Optical device and head-mounted display

Abstract

An object of the present invention is to provide an optical device and an HMD using the optical device that can obtain a stable image quality without being affected by a focal length when changing the focal length of an image in the HMD or the like. The present invention addresses the problem by having: a switching element that can be switched between a first phase difference and a second phase difference, the difference between the first phase difference and the second phase difference being 275 + / -20 nm at a wavelength of 550 nm; and a liquid crystal layer which is formed using a liquid crystal composition containing a liquid crystal compound having reverse wavelength dispersibility, and which has a liquid crystal alignment pattern in which the orientation derived from the optical axis of the liquid crystal compound changes while continuously rotating in at least one direction in the plane.

Description

Technical Field

[0001] The present invention relates to an optical device for use in head-mounted displays and the like, and a head-mounted display having the optical device. Background Technology

[0002] Devices that provide users with virtual reality (VR), augmented reality (AR), and mixed reality (MR) include head-mounted displays (HMDs).

[0003] The relatively small and portable HMD is expected to become a multifunctional device that can replace smartphones and tablets.

[0004] In such HMDs, for example in VR display devices, a semi-reflective mirror and a reflective polarizer are used to refract the light path (image) emitted from the image display device so that the user can observe it, thereby lengthening the light path and allowing the user to perceive the distance of the image.

[0005] Furthermore, in this optical device, for example, a semi-reflective mirror and a reflective polarizer are attached to a lens such as a convex lens, and light is focused through the lens, thereby expanding the field of view (FOV).

[0006] Patent Document 1 describes the following: In this HMD, by using a switchable half waveplate (SHWP) and a plurality of liquid crystal (LC) lens, the focal length of the HMD's optical system is dynamically changed to control the distance between the user and the viewed image.

[0007] In the HMD described in Patent Document 1, for example, a switching unit having a switchable half-wave plate and a liquid crystal lens is arranged between the optical system constituting the HMD and the position where the user observes the image.

[0008] A switchable half-wave plate is a half-wave plate that can be switched between an open state, which functions as a half-wave plate, and a closed state, which does not act on the incident light and allows it to pass through directly.

[0009] Furthermore, as is well known, a liquid crystal lens is a liquid crystal diffraction grating, and it has a liquid crystal alignment pattern that originates from the liquid crystal compound and rotates continuously in one direction. The liquid crystal lens focuses or diverges incident light depending on whether it is right-handed or left-handed circularly polarized. Specifically, a liquid crystal lens that focuses right-handed circularly polarized light will diverge left-handed circularly polarized light, and vice versa.

[0010] As an example, in an HMD, the following situation will be used as an illustration: the optical system directly upstream of the switching unit emits right-hand circularly polarized light, and the liquid crystal lens of the switching unit focuses the right-hand circularly polarized light.

[0011] In this structure, when the switchable half-wave plate is in the closed state and does not function as a half-wave plate, light is directly incident on the liquid crystal lens as right-hand circularly polarized light, and the focal point of the displayed image on the HMD is located at the position where the liquid crystal lens of the switching unit focuses the light.

[0012] In contrast, in the switching unit, when the switchable half-wave plate is in the open state (acting as a half-wave plate), the light passing through the switchable half-wave plate is converted into left-handed circularly polarized light. As described above, the liquid crystal lens of the switching unit focuses the right-handed circularly polarized light and thus diverges the left-handed circularly polarized light. Therefore, in this case, the light diverges through the switching unit (liquid crystal lens), and the focal length of the image displayed on the HMD is longer than when the switchable half-wave plate is in the closed state. That is, in this state, the position of the displayed image is closer to the user's eyes.

[0013] Various liquid crystal lenses are known as liquid crystal lenses.

[0014] For example, Non-Patent Document 1 discloses a liquid crystal lens that improves diffraction efficiency and expands the wavelength region that functions as a lens by stacking two liquid crystal layers.

[0015] The liquid crystal layer constituting this liquid crystal lens is a diffraction grating (PG) and has a liquid crystal alignment pattern that originates from the optical axis of the liquid crystal compound and rotates continuously in the same direction as the liquid crystal lens, and the liquid crystal compound is helically twisted in the thickness direction (chiral PG). In the liquid crystal lens of Non-Patent Document 1, by stacking liquid crystal layers with opposite twisting directions of the liquid crystal compound in the thickness direction, the diffraction efficiency is improved and the wavelength region in which it functions as a lens can be expanded.

[0016] Previous technical documents Patent documents Patent Document 1: US Patent No. 10379419 Non-patent literature Non-patent document 1: J.Escuti et al., Achromatic diffraction from polarizationgratings with high efficiency, OPTICS LETTERS Vol.33, No.20, pp.2287-2289 (October 15, 2008) Summary of the Invention

[0017] The technical problem to be solved by the invention As described in Patent Document 1, by incorporating a switching unit with a switchable half-wave plate and a liquid crystal lens into the HMD, the focal length of the HMD's optical system can be dynamically changed, thereby controlling the distance between the user and the viewed image. As a result, the user of the HMD can achieve natural stereoscopic vision by bringing their eye convergence distance and accommodation distance closer together. Consequently, VR motion sickness can be prevented.

[0018] However, according to the research of the inventors, in switching units that use conventional switchable half-wave plates and liquid crystal lenses, for example, when switching the focal length of an image in an HMD, sometimes undesirable situations occur, such as the image quality changing with the focal length.

[0019] The purpose of this invention is to solve the problems of the prior art, for example, to provide an optical device that can obtain a stable image quality regardless of the focal length when the focal length of the displayed image is changed in an HMD or the like, and an HMD using the optical device.

[0020] means for solving technical problems To achieve the above objectives, the present invention has the following structure.

[0021] [1] An optical device comprising a switching element and a liquid crystal layer, wherein, The switching element is a component that can switch between a first phase difference and a second phase difference, and the difference between the first phase difference and the second phase difference is 275±20nm at a wavelength of 550nm. The liquid crystal layer is formed using a liquid crystal composition containing a liquid crystal compound with reverse wavelength dispersion, and has a liquid crystal alignment pattern that changes as the orientation of the optical axis derived from the liquid crystal compound rotates continuously in at least one in-plane direction.

[0022] [2] According to the optical device described in [1], wherein, In a liquid crystal alignment pattern, when the orientation of the optical axis derived from the liquid crystal compound is rotated 180° in-plane as a period, there are regions with different lengths of one period in-plane.

[0023] [3] According to the optical device described in [1] or [2], wherein, The liquid crystal alignment pattern has multiple rings of different sizes, and within the plane, the larger rings successively contain the smaller rings.

[0024] [4] According to the optical device described in [3], wherein, The liquid crystal alignment pattern is concentric circles.

[0025] [5] The optical device according to any one of [1] to [4], wherein, The switching element is constructed using a liquid crystal cell.

[0026] [6] A head-mounted display having the optical element described in any one of [1] to [5].

[0027] [7] The head-mounted display according to [6] is one of a virtual reality image display device and an augmented reality image display device.

[0028] [8] The head-mounted display according to [7] is a virtual reality image display device with a focusing optical system, wherein, The optical components are located downstream of the focusing optical system.

[0029] [9] The head-mounted display according to [7] or [8] is an augmented reality image display device with a light guide plate, wherein, The optical components are located downstream of the light guide plate.

[0030] Invention Effects According to the present invention, for example, when the focal length of the displayed image is changed in an HMD or the like, a stable image quality can be obtained regardless of the focal length. Attached Figure Description

[0031] Figure 1 This is a diagram that conceptually illustrates an example of the VR image display device of the present invention.

[0032] Figure 2 This is a top view that conceptually illustrates an example of a liquid crystal lens.

[0033] Figure 3 It is a conceptual representation Figure 2 A partial cross-sectional view of the liquid crystal lens shown.

[0034] Figure 4 It is used for explanation Figure 2A top view of the polarization diffraction element shown.

[0035] Figure 5 It is used for explanation Figure 2 A conceptual diagram illustrating the function of a polarizing diffraction element.

[0036] Figure 6 It is used for explanation Figure 2 A conceptual diagram illustrating the function of a polarizing diffraction element.

[0037] Figure 7 This is a conceptual illustration of an exposure apparatus used to form liquid crystal alignment patterns.

[0038] Figure 8 This is a conceptual diagram used to illustrate the function of the optical device of the present invention.

[0039] Figure 9 This is a top view that conceptually illustrates another example of a liquid crystal lens.

[0040] Figure 10 This is a top view that conceptually illustrates another example of a liquid crystal lens.

[0041] Figure 11 This is a diagram that conceptually illustrates an example of the AR image display device of the present invention. Detailed Implementation

[0042] Hereinafter, the optical device and head-mounted display (HMD) of the present invention will be described in detail based on the preferred embodiments shown in the accompanying drawings.

[0043] The accompanying drawings shown below are conceptual diagrams for illustrating the present invention, and the shape, thickness, size, and positional relationship of each component may not be the same as those of the actual device.

[0044] Furthermore, the examples shown below are representative embodiments of the present invention. Therefore, the present invention is not limited to the embodiments shown below.

[0045] In addition, in this specification, the numerical range indicated by “~” refers to the range including the values ​​recorded before and after “~” as the lower and upper limits.

[0046] Furthermore, although not limited to this, light in the wavelength range of 420–490 nm is blue light (B light), light in the wavelength range of 495–570 nm is green light (G light), and light in the wavelength range of 580–700 nm is red light (R light).

[0047] exist Figure 1 The present invention provides an example of an HMD (Head-Mounted Display) or VR image display device that uses an optical unit of the present invention.

[0048] Figure 1 The VR image display device 10 shown is an image display device that displays (projects) virtual reality images (VR images) for observation by a user O. In the following description, the VR image display device 10 will also be simply referred to as "display device 10".

[0049] like Figure 1 As shown, the display device 10 includes a display 12, a circular polarizer 14, a semi-reflective mirror 16, a lens 18, a circularly polarized light reflector 24, a circular polarizer 26, and optical components 30.

[0050] The semi-reflective mirror 16, lens 18, circularly polarized light reflector 24, and circularly polarized sheet 26 form a focusing optical system in the display device 10.

[0051] Furthermore, the optical device 30 is the optical device of the present invention. In the example shown, the optical device 30 includes a switching element 32 and a liquid crystal lens 34. The liquid crystal lens 34 also includes a liquid crystal layer 36 (see reference). Figure 3 ).

[0052] Figure 1 The display device 10 shown is basically the same as a VR image display device with a known reflex optical system such as a pancake lens, except that it has the optical element 30 of the present invention.

[0053] In the display device 10, the image (light) displayed by the display 12 is converted into right-hand circularly polarized light by the circular polarizer 14, for example. About half of the light passes through the semi-reflective mirror 16 and the lens 18 and is incident on the circularly polarized light reflector 24.

[0054] As an example, the circularly polarized light reflecting polarizer 24 is a reflecting polarizer that selectively reflects right-handed circularly polarized light and allows left-handed circularly polarized light to pass through. Therefore, the image of right-handed circularly polarized light is reflected by the circularly polarized light reflecting polarizer 24 and then incident again into the half-reflector 16, where approximately half of it is reflected by the half-reflector 16.

[0055] The image of right-handed circularly polarized light reflected by the semi-reflecting mirror 16 is converted into left-handed circularly polarized light.

[0056] The image of the left-handed circularly polarized light reflected by the semi-reflecting mirror 16 is focused by the lens 18 and then re-enters the circularly polarized light reflecting polarizer 24. As described above, the circularly polarized light reflecting polarizer 24 is a reflective polarizer that selectively reflects right-handed circularly polarized light and allows left-handed circularly polarized light to pass through. Therefore, the image of the left-handed circularly polarized light that re-enters the circularly polarized light reflecting polarizer 24 is transmitted through the circularly polarized light reflecting polarizer 24.

[0057] The image of left-handed circularly polarized light, which has passed through the circularly polarized light reflecting polarizer 24, is incident on the circularly polarized plate 26. When the image of right-handed circularly polarized light first enters the circularly polarized light reflecting polarizer 24, the circularly polarized plate 26 blocks the right-handed circularly polarized light to prevent unwanted transmission of this light as stray light (ghosting). That is, the circularly polarized plate allows left-handed circularly polarized light to pass through and blocks, preferably absorbs, right-handed circularly polarized light. Therefore, the image of left-handed circularly polarized light incident on the circularly polarized plate 26 is transmitted through the circularly polarized plate 26.

[0058] The image of left-handed circularly polarized light passing through the circular polarizer 26 is then focused and incident into the optical device 30. Through the optical device 30, the focal length is adjusted and the image is observed by the user O as a virtual reality image.

[0059] Optical device 30 will be described in detail later.

[0060] In addition, the VR image display device of the present invention is basically a known VR image display device except that it has the optical device of the present invention, namely the optical device 30.

[0061] Therefore, the VR image display device of the present invention is not limited to Figure 1 The structure shown can utilize various known VR image display devices.

[0062] In the display device 10, the display 12 can utilize various known displays (image display devices).

[0063] As an example of the display 12, examples include liquid crystal display devices (LCDs), organic light-emitting diode (OLEDs), CRTs (cathode-ray tubes), plasma display devices, LED (light-emitting diode) display devices, micro LED display devices, laser displays, DLP (digital light processing) and MEMS (micro-electro-mechanical systems) type display devices, etc. Furthermore, in this invention, the liquid crystal display device includes LCOS (Liquid Crystal On Silicon), etc.

[0064] In the display device 10, there are no restrictions on the circular polarizer 14, and various known circular polarizers (circular polarizers) that convert the image (light) emitted from the display 12 into circularly polarized light with a specified cycloid direction can be used.

