Optical laminate, and polarizing plate, display panel, and image display device using the same

Abstract

To provide an optical laminate that allows an orientation layer and a positive A-layer to be laminated directly and has excellent adhesion properties between the orientation layer and the positive A-layer.SOLUTION: In an optical laminate having an orientation layer and a positive A-layer, the orientation layer and the positive A-layer are in contact, the positive A-layer contains a compound (a), the orientation layer contains the compound (a) shifted from the positive A-layer and other compounds, the compound (a) contains an atom X that the other compounds substantially do not contain, and an average detection amount of the atom X within the orientation layer is 23 or larger when the average detection amount of the atom X within the positive A-layer is standardized 100 on a mass basis.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] As an optical film applied to an image display device, etc., there is an optical laminate that imparts a desired phase difference to incident light. For example, a circular polarizer formed by combining a λ / 4 retardation layer and a linear polarizer is used for antireflection in an image display device.

[0003] It is well known that such optical stacks do not provide the same effect at all wavelengths. For example, a circular polarizer formed by laminating a λ / 4 retardation layer and a linear polarizer can circularly polarize light with a wavelength of 550 nm and significantly suppress external light reflection, but light with wavelengths longer or shorter than 550 nm becomes elliptically polarized light, resulting in a problem of reduced anti-reflection function. As a method for solving this problem, a method has been proposed in which the retardation layer of the circular polarizer is a combination of a λ / 4 retardation layer and a λ / 2 retardation layer.

[0004] However, image display devices having positive A layers such as λ / 4 retardation layers and λ / 2 retardation layers have a problem in that display quality (for example, contrast) decreases when viewed from an oblique direction. For this reason, an optical laminate comprising a combination of a positive A layer and a positive C layer has been proposed (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-215221 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-4142 Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, a layer in which a liquid crystal composition is aligned in-plane on a substrate and a layer in which a liquid crystal composition is aligned vertically on the substrate must be separately prepared, and these layers must be peeled off from the substrate and laminated together. Therefore, the optical laminate of Patent Document 1 has the problem of complicated processes. Furthermore, in Patent Document 1, the positive A layer and the positive C layer are laminated via an adhesive layer or a pressure-sensitive adhesive layer, which increases the thickness by the adhesive layer or the pressure-sensitive adhesive layer, hindering thinning.

[0007] In Patent Document 2, the positive A layer and the positive C layer are directly laminated together without an adhesive or pressure-sensitive adhesive layer therebetween, which can solve the problem of thinning. However, when the optical laminate of Patent Document 2 was attached to another member, there were many cases where peeling occurred at the interface between the positive A layer and the positive C layer. Furthermore, among the optical laminates of Patent Document 2, in an embodiment in which the positive C layer and the positive A layer are formed on a peelable substrate and the positive C layer and the positive A layer are transferred to another member, there were many cases in which the positive A layer and the positive C layer peeled off during transfer.

[0008] The present invention aims to provide an optical laminate which is formed by directly laminating an alignment layer such as a positive C layer and a positive A layer, and which has excellent adhesion between the alignment layer and the positive A layer, as well as a display panel and an image display device which use the same. [Means for solving the problem]

[0009] The present invention provides the following [1] to [4]. [1] An optical laminate having an alignment layer and a positive A layer, wherein the alignment layer and the positive A layer are in contact with each other, the positive A layer contains a compound a, the alignment layer contains the compound a migrated from the positive A layer and other compounds, the compound a contains an atom X that is substantially not contained in the other compounds, and when the average detectable amount of the atom X in the positive A layer is normalized to 100 on a mass basis, the average detectable amount of the atom X in the alignment layer is 23 or more. [2] A polarizing plate having a polarizer, a transparent protective plate A arranged on one side of the polarizer, and a transparent protective plate B arranged on the other side of the polarizer, wherein either the transparent protective plate A or the transparent protective plate B is the optical laminate described in [1] above. [3] A display panel comprising the optical laminate according to [1] above disposed on the light exit surface of a display element. [4] An image display device comprising the display panel according to [3] above. [Effects of the Invention]

[0010] According to the optical laminate of the present invention, and the display panel and image display device using the same, the alignment layer and the positive A layer are directly laminated, so that the optical laminate can be made thin, and the adhesion between the alignment layer and the positive A layer is excellent, so that workability and stability over time can be improved. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing one embodiment of an optical laminate of the present invention. [Figure 2] 1 is a cross-sectional view illustrating an embodiment of a polarizing plate of the present invention. [Figure 3] 1 is a cross-sectional view showing an embodiment of a display panel of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described. In this specification, the notation "AA~BB" means "AA or more and BB or less".

[0013] Also, in this specification, the in-plane retardation at a wavelength of 450 nm may be denoted as "Re(450)", the in-plane retardation at a wavelength of 550 nm may be denoted as "Re(550)", the in-plane retardation at a wavelength of 650 nm may be denoted as "Re(650)", and the retardation in the thickness direction at a wavelength of 550 nm may be denoted as "Rth(550)". The in-plane retardation (Re) and the retardation in the thickness direction (Rth) can be calculated from Nx, Ny, Nz, and the thickness d (nm) of the retardation layer by the following equations. In-plane retardation (Re) = (Nx - Ny) × d Retardation in the thickness direction (Rth) = ((Nx + Ny) / 2 - Nz) × d

[0014] Also, in this specification, the positive A layer is a layer that satisfies the relationship Nx > Ny ≒ Nz when the refractive index in the X-axis direction, which is the direction of the axis having the highest refractive index along the in-plane of the layer, is Nx, the refractive index in the Y-axis direction perpendicular to the X-axis along the in-plane direction of the layer is Ny, and the refractive index in the thickness direction of the layer is Nz. Also, in this specification, the positive C layer is a layer that satisfies the relationship Nx ≒ Ny < Nz.

[0015] [Optical laminate] The optical laminate of the present invention has an alignment layer and a positive A layer, the alignment layer and the positive A layer are in contact with each other, the positive A layer contains compound a, and the alignment layer contains the compound a transferred from the positive A layer and other compounds. Compound a contains atom X that is not substantially contained in the other compounds. When the average detected amount of atom X in the positive A layer is normalized to 100 on a mass basis, the average detected amount of atom X in the alignment layer is 23 or more.

[0016] FIG. 1 is a cross-sectional view showing an embodiment of the optical laminate of the present invention. The optical laminate 100 in Fig. 1 has an alignment layer 20 and a positive A layer 30, and the alignment layer 20 and the positive A layer 30 are in contact with each other. In the optical laminate in Fig. 1, the alignment layer 20 and the positive A layer 30 are formed on a substrate 10.

