Optical laminate and liquid crystal display device using the same

Abstract

To provide an optical laminate which suppresses reflection of external light and weakens the color tone observed when viewed from oblique angles.SOLUTION: An optical laminate provided herein comprises a λ / 4 retardation layer, a transparent base material, and a polarizer arranged in the described order. The transparent base material has a positive or negative birefringence and a thickness retardation in the thickness direction of 125 nm or greater, or -125 nm or less. A slow axis of the transparent base material and an absorption axis of the polarizer are arranged in parallel, or perpendicular to each other.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical laminate and a liquid crystal display device using the same. [Background technology]

[0002] Electroluminescent display elements (hereinafter sometimes abbreviated as EL elements) have a wide viewing zone due to their self-luminous nature and consume less power than plasma light-emitting elements, and therefore have been put to practical use in image display devices in recent years. In particular, organic EL elements, which use organic compounds as light-emitting materials, can reduce the applied voltage significantly compared to inorganic EL elements, which use inorganic compounds, and therefore various studies are being conducted on their use as display devices.

[0003] Organic EL elements are generally known to have a structure in which a first electrode, a light-emitting layer, and a second electrode are sequentially laminated on a transparent substrate. There are two types of organic EL elements: a bottom-emission type in which a transparent electrode is used as the first electrode and a metal electrode is used as the second electrode, and light emitted from the light-emitting layer is extracted from the transparent substrate side; and a top-emission type in which a metal electrode is used as the first electrode, a transparent electrode is used as the second electrode, and light emitted from the light-emitting layer is extracted from the second electrode side. In organic EL elements, regardless of type, metal electrodes with excellent reflectivity are often used to efficiently utilize the light from the light-emitting layer. However, organic EL elements using such metal electrodes may have a high degree of external light reflection, resulting in reduced contrast. In addition, the reduction in contrast due to external light reflection is also a problem in display devices other than those containing organic EL elements (for example, display devices containing micro LED display elements, and display devices with a resistive touch panel arranged on a display element).

[0004] Various methods for suppressing external light reflection in display devices have been investigated, and one such method is known to use a so-called circular polarizing plate, which is formed by laminating a retardation plate and a polarizing plate.

[0005] However, a general-purpose retardation plate has a wavelength dependency of retardation (positive dispersion of retardation) in which the retardation measured at a long wavelength is smaller than that measured at a short wavelength. Therefore, a circular polarizing plate using a general-purpose retardation plate can sufficiently reduce the reflectance in the vicinity of a wavelength of 550 nm, but the reduction in the reflectance in the low and high wavelength regions is insufficient, resulting in a problem of leakage of reflected light.

[0006] As a method for solving the above problem, for example, a method using a retardation plate formed by laminating a λ / 4 retardation layer and a λ / 2 retardation layer, and a method using a retardation plate using a liquid crystal compound having reverse dispersion characteristics have been proposed (Patent Document 1, etc.). The reverse dispersion characteristics are the wavelength dependency of the retardation, in which the retardation measured at a long wavelength is larger than the retardation measured at a short wavelength.

[0007] A circular polarizing plate using a retardation plate film such as that in Patent Document 1 can sufficiently reduce the reflectance in the front direction. However, the circular polarizing plate using a retardation plate film such as that in Patent Document 1 does not sufficiently reduce the reflectance in a direction oblique to the front direction. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 5-100114 [Patent Document 2] JP 2007-188033 A Summary of the Invention [Problem to be solved by the invention]

[0009] Patent Document 2 discloses an elliptical polarizing plate having a positive C layer in addition to a λ / 4 retardation layer and a λ / 2 retardation layer. The elliptically polarizing plate of Patent Document 2 can bring the reflectance in an oblique direction closer to the reflectance in a front direction. However, the elliptically polarizing plate of Patent Document 2 has a strong color when viewed from an oblique direction. The problem of color tone in oblique directions is also a problem that Patent Document 1 has. [Means for solving the problem]

[0010] An object of the present invention is to provide an optical laminate that suppresses reflection of external light and suppresses color when viewed from an oblique direction, and an image display device using the same.

[0011] That is, the present invention provides the following [1] to

[10] . [1] An optical laminate comprising a λ / 4 retardation layer, a transparent substrate, and a polarizer in this order, wherein the transparent substrate has positive birefringence or negative birefringence and a retardation in the thickness direction of 125 nm or more or −125 nm or less, and wherein a slow axis of the transparent substrate and an absorption axis of the polarizer are disposed approximately parallel or approximately perpendicular to each other. [2] The optical laminate according to [1], wherein the transparent substrate has an in-plane retardation of 40 nm or more. [3] The optical laminate according to [1] or [2], wherein the transparent substrate is a polyester film or a polycarbonate film. [4] The optical laminate according to any one of [1] to [3], further comprising a λ / 2 retardation layer between the λ / 4 retardation layer and the transparent substrate. [5] The optical laminate according to any one of [1] to [4], which has a total light transmittance of 35% or more and 80% or less.

[0012] [6] The optical laminate according to any one of [1] to [5], wherein 3σΔX and 3σΔY calculated from the following measurement 1 are both less than 0.019. <Measurement 1> A sample is prepared by laminating the optical laminate on an aluminum plate having an average spectral reflectance of 20% in the wavelength region of 380 nm to 780 nm inclusive. In the sample, the optical laminate is arranged such that the surface of the λ / 4 retardation layer side relative to the transparent substrate faces the aluminum plate. Light diffused by an integrating sphere is incident on the surface of the sample from the normal direction, and the reflected light is measured. The X and Y values ​​of the XYZ color system are calculated from the measured reflected light. The measurement and calculation are performed in 0.5 degree increments in the azimuth angle range of 0 degrees to 359.5 degrees with the elevation angle fixed at an angle of 60 degrees from the normal to the surface of the sample, to obtain X and Y values ​​at 720 points. The average of the X values ​​of 720 points is "Xave". The deviation of the X value of the nth measurement point from Xave is "ΔXn". The variation 3σ of ΔXn of the 720 points is "3σΔX". The average Y value of 720 points is "Yave". The deviation of the Y value of the nth measurement point from Yave is "ΔYn". The 3σ variation of ΔYn of 720 points is "3σΔY". [7] The optical laminate according to any one of [1] to [6], wherein an average of 3σΔX and 3σΔY calculated from the following measurement 1 is less than 0.018. <Measurement 1> A sample is prepared by laminating the optical laminate on an aluminum plate having an average spectral reflectance of 20% in the wavelength region of 380 nm to 780 nm inclusive. In the sample, the optical laminate is arranged such that the surface of the λ / 4 retardation layer side relative to the transparent substrate faces the aluminum plate. Light diffused by an integrating sphere is incident on the surface of the sample from the normal direction, and the reflected light is measured. The X and Y values ​​of the XYZ color system are calculated from the measured reflected light. The measurement and calculation are performed in 0.5 degree increments in the azimuth angle range of 0 degrees to 359.5 degrees with the elevation angle fixed at an angle of 60 degrees from the normal to the surface of the sample, to obtain X and Y values ​​at 720 points. The average of the X values ​​of 720 points is "Xave". The deviation of the X value of the nth measurement point from Xave is "ΔXn". The variation 3σ of ΔXn of the 720 points is "3σΔX". The average Y value of 720 points is "Yave". The deviation of the Y value of the nth measurement point from Yave is "ΔYn". The 3σ variation of ΔYn of 720 points is "3σΔY". [8] The optical laminate according to any one of [1] to [7], which is used for the front surface of an organic EL display element.

