Circularly polarizing plate, optical laminate, and image display device

Abstract

To provide a circularly polarizing plate having a novel configuration, a laminate comprising the same, and an image display device.SOLUTION: A circularly polarizing plate is provided, comprising a linearly polarizing plate and a cured liquid crystal layer, the linearly polarizing plate comprising a polarizer and a protective film laminated only on one surface of the polarizer, where the polarizer, the protective film, and the cured liquid crystal layer are arranged in the described order. The circularly polarizing plate also has a hard coat layer provided between the protective film and the cured liquid crystal layer, and a first adhesive layer provided between the hard coat layer and the cured liquid crystal layer. The protective film has a selective light absorbing property. An optical laminate comprising the circularly polarizing plate and an image display device are also provided.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a circularly polarizing plate, an optical laminate, and an image display device. [Background technology]

[0002] Among display devices typified by organic electroluminescence (EL) display devices, flexible displays that use flexible materials to enable the display device to be bent are known. It is known that organic EL display devices use circular polarizers or the like to improve anti-reflection performance in order to suppress a decrease in visibility due to reflection of external light (e.g., JP 2020-134934 A (Patent Document 1)). Circular polarizers can be obtained by laminating a linear polarizer and a retardation layer, and a cured layer of a polymerizable liquid crystal compound may be used as the retardation layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-134934 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a circularly polarizing plate having a new configuration, and an optical laminate and an image display device each including the same. [Means for solving the problem]

[0005] The present invention provides the following circularly polarizing plate, optical laminate, and image display device. [1] A circular polarizer comprising a linear polarizer and a cured liquid crystal layer, the linear polarizing plate includes a polarizer and a protective film laminated on only one surface of the polarizer, A circularly polarizing plate, comprising the polarizer, the protective film, and the cured liquid crystal layer arranged in this order. [2] The circularly polarizing plate according to [1], further comprising a hard coat layer between the protective film and the liquid crystal cured layer. [3] The circularly polarizing plate according to [1] or [2], wherein the polarizer has a boron content of 0.5% by mass or more and 5.5% by mass or less. [4] The circularly polarizing plate according to any one of [1] to [3], wherein the protective film is a cyclic polyolefin resin film. [5] The liquid crystal cured layer includes a first liquid crystal cured layer and a second liquid crystal cured layer, The circularly polarizing plate according to any one of [1] to [4], wherein the polarizer, the protective film, the first liquid crystal cured layer, and the second liquid crystal cured layer are arranged in this order. [6] The circularly polarizing plate according to any one of [1] to [5], wherein any layer other than the polarizer has light selective absorption properties. [7] The circularly polarizing plate according to any one of [1] to [6], comprising the polarizer, the protective film, the cured liquid crystal layer, and a pressure-sensitive adhesive layer in this order. [8] The circularly polarizing plate according to any one of [1] to [7], a front panel or a touch sensor panel; An optical laminate for a flexible image display device comprising: [9] An image display device comprising the circular polarizing plate according to any one of [1] to [7] or the optical laminate according to [8]. [Effects of the Invention]

[0006] It is possible to provide a circularly polarizing plate having a new configuration, as well as an optical laminate and an image display device including the same. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic cross-sectional view showing an example of a layer structure of a circularly polarizing plate according to the present invention. [Figure 2] FIG. 3 is a schematic cross-sectional view showing another example of the layer structure of the circularly polarizing plate according to the present invention. [Figure 3] FIG. 4 is a schematic cross-sectional view showing still another example of the layer structure of the circularly polarizing plate according to the present invention. [Figure 4]1 is a schematic cross-sectional view showing an example of a layer structure of an optical laminate according to the present invention. [Figure 5] FIG. 2 is a schematic cross-sectional view showing another example of the layer structure of the optical laminate according to the present invention. [Figure 6] FIG. 1 is an explanatory diagram illustrating microscopic Raman spectroscopy of a polarizing plate according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. All the drawings are shown to aid in understanding the present invention, and the size and shape of each component shown in the drawings do not necessarily correspond to the size and shape of the actual component.

[0009] <Circular polarizer> (1) Structure of the circular polarizer FIG. 1 is a schematic cross-sectional view showing an example of the layer structure of a circular polarizer according to the present invention (hereinafter also simply referred to as "circular polarizer"). The circular polarizer 1 shown in FIG. 1 includes a linear polarizer 10 and a retardation layer structure 20 which is a structure including a retardation layer. In the circular polarizer 1, the linear polarizer 10 and the retardation layer structure 20 are bonded to each other via a first bonding layer 30a. The retardation layer is a liquid crystal cured layer (a cured layer formed by polymerizing and curing a polymerizable liquid crystal compound). The term "circular polarizer" includes an elliptically polarizing plate. It is preferable that the circular polarizer used in the flexible image display device is bendable. "Bendable" means that the circular polarizer can be bent without causing cracks in the layers that make up the circular polarizer. Such a circular polarizer is required to be thinner in order to have good bending resistance (flexibility). Therefore, it is effective that the linear polarizer included in the circular polarizer is a so-called "one-sided protected polarizer" that has a protective film on only one side of the polarizer.

[0010] FIG. 2 is a schematic cross-sectional view showing another example of the layer structure of a circular polarizer, and shows a specific example of the layer structure of a linear polarizer 10 and a retardation layer structure 20. In the circular polarizer 2 shown in FIG. 2, the linear polarizer 10 and the retardation layer structure 20 are also bonded to each other via a first bonding layer 30a. As shown in FIG. 2, the linear polarizer 10 is a one-sided protected polarizer including a polarizer (linear polarizer) 101 and a protective film 102 laminated on only one side of the polarizer 101. The protective film 102 is laminated on the surface of the polarizer 101 facing the retardation layer structure 20. Although not shown, the protective film 102 is bonded to the polarizer 101 via an adhesive layer. In the circular polarizer 2, the outermost surface on the linear polarizer 10 side is the surface of the polarizer 101.

[0011] In the circular polarizer 2, a polarizer 101, a protective film 102, and a retardation layer structure 20 are arranged in this order, i.e., the polarizer 101, the protective film 102, and a liquid crystal hardened layer serving as a retardation layer are arranged in this order. In the circular polarizer 2, the retardation layer structure 20 includes, in this order from the linear polarizer 10 side, a first liquid crystal hardened layer 201, a second bonding layer 30b, and a second liquid crystal hardened layer 202. In order to bond the circular polarizer 2 to a display panel, for example, a third bonding layer 30c and a separate film 203 may be provided on the side of the second liquid crystal hardened layer 202 opposite to the second bonding layer 30b.

[0012] The layer structure of the circularly polarizing plate is not limited to the structure shown in FIG. a) The circular polarizer does not need to have either the first liquid crystal cured layer 201 or the second liquid crystal cured layer 202, and the retardation layer structure 20 only needs to have at least one liquid crystal cured layer (retardation layer). b) It may contain one or more alignment layers. c) The second bonding layer 30b may not be provided. d) A hard coat layer may be disposed between the protective film 102 and the first liquid crystal cured layer 201 (retardation layer structure 20).

[0013] FIG. 3 is a schematic cross-sectional view showing yet another example of the layer structure of a circular polarizer, illustrating specific examples of layer structures of a linear polarizer 11 and a retardation layer structure 20. In the circular polarizer 3 shown in FIG. 3, the linear polarizer 11 and the retardation layer structure 20 are also bonded to each other via a first bonding layer 30a. The circular polarizer 3 shown in FIG. 3 has a structure corresponding to d) above, and the linear polarizer 11 includes a polarizer (linear polarizer) 101, a protective film 102 laminated on only one side of the polarizer 101, and a hard coat layer 103 laminated on the surface of the protective film 102 facing the retardation layer structure 20. The protective film 102 is laminated on the surface of the polarizer 101 facing the retardation layer structure 20. Although not shown, the protective film 102 is bonded to the polarizer 101 via an adhesive layer. In the circular polarizer 3, the outermost surface facing the linear polarizer 11 is also the surface of the polarizer 101. 2, the circular polarizer 3 shown in FIG. 3 may also include a third bonding layer 30c and a separate film 203. In the case of the circular polarizer 2 shown in FIG.

[0014] When the circular polarizers 1, 2, and 3 are applied to an image display device such as an organic EL image display device, the circular polarizers 1, 2, and 3 are arranged so that the linear polarizers 10 and 11 are on the viewing side. In this case, as described above, the third bonding layer 30c can be used to bond the circular polarizers 1, 2, and 3 to the image display element (the separate film 203 is peeled off and removed). In other words, when the circular polarizers 1, 2, and 3 are applied to an image display device such as an organic EL image display device, the circular polarizers 1, 2, and 3 are arranged so that the retardation layer structure 20 is on the image display element side.

[0015] The circularly polarizing plate according to the present invention is advantageous in the following respects. A) The adhesion between the protective film 102 of the linear polarizer 10 and the first bonding layer 30a or the adhesion between the hard coat layer 103 of the linear polarizer 11 and the first bonding layer 30a is high, resulting in high durability of the circular polarizer. In particular, in a configuration in which the hard coat layer 103 and the first bonding layer 30a are in contact with each other, such as the circular polarizer 3 shown in Figure 3, good adhesion between these layers can be obtained even if the bonding surfaces are not subjected to corona treatment or even if the intensity of the corona treatment is low.

[0016] When corona treatment is performed over a long period of time, there is a problem that crystalline foreign matter (such as oxalic acid) adheres to the corona-treated material, resulting in a decrease in yield. It is also known that corona discharge generates ozone and nitrogen oxides (NOx). By being able to omit corona treatment or reduce the intensity of corona treatment, the above problems can be resolved or reduced.

[0017] B) When the polarizer 101 is a polyvinyl alcohol-based resin film in which iodine is adsorbed and aligned, the protective film 102 and further the hard coat layer 103 are present between the polarizer 101 and the image display element, and therefore, even when the circular polarizing plate of the present invention is held in a humid and hot environment, migration of iodine from the polarizer 101 to the image display element can be suppressed or prevented. This can suppress or prevent deterioration of the retardation layer structure 20, and when an input device such as a touch sensor panel is attached to the circular polarizing plate of the present invention, deterioration of the touch sensor panel or the like can be suppressed or prevented.

[0018] The elements that constitute or can constitute a circularly polarizing plate will be described in detail below. (2) Linear polarizer The linear polarizing plate includes a polarizer (linear polarizer) 101 and a protective film 102 laminated only on one side of the polarizer 101. The one side of the polarizer 101 is the surface of the polarizer 101 facing the retardation layer structure 20. The linear polarizing plate preferably includes the polarizer 101, a protective film 102 laminated only on one side of the polarizer 101, and a hard coat layer 103 laminated on the surface of the protective film 102 facing the retardation layer structure 20.

