TWI777075B - Polarizing plate with retardation layer and image display device using the same - Google Patents

Abstract

An object of the present invention is to provide a polarizing plate with a retardation layer that is thin, excellent in handleability, and excellent in optical properties.

The solution is as follows: the polarizing plate with retardation layer of the present invention has a polarizing plate and a retardation layer, and the polarizing plate includes a polarizing film and a protective layer on at least one side of the polarizing film. The polarizing film is composed of a polyvinyl alcohol-based resin film containing dichroic substances, its thickness is less than 8 μm, and the ratio of the orthogonal absorbance A ₅₅₀ at a wavelength of 550 nm to the orthogonal absorbance A ₂₁₀ at a wavelength of 210 nm ( A ₅₅₀ /A ₂₁₀ ) is 1.4~3.5. The retardation layer is an orientation cured layer of a liquid crystal compound.

Description

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

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

Background of the Invention

In recent years, image display devices represented by liquid crystal display devices and electroluminescence (EL) display devices (eg, organic EL display devices, inorganic EL display devices) have rapidly spread. The image display device is represented by the use of polarizing plates and retardation plates. In practical applications, a polarizing plate with a retardation layer formed by integrating a polarizing plate and a retardation plate is widely used (for example, Patent Document 1), and recently, with the increasing demand for thinner image display devices, the The demand for thinning of the polarizing plate of the layer has also increased. In addition, in recent years, the demand for curved image display devices and/or flexible or bendable image display devices has increased, and the polarizing plate and the polarizing plate with retardation layer are also required to be further thinned and further softening. For the purpose of reducing the thickness of the polarizing plate with retardation layer, the protective layer and retardation film of the polarizing film, which have a great influence on the thickness, are being reduced in thickness. However, if the protective layer and the retardation film are made thinner, the influence of the shrinkage of the polarizing film will be relatively large, and the problems of warpage of the image display device and the reduction of the operability of the polarizing plate with the retardation layer will occur.

In order to solve the above problems, even the polarizing film needs to be thinned type. However, if the thickness of the polarizing film is simply reduced, the optical properties will be degraded. More specifically, one or both of the polarization degree and the single transmittance, which have a trade-off relationship, are reduced to an unacceptable level in practical applications. As a result, the optical properties of the polarizing plate with the retardation layer will also become insufficient.

prior art literature

Patent Literature

Patent Document 1: Japanese Patent No. 3325560

Summary of Invention

The present invention was made in order to solve the conventional problems, and its main object is to provide a polarizing plate with a retardation layer that is thin, excellent in handleability, and excellent in optical properties.

The polarizing plate with retardation layer of the present invention has a polarizing plate and a retardation layer, and the polarizing plate comprises a polarizing film and a protective layer on at least one side of the polarizing film. The polarizing film is composed of a polyvinyl alcohol-based resin film containing dichroic substances, the thickness of which is less than 8 μm, and the ratio of the orthogonal absorbance A ₅₅₀ at a wavelength of 550 nm to the orthogonal absorbance A ₂₁₀ at a wavelength of 210 nm (A ₅₅₀ /A ₂₁₀ ) is 1.4~3.5. The retardation layer is an orientation cured layer of a liquid crystal compound.

In one embodiment, the above-mentioned polarizing plate with retardation layer has a basis weight of 6.5 mg/cm ² or less.

In one embodiment, the total thickness of the above-mentioned polarizing plate with retardation layer below 60μm.

In one embodiment, the retardation layer is a single layer of an orientationally solidified layer of a liquid crystal compound, the Re(550) of the retardation layer is 100 nm to 190 nm, and the slow axis of the retardation layer is the absorption axis of the polarizing film. The formed angle is 40°~50°.

In one embodiment, the retardation layer has a laminated structure of a first liquid crystal compound alignment layer and a second liquid crystal compound alignment layer; Re(550) of the first liquid crystal compound alignment layer is 200 nm to 300 nm , and the angle formed between the slow axis and the absorption axis of the polarizing film is 10°~20°; the Re(550) of the orientation cured layer of the second liquid crystal compound is 100nm~190nm, and the slow axis and the polarizing film are The angle formed by the absorption axis is 70°~80°.

In one embodiment, the ratio (A 470 /A 600 ) of the orthogonal absorbance A ₄₇₀ at a wavelength of 470 nm to the orthogonal absorbance A ₆₀₀ at a wavelength of 600 nm (A ₄₇₀ /A ₆₀₀ ) of the polarizing film is 0.7 to 2.00.

In one embodiment, the orthogonal b value of the polarizing film is greater than -10 and less than or equal to +10.

In one embodiment, the single transmittance of the polarizing film is 42.5% or more.

In one embodiment, the polarizing plate with the retardation layer further has another retardation layer outside the retardation layer, and the refractive index characteristic of the other retardation layer shows the relationship of nz>nx=ny.

In one embodiment, the polarizing plate with a retardation layer further has a conductive layer or an isotropic base material with a conductive layer on the outside of the retardation layer.

The present invention further provides a polarizing plate with a retardation layer, which has a polarizing plate and a retardation layer, and the polarizing plate comprises a polarizing film and a protective layer on at least one side of the polarizing film; the retardation layer is a liquid crystal compound Directionally cured layer; the polarizing film is composed of an iodine-containing polyvinyl alcohol-based resin film, and the thickness is below 8 μm; the orthogonal absorbance A of the polarizing film at a wavelength of 550 nm is ₅₅₀ and the orthogonal absorbance A at a wavelength of 210 nm The ratio of ₂₁₀ (A ₅₅₀ /A ₂₁₀ ) is 1.4~3.5, and the ratio of the orthogonal absorbance A ₄₇₀ of the polarizing film at a wavelength of 470nm to the orthogonal absorbance A ₆₀₀ of a wavelength of 600nm (A ₄₇₀ /A ₆₀₀ ) is 0.7 ~2.00, the orthogonal b value of the polarizing film is greater than -10 and below +10.

According to another aspect of the present invention, an image display device is provided. The 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, a thin polarizing film having excellent optical properties can be obtained by combining the following methods: adding a halide (representatively potassium iodide) to a polyvinyl alcohol (PVA)-based resin, including air-assisted stretching and 2-step stretching in water, drying and shrinking with heated rolls. By using the polarizing film, a thin polarizing plate with a retardation layer having excellent handling properties and excellent optical properties can be realized.

10: Polarizer

11: polarizing film

12: 1st layer of protection

13: 2nd layer of protection

20: retardation layer (first retardation layer)

21: The first directionally cured layer

22: The second directionally cured layer

50: Another retardation layer (second retardation layer)

60: Conductive layer or isotropic substrate with conductive layer

100, 101, 102: polarizing plate with retardation layer

200: Laminate

R1~R6: Conveying roller

G1~G4: Guide roller

FIG. 1 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to an embodiment of the present invention.

FIG. 2 is a polarizing plate with retardation layer according to another embodiment of the present invention A schematic cross-sectional view.

3 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to yet another embodiment of the present invention.

4 is a schematic diagram showing an example of drying shrinkage treatment using a heating roller in the manufacturing method of the polarizing film used in the polarizing plate with retardation layer of the present invention.

Form for carrying out the invention

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

(Definition of Terms and Symbols)

Definitions of terms and symbols in this specification are as follows.

(1) Refractive index (nx, ny, nz)

"nx" is the refractive index in the direction in which the in-plane refractive index becomes the largest (that is, the slow axis direction), "ny" is the refractive index in the in-plane 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 phase difference (Re)

"Re(λ)" is the in-plane retardation measured with light of wavelength λnm at 23°C. For example, "Re(550)" is the in-plane retardation measured with light having a wavelength of 550 nm at 23°C. Re(λ) can be obtained by the formula: Re(λ)=(nx-ny)×d when the thickness of the layer (film) is d(nm).

(3) Phase difference in thickness direction (Rth)

"Rth(λ)" is the retardation in the thickness direction measured with light having a wavelength of λ nm at 23°C. For example, "Rth(550)" is the retardation in the thickness direction measured with light having a wavelength of 550 nm at 23°C. Rth(λ) can be set when the layer (film) thickness is When d(nm), it can be obtained by the formula: Rth(λ)=(nx-nz)×d.

(4) Nz coefficient

The Nz coefficient can be obtained by Nz=Rth/Re.

(5) Angle

When referring to an angle in this specification, the angle includes both clockwise and counterclockwise relative to the reference direction. Thus, for example, "45°" means ±45°.

A. The overall composition of the polarizing plate with retardation layer

FIG. 1 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to an embodiment of the present invention. The polarizing plate 100 with a retardation layer of the present embodiment includes a polarizing plate 10 and a retardation layer 20 . The polarizing plate 10 includes a polarizing film 11 , a first protective layer 12 disposed on one side of the polarizing film 11 , and a second protective layer 13 disposed on the other side of the polarizing film 11 . Depending on the purpose, one of the first protective layer 12 and the second protective layer 13 may be omitted. For example, when the retardation layer 20 can function as a protective layer of the polarizing film 11, the second protective layer 13 may be omitted. In the embodiment of the present invention, the polarizing film is composed of a polyvinyl alcohol-based resin film containing a dichroic substance. The thickness of the polarizing film is 8 μm or less, and the ratio (A 550 /A 210 ) of the orthogonal absorbance A ₅₅₀ at a wavelength of 550 nm to the orthogonal absorbance A ₂₁₀ at a wavelength of 210 nm (A ₅₅₀ /A ₂₁₀ ) is 1.4 to 3.5.

As shown in FIG. 2 , in the polarizing plate 101 with retardation layer of another embodiment, another retardation layer 50 and/or a conductive layer or an isotropic substrate 60 with a conductive layer may also be provided. The other retardation layer 50 and the conductive layer or the isotropic substrate 60 with the conductive layer can be disposed on the outer side of the retardation layer 20 (the opposite side to the polarizer 10 ). Another retardation layer representative upper refractive index characteristic shows the relationship of nz>nx=ny. another retardation layer 50 and The conductive layer or the isotropic substrate 60 with the conductive layer is arranged in sequence from the side of the retardation layer 20 . The other retardation layer 50 and the conductive layer or the isotropic substrate 60 with the conductive layer represent any layers that can be provided as required, and either or both can be omitted. In addition, for the sake of convenience, the retardation layer 20 may be referred to as a first retardation layer, and the other retardation layer 50 may be referred to as a second retardation layer. In addition, when a conductive layer or an isotropic substrate with a conductive layer is to be provided, the polarizer with retardation layer can be applied to integrate a touch sensor between an image display unit (such as an organic EL unit) and the polarizer to form a The so-called inner touch panel type input display device.

