Polarizing plate and organic el display device

Abstract

This invention provides a novel polarizing plate that enables extended lifespan of the display device, even when used with an organic EL display panel. The linear polarizing plate of this invention comprises a polarizer with an absorbance A at a wavelength of 450 nm. 450 The absorbance A at a wavelength of 750 nm satisfies the following relationship (1). 750 The following relation (2) is satisfied: 1.6≤A 450 ≤2.7(1)0.7≤A 750 ≤2.3(2).

Description

Technical Field

[0001] The present invention relates to a polarizing plate and an organic EL display device including the same. Background Art

[0002] An organic electroluminescent (organic EL) display device is a self-emitting thin display device, and has advantages in display performance such as high visibility and less viewing angle dependence compared with a liquid crystal display device. In addition, on the basis of the advantages of being able to lighten and thin-layer an image display device (display), a flexible image display device can also be realized, and thus there is a possibility of realizing an image display device different from the previous ones.

[0003] However, since an organic EL display device sometimes uses a metal material or the like having a high reflectance as an electrode (metal electrode), external light is reflected at the interface of the metal electrode, and there is a case where problems such as a decrease in contrast and reflected glare (Japanese: 映り込み) caused by internal reflection (external light reflection) occur.

[0004] In order to suppress the adverse effects caused by external light reflection, a scheme of using a circular polarizing plate formed of a linear polarizing plate and a λ / 4 retardation layer as an antireflection plate has been proposed (for example, refer to Patent Documents 1 and 2).

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Laid-Open No. 7-142170

[0008] Patent Document 2: Japanese Patent Laid-Open No. 9-127885 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] In an organic EL display panel, there is a case where the lifetime of a blue light-emitting element is shorter than that of light-emitting elements of other colors. An object of the present invention is to provide a new type of polarizing plate that can achieve a long lifetime of a display device even when used together with an organic EL display panel, and to provide an organic EL display device including the polarizing plate.

[0011] Means for Solving the Problems

[0012] The present invention provides the following polarizing plate and organic EL display device.

[0013] [1] A polarizing plate including a polarizer, wherein in the polarizing plate,

[0014] The absorbance A at a wavelength of 450 nm , , , <0

[0015] Absorbance A at a wavelength of 750 nm 750 The following relation (2) is satisfied.

[0016] 1.6≤A 450 ≤2.7 (1)

[0017] 0.7≤A 750 ≤2.3 (2)

[0018] [2] According to the polarizing plate described in [1], the absorbance A at a wavelength of 700 nm is... 700 The following relation (3) is satisfied.

[0019] 1.7≤A 700 ≤4.5 (3)

[0020] [3] According to the polarizer described in [1] or [2], the b value of its orthogonal hue is less than -1.5.

[0021] [4] According to the polarizing plate described in [3], its orthogonal hue b value is -20 or higher.

[0022] [5] The polarizing plate described in any one of [1] to [4], wherein the thickness of the polarizing plate is 7 μm or more and 30 μm or less.

[0023] [6] The polarizing plate according to any one of [1] to [5] further comprises a protective film attached to at least one side of the polarizing plate.

[0024] [7] According to any one of [1] to [6], the polarizing plate also contains a λ / 4 phase difference layer.

[0025] [8] The polarizing plate described in [7] is used on the visible side surface of an organic EL display panel.

[0026] [9] An organic EL display device comprising an organic EL display panel and a polarizing plate as described in [8].

[0027] Invention Effects

[0028] The polarizing plate according to the present invention enables a long lifespan for the display device, even when used with an organic EL display panel. Attached Figure Description

[0029] Figure 1 This is a schematic cross-sectional view illustrating an example of the layered structure of the polarizing plate of the present invention.

[0030] Figure 2This is a schematic cross-sectional view illustrating another example of the layered structure of the polarizing plate of the present invention.

[0031] Figure 3 This is a cross-sectional view illustrating an example of a method for manufacturing a polarizer according to the present invention.

[0032] Figure 4 This is a schematic cross-sectional view showing an example of the layer configuration of a circular polarizing plate, which is one type of polarizing plate according to the present invention.

[0033] Figure 5 This is a schematic cross-sectional view showing another example of the layer configuration of a circular polarizing plate, which is one type of polarizing plate according to the present invention.

[0034] Explanation of reference numerals in the attached figures

[0035] 1, 2 polarizing plates, 1', 2' circular polarizing plates, 3 first protective film, 4 second protective film, 5 polarizing film, 6 first adhesive layer, 7 second adhesive layer, 8 first phase difference layer (λ / 4 phase difference layer), 10 raw material film containing polyvinyl alcohol resin, 11 raw material roll, 13 swelling bath, 15 dyeing bath, 17a crosslinking bath, 17b color matching bath, 19 cleaning bath, 21 drying oven, 23 polarizing film, 30-48, 60, 61 guide rollers, 50-52, 53a, 53b, 54, 55 clamping rollers. Detailed Implementation

[0036] <Polarizing film and polarizing plate>

[0037] (1) Basic structure of polarizing plate

[0038] Figure 1 This is a schematic cross-sectional view illustrating an example of the layered structure of the polarizing plate of the present invention. (Like) Figure 1 As shown in the polarizing plate 1, the polarizing plate of the present invention may be a polarizing plate having a polarizing film 5, a first protective film 3 laminated on one side via a first adhesive layer 6, and a second protective film 4 laminated on the other side via a second adhesive layer 7. The polarizing plate 1 may also have other optical functional layers, adhesive layers, etc. laminated on the first protective film 3 and / or the second protective film 4.

[0039] In addition, the polarizing plate of the present invention can also be like Figure 2 As shown in polarizing plate 2, it is a polarizing plate with a polarizer 5 and a first protective film 3 laminated on one side of it via a first adhesive layer 6. Polarizing plate 2 may also have other optical functional layers, adhesive layers, etc. laminated on the first protective film 3 and / or polarizer 5.

[0040] (2) Absorption characteristics of polarizing plate

[0041] The polarizing plate of the present invention includes a polarizer, wherein the absorbance A at a wavelength of 450 nm in the polarizing plate is... 450 The absorbance A at a wavelength of 750 nm satisfies the following relationship (1). 750 The following relation (2) is satisfied.

[0042] 1.6≤A 450 ≤2.7 (1)

[0043] 0.7≤A 750 ≤2.3 (2)

[0044] Here, the absorbance A of the polarizing plate 750 "and "absorbance A" 450 "Absorbance refers to the absorbance of the absorption band on the long wavelength side (red area) and the absorption band on the short wavelength side (blue area), respectively. Generally, the absorption bands on the long and short wavelength sides of a polarizing plate are very large. Therefore, if it is a UV-Vis spectrophotometer, its intensity is often difficult to determine due to saturation. The research results show that the intensity of the absorption bands on the long and short wavelength sides is respectively related to the absorbance A." 750 "and "absorbance A" 450 "Sufficiently correlated, they can be used separately using "absorbance A" 750 "and "absorbance A" 450 "To evaluate the intensity of the absorption bands on the long-wavelength side and the short-wavelength side."

[0045] The polarizing plate of the present invention, which satisfies the above relationships (1) and (2), has an absorbance A at a wavelength of 450 nm that is correlated with the absorption band of the blue region. 450 The absorbance A at a wavelength of 750 nm is correlated with the absorption on the longer wavelength side. 750 Compared to higher or equivalent levels, even if the amount of light emitted by the blue light-emitting elements in the organic EL display panel is reduced, blue light can still be fully transmitted, suppressing the shortening of the lifespan of the blue light-emitting elements that may be the cause of the shortened lifespan of the organic EL display elements, thereby contributing to the longevity of the organic EL display device.

[0046] Furthermore, regarding the polarizing plate of the present invention exhibiting the aforementioned absorption characteristics, although the rationale is not entirely clear, by setting the transmittance of the blue region within an appropriate range, the stability of the iodine complex in the polarizing plate is improved. Therefore, even after undergoing a heat resistance test, changes in polarization can be suppressed. The statement that changes in polarization can be suppressed even after a heat resistance test means that even after undergoing a heat resistance test, the absorbance A, which is correlated with the absorption of the blue region, can be maintained. 450 The absorbance A is correlated with the absorption on the longer wavelength side. 750Compared to higher (or equivalent) conditions, even when using organic EL display devices in high-temperature environments, the short lifespan of blue light-emitting elements can be suppressed, which helps to extend the lifespan of organic EL display devices.

