Optical Stacks and Near-Eye Displays

Abstract

The present invention aims to provide an optical laminate and a near-eye display that can suppress the occurrence of blackout and color unevenness in images displayed on an image display device when a near-eye display having polarization characteristics is attached. [Solution] The optical laminate of the present invention is an optical laminate including a depolarizing element and a polarizing element, wherein the in-plane retardation Re in the normal direction at a wavelength of 550 nm of the depolarizing element is 3000 to 100000 nm, and the difference ΔR between the above in-plane retardation Re and the retardation of the depolarizing element in the oblique direction at an angle of 30° from the normal direction at a wavelength of 550 nm is less than 500 nm.

Description

[Technical Field]

[0001] This invention relates to an optical laminate and a near-eye display that provide good visibility with minimal color unevenness when the screen is observed through a polarizing element. [Background technology]

[0002] Conventionally, phase difference films such as quarter-wave plates have been used to impart optical functions to image display devices. For example, when an observer wearing polarized sunglasses views an image displayed on an image display device that uses a polarizing plate on the light-emitting side, the screen appears completely black, which is a problem (blackout). In response to this, it is known that by installing a quarter-wave plate on the light-emitting side of the image display device such that the angle between the absorption axis of the polarizer of the polarizing plate of the image display device and the slow axis of the quarter-wave plate is approximately 45 degrees, the emitted light is made approximately circularly polarized, thereby preventing blackout (Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-174636 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Polarized sunglasses absorb one type of linearly polarized light and transmit the other type of linearly polarized light whose polarization direction is perpendicular to it. Therefore, by converting the light emitted from an image display device into circularly polarized light, blackout can be suppressed. On the other hand, near-eye displays such as AR (Augmented Reality) glasses, which have polarization properties, are also known as glasses that absorb or reflect a predetermined polarization. It has been found that when viewing an image display device while wearing such a near-eye display, phenomena such as blackout and color unevenness may occur. This is thought to be due to the interaction between the polarization state of the light emitted by the image display device and the polarization properties of the near-eye display.

[0005] Therefore, the present invention aims to provide an optical laminate that can suppress the occurrence of blackout and color unevenness in images displayed on an image display device when a near-eye display having polarization characteristics is attached. Furthermore, the present invention also aims to provide a near-eye display using this optical laminate. [Means for solving the problem]

[0006] The inventors of this invention have conducted extensive research on the above-mentioned problems and have found that the above objective can be achieved with the following configuration.

[0007] [1] An optical laminate comprising a depolarizing element and a polarizing element, wherein the in-plane retardation Re in the normal direction at a wavelength of 550 nm of the depolarizing element is 3000 to 100000 nm, and the difference ΔR between the in-plane retardation Re and the retardation of the depolarizing element in an oblique direction at an angle of 30° from the normal direction at a wavelength of 550 nm is less than 500 nm. [2] The optical laminate according to [1], wherein the depolarization element includes a phase difference film having negative birefringence and a phase difference film having positive birefringence. [3] The optical laminate according to [1] or [2], wherein the depolarization element includes a positive A plate and a negative A plate. [4] An optical laminate according to any one of [1] to [3], wherein the ratio of the difference ΔR to the in-plane retardation Re is 0.1000 or less. [5] An optical laminate comprising a depolarizing element, a phase difference element, and a polarizing element, wherein the in-plane retardation Re in the normal direction at a wavelength of 550 nm of the composite comprising the depolarizing element and the phase difference element is 3000 to 100000 nm, and the difference ΔR between the in-plane retardation Re and the retardation of the composite in an oblique direction at an angle of 30° from the normal direction at a wavelength of 550 nm is less than 500 nm. [6] The optical laminate according to [5], wherein the depolarization element includes a phase difference film having negative birefringence and a phase difference film having positive birefringence. [7] The optical laminate according to [5] or [6], wherein the depolarization element includes a positive A plate and a negative A plate. [8] An optical laminate according to any one of [5] to [7], wherein the ratio of the difference ΔR to the in-plane retardation Re is 0.1000 or less. [9] The optical laminate according to any one of [5] to [8], wherein the above-mentioned phase difference element is a positive C plate.

[10] The optical laminate according to [9], wherein the retardation Rth in the thickness direction at a wavelength of 550 nm of the positive C plate is -100 to -3000 nm.

[11] A near-eye display having an optical laminate as described in any of [1] to

[10] . [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an optical laminate that can suppress the occurrence of blackout and color unevenness in images displayed on an image display device when a near-eye display having polarization characteristics is attached. Furthermore, according to the present invention, a near-eye display using this optical laminate can be provided.

Brief Description of Drawings

[0009] [Figure 1] It is a schematic diagram showing an example of an optical laminate according to the first embodiment of the present invention. [Figure 2] It is a schematic diagram showing an example of an optical laminate according to the second embodiment of the present invention.

Modes for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments and specific examples, but the present invention is not limited to such embodiments. In this specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value.

[0011] In this specification, "orthogonal" does not strictly represent 90°, but represents 90° ± 10°, preferably 90° ± 5°. Also, "parallel" does not strictly represent 0°, but represents 0° ± 10°, preferably 0° ± 5°. Further, "45°" does not strictly represent 45°, but represents 45° ± 10°, preferably 45° ± 5°.

[0012] In this specification, the "absorption axis" means the polarization direction in which the absorbance is maximum in the plane when linearly polarized light is incident. The "reflection axis" means the polarization direction in which the reflectance is maximum in the plane when linearly polarized light is incident. The "transmission axis" means the direction orthogonal to the absorption axis or the reflection axis in the plane. Further, the "slow axis" means the direction in which the refractive index is maximum in the plane. In this specification, the retardation means in-plane retardation, denoted as Re(λ), unless otherwise specified. Here, Re(λ) represents the in-plane retardation at wavelength λ, and when not otherwise specified, the wavelength λ is 550 nm. Furthermore, the retardation in the thickness direction at wavelength λ is denoted as Rth(λ) in this specification. Unless otherwise specified, wavelength λ is assumed to be 550 nm. Re(λ) and Rth(λ) can be measured using an AxoScan OPMF-1 (manufactured by Axometrics) at wavelength λ. By inputting the average refractive index ((nx+ny+nz) / 3) and film thickness (d(μm)) into AxoScan, Slow axis direction (°) Re(λ)=R0(λ) The formula Rth(λ) = ((nx+ny) / 2-nz)×d is calculated.

