TWI801678B - Polarizing plate with retardation layer and image display device using same - Google Patents

Abstract

The present invention provides a polarizing plate with a retardation layer that is thin, has excellent handling properties, and has excellent optical properties. 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 made of polyvinyl alcohol-based resin film containing dichroic substances, its thickness is less than 8 μm, the single transmittance is more than 43.0%, and the orthogonal absorbance per 1 μm thickness is more than 0.85 at a wavelength of 550 nm. Re(550) of the retardation layer is 100 nm to 190 nm, and Re(450)/Re(550) is 0.8 or more and less than 1. The angle formed by the slow axis of the retardation layer and the absorption axis of the polarizing film is 40°-50°.

Description

Polarizing plate with retardation layer and image display device using same

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

Background of the invention In recent years, image display devices representing liquid crystal display devices and electroluminescent (EL) display devices (such as organic EL display devices and inorganic EL display devices) have become popular rapidly. Image display devices typically use polarizers and retardation plates. In practical applications, a polarizing plate with a retardation layer integrated with a polarizing plate and a retardation plate is widely used (for example, Patent Document 1). The demand for thinner polarizing plates is also enhanced. In addition, in recent years, the demand for curved image display devices and/or flexible or bendable image display devices has increased, and further thinning and further improvements are required for polarizers and polarizers with retardation layers. softening. For the purpose of reducing the thickness of the polarizing plate with a retardation layer, the thickness of the protective layer of the polarizing film and the retardation film, which have a large influence on the thickness, are being reduced. However, if the protective layer and the retardation film are thinned, the influence of the shrinkage of the polarizing film will be relatively greater, and problems such as warping of the image display device and poor operability of the polarizing plate with the retardation layer will arise.

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

prior art literature patent documents Patent Document 1: Japanese Patent No. 3325560

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

Means for Solving the Problems The polarizing plate with a retardation layer of the present invention has a polarizing plate and a retardation layer, and the polarizing plate includes a polarizing film and a protective layer on at least one side of the polarizing film. The polarizing film is composed of a polyvinyl alcohol-based resin film containing a dichroic substance, with a thickness of 8 μm or less, a single transmittance of 43.0% or more, and an orthogonal absorbance of 0.85 or more per 1 μm thickness at a wavelength of 550 nm . Re(550) of the retardation layer is 100nm~190nm, Re(450)/Re(550) is more than 0.8 and less than 1, the angle formed by the slow axis of the retardation layer and the absorption axis of the polarizing film is 40° ~50°. In one embodiment, the above-mentioned protective layer is composed of a base material having an elastic modulus of 3000 MPa or more. In one embodiment, the total thickness of the polarizing plate with retardation layer is 90 μm or less, the front reflection hue is 3.5 or less, and the protective layer is made of a resin film with an elastic modulus of 3000 MPa or more. In one embodiment, the above-mentioned protective layer is formed of a cellulose triacetate resin film. In one embodiment, the polarizing plate includes the polarizing film and the protective layer disposed only on one side of the polarizing film, and the retardation layer is bonded to the polarizing film through an adhesive layer. In one embodiment, the retardation layer is formed of a polycarbonate-based resin film. In one embodiment, the retardation layer is formed of a polycarbonate-based resin film having a thickness of 40 μm or less. 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 of the polarizing film is 0.7˜2.00. In one embodiment, the orthogonal b value of the polarizing film is greater than -10 and not more than +10. In one embodiment, the orthogonal absorbance A ₅₅₀ of the polarizing film at a wavelength of 550 nm is 2.0 or more. In one embodiment, the above-mentioned polarizing plate with a retardation layer further has another retardation layer outside the above-mentioned retardation layer, and the refractive index characteristic of the another 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 substrate with a conductive layer outside the retardation layer. In one embodiment, the above-mentioned polarizing plate with a retardation layer is strip-shaped, the above-mentioned polarizing film has an absorption axis in the strip direction, and the above-mentioned retardation layer is 40°~50° with respect to the strip direction. An obliquely stretched film with a slow axis in the direction of the angle. In one embodiment, the polarizing plate with a retardation layer is wound in a roll shape. 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 above image display device is an organic electroluminescence display device or an inorganic electroluminescence display device.

Invention effect According to the present invention, a thin polarizing film having excellent optical characteristics can be obtained by combining the following methods: adding a halide (typically potassium iodide) to a polyvinyl alcohol (PVA)-based resin, including auxiliary stretching in the air and water 2-stage stretching, drying and shrinking with heated rolls. By using the above-mentioned polarizing film, it is possible to realize a polarizing plate with a retardation layer that is thin, has excellent handling properties, and has excellent optical characteristics.

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) The definitions of terms and symbols in this manual are as follows. (1) Refractive index (nx, ny, nz) "nx" is the refractive index in the direction where the in-plane refractive index becomes the largest (that is, the direction of the slow axis), "ny" is the refractive index in the direction that is perpendicular to the slow axis in the plane (that is, the direction of the fast axis), and " nz" is the refractive index in the thickness direction. (2) In-plane retardation (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 at 23°C with light having a wavelength of 550nm. Re(λ) can be calculated by the formula: Re(λ)=(nx-ny)×d when the thickness of the layer (thin film) is d(nm). (3) Phase difference in thickness direction (Rth) "Rth(λ)" is the retardation in the thickness direction measured with light of wavelength λnm at 23°C. For example, "Rth(550)" is the retardation in the thickness direction measured at 23°C with light with a wavelength of 550nm. Rth(λ) can be obtained by the formula: Rth(λ)=(nx-nz)×d when the thickness of the layer (film) is d(nm). (4) Nz coefficient The Nz coefficient can be obtained by Nz=Rth/Re. (5) angle When an angle is mentioned in this specification, the angle includes both clockwise and counterclockwise relative to a reference direction. Thus, for example, "45°" means ±45°.

A. Overall composition of 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 with retardation layer 100 of this embodiment has a polarizing plate 10 and a retardation layer 20 . The polarizing plate 10 includes: a polarizing film 11 , a first protective layer 12 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 . One of the first protective layer 12 and the second protective layer 13 can also be omitted according to the purpose. For example, when the retardation layer 20 can function as a protective layer of the polarizing film 11, the second protective layer 13 can also be omitted. In the embodiment of the present invention, the polarizing film is typically composed of a polyvinyl alcohol-based resin film containing a dichroic substance. The thickness of the polarizing film is 8 μm or less, the single transmittance is 43.0% or more, and the orthogonal absorbance per 1 μm thickness at a wavelength of 550 nm (hereinafter referred to as unit absorbance) is 0.85 or more.

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

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

The above-mentioned embodiments may be combined appropriately, and changes obvious in the industry may be added to the constituent elements of the above-mentioned embodiments. For example, the structure in which the isotropic substrate 60 with a conductive layer is provided outside the second retardation layer 50 may be replaced with an optically equivalent structure (for example, a laminate of a second retardation layer and a conductive layer).

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

The polarizing plate with a retardation layer of the present invention may be in the form of a thin sheet or a strip. The term "elongated" in this specification means an elongated shape that is sufficiently long relative to the width, including, for example, an elongated shape whose length is 10 times or more relative to the width, preferably 20 times or more. . The long polarizer with retardation layer can be rolled into a roll. When the polarizing plate with the retardation layer is long, both the polarizing plate and the retardation layer are long. In this case, the polarizing film preferably has an absorption axis in the longitudinal direction. The first retardation layer is preferably an obliquely stretched film having a slow axis in a direction at an angle of 40° to 50° with respect to the elongated direction. As long as the polarizing film and the first retardation layer have the above configuration, a polarizing plate with a retardation layer can be produced by roll-to-roll.

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

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

The total thickness of the polarizing plate with retardation layer is preferably not more than 140 μm, more preferably not more than 120 μm, more preferably not more than 100 μm, more preferably not more than 90 μm, and more preferably not more than 85 μm. The lower limit of the total thickness may be, for example, 30 μm. According to the embodiment of the present invention, it is possible to realize a polarizing plate with an extremely thin retardation layer as described above. The polarizing plate with retardation layer can have excellent flexibility and bending durability. The polarizing plate with a retardation layer is particularly suitable for application in curved image display devices and/or flexible or bendable image display devices. In addition, the total thickness of the polarizing plate with a retardation layer refers to the polarized light with a retardation layer after deducting the adhesive layer used to make the polarizing plate with a retardation layer adhere to an external adherend such as a panel or glass. The total thickness of all layers of the plate (that is, the total thickness of the polarizing plate with a retardation layer does not include the adhesive layer used to attach the polarizing plate with a retardation layer to adjacent components such as image display units and temporarily adhered to The thickness of the release film on its surface).

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

B. Polarizer B-1. Polarizing film As mentioned above, the polarizing film 11 has a thickness of 8 μm or less, a single transmittance of 43.0% or more, and a unit absorbance of 0.85 or more at a wavelength of 550 nm. Generally speaking, there is a trade-off relationship between the monomer transmittance and the unit polarization degree, so if the monomer transmittance is increased, the unit polarization degree will decrease, and if the unit polarization degree is increased, the monomer transmittance will decrease. Therefore, conventionally, it has been difficult to provide a thin polarizing film satisfying the optical characteristics of a single transmittance of 43.0% or higher and a unit polarization degree of 0.85 or higher at a wavelength of 550 nm for practical use. One of the characteristics of the present invention is to use a thin polarizing film having excellent optical properties such that the transmittance of a single element is 43.0% or more and the unit absorbance at a wavelength of 550 nm is 0.85 or more.

