Lens, image display device, and virtual reality display device

Abstract

The present invention provides: a lens and an image display device in which ghosting is suppressed when applied to a virtual reality display device using a pancake lens; and a virtual reality display device in which ghosting is suppressed. A lens according to the present invention which has a retardation layer for converting circularly polarized light into linearly polarize light, wherein: said retardation layer includes a first optically anisotropic layer and a second optically anisotropic layer; the first optically anisotropic layer and the second optically anisotropic layer have reverse wavelength dispersibility; and at least one layer among the first optically anisotropic layer and the second optically anisotropic layer is a layer obtained by immobilizing a twist-oriented liquid crystal compound having a helical axis in the thickness direction. An image display device according to the present invention has an image display panel, an absorption-type polarizer, and said retardation layer, in this order. A virtual reality display device according to the present invention has said lens or said image display device.

Description

Lens, image display device, and virtual reality display device

[0001] The present invention relates to a lens, an image display device, and a virtual reality display device.

[0002] A virtual reality display device is a display device that allows a user to feel as if they are immersed in a virtual world by wearing a dedicated headset and viewing images displayed through a compound lens. While a known virtual reality display device includes an image display device and a Fresnel lens, the distance between the image display device and the Fresnel lens is large, resulting in a thick headset and poor wearability. To address this issue, as described in Patent Documents 1 and 2, a compound lens configuration called a pancake lens has been proposed, which includes an image display device, a half mirror, a retardation layer, and a reflective polarizer, and reduces the overall thickness of the headset by directing light emitted from the image display device back and forth between the half mirror and the reflective polarizer.

[0003] Here, a reflective polarizer is a polarizer that reflects one polarized light and transmits the other polarized light of incident light. For example, the reflected light and transmitted light of a reflective linear polarizer are linearly polarized light with orthogonal polarization states. On the other hand, the reflected light and transmitted light of a reflective circular polarizer are circularly polarized light with one rotation direction and circularly polarized light with the opposite rotation direction.

[0004] Known examples of reflective linear polarizers that produce linearly polarized transmitted and reflected light include stretched dielectric multilayer films and wire grid polarizers. Also, known examples of reflective circular polarizers that produce circularly polarized transmitted and reflected light include cholesteric liquid crystal layers having a light-reflecting layer in which a cholesteric liquid crystal phase is fixed.

[0005] JP 2020-519964 A U.S. Patent No. 10,394,040

[0006] Patent Document 1 discloses a virtual reality display device having a pancake lens in which an image display device, a half mirror, a first retardation layer, and a reflective linear polarizer are arranged in this order to obtain a wide field of view, low chromatic aberration, low distortion, and an excellent MTF (modulation transfer function). It also discloses a configuration in which a second retardation layer is provided on the surface of the image display device.

[0007] The present inventors created a virtual reality display device with a pancake lens with reference to Patent Document 1 and other documents, and after conducting detailed studies of its performance, found that there was room for further improvement in the prevention of ghosts (double images) caused by leaked light. The present invention was made in light of the above-mentioned problems, and the problem to be solved by the present invention is to provide an image display device and a lens that, when applied to a virtual reality display device using a pancake lens, suppresses the occurrence of ghosts. Another problem to be solved by the present invention is to provide a virtual reality display device in which the occurrence of ghosts is suppressed.

[0008] The present inventors have conducted extensive research into the above-mentioned problems and have found that the above-mentioned problems can be solved by the following configuration.

[0009] [1] A lens having a retardation layer that converts circularly polarized light into linearly polarized light, the retardation layer including a first optically anisotropic layer and a second optically anisotropic layer, the first optically anisotropic layer and the second optically anisotropic layer having reverse wavelength dispersion, and at least one of the first optically anisotropic layer and the second optically anisotropic layer being a layer containing a liquid crystal compound fixed in a twisted alignment with the thickness direction as a helical axis. [2] The lens according to [1], wherein the first optically anisotropic layer and the second optically anisotropic layer are both layers containing a liquid crystal compound fixed. [3] The lens according to [2], wherein the alignment direction of the liquid crystal compound contained in the first optically anisotropic layer and the alignment direction of the liquid crystal compound contained in the second optically anisotropic layer are continuous at the interface between the first optically anisotropic layer and the second optically anisotropic layer. [4] The lens according to any one of [1] to [3], wherein the first optically anisotropic layer is a positive A plate, and the second optically anisotropic layer is a layer formed by fixing a liquid crystal compound that is twistedly aligned with a helical axis in the thickness direction. [5] The lens according to any one of [1] to [3], wherein the first optically anisotropic layer and the second optically anisotropic layer are both layers formed by fixing a liquid crystal compound that is twistedly aligned with a helical axis in the thickness direction, and the helical pitch of the first optically anisotropic layer is different from the helical pitch of the second optically anisotropic layer. [6] The lens according to any one of [1] to [5], further comprising a reflective linear polarizer. [7] The lens according to any one of [1] to [5], further comprising a reflective circular polarizer. [8] The lens according to [7], wherein the reflective circular polarizer has a cholesteric liquid crystal layer. [9] The lens according to any one of [6] to [8], further comprising an absorptive polarizer.

[10] A virtual reality display device having an image display device and the lens according to any one of [1] to [3].

[11] An image display device having, in this order, an image display panel, an absorptive polarizer, and a retardation layer that converts circularly polarized light into linearly polarized light, wherein the retardation layer includes a first optically anisotropic layer and a second optically anisotropic layer, the first optically anisotropic layer and the second optically anisotropic layer have reverse wavelength dispersion, and at least one of the first optically anisotropic layer and the second optically anisotropic layer is a layer formed by fixing a liquid crystal compound that is twisted and aligned with a helical axis in the thickness direction.

[12] The image display device according to

[11] , wherein the first optically anisotropic layer and the second optically anisotropic layer are both layers formed by fixing a liquid crystalline compound.

[13] The image display device according to

[12] , wherein the alignment direction of the liquid crystalline compound contained in the first optically anisotropic layer and the alignment direction of the liquid crystalline compound contained in the second optically anisotropic layer are continuous at the interface between the first optically anisotropic layer and the second optically anisotropic layer.

[14] The image display device according to any one of

[11] to

[13] , wherein the first optically anisotropic layer is a positive A plate, and the second optically anisotropic layer is a layer formed by fixing a liquid crystalline compound that is twisted and aligned with a helical axis in the thickness direction.

[15] The image display device according to any one of

[11] to

[14] , wherein the first optically anisotropic layer and the second optically anisotropic layer are both layers formed by fixing a liquid crystal compound that is twisted and aligned with a helical axis in the thickness direction, and the helical pitch of the first optically anisotropic layer is different from the helical pitch of the second optically anisotropic layer.

[16] A virtual reality display device comprising a lens and the image display device according to any one of

[11] to

[13] .

[17] A virtual reality display device comprising the lens according to any one of [1] to [3] and the image display device according to any one of

[11] to

[13] .

[0010] According to the present invention, it is possible to provide an image display device and a lens that suppress the occurrence of ghosts when applied to a virtual reality display device using a pancake lens. Also, according to the present invention, it is possible to provide a virtual reality display device in which the occurrence of ghosts is suppressed.

[0011] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, and that the invention is not limited to the disclosed general description, and that the invention is not limited to the disclosed general description.

[0012] The present invention will be described in detail below. The following description of the constituent elements may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0013] In addition, the terms "liquid crystal composition" and "liquid crystal compound" in this specification also include, as a concept, those that no longer exhibit liquid crystallinity due to curing or the like.

[0014] The present invention will be described in detail below with reference to the drawings. The following description of the components may be based on representative embodiments or specific examples, but the present invention is not limited to such embodiments. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0015] In this specification, "orthogonal" does not mean an angle of exactly 90°, but means 90°±10°, preferably 90°±5°. "Parallel" does not mean an angle of exactly 0°, but means 0°±10°, preferably 0°±5°. "45°" does not mean an angle of exactly 45°, but means 45°±10°, preferably 45°±5°.

[0016] In this specification, "absorption axis" refers to the polarization direction in which absorbance is maximized in a plane when linearly polarized light is incident. "Reflection axis" refers to the polarization direction in which reflectance is maximized in a plane when linearly polarized light is incident. "Transmission axis" refers to the direction perpendicular to the absorption axis or reflection axis in a plane. "Slow axis" refers to the direction in which refractive index is maximized in a plane.

[0017] In this specification, unless otherwise specified, phase difference means in-plane retardation, and is referred to as Re(λ). Here, Re(λ) represents the in-plane retardation at wavelength λ, and unless otherwise specified, wavelength λ is 550 nm. Furthermore, in this specification, retardation in the thickness direction at wavelength λ is referred to as Rth(λ). Unless otherwise specified, wavelength λ is 550 nm. Re(λ) and Rth(λ) can be values ​​measured at wavelength λ using, for example, an AxoScan OPMF-1 (manufactured by OptoScience). By inputting the average refractive index ((nx + ny + nz) / 3) and film thickness (d (μm)) into AxoScan, the following can be calculated: slow axis orientation (°), Re(λ) = R0(λ), and Rth(λ) = ((nx + ny) / 2 - nz) × d. Note that R0(λ) is displayed as a numerical value calculated by AxoScan, but it means Re(λ).

