Circular Polarizing Plate, Optical Laminate, and Image Display Device

Abstract

A circularly polarizing plate having a new configuration, and an optical laminate and an image display device each including the same are provided. [Solution] A circular polarizing plate including a linear polarizing plate and a liquid crystal cured layer, wherein the linear polarizing plate includes a polarizer and a protective film laminated on only one side of the polarizer, and the polarizer, protective film, and liquid crystal cured layer are arranged in this order, as well as an optical laminate and an image display device including the same are provided.

Description

Technical Field

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

Background Art

[0002] In a display device typified by an organic electroluminescence (EL) display device, a flexible display that enables bending of the display device using a flexible material is known. In an organic EL display device, in order to suppress a decrease in visibility due to reflection of external light, it is known to improve the antireflection performance using a circular polarizing plate or the like [for example, Japanese Patent Application Laid-Open No. 2020-134934 (Patent Document 1)]. A circular polarizing plate can be obtained by laminating a linear polarizing plate and a retardation layer, and a cured product layer of a polymerizable liquid crystal compound may be used as the retardation layer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

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

Means for Solving the Problems

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

Advantages of the Invention

[0006] It is possible to provide a circular polarizing plate having a new configuration, and an optical laminate and an image display device including the same.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

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 the following drawings are shown to assist in understanding the present invention, and the sizes and shapes of the respective components 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 polymerizing and curing a polymerizable liquid crystal compound). The term "circular polarizing plate" includes an elliptical polarizing plate. Note that 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 protective 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. Also in the circular polarizing plate 2 shown in FIG. 2, the linear polarizing plate 10 and the retardation layer structure 20 are 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 a first liquid crystal cured layer 201, a second bonding layer 30b, and a second liquid crystal cured layer 202 in order from the side of the linear polarizing plate 10. 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 layer of 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] FIG. 3 is a schematic cross-sectional view showing still another example of the layer structure of the circularly polarizing plate, and shows a specific example of the layer structure of the linear polarizing plate 11 and the retardation layer structure 20. Also in the circularly polarizing plate 3 shown in FIG. 3, the linear polarizing plate 11 and the retardation layer structure 20 are bonded to each other via the first bonding layer 30a. The circularly polarizing plate 3 shown in FIG. 3 has a configuration corresponding to the above d), and the linear polarizing plate 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 surface of the protective film 102 on the side of the retardation layer structure 20. 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. Also in the circularly polarizing plate 3, the outermost surface on the linear polarizing plate 11 side is the surface of the polarizer 101. Also, similar to the circularly polarizing plate 2 shown in FIG. 2, the circularly polarizing plate 3 shown in FIG. 3 may also include a third bonding layer 30c and a separate film 203.

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

[0015] The circularly polarizing plate according to the present invention is advantageous in the following points. 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, and as a result, the durability of the circularly polarizing plate is high. In particular, in the configuration in which the hard coat layer 103 and the first bonding layer 30a are in contact with each other as in the circularly polarizing plate 3 shown in FIG. 3, good adhesion between these layers can be obtained without performing corona treatment on these bonding surfaces or with a low intensity of corona treatment.

[0016] When corona treatment is carried out over a long period, there is a problem that crystalline foreign substances (such as oxalic acid) adhere to the object to be corona-treated and the yield decreases. Also, it is known that ozone and nitrogen oxides (NOx) are generated by corona discharge. By being able to omit the corona treatment or reduce the intensity of the corona treatment, the above problems can be solved or reduced.

[0017] B) When the polarizer 101 is a polyvinyl alcohol-based resin film on which iodine is adsorbed and oriented, due to the presence of the protective film 102 and further the hard coat layer 103 between the polarizer 101 and the image display element, for example, even when the circular polarizing plate of the present invention is held in a humid and hot environment, the migration of iodine from the polarizer 101 to the image display element can be suppressed or prevented. Thereby, the deterioration of the retardation layer structure 20 and, when an input device such as a touch sensor panel is bonded to the circular polarizing plate of the present invention, the deterioration of the touch sensor panel etc. can be suppressed or prevented.

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

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

[0020] Examples of the polarizer 101 include those obtained by subjecting a PVA-based film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or an ethylene-vinyl acetate copolymer-based partially saponified film to a dyeing treatment with iodine and a uniaxial stretching treatment. Preferably, a PVA-based film in which iodine is adsorbed and oriented by a dyeing treatment is treated with an aqueous boric acid solution, and then a washing step of washing off the aqueous boric acid solution is carried out. Known methods can be adopted for each step.

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

[0022] The saponification degree of the PVA-based resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The PVA-based resin may be modified. For example, polyvinyl formal, polyvinyl acetal, etc. modified with aldehydes can also be used. The average degree of polymerization of the PVA-based resin is usually about 1000 to 10000, preferably about 1500 to 5000. The average degree of polymerization of the PVA-based resin 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 preferable polarization performance, and if it exceeds 10000, the film processability may be inferior.

[0023] The circular polarizing plate of the present invention is particularly suitable for application to a flexible image display device. For the circular polarizing plate configured for application to such a flexible image display device, it is preferable that the thickness of each member is small. The thickness of the polarizer 101 is usually 30 μm or less, preferably 15 μm or less, more preferably 13 μm or less, and still 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 with a preferable thickness, a manufacturing method can be mentioned in which a PVA-based film (thin film PVA-based film) with a thickness of about 15 to 40 μm is used as a starting material, and this thin film PVA film is subjected to a dyeing treatment and a uniaxial stretching treatment to obtain the polarizer 101. By using a thin film PVA-based film in advance, the thickness of the obtained polarizer 101 can be reduced (First manufacturing method).

[0025] As a starting material, a preferable thin-film PVA-based film can also realize an extremely thin thin-film PVA-based film by forming a resin layer made of a PVA-based resin on a suitable base film (second manufacturing method). In this case, the manufacturing method of the thin-film PVA film may include a step of preparing a base film, applying a solution of a resin such as a PVA-based resin (PVA-based resin solution, etc.) on the base film, and performing drying or the like to remove the solvent to form a resin layer on the base film. A primer layer can be formed in advance on the surface of the base film where the resin layer is to be formed. As the base 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-film PVA-based film, which is the starting material in the first manufacturing method or the second manufacturing method, can be induced into the polarizer 101 by performing a dyeing treatment and a uniaxial stretching treatment. In the second manufacturing method, a PVA-based resin solution is applied on a base film, then, if necessary, the amount of solvent such as moisture in the resin layer is adjusted, and then the base film and the resin layer are uniaxially stretched. Subsequently, the resin layer is dyed with iodine to adsorb and orient iodine in the resin layer.