[0013] [9] An image display device having an optical laminate on a display element, the optical laminate being the optical laminate according to any one of [1] to [7], and arranged so that a surface of the optical laminate on a λ / 4 retardation layer side relative to a transparent substrate faces the display element.

[10] The image display device according to [9], wherein the display element is an organic EL display element or a micro LED display element. Effect of the Invention

[0014] The optical laminate and the liquid crystal display device of the present invention can suppress reflection of external light and suppress color when viewed from an oblique direction. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic cross-sectional view showing one embodiment of an optical laminate of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing another embodiment of the optical laminate of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described. [Optical laminate] The optical laminate of the present invention comprises a λ / 4 retardation layer, a transparent substrate, and a polarizer in this order, the transparent substrate having positive birefringence or negative birefringence and a thickness direction retardation of 125 nm or more or −125 nm or less, and the slow axis of the transparent substrate and the absorption axis of the polarizer are arranged approximately parallel or approximately perpendicular to each other.

[0017] 1 and 2 are schematic cross-sectional views showing an embodiment of an optical laminate (100) of the present invention. The optical laminate (100) in Fig. 1 and Fig. 2 includes a λ / 4 retardation layer (10), a transparent substrate (30), and a polarizer (40) in this order. The optical laminate (100) in Fig. 2 includes a λ / 2 retardation layer (20) between the λ / 4 retardation layer (10) and the transparent substrate (30), and includes a surface protective material (50) on the opposite side of the polarizer (40) to the transparent substrate (30).

[0018] The principle of how the optical layered body of the present invention suppresses reflection of external light will be briefly explained with reference to FIG. When external light is incident on the polarizer (40) side of the optical laminate (100) in FIG. 1, the external light passing through the polarizer (40) becomes linearly polarized light. The linearly polarized light passes through the λ / 4 retardation layer (10) and becomes right-handed or left-handed circularly polarized light. The circularly polarized light reflected on the surface of the display element becomes reverse-handed circularly polarized light. When the reverse-handed circularly polarized light, which is the reflected light, passes through the λ / 4 retardation layer (10) again, it becomes linearly polarized light in a direction that does not pass through the polarizer (40), and reflection is suppressed. In the optical laminate (100) of FIG. 2, the λ / 4 retardation layer (10) and the λ / 2 retardation layer (20) can convert a wide wavelength range into circularly polarized light, thereby further suppressing the reflection of external light. As described above, the optical layered body of the present invention can suppress reflection of external light. In order to suppress reflection of external light based on the above principle, the slow axis of the transparent substrate (30) and the absorption axis of the polarizer (40) need to be arranged substantially parallel or perpendicular to each other. If the slow axis of the transparent substrate (30) and the absorption axis of the polarizer (40) are not arranged substantially parallel or perpendicular to each other, the polarization state of linearly polarized light is disturbed when it passes through the transparent substrate (30). When the direction of the slow axis is not uniform within the plane of the transparent substrate, the direction of the slow axis of the transparent substrate means the average direction of the slow axis within the plane of the transparent substrate.

[0019] In this specification, substantially parallel means within 0 degrees ±5 degrees, preferably within 0 degrees ±3 degrees, and more preferably within 0 degrees ±1 degree. In this specification, "approximately perpendicular" means within 90 degrees ±5 degrees, preferably within 90 degrees ±3 degrees, and more preferably within 90 degrees ±1 degree.

[0020] In this specification, the in-plane retardation (Re) and the retardation in the thickness direction (Rth) can be expressed by the following formula, where the refractive index in the in-plane slow axis direction is nx, the refractive index in the in-plane direction perpendicular to nx is ny, the refractive index in the direction perpendicular to nx and ny is nz, and the film thickness is d (nm). In-plane phase difference (Re)=(nx-ny)×d Retardation in the thickness direction (Rth) = ((nx + ny) / 2-nz) × d

[0021] In this specification, the in-plane retardation (Re) and the retardation in the thickness direction (Rth) refer to values ​​at a wavelength of 550 nm, unless otherwise specified. In this specification, the in-plane retardation at a wavelength of X nm may be expressed as "Re(X)", and the retardation in the thickness direction at a wavelength of X nm may be expressed as "Rth(X)". For example, the in-plane retardation at a wavelength of 450 nm may be expressed as "Re(450)", and the in-plane retardation at a wavelength of 650 nm may be expressed as "Re(650)".

[0022] The in-plane retardation (Re) and the retardation in the thickness direction (Rth) can be measured using, for example, a product name "RETS-100" manufactured by Otsuka Electronics Co., Ltd., or a product name "KOBRA-WR", "KOBRA-WPR", or "PAM-UHR100" manufactured by Oji Scientific Instruments Co., Ltd. When measuring the in-plane retardation (Re) and the like using Otsuka Electronics' product name "RETS-100", it is preferable to prepare for the measurement according to the following procedures (A1) to (A4).

[0023] (A1) First, turn on the RETS-100 light source and leave it for 60 minutes or more to stabilize it. After that, select the rotating analyzer method and select θ mode (angle direction phase difference measurement and Rth calculation mode). By selecting this θ mode, the stage becomes a tilt rotation stage. (A2) Next, enter the following measurement conditions into the RETS-100. (Measurement conditions) Retardation measurement range: Rotating analyzer method Measurement spot diameter: φ5mm Tilt angle range: 0° Measurement wavelength range: 400nm to 800nm - Average refractive index of the transparent substrate. For example, in the case of a PET film, N = 1.617. The average refractive index N of the transparent substrate can be calculated using nx, ny, and nz by the formula (N = (nx + ny + nz) / 3). Thickness: Thickness measured separately using SEM or optical microscope (A3) Next, background data is obtained without placing a sample in the instrument, in a closed system, and every time the light source is turned on. (A4) After that, the sample is placed on the stage inside the device and measured.

[0024] In this specification, various parameters such as in-plane retardation (Re), thickness retardation (Rth), total light transmittance, and spectral reflectance are calculated as the average value of 14 measured values ​​excluding the minimum and maximum values ​​of 16 measured values, unless otherwise specified. The variation 3σ in the angle of the orientation axis of the transparent substrate refers to the average of the variation 3σ measured at 16 points and the 14 points excluding the minimum and maximum values. When the measurement sample is a rectangle, it is preferable to measure 16 points at the intersections of lines obtained by dividing the region inside the rectangle into 5 equal parts vertically and horizontally, with a margin of 0.5 cm from the outer edge of the rectangle, and to calculate the average value. When the measurement sample is a shape other than a rectangle, such as a circle, ellipse, triangle, or pentagon, it is preferable to draw a rectangle with the maximum area inscribed in these shapes, and measure 16 points on the rectangle using the above method. In this specification, the various parameters are values ​​measured at a temperature of 23°C ± 5°C and a relative humidity of 40% to 65%. Before starting each measurement, the target sample is exposed to the above atmosphere for 30 minutes or more before measurement and evaluation.

