JP7355583B2 - Polarizing plate with retardation layer and image display device using the same - Google Patents

Description

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

In recent years, image display devices typified by liquid crystal display devices and electroluminescent (EL) display devices (eg, organic EL display devices and inorganic EL display devices) have rapidly become popular. Polarizing plates and retardation plates are typically used in image display devices. In practice, a polarizing plate with a retardation layer that integrates a polarizing plate and a retardation plate is widely used (for example, Patent Document 1), but recently there has been a strong demand for thinner image display devices. With this trend, there is an increasing demand for thinner polarizing plates with retardation layers. In addition, in recent years, there has been an increasing demand for curved image display devices and/or bendable or foldable image display devices, and polarizing plates and polarizing plates with retardation layers are also required to be thinner and more flexible. ing. In order to make polarizing plates with retardation layers thinner, protective layers and retardation films of polarizing films, which contribute significantly to the thickness, are becoming thinner. However, when the protective layer and the retardation film are made thinner, the effect of shrinkage of the polarizing film becomes relatively large, causing problems such as warping 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 reduce the thickness of the polarizing film as well. However, simply reducing the thickness of the polarizing film deteriorates the optical properties. More specifically, one or both of the degree of polarization and the single transmittance, which are in a trade-off relationship, decrease to a practically unacceptable degree. As a result, the optical properties of the polarizing plate with a retardation layer also become insufficient.

Patent No. 3325560

The present invention has been made to solve the above-mentioned conventional problems, and its main purpose is to provide a polarizing plate with a retardation layer that is thin, easy to handle, and has excellent optical properties. .

The polarizing plate with a retardation layer of the present invention includes 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 resin film containing a dichroic substance, has a thickness of 8 μm or less, a single transmittance of 43.5% or more, and a polarization degree of 99.940% or more. . Re(550) of the retardation layer is 100 nm to 190 nm, Re(450)/Re(550) is 0.8 or more and less than 1, and the slow axis of the retardation layer and the absorption axis of the polarizing film The angle between the two is 40° to 50°.
In one embodiment, the protective layer is made of a base material having an elastic modulus of 3000 MPa or more.
In one embodiment, the total thickness of the polarizing plate with a retardation layer is 90 μm or less, the front reflection hue is 3.5 or less, and the protective layer is made of a resin film having an elastic modulus of 3000 MPa or more. configured.
In one embodiment, the protective layer is composed of a triacetyl cellulose resin film.
In one embodiment, the polarizing plate includes the polarizing film and the protective layer disposed only on one side of the polarizing film, and the retardation layer connects to the polarizing film through an adhesive layer. is attached to.
In one embodiment, the retardation layer is made of a polycarbonate resin film.
In one embodiment, the retardation layer is made of a polycarbonate resin film having a thickness of 40 μm or less.
In one embodiment, the difference between the maximum value and the minimum value of the single transmittance within a 50 cm ² area of the polarizing film is 0.15% or less.
In one embodiment, the polarizing plate with a 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 a position along the width direction of the polarizing film is 0.3%. It is as follows.
In one embodiment, the polarizing film has a single transmittance of 44.0% or less and a polarization degree of 99.990% or less.
In one embodiment, the polarizing plate with a retardation layer further includes another retardation layer outside the retardation layer, and the retardation index characteristic of the another retardation layer satisfies nz>nx=ny. Show relationships.
In one embodiment, the polarizing plate with a retardation layer further includes a conductive layer or an isotropic substrate with a conductive layer on the outside of the retardation layer.
In one embodiment, the polarizing plate with a retardation layer has an elongated shape, the polarizing film has an absorption axis in the elongated direction, and the retardation layer has an angle of 40° to the elongated direction. It is an obliquely stretched film having a slow axis in a direction forming an angle of 50°. In one embodiment, the polarizing plate with a retardation layer is wound into a roll.
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 electroluminescent display device or an inorganic electroluminescent display device.

According to the present invention, addition of a halide (typically potassium iodide) to polyvinyl alcohol (PVA)-based resin, two-stage stretching including aerial assisted stretching and underwater stretching, and drying and shrinkage using heated rolls. By employing these in combination, it is possible to obtain a polarizing film that is thin and yet has extremely excellent optical properties. By using such a polarizing film, it is possible to realize a polarizing plate with a retardation layer that is thin, easy to handle, and has excellent optical properties.

1 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to one embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to another embodiment of the present invention. FIG. 2 is a schematic diagram showing an example of a dry shrinkage treatment using a heating roll in a method for manufacturing a polarizing film used in a polarizing plate with a retardation layer of the present invention.

Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

(Definition of terms and symbols)
Definitions of terms and symbols used herein 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 (i.e., slow axis direction), and "ny" is the direction perpendicular to the slow axis in the plane (i.e., fast axis direction) "nz" is the refractive index in the thickness direction.
(2) In-plane phase difference (Re)
"Re(λ)" is an in-plane retardation measured with light having a wavelength of λnm 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 determined by the formula: Re(λ)=(nx−ny)×d, where d (nm) is the thickness of the layer (film).
(3) Phase difference in thickness direction (Rth)
"Rth (λ)" is a retardation in the thickness direction measured with light having a wavelength of λ nm at 23°C. For example, "Rth (550)" is the retardation in the thickness direction measured with light having a wavelength of 550 nm at 23°C. Rth(λ) is determined by the formula: Rth(λ)=(nx−nz)×d, where d (nm) is the thickness of the layer (film).
(4) Nz coefficient The Nz coefficient is determined by Nz=Rth/Re.
(5) Angle When an angle is referred to in this specification, the angle includes both clockwise and counterclockwise directions 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 cross-sectional view of a polarizing plate with a retardation layer according to one embodiment of the present invention. A polarizing plate with a retardation layer 100 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 disposed on one side of the polarizing film 11, and a second protective layer 13 disposed on the other side of the polarizing film 11. . Depending on the purpose, one of the first protective layer 12 and the second protective layer 13 may be omitted. For example, if 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 an embodiment of the present invention, the polarizing film is composed of a polyvinyl alcohol resin film containing a dichroic substance. The thickness of the polarizing film is 8 μm or less, the single transmittance is 43.5% or more, and the polarization degree is 99.940% or more.

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

In the embodiment of the present invention, Re(550) of the first retardation layer 20 is 100 nm to 190 nm, and Re(450)/Re(550) is 0.8 or more and less than 1. Further, the angle between the slow axis of the first retardation layer 20 and the absorption axis of the polarizing film 11 is 40° to 50°.

The above embodiments may be combined as appropriate, and the components in the above embodiments may be modified in a manner obvious to those skilled in the art. For example, the configuration in which the isotropic base material 60 with a conductive layer is provided outside the second retardation layer 50 may be replaced with an optically equivalent configuration (for example, a laminate of a second retardation layer and a conductive layer). Good too.

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

The polarizing plate with a retardation layer of the present invention may have a single leaf shape or may have an elongated shape. In this specification, "elongated shape" means an elongated shape whose length is sufficiently longer than its width; for example, an elongated shape whose length is at least 10 times, preferably at least 20 times its width. include. The elongated polarizing plate with a retardation layer can be wound into a roll. When the polarizing plate with a retardation layer is elongated, the polarizing plate and the retardation layer are also elongated. In this case, the polarizing film preferably has an absorption axis in the longitudinal direction. The first retardation layer is preferably an obliquely stretched film having a slow axis in a direction forming an angle of 40° to 50° with respect to the longitudinal direction. If the polarizing film and the first retardation layer have such a configuration, a polarizing plate with a retardation layer can be manufactured by roll-to-roll.

Practically, an adhesive layer (not shown) is provided on the opposite side of the retardation layer to the polarizing plate, and the polarizing plate with the retardation layer can be attached to the image display cell. Furthermore, it is preferable that a release film is temporarily attached to the surface of the adhesive layer until the polarizing plate with a retardation layer is used. Temporarily attaching a release film protects the adhesive layer and enables roll formation.

The front reflection hue (√(a ^*2 +b ^*2 )) of the polarizing plate with a retardation layer is preferably 3.5 or less, more preferably 3.0 or less. If the front reflection hue is within the above range, undesired coloring and the like can be suppressed, and as a result, a polarizing plate with a retardation layer having excellent reflection properties can be obtained.

The total thickness of the polarizing plate with a retardation layer is preferably 140 μm or less, more preferably 120 μm or less, even more preferably 100 μm or less, even more preferably 90 μm or less, and even more preferably 85 μm or less. be. The lower limit of the total thickness may be, for example, 30 μm. According to the embodiments of the present invention, it is possible to realize such an extremely thin polarizing plate with a retardation layer. 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. Note that the total thickness of the polarizing plate with a retardation layer refers to the total thickness of the polarizing plate with a retardation layer, excluding the adhesive layer for adhering the polarizing plate with a retardation layer to an external adherend such as a panel or glass. Refers to the total thickness of all layers (in other words, the total thickness of a polarizing plate with a retardation layer is the adhesive layer for attaching the polarizing plate with a retardation layer to an adjacent member such as an image display cell, etc.) and the temporary layer on its surface. (not including the thickness of the release film that may be applied).

Hereinafter, the constituent elements of the polarizing plate with a retardation layer will be explained 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 43.5% or more, and a polarization degree of 99.940% or more. Generally, the single transmittance and the degree of polarization are in a trade-off relationship with each other; increasing the single transmittance may decrease the degree of polarization, and increasing the degree of polarization may decrease the single transmittance. For this reason, it has conventionally been difficult to put into practical use a thin polarizing film that satisfies the optical characteristics of a single transmittance of 43.5% or more and a polarization degree of 99.940% or more. It is important to use a thin polarizing film that has excellent optical properties such as a single transmittance of 43.5% or more and a polarization degree of 99.940% or more, and suppresses variations in optical properties. This is one of the features of the invention.