[0013] [Optical laminate] The optical laminate of the present invention will be described below.

[0014] An optical laminate according to the first embodiment of the present invention includes a depolarizing element and a polarizing element. Furthermore, in the optical laminate according to the first embodiment of the present invention, the in-plane retardation Re in the normal direction at a wavelength of 550 nm of the depolarization element is 3000 to 100000 nm, and the in-plane retardation Re is oblique retardation at an angle of 30° from the normal direction at a wavelength of 550 nm of the depolarization element (hereinafter referred to as "oblique retardation R"). 30 The difference ΔR (hereinafter also simply referred to as "difference ΔR") between the two values ​​is less than 500 nm.

[0015] An optical laminate according to the second embodiment of the present invention includes a depolarization element, a phase difference element, and a polarizing element. Furthermore, in the optical laminate according to the second embodiment of the present invention, the in-plane retardation Re in the normal direction at a wavelength of 550 nm of the composite, which includes a depolarizing element and a phase difference element, is 3000 to 100000 nm, and the in-plane retardation Re is oblique retardation R at an angle of 30° from the normal direction of the composite at a wavelength of 550 nm. 30 The difference ΔR is less than 500 nm.

[0016] The optical laminates according to the first and second embodiments of the present invention (hereinafter collectively referred to as "the optical laminates of the present invention") are suitable for applications in which a near-eye display having polarization characteristics, such as AR glasses, is worn to observe an image displayed on an image display device. By observing the image displayed by the image display device with a near-eye display having the optical laminates of the present invention, it is possible to achieve image display with suppressed blackout and color unevenness. Blackout and color unevenness are thought to occur due to the interaction between the polarization state of the light emitted by the image display device and the polarization characteristics of the near-eye display. The optical laminates of the present invention can effectively eliminate the polarization of incident light, and therefore can suppress the occurrence of these problems.

[0017] The detailed reasons why the optical laminate of the present invention can suppress blackout and color unevenness in images displayed on an image display device when a near-eye display having polarization characteristics is attached are not clear, but it is presumed to be due to the following reasons. The depolarization mechanism using a phase difference film with high retardation is due to the large change in retardation with respect to wavelength changes. As a result, the polarization state of transmitted light changes significantly with respect to wavelength changes. Consider a configuration in which a phase difference film with high retardation is placed between a polarizing element and an image display device. In this case, when the spectral radiance spectrum of the image display device is measured through the polarizing element, the spectral radiance becomes zero at a certain wavelength because the polarization characteristics are absorbed by the polarizing element, but at different wavelengths in the vicinity, the polarization characteristics are transmitted through the polarizing element, resulting in high spectral radiance. The optical laminate of the present invention has a depolarization element with high retardation, having an in-plane retardation Re of 3000 to 100000 nm. Due to this depolarization mechanism, light of all wavelengths is not cut off, but some wavelengths of light pass through, thus suppressing blackout.

[0018] On the other hand, this depolarization mechanism can cause color unevenness when the spectral radiance spectrum of an image display device has a narrow-band spectral light at a certain wavelength. For example, in the transmission spectrum obtained by a combination of an image display device, depolarization element, and polarizing element, if the wavelength range with low transmittance coincides with this narrow-band spectral light, this narrow-band spectral light does not reach the observer's eye. Conversely, if the wavelength range with high transmittance coincides with this narrow-band spectral light, this narrow-band spectral light reaches the observer's eye. The transmission characteristics of a combination of an image display device, depolarization element, and polarizing element are mainly determined by the retardation value of the depolarization element in that direction. Here, the angle between the direction the observer views and the normal changes depending on the position where the image is displayed on the image display device. However, if the difference ΔR between the retardation Re in the normal direction and the retardation in the oblique direction is large, the change in transmission characteristics due to the combination of the image display device / depolarization element / polarizing element in response to the change in angle becomes large. As a result, the color changes depending on the angle between the direction the observer views and the normal, and this is perceived as color unevenness. Therefore, the retardation Re in the normal direction of the depolarization element and the retardation R in the oblique direction, where the angle from the normal direction is 30°, are considered. 30 By designing and fabricating the phase difference characteristics of the depolarizing element so that the difference ΔR is small, less than 500 nm, it is possible to suppress color changes due to the angle between the direction of view seen by the observer and the normal, thereby suppressing the occurrence of color unevenness.

[0019] The optical laminate of the present invention, possessing these characteristics, is useful in fields requiring advanced optical performance utilizing polarization, such as AR glasses.

[0020] [Optical laminate according to the first embodiment] The optical laminate according to the first embodiment of the present invention will be described in more detail. Figure 1 is a schematic diagram showing an example of an optical laminate according to the first embodiment of the present invention. As conceptually shown in Figure 1, the optical laminate 1 according to this embodiment includes a depolarization element 11 and a polarizing element 12. As described above, in the optical laminate 1, the in-plane retardation Re and ΔR of the depolarization element 11 are each within a predetermined range.

[0021] [Depolarizing element] The depolarization element included in the optical laminate according to this embodiment is a high retardation film having a phase difference of several times or more the wavelength in the visible light region.

[0022] <In-plane retardation in the normal direction of the depolarization element Re> In this embodiment, the in-plane retardation Re in the normal direction at a wavelength of 550 nm of the depolarization element is 3000 to 100000 nm. A retardation Re of 3000 nm or higher enhances the depolarization ability due to wavelength scrambling, thereby suppressing color unevenness and blackout. Furthermore, a retardation Re of 100000 nm or lower suppresses the reduction in transmittance and deterioration of transmitted image clarity caused by excessive thickness of the phase difference film included in the depolarization element. The in-plane retardation Re of the depolarization element is preferably 5000 to 30000 nm, and more preferably 7500 to 15000 nm, in the above respects.

[0023] Here, the various retardations of the depolarizing element can be adjusted by, for example, the formation conditions, formation material, and film thickness of the phase difference film (phase difference layer) included in the depolarizing element, as well as the combination of phase difference films when multiple phase difference films are included.

