Liquid crystal diffraction element

Abstract

The present invention addresses the problem of providing a liquid crystal diffraction element capable of converting zero-order light into polarized light different from incident light. The present invention solves the problem by a liquid crystal diffraction element provided with an optically anisotropic layer having a liquid crystal orientation pattern in which the optical axis is continuously rotated in one in-plane direction and changes, the main surface of the optically anisotropic layer being observed under an orthogonal Nickle ear by an optical microscope, when a dark line thicker than the dark lines located on both sides is arbitrarily selected and 80 continuous dark lines are selected with the arbitrarily selected dark line as the first dark line, the width of the dark line at the even-numbered bit is narrower than the width of the adjacent dark line at the odd-numbered bit.

Description

Technical Field

[0001] The invention relates to a liquid crystal diffraction element for diffracting incident light. Background Art

[0002] There is known a liquid crystal diffraction element which diffracts and transmits incident light.

[0003] As such a liquid crystal diffraction element, there is known a liquid crystal diffraction element having an optically anisotropic layer formed using a liquid crystal composition containing a liquid crystal compound.

[0004] For example, Patent Document 1 discloses a liquid crystal device comprising: a first polarization diffraction grating configured to polarize and diffract incident light to form a first light beam and a second light beam having different polarizations from the incident light and having different propagation directions; a liquid crystal layer configured to receive the first light beam and the second light beam from the first polarization diffraction grating, and configured to switch between a first state and a second state, wherein the first state does not substantially change the polarization of each of the first light beam and the second light beam passing through the inside, and the second state changes the polarization of each of the first light beam and the second light beam passing through the inside; and a second polarization diffraction grating configured to receive the first light beam and the second light beam from the liquid crystal layer, and configured to analyze and diffract the first light beam and the second light beam, and change their propagation directions according to the state of the liquid crystal layer.

[0005] The first polarization diffraction grating and the second polarization diffraction grating in the liquid crystal device are liquid crystal diffraction elements.

[0006] The liquid crystal diffraction element has a liquid crystal orientation pattern in which the direction of the optical axis of the liquid crystal compound changes while continuously rotating in at least one direction in the plane.

[0007] The liquid crystal diffraction element having such a liquid crystal orientation pattern can diffract incident light at an angle corresponding to the wavelength. Furthermore, if the orientation pattern of the liquid crystal compound is constant, light of the same wavelength can be diffracted at a certain angle regardless of the incident position.

[0008] Liquid crystal diffraction elements can utilize such characteristics and can be used for various purposes, for example, in head-mounted displays that display AR (Augmented Reality) glasses and virtual reality (VR (Virtual Reality)) images.

[0009] Previous technical literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application No. 2012-505430 Summary of the invention

[0012] Technical issues to be solved by the invention

[0013] The liquid crystal diffraction element having such a liquid crystal orientation pattern diffracts right-handed circularly polarized light and left-handed circularly polarized light in opposite directions according to the rotation direction of the circularly polarized light component as the incident light.

[0014] Furthermore, the rotation direction of the light diffracted by the liquid crystal diffraction element is opposite, that is, right-handed circularly polarized light is converted into left-handed circularly polarized light, and left-handed circularly polarized light is converted into right-handed circularly polarized light.

[0015] Then, the light not diffracted by the liquid crystal diffraction element, that is, the 0th-order light, passes through the liquid crystal diffraction element as polarized light without changing its polarization state.

[0016] Here, in a device using a liquid crystal diffraction element, this zero-order light may become stray light and cause image quality degradation.

[0017] For example, in an image display device using a liquid crystal diffraction element, when left-handed circularly polarized light (left-handed circularly polarized light component) that is incident unpolarized light and diffracted by the liquid crystal diffraction element is used for image display, the left-handed circularly polarized light that is the primary light of the right-handed circularly polarized light component of the incident unpolarized light becomes the light used for image display.

[0018] At this time, the zero-order light of the right-handed circularly polarized light component of the incident light passes through the liquid crystal diffraction element in the form of right-handed circularly polarized light, and the left-handed circularly polarized light component of the incident light is diffracted and converted into right-handed circularly polarized light. Therefore, these right-handed circularly polarized lights can be removed by arranging a circular polarizer that absorbs right-handed circularly polarized light downstream of the liquid crystal diffraction element.

[0019] However, the 0th-order light of the left-handed circularly polarized light component of the incident light is left-handed circularly polarized light, and cannot be removed by the circular polarizer that absorbs right-handed circularly polarized light. As a result, the left-handed circularly polarized light as the 0th-order light and the left-handed circularly polarized light as the 1st-order light that becomes the right-handed circularly polarized light of the displayed image pass through the circular polarizer together, and are observed as stray light, which is one of the reasons for the reduction in image quality.

[0020] The object of the present invention is to solve the problems of the prior art and to provide a liquid crystal diffraction element that can convert 0th-order light that is transmitted without being diffracted into polarized light different from the incident light, for example, in an image display device where 0th-order light becomes stray light, the 0th-order light can be removed.

[0021] Means for solving technical problems

[0022] In order to solve the problem, the present invention has the following configuration.

[0023] [1] A liquid crystal diffraction element comprising an optically anisotropic layer formed using a liquid crystal composition containing a liquid crystal compound, wherein:

[0024] 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 continuously rotating in at least one direction in the plane.

[0025] The length of the direction of the optical axis derived from the liquid crystal compound in the liquid crystal orientation pattern rotated 180° in the plane is defined as 1 period, and the average period of 50 periods in one direction from the longest period of 1 period is defined as Λa. In a region having 1 period less than the average period Λa, the main surface of the optically anisotropic layer is observed under crossed Nicols with an optical microscope.

[0026] When the optical anisotropic layer is arranged so that the absorption axis of the polarizer constituting crossed Nicols is parallel to one direction, and the absorption axis of the polarizer parallel to the one direction is used as the observation direction, a dark line wider than the dark lines adjacent to both sides is randomly selected from among the observed bright lines and dark lines, and 80 dark lines are selected continuously in the observation direction with the randomly selected dark line as the first line,

[0027] Among the selected continuous 80 dark lines, the dark line width of the even-numbered bits is narrower than the dark line width of the adjacent odd-numbered bits, and the dark line width of the odd-numbered bits is wider than the dark line width of the adjacent even-numbered bits.

[0028] [2] The liquid crystal diffraction element according to [1], wherein:

[0029] The selected 80 continuous dark lines satisfy the following formula.

[0030] [Average of dark line widths of odd-numbered bits] - [Average of dark line widths of even-numbered bits] >

[0031] ([Standard deviation of dark line widths of odd-numbered digits] + [Standard deviation of dark line widths of even-numbered digits]) / 2

[0032] [3] The liquid crystal diffraction element according to [1] or [2], wherein:

[0033] The liquid crystal alignment pattern is a concentric circle pattern having concentric circles from the inside to the outside in one direction in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating.

[0034] Effects of the Invention

[0035] According to the present invention, there is provided a liquid crystal diffraction element capable of converting zero-order light into polarized light different from incident light. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1This is a diagram conceptually showing an example of the liquid crystal diffraction element of the present invention.

[0037] Figure 2 It is conceptually expressed Figure 1 A plan view of the liquid crystal diffraction element shown.

[0038] Figure 3 This is a conceptual diagram for explaining the function of a liquid crystal diffraction element.

[0039] Figure 4 This is a conceptual diagram for explaining the function of a liquid crystal diffraction element.

[0040] Figure 5 This is a conceptual diagram for explaining the liquid crystal diffraction element of the present invention.

[0041] Figure 6 This is a conceptual diagram for explaining the function of the liquid crystal diffraction element of the present invention.

[0042] Figure 7 This is a diagram conceptually showing another example of the liquid crystal diffraction element of the present invention.

[0043] Figure 8 This is a diagram conceptually showing another example of the liquid crystal diffraction element of the present invention.

[0044] Fig. 9 It is used to illustrate Figure 8 Conceptual diagram of the liquid crystal diffraction element shown.

[0045] Fig.10 This is a diagram conceptually showing another example of the liquid crystal diffraction element of the present invention.

[0046] Fig.11 This is a diagram conceptually showing another example of the liquid crystal diffraction element of the present invention.

[0047] Fig.12 This is a diagram conceptually showing an example of an exposure device for exposing an alignment film.

[0048] Fig.13 This is a diagram conceptually showing another example of an exposure device for exposing an alignment film.

[0049] Fig.14 This is a diagram conceptually showing a plane of a conventional liquid crystal diffraction element. DETAILED DESCRIPTION

[0050] Hereinafter, the liquid crystal diffraction element of the present invention will be described in detail based on the preferred embodiments shown in the accompanying drawings.

