TWI827961B - Polarizing plate and manufacturing method thereof, as well as polarizing plate and image display device with retardation layer using the polarizing plate - Google Patents

Abstract

The present invention provides a polarizing plate that can maintain excellent optical properties even in a high temperature and high humidity environment. The polarizing plate of the present invention includes a polarizing film and a protective layer arranged on at least one side of the polarizing film; the thickness of the polarizing film is less than 8 μm; the protective layer is composed of an iodine-dyed triacetyl cellulose film and contains X-ray fluorescence. The amount of iodine detected is iodine above 0.02kcps.

Description

Polarizing plate and manufacturing method thereof, as well as polarizing plate and image display device with retardation layer using the polarizing plate

The present invention relates to a polarizing plate, a manufacturing method thereof, a polarizing plate with a retardation layer using the polarizing plate, and an image display device.

In recent years, image display devices represented by liquid crystal display devices and electroluminescence (EL) display devices (eg, organic EL display devices, inorganic EL display devices) have rapidly become popular. Typical image display devices use polarizing plates and phase difference plates. In practical applications, polarizing plates with a retardation layer in which a polarizing plate and a retardation plate are integrated are widely used (for example, Patent Document 1). Recently, as the demand for thinner image display devices has increased, the demand for polarizing plates has increased. The demand for thinning polarizing plates with retardation layers is also increasing. One of the means for thinning the polarizing plate and the polarizing plate with a retardation layer is to thin the polarizing film. However, when a polarizing plate including a thin polarizing film or a polarizing plate with a retardation layer is used in an image display device, there is a problem that the reflection hue is bluish. Furthermore, when using triacetyl cellulose (TAC) film as the protective layer of a thin polarizing film, there is a problem that the optical properties are reduced in a high temperature and high humidity environment. Prior technical literature patent documents

Patent Document 1: Japanese Patent No. 3325560

The problem to be solved by the invention The present invention was developed to solve the above-mentioned conventional problems, and its main purpose is to provide a polarizing plate that can maintain excellent optical properties even in a high-temperature and high-humidity environment and a simple and low-cost manufacturing method thereof.

means to solve problems The polarizing plate according to the embodiment of the present invention includes a polarizing film and a protective layer arranged on at least one side of the polarizing film; the thickness of the polarizing film is 8 μm or less; the protective layer is composed of an iodine-dyed triacetyl cellulose film, and Contains iodine with an iodine detection amount of 0.02kcps or more based on X-ray fluorescence detection. In one embodiment, the initial monomer transmittance of the above-mentioned polarizing plate is 43.0%~43.5%, and the polarization reduction rate after being kept in an environment of 85°C and 85%RH for 48 hours is less than 0.75%. In one embodiment, the initial monomer transmittance of the above-mentioned polarizing plate is greater than 43.5% and less than 44.0%, and the polarization reduction rate after being maintained in an environment of 85°C and 85%RH for 48 hours is less than 2.0%. According to another aspect of the present invention, a method for manufacturing the above-mentioned polarizing plate is provided. The manufacturing method includes the following steps: forming a polyvinyl alcohol-based resin layer on one side of a long thermoplastic resin base material to form a laminated body; subjecting the laminated body to dyeing treatment and stretching treatment to make the polyvinyl alcohol-based resin layer Making a polarizing film; using iodine to dye the triacetyl cellulose film; and laminating the dyed triacetyl cellulose film to the polarizing film. In one embodiment, the dyeing includes immersing the cellulose triacetate film in an iodine aqueous solution with an iodine concentration of 0.1% by weight or more. According to yet another aspect of the present invention, a polarizing plate with a retardation layer is provided. The polarizing plate with a retardation layer includes the above-mentioned polarizing plate and a retardation layer arranged on the side opposite to the viewing side of the polarizing plate. In one embodiment, Re(550) of the retardation layer is 100nm~190nm, and Re(450)/Re(550) is 0.8 or more and less than 1; the slow axis of the retardation layer is consistent with the polarizing film of the polarizing plate. The angle formed by the absorption axis is 40°~50°. In another embodiment, the retardation layer has a laminated structure of a directionally solidified layer of a first liquid crystal compound and a directionally solidified layer of a second liquid crystal compound; Re(550) of the directionally solidified layer of the first liquid crystal compound is 200 nm~ 300nm, and the angle between its slow axis and the absorption axis of the polarizing film of the polarizing plate is 10°~20°; the Re(550) of the orientationally solidified layer of the second liquid crystal compound is 100nm~190nm, and its slow axis is between 100nm and 190nm. The angle formed by the absorption axis of the polarizing film is 70°~80°. According to yet another aspect of the present invention, an image display device is provided. The image display device includes the above-mentioned polarizing plate or a polarizing plate with a retardation layer.

Invention effect According to the present invention, by using an iodine-dyed cellulose triacetate film as the protective layer of the polarizing film, a polarizing plate that can maintain excellent optical properties even in a high temperature and high humidity environment can be realized.

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 reaches the maximum (that is, the slow axis direction), "ny" is the refractive index in the direction that is orthogonal to the slow axis in the plane (that is, the fast axis direction), and " nz" is the refractive index in the thickness direction. (2) In-plane phase difference (Re) "Re(λ)" is the in-plane phase difference measured with light of wavelength λnm at 23°C. For example, "Re(550)" is the in-plane phase difference measured using light with a wavelength of 550 nm at 23°C. Re(λ) can be calculated by the formula: Re(λ)=(nx-ny)×d when the thickness of the layer (film) is d(nm). (3) Phase difference in thickness direction (Rth) "Rth(λ)" is the phase difference in the thickness direction measured with light of wavelength λnm at 23°C. For example, "Rth(550)" is the phase difference in the thickness direction measured at 23°C using light with a wavelength of 550 nm. Rth(λ) can be calculated by the formula: Rth(λ)=(nx-nz)×d when the layer (film) thickness is d(nm). (4)Nz coefficient The Nz coefficient can be calculated by Nz=Rth/Re. (5)Angle When an angle is mentioned in this specification, the angle includes both clockwise and counterclockwise directions relative to the reference direction. So, for example, "45°" means ±45°.

A.Polarizing plate The polarizing plate according to the embodiment of the present invention includes a polarizing film and a protective layer arranged on at least one side of the polarizing film. That is, the protective layer may be provided on both sides of the polarizing film, may be provided only on the viewing side of the polarizing film, or may be provided only on the side opposite to the viewing side of the polarizing film. In an embodiment of the present invention, at least one of the protective layers is composed of an iodine-dyed triacetylcellulose (TAC) film (hereinafter sometimes referred to as a dyed TAC film). According to one embodiment, in a polarizing plate having a configuration of a viewing side protective layer/polarizing film, the viewing side protective layer is composed of a dyed TAC film. The typical transmittance of this dyed TAC film at a wavelength of 400nm is less than 65%, and the transmittance Y after visual sensitivity correction (hereinafter sometimes also referred to as Y value transmittance) is more than 80%. In addition, the dyed TAC film typically contains iodine that is 0.02kcps or more based on the iodine detection amount measured by X-ray fluorescence detection.

In one embodiment, the initial single transmittance of the polarizing plate (essentially a polarizing film) is 43.0% to 43.5%. At this time, the polarization reduction rate after keeping the polarizing plate in an environment of 85℃・85%RH for 48 hours is preferably 0.75% or less, more preferably 0.65% or less, more preferably 0.50% or less, especially 0.25% the following. The smaller the polarization reduction rate, the better, and ideally it is zero. According to embodiments of the present invention, by using the above-mentioned dyed TAC film as a protective layer, even if it is a polarizing plate including a thin polarizing film with a thickness of 8 μm or less, the decrease in polarization degree in a high-temperature and high-humidity environment can be significantly suppressed. Moreover, it is of great technical significance to use TAC film as a protective layer to achieve the above-mentioned excellent effects. In other words, the TAC film has high processability and can exhibit excellent effects in special-shaped processing (such as forming through holes and/or notches in the outer edge), which has been in high demand in recent years. On the other hand, the TAC film has high moisture permeability, so if it is used as a protective layer for a thin polarizing film with a high iodine concentration, there is a problem that the optical properties of the polarizing plate (essentially a polarizing film) are degraded, especially in a high-humidity environment. According to the embodiment of the present invention, by using a dyed TAC film, it is possible to significantly suppress the optical deterioration of the polarizing plate (essentially a polarizing film) in a high-temperature and high-humidity environment while maintaining the excellent effects of the TAC film (represented by processability). Characteristics are reduced.