[0024] <Difference ΔR> In-plane retardation Re of the depolarization element and oblique retardation Re at an angle of 30° from the normal direction. 30The difference ΔR is less than 500 nm. As mentioned above, having a difference ΔR of less than 500 nm suppresses color changes caused by the angle between the direction of view and the normal when observing the displayed image, thereby suppressing the occurrence of color unevenness. The difference ΔR of the depolarization element is preferably less than 300 nm, more preferably less than 150 nm, and even more preferably less than 50 nm, in terms of superior effect in suppressing the occurrence of color unevenness. There is no particular lower limit, and the difference ΔR may be 0 nm. Furthermore, the diagonal retardation Re in the above-mentioned depolarization element 30 The measurement method will be described in the later examples.

[0025] In this embodiment, the ratio of the difference ΔR to the in-plane retardation Re of the depolarizing element (ΔR / Re) is preferably 0.1000 or less, more preferably 0.0200 or less, even more preferably 0.0150 or less, and particularly preferably 0.0100 or less, in terms of having a superior effect in suppressing the occurrence of color unevenness. The lower limit is not particularly limited, and the above ratio (ΔR / Re) may be 0.

[0026] <Configuration of the depolarizing element> The depolarization element may have only one phase difference film, or it may have two or more phase difference films. There is no limit to the number of phase difference films in the depolarization element, but fewer than 20 layers are preferred, fewer than 10 layers are more preferred, fewer than 6 layers are even more preferred, and fewer than 3 layers are most preferred, as these reduce interfacial reflections and provide high transmitted image clarity.

[0027] By having multiple phase difference films in the depolarization element, high in-plane retardation Re can be obtained while precisely controlling retardation in the oblique direction, thus enabling a suitable depolarization effect for light sources with various polarization states and spectra. In other words, in a configuration with multiple phase difference films, it becomes possible to achieve desired retardation characteristics by combining phase difference films having different retardations. For example, in the optical laminate of the second embodiment described later, by adjusting the film thickness of each phase difference film in the depolarization element according to the retardation of the combined phase difference elements, the difference ΔR of the composite including the depolarization element and the phase difference layer can be reduced, suppressing blackout and color unevenness, and depolarizing the light.

[0028] There is no limit to the number of phase difference films when the depolarization element has multiple phase difference films. In terms of depolarization function, a larger number of phase difference films in the depolarization element is preferable because it results in a higher retardation Re and thus a higher blackout suppression ability. On the other hand, in terms of brightness of the image observed through the optical laminate and clarity of the transmitted image, a smaller number of phase difference films in the depolarization element is advantageous.

[0029] (Optical properties of phase difference film) The phase difference film of the depolarization element is preferably designed to exhibit a desired retardation at a specific wavelength. This effectively eliminates the polarization state of light, regardless of the polarization state of the incident light. The retardation of the phase difference film can be adjusted by known methods, such as the thickness of the phase difference film and the degree of optical anisotropy (birefringence) of the optical anisotropic material contained in the phase difference film.

[0030] (Rth, the retardation direction in the thickness direction of the phase difference film) When the depolarization element has multiple phase difference films with random axial distributions, it is preferable to control the value of the retardation Rth in the thickness direction (hereinafter also simply referred to as "Rth") for each phase difference film. By controlling the Rth value of each phase difference film, diagonal retardation R can be achieved. 30 Furthermore, the difference ΔR can be suitably controlled, and as a result, the occurrence of color unevenness in images displayed on the image display device can be suppressed.

[0031] When the depolarization element has multiple phase difference films, a preferred method for controlling Rth is to laminate a phase difference film having a negative Rth value and a phase difference film having a positive Rth value. Phase difference films with a negative Rth value can be fabricated, for example, by using a liquid crystal compound with positive birefringence in the fabrication of the phase difference film. Examples of liquid crystal compounds with positive birefringence include rod-shaped liquid crystal compounds. On the other hand, a phase difference film with a positive Rth value can be fabricated, for example, by using a liquid crystal compound with negative birefringence in the fabrication of the phase difference film. Examples of liquid crystal compounds with negative birefringence include disc-shaped liquid crystal compounds.

[0032] Furthermore, when the depolarization element has multiple phase difference films, the control of Rth is not limited to a configuration in which a phase difference film with a negative Rth value and a phase difference film with a positive Rth value are stacked, as described above, and various configurations can be used. For example, if the depolarization element has two phase difference films, a first phase difference film and a second phase difference film, as described above, the first phase difference film may have positive birefringence and the second phase difference film may have negative birefringence, or the first phase difference film may have negative birefringence and the second phase difference film may have positive birefringence. From the viewpoint of retardation changes when light is incident on the depolarization element from an oblique direction, that is, when the image display device is observed from an oblique direction, it is preferable that the first phase difference film has negative birefringence and the second phase difference film has positive birefringence, or that the first phase difference film has positive birefringence and the second phase difference film has negative birefringence.

[0033] The positive or negative nature of birefringence can be determined by measuring Rth. If Rth is negative, positive birefringence is present. If Rth is positive, negative birefringence is present.

[0034] <Materials for phase difference films> There are no restrictions on the material used to form the phase difference film (phase difference layer); various known materials used for forming phase difference films can be used. Examples include birefringent particles, birefringent polymers, and liquid crystal compounds. Among these, liquid crystal compounds that can form a phase difference film with uniform thickness and a high aspect ratio (in-plane length / thickness), and that also have high optical anisotropy, are preferred. Liquid crystal compounds having polymerizable groups are particularly suitable for use. By using liquid crystal compounds in the formation of phase difference films, in addition to excellent phase difference characteristics, processability and durability can also be improved.

[0035] Liquid crystal compounds can be easily immobilized by heating and UV irradiation, and maintain stable optical properties over long periods of time. Furthermore, liquid crystal compounds allow for precise adjustment of desired phase difference characteristics, and because they exhibit a liquid crystal phase within a specific temperature range, their phase difference characteristics can be optimized through temperature control during the manufacturing process.

[0036] There are no restrictions on the birefringence wavelength dispersion characteristics of liquid crystal compounds, but forward wavelength dispersion is preferred. Forward wavelength dispersion is defined as Re(450) / Re(550)>1.00 and Re(650) / Re(550)≦1.00. This allows for a larger phase change in response to wavelength changes. Here, phase is an index representing the state of a light wave and is a value obtained by Re(λ) / λ×2π. Therefore, by fabricating a phase difference film using a forward wavelength dispersive liquid crystal compound, color changes can be suppressed when observing an image display device that emits polarized light with a polarizing element attached.