[0047] The preferred absorbance A of the polarizing plate of the present invention is at a wavelength of 700 nm. 700 The following relation (3) is satisfied.

[0048] 1.7≤A 700 ≤4.5 (3)

[0049] From the viewpoint of efficiently transmitting short-wavelength light, the b-value of the orthogonal hue of the polarizing plate is preferably -1.5 or less, more preferably -3.0 or less. Furthermore, from the viewpoint of preventing decreased visibility due to excessive blue hue, the b-value of the orthogonal hue of the polarizing plate is preferably -20 or more, more preferably -19 or more. The b-value of the orthogonal hue is measured according to the description of one of the embodiments described later.

[0050] Absorbance A of the polarizing plate 450 Absorbance A 750 and absorbance A 700 Absorbance can be measured using an absorbance spectrophotometer such as a UV-Vis spectrophotometer. Natural light should be used as the incident light. When the incident light intensity is set to T0 and the transmitted light intensity is set to T, the absorbance (absorbance A) is... 450 Absorbance A 750 and absorbance A 700 The following formula can be used to find:

[0051] Absorbance = -log(T / T0)

[0052] It should be noted that if the incident light entering the sample (polarizing plate) is polarized, the absorbance value may vary depending on the orientation of the sample in the spectrophotometer. For example, depending on the spectrophotometer, some spectrophotometers may produce polarized light in the incident light due to the influence of mirrors, optical elements, etc., located between the light source and the sample, or they may have added polarization separation elements such as prisms. Therefore, care must be taken during measurement. When using this type of spectrophotometer, after measuring the polarizing plate at a certain angle (referring to a certain position around the optical axis), the measurement is repeated at a position rotated 90 degrees. The absorbance is calculated based on the average transmitted light intensity, thereby eliminating the influence of the polarization of the incident light.

[0053] (3) Polarization characteristics of polarizing plate

[0054] The polarization performance of a polarizing plate can be mainly represented by values ​​called single-cell transmittance and degree of polarization, which are defined by the following formulas:

[0055] Monomer transmittance (λ) = 0.5 × (Tp(λ) + Tc(λ))

[0056] Degree of polarization (λ)=100×(Tp(λ)-Tc(λ)) / (Tp(λ)+Tc(λ))

[0057] Here, Tp(λ) is the transmittance (%) of the polarizing plate determined by the relationship between the incident linearly polarized light with wavelength λnm and a parallel Nicol prism, and Tc(λ) is the transmittance (%) of the polarizing plate determined by the relationship between the incident linearly polarized light with wavelength λnm and an orthogonal Nicol prism. Both values ​​are obtained using polarized ultraviolet-visible absorption spectroscopy based on a spectrophotometer. Furthermore, the single-unit transmittance (λ) and polarization degree (λ) calculated for each wavelength are multiplied by a sensitivity correction called visibility correction, and the resulting values ​​are called visibility-corrected single-unit transmittance (Ty) and visibility-corrected polarization degree (Py), respectively. These Ty and Py values ​​can be easily measured, for example, using an absorber spectrophotometer (model: V7100) manufactured by Nippon Spectrophotometer Co., Ltd.

[0058] To ensure good image clarity when the polarizer is applied to a display device, the visibility correction unit transmittance (Ty) of the polarizer or polarizer of the present invention is 40.0% or more, preferably 42.0% or more, more preferably 44.0% or more, and even more preferably 45.0% or more. The visibility correction polarization degree (Py) is preferably 99% or more.

[0059] (4) Polarizing plate

[0060] The polarizer 5 can be a polarizer obtained by adsorbing dichroic pigments onto a polyvinyl alcohol-based resin layer that has undergone uniaxial stretching and orienting the dichroic pigments. In this invention, the thickness of the polarizer 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 even more preferably 12 μm or more and 25 μm or less. By using a polarizer 5 of this thickness, it is easy to obtain a polarizing plate that satisfies the above-mentioned relationships (1) and (2).

[0061] A polarizer can be an absorption-type polarizer that absorbs linearly polarized light with a vibration plane parallel to its absorption axis and transmits linearly polarized light with a vibration plane orthogonal to the absorption axis (parallel to the transmission axis). A representative polarizer is one obtained by adsorbing dichroic pigments onto a uniaxially stretched polyvinyl alcohol (PVA) resin film and orienting the dichroic pigments. Such polarizers can be manufactured, for example, using a process including uniaxial stretching of the PVA resin film; a process of adsorbing dichroic pigments by dyeing the PVA resin film with dichroic pigments (dyeing treatment); a process of treating the PVA resin film with adsorbed dichroic pigments with a crosslinking solution such as boric acid aqueous solution (crosslinking treatment); and a process of washing with water after treatment with the crosslinking solution (washing treatment).

[0062] As a polyvinyl alcohol-based resin, a resin obtained by saponifying a polyvinyl acetate-based resin can be used. In addition to polyvinyl acetate as a homopolymer of vinyl acetate, examples of polyvinyl acetate-based resins include copolymers of vinyl acetate with other monomers that can be copolymerized. Examples of other monomers that can be copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides containing ammonium groups.

[0063] In this specification, the term "(meth)acrylic acid" refers to at least one selected from acrylic acid and methacrylic acid. The same applies to "(meth)acryloyl" and "(meth)acrylate".

[0064] The degree of saponification of polyvinyl alcohol (PVA) resins is typically 85–100 mol%, preferably 98 mol% or higher. PVA resins can be modified; for example, aldehyde-modified PVA formal or PVA acetal can be used. The average degree of polymerization of PVA resins is typically 1000–10000, preferably 1500–5000. The average degree of polymerization of PVA resins can be determined according to JIS K 6726.

[0065] Examples of commercially available polyvinyl alcohol (PVA) resins suitable for use in this invention are indicated by trade names, including "PVA124" (saponification degree: 98.0–99.0 mol%), "PVA117" (saponification degree: 98.0–99.0 mol%), "PVA624" (saponification degree: 95.0–96.0 mol%), and "PVA617" (saponification degree: 94.5–95.5 mol%) manufactured by Kuraray Co., Ltd.; and "AH-26" (saponification degree: 97.0–98.8 mol%), "AH-22" (saponification degree: 97.5–98.5 mol%), and "NH-18" (saponification degree: 97.0–98.8 mol%) manufactured by Nippon Synthetic Chemicals Co., Ltd. Saponification degree: 98.0-99.0 mol%), "N-300" (Saponification degree: 98.0-99.0 mol%); "JC-33" (Saponification degree: ≥99.0 mol%), "JM-33" (Saponification degree: 93.5-95.5 mol%), "JM-26" (Saponification degree: 95.5-97.5 mol%), "JP-45" (Saponification degree: 86.5-89.5 mol%), "JF-17" (Saponification degree: 98.0-99.0 mol%), "JF-17L" (Saponification degree: 98.0-99.0 mol%), "JF-20" (Saponification degree: 98.0-99.0 mol%), and "JF-20" (Saponification degree: 98.0-99.0 mol%), all from VAM&POVAL Co., Ltd. of Japan.

[0066] The material obtained by forming a film from this polyvinyl alcohol-based resin is used as a raw material film (polyvinyl alcohol-based resin film) for manufacturing polarizers. The method of forming the polyvinyl alcohol-based resin film is not limited as long as it is a method that can obtain a polarizer constituting the polarizer of the present invention that satisfies the above-described relationships (1) and (2). Furthermore, the polarizer preferably satisfies the above-described relationships (1) and (2), and more preferably also satisfies relationship (3).

[0067] Uniaxial stretching of polyvinyl alcohol (PVA) resin films can be performed before, simultaneously with, or after dyeing with dichroic pigments. When uniaxial stretching is performed after dyeing, it can be done before or during crosslinking. Alternatively, uniaxial stretching can be performed multiple times within these various treatment stages.

[0068] In uniaxial stretching, when using a long strip of polyvinyl alcohol (PVA) resin film, the film can be placed on rollers with varying circumferential speeds, thereby stretching uniaxially between the rollers. Alternatively, a heated roller can be used for uniaxial stretching. Furthermore, uniaxial stretching can be dry stretching performed in the atmosphere or wet stretching performed while the PVA resin film is swollen using solvents or water. The stretching ratio is typically 3 to 8 times. When stretching the PVA resin film using multiple uniaxial stretching operations, the stretching ratio relative to the original length is typically 3 to 8 times. It should be noted that this stretching ratio can be selected to achieve the desired thickness of the final polarizer.