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

The polarizing film should exhibit absorption dichroism at any wavelength between 380nm and 780nm. The monomer transmittance of the polarizing film is preferably not more than 44.0%, more preferably not more than 43.5%. The degree of polarization of the polarizing film is preferably more than 99.990% and less than 99.998%. The above-mentioned monomer transmittance represents the Y value obtained by measuring with an ultraviolet-visible light spectrophotometer and correcting for optical performance. The above-mentioned degree of polarization is representatively based on the parallel transmittance Tp and the cross transmittance Tc obtained by using an ultraviolet-visible spectrophotometer and correcting the optical performance, and obtained through the following formula. Degree of polarization (%)={(Tp-Tc)/(Tp+Tc)} ^1/2 ×100

In one embodiment, the transmittance of a thin polarizing film below 8 μm is representative of 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 visible light spectrophotometry meter to measure. Due to the refractive index of the surface of the polarizing film and/or the refractive index of the surface of the protective film in contact with the air interface, the reflectance at the interface of each layer will change, resulting in a change in the measured value of the transmittance. Therefore, for example, when using a protective film with a refractive index other than 1.50, the measured value of the 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 corrected 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 at the interface between the protective film and the air layer. C=R ₁ -R ₀ R ₀ =((1.50-1) ² /(1.50+1) ² )×(T ₁ /100) R ₁ =((n ₁ -1) ² /(n ₁ +1) ² )×(T ₁ /100) Here, R ₀ is the reflectance on the transmission axis when using a protective film with a refractive index of 1.50, n ₁ is the refractive index of the protective film used, and T ₁ is the transmittance of the polarizing film Rate. For example, when using a substrate with a surface refractive index of 1.53 (cycloolefin-based film, hard-coated film, etc.) as a protective film, the correction amount C is about 0.2%. At this time, add 0.2% to the measured transmittance to convert the polarizing film with a surface refractive index of 1.53 into the transmittance when using a protective film with a refractive index of 1.50. In addition, after calculating according to the above formula, the change 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. Also, when the protective film has absorption other than surface reflection, appropriate correction can be made according to the amount of absorption.

The unit absorbance of the polarizing film at a wavelength of 550 nm is above 0.85, preferably above 0.9, preferably above 1.0, more preferably above 1.3, as described above. The upper limit of the unit absorbance may be 1.9, for example. The cross-absorbance A _λ at a wavelength of λ nm can be obtained by the following formula based on the above-mentioned cross-transmittance Tc. Orthogonal absorbance=log10(100/Tc) The unit absorbance at a wavelength of 550 nm can be obtained by dividing the above obtained orthogonal absorbance A ₅₅₀ by the thickness. In addition, the unit absorbance of the polarizing plate with retardation layer is substantially corresponding to the unit absorbance of the polarizing film. When the polarizing plate with retardation layer is used in organic electroluminescent (EL) display devices and inorganic EL display devices (such as quantum dot display devices), the orthogonal absorbance A ₅₅₀ can be, for example, more than 2.0 (for example, the unit absorbance is more than 0.85 and thickness of 2.5 μm or more). When the polarizing plate with a retardation layer is used in a liquid crystal display device, the crossed absorbance A ₅₅₀ can be, for example, 3.0 or more.

More ideally, the ratio (A ₄₇₀ /A ₆₀₀ ) 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 is 0.7 or more, preferably 0.75 or more, more preferably More than 0.80, especially more than 0.85. The ratio (A ₄₇₀ /A ₆₀₀ ) is preferably 2.00 or less, and is preferably 1.33 or less. If the ratio (A ₄₇₀ /A ₆₀₀ ) is within the above range, good polarization performance can be achieved in the entire range of visible light. Under the premise that the amount of iodine in the thin polarizing film is limited, it is difficult to control the above-mentioned unit absorbance and the ratio (A ₄₇₀ /A ₆₀₀ ) within the desired range by relying on the prior art, but the polarizing film used in the present invention can Keep both of them within the desired range.

In addition, the orthogonal b value of the polarizing film is, for example, greater than -10, preferably -7 or greater, more preferably -5 or greater. The orthogonal b value is preferably +10 or less, and preferably +5 or less. The orthogonal b value indicates the hue when the polarizing film (finally a polarizing plate with a retardation layer) is arranged in an orthogonal state. The larger the absolute value of the value, it means the orthogonal hue (black display of the image display device) ) looks more tinted. For example, when the orthogonal b value is lower than -10, that is, a black display will appear bluish, and the display performance will be degraded. That is, according to the embodiment of the present invention, a polarizing plate with a retardation layer capable of realizing an excellent hue in black display can be obtained. In addition, the orthogonal b value can be measured using a spectrophotometer represented by V-7100.

Any suitable polarizing film can be used as the polarizing film. Polarizing film can typically be produced using a laminate of more than two layers.

Specific examples of the polarizing film obtained using a laminate include a polarizing film obtained using a laminate of a resin base material and a PVA-based resin layer formed by coating on the resin base material. A polarizing film obtained by using a laminate of a resin substrate and a PVA-based resin layer coated and formed on the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate, and It is dried to form a PVA-based resin layer on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; and the laminate is stretched and dyed to make the PVA-based resin layer into a polarizing film. In this embodiment, stretching typically includes immersing the laminate in an aqueous solution of boric acid and stretching it. And, if necessary, the stretching may further include stretching the laminate in air at a high temperature (for example, 95° C. or higher) before stretching in a boric acid aqueous solution. The laminate of the obtained resin substrate/polarizing film can be directly used (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 the resin substrate/polarizing film and then Laminate any suitable protective layer according to the purpose and use it later. The details of the manufacturing method of the said polarizing film are described in Unexamined-Japanese-Patent No. 2012-73580, for example. In this specification, the entire description of the publication is incorporated by reference.

A method of manufacturing a 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 a long thermoplastic resin substrate to form a laminate; and, for the above-mentioned The laminate is sequentially subjected to air-assisted stretching, dyeing, underwater stretching, and drying shrinkage. The drying shrinkage is to heat the above-mentioned laminate while transporting it along the lengthwise direction, thereby shrinking it by 2% in the width direction. above. Thereby, a polarizing film with excellent optical properties can be provided, the thickness of which is less than 8 μm, the single transmittance is more than 43.0%, and the unit absorbance at a wavelength of 550 nm is more than 0.85. That is, by introducing auxiliary stretching, even when PVA is coated on a thermoplastic resin, the crystallinity of PVA can be improved, and high optical characteristics can be achieved. Also, at the same time, by improving the orientation of PVA in advance, it is possible to prevent problems such as decrease in orientation or dissolution of PVA when immersed in water in the subsequent dyeing step or stretching step, and achieve high optical characteristics. In addition, when the PVA-based resin layer is immersed in a liquid, the disorder of polyvinyl alcohol molecules and the decrease in orientation can be suppressed more than when the PVA-based resin layer does not contain halides. Therefore, the optical characteristics of the polarizing film obtained through the processing steps of immersing the laminate in liquid, such as dyeing processing and underwater stretching processing, can be improved. In addition, the optical properties can be improved by shrinking the laminate in the width direction through drying shrinkage treatment.

B-2. Protective layer The first protective layer 12 and the second protective layer 13 are each formed of any appropriate thin film that can be used as a protective layer of a polarizing film. Specific examples of the material constituting the main component of the film include cellulose-based resins such as cellulose triacetate (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyamide-based resins, etc. Imine-based, polyether-based, polystyrene-based, polystyrene-based, polynorbornene-based, polyolefin-based, (meth)acrylic-based and acetate-based transparent resins, etc. Further, thermosetting resins such as (meth)acrylic, urethane, (meth)acrylate urethane, epoxy, and silicone, or ultraviolet curable resins are also mentioned. Other examples include glassy polymers such as siloxane polymers. Furthermore, a polymer film described in JP-A-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 the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain can be used, such as A resin composition having an alternating copolymer of isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer may be mentioned. The polymer film can be, for example, an extruded product of the above-mentioned resin composition. In one embodiment, the protective layer (particularly, the protective layer on the viewing side) contains a TAC-based resin. By using a TAC-based resin film as a protective layer, the bending durability can be improved.

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. Therefore, the first protective layer 12 may also be subjected to surface treatments such as hard coating treatment, anti-reflection treatment, anti-adhesion treatment, and anti-glare treatment as required. And/or, the first protective layer 12 may also be treated to improve visibility through polarized sunglasses (typically, imparting (elliptical) polarizing function, imparting ultra-high retardation) as required. By performing such processing, excellent visibility can be achieved even when a displayed image is viewed through a polarized lens such as polarized sunglasses. Therefore, the polarizing plate with a retardation layer can also be suitably used in image display devices that can be used outdoors.

The thickness of the first protective layer is preferably 5 μm to 80 μm, preferably 10 μm to 40 μm, more preferably 10 μm to 35 μm. In addition, when surface treatment is applied, 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 isotropic optically. "Optically isotropic" in this specification means that the retardation Re(550) in the plane is 0nm~10nm, and the retardation Rth(550) in the thickness direction is -10nm~+10nm. In one embodiment, the second protective layer 13 is a retardation layer having any 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, more preferably 10 μm to 30 μm. From the viewpoint of thinning and reducing weight, it is desirable 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 including: forming a polyvinyl alcohol-based resin layer (PVA-based resin layer) on one side of a long thermoplastic resin substrate to form a laminate, and the polyvinyl alcohol-based resin layer Contains halides and polyvinyl alcohol-based resins (PVA-based resins); and, the laminate is sequentially subjected to air-assisted stretching treatment, dyeing treatment, underwater stretching treatment, and drying shrinkage treatment, and the drying shrinkage treatment is conveyed along the longitudinal direction The laminate is heated to shrink by 2% or more 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 done with heating rollers, and the temperature of the heating rollers should be 60°C~120°C. The shrinkage rate in the width direction obtained by drying and shrinking the laminate should be more than 2%. According to the production method, the polarizing film described in the above item B-1 can be obtained. In particular, a polarizing film with excellent optical characteristics (typically, the transmittance of a single substance and the unit polarization degree at a wavelength of 550 nm) can be obtained by the following method: After producing a laminate including a PVA-based resin layer containing a halide, The stretching of the above-mentioned laminate is carried out in multi-stage stretching including aerial auxiliary stretching and underwater stretching, and then the stretched laminate is heated with a heating roller.

B-3-1. Fabrication of laminated body Any appropriate method can be adopted for the method of producing the laminate of the thermoplastic resin base material and the PVA-based resin layer. Preferably, a coating solution containing halides and 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 mentioned above, the halide content in the PVA-based resin layer is preferably 5 to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.

Any appropriate method can be adopted for the coating method of the coating liquid. Examples thereof include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, knife coating (comma coating, etc.). The coating and drying temperature of the above-mentioned coating solution 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, the thermoplastic resin substrate can be subjected to surface treatment (such as corona treatment, etc.), and an easy-adhesive layer can also be formed on the thermoplastic resin substrate. By performing the above treatment, the adhesion between the thermoplastic resin substrate and the PVA-based resin layer can be improved.

B-3-1-1. Thermoplastic resin substrate The thickness of the thermoplastic resin substrate is preferably 20 μm to 300 μm, 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 is larger than 300 μm, for example, it may take a long time for the thermoplastic resin substrate to absorb water in the underwater stretching treatment described later, and there may be a possibility that an excessive load will be applied to the stretching.