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

[0028] The same applies to the polarizer 101 obtained by the second manufacturing method. That is, for example, the base film provided with the resin layer that has undergone a dyeing treatment and a uniaxial stretching treatment can be subjected to a crosslinking treatment by bringing it into contact with a boric acid-containing solution in its original form (without peeling off the base film). The base film provided with the resin layer after the crosslinking treatment can be subjected to a cleaning treatment if necessary.

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

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

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

[0032] The boron content in the polarizer 101 can be determined, for example, by dissolving a predetermined mass of the polarizer 101 in, for example, a mannitol aqueous 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 examples of the present 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 above boric acid treatment, the degree of washing off of the boric acid aqueous solution in the above washing step, and the like.

[0034] The "boric acid crosslinking degree index" of the polarizer 101 is preferably 0.5 or more, more preferably 0.8 or more, and still more preferably 1.0 or more. In this specification, the "boric acid crosslinking degree index" means an index representing the degree to which polyvinyl alcohol molecular chains are crosslinked with boric acid in a polarizer made of a polyvinyl alcohol-based resin film or the like. The higher the value of the boric acid crosslinking degree index, the more the boric acid crosslinking of the polyvinyl alcohol molecular chains has progressed, and it can be said that the polarizer is a polarizer in which the boric acid crosslinking degree index of the polarizer 101 is within such a range, iodine can be stably held. As a result, it becomes easy to prevent the polarization degree of the polarizer 101 from decreasing, and as a result, the durability of the circular polarizing plate is likely to be improved.

[0035] The boric acid crosslinking degree index of the polarizer 101 can be determined by performing microscopic Raman spectroscopic analysis. In microscopic Raman spectroscopic analysis, by using a laser Raman spectrophotometer (trade name: "NRS-5100", manufactured by JASCO Corporation), the Raman scattered light intensity at a wave number of 780 cm -1 of the polarizer, and the Raman scattered light intensity at a wave number of 850 cm -1 are respectively determined, and then the Raman scattered light intensities at these wave numbers are divided (Raman scattered light intensity at a wave number of 780 cm -1 / Raman scattered light intensity at a wave number of 850 cm -1 ), and the boric acid crosslinking degree index can be calculated.

[0036] Here, FIG. 6 is an explanatory diagram for explaining microscopic Raman spectroscopic analysis of the polarizing plate according to the present embodiment. As shown in FIG. 6, in a laser Raman spectrophotometer, laser light X is made incident on the end face of a polarizer 101 so that the traveling direction of the laser light X is orthogonal to the absorption axis direction of the polarizer 101. Here, the laser light X is polarized in the thickness direction of the polarizer 101. Also, the measurement position of the laser light is set to the central position in the thickness direction of the polarizer 101. It is preferable to perform cross-section processing of the polarizing plate using a microtome before Raman spectroscopic measurement. The Raman scattered light intensity at a wavenumber of 780 cm -1 means the Raman scattered light intensity attributable to the bond between polyvinyl alcohol and boron, and the Raman scattered light intensity at a wavenumber of 850 cm -1 means the Raman scattered light intensity attributable to polyvinyl alcohol.

[0037] Also, various conditions used in the above microscopic Raman spectroscopic analysis are as follows. Excitation wavelength: 532 nm Grating: 600 l / mm Slit width: 100×1000 μm Aperture: φ40 μm Objective lens: 100× Objective lens: 100×

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

[0039] Increasing the visual sensitivity correction polarization degree Py of the polarizer 101 is advantageous for enhancing the function as an antireflection film of the circular polarizing plate and the durability of the circular polarizing plate. If the visual sensitivity correction polarization degree Py of the polarizer 101 is less than 95%, it may not be able to function as an antireflection film.

[0040] The single - body transmittance Ty of the visual sensitivity correction of the polarizer 101 is usually 41% or more, preferably 41.1% or more, more preferably 41.2% or more, may be 42% or more, and may be 42.5% or more. The single - body transmittance Ty of the visual sensitivity correction of the polarizer 101 is usually 50% or less, may be 48% or less, may be 46% or less, may be 44% or less, and may be 43% or less. If the single - body transmittance Ty of the visual sensitivity correction is excessively high, the visual sensitivity correction polarization degree Py may become too low, and the circular polarizing plate may not be able to achieve the function as an antireflection film. The single - body transmittance Ty of the visual sensitivity correction can be calculated by performing visual sensitivity correction on the obtained transmittance according to the 2 - degree field of view (C light source) of "JIS Z 8701" using a spectrophotometer with an integrating sphere ( "V7100" manufactured by JASCO Corporation).

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

[0042] Examples of the thermoplastic resin include cellulose resins such as triacetyl cellulose; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polyethersulfone resin; polysulfone resin; polycarbonate resin; polyamide resins such as nylon and aromatic polyamide; polyimide resin; polyolefin resins such as polyethylene, polypropylene, and ethylene - propylene copolymer; cyclic polyolefin resins having a cyclic and norbornene structure (also referred to as norbornene - based 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, more preferably a cyclic polyolefin resin film.

[0044] The protective film 102 preferably has no retardation characteristics or has a small retardation value. Specifically, the in-plane retardation value of the protective film 102 at a wavelength of 550 nm is preferably from 0 nm to 10 nm, and the retardation value in the thickness direction at a wavelength of 550 nm is preferably from -10 nm to +10 nm. In the circular polarizing plate of the present invention, when having a hard coat layer 103 like the circular polarizing plate 3, it is preferable that the laminate of the protective film 102 and the hard coat layer 103 is a film having a small retardation value as described above.

[0045] The thickness of the protective film 102 is preferably 2 μm or more, more preferably 3 μm or more, still 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, still more preferably 30 μm or less.

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

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

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

[0049] In the circular polarizing plate of the present invention, preferably, any layer other than the polarizer has light selective absorbency. One or two or more layers can have light selective absorbency. In the circular polarizing plate of the present invention, more preferably, the layer (protective film 102, hard coat layer 103, or first bonding layer 30a) between the polarizer 101 and the retardation layer structure 20, typically between the polarizer 101 and the liquid crystal cured layer 201, has light selective absorbency. One or two or more layers can have light selective absorbency. In the present specification, "having light selective absorbency" preferably means having absorbency with respect to ultraviolet rays such as a wavelength of 350 nm, and more preferably means having absorbency with respect to ultraviolet rays such as a wavelength of 350 nm and short-wavelength visible light in the vicinity of a wavelength of 410 nm.