[0019] (2-1) Polarizer The polarizer 101 is an optical film that has the property of transmitting linearly polarized light having a vibration plane perpendicular to the absorption axis when unpolarized light is incident on the polarizer 101. The polarizer 101 is preferably a polyvinyl alcohol resin film (hereinafter also referred to as a "PVA film") in which iodine is adsorbed and oriented. The PVA film in which iodine is adsorbed and oriented, which is a preferred polarizer 101, will be described below.

[0020] The polarizer 101 may be, for example, a PVA film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or a partially saponified ethylene-vinyl acetate copolymer film, which has been dyed with iodine and uniaxially stretched. Preferably, the PVA film, which has been dyed to adsorb and align iodine, is treated with an aqueous boric acid solution, followed by a washing step in which the aqueous boric acid solution is washed away. Known methods can be used for each step.

[0021] Polyvinyl alcohol resins (hereinafter also referred to as "PVA resins") can be produced by saponifying polyvinyl acetate resins. Polyvinyl acetate resins can be polyvinyl acetate, which is a homopolymer of vinyl acetate, or a copolymer of vinyl acetate and another monomer copolymerizable with vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides having an ammonium group. In this specification, "(meth)acrylic" means either acrylic or methacrylic. The "(meth)" in (meth)acrylate has the same meaning.

[0022] The saponification degree of the PVA-based resin is usually about 85 to 100 mol %, preferably 98 mol % or more. The PVA-based resin may be modified; for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may also be used. The average polymerization degree of the PVA-based resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000. The average polymerization degree of the PVA-based resin can be determined in accordance with JIS K 6726 (1994). If the average polymerization degree is less than 1,000, it is difficult to obtain desirable polarizing performance, and if it exceeds 10,000, film processability may be poor.

[0023] The circularly polarizing plate of the present invention is particularly suitable for application to flexible image display devices. The thickness of each component constituting a circularly polarizing plate for application to such flexible image display devices is preferably small. The thickness of the polarizer 101 is usually 30 μm or less, preferably 15 μm or less, more preferably 13 μm or less, and even more preferably 10 μm or less. The thickness of the polarizer 101 is usually 2 μm or more, preferably 3 μm or more, and may be, for example, 5 μm or more.

[0024] To obtain polarizer 101 with a preferred thickness, a manufacturing method can be used in which a PVA-based film (thin film PVA-based film) with a thickness of about 15 to 40 μm is used as a starting material, and this thin film PVA film is dyed and uniaxially stretched to obtain polarizer 101. By using a thin film PVA-based film in advance, the thickness of the obtained polarizer 101 can be made thin (first manufacturing method).

[0025] A thin PVA-based film, which is preferred as a starting material, can also be realized as an extremely thin thin PVA-based film by forming a resin layer made of a PVA-based resin on a suitable substrate film (second manufacturing method). In this case, the manufacturing method for the thin PVA film may include the steps of preparing a substrate film, applying a solution of a resin such as a PVA-based resin (e.g., a PVA-based resin solution) onto the substrate film, and then drying to remove the solvent to form a resin layer on the substrate film. A primer layer can be formed in advance on the surface of the substrate film on which the resin layer is to be formed. As the substrate film, a film made of a thermoplastic resin that can be used for the protective film 102 described below can be used.

[0026] As described above, the thin PVA film, which is the starting material in the first or second production method, can be dyed and uniaxially stretched to form the polarizer 101. In the second production method, a PVA resin solution is applied to a substrate film, the amount of solvent such as water in the resin layer is adjusted as necessary, the substrate film and the resin layer are then uniaxially stretched, and the resin layer is then dyed with iodine to adsorb and align the iodine in the resin layer.

[0027] The PVA film that has been subjected to the dyeing treatment (iodine adsorption orientation) and uniaxial stretching treatment is preferably then subjected to a crosslinking treatment with boric acid. In the first production method, for example, after the dyeing treatment and uniaxial stretching treatment of the thin PVA film, the film may be brought into contact with a solution containing boric acid (boric acid-containing solution). A washing treatment may also be performed to wash off the boric acid-containing solution adhering to the surface of the film after such a crosslinking treatment.

[0028] The polarizer 101 obtained by the second production method is similar to that of the first production method. That is, the substrate film provided with the resin layer that has been subjected to the dyeing treatment and uniaxial stretching treatment can be subjected to a crosslinking treatment, for example, by contacting the substrate film as it is (without peeling off the substrate film) with a boric acid-containing solution. The substrate film provided with the resin layer after the crosslinking treatment can be subjected to a washing treatment, if necessary.

[0029] The boric acid-containing solution for crosslinking the PVA film or resin layer on which iodine is adsorbed and oriented is preferably a boric acid-containing aqueous solution. The amount of boric acid in the boric acid-containing aqueous solution is typically about 2 to 15 parts by mass, preferably about 5 to 12 parts by mass, per 100 parts by mass of water. This boric acid-containing aqueous solution preferably contains potassium iodide. The amount of potassium iodide in the boric acid-containing aqueous solution is typically about 0.1 to 15 parts by mass, preferably about 5 to 12 parts by mass, per 100 parts by mass of water. The immersion time in the boric acid-containing aqueous solution is typically about 60 to 1200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is typically 50°C or higher, preferably 50 to 85°C, and more preferably 60 to 80°C.

[0030] The PVA-based film, as well as the substrate film and resin layer, may be uniaxially stretched before dyeing, during dyeing, or during boric acid treatment after dyeing. Uniaxial stretching may be performed at each of these multiple stages. The total stretching ratio is usually 3 times or more, preferably 3.5 times or more, and more preferably 4 times or more. There is no particular upper limit to the stretching ratio, but from the viewpoint of preventing breakage, it is preferably 8 times or less, and more preferably 6 times or less.

[0031] The boron content of polarizer 101 is preferably 0.5% by mass or more, more preferably 1.5% by mass or more, even more preferably 2.5% by mass or more, and may be 3.5% by mass or more. A boron content of 0.5% by mass or more allows iodine to be stably retained, and an effect of suppressing a decrease in the polarization degree of polarizer 101 and, ultimately, an effect of improving the durability of the circular polarizing plate can be expected. The boron content of polarizer 101 is preferably 5.5% by mass or less, more preferably 5.0% by mass or less, and even more preferably 4.5% by mass or less. A boron content of 4.5% by mass or less allows shrinkage of polarizer 101 caused by heating to be suppressed.

[0032] The boron content in the polarizer 101 can be determined, for example, by dissolving a predetermined mass of the polarizer 101 in, for example, an aqueous mannitol solution and titrating the solution with an aqueous NaOH solution. A method for measuring the boron content in the polarizer 101 will be described in detail in the examples of the present application.

[0033] The boron content of polarizer 101 can be controlled by adjusting the boric acid concentration of the boric acid aqueous solution used in the boric acid treatment, or by adjusting the degree to which the boric acid aqueous solution is washed off in the washing step.

[0034] The "boric acid crosslinking index" of polarizer 101 is preferably 0.5 or more, more preferably 0.8 or more, and even more preferably 1.0 or more. In this specification, the "boric acid crosslinking index" refers to an index that indicates the degree to which polyvinyl alcohol molecular chains are crosslinked with boric acid in a polarizer made of a polyvinyl alcohol-based resin film or the like. The higher the boric acid crosslinking index, the more advanced the boric acid crosslinking between polyvinyl alcohol molecular chains in the polarizer. Having the boric acid crosslinking index of polarizer 101 within this range allows iodine to be stably retained. As a result, it becomes easier to prevent a decrease in the polarization degree of polarizer 101, which in turn improves the durability of the circular polarizing plate.

[0035] The boric acid crosslinking index of the polarizer 101 can be determined by micro-Raman spectroscopy. In the micro-Raman spectroscopy, a laser Raman spectrophotometer (product name: "NRS-5100", manufactured by JASCO Corporation) is used to measure the boric acid crosslinking index of the polarizer at a wave number of 780 cm. -1 Raman scattering intensity at 850 cm -1 The Raman scattering light intensity at each wavenumber is then calculated and divided by the Raman scattering light intensity at each wavenumber (wavenumber 780 cm). -1 Raman scattering light intensity at wavenumber 850cm -1 The boric acid crosslinking index can be calculated by measuring the Raman scattered light intensity at

[0036] FIG. 6 is an explanatory diagram for explaining microscopic Raman spectroscopy of the polarizing plate according to this embodiment. As shown in FIG. 6, in a laser Raman spectrophotometer, laser light is incident on the end face of the polarizer 101 so that the traveling direction of the laser light X and the absorption axis direction of the polarizer 101 are perpendicular to each other. Here, the laser light X is polarized in the thickness direction of the polarizer 101. The measurement position of the laser light is set to the center position in the thickness direction of the polarizer 101. It is preferable to process the cross section of the polarizing plate using a microtome before Raman spectroscopy measurement. Wavenumber 780 cm -1 The Raman scattering intensity at 850 cm is the Raman scattering intensity attributable to the bond between polyvinyl alcohol and boron. -1 The Raman scattered light intensity in the above means the Raman scattered light intensity attributed to polyvinyl alcohol.

[0037] The various conditions used in the above-mentioned microscopic Raman spectroscopic analysis are as follows: Excitation wavelength: 532 nm Grating: 600 l / mm Slit width: 100 x 1000 μm Aperture: φ40μm Objective lens: 100x Objective lens: 100x

[0038] The luminosity-corrected polarization degree Py of polarizer 101 is usually 95% or more, preferably 97% or more, more preferably 98% or more, even more preferably 98.7% or more, still more preferably 99.0% or more, particularly preferably 99.4% or more, and may be 99.9% or more. The luminosity-corrected polarization degree Py of polarizer 101 may be 99.99% or less. The luminosity-corrected polarization degree Py can be calculated by using an integrating sphere spectrophotometer ("V7100" manufactured by JASCO Corporation) to perform luminosity correction on the obtained polarization degree using a 2-degree visual field (C light source) according to "JIS Z 8701."

[0039] Increasing the luminous efficacy-corrected polarization degree Py of polarizer 101 is advantageous in improving the function of the circular polarizer as an antireflection film and the durability of the circular polarizer. If the luminous efficacy-corrected polarization degree Py of polarizer 101 is less than 95%, it may not function as an antireflection film.