The water absorption rate of the thermoplastic resin substrate is preferably above 0.2%, more preferably above 0.3%. The thermoplastic resin substrate absorbs water, and the water acts as a plasticizer for plasticization. As a result, the elongation stress can be greatly reduced and high-magnification elongation can be achieved. On the other hand, the water absorption of the thermoplastic resin substrate is preferably 3.0% or less, more preferably 1.0% or less. By using such a thermoplastic resin base material, it is possible to prevent problems such as deterioration of the appearance of the obtained polarizing film due to a marked decrease in the dimensional stability of the thermoplastic resin base material during production. It can also prevent the substrate from breaking when it is stretched in water, or the PVA-based resin layer from peeling off from the thermoplastic resin substrate. In addition, the water absorption rate of the thermoplastic resin substrate can be adjusted, for example, by introducing a modifying group into the constituent material. The water absorption is a value obtained in accordance with JIS K 7209.

The glass transition temperature (Tg) of the thermoplastic resin substrate is preferably below 120°C. 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, in consideration of plasticizing the thermoplastic resin substrate with water and good underwater stretching, it is more preferably below 100°C, more preferably below 90°C. On the other hand, the glass transition temperature of the thermoplastic resin substrate is preferably 60° C. or higher. By using such a thermoplastic resin substrate, it is possible to prevent defects such as deformation of the thermoplastic resin substrate (such as unevenness, drooping or wrinkling, etc.) when coating and drying the coating liquid containing the above-mentioned PVA-based resin, Thereby, a laminated body was produced satisfactorily. In addition, the stretching of the PVA-based resin layer can be favorably performed at an appropriate temperature (for example, about 60° C.). In addition, the glass transition temperature of the thermoplastic resin substrate can be adjusted by heating, for example, a crystallization material capable of introducing a modifying group into the constituent material. The glass transition temperature (Tg) is a value calculated based on JIS K 7121.

Any appropriate thermoplastic resin can be used as 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 norcamphene-based resins, olefin-based resins such as polypropylene, polyamide-based resins, polycarbonate-based resins, and Other copolymer resins, etc. Among these, norcamphene-based resins and amorphous polyethylene terephthalate-based resins are preferable.

In one embodiment, an amorphous (uncrystallized) polyethylene terephthalate resin is preferably used. Among them, it is particularly preferable to use an amorphous (difficult to crystallize) polyethylene terephthalate resin. Specific examples of amorphous polyethylene terephthalate resins include copolymers further containing isophthalic acid and/or cyclohexane dicarboxylic acid as dicarboxylic acids, or copolymers further containing cyclohexane dicarboxylic acid. Dimethanol or diethylene glycol as a copolymer of glycol.

In a preferred embodiment, the thermoplastic resin substrate is composed of a polyethylene terephthalate resin having an isophthalic acid unit. This is because such a thermoplastic resin substrate has extremely excellent elongation and can suppress crystallization during elongation. We speculate that this is due to the large deflection imparted to the main chain by the introduction of isophthalic acid units. The polyethylene terephthalate resin has a terephthalic acid unit and an ethylene glycol unit. The content ratio of the isophthalic acid unit is preferably at least 0.1 mol %, more preferably at least 1.0 mol %, based on the total of all repeating units. This is due to the fact that a thermoplastic resin base material with 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, based on the total of all repeating units. By setting the above-mentioned content ratio, the degree of crystallization can be favorably increased in the drying shrinkage treatment described later.

The thermoplastic resin substrate may also have been pre-stretched (before forming the PVA-based resin layer). In one embodiment, it is extended along the transverse direction of the elongated thermoplastic resin substrate. The lateral direction is preferably a direction perpendicular to the extending direction of the laminate described later. In addition, the term "orthogonal" in this specification also includes the case of being 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 stretching temperature of the thermoplastic resin substrate is preferably Tg-10°C~Tg+50°C relative to the glass transition temperature (Tg). The elongation ratio of the thermoplastic resin substrate should be 1.5 times to 3.0 times.

Any appropriate method can be used for the stretching method of the thermoplastic resin substrate. Specifically, it can be extended from a fixed end, or can be extended from a free end. The extension method can be dry or wet. The stretching of the thermoplastic resin substrate can be carried out in one stage or in multiple stages. When it is carried out in multiple stages, the above-mentioned elongation ratio is the product of the elongation ratios of each stage.

B-3-1-2. Coating solution 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 compound and the above-mentioned PVA-based resin in a solvent. Examples of the solvent include water, dimethylsulfide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, ethylene glycol, and the like. Amines such as diamine and diethylenetriamine. These may be used alone or in combination of two or more. Among them, water is the best. The concentration of the PVA-based resin in the solution is preferably 3 to 20 parts by weight relative to 100 parts by weight of the solvent. As long as it is the above-mentioned resin concentration, a uniform coating film can be formed in close contact with the thermoplastic resin substrate. The halide content in the coating liquid is preferably 5 to 20 parts by weight relative to 100 parts by weight of the PVA-based resin.

Additives may also be blended in the coating solution. Examples of additives include plasticizers and surfactants. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. The surfactant may, for example, be a nonionic surfactant. These can be used to further improve the uniformity, dyeability, and extensibility of the obtained PVA-based resin layer.

Any appropriate resin can be used as the above-mentioned PVA-based resin. Examples thereof include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymer can be obtained by saponifying ethylene-vinyl acetate copolymer. The saponification degree of the PVA-based resin is usually 85 mol %-100 mol %, preferably 95.0 mol %-99.95 mol %, more preferably 99.0 mol %-99.93 mol %. The degree of saponification is obtained in accordance with JIS K 6726-1994. A polarizing film excellent in durability can be obtained by using a PVA-based resin having such a degree of saponification. When the degree of saponification is too high, gelation may occur.

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

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

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

Generally speaking, the stretching of the PVA-based resin layer will increase the orientation of the polyvinyl alcohol molecules in the PVA resin layer, but if the stretched PVA-based resin layer is immersed in a liquid containing water, there will be polyethylene The situation where the alignment of alcohol molecules is disordered and the orientation is reduced. In particular, when stretching a laminate of a thermoplastic resin base material and a PVA-based resin layer in boric acid water, the laminate is stretched in boric acid water at a relatively high temperature in order to stabilize the stretching of the thermoplastic resin base material. The tendency to decrease the degree of orientation is significant. For example, the stretching of a PVA film monomer in boric acid water is generally carried out at 60°C. In contrast, the stretching of a laminate of A-PET (thermoplastic resin substrate) and PVA-based resin layer is at 70°C The temperature before and after is carried out at a higher temperature. At this time, the orientation of the PVA at the beginning of stretching will decrease in the stage before it is raised by stretching in water. In this regard, after making a laminate of a PVA-based resin layer containing a halide and a thermoplastic resin substrate, the laminate is stretched at a high temperature in air (assisted stretching) before being stretched in boric acid water, thereby facilitating post-stretching. 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. Thereby, the optical characteristic of the polarizing film obtained through the process step which immerses a laminated body in liquid, such as a dyeing process and an underwater stretching process, can be improved.

B-3-2. Air Assisted Extended Processing In particular, in order to obtain high optical properties, the method of combining dry stretching (assisted stretching) and boric acid underwater stretching is selected as a two-stage stretching method. Like the two-stage stretching method, by introducing auxiliary stretching, the stretching can be carried out while suppressing the crystallization of the thermoplastic resin base material, so as to solve the problem of the decrease in extensibility caused by the excessive crystallization of the thermoplastic resin base material in the subsequent stretching in boric acid water problem, so that the laminate can be extended at a higher magnification. In addition, when applying PVA-based resin to a thermoplastic resin substrate, in order to suppress the influence of the glass transition temperature of the thermoplastic resin substrate, the coating temperature must be lower than that of the case where the PVA-based resin is applied to a general metal roller. If it is lower, as a result, the crystallization of the PVA-based resin becomes relatively low, resulting in a problem that sufficient optical properties cannot be obtained. In contrast, by introducing auxiliary stretching, the crystallinity of the PVA-based resin can be improved even when the PVA-based resin is coated on a thermoplastic resin, and high optical characteristics can be achieved. Also, at the same time, improving the orientation of the PVA-based resin in advance can prevent problems such as a decrease in orientation or dissolution of the PVA-based resin when it is immersed in water in the subsequent dyeing step or stretching step, and high optical characteristics can be achieved.

The stretching method of aerial auxiliary stretching can be fixed end stretching (such as stretching method using a tenter stretching machine), or free end stretching (such as the method of uniaxial stretching the laminated body through rollers 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 process includes a heating roll stretching step of extending the above-mentioned layered product in the longitudinal direction while utilizing a peripheral speed difference between the heating rolls. The in-air stretching process represents the upper line including a zone stretching step and a heating roller stretching step. In addition, the order of the zone stretching step and the heating roller stretching step is not limited, and the zone stretching step or the heating roller stretching step may be performed first. The region extension step may also be omitted. In one embodiment, the region stretching step and the heating roll stretching step are performed sequentially. In another embodiment, the end of the film is held in a tenter stretching machine, and the distance between the tenters is increased in the traveling direction to stretch (the increase in the distance between the tenters is the stretching ratio). At this time, the distance of the tenter in the width direction (vertical direction with respect to the traveling direction) is set so as to be arbitrarily close. Preferably, it can be set as an extension ratio relative to the flow direction to use the extension of the free end for approaching. When the free end is extended, it is calculated as the shrinkage rate in the width direction = (1/extension ratio) ^1/2 .

Aerial assisted extension can be performed in one phase or in multiple phases. When it is carried out in multiple stages, the extension ratio is the product of the extension ratios of each stage. The direction of extension in aerial auxiliary extension should be approximately the same as that of underwater extension.

The extension magnification of the auxiliary extension in the air should be 2.0 times to 3.5 times. The maximum elongation magnification when combining aerial auxiliary elongation and underwater elongation is preferably 5.0 times or more, more preferably 5.5 times or more, and more preferably 6.0 times or more relative to the original length of the laminate. The "maximum elongation ratio" in this specification means the elongation ratio immediately before the laminate is broken, and is a value 0.2 lower than the value after separately confirming the elongation ratio at which the laminate is broken.