[0018] In this specification, the terms "in-plane retardation" and "slow axis" refer to the in-plane retardation value calculated from the change in polarization state for a specific polarized light, and the slow axis azimuth calculated in a similar manner. Specifically, the in-plane retardation and slow axis can be determined as follows. Specifically, using a KOBRA (registered trademark) 21ADH or WR (manufactured by Oji Scientific Instruments Co., Ltd.), linearly polarized light with a wavelength of λ nm is incident on the optical film in the normal direction, and the transmitted light intensity of the light transmitted through the optical film is measured through an analyzer (a linear polarizer arranged at a specific angle). The in-plane retardation and slow axis azimuth of the optical film are obtained by simulating the transmitted light intensity measured by varying the relative angles of the optical film and the analyzer with respect to the azimuth of the incident linearly polarized light. The measurement wavelength λ nm can be selected by manually changing the wavelength selection filter or by converting the measured value using a program or the like. Unless otherwise specified, the measurement wavelength is λ = 550 nm. This measurement method makes it possible to measure the in-plane retardation value and slow axis direction at each position in the plane of a composite retardation plate whose optical retardation effect changes depending on the incident polarized light.

[0019] The lens according to a first embodiment of the present invention includes a retardation layer that converts circularly polarized light into linearly polarized light, and the retardation layer is a specific retardation layer described below. The image display device according to a second embodiment of the present invention includes an image display panel, an absorptive polarizer, and a retardation layer that converts circularly polarized light into linearly polarized light, in this order, and the retardation layer is a specific retardation layer described below. The virtual reality display device according to a third embodiment of the present invention includes a lens having a retardation layer that converts circularly polarized light into linearly polarized light, and an image display device having a retardation layer that converts circularly polarized light into linearly polarized light, and at least one of the retardation layer of the lens and the retardation layer of the image display device is a specific retardation layer described below. In the virtual reality display device according to the third embodiment, it is preferable that the lens is the lens according to the first embodiment, or the image display device is the image display device according to the second embodiment, and it is more preferable that the virtual reality display device includes both the lens according to the first embodiment and the image display device according to the second embodiment. The above-mentioned "specific retardation layer" means a retardation layer that converts circularly polarized light into linearly polarized light, and includes a first optically anisotropic layer and a second optically anisotropic layer, wherein the first optically anisotropic layer and the second optically anisotropic layer have reverse wavelength dispersion, and at least one of the first optically anisotropic layer and the second optically anisotropic layer is a layer in which a liquid crystal compound is fixed that is twisted and aligned with the thickness direction as the helical axis.

[0020] FIG. 1 schematically illustrates an example of the configuration of a virtual reality display device according to the present invention. The virtual reality display device 1 illustrated in FIG. 1 includes a lens 2 and an image display device 3. The lens 2 includes a reflective linear polarizer 21, a first retardation layer 22, a lens substrate 23, and a half mirror 24, in this order. The image display device 3 includes a second retardation layer 31, an absorptive polarizer 32, and an image display panel 33. In the virtual reality display device 1 illustrated in FIG. 1, both the first retardation layer 22 and the second retardation layer 31 are specific retardation layers. That is, the lens 2 illustrated in FIG. 1 is an example of the configuration of a lens according to a first embodiment of the present invention, the image display device 3 is an example of the configuration of an image display device according to a second embodiment of the present invention, and the virtual reality display device 1 is an example of the configuration of a virtual reality display device according to a third embodiment of the present invention, in which the retardation layers of the lens and the image display device are both specific retardation layers.

[0021] To explain the operation of each embodiment of the present invention, FIG. 2 schematically shows an example of the configuration of a conventional virtual reality display device. The virtual reality display device 1000 shown in FIG. 2 includes, from the left side of the figure, a reflective linear polarizer 100, a first retardation layer 200, a lens substrate 600, a half mirror 300, a second retardation layer 400, and an image display device 500. The virtual reality display device 1000 folds light rays using the following mechanism, thereby reducing the overall thickness of the headset. Specifically, a light ray 10, which is a portion of the light rays emitted from the image display device 500, is converted into circularly polarized light by the second retardation layer 400, passes through the half mirror 300, and is further converted into linearly polarized light by the first retardation layer 200. The light ray 10 then enters the reflective linear polarizer 100 and is reflected. The light ray 10 then passes through the first retardation layer 200 again, is converted into circularly polarized light, and is reflected by the half mirror 300. At this time, the light ray 10 is converted into circularly polarized light that is opposite in direction to the circular polarization when it entered the half mirror 300. The light ray 10 reflected by the half mirror 300 is further transmitted through the first retardation layer 200, converted into linearly polarized light, and then enters the reflective linear polarizer 100. At this time, the light ray entering the reflective linear polarizer 100 is in a polarization state that is orthogonal to the polarization state when it entered the reflective linear polarizer 100 the first time, so the light ray 10 passes through the reflective linear polarizer 100 and reaches the user's eye. In this way, the virtual reality display device 1000 can reduce the overall thickness of the headset by folding back the light ray 10 between the half mirror 300 and the reflective linear polarizer 100.

[0022] First, the operation of an image display device according to a second embodiment of the present invention and the operation of a virtual reality display device according to a third embodiment of the present invention, in which the second retardation layer of the image display device is a specific retardation layer, will be described. According to the inventors' investigations, as shown in FIG. 3 , in a conventional virtual reality display device 1000, a portion of the light beams (light beams 11) emitted from the image display device 500 may be emitted without being reflected between the half mirror 300 and the reflective linear polarizer 100, resulting in a visual appearance of a ghost image. The inventors believe that this is because, among the light beams emitted from the image display device 500, light beams falling within a certain wavelength range may not be converted into completely linearly polarized light but may become elliptically polarized light when they pass through the second retardation layer 400, the half mirror 300, and then the first retardation layer 200. The reason why the light passing through the retardation layer 200 becomes elliptically polarized light is considered to be that the in-plane retardation (Re) of the first retardation layer 200 and the second retardation layer 400 is different from each other, or that the slow axis directions of the first retardation layer 200 and the second retardation layer 400 are not orthogonal to each other.

[0023] In contrast, the image display device 3 according to the second embodiment of the present invention includes a second retardation layer 31, which is a specific retardation layer, in addition to the absorptive polarizer 32 and the image display panel 33. As will be described later, the specific retardation layer is a retardation layer that can achieve a λ / 4 phase difference in in-plane retardation over a wide wavelength range of visible light. Therefore, the second retardation layer 31 can convert linearly polarized light into circularly polarized light and circularly polarized light into linearly polarized light over a wide wavelength range of visible light. In the image display device 3 having such a second retardation layer 31, the light ray 10 emitted from the image display panel 33 and transmitted through the absorptive polarizer 32, the second retardation layer 31, and the half mirror 24 becomes ideal circularly polarized light over a wide wavelength range in the visible range. Therefore, it is possible to reduce the light ray (light ray 11 shown in FIG. 3) that is emitted without traveling back and forth between the reflective linear polarizer 21 and the half mirror 24 and causes a ghost image. Furthermore, the light beam that passes through the half mirror 24 for the first time and reaches the first retardation layer 22 is ideally circularly polarized light over a wide wavelength range of visible light and does not have a polarization axis. Therefore, when assembling the lens 2 having the reflective linear polarizer 21 and the first retardation layer 22, ghost images do not increase even if the slow axis orientation of the first retardation layer 22 is not orthogonal to the slow axis orientation of the second retardation layer 31. That is, when manufacturing the virtual reality display device 1 using the image display device 3 according to the second embodiment, strict angle adjustment is not required when assembling the lens 2, which can significantly simplify the lens assembling process and further contribute to reducing the manufacturing cost of the virtual reality display device.

[0024] Next, the operation of the lens according to the first embodiment of the present invention and the operation of the virtual reality display device according to the third embodiment of the present invention, in which the first retardation layer of the lens is a specific retardation layer, will be described. According to the inventors' investigations, as shown in FIG. 4, in the conventional virtual reality display device 1000, a portion of the light beam (light beam 12) emitted from the image display device 500 may travel back and forth between the half mirror 300 and the reflective linear polarizer 100 two or more times, resulting in a visual appearance of a ghost image. The inventors believe that this is because, among the light beams (linearly polarized light) reflected by the reflective linear polarizer 100, light beams falling within a certain wavelength range are not converted into completely circularly polarized light but become elliptically polarized light when passing through the first retardation layer 200. If the light ray emitted from the first retardation layer 200 is elliptically polarized light, the light ray is reflected by the half mirror 300 and transmitted through the first retardation layer 200 again, and contains a component parallel to the reflection axis of the reflective linear polarizer 100. Therefore, it is considered that the light ray is reflected by the reflective linear polarizer 100 again, and a light ray 12 is generated that repeats a round trip.