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

The polarizing film preferably exhibits absorption dichroism at a wavelength of 380 nm to 780 nm. The single transmittance of the polarizing film is preferably 44.0% or less. The degree of polarization of the polarizing film is preferably 99.950% or more, more preferably 99.960% or more. On the other hand, the degree of polarization is preferably 99.990% or less. The above-mentioned single transmittance is typically a Y value measured using an ultraviolet-visible spectrophotometer and subjected to visibility correction. The degree of polarization is typically determined by the following formula based on parallel transmittance Tp and cross transmittance Tc measured using an ultraviolet-visible spectrophotometer and corrected for visibility.
Degree of polarization (%) = {(Tp-Tc)/(Tp+Tc)} ^1/2 ×100

In one embodiment, the transmittance of a thin polarizing film of 8 μm or less is typically a laminate of a polarizing film (surface refractive index: 1.53) and a protective film (refractive index: 1.50). It is measured using an ultraviolet-visible spectrophotometer using the body as the measurement object. Depending on the refractive index of the surface of the polarizing film and/or the refractive index of the surface of the protective film in contact with the air interface, the reflectance at the interface of each layer may change, and as a result, the measured value of transmittance may change. . Therefore, for example, when using a protective film with a refractive index other than 1.50, the measured value of transmittance may be corrected according to the refractive index of the surface of the protective film that is in contact with the air interface. Specifically, the transmittance correction value C is expressed by the following formula using the reflectance R ₁ (transmission axis reflectance) of polarized light parallel to the transmission axis at the interface between the protective film and the air layer.
C=R ₁ -R ₀
R ₀ =((1.50-1) ² /(1.50+1) ² )×(T ₁ /100)
R ₁ =((n ₁ -1) ² /(n ₁ +1) ² )×(T ₁ /100)
Here, R ₀ is the transmission axis reflectance when using a protective film with a refractive index of 1.50, n ₁ is the refractive index of the protective film used, and T ₁ is the transmittance of the polarizing film. It is. For example, when a base material (cycloolefin film, film with a hard coat layer, etc.) having a surface refractive index of 1.53 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 measurement, it is possible to convert it to the transmittance when using a protective film with a surface refractive index of 1.50. According to the calculation based on the above formula, when the transmittance _T1 of the polarizing film is changed by 2%, the amount of change in the correction value C is 0.03% or less, and the transmittance of the polarizing film is less than the correction value C. The effect on the value of is limited. Furthermore, when the protective film has absorption other than surface reflection, appropriate correction can be made depending on 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 width of 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 a position along the width direction of the polarizing film is preferably 0.3% or less, more preferably 0.25% or less. , more preferably 0.2% or less. The smaller D1 is, the more preferable it is, and the lower limit of D1 may be, for example, 0.01%. If D1 is within the above range, a polarizing plate with a retardation layer having excellent optical properties can be industrially produced. In another embodiment, the polarizing film has a difference (D2) between the maximum value and the minimum value of the single transmittance within a 50 cm ² area, preferably 0.15% or less, more preferably 0.1%. It is not more than 0.08%, more preferably not more than 0.08%. The smaller D2 is, the more preferable it is, and the lower limit of D2 may be, for example, 0.01%. If D2 is within the above range, variations in brightness on a display screen can be suppressed when the polarizing plate with a retardation layer is used in an image display device.

Any suitable polarizing film may be employed as the polarizing film. A polarizing film can typically be produced using a laminate of two or more layers.

A specific example of a polarizing film obtained using a laminate includes a polarizing film obtained using a laminate of a resin base material and a PVA-based resin layer coated on the resin base material. A polarizing film obtained using a laminate of a resin base material and a PVA resin layer coated on the resin base material can be obtained by, for example, applying a PVA resin solution to the resin base material and drying it. Forming a PVA-based resin layer thereon to obtain a laminate of a resin base material and a PVA-based resin layer; stretching and dyeing the laminate to make the PVA-based resin layer a polarizing film; obtain. In this embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching. Furthermore, the stretching may further include stretching the laminate in air at a high temperature (for example, 95° C. or higher) before stretching in the boric acid aqueous solution, if necessary. The obtained resin base material/polarizing film laminate may be used as is (that is, the resin base material may be used as a protective layer for the polarizing film), or the resin base material may be peeled from the resin base material/polarizing film laminate. However, any appropriate protective layer may be laminated 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 Publication No. 2012-73580. The entire description of this publication is incorporated herein by reference.

A method for producing a polarizing film typically involves forming a polyvinyl alcohol resin layer containing a halide and a polyvinyl alcohol resin on one side of a long thermoplastic resin base material to form a laminate; and subjecting the laminate to, in this order, an auxiliary stretching process in the air, a dyeing process, a stretching process in water, and a drying shrinkage process in which the laminate is shrunk by 2% or more in the width direction by heating while conveying in the longitudinal direction. including. As a result, a polarizing film with a thickness of 8 μm or less, a single transmittance of 43.5% or more, and a polarization degree of 99.940% or more, which has excellent optical properties and suppresses variations in optical properties. may be provided. That is, by introducing auxiliary stretching, even when PVA is applied onto a thermoplastic resin, it becomes possible to improve the crystallinity of PVA, and it becomes possible to achieve high optical properties. At the same time, by increasing the orientation of PVA in advance, it is possible to prevent problems such as deterioration of orientation and dissolution of PVA when it is immersed in water during the subsequent dyeing and stretching processes, resulting in high optical properties. becomes possible to achieve. Furthermore, when the PVA-based resin layer is immersed in a liquid, disturbance in the orientation of polyvinyl alcohol molecules and deterioration of orientation can be suppressed compared to when the PVA-based resin layer does not contain a halide. This can improve the optical properties of a polarizing film obtained through a treatment process performed by immersing the laminate in a liquid, such as dyeing treatment and underwater stretching treatment. Furthermore, optical properties can be improved by shrinking the laminate in the width direction by drying shrinkage 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 materials that are the main components of the film include cellulose resins such as triacetylcellulose (TAC), polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, and polysulfones. Examples include transparent resins such as polystyrene, polynorbornene, polyolefin, (meth)acrylic, and acetate. Further, thermosetting resins or ultraviolet curable resins such as (meth)acrylic, urethane, (meth)acrylic urethane, epoxy, and silicone resins may also be mentioned. Other examples include glassy polymers such as siloxane polymers. Furthermore, the polymer film described in JP-A-2001-343529 (WO01/37007) can also be used. Materials for this film include, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in its side chain, and a thermoplastic resin having a substituted or unsubstituted phenyl group and nitrile group in its side chain. For example, a resin composition containing an alternating copolymer of isobutene and N-methylmaleimide and an acrylonitrile/styrene copolymer can be used. The polymer film may be, for example, an extrusion molded product of the resin composition. In one embodiment, the protective layer (particularly the protective layer on the viewing side) contains a TAC-based resin. By using a TAC resin film as the protective layer, the bending durability can be improved.

The polarizing plate with a retardation layer of the present invention is typically placed on the viewing side of an image display device, as will be described later, and the first protective layer 12 is typically placed on the viewing side. Therefore, the first protective layer 12 may be subjected to surface treatments such as hard coat treatment, antireflection treatment, antisticking treatment, and antiglare treatment, as necessary. Furthermore/or, the first protective layer 12 may be treated, if necessary, to improve visibility when viewed through polarized sunglasses (typically, an (elliptical) circularly polarizing function is applied); (imparting an ultra-high phase difference) may also be applied. By performing such processing, excellent visibility can be achieved even when the display screen is viewed through polarized lenses 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, even more preferably 10 μm to 35 μm. In addition, when surface treatment is performed, the thickness of the outer protective layer is the thickness including the thickness of the surface treatment layer.

In one embodiment, the second protective layer 13 is preferably optically isotropic. In this specification, "optically isotropic" means that the in-plane retardation Re (550) is 0 nm to 10 nm and the thickness direction retardation Rth (550) is -10 nm to +10 nm. say. The second protective layer 13 may be a retardation layer having any suitable 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, even more preferably 10 μm to 30 μm. From the viewpoint of reducing the thickness and weight, the second protective layer can preferably be omitted.

B-3. Method for manufacturing a polarizing film A polarizing film is produced by, for example, forming a polyvinyl alcohol-based resin layer (PVA-based resin layer) containing a halide and a polyvinyl alcohol-based resin (PVA-based resin) on one side of a long thermoplastic resin base material. The laminate is subjected to an auxiliary stretching process in the air, a dyeing process, a stretching process in water, and a drying process in which the laminate is contracted by 2% or more in the width direction by heating while conveying in the longitudinal direction. and shrinkage treatment in this order. The content of the halide in the PVA resin layer is preferably 5 parts by weight to 20 parts by weight based on 100 parts by weight of the PVA resin. The drying shrinkage treatment is preferably carried out using a heating roll, and the temperature of the heating roll is preferably 60°C to 120°C. The shrinkage rate of the laminate in the width direction due to the drying shrinkage treatment is preferably 2% or more. According to such a manufacturing method, the polarizing film described in the above section B-1 can be obtained. In particular, by producing a laminate including a PVA resin layer containing a halide, stretching the laminate in multiple stages including auxiliary stretching in the air and stretching in water, and heating the laminate after stretching with a heating roll. , it is possible to obtain a polarizing film that has excellent optical properties (typically, single transmittance and degree of polarization) and suppresses variations in optical properties. Specifically, by using a heating roll in the drying shrinkage process, the entire laminate can be uniformly shrunk while being transported. This not only makes it possible to improve the optical properties of the resulting polarizing film, but also allows stable production of polarizing films with excellent optical properties, and suppresses variations in the optical properties (especially single transmittance) of the polarizing film. can do.

B-3-1. Preparation of Laminate Any suitable method may be adopted as a method for producing a laminate of a thermoplastic resin base material and a PVA-based resin layer. Preferably, a coating liquid containing a halide and a PVA resin is applied to the surface of the thermoplastic resin base material and dried to form a PVA resin layer on the thermoplastic resin base material. As mentioned above, the content of the halide in the PVA resin layer is preferably 5 parts by weight to 20 parts by weight based on 100 parts by weight of the PVA resin.

Any suitable method can be adopted as a method for applying the coating liquid. Examples include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, knife coating (comma coating, etc.). The coating and 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.

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

B-3-1-1. Thermoplastic resin base material The thickness of the thermoplastic resin base material 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 a PVA-based resin layer. If it exceeds 300 μm, for example, it may take a long time for the thermoplastic resin base material to absorb water in the underwater stretching treatment described below, and an excessive load may be required for stretching.