The stretching temperature of the air-assisted stretching can be set to any appropriate value according to the forming material and stretching method of the thermoplastic resin substrate. The stretching temperature is preferably above the glass transition temperature (Tg) of the thermoplastic resin base material, more preferably above the glass transition temperature (Tg) of the thermoplastic resin base material (Tg)+10°C, especially above Tg+15°C. On the other hand, the upper limit of the stretching temperature is preferably 170°C. Stretching at the above-mentioned temperature suppresses rapid progress of crystallization of the PVA-based resin, thereby suppressing problems caused by the crystallization (for example, interruption of orientation of the PVA-based resin layer due to stretching). The crystallization index of the PVA-based resin after air-assisted stretching is preferably 1.3-1.8, more preferably 1.4-1.7. The crystallization index of the PVA-based resin can be measured by the ATR method with a Fourier transform infrared spectrophotometer. Specifically, the measurement was carried out using polarized light as the measurement light, and the crystallization index was calculated according to the following formula using the intensities of 1141 cm ^-1 and 1440 cm ^-1 of the obtained spectrum. Crystallization index = ( _IC /I _R ) Where, _IC : the intensity at 1141 cm ^-1 when measuring light is incident and measured, and I _R : the intensity at 1440 cm ^-1 when measuring light is incident and measured.

B-3-3. Insoluble treatment Insolubilization treatment is performed after the air-assisted stretching treatment and before the underwater stretching treatment or dyeing treatment as necessary. The above-mentioned insolubilization treatment is typically carried out by immersing the PVA-based resin layer in a boric acid aqueous solution. By performing insolubilization treatment, water resistance can be imparted to the PVA-based resin layer, and the orientation of 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 liquid temperature of the insoluble bath (boric acid aqueous solution) should be 20°C~50°C.

B-3-4. Dyeing treatment The above dyeing process is typically performed by dyeing the PVA-based resin layer with a dichroic substance (typically iodine). Specifically, it is performed by adsorbing iodine on the PVA-based resin layer. Examples of the adsorption method include: a method of immersing the PVA resin layer (laminate) in a dyeing solution containing iodine, a method of applying the dyeing solution to the PVA resin layer, and spraying the dyeing solution onto the PVA. The method on the resin layer, etc. A method of immersing the laminate in a dyeing solution (dyeing bath) is preferable. Because it can absorb iodine well.

The above-mentioned dyeing solution is preferably iodine aqueous solution. The blending amount of iodine is preferably 0.05 to 0.5 parts by weight relative to 100 parts by weight of water. In order to increase the solubility of iodine in water, it is advisable to mix iodide in the iodine aqueous solution. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide and the like. Among these, potassium iodide is preferable. The blending amount of iodide is preferably 0.1 to 10 parts by weight, more preferably 0.3 to 5 parts by weight, relative to 100 parts by weight of water. In order to inhibit the dissolution of PVA-based resin, the liquid temperature of the dyeing solution during dyeing should be 20°C~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.

Dyeing conditions (concentration, liquid temperature, and immersion time) can be set so that the monomer transmittance and the unit absorbance at a wavelength of 550 nm of the finally obtained polarizing film become desired values. The dyeing condition is preferably to use an iodine aqueous solution as the dyeing solution, and set the content ratio of iodine and potassium iodide in the iodine aqueous solution to 1:5-1:20. 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 characteristics can be obtained.

When the dyeing treatment is performed after immersing the laminate in a treatment bath containing boric acid (typically insolubilization treatment), the boric acid contained in the treatment bath will be mixed into the dyeing bath, and the concentration of boric acid in the dyeing bath will be changed. As a result, dyeing properties may become unstable as a result of time changes. In order to suppress destabilization of dyeability as described above, the upper limit of the concentration of boric acid in the dyeing bath is adjusted to preferably 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 concentration of boric acid in the dyeing bath is preferably 0.1 part by weight, more preferably 0.2 part by weight, and still more preferably 0.5 part by weight with respect to 100 parts by weight of water. In one embodiment, the dyeing treatment is performed using a dyeing bath premixed with boric acid. Thereby, the rate at which the boric acid concentration changes when the boric acid in the treatment bath mentioned above is mixed into the dyeing bath can be reduced. The amount of boric acid mixed in the dyeing bath in advance (that is, the content of boric acid not derived from the above-mentioned treatment bath) is preferably 0.1 to 2 parts by weight, more preferably 0.5 parts by weight, relative to 100 parts by weight of water ~1.5 parts by weight.

B-3-5. Cross-linking treatment After the dyeing treatment and before the stretching treatment in water, a crosslinking treatment is performed as necessary. Typically, the above-mentioned crosslinking treatment can be performed by immersing the PVA-based resin layer in a boric acid aqueous solution. By performing cross-linking treatment, water resistance can be imparted to the PVA-based resin layer, and the orientation of 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 carrying out the crosslinking treatment after the above-mentioned dyeing treatment, it is preferable to further blend iodide. By mixing iodide, the elution of iodine adsorbed to the PVA-based resin layer can be suppressed. The blending amount of iodide is preferably 1 to 5 parts by weight relative to 100 parts by weight of water. Specific examples of iodide are as described above. The liquid temperature of the cross-linking bath (boric acid aqueous solution) should be 20°C~50°C.

B-3-6. Extended treatment in water The underwater stretching treatment is performed by immersing the laminate in a stretching bath. By stretching in water, it can be stretched at a temperature lower than the glass transition temperature (typically about 80°C) of the above-mentioned thermoplastic resin substrate or PVA-based resin layer, and can suppress the crystallization of the PVA-based resin layer at the same time Perform high-magnification extensions. As a result, a polarizing film with excellent optical properties can be produced.

Any appropriate method can be used for the stretching method of the laminate. Specifically, it may be a fixed end extension, or a free end extension (for example, a method of uniaxially extending a laminate through rollers with different circumferential speeds). Preferably a free end extension is selected. The extension of the laminate may be performed in one step or in multiple steps. When it is carried out in multiple stages, the elongation ratio (maximum elongation ratio) of the laminate described later is the product of the elongation ratios of each stage.

The underwater stretching is preferably carried out by immersing the laminate in an aqueous solution of boric acid (boric acid underwater stretching). By using an aqueous solution of boric acid as a stretching bath, the PVA-based resin layer can be given rigidity to withstand tension during stretching and water resistance that is insoluble in water. Specifically, boric acid generates tetrahydroxyboric acid anion in aqueous solution, which can cross-link with PVA-based resin through hydrogen bonding. As a result, rigidity and water resistance can be imparted to the PVA-based resin layer, and good stretching 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 as a solvent. The concentration of boric acid relative to 100 parts by weight of water is preferably 1 to 10 parts by weight, more preferably 2.5 to 6 parts by weight, especially preferably 3 to 5 parts by weight. By setting the concentration of boric acid 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, an aqueous solution obtained by dissolving a boron compound such as borax, glyoxal, glutaraldehyde, etc. in a solvent other than boric acid or borate can also be used.

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

The stretching temperature (liquid temperature of the stretching bath) is preferably 40°C~85°C, more preferably 60°C~75°C. As long as it is the above-mentioned temperature, the dissolution of the PVA-based resin layer can be suppressed, and at the same time, high-magnification stretching can be achieved. Specifically, as mentioned above, considering 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., good stretching may not be possible even considering plasticizing the thermoplastic resin base material with water. On the other hand, the higher the temperature of the stretching bath, the higher the solubility of the PVA-based resin layer, and it may not be possible to obtain excellent optical properties. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.

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

B-3-7. Drying shrinkage treatment The above-mentioned drying shrinkage treatment can be performed by heating the entire area by heating the region, or by heating the conveying roller (so-called use of a heating roller) (heating roller drying method). It is preferable to use both. By drying with a heating roll, heating curl of the laminate can be effectively suppressed, and a polarizing film having an excellent appearance can be produced. Specifically, by drying the laminated body along the heating roll, the crystallization of the above-mentioned thermoplastic resin substrate can be effectively promoted to increase the degree of crystallization, even at a relatively low drying temperature, It can still increase the crystallinity of thermoplastic resin substrates well. As a result, the rigidity of the thermoplastic resin substrate is increased to be able to withstand shrinkage of the PVA-based resin layer due to drying, thereby suppressing curling. Moreover, by using the heating roller, drying can be performed while maintaining the laminated body in a flat state, so not only the occurrence of curls but also the occurrence of wrinkles can be suppressed. At this time, the laminated body can be shrunk in the width direction through drying shrinkage treatment, so as to improve the optical properties. It is because it can effectively improve the orientation of PVA and PVA/iodine complexes. The shrinkage rate in the width direction obtained by drying and shrinking the laminate is preferably 1% to 10%, more preferably 2% to 8%, and especially preferably 4% to 6%. By using the heating roller, the laminate can be continuously shrunk in the width direction while being conveyed, and high productivity can be achieved.

Fig. 3 is a schematic view showing an example of drying shrinkage treatment. In the drying shrinkage process, the laminated body 200 is dried while being conveyed by conveying rollers R1 to R6 and guide rollers G1 to G4 heated to a predetermined temperature. In the example shown in the drawing, the transfer 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 transfer rollers R1 to R6 may be arranged so as to continuously heat only the laminated body 200 One of the sides (such as thermoplastic resin substrate side).

The drying conditions can be controlled by adjusting the heating temperature of the conveying roller (temperature of the heating roller), the number of the heating roller and the contact time with the heating roller, etc. The temperature of the heating roller is preferably 60°C~120°C, more preferably 65°C~100°C, especially 70°C~80°C. While the degree of crystallization of the thermoplastic resin can be increased favorably and curling can be suppressed favorably, an optical layered body excellent in durability can be manufactured. 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 laminate and the heating roller is preferably 1 second to 300 seconds, more preferably 1 to 20 seconds, more preferably 1 to 10 seconds.

The heating roller can be installed in a heating furnace (such as an oven), or it can be installed in a general production line (at room temperature). It should be installed in a heating furnace with an air supply mechanism. By combining drying with heating rolls and hot air drying, rapid temperature changes between heating rolls can be suppressed, and shrinkage in the width direction can be easily controlled. The temperature of hot air drying should be 30℃~100℃. Moreover, the hot air drying time should be 1 second to 300 seconds. The wind speed of hot air should be around 10m/s~30m/s. In addition, the wind speed refers to the wind speed in the heating furnace, which can be measured by a mini fan-type digital anemometer.

B-3-8. Other processing It is preferable to carry out the washing treatment after the stretching treatment in water and before the drying shrinkage treatment. Typically, the cleaning treatment described above can be performed by immersing the PVA-based resin layer in an aqueous potassium iodide solution.

C. The first retardation layer The first retardation layer 20 may have any appropriate optical properties and/or mechanical properties depending on the purpose. The first retardation layer 20 typically has a slow axis. In one embodiment, the angle θ formed by the slow axis of the first retardation layer 20 and the absorption axis of the polarizing film 11 is, as mentioned above, 40°-50°, preferably 42°-48°, more preferably about 45° . As long as the angle θ is within the above range, by making the first retardation layer into a λ/4 plate as described later, it is possible to obtain a retardation layer with very excellent circular polarization characteristics (resulting in very excellent antireflection characteristics). polarizer.