[0069] As a method for dyeing polyvinyl alcohol (PVA) resin films with dichroic dyes (dyeing treatment), typically, the PVA resin film is immersed in an aqueous solution containing the dichroic dye. Iodine and dichroic organic dyes are used as the dichroic dyes. It should be noted that the PVA resin film is preferably immersed in water before the dyeing treatment.

[0070] As a crosslinking treatment following dyeing with dichroic pigments, a common method is to immerse the dyed polyvinyl alcohol-based resin film in an aqueous solution containing boric acid. When iodine is used as the dichroic pigment, the aqueous solution containing boric acid preferably contains potassium iodide.

[0071] The dichroic pigments (adsorption-oriented) in polarizers can be iodine or dichroic organic dyes. Specific examples of dichroic organic dyes include Red BR, Red LR, Red R, Pink LB, Ruby 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 BlueG, Supra Blue GL, and Supra Orange. GL, Direct Sky Blue, Direct Fast Orange S, Fast Black. Dichroic pigments can be used alone or in combination with two or more.

[0072] Polarizing films can be manufactured from polyvinyl alcohol (PVA) resin films or from laminates (PVA resin laminates) in which a PVA resin layer is formed on a substrate. PVA resin laminates can be obtained, for example, by coating a substrate with a coating liquid containing PVA resin, or by laminating PVA resin onto a substrate. Polarizing films are manufactured by subjecting the PVA resin laminate to the following processes: uniaxial stretching of the PVA resin laminate; dyeing the uniaxially stretched PVA resin laminate with a dichroic dye to adsorb the dichroic dye; treating the PVA resin laminate with the adsorbed dichroic dye with a crosslinking solution such as a boric acid aqueous solution; and washing with water after treatment with the crosslinking solution.

[0073] Polarizing plates, such as Figure 1 and Figure 2 As shown, a polarizing plate can be manufactured by laminating a protective film on one or both sides of the polarizer, or it can be used as a polarizing plate on its own.

[0074] (5) First and second protective films

[0075] The first protective film 3 and the second protective film 4 can each be a transparent resin film comprising thermoplastic resins, such as chain polyolefin resins (polypropylene resins, etc.), cyclic polyolefin resins (norbornene resins, etc.); cellulose ester resins such as cellulose triacetate and cellulose diacetate; polyester resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; polycarbonate resins; (meth)acrylic resins; or mixtures or copolymers thereof. The first protective film 3 and the second protective film 4 can be the same type of protective film or different types of protective films.

[0076] Cyclic polyolefin resins are a general term for resins polymerized using cyclic olefins as polymerizing units. Examples include resins described in Japanese Patent Application Publication Nos. 1-240517, 3-14882, and 3-122137. Specific examples of cyclic polyolefin resins include ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins with chain olefins such as ethylene and propylene (typically random copolymers), graft polymers modified with unsaturated carboxylic acids or their derivatives, and their hydrides. Among these, norbornene-based resins that use norbornene monomers such as norbornene or polycyclic norbornene monomers as the cyclic olefin are preferred.

[0077] Cyclic polyolefin resins are available in various products on the market. Examples of commercially available cyclic polyolefin resins are indicated by trade names, including "Topas" (manufactured by Topas Advanced Polymers GmbH, available from Polyplastics Co., Ltd.), "Arton" (manufactured by JSR Co., Ltd.), "ZEONOR" (manufactured by ZEON Co., Ltd. of Japan), "ZEONEX" (manufactured by ZEON Co., Ltd. of Japan), and "APEL" (manufactured by Mitsui Chemicals Co., Ltd.).

[0078] In addition, all are indicated by product name, and commercially available products such as "ESCENA (Japanese: エスシーナ)" (manufactured by Sekisui Chemicals Co., Ltd.), "SCA40" (manufactured by Sekisui Chemicals Co., Ltd.), and "Zeonor Film" (manufactured by ZEON Co., Ltd. in Japan) which have undergone film forming can also be used as protective films.

[0079] Cellulose ester resins are esters of cellulose and fatty acids. Specific examples of cellulose ester resins include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Additionally, copolymers of these resins and resins in which a portion of the hydroxyl group is modified by other substituents can also be used. Among these, cellulose triacetate (TAC) is particularly preferred. Many products of cellulose triacetate are available on the market, which is advantageous from the perspectives of availability and cost. Examples of commercially available cellulose triacetate products are indicated by trade names, including "FUJITAC TD80" (manufactured by Fujifilm Corporation), "FUJITAC TD80UF" (manufactured by Fujifilm Corporation), "FUJITAC TD80UZ" (manufactured by Fujifilm Corporation), "FUJITAC TD40UZ" (manufactured by Fujifilm Corporation), "KC8UX2M" (manufactured by Konica Minolta Opto Corporation), and "KC4UY" (manufactured by Konica Minolta Opto Corporation).

[0080] The first protective film 3 and / or the second protective film 4 can also be a protective film with optical functions, such as a phase retardation film or a brightness enhancement film. For example, a phase retardation film with arbitrary phase difference values ​​can be produced by stretching (uniaxial stretching or biaxial stretching, etc.) a transparent resin film formed from the above materials, or by forming a liquid crystal layer on the film.

[0081] Surface treatment layers (coatings), such as hard coatings, anti-glare layers, anti-reflective layers, antistatic layers, and anti-fouling layers, may also be formed on the surface of the first protective film 3 and / or the second protective film 4 on the side opposite to the polarizer 5. There are no particular limitations on the method for forming the surface treatment layer on the protective film surface; known methods may be used.

[0082] 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.

[0083] (6) First and second adhesive layers

[0084] As the adhesive forming the first and second adhesive layers 6 and 7, water-based adhesives or light-curing adhesives can be used. The adhesive forming the first adhesive layer 6 and the adhesive forming the second adhesive layer 7 can be the same type or different types.

[0085] Examples of water-based adhesives include adhesives formed from aqueous solutions of polyvinyl alcohol resins and water-based two-component urethane emulsion adhesives. Among these, water-based adhesives formed from aqueous solutions of polyvinyl alcohol resins are suitable for use.

[0086] As polyvinyl alcohol (PVA) based resins, in addition to ethylene alcohol homopolymers obtained by saponifying polyvinyl acetate homopolymers, PVA copolymers obtained by saponifying copolymers of vinyl acetate and other monomers that can copolymerize with it, or modified PVA polymers whose hydroxyl groups have been partially modified, can also be used. Water-based adhesives may contain additives such as polyaldehydes, water-soluble epoxy compounds, melamine compounds, zirconium dioxide compounds, and zinc compounds. When using water-based adhesives, the thickness of the resulting adhesive layer is typically less than 1 μm.

[0087] There are no particular limitations on the bonding method between the polarizer 5 using a water-based adhesive and the protective film. Examples include uniformly applying or casting the water-based adhesive onto one bonding surface, overlapping the coated surface with the other and bonding it using rollers, followed by drying. Typically, the water-based adhesive is applied at a temperature of 15–40°C after its preparation, and the bonding temperature is usually in the range of 15–30°C.

[0088] When using a water-based adhesive, after lamination, a drying process is preferably performed to remove the water contained in the adhesive. Drying can be carried out, for example, by introducing the laminated film into a drying oven. The drying temperature (oven temperature) is preferably 30–90°C. If the temperature is below 30°C, the protective film tends to peel off easily from the polarizer 5. Furthermore, if the drying temperature is above 90°C, the polarization performance of the polarizer 5 may deteriorate due to heat. The drying time can be set, for example, from 10 to 1000 seconds.

[0089] After the drying process, a maturation process can be carried out at room temperature or slightly above room temperature, such as 20–45°C, for 12–600 hours. The maturation temperature is generally set lower than the drying temperature.

[0090] The aforementioned photocurable adhesives refer to adhesives that cure upon exposure to active energy rays such as ultraviolet light. Examples include adhesives containing polymerizable compounds and photopolymerization initiators, adhesives containing photoreactive resins, and adhesive resins containing photoreactive crosslinking agents. Examples of polymerizable compounds include photopolymerizable monomers such as photocurable epoxy monomers, photocurable acrylic monomers, and photocurable urethane monomers, as well as oligomers derived from photopolymerizable monomers. Examples of photopolymerization initiators include photopolymerization initiators containing substances that generate active species such as free radicals, anions, and cations upon exposure to active energy rays such as ultraviolet light. As a photocurable adhesive containing both a polymerizable compound and a photopolymerization initiator, a photocurable adhesive containing both a photocurable epoxy monomer and a photocationic polymerization initiator is preferred.

