Circular polarizer, 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 circular polarizer, an optical laminate, and an image display device. [Background technology]

[0002] In display devices such as organic electroluminescent (EL) displays, flexible displays are known that use flexible materials to enable bending of the display device. In organic EL displays, it is known that anti-reflective performance is improved by using circular polarizers to suppress the decrease in visibility due to the reflection of ambient light [for example, Japanese Patent Application Publication No. 2020-134934 (Patent Document 1)]. Circular polarizers can be obtained by laminating a linear polarizer and a phase difference layer, and a cured layer of polymerizable liquid crystal compound may be used as the phase difference layer. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-134934 [Overview of the project] [Problems that the invention aims to solve]

[0004] The object of the present invention is to provide a circular polarizing plate having a novel configuration, as well as an optical laminate and an image display device containing the same. [Means for solving the problem]

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

[0006] This invention provides a circular polarizing plate having a novel configuration, as well as an optical laminate and an image display device containing the same. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic cross-sectional view showing an example of the layer structure of a circular polarizing plate according to the present invention. [Figure 2] This is a schematic cross-sectional view showing another example of the layer configuration of the circular polarizing plate according to the present invention. [Figure 3] This is a schematic cross-sectional view showing yet another example of the layer configuration of the circular polarizing plate according to the present invention. [Figure 4]It is a schematic cross-sectional view showing an example of the layer structure of the optical laminate according to the present invention. [Figure 5] It is a schematic cross-sectional view showing another example of the layer structure of the optical laminate according to the present invention. [Figure 6] It is an explanatory diagram for explaining microscopic Raman spectroscopic analysis for a polarizing plate according to the present invention.

Embodiments for Carrying Out 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 of the following drawings are shown to assist in understanding the present invention, and the sizes and shapes of each component shown in the drawings do not necessarily match the sizes and shapes of the actual components.

[0009] <Circular polarizing plate> (1) Configuration of the circular polarizing plate FIG. 1 is a schematic cross-sectional view showing an example of the layer structure of a circular polarizing plate (hereinafter, also simply referred to as "circular polarizing plate") according to the present invention. The circular polarizing plate 1 shown in FIG. 1 includes a linear polarizing plate 10 and a retardation layer structure 20 which is a structure including a retardation layer. In the circular polarizing plate 1, the linear polarizing plate 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 product layer obtained by polymerization curing of a polymerizable liquid crystal compound). The term "circular polarizing plate" includes an elliptical polarizing plate. In addition, the circular polarizing plate applied to a flexible image display device is preferably bendable. Being bendable means that it can be bent without causing cracks in the layers constituting the circular polarizing plate. Such a circular polarizing plate is required to be thinner for good bending resistance (flexibility). Therefore, as the linear polarizing plate included in the circular polarizing plate, a so-called "single-protection polarizing plate" having a protection film only on one side of the polarizer is effective.

[0010] FIG. 2 is a schematic cross-sectional view showing another example of the layer structure of a circular polarizing plate, and shows a specific example of the layer structure of the linear polarizing plate 10 and the retardation layer structure 20. In the circular polarizing plate 2 shown in FIG. 2, the linear polarizing plate 10 and the retardation layer structure 20 are also bonded to each other via the first bonding layer 30a. As shown in FIG. 2, the linear polarizing plate 10 is a single-sided protective polarizing plate including a polarizer (linear polarizer) 101 and a protective film 102 laminated only on one side of the polarizer 101. The protective film 102 is laminated on the surface of the polarizer 101 on the side of 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 polarizing plate 2, the outermost surface on the side of the linear polarizing plate 10 is the surface of the polarizer 101.

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

[0012] The layer structure of the circular polarizing plate is not limited to the structure shown in FIG. 2. For example, a) The circular polarizing plate may not have either the first liquid crystal cured layer 201 or the second liquid crystal cured layer 202, and the retardation layer structure 20 may have at least one liquid crystal cured layer (retardation layer). b) It may include one or more alignment layers. c) It may not have the second bonding layer 30b. 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] Figure 3 is a schematic cross-sectional view showing yet another example of the layer configuration of a circular polarizer, illustrating a specific example of the layer configuration of the linear polarizer 11 and the phase difference layer structure 20. In the circular polarizer 3 shown in Figure 3, the linear polarizer 11 and the phase difference layer structure 20 are bonded to each other via a first bonding layer 30a. The circular polarizer 3 shown in Figure 3 has a configuration corresponding to d) above, and the linear polarizer 11 includes a polarizer (linear polarizer) 101, a protective film 102 laminated only on one side of the polarizer 101, and a hard coat layer 103 laminated on the phase difference layer structure 20 side surface of the protective film 102. The protective film 102 is laminated on the side of the polarizer 101 facing the phase difference 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 as well, the outermost surface on the linear polarizer 11 side is the surface of the polarizer 101. Furthermore, similar to the circular polarizer 2 shown in Figure 2, the circular polarizer 3 shown in Figure 3 may also include a third bonding layer 30c and a separator film 203.

[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 side is 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 separator film 203 is peeled off and removed). That is, 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 phase difference layer structure 20 side is the image display element side.

[0015] The circular polarizer according to the present invention is advantageous in the following respects. A) The adhesion between the protective film 102 of the linear polarizing plate 10 and the first bonding layer 30a, or the adhesion between the hard coat layer 103 of the linear polarizing plate 11 and the first bonding layer 30a, is high, resulting in high durability of the circular polarizing plate. In particular, in a configuration where the hard coat layer 103 and the first bonding layer 30a are in contact, as shown in Figure 3 of the circular polarizing plate 3, good adhesion between these layers can be obtained even without applying corona treatment to these bonding surfaces or even with low corona treatment intensity.

[0016] When corona treatment is performed over a long period, crystalline foreign matter (such as oxalic acid) adheres to the treated material, leading to a decrease in yield. Furthermore, it is known that ozone and nitrogen oxides (NOx) are generated by corona discharge. By omitting corona treatment or reducing the intensity of corona treatment, the above problems can be resolved or mitigated.

[0017] B) If the polarizer 101 is a polyvinyl alcohol-based resin film on which iodine is adsorbed and oriented, the presence of a protective film 102 and a hard coat layer 103 between the polarizer 101 and the image display element suppresses or prevents the transfer of iodine from the polarizer 101 to the image display element, even if the circular polarizer of the present invention is held in a humid and hot environment. This suppresses or prevents the deterioration of the phase difference layer structure 20, and when an input device such as a touch sensor panel is bonded to the circular polarizer of the present invention, it suppresses or prevents the deterioration of the touch sensor panel, etc.

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

[0019] (2-1) Polarizer The polarizer 101 is an optical film that, when unpolarized light is incident on it, transmits linearly polarized light having a vibration plane perpendicular to the absorption axis. Preferably, the polarizer 101 is a polyvinyl alcohol-based resin film (hereinafter also referred to as "PVA-based film") on which iodine is adsorbed and oriented. The following describes a preferred polarizer 101, which is a PVA-based film on which iodine is adsorbed and oriented.

[0020] The polarizer 101 can be, for example, a PVA-based 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 subjected to iodine dyeing and uniaxial stretching. Preferably, the PVA-based film, on which iodine has been adsorbed and oriented by the dyeing treatment, is treated with an aqueous boric acid solution, and then a washing step is performed to wash off the aqueous boric acid solution. Known methods can be used for each step.