[0051] In the present specification, a numerical range expressed using "to" means a range including the numerical values ​​described before and after "to" as the lower limit and the upper limit.

[0052] In this specification, "(meth)acrylate" is used to mean "one or both of acrylate and methacrylate".

[0053] Furthermore, the drawings shown below are all conceptual drawings for explaining the present invention, and the positional relationship, size, thickness, shape, etc. of each component are different from the actual ones.

[0054] Figure 1 An example of the liquid crystal diffraction element of the present invention is conceptually shown in FIG.

[0055] Figure 1 The liquid crystal diffraction element 10 shown includes a support 30 , an alignment film 32 , and an optically anisotropic layer 36 .

[0056] Figure 2 2 is a conceptual top view of the optically anisotropic layer 36.

[0057] In addition, the top view is Figure 1 The figure in which the liquid crystal diffraction element is observed from above is a figure in which the liquid crystal diffraction element is observed from the thickness direction. In addition, the thickness direction refers to the stacking direction of each layer (film). In other words, the top view is a figure in which the optical anisotropic layer 36 is observed from a direction orthogonal to the main surface. In addition, the main surface refers to the largest surface of a sheet (film, layer, plate-like object, layer), usually the two surfaces in the thickness direction of the sheet.

[0058] And, in Figure 2 In the figure, the liquid crystal compound 40 is shown only on the surface of the alignment film 32 to clearly show the structure of the liquid crystal diffraction element of the present invention. Figure 1 As shown, the optically anisotropic layer 36 has a structure in which liquid crystal compounds 40 are stacked from the liquid crystal compounds 40 on the surface of the alignment film 32 in the thickness direction.

[0059] In addition, Figure 2 In the description, a part of the surface of the optically anisotropic layer 36 is used as a representative example, but each position in the surface of the optically anisotropic layer has basically the same structure and function and effect.

[0060] The optically anisotropic layer 36 has a liquid crystal orientation pattern in which the direction of the optical axis 40A derived from the liquid crystal compound 40 changes while continuously rotating in the direction of the arrangement axis D within the plane of the optically anisotropic layer 36. The arrangement axis D direction coincides with the direction of the arrow X described later. In the example shown in the figure, a rod-shaped liquid crystal compound is exemplified as the liquid crystal compound 40, and therefore the optical axis coincides with the longitudinal direction of the rod-shaped liquid crystal compound.

[0061] In the following description, the “optical axis derived from the liquid crystal compound” is also simply referred to as the “optical axis of the liquid crystal compound”.

[0062] The orientation of the optical axis 40A changes while continuously rotating along the arrangement axis D direction (one direction). Specifically, it means that the angle formed by the optical axis 40A of the liquid crystal compound 40 arranged along the arrangement axis D direction and the arrangement axis D direction is different depending on the position in the arrangement axis D direction. Along the arrangement axis D direction, the angle formed by the optical axis 40A and the arrangement axis D direction changes from θ to θ+180° or θ-180° in sequence.

[0063] On the other hand, among the liquid crystal compounds 40 forming the optically anisotropic layer 36 , the liquid crystal compounds 40 having the same optical axis 40A are arranged at equal intervals in the Y direction orthogonal to the arrangement axis D direction, that is, in the Y direction orthogonal to a direction in which the optical axis 40A rotates continuously.

[0064] In other words, in the optically anisotropic layer 36 , the angles formed by the directions of the optical axes 40A and the direction of the arrangement axis D are equal among the liquid crystal compounds 40 aligned in the Y direction.

[0065] In the liquid crystal diffraction element of the present invention, in the liquid crystal orientation pattern of the liquid crystal compound 40, in one direction (in the illustrated example, the direction of the arrangement axis D) in which the orientation of the in-plane optical axis 40A changes by continuous rotation, the length (distance) of rotating the optical axis 40A by 180° is set as the length Λ of one period in the liquid crystal orientation pattern. In other words, the length of one period in the liquid crystal orientation pattern is defined by the distance from θ to θ+180° formed by the angle between the optical axis 40A and the direction of the arrangement axis D. 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.

[0066] That is, the distance between the centers of the two liquid crystal compounds 40 in the direction of the arrangement axis D, which have the same angle with respect to the direction of the arrangement axis D, is set to the length Λ of one period. Figure 2 As shown, the distance between the centers of the two liquid crystal compounds 40 whose arrangement axis D direction coincides with the direction of the optical axis 40A is defined as the length of one period Λ. In the following description, the length of one period Λ is also referred to as "one period Λ".

[0067] In the liquid crystal diffraction element of the present invention, the liquid crystal orientation pattern of the optically anisotropic layer repeats the one period Λ in one direction in which the direction of the arrangement axis D, ie, the direction of the optical axis 40A, changes by continuous rotation.

[0068] As described above, in the optically anisotropic layer, in the liquid crystal compound aligned in the Y direction, the angle formed by the optical axis 40A and the direction of the arrangement axis D, which is one direction in which the direction of the optical axis of the liquid crystal compound 40 is rotated, is equal. The region in which the liquid crystal compound 40 in the Y direction, in which the angle formed by the optical axis 40A and the arrangement axis D direction is equal, is arranged is referred to as region R.

[0069] In this case, it is preferable that the value of the in-plane retardation (Re) in each region R is half a wavelength, that is, λ / 2. These in-plane retardations are calculated by the product of the refractive index difference Δn associated with the refractive index anisotropy of the region R and the thickness of the optical anisotropic layer. Among them, the refractive index difference associated with the refractive index anisotropy of the region R in the optical 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 the region R and the refractive index in the direction orthogonal to the direction of the slow axis. That is, the refractive index difference Δn associated with the refractive index anisotropy of the region R is equal to the difference between the refractive index of the liquid crystal compound 40 in the direction of the optical axis 40A and the refractive index of the liquid crystal compound 40 in the direction perpendicular to the optical axis 40A in the plane of the region R. That is, the above-mentioned refractive index difference Δn is equal to the refractive index difference of the liquid crystal compound.

[0070] If circularly polarized light is incident on such an optically anisotropic layer 36 (liquid crystal diffraction element), the light is diffracted (refracted), and the rotation direction of the circularly polarized light is converted.

[0071] exist Figure 3 and Figure 4 This effect is conceptually shown in Figure 3 and Figure 4 In FIG. 1 , the optically anisotropic layer 36 shows only the liquid crystal compound 40 (liquid crystal compound molecules) on the surface of the alignment film to simplify the drawing and clearly show the structure of the liquid crystal diffraction element.

[0072] In addition, the optically anisotropic layer 36 is formed so that the value of the product of the refractive index difference of the liquid crystal compound and the thickness of the optically anisotropic layer is λ / 2.

[0073] like Figure 3 As shown, when the value of the product of the refractive index difference of the liquid crystal compound of the optical anisotropic layer 36 and the thickness of the optical anisotropic layer 36 is λ / 2, if the incident light L1 as left-handed circularly polarized light is incident on the optical anisotropic layer 36, the incident light L1 is given a phase difference of 180° by the optical anisotropic layer, so that the transmitted light L2 is converted into right-handed circularly polarized light.

[0074] Furthermore, the liquid crystal orientation pattern formed on the optical anisotropic layer 36 is a periodic pattern in the direction of the arrangement axis D, so the transmitted light L2 travels in a direction different from the traveling direction of the incident light L1. In this way, the incident light L1 of left-handed circularly polarized light is converted into the transmitted light L2 of right-handed circularly polarized light that is tilted by a predetermined angle in the direction of the arrangement axis D relative to the incident direction.

[0075] On the other hand, Figure 4 As shown, when the value of the product of the refractive index difference of the liquid crystal compound of the optical anisotropic layer 36 and the thickness of the optical anisotropic layer 36 is λ / 2, if the incident light L4 of right-handed circularly polarized light is incident on the optical anisotropic layer 36, the incident light L4 is given a phase difference of 180° by the optical anisotropic layer 36, and is thereby converted into the transmitted light L5 of left-handed circularly polarized light.

[0076] Furthermore, the liquid crystal orientation pattern formed on the optical anisotropic layer 36 is a periodic pattern in the direction of the arrangement axis D, so 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 direction different from the transmitted light L2, that is, in a direction opposite to the incident direction and the arrangement axis D direction. In this way, the incident light L4 is converted into the transmitted light L5 of left-handed circularly polarized light that is tilted by a predetermined angle in the direction opposite to the incident direction and the arrangement axis D direction.

[0077] Here, in the liquid crystal diffraction element of the present invention, the optically anisotropic layer 36 has the following characteristics.

