Optical element and image display device

Abstract

The purpose of the present invention is to provide an optical element capable of achieving a wide FOV, and an image display device using said optical element. An optical element according to the present invention comprises: a light guide plate; a light-entering part that has a liquid crystal diffraction layer and causes light to enter the light guide plate; and a light-emitting part that has a liquid crystal diffraction layer and emits the light from the light guide plate. In the liquid crystal diffraction layer, the direction of an optical axis derived from a liquid crystal compound changes while continuously rotating along at least one in-plane direction. The light-entering part includes, in the plane, at least four first regions of two or more types which have liquid crystal alignment patterns in which in-plane rotation directions are different from each other. The average area of the first regions is 9 mm2 or less. The light-emitting part includes, in the plane, at least 16 second regions (14A-14H) of three or more types which have liquid crystal alignment patterns in which in-plane rotation directions (D) are different from each other. The average area of the second regions (14A-14H) is 9 mm2 or less. In the light-emitting part, the area ratios of at least one type of the second regions (14A-14H) are different from each other in the plane.

Description

Optical elements and image display devices

[0001] The present invention relates to an optical element using a liquid crystal diffraction element that diffracts incident light, and to an image display device using this optical element.

[0002] In recent years, Augmented Reality (AR) glasses, such as those described in Non-Patent Document 1, which overlay virtual images and various types of information onto the actual view, have been put into practical use. AR glasses are also known as smart glasses, head-mounted displays (HMDs), and AR glasses.

[0003] As shown in Non-Patent Document 1, AR glasses, as an example, display a virtual image overlaid on the scene the user is actually seeing by having the image displayed by a display (optical engine) incident on one end of a light guide plate, propagating through it, and emitting it from the other end. In AR glasses, a diffraction element is used to diffract (refract) the light (projected light) from the display and have it incident on one end of the light guide plate. This introduces the light into the light guide plate at an angle, causing it to propagate within the light guide plate. The light that has propagated through the light guide plate is then diffracted again by a diffraction element at the other end of the light guide plate and emitted from the light guide plate to the user's observation position.

[0004] Furthermore, Patent Document 1 describes an AR glasses system in which an image consisting of three colors of light—red, green, and blue—is projected from a display, each light is diffracted by an incident diffraction element and incident on a light guide plate, propagated through the light guide plate, and emitted from the light guide plate to the user's observation position by an exit diffraction element, thereby displaying a superimposed image of the three colors of light to show a color image.

[0005] International Publication No. 2017 / 180403

[0006] Bernard C. Kress et al., Towards the Ultimate Mixed Reality Experience: HoloLens Display Architecture Choices, SID 2017 DIGEST, pp.127-131

[0007] AR glasses require a wide field of view (FOV), meaning that the user can observe a large area of ​​the image displayed on the screen without changing their gaze.

[0008] In response to this, the AR glasses described in Patent Document 1 describe that light incident from an incident diffraction element and propagating within the light guide plate is further diffracted by an intermediate diffraction element, propagated within the light guide plate, and then emitted by an exit diffraction element. In the AR glasses described in Patent Document 1, this expands the emission area of ​​light from the exit diffraction element, thereby expanding the field of view (FOV).

[0009] However, currently, the field of view (FOV) of AR glasses is still not sufficient, and there is a desire for AR glasses that can achieve a wider FOV.

[0010] The object of the present invention is to solve the problems of the prior art and to provide an optical element used in AR glasses and the like that can achieve a wider field of view (FOV), and an image display device using this optical element.

[0011] To solve this problem, the present invention has the following configuration: [1] A light guide plate, an incident part for injecting light into the light guide plate, and an outgoing part for emitting light from the light guide plate, wherein the incident part and the outgoing part have a liquid crystal diffraction layer formed using a composition containing a liquid crystal compound, the liquid crystal diffraction layer has a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, with at least one direction being the in-plane rotation direction, and the length of the rotation of the optical axis derived from the liquid crystal compound in the in-plane rotation direction being 180° being the in-plane period, the liquid crystal diffraction layer of the incident part contains at least four first regions of at least two types, each having a liquid crystal orientation pattern with different in-plane rotation directions, and the average area of ​​the first regions is 9 mm ２ The following is the case: The liquid crystal diffraction layer of the emission section contains at least 16 second regions of at least three different types, each having a liquid crystal orientation pattern with different in-plane rotation directions, and the average area of ​​the second regions is 9 mm².２ The optical element is characterized in that, in the liquid crystal diffraction layer of the output portion, the area ratio of at least one type of second region is different in plane. [2] The optical element according to [1], wherein when a region in the output portion is defined as a primary light guide region, which extends along the in-plane rotation direction X of one of the first regions in the input portion and has the width of the input portion in a direction perpendicular to the in-plane rotation direction X, the area ratio of the second region Y having an in-plane rotation direction parallel to the in-plane rotation direction X that exists in the primary light guide region of the output portion is smaller than the area ratio of the second region Y that exists in a region other than the primary light guide region of the output portion. [3] The device comprises a light guide plate, an incident part for injecting light into the light guide plate, and an outgoing part for emitting light from the light guide plate. The incident part and the outgoing part have a liquid crystal diffraction layer formed using a composition containing a liquid crystal compound. The liquid crystal diffraction layer has a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane. When at least one direction is defined as the in-plane rotation direction, and the length of the 180° rotation of the optical axis derived from the liquid crystal compound in the in-plane rotation direction is defined as the in-plane period, the outgoing part contains at least 16 third regions of at least two different types, each having a liquid crystal orientation pattern with a different in-plane rotation direction, and the average area of ​​the third regions is 9 mm². ２The optical element is characterized in that, in the liquid crystal diffraction layer of the output portion, the area ratio of at least one type of third region is different in plane. [4] The optical element according to [3], wherein when the region within the output portion that extends along the in-plane rotation direction X of the incident portion and has the width of the incident portion in a direction perpendicular to the in-plane rotation direction X is defined as the primary light guide region, the area ratio of the third region Y having an in-plane rotation direction parallel to the in-plane rotation direction X that exists within the primary light guide region of the output portion is smaller than the area ratio of the third region Y that exists in a region other than the primary light guide region of the output portion. [5] The optical element according to [1] or [2], wherein at least two of the first regions have different in-plane periods. [6] The optical element according to any one of [1] to [2] or [5], wherein at least two of the second regions have different in-plane periods. [7] The optical element according to [3] or [4], wherein at least two of the third regions have different in-plane periods. [8] The optical element according to any one of [1] to [2], [5] to [6], wherein the liquid crystal diffraction layer of the incident portion has a region without a liquid crystal alignment pattern between the first regions. [9] The optical element according to any one of [1] to [2], [5] to [6], or [8], wherein the liquid crystal diffraction layer of the exit portion has a region without a liquid crystal alignment pattern between the second regions.

[10] The optical element according to any one of [3] to [4], or [7], wherein the liquid crystal diffraction layer of the exit portion has a region without a liquid crystal alignment pattern between the third regions.

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

[10] , wherein the region without a liquid crystal alignment pattern is located in a plane other than the incident portion and the exit portion.

[12] The optical element according to any one of [8] to

[11] , wherein at least a portion of the plane of the region without a liquid crystal alignment pattern is optically isotropic.

[13] The optical element according to any one of [8] to

[11] , wherein at least a portion of the plane of the region without a liquid crystal alignment pattern is optically anisotropic.

[14] An optical element according to any one of [1] to [2], [5] to [6], [8] to [9], or

[11] to

[13] , wherein at least two first regions have different optical thicknesses from each other.

[15] An optical element according to any one of [1] to [2], [5] to [6], [8] to [9], or

[11] to

[14] , wherein at least two second regions have different optical thicknesses from each other.

[16] An optical element according to any one of [3] to [4], [7],

[10] to

[13] , wherein at least two third regions have different optical thicknesses from each other.

[17] An optical element according to any one of [1] to [2], [5] to [6], [8] to [9],

[11] to

[15] , wherein at least two first regions have different diffraction efficiencies from each other.

[18] An optical element according to any one of [1] to [2], [5] to [6], [8] to [9],

[11] to

[15] ,

[17] , wherein at least two second regions have different diffraction efficiencies from each other.

[19] An optical element according to any one of [3] to [4], [7],

[10] to

[13] ,

[16] , wherein at least two third regions have different diffraction efficiencies from each other.

[20] An optical element according to any one of [1] to

[19] , wherein the liquid crystal diffraction layer of at least one of the incident portion and the exit portion has a region that is a cholesterically oriented cholesteric liquid crystal layer in a region having a liquid crystal alignment pattern.

[21] The optical element according to

[20] , wherein the cholesteric liquid crystal layer has regions in the plane where the inclination angles of the bright and dark parts originating from the cholesteric liquid crystal phase are different with respect to the main surface of the cholesteric liquid crystal layer, as observed in a cross-section by a scanning electron microscope.

[22] The average area of ​​the first region is 0.3 mm. ２ An optical element described in any of the following: [1] to [2], [5] to [6], [8] to [9],

[11] to

[15] ,

[17] to

[18] , or

[20] to

[21] .

[23] The average area of ​​the second region is 0.3 mm ２ An optical element as described in any of the following: [1] to [2], [5] to [6], [8] to [9],

[11] to

[15] ,

[17] to

[18] , or

[20] to

[22] .

[24] An optical element having an average area of ​​0.3 mm in the third region. ２ An optical element according to any of the following: [3] to [4], [7],

[10] to

[13] ,

[16] ,

[19] to

[21] .

[25] An image display device having an optical element according to any of the following: [1] to

[24] , and a display element that illuminates an image onto an incident part.

[0012] According to the present invention, it is possible to provide an optical element capable of displaying a wide field of view (FOV) in, for example, AR glasses, and an image display device using this optical element.