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

The glass transition temperature (Tg) of the thermoplastic resin base material is preferably 120°C or lower. By using such a thermoplastic resin base material, it is possible to sufficiently ensure the stretchability of the laminate while suppressing crystallization of the PVA-based resin layer. Furthermore, in consideration of plasticizing the thermoplastic resin base material with water and performing underwater stretching satisfactorily, 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 base material is preferably 60°C or higher. By using such a thermoplastic resin base material, the thermoplastic resin base material may be deformed (e.g., unevenness, sagging, wrinkles, etc.) when applying and drying a coating solution containing the above-mentioned PVA-based resin. It is possible to prevent this problem and produce a good laminate. Further, the PVA resin layer can be stretched well at a suitable temperature (for example, about 60° C.). Note that the glass transition temperature of the thermoplastic resin base material can be adjusted by, for example, heating using a crystallizing material that introduces a modifying group into the constituent material. The glass transition temperature (Tg) is a value determined according to JIS K 7121.

Any suitable thermoplastic resin may be employed as the constituent material of the thermoplastic resin base material. Examples of thermoplastic resins include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymer resins thereof. can be mentioned. Among these, norbornene resins and amorphous polyethylene terephthalate resins are preferred.

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

In a preferred embodiment, the thermoplastic resin base material is comprised of a polyethylene terephthalate-based resin having isophthalic acid units. This is because such a thermoplastic resin base material has extremely excellent stretchability and can suppress crystallization during stretching. This is thought to be due to the fact that the introduction of the isophthalic acid unit imparts a large bend to the main chain. Polyethylene terephthalate resin has a terephthalic acid unit and an ethylene glycol unit. The content 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 base material with extremely excellent stretchability can be obtained. On the other hand, the content 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 the content to such a content ratio, the degree of crystallinity can be favorably increased in the drying shrinkage treatment described below.

The thermoplastic resin base material may be stretched in advance (before forming the PVA-based resin layer). In one embodiment, the elongated thermoplastic resin base material is stretched in the lateral direction. The lateral direction is preferably a direction perpendicular to the stretching direction of the laminate described below. In addition, in this specification, "orthogonal" also includes a case where they are substantially orthogonal. Here, "substantially orthogonal" includes a case where the angle is 90°±5.0°, preferably 90°±3.0°, and more preferably 90°±1.0°.

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

Any suitable method may be employed as a method for stretching the thermoplastic resin base material. Specifically, fixed end stretching or free end stretching may be used. The stretching method may be a dry method or a wet method. The thermoplastic resin base material may be stretched in one step or in multiple steps. In the case of multi-stage stretching, the above-mentioned stretching ratio is the product of the stretching ratios of each stage.

B-3-1-2. Coating Liquid The coating liquid contains a halide and a PVA resin as described above. The coating liquid is typically a solution in which the halide and the PVA resin are dissolved in a solvent. Examples of the solvent include water, dimethylsulfoxide, 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. Among these, water is preferred. The concentration of the PVA resin in the solution is preferably 3 to 20 parts by weight based on 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film that adheres to the thermoplastic resin base material can be formed. The content of the halide in the coating liquid is preferably 5 parts by weight to 20 parts by weight based on 100 parts by weight of the PVA resin.

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

Any suitable resin may be employed as the PVA resin. Examples include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymer can be obtained by saponifying ethylene-vinyl acetate copolymer. The degree of saponification of the PVA 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 degree of saponification can be determined according to JIS K 6726-1994. By using a PVA resin having such a degree of saponification, a polarizing film with excellent durability can be obtained. If the degree of saponification is too high, there is a risk of gelation.

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

Any suitable halide may be employed as the halide. Examples include iodide and sodium chloride. Iodides include, for example, potassium iodide, sodium iodide, and lithium iodide. Among these, potassium iodide is preferred.

The amount of halide in the coating liquid is preferably 5 parts by weight to 20 parts by weight based on 100 parts by weight of PVA resin, more preferably 10 parts by weight to 15 parts by weight based on 100 parts by weight of PVA resin. Department. If the amount of halide exceeds 20 parts by weight per 100 parts by weight of the PVA-based resin, the halide may bleed out and the polarizing film finally obtained may become cloudy.

Generally, by stretching the PVA resin layer, the orientation of the polyvinyl alcohol molecules in the PVA resin increases. However, when the stretched PVA resin layer is immersed in a liquid containing water, the orientation of the polyvinyl alcohol molecules increases. The orientation may be disturbed and the orientation may be deteriorated. In particular, when stretching a laminate of a thermoplastic resin base material and a PVA resin layer in boric acid water, the laminate is stretched in boric acid water at a relatively high temperature in order to stabilize the stretching of the thermoplastic resin base material. When stretching, the above-mentioned tendency for the degree of orientation to decrease is remarkable. For example, while it is common for a PVA film alone to be stretched in boric acid water at 60°C, a laminate of A-PET (thermoplastic resin base material) and a PVA resin layer is stretched. It is carried out at a high temperature of around 70°C, and in this case, the orientation of PVA at the initial stage of stretching may decrease before it increases due to underwater stretching. In contrast, by producing a laminate of a PVA resin layer containing a halide and a thermoplastic resin base material, and stretching the laminate at high temperature in air (auxiliary stretching) before stretching it in boric acid water. , crystallization of the PVA resin in the PVA resin layer of the laminate after auxiliary stretching can be promoted. As a result, when the PVA-based resin layer is immersed in a liquid, disturbance in the orientation of polyvinyl alcohol molecules and deterioration of orientation can be suppressed compared to when the PVA-based resin layer does not contain a halide. This can improve the optical properties of a polarizing film obtained through a treatment process performed by immersing the laminate in a liquid, such as dyeing treatment and underwater stretching treatment.

B-3-2. Auxiliary Stretching Treatment in Air In particular, in order to obtain high optical properties, a two-stage stretching method is selected that combines dry stretching (auxiliary stretching) and stretching in boric acid water. By introducing auxiliary stretching as in two-stage stretching, it is possible to stretch while suppressing crystallization of the thermoplastic resin base material, and prevent excessive crystallization of the thermoplastic resin base material during subsequent stretching in boric acid water. This solves the problem that the stretchability is lowered due to this, and the laminate can be stretched to a higher magnification. Furthermore, in order to suppress the influence of the glass transition temperature of the thermoplastic resin base material, when applying PVA resin on a thermoplastic resin base material, compared to the case where PVA resin is applied on a normal metal drum, As a result, the crystallization of the PVA-based resin becomes relatively low, which may cause a problem that sufficient optical properties cannot be obtained. On the other hand, by introducing auxiliary stretching, it is possible to increase the crystallinity of PVA-based resin even when applying PVA-based resin onto thermoplastic resin, making it possible to achieve high optical properties. Become. At the same time, by increasing the orientation of the PVA resin in advance, it is possible to prevent problems such as a decrease in orientation and dissolution of the PVA resin when it is immersed in water during the subsequent dyeing and stretching processes. , it becomes possible to achieve high optical properties.

The stretching method for aerial auxiliary stretching may be fixed end stretching (for example, stretching using a tenter stretching machine) or free end stretching (for example, uniaxial stretching by passing the laminate between rolls with different circumferential speeds). However, in order to obtain high optical properties, free end stretching may be actively employed. In one embodiment, the aerial stretching process includes a heating roll stretching step of stretching the laminate using a difference in peripheral speed between heating rolls while conveying the laminate in its longitudinal direction. The aerial stretching process typically includes a zone stretching process and a heated roll stretching process. Note that the order of the zone stretching step and the heating roll stretching step is not limited, and the zone stretching step may be performed first, or the heating roll stretching step may be performed first. The zone stretching step may be omitted. In one embodiment, the zone stretching step and the heated roll stretching step are performed in this order. In another embodiment, the film is stretched in a tenter stretching machine by gripping the end portion of the film and widening the distance between the tenters in the machine direction (the widening of the distance between the tenters becomes 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, the stretching ratio in the machine direction can be set to be closer to free end stretching. In the case of free end stretching, the shrinkage rate in the width direction = (1/stretching ratio) is calculated as ^1/2 .

Aerial assisted stretching may be performed in one step or in multiple steps. In the case of multi-stage stretching, the stretching ratio is the product of the stretching ratios of each stage. The stretching direction in the aerial auxiliary stretching is preferably substantially the same as the stretching direction in the underwater stretching.

The stretching ratio in the aerial auxiliary stretching is preferably 2.0 times to 3.5 times. The maximum stretching ratio when the aerial auxiliary stretching and underwater stretching are combined is preferably 5.0 times or more, more preferably 5.5 times or more, and even more preferably 6.0 times the original length of the laminate. That's all. In this specification, the "maximum stretching ratio" refers to the stretching ratio immediately before the laminate breaks, and the stretching ratio at which the laminate breaks is separately confirmed, and it refers to a value 0.2 lower than that 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 base material, the stretching method, etc. The stretching temperature is preferably at least the glass transition temperature (Tg) of the thermoplastic resin base material, more preferably at least the glass transition temperature (Tg) of the thermoplastic resin base material +10°C, particularly preferably at least Tg +15°C. On the other hand, the upper limit of the stretching temperature is preferably 170°C. By stretching at such a temperature, it is possible to suppress the rapid progress of crystallization of the PVA-based resin and to suppress defects caused by the crystallization (for example, preventing the orientation of the PVA-based resin layer due to stretching). can. The crystallization index of the PVA-based resin after in-air assisted stretching is preferably 1.3 to 1.8, more preferably 1.4 to 1.7. The crystallization index of the PVA-based resin can be measured by the ATR method using a Fourier transform infrared spectrophotometer. Specifically, measurements are performed using polarized light as measurement light, and the crystallization index is calculated according to the following formula using the intensities at 1141 cm ^-1 and 1440 cm ^-1 of the obtained spectrum.
Crystallization index = (I _C /I _R )
however,
I _C : Intensity of 1141 cm ⁻¹ when measured with measurement light incident. I _R : Intensity of 1440 cm ⁻¹ when measured with measurement light incident.

