Optical laminate

Abstract

The present invention provides an optical laminate that can reduce the change in reflected hue before and after being maintained in a high temperature and high humidity environment. The solution to the above problem is an optical laminate comprising, in sequence, a polarizer, a first adhesive layer, and a retardation layer. The retardation layer comprises a cured layer of a polymeric liquid crystal compound. The polarizer is an iodine-adsorbed polyvinyl alcohol resin film, and satisfies at least one of [a] and [b] below. [a] The absorbance A(295) at a wavelength of 295 nm is below 0.85. [b]The absorbance A(360) at a wavelength of 360 nm is less than 0.55.

Description

Technical Field

[0001] The present invention relates to an optical laminate. Prior Art

[0002] A polarizing plate in which iodine is adsorbed and aligned on a polyvinyl alcohol-based resin film is widely used as an optical member constituting an organic EL display device or a liquid crystal display device. In an organic EL display device, a circular polarizing plate having a polarizing plate and a retardation layer laminated thereon is generally used (for example, Patent Document 1). [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2020-126226 Summary of the Invention Problems to be Solved by the Invention

[0004] As described above, the present inventors have found that when a circular polarizing plate having a polarizing plate containing iodine is held in a high-temperature and high-humidity environment, the change in the retardation value becomes large and the reflected hue changes significantly.

[0005] An object of the present invention is to provide an optical laminate that can reduce the amount of change in the reflected hue before and after being held in a high-temperature and high-humidity environment. Means for Solving the Problems

[0006] The present invention provides an optical laminate as follows. [1] An optical laminate in which a polarizing plate in which iodine is adsorbed and aligned on a polyvinyl alcohol-based resin film, a first adhesive layer, and a retardation layer are laminated in this order, wherein the above-mentioned retardation layer includes a cured product layer of a polymerizable liquid crystal compound, the above-mentioned polarizing plate satisfies at least one of the following [a] and [b], [a] The absorbance A(295) at a wavelength of 295 nm is 0.85 or less, [b] The absorbance A(360) at a wavelength of 360 nm is 0.55 or less. [2] The optical laminate according to claim [1], wherein the above-mentioned polarizing plate satisfies the above [a] and [b]. [3] The optical laminate according to claim [1] or [2], wherein a protective film is further provided on the side of the above-mentioned polarizing plate opposite to the side of the above-mentioned first adhesive layer. [4] The optical laminate according to any one of claims [1] to [3], wherein the polarizing plate and the first adhesive layer are in direct contact. [5] The optical laminate according to any one of claims [1] to [4], wherein the first adhesive layer is in direct contact with the retardation layer. [6] The optical laminate according to any one of claims [1] to [5], wherein the retardation layer is a λ / 4 retardation layer. [7] The optical laminate according to any one of claims [1] to [6], wherein a second adhesive layer is further provided on the side of the retardation layer opposite to the first adhesive layer side. [8] The optical laminate according to any one of [1] to [4], wherein the protective film is laminated on the polarizing plate through a lamination layer, and the lamination layer is an adhesive layer formed using an aqueous adhesive. Advantages of the Invention

[0007] According to the optical laminate of the present invention, the amount of change in the reflected hue before and after being held in a high-temperature and high-humidity environment can be reduced. Brief Explanation of Drawings

[0008] FIG. 1 is a cross-sectional view schematically showing an example of an optical laminate according to an embodiment of the present invention. FIG. 2 is a cross-sectional view for explaining an example of a method for manufacturing a polarizer included in the optical laminate of the present invention. FIG. 3 is a cross-sectional view for explaining another example of a method for manufacturing a polarizing plate included in the optical laminate of the present embodiment. Embodiment

[0009] Hereinafter, a preferred embodiment of the optical laminate will be described with reference to the drawings. (Optical Laminate) FIG. 1 is a cross-sectional view schematically showing an example of the optical laminate of the present embodiment. The optical laminate 1 shown in FIG. 1 is sequentially laminated with a polarizing plate 12 in which iodine is adsorbed and aligned on a polyvinyl alcohol-based resin film, a first adhesive layer 3, and a retardation layer 15 including a cured product layer of a polymerizable liquid crystal compound.

[0010] The optical laminate 1 may also have a protective film 11 on one or both sides of the polarizer 12. In this case, the protective film 11 may be bonded to the polarizer 12 through an adhesive layer (adhesive layer or bonding agent layer) 13. The adhesive layer 13 is preferably an adhesive layer formed by a water-based adhesive such as a polyvinyl alcohol adhesive. As shown in FIG1, when the optical laminate 1 includes a protective film 11 bonded to the polarizer 12 through the adhesive layer 13, the polarizer 12, the adhesive layer 13, and the protective film 11 constitute a polarizing plate 10. In the optical laminate 1 shown in FIG1, it is shown that the protective film 11 is only on the side of the polarizer 12 opposite to the side of the first adhesive layer 31, but the optical laminate may only have a protective film on the side of the first adhesive layer 31 of the polarizer 12, or it may have a protective film on both sides of the polarizer 12.

