JP2022059257A - Polarizing plate and organic EL display device - Google Patents

Abstract

To provide a novel polarizing plate capable of extending the life of a display device even when used with an organic EL display panel.SOLUTION: A polarizing plate 1 has structure having a first protective film 3 and a second protective film 4 pasted on both surfaces of a polarizer 5, and is a linearly polarizing plate having an absorbance A450 that satisfies a conditional expression (1) below at a wavelength of 450 nm and an absorbance A750 that satisfies a conditional expression (2) below at a wavelength of 750 nm: 1.6≤A450≤2.7 ...(1), 0.7≤A750≤2.3 ...(2).SELECTED DRAWING: Figure 1

Description

The present invention relates to a polarizing plate and an organic EL display device including the polarizing plate.

The organic electroluminescence (organic EL) display device is a self-luminous thin display device, and has advantages of display performance such as high visibility and less viewing angle dependence as compared with a liquid crystal display device. Further, in addition to the advantages that the image display device (display) can be made lighter and thinner, a flexible image display device can be realized, so that there is a possibility that a different image display device can be realized.

However, since the organic EL display device may use a metal material having high reflectance as an electrode (metal electrode), external light is reflected at the interface of the metal electrode, and there is a problem of low contrast and reflection due to internal reflection. May occur (external light reflection).

In order to suppress the adverse effect of external light reflection, it has been proposed to use a circular polarizing plate composed of a linear polarizing plate and a λ / 4 retardation layer as an antireflection plate (see, for example, Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 7-142170 Japanese Unexamined Patent Publication No. 9-127885

In the organic EL display panel, the life of the blue light emitting element may be shorter than the life of the light emitting element of another color. An object of the present invention is to provide a novel polarizing plate capable of extending the life of a display device even when used together with an organic EL display panel, and an organic EL display device provided with the polarizing plate. ..

The present invention provides the following polarizing plate and organic EL display device.
[1] Including a polarizing element
The absorbance A ₄₅₀ at a wavelength of 450 nm satisfies the following relational expression (1).
A polarizing plate having an absorbance A ₇₅₀ at a wavelength of 750 nm satisfying the following relational expression (2).
1.6 ≤ A ₄₅₀ ≤ 2.7 (1)
0.7 ≤ A ₇₅₀ ≤ 2.3 (2)
[2] The polarizing plate according to [1], wherein the absorbance A ₇₀₀ at a wavelength of 700 nm satisfies the following relational expression (3).
1.7 ≤ A ₇₀₀ ≤ 4.5 (3)
[3] The polarizing plate according to [1] or [2], wherein the b value of the orthogonal hue is −1.5 or less.
[4] The polarizing plate according to [3], wherein the b value of the orthogonal hue is −20 or more.
[5] The polarizing plate according to any one of [1] to [4], wherein the polarizing element has a thickness of 7 μm or more and 30 μm or less.
[6] The polarizing plate according to any one of [1] to [5], further comprising a protective film bonded to at least one surface of the polarizing element.
[7] The polarizing plate according to any one of [1] to [6], further comprising a λ / 4 retardation layer.
[8] The polarizing plate according to [7], which is arranged and used on the visible side surface of the organic EL display panel.
[9] An organic EL display device including an organic EL display panel and the polarizing plate according to [8].

According to the polarizing plate of the present invention, the life of the display device can be extended even when it is used together with the organic EL display panel.

It is a schematic sectional drawing which shows an example of the layer structure of the polarizing plate which concerns on this invention. It is a schematic sectional drawing which shows another example of the layer structure of the polarizing plate which concerns on this invention. It is sectional drawing which shows an example of the manufacturing method of the polarizing element which concerns on this invention. It is a schematic sectional drawing which shows an example of the layer structure of the circular polarizing plate which is one form of the polarizing plate which concerns on this invention. It is schematic cross-sectional view which shows another example of the layer structure of the circular polarizing plate which is one form of the polarizing plate which concerns on this invention.

<Polarizer and polarizing plate>
(1) Basic Configuration of Polarizing Plate FIG. 1 is a schematic cross-sectional view showing an example of the layer configuration of the polarizing plate according to the present invention. Like the polarizing plate 1 shown in FIG. 1, the polarizing plate of the present invention includes a polarizing element 5, a first protective film 3 laminated on one surface thereof via a first adhesive layer 6, and the other. It can be provided with a second protective film 4 laminated on the surface via the second adhesive layer 7. The polarizing plate 1 may further have another optical functional layer, an adhesive layer, or the like laminated on the first protective film 3 and / or the second protective film 4.

Further, the polarizing plate of the present invention includes a polarizing element 5 and a first protective film 3 laminated on one surface of the polarizing plate 2 via the first adhesive layer 6, as in the polarizing plate 2 shown in FIG. A polarizing plate with a single-sided protective film may be used. The polarizing plate 2 may further have another optical functional layer, an adhesive layer, or the like laminated on the first protective film 3 and / or the polarizing element 5.

(2) Absorbance characteristics of the polarizing plate The polarizing plate of the present invention contains a polarizing element, the absorbance A ₄₅₀ at a wavelength of 450 nm satisfies the following relational expression (1), and the absorbance A ₇₅₀ at a wavelength of 750 nm is the following relational expression. Satisfy (2).
1.6 ≤ A ₄₅₀ ≤ 2.7 (1)
0.7 ≤ A ₇₅₀ ≤ 2.3 (2)

Here, the "absorbance A ₇₅₀ " and "absorbance A ₄₅₀ " of the polarizing plate indicate the absorbance at the base of the absorption band on the long wavelength side (red region) and the absorbance at the base of the absorption band on the short wavelength side (blue region), respectively. pointing. In general, since the absorption bands on the long wavelength side and the short wavelength side of the polarizing plate are very large, it is often saturated with an ultraviolet-visible spectrophotometer and its intensity cannot be grasped. The intensity of the absorption band on the side is sufficiently correlated with "absorbance A ₇₅₀ " and "absorbance A ₄₅₀ ", respectively, and the intensity of the absorption band on the long wavelength side and the short wavelength side is "absorbance A ₇₅₀ " and "absorbance A", respectively. It turned out that it can be evaluated by " ₄₅₀ ".

The polarizing plate of the present invention satisfying the above relational expressions (1) and (2) has an absorbance A ₄₅₀ at a wavelength of 450 nm, which correlates with the absorption band in the blue region, at a wavelength of 750 nm, which correlates with the absorption band on the long wavelength side. Since the absorbance A ₇₅₀ is higher or equivalent to that of A 750, blue light can be sufficiently transmitted even if the amount of light of the blue light emitting element in the organic EL display panel is reduced, and the life of the organic EL display element is long. It suppresses the shortening of the life of the blue light emitting element, which may cause the shortening of the wavelength, and contributes to the extension of the life of the organic EL display device.

Further, although the reason for the polarizing plate of the present invention exhibiting the above-mentioned absorption characteristics is not completely clear, the transmittance in the blue region is set in an appropriate range, and the stability of the iodine complex in the substituent is improved. Therefore, the change in the degree of polarization can be suppressed even if it is subjected to a heat resistance test. The fact that the change in the degree of polarization can be suppressed even when subjected to the heat resistance test means that the absorbance A ₄₅₀ , which correlates with the absorption band in the blue region, is correlated with the absorption band on the long wavelength side, and the absorbance A ₇₅₀ , which correlates with the absorption band on the long wavelength side. It is possible to maintain a relatively high (or equivalent) state, and even if the organic EL display device is used in a high temperature environment, it suppresses the shortening of the life of the blue light emitting element and contributes to the extension of the life of the organic EL display device.

In the polarizing plate of the present invention, it is preferable that the absorbance A ₇₀₀ at a wavelength of 700 nm satisfies the following relational expression (3).
1.7 ≤ A ₇₀₀ ≤ 4.5 (3)

The b value of the orthogonal hue of the polarizing plate is preferably −1.5 or less, more preferably −3.0 or less, from the viewpoint of efficiently transmitting light having a short wavelength. Further, the b value of the orthogonal hue of the polarizing plate is preferably -20 or more, more preferably -19 or more, from the viewpoint that the hue becomes too blue and the visibility deteriorates. The b value of the orthogonal hue is measured according to the description in the section of Examples described later.