B-3-3. Insolubilization treatment If necessary, insolubilization treatment is performed after the aerial auxiliary stretching treatment and before the underwater stretching treatment or dyeing treatment. The above-mentioned insolubilization treatment is typically performed by immersing the PVA resin layer in a boric acid aqueous solution. By performing the insolubilization treatment, it is possible to impart water resistance to the PVA-based resin layer and prevent a decrease in orientation of PVA when immersed in water. The concentration of the boric acid aqueous solution is preferably 1 to 4 parts by weight per 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 Process The above dyeing process is typically performed by dyeing the PVA-based resin layer with a dichroic substance (typically iodine). Specifically, this is carried out by adsorbing iodine to the PVA resin layer. The adsorption method includes, for example, immersing the PVA resin layer (laminate) in a dye containing iodine, applying the dye to the PVA resin layer, and applying the dye to the PVA resin layer. Examples include a method of spraying. Preferably, the method involves immersing the laminate in a dyeing solution (dyeing bath). This is because iodine can be adsorbed well.

The staining solution is preferably an aqueous iodine solution. The amount of iodine blended is preferably 0.05 part by weight to 0.5 part by weight per 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to add iodide to the iodine aqueous solution. Examples of iodides include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. etc. Among these, potassium iodide is preferred. The amount of iodide to be blended is preferably 0.1 parts by weight to 10 parts by weight, more preferably 0.3 parts by weight to 5 parts by weight, based on 100 parts by weight of water. The temperature of the dyeing solution during dyeing is preferably 20° C. to 50° C. in order to suppress dissolution of the PVA resin. When the PVA resin layer is immersed in the dyeing liquid, the immersion time is preferably 5 seconds to 5 minutes, more preferably 30 seconds to 90 seconds, in order to ensure the transmittance of the PVA resin layer.

The dyeing conditions (concentration, liquid temperature, immersion time) should be set so that the single transmittance of the final polarizing film is 43.5% or more and the degree of polarization is 99.940% or more. I can do it. As for such staining conditions, preferably, an iodine aqueous solution is used as the staining liquid, and the ratio of the contents of iodine and potassium iodide in the iodine aqueous solution is 1:5 to 1:20. The content ratio of iodine and potassium iodide in the iodine aqueous solution is preferably 1:5 to 1:10. Thereby, a polarizing film having the optical properties as described above can be obtained.

When dyeing is performed continuously after immersing the laminate in a treatment bath containing boric acid (typically, insolubilization treatment), the boric acid contained in the treatment bath may mix into the dyeing bath. The boric acid concentration in the dye bath may change over time, resulting in unstable dyeing properties. In order to suppress the destabilization of dyeability as described above, the upper limit of the concentration of boric acid in the dyeing bath is preferably 4 parts by weight, more preferably 2 parts by weight, based on 100 parts by weight of water. be 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, and still more preferably 0.5 part by weight, based on 100 parts by weight of water. It is. In one embodiment, the dyeing process is carried out using a dye bath pre-blended with boric acid. This can reduce the rate of change in boric acid concentration when boric acid in the treatment bath is mixed into the dyeing bath. The amount of boric acid added to the dyeing bath in advance (that is, the content of boric acid not derived from the treatment bath) is preferably 0.1 parts by weight to 2 parts by weight based on 100 parts by weight of water. , more preferably 0.5 parts by weight to 1.5 parts by weight.

B-3-5. Crosslinking treatment If necessary, crosslinking treatment is performed after the dyeing treatment and before the underwater stretching treatment. The above crosslinking treatment is typically performed by immersing the PVA resin layer in a boric acid aqueous solution. By performing the crosslinking treatment, water resistance is imparted to the PVA-based resin layer, and in the subsequent underwater stretching, it is possible to prevent a decrease in the orientation of PVA when immersed in high-temperature water. The concentration of the boric acid aqueous solution is preferably 1 to 5 parts by weight per 100 parts by weight of water. Moreover, when crosslinking treatment is performed after the above-mentioned dyeing treatment, it is preferable to further include an iodide. By blending iodide, it is possible to suppress elution of iodine adsorbed to the PVA-based resin layer. The amount of iodide to be blended is preferably 1 to 5 parts by weight per 100 parts by weight of water. Specific examples of iodides are as described above. The 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 base material or the PVA resin layer, and the PVA resin layer can be It is possible to stretch to a high magnification while suppressing the As a result, a polarizing film having excellent optical properties can be manufactured.

Any suitable method can be used to stretch the laminate. Specifically, fixed-end stretching or free-end stretching (for example, a method in which the laminate is passed between rolls having different circumferential speeds and uniaxially stretched) may be used. Preferably, free end stretching is chosen. The laminate may be stretched in one step or in multiple steps. When performing multi-stage stretching, the stretching ratio (maximum stretching ratio) of the laminate described below is the product of the stretching ratios of each stage.

Stretching in water is preferably performed by immersing the laminate in an aqueous boric acid solution (stretching in boric acid water). By using a boric acid aqueous solution as a stretching bath, it is possible to impart rigidity to the PVA-based resin layer to withstand 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 and crosslink with the PVA-based resin through hydrogen bonding. As a result, rigidity and water resistance can be imparted to the PVA-based resin layer, which can be stretched well, and a polarizing film having excellent optical properties can be manufactured.

The aqueous boric acid solution is preferably obtained by dissolving boric acid and/or a borate salt in water, which is a solvent. The boric acid concentration is preferably 1 to 10 parts by weight, more preferably 2.5 to 6 parts by weight, particularly preferably 3 to 5 parts by weight, based on 100 parts by weight of water. It is. By setting the boric acid concentration 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 a borate salt, an aqueous solution obtained by dissolving a boron compound such as borax, glyoxal, glutaraldehyde, etc. in a solvent can also be used.

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

The stretching temperature (the liquid temperature of the stretching bath) is preferably 40°C to 85°C, more preferably 60°C to 75°C. At such a temperature, it is possible to stretch to a high magnification while suppressing dissolution of the PVA-based resin layer. Specifically, as described above, the glass transition temperature (Tg) of the thermoplastic resin base material 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., there is a possibility that the stretching cannot be performed satisfactorily even if the plasticization of the thermoplastic resin base material by water is taken into consideration. On the other hand, as the temperature of the stretching bath increases, the solubility of the PVA-based resin layer increases, and there is a possibility that excellent optical properties may not be obtained. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.

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

B-3-7. Drying Shrinkage Treatment The drying shrinkage treatment described above may be performed by zone heating performed by heating the entire zone, or may be performed by heating a conveyance roll (using a so-called heating roll) (heated roll drying method). Preferably, both are used. By drying using a heating roll, heating curl of the laminate can be efficiently suppressed, and a polarizing film with excellent appearance can be manufactured. Specifically, by drying the laminate along a heating roll, it is possible to efficiently promote crystallization of the thermoplastic resin base material and increase the degree of crystallinity, which is relatively low. Even at drying temperatures, the degree of crystallinity of the thermoplastic resin base material can be increased favorably. As a result, the thermoplastic resin base material has increased rigidity and is in a state where it can withstand shrinkage of the PVA resin layer due to drying, thereby suppressing curling. Furthermore, by using a heating roll, the laminate can be dried while maintaining it in a flat state, so that not only curling but also wrinkles can be suppressed. At this time, the optical properties of the laminate can be improved by shrinking the laminate in the width direction by drying shrinkage treatment. This is because the orientation of PVA and PVA/iodine complex can be effectively improved. The shrinkage rate of the laminate in the width direction due to the drying shrinkage treatment is preferably 1% to 10%, more preferably 2% to 8%, particularly preferably 4% to 6%. By using a heating roll, the laminate can be continuously contracted in the width direction while being conveyed, and high productivity can be achieved.

FIG. 3 is a schematic diagram showing an example of drying shrinkage treatment. In the drying shrinkage process, the laminate 200 is dried while being transported by transport rolls R1 to R6 heated to a predetermined temperature and guide rolls G1 to G4. In the illustrated example, 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 base material. The transport rolls R1 to R6 may be arranged so as to continuously heat only the resin base material surface).

The drying conditions can be controlled by adjusting the heating temperature of the conveying roll (temperature of the heating roll), the number of heating rolls, the contact time with the heating roll, etc. The temperature of the heating roll is preferably 60°C to 120°C, more preferably 65°C to 100°C, particularly preferably 70°C to 80°C. It is possible to satisfactorily increase the degree of crystallinity of the thermoplastic resin, to satisfactorily suppress curling, and to produce an optical laminate having extremely excellent durability. Note that the temperature of the heating roll can be measured with a contact thermometer. In the illustrated example, six conveyance rolls are provided, but there is no particular restriction on the number of conveyance rolls as long as there is a plurality of conveyance rolls. Usually 2 to 40 conveyance rolls, preferably 4 to 30 conveyance rolls are provided. 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 even more preferably 1 to 10 seconds.

The heating roll may be provided within a heating furnace (for example, an oven) or may be provided on a normal production line (at room temperature). Preferably, it is provided in a heating furnace equipped with air blowing means. By using both heating roll drying and hot air drying, a sharp temperature change between the heating rolls can be suppressed, and shrinkage in the width direction can be easily controlled. The temperature of hot air drying is preferably 30°C to 100°C. Further, 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. Note that the wind speed is the wind speed within the heating furnace, and can be measured with a mini-vane 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 above cleaning treatment is typically performed by immersing the PVA resin layer in an aqueous potassium iodide solution.

C. First Retardation Layer The first retardation layer 20 may have any appropriate optical properties and/or mechanical properties depending on the purpose. The first retardation layer 20 typically has a slow axis. In one embodiment, the angle θ between the slow axis of the first retardation layer 20 and the absorption axis of the polarizing film 11 is 40° to 50°, preferably 42° to 48°, as described above. and more preferably about 45°. If the angle θ is in this range, by using a λ/4 plate as the first retardation layer as described later, very good circular polarization properties (as a result, very good antireflection properties) can be obtained. A polarizing plate with a retardation layer can be obtained.

The first retardation layer preferably exhibits a refractive index characteristic of nx>ny≧nz. The first retardation layer is typically provided to impart antireflection properties to the polarizing plate, and in one embodiment can function as a λ/4 plate. In this case, the in-plane retardation Re (550) of the first retardation layer is preferably 100 nm to 190 nm, more preferably 110 nm to 170 nm, even more preferably 130 nm to 160 nm. Note that "ny=nz" here includes not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, there may be a case where ny<nz within a range that does not impair the effects of the present invention.

