JP7831282B2 - Polarizing plates and organic electroluminescent display devices - Google Patents

Description

The present invention relates to a polarizing plate and an organic electroluminescent display device, and more particularly to a polarizing plate and an organic electroluminescent display device that, when used in a display device, especially an organic electroluminescent display device, can protect the display element from ambient light, prevent the display element from experiencing light emission loss, and improve the adhesion between the layer containing the dye compound and the adjacent layer.

In recent years, display devices such as smartphones are often used under strong ambient light. To improve visibility under ambient light, organic electroluminescent (EL) elements are increasingly being used as light sources. However, this has led to the problem of organic EL elements degrading due to ambient light. Therefore, a technology has been developed to suppress the degradation of organic EL elements due to ambient light by incorporating an ultraviolet absorber and a dye compound that absorbs light at longer wavelengths than the ultraviolet absorber into components such as polarizers placed on the viewing side of the organic EL element in organic EL display devices.

Specifically, for example, Patent Document 1 describes an adhesive sheet having an adhesive layer containing an acrylic polymer and a triazine-based ultraviolet absorber, with a total light transmittance of 85% or more and a light transmittance of 5% or less at a wavelength of 380 nm.

The adhesive sheet described in Patent Document 1 can control the transmittance of light with a wavelength of 380 nm. However, when this adhesive sheet is used in an organic EL display device, the organic EL element may degrade after prolonged use, indicating that it is not sufficient. This is because, although the adhesive sheet described in Patent Document 1 can absorb light with a wavelength of 380 nm, it does not sufficiently absorb light in the wavelength range (380-430 nm) shorter than the light-emitting region of the organic EL element (longer wavelengths than 430 nm), and degradation is thought to occur due to this transmitted light.

Furthermore, Patent Document 2 describes an organic EL display device having an organic EL element and an optical laminate in which a polarizer, a phase difference film, and at least one other layer, such as an adhesive layer, are laminated on the viewing side thereof. Patent Document 2 describes a technique for suppressing the degradation of the organic EL element by incorporating an ultraviolet absorber and a dye compound whose maximum absorption wavelength in the absorption spectrum is in the wavelength range of 380 to 430 nm into separate layers constituting the optical laminate, and arranging the layer containing the ultraviolet absorber so that it is on the viewing side of the layer containing the dye compound. Patent Document 2 states that by arranging each layer in such a specific order, it is possible to prevent the dye compound from degrading when exposed to ultraviolet light.

However, using a dye compound whose absorption region overlaps the light-emitting region of an organic EL element can result in light emission loss and a decrease in brightness. Therefore, it is necessary to use a compound that does not have an absorption region in the light-emitting region. However, in the case of the dye compound disclosed in Patent Document 2, the maximum absorption wavelength of the absorption spectrum is in the wavelength range of 380 to 430 nm. As a result, the absorption region of the dye compound overlaps the light-emitting region of the organic EL element, leading to a decrease in the brightness of the organic EL element.

In other words, in order to suppress the degradation of organic EL elements, it is necessary to suppress the transmission of light at wavelengths shorter than the light-emitting region of the organic EL element (380-430 nm) and to prevent brightness loss in the light emission of the organic EL element, the organic EL display device must be equipped with a mechanism that can sufficiently ensure the transmittance of visible light in the light-emitting region of the organic EL element.

On the other hand, when considering the outdoor use of display devices such as smartphones, it is known that a hard coat film is placed on the outermost surface on the viewing side. However, when durability tests are conducted on hard coat films in which a hard coat layer is provided on a base film, the adhesion between the base film and the hard coat layer may deteriorate. Patent Document 3 discloses a technology in which a UV-curable resin composition is used for the hard coat layer, with a specific urethane acrylate as the main component and a glass transition temperature of 110°C or higher as measured by a differential scanning calorimeter. Although the interlayer adhesion between the base film and the hard coat layer is improved to some extent before the durability test, the improvement in adhesion after the durability test was low.

Japanese Patent Publication No. 2013-75978 Japanese Patent Publication No. 2017-168430 Japanese Patent Publication No. 2009-62499

The present invention has been made in view of the above problems and circumstances, and its objective is to provide a polarizing plate and an organic electroluminescent display device that, when used in a display device, particularly an organic EL display device, can protect the display element from ambient light, prevent the display element from experiencing light emission loss, and improve the adhesion between the layer containing the dye compound and the adjacent layer.

In order to solve the above problems, the inventors of the present invention, in the process of investigating the causes of the above problems, found that by providing a polarizing plate with a layer containing an ultraviolet absorber (ultraviolet absorber-containing layer) and a layer containing a dye compound that absorbs light in a predetermined wavelength range longer than the ultraviolet absorber (dye compound-containing layer), and arranging the dye compound-containing layer on the visible side of the ultraviolet absorber layer, it is possible to obtain a polarizing plate that can protect the display element from external light, prevents light emission loss of the display element, and improves the adhesion between the dye compound-containing layer and the adjacent layer, thus leading to the present invention.

In other words, the above-mentioned problems according to the present invention are solved by the following means.

1. A polarizing plate having a hard coat layer, a protective film, a polarizer, and a phase difference film in this order from the viewing side,
At least one of the hard coat layer and the protective film contains a dye compound whose maximum absorption wavelength is within the range of 370 to 379 nm in the absorption spectrum of the 300 to 460 nm wavelength region, at least one of the protective film and the phase difference film contains an ultraviolet absorber, and the layer containing the dye compound is located on the visible side of the layer containing the ultraviolet absorber.
The ultraviolet absorber is a compound whose maximum absorption wavelength in the absorption spectrum of the 300-460 nm wavelength range is within the range of 349-355 nm .
A polarizing plate characterized in that the aforementioned dye compound contains a compound having a structure represented by the following general formula (1), or a compound having a structure represented by the following general formula (2).
(In the formula, R ₁₁ represents a hydrogen atom, halogen atom, alkyl group, alkoxy group, hydroxy group, amino group, alkyl-substituted amino group, carboxy group, alkyloxycarbonyl group, hydroxyalkyl group, alkylcarbonyloxyalkyl group, carboxyalkyl group, alkyloxycarbonylalkyl group, aryl group, acyl group, or sulfo group. R ₁₂ represents a hydrogen atom or a hydroxyl group.)
(In the formula, R ₂₁ represents a hydrogen atom or a hydroxyl group. _{R 22} , R ₂₃ , and R ₂₄ represent an alkyl group, an alkoxy group, an alkyl-substituted amino group, a carboxyl group, an alkyloxycarbonyl group, a hydroxyalkyl group, an alkylcarbonyloxyalkyl group, a carboxyalkyl group, an alkyloxycarbonylalkyl group, an aryl group, an acyl group, or a sulfo group.)

2. The polarizing plate according to paragraph 1, characterized in that the dye compound is contained in the hard coat layer and the ultraviolet absorber is contained in the protective film.

3. The polarizing plate according to paragraph 1 or 2 , characterized in that it comprises an adhesive layer on the side of the phase difference film opposite to the viewing side.

4. An organic electroluminescent display device characterized by having a polarizing plate described in any one of paragraphs 1 to 3 on the viewing side.

The above-described means of the present invention makes it possible to provide a polarizing plate and an organic electroluminescent display device that, when used in a display device, particularly an organic EL display device, can protect the display element from ambient light, prevent light emission loss of the display element, and improve the adhesion between the layer containing the dye compound and the adjacent layer.

Although the mechanism of action or mechanism of the present invention is not yet clear, it is speculated as follows.

The polarizing plate of the present invention has a hard coat layer, a protective film, a polarizer, and a phase difference film in this order from the viewing side, wherein at least one of the hard coat layer and the protective film contains a dye compound (hereinafter also simply referred to as "compound (D)") whose maximum absorption wavelength in the absorption spectrum of the 300 to 460 nm wavelength region is in the range of 360 to 379 nm, and at least one of the protective film and the phase difference film contains an ultraviolet absorber, and the layer containing compound (D) is located on the viewing side of the layer containing the ultraviolet absorber.

The polarizing plate of the present invention is configured such that, when used in a display device, particularly an organic EL display device, the layer containing compound (D) is positioned on the viewing side of the ultraviolet absorber-containing layer. Here, the ultraviolet absorber is a compound whose maximum absorption wavelength in the absorption spectrum of the 300-460 nm wavelength range is within the range of 300-359 nm.

The polarizing plate of the present invention, by using a combination of the compound (D)-containing layer and the ultraviolet absorber-containing layer, can sufficiently absorb light with wavelengths shorter than the light-emitting region of an organic EL element (longer wavelengths than 430 nm), for example, thereby protecting display elements such as organic EL elements from external light.

Furthermore, organic compounds can absorb light of a certain wavelength and convert it into thermal energy. It is believed that the polarizing plate of the present invention can improve the adhesion between the hard coat layer and the protective film by promoting molecular motion through the heat generated by this conversion, thereby strengthening the interaction with adjacent layers.

The present invention provides a polarizing plate and an organic electroluminescent display device that can protect the display element from ambient light, prevent luminance loss in the light emitted by the display element, and further improve the adhesion between the layer containing compound (D) according to the present invention and the adjacent layer.

Cross-sectional view showing an example of the configuration of the polarizing plate of the present invention. Cross-sectional view showing another polarizing plate configuration example of the present invention. Cross-sectional view showing an example configuration of the organic EL display device of the present invention. A schematic plan view showing the general configuration of a manufacturing apparatus for diagonally stretched film. Figure 4 shows a schematic plan view illustrating an example of the rail pattern of the stretching section of the oblique stretching film manufacturing apparatus.

The polarizing plate of the present invention is a polarizing plate having a hard coat layer, a protective film, a polarizer, and a phase difference film in this order from the viewing side, wherein at least one of the hard coat layer and the protective film contains a dye compound whose maximum absorption wavelength is in the range of 360 to 379 nm in the absorption spectrum of the 300 to 460 nm wavelength region, at least one of the protective film and the phase difference film contains an ultraviolet absorber, and the layer containing the dye compound is located on the viewing side of the layer containing the ultraviolet absorber. This feature is a technical feature common to or corresponding to the following embodiments.

In embodiments of the present invention, from the viewpoint of improving adhesion, it is preferable that the compound (D) is contained in the hard coat layer and the ultraviolet absorber is contained in the protective film.

In embodiments of the present invention, from the viewpoint of suppressing brightness loss with respect to the light emission of the display element, it is preferable that the compound (D) contains a compound having the structure represented by the general formula (1) or a compound having the structure represented by the general formula (2).

The polarizing plate of the present invention may further include an adhesive layer on the side of the phase difference film opposite to the viewing side. This improves the workability when manufacturing an organic EL display device in which the polarizing plate is placed on the viewing side of the organic EL element.

The organic EL display device of the present invention is characterized by having the polarizing plate of the present invention on the viewing side. As a result, the organic EL display device is an organic EL display device in which the deterioration of quality during long-term use is suppressed.

The present invention, its components, and embodiments for carrying out the present invention will be described in detail below. In this application, "~" is used to mean that the numerical values before and after it are included as the lower and upper limits. In this specification, a compound having the structure represented by general formula (1) is also referred to as compound (1). Similarly, a compound having the structure represented by general formula (2) is also referred to as compound (2).

<Overview of the polarizing plate of the present invention>
The polarizing plate of the present invention is a polarizing plate having a hard coat layer, a protective film, a polarizer, and a phase difference film in this order from the viewing side, wherein at least one of the hard coat layer and the protective film contains a dye compound whose maximum absorption wavelength is in the range of 360 to 379 nm in the absorption spectrum of the wavelength region of 300 to 460 nm, at least one of the protective film and the phase difference film contains an ultraviolet absorber, and the layer containing the dye compound is located on the viewing side of the layer containing the ultraviolet absorber.

In this specification, the term "ultraviolet absorber" refers to a compound whose maximum absorption wavelength in the absorption spectrum of the 300-460 nm wavelength range is within the range of 300-359 nm. Furthermore, the "maximum absorption wavelength" in the absorption spectrum of a specific wavelength range means the absorption maximum wavelength that shows the greatest absorbance among multiple absorption maxima in the spectral absorption spectrum of that specific wavelength range. In addition, the absorption spectra of various compounds are those measured by a spectrophotometer after dissolving the compound in chloroform.
(Measurement of maximum absorption wavelength)
The maximum absorption wavelength of the above compound can be determined, for example, by measuring the absorption spectrum of the dye compound in chloroform using a UV-2450 ultraviolet-visible spectrophotometer manufactured by Shimadzu Corporation.
In this invention, "maximum absorption wavelength" refers to the wavelength (nm) that exhibits the maximum and highest absorbance (absorption intensity) in the absorption spectrum of the compound obtained when the absorption spectrum of the above compound is measured.

The polarizing plate of the present invention may further include an adhesive layer on the side of the phase difference film opposite to the viewing side. The polarizing plate of the present invention may further have other layers as needed, to the extent that they do not impair the effects of the present invention. Examples of other layers include a primer layer provided on one or both sides of the protective film depending on the material of the protective film, and adhesive layers provided between the protective film and the polarizer, and between the phase difference film and the polarizer, respectively.

The components of the present invention will be described in detail below with reference to the drawings.
Figure 1 is a cross-sectional view showing an example of the configuration of a polarizing plate 10A of the present invention, having a hard coat layer 1, a protective film 2, a polarizer 3, and a phase difference film 4 in that order from the viewing side. Figure 2 is a cross-sectional view showing an example of the configuration of a polarizing plate 10B of the present invention, having a hard coat layer 1, a protective film 2, a polarizer 3, a phase difference film 4, and an adhesive layer 5 in that order from the viewing side.

The polarizing plate of the present invention, for example, as an example using polarizing plate 10B, is used in such a manner that the adhesive layer 5 is arranged on the viewing side of the organic EL element 11, as shown in the organic EL display device 20 whose cross-sectional view is shown in Figure 3.

The polarizing plate of the present invention will be described below, mainly using polarizing plate 10A as an example, but the present invention is not limited thereto. In the present invention, polarizing plate 10A has a configuration that satisfies the following conditions (1) to (3).

(1) At least one of the hard coat layer 1 and the protective film 2 contains compound (D).

(2) At least one of the protective film 2 and the phase difference film 4 contains an ultraviolet absorber.

(3) The layer containing compound (D) of (1) above is located on the visible side of the layer containing the ultraviolet absorber of (2) above.

Table I shows an example of a polarizing plate 10A that satisfies all of the above (1) to (3), with configurations 1 to 5 being examples. In Table I, "(D)" indicates that the layer or film in the left column of Table I contains compound (D), and "UVA" indicates that the layer or film in the left column of Table I contains an ultraviolet absorber.

In the polarizing plate 10A, it is preferable that each of the layers containing compound (D) and the ultraviolet absorber be one layer, i.e., configurations 1, 2, and 3, from the viewpoint of ease of adjusting optical properties and ease of manufacturing. Furthermore, from the viewpoint of protecting the substrate on which the polarizing plate 10A is provided and the polarizer 3, it is preferable that compound (D) is contained in the hard coat layer 1 and the ultraviolet absorber is contained in the protective film 2, i.e., configurations 1 and 4, with configuration 1 being particularly preferred.

[Dye compound: Compound (D)]
The compound (D) used in this invention is any compound whose maximum absorption wavelength is located at 360 to 379 nm in the absorption spectrum in the wavelength range of 300 to 460 nm, and is not particularly limited otherwise. Hereinafter, unless otherwise specified, the maximum absorption wavelength of each compound refers to the maximum absorption wavelength in the absorption spectrum in the wavelength range of 300 to 460 nm.

The maximum absorption wavelength of compound (D) is more preferably in the wavelength range of 370 to 379 nm. Compound (D), having the above-mentioned absorption characteristics, can protect the display element, particularly the organic EL element, from ambient light and suppress degradation. While compound (D) is not particularly limited as long as it has the above-mentioned absorption characteristics, it is preferable that it does not have fluorescence or phosphorescence (photoluminescence) that would impair the display performance of the organic EL element.

Compound (D) is not particularly limited in structure, etc., as long as it has the above-mentioned light absorption properties. Examples of compound (D) include organic compounds and inorganic compounds. Compound (D) is contained in the hard coat layer and/or protective film, and from the viewpoint of dispersibility in resin components such as base polymers that are film-forming components of these layers or films and maintaining transparency, organic compounds are preferred.