[0025] In contrast, the lens 2 according to the first embodiment of the present invention has a first retardation layer 22, which is a specific retardation layer. As will be described later, the specific retardation layer is a retardation layer that can achieve a λ / 4 phase difference in in-plane retardation over a wide wavelength range of visible light. Therefore, the first retardation layer 22 can convert linearly polarized light into ideal circularly polarized light and circularly polarized light into ideal linearly polarized light over a wide wavelength range of visible light. In the lens 2 having such a first retardation layer 22, the linearly polarized light reflected from the reflective linear polarizer 21 is converted into ideal circularly polarized light over a wide wavelength range of the visible range when it passes through the first retardation layer 22. Next, when reflected by the half mirror 24, the light is converted into circularly polarized light with a rotation opposite to that of the circularly polarized light when it entered the half mirror 24, but this also becomes ideal circularly polarized light. Furthermore, the light that passes through the first retardation layer 22 again is converted into ideal linearly polarized light and passes through the reflective linear polarizer 21 with high efficiency. That is, it is possible to reduce the number of light rays (light rays 12 shown in FIG. 4) that travel back and forth between the reflective linear polarizer 21 and the half mirror 24 two or more times, thereby suppressing the occurrence of ghost images.

[0026] <Specific Retardation Layer> The specific retardation layer used in each embodiment of the present invention will be described. The specific retardation layer has the function of converting the emitted light into linearly polarized light when circularly polarized light is incident, and has the function of converting the emitted light into circularly polarized light when linearly polarized light is incident. In order to realize these functions, the specific retardation layer preferably has an in-plane retardation of λ / 4 with respect to the wavelength λ of the incident light. In addition, a specific retardation layer having an in-plane retardation of 3 / 4×λ or 5 / 4×λ is also preferable because it can exhibit the same function.

[0027] The specific retardation layer includes at least a first optically anisotropic layer and a second optically anisotropic layer, wherein the first optically anisotropic layer and the second optically anisotropic layer have reverse wavelength dispersion, and at least one of the first optically anisotropic layer and the second optically anisotropic layer is a layer in which a liquid crystal compound is fixed in a twisted orientation with the thickness direction as the helical axis. By adopting such a configuration, the specific retardation layer can achieve an in-plane retardation of λ / 4 retardation over a wide wavelength range of visible light. That is, the specific retardation layer can convert linearly polarized light into ideal circularly polarized light and can convert circularly polarized light into ideal linearly polarized light over a wide wavelength range of visible light. Hereinafter, when referring to the characteristics common to both the first optically anisotropic layer and the second optically anisotropic layer of the specific retardation layer, the first optically anisotropic layer and the second optically anisotropic layer will not be distinguished from each other and will be simply referred to as "optically anisotropic layer". An optically anisotropic layer having reverse wavelength dispersion and having fixed therein a liquid crystal compound that is twisted and aligned with the thickness direction as the helical axis is also referred to as an "optically anisotropic layer RT."

[0028] In this specification, reverse wavelength dispersion refers to the property that, when measuring the in-plane retardation (Re) value at a specific wavelength (visible light range), the Re value increases as the measured wavelength increases. Preferably, the optically anisotropic layer satisfies Re(450) / Re(550)<1.00 and Re(650) / Re(550)>1.00. Optically anisotropic layers having reverse wavelength dispersion can be produced by uniaxially stretching a polymer film such as a modified polycarbonate resin film having reverse wavelength dispersion, for example, with reference to JP-A-2017-049574. In addition, optically anisotropic layers having reverse wavelength dispersion can also be produced by orienting and fixing a rod-shaped liquid crystal compound having reverse wavelength dispersion, for example, with reference to JP-A-2020-084070.

[0029] The optically anisotropic layer RT, which is formed by fixing a liquid crystal compound that is twist-oriented with the thickness direction as the helical axis, is preferably a layer formed by fixing a rod-shaped liquid crystal compound with reverse wavelength dispersion twist-oriented with the thickness direction as the helical axis, and the molecular axis of the rod-shaped liquid crystal compound is parallel to the surface of the optically anisotropic layer, i.e., a layer formed by fixing a chiral nematic phase having a helical structure. When forming the layer, it is preferable to use a mixture of a liquid crystal compound exhibiting a nematic liquid crystal phase and a chiral agent. In this specification, the term "molecular axis" refers to the long axis (molecular long axis) when the liquid crystal compound is a rod-shaped liquid crystal compound, and to the axis parallel to the normal direction to the discotic surface of the discotic liquid crystal compound when the liquid crystal compound is a discotic liquid crystal compound. In this specification, the term "fixed" refers to a state in which the orientation of the liquid crystal compound is maintained. Specifically, it is preferable that the layer has no fluidity and can stably maintain the fixed orientation state without causing any change in the orientation state due to an external field or external force, usually within a temperature range of 0 to 50°C, or under more severe conditions, within a temperature range of −30 to 70°C.

[0030] The specific retardation layer preferably has at least an optically anisotropic layer RT in which the twist angle of the liquid crystal compound (the twist angle of the alignment direction of the liquid crystal compound) is within the range of 85±20°. That is, the twist angle of at least one optically anisotropic layer RT of the specific retardation layer is preferably 65 to 105°, more preferably 75 to 95°, and even more preferably 80 to 90°. Here, the twisted alignment of the liquid crystal compound refers to the twisting of the liquid crystal compound from one main surface of the optically anisotropic layer to the other main surface of the optically anisotropic layer around the thickness direction of the optically anisotropic layer. Accordingly, the alignment direction of the liquid crystal compound (the in-plane slow axis direction) varies depending on the position in the thickness direction of the optically anisotropic layer. There are two types of twist direction, and either a right-handed twist or a left-handed twist is acceptable. The right-handed twist means that when observing from one main surface of the optically anisotropic layer toward the other main surface, the in-plane slow axis shifts clockwise relative to the in-plane slow axis of the main surface on the observer side, which serves as the reference axis, as one moves toward the opposite main surface. The twist angle is measured using an Axometrics AxoScan (polarimeter) device and its instrument analysis software. The twist angle of the liquid crystal compound can be appropriately adjusted by selecting the type of liquid crystal compound, controlling the temperature during alignment fixation, and the type and amount of chiral agent, etc.

[0031] In the specific retardation layer, it is preferable that both the first optically anisotropic layer and the second optically anisotropic layer are layers formed by fixing a liquid crystal compound. The liquid crystal compound can align liquid crystal molecules in any direction using an alignment film or the like, so that the manufacturing process of the specific retardation layer can be simplified.

[0032] In addition, in specific retardation layer, the alignment direction of the liquid crystal compound contained in the first optically anisotropic layer and the alignment direction of the liquid crystal compound contained in the second optically anisotropic layer are preferably continuous at the interface between the first optically anisotropic layer and the second optically anisotropic layer.With this configuration, the refractive index difference at the interface between the first optically anisotropic layer and the second optically anisotropic layer can be reduced, and interface reflection can be suppressed, so that the polarization state of the light passing through specific retardation layer due to interface reflection can be suppressed, and ghost images can be further reduced.In addition, in this specification, the alignment direction of the liquid crystal compound is continuous at the interface means that the in-plane slow axis of the surface of the first optically anisotropic layer side of the second optically anisotropic layer is parallel to the in-plane slow axis of the surface of the second optically anisotropic layer side of the first optically anisotropic layer. That is, when the alignment direction of the liquid crystal compound is continuous at the interface, the angle formed by the in-plane slow axis of the first optically anisotropic layer on the surface facing the second optically anisotropic layer and the in-plane slow axis of the second optically anisotropic layer on the surface facing the first optically anisotropic layer is within 10° (0 to 10°).

[0033] The specific retardation layer is preferably an optically anisotropic layer RT in which the first optically anisotropic layer is a positive A plate and the second optically anisotropic layer is an optically anisotropic layer RT in which a liquid crystal compound is fixed in a twisted orientation with the thickness direction as the helical axis.Here, the positive A plate is a retardation layer in which Re has a value and Rth has a value that is substantially half of Re.The positive A plate can be obtained, for example, by horizontally aligning a rod-shaped liquid crystal compound.The optically anisotropic layer RT, including preferred embodiments, is as described above.

[0034] In the specific retardation layer in which the first optically anisotropic layer is a positive A plate and the second optically anisotropic layer is an optically anisotropic layer RT, it is preferable that the product of the refractive index anisotropy Δn1 at a wavelength of 550 nm and the thickness d1 of the first optically anisotropic layer satisfies the following formula (1): 140 nm≦Δn1d1≦220 nm Formula (1) Furthermore, in the specific retardation layer in which the first optically anisotropic layer is a positive A plate and the second optically anisotropic layer is an optically anisotropic layer RT, it is preferable that the product of the refractive index anisotropy Δn2 at a wavelength of 550 nm and the thickness d2 of the second optically anisotropic layer satisfies the following formula (2): 150 nm≦Δn2d2≦230 nm Formula (2) Furthermore, it is preferable that the twist angle of the second optically anisotropic layer is 85±20°. When the first optically anisotropic layer and the second optically anisotropic layer have the above-mentioned configuration, the specific retardation layer can be a λ / 4 retardation layer in a wider wavelength range. For the retardation layer as described above, for example, the contents described in International Publication No. 2021 / 261435 can be referred to.