[0040] The luminosity-corrected single transmittance Ty of the polarizer 101 is typically 41% or more, preferably 41.1% or more, more preferably 41.2% or more, and may be 42% or more, or 42.5% or more. The luminosity-corrected single transmittance Ty of the polarizer 101 is typically 50% or less, and may be 48% or less, 46% or less, 44% or less, or 43% or less. If the luminosity-corrected single transmittance Ty is excessively high, the luminosity-corrected polarization degree Py may become too low, and the circular polarizer may not function as an anti-reflection film. The luminosity-corrected single transmittance Ty can be calculated by using an integrating sphere spectrophotometer (JASCO Corporation's "V7100") to perform luminosity correction on the obtained transmittance using a 2-degree visual field (C light source) according to "JIS Z 8701."

[0041] (2-2) Protective film The protective film 102 laminated on one surface of the polarizer 101 is a film for protecting the polarizer, and may be, for example, a light-transmitting (preferably optically transparent) film made of a thermoplastic resin.

[0042] Thermoplastic resins include cellulose resins such as triacetyl cellulose; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polyethersulfone resins; polysulfone resins; polycarbonate resins; polyamide resins such as nylon and aromatic polyamide; polyimide resins; polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers; cyclic polyolefin resins having cyclo- and norbornene structures (also known as norbornene resins); (meth)acrylic resins; polyarylate resins; polystyrene resins; polyvinyl alcohol resins; and mixtures thereof.

[0043] The protective film 102 is preferably a cyclic polyolefin resin film, a polyethylene terephthalate film, or a polycarbonate film, and more preferably a cyclic polyolefin resin film.

[0044] It is preferable that protective film 102 has no retardation property or is a film with a small retardation value. Specifically, it is preferable that protective film 102 has an in-plane retardation value of 0 nm to 10 nm at a wavelength of 550 nm, and a retardation value in the thickness direction at a wavelength of 550 nm of -10 nm to +10 nm. When the circular polarizer of the present invention has hard coat layer 103 like circular polarizer 3, it is preferable that the laminate of protective film 102 and hard coat layer 103 is a film with a small retardation value as described above.

[0045] The thickness of the protective film 102 is preferably 2 μm or more, more preferably 3 μm or more, even more preferably 5 μm or more, and may be 10 μm or more. The thickness of the protective film 102 is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less.

[0046] The light transmittance of the protective film 102 for visible light is required to be a value that is common in the technical field of polarizing plates. For example, the light transmittance for visible light is preferably 85% or more, and more preferably 90% or more. When the circular polarizing plate of the present invention has a hard coat layer 103 like the circular polarizing plate 3, the laminate of the protective film 102 and the hard coat layer 103 preferably has the light transmittance as described above.

[0047] When the protective film 102 or a laminate of the protective film 102 and the hard coat layer 103 has a small retardation value and a high light transmittance, the luminous efficiency-corrected polarization degree Py and the luminous efficiency-corrected single transmittance Ty of the polarizer 101 can be replaced with the luminous efficiency-corrected polarization degree Py and the luminous efficiency-corrected single transmittance Ty of the polarizing plate 10 in which the polarizer 101 and the protective film 102 are laminated, or the polarizing plate 11 in which the polarizer 101, the protective film 102, and the hard coat layer 103 are laminated.

[0048] The distance from the surface of the polarizer 101 facing the retardation layer structure 20 to the surface of the retardation layer structure 20 facing the linear polarizers 10 and 11 is preferably 3 μm or more, more preferably 4 μm or more, even more preferably 5 μm or more, and still more preferably 10 μm or more, from the viewpoint of suppressing iodine migration. From the viewpoint of thinning and bending resistance (flexibility) of the circular polarizer, the distance is preferably 40 μm or less, more preferably 30 μm or less.

[0049] In the circular polarizing plate of the present invention, preferably, any layer other than the polarizer has light-selective absorption. One or more layers may have light-selective absorption. In the circular polarizing plate of the present invention, more preferably, a layer (protective film 102, hard coat layer 103, or first bonding layer 30a) between the polarizer 101 and the retardation layer structure 20, typically, a layer between the polarizer 101 and the liquid crystal cured layer 201, has light-selective absorption. One or more layers may have light-selective absorption. In this specification, "having light-selective absorption" preferably means having absorption for ultraviolet light with a wavelength of 350 nm or the like, more preferably having absorption for ultraviolet light with a wavelength of 350 nm or the like and short-wavelength visible light with a wavelength of around 410 nm.

[0050] The protective film 102 having selective light absorption, preferably having absorption for ultraviolet light with a wavelength of 350 nm or so, and more preferably having absorption for ultraviolet light with a wavelength of 350 nm or so and short-wavelength visible light with a wavelength of around 410 nm, is advantageous in the following respects. I) When the circularly polarizing plate is applied to an image display device, the image display element can be protected from ultraviolet rays and short-wavelength visible light. II) It is possible to suppress changes in the retardation value of the retardation layer structure 20 due to ultraviolet light or short-wavelength visible light. III) The reflection hue of the circular polarizer can be adjusted by absorbing short wavelength visible light. IV) The polarizer 101 can be prevented from being deteriorated by light reflected by an image display element such as an organic EL display element.

[0051] The protective film 102 may be imparted with selective light absorption properties by using a thermoplastic resin having selective light absorption properties as the thermoplastic resin constituting the protective film 102, by incorporating an additive (light absorber) having selective light absorption properties into the protective film 102, or by both. The protective film 102 is preferably imparted with selective light absorption properties by incorporating at least a light absorber into the protective film 102.

[0052] Specific examples of preferred light absorbents are listed below. Among light absorbents, from the viewpoint of the above-mentioned preferred light selective absorption, light absorbents for light with a wavelength of 350 nm (ultraviolet light) and light absorbents for light with a wavelength of 410 nm are preferably used in the present invention.

[0053] As a light absorber for 350 nm wavelength light, various ultraviolet absorbers are readily available on the market. Examples of such ultraviolet absorbers include organic ultraviolet absorbers such as oxybenzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, salicylic acid ester-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, and triazine-based ultraviolet absorbers. More specifically, 5-chloro-2-(3,5-di-sec-butyl-2-hydroxyphenyl)-2H-benzotriazole, (2-2H-benzotriazol-2-yl)-6-(linear and branched chain dodecyl)-4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc.

[0054] The ultraviolet absorber may be a commercially available product. Examples of such commercially available products include triazine-based ultraviolet absorbers such as "Kemisorb 102" manufactured by Chemipro Chemical Co., Ltd., "ADK STAB LA46" and "ADK STAB LAF70" manufactured by ADEKA Corporation, and "TINUVIN 109", "TINUVIN 171", "TINUVIN 234", "TINUVIN 326", "TINUVIN 327", "TINUVIN 328", "TINUVIN 928", "TINUVIN 400", "TINUVIN 460", "TINUVIN 405", and "TINUVIN 477" (all trade names) manufactured by BASF Japan Ltd. Examples of benzotriazole-based ultraviolet absorbers include "ADK STAB LA31" and "ADK STAB LA36" (all trade names) manufactured by ADEKA CORPORATION, "SUMISORB 200," "SUMISORB 250," "SUMISORB 300," "SUMISORB 340," and "SUMISORB 350" (all trade names) manufactured by Sumika Chemtex Corporation, "Kemisorb 74," "Kemisorb 79," and "Kemisorb 279" (all trade names) manufactured by Chemipro Chemical Co., Ltd., and "TINUVIN 99-2," "TINUVIN 900," and "TINUVIN 928" (all trade names) manufactured by BASF. Two or more types of ultraviolet absorbers may be used in combination in the circular polarizing plate of the present invention, and different light absorbers may be used in multiple layers constituting the circular polarizing plate of the present invention.

[0055] The ultraviolet absorber may be an inorganic ultraviolet absorber. Examples of inorganic ultraviolet absorbers include titanium oxide, zinc oxide, indium oxide, tin oxide, talc, kaolin, calcium carbonate, titanium oxide-based composite oxides, zinc oxide-based composite oxides, ITO (tin-doped indium oxide), and ATO (antimony-doped tin oxide). Examples of titanium oxide-based composite oxides include zinc oxide doped with silica and alumina. Two or more of these inorganic ultraviolet absorbers may be used in combination, and may be used in combination with, for example, the commercially available light absorbers (organic ultraviolet absorbers) listed above.

[0056] As a light absorber for light with a wavelength of 410 nm, a compound having a maximum absorption wavelength in the wavelength band of 360 to 430 nm can be synthesized by a known method and used in the present invention. For example, compounds known as photoselective absorbing compounds described in JP 2017-120430 A can be used as such a light absorber. It is preferable to include a compound having at least one absorption maximum in the wavelength range of 360 to 420 nm, and more preferably a compound having an absorption maximum in the wavelength range of 380 to 410 nm.

[0057] The amount of light absorber used is selected so as not to significantly impair the light transmittance of the layer containing the light absorber for visible light rays. For example, when the mass of the layer is taken as 100 parts by mass, the amount of light absorber contained in the layer is usually 0.01 to 20 parts by mass, preferably 0.05 to 15 parts by mass, and more preferably 0.1 to 10 parts by mass.

[0058] In the circular polarizing plate of the present invention, the laminate (protective film 102, hard coat layer 103 and first bonding layer 30a) between the polarizer and the liquid crystal cured layer has an absorbance of preferably 0.5 or more, more preferably 1.0 or more at a wavelength of 350 nm, and an absorbance of preferably 0.2 or more, more preferably 0.5 or more at a wavelength of 410 nm.

[0059] In another embodiment, in the circularly polarizing plate of the present invention, the laminate of layers excluding the polarizer (for example, a laminate consisting of the protective film 102, hard coat layer 103, first bonding layer 30a, first liquid crystal cured layer 201, second bonding layer 30b, second liquid crystal cured layer 202, and third bonding layer 30c), i.e., the laminate of layers present on the protective film side when the polarizer is used as the reference, has an absorbance at a wavelength of 350 nm of preferably 0.3 or more, more preferably 0.5 or more, more preferably 1.0 or more, even more preferably 2.0 or more, and particularly preferably 3.0 or more. The absorbance at a wavelength of 410 nm is preferably 0.2 or more, more preferably 0.5 or more, even more preferably 0.7 or more, and may usually be 2.0 or less, or 1.5 or less.