[0013] This figure conceptually shows an example of an image display device having the optical element of the present invention. This is a top view of the optical element in Figure 1. This figure conceptually shows an example of a liquid crystal diffraction layer divided into multiple regions. This figure conceptually shows an example of a cross-sectional view of a liquid crystal diffraction layer. This figure conceptually shows an example of a top view of a liquid crystal diffraction layer. This figure conceptually shows an example of a cross-sectional view of a liquid crystal diffraction layer. This figure conceptually shows an example of a cross-sectional view of a liquid crystal diffraction element of the present invention. This is a conceptual diagram for explaining the operation of light guidance in the optical element of the present invention. This figure shows an example of an exposure apparatus for an alignment film. This figure defines the angle of the orientation direction of the liquid crystal compound. This figure shows an example of an exposure mask for creating regions where the liquid crystal is not oriented between divided orientation regions. This figure shows the optical thickness profile of the liquid crystal diffraction layer in the optical element of the embodiment. This figure shows an example of the arrangement of regions in the liquid crystal diffraction layer of the incident and exit parts of the present invention. This is a vector diagram of k when light is guided from the incident part 131 to the exit part region 132 in Figure 13. This figure shows another example of the arrangement of regions in the liquid crystal diffraction layer of the incident and exit parts of the present invention. This is a vector diagram of k when light is guided from the incident portion 151 to the exit portion region 152 in Figure 15. This is another vector diagram of k when light is guided from the incident portion 151 to the exit portion region 152 in Figure 15. This is a diagram to explain the operation of the optical element of the present invention.

[0014] The optical element and image display device of the present invention will be described in detail below based on preferred embodiments shown in the attached drawings.

[0015] In this specification, numerical ranges expressed using "~" mean a range that includes the numbers before and after "~" as the lower and upper limits. In this specification, "(meth)acrylate" is used to mean "either acrylate or methacrylate, or both." In this specification, "identical" includes the error range generally accepted in the art. In this specification, when "all," "all," and "entire surface" are used, they include not only 100% but also the error range generally accepted in the art, such as 99% or more, 95% or more, or 90% or more. In terms of angles, "orthogonal" and "parallel" mean within ±5° of the exact angle, and in terms of angles, "identical" means that the difference from the exact angle is within 5 degrees unless otherwise specified. The difference from the exact angle is preferably less than 4 degrees, and more preferably less than 3 degrees.

[0016] In this specification, visible light refers to electromagnetic waves with wavelengths visible to the human eye, specifically light in the wavelength range of 380 to 780 nm. Invisible light refers to light in the wavelength range of less than 380 nm and light in the wavelength range of more than 780 nm. However, within visible light, light in the wavelength range of 420 to 490 nm is blue light, light in the wavelength range of 495 to 570 nm is green light, and light in the wavelength range of 620 to 750 nm is red light.

[0017] In this specification, the selective reflection center wavelength refers to the average value of two wavelengths that exhibit the half-maximum transmittance: T1 / 2 (%), given that Tmin (%) is the minimum transmittance of the object (component) in question. Formula for calculating half-maximum transmittance: T1 / 2 = 100 - (100 - Tmin) ÷ 2 Furthermore, the statement that the selective reflection center wavelengths of multiple layers are "equal" does not mean that they are strictly equal, and errors within a range that does not affect the optical performance are permitted. Specifically, the statement that the selective reflection center wavelengths of multiple objects are "equal" means that the difference in the selective reflection center wavelengths between each object is 20 nm or less, preferably 15 nm or less, and more preferably 10 nm or less.

[0018] [Optical element and image display device of the first embodiment] The optical element of the first embodiment of the present invention has a light guide plate, an incident part for injecting light into the light guide plate, and an outgoing part for emitting light from the light guide plate. The incident part and the outgoing part have a liquid crystal diffraction layer (liquid crystal diffraction element) formed using a composition containing a liquid crystal compound. The liquid crystal diffraction layer has a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane. When at least one direction is defined as the in-plane rotation direction, and the length of the 180° rotation of the orientation of the optical axis derived from the liquid crystal compound in the in-plane rotation direction is defined as the in-plane period, the incident part is divided into four or more regions consisting of at least two or more in-plane rotation directions, and the outgoing part is divided into sixteen or more regions consisting of at least three or more in-plane rotation directions. In other words, the liquid crystal diffraction layer of the incident portion contains at least four first regions of at least two types, each having a liquid crystal orientation pattern with different in-plane rotation directions, and the exit portion contains at least sixteen second regions of at least three types, each having a liquid crystal orientation pattern with different in-plane rotation directions. Furthermore, in the liquid crystal diffraction layer of the exit portion of the optical element of the present invention, the area ratio of at least one type of second region differs within the plane.

[0019] The image display device of the present invention is an image display device having the optical element and the display element described above, wherein the display element is arranged to illuminate the incident portion of the optical element with an image.

[0020] The optical element of the present invention has multiple regions with different in-plane rotation directions in the liquid crystal diffraction layer at the incident and exit portions, thereby enabling the expansion of the field of view (FOV) by multiple light guide paths when used in an image display device such as AR glasses. Furthermore, the optical element of the present invention has at least one type of second region with a different area ratio in the liquid crystal diffraction layer at the exit portion, thereby enabling the brightness of the image guided by the optical element to be made uniform across the plane. The operation of the optical element of the present invention will be described in detail later.

[0021] The number of in-plane divisions of the liquid crystal diffraction layer in the incident part, that is, the number of the first regions, is 4 or more, preferably 40 or more, and more preferably 400 or more. The number of in-plane divisions of the liquid crystal diffraction layer in the exit part, that is, the number of the second regions, is 16 or more, preferably 640 or more, and more preferably 6400 or more. The sizes of the divided regions, that is, the size of the first region and the size of the second region are each ２ 9 mm or less, preferably ２ 3 mm or less, and more preferably ２ 0.3 mm or less. By increasing the number of divisions and reducing the region size, excellent sharpness of the display image can be obtained.

[0022] In addition, in each first region of the liquid crystal diffraction layer in the incident part, two or more types of in-plane rotation directions are required in order to improve the FOV, and preferably 3 to 12 types. In each second region of the liquid crystal diffraction layer in the exit part, three or more types of in-plane rotation directions are required, preferably 4 to 36 types, and more preferably 7 to 12 types. By appropriately designing the in-plane rotation direction and the in-plane period of the aligned liquid crystal compound in the incident part and the exit part, it is possible to prevent color breakage of the display image even when a plurality of light guiding paths are formed.

[0023] In the liquid crystal diffraction layer in the incident part, the arrangement of the first regions having different in-plane rotation directions is not particularly limited, but is preferably random. In addition, their abundance ratios can be freely adjusted in consideration of the uniformity of luminance and color tone.

[0024] On the other hand, in the liquid crystal diffraction layer in the exit part, the arrangement of the second regions having different in-plane rotation directions is not particularly limited, but in the plane of the exit part, the abundance ratio (area ratio) of the second regions having a certain in-plane rotation direction is preferably different in the plane of the exit part.

[0025] Specifically, in the region of the discharge portion located in a plane extending from the discharge portion in a direction parallel to the in-plane rotation direction in the first region located in the discharge portion, it is more preferable that the ratio of divided regions where the parallel direction and the in-plane rotation direction are parallel is smaller than the ratio of the discharge portion region located in a different plane from the discharge portion located in the plane extending from the discharge portion in a parallel direction.

[0026] In other words, when the region within the output section that extends along the in-plane rotation direction X of one of the first regions within the input section and has a width of the input section perpendicular to the in-plane rotation direction X is defined as the primary light guide region, it is preferable that the area ratio of the second region Y having an in-plane rotation direction parallel to the in-plane rotation direction X and existing within the primary light guide region of the output section is smaller than the area ratio of the second region Y existing in regions other than the primary light guide region of the output section.

[0027] A second region Y1, which is parallel to the in-plane rotation direction X and has an in-plane rotation direction opposite to the in-plane rotation direction X, has a diffraction effect that causes light incident from the direction in which the diffracted light at the incident part propagates to be emitted from the light guide plate toward the user. Similarly, a second region Y2, which is parallel to the in-plane rotation direction X and has an in-plane rotation direction in the same direction as the in-plane rotation direction X, has a diffraction effect that causes light incident from the direction in which the diffracted light at the incident part propagates to be emitted from the light guide plate toward the opposite side from the user. These second regions Y1 and Y2 are collectively referred to as the second region Y. On the other hand, a second region having a different in-plane rotation direction from the second region Y diffracts light incident from the direction in which the diffracted light at the incident part propagates to propagate in other directions within the plane, and does not emit from the light guide plate. Therefore, if the area ratio of the second region Y within the primary light guide region of the emission section is large, the light diffracted at the incident section and guided through the light guide plate will be directly emitted from the light guide plate by the second region Y, resulting in the brightness of the part of the image emitted from the primary light guide region being higher than the brightness of the part of the image emitted from regions other than the primary light guide region. To address this, by making the area ratio of the second region Y within the primary light guide region smaller than the area ratio of the second region Y in regions other than the primary light guide region, the direct emission of light diffracted at the incident section and guided through the light guide plate by the second region Y is suppressed, and the light is diffracted by the second region other than the second region Y so that it propagates in other directions within the plane. As a result, the light is guided to spread two-dimensionally within the plane of the emission section, allowing light to be emitted uniformly from various positions within the plane of the emission section, thereby improving the uniformity of brightness and color of the displayed image.

[0028] In this way, by varying the relative proportions of the second region having different in-plane rotation directions within the emission section, the uniformity of brightness and color of the displayed image can be improved. Furthermore, these relative proportions can be freely adjusted while considering the uniformity of brightness and color.

[0029] In the primary light-guiding region of the output section, located in a plane extending from the input section toward the output section in a direction parallel to the in-plane rotation direction of the first region, the ratio of the existence of a second region Y where the direction parallel to the in-plane rotation direction of the first region is parallel to the in-plane rotation direction is preferably 1 / 2 or less, more preferably 1 / 10 or less, and even more preferably 1 / 20 or less, compared to the ratio of the existence of a second region Y located in a plane different from the output section, which is located in a plane different from the output section, which is located in a plane extending from the input section toward the output section in a direction parallel to the in-plane rotation direction of the first region.

