Optical components and image display devices

Abstract

The objective of this invention is to provide an optical element capable of achieving a wide field of view (FOV) and viewing area, and an image display device using the optical element. The optical element includes a light guide plate, an incident portion, and an exit portion. The incident and exit portions each have a diffraction portion, and the diffraction portion has a diffraction element. The diffraction element has a liquid crystal diffraction layer whose orientation changes while continuously rotating in one direction. When the direction in which the orientation of the optical axis changes is defined as the in-plane rotation direction, and the length of 180° rotation of the optical axis is defined as the in-plane period, the in-plane rotation directions of the liquid crystal diffraction layers of at least two of the incident diffraction elements in the plurality of incident diffraction portions are different from each other.

Description

Technical Field

[0001] The present invention relates to an optical element that propagates and emits incident light, and an image display device using the optical element. Background Technology

[0002] In recent years, AR (Augmented Reality) glass, which overlays virtual images and various information onto actually observed scenes as described in Non-Patent Document 1, has been put into practical use. AR glass is also known as smart glass, head-mounted display (HMD), and AR glasses.

[0003] As shown in Non-Patent Document 1, for example, AR glass propagates an image displayed by a display (optical engine) onto one end of a light guide plate and exits from the other end, thereby overlaying a virtual image onto the scene actually observed by the user.

[0004] In AR glass, diffraction elements are used to diffract (refract) light from the display (projected light) and direct it onto one end of a light guide plate. This guides the light at a specific angle and allows it to propagate within the light guide plate. The light propagating within the light guide plate is similarly diffracted at the other end and exits the light guide plate to the position observed by the user.

[0005] Furthermore, Patent Document 1 describes the following: In AR glass, red, green and blue light are irradiated from the display to form an image, and the light in each color is diffracted by the incident diffraction element and incident on the light guide plate, so that the light guide plate propagates, and the light is emitted from the light guide plate through the exiting diffraction element and emitted from the light guide plate to the image of the superimposed three colors of light based on the user's viewing position, thereby displaying a color image.

[0006] Previous technical documents

[0007] Patent documents

[0008] Patent Document 1: International Publication No. 2017 / 180403

[0009] Non-patent literature

[0010] Non-patent literature 1: Bernard C. Kress et al., Towards the Ultimate Mixed Reality Experience: HoloLens Display Architecture Choices, SID2017 DIGEST, pp.127-131 Summary of the Invention

[0011] The technical problem to be solved by the invention

[0012] AR glass requires users to be able to observe a wide area of ​​the image displayed on the screen without changing their line of sight, i.e., the field of view (FOV).

[0013] Furthermore, AR glass also requires a wide display area for the image so that the image can be viewed regardless of the user's line of sight, i.e., a wide viewpoint area.

[0014] Correspondingly, the AR glass described in Patent Document 1 describes a light that is incident from an incident diffraction element and propagates within a light guide plate, is then diffracted by an intermediate diffraction element and propagates within the light guide plate, and is emitted through an exiting diffraction element.

[0015] In the AR glass described in Patent Document 1, the emission area of ​​light from the emitted diffraction element is thus expanded, thereby attempting to expand the field of view (FOV) and the viewpoint area.

[0016] However, the FOV and viewpoint area of ​​AR glass are not yet sufficient, and there is a hope that AR glass with a wider FOV and viewpoint area will emerge.

[0017] The purpose of this invention is to solve the problems of the prior art and to provide an optical element for use in AR glass and the like that enables a wider FOV and viewpoint area, and an image display device using the optical element.

[0018] means for solving technical problems

[0019] To address this issue, the present invention has the following structure.

[0020] [1] An optical element having a light guide plate, an incident portion for incident light onto the light guide plate, and an exit portion for light emitted from the light guide plate.

[0021] The incident section has multiple incident diffraction sections, each with one or more incident diffraction elements; the exit section has multiple exit diffraction sections, each with one or more exit diffraction elements.

[0022] The incident diffraction element and the exit diffraction element have a liquid crystal diffraction layer formed using a composition containing a liquid crystal compound.

[0023] The liquid crystal diffraction layer has a liquid crystal alignment pattern that originates from the liquid crystal compound and whose orientation changes continuously as it rotates along at least one in-plane direction.

[0024] In a liquid crystal alignment pattern, the direction in which the orientation of the optical axis originating from the liquid crystal compound continuously rotates along at least one in-plane direction and changes is defined as the in-plane rotation direction. The length of 180° rotation of the orientation of the optical axis originating from the liquid crystal compound within the in-plane rotation direction is defined as the in-plane period.

[0025] At least two of the incident diffraction elements have liquid crystal diffraction layers with different in-plane rotation directions.

[0026] [2] According to the optical element described in [1], wherein,

[0027] At least two of the incident diffraction elements have liquid crystal diffraction layers with different in-plane periods and in-plane rotation directions.

[0028] At least one of the plurality of ejected diffraction elements has an in-plane period equal to that of at least one of the incident diffraction elements in the liquid crystal diffraction layer.

[0029] [3] According to the optical element described in [1] or [2], wherein,

[0030] At least two of the multiple ejected diffraction elements have equal in-plane periods for their liquid crystal diffraction layers.

[0031] [4] The optical element according to any one of [1] to [3], wherein,

[0032] The in-plane period and in-plane rotation direction of the liquid crystal diffraction layer of at least two of the multiple emission diffraction elements are different from each other.

[0033] [5] The optical element according to any one of [1] to [4], wherein,

[0034] The incident diffraction section has multiple incident diffraction elements.

[0035] At least two of the incident diffraction elements have liquid crystal diffraction layers with equal in-plane periods and different in-plane rotation directions.

[0036] The emission diffraction section has multiple emission diffraction elements.

[0037] At least two of the multiple ejected diffraction elements have liquid crystal diffraction layers with equal in-plane periods and different in-plane rotation directions.

[0038] [6] According to the optical element described in [5], wherein,

[0039] In the n incident diffraction sections of the incident section and the n emission diffraction sections of the emission section, there is a combination of incident diffraction sections and emission diffraction sections having n sets of incident diffraction elements whose in-plane period of the liquid crystal diffraction layer is equal to the in-plane period of the liquid crystal diffraction layer of the emission diffraction elements. Here, n is an integer greater than or equal to 1.

[0040] [7] The optical element according to any one of [1] to [6], wherein,

[0041] At least one of the incident diffraction sections has two incident diffraction elements.

[0042] In at least one of the incident diffraction sections having two incident diffraction elements, the angle formed by the in-plane rotation direction of the liquid crystal diffraction layer of each incident diffraction element is 90°.

[0043] [8] The optical element according to any one of [1] to [6], wherein,

[0044] The incident section is equipped with multiple incident diffraction sections, each with two incident diffraction elements.

[0045] At least two incident diffraction sections are identical, and the angle formed by the in-plane rotation directions of the liquid crystal diffraction layers of the two incident diffraction elements in the incident diffraction section is 45°.

[0046] [9] The optical element according to any one of [1] to [6], wherein,

[0047] The incident section is equipped with multiple incident diffraction sections, each with two incident diffraction elements.

[0048] At least two incident diffraction sections are identical, and the angle formed by the in-plane rotation directions of the liquid crystal diffraction layers of the two incident diffraction elements in the incident diffraction section is 90°.

[0049]

[10] The optical element according to any one of [1] to [9], wherein,

[0050] At least one of the emission diffraction sections has two emission diffraction elements.

[0051] In at least one of the emission diffraction sections having two emission diffraction elements, the angle formed by the in-plane rotation direction of the liquid crystal diffraction layer of each emission diffraction element is 90°.

[0052]

[11] The optical element according to any one of [1] to [9], wherein,

[0053] The emission section is equipped with multiple emission diffraction sections, each with two emission diffraction elements.

[0054] At least two of the ejection diffraction sections are identical, and the angle formed by the in-plane rotation directions of the liquid crystal diffraction layers of the two ejection diffraction elements in the ejection diffraction section is 45°.

[0055]

[12] The optical element according to any one of [1] to [9], wherein,

[0056] The emission section is equipped with multiple emission diffraction sections, each with two emission diffraction elements.

[0057] At least two of the ejection diffraction sections are identical, and the angle formed by the in-plane rotation directions of the liquid crystal diffraction layers of the two ejection diffraction elements in the ejection diffraction section is 90°.

[0058]

[13] The optical element according to any one of [1] to

[12] , wherein,

[0059] The liquid crystal diffraction layer is a cholesterol-type liquid crystal layer formed by fixing a cholesterol-type liquid crystal phase.

[0060]

[14] According to the optical element described in

[13] , wherein,

[0061] In cross-sections observed using a scanning electron microscope, the bright and dark portions of the cholesterol-type liquid crystal layer, originating from the cholesterol-type liquid crystal phase, are tilted relative to the main surface of the cholesterol-type liquid crystal layer. Furthermore...

[0062] When the angle between the main surface of the cholesterol-type liquid crystal layer and the bright and dark parts of the cross-section of the cholesterol-type liquid crystal layer is set as the tilt angle θ, there is a region with a tilt angle θ of 10° or more.

[0063]

[15] According to the optical element described in

[14] , wherein,

[0064] The cholesterol-type liquid crystal layer has a region in which the tilt angle θ continuously increases in one direction toward the thickness direction, and the difference between the maximum and minimum values ​​of the tilt angle θ in the thickness direction is greater than 10°.

[0065]

[16] The optical element according to any one of

[13] to

[15] , wherein,

[0066] The incident diffraction element has two cholesteric liquid crystal layers that selectively reflect circularly polarized light with different rotation directions.

[0067]

[17] The optical element according to any one of

[13] to

[16] , wherein,

[0068] The emission section has two emission diffraction sections, each containing a cholesteric liquid crystal layer with two emission diffraction elements that rotate in the same direction and selectively reflect circularly polarized light.

[0069] In the two emission diffraction sections, the rotation directions of the circularly polarized light selectively reflected by the cholesterol-type liquid crystal layer constituting the emission diffraction element of each emission diffraction section are different from each other.

[0070]

[18] The optical element according to

[16] or

[17] , wherein,

[0071] The in-plane rotation directions of the selectively reflected circularly polarized light differ by 180° from those of the cholesteric liquid crystal layers.

[0072]

[19] An image display device comprising:

[0073] Optical elements as described in any one of [1] to

[18] ; and

[0074] A display element that illuminates an image onto an incident diffraction section.

[0075] Invention Effects

[0076] According to the present invention, images can be displayed in a wide field of view and viewpoint area, for example, in AR glass. Attached Figure Description

[0077] Figure 1 This is a diagram that conceptually illustrates an example of the optical element of the present invention.

[0078] Figure 2 It is a conceptual representation Figure 1 A planar diagram of the optical element shown.

[0079] Figure 3 This is a diagram that conceptually illustrates an example of a liquid crystal diffraction element.

[0080] Figure 4 It is a conceptual representation Figure 3 A plan view of the liquid crystal layer of the liquid crystal diffraction element shown.

[0081] Figure 5 It is a conceptual representation Figure 4 The image shows a cross-sectional SEM (scanning electron microscope) image of the liquid crystal layer.

[0082] Figure 6 It is used for explanation Figure 4 The diagram shows a conceptual representation of the function of the liquid crystal layer.

[0083] Figure 7 This is a diagram that conceptually illustrates another example of a liquid crystal layer used for a liquid crystal diffraction element.

[0084] Figure 8 This is a diagram that conceptually illustrates another example of a liquid crystal layer used for a liquid crystal diffraction element.

[0085] Figure 9 This is a conceptual diagram of an exposure apparatus for exposing an alignment film.

[0086] Figure 10 This is a diagram that conceptually illustrates different examples of liquid crystal diffraction elements.

[0087] Figure 11 It is a conceptual representationFigure 10 A plan view of the liquid crystal layer of the liquid crystal diffraction element shown.

[0088] Figure 12 It is used for explanation Figure 10 The diagram shows a conceptual representation of the function of the liquid crystal layer.

[0089] Figure 13 It is used for explanation Figure 10 The diagram shows a conceptual representation of the function of the liquid crystal layer.

[0090] Figure 14 It is used for explanation Figure 1 A conceptual diagram of the emission section of the optical element shown.

[0091] Figure 15 It is used for explanation Figure 1 A conceptual diagram illustrating the function of the emission section of the optical element shown.

[0092] Figure 16 It is used for explanation Figure 1 A conceptual diagram illustrating the function of the emission section of the optical element shown.

[0093] Figure 17 It is used for explanation Figure 1 A conceptual diagram illustrating the function of the emission section of the optical element shown.

[0094] Figure 18 It is used for explanation Figure 1 A conceptual diagram illustrating the function of the incident portion of the optical element shown.

[0095] Figure 19 It is used for explanation Figure 1 A conceptual diagram illustrating the function of the incident portion of the optical element shown.

[0096] Figure 20 It is used for explanation Figure 1 A conceptual diagram illustrating the function of the incident portion of the optical element shown.

[0097] Figure 21 The figures are conceptual illustrations of different examples of the optical elements of the present invention.

[0098] Figure 22 This is a conceptual diagram used to illustrate Example 1.

[0099] Figure 23 This is a conceptual diagram used to illustrate Example 2.

[0100] Figure 24 This is a conceptual diagram used to illustrate Example 3.

[0101] Figure 25 This is a conceptual diagram used to illustrate Example 4.

[0102] Figure 26 This is a conceptual diagram used to illustrate Example 5.

[0103] Figure 27 This is a conceptual diagram used to illustrate Example 6.

[0104] Figure 28 This is a conceptual diagram used to illustrate embodiments 7 and 8.

[0105] Figure 29 This is a conceptual diagram used to illustrate embodiments 7 and 8.

[0106] Figure 30 This is a conceptual diagram used to illustrate Example 9.

[0107] Figure 31 This is a conceptual diagram used to illustrate Example 9. Detailed Implementation

[0108] Hereinafter, the optical elements and image display device of the present invention will be described in detail with reference to the preferred embodiments shown in the accompanying drawings.

[0109] In this specification, the numerical range indicated by “~” refers to the range encompassed by the values ​​recorded before and after “~” as the lower and upper limits.

[0110] In this specification, "(meth)acrylate" is used to mean "one or both of acrylate and methacrylate".

[0111] In this specification, "same" is defined to include the error range generally permissible in the technical field. Furthermore, in this specification, when the term "all," "uniform," or "whole surface" is used, in addition to the case of 100%, it also includes the error range generally permissible in the technical field, such as including, for example, 99% or more, 95% or more, or 90% or more.

[0112] In this specification, visible light refers to light of electromagnetic waves with wavelengths observable to the naked eye, specifically light in the wavelength range of 380–780 nm. Non-visible light refers to light in the wavelength range below 380 nm and above 780 nm.

[0113] Furthermore, it is not limited to this. In visible light, light in the wavelength region of 420–490 nm is blue light, light in the wavelength region of 495–570 nm is green light, and light in the wavelength region of 620–750 nm is red light.

[0114] Figure 1 The present invention is illustrated conceptually as an example of an optical element and an image display device.

[0115] Figure 2 The concept shows Figure 1A plan view of the optical element shown. Figure 2 From Figure 1 The image shown is based on the viewing direction of user U. Figure 1 A diagram of the optical components shown.

[0116] like Figure 1 and Figure 2 As shown, the optical element 10 has a light guide plate 12, an incident part 14 having an incident diffraction element, and an exit part 16 having an exit diffraction element.