The Nz coefficient of the first retardation layer is preferably 0.9 to 3, more preferably 0.9 to 2.5, even more preferably 0.9 to 1.5, particularly preferably 0.9 to 1. It is 3. By satisfying such a relationship, when the obtained polarizing plate with a retardation layer is used in an image display device, an extremely excellent reflected hue can be achieved.

The first retardation layer may exhibit inverse dispersion wavelength characteristics in which the retardation value increases according to the wavelength of the measurement light, and positive wavelength dispersion characteristics in which the retardation value decreases in accordance with the wavelength of the measurement light. Alternatively, the phase difference value may exhibit flat wavelength dispersion characteristics that hardly change depending on the wavelength of the measurement light. In one embodiment, the first retardation layer exhibits inverse dispersion wavelength characteristics. In this case, Re(450)/Re(550) of the retardation layer is preferably 0.8 or more and less than 1, more preferably 0.8 or more and 0.95 or less. With such a configuration, extremely excellent antireflection properties can be achieved.

The absolute value of the photoelastic coefficient of the first retardation layer is preferably 2×10 ⁻¹¹ m ² /N or less, more preferably 2.0×10 ⁻¹³ m ^{2 /} N to 1.5×10 ⁻¹¹ m ² /N, more preferably 1.0×10 ⁻¹² m ² /N to 1.2× ^{10 −11} m ² /N. If the absolute value of the photoelastic coefficient is within this range, phase difference changes are unlikely to occur when shrinkage stress occurs during heating. As a result, thermal unevenness in the resulting image display device can be effectively prevented.

The first retardation layer is typically composed of a stretched resin film. In one embodiment, the thickness of the first retardation layer is preferably 70 μm or less, more preferably 45 μm to 60 μm. If the thickness of the first retardation layer is within such a range, it is possible to satisfactorily suppress curling during heating and to satisfactorily adjust curling during bonding. Further, as described below, in an embodiment in which the first retardation layer is made of a polycarbonate resin film, the thickness of the first retardation layer is preferably 40 μm or less, more preferably 10 μm to 40 μm. The thickness is more preferably 20 μm to 30 μm. When the first retardation layer is made of a polycarbonate resin film having such a thickness, it can contribute to improving bending durability and reflected hue while suppressing curling.

The first retardation layer 20 may be made of any suitable resin film that can satisfy the above characteristics. Typical examples of such resins include polycarbonate resins, polyester carbonate resins, polyester resins, polyvinyl acetal resins, polyarylate resins, cyclic olefin resins, cellulose resins, polyvinyl alcohol resins, and polyamide resins. , polyimide resin, polyether resin, polystyrene resin, and acrylic resin. These resins may be used alone or in combination (for example, blended or copolymerized). When the first retardation layer is composed of a resin film exhibiting reverse dispersion wavelength characteristics, polycarbonate-based resin or polyester carbonate-based resin (hereinafter sometimes simply referred to as polycarbonate-based resin) may be suitably used.

As the polycarbonate resin, any suitable polycarbonate resin can be used as long as the effects of the present invention can be obtained. For example, polycarbonate resins contain structural units derived from fluorene-based dihydroxy compounds, structural units derived from isosorbide-based dihydroxy compounds, alicyclic diols, alicyclic dimethanols, di-, tri-, or polyethylene glycols, and alkylene-based dihydroxy compounds. a structural unit derived from at least one dihydroxy compound selected from the group consisting of glycol or spiroglycol. Preferably, the polycarbonate resin contains a structural unit derived from a fluorene dihydroxy compound, a structural unit derived from an isosorbide dihydroxy compound, a structural unit derived from an alicyclic dimethanol, and/or a di, tri, or polyethylene glycol. More preferably, it contains a structural unit derived from a fluorene dihydroxy compound, a structural unit derived from an isosorbide dihydroxy compound, and a structural unit derived from di, tri or polyethylene glycol. . The polycarbonate resin may contain structural units derived from other dihydroxy compounds as necessary. Note that details of the polycarbonate resin that can be suitably used in the present invention can be found in, for example, JP2014-10291A, JP2014-26266A, JP2015-212816A, and JP2015-212817A. , JP 2015-212818A, the description of which is incorporated herein by reference.

The glass transition temperature of the polycarbonate resin is preferably 110°C or more and 150°C or less, more preferably 120°C or more and 140°C or less. If the glass transition temperature is too low, heat resistance tends to deteriorate, dimensional changes may occur after film formation, and image quality of the resulting organic EL panel may be lowered. If the glass transition temperature is too high, the molding stability during film molding may deteriorate, and the transparency of the film may be impaired. Note that the glass transition temperature is determined according to JIS K 7121 (1987).

The molecular weight of the polycarbonate resin can be expressed in terms of reduced viscosity. The reduced viscosity is measured using methylene chloride as a solvent, precisely adjusting the polycarbonate concentration to 0.6 g/dL, and using an Ubbelohde viscosity tube at a temperature of 20.0° C.±0.1° C. The lower limit of the reduced viscosity is usually preferably 0.30 dL/g, more preferably 0.35 dL/g or more. The upper limit of the reduced viscosity is usually preferably 1.20 dL/g, more preferably 1.00 dL/g, still more preferably 0.80 dL/g. If the reduced viscosity is lower than the lower limit, a problem may arise in that the mechanical strength of the molded product decreases. On the other hand, if the reduced viscosity is greater than the upper limit, fluidity during molding may be reduced, leading to problems such as reduced productivity and moldability.

A commercially available film may be used as the polycarbonate resin film. Specific examples of commercially available products include Teijin's product names "Pure Ace WR-S," "Pure Ace WR-W," and "Pure Ace WR-M," and Nitto Denko's product name "NRF." It will be done.

The first retardation layer 20 is obtained, for example, by stretching a film formed from the polycarbonate resin described above. As a method for forming a film from polycarbonate resin, any suitable molding method may be employed. Specific examples include compression molding method, transfer molding method, injection molding method, extrusion molding method, blow molding method, powder molding method, FRP molding method, cast coating method (e.g. casting method), calendar molding method, hot press method. Laws etc. Extrusion molding or cast coating methods are preferred. This is because the smoothness of the resulting film can be improved and good optical uniformity can be obtained. The molding conditions can be appropriately set depending on the composition and type of the resin used, the desired characteristics of the retardation layer, and the like. In addition, as mentioned above, since many film products of polycarbonate resin are commercially available, the commercially available films may be directly subjected to the stretching treatment.

The thickness of the resin film (unstretched film) can be set to any appropriate value depending on the desired thickness of the first retardation layer, desired optical properties, stretching conditions described below, and the like. Preferably it is 50 μm to 300 μm.

For the above-mentioned stretching, any appropriate stretching method and stretching conditions (eg, stretching temperature, stretching ratio, stretching direction) may be employed. Specifically, various stretching methods such as free end stretching, fixed end stretching, free end shrinkage, and fixed end shrinkage can be used alone, simultaneously, or sequentially. Regarding the stretching direction, stretching can be carried out in various directions and dimensions, such as the length direction, width direction, thickness direction, and diagonal direction. The stretching temperature is preferably Tg-30°C to Tg+60°C, more preferably Tg-10°C to Tg+50°C, relative to the glass transition temperature (Tg) of the resin film.

By appropriately selecting the above stretching method and stretching conditions, a retardation film having the above desired optical properties (for example, refractive index properties, in-plane retardation, Nz coefficient) can be obtained.

In one embodiment, the retardation film is produced by uniaxially stretching or fixed end uniaxially stretching a resin film. A specific example of fixed end uniaxial stretching includes a method in which the resin film is stretched in the width direction (horizontal direction) while running in the longitudinal direction. The stretching ratio is preferably 1.1 to 3.5 times.

In another embodiment, the retardation film may be produced by continuously diagonally stretching a long resin film in the direction of the above angle θ with respect to the longitudinal direction. By employing diagonal stretching, a long stretched film having an orientation angle of angle θ (slow axis in the direction of angle θ) with respect to the longitudinal direction of the film can be obtained. Roll-to-roll is possible, which simplifies the manufacturing process. Note that the angle θ may be an angle between the absorption axis of the polarizing film and the slow axis of the retardation layer in the polarizing plate with a retardation layer. As mentioned above, the angle θ is preferably 40° to 50°, more preferably 42° to 48°, and even more preferably about 45°.

Examples of the stretching machine used for diagonal stretching include a tenter-type stretching machine that can apply feeding force, pulling force, or take-off force at different speeds on the left and right sides in the horizontal and/or longitudinal directions. The tenter type stretching machine includes a horizontal uniaxial stretching machine, a simultaneous biaxial stretching machine, etc., but any suitable stretching machine may be used as long as it can continuously stretch a long resin film diagonally.

By appropriately controlling the left and right speeds in the stretching machine, a retardation layer (substantially a long film) having the desired in-plane retardation and a slow axis in the desired direction retardation film) can be obtained.

The stretching temperature of the film may vary depending on the desired in-plane retardation value and thickness of the retardation layer, the type of resin used, the thickness of the film used, the stretching ratio, etc. Specifically, the stretching temperature is preferably Tg-30°C to Tg+30°C, more preferably Tg-15°C to Tg+15°C, and most preferably Tg-10°C to Tg+10°C. By stretching at such a temperature, a first retardation layer having appropriate characteristics in the present invention can be obtained. Note that Tg is the glass transition temperature of the constituent material of the film.

D. Second Retardation Layer As described above, the second retardation layer may be a so-called positive C plate whose refractive index characteristics exhibit the relationship nz>nx=ny. By using a positive C plate as the second retardation layer, reflection in an oblique direction can be effectively prevented, and the antireflection function can provide a wide viewing angle. In this case, the retardation Rth (550) in the thickness direction of the second retardation layer is preferably -50 nm to -300 nm, more preferably -70 nm to -250 nm, still more preferably -90 nm to -200 nm, particularly preferably -100 nm to -180 nm. Here, "nx=ny" includes not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal. That is, the in-plane retardation Re (550) of the second retardation layer may be less than 10 nm.

The second retardation layer having a refractive index characteristic of nz>nx=ny may be formed of any suitable material. The second retardation layer preferably consists of a film containing liquid crystal material fixed in homeotropic alignment. The liquid crystal material (liquid crystal compound) that can be homeotropically aligned may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the liquid crystal compound and the method for forming the retardation layer include the liquid crystal compound and the method for forming the retardation layer described in [0020] to [0028] of JP-A No. 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 even more preferably 0.5 μm to 5 μm.

