JP2020115227A - Polarizing plate with retardation layer and image display using the same - Google Patents

Abstract

To provide a thin polarizing plate with a retardation layer that is excellent in handleability and optical characteristics.SOLUTION: A polarizing plate with a retardation layer according to this invention has a polarizing plate including a polarizing film and a protective layer on at least one side of the polarizing film, and a retardation layer. The polarizing film is formed of a polyvinyl alcohol resin film containing a dichroic substance, and has the thickness of 8 μm or less and the orthogonal absorbance of 1.00 or less for a 1 μm thickness at a 210 nm wavelength. The retardation layer is an orientation solidification layer of a liquid crystal compound.SELECTED DRAWING: Figure 1

Description

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

In recent years, image display devices represented by liquid crystal display devices and electroluminescence (EL) display devices (for example, organic EL display devices and inorganic EL display devices) have rapidly become popular. A polarizing plate and a retardation plate are typically used in the image display device. Practically, a polarizing plate with a retardation layer in which a polarizing plate and a retardation plate are integrated is widely used (for example, Patent Document 1), and recently, there is a strong demand for thinner image display devices. Accordingly, there is an increasing demand for a thinner polarizing plate with a retardation layer. Further, in recent years, there has been an increasing demand for a curved image display device and/or an image display device that can be bent or folded, and thus a polarizing plate and a polarizing plate with a retardation layer are required to be thinner and more flexible. ing. For the purpose of thinning the polarizing plate with a retardation layer, the protective layer of the polarizing film and the retardation film, which make a large contribution to the thickness, are being thinned. However, when the protective layer and the retardation film are made thin, the influence of the shrinkage of the polarizing film becomes relatively large, which causes a problem that the image display device is warped and the operability of the polarizing plate with the retardation layer is deteriorated.

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

Japanese Patent No. 3325560

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

The polarizing plate with a retardation layer of the present invention has a polarizing plate including a polarizing film, a protective layer on at least one side of the polarizing film, and a retardation layer. The polarizing film is composed of a polyvinyl alcohol-based resin film containing a dichroic material, has a thickness of 8 μm or less, and has an orthogonal absorbance of 1.00 or less per 1 μm of thickness at a wavelength of 210 nm. The retardation layer is an alignment and solidification layer of a liquid crystal compound.
In one embodiment, the polarizing plate with a retardation layer has a unit weight of 6.5 mg/cm ² or less.
In one embodiment, the polarizing plate with a retardation layer has a total thickness of 60 μm or less.
In one embodiment, the retardation layer is a single layer of an alignment-fixed layer of a liquid crystal compound, Re(550) of the retardation layer is 100 nm to 190 nm, and the slow axis of the retardation layer and the above The angle formed by the absorption axis of the polarizing film is 40° to 50°.
In one embodiment, the retardation layer has a laminated structure of an alignment fixed layer of a first liquid crystal compound and an alignment fixed layer of a second liquid crystal compound; the alignment fixed layer of the first liquid crystal compound. Re(550) is 200 nm to 300 nm, and the angle formed by the slow axis and the absorption axis of the polarizing film is 10° to 20°; Re(550) of the alignment solidified layer of the second liquid crystal compound. ) Is 100 nm to 190 nm, and the angle between the slow axis and the absorption axis of the polarizing film is 70° to 80°.
In one embodiment, the ratio (A ₄₇₀ /A ₆₀₀ ) of the orthogonal absorbance A ₄₇₀ at a wavelength of ₄₇₀ nm and the orthogonal absorbance A ₆₀₀ of a wavelength of 600 nm of the polarizing film is 0.7 to 2.00.
In one embodiment, the orthogonal b value of the polarizing film is more than −10 and +10 or less.
In one embodiment, the iodine concentration of the polarizing film is 3.0% by weight or more.
In one embodiment, the single transmittance of the polarizing film is 42.5% or more.
In one embodiment, the above-mentioned polarizing plate with a retardation layer further has another retardation layer outside the above-mentioned retardation layer, and the refractive index characteristic of this another retardation layer is nz>nx=ny. Show the relationship.
In one embodiment, the polarizing plate with a retardation layer further has a conductive layer or an isotropic substrate with a conductive layer outside the retardation layer.
The present invention also provides a polarizing plate with a retardation layer, which comprises a polarizing film including a polarizing film and a protective layer on at least one side of the polarizing film, and a retardation layer, wherein the retardation layer is a liquid crystal. It is an oriented solidified layer of a compound, the polarizing film is composed of a polyvinyl alcohol-based resin film containing iodine, the thickness is 8 μm or less, and the orthogonal absorbance per 1 μm thickness at a wavelength of 210 nm of the polarizing film is 1.00 or less. The ratio (A ₄₇₀ /A ₆₀₀ ) of the orthogonal absorbance A ₄₇₀ at a wavelength of ₄₇₀ nm and the orthogonal absorbance A ₆₀₀ at a wavelength of 600 nm of the polarizing film is 0.7 to 2.00, and the orthogonal b value of the polarizing film is A polarizing plate with a retardation layer having a refractive index of more than -10 and +10 or less is provided.
According to another aspect of the present invention, an image display device is provided. This image display device includes the above-mentioned polarizing plate with a retardation layer.
In one embodiment, the image display device is an organic electroluminescence display device or an inorganic electroluminescence display device.

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

FIG. 3 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to one embodiment of the present invention. FIG. 6 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to another embodiment of the present invention. It is a schematic sectional drawing of the polarizing plate with a retardation layer by another embodiment of this invention. It is a schematic diagram showing an example of dry shrinkage processing using a heating roll in a manufacturing method of a polarizing film used for a polarizing plate with a phase contrast layer of the present invention.