[0091] There are no particular limitations on the bonding method between the polarizer 5 and the protective film using a photocurable adhesive. Examples include methods such as casting, Mayer rod coating, gravure coating, comma-type doctor blade coating, scraper coating, mold coating, dip coating, and spray coating, where the photocurable adhesive is applied to one bonding surface, the two are overlapped, and then bonded using clamping rollers or similar methods. The casting method involves moving the object being coated in a generally vertical, generally horizontal, or inclined direction in between while simultaneously applying and spreading the adhesive onto the bonding surface. The thickness of the adhesive layer after bonding using clamping rollers or similar methods, before drying or curing, is preferably 5 μm or less and 0.01 μm or more.

[0092] When using a photocurable adhesive, after the above-described bonding process, a drying process is performed as needed (if the photocurable adhesive contains solvents, etc.), followed by a curing process in which the photocurable adhesive is cured by irradiation with active energy rays. The light source for the active energy rays is not particularly limited; however, it is preferable to use active energy rays with a luminescence distribution at a wavelength below 400 nm. Specifically, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, metal halide lamps, etc., are preferred.

[0093] The light irradiation intensity of the photocurable adhesive can be appropriately determined according to the composition of the photocurable adhesive, preferably an irradiation intensity of 0.1 to 6000 mW / cm in the wavelength region effective for activating the polymerization initiator. 2 The method was set. The irradiation intensity was 0.1 mW / cm². 2 Under the above conditions, the reaction time will not be too long, at 6000mW / cm 2 In the following situations, the likelihood of yellowing of the photocurable adhesive and deterioration of the polarizer caused by heat radiated from the light source and heat generated during the curing of the photocurable adhesive is small.

[0094] The light irradiation time for the photocurable adhesive can be appropriately determined based on the composition of the photocurable adhesive, preferably such that the cumulative light intensity, expressed as the product of the irradiation intensity and irradiation time, is 10 to 10000 mJ / cm. 2 The method was set. The cumulative light intensity was 10 mJ / cm². 2 Under the above conditions, a sufficient amount of active species derived from the polymerization initiator can be generated to reliably advance the curing reaction, at 10000 mJ / cm². 2 In the following situations, the irradiation time will not be too long, and good productivity can be maintained.

[0095] It should be noted that 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.

[0096] <Methods for Manufacturing Polarizing Films>

[0097] One method for manufacturing the polarizer used in the polarizer of the present invention will be described. In this method, an unstretched polyvinyl alcohol resin film (raw material film) with a thickness preferably 80 μm or less, more preferably 60 μm or less, and more preferably 10 μm or more, more preferably 15 μm or more, is used as the starting material for manufacturing the polarizer. The width of the raw material film is not particularly limited, and can be, for example, 400 to 6000 mm. The raw material film is prepared, for example, in the form of a long roll of unstretched polyvinyl alcohol resin film (raw material roll).

[0098] While the aforementioned long strip of raw material film is wound out from the raw material roll, it is continuously transported along the film transport path of the polarizer manufacturing apparatus. After being immersed in a treatment solution (hereinafter also referred to as a "treatment bath") contained in a treatment tank, it is pulled out. After performing this prescribed treatment process, a drying process is performed, thereby continuously manufacturing polarizers in the form of long strips. It should be noted that the treatment process is not limited to the method of immersing the film in a treatment bath, as long as the treatment solution contacts the film. It can also be a method of treating the film by spraying, flowing, dripping, or other methods that allow the treatment solution to adhere to the film surface. When the treatment process is performed by immersing the film in a treatment bath, the treatment bath for one treatment process is not limited to one. The film can also be immersed in two or more treatment baths in sequence to complete one treatment process.

[0099] Examples of the aforementioned processing solutions include swelling solutions, dyeing solutions, crosslinking solutions, color-correcting solutions, and cleaning solutions. Furthermore, examples of the aforementioned processing steps include a swelling step where the swelling solution contacts the raw film for swelling treatment; a dyeing step where the dyeing solution contacts the swollen film for dyeing treatment; a crosslinking step where the crosslinking solution contacts the dyed film for crosslinking treatment; a color-correcting step where the color-correcting solution contacts the crosslinked film for color correction treatment; and a cleaning step where the cleaning solution contacts the color-corrected film for cleaning treatment. Additionally, during these series of processing steps (i.e., before and after any one or more processing steps and / or during any one or more processing steps), uniaxial stretching treatment is performed using either wet or dry methods. Other processing steps may be added as needed.

[0100] The following is in reference Figure 3 At the same time, an example of the method for manufacturing the polarizer of the present invention will be described in detail. Figure 3This is a cross-sectional view schematically illustrating an example of a method for manufacturing a polarizer according to this embodiment, as well as a method and apparatus for manufacturing a polarizer used therein. Figure 3 The polarizer manufacturing apparatus shown is configured as follows: a raw material (unstretched) film 10 containing polyvinyl alcohol resin is continuously wound from a raw material roll 11 and transported along a film transport path, thereby passing sequentially through a swelling bath (swelling liquid contained in a swelling tank) 13, a dyeing bath (dyeing liquid contained in a dyeing tank) 15, a crosslinking bath (crosslinking liquid contained in a crosslinking tank) 17a, a color-correcting bath (color-correcting liquid contained in a color-correcting tank) 17b, and a cleaning bath (cleaning liquid contained in a cleaning tank) 19 provided on the film transport path, and finally through a drying oven 21. The resulting polarizer 23 can be directly transported, for example, to the following polarizer manufacturing process (the process of laminating a protective film on one or both sides of the polarizer 23). Figure 3 The arrows in the diagram indicate the direction of membrane transport.

[0101] exist Figure 3 In the description, "treatment tank" is a general term that includes swelling tank, dyeing tank, cross-linking tank, color matching tank and cleaning tank; "treatment liquid" is a general term that includes swelling liquid, dyeing liquid, cross-linking liquid, color matching liquid and cleaning liquid; and "treatment bath" is a general term that includes swelling bath, dyeing bath, cross-linking bath, color matching bath and cleaning bath.

[0102] The film transport path of the polarizer manufacturing apparatus can be constructed by configuring guide rollers 30-48, 60, and 61, and clamping rollers 50-55 at appropriate positions, in addition to the aforementioned processing baths. The guide rollers 30-48, 60, and 61 can support the transported film or change its transport direction. The clamping rollers 50-55 can press and clamp the transported film, applying a driving force due to their rotation, or also change its transport direction. The guide rollers and clamping rollers can be positioned before, after, or within each processing bath, thereby enabling the introduction, impregnation, and removal of the film from the processing baths (see reference). Figure 3 For example, one or more guide rollers are provided in each treatment bath to transport the membrane, thereby allowing the membrane to be immersed in each treatment bath.

[0103] Figure 3 The polarizing film manufacturing apparatus shown has clamping rollers (clamping rollers 50 to 54) arranged before and after each processing bath. This allows for longitudinal uniaxial stretching to be performed in any one or more processing baths by establishing a circumferential speed difference between the clamping rollers arranged before and after them. Each process will be described below.

[0104] (Swelling process)

[0105] The swelling process is performed for purposes such as removing foreign matter from the surface of the raw material film 10, removing plasticizers from the raw material film 10, imparting dyeability, and plasticizing the raw material film 10. The processing conditions can be determined within the range that achieves these purposes and without causing extreme dissolution, devitrification, or other undesirable conditions in the raw material film 10.

[0106] Reference Figure 3 While continuously winding the raw material film 10 from the raw material roll 11, it is transported along the film transport path, immersed in the swelling bath 13 for a specified time, and then pulled out, thereby performing the swelling process. Figure 3 In the example, after the raw film 10 is rolled out until it is immersed in the swelling bath 13, the raw film 10 is transported along a film transport path constructed by guide rollers 60, 61 and clamping rollers 50. During the swelling process, it is transported along a film transport path constructed by guide rollers 30-32 and clamping rollers 51.

[0107] As the swelling solution for the swelling bath 13, in addition to pure water, an aqueous solution containing boric acid (Japanese Patent Application Laid-Open No. 10-153709), chloride (Japanese Patent Application Laid-Open No. 06-281816), inorganic acid, inorganic salt, water-soluble organic solvent, alcohol, etc., can also be used, in the range of about 0.01 to 10% by weight.