[0050] The fact that the protective film 102 has light selective absorbency, preferably has absorbency with respect to ultraviolet rays such as a wavelength of 350 nm, and more preferably has absorbency with respect to ultraviolet rays such as a wavelength of 350 nm and short-wavelength visible light in the vicinity of a wavelength of 410 nm is advantageous in the following points. I) When a circularly polarizing plate is applied to an image display device, the image display element can be protected from ultraviolet rays and visible light with short wavelengths. II) Changes in the retardation value of the retardation layer structure 20 due to ultraviolet rays and visible light with short wavelengths can be suppressed. III) The reflected hue of the circularly polarizing plate can be adjusted by absorption of visible light with short wavelengths. IV) It is possible to prevent the polarizer 101 from deteriorating due to light reflected by an image display element such as an organic EL display element.

[0051] The impartation of light selective absorbency to the protective film 102 may be performed by using a thermoplastic resin having light selective absorbency as the protective film 102, or by incorporating an additive (light absorbent) having light selective absorbency into the protective film 102, or by both. The impartation of light selective absorbency to the protective film 102 is preferably performed by incorporating at least a light absorbent into the protective film 102.

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

[0053] As a light absorbent for light with a wavelength of 350 nm, various ultraviolet absorbers can be easily obtained from the market. Such ultraviolet absorbers include, for example, organic ultraviolet absorbers such as oxybenzone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, salicylic acid ester-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, and triazine-based ultraviolet absorbers. More specifically, 5-chloro-2-(3,5-di-sec-butyl-2-hydroxyphenyl)-2H-benzotriazole, (2-2H-benzotriazol-2-yl)-6-(linear and branched dodecyl)-4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc. are included.

[0054] As for the ultraviolet absorber, commercially available products may be used as they are. Examples of such commercially available products include, as triazine-based ultraviolet absorbers, "Kemisorb 102" manufactured by Chemipro Kasei Co., Ltd., "Adekastab LA46" and "Adekastab LAF70" manufactured by ADEKA Corporation, "Tinuvin 109", "Tinuvin 171", "Tinuvin 234", "Tinuvin 326", "Tinuvin 327", "Tinuvin 328", "Tinuvin 928", "Tinuvin 400", "Tinuvin 460", "Tinuvin 405", "Tinuvin 477" (all are trade names) manufactured by BASF Japan Ltd., etc. Examples of benzotriazole-based ultraviolet absorbers include "Adekastab LA31" and "Adekastab LA36" (both are trade names) manufactured by ADEKA Corporation, "Sumisorb 200", "Sumisorb 250", "Sumisorb 300", "Sumisorb 340" and "Sumisorb 350" (all are trade names) manufactured by Sumitomo Chemical Tex Co., Ltd., "Kemisorb 74", "Kemisorb 79" and "Kemisorb 279" (all are trade names) manufactured by Chemipro Kasei Co., Ltd., "TINUVIN 99-2", "TINUVIN 900" and "TINUVIN 928" (all are trade names) manufactured by BASF Corporation, etc. Incidentally, two or more kinds of ultraviolet absorbers may be used in combination for the circularly polarized light plate of the present invention, and different light absorbers may be used for the plurality of layers constituting the circularly polarized light plate of the present invention.

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

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

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

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

[0059] In another embodiment, in the circular polarizing plate of the present invention, the laminate of the layers excluding the polarizer (for example, the laminate composed of the protective film 102, hard coat layer 103, first bonding layer 30a, first liquid crystal cured layer 201, second bonding layer 30b, second liquid crystal cured layer 202, and third bonding layer 30c), that is, the laminate of the layers existing on the protective film side when based on the polarizer, the absorbance at a wavelength of 350 nm is preferably 0.3 or more, more preferably 0.5 or more, still more preferably 1.0 or more, further 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, further preferably 0.7 or more, usually 2.0 or less, and may be 1.5 or less.

[0060] The protective film 102 can be laminated on the polarizer 101 via an adhesive layer. As the adhesive for forming the adhesive layer, an aqueous adhesive or an active energy ray-curable adhesive described later can be used. Examples of the aqueous adhesive include an adhesive in which a polyvinyl alcohol-based resin is dissolved or dispersed in water. Note that the thickness of the adhesive layer between the protective film 102 and the polarizer 101 is usually 0.01 μm or more in terms of ensuring adhesiveness, and usually 10 μm or less. As described above, when the circular polarizing plate of the present invention is applied to a flexible image display device, the thinner the thickness of each member constituting the circular polarizing plate, the better. However, if the thickness of the adhesive layer becomes extremely thin, the desired adhesiveness may be impaired. Therefore, the thickness of the adhesive layer is optimized in consideration of the flexibility when the circular polarizing plate of the present invention is applied to a flexible image display device and the adhesiveness between the polarizer 101 and the protective film 102.

[0061] (2-3) Hard coat layer The circular polarizing plate can further include a hard coat layer 103 between the protective film 102 and the liquid crystal cured layer (the retardation layer structure 20). The hard coat layer 103 is preferably laminated on the surface of the protective film 102 on the side of the retardation layer structure 20, and more preferably laminated directly on the 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 by irradiation with active energy rays or thermal energy. The hard coat composition is preferably one that cures by irradiation with active energy rays. In the present specification, examples of the "active energy rays" include visible light, ultraviolet rays, infrared rays, X-rays, α-rays, β-rays, γ-rays, electron beams, etc., and ultraviolet rays are preferred.

[0063] The hard coat composition contains a polymer of at least one of a radically polymerizable compound and a cationically polymerizable compound. The radically polymerizable compound is a compound having a radically polymerizable group. The radically polymerizable group possessed by the radically polymerizable compound may be any functional group capable of causing a radical polymerization reaction, and examples thereof include groups containing a carbon-carbon unsaturated double bond. Specifically, a vinyl group, a (meth)acryloyl group, etc. may be mentioned.

[0064] As the radically polymerizable compound, from the viewpoint of high reactivity, a compound having a (meth)acryloyl group is preferable, and a compound called a polyfunctional acrylate monomer having 2 to 6 (meth)acryloyl groups in one molecule, or an oligomer having several (meth)acryloyl groups in the molecule and a molecular weight of several hundreds to several thousands called epoxy (meth)acrylate, urethane (meth)acrylate, or polyester (meth)acrylate can be preferably used. It is preferable to contain one or more selected from epoxy (meth)acrylate, urethane (meth)acrylate, and polyester (meth)acrylate.

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

[0066] Examples of the cationic polymerizable compound having an epoxy group include polyglycidyl ethers of polyhydric alcohols having an alicyclic ring, or alicyclic epoxy resins obtained by epoxidizing compounds containing a cyclohexene ring or a cyclopentene ring 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, homopolymers and copolymers of glycidyl (meth)acrylate; glycidyl ethers produced by the reaction of bisphenols such as bisphenol A, bisphenol F and hydrogenated bisphenol A, or their derivatives such as alkylene oxide adducts and caprolactone adducts, with epichlorohydrin, and novolac epoxy resins, etc., and glycidyl ether type epoxy resins derived from bisphenols, etc.

