Optical element, light guide element, display optical system, near eye display, measurement optical system, and image display device

Abstract

The present invention addresses the problem of providing: an optical element having an optically anisotropic layer excellent in light utilization efficiency; a light guide element having the optical element; a display optical system; a near-eye display; a measurement optical system; and an image display device.　This optical element includes an optically anisotropic layer. The optically anisotropic layer has an absorbance of less than 0.010 at a wavelength of 405 nm, and has an absorbance of 0.020 or more at a wavelength of 380 nm. The optically anisotropic layer includes an alignment pattern region, and includes a cured layer obtained by curing a composition containing a liquid crystalline compound. The alignment pattern region includes an alignment pattern in which the orientation of an optical axis derived from the liquid crystalline compound continuously changes in a rotational manner along at least one in-plane direction.

Description

Optical elements, light guide elements, display optical systems, near-eye displays, measurement optical systems, image display devices

[0001] The present invention relates to an optical element, a light guide element, a display optical system, a near-eye display, a measurement optical system, and an image display device.

[0002] Nowadays, polarized light is used in many optical devices or systems, and there is a demand for optical elements that can control the reflection, collection, divergence, etc. of polarized light. For example, Patent Document 1 discloses an optical element that is capable of obtaining diffracted light with a large diffraction angle and high diffraction efficiency, and that includes an optically anisotropic layer that is made of a cured layer of a liquid crystalline composition containing a tolan compound as a liquid crystalline compound and has a predetermined liquid crystal orientation pattern.

[0003] International Publication No. 2020 / 022496

[0004] The present inventors prepared and examined a film made of a liquid crystalline composition containing a tolan compound with reference to Patent Document 1. They confirmed that the prepared film exhibited diffraction efficiency equivalent to that of conventional liquid crystalline compositions, despite being thinner. However, there was still a problem with the ratio of the amount of diffracted light emitted to the amount of light incident on the film. In other words, they found that there was room for improvement in light utilization efficiency based on the amount of incident light.

[0005] Therefore, an object of the present invention is to provide an optical element having an optically anisotropic layer with excellent light utilization efficiency, and a light guide element, a display optical system, a near-eye display, a measurement optical system, and an image display device, each of which includes the optical element.

[0006] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by the following configuration.

[0007] [1] An optical element having an optically anisotropic layer having an absorbance of less than 0.010 at a wavelength of 405 nm and an absorbance of 0.020 or more at a wavelength of 380 nm, the optically anisotropic layer including a cured layer obtained by curing a composition containing a liquid crystalline compound, and an alignment pattern region, the alignment pattern region including an alignment pattern in which the direction of the optical axis derived from the liquid crystalline compound is continuously rotated along at least one direction in the plane. [2] The optical element according to [1], wherein the liquid crystalline compound has an average refractive index nk of 1.70 or more at a wavelength of 550 nm. [3] The optical element according to [1] or [2], wherein the composition includes a polymerization initiator, and the peak wavelength Pmax of the longest absorption peak of the polymerization initiator is 390 nm or more. [4] The molar extinction coefficient of the polymerization initiator at the peak wavelength Pmax is 650 mol －１ ・cm －１The optical element according to [3], wherein the above-mentioned. [5] The optical element according to any one of [1] to [4], wherein the optically anisotropic layer has an orientation that is twisted in the thickness direction in the orientation pattern region. [6] The optical element according to [5], wherein the total twist angle of the orientation that is twisted in the thickness direction of the optically anisotropic layer is 360° or more. [7] The optical element according to [6], further comprising a substrate that guides image light incident on the substrate by total internal reflection, and the orientation pattern region of the optically anisotropic layer has at least one function selected from the group consisting of a function of changing the optical path of the image light to a direction in which at least a portion of the guided image light exits the substrate, a function of changing the total reflection direction in the internal total reflection of the guided image light, and a function of changing the optical path of the image light that is incident on the substrate from the outside to a direction in which it is totally internally reflected within the substrate. [8] The optical element according to [7], wherein the diffraction efficiency in the orientation pattern region of the optically anisotropic layer varies along at least one direction in the plane of the optically anisotropic layer. [9] The optical element according to [7] or [8], wherein, in the orientation pattern region of the optically anisotropic layer, the average value Δna of the birefringence in the thickness direction of the optically anisotropic layer varies along at least one direction in the plane of the optically anisotropic layer.

[10] The optical element according to any one of [1] to [9], wherein, in an orientation pattern in which the direction of the optical axis derived from the liquid crystalline compound is continuously rotationally changed along at least one direction in the plane, the period of the rotational change varies within the plane of the optically anisotropic layer.

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

[10] , wherein the optically anisotropic layer includes a region without an orientation pattern in the same plane.

[12] A light guide element comprising the optical element according to any one of [1] to

[11] and a light guide plate.

[13] A display optical system comprising the optical element according to any one of [1] to

[11] and a display element.

[14] A near-eye display comprising the display optical system according to

[13] .

[15] A measurement optical system comprising the optical element according to any one of [1] to

[11] and a light-receiving element.

[16] An image display device comprising the measurement optical system according to

[15] .

[0008] According to the present invention, an optical element having an optically anisotropic layer with excellent light utilization efficiency as an optical element using diffraction can be provided. Furthermore, according to the present invention, a light guide element, a display optical system, a near-eye display, a measurement optical system, and an image display device each having an optical element with excellent light utilization efficiency can be provided.

[0009] FIG. 1 is a schematic diagram showing an example of an embodiment of an optically anisotropic layer. FIG. 2 is a schematic plan view of the optically anisotropic layer shown in FIG. 1. FIG. 3 is a conceptual diagram showing the function of the optically anisotropic layer shown in FIG. 2. FIG. 3 is a conceptual diagram showing the function of the optically anisotropic layer shown in FIG. 2. FIG. 4 is a schematic diagram showing another example of an optically anisotropic layer. FIG. 5 is a diagram showing the amount of light irradiation depending on the position of the optically anisotropic layer. FIG. 6 is a diagram showing the thickness of a high birefringence layer depending on the position of the optically anisotropic layer. FIG. 7 is a conceptual diagram showing a method for measuring diffraction efficiency in Examples. FIG. 8 is a schematic diagram showing an example of an embodiment of an optical element.

[0010] The present invention will be described in detail below. The following description of the components may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In each drawing, the scale of the components is appropriately different from the actual scale for easier viewing. In this specification, a numerical range expressed using "to" means a range including the numerical values ​​before and after "to" as the lower and upper limits. In this specification, the terms "perpendicular" and "parallel" refer to angles within a range of ±10°. In this specification, Re(λ) represents the in-plane retardation at a wavelength λ. Unless otherwise specified, the wavelength λ is 550 nm. In this specification, Re(λ) is a value measured at a wavelength λ using an AxoScan (manufactured by Axometrics). By inputting the average refractive index ((nx+ny+nz) / 3) and film thickness (d (μm)) into AxoScan, the slow axis direction (°) Re(λ) = R0(λ) is calculated. Note that R0(λ) is displayed as a numerical value calculated by AxoScan, but it means Re(λ).

[0011] Furthermore, in this specification, the term "(meth)acryloyloxy group" refers to both an acryloyloxy group and a methacryloyloxy group, and "(meth)acrylate" refers to both an acrylate and a methacrylate. Furthermore, in the description of a group (atomic group) in this specification, a description that does not specify whether it is substituted or unsubstituted encompasses both a group having a substituent and a group having a substituent. For example, the term "alkyl group" encompasses not only an alkyl group having no substituent (an unsubstituted alkyl group) but also an alkyl group having a substituent (a substituted alkyl group).

[0012] In addition, in this specification, when the term "substituent" is simply used, examples of the substituent include the following substituent L.

[0013] (Substituent L) Examples of the substituent L include an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkylamino group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an alkanoyl group having 1 to 10 carbon atoms, an alkanoyloxy group having 1 to 10 carbon atoms, an alkanoylamino group having 1 to 10 carbon atoms, an alkanoylthio group having 1 to 10 carbon atoms, an alkyloxycarbonyl group having 2 to 10 carbon atoms, an alkylaminocarbonyl group having 2 to 10 carbon atoms, an alkylthiocarbonyl group having 2 to 10 carbon atoms, a hydroxy group, an amino group, a mercapto group, a carboxy group, a sulfo group, an amido group, a cyano group, a nitro group, a halogen atom, and a polymerizable group. However, when the above groups described as the substituent L are not -CH ２ When - (methylene group) is contained, -CH contained in the above group ２ The substituent L also includes a group in which at least one of - is replaced by -O-, -CO-, -CH=CH-, or -C≡C-. For example, a group in which the above group is two or more -CH ２ -, one -CH ２ - is replaced with -O-, and one adjacent -CH ２- may be replaced with -CO- to form an ester group (-O-CO-). When the above group described as the substituent L has a hydrogen atom, a group in which at least one of the hydrogen atoms contained in the above group is replaced with at least one selected from the group consisting of a fluorine atom and a polymerizable group is also included in the substituent L. Examples of the polymerizable group include an ethylenically unsaturated group and a ring-polymerizable group, and among these, a substituent selected from the polymerizable group P described below is preferred. As the substituent L, among others, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkanoyl group having 1 to 10 carbon atoms, an alkanoyloxy group having 1 to 10 carbon atoms, an alkyloxycarbonyl group having 2 to 10 carbon atoms, a trifluoromethyl group, a hydroxy group, a carboxy group, a cyano group, a nitro group, or a halogen atom is preferred, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkanoyl group having 2 to 10 carbon atoms, an alkanoyloxy group having 2 to 10 carbon atoms, an alkyloxycarbonyl group having 2 to 10 carbon atoms, a trifluoromethyl group, or a halogen atom is more preferred, and an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkanoyl group having 2 to 6 carbon atoms, an alkanoyloxy group having 2 to 6 carbon atoms, an alkyloxycarbonyl group having 2 to 6 carbon atoms, a trifluoromethyl group, or a fluorine atom is even more preferred.

[0014] In addition, in this specification, when the term "polymerizable group" is simply used, examples of the polymerizable group include the polymerizable group P shown below.

[0015] (Polymerizable Group P) Examples of the polymerizable group P include groups represented by any of the following formulae (P-1) to (P-19). In the following formulae, * represents a bonding position, Me represents a methyl group, and Et represents an ethyl group. Of these, formula (P-1) or formula (P-2) ((meth)acryloyloxy group) are preferred.

[0016]

[0017] In addition, in this specification, the "solid content" of a composition means components that form a composition layer formed using the composition, and when the composition contains a solvent (organic solvent, water, etc.), it means all components excluding the solvent. Furthermore, liquid components that form a composition layer are also considered to be solid content.

[0018] In this specification, unless otherwise specified, the thickness of a layer is a value obtained by observing a cross section cut by a microtome with a SEM (scanning electron microscope) or a TEM (transmission electron microscope) and measuring the thickness at 10 points, and averaging the thickness.

[0019] <Optical Element> The optical element of the present invention has an optically anisotropic layer. The optically anisotropic layer includes a cured layer obtained by curing a composition containing a liquid crystalline compound (hereinafter also referred to as "liquid crystal composition"), and has an alignment pattern region. The alignment pattern region includes an alignment pattern in which the direction of the optical axis derived from the liquid crystalline compound contained in the composition is continuously rotated along at least one direction in the plane. The optically anisotropic layer has an absorbance of less than 0.010 at a wavelength of 405 nm and an absorbance of 0.020 or more at a wavelength of 380 nm.

[0020] The use of the optical element is not particularly limited, and it can be used for various purposes that transmit light in a direction different from the incident direction, such as a light path changing member in an optical device, a light focusing element, a light diffusing element in a predetermined direction, and a diffraction element. A preferred use among these is a light guide element. A light guide element typically includes a light guide plate and a diffraction element disposed on the light guide plate (preferably disposed at a distance from the light guide plate). The optical element of the present invention is suitably used as a diffraction element.

[0021] [Optically Anisotropic Layer] The optically anisotropic layer of the optical element of the present invention is formed using a liquid crystal composition containing a liquid crystal compound. The optically anisotropic layer has an alignment pattern region containing an alignment pattern in which the direction of the optical axis derived from the liquid crystal compound contained in the composition is continuously rotated along at least one direction in the plane. First, the alignment pattern and the alignment pattern region will be described.

[0022] 1 and 2 show schematic cross-sectional views of an optically anisotropic layer 1. Fig. 1 is a side view showing the optically anisotropic layer 1, and Fig. 2 is a plan view showing the liquid crystal alignment pattern of the optically anisotropic layer 1 shown in Fig. 1. In the drawings, the sheet surface of the sheet-like optically anisotropic layer 1 is defined as the xy plane, and the thickness direction is defined as the z direction.