[0117] In the optical element 10 shown in the figure, the incident portion 14 is provided at one corner of the main surface of the rectangular light guide plate 12. The emitting portion 16 is provided on the other main surface of the light guide plate 12 so as to completely cover the area of ​​the light guide plate 12 except for the incident portion 14 in the planar direction. In addition, the main surface is the largest surface of the sheet-like object (plate, film, layer).

[0118] like Figure 1 As shown in the example image display device, light carrying an image displayed by the display 20 is diffracted and reflected by the incident portion 14, thereby incident on the light guide plate 12. The light incident on the light guide plate 12 propagates within the light guide plate 12 and is incident on the emission portion 16. The emission portion 16 diffracts and reflects the incident light, thereby emitting it from the light guide plate 12 and to the observation position based on the user U.

[0119] In the example shown, the incident section 14 is constructed by stacking incident diffraction elements 24A1, 24A2, 24B1, and 24B2 from the side of the light guide plate 12. The incident diffraction elements 24A1 and 24A2 constitute the first incident diffraction section 26. Furthermore, the incident diffraction elements 24B1 and 24B2 constitute the second incident diffraction section 28. The incident diffraction section may have one or more incident diffraction elements, and therefore the incident section 14 may have three or more incident diffraction sections.

[0120] On the other hand, the emission section 16 is configured to emit diffraction elements 30A1, 30A2, 30B1, and 30B2 in a stacked manner from the light guide plate 12 side. The first emission diffraction section 32 is formed by the emission diffraction elements 30A1 and 30A2. Furthermore, the second emission diffraction section 34 is formed by the emission diffraction elements 30B1 and 30B2. The emission diffraction section may have three or more emission diffraction elements, and therefore the emission section 16 may also have three or more emission diffraction sections.

[0121] In the example shown, both the incident diffraction element and the emitted diffraction element have liquid crystal diffraction layers, and preferably, both are reflective diffraction elements.

[0122] In the optical element 10 shown in the figure, incident diffraction elements 24A1, 24A2, 24B1, and 24B2, as well as exit diffraction elements 30A1, 30A2, 30B1, and 30B2, selectively reflect light of the same wavelength range.

[0123] Here, the image display device using the optical element 10 of the present invention can display color images or monochrome images.

[0124] When displaying a monochrome image using an image display device with optical element 10, each incident diffraction element and the emitted diffraction element has a liquid crystal diffraction layer that selectively reflects light in the wavelength range of the corresponding color.

[0125] On the other hand, when displaying a color image using an image display device with optical element 10, the incident part 14 and the emitted part 16 can reflect blue light, green light and red light in one liquid crystal diffraction layer, or they can have liquid crystal diffraction layers corresponding to blue light, green light and red light respectively, or they can have liquid crystal diffraction layers corresponding to two of the blue light, green light and red light and liquid crystal diffraction layers corresponding to the other one color.

[0126] Alternatively, when displaying a color image using an image display device with optical element 10, it may have an incident and emitted portion for blue light, an incident and emitted portion for green light, and an incident and emitted portion for red light. It may also have incident and emitted portions corresponding to two of the three colors (blue, green, and red) and incident and emitted portions corresponding to the other color. When optical element 10 has multiple incident and emitted portions, the incident and emitted portions may be stacked or arranged at different positions in the surface direction of light guide plate 12.

[0127] In the optical element 10, the stacked components are attached to each other as needed by an attachment layer.

[0128] As an adhesive layer, as long as it has sufficient light transmittance, it can be a layer formed by an adhesive that is fluid during bonding and then becomes solid; it can also be a layer formed by an adhesive that is a soft solid in a gel-like (rubber-like) state during bonding and does not change its gel-like state afterward; or it can be a layer formed by a material that has the characteristics of both an adhesive and an adhesive. Therefore, the adhesive layer can be any known layer used in optical devices and optical elements for bonding sheet-like objects, such as optically clear adhesives (OCA), optically clear double-sided tapes, and UV-curable resins.

[0129] Alternatively, the optical elements of the present invention can be constructed by holding the components in a frame or clamp, rather than by bonding them together with an adhesive layer.

[0130] The image display device using the optical element 10 of the present invention can display color images or monochrome images.

[0131] When displaying a color image, the incident part 14 and the emitted part 16 reflect blue light, green light and red light.

[0132] The constituent elements of the image display device and display element of the present invention will be described below.

[0133] [Display (Display Component)]

[0134] In the image display device of the present invention, the display is not limited, and for example, a known display 20 used in various AR glasses can be used.

[0135] As examples of displays, liquid crystal displays (including LCOS: Liquid Crystal On Silicon), organic electroluminescent displays, and scanning displays using DLP (Digital Light Processing) or MEMS (Micro Electro Mechanical Systems) mirrors can be cited.

[0136] The monitor can display color images or monochrome images. Furthermore, when the display device displays color images, it can have three monitors, one for blue images, one for green images, and one for red images.

[0137] In the image display device of the present invention, a known projection lens for AR glass or the like can be provided between the display 20 and the light guide plate (incident section) as needed.

[0138] In the image display device of the present invention, the light irradiated by the display element 20 is not limited, but is preferably unpolarized light (natural light) or circularly polarized light.

[0139] Between the display 20 and the light guide plate 12, a circular polarizer consisting of a linear polarizer and a λ / 4 plate, etc., can be provided as needed to correspond to the polarization of the light irradiated by the display.

[0140] [Light guide plate]

[0141] The light guide plate 12 is a known light guide plate that reflects and propagates (guides) light incident into the interior.

[0142] The light guide plate 12 is not limited and can utilize known light guide plates used in various AR glasses and backlight units of LCD displays.

[0143] The refractive index of the light guide plate 12 is not limited, but a high refractive index is preferred. Specifically, the refractive index of the light guide plate 12 is preferably 1.7 to 2.0, and more preferably 1.8 to 2.0. By setting the refractive index of the light guide plate 12 to 1.7 to 2.0, the range of angles that can be propagated by total internal reflection within the light guide plate 12 can be expanded.

[0144] [Ingress and Ejection Sections]

[0145] The incident section 14 has a first incident diffraction section 26 and a second incident diffraction section 28. The first incident diffraction section 26 has incident diffraction elements 24A1 and 24A2. The second incident diffraction section 28 has incident diffraction elements 24B1 and 24B2.

[0146] The ejection section 16 has a first ejection diffraction section 32 and a second ejection diffraction section 34. The first ejection diffraction section 32 has an ejection diffraction element 30A1 and an ejection diffraction element 30A2. The second ejection diffraction section 34 has an ejection diffraction element 30B1 and an ejection diffraction element 30B2.

[0147] In the following description, the incident diffraction element will also be referred to as the incident element, and the exiting diffraction element will also be referred to as the exiting element.

[0148] Both the incident element and the emitting element are reflective polarized light diffraction elements. Specifically, as a preferred embodiment, both the incident element and the emitting element have a cholesterol-type liquid crystal layer as a liquid crystal diffraction layer, selectively reflecting right-circularly polarized light or left-circularly polarized light.

[0149] As described above, incident elements 24A1, 24A2, 24B1, and 24B2, as well as emission elements 30A1, 30A2, 30B1, and 30B2, selectively reflect light within the same wavelength range. That is, the selective reflection center wavelength and selective reflection wavelength region of the cholesterol-type liquid crystal layer constituting each incident element and emission element are equal.

[0150] Here, incident elements 24A1, 24A2, 24B1 and 24B2, and ejector elements 30A1, 30A2 and 30B1 and 30B2 have essentially the same configuration, except for the different in-plane rotation directions and / or in-plane periods described later.

[0151] Therefore, in the following description, without needing to distinguish between incident elements and emission elements, these will be collectively referred to as "liquid crystal diffraction elements".

[0152] (Liquid crystal diffraction element)

[0153] use Figures 3-5 The liquid crystal diffraction element is explained.

[0154] Figure 3 This is a conceptual diagram illustrating the layered structure of a liquid crystal diffraction element. (Example) Figure 3 As shown conceptually, the liquid crystal diffraction element has a support 50, an alignment film 52, and a liquid crystal diffraction layer, namely a cholesterol-type liquid crystal layer 54, which functions as a diffraction element.

[0155] Figure 4 This is a schematic diagram showing the orientation state of the in-plane liquid crystal compound on the main surface of the cholesterol-type liquid crystal layer 54.

[0156] In the following description, the main surface of the cholesterol-type liquid crystal layer 54 will be defined as the XY plane, and the cross-section perpendicular to the XY plane will be defined as the XZ plane. That is, Figure 3 A schematic diagram of the XZ plane of the cholesterol-type liquid crystal layer 54. Figure 4 A schematic diagram of the XY plane, which corresponds to the cholesterol-type liquid crystal layer 54.

[0157] like Figures 3-5 As shown, the cholesterol-type liquid crystal layer 54 is a layer in which the liquid crystal compound is oriented in a cholesterol-type manner. Furthermore, Figures 3-5 This is an example of a rod-shaped liquid crystal compound constituting a cholesterol-type liquid crystal layer.

[0158] In the following description, the cholesterol-type liquid crystal layer will also be referred to simply as a liquid crystal layer.

[0159] in addition, Figure 3 The liquid crystal diffraction element shown has a support 50, an alignment film 52, and a liquid crystal layer 54, but the present invention is not limited thereto. For example, the liquid crystal diffraction element can be a liquid crystal diffraction element that has been bonded to a light guide plate 12, etc., and then the support 50 has been peeled off, leaving only the alignment film 52 and the liquid crystal layer 54. Alternatively, the liquid crystal diffraction element can be a liquid crystal diffraction element that has been bonded to a light guide plate 12, etc., and then the support 50 and the alignment film 52 have been peeled off, leaving only the liquid crystal layer 54.

[0160] <Support>

[0161] The support 50 supports the alignment film 52 and the liquid crystal layer 54.

[0162] As long as the alignment film 52 and the liquid crystal layer 54 can be supported, the support 50 can utilize various sheet-like materials (films, plates).

[0163] Furthermore, the transmittance of the support 50 relative to the corresponding light is preferably 50% or more, more preferably 70% or more, and even more preferably 85% or more.

[0164] There is no limitation on the thickness of the support 50. As long as the thickness is appropriately set according to the application of the liquid crystal diffraction element and the forming material of the support 50, the thickness of the alignment film 52 and the liquid crystal layer 54 can be maintained.

[0165] The thickness of the support 50 is preferably 1 to 2000 μm, more preferably 3 to 500 μm, and even more preferably 5 to 250 μm.

[0166] The support 50 can be a single layer or multiple layers.

[0167] Examples of single-layer supports 50 include supports 50 made of glass, triacetyl cellulose (TAC), polyethylene terephthalate (PET), polycarbonate, polyvinyl chloride, acrylic acid, and polyolefins. Examples of multi-layer supports 50 include supports that include any of the aforementioned single-layer supports as a substrate, and supports with other layers disposed on the surface of the substrate.

[0168] <Orientation film>

[0169] In a liquid crystal diffraction element, an alignment film 52 is formed on the surface of a support 50.

[0170] The alignment film 52 is an alignment film used to align the liquid crystal compound 40 into a predetermined liquid crystal alignment pattern when forming the liquid crystal layer 54.

[0171] As will be described later, however, in this invention, the liquid crystal layer 54 has an optical axis 40A derived from the liquid crystal compound 40 (see reference). Figure 4 The orientation of the liquid crystal is a liquid crystal alignment pattern that changes as it rotates continuously in one direction within the plane. Therefore, the alignment film 52 can be formed into the liquid crystal layer 54 to form this liquid crystal alignment pattern.

[0172] In the following description, "orientation rotation of optical axis 40A" will also be referred to as "rotation of optical axis 40A".

[0173] The alignment film 52 can utilize various known alignment films.

[0174] Examples include triboelectric films formed from organic compounds such as polymers, tilted vapor-deposited films of inorganic compounds, films with microgrooves, and films formed by accumulating organic compounds such as ω-trisanoic acid, dioctadecylmethylammonium chloride, and methyl stearate using the Langmuir-Blodgett process.

[0175] The orientation film 52 based on friction treatment can be formed by rubbing the surface of the polymer layer multiple times in a specified direction with paper or cloth.

[0176] The preferred materials used in the alignment film 52 are polyimide, polyvinyl alcohol, polymers with polymerizable groups as described in Japanese Patent Application Publication No. 9-152509, and materials used in the formation of the alignment film 52 as described in Japanese Patent Application Publication Nos. 2005-97377, 2005-99228, and 2005-128503.

[0177] In a liquid crystal diffraction element, the alignment film 52 is preferably a so-called photoalignment film formed by irradiating polarized or unpolarized light with a light-oriented raw material. That is, in a liquid crystal diffraction element, the photoalignment film 52 formed by coating a light-oriented material onto a support 50 is preferred.

[0178] Regarding the irradiation of polarized light, it can be performed from a direction perpendicular to or inclined relative to the photo-alignment film; regarding the irradiation of unpolarized light, it can be performed from a direction inclined relative to the photo-alignment film.

[0179] Examples of photoalignment materials that can be used in the alignment film of the present invention include Japanese Patent Application Publication Nos. 2006-285197, 2007-76839, 2007-138138, 2007-94071, 2007-121721, 2007-140465, and 2007-1564. Azo compounds described in Japanese Patent Publication No. 39, Japanese Patent Application Publication No. 2007-133184, Japanese Patent Application Publication No. 2009-109831, Japanese Patent Publication No. 3883848 and Japanese Patent Publication No. 4151746, aromatic ester compounds described in Japanese Patent Application Publication No. 2002-229039, and Japanese Patent Application Publication No. 2002-265541 and Japanese Patent Application Publication No. 2002-317013. Maleimides having photooriented units and / or alkenyl-substituted nadicimide compounds, photocrosslinkable silane derivatives described in Japanese Patent Nos. 4205195 and 4205198, photocrosslinkable polyimides, photocrosslinkable polyamides and photocrosslinkable polyimides described in Japanese Patent Nos. 2003-520878, 2004-529220 and 4162850. Esters and photodimerizable compounds, particularly cinnamic acid esters, 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, are preferred examples.

[0180] Among them, azo compounds, photocrosslinkable polyimides, photocrosslinkable polyamides, photocrosslinkable polyesters, cinnamic acid ester compounds and chalcone compounds are preferred.

[0181] There is no limitation on the thickness of the alignment film 52. As long as the thickness is appropriately set according to the forming material of the alignment film 52, the required alignment function can be obtained.

[0182] The thickness of the alignment film 52 is preferably 0.01 to 5 μm, more preferably 0.05 to 2 μm.

[0183] There are no limitations on the method of forming the alignment film 52, and various known methods corresponding to the forming materials of the alignment film 52 can be used. As an example, a method can be illustrated by coating the alignment film 52 on the surface of the support 50 and drying it, and then exposing the alignment film 52 with a laser beam to form an alignment pattern.

[0184] exist Figure 9The image shows an example of an exposure apparatus that exposes an alignment film 52 to form an alignment pattern.

[0185] Figure 9 The exposure apparatus 60 shown includes: a light source 64 with a laser 62; a λ / 2 plate 65 for changing the polarization direction of the laser beam M emitted from the laser 62; a polarization beam splitter 68 for separating the laser beam M emitted from the laser 62 into two beams, MA and MB; mirrors 70A and 70B respectively disposed on the optical paths of the two separated beams MA and MB; and λ / 4 plates 72A and 72B.