The absorbance A ₄₅₀ , absorbance A ₇₅₀ and absorbance A ₇₀₀ of the polarizing plate can be measured using an absorptiometer such as an ultraviolet-visible spectrophotometer. Natural light is used as the incident light. When the incident light intensity is T ₀ and the transmitted light intensity is T, the absorbance (absorbance A ₄₅₀ , absorbance A ₇₅₀ and absorbance A ₇₀₀ ) is as follows.
Absorbance = -log (T / T ₀ ).

If the incident light incident on the sample (polarizing plate) has polarization property, the obtained absorbance value may fluctuate depending on the orientation when the sample is set in the absorptiometer. For example, depending on the absorptiometer, some polarization may occur in the incident light due to the influence of the mirror or optical element between the light source and the sample, or a polarization separation element such as a prism may be included. Sometimes you need to be careful. When such an absorptiometer is used, the polarizing plate is measured at a certain angle (meaning a certain direction around the optical axis), then measured again at a direction turned 90 degrees, and the average transmitted light thereof is measured. By calculating the absorbance from the intensity, the influence of the polarization of the incident light can be eliminated.

(3) Polarizing characteristics of the polarizing plate The polarization performance of the polarizing plate can be expressed mainly by numerical values called single transmittance and degree of polarization, and the following equations:
Single transmittance (λ) = 0.5 × (Tp (λ) + Tc (λ))
Degree of polarization (λ) = 100 × (Tp (λ) -Tc (λ)) / (Tp (λ) + Tc (λ))
Defined in.

Here, Tp (λ) is the transmittance (%) of the polarizing plate measured in relation to the incident linear polarization at the wavelength λ nm and parallel Nicol, and Tc (λ) is the cross with the incident linear polarization at the wavelength λ nm. It is the transmittance (%) of the polarizing plate measured in relation to Nicole, and both are measured values obtained by measuring the polarized ultraviolet visible absorption spectrum with a spectrophotometer. Further, the single transmittance (λ) and the degree of polarization (λ) obtained for each wavelength are subjected to a sensitivity correction called luminosity factor correction, and the luminosity factor correction single transmittance (Ty) and the luminosity factor correction polarization are obtained, respectively. It is called degree (Py). These Ty and Py values can be easily measured with, for example, an absorptiometer (model number: V7100) manufactured by JASCO Corporation.

In order to ensure good clarity of the image when the polarizing plate is applied to the display device, the polarizing plate or the polarizing element according to the present invention has a luminous efficiency correction single transmittance (Ty) of 40.0% or more. It is preferably 42.0% or more, more preferably 44.0% or more, still more preferably 45.0% or more. The luminous efficiency correction degree of polarization (Py) is preferably 99% or more.

(4) Polarizer The polarizing element 5 can be a uniaxially stretched polyvinyl alcohol-based resin layer in which a dichroic dye is adsorbed and oriented. In the present invention, the thickness of the splitter 5 is, for example, 7 μm or more and 30 μm or less, more preferably 10 μm or more and 30 μm or less, and further preferably 12 μm or more and 25 μm or less. By using the polarizing element 5 having such a thickness, it is easy to obtain a polarizing plate satisfying the above relational expressions (1) and (2).

The splitter is an absorption-type splitter that has the property of absorbing linearly polarized light having a vibration plane parallel to its absorption axis and transmitting linear polarization having a vibration plane orthogonal to the absorption axis (parallel to the transmission axis). There can be. As a typical polarizing element, a dichroic dye is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol-based resin film. Such a polarizing element is, for example, a step of uniaxially stretching a polyvinyl alcohol-based resin film; a step of adsorbing a bicolor dye by dyeing a polyvinyl alcohol-based resin film with a bicolor dye (dyeing treatment); two colors. It can be produced by a method including a step of treating a polyvinyl alcohol-based resin film on which a sex dye is adsorbed with a cross-linking solution such as a boric acid aqueous solution (cross-linking treatment); and a step of washing with water after the treatment with the cross-linking liquid (washing treatment).

As the polyvinyl alcohol-based resin, a saponified polyvinyl acetate-based resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group.

As used herein, the term "(meth) acrylic" means at least one selected from acrylic and methacrylic. The same applies to "(meth) acryloyl", "(meth) acrylate" and the like.

The saponification degree of the polyvinyl alcohol-based resin is usually 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The average degree of polymerization of the polyvinyl alcohol-based resin is usually 1000 to 10000, preferably 1500 to 5000. The average degree of polymerization of the polyvinyl alcohol-based resin can be determined in accordance with JIS K 6726.

Examples of commercially available polyvinyl alcohol-based resins preferably used in the present invention are all trade names, "PVA124" manufactured by Kuraray Co., Ltd. (saponification degree: 98.0 to 99.0 mol%), " "PVA117" (saponification degree: 98.0-99.0 mol%), "PVA624" (saponification degree: 95.0-96.0 mol%), "PVA617" (saponification degree: 94.5-95.0 mol%) .5 mol%); "AH-26" (saponification degree: 97.0-98.8 mol%), "AH-22" (saponification degree: 97.5-) manufactured by Nippon Synthetic Chemical Industry Co., Ltd. 98.5 mol%), "NH-18" (saponification degree: 98.0-99.0 mol%), "N-300" (saponification degree: 98.0-99.0 mol%); Japan "JC-33" (saponification degree: 99.0 mol% or more), "JM-33" (saponification degree: 93.5-95.5 mol%), "JM-" of Vinegar Poval Co., Ltd. 26 "(saponification degree: 95.5-97.5 mol%)," JP-45 "(saponification degree: 86.5-89.5 mol%)," JF-17 "(saponification degree: 98) 9.0-99.0 mol%), "JF-17L" (saponification degree: 98.0-99.0 mol%), "JF-20" (saponification degree: 98.0-99.0 mol%) )including.

A film obtained by forming such a polyvinyl alcohol-based resin is used as a raw film (polyvinyl alcohol-based resin film) for producing a polarizing element. The method for forming a film of a polyvinyl alcohol-based resin is not limited as long as it is a method for obtaining a polarizing element constituting the polarizing plate of the present invention satisfying the above relational expressions (1) and (2). Further, it is preferable that the polarizing element satisfies the above relational expressions (1) and (2), and more preferably it satisfies the equation (3).

The uniaxial stretching of the polyvinyl alcohol-based resin film may be performed before the dyeing treatment with the dichroic dye, at the same time as the dyeing treatment, or after the dyeing treatment. When the uniaxial stretching is performed after the staining treatment, the uniaxial stretching may be performed before the crosslinking treatment or during the crosslinking treatment. Further, the uniaxial stretching may be performed in a plurality of times at the stages of these plurality of treatments.

In uniaxial stretching, when a long polyvinyl alcohol-based resin film is used, for example, the polyvinyl alcohol-based resin film is hung on a roll and the peripheral speeds of the rolls are made different so that the rolls are uniaxially stretched. Alternatively, it may be stretched uniaxially using a thermal roll. Further, the uniaxial stretching may be a dry stretching performed in the atmosphere, or a wet stretching performed in a state where the polyvinyl alcohol-based resin film is swollen with a solvent or water. The draw ratio is usually 3 to 8 times. When the polyvinyl alcohol-based resin film is stretched by uniaxial stretching a plurality of times, the stretching ratio is usually 3 to 8 times the original length. The draw ratio can be selected so that the finally obtained polarizing element has a desired thickness.

As a method of dyeing a polyvinyl alcohol-based resin film with a dichroic dye (dyeing treatment), a method of immersing the polyvinyl alcohol-based resin film in an aqueous solution containing a dichroic dye is typically adopted. .. As the dichroic dye, iodine or a dichroic organic dye is used. The polyvinyl alcohol-based resin film is preferably immersed in water before the dyeing treatment.

As the cross-linking treatment after the dyeing treatment with the dichroic dye, a method of immersing the dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution or the like is usually adopted. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide.

The dichroic dye contained (adsorption orientation) in the polarizing element can be iodine or a dichroic organic dye. Specific examples of the bicolor organic dyes are Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL, Direct Includes Sky Blue, Direct First Orange S, and First Black. As the dichroic dye, only one kind may be used alone, or two or more kinds may be used in combination.

The polarizing element may be produced from a polyvinyl alcohol-based resin film, or may be produced from a laminate (polyvinyl alcohol-based resin laminate) in which a polyvinyl alcohol-based resin layer is formed on a substrate. The polyvinyl alcohol-based resin laminate can be obtained, for example, by a method of applying a coating liquid containing a polyvinyl alcohol-based resin to a base material, a method of laminating a polyvinyl alcohol-based resin on a base material, or the like. A step of uniaxially stretching a polyvinyl alcohol-based resin laminate; a step of adsorbing a bicolor dye by dyeing a uniaxially stretched polyvinyl alcohol-based resin laminate with a bicolor dye; The polyvinyl alcohol-based resin laminate on which the sex dye is adsorbed is subjected to a step of treating with a cross-linking solution such as a boric acid aqueous solution; and a step of washing with water after the treatment with the cross-linking solution to produce a substituent.