[0078] First, the longest period of one period in the liquid crystal orientation pattern is calculated, and the average period of 50 periods is calculated along one direction of continuous rotation of the optical axis 40A, that is, the direction of the arrangement axis D, and is set as the average period Λa. In the following description, one direction of continuous rotation of the optical axis 40A is also referred to as "one direction of rotation of the optical axis 40A".

[0079] Next, a region having one period less than the average period Λa is arbitrarily selected, and in this region, the main surface of the optical anisotropic layer 36 (liquid crystal diffraction element 10) is observed under crossed Nicols by an optical microscope. Specifically, the liquid crystal diffraction element 10 is arranged between the polarizers arranged in crossed Nicols, and in the region arbitrarily selected as described above, the main surface of the optical anisotropic layer 36 is observed by an optical microscope. At this time, the optical anisotropic layer 36 is arranged in a manner that the absorption axis of one of the polarizers constituting the crossed Nicols is parallel to the direction of the arrangement axis D, i.e., one direction in which the optical axis 40A rotates, and observation based on the optical microscope is performed.

[0080] As described above, in the optically anisotropic layer 36 , the optical axis 40A of the liquid crystal compound 40 continuously rotates toward the arrangement axis D. In addition, the optical axis of the liquid crystal compound 40 is aligned in the Y direction orthogonal to the arrangement axis D (X direction).

[0081] Therefore, in the region where the optical axis 40A coincides with the absorption axis of the polarizer constituting the crossed Nicols and in the region where the angle formed with the absorption axis is small, light is blocked and a dark line extending in the Y direction is observed. In contrast, in the region where the optical axis 40A is orthogonal to the absorption axis of the polarizer constituting the crossed Nicols and in the region where the angle formed with the absorption axis is close to orthogonal, a bright line extending in the Y direction through which light is transmitted is observed.

[0082] In the following description, for convenience, "the region where the optical axis 40A coincides with the absorption axis of the polarizer constituting orthogonal Nicols and the region where the angle with the absorption axis is small" is also referred to as "the region where the optical axis 40A (approximately) coincides with the absorption axis of the polarizer".

[0083] Furthermore, for the sake of convenience, “the region where the optical axis 40A is orthogonal to the absorption axis of the polarizer constituting crossed Nicols and the region where the angle between the optical axis 40A and the absorption axis is close to orthogonal” is also referred to as “the region where the optical axis 40A is (approximately) orthogonal to the absorption axis of the polarizer”.

[0084] Then, the absorption axis of the polarizer parallel to the arrangement axis D is set as the observation direction, and a dark line wider than the dark lines on both sides is arbitrarily selected from the observed bright lines and dark lines. In other words, a dark line sandwiched by dark lines thinner than itself in the arrangement axis D direction is arbitrarily selected.

[0085] Then, the dark line thus arbitrarily selected is made the first dark line, and 80 dark lines that are continuous in the observation direction, that is, the direction of the arrangement axis D (one direction), that is, the direction of the absorption axis of the polarizer are selected.

[0086] The optically anisotropic layer of the liquid crystal diffraction element of the present invention has 80 continuous dark lines selected as follows: Figure 5 As conceptually shown in FIG. 1 , the width of the dark line e of the even-numbered bits is narrower than the width of the adjacent dark line o of the odd-numbered bits, and the width of the dark line o of the odd-numbered bits is wider than the width of the adjacent dark line e of the even-numbered bits.

[0087] That is, the main surface of the optical anisotropic layer 36 constituting the liquid crystal diffraction element of the present invention is observed with an optical microscope under the orthogonal Nicol condition in which the direction of the arrangement axis D, i.e., the direction in which the optical axis 40A rotates continuously, coincides with the direction of the absorption axis of one polarizer. At this time, in the optical anisotropic layer 36 constituting the liquid crystal diffraction element of the present invention, Figure 5As conceptually shown in the figure, repetition of bright lines and dark lines extending along the Y direction orthogonal to the arrangement axis D direction is observed, and the dark lines in the repetition are observed to be thicker than adjacent lines → thinner than adjacent lines → thicker than adjacent lines → thinner than adjacent lines... between adjacent dark lines in the arrangement axis D direction.

[0088] The liquid crystal diffraction element of the present invention includes such an optical anisotropic layer 36, and can convert the polarization of the 0th-order light transmitted through the liquid crystal diffraction element 10 (optical anisotropic layer 36) into polarization different from that of the incident light.

[0089] In the conventional liquid crystal diffraction element as 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 rotates continuously in one direction is provided. Fig.14 As in the optically anisotropic layer 36Z conceptually shown in FIG. 1 , the rotation of the optical axis 40A in one period Λ in the direction of the arrangement axis D is constant.

[0090] That is, in the conventional optical anisotropic layer 36Z of the liquid crystal diffraction element, the rotation angle of the optical axis 40A is almost constant in one period Λ in which the optical axis 40A changes from being parallel to the arrangement axis D to being orthogonal to the arrangement axis D and then becomes parallel to the arrangement axis D again. In other words, in the conventional optical anisotropic layer 36Z of the liquid crystal diffraction element, the rotation of the optical axis 40A in one period Λ is a linear rotation with a constant rotation angle.

[0091] In the following description, for convenience, a liquid crystal alignment pattern in which the rotation of the optical axis 40A in one period Λ is constant is also referred to as a “linear liquid crystal alignment pattern”.

[0092] 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. Therefore, when the liquid crystal alignment pattern is linear, the thickness of the dark lines arranged in the arrangement axis D direction is almost constant.

[0093] It is known that in a conventional liquid crystal diffraction element having such an optically anisotropic layer 36Z having a linear liquid crystal orientation pattern, the polarization state of the 0th-order light that is not diffracted by the liquid crystal diffraction element (optically anisotropic layer) but goes straight through and passes through is the same as that of the incident light.

[0094] That is, Figure 6 As conceptually shown in the upper section of , in the conventional optically anisotropic layer 36Z having a linear liquid crystal alignment pattern, when the incident light is right-handed circularly polarized light, the zero-order light is also right-handed circularly polarized light as it is.

[0095] In contrast, Figure 2As conceptually shown in FIG. 1 , the rotation of the optical axis 40A of the optically anisotropic layer 36 in the liquid crystal diffraction element 10 of the present invention within one period Λ is not constant.

[0096] In the optical anisotropic layer 36 of the illustrated example, within one period Λ, the optical axis 40A rotates from a state parallel to the arrangement axis D to an angle close to being orthogonal to the arrangement axis D at a relatively large rotation angle, then rotates at a relatively small rotation angle to become orthogonal to the arrangement axis D, and after further rotating at a relatively small rotation angle, the rotation angle becomes larger and becomes parallel to the arrangement axis D again. That is, in the optical anisotropic layer 36 in the liquid crystal diffraction element 10 of the present invention, the rotation angle of the optical axis 40A in one period Λ becomes smaller from a relatively large state and becomes larger again. In other words, in the optical anisotropic layer 36 of the liquid crystal diffraction element 10 of the present invention, the rotation of the optical axis 40A in one period Λ is a nonlinear rotation in which the rotation angle changes.

[0097] In the following description, for convenience, a liquid crystal alignment pattern in which the rotation of the optical axis 40A in one period Λ is not constant is also referred to as a “linear liquid crystal alignment pattern”.

[0098] As described above, in the region where the optical axis 40A (approximately) coincides with the absorption axis of the polarizer, light is blocked and a dark line extending in the Y direction is observed.

[0099] Here, when the liquid crystal alignment pattern is nonlinear, the width of the region where the optical axis 40A (approximately) coincides with the absorption axis of the polarizer arranged in crossed Nicols changes in the direction of the arrangement axis D in one period. Figure 2 In the optically anisotropic layer 36 shown, the width of the region in the arrangement axis D direction (roughly) coincident with the absorption axis in the arrangement axis D direction is narrow, and the width of the region in the arrangement axis D direction (roughly) coincident with the absorption axis in the Y direction orthogonal to the arrangement axis D direction is wide.

[0100] As a result, in the optically anisotropic layer 36 in which the liquid crystal orientation pattern is nonlinear, as Figure 5 As shown, thick dark lines and thin dark lines are observed alternately in the arrangement axis D direction.

[0101] In other words, the optically anisotropic layer 36 has a nonlinear liquid crystal orientation pattern in which the rotation of the optical axis 40A in one cycle is not constant among the 80 consecutive dark lines selected as described above, and the width of the dark line e in the even-numbered position is narrower than the width of the adjacent dark line o in the odd-numbered position, and the width of the dark line o in the odd-numbered position is wider than the width of the adjacent dark line e in the even-numbered position. That is, the optically anisotropic layer in which thick dark lines and thin dark lines are alternately observed in the arrangement axis D direction has a nonlinear liquid crystal orientation pattern in which the rotation of the optical axis 40A in the arrangement axis D direction is not constant.