[0067] The hard coat composition can further contain a polymerization initiator. Examples of the polymerization initiator 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 to generate radicals or cations and promote radical polymerization and cationic polymerization.

[0068] Examples of the active energy ray radical polymerization initiator include Type 1 radical polymerization initiators that generate radicals by decomposition of molecules and Type 2 radical polymerization initiators that generate radicals by a hydrogen abstraction reaction in the coexistence of a tertiary amine, and they can be used alone or in combination. Examples of the thermal radical polymerization initiator include organic peroxides such as hydrogen peroxide and perbenzoic acid, and azo compounds such as azobisbutyronitrile. Examples of the cationic polymerization initiator include aromatic iodonium salts, aromatic sulfonium salts, and cyclopentadienyliron(II) complexes.

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

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

[0071] From the viewpoint of suppressing scratches that may occur when transporting the circularly polarized light plate of the present invention or during processing of the circularly polarized light plate, the thickness of the hard coat layer 103 is preferably 0.5 μm or more, more preferably 1 μm or more, still more preferably 3 μm or more, and may be 5 μm or more. From the viewpoints of bending resistance (flexibility) and production efficiency, the thickness of the hard coat layer 103 is preferably 30 μm or less, more preferably 20 μm or less, and still more preferably 10 μm or less.

[0072] The hard coat layer 103 may have light selective absorbency. It is preferable that at least one of the protective film 102 and the hard coat layer 103 has light selective absorbency, and both of them may have light selective absorbency. The advantages of the hard coat layer 103 having light selective absorbency are the same as those when the protective film 102 has light selective absorbency. The imparting of light selective absorbency to the hard coat layer 103 can be achieved by incorporating the above-mentioned light absorbent into the hard coat layer 103.

[0073] A protective film 102 (a protective film with a hard coat layer) having a hard coat layer 103 containing a light absorber is purchased from the market, and the protective film with the hard coat layer can be used as it is as a member of the circular polarizing plate of the present invention. Similarly, a protective film 102 that does not have a hard coat layer 103 but contains a light absorber can also be obtained. Although the content of the light absorber contained in such a protective film or a protective film with a hard coat layer may be unknown, in that case, an optimal one can be selected in consideration of the light transmittance of the protective film or the protective film with a hard coat layer with respect to visible light.

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

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

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

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

[0078] Examples of the polymerizable liquid crystal compound include rod-shaped polymerizable liquid crystal compounds and disc-shaped polymerizable liquid crystal compounds. One of these may be used, or a mixture containing both of these may be used. When the rod-shaped polymerizable liquid crystal compound is horizontally or vertically aligned with respect to the substrate layer, the optical axis of the polymerizable liquid crystal compound coincides with the major axis direction of the polymerizable liquid crystal compound. When the disc-shaped polymerizable liquid crystal compound is aligned, the optical axis of the polymerizable liquid crystal compound exists in a direction perpendicular to the disc plane of the polymerizable liquid crystal compound. As the rod-shaped polymerizable liquid crystal compound, for example, those described in Japanese Patent Application Laid-Open No. 2009-513019 (Claim 1, etc.) can be preferably used. As the disc-shaped polymerizable liquid crystal compound, those described in Japanese Patent Application Laid-Open No. 2007-108732 (paragraphs

[0020] to

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

[0013] to

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

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

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

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

[0082] As the alignment layer, it is preferable to have solvent resistance that does not dissolve by coating a composition for forming a liquid crystal layer containing a polymerizable liquid crystal compound, etc., and heat resistance against heat treatment for removing the solvent and aligning the polymerizable liquid crystal compound. Examples of the alignment layer include an alignment polymer layer formed of an alignment polymer, a photoalignment polymer layer formed of a photoalignment polymer, and a groove alignment layer having an uneven pattern or a plurality of grooves on the layer surface.

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

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

[0085] As the substrate layer, a film formed of a resin material can be used. For example, a film using the resin material described as the thermoplastic resin used for forming the above-described protective film 102 can be mentioned. The thickness of the substrate layer is not particularly limited, but generally, from the viewpoint of workability such as strength and handleability, it is preferably 1 to 300 μm, and more preferably 20 to 200 μm. The substrate layer may be incorporated into the circularly polarized light plate together with the liquid crystal cured layer, or the substrate layer may be peeled off, and only the liquid crystal cured layer, or the liquid crystal cured layer and the alignment layer may be incorporated into the circularly polarized light plate.

[0086] The second bonding layer 30b is an adhesive layer or an adhesive agent layer. The second bonding layer 30b is preferably an adhesive agent layer, more preferably an adhesive agent layer obtained by curing an active energy ray-curable adhesive, and even more preferably an adhesive agent layer obtained by curing an ultraviolet ray-curable adhesive. By making the second bonding layer 30b an adhesive agent layer, it is possible to suppress the occurrence of wrinkles in the liquid crystal cured layer when the circularly polarized light plate is bent or folded, which is preferable. As the adhesive layer, those described later can be used.

[0087] Examples of the active energy ray-curable adhesive include a solventless type active energy ray-curable adhesive containing a curable compound that cures by irradiation with active energy rays.

[0088] As a cationic polymerization curable compound, a radical polymerization curable compound, or both, it is preferable to include one or both of them because they exhibit good adhesiveness. The active energy ray curable adhesive may further include a cationic polymerization initiator such as a photo cationic polymerization initiator for initiating the curing reaction of the curable compound, or a radical polymerization initiator.

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

[0090] Examples of the radical polymerization curable compound include (meth)acrylic compounds (compounds having one or two or more (meth)acryloyloxy groups in the molecule), other vinyl compounds having a radical polymerization double bond, 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 from the viewpoint of further thinning, it is 15 μm or less, preferably 10 μm or less, particularly preferably 7 μm or less. When the second bonding layer 30b is an adhesive layer, the thickness is preferably 0.1 μm or more, may be 0.5 μm or more, and is preferably 10 μm or less, may be 5 μm or less.

[0092] (4) The first bonding layer and the third bonding layer The first bonding layer 30a is an adhesive layer or an adhesive agent layer, preferably an adhesive layer. The first bonding layer 30a bonds the linear polarizing plates 10, 11 and the retardation 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 polarizing plate to the image display element. The circular polarizing plate preferably includes a polarizer 101, a protective film 102, a liquid crystal cured layer (a first liquid crystal cured layer and further a second liquid crystal cured layer), and an adhesive layer (the third bonding layer 30c) in this order, and more preferably includes a polarizer 101, a protective film 102, a hard coat layer 103, a liquid crystal cured layer (a first liquid crystal cured layer and further a second liquid crystal cured layer), and an adhesive layer (the 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, preferably 3 μm or more and 20 μm or less. For example, it may be 10 μm or more, but in terms of further thinning, it is 15 μm or less, preferably 10 μm or less, particularly preferably 7 μm or less. When the first bonding layer 30a is an adhesive agent layer, the thickness is preferably 0.1 μm or more, may be 0.5 μm or more, and is preferably 10 μm or less, may be 5 μm or less.