Examples of the above-mentioned organic compounds include azomethine compounds, indole compounds, cinnamic acid compounds, pyrimidine compounds, methine compounds, porphyrin compounds, dicyanomethine compounds, benzotriazole compounds, and the like.

Since compound (D) is contained in the layer on the visible side of the layer containing the ultraviolet absorber, it is preferable that it has light resistance to light with wavelengths of 380 nm or less. Examples of such compound (D) include compound (1) and compound (2) having structures represented by the following general formulas (1) and (2).

(In the formula, R ₁₁ represents a hydrogen atom, halogen atom, alkyl group, alkoxy group, hydroxy group, amino group, alkyl-substituted amino group, carboxy group, alkyloxycarbonyl group, hydroxyalkyl group, alkylcarbonyloxyalkyl group, carboxyalkyl group, alkyloxycarbonylalkyl group, aryl group, acyl group, or sulfo group. R ₁₂ represents a hydrogen atom or a hydroxyl group.)

(In the formula, R ₂₁ represents a hydrogen atom or a hydroxyl group. _{R 22} , R ₂₃ , and R ₂₄ represent an alkyl group, an alkoxy group, an alkyl-substituted amino group, a carboxyl group, an alkyloxycarbonyl group, a hydroxyalkyl group, an alkylcarbonyloxyalkyl group, a carboxyalkyl group, an alkyloxycarbonylalkyl group, an aryl group, an acyl group, or a sulfo group.)

The number of carbon atoms in the alkyl group in the alkyl group, alkoxy group, alkynyl group, and alkyl-substituted amino group is preferably 1 to 20, and more preferably 1 to 10. The alkyl group and the alkyl group of the alkoxy group or alkyl-substituted amino group may be linear, branched, cyclic, or a combination thereof. The number of carbon atoms in the aryloxy group is typically 5 to 30. In the aryloxy group, the aryl group may have a heteroatom. The aromatic ring of the aryl group may be monocyclic or fused. Examples of aryloxy groups include phenoxy group, naphthyloxy group, and 2-methylphenoxy group.
The following are examples of compounds having structures represented by general formulas (1) and (2), but are not limited to these.

The compounds having the structures represented by general formulas (1) and (2) according to the present invention can be synthesized by conventionally known methods. That is, as shown in the reaction scheme below, nitroanilines can be diazotized, and the nitrophenylazo compound obtained by coupling with sesamol by a conventional method can be reduced to synthesize the target benzotriazole derivative.

[Synthesis of 6-(5-methoxycarbonyl-2H-benzotriazole-2-yl)benzo[1,3]dioxol-5-ol]

A 300 ml four-necked flask was fitted with a ball-type condenser, thermometer, and stirrer. 1.1 g (0.0037 mol) of 6-(5-carboxy-2H-benzotriazol-2-yl)benzo[1,3]dioxol-5-ol, 200 ml of toluene, 0.9 g (0.0076 mol) of thionyl chloride, and 0.2 ml of N,N-dimethylformamide were added, and the mixture was stirred at 65-70°C for 3 hours. After removing the solvent by distillation, 150 ml of toluene, 0.5 g (0.0156 mol) of methanol, and 0.8 g (0.0101 mol) of pyridine were added, and the mixture was stirred at 70-75°C for 2 hours. The solution was washed twice with 100 ml of warm water, 0.1 g of activated carbon was added, and the mixture was decolorized by reflux stirring. The solution was then filtered while still hot, the filtrate was cooled to 5°C, the precipitated crystals were filtered, washed with toluene, and dried at 60°C to obtain 0.5 g of compound (1-8). The yield was 43% (from 6-(5-carboxy-2H-benzotriazol-2-yl)benzo[1,3]dioxol-5-ol). The maximum absorption wavelength was 377 nm.

Compound (D) may be used alone or in combination of two or more compounds. The content of compound (D) in a layer containing compound (D) is expressed as parts by mass of compound (D) per 100 parts by mass of the resin component which is the film-forming component in each layer.

For example, in the case of configurations 1, 2, and 4 described above, in which compound (D) is contained only in the hard coat layer, the content of compound (D) per 100 parts by mass of the constituent resin of the hard coat layer is preferably in the range of 0.01 to 50 parts by mass, and more preferably in the range of 0.02 to 30 parts by mass.

Furthermore, in the case of configuration 3 in which compound (D) is contained only in the protective film, the content of compound (D) per 100 parts by mass of the constituent resin of the protective film is preferably in the range of 0.01 to 10 parts by mass, and more preferably in the range of 0.02 to 8 parts by mass. In the case of configuration 5 in which both the hard coat layer and the protective film contain compound (D), the total content of compound (D) in each layer is preferably in the range of 0.01 to 10 parts by mass, and more preferably in the range of 0.02 to 8 parts by mass, per 100 parts by mass of the total amount of constituent resin in each layer.

By setting the content of compound (D) within the above range, when the polarizing plate of the present invention is used in an organic EL display device, it is possible to sufficiently absorb light in a region that does not affect the light emission of the organic EL element, thereby suppressing the degradation of the organic EL element, which is preferable.

[UV absorber]
The ultraviolet absorber is not particularly limited as long as it has a maximum absorption wavelength in the wavelength range of 300 to 359 nm.

Examples of UV absorbers include triazine-based UV absorbers, benzotriazole-based UV absorbers, benzophenone-based UV absorbers, oxybenzophenone-based UV absorbers, salicylate-based UV absorbers, and cyanoacrylate-based UV absorbers. These can be used individually or in combination of two or more.

Among these, triazine-based UV absorbers and benzotriazole-based UV absorbers are preferred, and it is preferable that at least one UV absorber is selected from the group consisting of triazine-based UV absorbers having two or fewer hydroxyl groups per molecule and benzotriazole-based UV absorbers having one benzotriazole skeleton per molecule. These UV absorbers are preferred because they have good solubility in resin components such as base polymers, which are film-forming components of protective films and/or phase difference films containing the UV absorber. Furthermore, these UV absorbers are preferred because they have high UV absorption capacity around a wavelength of 380 nm.

Triazine-based UV absorbers having two or fewer hydroxyl groups in one molecule include, specifically, 2,4-bis-[{4-(4-ethylhexyloxy)-4-hydroxy}-phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine (Tinosorb S, manufactured by BASF), 2,4-bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine (TINUVIN 460, manufactured by BASF), and the reaction product of 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl)-5-hydroxyphenyl and [(C10-C16 (mainly C12-C13) alkyloxy)methyl]oxirane (TINUVIN 400 (BASF), 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl]-5-[3-(dodecyloxy)-2-hydroxypropoxy]phenol), reaction product of 2-(2,4-dihydroxyphenyl)-4,6-bis-(2,4-dimethylphenyl)-1,3,5-triazine and (2-ethylhexyl)-glycidic acid ester (TINUVIN 405, BASF), 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[(hexyl)oxy]-phenol (TINUVIN 1577, BASF), 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]-phenol (ADK STAB Examples include LA46 (manufactured by ADEKA Corporation), 2-(2-hydroxy-4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine (TINUVIN 479, manufactured by BASF), 6,6',6''-(1,3,5-triazine-2,4,6-triyl)tris(3-hexyloxy-2-methylphenol) (LA-F70, manufactured by ADEKA Corporation), etc.

Furthermore, examples of benzotriazole-based UV absorbers having one benzotriazole skeleton in one molecule include 2-(2H-benzotriazole-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol (TINUVIN 928, manufactured by BASF), 2-(2-hydroxy-5-tert-butylphenyl)-2H-benzotriazole (TINUVIN PS, manufactured by BASF), benzenepropanoic acid and 3-(2H-benzotriazole-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy(C7-9 side chain and linear alkyl) ester compounds (TINUVIN 384-2, manufactured by BASF), and 2-(2H-benzotriazole-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (TINUVIN Reaction product of methyl-3-(3-(2H-benzotriazole-2-yl)-5-t-butyl-4-hydroxyphenyl)propionate/polyethylene glycol 300 (TINUVIN 1130, BASF), 2-(2H-benzotriazole-2-yl)-p-cresol (TINUVIN P, BASF), 2(2H-benzotriazole-2-yl)-4-6-bis(1-methyl-1-phenylethyl)phenol (TINUVIN 234, BASF), 2-[5-chloro(2H)-benzotriazole-2-yl]-4-methyl-6-(tert-butyl)phenol (TINUVIN 326, BASF), 2-(2H-benzotriazole-2-yl)-4,6-di-tert-pentylphenol (TINUVIN 328 (BASF), 2-(2H-benzotriazole-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol (TINUVIN 329 (BASF)), reaction product of methyl 3-(3-(2H-benzotriazole-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionate and polyethylene glycol 300 (TINUVIN 213 (BASF)), 2-(2H-benzotriazole-2-yl)-6-dodecyl-4-methylphenol (TINUVIN Examples include 571 (manufactured by BASF), 2-[2-hydroxy-3-(3,4,5,6-tetrahydrophthalimidomethyl)-5-methylphenyl]benzotriazole (Sumisorb 250, manufactured by Sumitomo Chemical Co., Ltd.), 2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-chlorobenzotriazole (SeeSorb 703, manufactured by Cipro Chemical Co., Ltd., or KEMISORB 73, manufactured by Cipro Chemical Co., Ltd.).

Furthermore, examples of the above-mentioned benzophenone-based ultraviolet absorbers (benzophenone compounds) and oxybenzophenone-based ultraviolet absorbers (oxybenzophenone compounds) include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (anhydrous and trihydrate), 2-hydroxy-4-octyloxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 4-benzyloxy-2-hydroxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2,2'-dihydroxy-4,4-dimethoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone (SeeSorb 106, manufactured by Cipro Chemical Co., Ltd.), and 2,2'-dihydroxy-4-methoxybenzophenone (KEMISORB 111, manufactured by Chemipro Chemical Co., Ltd.).

Examples of the salicylic acid ester-based ultraviolet absorbers (salicylic acid ester compounds) mentioned above include phenyl-2-acryloyloxybenzoate, phenyl-2-acryloyloxy-3-methylbenzoate, phenyl-2-acryloyloxy-4-methylbenzoate, phenyl-2-acryloyloxy-5-methylbenzoate, phenyl-2-acryloyloxy-3-methoxybenzoate, phenyl-2-hydroxybenzoate, phenyl-2-hydroxy-3-methylbenzoate, phenyl-2-hydroxy-4-methylbenzoate, phenyl-2-hydroxy-5-methylbenzoate, phenyl-2-hydroxy-3-methoxybenzoate, 2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate (TINUVIN 120, manufactured by BASF), and the like.

Examples of the above-mentioned cyanoacrylate-based ultraviolet absorbers (cyanoacrylate compounds) include alkyl-2-cyanoacrylate, cycloalkyl-2-cyanoacrylate, alkoxyalkyl-2-cyanoacrylate, alkenyl-2-cyanoacrylate, and alkynyl-2-cyanoacrylate.

UV absorbers may be used alone or in mixtures of two or more types. The UV absorber content in a layer containing UV absorbers is expressed as parts by mass of UV absorber per 100 parts by mass of the resin component, which is the film-forming component in each layer.

For example, in configuration 1, in which the ultraviolet absorber is contained only in the protective film, the amount of ultraviolet absorber per 100 parts by mass of the constituent resin of the protective film is preferably in the range of 0.1 to 8 parts by mass, and more preferably in the range of 0.5 to 5 parts by mass. Similarly, in configurations 2, 3, and 5, in which the ultraviolet absorber is contained only in the phase difference film, the amount of ultraviolet absorber per 100 parts by mass of the constituent resin of the phase difference film is preferably within the same range as above. In configuration 4, in which both the protective film and the phase difference film contain the ultraviolet absorber, the amount of compound (D) in each layer is preferably within the same range as above.

By setting the content of the ultraviolet absorber within the above range, the ultraviolet absorber-containing layer can fully exhibit its ultraviolet absorption function, which is preferable. Furthermore, when the polarizing plate of the present invention is used in an organic EL display device, the layer containing compound (D) and the ultraviolet absorber-containing layer function to protect the organic EL element from ambient light, thereby maintaining the quality of the organic EL display device over a long period of time.

The following describes each layer constituting the polarizing plate 10A, starting from the viewing side. Note that the hard coat layer 1 is formed on the protective film 2 after the protective film 2 has been fabricated, and therefore will be described together with the protective film 2.

[Protective film]
The protective film 2 is provided to protect the polarizer 3 and is, for example, a film made of a thermoplastic resin. Preferably, the protective film 2 is made of a thermoplastic resin material that has excellent transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, etc.

Examples of thermoplastic resins used to form the protective film 2 include cellulose ester resin, polyester resin, polycarbonate resin, polyarylate resin, acrylic resin, polystyrene resin, acrylonitrile-styrene copolymer (AS resin), polyamide resin, polyimide resin, polysulfone resin, polyethersulfone resin, polyolefin resin, cycloolefin resin, polyvinyl chloride resin, polyvinyl alcohol resin, polyvinyl butyral resin, epoxy resin, norbornene resin, and fluororesin.

The thermoplastic resin may be used alone or in combination of two or more types. In addition to the thermoplastic resin described above, the protective film 2 may contain thermoplastic elastomers, rubbery polymers, organic fine particles, inorganic fine particles, etc., as film-forming components, to the extent that they do not impair the effects of this embodiment. Note that the organic fine particles include rubber particles, which will be explained later in the section on acrylic resins.

The protective film 2 contains compound (D) or an ultraviolet absorber, or neither, depending on the above configuration 1 to 5 of the polarizing plate 10A. If the protective film 2 contains compound (D) or an ultraviolet absorber, the type and content of these additives are as described above. In addition to compound (D) or the ultraviolet absorber, the protective film 2 may also contain other additives such as antioxidants, plasticizers, antistatic agents, release agents, and thickeners, to the extent that they do not impair the effects of this embodiment.

The protective film 2 may be a single-layer or a laminated film of two or more layers. If the protective film 2 is a laminated film and contains compound (D) or an ultraviolet absorber, the amount of these additives in each layer should be adjusted so that the total content of these additives in the protective film 2 is as described above. When the protective film 2 is a laminated film, the thermoplastic resins used to form each layer may be the same or different. Conventional known methods can be applied without particular limitation as a method for manufacturing the laminated film.

From the viewpoint of transparency and mechanical strength, cycloolefin resins, cellulose ester resins, and acrylic resins are preferred as thermoplastic resins used to form the protective film 2. Among these, cycloolefin resins are particularly preferred because they have low polarity, are less affected by moisture, and have a refractive index that does not change easily with wavelength.

(Cycloolefin resin)
Examples of cycloolefin resins used in the present invention include (co)polymers having a structure represented by the following general formula (3).

In general formula (3), ^R1 to ^R4 are each independently a hydrocarbon group substituted with a hydrogen atom, a hydrocarbon group, a halogen atom, a hydroxyl group, an ester group, an alkoxy group, a cyano group, an amide group, an imide group, a silyl group, or a polar group (i.e., a halogen atom, a hydroxyl group, an ester group, an alkoxy group, a cyano group, an amide group, an imide group, or a silyl group). However, two or more ^R1 to ^R4 may be bonded to each other to form an unsaturated bond, a monocyclic or polycyclic ring, and this monocyclic or polycyclic ring may have a double bond or form an aromatic ring. ^R1 and ^R2 , or ^R3 and ^R4 , may form an alkylidene group. p and m are integers of 0 or more.

In the above general formula (3), ^R1 and ^R3 are hydrogen atoms or hydrocarbon groups having 1 to 10 carbon atoms, more preferably 1 to 4 carbon atoms, and particularly preferably 1 or 2 carbon atoms. ^R2 and ^R4 are hydrogen atoms or monovalent organic groups, and at least one of ^R2 and ^R4 is a polar group having polarity other than a hydrogen atom or a hydrocarbon group. m is an integer from 0 to 3, and p is an integer from 0 to 3, more preferably m + p = 0 to 4, even more preferably 0 to 2, and particularly preferably m = 1 and p = 0. A specific monomer with m = 1 and p = 0 is preferred in that the resulting cycloolefin resin has a high glass transition temperature and excellent mechanical strength.

