Phase difference plate, circular polarizing plate, image display device

Abstract

To provide a retardation plate that includes a polymer film, the hue difference of which is small in the front and diagonal directions of an image display device obtained when applied to an image display element as a circular polarizing plate in combination with a polarizer.SOLUTION: Provided is a retardation plate that includes a first optical anisotropic layer and a second optical anisotropic layer, the first optical anisotropic layer being a polymer film, the in-plane retardation in a wavelength of 550 nm of the first optical anisotropic layer being 60 to 300 nm, the retardation in the thickness direction in a wavelength of 550 nm of the first optical anisotropic layer being -150 to -30 nm, the second optical anisotropic layer being a layer formed by fixing a liquid crystal compound that is torsion oriented, with the thickness direction as a spiral axis, the second optical anisotropic layer satisfying a prescribed relationship regarding Δnd.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a retardation plate, a circularly polarizing plate, and an image display device.

Background Art

[0002] An optically anisotropic layer (retardation plate) having retardation is used in many applications. For example, an organic electroluminescence (EL) display device has a structure using a metal electrode, and thus reflects external light, which may cause a decrease in contrast and a problem of reflection. Therefore, conventionally, a circularly polarizing plate composed of a retardation plate and a polarizer has been used to suppress the influence of external light reflection.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Patent Document 1 discloses a retardation plate having a plurality of liquid crystal layers. However, when forming a retardation plate including a plurality of liquid crystal layers, it is often necessary to perform the application of a composition containing a liquid crystal compound at least twice, and the large number of application times is not necessarily industrially preferable. In addition, the handleability of the retardation plate itself having a plurality of liquid crystal layers was not necessarily good. From such a viewpoint, it has been desired to provide a retardation plate including a polymer film. Further, when a retardation plate and a polarizer are combined and applied to an image display element as a circularly polarizing plate, it is required that the color difference is small between the front direction and the oblique direction of the obtained image display device.

[0005] Therefore, an object of the present invention is to provide a retardation plate including a polymer film that, when applied to an image display element as a circularly polarizing plate in combination with a polarizer, exhibits a small color difference between the front direction and the oblique direction of the resulting image display device. Another object of the present invention is to provide a circularly polarizing plate and an image display device.

Means for Solving the Problems

[0006] As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by the following configuration.

[0007] 〔1〕 It includes a first optically anisotropic layer and a second optically anisotropic layer, wherein the first optically anisotropic layer is a polymer film, the in-plane retardation of the first optically anisotropic layer at a wavelength of 550 nm is 60 to 300 nm, the retardation in the thickness direction of the first optically anisotropic layer at a wavelength of 550 nm is -150 to -30 nm, the second optically anisotropic layer is a layer formed by fixing a liquid crystal compound that is twisted and oriented with the thickness direction as the spiral axis, the second optically anisotropic layer is a retardation plate that satisfies the relationship of formula (1) described later. 〔2〕 The retardation plate according to 〔1〕, further including an optical alignment film between the first optically anisotropic layer and the second optically anisotropic layer. 〔3〕 The retardation plate according to 〔1〕 or 〔2〕, wherein the polymer film includes a polymer having at least one selected from the group consisting of a repeating unit derived from a styrene derivative and a repeating unit having a fluorene structure. 〔4〕 The retardation plate according to any one of 〔1〕 to 〔3〕, wherein the liquid crystal compound exhibits liquid crystallinity at 50°C. 〔5〕 The retardation plate according to any one of 〔1〕 to 〔4〕, wherein the glass transition temperature of the first optically anisotropic layer is 110°C or higher. 〔6〕 The in-plane slow axis of the first optically anisotropic layer is parallel to the in-plane slow axis on the surface of the second optically anisotropic layer on the side of the first optically anisotropic layer. The in-plane retardation of the first optically anisotropic layer at a wavelength of 550 nm is 151 to 211 nm, The twist angle of the liquid crystal compound in the second optically anisotropic layer is within the range of 81 ± 10°, The retardation plate according to any one of [1] to [5], wherein the second optically anisotropic layer satisfies the relationship of formula (1-A) described later. 〔7〕 The in-plane slow axis of the first optically anisotropic layer and the in-plane slow axis on the surface of the second optically anisotropic layer on the first optically anisotropic layer side are orthogonal to each other, The twist angle of the second optically anisotropic layer is within the range of 59 ± 10°, The in-plane retardation of the first optically anisotropic layer at a wavelength of 550 nm is 158 to 218 nm, The retardation plate according to any one of [1] to [5], wherein the second optically anisotropic layer satisfies the relationship of formula (1-B) described later. 〔8〕 The angle formed by the in-plane slow axis of the first optically anisotropic layer and the in-plane slow axis on the surface of the second optically anisotropic layer on the first optically anisotropic layer side is within the range of 30 to 70°, The twist angle of the second optically anisotropic layer is within the range of 40 ± 20°, The in-plane retardation of the first optically anisotropic layer at a wavelength of 550 nm is 67.5 to 127.5 nm, The retardation plate according to any one of [1] to [5], wherein the second optically anisotropic layer satisfies the relationship of formula (1-C) described later. 〔9〕 The retardation plate according to any one of [1] to [8], further including a third optically anisotropic layer having a retardation in the thickness direction of -100 to -35 nm at a wavelength of 550 nm. 〔10〕 A circular polarizing plate including the retardation plate according to any one of [1] to [9] and a polarizer. 〔11〕 An image display device including the retardation plate according to any one of [1] to [9], or the polarizer according to

[10] .

Advantages of the Invention

[0008] According to the present invention, when applied to an image display element as a circular polarizing plate in combination with a polarizer, it is possible to provide a retardation plate including a polymer film with a small color difference between the front direction and the diagonal direction of the obtained image display device. Further, the present invention can also provide a circular polarizing plate and an image display device.

Brief Description of the Drawings

[0009]

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BEST MODE FOR CARRYING OUT THE INVENTION

[0010] Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.

[0011] Hereinafter, the meaning of each description in this specification will be represented. In this specification, a numerical range represented by “~” means a range including the numerical values described before and after “~” as the lower limit value and the upper limit value.

[0012] In this specification, the in-plane slow axis is defined at 550 nm unless otherwise specified.

[0013] In this specification, with regard to orthogonality and parallelism, those including the error range acceptable in the technical field to which the present invention pertains are assumed. Specifically, it means within the range of the exact angle ±10°, and the error from the exact angle is preferably within the range of ±5°, and more preferably within the range of ±3°.

[0014] In this specification, Re(λ) and Rth(λ) respectively represent in-plane retardation and thickness-direction retardation at wavelength λ. When not otherwise specified, the wavelength λ is 550 nm. In this specification, Re(λ) and Rth(λ) are the values measured at wavelength λ in AxoScan (manufactured by Axometrics). They are calculated by inputting the average refractive index ((nx + ny + nz) / 3) and the film thickness (d (μm)) in AxoScan. Slow axis direction (°) Re(λ) = R0(λ) Rth(λ) = ((nx + ny) / 2 - nz) × d Note that R0(λ) is displayed as a numerical value calculated by AxoScan, but it means Re(λ).

[0015] As characteristic points of the retardation plate of the present invention, points satisfying the following two requirements can be mentioned. Requirement 1: The first optically anisotropic layer is a polymer film, the in-plane retardation of the first optically anisotropic layer at a wavelength of 550 nm is 60 to 300 nm, and the thickness-direction retardation of the first optically anisotropic layer at a wavelength of 550 nm is -150 to -30 nm. Requirement 2: The second optically anisotropic layer is a layer formed by fixing a liquid crystal compound twisted and oriented with the thickness direction as the helical axis, and the second optically anisotropic layer satisfies the relationship of formula (1) described later. When the retardation plate satisfies the above two requirements, when the retardation plate is applied as a circularly polarizing plate to an image display element, the color difference between the front direction and the diagonal direction of the obtained image display device is reduced. Hereinafter, "when the retardation plate is applied as a circularly polarizing plate to an image display element, the color difference between the front direction and the diagonal direction of the obtained image display device is further reduced" is also referred to as "the effect of the present invention is more excellent".

[0016] The retardation plate of the present invention includes a first optically anisotropic layer and a second optically anisotropic layer. The first optically anisotropic layer is a polymer film. The in-plane retardation of the first optically anisotropic layer at a wavelength of 550 nm is 60 to 300 nm, and the retardation in the thickness direction of the first optically anisotropic layer at a wavelength of 550 nm is -150 to -30 nm. The second optically anisotropic layer is a layer formed by fixing a liquid crystal compound that is twisted and oriented with the thickness direction as the helical axis, and the second optically anisotropic layer satisfies the relationship of formula (1). Formula (1) 100 nm ≦ Δnd ≦ 380 nm In formula (1), Δn represents the refractive index anisotropy of the second optically anisotropic layer at a wavelength of 550 nm, and d represents the thickness of the second optically anisotropic layer.

[0017] Hereinafter, based on the first to third embodiments of the present invention, the retardation plate of the present invention will be described.

[0018] <First Embodiment> Hereinafter, the first embodiment of the retardation plate of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic cross-sectional view of the first embodiment of the retardation plate of the present invention.

[0019] The retardation plate 10a has a first optically anisotropic layer 12a and a second optically anisotropic layer 14a. The first optically anisotropic layer 12a is a polymer film, and the second optically anisotropic layer 14a is a layer formed using a rod-shaped liquid crystal compound LC. In particular, the second optically anisotropic layer 14a is a layer formed by fixing a liquid crystal compound that is twisted and oriented with the thickness direction as the helical axis. In FIG. 1, an example in which a rod-shaped liquid crystal compound is used as the liquid crystal compound is shown. However, as will be described later, the liquid crystal compound is not limited to the rod-shaped liquid crystal compound. Hereinafter, the first optical anisotropic layer 12a and the second optical anisotropic layer 14a will be described.

[0020] [First optical anisotropic layer 12a] The first optical anisotropic layer 12a is a polymer film. A polymer film is mainly a film composed of a polymer, and a stretched polymer film is preferable in that it is likely to exhibit a predetermined retardation described later. A stretched polymer film is a polymer film subjected to a stretching process.

[0021] The material constituting the polymer film is not particularly limited as long as it satisfies a predetermined retardation described later. Since the above polymer film exhibits in-plane retardation, it is a member exhibiting birefringence. Such a polymer film is generally manufactured by stretching a polymer. Due to the difference in optical expressibility when stretched, polymers constituting the polymer film are classified into polymers with positive intrinsic birefringence and polymers with negative intrinsic birefringence. A polymer with positive intrinsic birefringence is a polymer in which the stretching direction becomes the slow axis. In other words, a polymer with positive intrinsic birefringence is a polymer in which the refractive index in the stretching direction is larger than the refractive index in the direction orthogonal thereto. Also, a polymer with negative intrinsic birefringence is a polymer in which the direction orthogonal to the stretching direction becomes the slow axis. In other words, a polymer with negative intrinsic birefringence is a polymer in which the refractive index in the stretching direction is smaller than the refractive index in the direction orthogonal thereto. The intrinsic birefringence of the polymer constituting the above polymer film may be either positive or negative, and it is preferable that the intrinsic birefringence of the polymer constituting the polymer film is negative.

[0022] Examples of polymers having positive intrinsic birefringence include polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyarylene sulfides such as polyphenylene sulfide; polyvinyl alcohol; polycarbonate; polyarylate; cellulose ester polymers such as cellulose acetate; polyethersulfone; polysulfone; polyallylsulfone; polyvinyl chloride; cyclic olefin polymers such as norbornene polymers; rod-like liquid crystal polymers; and the like. The polymer may be a homopolymer or a copolymer.

[0023] Examples of polymers having negative intrinsic birefringence include polystyrene-based polymers including homopolymers of styrene or styrene derivatives (e.g., polystyrene, polystyrene fluoride) and copolymers of styrene or styrene derivatives and any monomer; polyacrylonitrile polymers; (meth)acrylic polymers such as polymethyl methacrylate; polyester resins; or their multi-component copolymer polymers; and cellulose compounds such as cellulose esters. More specifically, examples include polymethyl methacrylate, polystyrene, polystyrene fluoride, polyvinyl naphthalene, and fumarate resins. The styrene derivatives include monomers in which one or more hydrogen atoms of the ethenyl group of styrene are substituted with substituents, and monomers in which one or more hydrogen atoms of the phenyl group of styrene are substituted with substituents. Examples of the substituents include alkyl groups, halogen atoms, alkoxy groups, acetoxy groups, amino groups, nitro groups, cyano groups, aryl groups, hydroxyl groups, and carbonyl groups. The number of substituents may be one or two or more. Further, the substituent may or may not have a further substituent. The styrene derivative may be one in which a phenyl group and another aromatic ring are condensed, or may be indenes or indanes in which the substituent forms a ring other than the phenyl group, or may have a structure having a bridged ring.

[0024] Examples of polymers having negative intrinsic birefringence include polymers containing repeating units having a fluorene structure. For example, polymers containing repeating units having a fluorene-9,9-diyl structure can be mentioned.

[0025] In the present invention, any polymer film can be used, but a polymer film containing a polymer having negative intrinsic birefringence is preferred. Among them, a polymer having at least one selected from the group consisting of repeating units derived from a styrene derivative and repeating units having a fluorene structure is preferred. As the above styrene derivative, those in which the hydrogen atom of the ethenyl group of styrene is substituted with a halogen atom are preferred. The stereoregularity of the resin having a structure derived from styrene or a structure derived from a styrene derivative in the repeating unit is not particularly limited and may be any of isotactic, syndiotactic, and atactic. Among them, the stereoregularity of the resin is preferably syndiotactic.

[0026] Further, the polymer film may contain two or more types of polymers. As described above, the polymer film is preferably a stretched polymer film (stretched film), and more preferably a stretched polymer film containing a polymer having negative intrinsic birefringence.

[0027] The content of the polymer having negative intrinsic birefringence in the polymer film is preferably 50 to 100% by mass, more preferably 75 to 100% by mass, based on the total mass of the polymer film, in terms of more excellent effects of the present invention.

