liquid temperature of 20 ° C. (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) (cleaning treatment).
Then, while being dried in an oven kept at 90 ° C., it was brought into contact with a SUS heating roll whose surface temperature was kept at 75 ° C. for about 2 seconds (dry shrinkage treatment). The shrinkage ratio in the width direction of the laminate due to the dry shrinkage treatment was 5.2%.
In this way, a polarizing film having a thickness of 5 μm was formed on the resin substrate.

2. Preparation of Polarizing Plate An acrylic film (surface refractive index 1.50, 40 μm) as a protective layer and an ultraviolet curable adhesive on the surface of the polarizing film obtained above (the surface opposite to the resin substrate). Pasted through. Specifically, the curable adhesive was applied so that the total thickness was 1.0 μm, and the curable adhesive was pasted using a roll machine. Then, UV rays were irradiated from the protective layer side to cure the adhesive. Next, after slitting both ends, the resin base material was peeled off to obtain a long polarizing plate (width: 1300 mm) having a structure of protective layer / polarizing film. The single transmittance of the polarizing plate (substantially, the polarizing film) was 48.48%, and the polarization degree was 87.036%. Furthermore, the variation of the optical characteristics of the long polarizing film was 0.58%, and the variation of the optical characteristics of the sheet-shaped polarizing film was 0.14%.

ポリエチレンテレフタレート（ＰＥＴ）フィルム（厚み３８μｍ）表面を、ラビング布を用いてラビングし、配向処理を施した。配向処理の方向は、偏光板に貼り合わせる際に偏光膜の吸収軸の方向に対して視認側から見て１５°方向となるようにした。この配向処理表面に、上記液晶塗工液をバーコーターにより塗工し、９０℃で２分間加熱乾燥することによって液晶化合物を配向させた。このようにして形成された液晶層に、メタルハライドランプを用いて１ｍＪ/ｃｍ^２の光を照射し、当該液晶層を硬化させることによって、ＰＥＴフィルム上に液晶配向固化層Ａを形成した。液晶配向固化層Ａの厚みは２．５μｍ、面内位相差Ｒｅ（５５０）は２７０ｎｍであった。さらに、液晶配向固化層Ａは、ｎｘ＞ｎｙ＝ｎｚの屈折率分布を有していた。
塗工厚みを変更したこと、および、配向処理方向を偏光膜の吸収軸の方向に対して視認側から見て７５°方向となるようにしたこと以外は上記と同様にして、ＰＥＴフィルム上に液晶配向固化層Ｂを形成した。液晶配向固化層Ｂの厚みは１．５μｍ、面内位相差Ｒｅ（５５０）は１４０ｎｍであった。さらに、液晶配向固化層Ｂは、ｎｘ＞ｎｙ＝ｎｚの屈折率分布を有していた。 3. Preparation of First Alignment Solidification Layer and Second Alignment Solidification Layer Constituting Retardation Layer 10 g of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF: trade name “Paliocolor LC242”, represented by the following formula): A liquid crystal composition (coating liquid) was prepared by dissolving 3 g of a photopolymerization initiator (manufactured by BASF: trade name “Irgacure 907”) for the polymerizable liquid crystal compound in 40 g of toluene.

The surface of the polyethylene terephthalate (PET) film (thickness 38 μm) was rubbed with a rubbing cloth for orientation treatment. The direction of the alignment treatment was set to be 15 ° with respect to the direction of the absorption axis of the polarizing film when it was attached to the polarizing plate when viewed from the viewing side. The liquid crystal coating liquid was applied to the surface of the alignment treatment by a bar coater, and the liquid crystal compound was aligned by heating and drying at 90 ° C. for 2 minutes. The liquid crystal layer thus formed was irradiated with light of 1 mJ / cm ² using a metal halide lamp to cure the liquid crystal layer, thereby forming a liquid crystal alignment solidified layer A on the PET film. The thickness of the liquid crystal alignment fixed layer A was 2.5 μm, and the in-plane retardation Re (550) was 270 nm. Further, the liquid crystal alignment fixed layer A had a refractive index distribution of nx> ny = nz.
On the PET film in the same manner as described above except that the coating thickness was changed and the alignment treatment direction was set to be the direction of 75 ° with respect to the absorption axis direction of the polarizing film when viewed from the viewing side. A liquid crystal alignment fixed layer B was formed. The thickness of the liquid crystal alignment fixed layer B was 1.5 μm, and the in-plane retardation Re (550) was 140 nm. Furthermore, the liquid crystal alignment fixed layer B had the refractive index distribution of nx> ny = nz.