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

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

A. Overall Configuration of Polarizing Plate with Retardation Layer FIG. 1 is a schematic sectional view of a polarizing plate with a retardation layer according to an embodiment of the present invention. The polarizing plate 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 arranged on one side of the polarizing film 11, and a second protective layer 13 arranged on the other side of the polarizing film 11. .. Depending on the purpose, one of the first protective layer 12 and the second protective layer 13 may be omitted. For example, when the retardation layer 20 can also function as a protective layer for the polarizing film 11, the second protective layer 13 may be omitted. In the embodiment of the present invention, the polarizing film is composed of a polyvinyl alcohol-based resin film containing a dichroic substance. The thickness of the polarizing film is 8 μm or less, and the orthogonal absorbance (hereinafter referred to as unit absorbance) per 1 μm of thickness at a wavelength of 210 nm is 1.00 or less.

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

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

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

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

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

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

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

The unit weight of the polarizing plate with a retardation layer according to the embodiment of the present invention is, for example, 6.5 mg/cm ² or less, preferably 2.0 mg/cm ^{2 to} 6.0 mg/cm ² , and more preferably 3 mg/cm ^{2. .0mg / cm 2 ~5.5mg / cm 2} , more preferably from ^{3.5mg / cm 2 ~5.0mg / cm 2} . When the display panel is thin, the panel may be slightly deformed due to the weight of the polarizing plate with a retardation layer and display defects may occur. Therefore, a polarizing plate with a retardation layer having a unit weight of 6.5 mg/cm ² or less may be used. The plate can prevent such deformation of the panel. Further, the polarizing plate with a retardation layer having the above unit weight has good handleability even when it is made thin, and can exhibit extremely excellent flexibility and bending durability.

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

B. Polarizing plate B-1. Polarizing Film As described above, the polarizing film 11 has a thickness of 8 μm or less and a unit absorbance of 1.00 or less at a wavelength of 210 nm. The polarizing film used in the present invention has an extremely small unit absorbance at a wavelength of 210 nm as compared with a normal thin polarizing film. This means that the content ratio of iodine ions (having absorption in the ultraviolet region near 210 nm) not forming a complex with PVA in the polarizing film is extremely small. In the polarizing film, iodine is roughly classified into iodine ions having absorption in the ultraviolet region and PVA-iodine complex having absorption in visible light. Among these, it is the PVA-iodine complex that contributes to the polarization characteristics of the polarizing film. Since the amount of iodine that can be contained in the polarizing film is finite, a decrease in iodine ions leads to an increase in PVA-iodine complex. That is, in a thin polarizing film having a thickness of 8 μm or less, it is possible to improve the optical characteristics by reducing the iodine ions. This tendency becomes remarkable especially in a polarizing film having a small thickness and a high iodine concentration in the film. The unit absorbance at a wavelength of 210 nm is preferably 0.80 or less, more preferably 0.60 or less. The lower limit of the unit absorbance at the wavelength of 210 nm can be, for example, 0.20. The unit absorbance is obtained by dividing the orthogonal absorbance A ₂₁₀ obtained by the following formula based on the orthogonal transmittance Tc of the polarizing plate measured when obtaining the polarization degree described later by the thickness. The unit absorbance of the polarizing plate substantially corresponds to the unit absorbance of the polarizing film.
Orthogonal absorbance = log10 (100/Tc)
The use of a thin polarizing film having such characteristics is one of the features of the present invention. The polarizing film has a unit absorbance as described above, and the ratio (A ₅₅₀ /A ₂₁₀ ) of the orthogonal absorbance A ₅₅₀ at a wavelength of ₅₅₀ nm and the orthogonal absorbance A ₂₁₀ at a wavelength of 210 nm is preferably 1 or less. It is at least 0.4, more preferably at least 1.8, even more preferably at least 2.0, and particularly preferably at least 2.2. The upper limit of the ratio (A ₅₅₀ /A ₂₁₀ ) may be 3.5, for example. This, in the polarizing film, decreasing the content ratio of iodine ion, PVA-I ₅ having an absorption in the vicinity of 600 nm ^- means that the content ratio of the complex is increased.

The thickness of the polarizing film is preferably 1 μm to 8 μm, more preferably 1 μm to 7 μm, further preferably 2 μm to 5 μm, particularly preferably 2 μm to 4 μm, particularly preferably 2 μm to 3 μm.

The polarizing film preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizing film is preferably 49.0% or less, more preferably 48.0% or less. On the other hand, the simple substance transmittance is preferably 41.5% or more, more preferably 42.0% or more, and further preferably 42.5% or more. The polarization degree of the polarizing film is preferably 99.990% or more, and preferably 99.998% or less. The single-piece transmittance is typically a Y value measured with an ultraviolet-visible spectrophotometer and subjected to luminosity correction. The degree of polarization is typically obtained by the following formula based on the parallel transmittance Tp and the orthogonal transmittance Tc measured by using an ultraviolet-visible spectrophotometer and subjected to the visibility correction.
Polarization degree (%)={(Tp−Tc)/(Tp+Tc)} ^1/2 ×100

In one embodiment, the transmittance of a thin polarizing film having a thickness of 8 μm or less is typically obtained by laminating a polarizing film (surface refractive index: 1.53) and a protective film (refractive index: 1.50). It is measured using an ultraviolet-visible spectrophotometer with the body as the measurement target. The reflectance at the interface of each layer may change 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, and as a result, the measured value of the transmittance may change. .. Therefore, for example, when using a protective film whose refractive index is not 1.50, the measured value of the transmittance may be corrected according to the refractive index of the surface of the protective film in contact with the air interface. Specifically, the transmittance correction value C is expressed by the following equation using the reflectance R ₁ of polarized light parallel to the transmission axis (transmission axis reflectance) at the interface between the protective film and the air layer.
C=R ₁ -R ₀
R ₀ =((1.50-1) ² /(1.50+1) ² )×(T ₁ /100)
R ₁ =((n ₁ −1) ² /(n ₁ +1) ² )×(T ₁ /100)
Here, R ₀ is the transmission axis reflectance when a protective film having a refractive index of 1.50 is used, n ₁ is the refractive index of the protective film used, and T ₁ is the transmittance of the polarizing film. Is. For example, when a base material having a surface refractive index of 1.53 (such as a cycloolefin film and a film with a hard coat layer) is used as the protective film, the correction amount C is about 0.2%. In this case, by adding 0.2% to the transmittance obtained by the measurement, the transmittance when the protective film having a refractive index of 1.50 was used for the polarizing film having a surface refractive index of 1.53. It is possible to convert it into a rate. According to the calculation based on the above formula, the change amount of the correction value C when the transmittance T _{1 of the} polarizing film is changed by 2% is 0.03% or less, and the transmittance of the polarizing film is the correction value C. The effect on the value of is limited. When the protective film has absorption other than surface reflection, appropriate correction can be performed according to the amount of absorption.

