Polarization diffraction element, optical element and optical device

Abstract

Provided are a polarization diffraction element, an optical element, and an optical device that can reduce components that can become stray light. When clockwise polarized light with an ellipticity εin of 0.95 or more is incident on the polarization diffraction element, the zero-order light transmitted through the polarization diffraction element is counterclockwise polarized light, linearly polarized light, or clockwise polarized light with an ellipticity ε0 that satisfies the relationship of formula (1), and when counterclockwise polarized light with an ellipticity εin of 0.95 or more is incident on the polarization diffraction element, the zero-order light transmitted through the polarization diffraction element is clockwise polarized light, linearly polarized light, or counterclockwise polarized light with an ellipticity ε0 that satisfies the relationship of formula (1): ellipticity εin - ellipticity ε0 ≥ 0.05.

Description

Polarization diffraction element, optical element, and optical device

[0001] The present invention relates to a polarization diffraction element that diffracts incident light, and to an optical element and an optical device that include this polarization diffraction element.

[0002] Liquid crystal diffraction elements that diffract and transmit incident light are known, including those having an optically anisotropic layer formed using a liquid crystal composition containing a liquid crystal compound.

[0003] For example, Patent Document 1 discloses a liquid crystal device including: a first polarization grating configured to polarize and diffract incident light into a first beam and a second beam having a different polarization and a different propagation direction from the incident light; a liquid crystal layer configured to receive the first beam and the second beam from the first polarization grating and configured to be switchable between a first state that does not substantially change the polarization of each of the first beam and the second beam passing therethrough and a second state that changes the polarization of each of the first beam and the second beam passing therethrough; and a second polarization grating configured to receive the first beam and the second beam from the liquid crystal layer and configured to analyze and diffract the first beam and the second beam and change their respective propagation directions depending on the state of the liquid crystal layer.

[0004] The first polarization diffraction grating and the second polarization diffraction grating in this liquid crystal device are liquid crystal diffraction elements.

[0005] This liquid crystal diffraction element has a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane. A liquid crystal diffraction element having such a liquid crystal orientation pattern can diffract incident light at an angle according to the wavelength. Furthermore, when the orientation pattern of the liquid crystal compound is constant, light of the same wavelength can be diffracted at a constant angle regardless of the incident position. Utilizing these properties, the liquid crystal diffraction element can be used for various applications, such as AR (Augmented Reality) glasses and head-mounted displays that display virtual reality (VR) images.

[0006] Special Publication No. 2012-505430

[0007] A liquid crystal diffraction element that diffracts light by changing the liquid crystal orientation pattern in a plane diffracts polarized light in different azimuth directions depending on the rotation direction of the circularly polarized light. Furthermore, such a liquid crystal diffraction element converts the diffracted circularly polarized light into circularly polarized light with the opposite rotation direction. However, optical devices using such liquid crystal diffraction elements (polarized diffraction elements) have a problem in that the zeroth-order light transmitted through the polarized diffraction element becomes stray light. Specifically, for example, when one of the circularly polarized lights (e.g., right-handed circularly polarized light) diffracted by the polarized diffraction element is used, the unused circularly polarized light (left-handed circularly polarized light) can be cut using a circular polarizer or the like. However, if the incident polarized light contains a right-handed circularly polarized component, the zeroth-order light corresponding to the right-handed circularly polarized component passes through the polarized diffraction element without its polarization state being converted, becoming circularly polarized light with the same rotation direction as the circularly polarized light being used (right-handed circularly polarized light), and therefore cannot be cut using a circular polarizer or the like. As a result, there is a risk that this zeroth-order light will reach the observer's eye as a ghost.

[0008] An object of the present invention is to solve the problems of the prior art and to provide a polarizing diffraction element, an optical element, and an optical device that can reduce components that can become stray light.

[0009] In order to solve this problem, the present invention has the following configuration. [1] A polarization diffraction element, wherein, when right-handed polarized light having an ellipticity εin of 0.95 or more is incident on the polarization diffraction element, the zeroth-order light transmitted through the polarization diffraction element is left-handed polarized light, linearly polarized light, or right-handed polarized light with an ellipticity ε0 that satisfies the relationship of formula (1), or, when left-handed polarized light having an ellipticity εin of 0.95 or more is incident on the polarization diffraction element, the zeroth-order light transmitted through the polarization diffraction element is right-handed polarized light, linearly polarized light, or left-handed polarized light with an ellipticity ε0 that satisfies the relationship of formula (1): Equation (1) Ellipticity εin - Ellipticity ε0 ≧ 0.05 [2] The polarization diffraction element according to [1], wherein, when right-handed polarized light and left-handed polarized light having an ellipticity εin of 0.95 or more are incident on the polarization diffraction element, the diffraction efficiency of at least one of the first-order diffracted light beams output from the polarization diffraction element is 90% or higher. [3] The polarization diffraction element according to [1] or [2], wherein, when right-handed polarized light and left-handed polarized light having an ellipticity εin of 0.95 or more are incident on the polarization diffraction element, the ratio of the diffraction efficiencies of the first-order diffracted light beams DE(1S) / DE(1L) is ≦0.95, where DE(1L) is the diffraction efficiency of the first-order diffracted light beam with a high diffraction efficiency and DE(1S) is the diffraction efficiency of the first-order diffracted light beam with a low diffraction efficiency. [4] The polarization diffraction element according to any one of [1] to [3], wherein, when right-handed polarized light and left-handed polarized light having the same ellipticity εin are incident on the polarization diffraction element, the polarization states of the zero-order light beams emitted from the polarization diffraction element are not reversed on the Poincaré sphere. [5] The polarization diffraction element according to any one of [1] to [4], wherein the absolute value of the difference between Δε(RH) and Δε(LH) satisfies the relationship of formula (2), when clockwise polarized light having an ellipticity εin(RH) of 0.95 or more is incident on the polarization diffraction element and the ellipticity ε0(RH) of the zeroth order light that has passed through the polarization diffraction element is Δε(RH) = εin(RH) - ellipticity ε0(RH), and when left-handed polarized light having an ellipticity εin(LH) of 0.95 or more is incident on the polarization diffraction element and the ellipticity ε0(LH) of the zeroth order light that has passed through the polarization diffraction element is Δε(LH) = ellipticity εin(LH) - ellipticity ε0(LH).Abs(Δε(LH)-Δε(RH))≧0.05 Formula (2) [6] The polarization diffraction element according to any one of [1] to [5], wherein the polarization diffraction element has a curved surface portion at least partially within its plane. [7] The polarization diffraction element according to any one of [1] to [6], wherein the polarization diffraction element has a region in which, when left-handed circularly polarized light or right-handed circularly polarized light having an ellipticity εin of 0.95 or more is incident on the polarization diffraction element at different positions within the plane, the polarization state of zero-order light varies depending on the position of incidence within the plane. [8] The polarization diffraction element according to any one of [1] to [7], wherein the polarization diffraction element has a region in which, when left-handed circularly polarized light or right-handed circularly polarized light having an ellipticity εin of 0.95 or more is incident on the polarization diffraction element at a partial region within the plane, the difference between the ellipticity ε0 of the zero-order light that has passed through the polarization diffraction element and the ellipticity ε0 is expressed as Δε=ellipticity εin-ellipticity ε0. [9] When left-handed circularly polarized light and right-handed circularly polarized light with an ellipticity εin of 0.95 or more are incident on a partial region within the plane of the polarization diffraction element, the difference between the ellipticity ε0(RH) of the zeroth-order light transmitted through the polarization diffraction element when right-handed polarized light with an ellipticity εin(RH) of 0.95 or more is incident on a partial region within the plane of the polarization diffraction element is Δε(RH)=ellipticity εin(RH)−ellipticity ε0(RH), and when left-handed polarized light with an ellipticity εin(LH) of 0.95 or more is incident on a partial region of the polarization diffraction element when the difference between the ellipticity ε0(LH) of the zeroth-order light transmitted through the polarization diffraction element is Δε(LH)=ellipticity εin(LH)−ellipticity ε0(LH), the absolute value of the difference between Δε(RH) and Δε(LH) is Abs(Δε(LH)−Δε(RH)). The polarization diffraction element according to any one of [1] to [8], wherein the polarization diffraction element has regions where the value of .alpha. varies in-plane.

[10] The polarization diffraction element according to any one of [1] to [9], wherein the polarization diffraction element has an optically anisotropic layer formed using a liquid crystal composition containing a liquid crystal compound, the optically anisotropic layer having a liquid crystal orientation pattern in which the direction of the optical axis derived from the liquid crystal compound changes while rotating continuously along at least one direction in-plane.

[11] The polarization diffraction element according to

[10] , wherein the optically anisotropic layer has regions where the length of one period varies in-plane, when the length of the rotation of the direction of the optical axis derived from the liquid crystal compound in the liquid crystal orientation pattern by 180° in-plane is defined as one period.

[12] The polarizing diffraction element according to

[10] or

[11] , wherein the optically anisotropic layer has a region in which the length of one period gradually changes along one direction, where the length of one period is defined as the length of a 180° rotation of the orientation of the optical axis derived from the liquid crystal compound in the liquid crystal orientation pattern in the plane.

[13] The polarizing diffraction element according to any of

[10] to

[12] , wherein the liquid crystal orientation pattern has one direction in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating radially from the inside to the outside.

[14] An optical element comprising the polarizing diffraction element according to any of [1] to

[13] and a substrate, wherein the substrate has at least a partially curved surface portion, and the polarizing diffraction element is disposed on at least the curved surface portion and has a curved shape that follows the curved surface portion.

[15] An optical element comprising the polarizing diffraction element according to any of [1] to

[13] and an external input means, wherein the external input means can change the orientation state of the liquid crystal compound in the optically anisotropic layer.

[16] The optical element according to

[15] , wherein the external input means includes a pair of substrates sandwiching the polarization diffraction element, at least one of the pair of substrates having a transparent electrode.

[17] An optical device including the polarization diffraction element according to any one of [1] to

[13] .

[18] An optical device including the optical element according to

[14] .

[19] The optical device according to

[17] or

[18] , further including a circular polarizer.

[20] The optical device according to any one of

[17] to

[19] , wherein the optical device is a device selected from the group consisting of a head-mounted display, a VR display device, a sensor, and a communication device.

[0010] According to the present invention, it is possible to solve the problems of the conventional techniques and provide a polarizing diffraction element, an optical element, and an optical device that can reduce components that can become stray light.

[0011] FIG. 1 is a conceptual diagram for explaining one example of the polarization diffraction element of the present invention. FIG. 1 is a conceptual diagram for explaining another ... an operation of the polarization diffraction element of the present invention. FIG. 1 is a conceptual diagram for explaining an example of a conventional polarization diffraction element. FIG. 1 is a conceptual diagram for explaining an example of a conventional polarization diffraction element. FIG. 1 is a conceptual diagram of an example of a liquid crystal diffraction element of the present invention. FIG. 1 is a conceptual diagram of a plan view of the liquid crystal diffraction element shown in FIG. 10. FIG. 1 is a conceptual diagram for explaining the operation of the liquid crystal diffraction element. FIG. 1 is a conceptual diagram for explaining the operation of the liquid crystal diffraction element. FIG. 1 is a conceptual diagram for explaining the liquid crystal diffraction element of the present invention. FIG. 1 is a conceptual diagram for explaining another example of the liquid crystal diffraction element of the present invention. FIG. 1 is a conceptual diagram for explaining the liquid crystal diffraction element shown in FIG. 16. FIG. 1 is a conceptual diagram for explaining another example of the liquid crystal diffraction element of the present invention. FIG. 1 is a conceptual diagram for explaining another example of the liquid crystal diffraction element of the present invention. 10 is a diagram conceptually showing another example of an exposure apparatus for exposing an alignment film.FIG. 11 is a diagram conceptually showing a plane of a conventional liquid crystal diffraction element.FIG.

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A polarizing diffraction element, an optical element, and an optical device according to the present invention will be described in detail below with reference to preferred embodiments shown in the accompanying drawings.

[0013] In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In this specification, "(meth)acrylate" is used to mean "either one or both of acrylate and methacrylate."

[0014] In this specification, visible light refers to electromagnetic waves with wavelengths visible to the human eye, in the wavelength range of 380 to 780 nm, while invisible light refers to light with wavelengths shorter than 380 nm and longer than 780 nm.

[0015] 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).

[0016] [Polarization Diffraction Element] The polarization diffraction element of the present invention is a polarization diffraction element, in which, when clockwise polarized light with an ellipticity εin of 0.95 or more is incident on the polarization diffraction element, the zeroth-order light transmitted through the polarization diffraction element is left-handed polarized light, linearly polarized light, or right-handed polarized light with an ellipticity ε0 that satisfies the relationship of formula (1), or, when left-handed polarized light with an ellipticity εin of 0.95 or more is incident on the polarization diffraction element, the zeroth-order light transmitted through the polarization diffraction element is right-handed polarized light, linearly polarized light, or left-handed polarized light with an ellipticity ε0 that satisfies the relationship of formula (1). Formula (1) Ellipticity εin - ellipticity ε0 ≧ 0.05

[0017] 1 to 6 are conceptual diagrams illustrating the polarization diffraction element of the present invention.

[0018] 1 to 6 diffracts incident circularly polarized light, and diffracts the polarized light in different (opposite) azimuth directions depending on the rotation direction of the incident circularly polarized light. For example, in the illustrated example, when light traveling from left to right in the figure is incident on the polarizing diffraction element 10, the polarizing diffraction element 10 diffracts the incident light into right-handed circularly polarized light I Rin In the case of , the incident light is diffracted in the upper right direction in the figure (Figs. 1 to 3), and the incident light is left-handed circularly polarized light I Lin In this case, the incident light is diffracted in the lower right direction in the figure (Figs. 4 to 6). At that time, the diffracted polarized light (first-order diffracted light) is converted into the opposite rotation direction. In other words, if the incident light is right-handed circularly polarized light I Rin In this case, the polarized light (first-order diffracted light) diffracted by the polarization diffraction element 10 is left-handed circularly polarized light IL1 (Figs. 1 to 3), and the incident light is converted into left-handed circularly polarized light I Lin In this case, the polarized light (first-order diffracted light) diffracted by the polarization diffraction element 10 is right-handed circularly polarized light I R1 (Figures 4 to 6)

[0019] Here, when the diffraction efficiency of the incident polarized light is not 100%, the polarized light is not diffracted by the polarizing diffraction element and passes through, resulting in so-called zeroth-order light. In all of the polarizing diffraction elements 10 shown in Figures 1 to 6, the polarization state of the zeroth-order light is different from that of the incident light, and the examples shown in Figures 1 to 6 are examples in which the polarization state of this zeroth-order light is different.

[0020] The polarization diffraction element 10 shown in Figure 1 is an example in which, when right-handed polarized light with an ellipticity εin of 0.95 or more is incident, the zero-order light transmitted through the polarization diffraction element 10 becomes right-handed polarized light with an ellipticity ε0 that satisfies the relationship of the above formula (1). Rin When the polarized light is incident on the polarization diffraction element 10, the zero-order light transmitted through the polarization diffraction element 10 is elliptically polarized light I RE0 The incident light is right-handed circularly polarized light I Rin The ellipticity εin of the right-handed elliptically polarized light I RE0 The difference between the ellipticity ε0 and the ellipticity ε10 is 0.05 or more. In other words, the polarization diffraction element 10 makes the polarization state of the zero-order light different from that of the incident light.

[0021] The polarization diffraction element 10 shown in Figure 2 is an example in which, when clockwise polarized light with an ellipticity εin of 0.95 or more is incident, the zero-order light transmitted through the polarization diffraction element 10 becomes counterclockwise polarized light. Rin When the left circularly polarized light I is incident on the polarization diffraction element 10, the zero-order light that passes through the polarization diffraction element 10 is L0 In other words, the polarization diffraction element 10 causes the polarization state of the zero-order light to be different from that of the incident light. In the example shown in FIG. 2, the zero-order light transmitted through the polarization diffraction element 10 is left-handed circularly polarized light I L0 However, the present invention is not limited to this, and the zero-order light may be elliptically polarized light having a left-handed rotation.

[0022] The polarization diffraction element 10 shown in Figure 3 is an example in which, when clockwise polarized light with an ellipticity εin of 0.95 or more is incident, the zero-order light transmitted through the polarization diffraction element 10 becomes linearly polarized light. Rin When the light is incident on the polarization diffraction element 10, the zero-order light transmitted through the polarization diffraction element 10 is linearly polarized light I S0 That is, the polarization diffraction element 10 makes the polarization state of the zero-order light different from that of the incident light.

[0023] The polarization diffraction element 10 shown in Figure 4 is an example in which, when left-handed polarized light with an ellipticity εin of 0.95 or more is incident, the zero-order light transmitted through the polarization diffraction element 10 becomes left-handed polarized light with an ellipticity ε0 that satisfies the relationship of the above formula (1). Lin When the polarized light is incident on the polarization diffraction element 10, the zero-order light transmitted through the polarization diffraction element 10 is elliptically polarized light I LE0 The left-handed circularly polarized light I Lin The ellipticity εin of the left-handed elliptically polarized light I LE0 The difference between the ellipticity ε0 and the ellipticity ε10 is 0.05 or more. In other words, the polarization diffraction element 10 makes the polarization state of the zero-order light different from that of the incident light.

[0024] The polarization diffraction element 10 shown in Figure 5 is an example in which, when left-handed polarized light with an ellipticity εin of 0.95 or more is incident, the zero-order light transmitted through the polarization diffraction element 10 becomes right-handed polarized light. Lin When the polarized light is incident on the polarization diffraction element 10, the zero-order light transmitted through the polarization diffraction element 10 is right-handed circularly polarized light I R0 In other words, the polarization diffraction element 10 causes the polarization state of the zero-order light to be different from that of the incident light. In the example shown in FIG. 5, the zero-order light transmitted through the polarization diffraction element 10 is right-handed circularly polarized light I R0 However, the present invention is not limited to this, and the zero-order light may be elliptically polarized light having a right-handed rotation.

[0025] The polarization diffraction element 10 shown in Figure 6 is an example in which, when left-handed polarized light with an ellipticity εin of 0.95 or more is incident, the zero-order light transmitted through the polarization diffraction element 10 becomes linearly polarized light.Lin When the light is incident on the polarization diffraction element 10, the zero-order light transmitted through the polarization diffraction element 10 is linearly polarized light I S0 That is, the polarization diffraction element 10 makes the polarization state of the zero-order light different from that of the incident light.

[0026] In a conventional polarization diffraction element, the polarization state of the zero-order light transmitted through the polarization diffraction element is the same as that of the incident light. That is, as shown in FIG. 8, a conventional polarization diffraction element 100 detects right-handed circularly polarized light I Rin When the polarized light is incident on the polarization diffraction element 100, the zero-order light transmitted through the polarization diffraction element 100 is right-handed circularly polarized light I R0 As shown in FIG. 9, the conventional polarization diffraction element 100 Lin When left circularly polarized light I is incident on the polarization diffraction element 100, the zero-order light transmitted through the polarization diffraction element 100 is L0 This becomes:

[0027] Therefore, as mentioned above, in an optical device using such a polarization diffraction element, there is a problem that the zero-order light transmitted through the polarization diffraction element becomes stray light. Specifically, as shown in FIG. 7, the right-handed circularly polarized light component (I Rin ) and left-handed circularly polarized component (I Lin ) is incident on the polarization diffraction element 100, and one of the circularly polarized light beams (left circularly polarized light I in the illustrated example) is diffracted by the polarization diffraction element 100. L1 ) is used, right circular polarization I is not used R1 can be cut using a circular polarizer 20 or the like that transmits left-handed circularly polarized light and blocks right-handed circularly polarized light. Lin The zero-order light that is transmitted without being diffracted by the polarization diffraction element is left-handed circularly polarized light I L0 (Right circular polarization I not used) R1 The left-handed circularly polarized light I of the zero-order light L0 is not diffracted, and is left-handed circularly polarized light I L1 However, the left-handed circularly polarized light I, which is the first-order diffracted light, passes through the circular polarizer 20, and the left-handed circularly polarized light I L1 In addition, the left circularly polarized light I, which is the zeroth order light, L0Therefore, in an optical device using a polarizing diffraction element, this zero-order light (left-handed circularly polarized light I) is L0 ) may reach the observer's eye as a ghost.

[0028] In contrast, the polarization diffraction element 10 of the present invention has a polarization state in which the zero-order light differs from that of the incident light in any of the configurations shown in Figures 1 to 6. Therefore, the amount of polarized light that passes through the polarization diffraction element 10 as zero-order light can be reduced by using a circular polarizer or the like. In other words, the polarization diffraction element 10 can reduce components that could become stray light. Therefore, ghosts can be reduced in optical devices that use polarization diffraction elements.

[0029] Specifically, in the example shown in Figure 1, the zero-order light is right-handed elliptically polarized light, but elliptically polarized light contains right-handed and left-handed circularly polarized components. Therefore, when combined with a circular polarizer that transmits right-handed circularly polarized light and blocks left-handed circularly polarized light, this circular polarizer can block the left-handed circularly polarized component contained in the zero-order light, thereby reducing the amount of zero-order light (a component that could become stray light).