4. Preparation of Polarizing Plate with Retardation Layer 2. On the surface of the polarizing film of the polarizing plate obtained in step 3, above. The liquid crystal alignment solidified layer A and the liquid crystal alignment solidified layer B obtained in 1. were transferred in this order. At this time, the angle between the absorption axis of the polarizing film and the slow axis of the alignment solidified layer A is 15 °, and the angle between the absorption axis of the polarization film and the slow axis of the oriented solidified layer B is 75 °. Transfer (bonding) was performed. In addition, each transfer (bonding) is performed in the above 2. The UV-curable adhesive (thickness 1.0 μm) used in 1. was used. In this way, a polarizing plate with a retardation layer having a structure of protective layer / adhesive layer / polarizing film / adhesive layer / retardation layer (first alignment solidified layer / adhesive layer / second alignment solidified layer) is obtained. It was The total thickness of the obtained polarizing plate with a retardation layer was 52 μm. The obtained polarizing plate with a retardation layer was subjected to the above evaluations (5) to (7). The amount of warpage was 1.8 mm.

[Example 2]
A polarizing plate with a retardation layer was produced in the same manner as in Example 1 except that an acrylic film having a thickness of 20 μm was used as the protective layer. The total thickness of the obtained polarizing plate with a retardation layer was 32 μm. The obtained polarizing plate with retardation layer was subjected to the same evaluations as in Example 1. The amount of warpage was 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 25 μm-thick triacetyl cellulose (TAC) film was used as the protective layer. The total thickness of the obtained polarizing plate with a retardation layer was 37 μm. The obtained polarizing plate with retardation layer was subjected to the same evaluations as in Example 1. The amount of warpage was 1.3 mm.

[Comparative Example 1]
1. Production of Polarizer A polyvinyl alcohol-based resin film having an average polymerization degree of 2,400, a saponification degree of 99.9 mol% and a thickness of 30 μm was prepared. The polyvinyl alcohol film was dipped in a swelling bath (water bath) at 20 ° C. for 30 seconds between rolls having different peripheral speed ratios and stretched 2.4 times in the transport direction while swelling (swelling step). Dyeing is performed by dipping in a dyeing bath at 30 ° C (an aqueous solution having an iodine concentration of 0.03% by weight and a potassium iodide concentration of 0.3% by weight) so that the single transmittance after the final stretching becomes a desired value. On the other hand, the original polyvinyl alcohol film (polyvinyl alcohol film which was not stretched at all in the transport direction) was stretched 3.7 times in the transport direction (dyeing step). The immersion time at this time was about 60 seconds. Then, while dipping the dyed polyvinyl alcohol film in a crosslinking bath at 40 ° C. (an aqueous solution having a boric acid concentration of 3.0 wt% and a potassium iodide concentration of 3.0 wt%), the original polyvinyl alcohol film was immersed. It was stretched to 4.2 times in the transport direction based on the standard (crosslinking step). Further, the obtained polyvinyl alcohol film was immersed in a stretching bath at 64 ° C. (an aqueous solution having a boric acid concentration of 4.0% by weight and a potassium iodide concentration of 5.0% by weight) for 50 seconds to obtain the original polyvinyl alcohol. After being stretched to 6.0 times in the transport direction based on the alcohol film (stretching step), it was immersed in a washing bath at 20 ° C. (aqueous solution having a potassium iodide concentration of 3.0% by weight) for 5 seconds (washing). Process). The washed polyvinyl alcohol film was dried at 30 ° C. for 2 minutes to prepare a polarizer (thickness 12 μm).

