Virtual image display device

Abstract

The purpose of the present invention is to provide a virtual image display device in which the sizes of ghosts vary little and the occurrence of ghosts is stably reduced.　A virtual image display device (100) according to the present invention comprises at least an image display device (500) and a folding optical system (600) including a reflective circular polarizer (200). The reflective circular polarizer (200) includes a cholesteric liquid crystal layer. In the cholesteric liquid crystal layer, the degree of orientation of a liquid crystal compound is 0.5 or more on an image display device-side surface, and the variation in the director orientation of the liquid crystal compound in an effective region is 30° or less.

Description

Virtual image display device

[0001] The present invention relates to a virtual image display device.

[0002] Virtual image display devices have become increasingly popular in recent years as display devices that realize virtual reality displays, augmented reality displays, and the like. Examples of virtual image display devices include head-mounted displays (HMDs) that include an image display device and a lens. When such a HMD is worn on the observer's head and an image is displayed through the lens, the user can observe a realistic image known as virtual reality. In recent years, in order to reduce the thickness of such HMDs, thin lenses known as pancake lenses have been introduced, which reflect light back and forth between a reflective polarizer and a half mirror. Due to their mechanism, pancake lenses are also referred to as folded optical systems or reflective optical systems. For example, Patent Document 1 discloses a virtual image display device that uses folded optical systems to reduce the size and thickness of the display unit.

[0003] Japanese Unexamined Patent Publication No. 7-120679

[0004] In a virtual image display device using a pancake lens, part of the light (image) emitted from the image display device passes through the half mirror, enters the reflective polarizer, is reflected and folded back, enters the half mirror again, is partially reflected and folded back toward the reflective polarizer, and when reflected by this half mirror, the light is converted into light that passes through the reflective polarizer, and the light that has passed through the reflective polarizer is observed by the user.

[0005] In the pancake lens described in Patent Document 1, a portion of the light emitted from the image display device does not travel back and forth between the reflective polarizer and the half mirror due to polarization disturbances, undesired reflections, etc., and when it first enters the reflective polarizer, it is transmitted without being reflected by the reflective polarizer. This transmitted light becomes so-called leakage light, which causes problems such as the occurrence of ghosts (double images) and a decrease in contrast.

[0006] Therefore, the present inventors attempted to reduce ghosting by using a reflective circular polarizer as a reflective polarizer and increasing the degree of circular polarization of reflected light. As a result, a pancake lens (folded optical system) including a reflective circular polarizer was effective in reducing ghosting. However, according to the inventors' investigations, among the pancake lenses manufactured using a reflective circular polarizer, some had relatively small levels of ghosting and others had relatively large levels. In other words, it was found that the pancake lenses manufactured using a reflective circular polarizer had variations in the size of the ghosting, and solving this variation became an issue.

[0007] The present invention has been made in consideration of the above-mentioned problems, and the problem that the present invention aims to solve is to provide a virtual image display device that reduces the variation in the size of ghosts and stably generates fewer ghosts in a virtual image display device that uses a folded optical system.

[0008] The present inventors have conducted extensive research to solve the above problems and have completed the present invention. That is, they have found that the above problems can be solved by the following configuration.

[0009] [1] A virtual image display device having at least an image display device and a folding optical system including a reflective circular polarizer, wherein the reflective circular polarizer includes a cholesteric liquid crystal layer, and the cholesteric liquid crystal layer has a degree of orientation of a liquid crystal compound of 0.5 or more on the surface facing the image display device, and the variation in director orientation of the liquid crystal compound within the effective area is 30° or less. [2] The virtual image display device according to [1], wherein the reflective circular polarizer includes a plurality of cholesteric liquid crystal layers. [3] The virtual image display device according to [2], wherein the reflective circular polarizer includes at least a cholesteric liquid crystal layer formed using a first liquid crystal compound consisting essentially of a rod-shaped liquid crystal compound and a cholesteric liquid crystal layer formed using a second liquid crystal compound consisting essentially of a discotic liquid crystal compound. [4] The virtual image display device according to any one of [1] to [3], wherein at least a λ / 4 wave plate and an absorptive linear polarizer are stacked in this order on the viewing-side surface of the reflective circular polarizer. [5] The virtual image display device according to any one of [1] to [4], wherein the reflective circular polarizer is formed into a curved shape.

[0010] According to the present invention, it is possible to provide a virtual image display device using a folding optical system in which the variation in the size of ghosts is small and the occurrence of ghosts is stably reduced.

[0011] FIG. 1 is a schematic diagram showing an example of a virtual image display device of the present invention. FIG. 2 is a schematic diagram showing an example of a virtual image display device of the present invention. FIG. 3 is a schematic diagram showing an example of a virtual image display device of the present invention. FIG. 4 is a Poincare sphere diagram showing a change in the polarization state of a light ray passing through a reflective circular polarizer in a virtual image display device of the present invention. FIG. 5 is a Poincare sphere diagram showing a change in the polarization state of a light ray passing through a reflective circular polarizer in a virtual image display device of the present invention. FIG. 6 is a Poincare sphere diagram showing a change in the polarization state of a light ray passing through a reflective circular polarizer in a virtual image display device of the present invention. FIG. 7 is a Poincare sphere diagram showing a change in the polarization state of a light ray passing through a reflective circular polarizer in a virtual image display device of the present invention.

[0012] The virtual image display device of the present invention will be described in detail below. The following description of the components will be based on representative embodiments and 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 ​​written before and after "to" as the lower and upper limits.

[0013] In this specification, "orthogonal" does not mean that the angle between two axes is strictly 90°, but rather 90°±10°, preferably 90°±5°. "Parallel" does not mean that the angle between two axes is strictly 0°, but rather 0°±10°, preferably 0°±5°. "45°" does not mean that the angle between two axes is strictly 45°, but rather 45°±10°, preferably 45°±5°.

[0014] 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 in a plane that is perpendicular to the absorption axis or reflection axis. "Slow axis" refers to the direction in a plane in which the refractive index is maximized. "Fast axis" refers to the direction in a plane in which the refractive index is minimized, and is the direction perpendicular to the slow axis.

[0015] 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 a wavelength λ, and unless otherwise specified, the wavelength λ is 550 nm. Furthermore, in this specification, the retardation in the thickness direction at a wavelength λ is referred to as Rth(λ). Unless otherwise specified, the wavelength λ is 550 nm. Re(λ) and Rth(λ) can be values ​​measured at a wavelength λ using 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 slow axis direction (°) can be calculated: Re(λ) = R0(λ) Rth(λ) = ((nx + ny) / 2 - nz) × d.

[0016] The virtual image display device of the present invention includes an image display device and a folding optical system including a reflective circular polarizer. The reflective circular polarizer includes a cholesteric liquid crystal layer. The cholesteric liquid crystal layer has a liquid crystal compound with a degree of orientation of 0.5 or more on the surface facing the image display device, and the director orientation of the liquid crystal compound within the effective area varies by 30° or less.

[0017] The mechanism by which the virtual image display device of the present invention generates a virtual image will be described using FIG. 1. FIG. 1 is a conceptual diagram illustrating an example of a virtual image display device of the present invention. The virtual image display device 1000 shown in FIG. 1 includes an image display device 500 and a folding optical system 600. In the virtual image display device 1000 of the present invention, the folding optical system 600 includes a reflective circular polarizer 200. Furthermore, the folding optical system 600 in the illustrated example includes a half mirror 300 in addition to the reflective circular polarizer 200. The reflective circular polarizer 200 includes a cholesteric liquid crystal layer. This reflective circular polarizer 200, i.e., the cholesteric liquid crystal layer, reflects right-handed circularly polarized light and transmits left-handed circularly polarized light, for example. Furthermore, in this cholesteric liquid crystal layer, the orientation degree of the liquid crystal compound on the surface facing the image display device 500 is 0.5 or more, and the variation in director orientation of the liquid crystal compound within the effective area is 30° or less.

[0018] The light ray 10 (image) emitted by the image display device 500 is circularly polarized light. In the illustrated example, the image display device 500 emits right-handed circularly polarized light, for example. The image display device 500 includes, for example, an image display element (display panel), a retardation layer (λ / 4 wavelength plate), a linear polarizer, and a retardation layer (λ / 4 wavelength plate), in this order. In this image display device 500, the light (unpolarized) emitted by the image display element passes through the retardation layer, is converted into linearly polarized light by the linear polarizer, is converted into right-handed circularly polarized light by the retardation layer, and is emitted as the light ray 10. The retardation layer immediately downstream of the image display element, together with the linear polarizer, constitutes an anti-reflection film of the image display element.

[0019] A portion of the light ray 10 (right-handed circularly polarized light) emitted from the image display device 500 passes through the half mirror 300 and then enters the reflective circular polarizer 200. As described above, the reflective circular polarizer 200 has a cholesteric liquid crystal layer that selectively reflects right-handed circularly polarized light. Therefore, the right-handed circularly polarized light ray 10 that enters the reflective circular polarizer 200 is reflected by the reflective circular polarizer 200, its optical path is folded back, and it again enters the half mirror 300, where a portion of it is reflected by the half mirror 300. During this reflection, the light ray 10 is converted into left-handed circularly polarized light and again enters the reflective circular polarizer 200. As described above, the reflective circular polarizer 200 is a cholesteric liquid crystal layer that selectively reflects right-handed circularly polarized light, and the light ray 10 is converted into left-handed circularly polarized light. Therefore, the light ray 10 passes through the reflective circular polarizer 200. In this way, a portion of the light ray 10 is folded back within the folding optical system 600.

[0020] 1 acts as a concave mirror when reflecting the light ray 10 due to the curved surface shape of the half mirror 300. Furthermore, the folding optical system 600 may refract the light ray 10 and generate lens power due to its shape. Due to these effects, the light ray 10 emitted from the image display device 500 is substantially parallelized and reaches the user's eye, allowing the user to view the image displayed on the image display device as a virtual image.

[0021] In the above example, the reflective circular polarizer 200 reflects right-handed circularly polarized light and transmits left-handed circularly polarized light, but the present invention is not limited to this. That is, the reflective circular polarizer 200 may reflect left-handed circularly polarized light and transmit right-handed circularly polarized light. In this case, an image display device that emits left-handed circularly polarized light may be used, and the effect of the present invention does not lose generality. The above points also apply to the following explanations.