The first retardation layer preferably exhibits a relationship of nx>ny≧nz in terms of refractive index characteristics. Typically, the first retardation layer is provided to impart antireflection properties to the polarizing plate, and can function as a λ/4 plate in one embodiment. In this case, the in-plane retardation Re(550) of the first retardation layer is preferably 100 nm to 190 nm, preferably 110 nm to 170 nm, more preferably 130 nm to 160 nm. In addition, here, "ny=nz" is not only the case where ny and nz are completely the same, but also the case where they are substantially the same. Therefore, ny>nz may be the case in the range which does not impair the effect of this invention.

The Nz coefficient of the first retardation layer is preferably 0.9~3, more preferably 0.9~2.5, more preferably 0.9~1.5, especially preferably 0.9~1.3. By satisfying the above relationship, when the obtained polarizing plate with a retardation layer is used in an image display device, a very excellent reflection hue can be achieved.

The first retardation layer can exhibit the inverse dispersion wavelength characteristic in which the retardation value increases with the wavelength of the measuring light, can also exhibit the normal wavelength dispersion characteristic in which the retardation value becomes smaller with the wavelength of the measuring light, and can exhibit the retardation value hardly changing. Flat wavelength dispersion characteristics that vary with the wavelength of the measurement light. In one embodiment, the first retardation layer exhibits reverse dispersion wavelength characteristics. In this case, Re(450)/Re(550) of the retardation layer is preferably not less than 0.8 and less than 1, more preferably not less than 0.8 and not more than 0.95. With such a configuration, very excellent antireflection characteristics can be realized.

The absolute value of the photoelastic coefficient contained in the first retardation layer is preferably not more than 2×10 ^-11 m ² /N, preferably 2.0×10 ^-13 m ² /N to 1.5× ^{10 -11} m ² /N, more preferably The resin is 1.0×10 ^-12 m ² /N~1.2×10 ^-11 m ² /N. As long as the absolute value of the photoelastic coefficient is within the above range, it is difficult to change the phase difference when shrinkage stress is generated during heating. As a result, thermal unevenness of the obtained image display device can be prevented favorably.

The first retardation layer is typically formed of a stretched film of a resin film. In one embodiment, the thickness of the first retardation layer is preferably 70 μm or less, and preferably 45 μm˜60 μm. As long as the thickness of the first retardation layer is within the above-mentioned range, curling at the time of heating can be well suppressed, and curling at the time of bonding can be well adjusted. Also, as described later, in the embodiment in which the first retardation layer is made of a polycarbonate resin film, the thickness of the first retardation layer is preferably 40 μm or less, preferably 10 μm to 40 μm, more preferably 20 μm to 30 μm. The first retardation layer is composed of a polycarbonate resin film having the above-mentioned thickness, which can suppress curling and contribute to improvement of bending durability and reflective hue.

The first retardation layer 20 may be formed of any appropriate resin film that satisfies the above characteristics. Representative examples of the resin include polycarbonate resins, polyester carbonate resins, polyester resins, polyvinyl acetal resins, polyarylate resins, cyclic olefin resins, cellulose resins, Polyvinyl alcohol-based resins, polyamide-based resins, polyimide-based resins, polyether-based resins, polystyrene-based resins, and acrylic resins. These resins may be used alone or in combination (for example, blending, copolymerization). When the first retardation layer is formed of a resin film exhibiting inverse dispersion wavelength characteristics, polycarbonate resin or polyester carbonate resin (hereinafter sometimes simply referred to as polycarbonate resin) can be suitably used.

As long as the effects of the present invention can be obtained, any appropriate polycarbonate-based resin can be used as the above-mentioned polycarbonate-based resin. For example, the polycarbonate-based resin comprises a structural unit derived from a stilbene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and a structural unit derived from a compound selected from alicyclic diol, alicyclic dimethanol, A structural unit of at least one dihydroxy compound selected from the group consisting of di, tri, or polyethylene glycol, alkylene glycol, or spiroglycerin. Preferably, the polycarbonate resin comprises a structural unit derived from a stilbene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and a structural unit derived from alicyclic dimethanol and/or derived from di, A structural unit of tri- or polyethylene glycol; more preferably, a structural unit derived from a terpene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and a structure derived from di-, tri-, or polyethylene glycol unit. The polycarbonate resin may also contain structural units derived from other dihydroxy compounds as needed. In addition, details of polycarbonate-based resins that can be suitably used in the present invention are described in, for example, JP-A-2014-10291, JP-A-2014-26266, JP-A-2015-212816, JP-A-2015 -212817 bulletin and JP2015-212818 bulletin, and this description refers to the description as a reference.

The glass transition temperature of the polycarbonate-based resin is preferably 110°C to 150°C, and preferably 120°C to 140°C. If the glass transition temperature is too low, the heat resistance tends to deteriorate, which may cause dimensional changes after film formation, or may reduce the image quality of the obtained organic EL panel. If the glass transition temperature is too high, the forming stability at the time of film forming may deteriorate, or the transparency of the film may be impaired. In addition, the glass transition temperature can be calculated|required based on JISK 7121 (1987).

The molecular weight of the aforementioned polycarbonate-based resin can be represented by a reduced viscosity. The reduced viscosity is measured by Ubbelohde viscosity tube at a temperature of 20.0℃±0.1℃ after the concentration of polycarbonate is precisely adjusted to 0.6g/dL by using dichloromethane as a solvent. The lower limit of the reduced viscosity is usually preferably 0.30dL/g, and more preferably 0.35dL/g or more. The upper limit of the reduced viscosity is usually preferably 1.20dL/g, preferably 1.00dL/g, more preferably 0.80dL/g. If the reduced viscosity is less than the aforementioned lower limit, there may be a problem that the mechanical strength of the molded product decreases. On the other hand, if the reduced viscosity exceeds the above-mentioned upper limit, the fluidity during molding may be lowered, and problems such as lowered productivity or moldability may arise.

As the polycarbonate-based resin film, a commercially available film can also be used. Specific examples of commercially available products include "PURE-ACE WR-S", "PURE-ACE WR-W", "PURE-ACE WR-M" manufactured by Teijin Corporation, and "NRF" manufactured by Nitto Denko Corporation. ".

The first retardation layer 20 can be obtained, for example, by stretching a film formed of the above-mentioned polycarbonate-based resin. As a method of forming a film from a polycarbonate-based resin, any appropriate molding method can be used. Specific examples include: compression molding method, transfer molding method, injection molding method, extrusion molding method, blow molding method, powder molding method, FRP molding method, casting coating method (such as casting method), calender molding method , hot pressing method, etc. Rather, it is preferably an extrusion molding method or a casting coating method. This is because the smoothness of the obtained film can be improved, thereby obtaining good optical uniformity. The molding conditions can be appropriately set according to the resin composition or type to be used, desired properties of the retardation film, and the like. In addition, as mentioned above, many film products of polycarbonate-based resins are sold on the market, so the commercially available films can be used for stretching treatment as they are.

The thickness of the resin film (unstretched film) can be set to any appropriate value in accordance with the desired thickness of the first retardation layer, desired optical characteristics, stretching conditions described later, and the like. It is preferably 50 μm to 300 μm.

Any suitable stretching method and stretching conditions (eg, stretching temperature, stretching ratio, stretching direction) can be used for the above-mentioned stretching. Specifically, various stretching methods such as free-end extension, fixed-end extension, free-end contraction, and fixed-end contraction may be used alone, or may be used simultaneously or sequentially. Regarding the extending direction, it can also be carried out in various directions or dimensions such as the longitudinal direction, the width direction, the thickness direction, and the oblique direction. The stretching temperature is preferably Tg-30°C to Tg+60°C relative to the glass transition temperature (Tg) of the resin film, and is preferably Tg-10°C to Tg+50°C.

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

In one embodiment, the retardation film can be produced by uniaxially stretching a resin film or uniaxially stretching a fixed end. A specific example of uniaxial stretching at the fixed end is a method of stretching the resin film in the width direction (horizontal direction) while moving in the longitudinal direction. The elongation ratio should be 1.1 times to 3.5 times.

In another embodiment, the retardation film can be produced by continuously stretching a long resin film obliquely in a direction forming the above-mentioned angle θ with respect to the longitudinal direction. By adopting oblique stretching, a long stretched film with an orientation angle of angle θ (with a slow axis in the direction of angle θ) can be obtained with respect to the long side direction of the film, for example, it can be rolled when it is laminated with a polarizing film To the roll, which can simplify the manufacturing steps. In addition, the angle θ may be the angle formed by the absorption axis of the polarizing film and the slow axis of the retardation layer in the polarizing plate with a retardation layer. As mentioned above, the angle θ is preferably 40° to 50°, preferably 42° to 48°, more preferably about 45°.

Stretching machines used for oblique stretching include tenter-type stretching machines, for example, which add conveying force, stretching force, or pulling force at different speeds in the horizontal and/or vertical directions. The tenter stretching machine includes a horizontal uniaxial stretching machine, a simultaneous biaxial stretching machine, and the like, and any suitable stretching machine can be used as long as the elongated resin film can be continuously stretched obliquely.

By properly controlling the left and right speeds in the stretching machine above, a retardation layer (essentially a strip-shaped retardation film) having the above-mentioned desired in-plane retardation and a slow axis in the above-mentioned desired direction can be obtained. ).

The stretching temperature of the above-mentioned film will vary depending on the desired in-plane retardation value and thickness of the retardation layer, the type of resin used, the thickness of the film used, and the stretching ratio. Specifically, the stretching temperature is preferably Tg-30°C~Tg+30°C, more preferably Tg-15°C~Tg+15°C, most preferably Tg-10°C~Tg+10°C. By stretching at the above temperature, a first retardation layer having properties suitable for the present invention can be obtained. In addition, Tg refers to the glass transition temperature of the constituent materials of the thin film.