[0025] <Retardation layer> The optical layered body of the present invention is required to have a λ / 4 retardation layer. The optical laminate of the present invention preferably has a λ / 2 retardation layer in addition to the λ / 4 retardation layer. When the optical laminate has a λ / 4 retardation layer and a λ / 2 retardation layer, the λ / 2 retardation layer is preferably disposed on the transparent substrate side. The optical laminate of the present invention preferably has a λ / 8 retardation layer in addition to the λ / 4 retardation layer.

[0026] The λ / 4 retardation layer preferably has an in-plane retardation of 100 nm or more and 180 nm or less, more preferably 110 nm or more and 160 nm or less, and further preferably 110 nm or more and 150 nm or less. The λ / 2 retardation layer has an in-plane retardation of 200 nm or more and 300 nm or less, more preferably 220 nm or more and 280 nm or less, and further preferably 220 nm or more and 270 nm or less.

[0027] The retardation in the thickness direction of the λ / 4 retardation layer and the λ / 2 retardation layer is preferably 30 nm or more and 120 nm or less, more preferably 50 nm or more and 100 nm or less. The above-mentioned retardation in the thickness direction is particularly suitable as a value when the λ / 4 retardation layer and the λ / 2 retardation layer are used in combination. When only the λ / 4 retardation layer is used, the retardation in the thickness direction of the λ / 4 retardation layer is preferably 120 nm or less, more preferably 30 nm or more and 100 nm or less.

[0028] The λ / 4 retardation layer and the λ / 2 retardation layer may exhibit normal dispersion or may exhibit reverse dispersion. However, from the viewpoint of converting a wide wavelength range into circularly polarized light, it is preferable that the retardation layer exhibits reverse dispersion. The reverse dispersibility is a characteristic in which the phase difference imparted to the transmitted light increases as the wavelength of the transmitted light becomes longer. Specifically, it is a characteristic in which the relationship between the in-plane phase difference (Re450) at a wavelength of 450 nm and the in-plane phase difference (Re550) at a wavelength of 550 nm is Re450 < Re550. On the other hand, the positive dispersibility is a characteristic in which Re450 > Re550.

[0029] When imparting reverse dispersion characteristics, the ratio (Re450 / Re550) of Re450 of the λ / 4 retardation layer to Re550 of the λ / 4 retardation layer is preferably 0.95 or less, more preferably 0.93 or less, still more preferably 0.91 or less, and even more preferably 0.89 or less. Also, Re450 / Re550 is preferably 0.78 or more, more preferably 0.80 or more, and still more preferably 0.82 or more.

[0030] When imparting reverse dispersion characteristics, the ratio (Re450 / Re550) of Re450 of the λ / 2 retardation layer to Re550 of the λ / 2 retardation layer is preferably 0.95 or less, more preferably 0.93 or less, still more preferably 0.91 or less, and even more preferably 0.89 or less. Also, Re450 / Re550 is preferably 0.78 or more, more preferably 0.80 or more, and still more preferably 0.82 or more.

[0031] The thicknesses of the λ / 4 retardation layer and the λ / 2 retardation layer can be appropriately adjusted within the range of 0.1 μm or more and 40 μm or less in consideration of the phase difference to be imparted.

[0032] Retardation layers such as the λ / 4 retardation layer and the λ / 2 retardation layer can be formed, for example, from a composition containing a liquid crystalline compound such as a polymerizable liquid crystalline compound, or by stretching a polymer film. Examples of the liquid crystalline compound include rod-shaped liquid crystalline compounds such as nematic liquid crystalline compounds and smectic liquid crystalline compounds, cholesteric liquid crystalline compounds, and discotic liquid crystalline compounds (disc-shaped liquid crystalline compounds). As the λ / 4 retardation layer and the λ / 2 retardation layer and other retardation layers, general-purpose retardation layers can be used.

[0033] The retardation layer formed from the composition containing the liquid crystal compound is preferably formed on a support. The retardation layer formed on the support may be used as it is, or may be transferred to another member (for example, a transparent substrate). The support may be a transparent substrate.

[0034] The slow axes of the λ / 4 retardation layer and the λ / 2 retardation layer and the absorption axis of the polarizer are preferably as follows. When the optical laminate has a λ / 4 retardation layer as in FIG. 1, the angle between the slow axis of the λ / 4 retardation layer and the absorption axis of the polarizer is preferably 45±5°, more preferably 45±2°. When a λ / 4 retardation layer and a λ / 2 retardation layer are used as in the optical laminate of FIG. 2, the angle between the alignment axis of each retardation layer and the absorption axis of the polarizer varies depending on the wavelength dispersion of the λ / 4 retardation layer and the λ / 2 retardation layer, but is preferably in the range of (i) or (ii) below. (i) As a first example, the angle between the slow axis of the λ / 2 retardation layer and the absorption axis of the polarizer layer is preferably 15±8°, more preferably 15±6°, and in this case, the angle between the slow axis of the λ / 4 retardation layer and the absorption axis of the polarizer layer is preferably 75±15°, more preferably 75±13°. (ii) As a second example, the angle between the slow axis of the λ / 2 retardation layer and the absorption axis of the polarizer layer is preferably 75±15°, more preferably 75±13°, and in this case, the angle between the slow axis of the λ / 4 retardation layer and the absorption axis of the polarizer layer is preferably 15±8°, more preferably 15±6°.

[0035] Furthermore, when a λ / 4 retardation layer and a λ / 2 retardation layer are used as shown in FIG. 2, the in-plane retardation (Re4) of the λ / 4 retardation layer and the in-plane retardation (Re2) of the λ / 2 retardation layer preferably satisfy 1.8≦Re2 / Re4≦2.2, and more preferably satisfy 1.9≦Re2 / Re4≦2.1.

[0036] <Polarizer> As the polarizer, any of an iodine-based polarizer, a dye-based polarizer using a dichroic dye, and a polyene-based polarizer may be used. Iodine-based polarizers and dye-based polarizers are generally manufactured using polyvinyl alcohol-based films. The absorption axis of the polarizer corresponds to the stretching direction of the film. Therefore, a polarizer stretched in the machine direction (transport direction) has an absorption axis parallel to the machine direction, and a polarizer stretched in the cross direction (perpendicular to the transport direction) has an absorption axis perpendicular to the machine direction.

[0037] The polarizer preferably has a polarization degree of 99.00% or more and a total light transmittance of 35% or more, more preferably a polarization degree of 99.90% or more and a total light transmittance of 37% or more, and even more preferably a polarization degree of 99.95% or more and a total light transmittance of 40% or more. The total light transmittance of the polarizer is preferably 65% ​​or less, more preferably 55% or less, and even more preferably 45% or less. In this specification, the total light transmittance refers to the total light transmittance defined in JIS K7361-1:1997.

[0038] It is preferable that the polarizer has a protective layer on both sides. The protective layer may be, for example, a general-purpose plastic film. The protective layer on the λ / 4 retardation layer side may be a transparent substrate as described below. The protective layer on the opposite side to the λ / 4 retardation layer may be a surface protective material as described below.