[0023] As shown in FIG. 1 , the optically anisotropic layer 1 has an alignment pattern region including a liquid crystal alignment pattern (having a length of one period Λ) in which the orientation of the optical axis derived from the liquid crystal compound 30 is continuously rotated along at least one in-plane direction. Note that in FIGS. 1 to 4 , in order to simplify the drawings and clearly show the configuration of the optically anisotropic layer 1, only the liquid crystal molecules present on one main surface of the optically anisotropic layer 1 are shown. However, the optically anisotropic layer 1 has a structure in which aligned liquid crystal compounds 30 are stacked, similar to an optically anisotropic layer formed using a composition containing a typical liquid crystal compound. Typically, when the in-plane retardation value of the optically anisotropic layer 1 is set to λ / 2, the optically anisotropic layer 1 functions as a typical λ / 2 plate, that is, imparts a phase difference of half the wavelength, i.e., 180°, to two orthogonal linearly polarized components contained in light incident on the optically anisotropic layer.

[0024] As shown in Fig. 2, the optically anisotropic layer 1 has a liquid crystal orientation pattern in which the direction of the optical axis 30A (hereinafter sometimes abbreviated as "optical axis 30A") derived from the liquid crystal compound 30 changes while continuously rotating in one direction within the plane of the optically anisotropic layer 1. Here, the one direction in which the optical axis 30A changes rotationally coincides with the direction of the x-axis in the xy plane. In the following description, the one direction in which the optical axis 30A changes rotationally is referred to as the x-direction.

[0025] The optical axis 30A derived from the liquid crystal compound 30 is the axis along which the refractive index of the liquid crystal compound 30 is highest, that is, the so-called slow axis. As shown in Fig. 1, when the liquid crystal compound 30 is a rod-shaped liquid crystal compound, the optical axis 30A is aligned with the long axis direction of the rod shape.

[0026] The phrase "the orientation of the optical axis 30A changes while continuously rotating in the x direction" specifically means that the angle formed between the optical axis 30A of the liquid crystal compound 30 aligned along the x direction and the x direction varies depending on the position in the x direction, and the angle formed between the optical axis 30A and the x direction gradually changes along the x direction from θ to θ+180° or θ−180°. Here, "the angle gradually changes" may mean that the angle changes at regular angle intervals or that the angle changes continuously. However, the difference in angle between the optical axes 30A of the liquid crystal compound 30 adjacent to each other in the x direction is preferably 45° or less, more preferably 15° or less, and even more preferably a smaller angle.

[0027] On the other hand, in the y direction perpendicular to the x direction in the plane, i.e., the y direction perpendicular to the one direction (x direction) in which the optical axis 30A continuously rotates, the liquid crystal compounds 30 having the same optical axis 30A orientation are arranged at equal intervals. In other words, among the liquid crystal compounds 30 forming the optically anisotropic layer 1, the liquid crystal compounds 30 aligned in the y direction have the same angle between the optical axis 30A orientation and the x direction. In the optically anisotropic layer 1, in the liquid crystal alignment pattern of such liquid crystal compounds 30, the length (distance) over which the optical axis 30A of the liquid crystal compound 30 rotates 180° in the x direction, in which the orientation of the optical axis 30A continuously rotates and changes in the plane, is defined as the length Λ of one period in the liquid crystal alignment pattern. In other words, the length of one period in the liquid crystal alignment pattern is defined as the distance from θ to θ+180°, in which the angle between the optical axis 30A of the liquid crystal compound 30 and the x direction becomes θ. 2, the distance between the centers in the x direction of two liquid crystal compounds 30 whose optical axes 30A coincide with the x direction is defined as the length of one period Λ (hereinafter, also referred to as "one period Λ" or "period Λ"). The liquid crystal alignment pattern of the optically anisotropic layer 1 is a pattern in which the liquid crystal alignment of this one period Λ is repeated in the x direction.

[0028] The period Λ of the liquid crystal alignment pattern in the optically anisotropic layer 1 can be determined from the period of light and dark by observing a light-dark periodic pattern of light and dark areas under crossed Nicols conditions using a polarizing microscope. Twice the period of the observed light-dark periodic pattern corresponds to the period Λ of the liquid crystal alignment pattern. The film thickness d of the optically anisotropic layer 1 can be measured, for example, by observing a cross section of the optically anisotropic layer using a scanning electron microscope.

[0029] As described above, in the optically anisotropic layer 1, the angle between the optical axis 30A of each liquid crystal compound 30 aligned in the y direction and the x direction, along which the optical axis of the liquid crystal compound 30 rotates, is equal. A region in which the liquid crystal compounds 30, each with the same angle between the optical axis 30A and the x direction, are arranged in the y direction, is referred to as region R. In this case, the in-plane retardation (Re) value in each region R is preferably half the wavelength of the light to be diffracted by the optically anisotropic layer (hereinafter referred to as "target light"), i.e., when the wavelength of the target light is λ, the in-plane retardation Re is λ / 2. These in-plane retardations are calculated by the product of the refractive index anisotropy Δn of region R and the thickness (film thickness) d of the optically anisotropic layer. Here, the refractive index difference associated with the refractive index anisotropy of region R in the optically anisotropic layer is a refractive index difference defined by the difference between the refractive index in the direction of the slow axis in the plane of region R and the refractive index in the direction perpendicular to the slow axis. That is, the refractive index difference Δn due to the refractive index anisotropy of region R is equal to the difference between the refractive index of the liquid crystal compound 30 in the direction of the optical axis 30A and the refractive index of the liquid crystal compound 30 in the direction perpendicular to the optical axis 30A in the plane of region R. In other words, the refractive index difference Δn depends on the liquid crystal compound, and the in-plane retardation of each region R is approximately equal. However, as described above, the direction of the optical axis 30A differs between each region R.

[0030] In the optically anisotropic layer 1, since the direction of the optical axis 30A is rotated in the plane, it is difficult to measure the in-plane retardation of the entire layer. However, the in-plane retardation of the optically anisotropic layer 1 can be theoretically estimated from the period and diffraction efficiency.

[0031] When circularly polarized light is incident on such an optically anisotropic layer 1, the light is refracted and the direction of the circularly polarized light is changed. This action is conceptually shown in FIG. 3, exemplifying the optically anisotropic layer 1. It is assumed that the in-plane retardation of the optically anisotropic layer 1 is λ / 2. In this case, as shown in FIG. 3, left-handed circularly polarized light P L When the incident light L1 is incident, the incident light L1 is given a phase difference of 180° by passing through the optically anisotropic layer 1, and the transmitted light L2 is converted into right-handed circularly polarized light P R 3. Furthermore, when the incident light L1 passes through the optically anisotropic layer 1, the absolute phase changes depending on the orientation of the optical axis 30A of each liquid crystal compound 30. At this time, the orientation of the optical axis 30A changes while rotating along the x direction, so the amount of change in the absolute phase of the incident light L1 varies depending on the orientation of the optical axis 30A. Furthermore, since the liquid crystal orientation pattern formed in the optically anisotropic layer 1 is a periodic pattern in the x direction, the incident light L1 that passes through the optically anisotropic layer 1 is given an absolute phase Q1 that is periodic in the x direction corresponding to the orientation of each optical axis 30A, as shown in FIG. 3. As a result, an equiphase surface E1 that is tilted in the opposite direction to the x direction is formed. Therefore, the transmitted light L2 is refracted so as to be tilted toward a direction perpendicular to the equiphase surface E1, and travels in a direction different from the traveling direction of the incident light L1. In this way, left-handed circularly polarized light P L The incident light L1 is right-handed circularly polarized light P R is converted into transmitted light L2.

[0032] On the other hand, as conceptually shown in FIG. 4, right-handed circularly polarized light P R When the incident light L4 is incident on the optically anisotropic layer 1, the incident light L4 is given a phase difference of 180° and is converted into left-handed circularly polarized light P L4, the incident light L4 is converted into transmitted light L5. Furthermore, when the incident light L4 passes through the optically anisotropic layer 1, the absolute phase changes depending on the orientation of the optical axis 30A of each liquid crystal compound 30. At this time, the orientation of the optical axis 30A changes while rotating along the x direction, so the amount of change in the absolute phase of the incident light L4 differs depending on the orientation of the optical axis 30A. Furthermore, since the liquid crystal orientation pattern formed in the optically anisotropic layer 1 is a periodic pattern in the x direction, the incident light L4 that has passed through the optically anisotropic layer 1 is given an absolute phase Q2 that is periodic in the x direction corresponding to the orientation of each optical axis 30A, as shown in FIG. 4. Here, the incident light L4 is right-handed circularly polarized light P R Therefore, the periodic absolute phase Q2 in the x direction corresponding to the direction of the optical axis 30A is P L The incident light L4 is refracted in a direction opposite to the x-direction, which is opposite to that of the incident light L1. As a result, an equiphase surface E2 is formed in the incident light L4 that is tilted in the x-direction opposite to that of the incident light L1. Therefore, the incident light L4 is refracted so as to be tilted toward a direction perpendicular to the equiphase surface E2, and travels in a direction different from the traveling direction of the incident light L4. In this way, the incident light L4 is converted into left-handed circularly polarized transmitted light L5 that is tilted at a certain angle in the direction opposite to the x-direction with respect to the incident direction.

[0033] As mentioned above, the in-plane retardation value of the optically anisotropic layer 1 is preferably half the wavelength of the target light. This is because the closer the in-plane retardation value is to half the wavelength of the target light, the higher the diffraction efficiency of the target light can be obtained. The in-plane retardation Re(λ) of the optically anisotropic layer for incident light having a wavelength of λ nm in the x direction is expressed as follows: λ ×d is preferably within the range defined by the following formula and can be set appropriately: 0.7 × (λ / 2) nm≦Δn λ ×d≦1.3×(λ / 2)nm

[0034] When a commercially available liquid crystal compound (for example, Paliocolor LC242 (available from BASF)) is used as the liquid crystal compound, Δn λis relatively small in the visible light region, so the film thickness d needs to be relatively large. It is known that when λ / d is small, the orientation on the air interface side during coating becomes easily disturbed, resulting in a decrease in diffraction efficiency. It is considered preferable that λ / d > 1. There is no particular upper limit for λ / d, but when used in the visible to near-infrared region, it is desirable that it be 10 or less.

[0035] Here, by using the compound described in Patent Document 1, Δn λ is large in the visible light region, and it is possible to reduce the film thickness d and increase λ / d compared to when other compounds are used, in other words, it is thought that an optically anisotropic layer with excellent diffraction efficiency can be formed. However, as a result of investigations by the present inventors, even when the compound described in Patent Document 1 is used, when the amount of outgoing light relative to the incident light is measured, Δn λ It was found that there are cases where the amount of emitted light does not reach the amount expected from ×d, that is, there is a problem with the light utilization efficiency.

[0036] As a result of extensive research, the inventors have discovered that the relative relationship between light absorption in the optically anisotropic layer and the absorbing components derived from the liquid crystal compound causes such a decrease in light utilization efficiency, and have found that light utilization efficiency can be improved by setting these two parameters within specified ranges.

[0037] That is, in the optical element of the present invention, the absorbance of the optically anisotropic layer at a wavelength of 405 nm is less than 0.010, and at a wavelength of 380 nm is 0.020 or more.

[0038] The alignment pattern in the optical element of the present invention will be further described in detail.

[0039] The period Λ of the orientation pattern can be appropriately set depending on the application. By changing the period Λ of the liquid crystal orientation pattern formed in the optically anisotropic layer 1, the refraction angle of the transmitted light L2 and L5 can be adjusted. Specifically, the shorter the period Λ of the liquid crystal orientation pattern, the stronger the interference between the lights passing through adjacent liquid crystal compounds 30, thereby allowing the transmitted light L2 and L5 to be refracted to a greater extent. The period Λ is preferably 50 μm or less, more preferably 25 μm or less, and even more preferably 5 μm or less. Furthermore, by reversing the rotation direction of the optical axis 30A of the liquid crystal compound 30, which rotates along the x direction, it is also possible to reverse the direction of refraction of the transmitted light.

[0040] It is also preferable to form an optically anisotropic layer with a substantially broadband wavelength for the wavelength of incident light by forming a twisted orientation in the thickness direction by adding a chiral agent described later to the liquid crystal composition, or by laminating different retardation layers. For example, JP 2014-089476 A discloses a method for realizing a broadband patterned λ / 2 plate by laminating two layers with different twist directions in the thickness direction in an optically anisotropic layer, and this method can be suitably used in the optically anisotropic layer of the present invention.

[0041] The optically anisotropic layer may have a so-called twist structure in which the orientation of the liquid crystal compound changes continuously from one interface side to the other interface side along the thickness direction. That is, the optically anisotropic layer may have an orientation twisted in the thickness direction in the orientation pattern region. In the orientation twisted in the thickness direction, when the twist angle is defined as the rotation angle defined by the difference between the molecular axis of the liquid crystal compound at one interface (e.g., the long axis direction in the case of a rod-shaped liquid crystal compound) and the molecular axis of the liquid crystal compound at the other interface, the twist angle is preferably 10° or more, more preferably 20° or more. It is known that the twist angle further stabilizes the orientation. The twist angle may be less than 360°. Furthermore, in the cholesteric liquid crystal phase described below, the total twist angle may be 360° or more.