[0186] Additionally, light source 64 emits linearly polarized light P0. Plate 72A (λ / 4) converts the linearly polarized light P0 (ray MA) into right-handed circularly polarized light P... R The λ / 4 plate 72B converts linearly polarized light P0 (ray MB) into left-handed circularly polarized light P L .

[0187] A support 50 having an alignment film 52 before the alignment pattern is formed is disposed in the exposure section, so that two light rays MA and MB cross and interfere on the alignment film 52, and the interference light is irradiated onto the alignment film 52 for exposure.

[0188] Through this interference, the polarization state of the light incident on the alignment film 52 changes periodically in the form of interference fringes. Thus, an alignment film with an alignment pattern that periodically changes in its alignment state can be obtained. In the following description, the alignment film with this alignment pattern will also be referred to as a "patterned alignment film".

[0189] In the exposure apparatus 60, the period of the alignment pattern can be adjusted by changing the cross angle α of the two light rays MA and MB. That is, in the exposure apparatus 60, by adjusting the cross angle α, in an alignment pattern in which the optical axis 40A originating from the liquid crystal compound 40 rotates continuously in one direction, the length of one cycle in which the optical axis 40A rotates 180° in the direction in which the optical axis 40A rotates can be adjusted.

[0190] By forming a cholesterol-type liquid crystal layer on an alignment film 52 having an alignment pattern that periodically changes in such an alignment state, as described later, a liquid crystal layer 54 having a liquid crystal alignment pattern that continuously rotates in one direction along an optical axis 40A derived from the liquid crystal compound 40 can be formed.

[0191] Furthermore, the rotation direction of optical axis 40A can be reversed by rotating the optical axes of λ / 4 plates 72A and 72B by 90° respectively.

[0192] As described above, the patterned alignment film has an alignment pattern that aligns the liquid crystal compound to form a liquid crystal alignment pattern in which the orientation of the optical axis of the liquid crystal compound in the liquid crystal layer formed on the patterned alignment film changes continuously as it rotates in at least one in-plane direction.

[0193] If the orientation axis of the patterned alignment film is defined as the axis that aligns the liquid crystal compound, then the patterned alignment film can be said to have an orientation pattern that changes while the orientation of the orientation axis rotates continuously in at least one direction within the plane. The orientation axis of the patterned alignment film can be detected by measuring absorption anisotropy. For example, when linearly polarized light is irradiated onto the patterned alignment film while rotating, and the amount of light transmitted through the patterned alignment film is measured, it can be observed that the direction in which the light amount becomes maximum or minimum gradually changes in one direction within the plane.

[0194] Furthermore, in this invention, the orientation film 52 is provided in a preferred manner, but is not a necessary component.

[0195] For example, an alignment pattern can be formed on the support 50 by methods such as rubbing the support 50 or processing the support 50 with a laser beam, thereby enabling the liquid crystal layer to have a liquid crystal alignment pattern that changes as it rotates continuously in at least one in-plane direction originating from the optical axis 40A of the liquid crystal compound 40. That is, in the present invention, the support 50 can also function as an alignment film.

[0196] <Liquid Crystal Layer (Cholesterol-type Liquid Crystal Layer)>

[0197] In a liquid crystal diffraction element, a liquid crystal layer 54 is formed on the surface of an alignment film 52.

[0198] The liquid crystal layer 54 is a cholesterol-type liquid crystal layer formed by fixing a cholesterol-type liquid crystal phase, and is a cholesterol-type liquid crystal layer having a liquid crystal alignment pattern that changes while continuously rotating in at least one direction in the plane, originating from the optical axis of the liquid crystal compound.

[0199] like Figure 3 As shown in the conceptual diagram, similar to a cholesterol-type liquid crystal layer formed by fixing a typical cholesterol-type liquid crystal phase, the liquid crystal layer 54 has a spiral structure formed by rotating and stacking liquid crystal compounds 40 in a spiral shape. The structure formed by rotating (360°) the liquid crystal compounds 40 in a spiral shape once and stacking them is defined as a spiral pitch 1 (spiral pitch P). The liquid crystal compounds 40 rotating in a spiral shape have a structure formed by stacking multiple pitches.

[0200] As is well known, cholesterol-type liquid crystal phases exhibit selective reflectivity relative to circularly polarized light at a specific wavelength, exhibiting selectivity for either right or left-handed polarization. Whether the reflected light is right-handed or left-handed circularly polarized depends on the direction of twist (helix) of the cholesterol-type liquid crystal phase's helix. Based on the selective reflection of circularly polarized light by cholesterol-type liquid crystal phases, when the helix twists to the right, it reflects right-handed circularly polarized light, and when the helix twists to the left, it reflects left-handed circularly polarized light.

[0201] For example, if the liquid crystal layer 54 is a selectively reflective right-circularly polarized light, then the twisting direction of the helix of the cholesterol-type liquid crystal phase is to the right.

[0202] Furthermore, the rotation direction of the cholesterol-type liquid crystal phase can be adjusted by the type of liquid crystal compound forming the cholesterol-type liquid crystal layer and / or the type of chiral reagent added.

[0203] Furthermore, the half-value width Δλ (nm) of the selective reflection wavelength region (circularly polarized light reflection wavelength region) depends on the cholesteric liquid crystal phase's Δn and helical pitch P, following the relationship Δλ = Δn × P. Therefore, the width of the selective reflection wavelength region can be controlled by adjusting Δn. Δn can be adjusted by the type and mixing ratio of the liquid crystal compound forming the cholesteric liquid crystal layer, as well as the temperature at which the orientation is fixed.

[0204] Therefore, regarding the wavelength of the light reflected (diffracted) by the liquid crystal diffraction element, the selective reflection wavelength region of the liquid crystal layer can be appropriately set, for example, by adjusting the helical pitch P of the liquid crystal layer 54.

[0205] The half-width of the reflection wavelength region is adjusted according to the application of the optical element 10, for example, it can be 10 to 500 nm, preferably 20 to 300 nm, and more preferably 30 to 100 nm.

[0206] like Figure 4 As shown, on the XY plane of the liquid crystal layer 54, the liquid crystal compound 40 is arranged along multiple parallel alignment axes D within the XY plane. On each alignment axis D, the orientation of the optical axis 40A of the liquid crystal compound 40 changes as it continuously rotates in one in-plane direction along the alignment axis D. In the example shown, the optical axis 40A rotates counterclockwise towards the alignment axis D. That is, the direction of the alignment axis D (i.e., the X direction) is the in-plane rotation direction in this invention.

[0207] For illustrative purposes, the arrangement axis D is assumed to face the X direction. Furthermore, in the Y direction, the liquid crystal compounds 40 with the same orientation along the optical axis 40A are oriented at equal intervals.

[0208] Furthermore, "the orientation of the optical axis 40A of the liquid crystal compound 40 changes while continuously rotating in one direction along the plane of the arrangement axis D" means that the angle formed by the optical axis 40A of the liquid crystal compound 40 and the arrangement axis D varies depending on the position of the direction of the arrangement axis D. The angle formed by the optical axis 40A and the arrangement axis D gradually changes from θ to θ+180° or θ-180° along the arrangement axis D. That is, as... Figure 4 As shown, the optical axis 40A of the multiple liquid crystal compounds 40 arranged along the arrangement axis D changes as each of them rotates by a predetermined angle along the arrangement axis D.

[0209] Furthermore, the angle difference between the optical axes 40A of the liquid crystal compounds 40 that are adjacent to each other in the direction of the arrangement axis D is preferably 45° or less, more preferably 15° or less, and even more preferably a smaller angle.

[0210] Furthermore, in this specification, when the liquid crystal compound 40 is a rod-shaped liquid crystal compound, the optical axis 40A of the liquid crystal compound 40 refers to the long axis of the molecules of the rod-shaped liquid crystal compound. On the other hand, when the liquid crystal compound 40 is a disk-shaped liquid crystal compound, the optical axis 40A of the liquid crystal compound 40 refers to an axis parallel to the normal direction relative to the disk surface of the disk-shaped liquid crystal compound.

[0211] In the liquid crystal layer 54, in the liquid crystal alignment pattern of this liquid crystal compound 40, the length (distance) of rotating the optical axis 40A of the liquid crystal compound 40 by 180° in the direction of the alignment axis D which changes due to continuous rotation of the in-plane optical axis 40A, i.e., the length of one cycle in the liquid crystal alignment pattern, is set as the in-plane period Λ.

[0212] That is, the distance between the centers of two liquid crystal compounds 40 with equal angles relative to the alignment axis D along the alignment axis D is defined as the in-plane period Λ. Specifically, as... Figure 4 As shown, the distance between the centers of the two liquid crystal compounds 40 whose alignment axis D direction is consistent with the direction of the optical axis 40A is set as the in-plane period Λ.

[0213] The liquid crystal alignment pattern of the liquid crystal layer 54 repeats the in-plane period Λ in a direction that changes as it rotates continuously along the alignment axis D, i.e., the orientation of the optical axis 40A. In the liquid crystal diffraction element, this in-plane period Λ becomes the period of the diffraction structure.

[0214] On the other hand, the liquid crystal compound 40 forming the liquid crystal layer 54 is in a direction orthogonal to the alignment axis D (in Figure 4 The direction in the middle (Y direction) is orthogonal to the direction of the optical axis 40A, which is the same as the direction of the optical axis 40A.

[0215] In other words, in the Y direction, the optical axis 40A of the liquid crystal compound 40 forming the liquid crystal layer 54 is equal to the angle formed by the alignment axis D (X direction).

[0216] If the cross-section of the cholesterol-type liquid crystal layer in the thickness direction is observed by SEM (scanning electron microscope), a stripe pattern with alternating bright and dark areas originating from the cholesterol-type liquid crystal phase is observed.

[0217] Here, if observed through SEM Figure 3 The XZ plane of the liquid crystal layer 54 shown, i.e., the cross-section in the thickness direction, reveals the following: Figure 5 The stripe pattern shown has the bright part 42 and the dark part 44 tilted at a specified angle θ relative to the main surface (XY plane).

[0218] The tilt angle θ is not limited, but it is preferably 10° or more, and more preferably 20° or more.

[0219] Setting the tilt angle θ to 10° or more is preferred in terms of obtaining a larger diffraction angle and higher diffraction efficiency.

[0220] In this SEM cross-section, the spacing in the normal direction of the lines formed by adjacent bright portions 42 to bright portions 42 or dark portions 44 to dark portions 44 corresponds to 1 / 2 pitch. That is, as in Figure 5 The two bright parts 42 and the two dark parts 44 correspond to the helical pitch (the number of turns of the helix once), i.e., the helical pitch P.

[0221] The following explains the effect of diffraction based on the liquid crystal layer.

[0222] In conventional cholesteric liquid crystal layers, the helical axis derived from the cholesteric liquid crystal phase is perpendicular to the main surface (XY plane), and its reflective surface is parallel to the main surface (XY plane). Furthermore, the optical axis of the liquid crystal compound is not tilted relative to the main surface (XY plane). In other words, the optical axis is parallel to the main surface (XY plane). Therefore, if the XZ plane of a conventional cholesteric liquid crystal layer is observed using SEM, the alternating arrangement of bright and dark areas is perpendicular to the main surface (XY plane).

[0223] Cholesterol-type liquid crystal phases are specularly reflective, so for example, when light is incident on a cholesterol-type liquid crystal layer from the normal direction, the light is reflected in the normal direction.

[0224] In contrast, the liquid crystal layer 54 causes the incident light to be reflected at an angle relative to the alignment axis D by the specular reflection. The liquid crystal layer 54 is a layer having a liquid crystal alignment pattern that changes while continuously rotating along the alignment axis D (a predetermined direction) within its plane. Hereinafter, reference will be made to... Figure 6 Please provide an explanation.

[0225] As an example, the liquid crystal layer 54 is configured to selectively reflect right-handed circularly polarized light R of red light. R The liquid crystal layer is a cholesterol-type liquid crystal layer. Therefore, if light is incident on the liquid crystal layer 54, the liquid crystal layer 54 only reflects the right-handed circularly polarized light R of red light. R This allows light other than that to pass through.

[0226] In the liquid crystal layer 54, the optical axis 40A of the liquid crystal compound 40 changes as it rotates along the arrangement axis D (one direction).

[0227] The liquid crystal alignment pattern formed on the liquid crystal layer 54 is a periodic pattern along the alignment axis D. Therefore, as... Figure 6 As shown conceptually, the right-handed circularly polarized light R of red light incident on the liquid crystal layer 54 R The reflected red light is diffracted in a direction corresponding to the period of the liquid crystal alignment pattern. The reflected red light is then circularly polarized to the right. R It reflects (diffracts) in a direction that is tilted towards the alignment axis D relative to the XY plane (the main surface of the cholesterol-type liquid crystal layer).

[0228] As a result, when the liquid crystal layer 54 is applied to optical elements, it can be used as a diffraction element that can reflect (diffuse) light incident from a direction perpendicular to the main surface of the light guide plate at an angle of total internal reflection within the light guide plate, and can reflect (diffuse) light that is totally internally reflected and guided within the light guide plate in a direction perpendicular to the main surface of the light guide plate.

[0229] In the liquid crystal layer 54, by appropriately setting the direction of the arrangement axis D, which is one direction of rotation of the optical axis 40A, the direction of light reflection (diffraction angle) can be adjusted.

[0230] For example, in the case of reflecting circularly polarized light with the same wavelength and the same direction of rotation, the reflection direction of the circularly polarized light can be reversed by setting the direction of the alignment axis D to the opposite direction.

[0231] Moreover, in liquid crystal layers with the same liquid crystal alignment pattern, the reflection direction is reversed according to the rotation direction of the spiral of the liquid crystal compound 40, which is the rotation direction of the reflected circularly polarized light.

[0232] For example, when the rotation direction of the spiral is right-handed, right-handed circularly polarized light is selectively reflected, and the right-handed circularly polarized light is reflected by a liquid crystal alignment pattern having an optical axis 40A that rotates counterclockwise along the alignment axis D.

[0233] Furthermore, for example, when the rotation direction of the spiral is left-handed, the liquid crystal layer with a liquid crystal alignment pattern having an optical axis 40A rotating counterclockwise along the alignment axis D causes the left-handed circularly polarized light to be tilted in the opposite direction to the alignment axis D and reflected.

[0234] That is, in a liquid crystal layer where the rotation direction of the spiral is opposite, by setting the direction of the arrangement axis D to be opposite, i.e., 180° apart, it is possible to tilt in the same direction and reflect light.

[0235] As described above, in this liquid crystal diffraction element, the length of 180° rotation of the optical axis of the liquid crystal compound in the liquid crystal layer, i.e., the in-plane period Λ, is the period of the diffraction structure (one period). Furthermore, in the liquid crystal layer, the direction in which the optical axis of the liquid crystal compound changes during rotation (the direction of the alignment axis D), i.e., the in-plane rotation direction, is the periodic direction of the diffraction structure.

[0236] In the optical element 10 of the present invention, the length of the in-plane period Λ of the liquid crystal diffraction element is not limited, and can be appropriately set according to the incident angle in the light guide plate 12, the size of the diffraction of the light emitted from the light guide plate 12, etc.

[0237] The length of one period of the liquid crystal diffraction element is preferably 0.1 to 10 μm, more preferably 0.1 to 1 μm, and from the viewpoint of enabling the light guide plate 12 to propagate by total internal reflection, the wavelength of the incident light is further preferably below λ.

[0238] In a liquid crystal layer with a liquid crystal alignment pattern, the shorter the in-plane period Λ, the larger the angle of the reflected light relative to the incident light. That is, the shorter the in-plane period Λ, the more significantly the reflected light can be tilted relative to the incident light for reflection.