[0065] In the example shown, the circular polarizer 14 is a circular polarizer composed of a linear polarizer 14a and a quarter-wave plate (λ / 4 wave plate) 14b. That is, the circular polarizer 14 converts the image emitted from the display 12 into linearly polarized light in a specified direction through the linear polarizer 14a, and then converts the linearly polarized light into circularly polarized light in a specified cycloid direction through the quarter-wave plate 14b.

[0066] As described above, in the display device 10 shown in the figure, the circular polarizer 14 converts the image emitted from the display 12 into right-hand circularly polarized light.

[0067] However, the present invention is not limited thereto. The circular polarizer 14 can convert the image emitted from the display 12 into left-handed circularly polarized light. In this case, the circularly polarized light reflecting polarizer 24, described later, selectively reflects the left-handed circularly polarized light and allows right-handed circularly polarized light to pass through.

[0068] That is, in the display device of the present invention, the cyclotron direction of the circularly polarized light of the image incident on the optical device 30 of the present invention is not limited. Therefore, in the display device of the present invention, as long as the cyclotron direction of the circularly polarized light passing through the polarizer is selected, and a half-wave plate or the like is used as needed, the set circularly polarized light can be incident on the optical device.

[0069] In the display device 10, there are no restrictions on the linear polarizer 14a and the quarter-wave plate 14b, and various known linear polarizers and quarter-wave plates can be used.

[0070] Therefore, the linear polarizer 1 / 4a can be a reflective polarizer or an absorptive polarizer. It can utilize various known linear polarizers, such as iodine-based polarizers, dye-based polarizers using dichroic dyes, polyolefin-based polarizers, metal wire grid polarizers, and thin films made by stretching multilayer dielectric films as described in Japanese Patent Application Publication No. 2011-053705.

[0071] Furthermore, the quarter-wave plate 14b can also utilize various known quarter-wave plates, such as stretched polycarbonate films, stretched norbornene polymer films, transparent films containing birefringent inorganic particles such as strontium carbonate for orientation, films of inorganic dielectrics deposited obliquely on a substrate, films of polymeric liquid crystal compounds uniaxially oriented and fixedly oriented, and films of liquid crystal compounds uniaxially oriented and fixedly oriented.

[0072] The same applies to other linear polarizers and quarter-wave plates.

[0073] In addition, if the display 12 emits linearly polarized light, such as an organic electroluminescent display device with a liquid crystal display device and an anti-reflective film, a quarter-wave plate 14b may be provided instead of a linear polarizer 14a.

[0074] In the display device 10 of the present invention, there is no limitation on the semi-reflective mirror 16, and various known semi-reflective mirrors can be used.

[0075] Furthermore, there are no restrictions on the lens 18 in the display device 10; various known lenses (convex lenses) that focus incident light can be used. In the example shown, lens 18 is a plano-convex lens.

[0076] In the display device 10 of the present invention, there are no restrictions on the circularly polarized light reflector 24. Various known reflective circular polarizers can be used, which selectively reflect right-handed or left-handed circularly polarized light and allow circularly polarized light with opposite rotation directions to pass through.

[0077] As a circularly polarized light reflector polarizer 24, a cholesteric liquid crystal layer can be preferably exemplified.

[0078] Cholesteric liquid crystal layer refers to a liquid crystal layer formed by fixing a liquid crystal phase (cholesteric liquid crystal phase) composed of cholesteric oriented liquid crystal compounds.

[0079] As is well known, cholesteric liquid crystal layers have a helical structure in which liquid crystal compounds are spirally rotated and stacked. The structure formed by rotating the liquid crystal compounds once (360°) and stacking them is considered as one pitch of the helix (helical pitch). The liquid crystal compounds spirally rotated have a structure formed by stacking multiple pitches.

[0080] Furthermore, it is well known that cholesteric liquid crystal layers selectively reflect right-handed or left-handed circularly polarized light in specific wavelength regions, depending on the helical direction (rotation direction) of the liquid crystal compound, while allowing other light to pass through.

[0081] Specifically, cholesteric liquid crystal layers selectively reflect light in specific wavelength ranges based on the length of one pitch of the helix, while allowing light in other wavelength ranges to pass through. The selective reflection center wavelength λ of the cholesteric liquid crystal layer depends on one pitch P of the helix in the cholesteric liquid crystal phase and follows the relationship between the average refractive index n of the cholesteric liquid crystal structure and λ = n × P. One pitch P of the helix in the helix refers to the period of the helix, which is the length of the liquid crystal compound in the thickness direction when rotated 360°.

[0082] Furthermore, depending on the spiral direction (helix direction), the cholesteric liquid crystal layer reflects right-handed circularly polarized light and transmits left-handed circularly polarized light, or reflects left-handed circularly polarized light and transmits right-handed circularly polarized light. The spiral direction of the circularly polarized light reflected by the cholesteric liquid crystal layer is consistent with the spiral direction of the cholesteric liquid crystal phase.

[0083] Regarding cholesteric liquid crystal layers, various known cholesteric liquid crystal layers formed by fixing cholesteric liquid crystal phases can be used.

[0084] Furthermore, the cholesteric liquid crystal layer can be a so-called pitch gradient structure (PG structure) cholesteric liquid crystal layer in which the helical pitch changes along the thickness direction.

[0085] As described above, the cholesteric liquid crystal layer selectively reflects light in a specific wavelength range and allows light in other wavelength ranges to pass through.

[0086] Therefore, when the circularly polarized light reflector 24 is composed of a cholesteric liquid crystal layer, the circularly polarized light reflector 24 may have only one cholesteric liquid crystal layer or multiple cholesteric liquid crystal layers, depending on the image displayed on the display 12.

[0087] For example, when the display 12 displays a full-color image or a black and white image, the circularly polarized light reflector 24 may have three cholesteric liquid crystal layers: a cholesteric liquid crystal layer with a selective reflection center wavelength in the blue light wavelength region, a cholesteric liquid crystal layer with a selective reflection center wavelength in the green light wavelength region, and a cholesteric liquid crystal layer with a selective reflection center wavelength in the red light wavelength region.

[0088] In the display device 10, the circular polarizer 26 can also be any known circular polarizer 26, which blocks circularly polarized light in a predetermined cycloid direction and allows circularly polarized light in another direction to pass through.

[0089] As described above, the circular polarizer 26 is used to block the unnecessary transmission of right-hand circularly polarized light when the image of right-hand circularly polarized light is first incident into the circularly polarized light reflecting polarizer 24.

[0090] As an example, the circular polarizer 26 can be illustrated by having a quarter-wave plate, a linear polarizer, and a quarter-wave plate in sequence. In this circular polarizer 26, the right-hand circularly polarized light that is unnecessarily transmitted through the circularly polarized light and reflected by the polarizer 24 is converted into linearly polarized light in the direction blocked by the linear polarizer, thereby blocking the right-hand circularly polarized light that is unnecessarily transmitted through the circularly polarized light and reflected by the polarizer 24. Considering this, an absorption-type linear polarizer is preferred.

[0091] On the other hand, if the appropriate left-handed circularly polarized light that has passed through the circularly polarized light reflection polarizer 24 is incident into the circularly polarized plate 26, the left-handed circularly polarized light is converted into linearly polarized light in the opposite direction to the right-handed circularly polarized light, which can pass through the linear polarizer. The linearly polarized light converted from the left-handed circularly polarized light is then converted back into left-handed circularly polarized light by the downstream quarter-wave plate.

[0092] The image of the left-handed circularly polarized light that has passed through the circular polarizer 26 is then incident into the optical device 30.

[0093] As described above, the optical device 30 is the optical device of the present invention, and has a switching element 32 and a liquid crystal lens 34.

[0094] The optical element 30 is switched by using the switching element 32, thereby lengthening or shortening the focal length of the display device 10. That is, by having the optical element 30, the display device 10 is able to change the focal length of the image (projected image) observed by the user O.

[0095] The switching element 32 is a component that can switch between a first phase difference and a second phase difference. Furthermore, the difference between the first phase difference and the second phase difference switched by the switching element 32 is 275±20nm at a wavelength of 550nm.

[0096] As an example, the switching element 32 is an element that can switch between a state with zero phase difference and a state with half a wavelength (λ / 2). That is, the switching element 32 is an element that can switch between a state in which the incident light passes directly and a state in which it acts as a half-wave plate for the incident light. Hereinafter, for convenience, the state with zero phase difference will also be referred to as "off", and the state with half a wavelength phase difference and acting as a half-wave plate will also be referred to as "on".

[0097] As described above, in the display device 10, the image incident on the optical device 30 is a left-handed circularly polarized light. Therefore, the switching element 32 is an element that can switch between a state in which the incident left-handed circularly polarized light is directly transmitted as left-handed circularly polarized light and a state in which it is converted to right-handed circularly polarized light and transmitted.

[0098] There are no restrictions on the switching element 32, and various elements that can switch between a first phase difference and a second phase difference with a phase difference of 275±20nm at a wavelength of 550nm can be used.

[0099] As an example, switching elements composed of liquid crystal cells can be shown. The liquid crystal cells preferably use the VA (Vertical Alignment) mode.

[0100] like Figure 1As shown, the optical device 30 has a liquid crystal lens 34 downstream of the switching element 32.

[0101] Therefore, either left-handed circularly polarized light directly passing through the switching element 32 or right-handed circularly polarized light converted by the switching element 32 is incident into the liquid crystal lens 34.

[0102] exist Figure 2 and Figure 3 The image shows a conceptual example of a liquid crystal lens 34. Additionally, Figure 2 This is a top view of the liquid crystal lens 34. Figure 3 It is a cross-sectional view in the thickness direction.

[0103] like Figure 2 and Figure 3 As shown, the liquid crystal lens 34 has a liquid crystal layer 36 formed using a liquid crystal composition containing a liquid crystal compound 38. In this invention, the liquid crystal compound 38 is a liquid crystal compound with reverse wavelength dispersion. This will be described in detail later.

[0104] The liquid crystal layer 36 has a liquid crystal alignment pattern in which the orientation of the optical axis originating from the liquid crystal compound 38 changes continuously as it rotates along at least one direction within the plane. Furthermore, preferably, in this liquid crystal alignment pattern, the liquid crystal layer 36 has regions in the plane with a different length of one cycle when the length of a 180° rotation of the orientation of the optical axis originating from the liquid crystal compound 38 within the plane is considered as one cycle.

[0105] like Figure 2 and Figure 3 As shown, the liquid crystal lens 34 has a substrate 50, an alignment film 52, and a liquid crystal layer 36 (optical anisotropy layer). Furthermore, in the liquid crystal lens 34, the liquid crystal layer 36 functions as a liquid crystal lens, i.e., a liquid crystal diffraction element.

[0106] Therefore, the liquid crystal lens 34 can be composed of only the liquid crystal layer 36, or the substrate 50 can be peeled off and composed of the alignment film 52 and the liquid crystal layer 36, or the liquid crystal layer 36 can be laminated on other substrates after the substrate 50 and the alignment film 52 are peeled off from the liquid crystal layer 36.

[0107] exist Figure 2 and Figure 3 In the liquid crystal lens 34 shown, the liquid crystal layer 36 is a liquid crystal layer formed by using a composition containing liquid crystal compound 38 on the alignment film 52, wherein the liquid crystal compound 38 is aligned and fixed in the liquid crystal alignment pattern described below.

[0108] Specifically, the liquid crystal layer 36 has a liquid crystal alignment pattern that radiates from the inside out, with the orientation originating from the optical axis of the liquid crystal compound 38 rotating continuously in one direction while changing. That is, Figure 2 and Figure 3 The liquid crystal alignment pattern of the liquid crystal layer 36 shown is a pattern with multiple rings, and is a concentric circle pattern that changes as the orientation of the optical axis of the liquid crystal compound 38 rotates continuously in one direction from the inside to the outside.

[0109] In addition, Figure 2 And as will be discussed later Figure 4 In order to simplify the accompanying drawings and clearly show the structure of the liquid crystal layer 36, only the liquid crystal compound 38 at the interface on the alignment film 52 side of the liquid crystal layer 36 is shown. However, the liquid crystal layer 36 as... Figure 3 As shown, the liquid crystal compound 38 is stacked in the thickness direction in the same manner as a liquid crystal layer formed using a conventional composition containing a liquid crystal compound.

[0110] Moreover, it is still Figure 2 and Figure 3 In this example, a rod-shaped liquid crystal compound is shown as liquid crystal compound 38, so the direction of the optical axis is consistent with the length direction of liquid crystal compound 38.

[0111] Specifically, in the liquid crystal layer 36, the orientation of the optical axis of the liquid crystal compound 38 changes as it rotates continuously along multiple directions from the center of the liquid crystal layer 36, i.e., the optical axis, outward, such as the direction indicated by arrow A1, the direction indicated by arrow A2, the direction indicated by arrow A3, the direction indicated by arrow A4, etc.

[0112] Therefore, in liquid crystal layer 36, the rotation direction of the optical axis of liquid crystal compound 38 is the same in all directions (one direction). In the example figure, in all directions indicated by arrow A1, arrow A2, arrow A3, and arrow A4, the rotation direction of the optical axis of liquid crystal compound 38 is counterclockwise.

[0113] That is, if arrows A1 and A4 are considered as a straight line, then along this line, at the center of the liquid crystal layer 36, the rotation direction of the optical axis of the liquid crystal compound 38 will be reversed. As an example, suppose the line formed by arrows A1 and A4 points to the right in the diagram (the direction of arrow A1). In this case, the optical axis of the liquid crystal compound 38 first rotates clockwise from the outside of the liquid crystal layer 36 towards the center, the rotation direction reverses at the center of the liquid crystal layer 36, and then rotates counterclockwise from the center of the liquid crystal layer 36 towards the outside. The center of the liquid crystal layer 36 is the optical axis of the liquid crystal lens 34.