[0035] The Δn1d1 and Δn2d2 in the optically anisotropic layer are measured using an AxoScan (polarimeter) device manufactured by Axometrics, Inc., and the device analysis software of the same company, in the same manner as in the method for measuring the twist angle.

[0036] In addition, it is also preferable that the specific retardation layer is a layer (optically anisotropic layer RT) in which both the first optically anisotropic layer and the second optically anisotropic layer are fixed with a liquid crystal compound twist-oriented with the thickness direction as the helical axis. The optically anisotropic layer RT, including preferred embodiments, is as described above. When both the first optically anisotropic layer and the second optically anisotropic layer are optically anisotropic layers RT, the helical pitch of the first optically anisotropic layer and the helical pitch of the second optically anisotropic layer may be the same or different, but are preferably different. Here, the helical pitch of the optically anisotropic layer means the length in the thickness direction of one helical rotation (360° rotation) of the liquid crystal compound stacked in the optically anisotropic layer. The helical pitch of the optically anisotropic layer is calculated from the twist angle and thickness of the optically anisotropic layer using the following formula. Helical pitch (μm)=thickness (μm) / (twist angle (°) / 360) The helical pitch of the optically anisotropic layer can be adjusted by the twist angle of the liquid crystal compound and the thickness of the optically anisotropic layer.

[0037] When the first optically anisotropic layer and the second optically anisotropic layer are both optically anisotropic layers RT, it is preferable that the product of the refractive index anisotropy Δn1 and the thickness d1 at a wavelength of 550 nm of the first optically anisotropic layer satisfies the following formula (3): 252 nm ≦ Δn1d1 ≦ 312 nm. When the first optically anisotropic layer and the second optically anisotropic layer are both optically anisotropic layers RT, it is preferable that the twist angle of the first optically anisotropic layer is 26.5±10°. Furthermore, when the first optically anisotropic layer and the second optically anisotropic layer are both optically anisotropic layers RT, it is preferable that the product of the refractive index anisotropy Δn2 and the thickness d2 at a wavelength of 550 nm of the second optically anisotropic layer satisfies the following formula (4): Formula (4) 110 nm ≦ Δn2d2 ≦ 170 nm Furthermore, when both the first optically anisotropic layer and the second optically anisotropic layer are optically anisotropic layers RT, the twist angle of the second optically anisotropic layer is preferably 78.6 ± 10 °. When the first optically anisotropic layer and the second optically anisotropic layer have the above-mentioned configuration, the specific retardation layer can be a λ / 4 retardation layer in a wider wavelength range. For example, the retardation layer as described above can be referred to those disclosed in International Publication No. 2021 / 261435.

[0038] [Method for manufacturing specific retardation layer] (Manufacturing specific retardation layer by bonding each layer) The manufacturing method of the specific retardation layer is not particularly limited, and the specific retardation layer can be manufactured based on a known method. The specific retardation layer may be manufactured by manufacturing the first optically anisotropic layer and the second optically anisotropic layer in separate processes and then laminating them together. The lamination can be performed using an adhesive layer such as an adhesive or pressure-sensitive adhesive. From the viewpoint of suppressing interfacial reflection, it is preferable that the refractive index of the adhesive layer between each layer is adjusted to match the refractive index of the first optically anisotropic layer and the second optically anisotropic layer (refractive index matching). In addition, the thickness of the adhesive layer can be set to an appropriate thickness so as to suppress interfacial reflection with the first optically anisotropic layer and the second optically anisotropic layer.

[0039] Furthermore, from the viewpoint of suppressing interfacial reflection, it is also preferable that the thickness of the adhesive layer between each layer is 100 nm or less. When the thickness of the adhesive layer is 100 nm or less, light in the visible range does not sense a difference in refractive index, and unnecessary reflection can be suppressed. The thickness of the adhesive layer is more preferably 50 nm or less. Examples of methods for forming an adhesive layer having a thickness of 100 nm or less include a method of depositing a ceramic adhesive such as silicon oxide (SiOx layer) on the adhesive surface of the optically anisotropic layer. The adhesive surface of the optically anisotropic layer can be subjected to surface modification treatments such as plasma treatment, corona treatment, and saponification treatment before bonding, and a primer layer can be applied. Furthermore, when the optically anisotropic layer has multiple adhesive surfaces, the type and thickness of the adhesive layer can be adjusted for each adhesive surface.

[0040] Specifically, an adhesive layer having a thickness of 100 nm or less can be formed, for example, by the following steps (1) to (3): (1) The layer to be laminated is bonded to a temporary support made of a glass substrate. (2) SiOx layers having a thickness of 100 nm or less are formed on both the surface of the layer to be laminated and the surface of the layer to be laminated by vapor deposition or the like. Vapor deposition can be performed using, for example, a vapor deposition device (model number ULEYES) manufactured by ULVAC, Inc., using SiOx powder as the vapor deposition source. It is also preferable to subject the surface of the formed SiOx layer to plasma treatment. (3) After the formed SiOx layers are bonded together, the temporary support is peeled off. Bonding is preferably performed at a temperature of, for example, 120°C. The application of adhesives and pressure-sensitive adhesives to each layer, the formation of adhesive layers such as SiOx layers, and bonding can be performed by roll-to-roll or sheet-to-sheet. The roll-to-roll method is preferred from the viewpoints of improving productivity and reducing axial misalignment of each layer. On the other hand, the sheet-fed method is preferable because it is suitable for small-lot, high-mix production and because it allows the selection of a special adhesion method such as the one described above, where the thickness of the adhesive layer is 100 nm or less. Examples of methods for applying adhesives and pressure-sensitive adhesives to adherends include known methods such as roll coating, gravure printing, spin coating, wire bar coating, extrusion coating, direct gravure coating, reverse gravure coating, die coating, spraying, and inkjet printing.

[0041] (Production of a specific retardation layer by direct coating of each layer) It is also preferable that there is no adhesive layer between the first optically anisotropic layer and the second optically anisotropic layer. When forming one optically anisotropic layer, the optically anisotropic layer-forming composition is directly applied onto the other optically anisotropic layer that has already been formed, thereby producing a specific retardation layer that does not have an adhesive layer between the first optically anisotropic layer and the second optically anisotropic layer. Furthermore, when one or both of the adjacent layers contain a liquid crystal compound, the refractive index difference in all directions in the plane is reduced, further reducing ghosts. Therefore, it is preferable to form a specific retardation layer in which the alignment direction of the liquid crystal compound continuously changes at the interface between the first optically anisotropic layer and the second optically anisotropic layer. For example, by directly coating a composition for forming a second optically anisotropic layer containing a liquid crystal compound onto the first optically anisotropic layer containing a liquid crystal compound, the liquid crystal compound in the second optically anisotropic layer can be aligned so that the alignment direction of the liquid crystal compound in both layers is continuous at the interface due to the alignment regulating force of the liquid crystal compound in the first optically anisotropic layer.

[0042] (Production of specific retardation layer by one-liquid two-layer coating) In addition, the first optically anisotropic layer and the second optically anisotropic layer can be produced by coating the same forming composition, and then separating them into two layers by various methods, and making them the first optically anisotropic layer and the second optically anisotropic layer, respectively. For example, they can be produced by the following steps 1 to 5. Step 1: A polymerizable liquid crystal composition containing a chiral agent containing a photosensitive chiral agent whose helical twisting force changes upon irradiation with light, and a liquid crystalline compound having a reverse wavelength dispersion and a polymerizable group (hereinafter, in the description of steps 1 to 5, simply referred to as "liquid crystal compound"). A step of applying a polymerizable liquid crystal composition containing a polymerizable liquid crystal composition to a support to form a composition layer. Step 2: A step of subjecting the composition layer to a heat treatment to align the liquid crystalline compound in the composition layer. Step 3: After step 2, a step of irradiating the composition layer with light under conditions of an oxygen concentration of 1% by volume or more. Step 4: After step 3, a step of subjecting the composition layer to a heat treatment. Step 5: After step 4, a step of subjecting the composition layer to a curing treatment to fix the alignment state of the liquid crystalline compound, forming a first optically anisotropic layer and a second optically anisotropic layer. The production process of the retardation layer as described above can be referred to, for example, the steps disclosed in WO 2021 / 261435.

[0043] The shape of the specific retardation layer may be flat or curved. In the virtual reality display device, in order to correct the aberration of the displayed image and achieve a higher quality display, it is preferable that the surface shape of the lens substrate is curved, and in this case, it is preferable that the specific retardation layer is also curved to match the surface shape of the lens substrate.

[0044] The thickness of the specific retardation layer is not particularly limited, but is preferably thinner from the viewpoint of making the virtual reality display device thinner. On the other hand, it is preferable that the specific retardation layer has a predetermined thickness from the viewpoint of achieving desired optical performance. The thickness of the specific retardation layer is preferably 0.1 to 20 μm, more preferably 0.2 to 15 μm, and even more preferably 0.5 to 10 μm.