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

The above-described embodiments may be appropriately combined, and changes obvious in the industry may be added to the components of the above-described embodiments. For example, a second retardation layer 50 and/or a conductive layer or an isotropic substrate 60 with a conductive layer may also be provided on the polarizing plate 102 with a retardation layer in FIG. 3 . For another example, the configuration in which the isotropic substrate 60 with the conductive layer is provided on the outside of the second retardation layer 50 may be replaced with an optically equivalent configuration (eg, a laminate of the second retardation layer and the conductive layer). .

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

The polarizing plate with retardation layer of the present invention may be in the form of a sheet or a long strip. In this specification, the term "stripe" means an elongated shape with a sufficiently long length relative to the width, and includes, for example, an elongated shape with a length of 10 times or more, and preferably a slender shape with a length of 20 times or more relative to the width. . The long polarizing plate with retardation layer can be rolled into roll.

In practical use, an adhesive layer (not shown) can be provided on the opposite side of the retardation layer to the polarizing plate, and the polarizing plate with the retardation layer can be attached to the image display unit. Also, the surface of the adhesive layer should be temporarily adhered to the release film before the polarizing plate with the retardation layer is used. By temporarily adhering the release film, the roll can be formed while protecting the adhesive layer.

The total thickness of the polarizing plate with the retardation layer is preferably 60 μm or less, preferably 55 μm or less, more preferably 50 μm or less, and particularly preferably 40 μm or less. The lower limit of the total thickness may be, for example, 28 μm. According to the embodiment of the present invention, the polarizing plate with the retardation layer as described above can be realized. The polarizing plate with retardation layer can have excellent flexibility and bending durability. The polarizing plate with retardation layer is particularly suitable for use in curved image display devices and/or flexible or bendable image display devices. In addition, the so-called total thickness of the polarizing plate with retardation layer refers to the total thickness of all the layers constituting the polarizing plate with retardation layer after deducting the adhesive layer used to make the polarizing plate and the external adherend such as panel or glass closely adhered. The total thickness (that is, the total thickness of the polarizing plate with retardation layer does not include the adhesive layer used to attach the polarizing plate with retardation layer to adjacent components such as image display units and the release film that can be temporarily adhered to its surface) thickness).

The unit weight of the polarizing plate with 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 preferably 3.0 mg/cm ² to 5.5 mg/cm 2 . cm ² , more preferably 3.5 mg/cm ² to 5.0 mg/cm ² . When the display panel is thin, the panel will be slightly ^deformed by the weight of the polarizing plate with retardation layer, which may cause poor display. , the panel can be prevented from being deformed. In addition, the polarizing plate with the retardation layer having the above-mentioned unit weight has good handleability even after being thinned, and can exhibit extremely excellent flexibility and bending durability.

Hereinafter, the constituent elements of the polarizing plate with 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 the ratio (A 550 /A 210 ) of the cross-absorbance A ₅₅₀ at a wavelength of 550 nm to the cross-absorbance A ₂₁₀ at a wavelength of 210 nm (A ₅₅₀ /A ₂₁₀ ) is 1.4 to 3.5. Compared with general thin polarizing films, the polarizing film used in the present invention has a very large ratio (A ₅₅₀ /A ₂₁₀ ), and in one embodiment, the ratio (A ₄₇₀ /A ₆₀₀ ) is also very large. It means that the content ratio of iodide ions that do not form complexes with PVA (with absorption in the ultraviolet region around 210 nm) in the polarizing film is very small, while the content ratio of PVA-iodine complexes (with absorption in the visible light region) is very small. big. More specifically, in the polarizing film, the content ratio of PVA ^- I ₅ -complex having absorption around 600 nm is very large, and the content ratio of PVA-I ₃ ^- complex having absorption around 480 nm is maintained. without a significant reduction. Here, the thickness of the polarizing film means the length of the optical path. Therefore, if the thickness of the polarizing film is simply reduced, the optical path will also be shortened, and the polarization performance will also be reduced. The amount of iodine that can be contained in the polarizing film is also limited. Therefore, in order to achieve both high polarization performance and thinning of the polarizing film, the iodine contained in the polarizing film must be effectively utilized. That is, by reducing the iodide ions that absorb light in ultraviolet light but do not contribute to the polarization performance, and increase the ratio of PVA-iodine complexes that absorb light in the visible light region, both high polarization performance and thinning of the polarizing film can be achieved. In other words, by increasing the ratio (A ₅₅₀ /A ₂₁₀ ), thin and high optical properties can be achieved. In addition, by maintaining the ratio (A ₄₇₀ /A ₆₀₀ ) at a predetermined value or more, good polarization performance can be achieved in the entire visible light region. When the amount of iodine in the thin polarizing film is limited, it is difficult to increase both the ratio (A ₅₅₀ /A ₂₁₀ ) and the ratio (A ₄₇₀ /A ₆₀₀ ) by the prior art, but the polarizing film used in the present invention can increase the Wait for both. The ratio (A ₅₅₀ /A ₂₁₀ ) is preferably at least 1.8, more preferably at least 2.0, more preferably at least 2.2. The upper limit of the ratio (A ₅₅₀ /A ₂₁₀ ) may be, for example, 3.5. In addition, the ratio (A ₄₇₀ /A ₆₀₀ ) is representatively 0.7 or more, preferably 0.75 or more, more preferably 0.80 or more, preferably 0.85 or more. The upper limit of the ratio (A ₄₇₀ /A ₆₀₀ ) is, for example, 2.00, preferably 1.33. In addition, the orthogonal absorbance can be calculated|required by the following formula based on the orthogonal transmittance Tc measured when the polarization degree is calculated later.

Orthogonal absorbance=log10(100/Tc)

One of the features of the present invention is the use of a thin polarizing film having the aforementioned properties.

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

The polarizing film should exhibit absorption dichroism at any wavelength from 380nm to 780nm. The transmittance of the polarizing film is preferably below 46.0%, more preferably below 45.0%. On the other hand, the transmittance of the monomer should preferably be 41.5% or more , and should be more than 42.0%, more preferably more than 42.5%. The degree of polarization of the polarizing film is preferably 99.990% or more, and preferably 99.998% or less. The above-mentioned monomer transmittance is representatively the Y value obtained by using an ultraviolet-visible light spectrophotometer to measure and correct the optical efficacy. The above degree of polarization is representatively obtained by the following equations based on the parallel transmittance Tp and the orthogonal transmittance Tc obtained by measuring using an ultraviolet-visible light spectrophotometer and calibrating the luminous efficacy.

Polarization (%)={(Tp-Tc)/(Tp+Tc)} ^1/2 ×100

In one embodiment, the transmittance of a thin polarizing film of 8 μm or less is represented by a laminate of a polarizing film (refractive index of the surface: 1.53) and a protective film (refractive index: 1.50) as the measurement object, using ultraviolet and visible light spectrophotometry meter to measure. Depending on the refractive index of the surface of the polarizing film and/or the surface of the protective film in contact with the air interface, the reflectance of each layer at the interface will change, and as a result, the measured value of transmittance may change. Therefore, for example, when a protective film with a refractive index other than 1.50 is used, the measured value of transmittance can also be corrected according to the refractive index of the surface of the protective film in contact with the air interface. Specifically, the correction value C of the transmittance is represented by the following formula using the reflectance R ₁ (transmission axis reflectance) of polarized light parallel to the transmission axis of 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 transmittance axis reflectance when a protective film with a refractive index of 1.50 is used, n ₁ is the refractive index of the protective film used, and T ₁ is the transmittance of the polarizing film. For example, when a substrate with a surface refractive index of 1.53 (cycloolefin film, film with a hard coat layer, etc.) is used as the protective film, the correction amount C is about 0.2%. At this time, adding 0.2% to the measured transmittance can convert the polarizing film with a surface refractive index of 1.53 to the transmittance when a protective film with a surface refractive index of 1.50 is used. In addition, after calculation according to the above formula, the change amount of the correction value C after changing the transmittance T1 _of the polarizing film by 2% is less than 0.03%, so the influence of the transmittance of the polarizing film on the value of the correction value C is: limited. In addition, when the protective film has absorption other than surface reflection, appropriate correction can be performed according to the amount of absorption.

In addition, the orthogonal b value of the polarizing film is, for example, greater than -10, preferably -7 or more, and more preferably -5 or more. The quadrature b value is preferably +10 or less, and preferably +5 or less. The quadrature b value represents the hue when the polarizing film (finally, the polarizing plate with retardation layer) is arranged in the quadrature state. ) looks more tinted. For example, when the quadrature b value is lower than -10, the black display looks bluish, and the display performance decreases. That is, according to the embodiment of the present invention, a polarizing plate with a retardation layer can be produced, which can realize excellent hue during black display. In addition, the quadrature b value can be measured with a spectrophotometer represented by V-7100.

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

As a specific example of the polarizing film obtained using the laminated body, the polarizing film obtained using the laminated body of the resin base material and the PVA-type resin layer formed in the resin base material by coating is mentioned. Formed using resin substrates and coating The polarizing film obtained by the laminate of the PVA-based resin layers on the resin substrate can be produced, for example, by applying the PVA-based resin solution to the resin substrate, drying it, and applying it on the resin substrate. A PVA-based resin layer is formed to obtain a laminate of a resin base material and a PVA-based resin layer; and the laminate is stretched and dyed to make the PVA-based resin layer a polarizing film. In the present embodiment, the stretching represents that the layered body is immersed in a boric acid aqueous solution and stretched. Further, if necessary, the stretching may further include in-air stretching of the layered body at a high temperature (eg, 95° C. or higher) before stretching in a boric acid aqueous solution. The obtained laminate of resin substrate/polarizing film can be used directly (that is, the resin substrate can also be used as a protective layer of the polarizing film), or the resin substrate can be peeled off from the laminate of resin substrate/polarizing film and then The surface is used by laminating an arbitrary and appropriate protective layer according to the purpose. The details of the manufacturing method of the polarizing film are described in, for example, Japanese Patent Laid-Open No. 2012-73580. In this specification, the entire description of this gazette is incorporated by reference.