[0114] As is well known, a liquid crystal layer having a liquid crystal alignment pattern that changes as the optical axis of a liquid crystal compound 38 rotates continuously in one direction functions as a transmissive liquid crystal diffraction element. The transmissive liquid crystal diffraction element diffracts the incident circularly polarized light in one direction and the opposite direction of the optical axis rotation according to the rotation direction of the optical axis and the cyclotron direction of the incident circularly polarized light.

[0115] In a liquid crystal layer 36 with a liquid crystal alignment pattern in which the orientation of the optical axis of the liquid crystal compound 38 changes as it rotates continuously in one direction, the diffraction direction (refractive direction) of transmitted light depends on the rotation direction of the optical axis of the liquid crystal compound 38. That is, in this liquid crystal alignment pattern, when the rotation direction of the optical axis of the liquid crystal compound 38 in one direction is opposite, the diffraction direction of transmitted light becomes the opposite direction relative to the direction of rotation of the optical axis.

[0116] Furthermore, in the liquid crystal layer 36 with a liquid crystal alignment pattern in which the orientation of the optical axis of the liquid crystal compound 38 changes as it rotates continuously in one direction, the diffraction direction of the transmitted light varies depending on the rotation direction of the incident circularly polarized light. That is, in this liquid crystal alignment pattern, the diffraction direction of the transmitted light is reversed when the incident light is right-handed circularly polarized light and when it is left-handed circularly polarized light.

[0117] Furthermore, when the in-plane retardation (retardation in the plane direction) value is set to λ / 2, the liquid crystal layer 36 functions as a general half-wave plate, that is, it imparts a phase difference of half a wavelength, i.e. 180°, to the polarized light component incident on the liquid crystal layer.

[0118] Therefore, the rotation direction of the circularly polarized light incident on the liquid crystal layer 36 and diffracted will be reversed. That is, the right-hand circularly polarized light incident on the liquid crystal layer 36 and diffracted will exit as left-hand circularly polarized light, and the left-hand circularly polarized light will exit as right-hand circularly polarized light.

[0119] In the liquid crystal layer 36 of the liquid crystal lens 34, regarding the liquid crystal alignment pattern, in a direction where the orientation of the optical axis of the liquid crystal compound 38 changes continuously with rotation, the length of one cycle gradually shortens from the inside to the outside when the length of a 180° rotation of the orientation of the optical axis originating from the liquid crystal compound is taken as a cycle. That is, the liquid crystal layer 36 in the example has regions with different lengths of one cycle in the plane.

[0120] In a liquid crystal layer with a liquid crystal alignment pattern in which the optical axis of the liquid crystal compound 38 rotates continuously in one direction while changing, the shorter the length of one period, the larger the diffraction angle becomes. Therefore, in a liquid crystal layer 36 with a concentric circle liquid crystal alignment pattern, the diffraction angle gradually increases from the center of the concentric circles outwards.

[0121] Therefore, the liquid crystal layer 36 with a concentric liquid crystal alignment pattern can diverge or focus the incident light and allow it to pass through, depending on the rotation direction of the optical axis of the liquid crystal compound 38 and the rotation direction of the incident circularly polarized light. The concentric liquid crystal alignment pattern has a radial liquid crystal alignment pattern that changes due to the continuous rotation of the optical axis of the liquid crystal compound.

[0122] In other words, the liquid crystal lens 34 having this liquid crystal layer 36 functions as a concave lens depending on the rotation direction of the incident circularly polarized light. For example, it functions as a convex lens when right-handed circularly polarized light is incident, and as a convex lens when left-handed circularly polarized light is incident. Alternatively, the liquid crystal lens 34 functions as a convex lens when right-handed circularly polarized light is incident, and as a concave lens when left-handed circularly polarized light is incident.

[0123] In the example shown in the figure, the liquid crystal layer 36 functions as a convex lens to focus the light when left-handed circularly polarized light is incident, and functions as a concave lens to diverge the light when right-handed circularly polarized light is incident.

[0124] To achieve natural stereoscopic vision in an HMD, it is preferable that the viewing image can be adjusted from infinity to near the user's hand. As an example, the distance between the user of the HMD and the viewing image is preferably adjustable from infinity to 25cm.

[0125] As described above, the optical device 30 is switched by using the switching element 32, thereby extending or shortening the focal length of the display device 10.

[0126] The refractive power of the optical device 30, which can be controlled by switching the switching element 32, is preferably controlled within a range of 1 to 5 diopters. As an example, when the refractive power is controlled within a range of 4 diopters, in one mode, the refractive power of the optical device 30 is in the range of 0 to 4 diopters, and in another mode, the refractive power of the optical device 30 is in the range of -2 to 2 diopters.

[0127] Diopter is the unit of refractive power of a lens, and it is the reciprocal of the focal length expressed in meters.

[0128] As long as the refractive power of the optical device 30 is controlled within a range of 1 diopter or more, the user can experience a near-natural stereoscopic vision effect. Furthermore, by setting the refractive power control range of the optical device 30 to 4 diopters, the distance between the user of the HMD and the viewed image can be adjusted from infinity to 25cm.

[0129] In order for the optical device 30 to achieve the above-mentioned control range of refractive power, the absolute value of the refractive power of the liquid crystal lens 34 is preferably 0.01 to 2.5 diopters.

[0130] As described above, the liquid crystal lens 34 functions as a concave lens depending on the cycloid direction of the incident circularly polarized light. For example, it functions as a convex lens when right-handed circularly polarized light is incident, and when left-handed circularly polarized light is incident. For instance, the liquid crystal lens 34, which has a diopter of 2.0 for left-handed circularly polarized light, becomes -2.0 for right-handed circularly polarized light. In this case, the refractive power of the optical device 30, which is switched by the switching element 32, is controlled within a range of 4 diopters.

[0131] The absolute value of the refractive power of the liquid crystal lens 34 is more preferably 0.01 to 1.5 diopters, and even more preferably 0.5 to 1.0 diopters. By setting the absolute value of the refractive power of the liquid crystal lens 34 within this range, it is possible to prevent the image quality from changing depending on the distance between the user of the HMD and the viewed image.

[0132] The optical device 30 can be a multi-stage structure with multiple switching elements and multiple liquid crystal lenses alternately arranged. In this manner, the refractive power of the optical device 30 can be controlled in stages. Using one set of switching elements and liquid crystal lenses, two refractive powers can be achieved; conversely, using two sets of switching elements and liquid crystal lenses, four refractive powers can be achieved. Furthermore, using four sets of switching elements and liquid crystal lenses, 16 refractive powers can be achieved.

[0133] By precisely controlling the refractive power, a natural stereoscopic visual experience can be provided to the user.

[0134] The liquid crystal lens 34 (liquid crystal layer 36) preferably adopts an orientation structure that exhibits the refractive power described above. A period in the liquid crystal layer 36 varies depending on the distance from the optical center. As an example, the minimum value of a period for a lens with a diameter of 5 cm and a refractive power of 1 diopter is approximately 20 μm.

[0135] In addition, Figure 2 In order to simplify the accompanying drawings and clearly show the structure of the liquid crystal lens 34, only the liquid crystal compound 38 (liquid crystal compound molecules) on the surface of the alignment film 52 is shown in the liquid crystal layer 36. However, the liquid crystal layer 36 as... Figure 3As conceptually shown, the structure consists of stacked and oriented liquid crystal compounds 38, in the same manner as a liquid crystal layer formed using a conventional composition containing liquid crystal compounds.

[0136] The following describes the function of the liquid crystal layer 36. Figure 4 The liquid crystal layer 36A, shown conceptually in a top view, is described in more detail below. The liquid crystal layer 36A has a liquid crystal alignment pattern that changes as the optical axis 38A of the liquid crystal compound 38 rotates continuously in a direction indicated by arrow A.

[0137] exist Figure 2 In the concentrically shaped liquid crystal alignment pattern with a radial orientation, where the optical axis continuously rotates and changes in one direction from the inside to the outside, the direction in which the optical axis continuously rotates and changes also exhibits the same characteristics as... Figure 4 The optical effects are the same as those of the liquid crystal alignment pattern shown.

[0138] In the following description, the optical axis 38A derived from the liquid crystal compound 38 will also be referred to as "optical axis 38A of liquid crystal compound 38" or "optical axis 38A".

[0139] In liquid crystal layer 36A, liquid crystal compound 38 is oriented in two dimensions in a plane parallel to a direction indicated by arrow A and a Y direction orthogonal to the direction indicated by arrow A. Furthermore, in Figure 3 And as will be discussed later Figure 5 and Figure 6 In the diagram, the Y direction is the direction orthogonal to the plane of the paper.

[0140] In the following explanation, "a direction indicated by arrow A" will also be referred to as "the direction of arrow A".

[0141] exist Figure 2 In the liquid crystal layer 36 shown, in the concentric circular liquid crystal alignment pattern, the circumferential direction of the concentric circles corresponds to... Figure 4 in the Y direction.

[0142] Regarding the liquid crystal layer 36A, within the surface of the liquid crystal layer 36A, there is a liquid crystal alignment pattern whose orientation changes as it rotates continuously along the direction of arrow A, originating from the optical axis 38A of the liquid crystal compound 38.

[0143] The orientation of the optical axis 38A of the liquid crystal compound 38 changes as it rotates continuously along the direction of arrow A (a specified direction). Specifically, the angle formed by the optical axis 38A of the liquid crystal compound 38 arranged along the direction of arrow A and the direction of arrow A varies depending on the position of the direction of arrow A. Along the direction of arrow A, the angle formed by the optical axis 38A and the direction of arrow A changes sequentially from θ to θ+180° or θ-180°.

[0144] On the other hand, in the liquid crystal compound 38 used to form the liquid crystal layer 36A, in the Y direction orthogonal to the direction of arrow A, that is, in the Y direction orthogonal to the direction of continuous rotation of the optical axis 38A, the liquid crystal compounds 38 with the same orientation to the optical axis 38A are arranged at equal intervals.

[0145] In other words, in the liquid crystal compound 38 used to form the liquid crystal layer 36, the orientation of the optical axis 38A between the liquid crystal compounds 38 arranged in the Y direction is equal to the angle formed by the direction of arrow A.

[0146] exist Figure 2 In the liquid crystal layer 36 shown, the regions with the same orientation of the optical axis 38A are formed into a centrally aligned annular shape to form a concentric liquid crystal alignment pattern.

[0147] As described above, in a liquid crystal alignment pattern in which the optical axis 38A rotates continuously in one direction, the length (distance) of the optical axis 38A of the liquid crystal compound 38 rotating by 180° becomes the length Λ of one cycle in the liquid crystal alignment pattern.

[0148] That is, as long as it is Figure 4 The liquid crystal layer 36A shown here has a length Λ in one period of the liquid crystal alignment pattern defined by rotating the optical axis 38A of the liquid crystal compound 38 by 180° in the direction of arrow A, which changes continuously with the orientation of the optical axis 38A. In other words, one period Λ in the liquid crystal alignment pattern is defined by the angle formed between the optical axis 38A of the liquid crystal compound 38 and the direction of arrow A, based on the distance from θ to θ+180°.

[0149] In other words, the distance between the centers of two liquid crystal compounds 38 at the direction of arrow A, which are at equal angles relative to the direction of arrow A, is one period Λ. Specifically, as... Figure 4 As shown, the distance between the centers of the two liquid crystal compounds 38 whose arrow A direction is consistent with the direction of the optical axis 38A is one period Λ.

[0150] In liquid crystal layer 36A (liquid crystal layer 36), the liquid crystal alignment pattern repeats one cycle Λ in a direction that changes as it rotates continuously in the direction of arrow A, i.e., the orientation of optical axis 38A.

[0151] As described above, the liquid crystal layer 36A with this liquid crystal alignment pattern is also a transmissive liquid crystal diffraction element, and one period Λ of it becomes the period (one period) of the diffraction structure.

[0152] In liquid crystal layer 36A, among the liquid crystal compounds arranged in the Y direction, the angle formed by the optical axis 38A and the direction of arrow A is equal. The region where the liquid crystal compounds 38 with this angle between the optical axis 38A and the direction of arrow A are arranged along the Y direction is designated as region R.

[0153] In this case, the value of the in-plane retardation (Re) in each region R is preferably half a wavelength, i.e., λ / 2. This in-plane retardation is calculated by multiplying the refractive index difference Δn caused by the refractive index anisotropy of region R by the thickness of the liquid crystal layer. The refractive index difference caused by the refractive index anisotropy of region R in the liquid crystal layer is defined as the difference between the refractive index in the slow axis direction of region R and the refractive index in the direction orthogonal to the slow axis direction. That is, the refractive index difference Δn caused by the refractive index anisotropy of region R is equal to the difference between the refractive index of the liquid crystal compound 38 in the direction of optical axis 38A and the refractive index of the liquid crystal compound 38 in the direction perpendicular to optical axis 38A in the plane of region R. In other words, the aforementioned refractive index difference Δn is equal to the refractive index difference of the liquid crystal compound.

[0154] Furthermore, in the liquid crystal lens 34 with a concentric circular liquid crystal alignment pattern, the areas with the same orientation of the centrally aligned annular optical axis 38A are equivalent to... Figure 4 In region R, the concentric liquid crystal alignment pattern is a radial liquid crystal alignment pattern that continuously rotates in one direction with an optical axis 38A.

[0155] If circularly polarized light is incident on this liquid crystal layer 36A, the light is diffracted, and the direction of the circularly polarized light is reversed.

[0156] exist Figure 5 and Figure 6 This function is conceptually illustrated in the diagram. In liquid crystal layer 36A, the product of the refractive index difference of the liquid crystal compound and the thickness of the liquid crystal layer is set to λ / 2.

[0157] Furthermore, as described above, this effect is exactly the same in a liquid crystal lens 34 having a concentric liquid crystal alignment pattern, which is a radial liquid crystal alignment pattern having an optical axis 38A that rotates continuously in one direction.