[0022] <Principle of Ghost Generation> Next, the principle of ghost generation in the virtual image display device 1000 will be described with reference to the conceptual diagram of FIG. 2 . As described above, in the virtual image display device 1000, a portion of the light ray 10 emitted from the image display device 500 passes through the half mirror 300, enters the reflective circular polarizer 200, and is reflected by the reflective circular polarizer 200. However, as schematically shown in FIG. 2 , a portion of the light ray 10 emitted from the image display device 500 passes through the half mirror 300, and then passes through the reflective circular polarizer 200 without being reflected by the reflective circular polarizer 200. Hereinafter, this portion of the light ray 10 will be referred to as light ray 11. Such light ray 11 is not substantially collimated and reaches the user's eye via an optical path length different from that of light ray 10, and is therefore perceived as an image different from the virtual image perceived by the user, i.e., as a ghost.

[0023] <Principle of Variation in Ghost Size> Although omitted in FIGS. 1 and 2 for the sake of simplicity, as shown in FIG. 3, the virtual image display device 1000 of the present invention preferably includes an absorptive circular polarizer 400. In the illustrated example, the light ray 10 emitted from the image display device 500 is right-handed circularly polarized light. Therefore, when the light ray 11 first enters the reflective circular polarizer 200 and unnecessarily passes through the reflective circular polarizer 200, the majority of the light ray 11 is right-handed circularly polarized light. Therefore, as conceptually shown in FIG. 3, ghosts can be significantly reduced by laminating an absorptive circular polarizer 400 that absorbs right-handed circularly polarized light on the viewing side (user side) of the reflective circular polarizer 200. Note that the absorptive circular polarizer 400 can be fabricated, for example, by laminating a λ / 4 wave plate (λ / 4 retardation layer) 401 and an absorptive linear polarizer 402. Furthermore, since the absorptive circular polarizer 400 transmits left-handed circularly polarized light, it has almost no effect on the display quality of the virtual image viewed by the user.

[0024] On the other hand, it has also been found that light ray 11 may be partially converted into left-handed circularly polarized light after passing through reflective circular polarizer 200. In FIG. 3 , the light ray converted from right-handed circularly polarized light 11 to left-handed circularly polarized light is referred to as light ray 12 to distinguish it from light ray 11, which is primarily right-handed circularly polarized light. According to the inventors' studies, the light intensity of light ray 12 varies greatly. It is presumed that this variation in the light intensity of light ray 12 is the cause of the variation in the size of ghosts in virtual image display devices using a folded optical system. Because light ray 12 is left-handed circularly polarized light, it cannot be absorbed by absorptive circular polarizer 400, which absorbs right-handed circularly polarized light. Therefore, it has been difficult to suppress the variation in ghosts caused by light ray 12 (left-handed circularly polarized light) with its large variation in light intensity.

[0025] The inventors speculate as follows about the mechanism by which a portion of the light ray 11 is converted into left-handed circularly polarized light (light ray 12) by the reflective circular polarizer 200. FIG. 4 conceptually illustrates, on the Poincaré sphere, the change in polarization state of the light ray 11 incident on the reflective circular polarizer 200 as it passes through the reflective circular polarizer 200. The light ray 11 is right-handed circularly polarized when it enters the reflective circular polarizer 200. Therefore, on the Poincaré sphere, it is represented at point S3 (the apex of the S3 axis). Furthermore, the reflective circular polarizer 200 selectively reflects right-handed circularly polarized light. Therefore, as the light ray 11, which is primarily right-handed circularly polarized light, travels inside the reflective circular polarizer 200, the amount of transmitted light decreases. In this specification, the distance from the center of the Poincaré sphere represents the amount of light. That is, in this specification, the decrease in the amount of transmitted light is described as a locus representing a change in the polarization state on the Poincaré sphere that draws a spiral near the S3 axis and approaches the center of the Poincaré sphere, as shown in FIG.

[0026] Figure 5 is a diagram of the Poincaré sphere in Figure 4 viewed from the direction of point S3 (S3 axis). In Figure 5, it can be seen that the locus representing the change in polarization state describes a spiral that is biased overall toward the first quadrant. In Figure 5, the first quadrant is the quadrant formed by the S1 axis and the S2 axis. When the locus representing the change in polarization state moves away from the S3 axis, this means that part of ray 11 is converted into left-handed circularly polarized light, i.e., ray 12.

[0027] The polarization state of light ray 11 changes due to the optical action of the liquid crystal compound contained in the cholesteric liquid crystal layer that constitutes reflective circular polarizer 200. According to the inventors' investigations, the direction in which the locus representing the change in polarization state initially moves on the Poincaré sphere is determined by the orientation of the director of the liquid crystal compound on the light-incident surface side of the cholesteric liquid crystal layer. Therefore, the direction of polarization in FIG. 5 is largely determined by the orientation of the director of the liquid crystal compound on the light-incident surface side of the cholesteric liquid crystal layer. However, in general, the orientation of the director of the liquid crystal compound in the cholesteric liquid crystal layer can be various, so the polarization state on the Poincaré sphere is not constant, and this is presumably the cause of the variations in the size of the ghost.

[0028] On the other hand, strictly speaking, light ray 10 emitted from image display device 500 is not circularly polarized light but is generally elliptically polarized light. In this case, if the polarization state of light ray 11 immediately before entering reflective circular polarizer 200 is represented on the Poincaré sphere, it will be represented at a position slightly away from the S3 axis (point S3), as shown by point A in FIGS. 6 and 7 . As shown in FIG. 6 , if the bias of the locus of change in polarization state caused by the cholesteric liquid crystal layer on the Poincaré sphere is oriented to cancel the polarization of light ray 11, the proportion of light ray 11 converted to left-handed circularly polarized light will be small, and ghosting will also be small. On the other hand, as shown in FIG. 7 , if the bias of the locus of change in polarization state is oriented to increase the polarization of light ray 11, the proportion of light ray 11 converted to left-handed circularly polarized light will be large, and ghosting will be large. In other words, ghosting can be reduced by adjusting the bias of the locus of change in polarization state caused by the cholesteric liquid crystal layer according to the polarization state of light ray 10. Alternatively, ghosting can be reduced by adjusting the polarization state of the light beam 10 according to the deviation of the locus of the change in the polarization state caused by the cholesteric liquid crystal layer. For example, as described above, the direction of deviation of the locus of the change in the polarization state caused by the cholesteric liquid crystal layer is largely determined by the orientation of the director of the liquid crystal compound on the light-incident surface side of the cholesteric liquid crystal layer. Therefore, ghosting can be reduced by adjusting the orientation of the director of the liquid crystal compound on the light-incident surface side of the cholesteric liquid crystal layer according to the polarization state of the light beam 10.

[0029] In the present invention, the variation in ghost size specifically has two meanings. The first variation in ghost size refers to the variation in ghost size between individual cholesteric liquid crystal layers (reflective circular polarizers), i.e., between individual virtual image display devices. In other words, this variation in ghost size is due to individual differences between multiple components and devices. The second variation in ghost size refers to the variation in ghost size within the plane of a single cholesteric liquid crystal layer (reflective circular polarizer), i.e., in the image displayed by a single virtual image display device. In other words, this variation in ghost size refers to, for example, the variation in which the ghost is small in the vertical center of the displayed virtual image and large at the top and bottom.

[0030] <Virtual Image Display Device of the Present Invention> Based on the above assumption, the inventors of the present invention estimated that the variation in the size of ghosts in a virtual image display device can be reduced by controlling the orientation of the director of the liquid crystal compound on the light-incident surface side of the cholesteric liquid crystal layer to a constant orientation, and thus arrived at the present invention. That is, as described above, the generation of left-handed circularly polarized light, which causes ghosts, is caused by a change in the polarization state of light ray 11, which is right-handed circularly polarized light passing through the cholesteric liquid crystal layer. Furthermore, the direction in which the locus representing the change in polarization state initially moves on the Poincaré sphere is determined by the orientation of the director of the liquid crystal compound on the light-incident surface side of the cholesteric liquid crystal layer. Therefore, the direction of polarization of the polarized light in FIG. 5 is largely determined by the orientation of the director of the liquid crystal compound on the light-incident surface side of the cholesteric liquid crystal layer. Variations in the orientation of this director cause variations in the size of ghosts. Therefore, if there is no variation in the orientation of the director of the liquid crystal compound on the light incident side of the cholesteric liquid crystal layer, the change in the polarization state of the circularly polarized light (elliptically polarized light) passing through the reflective circular polarizer 200 can be made uniform, thereby reducing the variation in ghosts.

[0031] The virtual image display device of the present invention includes at least an image display device and a folding optical system including a reflective circular polarizer, wherein the reflective circular polarizer includes a cholesteric liquid crystal layer, and the cholesteric liquid crystal layer has a degree of orientation of the liquid crystal compound of 0.5 or more on the surface facing the image display device, i.e., the surface onto which light ray 10 (light ray 11) is incident, and the variation in the director orientation of the liquid crystal compound within the effective area is 30° or less. By having such a configuration, the virtual image display device of the present invention can reduce variation in the size of ghosts in the virtual image display device. The effective area refers to the in-plane area of ​​the reflective circular polarizer incorporated in the virtual image display device through which light rays from the image display device pass when a user views a displayed virtual image.

[0032] In the virtual image display device of the present invention, if the degree of orientation of the liquid crystal compound in the cholesteric liquid crystal layer on the surface facing the image display device is less than 0.5, it will be difficult to sufficiently reduce the variation in ghosts, and circularly polarized light (e.g., right-handed circularly polarized light) that should be reflected will not be sufficiently reflected, resulting in inconveniences such as increased ghosts. The degree of orientation of the liquid crystal compound in the cholesteric liquid crystal layer on the surface facing the image display device is preferably 0.6 or more, and more preferably 0.65 or more. In the present invention, the higher the degree of orientation of the liquid crystal compound in the cholesteric liquid crystal layer on the surface facing the image display device, the more preferable, with the upper limit of 1 being most preferred.