2. Preparation of Polarizing Plate As an adhesive, a polyvinyl alcohol resin containing an acetoacetyl group (average polymerization degree: 1,200, saponification degree: 98.5 mol%, acetoacetylation degree: 5 mol%) and methylolmelamine were used. An aqueous solution containing a weight ratio of 3: 1 was used. Using this adhesive, a 25 μm thick triacetyl cellulose (TAC) film with a hard coat layer on one side of the polarizer obtained above and a 25 μm thick TAC film on the other side of the polarizer were obtained. After laminating with a roll laminating machine, it is heated and dried in an oven (temperature is 60 ° C., time is 5 minutes), and protective layer 1 (thickness 25 μm) / adhesive layer / polarizer / adhesive layer / protective layer 2 ( A polarizing plate having a thickness of 25 μm) was produced.

3. Preparation of Polarizing Plate with Retardation Layer 2. The liquid crystal alignment / solidification layer A and the liquid crystal alignment / solidification layer B were transferred in this order to the surface of the protective layer 2 of the polarizing plate obtained in 1. in the same manner as in Example 1, and protective layer 1 / adhesion layer / polarizer / adhesion A polarizing plate with a retardation layer having a structure of layer / protective layer 2 / adhesive layer / retardation layer (first orientation solidified layer / adhesion layer / second orientation solidified layer) was produced. The total thickness of the obtained polarizing plate with a retardation layer was 68 μm. The obtained polarizing plate with retardation layer was subjected to the same evaluations as in Example 1. The amount of warpage was 4.2 mm.

[Comparative Example 2]
Example except that potassium iodide was not added to the PVA aqueous solution (coating solution), the draw ratio in the in-air auxiliary drawing process was set to 1.8 times, and no heating roll was used in the dry shrinking process. An attempt was made to produce a polarizing film in the same manner as in Example 1, but the PVA resin layer was dissolved in the dyeing treatment and the underwater stretching treatment, and the polarizing film could not be produced. Therefore, a polarizing plate with a retardation layer could not be prepared.

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

2. Preparation of retardation film constituting retardation layer 2-1. Polymerization of Polyester Carbonate Resin Polymerization was carried out using a batch polymerization apparatus comprising two vertical reactors equipped with a stirring blade and a reflux condenser controlled to 100 ° C. Bis [9- (2-phenoxycarbonylethyl) fluoren-9-yl] methane 29.60 parts by mass (0.046 mol), isosorbide (ISB) 29.21 parts by mass (0.200 mol), spiroglycol (SPG) 42 .28 parts by mass (0.139 mol), diphenyl carbonate (DPC) 63.77 parts by mass (0.298 mol), and calcium acetate monohydrate as a catalyst 1.19 × 10 ⁻² parts by mass (6.78 × 10 ^{−). 5} mol) was charged. After the inside of the reactor was replaced with nitrogen under reduced pressure, heating was performed with a heating medium, and stirring was started when the internal temperature reached 100 ° C. After 40 minutes from the start of temperature increase, the internal temperature was made to reach 220 ° C., the temperature was controlled so as to be kept at the same time, and the depressurization was started at the same time. Phenol vapor produced as a by-product with the polymerization reaction was introduced into a reflux condenser at 100 ° C., a monomer component slightly contained in the phenol vapor was returned to the reactor, and uncondensed phenol vapor was introduced into a condenser at 45 ° C. and recovered. After introducing nitrogen into the first reactor to restore the pressure to atmospheric pressure once, the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Next, the temperature rise and pressure reduction in the second reactor were started, and the internal temperature was set to 240 ° C. and the pressure was set to 0.2 kPa in 50 minutes. Then, the polymerization was allowed to proceed until a predetermined stirring power was obtained. When the predetermined power was reached, nitrogen was introduced into the reactor to restore the pressure, the produced polyester carbonate resin was extruded into water, and the strands were cut to obtain pellets.