[0028] Further, the glass transition temperature (Tg) of the polymer film constituting the first optically anisotropic layer 12a is preferably 110°C or higher. By having Tg of 110°C or higher, wrinkles during the production of the retardation plate can be suppressed. The upper limit of Tg is not particularly limited, but is preferably 180°C or lower.

[0029] As described above, the in-plane retardation of the first optically anisotropic layer 12a at a wavelength of 550 nm is 60 to 300 nm. The in-plane retardation of the first optically anisotropic layer 12a at a wavelength of 550 nm is preferably 90 to 230 nm, and more preferably 151 to 211 nm, in terms of more excellent effects of the present invention. Also, as described above, the retardation in the thickness direction of the first optically anisotropic layer 12a at a wavelength of 550 nm is -150 to -30 nm. The retardation in the thickness direction of the first optically anisotropic layer 12a at a wavelength of 550 nm is preferably -115 to -45 nm, and more preferably -109 to -75 nm, in terms of more excellent effects of the present invention.

[0030] The in-plane slow axis of the first optically anisotropic layer 12a is parallel to the in-plane slow axis on the surface of the second optically anisotropic layer 14a on the side of the first optically anisotropic layer 12a.

[0031] The thickness of the first optically anisotropic layer 12a is not particularly limited, but is preferably 1 to 100 μm, more preferably 10 to 70 μm, and even more preferably 20 to 50 μm.

[0032] [Second optically anisotropic layer 14a] As shown in FIG. 1, the second optically anisotropic layer 14a is a layer formed by fixing a twisted and aligned rod-like liquid crystal compound LC having a thickness direction (z-axis direction in FIG. 1) as a helical axis. Note that the twisted alignment of the liquid crystal compound means that the liquid crystal compound is twisted from one main surface of the second optically anisotropic layer 14a to the other main surface with the thickness direction of the second optically anisotropic layer 14a as an axis. Accordingly, the alignment direction of the liquid crystal compound (that is, the in-plane slow axis direction) varies depending on the position in the thickness direction of the second optically anisotropic layer 14a. Note that the "fixed" state is a state in which the alignment of the liquid crystal compound is maintained. Specifically, usually, in the temperature range of 0 to 50 °C, and under more severe conditions, in the temperature range of -30 to 70 °C, it is preferably a state in which the layer has no fluidity and can stably maintain the fixed alignment form without changing the alignment form due to an external field or an external force.

[0033] The liquid crystal compound contained in the second optically anisotropic layer 14a is not limited to a rod-shaped liquid crystal compound as in the example shown in FIG. 1. The liquid crystal compound only needs to be a compound exhibiting liquid crystallinity, and the type of the liquid crystal compound is not particularly limited. Generally, liquid crystal compounds can be classified into a rod type (rod-shaped liquid crystal compound) and a disc type (discotic liquid crystal compound) according to their shapes. Further, liquid crystal compounds can be classified into a low molecular type and a high molecular type. A polymer generally refers to a substance having a degree of polymerization of 100 or more (Physical Polymer Science and Phase Transition Dynamics, written by Masao Doi, page 2, Iwanami Shoten, 1992). In the present invention, any liquid crystal compound can be used, but it is preferable to use a rod-shaped liquid crystal compound or a discotic liquid crystal compound, and it is more preferable to use a rod-shaped liquid crystal compound. A mixture of two or more rod-shaped liquid crystal compounds, two or more discotic liquid crystal compounds, or a rod-shaped liquid crystal compound and a discotic liquid crystal compound may also be used. As the rod-shaped liquid crystal compound, for example, those described in Claim 1 of JP-T-11-513019 and paragraphs 0026 to 0098 of JP-A-2005-289980 can be preferably used. As the discotic liquid crystal compound, for example, those described in paragraphs 0020 to 0067 of JP-A-2007-108732 and paragraphs 0013 to 0108 of JP-A-2010-244038 can be preferably used.

[0034] Further, the liquid crystal compound may have a polymerizable group. When the liquid crystal compound has a polymerizable group and liquid crystal compounds polymerize with each other or with other compounds via the polymerizable group, the orientation of the liquid crystal compound can be fixed. A liquid crystal compound having a polymerizable group is also referred to as a polymerizable liquid crystal compound. The polymerizable group is not particularly limited, but a functional group capable of addition polymerization reaction is preferable, a polymerizable ethylenic unsaturated group or a ring polymerizable group is more preferable, and a (meth)acryloyl group, a vinyl group, a styryl group, or an allyl group is even more preferable. Note that after the liquid crystal compound is fixed by polymerization or the like to form the second optically anisotropic layer 14a, the liquid crystal compound does not need to exhibit liquid crystallinity any more.

[0035] The above liquid crystal compound preferably exhibits liquid crystallinity at 50°C. Two or more of the above liquid crystal compounds may be used. When two or more are used, it is preferable that the mixture exhibits liquid crystallinity at 50°C.

[0036] The second optically anisotropic layer 14a may contain a chiral agent. A chiral agent refers to a compound that can induce a twisted orientation of a liquid crystal compound. The ability of the chiral agent to induce a twisted orientation (helix induction force) may or may not change upon light irradiation. Also, the direction of the helix induction force is not particularly limited. Also, the chiral agent may or may not exhibit liquid crystallinity.

[0037] Examples of chiral agents whose helix induction force changes upon light irradiation (photo-responsive chiral agents) include compounds having a chiral moiety and a photo-reactive moiety whose structure changes upon light irradiation. For example, compounds that greatly change the twisting force of a liquid crystal compound according to the irradiation amount are also included. Examples of photo-reactive moieties whose structure changes upon light irradiation include photochromic compounds (Kinugo Uchida, Masahiro Irie, Chemical Industry, vol. 64, 640p, 1999; Kinugo Uchida, Masahiro Irie, Fine Chemical, vol. 28(9), 15p, 1999). Also, the above structural change means decomposition, addition reaction, isomerization, racemization, [2+2] photocyclization, dimerization reaction, etc. caused by light irradiation to the photo-reactive moiety, and the above structural change may be irreversible. Also, as the chiral moiety, for example, asymmetric carbon described in Hiroyuki Nomura, Chemical Review, No. 22 Chemistry of Liquid Crystals, 73p: 1994 corresponds.

[0038] Two or more of the above chiral agents may be used simultaneously, or a photo-responsive chiral agent and a non-photo-responsive chiral agent may be used in combination.

[0039] The twist angle of the liquid crystal compound is preferably in the range of 81±10° (71 to 91°), and more preferably in the range of 81±6° (75 to 87°) in terms of more excellent effects of the present invention. Note that there are two types of twist directions, and it doesn't matter whether it is clockwise or counterclockwise. That is, regarding the above-mentioned twist angle, when it is indicated that the twist angle is within the range of 81 ± 10°, it shall refer to both the case of twisting within the range of 81 ± 10° clockwise and the case of twisting within the range of 81 ± 10° counterclockwise. Note that the twist angle is measured using the AxoScan (polarimeter) device of Axometrics and the attached device analysis software.

[0040] In addition, the second optically anisotropic layer 14a preferably satisfies the relationship of the following formula (1-A). Formula (1-A) 142 nm ≤ Δnd ≤ 202 nm In formula (1-A), Δn represents the refractive index anisotropy at a wavelength of 550 nm of the second optically anisotropic layer 14a. In formula (1-A), d represents the film thickness (nm) of the second optically anisotropic layer 14a. The second optically anisotropic layer 14a more preferably satisfies the relationship of the following formula (1-A1), and even more preferably satisfies the relationship of the following formula (1-A2). Formula (1-A1) 151 nm ≤ Δnd ≤ 211 nm Formula (1-A2) 136 nm ≤ Δnd ≤ 196 nm The above Δnd can be adjusted according to the type of liquid crystal compound, the twist angle, and the film thickness of the second optically anisotropic layer 14a. Note that the above Δnd is measured using the AxoScan (polarimeter) device of Axometrics and the attached device analysis software in the same manner as the measurement method of the twist angle.

[0041] The thickness of the second optically anisotropic layer 14a is not particularly limited, but is preferably 0.1 to 10.0 μm, more preferably 1.0 to 5.0 μm, and even more preferably 1.0 to 2.5 μm.

[0042] The first embodiment of the retardation plate of the present invention includes at least the above-mentioned first optically anisotropic layer 12a and the second optically anisotropic layer 14a, and may include other members.

[0043] [Other members] The first embodiment of the retardation plate of the present invention may further include a third optically anisotropic layer. As the third optically anisotropic layer, a layer having retardation in the thickness direction is preferable. An optically anisotropic layer showing negative retardation (Rth) in the thickness direction is preferable, that is, a so-called positive C plate is preferable. The retardation (Rth) in the thickness direction of the third optically anisotropic layer at a wavelength of 550 nm is preferably -200 to -30 nm, more preferably -150 to -35 nm, and even more preferably -100 to -35 nm in terms of more excellent effects of the present invention.

[0044] The first embodiment of the retardation plate of the present invention may further include an alignment film. In particular, an alignment film may be included between the first optically anisotropic layer and the second optically anisotropic layer.

[0045] The alignment film can be formed by means such as rubbing treatment of an organic compound (preferably a polymer), oblique vapor deposition of an inorganic compound, formation of a layer having microgrooves, or accumulation of an organic compound (e.g., ω-tricosanoic acid, dioctadecyldimethylammonium chloride, methyl stearate) by the Langmuir-Blodgett method (LB film). Furthermore, an alignment film in which an alignment function is generated by applying an electric field, applying a magnetic field, or irradiating with light (preferably polarized light) is also known. Examples of the alignment film include a photoalignment film. The material for forming the photoalignment film will be described in detail later. The thickness of the alignment film is not particularly limited as long as it can exhibit an alignment function, but is preferably 0.01 to 5.0 μm, more preferably 0.05 to 2.0 μm, and even more preferably 0.1 to 0.5 μm.

[0046] The first embodiment of the retardation plate of the present invention may further include a substrate. As the substrate, a transparent substrate is preferable. Note that the transparent substrate is intended to be a substrate having a visible light transmittance of 60% or more, and its transmittance is preferably 80% or more, and more preferably 90% or more. The thickness of the substrate is not particularly limited, but is preferably 10 to 200 μm, more preferably 10 to 100 μm, and even more preferably 20 to 90 μm.

[0047] Also, the substrate may be composed of a plurality of laminations. In order to improve the adhesion between the substrate and the layer provided thereon, a surface treatment (for example, glow discharge treatment, corona discharge treatment, ultraviolet (UV) treatment, flame treatment) may be performed on the surface of the substrate. Also, an adhesive layer (primer layer) may be provided on the substrate. Also, in order to impart slidability in the conveying process to the substrate or to prevent the back surface and the front surface from sticking together after winding, a polymer layer in which inorganic particles having an average particle diameter of about 10 to 100 nm are mixed at a solid content mass ratio of 5 to 40% by mass may be disposed on one side of the substrate.

[0048] The substrate may be a so-called temporary support. That is, after manufacturing the retardation plate, the substrate may be peeled off from the retardation plate.

[0049] [Circular polarizing plate] The first embodiment of the retardation plate of the present invention can be used as a circular polarizing plate in combination with a polarizer. The circular polarizing plate is an optical element that converts non-polarized light into circularly polarized light. The circular polarizing plate of the present invention having the above configuration is suitably used for anti-reflection applications of image display devices such as liquid crystal display devices (LCDs), plasma display panels (PDPs), electroluminescence displays (ELDs), and cathode ray tube display devices (CRTs), and is for improving the contrast ratio of display light.

[0050] The polarizer may be a member having a function of converting natural light into specific linearly polarized light, and examples thereof include absorption type polarizers. The type of the polarizer is not particularly limited, and commonly used polarizers can be used. Examples thereof include iodine-based polarizers, dye-based polarizers using dichroic substances, and polyene-based polarizers. Iodine-based polarizers and dye-based polarizers are generally produced by adsorbing iodine or dichroic dyes on polyvinyl alcohol and stretching it. A protective film may be disposed on one or both sides of the polarizer.

[0051] FIG. 2 shows a schematic cross-sectional view of an embodiment of a circular polarizing plate. FIG. 3 is a diagram showing the relationship between the absorption axis AA of the polarizer 20, the in-plane slow axis SA1 on the surface 121a on the polarizer 20 side of the first optically anisotropic layer 12a, the in-plane slow axis SA2 on the surface 122a on the second optically anisotropic layer 14a side of the first optically anisotropic layer 12a, the in-plane slow axis SA3 on the surface 141a on the first optically anisotropic layer 12a side of the second optically anisotropic layer, and the in-plane slow axis SA4 on the surface 142a on the side opposite to the first optically anisotropic layer 12a side of the second optically anisotropic layer in the circular polarizing plate 100a shown in FIG. 2. FIG. 4 is a diagram showing the angular relationship between the absorption axis AA of the polarizer 20 and the respective in-plane slow axes (SA1 to SA4) of the first optically anisotropic layer 12a and the second optically anisotropic layer 14a when observed from the white arrow in FIG. 2. Note that the arrow in the polarizer 20 in FIG. 3 represents the absorption axis, and the arrows in the first optically anisotropic layer 12a and the second optically anisotropic layer 14a represent the in-plane slow axes in the respective layers. Note that the rotation angle of the in-plane slow axis is represented by a positive angle value in the counterclockwise direction and a negative angle value in the clockwise direction with respect to the absorption axis AA of the polarizer 20 as a reference (0°) when observed from the white arrow in FIG. 2. Also, the twisting direction is determined to be clockwise or counterclockwise with respect to the in-plane slow axis (SA3) on the front side (polarizer 20 side) of the surface 141a in the second optically anisotropic layer 14a when observed from the white arrow in FIG. 2.