[0108] The temperature of the swelling bath 13 is, for example, 10–50°C, preferably 10–40°C, and more preferably 15–30°C. The immersion time of the raw material membrane 10 is preferably 10–300 seconds, and more preferably 20–200 seconds. Furthermore, when the raw material membrane 10 is a polyvinyl alcohol-based resin membrane that has been pre-stretched in a gas, the temperature of the swelling bath 13 is, for example, 20–70°C, and preferably 30–60°C. The immersion time of the raw material membrane 10 is preferably 30–300 seconds, and more preferably 60–240 seconds.

[0109] During the swelling process, it is easy for the raw film 10 to swell in the width direction, forming wrinkles in the film. As a method to remove these wrinkles while transporting the film, examples include using stretching rollers, twisting rollers, medium-high rollers, or other spreading rollers as guide rollers 30, 31, and / or 32, or using other spreading devices such as fabric guides, bending rollers, or tenter ferrules. Another method to suppress the formation of wrinkles is to perform a stretching process. For example, uniaxial stretching can be performed in the swelling bath 13 using the difference in circumferential speed between the clamping rollers 50 and 51.

[0110] During the swelling process, since the membrane also swells and expands in the transport direction, in order to eliminate membrane slack in the transport direction without actively stretching the membrane, it is preferable to control the speed of the clamping rollers 50 and 51 positioned before and after the swelling bath 13, for example. Furthermore, to stabilize membrane transport in the swelling bath 13, it is also useful to control the water flow in the swelling bath 13 using an underwater sprayer, or to use an EPC device (Edge Position Control device: a device that detects the membrane ends and prevents the membrane from meandering).

[0111] Figure 3 In the example shown, the film pulled out from the swelling bath 13 passes through the guide roller 32, the clamping roller 51, and the guide roller 33 in sequence before being introduced into the dyeing bath 15.

[0112] (Dyeing process)

[0113] The dyeing process is performed to adsorb dichroic pigments onto the swollen polyvinyl alcohol-based resin film and to orient them. Processing conditions are determined within a range that achieves this objective without causing extreme problems such as film dissolution or depermeability. (Refer to...) Figure 3 The membrane, after swelling treatment, is transported along a membrane transport path constructed by clamping rollers 51, guide rollers 33-36, and clamping rollers 52. It is then immersed in dyeing bath 15 (a treatment solution contained in a dyeing tank) for a specified time and pulled out, thereby enabling the dyeing process. To improve the dyeability of dichroic pigments, the membrane provided to the dyeing process is preferably a membrane that has undergone at least uniaxial stretching treatment, or preferably, uniaxial stretching treatment is performed during dyeing treatment instead of uniaxial stretching treatment before dyeing treatment, or uniaxial stretching treatment is performed during dyeing treatment in addition to uniaxial stretching treatment before dyeing treatment.

[0114] When using iodine as a dichroic dye, the dyeing solution in dyeing bath 15 can be, for example, an aqueous solution with a concentration of iodine / potassium iodide / water ratio of approximately 0.003–0.3 / approximately 0.1–10 / 100 by weight. Other iodides, such as zinc iodide, can be used instead of potassium iodide, or potassium iodide and other iodides can be used in combination. Additionally, compounds other than iodides, such as boric acid, zinc chloride, and cobalt chloride, can coexist. When boric acid is added, the inclusion of iodine differs from the crosslinking treatment described later; dyeing bath 15 can be considered as long as the aqueous solution contains approximately 0.003 parts by weight or more of iodine relative to 100 parts by weight of water. The temperature of dyeing bath 15 during membrane impregnation is typically 10–45°C, preferably 10–40°C, more preferably 20–35°C, and the membrane impregnation time is typically 30–600 seconds, preferably 60–300 seconds.

[0115] When using a water-soluble dichroic dye as the dichroic pigment, the dyeing solution in the dyeing bath 15 can be, for example, an aqueous solution with a concentration of approximately 0.001 to 0.1 / 100 by weight of dichroic dye / water. Dyeing auxiliaries, such as inorganic salts like sodium sulfate and surfactants, can coexist in this dyeing bath 15. A single dichroic dye can be used alone, or two or more dichroic dyes can be used in combination. The temperature of the dyeing bath 15 during membrane impregnation is, for example, 20 to 80°C, preferably 30 to 70°C, and the membrane impregnation time is typically 30 to 600 seconds, preferably 60 to 300 seconds.

[0116] As described above, uniaxial stretching of the membrane can be performed in the dyeing bath 15 during the dyeing process. Uniaxial stretching of the membrane can be performed by methods such as setting a circumferential speed difference between the clamping rollers 51 and 52 disposed before and after the dyeing bath 15.

[0117] In the dyeing process, in order to remove wrinkles from the polyvinyl alcohol resin film while conveying it, similar to the swelling process, rollers with widening functions such as stretching rollers, twisting rollers, and medium-high rollers can be used as guide rollers 33, 34, 35 and / or 36, or other widening devices such as fabric guides, bending rollers, and tenter ferrules can be used. Another method to suppress wrinkle formation, similar to the swelling process, is to perform a stretching process.

[0118] exist Figure 3 In the example shown, the film pulled from the dyeing bath 15 passes sequentially through the guide roller 36, the clamping roller 52, and the guide roller 37 before being introduced into the crosslinking bath 17a.

[0119] (Cross-linking process)

[0120] The cross-linking process is performed to utilize the water resistance achieved through cross-linking. (Refer to...) Figure 3 The film is transported along the film transport path constructed by clamping roller 52, guide rollers 37-40 and clamping roller 53a. The dyed film is immersed in crosslinking bath 17a (crosslinking liquid contained in crosslinking tank) for a specified time and then stretched, thereby performing the crosslinking process.

[0121] As the crosslinking liquid, a solution in which the crosslinking agent is dissolved in a solvent can be used. Examples of crosslinking agents include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. One or more of these can be used. As the solvent, water can be used, and it may also contain an organic solvent compatible with water. The concentration of the crosslinking agent in the crosslinking solution is preferably in the range of 1 to 20% by mass, more preferably 3 to 15% by mass, but is not limited thereto.

[0122] The crosslinking solution can be an aqueous solution containing, for example, about 1 to 10 parts by mass of boric acid relative to 100 parts by mass of water. When the dichroic pigment used in the dyeing process is iodine, the crosslinking solution preferably contains an iodide in addition to boric acid, and the amount of iodide can be, for example, 1 to 30 parts by mass relative to 100 parts by mass of water. Examples of iodides include potassium iodide and zinc iodide. Alternatively, compounds other than iodides can coexist, such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, and sodium sulfate.

[0123] In the crosslinking process, the concentrations of boric acid and iodide, as well as the temperature of the crosslinking bath 17a, can be appropriately varied. The crosslinking solution can be, for example, an aqueous solution with a mass ratio of boric acid / iodide / water of 3–10 / 1–20 / 100. Depending on the need, other crosslinking agents can be used instead of boric acid, or boric acid and other crosslinking agents can be used together. The temperature of the crosslinking bath 17a during membrane impregnation is typically 40–70°C, preferably 50–65°C, and the membrane impregnation time is typically 10–600 seconds, preferably 20–300 seconds, and more preferably 20–200 seconds.

[0124] Crosslinking treatment can be performed multiple times, typically 2 to 5 times. In this case, the composition and temperature of each crosslinking bath can be the same or different, as long as they are within the above-mentioned range.

[0125] The uniaxial stretching process can also be carried out in the crosslinking bath 17a by utilizing the difference in circumferential speed between the clamping roller 52 and the clamping roller 53a.

[0126] In the crosslinking process, in order to remove wrinkles from the film while transporting the polyvinyl alcohol resin film, similar to the swelling process, rollers with widening functions such as stretching rollers, twisting rollers, and medium-high rollers can be used as guide rollers, or other widening devices such as fabric guides, bending rollers, and tenter ferrules can be used. Another method to suppress wrinkle formation, similar to the swelling process, is to perform a stretching process.

[0127] exist Figure 3 In the example shown, the film pulled from the crosslinking bath 17a passes through the guide roller 49 and the clamping roller 53a in sequence before being introduced into the complementary color bath 17b.