[0060] The protective film 102 can be laminated to the polarizer 101 via an adhesive layer. The adhesive forming the adhesive layer can be a water-based adhesive or an active energy ray-curable adhesive, which will be described later. Examples of water-based adhesives include adhesives in which a polyvinyl alcohol resin is dissolved or dispersed in water. The thickness of the adhesive layer between the protective film 102 and the polarizer 101 is typically 0.01 μm or more and typically 10 μm or less, which facilitates adhesion. As described above, when the circular polarizer of the present invention is used in a flexible image display device, the thinner the thickness of each component constituting the circular polarizer, the better. However, if the adhesive layer is too thin, the desired adhesiveness may be impaired. Therefore, the thickness of the adhesive layer is optimized taking into consideration the flexibility of the circular polarizer of the present invention when used in a flexible image display device and the adhesiveness between the polarizer 101 and the protective film 102.

[0061] (2-3) Hard Coat Layer The circularly polarizing plate may further have a hard coat layer 103 between the protective film 102 and the liquid crystal cured layer (retardation layer structure 20). The hard coat layer 103 is preferably laminated on the surface of the protective film 102 on the retardation layer structure 20 side, and more preferably directly laminated on that surface.

[0062] The hard coat layer 103 can be formed by curing a hard coat composition containing a reactive material that forms a crosslinked structure upon irradiation with active energy rays or thermal energy. The hard coat composition is preferably one that is cured upon irradiation with active energy rays. In this specification, "active energy rays" include visible light, ultraviolet rays, infrared rays, X-rays, α rays, β rays, γ rays, electron beams, etc., and preferably ultraviolet rays.

[0063] The hard coat composition contains at least one polymer of a radically polymerizable compound and a cationic polymerizable compound. The radically polymerizable compound is a compound having a radically polymerizable group. The radically polymerizable group of the radically polymerizable compound may be any functional group capable of undergoing a radical polymerization reaction, such as a group containing a carbon-carbon unsaturated double bond. Specific examples include a vinyl group and a (meth)acryloyl group.

[0064] As the radical polymerizable compound, compounds having a (meth)acryloyl group are preferred from the viewpoint of high reactivity, and compounds called polyfunctional acrylate monomers having 2 to 6 (meth)acryloyl groups in one molecule, and oligomers having several (meth)acryloyl groups in one molecule and molecular weights of several hundred to several thousand, called epoxy (meth)acrylates, urethane (meth)acrylates, and polyester (meth)acrylates, are preferably used. Preferably, the compound contains one or more selected from epoxy (meth)acrylates, urethane (meth)acrylates, and polyester (meth)acrylates.

[0065] The cationically polymerizable compound is a compound having a cationically polymerizable group such as an epoxy group, an oxetanyl group, a vinyl ether group, etc. The cationically polymerizable compound is preferably a compound having at least one of an epoxy group and an oxetanyl group as the cationically polymerizable group.

[0066] Examples of the cationically polymerizable compound having an epoxy group include alicyclic epoxy resins obtained by epoxidizing polyglycidyl ethers of polyhydric alcohols having an alicyclic ring or cyclohexene ring- or cyclopentene ring-containing compounds with a suitable oxidizing agent such as hydrogen peroxide or peracid; aliphatic epoxy resins such as polyglycidyl ethers of aliphatic polyhydric alcohols or their alkylene oxide adducts, polyglycidyl esters of aliphatic long-chain polybasic acids, and glycidyl (meth)acrylate homopolymers and copolymers; and glycidyl ethers and novolac epoxy resins produced by reacting bisphenols such as bisphenol A, bisphenol F, and hydrogenated bisphenol A, or derivatives thereof such as alkylene oxide adducts or caprolactone adducts, with epichlorohydrin, and glycidyl ether-type epoxy resins derived from bisphenols.

[0067] The hard coat composition may further contain a polymerization initiator. Examples of the polymerization initiator include a radical polymerization initiator, a cationic polymerization initiator, and a combination thereof. These polymerization initiators are decomposed by at least one of active energy ray irradiation and heating to generate radicals or cations, thereby promoting radical polymerization and cationic polymerization.

[0068] Active energy ray radical polymerization initiators include Type 1 radical polymerization initiators, which generate radicals through molecular decomposition, and Type 2 radical polymerization initiators, which generate radicals through a hydrogen abstraction reaction in the presence of a tertiary amine. These can be used alone or in combination. Thermal radical polymerization initiators include organic peroxides such as hydrogen peroxide and perbenzoic acid, and azo compounds such as azobisbutyronitrile. Cationic polymerization initiators include aromatic iodonium salts, aromatic sulfonium salts, and cyclopentadienyl iron(II) complexes.

[0069] The content of the polymerization initiator is, for example, 0.1 to 10% by mass relative to the entire hard coat composition (100% by mass). If the content of the polymerization initiator is less than 0.1% by mass, curing cannot proceed sufficiently, and the mechanical properties and adhesion of the finally obtained hard coat layer 103 may be insufficient.

[0070] The hard coat composition may further contain a solvent, additives, etc. Examples of additives include inorganic particles, leveling agents, stabilizers, surfactants, antistatic agents, lubricants, and antifouling agents.

[0071] The thickness of the hard coat layer 103 is preferably 0.5 μm or more, more preferably 1 μm or more, even more preferably 3 μm or more, and may be 5 μm or more, from the viewpoint of suppressing scratches that may occur during transport or processing of the circular polarizer of the present invention. The thickness of the hard coat layer 103 is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less, from the viewpoint of bending resistance (flexibility) and production efficiency.

[0072] The hard coat layer 103 may have light-selective absorption properties. At least one of the protective film 102 and the hard coat layer 103 preferably has light-selective absorption properties, and both may have light-selective absorption properties. The advantages of the hard coat layer 103 having light-selective absorption properties are the same as when the protective film 102 has light-selective absorption properties. The light-selective absorption properties can be imparted to the hard coat layer 103 by incorporating the above-mentioned light absorber into the hard coat layer 103.

[0073] A protective film 102 (hard-coat layer-attached protective film) having a hard-coat layer 103 containing a light-absorbing agent can be purchased from the market, and the hard-coat layer-attached protective film can be used as a component of the circular polarizer of the present invention as is. Similarly, a protective film 102 that does not have a hard-coat layer 103 but contains a light-absorbing agent can also be obtained. The content of the light-absorbing agent contained in such a protective film or hard-coat layer-attached protective film may be unknown. In such cases, the optimal one can be selected taking into consideration the light transmittance of the protective film or hard-coat layer-attached protective film to visible light.

[0074] (3) Retardation layer structure The retardation layer structure 20 is a structure including at least one liquid crystal cured layer (a cured layer formed by polymerizing and curing a polymerizable liquid crystal compound). As shown in Fig. 2 and Fig. 3, the retardation layer structure 20 preferably includes a first liquid crystal cured layer 201 and a second liquid crystal cured layer 202, and the circular polarizer preferably includes a polarizer 101, a protective film 102, the first liquid crystal cured layer 201, and the second liquid crystal cured layer 202 in this order from the viewing side.

[0075] The liquid crystal cured layer is a layer (retardation layer) having retardation properties, and is a cured product layer in which a polymerizable liquid crystal compound is polymerized and cured in an aligned state to exhibit retardation properties. The retardation layer structure 20 includes at least one liquid crystal cured layer, and may include two or more liquid crystal cured layers. When including two or more liquid crystal cured layers, the retardation layer structure 20 may include an attachment layer (second attachment layer 30b) for attaching these liquid crystal cured layers to each other.

[0076] The liquid crystal cured layer can be a half-wave retardation layer, a quarter-wave retardation layer, or a positive C-plate. The quarter-wave retardation layer may have reverse wavelength dispersion. When the retardation layer structure 20 includes two or more liquid crystal cured layers, the liquid crystal cured layers may have the same retardation properties or different retardation properties.

[0077] As described above, the retardation layer structure 20 preferably includes a first liquid crystal hardened layer 201 and a second liquid crystal hardened layer 202. The first liquid crystal hardened layer 201 and the second liquid crystal hardened layer 202 are, for example, a half-wave retardation layer and a quarter-wave retardation layer, respectively. Alternatively, one of the first liquid crystal hardened layer 201 and the second liquid crystal hardened layer 202 is a quarter-wave retardation layer with reverse wavelength dispersion, and the other is a positive C plate. For example, the first liquid crystal hardened layer 201 and the second liquid crystal hardened layer 202 are a quarter-wave retardation layer with reverse wavelength dispersion, and a positive C plate, respectively.

[0078] Examples of polymerizable liquid crystal compounds include rod-shaped polymerizable liquid crystal compounds and discotic polymerizable liquid crystal compounds. Either one of these may be used, or a mixture containing both may be used. When a rod-shaped polymerizable liquid crystal compound is aligned horizontally or vertically relative to the substrate layer, the optical axis of the polymerizable liquid crystal compound coincides with the long axis direction of the polymerizable liquid crystal compound. When a discotic polymerizable liquid crystal compound is aligned, the optical axis of the polymerizable liquid crystal compound is perpendicular to the disc surface of the polymerizable liquid crystal compound. Suitable rod-shaped polymerizable liquid crystal compounds include those described in, for example, JP-A-11-513019 (claim 1, etc.). Suitable discotic polymerizable liquid crystal compounds include those described in JP-A-2007-108732 (paragraphs

[0020] to

[0067] , etc.) and JP-A-2010-244038 (paragraphs

[0013] to

[0108] , etc.).

[0079] In order for the liquid crystal cured layer formed by polymerizing a polymerizable liquid crystal compound to exhibit in-plane retardation, the polymerizable liquid crystal compound may be aligned in an appropriate direction. When the polymerizable liquid crystal compound is rod-shaped, the in-plane retardation is exhibited by aligning the optical axis of the polymerizable liquid crystal compound horizontally relative to the plane of the substrate layer, in which case the optical axis direction and the slow axis direction coincide. When the polymerizable liquid crystal compound is disc-shaped, the in-plane retardation is exhibited by aligning the optical axis of the polymerizable liquid crystal compound horizontally relative to the plane of the substrate layer, in which case the optical axis and the slow axis are perpendicular to each other. The orientation state of the polymerizable liquid crystal compound can be adjusted by combining the alignment layer and the polymerizable liquid crystal compound.

[0080] A polymerizable liquid crystal compound is a compound having at least one polymerizable group and liquid crystallinity. When two or more polymerizable liquid crystal compounds are used in combination, it is preferable that at least one of the compounds has two or more polymerizable groups in the molecule. The polymerizable group refers to a group that participates in a polymerization reaction, and is preferably a photopolymerizable group. Here, the photopolymerizable group refers to a group that can participate in a polymerization reaction by an active radical or acid generated from a photopolymerization initiator, which will be described later. Examples of the polymerizable group include a vinyl group, a vinyloxy group, a 1-chlorovinyl group, an isopropenyl group, a 4-vinylphenyl group, an acryloyloxy group, a methacryloyloxy group, an oxiranyl group, an oxetanyl group, a styryl group, and an allyl group. Among these, an acryloyloxy group, a methacryloyloxy group, a vinyloxy group, an oxiranyl group, and an oxetanyl group are preferred, and an acryloyloxy group is more preferred. The liquid crystallinity of the polymerizable liquid crystal compound may be either thermotropic liquid crystal or lyotropic liquid crystal, and when thermotropic liquid crystal is classified by the degree of order, it may be either nematic liquid crystal or smectic liquid crystal.