Examples of polar groups in the above-mentioned specific monomers include carboxyl groups, hydroxyl groups, alkoxycarbonyl groups, aryloxycarbonyl groups, amino groups, amide groups, and cyano groups, and these polar groups may be bonded via linking groups such as methylene groups. Also, hydrocarbon groups to which polar divalent organic groups such as carbonyl groups, ether groups, silyl ether groups, thioether groups, and imino groups are bonded via linking groups can also be listed as polar groups. Among these, carboxyl groups, hydroxyl groups, alkoxycarbonyl groups, or aryloxycarbonyl groups are preferred, and alkoxycarbonyl groups or aryloxycarbonyl groups are particularly preferred.

Furthermore, monomers in which at least one of ^R2 and ^R4 is a polar group represented by the formula -( _CH2 ) _nCOOR are preferred because the resulting cycloolefin resin has a high glass transition temperature, low hygroscopicity, and excellent adhesion to various materials. In the formula relating to the specific polar group described above, R is a hydrocarbon group having 1 to 12 carbon atoms, more preferably 1 to 4, particularly preferably 1 to 2 carbon atoms, and preferably an alkyl group.

Specific examples of copolymerizable monomers include cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, and dicyclopentadiene. The carbon number of the cycloolefin is preferably in the range of 4 to 20, and more preferably 5 to 12.

In this embodiment, the cycloolefin resin can be used alone or in combination of two or more types.

The preferred molecular weight of the cycloolefin resin in this embodiment is 0.2 to 5 dL/g in terms of intrinsic viscosity [η]inh, more preferably 0.3 to 3 dL/g, and particularly preferably 0.4 to 1.5 dL/g. The number average molecular weight (Mn) in terms of polystyrene, as measured by gel permeation chromatography (GPC), is 8,000 to 100,000, more preferably 10,000 to 80,000, and particularly preferably 12,000 to 50,000. The weight average molecular weight (Mw) is preferably in the range of 20,000 to 300,000, more preferably 30,000 to 250,000, and particularly preferably 40,000 to 200,000.

The intrinsic viscosity [η]inh, number-average molecular weight, and weight-average molecular weight being within the above range results in good heat resistance, water resistance, chemical resistance, and mechanical properties of the cycloolefin resin, as well as good moldability as a cycloolefin film in this embodiment.

The glass transition temperature (Tg) of the cycloolefin resin in this embodiment is typically within the range of 110°C or higher, preferably 110 to 350°C, more preferably 120 to 250°C, and particularly preferably 120 to 220°C. A Tg of 110°C or higher is preferable because it makes deformation less likely to occur under high-temperature conditions or during secondary processing such as coating or printing. On the other hand, setting the Tg to 350°C or lower avoids difficulties in molding and suppresses the possibility of resin degradation due to heat during molding.

Furthermore, commercially available cycloolefin resins can preferably be used. For example, commercially available products are sold by JSR Corporation under the trade names Arton (registered trademark) G (G7810, etc.), Arton F, Arton R, and Arton RX, and by Zeon Corporation under the trade names Zeonor (registered trademark) ZF14, ZF16, Zeonex (registered trademark) 250, or Zeonex 280. These can be used.

(Cellulose ester resin)
Examples of cellulose ester resins used in the present invention include triacetylcellulose, cellulose acetate propionate, cellulose diacetate, and cellulose acetate butyrate. In addition, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polycarbonate resins, polyolefin resins such as polyethylene and polypropylene, norbornene resins, fluororesins, and cycloolefin resins may be used in combination with the cellulose ester resin.

Examples of commercially available cellulose ester resin films (cellulose ester films) include Konica Minolta Tack KC8UX, KC4UX, KC8UY, KC4UY, KC6UA, KC4UA, KC2UA, KC4UE, and KC4UZ, KC4CT1, and KC2CT1 (all manufactured by Konica Minolta, Inc.). The refractive index of the cellulose ester film is preferably 1.45 to 1.55. The refractive index can be measured in accordance with JIS K7142-2008.

The cellulose ester used in the protective film according to the present invention is preferably a carboxylic acid ester having about 2 to 22 carbon atoms, and may also be an aromatic carboxylic acid ester, or preferably a lower fatty acid ester of cellulose. Here, "lower fatty acid" in "lower fatty acid ester of cellulose" means a fatty acid with 6 or fewer carbon atoms.

Furthermore, the acyl group bonded to the hydroxyl group of the glucose unit constituting the cellulose ester may be a linear hydrocarbon group, a branched hydrocarbon group, a cyclic hydrocarbon group, or the acyl group may be substituted with another substituent. When the degree of substitution of substituents bonded to the hydroxyl group of the cellulose ester is the same, if the number of carbon atoms in the lower fatty acid exceeds seven, the birefringence decreases. Therefore, the number of carbon atoms in the acyl group bonded to the hydroxyl group of the glucose unit constituting the cellulose ester is preferably 2 to 6, more preferably 2 to 4, and even more preferably 2 to 3.

In the present invention, the cellulose ester may also be an acyl group derived from a mixed acid, preferably an acyl group having 2 and 3 carbon atoms, or an acyl group having 2 and 4 carbon atoms. Specific examples of such cellulose esters include cellulose acetate propionate, cellulose acetate butyrate, or cellulose acetate propionate butyrate, which are mixed fatty acid esters of cellulose in which propionate groups or butyrate groups are bonded in addition to acetyl groups. The butyryl groups forming the butyrate may be linear or branched. The cellulose ester is preferably cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, or cellulose acetate phthalate.

The retardation value of the protective film 2 can be appropriately controlled by the type of acyl group contained in the cellulose ester and the degree of substitution of the acyl group with the pyranose ring of the cellulose resin skeleton.

The substituents bonded to the hydroxyl group of the glucose unit constituting the cellulose ester used in protective film 2 are preferably those that simultaneously satisfy formulas (4) and (5) below.

Formula (4): 2.0≦X+Y≦3.0
Formula (5): 0≦Y≦2.0
In formula (4) above, X is the degree of substitution of the acetyl group, and in formulas (4) and (5), Y is the degree of substitution of the propionyl group or the butyryl group. By satisfying the above two formulas, a protective film 2 exhibiting excellent optical properties can be produced. Among the above cellulose esters, triacetylcellulose and cellulose acetate propionate are preferably used. For cellulose acetate propionate, it is preferable that the degree of substitution X of the acetyl group is 1.0 ≤ X ≤ 2.5, and 0.1 ≤ Y ≤ 1.5 and 2.0 ≤ X + Y ≤ 3.0.

The degree of substitution of the acyl group can be measured according to ASTM-D817-96. If the degree of substitution of the acyl group is too low, there will be many unreacted portions of the hydroxyl groups of the pyranose rings that constitute the backbone of the cellulose resin, and many of these hydroxyl groups will remain. This is undesirable because the retardation value of the protective film 2 will change with humidity, and the ability of the polarizer protective film to protect the polarizer will decrease.

The number-average molecular weight of the above cellulose ester is preferably 60,000 to 300,000, and more preferably 70,000 to 200,000. By using a cellulose ester with such a number-average molecular weight, the mechanical strength of the protective film 2 can be increased. The number-average molecular weight of this cellulose ester shall be the value measured by high-performance liquid chromatography under the following conditions.

Solvent: Acetone Column: MPW x 1 (manufactured by Tosoh Corporation)
Sample concentration: 0.2 (mass/volume)%
Flow rate: 1.0 mL/min Sample injection volume: 300 μL
Standard sample: Standard polystyrene Temperature: 23°C

The cellulose used as a raw material for cellulose esters is not particularly limited, but examples include cotton linters, wood pulp, and kenaf. Furthermore, cellulose esters obtained from these materials may be mixed and used in any proportion.

When acid anhydrides such as acetic anhydride, propionic anhydride, and butyric anhydride are used as acyling agents for the above-mentioned cellulose raw materials, _{the reaction is carried out by an organic acid such as acetic acid or an organic solvent such as dichloromethane and a protic catalyst such as sulfuric acid. When acid chlorides (CH3COCl, C2H5COCl, C3H7COCl ) are used as} acyling agents, basic compounds such as amines are used as catalysts. The acylation of cellulose raw materials can be synthesized by the method described in Japanese Patent Publication No. 10-45804.

In the above-mentioned cellulose ester, the average degree of substitution of the acyl group at the 6th position of the glucose unit is preferably 0.5 to 0.9. The hydroxyl group at the 6th position of the glucose unit constituting the cellulose ester contains a primary hydroxyl group that is more reactive than the hydroxyl groups at the 2nd and 3rd positions. This primary hydroxyl group preferentially forms sulfate esters in the production process of cellulose esters using sulfuric acid as a catalyst. Therefore, by increasing the amount of sulfuric acid added as a catalyst in the cellulose esterification reaction, it is possible to obtain a cellulose ester with a higher average degree of substitution of the hydroxyl groups at the 2nd and 3rd positions of the glucose unit compared to ordinary cellulose esters.

Furthermore, in order to increase the average degree of substitution of the hydroxyl groups at positions 2 and 3, the cellulose ester may be tritylated as needed. By selectively protecting the hydroxyl group at position 6 of the glucose unit constituting the cellulose ester by tritylation, the hydroxyl groups at positions 2 and 3 of the glucose unit can be concentratedly esterified. Then, after esterifying the hydroxyl groups at positions 2 and 3 of the glucose unit, the trityl group (protecting group) protecting the hydroxyl group at position 6 of the glucose unit is removed, thereby increasing the average degree of substitution of the hydroxyl groups at positions 2 and 3 more than that of the hydroxyl group at position 6 of the glucose unit. As such an esterification method, it is preferable to use a cellulose ester produced by the method described in Japanese Patent Application Publication No. 2005-281645.

When using acetylcellulose as the cellulose ester, it is necessary to extend the reaction time of the acetic acid reaction in order to increase the degree of acetic acidization of acetylcellulose. However, extending the reaction time of the acetic acid reaction is undesirable because it can lead to cleavage of the cellulose chain and decomposition of the acetyl group. Therefore, in order to increase the degree of acetic acidization of acetylcellulose while suppressing its decomposition, it is preferable to set the reaction time of the acetic acid reaction within a specific range. However, it is difficult to uniformly determine a suitable numerical range for the reaction time because the optimal reaction time varies greatly depending on the reaction apparatus, reaction equipment, and other reaction conditions.

Therefore, it is preferable to use the weight-average molecular weight (Mw) / number-average molecular weight (Mn) value, which is one indicator of the degree of reaction, instead of the above reaction time. Since the molecular weight distribution of cellulose esters broadens as the decomposition progresses, similar to the decomposition of ordinary polymers, the degree of decomposition of cellulose esters can be grasped by the weight-average molecular weight (Mw) / number-average molecular weight (Mn) value. For example, by specifying the degree of reaction using the weight-average molecular weight (Mw) / number-average molecular weight (Mn), it is possible to prevent the acetic acid reaction time from becoming too long and causing excessive decomposition of cellulose triacetate, while ensuring a sufficient reaction time for acetic acid. The Mw/Mn ratio of cellulose esters is preferably 1.4 to 5.0.

An example of a method for producing cellulose ester is shown below. 100 parts by mass of cottonized linters are crushed as a cellulose raw material, 40 parts by mass of acetic acid are added, and the mixture is pre-treated and activated at 36°C for 20 minutes. Then, 8 parts by mass of sulfuric acid, 260 parts by mass of acetic anhydride, and 350 parts by mass of acetic acid are added, and esterification is carried out at 36°C for 120 minutes. After neutralization with 11 parts by mass of 24% magnesium acetate aqueous solution, acetylcellulose is obtained by saponification and aging at 63°C for 35 minutes. This acetylcellulose is stirred at room temperature for 160 minutes using a 10-fold aqueous solution of acetic acid (acetic acid:water = 1:1 (mass ratio)), then filtered and dried to obtain purified acetylcellulose with an acetyl substitution degree of 2.75. This acetylcellulose has a Mn of 92,000, a Mw of 156,000, and an Mw/Mn ratio of 1.7. Similarly, by adjusting the esterification conditions (temperature, time, stirring) and hydrolysis conditions of the cellulose ester, cellulose esters with different substitution degrees and Mw/Mn ratios can be synthesized.

The cellulose ester synthesized by the above method is preferably purified to remove low molecular weight components, and components that are not acetic acid or have a low degree of acetic acid are preferably removed by filtration. Furthermore, if the cellulose ester is a mixed acid cellulose ester, it can be obtained by the method described in Japanese Patent Application Publication No. 10-45804.

Furthermore, it is preferable that cellulose esters do not contain metals such as iron (Fe), calcium (Ca), and magnesium (Mg). This is because these metal ions form insoluble nuclei by forming salts with polymer decomposition products containing organic acidic groups. These trace metal components are thought to be present in the cellulose esters due to the water used in the manufacturing process.

The iron content in the cellulose ester is preferably 1 ppm or less. The calcium content in the cellulose ester is preferably 60 ppm or less, and more preferably 0 to 30 ppm. Calcium may form complexes with acidic components such as carboxylic acids or sulfonic acids, and may also form complexes with many ligands. These complexes may cause the formation of scum (insoluble sediment, turbidity) derived from insoluble calcium. The magnesium content in the cellulose ester is preferably 0 to 70 ppm, and more preferably 0 to 20 ppm. By keeping the magnesium content at 70 ppm or less, the formation of insoluble matter can be suppressed.

The content of the above metals is determined by decomposing oven-dried cellulose ester with nitrate in a microdigest wet decomposition apparatus, followed by pretreatment with alkaline fusion, and then analyzing the pretreated cellulose ester using ICP-AES (inductively coupled plasma emission spectrometer).

((meth)acrylic resin)
Acrylic resin is a resin composed of a (co)polymer obtained by (co)polymerizing monomers selected from (meth)acrylic acid and its derivatives. The monomer-derived units in the (co)polymer are called "structural units".

In this embodiment, "(meth)acrylic" refers to both "acrylic" and "methacrylic," "(meth)acrylate" refers to both "acrylate" and "methacrylate," and "(meth)acryloyl" refers to both "acryloyl" and "methacryloyl." For example, "urethane (meth)acrylate" refers to both "urethane acrylate" and "urethane methacrylate."

The acrylic resin used in protective film 2 is selected according to the required properties, including the type and combination of monomers and the monomer composition. Below, we will describe the acrylic resin using an example of a molecularly designed acrylic resin that adjusts the equilibrium water content of the protective film within a predetermined range and improves brittleness, but the acrylic resin used in the present invention is not limited to this. The acrylic resin preferably contains, for example, a structural unit (U1) derived from methyl methacrylate, a structural unit (U2) derived from phenylmaleimide, and a structural unit (U3) derived from alkyl acrylate.

The content of structural units (U1) derived from methyl methacrylate is preferably 50 to 95% by mass, and more preferably 70 to 90% by mass, relative to the total structural units constituting the acrylic resin.

The structural unit (U2) derived from phenylmaleimide has moderate polarity, which can enhance its affinity for moisture. Furthermore, because the structural unit (U2) derived from phenylmaleimide has a relatively bulky structure, it can contain microscopic voids that allow moisture to move within the resin matrix. This can improve the moisture mobility and discharge properties of the protective film.

The content of structural units (U2) derived from phenylmaleimide is preferably 1 to 25% by mass relative to the total structural units constituting the acrylic resin. When the content of structural units (U2) derived from phenylmaleimide is 1% by mass or more, it has appropriate polarity, making it easily compatible with water molecules, and also has sufficient microscopic voids that allow water molecules to move, thus easily increasing the equilibrium water content. When the content of structural units (U2) derived from phenylmaleimide is 25% by mass or less, the brittleness of the protective film 2 is less likely to be impaired. From the above viewpoint, the content of structural units (U2) derived from phenylmaleimide is more preferably 7 to 15% by mass.

The structural unit (U3) derived from alkyl acrylate has good affinity for rubber particles whose shell polymer, as described later, contains structural units derived from butyl acrylate, thus improving the dispersibility of rubber particles.

The alkyl acrylate is preferably an alkyl acrylate having 1 to 7 carbon atoms in the alkyl portion, more preferably 1 to 5 carbon atoms. Examples of alkyl acrylates include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-hydroxyethyl acrylate, hexyl acrylate, and 2-ethylhexyl acrylate.

The content of structural units (U3) derived from alkyl acrylate is preferably 1 to 25% by mass relative to the total structural units constituting the acrylic resin. If the content of structural units (U3) derived from alkyl acrylate is 1% by mass or more, it can impart appropriate flexibility to the acrylic resin, preventing the film from becoming too brittle and making it less prone to breakage. If the content of structural units (U3) derived from alkyl acrylate is 25% by mass or less, the Tg of the acrylic resin does not decrease excessively, thus not only preventing damage to the heat resistance of the protective film 2 but also preventing damage to its mechanical strength. From the above viewpoint, the content of structural units derived from alkyl acrylate is more preferably 5 to 15% by mass.