D. The second retardation layer As mentioned above, the second retardation layer may be a so-called positive C-plate whose refractive index characteristic exhibits the relationship of nz>nx=ny. By using the positive C plate as the second retardation layer, oblique reflection can be well prevented, and the antireflection 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 preferably -70nm~-250nm, more preferably -90nm~-200nm, especially 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 smaller 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) capable of homeotropic alignment may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the liquid crystal compound and the method for forming the retardation layer include those described in paragraphs [0020] to [0028] of JP-A-2002-333642 and the method for forming the retardation layer. In this case, the thickness of the second retardation layer is preferably 0.5 μm to 10 μm, preferably 0.5 μm to 8 μm, 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 appropriate substrate by any appropriate film-forming method (such as vacuum evaporation method, sputtering method, CVD method, ion plating method, spraying method, etc.). Examples of metal oxides include indium oxide, tin oxide, zinc oxide, indium-tin composite oxide, tin-antimony composite oxide, zinc-aluminum composite oxide, and indium-zinc composite oxide. Among them, indium tin composite oxide (ITO) is preferable.

When the conductive layer contains metal oxide, the thickness of the conductive layer is preferably not more than 50 nm, more preferably not more than 35 nm. The lower limit of the thickness of the conductive layer is preferably 10 nm.

The conductive layer can be transferred from the above substrate to the first retardation layer (or the second retardation layer if there is a second retardation layer), and the conductive layer can be used alone as a constituent layer of a polarizing plate with a retardation layer. 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). Ideally, the above-mentioned substrate is optically isotropic, so the conductive layer can be used as an isotropic substrate with a conductive layer for a polarizing plate with a retardation layer.

Any appropriate isotropic substrate can be used for the substrate that is optically isotropic (isotropic substrate). The material constituting the isotropic base material can be, for example, a material having a main skeleton of a resin without a conjugated system such as a norbornene-based resin or an olefin-based resin, or a material having a lactone ring or glutaryl in the main chain of an acrylic-based resin. Materials with ring structures such as imine rings, etc. If such a material is used, it is possible to suppress the phase difference exhibited accompanying molecular chain orientation when forming an isotropic base material to be small. The thickness of the isotropic substrate is preferably not more than 50 μm, more preferably not more than 35 μm. The lower limit of the thickness of the isotropic substrate is, for example, 20 μm.

The conductive layer and/or the conductive layer of the isotropic substrate with a conductive layer can be patterned as required. Conducting portions and insulating portions can be formed by patterning. As a result, an electrode can be formed. The electrodes may function as touch sensing electrodes for sensing contact to the touch panel. Any suitable method can be used for the patterning method. Specific examples of the patterning method include wet etching and screen printing.

F. Image display device The polarizing plate with a retardation layer described in items A to E above can be applied to an image display device. Therefore, the present invention includes an image display device using the polarizing plate with a retardation layer. Representative examples of image display devices include liquid crystal display devices and electroluminescence (EL) display devices (such as organic EL display devices and inorganic EL display devices). The image display device according to the embodiment of the present invention includes the polarizing plate with a retardation layer described in the above items A to E on the viewing side. The polarizing plate with retardation layer is laminated so that the retardation layer is on the side of the image display unit (for example, liquid crystal unit, organic EL unit, inorganic EL unit) (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 can be flexed or bent. In the image display device, the effect of the polarizing plate with a 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 measuring method of each characteristic is as follows. In addition, "parts" and "%" in Examples and Comparative Examples are based on weight unless otherwise noted. (1) A thickness of 10 μm or less was measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-3000"). The thickness greater than 10 μm was measured using a digital micrometer (manufactured by Anritsu Corporation, product name "KC-351C"). (2) Monomer transmittance, unit absorbance and orthogonal absorbance For the polarizing plates used in Examples and Comparative Examples, use an ultraviolet visible light spectrophotometer (manufactured by JASCO Corporation, product name "V7100") to measure, and the measured Single transmittance Ts, parallel transmittance Tp, and crossed transmittance Tc are used 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 optical performance. In addition, the refractive index of the protective film was 1.50, and the refractive index of the surface of the polarizing film opposite to the protective film was 1.53. From the orthogonal transmittance Tc ₅₅₀ measured at a measurement wavelength of 550 nm, the orthogonal absorbance A ₅₅₀ was obtained from the following formula, and divided by the thickness as the unit absorbance. Also, the cross-absorbance A 470 was obtained from the cross-transmittance Tc ₄₇₀ at a measurement wavelength of 470 _nm , and the cross-absorbance A 600 was obtained from the cross-transmittance Tc ₆₀₀ at a measurement wavelength of ₆₀₀ nm. Orthogonal absorbance=log10(100/Tc) In addition, a spectrophotometer such as LPF-200 manufactured by Otsuka Electronics Co., Ltd. can be used for equivalent measurement. (3) Orthogonal b value The polarizing plates used in Examples and Comparative Examples were measured using a UV-visible spectrophotometer (manufactured by JASCO Corporation, product name "V7100") to obtain the hue in the crossed polarization state. It shows that the lower the orthogonal b value (negative value and larger absolute value) of the polarizer, the more blue its hue will be rather than neutral. (4) Warpage The polarizing plates with retardation layers obtained in Examples and Comparative Examples were cut into a size of 110 mm×60 mm. At this time, cutting is performed with the absorption axis direction of the polarizing film being the long side direction. The cut-out polarizing plate with retardation layer was attached to a glass plate with a size of 120mm×70mm and a thickness of 0.2mm through an adhesive to make a test sample. The test sample was put into a heating oven maintained at 85° C. for 24 hours, and the amount of warpage was measured after taking it out. After placing the test sample on a flat surface with the glass plate down, the height of the highest part from the flat surface was taken as the amount of warpage. (5) Bending Durability The polarizing plates with retardation layers obtained in Examples and Comparative Examples were cut into a size of 50 mm×100 mm. At this time, the cutting is carried out with the direction of the absorption axis of the polarizing film as the direction of the short side. Using a folding tester (manufactured by YUASA, CL09 type-D01) with a constant temperature and humidity chamber, the cut out polarizing plate with a retardation layer was subjected to a bending test under the conditions of 20° C. and 50% RH. Specifically, the polarizing plate with a retardation layer is repeatedly bent in a direction parallel to the absorption axis direction with the retardation layer side as the outside, and measured until cracks, peeling or film breakage that may cause poor image display occur. The number of bending times is evaluated according to the following criteria (bending diameter: 2mmφ). >Evaluation criteria> Less than 10,000 times: Bad 10,000 times or more and less than 30,000 times: Good 30,000 times or more: Excellent (6) The front reflection hue will be the polarizing plate with a retardation layer obtained in the examples and comparative examples Use non-ultraviolet-absorbing acrylic adhesive to attach to the reflective plate (manufactured by TORAY Film Co., Ltd., trade name "DMS-X42"; reflectivity 86%, reflection hue a ^* = -0.22, b ^* = without polarizing plate 0.32), the test sample was prepared. At this time, the phase difference layer side of the polarizing plate with the phase difference layer bonded to face the reflection plate. The measurement sample was measured by the SCE method with a spectrophotometer (CM-2600d manufactured by Konica Minolta), and the values of a ^* and b ^* were substituted into √(a ^*2 +b ^*2 ) to obtain the front reflection hue. (7) Elastic coefficient Form the film to be measured into a tensile test dumbbell-shaped sheet with a parallel portion width of 10 mm and a length of 40 mm according to JIS K6734:2000, and conduct a tensile test according to JIS K7161:1994 to obtain the tensile elastic coefficient. Here, the longitudinal direction is generally consistent with the extending direction of the polarizing film.

[Example 1] 1. Make polarizing film As the thermoplastic resin substrate, a long amorphous isophthalic acid-copolymerized polyethylene terephthalate film (thickness: 100 μm) with a water absorption rate of 0.75% and a Tg of about 75°C was used. Corona treatment was performed on one side of the resin substrate. A PVA system made by mixing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mole%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z410") at a ratio of 9:1. After adding 13 parts by weight of potassium iodide to 100 parts by weight of resin, it was dissolved in water to prepare an aqueous PVA solution (coating solution). The above-mentioned PVA aqueous solution was applied to the corona-treated surface of the resin substrate and dried at 60° C. to form a PVA-based resin layer with a thickness of 13 μm, thereby producing a laminate. The obtained laminate was uniaxially stretched 2.4 times at the free end in the oven at 130° C. between rollers with different peripheral speeds along the longitudinal direction (longitudinal direction) (assisted stretching in the air). Next, the laminate was immersed in an insoluble bath (an aqueous solution of boric acid obtained by mixing 4 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40° C. for 30 seconds (insoluble treatment). Next, while adjusting the concentration of a dyeing bath at a liquid temperature of 30° C. (an iodine aqueous solution obtained by mixing iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by weight of water), the concentration of the polarizing film finally obtained is adjusted. The volume transmittance (Ts) and the unit absorbance at a wavelength of 550 nm were dipped for 60 seconds while attaining desired values (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) at a liquid temperature of 40°C for 30 seconds (crosslinking treatment). ). Then, while immersing the laminate in a boric acid aqueous solution (boric acid concentration: 4.0% by weight) at a liquid temperature of 70°C, uniaxial stretching was carried out in the longitudinal direction (longitudinal direction) between rollers with different peripheral speeds so that the total stretch The magnification is up to 5.5 times (extended treatment in water). Thereafter, the laminate 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. (washing treatment). Thereafter, while drying in an oven maintained at 90° C., the contact surface temperature was maintained at 75° C. with a heat roller made of SUS for about 2 seconds (drying shrinkage treatment). The shrinkage rate in the width direction obtained by drying and shrinking the laminate is 5.2%. Through the above procedures, a polarizing film with a thickness of 4.6 μm was formed on the resin substrate.

2. Make a polarizing plate. On the surface of the polarizing film obtained above (the side opposite to the resin substrate), a cycloolefin film (thickness: 28 μm, thickness: 28 μm, Elastic coefficient: 2100MPa) as a protective layer. Specifically, it was applied so that the total thickness of the hardening adhesive was 1.0 μm, and bonded using a rolling mill. Thereafter, UV rays are irradiated from the protective layer side to harden the adhesive. Next, after both ends were cut, the resin substrate was peeled off to obtain a long polarizing plate (width: 1300 mm) having a structure of a protective layer/adhesive layer/polarizing film. The single transmittance of the polarizing plate (essentially a polarizing film) is 43.15%, and the degree of polarization is 99.995%. In addition, the unit absorbance at a wavelength of 550 nm was 0.97, A ₄₇₀ /A ₆₀₀ was 0.87, and the orthogonal b value was -3.0.