[0081] The retardation layer structure 20 may include an alignment layer. The alignment layer has an alignment regulating force that aligns the polymerizable liquid crystal compound in a desired direction. The alignment layer may be a vertical alignment layer in which the molecular axis of the polymerizable liquid crystal compound is aligned vertically with respect to the substrate layer, a horizontal alignment layer in which the molecular axis of the polymerizable liquid crystal compound is aligned horizontally with respect to the substrate layer, or an inclined alignment layer in which the molecular axis of the polymerizable liquid crystal compound is aligned at an angle with respect to the substrate layer. When the retardation layer structure 20 includes two or more alignment layers, the alignment layers may be the same as or different from each other.

[0082] The alignment layer preferably has solvent resistance such that the liquid crystal layer-forming composition containing the polymerizable liquid crystal compound is not dissolved by coating or the like, and has heat resistance against heat treatment for removing the solvent and orienting the polymerizable liquid crystal compound. Examples of the alignment layer include an alignment polymer layer formed from an alignment polymer, a photoalignment polymer layer formed from a photoalignment polymer, and a groove alignment layer having a concavo-convex pattern or a plurality of grooves on the layer surface.

[0083] The thickness of the cured liquid crystal layer (first and second cured liquid crystal layer) may be 0.1 μm or more, 0.5 μm or more, 1 μm or more, or 2 μm or more, and is preferably 10 μm or less, and may be 8 μm or less, or 5 μm or less.

[0084] The liquid crystal cured layer can be formed by applying a liquid crystal layer-forming composition containing a polymerizable liquid crystal compound onto a base layer, drying the composition, and polymerizing the polymerizable liquid crystal compound. The liquid crystal layer-forming composition may be applied onto an alignment layer formed on the base layer.

[0085] The substrate layer can be a film formed from a resin material, such as a film made from the resin material described above as the thermoplastic resin used to form the protective film 102. The thickness of the substrate layer is not particularly limited, but is generally preferably 1 to 300 μm, more preferably 20 to 200 μm, from the standpoint of workability such as strength and ease of handling. The substrate layer may be incorporated into the circular polarizer together with the cured liquid crystal layer, or the substrate layer may be peeled off and only the cured liquid crystal layer, or the cured liquid crystal layer and the alignment layer, may be incorporated into the circular polarizer.

[0086] The second attaching layer 30b is a pressure-sensitive adhesive layer or an adhesive layer. The second attaching layer 30b is preferably an adhesive layer, more preferably an adhesive layer obtained by curing an active energy ray-curable adhesive, and even more preferably an adhesive layer obtained by curing an ultraviolet ray-curable adhesive. By using the second attaching layer 30b as an adhesive layer, it is possible to prevent the occurrence of wrinkles in the liquid crystal cured layer when the circularly polarizing plate is bent or folded, which is preferable. As the pressure-sensitive adhesive layer, those described below can be used.

[0087] Examples of the active energy ray-curable adhesive include solvent-free active energy ray-curable adhesives containing a curable compound that is cured by irradiation with active energy rays.

[0088] The active energy ray-curable adhesive preferably contains either or both of a cationically polymerizable curable compound and a radically polymerizable curable compound, as these exhibit good adhesive properties. The active energy ray-curable adhesive may further contain a cationic polymerization initiator, such as a photocationic polymerization initiator, or a radical polymerization initiator, for initiating the curing reaction of the curable compound.

[0089] Examples of the cationically polymerizable curable compound include epoxy compounds such as alicyclic epoxy compounds having an epoxy group bonded to an alicyclic ring, polyfunctional aliphatic epoxy compounds having two or more epoxy groups and no aromatic ring, monofunctional epoxy compounds having one epoxy group (excluding those included in alicyclic epoxy compounds), and polyfunctional aromatic epoxy compounds having two or more epoxy groups and an aromatic ring; oxetane compounds having one or more oxetane rings in the molecule; and combinations of these.

[0090] Examples of radically polymerizable curable compounds include (meth)acrylic compounds (compounds having one or more (meth)acryloyloxy groups in the molecule), other vinyl compounds having a radically polymerizable double bond, and combinations thereof.

[0091] The thickness of the second bonding layer 30b is not particularly limited. For example, it may be 2 μm or more and 30 μm or less, and preferably 3 μm or more and 20 μm or less. For example, it may be 10 μm or more, but from the viewpoint of further thinning, it is 15 μm or less, preferably 10 μm or less, and particularly preferably 7 μm or less. When the second bonding layer 30b is an adhesive layer, the thickness is preferably 0.1 μm or more, and may be 0.5 μm or more, and is preferably 10 μm or less, and may be 5 μm or less.

[0092] (4) First and third bonding layers The first bonding layer 30a is a pressure-sensitive adhesive layer or an adhesive layer, and is preferably a pressure-sensitive adhesive layer. The first bonding layer 30a bonds the linear polarizers 10 and 11 to the retardation layer structure 20. The third bonding layer 30c is usually a pressure-sensitive adhesive layer. The third bonding layer 30c can be used to bond the circular polarizer to an image display element. The circular polarizer preferably includes a polarizer 101, a protective film 102, a cured liquid crystal layer (a first cured liquid crystal layer, and a second cured liquid crystal layer), and a pressure-sensitive adhesive layer (the third bonding layer 30c) in this order, and more preferably includes a polarizer 101, a protective film 102, a hard coat layer 103, a cured liquid crystal layer (a first cured liquid crystal layer, and a second cured liquid crystal layer), and a pressure-sensitive adhesive layer (the third bonding layer 30c) in this order.

[0093] The thickness of the pressure-sensitive adhesive layer that is the first attaching layer 30a may be, for example, 2 μm or more and 30 μm or less, and preferably 3 μm or more and 20 μm or less. For example, it may be 10 μm or more, but in terms of further thinning, it is 15 μm or less, preferably 10 μm or less, and particularly preferably 7 μm or less. When the first attaching layer 30a is an adhesive layer, the thickness is preferably 0.1 μm or more, and may be 0.5 μm or more, and is preferably 10 μm or less, and may be 5 μm or less.

[0094] The first bonding layer 30a may have light-selective absorption properties. It is preferable that at least one layer of the protective film 102, the hard coat layer 103, and the first bonding layer 30a has light-selective absorption properties, and a plurality of layers among these may have light-selective absorption properties. The advantages of the first bonding layer 3aa having light-selective absorption properties are the same as when the protective film 102 has light-selective absorption properties. The light-selective absorption properties can be imparted to the first bonding layer 30a by incorporating the above-mentioned light absorbent into the first bonding layer 30a.

[0095] The thickness of the pressure-sensitive adhesive layer that is the third attaching layer 30c is not particularly limited and can be set appropriately depending on its use, but may be, for example, 250 μm or less, and from the viewpoint of thinning, preferably 100 μm or less, more preferably 50 μm or less, even more preferably 40 μm or less, particularly preferably 30 μm or less, and even more particularly preferably 20 μm or less. The lower limit of the thickness of the pressure-sensitive adhesive layer is not particularly limited, but from the viewpoint of durability, it may be, for example, 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 14 μm or more.

[0096] The adhesive may be a conventionally known adhesive having excellent optical transparency, such as an adhesive having a base polymer such as a (meth)acrylic, urethane, silicone, or polyvinyl ether base polymer. Alternatively, an active energy ray-curable adhesive or a thermosetting adhesive may be used. Among these, an adhesive having a (meth)acrylic resin as a base polymer is preferred, as it has excellent transparency, adhesive strength, removability (hereinafter also referred to as reworkability), weather resistance, heat resistance, and the like. The adhesive layer is preferably composed of a reaction product of an adhesive containing a (meth)acrylic resin, a crosslinking agent, and a silane compound, and may also contain other components.

[0097] The pressure-sensitive adhesive layer may be formed using an active energy ray-curable pressure-sensitive adhesive. The active energy ray-curable pressure-sensitive adhesive is prepared by blending an ultraviolet-curable compound such as a polyfunctional (meth)acrylate with the above-mentioned pressure-sensitive adhesive, forming a pressure-sensitive adhesive layer, and then curing the layer by irradiating it with ultraviolet light, thereby forming a harder pressure-sensitive adhesive layer. The active energy ray-curable pressure-sensitive adhesive has the property of being cured by irradiation with energy rays such as ultraviolet rays or electron beams. The active energy ray-curable pressure-sensitive adhesive has adhesiveness even before irradiation with energy rays, and therefore is a pressure-sensitive adhesive having the property of adhering to an adherend and curing by irradiation with energy rays, thereby adjusting the adhesive strength.

[0098] An active energy ray-curable pressure-sensitive adhesive generally contains a (meth)acrylic pressure-sensitive adhesive and an energy ray-polymerizable compound as main components, and usually further contains a cross-linking agent, and may also contain a photopolymerization initiator, a photosensitizer, etc., as needed.

[0099] (5) Separate film The circularly polarizing plate can include a separate film 203 for protecting the outer surface of the third bonding layer 30c. An example of the separate film 203 is a film in which a release treatment such as silicone treatment has been applied to the surface of the base film facing the third bonding layer 30c. The base film is, for example, a film made of a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, or a polyester-based resin such as polyethylene terephthalate.

[0100] <Optical laminate> The optical laminate according to the present invention (hereinafter also simply referred to as "optical laminate") includes the above-described circular polarizer according to the present invention and other components. Examples of the other components include an image display element 40 (see FIGS. 4 and 5) arranged on the liquid crystal cured layer side of the circular polarizer, i.e., the side opposite to the viewing side of the circular polarizer; a front panel 50 (see FIG. 5) arranged on the polarizer 101 side of the circular polarizer, more specifically, on the surface of the polarizer 101, which is the outermost surface of the circular polarizer; and a protective film (also referred to as a "surface protective film") for temporarily protecting the surface of the polarizer 101. The optical laminate preferably includes one or more members selected from the group consisting of a front panel 50 and an image display element 40 as the other components.