[0158] like Figure 5 As shown, when the product of the refractive index difference of the liquid crystal compound in liquid crystal layer 36 and the thickness of the liquid crystal layer is λ / 2, if the incident light L1, which is left-handed circularly polarized light, is incident into liquid crystal layer 36, the incident light L1 passes through liquid crystal layer 36A, thereby imparting a phase difference of 180°, and the transmitted light L2 is converted into right-handed circularly polarized light.

[0159] Furthermore, the liquid crystal alignment pattern formed on the liquid crystal layer 36 is a periodic pattern along the direction of arrow A, so the transmitted light L2 propagates in a direction different from the propagation direction of the incident light L1. In this way, the incident light L1 of left-handed circularly polarized light is converted into transmitted light L2 of right-handed circularly polarized light that is tilted at a predetermined angle relative to the incident direction in the direction of arrow A.

[0160] On the other hand, such as Figure 6 As conceptually shown, when the product of the refractive index difference of the liquid crystal compound in liquid crystal layer 36A and the thickness of the liquid crystal layer is λ / 2, if the incident light L4 of right-handed circularly polarized light is incident on liquid crystal layer 36A, the incident light L4 passes through liquid crystal layer 36A, thereby imparting a phase difference of 180°, and is thus converted into transmitted light L5 of left-handed circularly polarized light.

[0161] Furthermore, the liquid crystal alignment pattern formed on the liquid crystal layer 36A is a periodic pattern along the direction of arrow A. Therefore, the transmitted light L5 propagates in a direction different from the propagation direction of the incident light L4. At this time, the transmitted light L5 propagates in a direction different from the transmitted light L2, that is, in a direction opposite to the direction of arrow A relative to the incident direction. Thus, the incident light L4 is converted into transmitted light L5, which is left-handed circularly polarized light tilted at a predetermined angle relative to the incident direction towards the direction of arrow A.

[0162] In the liquid crystal layer 36A, the value of the in-plane retardation of the plurality of regions R is preferably half a wavelength, but more preferably the in-plane retardation Re(550) = Δn of the plurality of regions R of the liquid crystal layer 36A relative to incident light with a wavelength of 550 nm. 550 ×d is within the range specified in equation (1) below. Where Δn 550 The refractive index difference is the difference caused by the anisotropy of the refractive index in region R when the wavelength of the incident light is 550nm, and d is the thickness of the liquid crystal layer 36A.

[0163] 200nm≤Δn 550 ×d≤350nm (1) That is, as long as the in-plane retardation Re(550) of multiple regions R of the liquid crystal layer 36A is equal to Δn 550 If ×d satisfies equation (1), then a sufficient amount of circularly polarized light components incident on the liquid crystal layer 36A can be converted into circularly polarized light propagating in a direction inclined to the positive or negative direction relative to the direction of arrow A. In-plane retardation Re(550) = Δn 550 ×d is more preferably 225nm≤Δn 550 ×d≤340nm, further optimized 250nm≤Δn 550 ×d≤330nm.

[0164] Furthermore, the above equation (1) applies to the range of incident light with a wavelength of 550 nm, but for incident light with a wavelength of λ nm, the in-plane retardation Re(λ) = Δn in multiple regions R of the liquid crystal layer is different. λ ×d is preferably set appropriately within the range specified in the following formula (1-2).

[0165] 0.7×(λ / 2)nm≤Δn λ ×d≤1.3×(λ / 2)nm (1-2) Furthermore, in the liquid crystal layer 36A, the values ​​of the in-plane retardation of multiple regions R can be used outside the range of the above equation (1). Specifically, by setting it as Δn 550 ×d < 200nm or 350nm < Δn 550 ×d can be divided into light propagating in the same direction as the incident light and light propagating in a different direction than the incident light. If Δn 550 When ×d approaches 0nm or 550nm, the component of light propagating in the same direction as the incident light increases, while the component of light propagating in a different direction from the incident light decreases.

[0166] As described above, the diffraction angles of transmitted light L2 and L5 can be adjusted by changing one period Λ of the formed liquid crystal alignment pattern. Specifically, the shorter the one period Λ of the liquid crystal alignment pattern, the stronger the interference between adjacent liquid crystal compounds 38, thus enabling greater diffraction of transmitted light L2 and L5.

[0167] Furthermore, by reversing the rotation direction of the optical axis 38A of the liquid crystal compound 38 rotating along the direction of arrow A, the liquid crystal layer 36A can reverse the diffraction direction of the transmitted light.

[0168] Furthermore, as described above, the liquid crystal layer 36A reverses the direction of diffraction of transmitted light according to the rotation direction of the incident circularly polarized light. That is, in the liquid crystal layer 36A, the diffraction directions of transmitted light are reversed for right-handed and left-handed circularly polarized light.

[0169] Regarding the points mentioned above, the same applies to the liquid crystal layer 36 having a concentric circle liquid crystal alignment pattern.

[0170] Furthermore, when using a liquid crystal compound with reverse wavelength dispersion as described later, it is preferable that the product of the refractive index difference of the liquid crystal compound in liquid crystal layer 36A and the thickness of the liquid crystal layer is greater than λ / 2. Specifically, the thickness of the liquid crystal layer in this invention is particularly preferably satisfied by the following formulas (1-3).

[0171] 275nm<Δn 550×d≤310nm (1-3) The twist angle of the liquid crystal layer is preferably 0° to 30°. More preferably, the twist angle is 3° to 20°, and even more preferably, 3° to 10°. In this manner, a high diffraction efficiency can be obtained for light incident obliquely into the liquid crystal layer.

[0172] The liquid crystal layer 36 is formed using a liquid crystal composition containing a liquid crystal compound, the optical axis of which has a liquid crystal alignment pattern as described above.

[0173] An alignment film 52 having an alignment pattern corresponding to the liquid crystal alignment pattern described above is formed on a substrate 50. A liquid crystal composition is coated on the alignment film 52 and cured, thereby forming a liquid crystal layer 36 composed of a cured layer of the liquid crystal composition.

[0174] In addition, the liquid crystal composition used to form the liquid crystal layer 36 may contain a liquid crystal compound, and may also contain other components such as leveling agents, orientation control agents, polymerization initiators and orientation aids.

[0175] In this invention, the liquid crystal compound 38 constituting the liquid crystal layer 36 is a reverse wavelength dispersible liquid crystal compound. That is, the liquid crystal layer 36 is a liquid crystal layer formed using a liquid crystal composition containing a reverse wavelength dispersible liquid crystal compound 38.

[0176] The optical device of the present invention, having a liquid crystal layer 36 formed using a liquid crystal compound with inverse wavelength dispersion, can obtain a stable image quality regardless of the focal length when the focal length of the display device 10 is changed.

[0177] Reverse wavelength dispersive liquid crystal compounds refer to liquid crystal compounds in which the in-plane retardation (Re) value of a phase difference film made by aligning (horizontal alignment) of the liquid crystal compound increases with increasing measurement wavelength in the range of 450–650 nm when the in-plane retardation (Re) value is measured at a specific wavelength (visible light range).

[0178] The ratio of the retardation value Re450 at a wavelength of 450 nm to the retardation value Re550 at a wavelength of 550 nm, Re450 / Re550, is preferably 0.6 or more and less than 1.0. More preferably, Re450 / Re550 is 0.6 or more and less than 0.9, and even more preferably, it is 0.7 or more and less than 0.8.

[0179] The ratio of the delay value Re650 at a wavelength of 650nm to the delay value Re550 at a wavelength of 550nm, Re650 / Re550, is preferably greater than 1.0 and less than 1.3.

[0180] Δn of liquid crystal layer 36 550Preferably, the value is 0.01 or higher and less than 0.3, more preferably 0.01 or higher and less than 0.15, even more preferably 0.03 or higher and less than 0.1, and especially preferably 0.03 or higher and less than 0.06.

[0181] By using Δn of liquid crystal layer 36 550 By controlling the wavelength within this range, preferred optical properties with reverse wavelength dispersion can be obtained.

[0182] As a reverse wavelength dispersible liquid crystal compound, a polymeric liquid crystal compound having a partial structure represented by the following formula (I) is preferred.

[0183] -D 1 -Ar-D 2 - (I) In the above equation (I), D 1 and D 2 Each of these can be used independently to represent a single bond, -O-, -CO-, -CO-O-, -C(=S)O-, and -CR. 1 R 2 -、-CR 1 R 2 -CR 3 R 4 -、-O-CR 1 R 2 -、-CR 1 R 2 -O-CR 3 R 4 -、-CO-O-CR 1 R 2 -、-O-CO-CR 1 R 2 -、-CR 1 R 2 -CR 3 R 4 -O-CO-、-CR 1 R 2 -O-CO-CR 3 R 4 -、-CR 1 R 2 -CO-O-CR 3 R 4 -、-NR 1 -CR 2 R 3 -or-CO-NR 1 -

[0184] R 1 R 2 R 3 and R4 Each can independently represent a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 4 carbon atoms. In R 1 R 2 R 3 and R 4 When multiple R exist, multiple R 1 Multiple R 2 Multiple R 3 and multiple R 4 They can be the same as each other, or they can be different from each other.

[0185] Ar represents any aromatic ring selected from the group consisting of the groups represented by formulas (Ar-1) to (Ar-7). Furthermore, in the following formulas (Ar-1) to (Ar-7), Indicates D 1 Or D 2 The symbols used in the following equations (Ar-1) to (Ar-7) are the same as those used in Ar in equation (II) described later.

[0186] [Chemical Formula 1] As a polymeric liquid crystal compound having a partial structure represented by the above formula (I), a polymeric liquid crystal compound represented by the following formula (II) is preferred.

[0187] The polymeric liquid crystal compound represented by the following formula (II) is a compound that exhibits liquid crystal properties.

[0188] L 1 -G 1 -D 1 -Ar-D 2 -G 2 -L 2 (II) In equation (II) above, D 1 and D 2 Each of these can be used independently to represent a single bond, -O-, -CO-, -CO-O-, -C(=S)O-, and -CR. 1 R 2 -、-CR 1 R 2 -CR 3 R 4 -、-O-CR 1 R 2 -、-CR 1 R 2 -O-CR 3 R 4 -、-CO-O-CR 1 R 2-、-O-CO-CR 1 R 2 -、-CR 1 R 2 -CR 3 R 4 -O-CO-、-CR 1 R 2 -O-CO-CR 3 R 4 -、-CR 1 R 2 -CO-O-CR 3 R 4 -、-NR 1 -CR 2 R 3 -or-CO-NR 1 -

[0189] R 1 R 2 R 3 and R 4 Each can independently represent a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 4 carbon atoms. In R 1 R 2 R 3 and R 4 When multiple R exist, multiple R 1 Multiple R 2 Multiple R 3 and multiple R 4 They can be the same as each other, or they can be different from each other.

[0190] G 1 and G 2 Each of these groups independently represents a divalent alicyclic hydrocarbon group or aromatic hydrocarbon group with 5 to 8 carbon atoms, wherein the methylene group contained in the alicyclic hydrocarbon group can be substituted with -O-, -S- or -NH-.

[0191] L 1 and L 2 Each organic group, independently representing a monovalent group, is selected from L... 1 and L 2 At least one of the groups represents a monovalent group having a polymerizable group.

[0192] Ar represents any aromatic ring selected from the group consisting of the groups represented by formulas (Ar-1) to (Ar-7). Furthermore, in the following formulas (Ar-1) to (Ar-7), Indicates D 1 Or D 2 The bonding positions.

[0193] [Chemical Formula 2] In the above equation (Ar-1), Q 1 Represents N or CH, Q 2 Indicates -S-, -O-, or -N(R) 7 )-,R 7 Y represents an alkyl group having 1 to 6 hydrogen atoms or carbon atoms. 1 It indicates an aromatic hydrocarbon group with 6 to 12 carbon atoms or an aromatic heterocyclic group with 3 to 12 carbon atoms that may have substituents.

[0194] As R 7 The alkyl group represented has 1 to 6 carbon atoms, for example, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl and n-hexyl.

[0195] As Y 1 The aromatic hydrocarbon group represented has 6 to 12 carbon atoms, for example, phenyl, 2,6-diethylphenyl and naphthyl aryl groups.

[0196] As Y 1 The aromatic heterocyclic group represented has 3 to 12 carbon atoms. Examples of such heteroaryl groups include thienyl, thiazolyl, furanyl, and pyridyl.

[0197] And, as Y 1 It can have substituents, for example, alkyl, alkoxy and halogen atoms.

[0198] As an alkyl group, alkyl groups having 1 to 18 carbon atoms are preferred, alkyl groups having 1 to 8 carbon atoms are more preferred, alkyl groups having 1 to 4 carbon atoms are even more preferred, and methyl or ethyl groups are particularly preferred. The alkyl group can be any of the following: straight-chain, branched, or cyclic.

[0199] As an alkoxy group, for example, an alkoxy group having 1 to 18 carbon atoms is preferred, an alkoxy group having 1 to 8 carbon atoms is more preferred, an alkoxy group having 1 to 4 carbon atoms is even more preferred, and a methoxy or ethoxy group is particularly preferred.

[0200] Examples of halogen atoms include fluorine, chlorine, bromine, and iodine, with fluorine or chlorine atoms being preferred.

[0201] Furthermore, in the above equations (Ar-1) to (Ar-7), Z 1 Z 2 and Z 3Each of the following can be independently represented: a hydrogen atom, a monovalent aliphatic hydrocarbon group with 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group with 3 to 20 carbon atoms, a monovalent aromatic hydrocarbon group with 6 to 20 carbon atoms, a halogen atom, a cyano group, a nitro group, or -OR. 8 -NR 9 R 10 or -SR 11 R 8 ~R 11 Z represents, independently, either a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. 1 and Z 2 They can bond with each other to form aromatic rings.