[0239] Furthermore, in a liquid crystal layer with this liquid crystal alignment pattern, the reflection angle (diffraction angle) of light varies depending on the wavelength of the reflected light. Specifically, the longer the wavelength of light, the larger the angle between the reflected light and the incident light.

[0240] Figure 3 The example shown is a structure in which the optical axis 40 of the liquid crystal compound 40 is aligned parallel to the main surface (XY plane) in the XZ plane of the liquid crystal layer 54.

[0241] However, the present invention is not limited thereto. For example, such as Figure 7 As conceptually shown, it can also be a structure in which the liquid crystal compound 40 tilts its optical axis 40A relative to the main surface (XY plane) on the XZ plane of the liquid crystal layer 54.

[0242] Furthermore, in Figure 7In the example shown, on the XZ plane of the liquid crystal layer 54, the tilt angle (tilt angle) of the liquid crystal compound 40 relative to the main surface (XY plane) is the same in the thickness direction (Z direction), but the present invention is not limited thereto. The liquid crystal layer 54 may have regions where the tilt angle of the liquid crystal compound 40 differs in the thickness direction.

[0243] For example, Figure 8 The example shown is a structure as follows: at the interface of the liquid crystal layer on the alignment film 52 side, the optical axis 40A of the liquid crystal compound 40 is parallel to the main surface (pretilt angle is 0), and the tilt angle of the liquid crystal compound 40 increases as it separates from the interface on the alignment film 52 side along the thickness direction, and then the liquid crystal compound is oriented at a predetermined tilt angle until it reaches the other interface (air interface) side.

[0244] Figure 8 In the liquid crystal layer 54 shown, the angles (i.e., tilt angles θ) formed by the bright and dark portions originating from the aforementioned cholesterol-type liquid crystal phase relative to the main surface, as observed in a cross-section viewed by SEM (reference). Figure 5 The thickness gradually increases as the interface on the orientation film 52 side separates along the thickness direction.

[0245] The helical pitch P of the cholesterol-type liquid crystal phase in this liquid crystal layer 54 varies along the thickness direction. That is, the helical pitch P of the liquid crystal layer 54 gradually increases as it separates along the thickness direction from the interface on the alignment film 52 side.

[0246] As mentioned above, the wavelength of light selectively reflected by liquid crystal layer 54 (cholesterol-type liquid crystal phase) depends on the helical pitch P; the longer the helical pitch P, the more selectively it reflects longer wavelengths of light. Therefore, as... Figure 8 The tilt angle θ shown gradually increases as the liquid crystal layer 54 separates from the interface on the alignment film 52 side along the thickness direction, enabling it to reflect light over a wide wavelength range.

[0247] like Figure 8 The liquid crystal layer 54, whose tilt angle θ gradually increases as it separates from the interface on the alignment film 52 side along the thickness direction, preferably has a region with a tilt angle θ of 10° or more.

[0248] In this liquid crystal layer 54, it is preferable to have a region with an inclination angle θ of 10° or more, in terms of obtaining a large diffraction angle with high diffraction efficiency.

[0249] The liquid crystal layer 54 more preferably has a region with a tilt angle θ of 20° or more, and even more preferably has a region with a tilt angle of 30° or more.

[0250] Furthermore, the difference between the maximum and minimum values ​​of the tilt angle θ of the liquid crystal layer 54, which gradually increases as it separates from the interface on the alignment film 52 side along the thickness direction, is preferably 10° or more.

[0251] By setting the difference between the maximum and minimum values ​​of the tilt angle θ to 10° or more, the diffraction angle of light can be increased, which is preferable in terms of expanding the wavelength range of light selectively reflected by the liquid crystal layer 54.

[0252] The liquid crystal layer 54 preferably has a tilt angle θ with a maximum value of 15° or more, and more preferably 20° or more.

[0253] Thus, in the liquid crystal layer 54, there can be a structure in which the optical axis of the liquid crystal compound has a pretilt angle at one of the interfaces, or in which there is a pretilt angle at both interfaces. Furthermore, the pretilt angles at the two interfaces can also be different.

[0254] In this way, by giving the liquid crystal compound a tilt angle (tilt), the birefringence of the liquid crystal compound that is effective in diffracting light becomes higher, thereby improving the diffraction efficiency.

[0255] The average angle (average tilt angle) formed by the optical axis 40A of the liquid crystal compound 40 and the main surface (XY plane) is preferably 5 to 80°, more preferably 10 to 50°. Furthermore, the average tilt angle can be measured by observing the XZ plane of the liquid crystal layer 54 using a polarizing microscope. On the XZ plane of the liquid crystal layer 54, the liquid crystal compound 40 is preferably oriented such that its optical axis 40A is tilted in the same direction relative to the main surface (XY plane).

[0256] In addition, the above tilt angle is the following value: when observing the cross-section of the cholesterol-type liquid crystal layer with a polarizing microscope, the angle formed by the optical axis 40A of the liquid crystal compound 40 and the main surface is measured at any 5 or more positions, and the value is obtained by arithmetic averaging.

[0257] Light incident perpendicularly onto the liquid crystal diffraction element (liquid crystal layer 54) is subjected to a bending force along the tilt direction within the liquid crystal layer and travels at an angle. If the light travels within the liquid crystal layer, it will deviate from conditions such as the diffraction period, which are originally set to obtain the desired diffraction angle relative to perpendicular incidence, thus generating diffraction loss.

[0258] When the liquid crystal compound is tilted, there is a position where a higher birefringence occurs relative to the direction of light diffraction, compared to the non-tilted position. The effective anomalous refractive index increases in this direction, and therefore the birefringence, which is the difference between the anomalous and ordinary refractive indices, becomes higher.

[0259] By setting the tilt angle according to the orientation of the target diffraction, deviations from the original diffraction conditions in that orientation can be suppressed. As a result, it is believed that higher diffraction efficiency can be obtained when using liquid crystal compounds with tilt angles.

[0260] Furthermore, the tilt angle is preferably controlled based on the processing of the interface of the liquid crystal layer 54.

[0261] At the interface on the support side, the tilt angle of the liquid crystal compound can be controlled by pre-tilting the alignment film. For example, when forming the alignment film, after exposing it to ultraviolet light from the front side, it is exposed from an oblique side, thereby generating a pre-tilt angle in the liquid crystal compound in the liquid crystal layer formed on the alignment film. In this case, the pre-tilt is performed relative to the second irradiation direction in the direction where the uniaxial side of the liquid crystal compound can be observed. However, the liquid crystal compound in the direction perpendicular to the second irradiation direction is not pre-tilted, so there are pre-tilted and non-pre-tilted regions within the surface. This is because, when diffracting light towards the target direction, this direction is most conducive to improving birefringence, thus suitable for improving diffraction efficiency.

[0262] Furthermore, additives that promote the pretilt angle can be added to the liquid crystal layer or alignment film. In this case, the additives can be used as a factor to further improve diffraction efficiency.

[0263] This additive can also be used to control the pretilt angle of the air-side interface.

[0264] In the cross-section of the liquid crystal layer 54 observed using SEM, the bright and dark portions originating from the cholesterol-type liquid crystal phase are inclined relative to the main surface. In the liquid crystal layer, when measuring the in-plane retardation Re from the normal direction and the direction inclined relative to the normal, preferably, in either the slow-axis plane or the fast-axis plane, the direction in which the in-plane retardation Re is minimized is inclined from the normal direction. Specifically, preferably, the absolute value of the measurement angle formed by the direction of minimum in-plane retardation Re and the normal is 5° or more. In other words, preferably, the liquid crystal compound of the liquid crystal layer is inclined relative to the main surface, and the inclination direction is approximately consistent with the bright and dark portions of the liquid crystal layer. Furthermore, the normal direction is orthogonal to the main surface.

[0265] By giving the liquid crystal layer this structure, it is possible to diffract circularly polarized light with high diffraction efficiency compared to liquid crystal compounds and liquid crystal layers with parallel main surfaces.

[0266] In a structure where the liquid crystal compound in the liquid crystal layer is tilted relative to the main surface, and the tilt direction is approximately aligned with the bright and dark portions, the bright and dark portions corresponding to the reflective surface are aligned with the optical axis of the liquid crystal compound. Therefore, the effect of the liquid crystal compound on light reflection (diffraction) is increased, thereby improving diffraction efficiency. Consequently, the amount of reflected light relative to the incident light can be further increased.

[0267] On the fast axis or slow axis plane of the liquid crystal layer, the absolute value of the optical axis tilt angle of the liquid crystal layer is preferably 5° or more, more preferably 15° or more, and even more preferably 20° or more.

[0268] By setting the absolute value of the optical axis tilt angle to 15° or more, it is even more preferable to align the direction of the liquid crystal compound with the bright and dark areas, which is more advantageous from the viewpoint of improving diffraction efficiency.

[0269] Furthermore, the liquid crystal layer 54 can be a layer in which the helical pitch of the cholesteric liquid crystal phase gradually changes along the thickness direction without the tilt angle θ of the bright and dark regions gradually increasing. For example, the liquid crystal layer 54 can be a cholesteric liquid crystal layer in which the helical pitch P gradually increases as it separates from the interface on the alignment film 52 side along the thickness direction.

[0270] As mentioned above, the wavelength of light selectively reflected by the liquid crystal layer 54 (cholesterol-type liquid crystal phase) depends on the helical pitch P. The longer the helical pitch P, the more selectively it reflects longer wavelengths of light. Therefore, the liquid crystal layer 54, whose helical pitch P gradually increases along the thickness direction, can reflect a wide range of wavelengths of light.

[0271] <<Methods for forming liquid crystal layers>>

[0272] The liquid crystal layer 54 is formed by fixing a liquid crystal phase, in which a liquid crystal compound is oriented to a predetermined orientation state, into a layer. For example, in the case of a cholesterol-type liquid crystal layer, a cholesterol-type liquid crystal phase can be fixed into a layer.

[0273] The structure formed by fixing the cholesterol-type liquid crystal phase can be any structure that maintains the orientation of the liquid crystal compound that becomes the liquid crystal phase. Typically, the following structure is preferred: based on setting the polymerizable liquid crystal compound to a predetermined orientation state of the liquid crystal phase, it is polymerized and cured by ultraviolet irradiation, heating, etc. to form a non-flowing layer, and at the same time, it is changed to a state in which the orientation morphology will not change due to external field or external force.

[0274] Furthermore, in structures where a liquid crystal phase is fixed, as long as the optical properties of the liquid crystal phase are maintained, the liquid crystal compound 40 in the liquid crystal layer may not exhibit liquid crystal properties. For example, polymerizable liquid crystal compounds can lose their liquid crystal properties by undergoing a curing reaction to increase their molecular weight.

[0275] As an example of materials used in the formation of a liquid crystal layer, a liquid crystal composition comprising a liquid crystal compound can be cited. The liquid crystal compound is preferably a polymerizable liquid crystal compound.

[0276] Furthermore, the liquid crystal composition used in the formation of the liquid crystal layer may further include surfactants and chiral reagents.

[0277] --Polymerizable liquid crystal compounds--

[0278] Polymerizable liquid crystal compounds can be rod-shaped or disc-shaped.

[0279] Examples of rod-shaped polymerizable liquid crystal compounds include rod-shaped nematic liquid crystal compounds. Among rod-shaped nematic liquid crystal compounds, imine derivatives, azo derivatives, cyanobiphenyl derivatives, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexane derivatives, cyano-substituted phenylpyrimidine derivatives, alkoxy-substituted phenylpyrimidine derivatives, phenyl dioxane derivatives, diphenylacetylene derivatives, and alkenylcyclohexylbenzonitrile derivatives are preferred. Not only low-molecular-weight liquid crystal compounds but also high-molecular-weight liquid crystal compounds can be used.

[0280] Polymerizable liquid crystal compounds are obtained by introducing polymerizable groups into a liquid crystal compound. Examples of polymerizable groups include unsaturated polymerizable groups, epoxy groups, and acridine groups; unsaturated polymerizable groups are preferred, and olefinic unsaturated polymerizable groups are more preferred. Polymerizable groups can be introduced into the molecules of the liquid crystal compound using various methods. The number of polymerizable groups in the polymerizable liquid crystal compound is preferably 1 to 6, more preferably 1 to 3.

[0281] Examples of polymerizable liquid crystal compounds include Makromol. Chem., Vol. 190, pp. 2255 (1989), Advanced Materials. Compounds described in Volume 5, 107 pages (1993), US Patent No. 4,683,327, US Patent No. 5,622,648, US Patent No. 5,770,107, International Publications Nos. 95 / 022586, 95 / 024455, 97 / 000600, 98 / 023580, and 98 / 052905, Japanese Patent Application Publications Nos. 1-272551, 6-016616, 7-110469, 11-080081, and 2001-328973, etc. Two or more polymerizable liquid crystal compounds can be used simultaneously. Using two or more polymerizable liquid crystal compounds simultaneously can lower the orientation temperature.

[0282] Furthermore, as polymerizable liquid crystal compounds other than those mentioned above, cyclic organopolysiloxane compounds having a cholesterol phase, such as those disclosed in Japanese Patent Application Publication No. 57-165480, can be used. Moreover, as the aforementioned polymeric liquid crystal compounds, polymers in which liquid crystal-presenting mesocytic groups are introduced into the main chain, side chain, or both the main chain and side chain, polymeric cholesterol-type liquid crystals in which cholesterol groups are introduced into the side chain, liquid crystal polymers such as those disclosed in Japanese Patent Application Publication No. 9-133810, and liquid crystal polymers such as those disclosed in Japanese Patent Application Publication No. 11-293252 can be used.

[0283] --Disc-shaped liquid crystal compound--

[0284] As a disc-shaped liquid crystal compound, the disc-shaped liquid crystal compound described in Japanese Patent Application Publication No. 2007-108732 and Japanese Patent Application Publication No. 2010-244038 are preferred, for example.

[0285] Furthermore, the amount of polymerizable liquid crystal compound added to the liquid crystal composition is preferably 75 to 99.9% by mass relative to the mass of the solid components of the liquid crystal composition (mass after removing the solvent), more preferably 80 to 99% by mass, and even more preferably 85 to 90% by mass.

[0286] --surfactants--

[0287] The liquid crystal composition used to form the liquid crystal layer may contain a surfactant.

[0288] The surfactant is preferably a compound capable of functioning as an orientation control agent, which helps to stabilize or rapidly orient the cholesterol-type liquid crystal phase. Examples of surfactants include siloxane-based and fluorinated surfactants, with fluorinated surfactants being a preferred example.

[0289] Specific examples of surfactants include compounds described in paragraphs

[0082] to

[0090] of Japanese Patent Application Publication No. 2014-119605, compounds described in paragraphs

[0031] to

[0034] of Japanese Patent Application Publication No. 2012-203237, compounds exemplified in paragraphs

[0092] and

[0093] of Japanese Patent Application Publication No. 2005-99248, compounds exemplified in paragraphs

[0076] to

[0078] and

[0082] to

[0085] of Japanese Patent Application Publication No. 2002-129162, and fluoro(meth)acrylate polymers described in paragraphs

[0018] to

[0043] of Japanese Patent Application Publication No. 2007-272185.

[0290] In addition, one surfactant can be used alone, or two or more surfactants can be used at the same time.

[0291] As a fluorinated surfactant, the preferred choice is the compound described in paragraphs

[0082] to

[0090] of Japanese Patent Application Publication No. 2014-119605.