[0052] As shown in FIG. 2, the circular polarizing plate 100a includes a polarizer 20, a first optically anisotropic layer 12a, and a second optically anisotropic layer 14a in this order. As shown in FIGS. 3 to 4, the angle φa1 formed between the absorption axis AA of the polarizer 20 and the in-plane slow axis SA1 on the surface 121a on the polarizer 20 side of the first optically anisotropic layer 12a is 15°. More specifically, the in-plane slow axis SA1 on the surface 121a on the polarizer 20 side of the first optically anisotropic layer 12a is rotated 15° (15° counterclockwise) with respect to the absorption axis AA of the polarizer 20. In FIGS. 3 to 4, an embodiment is shown in which the in-plane slow axis SA1 on the surface 121a on the polarizer 20 side of the first optically anisotropic layer 12a is at a position 15° with respect to the absorption axis AA of the polarizer 20. However, the present invention is not limited to this embodiment, and it is preferably within the range of 15 ± 10°. That is, the angle formed between the absorption axis AA of the polarizer 20 and the in-plane slow axis SA1 on the surface 121a on the polarizer 20 side of the first optically anisotropic layer 12a is preferably within the range of 15 ± 10°. As shown in FIG. 3, in the first optically anisotropic layer 12a, the in-plane slow axis SA1 on the surface 121a on the polarizer 20 side of the first optically anisotropic layer 12a and the in-plane slow axis SA2 on the surface 122a on the second optically anisotropic layer 14a side of the first optically anisotropic layer 12a are parallel.

[0053] As shown in FIGS. 3 to 4, SA2 on the surface 122a on the second optically anisotropic layer 14a side of the first optically anisotropic layer 12a and the in-plane slow axis SA3 on the surface 141a on the first optically anisotropic layer 12a side of the second optically anisotropic layer 14a are parallel. As described above, the second optically anisotropic layer 14a is a layer in which a twisted alignment liquid crystal compound having a thickness direction as a helical axis is fixed. Therefore, as shown in FIGS. 3 to 4, the in-plane slow axis SA3 on the surface 141a on the polarizer 20 side of the second optically anisotropic layer 14a and the in-plane slow axis SA4 on the surface 142a on the side opposite to the first optically anisotropic layer 12a side of the second optically anisotropic layer 14a form the above-described twist angle (in FIG. 4, 81°). That is, the angle φa3 formed by the in-plane slow axis SA3 on the surface 141a on the polarizer 20 side of the second optically anisotropic layer 14a and the in-plane slow axis SA4 on the surface 142a on the side opposite to the first optically anisotropic layer 12a side of the second optically anisotropic layer 14a is 81°. More specifically, the in-plane slow axis of the second optically anisotropic layer 14a rotates by 81° (81° counterclockwise). Therefore, the angle formed by the absorption axis AA of the polarizer 20 and the in-plane slow axis SA4 on the surface 142a on the side opposite to the first optically anisotropic layer 12a side of the second optically anisotropic layer 14a is 96°. In FIGS. 3 to 4, a mode in which the in-plane slow axis of the second optically anisotropic layer 14a rotates by 81° is shown, but the present invention is not limited to this mode, and the rotation angle is preferably within the range of 81 ± 10°. That is, the angle formed by the in-plane slow axis SA3 on the surface 141a on the polarizer 20 side of the second optically anisotropic layer 14a and the in-plane slow axis SA4 on the surface 142a on the side opposite to the first optically anisotropic layer 12a side of the second optically anisotropic layer 14a is preferably within the range of 81 ± 10°.

[0054] As described above, in the mode of FIGS. 3 to 4, based on the absorption axis AA of the polarizer 20, the in-plane slow axis SA1 of the first optically anisotropic layer 12a is at a position of 15°, and the twist direction of the liquid crystal compound in the second optically anisotropic layer 14a indicates counterclockwise. In FIGS. 3 to 4, the mode in which the twist direction of the liquid crystal compound is counterclockwise has been described in detail. However, as long as a predetermined angle relationship is satisfied, a clockwise mode may also be used. More specifically, based on the absorption axis AA of the polarizer 20, a mode in which the in-plane slow axis SA1 of the first optically anisotropic layer 12a is at a position of -15° and the twist direction of the liquid crystal compound in the first optically anisotropic layer 12a is clockwise may also be used.

[0055] One embodiment of the circular polarizing plate shown in Fig. 2 has been described as above with reference to Figs. 3 to 4, but it may also be the embodiment shown in Figs. 5 to 6. Fig. 5, similar to Fig. 3, shows the relationship between the absorption axis AA of the polarizer 20, the in-plane slow axis SA1 on the surface 121a on the polarizer 20 side of the first optically anisotropic layer 12a, the in-plane slow axis SA2 on the surface 122a on the second optically anisotropic layer 14a side of the first optically anisotropic layer 12a, the in-plane slow axis SA3 on the surface 141a on the first optically anisotropic layer 12a side of the second optically anisotropic layer 14a, and the in-plane slow axis SA4 on the surface 142a on the side opposite to the first optically anisotropic layer 12a side of the second optically anisotropic layer 14a in the circular polarizing plate shown in Fig. 2. Further, Fig. 6 is a diagram showing the angular relationship between the absorption axis AA of the polarizer 20 and the respective in-plane slow axes (SA1 to SA4) of the first optically anisotropic layer 12a and the second optically anisotropic layer 14a when observed from the white arrow in Fig. 5. Note that the arrow in the polarizer 20 in Fig. 5 represents the absorption axis, and the arrows in the first optically anisotropic layer 12a and the second optically anisotropic layer 14a represent the in-plane slow axes in their respective layers. Note that the definition of the rotation angle of the in-plane slow axis is the same as above. Note that the embodiment shown in Figs. 5 to 6 is consistent with the embodiment shown in Figs. 3 to 4 in that the first optically anisotropic layer 12a and the second optically anisotropic layer 14a are fixed, and the arrangement direction of the polarizer 20 is rotated by 90°.

[0056] As shown in Figs. 5 to 6, the angle φa1 formed by the absorption axis AA of the polarizer 20 and the in-plane slow axis SA1 of the first optically anisotropic layer 12a is 105°. More specifically, the in-plane slow axis SA1 on the surface 121a on the polarizer 20 side of the first optically anisotropic layer 12a is rotated 105° (105° counterclockwise) with respect to the absorption axis AA of the polarizer 20. Note that in Figs. 5 to 6, an embodiment is shown in which the in-plane slow axis SA1 of the first optically anisotropic layer 12a is at the 105° position, but the present invention is not limited to this embodiment, and it is preferably within the range of 105 ± 10°. That is, the angle formed by the absorption axis AA of the polarizer 20 and the in-plane slow axis SA1 on the surface 121a on the polarizer 20 side of the first optically anisotropic layer 12a is preferably within the range of 105 ± 10°. Note that, as shown in FIG. 5, in the first optically anisotropic layer 12a, the in-plane slow axis SA1 on the surface 121a on the polarizer 20 side of the first optically anisotropic layer 12a and the in-plane slow axis SA2 on the surface 122a on the second optically anisotropic layer 14a side of the first optically anisotropic layer 12a are parallel.

[0057] In FIGS. 5 to 6, the relationship between the in-plane slow axes SA1 and SA2 of the first optically anisotropic layer 12a, the in-plane slow axis SA3 on the surface 141a on the first optically anisotropic layer 12a side of the second optically anisotropic layer 14a, and the in-plane slow axis SA4 on the surface 142a on the side opposite to the first optically anisotropic layer 12a side of the second optically anisotropic layer 14a is the same as the relationship in FIGS. 3 to 4 described above, and the preferred range of the angle is also the same. Note that the angle formed by the absorption axis AA of the polarizer 20 and the in-plane slow axis SA4 on the surface 142a on the side opposite to the first optically anisotropic layer 12a side of the second optically anisotropic layer 14a is 186°.

[0058] As described above, in the embodiments of FIGS. 5 to 6, based on the absorption axis AA of the polarizer 20, the in-plane slow axis SA1 on the surface 121a on the polarizer 20 side of the first optically anisotropic layer 12a is at the position of 105°, and the twisting direction of the liquid crystal compound in the second optically anisotropic layer 14a indicates counterclockwise. In FIGS. 5 to 6, the embodiment in which the twisting direction of the liquid crystal compound is counterclockwise has been described in detail. However, as long as the relationship of a predetermined angle is satisfied, a clockwise embodiment may also be acceptable. More specifically, based on the absorption axis AA of the polarizer 20, an embodiment in which the in-plane slow axis SA1 on the surface 121a on the polarizer 20 side of the first optically anisotropic layer 12a is at the position of -105° and the twisting direction of the liquid crystal compound in the first optically anisotropic layer 12a is clockwise may also be acceptable.

[0059] <Method for manufacturing a retardation plate> The method for manufacturing a retardation plate is not particularly limited, and a known method can be used. For example, a first optically anisotropic layer and a second optically anisotropic layer each having predetermined optical characteristics are produced, and these optically anisotropic layers and a support are bonded together in a predetermined order via an adhesive layer (for example, an adhesive layer or an adhesive bonding layer), whereby an optical film can be manufactured. Further, a polymerizable liquid crystal composition described below may be applied onto the first optically anisotropic layer to form a second optically anisotropic layer. Hereinafter, the manufacturing methods of the first optically anisotropic layer 12a and the second optically anisotropic layer 14a will be described in detail.

[0060] [First optically anisotropic layer 12a] The first optically anisotropic layer 12a is a polymer film and is preferably formed using the materials described above. The manufacturing method of the first optically anisotropic layer 12a is not particularly limited, and known methods can be applied. For example, the first optically anisotropic layer 12a can be manufactured by subjecting a film containing a predetermined resin to a stretching treatment. The stretching direction and the stretching ratio are not particularly limited and are appropriately selected. By adjusting the stretching direction and the stretching ratio, the direction of the in-plane slow axis of the first optically anisotropic layer 12a can be controlled. Note that the first optically anisotropic layer 12a can be used as a base material when forming the second optically anisotropic layer 14a.

[0061] [Second optically anisotropic layer 14a] The second optically anisotropic layer 14a is a layer formed by fixing a twisted nematic liquid crystal compound, and is preferably formed using a polymerizable liquid crystal composition containing the polymerizable liquid crystal compound, a chiral agent, and other components described above. More specifically, it is preferable to apply the polymerizable liquid crystal composition to form a composition layer, twist the liquid crystal compound in the composition layer, and then perform a curing treatment to form the second optically anisotropic layer 14a. Further, the polymerizable liquid crystal compound is preferably applied onto a photo-alignment film. As a method for forming the photo-alignment film, a method of applying a composition for forming a photo-alignment film for forming the photo-alignment film, drying it, and then forming it by irradiating ultraviolet rays with linearly polarized light is preferable. The polymerizable liquid crystal composition is a composition containing a liquid crystal compound having a polymerizable group. Various components contained in the polymerizable liquid crystal composition will be described in detail later. Hereinafter, the above procedure will be described in detail.

[0062] The procedure for forming the above-described composition layer is not particularly limited. For example, a method of applying a polymerizable liquid crystal composition onto an object to be coated and performing a drying treatment as necessary can be mentioned. The coating method is not particularly limited. For example, a wire bar coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, and a die coating method can be mentioned.

[0063] The film thickness of the composition layer is not particularly limited, but is preferably 0.1 to 20 μm, more preferably 0.2 to 15 μm, and even more preferably 0.5 to 10 μm.

[0064] Next, the formed composition layer is subjected to an alignment treatment to align the polymerizable liquid crystal compound in the composition layer. By including a chiral agent in the composition layer, the liquid crystal compound can be twisted and aligned. The alignment treatment can be performed by drying the coating film at room temperature or by heating the coating film. The liquid crystal phase formed by the alignment treatment can generally be transferred by a change in temperature or pressure in the case of a thermotropic liquid crystal compound. In the case of a lyotropic liquid crystal compound, it can also be transferred by a composition ratio such as the amount of solvent. In addition, the conditions when heating the composition layer are not particularly limited, but the heating temperature is preferably 50 to 250 °C, more preferably 50 to 150 °C, and the heating time is preferably 10 seconds to 10 minutes. Further, after heating the composition layer and before the curing treatment described later, the coating film may be cooled as necessary. The cooling temperature is preferably 20 to 200 °C, more preferably 30 to 150 °C. Also, after performing the heat treatment, light may be irradiated to change the helical induction force of the chiral agent, and then heated again to control the twist angle of the twisted alignment.

[0065] Next, a curing treatment is performed on the composition layer in which the polymerizable liquid crystal compound is aligned. The method of the curing treatment performed on the composition layer in which the polymerizable liquid crystal compound is aligned is not particularly limited, and examples thereof include light irradiation treatment and heat treatment. Among them, from the viewpoint of manufacturing suitability, light irradiation treatment is preferable, and ultraviolet irradiation treatment is more preferable. The irradiation conditions of the light irradiation treatment are not particularly limited, but an irradiation amount of 50 to 1000 mJ / cm 2 is preferable. The atmosphere during the light irradiation treatment is not particularly limited, but a nitrogen atmosphere is preferable.

[0066] In addition, although the method of applying the polymerizable liquid crystal composition to form a composition layer has been described above, a composition layer may be separately formed and transferred onto a predetermined substrate.

[0067] The polymerizable liquid crystal composition used above includes a liquid crystal compound having the polymerizable group described above, a chiral agent, and other components used as necessary (for example, a polymerization initiator, a photosensitizer, a polymerizable monomer, a surfactant, a polymer, and a solvent, etc.). The content of each component in the composition is preferably adjusted so as to be the content of each component in the composition layer described later.

[0068] The content of the liquid crystal compound in the polymerizable liquid crystal composition is not particularly limited, but from the viewpoint of easily controlling the alignment state of the liquid crystal compound, 60% by mass or more is preferable, and 70% by mass or more is more preferable with respect to the total solid content in the polymerizable liquid crystal composition. The upper limit is not particularly limited, but 99% by mass or less is preferable, and 97% by mass or less is more preferable. Note that the solid content means a component capable of forming an optically anisotropic layer from which the solvent has been removed, and even if its property is liquid, it is regarded as the solid content.