The ratio of structural units (U2) derived from phenylmaleimide to the total amount of structural units (U3) derived from phenylmaleimide (U2) and alkyl acrylate is preferably 20 to 70% by mass. If this ratio is 20% by mass or more, the heat resistance of the protective film 2 is easily improved, and if it is 70% by mass or less, the protective film 2 does not become too brittle.

The glass transition temperature (Tg) of the acrylic resin is preferably 110°C or higher, and more preferably 120 to 150°C. When the Tg of the acrylic resin is within this range, the heat resistance of the protective film 2 is easily improved. To adjust the Tg of the acrylic resin, it is preferable to adjust the content of structural units (U2) derived from phenylmaleimide and structural units (U3) derived from alkyl acrylate, for example.

The weight-average molecular weight (Mw) of the acrylic resin is preferably 500,000 or more. A weight-average molecular weight of 500,000 or more prevents the viscosity of the dope used in solution casting from becoming too low, thereby suppressing not only the aggregation of rubber particles but also preventing a decrease in the flatness of the surface of the protective film 2. Furthermore, a weight-average molecular weight of 500,000 or more provides sufficient mechanical strength (toughness) to the protective film 2. From the above viewpoint, the weight-average molecular weight of the acrylic resin is more preferably 500,000 to 3,000,000, and even more preferably 600,000 to 2,000,000. The weight-average molecular weight can be measured by the same method as described above.

The acrylic resin content is preferably 60% by mass or more, and more preferably 70% by mass or more, relative to the protective film 2.

When the protective film 2 is mainly composed of acrylic resin, it may contain rubber particles that have the function of imparting toughness (flexibility) to the protective film 2. The rubber particles are particles containing a rubbery polymer. The rubbery polymer is a soft crosslinked polymer with a glass transition temperature of 20°C or lower. Examples of such crosslinked polymers include butadiene-based crosslinked polymers, (meth)acrylic-based crosslinked polymers, and organosiloxane-based crosslinked polymers. Among these, (meth)acrylic-based crosslinked polymers are preferred, and acrylic-based crosslinked polymers (acrylic rubbery polymers) are more preferred, as they have a small refractive index difference with the acrylic resin and do not impair the transparency of the protective film 2.

The rubber particles are preferably particles containing an acrylic rubber-like polymer. The acrylic rubber-like polymer is a crosslinked polymer that mainly contains structural units derived from acrylic acid esters. "Mainly contains" means that the content of structural units derived from acrylic acid esters is 40% by mass or more. The acrylic rubber-like polymer is preferably a crosslinked polymer that contains structural units derived from acrylic acid esters, structural units derived from other monomers copolymerizable thereto, and structural units derived from polyfunctional monomers having two or more radical polymerizable groups (non-conjugated reactive double bonds) in one molecule.

The glass transition temperature (Tg) of the rubbery polymer is preferably 0°C or lower, and more preferably -10°C or lower. A glass transition temperature (Tg) of 0°C or lower can impart appropriate toughness to the film. The glass transition temperature (Tg) of the rubbery polymer is measured by the same method as described above.

The particles containing the acrylic rubbery polymer may be core-shell type particles having a core portion containing the acrylic rubbery polymer and a shell portion covering it. Preferably, the shell portion contains a methacrylic polymer mainly composed of structural units derived from methacrylic acid esters, which are grafted onto the acrylic rubbery polymer.

The average particle size of the rubber particles can be determined by measuring the dispersed particle size of the rubber particles in the dispersion using a zeta potential/particle size measurement system (ELSZ-2000ZS, manufactured by Otsuka Electronics Co., Ltd.). The average particle size of the rubber particles is preferably in the range of 100 to 300 nm. The rubber particle content is not particularly limited, but is preferably 5 to 25% by mass relative to the protective film 2, and more preferably 5 to 15% by mass.

(Manufacturing of protective film)
The protective film 2 can be manufactured by known molding methods such as molten casting, solution casting, and calendering. Molten casting and solution casting are preferred, and solution casting is particularly preferred.

Specifically, to manufacture the protective film 2 by solution casting, a manufacturing method including the following steps (1) to (3) is used. Furthermore, the manufacturing method preferably includes step (4).
(1) A step of obtaining a dope comprising a film-forming component containing a thermoplastic resin, a compound (D) or an ultraviolet absorber and any additives added as needed depending on the configuration of the polarizing plate 10A, and a solvent. (2) A step of casting the obtained dope onto a support, drying and peeling it off to obtain a film-like material. (3) A step of drying the obtained film-like material while stretching it as needed. (4) A step of winding the obtained protective film to obtain a roll body.

Regarding step (1), a dope is prepared by dissolving or dispersing a film-forming component containing a thermoplastic resin, compound (D) or an ultraviolet absorber and any additives that are added as needed based on the composition of the polarizing plate 10A, in a solvent.

The solvent used for doping includes at least an organic solvent (good solvent) capable of dissolving the thermoplastic resin. If compound (D) or an ultraviolet absorber is included, the organic solvent is preferably highly soluble in these additives as well. Examples of good solvents include chlorinated organic solvents such as dichloromethane; and non-chlorinated organic solvents such as methyl acetate, ethyl acetate, acetone, and tetrahydrofuran. Among these, dichloromethane is preferred.

The solvent used for doping may further contain a poor solvent. Examples of poor solvents include linear or branched aliphatic alcohols having 1 to 4 carbon atoms. A higher proportion of alcohol in the dope makes the film-like material more likely to gel, and easier to peel from the metal support. Examples of linear or branched aliphatic alcohols having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Of these, ethanol is preferred due to its dope stability, relatively low boiling point, and good drying properties.

(2) Step (2) The obtained dope is cast onto the support. Dope casting can be done by extruding it from a casting die.

Next, the solvent in the dope cast onto the support is evaporated and dried. The dried dope is peeled off the support to obtain a film-like material.

The amount of residual solvent in the dope when peeling it from the support (the amount of residual solvent in the film-like substance at the time of peeling) is preferably 20% by mass or more, and more preferably 20 to 30% by mass. If the amount of residual solvent at the time of peeling is 30% by mass or less, it is easier to suppress excessive stretching of the film-like substance due to peeling.

The amount of residual solvent in the dope after stripping is defined by the following formula. The same applies below.

Residual solvent content of dope (mass %) = (mass of dope before heat treatment - mass of dope after heat treatment) / mass of dope after heat treatment × 100
Note that the heat treatment used when measuring the amount of residual solvent refers to a heat treatment at 140°C for 30 minutes.

The amount of residual solvent during peeling can be adjusted by the drying temperature and time of the dope on the support, as well as the temperature of the support.

Regarding step (3), the obtained film-like material is dried. Drying may be carried out in one step or in multiple steps. Drying may also be carried out while stretching as needed.

For example, the drying process for a film-like material may include a step of pre-drying the film-like material (pre-drying step), a step of stretching the film-like material (stretching step), and a step of drying the stretched film-like material (main drying step).

(Pre-drying process)
The pre-drying temperature (drying temperature before stretching) can be higher than the stretching temperature. Specifically, when Tg is the glass transition temperature of the thermoplastic resin, it is preferably (Tg-50) to (Tg+50)°C. If the pre-drying temperature is (Tg-50)°C or higher, the solvent is easily evaporated to an appropriate degree, making it easier to improve transportability (handling), and if it is (Tg+50)°C or lower, the solvent does not evaporate too much, so the stretchability in the subsequent stretching process is less likely to be impaired. The initial drying temperature can be measured as the ambient temperature, such as the temperature inside the stretcher or the hot air temperature, when (a) drying is performed by non-contact heating while transporting with a tenter stretcher or rollers.

(Stretching process)
The stretching may be performed according to the required optical properties, such as the retardation value, and it is preferable to stretch in at least one direction, but it may also be stretched in two mutually orthogonal directions (for example, biaxial stretching in the width direction of the film (TD direction) and the transport direction (MD direction) perpendicular to it).

The stretching ratio when manufacturing the protective film 2 is preferably 5 to 100%, and more preferably 20 to 100%. In the case of biaxial stretching, it is preferable that the stretching ratio in each direction is within the above range.

The stretching ratio (%) is defined as (stretched size of the film after stretching - stretched size of the film before stretching) / (stretched size of the film before stretching) × 100. When biaxial stretching is performed, it is preferable to use the above stretching ratio for both the TD direction and the MD direction.

The stretching temperature (drying temperature during stretching) is preferably above Tg (°C), and more preferably between (Tg + 10) and (Tg + 50)°C, where Tg is the glass transition temperature of the thermoplastic resin, as described above. When the stretching temperature is above Tg (°C), preferably above (Tg + 10)°C, the solvent is easily evaporated to an appropriate degree, making it easier to adjust the stretching tension to an appropriate range. When it is below (Tg + 50)°C, the solvent does not evaporate excessively, so the stretchability is less likely to be impaired. The stretching temperature during the manufacture of the protective film 2 may be, for example, 115°C or higher. The stretching temperature is preferably determined by (a) measuring the ambient temperature, such as the temperature inside the stretching machine, as described above.

The amount of residual solvent in the film at the start of stretching is preferably about the same as the amount of residual solvent in the film at the time of peeling, for example, preferably 20 to 30% by mass, and more preferably 25 to 30% by mass.

The stretching of a film-like material in the TD direction (width direction) can be performed, for example, by fixing both ends of the film-like material with clips or pins and widening the distance between the clips or pins in the direction of travel (tenter method). The stretching of a film-like material in the MD direction can be performed, for example, by creating a difference in peripheral speed between multiple rolls and utilizing the difference in peripheral speed between them (roll method).

(Main drying process)
From the viewpoint of further reducing the amount of residual solvent, it is preferable to further dry the film-like material obtained after stretching. For example, it is preferable to further dry the film-like material obtained after stretching while conveying it with rolls or the like.

The drying temperature (drying temperature in the case of unstretched material) is preferably (Tg-50) to (Tg-30)°C, and more preferably (Tg-40) to (Tg-30)°C, where Tg is the glass transition temperature of the thermoplastic resin. If the post-drying temperature is (Tg-50)°C or higher, the solvent can be sufficiently volatilized and removed from the film-like material after stretching, and if it is (Tg-30)°C or lower, deformation of the film-like material can be highly suppressed. As described above, it is preferable to measure the ambient temperature, such as the hot air temperature, to determine the drying temperature.

Regarding step (4), the protective film obtained is preferably in a long form. The long protective film is wound into a roll to form a roll body.

The length of the long protective film is not particularly limited, but it may be, for example, about 100 to 10,000 meters. The width of the protective film is preferably 1 meter or more, and more preferably 1.3 to 4 meters.

The thickness of the protective film 2 can be determined as appropriate, but generally, it is preferable to be in the range of 1 to 500 μm from the viewpoint of strength, workability such as handling, and thinness. The thickness of the protective film 2 is more preferably in the range of 5 to 50 μm, and even more preferably in the range of 15 to 45 μm.

The polarizing plate 10A has a hard coat layer 1 on the viewing side of the protective film 2 and a polarizer 3 on the side opposite to the viewing side of the protective film 2. Depending on the type of resin that is the main constituent material of the protective film, a primer layer may be provided on one or both sides of the protective film 2. In particular, if the protective film 2 is formed mainly of cycloolefin resin, it is preferable to provide a primer layer. In particular, it is preferable to provide the primer layer on the side of the protective film 2 on which the hard coat layer 1 is provided.

(Primer layer)
Any material that can improve the adhesion and bonding between the protective film 2 and the hard coat layer 1 or polarizer 3 can be used as the material constituting the primer layer. In addition to adhesion and bonding, it is preferable that the material has excellent properties such as transparency and thermal stability. Examples of such materials include resins composed of polyurethane, polyolefin, polyester, polyvinylidene chloride, acrylic polymers, modified silicone polymers, styrene-butadiene rubber, carbodiimide compounds, isocyanates, etc.

The above-mentioned primer layer may also contain any additives as needed. Specific examples of additives include leveling agents, polymerization initiators, polymerization accelerators, viscosity modifiers, slip agents, dispersants, plasticizers, heat stabilizers, light stabilizers, lubricants, antioxidants, flame retardants, colorants, antistatic agents, compatibilizers, crosslinking agents, and the like. The type and amount of additives used can be appropriately determined depending on the purpose. For example, the amount of additive used is preferably 30 parts by mass or less, and more preferably 20 parts by mass or less, per 100 parts by mass of total solids in the primer layer.

As the material constituting the above primer layer, among the above resins, those mainly composed of polyurethane are preferably used. Specific examples of polyurethane include: DIC Corporation's "Hydran Series" AP-201, AP-40F, HW-140SF, WLS-202; Daiichi Kogyo Seiyaku Co., Ltd.'s "Superflex Series" SF-210, SF460, SF870, SF420, SF-420NS; and Mitsui Chemicals, Inc.'s "Takelac Series" Examples include W-615, W6010, W-6020, W-6061, W-405, W-5030, W-5661, W-512A-6, W-635, WPB-6601, WS-6021, WS-5000, WS-5100, WS-4000, WSA-5920, WF-764, and the development product "SPX-0882" manufactured by ADEKA Corporation. Furthermore, resins such as polyurethanes that have carboxyl groups in their side chains can be crosslinked with crosslinking agents such as isocyanates, oxazolines, and carbodiimides to improve the strength of the primer layer.

Specific examples of polyolefins that can be used as materials to constitute the above primer layer include: Unitika Ltd.'s "Arrow Base Series" SB-1200, SE-1010, SE-1013N, SE-1030N, SD-1010, TC-4010, TD-4010; Toho Chemical Co., Ltd.'s "High-Tech Series" S3148, S3121, S8512, P-5060N, P-9018; and Mitsui Examples include products from Chemical Co., Ltd., such as the "Unistol Series" (S-120, S-75N, V100, H-200, H-300, EV210H), products from Mitsui Chemicals, Inc., such as the "Chemipearl Series" (XHP-400), products from Sumitomo Seika Co., Ltd., such as the "Zychsen Series" (Zychsen A, Zychsen L), and products from Toyobo Co., Ltd., such as the "Hardren Series" (NZ-1004, NZ-1005, NZ-1022).

Specific examples of acrylic polymers that can be used as materials for the above-mentioned primer layer include WS-700 from Nippon Shokubai Co., Ltd.'s "Epocross WS Series" and CP-0101 from Shin Nakamura Chemical Co., Ltd.'s "New Coat Series" (development product).

Specific examples of modified silicone polymers that can be used as materials for the primer layer mentioned above include WSA1060 and WSA1070 from the "Ceranate series" manufactured by DIC Corporation, and H7620, H7630, and H7650 from Asahi Kasei Chemicals Corporation.

Specific examples of polyesters that can be used as materials for the above-mentioned primer layer include Toyobo Co., Ltd.'s "Vironal Series" MD1400, MD1480, MD1245, MD1500, and Go-O Chemical Industry Co., Ltd.'s "Pluscoat Series" Z-221, Z-561, Z-730, RZ-142, Z-687, etc.

Specific examples of styrene-butadiene rubber that can be used as a material for the primer layer mentioned above include NIPOL LX415, NIPOL LX407, NIPOL V1004, NIPOL MH8101, and SX1105, all manufactured by Nippon Zeon Co., Ltd.

Specific examples of polyvinylidene chloride that can be used as a material for the above-mentioned primer layer include Asahi Kasei Corporation's "Saran Latex Series" L509, among others.

Specific examples of carbodiimide compounds that can be used as materials for the above-mentioned primer layer include V-02, V-02-L2, SV-02, V-04, and E-02 from the "CarbodiLite Series" manufactured by Nisshinbo Chemical Co., Ltd.

As isocyanate compounds that can be used as materials constituting the above-mentioned primer layer, various compounds containing two or more isocyanate groups in one molecule can be used. Examples include hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, and xylylene diisocyanate. In addition, the isocyanate may be masked with a blocking agent.

To impart antiblocking properties to the primer layer, any suitable fine particles can be used. Specific examples of fine particles include KE-P20, KE-P30, the newly developed KE-W20, and the MX100W from the "Eposter Series," all manufactured by Nippon Shokubai Co., Ltd. The particle size of the fine particles is preferably 50 to 500 nm, and more preferably 100 to 300 nm. Within this range, both transparency and antiblocking properties of the primer layer can be achieved.