[0094] The first bonding layer 30a may have light selective absorbency. It is preferable that at least one of the protective film 102, the hard coat layer 103, and the first bonding layer 30a has light selective absorbency, and a plurality of these layers may have light selective absorbency. The advantageous points of the first bonding layer 3aa having light selective absorbency are the same as those when the protective film 102 has light selective absorbency. The imparting of light selective absorbency to the first bonding layer 30a can be achieved by including the above-mentioned light absorbent in the first bonding layer 30a.

[0095] The thickness of the adhesive layer which is the third bonding layer 30c is not particularly limited and can be appropriately set according to its use. For example, it may be 250 μm or less, preferably 100 μm or less, more preferably 50 μm or less, still more preferably 40 μm or less, particularly preferably 30 μm or less, and even more particularly preferably 20 μm or less from the viewpoint of thinning. The lower limit of the thickness of the adhesive layer is not particularly limited, but from the viewpoint of durability, for example, it may be 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and still more preferably 14 μm or more.

[0096] As the adhesive, a conventionally known adhesive excellent in optical transparency can be used. For example, an adhesive having a base polymer such as (meth)acrylic, urethane, silicone, polyvinyl ether, etc. can be used. Also, an active energy ray curable adhesive, a thermosetting adhesive, etc. may be used. Among these, an adhesive based on a (meth)acrylic resin excellent in transparency, adhesive strength, peelability (hereinafter also referred to as reworkability), weather resistance, heat resistance, etc. is suitable. The adhesive layer is preferably composed of a reaction product of an adhesive containing a (meth)acrylic resin, a crosslinking agent, and a silane compound, and may contain other components.

[0097] The adhesive layer may be formed using an active energy ray curable adhesive. The active energy ray curable adhesive is obtained by blending an ultraviolet curable compound such as a polyfunctional (meth)acrylate into the above-mentioned adhesive, and irradiating with ultraviolet rays after forming the adhesive layer to cure it, thereby forming a harder adhesive layer. The active energy ray curable adhesive has the property of curing upon irradiation with energy rays such as ultraviolet rays and electron beams. Since the active energy ray curable adhesive has adhesiveness even before irradiation with energy rays, it is an adhesive having the property of adhering to an adherend and adjusting the adhesive strength by curing upon irradiation with energy rays.

[0098] The active energy ray-curable pressure-sensitive adhesive generally contains a (meth)acrylic pressure-sensitive adhesive and an energy ray-polymerizable compound as main components. Usually, a crosslinking agent is further blended, and if necessary, a photopolymerization initiator, a photosensitizer, etc. can also be blended.

[0099] (5) Separate film The circular polarizing plate can include a separate film 203 for protecting the outer surface of the third bonding layer 30c. Examples of the separate film 203 include a film having a release treatment such as a silicone treatment on the surface of the base film on the side of the third bonding layer 30c. The base film is, for example, a film made of a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, a polyester-based 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") includes the above-described circular polarizing plate according to the present invention and other components. Examples of the other components include an image display element 40 (see FIGS. 4 and 5) disposed on the side of the liquid crystal cured layer in the circular polarizing plate, that is, on the side opposite to the visual recognition side of the circular polarizing plate; a front panel 50 (see FIG. 5) disposed on the side of the polarizer 101 in the circular polarizing plate, more specifically, on the surface of the polarizer 101 which is the outermost surface of the circular polarizing plate; a protective film (also called "surface protective film") for temporarily protecting the surface of the polarizer 101, etc. The optical laminate preferably includes at least one selected from the group consisting of the front panel 50 and the image display element 40 as the above-described other components.

[0101] <Image display device> The circular polarizing plates 1, 2, and 3 can be arranged on the front surface (viewing side) of the image display element and used as components of the image display device. The circular polarizing plate can also be used as an antireflection polarizing plate that imparts an antireflection function in the image display device. The image display device is not particularly limited, and examples include image display devices such as organic electroluminescence (organic EL) display devices, inorganic electroluminescence (inorganic EL) display devices, liquid crystal display devices, and field emission display devices. Hereinafter, the main part of the aspect in which the circular polarizing plate (circular polarizing plates 1, 2, and 3) of the present invention is applied to an image display device, particularly a flexible image display device, will be briefly described.

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

[0103] <Optical laminate for flexible image display device> The optical laminate for a flexible image display device includes the circular polarizing plate of the present invention and an organic EL display element, which is an image display element with bending resistance. Further, the optical laminate for a flexible image display device has a front panel with bending resistance. Furthermore, it may include a touch sensor panel as an input means. In this case, the lamination order of the circular polarizing plate, the front panel, and the touch sensor panel may be, for example, the front panel, the circular polarizing plate, and the touch sensor panel in this order from the viewing side. The lamination order is preferably the front panel, the touch sensor panel, and the circular polarizing plate. It is preferable that the circular polarizing plate is present on the viewing side of the touch sensor panel because the wiring pattern of the touch sensor panel is less visible and the visibility of the displayed image is improved. Each member can be laminated using an adhesive, an adhesive agent, or the like. Further, the optical laminate for a flexible image display device can include a light-shielding pattern formed on at least one surface of any layer of the front panel, the polarizing plate, and the touch sensor panel.

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

[0105] Examples of the front panel include those made of glass or a resin film, and a hard coat layer may be included on at least one surface thereof. As the glass, for example, highly transmissive glass or tempered glass can be used. Particularly when a thin transparent surface material is used, chemically strengthened glass is preferable. 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 panel to be used is required to have flexibility (flexible characteristics). From this point, the front panel is preferably made of a resin film, and as described above, a hard coat layer may be included on at least one surface thereof. The front panel made of a resin film and including a hard coat layer is not as rigid as existing glass and can have flexible characteristics. In this case, the thickness of the hard coat layer is not particularly limited as long as it does not impair the flexible characteristics, and may be, for example, 5 to 100 μm.