[0011] In the optical laminate 1, the polarizer 12 and the first adhesive layer 31 can be laminated in a manner that allows direct contact, for example, by means of a protective film disposed on one or both sides of the polarizer 12. When the optical laminate 1 includes a polarizing plate with a protective film on one or both sides of the polarizer 12, it is preferable to laminate the polarizing plate and the first adhesive layer 31 in a manner that allows direct contact.

[0012] In the optical stack 1, the first adhesive layer 31 and the phase retardation layer 15 can be stacked in a manner that allows them to be in direct contact. Alternatively, a support film, such as a coating layer used to support the polymeric liquid crystal compound during the formation of the phase retardation layer 15, can be provided between the first adhesive layer 31 and the phase retardation layer 15.

[0013] The optical laminate 1 may have a second adhesive layer 32 on the side of the phase retardation layer 15 opposite to the side of the first adhesive layer 31, and may also have a release film 33 for covering and protecting the surface of the second adhesive layer 32. When the optical laminate 1 is bonded to the image display element of a display device such as an organic EL display device through the second adhesive layer 32, the release film 33 is peeled off.

[0014] The optical stack 1 may also have one or more phase retardation layers different from the phase retardation layer 15 between the phase retardation layer 15 and the second adhesive layer 32. Other phase retardation layers may be deposited on the phase retardation layer 15 through an adhesive layer (adhesive layer or bonding agent layer).

[0015] (Polarizing film) In the optical stack 1, the polarizer 12 satisfies at least one of [a] and [b] below. Preferably, the polarizer 12 satisfies both [a] and [b] below. [a] The absorbance A(295) at a wavelength of 295 nm is below 0.85. [b]The absorbance A(360) at a wavelength of 360 nm is less than 0.55.

[0016] The absorbance A(295) of the polarizer 12 may be 0.80 or less, or 0.75 or less, or 0.70 or less, or 0.60 or less, or 0.55 or less, but is generally 0.3 or more. The absorbance A(360) of the polarizer 12 may be 0.50 or less, or 0.46 or less, or 0.45 or less, or 0.44 or less, but is generally 0.3 or more. The absorbance of the polarizer 12 may be measured by the method described in the following examples.

[0017] The absorbance A(295) and A(360) of the polarizer 12 represent the content of iodide ions I3- in the polarizer 12. The larger the absorbance value, the greater the amount of iodide ions I3- contained in the polarizer 12. The iodine components in the polarizer 12 include, for example, I-, I2, I3-, I5-, I3--PVA complexes, and I5--PVA complexes. It is generally believed that I-, I2, I3-, I3--PVA complexes, and I5--PVA complexes are present in the polarizer 12. The inventors have discovered that the iodide ions I3- in these iodine components are easily transferred from the polarizer 12 to the retardation layer 15 under high temperature and high humidity conditions, which affects the phase difference value and reflected hue of the optical stack 1. Since the polarizer 12 contained in the optical stack 1 has a smaller absorbance A(295) and absorbance A(360), the amount of iodine ions I3- in the polarizer 12 is relatively small. Therefore, even when the optical stack 1 is kept in a high temperature and high humidity environment (for example, kept in a high temperature and high humidity environment of 65°C and 90%RH for 168 hours), the amount of iodine ions I3- transferred from the polarizer 12 to the retardation layer 15 can be suppressed. In this way, when the optical stack 1 is kept in a high temperature and high humidity environment, the change in phase difference value can be suppressed before and after the holding, thereby suppressing the change in reflected hue, and thus reducing the amount of change in reflected hue before and after the holding.

[0018] The transmittance Tr(295) of the polarizer 12 at a wavelength of 295 nm can be, for example, 13.5 or more, or 16.0 or more, or 18.0 or more, or 20.0 or more, or 24.0 or more, but is typically 56.0 or less. The transmittance Tr(360) of the polarizer 12 at a wavelength of 360 nm can be, for example, 28.5 or more, or 30.0 or more, or 32.0 or more, or 33.0 or more, but is typically 56.0 or less. The transmittance of the polarizer 12 can be measured by the method described in the following examples.