[0101] <Image display device> Circular polarizers 1, 2, and 3 are disposed on the front surface (viewing side) of an image display element and can be used as components of an image display device. Circular polarizers can also be used as anti-reflection polarizers that impart anti-reflection functionality to image display devices. The image display device is not particularly limited, and examples include organic electroluminescence (organic EL) display devices, inorganic electroluminescence (inorganic EL) display devices, liquid crystal display devices, and electroluminescence display devices. Hereinafter, the main aspects of an embodiment in which the circular polarizers of the present invention (circular polarizers 1, 2, and 3) are applied to an image display device, particularly a flexible image display device, will be briefly described.

[0102] The image display device may be a flexible image display device. The flexible image display device includes an optical laminate for a flexible image display device, which will be described later, and an organic EL display element, and is configured to be bendable, with the optical laminate for a flexible image display device being disposed on the viewing side of the organic EL display element.

[0103] <Optical laminate for flexible image display devices> The optical laminate for a flexible image display device comprises the circular polarizer of the present invention and an organic EL display element, which is a bending-resistant image display element. The optical laminate for a flexible image display device also has a bending-resistant front panel. Furthermore, a touch sensor panel may be provided as an input means. In this case, the stacking order of the circular polarizer, front panel, and touch sensor panel may be, for example, from the viewing side: front panel, circular polarizer, touch sensor panel. The stacking order is preferably front panel, touch sensor panel, and circular polarizer. The presence of a circular polarizer on the viewing side of the touch sensor panel is preferable because it makes the wiring pattern of the touch sensor panel less visible, improving the visibility of the displayed image. Each component can be stacked using an adhesive, pressure-sensitive adhesive, or the like. The optical laminate for a flexible image display device may also include a light-shielding pattern formed on at least one surface of any of the front panel, polarizer, and touch sensor panel layers.

[0104] <Front plate> In an image display device, a front panel can be disposed on the viewing side of the circular polarizing plate. The front panel can usually be laminated to the polarizer 101 of the circular polarizing plate of the present invention via a pressure-sensitive adhesive layer or an adhesive layer.

[0105] The front panel may be made of glass or a resin film, and may have a hard coat layer on at least one surface. Examples of glass that can be used include high-transmittance glass and tempered glass. When using a particularly thin transparent surface material, chemically tempered glass is preferred. The thickness of the glass can be, for example, 100 μm to 5 mm.

[0106] When the circularly polarizing plate of the present invention is applied to a flexible image display device, the front panel used is required to be flexible (flexible). From this viewpoint, the front panel is preferably made of a resin film, and as described above, may include a hard coat layer on at least one surface thereof. A front panel made of a resin film and including a hard coat layer can have flexible properties, rather than being rigid like existing glass. In this case, the thickness of the hard coat layer is not particularly limited as long as it does not impair the flexible properties, and may be, for example, 5 to 100 μm.

[0107] Examples of resin film materials used as the front panel include the same materials as those exemplified for the protective film 102. Of course, two or more materials may be used, as long as the film has a practical light transmittance. The thickness and other properties of such resin films can be optimized, taking into account light transmittance, flexibility, durability, and other factors. While a resin film without retardation (unstretched film) is preferred as the front panel, uniaxially or biaxially stretched films may also be used as long as they have an acceptable retardation value. Among these, preferred resin films for the front panel include polyamideimide or polyimide films, which have excellent transparency and heat resistance; uniaxially or biaxially stretched polyester films; cycloolefin derivative films, polymethyl methacrylate films, and triacetyl cellulose and isobutyl ester cellulose films, which are transparent and optically non-anisotropic and can accommodate larger films. The resin film thickness in this case may be 5 to 200 μm, preferably 20 to 100 μm.

[0108] <Light blocking pattern> The light-shielding pattern is disposed around a portion of the periphery of the image display surface of the image display device, known as a bezel, for reasons such as preventing the wiring from being visible when a viewer views an image from the image display surface side. Such a light-shielding pattern is formed on at least one surface of either the front panel or the circularly polarizing plate constituting the optical laminate for an image display device. When a touch sensor panel is attached to the optical laminate for an image display device as an input means, the light-shielding pattern may also be provided on the touch sensor panel. As described above, the light-shielding pattern can conceal the wiring of the display device, making it invisible to the user. The color and material of the light-shielding pattern are not particularly limited, and the pattern can be formed from a resin substance having a variety of colors, such as black, white, or gold. In one embodiment, the thickness of the light-shielding pattern may be 2 μm to 50 μm, preferably 4 μm to 30 μm, and more preferably 6 μm to 15 μm. Furthermore, the light-shielding pattern may be shaped to prevent air bubbles from being trapped between the light-shielding pattern and the display area and to prevent the boundary from being visible due to a step between the light-shielding pattern and the display area.

[0109] <Touch sensor panel> The image display device equipped with the circular polarizer of the present invention can further include a touch sensor as an input means. In this case, this can usually be achieved by incorporating a touch sensor panel. Various touch sensor types have been proposed, including resistive, surface acoustic wave, infrared, electromagnetic induction, and capacitive types, and any of these types is acceptable. Among these, capacitive types are preferred. A capacitive touch sensor is divided into an active area and an inactive area located on the outer periphery of the active area. The active area corresponds to the area where the screen is displayed on the display panel (the display section) and is the area where a user's touch is sensed. The inactive area corresponds to the area where the screen is not displayed on the display device (the non-display section). The touch sensor panel can include a flexible substrate; a sensing pattern formed in the active area of ​​the substrate; and sensing lines formed in the inactive area of ​​the substrate for connecting to an external driving circuit via the sensing pattern and pad section. The flexible substrate can be made of the same material as the transparent substrate of the front panel 50. The substrate for the touch sensor panel preferably has a toughness of 2,000 MPa% or more in order to prevent cracks that may occur in the touch sensor panel. The toughness is more preferably 2,000 MPa% to 30,000 MPa%. Here, toughness is defined as the area under the stress (MPa)-strain (%) curve up to the breaking point obtained through a tensile test of the polymer material.

[0110] 5 is an attachment layer for attaching front plate 50 to polarizer 101, which is the uppermost layer of the circular polarizer. The description of the adhesive layer described above applies to fourth adhesive layer 30d.

[0111] The optical laminate (including the case of an optical laminate for a flexible image display device) can include a protective film for temporarily protecting the surface of the polarizer 101. The protective film is composed of a substrate film and an adhesive layer laminated thereon. The adhesive layer is described above. The resin constituting the substrate film can be, for example, a thermoplastic resin such as a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, a polyester-based resin such as polyethylene terephthalate or polyethylene naphthalate, or a polycarbonate-based resin. A polyester-based resin such as polyethylene terephthalate is preferred.

[0112] The optical laminate (including the case where it is an optical laminate for a flexible image display device) and the circular polarizing plate according to the present invention can be suitably applied to image displays, particularly organic EL image displays. [Example]

[0113] The present invention will be explained in more detail below by showing examples and comparative examples, but the present invention is not limited to these examples.

[0114] <Measurement and evaluation methods> (1) Measurement of boron content in polarizers 0.2 g of polarizer was dissolved in 200 g of a 1.9% by mass mannitol aqueous solution. The resulting solution was titrated with a 1 mol / L NaOH aqueous solution, and the boron content (% by mass) of the polarizer was calculated by comparing the amount of NaOH solution required for neutralization with a calibration curve. The results are shown in Table 1.

[0115] (2) Calculation of boric acid crosslinking index The cross section of the polarizing plate was processed using an ultramicrotome (manufactured by LEICA, product name "LEICA Ultramicrotome EM UC7i") The central position in the thickness direction of the polarizer on the cross section of the obtained polarizing plate was measured using a laser Raman spectrophotometer (product name: "NRS-5100", manufactured by JASCO Corporation) under the following conditions at a wavenumber of 780 cm -1Raman scattering intensity at 850 cm -1 The Raman scattering light intensity at each wavenumber is then calculated and divided by the Raman scattering light intensity at each wavenumber (wavenumber 780 cm). -1 Raman scattering light intensity at wavenumber 850cm -1 The boric acid crosslinking index was calculated from the Raman scattered light intensity at 1000 kJ / cm2 (Raman scattered light intensity at 1000 kJ / cm2). The results are shown in Table 1. Excitation wavelength: 532 nm Grating: 600 l / mm Slit width: 100 x 1000 μm Aperture: φ40μm Objective lens: 100x Objective lens: 100x

[0116] (3) Measurement of moisture permeability of peelable film The moisture permeability was measured based on JIS Z 0208. The temperature and humidity conditions were a temperature of 40°C and a relative humidity of 90% RH.

[0117] (4) Measurement of single unit transmittance and luminosity-corrected polarization The single-piece transmittance and luminosity-corrected polarization degree of the circular polarizer were measured using a spectrophotometer with an integrating sphere (JASCO Corporation, V7100) with linearly polarized light incident on the polarizer side of the circular polarizer. MD transmittance and TD transmittance were measured over a wavelength range of 380 nm to 780 nm, and the single-piece transmittance and polarization degree at each wavelength were calculated using formulas (A) and (B). Furthermore, luminosity correction was performed using a 2-degree viewing angle (illuminant C) according to JIS Z8701 to determine the luminosity-corrected polarization degree (Py). Note that "MD transmittance" refers to the transmittance when the direction of the polarized light exiting a Glan-Thompson prism is parallel to the transmission axis of the polarizer sample. In formulas (A) and (B), "MD transmittance" is abbreviated as "MD." Furthermore, "TD transmittance" is the transmittance when the direction of polarized light exiting the Glan-Thompson prism is perpendicular to the transmission axis of the polarizing plate sample, and in formulas (A) and (B), "TD transmittance" is represented as "TD." Single transmittance (%) = (MD + TD) / 2 Formula (A) Degree of polarization (%)={(MD-TD) / (MD+TD)}×100 Formula (B)

[0118] (5) Heat resistance test of circular polarizer The circularly polarizing plate obtained in the example was cut into a rectangle measuring 140 mm x 70 mm. At this time, the cutting was performed so that the absorption axis of the polarizer and the short side of the rectangle were parallel. The cut circularly polarizing plate was attached to a 0.7 mm thick alkali-free glass (manufactured by Corning, product number: EAGLE XG (registered trademark)) via an adhesive layer (2) to prepare an evaluation sample. This evaluation sample was subjected to a heat resistance test in which it was stored under dry conditions at a temperature of 85°C for 500 hours, and the evaluation sample after the test was visually observed. The results were classified according to the following criteria and are summarized in Table 1.