Preferably, the polarizing film has a ratio (A ₄₇₀ /A ₆₀₀ ) of the orthogonal absorbance A ₄₇₀ at a wavelength of ₄₇₀ nm and the orthogonal absorbance A ₆₀₀ at a wavelength of 600 nm of 0.7 or more, and more preferably 0.75 or more, It is more preferably 0.80 or more, and particularly preferably 0.85 or more. The ratio (A ₄₇₀ /A ₆₀₀ ) is preferably 2.00 or less, more preferably 1.33 or less. If the ratio _(A 470 _/ A ₆₀₀₎ is such a range, _{PVA-I 3} has an absorption in the vicinity of 480 nm ^- can be maintained without reducing the content ratio of the complex significantly. As a result, good polarization performance can be realized over the entire visible light range. While the amount of iodine in the thin polarizing film was limited, it was difficult for the conventional technique to set both the unit absorbance and the ratio (A ₄₇₀ /A ₆₀₀ ) in the desired range. The polarizing film used can have both of these in desired ranges.

Furthermore, the orthogonal b value of the polarizing film is, for example, larger than −10, preferably −7 or more, and more preferably −5 or more. The orthogonal b value is preferably +10 or less, more preferably +5 or less. The orthogonal b value indicates the hue when the polarizing film (finally, the polarizing plate with the retardation layer) is arranged in the orthogonal state. The larger the absolute value of this numerical value, the orthogonal hue (black in the image display device). (Indication) means that it looks tint. For example, when the orthogonal b value is as low as −10 or less, the black display looks blue and the display performance is deteriorated. That is, according to the embodiment of the present invention, it is possible to obtain a polarizing plate with a retardation layer that can realize an excellent hue during black display. The orthogonal b value can be measured by a spectrophotometer represented by V-7100.

The iodine concentration of the polarizing film is preferably 3% by weight or more, more preferably 4% by weight or more, and further preferably 6% by weight or more. The upper limit of iodine concentration can be, for example, 12% by weight. When the iodine concentration is in such a range, the effect of reducing the unit absorbance becomes remarkable. In other words, the above effect is remarkable in the thin polarizing film having such a high iodine concentration.

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

Specific examples of the polarizing film obtained by using the laminate include a polarizing film obtained by using a laminate of a resin base material and a PVA-based resin layer formed by coating on the resin base material. A polarizing film obtained by using a laminate of a resin base material and a PVA-based resin layer formed by coating on the resin base material is, for example, a resin base material obtained by applying a PVA-based resin solution to the resin base material and drying the solution. A PVA-based resin layer is formed thereon to obtain a laminate of a resin base material and a PVA-based resin layer; the laminate is stretched and dyed to form the PVA-based resin layer as a polarizing film. obtain. In the present embodiment, the stretching typically includes dipping the laminate in a boric acid aqueous solution and stretching. Further, the stretching may further include, if necessary, stretching the laminate at high temperature (for example, 95° C. or higher) in air before stretching in the aqueous boric acid solution. The obtained resin substrate/polarizing film laminate may be used as it is (that is, the resin substrate may be used as a protective layer for the polarizing film), or the resin substrate is peeled from the resin substrate/polarizing film laminate. However, any appropriate protective layer depending on the purpose may be laminated on the peeled surface and used. The details of the method for manufacturing such a polarizing film are described in, for example, JP 2012-73580 A. The entire disclosure of this publication is incorporated herein by reference.

The method for producing a polarizing film is typically one side of a long thermoplastic resin base material, and a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is formed into a laminate, And subjecting the laminate to an in-air auxiliary stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment of shrinking by 2% or more in the width direction by heating while conveying in the longitudinal direction in this order. including. This can provide a polarizing film having excellent optical characteristics, having a thickness of 8 μm or less and a unit absorbance at a wavelength of 210 nm of 1.00 or less. That is, by introducing the auxiliary stretching, the crystallinity of PVA can be increased and high optical characteristics can be achieved even when PVA is applied onto the thermoplastic resin. At the same time, by preliminarily enhancing the orientation of PVA, it is possible to prevent problems such as reduction in orientation and dissolution of PVA when immersed in water in a subsequent dyeing step or stretching step, and high optical characteristics. Can be achieved. Furthermore, when the PVA-based resin layer is dipped in a liquid, the alignment disorder of the polyvinyl alcohol molecules and the decrease in the orientation can be suppressed as compared with the case where the PVA-based resin layer does not contain a halide. This can improve the optical characteristics of the polarizing film obtained through a treatment process such as a dyeing treatment and an underwater stretching treatment performed by immersing the laminate in a liquid. Further, the optical characteristics can be improved by shrinking the laminate in the width direction by the dry shrinking treatment.

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

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

The thickness of the first protective layer is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, and further preferably 10 μm to 30 μm. When the surface treatment is applied, the thickness of the outer protective layer is the thickness including the thickness of the surface treated layer.