[0102] The liquid crystal diffraction element of the present invention has a nonlinear liquid crystal orientation pattern in the optically anisotropic layer, and can convert the polarization state of the zero-order light of the optically anisotropic layer into a polarization state different from that of the incident light.

[0103] That is, Figure 6 As conceptually shown in the lower section of , in the optically anisotropic layer 36 having a nonlinear liquid crystal orientation pattern used in the present invention, when the incident light is right-handed circularly polarized light, the 0th-order light can be converted into elliptically polarized light having a right-handed rotation direction, for example.

[0104] By using the liquid crystal diffraction element of the present invention, the zero-order light can be converted into polarized light different from the incident light, and the zero-order light can be removed in the application of image display in which the zero-order light becomes stray light as described above.

[0105] In the liquid crystal diffraction element of the present invention, the optical anisotropic layer 36 preferably has a large difference in width between the wide dark lines, that is, the odd-numbered dark lines o, and the narrow dark lines, that is, the even-numbered dark lines e. The larger the difference, the greater the difference in polarization state between the incident light and the zero-order light.

[0106] On the other hand, in the liquid crystal diffraction element of the present invention, the difference in thickness between the wide dark lines and the narrow dark lines is preferably small in the optical anisotropic layer 36. The difference is preferably as small as possible from the viewpoint of preventing the generation of multiple diffracted lights at unexpected angles.

[0107] Specifically, in the liquid crystal diffraction element of the present invention, it is preferred that the optically anisotropic layer 36 has 80 continuous dark lines selected as described above that satisfy the following formula.

[0108] [Average of dark line widths of odd-numbered bits] - [Average of dark line widths of even-numbered bits] >

[0109] ([Standard deviation of dark line widths of odd-numbered bits] + [Standard deviation of dark line widths of even-numbered bits]) / 2

[0110] When the optically anisotropic layer 36 satisfies this formula, the above-mentioned effects can be more appropriately exhibited.

[0111] The change of the 0th order light relative to the incident light is better expressed as the diffraction efficiency of the liquid crystal diffraction element 10 (optically anisotropic layer 36) is higher. That is, the higher the diffraction efficiency of the liquid crystal diffraction element 10 is, the greater the change of the 0th order light relative to the incident light is.

[0112] Specifically, the liquid crystal diffraction element 10 of the present invention preferably has a diffraction efficiency of 90% or more for at least one of the first-order diffracted lights emitted when left-handed circularly polarized light and right-handed circularly polarized light with an absolute value of incident ellipticity of 0.95 or more.

[0113] The liquid crystal diffraction element 10 of the present invention can significantly change the polarization state of the zero-order light with respect to the incident light by satisfying this condition.

[0114] The optical anisotropic layer 36 can adjust the diffraction (refraction) angle of the transmitted light L2 and L5 by changing one period Λ of the formed liquid crystal orientation pattern. Specifically, the shorter one period Λ of the liquid crystal orientation pattern of the optical anisotropic layer 36 is, the stronger the interference between the lights passing through the adjacent liquid crystal compounds 40 is, and thus the transmitted light L2 and L5 can be diffracted to a greater extent.

[0115] Therefore, the optically anisotropic layer 36 can diffract incident light in different directions by having regions with different lengths of one period Λ in the plane.

[0116] Moreover, the optical anisotropic layer 36 may have a region in which the length of one period in the plane gradually changes in one direction (in the illustrated example, the direction of the arrangement axis D) in which the liquid crystal compound rotates. By having such a region, a liquid crystal diffraction element that gathers or scatters diffracted light (primary light) can be made. For example, by gradually shortening one period Λ of the optical anisotropic layer in the direction of the arrangement axis D from the center of the arrangement axis D to the two outer sides, a liquid crystal diffraction element that gathers diffracted light to the center of the arrangement axis D direction can be obtained.

[0117] Furthermore, by setting the rotation direction of the optical axis 40A of the liquid crystal compound 40 rotating along the arrangement axis D to the opposite direction, the diffraction direction of the transmitted light can be set to the opposite direction. Figure 3-4 In the example shown, the rotation direction of the optical axis 40A toward the arrangement axis D is the clockwise direction, but by setting the rotation direction to the counterclockwise direction, the diffraction direction of the transmitted light can be set to the opposite direction.

[0118] Here, the angle of diffraction (refraction angle) based on the optical 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, in the case of red light, green light and blue light, the diffraction of red light is the largest, the diffraction of green light is the second largest, and the diffraction of blue light is the smallest.

[0119] As described above, the diffraction angle changes according to one period Λ in the liquid crystal orientation pattern of the optical anisotropic layer 36. Therefore, by making one period Λ in the liquid crystal orientation pattern of the optical anisotropic layer 36 uniform, light of the same wavelength can be diffracted at the same angle.

[0120] In the optically anisotropic layer 36, the in-plane retardation value of the plurality of regions R is preferably half a wavelength, but preferably the in-plane retardation Re(550) of the plurality of regions R of the optically anisotropic layer 36 with respect to incident light having a wavelength of 550 nm is = Δn 550 ×d is within the range specified 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 the incident light is 550 nm, and d is the thickness of the optically anisotropic layer 36 .

[0121] 200nm≤Δn 550 ×d≤350nm……(1)

[0122] That is, if the in-plane retardation Re(550) of the plurality of regions R of the optically anisotropic layer 36 is equal to Δn 550 ×d satisfies the formula (1), a sufficient amount of circularly polarized light components of the light incident on the optical anisotropic layer 36 can be converted into circularly polarized light traveling in a direction tilted in the positive direction or the reverse direction relative to the arrangement axis D. In-plane retardation Re(550)=Δn 550 More preferably, ×d is 225 nm ≤ Δn 550 ×d≤340nm, more preferably 250nm≤Δn 550 ×d≤330nm.

[0123] In addition, the above formula (1) is the range of the incident light with a wavelength of 550 nm, and the in-plane retardation Re(λ) of the plurality of regions R of the optical anisotropic layer with respect to the incident light with a wavelength of λ nm = Δn λ ×d is preferably within the range defined by the following formula (1-2), and can be appropriately set.

[0124] 0.7×(λ / 2)nm≤Δn λ ×d≤1.3×(λ / 2)nm……(1-2)

[0125] Furthermore, the in-plane retardation values ​​of the plurality of regions R in the optically anisotropic layer 36 may be outside the range of the above formula (1). Specifically, by setting Δn 550 ×d<200nm or 350nm<Δn 550 ×d, it can be divided 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 is close to 0 nm or 550 nm, the component of light traveling in the same direction as the traveling direction of the incident light increases, and the component of light traveling in a direction different from the traveling direction of the incident light decreases.

[0126] Furthermore, each in-plane retardation Re(450) of the region R of the optically anisotropic layer 36 with respect to incident light having a wavelength of 450 nm is equal to Δn 450 ×d, each in-plane retardation Re(550) of the region R of the optically anisotropic layer 36 with respect to incident light having a wavelength of 550 nm = Δn 550 ×d preferably satisfies the following formula (2). Here, Δn 450 It 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.

[0127] (Δn 450 ×d) / (Δn 550 ×d)<1.0……(2)

[0128] Formula (2) indicates that the liquid crystal compound 40 contained in the optically anisotropic layer 36 has an inverse wavelength dispersion property. That is, by satisfying Formula (2), the optically anisotropic layer 36 can respond to incident light of a wide wavelength band.

[0129] exist Figure 1 and Figure 2 In the optically anisotropic layer 36 of the liquid crystal diffraction element 10 shown, the optical axis 40A of the liquid crystal compound 40 continuously rotates toward one direction, that is, the alignment axis D direction.

[0130] However, the present invention is not limited to this, and in the optically anisotropic layer of the liquid crystal diffraction element of the present invention, the direction in which the optical axis 40A continuously rotates can be variously used, for example, two orthogonal directions.

[0131] Figure 7 An example thereof is conceptually shown.

[0132] exist Figure 7 In the optically anisotropic layer 36S shown, the liquid crystal alignment pattern has one direction (arrows A1 to A3, etc.) in which the orientation of the optical axis of the liquid crystal compound 40 changes while continuously rotating from the inside to the outside.