[0030] Furthermore, in the example shown in Figure 2, the zero-order light is left-handed circularly polarized light or left-handed elliptically polarized light. Therefore, when combined with a circular polarizer that transmits right-handed circularly polarized light and blocks left-handed circularly polarized light, the left-handed circularly polarized component contained in the zero-order light can be blocked by this circular polarizer, and the amount of zero-order light (a component that can become stray light) can be reduced.

[0031] In the example shown in Figure 3, the zero-order light is linearly polarized light, but linearly polarized light contains a right-handed circularly polarized component and a left-handed circularly polarized component. Therefore, when combined with a circular polarizer that transmits right-handed circularly polarized light and blocks left-handed circularly polarized light, the left-handed circularly polarized component contained in the zero-order light can be blocked by this circular polarizer, and the amount of zero-order light (a component that can become stray light) can be reduced.

[0032] In the example shown in Figure 4, the zero-order light is left-handed elliptically polarized light, but elliptically polarized light contains right-handed and left-handed circularly polarized components. Therefore, when combined with a circular polarizer that transmits left-handed circularly polarized light and blocks right-handed circularly polarized light, this circular polarizer can block the right-handed circularly polarized component contained in the zero-order light, thereby reducing the amount of zero-order light (a component that could become stray light).

[0033] Furthermore, in the example shown in Figure 5, the zero-order light is right-handed circularly polarized light or right-handed elliptically polarized light, so when combined with a circular polarizer that transmits left-handed circularly polarized light and blocks right-handed circularly polarized light, this circular polarizer can block the right-handed circularly polarized component contained in the zero-order light, and the amount of zero-order light (a component that can become stray light) can be reduced.

[0034] In the example shown in Figure 6, the zero-order light is linearly polarized light, but the linearly polarized light contains a right-handed circularly polarized component and a left-handed circularly polarized component. Therefore, when combined with a circular polarizer that transmits left-handed circularly polarized light and blocks right-handed circularly polarized light, the right-handed circularly polarized component contained in the zero-order light can be blocked by this circular polarizer, and the amount of zero-order light (a component that can become stray light) can be reduced.

[0035] Ellipticity refers to the ellipticity of polarized light. "Ellipticity" refers to the ratio of the length of the major axis to the length of the minor axis of an ellipse obtained from the trajectory of a light wave (the length of the minor axis / the length of the major axis). Therefore, the closer the ellipticity is to 1, the closer the light is to circular polarization, and the closer it is to 0, the closer it is to linear polarization. Ellipticity can be measured using a commercially available Stokes polarimeter or other polarization measurement device. For example, it can be measured using a Tokyo Instruments Poxi-spectra Stokes polarimeter, Meadowlark's PMI-VIS Stokes polarimeter, or Thorlabs' PAX1000VIS polarimeter. Furthermore, the polarization state of zero-order light can also be determined by measurement using a polarization measurement device such as a commercially available Stokes polarimeter. Although the polarization state of zero-order light may vary depending on the wavelength, it is also possible to measure the polarization state for each wavelength.

[0036] The specific configuration of the polarizing diffraction element of the present invention will be described in detail later.

[0037] Here, when clockwise polarized light with an ellipticity εin of 0.95 or more and counterclockwise polarized light with an ellipticity εin of 0.95 or more are incident on a polarization diffraction element, the diffraction efficiency of at least one of the first-order diffracted lights output from the polarization diffraction element is preferably 90% or more, more preferably 93% or more, and even more preferably 95% or more. By making the diffraction efficiency of the first-order diffracted light 90% or more, the polarization state of the zeroth-order light can be changed more significantly from the polarization state of the incident light. Therefore, the amount of light components that could become stray light can be further reduced.

[0038] The diffraction efficiency of first-order diffracted light is measured as follows. First, a laser beam having an output center wavelength of 405 nm, 450 nm, 532 nm, 633 nm, or 650 nm is irradiated from a light source and made perpendicularly incident on a polarizing diffraction element. The light intensity of the diffracted light (first-order light) diffracted in the desired direction from the polarizing diffraction element, the zeroth-order light emitted in other directions, and the -first-order light is measured with a photodetector, and the diffraction efficiency is calculated using the following formula. The zeroth-order light is light emitted in the same direction as the incident light. The -first-order light is light diffracted in the -θ direction, where θ is the diffraction angle of the first-order light relative to the zeroth-order light. Diffraction efficiency = first-order light / (first-order light + zeroth-order light + (-first-order light)). The average value of the diffraction efficiency is calculated from the measured values ​​for wavelengths of 405 nm, 450 nm, 532 nm, 633 nm, and 650 nm. The laser light is made to enter perpendicularly onto a circular polarizer corresponding to the wavelength of the laser light, and is then made to circularly polarize, and the light is then made to enter a polarizing diffraction element for evaluation.

[0039] Furthermore, when right-handed polarized light with an ellipticity εin of 0.95 or more and left-handed polarized light with an ellipticity εin of 0.95 or more are incident on a polarization diffraction element, the diffraction efficiency of the first-order diffracted light with a high diffraction efficiency output from the polarization diffraction element is DE(1L), and the diffraction efficiency of the first-order diffracted light with a low diffraction efficiency is DE(1S). The ratio of the diffraction efficiencies of the first-order diffracted light is preferably DE(1S) / DE(1L)≦0.95, more preferably 0.1≦DE(1S) / DE(1L)≦0.90, and even more preferably 0.2≦DE(1S) / DE(1L)≦0.85. By increasing the difference between the diffraction efficiency of the first-order diffracted light when right-handed polarized light is incident and the diffraction efficiency of the first-order diffracted light when left-handed polarized light is incident, the polarization state of the zeroth-order light can be changed more significantly from the polarization state of the incident light. Therefore, the amount of light of components that could become stray light can be further reduced.

[0040] Furthermore, when right-handed polarized light and left-handed polarized light having the same ellipticity εin are incident on a polarization diffraction element, it is preferable that the polarization states of the two zero-order light beams output from the polarization diffraction element are not in opposite positions on the Poincaré sphere. That is, it is preferable that the polarization state of the zero-order light when the incident light is right-handed polarized and the polarization state of the zero-order light when the incident light is left-handed polarized are not orthogonal to each other. By making the polarization states of the two zero-order light beams not orthogonal to each other, it is possible to change the polarization state of the zero-order light more significantly from the polarization state of the incident light.

[0041] When clockwise polarized light having an ellipticity εin(RH) of 0.95 or more is incident on the polarization diffraction element, the difference between the ellipticity ε0(RH) of the zeroth order light transmitted through the polarization diffraction element is Δε(RH)=εin(RH)-ellipticity ε0(RH), and when left-handed polarized light having an ellipticity εin(LH) of 0.95 or more is incident on the polarization diffraction element, the difference between the ellipticity ε0(LH) of the zeroth order light transmitted through the polarization diffraction element is Δε(LH)=ellipticity εin(LH)-ellipticity ε0(LH), it is preferable that the absolute value of the difference between Δε(RH) and Δε(LH) satisfy the relationship of formula (2): Abs(Δε(LH)-Δε(RH))≧0.05

[0042] By making the absolute value of the difference between Δε(RH) and Δε(LH) satisfy the relationship of equation (2), the polarization state of the zero-order light can be changed more significantly from the polarization state of the incident light, and the circular polarizer can reduce the amount of zero-order light (a component that can become stray light).

[0043] Furthermore, it is preferable that the polarization diffraction element has a region in which, when left-handed circularly polarized light with an ellipticity εin of 0.95 or more or right-handed circularly polarized light with an ellipticity εin of 0.95 or more is incident on the polarization diffraction element at different positions within the plane, the polarization state of the zero-order light is a different polarization state depending on the incident position within the plane.

[0044] In other words, when left-handed or right-handed circularly polarized light with an ellipticity εin of 0.95 or more is incident on a partial region within the plane of the polarization diffraction element, and the difference between the ellipticity ε0 of the zero-order light that passes through the polarization diffraction element is defined as Δε=ellipticity εin−ellipticity ε0, it is preferable for the polarization diffraction element to have regions where Δε takes different values ​​within the plane.

[0045] For example, when the diffraction angle and / or incident angle of light differs at each position in the plane of the polarization diffraction element, it is preferable to vary the polarization state of the zeroth-order light transmitted through each region depending on the diffraction angle and incident angle of the light. The amount of zeroth-order light transmitted may vary depending on the diffraction angle and / or incident angle of the light. Therefore, in the case of a polarization diffraction element in which the diffraction angle of light differs at each position in the plane, varying the polarization state of the zeroth-order light transmitted through each region depending on the diffraction angle of the light can improve the ability of the circular polarizer to block zeroth-order light in edge regions where zeroth-order light is likely to be generated. For example, in the case of a polarization diffraction element having a concentric circular pattern as shown in FIG. 15 (described later) and in which the diffraction angle of light (the length of one period) changes with increasing radial distance from the center, the length of one period is shorter than that of the central region, and the ability of the circular polarizer to block zeroth-order light can be improved in edge regions where zeroth-order light is likely to be generated.

[0046] Furthermore, when left-handed circularly polarized light and right-handed circularly polarized light with an ellipticity εin of 0.95 or more are incident on a partial region within the plane of the polarization diffraction element, the difference between the ellipticity ε0(RH) of the zeroth-order light that passes through the polarization diffraction element when right-handed polarized light with an ellipticity εin(RH) of 0.95 or more is incident on a partial region within the plane of the polarization diffraction element is defined as Δε(RH)=ellipticity εin(RH)−ellipticity ε0(RH), and when left-handed polarized light with an ellipticity εin(LH) of 0.95 or more is incident on a partial region of the polarization diffraction element, the difference between the ellipticity ε0(LH) of the zeroth-order light that passes through the polarization diffraction element is defined as Δε(LH)=ellipticity εin(LH)−ellipticity ε0(LH). The absolute value of the difference between Δε(RH) and Δε(LH) is Abs(Δε(LH)−Δε(RH)). It is preferable that the surface has regions where the values ​​are different.

[0047] By configuring the polarizing element to have an area where the difference between right-handed and left-handed circularly polarized light in the amount of change in the polarization state of zero-order light relative to incident light is a different value within the plane, the polarization state of the zero-order light can be changed more significantly relative to the incident light in areas where zero-order light is more likely to be generated, such as when the diffraction angle of light differs for each position within the plane of the polarizing diffraction element, and the circular polarizing plate can reduce the amount of zero-order light (component that can become stray light).

[0048] Furthermore, it is preferable that the polarization diffraction element has a curved surface portion at least in part of its surface. For example, in a VR (Virtual Reality) image display device such as a head-mounted display and AR (Augmented Reality) glasses, when the polarization diffraction element is disposed on the output surface side of the display, by configuring the polarization diffraction element to have a curved surface portion at least in part of its surface, the image light output from the display can be further expanded, thereby widening the viewing angle. Furthermore, by having a curved surface portion in the polarization diffraction element, chromatic aberration can be made less likely to occur.

[0049] When a polarization diffraction element has at least a partial curved surface, the position of the curved surface is not particularly limited and may be set appropriately depending on the configuration of the device in which the polarization diffraction element is placed. For example, when widening the viewing angle of a display, it is preferable to place the polarization diffraction element so that the curved surface of the polarization diffraction element is included in the front surface of the display (the direction in which the image is emitted). The shape of the curved surface of the polarization diffraction element can be various curved shapes, such as a convex shape, a concave shape, or a free-form surface, depending on the application. In addition, the radius of curvature of the curved surface in this case may also be set appropriately depending on the application. As an example, the radius of curvature of the curved surface can be in the range of 20 mm to 5000 mm.

[0050] Below, specific examples of polarization diffraction elements will be described in which, when clockwise polarized light with an ellipticity εin of 0.95 or more is incident, the zeroth-order light transmitted through the polarization diffraction element becomes left-handed polarized light, linearly polarized light, or right-handed polarized light with an ellipticity ε0 that satisfies the relationship in formula (1) above, or, when left-handed polarized light with an ellipticity εin of 0.95 or more is incident, the zeroth-order light transmitted through the polarization diffraction element becomes right-handed polarized light, linearly polarized light, or left-handed polarized light with an ellipticity ε0 that satisfies the relationship in formula (1) above.

[0051] The polarizing diffraction element of the present invention is preferably a liquid crystal diffraction element having an optically anisotropic layer formed using a liquid crystal composition containing a liquid crystal compound, the optically anisotropic layer having a liquid crystal orientation pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane. In the following description, the polarizing diffraction element of the present invention is also referred to as a liquid crystal diffraction element.

[0052] An example of a liquid crystal diffraction element of the present invention is conceptually shown in Fig. 10. The liquid crystal diffraction element 10 shown in Fig. 10 has a support 30, an alignment film 32, and an optically anisotropic layer 36.

[0053] FIG. 11 conceptually shows a plan view of the optically anisotropic layer 36. The plan view is a view of the liquid crystal diffraction element in FIG. 10 viewed from above, i.e., a view of the liquid crystal diffraction element in the thickness direction (i.e., the stacking direction of each layer (film)). In other words, the plan view is a view of the optically anisotropic layer 36 viewed from a direction perpendicular to the main surface. The main surface is the largest surface of a sheet-like material (film, layer, plate-like material, layer), and is usually both sides in the thickness direction of the sheet-like material. Also, in FIG. 11, in order to clearly show the configuration of the liquid crystal diffraction element of the present invention, only the liquid crystal compound 40 on the surface of the alignment film 32 is shown. However, the optically anisotropic layer 36 has a structure in which liquid crystal compounds 40 are stacked in the thickness direction, starting from the liquid crystal compound 40 on the surface of the alignment film 32, as shown in FIG. 10.

[0054] Although FIG. 11 illustrates a portion of the plane of the optically anisotropic layer 36 as a representative example, the optically anisotropic layer has basically the same configuration and effects at each position in the plane.

[0055] The optically anisotropic layer 36 has a liquid crystal alignment pattern in which the orientation of the optical axis 40A derived from the liquid crystal compound 40 changes while continuously rotating along the alignment axis D direction (the direction of arrow X, described later) within the plane of the optically anisotropic layer 36. In the illustrated example, a rod-shaped liquid crystal compound is used as the liquid crystal compound 40, and therefore the optical axis coincides with the longitudinal direction of the rod-shaped liquid crystal compound. In the following description, the "optical axis derived from the liquid crystal compound" will also be simply referred to as the "optical axis of the liquid crystal compound." Specifically, the phrase "the orientation of the optical axis 40A changes while continuously rotating along the alignment axis D direction (one direction)" means that the angle formed between the optical axis 40A of the liquid crystal compound 40 aligned along the alignment axis D direction and the alignment axis D direction varies depending on the position in the alignment axis D direction, and the angle formed between the optical axis 40A and the alignment axis D direction sequentially changes from θ to θ+180° or θ-180° along the alignment axis D direction.

[0056] On the other hand, the liquid crystal compounds 40 forming the optically anisotropic layer 36 are arranged at equal intervals in the Y direction perpendicular to the direction of the alignment axis D, i.e., the Y direction perpendicular to the direction in which the optical axes 40A continuously rotate. In other words, in the optically anisotropic layer 36, the liquid crystal compounds 40 aligned in the Y direction have the same angle between the direction of the optical axes 40A and the alignment axis D.

[0057] In the liquid crystal diffraction element of the present invention, the length (distance) of one period in the liquid crystal orientation pattern of the liquid crystal compound 40 is defined as the length of one period Λ, in which the optical axis 40A rotates 180° in one direction (the direction of the array axis D in the illustrated example) in which the orientation of the optical axis 40A continuously changes in plane. In other words, the length of one period in the liquid crystal orientation pattern is defined as the distance from when the angle between the optical axis 40A and the array axis D changes from θ to θ + 180°. The length of one period in the liquid crystal orientation pattern is the length of one period in the periodic structure of the diffraction element. In other words, the length of one period Λ is the distance between the centers of two liquid crystal compounds 40 that have the same angle with respect to the array axis D direction, in the array axis D direction. Specifically, as shown in FIG. 11, the length of one period Λ is the distance between the centers of two liquid crystal compounds 40 whose array axis D direction and the direction of the optical axis 40A coincide, in the array axis D direction. In the following description, this length of one period Λ is also referred to as "one period Λ." In the liquid crystal diffraction element of the present invention, the liquid crystal orientation pattern of the optically anisotropic layer repeats this one period Λ in the direction of the alignment axis D, that is, in one direction in which the direction of the optical axis 40A changes by continuously rotating.

[0058] As described above, in the optically anisotropic layer, the liquid crystal compounds aligned in the Y direction have an equal angle between their optical axes 40A and the alignment axis D, which is one direction in which the optical axes of the liquid crystal compounds 40 rotate. A region in which the liquid crystal compounds 40, with the equal angle between their optical axes 40A and the alignment axis D, 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, i.e., λ / 2. These in-plane retardations are calculated by the product of the refractive index difference Δn associated with the refractive index anisotropy of region R and the thickness 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 liquid crystal compound 40 in the direction of optical axis 40A and the refractive index of liquid crystal compound 40 in the direction perpendicular to optical axis 40A in the plane of region R. In other words, the refractive index difference Δn is equal to the refractive index difference of the liquid crystal compound.

[0059] When circularly polarized light is incident on such an optically anisotropic layer 36 (liquid crystal diffraction element), the light is diffracted (refracted) and the direction of rotation of the circularly polarized light is changed. This action is conceptually shown in Figures 12 and 13. Note that in Figures 12 and 13, in order to simplify the drawings and clearly show the configuration of the liquid crystal diffraction element, only the liquid crystal compound 40 (liquid crystal compound molecules) on the surface of the alignment film is shown in the optically anisotropic layer 36. Furthermore, the product of the refractive index difference of the liquid crystal compound and the thickness of the optically anisotropic layer is assumed to be λ / 2.

[0060] 12 , when the product of the refractive index difference between the liquid crystal compounds in the optically anisotropic layer 36 and the thickness of the optically anisotropic layer is λ / 2, when left-handed circularly polarized incident light L1 enters the optically anisotropic layer 36, the incident light L1 is given a phase difference of 180° as it passes through the optically anisotropic layer 36, and the transmitted light L2 is converted to right-handed circularly polarized light. Furthermore, because the liquid crystal alignment pattern formed in the optically anisotropic layer 36 is a periodic pattern in the direction of the alignment axis D, the transmitted light L2 travels in a direction different from the traveling direction of the incident light L1. In this way, the left-handed circularly polarized incident light L1 is converted to right-handed circularly polarized transmitted light L2, which is tilted at a certain angle toward the alignment axis D with respect to the incident direction.

[0061] On the other hand, as shown in Figure 13, when the product of the refractive index difference between the liquid crystal compounds in the optically anisotropic layer 36 and the thickness of the optically anisotropic layer 36 is λ / 2, when right-handed circularly polarized incident light L4 enters the optically anisotropic layer 36, the incident light L4 is given a phase difference of 180° as it passes through the optically anisotropic layer 36 and is converted into left-handed circularly polarized transmitted light L5. Furthermore, because the liquid crystal orientation pattern formed in the optically anisotropic layer 36 is a periodic pattern in the direction of the alignment axis D, the transmitted light L5 travels in a direction different from the traveling direction of the incident light L4. At this time, the transmitted light L5 travels in a different direction from the transmitted light L2, that is, in the direction opposite the direction of the alignment axis D with respect to the incident direction. In this way, the incident light L4 is converted into left-handed circularly polarized transmitted light L5 tilted at a certain angle in the direction opposite the direction of the alignment axis D with respect to the incident direction.

[0062] In the liquid crystal diffraction element of the present invention, the optically anisotropic layer 36 has the following characteristics.

[0063] First, at any position on the polarization diffraction element, the average period of 10 periods centered on the arbitrary position is calculated along the one direction in which the optical axis 40A continuously rotates, i.e., the direction of the array axis D, and this is referred to as the average period Λa. In the following description, the one direction in which the optical axis 40A continuously rotates is also simply referred to as the "one direction in which the optical axis 40A rotates." Next, a region having one period equal to or less than this average period Λa is arbitrarily selected, and in this region, the principal surface of the optically anisotropic layer 36 (liquid crystal diffraction element 10) is observed under crossed Nicols with an optical microscope. Specifically, the liquid crystal diffraction element 10 is placed between polarizers arranged in crossed Nicols, and the principal surface of the optically anisotropic layer 36 is observed with an optical microscope in the arbitrarily selected region as described above. At this time, the optically anisotropic layer 36 is positioned so that the absorption axis of one polarizer of the polarizers constituting the crossed Nicols is parallel to the direction of the array axis D, i.e., the one direction in which the optical axis 40A rotates, and observation is performed with an optical microscope.