[0042] The optical element of the present invention is not limited to the above-mentioned liquid crystal alignment pattern, and may include alignment pattern regions having various liquid crystal alignment patterns. For example, the optically anisotropic layer 2 shown in Figure 5 is an optically anisotropic layer in which liquid crystal compound 30 is cholesterically aligned in the thickness direction.

[0043] It is known that cholesteric liquid crystal phases exhibit selective reflectivity at specific wavelengths. The central wavelength of selective reflection (selective reflection central wavelength) λ depends on the pitch P (= helical period) of the helical structure in the cholesteric liquid crystal phase and follows the relationship λ = n × P with the average refractive index n of the cholesteric liquid crystal phase. Therefore, the selective reflection central wavelength can be adjusted by adjusting the pitch of this helical structure. Cholesteric orientation can also be referred to as an orientation twisted in the thickness direction, and in this case, it can be rephrased as a state in which the sum of the angles at which the orientation of the liquid crystal compound continuously changes from one interface side to the other interface side (total twist angle) is 360° or more.

[0044] Cholesteric liquid crystal phases exhibit selective reflection for either left- or right-handed circularly polarized light at a specific wavelength. Whether the reflected light is right-handed or left-handed circularly polarized depends on the twist direction (sense) of the helix of the cholesteric liquid crystal phase. When the twist direction of the helix of the cholesteric liquid crystal phase is right-handed, right-handed circularly polarized light is reflected, and when the twist direction of the helix is ​​left-handed, left-handed circularly polarized light is reflected.

[0045] Furthermore, the half-width Δλ (nm) of the selective reflection band (circularly polarized light reflection band) exhibiting selective reflection depends on Δn of the cholesteric liquid crystal phase and the helical pitch P, and follows the relationship Δλ = Δn × P. Therefore, the width of the selective reflection band can be controlled by adjusting Δn.

[0046] That is, the optically anisotropic layer 2 has the function of selectively reflecting light of a specific circularly polarized light (right-handed or left-handed circularly polarized light) in a predetermined wavelength range.

[0047] On the other hand, the orientation pattern of the optic axis 30A in the in-plane direction of the optically anisotropic layer 2 is the same as the orientation pattern in the optically anisotropic layer 1 shown in Fig. 1, and therefore exhibits the same effect as the optically anisotropic layer 1. That is, the optically anisotropic layer 2 exhibits the effect of changing the absolute phase of incident light and bending it in a predetermined direction, similar to the above-mentioned optically anisotropic layer 1. Therefore, the optically anisotropic layer 2 has both the effect of bending incident light in a direction different from the incident direction and the effect of the above-mentioned cholesteric orientation, and reflects light at a predetermined angle relative to the reflection direction of specular reflection.

[0048] For example, if the cholesteric liquid crystal phase of the optically anisotropic layer 2 is designed to reflect right-handed circularly polarized light, as shown in FIG. R When light L6 having a value of 1 / (x,y) is incident, reflected light L7 is generated in a direction tilted relative to the normal direction. That is, the optically anisotropic layer 2 functions as a reflective diffraction grating.

[0049] 1 to 5, the optical axis 30A of the liquid crystal compound 30 rotates continuously in the plane along only the x direction. However, in the optically anisotropic layer of the present invention, various configurations can be used as long as the optical axis 30A of the liquid crystal compound 30 rotates continuously along one direction.

[0050] FIG. 6 is a schematic plan view of an optically anisotropic layer 3 of a modified design. In FIG. 6, the liquid crystal orientation pattern is represented by the optical axis 30A of the liquid crystal compound. The optically anisotropic layer 3 has a liquid crystal orientation pattern in which regions with the same optical axis 30A orientation are arranged concentrically, and one direction in which the orientation of the optical axis 30A changes while continuously rotating is arranged radially from the center of the optically anisotropic layer 3. In the optically anisotropic layer 3, the orientation of the optical axis 30A changes while continuously rotating along multiple directions from the center of the optically anisotropic layer 3 toward the outside, for example, the direction indicated by arrow A1, the direction indicated by arrow A2, the direction indicated by arrow A3, etc. Circularly polarized light incident on the optically anisotropic layer 3 having this liquid crystal orientation pattern undergoes a change in absolute phase in each local region where the optical axis orientation of the liquid crystal compound 30 differs. The amount of change in each absolute phase differs depending on the orientation of the optical axis of the liquid crystal compound 30 into which the circularly polarized light is incident.

[0051] The optically anisotropic layer 3 having such a concentric liquid crystal orientation pattern, i.e., a liquid crystal orientation pattern in which the optical axis changes by continuous radial rotation, can transmit incident light as divergent or convergent light depending on the rotation direction of the optical axis of the liquid crystal compound 30 and the direction of the incident circularly polarized light. That is, by making the liquid crystal orientation pattern of the optically anisotropic layer concentric, the optically anisotropic layer exhibits the function of, for example, a convex lens or a concave lens.

[0052] Here, in the liquid crystal orientation pattern of the optically anisotropic layer, one period Λ may vary within the plane of the optically anisotropic layer. For example, when the liquid crystal orientation pattern of the optically anisotropic layer is concentric and the optically anisotropic layer is made to function as a convex lens, it is preferable to gradually shorten one period Λ, in which the optical axis rotates by 180°, from the center of the optically anisotropic layer 3 toward the outward direction in one direction in which the optical axis continuously rotates. The angle of refraction of light with respect to the incident direction increases as one period Λ in the liquid crystal orientation pattern becomes shorter. Therefore, by gradually shortening one period Λ in the liquid crystal orientation pattern from the center of the optically anisotropic layer 3 toward the outward direction in one direction in which the optical axis continuously rotates, the light focusing power of the optically anisotropic layer 3 can be further improved, and the performance as a convex lens can be improved.

[0053] Furthermore, depending on the application of the laminate, for example, when forming a concave lens, it is preferable to rotate one period Λ, in which the optical axis in the liquid crystal orientation pattern rotates by 180°, from the center of the optically anisotropic layer 3 in the opposite direction to the direction in which the optical axis continuously rotates, and gradually shorten the period Λ from the center of the optically anisotropic layer 3 toward the outside in one direction. The angle of refraction of light with respect to the incident direction increases as one period Λ in the liquid crystal orientation pattern becomes shorter. Therefore, by gradually shortening one period Λ in the liquid crystal orientation pattern from the center of the optically anisotropic layer 3 toward the outside in one direction in which the optical axis continuously rotates, the light divergence power of the optically anisotropic layer 3 can be further improved, and the performance as a concave lens can be improved.

[0054] For example, when the optically anisotropic layer is used as a concave lens, it is also preferable to reverse the rotation direction of the incident circularly polarized light.

[0055] Conversely, one period Λ in the concentric liquid crystal orientation pattern may be gradually lengthened from the center of the optically anisotropic layer 3 outward in one direction in which the optical axis continuously rotates. Furthermore, depending on the application of the optically anisotropic layer, for example, when it is desired to provide a light intensity distribution in transmitted light, it is also possible to use a configuration in which the period Λ is not gradually changed in one direction in which the optical axis continuously rotates, but has regions in which the period Λ is partially different in one direction in which the optical axis continuously rotates. In addition, the light-emitting element may have an optically anisotropic layer in which the period Λ is uniform throughout and an optically anisotropic layer having regions in which the period Λ is different.

[0056] As described above, the configuration in which the period Λ of the optical axis, which rotates 180°, changes in one direction within the plane in which the optical axis continuously rotates, can also be used in the configurations shown in Figures 1 to 4 in which the optical axis 30A of the liquid crystal compound 30 continuously rotates and changes only in one direction, the x direction. For example, by gradually shortening the period Λ of the liquid crystal alignment pattern in the x direction, an optically anisotropic layer that transmits light in a condensing manner can be obtained. Furthermore, by reversing the direction in which the optical axis rotates 180° in the liquid crystal alignment pattern, an optically anisotropic layer that transmits light in a diffusive manner only in the x direction can be obtained. Note that an optically anisotropic layer that transmits light in a diffusive manner only in the X direction indicated by the arrow can also be obtained by reversing the rotation direction of incident circularly polarized light. Furthermore, depending on the application of the optically anisotropic layer, for example, when it is desired to provide a light intensity distribution in the transmitted light, a configuration in which the period Λ is partially different in the x direction rather than gradually changing in the x direction can also be used.

[0057] In the present invention, the diffraction efficiency of the alignment pattern region is calculated by the ratio of the film thickness d of the optically anisotropic layer to Δn λ In order to control the orientation of the liquid crystal molecules independently, a region having an orientation state different from the above-mentioned orientation pattern may be provided in the film thickness direction. By changing the ratio of the film thickness region having the liquid crystal orientation pattern to the film thickness region having an orientation state different from the above-mentioned liquid crystal orientation pattern in one direction in the plane of the optically anisotropic layer, it is also possible to change the diffraction efficiency in the plane of the orientation pattern region.

[0058] The optically anisotropic layer included in the optical element may include multiple alignment pattern regions in its plane. These multiple alignment pattern regions may be directly adjacent to each other or may be arranged with a non-alignment pattern region interposed therebetween. Specifically, the non-alignment pattern region here refers to a region in which the optical axis derived from the compound is fixed in an isotropic phase state, a uniaxially aligned state, or a low alignment state intermediate between the isotropic phase and the uniaxially aligned state. The multiple alignment pattern regions may be identical and repeatedly arranged, or may be a combination of different alignment pattern regions from the various liquid crystal alignment patterns described above.

[0059] The film thickness d of the optically anisotropic layer 1 can be appropriately set depending on the application and the design of the optical element to be used, but is typically preferably 1 μm or less, more preferably 0.8 μm or less, and even more preferably 0.5 μm or less.

[0060] [Liquid Crystal Composition] The optically anisotropic layer included in the present invention is formed from a liquid crystal composition. Each component of the liquid crystal composition will be described below. In addition to the liquid crystal compound, the liquid crystal composition may further contain various components such as a polymerization initiator, which will be described later.

[0061] (Liquid Crystal Compound) Any known liquid crystal compound can be used. Generally, liquid crystal compounds can be classified into rod-shaped and discotic types based on their shape. Each type can further be divided into low molecular weight and high molecular weight types. High molecular weight generally refers to a compound with a degree of polymerization of 100 or more (Polymer Physics / Phase Transition Dynamics, by Masao Doi, page 2, Iwanami Shoten, 1992). The liquid crystal compound may be any of the above compounds, but rod-shaped liquid crystal compounds are preferred.

[0062] Suitable rod-shaped liquid crystal compounds include those described in claim 1 of JP-A-11-513019 and paragraphs

[0026] to

[0098] of JP-A-2005-289980. Suitable discotic liquid crystal compounds include those described in paragraphs

[0020] to

[0067] of JP-A-2007-108732 and paragraphs

[0013] to

[0108] of JP-A-2010-244038.

[0063] Furthermore, the liquid crystal compound is preferably a liquid crystal compound having a polymerizable group in the molecule (polymerizable liquid crystal compound). Examples of the polymerizable group include an ethylenically unsaturated group and a ring-polymerizable group, and specific examples include a vinyl group, a styryl group, an allyl group, and a substituent selected from the above-mentioned polymerizable group P. When the liquid crystal compound contains a polymerizable group, the number of polymerizable groups is not particularly limited, but is, for example, one or more. In order to fix the alignment, it is preferable that the liquid crystal compound has two or more polymerizable groups in one molecule. The upper limit is preferably six or less, more preferably three or less.

[0064] The average refractive index nk of the liquid crystal compound at a wavelength of 550 nm is preferably 1.70 or more, more preferably 1.79 or more. The upper limit of the average refractive index nk is not particularly limited and may be, for example, 3.5 or less. The average refractive index here refers to a value measured for the liquid crystal compound alone in accordance with JIS K0062:1992 "Method for measuring refractive index of chemical products." When the liquid crystal compound can only be obtained in an opaque state at room temperature, the refractive index of the solution obtained by dissolving it in a solvent with a known refractive index may be measured and extrapolated from the change in concentration. Furthermore, when the liquid crystal compound can only be obtained in an optically anisotropic state at room temperature, the three-dimensional refractive index may be measured using a means such as ellipsometry and then averaged to obtain the average refractive index.

[0065] Among these, it is preferable to use, as the liquid crystal compound, a compound (A) having a structure represented by the following general formulas (I) to (IV).

[0066]

[0067] In formula (I), A １ and A ２ each independently represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group, which may have a substituent. * represents a bonding position.

[0068] The aromatic hydrocarbon ring group may have a monocyclic structure or a polycyclic structure. The aromatic hydrocarbon ring group is not particularly limited, but is preferably an arylene group, more preferably an arylene group having 6 to 20 carbon atoms, still more preferably an arylene group having 6 to 10 carbon atoms, and particularly preferably a phenylene group or a naphthylene group.