[0069] As described above, the polymerizable liquid crystal composition may contain other components other than the liquid crystal compound. For example, the polymerizable liquid crystal composition may contain a polymerization initiator. When the polymerizable liquid crystal composition contains a polymerization initiator, the polymerization of the liquid crystal compound having a polymerizable group proceeds more efficiently. Known polymerization initiators can be used as the polymerization initiator, including photoinitiators and thermal polymerization initiators, and photoinitiators are preferred. The content of the polymerization initiator in the polymerizable liquid crystal composition is not particularly limited, but is preferably 0.01 to 20% by mass, more preferably 0.5 to 10% by mass, based on the total solid content in the polymerizable liquid crystal composition.

[0070] The polymerizable liquid crystal composition may contain a photosensitizer. The type of the photosensitizer is not particularly limited, and known photosensitizers can be mentioned. The content of the photosensitizer in the polymerizable liquid crystal composition is not particularly limited, but is preferably 0.01 to 20% by mass, more preferably 0.5 to 10% by mass, based on the total solid content in the polymerizable liquid crystal composition.

[0071] The polymerizable liquid crystal composition may contain a polymerizable monomer different from the liquid crystal compound having a polymerizable group. Examples of the polymerizable monomer include radical polymerizable compounds and cationic polymerizable compounds, and polyfunctional radical polymerizable monomers are preferred. Examples of the polymerizable monomer include, for example, the polymerizable monomers described in paragraphs 0018 to 0020 of JP-A-2002-296423. The content of the polymerizable monomer in the polymerizable liquid crystal composition is not particularly limited, but is preferably 1 to 50% by mass, more preferably 5 to 30% by mass, based on the total mass of the liquid crystal compound.

[0072] The polymerizable liquid crystal composition may contain a surfactant. Examples of the surfactant include conventionally known compounds, and fluorine-based compounds are preferred. Specifically, for example, the compounds described in paragraphs 0028 to 0056 of JP-A-2001-330725 and the compounds described in paragraphs 0069 to 0126 of Japanese Patent Application No. 2003-295212 can be mentioned.

[0073] The polymerizable liquid crystal composition may contain a polymer. Examples of the polymer include cellulose esters. Examples of the cellulose ester include those described in paragraph 0178 of JP-A-2000-155216. The content of the polymer in the alignment liquid crystal composition is not particularly limited, but is preferably 0.1 to 10% by mass, more preferably 0.1 to 8% by mass, based on the total mass of the liquid crystal compound.

[0074] <Second Embodiment> Hereinafter, a second embodiment of the retardation plate of the present invention will be described with reference to the drawings. FIG. 7 shows a schematic cross-sectional view of a second embodiment of the retardation plate of the present invention.

[0075] The retardation plate 10b has a first optically anisotropic layer 12b and a second optically anisotropic layer 14b. The first optically anisotropic layer 12b is a polymer film, and the second optically anisotropic layer 14b is a layer formed using a rod-like liquid crystal compound LC. In particular, the second optically anisotropic layer 14b is a layer formed by fixing a twisted alignment liquid crystal compound having a spiral axis in the thickness direction. In addition, in FIG. 7, an example in which a rod-like liquid crystal compound is used as the liquid crystal compound is shown, but as described later, the liquid crystal compound is not limited to the rod-like liquid crystal compound. Hereinafter, the first optically anisotropic layer 12b and the second optically anisotropic layer 14b will be described.

[0076] [First Optically Anisotropic Layer 12b] The first optically anisotropic layer 12b is a polymer film. A polymer film is mainly a film composed of a polymer, and a stretched polymer film is preferred in terms of being likely to exhibit a predetermined retardation described later. A stretched polymer film is a polymer film that has been subjected to a stretching treatment.

[0077] The material constituting the polymer film is not particularly limited as long as it satisfies a predetermined retardation described later, and the preferred embodiment is the same as that described for the first optically anisotropic layer 12a. As described above, the in-plane retardation of the first optically anisotropic layer 12b at a wavelength of 550 nm is 60 to 300 nm. The in-plane retardation of the first optically anisotropic layer 12b at a wavelength of 550 nm is preferably 158 to 218 nm, more preferably 178 to 198 nm, in terms of more excellent effects of the present invention. Also, as described above, the retardation in the thickness direction of the first optically anisotropic layer 12b at a wavelength of 550 nm is -150 to -30 nm. The retardation in the thickness direction of the first optically anisotropic layer 12b at a wavelength of 550 nm is preferably -109 to -79 nm, and more preferably -99 to -88 nm in terms of more excellent effects of the present invention.

[0078] The in-plane slow axis of the first optically anisotropic layer 12b is orthogonal to the in-plane slow axis on the surface of the second optically anisotropic layer 14b on the side of the first optically anisotropic layer 12b.

[0079] The thickness of the first optically anisotropic layer 12b is not particularly limited, but is preferably 1 to 100 μm, more preferably 10 to 70 μm, and even more preferably 20 to 50 μm.

[0080] [Second optically anisotropic layer 14b] As shown in FIG. 7, the second optically anisotropic layer 14b is a layer formed by fixing a twisted nematic rod-like liquid crystal compound LC having a thickness direction (z-axis direction in FIG. 7) as a helical axis. Note that when the liquid crystal compound is twisted, it is intended that the liquid crystal compound is twisted from one main surface of the second optically anisotropic layer 14b to the other main surface with the thickness direction of the second optically anisotropic layer 14b as an axis. Accordingly, the alignment direction of the liquid crystal compound (i.e., the in-plane slow axis direction) varies depending on the position in the thickness direction of the second optically anisotropic layer 14b. Note that the "fixed" state is a state in which the alignment of the liquid crystal compound is maintained, and the definition is the same as that of the second optically anisotropic layer 14a described above.

[0081] The liquid crystal compound contained in the second optically anisotropic layer 14b is not limited to a rod-like liquid crystal compound as in the example shown in FIG. 7. The liquid crystal compound may be any compound that exhibits liquid crystallinity, and the type of the liquid crystal compound is not particularly limited. The definition, specific examples, and preferred embodiments of the liquid crystal compound are the same as those of the liquid crystal compound of the second optically anisotropic layer 14a described above.

[0082] The second optically anisotropic layer 14b may contain a chiral agent. The definition, specific examples, and preferred embodiments of the chiral agent are the same as those of the chiral agent of the liquid crystal compound in the second optically anisotropic layer 14a described above.

[0083] The twist angle of the liquid crystal compound is preferably in the range of 59 ± 10° (49 to 69°), and more preferably in the range of 59 ± 6° (53 to 65°) in terms of more excellent effects of the present invention. Note that there are two types of twist directions, and it may be either right-handed or left-handed. That is, when referring to the twist angle within the range of 59 ± 10°, it refers to both the case of twisting within the range of 59 ± 10° clockwise and the case of twisting within the range of 59 ± 10° counterclockwise. The twist angle is measured using an AxoScan (polarimeter) device manufactured by Axometrics and the attached device analysis software.

[0084] In addition, the second optically anisotropic layer 14b preferably satisfies the relationship of the following formula (1-B). Formula (1-B) 203 nm ≤ Δnd ≤ 263 nm In formula (1-B), Δn represents the refractive index anisotropy at a wavelength of 550 nm of the second optically anisotropic layer 14b. In formula (1-B), d represents the film thickness (nm) of the second optically anisotropic layer 14b. The second optically anisotropic layer 14b more preferably satisfies the relationship of the following formula (1-B1), and even more preferably satisfies the relationship of the following formula (1-B2). Formula (1-B1) 213 nm ≤ Δnd ≤ 253 nm Formula (1-B2) 223 nm ≤ Δnd ≤ 243 nm The above Δnd can be adjusted according to the type of liquid crystal compound, the twist angle, and the film thickness of the second optically anisotropic layer 14b. Note that the above Δnd is measured using an AxoScan (polarimeter) device manufactured by Axometrics and the attached device analysis software in the same manner as the measurement method of the twist angle.

[0085] The thickness of the second optically anisotropic layer 14b is not particularly limited, but is preferably 0.1 to 10.0 μm, more preferably 1.0 to 5.0 μm, and even more preferably 1.0 to 2.5 μm.

[0086] The second embodiment of the retardation plate of the present invention includes at least the first optically anisotropic layer 12b and the second optically anisotropic layer 14b described above, and may include other members. The other members are the same as the other members described in the first embodiment above.

[0087] [Circular polarizing plate] The second embodiment of the retardation plate of the present invention can be used as a circular polarizing plate in combination with a polarizer. The circular polarizing plate of the present invention having the above configuration can be preferably used for the same applications as the circular polarizing plate described in the first embodiment above, and is for improving the contrast ratio of display light.

[0088] The polarizer may be a member having a function of converting natural light into specific linearly polarized light, and examples thereof include absorption type polarizers. The type of the polarizer is not particularly limited and is the same as the polarizer described in the first embodiment above. Note that a protective film may be disposed on one or both surfaces of the polarizer.

[0089] FIG. 8 shows a schematic cross-sectional view of an embodiment of a circular polarizing plate. FIG. 9 is a diagram showing the relationship between the absorption axis AA of the polarizer 20, the in-plane slow axis SA3 on the surface 141b on the polarizer 20 side of the second optically anisotropic layer 14b, the in-plane slow axis SA4 on the surface 142b on the first optically anisotropic layer 12b side of the second optically anisotropic layer 14b, the in-plane slow axis SA1 on the surface 121b on the second optically anisotropic layer 14b side of the first optically anisotropic layer 12b, and the in-plane slow axis SA2 on the surface 122b on the side opposite to the second optically anisotropic layer 14b side of the first optically anisotropic layer 12b in the circular polarizing plate 100b shown in FIG. 8. FIG. 10 is a diagram showing the angular relationship between the absorption axis AA of the polarizer 20 and the in-plane slow axes (SA1 to SA4) of the second optically anisotropic layer 14b and the first optically anisotropic layer 12b when observed from the white arrow in FIG. 9. In addition, the arrow in the polarizer 20 in FIG. 9 represents the absorption axis, and the arrows in the first optically anisotropic layer 12b and the second optically anisotropic layer 14b represent the in-plane slow axes in their respective layers. In addition, the rotation angle of the in-plane slow axis is represented by a positive angle value in the counterclockwise direction and a negative angle value in the clockwise direction with respect to the absorption axis AA of the polarizer 20 when observed from the white arrow in FIG. 8. Also, the twisting direction is determined to be clockwise or counterclockwise with respect to the in-plane slow axis (SA3) on the front surface (polarizer 20 side) of the second optically anisotropic layer 14b when observed from the white arrow in FIG. 8.

[0090] As shown in FIG. 8, the circular polarizing plate 100b includes a polarizer 20, a second optically anisotropic layer 14b, and a first optically anisotropic layer 12b in this order. As shown in FIGS. 9 to 10, the angle φb1 formed by the absorption axis AA of the polarizer 20 and the in-plane slow axis SA1 on the surface of the first optically anisotropic layer 12b on the polarizer 20 side is 30°. More specifically, the in-plane slow axis SA1 on the surface of the first optically anisotropic layer 12b on the polarizer 20 side is rotated -30° (30° clockwise) with respect to the absorption axis AA of the polarizer 20. In FIGS. 9 to 10, an aspect is shown in which the in-plane slow axis SA1 on the surface of the first optically anisotropic layer 12b on the polarizer 20 side is at a position of -30° with respect to the absorption axis AA of the polarizer 20, but the present invention is not limited to this aspect and preferably falls within the range of -30 ± 10°. That is, the angle formed by the absorption axis AA of the polarizer 20 and the in-plane slow axis SA1 of the first optically anisotropic layer 12b is preferably within the range of 30 ± 10°. As shown in FIG. 9, in the first optically anisotropic layer 12b, the in-plane slow axis SA1 on the surface 121b of the first optically anisotropic layer 12b on the polarizer 20 side and the in-plane slow axis SA2 on the surface 122b of the first optically anisotropic layer 12b on the side opposite to the polarizer 20 side are parallel.

[0091] As shown in FIGS. 9 to 10, the in-plane slow axis SA1 on the surface 121b of the first optically anisotropic layer 12b on the side of the second optically anisotropic layer 14b and the in-plane slow axis SA4 on the surface 142b of the second optically anisotropic layer 14b on the side of the first optically anisotropic layer 12b are orthogonal. That is, the angle φb2 formed by the in-plane slow axis SA1 on the surface 121b of the first optically anisotropic layer 12b on the side of the second optically anisotropic layer 14b and the in-plane slow axis SA4 on the surface 142b of the second optically anisotropic layer 14b on the side of the first optically anisotropic layer 12b is 90°. More specifically, the in-plane slow axis SA4 on the surface 142b of the second optically anisotropic layer 14b on the side of the first optically anisotropic layer 12b is rotated -90° (90° clockwise) with respect to the in-plane slow axis SA1 on the surface 121b of the first optically anisotropic layer 12b on the side of the second optically anisotropic layer 14b. In FIGS. 9 to 10, an aspect is shown in which the in-plane slow axis SA4 is at a position -90° with respect to the in-plane slow axis SA1, but the present invention is not limited to this aspect and preferably falls within the range of -90 ± 10°. That is, the angle formed by the in-plane slow axis SA1 on the surface 121b of the first optically anisotropic layer 12b on the side of the second optically anisotropic layer 14b and the in-plane slow axis SA4 on the surface 142b of the second optically anisotropic layer 14b on the side of the first optically anisotropic layer 12b is preferably within the range of 90 ± 10°.