The glass transition temperature (Tg) of the primer layer is preferably -40 to +130°C, more preferably -30 to +50°C, and particularly preferably 0 to +20°C. The glass transition temperature can be measured by reading the maximum value of the loss tangent (tanδ) obtained by dynamic viscoelasticity measurement.

Any thickness can be used for the primer layer. Preferably, the primer layer is 10 to 1000 nm thick, more preferably 20 to 500 nm thick, and most preferably 50 to 400 nm thick.

The primer layer described above is formed by coating the surface of the protective film 2 with a coating solution containing, for example, a thermoplastic resin such as polyurethane in a predetermined proportion, and then drying it. Any suitable method can be used to prepare the coating solution. For example, a commercially available solution or dispersion may be used, or a solvent may be added to a commercially available solution or dispersion, or solid components may be dissolved or dispersed in various solvents.

Any method may be used for applying the coating solution. For example, a coating method using a gravure die or a coater can be used. The primer layer may be formed on one side of the protective film 2 or on both sides, as needed.

When applying the above-mentioned primer layer to the protective film 2, the protective film surface can be subjected to solvent modification, corona treatment, or plasma treatment as a preliminary treatment to improve wettability.

The total solid content concentration of the above coating solution may vary depending on the type of primer layer forming material, its solubility, coating viscosity, wettability, and thickness after coating. To obtain a primer layer with high surface uniformity, the total solid content concentration is preferably 1 to 100 parts by mass of solids, and more preferably 1 to 50 parts by mass, per 100 parts by mass of solvent.

The viscosity of the coating liquid can be any appropriate viscosity within the range of coating. Preferably, the viscosity measured at a shear rate of 1000 (1/s) at 23°C is 1 to 50 (mPa·sec), and more preferably 2 to 10 (mPa·sec). Within this range, a primer layer with excellent surface uniformity can be formed.

The protective film 2, on which the above-mentioned primer layer is laminated, can be stretched at any magnification as needed. The stretching direction may be uniaxial (horizontal, vertical, or oblique) with respect to the transport direction, or it may be biaxial. The protective film 2 may be stretched as needed, such as before or after the application of the primer layer, and may be stretched once or more times before and after the application of the primer layer. The stretching conditions are as described above.

[Hard coat layer]
The polarizing plate 10A has a hard coat layer 1 as the outermost layer on the viewing side. The presence of the hard coat layer 1 improves the impact resistance and ease of handling of the polarizing plate 10A. The hard coat layer 1 contains compound (D) as appropriate, according to the above configurations 1 to 5 of the polarizing plate 10A. When the hard coat layer 1 contains compound (D), the type and content of compound (D) are as described above.

The hard coat layer 1 preferably exhibits a hardness of "HB" or higher in the pencil hardness test specified in JIS K5600-2014, and it is preferable that it contains a cured product of an active-ray curable resin to obtain this hardness. As the active-ray curable resin, a component containing a monomer having an ethylenically unsaturated double bond is preferably used. Examples of active-ray curable resins include ultraviolet-curable resins and electron-beam-curable resins, but resins that harden by ultraviolet irradiation are preferred because they exhibit excellent mechanical film strength (scratch resistance, pencil hardness).

Acrylic materials are preferably used as the active-ray curable resin. As acrylic materials, monofunctional or polyfunctional (meth)acrylate compounds such as (meth)acrylic acid esters of polyhydric alcohols, or polyfunctional urethane (meth)acrylate compounds synthesized from diisocyanates and hydroxyesters of polyhydric alcohols and (meth)acrylic acid can be used. In addition to these, polyether resins, polyester resins, epoxy resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiol polyene resins, etc., having acrylate-based functional groups can also be used.

In particular, UV-curable acrylate resins, UV-curable urethane acrylate resins, UV-curable polyester acrylate resins, UV-curable epoxy acrylate resins, UV-curable polyol acrylate resins, or UV-curable epoxy resins are preferably used, with UV-curable acrylate resins being the most preferred among them.

The hard coat layer 1 is formed using a hard coat layer forming composition containing, for example, an active-ray curable resin, a polymerization initiator, compound (D) if the hard coat layer 1 contains compound (D), and a solvent. The solvent included in the hard coat layer forming composition is preferably one that dissolves or swells the protective film 2, or the primer layer if the protective film 2 has a primer layer. By dissolving or swelling the protective film 2 or primer layer with the solvent, the hard coat layer forming composition can easily penetrate from the surface into the interior of the protective film 2 or primer layer, thereby improving the adhesion between the protective film 2 or primer layer and the hard coat layer 1.

Furthermore, a layer is formed near the surface of the protective film 2 or primer layer where the resin components of the protective film 2 or primer layer and the resin components of the hard coat layer are mixed. This layer allows for a gradient in the refractive index between the protective film 2 or primer layer and the hard coat layer, thereby preventing interference unevenness.

Alternatively, the hard coat layer forming composition may contain conventionally known fine particles, dispersants, surfactants, antistatic agents, silane coupling agents, thickeners, color inhibitors, colorants (pigments, dyes), defoamers, leveling agents, flame retardants, adhesion promoters, polymerization inhibitors, antioxidants, surface modifiers, etc., depending on the purpose of increasing the hardness of the hard coat layer, suppressing curing shrinkage, preventing blocking, controlling the refractive index, providing anti-glare properties, or controlling the properties of the hard coat layer surface. Furthermore, the hard coat layer forming composition may also contain a photosensitizer, specifically n-butylamine, triethylamine, poly-n-butylphosphone, etc.

In particular, the hard coat layer preferably contains fine particles. The fine particle content is preferably fine particles:active-ray curable resin = 100:100 to 400:100. Including fine particles in this ratio reduces dimensional variation in the hard coat layer. The fine particles here are not particularly limited, but are preferably composed of metal oxides (hereinafter also referred to as "metal oxide particles"). Examples of metal oxides here include silica, alumina, zirconia, titanium oxide, and antimony pentoxide. Among these, the metal oxide particles are preferably composed of silica. The silica fine particles may be hollow particles with cavities formed inside.

The fine particles are preferably coated with a polymer silane coupling agent. By coating the surface of the fine particles with a polymer silane coupling agent, the fine particles can be uniformly dispersed in the hard coat layer forming composition. The average particle size of the fine particles coated with the polymer silane coupling agent is preferably 5 to 500 nm, and more preferably 10 to 200 nm. By using fine particles with such an average particle size, the optical properties of the hard coat layer can be improved.

The polymer silane coupling agent described above is prepared by reacting a polymerizable monomer with a silane coupling agent (reactive silane compound). Examples of polymerizable monomers include monomers having an ethylenically unsaturated double bond, with monomers selected from (meth)acrylic acid and its derivatives being preferred. As the reactive silane compound, hydrolyzable silane compounds in which three alkoxy groups and one functional group are bonded to a silicon atom are preferred. Examples of functional groups bonded to the silicon atom include groups having one or more groups selected from (meth)acryloxy groups, epoxy groups (glycide groups), urethane groups, amino groups, fluoro groups, and mercapto groups.

The polymer silane coupling agent can be prepared, for example, by following the method for producing a reaction product between a polymerizable monomer and a reactive silane compound disclosed in Japanese Patent Application Publication No. 11-116240. The number-average molecular weight of the polymer silane coupling agent is preferably 2,000 to 150,000 in terms of polystyrene, and more preferably 2,500 to 100,000.

A method for coating the surface of fine particles with a polymer silane coupling agent will be explained using silica fine particles as an example. First, a dispersion is prepared by dispersing silica fine particles and the polymer silane coupling agent in an organic solvent. Alkali is added to this dispersion to generate OH groups on the surface of the silica fine particles, and the polymer silane coupling agent is adsorbed onto these OH groups. Alternatively, the OH groups of the polymer silane coupling agent and the OH groups of the polymer silane coupling agent are bonded by a dehydration reaction. Finally, the silica fine particles to which the polymer silane coupling agent has been adsorbed or bonded are separated from the dispersion and dried to obtain silica fine particles coated with the polymer silane coupling agent.

The method for preparing the above-mentioned hard coat layer forming composition is not particularly limited, as long as the solid components contained in the hard coat layer can be uniformly mixed with the solvent. For example, the composition can be prepared by mixing or dissolving each of the solid components and the solvent using known equipment such as a paint shaker, bead mill, kneader, or mixer.

The hard coat layer forming composition is applied to the surface of the protective film 2 or the primer layer, and the hard coat layer 1 is formed by curing the active-ray curable resin in the coating film. Conventional known methods can be applied without particular limitation as the coating method for the hard coat layer forming composition. For example, when forming a uniform thin film layer, the microgravure coating method is preferred, and when it is necessary to form a thick film layer, the die coating method is preferred. After removing the solvent from the coating film as needed, the hard coat layer is obtained by curing the active-ray curable resin by active-ray irradiation.

The thickness of the hard coat layer 1 is preferably in the range of 0.01 to 20 μm as an average thickness, and preferably in the range of 0.5 to 10 μm.

[Polarizer]
Polarizer 3 is an element that allows only light with a specific polarization plane to pass through. Examples of polarizers include hydrophilic polymer films such as polyvinyl alcohol-based films, partially formalized polyvinyl alcohol-based films, and partially saponified ethylene-vinyl acetate copolymer films, which are uniaxially stretched after adsorbing dichroic substances such as iodine or dichroic dyes, as well as polyene-based oriented films such as dehydrated polyvinyl alcohol or dehydrochlorinated polyvinyl chloride. Among these, polarizers made of polyvinyl alcohol-based films and dichroic substances such as iodine are preferred. The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 μm.

A polarizer made by dyeing a polyvinyl alcohol-based film with iodine and then uniaxially stretching it can be produced, for example, by dyeing the polyvinyl alcohol by immersing it in an aqueous solution of iodine and then stretching it to 3 to 7 times its original length. If necessary, it can also be immersed in an aqueous solution of potassium iodide, which may contain boric acid, zinc sulfate, zinc chloride, etc. Furthermore, if necessary, the polyvinyl alcohol-based film may be immersed in water and washed before dyeing. Washing the polyvinyl alcohol-based film with water removes dirt and anti-blocking agents from the film surface, and also prevents uneven dyeing by swelling the film. Stretching can be performed after dyeing with iodine, while dyeing, or after stretching. Stretching can also be performed in aqueous solutions of boric acid or potassium iodide, or even in a water bath.

Furthermore, in the present invention, thin polarizers with a thickness of 10 μm or less can also be used. From the viewpoint of thinning, a thickness of 1 to 7 μm is preferable. Such thin polarizers are preferable because they have less thickness variation, excellent visibility, excellent durability due to minimal dimensional change, and furthermore, the thickness of the polarizing film can be reduced.

Examples of thin polarizers include the thin polarizing films described in Japanese Patent Publication No. 51-069644, Japanese Patent Publication No. 2000-338329, International Publication No. 2010/100917, International Publication No. 2010/100917, Japanese Patent No. 4751481, and Japanese Patent Publication No. 2012-073563. These thin polarizing films can be obtained by a manufacturing method that includes a step of stretching a polyvinyl alcohol-based resin (hereinafter also referred to as PVA-based resin) layer and a stretching resin substrate in a laminated state, and a step of dyeing. With this manufacturing method, even if the PVA-based resin layer is thin, it can be stretched without problems such as breakage due to stretching because it is supported by the stretching resin substrate.

As for the thin polarizing film, among manufacturing methods that include a step of stretching in a laminated state and a step of dyeing, it is preferable to obtain one that includes a step of stretching in an aqueous boric acid solution, as described in International Publication No. 2010/100917, International Publication No. 2010/100917, or Japanese Patent Publication No. 4751481 or Japanese Patent Application Publication No. 2012-073563, in that it can be stretched to a high magnification and its polarization performance can be improved. In particular, it is preferable to obtain one that includes a step of auxiliary air stretching before stretching in an aqueous boric acid solution, as described in Japanese Patent Publication No. 4751481 or Japanese Patent Application Publication No. 2012-073563.

[Phase contrast film]
Any phase difference film 4 that has a phase difference and can function as an optical compensation layer can be used. When a transparent protective film with a phase difference is used, its phase difference characteristics can be appropriately adjusted to the value required for optical compensation.

As the phase difference film 4, for example, when the refractive index in the slow phase axis direction is nx, the refractive index in the in-plane fast phase axis direction is ny, and the refractive index in the thickness direction is nz, a film that satisfies the following relationships is selected and used according to various applications: nx = ny > nz, nx > ny > nz, nx > ny = nz, nx > nz > ny, nz = nx > ny, nz > nx > ny, nz > nx = ny. Note that nx = ny includes not only the case where nx and ny are completely identical, but also the case where nx and ny are substantially the same. Similarly, ny = nz includes not only the case where ny and nz are completely identical, but also the case where ny and nz are substantially the same.

When the polarizing plate 10A is used in an organic EL display device, the phase difference film 4 is preferably a quarter-wave plate with a front retardation of 1/4 wavelength (approximately 100 to 170 nm). This is preferable because laminating the polarizer 3 and the quarter-wave plate (phase difference film) 4 allows it to function as a circular polarizing plate for anti-reflection in the organic EL display device.

In other words, when external light incident on this organic EL display device, only the linearly polarized component is transmitted by the polarizer 3. This linearly polarized light is generally converted to elliptically polarized light by the phase difference film 4, but in particular, when the phase difference film 4 is a quarter-wave plate and the angle between the phase difference film 4 and the polarization direction is π/4, it becomes circularly polarized light.

This circularly polarized light passes through the transparent substrate, transparent electrodes, and organic thin film in the organic EL panel, is reflected by the metal electrodes, and then passes through the organic thin film, transparent electrodes, and transparent substrate again, becoming linearly polarized again by the phase difference film 4. Since this linearly polarized light is perpendicular to the polarization direction of the polarizer 3, it cannot pass through the polarizer 3. As a result, the mirror surface of the metal electrodes can be completely shielded.

As the phase difference film 4, a stretched film obtained by stretching a film in which a thermoplastic resin is the film-forming component can be suitably used. As the thermoplastic resin, the same thermoplastic resin as described for the constituent material of the protective film 2 above can be used.

The phase difference film 4 contains an ultraviolet absorber as appropriate, depending on the above configurations 1 to 5 of the polarizing plate 10A. The type and content of the ultraviolet absorber when the phase difference film 4 contains an ultraviolet absorber are as described above. In addition to the ultraviolet absorber, the phase difference film 4 may also contain other additives such as phase difference adjusters, antioxidants, plasticizers, antistatic agents, release agents, and thickeners, to the extent that they do not impair the effects of this embodiment.

The phase difference film 4 may be a single-layer or a laminated film of two or more layers. If the phase difference film 4 is a laminated film and contains an ultraviolet absorber, the amount added to each layer should be adjusted so that the total amount of ultraviolet absorber in the phase difference film 4 is as described above. When the phase difference film 4 is a laminated film, the thermoplastic resins used to form each layer may be the same or different. Conventional known methods can be applied without particular limitation as a method for manufacturing the laminated film.

In addition to the cycloolefin resin, cellulose ester resin, and acrylic resin mentioned above, polycarbonate resin is preferably used as the thermoplastic resin for forming the phase difference film 4. In particular, polycarbonate resin is preferred when manufacturing the obliquely stretched film described later. When the phase difference film 4 is a laminated film, for example, a combination of cellulose ester resin and a polycarbonate resin layer is preferred.

(Polycarbonate resin)
Various polycarbonate resins can be used without particular limitations, but aromatic polycarbonate resins are preferred in terms of chemical properties and physical properties, and polycarbonates having a fluorene skeleton and bisphenol A-based polycarbonate resins are particularly preferred. Among these, those using bisphenol A derivatives obtained by introducing a benzene ring, a cyclohexane ring, and an aliphatic hydrocarbon group to bisphenol A are more preferred. Furthermore, polycarbonate resins with a structure that reduces intramolecular anisotropy, obtained using derivatives in which the above functional groups are introduced asymmetrically to the central carbon of bisphenol A, are particularly preferred.