[0128] (Touch-up process)

[0129] The color correction process is performed for the purpose of adjusting color tone. (See reference...) Figure 3 The film is transported along the film transport path constructed by clamping roller 53a, guide rollers 41-44 and clamping roller 53b. The film after the crosslinking process is immersed in the color matching bath 17b (color matching liquid contained in the color matching tank) for a specified time and then pulled out, thereby performing the color matching process.

[0130] As a complementary color solution, a solution in which a crosslinking agent is dissolved in a solvent can be used. Examples of crosslinking agents include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. One or more of these can be used. As a solvent, water can be used, and it may also contain an organic solvent compatible with water. The concentration of the crosslinking agent in the complementary color solution is preferably in the range of 1 to 20% by mass, more preferably 6 to 15% by mass, but is not limited thereto.

[0131] The complementary color solution can be an aqueous solution containing, for example, about 1 to 10 parts by weight of boric acid relative to 100 parts by weight of water. When the dichroic pigment used in the dyeing process is iodine, the complementary color solution preferably contains an iodide in addition to boric acid, and the amount of iodide is, for example, 1 to 30 parts by weight relative to 100 parts by weight of water. Examples of iodides include potassium iodide and zinc iodide. Alternatively, compounds other than iodides, such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, and sodium sulfate, may also coexist.

[0132] When iodine is used as a dichroic pigment in the color-correcting solution, for example, a color-correcting solution with a concentration of boric acid / iodide / water ratio of 1–5 / 0.5–30 / 100 by weight can be used. The temperature of the color-correcting bath 17b during membrane impregnation is typically 10–45°C, and the membrane impregnation time is typically 1–300 seconds, preferably 2–100 seconds.

[0133] The uniaxial stretching process can also be performed in the complementary color bath 17b by utilizing the difference in circumferential speed between the clamping rollers 53a and 53b.

[0134] In the color correction process, in order to remove wrinkles from the film while conveying the polyvinyl alcohol resin film, similar to the swelling process, rollers with widening functions such as stretching rollers, twisting rollers, and medium-high rollers can be used as guide rollers, or other widening devices such as fabric guides, bending rollers, and tenter ferrules can be used. Another method to suppress wrinkle formation, similar to the swelling process, is to perform a stretching process.

[0135] exist Figure 3 In the example shown, the film pulled out from the color bath 17b passes through the guide roller 44 and the clamping roller 53b in sequence before being introduced into the cleaning bath 19.

[0136] (Cleaning process)

[0137] exist Figure 3The example shown includes a cleaning step following the color-correction process. The cleaning treatment is performed to remove excess boric acid, iodine, and other chemicals adhering to the polyvinyl alcohol (PVA) resin film. The cleaning process is performed, for example, by immersing the color-corrected PVA resin film in a cleaning bath 19. It should be noted that, instead of immersing the film in the cleaning bath 19, the cleaning solution can be sprayed onto the film as a spray solution, or the immersion in the cleaning bath 19 and the spraying of the cleaning solution can be combined to perform the cleaning process.

[0138] Figure 3 The image shows an example of cleaning a polyvinyl alcohol-based resin film by immersing it in a cleaning bath 19. The temperature of the cleaning bath 19 during the cleaning process is typically 2–40°C, and the immersion time of the film is typically 2–120 seconds.

[0139] It should be noted that during the cleaning process, in order to remove wrinkles while transporting the polyvinyl alcohol-based resin film, rollers with spreading functions such as stretching rollers, twisting rollers, and medium-high rollers can be used as guide rollers, or other spreading devices such as fabric guides, bending rollers, and stretching clips can be used. Additionally, during the film cleaning process, stretching treatment can be performed to suppress wrinkle formation.

[0140] (Stretching process)

[0141] As described above, the raw film 10 is subjected to uniaxial stretching treatment, either wet or dry, during the series of processing steps described above (i.e., before and after any one or more processing steps and / or during any one or more processing steps). Specific methods for uniaxial stretching treatment include, for example, inter-roll stretching where a circumferential speed difference is set between two clamping rollers constituting the film transport path (e.g., two clamping rollers arranged before and after the processing bath) to perform longitudinal uniaxial stretching, hot roll stretching as described in Japanese Patent No. 2731813, tenter frame stretching, etc., with inter-roll stretching being preferred. The uniaxial stretching process can be performed multiple times during the period from the raw film 10 to obtaining the polarizer 23. As described above, stretching treatment is also advantageous for suppressing the formation of wrinkles in the film.

[0142] The final cumulative stretching ratio of the polarizing film 23 based on the original film 10 is typically 4.5 to 7 times, preferably 5 to 6.5 times. The stretching process can be performed in any processing step, and even if the stretching process is performed in two or more processing steps, it can still be performed in any processing step.

[0143] (Drying process)

[0144] Preferably, the polyvinyl alcohol-based resin film is dried after the cleaning process. There are no particular limitations on the drying method; it can be performed as follows: Figure 3The drying process is performed using a drying oven 21, as shown in the example. The drying oven 21 can be, for example, a drying oven equipped with a hot air dryer. The drying temperature is, for example, 30–100°C, and the drying time is, for example, 30–600 seconds. The drying process of the polyvinyl alcohol-based resin film can also be performed using a far-infrared heater. The thickness of the polarizer 23 obtained as described above is, for example, 7 μm or more and 30 μm or less.

[0145] The resulting polarizer can be wound sequentially on a winding roller to form a roll, or it can be directly supplied to the polarizer manufacturing process (such as the process of laminating protective films on one or both sides of the polarizer) without being wound.

[0146] <Control of the Absorption Characteristics of Polarizing Plates>

[0147] When a polarizer 5 is obtained using the manufacturing method described above, and then a polarizer 1 with a protective film on both sides or a polarizer 2 with a protective film on one side is fabricated, the various processes in this manufacturing method include affecting the absorbance A of the polarizers 1 and 2. 450 Absorbance A 750 Several factors influence the suppression of changes in polarization degree before and after the heat resistance test. A prime example is the manufacturing method of polarizer 5:

[0148] a) The concentration of potassium iodide in the crosslinking solution used in the crosslinking process;

[0149] b) The concentration of potassium iodide in the color-correcting solution used in the color-correcting process;

[0150] c) The stretch ratio, shrinkage rate during stretching, and stretching temperature of polyvinyl alcohol resin films;

[0151] d) The temperature of the cleaning bath and the immersion time in the cleaning bath during the cleaning process;

[0152] e) Drying temperature and drying time in the drying process; etc.

[0153] In particular, b) and e) refer to the absorbance A of polarizers 1 and 2. 450 Absorbance A 750 It also affects the suppression of changes in polarization degree before and after the heat resistance test.

[0154] Specifically, regarding b) above, the concentration of potassium iodide in the color-correcting solution is preferably 0.5 to 10 parts by weight relative to 100 parts by weight of water, more preferably 1 to 5 parts by weight, and even more preferably 1.5 to 2.5 parts by weight. Furthermore, regarding e) above, the drying temperature is preferably 70 to 100°C, more preferably 80 to 100°C. Additionally, the thickness of the polarizer also affects the absorbance A of polarizers 1 and 2. 450 Absorbance A750 It also affects the suppression of changes in polarization degree before and after the heat resistance test.

[0155] <Circular Polarizing Plate>

[0156] (1) Basic structure of a circular polarizing plate

[0157] Figure 4 This is one method of the polarizing plate of the present invention. Figure 4 The polarizing plate described in the text (hereinafter sometimes referred to as circular polarizing plate 1') has... Figure 1 Based on the elements of the polarizer 1 shown, it also has a first phase retardation layer 8 stacked on the side opposite to the polarizer 5 of the second protective film 4. The second protective film 4 and the first phase retardation layer 8 can be bonded together via an adhesive layer, the adhesive layer used here referring to the description of the first and second adhesive layers above.

[0158] Figure 5 This is one method of the polarizing plate of the present invention. Figure 5 The polarizing plate described in the text (hereinafter sometimes referred to as circular polarizing plate 2') has... Figure 2 Based on the elements of the polarizer 2 shown, it also has a first phase difference layer 30 stacked on the side of the polarizer 5 opposite to the first protective film 10. The polarizer 5 and the first phase difference layer 30 can be bonded together via an adhesive layer, the adhesive layer used here referring to the description of the first and second adhesive layers above.

[0159] The definitions of the terms and symbols used in the description of the circular polarizer in this manual are as follows.