[0039] <Transparent base material> The optical laminate of the present invention has a specific transparent substrate between the λ / 4 retardation layer and the polarizer.

[0040] Hereinafter, the reason why the presence of a specific transparent substrate between the λ / 4 retardation layer and the polarizer can suppress the color tone when viewed obliquely will be described. First, the reason why a conventional circular polarizing plate causes a color to be seen in an oblique direction will be explained. A circular polarizing plate having a retardation layer and a polarizer is designed based on the principle of "suppressing reflection in the front direction" and "suppressing reflection in the vicinity of 550 nm where visibility is high", so its weaknesses are "suppressing reflection in oblique directions" and "suppressing reflection of wavelengths other than 550 nm". Circular polarizing plates that overcome these weaknesses have been proposed in Patent Documents 1 and 2, but it is difficult to completely overcome the weaknesses. For this reason, with conventional circular polarizing plates, the color of wavelengths other than 550 nm is visible in oblique directions. On the other hand, the optical laminate of the present invention has a specific transparent substrate between the λ / 4 retardation layer and the polarizer. Such a specific transparent substrate has a slow axis of the transparent substrate and an absorption axis of the polarizer arranged substantially parallel or perpendicular to each other, and therefore does not substantially act on linearly polarized light. That is, the external light that passes through the polarizer becomes linearly polarized light and transmits through the transparent substrate as linearly polarized light. Therefore, the transparent substrate does not impair the suppression of reflection of external light. In addition, the direction of the orientation main axis of the transparent substrate (when it exhibits positive birefringence, the orientation main axis is the direction of the slow axis, and when it exhibits negative birefringence, the direction perpendicular to the orientation main axis is the direction of the slow axis) is difficult to make completely uniform even by uniaxial stretching, and there is slight variation. In addition, during the production and processing of the optical laminate, there may be slight variations in the direction of the orientation main axis of the transparent substrate. When there is slight variation in the direction of the orientation main axis of the transparent substrate, the polarization state is slightly disturbed. As described later, such slight variation in the orientation main axis is considered to be one of the factors that can make the color in the oblique direction less noticeable. In addition, during the production of the optical laminate, it means, for example, when each member is bonded together. In addition, during the processing of the optical laminate, it means, for example, when the optical laminate is cut. Linearly polarized light that has passed through a transparent substrate passes through a λ / 4 retardation layer (or a λ / 2 retardation layer and a λ / 4 retardation layer) to become right-handed or left-handed circularly polarized light, but wavelengths outside the 550 nm range in the diagonal direction tend to deviate from the circularly polarized state. For this reason, in a conventional circular polarizer, light reflected on the surface of a display element and having wavelengths outside the 550 nm range in the diagonal direction does not become linearly polarized light when it passes through the λ / 4 retardation layer (or a λ / 2 retardation layer and a λ / 4 retardation layer) again, and passes through the polarizer. The optical laminate of the present invention can neutralize the color in the oblique direction and make it less noticeable by disturbing the light in the wavelength range that is not linearly polarized when retransmitted through the λ / 4 retardation layer (or the λ / 2 retardation layer and the λ / 4 retardation layer) by a specific transparent substrate (a transparent substrate having positive or negative birefringence and a thickness direction retardation of 125 nm or more or -125 nm or less). It is considered that the cause of the disturbance of the light in the wavelength range that is not linearly polarized by the transparent substrate is not only the above-mentioned characteristics (having positive or negative birefringence and a thickness direction retardation of 125 nm or more or -125 nm or less), but also a slight variation in the direction of the orientation main axis of the transparent substrate.

[0041] The transparent substrate must have either positive or negative birefringence. A transparent substrate that does not satisfy these requirements cannot solve the problem of color in oblique directions. For example, even if the retardation in the thickness direction of a transparent substrate is 125 nm or more or -125 nm or less, if the transparent substrate does not have positive birefringence or negative birefringence, the problem of color in oblique directions cannot be solved. Positive birefringence means that the refractive index (n1) in the direction of the in-plane orientation main axis and the refractive index (n2) in the direction perpendicular to the orientation main axis satisfy the relationship n1>n2, while negative birefringence means that the relationship n1<2. Transparent substrates having positive or negative birefringence include a positive A plate, a negative A plate, a positive B plate, and a negative B plate. A positive A plate indicates the relationship nx>ny≒nz, and a negative A plate indicates the relationship nz≒nx>ny. A positive B plate indicates the relationship nz>nx>ny, and a negative B plate indicates the relationship nx>ny>nz.

[0042] The transparent substrate must have a retardation in the thickness direction of 125 nm or more or −125 nm or less. A transparent substrate that does not satisfy these requirements cannot solve the problem of color in oblique directions. For example, even if the transparent substrate has positive birefringence or negative birefringence, if the retardation in the thickness direction of the transparent substrate is not 125 nm or more or -125 nm or less, the problem of color in oblique directions cannot be solved.

[0043] The retardation in the thickness direction of the transparent substrate is preferably 500 nm or more or -500 nm or less, more preferably 1000 nm or more or -1000 nm or less, even more preferably 3000 nm or more or -3000 nm or less, and even more preferably 5000 nm or more or -5000 nm or less.

[0044] The retardation in the thickness direction of the transparent substrate is preferably 30,000 nm or less or −30,000 nm or more, more preferably 15,000 nm or less or −15,000 nm or more, even more preferably 10,000 nm or less or −10,000 nm or more, and even more preferably 8,000 nm or less or −8,000 nm or more.

[0045] From the viewpoint of easily suppressing color when viewed from an oblique angle, the in-plane retardation of the transparent substrate is preferably 40 nm or more, more preferably 125 nm or more, more preferably 500 nm or more, more preferably 1000 nm or more, more preferably 3000 nm or more, and more preferably 5000 nm or more. If the in-plane retardation of the transparent substrate is too large, the thickness of the transparent substrate may increase or the tear resistance of the transparent substrate may decrease. Therefore, the in-plane retardation of the transparent substrate is preferably 50,000 nm or less, more preferably 30,000 nm or less, even more preferably 20,000 nm or less, and even more preferably 10,000 nm or less.

[0046] The transparent substrate preferably has a variation 3σ of the angle of the alignment axis of 0.01 or more. By having the variation 3σ of the angle of the alignment axis of 0.01 or more, it is possible to easily scatter light in a wavelength range that is not linearly polarized when retransmitted through the λ / 4 retardation layer (or the λ / 2 retardation layer and the λ / 4 retardation layer), and thus to neutralize the color in the oblique direction and make it less noticeable. If the variation 3σ of the angle of the alignment axis of the transparent substrate is too large, the external light antireflection properties of the optical laminate may be reduced. Therefore, the variation 3σ of the angle of the alignment axis of the transparent substrate is preferably 3.00 or less, and more preferably 1.50 or less.