Such polycarbonate resins are particularly preferred if they are obtained by replacing the two methyl groups on the central carbon of bisphenol A with benzene rings, or by asymmetrically substituting the hydrogen atoms on each benzene ring of bisphenol A with methyl groups or phenyl groups relative to the central carbon. Specifically, these are obtained from 4,4'-dihydroxydiphenylalkanes or halogen-substituted derivatives thereof by the phosgene method or transesterification method, and examples include 4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenylethane, and 4,4'-dihydroxydiphenylbutane. In addition, to give specific examples of polycarbonate resins, for instance, those described in Japanese Patent Publication No. 2006-215465, Japanese Patent Publication No. 2006-91836, Japanese Patent Publication No. 2005-121813, Japanese Patent Publication No. 2003-167121, Japanese Patent Publication No. 2009-126128, Japanese Patent Publication No. 2012-67300, and International Publication No. 2000/026705 are also examples.

(Manufacturing of phase difference film)
The phase difference film 4 can be manufactured by known molding methods such as molten casting, solution casting, and calendering, similar to the protective film 2 described above. It is preferable to use molten casting or solution casting, and solution casting is particularly preferable.

The phase difference film 4 can be manufactured in the same manner as described for the protective film 2, except that in the step of obtaining the dope in (1), the additives are adjusted to match the phase difference film 4, and include an ultraviolet absorber and any other additives added as needed according to the configuration of the polarizing plate 10A.

Furthermore, in the solution casting method described for protective film 2, the film obtained in step (3) or (4) can be used as a film substrate and further obliquely stretched in the following manner to obtain phase difference film 4.

To manufacture a long, obliquely stretched film using a film substrate, for example, an apparatus whose general configuration is schematically shown in Figures 4 and 5 is used. Figure 4 is a schematic plan view showing the general configuration of the obliquely stretched film manufacturing apparatus 80. Figure 5 is a schematic plan view showing an example of the rail pattern of the stretching section of the obliquely stretched film manufacturing apparatus 80. The manufacturing apparatus 80 comprises, in order from the upstream side in the conveying direction of the film substrate, a film feeding section 81, a conveying direction changing section 82, a guide roll 83, a stretching section 84, a guide roll 85, a conveying direction changing section 86, and a film winding section 87.

The film dispensing unit 81 dispenses the film substrate prepared as described above and supplies it to the stretching unit 84. The transport direction changing unit 82 changes the transport direction of the film substrate dispensed from the film dispensing unit 81 toward the entrance of the stretching unit 84, which acts as an oblique stretching tenter. At least one guide roll 83 is provided upstream of the stretching unit 84 to stabilize the trajectory of the film substrate during its movement. At least one guide roll 85 is provided downstream of the stretching unit 84 to stabilize the trajectory of the film that has been obliquely stretched in the stretching unit 84 during its movement. The transport direction changing unit 86 changes the transport direction of the stretched film transported from the stretching unit 84 toward the film winding unit 87. The film winding unit 87 winds up the film transported from the stretching unit 84 via the transport direction changing unit 86.

Details of the stretching section 84 will be explained with reference to Figure 5. The manufacture of obliquely stretched film can be carried out, for example, using an obliquely stretchable tenter (oblique stretching machine) as shown in Figure 5, as the stretching section 84. This tenter is a device that heats a film substrate to any stretchable temperature and obliquely stretches it, and comprises a heating zone Z, a pair of rails Ri and Ro on the left and right sides, and numerous grippers Ci and Co (only one set of grippers is shown in Figure 5) that travel along the rails Ri and Ro to transport the film. Details of the heating zone Z will be described later. Each of the rails Ri and Ro is composed of multiple rail sections connected by connecting sections (white circles in Figure 5 are examples of connecting sections). The grippers Ci and Co consist of clips that grip both ends of the film in the width direction.

In Figure 5, the feeding direction D1 of the film substrate differs from the winding direction D2 of the long diagonally stretched film after stretching, forming a feeding angle θi between the two. The feeding angle θi can be arbitrarily set to a desired angle within the range of greater than 0° and less than 90°.

Because the feeding direction D1 and the winding direction D2 are different, the tenter's rail pattern has an asymmetrical shape on the left and right sides. Furthermore, the rail pattern can be adjusted manually or automatically according to the orientation angle θ, stretching ratio, etc., to be applied to the long oblique stretched film to be manufactured. In the oblique stretching machine used in the manufacturing method of this embodiment, it is preferable that the positions of each rail section and rail connection section constituting the rails Ri and Ro can be freely set, and the rail pattern can be arbitrarily changed. This allows the orientation angle of the film to be freely set.

In the stretching section 84, the film substrate is gripped at both ends by the left and right grippers Ci and Co, and is transported within the heating zone Z as the grippers Ci and Co move. The left and right grippers Ci and Co are positioned at the entrance of the stretching section 84 (position A in the figure) in a direction substantially perpendicular to the direction of film travel (feed-out direction D1), and travel on asymmetrical rails Ri and Ro, respectively, releasing the gripped film at the exit (position B in the figure) when stretching is complete. The film released from the grippers Ci and Co is wound onto a core in the film winding section 87 described above.

Because the rails Ri and Ro are asymmetrical, in the example shown in Figure 5, the left and right grippers Ci and Co, which were facing each other at position A in the figure, will, as they travel along the rails Ri and Ro, have a positional relationship in which the gripper Ci traveling on the rail Ri side (inner course side) will lead the gripper Co traveling on the rail Ro side (outer course side).

In other words, at position A in the diagram, of the grippers Ci and Co, which were facing each other in a direction approximately perpendicular to the film unwinding direction D1, when one gripper Ci reaches position B at the end of film stretching first, the line connecting grippers Ci and Co is inclined by an angle θL with respect to a direction approximately perpendicular to the film winding direction D2. Through this action, the film substrate is stretched obliquely at an angle θL with respect to the width direction. Here, "approximately perpendicular" means within the range of 90 ± 1°.

The heating zone Z of the stretching section 84 is composed of a preheating zone Z1, a stretching zone Z2, and a heat-setting zone Z3. In the stretching section 84, the film gripped by the gripping device Ci・Co passes through the preheating zone Z1, the stretching zone Z2, and the heat-setting zone Z3 in that order. In this embodiment, the preheating zone Z1 and the stretching zone Z2 are separated by a partition wall, and the stretching zone Z2 and the heat-setting zone Z3 are separated by a partition wall.

The preheating zone Z1 refers to the section at the entrance of the heating zone Z in which the gripping devices Ci and Co, which grip both ends of the film, travel while maintaining a constant distance between them (in the film width direction).

The stretching zone Z2 refers to the section where the distance between the gripping devices Ci and Co, which grip both ends of the film, begins to widen until a predetermined distance is reached. This is how the diagonal stretching described above is performed. In other words, in stretching zone Z2, a diagonal stretching process is performed to obtain a diagonally stretched film by stretching a long film (film substrate) in a diagonal direction that is inclined with respect to both the width direction and the length direction within the film surface. Note that stretching in the vertical or horizontal direction may be performed before or after the diagonal stretching as needed.

The heat-setting zone Z3 is the section after the stretching zone Z2 where the distance between the gripping devices Ci and Co becomes constant again, and where the gripping devices Ci and Co at both ends remain parallel to each other as they travel. In other words, in the heat-setting zone Z3, a heat-setting process is performed in which the diagonally stretched film is conveyed while maintaining a constant width.

Furthermore, after the stretched film passes through the heat-setting zone Z3, it may also pass through a section (cooling zone) where the temperature within the zone is set to be below the glass transition temperature Tg (°C) of the thermoplastic resin constituting the film. In this case, considering the shrinkage of the film due to cooling, the rail pattern may be designed to narrow the distance between the opposing grippers Ci and Co in advance.

It is preferable to set the temperature of the preheating zone Z1 to Tg to Tg+30°C, the temperature of the stretching zone Z2 to Tg to Tg+30°C, and the temperatures of the heat-fixing zone Z3 and the cooling zone to Tg-30 to Tg+20°C, relative to the glass transition temperature Tg of the thermoplastic resin.

The lengths of the preheating zone Z1, stretching zone Z2, and heat-fixing zone Z3 can be selected as appropriate. Typically, the length of the preheating zone Z1 is 100-150% of the length of the stretching zone Z2, and the length of the heat-fixing zone Z3 is typically 50-100%.

Furthermore, if the width of the film before stretching is Wo (mm) and the width of the film after stretching is W (mm), the stretching ratio R (W/Wo) in the stretching process is preferably 1.3 to 3.0, more preferably 1.5 to 2.8. A stretching ratio within this range is preferable because it reduces thickness unevenness in the width direction of the film. In the stretching zone Z2 of the oblique stretching tenter, differentiating the stretching temperature in the width direction makes it possible to further improve the thickness unevenness in the width direction. Note that the above stretching ratio R is equal to the ratio (W/Wo) when the distance Wo between the ends of the clips gripped at the tenter inlet becomes the distance W at the tenter outlet.

The thickness of the phase difference film 4 can be determined as appropriate, but generally it is preferable to be in the range of 1 to 500 μm from the viewpoint of optical properties, strength, workability such as handling, and thin film properties. The thickness of the phase difference film 4 is more preferably in the range of 5 to 100 μm, and even more preferably in the range of 15 to 80 μm.

[Adhesive layer]
Preferably, the polarizer 3 and the protective film 2, and the polarizer 3 and the phase difference film 4 are adhered to each other via, for example, an adhesive layer. The adhesive layer may be a layer obtained by drying a water-based adhesive, or it may be a cured layer of an active-ray curable adhesive. The adhesive layer may also contain a metal compound filler.

Examples of water-based adhesives include isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latex adhesives, water-based polyurethanes, and water-based polyesters. Specifically, a polyvinyl alcohol adhesive is a fully saponifiable type of polyvinyl alcohol aqueous solution (water glue). Examples of active-beam-curable adhesives include ultraviolet-curable adhesives and electron beam-curable adhesives.

[Adhesive layer]
The adhesive layer is optionally provided on the polarizing plate of the present invention. Having the adhesive layer improves workability when manufacturing an organic EL display device in which the polarizing plate is positioned on the viewing side of the organic EL element. The polarizing plate 10B shown in Figure 2 is an example in which the polarizing plate has an adhesive layer. The polarizing plate 10B can be made similar to the polarizing plate 10A, including preferred embodiments, except that the adhesive layer 5 is on the side opposite to the polarizer 3 of the phase difference film 4.

The type of adhesive used to form the adhesive layer 5 is not particularly limited, and examples include rubber-based adhesives, acrylic-based adhesives, silicone-based adhesives, urethane-based adhesives, vinyl alkyl ether-based adhesives, polyvinyl alcohol-based adhesives, polyvinylpyrrolidone-based adhesives, polyacrylamide-based adhesives, and cellulose-based adhesives. Among these adhesives, acrylic-based adhesives are preferred because they exhibit excellent optical transparency, appropriate adhesion, cohesiveness, and bonding properties, and have excellent weather resistance and heat resistance. In the present invention, it is preferable to use an acrylic-based adhesive containing a (meth)acrylic polymer as the base polymer.

The method for forming the adhesive layer 5 is not particularly limited and can be formed by methods commonly used in this field. Specifically, it can be formed by coating at least one side of a substrate with the above-mentioned adhesive or an adhesive composition containing its raw materials and a solvent, and then drying the coating film formed from the adhesive composition, or by irradiating with an active ray such as ultraviolet light. In the case of an acrylic adhesive, the adhesive composition contains monomers that form the structural units of the polymer, a polymerization initiator, and a solvent.

The substrate to which the adhesive composition is applied is, for example, a release film or a phase difference film 4. When forming an adhesive layer 5 on a release film, the formed adhesive layer 5 is transferred to the phase difference film 4, and the release film is peeled off. The adhesive layer 5 may be protected with a release film until the polarizing plate 10B is put into practical use.

The thickness of the adhesive layer 5 is not particularly limited, but it is preferably about 10 to 75 μm, and more preferably about 12 to 50 μm.

[Polarizing plate]
The polarizing plate 10A is obtained by laminating the protective film 2 with the hard coat layer 1, the polarizer 3, and the phase difference film 4, which are manufactured as described above, so that from the viewing side, they are in the order of hard coat layer 1, protective film 2, polarizer 3, and phase difference film 4. When laminating, each of these layers is selected so that the combination of hard coat layer 1, protective film 2, and phase difference film 4 becomes one of the configurations 1 to 5 described above. Furthermore, it is preferable that the protective film 2 and the polarizer 3, and the polarizer 3 and the phase difference film 4 are bonded together with an adhesive as described above.

The polarizing plate 10B is obtained by laminating a protective film 2 with a hard coat layer 1, a polarizer 3, a phase difference film 4, and an adhesive layer 5, which are manufactured as described above. Similar to the polarizing plate 10A, when laminating, each of these layers is selected so that the combination of the hard coat layer 1, protective film 2, and phase difference film 4 becomes one of the configurations 1 to 5 described above. It is preferable that the protective film 2 and the polarizer 3, and the polarizer 3 and the phase difference film 4 are bonded together with an adhesive. When laminating as described above, the adhesive layer 5 may be pre-laminated with the phase difference film 4, or it may be laminated as an adhesive layer 5 formed on a release film.

In the polarizing plate of the present invention, the transmittance of the layer containing the ultraviolet absorber or compound (D) and the transmittance of the polarizing plate are preferably within the following ranges.

(i) Transmittance of the layer containing the ultraviolet absorber The transmittance of the layer containing the ultraviolet absorber at a wavelength of 380 nm is preferably 9% or less, more preferably 7% or less, even more preferably 5% or less, and particularly preferably 3% or less. By having the transmittance at a wavelength of 380 nm within the above range, the region of incident ultraviolet light near that wavelength can be blocked to a higher degree, and when used in an organic EL display device, the degradation of the organic EL element can be significantly suppressed.

Furthermore, the transmittance of the layer containing the above-mentioned ultraviolet absorber at a wavelength of 450 nm is preferably 60% or more, preferably 70% or more, and more preferably 75% or more. Having the transmittance at a wavelength of 450 nm within this range is preferable because, when used in an organic EL display device, it allows sufficient transmission of light emitted from the organic EL element, thereby ensuring sufficient display performance in the organic EL display device.

(ii) Transmittance of the layer containing compound (D) The transmittance of the layer containing compound (D) at a wavelength of 380 nm is preferably 9% or less, more preferably 7% or less, even more preferably 5% or less, and particularly preferably 3% or less. It is preferable that the transmittance at a wavelength of 380 nm is within the above range because incident ultraviolet rays can be blocked to a higher degree, thereby significantly suppressing the degradation of the organic EL element.
Furthermore, the transmittance of the layer containing compound (D) at a wavelength of 400 nm is preferably 60% or less, preferably 50% or less, and more preferably 40% or less. Having the transmittance at a wavelength of 400 nm within the above range is preferable because it allows for a higher degree of blocking of incident ultraviolet light, thereby significantly suppressing the degradation of the organic EL element.
Furthermore, the transmittance of the layer containing compound (D) at a wavelength of 440 nm is preferably 50% or more, preferably 60% or more, and more preferably 70% or more. Having the transmittance at 440 nm within this range is preferable because it allows sufficient transmission of light emitted from the organic EL element, thereby ensuring sufficient display performance in the organic EL display device.

(iii) Transmittance of the polarizing plate In the polarizing plate of the present invention, the transmittance at a wavelength of 380 nm is preferably 9% or less, more preferably 7% or less, even more preferably 5% or less, and particularly preferably 3% or less. Furthermore, the transmittance of the polarizing plate at a wavelength of 400 nm is preferably 20% or less, more preferably 15% or less, and more preferably 10% or less.

By having the transmittance of the polarizing plate at a wavelength of 380 nm and at a wavelength of 400 nm within the above range, incident ultraviolet light can be blocked to a higher degree. Therefore, when the polarizing plate is used in an organic EL display device, incident ultraviolet light can be blocked to a higher degree.

Furthermore, the transmittance of the polarizing plate of the present invention at a wavelength of 450 nm is preferably 25% or more, preferably 30% or more, and more preferably 33% or more. Having the transmittance at a wavelength of 450 nm within the above range is preferable because, when used in an organic EL display device, it allows sufficient transmission of light emitted from the organic EL element, thereby ensuring sufficient display performance in the organic EL display device.

[Organic EL display device]
The polarizing plate of the present invention can be used in various display devices such as liquid crystal displays (LCDs), organic light-emitting diodes (OLEDs), and touch panels. In particular, it is preferable to use the polarizing plate of the present invention as a circular polarizing plate in an organic light-emitting diode display device.