In one embodiment, the initial single transmittance of the polarizing plate (essentially a polarizing film) is greater than 43.5% and less than 44.0%. At this time, the polarization reduction rate after keeping the polarizing plate in an environment of 85°C and 85%RH for 48 hours is preferably 3.5% or less, more preferably 3.0% or less, more preferably 2.5% or less, especially 2.0%. the following. The smaller the polarization reduction rate, the better, and ideally it is zero.

A-1.Polarizing film Polarizing films are typically made of polyvinyl alcohol (PVA) resin films containing iodine. The thickness of the polarizing film is typically less than 8µm, preferably less than 7µm, more preferably less than 5µm, more preferably less than 3µm. The lower limit of the thickness of the polarizing film may be 1 μm in one embodiment, and may be 2 μm in another embodiment.

The polarizing film should show absorption dichroism at any wavelength between 380nm and 780nm. The monomer transmittance of the polarizing film is preferably above 42.0%, more preferably above 42.5%, and more preferably above 43.0%. On the other hand, the single transmittance is preferably 47.0% or less, more preferably 46.0% or less. The polarization degree of the polarizing film should be above 99.95%, more preferably above 99.99%. On the other hand, the degree of polarization is preferably 99.998% or less. As mentioned above, the polarizing film used in the embodiment of the present invention can achieve both high single transmittance and high degree of polarization. The above-mentioned monomer transmittance represents the Y value obtained by measuring it using a UV-visible spectrophotometer and correcting the visual sensitivity. In addition, the single transmittance is a value obtained by converting the refractive index of one surface of the polarizing plate to 1.50 and converting the refractive index of the other surface to 1.53. The above representative degree of polarization is based on the parallel transmittance Tp and the orthogonal transmittance Tc measured using a UV-visible spectrophotometer and corrected for visual sensitivity, and is calculated by the following formula. Polarization degree (%)={(Tp-Tc)/(Tp+Tc)} ^{1 /2} ×100

In one embodiment, the transmittance of a thin polarizing film of 8 μm or less is measured using a laminate of a polarizing film (refractive index of the surface: 1.53) and a protective film (refractive index: 1.50), using ultraviolet-visible light spectrophotometry. To measure. The reflectivity at the interface of each layer will change depending on the refractive index of the polarizing film surface and/or the refractive index of the surface of the protective film in contact with the air interface. As a result, the measured value of the transmittance may change. 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 correction value C of the transmittance is expressed by the following formula using the reflectance R ₁ (transmission axis reflectance) of the polarized light parallel to the transmission axis at the interface between the protective film and the air layer. C=R ₁ -R ₀ R ₀ =((1.50-1) ² /(1.50+1) ² )×(T ₁ /100) R ₁ =((n ₁ -1) ² /(n ₁ +1) ² )×(T ₁ /100) Here, R ₀ is the transmission axis reflectance when using a protective film with a refractive index of 1.50, n ₁ is the refractive index of the protective film used, and T ₁ is the transmission of the polarizing film Rate. For example, when a base material (cycloolefin-based film, hard-coated film, etc.) with a surface refractive index of 1.53 is used as a protective film, the correction amount C is approximately 0.2%. At this time, adding 0.2% to the measured transmittance can convert the polarizing film with a surface refractive index of 1.53 into the transmittance when using a protective film with a refractive index of 1.50. In addition, after calculation based on the above formula, the change in correction value C after changing the transmittance T ₁ of the polarizing film by 2% is less than 0.03%. Therefore, the impact of the transmittance of the polarizing film on the correction value C is limited. In addition, when the protective film has absorption other than surface reflection, appropriate correction can be performed based on the amount of absorption.

The iodine concentration of the polarizing film is preferably 4.0% by weight or more, more preferably 4.5% to 7.0% by weight, and more preferably 5.0% to 8.0% by weight. According to an embodiment of the present invention, by using a dyed TAC film, even if it is a polarizing plate including a thin polarizing film having the above-mentioned iodine concentration, it is possible to significantly suppress the decrease in polarization degree in a high-temperature and high-humidity environment.

The polarizing film can be made from a single resin film or from a laminate of two or more layers.

Specific examples of polarizing films obtained using a laminated body include polarizing films obtained using a laminated body of a resin base material and a PVA-based resin layer formed by coating on the resin base material. A polarizing film obtained by using a laminate of a resin base material and a PVA-based resin layer coated on the resin base material can be produced, for example, by applying a PVA-based resin solution to the resin base material, and It is dried to form a PVA-based resin layer on the resin base material to obtain a laminated body of the resin base material and the PVA-based resin layer; and the laminated body is stretched and dyed to form the PVA-based resin layer into a polarizing film. In this embodiment, stretching typically includes immersing the laminate in a boric acid aqueous solution and stretching. And if necessary, stretching may further include stretching the laminate in the air at a high temperature (for example, 95° C. or higher) before stretching in a boric acid aqueous solution.

More specifically, the manufacturing method of the polarizing film 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 The above-mentioned laminated body is sequentially subjected to air-assisted stretching treatment, dyeing treatment, water stretching treatment and drying shrinkage treatment. The drying and shrinking treatment is performed by heating the above-mentioned laminated body while conveying it in the longitudinal direction, thereby making it stretch in the width direction. Shrink more than 2%. With this, polarizing films with a thickness of 8µm or less and excellent optical properties can be provided. That is, by introducing auxiliary stretching, the crystallinity of PVA can be improved even when PVA is coated on a thermoplastic resin, and high optical properties can be achieved. In addition, by improving the orientation of PVA in advance, it can prevent problems such as reduction in orientation or dissolution of PVA when immersed in water in the subsequent dyeing step or stretching step, thereby achieving high optical properties. In addition, when the PVA-based resin layer is immersed in a liquid, compared with the case where the PVA-based resin layer does not contain halides, the orientation disorder and decrease in orientation of polyvinyl alcohol molecules can be suppressed. Thereby, the optical characteristics of the polarizing film obtained through the processing steps of immersing the laminate in a liquid, such as dyeing processing and water stretching processing, can be improved. In addition, the optical properties can be improved by shrinking the laminate in the width direction through drying and shrinkage treatment. The details of the manufacturing method of the polarizing film will be described in item B.

A-2.Protective layer As described above, in the embodiment of the present invention, at least one of the protective layer disposed on the viewing side (hereinafter referred to as the viewing side protective layer) and the protective layer disposed on the side opposite to the viewing side (hereinafter referred to as the inner protective layer) It is made of dyed TAC film. From the viewpoint of reducing the thickness and weight of the polarizing plate, the inner protective layer can be appropriately omitted. Therefore, according to one embodiment, in a polarizing plate having a configuration of a viewing side protective layer/polarizing film, the viewing side protective layer Made of dyed TAC film. By using a dyed TAC film for the viewing side protective layer and/or the inner protective layer, even when a thin (such as a thickness of less than 8µm) polarizing film is used, the decrease in polarization degree in a high temperature and high humidity environment can be significantly suppressed. Furthermore, when the polarizing plate is applied to an image display device, it can prevent the reflection hue of the image display device from being bluish, and as a result, a very excellent (neutral) reflection hue can be achieved.

When the visible side protective layer and the inner protective layer are arranged and only one of them is composed of a dyed TAC film, the other protective layer is formed of any appropriate film that can be used as a protective layer of the polarizing film. Specific examples of the material that is the main component of the film include cellulose-based resins such as triacetylcellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, and polyamide-based resins. Transparent resins of imide series, polyether series, polystyrene series, polystyrene series, polynorbornene series, polyolefin series, (meth)acrylic series and acetate series, etc. In addition, thermosetting resins such as (meth)acrylic type, urethane type, (meth)acrylic urethane type, epoxy type, polysilicone type, etc., or ultraviolet curing type resins may also be mentioned. Other examples include glassy polymers such as siloxane polymers. In addition, the polymer film described in Japanese Patent Application Laid-Open No. 2001-343529 (WO01/37007) can also be used. As the material of the film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted acyl imine 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. Examples thereof include resin compositions having an alternating copolymer of isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer. The polymer film may be, for example, an extruded product of the above-mentioned resin composition.

The transmittance of the dyed TAC film at a wavelength of 400 nm is typically 65% or less as mentioned above, preferably 60% or less, more preferably 55% or less, more preferably 40% or less, especially 35% or less. The lower limit of the transmittance may be, for example, 0.1%. If the transmittance is within the above range, the reflection hue will be more excellent. Furthermore, the Y value transmittance of the dyed TAC film is typically 80% or more as mentioned above, preferably 85% or more, and more preferably 90% or more. The higher the Y value transmittance, the better. The upper limit of the Y value transmittance may be, for example, 98%. One of the characteristics of dyed TAC films is that the transmittance at a wavelength of 400nm will be significantly reduced, while on the other hand, the Y value transmittance can maintain a high value.