[0021] Polyvinyl alcohol-based resins (hereinafter also referred to as "PVA-based resins") can be produced by saponifying polyvinyl acetate-based resins. Polyvinyl acetate-based resins can be polyvinyl acetate, which is a homopolymer of vinyl acetate, or copolymers of vinyl acetate and other monomers 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 ammonium groups. In this specification, "(meth)acrylic" means either acrylic or methacrylic. The "(meth)" in (meth)acrylate, etc., has the same meaning.

[0022] The degree of saponification of PVA resins is typically around 85-100 mol%, preferably 98 mol% or higher. PVA resins may be modified; for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can also be used. The average degree of polymerization of PVA resins is typically around 1000-10000, preferably 1500-5000. The average degree of polymerization of PVA resins can be determined in accordance with JIS K 6726 (1994). If the average degree of polymerization is less than 1000, it is difficult to obtain desirable polarization performance, and if it exceeds 10000, film processability may be poor.

[0023] The circular polarizer of the present invention is particularly suitable for application to flexible image display devices. For application to such a flexible image display device, the thickness of each component constituting the circular polarizer is preferably thin. 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 a polarizer 101 of a desirable thickness, one manufacturing method involves using a PVA-based film (thin-film PVA-based film) with a thickness of approximately 15 to 40 μm as a starting material, and then subjecting this thin-film PVA-based film to dyeing and uniaxial stretching treatments to obtain the polarizer 101. By using a thin-film PVA-based film beforehand, the thickness of the resulting polarizer 101 can be reduced (first manufacturing method).

[0025] A thin-film PVA-based film, preferably made from a starting material, can also be made extremely thin by forming a resin layer made of PVA-based resin on a suitable substrate film (second manufacturing method). In this case, the manufacturing method for the thin-film PVA film may include the steps of preparing a substrate film, applying a resin solution such as PVA-based resin (PVA-based resin solution, etc.) onto the substrate film, and 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 formed. As the substrate film, a film made of a thermoplastic resin that can be used for the protective film 102 described later can be used.

[0026] As described above, the thin PVA film, which is the starting material in the first or second manufacturing method, can be transformed into a polarizer 101 by dyeing and uniaxial stretching. In the second manufacturing method, a PVA resin solution is applied to the base film, then the amount of solvent such as water in the resin layer is adjusted as needed, the base film and the resin layer are then uniaxially stretched, and subsequently the resin layer is dyed with iodine to adsorb and orient the iodine into the resin layer.

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

[0028] The polarizer 101 obtained by the second manufacturing method is the same as that obtained by the first manufacturing method. That is, the base film equipped with a resin layer that has undergone dyeing and uniaxial stretching treatments can be crosslinked by, for example, contacting it with a boric acid-containing solution in its original state (without peeling off the base film). The base film equipped with the resin layer after the crosslinking treatment can be washed as needed.

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

[0030] Uniaxial stretching of the PVA film, as well as the base film and resin layer, may be performed before dyeing, during dyeing, or during the boric acid treatment after dyeing, and 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 suppressing breakage, etc., it is preferably 8 times or less, and more preferably 6 times or less.

[0031] The polarizer 101 preferably has a boron content of 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 also have a boron content of 3.5% by mass or more. A boron content of 0.5% by mass or more allows for stable retention of iodine, which can be expected to suppress the decrease in polarization degree of the polarizer 101 and, consequently, improve the durability of the circular polarizer. The boron content of the 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 can suppress the shrinkage of the polarizer 101 caused by heating.

[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 it with an aqueous NaOH solution. The means for measuring the boron content of such a polarizer 101 will be described in detail in the embodiments of this application.

[0033] The boron content of the 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 the degree to which the boric acid aqueous solution is washed off in the cleaning process.

[0034] The "boric acid crosslinking index" of the polarizer 101 is preferably 0.5 or higher, more preferably 0.8 or higher, and even more preferably 1.0 or higher. In this specification, the "boric acid crosslinking index" refers to an index that represents the extent 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 value of the boric acid crosslinking index, the more advanced the boric acid crosslinking of the polyvinyl alcohol molecular chains is in the polarizer, and by having the boric acid crosslinking index of the polarizer 101 within this range, iodine can be stably retained. As a result, it becomes easier to prevent a decrease in the polarization degree of the polarizer 101, and consequently, the durability of the circular polarizer is easier to improve.

[0035] The boric acid crosslinking index of polarizer 101 can be determined by micro-Raman spectroscopy. In micro-Raman spectroscopy, a laser Raman spectrophotometer (product name: "NRS-5100", manufactured by JASCO Corporation) is used to determine the polarizer's wavenumber of 780 cm⁻¹. -1 Raman scattering light intensity at wavenumber 850 cm⁻¹ -1 The Raman scattering light intensity at each point is determined, and then these Raman scattering light intensities at wavenumbers are divided (wavenumber 780 cm). -1 Raman scattering light intensity / wavenumber 850 cm -1 The boric acid crosslinking index can be calculated by measuring the Raman scattering light intensity at [location].

[0036] Figure 6 is an explanatory diagram illustrating micro-Raman spectroscopy analysis of a polarizer plate according to this embodiment. As shown in Figure 6, in the laser Raman spectrophotometer, the laser beam is incident on the end face of the polarizer 101 such that the direction of propagation of the laser beam X is perpendicular to the absorption axis direction of the polarizer 101. Here, the laser beam X is polarized in the thickness direction of the polarizer 101. The measurement position of the laser beam is set to the center in the thickness direction of the polarizer 101. It is preferable to perform cross-sectional processing of the polarizer plate using a microtome before the Raman spectroscopy measurement. Wavenumber 780 cm⁻¹ -1 The Raman scattering light intensity in this context refers to the Raman scattering light intensity attributed to the bond between polyvinyl alcohol and boron, at a wavenumber of 850 cm⁻¹. -1 In this context, the Raman scattering light intensity refers to the Raman scattering light intensity attributed to polyvinyl alcohol.

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

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

[0039] Increasing the luminous efficiency correction polarization degree Py of the polarizer 101 is advantageous in improving the function of the circular polarizer as an anti-reflective coating and the durability of the circular polarizer. If the luminous efficiency correction polarization degree Py of the polarizer 101 is less than 95%, it may not be able to perform its function as an anti-reflective coating.

[0040] The luminous efficiency-corrected single-unit transmittance Ty of polarizer 101 is usually 41% or higher, preferably 41.1% or higher, more preferably 41.2% or higher, and may also be 42% or higher, or 42.5% or higher. The luminous efficiency-corrected single-unit transmittance Ty of polarizer 101 is usually 50% or lower, and may also be 48% or lower, 46% or lower, 44% or lower, or 43% or lower. If the luminous efficiency-corrected single-unit transmittance Ty is excessively high, the luminous efficiency-corrected polarization degree Py may become too low, and the circular polarizer may not be able to achieve its function as an anti-reflective coating. The luminous efficiency-corrected single-unit transmittance Ty can be calculated by performing luminous efficiency correction on the obtained transmittance using a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation) with a 2-degree field of view (C light source) as specified in "JIS Z 8701".

[0041] (2-2) Protective film The protective film 102 laminated on one side of the polarizer 101 is a film for protecting the polarizer, and for example, a translucent (preferably optically transparent) film formed from a thermoplastic resin can be used.