As shown in FIGS. 1 and 2, the polarizing element may be a polarizing plate having a protective film bonded to one side or both sides of the polarizing element, or may be used alone as a polarizing plate.

(5) First and Second Protective Films The first protective film 3 and the second protective film 4 are thermoplastic resins such as a chain polyolefin resin (polypropylene resin and the like) and a cyclic polyolefin resin (norbornen resin, respectively). Polycarbonate resins such as cellulose triacetate, cellulose ester resins such as cellulose diacetate; polyester resins such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate; polycarbonate resins; (meth) acrylic resins It can be a transparent resin film made of a mixture thereof, a copolymer, or the like. The first protective film 3 and the second protective film 4 may be the same type of protective film as each other, or may be different types of protective films.

The cyclic polyolefin resin is a general term for resins polymerized using a cyclic olefin as a polymerization unit, and is described in, for example, JP-A No. 1-240517, JP-A-3-14882, JP-A-3-122137, and the like. The resin used is mentioned. Specific examples of the cyclic polyolefin resin include a ring-opened (co) polymer of a cyclic olefin, an addition polymer of a cyclic olefin, and a copolymer of a cyclic olefin and a chain olefin such as ethylene or propylene (typically). Is a random copolymer), a graft polymer obtained by modifying these with an unsaturated carboxylic acid or a derivative thereof, and a hydride thereof. Among them, a norbornene-based resin using a norbornene-based monomer such as a norbornene or a polycyclic norbornene-based monomer is preferably used as the cyclic olefin.

Various products of the cyclic polyolefin resin are commercially available. Examples of commercially available cyclic polyolefin resins are all trade names such as "Topas" (manufactured by Topas Advanced Polymers GmbH, available from Polyplastics Co., Ltd.), "Arton" (manufactured by JSR Corporation), Includes "ZEONOR" (manufactured by ZEON CORPORATION), "ZEONEX" (manufactured by ZEON Corporation), and "APEL" (manufactured by Mitsui Kagaku Co., Ltd.).

In addition, all of them are product names such as "Sushina" (manufactured by Sekisui Chemical Co., Ltd.), "SCA40" (manufactured by Sekisui Chemical Co., Ltd.), and "Zeonoa Film" (manufactured by Nippon Zeon Co., Ltd.). A commercially available filmed cyclic polyolefin resin film may be used as the protective film.

Cellulose ester-based resins are esters of cellulose and fatty acids. Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Further, these copolymers or those in which a part of the hydroxyl group is modified with another substituent can also be used. Among these, cellulose triacetate (triacetyl cellulose: TAC) is particularly preferable. Many products of cellulose triacetate are commercially available, which is advantageous in terms of availability and cost. Examples of commercially available cellulose triacetates are all trade names, "Fujitac TD80" (manufactured by FUJIFILM Corporation), "Fujitac TD80UF" (manufactured by FUJIFILM Corporation), and "Fujitac TD80UZ" (manufactured by FUJIFILM Corporation). ), "Fujitac TD40UZ" (manufactured by FUJIFILM Corporation), "KC8UX2M" (manufactured by Konica Minolta Opto Co., Ltd.), "KC4UY" (manufactured by Konica Minolta Opto Co., Ltd.).

The first protective film 3 and / or the second protective film 4 may be a protective film having an optical function such as a retardation film and a luminance improving film. For example, a retardation film to which an arbitrary retardation value is imparted by stretching a transparent resin film made of the above material (uniaxial stretching or biaxial stretching, etc.) or forming a liquid crystal layer or the like on the film. Can be.

The surface of the first protective film 3 and / or the second protective film 4 on the opposite side of the polarizing element 5 is surface-treated such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer. A layer (coating layer) can also be formed. The method for forming the surface treatment layer on the surface of the protective film is not particularly limited, and a known method can be used.

The thickness of the first and second protective films 3 and 4 is preferably 5 to 90 μm or less, more preferably 5 to 60 μm, and even more preferably 5 to 50 μm.

(6) As the adhesive forming the first and second adhesive layers 6 and 7, a water-based adhesive or a photocurable adhesive can be used. The adhesive forming the first adhesive layer 6 and the adhesive forming the second adhesive layer 7 may be of the same type or different types.

Examples of the water-based adhesive include an adhesive made of a polyvinyl alcohol-based resin aqueous solution, a water-based two-component urethane-based emulsion adhesive, and the like. Of these, a water-based adhesive composed of an aqueous solution of polyvinyl alcohol-based resin is preferably used.

The polyvinyl alcohol-based resin includes a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, and a co-polymer of vinyl acetate and other monomers copolymerizable therewith. A polyvinyl alcohol-based copolymer obtained by saponifying the polymer, or a modified polyvinyl alcohol-based polymer in which the hydroxyl groups thereof are partially modified can be used. The water-based adhesive may contain additives such as polyhydric aldehydes, water-soluble epoxy compounds, melamine-based compounds, zirconia compounds, and zinc compounds. When a water-based adhesive is used, the thickness of the adhesive layer obtained from the water-based adhesive is usually 1 μm or less.

The method of bonding the polarizing element 5 and the protective film using a water-based adhesive is not particularly limited, and the water-based adhesive is uniformly applied or poured on one bonding surface, and the other is overlapped on the coated surface and rolled. Examples thereof include a method of sticking and drying. Usually, the water-based adhesive is applied at a temperature of 15 to 40 ° C. after its preparation, and the bonding temperature is usually in the range of 15 to 30 ° C.

When a water-based adhesive is used, it is preferable to carry out a drying step of drying in order to remove water contained in the water-based adhesive after bonding. Drying can be performed, for example, by introducing the bonded film into a drying oven. The drying temperature (temperature of the drying oven) is preferably 30 to 90 ° C. If the temperature is lower than 30 ° C., the protective film tends to be easily peeled off from the polarizing element 5. Further, if the drying temperature exceeds 90 ° C., the polarization performance of the polarizing element 5 may deteriorate due to heat. The drying time can be, for example, 10 to 1000 seconds.

After the drying step, a curing step of curing at room temperature or slightly higher temperature, for example, 20 to 45 ° C. for 12 to 600 hours may be provided. The curing temperature is generally set lower than the drying temperature.

The photocurable adhesive refers to an adhesive that cures by irradiating it with active energy rays such as ultraviolet rays, and for example, one containing a polymerizable compound and a photopolymerization initiator, one containing a photoreactive resin, and a binder. Examples thereof include those containing a resin and a photoreactive cross-linking agent. Examples of the polymerizable compound include a photopolymerizable monomer such as a photocurable epoxy-based monomer, a photocurable acrylic-based monomer, and a photocurable urethane-based monomer, and an oligomer derived from a photopolymerizable monomer. Examples of the photopolymerization initiator include substances that generate active species such as radicals, anions, and cations when irradiated with active energy rays such as ultraviolet rays. As the photocurable adhesive containing the polymerizable compound and the photopolymerization initiator, those containing a photocurable epoxy monomer and a photocationic polymerization initiator can be preferably used.

The method of bonding the polarizing element 5 and the protective film using a photocurable adhesive is not particularly limited, and for example, a casting method, a Meyer bar coating method, a gravure coating method, a comma coater method, and a doctor plate method are used. , A method of applying a photocurable adhesive to one of the bonding surfaces by a die coating method, a dip coating method, a spray method, or the like, superimposing the two, and sandwiching the two with a nip roll or the like for bonding. The casting method is a method in which an adhesive is poured down on the bonded surface to spread the object to be coated while moving the object to be coated in a substantially vertical direction, a substantially horizontal direction, or an oblique direction between the two. The thickness of the adhesive layer after being bonded using a nip roll or the like before drying or curing is preferably 5 μm or less and 0.01 μm or more.

When a photocurable adhesive is used, after performing the above-mentioned bonding, a drying step is performed if necessary (for example, when the photocurable adhesive contains a solvent), and then light is irradiated by irradiating with active energy rays. A curing step is performed to cure the curable adhesive. The light source of the active energy ray is not particularly limited, but an active energy ray having a emission distribution having a wavelength of 400 nm or less is preferable, and specifically, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, and a black light lamp. , Microwave-excited mercury lamp, metal halide lamp and the like are preferably used.