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

B-3. Method for manufacturing polarizing film The polarizing film is, for example, 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 substrate. To form a laminated body, and the laminated body is subjected to an in-air auxiliary stretching treatment, a dyeing treatment, an underwater stretching treatment, and drying for shrinking 2% or more in the width direction by heating while conveying in the longitudinal direction. The shrinkage treatment and the shrinkage treatment may be performed in this order. The content of the halide in the PVA-based resin layer is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin. The drying shrinkage treatment is preferably performed using a heating roll, and the temperature of the heating roll is preferably 60°C to 120°C. The shrinkage ratio in the width direction of the laminate by the dry shrinkage treatment is preferably 2% or more. According to such a manufacturing method, the polarizing film described in the above section B-1 can be obtained. In particular, by producing a laminate including a PVA-based resin layer containing a halide, stretching the laminate by multistage stretching including in-air auxiliary stretching and underwater stretching, and heating the laminated body after heating with a heating roll. It is possible to obtain a polarizing film having excellent optical properties (typically, single transmittance and unit absorbance at a wavelength of 210 nm).

B-3-1. Production of Laminated Body Any appropriate method can be adopted as a method for producing a laminated body of a thermoplastic resin substrate and a PVA-based resin layer. Preferably, a PVA-based resin layer is formed on the thermoplastic resin substrate by applying a coating liquid containing a halide and a PVA-based resin on the surface of the thermoplastic resin substrate and drying the coating liquid. As described above, the content of the halide in the PVA-based resin layer is preferably 5 to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.

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

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

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

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

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

The glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 120° C. or lower. By using such a thermoplastic resin substrate, it is possible to sufficiently secure the stretchability of the laminate while suppressing the crystallization of the PVA-based resin layer. Further, in consideration of good plasticization of the thermoplastic resin substrate with water and favorable underwater stretching, the temperature is preferably 100° C. or lower, and more preferably 90° C. or lower. On the other hand, the glass transition temperature of the thermoplastic resin substrate is preferably 60°C or higher. By using such a thermoplastic resin base material, the thermoplastic resin base material may be deformed (for example, unevenness, wrinkles, wrinkles, etc.) when the coating liquid containing the PVA-based resin is applied and dried. It is possible to prevent the problems described above and to produce a good laminate. Moreover, the PVA-based resin layer can be stretched well at a suitable temperature (for example, about 60° C.). The glass transition temperature of the thermoplastic resin substrate can be adjusted, for example, by introducing a modifying group into the constituent material and heating it with a crystallization material. The glass transition temperature (Tg) is a value determined according to JIS K 7121.

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

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

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

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

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

Any appropriate method can be adopted as a method for stretching the thermoplastic resin substrate. Specifically, it may be fixed-end stretching or free-end stretching. The stretching method may be dry or wet. Stretching of the thermoplastic resin substrate may be performed in one stage or in multiple stages. When performing in multiple stages, the above-mentioned draw ratio is a product of the draw ratio of each stage.

B-3-1-2. Coating liquid The coating liquid contains a halide and a PVA-based resin as described above. The coating liquid is typically a solution prepared by dissolving the halide and the PVA resin in a solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These may be used alone or in combination of two or more. Of these, water is preferable. The PVA-based resin concentration of the solution is preferably 3 parts by weight to 20 parts by weight with respect to 100 parts by weight of the solvent. With such a resin concentration, it is possible to form a uniform coating film in close contact with the thermoplastic resin substrate. The content of the halide in the coating liquid is preferably 5 to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.

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

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

The average degree of polymerization of the PVA-based resin can be appropriately selected depending on the purpose. The average degree of polymerization is usually 1000 to 10000, preferably 1200 to 4500, and more preferably 1500 to 4300. The average degree of polymerization can be determined according to JIS K 6726-1994.

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

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

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

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

The stretching method for the in-air auxiliary stretching may be fixed-end stretching (for example, a stretching method using a tenter stretching machine) or free-end stretching (for example, a uniaxial stretching method in which a laminate is passed between rolls having different peripheral speeds). Although good, free end stretching can be positively adopted in order to obtain high optical characteristics. In one embodiment, the in-air stretching treatment includes a heating roll stretching step of stretching the laminate by the difference in peripheral speed between the heating rolls while conveying the laminate in the longitudinal direction. The in-air stretching treatment typically includes a zone stretching step and a heating roll stretching step. The order of the zone stretching step and the heating roll stretching step is not limited, and the zone stretching step may be performed first or the heating roll stretching step may be performed first. The zone stretching step may be omitted. In one embodiment, the zone stretching step and the heated roll stretching step are performed in this order. Further, in another embodiment, in the tenter stretching machine, the film is stretched by gripping the end portions of the film and widening the distance between the tenter in the flow direction (the spread of the distance between the tenter is the stretching ratio). At this time, the distance of the tenter in the width direction (direction perpendicular to the flow direction) is set to be arbitrarily close. Preferably, it can be set so as to be closer to the free end stretching with respect to the stretching ratio in the machine direction. In the case of free end stretching, the shrinkage ratio in the width direction=(1/stretching ratio) ^1/2 is calculated.