[0042] Examples of thermoplastic resins include cellulose resins such as triacetylcellulose; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polyethersulfone resins; polysulfone resins; polycarbonate resins; polyamide resins such as nylon and aromatic polyamides; polyimide resins; polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers; cyclic polyolefin resins having cyclo and norbornene structures (also called 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] The protective film 102 is preferably a film that does not have phase difference characteristics or has a small phase difference value. Specifically, the in-plane phase difference value of the protective film 102 at a wavelength of 550 nm is preferably 0 nm to 10 nm, and the phase difference value in the thickness direction at a wavelength of 550 nm is preferably -10 nm to +10 nm. In the case of the circular polarizer of the present invention, as in the case of the circular polarizer 3 which has a hard coat layer 103, it is preferable that the laminate of the protective film 102 and the hard coat layer 103 is a film with a small phase difference 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 the same as that which is common in the field of polarizing plates. For example, the light transmittance for visible light is preferably 85% or more, and more preferably 90% or more. If the circular polarizing plate of the present invention has a hard coat layer 103, as in the circular polarizing plate 3, it is preferable that the laminate of the protective film 102 and the hard coat layer 103 has the above-mentioned light transmittance.

[0047] If the protective film 102 or the laminate of the protective film 102 and the hard coat layer 103 has a small phase difference value and high light transmittance, the luminous efficiency correction polarization degree Py and the luminous efficiency correction single transmittance Ty of the polarizer 101 can be replaced with the luminous efficiency correction polarization degree Py and the luminous efficiency correction single transmittance Ty of the polarizer 101, which is laminated with the protective film 102, or the polarizer 11, which is laminated with the protective film 102 and the hard coat layer 103.

[0048] The distance from the polarizer 101's surface on the phase difference layer structure 20 side to the linear polarizer 10,11 side of the phase difference layer structure 20 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 the circular polarizer and bending resistance (flexibility), the distance is preferably 40 μm or less, and more preferably 30 μm or less.

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

[0050] The fact that the protective film 102 has light-selective absorption properties, preferably absorption properties for ultraviolet light such as 350 nm, and more preferably absorption properties for ultraviolet light such as 350 nm and short-wavelength visible light around 410 nm, is advantageous in the following respects. I) When a circular polarizing plate is applied to an image display device, the image display element can be protected from ultraviolet light and short-wavelength visible light. II) Changes in the phase difference value of the phase difference layer structure 20 due to ultraviolet light and short-wavelength visible light can be suppressed. III) The reflected hue of a circular polarizer can be adjusted by absorbing short-wavelength visible light. IV) This prevents the polarizer 101 from degrading due to light reflected by an image display element such as an organic EL display element.

[0051] The imparting of light-selective absorption properties to the protective film 102 may be done by using a thermoplastic resin that has light-selective absorption properties as a component of the protective film 102, by incorporating a light-selective absorption additive (light absorber) into the protective film 102, or by both. It is preferable that the imparting of light-selective absorption properties to the protective film 102 is done by incorporating a light absorber into the protective film 102.

[0052] The following are specific examples of preferred light absorbers. Among light absorbers, from the viewpoint of the preferred selective light absorption described above, light absorbers for light with a wavelength of 350 nm (ultraviolet light) and light absorbers for light with a wavelength of 410 nm are preferably used in the present invention.

[0053] Various UV absorbers are readily available from the market as light absorbers for light with a wavelength of 350 nm. Examples of such UV absorbers include organic UV absorbers such as oxybenzophenone-based UV absorbers, benzotriazole-based UV absorbers, salicylate-based UV absorbers, benzophenone-based UV absorbers, cyanoacrylate-based UV absorbers, and triazine-based UV absorbers. More specifically, examples include 5-chloro-2-(3,5-di-sec-butyl-2-hydroxylphenyl)-2H-benzotriazole, (2-2H-benzotriazole-2-yl)-6-(linear and side-chain dodecyl)-4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, and 2,4-benzyloxybenzophenone.

[0054] Commercially available UV absorbers may be used as is. Examples of such commercially available products include triazine-based UV absorbers such as "Kemisorb 102" from Chemipro Chemical Co., Ltd., "ADEKA Stab LA46" and "ADEKA Stab LAF70" from ADEKA Corporation, and "Chinubin 109," "Chinubin 171," "Chinubin 234," "Chinubin 326," "Chinubin 327," "Chinubin 328," "Chinubin 928," "Chinubin 400," "Chinubin 460," "Chinubin 405," and "Chinubin 477" (all are product names) from BASF Japan. Examples of benzotriazole-based UV absorbers include "ADEKA Stab LA31" and "ADEKA Stab LA36" (both product names) manufactured by ADEKA Corporation, "Sumisorb 200," "Sumisorb 250," "Sumisorb 300," "Sumisorb 340," and "Sumisorb 350" (all product names) manufactured by Sumika Chemtex Co., Ltd., "Kemisorb 74," "Kemisorb 79," and "Kemisorb 279" (all product names) manufactured by Chemipro Kasei Co., Ltd., and "TINUVIN 99-2," "TINUVIN 900," and "TINUVIN 928" (all product names) manufactured by BASF. Note that two or more UV absorbers may be used in combination in the circular polarizer of the present invention, and different light absorbers may be used in multiple layers constituting the circular polarizer of the present invention.

[0055] The UV absorber may also be an inorganic UV absorber. Examples of inorganic UV absorbers include titanium dioxide, zinc oxide, indium oxide, tin oxide, talc, kaolin, calcium carbonate, titanium dioxide-based composite oxides, zinc oxide-based composite oxides, ITO (tin-doped indium oxide), ATO (antimond-doped tin oxide), etc. Examples of titanium dioxide-based composite oxides include silica, alumina-doped zinc oxide, etc. Two or more of these inorganic UV absorbers may be used in combination, and they may also be used in combination with commercially available light absorbers (organic UV absorbers) as exemplified above.

[0056] As a light absorber for light with a wavelength of 410 nm, a compound having a maximum absorption wavelength in the 360-430 nm wavelength band can be synthesized by known methods and used in the present invention. Such a light absorber can be, for example, a compound known as a photoselective absorbent compound described in Japanese Patent Application Publication No. 2017-120430. It is preferable to include a compound having at least one absorption maximum in the 360 ​​nm-420 nm wavelength range, and more preferably a compound having an absorption maximum in the 380 nm-410 nm wavelength range.

[0057] The amount of light absorbent used is selected so as not to significantly impair the light transmittance of the layer containing the light absorbent to visible light. For example, when the mass of the layer is 100 parts by mass, the amount of light absorbent 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 between the polarizer and the liquid crystal hardened layer (protective film 102, hard coat layer 103, and first bonding layer 30a) preferably has an absorbance of 0.5 or more at a wavelength of 350 nm, more preferably 1.0 or more, and preferably has an absorbance of 0.2 or more at a wavelength of 410 nm, more preferably 0.5 or more.

[0059] In another embodiment, in the circular polarizer of the present invention, the laminate of layers excluding the polarizer (for example, a laminate consisting of a protective film 102, a hard coat layer 103, a first bonding layer 30a, a first liquid crystal curing layer 201, a second bonding layer 30b, a second liquid crystal curing layer 202, and a third bonding layer 30c), that is, the laminate of layers that exist on the protective film side when the polarizer is used as the reference, preferably has an absorbance of 0.3 or more at a wavelength of 350 nm, 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, usually 2.0 or less, and may also be 1.5 or less.

[0060] The protective film 102 can be laminated onto the polarizer 101 via an adhesive layer. As the adhesive forming the adhesive layer, a water-based adhesive or an active energy ray-curing adhesive (described later) can be used. Examples of water-based adhesives include adhesives in which a polyvinyl alcohol-based 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 usually 10 μm or less, in order to easily ensure adhesion. As described above, when applying the circular polarizer of the present invention to a flexible image display device, the thinner the thickness of each component constituting the circular polarizer, the preferable it is. However, if the thickness of the adhesive layer becomes extremely thin, the desired adhesion may be impaired. Therefore, the thickness of the adhesive layer is optimized considering the flexibility when applying the circular polarizer of the present invention to a flexible image display device and the adhesion between the polarizer 101 and the protective film 102.