[0119] [Heat resistance test evaluation criteria] A: No changes in appearance such as lifting, peeling, or foaming are observed. B: Changes in appearance such as lifting, peeling, and foaming are somewhat noticeable. C: Significant changes in appearance such as lifting, peeling, and foaming are observed.

[0120] (6) Humidity and heat durability test of circular polarizer The circularly polarizing plate obtained in the examples was cut into a square measuring 30 mm x 30 mm. At this time, the cutting was performed so that the absorption axis of the polarizer and the sides of the square were parallel to each other. The cut circularly polarizing plate was attached to a 40 mm x 40 mm alkali-free glass plate (manufactured by Corning Incorporated, product number: EAGLE XG (registered trademark)) via an adhesive layer (2), and further attached to a 40 mm x 40 mm alkali-free glass plate (manufactured by Corning Incorporated, product number: EAGLE XG (registered trademark)) on the polarizer surface via an adhesive layer to prepare an evaluation sample. The luminous efficiency-corrected polarization degree Py of this evaluation sample was measured.

[0121] Next, a humidity and heat durability test was performed on the evaluation samples, in which they were stored for 500 hours under conditions of a temperature of 60°C and a relative humidity of 95%RH. After the test, the luminosity-corrected polarization degree Py of the evaluation samples was measured. The luminosity-corrected polarization degree Py measured before and after the test, as well as the absolute value ΔPy of the difference between them, are listed in Table 1.

[0122] (7) Weather resistance test of circular polarizer The circularly polarizing plate obtained in the examples was cut into a square measuring 30 mm x 30 mm. At this time, the cutting was performed so that the absorption axis of the polarizer and the sides of the square were parallel to each other. The cut circularly polarizing plate was attached to a 40 mm x 40 mm alkali-free glass (manufactured by Corning, product number: EAGLE XG (registered trademark)) via an adhesive layer (2) to prepare an evaluation sample. The 450 nm single transmittance of this evaluation sample was measured.

[0123] Next, the evaluation sample was placed on an aluminum plate (reflector) so that it was exposed to ultraviolet light from the polarizer 101 side, and then placed in a Sunshine Weather Meter (manufactured by Suga Test Instruments Co., Ltd.) for 120 hours under conditions of a black panel temperature of 63°C and a relative humidity of 50% to perform a weather resistance test. After the test, the evaluation sample was measured for its 450 nm single transmittance. The absolute value of the difference in the 450 nm single transmittance measurements before and after the test is shown in Table 1.

[0124] (8) Measurement of absorbance of laminate A laminate was produced by laminating the protective film 102, hard coat layer 103, first attaching layer 30a, first liquid crystal cured layer 201, second attaching layer 30b, second liquid crystal cured layer 202, and third attaching layer 30c, excluding the polarizer 101. In addition, in layer configurations without a hard coat layer, the hard coat layer 103 was not laminated. The laminate was attached to glass via the third attaching layer 30c. A pressure-sensitive adhesive layer was attached to a cycloolefin polymer (COP) film (ZF-14 manufactured by Zeon Corporation), and then the COP film was attached to the protective film 102 via this pressure-sensitive adhesive layer. In this way, a laminate for evaluation was produced.

[0125] The evaluation laminate was set in a UV-2450 spectrophotometer (Shimadzu Corporation), and the absorbance was measured in 1 nm steps over the wavelength range of 300 to 800 nm using the double beam method. The absorbance at wavelengths of 350 nm and 410 nm for the prepared laminate is shown in Table 1. The combined absorbance of the glass and adhesive-backed COP film at wavelengths of 350 nm and 410 nm was 0.06 or less and therefore can be ignored.

[0126] <Preparation of components of circular polarizer> (1) Preparation of polarizer 1 A polyvinyl alcohol film having a thickness of 20 μm, a degree of polymerization of 2400, and a degree of saponification of 99% or more was uniaxially stretched to a stretching ratio of 4.1 times on a heated roll, and while maintaining tension, was immersed for 60 seconds at 28°C in a dye bath containing 0.05 parts by mass of iodine and 5 parts by mass of potassium iodide per 100 parts by mass of water.

[0127] Next, the film was immersed in a boric acid aqueous solution 1 containing 5.5 parts by mass of boric acid and 15 parts by mass of potassium iodide per 100 parts by mass of water at 64°C for 110 seconds. Next, the film was immersed in a boric acid aqueous solution 2 containing 5.5 parts by mass of boric acid and 15 parts by mass of potassium iodide per 100 parts by mass of water at 67°C for 30 seconds. Thereafter, the film was washed with pure water at 10°C and dried to obtain a polarizer 1. The polarizer 1 had a thickness of 8 μm and a boron content of 4.3% by mass.

[0128] (2) Preparation of polarizer 2 A polyvinyl alcohol film having a thickness of 20 μm, a degree of polymerization of 2400, and a degree of saponification of 99% or more was uniaxially stretched to a stretching ratio of 4.1 times on a heated roll, and while maintaining tension, was immersed for 60 seconds at 28°C in a dye bath containing 0.05 parts by mass of iodine and 5 parts by mass of potassium iodide per 100 parts by mass of water.

[0129] Next, the film was immersed in a boric acid aqueous solution 1 containing 5.5 parts by mass of boric acid and 15 parts by mass of potassium iodide per 100 parts by mass of water at 64°C for 110 seconds. Next, the film was immersed in a boric acid aqueous solution 2 containing 2.3 parts by mass of boric acid and 15 parts by mass of potassium iodide per 100 parts by mass of water at 67°C for 30 seconds. Thereafter, the film was washed with pure water at 10°C and dried to obtain a polarizer 2. The polarizer 2 had a thickness of 8 μm and a boron content of 3.2% by mass.

[0130] (3) Preparation of protective films A, B, C, D, E and peelable film F The following five types of protective films and one type of peelable film were prepared. Protective film A: Cycloolefin film (COP-HC) with a hard coat layer, 27 μm thick. The hard coat layer is 2 μm thick and has a moisture permeability of 10 g / m 2 -24 hours. Has UV absorption properties. Protective film B: 25 μm thick cycloolefin film (COP). Moisture permeability is 12 g / m 2 -24 hours. Has UV absorption properties. Protective film C: COP with a thickness of 23 μm. Does not absorb UV rays. Protective film D: 13 μm thick COP. UV absorbing. Protective film E: COP-HC with a thickness of 27 μm. It has UV absorption properties as well as short-wavelength visible light absorption properties around 410 nm. Peelable film F: TD80UL. Triacetyl cellulose film manufactured by Fujifilm Corporation. Thickness is 80 μm, moisture permeability is 502 g / m 2 It was 24 hours.

[0131] (4) Preparation of linear polarizer 1 Protective film A was attached to one surface of the prepared polarizer 1 via a water-based adhesive, and release film F was attached to the opposite surface of protective film A via pure water using a roll laminator, and then the resulting film was dried at 80°C for 3 minutes. Then, release film F was peeled from the polarizer to obtain linear polarizing plate 1 in which a protective film was laminated only on one surface of polarizer 1. Linear polarizing plate 1 was formed by laminating polarizer 1, an adhesive layer, and protective film A in this order.

[0132] (5) Preparation of linear polarizer 2 Linear polarizing plate 2 was produced in the same manner as polarizing plate 1, except that the temperature of the drying treatment after lamination using a roll laminator was changed to 100°C.

[0133] (6) Preparation of linear polarizer 3 A linear polarizing plate 3 was produced in the same manner as the linear polarizing plate 1, except that the polarizer 1 was changed to the polarizer 2.

[0134] (7) Preparation of linear polarizer 4 A linear polarizing plate 4 was prepared in the same manner as the linear polarizing plate 2, except that the polarizer 1 was changed to the polarizer 2.

[0135] (8) Preparation of linear polarizer 5 A linear polarizing plate 5 was produced in the same manner as in the linear polarizing plate 1, except that protective film A was changed to protective film B.

[0136] (9) Preparation of linear polarizer 6 A linear polarizing plate 6 was produced in the same manner as in the linear polarizing plate 1, except that protective film A was changed to protective film C.

[0137] (10) Preparation of linear polarizer 7 A linear polarizing plate 7 was produced in the same manner as in the linear polarizing plate 1, except that protective film A was changed to protective film D.

[0138] (11) Preparation of linear polarizer 8 A linear polarizing plate 8 was produced in the same manner as in the linear polarizing plate 1, except that protective film A was changed to protective film E.

[0139] (12) First Liquid Crystal Cured Layer A (Preparation of Half Wavelength Retardation Layer) A substrate layer made of a transparent resin was coated with an alignment layer-forming composition and dried to perform a λ / 2 alignment treatment. Next, a liquid crystal layer-forming composition containing a discotic polymerizable liquid crystal compound was coated on the alignment layer, and the alignment of the polymerizable liquid crystal compound was fixed by heating and UV irradiation, thereby forming a 1 / 2 wavelength retardation layer as a liquid crystal cured layer with a thickness of 2 μm on the alignment layer of the substrate layer.

[0140] (13) Second liquid crystal cured layer A (preparation of quarter-wave retardation layer) A liquid crystal layer-forming composition containing a rod-shaped nematic polymerizable liquid crystal compound (liquid crystal monomer) was applied to a rubbed alignment layer on a substrate layer formed from a transparent resin, and solidified while maintaining the refractive index anisotropy, thereby forming a quarter-wave retardation layer as a 1 μm-thick liquid crystal cured layer on the alignment layer of the substrate layer.

[0141] (14) Preparation of active energy ray curable adhesive A The following components were blended and mixed, and then degassed to prepare an active energy ray-curable adhesive A. [Cationic polymerizable compounds] Neopentyl glycol diglycidyl ether (product name: EX-211L, manufactured by Nagase ChemteX Corporation): 30 parts by mass 3-Ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane (trade name: OXT-221, manufactured by Toagosei Co., Ltd.): 13 parts by mass Bisphenol A epoxy resin (product name: EP-4100E, ADEKA Corporation, viscosity 13 Pa·s (temperature 25°C)): 12 parts by weight ·Aromatic-containing oxetane compound (product name: TCM-104, manufactured by TRONLY): 45 parts by mass [Cationic photopolymerization initiator] CPI-100P, manufactured by San-Apro Co., Ltd., 50% propylene carbonate solution: 2.25 parts by weight (solid content) [Photosensitizer] 1,4-diethoxynaphthalene: 1 part by mass

[0142] (15) Preparation of retardation layer structure A with substrate layer The surface of the first liquid crystal cured layer A (½ wavelength retardation layer) on the substrate layer and the surface of the second liquid crystal cured layer A (¼ wavelength retardation layer) on the substrate layer were each subjected to a corona treatment. The corona-treated surfaces of these two retardation layers were bonded together using the active energy ray-curable adhesive A prepared above so that the angle between the slow axes of these two retardation layers was 60°. Thereafter, an ultraviolet irradiation device (manufactured by Fusion UV Systems Co., Ltd.) was used to irradiate the quarter-wave retardation layer side with an integrated light dose of 400 mJ / cm. 2 The active energy ray-curable adhesive A was cured by ultraviolet irradiation with UV-B to form an adhesive layer. The lamination was performed using a laminator, and the active energy ray-curable adhesive A was applied so that the thickness of the adhesive layer after curing would be 3 μm. This resulted in a retardation layer structure A with a substrate layer, in which the substrate layer, alignment layer, ½ wavelength retardation layer (cured first liquid crystal layer), adhesive layer (second laminating layer), ¼ wavelength retardation layer (cured second liquid crystal layer), alignment layer, and substrate layer were laminated in this order. The total thickness of the ½ wavelength retardation layer (cured first liquid crystal layer), adhesive layer (second laminating layer), and ¼ wavelength retardation layer (cured second liquid crystal layer) was 6 μm.