[0017] The optical laminate of the present invention comprises an alignment layer and a positive A layer, and the alignment layer and the positive A layer are in contact with each other. As described above, in the optical laminate of the present invention, the alignment layer and the positive A layer are directly laminated without an adhesive layer or the like, so that the optical laminate can be thinned and can be easily produced.

[0018] <Average detected amount of X atoms in the alignment layer> The optical layered body of the present invention is required to have the following constitutions (1) to (3), and the average detectable amount of atom X in the alignment layer must satisfy the following condition (4). (1) The positive A layer contains compound a. (2) The alignment layer contains the compound a transferred from the positive A layer and other compounds. (3) The compound a contains an atom X that is not substantially contained in the other compounds. (4) When the average detectable amount of the atom X in the positive A layer is normalized to 100 on a mass basis, the average detectable amount of the atom X in the alignment layer is 23 or more.

[0019] The compound a means a liquid crystal compound contained in the positive A layer. The atom X contained in the compound a includes a sulfur atom and a nitrogen atom. The other compounds refer to all compounds constituting the alignment layer except for compound a. In this specification, the average detection amount in (4) above may be referred to as the "average detection amount of the alignment layer."

[0020] The average detection amount of the alignment layer satisfying the above condition (4) means that compound a in the positive A layer has penetrated into the alignment layer in a proportion exceeding a predetermined level. Thus, when compound a in the positive A layer has penetrated into the alignment layer in a proportion exceeding a predetermined level, the affinity between the positive A layer and the alignment layer increases, and an anchoring effect is generated. Therefore, the optical laminate of the present invention, which has the above configurations (1) to (3) and satisfies the above condition (4), can improve the adhesion between the positive A layer and the alignment layer. On the other hand, an optical laminate that does not satisfy the above condition (4) cannot achieve good adhesion between the positive A layer and the alignment layer, and peeling occurs at the interface between the positive A layer and the alignment layer due to stress generated during operations such as lamination and transfer.

[0021] The average detectable amount of the alignment layer is preferably 27 or more, more preferably 30 or more, and even more preferably 33 or more. The adhesion gradually improves as the average detection amount of the alignment layer increases, but there is a limit to how much adhesion can be improved. Furthermore, since compound a penetrates into the gaps in the alignment structure of the alignment layer, the alignment of the alignment layer is less affected by compound a that has penetrated into the alignment layer. However, if the average detection amount of the alignment layer becomes too high, it may become difficult to align the positive A layer, or problems may occur due to changes in the physical properties of the alignment layer. For this reason, the average detection amount is preferably 60 or less, more preferably 50 or less, and even more preferably 40 or less.

[0022] The average amount of detection in the alignment layer can be increased or decreased, for example, by the molecular weight of compound a in the positive A layer, the affinity between the alignment layer and the positive A layer, the solvent of the coating solution for forming the positive A layer, etc. Specifically, the smaller the molecular weight of compound a, the greater the average amount of detection, and the greater the molecular weight of compound a, the smaller the average amount of detection. Furthermore, the higher the affinity between the alignment layer and the positive A layer, the greater the average amount of detection, and the lower the affinity, the smaller the average amount of detection. Furthermore, the higher the permeability of the solvent in the coating solution for forming the positive A layer into the alignment layer, the greater the average amount of detection, and the lower the permeability of the solvent into the alignment layer, the smaller the average amount of detection. Furthermore, the higher the mass fraction of the solvent in the coating solution for forming the positive A layer, the greater the average amount of detection, and the lower the mass fraction of the solvent in the coating solution, the smaller the average amount of detection (mass fraction of solvent in coating solution ≒ total amount of coating solution - mass fraction of solids in coating solution). Furthermore, as will be described later, when a specific liquid crystal compound is used as a compound constituting an alignment layer such as a positive C layer, and compound a is a compound containing a sulfur atom, the average detectable amount can be easily increased. Furthermore, as will be described later, when compound a has a molecular structure that is easily mobile, the average detectable amount can be easily increased.

[0023] The mass-based detectable amount of atom X in the positive A layer and the alignment layer can be measured by cutting the optical laminate vertically to prepare a thin measurement sample and measuring the cross-section of the sample using scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX). Preferably, 20 measurement samples are prepared and the average values ​​of the 20 measurements are used as various parameters related to the detectable amount of atom X. The thin section measurement sample can be prepared, for example, by cutting the optical laminate to a predetermined size to prepare a cut sample, and then cutting the cut sample vertically with a diamond knife. The thickness of the thin section measurement sample is preferably 40 nm to 160 nm.

[0024] When measuring with an SEM-EDX analyzer, it is preferable to acquire characteristic X-ray spectra by adjusting the quantification conditions specific to each instrument (e.g., for the Hitachi High-Technologies SEM "SU8000" and the Oxford Instruments EDX "XMAX80," an acceleration voltage of 30 kV, a focal length of 15 mm, and a sample tilt of 0 degrees) and adjusting the irradiation current and measurement time appropriately to ensure sufficient detection of the target element. The concentration of each element can also be determined using the ZAF correction method (a method of determining the content of each element by applying atomic number correction Z, absorption correction A, and fluorescence correction F to the relative intensity of each element).

[0025] In this specification, unless otherwise specified, the measurement of the amount of detected atom X described above and other measurements and evaluations are carried out in an atmosphere with a temperature of 23°C ± 5°C and a humidity of 40% to 65%. Furthermore, before the measurement and evaluation, the sample is exposed to the atmosphere for 30 minutes or more.

[0026] <Coefficient of variation of detected amount, variation ratio> In the optical layered body of the present invention, it is preferable that the detected amount of the atom X in the alignment layer satisfies the following condition 1. (Condition 1) The amount of the atom X in the alignment layer is detected at 100 locations at intervals of 26 nm in a direction parallel to the interface, starting from a position 200 nm in the thickness direction from the interface between the alignment layer and the positive A layer, and the mass-based coefficient of variation of the amount of the atom X detected at the 100 locations is 0.16 or more.