The manufacturing method of the polarizing film typically includes the following steps: forming a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin on one side of an elongated thermoplastic resin substrate to form a laminate; and, for the above-mentioned The layered body is subjected to in-air auxiliary stretching treatment, dyeing treatment, underwater stretching treatment and drying shrinkage treatment in this order. The drying shrinkage treatment is to heat the above-mentioned layered body while transporting it in the longitudinal direction, thereby shrinking it by 2% in the width direction. above. Thereby, a polarizing film having a thickness of 8 μm or less and a ratio (A ₅₅₀ /A ₂₁₀ ) of 1.4 to 3.5 and having excellent optical properties can be provided. That is, by introducing the auxiliary extension, the crystallinity of the PVA can be improved even when the PVA is coated on the thermoplastic resin, and high optical properties can be achieved. In addition, by improving the orientation of PVA in advance, problems such as lowering of orientation or dissolution of PVA can be prevented when immersed in water in the subsequent dyeing step or stretching step, and high optical properties can be achieved. In addition, when the PVA-based resin layer is immersed in a liquid, the disorder of orientation of the polyvinyl alcohol molecules and the decrease in the orientation can be suppressed more than when the PVA-based resin layer does not contain a halide. Therefore, the optical properties of the polarizing film obtained by the processing steps of immersing the laminated body in a liquid, such as dyeing treatment and underwater stretching treatment, can be improved. In addition, by shrinking the laminate in the width direction by drying shrinkage treatment, the optical properties can be improved.

B-2. Protective layer

The first protective layer 12 and the second protective layer 13 are each formed of an arbitrary and appropriate thin film that can be used as a protective layer of a polarizing film. Specific examples of the material of the main component of the film include cellulose resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl-alcohol-based, polycarbonate-based, polyamide-based, polyamide-based Imine-based, polyether-based, poly-based, polystyrene-based, polynorbornene-based, polyolefin-based, (meth)acrylic-based and acetate-based transparent resins, etc. Moreover, (meth)acrylic type, urethane type, (meth)acrylate urethane type, epoxy type, polysiloxane type|system|group thermosetting resin, ultraviolet-curable resin, etc. are also mentioned. Other examples include glass-based polymers such as siloxane-based polymers. Moreover, the polymer film described in Unexamined-Japanese-Patent No. 2001-343529 (WO01/37007) can also be used. As the material of the film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in a side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain can be used, such as Alternating copolymers composed of isobutylene and N-methylmaleimide, and propylene Resin composition of vinyl nitrile-styrene copolymer. The polymer film may be, for example, an extruded product of the above-mentioned resin composition.

The polarizing plate with retardation layer of the present invention is arranged on the viewing side of the image display device as described later, and the first protective layer 12 is arranged on the viewing side of the image display device. Therefore, the first protective layer 12 may also be subjected to surface treatments such as hard coating treatment, anti-reflection treatment, anti-sticking treatment, and anti-glare treatment as required. And/or, the first protective layer 12 may also be subjected to treatment (representatively imparting (elliptical) polarizing function, imparting ultra-high retardation) that can improve the visibility when viewing through polarized sunglasses, as required. By performing the above-described processing, even if the displayed image is visually recognized through polarized lenses such as polarized sunglasses, excellent visibility can be achieved. Therefore, the polarizing plate with retardation layer can also be suitably used for the image display device which can be used outdoors.

The thickness of the first protective layer is preferably 5 μm to 80 μm, preferably 10 μm to 40 μm, and more preferably 10 μm to 30 μm. In addition, when the surface treatment is performed, the thickness of the outer protective layer includes the thickness of the surface treatment layer.

In one embodiment, the second protective layer 13 is preferably optically isotropic. In this specification, "optically isotropic" means that the in-plane retardation Re(550) is 0 nm to 10 nm, and the retardation Rth(550) in the thickness direction is -10 nm to +10 nm. In one embodiment, the second protective layer 13 is a retardation layer having an arbitrary and appropriate retardation value. At this time, 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, preferably 10 μm to 40 μm, and more preferably 10 μm to 30 μm. From the viewpoint of thinning and weight reduction, it is preferable to omit the second protective layer.

B-3. Manufacturing method of polarizing film

The polarizing film can be obtained, for example, by a production method comprising forming a polyvinyl alcohol-based resin layer (PVA-based resin layer) on one side of an elongated thermoplastic resin substrate to form a laminate, and the polyvinyl alcohol-based resin layer containing Halogen compound and polyvinyl alcohol-based resin (PVA-based resin); and, sequentially applying air-assisted stretching treatment, dyeing treatment, underwater stretching treatment, and drying shrinkage treatment to the laminate, and the drying shrinkage treatment conveys the laminate along the longitudinal direction. body and heat it to shrink by more than 2% in the width direction. The halide content in the PVA-based resin layer is preferably 5 to 20 parts by weight relative to 100 parts by weight of the PVA-based resin. The drying shrinkage treatment should be carried out with a heating roller, and the temperature of the heating roller should be 60℃~120℃. The shrinkage rate in the width direction of the laminate obtained by drying shrinkage treatment is preferably 2% or more. According to the above-mentioned production method, the polarizing film described in the above-mentioned item B-1 can be produced. In particular, a polarizing film having excellent optical properties (representatively, monomer transmittance and ratio (A ₅₅₀ /A ₂₁₀ )) can be produced by: After producing a laminate containing a PVA-based resin layer containing a halide , the stretching of the above-mentioned laminated body is carried out by multi-stage stretching including aerial auxiliary stretching and underwater stretching, and then the stretched laminated body is heated with a heating roller.

B-3-1. Fabrication of laminated body

Arbitrary and appropriate methods can be adopted as a method of producing the laminate of the thermoplastic resin base material and the PVA-based resin layer. Preferably, a coating liquid containing a halide and a PVA-based resin is coated on the surface of the thermoplastic resin substrate and dried, thereby forming a PVA-based resin layer on the thermoplastic resin substrate. As described above, the content of the halide in the PVA-based resin layer is preferably 5 to 20 parts by weight relative to 100 parts by weight of the PVA-based resin.

As the coating method of the coating liquid, an arbitrary and appropriate method can be adopted. 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 blade coating method (comma coating method, etc.) etc. are mentioned. The coating and drying temperature of the above-mentioned 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.

Before forming the PVA-based resin layer, a surface treatment (eg, corona treatment, etc.) may be performed on the thermoplastic resin substrate, and an easily bonding layer may be formed on the thermoplastic resin substrate. The adhesiveness between the thermoplastic resin base material and the PVA-based resin layer can be improved by performing the above-mentioned treatment.

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 a PVA-based resin layer. If it exceeds 300 micrometers, it may take a long time for the thermoplastic resin base material to absorb water, for example, during the underwater stretching treatment described later, and there may be a possibility that an excessive load is also applied to the stretching.

The water absorption rate of the thermoplastic resin substrate is preferably 0.2% or more, more preferably 0.3% or more. The thermoplastic resin substrate absorbs water, and water can act as a plasticizer for plasticization. As a result, elongation stress can be greatly reduced, and high-rate elongation can be achieved. On the other hand, the water absorption rate 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, the dimensional stability of the thermoplastic resin base material at the time of production can be prevented from being remarkably lowered, and the appearance of the polarizing film produced can be prevented from deteriorating. It can prevent the substrate from breaking when extending in water or the peeling of the PVA-based resin layer from the thermoplastic resin substrate. condition. In addition, the water absorption rate of the thermoplastic resin substrate can be adjusted, for example, by introducing a modified group into the constituent material. The water absorption rate is a value obtained by JIS K 7209.

The glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 120°C or lower. By using such a thermoplastic resin base material, the crystallization of the PVA-based resin layer can be suppressed, and the extensibility of the laminate can be sufficiently ensured. In addition, considering that the thermoplastic resin substrate can be plasticized with water and can be stretched well in water, 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 substrate, it is possible to prevent inconveniences such as deformation of the thermoplastic resin substrate (e.g., unevenness, slump, wrinkling, etc.) during coating and drying of the coating liquid containing the PVA-based resin, Thereby, a laminated body is produced favorably. In addition, the PVA-based resin layer can be well stretched at an appropriate temperature (for example, about 60° C.). In addition, the glass transition temperature of the thermoplastic resin substrate can be adjusted, for example, by heating using a crystallization material that can introduce a modified group into the constituent material. The glass transition temperature (Tg) is a value determined in accordance with JIS K 7121.

Arbitrary and appropriate thermoplastic resins can be used for the constituent material of the thermoplastic resin base material. Examples of thermoplastic resins include ester-based resins such as polyethylene terephthalate-based resins, cycloolefin-based resins such as norbornene-based resins, olefin-based resins such as polypropylene, polyamide-based resins, polycarbonate-based resins, and the like. Its copolymer resin and the like. Of these, norbornene-based resins and amorphous polyethylene terephthalate-based resins are preferred.

In one embodiment, amorphous (uncrystallized) of) polyethylene terephthalate resin. Among them, an amorphous (hardly crystallized) polyethylene terephthalate-based resin is preferably used. Specific examples of the amorphous polyethylene terephthalate resin include a copolymer further containing isophthalic acid and/or cyclohexanedicarboxylic acid as dicarboxylic acid, or a copolymer further containing cyclohexanedicarboxylic acid Methanol or diethylene glycol are used as copolymers of glycol.

In a preferred embodiment, the thermoplastic resin base material is composed of a polyethylene terephthalate-based resin having an isophthalic acid unit. This is because the thermoplastic resin base material has extremely excellent stretchability and can suppress crystallization during stretching. We speculate that it is due to the introduction of isophthalic acid units to impart a great flexibility to the main chain. The polyethylene terephthalate-based 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 extensibility 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, with respect to the total of all repeating units. By setting it to the said content ratio, the crystallinity degree can be favorably increased in the drying shrinkage process mentioned later.

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

The elongation temperature of the thermoplastic resin substrate is relative to the glass rotation The transfer temperature (Tg) should be Tg-10℃~Tg+50℃. The extension ratio of the thermoplastic resin substrate is preferably 1.5 times to 3.0 times.

An arbitrary and appropriate method can be adopted as the method for extending the thermoplastic resin substrate. Specifically, it can be a fixed end extension or a free end extension. The extension method can be dry or wet. The stretching of the thermoplastic resin substrate may be performed in one stage or in multiple stages. When it is carried out in multiple stages, the above stretching ratio is the product of the stretching ratio of each stage.

B-3-1-2. Coating liquid

The coating liquid system contains a halide and a PVA-based resin as described above. The above-mentioned coating liquid represents a solution obtained by dissolving the above-mentioned halide and the above-mentioned PVA-based resin in a solvent. Examples of the solvent include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyols such as trimethylolpropane, ethylene glycol Amines such as diamine and ethylene triamine. These may be used alone or in combination of two or more. Among these, water is preferred. The PVA-based resin concentration of the solution is preferably 3 parts by weight to 20 parts by weight relative to 100 parts by weight of the solvent. As long as it is the said resin density|concentration, a uniform coating film which adheres to a thermoplastic resin base material can be formed. The content of the halide in the coating liquid is preferably 5 parts by weight to 20 parts by weight relative to 100 parts by weight of the PVA resin.