[0047] The variation 3σ in the angle of the alignment axis of the transparent substrate is preferably measured at 16 points as described above. At each measurement point, the variation 3σ in the angle of the optical axis can be calculated by dividing each measurement point into minute regions and performing statistical processing of 3σ based on the angle of the optical axis measured for each divided minute region. The area of ​​the minute regions is 100 [μm 2 ] or more than 500[μm 2 In order to increase the reliability of the variation 3σ, the number of divisions of each measurement point (the number of minute regions of each measurement point) is preferably 1,000 or more, and more preferably 10,000 or more.

[0048] The variation 3σ in the angle of the orientation main axis can be measured, for example, using "AxoStep" (trade name) manufactured by Axomecrics, according to the following procedure.

[0049] <Operation Procedure> 1.Calibration execution (1)In the Measurement tab, set the wavelength value to “550” and the number to average value to “20”, and then click “Set Axostep”. (2) On the Calibration tab, click "DarkImage" and then "single calibrate." (3) The calibration result is displayed in the Calibration Result window. Check that the Y value (RMS Error value) is 3 or less. (4)Click Baseline. (5) On the Measurement tab, press “Measure Once” to measure and save the results. (6) Click Parameter to Plot and select “TotalRetardance(nm)”. (7) Open the Statistics window, select “Full Graph”, and confirm that the Mean value in the Statistics window is 0.0±0.1 nm. 2. Measurement of standard plate (1) Place the standard plate “CAL-VIS-1” on the stage and perform the measurement. (2) Select "Total Retardance (nm)" from "Parameter to Plot" and confirm that the Mean value is 191.6±1.0 nm. At the same time, select "Retardance Orientation (°)" and confirm that the Mean value is 0.0±0.05°. 3. Actual Measurement Place the sample on the stage and perform measurement. When actually measuring, in the Measurement tab, set the wavelength value to "550" and the number to average value to "20."

[0050] In the measurement using the above procedure, the angle of the optical axis (main alignment axis) for 160 x 128 = 20,480 pixels is measured for each measurement point. Then, the variation 3σ in the angle of the optical axis for each measurement point is calculated from the 20,480 optical axis angles. The size of one pixel is 432 [μm 2 ].

[0051] In the optical laminate, the transparent substrate needs to be arranged so that the slow axis of the transparent substrate and the absorption axis of the polarizer are substantially parallel or substantially perpendicular to each other. If these requirements are not met, the state of polarization is disturbed when linearly polarized light passes through the transparent substrate, making it impossible to suppress reflection of external light. The range of approximately parallel or approximately perpendicular is as described above.

[0052] The transparent substrate is preferably a stretched plastic film obtained by stretching a plastic film such as a polyester film, a polycarbonate film, a cycloolefin polymer film, an acrylic film, polystyrene, etc. Among these, a stretched polyester film or a stretched polycarbonate film is preferred from the viewpoint of easily increasing the in-plane retardation. Moreover, the transparent substrate preferably exhibits normal dispersion (the property that the birefringence increases toward the shorter wavelength side.) From this viewpoint, the transparent substrate is preferably a stretched polyester film (stretched polyester film). As the polyester film, a polyethylene terephthalate film (PET film), a polyethylene naphthalate film (PEN film), or the like is preferable. The transparent substrate may be a substrate in which a liquid crystal layer containing a liquid crystal compound such as a discotic liquid crystal compound is formed on a transparent support such as a plastic film. The transparent substrate may be a substrate obtained by transferring the liquid crystal layer formed on the transparent support as described above to another layer (such as a λ / 4 retardation layer or a polarizer).

[0053] Examples of the stretching include longitudinal uniaxial stretching, tenter stretching, sequential biaxial stretching, and simultaneous biaxial stretching. From the viewpoints of ease of handling and thinning, the thickness of the transparent substrate is preferably 5 μm or more and 300 μm or less, more preferably 10 μm or more and 200 μm or less, even more preferably 15 μm or more and 100 μm or less, and even more preferably 20 μm or more and 50 μm or less.

[0054] <Surface protection material> The optical laminate may have a surface protective material on the surface of the polarizer opposite to the transparent substrate. Examples of surface protective materials include transparent supports such as plastic films and glass. The surface protective material may have a functional layer on the transparent support, and the functional layer may be one or more layers selected from a hard coat layer, an antifouling layer, an antiglare layer, an antireflection layer, etc.

[0055] <Other layers> The optical laminate may further include other layers. Examples of other layers include an adhesive layer for adhering each layer together and an antistatic layer.

[0056] <Total light transmittance> The optical layered body of the present invention preferably has a total light transmittance of 35% or more and 80% or less, more preferably 37% or more and 65% or less, and even more preferably 40% or more and 55% or less. By setting the total light transmittance of the optical laminate to 35% or more, it is possible to easily improve the visibility of the display element. Also, by setting the total light transmittance of the optical laminate to 80% or less, it is possible to easily suppress the reflection of external light and furthermore, it is possible to easily suppress the color when viewed from an oblique angle. It is preferable that the total light transmittance shows the above value regardless of the side from which light is incident on the optical laminate.

[0057] <3σΔX, 3σΔY> In the optical layered body of the present invention, it is preferable that both 3σΔX and 3σΔY calculated from the following measurement 1 are less than 0.019. <Measurement 1> A sample is prepared by laminating the optical laminate on an aluminum plate having an average spectral reflectance of 20% in the wavelength region of 380 nm to 780 nm inclusive. In the sample, the optical laminate is arranged such that the surface of the λ / 4 retardation layer side relative to the transparent substrate faces the aluminum plate. Light diffused by an integrating sphere is incident on the surface of the sample from the normal direction, and the reflected light is measured. The X and Y values ​​of the XYZ color system are calculated from the measured reflected light. The measurement and calculation are performed in 0.5 degree increments in the azimuth angle range of 0 degrees to 359.5 degrees with the elevation angle fixed at an angle of 60 degrees from the normal to the surface of the sample, to obtain X and Y values ​​at 720 points. The average of the X values ​​of 720 points is "Xave". The deviation of the X value of the nth measurement point from Xave is "ΔXn". The variation 3σ of ΔXn of the 720 points is "3σΔX". The average Y value of 720 points is "Yave". The deviation of the Y value of the nth measurement point from Yave is "ΔYn". The 3σ variation of ΔYn of 720 points is "3σΔY".

[0058] "An angle of 60 degrees from the normal to the surface of the sample" is, in other words, "an angle of 30 degrees from a direction parallel to the surface of the sample."

[0059] By making both 3σΔX and 3σΔY less than 0.019, the change in color when viewed from an oblique angle can be further suppressed. Each of 3σΔX and 3σΔY is more preferably 0.018 or less, further preferably 0.017 or less, and even more preferably 0.016 or less. There is no lower limit for 3σΔX and 3σΔY, but each is preferably 0.005 or more, and more preferably 0.010 or more.

[0060] In the optical layered body of the present invention, the average of 3σΔX and 3σΔY calculated from the above measurement 1 is preferably less than 0.018. By setting the average of 3σΔX and 3σΔY to less than 0.018, the change in color when viewed from an oblique angle can be further suppressed. The average of 3σΔX and 3σΔY is more preferably 0.017 or less, even more preferably 0.016 or less, and even more preferably 0.015 or less. The lower limit of the average of 3σΔX and 3σΔY is not limited, but is preferably 0.005 or more, and more preferably 0.010 or more.