[0027] Satisfying condition 1 means that the amount of compound A permeated into the alignment layer varies from place to place in the alignment layer, and the degree of variation is greater than or equal to a predetermined value. By varying the permeability of compound A from place to place in the alignment layer, the adhesion between the alignment layer and the positive A layer can be improved. The coefficient of variation in condition 1 is preferably 0.20 or more, and more preferably 0.25 or more. The upper limit of the coefficient of variation in Condition 1 is preferably 0.60 or less, more preferably 0.50 or less, even more preferably 0.40 or less, and even more preferably 0.35 or less, from the viewpoint of suppressing fluctuations in physical properties in fine regions. The coefficient of variation is a dimensionless parameter obtained by dividing the standard deviation (variation) by the average value.

[0028] In the optical laminate of the present invention, it is preferable that the detected amount of the atom X in the positive A layer and the alignment layer satisfies the following condition 2. (Condition 2) The amount of atom X in the positive A layer is detected at 100 locations every 26 nm in a direction parallel to the interface, starting from a position 200 nm in the thickness direction from the interface between the positive A layer and the alignment layer. The mass-based coefficient of variation of the detected atom X is defined as CV1. The amount of atom X in the alignment layer is detected at 100 locations every 26 nm in a direction parallel to the interface, starting from a position 200 nm in the thickness direction from the interface between the alignment layer and the positive A layer. The mass-based coefficient of variation of the detected atom X is defined as CV2. The ratio of the CV1 to the CV2 (CV2 / CV1) is 2.00 or more.

[0029] Satisfying condition 2 means that the amount of compound A permeated into the alignment layer varies from place to place in the alignment layer, and the degree of variation is greater than or equal to a predetermined value, similar to condition 1. By varying the permeability of compound A from place to place in the alignment layer in this way, the adhesion between the alignment layer and the positive A layer can be improved. The ratio of condition 2 is preferably 2.10 or more, and more preferably 2.20 or more. The upper limit of the ratio in Condition 2 is preferably 4.00 or less, more preferably 3.00 or less, and even more preferably 2.50 or less, from the viewpoint of suppressing variations in physical properties in the fine regions.

[0030] Conditions 1 and 2 can be adjusted, for example, by the in-plane uniformity of the orientation degree of the orientation layer. Specifically, the lower the in-plane uniformity of the orientation degree of the orientation layer, the larger the coefficient of variation of condition 1 and the ratio of condition 2 tend to be, and the higher the in-plane uniformity of the orientation degree of the orientation layer, the smaller the coefficient of variation of condition 1 and the ratio of condition 2 tend to be.

[0031] <Alignment layer> The alignment layer is disposed at a position in contact with the positive A layer in the thickness direction of the optical laminate. When an alignment layer and a positive A layer are formed on a substrate, it is preferable to first form the alignment layer on the substrate, and then form the positive A layer.

[0032] The alignment layer contains compound a transferred from the positive A layer and other compounds. The other compounds are all compounds constituting the alignment layer except compound a. The main component of the other compounds is a liquid crystal compound, and the liquid crystal compound is preferably a liquid crystal compound having a photosensitive group. The other compounds are those that do not substantially contain atom X contained in compound a. In this specification, "other compounds substantially do not contain atom X" means that the other compounds contain 0.1% by mass or less, more preferably 0.01% by mass or less, of the total amount of the other compounds.

[0033] The alignment layer may be, for example, a homeotropic alignment layer. Homeotropic alignment refers to a state in which the liquid crystal compound is aligned parallel and uniformly to the normal direction of the layer, that is, a state in which the liquid crystal compound is aligned vertically. A typical example of a homeotropic alignment layer is a positive C layer. That is, the alignment layer may be a positive C layer. Hereinafter, an embodiment of a positive C layer, which is a typical example of an alignment layer, will be mainly described.

[0034] The liquid crystal compound of the positive C layer may be a material made of a liquid crystal polymer or a material made of a liquid crystal monomer. The liquid crystal compound of the positive C layer is preferably a liquid crystal compound having a photosensitive group from the viewpoint of the alignment of the positive A layer formed on the positive C layer. That is, the alignment layer preferably contains a liquid crystal compound having a photosensitive group as another compound.

[0035] In this specification, a photosensitive group refers to a functional group that bonds with other molecules upon irradiation with light. Also, in this specification, a liquid crystal compound refers to a material that exhibits liquid crystallinity when a physical external stimulus (such as heating, cooling, application of an electric field, a magnetic field, or shear) is applied to the material alone, or that exhibits liquid crystallinity when mixed with a solvent or a non-liquid crystal component.

[0036] Examples of the liquid crystal compound having a photosensitive group include a photosensitive side-chain liquid crystal polymer having a side chain containing a structure in which the following (i) and (ii) are bonded with or without a spacer: As the liquid crystal compound having such a photosensitive group, the one described in JP 2016-4142 A can also be used. (i) Photosensitive groups such as a cinnamoyl group, a chalcone group, a cinnamylidene group, a biphenylacryloyl group, a furylacryloyl group, a naphthylacryloyl group (or derivatives thereof). (ii) Substituents such as biphenyl, terphenyl, phenylbenzoate, and azobenzene, which are often used as mesogenic components of liquid crystal polymers.

[0037] Examples of photosensitive side chain liquid crystalline polymers include polymers that have photosensitive side chains with carboxyl groups at the side chain terminals, form a rigid structure by dimerization through hydrogen bonding of the carboxyl groups at the side chain terminals, and exhibit liquid crystallinity without including a mesogenic group in the structure of the side chain itself. Examples of the main chain constituting the photosensitive side-chain liquid crystalline polymer include hydrocarbons, acrylates, methacrylates, siloxanes, maleimides, and N-phenylmaleimides, to which the above-mentioned side chains are bonded via spacers. These polymers may be homopolymers consisting of the same repeating units, copolymers consisting of multiple units having side chains with different structures, or copolymers obtained by blending units having side chains containing photosensitive groups with units having side chains without photosensitive groups to an extent that does not impair liquid crystallinity. Furthermore, a low molecular weight compound may be added to enhance alignment.

[0038] The photosensitive side chain liquid crystal polymer may be a polymer into which a crosslinked structure is introduced using a crosslinking agent such as an isocyanate material or an epoxy material, for the purpose of improving heat resistance or the like.

[0039] The photosensitive side chain type liquid crystalline polymer is preferably a polymer formed using a monomer having a side chain represented by the following general formulas (1) to (3). Polymers formed using monomers having side chains represented by the following general formulas (1) to (3) have high affinity with compounds containing sulfur atoms. That is, when an alignment layer such as a positive C layer contains a polymer formed using a monomer having a side chain represented by the following general formulas (1) to (3), and compound a in the positive A layer contains a sulfur atom, compound a easily penetrates into the positive C layer, which is preferable in that the detectable amount of atom X (e.g., sulfur) easily falls within the above range.