[0069] The aromatic heterocyclic group may have a monocyclic structure or a polycyclic structure. Among these, the aromatic heterocyclic group is preferably a 5- or 6-membered monocyclic aromatic heterocyclic group. The heteroatom contained in the aromatic heterocyclic group is not particularly limited, and examples thereof include a nitrogen atom, an oxygen atom, and a sulfur atom. The aromatic heterocyclic group is not particularly limited, but is preferably a heteroarylene group, more preferably a heteroarylene group having 3 to 20 carbon atoms, and even more preferably a heteroarylene group having 3 to 10 carbon atoms. The heteroatom contained in the heteroarylene group is preferably at least one selected from the group consisting of a nitrogen atom, an oxygen atom, and a sulfur atom.

[0070] The substituents that the above-mentioned aromatic hydrocarbon ring group and aromatic heterocyclic group may have are not particularly limited, but are preferably substituents selected from the above-mentioned substituents L.

[0071] The molecular weight of the liquid crystal compound is, for example, preferably 200 to 100,000, more preferably 300 to 10,000, and even more preferably 400 to 2500. When the liquid crystal compound is a polymer, the molecular weight means the weight average molecular weight.

[0072] As the liquid crystal compound, a compound represented by the following formula (II) is preferred, and a compound represented by the following formula (III) or formula (IV) is more preferred, in terms of more excellent effects of the present invention. The compounds represented by formulas (II) to (IV) are described below.

[0073]

[0074] In formula (II), P １ and P ２ each independently represents a hydrogen atom, a halogen atom, —CN, —NCS, or a polymerizable group. １and P ２ is preferably each independently a polymerizable group. The polymerizable group is not particularly limited, but examples thereof include an ethylenically unsaturated group and a ring-polymerizable group, and is preferably a substituent selected from the polymerizable groups P described above.

[0075] In formula (II), Sp １ and Sp ２ each independently represents a single bond or a divalent linking group. １ and Sp ２ does not represent a divalent linking group containing at least one group selected from the group consisting of an aromatic hydrocarbon ring group, an aromatic heterocyclic group, and an aliphatic hydrocarbon ring group. １ and Sp ２ The divalent linking group represented by the formula (I) is not particularly limited, but may be an alkylene group (preferably an alkylene group having 1 to 20 carbon atoms), an alkenylene group (preferably an alkenylene group having 2 to 20 carbon atoms), -O-, -S-, -CO-, -SO-, -SO ２ -, -COO-, -OCO-, -CO-S-, -S-CO-, -O-CO-O-, or a divalent linking group formed by combining a plurality of these groups is preferred. １ and Sp ２ Among these, each independently is preferably a single bond, an alkylene group having 1 to 10 carbon atoms, -O-, -S-, -CO-, -COO-, -OCO-, or a divalent linking group formed by combining a plurality of these; more preferably a single bond, an alkylene group having 1 to 6 carbon atoms, -O-, -S-, or a divalent linking group formed by combining a plurality of these; and even more preferably a single bond, an alkylene group having 1 to 4 carbon atoms, -O-, -S-, or a divalent linking group formed by combining a plurality of these.

[0076] In formula (II), Z １ and Z ２ each independently represents a single bond or a divalent linking group. １ and Z ２ If there are multiple Zs, there are multiple Zs. １ Z ２ may be the same or different. １ and Z ２does not represent a divalent linking group containing at least one group selected from the group consisting of an aromatic hydrocarbon ring group, an aromatic heterocyclic group, and an aliphatic hydrocarbon ring group. １ and Z ２ The divalent linking group represented by the formula (I) is not particularly limited, and may be an alkylene group (preferably an alkylene group having 1 to 20 carbon atoms), an alkenylene group (preferably an alkenylene group having 2 to 20 carbon atoms), an alkynylene group (preferably an alkynylene group having 2 to 20 carbon atoms), -O-, -S-, -CO-, -SO-, -SO ２ -, -COO-, -OCO-, -CO-S-, -S-CO-, -O-CO-O-, or a divalent linking group formed by combining a plurality of these is preferred. １ and Z ２ Specific examples of the divalent linking group represented by the formula: ２ -, -COO-, -OCO-, -CO-S-, -S-CO-, -O-CO-O-, -CO-NR-, -NR-CO-, -SCHR-, -CHRS-, -SO-CHR-, -CHR-SO-, -SO ２ -CHR-, -CHR-SO ２ -, -CF ２ O-, -OCF ２ -, -CF ２ S-, -SCF ２ -, -OCHRCHRO-, -SCHRCHRS-, -SO-CHRCHR-SO-, -SO ２ -CHRCHR-SO ２-, -CH=CH-COO-, -CH=CH-OCO-, -COO-CH=CH-, -OCO-CH=CH-, -COO-CHRCHR-, -OCO-CHRCHR-, -CHRCHR-COO-, -CHRCHR-OCO-, -COO-CHR-, -OCO-CHR-, -CHR-COO-, -CHR-OCO-, -CR=CR-, -CR=N-, -N=CR-, -N=N-, -CR=N-N=CR-, -CF=CF-, and -C≡C- are mentioned. R represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. R is preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and even more preferably a hydrogen atom. When multiple R are present, the multiple R may be the same or different.

[0077] Z １ and Z ２ Among these, each independently is preferably —CHRCHR—, —OCHR—, —CHRO—, —COO—, —OCO—, —CO—NH—, —NH—CO—, or —C≡C—, and more preferably —CHRCHR—, —OCHR—, —CHRO—, or —C≡C—.

[0078] In formula (II), A １ and A ２ each independently represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group, which may have a substituent. １ and A ２ As the group, A in formula (I) １ and A ２ The same definition and preferred embodiments are also the same.

[0079] B １ and B ２ each independently represents an aromatic hydrocarbon ring group, an aromatic heterocyclic group, or an aliphatic hydrocarbon ring group, which may have a substituent. １ and B ２ If there are multiple B １ B ２ They may be the same or different from each other.

[0080] The aromatic hydrocarbon ring group may have a monocyclic structure or a polycyclic structure. The aromatic hydrocarbon ring group is not particularly limited, but is preferably an arylene group, more preferably an arylene group having 6 to 20 carbon atoms, still more preferably an arylene group having 6 to 10 carbon atoms, and particularly preferably a phenylene group or a naphthylene group.

[0081] The aromatic heterocyclic group may have a monocyclic structure or a polycyclic structure. Among these, the aromatic heterocyclic group is preferably a 5- or 6-membered monocyclic aromatic heterocyclic group. The heteroatom contained in the aromatic heterocyclic group is not particularly limited, and examples thereof include a nitrogen atom, an oxygen atom, and a sulfur atom. The aromatic heterocyclic group is not particularly limited, but is preferably a heteroarylene group, more preferably a heteroarylene group having 3 to 20 carbon atoms, and even more preferably a heteroarylene group having 3 to 10 carbon atoms. The heteroatom contained in the heteroarylene group is preferably at least one selected from the group consisting of a nitrogen atom, an oxygen atom, and a sulfur atom.

[0082] The aliphatic hydrocarbon ring group may have a monocyclic structure or a polycyclic structure. The aliphatic hydrocarbon ring group is not particularly limited, and examples thereof include a cycloalkylene group. Among these, a cycloalkylene group having 3 to 20 carbon atoms is preferred, and a cycloalkylene group having 3 to 10 carbon atoms is more preferred.

[0083] The substituents that the above-mentioned aromatic hydrocarbon ring group, aromatic heterocyclic group, and aliphatic hydrocarbon ring group may have are not particularly limited, but are preferably substituents selected from the above-mentioned substituents L.

[0084] In formula (II), n and m each independently represent an integer of 0 to 4. In particular, n and m each independently preferably represent an integer of 0 to 3, and more preferably represent an integer of 0 to 2.

[0085]

[0086]

[0087] In formula (III) and formula (IV), T １ and T ２Each of X independently represents a hydrogen atom or a methyl group. １ and X ２ Each independently represents a methylene group, an oxygen atom, or a sulfur atom. r represents an integer of 1 to 5. t and v each independently represent 0 or 1. u represents 1 or 2. w represents an integer of 1 to 5. Q １ ~Q １６ Each independently represents a hydrogen atom or a substituent. １ ~E ６ each independently represents a hydrogen atom or a substituent.

[0088] Q １ ~Q １６ The substituent represented by the formula (I) is not particularly limited, but is preferably a substituent selected from the above-mentioned substituents L.

[0089] E １ ~E ６ The substituent represented by the formula (I) is not particularly limited, but is preferably a substituent selected from the above-mentioned substituents L.

[0090] Specific examples of the liquid crystal compound are not particularly limited, and include, for example, JP 2009-102245 A, JP 4655348 A, JP 4524827 A, JP 4720200 A, JP 2004-091380 A, JP 3972430 A, JP 4517416 A, JP 2002-128742 A, JP 4810750 A, JP 5888544 A, JP 2014-019654 A, JP 6241654 A, JP 6372060 A, JP 6323144 A, JP 2005-015406 A, JP 2007-230 A 968, Japanese Patent No. 6761484, Japanese Patent No. 6681992, International Publication No. 19 / 182129, CN01134217A, KR101069555B, KR101690767B, CN20120229730A, Japanese Patent No. 4053782, Japanese Patent Application Laid-Open No. 2009-249406, Japanese Patent No. 4121075, Japanese Patent Publication No. 2005-528416, US6514578, International Publication No. 06 / 006819, Japanese Patent Application Laid-Open No. 2011-184417, Japanese Patent Application Laid-Open No. 2013-095685, Japanese Patent Application Laid-Open No. 2013-103897, Japanese Patent Application Laid-Open No. 2002 -088008, JP 2002-226412, JP 2012-167214, JP 2012-167068, JP 2018-084511, JP 2003-055317, JP 2001-329264, JP 2002-0300 No. 16, JP 2003-055664 A, JP 2018-070889 A, CN102557896 A, US2015369982 A, JP 2020-105264 A, JP 2014-224237 A, JP 2012-051862 A, JP 2010-106274, JP 2005-179557, JP 2005-035985, JP 2002-012579, JP 2002-003845, JP 2001-233837, JP 2019-532167, JP 2016-509247, JP 2010-503733, JP 2003-533557, WO 19 / 098115, WO 18 / 034216, WO 18 / 221236, WO 18 / 123396, WO 18 / 003482,Examples of the compounds include those described in WO 17 / 086143, WO 14 / 192655, WO 13 / 161669, and WO 09 / 104468.

[0091] In addition to the above, the liquid crystal compounds also include the compounds shown below.

[0092]

[0093] Here, the liquid crystalline compound refers to a compound having a partial structure represented by formula (I) above, which has a transition temperature to a liquid crystal phase of 1° C. or higher when cooled. The refractive index anisotropy Δn of the liquid crystalline compound at a wavelength of 550 nm is preferably 0.20 or higher, more preferably 0.24 or higher, and even more preferably 0.28 or higher.

[0094] The above-mentioned liquid crystal compounds may be used alone or in combination of two or more. When a plurality of liquid crystal compounds are used in combination, it is also preferable that at least one of the liquid crystal compounds is a polymerizable liquid crystal compound.

[0095] (Polymerization initiator) The liquid crystal composition preferably contains a polymerization initiator. The polymerization initiator is preferably a photopolymerization initiator that can initiate a polymerization reaction by ultraviolet irradiation. Examples of the photopolymerization initiator include α-carbonyl compounds (described in U.S. Pat. Nos. 2,367,661 and 2,367,670), acyloin ethers (described in U.S. Pat. No. 2,448,828), α-hydrocarbon-substituted aromatic acyloin compounds (described in U.S. Pat. No. 2,722,512), polynuclear quinone compounds (described in U.S. Pat. Nos. 3,046,127 and 2,951,758), and combinations of triarylimidazole dimers and p-aminophenyl ketones. Examples of polymerization initiators include α-carbonyl compounds and acylphosphine oxide compounds (described in U.S. Pat. No. 3,549,367), acridine and phenazine compounds (described in JP-A-60-105667 and U.S. Pat. No. 4,239,850), oxadiazole compounds (described in U.S. Pat. No. 4,212,970), and acylphosphine oxide compounds (described in JP-B-63-040799, JP-B-5-029234, JP-A-10-95788, and JP-A-10-29997). Among these, preferred polymerization initiators are α-carbonyl compounds or acylphosphine oxide compounds, with acylphosphine oxide compounds being more preferred. Examples of acylphosphine oxide compounds include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name: Omnirad (registered trademark) 819).

[0096] In the present invention, it is preferable that the peak wavelength Pmax (hereinafter simply referred to as "Pmax") of the longest wavelength peak among the absorption peaks of the polymerization initiator is 390 nm or more. If this condition is satisfied, sufficient energy can be imparted to the polymerization initiator via light in the process of forming the optically anisotropic layer of the present invention, and an optically anisotropic layer with good properties can be obtained. The upper limit of Pmax of the polymerization initiator is not particularly limited, and may be, for example, 450 nm or less.