[0030] In this invention, the area ratio (proportion of existence) of a certain type of second region (the second region Y described above) is determined by dividing the liquid crystal diffraction layer of the output section into four or more equal-area regions, calculating the area ratio of this second region in each region, and determining if the variation in the area ratio of this second region calculated in each region: {(maximum value - minimum value) / maximum value} × 100% is 5% or more, then the area ratios are considered to be different. The number of regions to which the region is divided is not particularly limited as long as it is less than or equal to "total number of second regions in the liquid crystal diffraction layer of the output section / number of types of second regions". As an example, in the example shown in Figure 2, the output section 3 is divided into three equal-area regions in the vertical direction in the figure, and also divided into three equal-area regions in the horizontal direction, for a total of nine regions. The area ratio of the second region Y in each region is then calculated, and the variation in area ratio: {(maximum value - minimum value) / maximum value} × 100% is determined.

[0031] It is preferable to have a region without a liquid crystal alignment pattern between adjacent liquid crystal pattern alignment regions. That is, in the liquid crystal diffraction layer of the incident portion, it is preferable to have a region without a liquid crystal alignment pattern between the first regions. Similarly, in the liquid crystal diffraction layer of the emission portion, it is preferable to have a region without a liquid crystal alignment pattern between the second regions. Further, the region without a liquid crystal alignment pattern is preferably optically isotropic. Alternatively, the region without a liquid crystal alignment pattern may be optically anisotropic. For example, the region without a liquid crystal alignment pattern may be a region where the liquid crystal compound is uniaxially aligned, twisted, or cholesterically aligned. The distance between adjacent alignment regions, that is, the width of the region without a liquid crystal alignment pattern, is preferably 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.1 mm or less. By providing a region without a liquid crystal alignment pattern, the contrast of the displayed image can be improved.

[0032] Further, it is preferable that the incident portion and the emission portion each have a region composed of at least two or more types of in-plane periods. That is, in the liquid crystal diffraction layer of the incident portion, at least two of the first regions preferably have different in-plane periods from each other. Also, in the liquid crystal diffraction layer of the emission portion, at least two of the second regions preferably have different in-plane periods from each other.

[0033] Specifically, for example, in the liquid crystal diffraction layer of the incident portion, the first A region and the first B region having different in-plane rotation directions may have different in-plane periods from each other. Alternatively, in the liquid crystal diffraction layer of the incident portion, the first A-1 region and the first A-2 region having the same in-plane rotation direction may have different in-plane periods from each other.

[0034] Similarly, for example, in the liquid crystal diffraction layer of the emission portion, the second A region and the second B region having different in-plane rotation directions may have different in-plane periods from each other. Alternatively, in the liquid crystal diffraction layer of the emission portion, the second A-1 region and the second A-2 region having the same in-plane rotation direction may have different in-plane periods from each other.

[0035] Further, in the incident portion or the exit portion, it is preferable that each divided region has regions with different optical thicknesses. That is, in the liquid crystal diffraction layer of the incident portion, at least two of the first regions preferably have different optical thicknesses from each other. Also, in the liquid crystal diffraction layer of the exit portion, at least two of the second regions preferably have different optical thicknesses from each other. Here, the optical thickness of the liquid crystal diffraction layer is Δn×d, where d is the thickness of the liquid crystal diffraction layer and Δn is the birefringence of the liquid crystal compound contained in the liquid crystal diffraction layer. Therefore, the optical thickness can be made different by varying Δn or the thickness d.

[0036] Note that the first regions having different optical thicknesses from each other may have the same in-plane rotation direction or different in-plane rotation directions. Similarly, the second regions having different optical thicknesses from each other may have the same in-plane rotation direction or different in-plane rotation directions.

[0037] An example of an image display device including the optical element of the first embodiment of the present invention is shown in FIG. 1. Also, a top view of the optical element shown in FIG. 1 is shown in FIG. 2.

[0038] The image display device 18 shown in FIG. 1 has an optical element 10 and a display (display element) 1.

[0039] The optical element 10 has a light guide plate 4, an incident portion 2 and an exit portion 3 disposed on one main surface of the light guide plate 4. The incident portion 2 is a diffraction element that diffracts light (image) from the display 1 at an angle that allows total internal reflection within the light guide plate 4 and causes it to enter the light guide plate 4. The exit portion 3 is a diffraction element that diffracts the light guided within the light guide plate 4 at an angle deviating from the total internal reflection angle and causes it to exit the light guide plate 4. The incident portion 2 and the exit portion 3 are formed using a composition containing a liquid crystal compound and have a liquid crystal diffraction layer (liquid crystal diffraction element) having a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound continuously changes while rotating along at least one direction in the plane. Note that the main surface is the largest surface of a plate-like object (sheet-like object, film-like object).

[0040] Furthermore, in the example shown in Figure 2, the shape of the light guide plate 4 when viewed from a direction perpendicular to the main surface (hereinafter also referred to as a plan view) has the shape of one lens in the AR glasses. Also, in the plan view, the incident portion 2 is approximately circular and is provided at the left and right ends of the light guide plate 4. Also, in the plan view, the output portion 3 is approximately rectangular and is provided so as to surround the position where the incident portion 2 is located. The size (area) of the output portion 3 is larger than that of the incident portion 2.

[0041] The display 1 is positioned on the side of the optical element 10 opposite to the side on which the incident portion 2 is located, at a position facing the incident portion 2. The position on the side of the optical element 10 opposite to the side on which the output portion 3 is located, at a position facing the output portion 3, is the observation position for the user 5.

[0042] In the image display device 18, light emitted from the display 1 is diffracted by the incident part 2, guided through the exit part 3 and the light guide plate 4, and a portion of the light is emitted towards the user by the exit part 3. The shape and arrangement of the incident part 2 and the exit part 3 can be adjusted according to the design of the AR glasses.

[0043] In the example shown in Figure 1, the incident section 2 and the outgoing section 3 are reflective diffracting elements that reflect and diffract light, but the system is not limited to this. The incident section 2 and / or the outgoing section 3 may also be transmissive diffracting elements that transmit and diffract light. In this case, the display 1 is positioned on the surface where the incident section 2 is located, facing the incident section 2. The position on the surface where the outgoing section 3 is located, facing the outgoing section 3, becomes the observation position for the user 5.

[0044] Furthermore, in the example shown in Figure 1, the incident section 2 and the outgoing section 3 are arranged on the same main surface of the light guide plate 4, but the configuration is not limited to this. The incident section 2 may be arranged on one main surface of the light guide plate 4, and the outgoing section 3 may be arranged on the other main surface of the light guide plate 4.

[0045] The inlet section 2 and the outlet section 3 may be provided integrally as a single layer, or they may be provided separately. Furthermore, if they are provided integrally, there may be a region between the inlet section 2 and the outlet section 3 that does not have a liquid crystal alignment pattern.

[0046] In the optical element of the present invention, the incident portion 2 includes four or more first regions of two or more types, each having a different direction (in-plane rotation direction) in the liquid crystal alignment pattern, and the exit portion 3 includes sixteen or more second regions of three or more types, each having a different direction (in-plane rotation direction) in the liquid crystal alignment pattern. This point will be explained using Figure 3. Note that the liquid crystal diffraction layer in the incident portion 2 and the liquid crystal diffraction layer in the exit portion 3 have similar configurations except for the number of types of regions with different in-plane rotation directions and the total number of regions. Therefore, the liquid crystal diffraction layer of the exit portion 3 will be described as a representative example below.

[0047] Figure 3 is a magnified view of a portion of the liquid crystal diffraction layer of the ejection section 3. In the example shown in Figure 3, the liquid crystal diffraction layer has 16 second regions 14A to 14H of eight different types, each with a different in-plane rotation direction.

[0048] First, the in-plane rotation direction will be explained using Figure 5. Figure 5 is a partially enlarged view of one second region as seen from a direction perpendicular to the main plane. As shown in Figure 5, within one second region, the liquid crystal compound 6 is oriented in a liquid crystal orientation pattern in which the orientation of the optical axis 6A originating from the liquid crystal compound 6 changes while continuously rotating along one direction in the plane. The optical axis 6A originating from the liquid crystal compound 6 is the axis in the liquid crystal compound 6 where the refractive index is highest, the so-called slow axis. For example, if the liquid crystal compound 6 is a rod-shaped liquid crystal compound, the optical axis 6A is along the long axis of the rod shape.

[0049] The liquid crystal compound 6 that forms the liquid crystal diffraction layer has a liquid crystal orientation pattern in which the orientation of the optical axis 6A changes while continuously rotating along the direction of arrow D within the plane of the liquid crystal diffraction layer. In the example shown in Figure 5, the liquid crystal compound 6 has a liquid crystal orientation pattern in which the optical axis 6A changes while continuously rotating counterclockwise along the direction of arrow D. In the present invention, the direction of arrow D in this liquid crystal orientation pattern is defined as the in-plane rotation direction.

[0050] Specifically, the statement that the orientation of the optical axis 6A of the liquid crystal compound 6 changes while continuously rotating in the direction of arrow D (a predetermined one direction) means that the angle between the optical axis 6A of the liquid crystal compound 6 arranged along the direction of arrow D and the direction of arrow D differs depending on the position in the direction of arrow D, and that the angle between the optical axis 6A and the direction of arrow D changes sequentially from θ to θ+180° or θ-180° along the direction of arrow D.

[0051] Furthermore, the difference in angle between the optical axes 6A of adjacent liquid crystal compounds 6 in the direction of arrow D is preferably 45° or less, more preferably 15° or less, and even more preferably a smaller angle.

[0052] Furthermore, in this invention, the rotation direction of the optical axis 6A of the liquid crystal compound 6 in the direction of arrow D is assumed to be such that the liquid crystal compound 6 (optical axis 6A) rotates in a direction that reduces the angle between the optical axes 6A of adjacent liquid crystal compounds 6 in the direction of arrow D. Therefore, in the example shown in Figure 5, the optical axis 6A of the liquid crystal compound 6 rotates counterclockwise along the direction of arrow D.