[0061] In the sample, the aluminum plate and the optical laminate are preferably laminated so that there is no air interface between the aluminum plate and the optical laminate. For this reason, the aluminum plate and the optical laminate are preferably bonded together via an adhesive layer or water-bonded together.

[0062] The reason why an aluminum plate with an average spectral reflectance of 20% for wavelengths between 380 nm and 780 nm was used in Measurement 1 is because it is a substitute for display elements with high reflectance, such as organic EL display elements and micro LED display elements.

[0063] In this specification, the average of the spectral reflectance at wavelengths of 380 nm to 780 nm refers to the reflectance of the SCI method. SCI is a reflectance calculated from the measured values ​​by applying light from all directions to the sample surface using an integrating sphere, closing the light trap and measuring all reflected light including the specular reflection direction. A representative SCI measuring device is configured in accordance with the geometric condition c of JIS Z8722:2009. More specifically, in a representative SCI and SCE measuring device, the position of the light receiver is +8 degrees relative to the normal line of the sample, the aperture angle of the light receiver is 10 degrees, the position of the light trap is -8 degrees relative to the normal line of the sample, and the coverage range of the light trap is 10 degrees. An example of such a measuring device is the product name CM-2002 manufactured by Konica Minolta, Inc.

[0064] The measurement 1 is performed by fixing the elevation angle at an angle inclined at 60 degrees from the normal to the surface of the sample, and varying the azimuth angle in increments of 0.5 degrees within the range of 0 to 359.5 degrees. An example of an apparatus capable of such measurements is Ez-Contrast160, a product name of ELDIM Corporation.

[0065] <Application> The optical laminate of the present invention can be used, for example, as an optical laminate for the front surface of a display element. Examples of the display element include a liquid crystal display element, an organic EL display element, a micro LED display element, etc. Among these, an organic EL display element and a micro LED display element are preferred in that the reflectance of the display element is high and the effects of the present invention can be easily achieved.

[0066] [Image display device] The image display device of the present invention has an optical laminate on a display element, the optical laminate being the optical laminate of the present invention described above, and is arranged so that the surface of the optical laminate on the λ / 4 retardation layer side relative to the transparent substrate faces the display element.

[0067] Examples of the display element include a liquid crystal display element, an organic EL display element, a micro LED display element, etc. Among these, an organic EL display element and a micro LED display element are preferred in that the reflectance of the display element is high and the effects of the present invention can be easily achieved.

[0068] The display element preferably has an average spectral reflectance of 10% or more, more preferably 15% or more, and even more preferably 17% or more, in the wavelength region of 380 nm or more and 780 nm or less. Such a display element is preferable in that it can easily exert the effects of the present invention. If the average spectral reflectance of the display element is too high, it tends to be difficult to suppress the color when viewed from an oblique angle. Therefore, the average spectral reflectance of the display element is preferably 50% or less, more preferably 40% or less, even more preferably 35% or less, and even more preferably 30% or less. EXAMPLES

[0069] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. In addition, "parts" and "%" are based on mass unless otherwise specified.

[0070] 1. Material Preparation and Fabrication 1-1. Preparation of polarizing plate The following polarizing plates A to C were prepared. <Polarizing plate A> A polarizing plate (polarization degree 99.95%, total light transmittance 40.5%) in which both sides of an iodine-based polarizer made of polyvinyl alcohol and iodine are protected with optically isotropic triacetyl cellulose film. <Polarizing plate B> A polarizing plate (polarization degree 99.5%, total light transmittance 43%) in which both sides of a dye-based polarizer made of polyvinyl alcohol and a dichroic dye are protected with optically isotropic triacetyl cellulose film. <Polarizing plate C> A polarizing plate (polarization degree 90%, total light transmittance 45%) consisting of a dye-based polarizer made of liquid crystal material and dichroic dye, protected on both sides with optically isotropic triacetyl cellulose film.

[0071] 1-2. Preparation of λ / 4 retardation layer The following λ / 4 retardation layers A to J were prepared. <λ / 4 retardation layer A> A laminate having a λ / 4 retardation layer made of a polymerizable liquid crystal compound on an optically isotropic triacetyl cellulose film. Re(550)=140 nm, Re(450) / Re(550)=0.85. <λ / 4 retardation layer B> A laminate having a λ / 4 retardation layer made of a polymerizable liquid crystal compound consisting of a mixture of reverse dispersion liquid crystal and normal dispersion liquid crystal on an optically isotropic triacetyl cellulose film. Re(550)=140nm, Re(450) / Re(550)=1.00. <λ / 4 retardation layer C> A laminate having a λ / 4 retardation layer made of a polymerizable liquid crystal compound on an optically isotropic triacetyl cellulose film. Re(550)=140 nm, Re(450) / Re(550)=1.09. <λ / 4 retardation layer D> A laminate having a λ / 4 retardation layer made of a polymerizable liquid crystal compound on an optically isotropic triacetyl cellulose film. Re(550)=140 nm, Re(450) / Re(550)=0.90. <λ / 4 retardation layer E> λ / 4 retardation layer made of cycloolefin polymer. Re(550)=140nm, Re(450) / Re(550)=1.0. <λ / 4 retardation layer F> λ / 4 retardation layer made of polycarbonate polymer. Re(550)=140nm, Re(450) / Re(550)=1.1. <λ / 4 retardation layer G> A laminate having a λ / 4 retardation layer made of a polymerizable liquid crystal compound on an optically isotropic triacetyl cellulose film. Re(550)=120 nm, Re(450) / Re(550)=1.09. <λ / 4 retardation layer H> A laminate having a λ / 4 retardation layer made of a polymerizable liquid crystal compound on an optically isotropic triacetyl cellulose film. Re(550)=120 nm, Re(450) / Re(550)=1.0. <λ / 4 retardation layer I> A laminate having a λ / 4 retardation layer made of a polymerizable liquid crystal compound on an optically isotropic triacetyl cellulose film. Re(550)=80 nm, Re(450) / Re(550)=1.09. <λ / 4 retardation layer J> λ / 4 retardation layer made of polycarbonate polymer. Re(550)=120nm, Re(450) / Re(550)=1.1.

[0072] 1-3. Preparation of λ / 2 retardation layer The following λ / 2 retardation layers A to E were prepared. <λ / 2 retardation layer A> A laminate having a λ / 2 retardation layer made of a polymerizable liquid crystal compound on an optically isotropic triacetyl cellulose film. Re(550)=260 nm, Re(450) / Re(550)=1.09. <λ / 2 retardation layer B> A laminate having a λ / 2 retardation layer made of a polymerizable liquid crystal compound on an optically isotropic triacetyl cellulose film. Re(550)=240 nm, Re(450) / Re(550)=1.0. <λ / 2 retardation layer C> A laminate having a λ / 2 retardation layer made of a polymerizable liquid crystal compound on an optically isotropic triacetyl cellulose film. Re(550)=160 nm, Re(450) / Re(550)=1.09. <λ / 2 retardation layer D> λ / 2 retardation layer made of cycloolefin polymer. Re(550)=275nm, Re(450) / Re(550)=1.0. <λ / 2 retardation layer E> λ / 2 retardation layer made of polycarbonate polymer. Re(550)=240nm, Re(450) / Re(550)=1.1.