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

The draw ratio in the in-air auxiliary drawing is preferably 2.0 to 3.5 times. The maximum draw ratio in the case of combining the in-air auxiliary drawing and the underwater drawing is preferably 5.0 times or more, more preferably 5.5 times or more, and further preferably 6.0 times the original length of the laminate. That is all. In the present specification, the "maximum stretch ratio" refers to the stretch ratio immediately before the laminate is broken, and the stretch ratio at which the laminate is broken is confirmed separately, and is 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 substrate, the stretching method and the like. The stretching temperature is preferably the glass transition temperature (Tg) or higher of the thermoplastic resin substrate, more preferably the glass transition temperature (Tg)+10° C. or higher of the thermoplastic resin substrate, and particularly preferably Tg+15° C. or higher. On the other hand, the upper limit of the stretching temperature is preferably 170°C. By stretching at such a temperature, it is possible to suppress rapid crystallization of the PVA-based resin and suppress defects due to the crystallization (for example, to prevent orientation of the PVA-based resin layer due to stretching). it can. The crystallization index of the PVA-based resin after the in-air auxiliary stretching is preferably 1.3 to 1.8, more preferably 1.4 to 1.7. The crystallization index of the PVA-based resin can be measured by the ATR method using a Fourier transform infrared spectrophotometer. Specifically, measurement is performed using polarized light as the measurement light, and the crystallization index is calculated according to the following formula using the intensities of 1141 cm ⁻¹ and 1440 cm ⁻¹ of the obtained spectrum.
Crystallization index=(I _C /I _R ).
However,
I _C: intensity _{I R} of 1141cm ^-1 when measured by the incident measurement light: the intensity of 1440cm ^-1 when measured by the incident measurement light.

B-3-3. Insolubilization treatment If necessary, an insolubilization treatment is performed after the in-air auxiliary stretching treatment and before the underwater stretching treatment or the dyeing treatment. The insolubilization treatment is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. By performing the insolubilization treatment, it is possible to impart water resistance to the PVA-based resin layer and prevent the PVA from being lowered in orientation when immersed in water. The concentration of the aqueous boric acid solution is preferably 1 part by weight to 4 parts by weight with respect to 100 parts by weight of water. The liquid temperature of the insolubilization bath (boric acid aqueous solution) is preferably 20°C to 50°C.

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

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

The dyeing conditions (concentration, liquid temperature, immersion time) can be set so that the single transmittance of the finally obtained polarizing film and the unit absorbance at a wavelength of 210 nm have desired values. As such a dyeing condition, preferably, an iodine aqueous solution is used as the dyeing solution, and the ratio of the contents of iodine and potassium iodide in the iodine aqueous solution is 1:5 to 1:20. The ratio of the contents of iodine and potassium iodide in the aqueous iodine solution is preferably 1:5 to 1:10. As a result, a polarizing film having the above optical characteristics can be obtained.

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

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

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

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

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

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

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

The stretching temperature (liquid temperature of the stretching bath) is preferably 40°C to 85°C, more preferably 60°C to 75°C. At such a temperature, the PVA-based resin layer can be stretched at a high ratio while suppressing the dissolution. 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., it may not be possible to stretch well even if the plasticization of the thermoplastic resin substrate by water is taken into consideration. On the other hand, the higher the temperature of the drawing bath, the higher the solubility of the PVA-based resin layer, and there is a possibility that excellent optical characteristics will not be obtained. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.

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

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

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

The drying conditions can be controlled by adjusting the heating temperature of the transport roll (temperature of the heating roll), the number of heating rolls, the contact time with the heating roll, and the like. The temperature of the heating roll is preferably 60°C to 120°C, more preferably 65°C to 100°C, and particularly preferably 70°C to 80°C. It is possible to satisfactorily increase the crystallinity of the thermoplastic resin, satisfactorily suppress curling, and manufacture an optical laminate having extremely excellent durability. The temperature of the heating roll can be measured with a contact thermometer. In the illustrated example, six transport rolls are provided, but there is no particular limitation as long as there are multiple transport rolls. The number of transport rolls is usually 2 to 40, preferably 4 to 30. The contact time (total contact time) between the laminate and the heating roll is preferably 1 second to 300 seconds, more preferably 1 to 20 seconds, and further preferably 1 to 10 seconds.

The heating roll may be provided in a heating furnace (for example, an oven) or may be provided in a normal production line (under room temperature environment). Preferably, it is provided in a heating furnace provided with a blowing means. By using the drying with the heating roll and the hot air drying together, a sharp temperature change between the heating rolls can be suppressed, and the shrinkage in the width direction can be easily controlled. The temperature of hot air drying is preferably 30°C to 100°C. The hot air drying time is preferably 1 second to 300 seconds. The wind speed of the hot air is preferably about 10 m/s to 30 m/s. The wind speed is the wind speed in the heating furnace, and can be measured by a mini vane type digital anemometer.

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

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

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

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

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

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

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

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

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

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

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

As another example of the alignment fixed layer, there is a form in which the discotic liquid crystal compound is aligned in any state of vertical alignment, hybrid alignment and tilt alignment. In the discotic liquid crystal compound, typically, the disc surface of the discotic liquid crystal compound is oriented substantially perpendicular to the film surface of the first retardation layer. When the discotic liquid crystal compound is substantially vertical, the average value of the angles formed by the film surface and the disc surface of the discotic liquid crystal compound is preferably 70° to 90°, more preferably 80° to 90°. , And more preferably 85° to 90°. The discotic liquid crystal compound generally has a cyclic mother nucleus such as benzene, 1,3,5-triazine, and calixarene arranged at the center of the molecule, and has a straight chain alkyl group, alkoxy group, or substituted benzoyl group. It refers to a liquid crystal compound having a disk-shaped molecular structure in which an oxy group or the like is radially substituted as a side chain. Typical examples of discotic liquid crystals include C.I. Report of Destrade et al., Mol. Cryst. Liq. Cryst. 71, 111 (1981), benzene derivatives, triphenylene derivatives, truxene derivatives, phthalocyanine derivatives and B.I. Kohne et al., Angew. Chem. 96, 70 (1984), and cyclohexane derivatives described in J. M. Lehn et al., J. Chem. Soc. Chem. Commun. Pp. 1794 (1985), J. Zhang et al., J. Am. Chem. Soc. 116, 2655 (1994) and azacrown-type and phenylacetylene-type macrocycles. Further specific examples of the discotic liquid crystal compound include compounds described in JP-A-2006-133652, JP-A-2007-108732, and JP-A-2010-244038. The descriptions in the above documents and publications are incorporated herein by reference.