[0053] On the other hand, in the liquid crystal compound 6 that forms the liquid crystal diffraction layer, the orientation of the optical axis 6A is the same in the Y direction, which is perpendicular to the direction of arrow D, that is, in the Y direction, which is perpendicular to the direction in which the optical axis 6A rotates continuously. In other words, in the liquid crystal compound 6 that forms the liquid crystal diffraction layer, the angle between the optical axis 6A of the liquid crystal compound 6 and the direction of arrow X is equal in the Y direction.

[0054] In this invention, in such a liquid crystal alignment pattern, the length (distance) over which the optical axis 6A of the liquid crystal compound 6 rotates by 180° in the direction of arrow D (in-plane rotation direction), where the optical axis 6A continuously rotates and changes within the plane, is defined as the length of one period Λ in the liquid crystal alignment pattern. That is, the length of one period Λ is defined as the distance between the centers in the direction of arrow D of two liquid crystal compounds 6 whose angles with respect to the direction of arrow D are equal. Specifically, as shown in Figure 5, the length of one period Λ is defined as the distance between the centers in the direction of arrow D of two liquid crystal compounds 6 whose directions of arrow D and the direction of the optical axis 6A coincide. The length of one period Λ is the in-plane period in this invention. The liquid crystal alignment pattern repeats this one period Λ in one direction, the direction of arrow D (in-plane rotation direction), that is, the direction in which the orientation of the optical axis 6A continuously rotates and changes.

[0055] An optically anisotropic layer having such a liquid crystal alignment pattern exhibits diffraction for specific polarizations due to the refractive index distribution originating from the optical axis 6A. Characteristics such as the diffracted polarization, its wavelength, emission angle (diffraction angle), the diffracting orientation, and the diffraction efficiency are determined by the in-plane period of the optical axis in the plane (1 period Λ), the direction of in-plane rotation, the degree of change of the optical axis in the thickness direction, and the refractive index anisotropy Δn and wavelength dispersibility of the liquid crystal compound. By appropriately setting these parameters, desired diffraction characteristics can be obtained.

[0056] As shown in Figure 3, the liquid crystal diffraction layer of the output section 3 has 16 second regions 14A to 14H, each with eight different in-plane rotation directions. In Figure 3, the in-plane rotation direction in each region is indicated by an arrow. The direction of the arrow represents the direction of the k-vector of the liquid crystal diffraction layer. The k-vector refers to the wave vector (or grating vector). Figure 3 also shows superimposed fringe patterns of light and dark areas observed due to the liquid crystal alignment pattern. The direction along the light and dark areas is the Y direction, and liquid crystal compounds are arranged in the same orientation.

[0057] Specifically, the second region 14A is a region having a liquid crystal alignment pattern in the rightward in-plane rotation direction. Hereafter, the rightward arrow is defined as the 0° direction, and the angle of the in-plane rotation direction is defined counterclockwise. The second region 14B is a region having a liquid crystal alignment pattern in the 45° in-plane rotation direction. The second region 14C is a region having a liquid crystal alignment pattern in the 90° in-plane rotation direction. The second region 14D is a region having a liquid crystal alignment pattern in the 135° in-plane rotation direction. The second region 14E is a region having a liquid crystal alignment pattern in the 180° in-plane rotation direction. The second region 14F is a region having a liquid crystal alignment pattern in the 225° in-plane rotation direction. The second region 14G is a region having a liquid crystal alignment pattern in the 270° in-plane rotation direction. The second region 14H is a region having a liquid crystal alignment pattern in the 315° in-plane rotation direction.

[0058] In the illustrated example, each of the second regions 14A to 14H is approximately square in shape. Furthermore, the shape and size of each of the second regions 14A to 14H are approximately identical. In the illustrated example, there are two of each of the second regions 14A to 14H, resulting in 16 second regions 14A to 14H arranged in a 4x4 grid.

[0059] Furthermore, the shape of the second regions 14A to 14H is not limited to a square shape, but can be various shapes such as rectangles, triangles, other polygons, circles, ellipses, or irregular shapes. Also, the shapes of the second regions 14A to 14H are not limited to being all the same, and at least two of the second regions may have different shapes. In this case, the shapes of the second regions may differ if they are of different types and have different in-plane rotation directions, or the shapes of the same type of second regions may differ if they have the same in-plane rotation direction. Also, the sizes of the second regions 14A to 14H are not limited to being all the same, and at least two of the second regions may have different sizes. In this case, the sizes may differ if they are of different types and have different in-plane rotation directions, or the sizes of the same type of second regions may differ if they have the same in-plane rotation direction.

[0060] In the illustrated example, the left column in the figure is arranged from top to bottom as follows: second region 14E, second region 14F, second region 14A, and second region 14B. The right column of this column is arranged from top to bottom as follows: second region 14D, second region 14C, second region 14H, and second region 14G. These two columns are repeated in the left-right direction.

[0061] As mentioned above, the types of second regions in the liquid crystal diffraction layer of the ejection unit 3 are not limited to eight types, but are sufficient if there are three or more types. Furthermore, there are no limitations on the combination of the in-plane rotation directions of the three or more second regions in the liquid crystal diffraction layer of the ejection unit 3.

[0062] Furthermore, as mentioned above, the liquid crystal diffraction layer of the incident section 2 has two or more types of first regions. There are no limitations on the combination of the in-plane rotation directions of each of the two or more types of first regions of the liquid crystal diffraction layer of the incident section 2.

[0063] The optical element of the present invention has multiple regions with different in-plane rotation directions D in the incident and exit liquid crystal diffraction layers, respectively. As shown in the k vector diagram in Figure 8, regions that cannot be guided by a single light guide path can be supplemented by other light guide paths, enabling a high FOV. This point will be explained below.

[0064] Figure 8 shows Ewald spheres representing the diffraction action in a liquid crystal diffraction layer in terms of in-plane rotation direction, in-plane period, and wavelength. The left figure in Figure 8 shows an Ewald sphere with a red wavelength, the middle figure shows an Ewald sphere with a green wavelength, and the right figure shows an Ewald sphere with a blue wavelength. In each figure in Figure 8, the region between two concentric circles represents the light-guided region where light is guided (total internal reflection) by the light guide plate 4, and the size of the outer circle changes depending on the refractive index of the light guide plate. The regions indicated by squares (Q0, Q1, Q2, Q3) represent the guided images. The arrows in the left figure in Figure 8 are k-vectors (grating vectors) of the liquid crystal diffraction layer, indicating the diffraction ability of the liquid crystal diffraction layer. The direction of the arrows corresponds to the in-plane rotation direction, and the length of the arrows corresponds to the diffraction angle, i.e., the in-plane period. In Figure 8, the k-vector of one type of first region of the liquid crystal diffraction layer at the incident point is shown, and the k-vectors of four types of second regions of the liquid crystal diffraction layer at the exit point are shown.

[0065] The center of region Q0, the center of the concentric circles, means that the image was incident perpendicular to the incident area. The arrow pointing left from region Q0 represents the k-vector of the incident area, and the fact that region Q1 at the end of the arrow lies between the two circles (light guide region) means that the image diffracted at the incident area is guided through the light guide plate. When the guided image is incident at the exit area, it is diffracted by the exit area. As described above, the liquid crystal diffraction layer of the exit area has multiple second regions, so it is diffracted in multiple directions. In the illustrated example, a part of the image is diffracted by a second region having an in-plane rotation direction corresponding to the arrow pointing to the upper right, and another part of the image is diffracted by a second region having an in-plane rotation direction corresponding to the arrow pointing to the lower right. Since the diffracted images (regions Q2 and Q3) are each within the light guide region, they are further guided through the light guide plate and diffracted again by the exit area. In the illustrated example, the image corresponding to region Q2 is partially diffracted by a second region having an in-plane rotation direction corresponding to the downward arrow, and the image corresponding to region Q3 is partially diffracted by a second region having an in-plane rotation direction corresponding to the upward arrow. Since the tips of these arrows are located at the centers of the concentric circles, the diffracted images are emitted from the light guide plate in a direction approximately perpendicular to it.

[0066] As described above, the optical element of the present invention guides the image (light) through multiple light guide paths, as each of the liquid crystal diffraction layers in the incident and exit portions has multiple regions with different k-vector directions D within the plane. Here, in Figure 8, parts of regions Q2 and Q3 are outside the light guide region. In this case, with this single light guide path, light from a part of the image is not guided, and the displayed image is incomplete. In contrast, since the optical element of the present invention guides the image (light) through multiple light guide paths, regions that cannot be guided by a single light guide path can be compensated for by other light guide paths, making it possible to achieve a high FOV.

[0067] Furthermore, as shown in the three figures in Figure 8, the diffraction angle due to the liquid crystal diffraction layer differs depending on the wavelength of light. Therefore, even if a light guide path does not cause image loss at one wavelength, image loss may occur at other wavelengths. In contrast, the optical element of the present invention guides the image (light) through multiple light guide paths, making it possible to achieve a high FOV across multiple wavelength ranges (a wide wavelength range).

[0068] Furthermore, as shown in Figure 18, the optical element of the present invention guides an image (light) through multiple light guide paths, allowing the image to be emitted from various positions in the plane at the emission section. In other words, the emission area can be expanded two-dimensionally (gray arrows), and the field of view (FOV) can be expanded by expanding the exit pupil without providing a separate intermediate diffraction element.

[0069] Furthermore, in the optical element of the present invention, the area ratio of at least one type of second region differs within the surface of the liquid crystal diffraction layer of the output portion. This improves the uniformity of brightness and color of the displayed image. This point will be explained below with reference to Figures 13 to 17.

[0070] Figure 13 shows an example of arrangement in which, in the region of the exiting section (primary light guide region) located in a plane extending from the incident section toward the exiting section in a direction parallel to the in-plane rotation direction D in the first region located in the incident section, the ratio of the existence of the second region where the parallel direction and the in-plane rotation direction D are parallel (area ratio) is smaller than that of the exiting section plane located in a different plane from the exiting section located in the plane extending from the incident section toward the exiting section in a parallel direction.