The light irradiation intensity to the photocurable adhesive is appropriately determined by the composition of the photocurable adhesive so that the irradiation intensity in the wavelength region effective for activating the polymerization initiator is 0.1 to 6000 mW / cm ² . It is preferable to set to. When the irradiation intensity is 0.1 mW / cm ² or more, the reaction time does not become too long, and when it is 6000 mW / cm ² or less, the heat radiated from the light source and the light generated by the heat generated when the photocurable adhesive is cured. There is little risk of yellowing of the curable adhesive or deterioration of the polarizing element.

The light irradiation time of the photocurable adhesive is also appropriately determined by the composition of the photocurable adhesive, and the integrated light amount expressed as the product of the irradiation intensity and the irradiation time is 10 to 10000 mJ / cm ² . It is preferable to set to. When the integrated light amount is 10 mJ / cm ² or more, a sufficient amount of the active species derived from the polymerization initiator can be generated and the curing reaction can proceed more reliably. When the integrated light amount is 10000 mJ / cm ² or less, the irradiation time is long. Good productivity can be maintained without becoming too much.

The thickness of the adhesive layer after irradiation with active energy rays is usually 0.01 to 5 μm, preferably 0.01 to 2 μm, and more preferably 0.01 to 1 μm.

<Manufacturing method of modulator>
A form of a method for manufacturing a polarizing element used in the polarizing plate of the present invention will be described. In the present embodiment, an unstretched polyvinyl alcohol-based resin film (raw film) having a thickness of preferably 80 μm or less, more preferably 60 μm or less, preferably 10 μm or more, and more preferably 15 μm or more is used as a starting material for producing a polarizing element. Use. The width of the raw film is not particularly limited and can be, for example, 400 to 6000 mm. The raw fabric film is prepared, for example, as a roll of a long unstretched polyvinyl alcohol-based resin film (raw fabric roll).

The splitter unwinds the above-mentioned long raw fabric film from the raw fabric roll and continuously conveys it along the film transport path of the polarizing element manufacturing apparatus, and the treatment liquid contained in the treatment tank (hereinafter referred to as a treatment liquid). By carrying out a predetermined treatment step of immersing the film in a "treatment bath" and then pulling it out, and then carrying out a drying step, the film can be continuously produced as a long polarizing element. The treatment step is not limited to the method of immersing the film in the treatment bath as long as the treatment liquid is brought into contact with the film, and the treatment liquid adheres to the film surface by spraying, flowing down, dropping or the like. It may be a method of processing the film. When the treatment step is performed by a method of immersing the film in a treatment bath, the treatment bath for performing one treatment step is not limited to one, and the film is sequentially immersed in two or more treatment baths. One processing step may be completed.

Examples of the treatment liquid include a swelling liquid, a staining liquid, a cross-linking liquid, a complementary color liquid, and a cleaning liquid. The treatment steps include a swelling step in which the swelling liquid is brought into contact with the raw fabric to perform the swelling treatment, a dyeing step in which the dyeing liquid is brought into contact with the film after the swelling treatment to perform the dyeing treatment, and a dyeing step after the dyeing treatment. A cross-linking step in which a cross-linking liquid is brought into contact with a film to carry out a cross-linking treatment, a complementary color step in which a complementary color liquid is brought into contact with the film after the cross-linking treatment to perform a complementary color treatment, and a cleaning treatment in which the cleaning liquid is brought into contact with the film after the cross-linking treatment. An example is a cleaning step to be performed. In addition, uniaxial stretching treatment is performed wet or dry between these series of treatment steps (that is, before and after any one or more treatment steps and / or during any one or more treatment steps). Other processing steps may be added if necessary.

Hereinafter, an example of a method for manufacturing a polarizing element according to the present invention will be described in detail with reference to FIG. FIG. 3 is a cross-sectional view schematically showing an example of a method for manufacturing a polarizing element according to the present invention, a method for manufacturing a polarizing element used thereof, and a manufacturing apparatus. The polarizing element manufacturing apparatus shown in FIG. 3 transports a raw fabric (unstretched) film 10 made of a polyvinyl alcohol-based resin along a film transport path while continuously unwinding the raw fabric (unstretched) film 10 from the raw fabric roll 11. Swelling bath (swelling liquid housed in the swelling tank) 13, dyeing bath (staining liquid housed in the dyeing tank) 15, cross-linking bath (cross-linking liquid housed in the cross-linking tank) 17a provided on the transport path. , The complementary color bath (complementary color liquid housed in the complementary color tank) 17b, and the washing bath (cleaning liquid housed in the washing tank) 19 are sequentially passed through, and finally passed through the drying furnace 21. The obtained polarizing element 23 can be conveyed, for example, to the next polarizing plate manufacturing step (step of attaching a protective film to one or both sides of the polarizing element 23) as it is. The arrow in FIG. 3 indicates the transport direction of the film.

In the description of FIG. 3, "treatment tank" is a general term including a swelling tank, a dyeing tank, a cross-linking tank, a complementary color tank and a washing tank, and "treatment liquid" is a swelling liquid, a dyeing liquid, a cross-linking liquid, a complementary color liquid and It is a general term including a washing liquid, and "treatment bath" is a general term including a swelling bath, a dyeing bath, a cross-linking bath, a complementary color bath and a washing bath.

In addition to the above-mentioned treatment bath, the film transport path of the polarizing element manufacturing apparatus includes guide rolls 30 to 48, 60, 61 that can support the film to be transported or further change the film transport direction, and the film to be transported. Can be constructed by arranging nip rolls 50 to 55 capable of pressing and holding the film and applying a driving force due to its rotation to the film, or further changing the film transport direction, at appropriate positions. The guide roll and the nip roll can be arranged before and after each treatment bath or in the treatment bath, whereby the film can be introduced / immersed in the treatment bath and withdrawn from the treatment bath [see FIG. 3]. For example, by providing one or more guide rolls in each treatment bath and transporting the film along these guide rolls, the film can be immersed in each treatment bath.

In the polarizing film manufacturing apparatus shown in FIG. 3, nip rolls are arranged before and after each treatment bath (nip rolls 50 to 54), whereby the nip rolls are arranged before and after in any one or more of the treatment baths. It is possible to carry out inter-roll stretching in which vertical uniaxial stretching is performed with a difference in peripheral speed between them. Hereinafter, each step will be described.

(Swelling process)
The swelling step is performed for the purpose of removing foreign matter on the surface of the raw fabric film 10, removing the plasticizer in the raw fabric film 10, imparting easy dyeability, and plasticizing the raw fabric film 10. The treatment conditions are determined within a range in which the object can be achieved and within a range in which defects such as extreme dissolution and devitrification of the raw film 10 do not occur.

In the swelling step, referring to FIG. 3, in the swelling step, the raw film 10 is continuously unwound from the raw fabric roll 11 and conveyed along the film transport path, and the raw fabric film 10 is immersed in the swelling bath 13 for a predetermined time. , Then can be carried out by pulling out. In the example of FIG. 3, from unwinding the raw film 10 to immersing it in the swelling bath 13, the raw film 10 is conveyed along the film transport path constructed by the guide rolls 60 and 61 and the nip roll 50. Will be done. In the swelling treatment, the film is conveyed along the film transport path constructed by the guide rolls 30 to 32 and the nip roll 51.

The swelling liquid of the swelling bath 13 includes pure water, boric acid (Japanese Patent Laid-Open No. 10-153709), chloride (Japanese Patent Laid-Open No. 06-281816), inorganic acids, inorganic salts, water-soluble organic solvents, and alcohols. It is also possible to use an aqueous solution to which the like is added in the range of about 0.01 to 10% by weight.

The temperature of the swelling bath 13 is, for example, 10 to 50 ° C, preferably 10 to 40 ° C, and more preferably 15 to 30 ° C. The immersion time of the raw film 10 is preferably 10 to 300 seconds, more preferably 20 to 200 seconds. When the raw film 10 is a polyvinyl alcohol-based resin film previously stretched in a gas, the temperature of the swelling bath 13 is, for example, 20 to 70 ° C, preferably 30 to 60 ° C. The immersion time of the raw film 10 is preferably 30 to 300 seconds, more preferably 60 to 240 seconds.