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

The first retardation layer typically has a refractive index characteristic of nx>ny=nz. The first retardation layer is typically provided to impart antireflection properties to the polarizing plate, and functions as a λ/4 plate when the first retardation layer is a single layer of the orientation solidification layer. You can In this case, the in-plane retardation Re(550) of the first retardation layer is preferably 100 nm to 190 nm, more preferably 110 nm to 170 nm, still more preferably 130 nm to 160 nm. Here, “ny=nz” includes not only the case where ny and nz are completely equal but also the case where they are substantially equal. Therefore, ny>nz or ny<nz may occur as long as the effect of the present invention is not impaired.

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

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

The angle θ formed by the slow axis of the first retardation layer 20 and the absorption axis of the polarizing film 11 is preferably 40° to 50°, more preferably 42° to 48°, and further preferably about. It is 45°. When the angle θ is in such a range, by using the λ/4 plate as the first retardation layer as described above, very excellent circular polarization characteristics (as a result, very excellent antireflection characteristics) are obtained. A polarizing plate with a retardation layer having is obtained.

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

D. Second Retardation Layer As described above, the second retardation layer may be a so-called positive C plate whose refractive index characteristics show a relationship of nz>nx=ny. By using the positive C plate as the second retardation layer, it is possible to favorably prevent the reflection in the oblique direction, and it is possible to widen the viewing angle of the antireflection function. 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, further preferably −90 nm to −200 nm, particularly preferably -100 nm to -180 nm. Here, “nx=ny” includes not only the case where nx and ny are exactly equal, but also the case where nx and ny are substantially equal. That is, the in-plane retardation Re(550) of the second retardation layer may be less than 10 nm.

The second retardation layer having a refractive index characteristic of nz>nx=ny can be formed of any appropriate material. The second retardation layer preferably comprises a film containing a liquid crystal material fixed in homeotropic alignment. The liquid crystal material (liquid crystal compound) capable of homeotropic alignment may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the method of forming the liquid crystal compound and the retardation layer include the liquid crystal compound and the method of forming the retardation layer described in JP-A-2002-333642, [0020] to [0028]. In this case, the thickness of the second retardation layer is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 8 μm, and further preferably 0.5 μm to 5 μm.

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

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

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

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

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

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

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. The measuring method of each characteristic is as follows. In the examples and comparative examples, "parts" and "%" are based on weight unless otherwise specified.
(1) Thickness The thickness of 10 μm or less was measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name “MCPD-3000”). The thickness exceeding 10 μm was measured using a digital micrometer (manufactured by Anritsu Corporation, product name “KC-351C”).
(2) Single Transmittance, Unit Absorbance, and Cross Absorbance Single-polarized transmission measured using an ultraviolet-visible spectrophotometer (V-7100 manufactured by JASCO Corporation) for the polarizing plates (protective film/polarizing film) of Examples and Comparative Examples. The transmittance Ts, the parallel transmittance Tp, and the orthogonal transmittance Tc are defined as Ts, Tp, and Tc of the polarizing film, respectively. These Ts, Tp, and Tc are Y values measured by the 2-degree visual field (C light source) of JIS Z8701 and subjected to luminosity correction. The refractive index of the protective film was 1.50, and the refractive index of the surface of the polarizing film on the side opposite to the protective film was 1.53.
The orthogonal absorbance A ₂₁₀ was determined from the orthogonal transmittance Tc ₂₁₀ measured at a measurement wavelength of 210 nm using UV-3150 manufactured by Shimadzu Corporation according to the following formula, and divided by the thickness to obtain a unit absorbance. Further, an orthogonal absorbance _{A 470} from the perpendicular transmittance _{Tc 470} for measuring wavelength 470 nm, and, an orthogonal absorbance _{A 600} from the perpendicular transmittance _{Tc 600} for measuring wavelength 600 nm, respectively determined using a JASCO Corp. V-7100.
Orthogonal absorbance = log10 (100/Tc)
Note _that the _{A 470} and _{A 600} are Otsuka also like Denshi LPF-200 can be the same measurement.
(3) Iodine Concentration Regarding the polarizing films obtained in Examples and Comparative Examples, fluorescent X-ray intensity (measurement diameter: φ10 mm, manufactured by Rigaku Corporation, trade name “ZSX-PRIMUS II”) was used. kcps) was measured. The iodine concentration (% by weight) was determined from the obtained fluorescent X-ray intensity and thickness using the following formula.
(Iodine concentration)=20.5×(fluorescent X-ray intensity)/(film thickness)
The coefficient for calculating the concentration differs depending on the measuring device, but the coefficient can be obtained using an appropriate calibration curve. In this example, a plurality of samples were prepared by adding KI (I:K=1:1 (molar ratio)) to PVA at an arbitrary value, and the samples were measured to obtain a calibration curve.
(4) Orthogonal b value The polarizing plates used in Examples and Comparative Examples were measured using an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, product name "V7100") to determine the hue in the crossed Nicols state. .. It is shown that the lower the orthogonal b value is (the negative value is and the larger the absolute value is), the more the hue is not neutral but blue.
(5) Warpage The polarizing plate with a retardation layer obtained in each of Examples and Comparative Examples was cut into a size of 110 mm×60 mm. At this time, the polarizing film was cut out so that the absorption axis direction was the long side direction. The cut out polarizing plate with a retardation layer was attached to a glass plate having a size of 120 mm×70 mm and a thickness of 0.2 mm via an adhesive to give a test sample. The test sample was placed in a heating oven maintained at 85° C. for 24 hours, and the amount of warp after taking out was measured. When the test sample was placed on a flat surface with the glass plate facing down, the height of the highest portion from the flat surface was defined as the amount of warpage.
(6) Unit Weight The polarizing plate with a retardation layer obtained in each of Examples and Comparative Examples was cut into a predetermined size, and the weight (mg) was divided by the area (cm ² ) to obtain a polarizing plate with a retardation layer. The weight per unit area (unit weight) was calculated.
(7) Bending resistance The polarizing plate with a retardation layer obtained in each of Examples and Comparative Examples was 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 the short side direction. Using a folding tester with a constant temperature and humidity chamber (CL09 type-D01 manufactured by YUASA), the cut out polarizing plate with a retardation layer was subjected to a bending test under the condition of 20° C. and 50% RH. Specifically, the polarizing plate with a retardation layer, so that the retardation layer side is the outer side, repeatedly bent in a direction parallel to the absorption axis direction, such as cracks that cause display failure, peeling or film breakage, etc. The number of times of bending before occurrence was measured and evaluated according to the following criteria (bending diameter: 2 mmφ).
<Evaluation criteria>
Less than 10,000 times: Poor 10,000 to less than 30,000 times: Good 30,000 times or more: excellent