[0071] The lower right figure of Figure 13 shows a magnified view of a portion of the liquid crystal diffraction layer of the incident portion 131 of the optical element shown in the center. The left figure shows a magnified view of a portion of the liquid crystal diffraction layer of the primary light guide region 132 of the output portion of the optical element. The upper right figure shows a magnified view of a portion of the liquid crystal diffraction layer of the region 133 other than the primary light guide region of the output portion of the optical element. As shown by the dashed line in the central figure of Figure 13, the primary light guide region 132 is a region of the output portion that extends to the left from the incident portion 131 and has the same width as the vertical width of the incident portion 131. The region 133 other than the primary light guide region is the region of the output portion that is above the primary light guide region 132.

[0072] In the example shown in Figure 13, the incident section 131 has a total of nine first regions, three of each of three types: a first region 12C having an in-plane rotation direction in the 90° direction, a first region 12E having an in-plane rotation direction in the 180° direction, and a first region 12G having an in-plane rotation direction in the 270° direction. In this case, for example, the region within the exit section that extends along the in-plane rotation direction X of the first region 12E and has the width of the incident section in a direction perpendicular to the in-plane rotation direction X corresponds to the primary light guide region 132.

[0073] In the example shown in Figure 13, the region 133 other than the primary light guide region equally comprises a second region 14A having an in-plane rotation direction in the 0° direction, a second region 14B having an in-plane rotation direction in the 45° direction, a second region 14C having an in-plane rotation direction in the 90° direction, a second region 14D having an in-plane rotation direction in the 135° direction, a second region 14E having an in-plane rotation direction in the 180° direction, a second region 14F having an in-plane rotation direction in the 225° direction, a second region 14G having an in-plane rotation direction in the 270° direction, and a second region 14H having an in-plane rotation direction in the 315° direction, similar to the example shown in Figure 3. On the other hand, the primary light guide region 132 has a second region 14B with an in-plane rotation direction in the 45° direction, a second region 14C with an in-plane rotation direction in the 90° direction, a second region 14D with an in-plane rotation direction in the 135° direction, a second region 14F with an in-plane rotation direction in the 225° direction, a second region 14G with an in-plane rotation direction in the 270° direction, and a second region 14H with an in-plane rotation direction in the 315° direction, but does not have a second region 14A with an in-plane rotation direction in the 0° direction or a second region 14E with an in-plane rotation direction in the 180° direction.

[0074] As mentioned above, light emitted from the display and diffracted at the incident section is guided through the exit section and light guide plate, and some of the light is diffracted again at the exit section, changing its direction of guidance. Some of that light is then diffracted again at the exit section and emitted towards the user. This method of guiding light through the exit section and light guide plate, and having the guided light spread out in a planar manner before being emitted to the user, improves the uniformity of brightness and color of the displayed image and widens the eye box. An example of this is shown in the k vector diagram in Figure 14 (an example of guiding light from the incident section 131 to the area 132 of the exit section in Figure 13). As shown in Figure 14, the light diffracted at the incident section changes its direction of guidance by being diffracted once at the exit section, is diffracted again at the exit section, and is emitted outside the light guide plate.

[0075] Here, the second region 14A, which has an in-plane rotation direction in the 0° direction, corresponds to the second region Y1, which is located within the primary light guide region of the emission section and has an in-plane rotation direction parallel to the in-plane rotation direction X and opposite to the in-plane rotation direction X.

[0076] If, in the primary light guide region of the output section located in a plane extending from the input section toward the output section in a direction parallel to the in-plane rotation direction D in the first region located in the input section, there is a second region Y1 in which the parallel direction and the in-plane rotation direction D are parallel (for example, Figure 15), then the light emitted from the display and diffracted at the input section is guided through the output section and the light guide plate, and some of that light is diffracted at the output section and emitted to the user. In this case, the light guided at the output section does not spread out in a planar manner but is emitted to the user, which can lead to a deterioration in the uniformity of the brightness and color of the displayed image, and a narrowing of the eye box. An example of this is shown in the k vector diagram of Figure 16 (an example of guiding light from the input section 151 to the output section region 152 in Figure 15). As shown in Figure 16, the light diffracted at the input section is diffracted at the output section and emitted outside the light guide plate. Even in the arrangement shown in Figure 15, there is light that follows the same light guide path as shown in Figure 14, as shown in the k vector diagram in Figure 17. The presence of some light following the light guide path shown in Figure 16 causes a deterioration in the uniformity of brightness and color of the displayed image.

[0077] As described above, the region 133 other than the primary light guide region has a second region 14A, and the primary light guide region 132 does not have a second region 14A. Therefore, the area ratio of the second region 14A (second region Y1) within the primary light guide region 132 is smaller than the area ratio of the second region 14A (second region Y1) within the region 133 other than the primary light guide region.

[0078] As a result, the light diffracted at the incident section 131 and guided within the light guide plate is prevented from being directly emitted from the light guide plate by the second region 14A (second region Y1), and the second region other than the second region 14A (second region Y1) diffracts the light so that it propagates in other directions within the plane. As a result, the light is guided to spread two-dimensionally within the plane of the emission section, and light can be emitted uniformly from various positions within the plane of the emission section, thereby improving the uniformity of brightness and color of the displayed image.

[0079] Therefore, even when light in a light guide path as shown in Figure 16 exists, it is preferable that the optical element of the present invention is arranged such that, in the primary light guide region of the output portion located in a plane extended from the input portion toward the output portion in a direction parallel to the in-plane rotation direction D in the first region located in the input portion, the area ratio of the second region Y, in which the parallel direction and the in-plane rotation direction D are parallel, is smaller than that of the output portion plane located in a different plane (a region other than the primary light guide region) from the output portion located in a plane extended from the input portion toward the output portion in a parallel direction.

[0080] Here, as shown in the example in Figure 15, when the incident section 151 has multiple types of first regions, it is preferable that in at least one of the primary light guide regions corresponding to each first region, the area ratio of the second region Y is smaller than the area ratio of the second region Y in regions other than the primary light guide regions, and it is more preferable that in all primary light guide regions, the area ratio of the second region Y is smaller than the area ratio of the second region Y in regions other than the primary light guide regions. For example, in the example shown in Figure 15, the primary light guide region corresponding to the first region 12C has an in-plane rotation direction X in the 90° direction, so in the central figure, the region extending from the incident section 131 in the 90° direction is defined as the primary light guide region, and the in-plane rotation direction parallel to the in-plane rotation direction X and in the opposite direction to the in-plane rotation direction X is the 270° direction, so the second region 14G which has an in-plane rotation direction in the 270° direction corresponds to the second region Y1. Therefore, in the primary light guide region corresponding to the first region 12C, it is preferable that the area ratio of the second region 14G is smaller than the area ratio of the second region 14G in regions other than the primary light guide region. Similarly, since the primary light guide region corresponding to the first region 12G has an in-plane rotation direction X in the 270° direction, in the central figure, the region extending from the incident portion 131 in the 270° direction is defined as the primary light guide region, and the in-plane rotation direction parallel to the in-plane rotation direction X and opposite to the in-plane rotation direction X is the 90° direction, so the second region 14C having an in-plane rotation direction in the 90° direction corresponds to the second region Y1. Therefore, in the primary light guide region corresponding to the first region 12G, it is preferable that the area ratio of the second region 14C is smaller than the area ratio of the second region 14C in regions other than the primary light guide region. Thus, when the incident portion has multiple types of first regions, a primary light guide region can be defined corresponding to each first region, and the type of second region Y corresponding to each first region will be different.

[0081] Furthermore, in the example shown in Figure 13, a preferred embodiment is that the area ratio of the second region Y1, which is located within the primary light guide region of the emission section, is parallel to the in-plane rotation direction X and has an in-plane rotation direction opposite to the in-plane rotation direction X, is smaller than the area ratio of the second region Y1 located in a region other than the primary light guide region. In addition, the area ratio of the second region Y2, which is located within the primary light guide region of the emission section, is parallel to the in-plane rotation direction X and has an in-plane rotation direction in the same direction as the in-plane rotation direction X, is smaller than the area ratio of the second region Z located in a region other than the primary light guide region. In the example shown in Figure 13, the second region 14E corresponds to the second region Y2, and the area ratio of the second region 14E (second region Y2) in the primary light guide region 132 is smaller than the area ratio of the second region 14E (second region Y2) in the region 133 other than the primary light guide region. By reducing the area ratio of the second region Y2 in the primary light guide region 132, it is possible to suppress light from being emitted from the light guide plate on the side away from the user, thereby suppressing a decrease in the amount of light in the image observed by the user.

[0082] Furthermore, when the display and the user are positioned on opposite sides of the light guide plate, the second region Y2 having an in-plane rotation direction in the same direction as the in-plane rotation direction X corresponds to the second region that emits light toward the user, and the second region Y1 having an in-plane rotation direction opposite to the in-plane rotation direction X corresponds to the second region that emits light toward the opposite side of the user. Therefore, in either configuration, by making the area ratio of the second region Y having an in-plane rotation direction parallel to the in-plane rotation direction X, which is located within the primary light guide region of the emission section, smaller than the area ratio of the second region Y located in areas other than the primary light guide region, the uniformity of brightness and color of the displayed image can be improved. Although the above explanation illustrates the case where the liquid crystal diffraction layer is on the same plane as the light guide plate, the present invention is not limited to this.

[0083] [Optical element and image display device of the second embodiment] The optical element of the second embodiment of the present invention has a light guide plate, an incident part for injecting light into the light guide plate, and an outgoing part for emitting light from the light guide plate. The incident part and the outgoing part have a liquid crystal diffraction layer formed using a composition containing a liquid crystal compound. The liquid crystal diffraction layer has a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane. When at least one direction is defined as the in-plane rotation direction, and the length of the rotation of the optical axis derived from the liquid crystal compound in the in-plane rotation direction is defined as the in-plane period, the outgoing part has at least 16 third regions of at least two types, each having a liquid crystal orientation pattern with different in-plane rotation directions, and the average area of ​​the third regions is 9 mm². ２ The following is observed: In the liquid crystal diffraction layer of the emission section, the area ratio of at least one type of third region differs within the plane.