3. Fabrication of the retardation film constituting the retardation layer 3-1. Polymerization of polyester carbonate resin using a batch polymerization consisting of two vertical reactors equipped with stirring blades and a reflux cooler controlled at 100°C The device is polymerized. Feed 29.60 parts by mass (0.046mol) of bis[9-(2-phenoxycarbonylethyl)-9-yl]methane, 29.21 parts by mass (0.200mol) of isosorbide (ISB), spiroglycerin (SPG) 42.28 parts by mass (0.139 mol), 63.77 parts by mass (0.298 mol) of diphenyl carbonate (DPC), and 1.19×10 ^-2 parts by mass (6.78×10 ^-5 mol) of calcium acetate monohydrate as a catalyst. After substituting nitrogen under reduced pressure in the reactor, it was heated with a heating medium, and stirring was started when the internal temperature reached 100°C. 40 minutes after the start of the temperature rise, the internal temperature reached 220° C., and at the same time the temperature was controlled and maintained, and the pressure was reduced to 13.3 kPa 90 minutes after reaching 220° C. The phenol vapor produced by the polymerization reaction is introduced into the 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 is introduced into the condenser at 45°C for recovery. After introducing nitrogen into the first reactor and temporarily returning it to atmospheric pressure, the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Next, temperature rise and pressure reduction in the second reactor were started, and after 50 minutes, the internal temperature was 240° C. and the pressure was 0.2 kPa. Thereafter, polymerization is performed until a predetermined stirring power is achieved. When the predetermined power is reached, nitrogen is introduced into the reactor to restore the pressure, and the resulting polyester carbonate resin is extruded into water, and the bundles are cut to obtain pellets.

3-2. Fabrication of retardation film After vacuum-drying the obtained polyester carbonate resin (pellets) at 80° C. for 5 hours, a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder set temperature: 250° C.), a T-die (wide 200mm, set temperature: 250°C), cooling roll (set temperature: 120~130°C) and the film-making device of the coiler to produce a long strip-shaped resin film with a thickness of 130μm. The obtained elongated resin film was stretched while being adjusted so that a predetermined retardation could be obtained, and a retardation film with a thickness of 48 μm was obtained. The stretching conditions are along the width direction, the stretching temperature is 143° C., and the stretching ratio is 2.8 times. Re(550) of the obtained retardation film was 141 nm, Re(450)/Re(550) was 0.86, and Nz coefficient was 1.12.

4. Production of polarizing plate with retardation layer The retardation film obtained in the above 3. was attached to the surface of the polarizing film of the polarizing plate obtained in the above 2. through an acrylic adhesive (thickness: 5 μm). At this time, it bonded so that the absorption axis of the polarizing film and the slow axis of the retardation film could form an angle of 45°. According to the above method, a polarizing plate with a retardation layer comprising a protective layer/adhesive layer/polarizing film/adhesive layer/retardation layer is obtained. The total thickness of the obtained polarizing plate with retardation layer was 87 μm. The obtained polarizing plate with a retardation layer was used for the evaluation of (4) to (6) above. List the results in Table 1.

[Example 2-1] 1. Make polarizing film In the same manner as in Example 1, a polarizing film with a thickness of 4.6 μm was formed on a resin substrate.

2. To make a polarizing plate, use a triacetyl cellulose (TAC) film with a hard coat (thickness of the hard coat: 7 μm, thickness of TAC: 25 μm, modulus of elasticity: 3600 MPa) as a protective layer, and follow the same method as in Example 1 A polarizing plate having a protective layer/adhesive layer/polarizing film was produced. The single transmittance of the polarizing plate (essentially a polarizing film) is 43.0%, and the degree of polarization is 99.995%. Also, the unit absorbance at a wavelength of 550 nm was 0.97, A ₄₇₀ /A ₆₀₀ was 0.87, and the orthogonal b value was -2.0.

3. Fabrication of the retardation film that constitutes the retardation layer Obtain polyester carbonate resin (pill) in the same manner as in Example 1 except for the PMMA of melt-kneading 0.7 parts by mass, and after vacuum-drying it at 80° C. for 5 hours, use a single-screw extruder (Toshiba Manufactured by Machinery Co., Ltd., cylinder barrel set temperature: 250°C), T-die (width 200mm, set temperature: 250°C), cooling roll (set temperature: 120~130°C) and film-making device of the coiler, produced A strip-shaped resin film with a thickness of 105 μm. The obtained elongated resin film was stretched 2.8 times in the width direction at 138° C. while adjusting to obtain a predetermined retardation to obtain a retardation film with a thickness of 38 μm. Re(550) of the obtained retardation film was 144 nm, and Re(450)/Re(550) was 0.86.

4. Production of polarizing plate with retardation layer The retardation film obtained in the above 3. was attached to the surface of the polarizing film of the polarizing plate obtained in the above 2. through an acrylic adhesive (thickness: 5 μm). At this time, it bonded so that the absorption axis of the polarizing film and the slow axis of the retardation film could form an angle of 45°. According to the above method, a polarizing plate with a retardation layer comprising a protective layer/adhesive layer/polarizing film/adhesive layer/retardation layer is obtained. The total thickness of the obtained polarizing plate with retardation layer was 81 μm. The obtained polarizing plate with retardation layer was subjected to the same evaluation as in Example 1. List the results in Table 1.

[Example 2-2] The elongated polyester carbonate resin film with a thickness of 105 μm obtained in the same manner as in Example 2-1 was stretched in the width direction while being adjusted to obtain a predetermined phase difference to obtain a phase difference film with a thickness of 38 μm. The Re(550) of the obtained retardation film was 140 nm. Except using the retardation film mentioned above as the retardation layer, a polarizing plate with a retardation layer having the composition of protective layer/adhesive layer/polarizing film/adhesive layer/retardation layer was obtained in the same manner as in Example 2-1 . The total thickness of the obtained polarizing plate with retardation layer was 81 μm. The obtained polarizing plate with retardation layer was subjected to the same evaluation as in Example 1. List the results in Table 1.

[Example 2-3] The elongated polyester carbonate resin film with a thickness of 105 μm obtained in the same manner as in Example 2-1 was stretched in the width direction while being adjusted to obtain a predetermined phase difference to obtain a phase difference film with a thickness of 38 μm. The Re(550) of the obtained retardation film was 149 nm. Except using the retardation film mentioned above as the retardation layer, a polarizing plate with a retardation layer having the composition of protective layer/adhesive layer/polarizing film/adhesive layer/retardation layer was obtained in the same manner as in Example 2-1 . The total thickness of the obtained polarizing plate with retardation layer was 81 μm. Will place The obtained polarizing plate with retardation layer was subjected to the same evaluation as in Example 1. List the results in Table 1.

[Comparative example 1] 1. Make a polarizer A polyvinyl alcohol-based resin film having an average degree of polymerization of 2,400, a degree of saponification of 99.9 mol%, and a thickness of 30 μm was prepared. While immersing the polyvinyl alcohol film in a swelling bath (water bath) at 20°C for 30 seconds between rollers with different circumferential speed ratios to make it swell, extend it 2.4 times along the conveying direction (swelling step), and then swell it at 30°C. In a dyeing bath (an aqueous solution with an iodine concentration of 0.03% by weight and a potassium iodide concentration of 0.3% by weight) at ℃, dipping and dyeing so that the monomer transmittance after final stretching becomes a desired value, while using the original polyvinyl alcohol The film (polyvinyl alcohol film not stretched in the conveying direction at all) was stretched 3.7 times in the conveying direction based on the reference (dyeing step). The immersion time at this time was about 60 seconds. Next, while immersing the dyed polyvinyl alcohol film in a 40°C cross-linking bath (an aqueous solution with a concentration of boric acid of 3.0% by weight and a concentration of potassium iodide of 3.0% by weight), it was transported along the original polyvinyl alcohol film. The direction is extended up to 4.2 times (cross-linking step). The obtained polyvinyl alcohol film was then immersed in a stretching bath (an aqueous solution with a boric acid concentration of 4.0% by weight and a potassium iodide concentration of 5.0% by weight) at 64°C for 50 seconds, and stretched the original polyvinyl alcohol film along the conveying direction to After reaching 6.0 times (stretching step), immerse in a 20°C cleaning bath (aqueous solution with a potassium iodide concentration of 3.0% by weight) for 5 seconds (washing step). The washed polyvinyl alcohol film was dried at 30° C. for 2 minutes to produce a polarizer (thickness 12 μm).

2. Make polarizer Adhesives use the following aqueous solution: polyvinyl alcohol resin containing acetoacetyl group (average degree of polymerization 1,200, degree of saponification 98.5 mole%, degree of acetylation 5 mole%) and methylol melamine . Using this adhesive and making the thickness of the adhesive layer 0.1 μm, a hard-coated cellulose triacetate (TAC) film (hard-coated thickness 7 μm, TAC thickness is 25μm, modulus of elasticity: 3600MPa), and a TAC film with a thickness of 25μm is pasted on the other side of the polarizer, and then heated and dried in an oven (at a temperature of 60°C for 5 minutes) to produce a protective Polarizing plate composed of layer 1 (thickness 32 μm)/adhesive layer/polarizer/adhesive layer/protective layer 2.

3. Production of polarizing plate with retardation layer Lay the retardation film on the surface of the protective layer 2 of the polarizing plate obtained in the above 2. in the same manner as in Example 1 to produce a protective layer 1/adhesive layer/polarizer/adhesive layer/protective layer 2/adhesive A polarizing plate with a retardation layer composed of an agent layer/retardation layer. The total thickness of the obtained polarizing plate with retardation layer was 122 μm. The obtained polarizing plate with retardation layer was subjected to the same evaluation as in Example 1.

[Comparative example 2] 1. Make a polarizer A polarizer (thickness: 12 μm) was produced in the same manner as in Comparative Example 1.

2. Make polarizer In the same manner as Comparative Example 1, a polarizing plate having a composition of protective layer 1 (thickness 32 μm)/adhesive layer/polarizer/adhesive layer/protective layer 2 (thickness 25 μm) was produced.