E. Conductive layer or isotropic base material with conductive layer The conductive layer can be formed on any suitable base material by any suitable film forming method (e.g., vacuum evaporation method, sputtering method, CVD method, ion plating method, spray method, etc.). It can be formed by depositing a metal oxide film thereon. Examples of metal oxides include indium oxide, tin oxide, zinc oxide, indium-tin composite oxide, tin-antimony composite oxide, zinc-aluminum composite oxide, and indium-zinc composite oxide. Among them, indium-tin composite oxide (ITO) is preferred.

When the conductive layer contains a metal oxide, the thickness of the conductive layer is preferably 50 nm or less, 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 base material to the first retardation layer (or the second retardation layer if present) and the conductive layer alone may be used as a constituent layer of a polarizing plate with a retardation layer. Often, it may be laminated on the first retardation layer (or the second retardation layer if present) as a laminate with a base material (base material with conductive layer). Preferably, the base material is optically isotropic, and therefore, the conductive layer can be used as an isotropic base material with a conductive layer in a polarizing plate with a retardation layer.

Any suitable isotropic base material can be employed as the optically isotropic base material (isotropic base material). Materials constituting the isotropic base material include, for example, materials whose main skeleton is a resin without a conjugated system such as norbornene resins and olefin resins, and materials with cyclic structures such as lactone rings and glutarimide rings such as acrylic resins. Examples include materials contained in the main chain. When such a material is used, when an isotropic base material is formed, the development of retardation due to the orientation of molecular chains can be suppressed to a small level. The thickness of the isotropic base material is preferably 50 μm or less, more preferably 35 μm or less. The lower limit of the thickness of the isotropic base material is, for example, 20 μm.

The conductive layer and/or the conductive layer of the isotropic base material with a conductive layer may be patterned as necessary. A conductive part and an insulating part can be formed by patterning. As a result, an electrode can be formed. The electrode can function as a touch sensor electrode that senses contact with the touch panel. Any suitable method can be adopted as the patterning method. Specific examples of patterning methods include wet etching and screen printing.

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 image display devices include liquid crystal display devices and electroluminescence (EL) display devices (eg, organic EL display devices and inorganic EL display devices). The image display device according to the embodiment of the present invention includes the polarizing plate with a retardation layer described in the above sections A to E on the viewing side. The polarizing plate with a retardation layer is laminated so that the retardation layer is on the image display cell (eg, liquid crystal cell, organic EL cell, inorganic EL cell) side (with the polarizing film 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）折り曲げ耐久性
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等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
（７）正面反射色相
実施例および比較例で得られた位相差層付偏光板を、紫外線吸収機能の無いアクリル系粘着剤を用いて反射板（東レフィルム社製、商品名「ＤＭＳ－Ｘ４２」；反射率８６％、偏光板なしでの反射色相ａ^＊＝－０．２２、ｂ^＊＝０．３２）上に貼り合せて測定サンプルを作製した。このとき、位相差層付偏光板の位相差層側が反射板と対向するように貼り合せた。当該測定サンプルに対して、分光測色計（コニカミノルタ製のＣＭ－２６００ｄ）を用いてＳＣＥ方式で測定し、ａ^＊およびｂ^＊の値を√（ａ^＊２＋ｂ^＊２）に代入して、正面反射色相を求めた。
（８）弾性率
測定対象のフィルムを、ＪＩＳ Ｋ６７３４：２０００に基づき平行部幅１０ｍｍ、長さ４０ｍｍの引張試験ダンベルに成形し、ＪＩＳ Ｋ７１６１：１９９４に準拠して引張試験を行い、引張弾性率を求めた。ここで、長さ方向は、通常、偏光膜の延伸方向と一致する。 EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples. The method for measuring each characteristic is as follows. Note that unless otherwise specified, "parts" and "%" in 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”). 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 polarizing film/protective layer laminate (polarizing plate) used in Examples and Comparative Examples was measured using an ultraviolet-visible spectrophotometer (V-7100 manufactured by JASCO Corporation). Single transmittance Ts, parallel transmittance Tp, and orthogonal transmittance Tc were defined as Ts, Tp, and Tc of the polarizing film, respectively. These Ts, Tp, and Tc are Y values measured using a 2-degree visual field (C light source) according to JIS Z8701 and subjected to visibility 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 determined from the obtained Tp and Tc using the following formula.
Polarization degree P (%) = {(Tp-Tc)/(Tp+Tc)} ^1/2 ×100
Note that a spectrophotometer such as LPF-200 manufactured by Otsuka Electronics Co., Ltd. can also perform equivalent measurements. As an example, Table 1 shows the measured values of the single transmittance Ts and polarization degree P obtained by measurements using V-7100 and LPF-200 for polarizing plates Samples 1 to 3 having the same configuration as in the example below. 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 is less than 0.1%, and both spectrophotometers were used. It can be seen that equivalent measurement results can be obtained even if the

For example, when measuring a polarizing plate equipped with an anti-glare (AG) surface treatment or an adhesive with diffusion performance, different measurement results may be obtained depending on the spectrophotometer. By performing numerical conversion based on the measured values when the polarizing plate is measured with each spectrophotometer, it is possible to compensate for differences in the measured values depending on the spectrophotometer.
(3) Variation in optical properties of long polarizing film Measurement samples were cut out from the polarizing plates used in the Examples and Comparative Examples at five positions equally spaced along the width direction, and five measurements were taken. The single transmittance of the central portion of the sample was measured in the same manner as in (2) above. Next, the difference between the maximum value and the minimum value of the single transmittance measured at each measurement position was calculated, and this value was taken as the variation in the optical properties of the long polarizing film.
(4) Variation in the optical properties of the sheet-shaped polarizing film A 100 mm x 100 mm measurement sample was cut out from the polarizing plate used in the Examples and Comparative Examples, and the variation in the optical properties of the sheet-shaped polarizing plate (50 cm ² ) was determined. Ta. Specifically, the single transmittance was determined in the same way as in (2) above at a total of five locations, including positions approximately 1.5 cm to 2.0 cm inward from the midpoint of each of the four sides of the measurement sample, and the central portion. It was measured using Next, the difference between the maximum value and the minimum value of the single transmittance measured at each measurement position was calculated, and this value was taken as the variation in the optical properties of the sheet-shaped polarizing film.
(5) Warpage The polarizing plates with retardation layers obtained in Examples and Comparative Examples were cut into a size of 110 mm x 60 mm. At this time, the polarizing film was cut out so that the absorption axis direction was in the long side direction. The cut out polarizing plate with a retardation layer was bonded to a glass plate with a size of 120 mm x 70 mm and a thickness of 0.2 mm via an adhesive to prepare a test sample. The test sample was placed in a heating oven maintained at 85° C. for 24 hours, and the amount of warpage after taking it out was measured. When the test sample was placed on a flat surface with the glass plate facing down, the height of the highest part from the flat surface was defined as the amount of warpage.
(6) Bending durability The polarizing plates with retardation layers obtained in Examples and Comparative Examples were cut 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 in the short side direction. Using a folding tester with a constant temperature and humidity chamber (manufactured by YUASA, CL09 type-D01), the cut polarizing plate with a retardation layer was subjected to a bending test under conditions of 20° C. and 50% RH. Specifically, a polarizing plate with a retardation layer is repeatedly bent in a direction parallel to the absorption axis direction with the retardation layer side facing outward to prevent cracks, peeling, or film breakage that would result in poor display. The number of times the bending occurred was measured and evaluated based on the following criteria (bending diameter: 2 mmφ).
<Evaluation criteria>
Less than 10,000 times: Poor 10,000 times or more and less than 30,000 times: Good 30,000 times or more: Excellent (7) Front reflection hue The polarizing plate with the retardation layer obtained in the Examples and Comparative Examples was A reflective plate (manufactured by Toray Film Co., Ltd., product name "DMS-X42"; reflectance 86%, reflected hue without polarizing plate a ^* = -0.22, b ^* = 0.32) using an acrylic adhesive A measurement sample was prepared by pasting it on top. At this time, the polarizing plate with a retardation layer was attached so that the retardation layer side faced the reflection plate. The measurement sample was measured using the SCE method using a spectrophotometer (CM-2600d manufactured by Konica Minolta), and the values of a ^* and b ^* were substituted into √(a ^*2 + b ^*2 ). , the frontal reflection hue was determined.
(8) Elastic modulus The film to be measured was formed into a tensile test dumbbell with a parallel part width of 10 mm and a length of 40 mm based on JIS K6734:2000, and a tensile test was performed based on JIS K7161:1994 to determine the tensile elastic modulus. I asked for it. Here, the length direction usually coincides with the stretching direction of the polarizing film.

[Example 1]
1. Preparation of Polarizing Film As a thermoplastic resin base material, a long, amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) having a water absorption rate of 0.75% and a Tg of about 75° C. was used. One side of the resin base material was subjected to corona treatment.
100 weight PVA resin prepared by mixing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd., trade name "Gosefaimer Z410") at a ratio of 9:1. To this part, 13 parts by weight of potassium iodide was added and dissolved in water to prepare a PVA aqueous solution (coating liquid).
The PVA aqueous solution was applied to the corona-treated surface of the resin base material and dried at 60° C. to form a PVA-based resin layer with a thickness of 13 μm, thereby producing a laminate.
The obtained laminate was uniaxially stretched free end to 2.4 times in the longitudinal direction (longitudinal direction) between rolls having different circumferential speeds in an oven at 130° C. (in-air auxiliary stretching treatment).
Next, the laminate was immersed for 30 seconds in an insolubilization bath (boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40° C. (insolubilization treatment).
Next, the final polarizing film was added to a dyeing bath (an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 to 100 parts by weight of water) at a liquid temperature of 30°C. It was immersed for 60 seconds while adjusting the concentration so that the single transmittance (Ts) was 43.5% or more (staining treatment).
Next, it was immersed for 30 seconds in a crosslinking bath (an aqueous boric acid solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40°C. (Crosslinking treatment).
Thereafter, while immersing the laminate in a boric acid aqueous solution (boric acid concentration 4.0% by weight) at a liquid temperature of 70°C, the total stretching ratio was 5.5 in the longitudinal direction between rolls having different circumferential speeds. Uniaxial stretching was performed to double the size (underwater stretching treatment).
Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20° C. (cleaning treatment).
Thereafter, while drying in an oven maintained at 90°C, it was brought into contact with a SUS heating roll whose surface temperature was maintained at 75°C for about 2 seconds (drying shrinkage treatment). The shrinkage rate of the laminate in the width direction due to the drying shrinkage treatment was 5.2%.
In this way, a polarizing film with a thickness of 5.0 μm was formed on the resin base material.