Figure 3 shows a cross-sectional view of one example configuration of the organic EL display device of the present invention. The organic EL display device 20 shown in Figure 3 has an organic EL element 11 and a polarizing plate 10B of the present invention on its viewing side. The organic EL display element 11 includes, for example, a light-reflecting electrode, a light-emitting layer, a transparent electrode layer, and a transparent plastic film substrate.

The organic EL display device 20 can display an image when current is passed between the light-reflecting electrode and the transparent electrode layer, causing the light-emitting layer to emit light. Furthermore, since all light incident on the organic EL display device from the outside is absorbed by the polarizer 3 of the polarizing plate 10B, even if it is reflected by the light-reflecting electrode of the organic EL element 11, it does not emit outwards, thus suppressing the deterioration of display characteristics due to reflection of the background.

In the organic EL display device 20, the polarizing plate 10B is configured such that, as in configurations 1 to 5 above, at least one of the hard coat layer 1 and the protective film 2 contains compound (D), at least one of the protective film 2 and the phase difference film 4 contains an ultraviolet absorber, and the layer containing compound (D) is located on the viewing side of the layer containing the ultraviolet absorber.

In this way, by arranging the polarizing plate 10B, which has a dye compound-containing layer and an ultraviolet absorber-containing layer, on the viewing side of the organic EL element 11, the polarizing plate 10B can sufficiently absorb light with wavelengths shorter than the light-emitting region of the organic EL element 11 (longer wavelengths than 430 nm), thereby protecting the organic EL element 11 from external light and suppressing light emission loss. Furthermore, by arranging the dye compound-containing layer and the ultraviolet absorber-containing layer in the specific order described above, the heat generated from compound (D) can be released to the outside from the surface of the organic EL display device 20 without being hindered by the heat generated by the ultraviolet absorption layer. This suppresses deterioration such as fluctuations in the optical value of the phase difference film 4 and deterioration such as shrinkage of the polarizer 3 due to the heat generated by compound (D).

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the examples, the units "parts" or "%" are used, and unless otherwise specified, they represent "parts by mass" or "mass%".

(Measurement of maximum absorption wavelength)
The maximum absorption wavelength of compound (D), a dye compound used in the examples according to the present invention whose maximum absorption wavelength is in the range of 360 to 379 nm, and the maximum absorption wavelength of a comparative dye compound were determined by measuring the absorption spectrum of the dye compound in chloroform using a UV-2450 ultraviolet-visible spectrophotometer manufactured by Shimadzu Corporation, and are shown in Table II.
In this invention, "maximum absorption wavelength" refers to the wavelength (nm) that exhibits the maximum and highest absorbance (absorption intensity) in the absorption spectrum of the compound obtained when the absorption spectrum of the above compound is measured.

The structural formulas of D-1 to D-3 in Table II, and the compounds of the comparative examples (BONASORB3912 and FDB009) are shown below.

Comparative compound 1: BONASORB UA3912 (manufactured by Orient Chemical Industry Co., Ltd.)
Comparative compound 2: FDB-009 (manufactured by Yamada Chemical Industries, Ltd.)

[1] Manufacturing of protective film with hard coat layer (protective film with HD layer) (1) Manufacturing of cycloolefin resin film with hard coat layer (1-1) Manufacturing of cycloolefin resin film (preparation of dope)
Each component of Table III was placed in a sealed container, heated, and stirred until completely dissolved. This was filtered using Asaka Filter Paper No. 24 manufactured by Asaka Filter Paper Co., Ltd. to obtain dopes (COP-1 to COP-7). As for the cycloolefin resin in Table III, Arton G7810 (manufactured by JSR Corporation) was used. LA-F70 is an ultraviolet absorber manufactured by ADEKA Corporation with a maximum absorption wavelength of 355 nm, and Chinuvin 928 is an ultraviolet absorber manufactured by BASF Japan Ltd. with a maximum absorption wavelength of 349 nm; both are ultraviolet absorbers represented as "UVA" in the table. Compound D-1, Compound (1)-1, and Compound (2)-3 correspond to Compound (D) ("(D)" in the table).

(Formation of protective film)
The obtained dope was kept at 30°C and uniformly cast onto a stainless steel belt, which was a metal support maintained at 30°C. The cast dope was then dried until the residual solvent content reached 30% by mass, and then peeled off the stainless steel belt to obtain a film-like material.

Next, the obtained film was dried at 40°C until the residual solvent content was 10% by mass, and then stretched in the width direction at a stretching ratio of 1.4 times (40%). The obtained film was then further dried at 150°C while being transported by multiple rolls to obtain a protective film with a length of 3000 m and a thickness of 20 μm. The obtained protective films were designated as protective films COP-1 to COP-7, corresponding to the type of dope.

(1-2) Formation of the primer layer (Preparation of primer coating solution 1 for the hard coat layer)
100 parts by mass of a thermosetting water-based polyolefin resin (Arrowbase SB-1200 (product name), solids content 25%, manufactured by Unitika Ltd.) and 8 parts by mass of an oxazoline crosslinking agent (WS-700, manufactured by Nippon Shokubai Co., Ltd.) were diluted with a diluent (water/methanol = 30/70 (mass%)) until the solids content concentration was 5%, and then stirred at room temperature to prepare primer layer coating solution 1.

(Formation of the primer layer on the hard coat side)
The primer layer coating solution 1 prepared above was applied to the hard coat layer side of a 20 μm thick protective film using a bar coater, and the film was formed by drying in an 80°C drying oven for 40 seconds, creating a hard coat layer primer layer with a dry film thickness of 0.4 μm.

(Preparation of the primer layer coating solution 2 for the polarizer side)
100 parts by mass of a water-based urethane resin (Hydran AP-40F (trade name), 20% solids content, manufactured by DIC Corporation) and 5 parts by mass of an oxazoline crosslinking agent (WS-700, trade name, manufactured by Nippon Shokubai Co., Ltd.) were diluted with a diluent (water/methanol = 30/70 (mass%)) until the solids content concentration was 5%, and then stirred at room temperature to prepare primer layer coating solution 2.

(Formation of the polarizer-side primer layer)
The primer layer coating solution 2 prepared above was applied to the polarizer-side surface of a 20 μm thick protective film using a bar coater, and the film was formed by drying in a 120°C drying oven for 120 seconds, creating a polarizer-side primer layer with a film thickness of 0.5 μm.

(1-3) Formation of the hard coat layer (Preparation of the composition for forming the hard coat layer)
The hard coat layer-forming compositions (CHD-1 to CHD-7) were prepared by mixing each material in the proportions shown in Table IV. In Table IV, urethane acrylate UA-306H (trade name, manufactured by Kyoeisha Chemical Co., Ltd.) was used as the hard coat resin. Irgacure 184 (manufactured by BASF Japan Ltd.) was used as a photopolymerization initiator, and KF-351A (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) was used as a surfactant. Propylene glycol monomethyl ether (PGME) and methyl acetate (MA) (solvent mass ratio: PGME/MA = 40/60) were used as dilution solvents.

(Formation of Hard Coat Layer) On the hard coat layer side primer layer of the protective film with the primer layer prepared above, the hard coat layer forming composition prepared above was combined as shown in Table V and applied with a bar coater to a dry film thickness of 2.5 μm. The solvent was evaporated by drying in a 50°C drying oven for 40 seconds. Then, while purging with nitrogen to maintain an atmosphere with an oxygen concentration of 1.0 volume% or less, the coated layer was cured using an ultraviolet lamp with an irradiation intensity of 100 mW/ ^cm² and an irradiation dose of 0.2 J/ ^cm² to produce protective films with hard coat layers (protective films with HD layer 1 to 14).

(2) Manufacturing of cellulose ester resin film with hard coat layer (2-1) Manufacturing of cellulose ester resin film

(Preparation of dope)
A dope with the following composition was prepared. First, dichloromethane and ethanol were added to a pressurized dissolution tank. Then, cellulose ester was added to the pressurized dissolution tank containing the solvent while stirring, and the mixture was heated and stirred until completely dissolved.
Cellulose ester;
Triacetylcellulose 100 parts by mass, polycondensed ester compound N 2 parts by mass, polycondensed ester compound M 7 parts by mass, solvent;
Dichloromethane 540 parts by mass, Ethanol 35 parts by mass (additives);
Fine particles; silicon dioxide dispersion dilution; 3 parts by mass; ultraviolet absorber; further, the above additive components were placed in a sealed container, dissolved while stirring, and filtered using Asaka Filter Paper No. 244 manufactured by Asaka Filter Paper Co., Ltd. to prepare the dope.

Ester compound N, ester compound M, and silicon dioxide dispersion dilution were prepared as follows. Furthermore, Chinuvin 928 (trade name, manufactured by BASF Japan Ltd.) was used as the ultraviolet absorber.

(Ester compound N)
First, 251 g of 1,2-propylene glycol, 354 g of terephthalic acid, 680 g of p-troylic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were placed in a 2 L four-necked flask equipped with a thermometer, stirrer, and slow cooler. Next, a stream of nitrogen gas was blown into the four-necked flask, and the solution was gradually heated while stirring until the solution temperature reached 230°C, allowing the dehydration condensation reaction to proceed while observing the degree of polymerization. After the reaction was complete, the unreacted 1,2-propylene glycol was removed by vacuum distillation at 200°C to obtain the polycondensed ester compound N. This ester compound N had an acid value of 0.30 and a number-average molecular weight of 400.

(Ester compound M)
First, 251 g of 1,2-propylene glycol, 244 g of phthalic anhydride, 103 g of adipic acid, 610 g of benzoic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were placed in a 2 L four-necked flask equipped with a thermometer, stirrer, and condenser. Next, a stream of nitrogen gas was blown into the four-necked flask, and the solution was gradually heated while stirring until the solution temperature reached 230°C, allowing the dehydration condensation reaction to proceed while observing the degree of polymerization. After the reaction was complete, the unreacted 1,2-propylene glycol was removed by vacuum distillation at 200°C to obtain polycondensed ester compound M. This ester compound M had an acid value of 0.10 and a number-average molecular weight of 450.

(Silicon dioxide dispersion)
First, 10 parts by mass of Aerosil R812 (trade name, manufactured by Nippon Aerosil Co., Ltd.) and 90 parts by mass of ethanol were mixed and stirred in a dissolver for 30 minutes, and then silicon dioxide was dispersed in the ethanol using a Manton Gorin. 88 parts by mass of methylene chloride was added to this dispersion while stirring, and the dispersion was diluted by mixing in a dissolver for 30 minutes. This diluted dispersion was filtered using a fine particle dispersion diluent filter (Advantec Toyo Co., Ltd.: polypropylene wind cartridge filter TCW-PPS-1N) to obtain a silicon dioxide dispersion.

(Formation of protective film)
The dope prepared above was uniformly cast onto a stainless steel band support at a temperature of 22°C and a width of 1.8 m using a belt casting apparatus. The solvent was evaporated from the stainless steel band support until the residual solvent content reached 20% by mass, and the doped film (web) was peeled off from the stainless steel band support.

Next, the peeled web was evaporated of the solvent at 35°C, slit into 1.6 m widths, and then stretched to 1.1 times its original width in the widthwise direction (TD direction) at 160°C using a tenter stretcher. At this time, the amount of residual solvent at the start of stretching with the tenter was 4% by mass.

Subsequently, the film was dried by transporting it through drying zones at 120°C and 140°C using numerous rollers. It was then slit to a width of 1.3 m, and knurling with a width of 10 mm and a height of 2.5 μm was applied to both ends of the film. Finally, it was wound onto a core to produce protective film TAC-1. The thickness of protective film TAC-1 was 25 μm, and the length of the winding was 6000 m.

(2-2) Formation of the hard coat layer (Preparation of the composition for forming the hard coat layer)
The following materials were mixed in the specified ratios to prepare a hard coat layer forming composition.
Hard coat resin;
Pentaerythritol tri/tetraacrylate (NK Ester A-TMM-3L, trade name, manufactured by Shin Nakamura Chemical Industry Co., Ltd.) 100 parts by mass; Photopolymerization initiator;
Irgacure 184 (trade name, manufactured by BASF Japan Ltd.) 9 parts by mass; Solvent;
Propylene glycol monomethyl ether 20 parts by mass, methyl acetate 30 parts by mass, methyl ethyl ketone 70 parts by mass (additives)
Surfactant: KF-351A (product name, polyether-modified silicone oil, manufactured by Shin-Etsu Chemical Co., Ltd.) 2 parts by mass; Fine particles: Polymer silane coupling agent coated silica (1)
100 parts by mass Compound (D); Compound 1-12 5 parts by mass

The polymer silane coupling agent-coated silica (1) described above was prepared as follows: 30 mL of methyl methacrylate (manufactured by Kyoeisha Chemical Co., Ltd.: Light Ester M), 1 mL of 3-mercaptopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.: KBM-803), 100 mL of tetrahydrofuran as a solvent, and 50 mg of azoisobutyronitrile (manufactured by Kanto Chemical Co., Ltd.: AIBN) as a polymerization initiator were added to a container, and after purging with _N2 gas, the mixture was heated at 80°C for 3 hours to prepare the polymer silane coupling agent. The molecular weight of the obtained polymer silane coupling agent was 16,000. The molecular weight was measured using a gel permeation chromatography apparatus.

Next, silica sol (manufactured by JGC Catalysts & Chemicals Co., Ltd.: Si-45P, trade name, _SiO2 concentration 30% by mass, average particle size 45 nm, dispersion medium: water) was ion-exchanged using an ion-exchange resin, and the water was replaced with ethanol by ultrafiltration to prepare 100 g of an ethanol dispersion of silica fine particles ( _SiO2 concentration 30% by mass).

100 g of this silica microparticle ethanol dispersion and 1.5 g of polymer silane coupling agent were dispersed in 20 g (25 mL) of acetone. 20 mg of 29.8% by mass aqueous ammonia was added to this mixture, and the mixture was stirred at room temperature for 30 hours to adsorb the polymer silane coupling agent onto the silica microparticles.

Subsequently, silica particles with an average particle size of 5 μm were added and stirred for 2 hours to adsorb the unadsorbed polymer silane coupling agent in the solution onto the silica particles. Then, the silica particles with an average particle size of 5 μm that had adsorbed the unadsorbed polymer silane coupling agent were removed by centrifugation. 1000 g of ethanol was added to the silica microparticle dispersion containing the adsorbed polymer silane coupling agent, causing the silica microparticles to settle. This precipitate was then separated, dried under reduced pressure, and dried at 25°C for 8 hours to obtain polymer silane coupling agent-coated silica (1). The average particle size of the obtained polymer silane coupling agent-coated silica (1) was 57 nm. The average particle size was measured using a laser particle size analyzer.

(Formation of the hard coat layer)
The hard coat layer forming composition prepared above was applied to the visible surface of the protective film prepared above using a bar coater to a dry film thickness of 2.5 μm, and the solvent was evaporated by drying in a 50°C drying oven for 40 seconds. Then, while purging with nitrogen to maintain an oxygen concentration of 1.0 volume% or less, the coated layer was cured using an ultraviolet lamp with an irradiation intensity of 100 mW/ ^cm² and an irradiation dose of 0.2 J/ ^cm² to produce a protective film with a hard coat layer. The obtained hard coat layer is also referred to as "THD1". The obtained protective film with a hard coat layer is also referred to as "HD layer protective film 21" below.

(3) Manufacturing of acrylic resin film with hard coat layer (3-1) Manufacturing of acrylic resin film

(Preparation of dope)
A dope with the following composition was prepared. First, dichloromethane and ethanol were added to a pressurized dissolution tank. Next, the resin was added to the pressurized dissolution tank while stirring. Then, the rubber particle dispersion prepared above was added and dissolved completely while stirring. This was filtered using an SHP150 manufactured by Rokitechno Co., Ltd. to obtain the dope.

Resin ((meth)acrylic resin) 100 parts by mass Dichloromethane 200 parts by mass Ethanol 40 parts by mass Rubber particle dispersion 200 parts by mass Chinuvin 928 (trade name, manufactured by BASF Japan Ltd.) 5 parts by mass The (meth)acrylic resin used above is methyl methacrylate (MMA)/N-phenylmaleimide (PMI)/butyl acrylate (BA-polymer (80/10/10 mass ratio), Tg: 120°C, Mw: 2 million).