[0061] (2-3) Hard coat layer The circular polarizing plate may further have a hard coat layer 103 between the protective film 102 and the liquid crystal hardened layer (phase difference layer structure 20). The hard coat layer 103 is preferably laminated on the surface of the protective film 102 that faces the phase difference layer structure 20, and more preferably laminated directly 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 when irradiated with active energy rays or thermal energy. The hard coat composition is preferably curable by irradiation with active energy rays. In this specification, "active energy rays" include visible light, ultraviolet rays, infrared rays, X-rays, alpha rays, beta rays, gamma rays, electron beams, etc., and ultraviolet rays are preferred.

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

[0064] As radical polymerizable compounds, compounds having (meth)acryloyl groups are preferred in terms of their high reactivity. Compounds referred to as polyfunctional acrylate monomers having 2 to 6 (meth)acryloyl groups in one molecule, or oligomers with molecular weights of several hundred to several thousand having several (meth)acryloyl groups in the molecule, referred to as epoxy (meth)acrylate, urethane (meth)acrylate, and polyester (meth)acrylate, can be preferably used. It is preferable to include one or more selected from epoxy (meth)acrylate, urethane (meth)acrylate, and polyester (meth)acrylate.

[0065] Cationic polymerizable compounds are compounds having cationic polymerizable groups such as epoxy groups, oxetanyl groups, and vinyl ether groups. Preferably, cationic polymerizable compounds have at least one of epoxy groups and oxetanyl groups as cationic polymerizable groups.

[0066] Examples of cationic polymerizable compounds having epoxy groups include alicyclic epoxy resins obtained by epoxidizing polyglycidyl ethers of polyhydric alcohols having alicyclic rings, or compounds containing cyclohexene rings or cyclopentene rings, 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 homopolymers and copolymers of glycidyl (meth)acrylates; glycidyl ethers and novolac epoxy resins produced by the reaction of bisphenols such as bisphenol A, bisphenol F, and hydrogenated bisphenol A, or derivatives thereof such as alkylene oxide adducts and 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 polymerization initiators include radical polymerization initiators, cationic polymerization initiators, and combinations thereof. These polymerization initiators are decomposed by at least one of active energy ray irradiation and heating, generating radicals or cations to promote 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 in a hydrogen abstraction reaction in the presence of tertiary amines. Each can be used alone or in combination. Examples of thermal radical polymerization initiators include hydrogen peroxide, organic peroxides such as perbenzoic acid, and azo compounds such as azobisbutyronitrile. Examples of cationic polymerization initiators include aromatic iodonium salts, aromatic sulfonium salts, and cyclopentadienyl iron(II) complexes.

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

[0070] The hard coat composition may further contain solvents, 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 when transporting the circular polarizing plate of the present invention or when processing the circular polarizing plate. 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. Preferably, at least one of the protective film 102 and the hard coat layer 103 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. 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 (protective film with hard coat layer) equipped with a hard coat layer 103 containing a light absorber can be purchased from the market and used as is as a component of the circular polarizer of the present invention. Similarly, protective films 102 containing a light absorber but without a hard coat layer 103 are also available. The amount of light absorber contained in such protective films or protective films with hard coat layers may be unknown, but in such cases, the optimal amount can be selected by considering the light transmittance of the protective film or protective film with hard coat layer to visible light.

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

[0075] The liquid crystal curing layer is a layer having phase difference characteristics (phase difference layer), and is a cured layer in which a polymerizable liquid crystal compound polymerizes and hardens in an oriented state, exhibiting phase difference characteristics. The phase difference layer structure 20 includes at least one liquid crystal curing layer, and may include two or more liquid crystal curing layers. If it includes two or more liquid crystal curing layers, the phase difference layer structure 20 may include a bonding layer (second bonding layer 30b) for bonding these liquid crystal curing layers to each other.

[0076] The liquid crystal curing layer can be a half-wavelength phase difference layer, a quarter-wavelength phase difference layer, or a positive C plate. The quarter-wavelength phase difference layer may also be inverse-wavelength dispersive. If the phase difference layer structure 20 includes two or more liquid crystal curing layers, the liquid crystal curing layers may have the same phase difference characteristics or may have different phase difference characteristics.

[0077] As described above, the phase difference layer structure 20 preferably includes a first liquid crystal curing layer 201 and a second liquid crystal curing layer 202. The first liquid crystal curing layer 201 and the second liquid crystal curing layer 202 are, for example, a 1 / 2 wavelength phase difference layer and a 1 / 4 wavelength phase difference layer, respectively. Alternatively, one of the first liquid crystal curing layer 201 and the second liquid crystal curing layer 202 is an inverse wavelength dispersive 1 / 4 wavelength phase difference layer and the other is a positive C plate. For example, the first liquid crystal curing layer 201 and the second liquid crystal curing layer 202 are an inverse wavelength dispersive 1 / 4 wavelength phase difference layer and a positive C plate, respectively.

[0078] Examples of polymerizable liquid crystal compounds include rod-shaped polymerizable liquid crystal compounds and disc-shaped 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 oriented horizontally or vertically with respect to the substrate layer, the optical axis of the polymerizable liquid crystal compound coincides with the longitudinal axis of the polymerizable liquid crystal compound. When a disc-shaped polymerizable liquid crystal compound is oriented, the optical axis of the polymerizable liquid crystal compound exists in a direction perpendicular to the disc surface of the polymerizable liquid crystal compound. As a rod-shaped polymerizable liquid crystal compound, for example, the one described in Japanese Patent Publication No. 11-513019 (Claim 1, etc.) can be suitably used. As a disc-shaped polymerizable liquid crystal compound, the one described in Japanese Patent Application Publication No. 2007-108732 (paragraphs

[0020] to

[0067] , etc.) and Japanese Patent Application Publication No. 2010-244038 (paragraphs

[0013] to

[0108] , etc.) can be suitably used.

[0079] For a liquid crystal cured layer formed by polymerizing a polymerizable liquid crystal compound to exhibit an in-plane phase difference, the polymerizable liquid crystal compound should be oriented in a suitable direction. When the polymerizable liquid crystal compound is rod-shaped, an in-plane phase difference is exhibited by oriented the optical axis of the polymerizable liquid crystal compound horizontally to the substrate layer plane, in which case the optical axis direction and the slow phase axis direction coincide. When the polymerizable liquid crystal compound is disc-shaped, an in-plane phase difference is exhibited by oriented the optical axis of the polymerizable liquid crystal compound horizontally to the substrate layer plane, in which case the optical axis and the slow phase axis are orthogonal. The orientation state of the polymerizable liquid crystal compound can be adjusted by the combination of the orientation layer and the polymerizable liquid crystal compound.

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

[0081] The phase difference layer structure 20 may include an alignment layer. The alignment layer has an alignment restricting 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 perpendicularly to the substrate layer, a horizontal alignment layer in which the molecular axis of the polymerizable liquid crystal compound is aligned horizontally to the substrate layer, or a gradient alignment layer in which the molecular axis of the polymerizable liquid crystal compound is tilted relative to the substrate layer. If the phase difference layer structure 20 includes two or more alignment layers, the alignment layers may be the same as each other or may be different from each other.