[0292] The amount of surfactant added to the liquid crystal composition is preferably 0.01 to 10% by mass relative to the total mass of the liquid crystal compound, more preferably 0.01 to 5% by mass, and even more preferably 0.02 to 1% by mass.

[0293] --Chiral reagents (optically active compounds)--

[0294] Chiral agents induce helical structures in cholesterol-type liquid crystal phases. Since the direction of helical twist or the pitch of the helix induced by the compound varies, the chiral agent can be selected based on the desired outcome.

[0295] There are no particular restrictions on the use of chiral reagents, and well-known compounds can be used (e.g., those described in the Liquid Crystal Device Handbook, Chapter 3, Item 4-3, TN (twisted nematic), STN (Super Twisted Nematic) chiral reagents, page 199, edited by the 142nd Committee of the Japan Society for the Promotion of Science, 1989), isosorbide (a chiral reagent with an isosorbide structure), and isomannitol derivatives, etc.

[0296] Furthermore, chiral reagents that undergo deisomerization, dimerization, and isomerization and dimerization through light irradiation, and chiral reagents that reduce helical torsion power (HTP) can also be preferentially utilized.

[0297] Chiral reagents typically contain asymmetric carbon atoms, but axially asymmetric or surface-asymmetric compounds that do not contain asymmetric carbon atoms can also be used as chiral reagents. Examples of axially asymmetric or surface-asymmetric compounds include naphthalene, helicene, p-xylene dimers, and their derivatives. Chiral reagents may also have polymerizable groups. When both the chiral reagent and the liquid crystal compound have polymerizable groups, a polymer having repeating units derived from the polymerizable liquid crystal compound and repeating units derived from the chiral reagent can be formed by the polymerization reaction of the polymerizable chiral reagent and the polymerizable liquid crystal compound. In this manner, the polymerizable groups possessed by the polymerizable chiral reagent are preferably the same as those possessed by the polymerizable liquid crystal compound. Therefore, the polymerizable groups of the chiral reagent are preferably unsaturated polymerizable groups, epoxy groups, or acridine groups, more preferably unsaturated polymerizable groups, and even more preferably olefinic unsaturated polymerizable groups.

[0298] Furthermore, the chiral reagent can also be a liquid crystal compound.

[0299] When the chiral reagent has a photoisomerizing group, it is preferable that a pattern corresponding to the emission wavelength can be formed by irradiation with a photomask such as activated light after coating and orientation. As the photoisomerizing group, it is preferable to be an isomerization site of a compound exhibiting photochromic properties, an azo group, an oxyazo group, or a cinnamyl group. As specific compounds, the compounds described in Japanese Patent Application Publication Nos. 2002-080478, 2002-080851, 2002-179668, 2002-179669, 2002-179670, 2002-179681, 2002-179682, 2002-338575, 2002-338668, 2003-313189, and 2003-313292 may be used.

[0300] The content of the chiral reagent in the liquid crystal composition is preferably 0.01 to 200 mol% relative to the molar content of the liquid crystal compound, and more preferably 1 to 30 mol%.

[0301] --Polymerization Initiator--

[0302] When the liquid crystal composition contains a polymerizable compound, it preferably contains a polymerization initiator. In the case of polymerization reaction carried out by ultraviolet irradiation, the polymerization initiator used is preferably a photopolymerization initiator that can initiate the polymerization reaction by ultraviolet irradiation.

[0303] Examples of photopolymerization initiators include α-carbonyl compounds (described in U.S. Patent Nos. 2,367,661 and 2,367,670), azobin ethers (described in U.S. Patent No. 2,448,828), α-hydrocarbon-substituted aromatic azobin compounds (described in U.S. Patent No. 2,722,512), polynucleoquinone compounds (described in U.S. Patent Nos. 3,046,127 and 2,951,758), combinations of triarylimidazolium dimers and p-aminophenyl ketones (described in U.S. Patent No. 3,549,367), acridine and phenazine compounds (described in Japanese Patent Application Publication No. 60-105,667 and U.S. Patent No. 4,239,850), and oxadiazole compounds (described in U.S. Patent No. 4,212,970).

[0304] The content of the photopolymerization initiator in the liquid crystal composition is preferably 0.1 to 20% by mass relative to the content of the liquid crystal compound, and more preferably 0.5 to 12% by mass.

[0305] --Cross-linking agent--

[0306] To improve the strength and durability of the cured film, the liquid crystal composition may contain any crosslinking agent. As a crosslinking agent, a crosslinking agent that is cured by ultraviolet light, heat, or moisture is preferred.

[0307] There are no particular limitations on the crosslinking agent; it can be appropriately selected according to the purpose. Examples include polyfunctional acrylate compounds such as trimethylolpropane tri(meth)acrylate and pentaerythritol tri(meth)acrylate; epoxy compounds such as glycidyl methacrylate and ethylene glycol diglycidyl ether; acrylidine compounds such as 2,2-dihydroxymethylbutanol-tris[3-(1-acrylidinyl)propionate] and 4,4-bis(ethyleneiminocarbonylamino)diphenylmethane; isocyanate compounds such as hexamethylene diisocyanate and biuret-type isocyanate; polyoxazoline compounds with oxazoline groups on the side chains; and alkoxysilane compounds such as vinyltrimethoxysilane and N-(2-aminoethyl)3-aminopropyltrimethoxysilane. Furthermore, known catalysts can be used depending on the reactivity of the crosslinking agent, which can improve not only film strength and durability but also productivity. One of these can be used alone, or two or more can be used simultaneously.

[0308] The content of the crosslinking agent is preferably 3 to 20% by mass relative to the solid components of the liquid crystal composition, more preferably 5 to 15% by mass. As long as the content of the crosslinking agent is within the above range, it is easy to obtain the effect of increasing the crosslinking density, thereby further improving the stability of the liquid crystal phase.

[0309] --Other Additives--

[0310] In the liquid crystal composition, polymerization inhibitors, antioxidants, ultraviolet absorbers, light stabilizers, colorants, and metal oxide particles can be further added as needed, without reducing optical performance, etc.

[0311] When forming a liquid crystal layer, the liquid crystal composition is preferably used as a liquid.

[0312] The liquid crystal composition may contain a solvent. There are no limitations on the solvent; it can be appropriately selected depending on the purpose, but organic solvents are preferred.

[0313] There are no restrictions on the organic solvents used; they can be appropriately selected according to the purpose. Examples include ketones, haloalkanes, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, and ethers. One or more of these can be used individually or simultaneously. Among these, ketones are preferred, considering their environmental impact.

[0314] When forming a liquid crystal layer, it is preferable to coat the liquid crystal composition onto the forming surface of the liquid crystal layer, orient the liquid crystal compound to the desired liquid crystal phase state, and then cure the liquid crystal compound to form a liquid crystal layer.

[0315] That is, when a cholesterol-type liquid crystal layer is formed on the alignment film 52, it is preferable to coat the liquid crystal composition onto the alignment film 52, align the liquid crystal compound to a state of cholesterol-type liquid crystal phase, and then cure the liquid crystal compound to form a liquid crystal layer that fixes the cholesterol-type liquid crystal phase.

[0316] Regarding the coating of liquid crystal compositions, known methods that can uniformly coat liquid onto sheets can be used, such as all inkjet and roll printing methods, as well as spin coating, bar coating, and spray coating.

[0317] The coated liquid crystal composition is dried and / or heated as needed, and then cured to form a liquid crystal layer. In this drying and / or heating process, the liquid crystal compound in the liquid crystal composition only needs to be oriented as a cholesterol-type liquid crystal phase. When heating is performed, the heating temperature is preferably below 200°C, more preferably below 130°C.

[0318] The oriented liquid crystal compound is further polymerized as needed. Polymerization can be either thermal polymerization or photopolymerization based on light irradiation, but photopolymerization is preferred. Ultraviolet light is preferably used for light irradiation. The irradiation energy is preferably 20 mJ / cm². 2 ~50J / cm 2 More preferably, it is 50–1500 mJ / cm². 2 To promote the photopolymerization reaction, light irradiation can also be carried out under heating conditions or in a nitrogen atmosphere. The wavelength of the irradiated ultraviolet light is preferably 250–430 nm.

[0319] As a chiral agent added to the liquid crystal composition, when using a agent that modifies the chirality of HTP by light irradiation, the HTP used to modify the chirality of the agent can be irradiated with light before the polymerization of the liquid crystal compound. Alternatively, the light irradiation based on the photopolymerization of the liquid crystal compound can also be combined with the light irradiation of HTP used to modify the chirality of the agent. Thus, a liquid crystal layer with a gradually changing helical pitch P of the cholesterol-type liquid crystal phase described above can be obtained.

[0320] There is no limitation on the thickness of the liquid crystal layer 54. As long as the thickness is appropriately set according to the application of the optical element, the required light reflectivity in the liquid crystal layer, and the forming material of the liquid crystal layer 54, the required light reflectivity can be obtained.

[0321] <Other Liquid Crystal Layers (Liquid Crystal Diffraction Elements)>

[0322] The optical element illustrated in the figure uses a reflective liquid crystal diffraction element with a liquid crystal layer 54 serving as a cholesterol-type liquid crystal layer for both the incident and emission elements, but the present invention is not limited thereto.

[0323] As an example, a liquid crystal diffraction element having a liquid crystal alignment pattern that rotates continuously in at least one in-plane direction and in which the liquid crystal compound does not form a cholesterol-type liquid crystal phase in the thickness direction can also be used. Furthermore, the liquid crystal diffraction element can have a structure that rotates and twists along the thickness direction to the point that the liquid crystal compound does not form a cholesterol-type liquid crystal phase.

[0324] exist Figure 10 and Figure 11 Other liquid crystal diffraction elements are illustrated below, and this example is explained.

[0325] Figure 10 and Figure 11 The liquid crystal diffraction element shown has a support 50, an alignment film 52, and a liquid crystal layer 56. The support 50 and the alignment film 52 are the same as those described above.

[0326] Similar to liquid crystal layer 54, Figure 11 The (cholesterol-type) liquid crystal layer 56 of the liquid crystal diffraction element shown also has a liquid crystal alignment pattern in which the optical axis 40A of the liquid crystal compound 40 rotates continuously along the alignment axis D. Furthermore, similar to the above... Figure 4 Similarly, Figure 11 Only the liquid crystal compound on the surface of the alignment film 52 is shown.

[0327] exist Figure 10 In the liquid crystal diffraction element shown, the liquid crystal compound 40 forming the liquid crystal layer 56 does not rotate in a spiral shape along the thickness direction, and the optical axis 40A is located at the same position in the planar direction. Regarding this liquid crystal layer, it can be formed without adding a chiral reagent to the liquid crystal composition during its formation.

[0328] As described above, the liquid crystal layer 56 has a liquid crystal alignment pattern in which the orientation of the optical axis 40A derived from the liquid crystal compound 40 changes as it rotates continuously in-plane along the alignment axis D direction, i.e., the X direction. That is, in this example, the in-plane rotation direction is also the alignment axis D direction, i.e., the X direction.

[0329] On the other hand, in the liquid crystal compound 40 forming the liquid crystal layer 56, liquid crystal compounds 40 with the same orientation of the optical axis 40A are arranged at equal intervals in the Y direction orthogonal to the X direction, that is, in the Y direction orthogonal to the arrangement axis D, which is a direction that rotates continuously with the optical axis 40A.

[0330] In other words, in the liquid crystal compound 40 that forms the liquid crystal layer 56, the orientation of the optical axis 40A of the liquid crystal compounds 40 arranged in the Y direction is equal to the angle formed by the direction of the arrangement axis D.

[0331] In the liquid crystal layer 56, among the liquid crystal compounds arranged in the Y direction, the angle formed by the optical axis 40A and the X direction (a direction in which the optical axis of the liquid crystal compound 40 is rotated) is equal. The region in the Y direction where the liquid crystal compound 40 with the angle formed by the optical axis 40A and the arrangement axis D is arranged is designated as region R.

[0332] In this case, the preferred value of the in-plane retardation (Re) in each region R is half the wavelength, i.e., λ / 2. These in-plane retardations are calculated by multiplying the refractive index difference Δn associated with the refractive index anisotropy of region R by the thickness of the optical anisotropy layer. The refractive index difference associated with the refractive index anisotropy of region R in the optical anisotropy layer is defined as the difference between the refractive index in the direction passing through the slow axis within the plane of region R and the refractive index in the direction orthogonal to the slow axis. That is, the refractive index difference Δn associated with the refractive index anisotropy of region R is equal to the difference between the refractive index of the liquid crystal compound 40 in the direction of the optical axis 40A and the refractive index of the liquid crystal compound 40 in the direction perpendicular to the optical axis 40A within the plane of region R. In other words, the refractive index difference Δn is equal to the refractive index difference of the liquid crystal compound 40.

[0333] If circularly polarized light is incident on this liquid crystal layer 56, the light is refracted and the direction of the circularly polarized light changes.

[0334] exist Figure 12 and Figure 13 This function is conceptually illustrated in the diagram. Furthermore, the liquid crystal layer 56 is set such that the product of the refractive index difference of the liquid crystal compound and the thickness of the optically anisotropic layer is λ / 2.

[0335] like Figure 12 As shown, when the product of the refractive index difference of the liquid crystal compound in the liquid crystal layer 56 and the thickness of the optical anisotropic layer is λ / 2, if the incident light L1, which is left-handed circularly polarized light, is incident on the liquid crystal layer 56, the incident light L1 passes through the liquid crystal layer 56 and is given a phase difference of 180°, thereby converting the transmitted light L2 into right-handed circularly polarized light.

[0336] Furthermore, the liquid crystal alignment pattern formed on the liquid crystal layer 56 is a periodic pattern along the alignment axis D, so the transmitted light L2 travels in a direction different from the direction of travel of the incident light L1. In this way, the incident light L1 of left-handed circularly polarized light is converted into the transmitted light L2 of right-handed circularly polarized light that is tilted at a predetermined angle relative to the incident direction along the alignment axis D.

[0337] On the other hand, such as Figure 13As shown, when the product of the refractive index difference of the liquid crystal compound in the liquid crystal layer 56 and the thickness of the optical anisotropic layer is λ / 2, if the incident light L4 of right-hand circularly polarized light is incident on the liquid crystal layer 56, the incident light L4 passes through the liquid crystal layer 56 and is given a phase difference of 180°, thereby being converted into the transmitted light L5 of left-hand circularly polarized light.

[0338] Furthermore, the liquid crystal alignment pattern formed on the liquid crystal layer 56 is a periodic pattern along the alignment axis D, so the transmitted light L5 travels in a direction different from the direction of travel of the incident light L4. At this time, the transmitted light L5 travels in a direction different from the transmitted light L2, that is, in a direction opposite to the direction of the alignment axis D relative to the incident direction. In this way, 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 direction of the alignment axis D relative to the incident direction.

[0339] Similar to liquid crystal layer 54, liquid crystal layer 56 can also adjust the refraction angles of transmitted light L2 and L5 by changing the in-plane period Λ of the formed liquid crystal alignment pattern. Specifically, the shorter the in-plane period Λ of the liquid crystal alignment pattern in liquid crystal layer 56, the stronger the interference between the light passing through adjacent liquid crystal compounds 40, thus enabling the transmitted light L2 and L5 to be refracted more.