[0133] The so-called concentric circle pattern is a pattern in which the lines connecting the liquid crystal compounds whose optical axes are oriented in the same direction are circular, and the line segments of the circles are concentric circles. In other words, Figure 7 The liquid crystal orientation pattern of the optically anisotropic layer 36S shown is a liquid crystal orientation pattern in which the direction of the optical axis of the liquid crystal compound 40 changes while continuously rotating and radially arranged from the center of the optically anisotropic layer 36S. Figure 7In the liquid crystal alignment pattern shown, directions such as arrow A1, arrow A2, arrow A3, etc. extending radially outward from the center of the optically anisotropic layer 36S correspond to the arrangement axis D direction in the optically anisotropic layer 36 described above.

[0134] As mentioned above, Figure 7 The optical anisotropic layer 36S shown has a concentric liquid crystal orientation pattern. Therefore, in this example, for example, the direction of arrow A2 in the figure is used as an absorption axis in a polarizer, and when the optical anisotropic layer 36S (liquid crystal diffraction element) is observed with an optical microscope under orthogonal Nicols, dark lines and bright lines are observed alternately in concentric circles.

[0135] And, in Figure 7 In the optically anisotropic layer 36S shown in FIG. 1 , among the 80 dark lines selected in the same manner as in the above example, the dark line width of the even-numbered bit is narrower than the dark line width of the adjacent odd-numbered bit, and the dark line width of the odd-numbered bit is wider than the dark line width of the adjacent even-numbered bit. Therefore, in this example, Figure 7 As conceptually shown in FIG. 1 , dark lines having a narrower width than adjacent dark lines and dark lines having a wider width than adjacent dark lines are alternately observed in a concentric circle shape.

[0136] In addition, Figure 7 In order to clearly show the liquid crystal alignment pattern, the liquid crystal alignment pattern oriented in one direction is described as a linear liquid crystal alignment pattern.

[0137] However, as described above, in the optically anisotropic layer 36S where dark lines narrower than adjacent dark lines and dark lines wider than adjacent dark lines are alternately observed in concentric circles, the liquid crystal orientation pattern is nonlinear. Therefore, in this example, the polarization state of the 0th-order light is also converted to a state different from that of the incident light.

[0138] exist Figure 7 In the optically anisotropic layer 36S shown, the optical axis (not shown) of the liquid crystal compound 40 is also the longitudinal direction of the liquid crystal compound 40 .

[0139] In the optically anisotropic layer 36S, the orientation of the optical axis of the liquid crystal compound 40 changes while continuously rotating in a plurality of directions from the center of the optically anisotropic layer 36 toward the outside, for example, the direction indicated by arrow A1, the direction indicated by arrow A2, the direction indicated by arrow A3, etc. Arrow A1, arrow A2, and arrow A3 are the same arrangement axes as the above-mentioned arrangement axis D.

[0140] Furthermore, in this example, the same concentric circles in which the optical axes of the liquid crystal compound 40 face the same direction correspond to the Y direction of the optically anisotropic layer 36 .

[0141] thus, Figure 7 The optically anisotropic layer 36S shown also diffracts the incident light in the directions of arrow A1, arrow A2, arrow A3, ... by the same action and effect. Also, as in the previous example, the 0th-order light is converted into a polarized light different from the incident light.

[0142] The optically anisotropic layer 36S included in the liquid crystal diffraction element has regions where one period Λ of the liquid crystal alignment pattern is different within the plane.

[0143] Specifically, Figure 7 For example, in the direction along the arrow A1, the structure is as follows: in the direction in which the direction of the optical axis of the liquid crystal compound 40 changes while continuously rotating, one period Λ gradually becomes shorter as it moves from the center toward the outside. Figure 7 In the figure, one period near the outer side is shorter than one period near the center.

[0144] In the present invention, the gradual change of one cycle Λ refers to the continuous change of one cycle Λ and the step-wise change of one cycle Λ. This is also the same as the above example.

[0145] As described above, the diffraction angle based on the liquid crystal diffraction element depends on one period Λ of the liquid crystal orientation pattern. The smaller the one period Λ is, the larger the diffraction angle is.

[0146] Therefore, in this example, the optical anisotropic layer 36S diffracts the incident light toward the center. That is, the liquid crystal diffraction element having the optical anisotropic layer 36S can transmit the incident light as focused light, and, for example, functions as a convex lens.

[0147] 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 alignment pattern in which the direction of the optical axis of the liquid crystal compound changes continuously in at least one direction in the plane.

[0148] Here, Figure 1 In the optically anisotropic layer shown, the liquid crystal compounds 40 are oriented in the same direction in the thickness direction.

[0149] However, the present invention is not limited thereto. Figure 8 Like the optically anisotropic layer 36A conceptually shown in FIG. 1 , the liquid crystal compound 40 may be oriented in a spiral twisted shape in the thickness direction.

[0150] The optically anisotropic layer having the above-described liquid crystal alignment pattern has bright portions 42 and dark portions 44 extending from one surface to the other surface in a cross-sectional image of a cross section cut in the thickness direction along a direction in which the optical axis is continuously rotated observed using a scanning electron microscope (SEM).

[0151] In the following description, for convenience, an image of a cross section of such an optically anisotropic layer observed with a SEM is also referred to as a “cross-sectional SEM image”.

[0152] The bright portion 42 and the dark portion 44 in the cross-sectional SEM image are observed due to the liquid crystal phase having the liquid crystal orientation pattern.

[0153] Figure 1 and Figure 2 The optically anisotropic layer 36 in which the liquid crystal compound 40 is not oriented in a spiral twist in the thickness direction has a bright portion 42 and a dark portion 44 extending from one surface to the other surface in a cross-sectional SEM image (see FIG. Fig.10 ).

[0154] In contrast, Fig. 9 As conceptually shown in FIG. 1 , the optically anisotropic layer 36A in which the liquid crystal compound 40 is spirally twisted in the thickness direction has a bright portion 42 and a dark portion 44 that are inclined with respect to the thickness direction of the optically anisotropic layer 36A, that is, the main surface, and extend from one surface to the other surface in a cross-sectional SEM image.

[0155] In this way, in the optically anisotropic layer, by aligning the liquid crystal compound in a helical twisted orientation in the thickness direction, it is possible to improve the diffraction efficiency and further increase the change in the zero-order light with respect to the incident light.

[0156] In will Figure 8 In the optically anisotropic layer 36A shown in which the liquid crystal compound 40 is spirally twisted and oriented in the thickness direction, the angle of the dark portion 44 (bright portion 42) in the cross-sectional SEM image relative to the main surface can be adjusted according to the length of one period in the above-mentioned liquid crystal orientation pattern and the size of the twist of the liquid crystal compound 40 twisted and oriented in the thickness direction.

[0157] Specifically, the shorter one period in the liquid crystal alignment pattern is, the larger the angle with respect to the dark portion 44 of the main surface is. Also, the smaller the twist in the thickness direction is, the larger the angle with respect to the dark portion 44 of the main surface is.

[0158] The helical twisted orientation of the liquid crystal compound in the optical anisotropic layer can be achieved by adding a chiral agent to the liquid crystal composition for forming the optical anisotropic layer described later. The twisting direction and degree of the liquid crystal compound 40 can be adjusted by selecting and adjusting the type and amount of the chiral agent.

[0159] In the liquid crystal compound of the present invention, the optically anisotropic layer is not limited to Fig. 9 The bright portion 42 and the dark portion 44 are shown as straight lines.

[0160] As an example, Fig.10 The optically anisotropic layer 36B conceptually shown in the figure can be structured as follows: regions where the liquid crystal compound is not oriented in a spiral twisted shape are clamped by regions where the liquid crystal compound 40 is oriented in a spiral twisted shape in the thickness direction, thereby allowing the region having the bright portion 42 and the dark portion 44 extending in the thickness direction to be clamped by regions where the bright portion 42 and the dark portion 44 are inclined in opposite directions.

[0161] Figure 1 and Figure 2 The example shown is a structure in which, on the XZ plane of the optically anisotropic layer 36 , the optical axis 40A of the liquid crystal compound 40 is aligned parallel to the main surface (XY plane).

[0162] However, the present invention is not limited thereto. Fig.11 As conceptually shown in FIG. 1 , the optical axis 40A of the liquid crystal compound 40 may be tilted, ie, pitched, aligned with respect to the main surface (XY plane) on the XZ plane of the optically anisotropic layer 36C.

[0163] And, in Fig.11 In the example shown, on the XZ plane of the optical anisotropic layer 36C, the tilt angle (pitch angle) of the optical axis 40A of the liquid crystal compound 40 relative to the main surface (XY plane) is the same in the thickness direction (Z direction), but the present invention is not limited to this. That is, in the optical anisotropic layer 36C, there may be regions where the pitch angles of the optical axis 40A are different in the thickness direction.