The above-mentioned effects brought about by the dyed TAC film are speculated to be due to the following mechanism: the iodine content (absolute amount) of the thin polarizing film is small. The polarizing film according to the embodiment of the present invention is produced by the method described in Item B below. Even if the iodine content (absolute amount) is small, it can be converted into PVA-I ₅ ^-complex and PVA-I that contribute to visible light absorption. The total amount of I ₅ ^- ions and I ₃ ^- ions in the 3-complex source is maintained within a desired range. Therefore, although it is thin _, the ^monomer transmittance and polarization degree can be maintained to a high degree. Having said that, thin polarizing films tend to have smaller absorption of light with short wavelengths (for example, 400 nm or less) due to their small iodine content (absolute amount). According to an embodiment of the present invention, by using a dyed TAC film as a protective layer, the protective layer can absorb short-wavelength light. As a result, the entire polarizing plate can fully absorb short-wavelength light, thereby making up for the short-wavelength absorptivity of the thin polarizing film. As a result, the excellent characteristics of the thin polarizing film used in the embodiment of the present invention can be maintained, and at the same time, the reflection hue of the image display device can be prevented from being bluish. As a result, a very excellent (neutral) reflection hue can be achieved. Moreover, if the thin polarizing film contains too much iodine, PVA-iodine complex will be formed, so the Y value transmittance will also be reduced at the same time. On the other hand, iodine does not complex in the TAC film, so the absorption of iodine is not limited to short wavelengths, and the transmittance of short wavelengths can be suppressed while maintaining the Y value transmittance. In addition, in this specification, "iodine content (absolute amount)" and "iodine concentration" have different meanings. That is, in a thin polarizing film, the iodine concentration (iodine density) becomes high, but on the other hand, because the thickness is particularly thin, the absolute amount of iodine in the polarizing film becomes small.

The dyed TAC film is representative of the above and contains an iodine detection amount of 0.02kcps or more based on X-ray fluorescence detection. The iodine content of the dyed TAC film (the amount of iodine detected by X-ray fluorescence detection) is preferably above 0.05kcps, more preferably above 0.08kcps, and more preferably above 0.12kcps. The iodine content of the dyed TAC film may be, for example, 0.5 kcps or less. If the iodine content of the dyed TAC film is within the above range, it can significantly suppress the degradation of the optical properties of the polarizing plate (essentially a polarizing film) in a high temperature and high humidity environment. More details are as follows. Compared with general polarizers, the high-performance thin polarizing film used in the embodiment of the present invention has a higher concentration of iodine in the polarizing film, so the reliability is significantly reduced in high temperature and high humidity environments. In particular, this tendency is more significant when a TAC film is used as a protective layer. It is known that one of the reasons is that the iodine in the polarizing film moves into the TAC film and/or the adhesive layer and adhesive layer. Therefore, by dyeing the TAC film with iodine in advance and using the dyed TAC film (containing more than a predetermined amount of iodine) as a protective layer, it is possible to suppress the movement of iodine from the polarizing film to the TAC film, thereby preventing optical damage of the polarizing plate. Reliability is reduced.

The protective layer on the viewing side can also be treated with hard coating, anti-reflective, anti-adhesive, anti-glare and other surface treatments as needed. And/or, the viewing side protective layer may also be subjected to processing to improve the visibility when viewed through polarized sunglasses (representatively, imparting (elliptical) polarization function and imparting ultra-high phase difference) as needed. By performing the above processing, excellent visibility can be achieved even when the display screen is viewed through polarized lenses such as polarized sunglasses. Therefore, the polarizing plate or the polarizing plate with a retardation layer can also be suitably used in an image display device that can be used outdoors.

The thickness of the protective layer on the viewing side should be 5µm~80µm, more preferably 10µm~40µm, more preferably 10µm~35µm. In addition, when surface treatment is applied, the thickness of the protective layer on the viewing side includes the thickness of the surface treatment layer.

In one embodiment, the inner protective layer is preferably optically isotropic. In this specification, "optically isotropic" means that the in-plane phase difference Re (550) is 0 nm to 10 nm, and the phase difference Rth (550) in the thickness direction is -10 nm to +10 nm. In one embodiment, the inner protective layer can be a phase difference layer with any appropriate phase difference value. At this time, the in-plane phase difference Re (550) of the retardation layer is, for example, 110 nm to 150 nm. The thickness of the inner protective layer should be 5µm~80µm, more preferably 10µm~40µm, more preferably 10µm~30µm. As mentioned above, from the viewpoint of thinning and weight reduction, it is preferable to omit the inner protective layer.

B. Manufacturing method of polarizing plate B-1. Manufacturing method of polarizing film The polarizing film can be obtained, for example, by a manufacturing method including the following steps: forming a polyvinyl alcohol-based resin layer (PVA-based resin) containing a halide and a polyvinyl alcohol-based resin (PVA-based resin) on one side of a long thermoplastic resin base material. layer) to form a laminated body; and, sequentially subject the laminated body to air-assisted stretching treatment, dyeing treatment, water stretching treatment and drying shrinkage treatment, and the drying and shrinking treatment is performed by heating while transporting the laminated body along the longitudinal direction, This causes it to shrink by more than 2% in the width direction. The content of the halide in the PVA resin layer is preferably 5 to 20 parts by weight relative to 100 parts by weight of the PVA resin. The drying shrinkage treatment should be carried out using a heated roller, and the temperature of the heated roller should be 60℃~120℃. The shrinkage rate in the width direction of the laminate under drying shrinkage treatment is preferably 2% or more. According to the manufacturing method, the polarizing film described in the above item A-1 can be obtained. In particular, a polarizing film with excellent optical properties (typically single transmittance and polarization degree) can be obtained by producing a laminate including a halide-containing PVA-based resin layer and then stretching the above-mentioned laminate. A multi-stage stretching including air auxiliary stretching and underwater stretching is performed, and the stretched laminate is heated with a heating roller.

B-1-1. Production of laminated body Any appropriate method may be used as a method of producing a laminate of a thermoplastic resin base material and a PVA-based resin layer. It is preferable to apply a coating liquid containing a halide and a PVA-based resin on the surface of a thermoplastic resin base material and dry it, thereby forming a PVA-based resin layer on the thermoplastic resin base material. As mentioned above, the content of the halide in the PVA-based resin layer is preferably 5 to 20 parts by weight relative to 100 parts by weight of the PVA-based resin.

The coating liquid may be applied by any appropriate method. Examples include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, blade coating (notched wheel coating, etc.). The coating and drying temperature of the above-mentioned coating liquid is preferably 50°C or above.

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

Before forming the PVA-based resin layer, the thermoplastic resin base material may be subjected to surface treatment (such as corona treatment, etc.), or an easy-adhesion layer may be formed on the thermoplastic resin base material. By performing the above-described treatment, the adhesion between the thermoplastic resin base material and the PVA-based resin layer can be improved.

B-1-1-1. Thermoplastic resin base material As the thermoplastic resin base material, any appropriate thermoplastic resin film can be used. Details of the thermoplastic resin film base material are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580 or Japanese Patent No. 6470455. The entire contents of these publications are cited in this specification.

B-1-1-2. Coating liquid The coating liquid system contains a halide and a PVA-based resin as described above. The above-mentioned coating liquid is a solution in which the above-mentioned halide and the above-mentioned PVA-based resin are dissolved in a solvent. Examples of the solvent include water, dimethylstyrene, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyols such as trimethylolpropane, and ethylene glycol. Amines such as ethylenediamine and diethylenetriamine. These may be used individually or in combination of two or more types. Of these, water is the best. The PVA resin concentration of the solution is preferably 3 to 20 parts by weight relative to 100 parts by weight of the solvent. If the resin concentration is the above, a uniform coating film closely adhered to the thermoplastic resin base material can be formed. The halide content in the coating liquid is preferably 5 to 20 parts by weight based on 100 parts by weight of the PVA resin.

Additives may also be blended into the coating liquid. Examples of additives include plasticizers, surfactants, and the like. Examples of plasticizers include polyhydric alcohols such as ethylene glycol and glycerol. Examples of surfactants include nonionic surfactants. These can be used in order to further improve the uniformity, dyeability, and extensibility of the PVA-based resin layer obtained.

Any appropriate resin can be used as the above-mentioned PVA-based resin. Details of the PVA-based resin are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580 or Japanese Patent No. 6470455 (mentioned above).