[0033] In the virtual image display device of the present invention, if the variation in the director orientation of the liquid crystal compound within the effective region of the cholesteric liquid crystal layer on the surface facing the image display device exceeds 30°, the variation in ghosts cannot be sufficiently reduced, which is disadvantageous. The variation in the director orientation of the liquid crystal compound within the effective region of the cholesteric liquid crystal layer on the surface facing the image display device is preferably 10° or less, and more preferably 5° or less. In the present invention, the variation in the director orientation of the liquid crystal compound within the effective region of the cholesteric liquid crystal layer on the surface facing the image display device is preferably as small as possible, and 0° is most preferred.

[0034] Furthermore, according to the studies of the present inventors, when the cholesteric liquid crystal layer on the image display device side of the reflective circular polarizer is a layer made of a rod-shaped liquid crystal compound, the orientation of the polarization axis of the elliptically polarized light at a wavelength of 550 nm emitted from the image display device and the orientation of the director of the liquid crystal compound on the surface of the cholesteric liquid crystal layer facing the image display device preferably form an angle of 45 to 90 degrees, more preferably an angle of 55 to 80 degrees. Furthermore, when the cholesteric liquid crystal layer on the image display device side of the reflective circular polarizer is a layer made of a discotic liquid crystal compound, the orientation of the polarization axis of the elliptically polarized light at a wavelength of 550 nm emitted from the image display device and the orientation of the director of the liquid crystal compound on the surface of the cholesteric liquid crystal layer facing the image display device preferably form an angle of 0 to 45 degrees, more preferably an angle of 10 to 35 degrees. When this angle is in the above range, the position of the elliptically polarized light on the Poincaré sphere is a position that cancels out the polarization state bias caused by the cholesteric liquid crystal layer, thereby minimizing ghosting. Furthermore, the ellipticity of the elliptically polarized light emitted by the image display device preferably has an average value of 0.8 to 0.99 for wavelengths of 450 to 650 nm. This range of ellipticity is preferable because it can further reduce ghosting. The average ellipticity is more preferably 0.85 to 0.98, and even more preferably 0.93 to 0.98.

[0035] The orientation of the ellipse axis of elliptically polarized light refers to the orientation of the major axis of the ellipse in the elliptical orbit traced by the change in the electric field in the elliptically polarized light. Furthermore, the ellipticity refers to the ratio of the lengths of the major and minor axes in the elliptical orbit. The orientation of the ellipse axis and the ellipticity of the elliptically polarized light emitted by the image display device can be obtained, for example, by peeling the circular polarizer from the surface of the image display device and measuring the light at a wavelength of 550 nm using an AxoScan OPMF-1 (manufactured by OptoScience Corporation).

[0036] <Reflective Circular Polarizer> A reflective circular polarizer is a polarizer that transmits right-handed or left-handed circularly polarized light and reflects circularly polarized light having the opposite rotation direction to the transmitted circularly polarized light. The reflective circular polarizer included in the virtual image display device of the present invention has a cholesteric liquid crystal layer. The cholesteric liquid crystal layer is a liquid crystal phase formed by fixing a cholesterically oriented liquid crystal phase (cholesteric liquid crystal phase).

[0037] As is well known, a cholesteric liquid crystal layer has a helical structure in which liquid crystal compounds are stacked in a spiral. One helical period (helical period (helical pitch)) is defined as a configuration in which the liquid crystal compounds are stacked in a spiral with one rotation (360° rotation) of the liquid crystal compounds. The helical period (helical pitch) is a single helical period. The cholesteric liquid crystal layer reflects right-handed or left-handed circularly polarized light in a specific wavelength range and transmits other light depending on the length of the helical period and the direction of helical rotation (sense) of the liquid crystal compounds. Therefore, when a virtual reality display device displays color images, the reflective circular polarizer may have multiple cholesteric liquid crystal layers, such as a cholesteric liquid crystal layer having a central wavelength that selectively reflects red light, a cholesteric liquid crystal layer having a central wavelength that selectively reflects green light, and a cholesteric liquid crystal layer having a central wavelength that selectively reflects blue light.

[0038] Furthermore, the reflective circular polarizer may have, in addition to the cholesteric liquid crystal layer, a support and an alignment film for aligning the liquid crystal compound in the cholesteric liquid crystal layer.

[0039] In the virtual image display device of the present invention, the reflective circular polarizer included in the folding optical system includes a cholesteric liquid crystal layer. The cholesteric liquid crystal layer has a liquid crystal compound orientation degree of 0.5 or more on the surface facing the image display device, and the variation in director orientation of the liquid crystal compound within the effective area is 30° or less. The above-mentioned orientation degree and variation in director orientation on the surface facing the image display device of the cholesteric liquid crystal layer can be achieved by performing an orientation treatment to align the liquid crystal compound in one direction when forming the cholesteric liquid crystal layer. The orientation treatment can be performed, for example, by applying a photo-alignment film to a support, irradiating the photo-alignment film with polarized ultraviolet light, etc., and then applying a liquid crystal composition containing a liquid crystal compound to orient the liquid crystal compound in a cholesteric liquid crystal phase, and then curing the liquid crystal compound to form a cholesteric liquid crystal layer with the cholesteric liquid crystal phase fixed. The director orientation of the liquid crystal compound can be controlled by the orientation of the polarization axis of polarized light irradiated onto the photo-alignment film. Alternatively, the alignment treatment can be performed by rubbing the support or the alignment film coated on the support. The alignment-treated surface of the cholesteric liquid crystal layer thus formed, i.e., the surface on the alignment film side, faces the image display device, i.e., the incident side of light ray 10 (light ray 11). This allows the alignment degree of the liquid crystal compound on the surface of the cholesteric liquid crystal layer facing the image display device to be 0.5 or more, and the variation in the director orientation of the liquid crystal compound within the effective area to be 30° or less.

[0040] The degree of orientation and director direction of the liquid crystal compound on the surface of the cholesteric liquid crystal layer can be measured by SHG (Second Harmonic Generation) measurement or the like. Here, the degree of orientation is an index representing the local degree of order of the liquid crystal compound and is also called the order parameter. The degree of orientation can be determined by performing SHG measurements at five locations within the effective area when the reflective circular polarizer is incorporated into a virtual image display device, and all of the measurements should be 0.5 or greater. The director orientation refers to the principal axis direction of the liquid crystal compound. The variation in the director orientation of the liquid crystal compound within the effective area is the maximum value of the angle between the director orientations at different locations when SHG measurements are performed at five locations within the effective area when the reflective circular polarizer is incorporated into a virtual image display device and the local director orientations are measured.

[0041] Specifically, the photo-alignment film is an alignment film containing a photo-alignment material. Examples of the photo-alignment material contained in the photo-alignment film include those disclosed in JP-A-2006-285197, JP-A-2007-76839, JP-A-2007-138138, JP-A-2007-94071, JP-A-2007-121721, JP-A-2007-140465, JP-A-2007-156439, and JP-A-2007-160466. azo compounds described in JP-A-07-133184, JP-A-2009-109831, Japanese Patent No. 3883848, and Japanese Patent No. 4151746; aromatic ester compounds described in JP-A-2002-229039; maleic anhydrides having photo-orienting units described in JP-A-2002-265541 and JP-A-2002-317013; and photocrosslinkable polyimides, polyamides, or esters described in JP-A-9-118717, JP-A-10-506420, JP-A-2003-505561, WO 2010 / 150748, JP-A-2013-177561, and JP-A-2014-12823, in particular cinnamate compounds, chalcone compounds, and coumarin compounds. Particularly preferred examples of the photo-alignment material include azo compounds, photo-crosslinkable polyimides, polyamides, esters, cinnamate compounds, and chalcone compounds.

[0042] The photo-alignment film can be formed by applying a composition containing the photo-alignment material to form a coating film, and then irradiating the coating film with light to impart an alignment control force. The light irradiation is preferably polarized light irradiated from a direction perpendicular to the surface of the coating film or a direction tilted from the perpendicular direction. The light irradiation may also be non-polarized light irradiated from a direction tilted from the direction perpendicular to the surface of the coating film. The composition containing the photo-alignment material may contain components other than the photo-alignment material that can form a photo-alignment film.

[0043] The refractive index of the photo-alignment film can be adjusted by the type of the photo-alignment material, and also by other components that may be contained together with the photo-alignment material.

[0044] The photo-alignment film is a layer having a liquid crystal aligning ability, which specifically means an ability to impart alignment to liquid crystal compounds.

[0045] (Method of Forming Cholesteric Liquid Crystal Layer) A cholesteric liquid crystal layer can be formed by fixing a cholesteric liquid crystal phase in a layered form. The structure in which the cholesteric liquid crystal phase is fixed may be any structure in which the orientation of the liquid crystal compound in the cholesteric liquid crystal phase is maintained. Typically, a polymerizable liquid crystal compound is oriented in the cholesteric liquid crystal phase, and then polymerized and cured by ultraviolet irradiation, heating, or the like to form a non-fluid layer, and at the same time, a structure in which the orientation is changed to a state in which it does not change due to an external field or external force is preferred. Note that in the structure in which the cholesteric liquid crystal phase is fixed, it is sufficient that the optical properties of the cholesteric liquid crystal phase are maintained; in the cholesteric liquid crystal layer, the liquid crystal compound does not need to exhibit liquid crystallinity. For example, the polymerizable liquid crystal compound may be polymerized by a curing reaction and lose its liquid crystallinity.

[0046] An example of a material used to form a cholesteric liquid crystal layer formed by fixing a cholesteric liquid crystal phase is a liquid crystal composition containing a liquid crystal compound. The liquid crystal compound is preferably a polymerizable liquid crystal compound. The liquid crystal composition used to form the cholesteric liquid crystal layer may further contain a surfactant and a chiral agent.