[0019] The chromaticity of the polarizer, i.e., the monomer b, can be 2.0 or higher, or 2.3 or higher, or 4.5 or lower, or 4.3 or lower, or 4.0 or lower. The monomer b of the polarizer can be measured by the method described in the following examples.

[0020] The thickness of the polarizer 12 is not particularly limited, but it is preferably less than 25μm, but can also be less than 20μm, less than 15μm, or less than 12μm. It is usually more than 5μm, but can also be more than 7μm.

[0021] Figures 2 and 3 are cross-sectional views illustrating an example of a method for manufacturing a polarizer 12 in the optical laminate 1 of this embodiment. The polarizer 12 having the aforementioned absorbance and transmittance can be obtained, for example, by the following methods: [i] adjusting the drying conditions of a drying process performed while the protective film 11 is bonded to the raw polarizer 22 via an adhesive (adhesive or binder) 23 (Figure 2), or [ii] performing a wet heat treatment while the raw polarizer 22 is bonded with the protective film 40 (Figure 3), and then peeling off the protective film 40 after the wet heat treatment. The protective film 40 is formed on a substrate film 43 with a third adhesive layer 42, and is bonded to the raw polarizer 22 via the third adhesive layer 42.

[0022] In the case described in [i] above, the protective film 11 bonded to one side of the raw material polarizer 22 via the adhesive 23 can be dried as shown in FIG2, and the protective film bonded to both sides of the raw material polarizer 22 via the adhesive can also be dried. The adhesive 23 can form the bonding layer 13 directly or through drying or hardening processes, depending on its type. Therefore, when drying or hardening is required when forming the bonding layer 13 from the adhesive 23, the drying process described in [i] above can also be used for forming the bonding layer 13 from the adhesive 23. By performing the drying process as described in [i] above, a polarizer 12 with the above-mentioned absorbance can be obtained. The protective film 11 bonded to the raw material polarizer 22 can be directly assembled into the optical laminate 1.

[0023] In the case described in [i] above, the drying process can be carried out in one or more stages, preferably in two stages. The drying conditions for the first stage of the drying process depend on the type and thickness of the adhesive 23, but for example, the temperature can be set to 50±10℃ and the drying time to 75±20 seconds. Similarly, the drying conditions for the second stage can be set to 80±10℃ and the drying time to 75±20 seconds. Alternatively, the drying conditions for the first stage can be set to 50±5℃ and 75±10 seconds, and the drying conditions for the second stage can also be set to 80±5℃ and 75±10 seconds. The drying temperature for the second stage is preferably higher than that for the first stage; for example, the drying temperature for the second stage can be set to be 10℃ to 30℃ higher than that for the first stage. The drying time for the second stage can be the same as that for the first stage, or it can be shorter or longer.

[0024] In the case described in [ii] above, as shown in Figure 3, a raw material polarizing plate 20 with a protective film 11 bonded to one surface of the raw material polarizing plate 22 via an adhesive layer 13 can be prepared, and a laminate containing a protective film 40 bonded to the raw material polarizing plate 20 on the raw material polarizing plate 22 side can be subjected to a heat treatment. Alternatively, the raw material polarizing plate 20 can be subjected to a heat treatment, but the laminate containing the protective film 40 bonded to the raw material polarizing plate 22 can be subjected to a heat treatment. The raw material polarizing plate 20 containing the raw material polarizing plate 22 generally does not have the absorbance ranges described in [a] and [b] above.

[0025] The peeling of the protective film 40 after the hygrothermal treatment is preferably performed after the laminate that has undergone hygrothermal treatment has cooled. By attaching the protective film 40 to the raw material polarizer 22 and performing hygrothermal treatment, iodine ions I3- in the raw material polarizer 22 can move to the third adhesive layer 42 of the protective film 40. This reduces the amount of iodine ions I3- in the raw material polarizer 22, thus obtaining a polarizer 12 with the aforementioned absorbance. The protective film 11 attached to the raw material polarizer 22 can be directly assembled into the optical laminate 1.

[0026] In the case described in [ii] above, the damp heat treatment conditions can be, for example, set the temperature to 65±10℃, the relative humidity to 90±5%RH, and the treatment time to 50±5 hours. The temperature can be 65±7℃ or 65±5℃. The relative humidity can also be 90±3%RH. The treatment time can be 50±3 hours.

[0027] (Phase difference layer) The retardation layer 15 may be a cured layer of a polymeric liquid crystal compound, and in addition to the cured layer, it may also include an alignment film for controlling the alignment of the polymeric liquid crystal compound. The alignment film depends on the alignment direction of the polymeric liquid crystal compound, but may be, for example, a horizontal alignment film or a vertical alignment film. When the retardation layer 15 includes an alignment film, the cured layer side of the retardation layer 15 may be disposed on the side of the first adhesive layer 31, or the alignment film side of the retardation layer 15 may be disposed on the side of the first adhesive layer 31.