[0202] As a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms, an alkyl group having 1 to 15 carbon atoms is preferred, an alkyl group having 1 to 8 carbon atoms is more preferred, methyl, ethyl, isopropyl, tert-amyl (1,1-dimethylpropyl), tert-butyl or 1,1-dimethyl-3,3-dimethyl-butyl is even more preferred, and methyl, ethyl or tert-butyl is particularly preferred.

[0203] Examples of monocyclic alicyclic hydrocarbon groups with 3 to 20 carbon atoms include monocyclic saturated hydrocarbon groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclodecyl, methylcyclohexyl, and ethylcyclohexyl; monocyclic unsaturated hydrocarbon groups such as cyclobutenyl, cyclopentenyl, cyclohexenyl, cycloheptenyl, cyclooctenyl, cyclodecenyl, cyclopentadienyl, cyclohexadienyl, cyclooctadienyl, and cyclodecadienyl; and bicyclic [2.2.1]heptyl, bicyclic [2.2.2]octyl, and tricyclic [5.2.1.0]heptyl. 2,6 ] decyl, tricyclic [3.3.1.1] 3,7 ] decyl, tetracyclic [6.2.1.1 3,6 .0 2,7 Polycyclic saturated hydrocarbon groups such as dodecyl and adamantyl; etc.

[0204] Examples of monovalent aromatic hydrocarbon groups with 6 to 20 carbon atoms include phenyl, 2,6-diethylphenyl, naphthyl and biphenyl, with aryl groups having 6 to 12 carbon atoms being preferred (especially phenyl).

[0205] Examples of halogen atoms include fluorine, chlorine, bromine, and iodine, with fluorine, chlorine, or bromine being preferred.

[0206] Furthermore, in the above equations (Ar-2) and (Ar-3), A 1 and A 2 Represent the selection independently of -O- and -N(R) 12 The group consisting of -, -S- and -CO-, R 12It represents a hydrogen atom or a substituent.

[0207] As R 12 The substituents represented can be exemplified by Y in the above formula (Ar-1). 1 It can have the same substituents as the group.

[0208] Furthermore, in the above formula (Ar-2), X represents a nonmetallic atom from groups 14 to 16 that can be bonded with substituents.

[0209] Examples of nonmetallic atoms in groups 14-16 represented by X include oxygen atoms, sulfur atoms, hydrogen atoms, or nitrogen atoms bonded to substituents [=NR]. N1 R N1 Represents a hydrogen atom or substituent. The carbon atom bonded to the hydrogen atom or substituent [=C-(R] C1 )2,R C1 Represents a hydrogen atom or substituent. [R] N1 or R C1 The substituent is preferably CN.

[0210] Furthermore, in the above equation (Ar-3), D 4 and D 5 Each can independently represent a single bond or -CO-, -O-, -S-, -C(=S)-, -CR 1a R 2a -、-CR 3a =CR 4a -、-NR 5a - or a divalent linker consisting of two or more of them, R 1a ~R 5a Each can be independently represented by a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 4 carbon atoms.

[0211] Examples of divalent linking groups include -CO-, -O-, -CO-O-, -C(=S)O-, and -CR. 1b R 2b -、-CR 1b R 2b -CR 1b R 2b -、-O-CR 1b R 2b -、-CR 1b R 2b -O-CR 1b R 2b -、-CO-O-CR 1b R 2b -、-O-CO-CR 1b R 2b -、-CR1b R 2b -O-CO-CR 1b R 2b -、-CR 1b R 2b -CO-O-CR 1b R 2b -、-NR 3b -CR 1b R 2b -and-CO-NR 3b -. R 1b R 2b and R 3b Each can be independently represented by a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 4 carbon atoms.

[0212] Furthermore, in the above formula (Ar-3), SP 1 and SP 2 Each of the following groups independently represents a single bond, a straight-chain or branched alkylene group having 1 to 12 carbon atoms, or a divalent linker group in the -CH2- group constituting a straight-chain or branched alkylene group having 1 to 12 carbon atoms, wherein one or more of these groups are substituted with -O-, -S-, -NH-, -N(Q)-, or -CO-, and Q represents a substituent. Examples of substituents include Y in the above formula (Ar-1). 1 It can have the same substituents as the substituents.

[0213] Furthermore, in the above equation (Ar-3), L 3 and L 4 Each of these represents a monovalent organic group independently.

[0214] Examples of monovalent organic groups include alkyl, aryl, and heteroaryl groups. Alkyl groups can be straight-chain, branched, or cyclic, but straight-chain is preferred. The alkyl group preferably has 1 to 30 carbon atoms, more preferably 1 to 20, and even more preferably 1 to 10. Furthermore, aryl groups can be monocyclic or polycyclic, but monocyclic is preferred. The aryl group preferably has 6 to 25 carbon atoms, more preferably 6 to 10. Furthermore, heteroaryl groups can be monocyclic or polycyclic. The number of heteroatoms constituting the heteroaryl group is preferably 1 to 3. The heteroatoms constituting the heteroaryl group are preferably nitrogen, sulfur, or oxygen atoms. The number of carbon atoms in the heteroaryl group is preferably 6 to 18, more preferably 6 to 12. Furthermore, alkyl, aryl, and heteroaryl groups can be unsubstituted or have substituents. Examples of substituents include Y in the above formula (Ar-1). 1 It can have the same substituents as the substituents.

[0215] Furthermore, in the above formulas (Ar-4) to (Ar-7), Ax represents an organic group having at least one aromatic ring selected from the group consisting of aromatic hydrocarbon rings and aromatic heterocycles, with a carbon number of 2 to 30.

[0216] Furthermore, in the above formulas (Ar-4) to (Ar-7), Ay represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms that may have substituents, or an organic group having 2 to 30 carbon atoms of at least one aromatic ring selected from the group consisting of aromatic hydrocarbon rings and aromatic heterocycles.

[0217] Among them, the aromatic rings in Ax and Ay can have substituents, and Ax and Ay can also bond to form a ring.

[0218] And Q 3 It represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms that may have substituents.

[0219] As for Ax and Ay, the groups described in paragraphs

[0039] to

[0095] of Patent Document 1 (International Publication No. 2014 / 010325) can be cited.

[0220] And, as Q 3 The alkyl group represented has 1 to 6 carbon atoms. Specifically, examples include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, and n-hexyl. Substituents include those corresponding to Y in the above formula (Ar-1). 1 It can have the same substituents as the substituents.

[0221] Regarding the definition and preferred range of each substituent in the liquid crystal compound represented by formula (II), for D1, D2, G1, G2, L1, L2, R 1 R 2 R 3 R 4 Q1, Y1, Z1, and Z2 can be referenced respectively to the D of compound (A) disclosed in Japanese Patent Application Publication No. 2012-021068. 1 D 2 G 1 G 2 L 1 L 2 R 4 R 5 R 6 R 7 X 1 Y 1 Q 1 Q 2Regarding the relevant records, for A1, A2, and X, reference can be made to the records relating to A1, A2, and X of the compound represented by general formula (I) disclosed in Japanese Patent Application Publication No. 2008-107767, respectively; for Ax, Ay, and Q2, reference can be made to Ax, Ay, and Q2 of the compound represented by general formula (I) disclosed in International Publication No. 2013 / 018526, respectively. 1 The relevant records. Regarding Z3, reference can be made to Q related to compound (A) disclosed in Japanese Patent Application Publication No. 2012-21068. 1 The records.

[0222] In particular, as a result of L 1 and L 2 The organic groups represented are preferably derived from -D 3 -G 3 -Sp-P 3 The group indicated.

[0223] D 3 The meaning of D 1 The meanings are the same.

[0224] G 3 This refers to a single bond, a divalent aromatic or heterocyclic group with 6 to 12 carbon atoms, or a divalent alicyclic hydrocarbon group with 5 to 8 carbon atoms, wherein the methylene group contained in the above-mentioned alicyclic hydrocarbon group can be -O-, -S-, or -NR. 7 - Replacement, where R 7 It refers to an alkyl group having 1 to 6 hydrogen atoms or carbon atoms.

[0225] Sp represents a single bond, -(CH2) n -、-(CH2) n -O-、-(CH2-O-) n -、-(CH2CH2-O-) m -O-(CH2) n -、-O-(CH2) n -O-, -O- (CH2-O-) n -、-O-(CH2CH2-O-) m -C(=O)-O-(CH2) n -、-C(=O)-O-(CH2) n -O-, -C(=O)-O-(CH2-O-) n -, -C(=O)-O-(CH2CH2-O-) m -C(=O)-N(R) 8 )-(CH2) n -、-C(=O)-N(R 8 )-(CH2)n -O-、-C(=O)-N(R 8 )-(CH2-O-) n -、-C(=O)-N(R 8 )-(CH2CH2-O-) m Or - (CH2) n -O-(C=O)-(CH2) n -C(=O)-O-(CH2) n - represents the spacer group. Where n represents an integer from 2 to 12, m represents an integer from 2 to 6, and R... 8 This refers to an alkyl group having 1 to 6 hydrogen atoms or carbon atoms. Furthermore, the hydrogen atom in the -CH2- group can be replaced by a methyl group.

[0226] P 3 It indicates a polymerizable group.

[0227] Polymerizable groups are not particularly restricted, but polymerizable groups capable of free radical polymerization or cationic polymerization are preferred.

[0228] As a free radical polymerizable group, known free radical polymerizable groups can be cited, with acryloyl or methacryloyl being preferred. Acryloyl groups are known to generally polymerize faster, and from the viewpoint of improving productivity, acryloyl groups are preferred. However, methacryloyl groups can also be used in the same way as polymerizable groups for highly birefringent liquid crystals.

[0229] As cationic polymerizable groups, known cationic polymerizable groups can be cited, such as alicyclic ether groups, cyclic acetal groups, cyclic lactone groups, cyclic thioether groups, spirocyclic orthoester groups, and ethyleneoxy groups. Among these, alicyclic ether groups or ethyleneoxy groups are preferred, and epoxy groups, oxetyl groups, or ethyleneoxy groups are more preferred.

[0230] As described above, the liquid crystal lens 34 has a substrate 50, an alignment film 52, and the liquid crystal layer 36.

[0231] The substrate 50 constituting this liquid crystal lens 34 can be made of various sheet materials as long as it can support the alignment film 52 and the liquid crystal layer 36 described later.

[0232] As substrate 50, a transparent substrate is preferred, and examples include polyacrylic resin films such as polymethyl methacrylate, cellulose resin films such as cellulose triacetate, cyclic olefin polymer films, polyethylene terephthalate (PET), polycarbonate, and polyvinyl chloride. Examples of cyclic olefin polymer films include those manufactured under the trade name "ARTON" by JSR Corporation and those manufactured under the trade name "ZEONOR" by ZEON CORPORATION. Furthermore, a glass substrate can also be preferably used as substrate 50.

[0233] An alignment film 52 is formed on the surface of this substrate 50.

[0234] The liquid crystal alignment pattern in liquid crystal layer 36 follows the alignment pattern formed on alignment film 52. Therefore, the alignment film 52, which is used to form the liquid crystal layer having this liquid crystal alignment pattern, has the same alignment pattern as the liquid crystal alignment pattern in liquid crystal layer 36.

[0235] exist Figure 7 The following is a conceptual example of an exposure apparatus: an alignment film 52 (optical alignment film) used to form liquid crystal layer 36 is exposed to form an alignment pattern corresponding to a concentric liquid crystal alignment pattern that changes as the optical axis rotates radially.

[0236] Figure 7 The exposure apparatus 80 shown includes a light source 84 with a laser 82, a polarization beam splitter 86 that separates the laser beam M from the laser 82 into S-polarized light MS and P-polarized light MP, a reflector 90A disposed in the optical path of P-polarized light MP and a reflector 90B disposed in the optical path of S-polarized light MS, a lens 92 disposed in the optical path of S-polarized light MS, a beam splitter 94, and a quarter-wave plate 96.

[0237] The P-polarized light MP, separated by the polarization beam splitter 86, is reflected by the mirror 90A and then enters the beam splitter 94. On the other hand, the S-polarized light MS, separated by the polarization beam splitter 86, is reflected by the mirror 90B and then focused by the lens 92 before entering the beam splitter 94.

[0238] After being combined by beam splitter 94, P-polarized light MP and S-polarized light MS are converted into right-hand circularly polarized light and left-hand circularly polarized light respectively by quarter-wave plate 96 according to the polarization direction, and then incident on alignment film 52 on substrate 50.

[0239] In this process, the polarization state of the light illuminating the alignment film 52 changes periodically in the form of interference fringes due to the interference of right-handed and left-handed circularly polarized light. Since the crossing angle between the left-handed and right-handed circularly polarized light changes from the inside to the outside of the concentric circles, an exposure pattern in which the spacing (one period) gradually shortens from the inside to the outside can be obtained. Thus, a concentric (radial) alignment pattern in the alignment film 52 with a periodically changing alignment state can be obtained.

[0240] In this exposure apparatus 80, one cycle Λ of the liquid crystal alignment pattern in which the optical axis of the liquid crystal compound 38 rotates continuously by 180° in one direction can be controlled by changing the refractive power of the lens 92, the focal length of the lens 92, and the distance between the lens 92 and the alignment film 52.

[0241] Furthermore, by adjusting the refractive power (F-value) of lens 92, the length of one cycle of the liquid crystal alignment pattern can be changed in one direction of continuous rotation of the optical axis.

[0242] Specifically, by generating anti-interference with parallel light and utilizing the diffusion angle of the light diffused by lens 92, the length of one period of the liquid crystal alignment pattern can be changed in one direction of continuous rotation of the optical axis. More specifically, if the refractive power of lens 92 is reduced, the light approaches parallelism, and therefore the length Λ of one period of the liquid crystal alignment pattern shortens slowly from the inside to the outside. Conversely, if the refractive power of lens 92 is increased, the length Λ of one period of the liquid crystal alignment pattern shortens sharply from the inside to the outside.