[0092] As described above, the second optically anisotropic layer 14b is a layer in which a twisted alignment liquid crystal compound having a thickness direction as a helical axis is fixed. Therefore, as shown in FIGS. 9 to 10, the in-plane slow axis SA3 on the surface 141b of the second optically anisotropic layer 14b on the side of the polarizer 20 and the in-plane slow axis SA4 on the surface 142b of the second optically anisotropic layer 14b on the side of the first optically anisotropic layer 12b form the above-described twist angle (in FIG. 10, 59°). That is, the angle φb3 formed by the in-plane slow axis SA3 on the surface 141b of the second optically anisotropic layer 14b on the side of the polarizer 20 and the in-plane slow axis SA4 on the surface 142b of the second optically anisotropic layer 14b on the side of the first optically anisotropic layer 12b is 59°. More specifically, the in-plane slow axis of the second optically anisotropic layer rotates -59° (59° clockwise). Therefore, the angle formed by the absorption axis AA of the polarizer 20 and the in-plane slow axis SA3 on the surface 141b of the second optically anisotropic layer 14b on the side of the polarizer 20 is 59°. In FIGS. 9 to 10, a mode in which the in-plane slow axis of the second optically anisotropic layer 14b is rotated by -59° is shown, but the present invention is not limited to this mode, and the rotation angle may be within the range of -59 ± 10°. That is, the angle formed by the in-plane slow axis SA3 on the surface 141b on the polarizer 20 side of the second optically anisotropic layer 14b and the in-plane slow axis SA4 on the surface 142b on the first optically anisotropic layer 12b side of the second optically anisotropic layer 14b is preferably within the range of 59 ± 10°.

[0093] As described above, in the mode of FIGS. 9 to 10, based on the absorption axis AA of the polarizer 20, the in-plane slow axis SA1 on the surface 142b on the second optically anisotropic layer 14b side of the first optically anisotropic layer 12b is at a position of -30°, and the in-plane slow axis SA4 on the surface 142b on the first optically anisotropic layer 12b side of the second optically anisotropic layer 14b is at a position of -90° with respect to the in-plane slow axis SA1 on the surface 142b on the second optically anisotropic layer 14b side of the first optically anisotropic layer 12b, and the twisting direction of the liquid crystal compound in the second optically anisotropic layer 14b indicates clockwise. In FIGS. 9 to 10, the mode in which the twisting direction of the liquid crystal compound is clockwise has been described in detail. However, as long as a predetermined angular relationship is satisfied, a mode in which the twisting direction is counterclockwise may also be used. More specifically, based on the absorption axis AA of the polarizer 20, the in-plane slow axis SA1 on the surface 142b on the second optically anisotropic layer 14b side of the first optically anisotropic layer 12b is at a position of 30°, and the in-plane slow axis SA4 on the surface 142b on the first optically anisotropic layer 12b side of the second optically anisotropic layer 14b is at a position of 90° with respect to the in-plane slow axis SA1 on the surface 142b on the second optically anisotropic layer 14b side of the first optically anisotropic layer 12b, and a mode in which the twisting direction of the liquid crystal compound in the second optically anisotropic layer 14b is counterclockwise may also be used.

[0094] Note that, as in FIGS. 5 to 6 described in the first embodiment above, in the embodiment shown in FIGS. 9 to 10, the first optically anisotropic layer 12b and the second optically anisotropic layer 14b may be fixed, and the arrangement direction of the polarizer 20 may be rotated by 90°.

[0095] <Third Embodiment> Hereinafter, a third embodiment of the retardation plate of the present invention will be described with reference to the drawings. FIG. 11 shows a schematic cross-sectional view of the third embodiment of the retardation plate of the present invention.

[0096] The retardation plate 10c has a first optically anisotropic layer 12c and a second optically anisotropic layer 14c. The first optically anisotropic layer 12c is a polymer film, and the second optically anisotropic layer 14c is a layer formed using a rod-like liquid crystal compound LC. In particular, the second optically anisotropic layer 14c is a layer formed by fixing a twisted and aligned liquid crystal compound having a thickness direction as a helical axis. In FIG. 11, an example using a rod-like liquid crystal compound as the liquid crystal compound is shown, but as will be described later, the liquid crystal compound is not limited to the rod-like liquid crystal compound. Hereinafter, the first optically anisotropic layer 12c and the second optically anisotropic layer 14c will be described.

[0097] [First Optically Anisotropic Layer 12c] The first optically anisotropic layer 12c is a polymer film. A polymer film is mainly a film composed of a polymer, and a stretched polymer film is preferable in terms of easily showing a predetermined retardation described later. A stretched polymer film is a polymer film subjected to a stretching process.

[0098] The material constituting the polymer film is not particularly limited as long as it satisfies a predetermined retardation described later, and the preferred embodiment is the same as that described for the first optically anisotropic layer 12a. As described above, the in-plane retardation of the first optically anisotropic layer 12c at a wavelength of 550 nm is 60 to 300 nm. The in-plane retardation of the first optically anisotropic layer 12c at a wavelength of 550 nm is preferably 67.5 to 127.5 nm, more preferably 77.5 to 117.5 nm, and even more preferably 87.5 to 107.5 nm in terms of more excellent effects of the present invention. Also, as described above, the retardation in the thickness direction of the first optically anisotropic layer 12c at a wavelength of 550 nm is -150 to -30 nm. The retardation in the thickness direction of the first optically anisotropic layer 12c at a wavelength of 550 nm is preferably -64 to -33 nm, more preferably -59 to -38 nm, in terms of more excellent effects of the present invention.

[0099] The angle formed between the in-plane slow axis of the first optically anisotropic layer 12c and the in-plane slow axis on the surface of the second optically anisotropic layer 14c on the first optically anisotropic layer 12c side is preferably 30 to 70°. The in-plane slow axis on the surface of the second optically anisotropic layer 14c on the first optically anisotropic layer side may be positioned clockwise or counterclockwise with respect to the in-plane slow axis of the first optically anisotropic layer 12c.

[0100] The thickness of the first optically anisotropic layer 12c is not particularly limited, but is preferably 1 to 100 μm, more preferably 10 to 70 μm, and even more preferably 20 to 50 μm.

[0101] [Second optically anisotropic layer 14c] As shown in FIG. 11, the second optically anisotropic layer 14c is a layer formed by fixing a twisted nematic rod-like liquid crystal compound LC having a spiral axis in the thickness direction (z-axis direction in FIG. 11). Note that the twisting alignment of the liquid crystal compound means that the liquid crystal compound twists from one main surface to the other main surface of the second optically anisotropic layer 14c with the thickness direction of the second optically anisotropic layer 14c as the axis. Accordingly, the alignment direction of the liquid crystal compound (i.e., the in-plane slow axis direction) varies depending on the position in the thickness direction of the second optically anisotropic layer 14c. Note that the "fixed" state is a state in which the alignment of the liquid crystal compound is maintained, and the definition is the same as that of the second optically anisotropic layer 14a described above.

[0102] The liquid crystal compound contained in the second optically anisotropic layer 14c is not limited to a rod-like liquid crystal compound as in the example shown in FIG. 11. The liquid crystal compound may be any compound that exhibits liquid crystallinity, and the type of the liquid crystal compound is not particularly limited. The definition, specific examples, and preferred embodiments of the liquid crystal compound are the same as those of the liquid crystal compound in the second optically anisotropic layer 14a described above.

[0103] The second optically anisotropic layer 14c may contain a chiral agent. The definition, specific examples, and preferred embodiments of the chiral agent are the same as those of the chiral agent of the liquid crystal compound in the second optically anisotropic layer 14a described above.

[0104] The twist angle of the liquid crystal compound is preferably in the range of 40 ± 20° (20 to 60°), and more preferably in the range of 40 ± 10° (30 to 50°) in terms of more excellent effects of the present invention. Note that there are two types of twist directions, and it may be either a right twist or a left twist. That is, when referring to the twist angle within the range of 40 ± 20°, it refers to both the case of twisting within the range of 40 ± 20° clockwise and the case of twisting within the range of 40 ± 20° counterclockwise. The twist angle is measured using the AxoScan (polarimeter) device of Axometrics and the attached device analysis software.

[0105] Note that when the in-plane slow axis on the surface of the second optically anisotropic layer 14c on the side of the first optically anisotropic layer is located in the clockwise rotation direction with respect to the in-plane slow axis of the first optically anisotropic layer 12c, it is preferable that the twist direction of the second optically anisotropic layer 14c is twisted in the clockwise direction. Also, when the in-plane slow axis on the surface of the second optically anisotropic layer 14c on the side of the first optically anisotropic layer is located in the counterclockwise rotation direction with respect to the in-plane slow axis of the first optically anisotropic layer 12c, it is preferable that the twist direction of the second optically anisotropic layer 14c is twisted in the counterclockwise direction.

[0106] In addition, the second optically anisotropic layer 14c preferably satisfies the following relationship of formula (1-C). Formula (1-C): 317 nm ≤ Δnd ≤ 377 nm In formula (1-C), Δn represents the refractive index anisotropy at a wavelength of 550 nm of the second optically anisotropic layer 14c. In formula (1-C), d represents the film thickness (nm) of the second optically anisotropic layer 14c. The second optically anisotropic layer 14c more preferably satisfies the relationship of the following formula (1-C1), and even more preferably satisfies the relationship of formula (1-C2). Formula (1-C1) 327 nm ≤ Δnd ≤ 367 nm Formula (1-C2) 337 nm ≤ Δnd ≤ 357 nm The above Δnd can be adjusted according to the type of liquid crystal compound, the twist angle, and the film thickness of the second optically anisotropic layer 14c. Note that the above Δnd is measured using the AxoScan (polarimeter) device of Axometrics and the attached device analysis software in the same manner as the measurement method of the twist angle.

[0107] The thickness of the second optically anisotropic layer 14c is not particularly limited, but is preferably 0.1 to 10.0 μm, more preferably 1.0 to 5.0 μm, and even more preferably 1.0 to 2.5 μm.

[0108] The third embodiment of the retardation plate of the present invention includes at least the above-described first optically anisotropic layer 12c and second optically anisotropic layer 14c, and may include other members. The other members are the same as the other members described in the first embodiment.

[0109] [Circular polarizing plate] The third embodiment of the retardation plate of the present invention can be used as a circular polarizing plate in combination with a polarizer. The circular polarizing plate of the present invention having the above configuration can be preferably used for the same applications as the circular polarizing plate described in the first embodiment, and is for improving the contrast ratio of display light.

[0110] The polarizer may be a member having a function of converting natural light into a specific linearly polarized light, and examples thereof include absorption type polarizers. The type of the polarizer is not particularly limited and is the same as the polarizer described in the first embodiment. Note that a protective film may be disposed on one side or both sides of the polarizer.

[0111] Fig. 12 shows a schematic cross-sectional view of an embodiment of a circular polarizing plate. Fig. 13 is a diagram showing the relationship between the absorption axis AA of the polarizer 20, the in-plane slow axis SA3 on the surface 141c on the polarizer 20 side of the second optically anisotropic layer 14c, the in-plane slow axis SA4 on the surface 142c on the first optically anisotropic layer 12c side of the second optically anisotropic layer 14c, the in-plane slow axis SA1 on the surface 121c on the second optically anisotropic layer 14c side of the first optically anisotropic layer 12c, and the in-plane slow axis SA2 on the surface 122c on the side opposite to the second optically anisotropic layer 14c side of the first optically anisotropic layer 12c in the circular polarizing plate 100c shown in Fig. 12. Fig. 14 is a diagram showing the angular relationship between the absorption axis AA of the polarizer 20 and the in-plane slow axes (SA1 to SA4) of the second optically anisotropic layer 14c and the first optically anisotropic layer 12c when observed from the white arrow in Fig. 12. Note that the arrow in the polarizer 20 in Fig. 13 represents the absorption axis, and the arrows in the first optically anisotropic layer 12c and the second optically anisotropic layer 14c represent the in-plane slow axes in their respective layers. Note that the rotation angle of the in-plane slow axis is represented by a positive angle value in the counterclockwise direction and a negative angle value in the clockwise direction with respect to the absorption axis AA of the polarizer 20 as a reference (0°) when observed from the white arrow in Fig. 12. Also, the twisting direction is determined to be clockwise or counterclockwise with respect to the in-plane slow axis (SA3) on the front side (polarizer 20 side) of the surface 141c in the second optically anisotropic layer 14c when observed from the white arrow in Fig. 12.

[0112] As shown in Fig. 12, the circular polarizing plate 100c includes a polarizer 20, a second optically anisotropic layer 14c, and a first optically anisotropic layer 12c in this order. As shown in Figs. 13 to 14, the absorption axis AA of the polarizer 20 and the in-plane slow axis SA1 on the surface 121c on the second optically anisotropic layer 14c side of the first optically anisotropic layer 12c are parallel. In Figs. 13 to 14, an embodiment is shown in which the in-plane slow axis SA1 of the first optically anisotropic layer 12c is in a position parallel to the absorption axis AA of the polarizer 20. As shown in FIG. 13, in the first optically anisotropic layer 12c, the in-plane slow axis SA1 on the surface 121c on the polarizer 20 side of the first optically anisotropic layer 12c and the in-plane slow axis SA2 on the surface 122c on the side opposite to the polarizer 20 side of the first optically anisotropic layer 12c are parallel.

[0113] As shown in FIGS. 13 to 14, the angle formed by the in-plane slow axis SA1 on the surface 121c on the second optically anisotropic layer 14c side of the first optically anisotropic layer 12c and the in-plane slow axis SA4 on the surface 142c on the first optically anisotropic layer 12c side of the second optically anisotropic layer 14c is 50°. That is, the angle φc2 formed by the in-plane slow axis SA1 on the surface 121c on the second optically anisotropic layer 14c side of the first optically anisotropic layer 12c and the in-plane slow axis SA4 on the surface 142c on the first optically anisotropic layer 12c side of the second optically anisotropic layer 14c is 50°. More specifically, the in-plane slow axis SA4 on the surface 142c on the first optically anisotropic layer 12c side of the second optically anisotropic layer 14c is rotated 50° (50° counterclockwise) with respect to the in-plane slow axis SA1 on the surface 121c on the second optically anisotropic layer 14c side of the first optically anisotropic layer 12c. In FIGS. 13 to 14, the aspect where the in-plane slow axis SA4 on the surface 142c on the first optically anisotropic layer 12c side of the second optically anisotropic layer 14c is at a position 50° with respect to the in-plane slow axis SA1 on the surface 121c on the second optically anisotropic layer 14c side of the first optically anisotropic layer 12c is shown, but the present invention is not limited to this aspect, and it is preferably within the range of 50 ± 20°. That is, the angle formed by the in-plane slow axis SA1 on the surface 121c on the second optically anisotropic layer 14c side of the first optically anisotropic layer 12c and the in-plane slow axis SA4 on the surface 142c on the first optically anisotropic layer 12c side of the second optically anisotropic layer 14c is preferably within the range of 50 ± 20°.