[0340] Furthermore, by reversing the rotation direction of the optical axis 40A of the liquid crystal compound 40, which rotates along the alignment axis D, the direction of refraction of transmitted light can be reversed. That is, in Figures 10-13 In the example shown, the optical axis 40A, which is oriented toward the alignment axis D, rotates clockwise. However, by setting the rotation direction to counterclockwise, the direction of refraction of the transmitted light can be reversed.

[0341] Furthermore, from the viewpoint of diffraction efficiency, even when using a liquid crystal diffraction element that transmits and diffracts incident light, it is preferable to use a liquid crystal diffraction element having a region where the liquid crystal compound is twisted and rotated (twist angle less than 360°). In particular, when diffracting light at an angle reflected within the light guide plate, from the viewpoint of diffraction efficiency, it is preferable to use a liquid crystal diffraction element having a region where the liquid crystal compound is twisted and rotated. Moreover, from the viewpoint of diffraction efficiency, it is more preferable to stack liquid crystal diffraction elements with different angles of twisted rotation of the liquid crystal compound and to stack liquid crystal diffraction elements with different directions of twisted rotation of the liquid crystal compound.

[0342] In the optical element of the present invention, when using a transmissive incident element and an exiting element, the positional relationship between the incident element and the exiting element and the display 20 and the user U is the opposite of that when using a reflective incident element and an exiting element. That is, the optical element is configured such that the image from the display 20 is incident from the incident portion side instead of from the light guide plate 12, and is incident from the light guide plate to the exiting portion, and is emitted through the exiting portion to the viewing position based on the user U.

[0343] Furthermore, the optical elements of the present invention can use different liquid crystal diffraction elements in the incident element and the emission element.

[0344] For example, in the incident section 14, a transmissive liquid crystal diffraction element having a liquid crystal layer 56 can be used, and in the ejection section 16, a reflective liquid crystal diffraction element having a liquid crystal layer 54 can be used.

[0345] As described above, in the optical element 10 of the example figure, the incident section 14 has a first incident diffraction section 26 and a second incident diffraction section 28. The first incident diffraction section 26 has incident elements 24A1 and 24A2. The second incident diffraction section 28 has incident elements 24B1 and 24B2.

[0346] The ejection section 16 has a first ejection diffraction section 32 and a second ejection diffraction section 34. The first ejection diffraction section 32 has an ejection element 30A1 and an ejection element 30A2. The second ejection diffraction section 34 has an ejection element 30B1 and an ejection element 30B2.

[0347] In the incident section 14, the liquid crystal layers 54 constituting the incident elements 24A1 and 24A2 of the first incident diffraction section 26 have equal in-plane periods Λ but different in-plane rotation directions (direction of the alignment axis D (X direction)). Similarly, the liquid crystal layers 54 constituting the incident elements 24B1 and 24B2 of the second incident diffraction section 28 have equal in-plane periods Λ but different in-plane rotation directions.

[0348] In the following description, the term liquid crystal layer 54 will be omitted, and it will be referred to as "the in-plane period Λ of the incident element 24A1" or "the rotation direction of the incident element 24A1".

[0349] Furthermore, the in-plane period Λ and in-plane rotation direction of incident elements 24A1, 24A2, 24B1, and 24B2 are different. That is, the in-plane period Λ and in-plane rotation direction of the incident elements formed by the first incident diffraction section 26 and the second incident diffraction section 28 are different.

[0350] When the incident diffraction section has three or more incident elements, at least two of the incident elements need to have the same in-plane period and different in-plane rotation directions.

[0351] Furthermore, when the incident part has three or more incident diffraction parts, at least two of the incident diffraction parts need to have different in-plane periods Λ and in-plane rotation directions.

[0352] The same applies to the ejection section and the ejection diffraction section.

[0353] In the optical element 10 illustrated in the figure, in the emission section 16, the in-plane periods Λ of the emission elements 30A1 and 30A2 constituting the first emission diffraction section 32 are equal, but their in-plane rotation directions are different. Similarly, the in-plane periods Λ of the emission elements 30B1 and 30B2 constituting the second emission diffraction section 34 are equal, but their in-plane rotation directions are different.

[0354] Furthermore, the in-plane period Λ and in-plane rotation direction of the ejector elements 30A1, 30A2, 30B1, and 30B2 are different. That is, the in-plane period Λ and in-plane rotation direction of the incident elements formed by the first ejector diffraction section 32 and the second ejector diffraction section 34 are different.

[0355] Figure 14 The example shown is the ejection section 16, which is a conceptual illustration.

[0356] The relationship between the in-plane period Λ and the in-plane rotation direction in each ejection element and ejection diffraction section is the same as that in the incident element and ejection diffraction section of the incident section 14.

[0357] Figure 14 In the diagram of the various ejection elements shown, the arrows indicate the in-plane rotation direction.

[0358] The in-plane periods Λ of the ejection elements 30A1 and 30A2 constituting the first ejection diffraction section 32 are equal, and the angle between the in-plane rotation direction of the ejection element 30A1 and the in-plane rotation direction of the ejection element 30A2 is 90°.

[0359] Furthermore, the in-plane periods Λ of the ejection elements 30B1 and 30B2 constituting the second ejection diffraction section 34 are equal, and the angle between the in-plane rotation direction of the ejection element 30B1 and the in-plane rotation direction of the ejection element 30B2 is 90°.

[0360] Furthermore, the angle (cross angle γ) between the in-plane rotation direction of the ejection element constituting the first ejection diffraction section 32 and the in-plane rotation direction of the ejection element constituting the second ejection diffraction section 34 is 45°.

[0361] As an example, if the in-plane rotation direction of the injection element 30A1 is set to 0°, then the in-plane rotation direction of the injection element 30A2 becomes 90°, the in-plane rotation direction of the injection element 30B1 becomes 45°, and the in-plane rotation direction of the injection element 30B2 becomes -45° (315°).

[0362] To prevent multiplexing of the displayed image, the in-plane period Λ of the emission element constituting the first emission diffraction section 32 is preferably [missing information]. A The in-plane period Λ of the emission element constituting the second emission diffraction section 34 B The relationship is as follows.

[0363] Λ B =Λ A / |2cosγ|

[0364] The optical element 10 of the present invention has such a structure that, through diffraction in the emission diffraction section 32 and emission diffraction section 34 constituting the emission section 16, for example... Figure 15 and Figure 16 As shown, light can propagate in two dimensions (black arrow) within the light guide plate 12 and can also be emitted in two dimensions (white arrow) from the light guide plate 12. The incident section 14 is similar in this respect.

[0365] As a result, when the optical element 10 of the present invention is used in, for example, AR glass, a wide field of view (FOV) and viewing area (field of view) can be achieved.

[0366] A preferred embodiment of the incident section is that it comprises multiple incident diffraction sections each having two incident diffraction elements, at least two of which are identical, and the angle between the in-plane rotation directions of the liquid crystal diffraction layers of the two incident diffraction elements in each incident diffraction section is 45°. Alternatively, it is also preferable to comprise multiple incident diffraction sections each having two incident diffraction elements, at least two of which are identical, and the angle between the in-plane rotation directions of the liquid crystal diffraction layers of the two incident diffraction elements in each incident diffraction section is 90°.

[0367] A preferred embodiment of the ejection section is that it comprises a plurality of ejection diffraction sections each having two ejection diffraction elements, at least two of which are identical, and the angle between the in-plane rotation directions of the liquid crystal diffraction layers of the two ejection diffraction elements is 45°. Alternatively, it is also preferable to comprise a plurality of ejection diffraction sections each having two ejection diffraction elements, at least two of which are identical, and the angle between the in-plane rotation directions of the liquid crystal diffraction layers of the two ejection diffraction elements is 90°.

[0368] Thus, according to the optical element 10 of the present invention, in the incident section 14, the incident light is two-dimensionally extended and propagates through the light guide plate 12, and as... Figure 17As conceptually shown, light can propagate fully through the emission section 16 and be emitted from the light guide plate 12.

[0369] As a result, as described above, the optical element 10 according to the present invention can expand the viewpoint area in AR glass or the like.

[0370] Here, in the first emission diffraction section 32 and the second emission diffraction section 34, the angle formed by the in-plane rotation direction of the emission element is 45°.

[0371] That is, light diffracted by the first emitted diffraction section 32 is difficult to diffract in the second emitted diffraction section 34, and light diffracted by the second emitted diffraction section 34 is difficult to diffract in the first emitted diffraction section 32. Therefore, light diffracted in both the first emitted diffraction section 32 and the second emitted diffraction section 34 will not be generated, thus preventing the generation of multiple images.

[0372] In the optical element 10 of the present invention, there are no limitations on the angle formed by the in-plane rotation directions of the incident element 24A1 and the incident element 24A2 of the first incident diffraction section 26, the angle formed by the in-plane rotation directions of the incident element 24B1 and the incident element 24B2 of the second incident diffraction section, the angle formed by the in-plane rotation directions of the emission element 30A1 and the emission element 30A2 of the first emission diffraction section 32, and the angle formed by the in-plane rotation directions of the emission element 30B1 and the emission element 30B2 of the second emission diffraction section 34.

[0373] Furthermore, there are no restrictions on the angles formed by the in-plane rotation directions of the incident elements 24A1 and 24A2 of the first incident diffraction section 26 and the incident elements 24B1 and 24B2 of the second incident diffraction section, as well as the angles formed by the in-plane rotation directions of the ejection elements 30A1 and 30A2 of the first ejection diffraction section 32 and the ejection elements 30B1 and 30B2 of the second ejection diffraction section 34.

[0374] The effect of preventing multiple images is higher when the angle formed by the rotation direction within the plane is large. Furthermore, as mentioned above, it is also preferable that the angle formed by the rotation direction within the plane of incident elements 24A1 and 24A2 is relatively large.

[0375] Taking this aspect into consideration, it is also preferable that the angle between the in-plane rotation directions of the incident elements 24A1 and 24A2 of the first incident diffraction section 26 and the incident elements 24B1 and 24B2 of the second incident diffraction section is larger.

[0376] On the other hand, in the optical element 10, the in-plane period Λ of the incident elements 24A1 and 24A2 of the first incident diffraction section 26 is equal, and the in-plane period Λ of the incident elements 24B1 and 24B2 of the second incident diffraction section 28 is equal. Furthermore, the in-plane period Λ of the incident elements 24A1 and 24A2 of the first incident diffraction section 26 is different from that of the incident elements 24B1 and 24B2 of the second incident diffraction section 28.

[0377] Similarly, in optical element 10, the in-plane period Λ of the emission elements 30A1 and 30A2 of the first emission diffraction section 32 is equal, and the in-plane period Λ of the emission elements 30B1 and 30B2 of the second emission diffraction section 34 is equal. Furthermore, the in-plane period Λ of the emission elements 30A1 and 30A2 of the first emission diffraction section 32 is different from that of the emission elements 30B1 and 30B2 of the second emission diffraction section 34.

[0378] Furthermore, in the optical element 10 of the example figure, as an example, the in-plane period Λ of the incident element 24A1 and incident element 24A2 of the first incident diffraction section 26 is equal to that of the emission element 30A1 and emission element 30A2 of the first emission diffraction section 32, and the in-plane period Λ of the incident element 24B1 and incident element 24B2 of the second incident diffraction section 28 is equal to that of the emission element 30B1 and emission element 30B2 of the second emission diffraction section 34.

[0379] The optical element 10 of the present invention has such a structure that when used in AR glass or the like, a wide field of view (FOV) can be obtained.

[0380] In order to ensure a wide field of view (FOV) to display an accurate image, the image illuminated by the display 20 needs to be incident on the incident portion 14 of the light guide plate 12 at an angle that allows total reflection of the light (image) from the display surface of the display 20 to be incident on the light guide plate 12.

[0381] However, the angle of light incident from the display 20 onto the incident portion 14 varies depending on its position on the display surface of the display 20. Therefore, it is difficult to ensure that light from the entire display surface of the display 20 is incident onto the light guide plate 12 at an angle that allows total reflection of the light guide plate 12 within a single diffraction element.

[0382] In contrast, the optical element 10 of the present invention uses incident elements with different in-plane periods Λ in the first incident diffraction section 26 and the second incident diffraction section 28.

[0383] As described above, the liquid crystal layer 54 of the liquid crystal diffraction element diffracts light at different angles depending on the in-plane period Λ. Specifically, the shorter the in-plane period Λ, the more light is bent, diffracted, and reflected. Therefore, by using incident elements with different in-plane periods Λ, light can be incident on the light guide plate 12 at an angle that allows total reflection, depending on the display position of the display 20.

[0384] As an example, such as Figure 18 As shown conceptually, the incident elements 24A1 and 24A2 of the first incident diffraction section 26 are set with an in-plane period Λ such that the light guide plate 12 can totally reflect light from the angle range φ1 from the solid line to the dashed line on the left side of the display 20, so that the light is incident on the light guide plate 12.

[0385] Therefore, even if light other than the angle range φ1 is incident on the first incident diffraction section 26, it will not be propagated by total internal reflection in the light guide plate 12.

[0386] Furthermore, as described above, the in-plane period Λ of the incident elements 24A1 and 24A2 of the first incident diffraction section 26 is equal to that of the exiting elements 30A1 and 30A2 of the first exiting diffraction section 32. Therefore, the light diffracted in the first incident diffraction section 26 and incident on the light guide plate 12 is diffracted in the first exiting diffraction section 32 and emitted.

[0387] On the other hand, such as Figure 19 As shown conceptually, the incident elements 24B1 and 24B2 of the second incident diffraction section 28 are set with an in-plane period Λ such that the light guide plate 12 can totally reflect light from the angle range φ2 from the solid line to the dashed line on the right side of the display 20, so that the light is incident on the light guide plate 12.

[0388] Therefore, even if light other than the angle range φ2 is incident on the first incident diffraction section 26, it will not propagate by total internal reflection in the light guide plate 12.

[0389] Furthermore, as described above, the in-plane period Λ of the incident elements 24B1 and 24B2 of the second incident diffraction section 28 is equal to that of the exiting elements 30B1 and 30B2 of the second exiting diffraction section 34. Therefore, the light diffracted in the second incident diffraction section 28 and incident on the light guide plate 12 is diffracted in the second exiting diffraction section 34 and emitted.

[0390] Within the angle range φ2, the light propagation direction in the light guide plate 12 is that the light travels in the opposite direction. Therefore, the incident element 24B1 and the like shorten the in-plane period Λ in a way that bends and diffracts more light than the incident element 24A1 and the like.

[0391] Therefore, according to the optical element 10 of the present invention, such as Figure 20As shown conceptually, light from the entire display surface of the display 20 is incident onto the light guide plate 12 via the incident section 14 at an angle that allows it to propagate through total internal reflection within the light guide plate 12, and the light propagating through the light guide plate 12 is emitted from the emission section 16 to the observation section based on the user U.

[0392] Therefore, the optical element 10 of the present invention can achieve the aforementioned wide viewpoint area and can also expand the field of view (FOV).

[0393] In the optical element 10 of the present invention, the in-plane period Λ of the incident elements 24A1 and 24A2 of the first incident diffraction section 26, the incident elements 24B1 and 24B2 of the second incident diffraction section 28, the emission elements 30A1 and 30A2 of the first emission diffraction section 32, and the emission elements 30B1 and 30B2 of the second emission diffraction section 34 is not limited.

[0394] That is, the in-plane period Λ of these elements is appropriately set according to the refractive index of the light guide plate 12, the size of the display surface of the display 20, the distance between the display 20 and the light guide plate 12, so that the angle of propagation that can be totally internally reflected in the light guide plate 12 can be the in-plane period Λ of the light that is incident on the entire display surface of the display 20.