[0045] <Laminated Optical Body> The specific retardation layer may be laminated with other functional layers to form a laminated optical body. Examples of the other functional layers include polarizers such as a reflective linear polarizer, a reflective circular polarizer, and an absorptive polarizer. By laminating polarizers, various optical functions of a virtual reality display device can be integrated. This allows the laminated optical body to be attached to an image display device or a lens substrate in a single step, thereby reducing manufacturing costs. Examples of reflective linear polarizers that can be used include a film obtained by stretching a dielectric multilayer film and a wire grid polarizer. Examples of reflective circular polarizers that can be used include a reflective circular polarizer including a cholesteric liquid crystal layer. The cholesteric liquid crystal layer is a layer having a liquid crystal phase (cholesteric liquid crystal phase) in which the liquid crystal compound is in a cholesteric alignment state. Examples of reflective circular polarizers having a cholesteric liquid crystal layer include films obtained by curing a liquid crystal compound in a state exhibiting a cholesteric liquid crystal phase. The absorptive polarizer may be a polarizer made by stretching a polyvinyl alcohol film and impregnating it with an iodine complex, or a polarizer made by incorporating a dichroic dye into a stretched polymer or a uniformly oriented liquid crystal compound.

[0046] The laminated optical body is preferably a laminate having a specific retardation layer, a reflective linear polarizer or a reflective circular polarizer, and an absorptive polarizer. When the laminated optical body has a reflective linear polarizer, it is preferable that the absorptive polarizer, the reflective linear polarizer, and the specific retardation layer are arranged in this order, and when the laminated optical body has a reflective circular polarizer, it is preferable that the absorptive polarizer, the specific retardation layer, and the reflective circular polarizer are arranged in this order.

[0047] Furthermore, the laminated optical body may have a functional layer other than the polarizer for the purpose of further improving the optical effect. Examples of the functional layer include a positive C plate, an antireflection layer, an ultraviolet absorbing layer, and a hard coat layer. It is also preferable that the laminated optical body has a functional layer.

[0048] A positive C plate is a retardation layer having an Re of substantially zero and an Rth of a negative value. A positive C plate can be obtained, for example, by vertically aligning a rod-shaped liquid crystal compound. Details of the manufacturing method of a positive C plate can be found in, for example, JP 2017-187732 A, JP 2016-053709 A, and JP 2015-200861 A. The positive C plate functions as an optical compensation layer for increasing the degree of polarization of transmitted light with respect to obliquely incident light. The positive C plate can be installed at any position in the laminated optical body, and multiple positive C plates may be installed.

[0049] The positive C plate may be disposed adjacent to or within the specific retardation layer. For example, when a layer formed by immobilizing a rod-shaped liquid crystal compound is used as the specific retardation layer, the specific retardation layer has a negative Rth. In this case, when light is incident on the specific retardation layer from an oblique direction, the polarization state of the transmitted light may change due to the action of Rth, resulting in a decrease in the degree of polarization of the transmitted light. Having a positive C plate within or near the specific retardation layer is preferable because it can suppress changes in the polarization state of obliquely incident light and suppress a decrease in the degree of polarization of the transmitted light. The positive C plate is preferably disposed on the opposite side of the specific retardation layer from the reflective linear polarizer, but may also be disposed elsewhere. In this case, the Re of the positive C plate is preferably approximately 10 nm or less, and the Rth is preferably -120 nm to -20 nm, more preferably -90 to -40 nm.

[0050] [Support] The laminated optical body may further have a support. The support can be installed in any location. For example, when the specific retardation layer is a film to be transferred from a temporary support, the support can be used as the transfer destination. The type of support is not particularly limited, but it is preferably transparent. For example, films such as cellulose acylate, polycarbonate, polysulfone, polyethersulfone, polyacrylate and polymethacrylate, cyclic polyolefin, polyolefin, polyamide, polystyrene, and polyester can be used. Among them, cellulose acylate film, cyclic polyolefin film, polyacrylate film, and polymethacrylate film are preferred. Commercially available cellulose acetate films (for example, "TD80U" and "Z-TAC" manufactured by Fujifilm Corporation) can also be used. The support preferably has a small retardation from the viewpoint of suppressing the influence on the polarization degree of transmitted light and facilitating optical inspection of the laminated optical body. Specifically, the Re value is preferably 10 nm or less, and the absolute value of the Rth value is preferably 50 nm or less.

[0051] When the laminated optical body is to be stretched or molded, the support preferably has a tan δ peak temperature of 170° C. or less. From the viewpoint of enabling molding at low temperatures, the tan δ peak temperature is preferably 150° C. or less, and more preferably 130° C. or less.

[0052] Here, the method for measuring tan δ will be described. Using a dynamic viscoelasticity measuring device (DVA-200 manufactured by IT Measurement Control Co., Ltd.), E" (loss modulus) and E' (storage modulus) are measured under the following conditions for a film sample that has been previously conditioned for at least 2 hours in an atmosphere at a temperature of 25°C and a humidity of 60% Rh, and tan δ (= E" / E') is the value obtained. Device: DVA-200 manufactured by IT Measurement Control Co., Ltd. Sample: 5 mm, length 50 mm (gap 20 mm) Measurement conditions: tension mode Measurement temperature: -150°C to 220°C Heating conditions: 5°C / min Frequency: 1 Hz In general, in optical applications, resin substrates that have been subjected to a stretching treatment are often used, and the peak temperature of tan δ often becomes high due to the stretching treatment. For example, the peak temperature of tan δ for a TAC (triacetyl cellulose) substrate (TG40, manufactured by Fujifilm Corporation) is 180°C or higher.

[0053] As the support having a tan δ peak temperature of 170°C or less, various resin substrates can be used without any particular limitation. Examples include polyolefins such as polyethylene, polypropylene, and norbornene-based polymers; cyclic olefin-based resins; polyvinyl alcohol; polyethylene terephthalate; acrylic resins such as polymethacrylic acid esters and polyacrylic acid esters; polyethylene naphthalate; polycarbonate; polysulfone; polyethersulfone; polyether ketone; and polyphenylene sulfide and polyphenylene oxide. Among these, cyclic olefin-based resins, polyethylene terephthalate, and acrylic resins are preferred, and cyclic olefin-based resins and polymethacrylic acid esters are more preferred, in terms of easy commercial availability and excellent transparency.

[0054] Examples of commercially available resin substrates include Technolloy S001G, Technolloy S014G, Technolloy S000, Technolloy C001, and Technolloy C000 (Sumika Acrylic Sales Co., Ltd.), Lumirror U Type, Lumirror FX10, and Lumirror SF20 (Toray Industries, Inc.), HK-53A (Higashiyama Films Co., Ltd.), Teflex FT3 (Teijin DuPont Films Co., Ltd.), S-Cina and SCA40 (Sekisui Chemical Co., Ltd.), Zeonor Film (Optes Co., Ltd.), and Arton Film (JSR Corporation).

[0055] The thickness of the support is not particularly limited, but is preferably from 5 to 300 μm, more preferably from 5 to 100 μm, and even more preferably from 5 to 30 μm.

[0056] <Lens> The lens according to the first embodiment of the present invention is a compound lens having the specific retardation layer described above. The lens may have a lens substrate, and preferably has a lens substrate. The material of the lens substrate is preferably glass or transparent resin. The lens substrate preferably does not change the polarization state of light, and preferably has a retardation (Re and Rth) of zero.

[0057] The lens may have layers other than the specific retardation layer and the lens substrate. Examples of such layers include a half mirror, an antireflection layer, an ultraviolet absorbing layer, and a hard coat layer. Examples of the half mirror include a vapor-deposited film of a metal such as aluminum. The lens may further have at least one polarizer selected from the group consisting of a reflective linear polarizer, a reflective circular polarizer, and an absorptive polarizer. These polarizers may be included in the laminated optical body provided together with the specific retardation layer. Among these, a lens having a reflective linear polarizer or a reflective circular polarizer and an absorptive polarizer is preferred. When the reflective circular polarizer has a cholesteric liquid crystal layer, it is preferable that the absorbing polarizer, the specific retardation layer, and the reflective circular polarizer are arranged in this order.

[0058] Specific configuration examples of the lens according to the first embodiment are as follows: A lens having, in this order, a reflective linear polarizer, a first retardation layer which is a specific retardation layer, a lens substrate, and a half mirror. A lens having, in this order, an absorptive polarizer, a reflective linear polarizer, a first retardation layer which is a specific retardation layer, a lens substrate, and a half mirror. A lens having, in this order, a first retardation layer which is a specific retardation layer, a reflective linear polarizer, an absorptive polarizer, and a lens substrate. A lens having, in this order, a first retardation layer which is a specific retardation layer, and a lens substrate. A lens having, in this order, an absorptive polarizer, a first retardation layer which is a specific retardation layer, a reflective circular polarizer, a lens substrate, and a half mirror. A lens having, in this order, a reflective circular polarizer, a first retardation layer which is a specific retardation layer, an absorptive polarizer, and a lens substrate. Preferred aspects of the components included in the above configuration examples are as described above.