[0064] As described above, in the optically anisotropic layer 36, the optical axis 40A of the liquid crystal compound 40 continuously rotates toward the direction of the alignment axis D. Furthermore, the direction of the optical axis of the liquid crystal compound 40 is aligned in the Y direction, which is perpendicular to the direction of the alignment axis D (X direction). Therefore, in regions where the optical axis 40A coincides with the absorption axis of the polarizers constituting the crossed Nicols configuration and in regions where the angle between the optical axis 40A and the absorption axis is small, light is blocked, and dark lines extending in the Y direction are observed. In contrast, in regions where the optical axis 40A is perpendicular to the absorption axis of the polarizers constituting the crossed Nicols configuration and in regions where the angle is close to perpendicular, light is transmitted, and bright lines extending in the Y direction are observed.

[0065] In the following description, for convenience, the "region where the optical axis 40A coincides with the absorption axis of the polarizer constituting the crossed Nicols and the region where the angle with the absorption axis is small" will also be referred to as the "region where the optical axis 40A (almost) coincides with the absorption axis of the polarizer." Also, the "region where the optical axis 40A is perpendicular to the absorption axis of the polarizer constituting the crossed Nicols and the region where the angle is close to perpendicular" will also be referred to as the "region where the optical axis 40A is (almost) perpendicular to the absorption axis of the polarizer."

[0066] Then, with the direction of the absorption axis of the polarizer, which is parallel to the array axis D, as the observation direction, a dark line that is wider than the dark lines on either side of it is arbitrarily selected from the bright and dark lines observed. That is, a dark line sandwiched between dark lines thinner than itself in the array axis D direction is arbitrarily selected. Furthermore, with the arbitrarily selected dark line thus selected as the first, 20 consecutive dark lines are selected in the observation direction, i.e., the array axis D direction (one direction), i.e., the direction of the absorption axis of the polarizer.

[0067] In the optically anisotropic layer of the liquid crystal diffraction element of the present invention, among the 20 consecutive dark lines selected in this manner, the width of the even-numbered dark line e is narrower than the width of the adjacent odd-numbered dark line o, and the width of the odd-numbered dark line o is wider than the width of the adjacent even-numbered dark line e, as conceptually shown in Figure 14. That is, the principal surface of the optically anisotropic layer 36 constituting the liquid crystal diffraction element of the present invention is observed under a crossed Nicol arrangement in which the direction of the alignment axis D, i.e., one direction in which the optical axis 40A continuously rotates, is aligned with the direction of the absorption axis of one polarizer. In this case, in the optically anisotropic layer 36 constituting the liquid crystal diffraction element of the present invention, as conceptually shown in Figure 14, a repetition of bright and dark lines extending in the Y direction perpendicular to the alignment axis D is observed, and the dark lines in this repetition are observed in the direction of the alignment axis D, with adjacent dark lines being thicker than the adjacent dark line → thinner than the adjacent dark line → thicker than the adjacent dark line → thinner than the adjacent dark line ... The liquid crystal diffraction element of the present invention has such an optically anisotropic layer 36, and can convert the polarized light of zero-order light transmitted without being diffracted by the liquid crystal diffraction element 10 (optically anisotropic layer 36) into a polarized light different from that of the incident light. That is, by configuring the optically anisotropic layer 36 of the liquid crystal diffraction element so that the width of the dark line repeats in the direction of the alignment axis D, from thicker than the adjacent line → thinner than the adjacent line → thicker than the adjacent line → thinner than the adjacent line ..., when clockwise polarized light with an ellipticity εin of 0.95 or more is incident, the zero-order light transmitted through the liquid crystal diffraction element becomes left-handed polarized light, linearly polarized light, or right-handed polarized light with an ellipticity ε0 that satisfies the relationship of the above formula (1), or when left-handed polarized light with an ellipticity εin of 0.95 or more is incident, the zero-order light transmitted through the liquid crystal diffraction element becomes right-handed polarized light, linearly polarized light, or left-handed polarized light with an ellipticity ε0 that satisfies the relationship of the above formula (1), a liquid crystal diffraction element can be obtained.

[0068] In a conventional liquid crystal diffraction element such as that described in Patent Document 1, an optically anisotropic layer having a liquid crystal orientation pattern in which the optical axis of the liquid crystal compound continuously rotates in one direction has a constant rotation of the optical axis 40A over one period Λ toward the alignment axis D, as in the optically anisotropic layer 36Z conceptually shown in FIG. 22 . That is, in the optically anisotropic layer 36Z of the conventional liquid crystal diffraction element, the rotation angle of the optical axis 40A is approximately constant over one period Λ in which the optical axis 40A changes from a state parallel to the alignment axis D to a state perpendicular to the alignment axis D, and then returns to a state parallel to the alignment axis D. In other words, in the optically anisotropic layer 36Z of the conventional liquid crystal diffraction element, the rotation of the optical axis 40A over one period Λ is a linear rotation with a constant rotation angle. In the following description, for convenience, a liquid crystal orientation pattern in which the rotation of the optical axis 40A over one period Λ is constant will also be referred to as a "linear liquid crystal orientation pattern." As described above, in the region where the optical axis 40A (approximately) coincides with the absorption axis of the polarizer, light is blocked and dark lines extending in the Y direction are observed. Therefore, when the liquid crystal orientation pattern is linear, the thickness of the dark lines aligned in the direction of the alignment axis D is approximately constant.

[0069] In a conventional liquid crystal diffraction element having an optically anisotropic layer 36Z with such a linear liquid crystal orientation pattern, it is known that the polarization state of the zeroth-order light that travels straight through the liquid crystal diffraction element (optically anisotropic layer) without being diffracted is the same as that of the incident light. That is, as conceptually shown in Figure 9, in a conventional optically anisotropic layer 36Z having a linear liquid crystal orientation pattern, when the incident light is right-handed circularly polarized light, the zeroth-order light also remains right-handed circularly polarized.

[0070] In contrast, in the optically anisotropic layer 36 of the liquid crystal diffraction element 10, as conceptually shown in FIG. 11, the rotation of the optic axis 40A over one period Λ is not constant. In the optically anisotropic layer 36 of the illustrated example, over one period Λ, the optic axis 40A rotates from a state parallel to the arrangement axis D at a large rotation angle to an angle nearly perpendicular to the arrangement axis D, then rotates at a small rotation angle to become perpendicular to the arrangement axis D, and then rotates at a further small rotation angle, after which the rotation angle increases and the optic axis 40A is again parallel to the arrangement axis D. That is, in the optically anisotropic layer 36 of the liquid crystal diffraction element 10 of the present invention, the rotation angle of the optic axis 40A over one period Λ decreases from a large state, and then increases again. In other words, in the optically anisotropic layer 36 of the liquid crystal diffraction element 10 of the present invention, the rotation of the optic axis 40A over one period Λ is a nonlinear rotation in which the rotation angle changes. In the following description, such a liquid crystal alignment pattern in which the rotation of the optical axis 40A per period Λ is not constant will also be referred to as a "nonlinear liquid crystal alignment pattern" for convenience.

[0071] As described above, in the region where the optical axis 40A (substantially) coincides with the absorption axis of the polarizer, light is blocked, and dark lines extending in the Y direction are observed. Here, when the liquid crystal alignment pattern is nonlinear, the width in the alignment axis D direction of the region where the optical axis 40A (substantially) coincides with the absorption axis of the polarizer arranged in a crossed Nicol configuration changes over one period. In the optically anisotropic layer 36 shown in FIG. 11 , the width in the alignment axis D direction of the region where the absorption axis (substantially) coincides with the absorption axis in the alignment axis D direction is narrow, and the width in the alignment axis D direction of the region where the absorption axis (substantially) coincides with the absorption axis in the Y direction, which is perpendicular to the alignment axis D direction, is wide. As a result, in the optically anisotropic layer 36 with a nonlinear liquid crystal alignment pattern, thick and thin dark lines are alternately observed in the alignment axis D direction, as shown in FIG. 14 .

[0072] In other words, an optically anisotropic layer 36 in which, among 20 consecutive dark lines selected as described above, the width of the even-numbered dark line e is narrower than the width of the adjacent odd-numbered dark line o and the width of the odd-numbered dark line o is wider than the width of the adjacent even-numbered dark line e has a nonlinear liquid crystal orientation pattern in which the rotation of the optic axis 40A in one period is not constant. That is, an optically anisotropic layer in which thick and thin dark lines are observed alternately in the direction of the alignment axis D has a nonlinear liquid crystal orientation pattern in which the rotation of the optic axis 40A facing the alignment axis D is not constant.

[0073] The liquid crystal diffraction element of the present invention can convert the polarization state of the zeroth-order light of the optically anisotropic layer into a polarization state different from that of the incident light by having an optically anisotropic layer with a nonlinear liquid crystal orientation pattern. That is, as conceptually shown in each of Figures 1 to 6 described above, the optically anisotropic layer 36 having a nonlinear liquid crystal orientation pattern used in the present invention can convert the polarization state of the zeroth-order light of the optically anisotropic layer into a polarization state different from that of the incident light. For example, as shown in the example of Figure 1, when the incident light is right-handed circularly polarized light, the optically anisotropic layer 36 can convert the zeroth-order light into elliptically polarized light with a right-handed rotation direction.

[0074] By using such a liquid crystal diffraction element of the present invention, it is possible to convert zero-order light into a polarized light different from that of the incident light, and for example, in image display applications where zero-order light becomes stray light as described above, it is possible to remove the zero-order light.

[0075] In the liquid crystal diffraction element of the present invention, the optically anisotropic layer 36 preferably has a large difference in width between the wide dark lines, i.e., the odd-numbered dark lines o, and the narrow dark lines, i.e., the even-numbered dark lines e. The larger this difference, the greater the difference in polarization state between the incident light and the zero-order light. On the other hand, in the liquid crystal diffraction element of the present invention, the optically anisotropic layer 36 preferably has a small difference in thickness between the wide dark lines and the narrow dark lines. The smaller this difference, the more preferable it is in terms of, for example, reducing the likelihood of diffracted light becoming stray light.

[0076] Specifically, in the liquid crystal diffraction element of the present invention, the optically anisotropic layer 36 preferably has 20 consecutive dark lines selected as described above that satisfy the following formula: [average odd-numbered dark line width] - [average even-numbered dark line width] > ([standard deviation of odd-numbered dark line width] + [standard deviation of even-numbered dark line width]) / 2 When the optically anisotropic layer 36 satisfies this formula, the above-mentioned effects can be more suitably exhibited.

[0077] The optically anisotropic layer 36 can adjust the diffraction (refraction) angle of the transmitted light L2 and L5 by changing the period Λ of the liquid crystal orientation pattern formed. Specifically, the shorter the period Λ of the liquid crystal orientation pattern, the stronger the interference between light passing through adjacent liquid crystal compounds 40, resulting in greater diffraction of the transmitted light L2 and L5. Therefore, by having regions in the plane of the optically anisotropic layer 36 with different lengths of the period Λ, incident light can be diffracted in different directions. Furthermore, the optically anisotropic layer 36 may have regions in the plane where the length of the period gradually changes in one direction of rotation of the liquid crystal compound, in the illustrated example, along the alignment axis D. By having such regions, a liquid crystal diffraction element can be formed that focuses or diverges diffracted light (primary light). For example, by gradually shortening the period Λ of the optically anisotropic layer in the alignment axis D direction from the center of the alignment axis D to both sides, a liquid crystal diffraction element can be obtained that focuses (or diverges) diffracted light at the center along the alignment axis D.

[0078] Furthermore, the direction of diffraction of transmitted light can be reversed by reversing the direction of rotation of the optical axis 40A of the liquid crystal compound 40, which rotates along the direction of the alignment axis D. That is, in the examples shown in Figures 12 and 13, the direction of rotation of the optical axis 40A facing the direction of the alignment axis D is clockwise, but by changing this rotation direction to counterclockwise, the direction of diffraction of transmitted light can be reversed.

[0079] Here, the angle of diffraction (refraction angle) by the optically anisotropic layer 36 varies depending on the wavelength of the incident light. Specifically, the longer the wavelength of light, the greater the diffraction. That is, among red, green, and blue light, red light is diffracted most, green light is diffracted next most, and blue light is diffracted least. As described above, the angle of diffraction varies depending on one period Λ of the liquid crystal orientation pattern of the optically anisotropic layer 36. Therefore, by making one period Λ of the liquid crystal orientation pattern of the optically anisotropic layer 36 uniform, light of the same wavelength can be diffracted at the same angle.

[0080] In the optically anisotropic layer 36, the in-plane retardation value of the plurality of regions R is preferably a half wavelength. The in-plane retardation Re(550) of the plurality of regions R of the optically anisotropic layer 36 for incident light having a wavelength of 550 nm is Re(550)=Δn 550 ×d is preferably within the range defined by the following formula (1): 550 is the refractive index difference associated with the refractive index anisotropy of the region R when the wavelength of incident light is 550 nm, and d is the thickness of the optically anisotropic layer 36. 550 ×d≦350 nm (1) That is, the in-plane retardation Re(550) of the plurality of regions R of the optically anisotropic layer 36=Δn 550 When ×d satisfies the formula (1), a sufficient amount of the circularly polarized component of the light incident on the optically anisotropic layer 36 can be converted into circularly polarized light traveling in a direction tilted in the forward or backward direction with respect to the direction of the alignment axis D. In-plane retardation Re(550)=Δn 550 ×d is 225 nm≦Δn 550 ×d≦340 nm is more preferable, and 250 nm≦Δn 550 It is more preferable that ×d≦330 nm. The above formula (1) is a range for incident light having a wavelength of 550 nm, but the in-plane retardation Re(λ) of the plurality of regions R of the optically anisotropic layer for incident light having a wavelength of λ nm is λ ×d is preferably within the range defined by the following formula (1-2), and can be set appropriately: 0.7×(λ / 2) nm≦Δn λ ×d≦1.3×(λ / 2)nm...(1-2)

[0081] In addition, the in-plane retardation values ​​of the regions R in the optically anisotropic layer 36 may be outside the range of the above formula (1). 550 ×d<200 nm or 350 nm<Δn 550 ×d, it is possible to separate light into light traveling in the same direction as the incident light and light traveling in a direction different from the incident light. 550 When ×d approaches 0 nm or 550 nm, the component of light traveling in the same direction as the incident light increases, and the component of light traveling in a direction different from the incident light decreases.

[0082] Furthermore, the in-plane retardation Re(450) of each region R of the optically anisotropic layer 36 for incident light having a wavelength of 450 nm is expressed as Re(450)=Δn 450 ×d and the in-plane retardation Re(550)=Δn of the region R of the optically anisotropic layer 36 for incident light having a wavelength of 550 nm. 550 ×d preferably satisfies the following formula (2): 450 is the refractive index difference associated with the refractive index anisotropy of the region R when the wavelength of the incident light is 450 nm. (Δn 450 × d) / (Δn 550 ×d)<1.0 (2) Formula (2) indicates that the liquid crystal compound 40 contained in the optically anisotropic layer 36 has reverse dispersion. That is, when formula (2) is satisfied, the optically anisotropic layer 36 can accommodate incident light of a wide wavelength band.

[0083] 10 and 11 , the optical anisotropic layer 36 has the optical axis 40A of the liquid crystal compound 40 continuously rotated in one direction, i.e., the direction of the alignment axis D. However, the present invention is not limited to this, and in the optical anisotropic layer of the liquid crystal diffraction element of the present invention, the optical axis 40A continuously rotates in various directions, such as two perpendicular directions.

[0084] An example of this is conceptually shown in Figure 15. The optically anisotropic layer 36S shown in Figure 15 has a concentric liquid crystal orientation pattern in which the direction of the optical axis of the liquid crystal compound 40 changes while continuously rotating (arrows A1 to A3, etc.), radially from the inside to the outside. A concentric pattern is a pattern in which the lines connecting liquid crystal compounds whose optical axes are oriented in the same direction form a circle, and the line segments of the circle form concentric circles. In other words, the liquid crystal orientation pattern of the optically anisotropic layer 36S shown in Figure 15 is a liquid crystal orientation pattern in which the direction of the optical axis of the liquid crystal compound 40 changes while continuously rotating is provided radially from the center of the optically anisotropic layer 36S. That is, in the liquid crystal orientation pattern shown in Figure 15, each of the directions radially outward from the center of the optically anisotropic layer 36S, such as the direction of arrow A1, the direction of arrow A2, the direction of arrow A3, etc., corresponds to the direction of the alignment axis D in the optically anisotropic layer 36 described above.

[0085] As described above, the optically anisotropic layer 36S shown in Figure 15 has a concentric liquid crystal orientation pattern. Therefore, in this example, when the optically anisotropic layer 36S (liquid crystal diffraction element) is observed under crossed Nicols with an optical microscope, for example, with the direction of arrow A2 in the figure as the absorption axis of one polarizer, concentric dark and bright lines are observed alternately. Furthermore, in the optically anisotropic layer 36S shown in Figure 15, of the 80 dark lines selected in the same manner as in the above example, the even-numbered dark line widths are narrower than the adjacent odd-numbered dark lines, and the odd-numbered dark line widths are wider than the adjacent even-numbered dark lines. Therefore, in this example, as conceptually shown in Figure 15, dark lines narrower than adjacent dark lines and dark lines wider than adjacent dark lines are observed alternately in a concentric pattern.

[0086] 15, in order to clearly show the liquid crystal orientation pattern, the liquid crystal orientation pattern directed in one direction is depicted as a linear liquid crystal orientation pattern. However, as described above, in the optically anisotropic layer 36S in which dark lines narrower than adjacent dark lines and dark lines wider than adjacent dark lines are observed alternately in a concentric pattern, the liquid crystal orientation pattern is nonlinear. Therefore, in this example as well, the polarization state of the zero-order light is converted to a state different from that of the incident light.

[0087] In the optically anisotropic layer 36S shown in FIG. 15 , the optical axis (not shown) of the liquid crystal compound 40 is also in the longitudinal direction of the liquid crystal compound 40. In the optically anisotropic layer 36S, the direction of the optical axis of the liquid crystal compound 40 changes while continuously rotating along multiple directions from the center of the optically anisotropic layer 36 toward the outside, such as the direction indicated by arrow A1, the direction indicated by arrow A2, the direction indicated by arrow A3, etc. Arrows A1, A2, and A3 are alignment axes similar to the alignment axis D described above. In this example, the same concentric circle on which the optical axes of the liquid crystal compound 40 are oriented corresponds to the Y direction of the optically anisotropic layer 36 described above. As a result, the optically anisotropic layer 36S shown in FIG. 15 also diffracts incident light in the directions indicated by arrows A1, A2, A3, etc. due to the same effect. As in the previous example, the zero-order light is converted into a polarized light different from that of the incident light.

[0088] The optically anisotropic layer 36S of the liquid crystal diffraction element has regions in which the period Λ of the liquid crystal orientation pattern varies within the plane. Specifically, in FIG. 15, for example, in the direction along arrow A1, the direction in which the orientation of the optical axis of the liquid crystal compound 40 changes while continuously rotating, the period Λ is configured to gradually shorten from the center to the outside. That is, in FIG. 15, the period near the outside is shorter than the period near the center. In this invention, the gradual change of the period Λ means that the period Λ changes continuously and that the period Λ changes stepwise. In this respect, the same applies to the above-mentioned examples.

[0089] As described above, the diffraction angle of the liquid crystal diffraction element depends on the period Λ of the liquid crystal orientation pattern, and the smaller the period Λ, the larger the diffraction angle. Therefore, in this example, the optically anisotropic layer 36S diffracts incident light toward the center. In other words, the liquid crystal diffraction element having the optically anisotropic layer 36S can transmit incident light as focused light, and exhibits the function of, for example, a convex lens.

[0090] As described above, in the liquid crystal diffraction element of the present invention, the optically anisotropic layer 36 is formed using a liquid crystal composition containing a liquid crystal compound, and has a liquid crystal orientation pattern in which the direction of the optical axis of the liquid crystal compound changes continuously in at least one direction in the plane. Here, in the optically anisotropic layer shown in Figure 10, the liquid crystal compound 40 is oriented in the same direction in the thickness direction. However, the present invention is not limited to this, and the liquid crystal compound 40 may be oriented in a helical twist in the thickness direction, as in the optically anisotropic layer 36A conceptually shown in Figure 16.

[0091] An optically anisotropic layer having the above-described liquid crystal orientation pattern has bright areas 42 and dark areas 44 extending from one surface to the other surface in a cross-sectional image obtained by observing a cross section cut in the thickness direction along the direction in which the optical axis continuously rotates with a scanning electron microscope (SEM). In the following description, an image obtained by observing a cross section of such an optically anisotropic layer with an SEM will also be referred to as a "cross-sectional SEM image" for convenience. The bright areas 42 and dark areas 44 observed in the cross-sectional SEM image are derived from the liquid crystal phase having the liquid crystal orientation pattern.