[0073] 1-4. Preparation of transparent substrate The following transparent substrates A to I were prepared. The transparent substrates A to F and I had a variation 3σ in the angle of the alignment main axis of 0.01 or more. <Transparent base material A> Polyethylene terephthalate film, positive A plate satisfying nx>ny, thickness direction retardation: 2500 nm, in-plane retardation: 5000 nm. <Transparent base material B> Polyethylene terephthalate film, positive A plate satisfying nx>ny, thickness direction retardation: 5000 nm, in-plane retardation: 10000 nm. <Transparent base material C> Polyethylene naphthalate film, positive A plate satisfying nx>ny, thickness direction retardation: 7500 nm, in-plane retardation: 15000 nm. <Transparent base material D> Polyethylene terephthalate film, positive A plate satisfying nx>ny, thickness direction retardation: 2000 nm, in-plane retardation: 1000 nm. <Transparent base material E> A film having a liquid crystal layer made of a polymerizable liquid crystal compound on an optically isotropic triacetyl cellulose film, a positive A plate satisfying nx>ny, a thickness direction retardation: 25 nm, an in-plane retardation: 50 nm. <Transparent base material F> Polyethylene naphthalate film, positive A plate satisfying nx>ny, thickness direction retardation: 5000 nm, in-plane retardation: 10000 nm. <Transparent base material G> A film having a liquid crystal layer formed by vertically aligning polymerizable liquid crystals on an optically isotropic triacetyl cellulose film, a positive C plate, and a retardation in the thickness direction: -1000 nm <Transparent base material H> A film having a cholesteric liquid crystal layer on an optically isotropic triacetyl cellulose film, negative C plate, retardation in the thickness direction: 1000 nm <Transparent base material I> Triacetyl cellulose film, negative biaxial film (negative B plate) satisfying nx>ny>nz, thickness direction retardation: 250 nm, in-plane retardation: 60 nm.

[0074] 2. Preparation of optical laminates [Example 1] The λ / 4 retardation layer A, the transparent substrate A, and the polarizing plate A were laminated in this order via an adhesive layer to obtain an optical laminate of Example 1. The angle between the absorption axis of the polarizer and the slow axis of the transparent substrate was 90 degrees. The angle between the absorption axis of the polarizer and the slow axis of the λ / 4 retardation layer was 45 degrees.

[0075] [Examples 2-7, 13-17], [Comparative Examples 1-4] The optical laminates of Examples 2 to 7, 13 to 17 and Comparative Examples 1 to 4 were obtained in the same manner as in Example 1, except that the materials for the λ / 4 retardation layer, transparent substrate and polarizing plate were those shown in Table 1 and the angle between the absorption axis of the polarizer and the slow axis of the transparent substrate was changed to an angle shown in Table 1.

[0076] [Example 8] The λ / 4 retardation layer H, the λ / 2 retardation layer B, the transparent substrate B, and the polarizing plate A were laminated in this order via an adhesive layer to obtain an optical laminate of Example 8. The angle between the absorption axis of the polarizer and the slow axis of the transparent substrate was 90 degrees. The angle between the absorption axis of the polarizer and the slow axis of the λ / 4 retardation layer was 75 degrees. The angle between the absorption axis of the polarizer and the slow axis of the λ / 2 retardation layer was 15 degrees.

[0077] [Examples 9 to 12], [Comparative Example 5] The materials for the λ / 4 retardation layer, the λ / 2 retardation layer, the transparent substrate, and the polarizing plate were those shown in Table 1, and the angles between the absorption axis of the polarizer and the slow axis of the λ / 4 retardation layer and between the absorption axis of the polarizer and the slow axis of the λ / 2 retardation layer were changed to those shown in Table 1. The optical laminates of Examples 9 to 12 and Comparative Example 5 were obtained in the same manner as in Example 8, except that the materials for the λ / 4 retardation layer, the λ / 2 retardation layer, the transparent substrate, and the polarizing plate were changed to those shown in Table 1.

[0078] [Comparative Examples 6 to 7] The λ / 4 retardation layer E and the polarizing plate A were laminated via an adhesive layer to obtain an optical laminate of Comparative Example 6. The λ / 4 retardation layer F and the polarizing plate A were laminated via an adhesive layer to obtain an optical laminate of Comparative Example 7. The angle between the absorption axis of the polarizer and the slow axis of the λ / 4 retardation layer was 45 degrees.

[0079] 3. Creation of a simulated image display device An aluminum-deposited film was prepared by depositing an aluminum layer on an optically isotropic acrylic film. The thickness of the deposited layer was changed to produce three types of aluminum-deposited films with average spectral reflectances of 20%, 30%, and 40% in the wavelength range of 380 to 780 nm. The surface of an aluminum vapor deposition film having a spectral reflectance of 40% on the vapor deposition film side and the surface of the λ / 4 retardation layer side of the optical laminate of Example 1 were bonded together via an adhesive layer to obtain a simulated image display device of Example 1. Except for changing the aluminum vapor deposition film to one having the spectral reflectance shown in Table 1, the simulated image display devices of Examples 2 to 17 and Comparative Examples 1 to 7 were obtained in the same manner as in Example 1.

[0080] 4. Measurement and Evaluation The simulated image display devices of the examples and comparative examples were irradiated with light from a three-wavelength fluorescent lamp from the polarizing plate side, and the anti-reflection properties and color in oblique directions were evaluated according to the following criteria. The light source was a three-wavelength fluorescent lamp only, and the environment was set so that the brightness on the simulated image display device was 300 to 1000 lux. The results are shown in Tables 1 and 2. Furthermore, the total light transmittance was measured for the optical laminates of the examples and comparative examples. The results are shown in Tables 1 and 2. Furthermore, 3σΔX and 3σΔY were calculated for some of the optical laminates of the Examples and Comparative Examples. The results are shown in Table 2.

[0081] 4-1. Anti-reflection of external light When the simulated image display device was viewed from the front and at an angle, those for which light leakage due to insufficient anti-reflection was not noticeable were given a score of 3, those for which it was neither noticeable nor noticeable were given a score of 2, and those for which light leakage due to insufficient anti-reflection was noticeable were given a score of 1. The average scores of the 20 subjects were calculated and ranked according to the following criteria. <Evaluation criteria> A: Average score of 2.5 or higher B: Average score is between 2.0 and 2.5 C: Average score is 1.5 or more but less than 2.0 D: Average score is less than 1.5

[0082] 4-2. Color in diagonal directions When the simulated image display device was viewed from an angle, 20 subjects were given a score of 3 if the surface color was not bothersome, a score of 2 if it was neither, and a score of 1 if the surface color was very bothersome. The average score was calculated and the items were ranked according to the following criteria. <Evaluation criteria> A: Average score of 2.7 or higher B+: Average score is between 2.5 and 2.7 B: Average score is between 2.0 and 2.5 C: Average score is 1.5 or more but less than 2.0 D: Average score is less than 1.5

[0083] 4-3.Total light transmittance The total light transmittance of the optical laminates of the examples and comparative examples at wavelengths of 380 nm to 780 nm was measured, and the average value was calculated. The measuring device used was "HM-150" manufactured by Murakami Shikisai Co., Ltd. The light incident surface was the polarizing plate side.