[0107] As the material of the resin film used as the front panel, the same materials as those exemplified as the material of the protective film 102 can be mentioned. Of course, even if it is two or more kinds of materials, a film having a practical light transmittance may be used. From such a resin film of this material, the thickness and the like can be optimized in consideration of the light transmittance, flexible characteristics, durability, and the like. As the front panel, a film having no retardation characteristics (unstretched film) is preferable, but a uniaxially or biaxially stretched film may be used as long as the retardation value is acceptable. Among them, as the resin film used for the front panel, a polyamideimide film or a polyimide film excellent in transparency and heat resistance, a uniaxially or biaxially stretched polyester film, a cycloolefin-based derivative film excellent in transparency and heat resistance and capable of coping with the enlargement of the film, a polymethyl methacrylate film, and a triacetyl cellulose and isobutyl ester cellulose film having no optical anisotropy with transparency are preferable. The thickness of the resin film in this case may be 5 to 200 μm, preferably 20 to 100 μm.

[0108] <Light-shielding pattern> The light-shielding pattern is disposed, for example, in a part around the image display surface of the image display device called a bezel so that the wiring is not visible when the viewer views the image from the image display surface side or for other reasons. Such a light-shielding pattern is formed on at least one surface of either the front panel or the circularly polarized plate constituting the optical laminate for the image display device. When a touch sensor panel is attached as an input means to the optical laminate for the image display device, a light-shielding pattern may be provided on the touch sensor panel. As described above, the light-shielding pattern can hide each wiring of the display device so that it is not visible to the user. The color and material of the light-shielding pattern are not particularly limited, and it can be formed of a resinous substance 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. Further, in order to suppress the mixing of air bubbles due to the step between the light-shielding pattern and the display portion and the visibility of the boundary portion, a shape can be imparted to the light-shielding pattern.

[0109] <Touch sensor panel> The image display device provided with the circular polarizing plate of the present invention can further include a touch sensor as an input means. In this case, it can usually be realized by incorporating a touch sensor panel. As the method of the touch sensor, various methods such as a resistive film method, a surface acoustic wave method, an infrared method, an electromagnetic induction method, and a capacitance method have been proposed, and any method may be used. Among them, the capacitance method is preferable. The capacitance type touch sensor is divided into an active region and an inactive region located on the outer periphery of the active region. The active region is a region corresponding to the region (display portion) where the screen is displayed on the display panel and is a region where the touch of the user is sensed, and the inactive region is a region corresponding to the region (non-display portion) where the screen is not displayed on the display device. The touch sensor panel can include a substrate having flexible characteristics; a sensing pattern formed in the active region of the substrate; and each sensing line formed in the inactive region of the substrate and connected to an external drive circuit via the sensing pattern and a pad portion. As the substrate having flexible characteristics, the same material as the transparent substrate of the front panel 50 can be used. The substrate of the touch sensor panel is preferably one having 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, the toughness is defined as the lower area of the curve up to the breaking point in the stress (MPa)-strain (%) curve (Stress-Strain Curve) obtained through the tensile test of the polymer material.

[0110] The fourth adhesive layer 30d shown in FIG. 5 is an adhesive layer for bonding the front panel 50 and the polarizer 101 which is the uppermost layer of the circular polarizing plate. Regarding the fourth adhesive layer 30d, the description of the above-mentioned adhesive layer is cited.

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

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

Examples

[0113] Hereinafter, the present invention will be described more specifically by showing examples and comparative examples, but the present invention is not limited by these examples.

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

[0115] (2) Calculation of boric acid crosslinking degree index Cross-section processing of the polarizing plate was performed using an ultramicrotome (trade name "LEICA Ultramicrotome EM UC7i" manufactured by LEICA). Regarding the position at the center in the thickness direction of the polarizer in the cross-section of the obtained polarizing plate, using a laser Raman spectrophotometer (trade name: "NRS-5100", manufactured by JASCO Corporation), under the following conditions, at a wave number of 780 cm -1The Raman scattering light intensity at [specific condition], and the Raman scattering light intensity at a wavenumber of 850 cm -1 The Raman scattering light intensities at [specific condition] were determined respectively, and then the Raman scattering light intensities at these wavenumbers were divided (the Raman scattering light intensity at a wavenumber of 780 cm -1 / the Raman scattering light intensity at a wavenumber of 850 cm -1 ), and the boric acid crosslinking degree index was calculated. 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 the visually corrected polarization degree The single transmittance and the visually corrected polarization degree of the circular polarizing plate were measured by irradiating linearly polarized light from a prism onto 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-degree field of view (C light source) of JIS Z8701 to obtain the visually corrected polarization degree (Py). Here, 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) Polarization degree (%) = {(MD - TD) / (MD + TD)} × 100 Formula (B)

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

[0119] [Evaluation criteria for heat resistance test] A: No appearance changes such as floating, peeling, and foaming are observed. B: Appearance changes such as floating, peeling, and foaming are slightly noticeable. C: Appearance changes such as floating, peeling, and foaming are significantly recognized.

[0120] (6) Damp heat durability test of the circular polarizing plate The circular polarizing plate obtained in the example was cut into a square with a size of 30 mm × 30 mm. At this time, it was cut so that the absorption axis of the polarizer was parallel to the side of the square. The cut circular polarizing plate was bonded to an alkali-free glass (manufactured by Corning, product number: EAGLE XG (registered trademark)) with a size of 40 mm × 40 mm through the adhesive layer (2), and further bonded to an alkali-free glass (manufactured by Corning, product number: EAGLE XG (registered trademark)) with a size of 40 mm × 40 mm through the adhesive layer on the polarizer surface to prepare an evaluation sample. For this evaluation sample, the visually corrected polarization degree Py was measured.

[0121] Next, the evaluation sample was subjected to a damp heat durability test of storing it for 500 hours under the conditions of a temperature of 60°C and a relative humidity of 95%RH, and for the evaluation sample after the test, the visually corrected polarization degree Py was measured. The measured values of the visually corrected polarization degree Py before and after the test, and the absolute value ΔPy of the difference between them were described in Table 1.

[0122] (7) Weather resistance test of the circular polarizing plate The circular polarizing plate obtained in the example was cut into a square with a size of 30 mm × 30 mm. At this time, it was cut so that the absorption axis of the polarizer was parallel to the side of the square. The cut circular polarizing plate was bonded to a 40 mm × 40 mm non-alkali glass (manufactured by Corning, product number: EAGLE XG (registered trademark)) via the adhesive layer (2) to prepare an evaluation sample. For this evaluation sample, the single transmittance at 450 nm was measured.

[0123] Next, the evaluation sample was placed on an aluminum plate (reflector) so as to be irradiated with ultraviolet rays from the polarizer 101 side, and was put into a sunshine weather meter (manufactured by Suga Test Instruments Co., Ltd.) under the conditions of a black panel temperature of 63 °C and a relative humidity of 50% for 120 hours to conduct a weather resistance test. For the evaluation sample after the test, the single transmittance at 450 nm was measured. The absolute value of the difference in the measured values of the single transmittance at 450 nm before and after the test was described in Table 1.