Additives can also be mixed in the coating liquid. Examples of additives include plasticizers, surfactants, and the like. As a plasticizer, polyhydric alcohols, such as ethylene glycol and glycerol, are mentioned, for example. As a surfactant, a nonionic surfactant is mentioned, for example. These can be used in order to further improve the uniformity, dyeability, and extensibility of the obtained PVA-based resin layer.

Arbitrary and appropriate resin can be employ|adopted for the said PVA-type resin. For example, polyvinyl alcohol and ethylene-vinyl alcohol copolymer are mentioned. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymers can be obtained by saponifying ethylene-vinyl acetate copolymers. The degree of saponification of the PVA resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, more preferably 99.0 mol% to 99.93 mol%. The degree of saponification can be obtained according to JIS K 6726-1994. By using the PVA-based resin having the above degree of saponification, a polarizing film excellent in durability can be obtained. When the degree of saponification is too high, there is a risk of gelation.

The average degree of polymerization of the PVA-based resin can be appropriately selected according to the purpose. The average degree of polymerization is usually 1000~10000, preferably 1200~4500, more preferably 1500~4300. In addition, the average degree of polymerization can be calculated|required based on JISK6726-1994.

As the above-mentioned halide, any and appropriate halide can be used. For example, iodide and sodium chloride are mentioned. Examples of the iodide include potassium iodide, sodium iodide, and lithium iodide. Among them, potassium iodide is preferred.

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

Generally speaking, when the PVA-based resin layer is stretched, the orientation of the polyvinyl alcohol molecules in the PVA-based resin layer will become higher, but if the stretched PVA-based resin layer is immersed in a water-containing liquid, there will be polyethylene The situation in which the orientation of alcohol molecules is disordered and the orientation is reduced. In particular, when the laminate of the thermoplastic resin substrate and the PVA-based resin layer is stretched in boric acid water, in order to When the above-mentioned laminate is extended in boric acid water at a relatively high temperature to stabilize the extension of the thermoplastic resin substrate, the above-mentioned tendency to decrease the degree of orientation is remarkable. For example, the extension of the PVA film monomer in boric acid water is generally carried out at 60°C, while the extension of the laminate of A-PET (thermoplastic resin substrate) and the PVA-based resin layer is performed at 70°C The temperature before and after is carried out at a higher temperature, and at this time, the orientation of the PVA at the beginning of the stretching will decrease at the stage before it rises due to the stretching in water. In this regard, after producing a laminate of a PVA-based resin layer containing a halide and a thermoplastic resin substrate, the laminate is subjected to high temperature stretching (assisted stretching) in the air before stretching in boric acid water, whereby the post-assisted stretching can be accelerated. Crystallization of the PVA-based resin in the PVA-based resin layer of the laminate. As a result, when the PVA-based resin layer is immersed in a liquid, the disorder of orientation of the polyvinyl alcohol molecules and the decrease in orientation can be suppressed more than when the PVA-based resin layer does not contain a halide. Therefore, the optical properties of the polarizing film obtained by the processing steps of immersing the laminated body in a liquid, such as dyeing treatment and underwater stretching treatment, can be improved.

B-3-2. Air Auxiliary Extension Processing

In particular, in order to obtain high optical properties, a two-stage stretching method combining dry stretching (assisted stretching) and boric acid water stretching is selected. For example, in the two-stage stretching method, by introducing auxiliary stretching, the crystallization of the thermoplastic resin substrate can be suppressed and the stretching can be performed, so as to solve the problem that the elongation is reduced due to excessive crystallization of the thermoplastic resin substrate during the subsequent stretching in boric acid water. problem, so that the laminate can be stretched at a higher magnification. In addition, in order to suppress the influence of the glass transition temperature of the thermoplastic resin substrate when applying the PVA-based resin to the thermoplastic resin substrate, the application temperature must be higher than that of applying the PVA-based resin to a general The situation is even lower on the metal roller of 200°C, resulting in a problem that the crystallization of the PVA-based resin becomes relatively low and sufficient optical properties cannot be obtained. In this regard, by introducing auxiliary stretching, the crystallinity of the PVA-based resin can be improved even when the PVA-based resin is coated on the thermoplastic resin, and high optical properties can be achieved. In addition, by improving the orientation of the PVA-based resin in advance, problems such as lowering of the orientation and dissolution of the PVA-based resin when immersed in water in the subsequent dyeing step and stretching step can be prevented, and high optical properties can be achieved.

The stretching method of aerial auxiliary stretching can be either fixed-end stretching (such as a method of stretching using a tenter stretching machine) or free-end stretching (such as a method of uniaxial stretching of the laminated body through rolls with different peripheral speeds) , but in order to obtain high optical properties, the free end extension can be actively used. In one embodiment, the in-air stretching treatment includes a heating roll stretching step in which the above-mentioned layered body is conveyed in the longitudinal direction thereof while being stretched using the difference in peripheral speed between the heating rolls. The in-air stretching process typically includes a zone stretching step and a heating roll stretching step. In addition, the sequence of the zone stretching step and the heating roller stretching step is not limited, and the zone stretching step may be performed first, or the heating roller stretching step may be performed first. The region extension step can also be omitted. In one embodiment, the zone stretching step and the heating roll stretching step are performed in sequence. Moreover, in another embodiment, the film end is held in a tenter stretching machine, and the distance between the tenters is expanded in the flow direction to stretch (the increase in the distance between the tenters is a stretching magnification). At this time, the distance of the tenter in the width direction (vertical direction with respect to the flow direction) is set to be arbitrarily close. Preferably, the extension ratio relative to the flow direction can be set to use the extension of the free end for approaching. When it is extended at the free end, it is calculated by the shrinkage rate in the width direction = (1/extension ratio) ^1/2 .

Aerial assist extension can be performed in one stage or in multiple stages. When it is carried out in multiple stages, the stretching ratio is the product of the stretching ratios of each stage. The extension direction of the aerial auxiliary extension is substantially the same as the extension direction of the underwater extension.

The extension magnification of the aerial auxiliary extension should be 2.0 times to 3.5 times. The maximum stretching magnification when combining aerial auxiliary stretching and underwater stretching is preferably 5.0 times or more, preferably 5.5 times or more, and more preferably 6.0 times or more relative to the original length of the laminate. In this specification, the "maximum stretching ratio" means the stretching ratio before the layered body breaks, and is a value lower than the value by 0.2 after confirming the stretching ratio at which the layered body breaks.

The stretching temperature of the air-assisted stretching can be set to an arbitrary and appropriate value according to the forming material of the thermoplastic resin substrate, the stretching method, and the like. The elongation temperature is preferably above the glass transition temperature (Tg) 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. The rapid progress of crystallization of the PVA-based resin can be suppressed by elongation at such a temperature, and thus the inconvenience caused by the crystallization (for example, hindering the orientation of the PVA-based resin layer due to elongation) can be suppressed. The crystallization index of the PVA-based resin after air-assisted extension 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, the measurement was performed using polarized light as the measurement light, and the crystallization index was calculated by the following formula using the intensities of 1141 cm ^-1 and 1440 cm ^-1 of the obtained spectrum.

Crystallization Index=( _{IC /} IR )

However, IC: the intensity of ₁₁₄₁ cm _- ¹ when the measurement light is incident and measured, and IR: the intensity of 1440 cm ^-1 when the measurement light is incident and measured.

B-3-3. Insolubility Treatment

If necessary, insolubilization treatment may be performed after the air-assisted extension treatment and before the water extension treatment or dyeing treatment. The above-mentioned insolubilization treatment is performed by immersing the PVA-based resin layer in an aqueous solution of boric acid. By performing the insolubilization treatment, water resistance can be imparted to the PVA-based resin layer, and the orientation of the PVA can be prevented from being lowered when immersed in water. The concentration of the boric acid aqueous solution is preferably 1 to 4 parts by weight relative to 100 parts by weight of water. The temperature of the insoluble bath (boric acid aqueous solution) is preferably 20°C to 50°C.

B-3-4. Dyeing treatment

The above dyeing treatment is performed by dyeing the PVA-based resin layer with a dichroic substance (iodine in the representative). Specifically, it is performed by adsorbing iodine to the PVA-based resin layer. The adsorption method includes, for example, a method of immersing a PVA-based resin layer (layered body) in an iodine-containing dyeing solution, a method of applying the dyeing solution to the PVA-based resin layer, and spraying the dyeing solution to PVA method on the resin layer, etc. A method of immersing the layered product in a dyeing liquid (dyeing bath) is preferred. This is because it can adsorb iodine well.

The above-mentioned dyeing solution is preferably an aqueous iodine solution. The blending amount of iodine is preferably 0.05 part by weight to 0.5 part by weight with respect to 100 parts by weight of water. In order to improve the solubility of iodine in water, it is suitable to mix iodide in the iodine aqueous solution. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, and iodine. Lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, etc. Among them, potassium iodide is preferred. The blending amount of the iodide is preferably 0.1 to 10 parts by weight, preferably 0.3 to 5 parts by weight, relative to 100 parts by weight of water. In order to inhibit the dissolution of the PVA resin, the temperature of the dyeing solution during dyeing is preferably 20°C to 50°C. When immersing the PVA-based resin layer in the dyeing solution, in order to ensure the transmittance of the PVA-based resin layer, the immersion time is preferably 5 seconds to 5 minutes, and more preferably 30 seconds to 90 seconds.

The dyeing conditions (concentration, liquid temperature, immersion time) can be set so that the individual transmittance and ratio (A ₅₅₀ /A ₂₁₀ ) of the polarizing film finally obtained may be desired values. The dyeing conditions are preferably to use an aqueous iodine solution as the dyeing solution, and the content ratio of iodine to potassium iodide in the aqueous iodine solution is set to 1:5 to 1:20. The content ratio of iodine and potassium iodide in the iodine aqueous solution should be 1:5~1:10. Thereby, a polarizing film having the above-mentioned optical properties can be produced.