[0037] Furthermore, when selecting a liquid crystal compound, it is preferable to pay attention to physical properties such as heat resistance, light resistance, and moisture resistance, and to select a material with durability appropriate to the usage environment. This makes it possible to ensure long-term reliability in wearable devices such as AR glasses, as well as other optical devices.

[0038] The phase difference film of the depolarization element preferably contains a liquid crystal compound. For example, as described above, if the depolarization element has a first phase difference film and a second phase difference film, it is preferable that both the first phase difference film and the second phase difference film contain a liquid crystal compound. The preferred embodiment of the liquid crystal compound in each phase difference film is the same as described above.

[0039] (Method of manufacturing phase difference film) There are no restrictions on the method for manufacturing the phase difference film; known methods can be used depending on the material used to form the phase difference film. As an example, a method for producing a phase difference film is described, which involves uniformly coating a liquid crystalline material having crosslinkable groups onto a support, heat-treating it at a specific temperature, and then curing it by ultraviolet irradiation or the like. In other words, a liquid crystalline material having crosslinkable groups is a liquid crystal composition containing a liquid crystal compound having crosslinkable groups.

[0040] A typical phase difference film using liquid crystal compounds is manufactured by applying a liquid crystal composition to a substrate (alignment film) that has liquid crystal alignment restricting force and a uniform orientation restricting direction, and then curing it to form a phase difference layer. Methods for making the orientation restricting direction uniform in the plane include rubbing the substrate and uniform linearly polarized light irradiation of the photo-alignment film.

[0041] Furthermore, in order to create a phase difference in the phase difference film, it is preferable to orient the rod-shaped liquid crystal compounds horizontally and the disc-shaped liquid crystal compounds vertically. To achieve this, it is preferable to control the surface energy of the underlying layer. Specifically, when producing a phase difference film containing rod-shaped liquid crystal compounds, it is preferable to make the underlying layer hydrophobic. On the other hand, when producing a phase difference film containing disc-shaped liquid crystal compounds, it is preferable to make the underlying layer hydrophilic.

[0042] The depolarization element preferably includes a positive A plate and a negative A plate. Here, if we let nx be the refractive index in the slow axis direction (the direction in which the refractive index is maximum within the plane) within the phase difference film plane, ny be the refractive index in the direction perpendicular to the slow axis within the plane, and nz be the refractive index in the thickness direction, then the positive A plate satisfies the relationship in equation (A1), and the negative A plate satisfies the relationship in equation (A2). Formula (A1) nx>ny≒nz Formula (A2) ny <nx≒nz The above "≒" includes not only cases where the two are completely identical, but also cases where they are substantially identical. "Substantially identical" means, for example, that (ny-nz)×d (where d is the thickness of the phase difference film) is -10 to 10 nm, preferably -5 to 5 nm, and that (nx-nz)×d is -10 to 10 nm, preferably -5 to 5 nm, and that that is also included in "nx≒nz". A positive A plate is a phase difference film having positive birefringence and a negative Rth value, and can be manufactured, for example, by horizontally oriented rod-shaped liquid crystalline compounds. A negative A plate is a phase difference film having negative birefringence and a positive Rth value, and can be manufactured, for example, by vertically oriented disc-shaped liquid crystalline compounds.

[0043] The depolarization element in the optical laminate of the present invention may consist only of a phase difference film, or it may have the above-mentioned support (substrate) and underlayer. As a support, various known materials can be used, as long as they can support a depolarizing element, a phase difference element, or a polarizing element, and can transmit the target light, such as visible light. For example, examples of materials for forming a transparent support include cellulosic polymers (hereinafter referred to as cellulose acylates), such as triacetylcellulose; thermoplastic norbornene resins (such as Zeonex and Zeonor from Nippon Zeon Co., Ltd., and Arton from JSR Corporation); acrylic resins; plastic films such as polyester resins; and glass.

[0044] [Polarizing element] The polarizing elements included in the optical laminate of the present invention include elements having the property of absorbing or reflecting a portion of the polarized light. Specifically, these include linear polarizers, circular polarizers, reflective polarizers and reflective circular polarizers, polarizing glasses having any of these, display units for AR glasses having any of these, and photochromic filters that utilize the above-mentioned polarization properties.

[0045] The optical laminate of the present invention may optionally include other layers besides the depolarizing element and the polarizing element. Examples of other layers include various layers (films) such as an anti-reflective layer, a phase difference layer, a depolarizing layer made of a high birefringence material, a polarizer layer, a color absorption layer, a transparent conductive layer, and an antistatic layer.

[0046] [Optical laminate according to the second embodiment] The optical laminate according to the second embodiment of the present invention will be described in more detail. Figure 2 is a schematic diagram showing an example of an optical laminate according to a second embodiment of the present invention. As conceptually shown in Figure 2, the optical laminate 1 according to this embodiment includes a depolarization element 11, a phase difference element 13, and a polarizing element 12. As described above, in the optical laminate 1, the in-plane retardation Re and ΔR of the composite 2 including the depolarization element 11 and the phase difference element 13 are each within a predetermined range.

[0047] The depolarizing element included in the optical laminate according to this embodiment is the same as the depolarizing element included in the optical laminate according to the first embodiment, including preferred embodiments, except that the retardation of the depolarizing element is adjusted so that the composite with the phase difference element has a predetermined retardation. The polarizing element included in the optical laminate according to this embodiment is the same as the polarizing element included in the optical laminate according to the first embodiment, including in preferred embodiments.

[0048] [Phase difference element] The phase difference elements included in the optical laminate according to this embodiment include optical elements that transmit at least a portion of light and change its polarization state. Specifically, these include a positive C plate, a guest host cell, a quarter-wave plate, a layer bonded to and held with a depolarization element, and a housing for a dimming filter having a phase difference, with the positive C plate being preferred.

[0049] A positive C plate is a phase difference layer in which the in-plane retardation Re is substantially zero and the thickness-direction retardation Rth has a negative value. A positive C plate can be obtained, for example, by vertically oriented rod-shaped liquid crystalline compounds. Details of the method for manufacturing a positive C plate can be found in, for example, Japanese Patent Publication No. 2017-187732, Japanese Patent Publication No. 2016-053709, and Japanese Patent Publication No. 2015-200861. The in-plane retardation Re of the positive C plate is preferably 10 nm or less. Furthermore, the retardation Rth in the thickness direction of the positive C plate is preferably -100 to -3000 nm, and more preferably -200 to -2000 nm.