[0082] The orientation layer is preferably one that has solvent resistance, meaning it does not dissolve when coated with a liquid crystal layer forming composition containing a polymerizable liquid crystal compound, and has heat resistance to solvent removal and heat treatment for orientation of the polymerizable liquid crystal compound. Examples of orientation layers include an orientation polymer layer formed from an orientation polymer, a photo-orientation polymer layer formed from a photo-orientation polymer, and a groove orientation layer having an uneven pattern or multiple grooves on its surface.

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

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

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

[0086] The second bonding layer 30b is an adhesive layer or a bonding agent layer. Preferably, the second bonding layer 30b is a bonding agent layer, more preferably an adhesive layer obtained by curing an active energy ray curing type adhesive, and even more preferably an adhesive layer obtained by curing an ultraviolet-curing type adhesive. Using an adhesive layer for the second bonding layer 30b is preferable because it can suppress the occurrence of wrinkles in the liquid crystal curing layer when the circular polarizing plate is bent or folded. As the adhesive layer, those described later can be used.

[0087] Examples of active energy ray curing adhesives include solvent-free active energy ray curing adhesives containing a curable compound that hardens upon irradiation with active energy rays.

[0088] As an active energy ray curable adhesive, it is preferable to include either a cationic curable compound, a radical curable compound, or both, as these exhibit good adhesion. 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 above-mentioned curable compound.

[0089] Examples of cationically polymerizable curable compounds include epoxy compounds such as alicyclic epoxy compounds having epoxy groups bonded to an alicyclic ring, polyfunctional aliphatic epoxy compounds having two or more epoxy groups but no aromatic ring, monofunctional epoxy groups 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 thereof.

[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 radically polymerizable double bonds, or 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, 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, 15 μm or less, preferably 10 μm or less, and particularly 7 μm or less is preferred. If the second bonding layer 30b is an adhesive layer, its thickness is preferably 0.1 μm or more, may be 0.5 μm or more, preferably 10 μm or less, and may be 5 μm or less.

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

[0093] The thickness of the adhesive layer, which is the first bonding 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, 15 μm or less, preferably 10 μm or less, and particularly 7 μm or less is preferred. When the first bonding layer 30a is an adhesive layer, its thickness is preferably 0.1 μm or more, may be 0.5 μm or more, and preferably 10 μm or less, and may be 5 μm or less.

[0094] The first laminated layer 30a may have light-selective absorption properties. Preferably, at least one layer of the protective film 102, the hard coat layer 103, and the first laminated layer 30a has light-selective absorption properties, and multiple of these layers may have light-selective absorption properties. The advantages of the first laminated layer 3aa having light-selective absorption properties are the same as when the protective film 102 has light-selective absorption properties. Light-selective absorption properties can be imparted to the first laminated layer 30a by incorporating the above-mentioned light absorber into the first laminated layer 30a.

[0095] The thickness of the adhesive layer, which is the third bonding layer 30c, is not particularly limited and can be set appropriately depending on the application, but for example it may be 250 μm or less, 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 most particularly preferably 20 μm or less. The lower limit of the thickness of the adhesive layer is not particularly limited, but from the viewpoint of durability it may be 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 14 μm or more.

[0096] As the adhesive, conventionally known adhesives with excellent optical transparency can be used. For example, adhesives having base polymers such as (meth)acrylic, urethane, silicone, or polyvinyl ether can be used. Active energy ray curing adhesives and thermosetting adhesives may also be used. Among these, adhesives with (meth)acrylic resin as the base polymer, which have excellent transparency, adhesive strength, re-peelability (hereinafter also referred to as reworkability), weather resistance, and heat resistance, are preferred. The adhesive layer is preferably composed of a reaction product of an adhesive containing (meth)acrylic resin, a crosslinking agent, and a silane compound, and may contain other components.

[0097] The adhesive layer may be formed using an active energy ray curable adhesive. An active energy ray curable adhesive can be formed by blending an ultraviolet-curable compound such as a polyfunctional (meth)acrylate with the above-mentioned adhesive, forming the adhesive layer, and then curing it by irradiating it with ultraviolet light to form a harder adhesive layer. Active energy ray curable adhesives have the property of curing when irradiated with energy rays such as ultraviolet light or electron beams. Because active energy ray curable adhesives are tacky even before energy ray irradiation, they adhere closely to the adherend, and the adhesion strength can be adjusted by curing with energy ray irradiation.

[0098] Active energy ray curing adhesives generally contain (meth)acrylic adhesives and energy ray polymerizable compounds as their main components. Typically, a crosslinking agent is also included, and photopolymerization initiators and photosensitizers may be added as needed.

[0099] (5) Separation film The circular polarizer may be equipped with a separator film 203 to protect the outer surface of the third laminate layer 30c. The separator film 203 may be a film in which a release treatment such as silicone treatment has been applied to the surface of the base film on the side of the third laminate layer 30c. The base film is, for example, a film made of polyethylene resin such as polyethylene, polypropylene resin such as polypropylene, polyester resin such as polyethylene terephthalate, etc.

[0100] <Optical laminate> The optical laminate according to the present invention (hereinafter also simply referred to as "optical laminate") comprises the circular polarizer according to the present invention and other components. Examples of other components include an image display element 40 (see Figures 4 and 5) positioned on the liquid crystal hardened layer side of the circular polarizer, that is, on the side opposite to the viewing side of the circular polarizer; a front plate 50 (see Figure 5) positioned 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 called a "surface protection film") for temporarily protecting the surface of the polarizer 101. The optical laminate preferably includes one or more components selected from the group consisting of a front plate 50 and an image display element 40.

[0101] <Image display device> The circular polarizers 1, 2, and 3 can be placed on the front (viewing side) of an image display element and used as components of an image display device. The circular polarizers can also be used as anti-reflective polarizers to provide an anti-reflective function in an image display device. The image display device is not particularly limited and examples include organic electroluminescent (organic EL) display devices, inorganic electroluminescent (inorganic EL) display devices, liquid crystal display devices, and electroluminescent display devices. The main parts of an embodiment in which the circular polarizers (circular polarizers 1, 2, and 3) of the present invention are applied to an image display device, particularly a flexible image display device, will be briefly described below.

[0102] The image display device may be a flexible image display device. The flexible image display device consists of an optical laminate for flexible image display devices (described later) and an organic EL display element, wherein the optical laminate for flexible image display devices is positioned on the viewing side relative to the organic EL display element and is configured to be bendable.

[0103] <Optical laminate for flexible image display devices> The optical laminate for flexible image display devices comprises a circular polarizing plate of the present invention and an organic EL display element, which is an image display element with bending resistance. The optical laminate for flexible image display devices also has a bending-resistant front plate. Furthermore, it may be equipped with a touch sensor panel as an input means. In this case, the stacking order of the circular polarizing plate, front plate and touch sensor panel may be, for example, front plate, circular polarizing plate, and touch sensor panel from the viewing side. The stacking order is preferably front plate, touch sensor panel, and circular polarizing plate. It is preferable that the circular polarizing plate is located on the viewing side of the touch sensor panel, as this makes the wiring pattern of the touch sensor panel less visible and improves the visibility of the displayed image. Each component can be stacked using an adhesive, tack, etc. Furthermore, the optical laminate for flexible image display devices may have a light-shielding pattern formed on at least one surface of any of the layers of the front plate, polarizing plate, or touch sensor panel.