[0047] --Polymerizable Liquid Crystal Compound-- The polymerizable liquid crystal compound may be a rod-shaped liquid crystal compound or a discotic liquid crystal compound. Examples of rod-shaped polymerizable liquid crystal compounds that form a cholesteric liquid crystal phase include rod-shaped nematic liquid crystal compounds. Preferred rod-shaped nematic liquid crystal compounds include azomethines, azoxy compounds, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes, and alkenylcyclohexylbenzonitriles. Not only low-molecular-weight liquid crystal compounds but also high-molecular-weight liquid crystal compounds can be used.

[0048] A polymerizable liquid crystal compound can be obtained by introducing a polymerizable group into a liquid crystal compound. Examples of the polymerizable group include an unsaturated polymerizable group, an epoxy group, and an aziridinyl group, with an unsaturated polymerizable group being preferred, and an ethylenically unsaturated polymerizable group being more preferred. The polymerizable group can be introduced into the molecule of the liquid crystal compound by various methods. The number of polymerizable groups contained in the polymerizable liquid crystal compound is preferably 1 to 6, more preferably 1 to 3. Examples of polymerizable liquid crystal compounds are described in Makromol. Chem. , Vol. 190, p. 2255 (1989), Advanced Materials Vol. 5, p. 107 (1993), U.S. Pat. No. 4,683,327, U.S. Pat. No. 5,622,648, U.S. Pat. No. 5,770,107, WO 95 / 22586, WO 95 / 24455, WO 97 / 00600, WO 98 / 23580, WO 98 / 52905, JP-A Nos. 1-272551, 6-016616, 7-110469, 11-080081, and 2001-328973. Two or more polymerizable liquid crystal compounds may be used in combination. The use of two or more polymerizable liquid crystal compounds in combination can lower the alignment temperature.

[0049] Other examples of polymerizable liquid crystal compounds that can be used include cyclic organopolysiloxane compounds having a cholesteric phase, such as those disclosed in JP-A-57-165480. Examples of the polymeric liquid crystal compounds that can be used include polymers having mesogen groups exhibiting liquid crystallinity introduced into the main chain, side chain, or both the main chain and side chain, polymeric cholesteric liquid crystals having cholesteryl groups introduced into the side chain, liquid crystalline polymers such as those disclosed in JP-A-9-133810, and liquid crystalline polymers such as those disclosed in JP-A-11-293252.

[0050] --Discotic Liquid Crystal Compound-- As the discotic liquid crystal compound, for example, those described in JP-A Nos. 2007-108732 and 2010-244038 can be preferably used.

[0051] From the viewpoint of increasing the reflectance of circularly polarized light of the reflective circular polarizer and reducing ghosting, the reflective circular polarizer preferably includes at least a cholesteric liquid crystal layer formed using a first liquid crystal compound substantially consisting of a rod-shaped liquid crystal compound and a cholesteric liquid crystal layer formed using a second liquid crystal compound substantially consisting of a discotic liquid crystal compound. The term "substantially consisting of rod-shaped liquid crystal compounds" means that 95% by mass or more of the liquid crystal compounds contained in the cholesteric liquid crystal layer are rod-shaped liquid crystal compounds. The term "substantially consisting of discotic liquid crystal compounds" means that 95% by mass or more of the liquid crystal compounds contained in the cholesteric liquid crystal layer are discotic liquid crystal compounds.

[0052] The amount of the polymerizable liquid crystal compound added in the liquid crystal composition is preferably 75 to 99.9 mass %, more preferably 80 to 99 mass %, and even more preferably 85 to 90 mass %, based on the solid content mass (mass excluding the solvent) of the liquid crystal composition.

[0053] --Surfactant-- The liquid crystal composition used to form the cholesteric liquid crystal layer may contain a surfactant. The surfactant is preferably a compound that can function as an alignment control agent that contributes to the stable or rapid alignment of the cholesteric liquid crystal phase. Examples of surfactants include silicone surfactants and fluorine surfactants, with fluorine surfactants being preferred.

[0054] Specific examples of surfactants include the compounds described in paragraphs

[0082] to

[0090] of JP-A No. 2014-119605, the compounds described in paragraphs

[0031] to

[0034] of JP-A No. 2012-203237, the compounds exemplified in paragraphs

[0092] and

[0093] of JP-A No. 2005-099248, the compounds exemplified in paragraphs

[0076] to

[0078] and paragraphs

[0082] to

[0085] of JP-A No. 2002-129162, and fluorine (meth)acrylate polymers described in paragraphs

[0018] to

[0043] of JP-A No. 2007-272185, etc. One type of surfactant may be used alone, or two or more types may be used in combination. As the fluorine-based surfactant, the compounds described in paragraphs

[0082] to

[0090] of JP-A-2014-119605 are preferred.

[0055] The amount of the surfactant added in the liquid crystal composition is preferably 0.01 to 10% by mass, more preferably 0.01 to 5% by mass, and even more preferably 0.02 to 1% by mass, based on the total mass of the liquid crystal compound.

[0056] --Chiral Agents (Optically Active Compounds)--Chiral agents (chiral agents) have the function of inducing a helical structure in a cholesteric liquid crystal phase. Chiral agents can be selected according to the purpose, as the twist direction or helical period of the helix they induce varies depending on the compound. The chiral agent is not particularly limited, and known compounds (e.g., those described in "Liquid Crystal Device Handbook," Chapter 3, Section 4-3, Chiral Agents for TN (Twisted Nematic) and STN (Super Twisted Nematic)," p. 199, edited by the 142nd Committee of the Japan Society for the Promotion of Science, 1989), isosorbide, and isomannide derivatives can be used. Chiral agents generally contain an asymmetric carbon atom, but axially asymmetric or planarly asymmetric compounds without an asymmetric carbon atom can also be used as chiral agents. Examples of axially asymmetric or planarly asymmetric compounds include binaphthyl, helicene, paracyclophane, and their derivatives. The chiral agent may have a polymerizable group. When both the chiral agent and the liquid crystal compound have a polymerizable group, a polymer having a repeating unit derived from the polymerizable liquid crystal compound and a repeating unit derived from the chiral agent can be formed by a polymerization reaction between the polymerizable chiral agent and the polymerizable liquid crystal compound.In this embodiment, the polymerizable group of the polymerizable chiral agent is preferably the same type of group as the polymerizable group of the polymerizable liquid crystal compound.Therefore, the polymerizable group of the chiral agent is also preferably an unsaturated polymerizable group, an epoxy group, or an aziridinyl group, more preferably an unsaturated polymerizable group, and even more preferably an ethylenically unsaturated polymerizable group.In addition, the chiral agent may be a liquid crystal compound.

[0057] When the chiral agent has a photoisomerizable group, it is possible to form a pattern of a desired reflection wavelength corresponding to the emission wavelength by irradiating the chiral agent with actinic rays or the like through a photomask after coating and alignment. The photoisomerizable group is preferably an isomerization site of a compound exhibiting photochromic properties, an azo group, an azoxy group, or a cinnamoyl group. Specific compounds that can be used include those described in JP-A-2002-080478, JP-A-2002-080851, JP-A-2002-179668, JP-A-2002-179669, JP-A-2002-179670, JP-A-2002-179681, JP-A-2002-179682, JP-A-2002-338575, JP-A-2002-338668, JP-A-2003-313189, and JP-A-2003-313292.

[0058] The content of the chiral dopant in the liquid crystal composition is preferably 0.01 to 200 mol %, more preferably 1 to 30 mol %, based on the molar amount of the liquid crystal compound.

[0059] --Polymerization initiator-- When the liquid crystal composition contains a polymerizable compound, it preferably contains a polymerization initiator. In an embodiment in which the polymerization reaction is caused to proceed by ultraviolet irradiation, the polymerization initiator used is preferably a photopolymerization initiator that can initiate the polymerization reaction by ultraviolet irradiation. Examples of photopolymerization initiators include α-carbonyl compounds (described in U.S. Pat. Nos. 2,367,661 and 2,367,670), acyloin ethers (described in U.S. Pat. No. 2,448,828), α-hydrocarbon-substituted aromatic acyloin compounds (described in U.S. Pat. No. 2,722,512), polynuclear quinone compounds (described in U.S. Pat. Nos. 3,046,127 and 2,951,758), combinations of triarylimidazole dimers and p-aminophenyl ketones (described in U.S. Pat. No. 3,549,367), acridine and phenazine compounds (described in JP-A No. 60-105,667 and U.S. Pat. No. 4,239,850), and oxadiazole compounds (described in U.S. Pat. No. 4,212,970). The content of the photopolymerization initiator in the liquid crystal composition is preferably 0.1 to 20% by mass, more preferably 0.5 to 12% by mass, based on the content of the liquid crystal compound.

[0060] Crosslinking Agent The liquid crystal composition may optionally contain a crosslinking agent to improve the film strength and durability after curing. Suitable crosslinking agents are those that cure under ultraviolet light, heat, moisture, or the like. The crosslinking agent is not particularly limited and can be appropriately selected depending on the purpose. Examples include polyfunctional acrylate compounds such as trimethylolpropane tri(meth)acrylate and pentaerythritol tri(meth)acrylate; epoxy compounds such as glycidyl (meth)acrylate and ethylene glycol diglycidyl ether; aziridine compounds such as 2,2-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate] and 4,4-bis(ethyleneiminocarbonylamino)diphenylmethane; isocyanate compounds such as hexamethylene diisocyanate and biuret-type isocyanate; polyoxazoline compounds having an oxazoline group in the side chain; and alkoxysilane compounds such as vinyltrimethoxysilane and N-(2-aminoethyl)3-aminopropyltrimethoxysilane. Furthermore, known catalysts can be used depending on the reactivity of the crosslinking agent, which can improve productivity in addition to improving film strength and durability. These may be used alone or in combination of two or more. The content of the crosslinking agent is preferably 3 to 20% by mass, more preferably 5 to 15% by mass, based on the mass of the solid content of the liquid crystal composition. When the content of the crosslinking agent is within the above range, the effect of improving the crosslink density is easily obtained, and the stability of the cholesteric liquid crystal phase is further improved.

[0061] --Other Additives-- If necessary, polymerization inhibitors, antioxidants, ultraviolet absorbers, light stabilizers, colorants, metal oxide fine particles, and the like may be added to the liquid crystal composition within a range that does not impair optical performance, etc.