[0028] The retardation layer 15 can also be a λ / 4 retardation layer. In this case, the optical stack 1 can function as a circular polarizer. When the retardation layer 15 is a λ / 4 retardation layer, the absorption axis of the polarizer 12 and the slow axis of the retardation layer 15 are preferably stacked at an angle of 45±10° or 135°±10° in the optical stack 1. The angle can be within the range of 45°±5° or 135°±5°, or within the range of 45°±3° or 135°±3°, or 45° or 135°.

[0029] The thickness of the phase retardation layer 15 can be 0.1 μm or more, or 0.5 μm or more, or 1 μm or more, or 2 μm or more, and preferably 10 μm or less, or 8 μm or less, or 5 μm or less.

[0030] When the phase retardation layer 15 is a λ / 4 phase retardation layer, the optical stack 1 may, for example, have other phase retardation layers on the side of the phase retardation layer 15 opposite to the first adhesive layer 31. In this case, the other phase retardation layers may also be, for example, a λ / 2 phase retardation layer or a positive C layer.

[0031] When the optical stack 1 is a circular polarizer, the phase difference layer 15 can also be a λ / 2 phase difference layer or a positive C layer, and other phase difference layers can also be λ / 4 phase difference layers.

[0032] Other phase retardation layers may be extended films or hardened layers comprising polymerized and hardened polymeric liquid crystal compounds. When other phase retardation layers comprise the aforementioned hardened layers, they may also comprise alignment films for aligning the polymeric liquid crystal compounds.

[0033] When the other retardation layers are extended films, their thickness can be, for example, 5 μm or more, 10 μm or more, 15 μm or more, 20 μm or more, or less than 50 μm, 40 μm or less, or less than 30 μm. When the other retardation layers include the aforementioned hardened layer, the thickness of the other retardation layers can be 0.1 μm or more, 0.5 μm or more, 1 μm or more, 2 μm or more, and preferably less than 10 μm, or less than 8 μm, or less than 5 μm.

[0034] The following is a detailed description of the components that make up the optical laminate and the components used to manufacture the optical laminate. (Raw material polarizing film) The raw material polarizing film refers to the polarizing film before it undergoes drying or damp heat treatment. The raw material polarizing film is a polyvinyl alcohol resin film (hereinafter sometimes referred to as "PVA film") with iodine adsorption and orientation. At least one of the absorbance A(295) and A(360) of the raw material polarizing film is usually greater than the absorbance A(295) and / or A(360) of the polarizing film.

[0035] The raw material polarizing film can be manufactured through the following steps: a step of uniaxially stretching a PVA-based film; a step of dyeing the PVA-based film with an iodine aqueous solution as a dyeing solution to allow it to adsorb iodine; a step of treating the iodine-adsorbed PVA-based film with a boric acid aqueous solution; and a step of washing with water after treatment with boric acid aqueous solution.

[0036] Polyvinyl alcohol (PVA) resins are obtained by saponifying polyvinyl acetate (PVC) resins. Besides PVC, a homopolymer of PVC, copolymers of PVC and other monomers that can copolymerize with PVC can also be used as PVC resins. Examples of other monomers that can copolymerize with PVC include: unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides containing ammonium groups.

[0037] The degree of saponification of polyvinyl alcohol (PVA) resins is typically around 85 to 100 moles, preferably above 98 moles. PVA resins can also be modified; for example, aldehyde-modified polyvinylformaldehyde or polyvinyl acetal can be used. The degree of polymerization of PVA resins is typically around 1,000 to 10,000, preferably in the range of 1,500 to 5,000. The degree of saponification and average degree of polymerization of PVA resins can be determined according to JIS K6726 (1994).

[0038] Films made from this type of polyvinyl alcohol resin can be used as preforms for polarizing films. There are no particular limitations on the method for forming films from polyvinyl alcohol resins; known methods can be used. The film thickness of polyvinyl alcohol-based raw material films can be, for example, set to approximately 10 to 150 μm.

[0039] Uniaxial stretching of PVA films can be performed before, during, or after dyeing with anisotropic absorbent pigments. When uniaxial stretching is performed after dyeing, it can be performed before or during boric acid treatment. Furthermore, uniaxial stretching can be performed in multiple stages. During uniaxial stretching, it can be performed between rollers with different circumferential speeds, or it can be performed using hot rollers. Furthermore, uniaxial stretching can be dry stretching performed in the atmosphere, or wet stretching performed using a solvent while the PVA film is swollen. The stretching ratio is typically around 3 to 8 times.