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

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

[0106] When the circular polarizing plate of the present invention is applied to a flexible image display device, the front plate used is required to be flexible. From this point of view, the front plate is preferably made of a resin film, and as described above, it may include a hard coat layer on at least one surface. A front plate 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] The resin film used as the front panel can be made of the same material as exemplified for the protective film 102. Of course, any film with a practical light transmittance can be made of two or more materials. The thickness can be optimized from such a resin film, taking into consideration light transmittance, flexibility, durability, etc. A film without phase difference characteristics (unstretched film) is preferred as the front panel, but a uniaxial or biaxially stretched film may be used if the phase difference value is acceptable. Among these, polyamide-imide film or polyimide film with excellent transparency and heat resistance, uniaxial or biaxially stretched polyester film, cycloolefin derivative film with excellent transparency and heat resistance that can accommodate larger film sizes, polymethyl methacrylate film, and triacetylcellulose and isobutyl ester cellulose film with transparency and no optical anisotropy are preferred for use as the resin film for the front panel. In this case, the thickness of the resin film may be 5 to 200 μm, preferably 20 to 100 μm.

[0108] <Light-blocking pattern> The light-shielding pattern is provided on a part of the periphery of the image display surface of the image display device, called the bezel, for reasons such as preventing the wiring from being visible when a viewer looks at the image from the image display surface side. Such a light-shielding pattern is formed on at least one surface of either the front plate or the circular polarizing plate that constitutes the optical laminate for the image display device. When a touch sensor panel is attached to the optical laminate for the 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 hide the wiring of the display device and prevent it from being visible to the user. The color and material of the light-shielding pattern are not particularly limited and can be formed from a resin material having various colors such as black, white, and 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 in the range of 6 μm to 15 μm. Furthermore, a shape can be given to the light-shielding pattern to suppress the inclusion of air bubbles due to the step between the light-shielding pattern and the display part and the visibility of the boundary.

[0109] <Touch sensor panel> The image display device equipped with the circular polarizer of the present invention may further be equipped with a touch sensor as an input means, which can usually be realized by incorporating a touch sensor panel. Various types of touch sensors have been proposed, such as resistive film type, surface acoustic wave type, infrared type, electromagnetic induction type, and capacitive type, and any of these types may be used. Among these, the capacitive type is preferred. The capacitive touch sensor is divided into an active region and an inactive region located on the outer edge of the active region. The active region is the region corresponding to the area on the display panel where the screen is displayed (display area) and is the region where the user's touch is detected, and the inactive region is the region corresponding to the area on the display device where the screen is not displayed (non-display area). The touch sensor panel may include a substrate having flexible properties; a sensing pattern formed in the active region of the substrate; and sensing lines formed in the inactive region of the substrate for connecting to an external drive circuit via the sensing pattern and pad portion. As the substrate having flexible properties, the same material as the transparent substrate of the front panel 50 can be used. The substrate for the touch sensor panel is preferably one with a toughness of 2,000 MPa% or more from the viewpoint of suppressing cracks that may occur in the touch sensor panel. More preferably, the toughness is 2,000 MPa% to 30,000 MPa%. Here, toughness is defined as the area under the curve up to the fracture point in the stress (MPa)-strain (%) curve obtained through a tensile test of the polymer material.

[0110] The fourth adhesive layer 30d shown in Figure 5 is a bonding layer for bonding the front plate 50 and the polarizer 101, which is the uppermost layer of the circular polarizer. The description of the adhesive layer above is referenced for the fourth adhesive layer 30d.

[0111] The optical laminate (including the case of an optical laminate for a flexible image display device) may include a protective film for temporarily protecting the surface of the polarizer 101. The protective film consists of a base film and an adhesive layer laminated thereon. The adhesive layer is described above by reference. The resin constituting the base film can be a thermoplastic resin such as polyethylene resin such as polyethylene, polypropylene resin such as polypropylene, polyester resin such as polyethylene terephthalate or polyethylene naphthalate, or polycarbonate resin. Preferably, it is a polyester resin such as polyethylene terephthalate.

[0112] The optical laminate (including the case of an optical laminate for a flexible image display device) and the circular polarizer according to the present invention can be suitably applied to image display devices, particularly organic EL image display devices. [Examples]

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

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

[0115] (2) Calculation of the degree of boric acid crosslinking index The cross-section of the polarizer was processed using an ultramicrotome (LEICA, product name "LEICA Ultramicrotome EM UC7i"). The position of the center of the polarizer in the thickness direction of the obtained cross-section of the polarizer was measured using a laser Raman spectrophotometer (product name: "NRS-5100", manufactured by JASCO Corporation) under the following conditions, with a wavenumber of 780 cm⁻¹. -1The Raman scattering light intensity at [specific condition], and the Raman scattering light intensity at a wave number of 850 cm -1 The Raman scattering light intensity at [specific condition] was determined respectively, and then the Raman scattering light intensities at these wave numbers were divided (the Raman scattering light intensity at a wave number of 780 cm -1 The Raman scattering light intensity at [specific condition] / the Raman scattering light intensity at a wave number of 850 cm -1 The Raman scattering light intensity at [specific condition]) to calculate the boric acid crosslinking degree index. The results are shown in Table 1. Excitation wavelength: 532 nm Grating: 600 l / mm Slit width: 100×1000 μm Aperture: φ40 μm Objective lens: 100× Objective lens: 100×

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

[0117] (4) Measurement of the single transmittance and visually sensitivity corrected polarization degree The single transmittance and visually sensitivity corrected polarization degree of the circular polarizing plate were measured by making linearly polarized light from the prism incident on the polarizer side of the circular polarizing plate and using a spectrophotometer with an integrating sphere (manufactured by JASCO Corporation, V7100). The MD transmittance and TD transmittance were determined in the wavelength range of 380 nm to 780 nm, and the single transmittance and polarization degree at each wavelength were calculated based on Equation (A) and Equation (B). Further, visual sensitivity correction was performed according to the 2° field of view (C light source) of JIS Z8701 to obtain the visually sensitivity corrected polarization degree (Py). Note that the "MD transmittance" is the transmittance when the direction of the polarized light emerging from the Glan-Thompson prism is parallel to the transmission axis of the polarizing plate sample. In Equation (A) and Equation (B), the "MD transmittance" is represented as "MD". Also, the "TD transmittance" is the transmittance when the direction of the polarized light emerging from the Glan-Thompson prism is perpendicular to the transmission axis of the polarizing plate sample, and in Equation (A) and Equation (B), the "TD transmittance" is represented as "TD". Single transmittance (%) = (MD + TD) / 2 Equation (A) Degree of polarization (%)={(MD-TD) / (MD+TD)}×100 Formula (B)

[0118] (5) Heat resistance test of circular polarizing plate The circular polarizer obtained in the example was cut into a rectangle measuring 140 mm x 70 mm. The cutting was done so that the absorption axis of the polarizer was parallel to the shorter side of the rectangle. The cut circular polarizer was bonded to an alkali-free glass (Corning, part number: EAGLE XG®) with a thickness of 0.7 mm via an adhesive layer (2) to prepare an evaluation sample. This evaluation sample was subjected to a heat resistance test, stored at 85°C under dry conditions for 500 hours. The evaluation sample was then visually inspected. The results were classified according to the following criteria and summarized in Table 1.

[0119] [Evaluation Criteria for Heat Resistance Tests] A: No external changes such as lifting, peeling, or foaming are observed. B: Some noticeable changes in appearance such as lifting, peeling, and foaming. C: Significant changes in appearance such as lifting, peeling, and foaming are observed.