[0040] [ka]

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[0042] In each of Chemical Formula 1 and Chemical Formula 2, n represents an integer of 1 to 12, and m represents an integer of 1 to 12; X and Y represent none, -COO, -OCO-, -N=N-, -C=C-, or -CH-; W1 represents a cinnamoyl group, a chalcone group, a cinnamylidene group, a biphenylacryloyl group, a furylacryloyl group, a naphthylacryloyl group, or a derivative thereof, or represents -H, -OH, or -CN; and W2 represents a cinnamoyl group, a chalcone group, a cinnamylidene group, a biphenylacryloyl group, a furylacryloyl group, a naphthylacryloyl group, or a derivative thereof, or represents -H, -OH, or -CN. In each of the general formulas (1) and (2), n represents an integer of 1 to 12, m represents an integer of 1 to 12, X or Y represents a single bond, -COO, -OCO-, -N=N-, -C=C- or -CH-, W1 represents a cinnamoyl group, a chalcone group, a cinnamylidene group, a biphenylacryloyl group, a furylacryloyl group, a naphthylacryloyl group, or a derivative thereof, or -H, -OH or -CN, and W2 represents a cinnamoyl group, a chalcone group, a cinnamylidene group, a biphenylacryloyl group, a furylacryloyl group, a naphthylacryloyl group, or a derivative thereof, or -H, -OH or -CN.

[0043] Among the side chains represented by the above formula, monomers having side chains where W1 and W2 are represented by -H, -OH, and -CN do not exhibit photosensitivity, but can be copolymerized with a monomer having a photosensitive group in the side chain to obtain a liquid crystalline polymer having a photosensitive group. In the copolymerization, the higher the proportion of the monomer not exhibiting photosensitivity represented by the above formula, the easier it is to obtain a polymer that is more likely to exhibit homeotropic alignment, but the copolymerization proportion can be appropriately set by considering the balance between homeotropic alignment and liquid crystallinity.

[0044] [ka]

[0045] In the general formula (3), s represents 0 or 1, t represents an integer of 1 to 3, and R represents H, an alkyl group, an alkyloxy group, or a halogen.

[0046] The alignment layer such as the positive C layer may contain additives such as a light stabilizer and an antioxidant within a range that does not impair the effects of the present invention.

[0047] The positive C layer can be formed, for example, by preparing a coating liquid for the positive C layer by dissolving or diluting the components constituting the positive C layer (e.g., a liquid crystalline polymer formed from a monomer unit having a side chain represented by general formulas (1) to (3) and an additive) in a solvent, and then applying the coating liquid onto a substrate and drying it.

[0048] Examples of solvents for the coating solution for the positive C layer include dioxane, dichloroethane, cyclohexanone, toluene, tetrahydrofuran, o-dichlorobenzene, methyl ethyl ketone, and methyl isobutyl ketone, and these solvents can be used alone or in combination.

[0049] In the process of applying the coating solution for the positive C layer to a substrate and removing the solvent, the positive C layer begins to exhibit homeotropic alignment, and the homeotropic alignment is enhanced by further heating after drying. Specifically, homeotropic alignment is induced by heating to a temperature above the liquid crystal phase transition temperature and below the isotropic transition temperature (preferably below the isotropic transition temperature) and then cooling. Furthermore, the homeotropically aligned layer is irradiated with linearly polarized ultraviolet light. By irradiating with linearly polarized ultraviolet light, the photoreaction of the photosensitive group in the liquid crystal polymer having a photosensitive group proceeds anisotropically, imparting a liquid crystal alignment ability that aligns the liquid crystal compound in the positive A layer. The wavelength of the irradiated light is preferably 200 nm to 500 nm, more preferably 250 nm to 400 nm. Even when such linearly polarized ultraviolet light is irradiated, the alignment of the homeotropically aligned layer is not substantially affected.

[0050] It is preferable to irradiate the positive C layer with linearly polarized UV light after forming the positive A layer on the positive C layer, followed by irradiating with unpolarized UV light. Irradiation with unpolarized UV light promotes dimerization of the liquid crystal polymer having a photosensitive group, fixing the orientation and forming a stable homogeneously oriented layer. Since the homeotropic orientation of the positive A layer is already completed before irradiation with unpolarized UV light, the homeotropic orientation of the positive A layer is not substantially disturbed by the unpolarized UV light. Furthermore, irradiation with unpolarized UV light is expected to cause a reaction between the photosensitive groups of the positive C layer and the photosensitive groups of the positive A layer, further improving adhesion.

[0051] The alignment layer such as the positive C layer preferably has Rth(550) of −100 nm to −50 nm, more preferably −90 nm to −60 nm. By setting Rth(550) of the alignment layer in this range, visibility in oblique directions can be easily improved.

[0052] The alignment layer such as the positive C layer preferably has a small Re(550), preferably 20 nm or less, more preferably 10 nm or less, even more preferably 5 nm or less, and still more preferably 1 nm or less.

[0053] In this specification, the in-plane retardation, thickness retardation, haze, and total light transmittance refer to the average values ​​of measurements taken at 16 locations. The 16 measurement locations are preferably determined by dividing the area inside the margin into five equal parts in the vertical and horizontal directions by a margin of 1 cm from the outer edge of the measurement sample, and by drawing lines to divide the area inside the margin into five equal parts in the vertical and horizontal directions. When the measurement sample is rectangular, it is preferable to measure the area inside the margin into five equal parts in the vertical and horizontal directions by a margin of 1 cm from the outer edge of the rectangle, and then measure the area inside the margin by dividing the area inside the margin into five equal parts in the vertical and horizontal directions by the 16 intersections of the lines, and calculate the average value. When the measurement sample has a shape other than a rectangle, such as a circle, ellipse, triangle, or pentagon, it is preferable to draw a rectangle with the largest area inscribed in the shape, and measure 16 locations on the rectangle using the above method. The in-plane retardation and the retardation in the thickness direction can be measured using, for example, a product name "KOBRA-WR" manufactured by Oji Keisoku Co., Ltd.

[0054] The thickness of an alignment layer such as a positive C layer is preferably 100 nm to 5 μm, more preferably 50 nm to 3 μm, and even more preferably 100 nm to 2 μm. The thickness of each layer, such as the alignment layer such as the positive C layer, the positive A layer, and the substrate, can be calculated, for example, by observing a cross-sectional image of the optical laminate with a scanning transmission electron microscope (STEM) or the like and averaging the thicknesses at 20 points.