[0114] As described above, the second optically anisotropic layer 14c is a layer in which a twisted alignment liquid crystal compound having the thickness direction as the helical axis is fixed. Therefore, as shown in FIGS. 13 to 14, the in-plane slow axis SA3 on the surface 141c on the polarizer 20 side of the second optically anisotropic layer 14c and the in-plane slow axis SA4 on the surface 142c on the side opposite to the first optically anisotropic layer 12c side of the second optically anisotropic layer 14c form the above-described twist angle (in FIG. 14, 40°). That is, the angle φc3 formed by the in-plane slow axis SA3 on the surface 141c on the polarizer 20 side of the second optically anisotropic layer 14c and the in-plane slow axis SA4 on the surface 142c on the side opposite to the first optically anisotropic layer 12c side of the second optically anisotropic layer 14c is 40°. More specifically, the in-plane slow axis of the second optically anisotropic layer 14c rotates by -40° (40° clockwise). Therefore, the angle formed by the absorption axis AA of the polarizer 20 and the in-plane slow axis SA3 on the surface 141c on the polarizer 20 side of the second optically anisotropic layer 14c is 90°. In FIGS. 13 to 14, the mode in which the in-plane slow axis of the second optically anisotropic layer 14c is rotated by -40° is shown, but the present invention is not limited to this mode, and the rotation angle may be within the range of -40±20°. That is, the angle formed by the in-plane slow axis SA3 on the surface 141c on the polarizer 20 side of the second optically anisotropic layer 14c and the in-plane slow axis SA4 on the surface 142c on the first optically anisotropic layer 12c side of the second optically anisotropic layer 14c is preferably within the range of 40±20°.

[0115] As described above, in the mode of FIGS. 13 to 14, based on the absorption axis AA of the polarizer 20, the in-plane slow axis SA4 on the surface 142 on the first optically anisotropic layer 12c side of the second optically anisotropic layer 14c is at the position of 50°, and the twist direction of the liquid crystal compound in the second optically anisotropic layer 14c indicates clockwise. In FIGS. 13 to 14, the mode in which the twist direction of the liquid crystal compound is clockwise has been described in detail. However, as long as a predetermined angle relationship is satisfied, a counterclockwise mode may also be acceptable. More specifically, based on the absorption axis AA of the polarizer 20, the in-plane slow axis SA4 on the surface 142 on the first optically anisotropic layer 12c side of the second optically anisotropic layer 14c is at the position of -50°, and the twist direction of the liquid crystal compound in the first optically anisotropic layer 12c is counterclockwise.

[0116] Note that, as shown in FIGS. 5 to 6 described in the first embodiment, in the embodiment shown in FIGS. 13 to 14, the first optically anisotropic layer 12c and the second optically anisotropic layer 14c may be fixed and the arrangement direction of the polarizer 20 may be rotated by 90°. Furthermore, in the embodiment where the twisting direction of the liquid crystal compound is counterclockwise, the first optically anisotropic layer 12c and the second optically anisotropic layer 14c may be fixed and the arrangement direction of the polarizer 20 may be rotated by 90°.

[0117] <Image display device> The retardation plate and the circular polarizing plate (first to third embodiments) of the present invention can be suitably applied to an image display device. The image display device of the present invention includes an image display element and the above-described retardation plate or circular polarizing plate. When applying the retardation plate of the present invention to an image display device, it is preferably applied as the above-described circular polarizing plate. In this case, the circular polarizing plate is disposed on the viewing side, and in the circular polarizing plate, the polarizer is disposed on the viewing side. The image display element is not particularly limited, and examples thereof include an organic electroluminescence display element and a liquid crystal display element.

Examples

[0118] The present invention will be described in more detail below based on examples. The materials, amounts used, ratios, processing contents, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the examples shown below.

[0119] <Manufacture of circular polarizing plate> The manufacturing procedure of the circular polarizing plate using the retardation plate in each example and each comparative example will be described in detail. First, after describing the manufacturing method of each layer used in each example and each comparative example, the configurations of each example and each comparative example will be described.

[0120] [Polarizer] A polyvinyl alcohol film with a thickness of 80 μm was immersed in an aqueous iodine solution with an iodine concentration of 0.05% by mass at 30 °C for 60 seconds for dyeing. Next, while the obtained film was immersed in an aqueous boric acid solution with a boric acid concentration of 4% by mass for 60 seconds, it was longitudinally stretched to 5 times its original length and then dried at 50 °C for 4 minutes to obtain a polarizer with a thickness of 20 μm.

[0121] [Polymer film] The manufacturing methods of polymer films 1 to 7 corresponding to the first optically anisotropic layer will be described. The in-plane retardation Re, retardation Rth in the thickness direction, film thickness, in-plane slow axis direction, and glass transition temperature of each polymer film were as shown in Table 1 in the following stage.

[0122] (Polymer film 1) Based on the total mass of poly(methyl methacrylate) (PMMA) and poly(α,β,β-trifluorostyrene) (PTFS) solids described in Example 1 of Japanese Patent Publication No. 2018-510921, a polymer blend solution was prepared so that the ratio of PMMA / PTFS = 20 (mass%) / 80 (mass%). The prepared polymer blend solution was applied to a flat glass substrate using a blade casting method to obtain a coating film. The obtained coating film was dried overnight in air and further dried in a vacuum oven at room temperature for 8 hours. After drying, the film was peeled off from the glass substrate to obtain Substrate 1. The obtained Substrate 1 was stretched at 110 °C with a stretch ratio of 30% so as to have the characteristics shown in Table 1 described later to obtain Polymer Film 1.

[0123] (Polymer film 2) Polymer Film 2 was obtained according to the same procedure as the manufacturing method of Polymer Film 1, except that the stretching conditions were adjusted so that the in-plane slow axis direction was as shown in Table 1 in the following stage.

[0124] (Polymer film 3) The polymer film 3 was obtained according to the same procedure as the manufacturing method of the polymer film 1, except that the stretching conditions were adjusted so that the in-plane retardation Re, the thickness-direction retardation Rth, the thickness, and the in-plane slow-axis direction were as shown in Table 1 in the subsequent stage.

[0125] (Polymer film 4) The polymer film 4 was obtained according to the same procedure as the manufacturing method of the polymer film 1, except that the stretching conditions were adjusted so that the in-plane retardation Re, the thickness-direction retardation Rth, the thickness, and the in-plane slow-axis direction were as shown in Table 1 in the subsequent stage.

[0126] (Polymer film 5) 90 parts by mass of syndiotactic polystyrene (manufactured by Idemitsu Kosan Co., Ltd., "130-ZC", glass transition temperature 98 °C, crystallization temperature 140 °C) and 10 parts by mass of poly(2,6-dimethyl-1,4-phenylene oxide) (Aldrich catalog No. 18242-7) were kneaded with a twin-screw extruder to obtain pellets of a transparent resin R2. The glass transition temperature of the obtained resin R2 was 105 °C. It was supplied to a twin-screw extruder and melt-extruded into a sheet shape at about 280 °C to obtain a resin sheet with a thickness of 80 μm. This unstretched sheet was stretched 1.5 times in the longitudinal direction and 1.8 times in the transverse direction under the temperature condition of 140 °C to obtain a polymer film 5.

[0127] (Polymer film 6) 64 parts by mass of syndiotactic polystyrene (manufactured by Idemitsu Kosan Co., Ltd., "130-ZC", glass transition temperature 98 °C, crystallization temperature 140 °C) and 36 parts by mass of poly(2,6-dimethyl-1,4-phenylene oxide) (Aldrich catalog No. 18242-7) were kneaded with a twin-screw extruder to obtain pellets of a transparent resin R3. The glass transition temperature of the obtained resin R3 was 134 °C. Next, a film forming apparatus for two - component two - layer co - extrusion molding (a molding apparatus of a type capable of forming a two - layer film from two types of resins) equipped with a single - screw extruder having a double - flight screw was prepared. Pellets of resin R3 were put into one of the single - screw extruders of the above - mentioned film forming apparatus and melted. Also, pellets of impact - resistant polymethyl methacrylate resin R6 (Sumitomo Chemical's "Sumipex HT55X") were put into the other single - screw extruder of the above - mentioned film forming apparatus and melted. The melted resin R3 at 290 °C was supplied to one of the manifolds of a multi - manifold die (surface roughness Ra of the die lip: 0.1 μm) through a leaf - disk - shaped polymer filter with an opening of 10 μm. Also, the melted resin R6 at 260 °C was supplied to the other manifold of the multi - manifold die through a leaf - disk - shaped polymer filter with an opening of 10 μm. Resins R3 and R6 were simultaneously extruded from the multi - manifold die at 280 °C and formed into a film shape. The formed film - like molten resin was cast onto a casting roll adjusted to a surface temperature of 110 °C, and then passed between two cooling rolls adjusted to a surface temperature of 50 °C. The resin cooled and solidified on the casting roll, and a pre - stretched film having a layer made of resin R3 and a layer made of resin R6 was obtained. At this time, by adjusting the rotation speed of the casting roll, a pre - stretched film PF - 4 (thickness 100 μm) having a layer made of resin R3 (thickness 50 μm) and a layer made of resin R6 (thickness 50 μm) was produced.

[0128] The pre - stretched film PF - 4 was uniaxially stretched freely in the longitudinal direction of the pre - stretched film, and then the layer made of resin R6 was peeled off to obtain a polymer film 6 made of resin R3. At this time, the stretching temperature and the stretching ratio were in the range of 134 - 144 °C at a stretching ratio of 1.6 times.

[0129] (Polymer film 7) FDPM (1.00 mol), BPEF (0.80 mol), EG (2.20 mol), with manganese acetate tetrahydrate 2×10 as a transesterification catalyst -4Moles and 8×10 moles of calcium acetate monohydrate -4 moles were added and gradually heated to melt with stirring. After the temperature was raised to 230 °C, 14×10 -4 moles of trimethyl phosphate and 20×10 -4 moles of germanium oxide were added, and EG was removed while gradually raising the temperature and reducing the pressure until 270 °C and 0.13 kPa or less were reached. After reaching a predetermined stirring torque, the contents were taken out of the reactor to obtain pellets of polyester resin 1. In addition, FDPM, BPEF, and EG represent the following compounds. FDPM: 9,9-bis(2-methoxycarbonylethyl)fluorene [dimethyl ester of 9,9-bis(2-carboxyethyl)fluorene (or fluorene-9,9-dipropionic acid)] BPEF: 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene, manufactured by Osaka Gas Chemical Co., Ltd. EG: Ethylene glycol In addition, FDPM was synthesized in the same manner as in Example 1 of JP-A-2005-89422, except that t-butyl acrylate described in Example 1 of JP-A-2005-89422 was changed to 37.9 g (0.44 mol) of methyl acrylate, and this was used.

[0130] The obtained pellets were 1 Analyzed by 1H-NMR, 100 mol% of the dicarboxylic acid component introduced into polyester resin 1 was derived from FDPM, 80 mol% of the introduced diol component was derived from BPEF, and 20 mol% was derived from EG. The glass transition temperature Tg of polyester resin 1 was 125 °C, and the weight average molecular weight Mw was 66,500. The obtained polyester resin 1 was melt-extruded at a temperature of 260 °C using a twin-screw extruder ("KZW15-30MG" manufactured by Technovel Corporation, L / D = 45, screw diameter D 15 mm, rotation speed 200 rpm), and a film base was produced using a T-die and a winding device. The obtained film base was uniaxially stretched at a draw ratio of 300% (drawing speed 120 mm / min) in the transport direction to obtain polymer film 7.

[0131] (Polymer Film 8) Pellets of a thermoplastic norbornene resin (manufactured by Zeon Corporation, trade name "ZEONOR1420R") were dried at 90°C for 5 hours. The dried pellets were fed into an extruder, melted within the extruder, passed through a polymer pipe and a polymer filter, and extruded in a sheet form onto a casting drum from a T-die, cooled, wound up, and a roll of the base material before stretching was obtained. The obtained base material before stretching was pulled out from the roll, fed into a tenter stretching machine, stretched, and further, both ends in the width direction of the film were trimmed, wound up, and Polymer Film 8 was obtained.

[0132] (Polymer Film 9) In the production of the above Polymer Film 8, Polymer Film 9 was obtained in the same manner as Polymer Film 8, except that the stretching conditions were adjusted so that the in-plane retardation Re, the retardation Rth in the thickness direction, the in-plane slow axis direction, and the film thickness were as shown in Table 1 in the subsequent stage.

[0133] Note that the in-plane slow axis direction in Table 1 is a value represented by a positive value in the counterclockwise direction when observed from the side where the optical anisotropic layer described later is disposed, with the conveyance direction (longitudinal direction) of the polymer film as a reference (0°).

[0134]

Table 1

[0135] [Example 1] The surface of the above Polymer Film 1 was subjected to corona treatment. Using a kiss coater, an optical anisotropic layer forming composition T1 containing a rod-like liquid crystal compound was coated on the surface of Polymer Film 1 subjected to corona treatment, and the polymer film on which the composition layer was formed was heated at 90°C for 80 seconds. Thereafter, under a nitrogen atmosphere, at 55°C, light from a metal halide lamp (manufactured by Eye Graphics Co., Ltd.) was irradiated onto the composition layer (irradiation dose: 500 mJ / cm 2By doing so, an optically anisotropic layer T1 (film thickness: 1.4 μm) with the alignment of the liquid crystal compound fixed was formed, and a laminate 1 including the polymer film 1 and the optically anisotropic layer T1 was obtained. The in-plane slow axis direction of the polymer film 1 and the in-plane slow axis direction on the surface of the optically anisotropic layer T1 on the polymer film 1 side were in agreement.