In the swelling treatment, the problem that the raw film 10 swells in the width direction and the film is wrinkled tends to occur. As one means for transporting the film while removing the wrinkles, a roll having a widening function such as an expander roll, a spiral roll, or a crown roll is used for the guide rolls 30, 31 and / or 32, or a cross guider or a bend bar is used. , Other widening devices such as tenter clips may be used. Another means for suppressing the occurrence of wrinkles is to apply a stretching treatment. For example, the uniaxial stretching process can be performed in the swelling bath 13 by utilizing the difference in peripheral speed between the nip roll 50 and the nip roll 51.

In the swelling treatment, the film swells and expands in the transport direction of the film. Therefore, when the film is not actively stretched, it is arranged before and after the swelling bath 13, for example, in order to eliminate the slack in the film in the transport direction. It is preferable to take measures such as controlling the speed of the nip rolls 50 and 51. Further, for the purpose of stabilizing the film transfer in the swelling bath 13, the water flow in the swelling bath 13 is controlled by an underwater shower, and an EPC device (Edge Position Control device: the edge of the film is detected to meander the film. It is also useful to use a device to prevent the problem.

In the example shown in FIG. 3, the film drawn from the swelling bath 13 passes through the guide roll 32, the nip roll 51, and the guide roll 33 in this order and is introduced into the dyeing bath 15.

(Dyeing process)
The dyeing step is performed for the purpose of adsorbing and orienting the dichroic dye on the polyvinyl alcohol-based resin film after the swelling treatment. The treatment conditions are determined within a range in which the object can be achieved and within a range in which problems such as extreme dissolution and devitrification of the film do not occur. With reference to FIG. 3, in the dyeing step, the film is conveyed along the film transfer path constructed by the nip roll 51, the guide rolls 33 to 36, and the nip roll 52, and the film after the swelling treatment is housed in the dyeing bath 15 (dyeing tank). It can be carried out by immersing it in the treatment liquid) for a predetermined time and then withdrawing it. In order to improve the dyeability of the dichroic dye, the film to be subjected to the dyeing step is preferably a film that has been subjected to at least a uniaxial stretching treatment, or instead of the uniaxial stretching treatment before the dyeing treatment, or a dyeing treatment. In addition to the previous uniaxial stretching treatment, it is preferable to perform the uniaxial stretching treatment during the dyeing treatment.

When iodine is used as the dichroic dye, in the dyeing solution of the dyeing bath 15, for example, the concentration is iodine / potassium iodide / water = about 0.003 to 0.3 / about 0.1 to 10 / by weight ratio. An aqueous solution of 100 can be used. Instead of potassium iodide, other iodides such as zinc iodide may be used, or potassium iodide and other iodides may be used in combination. Further, compounds other than iodide, for example, boric acid, zinc chloride, cobalt chloride and the like may coexist. When boric acid is added, it is distinguished from the cross-linking treatment described later in that it contains iodine, and if the aqueous solution contains about 0.003 parts by mass or more of iodine with respect to 100 parts by weight of water, the dyeing bath 15 Can be regarded as. The temperature of the dyeing bath 15 when immersing the film is usually 10 to 45 ° C., preferably 10 to 40 ° C., more preferably 20 to 35 ° C., and the immersing time of the film is usually 30 to 600 seconds. It is preferably 60 to 300 seconds.

When a water-soluble bicolor dye is used as the bicolor dye, the dyeing solution of the dyeing bath 15 has, for example, a concentration of the bicolor dye / water = about 0.001 to 0.1 / 100 in terms of weight ratio. An aqueous solution can be used. The dyeing bath 15 may be allowed to coexist with a dyeing aid or the like, and may contain, for example, an inorganic salt such as sodium sulfate or a surfactant. Only one kind of dichroic dye may be used alone, or two or more kinds of dichroic dyes may be used in combination. The temperature of the dyeing bath 15 when immersing the film is, for example, 20 to 80 ° C., preferably 30 to 70 ° C., and the immersing time of the film is usually 30 to 600 seconds, preferably 60 to 300 seconds.

As described above, in the dyeing step, the film can be uniaxially stretched in the dyeing bath 15. The uniaxial stretching of the film can be performed by a method such as providing a peripheral speed difference between the nip roll 51 and the nip roll 52 arranged before and after the dyeing bath 15.

In the dyeing treatment as well, in order to convey the polyvinyl alcohol-based resin film while removing the wrinkles of the film as in the swelling treatment, the guide rolls 33, 34, 35 and / or 36 are provided with expander rolls, spiral rolls, crown rolls and the like. A roll having a widening function can be used, or other widening devices such as a cross guider, a bend bar, and a tenter clip can be used. Another means for suppressing the occurrence of wrinkles is to perform a stretching treatment as in the swelling treatment.

In the example shown in FIG. 3, the film drawn from the dyeing bath 15 passes through the guide roll 36, the nip roll 52, and the guide roll 37 in order and is introduced into the cross-linking bath 17a.

(Crosslinking process)
The cross-linking step is a process performed for the purpose of making water resistant by cross-linking. With reference to FIG. 3, the cross-linking step is carried out along the film transport path constructed by the nip roll 52, the guide rolls 37 to 40 and the nip roll 53a, and dyed in the cross-linking bath 17a (cross-linking liquid contained in the cross-linking tank). It can be carried out by immersing the treated film for a predetermined time and then pulling it out.

As the cross-linking liquid, a solution in which a cross-linking agent is dissolved in a solvent can be used. Examples of the cross-linking agent include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. These may be one kind, or two or more kinds may be used in combination. As the solvent, for example, water can be used, but an organic solvent compatible with water may be further contained. The concentration of the cross-linking agent in the cross-linking solution is not limited to this, but is preferably in the range of 1 to 20% by mass, and more preferably 3 to 15% by mass.

The cross-linking liquid can be an aqueous solution containing, for example, about 1 to 10 parts by mass of boric acid with respect to 100 parts by mass of water. When the dichroic dye used in the dyeing treatment is iodine, the cross-linking solution preferably contains iodide in addition to boric acid, and the amount thereof is, for example, 1 to 30 parts by mass with respect to 100 parts by mass of water. Can be. Examples of the iodide include potassium iodide and zinc iodide. Further, compounds other than iodide, for example, zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate and the like may coexist.

In the crosslinking treatment, the concentrations of boric acid and iodide and the temperature of the crosslinking bath 17a can be appropriately changed. The cross-linking solution can be, for example, an aqueous solution having a concentration of boric acid / iodide / water = 3 to 10/1 to 20/100 in terms of mass ratio. If necessary, another cross-linking agent may be used instead of boric acid, or boric acid and another cross-linking agent may be used in combination. The temperature of the cross-linked bath 17a when immersing the film is usually 40 to 70 ° C., preferably 50 to 65 ° C., and the immersing time of the film is usually 10 to 600 seconds, preferably 20 to 300 seconds, more preferably. It takes 20 to 200 seconds.

The cross-linking treatment may be performed a plurality of times, and is usually performed 2 to 5 times. In this case, the composition and temperature of each crosslinked bath used may be the same or different as long as it is within the above range.

Uniaxial stretching treatment can also be performed in the cross-linking bath 17a by utilizing the difference in peripheral speed between the nip roll 52 and the nip roll 53a.

In the cross-linking treatment as well, in order to convey the polyvinyl alcohol-based resin film while removing the wrinkles of the film as in the swelling treatment, a roll having a widening function such as an expander roll, a spiral roll, or a crown roll may be used as the guide roll. Other widening devices such as cross-guiders, bend bars and tenter clips can be used. Another means for suppressing the occurrence of wrinkles is to perform a stretching treatment as in the swelling treatment.

In the example shown in FIG. 3, the film drawn from the crosslinked bath 17a passes through the guide roll 49 and the nip roll 53a in this order and is introduced into the complementary color bath 17b.

(Complementary color process)
The complementary color step is a process performed for the purpose of adjusting the hue. With reference to FIG. 3, the complementary color step is carried along the film transport path constructed by the nip rolls 53a, guide rolls 41 to 44 and the nip rolls 53b and crosslinked to the complementary color bath 17b (complementary color liquid contained in the complementary color tank). It can be carried out by immersing the film after the step for a predetermined time and then pulling it out.

As the complementary color solution, a solution in which a cross-linking agent is dissolved in a solvent can be used. Examples of the cross-linking agent include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. These may be one kind, or two or more kinds may be used in combination. As the solvent, for example, water can be used, but an organic solvent compatible with water may be further contained. The concentration of the cross-linking agent in the complementary color solution is not limited to this, but is preferably in the range of 1 to 20% by mass, more preferably 6 to 15% by mass.