[0243] That is, by adjusting the refractive index of lens 92, the refractive index of liquid crystal lens 34 (liquid crystal layer 36), which functions as a concave or convex lens, can be adjusted according to the rotation direction of the incident circularly polarized light.

[0244] On the exposed alignment film 52 formed by the above method, the liquid crystal composition containing liquid crystal compound for forming liquid crystal layer 36 is coated and dried, and then cured by ultraviolet irradiation or the like as needed.

[0245] Thus, a liquid crystal layer 36 with a concentric circular liquid crystal alignment pattern as described above and a period that gradually shortens from the center outwards can be formed, thereby producing a liquid crystal layer 36 as described above. Figure 2 and Figure 3 The liquid crystal lens 34 shown.

[0246] As a compound having photo-orientation groups, i.e., a photo-orientation material used in a photo-orientation film, examples include, for example, Japanese Patent Application Publication Nos. 2006-285197, 2007-76839, 2007-138138, 2007-94071, 2007-121721, 2007-140465, and 20... Japanese Patent Application Publication No. 07-156439, Japanese Patent Application Publication No. 2007-133184, Japanese Patent Application Publication No. 2009-109831, Japanese Patent No. 3883848 and Japanese Patent No. 4151746, Japanese Patent Application Publication No. 2002-229039, Japanese Patent Application Publication No. 2002-265541 and Japanese Patent Application Publication No. 2002-317013, as well as the azo compounds described therein. The following are examples of photocrosslinked polyimides, photocrosslinked polyamides, and photocrosslinked esters described in the publications: maleimides with photoorientation units and / or alkenyl-substituted nadicimides; photocrosslinked silane derivatives described in Japanese Patent Nos. 4205195 and 4205198; photocrosslinked polyimides, photocrosslinked polyamides, and photocrosslinked esters described in Japanese Patent Nos. 2003-520878, 2004-529220, and 4162850. Preferred examples include compounds capable of photodimerization, particularly cinnamic acid ester compounds, chalcone compounds, and coumarin compounds, as described in Japanese Patent Application Publication Nos. 9-118717, 10-506420, 2003-505561, International Publication No. 2010 / 150748, 2013-177561, and 2014-12823.

[0247] Preferably, azo compounds, photocrosslinked polyimides, photocrosslinked polyamides, photocrosslinked esters, cinnamic acid ester compounds, and chalcone compounds are used.

[0248] The following is based on reference Figure 8 The conceptual diagram illustrates the function of the optical device 30, thereby providing a more detailed explanation of the display device 10.

[0249] As described above, the image emitted from the focusing optical system of the display device 10, which is composed of a semi-reflective mirror 16, a lens 18, a circularly polarized light reflecting polarizer 24, and a circularly polarized plate 26, is an image of left-handed circularly polarized light.

[0250] Furthermore, the image of the left-hand circularly polarized light is incident on the optical device 30, namely the switching element 32 and the liquid crystal lens 34, under the condition of being focused by the focusing optical system (lens 18).

[0251] In the optical device 30, the switching element 32 is an element that switches between a closed state with zero phase difference and an open state with a phase difference of half a wavelength and functioning as a half-wave plate.

[0252] Furthermore, the liquid crystal lens 34 (liquid crystal layer 36), as an example, functions as a convex lens to focus left-handed circularly polarized light and as a concave lens to diverge right-handed circularly polarized light. However, the present invention is not limited to this; the liquid crystal lens 34 (liquid crystal layer 36) can also be a liquid crystal lens that diverges left-handed circularly polarized light and focuses right-handed circularly polarized light.

[0253] exist Figure 8 In the diagram, a dashed line represents the state in which the image of left-handed circularly polarized light is focused by a focusing optical system consisting of a semi-reflecting mirror 16, a lens 18, a circularly polarized light reflecting polarizer 24, and a circular polarizer 26. Furthermore, this focal point, i.e., the focal point of lens 18, is designated as FO.

[0254] The image emitted from the focusing optical system (circular polarizer 26) is an image of left-handed circularly polarized light.

[0255] Therefore, when the switching element 32 is in the off state, the image of the left-hand circularly polarized light passes directly through the switching element 32 and is incident on the liquid crystal lens 34 in the state of left-hand circularly polarized light.

[0256] The liquid crystal lens 34 (liquid crystal layer 36) focuses left-handed circularly polarized light and diverges right-handed circularly polarized light.

[0257] Therefore, in this state, with the light focused by the focusing optical system, the image of the left-handed circularly polarized light incident on the liquid crystal lens 34 is as follows: Figure 8 As indicated by the dashed line, the light is further focused by the liquid crystal lens 34 and converted into right-hand circularly polarized light. As a result, the image of this right-hand circularly polarized light is focused at the focal point FL, which has a focal length shorter than the focal point FP.

[0258] On the other hand, when the switching element 32 is turned on, the image of left-hand circularly polarized light is converted into right-hand circularly polarized light by the switching element 32, which acts as a half-wave plate, and then incident into the liquid crystal lens 34.

[0259] The liquid crystal lens 34 (liquid crystal layer 36) focuses left-handed circularly polarized light and diverges right-handed circularly polarized light.

[0260] Therefore, in this state, with the light focused by the focusing optical system, the image of the right-hand circularly polarized light incident on the liquid crystal lens 34 is as follows: Figure 8As indicated by the double-dotted line, the light is diffused by the liquid crystal lens 34 in a way that maintains a focused state, and is converted into left-handed circularly polarized light. That is, when the light is focused by the focusing optical system, the image of the right-handed circularly polarized light incident on the liquid crystal lens 34 is as follows: Figure 8 As indicated by the double-dotted line, the light concentration is reduced by the liquid crystal lens 34 and converted into left-handed circularly polarized light. As a result, the image of this left-handed circularly polarized light is concentrated at the focal point FR, which has a longer focal length than the focal point FP.

[0261] Thus, the display device 10 using the optical device of the present invention can switch the phase difference by switching element 32, thereby changing the focal length of the image observed by user O, and can also change the depth perception of virtual reality images, etc.

[0262] Among them, the display device 10 using the optical device 30 of the present invention is able to display (project) a stable image quality regardless of the focus of the image observed by the user O when the focus is changed.

[0263] As described in Patent Document 1, the focal length of the observed image in the HMD can be switched by using a switchable half-wave plate (SHWP) and a liquid crystal lens.

[0264] However, according to the inventor's research, in conventional HMDs, if a switchable half-wave plate and liquid crystal lens are used to switch the focal length, an appropriate image can be displayed at a certain focal length, but at another focal length, ghosting caused by light leakage and other factors will increase. In the case of full-color images, when changing the focal length, adverse conditions such as deterioration of the image quality of any of the red, green, and blue images will occur, resulting in unstable image quality with varying focal lengths.

[0265] In contrast, the optical device 30 of the present invention, which has a switching element capable of switching phase differences and a liquid crystal layer, uses a liquid crystal layer 36 formed using a liquid crystal composition comprising a liquid crystal compound with reverse wavelength dispersion. That is, the optical device of the present invention has a liquid crystal layer 36 formed using a liquid crystal compound with reverse wavelength dispersion.

[0266] Therefore, according to the optical device of the present invention, as shown in the following embodiments, the image quality changes little when switching focal lengths in HMDs and the like, and is not affected by the focal length; stable image quality can be obtained for any of the red, green, and blue images.

[0267] Furthermore, when using the optical device of the present invention to change the focal length of HMDs, etc., it is only necessary to slightly focus or diffuse the light in the focusing state.

[0268] exist Figure 1 and Figure 8In the example shown, the display device 10 has only one optical element 30 of the present invention, but the present invention is not limited thereto.

[0269] That is, HMD and other display devices using the optical devices of the present invention can have multiple optical devices 30 of the present invention, which are composed of switching elements and liquid crystal layers.

[0270] Furthermore, when the display device has multiple optical elements 30, the liquid crystal layer 36 of at least one optical element is preferably different from the period Λ of the liquid crystal layer 36 of the other optical elements 30. Moreover, when the display device has multiple optical elements 30, it is more preferable that the period Λ of the liquid crystal layer 36 of all optical elements is different from each other.

[0271] like Figure 1 and Figure 8 As shown, when the display device has only one optical element 30, it can switch between two focal lengths. In contrast, when it has multiple optical elements 30, depending on the number of optical elements 30, it can switch between three or more focal lengths of the display device.

[0272] In particular, by varying a cycle Λ of the liquid crystal layer 36 of the optical device 30, the focal length of the display device can be switched to more different types.

[0273] For example, a display device has two optical devices, a first optical device and a second optical device. When the period Λ of the liquid crystal layer of the two optical devices is equal, three focal lengths can be achieved as the focal length: first device on / second device on, first device off / second device off, and first device on / second device off. Furthermore, the "on / off" of each device mentioned here refers to the on / off of the switching element of the aforementioned optical device. Additionally, in this case, the focal lengths for first device on / second device off and first device off / second device on are the same.

[0274] In contrast, the display device has two optical devices, a first optical device and a second optical device. When the liquid crystal layer of the two optical devices has a different period Λ, four focal lengths can be achieved: first device on / second device on, first device off / second device off, first device on / second device off, and first device off / second device on. Furthermore, by having three or more optical devices, more focal lengths can be switched by turning each device on and off.

[0275] exist Figure 1 In the display device 10 shown, as a preferred embodiment, the optical device of the present invention is disposed downstream of the focusing optical system.

[0276] However, the present invention is not limited thereto. The optical device of the present invention can also be configured upstream of the condensing optical system, or it can be configured within the condensing optical system. However, in this configuration, the following problems may occur: an additional quarter-wave plate is required to make the circularly polarized light emitted from the condensing optical system follow a predetermined cycloid direction, and the control of the focal length becomes complicated.

[0277] and, Figure 2 The liquid crystal layer shown has a concentric circle liquid crystal alignment pattern, but the present invention is not limited thereto, and various liquid crystal alignment patterns can be used.

[0278] As an example, the following can be illustrated: Figure 9 The conceptual illustration shows circular patterns of varying sizes arranged in a liquid crystal alignment pattern, with larger circles containing smaller circles, and their centers offset. Furthermore, the liquid crystal alignment pattern is not limited to circles; it can also be, for example... Figure 10 The pattern is a conceptual representation of an oblong or elliptical shape.

[0279] That is, in this invention, various liquid crystal alignment patterns can be used, which have multiple rings of different sizes, and within a plane, larger rings successively contain smaller rings. Furthermore, in this invention, "ring" refers to a shape without ends, such as a circle, ellipse, or quadrilateral.

[0280] Furthermore, in this invention, the liquid crystal alignment pattern in the liquid crystal layer is not limited to a liquid crystal alignment pattern having multiple rings; for example, it can also be as follows: Figure 4 The illustrated liquid crystal alignment pattern is a linear pattern in which the orientation of the optical axis of the liquid crystal compound changes continuously in only one direction.

[0281] A liquid crystal layer with a linear liquid crystal alignment pattern varies according to the cyclotron direction of the incident circularly polarized light, such as... Figure 5 and Figure 6 As shown, circularly polarized light is refracted along the direction of rotation of the optical axis, i.e., in the direction of arrow A or the opposite direction of arrow A. That is, by using a liquid crystal layer with a linear liquid crystal alignment pattern, the direction of light propagation can be changed to two (or more) different directions. For example, by using an optical device with such a liquid crystal layer in an image display device, the display position of the image can be changed.

[0282] Regarding such linear liquid crystal alignment patterns, as an example, they can be achieved by using methods such as those described in Japanese Patent Application Publication No. 2022-36995. Figure 7 The alignment film 52 is formed by exposing it with the exposure apparatus shown.

[0283] Furthermore, even in these various liquid crystal alignment patterns, it is preferable to have a region with a different period within the plane, which is the same as for concentric circle liquid crystal alignment patterns.

[0284] The number of optical components, the position of the optical components, and the liquid crystal alignment pattern of the liquid crystal layer of the optical components in the aforementioned display device are also the same in AR glasses and the like shown below.

[0285] The above examples illustrate the use of the optical device 30 of the present invention in a VR image display device 10 as an HMD, but the present invention is not limited thereto.

[0286] As an example, the optical device 30 of the present invention can also be used as an AR image display device (AR glasses) as an HMD.

[0287] Figure 11 The concept illustrates one example.

[0288] in addition, Figure 11 Since the AR glasses 60 shown uses multiple components that are the same as those in the display device 10 described above, the same symbols are used for the same components, and the different parts are mainly described.

[0289] Figure 11 The AR glasses 60 shown are, for example, mounted on glasses, allowing the user to observe the image displayed on the display 12 superimposed on the background, which is called observing augmented reality (AR).

[0290] In the AR glasses 60, the image displayed on the display 12 is focused by the lens 62 and then incident on the incident diffraction element 64 through the light guide plate 68.

[0291] The incident diffraction element 64 is a reflective diffraction element, and by diffracting and reflecting the image incident through the light guide plate 68, it is incident into the light guide plate 68 at an angle of total internal reflection propagation within the light guide plate 68.

[0292] The image propagating within the light guide plate 68 is then incident on the exiting diffraction element 70. The exiting diffraction element 70 is a reflective diffraction element, and it exits the light guide plate 68 by diffracting and reflecting the image propagating within the light guide plate 68 through total internal reflection.

[0293] Lens 62 (focusing lens) and light guide plate 68 can utilize various known lenses and light guide plates used in AR glasses.