[0050] [Complex] The composite included in the optical laminate according to this embodiment includes a depolarizing element and a phase difference element. By designing the retardation of the composite, which combines a depolarizing element and a phase difference element placed between the optical element and the image display device, to a predetermined range, the image quality when the displayed image on the image display device is observed through the polarizing element can be improved. More specifically, as described above, blackout of the displayed image can be suppressed, and the change in color due to the angle between the direction of view of the observer and the normal can be suppressed, thereby suppressing the occurrence of color unevenness.

[0051] <In-plane retardation of the normal direction of the composite Re> In this embodiment, the in-plane retardation Re in the normal direction of the composite at a wavelength of 550 nm is 3000 to 100000 nm. A composite in-plane retardation Re of 3000 nm or higher enhances the depolarization ability due to wavelength scrambling, thereby suppressing color unevenness and blackout. Furthermore, a composite in-plane retardation Re of 100000 nm or lower suppresses the reduction in transmittance and deterioration of the clarity of the transmitted image caused by excessive thickness of the phase difference film included in the depolarization element. The in-plane retardation Re of the composite is preferably 5000 to 30000 nm, and more preferably 7500 to 15000 nm, in the above respects.

[0052] Various retardations of the composite can be adjusted, for example, by adjusting the formation conditions, formation material, film thickness, and combination of phase difference film and phase difference element for the phase difference film included in the phase difference element and the depolarization element.

[0053] <Difference ΔR> The in-plane retardation Re of the composite and the oblique retardation Re at an angle of 30° from the normal direction. 30 The difference ΔR is less than 500 nm. As mentioned above, having a difference ΔR of less than 500 nm suppresses color changes caused by the angle between the direction of view and the normal when observing the displayed image, thereby suppressing the occurrence of color unevenness. The difference ΔR of the composite is preferably less than 300 nm, more preferably less than 150 nm, and even more preferably less than 50 nm, in terms of superior effect in suppressing the occurrence of color unevenness. There is no particular lower limit, and the difference ΔR may be 0 nm. Furthermore, the diagonal retardation Re in the above composite 30 The measurement method will be described in the later examples.

[0054] In this embodiment, the ratio of the difference ΔR to the in-plane retardation Re of the depolarizing element (ΔR / Re) is preferably 0.1000 or less, more preferably 0.0500 or less, even more preferably 0.0200 or less, and particularly preferably 0.0150 or less, as this provides a better effect in suppressing the occurrence of color unevenness. The lower limit is not particularly limited, and the above ratio (ΔR / Re) may be 0.

[0055] The optical laminate of the present invention can be used as a component of an optical device such as a near-eye display or a head-up display, while simultaneously being used to observe an image displayed on an image display device located outside the optical device. In particular, the optical laminate of the present invention can be suitably used as an optical component constituting a near-eye display.

[0056] [Near-eye display] The near-eye display of the present invention has the optical laminate of the present invention. Besides having the optical laminate of the present invention, various known near-eye displays can be used as the near-eye display. By having the optical laminate of the present invention, it is possible to manufacture a near-eye display that can suppress the occurrence of blackout and color unevenness in images displayed on an image display device. Specific examples of near-eye displays include AR glasses, VR (Virtual Reality) glasses, and MR (Mixed Reality) glasses.

Example

[0057] Hereinafter, the present invention will be specifically described based on examples. The materials, reagents, amounts of substances and their ratios, operations, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the spirit of the present invention. Therefore, the present invention is not limited or restricted by the following examples.

[0058] [Example 1] [Production of the retardation film 1] As a support, a PET film with a thickness of 100 μm (manufactured by Toyobo Co., Ltd., Cosmo Shine A4265) was prepared. This PET film has an easy-adhesion layer on one surface. The surface of the PET film without the easy-adhesion layer was subjected to rubbing treatment, and the coating solution 1 for the retardation layer having the following composition was applied with a wire bar coater. Then, it was dried at 25 °C for 15 seconds, and then heated at 100 °C for 80 seconds for liquid crystal alignment. Next, at 100 °C, ultraviolet rays of 340 mJ / cm 2 were irradiated using an ultraviolet irradiation device with a mercury lamp as the ultraviolet light source to form a retardation layer with a film thickness of 5.4 μm, thereby forming a rod-like liquid crystal layer 1 on the PET support. The rod-like liquid crystal layer 1 is a positive A plate having positive birefringence.

[0059] [Coating solution 1 for the retardation layer] Methyl ethyl ketone 58.0 parts by mass Cyclohexanone 86.9 parts by mass Mixture X of the following rod-like liquid crystal compounds 100.0 parts by mass The following photoinitiator A 3.00 parts by mass The following surfactant S1 0.04 parts by mass

[0060] Mixture X of rod-like liquid crystal compounds

Chemical formula

[0061] In the above mixture, the numerical values ​​represent the mass percentage of each rod-shaped liquid crystal compound. R represents a group bonded to an oxygen atom. Furthermore, the average molar extinction coefficient of the above rod-shaped liquid crystal compounds at wavelengths of 300-400 nm was 140 / mol·cm.

[0062] Photopolymerization initiator A; Omnirad127 (manufactured by IGM Resins) [ka]

[0063] Surfactant S1 [ka]

[0064] A rod-shaped liquid crystal layer 1 discharges at a rate of 150 W·min / m 2 After corona treatment, a phase difference layer coating solution 2 with the following composition was applied using a wire bar coater. The material was then dried at 25°C for 15 seconds, followed by heating at 100°C for 80 seconds for liquid crystal alignment. Subsequently, at 100°C, it was irradiated with ultraviolet light at 340 mJ / cm² using a mercury lamp as the ultraviolet light source. 2 By irradiating with ultraviolet light, a phase difference layer with a thickness of 3.6 μm was formed, thereby creating a disc-shaped liquid crystal layer 1 on a rod-shaped liquid crystal layer 1. The disc-shaped liquid crystal layer 1 was a negative A plate having negative birefringence. This resulted in obtaining a phase difference film 1 containing the rod-shaped liquid crystal layer 1 and the disc-shaped liquid crystal layer 1.