The complementary color liquid can be an aqueous solution containing, for example, about 1 to 10 parts by mass of boric acid with respect to 100 parts by mass of water. When the dichroic dye used in the dyeing treatment is iodine, the complementary color solution preferably contains iodide in addition to boric acid, and the amount thereof is, for example, 1 to 30 parts by mass with respect to 100 parts by mass of water. Can be. Examples of the iodide include potassium iodide and zinc iodide. Further, compounds other than iodide, for example, zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate and the like may coexist.

When iodine is used as the dichroic dye in the complementary color solution, for example, the complementary color solution should have a concentration of boric acid / iodide / water = 1 to 5 / 0.5 to 30/100 in terms of weight ratio. Can be done. The temperature of the complementary color bath 17b when immersing the film is usually 10 to 45 ° C., and the immersing time of the film is usually 1 to 300 seconds, preferably 2 to 100 seconds.

Uniaxial stretching treatment can also be performed in the complementary color bath 17b by utilizing the difference in peripheral speed between the nip roll 53a and the nip roll 53b.

In the complementary color treatment, in order to convey the polyvinyl alcohol-based resin film while removing the wrinkles of the film as in the swelling treatment, a roll having a widening function such as an expander roll, a spiral roll, and a crown roll may be used as the guide roll. Other widening devices such as cross guiders, bend bars and tenter clips can be used. Another means for suppressing the occurrence of wrinkles is to perform a stretching treatment as in the swelling treatment.

In the example shown in FIG. 3, the film drawn from the complementary color bath 17b passes through the guide roll 44 and the nip roll 53b in this order and is introduced into the washing bath 19.

(Washing process)
The example shown in FIG. 3 includes a cleaning step after the complementary color step. The cleaning treatment is performed for the purpose of removing excess chemicals such as boric acid and iodine adhering to the polyvinyl alcohol-based resin film. The cleaning step is performed, for example, by immersing the complementary color-treated polyvinyl alcohol-based resin film in the cleaning bath 19. The cleaning step is performed by spraying the cleaning liquid on the film as a shower instead of immersing the film in the cleaning bath 19, or by using the immersion in the cleaning bath 19 and the spraying of the cleaning liquid in combination. You can also do it.

FIG. 3 shows an example in which a polyvinyl alcohol-based resin film is immersed in a cleaning bath 19 to perform a cleaning treatment. The temperature of the washing bath 19 in the washing treatment is usually 2 to 40 ° C., and the immersion time of the film is usually 2 to 120 seconds.

In the cleaning process, for the purpose of transporting the polyvinyl alcohol-based resin film while removing wrinkles, a roll having a widening function such as an expander roll, a spiral roll, or a crown roll may be used as a guide roll, or a cross guider, a bend bar, or the like. Other widening devices such as tenter clips may be used. Further, in the film cleaning treatment, a stretching treatment may be performed in order to suppress the occurrence of wrinkles.

(Stretching process)
As described above, the raw film 10 is uniaxially stretched wet or dry during the series of treatment steps (that is, before and after any one or more treatment steps and / or during any one or more treatment steps). It is processed. A specific method of uniaxial stretching treatment is, for example, between rolls for performing longitudinal uniaxial stretching with a peripheral speed difference between two nip rolls constituting a film transport path (for example, two nip rolls arranged before and after the treatment bath). Stretching, thermal roll stretching as described in Japanese Patent No. 2731813, tenter stretching and the like can be performed, and stretching between rolls is preferable. The uniaxial stretching step can be carried out a plurality of times during the period from the raw film 10 to the obtained the splitter 23. As described above, the stretching treatment is also advantageous in suppressing the occurrence of wrinkles in the film.

The final cumulative draw ratio of the polarizing film 23 based on the raw film 10 is usually 4.5 to 7 times, preferably 5 to 6.5 times. The stretching step may be performed in any of the treatment steps, and even when the stretching treatment is performed in two or more treatment steps, the stretching treatment may be performed in any of the treatment steps.

(Drying process)
After the washing step, it is preferable to carry out a treatment for drying the polyvinyl alcohol-based resin film. The drying of the film is not particularly limited, but it can be performed using the drying oven 21 as in the example shown in FIG. The drying oven 21 may be equipped with, for example, a hot air dryer. The drying temperature is, for example, 30 to 100 ° C., and the drying time is, for example, 30 to 600 seconds. The process of drying the polyvinyl alcohol-based resin film can also be performed using a far-infrared heater. The thickness of the polarizing element 23 obtained as described above is, for example, 7 μm or more and 30 μm or less.

The obtained polarizing element may be sequentially wound on a winding roll to form a roll, or may be used as it is in a polarizing plate manufacturing step (a step of laminating a protective film or the like on one or both sides of the polarizing element) without winding. You can also.

<Control of absorbance characteristics of polarizing plate>
When the polarizing element 5 is obtained by the above-mentioned manufacturing method and then the polarizing plate 1 with a double-sided protective film or the polarizing plate 2 with a single-sided protective film 2 is manufactured, various treatments in the manufacturing method are performed on the polarizing plates 1 and 2. It contains absorbance A ₄₅₀ and absorbance A ₇₅₀ , as well as several factors that affect the suppression of changes in polarization before and after the heat resistance test. To give a main example, a) Potassium iodide concentration of the cross-linking liquid used for the cross-linking treatment in the method for producing the ligand 5.
b) Potassium iodide concentration of the complementary color solution used for the complementary color treatment,
c) Stretching ratio of polyvinyl alcohol-based resin film, neck-in rate during stretching, stretching temperature,
d) The temperature of the washing bath in the washing process, the immersion time in the washing bath,
e) Drying temperature, drying time, in the drying process,
And so on.

Among the above, b) and e) affect the absorbance A ₄₅₀ and the absorbance A ₇₅₀ of the polarizing plates 1 and 2 and the suppression of the change in the degree of polarization before and after the heat resistance test.

Specifically, regarding b) above, the concentration of potassium iodide in the complementary color solution is preferably 0.5 to 10 parts by weight, more preferably 1 to 5 parts by weight, and further, with respect to 100 parts by weight of water. It is preferably 1.5 to 2.5 parts by weight. Further, regarding the above e), the drying temperature is preferably 70 to 100 ° C, more preferably 80 to 100 ° C. The thickness of the polarizing element also affects the absorbance A ₄₅₀ and absorbance A ₇₅₀ of the polarizing plates 1 and 2 and the suppression of changes in the degree of polarization before and after the heat resistance test.

<Circular polarizing plate>
(1) Basic Configuration of Circular Polarizing Plate FIG. 4 is a form of the polarizing plate of the present invention. The polarizing plate shown in FIG. 4 (hereinafter, may be referred to as a circular polarizing plate 1') is on the side opposite to the polarizing element 5 of the second protective film 4 in addition to the elements of the polarizing plate 1 shown in FIG. It further has a laminated first retardation layer 8. The second protective film 4 and the first retardation layer 8 may be bonded to each other via an adhesive layer, and the adhesive layer used here is the above-mentioned first and second adhesive layers. The explanation is used.

FIG. 5 is a form of the polarizing plate of the present invention. The polarizing plate shown in FIG. 5 (hereinafter, may be referred to as a circular polarizing plate 2') is located on the opposite side of the polarizing element 5 from the first protective film 10 in addition to the elements of the polarizing plate 2 shown in FIG. It further has a laminated first retardation layer 30. The polarizing element 5 and the first retardation layer 30 may be bonded to each other via an adhesive layer, and the adhesive layer used here is described above with the first and second adhesive layers. It will be used.

Definitions of terms and symbols used in the description of the circularly polarizing plate in the present specification are as follows.

(Refractive index (nx, ny, nz))
"Nx" is the refractive index in the direction in which the refractive index in the plane is maximized (that is, the slow phase axis direction), "ny" is the direction orthogonal to the slow phase axis in the plane, and "nz" is the thickness direction. Refractive index.

(In-plane phase difference value)
The in-plane retardation value (Re (λ)) refers to the in-plane retardation value of the film at a wavelength of λ (nm) at 23 ° C. Re (λ) is when the film thickness is d (nm).
Re (λ) = (nx-ny) × d
Is required by. Re (550) indicates the in-plane retardation value of the film in light having a wavelength of 550 nm.

(Phase difference value in the thickness direction)
The thickness direction retardation value (thickness direction retardation value; Rth (λ)) refers to the thickness direction retardation value of the film in light having a wavelength of λ (nm) at 23 ° C. Rth (λ) is when the film thickness is d (nm).
Rth (λ) = ((nx + ny) /2-nz) × d
Is required by. Rth (550) indicates the thickness direction retardation value of the film in light having a wavelength of 550 nm.