[0143] (16) Preparation of first liquid crystal cured layer B (quarter wavelength retardation layer) An alignment layer was formed on a substrate layer made of a transparent resin, and a liquid crystal layer-forming composition containing a rod-shaped nematic polymerizable liquid crystal compound was applied to produce a first liquid crystal cured layer B. The first liquid crystal cured layer B had quarter-wave retardation properties. The thickness of the first liquid crystal cured layer B was 2 μm.

[0144] (17) Preparation of second liquid crystal cured layer B (positive C layer) An alignment layer-forming composition was prepared by dissolving 10.0 parts by weight of polyethylene glycol di(meth)acrylate, 10.0 parts by weight of trimethylolpropane triacrylate, 10.0 parts by weight of 1,6-hexanediol di(meth)acrylate, and 1.50 parts by weight of Irgacure 907 as a photopolymerization initiator in 70.0 parts by weight of methyl ethyl ketone as a solvent. Subsequently, a liquid crystal layer-forming composition was prepared by dissolving 20.0 parts by weight of a photopolymerizable nematic liquid crystal compound and 1.0 part by weight of Irgacure 907 as a photopolymerization initiator in 80.0 parts by weight of propylene glycol monomethyl ether acetate as a solvent.

[0145] One surface of the substrate layer was subjected to a corona treatment. The alignment layer-forming composition prepared above was applied to the corona-treated surface using a bar coater. The coated layer was heat-treated at 80°C for 60 seconds, and then irradiated with ultraviolet light to polymerize and harden the alignment layer-forming composition. In this way, an alignment layer with a thickness of 2.2 μm was formed on the substrate layer. The liquid crystal layer-forming composition prepared above was coated on the alignment layer. The coated layer was heat-treated at 80°C for 60 seconds, and then irradiated with ultraviolet light to polymerize and harden the liquid crystal layer-forming composition. In this way, a second liquid crystal cured layer B with a thickness of 0.7 μm was formed on the alignment layer. The second liquid crystal cured layer B was a positive C layer.

[0146] (18) Preparation of active energy ray curable adhesive B The components shown below were mixed to prepare an active energy ray-curable adhesive B. 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (trade name: CEL2021P, manufactured by Daicel Corporation): 70 parts by mass Neopentyl glycol diglycidyl ether (product name: EX-211, manufactured by Nagase ChemteX Corporation): 20 parts by mass 2-Ethylhexyl glycidyl ether (product name: EX-121, manufactured by Nagase ChemteX Corporation): 10 parts by mass Cationic polymerization initiator (product name: CPI-100, 50% solution, manufactured by San-Apro Co., Ltd.): 4.5 parts by mass (actual solid content: 2.25 parts by mass) 1,4-diethoxynaphthalene: 2.0 parts by mass

[0147] (19) Preparation of retardation layer structure B with substrate layer The first liquid crystal cured layer B and the second liquid crystal cured layer B were bonded together using an active energy ray-curable adhesive B (thickness: 1 μm) so that the liquid crystal cured layer surfaces (the surfaces opposite to the substrate film) became the bonding surfaces. The active energy ray-curable adhesive B was cured by irradiating with ultraviolet light to obtain a retardation layer structure B with a substrate layer, in which the substrate layer, alignment layer, first liquid crystal cured layer B, adhesive layer (second bonding layer), second liquid crystal cured layer B, alignment layer, and substrate layer were laminated in this order. The thickness of the retardation laminate including the first liquid crystal cured layer B, adhesive layer (second bonding layer), and second liquid crystal cured layer B was 6 μm. The retardation layer structure B with a substrate layer has ultraviolet absorption properties.

[0148] (20) Preparation of adhesive layer The following adhesive layers were prepared. Adhesive layer (1A): 5 μm thick acrylic adhesive layer Adhesive layer (1B): A 5 μm thick acrylic adhesive layer that absorbs short wavelength visible light around 410 nm. Adhesive layer (2): 15 μm thick adhesive layer

[0149] <Preparation of circular polarizing plate> Example 1 The substrate layer and alignment layer on the half-wave retardation layer side of the substrate layer-attached retardation layer structure A prepared above were peeled off to expose the half-wave retardation layer, which was then bonded to the protective film A side (the surface of the hard coat layer) of the linear polarizer 1 prepared above using a pressure-sensitive adhesive layer (1A) as a first bonding layer. The half-wave retardation layer and linear polarizer 1 were bonded together so that the angle between the slow axis of the half-wave retardation layer and the transmission axis of the polarizer 1 was 15°. Next, the alignment layer and substrate layer on the quarter-wave retardation layer side were peeled off to expose the quarter-wave retardation layer, and a pressure-sensitive adhesive layer (2) was bonded to the exposed quarter-wave retardation layer, to obtain a circular polarizer (1). Each bonding surface was subjected to a corona treatment.

[0150] Example 2 A circularly polarizing plate (2) was obtained in the same manner as in Example 1, except that corona treatment was not performed on the bonding surface of the protective film A of the linear polarizing plate 1 (the surface of the hard coat layer) and the bonding surface of the adhesive layer (1A).

[0151] Example 3 A circularly polarizing plate (3) was obtained in the same manner as in Example 1, except that the linearly polarizing plate 2 was used instead of the linearly polarizing plate 1.

[0152] Example 4 A circularly polarizing plate (4) was obtained in the same manner as in Example 1, except that the linearly polarizing plate 3 was used instead of the linearly polarizing plate 1.

[0153] Example 5 A circularly polarizing plate (5) was obtained in the same manner as in Example 1, except that the linearly polarizing plate 4 was used instead of the linearly polarizing plate 1.

[0154] Example 6 A circularly polarizing plate (6) was obtained in the same manner as in Example 1, except that the linearly polarizing plate 5 was used instead of the linearly polarizing plate 1.

[0155] Example 7 A circularly polarizing plate (7) was obtained in the same manner as in Example 1, except that the linearly polarizing plate 6 was used instead of the linearly polarizing plate 1.

[0156] Example 8 A circularly polarizing plate (8) was obtained in the same manner as in Example 1, except that the linearly polarizing plate 6 was used instead of the linearly polarizing plate 1 and the pressure-sensitive adhesive layer (1B) was used as the first attaching layer.

[0157] Example 9 A circularly polarizing plate (9) was obtained in the same manner as in Example 1, except that the linearly polarizing plate 7 was used instead of the linearly polarizing plate 1.

[0158] Example 10 A circularly polarizing plate (10) was obtained in the same manner as in Example 1, except that the linearly polarizing plate 8 was used instead of the linearly polarizing plate 1.

[0159] Example 11 The substrate layer on the first liquid crystal cured layer B side of the substrate layer-attached retardation layer structure B prepared above was peeled off to expose the first liquid crystal cured layer B, which was then bonded to the protective film C side of the linear polarizer 6 prepared above using a pressure-sensitive adhesive layer (1A) as a first bonding layer. The first liquid crystal cured layer B was bonded to the linear polarizer 6 so that the angle between the slow axis of the first liquid crystal cured layer B and the transmission axis of the polarizer 1 was 45°. Next, the substrate layer on the second liquid crystal cured layer B side was peeled off to expose the second liquid crystal cured layer B, which was then bonded to a pressure-sensitive adhesive layer (2) to obtain a circular polarizer (11). Each bonding surface was subjected to a corona treatment.

[0160] The obtained circularly polarizing plate was subjected to the above-mentioned heat resistance test, moist heat durability test, and weather resistance test. The results are shown in Table 1.

[0161] [Table 1] [Explanation of symbols]

[0162] 1, 2, 3 Circular polarizing plate, 4, 5 Optical laminate, 10, 11 Linear polarizing plate, 20 Retardation layer structure, 30a First bonding layer, 30b Second bonding layer, 30c Third bonding layer, 30d Fourth bonding layer, 40 Image display element, 50 Front plate, 101 Polarizer, 102 Protective film, 103 Hard coat layer, 201 First liquid crystal cured layer, 202 Second liquid crystal cured layer, 203 Separation film.

Claims

1. A circular polarizer including a linear polarizer and a cured liquid crystal layer, the linear polarizing plate includes a polarizer and a protective film laminated on only one surface of the polarizer, the polarizer, the protective film, and the liquid crystal cured layer are arranged in this order; a hard coat layer is further provided between the protective film and the liquid crystal cured layer, a first bonding layer between the hard coat layer and the liquid crystal cured layer; The protective film has light selective absorption properties.

2. 2. The circularly polarizing plate according to claim 1, wherein the polarizer has a boric acid crosslinking index of 1.0 or more and 1.3 or less.

3. 3. The circular polarizing plate according to claim 1, wherein the protective film is a cyclic polyolefin resin film.

4. the liquid crystal cured layer includes a first liquid crystal cured layer and a second liquid crystal cured layer, 4. The circularly polarizing plate according to claim 1, wherein the polarizer, the protective film, the first liquid crystal cured layer, and the second liquid crystal cured layer are arranged in this order.

5. 5. The circularly polarizing plate according to claim 1, comprising the polarizer, the protective film, the liquid crystal cured layer, and a pressure-sensitive adhesive layer in this order.

6. 6. The circularly polarizing plate according to claim 1, wherein the hard coat layer further has a selective light absorption property.

7. The circularly polarizing plate according to any one of claims 1 to 6, a front panel or a touch sensor panel; An optical laminate for a flexible image display device comprising:

8. An image display device comprising the circular polarizing plate according to any one of claims 1 to 6 or the optical laminate according to claim 7.

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