[0055] <Positive A layer> The positive A layer is disposed in a position in the thickness direction of the optical laminate where it is in contact with the positive C layer. The positive A layer contains a compound a.

[0056] Compound a contains an atom X that is not substantially contained in other compounds contained in the positive C layer. Examples of the atom X contained in compound a include a sulfur atom and a nitrogen atom, and a sulfur atom is preferred. The positive A layer is preferably formed from a liquid crystal compound. The liquid crystal compound is preferably a polymerizable liquid crystal compound. That is, compound a is preferably a liquid crystal compound, more preferably a polymerizable liquid crystal compound. Furthermore, compound a is preferably a polymerizable liquid crystal compound containing a sulfur atom or a nitrogen atom as the atom X, more preferably a polymerizable liquid crystal compound containing a sulfur atom as the atom X.

[0057] The positive A layer is a layer that exhibits homogeneous alignment. Homogeneous alignment refers to a state in which the liquid crystalline material is aligned parallel to the layer surface and in the same direction (optically uniaxial). Liquid crystal compounds that can be homogeneously aligned may be materials made of liquid crystalline polymers or materials made of liquid crystalline monomers. As described above, when a homeotropically aligned positive C layer is irradiated with linearly polarized ultraviolet light, the photoreaction of the photosensitive groups in the liquid crystalline polymer having photosensitive groups proceeds anisotropically, imparting a liquid crystal alignment ability that aligns the liquid crystal compound in the positive A layer. Therefore, even if the coating liquid for the positive A layer is directly applied to the positive C layer, dried, and cured, a homogeneously aligned positive A layer can be obtained on the homeotropically aligned positive C layer.

[0058] It is preferable that the positive A layer has Re(450), Re(550), and Re(650) satisfy the relationship (i) below. That is, it is preferable that the positive A layer has reverse dispersion. By using a positive A layer with reverse dispersion that satisfies the relationship (i) below, it is possible to easily impart reverse dispersion to the entire optical laminate including the positive A layer and the positive C layer, and it is possible to easily improve visibility, antireflection properties, etc. in wavelength ranges outside 550 nm. Re(450) <Re(550)<Re(650) (i)

[0059] The Re(450), Re(550) and Re(650) of the positive A layer are not particularly limited, but are preferably in the following ranges when the positive A layer is a λ / 4 retardation layer, and in the following ranges when the positive A layer is a λ / 2 retardation layer.

[0060] <In the case of a λ / 4 retardation layer> Re(450) is preferably 82 nm to 143 nm, more preferably 90 nm to 135 nm. Re(550) is preferably 100 nm to 175 nm, more preferably 110 nm to 165 nm. Re(650) is preferably 119 nm to 206 nm, more preferably 130 nm to 195 nm. Furthermore, the laminate of the positive A layer (λ / 4 retardation layer) and the positive C layer preferably has Rth(550) of −40 nm to 40 nm, more preferably −25 nm to 25 nm.

[0061] <In the case of a λ / 2 retardation layer> Re(450) is preferably 165 nm to 286 nm, more preferably 180 nm to 270 nm. Re(550) is preferably 201 nm to 349 nm, more preferably 220 nm to 230 nm. Re(650) is preferably 237 nm to 412 nm, more preferably 260 nm to 390 nm. Furthermore, the laminate of the positive A layer (λ / 2 retardation layer) and the positive C layer preferably has Rth(550) of −50 nm to 50 nm, more preferably −30 nm to 30 nm.

[0062] The thickness of the positive A layer is preferably 100 nm to 5 μm, more preferably 500 nm to 4 μm, and even more preferably 1.5 μm to 3.0 μm.

[0063] The reverse dispersion positive A layer can be formed from a liquid crystal compound exhibiting reverse dispersion, and such a liquid crystal compound is preferably polymerizable. Examples of polymerizable liquid crystal compounds exhibiting reverse dispersion include those represented by general formula (1) in JP-A-2019-73712 and those represented by general formula (II) in WO2017 / 043438.

[0064] Specific examples of polymerizable liquid crystal compounds exhibiting reverse dispersion include compounds represented by the following chemical formulas (4) to (29): All of the compounds represented by the following chemical formulas (4) to (29) contain a sulfur atom and a nitrogen atom in the molecule. The compounds represented by the following chemical formulas (4) to (29) have a molecular structure in which the left and right sides thereof are easily movable around the biphenyl group, and are therefore preferred in that they easily penetrate into the alignment film and make it easy to keep the average detectable amount of atom X in the alignment film within the above range.

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[0075] The positive A layer may contain additives such as a light stabilizer and an antioxidant, as long as the effects of the present invention are not impaired.

[0076] The positive A layer can be formed, for example, by preparing a coating liquid for the positive A layer by dissolving or diluting the components constituting the positive A layer in a solvent, applying the coating liquid onto the positive C layer, drying it, and, if necessary, curing it by irradiating it with ionizing radiation.

[0077] Examples of solvents for the coating liquid for the positive A layer include ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.), ethers (dioxane, tetrahydrofuran, 1,3-dioxolane, etc.), aliphatic hydrocarbons (hexane, etc.), alicyclic hydrocarbons (cyclohexane, etc.), aromatic hydrocarbons (toluene, xylene, etc.), halogenated carbons (dichloromethane, dichloroethane, etc.), esters (methyl acetate, ethyl acetate, butyl acetate, etc.), alcohols (isopropanol, butanol, cyclohexanol, etc.), cellosolves (methyl cellosolve, ethyl cellosolve, etc.), glycol ethers (propylene glycol monomethyl ether acetate, etc.), cellosolve acetates, sulfoxides (dimethyl sulfoxide, etc.), amides (dimethylformamide, dimethylacetamide, etc.), and mixtures of these may also be used.

[0078] Among the above solvents, it is preferable to use methyl isobutyl ketone, cyclohexanone, 1,3-dioxolane, toluene, etc., and it is more preferable to use cyclohexanone and 1,3-dioxolane, which have high polarity and easily penetrate into the alignment layer.

[0079] The proportion of the solvent in the coating liquid for the positive A layer is preferably 70% by mass to 95% by mass, and more preferably 75% by mass to 90% by mass.