[0294] The incident diffraction element 64 and the exit diffraction element 70 can also utilize various known reflective diffraction elements (diffraction gratings), such as surface-embossed diffraction elements, holographic diffraction elements, and reflective liquid crystal diffraction elements. Furthermore, in the AR glasses 60 of the example figure, reflective diffraction elements are used to incident and exit images onto the light guide plate 68; however, the present invention is not limited to this, and transmissive diffraction elements can also be used to incident and exit images onto the light guide plate 68. In this case, transmissive diffraction elements can also utilize known diffraction elements such as transmissive liquid crystal diffraction elements.

[0295] The image emitted from the light guide plate 68 is converted into left-handed circularly polarized light by the circular polarizer 14, for example, and then incident on the optical device 30 of the present invention described above.

[0296] As an example Figure 8 As explained, in the AR glasses 60, by setting the switching element 32 of the optical device 30 to the off state, left-handed circularly polarized light is directly incident on the liquid crystal lens 34 (liquid crystal layer 36) as left-handed circularly polarized light, thereby focusing the image at the focal point FL with a short focal length. Furthermore, by setting the switching element 32 of the optical device 30 to the on state, the left-handed circularly polarized light is converted to right-handed circularly polarized light and incident on the liquid crystal lens 34, thereby focusing the image at the focal point FR with a longer focal length.

[0297] Even at this time, the AR glasses using the optical device 30 of the present invention show little change in image quality when switching focal lengths and are unaffected by focal length; stable image quality can be obtained for any of the red, green, and blue images.

[0298] The above examples illustrate the application of the optical device of the present invention in VR image display devices and AR glasses, but the present invention is not limited thereto. That is, the optical device of the present invention can be used for various applications.

[0299] As an example, processing devices that change the propagation direction of electromagnetic waves in communication applications can be cited.

[0300] The optical device and head-mounted display of the present invention have been described in detail above. However, the present invention is not limited to the above examples. Various improvements and modifications can be made without departing from the spirit of the present invention.

[0301] Example The following examples further illustrate the features of the present invention. The materials, reagents, dosages, quantities, ratios, processing contents, and processing steps shown in the following examples can be appropriately modified without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should not be limited by the specific examples shown below.

[0302] <Fabrication of Liquid Crystal Layer (Liquid Crystal Lens)> [Comparative Example 1] (Support structure) A glass substrate was prepared as a support.

[0303] (Formation of the orientation film) The following coating liquid for forming an alignment film is applied to a support by spin coating. The support with the coating liquid for forming the alignment film is dried on a hot plate at 60°C for 60 seconds, thereby forming an alignment film.

[0304] Coating liquid for forming alignment film ―――――――――――――――――――――――――――――――― Raw material A for photoorientation, 1.00 parts by weight 16.00 parts by weight of water 42.00 parts by weight of butoxyethanol 42.00 parts by weight of propylene glycol monomethyl ether ―――――――――――――――――――――――――――――――― -Raw material A for photoorientation- [Chemical Formula 3] (Exposure of the alignment film) use Figure 7 The exposure apparatus 80 shown exposes the formed alignment film, thereby forming an alignment film P-1 with an alignment pattern, as shown in the figure. Figure 2 The pattern shown is a continuous rotation of concentric circles (radial) with short straight lines (short lines) in one direction, which changes as the pattern changes.

[0305] Furthermore, a period Λ in the orientation pattern of the alignment film varies in-plane, but its minimum value is set to 10 μm. A period Λ in the orientation pattern is... Figure 7 The focal length of the lens 92 used in the exposure apparatus 80 shown is adjusted.

[0306] The light source used was a laser beam with an emission wavelength of 355 nm. The exposure dose of the interference light was set to 1000 mJ / cm². 2 .

[0307] (Formation of the liquid crystal layer) As a liquid crystal composition for forming liquid crystal layer A-1, the following liquid crystal composition A-1 was prepared.

[0308] In addition, the liquid crystal compound L-1 described below is a liquid crystal compound with positive wavelength dispersiveness.

[0309] Liquid crystal composition A-1 ―――――――――――――――――――――――――――――――― Liquid crystal compound L-1 100.00 parts by weight Polymerization initiator (manufactured by BASF, Irgacure OXE01) 1.00 parts by weight Leveling agent T-1 0.08 parts by weight 1050.00 parts by weight of methyl ethyl ketone ―――――――――――――――――――――――――――――――― Liquid crystal compound L-1 [Chemical Formula 4] Leveling agent T-1 [Chemical Formula 5] The liquid crystal layer is formed by multilayer coating of liquid crystal composition A-1 onto alignment film P-1.

[0310] Multilayer coating refers to a process involving repeated application of the following steps: First, a first layer of liquid crystal composition A-1 is coated onto an alignment film. After heating and UV curing to form a liquid crystal fixing layer, subsequent layers are coated onto this liquid crystal fixing layer in an overlapping manner, and then cured under UV light in the same manner. Because it is formed through multilayer coating, even when the total thickness of the liquid crystal layer increases, the alignment direction of the alignment film is still reflected from the lower surface of the liquid crystal layer to the upper surface.

[0311] First, in the first layer, the aforementioned liquid crystal composition A-1 is coated onto the alignment film P-1, and the coating is heated to 80°C on a hot plate. Then, under a nitrogen atmosphere, a high-pressure mercury lamp at 300 mJ / cm² is used. 2 The coating is irradiated with ultraviolet light at a wavelength of 365 nm, thereby fixing the orientation of the liquid crystal compound.

[0312] After the second layer, the liquid crystal fixing layer is overlapped and coated, and then heated under the same conditions as above and cured with ultraviolet light to produce the liquid crystal fixing layer.

[0313] By repeatedly overlapping the coatings as described above until the total thickness reaches the desired film thickness, liquid crystal layer A-1 (transmissive liquid crystal lens (liquid crystal diffraction element)) is produced.

[0314] Furthermore, the refractive index difference Δn of the cured layer of liquid crystal composition A-1 is determined by measuring the retardation value and film thickness of the liquid crystal fixing layer (cured layer). This liquid crystal fixing layer is obtained by coating liquid crystal composition A-1 onto a separately prepared support with an alignment film for retardation measurement, aligning the liquid crystal compound so that its orientation is horizontal relative to the substrate, and then fixing it by irradiation with ultraviolet light. Δn can be calculated by dividing the retardation value by the film thickness.

[0315] The retardation value was measured at the target wavelength using Axometrix's Axoscan, and the film thickness was measured using a scanning electron microscope (SEM).

[0316] In liquid crystal layer A-1, the final liquid crystal Δn 550 The thickness (=Re(550)) is 275 nm, and it was confirmed using a polarizing microscope that it has the following characteristics. Figure 2 The concentric circle liquid crystal alignment pattern shown.

[0317] In addition, in the liquid crystal alignment pattern of liquid crystal layer A-1, in one cycle of rotating the optical axis of the liquid crystal compound by 180°, one cycle at a distance of about 10 mm from the center is 53 μm, one cycle at a distance of 20 mm from the center is 27 μm, and one cycle at a distance of 25 mm from the center is 10.7 μm. It is a liquid crystal alignment pattern with the period gradually shortening towards the outside.

[0318] Furthermore, in liquid crystal layer A-1, the twist angle of the liquid crystal compound in the thickness direction is 0° in-plane.

[0319] The resulting liquid crystal layer A-1 has the following characteristics: it diverges the incident light when it is incident with right-handed circularly polarized light, and converges the incident light when it is incident with left-handed circularly polarized light.

[0320] Furthermore, the effective diameter of the liquid crystal layer A-1 is 50 mm, and its refractive power is 2D.

[0321] [Comparative Example 2] As a liquid crystal composition for forming the first region of liquid crystal layer B-1, liquid crystal composition B-1 was obtained by adding 0.33 parts by mass of the following chiral reagent C-2 to liquid crystal composition A-1.

[0322] Chiral reagent C-2 [Chemical Formula 6] Liquid crystal composition B-1 was used instead of liquid crystal composition A-1, and the film thickness of the liquid crystal layer was adjusted. Otherwise, the first region of liquid crystal layer B-1 was formed in the same manner as liquid crystal layer A-2.

[0323] In region 1, the final liquid crystal Δn 550 The thickness (=Re(550)) is 180 nm, and it was confirmed using a polarizing microscope that it has the following characteristics. Figure 2 The concentric circle liquid crystal alignment pattern shown.

[0324] Furthermore, in the liquid crystal alignment pattern of the first region, in one cycle of rotating the optical axis of the liquid crystal compound by 180°, one cycle at a distance of about 10 mm from the center is 53 μm, one cycle at a distance of 20 mm from the center is 27 μm, and one cycle at a distance of 25 mm from the center is 10.7 μm, which is a liquid crystal alignment pattern with a period that gradually shortens towards the outside.

[0325] Furthermore, in the first region, the twist angle of the liquid crystal compound in the thickness direction is 80° in-plane.

[0326] Next, on the first region of liquid crystal layer B-1, liquid crystal composition A-1 is used to adjust the film thickness of the liquid crystal layer. Otherwise, the second region of liquid crystal layer B-1 is formed using the same steps.

[0327] In region 2, the final Δn of the liquid crystal 550 The thickness (=Re(550)) is 365 nm, and it was confirmed using a polarizing microscope that it has the following characteristics. Figure 2 The concentric circle liquid crystal alignment pattern shown.

[0328] Furthermore, in the liquid crystal alignment pattern of the second region, in one cycle of rotating the optical axis of the liquid crystal compound by 180°, one cycle at a distance of about 10 mm from the center is 53 μm, one cycle at a distance of 20 mm from the center is 27 μm, and one cycle at a distance of 25 mm from the center is 10.7 μm. It is a liquid crystal alignment pattern with a period that gradually shortens towards the outside.

[0329] Furthermore, in the second region of liquid crystal layer B-1, the twist angle of the liquid crystal compound in the thickness direction is 0° in-plane.

[0330] Liquid crystal composition C-1 was obtained by adding 0.54 parts by mass of the following chiral reagent C-1 to liquid crystal composition A-1.

[0331] Chiral reagent C-1 [Chemical Formula 7] In addition to using liquid crystal composition C-1, a third region of the liquid crystal layer is formed on the second region in the same manner as the first region, thereby creating a liquid crystal layer B-1 (transmissive liquid crystal lens) composed of the first region, the second region and the third region.

[0332] In region 3, the final Δn of the liquid crystal 550 The thickness (=Re(550)) is 180 nm, and it was confirmed using a polarizing microscope that it has the following characteristics. Figure 7 The concentric circle liquid crystal alignment pattern shown.

[0333] Furthermore, in the liquid crystal alignment pattern of the first region, in one cycle of rotating the optical axis of the liquid crystal compound by 180°, one cycle at a distance of about 10 mm from the center is 53 μm, one cycle at a distance of 20 mm from the center is 27 μm, and one cycle at a distance of 25 mm from the center is 10.7 μm, which is a liquid crystal alignment pattern with a period that gradually shortens towards the outside.

[0334] Furthermore, in the third region, the twist angle of the liquid crystal compound in the thickness direction is -80° in-plane.

[0335] The resulting liquid crystal layer B-1 has the following characteristics: it diverges the incident light when it is incident with right-handed circularly polarized light, and converges the incident light when it is incident with left-handed circularly polarized light.

[0336] Furthermore, the effective diameter of the liquid crystal layer B-1 is 50 mm, and its refractive power is 2D.

[0337] [Example 1] In liquid crystal composition A-1, liquid crystal compound L-1 was replaced with liquid crystal compound L-2 and 0.02 parts by mass of chiral reagent C-2 were added. Otherwise, liquid crystal composition A-2 was prepared in the same manner.

[0338] The liquid crystal compound L-2 is a liquid crystal compound with reverse wavelength dispersion.

[0339] Liquid crystal compound L-2 [Chemical Formula 8] Liquid crystal composition A-2 was used instead of liquid crystal composition A-1. Otherwise, liquid crystal layer A-2 (transmissive liquid crystal lens) was fabricated using the same steps as liquid crystal layer A-1.

[0340] In liquid crystal layer A-2, the final Δn of the liquid crystal 550 The thickness (=Re(550)) is 275 nm, and it was confirmed using a polarizing microscope that it has the following characteristics. Figure 2 The concentric circle liquid crystal alignment pattern shown.

[0341] Furthermore, in the liquid crystal alignment pattern of liquid crystal layer A-2, in one cycle of rotating the optical axis of the liquid crystal compound by 180°, one cycle at a distance of about 10 mm from the center is 53 μm, one cycle at a distance of 20 mm from the center is 27 μm, and one cycle at a distance of 25 mm from the center is 10.7 μm, which is a liquid crystal alignment pattern with a period that gradually shortens towards the outside.

[0342] Furthermore, in liquid crystal layer A-2, the twist angle of the liquid crystal compound in the thickness direction is 7° in-plane.

[0343] The resulting liquid crystal layer A-2 has the following characteristics: it diverges the incident light when it is incident with right-handed circularly polarized light, and converges the incident light when it is incident with left-handed circularly polarized light.

[0344] Furthermore, the effective diameter of the liquid crystal layer A-2 is 50 mm, and its refractive power is 2D.

[0345] [Examples 1-2] During the exposure of the alignment film, for Figure 7 The focal length of the lens 92 in the exposure apparatus 80 shown was adjusted. In addition, liquid crystal layer A-3 (transmissive liquid crystal lens) was fabricated in the same manner as liquid crystal layer A-2.

[0346] In the liquid crystal alignment pattern of liquid crystal layer A-3, in one cycle of rotating the optical axis of the liquid crystal compound by 180°, one cycle at a distance of about 10 mm from the center is 107 μm, one cycle at a distance of 20 mm from the center is 53 μm, and one cycle at a distance of 25 mm from the center is 21.3 μm. It is a liquid crystal alignment pattern with the period gradually shortening towards the outside.

[0347] The effective diameter of the liquid crystal layer A-3 is 50 mm, and its refractive power is 1D.