[0040] The dyeing of PVA-based films using iodine is performed by immersing the PVA-based film in an iodine aqueous solution containing iodine and potassium iodide. The iodine content in the aqueous solution is typically about 0.01 to 1 part by mass relative to water per 100 parts by mass. Furthermore, The potassium iodide content relative to 100 parts by weight of water is typically around 0.5 to 20 parts by weight. The temperature of the iodine aqueous solution is typically around 20 to 40°C. Furthermore, the immersion time (staining time) in the iodine aqueous solution is typically around 20 to 1,800 seconds.

[0041] Boric acid treatment following staining with iodine aqueous solution is typically performed by immersing the stained PVA membrane in a boric acid aqueous solution. The boric acid content in this solution, relative to 100 parts by weight of water, is typically about 2 to 15 parts by weight, preferably 5 to 12 parts by weight. The boric acid aqueous solution preferably contains potassium iodide, in which case the potassium iodide content, relative to 100 parts by weight of water, is typically about 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight. The immersion time in the boric acid aqueous solution is typically about 60 to 1,200 seconds, preferably 150 to 600 seconds, and more preferably 200 to 400 seconds. The temperature for boric acid treatment is typically above 50°C, preferably 50 to 85°C, and more preferably 60 to 80°C.

[0042] PVA-based films treated with boric acid are typically subjected to a water washing process. This washing can be performed, for example, by immersing the boric acid-treated PVA-based film in water. The water temperature during the washing process is typically between 5 and 40°C, and the immersion time is typically between 1 and 120 seconds.

[0043] After washing, the material is dried to obtain a polarizing film. Drying can be performed using a hot air dryer or a far-infrared heater. The drying temperature is typically around 30 to 100°C, preferably 50 to 80°C. The drying time is typically around 60 to 600 seconds, preferably 120 to 600 seconds. Through drying, the moisture content of the polarizing film is reduced to a practical level. Its moisture content is typically around 5 to 20% by weight, preferably 8 to 15% by weight.

[0044] (Polarizing plate) As shown in Figure 1, the polarizer 12 can also be assembled onto the optical laminate 1 as a polarizing plate 10 with a protective film 11 on one or both sides of its surface. The protective film may also have anti-reflective properties, anti-glare properties, hard coating properties, etc. (Hereinafter, a protective film with these properties is sometimes referred to as a "functional protective film"). In the case where the protective film is not a functional protective film, a surface functional layer such as an anti-reflective layer, an anti-glare layer, or a hard coating layer may also be provided on one side of the polarizing plate. When the polarizing plate has a protective film only on one side of the polarizer, the surface functional layer may be provided on the protective film or on the polarizer.

[0045] (Protective film) Protective films, for example, are made from thermoplastic resins with excellent transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, and elongation.

[0046] Specific examples of such thermoplastic resins include: cellulose resins such as triacetyl cellulose; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polyether resins; polyether resins; polycarbonate resins; polyamide resins such as nylon or aromatic polyamides; polyimide resins; polyolefin resins such as polyethylene, polypropylene, and ethylene / propylene copolymers; cyclic polyolefin resins having cyclic and norcamphene structures (also known as norcamphene-based resins); (meth)acrylic resins; polyarylate resins; polystyrene resins; polyvinyl alcohol resins; and mixtures thereof. When a protective film is present on the double-layer surface of the polarizing film, the resin composition of the two protective films may be the same or different. Furthermore, in this specification, "(meth)acrylic acid" means either acrylic acid or methacrylic acid. The same applies to "(meth)acrylic acid" in (meth)acrylates, etc.

[0047] The thickness of the protective film is preferably 3 μm or more, and more preferably 5 μm or more. Furthermore, the thickness of the protective film is typically 100 μm or less, but can also be 70 μm or less, preferably 50 μm or less, and more preferably 30 μm or less. Moreover, the above upper and lower limits can be combined arbitrarily.

[0048] Furthermore, as a protective film, examples include hardened resins that are cured by irradiation with active energy rays such as ultraviolet light, also known as hardened layers. The thickness of the hardened layer is typically between 1 μm and 10 μm.

[0049] From the viewpoint of further reducing the amount of change in reflected hue, the protective film is preferably formed of cellulose resin. However, according to the optical laminate of this embodiment, even when using a cured layer of cyclic polyolefin resin, polyester resin, or active energy line curing resin, which tends to increase the amount of change in reflected hue, i.e., the protective film, the amount of change in reflected hue can be effectively suppressed.