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

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

Generally speaking, when the PVA resin layer is stretched, the orientation of the polyvinyl alcohol molecules in the PVA resin layer will become higher. However, if the stretched PVA resin layer is immersed in a water-containing liquid, the polyvinyl alcohol molecules will A situation in which orientation is disordered and orientation is reduced. Especially when the laminate of a thermoplastic resin base material and a PVA-based resin layer is stretched in boric acid water, in order to stabilize the stretching of the thermoplastic resin base material, the above-mentioned laminate is stretched in boric acid water at a relatively high temperature. The tendency of orientation reduction is obvious. For example, the stretching of a PVA film monomer in boric acid water is generally performed at 60°C. On the other hand, the stretching of a laminate of A-PET (thermoplastic resin base material) and a PVA-based resin layer is around 70°C. At a higher temperature, at this time, the orientation of PVA at the beginning of stretching will decrease in the stage before it rises by stretching in water. In this regard, by preparing a laminate of a halide-containing PVA-based resin layer and a thermoplastic resin base material, and subjecting the laminate to high-temperature stretching (auxiliary stretching) in the air before stretching in boric acid water, it is possible to promote the post-auxiliary 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 orientation disorder and decrease in orientation of polyvinyl alcohol molecules can be suppressed more than when the PVA-based resin layer does not contain a halide. Thereby, the optical characteristics of the polarizing film obtained through the processing steps of immersing the laminate in a liquid, such as dyeing processing and water stretching processing, can be improved.

B-1-2. Aerial auxiliary extended processing In particular, in order to obtain high optical properties, a two-stage stretching method that combines dry stretching (auxiliary stretching) and boric acid water stretching is chosen. For example, in the two-stage stretching method, by introducing auxiliary stretching, the crystallization of the thermoplastic resin base material can be suppressed while stretching, and the problem of reduced ductility caused by excessive crystallization of the thermoplastic resin base material during the subsequent boric acid water stretching can be solved. , and the laminated body can be stretched at a higher magnification. Furthermore, when applying PVA-based resin to a thermoplastic resin base material, in order to suppress the influence of the glass transition temperature of the thermoplastic resin base material, the coating temperature must be lower than when the PVA-based resin is applied to a general metal roller. If it is lower, the crystallization of the PVA-based resin becomes relatively low, resulting in the problem that sufficient optical properties cannot be obtained. In this regard, by introducing auxiliary stretching, the crystallinity of the PVA-based resin can be improved even when the PVA-based resin is coated on the thermoplastic resin, and high optical properties can be achieved. In addition, by improving the orientation of the PVA resin in advance, it can prevent problems such as the decrease in orientation or dissolution of the PVA resin when it is immersed in water in the subsequent dyeing step or stretching step, thereby achieving high optical properties.

The stretching method of aerial auxiliary stretching can be fixed end stretching (for example, the method of stretching using a tenter stretching machine), or free end stretching (for example, the method of uniaxial stretching of the laminate through rollers with different peripheral speeds) , but in order to obtain high optical properties, free end extension can be actively used. In one embodiment, the in-air stretching process includes a heating roller stretching step in which the laminate is stretched by utilizing the difference in circumferential speed between the heating rollers while conveying the laminate in its longitudinal direction. The air stretching process typically includes a zone stretching step and a heated roller stretching step. In addition, the order of the area extending step and the heating roller extending step is not limited. The area extending step may be performed first, or the heating roller extending step may be performed first. The region extension step can also be omitted. In one embodiment, the area stretching step and the heating roller stretching step are performed sequentially. In another embodiment, the ends of the film are held in a tenter stretching machine, and the distance between the tenters is widened in the traveling direction (the increase in the distance between the tenters is the stretching ratio). At this time, the distance of the tenter in the width direction (perpendicular direction with respect to the traveling direction) is set so as to be arbitrarily close. It is advisable to set the extension ratio relative to the direction of travel to utilize the extension of the free end for approach. When the free end is extended, it is calculated based on the shrinkage rate in the width direction = (1/extension ratio) ^1/2 .

Aerial assisted extension can be performed in one stage or in multiple stages. When it is carried out in multiple stages, the extension ratio is the product of the extension ratios of each stage. The extension direction of the auxiliary extension in the air should be roughly the same as the extension direction of the extension in the water.

The extension ratio of auxiliary extension in the air should be 2.0 times to 3.5 times. The maximum extension ratio when combining auxiliary extension in the air and extension in water is preferably 5.0 times or more relative to the original length of the laminated body, more preferably 5.5 times or more, and more preferably 6.0 times or more. The "maximum elongation ratio" in this specification means the elongation ratio before the laminated body is about to break, which is a value 0.2 lower than the value obtained by confirming the elongation ratio when the laminated body breaks.

The stretching temperature of the in-air auxiliary stretching can be set to any appropriate value according to the forming material of the thermoplastic resin base material, stretching method, etc. The extension 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 + 10°C, especially above Tg + 15°C. On the other hand, the upper limit of the extension temperature is preferably 170°C. By stretching at the above temperature, rapid progress of crystallization of the PVA-based resin can be suppressed, and problems caused by the crystallization (for example, obstruction of the orientation of the PVA-based resin layer due to stretching) can be suppressed. The crystallization index of the PVA resin after air-assisted stretching is preferably 1.3~1.8, more preferably 1.4~1.7. The crystallization index of PVA resin can be measured using a Fourier transform infrared spectrophotometer and the ATR method. Specifically, the measurement is performed using polarized light as the measurement light, and the crystallization index is calculated according to the following formula using the intensities of 1141 cm ^-1 and 1440 cm ^-1 of the obtained spectrum. Crystallization index = (I _C / _IR ) However, I _C : the intensity at 1141 cm ^-1 when measurement light is incident and measurement is performed, and _IR : the intensity at 1440 cm ^-1 when measurement light is incident on it.

B-1-3. Insolubilization treatment, dyeing treatment and cross-linking treatment If necessary, insolubilization treatment is performed after the air-assisted stretching treatment and before the water stretching treatment or dyeing treatment. The above-mentioned insolubilization treatment is typically performed by immersing the PVA-based resin layer in a boric acid aqueous solution. The above dyeing treatment is typically performed by dyeing the PVA-based resin layer with a dichroic substance (typically iodine). If necessary, cross-linking treatment is performed after the dyeing treatment and before the extension treatment in water. The above-mentioned cross-linking treatment can typically be performed by immersing the PVA-based resin layer in a boric acid aqueous solution. Details of the insolubilization treatment, dyeing treatment and cross-linking treatment are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580 or Japanese Patent No. 6470455 (mentioned above).

B-1-4. Extension treatment in water The underwater stretching treatment is performed by immersing the laminate in a stretching bath. Through the water stretching treatment, it is possible to stretch at a temperature lower than the glass transition temperature of the above-mentioned thermoplastic resin base material or PVA-based resin layer (typically about 80°C), thereby suppressing the crystallization of the PVA-based resin layer. Perform high-magnification extension. As a result, a polarizing film with excellent optical properties can be produced.

The laminate may be extended by any appropriate method. Specifically, it may be fixed-end stretching or free-end stretching (for example, a method of uniaxial stretching by passing the laminate between rollers with different peripheral speeds). It is advisable to choose free end extension. The extension of the laminated body can be carried out in one stage or in multiple stages. When the process is carried out in multiple stages, the stretching ratio (maximum stretching ratio) of the laminate described below is the product of the stretching ratios in each stage.

The underwater stretching is preferably performed by immersing the laminate in a boric acid aqueous solution (boric acid underwater stretching). By using a boric acid aqueous solution as a stretching bath, the PVA-based resin layer can be provided with rigidity that can withstand the tension applied during stretching and water resistance that is insoluble in water. Specifically, boric acid will generate tetrahydroxyborate anions in aqueous solution and can cross-link with PVA-based resin through hydrogen bonds. As a result, the PVA-based resin layer can be given rigidity and water resistance, and can be stretched well, 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 that is a solvent. The boric acid concentration is preferably 1 to 10 parts by weight relative to 100 parts by weight of water, more preferably 2.5 to 6 parts by weight, and especially 3 to 5 parts by weight. By setting the boric acid concentration to 1 part by weight or more, the dissolution of the PVA-based resin layer can be effectively suppressed and a polarizing film with higher characteristics can be produced. In addition to boric acid or borate, an aqueous solution obtained by dissolving boron compounds such as borax, glyoxal, glutaraldehyde, etc. in a solvent can also be used.

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

The extension temperature (liquid temperature of the extension bath) is preferably 40°C to 85°C, more preferably 60°C to 75°C. At this temperature, dissolution of the PVA-based resin layer can be suppressed and high-magnification elongation can be achieved. Specifically, as mentioned above, in relation to the formation of the PVA-based resin layer, the glass transition temperature (Tg) of the thermoplastic resin base material is preferably 60° C. or higher. At this time, if the stretching temperature is lower than 40° C., even if it is considered to plasticize the thermoplastic resin base material with water, it may not be able to be stretched satisfactorily. On the other hand, the higher the temperature of the extension bath, the higher the solubility of the PVA-based resin layer, and excellent optical properties may not be obtained. The immersion time of the laminate in the extension bath is preferably 15 seconds to 5 minutes.