[0084] The image display device of the second embodiment of the present invention is an image display device having the optical element and display element of the second embodiment described above, wherein the display element is arranged to illuminate the incident portion of the optical element with an image.

[0085] In the second embodiment, the optical element has a liquid crystal diffraction layer in the emission section that has multiple regions with different in-plane rotation directions within its plane, which allows for an expansion of the field of view (FOV) by multiple light guide paths when used in an image display device such as AR glasses. Furthermore, in the second embodiment, the optical element has a liquid crystal diffraction layer in the emission section where the area ratio of at least one type of second region differs within its plane, which makes it possible to make the brightness of the image guided by the optical element uniform within its plane.

[0086] The number of in-plane divisions in the liquid crystal diffraction layer of the emission section, i.e., the number of third regions, is 16 or more, preferably 640 or more, and more preferably 6400 or more. The size of the divided region, i.e., the size of the third region, is 9 mm. ２ The following is 3 mm ２ The following is preferable: 0.3 mm ２ The following is even preferable: By increasing the number of divisions and decreasing the area size, superior image clarity can be achieved.

[0087] Furthermore, in each third region of the liquid crystal diffraction layer in the output section, at least two types of in-plane rotation directions are required, preferably three or more, more preferably four to 36, and even more preferably seven to 12. By appropriately designing the in-plane rotation direction and in-plane period of the oriented liquid crystal compound in the output section, it is possible to prevent color breakage of the displayed image even when multiple light guide paths are formed.

[0088] In the liquid crystal diffraction layer of the emission section, the arrangement of the third region having different in-plane rotation directions is not particularly limited, but it is preferable that it be random. Furthermore, the relative abundance of these regions can be freely adjusted considering the uniformity of brightness and color, etc.

[0089] In the liquid crystal diffraction layer of the ejection portion, it is preferable that the proportion of a third region having a certain in-plane rotation direction (area ratio) differs within the plane of the ejection portion.

[0090] Specifically, when the region within the output section that extends along the in-plane rotation direction X within the input section and has a width of the input section perpendicular to the in-plane rotation direction X is defined as the primary light guide region, it is preferable that the area ratio of the third region Y having an in-plane rotation direction parallel to the in-plane rotation direction X within the primary light guide region of the output section is smaller than the area ratio of the third region Y existing in areas other than the primary light guide region of the output section.

[0091] A third region Y, having an in-plane rotation direction parallel to the in-plane rotation direction X, has a diffracting effect that causes light incident from the direction in which the light diffracted at the incident point propagates to exit from the light guide plate towards the user or away from the user. Therefore, by making the area ratio of the third region Y within the primary light guide region smaller than the area ratio of the third region Y in regions other than the primary light guide region, the direct exit of light from the light guide plate by the third region Y after it has been diffracted at the incident point and guided through the light guide plate is suppressed, and the light is diffracted by the third region other than the third region Y so that it propagates in other directions within the plane. As a result, the light is guided to spread two-dimensionally within the plane of the exit point, and light can be emitted uniformly from various positions within the plane of the exit point, improving the uniformity of brightness and color of the displayed image.

[0092] Furthermore, the composition and preferred range of the abundance ratio of the third region Y are the same as those of the second region Y.

[0093] It is preferable to have a region without a liquid crystal alignment pattern between adjacent liquid crystal pattern alignment regions. That is, in the liquid crystal diffraction layer of the output section, it is preferable to have a region without a liquid crystal alignment pattern between third regions. Furthermore, it is preferable that the region without an alignment pattern is optically isotropic. Alternatively, the region without a liquid crystal alignment pattern may be optically anisotropic. For example, the region without a liquid crystal alignment pattern may be a region in which the liquid crystal compound is uniaxially oriented, twisted, or cholesterically oriented. The distance between adjacent alignment regions, that is, the width of the region without a liquid crystal alignment pattern, is preferably 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.1 mm or less. By providing a region without an alignment pattern, the contrast of the displayed image can be improved.

[0094] Furthermore, it is preferable that each ejection section has regions consisting of at least two different in-plane periods. That is, in the liquid crystal diffraction layer of the ejection section, it is preferable that at least two of the second regions have different in-plane periods.

[0095] Specifically, for example, in the liquid crystal diffraction layer of the output section, the third A region and the third B region, which have different in-plane rotation directions, may have different in-plane periods. Alternatively, in the liquid crystal diffraction layer of the output section, the third A-1 region and the third A-2 region, which have the same in-plane rotation direction, may have different in-plane periods.

[0096] Furthermore, in the ejection section, it is preferable that each divided region has regions with different optical thicknesses. That is, in the liquid crystal diffraction layer of the ejection section, it is preferable that at least two of the third regions have different optical thicknesses from each other.

[0097] Furthermore, the third region, which has a different optical thickness from one another, may or may not have the same in-plane rotation direction.

[0098] An example of the configuration of an image display device according to the second embodiment of the present invention has the same configuration as the image display device 18 shown in Figure 1, except that it has the optical elements of the second embodiment.

[0099] Furthermore, the liquid crystal diffraction layer of the output portion of the optical element of the second embodiment has the same configuration as the liquid crystal diffraction layer of the output portion of the optical element of the first embodiment, except that there must be two or more types of regions with mutually different in-plane rotation directions, so a detailed explanation will be omitted.

[0100] Furthermore, the liquid crystal diffraction layer of the incident portion of the optical element of the second embodiment may have a configuration similar to that of the incident portion in the first embodiment, having multiple regions of two or more types with different in-plane rotation directions, or it may have a liquid crystal diffraction layer consisting of one type of region with a uniform in-plane rotation direction.

[0101] [Liquid Crystal Diffraction Layer] The configuration of the liquid crystal diffraction layer other than those described above will now be explained. As mentioned above, the liquid crystal diffraction layer may be a reflective diffraction element or a transmissive diffraction element. When the liquid crystal diffraction layer is a reflective diffraction element, the liquid crystal compound in the liquid crystal diffraction layer is cholesterically oriented in the thickness direction. Figure 4 is an example of a cross-sectional view of a liquid crystal diffraction layer, conceptually showing the state in which the liquid crystal compound 6 is oriented on the support 8 and orientation 7. Note that Figure 4 shows the orientation of the liquid crystal compound 6 in one region. As shown in Figure 4, in the liquid crystal compound 6 that is cholesterically oriented in the thickness direction, the orientation of the optical axis 6A originating from the liquid crystal compound 6 changes in the thickness direction.

[0102] If the cholesteric liquid crystal layer has a liquid crystal orientation pattern in which the orientation of the molecular axes of the liquid crystal compound changes while continuously rotating along at least one direction in the plane, the arrangement direction of the light and dark areas originating from the cholesteric liquid crystal phase, as observed by scanning electron microscopy (SEM) in a cross section perpendicular to the main surface of the cholesteric liquid crystal layer, will be inclined with respect to the main surface of the cholesteric liquid crystal layer (Figure 6).

[0103] Furthermore, in the cholesteric liquid crystal layer, the liquid crystal compound may be oriented at an inclination with respect to the main surface. Figure 7 is a schematic cross-sectional diagram showing another example of the state of the cholesteric liquid crystal phase in a cross-section perpendicular to the main surface. In the cross-section of the cholesteric liquid crystal layer shown in Figure 7, the liquid crystal compound 6 is oriented with its molecular axis inclined with respect to the main surface. It is preferable that, in the cross-section of the cholesteric liquid crystal layer, the liquid crystal compound 6 has its molecular axis inclined in the same direction with respect to the main surface.

[0104] When the cross-section of the cholesteric liquid crystal layer shown in Figure 7 is observed using a scanning electron microscope (SEM), a striped pattern is observed in which light and dark areas are arranged alternately, as shown in Figure 6, and the arrangement direction is inclined at a predetermined angle θ with respect to the main surface. Note that two light areas and two dark areas in Figure 6 correspond to one helical pitch (one turn of the helix).

[0105] On the other hand, when the liquid crystal diffraction layer is a transmissive diffraction element, the liquid crystal compound 6 in the liquid crystal diffraction layer is configured such that the orientation of the optical axis 6A does not change in the thickness direction. Furthermore, the liquid crystal compound 6 in the liquid crystal diffraction layer may be torsion-oriented to the extent that it is not cholesterically oriented (torsion angle less than 360°).

[0106] The liquid crystal composition for forming the liquid crystal diffraction layer may contain other components in addition to the liquid crystal compound, such as chiral agents, leveling agents, orientation control agents, polymerization initiators, and orientation aids. By forming an alignment film on a support and coating and curing the liquid crystal composition on the alignment film, an optically anisotropic layer (liquid crystal diffraction layer) with a predetermined liquid crystal alignment pattern fixed, consisting of a cured layer of the liquid crystal composition, can be obtained. Specifically, a polarizing diffraction element formed by the method described in Japanese Patent Publication No. 2022-95795, Japanese Patent Publication No. 2014-16632, Japanese Patent Publication No. 2010-525394, Japanese Patent Publication No. 2023-27201, etc., can be used. Here, the creation of regions divided in a plane with different in-plane rotation directions can be performed with any pattern by methods such as directly forming a pattern on the alignment film by a direct drawing method or by multiple interference exposures using a light-shielding mask.

[0107] As an example, Figure 9 shows an exposure apparatus for forming an alignment film having a pattern that aligns a liquid crystal compound to a predetermined liquid crystal alignment pattern. The exposure apparatus 60 shown in Figure 9 comprises a light source 64 equipped with a laser 62 and a λ / 2 plate (not shown), a beam splitter 68 that separates the laser light M emitted from the light source 64 into two rays MA and MB, mirrors 70A and 70B arranged on the optical paths of the two separated rays MA and MB, respectively, and λ / 4 plates 72A and 72B. Although not shown, the light source 64 has a λ / 2 plate that changes the polarization direction of the laser light M emitted from the laser 62 to emit linearly polarized light P0. The λ / 4 plates 72A and 72B have optical axes parallel to each other. The λ / 4 plate 72A converts the linearly polarized light P0 (ray MA) into right-circularly polarized light P R The λ / 4 plate 72B converts linearly polarized light P0 (light ray MB) to left-circularly polarized light P L Convert each of them accordingly.