[0084] 4-4.3σΔX, 3σΔY A sample was prepared by laminating the optical laminate of Example 14 on an aluminum plate having an average spectral reflectance of 20% in the wavelength region of 380 nm or more and 780 nm or less. Measurement 1 described in the specification was carried out on the sample, and 3σΔX and 3σΔY of the sample were calculated. The optical laminate of Example 14 was replaced with the optical laminates of Examples 15 to 17 and the optical laminate of Comparative Example 6, and 3σΔX and 3σΔY of the sample were calculated in the same manner. An ELDIM product name "Ez-Contrast160" was used as the measuring device.

[0085] [Table 1]

[0086] [Table 2]

[0087] Note 1: In Tables 1 and 2, "Angle 1" means the angle between the absorption axis of the polarizer and the slow axis of the transparent substrate. Note 2: In Table 1, "angle 2" means the angle between the absorption axis of the polarizer and the slow axis of the λ / 2 retardation layer. Note 3: In Tables 1 and 2, "angle 3" means the angle between the absorption axis of the polarizer and the slow axis of the λ / 4 retardation layer.

[0088] From the results in Tables 1 and 2, it can be confirmed that the optical laminates of the examples can suppress the reflection of external light and can suppress the color when viewed from an oblique angle. Moreover, from Example 13, it can be confirmed that, as long as the transparent substrate has "positive birefringence or negative birefringence and a thickness retardation of 125 nm or more or -125 nm or less", the color in the oblique direction can be suppressed even if the in-plane retardation of the transparent substrate is low. Note that, from the comparison between Example 13 and other examples, it can be confirmed that the larger the thickness retardation and in-plane retardation, the easier it is to suppress the color in the oblique direction. [Explanation of symbols]

[0089] 10:λ / 4 retardation layer 20:λ / 2 retardation layer 30: Transparent base material 40: Polarizer 50: Surface protection material 100: Optical laminate

Claims

1. The optical element comprises a λ / 4 retardation layer, a transparent substrate, and a polarizer in this order. the transparent substrate has positive birefringence or negative birefringence and a retardation in a thickness direction of 500 nm or more or −125 nm or less; the transparent substrate is a positive A plate satisfying a relationship of nx>ny≈nz or a negative B plate satisfying a relationship of nx>ny>nz, where nx is a refractive index in an in-plane slow axis direction, ny is a refractive index in an in-plane direction perpendicular to nx, and nz is a refractive index in a direction perpendicular to nx and ny, An optical laminate, in which a slow axis of the transparent substrate and an absorption axis of the polarizer are arranged approximately parallel or approximately perpendicular to each other.

2. The optical laminate according to claim 1 , wherein the transparent substrate has an in-plane retardation of 1000 nm or more.

3. The optical laminate according to claim 1 or 2, wherein the transparent substrate is a polyester film or a polycarbonate film.

4. The optical laminate according to any one of claims 1 to 3, further comprising a λ / 2 retardation layer between the λ / 4 retardation layer and the transparent substrate.

5. The optical laminate according to any one of claims 1 to 4, having a total light transmittance of 35% or more and 80% or less.

6. The optical laminate according to any one of claims 1 to 3, wherein 3σΔX and 3σΔY calculated from the following measurement 1 are both less than 0.

019. <Measurement 1> A sample is prepared by laminating the optical laminate on an aluminum plate having an average spectral reflectance of 20% in the wavelength region of 380 nm to 780 nm, and the optical laminate is arranged such that the surface of the optical laminate on the λ / 4 retardation layer side relative to the transparent substrate faces the aluminum plate. Light diffused by an integrating sphere is incident on the surface of the sample from the normal direction, and the reflected light is measured. The X and Y values ​​of the XYZ color system are calculated from the measured reflected light. The measurements and calculations are performed at azimuth angles of 0 to 359.5 degrees in increments of 0.5 degrees with the elevation angle fixed at 60 degrees from the normal to the surface of the sample, to obtain X and Y values ​​at 720 points. The average value of the X values ​​at 720 points is defined as "Xave." The deviation of the X value at the nth measurement point from Xave is defined as "ΔXn." The variation 3σ of ΔXn at 720 points is defined as "3σΔX." The average value of the Y values ​​of the 720 points is defined as "Yave." The deviation of the Y value of the nth measurement point from Yave is defined as "ΔYn." The variation 3σ of ΔYn of the 720 points is defined as "3σΔY."

7. The optical laminate according to any one of claims 1 to 3, wherein the average of 3σΔX and 3σΔY calculated from the following measurement 1 is less than 0.

018. <Measurement 1> A sample is prepared by laminating the optical laminate on an aluminum plate having an average spectral reflectance of 20% in the wavelength region of 380 nm to 780 nm, and the optical laminate is arranged such that the surface of the optical laminate on the λ / 4 retardation layer side relative to the transparent substrate faces the aluminum plate. Light diffused by an integrating sphere is incident on the surface of the sample from the normal direction, and the reflected light is measured. The X and Y values ​​of the XYZ color system are calculated from the measured reflected light. The measurements and calculations are performed at azimuth angles of 0 to 359.5 degrees in increments of 0.5 degrees with the elevation angle fixed at 60 degrees from the normal to the surface of the sample, to obtain X and Y values ​​at 720 points. The average value of the X values ​​at 720 points is defined as "Xave." The deviation of the X value at the nth measurement point from Xave is defined as "ΔXn." The variation 3σ of ΔXn at 720 points is defined as "3σΔX." The average value of the Y values ​​of the 720 points is defined as "Yave." The deviation of the Y value of the nth measurement point from Yave is defined as "ΔYn." The variation 3σ of ΔYn of the 720 points is defined as "3σΔY."

8. The optical element comprises a λ / 4 retardation layer, a transparent substrate, and a polarizer in this order. the transparent substrate has positive birefringence or negative birefringence, a thickness direction retardation of 125 nm or more or −125 nm or less, and an in-plane retardation of 500 nm or more; An optical laminate, in which a slow axis of the transparent substrate and an absorption axis of the polarizer are arranged approximately parallel or approximately perpendicular to each other.

9. The optical element comprises a λ / 4 retardation layer, a transparent substrate, and a polarizer in this order. The transparent substrate has positive birefringence or negative birefringence and a retardation in a thickness direction of 500 nm or more; An optical laminate, in which a slow axis of the transparent substrate and an absorption axis of the polarizer are arranged approximately parallel or approximately perpendicular to each other.

10. The optical laminate according to any one of claims 1 to 9, which is used for the front surface of an organic EL display element.

11. An image display device having an optical laminate on a display element, the optical laminate being the optical laminate according to any one of claims 1 to 9, and the image display device being arranged such that a surface of the optical laminate on a λ / 4 retardation layer side with respect to a transparent substrate faces the display element.

12. The image display device according to claim 11 , wherein the display element is an organic EL display element or a micro LED display element.

Images