The extension ratio for stretching in water is preferably 1.5 times or more, more preferably 3.0 times or more. The total extension ratio of the laminated body is preferably 5.0 times or more, more preferably 5.5 times or more relative to the original length of the laminated body. By achieving such a high stretching ratio, a polarizing film with extremely excellent optical properties can be produced. The high stretching ratio can be achieved by using a water stretching method (boric acid water stretching).

B-1-5. Drying and shrinkage treatment The above-mentioned drying and shrinkage treatment can be performed by regional heating in which the entire region is heated, or by heating a transport roller (so-called use of a heating roller) (heated roller drying method). It is better to use both. By drying using a heating roller, heat curling of the laminate can be effectively suppressed and a polarizing film with excellent appearance can be produced. Specifically, by drying the laminated body while passing through a heated roller, the crystallization of the thermoplastic resin base material can be effectively promoted to increase the crystallinity, even at a relatively low drying temperature. It can effectively increase the crystallinity of thermoplastic resin base materials. As a result, the rigidity of the thermoplastic resin base material increases and becomes a state that can withstand shrinkage of the PVA-based resin layer due to drying, thereby suppressing curling. Furthermore, by using a heating roller, the laminated body can be dried while maintaining a flat state, thereby suppressing not only curling but also wrinkles. At this time, the laminated body can be shrunk in the width direction through drying and shrinkage treatment to improve the optical properties. This is because it can effectively improve the orientation of PVA and PVA/iodine complexes. The shrinkage rate of the laminate in the width direction under drying shrinkage treatment is preferably 1% to 10%, more preferably 2% to 8%, and especially 4% to 6%. By using a heated roller, the laminated body can be continuously shrunk in the width direction while being conveyed, thereby achieving high productivity.

FIG. 1 is a schematic diagram showing an example of drying shrinkage treatment. In the drying shrinkage process, the laminated body 200 is dried while being conveyed using the conveyance rollers R1 to R6 and the guide rollers G1 to G4 heated to a predetermined temperature. In the illustrated example, the conveying rollers R1 to R6 are arranged to alternately and continuously heat the surface of the PVA resin layer and the thermoplastic resin base material. However, for example, the conveying rollers R1 to R6 may also be arranged to continuously heat only the laminated body 200 One side (such as the thermoplastic resin base material side).

Drying conditions can be controlled by adjusting the heating temperature of the conveyor roller (temperature of the heating roller), the number of heating rollers, and the contact time with the heating roller. The temperature of the heating roller is preferably 60°C~120°C, more preferably 65°C~100°C, especially 70°C~80°C. It can satisfactorily increase the crystallinity of the thermoplastic resin and suppress curling, and at the same time, it can produce an optical laminate with extremely excellent durability. In addition, the temperature of the heating roller can be measured with a contact thermometer. In the example of the drawing, six conveying rollers are provided, but there are no particular restrictions on the number of conveying rollers. There are usually 2 to 40 conveying rollers, and 4 to 30 should be set. The contact time (total contact time) between the laminate and the heating roller is preferably 1 to 300 seconds, preferably 1 to 20 seconds, and more preferably 1 to 10 seconds.

The heating roller can be installed in a heating furnace (such as an oven) or in a general manufacturing production line (at room temperature). It should be installed in a heating furnace with an air supply mechanism. By combining drying with heated rollers and hot air drying, rapid temperature changes between the heated rollers 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 about 10m/s~30m/s. In addition, the wind speed is the wind speed in the heating furnace, which can be measured with a mini fan blade type digital anemometer.

B-1-6.Other processing It is advisable to perform cleaning treatment after stretching in water and before drying and shrinking. The above-described cleaning treatment can typically be performed by immersing the PVA-based resin layer in a potassium iodide aqueous solution.

In the above manner, a laminate of thermoplastic resin substrate/polarizing film can be produced.

B-2. Dyeing of TAC film On the other hand, the TAC film was dyed with iodine. Dyeing can be performed in any suitable manner. Dyeing can be performed, for example, by immersing a long TAC film in a dyeing solution (typically an iodine aqueous solution) while being conveyed by a roller. Dyeing is performed so that the transmittance of the obtained dyed TAC film at a wavelength of 400 nm becomes 65% or less and the Y value transmittance becomes 80% or more. The transmittance and Y value transmittance can be controlled by appropriately adjusting the iodine concentration of the iodine aqueous solution, the temperature of the iodine aqueous solution, and the dyeing time (immersion time). The iodine concentration of the iodine aqueous solution can change according to the dyeing time (immersion time). The iodine concentration of the iodine aqueous solution is preferably 0.1% by weight or more, more preferably 0.5% to 5.0% by weight, and more preferably 1.0% to 3.0% by weight. If the iodine concentration is too low, the desired transmittance may not be obtained even if the dyeing process is performed for a long time. The temperature of the iodine aqueous solution should be 20℃~30℃. The staining time can vary according to the iodine concentration of the iodine aqueous solution. The dyeing time should be more than 30 seconds, preferably 50 seconds to 800 seconds, more preferably 100 seconds to 700 seconds, especially 150 seconds to 650 seconds. If the dyeing time is too short, the desired transmittance may not be obtained. On the other hand, considering manufacturing efficiency, it is not effective to extend the dyeing time for no reason.

B-3. Production of polarizing plate The dyed TAC film obtained in the above item B-2 is bonded to the surface of the polarizing film of the laminate of the thermoplastic resin substrate/polarizing film obtained in the above item B-1 through any appropriate adhesive. Examples of the adhesive include water-based adhesives and active energy ray-curable adhesives. In the above manner, a laminate of thermoplastic resin base material/polarizing film/dyed TAC film can be produced. This laminated body can also be used directly as a polarizing plate. In this case, the thermoplastic resin base material can function as an inner protective layer. Alternatively, the thermoplastic resin base material may be peeled off from the laminated body of the thermoplastic resin base material/polarizing film/dyed TAC film, and the laminated body of the dyed TAC film/polarizing film may be used as a polarizing plate. Alternatively, the thermoplastic resin base material may be peeled off from the laminate of the thermoplastic resin base material/polarizing film/dyed TAC film, and the resin film may be bonded to the peeled surface as an inner protective layer, and the dyed TAC film/polarizing film/inner protective layer may be The laminate of layers is used as a polarizing plate.

C. Polarizing plate with phase difference layer C-1. Overall composition of polarizing plate with retardation layer FIG. 2 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 the polarizing plate 10 and the retardation layer 20 . The polarizing plate is the polarizing plate described in items A and B above. The polarizing plate 10 in the illustrated example includes a polarizing film 11 , a viewing side protective layer 12 and an inner protective layer 13 . As mentioned above, the inner protective layer 13 can be omitted. In a polarizing plate with a retardation layer, the retardation layer is typically disposed on the side of the polarizing plate opposite to the viewing side.

As shown in FIG. 3 , the polarizing plate 101 with a retardation layer in another embodiment may also be provided with another retardation layer 50 and/or a conductive layer or an isotropic base material 60 with a conductive layer. The other retardation layer 50 and the conductive layer or the isotropic base material 60 with the conductive layer can typically be provided on the side of the retardation layer 20 opposite to the polarizing plate 10 (the side opposite to the viewing side). The other retardation layer represents the upper refractive index characteristic showing the relationship nz>nx=ny. Another phase difference layer 50 and a conductive layer or an isotropic substrate 60 with a conductive layer are arranged sequentially from the phase difference layer 20 side. The other phase difference layer 50 and the conductive layer or the isotropic substrate 60 with the conductive layer represent any of the above layers that can be provided as needed, and any one or both of them can be omitted. In addition, for convenience, the phase difference layer 20 may be called a first phase difference layer, and the other phase difference layer 50 may be called a second phase difference layer. In addition, when a conductive layer or an isotropic substrate with a conductive layer can be provided, the polarizing plate with a phase difference layer can be used to integrate a touch sensor between an image display unit (such as an organic EL unit) and the polarizing plate. A so-called in-touch panel type input display device.

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

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

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

The polarizing plate with the retardation layer can be in the form of a single piece or a strip. The "elongated shape" in this specification means an elongated shape with a length that is sufficiently long relative to the width, and includes, for example, an elongated shape with a length that is 10 times or more, and preferably 20 times or more, with respect to the width. The long polarizing plate with retardation layer can be rolled into a roll. When the polarizing plate with the retardation layer is in a strip shape, the polarizing plate and the retardation layer are also in a strip shape. In this case, it is preferable that the polarizing film has an absorption axis in the longitudinal direction. The first retardation layer is preferably an obliquely extending film having a slow axis in a direction at an angle of 40° to 50° with respect to the long direction. If the polarizing film and the first retardation layer have the above-mentioned structures, a polarizing plate with a retardation layer can be produced by roll-to-roll production.