[0059] The shape of the lens substrate is not particularly limited, but it is preferable that at least one surface is curved. When the lens substrate has a curved surface, aberration of the displayed image can be corrected in the virtual reality display device, resulting in a higher quality display. The curved surface may be a part of a spherical surface or may be an aspherical surface. As the lens substrate, a convex lens, a concave lens, a meniscus lens, etc. can be used. As the convex lens, a biconvex lens, a plano-convex lens, and a convex meniscus lens can be used. As the concave lens, a biconcave lens, a plano-concave lens, and a concave meniscus lens can be used.

[0060] <Image Display Device> The image display device according to a second embodiment of the present invention includes, in this order, an image display panel, an absorptive polarizer, and the above-described specific retardation layer. Examples of image display panels include liquid crystal display panels, organic EL display panels, and micro LED display panels. The image display device according to this embodiment includes an image display panel and an absorptive polarizer disposed on the image display panel, and preferably further includes a specific retardation layer disposed on the outer side of the absorptive polarizer, i.e., on the surface from which light is emitted. This allows the image display device to emit ideal circularly polarized light.

[0061] The image display device according to this embodiment has at least an image display panel, an absorptive polarizer, and a specific retardation layer, in this order. A preferred embodiment of the specific retardation layer in this embodiment is the same as the specific retardation layer of the lens according to the first embodiment. In addition to the specific retardation layer, the image display device may also include known components for image display devices, such as an antireflection layer, an ultraviolet absorbing layer, and a hard coat layer.

[0062] <Virtual reality display device> A virtual reality display device according to a third embodiment of the present invention includes an image display device and a lens, and is characterized in that at least one of the retardation layer of the image display device and the retardation layer of the lens is a specific retardation layer. This makes it possible for the virtual reality display device to suppress the occurrence of ghost images. The virtual reality display device according to this embodiment preferably includes at least one of the image display device according to the second embodiment and the lens according to the first embodiment.

[0063] When the virtual reality display device according to the present embodiment has the lens according to the first embodiment, the image display device included in the virtual reality display device may be the image display device according to the second embodiment, or may be an image display device having a retardation layer different from the specific retardation layer. The latter image display device may have the same configuration as the image display device according to the second embodiment, including preferred aspects, except for having a retardation layer different from the specific retardation layer. Furthermore, when the virtual reality display device according to the present embodiment has the image display device according to the second embodiment, the lens included in the virtual reality display device may be the lens according to the first embodiment, or may be a known lens having a retardation layer different from the specific retardation layer. The latter lens may have the same configuration as the lens according to the first embodiment, including preferred aspects, except for having a retardation layer different from the specific retardation layer. By including the image display device according to the second embodiment in the virtual reality display device, it is not necessary to strictly adjust the angle between the image display device and the lens when assembling the lens, which simplifies the lens assembling process and reduces the manufacturing cost of the virtual reality display device.

[0064] The virtual reality display device according to this embodiment preferably includes both the image display device according to the second embodiment and the lens according to the first embodiment. In this case, it is preferable that the specific retardation layer included in the image display device and the specific retardation layer included in the lens are substantially the same retardation layer. This configuration makes it possible to further reduce the occurrence of ghosts in the virtual reality display device. The virtual reality display device may further include additional optical components such as an aberration correction lens and a diopter adjustment lens. The virtual reality display device may further include various sensors that use near-infrared light as a light source, such as eye tracking, facial expression recognition, and iris authentication.

[0065] The virtual reality display device according to the present embodiment can be used as a glasses or goggle-type headset, and can also be suitably used as an electronic viewfinder for a digital camera or an imager for an in-vehicle display.

[0066] The features of the present invention will be explained in more detail below with reference to examples. Note that the materials, amounts used, ratios, processing details, processing procedures, etc. shown below can be changed as appropriate without departing from the spirit of the present invention. Furthermore, configurations other than those shown below can also be used without departing from the spirit of the present invention.

[0067] [Preparation of Cellulose Acylate Film] (Preparation of Core Layer Cellulose Acylate Dope) The following composition was charged into a mixing tank and stirred to dissolve each component, thereby preparing a cellulose acetate solution to be used as the core layer cellulose acylate dope. ------------------------------------------------ Core Layer Cellulose Acylate Dope------------------------------------------------ - 100 parts by mass of cellulose acetate having an acetyl substitution degree of 2.88 - 12 parts by mass of polyester compound B described in the examples of JP 2015-227955 A - 2 parts by mass of compound F below - 430 parts by mass of methylene chloride (first solvent) - 64 parts by mass of methanol (second solvent)------------------------------------------------

[0068] Compound F

[0069]

[0070] (Preparation of Outer Layer Cellulose Acylate Dope) 10 parts by weight of the following matting agent solution was added to 90 parts by weight of the above core layer cellulose acylate dope to prepare a cellulose acetate solution to be used as the outer layer cellulose acylate dope.

[0071] ------------------------------------------------------------------ Matting agent solution -------------------------------------------------- Silica particles with an average particle size of 20 nm (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd.) 2 parts by mass Methylene chloride (first solvent) 76 parts by mass Methanol (second solvent) 11 parts by mass The above-mentioned cellulose acylate dope for the core layer 1 part by mass ------------------------------------------------------------------

[0072] (Preparation of Cellulose Acylate Film 1) The core layer cellulose acylate dope and the outer layer cellulose acylate dope were filtered through a filter paper with an average pore size of 34 μm and a sintered metal filter with an average pore size of 10 μm. The core layer cellulose acylate dope and the outer layer cellulose acylate dope on both sides were simultaneously cast onto a drum at 20°C from a casting nozzle (band caster). The film was then peeled off while the solvent content was approximately 20% by mass. Both ends of the film in the width direction were fixed with tenter clips, and the film was stretched transversely at a stretch ratio of 1.1 times while being dried. The film was then further dried by conveying it between the rolls of a heat treatment device to prepare an optical film with a thickness of 40 μm. This was designated as Cellulose Acylate Film 1, which was used as a temporary support for the specific retardation layer. The in-plane retardation of the resulting Cellulose Acylate Film 1 was 0 nm.

[0073] [Formation of Retardation Layer] (Formation of Retardation Layer 1) The cellulose acylate film 1 prepared above was used as a temporary support. A coating solution E1 for forming a photo-alignment film having the following composition was continuously applied to the cellulose acylate film 1 using a wire bar. The support on which the coating film was formed was dried with hot air at 140°C for 120 seconds, and then the coating film was irradiated with polarized ultraviolet light (10 mJ / cm ２ , an ultra-high pressure mercury lamp was used) to form a photo-alignment film E1 having a thickness of 0.2 μm, thereby obtaining a film with a photo-alignment film.

[0074] -------------------------------------------------- Coating liquid E1 for forming photoalignment film -------------------------------------------------- Polymer PA-2 (shown below) 100.00 parts by mass Acid generator PAG-1 (shown below) 5.00 parts by mass Acid generator CPI-110TF (shown below) 0.005 parts by mass Isopropyl alcohol 16.50 parts by mass Butyl acetate 1072.00 parts by mass Methyl ethyl ketone 268.00 parts by mass --------------------------------------------------

[0075] Acid generator CPI-110TF

[0076] Polymer PA-2

[0077] Acid generator PAG-1

[0078]

[0079] An optically anisotropic layer coating solution (A) having the following composition was applied to the photo-alignment film E1 using a bar coater and heated at 80°C for 60 seconds. The film on which the coating was formed was then irradiated with light from a metal halide lamp (manufactured by Eye Graphics Co., Ltd.) at 80°C with an exposure dose of 500 mJ under a nitrogen atmosphere to fix the alignment state of the liquid crystalline compound, thereby producing a second optically anisotropic layer A2. The product Δnd of Δn and d at a wavelength of 550 nm of the second optically anisotropic layer A2 was 194 nm, and the twist angle of the second optically anisotropic layer A2 was 85°. The thickness of the second optically anisotropic layer A2 was 4.1 μm. The molecular axis of the liquid crystalline compound was parallel to the surface of the cellulose acylate film (or the surface of the optically anisotropic layer).