[0097] The polymerization initiator is a polymerization initiator having a molar absorption coefficient of 650 mol at the above Pmax. －１ ・cm －１ It is preferable that the content is 690 mol or more.－１ ・cm －１ If this condition is satisfied, sufficient energy can be imparted to the polymerization initiator via light in the step of forming the optically anisotropic layer of the present invention, resulting in excellent curability. There is no particular upper limit to the molar absorption coefficient at Pmax of the polymerization initiator, and it is, for example, 2000 mol －１ ・cm －１ It may be the following:

[0098] The molar absorption coefficient of the polymerization initiator at a wavelength of 405 nm is 550 mol －１ ・cm －１ Preferably, it is 520 mol or less. －１ ・cm －１ It is more preferable that the molar absorption coefficient is 50 mol or less. If this condition is satisfied, the difference in reaction rate between the side closer to the light source and the side farther from the light source in the thickness direction of the layer is small, and optical anisotropy with good characteristics can be obtained. Although there is no particular restriction on the lower limit of the molar absorption coefficient of the polymerization initiator at a wavelength of 405 nm, a molar absorption coefficient of 50 mol or less is preferable in terms of better curability since sufficient energy can be imparted to the polymerization initiator via light in the process of forming the optically anisotropic layer of the present invention. －１ ・cm －１ The above is preferable.

[0099] When the liquid crystal composition contains a polymerization initiator, the content of the polymerization initiator in the liquid crystal composition is preferably 0.1 to 20 mass %, more preferably 1 to 10 mass %, relative to the content of the liquid crystal compound contained in the liquid crystal composition. In the liquid crystal composition, the polymerization initiator may be used alone or in combination of two or more. When two or more types are used, the total content thereof is preferably within the above range.

[0100] (Surfactant) The liquid crystal composition may contain a surfactant that contributes to stable or rapid formation of a liquid crystal phase. Examples of the surfactant include fluorine-containing (meth)acrylate polymers, alkylsilane acrylate polymers, hydrophilic group-containing polysiloxane polymers, compounds represented by general formulas (X1) to (X3) described in WO 2011 / 162291, compounds represented by general formula (I) described in paragraphs

[0082] to

[0090] of JP 2014-119605, and compounds described in paragraphs

[0020] to

[0031] of JP 2013-047204. Examples of fluorine-containing (meth)acrylate polymers that can be used as surfactants include polymers described in paragraphs

[0018] to

[0043] of JP 2007-272185.

[0101] Some of these compounds can reduce the tilt angle of the molecules of the liquid crystal compound at the air interface of the layer, or can align the liquid crystal compound substantially horizontally. In this specification, "horizontal alignment" refers to the molecular axis of the liquid crystal compound (corresponding to the long axis of the liquid crystal compound when the liquid crystal compound is a rod-shaped liquid crystal compound) being parallel to the film surface, but does not require strict parallelism. In this specification, it means an alignment in which the tilt angle with the film surface is less than 20 degrees. When the liquid crystal compound is horizontally aligned near the air interface, alignment defects are unlikely to occur, and the application of an appropriate compound has the effect of increasing transparency in the visible light region.

[0102] Some of these compounds can increase the tilt angle of the molecules of the liquid crystal compound at the air interface of the layer, or can obliquely align the liquid crystal compound. In this specification, "oblique alignment" refers to a state in which the molecular axis of the liquid crystal compound (corresponding to the long axis of the liquid crystal compound when the liquid crystal compound is a rod-shaped liquid crystal compound) is not parallel to the film surface, and refers to an alignment in which the tilt angle with the film surface is 20 degrees or more and less than 85 degrees. When the liquid crystal compound has a twisted alignment or cholesteric alignment, alignment defects are less likely to occur if the alignment is oblique near the air interface, so the application of an appropriate compound has the effect of increasing transparency in the visible light region.

[0103] When the liquid crystal composition contains a surfactant, the content of the surfactant in the liquid crystal composition is not particularly limited, but is preferably 0.001 to 10 mass %, more preferably 0.05 to 3 mass %, based on the total mass of the liquid crystal compound contained in the liquid crystal composition. The liquid crystal composition may contain one surfactant alone or two or more surfactants. When two or more surfactants are used, the total content thereof is preferably within the above range.

[0104] (Solvent) The liquid crystal composition may contain a solvent. The solvent is preferably a solvent capable of dissolving each component to be blended in the liquid crystal composition, and examples thereof include ketones (e.g., acetone, 2-butanone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and cyclopentanone), ethers (e.g., dioxane and tetrahydrofuran), aliphatic hydrocarbons (e.g., hexane), alicyclic hydrocarbons (e.g., cyclohexane), aromatic hydrocarbons (e.g., toluene, xylene, and trimethylbenzene), halogenated carbons (e.g., dichloromethane, dichloroethane, dichlorobenzene, and chlorotoluene), esters (e.g., methyl acetate, ethyl acetate, and butyl acetate), water, alcohols (e.g., ethanol, isopropanol, butanol, and cyclohexanol), cellosolves (e.g., methyl cellosolve and ethyl cellosolve), cellosolve acetates, sulfoxides (e.g., dimethyl sulfoxide), and amides (e.g., dimethylformamide and dimethylacetamide). When the liquid crystal composition contains a solvent, the content of the solvent in the liquid crystal composition is preferably an amount that results in a solids concentration of 0.5 to 30% by mass, more preferably an amount that results in a solids concentration of 1 to 20% by mass. The liquid crystal composition may use one solvent alone or two or more solvents. When two or more solvents are used, the total content thereof is preferably within the above range. The solids concentration means the total content of components other than the solvent relative to the total mass of the liquid crystal composition.

[0105] (Chiral Agent) The liquid crystal composition may contain a chiral agent. A chiral agent (optically active compound) has the function of inducing a twisted orientation in the thickness direction or a helical structure of a cholesteric liquid crystal phase. The chiral agent may be selected according to the purpose, since the twist direction or helical pitch of the helix induced varies depending on the compound. The chiral agent is not particularly limited, and examples thereof include the compounds described in "Liquid Crystal Device Handbook, Chapter 3, Section 4-3, Chiral Agents for TN (Twisted Nematic) and STN (Super Twisted Nematic)," page 199, edited by the 142nd Committee of the Japan Society for the Promotion of Science, 1989," isosorbide, and isomannide derivatives. Chiral agents generally contain an asymmetric carbon atom, but axially asymmetric compounds or planar asymmetric compounds that do not contain an asymmetric carbon atom can also be used as chiral agents. Examples of axially asymmetric compounds or planarly asymmetric compounds include binaphthyl, helicene, paracyclophane, and derivatives thereof. The chiral agent may also have a polymerizable group. When both the chiral agent and the liquid crystal compound have a polymerizable group, a polymer having a repeating unit derived from the polymerizable liquid crystal compound and a repeating unit derived from the chiral agent can be formed by a polymerization reaction between the polymerizable chiral agent and the polymerizable liquid crystal compound. In this embodiment, the polymerizable group of the polymerizable chiral agent is preferably the same type of group as the polymerizable group of the polymerizable liquid crystal compound. Furthermore, the chiral agent itself may be a liquid crystal compound.

[0106] When the chiral agent has a photoisomerizable group, a pattern of a desired reflection wavelength corresponding to the emission wavelength can be formed by irradiating the chiral agent with actinic rays or the like through a photomask after coating and alignment. The photoisomerizable group is preferably an isomerization site of a compound exhibiting photochromic properties, an azo group, an azoxy group, or a cinnamoyl group. Specific compounds that can be used include those described in JP-A-2002-080478, JP-A-2002-080851, JP-A-2002-179668, JP-A-2002-179669, JP-A-2002-179670, JP-A-2002-179681, JP-A-2002-179682, JP-A-2002-338575, JP-A-2002-338668, JP-A-2003-313189, and JP-A-2003-313292.

[0107] When the liquid crystal composition contains a chiral dopant, the content of the chiral dopant in the liquid crystal composition is not particularly limited, but is preferably 0.01% by mass to 15% by mass, and more preferably 1.0% by mass to 10% by mass, based on the content of the liquid crystal compound.

[0108] (Other Additives) The liquid crystal composition may contain additives other than the above-mentioned components, such as antioxidants, ultraviolet absorbers, sensitizers, stabilizers, plasticizers, chain transfer agents, polymerization inhibitors, antifoaming agents, leveling agents, thickeners, flame retardants, surfactants, dispersants, and coloring materials such as dyes and pigments.

[0109] (Δn of Liquid Crystal Composition) The refractive index anisotropy Δn of the liquid crystal composition is preferably 0.21 or more, more preferably 0.25 or more, even more preferably 0.28 or more, and particularly preferably 0.30 or more at a wavelength of 550 nm, in order to increase the diffraction efficiency of the resulting film. The upper limit is not particularly limited, but is preferably 0.80 or less, for example. The refractive index anisotropy Δn of the liquid crystal composition can be measured by a method using a wedge-shaped liquid crystal cell described on page 202 of Liquid Crystal Handbook (edited by the Liquid Crystal Handbook Editorial Committee, published by Maruzen Co., Ltd.). When the liquid crystal composition contains a solvent, the solvent is removed from the liquid crystal composition before measuring Δn.

[0110] [Method for Producing Optically Anisotropic Layer 1] A specific example of a method for producing the optically anisotropic layer 1 includes a step X of bringing a liquid crystalline composition into contact with a substrate having an alignment film with a predetermined alignment pattern to form a composition layer on the alignment film on the substrate, and a step Y of subjecting the composition layer to a heat treatment to align the liquid crystalline compound, followed by a curing treatment. After producing the optically anisotropic layer 1, the substrate may or may not be removed from the optically anisotropic layer. Similarly, the alignment film may or may not be removed from the optically anisotropic layer after producing the optically anisotropic layer 1. The substrate may also be an oxygen barrier layer (e.g., a glass substrate) as described below.

[0111] The specific procedures of Step X and Step Y are described in detail below. (Step X) Substrate The type of substrate used in Step X is not particularly limited, and examples thereof include known substrates (for example, resin substrates, glass substrates, ceramic substrates, semiconductor substrates, and metal substrates).

[0112] Alignment film An alignment film is disposed on the substrate. The presence of the alignment film facilitates orienting the liquid crystal compound 30 in a predetermined liquid crystal alignment pattern during the production of the optically anisotropic layer 1. As described above, the optically anisotropic layer 1 has a liquid crystal alignment pattern in which the direction of the optical axis 30A (see FIG. 2) derived from the liquid crystal compound 30 changes while continuously rotating along one in-plane direction (x direction). Therefore, the alignment film is formed so that the optically anisotropic layer can form this liquid crystal alignment pattern.

[0113] Various known alignment films can be used, including, for example, a rubbed film made of an organic compound such as a polymer, an obliquely evaporated film of an inorganic compound, a film having microgrooves, and a film obtained by accumulating LB (Langmuir-Blodgett) films made of organic compounds such as ω-tricosanoic acid, dioctadecylmethylammonium chloride, and methyl stearate by the Langmuir-Blodgett method.

[0114] The alignment film formed by rubbing treatment can be formed by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth. Suitable materials for the alignment film include polyimide, polyvinyl alcohol, polymers having polymerizable groups as described in JP-A-9-152509, and materials used to form alignment films as described in JP-A-2005-097377, JP-A-2005-099228, and JP-A-2005-128503.

[0115] As the alignment film, a so-called photo-alignment film can be suitably used, which is formed by irradiating a photo-alignment material with polarized or non-polarized light. When irradiating with polarized light to form an alignment film, the photo-alignment material can be irradiated from a vertical direction or an oblique direction to form the alignment film, and when irradiating with non-polarized light to form an alignment film, the photo-alignment material can be irradiated from an oblique direction to form the alignment film. Examples of photo-alignment materials used for the photo-alignment film include those described in JP 2006-285197 A, JP 2007-76839 A, JP 2007-138138 A, JP 2007-94071 A, JP 2007-121721 A, JP 2007-140465 A, JP 2007-156439 A, and JP 2007 azo compounds described in JP-A-133184, JP-A-2009-109831, Japanese Patent Nos. 3883848 and 4151746, aromatic ester compounds described in JP-A-2002-229039, maleic anhydrides having photo-orientable units described in JP-A-2002-265541 and JP-A-2002-317013, and the like. Examples thereof include imide and / or alkenyl-substituted nadimide compounds, photocrosslinkable silane derivatives described in Japanese Patent Nos. 4205195 and 4205198, photocrosslinkable polyimides, photocrosslinkable polyamides, and photocrosslinkable esters described in JP-T-2003-520878, JP-T-2004-529220, and JP-T-4162850, and photodimerizable compounds described in JP-A-9-118717, JP-A-10-506420, JP-A-2003-505561, WO 2010 / 150748, JP-A-2013-177561, and JP-A-2014-12823, in particular cinnamate compounds, chalcone compounds, and coumarin compounds. Among these, azo compounds, photocrosslinkable polyimides, photocrosslinkable polyamides, photocrosslinkable esters, cinnamate compounds, chalcone compounds, and the like can be suitably used.