[0062] The liquid crystal composition is preferably used as a liquid when forming a cholesteric liquid crystal layer. The liquid crystal composition may contain a solvent. The solvent is not limited and can be appropriately selected depending on the purpose, but organic solvents are preferred. The organic solvent is not limited and can be appropriately selected depending on the purpose, and examples thereof include ketones, alkyl halides, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, and ethers. These may be used alone or in combination of two or more. Among these, ketones are preferred when considering the environmental impact.

[0063] When forming a cholesteric liquid crystal layer, it is preferable to apply a liquid crystal composition to the surface on which the cholesteric liquid crystal layer is to be formed, align the liquid crystal compound in a cholesteric liquid crystal phase, and then harden the liquid crystal compound to form a cholesteric liquid crystal layer. That is, when forming a cholesteric liquid crystal layer on an alignment film, it is preferable to apply a liquid crystal composition to the alignment film, align the liquid crystal compound in a cholesteric liquid crystal phase, and then harden the liquid crystal compound to fix the cholesteric liquid crystal phase, thereby forming a cholesteric liquid crystal layer. Furthermore, when multiple cholesteric liquid crystal layers are laminated, it is possible to apply a liquid crystal composition to an already formed cholesteric liquid crystal layer, align the liquid crystal compound in a cholesteric liquid crystal phase, and then harden the liquid crystal compound to form a second cholesteric liquid crystal layer. The liquid crystal composition can be applied by any known method capable of uniformly applying a liquid to a sheet-like material, including printing methods such as inkjet printing and scroll printing, as well as spin coating, bar coating, and spray coating.

[0064] The applied liquid crystal composition is dried and / or heated as necessary, and then cured to form a cholesteric liquid crystal layer. During this drying and / or heating process, the liquid crystal compounds in the liquid crystal composition may be oriented in a cholesteric liquid crystal phase. When heating is performed, the heating temperature is preferably 200° C. or lower, and more preferably 130° C. or lower.

[0065] The aligned liquid crystal compound is further polymerized as needed. The polymerization may be either thermal polymerization or photopolymerization by light irradiation, but photopolymerization is preferred. The light irradiation is preferably performed using ultraviolet light. The irradiation energy is 20 mJ / cm. 2 ~50 J / cm 2 is preferred, and 50 to 1500 mJ / cm 2 In order to promote the photopolymerization reaction, the irradiation may be carried out under heated conditions or in a nitrogen atmosphere. The wavelength of the ultraviolet light to be irradiated is preferably 250 to 430 nm.

[0066] There is no restriction on the thickness of the cholesteric liquid crystal layer, and the thickness may be appropriately set to obtain the required light reflectance depending on the light reflectance required for the cholesteric liquid crystal layer and the material from which the cholesteric liquid crystal layer is formed.

[0067] <Other Layers> (Absorptive Linear Polarizer) As illustrated in Fig. 3, the virtual image display device of the present invention may have a λ / 4 wavelength plate 401 and an absorbing linear polarizer 402, in this order, on the viewing side surface of the reflective circular polarizer. Combining the λ / 4 wavelength plate 401 and the absorbing linear polarizer 402 can function as an absorbing circular polarizer 400. For example, when the reflective circular polarizer reflects right-handed circularly polarized light, it is preferable to convert the right-handed circularly polarized light that is not completely reflected by the reflective circular polarizer into linearly polarized light by the λ / 4 wavelength plate and then have it absorbed by the absorbing linear polarizer, thereby reducing ghosts.

[0068] The material constituting the λ / 4 wavelength plate is not particularly limited, and examples thereof include liquid crystal compounds and polymers. A liquid crystal compound can form a retardation layer by orienting a liquid crystal material to exhibit refractive index anisotropy. A polymer can form a λ / 4 wavelength plate by exhibiting refractive index anisotropy through stretching or the like of a polymer film obtained by casting, coating, or the like. The λ / 4 wavelength plate is preferably a layer formed using a liquid crystal compound, and more preferably a layer formed using a liquid crystal compound having a polymerizable group. The liquid crystal compound used in the λ / 4 wavelength plate is preferably a liquid crystal compound having a polymerizable group.

[0069] The liquid crystal compound may be a liquid crystal compound that exhibits either normal wavelength dispersion or reverse wavelength dispersion. When a retardation layer that exhibits the characteristics of a wide-band λ / 4 wavelength plate as a single film is used, a liquid crystal compound that exhibits reverse wavelength dispersion is preferred, and a liquid crystal compound that has two or more polymerizable groups and exhibits reverse wavelength dispersion is more preferred.

[0070] In this specification, the term "liquid crystal compound exhibiting reverse wavelength dispersion" refers to a compound that satisfies the relationship between the following formulas (A) and (B) when the in-plane retardation (Re) value at a specific wavelength (visible light range) of an optically anisotropic layer prepared using this compound is measured.

[0071] Formula (A) Re(450) / Re(550)<1.00 Formula (B) Re(650) / Re(550)>1.00

[0072] As described above, the λ / 4 wavelength plate is preferably a layer formed using a liquid crystal compound having a polymerizable group, and more preferably a layer formed by fixing the orientation state of a liquid crystal compound having a polymerizable group.

[0073] The orientation state that a liquid crystal compound having a polymerizable group can assume is not particularly limited, and examples thereof include homogeneous orientation, homeotropic orientation, twisted orientation, cholesteric orientation, hybrid orientation, and tilted orientation. Specifically, hybrid orientation refers to an orientation in which the tilt angle of the liquid crystal compound changes continuously from one surface to the other. Specifically, tilted orientation refers to an orientation in which the tilt angle of the liquid crystal compound is constant from one surface to the other. Furthermore, twisted orientation refers to an orientation in which the liquid crystal compound is twisted around the thickness direction as the axis of rotation. When the liquid crystal compound is twisted and has a predetermined tilt angle (tilt angle greater than 0°), this corresponds to twisted hybrid orientation. In this specification, twisted orientation refers to an embodiment in which the twist angle of the liquid crystal compound is less than 360°, and the above-mentioned cholesteric orientation refers to an embodiment in which the twist angle of the liquid crystal compound is 360° or greater.

[0074] A λ / 4 wave plate formed using a liquid crystal compound may have a plurality of regions along the thickness direction in which the liquid crystal compound has different alignment states. For example, the λ / 4 wave plate may have a region along the thickness direction in which the liquid crystal compound is fixed in a homogeneously aligned state and a region in which the liquid crystal compound is fixed in a twisted aligned state.

[0075] The thickness of the λ / 4 wave plate is not particularly limited, but is preferably 0.1 to 10.0 μm, more preferably 0.5 to 5.0 μm.

[0076] Specific examples of the configuration of a wideband λ / 4 wave plate include those configured with a single-layer retardation layer, such as WO 2019 / 160016, JP 2020-173460 A and WO 2021 / 157694 A. Retardation layers using liquid crystal compounds exhibiting reverse wavelength dispersion, as disclosed in WO 2022 / 030308 and JP 2022-184691 A. λ / 4 wave plates having a plurality of regions along the thickness direction in which the orientation states of the liquid crystal compounds disclosed in WO 2022 / 030308 and JP 2022-184691 A are different. Examples of a laminate of two or more retardation layers include a combination of a λ / 4 retardation layer and a λ / 2 retardation layer as disclosed in JP 2001-108825 A, JP 2001-91741 A, and WO 2013 / 137464, etc., and a combination of a retardation layer having a twisted orientation and another retardation layer as disclosed in JP 2001-21720 A, JP 2014-209219 A, and WO 2022 / 255105, etc. Further, other retardation layers such as a positive C plate and a negative C plate may be added to the λ / 4 wave plate to compensate for the phase difference change with respect to obliquely incident light.

[0077] (Absorptive Linear Polarizer) An absorptive linear polarizer refers to a linear polarizer that absorbs incident light that is linearly polarized in the absorption axis direction and transmits light that is linearly polarized in the transmission axis direction.

[0078] As the absorptive linear polarizer, a known absorptive linear polarizer can be used, for example, a polarizer in which a dichroic material is dyed onto polyvinyl alcohol or other polymer resin and then stretched to be oriented, or a polarizer in which a dichroic material is oriented by utilizing the orientation of a liquid crystal compound. The thickness of the absorptive linear polarizer is preferably 10 μm or less, more preferably 7 μm or less, and even more preferably 5 μm or less. If the absorptive linear polarizer is thin, it is possible to prevent cracks, breakage, etc. from occurring when the absorptive linear polarizer is stretched or molded.

[0079] The single-plate transmittance of the absorptive linear polarizer is preferably 40% or more, more preferably 42% or more. The degree of polarization is preferably 90% or more, more preferably 95% or more, and even more preferably 99% or more. In this specification, the single-plate transmittance and degree of polarization of the absorptive linear polarizer are measured using an automatic polarizing film measuring device: VAP-7070 (manufactured by JASCO Corporation).

[0080] The angle formed between the transmission axis of the absorptive linear polarizer and the slow axis of the λ / 4 wavelength plate is preferably 45±10°, more preferably 45±5°, and even more preferably 45±3°.

[0081] As described above, the absorptive linear polarizer is preferably a light-absorption anisotropic layer containing a liquid crystal compound and a dichroic substance. A linear polarizer containing a liquid crystal compound and a dichroic substance is preferred because it can be made thin and is less likely to crack or break even when stretched, molded, etc. The thickness of the light-absorption anisotropic layer is not particularly limited, but is preferably 0.1 to 8 μm, more preferably 0.3 to 5 μm, from the viewpoint of thinning.

[0082] A linear polarizer containing a liquid crystal compound and a dichroic material can be produced, for example, by reference to JP 2020-023153 A. From the viewpoint of improving the polarization degree of the linear polarizer, the light-absorbing anisotropic layer preferably has an orientation degree of the dichroic material of 0.95 or more, more preferably 0.97 or more. The liquid crystal compound contained in the light-absorbing anisotropic layer-forming composition for forming the light-absorbing anisotropic layer is preferably a liquid crystal compound that does not exhibit dichroism in the visible range. Both low-molecular-weight liquid crystal compounds and polymeric liquid crystal compounds can be used as the liquid crystal compound. Here, "low-molecular-weight liquid crystal compound" refers to a liquid crystal compound that does not have a repeating unit in its chemical structure. Furthermore, "polymeric liquid crystal compound" refers to a liquid crystal compound that has a repeating unit in its chemical structure.