[0065] [Coating solution for phase difference layer 2] 40 parts by mass of the following disc-shaped liquid crystal compound (A) 60 parts by mass of the following disc-shaped liquid crystal compound (B) The following surfactant S2: 0.3 parts by mass Photopolymerization initiator A (Manufactured by IGM Resins, Omnirad127) 3.0 parts by mass Methyl ethyl ketone 340 parts by mass

[0066] Disc-shaped liquid crystal compound (A) [ka]

[0067] Disc-shaped liquid crystal compound (B) [ka]

[0068] Surfactant S2 [ka]

[0069] <Preparation of phase difference films 2-3> Phase difference film 2 was manufactured using the same method as phase difference film 1, except that it did not form a disc-shaped liquid crystal layer 1. Phase difference film 3 was manufactured in the same manner as phase difference film 1, except that the film thickness of each layer was changed to the film thicknesses listed in Table 1.

[0070] ≪Measurement≫ The film thickness and retardation were measured for each phase difference film that was fabricated. Retardation was measured by transferring each phase difference film to a glass plate. The transfer method involved first bonding the coated side (phase difference layer side) of each phase difference film to the glass plate via an adhesive. Next, the PET support was peeled off. This created a measurement sample consisting of a glass plate, adhesive, and phase difference layer.

[0071] (Measurement of retardation) Regression measurements were performed using the Axoscan OPMF-1 from Axometrics. The in-plane retardation Re was obtained by measuring the retardation in the normal direction (polar angle θ=0°) of the sample used for measurement. Diagonal retardation measurements were performed using OPMF-1, similar to the in-plane retardation Re measurement, for four directions: diagonal (polar angle θ = 30°, angle with normal direction = 30°) with azimuth angles φ = 0°, 45°, 90°, and 135° relative to the measurement sample. Here, the azimuth angle φ = 0° was set to coincide with the orientation of the phase advance axis of the phase difference film, and diagonal retardation was measured. For the four obtained diagonal retardation measurements, the absolute value of the difference between each and the in-plane retardation Re was calculated, and the maximum value among the four points was found to calculate the difference ΔR between the in-plane retardation Re and the diagonal retardation. The retardation Rth in the thickness direction was calculated using the method described above from the average refractive index measured using the Axoscan and the film thickness measured by the method described later.

[0072] (Measurement of film thickness) Using a scanning electron microscope (product name "S-4800," manufactured by Hitachi High-Technologies Corporation), cross-sectional images of the sample were taken, and the film thickness of each phase difference layer was measured.

[0073] The measurement results for each phase difference film are shown in Table 1.

[0074] [Table 1]

[0075] <Fabrication of optical laminates> A phase difference film 1 was bonded to a glass plate via an adhesive so that the surface on the phase difference layer side faced the glass plate. Then, the PET support was peeled off and removed to obtain a laminate having the glass plate / adhesive / disk-shaped liquid crystal layer 1 / rod-shaped liquid crystal layer 1 in this order. The series of steps of bonding the phase difference film 1 to the surface on the rod-shaped liquid crystal layer 1 side of the obtained laminate via an adhesive, followed by peeling off the PET support, was repeated so that the number of bonded rod-shaped liquid crystal layers 1 and disc-shaped liquid crystal layers 1 each matched the number (6) listed in the Example 1 column of Table 2 below, thereby obtaining a depolarizing element 1. When the retardation was measured according to the measurement method described above, the in-plane retardation Re of the depolarization element 1 was 10404 nm, and the difference ΔR between the in-plane retardation Re and the retardation in the oblique direction was 174 nm. By bonding a linear polarizing plate to the depolarizing element 1 via an adhesive, an optical laminate of Example 1, including the depolarizing element and the polarizing element, was obtained.

[0076] [Examples 2-5, Comparative Example 1] <Fabrication of optical laminates> Using the number of layers listed in Table 2 and the phase difference films listed in Table 2, a phase difference layer was transferred and laminated in the same manner as in Example 1 to produce a depolarizing element. Then, a polarizing element was laminated to the obtained depolarizing element in the same manner as in Example 1 to produce the optical laminates of Examples 2 to 5 and Comparative Example 1.

[0077] For the depolarization elements fabricated in Examples 1-5 and Comparative Example 1, the in-plane retardation Re and diagonal retardation were measured according to the measurement method described above, and the difference ΔR between the in-plane retardation Re and the diagonal retardation, and the ratio of the difference ΔR to the in-plane retardation Re (ΔR / Re) were calculated. Table 2, shown below, shows the respective values ​​obtained through measurement and calculation.

[0078] ≪Evaluation Test 1: Evaluation of Optical Laminates≫ The optical laminates obtained in Examples 1-5 and Comparative Example 1 were visually evaluated for blackout and color unevenness using the method described below. The evaluation results are shown in Table 2.

[0079] <Evaluation Method for Blackout Suppression> The blackout suppression effect was evaluated using the following method. An Apple iMac® (Retina 5K, 27-inch, 2019), a liquid crystal display that emits linearly polarized light, was prepared, and white was displayed across the entire screen. The displayed image was then observed visually through each optical stack. The optical stack was positioned 30 cm away from the center of the liquid crystal display screen in the direction normal to the screen, with the depolarization element facing the liquid crystal display and the polarizing element facing the observer. In this state, the optical stack was rotated in the plane from 0 to 180 degrees, and the blackout suppression effect was evaluated according to the following evaluation criteria. (Evaluation criteria for blackout suppression) A: It won't black out. B: It blacks out.

[0080] <Method for evaluating color unevenness> The following method was used to evaluate color unevenness. An Apple iMac® (Retina 5K, 27-inch, 2019), a liquid crystal display that emits linearly polarized light, was prepared, and white was displayed across the entire screen. The displayed image was then observed visually through each optical layer. The optical layers of the liquid crystal display were positioned 30 cm away from the center of the screen in the direction normal to the liquid crystal display, with the depolarization element facing the liquid crystal display and the polarizing element facing the observer. The entire screen was observed in this state, and the level of color unevenness was evaluated based on the changes in color depending on the position of the screen observed, according to the following evaluation criteria. (Evaluation criteria for color unevenness) A: No change in color is visible. B: A slight change in color is visible. C: A change in color is visible, but it is within an acceptable range. D: The change in color is clearly visible as uneven coloring.