[0080] <Base material> The optical laminate may have a substrate. The substrate is preferably a plastic film. Examples of polymers that can be used to make plastic films include cellulose acylate, polycarbonate polymers, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, acrylic polymers such as polymethyl methacrylate, styrene polymers such as polystyrene and acrylonitrile-styrene copolymer (AS resin), polyolefin polymers such as polyethylene, polypropylene, and ethylene-propylene copolymer, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers, polyethersulfone polymers, polyetheretherketone polymers, polyphenylene sulfide polymers, vinylidene chloride polymers, vinyl alcohol polymers, vinyl butyral polymers, arylate polymers, polyoxymethylene polymers, and epoxy polymers.

[0081] Considering the need to reduce the thickness of image display devices, the substrate is preferably one from which the alignment layer and the positive A layer can be peeled off. By using a peelable substrate, the alignment layer and the positive A layer can be transferred to other members of the image display device. The optical laminate of the present invention has good adhesion between the alignment layer and the positive A layer, and therefore can prevent peeling at the interface between the alignment layer and the positive A layer due to stress generated during transfer, making it preferable in that it is easy to use a peelable substrate. Examples of the releasable substrate include the above-mentioned plastic film itself, or the above-mentioned plastic film whose surface has been subjected to a release treatment with a general-purpose release agent or the like.

[0082] The thickness of the substrate is usually about 25 μm to 150 μm, preferably 30 μm to 125 μm, and more preferably 40 μm to 100 μm.

[0083] <Other layers> The optical laminate may have other layers, such as a gas barrier layer, an adhesive layer, and a retardation layer, provided that the effects of the present invention are not impaired.

[0084] <Physical properties of optical laminates> The optical laminate of the present invention preferably satisfies the relationship of the following formula (A), where the in-plane retardation of the optical laminate at a wavelength of 450 nm is defined as Re(450), the in-plane retardation of the optical laminate at a wavelength of 550 nm is defined as Re(550), and the in-plane retardation of the optical laminate at a wavelength of 650 nm is defined as Re(650). Re(450) <Re(550)<Re(650) (A)

[0085] By satisfying formula (A), the optical laminate as a whole exhibits reverse wavelength dispersion characteristics, which makes it easier to improve visibility and antireflection properties in wavelength regions outside 550 nm.

[0086] The optical layered body preferably has a haze according to JIS K7136:2000 of 1.0% or less, more preferably 0.9% or less, and even more preferably 0.8% or less. Furthermore, the optical laminate preferably has a total light transmittance according to JIS K7361-1:1997 of 80% or more, more preferably 85% or more, and even more preferably 90% or more.

[0087] The total thickness of the optical laminate is not particularly limited, but from the viewpoint of improving handleability and mechanical strength, it is preferably 15 μm to 300 μm, more preferably 20 μm to 200 μm, and even more preferably 25 μm to 100 μm.

[0088] <Size, shape, etc.> The optical laminate may be in the form of a sheet or a roll. The size of the sheet is not particularly limited, but is generally about 2 to 500 inches diagonally. The width and length of the roll are not particularly limited, but generally, the width is about 500 to 3000 mm, and the length is about 500 to 5000 m. The shape of the sheets is not particularly limited either, and may be, for example, polygonal (triangle, square, pentagon, etc.) or circular, or may be a random, indeterminate shape.

[0089] [Polarizing plate] The polarizing plate of the present invention is a polarizing plate having a polarizer, a transparent protective plate A arranged on one side of the polarizer, and a transparent protective plate B arranged on the other side of the polarizer, wherein either the transparent protective plate A or the transparent protective plate B is the optical laminate of the present invention described above.

[0090] FIG. 2 is a cross-sectional view showing an embodiment of the polarizing plate of the present invention. The polarizing plate 200 in Fig. 2 includes a polarizer 50, a transparent protective plate A (61) disposed on one side of the polarizer, and a transparent protective plate B (62) disposed on the other side of the polarizer. The transparent protective plate A (61) in Fig. 2 is an optical laminate 100.

[0091] <Polarizer> Examples of polarizers include sheet-type polarizers such as polyvinyl alcohol films, polyvinyl formal films, polyvinyl acetal films, and saponified ethylene-vinyl acetate copolymer films dyed with iodine or the like, and stretched, wire-grid polarizers made of a large number of parallel-arranged metal wires, coated polarizers coated with lyotropic liquid crystals or dichroic guest-host materials, and multilayer thin-film polarizers. These polarizers may also be reflective polarizers that have the function of reflecting polarized light components that are not transmitted.

[0092] <Transparent protection plate> On one side of the polarizer is disposed a transparent protective plate A, and on the other side is disposed a transparent protective plate B. One of the transparent protective plate A and the transparent protective plate B is the above-described optical laminate of the present invention.

[0093] Examples of the transparent protective plate A and the transparent protective plate B other than the optical laminate include plastic films and glass. Examples of the plastic film include polyester films, polycarbonate films, cycloolefin polymer films, and acrylic films, and stretched films of these are preferred from the viewpoint of mechanical strength. Examples of the glass include alkali glass, nitride glass, soda-lime glass, borosilicate glass, and lead glass. Furthermore, it is preferable that the glass serving as the transparent protective plate protecting the polarizer is also used as another member of the image display device (for example, the glass substrate of a liquid crystal display element, the faceplate of the image display device). The polarizer and the transparent protective plate are preferably attached to each other via an adhesive, which may be a general-purpose adhesive, and is preferably a PVA-based adhesive.

[0094] The polarizing plate of the present invention is preferably used as a polarizing plate disposed on the light-exiting surface side of a display element. When used as described above, the transparent protective plate on the light-incident surface side of the polarizer is preferably the optical laminate of the present invention. From the viewpoint of making the polarizing plate function as a circular polarizing plate, the orientation of the slow axis of the positive A layer relative to the absorption axis of the polarizer is preferably in the range of 30° to 60°, more preferably in the range of 40° to 50°.

[0095] [Display Panel] The display panel of the present invention comprises the above-described optical laminate of the present invention disposed on the light-emitting surface side of a display element.

[0096] 3 is a cross-sectional view showing an embodiment of a display panel 500 of the present invention. The display panel 500 in FIG. 3 has an optical laminate 100 laminated on the light-emitting surface side of a display element 300.

[0097] When the display element of the display panel is a liquid crystal display element, a backlight (not shown) is required behind the liquid crystal display element. The backlight may be either an edge-lit backlight or a direct-type backlight. Examples of light sources for the backlight include LEDs and CCFLs. However, backlights using quantum dots as the light source are preferred because they tend to improve color reproducibility.

[0098] The display panel preferably has a polarizer on the surface of the optical laminate opposite to the display element. By adopting such a configuration, the image display device is endowed with an anti-reflection function for external light and can suppress loss of color when viewed from an oblique angle.