[0050] (Protective film) As shown in Figure 3, the protective film 40 has a third adhesive layer 42 disposed on the substrate film 43. The substrate film may be formed, for example, from a thermoplastic resin used to form the protective film. The third adhesive layer may be formed from the following materials.

[0051] (First adhesive layer, second adhesive layer, third adhesive layer, bonding layer (adhesive layer)) The first adhesive layer, the second adhesive layer, the third adhesive layer, and the adhesive layer serving as an bonding layer (hereinafter, they are sometimes collectively referred to as "adhesive layers") are layers formed using adhesives. In this specification, "adhesive" refers to an adhesive that exhibits adhesion by adhering itself to the substrate, also known as a pressure-sensitive adhesive. As an adhesive, previously known adhesives with excellent optical transparency can be used without particular limitation, such as adhesives based on acrylic, urethane, polysiloxane, or polyvinyl ether polymers. The thickness of the adhesive layer can be 3 μm or more, 5 μm or more, 7 μm or more, 10 μm or more, or 35 μm or less, 30 μm or less, or 25 μm or less.

[0052] The adhesive layer may also contain additives such as antistatic agents using ultraviolet absorbers and ionic compounds, solvents, crosslinking catalysts, adhesive-improving resins (tackifiers), plasticizers, softeners, dyes, pigments, and inorganic fillers.

[0053] (Adhesive layer) The adhesive layer, serving as the bonding layer, can be formed by curing the curing component of the adhesive. The adhesive used to form the adhesive layer is any adhesive other than pressure-sensitive adhesives (adhesives), such as water-based adhesives like polyvinyl alcohol adhesives and UV-curing adhesives like UV-curing adhesives. The thickness of the adhesive layer is selected according to the type of adhesive; for example, it can be 0.05 μm or more, or 0.1 μm or more, or 0.5 μm or more, or 1 μm or more, or 3 μm or more, typically 20 μm or less, or 15 μm or less, or 10 μm or less, or 8 μm or less.

[0054] (Release film) The release film 33 shown in Figure 1 is designed to be peelable relative to the second adhesive layer 32, and is used to cover and protect the surface of the second adhesive layer 32. Examples of release films include those that perform a release treatment on a substrate film formed using a resin. The resin used to form the substrate film is not particularly limited; examples include polyethylene terephthalate, polybutylene terephthalate, polycarbonate, and polyarylate. Furthermore, any known release treatment can be performed on the substrate film; preferably, a method of coating the substrate film with a release agent such as a fluorinated compound or a polysiloxane compound is preferred. [Example]

[0055] The present invention will be described in more detail below with reference to embodiments, but the present invention is not limited to these embodiments.

[0056] [Damp heat durability test] The optical laminates obtained in the examples and comparative examples were cut into 30mm × 30mm pieces using a super cutter, and then bonded to a glass plate through the second adhesive layer of the optical laminate to prepare evaluation sample (1). The evaluation sample (1) was placed in an oven at 65°C and 90% RH for 168 hours to conduct a damp heat durability test on the optical laminate.

[0057] Furthermore, the hardened layer side of the retardation layer used in Example 1 was bonded to a glass plate through an acrylic adhesive layer (15 μm thick). Subsequently, an acrylic adhesive layer (25 μm thick) and a cyclic olefin (COP) film (manufactured by ZEON Corporation, Japan, ZF-14, 13 μm thick) were sequentially bonded to the horizontal alignment film side of the retardation layer to prepare evaluation sample (2). The evaluation sample (2) was placed in an oven at 65°C and 90% RH for 168 hours to conduct a damp heat durability test on the retardation layer.

[0058] [Determination of in-plane phase difference] The phase difference values ​​of the evaluation sample (1) before and after the damp heat durability test and the phase difference values ​​of the evaluation sample (2) before and after the damp heat durability test were measured using a phase difference measuring device (KOBRA-WPR manufactured by Oji Measurement & Testing Co., Ltd.).

[0059] [Determination of Reflected Hue] The reflected hue (a*b*) of the evaluation sample (1) before and after the damp heat durability test was determined in the following order. The evaluation sample (1) was placed on a reflector (MIRO (5011GP) manufactured by ALANOD Corporation), and the reflected hue was determined using a spectrophotometer (CM-2600d manufactured by Konica Minolta Corporation) with a light source of D65 using the SCI method (including positive reflection light). The reflector was a mirror reflector with a reflective surface formed by vapor deposition.