[0108] A support 20 having an alignment film 24 before the alignment pattern is formed is placed in the exposure section, and two light rays MA and MB are intersected and interfered with on the alignment film 24, and the resulting interfered light is irradiated onto the alignment film 24 for exposure. Due to this interference, the polarization state of the light irradiated onto the alignment film 24 changes periodically in an interference fringe pattern. As a result, an alignment pattern in which the alignment state changes periodically is obtained on the alignment film 24. In the exposure apparatus 60, the period of the alignment pattern can be adjusted by changing the intersection angle α of the two light rays MA and MB. That is, in the exposure apparatus 60, by adjusting the intersection angle α, the length of one period in which the optical axis 6A rotates 180° in one direction in an alignment pattern in which the optical axis 6A derived from the liquid crystal compound 6 rotates continuously in one direction can be adjusted. By forming a liquid crystal composition layer on an alignment film having such an alignment pattern in which the alignment state changes periodically, an optically anisotropic layer having a liquid crystal alignment pattern in which the optical axis 6A derived from the liquid crystal compound 6 rotates continuously in one direction can be formed. Furthermore, by rotating the optical axes of the λ / 4 plates 72A and 72B by 90°, the rotation direction of the optical axis 30A can be reversed.

[0109] Furthermore, the in-plane rotation direction (unidirectional) can be adjusted by the orientation of the support 20 having the alignment film 24 when it is placed in the exposure apparatus 60. Therefore, when forming multiple types of regions in a plane that have liquid crystal alignment patterns with different in-plane rotation directions, a light-shielding mask is placed on the alignment film 24 to expose only a predetermined region in the first exposure, the orientation of the alignment film 24 and the support 20 is changed, the relative position of the light-shielding mask and the alignment film in the in-plane direction is changed, or the light-shielding mask is changed to expose a different region in the second exposure, and further, the orientation of the alignment film 24 and the support 20 is changed, the relative position of the light-shielding mask and the alignment film in the in-plane direction is changed, or the light-shielding mask is changed to expose a different region in the third exposure, different from the first and second exposures. By performing such exposures using a light-shielding mask in accordance with the number of types of regions that have liquid crystal alignment patterns with different in-plane rotation directions, an alignment film for forming a liquid crystal diffraction layer having multiple types of regions in a plane that have liquid crystal alignment patterns with different in-plane rotation directions can be formed.

[0110] With respect to the liquid crystal compound, from the viewpoint of improving the FOV, the refractive index at wavelengths of 450 nm to 650 nm is preferably 1.6 or higher, more preferably 1.9 or higher, and even more preferably 2.0 or higher.

[0111] The liquid crystal diffraction layer can be formed from a cholesteric liquid crystal layer in which a cholesteric liquid crystal phase is fixed. To improve the uniformity of color and color reproducibility of AR images, it is preferable that the periods of the bright and dark areas originating from the cholesteric liquid crystal phase are adjusted in the cholesteric liquid crystal layer in a cross-section observed by a scanning electron microscope, between the incident and exit sections, and / or within the incident and exit sections. Furthermore, to improve the uniformity of color and color reproducibility of AR images, it is also preferable that the inclination angles of the bright and dark areas originating from the cholesteric liquid crystal phase with respect to the main surface of the cholesteric liquid crystal layer differ between the incident and exit sections, and / or within the incident and exit sections, in a cross-section observed by a scanning electron microscope. In addition, to improve the brightness uniformity of AR images, the physical thickness and optical thickness (Δnd) can be varied within the plane of the diffraction element. Specifically, it is more preferable to reduce the physical thickness and / or optical thickness of the second region formed near the incident section of the exit section.

[0112] [Light Guide Plate] The light guide plate can be selected from resin materials such as polycarbonate and acrylic, or transparent substrates such as glass, lithium niobate, and silicone carbide. From the viewpoint of improving the FOV, the refractive index of the substrate is preferably 1.6 or higher, and more preferably 1.9 or higher. The thickness of the substrate is preferably 0.1 mm to 2.0 mm, and more preferably 0.3 mm to 1.0 mm.

[0113] Although the optical element and image display device of the present invention have been described in detail above, the present invention is not limited to the examples described above, and various improvements and modifications may be made without departing from the spirit of the present invention.

[0114] The features of the present invention will be further described in detail below with reference to examples. The materials, reagents, amounts used, amounts of substance, ratios, processing content, and processing procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below.

[0115] [Example 1] (Formation of alignment film) A glass substrate was prepared as a support. The following alignment film forming coating solution was applied to the support by spin coating. The support coated with this alignment film forming coating solution was dried on a 60°C hot plate for 60 seconds to form an alignment film.

[0116] Coating solution for forming alignment film ----------------

[0117] -Material for photo alignment-

[0118]

[0119] (Exposure of alignment film) Using the exposure apparatus shown in Figure 9, a light-shielding mask on a grid was placed in front of the sample, the setting angle of the sample was adjusted, and the sample was exposed multiple times to obtain the desired in-plane rotation direction of orientation. This formed orientation patterns for the incident section (size 5 mmφ, 6 divisions, in-plane rotation direction: θ = 90°, 180°, 270°, 3 types, 2 sets) and the exit section (size 30 × 40 mm, 140 divisions, in-plane rotation direction: θ = 0°, 45°, 90°, 135°, 225°, 270°, 315°, 20 sets, 7 types). When forming the orientation pattern for the exit section, the ratio of the in-plane rotation directions of the divided second region was changed within the plane of the exit section; that is, the area ratio of the second region was varied within the plane, and the orientation film was exposed. Specifically, in each primary light guide region of the output section, located in a plane extending from the input section toward the output section in a direction parallel to the in-plane rotation directions (θ = 90°, 180°, 270°) in each first region of the input section (size 5 mmφ), the area ratio of the second region Y (Y1), which has an in-plane rotation direction parallel to and opposite to the in-plane rotation directions X (θ = 90°, 180°, 270°) of the input section (θ = 270°, 0°, 90°), is set to be 1 / 20 of the area ratio of the region located in the plane of the other output sections in the corresponding primary light guide region.

[0120] Figure 10 shows a schematic diagram of the liquid crystal diffraction layer to be fabricated and its relationship to the direction of in-plane rotation (angle θ). As shown in Figure 10, the incident portion is positioned in the center near the end of the long side of the exit portion (near one end), and the direction of the incident portion on the long side of the exit portion is set to 0°.

[0121] In the exposure apparatus, a laser with a wavelength of 355 nm was used. The exposure dose due to interference was 300 mJ / cm². 2 The following was done. The period Λ of the orientation pattern formed by the interference of the two laser beams (the length of a 180° rotation of the optical axis) was controlled by changing the intersection angle (intersection angle α) of the two beams so that it was 255 nm when θ = 0°, 90°, 180°, and 270°, and 360.6 nm when θ = 45°, 135°, 225°, and 315°.

[0122] (Formation of diffractive element) The following composition LC-1 was prepared as a liquid crystal composition for forming a diffractive element.

[0123] Composition LC-1 --------------------------------------------------- Rod-shaped liquid crystal compound L-1 90.00 parts by mass Rod-shaped liquid crystal compound L-2 10.00 parts by mass Polymerization initiator (BASF, Omnirad® 819) 3.00 parts by mass Chiral agent Ch-1 5.20 parts by mass Leveling agent T-1 0.10 parts by mass Methyl ethyl ketone 126.7 parts by mass Cyclopentanone 126.7 parts by mass ---------------------------------------------------

[0124] Rod-shaped liquid crystal compound L-1

[0125]

[0126] Rod-shaped liquid crystal compound L-2 (the number next to the structure represents mass %)

[0127]

[0128] Chiral agent Ch-1

[0129]

[0130] Leveling agent T-1

[0131]

[0132] The prepared composition LC-1 was coated onto the alignment film P-1 to form a composition layer. The support having the composition layer was heated on a hot plate at 90°C for 1 minute. Subsequently, a grid-like mask with a line width of 100 μm (see Figure 11) was placed on the composition according to the divided regions, and ultraviolet light at a wavelength of 365 nm was applied at 500 mJ / cm using a 365 nm LED UV exposure machine at 40°C in a nitrogen atmosphere. 2 The coating was exposed to light at the specified irradiation dose. Afterward, the grid-like mask was removed, the temperature was raised to 150°C, and ultraviolet light with a wavelength of 365 nm was applied at a rate of 200 mJ / cm².2 The coating film was exposed to light with the specified irradiation dose. The thickness of the fabricated liquid crystal diffraction element layer was 500 nm. The incident and exit portions of the fabricated liquid crystal diffraction layer were observed with a polarizing microscope to confirm that regions divided to the target size were formed, and that the second region Y was formed in the target area ratio. Furthermore, each divided region was observed with a cross-sectional SEM to confirm that each region of the liquid crystal diffraction layer was formed in the target in-plane rotation direction and in-plane period. In addition, it was confirmed that regions masked with a grid-like mask with a line width of 100 μm formed regions that did not have a liquid crystal alignment pattern.

[0133] (Formation and Evaluation of Optical Elements) The fabricated liquid crystal diffraction layer was peeled from the glass substrate and alignment film, and bonded to a glass substrate (light guide plate) with a refractive index of 1.8 and a thickness of 500 μm to create an optical element (light guide element). An LCOS (Liquid Crystal On Silicon) display for AR glasses was placed facing the incident side of the fabricated optical element to create an image display device. Light was incident from the display, and the visibility of the divided regions in the image and the uniformity of the image brightness were evaluated. Regarding the visibility of the divided regions, if the number of divisions in the region is coarse, dark areas appear as a mesh. The visibility of the divided regions in the image was evaluated using the following index: D: The divided regions are visible in the image and are at an unacceptable level. C: The divided regions are slightly visible in the image but are at an acceptable level. B: The divided regions are hardly visible in the image and are at an acceptable level. A: The divided regions are not visible in the image. The uniformity of the brightness of the image was evaluated using the following index: D: Brightness non-uniformity is strongly visible and is at an unacceptable level. C: Brightness non-uniformity is visible but is at an acceptable level. B: Brightness non-uniformity is slightly visible but is at an acceptable level. A: Brightness uniformity is good.