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

The total thickness of the polarizing plate with the retardation layer is preferably 140µm or less, more preferably 120µm or less, more preferably 100µm or less, more preferably 90µm or less, still more preferably 85µm or less. The lower limit of the total thickness may be, for example, 80 µm. According to the embodiment of the present invention, it is possible to realize the extremely thin polarizing plate with a retardation layer as described above. The polarizing plate with a retardation layer can have excellent flexibility and bending durability. The polarizing plate with a retardation layer is particularly suitable for use 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 the retardation layer after deducting the adhesive layer used to adhere the polarizing plate with a retardation layer 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 the retardation layer to adjacent components such as the image display unit and the adhesive layer that can be temporarily adhered to The thickness of the peeling film on its surface).

Hereinafter, the first retardation layer, the second retardation layer, the conductive layer or the isotropic base material with the conductive layer will be described in detail. In addition, the first retardation layer may also be an orientationally solidified layer of a liquid crystal compound (hereinafter referred to as a liquid crystal orientationally solidified layer). Regarding the liquid crystal alignment solidified layer, a modification of the first retardation layer will be described in Section C-4.

C-2. 1st phase difference layer The first retardation layer 20 can have any appropriate optical properties and/or mechanical properties according to the purpose. The first phase difference 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 40° to 50°, preferably 42° to 48°, and more preferably about 45° as mentioned above. . If the angle θ is within the above range, as will be described later, by forming the first retardation layer into a λ/4 plate, it is possible to obtain an attached phase having very excellent circular polarization characteristics (and as a result, very excellent anti-reflection characteristics). Differential layer of polarizing plate.

The refractive index characteristics of the first phase difference layer should show the relationship nx>ny≧nz. The first retardation layer is typically provided to impart anti-reflective properties to the polarizing plate, and in one embodiment can function as a λ/4 plate. At this time, the in-plane phase difference Re (550) of the first retardation layer is 100 nm to 190 nm as mentioned above, preferably 110 nm to 170 nm, and more preferably 130 nm to 160 nm. In addition, "ny=nz" here includes not only the case where ny and nz are exactly the same, but also the case where they are substantially the same. Therefore, ny<nz may be satisfied as long as the effect of the present invention is not impaired.

The Nz coefficient of the first phase difference layer is preferably 0.9~3, more preferably 0.9~2.5, more preferably 0.9~1.5, especially 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 phase difference layer can exhibit inverse dispersion wavelength characteristics in which the phase difference value becomes larger with the wavelength of the measurement light. It can exhibit normal wavelength dispersion characteristics in which the phase difference value becomes smaller with the wavelength of the measurement light. It can also exhibit that the phase difference value hardly changes with the wavelength of the measurement light. Flat wavelength dispersion characteristics that measure changes in wavelength of light. In one embodiment, the first phase difference layer exhibits reverse dispersion wavelength characteristics. At this time, Re(450)/Re(550) of the phase difference layer is 0.8 or more and less than 1 as mentioned above, and is preferably 0.8 or more and 0.95 or less. With this configuration, very excellent anti-reflection properties can be achieved.

The absolute value of the photoelastic coefficient included in the first phase difference layer is preferably 2×10 ^-11 m ² /N or less, more preferably 2.0×10 ^-13 m ² /N~1.5×10 ^-11 m ² /N, and more preferably The resin is 1.0×10 ^-12 m ² /N~1.2×10 ^-11 m ² /N. If the absolute value of the photoelastic coefficient is within the above range, the phase difference will not easily change when shrinkage stress occurs during heating. As a result, thermal unevenness of the resulting image display device can be prevented satisfactorily.

The first retardation layer is typically composed of a stretched film of a resin film. The thickness of the first retardation layer is preferably 70µm or less, more preferably 45µm~60µm. If the thickness of the first retardation layer is within the above range, curling during heating can be well suppressed and curling during lamination can be well adjusted.

The first retardation layer 20 can be composed of any appropriate resin film that satisfies the above characteristics. Representative examples of the resin include polycarbonate resin, polyester carbonate resin, polyester resin, polyvinyl acetal resin, polyarylate resin, cyclic olefin resin, cellulose resin, Polyvinyl alcohol resin, polyamide resin, polyimide resin, polyether resin, polystyrene resin, acrylic resin. These resins can be used individually or in combination (eg blending, copolymerization). When the first retardation layer is composed of a resin film showing reverse dispersion wavelength characteristics, polycarbonate resin or polyestercarbonate resin (hereinafter sometimes referred to simply as polycarbonate resin) can be suitably used.

As long as the effects of the present invention can be obtained, any appropriate polycarbonate resin may be used as the polycarbonate resin. For example, the polycarbonate resin includes a structural unit derived from a fluorine-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and a structural unit derived from an alicyclic diol, an alicyclic dimethanol, The structural unit of at least one dihydroxy compound in the group consisting of di, tri or polyethylene glycol, and alkylene glycol or spiroglycerol. The polycarbonate resin preferably contains structural units derived from fluorine-based dihydroxy compounds, structural units derived from isosorbide-based dihydroxy compounds, structural units derived from alicyclic dimethanol, and/or derived from di- or tri-hydroxy compounds. Or structural units of polyethylene glycol; more preferably, it includes structural units derived from fluorine dihydroxy compounds, structural units derived from isosorbide dihydroxy compounds and structural units derived from di, tri or polyethylene glycol. The polycarbonate resin may also contain structural units derived from other dihydroxy compounds as needed. In addition, details of a polycarbonate-based resin suitably used for the first retardation layer and a method of forming the first retardation layer are described in, for example, Japanese Patent Laid-Open No. 2014-10291 and Japanese Patent Laid-Open No. 2014-26266 Publication No. 2015-212816, Japanese Patent Application Publication No. 2015-212817, and Japanese Patent Application Publication No. 2015-212818, the descriptions of these publications are incorporated into this specification as a reference.

C-3. Second phase difference layer As mentioned above, the second retardation layer may be a so-called positive C-plate whose refractive index characteristics exhibit the relationship nz>nx=ny. By using the positive C plate as the second retardation layer, oblique reflection can be effectively prevented, and the anti-reflection function can be widened to a wider viewing angle. At this time, the retardation Rth (550) in the thickness direction of the second retardation layer is preferably -50nm~-300nm, more preferably -70nm~-250nm, more preferably -90nm~-200nm, especially -100nm~ -180nm. Here, "nx=ny" includes not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal. That is, the in-plane phase difference Re(550) of the second retardation layer may be less than 10 nm.

The second retardation layer having the refractive index characteristic of nz>nx=ny can be formed of any appropriate material. The second retardation layer is preferably composed of a thin film containing a liquid crystal material fixed in a vertical alignment orientation. The liquid crystal material (liquid crystal compound) that can align the vertical plane can be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the method of forming the liquid crystal compound and the retardation layer include the liquid crystal compound and the method of forming the retardation layer described in paragraphs [0020] to [0028] of Japanese Patent Application Laid-Open No. 2002-333642. At this time, the thickness of the second retardation layer is preferably 0.5µm~10µm, more preferably 0.5µm~8µm, and more preferably 0.5µm~5µm.

C-4. Modification of the first phase difference layer The first retardation layer 20 may have a laminated structure of a first liquid crystal alignment solidified layer and a second liquid crystal alignment solidified layer. At this time, either one of the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer can function as a λ/4 plate, and the other can function as a λ/2 plate. Therefore, the thickness of the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer can be adjusted to obtain the desired in-plane phase difference of the λ/4 plate or the λ/2 plate. For example, when the first liquid crystal alignment solidified layer functions as a λ/2 plate and the second liquid crystal alignment solidified layer functions as a λ/4 plate, the thickness of the first liquid crystal alignment solidified layer is, for example, 2.0µm~3.0µm, and the second liquid crystal alignment solidified layer functions as a λ/4 plate. The thickness of the liquid crystal alignment solidified layer is, for example, 1.0µm~2.0µm. At this time, the in-plane phase difference Re(550) of the first liquid crystal alignment solidified layer is preferably 200nm~300nm, more preferably 230nm~290nm, and more preferably 250nm~280nm. The in-plane phase difference Re(550) of the second liquid crystal alignment solidified layer is preferably 100nm~190nm, more preferably 110nm~170nm, and more preferably 130nm~160nm. The angle formed by the slow axis of the first liquid crystal alignment solidified layer and the absorption axis of the polarizing film is preferably 10° to 20°, more preferably 12° to 18°, and more preferably about 15°. The angle formed by the slow axis of the second liquid crystal alignment solidified layer and the absorption axis of the polarizing film is preferably 70° to 80°, more preferably 72° to 78°, and more preferably about 75°. With the above-mentioned structure, characteristics close to ideal reverse wavelength dispersion characteristics can be obtained, and as a result, very excellent anti-reflection characteristics can be achieved. The refractive index characteristics of the first liquid crystal orientation solidified layer and the second liquid crystal orientation solidified layer represent the relationship of nx>ny=nz. The Nz coefficient of both the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer is preferably 0.9~1.5, more preferably 0.9~1.3. The liquid crystal compound constituting the first liquid crystal orientation solidified layer and the second liquid crystal orientation solidified layer, and the formation method of the first liquid crystal orientation solidified layer and the second liquid crystal orientation solidified layer are described in, for example, Japanese Patent Laid-Open No. 2006-163343 . The records in this publication are cited in this specification as a reference. In addition, when the first retardation layer has the above-mentioned multilayer structure, the second retardation layer can be omitted.