When the layered body is immersed in a treatment bath containing boric acid (representatively, an insolubility treatment) followed by a dyeing treatment, the boric acid contained in the treatment bath is mixed into the dyeing bath, and the concentration of boric acid in the dyeing bath varies with the As time changes, the dyeability may become unstable as a result. In order to suppress the instability of dyeability as described above, the upper limit of the boric acid concentration in the dyeing bath is preferably adjusted to 4 parts by weight, more preferably 2 parts by weight, relative to 100 parts by weight of water. On the other hand, the lower limit of the boric acid concentration in the dyeing bath is preferably 0.1 part by weight, more preferably 0.2 part by weight, and still more preferably 0.5 part by weight with respect to 100 parts by weight of water. In one embodiment, the dyeing treatment is performed using a dyeing bath pre-mixed with boric acid. Thereby, the ratio of the concentration change of boric acid when the boric acid of the above-mentioned treatment bath is mixed into the dyeing bath can be reduced. Boron pre-blended into the dye bath The mixing amount of the acid (that is, the content of boric acid not derived from the treatment bath) is preferably 0.1 to 2 parts by weight, more preferably 0.5 to 1.5 parts by weight, relative to 100 parts by weight of water.

B-3-5. Crosslinking Treatment

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

B-3-6. Water extension treatment

The underwater stretching treatment is performed by immersing the layered body in a stretching bath. By the underwater stretching treatment, it can be stretched at a temperature lower than the glass transition temperature (about 80°C in the representative) of the thermoplastic resin substrate or the PVA-based resin layer, and the crystallization of the PVA-based resin layer can be suppressed while at the same time. Perform high magnification extension. As a result, a polarizing film with excellent optical properties can be produced.

An arbitrary and appropriate method can be adopted as a method of extending the layered body. Specifically, it may be either fixed-end stretching or free-end stretching (for example, a method of uniaxially stretching the layered body through rolls having different peripheral speeds). better To select the free end extension. The extension of the laminate may be performed in one stage or in multiple stages. When it is carried out in multiple stages, the stretching ratio (maximum stretching ratio) of the layered body described later is the product of the stretching ratios of the respective stages.

The stretching in water is preferably performed by immersing the layered body in an aqueous boric acid solution (stretching in water with boric acid). By using the boric acid aqueous solution as the stretching bath, the PVA-based resin layer can be provided with rigidity and water-insoluble water resistance capable of withstanding the tension applied during stretching. Specifically, boric acid generates tetrahydroxyboronic acid anion in an aqueous solution and can be cross-linked with PVA-based resin by hydrogen bonding. As a result, rigidity and water resistance can be imparted to the PVA-based resin layer, and good extension can be performed, thereby producing a polarizing film with excellent optical properties.

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

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

The extension temperature (the liquid temperature of the extension bath) is preferably 40°C to 85°C, more preferably 60°C to 75°C. As long as it is the above-mentioned temperature, the PVA phylogeny can be suppressed The lipid layer dissolves and can be extended at high magnification at the same time. Specifically, as described above, in consideration of the relationship with the formation of the PVA-based resin layer, the glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 60° C. or higher. At this time, if the stretching temperature is lower than 40° C., even if it is considered that the thermoplastic resin base material is plasticized with water, it may not be able to be stretched well. On the other hand, the higher the temperature of the stretching bath, the higher the solubility of the PVA-based resin layer, and there is a fear that excellent optical properties cannot be obtained. The immersion time for the layered body to be immersed in the stretching bath is preferably 15 seconds to 5 minutes.

The stretching ratio for underwater stretching is preferably 1.5 times or more, preferably 3.0 times or more. The total stretching magnification of the layered body is preferably 5.0 times or more, more preferably 5.5 times or more, with respect to the original length of the layered body. By achieving the high draw ratio, a polarizing film having extremely excellent optical properties can be produced. The high elongation ratio can be achieved by using an underwater extension method (boric acid water extension).

B-3-7. Drying shrinkage treatment

The above-mentioned drying shrinkage treatment can be performed by zone heating by heating the entire zone, or by heating a conveying roller (so-called using a heating roller) (heating roller drying method). It is preferable to use both. By drying it using a heating roll, the heating curl of a laminated body can be suppressed efficiently, and the polarizing film excellent in appearance can be manufactured. Specifically, the crystallization of the thermoplastic resin base material can be effectively promoted to increase the degree of crystallization by drying the layered body in a state where the laminate is allowed to run along the heating roller, even at a relatively low drying temperature. The crystallinity of the thermoplastic resin substrate can still be well increased. As a result, the rigidity of the thermoplastic resin base material increases, and the PVA-based resin layer is in a state of being able to withstand shrinkage due to drying, and curling is suppressed. In addition, by using a heating roller, it is possible to dry the laminate while maintaining a flat state. Therefore, not only the generation of curl but also the generation of wrinkles can be inhibited. At this time, the layered body can be shrunk in the width direction by drying shrinkage treatment to improve optical properties. This is because it can effectively improve the orientation of PVA and PVA/iodine complexes. The shrinkage rate in the width direction of the laminated body obtained by drying shrinkage treatment is preferably 1% to 10%, more preferably 2% to 8%, especially 4% to 6%. By using a heating roller, the laminated body can be continuously shrunk in the width direction while being conveyed, and high productivity can be realized.

FIG. 4 is a schematic diagram showing an example of drying shrinkage treatment. In the drying shrinkage treatment, the layered body 200 is dried while being conveyed by the conveyance rollers R1 to R6 and the guide rollers G1 to G4 heated to a predetermined temperature. In the illustrated example, the conveying rollers 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, the conveying rollers R1 to R6 may be arranged to continuously heat only the layered body 200 . one of the sides (such as the thermoplastic resin substrate side).

Drying conditions can be controlled by adjusting the heating temperature of the conveying roller (the temperature of the heating roller), the number of heating rollers, and the contact time with the heating roller. The temperature of the heating roller is preferably 60°C to 120°C, more preferably 65°C to 100°C, and particularly preferably 70°C to 80°C. The degree of crystallinity of the thermoplastic resin can be favorably increased, and curling can be favorably suppressed, and an optical laminate having extremely excellent durability can be produced. In addition, the temperature of the heating roller can be measured with a contact thermometer. In the illustrated example, six conveying rollers are provided, but there is no particular limitation as long as there are a plurality of conveying rollers. The number of conveying rollers is usually 2 to 40, preferably 4 to 30. The contact time (total contact time) between the laminated body and the heating roller is preferably 1 to 300 seconds, preferably 1 to 20 seconds, and more preferably 1 to 10 seconds.

The heating roller can be installed in a heating furnace (eg, an oven), or can be installed in a general manufacturing line (at room temperature). It should be installed in a heating furnace with an air supply mechanism. The rapid temperature change between the heating rollers can be suppressed by combining the drying with the heating roller and the hot air drying, and the shrinkage in the width direction can be easily controlled. The temperature of hot air drying should be 30℃~100℃. In addition, the hot air drying time is preferably 1 second to 300 seconds. The wind speed of the hot air should be about 10m/s~30m/s. In addition, the wind speed is the wind speed in the heating furnace, which can be measured by a miniature fan-blade digital anemometer.

B-3-8. Other processing

It is preferable to perform a washing treatment after the stretching treatment in water and before the drying shrinkage treatment. The above-mentioned cleaning treatment can be typically performed by immersing the PVA-based resin layer in an aqueous potassium iodide solution.

C. The first retardation layer

The first retardation layer 20 is, for example, an alignment cured layer of the above-mentioned liquid crystal compound. By using a liquid crystal compound, the difference between nx and ny of the obtained retardation layer can be much larger than that of the non-liquid crystal material, so the thickness of the retardation layer required to obtain the desired in-plane retardation can be reduced even more. many. As a result, further thinning and weight reduction of the polarizing plate with retardation layer can be realized. The term "orientation-cured layer" in this specification refers to a layer in which the liquid crystal mixture is oriented in a predetermined direction within the layer, and the orientation state has been fixed. In addition, the concept of an "orientation hardening layer" includes an orientation hardening layer obtained by hardening a liquid crystal monomer as described later. In the present embodiment, it means that the rod-like liquid crystal compound is aligned in a state in which the rod-like liquid crystal compound is aligned in the slow axis direction of the first retardation layer (grain alignment).

The liquid crystal compound includes, for example, a liquid whose liquid crystal phase is a nematic phase. crystalline compound (nematic liquid crystal). As the liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The expression mechanism of the liquid crystallinity of the liquid crystal compound may be lyotropic or thermotropic. The liquid crystal polymer and the liquid crystal monomer may be used alone or in combination.

When the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer and a crosslinkable monomer. This is because the orientation state of the liquid crystal monomer can be fixed by polymerizing or crosslinking (ie, hardening) the liquid crystal monomer. After the liquid crystal monomers are aligned, for example, the above-mentioned alignment state can be fixed by polymerizing or crosslinking the liquid crystal monomers with each other. Here, a polymer is formed by polymerization, and a three-dimensional network structure is formed by cross-linking, but these are non-liquid crystalline. Therefore, the formed first retardation layer does not change into a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change, which is peculiar to a liquid crystal compound, for example. As a result, the first retardation layer becomes a retardation layer that is extremely stable without being affected by temperature changes.

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

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

The alignment cured layer of the liquid crystal compound can be formed by performing alignment treatment on the surface of a predetermined substrate, and coating the surface with a coating liquid containing the liquid crystal compound so that the liquid crystal compound is aligned in the direction corresponding to the above alignment treatment Orientation, and then fix the orientation state. In one embodiment, the base material is any appropriate resin film, and the orientation cured layer formed on the base material can be transferred to the surface of the polarizing plate 10 . In another embodiment, the base material may be the second protective layer 13 . In this case, the transfer step is omitted, and the layering can be performed in a roll-to-roll manner after forming the directionally solidified layer (the first retardation layer), so that the productivity can be further improved.

The above-mentioned orientation process can adopt any suitable orientation process. Specifically, a mechanical orientation treatment, a physical orientation treatment, and a chemical orientation treatment can be mentioned. Specific examples of the mechanical orientation treatment include rubbing treatment and stretching treatment. Specific examples of the physical alignment treatment include magnetic field alignment treatment and electric field alignment treatment. Specific examples of the chemical alignment treatment include oblique vapor deposition and photo alignment treatment. The treatment conditions for the various orientation treatments can be any appropriate conditions according to the purpose.

The alignment of the liquid crystal compound can be performed by processing at a temperature at which a liquid crystal phase can be exhibited according to the type of the liquid crystal compound. By performing the temperature treatment, the liquid crystal compound becomes a liquid crystal state, and the liquid crystal compound is oriented according to the orientation treatment direction of the surface of the substrate.