[0092] 10 and 11, the optically anisotropic layer 36 in which the liquid crystal compound 40 is not helically twisted in the thickness direction has, in a cross-sectional SEM image, bright regions 42 and dark regions 44 extending from one surface to the other surface, perpendicular to the thickness direction, i.e., the main surface. In contrast, the optically anisotropic layer 36A in which the liquid crystal compound 40 is helically twisted in the thickness direction has, in a cross-sectional SEM image, bright regions 42 and dark regions 44 extending from one surface to the other surface, tilted relative to the thickness direction, i.e., the main surface, of the optically anisotropic layer 36A, as conceptually shown in FIG.

[0093] In this way, by helically orienting the liquid crystal compound in the thickness direction in the optically anisotropic layer, the effective birefringence of the liquid crystal compound is increased when light is diffracted, thereby improving the diffraction efficiency and further increasing the change in the zero-order light relative to the incident light. Furthermore, the difference between the diffraction efficiency of the first-order diffracted light emitted from the liquid crystal diffraction element when clockwise polarized light with an ellipticity εin of 0.95 or more is incident on the liquid crystal diffraction element and the diffraction efficiency of the first-order diffracted light emitted from the liquid crystal diffraction element when counterclockwise polarized light with an ellipticity εin of 0.95 or more is incident on the liquid crystal diffraction element can be increased. That is, the ratio DE(1S) / DE(1L) between the diffraction efficiency DE(1L) of the first-order diffracted light with high diffraction efficiency and the diffraction efficiency DE(1S) of the first-order diffracted light with low diffraction efficiency can be made 0.95 or less.

[0094] In an optically anisotropic layer 36A in which liquid crystal compound 40 is helically twisted in the thickness direction as shown in FIG. 16 , the angle of the dark region 44 (light region 42) relative to the principal surface in a cross-sectional SEM image can be adjusted by the length of one period in the liquid crystal orientation pattern described above and the magnitude of the twist of the liquid crystal compound 40 twisted in the thickness direction. Specifically, the shorter the period in the liquid crystal orientation pattern, the larger the angle of the dark region 44 relative to the principal surface. Furthermore, the smaller the twist in the thickness direction, the larger the angle of the dark region 44 relative to the principal surface. The helically twisted orientation of the liquid crystal compound in the optically anisotropic layer can be achieved by adding a chiral dopant to the liquid crystal composition for forming the optically anisotropic layer, as described below. The twist direction and degree of twist of the liquid crystal compound 40 can be adjusted by selecting and adjusting the type and amount of chiral dopant.

[0095] In the liquid crystal compound of the present invention, the optically anisotropic layer is not limited to having linear light regions 42 and dark regions 44 as shown in Fig. 17. As an example, as in optically anisotropic layer 36B conceptually shown in Fig. 18, a region in which the liquid crystal compound 40 is helically twisted in the thickness direction sandwiches a region in which the liquid crystal compound is not helically twisted and oriented, so that a region having light regions 42 and dark regions 44 extending in the thickness direction is sandwiched between regions in which the light regions 42 and dark regions 44 are tilted in opposite directions.

[0096] 10 and 11 show a configuration in which the optical axis 40A of the liquid crystal compound 40 is aligned parallel to the main surface (X-Y plane) in the X-Z plane of the optically anisotropic layer 36. However, the present invention is not limited to this. For example, as conceptually shown in FIG. 19, a configuration in which the optical axis 40A of the liquid crystal compound 40 is aligned inclined, i.e., tilted, with respect to the main surface (X-Y plane) in the X-Z plane of the optically anisotropic layer 36C may be used.

[0097] 19, the tilt angle (tilt angle) of the optical axis 40A of the liquid crystal compound 40 relative to the main surface (X-Y plane) in the X-Z plane of the optically anisotropic layer 36C is uniform in the thickness direction (Z direction), but the present invention is not limited to this. That is, the optically anisotropic layer 36C may have a region in which the tilt angle of the optical axis 40A varies in the thickness direction. For example, the liquid crystal compound 40 may be oriented such that the optical axis 40A is parallel to the main surface (tilt angle 0°) at the interface on the alignment film 32 side of the optically anisotropic layer 36C, the tilt angle of the optical axis 40A increases with increasing distance in the thickness direction from the interface on the alignment film 32 side, and thereafter the tilt angle of the optical axis 40A remains constant up to the other interface (air interface).

[0098] In this way, in the optically anisotropic layer, the optical axis 40A of the liquid crystal compound 40 may have a tilt angle at one of the upper and lower interfaces, or may have a tilt angle at both interfaces. The tilt angles may also be different at both interfaces. When the optical axis 40A of the liquid crystal compound 40 has a tilt angle (is inclined), the effective birefringence of the liquid crystal compound increases when light is diffracted, thereby increasing the diffraction efficiency and further increasing the change in the zero-order light relative to the incident light.

[0099] The optically anisotropic layer of the liquid crystal diffraction element of the present invention may have only one or both of the following configurations: a configuration having a dark area 44 inclined with respect to the main surface (thickness direction) in a cross-sectional SEM image; and a configuration in which the optical axis 40A of the liquid crystal compound 40 is tilted.

[0100] Specifically, a preferred example is a configuration in which the average tilt angle of the dark areas 44 in the cross-sectional SEM image is 5° or more relative to the main surface of the optically anisotropic layer, and the tilt angle of the optical axis 40A of the liquid crystal compound 40 in the thickness direction is less than 5°. Another preferred example is a configuration in which the average tilt angle of the dark areas 44 in the cross-sectional SEM image is less than 5° relative to the main surface of the optically anisotropic layer, and the tilt angle of the optical axis 40A of the liquid crystal compound 40 in the thickness direction is 5° or more. Another preferred example is a configuration in which the average tilt angle of the dark areas 44 in the cross-sectional SEM image is 5° or more relative to the main surface of the optically anisotropic layer, and the tilt angle of the optical axis 40A of the liquid crystal compound 40 in the thickness direction is 5° or more. By having such a configuration for the optically anisotropic layer, the liquid crystal diffraction element of the present invention can further increase the change in the polarization state of zero-order light relative to incident light. As a result, for example, the effect of suppressing stray light when zero-order light becomes stray light and the effect of improving light utilization efficiency can be more preferably obtained.

[0101] As described above, the liquid crystal diffraction element 10 shown in FIGS. 10 and 11 has the support 30, the alignment film 32, and the optically anisotropic layer .

[0102] The liquid crystal diffraction element of the present invention is not limited to the example shown in FIG. 10 , and various layer structures can be used. For example, the liquid crystal diffraction element of the present invention may be a liquid crystal diffraction element shown in FIG. 10 , with the support 30 peeled off, and consisting of an alignment film 32 and an optically anisotropic layer 36. The liquid crystal diffraction element of the present invention may also be a liquid crystal diffraction element shown in FIG. 10 , with the support 30 and alignment film 32 peeled off, and consisting of only the optically anisotropic layer 36. The liquid crystal diffraction element of the present invention may also be a liquid crystal diffraction element consisting of the support 30 and the optically anisotropic layer 36. Furthermore, the liquid crystal diffraction element of the present invention may have other layers, such as a protective layer (hard coat layer) and an antireflection layer, in addition to these structures. That is, the liquid crystal diffraction element of the present invention may have various layer structures as long as it has the optically anisotropic layer described below.

[0103] <<Support>> The support 30 supports the alignment film 32 and the optically anisotropic layer 36. Various sheet-like materials (films, plates) can be used as the support 30 as long as they can support the alignment film and the optically anisotropic layer. Transparent supports are preferred for the support 30, and examples of such materials include polyacrylic resin films such as polymethyl methacrylate, cellulose resin films such as cellulose triacetate, cycloolefin polymer films (e.g., "Arton" manufactured by JSR Corporation, "Zeonor" manufactured by Nippon Zeon Co., Ltd.), polyethylene terephthalate (PET), polycarbonate, and polyvinyl chloride. The support is not limited to flexible films, and may also be non-flexible substrates such as glass substrates. The support 30 may also be multilayered. Examples of multilayer supports include those that include any of the above-mentioned supports as a substrate, with other layers provided on the surface of this substrate.

[0104] There is no limitation on the thickness of the support 30, and it may be set appropriately to a thickness that can support the alignment film and the optically anisotropic layer depending on the application of the liquid crystal diffraction element and the material forming the support 30. The thickness of the support 30 is preferably 1 to 1000 μm, more preferably 3 to 250 μm, and even more preferably 5 to 150 μm.

[0105] <<Alignment Film>> An alignment film 32 is formed on the surface of the support 30. The alignment film 32 is an alignment film for orienting the liquid crystal compound 40 in the above-described predetermined liquid crystal alignment pattern when the optically anisotropic layer 36 is formed.

[0106] As described above, in the liquid crystal diffraction element of the present invention, the optically anisotropic layer has a liquid crystal orientation pattern in which the orientation of the optical axis 40A (see FIG. 11 ) of the liquid crystal compound 40 changes while continuously rotating along one in-plane direction (the direction of the arrow X described below). Therefore, the orientation film is formed so that the optically anisotropic layer can form this liquid crystal orientation pattern. Furthermore, in the liquid crystal orientation pattern, the length over which the orientation of the optical axis 40A rotates 180° in one direction in which the orientation of the optical axis 40A changes while continuously rotating is defined as one period Λ (optical axis rotation period).

[0107] 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 formed 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.

[0108] An 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. Preferred examples of materials used for the alignment film include polyimide, polyvinyl alcohol, polymers having polymerizable groups described in JP-A-9-152509, and materials used to form alignment films described in JP-A-2005-97377, JP-A-2005-99228, and JP-A-2005-128503.

[0109] In the liquid crystal diffraction element of the present invention, the alignment film is preferably a so-called photo-alignment film, which is formed by irradiating a photo-alignable material with polarized or non-polarized light. That is, in the liquid crystal diffraction element of the present invention, the alignment film is preferably a photo-alignment film formed by applying a photo-alignment material onto a support 30. Irradiation with polarized light can be performed vertically or obliquely to the photo-alignment film, and irradiation with non-polarized light can be performed obliquely to the photo-alignment film.

[0110] Examples of photo-alignment materials that can be used in the photo-alignment film of the present invention include those disclosed in JP-A-2006-285197, JP-A-2007-76839, JP-A-2007-138138, JP-A-2007-94071, JP-A-2007-121721, JP-A-2007-140465, JP-A-2007-156439, and JP-A-2007-160466. azo compounds described in JP-A-07-133184, JP-A-2009-109831, Japanese Patent No. 3883848 and Japanese Patent No. 4151746, aromatic ester compounds described in JP-A-2002-229039, maleimides having photo-alignable units described in JP-A-2002-265541 and JP-A-2002-317013, 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, are exemplified as preferred examples. Among these, azo compounds, photocrosslinkable polyimides, photocrosslinkable polyamides, photocrosslinkable esters, cinnamate compounds, and chalcone compounds are preferably used.

[0111] There is no limitation on the thickness of the alignment film, and it may be set appropriately depending on the material of which the alignment film is formed so as to obtain the necessary alignment function. The thickness of the alignment film is preferably 0.01 to 5 μm, and more preferably 0.05 to 2 μm.

[0112] There is no limitation on the method for forming the alignment film, and various known methods can be used depending on the material for forming the alignment film. One example is a method in which an alignment film is applied to the surface of the support 30, dried, and then exposed to laser light to form an alignment pattern.

[0113] Figure 20 conceptually shows an example of an exposure device that exposes an alignment film to form an alignment pattern corresponding to a liquid crystal alignment pattern in which the optical axis 40A of the liquid crystal compound 40 continuously rotates in one direction, i.e., the direction of the alignment axis D, shown in Figure 11.

[0114] 20 includes a light source 64 equipped with a laser 62, a λ / 2 plate 65 that changes the polarization direction of laser light M emitted by the laser 62, a beam splitter 68 that splits the laser light M emitted from the laser 62 into two beams MA and MB, mirrors 70A and 70B that are respectively arranged on the optical paths of the two split beams MA and MB, and λ / 4 plates 72A and 72B. Although not shown, the light source 64 emits linearly polarized light P0. The λ / 4 plate 72A converts the linearly polarized light P0 (beam MA) into right-handed circularly polarized light P R The λ / 4 plate 72B converts the linearly polarized light P0 (light beam MB) into left-handed circularly polarized light P L are converted to , respectively.

[0115] A support 30 having an alignment film 32 before an alignment pattern is formed is placed in an exposure unit, and two light beams MA and MB are caused to intersect and interfere on the alignment film 32, and the alignment film 32 is exposed to the interference light. This interference causes the polarization state of the light irradiating the alignment film 32 to periodically change in the form of interference fringes. This results in an alignment pattern in the alignment film 32 in which the alignment state periodically changes. That is, an alignment film having an alignment pattern in which the alignment state periodically changes (hereinafter also referred to as a pattern alignment film) is obtained. In the exposure device 60, the period of the alignment pattern can be adjusted by changing the crossing angle α of the two light beams MA and MB. That is, in the exposure device 60, in an alignment pattern in which the optical axis 40A of the liquid crystal compound 40 continuously rotates along one direction, the length of one period (one period Λ) in which the optical axis 40A rotates 180° in one direction of the rotation of the optical axis 40A can be adjusted by adjusting the crossing angle α. By forming an optically anisotropic layer on a patterned alignment film having such an alignment pattern in which the alignment state changes periodically, it is possible to form an optically anisotropic layer 36 having a liquid crystal alignment pattern in which the optical axis 40A of the liquid crystal compound 40 continuously rotates in one direction, as will be described later. In addition, by rotating the optical axes of the λ / 4 plates 72A and 72B by 90° each, the rotation direction of the optical axis 40A can be reversed.

[0116] FIG. 21 conceptually shows an example of an exposure apparatus for forming an alignment pattern corresponding to the concentric circular liquid crystal alignment pattern shown in FIG.

[0117] The exposure device 80 shown in Figure 21 has a light source 84 equipped with a laser 82, a polarizing beam splitter 86 that splits laser light M from the laser 82 into S-polarized light MS and P-polarized light MP, a mirror 90A arranged in the optical path of the P-polarized light MP and a mirror 90B arranged in the optical path of the S-polarized light MS, a lens 92 arranged in the optical path of the S-polarized light MS, a polarizing beam splitter 94, and a λ / 4 plate 96.

[0118] The P-polarized light MP split by the polarizing beam splitter 86 is reflected by a mirror 90A and enters a polarizing beam splitter 94. On the other hand, the S-polarized light MS split by the polarizing beam splitter 86 is reflected by a mirror 90B, collected by a lens 92, and enters the polarizing beam splitter 94. The P-polarized light MP and the S-polarized light MS are combined by the polarizing beam splitter 94 and converted into right- and left-circularly polarized light according to the polarization direction by a λ / 4 plate 96. The combined light then enters the alignment film 32 on the support 30. Here, due to interference between the right- and left-circularly polarized light, the polarization state of the light irradiated onto the alignment film changes periodically, like an interference fringe pattern. The crossing angle between the left- and right-circularly polarized light changes from the inside to the outside of the concentric circles, resulting in an exposure pattern whose pitch changes from the inside to the outside. This results in a concentric alignment pattern in the alignment film, in which the alignment state changes periodically.

[0119] In this exposure device 80, one period Λ of the liquid crystal orientation pattern in which the optical axis of the liquid crystal compound 40 continuously rotates 180° along one direction can be controlled by changing the refractive power of the lens 92 (the F-number of the lens 92), the focal length of the lens 92, and the distance between the lens 92 and the orientation film 32. Furthermore, by adjusting the refractive power of the lens 92 (the F-number of the lens 92), the length Λ of one period of the liquid crystal orientation pattern can be changed in one direction in which the optical axis continuously rotates. Specifically, the length Λ of one period of the liquid crystal orientation pattern in one direction in which the optical axis continuously rotates can be changed by adjusting the spread angle of the light expanded by the lens 92, which interferes with the parallel light. More specifically, when the refractive power of the lens 92 is weakened, the light approaches parallel light, so the length Λ of one period of the liquid crystal orientation pattern gradually shortens from the inside to the outside, and the F-number increases. Conversely, when the refractive power of the lens 92 is increased, the length Λ of one period of the liquid crystal alignment pattern suddenly decreases from the inside to the outside, and the F-number decreases.

[0120] As described above, the patterned alignment film has an alignment pattern that aligns the liquid crystal compound 40 so that the direction of the optical axis of the liquid crystal compound in the optically anisotropic layer formed on the patterned alignment film changes while continuously rotating along at least one in-plane direction. If the axis along which the patterned alignment film aligns the liquid crystal compound 40 is defined as the alignment axis, the patterned alignment film can be said to have an alignment pattern in which the direction of the alignment axis changes while continuously rotating along at least one in-plane direction. The alignment axis of the patterned alignment film can be detected by measuring absorption anisotropy. For example, when the patterned alignment film is irradiated with linearly polarized light while being rotated and the amount of light transmitted through the patterned alignment film is measured, the direction in which the amount of light is maximized or minimized is observed to gradually change along one in-plane direction.

[0121] In the liquid crystal diffraction element of the present invention, the alignment film is provided as a preferred embodiment but is not an essential component. For example, by forming an alignment pattern on the support 30 by a method of rubbing the support 30 or a method of processing the support 30 with laser light or the like, it is possible to configure the optically anisotropic layer 36 or the like to have a liquid crystal alignment pattern in which the direction of the optical axis 40A of the liquid crystal compound 40 changes while continuously rotating along at least one direction in the plane.

[0122] Depending on the application of the liquid crystal diffraction element, for example, when it is desired to provide a light intensity distribution to transmitted light, it is also possible to use a configuration in which the period Λ is not gradually changed toward the direction of the array axis D, but has regions in which the period Λ is partially different in the direction of the array axis D. For example, as a method for partially changing the period Λ, a method can be used in which a photo-alignment film is subjected to scan exposure and patterning while arbitrarily changing the polarization direction of focused laser light.

[0123] The wavelength of the laser used to expose the alignment film can be set appropriately depending on the type of alignment film used, etc. For example, a laser with a wavelength ranging from deep ultraviolet to visible light to infrared can be preferably used. As an example, lasers with wavelengths of 266 nm, 325 nm, 355 nm, 370 nm, 385 nm, 405 nm, and 460 nm can be used, but the wavelengths are not limited to these, and lasers with various wavelengths can be used depending on the type of alignment film, etc.

[0124] After providing the optically anisotropic layer on the alignment film, the optically anisotropic layer may be peeled and / or transferred from the alignment film. Transfer may be performed multiple times depending on the surface to which the optically anisotropic layer is attached. The peeling and / or transfer method can be freely selected depending on the purpose. For example, the optically anisotropic layer may be transferred to a substrate having an adhesive layer, then retransferred to the object to which it is to be transferred, and the substrate may be peeled off, so that the interface of the optically anisotropic layer facing the alignment film faces the object to which it is to be transferred. Alternatively, if the surface of the optically anisotropic layer opposite the alignment film faces the object to which it is to be transferred, the optically anisotropic layer and the object to which it is to be transferred may be attached together with an adhesive, and then the optically anisotropic layer may be peeled off from the alignment film. When peeling the optically anisotropic layer from the alignment film, it is preferable to adjust the peeling angle and speed to reduce damage (e.g., tears, nicks) to the optically anisotropic layer and the alignment film. The alignment film may be used repeatedly as long as it does not affect the alignment. Before providing the optically anisotropic layer on the alignment film, the alignment film may be washed with an organic solvent or the like.

[0125] <<Optically Anisotropic Layer>> An optically anisotropic layer 36 is formed on the surface of the alignment film 32. The optically anisotropic layer is formed by forming the alignment film 32 having the above-described alignment pattern on the support 30, and then applying and curing a liquid crystal composition on this alignment film. Furthermore, a structure in which the optical axes of the liquid crystal compounds in the optically anisotropic layer are helically twisted and aligned in the thickness direction of the optically anisotropic layer, i.e., a configuration in which the dark portions 44 are tilted with respect to the main surface (thickness direction), can be formed by adding a chiral agent that helically aligns the liquid crystal compounds in the thickness direction to the liquid crystal composition.

[0126] As described above, the magnitude of the twisted orientation of the liquid crystal compound that is helically twisted in the thickness direction can be adjusted by the type and amount of chiral dopant added to the liquid crystal composition. In addition, the twisted direction (right-handed / left-handed) of the liquid crystal compound in the thickness direction can also be selected by selecting the type of chiral dopant added to the liquid crystal composition.

[0127] Although it is the optically anisotropic layer that functions as a so-called λ / 2 plate, the present invention also includes an embodiment in which a laminate integrally comprising a support and an alignment film functions as a λ / 2 plate. The liquid crystal composition for forming the optically anisotropic layer contains a rod-shaped liquid crystal compound or a discotic liquid crystal compound, and may further contain other components such as a leveling agent, an alignment control agent, a polymerization initiator, and an alignment aid.

[0128] In the present invention, there is no limitation on the thickness of the optically anisotropic layer, and the thickness may be appropriately set so as to obtain the desired optical characteristics depending on one period Λ of the liquid crystal alignment pattern, the required angle of diffraction, the diffraction efficiency, etc.