[0395] Preferably, among the n incident diffraction sections in the incident section and the n emission diffraction sections in the emission section, there is a combination of incident diffraction sections and emission diffraction sections having n sets of incident diffraction elements whose in-plane period of the liquid crystal diffraction layer is equal to the in-plane period of the liquid crystal diffraction layer of the emission diffraction elements. Here, n is set to be one or more integers.

[0396] In the optical element 10 of the present invention, the incident elements 24A1 and 24A2 of the first incident diffraction section 26 and the incident elements 24B1 and 24B2 of the second incident diffraction section 28 in the incident section 14 can be composed of multiple incident elements (incident diffraction elements).

[0397] For example, incident element 24A1 and incident element 24A2 can both be composed of a first incident element and a second incident element. Furthermore, incident element 24B1 and incident element 24B2 can both be composed of a first incident element and a second incident element.

[0398] When the incident element 24A1 and / or the incident element 24A2 are composed of a first incident element and a second incident element, the first incident element and the second incident element preferably have liquid crystal diffraction elements that selectively reflect circularly polarized light with opposite rotation directions. For example, if the first incident element has a liquid crystal diffraction element that selectively reflects right-handed circularly polarized light, the second incident element preferably has a liquid crystal diffraction element that selectively reflects left-handed circularly polarized light.

[0399] That is, in the optical element 10 of the present invention, the incident elements 24A1 and 24A2 of the first incident diffraction section 26 and the incident elements 24B1 and 24B2 of the second incident diffraction section 28 in the incident section 14 may have a liquid crystal layer 54 that selectively reflects right circularly polarized light and a liquid crystal layer 54 that selectively reflects left circularly polarized light.

[0400] By configuring it in this way, the brightness of the light emitted from the light guide plate 12 can be increased without using the light carrying the image emitted by the display 20, and the displayed image can be made brighter.

[0401] When an incident element is composed of a first incident element and a second incident element, the incident element can have two Figure 3 The liquid crystal diffraction element shown is used as the first incident element and the second incident element.

[0402] Alternatively, in the case where one incident element is composed of a first incident element and a second incident element, one Figure 3 The liquid crystal diffraction element shown can have both a liquid crystal layer 54 that selectively reflects right-circularly polarized light and a liquid crystal layer 54 that selectively reflects left-circularly polarized light. In this case, the two liquid crystal layers 54 are regarded as the first incident element and the second incident element, respectively.

[0403] Figure 3 The liquid crystal diffraction element shown may not have a support 50, or it may not have a support 50 and an alignment film 52 as described above.

[0404] Here, as described above, the diffraction direction of the liquid crystal layer 54 is opposite in right-circularly polarized light and left-circularly polarized light. Therefore, in order to diffract light in the same direction in both the liquid crystal layer 54 that selectively reflects right-circularly polarized light and the liquid crystal layer 54 that selectively reflects left-circularly polarized light, the angle formed by the in-plane rotation direction needs to be set to 180°. That is, in order to diffract light in the same direction, the in-plane rotation direction needs to be set to be opposite in both the liquid crystal layer 54 that selectively reflects right-circularly polarized light and the liquid crystal layer 54 that selectively reflects left-circularly polarized light.

[0405] Therefore, light can be diffracted in the same direction in the first and second incident elements that constitute a single incident element. In other words, in this structure, the first and second incident elements that constitute a single incident element can be essentially called liquid crystal diffraction elements with the same optical function, except that the rotation direction of the selectively reflected circularly polarized light is different.

[0406] Furthermore, when an incident element is composed of a first incident element and a second incident element, it is preferable to make the in-plane period Λ of the first incident element and the second incident element constituting the incident element consistent.

[0407] Furthermore, in the incident section 14, if one incident element is composed of a first incident element and a second incident element, and has a liquid crystal layer 54 that selectively reflects right-circularly polarized light and a liquid crystal layer 54 that selectively reflects left-circularly polarized light, then correspondingly, the emission section 16 also preferably has a liquid crystal layer 54 that selectively reflects right-circularly polarized light and a liquid crystal layer 54 that selectively reflects left-circularly polarized light.

[0408] At this time, for example, the emission element of the first emission diffraction section 32 can selectively reflect right-circularly polarized light or left-circularly polarized light, and the emission element of the second emission diffraction section 34 can selectively reflect the other circularly polarized light.

[0409] In this regard, both the first incident diffracting section 26 and the second incident diffracting section 28 described later have only one incident element, and the case that one incident diffracting section selectively reflects right-circularly polarized light and the other incident diffracting section selectively reflects left-circularly polarized light is the same.

[0410] In the aforementioned optical element 10, the first incident diffraction section 26 has multiple incident elements, namely incident element 24A1 and incident element 24A2. Furthermore, the second incident diffraction section 28 also has multiple incident elements, namely incident element 24B1 and incident element 24B2.

[0411] However, the present invention is not limited thereto. That is, in the optical element of the present invention, the first incident diffraction section 26 may have only incident element 24A1 and / or the second incident diffraction section 28 may have only incident element 24B1.

[0412] Since the first incident diffraction section 26 has only an incident element 24A1, various structures can be utilized when the second incident diffraction section 28 also has only an incident element 24B1.

[0413] For example, if the first incident diffraction section 26 has only an incident element 24A1 and the second incident diffraction section 28 has only an incident element 24B1, as described above, the incident element 24A1 is composed of a first incident element that selectively reflects right-circularly polarized light or left-circularly polarized light and a second incident element that selectively reflects the other circularly polarized light. Similarly, the incident element 24B1 can also be composed of a first incident element that selectively reflects right-circularly polarized light or left-circularly polarized light and a second incident element that selectively reflects the other circularly polarized light.

[0414] Furthermore, when the first incident diffraction section 26 has only an incident element 24A1 and the second incident diffraction section 28 has only an incident element 24B1, it can be a structure in which the incident element 24A1 selectively reflects right-circularly polarized light or left-circularly polarized light and the incident element 24B1 selectively reflects the other circularly polarized light.

[0415] Furthermore, when the first incident diffraction section 26 has only an incident element 24A1 and the second incident diffraction section 28 has only an incident element 24B1, it can be a structure in which the incident element 24A1 selectively reflects right-circularly polarized light or left-circularly polarized light and the incident element 24B1 selectively reflects circularly polarized light with the same rotation direction.

[0416] In the optical element 10 shown in the figure, the in-plane periods Λ of the emission elements 30A1 and 30A2 of the first emission diffraction section 32 in the emission section 16 are equal, and the in-plane periods Λ of the emission elements 30B1 and 30B2 of the second emission diffraction section 34 are equal.

[0417] However, the present invention is not limited thereto. For example, as described above, when the first incident diffraction section 26 has only incident element 24A1 and the second incident diffraction section 28 also has only incident element 24B1, the in-plane period Λ of the ejection elements 30A1 and 30A2 of the first ejection diffraction section 32 and the in-plane period Λ of the ejection elements 30B1 and 30B2 of the second ejection diffraction section 34 may be different.

[0418] At this point, the in-plane period Λ2 of the ejector element 30A2 and the ejector element 30B2 can be calculated as follows.

[0419] The in-plane period of the incident element constituting the incident diffraction section is set as Λ. in Furthermore, the angle formed by the in-plane rotation directions of the ejector elements 30A1 and 30A2, and the angle formed by the in-plane rotation directions of the ejector elements 30B1 and 30B2, are set as the cross angle ρ.

[0420] Then, the in-plane period Λ2 of the ejector element 30A2 and the ejector element 30B2 is obtained by the following formula.

[0421] Λ2=Λ in / |2cosρ|

[0422] At this time, the in-plane period Λ of the ejection element 30A1 of the first ejection diffraction section 32 corresponds to the in-plane period Λ of the incident element 24A1 of the first incident diffraction section 26, and the in-plane period Λ of the ejection element 30B1 of the second ejection diffraction section 34 is aligned with the in-plane period Λ of the incident element 24B1 of the second incident diffraction section 28.

[0423] Figure 1 In the optical element 10 shown, all the emission elements of the emission section 16 are arranged on one side of the light guide plate 12, but the present invention is not limited thereto. That is, the emission elements of the emission section 16 can be arranged separately from the two sides of the light guide plate 12.

[0424] As an example, such as Figure 21The optical element 10A shown in the conceptual diagram illustrates a structure in which emission elements 30A1 and 30B1 are provided on the side of the light guide plate based on the user U's observation position, and emission elements 30A2 and 30B2 are provided on the other side.

[0425] In this structure, the emitting elements 30A1 and 30B1 diffract and reflect light in a direction opposite to the observation position based on user U, but also as shown in later embodiments, with Figure 1 Similarly, with the optical element 10 shown, the user U is able to observe an image based on the light emitted from the light guide plate 12.

[0426] The optical element and image display device of the present invention have been described in detail above. However, the present invention is not limited to the above examples. Various improvements or modifications can be made without departing from the spirit of the present invention.

[0427] Example

[0428] The following examples illustrate the features of the present invention in more detail. The materials, reagents, dosages, quantities, proportions, processing contents, and processing steps shown in the following examples can be appropriately modified without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be limited by the specific examples shown below.

[0429] (Formation of liquid crystal diffraction element R-1)

[0430] (Formation of the orientation film)

[0431] A glass substrate was prepared as a support.

[0432] The following alignment film forming coating solution was applied to the support at 2500 rpm for 30 seconds using a spin coating method. The support with the coating solution was then dried on a hot plate at 60°C for 60 seconds, thereby forming the alignment film.

[0433] Coating solution for oriented film formation

[0434]

[0435] -Raw materials for photoorientation-

[0436] [Chemical Formula 1]

[0437]

[0438] (Exposure of the alignment film (exposure process))

[0439] use Figure 9 The exposure apparatus shown exposes the alignment film, thereby forming an alignment film P-1 with an alignment pattern.

[0440] In the exposure apparatus, a device that emits a laser beam with an emission wavelength of 355 nm is used as the laser. The exposure dose based on interference light is set to 3000 mJ / cm². 2 The cross angle (cross angle α) of the two beams is adjusted so that the in-plane period Λ (the length of the optical axis rotated 180°) of the orientation pattern formed by the interference of the two laser beams is 0.490 μm.

[0441] (Formation of a cholesterol-type liquid crystal layer)

[0442] As a liquid crystal composition for forming a cholesterol-type liquid crystal layer, the following liquid crystal composition LC-1 was prepared.

[0443] Liquid crystal composition LC-1

[0444]

[0445] Liquid crystal compound L-1

[0446] [Chemical Formula 2]

[0447]

[0448] Chiral reagent Ch-1

[0449] [Chemical Formula 3]

[0450]

[0451] The chiral reagent Ch-1 is a chiral reagent that forms a right-handed helix (right rotation).

[0452] The liquid crystal composition LC-1 described above was coated onto the alignment film P-1 using a spin coating method. Here, the film thickness was adjusted to be 14 μm after completion.

[0453] The coating of liquid crystal composition LC-1 was heated on a hot plate at 80°C for 3 minutes (180 seconds).

[0454] Next, the liquid crystal composition was exposed to a nitrogen atmosphere using a high-pressure mercury lamp through a 300 nm long-wavelength filter and a 350 nm short-wavelength filter at 80°C. Exposure was performed to ensure that the light irradiation dose, measured at a wavelength of 315 nm, was 20 mJ / cm². 2 .

[0455] Subsequently, a high-pressure mercury lamp at 1000 mJ / cm² was used in a nitrogen atmosphere at 80°C. 2 The coating is irradiated with ultraviolet light of wavelength 365nm, thereby curing the liquid crystal composition LC-1 and fixing the orientation of the liquid crystal compound to form a cholesterol-type liquid crystal layer.

[0456] Thus, a structure with a support, an alignment film, and a cholesterol-type liquid crystal layer was fabricated. Figure 3 The liquid crystal diffraction element shown.

[0457] The liquid crystal diffraction element was cut along the rotation direction of the optical axis, and the cross-section was observed using SEM. By resolving the SEM images, the film thickness d of the cholesterol-type liquid crystal layer, the period Λ in the liquid crystal alignment pattern, the length of the helical pitch P, and the slope (tilt angle θ) of the bright and dark parts relative to the main surface were measured. As a result, a shape was observed from the alignment film side toward the side separated from the alignment film, where the helical pitch P continuously increases along the thickness direction and the tilt angle θ also continuously increases.

[0458] The interface with the alignment film is set to 0 μm. The average helical pitch P in the thickness direction from 0 to 2.0 μm is 0.33 μm, and the tilt angle θ is 20°. The average helical pitch P in the thickness direction from 12.0 to 14.0 μm is 0.51 μm, and the tilt angle θ is 31°.

[0459] (Formation of liquid crystal diffraction elements R-2~6, L-1~5)

[0460] As shown in Table 1, the cross angle α (in-plane period Λ) during exposure of the alignment film P-1, the composition of the liquid crystal composition, and the film thickness were changed. Otherwise, the liquid crystal diffraction element was fabricated in the same manner as the liquid crystal diffraction element R-1, and the same measurements were performed.

[0461] In the liquid crystal diffraction elements L-1 to 5, the chiral reagent Ch-2 was used instead of the chiral reagent Ch-1.

[0462] Chiral reagent Ch-2

[0463] [Chemical Formula 4]

[0464]

[0465] The chiral reagent Ch-2 is a chiral reagent that forms a left-handed helix (left-handed rotation).

[0466] [Table 1]

[0467]

[0468]

[0469] [Example 1 and Comparative Example 1]

[0470] (Application in AR Glass)

[0471] Liquid crystal diffraction elements R-1 to 4, which are fabricated by peeling off the support, become... Figure 21The optical element was then transferred to the light guide plate as shown in Table 2, thereby fabricating the optical component and confirming the display effect in the AR glass. The planar shape of the optical component is similar to... Figure 2 same.

[0472] A glass plate (refractive index 1.70, thickness 0.50mm) was used as the light guide plate.

[0473] The in-plane rotation directions of each incident and ejector element are shown in Table 2, based on the viewing angle from the AR glass. Figure 22 In this example, for convenience, the in-plane rotation direction of the incident element A1 is set to 0°. The same applies to embodiments 2-6 shown below.

[0474] Figure 22 In the diagram, arrow A1 of the incident portion indicates the in-plane rotation direction of the incident element 24A1, arrow A2 indicates the in-plane rotation direction of the incident element 24A2, arrow B1 indicates the in-plane rotation direction of the incident element 24B1, and arrow B2 indicates the in-plane rotation direction of the incident element 24B2. Furthermore, Figure 22 In the diagram, arrow A1 of the ejection section indicates the in-plane rotation direction of the ejection element 30A1, arrow A2 of the ejection section indicates the in-plane rotation direction of the same ejection element 30A2, arrow B1 of the ejection section indicates the in-plane rotation direction of the ejection element 30B1, and arrow B2 of the ejection section indicates the in-plane rotation direction of the ejection element 30B2. Regarding this aspect, embodiments 2 to 6 are shown below. Figures 23-27 The same applies.

[0475] As shown in Table 2, Comparative Example 1 does not have a second incident diffraction section and a second exit diffraction section. That is, in Comparative Example 1, neither the second incident diffraction section nor the second exit diffraction section has the same characteristics as... Figure 22 The incident elements corresponding to arrows B1 and B2 are shown.

[0476] Furthermore, the display, which is an AR glass, uses a DLP projector.