[0164] For example, the liquid crystal compound 40 can be oriented as follows: the optical axis 40A is parallel to the main surface (pitch angle 0°) at the interface on the orientation film 32 side of the optical anisotropic layer 36C, and the pitch angle of the optical axis 40A increases as it moves away from the interface on the orientation film 32 side in the thickness direction, and then the pitch angle of the optical axis 40A is constant until the other interface (air interface) side.

[0165] Thus, in the optically anisotropic layer, the optical axis 40A of the liquid crystal compound 40 may have a pitch angle at one of the upper and lower interfaces or at both interfaces. Furthermore, the pitch angles may be different at the two interfaces.

[0166] In this way, when the optical axis 40A of the liquid crystal compound 40 has a pitch angle (that is, is tilted), the diffraction efficiency can be improved, and further, the change of the zero-order light with respect to the incident light can be made larger.

[0167] The optically anisotropic layer of the liquid crystal diffraction element of the present invention may have one or both of the following two structures: a structure having a dark portion 44 tilted relative to the main surface (thickness direction) in a cross-sectional SEM image and a structure in which the optical axis 40A of the liquid crystal compound 40 is tilted.

[0168] Specifically, a structure in which the average tilt angle of the dark portion 44 in the cross-sectional SEM image is 5° or more relative to the main surface of the optical anisotropic layer and the pitch angle of the optical axis 40A of the liquid crystal compound 40 in the thickness direction is less than 5° is preferably exemplified.

[0169] In addition, a structure in which the average tilt angle of the dark portion 44 in the cross-sectional SEM image is less than 5° with respect to the main surface of the optical anisotropic layer and the pitch angle of the optical axis 40A of the liquid crystal compound 40 in the thickness direction is 5° or more is also preferably exemplified.

[0170] In addition, a structure in which the average tilt angle of the dark portion 44 in the cross-sectional SEM image is 5° or more relative to the main surface of the optical anisotropic layer and the pitch angle of the optical axis 40A of the liquid crystal compound 40 in the thickness direction is 5° or more is also preferably exemplified.

[0171] The liquid crystal diffraction element of the present invention has such a structure through the optical anisotropic layer, which can make the change of the polarization state of the zero-order light relative to the incident light greater. As a result, for example, the stray light suppression effect when the zero-order light becomes stray light and the improvement effect of the utilization rate of light can be more appropriately obtained.

[0172] As mentioned above, Figure 1 and Figure 2 The liquid crystal diffraction element 10 shown includes a support 30 , an alignment film 32 , and an optically anisotropic layer 36 .

[0173] In addition, the liquid crystal diffraction element of the present invention is not limited to Figure 1 As shown in the examples, various layer structures can be utilized.

[0174] For example, the liquid crystal diffraction element of the present invention can be made from Figure 1The liquid crystal diffraction element shown in FIG. 1 is formed by peeling off the support 30, and is composed of an alignment film 32 and an optical anisotropic layer 36. Furthermore, the liquid crystal diffraction element of the present invention may be formed only by peeling off the support 30. Figure 1 The liquid crystal diffraction element shown in the figure is composed of an optical anisotropic layer 36 formed by peeling off the support 30 and the alignment film 32. In addition, the liquid crystal diffraction element of the present invention can be composed of the support 30 and the optical anisotropic layer 36. In addition, the liquid crystal diffraction element of the present invention can also have other layers such as a protective layer (hard coating layer) and an anti-reflection layer in addition to these structures.

[0175] That is, the liquid crystal diffraction element of the present invention can use various layer structures as long as it has an optically anisotropic layer described later.

[0176] <<Support body>>

[0177] The support 30 supports the alignment film 32 and the optically anisotropic layer 36 .

[0178] As the support 30 , various sheet-like objects (films, plates) can be used as long as they can support the alignment film and the optically anisotropic layer.

[0179] As the support 30, a transparent support is preferred, and examples thereof include polyacrylic resin films such as polymethyl methacrylate, cellulose resin films such as cellulose triacetate, cycloolefin polymer films, polyethylene terephthalate (PET), polycarbonate, and polyvinyl chloride. The support is not limited to a flexible film, and may also be a non-flexible substrate such as a glass substrate. Regarding cycloolefin polymer films, for example, commercial products such as "ARTON" manufactured by JSR Corporation and "ZEONOR" manufactured by ZEON CORPORATION can be exemplified.

[0180] Furthermore, the support 30 may be a multilayer support. As a multilayer support, there can be exemplified a support including any of the above supports as a substrate and other layers provided on the surface of the substrate.

[0181] The thickness of the support 30 is not limited, and may be appropriately set to a thickness capable of maintaining the alignment film and the optically anisotropic layer, depending on the application of the liquid crystal diffraction element and the material of the support 30 .

[0182] The thickness of the support 30 is preferably 1 to 1000 μm, more preferably 3 to 250 μm, and further preferably 5 to 150 μm.

[0183] <<Oriented film>>

[0184] An alignment film 32 is formed on the surface of the support 30 .

[0185] The alignment film 32 is an alignment film for aligning the liquid crystal compound 40 in the above-described predetermined liquid crystal alignment pattern when the optically anisotropic layer 36 is formed.

[0186] As described above, in the liquid crystal diffraction element of the present invention, the optically anisotropic layer has an optical axis 40A of the liquid crystal compound 40 (reference Figure 2 ) changes while continuously rotating in one direction in the plane (direction of arrow X described later). Therefore, the alignment film is formed so that the optically anisotropic layer can form the liquid crystal alignment pattern.

[0187] In the liquid crystal alignment pattern, in one direction in which the orientation of the optical axis 40A changes while continuously rotating, the length of the orientation of the optical axis 40A rotating by 180° is defined as one period Λ (rotation period of the optical axis).

[0188] As the alignment film, various known alignment films can be used.

[0189] For example, there can be cited friction-treated films composed of organic compounds such as polymers, oblique vapor-deposited films of inorganic compounds, films having microgrooves, and films formed by accumulating LB (Langmuir-Blodgett) films based on the Langmuir-Blodgett method of organic compounds such as ω-tricosanoic acid, dioctadecylmethylammonium chloride, and methyl stearate.

[0190] The rubbing-treated alignment film can be formed by rubbing the surface of the polymer layer several times in a predetermined direction with paper or cloth. As the material used in the alignment film, preferably exemplified are the materials used in the formation of the alignment film such as polyimide, polyvinyl alcohol, polymers having polymerizable groups described in Japanese Patent Laid-Open No. 9-152509, Japanese Patent Laid-Open No. 2005-97377, Japanese Patent Laid-Open No. 2005-99228 and Japanese Patent Laid-Open No. 2005-128503.

[0191] In the liquid crystal diffraction element of the present invention, the alignment film is appropriately formed by irradiating polarized light or non-polarized light to a raw material having a photo-alignment property. That is, in the liquid crystal diffraction element of the present invention, as the alignment film, the alignment film is appropriately formed by coating a photo-alignment material on the support 30.

[0192] Irradiation with polarized light can be performed from a vertical direction or an oblique direction with respect to the photo-alignment film, and irradiation with unpolarized light can be performed from an oblique direction with respect to the photo-alignment film.

[0193] Examples of the photo-alignment material that can be used in the photo-alignment film of the present invention include Japanese Patent Application Publication No. 2006-285197, Japanese Patent Application Publication No. 2007-76839, Japanese Patent Application Publication No. 2007-138138, Japanese Patent Application Publication No. 2007-94071, Japanese Patent Application Publication No. 2007-121721, Japanese Patent Application Publication No. 2007-140465, Japanese Patent Application Publication No. 2007-15 Azo compounds described in Japanese Patent Publication No. 6439, Japanese Patent Publication No. 2007-133184, Japanese Patent Publication No. 2009-109831, Japanese Patent No. 3883848 and Japanese Patent No. 4151746, aromatic ester compounds described in Japanese Patent Publication No. 2002-229039, and aromatic ester compounds described in Japanese Patent Publication No. 2002-265541 and Japanese Patent Publication No. 2002-317013 Maleimide and / or alkenyl-substituted nadic imide compounds having photo-alignment units described in Japanese Patent Nos. 4205195 and 4205198, photo-crosslinkable silane derivatives described in Japanese Patent Nos. 2003-520878, 2004-529220, and 4162850, photo-crosslinkable polyimides, photo-crosslinkable polyamides, and photo-crosslinkable esters Preferred examples include compounds capable of photodimerization described in JP-A-9-118717, JP-A-10-506420, JP-A-2003-505561, International Publication No. 2010 / 150748, JP-A-2013-177561, and JP-A-2014-12823, in particular cinnamate compounds, chalcone compounds, and coumarin compounds.