[0129] Rod-shaped liquid crystal compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoates, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes, and alkenylcyclohexylbenzonitriles. Not only low-molecular-weight liquid crystal molecules such as those mentioned above, but also polymeric liquid crystal molecules can be used.

[0130] It is more preferable to fix the alignment of the rod-shaped liquid crystal compound by polymerization. Examples of polymerizable rod-shaped liquid crystal compounds include those described in Makromol. Chem. , Vol. 190, p. 2255 (1989), Advanced Materials Vol. 5, p. 107 (1993), U.S. Patent Nos. 4,683,327, 5,622,648, 5,770,107, WO 95 / 22586, 95 / 24455, 97 / 00600, 98 / 23580, 98 / 52905, JP-A-1-272551, JP-A-6-16616, JP-A-7-110469, JP-A-11-80081, and compounds described in Japanese Patent Application No. 2001-64627 can be used. Furthermore, as the rod-shaped liquid crystal compound, for example, those described in JP-A-11-513019 and JP-A-2007-279688 can also be preferably used.

[0131] —Discotic Liquid Crystal Compound— As the discotic liquid crystal compound, for example, those described in JP-A Nos. 2007-108732 and 2010-244038 can be preferably used. When a discotic liquid crystal compound is used in the optically anisotropic layer, liquid crystal compound 40 stands up in the thickness direction in the optically anisotropic layer, and optical axis 40A derived from liquid crystal compound 40 is defined as an axis perpendicular to the disc surface, i.e., a so-called fast axis.

[0132] As the liquid crystal compound, a liquid crystal compound with a high refractive index difference Δn can be preferably used to obtain high diffraction efficiency. By increasing the refractive index anisotropy, it is possible to maintain high diffraction efficiency when the incident angle changes. The liquid crystal compound with a high refractive index difference Δn is not particularly limited, but the compounds exemplified in International Publication No. 2019 / 182129 and compounds represented by the following general formula (I) can be preferably used.

[0133]

[0134] In general formula (I), P 1 and P 2 each independently represents a hydrogen atom, —CN, —NCS, or a polymerizable group. 1 and Sp 2each 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 , Z 2 and Z 3 each independently represents a single bond, —O—, —S—, —CHR—, —CHRCHR—, —OCHR—, —CHRO—, —SO—, or —SO ２ -, -COO-, -OCO-, -CO-S-, -S-CO-, -O-CO-O-, -CO-NR-, -NR-CO-, -SCHR-, -CHRS-, -SO-CHR-, -CHR-SO-, -SO ２ -CHR-, -CHR-SO2-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -OCHRCHRO-, -SCHRCHRS-, -SO-CHRC HR-SO-, -SO2-CHRCHR-SO2-, -CH=CH-COO-, -CH=CH-OCO-, -COO-CH=CH-, -OCO-CH=CH-, -C represents OO-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- or C≡C-. R represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. When there are multiple Rs, they may be the same or different. Z 1 and Z 2 When there are a plurality of Z, they may be the same or different. 3 may be the same or different, provided that Sp 2 Z connected to 3 represents a single bond. 1 and X 2 Each of X independently represents a single bond or S-. 1 and X 2 may be the same or different. 1and multiple Xs 2 At least one of the groups represents -S-. k represents an integer of 2 to 4. m and n each independently represent an integer of 0 to 3. Multiple m's may be the same or different. A 1 , A 2 , A 3 and A 4 each independently represents a group represented by any one of the following general formulae (B-1) to (B-7), or a group formed by linking two to three groups represented by any one of the following general formulae (B-1) to (B-7). 2 and A 3 may be the same or different. 1 and A 4 When there are a plurality of each, they may be the same or different.

[0135] In general formulas (B-1) to (B-7), W 1 ~W 18 are each independently CR 1 or N, R 1 represents a hydrogen atom or the following substituent L. 1 ~Y 6 are each independently NR 2 , O or S, R 2 represents a hydrogen atom or the following substituent L. 1 ~G 4 are each independently CR 3 R 4 , N.R. 5 , O or S, R 3 ~R 5 each independently represents a hydrogen atom or the following substituent L. 1 and M 2 are each independently CR 6 or N, R 6represents a hydrogen atom or the following substituent L. * represents a bonding position. The substituent L is 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, or a polymerizable group. However, when the above groups described as the substituent L are not —CH ２ When the group described as the substituent L has a hydrogen atom, a group in which at least one of the —CH— groups contained in the above group is replaced with —O—, —CO—, —CH═CH— or C≡C— is also included in the substituent L. 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.

[0136] In order to maintain high diffraction efficiency when the incident angle changes, the refractive index difference Δn 550 is preferably 0.15 or more, more preferably 0.2 or more, even more preferably 0.25 or more, and most preferably 0.3 or more.

[0137] In addition, the liquid crystal diffraction element of the present invention may have an optically anisotropic layer whose refractive index difference Δn or average refractive index is changed in-plane, which allows the diffraction efficiency to be appropriately adjusted for light incident at different positions.

[0138] Chiral Agents Chiral agents have the function of inducing a helical structure, twisting and aligning a liquid crystal compound in the thickness direction. The direction and / or degree of twist (helical pitch) of the induced helix varies depending on the chiral agent, so a chiral agent may be selected according to the purpose. There are no particular limitations on the chiral agent, and known compounds (for example, those described in "Liquid Crystal Device Handbook," Chapter 3, Section 4-3, Chiral Agents for TN (Twisted Nematic) and STN (Super Twisted Nematic)," p. 199, edited by the 142nd Committee of the Japan Society for the Promotion of Science, 1989), isosorbide (a chiral agent having an isosorbide structure), and isomannide derivatives can be used. In addition, chiral agents that undergo back isomerization, dimerization, or both isomerization and dimerization upon irradiation with light, thereby reducing helical twisting power (HTP), can also be suitably used.

[0139] Chiral agents generally contain an asymmetric carbon atom, but axially asymmetric or planarly asymmetric compounds without an asymmetric carbon atom can also be used as chiral agents. Examples of axially asymmetric or planarly asymmetric compounds include binaphthyl, helicene, paracyclophane, and derivatives thereof. The chiral agent may have a polymerizable group. When both the chiral agent and the liquid crystal compound have a polymerizable group, a polymer having a repeating unit derived from the polymerizable liquid crystal compound and a repeating unit derived from the chiral agent can be formed by polymerization of the polymerizable chiral agent and the polymerizable liquid crystal compound. In this embodiment, the polymerizable group of the polymerizable chiral agent is preferably the same type of group as the polymerizable group of the polymerizable liquid crystal compound. Therefore, the polymerizable group of the chiral agent is preferably an unsaturated polymerizable group, an epoxy group, or an aziridinyl group, more preferably an unsaturated polymerizable group, and even more preferably an ethylenically unsaturated polymerizable group. The chiral agent may also be a liquid crystal compound.

[0140] When the chiral agent has a photoisomerizable group, it is possible to form a pattern of a desired reflection wavelength corresponding to the emission wavelength by irradiating the chiral agent with actinic rays or the like through a photomask after coating and alignment. The photoisomerizable group is preferably an isomerization site of a compound exhibiting photochromic properties, an azo group, an azoxy group, or a cinnamoyl group. Specific compounds that can be used include those described in JP-A-2002-080478, JP-A-2002-080851, JP-A-2002-179668, JP-A-2002-179669, JP-A-2002-179670, JP-A-2002-179681, JP-A-2002-179682, JP-A-2002-338575, JP-A-2002-338668, JP-A-2003-313189, and JP-A-2003-313292.

[0141] The content of the chiral agent in the liquid crystal composition may be appropriately set depending on the desired amount of helical twist in the thickness direction, the type of chiral agent, and the like.

[0142] As described above, in the liquid crystal diffraction element of the present invention, the optically anisotropic layer has 80 consecutive dark lines selected as described above, in which the width of the even-numbered dark line e is narrower than the width of the adjacent odd-numbered dark line o, and the width of the odd-numbered dark line o is wider than the width of the adjacent even-numbered dark line e, as conceptually shown in Figure 14. That is, as described above, in the liquid crystal diffraction element of the present invention, the optically anisotropic layer has a nonlinear liquid crystal orientation pattern in which the rotation of the optical axis of the liquid crystal compound within one period is not constant.

[0143] Such a nonlinear liquid crystal alignment pattern can be formed by appropriately selecting a liquid crystal compound, mixing liquid crystal compounds, selecting and adjusting the amount of chiral agent added, and mixing a leveling agent in the liquid crystal composition forming the optically anisotropic layer. The nonlinear liquid crystal alignment pattern can be formed by applying a liquid crystal composition with these adjusted properties to an alignment film having an alignment pattern corresponding to a normal linear liquid crystal alignment pattern, drying the liquid crystal composition, and polymerizing the liquid crystal compound as needed. After applying the liquid crystal composition, a heat treatment may be performed as needed to helically align the liquid crystal compound in the thickness direction.

[0144] Specifically, for liquid crystal compounds, the nonlinearity of the liquid crystal alignment pattern can be changed depending on the elastic constants of the liquid crystal compound. Specifically, the nonlinearity of the liquid crystal alignment pattern can be changed by balancing the values ​​of the elastic constants K11 for splay deformation, K22 for twist deformation, and K33 for bend deformation. As an example, a nonlinear liquid crystal alignment pattern can be formed when the value of K11 / K33 or K33 / K11 is large, or when the value of K22 / K11 and / or K22 / K33 is small.

[0145] Furthermore, with regard to the chiral agent, adding a chiral agent to the liquid crystal composition for forming the optically anisotropic layer can cause the liquid crystal compound to be twisted in the thickness direction. By twisting the liquid crystal compound in the thickness direction, the nonlinearity of the liquid crystal alignment pattern can be changed by combining it with a liquid crystal compound having a large value of K11 / K33 or K33 / K11, or a liquid crystal compound having a small value of K22 / K11 and / or K22 / K33, and a nonlinear liquid crystal alignment pattern can be formed.

[0146] Regarding the leveling agent, the liquid crystal compound can be tilted with respect to the main surface of the optically anisotropic layer depending on the type and amount of the leveling agent, etc. By tilting the liquid crystal compound, the nonlinearity of the liquid crystal alignment pattern can be changed by combining it with a liquid crystal compound having a large value of K11 / K33 or K33 / K11, or a liquid crystal compound having a small value of K22 / K11 and / or K22 / K33, and a nonlinear liquid crystal alignment pattern can be formed.

[0147] The selection and adjustment of only one of the liquid crystal compound, the chiral agent and the leveling agent may be carried out, or all of the selection and adjustment of the liquid crystal compound, the chiral agent and the leveling agent may be carried out.

[0148] [Optical Element and Optical Device] The polarizing diffraction element of the present invention can be suitably used as an optical element, an optical unit, an optical module, an optical device, etc. in combination with various members.

[0149] For example, as described above, the polarization diffraction element of the present invention may have at least a portion of its surface curved. By having a curved surface portion in the polarization diffraction element, for example, when the polarization diffraction element is used in a VR image display device such as a head-mounted display, an AR glass, or the like, it is possible to expand the viewing angle. Furthermore, by having a curved surface portion in the polarization diffraction element, it is possible to make it less likely that chromatic aberration will occur.

[0150] Here, in the polarization diffraction element of the present invention, there are no limitations on the method for forming the curved surface portion, and various known methods for making at least a portion of a sheet-like material into a curved shape can be used, but the following method is a preferred example. For example, a substrate having opposing principal surfaces A and B, at least one of which is curved, is prepared. The polarization diffraction element of the present invention is attached to the curved principal surface of principal surface A or B. This results in an optical element consisting of the substrate and the polarization diffraction element of the present invention, with the polarization diffraction element having a curved shape that follows the curved surface of the substrate.

[0151] The substrate is not limited, and substrates made of various known materials that transmit light diffracted by the polarization diffraction element, such as various resin materials, can be used. The substrate may have one curved main surface and the other flat main surface, or both main surfaces may be curved. The substrate and the polarization diffraction element may be attached by a known method using an OCA (Optical Clear Adhesive) or the like. The polarization diffraction element may be attached to one or both of the main surfaces A and B.

[0152] Furthermore, the polarization diffraction element of the present invention may be an optical unit (optical element) in which the liquid crystal compound in the optically anisotropic layer is not fixed, but the alignment state of the optically anisotropic layer is changed by combining it with an external input means. For example, by changing one period of the optically anisotropic layer using the external input means, a variable-focus lens can be realized in the polarization diffraction element having the above-mentioned concentric liquid crystal alignment pattern that acts as a lens. As the external input means, various known means capable of changing the alignment state of the liquid crystal compound in various optical devices having a liquid crystal layer can be used. One example is an external input means having a pair of substrates sandwiching the polarization diffraction element and a transparent electrode provided on at least one of the substrates.

[0153] Furthermore, an optical unit having the polarization diffraction element of the present invention and an external input means may be further combined with a liquid crystal cell to form an optical unit. In this optical unit, the driving means for the liquid crystal cell may be shared with the external input means that changes the alignment state of the polarization diffraction element of the present invention, or a separate driving means for the liquid crystal cell, etc. may be provided.

[0154] Furthermore, the polarization diffraction element of the present invention is also suitable for use as an optical unit in combination with a circular polarizer. By combining the polarization diffraction element of the present invention with a circular polarizer, it becomes possible to input desired circularly polarized light to the polarization diffraction element of the present invention. Furthermore, by combining the polarization diffraction element of the present invention with a circular polarizer, it becomes possible to output circularly polarized light diffracted by the polarization diffraction element of the present invention as linearly polarized light. There are no limitations on the circular polarizer, and various known circular polarizers can be used, such as a circular polarizer that combines a wave plate (phase difference plate) such as a quarter-wave plate (λ / 4 plate) with a linear polarizer.

[0155] The retardation plate used in the present invention may be a single-layer type constituted by one optically anisotropic layer, or may be a multi-layer type constituted by laminating two or more optically anisotropic layers each having a plurality of different slow axes. Examples of multi-layer type retardation plates include those disclosed in WO13 / 137464, WO2016 / 158300, JP2014-209219A, JP2014-209220A, WO14 / 157079A, JP2019-215416A, WO2019 / 160044A, and JP2014-026 266, WO2022 / 030266, WO2021 / 132624, WO2021 / 033631, WO2022 / 045185, WO2022 / 045185, WO19 / 160016, and WO20 / 100813 are examples of such publications, but are not limited thereto.

[0156] In the embodiment of the present invention in which the polarization diffraction element and a circular polarizer are combined, other optical elements may be used in combination downstream of the circular polarizer. As an example, a retardation plate may be disposed downstream of the circular polarizer. A configuration in which linearly polarized light transmitted through a circular polarizer (a retardation plate and a linear polarizer disposed in this order) is converted into circularly polarized light, elliptically polarized light, or linearly polarized light with a different polarization direction by a retardation plate disposed downstream of the circular polarizer is also preferably used. Furthermore, instead of a retardation plate, a depolarization layer that depolarizes the polarization state of light in at least a certain wavelength range may be used. Examples of depolarization layers that can be used include high-retardation films (with an in-plane retardation of 3000 nm or more) and light-scattering layers. By controlling the polarization state of light emitted from the circular polarizer in this way, the polarization state can be tailored to suit the application. As another example, an optical element that polarizes light may be disposed downstream of the circular polarizer. For example, by disposing an optical element that polarizes light, such as a lens, downstream of the circular polarizer, the traveling direction of the light emitted from the circular polarizer can be changed. By controlling the polarization direction of the light emitted from the circular polarizer in this way, the light emission direction can be adjusted depending on the application.

[0157] <Adhesive Layer (Pressure-Sensitive Adhesive Layer), Adhesive> The optical film may include an adhesive layer for adhering each layer. In this specification, the term "adhesion" is used to include the concept of "tackiness." Examples of such adhesives include water-soluble adhesives, UV-curable adhesives, emulsion adhesives, latex adhesives, mastic adhesives, multilayer adhesives, paste-like adhesives, foam adhesives, supported film adhesives, thermoplastic adhesives, hot-melt adhesives, heat-setting adhesives, heat-activated adhesives, heat-seal adhesives, thermosetting adhesives, contact adhesives, pressure-sensitive adhesives (i.e., pressure-sensitive adhesives), polymerization adhesives, solvent-based adhesives, solvent-activated adhesives, and ceramic adhesives. Specific examples include an aqueous solution of a boron compound, a curable adhesive of an epoxy compound that does not contain an aromatic ring in the molecule, as disclosed in JP 2004-245925 A, an active energy ray-curable adhesive described in JP 2008-174667 A, which contains as essential components a photopolymerization initiator having a molar absorption coefficient of 400 or more at a wavelength of 360 to 450 nm and an ultraviolet-curable compound, and an active energy ray-curable adhesive described in JP 2008-174667 A, which contains, per 100 parts by mass of the total amount of (meth)acrylic compounds, (a) a (meth)acrylic compound having two or more (meth)acryloyl groups in the molecule, (b) a (meth)acrylic compound having a hydroxyl group in the molecule and only one polymerizable double bond, and (c) a phenol ethylene oxide-modified acrylate or nonylphenol ethylene oxide-modified acrylate. Various adhesives can be used alone or in combination as needed.

[0158] In laminated optical films, from the viewpoint of reducing unnecessary reflection, it is preferable that the difference in refractive index between the adhesive layer and adjacent layers is small. Specifically, the difference in refractive index between adjacent layers is preferably 0.05 or less, more preferably 0.01 or less. There are no particular limitations on the method for adjusting the refractive index of the adhesive layer, but known methods such as adding zirconia-based, silica-based, acrylic, acrylic-styrene-based, or melamine-based particles, adjusting the resin refractive index, and the method described in JP-A-11-223712 can be used. Furthermore, when adjacent layers have in-plane refractive index anisotropy, it is preferable that the difference in refractive index between adjacent layers is 0.05 or less in all directions in the plane. Therefore, the adhesive layer may have in-plane refractive index anisotropy. When the refractive index difference between the interfaces to be bonded is large, the interface reflectance can be reduced by providing a refractive index distribution in the thickness direction of the adhesive layer. Methods for providing a refractive index distribution in the thickness direction include providing multiple adhesive layers, mixing the interfaces between multiple adhesive layers, and controlling the uneven distribution of materials within the adhesive layers to provide a refractive index distribution.

[0159] The adhesive layer can be formed on one or both of the components to be bonded by any method, such as coating, vapor deposition, or transfer. To increase adhesive strength, post-treatments such as heat treatment and ultraviolet irradiation can be performed depending on the type of adhesive. The thickness of the adhesive layer can be adjusted as desired, but is preferably 20 μm or less, and more preferably 0.1 μm or less. An example of a method for forming an adhesive layer of 0.1 μm or less is vapor deposition of a ceramic adhesive such as silicon oxide (SiOx layer) onto the bonding surface. The bonding surfaces of the bonding components can be subjected to surface modification treatments such as plasma treatment, corona treatment, and saponification treatment before bonding, or a primer layer can be applied. When there are multiple bonding surfaces, the type and thickness of the adhesive layer can be adjusted for each bonding surface.

[0160] <Cutting the Laminate> The produced laminate can be cut to a predetermined size. There are no limitations on the method for cutting the laminate, and various known methods can be used, such as physical cutting using a blade such as a Thomson blade or cutting by irradiating a laser. When using a laser, it is preferable to select the pulse width (nanoseconds, picoseconds, femtoseconds) and wavelength taking into consideration the cutting ability and damage to the material. Furthermore, after processing the laminate into a predetermined shape, for example, polishing of the end faces may be performed. From the viewpoint of improving processability during cutting and suppressing dust generation, cutting can also be performed with a peelable protective film attached. Furthermore, by cutting while observing the liquid crystal alignment pattern, for example, using the method disclosed in JP 2004-141889 A, it is possible to arbitrarily determine the cutting position. At this time, observation can be made through a polarizing plate, a retardation film, or the like to make the liquid crystal alignment pattern more visible. Furthermore, when multiple optical elements are provided on a single substrate, it is preferable to cut the multiple optical elements simultaneously.

[0161] <Other Treatments> Markers of any shape can be added as needed to accurately install the laminate in a device, improve the accuracy of the cutting axis and cutting position, etc. The type of mark can be selected as desired, and methods such as physically adding the mark using a laser or inkjet method, partially changing the alignment state of the liquid crystal, and partially adding a bleached or dyed region can be selected. Furthermore, to protect the liquid crystal layer, a protective layer (such as a gas barrier layer, a moisture-blocking layer, an ultraviolet-absorbing layer, or a scratch-resistant layer) can be provided as needed. The protective layer can be formed directly on the liquid crystal layer, or it can be provided via an adhesive layer, another optical film, or the like. An anti-reflection layer (such as a low reflection (LR) layer, an anti-reflective (AR) layer, or a moth-eye layer) can be provided to reduce the reflectance of the surface. Various protective layers can be appropriately selected from known materials. When a gas barrier layer is provided, polyvinyl alcohol is preferred. Polyvinyl alcohol can also function as a polarizer. The ultraviolet absorbing layer is a layer containing an ultraviolet absorber, and from the viewpoint of good display properties, it is preferable to use an ultraviolet absorber that has excellent absorption ability for ultraviolet rays with wavelengths of 370 nm or less and little absorption of visible light with wavelengths of 400 nm or more. Only one ultraviolet absorber may be used, or two or more ultraviolet absorbers may be used in combination. Examples of ultraviolet absorbers include those described in JP-A No. 2001-072782 and JP-A No. 2002-543265. Specific examples of ultraviolet absorbers include oxybenzophenone-based compounds, benzotriazole-based compounds, salicylic acid ester-based compounds, benzophenone-based compounds, cyanoacrylate-based compounds, and nickel complex salt-based compounds.