[0160] (Refractive index (nx, ny, nz))

[0161] “nx” is the refractive index in the direction where the refractive index reaches its maximum in the plane (i.e., the slow axis direction), “ny” is the refractive index in the direction orthogonal to the slow axis in the plane, and “nz” is the refractive index in the thickness direction.

[0162] (In-plane phase difference value)

[0163] The in-plane phase difference (Re(λ)) refers to the in-plane phase difference of the film at 23℃ and wavelength λ (nm). Re(λ) is calculated using the following formula when the film thickness is set to d (nm):

[0164] Re(λ)=(nx-ny)×d

[0165] The term Re(550) represents the in-plane phase difference of the film when light with a wavelength of 550 nm is emitted.

[0166] (Phase difference in the thickness direction)

[0167] The phase difference along the thickness direction (Rth(λ)) refers to the phase difference along the thickness direction of the film when exposed to light at 23°C and wavelength λ (nm). Rth(λ) is calculated using the following formula when the film thickness is set to d (nm):

[0168] Rth(λ)=((nx+ny) / 2-nz)×d

[0169] Rth(550) represents the phase difference in the thickness direction of the film when light with a wavelength of 550nm is emitted.

[0170] (2) First phase difference layer

[0171] The first phase difference layer of circular polarizers 1' and 2' ( Figure 4 , Figure 5 The first phase retardation layer (8) is a layer that converts linearly polarized light into circularly polarized light. The in-plane phase difference value Re1(550) of the first phase retardation layer is a value satisfying equation (a) below, and preferably a value satisfying equation (a1) below. The material of the first phase retardation layer is not particularly limited.

[0172] 110nm≤Re1(550)≤160nm (a)

[0173] 120nm≤Re1(550)≤150nm (a1)

[0174] The first phase difference layer is the layer that satisfies equation (a) above, and is also called the λ / 4 phase difference layer. A circular polarizer can also be configured to have not only a λ / 4 phase difference layer but also a λ / 2 phase difference layer that satisfies equation (d) described later (hereinafter also called the "second phase difference layer"). Hereinafter, a circular polarizer having a λ / 4 phase difference layer but not a λ / 2 phase difference layer (hereinafter referred to as "the first type") will be described. Other types of circular polarizers that have both a λ / 4 and a λ / 2 phase difference layer (hereinafter referred to as "the second type") will be described later.

[0175] In the first embodiment, the first phase difference layer preferably has an angle of approximately 45° between its slow axis and the absorption axis of the polarizer 5. Here, "approximately 45°" is not limited to the case of strictly "45°", but includes the case of "45° ± 5°".

[0176] In the first method, the first phase difference layer uses the wavelength dispersion of the in-plane phase difference value Re1(λ) to satisfy the following equations (b) and (c).

[0177] Re1(450) / Re1(550)≤1.00 (b)

[0178] 1.00≤Re1(650) / Re1(550) (c)

[0179] Alternatively, a commercially available retardation film can be used directly as the first retardation layer. Examples of such commercially available products include "PURE-ACE WR-S", "PURE-ACE WR-W", and "PURE-ACE WR-M" manufactured by Teijin Corporation, and "NRF" manufactured by Nitto Denko Corporation.

[0180] Another example of a retardation film is a retardation film containing a cured polymeric liquid crystal compound (hereinafter referred to as a "liquid crystal retardation film"). Liquid crystal retardation films can typically be made with thicknesses as thin as 0.2 μm to 10 μm, and are therefore preferred from the viewpoint of thin-film circular polarizers.

[0181] Examples of polymeric liquid crystal compounds capable of forming liquid crystal retardation films include those disclosed in Japanese Patent Application Publication Nos. 2009-173893, 2010-31223, WO2012 / 147904, WO2014 / 10325, and WO2017-43438. These polymeric liquid crystal compounds can form liquid crystal retardation films with inverse wavelength dispersion that achieve the same polarization conversion over a wide wavelength range.

[0182] A simplified explanation of the method for forming a liquid crystal retardation film is provided. First, a suitable support is prepared. After forming an alignment film on the support as needed, a liquid composition containing a polymerizable liquid crystal compound is coated and dried, thereby forming a layer containing the polymerizable liquid crystal compound on the support. The polymerizable liquid crystal compound contained in this layer is then irradiated with light, for example, while the polymerizable liquid crystal compound in this layer is aligned in a predetermined direction, thereby causing the polymerizable liquid crystal compound contained in the layer to polymerize, thus forming a liquid crystal retardation film.

[0183] (3) Third phase difference layer

[0184] In the circular polarizer of the first type, a third phase retardation layer may also be provided, exhibiting a refractive index characteristic showing the relationship nz>nx≥ny. By providing a third phase retardation layer with this refractive index characteristic, for example, when used as an anti-reflective polarizer, the angle dependence of the effect of absorbing reflected light is reduced, and reflected light reflected at various angles can be prevented from escaping, which is therefore preferable. The third phase retardation layer may be stacked between the first phase retardation layer 8 and the polarizer 5, or it may be stacked on the side of the first phase retardation layer 8 opposite to the side opposite to the polarizer 5.

[0185] In the third phase difference layer, the refractive index sometimes exhibits a relationship of nx = ny. Here, "nx = ny" includes not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal. Specifically, it is preferred that Re(550) be less than 10 nm.

[0186] The phase difference Rth(550) in the thickness direction of the third phase difference layer is preferably -260nm to -10nm, more preferably -230nm to -15nm, and even more preferably -215nm to -20nm. By setting it to this range, the above-mentioned effect becomes significant, and therefore it is preferred.

[0187] The third retardation layer can be formed from any suitable material without particular limitation; however, it is preferable that the liquid crystal compound is fixed in a vertically oriented retardation layer. The vertically oriented liquid crystal compound can 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, for instance, the liquid crystal compound and the method for forming described in Japanese Patent Application Publication Nos. 2002-333642,

[0020] to

[0042] . In this case, the thickness is preferably 0.1 μm to 5 μm, more preferably 0.2 μm to 3 μm.

[0188] (4) Other methods of using circular polarizing plates

[0189] For other types (Type 2) of circular polarizers, only the aspects that differ from those of Type 1 circular polarizers will be described. In addition to having a first phase difference layer, the Type 2 circular polarizer also has a second phase difference layer between the polarizer 5 and the first phase difference layer 8. If the in-plane phase difference value of the second phase difference layer is set to Re2(λ), then the second phase difference layer uses a phase difference layer whose in-plane phase difference value Re2(550) satisfies the following equation (d), preferably a phase difference layer satisfying the following equation (d1). The material of the second phase difference layer is not particularly limited; for example, the material exemplified in the first phase difference layer can be used.

[0190] 210nm≤Re2(550)≤300nm (d)

[0191] 220nm≤Re2(550)≤290nm (d1)

[0192] In the second embodiment, the second retardation layer preferably has an angle of approximately 15° between its slow axis and the absorption axis of the polarizer. In the second embodiment, the first retardation layer preferably has an angle of approximately 75° between its slow axis and the absorption axis of the polarizer. Here, "approximately 15°" and "approximately 75°" are not limited to strictly "15°" and "75°", but include ranges from "15°±5°" to "75°±5°".

[0193] <Circular polarizing plate with adhesive>

[0194] The circular polarizer of the present invention can be manufactured by providing an adhesive layer on at least one surface. This adhesive layer is typically used to attach the circular polarizer of the present invention to an image display panel. The adhesive used to form this adhesive layer is not particularly limited; known adhesives can be used.

[0195] As the adhesive layer, any adhesive layer that exhibits excellent optical transparency and moderate adhesive properties such as wettability, cohesiveness, and adhesion is acceptable, and an adhesive layer with excellent durability is preferred. Specifically, as the adhesive forming the adhesive layer, pressure-sensitive adhesives (also known as acrylic adhesives or rubber adhesives) comprising acrylic resins or rubber resins can be cited as examples.

[0196] The adhesive layer formed from an acrylic adhesive, preferably one of the adhesives capable of forming the adhesive layer, is not particularly limited. However, it is preferable to use a methacrylate resin polymerized from methacrylates such as butyl methacrylate, ethyl methacrylate, isooctyl methacrylate, and 2-ethylhexyl methacrylate, or a copolymer resin using two or more of these methacrylates as the base polymer. Alternatively, polar monomers can be copolymerized with these resins. Examples of polar monomers include (meth)acrylic acid, 2-hydroxypropyl methacrylate, 2-hydroxyethyl methacrylate, (meth)acrylamide, 2-N,N-dimethylaminoethyl methacrylate, and glycidyl methacrylate, which have polar functional groups such as carboxyl, hydroxyl, amide, amino, and epoxy groups. It should be noted that the base polymer referred to here is the polymer that is the main component in the solid components constituting the acrylic adhesive. Furthermore, a crosslinking agent is usually incorporated into the adhesive along with the acrylic resin.