The glass transition temperature (Tg) of the acrylic resin was measured using DSC (Differential Scanning Colorimetry) in accordance with JIS K7121-2012.

Furthermore, the weight-average molecular weight (Mw) of the acrylic resin was measured using gel permeation chromatography (HLC8220GPC, Tosoh Corporation) and a column (TSK-GELG6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL in series, Tosoh Corporation). 20 mg ± 0.5 mg of the sample was dissolved in 10 mL of tetrahydrofuran and filtered through a 0.45 mm filter. 100 mL of this solution was injected into a column (at 40°C), and the value was measured at a detector RI temperature of 40°C. The value converted to styrene equivalent was used.

The rubber particle dispersion used above was obtained by mixing 10 parts by mass of acrylic rubber particles M-210 (core: multilayer acrylic rubber polymer, shell: methacrylate ester polymer mainly composed of methyl methacrylate, Tg of acrylic rubber polymer: approximately -10°C, average particle diameter: 220 nm) and 190 parts by mass of dichloromethane in a dissolver for 50 minutes, and then dispersing them at 1500 rpm using a Milder disperser (manufactured by Taiheiyo Kiko Co., Ltd.).

The average particle size of the rubber particles was obtained by measuring the dispersed particle size of the rubber particles in the dispersion using a zeta potential/particle size measurement system (ELSZ-2000ZS, manufactured by Otsuka Electronics Co., Ltd.).

(Formation of protective film)
The above-mentioned dope was used to form the film. Specifically, an endless belt casting apparatus was used to uniformly cast the dope onto a stainless steel belt support at a temperature of 30°C and a width of 1800 mm. The temperature of the stainless steel belt was controlled to 28°C.

The solvent in the dope cast onto the stainless steel belt support was evaporated until the residual solvent content reached 30% by mass. Then, the dope was peeled from the stainless steel belt support with a peeling tension of 128 N/m to obtain a film-like material. The residual solvent content of the film-like material at the time of peeling was 30% by mass.

Next, while the peeled film was conveyed by multiple rollers, the resulting film-like material was stretched by 20% in the width direction (TD direction) under conditions of 140°C (Tg + 20°C) using a tenter. After that, while being conveyed on a roll, it was further dried at 100°C (Tg - 20°C), and the ends, which were held in place by tenter clips, were slit and wound into a roll to obtain protective film Ac-1 (roll body) with a length of 3000 m, a width of 1.5 m, and a film thickness of 40 μm.

(3-2) Formation of the hard coat layer (Preparation of the composition for forming the hard coat layer)
The hard coat layer forming composition was prepared by mixing the materials in the following proportions. The polymer silane coupling agent coated silica (1) was obtained in the same manner as the polymer silane coupling agent coated silica (1) prepared in the production of the cellulose ester resin film with the hard coat layer described above.

Hard coat resin;
Urethane acrylate (U-4H, product name, manufactured by Shin-Nakamura Chemical Industry Co., Ltd.)
35 parts by mass of photopolymerization initiator;
Irgacure 184 (trade name, manufactured by BASF Japan Ltd.) 5 parts by mass; Solvent;
Propylene glycol monomethyl ether 80 parts by mass, methyl acetate 20 parts by mass (additives)
Surfactant: KF-642 (trade name, polyether-modified silicone oil, manufactured by Shin-Etsu Chemical Co., Ltd.) 2 parts by mass Fine particles: Polymer silane coupling agent coated silica (1) 10 parts by mass Compound (D): Compound 2-3 5 parts by mass

(Formation of the hard coat layer)
On the surface of the protective film prepared above that is not in contact with the casting belt, the hard coat layer forming composition prepared above was applied using an extruder to a dry film thickness of 2.5 μm. After drying at a constant drying temperature of 50°C and a decrease drying temperature of 50°C, the coated layer was cured using an ultraviolet lamp with an irradiation intensity of 100 mW/ ^cm² and an irradiation dose of 0.25 J/ ^cm² while purging with nitrogen to create an atmosphere with an oxygen concentration of 1.0 volume% or less, thereby forming a hard coat layer. The obtained hard coat layer is also referred to as "AHD1". The obtained protective film with the hard coat layer is also referred to as "protective film with HD layer 31" below.

[2] Production of polarizers A polyvinyl alcohol-based film with a thickness of 25 μm was swollen with water at 35°C. The resulting film was immersed for 60 seconds in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide, and 100 g of water, and then immersed again in an aqueous solution at 45°C consisting of 3 g of potassium iodide, 7.5 g of boric acid, and 100 g of water. The resulting film was uniaxially stretched at a stretching temperature of 55°C and a stretching ratio of 5 times. After washing the uniaxially stretched film with water, it was dried to obtain a polarizer (1) with a thickness of 12 μm.

[3] Manufacturing of phase difference film (Phase difference film 1)
Polycarbonate resin film (PC film) was manufactured using the following manufacturing method (melt casting method).

Polymerization was carried out using a batch polymerization apparatus consisting of two vertical reactors equipped with stirring blades and reflux condensers controlled to 100°C. 9,9-[4-(2-hydroxyethoxy)phenyl]fluorene (BHEPF), isosorbide (ISB), diethylene glycol (DEG), diphenyl carbonate (DPC), and magnesium acetate tetrahydrate were charged in a molar ratio of BHEPF/ISB/DEG/DPC/magnesium acetate = 0.348/0.490/0.162/1.005/1.00 × ^10⁻⁵ . After thoroughly purging the reactor with nitrogen (oxygen concentration 0.0005–0.001 vol%), the reactor was heated with a heat transfer medium, and stirring was started when the internal temperature reached 100°C. Forty minutes after the start of heating, the internal temperature was raised to 220°C, and while controlling the system to maintain this temperature, the pressure was reduced to 13.3 kPa 90 minutes after reaching 220°C. The phenol vapor produced as a by-product of the polymerization reaction was guided to a reflux condenser at 100°C, the monomer components contained in small amounts in the phenol vapor were returned to the reactor, and the non-condensing phenol vapor was guided to a condenser at 45°C and recovered.

Nitrogen was introduced into the first reactor to restore pressure to atmospheric pressure, and then the oligomerized reaction solution in the first reactor was transferred to the second reactor. Next, heating and depressurization were started in the second reactor, and the internal temperature was raised to 240°C and the pressure to 0.2 kPa in 50 minutes. Polymerization was then carried out until the predetermined stirring power was reached. When the predetermined power was reached, nitrogen was introduced into the reactor to restore pressure, the reaction solution was extracted in strand form, and pelletized using a rotary cutter to obtain polycarbonate resin A with a copolymer composition of BHEPF/ISB/DEG = 34.8/49.0/16.2 [mol%]. The reduced viscosity of this polycarbonate resin A was 0.430 dL/g, and the glass transition temperature was 138°C.

The obtained polycarbonate resin A was vacuum-dried at 80°C for 5 hours. Then, a polycarbonate resin film (PC film 1) with a thickness of 130 μm was produced as a long film roll (film roll) using a film manufacturing apparatus equipped with a single-screw extruder (manufactured by Isuzu Chemical Machinery Co., Ltd., screw diameter 25 mm, cylinder setting temperature: 220°C), a T-die (width 900 mm, setting temperature: 220°C), a chill roll (setting temperature: 120-130°C), and a winding machine.

The roll of PC film 1 prepared as described above was set in the obliquely stretched film manufacturing apparatus 80 (see Figures 4 and 5) and the PC film 1 was unwound. Then, the PC film 1 was passed through the preheating zone Z1 of the stretching section to heat it to the preheating temperature, then passed through the stretching zone Z2 to be obliquely stretched at a stretching ratio of 3, and subsequently passed through the heat-setting zone Z3 to produce an obliquely stretched PC film 1 with a film thickness of 50 μm, a width of 1500 mm, and an orientation angle θ = 45° (value at the center of the width). The produced obliquely stretched PC film 1 was wound up to form a film roll. The temperature T1 (preheating temperature) of the preheating zone Z1 in the stretching section was set to (Tg + 15) °C, the temperature T2 (stretching temperature) of the stretching zone Z2 was set to (Tg + 11) °C, and the temperature T3 of the heat-setting zone Z3 was set to (Tg + 9) °C. The resulting phase difference film is designated as phase difference film 1.

(Phase difference film 2)
The phase difference film 2 is a film in which the TAC-1 is laminated onto the phase difference film 1 obtained above. The adhesive layer (A1) used in the fabrication of the organic EL display device described in [5] below was used to bond the phase difference film 1 and the TAC-1.

[4] Fabrication of polarizing plates Polarizing plates 1 to 11 were fabricated by laminating the layers obtained in [1] to [3] above in the combinations shown in Table VII. The gaps between the phase difference film and the polarizer, and between the protective film and the polarizer were bonded using a fully saponifiable polyvinyl alcohol aqueous solution (water glue). In addition, the lamination of the phase difference film 2 was carried out with the TAC-1 side facing the polarizer side.

[5] Fabrication of Organic EL Display Devices The polarizing plates 1 to 11 shown in Table VII were laminated with organic EL elements via the following adhesive layer (A1) to fabricate and evaluate organic EL display devices. Specifically, a SAMSUNG GALAXY S10 (product name) equipped with an organic EL panel was disassembled, the circular polarizing plate was peeled off from the organic EL element, and the polarizing plates 1 to 11 shown in Table VII were bonded to the peeled surface via the adhesive layer (A1), with the hard coat layer side facing the viewing side and the phase difference film side facing the organic EL element, to fabricate organic EL display devices.

(Manufacturing of adhesive composition (A1))
A monomer mixture consisting of 78 parts by mass of 2-ethylhexyl acrylate (2EHA), 18 parts by mass of N-vinyl-2-pyrrolidone (NVP), and 15 parts by mass of 2-hydroxyethyl acrylate (HEA) was mixed with 0.035 parts by mass of 1-hydroxycyclohexyl phenyl ketone (trade name: Irgacure 184, manufactured by BASF Japan Ltd.) and 0.035 parts by mass of 2,2-dimethoxy-1,2-diphenylethane-1-one (trade name: Irgacure 651, manufactured by BASF Japan Ltd.) as photopolymerization initiators. The mixture was then irradiated with ultraviolet light until the viscosity (measurement conditions: BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30°C) reached approximately 20 Pa·s, thereby obtaining a prepolymer composition (polymerization rate: 8%) in which a portion of the above monomer components had polymerized. Next, 0.15 parts by mass of hexanediol diacrylate (HDDA) and 0.3 parts by mass of a silane coupling agent (product name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) were added to the prepolymer composition and mixed to obtain acrylic adhesive composition (a).

To the obtained acrylic adhesive composition (a), 100 parts by mass of monomer components that form an acrylic polymer and 0.2 parts by mass of bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (trade name: Irgacure 819, manufactured by BASF Japan Ltd.) were added and stirred to obtain adhesive composition (A1).

(Formation of adhesive layer (A1))
The adhesive composition (A1) was applied to a film that had been peeled off from a release film, so that the thickness of the adhesive layer after formation was 150 μm. Then, the release film was bonded to the surface of the adhesive composition layer. Subsequently, ultraviolet irradiation was performed under conditions of illuminance: 6.5 mW/ ^cm² , light intensity: 1500 mJ/ ^cm² , and peak wavelength: 350 nm to photocur the adhesive composition layer and form the adhesive layer (A1).

≪Rating≫
(1) Evaluation of Light Transmittance The light transmittance of the HD layered protective film described in Table V above was measured using a spectrophotometer (Hitachi High-Tech Science U-3300) at different measurement wavelengths. The results obtained are shown in Table VI.

(2) Evaluation of adhesion The polarizing plates prepared above were cut into 10 cm x 10 cm pieces and subjected to 500 cycles in a cycle thermostat (alternating between -40°C for 30 minutes and 95°C for 30 minutes) simulating outdoor use. After that, they were irradiated with light for 150 hours using a lightfastness tester (I-Super UV Tester, manufactured by Iwasaki Electric Co., Ltd.).
After durability testing, each polarizing plate was conditioned for 12 hours in an atmosphere of 23°C and 55% RH. Then, in accordance with JIS K5400, 11 cuts were made vertically and horizontally at 1 mm intervals in the hard coat layer of each polarizing plate, creating 100 grids of 1 mm squares. Cellophane tape was applied to these grids and quickly peeled off at a 90-degree angle. The cellophane tape was replaced after each peeling, and after the tape peeling process was performed six times, the area of the grids that remained intact was evaluated according to the following criteria.
○: The area percentage of the grid pattern that was peeled off was less than 5%. △: The area percentage of the grid pattern that was peeled off was 5% or more but less than 10%. ×: The area percentage of the grid pattern that was peeled off was 10% or more.

As can be seen from Tables VI and VII, when the layer containing compound (D) is placed on the visible side of the layer containing the ultraviolet absorber, the light transmittance at 380-440 nm can be appropriately controlled regardless of the type of compound (D), ultraviolet absorber, or protective film resin, protecting the display element from ambient light, preventing light loss from the display element, and improving the adhesion between the layer containing the dye compound and the adjacent layer. In Table VII, replace "the present invention" with "reference example" in the remarks column for polarizers No. 2, 4, 5, 7, and 8.

In the polarizing plate of the present invention, the compound (D) contained in the hard coat layer and protective film and the ultraviolet absorber are arranged in a specific order. This arrangement promotes molecular motion due to the heat generated from compound (D), strengthens the interaction with adjacent layers, and improves the adhesion between the hard coat layer and the protective film.

Furthermore, it was confirmed that the adhesion is further improved when compound (D) is incorporated into the hard coat layer and the UV absorber into the protective film, i.e., in the cases of configurations 1 and 4.

In this invention, when used in a display device, particularly an organic EL display device, a polarizing plate can be provided that can protect the display element from ambient light, prevents light emission loss in the display element, and improves the adhesion between the layer containing the dye compound and the adjacent layer. Furthermore, by using this polarizing plate, an organic electroluminescent display device with reduced light emission loss can be provided.

10A, 10B Polarizing plate 1 Hard coat layer 2 Protective film 3 Polarizer 4 Phase difference film 5 Adhesive layer 20 Organic EL display device 11 Organic EL element 80 Manufacturing apparatus for obliquely stretched film 81 Film feeding section 82, 86 Conveying direction changing section 83, 85 Guide roll 84 Stretching section 87 Film winding section

Claims (4)

A polarizing plate having a hard coat layer, a protective film, a polarizer, and a phase difference film in this order from the viewing side,
At least one of the hard coat layer and the protective film contains a dye compound whose maximum absorption wavelength is within the range of 370 to 379 nm in the absorption spectrum of the 300 to 460 nm wavelength region, at least one of the protective film and the phase difference film contains an ultraviolet absorber, and the layer containing the dye compound is located on the visible side of the layer containing the ultraviolet absorber.
The ultraviolet absorber is a compound whose maximum absorption wavelength in the absorption spectrum of the 300-460 nm wavelength range is within the range of 349-355 nm .
A polarizing plate characterized in that the aforementioned dye compound contains a compound having a structure represented by the following general formula (1), or a compound having a structure represented by the following general formula (2).
(In the formula, R ₁₁ represents a hydrogen atom, halogen atom, alkyl group, alkoxy group, hydroxy group, amino group, alkyl-substituted amino group, carboxy group, alkyloxycarbonyl group, hydroxyalkyl group, alkylcarbonyloxyalkyl group, carboxyalkyl group, alkyloxycarbonylalkyl group, aryl group, acyl group, or sulfo group. R ₁₂ represents a hydrogen atom or a hydroxyl group.)
(In the formula, R ₂₁ represents a hydrogen atom or a hydroxyl group. _{R 22} , R ₂₃ , and R ₂₄ represent an alkyl group, an alkoxy group, an alkyl-substituted amino group, a carboxyl group, an alkyloxycarbonyl group, a hydroxyalkyl group, an alkylcarbonyloxyalkyl group, a carboxyalkyl group, an alkyloxycarbonylalkyl group, an aryl group, an acyl group, or a sulfo group.) The polarizing plate according to claim 1, characterized in that the dye compound is contained in the hard coat layer and the ultraviolet absorber is contained in the protective film. The polarizing plate according to claim 1 or 2, characterized in that it comprises an adhesive layer on the side of the phase difference film opposite to the viewing side. An organic electroluminescent display device characterized by having a polarizing plate according to any one of claims 1 to 3 on the viewing side.