[0136] ――――――――――――――――――――――――――――――――――――― Composition of the composition T1 for forming the optically anisotropic layer ――――――――――――――――――――――――――――――――――――― · 80 parts by mass of the following rod-like liquid crystal compound (A) · 10 parts by mass of the following rod-like liquid crystal compound (B) · 10 parts by mass of the following rod-like liquid crystal compound (C) · Ethylene oxide-modified trimethylolpropane triacrylate (V#360, manufactured by Osaka Organic Chemical Co., Ltd.) 4 parts by mass · Photoinitiator (Irgacure 819, manufactured by Ciba Japan Co., Ltd.) 3 parts by mass · 0.32 part by mass of the following chiral agent (A) · 0.08 part by mass of the following polymer (A) · Methyl isobutyl ketone 117 parts by mass · Ethyl propionate 39 parts by mass ―――――――――――――――――――――――――――――――――――――

[0137] Rod-like liquid crystal compound (A) (corresponding to the mixture of liquid crystal compounds shown below)

[0138]

Chemical formula

[0139] Rod-like liquid crystal compound (B)

[0140]

Chemical formula

[0141] Rod-like liquid crystal compound (C)

[0142]

Chem.

[0143] Incidentally, the mixture of rod-like liquid crystal compounds (A) to (C) exhibited liquid crystallinity at 50°C.

[0144] Chiral agent (A)

[0145]

Chem.

[0146] Polymer (A) (wherein the numerical values described in each repeating unit represent the content (% by mass) of each repeat with respect to all repeating units.)

[0147]

Chem.

[0148] Next, a polarizer was bonded via an adhesive (manufactured by Lintec Corporation) onto the surface of the polymer film 1 side of the laminate 1 to obtain a circular polarizing plate 1. In the circular polarizing plate 1, the polarizer, the polymer film 1, and the optically anisotropic layer T1 were arranged in this order from the polarizer side. Also, when the circular polarizing plate 1 was observed from the polarizer side, with the absorption axis direction of the polarizer as a reference (0°), the in-plane slow axis direction of the polymer film 1 was positioned at an angle of 10°. Further, when the circular polarizing plate 1 was observed from the polarizer side, with the absorption axis direction of the polarizer as a reference (0°), the in-plane slow axis on the front surface (the polarizer side surface) of the optically anisotropic layer T1 was positioned at an angle of 10°, and on the back surface (the side opposite to the polarizer side) of the optically anisotropic layer T1, it was positioned at an angle of 90°, and in the optically anisotropic layer T1, the liquid crystal compound was twisted counterclockwise by 80°. Note that when observing the circular polarizing plate 1 from the polarizer side, the above rotation angle is displayed with a positive value for counterclockwise and a negative value for clockwise, based on the absorption axis direction of the polarizer. When observing the circular polarizing plate 1 from the polarizer side, the twisting direction of the liquid crystal compound is determined to be clockwise or counterclockwise based on the in-plane slow axis on the front side (polarizer side) surface in the optically anisotropic layer.

[0149] [Example 2] Using polymer film 2 instead of polymer film 1, changing the film thickness of the optically anisotropic layer from 1.4 μm to 2.1 μm, and changing the usage amount of the chiral agent from 0.32 parts by mass to 0.21 parts by mass, a laminate 2 including polymer film 2 and optically anisotropic layer T2 was obtained according to the same procedure as in Example 1.

[0150] Using a bar coater, a composition (1c) for forming an optically anisotropic layer containing a rod-shaped liquid crystal compound with the following composition was applied to the surface of a cellulose acetate film to form a coating film. Note that the rod-shaped liquid crystal compound (A) exhibited liquid crystallinity at 50°C. Thereafter, both ends of the film were held, a cooling plate (9°C) was installed on the side where the coating film of the film was formed so that the distance from the film was 5 mm, and a heater (75°C) was installed on the side opposite to the side where the coating film of the film was formed so that the distance from the film was 5 mm, and it was dried for 2 minutes. Next, it was heated at 60°C for 1 minute with warm air, and while purging with nitrogen so that the oxygen concentration was 100 ppm by volume or less, ultraviolet rays with an irradiation amount of 100 mJ / cm 2 were irradiated using a 365 nm UV-LED. Thereafter, an annealing was performed at 120°C for 1 minute with warm air to obtain a cellulose acetate film with an optically anisotropic layer C. Note that the film thickness of the formed optically anisotropic layer C was 0.5 μm. The in-plane retardation Re at a wavelength of 550 nm was 0 nm, and the thickness-direction retardation Rth at a wavelength of 550 nm was -70 nm. The average inclination angle of the long axis direction of the rod-shaped liquid crystal compound with respect to the film surface was 90°, and it was confirmed that it was vertically oriented with respect to the film surface.

[0151] ――――――――――――――――――――――――――――――――― Composition for forming optically anisotropic layer (1c) ――――――――――――――――――――――――――――――――― · 100 parts by mass of the above rod-like liquid crystal compound (A) · 4.0 parts by mass of polymerizable monomer (A-400, manufactured by Shin-Nakamura Chemical Co., Ltd.) · 5.0 parts by mass of the following polymerization initiator S-1 (oxime type) · 3.0 parts by mass of the following photoacid generator D-1 · 2.0 parts by mass of the following polymer M-1 · 2.0 parts by mass of the following vertical alignment agent S01 · 0.2 parts by mass of the following surfactant B-1 · 42.3 parts by mass of methyl ethyl ketone · 627.5 parts by mass of methyl isobutyl ketone ―――――――――――――――――――――――――――――――――

[0152] Polymerization initiator S-1

[0153]

Chem.

[0154] Photoacid generator D-1

[0155]

Chem.

[0156] Polymer M-1

[0157]

Chem.

[0158] Vertical alignment agent S01

[0159]

Chem.

[0160] Surfactant B-1 (The weight average molecular weight was 2200.)

[0161] [Chemical formula]

[0162] They were bonded via an adhesive (manufactured by Lintec Corporation) so that the surface on the optical anisotropic layer T2 side of the laminate 2 faced the surface on the optical anisotropic layer C side of the cellulose acetate film with the optical anisotropic layer C. Next, the cellulose acetate film on the optical anisotropic layer C side was peeled off, and the surface that had been in contact with the cellulose acetate film of the optical anisotropic layer C was exposed. By the above procedure, a laminate 2 having the polymer film 2, the optical anisotropic layer T2, and the optical anisotropic layer C in this order was obtained. Next, a polarizer was bonded via an adhesive (manufactured by Lintec Corporation) onto the surface of the laminate 2 on the polymer film 2 side, and a circular polarizing plate 2 was obtained. In the circular polarizing plate 2, the polarizer, the polymer film 2, the optical anisotropic layer T2, and the optical anisotropic layer C were arranged in this order from the polarizer side. When the circular polarizing plate 2 was observed from the polarizer side, with the absorption axis direction of the polarizer as a reference (0°), the in-plane slow axis direction of the polymer film 2 was positioned at an angle of 105°. Further, when the circular polarizing plate 2 was observed from the polarizer side, with the absorption axis direction of the polarizer as a reference (0°), the in-plane slow axis on the front surface (the polarizer side surface) of the optical anisotropic layer T2 was positioned at an angle of 105°, and on the back surface (the side opposite to the polarizer side) of the optical anisotropic layer T2, it was positioned at an angle of 185°. In the optical anisotropic layer T2, the liquid crystal compound was twisted counterclockwise by 80°. Note that when observing the circular polarizing plate 2 from the polarizer side, with the absorption axis direction of the polarizer as a reference, the counterclockwise direction is displayed as a positive value, and the clockwise direction is displayed as a negative value. The twisting direction of the liquid crystal compound is determined to be clockwise or counterclockwise based on the in-plane slow axis on the surface of the front side (polarizer side) in the optically anisotropic layer when observing the circular polarizing plate 2 from the polarizer side.

[0163] [Example 3] A laminate 3 having a polymer film 2, an optical alignment film, an optically anisotropic layer T2, and an optically anisotropic layer C in this order was obtained according to the same procedure as in Example 2, except that the following optical alignment film forming treatment was performed instead of the corona treatment.

[0164] (Optical alignment film forming treatment) On one side surface of the polymer film 2, the following optical alignment film composition 1 was continuously coated with a bar coater. After coating, it was dried in a heating zone at 120 °C for 1 minute to remove the solvent, and an optical alignment film composition layer with a thickness of 0.3 μm was formed. Subsequently, while winding it around a mirror-finished backup roll, polarized ultraviolet irradiation (10 mJ / cm 2 , using an ultra-high pressure mercury lamp) was performed to form a long-strip optical alignment film. Note that the irradiation direction of the polarized ultraviolet light was adjusted so that the in-plane slow axis in the optically anisotropic layer T2 formed on the optical alignment film would be the in-plane slow axis direction described in Table 2 below. Also, as the following polymer A5, the polymer A5 described in paragraphs 0095 to 0098 of International Publication No. 2017 / 069252 was used. Polymer A5 is a polyorganosiloxane having a cinnamate group and an acrylic group in its repeating structure.

[0165] ───────────────────────────────── Optical alignment film composition 1 ───────────────────────────────── · 100 parts by mass of polymer A5 · 15.2 parts by mass of Nomucote TAB (manufactured by Nisshin Oillio Group, Ltd.) · 122 parts by mass of a crosslinking agent (Epolide GT401, manufactured by Daicel Corporation) · 10.0 parts by mass of the following thermal acid generator D1 · 0.5 parts by mass of diisopropylethylamine · 1100 parts by mass of diisobutyl ketone ―――――――――――――――――――――――――――――――――

[0166] Nomcoat TAB

[0167]

Chem.

[0168] Thermal acid generator D1

[0169]

Chem.

[0170] By the above procedure, a laminate 3 having a polymer film 2, an optically oriented film, an optically anisotropic layer T2, and an optically anisotropic layer C in this order was obtained. Next, a polarizer was laminated via an adhesive (manufactured by Lintec Corporation) on the surface of the laminate 2 on the side of the polymer film 2 to obtain a circular polarizing plate 3. In the circular polarizing plate 3, from the polarizer side, the polarizer, the polymer film 2, the optically anisotropic layer T2, and the optically anisotropic layer C were arranged in this order. Also, when the circular polarizing plate 3 was observed from the polarizer side, with the absorption axis direction of the polarizer as a reference (0°), the in-plane slow axis direction of the polymer film 2 was located at an angle of 105°. Further, when the circular polarizing plate 3 was observed from the polarizer side, with the absorption axis direction of the polarizer as a reference (0°), the in-plane slow axis on the front surface (the surface on the polarizer side) of the optically anisotropic layer T2 was located at an angle of 105°, and on the back surface (the side opposite to the polarizer side) of the optically anisotropic layer T2, it was located at an angle of 185°. In the optically anisotropic layer T2, the liquid crystal compound was twisted counterclockwise by 80°. Note that the above rotation angle is expressed with the counterclockwise direction as a positive value and the clockwise direction as a negative value with the absorption axis direction of the polarizer as a reference when the circular polarizing plate 3 is observed from the polarizer side. The twisting direction of the liquid crystal compound is determined to be clockwise or counterclockwise based on the in-plane slow axis on the front surface (polarizer side) in the optically anisotropic layer when observing the circular polarizing plate 3 from the polarizer side.

[0171] [Example 4] A photo-alignment film was formed on the polymer film 3 according to the procedure of (photo-alignment film formation treatment) described in Example 3. However, the irradiation direction of the polarized ultraviolet light was adjusted so that the in-plane slow axis in the optically anisotropic layer T3 formed on the photo-alignment film would be the in-plane slow axis direction described in Table 2 below. Using the polymer film 3 having the above photo-alignment film instead of the polymer film 1 subjected to corona treatment, changing the film thickness of the optically anisotropic layer from 1.4 μm to 2.7 μm, changing the chiral agent (A) to the following chiral agent (B), and changing the usage amount of the chiral agent (B) from 0.32 parts by mass to 0.08 parts by mass, a laminate 4 including the polymer film 3 and the optically anisotropic layer T3 was obtained according to the same procedure as in Example 1.

[0172] Chiral agent (B)

[0173] [Chemical formula]

[0174] Note that the angle formed between the in-plane slow axis of the polymer film 3 and the in-plane slow axis on the surface of the optically anisotropic layer T3 on the polymer film 3 side was 50°.

[0175] Next, a polarizer was bonded via an adhesive (manufactured by Lintec Corporation) onto the surface of the laminate 4 on the optically anisotropic layer T3 side to obtain a circular polarizing plate 4. In the circular polarizing plate 4, the polarizer, the optically anisotropic layer T3, and the polymer film 3 were arranged in this order from the polarizer side. When the circular polarizing plate 4 was observed from the polarizer side, with the absorption axis direction of the polarizer as the reference (0°), the in-plane slow axis direction of the polymer film 3 was positioned at an angle of 0°. Further, when the circular polarizing plate 4 was observed from the polarizer side, with the absorption axis direction of the polarizer as the reference (0°), the in-plane slow axis on the front surface (the surface on the polarizer side) of the optical anisotropic layer T3 was positioned at an angle of -90°, and on the back surface of the optical anisotropic layer T3 (the side opposite to the polarizer side) it was positioned at an angle of -50°. In the optical anisotropic layer T3, the liquid crystal compound was twisted clockwise by 40°. Note that the above rotation angle is expressed with counterclockwise as a positive value and clockwise as a negative value, with the absorption axis direction of the polarizer as the reference when the circular polarizing plate 4 is observed from the polarizer side. The twisting direction of the liquid crystal compound is determined to be clockwise or counterclockwise based on the in-plane slow axis on the front surface (the polarizer side) in the optical anisotropic layer when the circular polarizing plate 4 is observed from the polarizer side.

[0176] [Example 5] The irradiation direction of the polarized ultraviolet light was adjusted so that the in-plane slow axis in the optical anisotropic layer T4 formed on the photo-alignment film would be the in-plane slow axis direction described in Table 2 below. A laminate 5 including the polymer film 4 and the optical anisotropic layer T4 was obtained according to the same procedure as in Example 4, except that the polymer film 4 was used instead of the polymer film 3.