[0116] The thickness of the alignment film is not particularly limited, and may be appropriately set to a thickness that provides the necessary alignment function depending on the material used to form the alignment film. The thickness of the alignment film is preferably 0.01 to 5 μm, and more preferably 0.05 to 2 μm.

[0117] The method for forming the alignment film is not particularly limited, and known methods depending on the material for forming the alignment film can be used. A photo-alignment film formed by irradiating a photo-alignment material with polarized or non-polarized light is preferred, as this makes it easier to form an alignment pattern in the optically anisotropic layer 1. The methods described in paragraphs

[0078] to

[0080] of International Publication No. 2020 / 022496 can be suitably applied. The alignment film may also be reusable.

[0118] Step X: The method for contacting a substrate provided with an alignment film having a predetermined alignment pattern (hereinafter also referred to as "alignment film-attached substrate") with a liquid crystalline composition is not particularly limited, and examples thereof include a method of applying the composition to the alignment film on the substrate and a method of immersing the alignment film-attached substrate in the composition. After contacting the alignment film-attached substrate with the composition, a drying treatment may be performed, if necessary, to remove the solvent from the composition layer disposed on the alignment film on the substrate. Furthermore, an alignment film-attached substrate that has been used at least once to form an optically anisotropic layer may be reused as the alignment film-attached substrate. That is, after being used to form a first optically anisotropic layer, the optically anisotropic layer can be removed by peeling or transfer, thereby reproducing the alignment film-attached substrate. Before providing a liquid crystalline compound on the alignment film again, the alignment film may be subjected to a cleaning treatment or a foreign matter removal treatment.

[0119] (Step Y) Step Y is a step of subjecting the composition layer to a heat treatment to align the liquid crystalline compound, followed by a curing treatment. By subjecting the composition layer to a heat treatment, the liquid crystalline compound is oriented to form a liquid crystal phase. For example, when the composition layer contains a chiral agent, a twisted orientation in the thickness direction or a cholesteric liquid crystal phase is formed. The conditions for the heat treatment are not particularly limited, and optimal conditions are selected depending on the type of liquid crystalline compound. The curing method is not particularly limited, and examples include photocuring and heat curing. Among these, photoirradiation is preferred, with irradiation with light in the ultraviolet to visible light range being more preferred, irradiation with light with a wavelength of 360 to 420 nm being even more preferred, and irradiation with light with a wavelength of 405 nm being particularly preferred. Light sources such as ultraviolet lamps and LEDs are used for irradiation. The cured product obtained by the above treatment corresponds to a layer in which a liquid crystalline phase is fixed. In particular, when the liquid crystalline composition contains a chiral agent, a layer in which a cholesteric liquid crystalline phase is fixed is formed. These layers no longer need to exhibit liquid crystallinity. More specifically, for example, the state in which the cholesteric liquid crystal phase is "fixed" is the most typical and preferred state in which the orientation of the liquid crystalline compound in the cholesteric liquid crystal phase is maintained. More specifically, it is preferred that the layer has no fluidity and the fixed orientation can be stably maintained without causing any change in the orientation due to an external field or external force, usually in a temperature range of 0 to 50°C, or under more severe conditions in a temperature range of -30 to 70°C.

[0120] Furthermore, by subjecting only a portion of the composition layer in the thickness direction to the above-described curing treatment and then adding a second heating step, it is possible to create regions with different alignment states in the thickness direction of the optically anisotropic layer. Specifically, only a portion of the composition in the thickness direction is fixed, while the remaining portion is made to exhibit liquid crystallinity. A second heating step is then performed, in which the composition is heated from the liquid crystallinity state until it changes to an isotropic phase, thereby fixing the remaining portion in the isotropic phase state. This method allows the thickness at which the liquid crystal phase is fixed to be varied in the in-plane direction of the composition layer. Specifically, the thickness at which the liquid crystal phase is fixed can be varied by providing a light irradiation amount or temperature distribution in the plane. By employing this method, it is possible to fabricate an optical element including an optically anisotropic layer in which the diffraction efficiency in the alignment pattern region changes in at least one in-plane direction.

[0121] A step of laminating other layers described below and a step of peeling or transferring the optically anisotropic layer may be added after the step Y. To peel or transfer the optically anisotropic layer, the carrier substrate and the optically anisotropic layer may be bonded in advance with an adhesive layer or the like, and then the substrate with the alignment film may be removed.

[0122] [Other Layers] The optical element of the present invention may have other layers in addition to the optically anisotropic layer described above, such as a substrate, a light guide plate, an oxygen barrier layer, an antireflection layer, a polarizer, a wave plate, a retardation plate, and an absorption filter.

[0123] The substrate is not particularly limited in type, and examples thereof include known substrates (e.g., resin substrates, glass substrates, ceramic substrates, semiconductor substrates, and metal substrates). The substrate may be flexible or rigid. The substrate used in the manufacturing process of the optically anisotropic layer described above may be used as is, or may be peeled from the substrate used in the manufacturing process and laminated with any substrate. For lamination, bonding may be performed via an adhesive layer, a pressure-sensitive adhesive layer, or the like, or activated surfaces may be directly bonded together after surface activation treatment such as plasma treatment or corona treatment.

[0124] The substrate may be light-transmitting, light-reflective, or light-absorbing. For example, in the case of an optical element for near-eye displays described below, the substrate is preferably light-transmitting, and a glass substrate, a quartz substrate, or a transparent resin substrate is preferred.

[0125] The light guide plate can be obtained by processing a glass substrate, a quartz substrate, or a transparent resin substrate. An optical element (i.e., a light guide element) including the light guide plate can be suitably used for near-eye displays, which will be described later.

[0126] The optical element may have an optically anisotropic layer and an oxygen barrier layer disposed on at least one side of the optically anisotropic layer. The presence of the oxygen barrier layer can prevent unexpected denaturation of compounds present in the optically anisotropic layer, thereby reducing light absorption at 405 nm. It also has the effect of suppressing an increase in light absorption at 405 nm over long-term use. In particular, providing an oxygen barrier layer is particularly preferable for applications requiring light resistance. It is particularly preferable for the optical element to have oxygen barrier layers on both sides of the optically anisotropic layer, as this provides better light resistance.

[0127] The oxygen permeability coefficient of the oxygen barrier layer at 25°C and 50% RH is 1.0 x 10 －１１ cm ３ cm / (cm ２ s mmHg) or less, and the effect of the present invention is more excellent. －１２ cm ３ cm / (cm ２ s mmHg) or less, and more preferably 1.0 x 10 －１３ cm ３ cm / (cm ２ The lower limit is not particularly limited, but may be, for example, 1.0×10 －２０ cm ３ cm / (cm ２ The oxygen permeability coefficient of the oxygen barrier layer at 25° C. and 50% RH can be measured by the isobaric method in accordance with ISO 15105-2.

[0128] In addition, the oxygen barrier layer has an oxygen permeability coefficient [cm ３ cm / (cm ２ The value obtained by dividing the film thickness [μm] by the film thickness [μm] is 1.0 × 10 －１１ Preferably, the value is 1.0 x 10 or less. －１２ More preferably, 1.0 x 10 －１３ The lower limit is not particularly limited, but for example, 1.0 × 10 －２０ The above is preferable.

[0129] The oxygen barrier layer preferably has a transmittance of 70% or more, more preferably 80% or more, and even more preferably 90% or more. The transmittance refers to the average transmittance of visible light with a wavelength of 400 to 700 nm. The transmittance is a value measured at 25°C using a spectrophotometer (for example, a UV-3100PC spectrophotometer manufactured by Shimadzu Corporation).

[0130] Examples of materials constituting the oxygen barrier layer include glass and resin. The resin constituting the oxygen barrier layer is not particularly limited, and examples include ethylene-vinyl alcohol copolymer, polyamide, polyvinyl alcohol, polyacrylonitrile, and polyvinylidene chloride. The organic molecular films described in JP-A-2014-218444 and JP-A-2014-218548, the barrier films described in JP-A-2020-188047, and the coating films described in JP-A-2020-186281 can also be used as the oxygen barrier layer. The oxygen barrier layer may also be a polarizing plate. The oxygen barrier layer may also contain an inorganic filler.

[0131] The lower limit of the thickness of the oxygen barrier layer is not particularly limited, but from the viewpoint of more excellent oxygen barrier properties, it is preferably 0.01 μm or more, more preferably 0.1 μm or more, and even more preferably 1 μm or more. The thicker the oxygen barrier layer, the higher the oxygen barrier properties. Therefore, the upper limit of the thickness of the oxygen barrier layer is not particularly limited, but for example, when the oxygen barrier layer is made of glass, it is preferably 2 cm or less, more preferably 1 cm or less, and even more preferably 5 mm or less, from the viewpoint of reducing the overall thickness of the optical element and suppressing its weight. Furthermore, for example, when the oxygen barrier layer is made of resin, it is preferably 2 cm or less, more preferably 1 cm or less, even more preferably 5 mm or less, even more preferably 100 μm or less, particularly preferably 50 μm or less, particularly more preferably 30 μm or less, and most preferably 10 μm or less, from the viewpoint of reducing the overall thickness of the optical element and achieving excellent productivity.

[0132] <Display Optical System> The display optical system of the present invention includes the above-described optical element of the present invention and a display element. Image light emitted from the display element or light rays for forming an image is emitted to an observer via the optical element of the present invention, allowing the observer to view the image.

[0133] Examples of image display devices including such display optical systems include near-eye displays, head-up displays, projectors, rear-projection displays, and light guide displays. Examples of near-eye displays include head-mounted displays having a folded optical system as described in JP-A-2010-526321 and light guide plate-type near-eye displays as described in Utility Model Registration No. 3222983. The optical element of the present invention can be used for light directivity control, lenses, phase conversion, wavelength dispersion control, and aberration correction in these displays, or for combining optical paths using diffraction effects.

[0134] In particular, in near-eye displays that utilize total internal reflection from a light guide plate, light is repeatedly incident on the optical element of the present invention included in the display optical system, and therefore the benefit of improving light utilization efficiency, which is the effect of the present invention, is particularly significant and can be preferably utilized. A preferred embodiment of the optical element used in a near-eye display that utilizes total internal reflection from a light guide plate is an optical element comprising the above-mentioned optically anisotropic layer and a substrate, wherein the substrate guides image light incident on the substrate by total internal reflection, and the orientation pattern region of the optically anisotropic layer has at least one function selected from the group consisting of: a function to change the optical path of the image light so that at least a portion of the guided image light exits the substrate; a function to change the total reflection direction in the internal total reflection of the guided image light; and a function to change the optical path of the image light incident on the substrate from the outside so that the image light is totally internally reflected within the substrate. The substrate referred to here can also be referred to as a light guide plate.

[0135] In particular, when image light is emitted from a light guide plate, it is preferable that the diffraction efficiency in the orientation pattern region of the optically anisotropic layer varies along at least one direction in the plane. This configuration allows an image with uniform brightness to be observed regardless of the pupil position. For example, as described above, this configuration can be achieved by using an optically anisotropic layer in which the average value Δna of birefringence in the thickness direction varies along at least one direction in the plane in the orientation pattern region of the optically anisotropic layer. The average value Δna of birefringence in the thickness direction of the optically anisotropic layer can generally be measured using a method using a wedge-shaped liquid crystal cell as described on page 202 of "Liquid Crystal Handbook" (edited by the Liquid Crystal Handbook Editorial Committee, published by Maruzen Co., Ltd.). The above Δna corresponds to a value measured at a wavelength of 550 nm at 30°C. Furthermore, the Δn in the thickness direction of the cured liquid crystal layer can be determined by peeling the layer in the thickness direction to obtain a thin film sample, measuring the physical thickness, and then measuring the polarization characteristics using a measuring device (e.g., Axoscan by Axometrics).

[0136] The optically anisotropic layer can be provided in a plane corresponding to one or more of the image display region, the region for changing the total reflection direction, and the image incidence region set in the plane of the light guide plate, with an in-plane shape that matches each of the regions. Alternatively, a single optically anisotropic layer may be provided to include the three regions described above, with only the regions corresponding to these three regions being alignment pattern regions, and the remaining regions being connected by regions without an alignment pattern (non-alignment pattern regions). That is, the optically anisotropic layer may include a region without an alignment pattern within the same plane. Note that an optically anisotropic layer including a region without an alignment pattern within its plane is not limited to including the three alignment pattern regions described above, and may include one, two, or four or more alignment pattern regions.

[0137] <Measurement Optical System> The measurement optical system of the present invention includes the above-described optical element of the present invention and a light receiving element. By optically coupling light emitted from or reflected from a measurement object to the light receiving element via the optical element of the present invention, it is possible to measure the state of the measurement object.