[0162] That is, the polarization diffraction element of the present invention can be used as an optical unit in combination with various components. Furthermore, the polarization diffraction element of the present invention and an optical unit including the polarization diffraction element of the present invention can be used as an optical module in combination with various components. Furthermore, the polarization diffraction element of the present invention, an optical unit (optical element) including the polarization diffraction element of the present invention, and an optical module including the polarization diffraction element of the present invention can be used in various optical devices. Examples of optical devices including the polarization diffraction element of the present invention include head-mounted displays, VR display devices, sensors, and communication devices.

[0163] <Combination of Multiple Polarizing Diffraction Elements> The polarizing diffraction element of the present invention can be used by combining multiple polarizing diffraction elements. For example, as disclosed in Optics Express, Vol. 28, No. 16 / 3 August 2020, by combining multiple polarizing diffraction elements and changing the polarization state of light incident on the polarizing diffraction element, it is possible to switch between multiple converging and diverging properties of the emitted light. By combining multiple polarizing diffraction elements in this way, it is possible to provide a foveated display in a head-mounted display (HMD) such as AR glasses and VR glasses.

[0164] <Combination with Phase Modulation Element> The polarization diffraction element of the present invention can also be preferably used in combination with a phase modulation element. For example, by combining a switchable λ / 2 plate (switchable half waveplate) capable of modulating the phase difference with a voltage, as disclosed in U.S. Pat. No. 10,379,419 B1, with the polarization diffraction element of the present invention (used as a passive element), a variable-focus lens with high diffraction efficiency can be realized regardless of the incident position of light within the element surface. Furthermore, by combining multiple sets of combinations of a phase modulation element and a polarization diffraction element, the number of adjustable focal lengths can be increased. By using such a variable-focus lens in an HMD such as AR glasses or VR glasses, the focal position of the displayed image on the HMD can be arbitrarily changed.

[0165] <Combination with Lenses> The polarized diffraction element of the present invention can also be preferably used in combination with other lens elements. For example, by using the polarized diffraction element of the present invention in a combination of a Fresnel lens and a polarized diffraction element as disclosed in SID 2020 DIGEST, 40-4, pp. 579-582, the chromatic aberration of the lens can be improved with high diffraction efficiency regardless of the incident position of light within the element surface. There are no restrictions on the lens to be combined, and combinations with refractive index lenses, U.S. Pat. No. 3,443,858, and pancake lenses as disclosed in Optics Express, Vol. 29, No. 4 / 15 February 2021, pp. 6011-6014, etc., can also be suitably used. By using an optical system combining such a lens and a polarized diffraction element in AR glasses, VR glasses, etc., the color shift (chromatic aberration of the lens) of the displayed image of the HMD can be improved.

[0166] <Combination with Light Guide Plate> The polarizing diffraction element of the present invention can also be preferably used in combination with a light guide plate. For example, in a combination of a light guide plate and a lens as disclosed in Proc. of SPIE Vol. 11062, Digital Optical Technologies 2019, 110620J (16 July 2019), by using the polarizing diffraction element of the present invention as the lens, the focal position of the display image output from the light guide plate can be changed. By combining it with a light guide plate in this way, the focal position of the display image of an HMD such as AR glasses or VR glasses can be adjusted. Note that when used with AR glasses, as disclosed in Proc. of SPIE Vol. 11062, Digital Optical Technologies 2019, 110620J (16 July 2019), by using the polarizing diffraction element of the present invention as lenses with different positive and negative polarities between them, both the actual scene and the display image output from the light guide plate can be observed without distortion.

[0167] <Combination with Image Display Device> The polarizing diffraction element of the present invention can also be preferably used in combination with an image display device. For example, by combining an image display device such as that disclosed in Crystals 2021, 11, 107 with a polarizing diffraction element (used as a Diffractive Deflection Film), the luminance distribution of light emitted from the image display device can be adjusted. By combining an image display device with an image display unit in this way, the luminance distribution of HMDs such as AR glasses and VR glasses can be suitably adjusted. In addition, while the above example shows how the amount of zero-order light can be reduced by combining the polarizing diffraction element of the present invention with a circular polarizer, the amount of zero-order light can also be reduced by combining a polarizing optical unit such as a pancake lens with an image display device unit that combines such an image display device with the polarizing diffraction element of the present invention.

[0168] <Combination with Image Display Device> The polarizing diffraction element of the present invention can also be preferably used in combination with an image display device that uses a polarization optical unit. For example, by using the polarizing diffraction element of the present invention as a holographic lens in an HMD that uses an image display device and a polarization optical unit (polarization-based optical folding, pancake optics) as disclosed in ACM Trans. Graph., Vol. 39, No. 4, Article 67, it is possible to reduce ghosts in a thin and lightweight HMD.

[0169] <Combination with Beam Steering> The polarizing diffraction element of the present invention can also be preferably used in combination with an optical deflection element (beam steering). For example, by using the polarizing diffraction element of the present invention as a diffraction element of an optical deflection element such as that disclosed in WO 2019 / 189675, it is possible to achieve a high diffraction efficiency and a high deflection angle of emitted light. By combining it with an optical deflection element (beam steering) in this way, it is possible to suitably widen the light irradiation angle of a distance measurement sensor such as LiDAR (Light Detection and Ranging).

[0170] The above describes in detail the polarizing diffraction element, optical element, and optical device of the present invention, but the present invention is not limited to the above examples, and various improvements and modifications may be made within the scope of the gist of the present invention.

[0171] 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.

[0172] Comparative Example 1 A commercially available liquid crystal lens (Edmund, polarized direct flat lens, #14-778) was prepared. It was confirmed with a polarizing microscope that the optically anisotropic layer of this liquid crystal lens had a concentric pattern as shown in FIG. 15 . In this liquid crystal alignment pattern, the optical axis of the liquid crystal compound rotated 180° over one period, which was 4.0 μm at a distance of approximately 5 mm from the center and 2.0 μm at a distance of 10 mm from the center, resulting in a liquid crystal alignment pattern in which the period became shorter outward.

[0173] Furthermore, the principal surface of the liquid crystal lens was observed under crossed Nicols with an optical microscope at positions 5 mm and 10 mm from the center. The observation was performed so that the absorption axis of one polarizer was parallel to the direction in which the optical axis derived from the liquid crystal compound in the liquid crystal lens rotates. The absorption axis of the polarizer parallel to this direction was used as the observation direction, and among the bright and dark lines observed, dark lines whose width was wider than the dark lines on either side were searched for. However, in this liquid crystal lens, the width of the dark lines was almost uniform, and no dark lines whose width was wider than the dark lines on either side were found. In other words, it was confirmed that the optically anisotropic layer of this liquid crystal lens had a linear liquid crystal orientation pattern.

[0174] Comparative Example 2 <Preparation of Liquid Crystal Diffraction Element> (Support) A glass substrate was prepared as a support.

[0175] (Formation of Orientation Film) The following coating solution for forming an alignment film was applied to a support by spin coating. The support on which the coating film of the coating solution 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.

[0176] Coating liquid for forming alignment film ----------------------------------- Photoalignment material A 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 ---------------------------------------------------

[0177] -Photo alignment material A-

[0178] (Exposure of Alignment Film) The alignment film was exposed using the exposure device shown in Figure 21 to form an alignment film P-1 having an alignment pattern. In the exposure device, a laser emitting laser light with a wavelength of 355 nm was used. The exposure amount by the interference light was 1000 mJ / cm 2 It was decided.

[0179] (Formation of Optically Anisotropic Layer) <Formation of First Region> The following composition A-1 was prepared as a liquid crystal composition for forming the first region of the optically anisotropic layer. Composition A-1 ----------------------------------- Liquid crystal compound L-1 100.00 parts by mass Chiral agent C-1 0.33 parts by mass Polymerization initiator (Irgacure OXE01, manufactured by BASF) 1.00 parts by mass Leveling agent T-1 0.08 parts by mass Methyl ethyl ketone 1050.00 parts by mass

[0180] Liquid crystal compound L-1

[0181] Chiral agent C-1

[0182] Leveling agent T-1

[0183] The first region of the optically anisotropic layer was formed by applying composition A-1 in multiple layers onto the alignment film P-1. "Multi-layer application" refers to the process of first applying composition A-1 as a first layer onto the alignment film, heating it, and then curing it with ultraviolet light to form a liquid crystal fixing layer, and then repeatedly applying layers from the second layer onwards onto the liquid crystal fixing layer, and similarly heating it and curing it with ultraviolet light.

[0184] First, the first layer was formed by applying the following composition A-1 onto the alignment film P-1, heating the coating to 80°C on a hot plate, and then irradiating the coating with ultraviolet light having a wavelength of 365 nm at 300 mJ / cm using a high-pressure mercury lamp in a nitrogen atmosphere. 2 The coating film was irradiated with an irradiation dose of 1000 .mu.m to fix the alignment of the liquid crystal compound.

[0185] The second and subsequent layers were coated on top of the liquid crystal fixing layer, and then heated and cured with ultraviolet light under the same conditions as above to form the liquid crystal fixing layer. In this manner, coating was repeated until the desired total thickness was reached, thereby forming the first region of the optically anisotropic layer.

[0186] The refractive index difference Δn of the cured layer of Composition A-1 was determined by measuring the retardation value and film thickness of the liquid crystal fixed layer (cured layer) obtained by applying Composition A-1 to a separately prepared support with an alignment film for retardation measurement, aligning the director of the liquid crystal compound so that it was horizontal to the substrate, and then irradiating it with ultraviolet light to fix it. Δn can be calculated by dividing the retardation value by the film thickness. The retardation value was measured at the desired wavelength using an Axoscan manufactured by Axometrix, and the film thickness was measured using a SEM.

[0187] The first region finally becomes the Δn 550 It was confirmed using a polarizing microscope that the thickness (=Re(550)) of the first region was 180 nm and that the liquid crystal had a concentric circular liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the first region, the period in which the optical axis of the liquid crystal compound rotates by 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter toward the outside. In addition, the twist angle of the liquid crystal compound in the thickness direction in the first region was 80°.

[0188] Hereinafter, unless otherwise specified, "Δn 550 Measurements such as "×thickness" were carried out in the same manner.

[0189] <Formation of Second Region> Composition A-2 was prepared, which was the same as composition A-1 except that it did not contain chiral agent C-1. A second region of the optically anisotropic layer was formed on the first region in the same manner as for the first region, except that composition A-2 was used.

[0190] The second region finally becomes the Δn 550It was confirmed using a polarizing microscope that the thickness (=Re(550)) of the second region was 365 nm and that it had a concentric liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the second region, the period in which the optical axis of the liquid crystal compound rotates by 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter toward the outside. In addition, the twist angle of the liquid crystal compound in the thickness direction in the second region was 0°.

[0191] <Formation of Third Region> Composition A-3 was prepared in the same manner as composition A-1, except that the chiral agent C-2 below was used instead of chiral agent C-1 and the content of the chiral agent was 0.54 parts by mass. Except for using composition A-3, the third region of the optically anisotropic layer was formed on the second region in the same manner as for the first region, to produce a liquid crystal diffraction element having an optically anisotropic layer consisting of the first region, the second region, and the third region.

[0192] Chiral agent C-2

[0193] The third region finally becomes the Δn 550 It was confirmed by a polarizing microscope that the thickness (=Re(550)) of the third region was 185 nm and that it had a concentric liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the third region, the period in which the optical axis of the liquid crystal compound rotated by 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter toward the outside. In other words, in this example, the liquid crystal orientation pattern in each region was the same. In addition, in the third region, the twist angle of the liquid crystal compound in the thickness direction was -80°.

[0194] When the cross section of the optically anisotropic layer was examined with an SEM, bright and dark areas were confirmed as shown in FIG.

[0195] The liquid crystal orientation pattern of the prepared optically anisotropic layer was observed under crossed Nicols on the principal surface of the liquid crystal diffraction element at positions 5 mm, 10 mm, and 23 mm from the center using an optical microscope. The observation was performed so that the absorption axis of one polarizer was parallel to the direction in which the optical axis of the liquid crystal compound in the liquid crystal diffraction element rotates. The absorption axis of the polarizer parallel to this direction was used as the observation direction, and among the observed bright and dark lines, dark lines whose width was wider than the dark lines on either side were searched for. However, in this liquid crystal diffraction element, the width of the dark lines was almost uniform, and no dark lines whose width was wider than the dark lines on either side were found. In other words, it was confirmed that the optically anisotropic layer of this liquid crystal diffraction element had a linear liquid crystal orientation pattern.

[0196] Example 1 In the same manner as in Comparative Example 2, an alignment film was formed on a glass substrate and exposed to light to form an alignment film P-1 having an alignment pattern.

[0197] (Formation of Optically Anisotropic Layer) <Formation of First Region> The following composition B-1 was prepared as a liquid crystal composition for forming the first region of the optically anisotropic layer. Composition B-1 ----------------------------------- Liquid crystal compound L-1 10.00 parts by mass Liquid crystal compound L-2 90.00 parts by mass Chiral agent C-1 0.62 parts by mass Polymerization initiator (Irgacure OXE01, manufactured by BASF) 1.00 parts by mass Leveling agent T-1 0.02 parts by mass Leveling agent T-2 0.02 parts by mass Methyl ethyl ketone 1050.00 parts by mass

[0198] Liquid crystal compound L-2

[0199] Leveling agent T-2

[0200] Composition B-1 was coated in multiple layers on the alignment film P-1 in the same manner as above to form a first region of the optically anisotropic layer.

[0201] The first region finally becomes the Δn 550 It was confirmed using a polarizing microscope that the thickness (=Re(550)) of the first region was 180 nm and that the liquid crystal had a concentric circular liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the first region, the period in which the optical axis of the liquid crystal compound rotates by 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter toward the outside. In addition, the twist angle of the liquid crystal compound in the thickness direction in the first region was 80°.

[0202] <Formation of Second Region> Composition B-2 was prepared in the same manner as composition B-1 except that it did not contain chiral agent C-1. A second region of the optically anisotropic layer was formed on the first region in the same manner as the first region, except that composition B-2 was used.

[0203] The second region finally becomes the Δn 550 It was confirmed using a polarizing microscope that the thickness (=Re(550)) of the second region was 365 nm and that it had a concentric liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the second region, the period in which the optical axis of the liquid crystal compound rotates by 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter toward the outside. In addition, the twist angle of the liquid crystal compound in the thickness direction in the second region was 0°.

[0204] <Formation of the third region> Composition B-3 was prepared in the same manner as composition B-1, except that chiral agent C-2 was used instead of chiral agent C-1 and the content of the chiral agent was 0.54 parts by mass. Except for using composition B-3, the third region of the optically anisotropic layer was formed on the second region in the same manner as for the first region, to produce a liquid crystal diffraction element having an optically anisotropic layer consisting of the first region, the second region, and the third region.

[0205] The third region finally becomes the Δn 550 It was confirmed by a polarizing microscope that the thickness (=Re(550)) of the third region was 185 nm and that it had a concentric liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the third region, the period in which the optical axis of the liquid crystal compound rotated by 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter toward the outside. In other words, in this example, the liquid crystal orientation pattern in each region was the same. In addition, in the third region, the twist angle of the liquid crystal compound in the thickness direction was -80°.

[0206] Furthermore, when the cross section of the optically anisotropic layer was examined with an SEM, dark areas as shown in FIG. 18 were confirmed.

[0207] In the liquid crystal orientation pattern of the prepared optically anisotropic layer, the principal surface of the liquid crystal diffraction element was observed under crossed Nicols at positions 5 mm, 10 mm, and 23 mm from the center using an optical microscope. The observation was performed so that the absorption axis of one polarizer was parallel to the direction in which the optical axis of the liquid crystal compound in the liquid crystal diffraction element rotates. The absorption axis of the polarizer parallel to this direction was used as the observation direction, and a dark line whose width was wider than the dark lines on either side was arbitrarily selected from the observed bright and dark lines. Twenty consecutive dark lines were selected in the observation direction, with this arbitrarily selected dark line as the first, and the width of each dark line was confirmed. It was confirmed that the width of the even-numbered dark lines was narrower than the width of the adjacent odd-numbered dark lines, and the width of the odd-numbered dark lines was wider than the width of the adjacent even-numbered dark lines. In other words, it was confirmed that the optically anisotropic layer of this liquid crystal diffraction element had a nonlinear liquid crystal orientation pattern.

[0208] Example 2 In the same manner as in Comparative Example 2, an alignment film was formed on a glass substrate and exposed to light to form an alignment film P-1 having an alignment pattern.

[0209] (Formation of Optically Anisotropic Layer) <Formation of First Region> The following composition C-1 was prepared as a liquid crystal composition for forming the first region of the optically anisotropic layer. Composition C-1 ----------------------------------- Liquid crystal compound L-3 100.00 parts by mass Chiral agent C-1 0.62 parts by mass Polymerization initiator (Irgacure OXE01, manufactured by BASF) 1.00 parts by mass Leveling agent T-1 0.02 parts by mass Leveling agent T-2 0.02 parts by mass Methyl ethyl ketone 1050.00 parts by mass

[0210] Liquid crystal compound L-3

[0211] The composition C-1 was coated in multiple layers on the alignment film P-1 in the same manner as above to form a first region of the optically anisotropic layer.

[0212] The first region finally becomes the Δn 550 It was confirmed using a polarizing microscope that the thickness (=Re(550)) of the first region was 180 nm and that the liquid crystal had a concentric circular liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the first region, the period in which the optical axis of the liquid crystal compound rotates by 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter toward the outside. In addition, the twist angle of the liquid crystal compound in the thickness direction in the first region was 80°.

[0213] <Formation of Second Region> Composition C-2 was prepared, which was the same as composition C-1 except that it did not contain chiral agent C-1. A second region of the optically anisotropic layer was formed on the first region in the same manner as for the first region, except that composition C-2 was used.

[0214] The second region finally becomes the Δn 550 The thickness (=Re(550)) of the second region was 365 nm, and it was confirmed using a polarizing microscope that the film had a concentric liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern in the second region, the optical axis of the liquid crystal compound rotated 180° over one period of 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter outward. In addition, the twist angle of the liquid crystal compound in the thickness direction in the second region was 0°.

[0215] <Formation of the third region> Composition C-3 was prepared in the same manner as composition C-1, except that chiral agent C-2 was used instead of chiral agent C-1 and the content of the chiral agent was 0.54 parts by mass. Except for using composition C-3, the third region of the optically anisotropic layer was formed on the second region in the same manner as for the first region, to produce a liquid crystal diffraction element having an optically anisotropic layer consisting of the first region, the second region, and the third region.

[0216] The third region finally becomes the Δn550 The thickness (=Re(550)) of the sample was 185 nm, and it was confirmed using a polarizing microscope that the sample had a concentric liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the third region, the period in which the optical axis of the liquid crystal compound rotated 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter toward the outside. In other words, in this example, the liquid crystal orientation pattern in each region was the same. In addition, the twist angle of the liquid crystal compound in the thickness direction in the third region was -80°.

[0217] When the cross section of the optically anisotropic layer was examined with an SEM, bright and dark areas were confirmed as shown in FIG.

[0218] In the liquid crystal orientation pattern of the prepared optically anisotropic layer, the principal surface of the liquid crystal diffraction element was observed under crossed Nicols at positions 5 mm, 10 mm, and 23 mm from the center using an optical microscope. The observation was performed so that the absorption axis of one polarizer was parallel to the direction in which the optical axis of the liquid crystal compound in the liquid crystal diffraction element rotates. The absorption axis of the polarizer parallel to this direction was used as the observation direction, and a dark line whose width was wider than the dark lines on either side was arbitrarily selected from the observed bright and dark lines. Twenty consecutive dark lines were selected in the observation direction, with this arbitrarily selected dark line as the first, and the width of each dark line was confirmed. It was confirmed that the width of the even-numbered dark lines was narrower than the width of the adjacent odd-numbered dark lines, and the width of the odd-numbered dark lines was wider than the width of the adjacent even-numbered dark lines. In other words, it was confirmed that the optically anisotropic layer of this liquid crystal diffraction element had a nonlinear liquid crystal orientation pattern.

[0219] Comparative Example 3 In the same manner as in Comparative Example 2, an alignment film was formed on a glass substrate, and the alignment film was exposed to light.