[0194] Among them, azo compounds, photo-crosslinkable polyimides, photo-crosslinkable polyamides, photo-crosslinkable esters, cinnamate compounds, and chalcone compounds are suitably used.

[0195] The thickness of the alignment film is not limited, and may be appropriately set according to the material forming the alignment film so as to obtain a desired alignment function.

[0196] The thickness of the alignment film is preferably 0.01 to 5 μm, more preferably 0.05 to 2 μm.

[0197] The method for forming the alignment film is not limited, and various known methods corresponding to the materials for forming the alignment film can be used. As an example, a method of forming an alignment pattern by coating the alignment film on the surface of the support 30 and drying it, and then exposing the alignment film with a laser beam can be illustrated.

[0198] Fig.12The exposure of the alignment film to form an alignment film aligned with the optical axis 40A of the liquid crystal compound 40 is conceptually shown in FIG. Figure 2 An example of an exposure device for an alignment pattern corresponding to a liquid crystal alignment pattern that rotates continuously in one direction, that is, in the direction of the arrangement axis D shown.

[0199] Fig.12 The exposure device 60 shown comprises: a light source 64 having a laser 62; a λ / 2 plate 65 for changing the polarization direction of the laser beam M emitted by the laser 62; a beam splitter 68 for separating the laser beam M emitted by the laser 62 into two light beams MA and MB; reflectors 70A and 70B respectively arranged on the optical paths of the two separated light beams MA and MB; and λ / 4 plates 72A and 72B.

[0200] Although not shown in the figure, the light source 64 emits linearly polarized light P0. The λ / 4 plate 72A converts the linearly polarized light P0 (light beam MA) into right-handed circularly polarized light P R , the λ / 4 plate 72B converts the linear polarized light P0 (light MB) into left-handed circularly polarized light P L .

[0201] The support 30 having the alignment film 32 before the alignment pattern is formed is placed in the exposure section, and two light beams MA and MB are made to intersect and interfere on the alignment film 32, and then the interference light is irradiated onto the alignment film 32 for exposure.

[0202] By the interference at this time, the polarization state of the light irradiated on the orientation film 32 changes periodically in the form of interference fringes. As a result, in the orientation film 32, an orientation pattern in which the orientation state changes periodically can be obtained. That is, an orientation film having an orientation pattern in which the orientation state changes periodically can be obtained. In the following description, the orientation film having this orientation pattern is also referred to as a "patterned orientation film".

[0203] In the exposure device 60, the period of the orientation pattern can be adjusted by changing the cross angle α of the two light beams MA and MB. That is, in the exposure device 60, by adjusting the cross angle α, in the orientation pattern in which the optical axis 40A of the liquid crystal compound 40 continuously rotates in one direction, the length of one period (one period Λ) in which the optical axis 40A is rotated 180° in one direction in which the optical axis 40A is rotated can be adjusted.

[0204] By forming an optically anisotropic layer on the patterned alignment film having such an alignment pattern in which the alignment state periodically changes, as described later, 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 can be formed.

[0205] Furthermore, the rotation direction of the optical axis 40A can be reversed by rotating the optical axes of the λ / 4 plates 72A and 72B by 90° respectively.

[0206] exist Fig.13 The formation and Figure 7 An example of an exposure device for an orientation pattern corresponding to the concentric circular liquid crystal orientation pattern shown.

[0207] Fig.13 The exposure device 80 shown has: a light source 84 provided with a laser 82, a polarization beam splitter 86 for splitting the laser beam M from the laser 82 into S-polarized light MS and P-polarized light MP, a reflector 90A arranged in the optical path of the P-polarized light MP and a reflector 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 polarization beam splitter 94, and a λ / 4 plate 96.

[0208] The P polarization MP split by the polarization beam splitter 86 is reflected by the mirror 90A and enters the polarization beam splitter 94. On the other hand, the S polarization MS split by the polarization beam splitter 86 is reflected by the mirror 90B, converged by the lens 92 and enters the polarization beam splitter 94.

[0209] The P-polarized light MP and the S-polarized light MS are combined by the polarization beam splitter 94 , pass through the λ / 4 plate 96 to become right-handed circularly polarized light and left-handed circularly polarized light corresponding to the polarization directions, and enter the alignment film 32 on the support 30 .

[0210] Here, due to the interference of right-handed circularly polarized light and left-handed circularly polarized light, the polarization state of light irradiated on the alignment film changes periodically in the form of interference fringes. Since the crossing angle of left-handed circularly polarized light and right-handed circularly polarized light changes from the inside to the outside of the concentric circle, an exposure pattern in which the pitch changes from the inside to the outside can be obtained. As a result, a concentric circular alignment pattern in which the alignment state changes periodically can be obtained in the alignment film.

[0211] In the 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° in one direction can be controlled by changing the refractive power of lens 92 (F value of lens 92), the focal distance of lens 92, and the distance between lens 92 and the orientation film 32.

[0212] Furthermore, by adjusting the optical power of the lens 92 , it is possible to change the length Λ of one cycle of the liquid crystal alignment pattern in one direction in which the optical axis continuously rotates.

[0213] Specifically, the length Λ of one cycle of the liquid crystal orientation pattern can be changed in one direction of continuous rotation of the optical axis by the diffusion angle of the light diffused by the lens 92 that interferes with the parallel light. More specifically, if the refractive power of the lens 92 is weakened, it approaches parallel light, so the length Λ of one cycle of the liquid crystal orientation pattern gradually shortens from the inside to the outside, and the F value increases. On the contrary, if the refractive power of the lens 92 is strengthened, the length Λ of one cycle of the liquid crystal orientation pattern suddenly shortens from the inside to the outside, and the F value decreases.

[0214] As described above, the patterned orientation film has an orientation pattern as follows: the liquid crystal compound 40 is oriented so as to become a liquid crystal orientation pattern in which the direction of the optical axis of the liquid crystal compound in the optically anisotropic layer formed on the patterned orientation film changes while continuously rotating in at least one direction in the plane. If the axis of the patterned orientation film along the direction in which the liquid crystal compound 40 is oriented is set as the arrangement axis, it can be said that the patterned orientation film has an orientation pattern in which the direction of the arrangement axis changes while continuously rotating in at least one direction in the plane. The arrangement axis of the patterned orientation film can be detected by measuring absorption anisotropy. For example, when linearly polarized light is irradiated onto the patterned orientation film while rotating and the amount of light transmitted through the patterned orientation film is measured, it is observed that the direction in which the amount of light becomes maximum or minimum gradually changes along one direction in the plane.

[0215] In the liquid crystal diffraction element of the present invention, the alignment film is preferably provided, but is not an essential constituent element.

[0216] For example, an orientation pattern can be formed on the support 30 by a method of rubbing the support 30, processing the support 30 with a laser beam, etc., so that the optical anisotropic layer 36 and the like can be provided with a structure of a liquid crystal orientation pattern in which the direction of the optical axis 40A of the liquid crystal compound 40 changes while continuously rotating in at least one direction within the plane.

[0217] In addition, for example, when it is desired to set a light quantity distribution for the transmitted light, depending on the purpose of the liquid crystal diffraction element, it is also possible to use a structure in which one period Λ is not gradually changed in the direction of the arrangement axis D, but a region with a different one period Λ locally in the direction of the arrangement axis D. For example, as a method of locally changing one period Λ, a method of patterning the photo-alignment film by scanning and exposing the same while arbitrarily changing the polarization direction of the focused laser beam can be used.

[0218] Furthermore, the wavelength of the laser used for exposure of the alignment film can be appropriately set according to the type of alignment film used. For example, a laser with a wavelength of deep ultraviolet to visible light to infrared can be preferably used. As an example, lasers with wavelengths of 266nm, 325nm, 355nm, 370nm, 385nm, 405nm and 460nm can be used. However, the laser is not limited thereto, and lasers of various wavelengths can be used according to the type of alignment film.

[0219] After the optical anisotropic layer is provided on the orientation film, the optical anisotropic layer can be peeled off and transferred from the orientation film. The transfer can also be performed multiple times according to the bonding surface of the optical anisotropic layer. The peeling and transfer method can be freely selected according to the purpose, but, for example, after transferring once on a substrate having an adhesive layer, it is transferred to an object to be transferred. By peeling off the substrate, the interface of the orientation film side of the optical anisotropic layer can be made the object side to be transferred. In addition, in the case where the surface of the optical anisotropic layer on the opposite side of the orientation film is set as the object side to be transferred, the optical anisotropic layer can be peeled off from the orientation film after bonding the optical anisotropic layer and the object to be transferred by an adhesive.

[0220] When the optically anisotropic layer is peeled off from the alignment film, it is preferred to adjust the peeling angle, speed, etc. in order to reduce damage (cracking, cracking, etc.) to the optically anisotropic layer and the alignment film.