[0080] Composition of coating solution (A) for optically anisotropic layer ------------------------------------------------ 40 parts by mass of rod-shaped liquid crystal compound (A) below 40 parts by mass of rod-shaped liquid crystal compound (B) below 20 parts by mass of rod-shaped liquid crystal compound (C) below 4 parts by mass of ethylene oxide-modified trimethylolpropane triacrylate (V#360, manufactured by Osaka Organic Chemical Industry Co., Ltd.) 3 parts by mass of photopolymerization initiator (Irgacure 819, manufactured by Ciba Japan KK) 0.46 parts by mass of chiral agent (A) below 0.5 parts by mass of polymerizable polymer (X) below 0.1 part by mass of polymer (A) below 325 parts by mass of methyl isobutyl ketone ------------------------------------------------

[0081] Rod-shaped liquid crystal compound (A)

[0082]

[0083] Rod-shaped liquid crystal compound (B)

[0084]

[0085] Rod-like liquid crystal compound (C) (hereinafter referred to as a mixture of liquid crystal compounds)

[0086]

[0087] Chiral Agent (A)

[0088]

[0089] Polymerizable polymer (X)

[0090]

[0091] Polymer (A)

[0092]

[0093] Next, a coating solution obtained by removing the chiral agent (A) from the optically anisotropic layer coating solution (A) was applied onto the second optically anisotropic layer A2 using a bar coater and heated at 80°C for 60 seconds. Thereafter, under a nitrogen atmosphere, the film on which the coating film was formed was irradiated with light from a metal halide lamp (manufactured by Eye Graphics Co., Ltd.) at an exposure dose of 500 mJ at 80°C to fix the alignment state of the liquid crystalline compound, thereby producing a first optically anisotropic layer A1. The first optically anisotropic layer A1 was a positive A plate having a product Δnd of 205 nm at a wavelength of 550 nm, and the slow axis orientation of the first optically anisotropic layer A1 was the same orientation as that of the uppermost layer of the second optically anisotropic layer A2. The thickness of the first optically anisotropic layer A1 was 4.4 μm. In this way, a retardation layer 1 having a cellulose acylate film 1 (temporary support), a photo-alignment film E1, a second optically anisotropic layer A2, and a first optically anisotropic layer A1 in this order was prepared. The in-plane retardation of the retardation layer 1 was in the range of λ / 4±5% in the wavelength λ range of 450 nm to 650 nm. Furthermore, both the first optically anisotropic layer A1 and the second optically anisotropic layer A2 had reverse wavelength dispersion. In other words, the retardation layer 1 was a specific retardation layer.

[0094] (Formation of Retardation Layer 2) A retardation layer 2 having a cellulose acylate film 1 (temporary support), a photo-alignment film E1, a second optically anisotropic layer B2, and a first optically anisotropic layer B1 in this order was prepared in the same manner as in the retardation layer 1, except that the film thickness of each optically anisotropic layer and the amount of chiral agent (A) contained in each optically anisotropic layer were adjusted. The product Δnd of Δn and d of the second optically anisotropic layer B2 in the retardation layer 2 at a wavelength of 550 nm was 157 nm, and the twist angle was 81 °. The product Δnd of Δn and d of the first optically anisotropic layer B1 in the retardation layer 2 at a wavelength of 550 nm was 310 nm, and the twist angle was 24 °. Furthermore, both the first optically anisotropic layer B1 and the second optically anisotropic layer B2 had reverse wavelength dispersion. The in-plane retardation of the retardation layer 2 was in the range of λ / 4±5% in the wavelength λ range of 450 nm to 650 nm, that is, the retardation layer 2 was a specific retardation layer.

[0095] (Formation of Retardation Layer 3) A coating solution obtained by removing the chiral agent (A) from the optically anisotropic layer coating solution (A) was applied to the photo-alignment film E1 using a bar coater and heated at 80°C for 60 seconds. Then, under a nitrogen atmosphere, the film on which the coating film was formed was irradiated with light from a metal halide lamp (manufactured by Eye Graphics Co., Ltd.) at an exposure dose of 500 mJ at 80°C to fix the alignment state of the liquid crystalline compound, thereby producing a retardation layer 3. The retardation layer 3 was a positive A plate having a product Δnd of 141 nm of Δn and d at a wavelength of 550 nm. The retardation layer 3 also had reverse wavelength dispersion. The in-plane retardation of the retardation layer 3 was in the range of λ / 4±5% when the wavelength λ was in the range of 450 nm to 550 nm, but was outside the range of λ / 4±5% when the wavelength λ was 650 nm.

[0096] (Formation of Retardation Layer 4) A retardation layer 4 having, in this order, a cellulose acylate film 1, a photo-alignment film E1, a second optically anisotropic layer C2, and a first optically anisotropic layer C1 was prepared according to the method for forming the retardation layer 1, except that, when preparing the second optically anisotropic layer, the optically anisotropic layer coating liquid (A2) having the following composition was used instead of the optically anisotropic layer coating liquid (A), and, when preparing the first optically anisotropic layer, a coating liquid obtained by removing the chiral agent (A) from the optically anisotropic layer coating liquid (A2) was used instead of the coating liquid obtained by removing the chiral agent (A) from the optically anisotropic layer coating liquid (A).

[0097] Composition of coating solution for optically anisotropic layer (A2) ------------------------------------------------ 70 parts by mass of liquid crystal compound L-1 shown below 30 parts by mass of liquid crystal compound L-2 shown below 4 parts by mass of ethylene oxide-modified trimethylolpropane triacrylate (V#360, manufactured by Osaka Organic Chemical Industry Co., Ltd.) 3 parts by mass of photopolymerization initiator (Irgacure 819, manufactured by Ciba Japan KK) 0.46 parts by mass of chiral agent (A) shown below 0.5 parts by mass of polymerizable polymer (X) shown below 0.1 part by mass of polymer (A) shown below Methyl ethyl ketone (solvent) 200 parts by mass Cyclopentanone (solvent) 200 parts by mass --------------------------------------------------

[0098] Liquid crystal compound L-1

[0099]

[0100] Liquid crystal compound L-2

[0101]

[0102] Polymerization initiator S-1

[0103]

[0104] The second optically anisotropic layer C2 had a product Δnd of 194 nm and a twist angle of 85° at a wavelength of 550 nm. The molecular axis of the liquid crystal compound was parallel to the cellulose acylate film surface (or the optically anisotropic layer surface). The first optically anisotropic layer C1 was a positive A plate having a product Δnd of 205 nm at a wavelength of 550 nm, and the slow axis orientation of the first optically anisotropic layer C1 was the same as that of the uppermost layer of the second optically anisotropic layer C2. Both the first optically anisotropic layer C1 and the second optically anisotropic layer C2 had reverse wavelength dispersion. The in-plane retardation of the retardation layer 4 was in the range of λ / 4±5% at a wavelength λ of 450 nm to 650 nm. That is, the retardation layer 4 was a specific retardation layer.

[0105] [Preparation of Laminated Optical Body 1] The liquid crystal display of an Apple tablet computer "iPad (registered trademark)" was removed, and a linear polarization type reflective polarizer (3M trademark "APF") made of a wideband dielectric multilayer film was peeled off from the polarizing plate attached to the back of the liquid crystal display. Next, a retardation layer 1 was attached to one side of the peeled reflective polarizer APF using a Lintec adhesive sheet "NCF-D692 (5)", and the temporary support of the retardation layer 1 was peeled off. At this time, the reflection axis orientation of the reflective polarizer APF and the effective slow axis orientation in the entire thickness direction of the retardation layer 1 were adjusted to be 45° to each other. Furthermore, an absorbing polarizer was attached to the opposite side of the reflective polarizer APF. At this time, the reflection axis orientation of the reflective polarizer APF and the absorption axis orientation of the absorbing polarizer were adjusted to be parallel. In this way, a laminated optical body 1 was obtained.

[0106] [Preparation of Laminated Optical Bodies 2, 3, and 4] Laminated optical bodies 2, 3, and 4 were prepared in the same manner as above, except that retardation layer 1 was replaced with retardation layer 2, retardation layer 3, and retardation layer 4, respectively.

[0107] [Preparation of Lens 1] Aluminum was vapor-deposited on the convex side of a plano-convex lens "#45-247 (manufactured by Edmund)" having a curved surface with a curvature radius of 65 mm, to form a half mirror. Next, laminated optical body 1 was attached to the flat side of the plano-convex lens using an adhesive sheet "NCF-D692(15)" manufactured by Lintec Corporation, with the retardation layer 1 facing the plano-convex lens side. In this manner, lens 1 was prepared.

[0108] [Preparation of Lenses 2, 3, and 4] Lenses 2, 3, and 4 were prepared in the same manner as Lens 1, except that Laminated Optical Body 1 was replaced with Laminated Optical Body 2, Laminated Optical Body 3, and Laminated Optical Body 4, respectively.

[0109] Table 1 shows the configurations of the lenses 1 to 4 fabricated above.

[0110]

[0111] Example 1: Fabrication of Virtual Reality Display Device 1 A virtual reality display device using a pancake lens, "Huawei (registered trademark) VR Glass" manufactured by Huawei, was disassembled, and all of the compound lenses (hereinafter also referred to as "Lens X") arranged on the viewing side were removed. Lens 1 described above was incorporated into the main body (i.e., the "Huawei VR Glass" from which Lens X had been removed) in place of the removed Lens X, thereby fabricating the virtual reality display device 1 of Example 1.

[0112] Example 2: Fabrication of Virtual Reality Display Device 2 A virtual reality display device 2 of Example 2 was fabricated in the same manner as Example 1, except that lens 1 was replaced with lens 2.