C-5. Conductive layer or isotropic substrate with conductive layer The conductive layer can be formed by forming a metal oxide film on any appropriate substrate using any appropriate film forming method (such as vacuum evaporation, sputtering, CVD, ion plating, spraying, 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 preferred.

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

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

Any appropriate isotropic base material can be used as the optically isotropic base material (isotropic base material). Examples of materials constituting the isotropic base material include materials having a main skeleton of a resin without a conjugated system, such as norbornene resin or olefin resin, and acrylic resin having a lactone ring or glutaryl ring in the main chain. Materials with cyclic structures such as imine rings, etc. If such a material is used, the phase difference accompanying the orientation of the molecular chain can be suppressed to be smaller when the isotropic base material is formed. The thickness of the isotropic substrate should be less than 50µm, more preferably less than 35µm. The lower limit of the thickness of the isotropic substrate is, for example, 20 μm.

The conductive layer and/or the conductive layer of the isotropic substrate with the conductive layer can be patterned as needed. Conductive portions and insulating portions can be formed through patterning. As a result, electrodes can be formed. The electrodes may function as touch sensing electrodes for sensing contact with the touch panel. The patterning method may employ any suitable method. Specific examples of the patterning method include wet etching and screen printing.

D.Image display device The polarizing plate described in the above items A and B or the polarizing plate with a retardation layer described in the above item C can be applied to an image display device. Therefore, embodiments of the present invention include an image display device using the polarizing plate or the polarizing plate with a retardation layer. Representative examples of image display devices include liquid crystal display devices and electroluminescence (EL) display devices (for example, organic EL display devices and inorganic EL display devices). The image display device according to the embodiment of the present invention is equipped with a polarizing plate or a polarizing plate with a phase difference layer on the viewing side. The polarizing plate with the retardation layer is laminated so that the retardation layer becomes the side of the image display unit (for example, liquid crystal unit, organic EL unit, inorganic EL unit) (the polarizing film becomes the viewing side). In one embodiment, the image display device has a curved shape (substantially a curved display screen) and/or is flexible or bendable. By using the above-mentioned polarizing plate or a polarizing plate with a retardation layer, the reflection hue of the image display device can be made close to neutral. Therefore, according to the embodiment of the present invention, an image adjustment method of the image display device can also be provided.

EXAMPLES The present invention will be specifically described below using examples, but the present invention is not limited by these examples. The measurement method of each characteristic is as follows. In addition, unless otherwise noted, "parts" and "%" in the examples and comparative examples are based on weight. (1) The thickness of 10 μm or less is measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-3000"). Thickness greater than 10µm is measured using a digital micrometer (manufactured by Anritsu Co., Ltd., product name "KC-351C"). (2) Monomeric transmittance and polarization degree The polarizing plates used in the examples and comparative examples were measured using an ultraviolet-visible spectrophotometer (V-7100 manufactured by JASCO Corporation), and the measured monomer transmittance Ts, parallel The transmittance Tp and the cross transmittance Tc are respectively regarded as Ts, Tp and Tc of the polarizing film. These Ts, Tp and Tc are Y values measured using the 2-degree field of view (C light source) of JIS Z8701 and corrected for visual sensitivity. In addition, the protective layer of the polarizing plate used in the examples and comparative examples has a hard coat (HC) layer on the surface. The refractive index of the protective layer is 1.50 and the refractive index of the HC layer is 1.53. Furthermore, the refractive index of the surface of the polarizing film on the side opposite to the protective layer is 1.53. The degree of polarization P was calculated from the obtained Tp and Tc using the following formula. Polarization degree P (%) = {(Tp-Tc)/(Tp+Tc)} ^{1 /2} ×100 In addition, a spectrophotometer such as LPF-200 manufactured by Otsuka Electronics Co., Ltd. can also be used to perform equivalent measurements. In terms of transmittance, whether it is the transmittance of the protective layer or the transmittance of the polarizing plate, the refractive index of the surface is the value when it is 1.50/1.53, but when the combination of the surface refractive index of the measured composition is different from this , a theoretical correction will be made based on the change in surface refractive index from the change in reflection from the air interface (surface reflection). For example, when measuring the composition of a TAC/polarizing film with an HC layer (set to a transmittance of 40%), the surface refractive index combination is 1.53/1.53. Therefore, by setting the measured value + 0.2%, it can be converted to 1.50/ The transmittance of the polarizing plate is 1.53 meters. The transmittance of the TAC film alone with the HC layer has a refractive index combination of 1.50/1.53, so no correction is performed. (3) Polarization degree reduction rate The polarizing plates with retardation layers obtained in Examples and Comparative Examples were subjected to a reliability test in an environment of 85°C and 85%RH for 48 hours. Assuming that the polarization degree of the polarizing film in the polarizing plate with a retardation layer after the reliability test is P ₄₈ and the initial polarization degree is P ₀ , the polarization degree reduction rate ΔP is calculated from the following formula. In addition, the initial polarization degree P ₀ is the polarization degree obtained in the above (2). ΔP(%)=P ₀ -P ₄₈

[Example 1-1] 1. Production of polarizing film The thermoplastic resin base material is a long amorphous isophthalic acid copolymer polyethylene terephthalate film (thickness: 100µm) with a water absorption rate of 0.75% and a Tg of approximately 75°C. And corona treatment is applied to one side of the resin substrate. A PVA system made by mixing polyvinyl alcohol (degree of polymerization 4200, saponification degree 99.2 mol%) and acetyl-acetyl modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z410") at a ratio of 9:1 13 parts by weight of potassium iodide was added to 100 parts by weight of the resin, and then dissolved in water to prepare a PVA aqueous solution (coating liquid). The above-mentioned PVA aqueous solution was applied to the corona-treated surface of the resin base material and dried at 60°C to form a PVA-based resin layer with a thickness of 13 μm, thereby producing a laminate. The obtained laminate was uniaxially stretched in the longitudinal direction (long side direction) at the free end between rollers with different circumferential speeds in an oven at 130°C to 2.4 times (air-assisted stretching treatment). Next, the laminated body was immersed in an insolubilization bath (a boric acid aqueous solution in which 4 parts by weight of boric acid was mixed with 100 parts by weight of water) having a liquid temperature of 40°C for 30 seconds (insolubilization treatment). Next, the concentration was adjusted in a dyeing bath (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) with a liquid temperature of 30°C, and the concentration was immersed in the dyeing bath for 60 seconds. The monomer transmittance (Ts) of the finally obtained polarizing film is made into a desired value (dyeing process). 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 to 100 parts by weight of water) with a liquid temperature of 40° C. for 30 seconds (crosslinking treatment) ). Then, while immersing the laminate in an aqueous solution with a liquid temperature of 70° C. (boric acid concentration 4.0 wt%, potassium iodide 5.0 wt%), the laminate was uniaxially stretched in the longitudinal direction (longitudinal direction) between rollers with different circumferential speeds. The total extension ratio reaches 5.5 times (extension treatment in water). Thereafter, the laminated body was immersed in a cleaning bath (an aqueous solution in which 4 parts by weight of potassium iodide was mixed with 100 parts by weight of water) having a liquid temperature of 20° C. (washing treatment). Thereafter, it was dried in an oven maintained at 90° C. while keeping the surface temperature in contact with a SUS heated roller kept at 75° C. for about 2 seconds (drying shrinkage treatment). The shrinkage rate of the laminate in the width direction under drying shrinkage treatment was 5.2%. Through the above procedures, a polarizing film with a thickness of 5µm was formed on the resin substrate.