2. Preparation of polarizing plate A cycloolefin film (thickness: 28 μm, elastic 2100 MPa) were bonded together via an ultraviolet curable adhesive. Specifically, the curable adhesive was applied to have a total thickness of 1.0 μm, and then bonded together using a roll machine. Thereafter, the adhesive was cured by irradiating UV light from the protective layer side. Next, after slitting both ends, the resin base material was peeled off to obtain a long polarizing plate (width: 1300 mm) having a protective layer/adhesive layer/polarizing film configuration. The single transmittance of the polarizing plate (substantially, a polarizing film) was 43.76%, and the degree of polarization was 99.980%. Further, the variation in the optical properties of the long polarizing film was 0.14%, and the variation in the optical properties of the sheet polarizing film was 0.06%.

3. Preparation of retardation film constituting retardation layer 3-1. Polymerization of polyester carbonate resin Polymerization was carried out using a batch polymerization apparatus consisting of two vertical reactors equipped with a stirring blade and a reflux condenser controlled at 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), 63.77 parts by mass (0.298 mol) of diphenyl carbonate (DPC), and 1.19×10 ⁻² parts by mass (6.78×10 −2 of calcium acetate monohydrate as a catalyst ^{). 5} mol) was prepared. After the inside of the reactor was replaced with nitrogen under reduced pressure, it was heated with a heating medium, and when the internal temperature reached 100°C, stirring was started. 40 minutes after the start of temperature rise, the internal temperature was controlled to reach 220°C, and at the same time, pressure reduction was started to maintain this temperature, and the pressure was reduced to 13.3 kPa in 90 minutes after reaching 220°C. Phenol vapor produced as a by-product during the polymerization reaction was led to a reflux condenser at 100°C, a small amount of monomer component contained in the phenol vapor was returned to the reactor, and uncondensed phenol vapor was led to a condenser at 45°C for recovery. After nitrogen was introduced into the first reactor and the pressure was once restored to atmospheric pressure, the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Next, temperature increase and pressure reduction in the second reactor were started, and the internal temperature was 240° C. and the pressure was 0.2 kPa in 50 minutes. Thereafter, polymerization was allowed to proceed until a predetermined stirring power was reached. When a 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.

3-2. Preparation of retardation film After drying the obtained polyester carbonate resin (pellets) in vacuum at 80°C for 5 hours, a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder temperature setting: 250°C) and a T-die (width 200mm) were used. A long resin film with a thickness of 130 μm was produced using a film forming apparatus equipped with a chill roll (set temperature: 250° C.), a chill roll (set temperature: 120 to 130° C.), and a winder. The obtained elongated resin film was stretched while adjusting to obtain a predetermined retardation to obtain a retardation film having a thickness of 48 μm. The stretching conditions were a stretching temperature of 143° C. and a stretching ratio of 2.8 times in the width direction. The obtained retardation film had Re(550) of 141 nm, Re(450)/Re(550) of 0.86, and Nz coefficient of 1.12.

4. Preparation of polarizing plate with retardation layer 2 above. The above 3. is applied to the surface of the polarizing film of the polarizing plate obtained in step 3. The retardation films obtained in the above were bonded together via an acrylic adhesive (thickness: 5 μm). At this time, they were bonded together 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 the structure of protective layer/adhesive layer/polarizing film/adhesive layer/retardation layer was obtained. The total thickness of the obtained polarizing plate with a retardation layer was 87 μm. The obtained polarizing plate with a retardation layer was subjected to the evaluations in (5) and (6) above. The amount of warpage was 3.4 mm. The results are shown in Table 2.

[Example 2]
1. Preparation of polarizing film A film was formed on the resin base material to a thickness of 5.0% in the same manner as in Example 1, except that the concentration of the dyeing bath was adjusted so that the single transmittance (Ts) of the polarizing film was 44.0%. A 0 μm polarizing film was formed.

2. Preparation of polarizing plate 1 above. A polarizing plate having a protective layer/adhesive layer/polarizing film structure was produced in the same manner as in Example 1 except that the polarizing film obtained in Example 1 was used. The single transmittance of the polarizing plate (substantially, a polarizing film) was 44.0%, and the degree of polarization was 99.960%.

3. Preparation of retardation film constituting retardation layer A retardation film was obtained in the same manner as in Example 1, except that the Re (550) of the retardation film was stretched to 144 nm.

4. Preparation of polarizing plate with retardation layer 2 above. The above 3. was applied to the surface of the polarizing film of the polarizing plate obtained in Example 1 in the same manner as in Example 1. The retardation films obtained in the above were laminated together to produce a polarizing plate with a retardation layer having a structure of protective layer/adhesive layer/polarizer/adhesive layer/retardation layer. The total thickness of the obtained polarizing plate with a retardation layer was 87 μm. The obtained polarizing plate with a retardation layer was subjected to the evaluations (5) to (7) above. The results are shown in Table 2.

[Example 3-1]
1. Preparation of Polarizing Film A polarizing film having a thickness of 5.0 μm was formed on a resin base material in the same manner as in Example 2.

2. Preparation of polarizing plate The protective layer/ A polarizing plate having an adhesive layer/polarizing film structure was produced. The single transmittance of the polarizing plate (substantially, a polarizing film) was 44.0%, and the degree of polarization was 99.960%.

3. Preparation of retardation film constituting the retardation layer A polyester carbonate resin (pellet) obtained in the same manner as in Example 1 except that 0.7 parts by mass of PMMA was melt-kneaded was vacuum-dried at 80°C for 5 hours. After that, it was equipped with a single screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder temperature setting: 250°C), a T-die (width 200mm, setting temperature: 250°C), a chill roll (setting temperature: 120 to 130°C), and a winding machine. A long resin film with a thickness of 105 μm was produced using a film forming apparatus. The obtained elongated resin film was stretched 2.8 times in the width direction at 138° C. while adjusting to obtain a predetermined retardation to obtain a retardation film with a thickness of 38 μm. Re(550) of the obtained retardation film was 144 nm, and Re(450)/Re(550) was 0.86.

4. Preparation of polarizing plate with retardation layer 2 above. The above 3. is applied to the surface of the polarizing film of the polarizing plate obtained in step 3. The retardation films obtained in the above were bonded together via an acrylic adhesive (thickness: 5 μm). At this time, they were bonded together 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 the structure of protective layer/adhesive layer/polarizing film/adhesive layer/retardation layer was obtained. The total thickness of the obtained polarizing plate with a retardation layer was 81 μm. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 2. The results are shown in Table 2.

[Example 3-2]
A long polyester carbonate resin film with a thickness of 105 μm obtained in the same manner as in Example 3-1 was stretched in the width direction while adjusting to obtain a predetermined retardation to obtain a retardation film with a thickness of 38 μm. Obtained. The obtained retardation film had Re(550) of 140 nm.
A polarizing plate with a retardation layer having the structure of protective layer/adhesive layer/polarizing film/adhesive layer/retardation layer was prepared in the same manner as in Example 3-1 except that the above retardation film was used as the retardation layer. I got it. The total thickness of the obtained polarizing plate with a retardation layer was 81 μm. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 2. The results are shown in Table 2.

[Example 4]
A polycarbonate resin film obtained in the same manner as in Example 1 was diagonally stretched in a manner similar to Example 2 of JP-A-2014-194483 to obtain a retardation film with a thickness of 58 μm. The obtained retardation film had Re(550) of 144 nm, Re(450)/Re(550) of 0.86, Nz coefficient of 1.21, and orientation angle (direction of slow axis). was 45° with respect to the longitudinal direction. This retardation film and the polarizing plate of Example 2 were laminated by roll-to-roll via an acrylic adhesive (thickness: 5 μm) to form a protective layer/adhesive layer/polarizing film/adhesive layer/retardation layer structure. A polarizing plate with a retardation layer was obtained. The total thickness of the obtained polarizing plate with a retardation layer was 97 μm. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 2. The amount of warpage was 4.1 mm. The results are shown in Table 2.

[Comparative example 1]
1. Preparation of Polarizer A polyvinyl alcohol resin film having an average degree of polymerization of 2,400, a degree of saponification of 99.9 mol %, and a thickness of 30 μm was prepared. The polyvinyl alcohol film was immersed in a 20°C swelling bath (water bath) for 30 seconds between rolls with different circumferential speed ratios and stretched 2.4 times in the transport direction while swelling (swelling step). Dye by immersing in a dyeing bath at 30°C (an aqueous solution with an iodine concentration of 0.03% by weight and a potassium iodide concentration of 0.3% by weight) so that the single transmittance after final stretching becomes the desired value. Meanwhile, the original polyvinyl alcohol film (polyvinyl alcohol film not stretched at all in the transport direction) was stretched 3.7 times in the transport direction (dying step). The immersion time at this time was about 60 seconds. Next, the dyed polyvinyl alcohol film was immersed in a 40°C crosslinking bath (an aqueous solution with a boric acid concentration of 3.0% by weight and a potassium iodide concentration of 3.0% by weight) while the original polyvinyl alcohol film was immersed. The film was stretched to 4.2 times in the transport direction (crosslinking step). Furthermore, the obtained polyvinyl alcohol film was immersed for 50 seconds in a 64°C stretching bath (an aqueous solution with a boric acid concentration of 4.0% by weight and a potassium iodide concentration of 5.0% by weight) to restore the original polyvinyl alcohol film. After stretching the alcohol film up to 6.0 times in the transport direction (stretching step), the film was immersed in a 20°C cleaning bath (an aqueous solution with a potassium iodide concentration of 3.0% by weight) for 5 seconds (cleaning). process). The washed polyvinyl alcohol film was dried at 30° C. for 2 minutes to produce a polarizer (thickness: 12 μm).