(2) First Phase Difference Layer The first phase difference layer in the circularly polarizing plate 1'2'(the first retardation layer 8 in FIGS. 4 and 5) is a layer that converts linearly polarized light into circularly polarized light. As the in-plane retardation value Re1 (550) of the first retardation layer, one satisfying the following formula (a) is used, and preferably one satisfying the following formula (a1) is used. The material of the first retardation layer is not particularly limited.
110nm ≤ Re1 (550) ≤ 160nm (a)
120nm ≤ Re1 (550) ≤ 150nm (a1)

The first retardation layer satisfies the above equation (a) and is also called a λ / 4 retardation layer. The circular polarizing plate may be configured to include a λ / 2 retardation layer (hereinafter, also referred to as “second retardation layer”) satisfying the formula (d) described later together with the λ / 4 retardation layer. Hereinafter, a circularly polarizing plate having a λ / 4 phase difference and not having a λ / 2 retardation layer (hereinafter referred to as “first aspect”) will be described. A circularly polarizing plate having a λ / 2 retardation layer together with a λ / 4 retardation layer (hereinafter referred to as “second aspect”) will be described later as another aspect of the circular polarizing plate.

In the first aspect, it is preferable that the angle formed by the slow axis of the first retardation layer and the direction of the absorption axis of the substituent 5 is approximately 45 °. Here, "substantially 45 °" is not limited to the case of strictly "45 °", but includes the case of being within the range of "45 ° ± 5 °".

In the first embodiment, the first retardation layer uses a layer in which the wavelength dispersion of the in-plane retardation value Re1 (λ) satisfies the following equations (b) and (c).
Re1 (450) / Re1 (550) ≤ 1.00 (b)
1.00 ≤ Re1 (650) / Re1 (550) (c)

As the first retardation layer, a retardation film (commercially available) easily available on the market can be used as it is. Examples of such commercial products include the product names "Pure Ace WR-S", "Pure Ace WR-W", "Pure Ace WR-M" manufactured by Teijin Limited, and the product name "NRF" manufactured by Nitto Denko Corporation. Can be mentioned.

Another example of the retardation film is a cured product of a polymerizable liquid crystal compound (hereinafter referred to as "liquid crystal retardation film"). Since the liquid crystal retardation film can usually be as thin as 0.2 μm to 10 μm, it is preferably used from the viewpoint of thinning the circular polarizing plate.

Examples of the polymerizable liquid crystal compound that can form a liquid crystal retardation film are described in JP-A-2009-173893, JP-A-2010-31223, WO2012 / 147904, WO2014 / 10325 and WO2017-433438. The disclosed ones can be mentioned. The polymerizable liquid crystal compounds described in these publications can form a liquid crystal retardation film having anti-wavelength dispersibility, which enables uniform polarization conversion in a wide wavelength range.

A method of forming a liquid crystal retardation film will be briefly described. First, prepare a suitable support. After forming an alignment film on the support, if necessary, a liquid composition containing the polymerizable liquid crystal compound is applied and dried to form a layer containing the polymerizable liquid crystal compound on the support. Form. A liquid crystal retardation film is formed by polymerizing the polymerizable liquid crystal compound contained in the layer by, for example, irradiating with light in a state where the polymerizable liquid crystal compound contained in the layer is oriented in a predetermined direction. To.

(3) Third Phase Difference Layer The circularly polarizing plate of the first aspect may further have a third retardation layer having a refractive index characteristic of nz> nz ≧ ny. By providing a third retardation layer having such a refractive index characteristic, for example, when used as an antireflection polarizing plate, the angle dependence of the effect of absorbing reflected light is reduced, and reflection is performed at various angles. It is preferable because it can prevent the reflected light from being emitted. The third retardation layer may be laminated between the first retardation layer 8 and the polarizing element 5, or may be laminated on the side opposite to the splitter 5 side of the first retardation layer 8. ..

In the third retardation layer, the refractive index may show the relationship of nx = ny. Here, "nx = ny" includes not only the case where nx and ny are exactly equal to each other, but also the case where nx and ny are substantially equal to each other. Specifically, it is preferable that Re (550) is less than 10 nm.

The retardation Rth (550) in the thickness direction of the third retardation layer is preferably -260 nm to −10 nm, more preferably −230 nm to −15 nm, and even more preferably -215 nm to −20 nm. Within such a range, the above effect becomes remarkable, which is preferable.

The third retardation layer can be formed of any suitable material, and is not particularly limited, but is preferably a retardation layer in which the liquid crystal compound is fixed in a homeotropic orientation. The liquid crystal compound that can be homeotropically oriented may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the liquid crystal compound and the method for forming the liquid crystal layer include the liquid crystal compounds and the forming methods described in [0020] to [0042] of JP-A-2002-333642. In this case, the thickness is preferably 0.1 μm to 5 μm, more preferably 0.2 μm to 3 μm.

(4) Other Aspects of the Circular Polarizing Plate The circular polarizing plate of the other aspect (second aspect) will be described only with respect to the difference from the circular polarizing plate of the first aspect described above. The circular polarizing plate of the second aspect has a second retardation layer between the polarizing element 5 and the first retardation layer 8 in addition to the first retardation layer. Assuming that the in-plane retardation value of the second retardation layer is Re2 (λ), the second retardation layer uses one in which the in-plane retardation value Re2 (550) satisfies the following equation (d), preferably the following equation. Use one that satisfies (d1). The material of the second retardation layer is not particularly limited, and for example, the material exemplified in the first retardation layer can be used.
210nm ≤ Re2 (550) ≤ 300nm (d)
220 nm ≤ Re2 (550) ≤ 290 nm (d1)

In the second aspect, it is preferable that the angle between the slow axis of the second retardation layer and the direction of the absorption axis of the substituent is approximately 15 °. In the second aspect, it is preferable that the angle formed by the slow axis of the first retardation layer and the direction of the absorption axis of the substituent is approximately 75 °. Here, "approximately 15 °" and "approximately 75 °" are not limited to strictly "15 °" and "75 °", but are "15 ° ± 5 °" and "75 ° ± 5 °". Including the case where it is within the range of.

<Circular polarizing plate with adhesive>
The circular polarizing plate of the present invention can be a circular polarizing plate with an adhesive layer by providing an adhesive layer on at least one of the surfaces. Such a pressure-sensitive adhesive layer is usually used for attaching the circular polarizing plate of the present invention to an image display panel. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited, and known adhesives can be used.

The pressure-sensitive adhesive layer may be any one that has excellent optical transparency and exhibits adhesive properties such as appropriate wettability, cohesiveness, and adhesiveness, but a pressure-sensitive adhesive layer having excellent durability and the like is preferably used. Specific examples of the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer include pressure-sensitive adhesives made of acrylic resins and rubber-based resins (also referred to as acrylic-based pressure-sensitive adhesives and rubber-based pressure-sensitive adhesives).

Among the pressure-sensitive adhesives that can form the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer formed from a preferable acrylic pressure-sensitive adhesive is not particularly limited, but is not particularly limited, but is limited to butyl (meth) acrylate and ethyl (meth) acrylate. , (Meta) acrylic acid ester-based resins obtained by polymerizing (meth) acrylic acid SL such as (meth) isooctyl acrylate and (meth) 2-ethylhexyl acrylate, and these (meth) acrylic acid esters. A copolymerized resin using two or more kinds is preferably used as the base polymer. Further, polar monomers may be copolymerized with these resins. Examples of the polar monomer include (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) acrylamide, 2-N, and N-dimethylaminoethyl (meth). Examples thereof include monomers having polar functional groups such as carboxyl groups such as acrylates and glycidyl (meth) acrylates, hydroxyl groups, amide groups, amino groups, and epoxy groups. The base polymer referred to here refers to a polymer that is the main component of the solid content constituting the acrylic pressure-sensitive adhesive. Further, the pressure-sensitive adhesive usually contains a cross-linking agent together with an acrylic resin.

In addition to this, various additives may be blended in the pressure-sensitive adhesive. Suitable additives include silane coupling agents and antistatic agents. The silane coupling agent is effective in enhancing the adhesive force with glass. Antistatic agents are effective in reducing or preventing the generation of static electricity.