[0197] In addition, various additives can be incorporated into the adhesive. Suitable additives include silane coupling agents and antistatic agents. Silane coupling agents are effective in improving adhesion to glass. Antistatic agents are effective in reducing or preventing the generation of static electricity.

[0198] The thickness of the adhesive layer used for bonding to the image display panel is preferably 3 to 50 μm. More preferably, it is 5 to 30 μm. It should be noted that in the circular polarizer of the present invention, an adhesive layer for bonding to the front panel may also be provided on the opposite side of the adhesive layer used for bonding to the image display panel. In the case where adhesive layers are provided on both sides of the circular polarizer of the present invention, it is preferable to set the thickness of at least one of the two adhesive layers to 3 to 50 μm. More preferably, it is 5 to 30 μm.

[0199] To prevent debris or foreign matter from adhering to the adhesive layer during transportation, a release film is sometimes applied to the adhesive layer. When peeling off this release film, undesirable conditions may occur, such as static electricity being generated in the adhesive layer. To prevent this, the adhesive layer may be made moderately conductive. When making the adhesive layer conductive, its resistance value can be appropriately selected; for example, 1 × 10⁻⁶ is preferred. 9 ~1×10 11 The range of Ω / □.

[0200] The method for forming the adhesive layer in the circular polarizing plate of the present invention can sometimes be carried out using known methods.

[0201] [Image display device]

[0202] An image display device is formed by attaching the polarizing plate of the present invention to an image display panel. The image display device will now be described.

[0203] The type of image display device is not limited, and known image display devices can be used. For example, the polarizer of the present invention can be suitably used in an organic EL display device. The polarizer of the present invention can be used by setting it on the visible side of the organic EL display panel in such a way that a first phase difference layer is disposed on the organic EL display panel side.

[0204] Example

[0205] The present invention will be further described in detail below with reference to embodiments and comparative examples; however, the present invention is not limited to these examples.

[0206] <Example 1>

[0207] A transparent, unstretched polyvinyl alcohol (PE60, average degree of polymerization 2400, manufactured by KURARAY) resin film, with a length and width of 100 cm, a thickness of 30 μm, and a saponification degree of 99.9 mol% or higher, was immersed in water (deionized water) at 25°C for 1 minute and 20 seconds to induce swelling (swelling treatment). Subsequently, it was immersed in a dyeing solution at 30°C containing iodine / potassium iodide / boric acid / water in a mass ratio of 0.3 / 1.2 / 0.3 / 100 for 2 minutes and 30 seconds to induce dyeing (dyeing treatment). During both the swelling treatment and dyeing treatment, the film was stretched at stretch ratios of 1.56 and 1.64, respectively, to achieve a cumulative stretch ratio of 2.56 until the end of the dyeing treatment.

[0208] Then, while immersing in a crosslinking solution at 54°C for 26 seconds (first crosslinking treatment) containing these substances in a mass ratio of potassium iodide / boric acid / water = 7.1 / 1.8 / 100, the mixture was stretched at a stretch ratio of 1.5. Subsequently, while immersing in a crosslinking solution at 54°C for 20 seconds (second crosslinking treatment) containing these substances in a mass ratio of potassium iodide / boric acid / water = 7 / 3.4 / 100, the mixture was stretched at a stretch ratio of 1.6. Then, in the color-correcting treatment, while immersing in a color-correcting aqueous solution at 40°C for 10 seconds containing these substances in a mass ratio of potassium iodide / boric acid / water = 1.5 / 3.4 / 100, the mixture was stretched at a stretch ratio of 1.01. At this point, the total cumulative stretch ratio of the swelling treatment, dyeing treatment, crosslinking treatment, and color-correcting treatment was 5.9.

[0209] After the color correction process is completed, the polarizer is washed with pure water at 6°C for 7 seconds to remove foreign matter adhering to the surface of the polarizer (cleaning process). After washing, the polarizer is dried under the temperature conditions specified in Table 1 below (drying process) to produce the polarizer.

[0210] The obtained polarizer was coated with a triacetyl cellulose film (trade name "DSG17Z" manufactured by Dai Nippon Printing Co., Ltd.) as the first protective film on one side using a water-based adhesive, and a triacetyl cellulose film (zero phase difference triacetyl cellulose film "ZRT" manufactured by Fujifilm Co., Ltd.) as the second protective film on the other side. The coated film was then dried at 80°C for 5 minutes to produce a polarizer plate.

[0211] The above-mentioned water-based adhesive was prepared using the following steps: Polyvinyl alcohol powder (trade name "KL-318" manufactured by Kuraray Co., Ltd., average degree of polymerization 1800) was dissolved in hot water at 95°C to prepare a 3% by weight aqueous solution of polyvinyl alcohol. A crosslinking agent (trade name "Sumirez Resin 650" manufactured by Taoka Chemical Co., Ltd.) was mixed into the resulting aqueous solution at a ratio of 1 part by weight to 2 parts by weight of polyvinyl alcohol powder to obtain the water-based adhesive.

[0212] <Example 2, Comparative Example 1>

[0213] For Example 2 and Comparative Example 1, except that the weight of potassium iodide in the color-correcting solution used in the color-correcting process relative to 100 parts by weight of water, and the temperature in the drying process were changed as shown in Table 1 below, and a triacetyl cellulose membrane (manufactured by Dai Nippon Printing Co., Ltd., trade name "LQ9" with a reflectance of 0.1%) was used as the first protective film, the polarizing film and the polarizing plate were manufactured using the same method as in Example 1.

[0214] <Evaluation Experiment>

[0215] (1) Determination of orthogonal b

[0216] The polarizing plates manufactured in the examples and comparative examples were cut into 4cm × 4cm sizes, and the orthogonality b was measured using a UV-Vis spectrometer (JASC V-7100). The results are shown in Table 1.

[0217] (2) Determination of polarization degree

[0218] The polarizing plates manufactured in the examples and comparative examples were cut into 4cm × 4cm sizes, and the visibility-corrected polarization degree and visibility-corrected monomer transmittance (Ty) were measured using a UV-Vis spectrometer (V-7100, JASC). Subsequently, after being placed in an oven at 80°C for 250 hours, the visibility-corrected polarization degree was measured using the same method. The absolute value of the difference between the visibility-corrected polarization degree before and after oven drying is defined as ΔPy. From the viewpoint of providing a polarizing plate with excellent heat resistance, ΔPy is preferably 0.3 or less. The results are shown in Table 1.

[0219] (3) Measurement of absorbance

[0220] For the polarizing plates manufactured in the examples and comparative examples, the absorbance A at a wavelength of 450 nm was measured using a UV-Vis spectrometer (JASC V-7100). 450 Absorbance A at a wavelength of 700 nm 700 and absorbance A at a wavelength of 750 nm 750 The results are shown in Table 1.

[0221] Table 1

[0222]

Claims

1. A polarizing plate comprising polarizing plates, In the polarizing plate Absorbance A at wavelength 450 nm 450 satisfies the following relational expression (1), Absorbance A at a wavelength of 750 nm 750 The following relation (2) is satisfied. Absorbance A at a wavelength of 700 nm 700 The following relation (3) is satisfied. 1.6≤A 450 ≤2.7 （1） 0.7≤A 750 ≤2.3 （2） 3.11≤A 700 ≤4.5 （3）。 2. The polarizing plate according to claim 1, wherein the b-value of its orthogonal hue is -1.5 or less.

3. The polarizing plate according to claim 2, wherein the b-value of its orthogonal hue is -20 or higher.

4. The polarizing plate according to any one of claims 1 to 3, wherein, The thickness of the polarizer is greater than 7 μm and less than 30 μm.

5. The polarizing plate according to claim 1 or 2, further comprising a protective film adhered to at least one side of the polarizing plate.

6. The polarizing plate according to claim 1 or 2, further comprising a λ / 4 phase retardation layer.

7. The polarizing plate according to claim 6, which is disposed on the visible side surface of an organic EL display panel for use.

8. An organic EL display device comprising an organic EL display panel and a polarizing plate as claimed in claim 7.

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