[0081] [Table 2]

[0082] As shown in the table above, in the optical laminate of Comparative Example 1, where the difference ΔR between the in-plane retardation Re and the diagonal retardation of the depolarization element is 500 nm or more, it was confirmed that clear color unevenness was visible. On the other hand, in the optical laminates of Examples 1 to 5, where the in-plane retardation Re of the depolarization element is 3000 to 100000 nm and the difference ΔR is less than 500 nm, it was confirmed that blackout was suppressed and the change in color was within acceptable limits.

[0083] From a comparison of Examples 1 to 5, it was confirmed that in the optical laminate according to the first embodiment of the present invention, when the ratio of the difference ΔR to the in-plane retardation Re of the depolarization element (ΔR / Re) is 0.0150 or less, the effect of suppressing color unevenness is superior.

[0084] [Example 11] <Fabrication of Phase Difference Element 1 (Positive C Plate)> (Preparation of a temporary support) The following composition was placed in a mixing tank, stirred, and then heated at 90°C for 10 minutes. The resulting composition was then filtered through filter paper with an average pore size of 34 μm and a sintered metal filter with an average pore size of 10 μm to prepare a dope. The solid content concentration of the dope was 23.5% by mass, the amount of plasticizer added was a ratio to the cellulose acylate, and the solvent of the dope was methylene chloride / methanol / butanol = 81 / 18 / 1 (by mass).

[0085] ------------------------------------------------------------------ Cellulose acylate dope ------------------------------------------------------------------ • Cellulose acylate (Acetyl substitution degree 2.86, viscosity-average degree of polymerization 310) 100 parts by mass • Sugar ester compound 1 (formula (S4) below): 6.0 parts by mass • Sugar ester compound 2 (formula (S5) below): 2.0 parts by mass • Silica particle dispersion (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd.) 0.1 parts by mass • Solvent (methylene chloride / methanol / butanol) 351.9 parts by mass ------------------------------------------------------------------

[0086] [ka]

[0087] [ka]

[0088] The dope prepared as described above was cast using a drum film-forming machine. The dope was cast from the die so that it was in contact with a metal support cooled to 0°C, and then the resulting web (film) was peeled off the drum. The drum was made of SUS (stainless steel).

[0089] After the casting process, the resulting web (film) was peeled from the drum and dried for 20 minutes in a tenter device at 30-40°C during film transport, with clips holding both ends of the web in place. Subsequently, the web was further dried by zone heating while being transported on a roll. The resulting web was then knurled and wound up to form cellulose acylate film A1. The obtained cellulose acylate film A1 had a thickness of 60 μm, an in-plane retardation Re(550) at a wavelength of 550 nm of 1 nm, and a thickness-direction retardation Rth(550) at a wavelength of 550 nm of 35 nm.

[0090] (Fabrication of a positive C-plate layer) The cellulose acylate film A1 described above was used as a temporary support. Cellulose acylate film A1 is passed through a dielectric heating roll at a temperature of 60°C to raise the surface temperature of the film to 40°C. Then, an alkaline solution with the composition shown below is applied to one side of the film using a bar coater at a rate of 14 mL / m². 2 The material was applied, heated to 110°C, and then transported for 10 seconds under a steam-type far-infrared heater manufactured by Noritake Co., Limited. Next, using the same bar coater, pure water is applied to the film at a rate of 3 mL / m². 2 The film was then coated. Next, after repeating the process of rinsing with a fountain coater and removing the water with an air knife three times, the film was transported to a 70°C drying zone for 10 seconds to dry, thereby producing an alkali-saponified cellulose acylate film A1.

[0091] ------------------------------------------------------------------ (Alkaline solution) ------------------------------------------------------------------ • Potassium hydroxide 4.7 parts by mass ·Water 15.8 parts by mass Isopropanol 63.7 parts by mass Fluorine-containing surfactant SF-1 (C 14 H 29 O(CH2CH2O) 20 H) 1.0 parts by mass • Propylene glycol 14.8 parts by mass ------------------------------------------------------------------

[0092] A coating solution G1 for forming an orientation film, having the composition described below, was continuously applied to the alkali-saponified cellulose acylate film A1 using a #8 wire bar. The resulting film was dried with 60°C hot air for 60 seconds, and then with 100°C hot air for 120 seconds to form the orientation film G1.

[0093] ------------------------------------------------------------------ Orientation film forming coating solution G1 ------------------------------------------------------------------ • Polyvinyl alcohol (manufactured by Kuraray, PVA103) 2.4 parts by mass • Isopropyl alcohol 1.6 parts by mass • Methanol 36 parts by mass ·Water 60 parts by mass ------------------------------------------------------------------

[0094] A coating solution H1 for forming positive C plates, with the composition described below, is applied onto the orientation film G1. The resulting coating film is then aged at 60°C for 60 seconds, followed by exposure to air at 70 mW / cm². 2 Using an air-cooled metal halide lamp (manufactured by iGraphics Co., Ltd.), 1000 mJ / cm² 2 By irradiating with ultraviolet light to fix its orientation, the liquid crystal compound was vertically oriented, and a transfer film having a 1.0 μm thick positive C plate H1 and a temporary support was fabricated. The obtained transfer film was bonded to the glass plate via an adhesive so that the coated surface of the positive C plate H1 faced the glass plate, and the temporary support cellulose acylate film A1 was peeled off to obtain a laminate having the glass plate / adhesive / positive C plate H1 in this order. The Rth(550) of the positive C plate in the obtained laminate was -125 nm. The series of steps of bonding the transfer film to the positive C plate H1 side of the obtained laminate via an adhesive and peeling off the temporary support was repeated to transfer eight positive C plates H1 to obtain a phase difference element 1 which is a positive C plate. The Rth of the obtained phase difference element 1 was -1000 nm.