2-2. Preparation of retardation film The obtained polyester carbonate-based resin (pellet) was vacuum dried at 80 ° C for 5 hours, then a single-screw extruder (Toshiba Kikai Co., Ltd., cylinder setting temperature: 250 ° C), T-die (width 200 mm). , Setting temperature: 250 ° C.), a chill roll (setting temperature: 120 to 130 ° C.) and a film forming apparatus equipped with a winder were used to produce a long resin film having a thickness of 135 μm. 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 having 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. Preparation of Polarizing Plate with Retardation Layer Above 1. On the surface of the polarizing film of the polarizing plate obtained in step 2, above. The retardation film obtained in (1) was attached via an acrylic pressure-sensitive adhesive (thickness 5 μm). At this time, they were laminated so that the absorption axis of the polarizing film and the slow axis of the retardation film formed an angle of 45 °. In this way, a polarizing plate with a retardation layer having a structure of protective layer / adhesive layer / polarizing film / adhesive layer / retarder was obtained. The total thickness of the obtained polarizing plate with a retardation layer was 89 μm. The obtained polarizing plate with a retardation layer was subjected to the evaluations in (6) and (7) above.

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

[Evaluation]
As is clear from Table 2 and a comparison between Example 1 and Comparative Example 2, the polarizing plate with a retardation layer of the Example of the present invention is thin, the warpage after the heating test is suppressed, and the optical characteristics are excellent. Excel. Further, it can be seen that the bending resistance is improved when the weight per unit area of the polarizing plate with a retardation layer is a predetermined value or less.

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

DESCRIPTION OF SYMBOLS 10 Polarizing plate 11 Polarizing film 12 1st protective layer 13 2nd protective layer 20 Retardation layer 100 Polarizing plate with retardation layer 101 Polarizing plate with retardation layer 102 Polarizing plate with retardation layer

Claims (12)

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 a thickness of 8 μm or less, a single transmittance of 48% or more, and a polarization degree of 85% or more,
The retardation layer is an alignment and solidification layer of a liquid crystal compound,
Polarizing plate with retardation layer. The polarizing plate with a retardation layer according to claim 1, having a unit weight of 6.5 mg / cm ² or less.   The polarizing plate with a retardation layer according to claim 1, which has a total thickness of 60 μm or less. The retardation layer is a single layer of an alignment solidified layer of a liquid crystal compound,
Re (550) of the retardation layer is 100 nm to 190 nm,
An angle formed by the slow axis of the retardation layer and the absorption axis of the polarizing film is 40 ° to 50 °,
The polarizing plate with a retardation layer according to claim 1. The retardation layer has a laminated structure of an alignment solidified layer of a first liquid crystal compound and an alignment solidified layer of a second liquid crystal compound,
Re (550) of the oriented solidified layer of the first liquid crystal compound is 200 nm to 300 nm, and an angle formed by the slow axis thereof and the absorption axis of the polarizing film is 10 ° to 20 °,
Re (550) of the alignment-solidified layer of the second liquid crystal compound is 100 nm to 190 nm, and the angle between the slow axis and the absorption axis of the polarizing film is 70 ° to 80 °.
The polarizing plate with a retardation layer according to claim 1. The polarizing plate with a retardation layer according to any one of claims 1 to 5, wherein a difference between the maximum value and the minimum value of the single-piece transmittance in the area of 50 cm ² of the polarizing film is 0.5% or less.   The phase difference according to any one of claims 1 to 5, wherein the width is 1000 mm or more, and the difference between the maximum value and the minimum value of the single-piece transmittance at a position along the width direction of the polarizing film is 1% or less. Layered polarizing plate.   8. The polarizing plate with a retardation layer according to claim 1, wherein the polarizing film has a single transmittance of 50% or less and a polarization degree of 92% or less.   9. The unit according to claim 1, further comprising another retardation layer outside the retardation layer, and the refractive index characteristics of the another retardation layer exhibit a relationship of nz> nx = ny. Polarizing plate with retardation layer.   The polarizing plate with a retardation layer according to claim 1, further comprising a conductive layer or an isotropic substrate with a conductive layer outside the retardation layer.   An image display device comprising the polarizing plate with a retardation layer according to claim 1.   The image display device according to claim 11, which is an organic electroluminescence display device or an inorganic electroluminescence display device.

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