[Example 1]
1. Production of Polarizing Film As the thermoplastic resin substrate, an amorphous isophthalic copolymer polyethylene terephthalate film (thickness: 100 μm) having a long shape, a water absorption of 0.75% and a Tg of about 75° C. was used. Corona treatment was applied to one surface of the resin substrate.
Polyvinyl alcohol (polymerization degree: 4200, saponification degree: 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosephimmer Z410") mixed at 9:1 100 weight of PVA-based resin What added 13 parts by weight of potassium iodide to a part was dissolved in water to prepare a PVA aqueous solution (coating solution).
The PVA aqueous solution was applied onto the corona-treated surface of the resin substrate and dried at 60° C. to form a PVA-based resin layer having a thickness of 13 μm, and a laminate was prepared.
The obtained laminated body was uniaxially stretched by 2.4 times in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 130° C. (in-air auxiliary stretching treatment).
Next, the laminate was immersed in an insolubilizing bath (solution of boric acid obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) having a liquid temperature of 40° C. for 30 seconds (insolubilization treatment).
Then, a dyeing bath having a liquid temperature of 30° C. (an iodine aqueous solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with respect to 100 parts by weight of water) was used to prepare the finally obtained polarizing film. Immersion was performed for 60 seconds while adjusting the concentration so that the single-piece transmittance (Ts) and the unit absorbance at a wavelength of 210 nm were desired values (dyeing treatment).
Then, it was immersed in a crosslinking bath at a liquid temperature of 40° C. (boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds. (Crosslinking treatment).
Then, while the laminated body was immersed in a boric acid aqueous solution (boric acid concentration 4.0% by weight) having a liquid temperature of 70° C., the total draw ratio in the longitudinal direction (longitudinal direction) was 5.5 between rolls having different peripheral speeds. Uniaxial stretching was performed so as to double the length (underwater stretching treatment).
After that, the laminate was immersed in a cleaning bath having a liquid temperature of 20° C. (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) (cleaning treatment).
Then, while being dried in an oven kept at 90° C., it was brought into contact with a heating roll made of SUS whose surface temperature was kept at 75° C. for about 2 seconds (dry shrinkage treatment). The shrinkage ratio in the width direction of the laminate due to the dry shrinkage treatment was 2%.
In this way, a polarizing film having a thickness of 4.6 μm was formed on the resin substrate.

2. Preparation of Polarizing Plate An acrylic film (surface refractive index 1.50, 40 μm) as a protective layer and an ultraviolet curable adhesive on the surface (the surface opposite to the resin substrate) of the polarizing film obtained above. Pasted together. Specifically, the curable adhesive was applied so that the total thickness was 1.0 μm, and the curable adhesive was attached using a roll machine. Then, UV rays were irradiated from the protective layer side to cure the adhesive. Next, after slitting both ends, the resin base material was peeled off to obtain a long polarizing plate (width: 1300 mm) having a structure of protective layer/polarizing film. The single transmittance of the polarizing plate (substantially, the polarizing film) is 43.5%, the unit absorbance at a wavelength of 210 nm is 0.91, A ₄₇₀ /A ₆₀₀ is 0.87, and the orthogonal b value is Was -3.00.

3. Preparation of First Alignment Solidification Layer and Second Alignment Solidification Layer Constituting Retardation Layer 10 g of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF: trade name “Paliocolor LC242”, represented by the following formula): A liquid crystal composition (coating liquid) was prepared by dissolving 3 g of a photopolymerization initiator (manufactured by BASF: trade name “Irgacure 907”) for the polymerizable liquid crystal compound in 40 g of toluene.
The surface of the polyethylene terephthalate (PET) film (thickness: 38 μm) was rubbed with a rubbing cloth for orientation treatment. The direction of the orientation treatment was set to be 15° with respect to the direction of the absorption axis of the polarizing film when it was attached to the polarizing plate, as viewed from the viewing side. The liquid crystal coating liquid was applied to the surface of this alignment treatment with a bar coater, and the liquid crystal compound was aligned by heating and drying at 90° C. for 2 minutes. The liquid crystal layer thus formed was irradiated with light of 1 mJ/cm ² using a metal halide lamp to cure the liquid crystal layer, thereby forming a liquid crystal alignment solidified layer A on the PET film. The thickness of the liquid crystal alignment fixed layer A was 2.5 μm, and the in-plane retardation Re(550) was 270 nm. Furthermore, the liquid crystal alignment fixed layer A had the refractive index distribution of nx>ny=nz.
On the PET film in the same manner as above except that the coating thickness was changed and the orientation treatment direction was set to be the direction of 75° with respect to the absorption axis direction of the polarizing film when viewed from the viewing side. A liquid crystal alignment fixed layer B was formed. The thickness of the liquid crystal alignment fixed layer B was 1.5 μm, and the in-plane retardation Re(550) was 140 nm. Furthermore, the liquid crystal alignment fixed layer B had the refractive index distribution of nx>ny=nz.