使用擦拭布擦拭聚對苯二甲酸乙二酯(PET)薄膜(厚度38μm)表面，施行定向處理。定向處理之方向係設為貼合至偏光板時由視辨側觀看時相對於偏光件之吸收軸方向呈15°方向。利用棒塗機將上述液晶塗敷液塗敷至該定向處理表面，並於90℃下進行2分鐘加熱乾燥，藉此使液晶化合物定向。使用金屬鹵素燈以1mJ/cm² 的光照射依上述方式形成的液晶層，使該液晶層硬化，藉此於PET薄膜上形成液晶定向固化層A。液晶定向固化層A的厚度為2.5μm，面內相位差Re(550)為270nm。並且，液晶定向固化層A具有nx＞ny＝nz之折射率分布。 變更塗敷厚度，並將定向處理方向設為由視辨側觀看時相對於偏光件之吸收軸方向呈75°方向，除此之外依與上述相同方式於PET薄膜上形成液晶定向固化層B。液晶定向固化層B的厚度為1.5μm，面內相位差Re(550)為140nm。並且，液晶定向固化層B具有nx＞ny＝nz之折射率分布。又，液晶定向固化層A及B的Re(450)/Re(550)為1.11。3. Make the first oriented solidified layer and the second oriented solidified layer constituting the retardation layer. 10 g of a polymerizable liquid crystal (manufactured by BASF Corporation: trade name "Paliocolor LC242", represented by the following formula) that will display a nematic liquid crystal phase and a pair of 3 g of a photopolymerization initiator (manufactured by BASF Corporation: trade name "IRGACURE 907") of this polymerizable liquid crystal compound was dissolved in 40 g of toluene to prepare a liquid crystal composition (coating solution). [chemical formula 1]

The surface of a polyethylene terephthalate (PET) film (thickness: 38 μm) was wiped with a wiping cloth to perform an orientation treatment. The direction of the orientation treatment is set to be 15° relative to the direction of the absorption axis of the polarizer when viewed from the viewing side when it is attached to the polarizer. The above-mentioned liquid crystal coating liquid was applied to the alignment-treated surface using a bar coater, and heat-dried at 90° C. for 2 minutes, thereby aligning the liquid crystal compound. 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 solidified layer A on the PET film. The liquid crystal alignment and solidification layer A has a thickness of 2.5 μm and an in-plane retardation Re(550) of 270 nm. In addition, the liquid crystal alignment and solidification layer A has a refractive index distribution of nx>ny=nz. Change the coating thickness, and set the orientation treatment direction to be 75° relative to the absorption axis direction of the polarizer when viewed from the viewing side. In addition, form a liquid crystal orientation solidification layer B on the PET film in the same manner as above . The thickness of the liquid crystal alignment and solidification layer B is 1.5 μm, and the in-plane retardation Re(550) is 140 nm. In addition, the liquid crystal alignment solidification layer B has a refractive index distribution of nx>ny=nz. In addition, Re(450)/Re(550) of the liquid crystal alignment and hardening layers A and B was 1.11.

4. Production of polarizing plate with retardation layer On the surface of the protective layer 2 side of the polarizing plate obtained in the above 2., the liquid crystal alignment and solidification layer A and the liquid crystal alignment and solidification layer B obtained in the above 3. were sequentially transferred. At this time, the transfer was carried out in such a way that the angle formed by the absorption axis of the polarizer and the slow axis of the orientation hardened layer A was 15° and the angle formed by the absorption axis of the polarizer and the slow axis of the orientation hardened layer B was 75° ( fit). In addition, each transfer (bonding) is performed through an ultraviolet curable adhesive (thickness 1 μm). According to the above method, a phase-attached layer with the composition of protective layer 1/adhesive layer/polarizer/adhesive layer/protective layer 2/adhesive layer/retardation layer (first directional solidified layer/adhesive layer/second directional solidified layer) is obtained. The polarizer of the poor layer. The total thickness of the obtained polarizing plate with retardation layer was 75 μm. The obtained polarizing plate with retardation layer was subjected to the same evaluation as in Example 1. List the results in Table 1.

[Comparative example 3] 1. Make polarizing film In the same manner as in Example 2-1, a polarizing film with a thickness of 4.6 μm was formed on a resin substrate.

2. Fabrication of a polarizing plate An acrylic film (surface refractive index 1.50, 20 μm) was pasted on the surface of the polarizing film obtained above (the surface opposite to the resin substrate) through a UV-curable adhesive as a protective layer. Specifically, it was applied so that the total thickness of the hardening adhesive was 1.0 μm, and bonded using a rolling mill. Thereafter, UV rays are irradiated from the protective layer side to harden the adhesive. Next, after both ends were cut, the resin substrate was peeled off to obtain a long polarizing plate (width: 1300 mm) having a structure of a protective layer/adhesive layer/polarizing film. The single transmittance of the polarizing plate (essentially a polarizing film) is 43.0%, and the degree of polarization is 99.995%. Also, the unit absorbance at a wavelength of 550 nm was 0.97, A ₄₇₀ /A ₆₀₀ was 0.87, and the orthogonal b value was -2.0.

3. Production of polarizing plate with retardation layer In the same manner as in Comparative Example 2, the liquid crystal alignment and solidification layer A and the liquid crystal alignment and solidification layer B obtained in the same manner as in Comparative Example 2 were sequentially transferred on the surface of the polarizing film of the polarizing plate obtained in the above 2. In the above manner, a polarizing plate with a retardation layer having a composition of protective layer/adhesive layer/polarizing film/adhesive layer/retardation layer (first directional solidified layer/adhesive layer/second directional solidified layer) was obtained. The total thickness of the obtained polarizing plate with retardation layer was 32 μm. The obtained polarizing plate with retardation layer was subjected to the same evaluation as in Example 1. List the results in Table 1.

[Comparative example 4] Potassium iodide is not added to the PVA aqueous solution (coating solution), the shrinkage rate in the width direction is 0.1% or less without using a heating roller in the drying shrinkage treatment, and the single transmittance of the polarizing film is adjusted by adjusting the concentration of the dyeing bath , except that a polarizing film and a polarizing plate were produced in the same manner as in Example 1. The single transmittance of the polarizing plate (essentially a polarizing film) is 43.13%, and the degree of polarization is 99.881%. In addition, the unit absorbance at a wavelength of 550 nm was 0.67. A polarizing plate with a retardation layer was produced in the same manner as in Example 1 except for using this polarizing plate.

[Table 1]

[Evaluate] Comparing Example 1 with Comparative Examples 1, 2 and 4, it is obvious that the polarizing film produced by a predetermined method exhibits excellent optical properties although it is thin. It can be seen that by using the above-mentioned polarizing film, a polarizing plate with a retardation layer which is thin and has excellent optical characteristics and whose warping after the heating test is significantly suppressed (resulting in good handling properties) can be obtained. Moreover, it turned out that excellent reflection hue can be acquired by combining and using the retardation layer which consists of a polycarbonate resin (including polyester carbonate resin) film. In addition, the thickness of the polycarbonate resin is reduced to less than 40 μm, the total thickness of the polarizing plate with a retardation layer is less than 85 μm, and a substrate with an elastic modulus of 3000 MPa or more is used, preferably TAC film is used as a protective layer. Thereby, the bending characteristics can be further improved. On the other hand, the polarizing plate with a retardation layer of Comparative Example 3 is thin and has excellent optical characteristics, and the warpage after the heating test is significantly suppressed, but the reflection hue is large and is not satisfactory from the viewpoint of display characteristics.

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: The first protective layer 13: The second protective layer 20: Retardation layer (1st retardation layer) 50: Another retardation layer (the second retardation layer) 60: Conductive layer or isotropic substrate with conductive layer 100, 101: Polarizing plate with retardation layer 200: laminated body G1~G4: guide roller R1~R6: conveyor roller θ: angle

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 schematic cross-sectional view of a polarizing plate with a retardation layer according to another embodiment of the present invention. Fig. 3 is a schematic view showing an example of drying shrinkage treatment using a heating roller in the method for producing a polarizing film used in a polarizing plate with a retardation layer according to the present invention.

10: polarizer

11: Polarizing film

12: The first protective layer

13: The second protective layer

20: Retardation layer (1st retardation layer)

100: Polarizing plate with retardation layer

Claims (13)

A polarizing plate with a retardation layer, comprising a polarizing plate and a retardation layer, 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 polyvinyl alcohol containing a dichroic substance It is composed of a resin film with a thickness of less than 8 μm, a single transmittance of more than 43.0%, and an orthogonal absorbance of more than 0.85 per 1 μm thickness at a wavelength of 550nm; the Re(550) of the retardation layer is 100nm~190nm , Re(450)/Re(550) is more than 0.8 and less than 1, Re(550) is the in-plane retardation measured with light with a wavelength of 550nm at 23°C, Re(450) is measured at 23°C with a wavelength of The in-plane retardation measured by light at 450nm; the angle formed by the slow axis of the retardation layer and the absorption axis of the polarizing film is 40°~50°; the orthogonal absorbance A ₄₇₀ of the polarizing film at a wavelength of 470nm The ratio of orthogonal absorbance A ₆₀₀ (A ₄₇₀ /A ₆₀₀ ) at a wavelength of 600nm is above 0.7; the orthogonal b value of the polarizing film is greater than -10. A polarizing plate with a retardation layer as claimed in claim 1, wherein the protective layer is made of a cellulose triacetate resin film. A polarizing plate with a retardation layer according to claim 1, wherein the polarizing plate comprises the polarizing film and the protective layer disposed on only one side of the polarizing film, and the retardation layer is bonded to the polarizing film through an adhesive layer. membrane. A polarizing plate with a retardation layer according to claim 1, wherein the retardation layer is made of a polycarbonate resin film. A polarizing plate with a retardation layer as claimed in claim 1, wherein the ratio (A ₄₇₀ /A ₆₀₀ ) of the aforementioned polarizing film at a wavelength of 470nm to the orthogonal absorbance A ₆₀₀ at a wavelength _of 600nm 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. A polarizing plate with a retardation layer as claimed in claim 1, wherein the orthogonal absorbance A ₅₅₀ of the polarizing film at a wavelength of 550 nm is above 2.0. A polarizing plate with a retardation layer as claimed in claim 1, wherein there is another retardation layer outside the aforementioned retardation layer, and the refractive index characteristics of the other retardation layer show the relationship of nz>nx=ny, and nx is The direction in which the in-plane refractive index becomes the largest is the slow axis direction, ny is the refractive index in the in-plane direction perpendicular to the slow axis, that is, the fast axis direction, and nz is the refractive index in the thickness direction. The polarizing plate with a retardation layer according to claim 1, wherein a conductive layer or an isotropic substrate with a conductive layer is further provided outside the retardation layer. A polarizing plate with a retardation layer according to any one of Claims 1 to 9, which is elongated, the polarizing film has an absorption axis in the elongated direction, and the retardation layer is formed relative to the elongated direction An obliquely stretched film with a slow axis in the direction of an angle of 40°~50°. The polarizing plate with a retardation layer as claimed in Claim 10 is wound into a roll. An image display device, which has the following requirements in items 1 to 9 Any one of the polarizing plates with a retardation layer. The image display device of claim 12 is an organic electroluminescent display device or an inorganic electroluminescent display device.

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