[0138] Examples of measuring devices that include such optical measurement systems include vital sensors such as eye tracking devices, photoplethysmography devices, blood oxygen concentration measuring devices, blood glucose level measuring devices, sphygmomanometers, and blood flow meters, as well as objective measurement devices such as LiDAR, optical range finders, radiation thermometers, spectroscopes, and cameras, as well as fingerprint sensors, face recognition devices, and gesture capture devices. These measuring devices must detect weak signal light, and therefore, using the optical element of the present invention has the advantage of improving light utilization efficiency.

[0139] An image display device including the exemplified measuring instruments, i.e., an image display device including the above-mentioned measurement optical system, is also a preferred embodiment of the present invention. By including these measuring instruments in the image display device, it is possible to obtain various information about the observer and three-dimensional information about the surroundings of the image display device, thereby improving the quality of the image display.

[0140] A specific example is a near-eye display that includes an eye-tracking device that includes the measurement optical system of the present invention and corrects the amount of light, focus, and image to suit the observer. This near-eye display can include, as its display optical system, a display optical system that includes the optical element of the present invention described above.

[0141] The features of the present invention will be explained in more detail below with reference to examples. The materials, reagents, amounts used, amounts of substances, ratios, treatment details, and treatment procedures shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0142] Example 1 (Formation of Alignment Film) A glass substrate was prepared as a support. The following coating liquid for forming an alignment film was applied to the support by spin coating. The support on which the coating film of the coating liquid for forming an alignment film had been formed was dried on a hot plate at 60°C for 60 seconds to form an alignment film.

[0143] -------------------------------------------------- Coating liquid for forming alignment film -------------------------------------------------- Photoalignment material below: 1.00 parts by mass Water 16.00 parts by mass Butoxyethanol 42.00 parts by mass Propylene glycol monomethyl ether 42.00 parts by mass --------------------------------------------------

[0144] -Material for photo alignment-

[0145]

[0146] (Exposure of Alignment Film) Regions 1 and 2 of the alignment film were exposed using the exposure device shown in

[0078] to

[0080] of WO 2020 / 022496 and FIG. 5 to form an alignment film P-1 having an alignment pattern. In the exposure process, the orientation of the alignment film in region 2 was rotated 180° relative to region 1 before exposure, thereby inverting the alignment patterns in regions 1 and 2 by 180°. In the exposure device, a laser emitting laser light with a wavelength (325 nm) was used. The exposure dose by interference light was 300 mJ / cm. 2 The period Λ (the length of 180° rotation of the optical axis) of the orientation pattern formed by the interference of the two laser beams was controlled to be 0.43 μm by changing the crossing angle (crossing angle α) of the two beams.

[0147] (Formation of Optically Anisotropic Layer) The following composition LC-1 was prepared as a liquid crystal compound for forming an optically anisotropic layer.

[0148] ------------------------------------------------ Composition LC-1------------------------------------------------ Rod-shaped liquid crystalline compound L-1 80.00 parts by mass Rod-shaped liquid crystalline compound L-2 20.00 parts by mass Polymerization initiator PI-A (manufactured by BASF, Omnirad (registered trademark) 819) 3.00 parts by mass Chiral agent Ch-1 5.50 parts by mass Leveling agent T-1 0.05 parts by mass Leveling agent T-2 0.05 parts by mass Methyl ethyl ketone 126.7 parts by mass Cyclopentanone 126.7 parts by mass

[0149] Rod-shaped liquid crystal compound L-1

[0150]

[0151] Rod-shaped liquid crystal compound L-2

[0152]

[0153] Chiral agent Ch-1

[0154]

[0155] Leveling agent T-1

[0156]

[0157] Leveling agent T-2

[0158]

[0159] The Pmax of the polymerization initiator PI-A was 390 nm. The molar absorption coefficients of the polymerization initiator PI-A at Pmax and 405 nm were 690 mol / s. －１ ・cm －１ and 520 mol －１ ・cm －１ It was.

[0160] The prepared composition LC-1 was applied onto the alignment film P-1 to form a composition layer. The application was performed using a spin coater at 1500 rpm. The support having the composition layer was heated on a hot plate at 90°C for 1 minute. Subsequently, a mask MK-1 was placed on the composition layer, and light with a wavelength of 405 nm was irradiated onto the composition layer at 10 mW / cm using an LED exposure device at 40°C under atmospheric conditions through the mask MK-1. ２ The composition layer was exposed to ultraviolet light for 20 seconds at an illuminance of 300 mJ / cm. The positional relationship between the amount of ultraviolet light irradiated onto the composition layer through the mask MK-1 and each region of the alignment film is as shown in FIG. 7. Subsequently, the composition layer was subjected to a heat treatment at 200°C (above the liquid crystal phase-isotropic phase (Iso) of the liquid crystal compound) for 1 minute, and then exposed to light with a wavelength of 405 nm at 300 mJ / cm using an LED exposure device in a nitrogen atmosphere at 200°C. ２ By irradiating the coating film with an irradiation dose of 1000 u / s, the orientation of the liquid crystal compound was fixed, and an optically anisotropic layer was formed. From cross-sectional SEM measurement, it was confirmed that the optically anisotropic layer has a high birefringence region in which light and dark areas are visible in the thickness direction, i.e., a region in which an orientation pattern is formed, and an optically isotropic region in which light and dark areas are not visible, and the thickness of the high birefringence region gradually changes. The thickness of the high birefringence layer is shown in Figure 8.

[0161] [Measurement and Evaluation] (Evaluation of Diffraction Efficiency) As shown in Figure 9, the optically anisotropic layer 24 prepared above was placed on the surface of a Dove prism 110, and the diffraction efficiency for each position on the optically anisotropic layer was evaluated. A glass Dove prism with a refractive index of 1.5 was used as the Dove prism 110 shown in Figure 9. The optically anisotropic layer was peeled off from the glass substrate before use. The optically anisotropic layer and the Dove prism were bonded together using a heat-sensitive adhesive (not shown).

[0162] An optically anisotropic layer 24 was placed on the upper surface of the Dove prism, a laser was placed facing the inclined surface of the Dove prism 110, and a linear polarizer 112 and a λ / 4 plate 114 were placed between the laser and the Dove prism 110.

[0163] Light emitted by the laser passes through linear polarizer 112 and λ / 4 plate 114, becoming right-handed circularly polarized light, which then enters Dove prism 110, propagates through Dove prism 110, and enters the optically anisotropic layer. The diffracted light reflected and diffracted by the optically anisotropic layer propagates through Dove prism 110 in the direction opposite to the surface on which the optically anisotropic layer is disposed. The light propagated through Dove prism 110 reaches the lower surface of Dove prism 110 and is emitted.

[0164] 9, the position of the end of the optically anisotropic layer 24 on the side where the laser light is incident is set to 0 mm, and laser light was incident at each position at 5 mm intervals to measure the diffraction efficiency at each position. The wavelength of the laser light was 532 nm, and the incident angle of the laser light was set so that it was incident at an angle of 55.6° with respect to the normal direction of the optically anisotropic layer 24. Then, the light intensity of the light reflected and diffracted by the optically anisotropic layer 24 and emitted in the normal direction of the optically anisotropic layer (the normal direction of the lower surface of the Dove prism 110) was measured.

[0165] The diffraction efficiency Deff of the fabricated optically anisotropic layer is calculated by multiplying the light intensity of the laser beam incident on the Dove prism 110 by I ｉｎ , the light intensity of the light (outgoing light) diffracted by the optically anisotropic layer 24 and emitted from the Dove prism 110 is expressed as I ｏｕｔ , the diffraction efficiency is calculated by the following formula: Deff = I ｏｕｔ / I ｉｎIn addition, the diffraction efficiency was calculated excluding the loss of transmittance at the interface when light was incident on and emitted from the Dove prism 110 .

[0166] The diffraction efficiency of the optically anisotropic layer prepared by the above method was evaluated, and the diffraction efficiency η1 at the position of 25 mm was 14%, the diffraction efficiency η2 at the position of 35 mm was 22%, and the diffraction efficiency η3 at the position of 45 mm was 61%.

[0167] (Evaluation of Emitted Light Intensity Distribution) As shown in Fig. 10, an optical element (light guide element) was produced by disposing the optically anisotropic layer 24 produced above on the surface of a light guide plate 144. In Fig. 9, a glass light guide plate with a refractive index of 1.5 and a thickness of 1 mm was used as the light guide plate 144. The optically anisotropic layer 24 was peeled off from the glass substrate described above. The optically anisotropic layer 24 and the light guide plate 144 were bonded together using a heat-sensitive adhesive (not shown).

[0168] As shown in FIG. 10 , a laser (not shown) was placed facing the end of the light guide plate 144 where the first diffraction region 45a was located, opposite the surface where the optically anisotropic layer 24 was located, and a linear polarizer 100 and a λ / 4 plate 102 were placed between the laser and the light guide plate 144. A power meter (not shown) was placed 10 cm from the optically anisotropic layer 24, facing the end of the light guide plate 144 where the second diffraction region 45c was located, opposite the surface where the optically anisotropic layer 24 was located. The wavelength of the laser light was 532 nm, and the beam diameter of the laser light was 1 mm. In the optically anisotropic layer 24, a non-diffraction region 45b was placed between the first diffraction region 45a and the second diffraction region 45c.

[0169] When light is emitted from the laser, it passes through the linear polarizer 100 and the λ / 4 plate 102, becomes right-handed circularly polarized light, and enters the light guide plate 144. The light that entered the light guide plate 144 is incident on the first diffraction region 45a of the optically anisotropic layer 24. Due to the diffraction action and selective reflection action of the first diffraction region 45a of the optically anisotropic layer 24, the diffracted light that is reflected and diffracted propagates within the light guide plate 144. The light that propagates within the light guide plate 144 is reflected and diffracted by the second diffraction region 45c of the optically anisotropic layer 24, and is emitted in the direction of the power meter.

[0170] A light-shielding plate 104 was placed between the light guide plate 144 and the power meter, facing the surface opposite to the surface on which the optically anisotropic layer 24 was placed. A pinhole 104a having a diameter of 2 mm was formed in the light-shielding plate 104.

[0171] The intensity of light emitted from the light guide plate 144 (emitted light intensity) was measured through the pinhole 104a in the light blocking plate 104. By changing the position of the pinhole 104a, the emitted light intensity was measured for each position of the second diffraction region 45c. The emitted light intensity was measured using a Newport Power Meter 1918-C.

[0172] When the amount of light emitted from the light guide plate 144 was checked, it was confirmed that the intensity of the emitted light was uniform.

[0173] (Light Utilization Efficiency) The total value of the diffraction efficiency η1 at a position of 25 mm, the diffraction efficiency η2 at a position of 35 mm, and the diffraction efficiency η3 at a position of 45 mm of the optically anisotropic layer measured in the above diffraction efficiency evaluation was calculated and evaluated as the light utilization efficiency.

[0174] (Absorbance of Optically Anisotropic Layer) The optically anisotropic layer was set in a spectrometer (UV-Visible-Near-Infrared Spectrophotometer "V-750" manufactured by JASCO Corporation), and the absorbance of the optically anisotropic layer was measured using the absorbance of the substrate glass as a baseline. As a result, the absorbance at a wavelength of 380 nm was 0.020 (A.U.), and the absorbance at 405 nm was 0.007 (A.U.). Furthermore, as a result of measurement according to the above-mentioned method, the average refractive index nk of the liquid crystal compound contained in the optically anisotropic layer at a wavelength of 550 nm was 1.72.

[0175] Example 2 An optically anisotropic layer was formed in the same manner as in Example 1, except that the composition used was changed to composition LC-2, except that the exposure time was set to 50 seconds.

[0176] ------------------------------------------------ Composition LC-2------------------------------------------------ Rod-shaped liquid crystalline compound L-1 80.00 parts by mass Rod-shaped liquid crystalline compound L-2 20.00 parts by mass Polymerization initiator PI-1 3.00 parts by mass Chiral agent Ch-1 5.50 parts by mass Leveling agent T-1 0.05 parts by mass Leveling agent T-2 0.05 parts by mass Methyl ethyl ketone 126.7 parts by mass Cyclopentanone 126.7 parts by mass------------------------------------------------

[0177] Polymerization initiator PI-1

[0178]

[0179] The Pmax of the polymerization initiator PI-1 was 380 nm. The molar extinction coefficients of the polymerization initiator PI-1 at Pmax and 405 nm were 600 mol / L, respectively. －１ ・cm －１ and 300 mol －１ ・cm －１ It was.

[0180] The diffraction efficiency of the optically anisotropic layer was evaluated using the same method as in Example 1. The diffraction efficiency η1 at a position of 25 mm was 13%, the diffraction efficiency η2 at a position of 35 mm was 20%, and the diffraction efficiency η3 at a position of 45 mm was 58%. A light guide element was fabricated using the same method as in Example 1, and the amount of emitted light was confirmed to be uniform. The light utilization efficiency of the optically anisotropic layer was measured using the same method as in Example 1. The light utilization efficiency of the optically anisotropic layer was 91%. Measurements using the same method as in Example 1 revealed that the absorbance of the optically anisotropic layer at a wavelength of 380 nm was 0.025 (A.U.) and the absorbance of the optically anisotropic layer at a wavelength of 405 nm was 0.007 (A.U.). The average refractive index nk of the liquid crystal compound contained in the optically anisotropic layer at a wavelength of 550 nm was 1.72.