2. Dyeing of TAC film The HC-TAC film on which the HC layer with a thickness of 7 µm and a refractive index of 1.53 was formed on a long TAC film (trade name "KC-2UA" manufactured by Konica Minolta Co., Ltd., thickness 25 µm) was immersed in liquid temperature while being conveyed. In a dyeing bath at 25°C (iodine aqueous solution with an iodine concentration of 1.0% by weight). The soaking time is 180 seconds. The iodine content (iodine detection amount by X-ray fluorescence detection) of the obtained dyed TAC film was 0.058kcps. In addition, the iodine content can be measured with a scanning X-ray fluorescence analyzer ("ZSX Primus IV" manufactured by Rigaku Corporation).

3. Production of polarizing plates The dyed TAC film with the HC layer obtained in the above 2. is bonded to the surface of the polarizing film obtained in the above 1. (the side opposite to the resin base material) through an ultraviolet curable adhesive. Specifically, the hardened adhesive is applied to a total thickness of 1.0µm and bonded using a roller. Then, UV light is irradiated from the TAC film side to harden the adhesive. Next, both ends were cut, and the resin base material was peeled off to obtain a long polarizing plate (width: 1300 mm) having a structure of protective layer (dyed TAC film)/adhesive layer/polarizing film. The single transmittance of the polarizing plate (essentially a polarizing film) is 43.2%, and the polarization degree is 99.995%.

4. Preparation of retardation film constituting the retardation layer 4-1. Polymerization of polyester carbonate resin using a batch consisting of two vertical reactors equipped with stirring blades and a reflux cooler controlled to 100°C The polymerization device performs polymerization. Feed in 29.60 parts by mass (0.046 mol) of bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane, 29.21 parts by mass (0.200 mol) of isosorbide (ISB), and spiroglycerol (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 the reactor was replaced with nitrogen under reduced pressure, it was heated with a heat medium, and stirring was started when the internal temperature reached 100°C. The internal temperature was brought to 220°C 40 minutes after the start of the temperature rise, and the pressure was reduced while maintaining the temperature. After reaching 220°C, it was adjusted to 13.3 kPa in 90 minutes. The phenol vapor generated by the polymerization reaction is introduced into the reflux cooler at 100°C, so that a small amount of monomer components contained in the phenol vapor is returned to the reactor, and the uncondensed phenol vapor is introduced into the condensator 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 is moved to the second reactor. Next, the temperature increase and pressure reduction in the second reactor were started, and the internal temperature was adjusted to 240° C. and the pressure to 0.2 kPa over 50 minutes. Then, polymerization is performed until a predetermined stirring power is reached. At the time point when the predetermined power is reached, nitrogen is introduced into the reactor to restore the pressure, the generated polyester carbonate resin is extruded into water, and the bundles are cut to obtain pellets.

4-2. Production of phase difference film The obtained polyester carbonate resin (pellets) was vacuum-dried at 80°C for 5 hours, and then used a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder set temperature: 250°C) and a T-die (width 200mm). , set temperature: 250℃), cooling roller (set temperature: 120~130℃) and film forming device of the winding machine to produce a long resin film with a thickness of 135µm. The obtained long resin film was stretched in the width direction at a stretching temperature of 133°C and a stretching ratio of 2.8 times to obtain a phase difference film with a thickness of 48µm. The Re(550) of the obtained retardation film was 144 nm, Re(450)/Re(550) was 0.82, and the Nz coefficient was 1.12.

5. Production of polarizing plate with phase difference layer The retardation film obtained in the above 4. is bonded to the surface of the polarizing film of the polarizing plate obtained in the above 3. through an acrylic adhesive (thickness: 5µm). At this time, they are bonded so that the absorption axis of the polarizing film and the slow axis of the retardation film form an angle of 45°. In the above manner, a polarizing plate with a retardation layer composed of a protective layer/adhesive layer/polarizing film/adhesive layer/retardation layer is obtained. The total thickness of the polarizing plate with the retardation layer obtained was 84µm. The obtained polarizing plate with a retardation layer was used for the evaluation of (3) above. The results are listed in Table 1.

[Example 1-2] The TAC film was dyed in the same manner as in Example 1-1 except that the dyeing time was set to 300 seconds. The iodine content of the obtained dyed TAC film was 0.090kcps. Except using the dyed TAC film, a polarizing plate with a retardation layer was produced in the same manner as in Example 1-1. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1-1. The results are listed in Table 1.

[Example 1-3] The TAC film was dyed in the same manner as in Example 1-1 except that the dyeing time was set to 600 seconds. The iodine content of the obtained dyed TAC film was 0.140kcps. Except using the dyed TAC film, a polarizing plate with a retardation layer was produced in the same manner as in Example 1-1. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1-1. The results are listed in Table 1.

[Comparative example 1] Except using undyed TAC film, a polarizing plate with a retardation layer was produced in the same manner as in Example 1-1. No iodine was detected in the unstained TAC film. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1-1. The results are listed in Table 1.

[Example 2] Adjust the dyeing conditions to produce a polarizing film with a monomer transmittance of 43.7%. Except using the polarizing film, a polarizing plate with a retardation layer was produced in the same manner as in Example 1-2. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1-1. The results are listed in Table 1.

[Comparative example 2] Except using an undyed TAC film, a polarizing plate with a retardation layer was produced in the same manner as in Example 2. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1-1. The results are listed in Table 1.

[Table 1]

[evaluate] It can be clearly seen from Table 1 that according to embodiments of the present invention, by using a dyed TAC film as a protective layer, the decrease in polarization degree in a high-temperature and high-humidity environment can be significantly suppressed.

industrial availability The polarizing plate with a 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:Polarizing plate 11:Polarizing film 12:Visual side protective layer 13:Inner protective layer 20: Phase difference layer (first phase difference layer) 50: Another phase difference layer (second phase difference layer) 60: Conductive layer or isotropic substrate with conductive layer 100: Polarizing plate with phase difference layer 101: Polarizing plate with phase difference layer 200:Laminated body G1~G4: guide roller R1~R6: conveyor roller

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

10:Polarizing plate

11:Polarizing film

12:Visual side protective layer

13:Inner protective layer

20: Phase difference layer (first phase difference layer)

100: Polarizing plate with phase difference layer

Claims (9)

A polarizing plate, comprising a polarizing film and a protective layer arranged on at least one side of the polarizing film; The thickness of the polarizing film is less than 8µm; The protective layer is composed of an iodine-dyed cellulose triacetate film, and contains an iodine detection amount of 0.02 kcps or more based on X-ray fluorescence detection. For example, the polarizing plate in claim 1 has an initial monomer transmittance of 43.0%~43.5%, and the polarization reduction rate after being kept in an environment of 85°C and 85%RH for 48 hours is less than 0.75%. For example, the polarizing plate in claim 1 has an initial monomer transmittance greater than 43.5% and less than 44.0%, and the polarization reduction rate after being maintained in an environment of 85°C and 85%RH for 48 hours is less than 2.0%. A method of manufacturing a polarizing plate is a method of manufacturing a polarizing plate according to any one of claims 1 to 3, which includes the following steps: A polyvinyl alcohol-based resin layer is formed on one side of a long thermoplastic resin base material to form a laminate; subjecting the laminate to dyeing treatment and stretching treatment to form a polyvinyl alcohol-based resin layer into a polarizing film; Dyeing the cellulose triacetate film with iodine; and The dyed cellulose triacetate film is bonded to the polarizing film. The method for manufacturing a polarizing plate according to claim 4, wherein the dyeing includes immersing the cellulose triacetate film in an iodine aqueous solution with an iodine concentration of 0.1% by weight or more. A polarizing plate with a retardation layer, including the polarizing plate according to any one of claims 1 to 3 and a retardation layer arranged on the side opposite to the viewing side of the polarizing plate; Re(550) of the phase difference layer is 100nm~190nm, 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 of the polarizing plate is 40° to 50°. A polarizing plate with a retardation layer, including the polarizing plate according to any one of claims 1 to 3 and a retardation layer arranged on the side of the polarizing plate opposite to the viewing side; The retardation layer has a laminated structure of a directionally solidified layer of a first liquid crystal compound and a directionally solidified layer of a second liquid crystal compound; The Re(550) of the orientationally solidified layer of the first liquid crystal compound is 200nm~300nm, and the angle formed by its slow axis and the absorption axis of the polarizing film is 10°~20°; The Re(550) of the orientationally solidified layer of the second liquid crystal compound is 100nm~190nm, and the angle formed by its slow axis and the absorption axis of the polarizing film is 70°~80°. An image display device provided with the polarizing plate according to any one of claims 1 to 3. An image display device provided with a polarizing plate with a retardation layer according to claim 6 or 7.