[0099] <Display element> Examples of the display element include a liquid crystal display element, an organic EL display element, an inorganic EL display element, a plasma display element, an electronic paper display element, an LED display element (such as a micro LED), a display element using quantum dots, etc. These display elements may have a touch panel function inside the display element.

[0100] [Image display device] The image display device of the present invention is not particularly limited as long as it comprises the display panel of the present invention, but it is preferable that it comprises the display panel of the present invention, a drive control unit electrically connected to the display panel, and a housing that houses these.

[0101] The image display device may be a foldable image display device or a rollable image display device, or may be an image display device with a touch panel. [Example]

[0102] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. Note that "parts" and "%" are by mass unless otherwise specified.

[0103] 1. Measurement and evaluation The optical laminates obtained in the examples and comparative examples were subjected to the following measurements and evaluations. The results are shown in Table 1.

[0104] 1-1. Measurement of sulfur atoms The optical laminates of the examples and comparative examples were cut to a predetermined size to prepare cut samples, which were then embedded in epoxy resin to prepare embedded samples.The embedded samples were then cut vertically with a diamond knife to prepare 20 thin-section measurement samples (thickness: 0.08 μm) for each sample. Next, the mass-based detected amount of sulfur atoms in the positive A layer and the alignment layer of the measurement sample was measured using scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX). Based on the measurement results, the average mass-based detected amount of sulfur atoms in the positive A layer was normalized to 100, and the average detected amount of X atoms in the alignment layer (positive C layer) was calculated, and the average value for 20 samples was calculated. The results are shown in Table 1. Furthermore, based on the above measurement results, the "coefficient of variation under condition 1" and the "ratio under condition 2" in the main text of the specification were calculated. The results are shown in Table 1. The SEM-EDX measurement equipment used was a Hitachi High-Technologies SEM “SU8000” and an Oxford Instruments EDX “XMAX80.” The measurement conditions for the equipment were set as follows: <Measurement conditions> The characteristic X-ray spectrum was acquired by adjusting the accelerating voltage to 30 kV, the focal length to 15 mm (sample tilt 0 degrees), and the irradiation current and measurement time appropriately to ensure sufficient detection of the target elements. The concentration of each element was calculated using the ZAF correction method (a method of determining the content of each element by applying atomic number correction Z, absorption correction A, and fluorescence correction F to the relative intensity of each element).

[0105] 1-2. Adhesion The intermediate optical laminates of Examples and Comparative Examples were stored for 24 hours in an environment of 23°C and 50% relative humidity, and then the alignment layer (positive C layer) and the positive A layer of the intermediate optical laminates of Examples and Comparative Examples were transferred to glass with an adhesive layer to form a glass laminate, and a blade was inserted from the alignment layer (positive C layer) side of the glass laminate into a 100-square grid (10 squares vertically × 10 squares horizontally) and cross-cut so that the tip of the blade reached the adhesive layer. Two types of grid cut intervals were prepared: 1 mm and 2 mm. A strip of adhesive tape (manufactured by Nichiban Co., Ltd., product name "3M Scotch Removable Tape, Cat. No. 811-3-18") was applied to the cross-cut surface of the cross-cut sample, and a peel test was performed in accordance with the cross-cut method specified in JIS K5600-5-6:1999. For cut intervals of 1 mm and 2 mm, the number of peeled holes was evaluated using a microscope (Keyence VH5500 digital microscope, set at 100x magnification). The results are shown in Table 1. "0 / 100" indicates that 0 holes were peeled, indicating the best adhesion between the alignment layer (positive C layer) and the positive A layer, and "100 / 100" indicates that all holes were peeled, indicating poor adhesion between the alignment layer (positive C layer) and the positive A layer.

[0106] 1-3. Transferability The optical laminates of the Examples and Comparative Examples (laminates in which the alignment layer (positive C layer) of the intermediate of the optical laminate of the Examples and Comparative Examples and the positive A layer were transferred to glass) were evaluated using a microscope (Keyence Corporation digital microscope VH5500, set magnification 100x) to determine whether or not peeling occurred at the interface between the positive A layer and the positive C layer. Those in which no peeling was observed were rated "A," and those in which peeling was observed were rated "C." The results are shown in Table 1.

[0107] 2. Synthesis of alignment layer compounds 2-1. Synthesis of compounds used in the examples (Monomer 1) 4-Hydroxy-4'-hydroxyethoxybiphenyl was synthesized by heating 4,4'-biphenyldiol and 2-chloroethanol under alkaline conditions. This product was reacted with 1,6-dibromohexane under alkaline conditions to synthesize 4-(6-bromohexyloxy)-4'-hydroxyethoxybiphenyl. Subsequently, lithium methacrylate was reacted to synthesize Monomer 1, represented by the following chemical formula (30).

[0108] (Monomer 2) Cinnamoyl chloride was added to Monomer 1 under basic conditions to synthesize Monomer 2 represented by the following chemical formula (31). [ka]

[0109] (Polymer 1) Monomer 1 and monomer 2 were dissolved in tetrahydrofuran in a molar ratio of 3:7, and AIBN (azobisisobutyronitrile) was added as a reaction initiator. Polymerization was carried out at 70°C for 24 hours to obtain photosensitive polymer 1. This polymer 1 exhibited liquid crystallinity.

[0110] 2-2. Preparation of compounds used in comparative examples For the alignment film of the comparative example, an alignment film-forming composition containing a polycinnamate compound was used.

[0111] 3. Synthesis of compounds for the positive A layer The following sulfur atom-containing compound a (compound of chemical formula (5)) was synthesized according to the description of Production Example 10 in the Examples of JP 2019-73712 A.