[0113] Example 3: Fabrication of Virtual Reality Display Device 3 The Huawei VR Glass was disassembled, and the image display device (hereinafter also referred to as "image display device X") installed therein was removed. An absorptive polarizer and a retardation layer (hereinafter also referred to as "retardation layer X") consisting of a single optically anisotropic layer were bonded to the liquid crystal display panel of the removed image display device X in this order. The retardation layer X was peeled off from the image display device X, and instead, a retardation layer 1 was bonded. The absorption axis of the absorptive polarizer and the effective slow axis direction of the retardation layer 1 in the entire thickness direction were adjusted to form an angle of 45°. In this way, an image display device 1 having a liquid crystal display panel, an absorptive polarizer, and a retardation layer 1 in this order was fabricated. The obtained image display device 1 was incorporated into the Huawei VR Glass from which the image display device X was removed, thereby fabricating the virtual reality display device 3 of Example 3.

[0114] Example 4: Fabrication of Virtual Reality Display Device 4 A virtual reality display device 4 of Example 4 was fabricated in the same manner as in Example 3, except that the retardation layer 1 was replaced with the retardation layer 2.

[0115] Example 5: Fabrication of Virtual Reality Display Device 5 All lenses X and image display device X were removed from "Huawei VR Glass." As in Example 3, the retardation layer X was peeled off from the removed image display device X, and instead, a retardation layer 1 was attached to fabricate an image display device 1. At this time, the absorption axis of the absorptive polarizer and the effective slow axis direction of the retardation layer 1 in the entire thickness direction were adjusted to form an angle of 45°. The obtained image display device 1 was incorporated into the "Huawei VR Glass" from which the image display device X and lenses X were removed, and further, the lens 1 was incorporated, thereby fabricating a virtual reality display device 5 of Example 5.

[0116] [Example 6: Preparation of virtual reality display device 6] A virtual reality display device 6 of Example 6 was prepared in the same manner as in Example 5, except that lens 1 was replaced with lens 2 and retardation layer 1 used in the image display device was replaced with retardation layer 2.

[0117] Example 7: Fabrication of Virtual Reality Display Device 9 All of the lenses X and the image display device X were removed from the Huawei VR Glass. As in Example 3, the retardation layer X was peeled off from the removed image display device X, and instead, a retardation layer 4 was attached to fabricate an image display device 4. At this time, the absorption axis of the absorptive polarizer and the effective slow axis direction of the retardation layer 4 in the entire thickness direction were adjusted to form an angle of 45°. The obtained image display device 4 was incorporated into the Huawei VR Glass from which the image display device X and the lenses X were removed, and further, the lenses 4 were incorporated, thereby fabricating the virtual reality display device 7 of Example 7.

[0118] Comparative Example 1: Fabrication of Virtual Reality Display Device 8 A virtual reality display device 8 of Comparative Example 1 was fabricated in the same manner as in Example 1, except that lens 1 was replaced with lens 3.

[0119] Comparative Example 2: Virtual Reality Display Device 9 "Huawei VR Glass" was used as the virtual reality display device 9 of Comparative Example 2. The "Huawei VR Glass" had an image display device X having a liquid crystal display panel, an absorptive polarizer, and a retardation layer X, and a lens X having a retardation layer formed of a single optically anisotropic layer and a lens substrate.

[0120] <Evaluation of ghost visibility> For each of the manufactured virtual reality display devices, a black and white checkered pattern was displayed on the image display device. The virtual reality display device was worn, and the displayed black and white checkered pattern was visually observed, and the ghost visibility was evaluated based on the following four-level evaluation criteria: A: No ghost was visible, or a slight ghost was visible but not bothersome. B: A weak ghost was visible. C: A somewhat strong ghost was visible. D: A strong ghost was visible.

[0121] The configurations and evaluation results of the virtual reality display devices of each example and comparative example are shown in Table 2. As shown in Table 2, the virtual reality display devices of the present invention manufactured in each example had good ghost visibility across the entire field of view. Furthermore, when manufacturing the virtual reality display device, the lenses were assembled by varying the angle, as viewed from the viewing direction, between the slow axis of the retardation layer of the image display device and the slow axis of the retardation layer of the lens. As a result, it was confirmed that the evaluation of ghost visibility did not change regardless of the angle at which the lenses were assembled in the virtual reality display devices of the present invention manufactured in each example.

[0122]

[0123] As shown in the table above, it was confirmed that the lens of the present invention has an excellent effect of suppressing the occurrence of ghosts when applied to a virtual reality display device using a pancake lens (comparison between Examples 1 and 2 and Comparative Examples 1 and 2). It was also confirmed that the image display device of the present invention has an excellent effect of suppressing the occurrence of ghosts when applied to a virtual reality display device using a pancake lens (comparison between Examples 3 and 4 and Comparative Examples 1 and 2). It was also confirmed that the virtual reality display device of the present invention has an excellent effect of suppressing the occurrence of ghosts (comparison between Examples 1 to 7 and Comparative Examples 1 and 2). In particular, a comparison between Examples 1 to 4 and Examples 5 to 7 confirmed that when a virtual reality display device has both the lens of the present invention and the image display device of the present invention, the effect of suppressing the occurrence of ghosts is even better.

[0124] 1,1000 Virtual reality display device 2 Lens 3,500 Image display device 10 Light beam forming a main image 11, 12 Light beam forming a ghost image 21,100 Reflective linear polarizer 22,200 First retardation layer 23,600 Lens substrate 24,300 Half mirror 31,400 Second retardation layer 32 Absorptive polarizer 33 Image display panel

Claims

1. A lens having a retardation layer that converts circularly polarized light into linearly polarized light, the retardation layer comprising a first optically anisotropic layer and a second optically anisotropic layer, the first optically anisotropic layer and the second optically anisotropic layer having reverse wavelength dispersion, and at least one of the first optically anisotropic layer and the second optically anisotropic layer being a layer in which a liquid crystal compound is fixed that is twisted and aligned with the thickness direction as the helical axis.

2. The lens according to claim 1, wherein the first optically anisotropic layer and the second optically anisotropic layer are both layers in which a liquid crystalline compound is fixed.

3. The lens according to claim 2, wherein the alignment direction of the liquid crystal compound contained in the first optically anisotropic layer and the alignment direction of the liquid crystal compound contained in the second optically anisotropic layer are continuous at the interface between the first optically anisotropic layer and the second optically anisotropic layer.

4. The lens according to any one of claims 1 to 3, wherein the first optically anisotropic layer is a positive A plate, and the second optically anisotropic layer is a layer in which a liquid crystalline compound is fixed and twisted and aligned with a helical axis in the thickness direction.

5. The lens according to any one of claims 1 to 3, wherein the first optically anisotropic layer and the second optically anisotropic layer are both layers formed by fixing liquid crystal compounds that are twisted and aligned with a helical axis in the thickness direction, and the helical pitch of the first optically anisotropic layer is different from the helical pitch of the second optically anisotropic layer.

6. The lens of claim 1 further comprising a reflective linear polarizer.

7. The lens of claim 1 further comprising a reflective circular polarizer.

8. The lens of claim 7, wherein the reflective circular polarizer comprises a cholesteric liquid crystal layer.

9. The lens of any one of claims 6 to 8, further comprising an absorptive polarizer.

10. A virtual reality display device comprising: an image display device; and a lens according to any one of claims 1 to 3.

11. An image display device having, in this order, an image display panel, an absorptive polarizer, and a retardation layer that converts circularly polarized light into linearly polarized light, wherein the retardation layer includes a first optically anisotropic layer and a second optically anisotropic layer, the first optically anisotropic layer and the second optically anisotropic layer have reverse wavelength dispersion properties, and at least one of the first optically anisotropic layer and the second optically anisotropic layer is a layer in which a liquid crystal compound is fixed that is twisted and oriented with the thickness direction as the helical axis.

12. The image display device according to claim 11, wherein the first optically anisotropic layer and the second optically anisotropic layer are both layers in which a liquid crystalline compound is fixed.

13. The image display device according to claim 12, wherein the alignment direction of the liquid crystal compound contained in the first optically anisotropic layer and the alignment direction of the liquid crystal compound contained in the second optically anisotropic layer are continuous at the interface between the first optically anisotropic layer and the second optically anisotropic layer.

14. An image display device according to any one of claims 11 to 13, wherein the first optically anisotropic layer is a positive A plate, and the second optically anisotropic layer is a layer in which a liquid crystal compound is fixed and twisted and aligned with the thickness direction as the helical axis.

15. An image display device according to any one of claims 11 to 13, wherein the first optically anisotropic layer and the second optically anisotropic layer are both layers formed by fixing liquid crystal compounds that are twisted and aligned with the thickness direction as the helical axis, and the helical pitch of the first optically anisotropic layer is different from the helical pitch of the second optically anisotropic layer.

16. A virtual reality display device comprising: a lens; and an image display device according to any one of claims 11 to 13.

17. A virtual reality display device comprising: a lens according to any one of claims 1 to 3; and an image display device according to any one of claims 11 to 13.

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