[0220] (Formation of optically anisotropic layer) <Formation of first region> The first region of the optically anisotropic layer was formed on the alignment film in the same manner as in the formation of the second region of Comparative Example 2, except that the film thickness of the optically anisotropic layer was adjusted.

[0221] The first region finally becomes the Δn 550 It was confirmed using a polarizing microscope that the thickness (=Re(550)) of the first region was 275 nm and that the liquid crystal had a concentric circular liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the first region, the period in which the optical axis of the liquid crystal compound rotated by 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter outward. In addition, the twist angle of the liquid crystal compound in the thickness direction in the first region was 0°.

[0222] The liquid crystal orientation pattern of the prepared optically anisotropic layer was observed under crossed Nicols on the principal surface of the liquid crystal diffraction element at positions 5 mm, 10 mm, and 23 mm from the center using an optical microscope. The observation was performed so that the absorption axis of one polarizer was parallel to the direction in which the optical axis of the liquid crystal compound in the liquid crystal diffraction element rotates. The absorption axis of the polarizer parallel to this direction was used as the observation direction, and among the observed bright and dark lines, dark lines whose width was wider than the dark lines on either side were searched for. However, in this liquid crystal diffraction element, the width of the dark lines was almost uniform, and no dark lines whose width was wider than the dark lines on either side were found. In other words, it was confirmed that the optically anisotropic layer of this liquid crystal diffraction element had a linear liquid crystal orientation pattern.

[0223] Example 3 In the same manner as in Example 1, an alignment film was formed on a glass substrate, and the alignment film was exposed to light.

[0224] (Formation of Optically Anisotropic Layer) <Formation of First Region> The first region of the optically anisotropic layer was formed on the alignment film in the same manner as in the formation of the second region in Example 1, except that the film thickness of the optically anisotropic layer was adjusted.

[0225] The first region finally becomes the Δn 550It was confirmed using a polarizing microscope that the thickness (=Re(550)) of the first region was 275 nm and that the liquid crystal had a concentric circular liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the first region, the period in which the optical axis of the liquid crystal compound rotated by 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter outward. In addition, the twist angle of the liquid crystal compound in the thickness direction in the first region was 0°.

[0226] In the liquid crystal orientation pattern of the prepared optically anisotropic layer, the principal surface of the liquid crystal diffraction element was observed under crossed Nicols at positions 5 mm, 10 mm, and 23 mm from the center using an optical microscope. The observation was performed so that the absorption axis of one polarizer was parallel to the direction in which the optical axis of the liquid crystal compound in the liquid crystal diffraction element rotates. The absorption axis of the polarizer parallel to this direction was used as the observation direction, and a dark line whose width was wider than the dark lines on either side was arbitrarily selected from the observed bright and dark lines. Twenty consecutive dark lines were selected in the observation direction, with this arbitrarily selected dark line as the first, and the width of each dark line was confirmed. It was confirmed that the width of the even-numbered dark lines was narrower than the width of the adjacent odd-numbered dark lines, and the width of the odd-numbered dark lines was wider than the width of the adjacent even-numbered dark lines. In other words, it was confirmed that the optically anisotropic layer of this liquid crystal diffraction element had a nonlinear liquid crystal orientation pattern.

[0227] Example 4 In the same manner as in Example 1, an alignment film was formed on a glass substrate, and the alignment film was exposed to light.

[0228] (Formation of optically anisotropic layer) <Formation of first region> The first region of the optically anisotropic layer was formed on the alignment film in the same manner as in Example 1, except that the content of chiral agent C-1 in composition B-1 was changed.

[0229] The first region finally becomes the Δn 550It was confirmed using a polarizing microscope that the thickness (=Re(550)) of the first region was 180 nm and that the liquid crystal had a concentric circular liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the first region, the period in which the optical axis of the liquid crystal compound rotated by 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter toward the outside. In addition, the twist angle of the liquid crystal compound in the thickness direction in the first region was 85°.

[0230] <Formation of second region> The second region of the optically anisotropic layer was formed on the first region in the same manner as in the formation of the first region in Example 1, except that the content of chiral agent C-1 in composition B-1 and the film thickness were changed.

[0231] The second region finally becomes the Δn 550 It was confirmed using a polarizing microscope that the thickness (=Re(550)) of the second region was 365 nm and that it had a concentric liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the second region, the period in which the optical axis of the liquid crystal compound rotates by 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter toward the outside. In addition, the twist angle of the liquid crystal compound in the thickness direction in the second region was 13°.

[0232] <Formation of third region> In the formation of the third region of Example 1, the third region of the optically anisotropic layer was formed on the second region in the same manner as in Example 1, except that the content of chiral agent C-2 in composition B-3 was changed, thereby producing a liquid crystal diffraction element having an optically anisotropic layer consisting of the first region, the second region, and the third region.

[0233] The third region finally becomes the Δn 550It was confirmed by a polarizing microscope that the thickness (=Re(550)) of the third region was 185 nm and that it had a concentric liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the third region, the period in which the optical axis of the liquid crystal compound rotated by 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter toward the outside. In other words, in this example, the liquid crystal orientation pattern in each region was the same. In addition, in the third region, the twist angle of the liquid crystal compound in the thickness direction was -73°.

[0234] Furthermore, when the cross section of the optically anisotropic layer was examined with an SEM, a pattern of dark and bright areas was confirmed.

[0235] In the liquid crystal orientation pattern of the prepared optically anisotropic layer, the principal surface of the liquid crystal diffraction element was observed under crossed Nicols at positions 5 mm, 10 mm, and 23 mm from the center using an optical microscope. The observation was performed so that the absorption axis of one polarizer was parallel to the direction in which the optical axis of the liquid crystal compound in the liquid crystal diffraction element rotates. The absorption axis of the polarizer parallel to this direction was used as the observation direction, and a dark line whose width was wider than the dark lines on either side was arbitrarily selected from the observed bright and dark lines. Twenty consecutive dark lines were selected in the observation direction, with this arbitrarily selected dark line as the first, and the width of each dark line was confirmed. It was confirmed that the width of the even-numbered dark lines was narrower than the width of the adjacent odd-numbered dark lines, and the width of the odd-numbered dark lines was wider than the width of the adjacent even-numbered dark lines. In other words, it was confirmed that the optically anisotropic layer of this liquid crystal diffraction element had a nonlinear liquid crystal orientation pattern.

[0236] [Polarization state of zero-order light] A laser (wavelength: 532 nm) was used as a light source, and the light emitted from the light source was incident on a circular polarizer (linear polarizer: SPF-50C-32 manufactured by Sigma Koki, λ / 4 plate: WPQSM05-532 manufactured by Thorlabs) to form right-handed polarized light. The ellipticity εin of this right-handed polarized light was measured using a Thorlabs polarimeter (PAX1000VIS / M). As a result, the ellipticity εin of the right-handed polarized light used as incident light was 0.99. Similarly, the above-mentioned laser (wavelength: 532 nm) was used as a light source, and the light emitted from the light source was incident on a circular polarizer (linear polarizer: SPF-50C-32 manufactured by Sigma Koki, λ / 4 plate: WPQSM05-532 manufactured by Thorlabs) to form left-handed polarized light. The ellipticity εin of this left-handed polarized light was measured using a polarimeter (PAX1000VIS / M) manufactured by Thorlabs, Inc. As a result, the ellipticity εin of the left-handed polarized light used as incident light was found to be 0.99.

[0237] The polarization state of the zero-order light was measured using a Thorlabs polarimeter (PAX1000VIS / M) when the above-mentioned right-handed polarized light with an ellipticity εin of 0.95 or more and left-handed polarized light with an ellipticity εin of 0.95 or more were incident from the front (at an angle of 0° relative to the normal) on the liquid crystal lens of Comparative Example 1 and the prepared liquid crystal diffraction element at a position approximately 5 mm from the center. As a result, in all Examples and Comparative Examples, the zero-order light was polarized light rotating in the same direction as the incident light. Therefore, the difference between the ellipticity εin of the incident light and the ellipticity ε0 of the zero-order light was calculated.

[0238] [Diffraction Efficiency of First-Order Light] The above-mentioned right-handed polarized light having an ellipticity εin of 0.95 or more and left-handed polarized light having an ellipticity εin of 0.95 or more were incident from the front (direction at an angle of 0° with respect to the normal) at a position approximately 5 mm from the center of the liquid crystal lens of Comparative Example 1 and the prepared liquid crystal diffraction element, and the light intensities of the diffracted light (first-order light) diffracted in the desired direction from the polarized diffraction element, the zeroth-order light emitted in other directions, and the −first-order light were measured with a photodetector, and the diffraction efficiency was calculated using the following formula: Diffraction Efficiency = first-order light / (first-order light + zeroth-order light + (−first-order light))

[0239] The diffraction efficiency DE of the first-order diffracted light and the ratio of the diffraction efficiencies DE(1S) / DE(1L) of the first-order diffracted light were evaluated according to the following criteria.

[0240] [Diffraction efficiency DE of first-order light] A: DE≧95% B: 90%≦DE<95% C: 80%≦DE<90% D: DE<80%

[0241] [Diffraction efficiency ratio DE(1S) / DE(1L)] Q: DE(1S) / DE(1L)>0.95 R: 0.90<DE(1S) / DE(1L)≦0.95 S: 0.80<DE(1S) / DE(1L)≦0.90 The results are shown in Table 1.

[0242]

[0243] Similar measurements were made at a position about 10 mm from the center of the liquid crystal lens of Comparative Example 1 and the fabricated liquid crystal diffraction element. The results are shown in Table 2.

[0244]

[0245] The same measurement was carried out at a position about 23 mm from the center of the fabricated liquid crystal diffraction element. The results are shown in Table 3.

[0246]

[0247] [Evaluation] Right-handed polarized light with an ellipticity εin of 0.95 or more (0.99) and left-handed polarized light with an ellipticity εin of 0.95 or more (0.99) were incident from the front (direction at an angle of 0° with respect to the normal) at a position approximately 5 mm from the center of the liquid crystal lens of Comparative Example 1 and the prepared liquid crystal diffraction element, respectively, and the light intensity of the incident light and the light intensity of the zeroth-order light from the polarized diffraction element out of the output light were measured with a photodetector, and the light amount of the zeroth-order light (light amount of the zeroth-order light when the light amount of the incident light is 1) was calculated using the following formula: Light amount (A) of zeroth-order light = Light intensity of zeroth-order light / Light intensity of incident light

[0248] The average light intensity (0th order LL(A)) of the 0th order light was calculated when the clockwise polarized light with an ellipticity εin of 0.95 or more (0.99) and the counterclockwise polarized light with an ellipticity εin of 0.95 or more (0.99) were incident.

[0249] Next, in the above evaluation, downstream of the liquid crystal lens of Comparative Example 1 and the prepared liquid crystal diffraction element, a circular polarizer (λ / 4 plate: Thorlabs WPQSM05-532, linear polarizer: Sigma Koki SPF-50C-32) was placed in front of the zero-order light (at an angle of 0° relative to the normal). At this time, as shown in FIG. 7, the circular polarizer was arranged to transmit left-handed circularly polarized light and absorb right-handed circularly polarized light. Clockwise polarized light with an ellipticity εin of 0.95 or more (0.99) and counterclockwise polarized light with an ellipticity εin of 0.95 or more (0.99) were incident, and the light intensity of the incident light and the light intensity of the zero-order light emitted from the circular polarizer were measured with a photodetector, and the light intensity of the zero-order light was calculated using the following formula: Light intensity (B) of zero-order light = Light intensity of zero-order light / Light intensity of incident light

[0250] The average light intensity (0th order LL(B)) of the 0th order light was calculated when the right-handed polarized light with an ellipticity εin of 0.95 or more (0.99) and the left-handed polarized light with an ellipticity εin of 0.95 or more (0.99) were incident.

[0251] The zeroth-order LL (A) without a circular polarizer was compared with the zeroth-order LL (B) with a circular polarizer. As a result, compared to Comparative Examples 1 and 2, Examples 1, 2, and 4 had a higher ability to cut off zeroth-order light with the circular polarizer, and were able to suppress light leakage of zeroth-order light from the circular polarizer. Similarly, compared to Comparative Example 3, Example 3 also had a higher ability to cut off zeroth-order light with the circular polarizer.

[0252] Similarly, light leakage of zero-order light was evaluated at a position approximately 10 mm from the center of the liquid crystal lens of Comparative Example 1 and the fabricated liquid crystal diffraction element. The zero-order LL (A) without a circular polarizer was compared with the zero-order LL (B) with a circular polarizer. As a result, compared to Comparative Examples 1 and 2, Examples 1, 2, and 4 had a higher ability to cut zero-order light with the circular polarizer, and were able to suppress light leakage of zero-order light from the circular polarizer. Similarly, compared to Comparative Example 3, Example 3 also had a higher ability to cut zero-order light with the circular polarizer.

[0253] Similarly, light leakage of zero-order light was evaluated at a position approximately 23 mm from the center of the fabricated liquid crystal diffraction element. The zero-order LL (A) without a circular polarizer was compared with the zero-order LL (B) with a circular polarizer. As a result, compared to Comparative Example 2, Examples 1, 2, and 4 had a higher ability to cut zero-order light with the circular polarizer, and were able to suppress light leakage of zero-order light from the circular polarizer. Example 4 had a higher ability to cut zero-order light with the circular polarizer than Example 1.

[0254] Furthermore, when the incident position of the polarized diffraction element produced in Example 2 was changed to 5 mm, 10 mm, and 23 mm from the center of the element, the polarization state of the zeroth-order light changed depending on the incident position of the light, and the ellipticity difference εin-ε0 between the incident polarized light and the zeroth-order light changed. Furthermore, the absolute value Abs (Δε(LH)-Δε(RH)) of the difference between the ellipticity difference Δε(RH) between the incident light and the zeroth-order light when clockwise polarized light was incident and the ellipticity difference Δε(LH) between the incident light and the zeroth-order light when counterclockwise polarized light was incident increased as the incident position of the light moved away from the center of the element (5 mm → 10 mm → 23 mm). At each incident position of light, when comparing the zeroth-order LL(A) when there was no circular polarizer and the zeroth-order LL(B) when there was a circular polarizer, the circular polarizer's ability to cut off zeroth-order light was improved.

[0255] In addition, when the liquid crystal diffraction element prepared in Example 4 was changed from the center of the element to 5 mm, 10 mm, and 23 mm, the polarization state of the zero-order light changed depending on the incident position of the light, and the ellipticity difference εin-ε0 between the incident polarized light and the zero-order light changed. Furthermore, the absolute value Abs (Δε(LH)-Δε(RH)) of the difference between the ellipticity difference Δε(RH) between the incident light and the zero-order light when clockwise polarized light was incident and the ellipticity difference Δε(LH) between the incident light and the zero-order light when counterclockwise polarized light was incident increased as the incident position of the light moved away from the center of the element (5 mm → 10 mm → 23 mm). At each incident position of light, when comparing the zero-order LL(A) when there was no circular polarizer and the zero-order LL(B) when there was a circular polarizer, the ability of the circular polarizer to cut off the zero-order light increased. In Example 4, when the incident position of the element was changed from 10 mm to 23 mm, the change in Abs(Δε(LH)−Δε(RH)) and the change in the ability of the circular polarizer to cut off zero-order light were large compared to Example 2, and the ability of the circular polarizer to cut off zero-order light at 23 mm was high.

[0256] [Comparative Example 11] <Preparation of liquid crystal diffraction element>

[0257] (Formation of Alignment Film) In the same manner as in Comparative Example 2, an alignment film was formed on a glass substrate.

[0258] (Exposure of Alignment Film) The alignment film was exposed using the exposure device shown in Figure 21 to form an alignment film P-2 having an alignment pattern. In the exposure device, a laser emitting laser light with a wavelength of 355 nm was used. The exposure amount by the interference light was 1000 mJ / cm 2 21, the spherical wave circularly polarized light and the plane wave circularly polarized light were set to the opposite polarized states to those used in the exposure of Comparative Example 2, and exposure was performed.

[0259] (Formation of optically anisotropic layer) <Formation of first region> The first region of the optically anisotropic layer was formed on the alignment film in the same manner as in the formation of the first region of Comparative Example 2, except that the chiral agent C-1 in composition A-1 was changed to chiral agent C-2, the content of the chiral agent was changed, and the film thickness was adjusted.

[0260] The first region finally becomes the Δn550 It was confirmed by a polarizing microscope that the thickness (=Re(550)) of the first region was 180 nm and that the liquid crystal had a concentric circular liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the first region, the period in which the optical axis of the liquid crystal compound rotates by 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter outward. In addition, the twist angle of the liquid crystal compound in the thickness direction in the first region was -80°.

[0261] <Formation of Second Region> In the same manner as in Comparative Example 2, the second region of the optically anisotropic layer was formed on the first region.

[0262] The second region finally becomes the Δn 550 It was confirmed using a polarizing microscope that the thickness (=Re(550)) of the second region was 365 nm and that it had a concentric liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the second region, the period in which the optical axis of the liquid crystal compound rotates by 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter toward the outside. In addition, the twist angle of the liquid crystal compound in the thickness direction in the second region was 0°.

[0263] <Formation of third region> In the formation of the third region of Comparative Example 2, the chiral agent C-2 in composition A-3 was changed to chiral agent C-1, the content of the chiral agent was changed, and the film thickness was adjusted in the same manner as above, to form the third region of the optically anisotropic layer on the second region, thereby producing a liquid crystal diffraction element having an optically anisotropic layer consisting of the first region, the second region, and the third region.

[0264] The third region finally becomes the Δn 550It was confirmed using a polarizing microscope that the thickness (=Re(550)) of the third region was 185 nm and that it had a concentric liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the third region, the period in which the optical axis of the liquid crystal compound rotated 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter toward the outside. In other words, in this example, the liquid crystal orientation pattern in each region was the same. In addition, in the third region, the twist angle of the liquid crystal compound in the thickness direction was 80°.

[0265] Furthermore, when the cross section of the optically anisotropic layer was examined with an SEM, dark areas as shown in FIG. 18 were confirmed.

[0266] The liquid crystal orientation pattern of the prepared optically anisotropic layer was observed on the principal surface of the liquid crystal diffraction element at positions 5 mm, 10 mm, and 23 mm from the center under crossed Nicols using an optical microscope. The observation was performed so that the absorption axis of one polarizer was parallel to the direction in which the optical axis of the liquid crystal compound in the liquid crystal diffraction element rotates. The absorption axis of the polarizer parallel to this direction was used as the observation direction, and among the observed bright and dark lines, dark lines whose width was wider than the dark lines on either side were searched for. However, in this liquid crystal diffraction element, the width of the dark lines was almost uniform, and no dark lines whose width was wider than the dark lines on either side were found. In other words, it was confirmed that the optically anisotropic layer of this liquid crystal diffraction element had a linear liquid crystal orientation pattern.

[0267] [Example 11] <Preparation of liquid crystal diffraction element>

[0268] (Formation of Alignment Film) In the same manner as in Comparative Example 11, an alignment film P-2 was formed on a glass substrate and exposed to light.

[0269] (Formation of optically anisotropic layer) <Formation of first region> The first region of the optically anisotropic layer was formed on the alignment film in the same manner as in the formation of the first region of Example 1, except that the chiral agent C-1 in composition B-1 was changed to chiral agent C-2, the content of the chiral agent was changed, and the film thickness was adjusted.

[0270] The first region finally becomes the Δn 550 It was confirmed by a polarizing microscope that the thickness (=Re(550)) of the first region was 180 nm and that the liquid crystal had a concentric circular liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the first region, the period in which the optical axis of the liquid crystal compound rotates by 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter outward. In addition, the twist angle of the liquid crystal compound in the thickness direction in the first region was -80°.

[0271] <Formation of Second Region> In the same manner as in Example 1, the second region of the optically anisotropic layer was formed on the first region.

[0272] The second region finally becomes the Δn 550 It was confirmed using a polarizing microscope that the thickness (=Re(550)) of the second region was 365 nm and that it had a concentric liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the second region, the period in which the optical axis of the liquid crystal compound rotates by 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter toward the outside. In addition, the twist angle of the liquid crystal compound in the thickness direction in the second region was 0°.

[0273] <Formation of third region> In the formation of the third region in Example 1, the chiral agent C-2 in composition B-3 was changed to chiral agent C-1, the content of the chiral agent was changed, and the film thickness was adjusted in the same manner as in Example 1, and the third region of the optically anisotropic layer was formed on the second region, thereby producing a liquid crystal diffraction element having an optically anisotropic layer consisting of the first region, the second region, and the third region.

[0274] The third region finally becomes the Δn 550It was confirmed using a polarizing microscope that the thickness (=Re(550)) of the third region was 185 nm and that it had a concentric liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the third region, the period in which the optical axis of the liquid crystal compound rotated 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter toward the outside. In other words, in this example, the liquid crystal orientation pattern in each region was the same. In addition, in the third region, the twist angle of the liquid crystal compound in the thickness direction was 80°.