The thickness of the pressure-sensitive adhesive layer for bonding to the image display panel is preferably 3 to 50 μm. More preferably, it is 5 to 30 μm. In the circular polarizing plate of the present invention, the pressure-sensitive adhesive layer for bonding to the front plate may be provided on the opposite side of the pressure-sensitive adhesive layer for bonding to the image display panel. As described above, when the pressure-sensitive adhesive layers are provided on both side surfaces of the circularly polarizing plate of the present invention, it is preferable that the thickness of at least one of the two pressure-sensitive adhesive layers is 3 to 50 μm. More preferably, it is 5 to 30 μm.

Usually, a release film may be attached to the pressure-sensitive adhesive layer for the purpose of preventing dust or foreign matter from adhering to the pressure-sensitive adhesive layer during transportation or the like. When the release film is peeled off, a problem such as static electricity being generated in the adhesive layer may occur. In order to prevent such a defect, the pressure-sensitive adhesive layer may be provided with appropriate conductivity. When the pressure-sensitive adhesive layer is to have conductivity, its resistance value may be appropriately selected, but is preferably in the range of, for example, 1 × 10 ⁹ to 1 × 10 ¹¹ Ω / □.

The method for forming the pressure-sensitive adhesive layer, which may be formed on the circular polarizing plate of the present invention, can be performed by a known method.

[Image display device]
The polarizing plate of the present invention forms an image display device by being attached to an image display panel. Hereinafter, such an image display device will be described.

A known image display device can be used regardless of the type. For example, the polarizing plate of the present invention can be suitably used for an organic EL display device. The polarizing plate of the present invention can be provided on the visible side of the organic EL display panel so that the first retardation layer is arranged on the organic EL display panel side.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these examples.

<Example 1>
A transparent unstretched polyvinyl alcohol-based resin film (PE60, average degree of polymerization 2400, manufactured by KURARAY) having a length and width of 100 cm, a thickness of 30 μm, and a saponification degree of 99.9 mol% or more is watered at 25 ° C. (deionized water). ) Was immersed for 1 minute and 20 seconds to swell (swelling treatment). Then, it was dyed by immersing it in a dyeing solution at 30 ° C. containing iodine / potassium iodide / boric acid / water = 0.3 / 1.2 / 0.3 / 100 (mass ratio) for 2 minutes and 30 seconds (. Dyeing process). At this time, in the swelling treatment and the dyeing treatment, the stretching ratios were 1.56 times and 1.64 times, respectively, and the cumulative stretching ratio until the dyeing treatment was completed was 2.56 times.

Next, 1 is immersed in a cross-linking solution containing potassium iodide / boric acid / water = 7.1 / 1.8 / 100 (mass ratio) at 54 ° C. for 26 seconds (first cross-linking treatment) for cross-linking. It was stretched at a stretching ratio of 5.5 times. Then, it is immersed in a cross-linking solution at 54 ° C. containing potassium iodide / boric acid / water = 7 / 3.4 / 100 (mass ratio) for 20 seconds (second cross-linking treatment) to cross-link while 1.6. It was stretched at a double stretching ratio. Then, in the complementary color treatment, the mixture was stretched 1.01 times while being immersed in a complementary color aqueous solution at 40 ° C. containing potassium iodide / boric acid / water = 1.5 / 3.4 / 100 (mass ratio) for 10 seconds. (Complementary color processing). At this time, the total cumulative stretching ratio of the swelling treatment, the dyeing treatment, the cross-linking treatment, and the complementary color treatment was increased to 5.9 times.

After the complementary color treatment was completed, the product was washed with pure water at 6 ° C. for 7 seconds to remove foreign substances adhering to the surface of the polarizing element (cleaning treatment). After the washing with water was completed, the splitter was dried at the temperatures shown in Table 1 below (drying treatment) to produce a splitter.

The obtained polarizing element is protected on one side by using a water-based adhesive with a triacetyl cellulose film (trade name "DSG17Z" manufactured by Dainippon Printing Co., Ltd.), which is the first protective film, on the other side. After laminating a film (zero phase difference triacetyl cellulose film "ZRT" manufactured by Fujifilm Co., Ltd.), the film was dried at 80 ° C. for 5 minutes to produce a polarizing plate.

The above water-based adhesive was prepared by the following procedure. Polyvinyl alcohol powder (trade name "KL-318" manufactured by Kuraray Co., Ltd., average degree of polymerization of 1800) was dissolved in hot water at 95 ° C. to prepare a polyvinyl alcohol aqueous solution having a concentration of 3% by weight. A cross-linking agent (trade name "Smiley's Resin 650" manufactured by Taoka Chemical Industry Co., Ltd.) is mixed with the obtained aqueous solution at a ratio of 1 part by weight to 2 parts by weight of polyvinyl alcohol powder to obtain a water-based adhesive. rice field.

<Example 2, Comparative Example 1>
In Example 2 and Comparative Example 1, the parts by weight of the potassium iodide used in the complementary color treatment with respect to 100 parts by weight of water and the temperature in the drying treatment were changed as shown in Table 1 below. A polarizing element and polarization are carried out in the same manner as in Example 1 except that a triacetyl cellulose film (manufactured by Dai Nippon Printing Co., Ltd., trade name "LQ9" with a reflectance of 0.1%) is used as the first protective film. Manufactured a board.

<Evaluation test>
(1) Measurement of Orthogonal b After cutting the polarizing plates manufactured in Examples and Comparative Examples into a size of 4 cm × 4 cm, orthogonal b was measured with an ultraviolet-visible spectroscope (V-7100 manufactured by JASC). The results are shown in Table 1.

(2) Measurement of degree of polarization After cutting the polarizing plates manufactured in Examples and Comparative Examples into a size of 4 cm × 4 cm, the luminous efficiency correction degree of polarization and the degree of polarization corrected by an ultraviolet-visible light spectrometer (V-7100, manufactured by JASC) are used. Luminous efficiency correction single transmittance (Ty) was measured. Then, after putting it in an oven at 80 ° C. for 250 hours, the luminous efficiency correction degree of polarization was measured by the same method. The absolute value of the difference between the luminosity factor correction polarization degrees before and after passing through the oven was defined as ΔPy. From the viewpoint of providing a polarizing plate having excellent heat resistance, ΔPy is preferably 0.3 or less. The results are shown in Table 1.

(3) Measurement of Absorbance With respect to the polarizing plates manufactured in Examples and Comparative Examples, the absorbance at a wavelength of 450 nm A ₄₅₀ and the absorbance at a wavelength of 700 nm using an ultraviolet-visible spectroscope (V-7100 manufactured by JASC). A ₇₀₀ and the absorbance A ₇₅₀ at a wavelength of 750 nm were measured. The results are shown in Table 1.

1, 2, polarizing plate, 1', 2'circular polarizing plate, 3 first protective film, 4 second protective film, 5 polarizing element, 6 first adhesive layer, 7 second adhesive layer, 8 first phase difference Layer (λ / 4 retardation layer), 10 raw fabric film made of polyvinyl alcohol resin, 11 raw fabric roll, 13 swelling bath, 15 dyeing bath, 17a cross-linking bath, 17b complementary color bath, 19 washing bath, 21 drying furnace, 23 Polarizer, 30-48,60,61 guide roll, 50-52,53a, 53b, 54,55 nip roll.

Claims (9)

Including modulator,
The absorbance A ₄₅₀ at a wavelength of 450 nm satisfies the following relational expression (1).
A polarizing plate having an absorbance A ₇₅₀ at a wavelength of 750 nm satisfying the following relational expression (2).
1.6 ≤ A ₄₅₅ ≤ 2.7 (1)
0.7 ≤ A ₇₅₀ ≤ 2.3 (2) The polarizing plate according to claim 1, wherein the absorbance A ₇₀₀ at a wavelength of 700 nm satisfies the following relational expression (3).
1.7 ≤ A ₇₀₀ ≤ 4.5 (3) The polarizing plate according to claim 1 or 2, wherein the b value of the orthogonal hue is −1.5 or less. The polarizing plate according to claim 3, wherein the b value of the orthogonal hue is −20 or more. The polarizing plate according to any one of claims 1 to 4, wherein the polarizing element has a thickness of 7 μm or more and 30 μm or less. The polarizing plate according to any one of claims 1 to 5, further comprising a protective film bonded to at least one surface of the polarizing element. The polarizing plate according to any one of claims 1 to 6, further comprising a λ / 4 retardation layer. The polarizing plate according to claim 7, which is used by arranging it on the visible surface of an organic EL display panel. An organic EL display device including the organic EL display panel and the polarizing plate according to claim 8.

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