[0083] Examples of polymeric liquid crystal compounds include the thermotropic liquid crystal polymers described in JP 2011-237513 A. The polymeric liquid crystal compounds preferably have a crosslinkable group (e.g., an acryloyl group or a methacryloyl group) at the terminal. The liquid crystal compounds may be used alone or in combination of two or more. It is also preferable to use a polymeric liquid crystal compound and a low molecular weight liquid crystal compound in combination.

[0084] The content of the liquid crystal compound is preferably 25 to 2000 parts by mass, more preferably 33 to 1000 parts by mass, and even more preferably 50 to 500 parts by mass, relative to 100 parts by mass of the content of the dichroic substance in the composition. When the content of the liquid crystal compound is within the above range, the degree of orientation of the polarizer is further improved.

[0085] The dichroic substance contained in the composition for forming an optically absorptive anisotropic layer for forming the optically absorptive anisotropic layer is not particularly limited, and examples thereof include visible light absorbing substances (dichroic dyes), ultraviolet absorbing substances, infrared absorbing substances, nonlinear optical substances, carbon nanotubes, etc., and any conventionally known dichroic substance (dichroic dye) can be used. In an absorptive linear polarizer, two or more dichroic substances may be used in combination. For example, from the viewpoint of obtaining a high degree of polarization over a wider wavelength range, it is preferable to use in combination at least one dichroic substance having a maximum absorption wavelength in the wavelength range of 370 to 550 nm and at least one dichroic substance having a maximum absorption wavelength in the wavelength range of 500 to 700 nm.

[0086] The reflective circular polarizer, λ / 4 wavelength plate, and absorptive linear polarizer used in the virtual image display device of the present invention may include a support and / or an alignment layer. Alternatively, the reflective circular polarizer, λ / 4 wavelength plate, and absorptive linear polarizer used in the virtual image display device of the present invention may have a support and / or alignment layer during production, and the support or even the alignment layer may be peeled off in the end. That is, the support and alignment layer may be a temporary support that is finally peeled off and removed. Peeling off and removing the temporary support is preferable because it makes it possible to reduce the thickness of the virtual image display device and also eliminates the adverse effect that the retardation of the temporary support has on the polarization degree of transmitted light.

[0087] The type of support is not particularly limited, but is preferably transparent to visible light. Examples of the support include films (sheets) made of triacetyl cellulose, polyethylene terephthalate film, 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; polyetherketone; polyphenylene sulfide, polyphenylene oxide, etc. In addition, commercially available products can also be used as the support. Commercially available products 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).

[0088] Furthermore, in order to minimize the influence on various sensors that use near-infrared light as a light source, such as those for eye tracking, facial expression recognition, and iris authentication, which are incorporated into optical systems such as virtual reality display devices and electronic viewfinders, the reflective circular polarizer, λ / 4 wave plate, and absorptive linear polarizer used in the virtual image display device of the present invention are preferably transparent to near-infrared light.

[0089] (Other Functional Layers) The virtual image display device of the present invention may have other functional layers in addition to the reflective circular polarizer, the λ / 4 wavelength plate, and the absorptive linear polarizer. Suitable examples of these functional layers include a positive C plate and an anti-reflection layer, and the virtual image display device of the present invention preferably includes these.

[0090] (Folded Optical System) The reflective circular polarizer, λ / 4 wavelength plate, and absorptive linear polarizer used in the virtual image display device of the present invention are preferably bonded to the surface of a lens to form a folded optical system. In this case, a half mirror is preferably formed on the surface of the lens opposite to the surface to which the reflective circular polarizer is bonded. The reflective circular polarizer, λ / 4 wavelength plate, and absorptive linear polarizer may be molded into a curved shape to match the surface shape of the lens. In order to reduce image distortion and aberration, these components are preferably molded into a curved shape to match the surface shape of the lens. There are no limitations on the method for molding the reflective circular polarizer, λ / 4 wavelength plate, and absorptive linear polarizer into a curved surface, and various known methods can be used depending on the forming material and layer structure of the reflective circular polarizer, etc. The lens is not limited, and various known lenses can be used. Examples of lenses include convex lenses and concave lenses. Examples of convex lenses include biconvex lenses, plano-convex lenses, and convex meniscus lenses. As the concave lens, for example, a biconcave lens, a plano-concave lens, a concave meniscus lens, or the like can be used.

[0091] Lens materials that are transparent to visible light include glass, crystal, and plastic. Because birefringence of lenses can cause rainbow irregularities and light leakage, it is preferable that it is small, and more preferable that the birefringence of the lens is substantially zero.

[0092] <Image Display Device> In the virtual image display device of the present invention, there are no limitations on the image display device (image display element (display panel)), and various known image display devices used in virtual image display devices and the like can be used. Examples of image display devices include liquid crystal displays (LCDs (Liquid Crystal Displays)), organic electroluminescence display devices (OLEDs (Organic Light Emitting Diodes)), CRTs (Cathode-ray tubes), electronic paper, LED (Light Emitting Diode) display devices, micro LED display devices, DLPs (Digital Light Processing), and MEMS (Micro-Electro-Mechanical Systems) display devices. Note that in the virtual image display device of the present invention, the image display device may, as necessary, have optical elements such as a retardation layer (λ / 4 wave plate) and a linear polarizer, as described above. Note that if the image display element emits linearly polarized light, such as a liquid crystal display, a linear polarizer is not necessary.

[0093] The present invention will be described in more detail below with reference to examples. The materials, amounts used, ratios, treatment details, and treatment procedures shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the examples shown below.

[0094] [Preparation of Coating Liquid for Reflective Layer] [Coating Liquid R-1 for Reflective Layer] The composition shown below was stirred and dissolved in a container kept at 70° C. to prepare Coating Liquid R-1 for Reflective Layer, where R represents a coating liquid using a rod-like liquid crystal compound.

[0095] -------------------------------------------------- Coating liquid R-1 for reflective layer -------------------------------------------------- Methyl ethyl ketone 120.9 parts by mass Cyclohexanone 21.3 parts by mass Mixture X of the following rod-shaped liquid crystal compounds 100.0 parts by mass Photopolymerization initiator B 1.00 part by mass Chiral agent A 4.18 parts by mass Surfactant F1 0.1 part by mass -------------------------------------------------- Mixture X of rod-shaped liquid crystal compounds

[0096] In the above mixture X, the numerical values ​​are in mass %. R is a group bonded via an oxygen atom. Furthermore, the average molar absorption coefficient of the above rod-shaped liquid crystal compound in the wavelength range of 300 to 400 nm was 140 / mol cm.

[0097] Chiral agent A

[0098] Surfactant F1

[0099] Photopolymerization initiator B

[0100] The chiral agent A is a chiral agent whose helical twisting power (HTP) is reduced by light.

[0101] [Reflective Layer Coating Solution R-2] This was prepared in the same manner as Reflective Layer Coating Solution R-1, except that the amount of chiral agent A added was changed as shown in Table 1 below.

[0102]

[0103] [Reflective layer coating solution D-1] The composition shown below was stirred and dissolved in a container kept at 50° C. to prepare a reflective layer coating solution D-1, where D represents a coating solution using a discotic liquid crystal compound.

[0104] -------------------------------------------------- Coating liquid D-1 for reflective layer -------------------------------------------------- 80 parts by mass of discotic liquid crystal compound (A) below 20 parts by mass of discotic liquid crystal compound (B) below 10 parts by mass of polymerizable monomer E1 below 0.3 parts by mass of surfactant F2 below 3 parts by mass of photopolymerization initiator (Irgacure 907, manufactured by BASF) 5.45 parts by mass of the chiral agent A above Methyl ethyl ketone 290 parts by mass Cyclohexanone 50 parts by mass --------------------------------------------------

[0105] Discotic Liquid Crystal Compound (A)

[0106] Discotic Liquid Crystal Compound (B)

[0107] Polymerizable Monomer E1

[0108] Surfactant F2

[0109] [Reflective Layer Coating Solutions D-2 and D-3] These were prepared in the same manner as Reflective Layer Coating Solution D-1, except that the amount of chiral agent A added was changed as shown in Table 2 below.

[0110]

[0111] [Preparation of Reflective Circular Polarizer 1] A 100 μm thick PET film (A4265, manufactured by Toyobo Co., Ltd.) was prepared as a temporary support, and the PET surface on which the easy-adhesive layer was not formed was subjected to a rubbing treatment. The prepared reflective layer coating solution R-1 was applied using a wire bar coater, and then dried at 110°C for 72 seconds. Thereafter, the reflective circular polarizer was subjected to a rubbing treatment at 100°C under a low-oxygen atmosphere (100 ppm or less) with an illuminance of 80 mW / cm. 2 , irradiation amount 500mJ / cm 2The coating was cured by irradiating it with light from a metal halide lamp at 1000 kJ / min, thereby forming a first blue light reflective layer (first cholesteric liquid crystal layer) made of a cholesteric liquid crystal layer. The light irradiation was performed from the cholesteric liquid crystal layer side. The coating thickness was adjusted so that the film thickness of the first blue light reflective layer after curing was 2.6 μm.

[0112] Next, the first blue light reflecting layer surface was subjected to a discharge of 150 W·min / m 2 After corona treatment, the reflective layer coating solution D-1 was applied to the corona-treated surface using a wire bar coater. Subsequently, the coating film was dried at 70°C for 2 minutes, and after the solvent was evaporated, it was heat-aged at 115°C for 3 minutes to obtain a uniform alignment state. Thereafter, this coating film was kept at 45°C and irradiated with ultraviolet light (300 mJ / cm) using a metal halide lamp under a nitrogen atmosphere. 2 ) and cured to form a second blue light reflective layer (second cholesteric liquid crystal layer) on the first blue light reflective layer. Light was irradiated from the cholesteric liquid crystal layer side. At this time, the coating thickness was adjusted so that the film thickness of the second blue light reflective layer after curing was 2.0 μm.