[0112] [ka]

[0113] 4. Fabrication of Optical Laminates [Example 1] Polymer 1 obtained in 2-1 above was dissolved in cyclohexanone, and a photopolymerization initiator (4,4'-bis(diethylamino)benzophenone from Tokyo Chemical Industry Co., Ltd.) was added to prepare coating solution 1 for positive C layer. The content of the photopolymerization initiator in coating solution 1 for positive C layer was 2 parts by weight per 100 parts by mass of polymer 1. Positive C layer coating solution 1 was applied to a substrate (100 μm thick polyethylene terephthalate (PET) film, product name "A4100", Toyobo Co., Ltd.) using a Mayer bar to a thickness of 0.6 μm and dried at room temperature (approximately 25°C). It was then heated to 130°C and cooled to form a positive C layer, which is a homeotropic alignment layer. The positive C layer had an Re(550) of 3.2 nm and an Rth(550) of -73 nm. Next, the positive C layer was irradiated with linearly polarized ultraviolet light (ultraviolet light obtained by linearly polarizing light from a high-pressure mercury lamp through a Glan-Teller prism) for 15 seconds, causing the photoreaction of the photosensitive group of polymer 1 to proceed anisotropically. Next, the following coating solution 1 for the positive A layer was applied onto the positive C layer so that the thickness after curing would be 2 μm, forming a film. After that, it was dried at 120°C for 60 seconds, and then irradiated with ultraviolet light (unpolarized ultraviolet light) at a dose of 400 mJ / cm using an H bulb manufactured by Fusion. 2 to form a positive A layer, thereby obtaining an intermediate for the optical laminate of Example 1. The positive A layer had Re(550) of 161 nm, and the laminate had Rth(550) of -5 nm. Next, a transparent adhesive layer (manufactured by PANAC Corporation, product name: Panaclean PD-S1, thickness 25 μm) was formed on the glass substrate, and the surface of the positive A layer side of the optical laminate of the Examples and Comparative Examples was attached to the transparent adhesive layer. Next, the releasable substrate (PET film) was peeled off to obtain the optical laminate of Example 1, which had the glass substrate, transparent adhesive layer, positive A layer, and positive C layer in this order. The optical laminate had an Re(450) of 136 nm, an Re(550) of 161 nm, an Re(650) of 164 nm, and an Rth(550) of -5 nm.

[0114] <Positive A layer coating solution 1> 100 parts by mass of the compound a containing sulfur atoms obtained in step 3 above Photopolymerization initiator 4 parts by mass (2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, IGM Resins BV, trade name "Omnirad 907") Toluene 70 parts by mass Cyclohexanone 30 parts by mass

[0115] [Comparative Example 1] An optical laminate of Comparative Example 1 was obtained in the same manner as in Example 1, except that the coating solution 1 for positive C layer was changed to the following coating solution 2 for positive C layer. The positive C layer of Comparative Example 1 had an Re(550) of 0.5 nm and an Rth(550) of −0.2 nm.

[0116] <Positive C layer coating solution 2> ·Polymerizable liquid crystal compound 4 parts by mass (Polycinnamate compounds) Propylene glycol monomethyl ether 96 parts by mass

[0117] [Table 1]

[0118] From the results of the examples, it can be confirmed that the optical laminate of the examples can contribute to thinner products because the alignment layer and the positive A layer are directly laminated together, and that the adhesion between the alignment layer and the positive A layer is excellent. [Explanation of symbols]

[0119] 10: Base material 20: Orientation layer 30: Positive A layer 50: Polarizer 61: Transparent protection plate A 62:Protective protection plate B 100: Optical laminate 200: Polarizing plate 300: Display element 500: Display panel

Claims

1. An optical stack having an alignment layer and a positive A layer, the alignment layer and the positive A layer are in contact with each other, The positive A layer contains compound a, the alignment layer contains the compound a transferred from the positive A layer and other compounds, The compound a contains an atom X that is not substantially contained in the other compounds, "The other compounds are substantially free of the atom X" means that the content of the atom X relative to the total amount of the other compounds is 0.1 mass% or less, the average detectable amount of the atom X in the alignment layer is 27 or more when the average detectable amount of the atom X in the positive A layer is normalized to 100 on a mass basis, the average detected amount of the atom X in the positive A layer is an average value of detected amounts of the atom X detected at 100 points every 26 nm in a direction parallel to the interface, at a position 200 nm in a thickness direction from the interface between the positive A layer and the alignment layer, the average detected amount of the atom X in the alignment layer is an average value of detected amounts of the atom X detected at 100 points at intervals of 26 nm in a direction parallel to the interface, the position being 200 nm from the interface between the alignment layer and the positive A layer in a thickness direction, the detected amount of the atom X in the positive A layer and the alignment layer satisfies the following condition 2: The optical stack, wherein the alignment layer is a positive C layer. (Condition 2) The amount of the atom X in the positive A layer is detected at 100 locations every 26 nm in a direction parallel to the interface, starting from a position 200 nm in the thickness direction from the interface between the positive A layer and the alignment layer. The mass-based coefficient of variation of the detected atom X is defined as CV1. The amount of the atom X in the alignment layer is detected at 100 locations every 26 nm in a direction parallel to the interface, starting from a position 200 nm in the thickness direction from the interface between the alignment layer and the positive A layer. The mass-based coefficient of variation of the detected atom X is defined as CV2. The ratio of the CV1 to the CV2 (CV2 / CV1) is 2.00 or more.

2. The optical laminate according to claim 1 , wherein the detected amount of the atom X in the alignment layer satisfies the following condition 1: (Condition 1) The amount of the atom X in the alignment layer is detected at 100 locations at intervals of 26 nm in a direction parallel to the interface, starting from a position 200 nm in the thickness direction from the interface between the alignment layer and the positive A layer, and the mass-based coefficient of variation of the amount of the atom X detected at the 100 locations is 0.16 or more.

3. The optical laminate according to claim 1 or 2, wherein the atom X is a sulfur atom.

4. 4. The optical laminate according to claim 1, wherein the compound a is a polymerizable liquid crystal compound containing a sulfur atom as the atom X.

5. 5. The optical laminate according to claim 1, wherein the other compounds include a liquid crystal compound having a photosensitive group.

6. The optical laminate according to any one of claims 1 to 5, wherein Rth(550) is defined as the retardation in the thickness direction of the alignment layer at a wavelength of 550 nm, and Rth(550) is -100 nm to -50 nm.

7. The optical laminate according to any one of claims 1 to 6, wherein the in-plane retardation of the optical laminate at a wavelength of 450 nm is defined as Re (450), the in-plane retardation of the optical laminate at a wavelength of 550 nm is defined as Re (550), and the in-plane retardation of the optical laminate at a wavelength of 650 nm is defined as Re (650), and the relationship of the following formula (A) is satisfied. Re(450)<Re(550)<Re(650) (A)

8. A polarizing plate having a polarizer, a transparent protective plate A arranged on one side of the polarizer, and a transparent protective plate B arranged on the other side of the polarizer, wherein either the transparent protective plate A or the transparent protective plate B is an optical laminate according to any one of claims 1 to 7.

9. A display panel comprising the optical laminate according to any one of claims 1 to 7 disposed on a light exit surface of a display element.

10. An image display device comprising the display panel according to claim 9.

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