[0348] [Examples 1-3] During the exposure of the alignment film, for Figure 7 The focal length of the lens 92 in the exposure apparatus 80 shown was adjusted. In addition, liquid crystal layer A-4 (transmissive liquid crystal lens) was fabricated in the same manner as liquid crystal layer A-2.

[0349] In the liquid crystal alignment pattern of liquid crystal layer A-4, in one cycle of rotating the optical axis of the liquid crystal compound by 180°, one cycle at a distance of about 10 mm from the center is 213 μm, one cycle at a distance of 20 mm from the center is 107 μm, and one cycle at a distance of 25 mm from the center is 42.6 μm. It is a liquid crystal alignment pattern with the period gradually shortening towards the outside.

[0350] The effective diameter of the liquid crystal layer A-4 is 50 mm, and its refractive power is 0.5 D.

[0351] [Examples 1-4] During the exposure of the alignment film, for Figure 7 The focal length of the lens 92 in the exposure apparatus 80 shown was adjusted. In addition, liquid crystal layer A-5 (transmissive liquid crystal lens) was fabricated in the same manner as liquid crystal layer A-2.

[0352] In the liquid crystal alignment pattern of liquid crystal layer A-5, in one cycle of rotating the optical axis of the liquid crystal compound by 180°, one cycle at a distance of about 10 mm from the center is 426 μm, one cycle at a distance of 20 mm from the center is 213 μm, and one cycle at a distance of 25 mm from the center is 85 μm. It is a liquid crystal alignment pattern with the period gradually shortening towards the outside.

[0353] The effective diameter of the liquid crystal layer A-5 is 50 mm, and its refractive power is 0.25D.

[0354] [Example 2] In liquid crystal composition A-2, liquid crystal compound L-1 was replaced with liquid crystal compound L-3. Otherwise, liquid crystal composition A-6 was prepared in the same manner.

[0355] The liquid crystal compound L-3 is a liquid crystal compound with reverse wavelength dispersion.

[0356] Liquid crystal compound L-3 [Chemical Formula 9] Liquid crystal composition A-6 was used instead of liquid crystal composition A-2. Otherwise, liquid crystal layer A-6 (transmissive liquid crystal lens) was fabricated using the same steps as liquid crystal layer A-2.

[0357] In liquid crystal layer A-6, the twist angle of the liquid crystal compound in the thickness direction is 7° in-plane.

[0358] [Example 3] As a liquid crystal composition for forming liquid crystal layer A-7, the following liquid crystal composition A-7 was prepared.

[0359] In addition, the liquid crystal compounds L-3 and L-4 described below are liquid crystal compounds with reverse wavelength dispersion, and the liquid crystal compounds L-1 and L-5 are liquid crystal compounds with positive wavelength dispersion, but the composition as a whole exhibits reverse wavelength dispersion.

[0360] Liquid crystal composition A-7 ―――――――――――――――――――――――――――――――― Liquid crystal compound L-1 10.34 parts by mass Liquid crystal compound L-3 43.10 parts by weight Liquid crystal compound L-4, 20.75 parts by weight Liquid crystal compound L-5 4.95 parts by weight Polymerization initiator (manufactured by BASF, Irgacure OXE01) 1.00 parts by weight Leveling agent T-1 0.08 parts by weight 805.00 parts by weight of methyl ethyl ketone Cyclopentanone 245.00 parts by weight ―――――――――――――――――――――――――――――――― Liquid crystal compound L-4 [Chemical Formula 10] Liquid crystal composition L-5 [Chemical Formula 11] Liquid crystal composition A-7 was used instead of liquid crystal composition A-2. Otherwise, liquid crystal layer A-7 (transmissive liquid crystal lens) was fabricated using the same steps as liquid crystal layer A-2.

[0361] In liquid crystal layer A-7, the twist angle of the liquid crystal compound in the thickness direction is 7° in-plane.

[0362] [Example 4] By changing the thickness of liquid crystal layer A-2, the Δn of the liquid crystal can ultimately be increased. 550 The thickness (=Re(550)) was set to 300nm. In addition, liquid crystal layer A-8 (transmissive liquid crystal lens) was fabricated in the same order as liquid crystal layer A-2.

[0363] In liquid crystal layer A-8, the twist angle of the liquid crystal compound in the thickness direction is 7° in-plane.

[0364] (Evaluation of the liquid crystal layer) The fabricated liquid crystal layer (liquid crystal lens) was evaluated according to the following criteria.

[0365] In a direction in which the orientation of the optical axis of the liquid crystal compound changes continuously during rotation, the position with a length of 40 μm for one cycle is set as the evaluation coordinate when the length of the 180° rotation of the orientation of the optical axis originating from the liquid crystal compound is taken as a cycle.

[0366] In the evaluation coordinate system, blue (450 nm), green (532 nm), and red (650 nm) laser beams were incident at a 40° angle relative to the liquid crystal layer. Furthermore, the laser beams were incident perpendicularly onto a circular polarizer corresponding to their wavelengths, and after being converted into left-handed and right-handed circularly polarized light, the light was incident onto the fabricated liquid crystal diffraction element. Among a total of six conditions—two for left-handed and right-handed circularly polarized light and three for the incident light wavelength—the maximum value of the zero-order leakage light (maximum transmittance of the forward component) that passes through the liquid crystal diffraction element without diffraction was used as the evaluation value.

[0367] A+: The maximum value of zero-order light leakage is less than 1.6%. A: The maximum value for zero-order light leakage is above 1.6% and less than 2%. B: The maximum value for zero-order light leakage is greater than 2% but less than 5%. C: The maximum value for zero-order light leakage is greater than 5% and less than 8%. D: The maximum value of zero-order light leakage is above 8%. The results are shown in Table 1 below.

[0368] Furthermore, Table 1 records the Δn (550) of the liquid crystal layer at 550 nm, the dispersion on the short wavelength side, the dispersion on the long wavelength side, the minimum period (minimum pitch width) in the liquid crystal alignment pattern, and the refractive power.

[0369] [Table 1]

[0370] <Fabrication of Optical Component 101> A VA mode liquid crystal cell is prepared as a switching element 51.

[0371] In this switching element, the phase difference of the liquid crystal cell is 275nm when the voltage is on, and less than 5nm when the voltage is off. Both phase differences are at a wavelength of 550nm.

[0372] When right-hand circularly polarized light is incident on a switching element in the voltage-on state, the transmitted light is left-hand circularly polarized light; and when right-hand circularly polarized light is incident on a switching element in the voltage-off state, the transmitted light is right-hand circularly polarized light.

[0373] The liquid crystal layer A-2 is peeled off from the support and attached to one side of the switching element 51 via an adhesive, thereby obtaining an optical device 101 having the switching element 51, adhesive, and liquid crystal layer A-2 in sequence.

[0374] When right-handed circularly polarized light is incident from the switching element 51 side of the optical device 101, the optical device 101 functions as a condensing lens with a refractive power of 2D when the voltage of the switching element 51 is turned on. Furthermore, when the voltage of the switching element 51 is turned off, the optical device 101 functions as a diverging lens with a refractive power of -2D. By switching the voltage of the switching element 51 between the on and off states, it can be confirmed that two refractive powers can be switched.

[0375] <Fabrication of Optical Components 102-105> Instead of liquid crystal layer A-2, liquid crystal layers A-6 and A-7, as well as liquid crystal layers A-1 and B-1, were used. Otherwise, optical devices 102 to 105 were obtained in the same manner as optical device 101.

[0376] <Fabrication of Optical Component 111> The liquid crystal layer A-3 is peeled off from the support and bonded to one side of the first switching element 51 via adhesive. The second switching element 51 is then bonded to the other side of the liquid crystal layer A-3 via adhesive. Furthermore, the second liquid crystal layer A-3 is also bonded via adhesive.

[0377] Through the above method, an optical device 111 was obtained having a first switching element 51, an adhesive, a first liquid crystal layer A-3, an adhesive, a second switching element 51, an adhesive, and a second liquid crystal layer A-3 in sequence.

[0378] Since the optical device 111 includes a first switching element 51 and a second switching element 51, there are four voltage application states.

[0379] When right-handed circularly polarized light is incident from the first switching element 51 side of the optical device 111, and when the voltage of the first switching element is set to "on" and the voltage of the second switching element is set to "off", the optical device 111 functions as a condensing lens with a refractive power of 2D. Furthermore, when the voltage of the first switching element is set to "off" and the voltage of the second switching element is set to "on", the optical device 111 functions as a diverging lens with a refractive power of -2D.

[0380] Furthermore, when the voltage of the first switching element is set to off and the voltage of the second switching element is set to on, and when the voltage of the first switching element is set to on and the voltage of the second switching element is set to off, the refractive power is 0, meaning it does not function as a lens.

[0381] From the above points, it can be confirmed that optical device 111 can switch between three refractive powers.

[0382] <Fabrication of Optical Component 112> By repeatedly performing the same steps as optical device 111, optical device 112 is obtained having a first switching element 51, an adhesive, a first liquid crystal layer A-3, an adhesive, a second switching element 51, an adhesive, a second liquid crystal layer A-4, an adhesive, a third switching element 51, an adhesive, and a third liquid crystal layer A-4 in sequence.

[0383] Since the optical device 112 includes a first switching element 51, a second switching element 51, and a third switching element 51, there are eight voltage application states. By switching the voltage application states, it can be confirmed that a total of five refractive powers can be switched: 2D, 1D, 0, -1D, and -2D.

[0384] <Fabrication of Optical Component 113> By repeatedly performing the same steps as optical device 111, optical device 113 is obtained having, in sequence, a first switching element 51, an adhesive, a first liquid crystal layer A-3, an adhesive, a second switching element 51, an adhesive, a second liquid crystal layer A-4, an adhesive, a third switching element 51, an adhesive, a third liquid crystal layer A-5, an adhesive, a fourth switching element 51, an adhesive, and a fourth liquid crystal layer A-5.

[0385] The optical device 112 includes a first switching element 51, a second switching element 51, a third switching element 51, and a fourth switching element 51, thus allowing for 16 voltage application states. By switching the voltage application states, it can be confirmed that a total of 9 refractive powers can be switched: 2D, 1.5D, 1D, 0.5D, 0, -0.5D, -1D, -1.5D, and -2D.

[0386] <The Creation of Virtual Reality Image Display Devices> The commercially available miniature display (manufactured by SeeYA Technology, screen size 0.49 inches) features a plano-convex lens on its front surface (manufactured by Thorlabs, Inc., LA1145-A).

[0387] By observing the microdisplay through a plano-convex lens, an observer can observe the virtual image displayed on the microdisplay and confirm that it functions as a virtual reality image display device.

[0388] By further configuring optical devices 101 to 105 on the observer side of the plano-convex lens, virtual reality image display devices 101 to 105 were obtained.

[0389] By switching the applied voltage, the position of the virtual image displayed on the microdisplay can be changed.

[0390] In virtual reality display devices 101-105, when an observer observes the virtual image of the image displayed on the microdisplay, the visually recognized ghosting is compared. Ghosting is clearly visually recognized in virtual reality display devices 104 and 105. In contrast, the visually recognized ghosting in virtual reality display devices 101-103, corresponding to the HMD (Head-Mounted Display) of the present invention, is slight, resulting in a good display effect.

[0391] Furthermore, compared to virtual reality display devices 102 and 103, virtual reality display device 101 exhibits less noticeable ghosting and provides a better display effect.

[0392] By further configuring optical devices 111-113 on the observer side of the plano-convex lens, virtual reality image display devices 111-113 corresponding to the HMD of the present invention are obtained. By switching the voltage application state, it is possible to confirm that the position of the virtual image of the image displayed on the microdisplay can be switched in multiple stages.

[0393] Industrial availability It can be preferably used in HMDs such as VR image display devices.

[0394] Symbol Explanation 10 - (VR image) display device; 12 - display; 14, 26 - circular polarizer; 14a - linear polarizer; 14b - quarter-wave plate; 16 - semi-reflective mirror; 18, 62 - lens; 24 - circularly polarized light reflective polarizer; 30 - optical device; 32 - switching element; 34 - liquid crystal lens; 36, 36A - liquid crystal layer; 38 - liquid crystal compound; 50 - substrate; 52 - alignment film; 60 - AR glasses; 64 - incident diffraction element; 68 - light guide plate; 70 - outgoing diffraction element.

Claims

1. An optical device comprising a switching element and a liquid crystal layer, wherein, The switching element is a component capable of switching between a first phase difference and a second phase difference, and the difference between the first phase difference and the second phase difference is 275 ± 20 nm at a wavelength of 550 nm. The liquid crystal layer is formed using a liquid crystal composition comprising a liquid crystal compound with inverse wavelength dispersion, and has a liquid crystal alignment pattern that changes as the orientation of the optical axis originating from the liquid crystal compound rotates continuously in at least one in-plane direction.

2. The optical device according to claim 1, wherein, In the liquid crystal alignment pattern, when the length of the orientation of the optical axis originating from the liquid crystal compound rotated 180° in the plane as a period, there are regions in the plane with different lengths of the one period.

3. The optical device according to claim 1, wherein, The liquid crystal alignment pattern has multiple rings of different sizes, and within the plane, the larger rings successively contain smaller rings.

4. The optical device according to claim 3, wherein, The liquid crystal alignment pattern is concentric circles.

5. The optical device according to claim 1, wherein, The switching element is constructed using a liquid crystal cell.

6. A head-mounted display having the optical element of any one of claims 1 to 5.

7. The head-mounted display according to claim 6, wherein, The head-mounted display is one of a virtual reality image display device and an augmented reality image display device.

8. The head-mounted display according to claim 7, wherein, The head-mounted display is a virtual reality image display device with a focusing optical system. The optical device is located downstream of the focusing optical system.

9. The head-mounted display according to claim 7, wherein, The head-mounted display is an augmented reality image display device with a light guide plate. The optical device is located downstream of the light guide plate.

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