[0095] ------------------------------------------------------------------ Coating solution H1 for forming positive C plates ------------------------------------------------------------------ • 80 parts by mass of the following liquid crystal compound LC-1 • 20 parts by mass of the following liquid crystal compound LC-2 • 1 part by mass of the following vertically oriented liquid crystal compound facilitator S01 • Ethylene oxide modified trimethylolpropane triacrylate (V#360, manufactured by Osaka Organic Chemical Co., Ltd.) 8 parts by mass • IrgaCure 907 (BASF) 3 parts by mass • Kayacure DETX (manufactured by Nippon Kayaku Co., Ltd.) 1 part by mass • Compound B03 (listed below): 0.4 parts by mass • Methyl ethyl ketone 170 parts by mass • Cyclohexanone 30 parts by mass ------------------------------------------------------------------

[0096] Liquid crystal compound LC-1 [ka]

[0097] Liquid crystal compound LC-2 [ka]

[0098] Vertically oriented liquid crystal compound targeting agent S01 [ka]

[0099] Compound B03 (weight average molecular weight: 15000) (In the formula below, the numerical values ​​listed for each repeating unit represent the mass percentage of each repeating unit relative to the total number of repeating units.) [ka]

[0100] <Fabrication of optical laminates> Using the same method as in Example 1, a phase difference film 2 was used to transfer and laminate a rod-shaped liquid crystal layer 1 onto a glass plate so that the number of laminated rod-shaped liquid crystal layers 1 was 10. A polarizing element 11 was then laminated using the same method as in Example 1 to obtain a depolarizing element 11. The in-plane retardation Re of the obtained depolarizing element 11 was 10,000 nm. The phase difference element 1 obtained above and the linear polarizing plate as a polarizing element were bonded to this depolarizing element 11 in that order via an adhesive to obtain the optical laminate of Example 11.

[0101] [Examples 12-13, Comparative Example 11] <Fabrication of optical laminates> Using the number of layers listed in Table 3 and the phase difference films listed in Table 3, a depolarizing element was fabricated by transferring and laminating the phase difference layer in the same manner as in Example 11. Then, the optical laminates of Examples 12-13 and Comparative Example 11 were fabricated by laminating the resulting depolarizing element with the phase difference element 1 and the polarizing element in the same manner as in Example 11.

[0102] For the composites containing the depolarizing element and the phase difference element before bonding the polarizing element, which were fabricated in Examples 11-13 and Comparative Example 11, the in-plane retardation Re and the diagonal retardation were measured according to the measurement method described above, and the difference ΔR between the in-plane retardation Re and the diagonal retardation, and the ratio of the difference ΔR to the in-plane retardation Re (ΔR / Re) were calculated. Table 3, shown below, shows the respective values ​​obtained through measurement and calculation.

[0103] The optical laminates obtained in Examples 11-13 and Comparative Example 11 were visually evaluated for blackout and color unevenness using the method described in Evaluation Test 1. The evaluation results are shown in Table 3.

[0104] [Table 3]

[0105] As shown in the table above, in the optical laminates of Comparative Examples 1 and 11, where the difference ΔR between the in-plane retardation Re and the diagonal retardation of the composite was 500 nm or more, it was confirmed that clear color unevenness was visible. On the other hand, in the optical laminates of Examples 1-5 and 11-13, where the in-plane retardation Re of the depolarization element or composite was 3000-100000 nm and the difference ΔR was less than 500 nm, it was confirmed that blackout was suppressed and the change in color was within acceptable limits.

[0106] From a comparison of Examples 11-13, it was confirmed that when the ratio of the difference ΔR to the in-plane retardation Re (ΔR / Re) is 0.0150 or less, the effect of suppressing color unevenness is superior.

[0107] ≪Evaluation 2: Evaluation of Near-Eye Displays≫ For each example and comparative example, a near-eye display having an optical laminate was fabricated by following the same procedure as for each example and comparative example, except that the depolarization element fabricated in each example (a composite including a polarizing element and a phase difference element 1 in the case of Examples 11-13 and Comparative Example 11) was bonded to AR glasses (XREAL Air2 Pro, manufactured by XREAL Inc.) used as a polarizing element instead of a linear polarizer. It was confirmed that these AR glasses have the properties of a circular polarizer that cuts the left circularly polarized component of ambient light and transmits the right circularly polarized component. We observed a solid white image displayed on an image display device (Apple's "iPad® Pro," 2021 model, 11-inch, using an LCD display) through a fabricated near-eye display. We confirmed that this image display device mainly emits left-circular polarization. Therefore, when observing the image displayed on the image display device through the AR glasses without the optical stacking in each example, the image blacked out. The observation tests described above, which involved observing images displayed on the image display device using the AR glasses having the optical laminates of each example or comparative example, confirmed that the same evaluation results as in Tables 2 and 3 were obtained for both blackout and color unevenness. [Explanation of symbols]

[0108] 1 Optical laminate 2 complex 11. Depolarizing element 12 Polarizing elements 13 Phase difference element

Claims

1. An optical laminate comprising a depolarizing element and a polarizing element, The in-plane retardation Re in the normal direction at a wavelength of 550 nm of the aforementioned depolarization element is 3000 to 100000 nm. The difference ΔR between the in-plane retardation Re and the diagonal retardation of the depolarization element, where the angle from the normal direction at a wavelength of 550 nm is 30°, is less than 500 nm. Optical laminate.

2. The optical laminate according to claim 1, wherein the depolarization element includes a phase difference film having negative birefringence and a phase difference film having positive birefringence.

3. The optical laminate according to claim 1, wherein the depolarization element includes a positive A plate and a negative A plate.

4. The optical laminate according to claim 1, wherein the ratio of the difference ΔR to the in-plane retardation Re is 0.1000 or less.

5. An optical laminate comprising a polarization depolarization element, a phase difference element, and a polarizing element, The composite including the depolarization element and the phase difference element has an in-plane retardation Re in the normal direction at a wavelength of 550 nm of 3,000 to 100,000 nm. The difference ΔR between the in-plane retardation Re and the oblique retardation of the composite, where the angle from the normal direction at a wavelength of 550 nm is 30°, is less than 500 nm. Optical laminate.

6. The optical laminate according to claim 5, wherein the depolarization element includes a phase difference film having negative birefringence and a phase difference film having positive birefringence.

7. The optical laminate according to claim 5, wherein the depolarization element includes a positive A plate and a negative A plate.

8. The optical laminate according to claim 5, wherein the ratio of the difference ΔR to the in-plane retardation Re is 0.1000 or less.

9. The optical laminate according to claim 5, wherein the phase difference element is a positive C plate.

10. The optical laminate according to claim 9, wherein the retardation Rth in the thickness direction of the positive C plate at a wavelength of 550 nm is -100 to -3000 nm.

11. A near-eye display having an optical laminate according to any one of claims 1 to 10.

Images