[0275] Furthermore, when the cross section of the optically anisotropic layer was examined with an SEM, dark areas as shown in FIG. 18 were confirmed.

[0276] In the liquid crystal orientation pattern of the prepared optically anisotropic layer, the principal surface of the liquid crystal diffraction element was observed under crossed Nicols at positions 5 mm, 10 mm, and 23 mm from the center using an optical microscope. The observation was performed so that the absorption axis of one polarizer was parallel to one direction in which the optical axis of the liquid crystal compound in the liquid crystal diffraction element rotates. The absorption axis of the polarizer parallel to this one direction was used as the observation direction, and among the observed bright and dark lines, a dark line whose width was wider than the dark lines on either side was arbitrarily selected. Twenty consecutive dark lines in the observation direction, with this arbitrarily selected dark line as the first, were selected, and the width of each dark line was confirmed. It was confirmed that the width of the even-numbered dark lines was narrower than the width of the adjacent odd-numbered dark lines, and the width of the odd-numbered dark lines was wider than the width of the adjacent even-numbered dark lines. In other words, it was confirmed that the optically anisotropic layer of this liquid crystal diffraction element had a nonlinear liquid crystal orientation pattern.

[0277] [Example 12] <Preparation of liquid crystal diffraction element>

[0278] (Formation of Alignment Film) In the same manner as in Comparative Example 11, an alignment film P-2 was formed on a glass substrate and exposed to light.

[0279] (Formation of optically anisotropic layer) <Formation of first region> The first region of the optically anisotropic layer was formed on the alignment film in the same manner as in the formation of the first region of Example 2, except that the chiral agent C-1 in composition C-1 was changed to chiral agent C-2, the content of the chiral agent was changed, and the film thickness was adjusted.

[0280] The first region finally becomes the Δn 550 It was confirmed by a polarizing microscope that the thickness (=Re(550)) of the first region was 180 nm and that the liquid crystal had a concentric circular liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the first region, the period in which the optical axis of the liquid crystal compound rotates by 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter outward. In addition, the twist angle of the liquid crystal compound in the thickness direction in the first region was -80°.

[0281] <Formation of Second Region> In the same manner as in Example 2, the second region of the optically anisotropic layer was formed on the first region.

[0282] The second region finally becomes the Δn 550 It was confirmed using a polarizing microscope that the thickness (=Re(550)) of the second region was 365 nm and that it had a concentric liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the second region, the period in which the optical axis of the liquid crystal compound rotates by 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter toward the outside. In addition, the twist angle of the liquid crystal compound in the thickness direction in the second region was 0°.

[0283] <Formation of third region> In the formation of the third region of Example 2, the chiral agent C-2 in composition C-3 was changed to chiral agent C-1, the content of the chiral agent was changed, and the film thickness was adjusted in the same manner as in Example 2, and the third region of the optically anisotropic layer was formed on the second region, thereby producing a liquid crystal diffraction element having an optically anisotropic layer consisting of the first region, the second region, and the third region.

[0284] The third region finally becomes the Δn 550 It was confirmed using a polarizing microscope that the thickness (=Re(550)) of the third region was 185 nm and that it had a concentric liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the third region, the period in which the optical axis of the liquid crystal compound rotated 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter toward the outside. In other words, in this example, the liquid crystal orientation pattern in each region was the same. In addition, in the third region, the twist angle of the liquid crystal compound in the thickness direction was 80°.

[0285] Furthermore, when the cross section of the optically anisotropic layer was examined with an SEM, dark areas as shown in FIG. 18 were confirmed.

[0286] In the liquid crystal orientation pattern of the prepared optically anisotropic layer, the principal surface of the liquid crystal diffraction element was observed under crossed Nicols at positions 5 mm, 10 mm, and 23 mm from the center using an optical microscope. The observation was performed so that the absorption axis of one polarizer was parallel to one direction in which the optical axis of the liquid crystal compound in the liquid crystal diffraction element rotates. The absorption axis of the polarizer parallel to this one direction was used as the observation direction, and among the observed bright and dark lines, a dark line whose width was wider than the dark lines on either side was arbitrarily selected. Twenty consecutive dark lines in the observation direction, with this arbitrarily selected dark line as the first, were selected, and the width of each dark line was confirmed. It was confirmed that the width of the even-numbered dark lines was narrower than the width of the adjacent odd-numbered dark lines, and the width of the odd-numbered dark lines was wider than the width of the adjacent even-numbered dark lines. In other words, it was confirmed that the optically anisotropic layer of this liquid crystal diffraction element had a nonlinear liquid crystal orientation pattern.

[0287] [Example 13] <Preparation of liquid crystal diffraction element>

[0288] (Formation of Alignment Film) In the same manner as in Comparative Example 11, an alignment film P-2 was formed on a glass substrate and exposed to light. (Formation of Optically Anisotropic Layer)

[0289] <Formation of first region> The first region of the optically anisotropic layer was formed on the alignment film in the same manner as in the formation of the first region of Example 4, except that the chiral agent C-1 in the composition was changed to the chiral agent C-2, the content of the chiral agent was changed, and the film thickness was adjusted.

[0290] The first region finally becomes the Δn 550 It was confirmed by a polarizing microscope that the thickness (=Re(550)) of the first region was 180 nm and that the liquid crystal had a concentric circular liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the first region, the period in which the optical axis of the liquid crystal compound rotates by 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter outward. In addition, the twist angle of the liquid crystal compound in the thickness direction in the first region was -85°.

[0291] <Formation of second region> The second region of the optically anisotropic layer was formed on the first region in the same manner as in the formation of the first region in Example 4, except that the chiral agent C-1 in the composition was changed to the chiral agent C-2, the content of the chiral agent was changed, and the film thickness was adjusted.

[0292] The second region finally becomes the Δn 550 It was confirmed by a polarizing microscope that the thickness (=Re(550)) of the second region was 365 nm and that the film had a concentric liquid crystal orientation pattern as shown in FIG. 15. In the liquid crystal orientation pattern of the second region, the optical axis of the liquid crystal compound rotated 180° over one period of 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter outward. In addition, the twist angle of the liquid crystal compound in the thickness direction in the second region was -13°.

[0293] <Formation of third region> In the formation of the third region in Example 1, the chiral agent C-2 in the composition was changed to the chiral agent C-1, the content of the chiral agent was changed, and the film thickness was adjusted in the same manner as in Example 1, and the third region of the optically anisotropic layer was formed on the second region, thereby producing a liquid crystal diffraction element having an optically anisotropic layer consisting of the first region, the second region, and the third region.

[0294] The third region finally becomes the Δn 550 It was confirmed using a polarizing microscope that the thickness (=Re(550)) of the third region was 185 nm and that it had a concentric liquid crystal orientation pattern as shown in Figure 15. In the liquid crystal orientation pattern of the third region, the period in which the optical axis of the liquid crystal compound rotated 180° was 4.0 μm at a distance of approximately 5 mm from the center, 2.0 μm at a distance of 10 mm from the center, and 1.0 μm at a distance of 23 mm from the center, resulting in a liquid crystal orientation pattern in which the period became shorter toward the outside. That is, in this example, the liquid crystal orientation pattern in each region was the same. Furthermore, in the third region, the twist angle of the liquid crystal compound in the thickness direction was 73°.

[0295] Furthermore, when the cross section of the optically anisotropic layer was examined with an SEM, a pattern of dark and bright areas was confirmed.

[0296] In the liquid crystal orientation pattern of the prepared optically anisotropic layer, the principal surface of the liquid crystal diffraction element was observed under crossed Nicols at positions 5 mm, 10 mm, and 23 mm from the center using an optical microscope. The observation was performed so that the absorption axis of one polarizer was parallel to one direction in which the optical axis of the liquid crystal compound in the liquid crystal diffraction element rotates. The absorption axis of the polarizer parallel to this one direction was used as the observation direction, and among the observed bright and dark lines, a dark line whose width was wider than the dark lines on either side was arbitrarily selected. Twenty consecutive dark lines in the observation direction, with this arbitrarily selected dark line as the first, were selected, and the width of each dark line was confirmed. It was confirmed that the width of the even-numbered dark lines was narrower than the width of the adjacent odd-numbered dark lines, and the width of the odd-numbered dark lines was wider than the width of the adjacent even-numbered dark lines. In other words, it was confirmed that the optically anisotropic layer of this liquid crystal diffraction element had a nonlinear liquid crystal orientation pattern.

[0297] The polarization state of the zeroth-order light and the diffraction efficiency of the first-order light were measured in the same manner as described above. The results are shown in Tables 4 and 5.

[0298]

[0299]

[0300] [Evaluation] The above-mentioned right-handed polarized light with an ellipticity εin of 0.95 or more (0.99) and left-handed polarized light with an ellipticity εin of 0.95 or more (0.99) were incident from the front (direction at an angle of 0° with respect to the normal) at a position approximately 10 mm from the center of the fabricated liquid crystal diffraction element, and the light intensity of the incident light and the light intensity of the zeroth-order light from the polarized diffraction element out of the output light were measured with a photodetector, and the light intensity of the zeroth-order light was calculated using the following formula: Light intensity (A) of zeroth-order light = Light intensity of zeroth-order light / Light intensity of incident light

[0301] The average light intensity (0th order LL(A)) of the 0th order light was calculated when the clockwise polarized light with an ellipticity εin of 0.95 or more (0.99) and the counterclockwise polarized light with an ellipticity εin of 0.95 or more (0.99) were incident.

[0302] Next, in the above evaluation, downstream of the prepared liquid crystal diffraction element, a circular polarizer (λ / 4 plate: Thorlabs WPQSM05-532, linear polarizer: Sigma Koki SPF-50C-32) was placed in front of the zero-order light (at an angle of 0° relative to the normal). At this time, the circular polarizer was arranged to transmit right-handed circularly polarized light and absorb left-handed circularly polarized light. Right-handed polarized light with an ellipticity εin of 0.95 or more (0.99) and left-handed polarized light with an ellipticity εin of 0.95 or more (0.99) were incident, and the light intensity of the incident light and the light intensity of the zero-order light emitted from the circular polarizer were measured with a photodetector, and the light intensity of the zero-order light was calculated using the following formula. Light intensity of zero-order light (B) = light intensity of zero-order light / light intensity of incident light

[0303] The average light intensity (0th order LL(B)) of the 0th order light was calculated when the right-handed polarized light with an ellipticity εin of 0.95 or more (0.99) and the left-handed polarized light with an ellipticity εin of 0.95 or more (0.99) were incident.

[0304] The zeroth-order LL (A) without a circular polarizer was compared with the zeroth-order LL (B) with a circular polarizer. As a result, compared to Comparative Example 11, Examples 11, 12, and 13 had a higher ability to cut off zeroth-order light with the circular polarizer, and were able to suppress light leakage of zeroth-order light from the circular polarizer.

[0305] Similarly, light leakage of zero-order light was evaluated at a position approximately 23 mm from the center of the fabricated liquid crystal diffraction element. The zero-order LL (A) without a circular polarizer was compared with the zero-order LL (B) with a circular polarizer. As a result, compared to Comparative Example 11, Examples 11, 12, and 13 had a higher ability to cut zero-order light with the circular polarizer, and were able to suppress light leakage of zero-order light from the circular polarizer. Furthermore, Example 13 had a higher ability to cut zero-order light with the circular polarizer than Example 11.

[0306] In the liquid crystal diffraction element prepared in Example 12, when the incident position of light was changed to 5 mm, 10 mm, and 23 mm from the center of the element, the polarization state of the zero-order light changed depending on the incident position of light, and the ellipticity difference εin-ε0 between the incident polarized light and the zero-order light changed. In addition, the absolute value Abs (Δε(LH)-Δε(RH)) of the difference between the ellipticity difference Δε(RH) between the incident light and the zero-order light when right-handed polarized light was incident, and the absolute value Abs (Δε(LH)-Δε(RH)) of the difference between the ellipticity difference Δε(LH) between the incident light and the zero-order light when left-handed polarized light was incident, increased as the incident position of light moved away from the center of the element (5 mm → 10 mm → 23 mm), and at each incident position of light, when comparing the zero-order LL(A) when there was no circular polarizer and the zero-order LL(B) when there was a circular polarizer, the ability to cut off the zero-order light with the circular polarizer was improved.

[0307] In the liquid crystal diffraction element prepared in Example 13, when the incident position of light was changed to 5 mm, 10 mm, and 23 mm from the center of the element, the polarization state of the zero-order light changed depending on the incident position of light, and the ellipticity difference εin-ε0 between the incident polarized light and the zero-order light changed. In addition, the absolute value Abs (Δε(LH)-Δε(RH)) of the difference between the ellipticity difference Δε(RH) between the incident light and the zero-order light when right-handed polarized light was incident, and the absolute value Abs (Δε(LH)-Δε(RH)) of the difference between the ellipticity difference Δε(LH) between the incident light and the zero-order light when left-handed polarized light was incident, increased as the incident position of light moved away from the center of the element (5 mm → 10 mm → 23 mm), and at each incident position of light, when comparing the zero-order LL(A) when there was no circular polarizer and the zero-order LL(B) when there was a circular polarizer, the ability to cut off the zero-order light with the circular polarizer was improved. In Example 13, when the incident position of the element was changed from 10 mm to 23 mm, the change in Abs(Δε(LH)-Δε(RH)) and the change in the ability of the circular polarizer to cut off zero-order light were large compared to Example 12, and the ability of the circular polarizer to cut off zero-order light at 23 mm was high. From the above results, the effects of the present invention are clear.

[0308] The present invention can be suitably used in various devices such as optical devices including head-mounted displays and virtual reality display devices.

[0309] 10 Polarization diffraction element (liquid crystal diffraction element) 20 Circular polarizer 30 Support 32 Alignment film 36, 36Z, 36S, 36B Optically anisotropic layer 40 Liquid crystal compound 40A Optical axis 42 Light area 44 Dark area 60, 80 Exposure device 62, 82 Laser 64, 84 Light source 65 λ / 2 plate 68 Beam splitter 70A, 70B, 90A, 90B Mirror 72A, 72B, 96 λ / 4 plate 86, 94 Polarization beam splitter 92 Lens I Rin Right-handed circularly polarized incident light I Lin Left circularly polarized incident light I L1 Left-handed circularly polarized light I R1 Right-handed circularly polarized first-order light I R0 Right circularly polarized zeroth order light I L0 Left circularly polarized zeroth order light I RE0 Right-handed elliptically polarized zero-order light I LE0Left-handed elliptically polarized zero-order light I S0 0th order linearly polarized light D Array axis R Region e Dark line o Dark line Λ 1 period L1, L4 Incident light L2, L5 Transmitted light A1, A2, A3 Arrow

Claims

1. A polarization diffraction element, When right-handed polarized light having an ellipticity εin of 0.95 or more is incident on the polarizing diffraction element, the zero-order light transmitted through the polarizing diffraction element is left-handed polarized light, linearly polarized light, or right-handed polarized light with an ellipticity ε0 that satisfies the relationship of formula (1), or A polarizing diffraction element, in which, when left-handed polarized light with an ellipticity εin of 0.95 or more is incident on the polarizing diffraction element, the zero-order light transmitted through the polarizing diffraction element is right-handed polarized light, linearly polarized light, or left-handed polarized light with an ellipticity ε0 that satisfies the relationship of formula (1). Equation (1) Ellipticity εin-Ellipticity ε0≧0.05

2. 2. The polarizing diffraction element according to claim 1, wherein when right-handed polarized light and left-handed polarized light having an ellipticity εin of 0.95 or more are incident on the polarizing diffraction element, at least one of the first-order diffracted lights output from the polarizing diffraction element has a diffraction efficiency of 90% or more.

3. 2. The polarizing diffraction element according to claim 1, wherein when right-handed polarized light and left-handed polarized light having an ellipticity εin of 0.95 or more are incident on the polarizing diffraction element, the ratio of the diffraction efficiencies of the first-order diffracted light output from the polarizing diffraction element, DE(1S) / DE(1L), satisfies 0.95, where DE(1L) is the diffraction efficiency of the first-order diffracted light having a high diffraction efficiency and DE(1S) is the diffraction efficiency of the first-order diffracted light having a low diffraction efficiency.

4. 2. The polarizing diffraction element according to claim 1, wherein when right-handed polarized light and left-handed polarized light having the same ellipticity εin are incident on the polarizing diffraction element, the polarization states of the zero-order light output from the polarizing diffraction element are not in opposite positions on the Poincaré sphere.

5. The difference between the ellipticity ε(RH) of the zero-order light transmitted through the polarizing diffraction element and the ellipticity ε(RH) of the right-handed polarized light having an ellipticity ε(RH) of 0.95 or more incident on the polarizing diffraction element is Δε(RH)=ellipticity εin(RH)−ellipticity ε0(RH) year, The difference between the ellipticity ε(LH) of the zero-order light transmitted through the polarizing diffraction element and the ellipticity ε(LH) of the left-handed polarized light having an ellipticity ε(LH) of 0.95 or more incident on the polarizing diffraction element is Δε (LH) = Ellipticity εin (LH) - Ellipticity ε0 (LH) 2. The polarizing diffraction element according to claim 1, wherein, when Δε(RH) and Δε(LH) are expressed as: Formula (2) Abs(Δε(LH)−Δε(RH))≧0.05

6. The polarizing diffraction element according to claim 1 , wherein the polarizing diffraction element has a curved portion in at least a part of its plane.

7. When left-handed circularly polarized light or right-handed circularly polarized light having an ellipticity εin of 0.95 or more is incident on the polarization diffraction element at different positions within the plane of the polarization diffraction element, 2. The polarizing diffraction element according to claim 1, further comprising an area in which the polarization state of the zero-order light varies depending on the position of incidence within the plane.

8. The difference between the ellipticity ε of the zero-order light transmitted through the polarization diffraction element and the ellipticity ε of the left-handed circularly polarized light or the right-handed circularly polarized light having an ellipticity ε of 0.95 or more incident on a partial region in the plane of the polarization diffraction element is Δε = ellipticity εin - ellipticity ε0 When The polarizing diffraction element according to claim 1 , having regions in which Δε has different values ​​within a plane.

9. When left-handed circularly polarized light and right-handed circularly polarized light having an ellipticity εin of 0.95 or more are incident on a partial area within the surface of the polarization diffraction element, The difference between the ellipticity ε(RH) of the zero-order light transmitted through the polarizing diffraction element and the ellipticity ε(RH) of the right-handed polarized light having an ellipticity ε(RH) of 0.95 or more incident on a partial area in the plane of the polarizing diffraction element is Δε(RH)=ellipticity εin(RH)−ellipticity ε0(RH) year, The difference between the ellipticity ε(LH) of the zero-order light transmitted through the polarizing diffraction element when left-handed polarized light having an ellipticity ε(LH) of 0.95 or more is incident on the partial region of the polarizing diffraction element and the ellipticity ε(LH) of the zero-order light transmitted through the polarizing diffraction element is Δε (LH) = Ellipticity εin (LH) - Ellipticity ε0 (LH) Then, the absolute value of the difference between Δε(RH) and Δε(LH) Abs(Δε(LH)−Δε(RH)) The polarizing diffraction element according to claim 1 , having regions in which the values ​​of are different within the plane.

10. the polarizing diffraction element includes an optically anisotropic layer formed using a liquid crystal composition containing a liquid crystal compound; The polarizing diffraction element according to claim 1 , wherein the optically anisotropic layer has a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound changes while rotating continuously along at least one direction in a plane.

11. The polarizing diffraction element according to claim 10, wherein the optically anisotropic layer has an area in which the length of one period varies in the plane when the length of the optical axis direction derived from the liquid crystal compound in the liquid crystal orientation pattern rotates 180° in the plane is defined as one period.

12. The polarizing diffraction element according to claim 10, wherein the optically anisotropic layer has a region in which the length of one period gradually changes along the one direction when the length of the optical axis direction derived from the liquid crystal compound in the liquid crystal orientation pattern rotates 180° in-plane is defined as one period.

13. The polarizing diffraction element according to claim 10 , wherein the liquid crystal orientation pattern has the one direction in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating radially from the inside to the outside.

14. The polarizing diffraction element according to any one of claims 1 to 13, A substrate, The substrate has at least a curved surface portion, An optical element, wherein the polarizing diffraction element is disposed at least on the curved surface portion and has a curved shape that conforms to the curved surface portion.

15. The polarizing diffraction element according to any one of claims 1 to 13, An external input means, The external input means is an optical element capable of changing the alignment state of the liquid crystal compound in the optically anisotropic layer.

16. the external input means includes a pair of substrates that sandwich the polarization diffraction element, The optical element according to claim 15 , wherein at least one of the pair of substrates has a transparent electrode.

17. An optical device comprising the polarizing diffraction element according to any one of claims 1 to 13.

18. An optical device comprising the optical element according to claim 14.

19. 20. The optical device of claim 17, further comprising a circular polarizer.

20. The optical device according to claim 17 , wherein the optical device is a device selected from the group consisting of a head mounted display, a VR display device, a sensor, and a communication device.