In one embodiment, the fixation of the alignment state is carried out by cooling the liquid crystal compound that has been aligned in the manner described above. in liquid crystal compounds In the case of a polymerizable monomer or a crosslinkable monomer, the alignment state is fixed by subjecting the liquid crystal compound oriented in the above-described manner to a polymerization treatment or a crosslinking treatment.

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

、杯芳烴等之環狀母核配置於分子中心，且直鏈的烷基、烷氧基、取代苄醯氧基等作為其側鏈呈放射狀取代者。盤狀液晶之代表例可舉：C.Destrade等人之研究報告，Mol.Cryst.Liq.Cryst.第71期第111頁(1981年)所記載之苯衍生物、聯伸三苯衍生物、參茚并苯衍生物、酞青素衍生物；B.Kohne等人之研究報告，Angew.Chem.第96期第70頁(1984年)所記載之環己烷衍生物；以及J.M.Lehn等人之研究報告，J.Chem.Soc.Chem.Commun.第1794頁(1985年)、J.Zhang等人之研究報告，J.Am.Chem.Soc.第116期第 2655頁(1994年)所記載之氮雜冠醚系或苯乙炔系的大環。盤狀液晶化合物的更多具體例可舉例如日本專利特開2006-133652號公報、日本專利特開2007-108732號公報、日本專利特開2010-244038號公報所記載之化合物。本說明書中係援用上述文獻及公報之記載作為參考。 Another example of the alignment cured layer includes a form in which the discotic liquid crystal compound is aligned in any state of vertical alignment, hybrid alignment, and oblique alignment. The discotic liquid crystal compound is oriented so that the disk surface of the discotic liquid crystal compound is substantially perpendicular to the film surface of the first retardation layer. The so-called discotic liquid crystal compound is substantially vertical means that the average value of the angle formed by the film surface and the disc surface of the discotic liquid crystal compound is preferably 70°~90°, more preferably 80°~90°, 85°~90°. °Better. The so-called discotic liquid crystal compound generally refers to a liquid crystal compound with a discotic molecular structure, which is a combination of benzene, 1,3,5-tris

The cyclic core nucleus of calixarene, etc. is arranged in the center of the molecule, and straight-chain alkyl groups, alkoxy groups, substituted benzyloxy groups, etc. are radially substituted as their side chains. Representative examples of discotic liquid crystals include: the research report of C. Destrade et al., Mol. Cryst. Liq. Cryst. No. 71, p. 111 (1981), the benzene derivatives, the triphenyl derivatives, the reference Indenacene derivatives, phthalocyanin derivatives; the research report of B. Kohne et al., the cyclohexane derivatives recorded in Angew. Chem. No. 96, p. 70 (1984); and the research of JMLehn et al. Report, J. Chem. Soc. Chem. Commun. p. 1794 (1985), research report by J. Zhang et al., J. Am. Chem. Soc. No. 116 p. 2655 (1994) Recorded Macrocycle of azacrown ether system or phenylacetylene system. More specific examples of the discotic liquid crystal compound include compounds described in JP 2006-133652 A, JP 2007-108732 A, and JP 2010-244038 A. In the present specification, the descriptions of the above-mentioned documents and gazettes are incorporated by reference.

In one embodiment, as shown in FIGS. 1 and 2 , the first retardation layer 20 is a single layer of a directionally cured layer of a liquid crystal compound. When the first retardation layer 20 is constituted by a single layer of a directionally solidified layer of a liquid crystal compound, its thickness is preferably 0.5 μm to 7 μm, and more preferably 1 μm to 5 μm. By using the liquid crystal compound, the in-plane retardation equivalent to that of the resin film can be realized at a thickness much thinner than that of the resin film.

The first retardation layer represents that the upper refractive index characteristic exhibits the relationship of nx>ny=nz. The first retardation layer is typically provided to impart anti-reflection properties to the polarizing plate, but can function as a λ/4 plate when the first retardation layer is a single layer of the directionally cured layer. At this time, the in-plane retardation Re(550) of the first retardation layer is preferably 100 nm to 190 nm, preferably 110 nm to 170 nm, and more preferably 130 nm to 160 nm. In addition, "ny=nz" here includes not only the case where ny and nz are completely identical, but also the case where they are substantially the same. Therefore, the situation of ny>nz or ny<nz may be present in the range which does not impair the effect of the present invention.

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

The first retardation layer can exhibit the retardation value according to the wave of the measurement light The reverse dispersion wavelength characteristic of the longer length can also exhibit the positive wavelength dispersion characteristic that the retardation value decreases with the wavelength of the measurement light, and the flat wavelength dispersion characteristic that the retardation value hardly changes with the wavelength of the measurement light can be exhibited. In one embodiment, the first retardation layer exhibits reverse dispersion wavelength characteristics. At this time, Re(450)/Re(550) of the retardation layer is preferably 0.8 or more and less than 1, and more preferably 0.8 or more and 0.95 or less. With such a configuration, very excellent antireflection properties can be realized.

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°, preferably 42° to 48°, and more preferably about 45°. As long as the angle θ is within the above-mentioned range, by using the first retardation layer as the λ/4 plate as described above, it is possible to obtain a phase-difference layer with a very excellent circular polarization characteristic (resulting in a very good antireflection characteristic). polarizer.

In another embodiment, as shown in FIG. 3 , the first retardation layer 20 has a laminated structure of the first directional solidification layer 21 and the second directional solidification layer 22 . At this time, either one of the first directional hardening layer 21 and the second directional hardening 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 directionally solidified layer 21 and the second directionally solidified layer 22 can be adjusted in order to obtain a desired in-plane retardation of a λ/4 plate or a λ/2 plate. For example, when the first directionally solidified layer 21 functions as a λ/2 plate and the second directionally solidified layer 22 functions as a λ/4 plate, the thickness of the first directionally solidified layer 21 is, for example, 2.0 μm to 3.0 μm, and the thickness of the second directionally solidified layer 21 is, for example, 2.0 μm to 3.0 μm. The thickness of the directionally solidified layer 22 is, for example, 1.0 μm to 2.0 μm. At this time, the in-plane retardation Re(550) of the first directionally solidified layer is preferably 200 nm to 300 nm, preferably 230 nm to 290 nm, and more preferably 250 nm to 280 nm. On the other hand, the in-plane retardation of the second directionally cured layer Re (550), the directionally cured layer of the single layer is as described above. The angle formed by the slow axis of the first orientationally solidified layer and the absorption axis of the polarizing film is preferably 10° to 20°, preferably 12° to 18°, and more preferably about 15°. The angle formed by the slow axis of the second orientationally solidified layer and the absorption axis of the polarizing film is preferably 70° to 80°, preferably 72° to 78°, and more preferably about 75°. With the above configuration, properties close to ideal reverse wavelength dispersion properties can be obtained, and as a result, very excellent antireflection properties can be realized. Regarding the liquid crystal compound constituting the first and second orientationally cured layers, the method for forming the first and second orientationally cured layers, optical properties, etc., the single-layered orientationally cured layers are as described above.

D. Second retardation layer

As mentioned above, the second retardation layer can be a so-called positive C-plate which exhibits the relation of nz>nx=ny in the refractive index characteristic. By using a positive C plate as the second retardation layer, the oblique reflection can be prevented well, and the anti-reflection function can be widened. At this time, the retardation Rth(550) in the thickness direction of the second retardation layer is preferably -50nm~-300nm, and is preferably -70nm~-250nm, more preferably -90nm~-200nm, particularly preferably -100nm~ -180nm. 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 the refractive index characteristic of nz>nx=ny can be formed of any appropriate material. The second retardation layer is preferably composed of a thin film containing a liquid crystal material fixed in a homeotropic orientation. The liquid crystal material (liquid crystal compound) that can be homeotropically oriented can be either a liquid crystal monomer or a liquid crystal polymer. Specific examples of the liquid crystal compound and the method for forming the retardation layer can be exemplified in Japan The liquid crystal compound and the method for forming the retardation layer described in paragraphs [0020] to [0028] of Japanese Patent Laid-Open No. 2002-333642. At this time, the thickness of the second retardation layer is preferably 0.5 μm to 10 μm, preferably 0.5 μm to 8 μm, and more preferably 0.5 μm to 5 μm.

E. Conductive layer or isotropic substrate with conductive layer

The conductive layer can be formed by forming a metal oxide film on any suitable substrate by any suitable film-forming method (eg, vacuum evaporation method, sputtering method, CVD method, ion plating method, spray method, etc.). The metal oxide includes, for example, indium oxide, tin oxide, zinc oxide, indium-tin composite oxide, tin-antimony composite oxide, zinc-aluminum composite oxide, and indium-zinc composite oxide. Among them, indium tin composite oxide (ITO) is suitable.

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 can be transferred from the above-mentioned base material to the first retardation layer (or the second retardation layer if there is a second retardation layer), and the conductive layer alone can be used as the constituent layer of the polarizing plate with the retardation layer, and also It can be laminated on the first retardation layer (or the second retardation layer if there is a second retardation layer) in the form of a laminate of a conductive layer and a substrate (substrate with a conductive layer). Preferably, the above-mentioned substrate is optically isotropic, so the conductive layer can be used as an isotropic substrate with a conductive layer for a polarizer with a retardation layer.

Any suitable isotropic substrate can be used as the optically isotropic substrate (isotropic substrate). Materials constituting the isotropic base material include, for example, norbornene-based resins, olefin-based resins, and the like that do not have a conjugated system The main skeleton of the resin is a material, a material having a cyclic structure such as a lactone ring or a glutarimide ring in the main chain of the acrylic resin, and the like. If such a material is used, the retardation exhibited by the molecular chain orientation when the isotropic substrate is formed can be suppressed to be small. The thickness of the isotropic base material is preferably 50 μm or less, and more preferably 35 μm or less. The lower limit of the thickness of the isotropic substrate is, for example, 20 μm.

The conductive layer of the above-mentioned conductive layer and/or the above-mentioned conductive layer of the isotropic substrate with the conductive layer can be patterned as required. The conducting portion and the insulating portion can be formed by patterning. As a result, electrodes can be formed. The electrodes can function as touch sensing electrodes for sensing contact with the touch panel. As the patterning method, any suitable method can be used. Specific examples of the patterning method include wet etching and screen printing.