[0134] The display showed monochromatic blue, green, and red images, and the light emitted from the optical element's emitter was captured by an imaging camera. The diagonal field of view (FOV) was calculated based on the acquired images. The field of view covered by all three displays (blue, green, and red) was evaluated as the FOV value. The results are shown in Table 1.

[0135] Optical elements for Examples 2-4, 6-7, and Comparative Examples 1-2 were fabricated and evaluated in the same manner as in Example 1, except that the type of liquid crystal compound used, the type of light guide plate, the number of region divisions, and the type and number of in-plane rotation directions were changed. Here, the types of in-plane rotation directions for Examples 2-4 and 6-7 were the same as in Example 1. In addition, in the emission sections of Examples 2-4, the area ratios for each type of divided second region were the same as in Example 1. In addition, in the emission sections of Examples 6-7, the area ratios of the second region Y were set to 1 / 10 and 1 / 2, respectively.

[0136] In Comparative Example 1, instead of in-plane division, an incident section, an intermediate section (intermediate diffraction element), and an exit section were formed, and the orientation pitch and angle were adjusted to maximize the FOV for evaluation.

[0137] In Comparative Example 2, the incident section had two types of first regions with in-plane rotation directions of θ = 135° and 225°, and the exit section had five types of second regions with in-plane rotation directions of θ = 0°, 45°, 90°, 270°, and 315°. In Comparative Example 2, the area ratio of each divided second region was kept constant within the plane of the exit section.

[0138] In Example 5, after the alignment film was oriented in the same manner as in Example 4, the optical thickness of the output section was adjusted in-plane by the following method. The prepared composition LC-1 was applied to the alignment film P-1 to form a composition layer. The support having the composition layer was heated on a hot plate at 90°C for 1 minute. Subsequently, a grid-like mask with a line width of 100 μm was placed on the composition according to the divided regions, and an ND (Neutral Density) filter with a transmittance gradient in-plane was placed on the output section. Under an atmosphere of 40°C and an oxygen concentration of 5%, ultraviolet light with a wavelength of 365 nm was applied at a rate of 500 mJ / cm using a 365 nm LED UV exposure machine. 2 The coating was exposed to light at the specified irradiation dose. Afterward, the grid-like mask was removed, the temperature was raised to 150°C, and ultraviolet light with a wavelength of 365 nm was applied at a rate of 200 mJ / cm². 2The coating was exposed to light with the specified irradiation dose. The thickness of the fabricated liquid crystal diffraction layer was 500 nm. As a result, an optical element having the optical thickness profile shown in Figure 12 was formed in the x-axis direction (0° to 180° direction) of the output section.

[0139] As shown in Table 1, the image display device with the optical element fabricated in the example showed a higher FOV and better clarity compared to the comparative example. Comparative Example 2 produced a coarse image, making FOV evaluation impossible. Furthermore, the example in which the area ratio of the second region Y in the primary light guide region was reduced showed higher brightness uniformity compared to the comparative example. Example 5 showed even better brightness uniformity than Example 4. Also, from a comparison of Examples 1-3, the region size was 3 mm. ２ The following is preferable: 0.3 mm ２ The following is even more preferable. In Table 1, the item for the area ratio of the second region Y shows the ratio of the area ratio of the second region Y in the primary light guide region to the area ratio of the second region Y in regions other than the primary light guide region. From the above results, the effects of the present invention are clear.

[0140]

[0141] In AR glasses, it can be suitably used for various applications of guiding light in optical devices, such as light guide elements that guide light from display elements.

[0142] 1 Display 2, 131, 151 Incident section 3 Output section 4 Light guide plate 5 User 6 Liquid crystal compound 6A Optical axis 7 Alignment film 8 Support 10 Optical elements 12C, 12E, 12G First region 14A-14H Second region 20 Image display device 132, 152 Primary light guide region 133, 153 Regions other than the primary light guide region D Alignment axis Λ In-plane period P Helical pitch 20 Support 24 Alignment film 60 Exposure device 62 Laser 64 Light source 68 Beam splitter 70A, 70B Mirror 72A, 72B λ / 4 plate M Laser light MA, MB Light beam P O Linear polarized light P Ｒ Right-circular polarization P Ｌ Left circular polarization α crossing angle

Claims

1. The device comprises a light guide plate, an incident portion for injecting light into the light guide plate, and an outgoing portion for emitting light from the light guide plate, wherein the incident portion and the outgoing portion have a liquid crystal diffraction layer formed using a composition containing a liquid crystal compound, the liquid crystal diffraction layer has a liquid crystal orientation pattern in which the orientation of the optical axis originating from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, and when the at least one direction is defined as the in-plane rotation direction, and the length over which the orientation of the optical axis originating from the liquid crystal compound rotates by 180° in the in-plane rotation direction is defined as the in-plane period, the liquid crystal diffraction layer of the incident portion contains at least four first regions of at least two types, each having a liquid crystal orientation pattern with a different in-plane rotation direction, and the average area of ​​the first regions is 9 mm². ２ The following is the case: The liquid crystal diffraction layer of the emission section contains 16 or more second regions of at least three different types, each having a liquid crystal orientation pattern with different in-plane rotation directions, and the average area of ​​the second regions is 9 mm². ２ The optical element is characterized in that, in the liquid crystal diffraction layer of the emission portion, at least one type of area ratio of the second region is different in plane.

2. The optical element according to claim 1, wherein when a region within the output section is defined as the primary light guide region, extending along the in-plane rotation direction X of one of the first regions within the input section and having a width of the input section perpendicular to the in-plane rotation direction X, the area ratio of the second region Y having an in-plane rotation direction parallel to the in-plane rotation direction X and existing within the primary light guide region of the output section is smaller than the area ratio of the second region Y existing in a region of the output section other than the primary light guide region.

3. The device comprises a light guide plate, an incident portion for injecting light into the light guide plate, and an outgoing portion for emitting light from the light guide plate, wherein the incident portion and the outgoing portion have a liquid crystal diffraction layer formed using a composition containing a liquid crystal compound, the liquid crystal diffraction layer has a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, and when the at least one direction is defined as the in-plane rotation direction, and the length over which the orientation of the optical axis derived from the liquid crystal compound rotates by 180° in the in-plane rotation direction is defined as the in-plane period, the outgoing portion contains at least 16 third regions in the plane, each having at least two types of liquid crystal orientation patterns with different in-plane rotation directions, and the average area of ​​the third regions is 9 mm². ２ The optical element is characterized in that, in the liquid crystal diffraction layer of the emission portion, at least one type of area ratio of the third region is different in plane.

4. The optical element according to claim 3, wherein when the region within the output portion that extends along the in-plane rotation direction X of the incident portion and has the width of the incident portion in a direction perpendicular to the in-plane rotation direction X is defined as the primary light guide region, the area ratio of the third region Y having an in-plane rotation direction parallel to the in-plane rotation direction X and existing within the primary light guide region of the output portion is smaller than the area ratio of the third region Y existing in a region of the output portion other than the primary light guide region.

5. The optical element according to claim 1, wherein at least two of the first regions have different in-plane periods.

6. The optical element according to claim 1, wherein at least two of the second regions have different in-plane periods.

7. The optical element according to claim 3, wherein at least two of the third regions have different in-plane periods.

8. The optical element according to claim 1, wherein the liquid crystal diffraction layer of the incident portion has regions between the first regions that do not have a liquid crystal orientation pattern.

9. The optical element according to claim 1, wherein the liquid crystal diffraction layer of the emission portion has a region between the second regions that does not have a liquid crystal orientation pattern.

10. The optical element according to claim 3, wherein the liquid crystal diffraction layer of the emission portion has regions between the third regions that do not have a liquid crystal orientation pattern.

11. The optical element according to claim 1, wherein a region without a liquid crystal alignment pattern is located in a plane other than the incident portion and the exit portion.

12. The optical element according to any one of claims 8 to 11, wherein at least a portion of the plane of the region that does not have the liquid crystal alignment pattern is optically isotropic.

13. The optical element according to any one of claims 8 to 11, wherein at least a portion of the plane of the region that does not have the liquid crystal alignment pattern is optically anisotropic.

14. The optical element according to claim 1, wherein at least two of the first regions have different optical thicknesses from each other.

15. The optical element according to claim 1, wherein at least two of the second regions have different optical thicknesses from each other.

16. The optical element according to claim 3, wherein at least two of the third regions have different optical thicknesses from each other.

17. The optical element according to claim 1, wherein at least two of the first regions have different diffraction efficiencies.

18. The optical element according to claim 1, wherein at least two of the second regions have different diffraction efficiencies.

19. The optical element according to claim 3, wherein at least two of the third regions have different diffraction efficiencies.

20. The optical element according to claim 1, wherein the liquid crystal diffraction layer of at least one of the incident portion and the exit portion has a region in which the region having the liquid crystal orientation pattern is a cholesteric liquid crystal layer that is cholesteric oriented.

21. The optical element according to claim 20, wherein the cholesteric liquid crystal layer has regions in its plane where the inclination angles of the bright and dark parts originating from the cholesteric liquid crystal phase are different with respect to the main surface of the cholesteric liquid crystal layer, as observed in a cross-section by a scanning electron microscope.

22. The average area of ​​the first region is 0.3 mm². ２ The optical element according to claim 1, which is as follows:

23. The average area of ​​the second region is 0.3 mm². ２ The optical element according to claim 1, which is as follows:

24. The average area of ​​the third region is 0.3 mm². ２ The optical element according to claim 3, which is as follows:

25. An image display device having an optical element according to any one of claims 1 to 11 or 14 to 24, and a display element for irradiating an image onto the incident portion.

Images