2. Preparation of polarizing plate As an adhesive, polyvinyl alcohol resin containing an acetoacetyl group (average degree of polymerization 1,200, degree of saponification 98.5 mol%, degree of acetoacetylation 5 mol%) and methylolmelamine were used. An aqueous solution containing the following was used. Using this adhesive, apply a triacetylcellulose (TAC) film with a hard coat layer (hard coat thickness 7 μm, TAC A TAC film with a thickness of 25 μm and an elastic modulus of 3600 MPa) was laminated on the other side of the polarizer using a roll laminating machine, and then heated and dried in an oven (temperature: 60°C, time: 5 minutes). In this way, a polarizing plate having the structure of protective layer 1 (thickness: 32 μm)/adhesive layer/polarizer/adhesive layer/protective layer 2 was produced.

3. Preparation of polarizing plate with retardation layer 2 above. A retardation film was laminated on the surface of the protective layer 2 of the polarizing plate obtained in Example 1 in the same manner as in Example 1, and the protective layer 1/adhesive layer/polarizer/adhesive layer/protective layer 2/adhesive layer/position was formed. A polarizing plate with a retardation layer having a structure of a retardation layer was produced. The total thickness of the obtained polarizing plate with a retardation layer was 122 μm. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 2. The amount of warpage was 5.3 mm.

[Comparative example 2]
1. Preparation of Polarizer A polarizer (thickness: 12 μm) was prepared in the same manner as in Comparative Example 1.

2. Production of Polarizing Plate In the same manner as in Comparative Example 1, a polarizing plate having the structure of protective layer 1 (thickness: 32 μm)/adhesive layer/polarizer/adhesive layer/protective layer 2 (thickness: 25 μm) was produced.

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子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子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。また、液晶配向固化層ＡおよびＢのＲｅ（４５０）／Ｒｅ（５５０）は１．１１であった。 3. Preparation of the first alignment fixed layer and the second alignment fixed layer constituting the retardation layer 10 g of 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 for the polymerizable liquid crystal compound (manufactured by BASF, trade name "Irgacure 907") in 40 g of toluene.

The surface of a polyethylene terephthalate (PET) film (thickness: 38 μm) was rubbed using a rubbing cloth to perform orientation treatment. The orientation treatment direction was set to be 15 degrees from the viewing side with respect to the direction of the absorption axis of the polarizer when bonding to the polarizing plate. The above-mentioned liquid crystal coating solution was applied to this alignment-treated surface using a bar coater, and the liquid crystal compound was aligned by heating and drying at 90° C. for 2 minutes. The thus formed liquid crystal layer 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 solidified layer A was 2.5 μm, and the in-plane retardation Re (550) was 270 nm. Furthermore, the liquid crystal alignment solidified layer A had a refractive index distribution of nx>ny=nz.
The coating was applied on the PET film in the same manner as above, except that the coating thickness was changed and the orientation treatment direction was set at 75° when viewed from the viewing side with respect to the direction of the absorption axis of the polarizer. A liquid crystal alignment solidified layer B was formed. The thickness of the liquid crystal alignment solidified layer B was 1.5 μm, and the in-plane retardation Re (550) was 140 nm. Furthermore, the liquid crystal alignment solidified layer B had a refractive index distribution of nx>ny=nz. Further, Re(450)/Re(550) of the liquid crystal alignment solidified layers A and B was 1.11.

4. Preparation of polarizing plate with retardation layer 2 above. The above 3. is applied to the surface of the protective layer 2 side of the polarizing plate obtained in 3. The liquid crystal alignment solidified layer A and the liquid crystal alignment solidified layer B obtained in the above were transferred in this order. At this time, the angle between the absorption axis of the polarizer and the slow axis of the fixed alignment layer A is 15°, and the angle between the absorption axis of the polarizer and the slow axis of the fixed alignment layer B is 75°. Transfer (pasting) was performed using Note that each transfer (bonding) was performed using an ultraviolet curable adhesive (thickness: 1 μm). In this way, it has the structure of protective layer 1/adhesive layer/polarizer/adhesive layer/protective layer 2/adhesive layer/retardation layer (first alignment fixed layer/adhesive layer/second alignment fixed layer). A polarizing plate with a retardation layer was obtained. The total thickness of the obtained polarizing plate with a retardation layer was 75 μm. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 2. The results are shown in Table 2.

[Comparative example 3]
1. Preparation of Polarizing Film A polarizing film with a thickness of 5.0 μm was formed on a resin base material in the same manner as in Example 1 except that the single transmittance (Ts) of the polarizing film was set to 43.0%.

2. Preparation of polarizing plate An acrylic film (surface refractive index 1.50, 20 μm) as a protective layer and an ultraviolet curable adhesive were applied to the surface of the polarizing film obtained above (the surface opposite to the resin base material). Attached through. Specifically, the curable adhesive was applied to have a total thickness of 1.0 μm, and then bonded together using a roll machine. Thereafter, the adhesive was cured by irradiating UV light from the protective layer side. Next, after slitting both ends, the resin base material was peeled off to obtain a long polarizing plate (width: 1300 mm) having a protective layer/adhesive layer/polarizing film configuration. The single transmittance of the polarizing plate (substantially a polarizing film) was 43.0%, and the degree of polarization was 99.995%.

3. Preparation of polarizing plate with retardation layer In the same manner as in Comparative Example 2, the above 2. Liquid crystal alignment fixed layer A and liquid crystal alignment fixed layer B obtained in the same manner as in Comparative Example 2 were transferred in this order onto the polarizing film surface of the polarizing plate obtained in . In this way, a polarizing plate with a retardation layer having the structure of protective layer/adhesive layer/polarizing film/adhesive layer/retardation layer (first alignment fixed layer/adhesive layer/second alignment fixed layer) was obtained. Ta. The total thickness of the obtained polarizing plate with a retardation layer was 32 μm. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 2. The results are shown in Table 2.

[Comparative example 4]
Example except that potassium iodide was not added to the PVA aqueous solution (coating solution), the stretching ratio in the aerial auxiliary stretching treatment was 1.8 times, and no heating roll was used in the drying shrinkage treatment. A polarizing film and a polarizing plate were produced in the same manner as in Example 1. The single transmittance of the polarizing plate (substantially, a polarizing film) was 43.13%, and the degree of polarization was 99.881%. A polarizing plate with a retardation layer was produced in the same manner as in Example 1 except that this polarizing plate was used.

[evaluation]
As is clear from comparing the Examples and the Comparative Examples, the Examples of the present invention have excellent optical properties of the polarizing film and can significantly suppress warping after the heating test. Furthermore, it can be seen that an excellent reflected hue can be obtained by using it in combination with a retardation layer made of a polycarbonate resin (including polyester carbonate resin) film. In addition, by thinning the polycarbonate resin to 40 μm or less, making the layer thickness of the polarizing plate 85 μm or less, and using a base material with an elastic modulus of 3000 MPa or more, preferably a TAC film, as a protective layer, the bending characteristics can be further improved. It can be improved. On the other hand, although the polarizing plate with a retardation layer of Comparative Example 3 was thin and warping after the heating test was significantly suppressed, the reflected hue was large and the display characteristics were not satisfactory.

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.

10 Polarizing plate 11 Polarizing film 12 First protective layer 13 Second protective layer 20 Retardation layer 100 Polarizing plate with retardation layer 101 Polarizing plate with retardation layer

Claims (10)

A polarizing film (however, a polarizing plate including a protective layer on at least one side of the polarizing film (excluding those with a single transmittance of 44.0% or more) , and a polarizing plate having Re(550) of 100 nm to 190 nm, and having Re(450)/Re A method for producing a polarizing plate with a retardation layer, the retardation layer having (550) of 0.8 or more and less than 1,
A polyvinyl alcohol resin layer containing iodide or sodium chloride and a polyvinyl alcohol resin is formed on one side of a long thermoplastic resin base material to form a laminate, and the laminate is provided with an aerial support. Stretching treatment, dyeing treatment, underwater stretching treatment, and heating in a heating furnace using heating rolls while conveying in the longitudinal direction so that the total contact time with the heating rolls is 20 seconds or less. and a drying shrinkage treatment to shrink the polarizing film by 2% to 10% in this order to obtain the polarizing film,
The angle between the slow axis of the retardation layer and the absorption axis of the polarizing film is 40° to 50°.
A method for manufacturing a polarizing plate with a retardation layer. The method for manufacturing a polarizing plate with a retardation layer according to claim 1, wherein the protective layer is composed of a triacetyl cellulose resin film. The method for manufacturing a polarizing plate with a retardation layer according to claim 1 or 2, wherein the retardation layer is composed of a polycarbonate resin film. Manufacturing the polarizing plate with a retardation layer according to any one of claims 1 to 3, wherein the difference between the maximum value and the minimum value of the single transmittance within a 50 cm ² area of the polarizing film is 0.15% or less. Method. 5. The polarizing film according to claim 1, wherein the polarizing film has a width of 1000 mm or more, and a difference between a maximum value and a minimum value of single transmittance at a position along the width direction is 0.3% or less. A method for manufacturing a polarizing plate with a retardation layer. 6. The method for manufacturing a polarizing plate with a retardation layer according to claim 1, wherein the degree of polarization of the polarizing film is 99.990% or less. The polarizing plate with a retardation layer further has another retardation layer outside the retardation layer,
Providing the other retardation layer outside the retardation layer,
7. The method for manufacturing a polarizing plate with a retardation layer according to claim 1, wherein the refractive index characteristics of the other retardation layer exhibit a relationship of nz>nx=ny. The polarizing plate with a retardation layer further has a conductive layer or an isotropic base material with a conductive layer on the outside of the retardation layer,
8. The method for producing a polarizing plate with a retardation layer according to claim 1, comprising providing the conductive layer or the isotropic substrate with the conductive layer on the outside of the retardation layer. The polarizing plate with a retardation layer is elongated,
A long polarizing film having an absorption axis in the longitudinal direction, and a long retardation layer that is an obliquely stretched film having a slow axis in a direction forming an angle of 40° to 50° with respect to the longitudinal direction. and roll-to-roll lamination,
A method for manufacturing a polarizing plate with a retardation layer according to any one of claims 1 to 8. The method for manufacturing a polarizing plate with a retardation layer according to claim 9, comprising winding the elongated polarizing plate with a retardation layer into a roll shape.

Images