[0060] [Determination of absorbance and transmittance] The polarizing plates obtained in the examples and comparative examples were placed on a UV-2450 spectrophotometer (manufactured by Shimadzu Corporation), and the absorbance and transmittance were measured using the single-beam method in a wavelength range of 250 to 800 nm with a 1 nm step. The absorbance of the COP film attached to the polarizer at a wavelength of 295 nm was 0.06 and the transmittance was 87%, while the absorbance at a wavelength of 360 nm was 0.03 and the transmittance was 93%. Therefore, the absorbance A(295) and transmittance Tr(295) of the polarizer at a wavelength of 295 nm, and the absorbance A(360) and transmittance Tr(360) of the polarizer at a wavelength of 360 nm, were determined by correcting the absorbance and transmittance values ​​of the polarizing plate at each wavelength based on the absorbance and transmittance values ​​of the COP film at each wavelength.

[0061] [Determination of monomer beta] The monomer hue, i.e., monomer b, of the polarizing plates obtained in the examples and comparative examples was determined using a V7100 spectrophotometer with an integrating sphere (manufactured by Nippon Spectrophotometer Co., Ltd.). Since the COP film bonded to the polarizing film is colorless and transparent, the monomer b measured on the polarizing plate can be regarded as the monomer b of the polarizing film.

[0062] [Example 1] (Production of polarizing film) A polyvinyl alcohol-based resin film with a thickness of 20 μm, a degree of polymerization of 2,400, and a saponification degree of 99.9% or higher was dry-stretched uniaxially to a stretch ratio of 4.5 times. While under tension, it was immersed in a dyeing bath containing 0.05 parts by weight of iodine and 5 parts by weight of potassium iodide per 100 parts by weight of water for 60 seconds.

[0063] Then, it was immersed in a boric acid aqueous solution (1) containing 5.5 parts by weight of boric acid and 15 parts by weight of potassium iodide per 100 parts by weight of water for 110 seconds at a temperature of 64°C. Then, it was immersed in a boric acid aqueous solution (2) containing 5.5 parts by weight of boric acid and 15 parts by weight of potassium iodide per 100 parts by weight of water for 30 seconds at a temperature of 67°C. After that, it was washed with pure water at a temperature of 3°C and dried to obtain a polarizer.

[0064] (Production of polarizing plates) A cyclic olefin polymer (COP) film (manufactured by ZEON Corporation, Japan, ZF-14, 13 μm thick) was bonded to one side of the aforementioned polarizer using a roller clamping agent to obtain a laminate. The laminate was dried at 50°C for 75 seconds while maintaining a tension of 240 N / m, followed by drying at 80°C for 75 seconds to obtain the polarizer plate. The aforementioned aqueous adhesive was prepared by adding 3 parts by weight of carboxyl-modified polyvinyl alcohol (Kuraray Poval KL318 manufactured by Kuraray Corporation) and 1.5 parts by weight of water-soluble polyamide epoxy resin (Sumirez Resin 650 aqueous solution with a solid content of 30% manufactured by Taji Chemical Industry Co., Ltd.) to 100 parts by weight of water. The prepared polyvinyl alcohol adhesive was colorless and transparent, and its dried product was also colorless and transparent.

[0065] The polarizing plate obtained above has a layer composition of COP film / water-based adhesive layer / polarizer, with the thickness of the water-based adhesive layer less than 1 μm. The monomer b, absorbance, and transmittance of the obtained polarizing plate were measured, and corrected based on the absorbance and transmittance of the COP film to determine the absorbance A(295) and A(360) and transmittance Tr(295) and Tr(360) of the polarizer. Furthermore, the absorbance of the water-based adhesive layer is approximately 0, and the transmittance of the water-based adhesive layer is approximately 100%. The results are shown in Table 1.

[0066] (Fabrication of optical laminates) The polarizer side and the retardation layer of the obtained polarizing plate are bonded together through a first adhesive layer (acrylic adhesive layer, 5 μm thick). A second adhesive layer (acrylic adhesive layer, 15 μm thick) is then deposited on the retardation layer to obtain an optical laminate. The retardation layer is a laminate of a cured polymeric liquid crystal compound layer and a horizontal alignment film, with the cured layer side positioned on the polarizer side. The retardation layer is a λ / 4 retardation layer. The layer structure of the optical laminate is COP film / aqueous adhesive layer / polarizer / first adhesive layer / horizontal alignment film / cured polymeric liquid crystal compound layer / second adhesive layer. The angle between the absorption axis of the polarizer and the slow axis of the retardation layer is 45°. The obtained optical laminate was subjected to a damp heat durability test. Based on the reflectance hue value of the optical laminate before and after the damp heat durability test, the change in reflectance hue of the optical laminate before and after the damp heat durability test was calculated according to the following formula △a*b*. Aa*b*=(△a*2△b*2)1 / 2 [In the formula, △a*2=(a*back-a*front)2, △b*2=(b*back-b*front)2. a* before and a* after represent a* before and after the damp heat durability test, respectively. b* before and b* after represent b* before and after the damp heat durability test, respectively.