F. Video display device

The polarizing plate with retardation layer described in the above items A to E can be applied to an image display device. Therefore, the present invention includes an image display device using the polarizing plate with the retardation layer. Typical examples of image display devices include liquid crystal display devices and electroluminescence (EL) display devices (eg, organic EL display devices, inorganic EL display devices). The image display device according to the embodiment of the present invention is provided with the polarizing plate with the retardation layer described in the above-mentioned items A to E on the viewing side. The polarizing plate with retardation layer is laminated so that the retardation layer is on the image display unit (eg liquid crystal unit, organic EL unit, inorganic EL unit) side (so that 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 flexible or bendable. In the image display device, the effect of the polarizing plate with retardation layer of the present invention is more remarkable.

Example

Hereinafter, the present invention will be specifically described with examples, but the present invention is not limited by these examples. The measurement method of each characteristic is as follows. In addition, unless otherwise noted, "parts" and "%" in Examples and Comparative Examples are based on weight.

(1) Thickness

The thickness of 10 μm or less was measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name “MCPD-3000”). On the other hand, the thickness of more than 10 μm was measured using a digital micrometer (manufactured by Anritsu, product name “KC-351C”).

(2) Monomer transmittance and orthogonal absorbance

The polarizing plates (protective films/polarizing films) of the examples and comparative examples were measured using an ultraviolet-visible light spectrophotometer (V-7100 manufactured by JASCO Corporation), and the measured monomer transmittance Ts and parallel transmittance Tp were measured. and the orthogonal transmittance Tc as Ts, Tp and Tc of the polarizing film, respectively. These Ts, Tp and Tc are the Y values obtained by measuring with the 2-degree field of view (C light source) of JIS Z8701 and correcting the luminous efficacy. In addition, the refractive index of the protective film was 1.50, and the refractive index of the surface of the polarizing film on the opposite side to the protective film was 1.53.

In addition, using the Tc measured at each wavelength, the orthogonal absorbance was calculated|required by the following formula.

Orthogonal absorbance=log10(100/Tc)

Using UV-3150 manufactured by Shimadzu Corporation, the orthogonal absorbance A ₂₁₀ was obtained from the orthogonal transmittance Tc ₂₁₀ at the measurement wavelength of 210 nm, and the orthogonal absorbance A ₅₅₀ was obtained from the orthogonal transmittance Tc ₅₅₀ at the measurement wavelength of 550 nm. In addition, the orthogonal absorbance A ₄₇₀ was obtained from the orthogonal transmittance Tc ₄₇₀ at the measurement wavelength of 470 nm using V-7100 manufactured by JASCO Corporation, and the orthogonal absorbance A ₆₀₀ was obtained from the orthogonal transmittance Tc ₆₀₀ at the measurement wavelength of 600 nm.

In addition, for _A470 and _A600 , an equivalent measurement can also be performed using LPF-200 manufactured by Otsuka Electronics Corporation.

(3) Orthogonal b value

The polarizing plates used in the examples and comparative examples were measured using an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, product name "V7100"), and the hue in the cross-polarized state was obtained. It shows that the lower the quadrature b value (negative value and larger absolute value) of the polarizing plate, the more blue rather than neutral the hue will be.

(4) Warping

The polarizing plates with retardation layers prepared in Examples and Comparative Examples were cut into a size of 110 mm×60 mm. At this time, it is cut so that the absorption axis direction of the polarizing film becomes the longitudinal direction. The cut polarizing plate with retardation layer was attached to a glass plate with a size of 120 mm×70 mm and a thickness of 0.2 mm through an adhesive to prepare a test sample. The test sample was put into a heating oven maintained at 85° C. for 24 hours, and the warpage amount was measured after taking out. After placing the test sample on a flat surface with the glass plate under it, the height of the highest part from the flat surface was taken as the amount of warpage.

(5) Unit weight

The polarizing plates with retardation layers prepared in the Examples and Comparative Examples were cut into predetermined sizes, and the weight (mg) was divided by the area (cm ² ) to calculate the unit of the polarizing plates with retardation layers. The weight of the area (unit weight).

(6) Bending resistance

The polarizing plates with retardation layers prepared in Examples and Comparative Examples were cut into a size of 50 mm×100 mm. At this time, it is cut so that the absorption axis direction of the polarizing film becomes the short side direction. Using a folding endurance tester (manufactured by YUASA Co., Ltd., CL09 type-D01) with a constant temperature and humidity chamber, the polarizing plate with retardation layer cut out under the conditions of 20°C and 50% RH was subjected to a bending test. Specifically, the polarizing plate with the retardation layer is repeatedly bent in a direction parallel to the absorption axis direction with the retardation layer side as the outer side, and is measured until a crack, peeling, or film breakage, which may cause poor display, occurs. The number of bending times was evaluated according to the following criteria (bending diameter: 2 mmφ).

<Evaluation Criteria>

Less than 10,000 times: bad

More than 10,000 times and less than 30,000 times: good

More than 30,000 times: excellent

[Example 1]

1. Make polarizing film

As the thermoplastic resin substrate, an amorphous isophthalic acid copolymer polyethylene terephthalate film (thickness: 100 μm) having a water absorption rate of 0.75% and a Tg of about 75° C. was used. Corona treatment was performed on one side of the resin substrate.

The PVA system is a 9:1 mixture of polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetylacetate modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z410") To 100 parts by weight of resin, 13 parts by weight of potassium iodide was added, and the resultant was dissolved in water to prepare an aqueous PVA solution (coating liquid).

The above-mentioned PVA aqueous solution was coated on the corona-treated surface of the resin substrate, and the By drying at 60 degreeC, the PVA-type resin layer of thickness 13 micrometers was formed, and the laminated body was produced.

The obtained layered body was uniaxially stretched 2.4 times at the free end in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds in an oven at 130° C. (aerial-assisted stretching treatment).

Next, the layered body was immersed in an insolubilization bath (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40° C. for 30 seconds (insolubility treatment).

Next, adjust the concentration of a dyeing bath with a liquid temperature of 30° C. (with respect to 100 parts by weight of water, an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7) so that the final polarizing film has a single density. The volume transmittance (Ts) and the ratio (A ₅₅₀ /A ₂₁₀ ) became desired values while being immersed therein for 60 seconds (dyeing treatment).

Next, it was immersed in a crosslinking bath (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds (crosslinking treatment) at a liquid temperature of 40°C. ).

Then, while immersing the layered body in a boric acid aqueous solution (boric acid concentration: 4.0% by weight) at a liquid temperature of 70°C, uniaxial stretching was performed in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds so that the total stretching ratio was Up to 5.5 times (extension treatment in water).

Then, the layered body was immersed in a cleaning bath (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 20°C (cleaning treatment).

After that, while keeping it dry in an oven at 90°C, it was brought into contact with The surface temperature was maintained at 75°C with a heating roll made of SUS for about 2 seconds (drying shrinkage treatment). The shrinkage rate in the width direction of the laminate obtained by drying shrinkage treatment was 2%.

Through the above procedure, a polarizing film with a thickness of 4.6 μm was formed on the resin substrate.

2. Make a polarizer

An acrylic film (surface refractive index 1.50, 40 μm) was attached to the surface of the polarizing film obtained above (the surface opposite to the resin substrate) through an ultraviolet curable adhesive as a protective layer. Specifically, it was applied so that the total thickness of the hardening adhesive was 1.0 μm, and was bonded using a rolling mill. Then, the adhesive was cured by irradiating UV light from the protective layer side. Next, after cutting both ends, the resin substrate was peeled off to obtain a long polarizing plate (width: 1300 mm) having a protective layer/polarizing film configuration. The single transmittance of the polarizing plate (essentially a polarizing film) was 43.5%, A ₅₅₀ /A ₂₁₀ was 1.50, A ₄₇₀ /A ₆₀₀ was 0.87, and the orthogonal b value was -3.00.

3. Preparation of the first directional solidified layer and the second directional solidified layer constituting the 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) and a photopolymerization initiator (manufactured by BASF: trade name "IRGACURE" of the polymerizable liquid crystal compound) were prepared. 907") 3 g was dissolved in 40 g of toluene to prepare a liquid crystal composition (coating liquid).

[Chemical formula 1]

The surface of a polyethylene terephthalate (PET) film (thickness 38 μm) was wiped with a wiping cloth to perform orientation treatment. The direction of the orientation treatment was set to be a 15° direction with respect to the absorption axis direction of the polarizing film when viewed from the viewing side when it was attached to the polarizing plate. The above-mentioned liquid crystal coating liquid was applied to the alignment-treated surface by a bar coater, and the liquid crystal compound was aligned by heating and drying at 90° C. for 2 minutes. The liquid crystal layer formed as described above was irradiated with light of 1 mJ/cm ² using a metal halide lamp to harden the liquid crystal layer, thereby forming a liquid crystal alignment cured layer A on the PET film. The thickness of the liquid crystal alignment cured layer A was 2.5 μm, and the in-plane retardation Re(550) was 270 nm. In addition, the liquid crystal alignment cured layer A has a refractive index distribution of nx>ny=nz.

The liquid crystal alignment cured layer B was formed 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 75° with respect to the absorption axis direction of the polarizing film when viewed from the viewing side. . The thickness of the liquid crystal alignment cured layer B was 1.5 μm, and the in-plane retardation Re(550) was 140 nm. In addition, the liquid crystal alignment cured layer B has a refractive index distribution of nx>ny=nz.

4. Production of polarizing plate with retardation layer

The liquid crystal alignment cured layer A and the liquid crystal alignment cured layer B prepared in the above 3. were transferred sequentially on the surface of the polarizing film of the polarizing plate prepared in the above 2. At this time, the transfer was performed in such a way that the angle formed by the absorption axis of the polarizing film and the slow axis of the directionally solidified layer A was 15°, and the angle formed by the absorption axis of the polarizing film and the slow axis of the directionally solidified layer B was 75° ( fit). In addition, the respective transfer (paste The bonding) is carried out through the ultraviolet curable adhesive (thickness 1.0 μm) used in 2. above. In the above-described manner, a polarizing plate with retardation layer having a configuration of protective layer/adhesive layer/polarizing film/adhesive layer/retardation layer (first directional solidified layer/adhesive layer/second directional solidified layer) was produced. The total thickness of the obtained polarizing plate with retardation layer was 52 μm. The obtained polarizing plate with retardation layer was used for the evaluation of the above (4) to (6). The amount of warpage was 1.8 mm.

[Example 2]

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

[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 triacetate cellulose (TAC) film was used as a protective layer. The total thickness of the obtained polarizing plate with retardation layer was 37 μm. The obtained polarizing plate with retardation layer was used for the same evaluation as in Example 1. The amount of warpage was 1.3 mm.