[0124] (8) Measurement of absorbance of the laminate A laminate was prepared by laminating the protective film 102, the hard coat layer 103, the first bonding layer 30a, the first liquid crystal cured layer 201, the second bonding layer 30b, the second liquid crystal cured layer 202, and the third bonding layer 30c excluding the polarizer 101. In the layer structure without the 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 on a spectrophotometer UV-2450 (manufactured by Shimadzu Corporation), and the absorbance was measured in the wavelength range of 300 to 800 nm at 1 nm steps by the double-beam method. The absorbances of the fabricated laminate at wavelengths of 350 nm and 410 nm are shown in Table 1. Since the combined absorbance of the glass and the COP film with an adhesive at wavelengths of 350 nm and 410 nm is 0.06 or less, it can be ignored.

[0126] <Preparation of Components of Circular Polarizing Plate> (1) Preparation of Polarizer 1 A polyvinyl alcohol film with a thickness of 20 μm, a degree of polymerization of 2400, and a saponification degree of 99% or more was uniaxially stretched 4.1 times on a hot roll, and while maintaining the tension state, it was immersed in a dyeing bath containing 0.05 parts by mass of iodine and 5 parts by mass of potassium iodide per 100 parts by mass of water at 28°C for 60 seconds.

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

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

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

[0130] (3) Preparation of protective films A, B, C, D, E and release film F The following five types of protective films and one type of release film were prepared. · Protective film A: Cycloolefin film with a hard coat layer (COP-HC) having a thickness of 27 μm. The thickness of the hard coat layer is 2 μm, and the water vapor transmission rate is 10 g / m 2 · It was 24 hr. It has ultraviolet light absorbency. · Protective film B: Cycloolefin film (COP) with a thickness of 25 μm. The water vapor transmission rate is 12 g / m 2 · It was 24 hr. It has ultraviolet light absorbency. · Protective film C: COP with a thickness of 23 μm. It does not have ultraviolet light absorbency. · Protective film D: COP with a thickness of 13 μm. It has ultraviolet light absorbency. · Protective film E: COP-HC with a thickness of 27 μm. It has ultraviolet light absorbency and also has absorbency for short-wavelength visible light near a wavelength of 410 nm. · Release film F: TD80UL. A triacetyl cellulose film manufactured by Fuji Film Co., Ltd. The thickness is 80 μm, and the water vapor transmission rate is 502 g / m 2 · It was 24 hr.

[0131] (4) Preparation of linear polarizer 1 A protective film A was laminated on one side of the produced polarizer 1 via an aqueous adhesive, and a peelable film F was laminated on the opposite side of the protective film A via pure water. After laminating using a roll laminator, a drying treatment was performed at 80 °C for 3 minutes. Thereafter, the peelable film F was peeled off from the polarizer to obtain a linearly polarized light plate 1 having a protective film laminated only on one side of the polarizer 1. The linearly polarized light plate 1 was composed of the polarizer 1, an adhesive layer, and the protective film A laminated in this order.

[0132] (5) Production of linearly polarized light plate 2 A linearly polarized light plate 2 was produced in the same manner as the linearly polarized light plate 1, except that the temperature of the drying treatment after lamination using a roll laminator was changed to 100 °C.

[0133] (6) Production of linearly polarized light plate 3 A linearly polarized light plate 3 was produced in the same manner as the linearly polarized light plate 1, except that the polarizer 1 was changed to a polarizer 2.

[0134] (7) Production of linearly polarized light plate 4 A linearly polarized light plate 4 was produced in the same manner as the linearly polarized light plate 2, except that the polarizer 1 was changed to a polarizer 2.

[0135] (8) Production of linearly polarized light plate 5 A linearly polarized light plate 5 was produced in the same manner as the linearly polarized light plate 1, except that the protective film A was changed to a protective film B.

[0136] (9) Production of linearly polarized light plate 6 A linearly polarized light plate 6 was produced in the same manner as the linearly polarized light plate 1, except that the protective film A was changed to a protective film C.

[0137] (10) Production of linearly polarized light plate 7 A linearly polarized light plate 7 was produced in the same manner as the linearly polarized light plate 1, except that the protective film A was changed to a protective film D.

[0138] (11) Production of linearly polarized light plate 8 A linearly polarized light plate 8 was produced in the same manner as the linearly polarized light plate 1, except that the protective film A was changed to a protective film E.

[0139] (12) First Liquid Crystal Hardening Layer A (Production of 1 / 2 Wavelength Retardation Layer) On a substrate layer formed of a transparent resin, an alignment layer-forming composition was applied and dried to perform λ / 2 alignment treatment. Next, a liquid crystal layer-forming composition containing a discotic polymerizable liquid crystal compound was applied onto the alignment layer, and by heating and irradiating with UV to fix the alignment of the polymerizable liquid crystal compound, a 1 / 2 wavelength retardation layer as a liquid crystal hardening layer with a thickness of 2 μm was formed on the alignment layer of the substrate layer.

[0140] (13) Second Liquid Crystal Hardening Layer A (Production of 1 / 4 Wavelength Retardation Layer) A liquid crystal layer-forming composition containing a rod-shaped nematic polymerizable liquid crystal compound (liquid crystal monomer) was applied onto the rubbed alignment layer on a substrate layer formed of a transparent resin, and by solidifying while maintaining the refractive index anisotropy, a 1 / 4 wavelength retardation layer as a liquid crystal hardening layer with a thickness of 1 μm was formed on the alignment layer of the substrate layer.

[0141] (14) Preparation of Active Energy Ray Curable Adhesive A The following components were blended and mixed, and then defoamed to prepare an active energy ray curable adhesive A. [Cationic Polymerizable Compound] · Neopentyl Glycol Diglycidyl Ether (trade name: EX-211L, manufactured by Nagase ChemteX Corporation): 30 parts by mass · 3-Ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane (trade name: OXT-221, manufactured by Toagosei Co., Ltd.): 13 parts by mass · Bisphenol A type epoxy resin (trade name: EP-4100E, manufactured by ADEKA Corporation, viscosity 13 Pa·s (temperature 25°C)): 12 parts by mass · Aromatic-containing oxetane compound (trade name: TCM-104, manufactured by TRONLY): 45 parts by mass [Photo Cationic Polymerization Initiator] · CPI-100P, manufactured by San-Apro Ltd., 50% propylene carbonate solution: 2.25 parts by mass (solid content) [Photosensitizer Auxiliary Agent] · 1,4-Diethoxynaphthalene: 1 part by mass