[0181] Example 3 An optically anisotropic layer was formed in the same manner as in Example 1, except that the composition used was changed to composition LC-3.

[0182] ------------------------------------------------ Composition LC-3------------------------------------------------ Rod-shaped liquid crystalline compound L-1 80.00 parts by mass Rod-shaped liquid crystalline compound L-2 20.00 parts by mass Polymerization initiator PI-2 3.00 parts by mass Chiral agent Ch-1 5.50 parts by mass Leveling agent T-1 0.05 parts by mass Leveling agent T-2 0.05 parts by mass Methyl ethyl ketone 126.7 parts by mass Cyclopentanone 126.7 parts by mass------------------------------------------------

[0183] Polymerization initiator PI-2

[0184]

[0185] The Pmax of the polymerization initiator PI-2 was 330 nm. The molar extinction coefficients of the polymerization initiator PI-2 at Pmax and 405 nm were 240 mol / L, respectively. －１ ・cm －１ and 50 mol －１ ・cm －１ It was.

[0186] The diffraction efficiency of the optically anisotropic layer was evaluated using the same method as in Example 1. The diffraction efficiency η1 at a position of 25 mm was 10%, the diffraction efficiency η2 at a position of 35 mm was 16%, and the diffraction efficiency η3 at a position of 45 mm was 50%. A light guide element was fabricated using the same method as in Example 1, and the amount of emitted light was confirmed to be uniform. The light utilization efficiency of the optically anisotropic layer was measured using the same method as in Example 1. The light utilization efficiency of the optically anisotropic layer was 76%. Measurements using the same method as in Example 1 revealed that the absorbance of the optically anisotropic layer at a wavelength of 380 nm was 0.027 (A.U.) and the absorbance of the optically anisotropic layer at a wavelength of 405 nm was 0.009 (A.U.). The average refractive index nk of the liquid crystal compound contained in the optically anisotropic layer at a wavelength of 550 nm was 1.72.

[0187] Comparative Example 1 An optically anisotropic layer was formed in the same manner as in Example 1, except that the composition used was changed to composition LC-4.

[0188] ------------------------------------------------ Composition LC-4 ------------------------------------------------ Rod-shaped liquid crystalline compound L-1 80.00 parts by mass Rod-shaped liquid crystalline compound L-2 20.00 parts by mass Polymerization initiator PI-3 3.00 parts by mass Chiral agent Ch-1 5.50 parts by mass Leveling agent T-1 0.05 parts by mass Leveling agent T-2 0.05 parts by mass Methyl ethyl ketone 126.7 parts by mass Cyclopentanone 126.7 parts by mass ------------------------------------------------

[0189] Polymerization initiator PI-3

[0190]

[0191] The Pmax of the polymerization initiator PI-3 was 340 nm. The molar extinction coefficients of the polymerization initiator PI-3 at Pmax and 405 nm were 1800 mol / L, respectively. －１ ・cm －１ and 30 mol －１ ・cm －１ It was.

[0192] The diffraction efficiency of the optically anisotropic layer was evaluated using the same method as in Example 1. The diffraction efficiency η1 at a position of 25 mm was 8%, the diffraction efficiency η2 at a position of 35 mm was 13%, and the diffraction efficiency η3 at a position of 45 mm was 38%. A light guide element was fabricated using the same method as in Example 1, and the amount of emitted light was confirmed to be uniform. The light utilization efficiency of the optically anisotropic layer was measured using the same method as in Example 1. The light utilization efficiency of the optically anisotropic layer was 59%. Measurements using the same method as in Example 1 revealed that the absorbance of the optically anisotropic layer at a wavelength of 380 nm was 0.043 (A.U.) and the absorbance of the optically anisotropic layer at a wavelength of 405 nm was 0.013 (A.U.). The average refractive index nk of the liquid crystal compound contained in the optically anisotropic layer at a wavelength of 550 nm was 1.72.

[0193] Comparative Example 2 An optically anisotropic layer was formed in the same manner as in Example 1, except that the composition used was changed to composition LC-5.

[0194] ------------------------------------------------ Composition LC-5 ------------------------------------------------ Rod-shaped liquid crystalline compound L-3 100.00 parts by mass Polymerization initiator PI-A (manufactured by BASF, Omnirad (registered trademark) 819) 3.00 parts by mass Chiral agent Ch-1 5.50 parts by mass Leveling agent T-1 0.05 parts by mass Leveling agent T-2 0.05 parts by mass Methyl ethyl ketone 126.7 parts by mass Cyclopentanone 126.7 parts by mass ------------------------------------------------

[0195] Rod-shaped liquid crystal compound L-3 (a mixture of the following three compounds)

[0196]

[0197] The diffraction efficiency of the optically anisotropic layer was evaluated using the same method as in Example 1. The diffraction efficiency η1 at a position of 25 mm was 8%, the diffraction efficiency η2 at a position of 35 mm was 14%, and the diffraction efficiency η3 at a position of 45 mm was 41%. A light guide element was fabricated using the same method as in Example 1, and the amount of emitted light was confirmed to be uniform. The light utilization efficiency of the optically anisotropic layer was measured using the same method as in Example 1. The light utilization efficiency of the optically anisotropic layer was 63%. Measurements using the same method as in Example 1 revealed that the absorbance of the optically anisotropic layer at a wavelength of 380 nm was 0.018 (A.U.) and the absorbance of the optically anisotropic layer at a wavelength of 405 nm was 0.009 (A.U.). The average refractive index nk of the liquid crystal compound contained in the optically anisotropic layer at a wavelength of 550 nm was 1.65.

[0198] Comparative Example 3 An optically anisotropic layer was formed in the same manner as in Example 1, except that the composition used was changed to composition LC-6 and the light used to expose the composition layer was changed to ultraviolet light with a wavelength of 365 nm.

[0199] ------------------------------------------------ Composition LC-6 ------------------------------------------------ Rod-shaped liquid crystalline compound L-4 100.00 parts by mass Polymerization initiator PI-A (manufactured by BASF, Omnirad (registered trademark) 819) 3.00 parts by mass Chiral agent Ch-1 5.50 parts by mass Leveling agent T-1 0.05 parts by mass Leveling agent T-2 0.05 parts by mass Methyl ethyl ketone 126.7 parts by mass Cyclopentanone 126.7 parts by mass ------------------------------------------------

[0200] Rod-shaped liquid crystal compound L-4

[0201]

[0202] The diffraction efficiency of the optically anisotropic layer was evaluated using the same method as in Example 1. The diffraction efficiency η1 at a position of 25 mm was 9%, the diffraction efficiency η2 at a position of 35 mm was 16%, and the diffraction efficiency η3 at a position of 45 mm was 42%. A light guide element was fabricated using the same method as in Example 1, and the amount of emitted light was confirmed to be uniform. The light utilization efficiency of the optically anisotropic layer was measured using the same method as in Example 1. The light utilization efficiency of the optically anisotropic layer was 67%. Measurements using the same method as in Example 1 showed that the absorbance of the optically anisotropic layer at a wavelength of 380 nm was 0.045 (A.U.) and the absorbance of the optically anisotropic layer at a wavelength of 405 nm was 0.015 (A.U.).

[0203] Table 1 shows the physical properties measured for the optically anisotropic layer of the optical element formed in each example, and the evaluation results of the optically anisotropic layer. The optically anisotropic layers formed in Examples 1 to 3 were all layers in which the liquid crystal compound twisted in the thickness direction in the alignment pattern region, and the total twist angle in the layer was 360° or more. Furthermore, the optically anisotropic layers formed in Examples 1 to 3 were measured according to the above-mentioned method, and it was confirmed that the average value Δna of the birefringence in the thickness direction in the alignment pattern region of the optically anisotropic layer changed along at least one direction in the plane of the optically anisotropic layer.

[0204] Furthermore, light was incident on the optical elements fabricated in Examples 1 to 3 while varying the angle of incidence, and the diffraction angle of the emitted light was evaluated. Specifically, laser light having an output center wavelength λ of 532 nm was irradiated from a light source and incident on the optical element. The angle θ (Littrow configuration) at which the diffracted light (first-order light) of the emitted light was diffracted exactly in the direction of the incident light was measured using a diffraction light detector, and the rotational change period P was calculated using the following formula: λ = 2 × P × sin θ, where λ represents the wavelength of the measured diffracted light, θ represents the angle θ, and P represents the rotational change period. From the calculated rotational change period P, it was confirmed that in the alignment pattern region of the optically anisotropic layer formed in Examples 1 to 3, the rotational change period when the orientation of the optical axis derived from the liquid crystal compound continuously rotates along one in-plane direction changes within the plane of the optically anisotropic layer.

[0205]

[0206] As shown in the above table, it was confirmed that the present invention can provide an optical element having an optically anisotropic layer with excellent light utilization efficiency.

[0207] Comparison of Example 1 with Examples 2 and 3 confirmed that when the Pmax of the polymerization initiator contained in the composition used to form the optically anisotropic layer is 390 nm or more, the light utilization efficiency of the optically anisotropic layer is superior.

[0208] The optical element of the present invention can be suitably used for various applications that reflect light in optical devices, such as a diffraction element that causes light to enter and exit an AR glass light guide plate.

[0209] 1, 2, 3, 24 Optically anisotropic layer xy plane Sheet surface z direction Thickness direction 30 Liquid crystal compound Λ Length of one period 30A Optical axis derived from liquid crystal compound 30 R Region d Thickness (film thickness) of optically anisotropic layer P L Left circularly polarized light P R Right-handed circularly polarized light L1, L4, L6 Incident light L2, L5, L7 Transmitted light Q1, Q2 Absolute phase E1, E2 Equiphase surface A1, A2, A3 Direction 20 Base material 45a First diffraction area 45b Non-diffraction area 45c Second diffraction area 100, 112 Linear polarizer 102, 114 λ / 4 plate 104 Light blocking plate (aperture) 104a Pinhole 110 Dove prism 144 Light guide plate

Claims

1. An optical element having an optically anisotropic layer, wherein the absorbance of the optically anisotropic layer at a wavelength of 405 nm is less than 0.010 and the absorbance of the optically anisotropic layer at a wavelength of 380 nm is 0.020 or more, the optically anisotropic layer includes a cured layer obtained by curing a composition containing a liquid crystalline compound, and has an alignment pattern region, the alignment pattern region including an alignment pattern in which the direction of the optical axis derived from the liquid crystalline compound is continuously rotated and changed along at least one direction in the plane.

2. The optical element according to claim 1, wherein the liquid crystal compound has an average refractive index nk of 1.70 or more at a wavelength of 550 nm.

3. The optical element according to claim 1, wherein the composition contains a polymerization initiator, and the peak wavelength Pmax of the longest absorption peak of the polymerization initiator is 390 nm or longer.

4. The molar absorption coefficient of the polymerization initiator at the peak wavelength Pmax is 650 mol －１ ・cm －１ The optical element according to claim 3 .

5. The optical element according to any one of claims 1 to 4, wherein the optically anisotropic layer has an orientation that is twisted in the thickness direction in the orientation pattern region.

6. The optical element according to claim 5, wherein the total twist angle in the orientation twisted in the thickness direction of the optically anisotropic layer is 360° or more.

7. An optical element according to claim 6, further comprising a substrate that guides image light incident on the substrate by total internal reflection, and the orientation pattern region of the optically anisotropic layer has at least one function selected from the group consisting of a function to change the optical path of the image light in a direction in which at least a portion of the guided image light exits the substrate, a function to change the direction of total reflection in the internal total reflection of the guided image light, and a function to change the optical path of the image light that has entered the substrate from the outside in a direction in which it is totally internally reflected within the substrate.

8. The optical element according to claim 7, wherein the diffraction efficiency in the orientation pattern region of the optically anisotropic layer varies along at least one direction in the plane of the optically anisotropic layer.

9. The optical element according to claim 7, wherein in the orientation pattern region of the optically anisotropic layer, the average value Δna of the birefringence in the thickness direction of the optically anisotropic layer varies along at least one direction in the plane of the optically anisotropic layer.

10. An optical element according to any one of claims 1 to 4, wherein the orientation of the optical axis derived from the liquid crystalline compound undergoes continuous rotational change along at least one direction in the plane, and the period of the rotational change changes in the plane of the optically anisotropic layer.

11. The optical element according to any one of claims 1 to 4, wherein the optically anisotropic layer includes a region in the same plane that does not have an alignment pattern.

12. A light guide element comprising the optical element according to any one of claims 1 to 4 and a light guide plate.

13. A display optical system comprising an optical element according to any one of claims 1 to 4 and a display element.

14. A near-eye display comprising the display optical system of claim 13.

15. A measurement optical system comprising the optical element according to any one of claims 1 to 4 and a light receiving element.

16. An image display device comprising the measurement optical system according to claim 15.

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