[Comparative Example 1]

1. Make polarizers

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 immersed in a swelling bath (water bath) at 20°C for 30 seconds between rolls with different peripheral speed ratios to swell, while extending 2.4 times in the conveying direction (swelling step), and then at 30°C In a dyeing bath (aqueous solution with an iodine concentration of 0.03 wt % and a potassium iodide concentration of 0.3 wt %), it was immersed and dyed so that the transmittance of the monomer after final stretching became a desired value, while the original polyvinyl alcohol film was dipped and dyed. (The polyvinyl alcohol film that is not stretched at all in the conveying direction) is stretched 3.7 times in the conveying direction as a reference (dyeing step). The immersion time at this time was about 60 seconds. Next, the dyed polyvinyl alcohol film was immersed in a crosslinking bath (aqueous solution with a boric acid concentration of 3.0 wt % and a potassium iodide concentration of 3.0 wt %) at 40° C. while moving in the conveying direction based on the original polyvinyl alcohol film. Extend up to 4.2 times (crosslinking step). The obtained polyvinyl alcohol film was then immersed in a stretching bath at 64° C. (an aqueous solution with a boric acid concentration of 4.0 wt % and a potassium iodide concentration of 5.0 wt %) for 50 seconds, and extended to the conveying direction based on the original polyvinyl alcohol film. After reaching 6.0 times (stretching step), it was immersed for 5 seconds in a cleaning bath (aqueous solution having a potassium iodide concentration of 3.0 wt %) at 20°C (cleaning step). The cleaned polyvinyl alcohol film was dried at 30° C. for 2 minutes to prepare a polarizer (thickness: 12 μm).

2. Make a polarizer

The following aqueous solution is used as the adhesive: a polyvinyl alcohol resin containing an acetoacetyl group in a weight ratio of 3:1 (average degree of polymerization 1,200, degree of saponification 98.5 mol%, degree of acetoacetylation 5 mol%) with methylol melamine. Using this adhesive, a 25 μm thick triacetin cellulose (TAC) film with a hard coating was attached to one side of the polarizer prepared above by a roll laminating machine, and the thickness was attached to the other side of the polarizer. After the TAC film is 25 μm, it is heated and dried in an oven (temperature is 60 ° C, time is 5 minutes), and a protective layer 1 (thickness 25 μm) / adhesive layer / polarizer / adhesive layer / protective layer 2 ( A polarizing plate with a thickness of 25 μm).

3. Make a polarizing plate with retardation layer

On the surface of the protective layer 2 of the polarizing plate prepared in the above 2. in the same manner as in Example 1, the liquid crystal alignment solidified layer A and the liquid crystal alignment solidified layer B were sequentially transferred to produce a protective layer 1/adhesive layer. Polarizing plate with retardation layer consisting of /polarizer/adhesive layer/protective layer 2/adhesive layer/retardation layer (first directional solidified layer/adhesive layer/second directional solidified layer). The total thickness of the obtained polarizing plate with retardation layer was 68 μm. The obtained polarizing plate with retardation layer was used for the same evaluation as in Example 1. The amount of warpage was 4.2mm.

[Comparative Example 2]

Potassium iodide was not added to the PVA aqueous solution (coating solution), the thickness of the polarizing film obtained after changing the PVA aqueous solution (coating solution) was 3.3 μm, and the shrinkage rate in the width direction was 0.1 without using a heating roller in the drying shrinkage treatment. A polarizing film and a polarizing plate were produced in the same manner as in Example 1, except that the concentration of the dyeing bath was adjusted to % or less and the monomer transmittance of the polarizing film was adjusted. The single transmittance of the polarizing plate (substantially a polarizing film) was 43.4%, and A ₅₅₀ /A ₂₁₀ was 0.75. A polarizing plate with a retardation layer was produced in the same manner as in Example 1 except that the polarizing plate was used.

[Comparative Example 3]

1. Make a polarizer

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

2. Fabrication of the retardation film constituting the retardation layer

2-1. Polymerization of polyester carbonate resin

The polymerization was carried out using a batch polymerization apparatus consisting of two vertical reactors equipped with stirring blades and a reflux cooler controlled at 100°C. 29.60 parts by mass (0.046 mol) of bis[9-(2-phenoxycarbonylethyl)perpen-9-yl]methane, 29.21 parts by mass (0.200 mol) of isosorbide (ISB), spiroglycerol (SPG) were fed 42.28 parts by mass (0.139 mol), 63.77 parts by mass (0.298 mol) of diphenyl carbonate (DPC), and 1.19×10 ^-2 parts by mass (6.78×10 ^-5 mol) of calcium acetate monohydrate as a catalyst. After the inside of the reactor was replaced with nitrogen under reduced pressure, it was heated with a heating medium, and stirring was started when the internal temperature reached 100°C. The internal temperature was brought to 220° C. 40 minutes after the start of the temperature increase, and the pressure was reduced while maintaining the temperature so that it became 13.3 kPa 90 minutes after reaching 220° C. The phenol vapor produced by the polymerization reaction was introduced into a reflux cooler at 100°C to return a small amount of monomer components contained in the phenol vapor to the reactor, and the uncondensed phenol vapor was introduced into a condenser at 45°C for recovery. After nitrogen was introduced into the first reactor and the pressure was temporarily returned to atmospheric pressure, the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Next, the temperature increase and pressure reduction in the second reactor were started, and after 50 minutes, the internal temperature was set to 240° C. and the pressure was set to 0.2 kPa. Thereafter, polymerization is performed until a predetermined stirring power is reached. When the predetermined power was reached, nitrogen was introduced into the reactor to recover the pressure, the produced polyester carbonate-based resin was extruded into water, and the bundle was cut to obtain pellets.

2-2. Fabrication of retardation film

The obtained polyester carbonate-based resin (pellet) was vacuum-dried at 80° C. for 5 hours, and then used a uniaxial extruder (manufactured by Toshiba Machine Co., Ltd., cylinder set temperature: 250° C.) and a T-die (width 200mm, set temperature: 250℃), A cooling roll (set temperature: 120~130°C) and a film forming device of a winder were used to produce a long resin film with 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 with a thickness of 53 μm. Re(550) of the obtained retardation film was 141 nm, Re(450)/Re(550) was 0.82, and Nz coefficient was 1.12.

3. Make a polarizing plate with retardation layer

The retardation film obtained in the above 2. was pasted on the surface of the polarizing film of the polarizing plate obtained in the above 1. through an acrylic adhesive (thickness 5 μm). At this time, the absorption axis of the polarizing film and the slow axis of the retardation film were bonded together at an angle of 45°. In the above-described manner, a polarizing plate with retardation layer having a configuration of protective layer/adhesive layer/polarizing film/adhesive layer/retardation layer was obtained. The total thickness of the obtained polarizing plate with retardation layer was 89 μm. The obtained polarizing plate with retardation layer was used for the evaluation of (5) and (6) above.

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

[Evaluate]

As is apparent from Table 1 and the comparison between Example 1 and Comparative Example 2, the polarizing plates with retardation layers of the examples of the present invention are thin, have suppressed warpage after the heating test, and are excellent in optical properties. Moreover, since the weight per unit area of the polarizing plate with retardation layer is below a predetermined value, it turns out that bending resistance improves.

industrial availability

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

10: Polarizer

11: polarizing film

12: 1st layer of protection

13: 2nd layer of protection

20: retardation layer (first retardation layer)

100: Polarizing plate with retardation layer

Claims (11)

A polarizing plate with a retardation layer, comprising a polarizing plate and a retardation layer, and the polarizing plate comprises a polarizing film and a protective layer on at least one side of the polarizing film; the polarizing film is made of polyethylene containing dichroic substances The alcohol-based resin film has a thickness of 8 μm or less, and the ratio of the orthogonal absorbance A ₅₅₀ at a wavelength of 550 nm to the orthogonal absorbance A ₂₁₀ at a wavelength of 210 nm (A ₅₅₀ /A ₂₁₀ ) is 1.4~3.5; the The retardation layer is a directional solidification layer of the liquid crystal compound; the total thickness of the polarizing plate with the retardation layer is below 60 μm. The polarizing plate with retardation layer as claimed in claim 1, wherein the retardation layer is a single layer of a directionally cured layer of a liquid crystal compound, the Re(550) of the retardation layer is 100 nm to 190 nm, and the retardation layer is slow The angle formed by the axis and the absorption axis of the polarizing film is 40° to 50°. The polarizing plate with retardation layer according to claim 1, wherein the retardation layer has a laminated structure of an orientationally cured layer of a first liquid crystal compound and an orientationally cured layer of a second liquid crystal compound; Re(550) is 200nm~300nm, and the angle formed by its slow axis and the absorption axis of the polarizing film is 10°~20°; the Re(550) of the orientation cured layer of the second liquid crystal compound is 100nm~190nm, and The angle formed between the slow axis and the absorption axis of the polarizing film is 70°~80°. The polarizing plate with retardation layer as claimed in claim 1, wherein 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 (A ₄₇₀ /A ₆₀₀ ) of the polarizing film is 0.7~ 2.00. The polarizing plate with retardation layer according to claim 1, wherein the orthogonal b value of the polarizing film is greater than -10 and less than +10. The polarizing plate with retardation layer according to claim 1, wherein the single transmittance of the polarizing film is 42.5% or more. The polarizing plate with retardation layer according to claim 1, further comprising another retardation layer outside the aforementioned retardation layer, and the refractive index characteristic of the other retardation layer shows the relationship of nz>nx=ny. The polarizing plate with retardation layer according to claim 1, further comprising a conductive layer or an isotropic substrate with a conductive layer on the outside of the retardation layer. A polarizing plate with a retardation layer, comprising a polarizing plate and a retardation layer, and the polarizing plate comprises a polarizing film and a protective layer on at least one side of the polarizing film; the retardation layer is a directional curing layer of a liquid crystal compound; the The polarizing film is composed of an iodine-containing _polyvinyl alcohol-based resin film with a thickness of 8 _μm or less. ₅₅₀ /A ₂₁₀ ) is 1.4~3.5, the ratio of the orthogonal absorbance A ₄₇₀ under the wavelength of 470nm and the orthogonal absorbance A ₆₀₀ under the wavelength of 600nm (A ₄₇₀ /A ₆₀₀ ) is 0.7~2.00, the polarized light The orthogonal b value of the film is greater than -10 and less than +10; the total thickness of the polarizing plate with retardation layer is less than 60 μm. An image display device comprising the polarizing plate with a retardation layer according to any one of claims 1 to 9. The image display device of claim 10, which is an organic electroluminescence display device or an inorganic electroluminescence display device.

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