[0067] Furthermore, the phase difference at wavelength 550 nm after the damp heat durability test of the optical laminate was subtracted from the phase difference at wavelength 550 nm before the damp heat durability test. This value was taken as the change in the phase difference at wavelength 550 nm of the optical laminate before and after the damp heat durability test, ΔRe(550). The results are shown in Table 1.

[0068] [Comparative Example 1] The drying conditions for the laminate were set at 50°C for 75 seconds, followed by drying at 100°C for 75 seconds. Otherwise, a polarizing plate was fabricated in the same order as in Example 1, and an optical laminate was fabricated using this polarizing plate. The monomer b, absorbance A(295) and A(360), and transmittance Tr(295) and Tr(360) of the obtained polarizing plate were measured. The changes in reflected hue ΔA*b* and phase difference ΔRe(550) of the optical laminate before and after the damp heat durability test were calculated. The results are shown in Table 1.

[0069] [Comparative Example 2] The drying conditions for the laminate were set at 50°C for 75 seconds, followed by drying at 110°C for 75 seconds. Otherwise, a polarizing plate was fabricated in the same order as in Example 1, and an optical laminate was fabricated using this polarizing plate. The monomer b, absorbance A(295) and A(360), and transmittance Tr(295) and Tr(360) of the obtained polarizing plate were measured. The changes in reflected hue ΔA*b* and phase difference ΔRe(550) of the optical laminate before and after the damp heat durability test were calculated. The results are shown in Table 1.

[0070] [Reference Example 1] For the phase difference layer used in Example 1, the damp heat durability test of the evaluation sample (2) was performed in the order described above, and the change in phase difference value ARe (550) of the phase difference layer before and after the damp heat durability test was calculated. The results are shown in Table 1.

[0071] [Example 2] A protective film with a third adhesive layer was attached to the polarizer side of the polarizer obtained in Comparative Example 2 to obtain a polarizer with a protective film (PF). The protective film has a laminated structure of a substrate film and a third adhesive layer. The layer structure of the polarizer with the protective film (PF) is COP film / water-based adhesive layer / polarizer / third adhesive layer / substrate film. The polarizer with the protective film (PF) was placed in an oven at 65°C and 90% RH for 50 hours, then cooled and the protective film was peeled off.

[0072] Except for the polarizing plate after the protective film was peeled off, the optical laminate was fabricated in the same order as in Example 1. The monomer b, absorbance A (295) and A (360), and transmittance Tr (295) and Tr (360) of the obtained polarizing plate were measured, and the changes in reflected hue Δa*b* and phase difference ΔRe (550) of the optical laminate before and after the damp heat durability test were calculated. The results are shown in Table 1.

[0073] [Table 1]

[0074] 1: Optical stack 10:Polarizing plate 11: Protective film 12: Polarizing film 13: Adhesive layer 15: Phase Difference Layer 20: Raw material polarizing plate 22: Raw material polarizing film 23: Adhesive 31: First adhesive layer 32: Second adhesive layer 33: Peel-off membrane 40: Protective film 42: Third adhesive layer 43: Substrate film

Claims

1. An optical laminate, comprising, sequentially laminated, a polarizer having iodine adsorption and alignment to a polyvinyl alcohol-based resin film, a first adhesive layer, and a phase retardation layer, wherein, The polarizer has a protective film on the side opposite to the first adhesive layer. The polarizer is in direct contact with the first adhesive layer. The first adhesive layer is in direct contact with the retardation layer. The retardation layer contains a hardened layer of a polymeric liquid crystal compound. The polarizer satisfies at least one of the following [a] and [b]: [a] the absorbance A(295) at a wavelength of 295 nm is 0.85 or less, and [b] the absorbance A(360) at a wavelength of 360 nm is 0.55 or less.

2. The optical laminate as described in claim 1, wherein, The aforementioned polarizer satisfies [a] and [b] above.

3. The optical laminate as described in claim 1, wherein, The aforementioned phase difference layer is a λ / 4 phase difference layer.

4. The optical laminate as described in any one of claims 1 to 3, wherein, A second adhesive layer is further provided on the side opposite to the first adhesive layer side of the aforementioned phase difference layer.

5. The optical laminate as described in claim 1, wherein, The protective film is attached to the polarizer through an adhesive layer, which is an adhesive layer formed using a water-based adhesive.

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