[0477] As a result, it was confirmed that, compared with Comparative Example 1 which does not have a second incident diffraction section and a second emitted diffraction section, Example 1 is able to perform full RGB color display of the display surface over a wide range.

[0478] [Table 2]

[0479]

[0480] [Example 2]

[0481] As per Table 2 and Figure 23The structure and angle configuration of the liquid crystal diffraction elements R-1 to R-3 and L-1, L-2 and L-4 shown are otherwise confirmed in the same manner as in Example 1.

[0482] In Example 2, incident elements A1 and A2 are used by stacking a right-handed spiral liquid crystal diffraction element R-1 that selectively reflects right-handed circularly polarized light and a left-handed spiral liquid crystal diffraction element L-1 that selectively reflects left-handed circularly polarized light. Similarly, incident elements B1 and B2 are used by stacking a right-handed spiral liquid crystal diffraction element R-2 that selectively reflects right-handed circularly polarized light and a left-handed spiral liquid crystal diffraction element L-2 that selectively reflects left-handed circularly polarized light. The liquid crystal diffraction elements are arranged in a right-handed spiral to a left-handed spiral order from the light guide plate side. That is, in this example, one incident element is composed of a first incident element and a second incident element.

[0483] In this example, among the incident elements A1, A2, B1, and B2, the in-plane rotation directions of the right-handed spiral liquid crystal diffraction element R-1 and the left-handed spiral liquid crystal diffraction element L-1, as well as the right-handed spiral liquid crystal diffraction element R-2 and the left-handed spiral liquid crystal diffraction element L-2, differ by 180°. Therefore, in Figure 23 The center arrow indicates a two-way direction.

[0484] Similar to Example 1, the display effect in the AR glass was confirmed. As a result, it was confirmed that Example 2, compared to Comparative Example 1, also enables RGB color display across a wide range and covering the entire display surface. Furthermore, in Example 2, where the incident element is a left-handed liquid crystal diffraction element with a stacked spiral, a brighter and clearer display is achieved compared to Example 1.

[0485] [Example 3]

[0486] Figure 1 The configuration shown is based on Table 2 and Figure 24 The structure and angle configuration of the liquid crystal diffraction elements R-1 to R-3 and L-1, L-2 and L-4 shown are otherwise confirmed in the same manner as in Example 1.

[0487] Similar to Example 2, in Example 3, incident elements A1 and A2 are also stacked with a right-handed spiral liquid crystal diffraction element R-1 that selectively reflects right-handed circularly polarized light and a left-handed spiral liquid crystal diffraction element L-1 that selectively reflects left-handed circularly polarized light. Furthermore, in incident elements B1 and B2, a right-handed spiral liquid crystal diffraction element R-2 that selectively reflects right-handed circularly polarized light and a left-handed spiral liquid crystal diffraction element L-2 that selectively reflects left-handed circularly polarized light are stacked. Each liquid crystal diffraction element is arranged in a right-handed spiral, then a left-handed spiral order from the light guide plate side. That is, in this example, one incident element is also composed of a first incident element and a second incident element.

[0488] In this example, among the incident elements A1, A2, B1, and B2, the in-plane rotation directions of the right-handed spiral liquid crystal diffraction element R-1 and the left-handed spiral liquid crystal diffraction element L-1, as well as the right-handed spiral liquid crystal diffraction element R-2 and the left-handed spiral liquid crystal diffraction element L-2, differ by 180°. Therefore, in Figure 24 The center arrow also becomes bidirectional.

[0489] As a result, it was confirmed that Example 3, compared to Comparative Example 1, was able to perform RGB color display across a wider range and covering the entire display surface. Furthermore, in Example 3, which uses a stacked right-rotating liquid crystal diffraction element and a left-rotating liquid crystal diffraction element in the incident element, a brighter and clearer display was achieved compared to Example 1.

[0490] [Example 4]

[0491] Figure 1 The configuration shown is based on Table 2 and Figure 25 The liquid crystal diffraction elements R-1 to 3 and 5 and liquid crystal diffraction elements L-1, 2, 4 and 5 are configured and angled as shown. Except for this, the display of the AR glass was confirmed in the same manner as in Example 1. That is, in this example, the first incident diffraction section does not have incident element A2, and the second incident diffraction section does not have incident element B2.

[0492] Similar to Example 2, in this example, the incident element A1 is also stacked with a right-handed spiral liquid crystal diffraction element R-1 that selectively reflects right-handed circularly polarized light and a left-handed spiral liquid crystal diffraction element L-1 that selectively reflects left-handed circularly polarized light. Furthermore, in the incident element B1, a right-handed spiral liquid crystal diffraction element R-2 that selectively reflects right-handed circularly polarized light and a left-handed spiral liquid crystal diffraction element L-2 that selectively reflects left-handed circularly polarized light are stacked. The liquid crystal diffraction elements are arranged in a right-handed spiral, then a left-handed spiral order from the light guide plate side. That is, in this example, one incident element is composed of a first incident element and a second incident element.

[0493] In this example, in incident elements A1 and B1, the in-plane rotation directions of the right-handed spiral liquid crystal diffraction element R-1 and the left-handed spiral liquid crystal diffraction element L-1, as well as the right-handed spiral liquid crystal diffraction element R-2 and the left-handed spiral liquid crystal diffraction element L-2, differ by 180°. Therefore, in Figure 25 The center arrow also becomes bidirectional.

[0494] As a result, it was confirmed that Example 4, compared with Comparative Example 1, was able to perform RGB color display across a wide range and on the entire display surface of the monitor.

[0495] [Example 5]

[0496] Figure 1The configuration shown is based on Table 2 and Figure 26 The liquid crystal diffraction elements R-1, R-3, and R-5, and liquid crystal diffraction elements L-2, L-4, and L-5 are configured and angled as shown. Except for this, the AR glass display was confirmed in the same manner as in Example 1. That is, in this example, the first incident diffraction section does not have incident element A2, and the second incident diffraction section does not have incident element B2.

[0497] As a result, it was confirmed that Example 5, compared with Comparative Example 1, was able to perform RGB color display across a wide range and on the entire display surface of the monitor.

[0498] [Example 6]

[0499] Figure 1 The configuration shown is based on Table 2 and Figure 27 The structure and angle configuration of the liquid crystal diffraction elements R-1 to R-6 are shown. Apart from this, the AR glass display was confirmed in the same manner as in Example 1. That is, in this example, the first incident diffraction section does not have incident element A2, and the second incident diffraction section does not have incident element B2.

[0500] As a result, it was confirmed that Example 6, compared with Comparative Example 1, was able to perform RGB color display across a wide range and on the entire display surface of the monitor.

[0501] [Table 3]

[0502]

[0503] [Example 7]

[0504] Table 3 and Figure 28 and Figure 29 The configuration and angle arrangement of the liquid crystal diffraction elements R-1, R-2 and R-3 and the liquid crystal diffraction elements L-1, L-2 and L-4 shown are otherwise confirmed in the same manner as in Example 1.

[0505] As a result, it was confirmed that Example 7, compared with Comparative Example 1, is able to perform RGB color display across a wide range and on the entire display surface of the monitor.

[0506] [Example 8]

[0507] Table 3 and Figure 28 and Figure 29 The liquid crystal diffraction elements R-1, R-2, R-3 and R-4 and liquid crystal diffraction elements L-1, L-2, L-3 and L-4 are configured and angled as shown. Otherwise, the display of the AR glass was confirmed in the same manner as in Example 1.

[0508] As a result, it was confirmed that Example 8, compared with Comparative Example 1, was able to perform RGB color display across a wide range and on the entire display surface of the monitor.

[0509] [Example 9]

[0510] Table 3 and Figure 30 and Figure 31 The configuration and angle arrangement of liquid crystal diffraction elements R-1 and R-3 and liquid crystal diffraction elements L-1 and L-3 are shown. Otherwise, the display of AR glass was confirmed in the same manner as in Example 1.

[0511] As a result, it was confirmed that Example 9, compared with Comparative Example 1, is able to perform RGB color display across a wide range and on the entire display surface of the monitor.

[0512] Based on the above results, the effectiveness of the present invention can be clearly demonstrated.

[0513] Industrial availability

[0514] It can be preferentially used in image display devices such as AR glass.

[0515] Symbol Explanation

[0516] 10, 10A - Optical element; 12 - Light guide plate; 14 - Incident section; 16 - Emission section; 20 - Display; 24A1, 24A2, 24B1, 24B2 - Incident diffraction element; 26 - First incident diffraction section; 28 - Second incident diffraction section; 30A1, 30A2, 30B1, 30B2 - Emission diffraction element; 32 - First emission diffraction section; 34 - Second emission diffraction section 50-Support, 52-Orientation film, 54-Liquid crystal layer, 40-Liquid crystal compound, 40A-Optical axis, 42-Bright area, 44-Dark area, 50-Support, 52-Orientation film, 54-Liquid crystal layer, 60-Exposure device, 62-Laser, 64-Light source, 65-λ / 2 plate, 68-Polarization beam splitter, 70A, 70B-Mirrors, 72A, 72B-λ / 4 plate, R R - Right-handed circularly polarized light, red light; M - laser beam; MA, MB - ray; P O - Linearly polarized light, P R - Right-handed circularly polarized light, P L - Left-handed circularly polarized light, L1, L4 - Incident light, L2, L5 - Transmitted light, U - User, D - Arrangement axis, Λ - In-plane period, P - Spiral pitch.

Claims

1. An optical element having a light guide plate, an incident portion that makes an incident light incident on the light guide plate, and an emission portion that emits a light from the light guide plate, the incident portion has a plurality of incident diffraction portions each having one or more incident diffraction elements, and the emission portion has a plurality of emission diffraction portions each having one or more emission diffraction elements, the incident diffraction elements and the emission diffraction elements have liquid crystal diffraction layers formed using a composition containing a liquid crystal compound, the liquid crystal diffraction layers have a liquid crystal alignment pattern in which an orientation of an optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in-plane, in the liquid crystal alignment pattern, a direction in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in-plane is defined as an in-plane rotation direction, and a length in the in-plane rotation direction in which the orientation of the optical axis derived from the liquid crystal compound rotates by 180° is defined as an in-plane period, the in-plane rotation directions of the liquid crystal diffraction layers of at least two of the plurality of incident diffraction elements are different from each other, the in-plane rotation directions of the liquid crystal diffraction layers of at least two of the plurality of emission diffraction elements are different from each other.

2. The optical element according to claim 1, wherein the in-plane periods and the in-plane rotation directions of the liquid crystal diffraction layers of at least two of the plurality of incident diffraction elements are different from each other, the in-plane periods of the liquid crystal diffraction layers of at least one of the incident diffraction elements and at least one of the emission diffraction elements are equal to each other.

3. The optical element according to claim 1, wherein the in-plane periods of the liquid crystal diffraction layers of at least two of the plurality of emission diffraction elements are equal to each other.

4. The optical element according to any one of claims 1 to 3, wherein the in-plane periods of the liquid crystal diffraction layers of at least two of the plurality of emission diffraction elements are different from each other.

5. The optical element according to any one of claims 1 to 3, wherein the incident diffraction portion has a plurality of the incident diffraction elements, the in-plane periods of the liquid crystal diffraction layers of at least two of the plurality of incident diffraction elements are equal to each other and the in-plane rotation directions thereof are different from each other, the emission diffraction portion has a plurality of the emission diffraction elements, the in-plane periods of the liquid crystal diffraction layers of at least two of the plurality of emission diffraction elements are equal to each other and the in-plane rotation directions thereof are different from each other.

6. The optical element according to claim 5, wherein in n of the incident diffraction portions in the incident portion and n of the emission diffraction portions in the emission portion, there are n groups of combinations of the incident diffraction portions and the emission diffraction portions each having the in-plane periods of the liquid crystal diffraction layers of the incident diffraction elements equal to the in-plane periods of the liquid crystal diffraction layers of the emission diffraction elements, where n is an integer of 1 or more.

7. The optical element according to any one of claims 1 to 3, wherein at least one of the incident diffraction portions has two of the incident diffraction elements, In at least one of the incident diffraction sections having two of the incident diffraction elements, the in-plane rotation directions of the liquid crystal diffraction layers of the two incident diffraction elements form an angle of 90°.

8. The optical element according to any one of claims 1 to 3, wherein the incident section includes a plurality of the incident diffraction sections each having two incident diffraction elements, at least two of the incident diffraction sections are identical, and the in-plane rotation directions of the liquid crystal diffraction layers of the two incident diffraction elements included in the incident diffraction sections form an angle of 45°.

9. The optical element according to any one of claims 1 to 3, wherein the incident section includes a plurality of the incident diffraction sections each having two incident diffraction elements, at least two of the incident diffraction sections are identical, and the in-plane rotation directions of the liquid crystal diffraction layers of the two incident diffraction elements included in the incident diffraction sections form an angle of 90°.

10. The optical element according to any one of claims 1 to 3, wherein at least one of the exit diffraction sections has two of the exit diffraction elements, in at least one of the exit diffraction sections having two of the exit diffraction elements, the in-plane rotation directions of the liquid crystal diffraction layers of the two exit diffraction elements form an angle of 90°.

11. The optical element according to any one of claims 1 to 3, wherein the exit section includes a plurality of the exit diffraction sections each having two exit diffraction elements, at least two of the exit diffraction sections are identical, and the in-plane rotation directions of the liquid crystal diffraction layers of the two exit diffraction elements included in the exit diffraction sections form an angle of 45°.

12. The optical element according to any one of claims 1 to 3, wherein the exit section includes a plurality of the exit diffraction sections each having two exit diffraction elements, at least two of the exit diffraction sections are identical, and the in-plane rotation directions of the liquid crystal diffraction layers of the two exit diffraction elements included in the exit diffraction sections form an angle of 90°.

13. The optical element according to any one of claims 1 to 3, wherein the liquid crystal diffraction layer is a cholesteric liquid crystal layer formed of a fixed cholesteric phase.

14. The optical element according to claim 13, wherein in a cross section observed by a scanning electron microscope, bright and dark portions derived from the cholesteric phase of the cholesteric liquid crystal layer are inclined with respect to a main surface of the cholesteric liquid crystal layer, and when an angle formed by the main surface of the cholesteric liquid crystal layer and the bright and dark portions of the cross section of the cholesteric liquid crystal layer is set as an inclination angle θ, the cholesteric liquid crystal layer has a region in which the inclination angle θ is 10° or more.

15. The optical element according to claim 14, wherein the cholesteric liquid crystal layer has a region in which the inclination angle θ continuously increases toward one direction in a thickness direction, and a difference between a maximum value and a minimum value of the inclination angle θ in the thickness direction is 10° or more.

16. The optical element according to claim 13, wherein The incident diffraction elements have two layers of the cholesteric liquid crystal layer whose selective reflection circularly polarized light rotation directions are different from each other.

17. The optical element according to claim 13, wherein The emission portion has two emission diffraction portions including two emission diffraction elements, the two emission diffraction elements having the cholesteric liquid crystal layer whose selective reflection circularly polarized light rotation directions are the same, In the two emission diffraction portions, the cholesteric liquid crystal layers of the emission diffraction elements constituting each of the emission diffraction portions have selective reflection circularly polarized light rotation directions different from each other.

18. The optical element according to claim 16, wherein The in-plane rotation directions of the cholesteric liquid crystal layers whose selective reflection circularly polarized light rotation directions are different from each other are different by 180°.

19. An image display device, comprising: The optical element according to any one of claims 1 to 18; and A display element that irradiates the incident diffraction portion with an image.

Images