[0142] (15) Fabrication of the retardation layer structure A with a substrate layer Corona treatment was performed on the surface of the first liquid crystal cured layer A (1 / 2 wavelength retardation layer) on the substrate layer and the surface of the second liquid crystal cured layer A (1 / 4 wavelength retardation layer) on the substrate layer. The corona-treated surfaces were bonded to each other using the active energy ray-curable adhesive A prepared above so that the angle formed by the slow axes of these two retardation layers was 60°. Then, from the 1 / 4 wavelength retardation layer side, using an ultraviolet irradiation device [manufactured by Fusion UV Systems Co., Ltd.], ultraviolet irradiation was performed with an integrated light amount of 400 mJ / cm 2 (UV-B) to cure the active energy ray-curable adhesive A and form an adhesive layer. The bonding 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. As a result, a retardation layer structure A with a substrate layer in which a substrate layer, an alignment layer, a 1 / 2 wavelength retardation layer (first liquid crystal cured layer), an adhesive layer (second bonding layer), a 1 / 4 wavelength retardation layer (second liquid crystal cured layer), an alignment layer, and a substrate layer were laminated in this order was obtained. The total thickness of the 1 / 2 wavelength retardation layer (first liquid crystal cured layer), the adhesive layer (second bonding layer), and the 1 / 4 wavelength retardation layer (second liquid crystal cured layer) was 6 μm.

[0143] (16) Fabrication of the first liquid crystal cured layer B (1 / 4 wavelength retardation layer) An alignment layer was formed on a substrate layer made of a transparent resin, and a composition for forming a liquid crystal layer containing a rod-shaped nematic polymerizable liquid crystal compound was applied to fabricate the first liquid crystal cured layer B. The first liquid crystal cured layer B had 1 / 4 wavelength retardation characteristics. The thickness of the first liquid crystal cured layer B was 2 μm.

[0144] (17) Fabrication of the second liquid crystal cured layer B (positive C layer) 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 were dissolved in 70.0 parts by mass of methyl ethyl ketone as a solvent to prepare an alignment layer - forming composition. Subsequently, 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 were dissolved in 80.0 parts by mass of propylene glycol monomethyl ether acetate as a solvent to prepare a liquid crystal layer - forming composition.

[0145] One side of the base material layer was subjected to corona treatment. The alignment layer - forming composition prepared above was coated on the corona - treated surface with a bar coater. After heat - treating the coated layer at 80°C for 60 seconds, ultraviolet rays were irradiated to polymerize and cure the alignment layer - forming composition. Thus, an alignment layer with a thickness of 2.2 μm was formed on the base material layer. The liquid crystal layer - forming composition prepared above was coated on the alignment layer. After heat - treating the coated layer at 80°C for 60 seconds, ultraviolet rays were irradiated to polymerize and cure the liquid crystal layer - forming composition. Thus, a second liquid crystal cured layer B with a thickness of 0.7 μm was formed on the alignment layer. The second liquid crystal cured layer B was a positive C layer.

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

[0147] (19) Preparation of the retardation layer structure B with a substrate layer The first liquid crystal cured layer B and the second liquid crystal cured layer B were bonded together with an active energy ray curable adhesive B (thickness 1 μm) such that the surface of each liquid crystal cured layer (the surface opposite to the substrate film) became the bonding surface. Ultraviolet rays were irradiated to cure the active energy ray curable adhesive B, and a retardation layer structure B with a substrate layer in which a substrate layer, an alignment layer, the first liquid crystal cured layer B, an adhesive layer (the second bonding layer), the second liquid crystal cured layer B, an alignment layer, and a substrate layer were laminated in this order was obtained. The thickness of the retardation laminate including the first liquid crystal cured layer B, the adhesive layer (the second bonding layer), and the second liquid crystal cured layer B was 6 μm. The retardation layer structure B with a substrate layer has ultraviolet absorption properties.

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

[0149] <Production of a circular polarizing plate> [Example 1] The substrate layer and the alignment layer on the 1 / 2 - wavelength retardation layer side of the retardation layer structure A with a substrate layer prepared above were peeled off to expose the 1 / 2 - wavelength retardation layer, and it was bonded to the protective film A side (the surface of the hard coat layer) of the linear polarizing plate 1 prepared above using the adhesive layer (1A) which is the first bonding layer. The bonding of the 1 / 2 - wavelength retardation layer and the linear polarizing plate 1 was performed such that the angle formed by the slow axis of the 1 / 2 - wavelength retardation layer and the transmission axis of the polarizer 1 was 15°. Next, the alignment layer and the substrate layer on the 1 / 4 - wavelength retardation layer side were peeled off to expose the 1 / 4 - wavelength retardation layer, and the adhesive layer (2) was bonded thereto to obtain a circular polarizing plate (1). Corona treatment was performed on each bonding surface.

[0150] [Example 2] A circular polarizing plate (2) was obtained in the same manner as in Example 1, except that the corona treatment was not performed on the bonding surface (the 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 polarizing plate (3) was obtained in the same manner as in Example 1, except that the linear polarizing plate 2 was used instead of the linear polarizing plate 1.

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

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

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

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

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

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

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

[0159] [Example 11] The first liquid crystal cured layer B exposed by peeling the base material layer on the first liquid crystal cured layer B side of the retardation layer structure B with a base material layer produced above and the protective film C side of the linear polarizing plate 6 produced above were bonded using an adhesive layer (1A) which is a 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 formed by 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 the base material layer on the second liquid crystal cured layer B side and the adhesive layer (2) were bonded to obtain a circular polarizing plate (11). Corona treatment was carried out on each bonding surface.

[0160] Regarding the obtained circular polarizing plate, the above-mentioned heat resistance test, damp heat durability test, and weather resistance test were carried out. The results are shown in Table 1.

[0161]

Table 1

Explanation of symbols

[0162] 1, 2, 3 circular polarizing plate, 4, 5 optical laminate, 10, 11 linear polarizing plate, 20 retardation layer structure, 30a first bonding layer, 30b second bonding layer, 30c third bonding layer, 30d fourth bonding layer, 40 image display element, 50 front panel, 101 polarizer, 102 protective film, 103 hard coat layer, 201 first liquid crystal cured layer, 202 second liquid crystal cured layer, 203 separator film.

Claims

1. A circular polarizing plate including a linear polarizer and a liquid crystal cured layer, wherein the linear polarizer includes a polarizer and a protective film laminated only on one side of the polarizer, the polarizer, the protective film, and the liquid crystal cured layer are arranged in this order, the polarizer has a boric acid crosslinking degree index of 1.0 or more and a boron content of 3.5% by mass or more and 5.5% by mass or less, further having a hard coat layer between the protective film and the liquid crystal cured layer, further having a first bonding layer between the hard coat layer and the liquid crystal cured layer, the protective film has light selective absorption properties, a circular polarizing plate.

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

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

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

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

6. The circular polarizing plate according to any one of claims 1 to 5, wherein the hard coat layer further has light selective absorption properties.

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

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

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