[0177] Next, a polarizer was bonded via an adhesive (manufactured by Lintec Corporation) onto the surface of the laminate 5 on the side of the optical anisotropic layer T4, and a circular polarizing plate 5 was obtained. In the circular polarizing plate 5, the polarizer, the optical anisotropic layer T4, and the polymer film 4 were arranged in this order from the polarizer side. When the circular polarizing plate 5 was observed from the polarizer side, with the absorption axis direction of the polarizer as the reference (0°), the in-plane slow axis direction of the polymer film 4 was positioned at an angle of -90°. Further, when the circular polarizing plate 4 was observed from the polarizer side, with the absorption axis direction of the polarizer as the reference (0°), the in-plane slow axis on the front side surface (the surface on the polarizer side) of the optical anisotropic layer T4 was positioned at an angle of 0°, and on the back side surface (the side opposite to the polarizer side) of the optical anisotropic layer T4, it was positioned at an angle of -40°. In the optical anisotropic layer T4, the liquid crystal compound was twisted clockwise by 40°. Note that the above rotation angle is displayed with counterclockwise as a positive value and clockwise as a negative value with the absorption axis direction of the polarizer as the reference when the circular polarizing plate 5 is observed from the polarizer side. The twisting direction of the liquid crystal compound is determined to be clockwise or counterclockwise based on the in-plane slow axis on the front side surface (the surface on the polarizer side) in the optical anisotropic layer when the circular polarizing plate 5 is observed from the polarizer side.

[0178] [Example 6] A laminate 6 and a circular polarizing plate 6 including a polymer film 5 and an optical anisotropic layer T3 were obtained according to the same procedure as in Example 4, except that the polymer film 5 was used instead of the polymer film 3.

[0179] [Example 7] A laminate 7 and a circular polarizing plate 7 including a polymer film 6 and an optical anisotropic layer T3 were obtained according to the same procedure as in Example 4, except that the polymer film 6 was used instead of the polymer film 3.

[0180] [Example 8] A laminate 8 and a circular polarizing plate 8 including a polymer film 7 and an optical anisotropic layer T3 were obtained according to the same procedure as in Example 4, except that the polymer film 7 was used instead of the polymer film 3.

[0181] [Example 9] A laminate 9 and a circular polarizing plate 9 including a polymer film 3 and an optically anisotropic layer T5 were obtained in the same procedure as in Example 4, except that the rod-like liquid crystal compounds (A) to (C) (total 100 parts by mass) in the composition T1 for forming the optically anisotropic layer were changed to the rod-like liquid crystal compound (C) (100 parts by mass). Note that the rod-like liquid crystal compound (C) did not exhibit liquid crystallinity at 50°C.

[0182] [Comparative Example 1] An optical alignment film was formed on the polymer film 8 according to the procedure of the (optical alignment film forming treatment) described in Example 3. However, the irradiation direction of the polarized ultraviolet rays was adjusted so that the in-plane slow axis in the optically anisotropic layer T6 formed on the optical alignment film would be in the in-plane slow axis direction described in Table 2 below. A laminate C1 including the polymer film 8 and the optically anisotropic layer T6 was obtained in the same procedure as in Example 1, except that the polymer film 8 having the above optical alignment film was used instead of the polymer film 1 subjected to the corona treatment, the film thickness of the optically anisotropic layer was changed from 1.4 μm to 2.1 μm, and the amount of the chiral agent used was changed from 0.32 part by mass to 0 part by mass.

[0183] Next, a polarizer was bonded via an adhesive (manufactured by Lintec Corporation) onto the surface of the laminate C1 on the polymer film 8 side to obtain a circular polarizing plate C1. In the circular polarizing plate C1, the polarizer, the polymer film 8, and the optically anisotropic layer T6 were arranged in this order from the polarizer side. Also, when the circular polarizing plate C1 was observed from the polarizer side, with the absorption axis direction of the polarizer as a reference (0°), the in-plane slow axis direction of the polymer film 8 was located at an angle of 15°, and the in-plane slow axis direction of the optically anisotropic layer T6 was located at an angle of 75°. Note that the above rotation angle is expressed with counterclockwise as a positive value and clockwise as a negative value with respect to the absorption axis direction of the polarizer when the circular polarizing plate C1 is observed from the polarizer side.

[0184] [Comparative Example 2] A laminate C2 and a circular polarizing plate C2 were obtained in the same procedure as in Example 1, except that the polymer film 9 was used instead of the polymer film 1.

[0185] <Evaluation method> The evaluation method for each evaluation item will be described.

[0186] [Curl] In terms of improving the handleability during manufacturing, it is preferable that the curl of the circular polarizing plate in each example and comparative example is small. Therefore, the curl was evaluated. The curl value of the circular polarizing plate in each example and comparative example can be measured according to the measurement method specified by the American National Standards Institute (ANSI / ASC PH1.29-1985, Method-A). The specific procedure will be described below. After cutting out a circular polarizing plate with a size of 35 mm in the width direction and 2 mm in the longitudinal direction, it was placed on a curl plate. The circular polarizing plate placed on the curl plate was conditioned for 6 hours in an environment of 25°C and 80% relative humidity, and the curl value was read. The curl value is expressed in terms of the radius of curvature (cm), and the worse the transportability is, the smaller the radius of curvature. The edge curl was evaluated based on the following criteria. Among the following criteria, 1 to 3 are levels without practical problems. A: (Absolute value of curl value) ≥ 30 cm B: 30 cm > (Absolute value of curl value) ≥ 20 cm C: 20 cm > (Absolute value of curl value)

[0187] [Wrinkle] The wrinkles of the circular polarizing plate in each example and comparative example were evaluated according to the following criteria. A: There are no wrinkles or they are minor and not visually recognized as optical unevenness when observed with a shaker tester. B: Coating optical unevenness due to wrinkles is visually recognized.

[0188] [Orientation] The polarizing microscope was set in the cross-nicol state, and the optical anisotropic layer in the obtained retardation plate was observed. The orientation of the optical anisotropic layer was evaluated according to the following criteria. A: No optical defects are observed. B: Slight optical defects are observed, but it is at a level without practical problems. C: Many optical defects are observed, and it is at a level that causes practical problems.

[0189] [Color difference] According to the following procedure, the color difference between the front direction and the diagonal direction of the display device using the circular polarizing plates of each example and comparative example was evaluated. The OLED55B8PJA manufactured by LG Electronics equipped with an organic EL panel (organic EL display element) was disassembled, and the touch panel with a circular polarizing plate was peeled off from the organic EL display device. The circular polarizing plate prepared above was bonded to the peeled surface of the touch panel with a circular polarizing plate so that air did not enter, and an organic EL display device was prepared. The prepared organic EL display device was set to black display, and the reflected light was observed when the fluorescent lamp was projected from the front and the polar angle of 60° under bright light. The display quality in the front and at the polar angle of 60° was evaluated based on the following criteria. A: No color tint is visually recognized, or if it is recognized, it is only slight. B: A slight color difference is visually recognized, but the reflected light is small and there is no problem in use. C: A color difference is visually recognized, and the reflected light is also large and unacceptable.

[0190] [Color unevenness] When manufacturing the image display device, since it is preferable that the degree of the above color difference is the same for each manufactured display device, the color unevenness of each display device using the circular polarizing plates of each example and comparative example was evaluated. Twenty organic EL display devices were manufactured in the same manner as the above color difference evaluation procedure, and the color difference of each manufactured organic EL display device was evaluated. The individual differences of each organic EL display device when evaluating the color difference were evaluated based on the following criteria. In terms of manufacturing, an evaluation of A or B is preferable. A: No individual difference is visually recognized, or if it is recognized, it is only slight. B: Slight individual differences are visually recognized, but the reflected light is small and there is no problem in use. C: Individual differences are visually recognized, and the reflected light is also large and unacceptable.

[0191] [Results] The evaluation results of curl, wrinkle, orientation, color difference, and color unevenness are shown in Table 2. In the table, the "angle with respect to the absorption axis of the polarizer" represents the angle of the in-plane slow axis direction on the front surface of each layer with respect to the absorption axis of the polarizer when the circular polarizing plate of each example and each comparative example is viewed from the polarizer side. The angle is represented with a positive value for counterclockwise and a negative value for clockwise, based on the absorption axis of the polarizer. In the table, the "twist angle of the optically anisotropic layer T" is the same as the twist angle described in Table 2, and represents that the in-plane slow axis direction is twisted toward the back surface of each layer when the circular polarizing plate of each example and each comparative example is viewed from the polarizer side, starting from the above "angle with respect to the absorption axis of the polarizer". The angle is represented with a positive value for counterclockwise and a negative value for clockwise, based on the absorption axis of the polarizer.

[0192]

Table 2

[0193] From the results in Table 2, it was confirmed that when the circular polarizing plate using the retardation plate of the present invention was applied to an image display device, the color difference was small in the front direction and the diagonal direction. From the comparison between Examples 1 and 2 and other examples, it was confirmed that when a photo-alignment film was included between the polymer film and the optically anisotropic layer T, color unevenness was suppressed. From the comparison between Example 9 and other examples, it was confirmed that when the liquid crystal compound contained in the optically anisotropic layer T exhibited liquid crystallinity at 50°C, the orientation was excellent. From the comparison between Example 6 and other examples, it was confirmed that when the glass transition temperature of the polymer film was 110°C or higher, wrinkles in the retardation plate were suppressed. From the comparison between Examples 2 and 3 and other examples, it was confirmed that when the circular polarizing plate had the optically anisotropic layer C, the color difference in the front direction and the diagonal direction when the circular polarizing plate was applied to an image display device was small.

Explanation of Signs

[0194] 10a, 10b, 10c Retardation plate 12a, 12b, 12c First optical anisotropic layer 14a, 14b, 14c Second optical anisotropic layer 20 Polarizer 100a, 100b, 100c Circular polarizing plate

Claims

1. comprising a first optically anisotropic layer and a second optically anisotropic layer, wherein the first optically anisotropic layer is a polymer film, the in-plane retardation of the first optically anisotropic layer at a wavelength of 550 nm is 151 to 211 nm, the retardation in the thickness direction of the first optically anisotropic layer at a wavelength of 550 nm is -150 to -30 nm, the second optically anisotropic layer is a layer formed by fixing a liquid crystal compound twisted and oriented with the thickness direction as the helical axis, the twist angle of the liquid crystal compound in the second optically anisotropic layer is within the range of 81 ± 10°, the second optically anisotropic layer satisfies the relationship of formula (1-A), a retardation plate in which the in-plane slow axis of the first optically anisotropic layer is parallel to the in-plane slow axis on the surface of the second optically anisotropic layer on the side of the first optically anisotropic layer. Formula (1-A) 142 nm ≦ Δnd ≦ 202 nm In formula (1-A), Δn represents the refractive index anisotropy of the second optically anisotropic layer at a wavelength of 550 nm, and d represents the thickness of the second optically anisotropic layer.

2. Comprising a first optically anisotropic layer and a second optically anisotropic layer, wherein the first optically anisotropic layer is a polymer film, the in-plane retardation of the first optically anisotropic layer at a wavelength of 550 nm is 158 to 218 nm, the retardation in the thickness direction of the first optically anisotropic layer at a wavelength of 550 nm is -150 to -30 nm, the second optically anisotropic layer is a layer formed by fixing a liquid crystal compound twisted and oriented with the thickness direction as the helical axis, the twist angle of the second optically anisotropic layer is within the range of 59 ± 10°, the second optically anisotropic layer satisfies the relationship of formula (1-B), a retardation plate in which the in-plane slow axis of the first optically anisotropic layer is orthogonal to the in-plane slow axis on the surface of the second optically anisotropic layer on the side of the first optically anisotropic layer. Formula (1-B) 203 nm ≦ Δnd ≦ 263 nm In formula (1-B), Δn represents the refractive index anisotropy of the second optically anisotropic layer at a wavelength of 550 nm, and d represents the thickness of the second optically anisotropic layer.

3. Comprising a first optically anisotropic layer and a second optically anisotropic layer, wherein the first optically anisotropic layer is a polymer film, the in-plane retardation of the first optically anisotropic layer at a wavelength of 550 nm is 67.5 to 127.5 nm, the retardation in the thickness direction of the first optically anisotropic layer at a wavelength of 550 nm is -150 to -30 nm, The second optically anisotropic layer is a layer formed by fixing a liquid crystal compound that is twisted and oriented with the thickness direction as the helical axis, the twist angle of the second optically anisotropic layer is within the range of 40 ± 20°, the second optically anisotropic layer satisfies the relationship of formula (1-C), A retardation plate in which the angle formed by the in-plane slow axis of the first optically anisotropic layer and the in-plane slow axis on the surface of the second optically anisotropic layer on the side of the first optically anisotropic layer is within the range of 30 to 70°. Formula (1-C) 317 nm ≤ Δnd ≤ 377 nm In formula (1-C), Δn represents the refractive index anisotropy at a wavelength of 550 nm of the second optically anisotropic layer, and d represents the thickness of the second optically anisotropic layer.

4. The retardation plate according to any one of claims 1 to 3, further comprising an optical alignment film between the first optically anisotropic layer and the second optically anisotropic layer.

5. The retardation plate according to any one of claims 1 to 4, wherein the polymer film contains a polymer having at least one selected from the group consisting of repeating units derived from a styrene derivative and repeating units having a fluorene structure.

6. The retardation plate according to any one of claims 1 to 5, wherein the liquid crystal compound exhibits liquid crystallinity at 50°C.

7. The retardation plate according to any one of claims 1 to 6, wherein the glass transition temperature of the first optically anisotropic layer is 110°C or higher.

8. The retardation plate according to any one of claims 1 to 7, further comprising a third optically anisotropic layer having a retardation in the thickness direction at a wavelength of 550 nm of -100 to -35 nm.

9. A circular polarizing plate comprising the retardation plate according to any one of claims 1 to 8 and a polarizer.

10. An image display device comprising the retardation plate according to any one of claims 1 to 8, or the polarizing plate according to claim 9.

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