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

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

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

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

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

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

[Comparative example 2]
No potassium iodide was added to the PVA aqueous solution (coating solution), the thickness of the polarizing film obtained by changing the PVA aqueous solution (coating solution) was 3.3 μm, and no heating roll was used in the drying shrinkage treatment. A polarizing film and a polarizing plate were prepared in the same manner as in Example 1 except that the shrinkage in the width direction was set to 0.1% or less, and the single transmittance of the polarizing film was adjusted by adjusting the concentration of the dyeing bath. Was produced. The single transmittance of the polarizing plate (substantially, the polarizing film) was 43.4%, and the unit absorbance at a wavelength of 210 nm was 1.32. A polarizing plate with a retardation layer was produced in the same manner as in Example 1 except that this polarizing plate was used.

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

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

2-2. Preparation of Retardation Film The obtained polyester carbonate resin (pellet) was vacuum dried at 80° C. for 5 hours, then a single screw extruder (Toshiba Machine Co., Ltd., cylinder setting temperature: 250° C.), T die (width 200 mm). , Setting temperature: 250° C.), a chill roll (setting temperature: 120 to 130° C.) and a film forming apparatus equipped with a winder were used to prepare a long resin film having a thickness of 135 μm. The obtained long resin film was stretched in the width direction at a stretching temperature of 133° C. and a stretching ratio of 2.8 times to obtain a retardation film having a thickness of 53 μm. The Re(550) of the obtained retardation film was 141 nm, Re(450)/Re(550) was 0.82, and the Nz coefficient was 1.12.

3. Preparation of Polarizing Plate with Retardation Layer 1. On the surface of the polarizing film of the polarizing plate obtained in step 2, above. The retardation film obtained in (1) was attached via an acrylic pressure-sensitive adhesive (thickness 5 μm). At this time, they were laminated so that the absorption axis of the polarizing film and the slow axis of the retardation film formed an angle of 45°. In this way, a polarizing plate with a retardation layer having a structure of protective layer/adhesive layer/polarizing film/adhesive layer/retarder was obtained. The total thickness of the obtained polarizing plate with a retardation layer was 89 μm. The obtained polarizing plate with a retardation layer was subjected to the evaluations in (6) and (7) above.

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

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

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

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

Claims (14)

A polarizing plate including a polarizing film and a protective layer on at least one side of the polarizing film, and a retardation layer,
The polarizing film is composed of a polyvinyl alcohol-based resin film containing a dichroic material, the thickness thereof is 8 μm or less, and the orthogonal absorbance per 1 μm of thickness at a wavelength of 210 nm is 1.00 or less,
The retardation layer is an alignment and solidification layer of a liquid crystal compound,
Polarizing plate with retardation layer. The polarizing plate with a retardation layer according to claim 1, having a unit weight of 6.5 mg/cm ² or less. The polarizing plate with a retardation layer according to claim 1, which has a total thickness of 60 μm or less. The retardation layer is a single layer of an alignment solidified layer of a liquid crystal compound,
Re(550) of the retardation layer is 100 nm to 190 nm,
An angle formed by a slow axis of the retardation layer and an absorption axis of the polarizing film is 40° to 50°,
The polarizing plate with a retardation layer according to claim 1. The retardation layer has a laminated structure of an alignment solidified layer of a first liquid crystal compound and a alignment solidified layer of a second liquid crystal compound,
Re(550) of the alignment solidified layer of the first liquid crystal compound is 200 nm to 300 nm, and an angle formed by the slow axis thereof and the absorption axis of the polarizing film is 10° to 20°,
Re(550) of the oriented solidified layer of the second liquid crystal compound is 100 nm to 190 nm, and the angle formed by the slow axis thereof and the absorption axis of the polarizing film is 70° to 80°,
The polarizing plate with a retardation layer according to claim 1. The ratio (A ₄₇₀ /A ₆₀₀ ) between the orthogonal absorbance A ₄₇₀ at a wavelength of ₄₇₀ nm and the orthogonal absorbance A ₆₀₀ at a wavelength of 600 nm of the polarizing film (A ₄₇₀ /A ₆₀₀ ) is 0.7 to 2.00. Polarizing plate with retardation layer. The polarizing plate with a retardation layer according to claim 1, wherein the orthogonal b value of the polarizing film is greater than −10 and +10 or less. The polarizing plate with a retardation layer according to claim 1, wherein the polarizing film has an iodine concentration of 3.0% by weight or more. The polarizing plate with a retardation layer according to claim 1, wherein the single transmittance of the polarizing film is 42.5% or more. 10. The unit according to claim 1, further comprising another retardation layer outside the retardation layer, and the refractive index characteristics of the another retardation layer exhibit a relationship of nz>nx=ny. Polarizing plate with retardation layer. The polarizing plate with a retardation layer according to any one of claims 1 to 10, further comprising a conductive layer or an isotropic substrate with a conductive layer outside the retardation layer. A polarizing plate with a retardation layer, comprising a polarizing film and a polarizing plate including a protective layer on at least one side of the polarizing film, and a retardation layer,
The retardation layer is an alignment and solidification layer of a liquid crystal compound,
The polarizing film is composed of a polyvinyl alcohol-based resin film containing iodine, and has a thickness of 8 μm or less,
The orthogonal absorbance per 1 μm in thickness of the polarizing film at a wavelength of 210 nm is 1.00 or less,
The ratio (A ₄₇₀ /A ₆₀₀ ) of the orthogonal absorbance A ₄₇₀ at a wavelength of ₄₇₀ nm and the orthogonal absorbance A ₆₀₀ at a wavelength of 600 nm of the polarizing film is 0.7 to 2.00,
The orthogonal b value of the polarizing film is larger than −10 and is +10 or less,
Polarizing plate with retardation layer. An image display device comprising the polarizing plate with a retardation layer according to claim 1. The image display device according to claim 13, which is an organic electroluminescence display device or an inorganic electroluminescence display device.