[0120] (6) Moisture heat resistance test of circular polarizing plates The circular polarizer obtained in the example was cut into a 30mm x 30mm square. The cutting was done so that the absorption axis of the polarizer was parallel to the sides of the square. The cut circular polarizer was bonded to a 40mm x 40mm alkali-free glass (Corning, part number: EAGLE XG®) via an adhesive layer (2), and then further bonded to a 40mm x 40mm alkali-free glass (Corning, part number: EAGLE XG®) via an adhesive layer on the polarizer surface to prepare an evaluation sample. The luminous efficiency-corrected polarization degree Py was measured for this evaluation sample.

[0121] Next, a heat-resistant test was conducted on the evaluation samples, storing them for 500 hours under conditions of 60°C and 95% RH relative humidity. After the test, the luminous efficiency-corrected polarization degree Py was measured for the evaluation samples. Table 1 shows the measured values ​​of the luminous efficiency-corrected polarization degree Py before and after the test, as well as the absolute difference between them, ΔPy.

[0122] (7) Weather resistance test of circular polarizing plates The circular polarizer obtained in the example was cut into a 30mm x 30mm square. The cutting was done so that the absorption axis of the polarizer was parallel to the sides of the square. The cut circular polarizer was bonded to a 40mm x 40mm alkali-free glass (Corning, part number: EAGLE XG®) via an adhesive layer (2) to prepare an evaluation sample. The transmittance of this evaluation sample at 450nm was measured.

[0123] Next, the evaluation sample was placed on an aluminum plate (reflector) so that ultraviolet light was irradiated from the polarizer 101 side, and a weather resistance test was conducted by placing it 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 relative humidity of 50%. After the test, the transmittance of the evaluation sample at 450nm was measured. The absolute difference in the measured transmittance of 450nm before and after the test is shown in Table 1.

[0124] (8) Absorbance measurement of the laminate A laminate was prepared by laminating the protective film 102, hard coat layer 103, first bonding layer 30a, first liquid crystal curing layer 201, second bonding layer 30b, second liquid crystal curing layer 202, and third bonding layer 30c, excluding the polarizer 101. In the layer configuration without a hard coat layer, the hard coat layer 103 was not laminated. The laminate was bonded to glass via the third bonding layer 30c. After bonding an adhesive layer to a cycloolefin polymer (COP) film (ZF-14 manufactured by Nippon Zeon Co., Ltd.), the COP film was bonded to the protective film 102 via this adhesive layer. In this way, an evaluation laminate was prepared.

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

[0126] <Preparation of components for circular polarizers> (1) Fabrication of polarizer 1 A polyvinyl alcohol film with 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 hot roll, and while maintaining tension, was immersed for 60 seconds at 28°C in a staining 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 polarizer was immersed in an aqueous boric acid 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 for 110 seconds at 64°C. Then, it was immersed in an aqueous boric acid 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 for 30 seconds at 67°C. After that, it was washed with pure water at 10°C and dried to obtain polarizer 1. Polarizer 1 had a thickness of 8 μm and a boron content of 4.3% by mass.

[0128] (2) Fabrication of polarizer 2 A polyvinyl alcohol film with 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 hot roll, and while maintaining tension, was immersed for 60 seconds at 28°C in a staining 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 polarizer was immersed in aqueous boric acid solution 1, which contained 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. Then, it was immersed in aqueous boric acid solution 2, which contained 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. After that, it was washed with pure water at 10°C and dried to obtain polarizer 2. 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 release film F We prepared the following five types of protective films and one type of release film. • Protective film A: Cycloolefin film (COP-HC) with a 27μm thick hard coat layer. The hard coat layer is 2μm thick and has a moisture permeability of 10g / m². 2 It was 24 hours. It has UV-absorbing properties. • Protective film B: 25μm thick cycloolefin film (COP). Moisture permeability is 12g / m². 2 It was 24 hours. It has UV-absorbing properties. • Protective film C: COP with a thickness of 23 μm. Does not absorb ultraviolet light. • Protective film D: 13μm thick COP. Has UV absorption properties. • Protective film E: COP-HC with a thickness of 27 μm. It has ultraviolet absorption properties as well as absorption properties for short-wavelength visible light around 410 nm. • Release film F:TD80UL. Triacetylcellulose film manufactured by Fujifilm Corporation. Thickness is 80 μm, and moisture permeability is 502 g / m². 2 It was 24 hours.

[0131] (4) Fabrication of linear polarizing plate 1 A protective film A was bonded to one side of the fabricated polarizer 1 via a water-based adhesive, and a release film F was bonded to the opposite side of protective film A via pure water using a roll laminating machine. The polarizer was then dried at 80°C for 3 minutes. After that, the release film F was peeled off the polarizer to obtain a linear polarizer 1 in which the protective film was laminated only on one side of the polarizer 1. The linear polarizer 1 consisted of the polarizer 1, adhesive layer, and protective film A laminated in this order.

[0132] (5) Fabrication of Linear Polarizing Plate 2 A linear polarizing plate 2 was manufactured in the same manner as the linear polarizing plate 1, except that the drying temperature after lamination using a roll laminating machine was changed to 100°C.

[0133] (6) Fabrication of linear polarizing plate 3 A linear polarizer 3 was fabricated in the same manner as linear polarizer 1, except that polarizer 1 was replaced with polarizer 2.

[0134] (7) Fabrication of linear polarizing plate 4 A linear polarizer 4 was fabricated in the same manner as linear polarizer 2, except that polarizer 1 was replaced with polarizer 2.

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

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

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

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

[0139] (12) First liquid crystal hardened layer A (fabrication of half-wavelength phase difference layer) A λ / 2 orientation treatment was performed by applying an orientation layer-forming composition to a substrate layer made of transparent resin and drying it. Next, a liquid crystal layer-forming composition containing a discotic polymerizable liquid crystal compound was applied to the orientation layer, and the orientation of the polymerizable liquid crystal compound was fixed by heating and UV irradiation, thereby forming a 2 μm thick liquid crystal cured layer, or 1 / 2 wavelength phase difference layer, on the orientation layer of the substrate layer.

[0140] (13) Second liquid crystal curing layer A (fabrication of a quarter-wavelength phase difference layer) A liquid crystal layer-forming composition containing a rod-shaped nematic polymerizable liquid crystal compound (liquid crystal monomer) was applied to a rubbing-treated orientation layer on a substrate layer made of transparent resin, and solidified while maintaining refractive index anisotropy. This formed a quarter-wavelength phase difference layer as a liquid crystal curing layer with a thickness of 1 μm on the orientation layer of the substrate layer.