[0113] Next, the reflective layer coating solution D-2 was applied onto the second blue light reflective layer using a wire bar coater. Subsequently, the coating film was dried at 70°C for 2 minutes, and after the solvent was evaporated, it was heat-aged at 115°C for 3 minutes to obtain a uniformly oriented state. Thereafter, this coating film was kept at 45°C and irradiated with ultraviolet light (300 mJ / cm) using a metal halide lamp under a nitrogen atmosphere. 2 ) and cured to form a green light reflective layer (third cholesteric liquid crystal layer) on the second blue light reflective layer. Light was irradiated from the cholesteric liquid crystal layer side. At this time, the coating thickness was adjusted so that the film thickness of the green light reflective layer after curing was 2.7 μm.

[0114] Next, the reflective layer coating solution R-2 was applied onto the green light reflective layer using a wire bar coater, and then dried at 110°C for 72 seconds. Thereafter, the coating solution was dried in a low-oxygen atmosphere (100 ppm or less) at 100°C with an illuminance of 80 mW and an irradiation dose of 500 mJ / cm. 2The coating was cured by irradiating it with light from a metal halide lamp (1000 W / m²), thereby forming a red light reflective layer (fourth cholesteric liquid crystal layer) on the green light reflective layer. The light was irradiated from the cholesteric liquid crystal layer side. The coating thickness was adjusted so that the red light reflective layer after curing had a thickness of 3.4 μm.

[0115] Next, the red light reflecting layer surface was subjected to a discharge of 150 W·min / m 2 After corona treatment at 70°C, the reflective layer coating solution D-3 was applied to the corona-treated surface using a wire bar coater. Subsequently, the coating film was dried at 70°C for 2 minutes, and after the solvent was evaporated, it was heat-aged at 115°C for 3 minutes to obtain a uniform alignment state. Thereafter, this coating film was kept at 45°C and irradiated with ultraviolet light (300 mJ / cm) using a metal halide lamp under a nitrogen atmosphere. 2 ) and cured to form a yellow light reflective layer (fifth cholesteric liquid crystal layer) on the red light reflective layer. Light was irradiated from the cholesteric liquid crystal layer side. At this time, the coating thickness was adjusted so that the film thickness of the yellow light reflective layer after curing was 3.4 μm.

[0116] By the above procedure, a reflective circular polarizer 1 having the first to fifth cholesteric liquid crystal layers in this order was obtained.

[0117] The central reflection wavelength and film thickness of each cholesteric liquid crystal layer of the produced reflective circular polarizer 1 are shown in Table 3. Here, the central reflection wavelength shown in Table 3 corresponds to the central wavelength of the reflected light of the above-mentioned cholesteric liquid crystal layer. The central reflection wavelength (central wavelength of the reflected light) was confirmed by creating a film in which each cholesteric liquid crystal layer was coated in a single layer. The film thickness was confirmed using an SEM.

[0118]

[0119] Furthermore, the temporary support (PET film) of the obtained reflective circular polarizer 1 was peeled off, and SHG measurement of the surface of the first cholesteric liquid crystal layer (first layer) was performed, and the degree of orientation of the liquid crystal compound was 0.65. Furthermore, within the effective area when incorporated into a virtual image display device, the variation in the director orientation of the liquid crystal compound was 3.2°. Furthermore, SHG measurement of the surface of the reflective circular polarizer 1 on the side of the fifth cholesteric liquid crystal layer (fifth layer) was performed, and the degree of orientation of the liquid crystal compound was 0.62. Furthermore, within the effective area when incorporated into a virtual image display device, the variation in the director orientation of the liquid crystal compound was 85°.

[0120] [Preparation of Reflective Circular Polarizer 2] [Reflective Layer Coating Solution R-3] The composition shown below was stirred and dissolved in a container kept at 70° C. to prepare a reflective layer coating solution R-3, where R represents a coating solution using a rod-like liquid crystal compound.

[0121] Coating liquid R-3 for reflective layer -------------------------------------------------- Methyl ethyl ketone 120.9 parts by mass Cyclohexanone 21.3 parts by mass Rod-like liquid crystal compound X2 below 100.0 parts by mass Photopolymerization initiator B above 1.00 part by mass Chiral agent A above 4.18 parts by mass Surfactant F1 above 0.1 part by mass

[0122] Rod-shaped liquid crystal compound X2

[0123] [Reflective Layer Coating Solution R-4] This was prepared in the same manner as Reflective Layer Coating Solution R-3, except that the amount of chiral agent A added was changed as shown in Table 4 below.

[0124]

[0125] [Reflective Layer Coating Solution D-4] The following composition was stirred and dissolved to prepare Reflective Layer Coating Solution D-4, where D represents a coating solution using a discotic liquid crystal compound.

[0126] -------------------------------------------------- Reflective layer coating liquid D-4 -------------------------------------------------- 100 parts by mass of the following discotic liquid crystal compound (C) -------------------------------------------------- 10 parts by mass of the above polymerizable monomer E1 -------------------------------------------------- 0.3 parts by mass of the above surfactant F2 -------------------------------------------------- 3 parts by mass of photopolymerization initiator (Irgacure 907, manufactured by BASF) ---------------------------------- 5.45 parts by mass of the above chiral agent A -------------------------------------------------- 340 parts by mass of methylene chloride --------------------------------------------------

[0127] Discotic Liquid Crystal Compound (C)

[0128] [Reflective Layer Coating Solutions D-5 and D-6] These were prepared in the same manner as Reflective Layer Coating Solution D-4, except that the amount of chiral agent A added was changed as shown in Table 5 below.

[0129]

[0130] Using these coating solutions, reflective circular polarizers 2 were produced by coating in the same manner as reflective circular polarizer 1, except that the film thickness after curing was adjusted to the values ​​shown in Table 6. Therefore, in reflective circular polarizer 2, as in reflective circular polarizer 1, the first layer (first cholesteric liquid crystal layer) is formed on the alignment film.

[0131]

[0132] The temporary support (PET film) of the obtained reflective circular polarizer 2 was peeled off, and SHG measurement of the surface of the first cholesteric liquid crystal layer (first layer) was performed, and the degree of orientation of the liquid crystal compound was 0.67. Furthermore, within the effective area when incorporated into a virtual image display device, the variation in the director orientation of the liquid crystal compound was 2.6°. Furthermore, SHG measurement of the surface of the reflective circular polarizer 2 on the side of the fifth cholesteric liquid crystal layer (fifth layer) was performed, and the degree of orientation of the liquid crystal compound was 0.64. Furthermore, within the effective area when incorporated into a virtual image display device, the variation in the director orientation of the liquid crystal compound was 79°.

[0133] [Fabrication of λ / 4 Waveplate] A λ / 4 waveplate 1 with reverse wavelength dispersion was fabricated with reference to the method described in paragraphs 0151 to 0163 of JP 2020-084070 A. The λ / 4 waveplate 1 had Re = 141 nm and Rth = 71 nm.

[0134] [Preparation of Positive C Plate 2] Positive C Plate 2 was prepared by adjusting the film thickness with reference to the method described in paragraphs 0132 to 0134 of JP 2016-053709 A. However, the support was changed from a polyethylene terephthalate film (PET film) to a triacetyl cellulose film (TAC film). Positive C Plate 2 had Re = 0.1 nm and Rth = -80 nm.

[0135] [Preparation of Linear Polarizer] A linear polarizer was prepared by the following procedure.

[0136] (Preparation of Cellulose Acylate Film 1) <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------------------------------------------------ - Cellulose acetate having an acetyl substitution degree of 2.88: 100 parts by mass - Polyester compound B described in the examples of JP2015-227955A: 12 parts by mass - Compound F below: 2 parts by mass - Methylene chloride (first solvent): 430 parts by mass - Methanol (second solvent): 64 parts by mass

[0137] Compound F

[0138] <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.

[0139] 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 -

[0140] <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 still containing approximately 20% solvent by weight. Both ends of the film in the width direction were fixed with tenter clips, and the film was stretched transversely at a draw ratio of 1.1 times while being dried. The film was then further dried by being transported between the rolls of a heat treatment device to produce an optical film with a thickness of 40 μm, designated as Cellulose Acylate Film 1. The Re of the resulting Cellulose Acylate Film 1 was 0 nm.

[0141] (Formation of Photo-Alignment Layer PA1) The coating liquid S-PA-1 for forming an alignment layer, which will be described later, was continuously applied onto 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 A photo-alignment layer PA1 was formed by irradiating the substrate with light (using an ultra-high pressure mercury lamp). The film thickness was 0.3 μm.

[0142] ------------------------------------------------------------------ (Coating liquid for forming alignment layer S-PA-1) ------------------------------------------------------------------ Polymer M-PA-1 (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 Xylene 1220.00 parts by mass Methyl isobutyl ketone 122.00 parts by mass

[0143] Polymer M-PA-1

[0144] Acid generator PAG-1

[0145] Acid generator CPI-110TF

[0146] (Formation of Optically Absorbent Anisotropic Layer P1) On the obtained photo-alignment layer PA1, the following coating solution S-P-1 for forming an optically absorbent anisotropic layer was continuously applied using a wire bar to form a coating layer. The formed coating layer was then heated at 140°C for 30 seconds and cooled to room temperature (23°C). Next, it was heated at 90°C for 60 seconds and cooled again to room temperature. Thereafter, an LED lamp (center wavelength 365 nm) was used to apply the coating solution S-P-1 to form an optically absorbent anisotropic layer. The coating layer was then heated at 140°C for 30 seconds and cooled to room temperature again. The coating layer was then heated at 90°C for 60 seconds and cooled again to room temperature. After that, an LED lamp (center wavelength 365 nm) was used to apply the coating solution S-P-1 to form an optically absorbent anisotropic layer. The coating layer was then heated at 90°C for 60 seconds and cooled again to room temperature. The coating layer was then heated at an illuminance of 200 mW / cm. 2 The optically absorptive anisotropic layer P1 was formed on the photo-alignment layer PA1 by irradiating the layer for 2 seconds under the irradiation conditions of 1.6 μm.

[0147] 0.25 parts by mass of dichroic substance D-1 shown below 0.36 parts by mass of dichroic substance D-2 shown below 0.59 parts by mass of dichroic substance D-3 shown below 2.21 parts by mass of polymer liquid crystal compound M-P-1 shown below 1.36 parts by mass of low molecular weight liquid crystal compound M-1 shown below 0.200 parts by mass of polymerization initiator IRGACURE OXE-02 (manufactured by BASF) 0.026 parts by mass of surfactant F-3 shown below Cyclopentanone 46.00 parts by mass Tetrahydrofuran 46.00 parts by mass Benzyl alcohol 3.00 parts by mass

[0148] Dichroic substance D-1

[0149] Dichroic substance D-2

[0150] Dichroic substance D-3

[0151] Polymer liquid crystal compound M-P-1

[0152] Low molecular liquid crystal compound M-1

[0153] Surfactant F-3

[0154] [Preparation of Laminated Films] The above members were laminated together to obtain laminated films 1 and 2 according to the following procedure.

[0155] A PMMA substrate was coated with UV adhesive Chemiseal U2084B (manufactured by Chemitech Corporation, refractive index after curing: n 1.60) to a thickness of 2 μm using a wire bar coater. The optically absorptive anisotropic layer P1 was laminated onto the formed adhesive layer. The lamination was performed using a laminator so that the surface of the optically absorptive anisotropic layer P1 opposite the temporary support (cellulose acylate film 1) was in contact with the adhesive layer. Next, the purge box was purged with nitrogen until the oxygen concentration was 100 ppm or less, and then ultraviolet light from a high-pressure mercury lamp was irradiated from the temporary support side of the optically absorptive anisotropic layer P1 to cure the adhesive layer. The illuminance was 25 mW / cm. 2 , the irradiation dose is 1000 mJ / cm 2 Finally, the temporary support of the optically absorptive anisotropic layer P1 was peeled off.

[0156] A UV adhesive layer was formed on the exposed surface of the optically absorptive anisotropic layer P1 using the same procedure as above, and a λ / 4 wavelength plate 1 was attached thereto. However, the lamination was performed so that the angle between the slow axis of the λ / 4 wavelength plate 1 and the absorption axis of the optically absorptive anisotropic layer P1 was 45°. Next, a UV adhesive layer was formed on the λ / 4 wavelength plate 1 using the same transfer procedure as above, and a positive C plate 2 was attached thereto. Finally, a UV adhesive layer was formed on the positive C plate 2 using the same procedure as above, and a reflective circular polarizer 1 was attached thereto, thereby producing a laminate film 1. The attachment was performed so that the surface of the reflective circular polarizer 1 facing the fifth cholesteric liquid crystal layer was in contact with the UV adhesive layer. Furthermore, the PET film of the reflective circular polarizer 1 of the laminate film 1 was peeled off to expose the surface of the first cholesteric liquid crystal layer. The laminate film 1 had a reflective circular polarizer 1, a positive C plate 2, a λ / 4 wavelength plate 1, and an optically absorptive anisotropic layer 1, in this order.

[0157] A laminate film 2 having a reflective circular polarizer 2 was produced in the same manner as the procedure for producing the laminate film 1, except that the reflective circular polarizer 2 was used instead of the reflective circular polarizer 1.

[0158] [Fabrication of folding optical system] [Formation of half mirror on lens] Aluminum was vapor-deposited on the convex side of a lens (a convex meniscus lens LE1076-A (diameter 2 inches, focal length 100 mm) manufactured by Thorlab) to give a reflectance of 40%, forming a half mirror. Lens 1 with a half mirror was obtained by the above procedure.

[0159] [Molding of Reflective Circular Polarizer and Fabrication of Folded Optical System 1] The fabricated reflective circular polarizer 1 was molded and attached to the concave side of a half-mirror-equipped lens 1 to fabricate a folded optical system 1. The reflective circular polarizer 1 was molded and attached to the curved surface by the following procedure. First, a Lintec Corporation adhesive sheet "NCF-D692(5)" was attached to the surface of the first cholesteric liquid crystal layer of the reflective circular polarizer 1. With the separator film of the adhesive sheet peeled off, the first cholesteric liquid crystal layer was placed with the adhesive sheet facing the concave surface of the half-mirror-equipped lens 1, and vacuum molding was performed using the method described in JP 2012-116094 A. The molding temperature was 110°C. In this way, a reflective circular polarizer 1 was molded, and a folded optical system 1 was fabricated in which the reflective circular polarizer 1 was attached to the concave surface of the half-mirror-equipped lens 1.

[0160] [Fabrication of the Virtual Image Display Device of Example 1] The lens portion of a virtual reality display device "PICO4" manufactured by PICO Corporation was removed, and the folding optical system was taken out. Since the PICO4 image display device emits left-handed circularly polarized light, the polarizing plate on the surface of the image display device was peeled off, and a circular polarizing plate that emits right-handed circularly polarized light was attached instead. Next, the folded optical system 1 thus fabricated was assembled in place of the removed folded optical system, and the virtual image display device of Example 1 was fabricated. In this case, the folding optical system 1 was installed so that the convex side, i.e., the half mirror side, faced the image display device. Therefore, in this example, the first cholesteric liquid crystal layer (first layer) of the reflective circular polarizer 1 faced the image display device.

[0161] [Fabrication of Virtual Image Display Device of Example 2] A folded optical system was fabricated in the same manner as folded optical system 1, except that reflective circular polarizer 2 was used instead of reflective circular polarizer 1. A virtual image display device of Example 2 was fabricated in the same manner as Example 1, except that this folded optical system was used. Therefore, in this example, the first cholesteric liquid crystal layer (first layer) of reflective circular polarizer 2 is the surface facing the image display device.

[0162] [Fabrication of Virtual Image Display Device of Example 3] A folded optical system was fabricated in the same manner as the folded optical system 1, except that a laminate film 1 was used instead of the reflective circular polarizer 1. A virtual image display device of Example 3 was fabricated in the same manner as Example 1, except that this folded optical system was used. When molding the laminate film 1 into the lens with a half mirror 1, the side of the first cholesteric liquid crystal layer of the reflective circular polarizer 1 in the laminate film 1 was positioned on the concave side of the lens with a half mirror 1, and the molding temperature was 110°C. Therefore, in this example, the first cholesteric liquid crystal layer (first layer) of the reflective circular polarizer 1 of the laminate film 1 was positioned on the image display device side.

[0163] [Fabrication of Virtual Image Display Device of Example 4] A folded optical system was fabricated in the same manner as the folded optical system 1, except that a laminate film 2 was used instead of the reflective circular polarizer 1. A virtual image display device of Example 4 was fabricated in the same manner as Example 1, except that this folded optical system was used. When molding the laminate film 2 into the lens with a half mirror 1, the side of the first cholesteric liquid crystal layer of the reflective circular polarizer 2 in the laminate film 2 was positioned on the concave side of the lens with a half mirror 1, and the molding temperature was 110°C. Therefore, in this example, the first cholesteric liquid crystal layer (first layer) of the reflective circular polarizer 2 of the laminate film 2 was positioned on the image display device side.

[0164] [Fabrication of Virtual Image Display Device of Comparative Example 1] A folded optical system was fabricated in the same manner as the folded optical system 1, except that when the reflective circular polarizer 1 was molded into the half-mirror-equipped lens 1, the fifth cholesteric liquid crystal layer side of the reflective circular polarizer 1 was positioned on the concave side of the half-mirror-equipped lens 1. Except for using this folded optical system, a virtual image display device of Comparative Example 1 was fabricated in the same manner as Example 1. Therefore, in this example, the fifth cholesteric liquid crystal layer (fifth layer) of the reflective circular polarizer 1 is the surface facing the image display device.

[0165] [Evaluation] [Evaluation of Ghosts] The virtual image display devices of the example and comparative example were each produced five times using the same production procedure. A black and white checkered pattern was displayed on the image display panel of the produced virtual image display device, and the visibility of ghosts was visually evaluated according to the following criteria. In practice, ratings A to C are preferable, with ratings A or B being more preferable. A: Not visible at all. B: Slightly visible but not bothersome. C: Weak ghosts are visible. D: A somewhat strong ghost is visible. E: Strong ghosts are visible.

[0166] The evaluation results of ghosts in the examples and comparative examples are shown in Table 7. The evaluation values ​​shown are the evaluation values ​​for the smallest ghost and the evaluation values ​​for the largest ghost out of the five evaluations performed.

[0167]

[0168] From the results shown in Table 7, the visibility of ghosts was stable and small with little variation in the virtual image display devices of Examples 1 to 4. On the other hand, in the virtual image display device of Comparative Example 1, the visibility of ghosts varied from device to device, with the worst device showing strong ghost visibility.

[0169] 10, 11, 12 Light beam 200 Reflective circular polarizer 300 Half mirror 400 Circular polarizer 401 λ / 4 wave plate 402 Absorption type linear polarizer 500 Image display device 600 Folding optical system 1000 Virtual image display device

Claims

1. A virtual image display device having at least an image display device and a folding optical system including a reflective circular polarizer, wherein the reflective circular polarizer includes a cholesteric liquid crystal layer, and the cholesteric liquid crystal layer has a degree of orientation of a liquid crystal compound of 0.5 or more on the surface facing the image display device, and the variation in director orientation of the liquid crystal compound within the effective area is 30° or less.

2. The virtual image display of claim 1, wherein the reflective circular polarizer comprises a plurality of cholesteric liquid crystal layers.

3. The virtual image display device according to claim 2, wherein the reflective circular polarizer includes at least a cholesteric liquid crystal layer formed using a first liquid crystal compound consisting essentially of a rod-shaped liquid crystal compound, and a cholesteric liquid crystal layer formed using a second liquid crystal compound consisting essentially of a discotic liquid crystal compound.

4. The virtual image display device according to any one of claims 1 to 3, wherein at least a λ / 4 wavelength plate and an absorptive linear polarizer are laminated in this order on the viewing side surface of the reflective circular polarizer.

5. The virtual image display device according to any one of claims 1 to 3, wherein the reflective circular polarizer is formed into a curved shape.