[0141] (14) Preparation of active energy ray curing adhesive A After mixing the following components and then removing the foam, an active energy ray-curing adhesive A was prepared. [Cationically polymerizable compounds] • Neopentyl glycol diglycidyl ether (product name: EX-211L, manufactured by Nagase ChemteX Co., Ltd.): 30 parts by mass · 3-Ethyl-3{[(3-ethyloxetane-3-yl)methoxy]methyl}oxetane (trade name: OXT-221, manufactured by Toagosei Co., Ltd.): 13 parts by mass • Bisphenol A type epoxy resin (product name: EP-4100E, ADEKA Corporation, viscosity 13 Pa·s (temperature 25℃)): 12 parts by mass ·Aromatic-containing oxetane compound (product name: TCM-104, manufactured by TRONLY): 45 parts by mass [Photocationic polymerization initiator] • CPI-100P, manufactured by Sunapro Co., Ltd., 50% propylene carbonate solution: 2.25 parts by mass (solid content) [Photosensitizer] • 1,4-Diethoxynaphthalene: 1 part by mass

[0142] (15) Fabrication of a phase difference layer structure A with a base layer The surface of the first liquid crystal curing layer A (1 / 2 wavelength phase difference layer) on the substrate layer and the surface of the second liquid crystal curing layer A (1 / 4 wavelength phase difference layer) on the substrate layer were each subjected to corona treatment. The corona-treated surfaces of these two phase difference layers were bonded together using the activated energy ray curing adhesive A prepared above, so that the angle between the slow phase axes of these two phase difference layers was 60°. Subsequently, an ultraviolet irradiation device [manufactured by Fusion UV Systems Co., Ltd.] was used to irradiate the 1 / 4 wavelength phase difference layer side with an integrated light intensity of 400 mJ / cm². 2 The active energy ray-curable adhesive A was cured by UV-B irradiation to form an adhesive layer. Lamination was performed using a laminator, and the active energy ray-curable adhesive A was applied so that the thickness of the cured adhesive layer was 3 μm. This resulted in a phase difference layer structure A with a substrate layer, in which the substrate layer, alignment layer, 1 / 2 wavelength phase difference layer (first liquid crystal cured layer), adhesive layer (second bonding layer), 1 / 4 wavelength phase difference layer (second liquid crystal cured layer), alignment layer, and substrate layer were laminated in this order. The total thickness of the 1 / 2 wavelength phase difference layer (first liquid crystal cured layer), adhesive layer (second bonding layer), and 1 / 4 wavelength phase difference layer (second liquid crystal cured layer) was 6 μm.

[0143] (16) Fabrication of the first liquid crystal curing layer B (quarter wavelength phase difference layer) An orientation layer was formed on a substrate layer made of transparent resin, and a liquid crystal layer forming composition containing a rod-shaped nematic polymerizable liquid crystal compound was applied to prepare a first liquid crystal cured layer B. The first liquid crystal cured layer B had a quarter-wavelength phase difference characteristic. The thickness of the first liquid crystal cured layer B was 2 μm.

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

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

[0146] (18) Preparation of active energy ray curing adhesive B The following components were mixed to prepare activated 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-Ethylhexylglycidyl 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 Sunapro 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) Fabrication of a phase difference layer structure B with a base 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 surfaces of each liquid crystal cured layer (the surfaces opposite to the base film) were the bonding surfaces. The active energy ray curable adhesive B was cured by irradiation with ultraviolet light to obtain a phase difference layer structure B with a base layer, in which the base layer, alignment layer, first liquid crystal cured layer B, adhesive layer (second bonding layer), second liquid crystal cured layer B, alignment layer, and base layer were laminated in this order. The thickness of the phase difference 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 phase difference layer structure B with a base layer has ultraviolet absorption properties.

[0148] (20) Preparation of the adhesive layer The following adhesive layers were prepared. Adhesive layer (1A): 5 μm thick acrylic adhesive layer Adhesive layer (1B): An acrylic adhesive layer with a thickness of 5 μm. It has absorption properties for short-wavelength visible light around 410 nm. Adhesive layer (2): Adhesive layer with a thickness of 15 μm

[0149] <Fabrication of circular polarizing plates> [Example 1] The 1 / 2 wavelength phase difference layer was exposed by peeling off the substrate layer and orientation layer on the 1 / 2 wavelength phase difference layer side of the phase difference layer structure A with a substrate layer prepared as described above, and this was bonded to the protective film A side (surface of the hard coat layer) of the linear polarizer 1 prepared as described above, using an adhesive layer (1A), which is the first bonding layer. The bonding of the 1 / 2 wavelength phase difference layer and the linear polarizer 1 was performed so that the angle between the slow axis of the 1 / 2 wavelength phase difference layer and the transmission axis of the polarizer 1 was 15°. Next, the adhesive layer (2) was bonded to the 1 / 4 wavelength phase difference layer exposed by peeling off the orientation layer and substrate layer on the 1 / 4 wavelength phase difference layer side to obtain a circular polarizer (1). Corona treatment was performed on each bonded surface.

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

[0151] [Example 3] A circular polarizer (3) was obtained in the same manner as in Example 1, except that a linear polarizer 2 was used instead of a linear polarizer 1.

[0152] [Example 4] A circular polarizer (4) was obtained in the same manner as in Example 1, except that a linear polarizer 3 was used instead of a linear polarizer 1.

[0153] [Example 5] A circular polarizer (5) was obtained in the same manner as in Example 1, except that a linear polarizer 4 was used instead of a linear polarizer 1.

[0154] [Example 6] A circular polarizer (6) was obtained in the same manner as in Example 1, except that a linear polarizer 5 was used instead of a linear polarizer 1.

[0155] [Example 7] A circular polarizer (7) was obtained in the same manner as in Example 1, except that a linear polarizer 6 was used instead of linear polarizer 1.

[0156] [Example 8] A circular polarizer (8) was obtained in the same manner as in Example 1, except that a linear polarizer 6 was used instead of linear polarizer 1, and an adhesive layer (1B) was used as the first bonding layer.

[0157] [Example 9] A circular polarizer (9) was obtained in the same manner as in Example 1, except that a linear polarizer 7 was used instead of a linear polarizer 1.

[0158] [Example 10] A circular polarizer (10) was obtained in the same manner as in Example 1, except that a linear polarizer 8 was used instead of a linear polarizer 1.

[0159] [Example 11] The first liquid crystal cured layer B, exposed by peeling off the substrate layer on the first liquid crystal cured layer B side of the phase difference layer structure B with a substrate layer prepared as described above, was bonded to the protective film C side of the linear polarizing plate 6 prepared as described above using the adhesive layer (1A), which is the first bonding layer. The bonding of the first liquid crystal cured layer B and the linear polarizing plate 6 was performed 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 second liquid crystal cured layer B, exposed by peeling off the substrate layer on the second liquid crystal cured layer B side, was bonded to the adhesive layer (2) to obtain a circular polarizing plate (11). Corona treatment was performed on each bonding surface.

[0160] The obtained circular polarizing plates were subjected to the heat resistance test, moist heat durability test, and weather resistance test described above. The results are shown in Table 1.

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

[0162] 1,2,3 Circular polarizers, 4,5 Optical laminates, 10,11 Linear polarizers, 20 Phase difference 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 hardening layer, 202 Second liquid crystal hardening layer, 203 Separating film.

Claims

1. A circular polarizing plate comprising a linear polarizing plate and a liquid crystal hardening layer, The linear polarizing plate includes a polarizer and a protective film laminated on only one side of the polarizer. The polarizer, the protective film, and the liquid crystal curing layer are arranged in this order. The protective film and the liquid crystal curing layer further have a hard coat layer, A first bonding layer is further provided between the hard coat layer and the liquid crystal curing layer. The protective film is a circular polarizer having light selective absorption properties.

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

3. The circular polarizer according to claim 1 or 2, wherein the protective film is a cyclic polyolefin resin film.

4. The liquid crystal curing layer includes a first liquid crystal curing layer and a second liquid crystal curing layer. The circular polarizer according to any one of claims 1 to 3, wherein the polarizer, the protective film, the first liquid crystal hardened layer, and the second liquid crystal hardened layer are arranged in this order.

5. A circular polarizing plate according to any one of claims 1 to 4, comprising the polarizer, the protective film, the liquid crystal curing layer, and the adhesive layer in this order.

6. The circular polarizer according to any one of claims 1 to 5, further comprising the hard coat layer having light selective absorption properties.

7. A circular polarizer according to any one of claims 1 to 6, Front panel or touch sensor panel, An optical laminate for a flexible image display device, comprising the following features.

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

Images