[0221] Furthermore, the alignment film can be repeatedly used within a range where there is no problem with the alignment property. Before providing the optically anisotropic layer on the alignment film, the alignment film can be cleaned with an organic solvent or the like.

[0222] <<Optically anisotropic layer>>

[0223] An optically anisotropic layer 36 is formed on the surface of the alignment film 32 .

[0224] The optically anisotropic layer is formed by forming an alignment film 32 having the above-mentioned alignment pattern on a support 30, and applying a liquid crystal composition on the alignment film and curing the composition.

[0225] Furthermore, a structure in which the optical axis of the liquid crystal compound of the optically anisotropic layer is spirally twisted and oriented in the thickness direction of the optically anisotropic layer, that is, a structure in which the dark portion 44 is inclined relative to the main surface (thickness direction), can be formed by adding a chiral agent that causes the liquid crystal compound to be spirally oriented in the thickness direction to the liquid crystal composition.

[0226] As described above, the magnitude of the twisted orientation of the liquid crystal compound twisted in a helical orientation in the thickness direction can be adjusted by the type and amount of the chiral agent added to the liquid crystal composition.

[0227] Furthermore, the twist direction (right twist / left twist) of the liquid crystal compound in the thickness direction can also be selected by selecting the type of chiral agent added to the liquid crystal composition.

[0228] Furthermore, it is the optically anisotropic layer that functions as a so-called λ / 2 plate, but the present invention includes an embodiment in which a laminate integrally provided with a support and an alignment film functions as a λ / 2 plate.

[0229] Furthermore, the liquid crystal composition for forming the optically anisotropic layer contains a rod-like 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.

[0230] In the present invention, the thickness of the optically anisotropic layer is not limited, and the thickness may be appropriately set to obtain target optical characteristics according to one period Λ of the liquid crystal alignment pattern, the required diffraction angle and diffraction efficiency, and the like.

[0231] -Rod-like liquid crystal compound-

[0232] As the rod-like liquid crystal compound, preferably used are azomethines, azoxyls, cyanobiphenyls, cyanophenyl esters, benzoates, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolans and alkenylcyclohexylbenzonitriles. Not only the above low molecular weight liquid crystal molecules but also high molecular weight liquid crystal molecules can be used.

[0233] It is more preferable to fix the alignment of the rod-like liquid crystal compound by polymerization. As the polymerizable rod-like liquid crystal compound, there can be used Makromol. Chem., Vol. 190, p. 2255 (1989), Advanced Materials 5, page 107 (1993), U.S. Patent No. 4,683,327, U.S. Patent No. 5,622,648, U.S. Patent No. 5,770,107, International Publication No. 95 / 22586, International Publication No. 95 / 24455, International Publication No. 97 / 00600, International Publication No. 98 / 23580, International Publication No. 98 / 52905, Japanese Patent Application No. 1-272551, Japanese Patent Application No. 6-16616, Japanese Patent Application No. 7-110469, Japanese Patent Application No. 11-80081 and Japanese Patent Application No. 2001-64627. Furthermore, as the rod-like liquid crystal compound, for example, compounds described in JP-A-11-513019 and JP-A-2007-279688 can also be preferably used.

[0234] -Disc-like liquid crystal compounds-

[0235] As the discotic liquid crystal compound, for example, the discotic liquid crystal compounds described in JP-A-2007-108732 and JP-A-2010-244038 can be preferably used.

[0236] When a discotic liquid crystal compound is used in the optically anisotropic layer, the liquid crystal compound 40 rises in the thickness direction of the optically anisotropic layer, and an optical axis 40A derived from the liquid crystal compound 40 is defined as an axis perpendicular to the disc surface, so-called a fast axis.

[0237] As a liquid crystal compound, in order to obtain a high diffraction efficiency, a liquid crystal compound with a high refractive index difference Δn can be preferably used. By increasing the refractive index anisotropy, the diffraction efficiency when the incident angle changes can be maintained at a high level. As a liquid crystal compound with a high refractive index difference Δn, there is no particular limitation, and the compounds exemplified in International Publication No. 2019 / 182129 and the compounds represented by the following general formula (I) can be preferably used.

[0238] [Chemical formula 1]

[0239]

[0240] In the general formula (I),

[0241] P 1 and P 2 Each independently represents a hydrogen atom, -CN, -NCS or a polymerizable group.

[0242] Sp 1 and Sp 2 Each independently represents a single bond or a divalent linking group. 1 and Sp 2 It does not mean a divalent linking group including 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.

[0243] Z 1 , Z 2 and Z 3Each independently represents a single bond, -O-, -S-, -CHR-, -CHRCHR-, -OCHR-, -CHRO-, -SO-, -SO2-, -COO-, -OCO-, -CO-S-, -S-CO-, -O-CO-O-, -CO-NR-, -NR-CO-, -SCHR-, -CHRS-, -SO-CHR-, -CHR-SO-, -SO2-CHR-, -CHR-SO2-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -OCHRCHRO-, -SCHRCHRS-, -SO-CH RCHR-SO-, -SO2-CHRCHR-SO2-, -CH=CH-COO-, -CH=CH-OCO-, -COO-CH=CH-, -OCO-CH=CH-, -COO-CHRCHR-, -OCO-CHRCHR-, -CHRCHR-COO-, -CHRCHR-OCO-, -COO-CHR-, -OCO-CHR-, -CHR-COO-, -CHR-OCO-, -CR=CR-, -CR=N-, -N=CR-, -N=N-, -CR=NN=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. When Z 1 and Z 2 When there are multiple Z, they may be the same or different. 3 They can be the same or different. 2 Z 3 Represents a single bond.

[0244] X 1 and X 2 Each independently represents a single bond or S-. 1 and X 2 They can be the same or different. 1 And there are multiple X 2 At least one of them represents -S-.

[0245] k represents an integer of 2 to 4.

[0246] m and n each independently represent an integer of 0 to 3. A plurality of m may be the same or different.

[0247] A 1 , A 2 , A 3 and A 4Each independently represents a group represented by any one of the following general formulae (B-1) to (B-7) or a group formed by connecting two or three groups represented by any one of the following general formulae (B-1) to (B-7). 2 and A 3 They can be the same or different. 1 and A 4 When there are multiple ones, they may be the same or different.

[0248] [Chemical formula 2]

[0249]

[0250] In the general formulas (B-1) to (B-7),

[0251] W 1 ~W 18 Represent CR independently 1 or N, R 1 represents a hydrogen atom or a substituent L described below.

[0252] Y 1 ~Y 6 NR 2 , O or S, R 2 represents a hydrogen atom or a substituent L described below.

[0253] G 1 ~G 4 Represent CR independently 3 R 4 NR 5 , O or S, R 3 ~R 5 Each independently represents a hydrogen atom or a substituent L described below.

[0254] M 1 and M 2 Represent CR independently 6 or N, R 6 represents a hydrogen atom or a substituent L described below.

[0255] *Indicates bonding position.

[0256] 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 alkoxycarbonyl 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 hydroxyl group, an amino group, a mercapto group, a carboxyl group, a sulfo group, an amide group, a cyano group, a nitro group, a halogen atom or a polymerizable group. In the case where the above-mentioned group described as the substituent L has -CH2-, a group in which at least one of the -CH2- contained in the above-mentioned group is substituted with -O-, -CO-, -CH=CH- or -C≡C- is also included in the substituent L. Furthermore, when the above group described as the substituent L has a hydrogen atom, the substituent L also includes a group in which at least one of the hydrogen atoms contained in the above group is substituted with at least one selected from the group consisting of a fluorine atom and a polymerizable group.

[0257] In order to maintain high diffraction efficiency when the incident angle changes, the refractive index difference Δn of the liquid crystal compound 550 It is preferably 0.15 or more, more preferably 0.2 or more, further preferably 0.25 or more, and most preferably 0.3 or more.

[0258] Furthermore, the liquid crystal diffraction element of the present invention can also change the refractive index difference Δn or the average refractive index of the optical anisotropic layer in the plane. By changing the refractive index difference Δn or the average refractive index of the optical anisotropic layer in the plane, the diffraction efficiency can be appropriately adjusted for light with different incident positions.

[0259] -Chiral Reagents-

[0260] The chiral agent has the function of inducing a helical structure that twists and orients the liquid crystal compound in the thickness direction. Since the twist direction and / or twist degree (helical pitch) of the helix induced by the compound are different, the chiral agent can be selected according to the purpose.

[0261] There are no particular restrictions on the chiral agent, and known compounds (for example, those recorded in Handbook of Liquid Crystal Devices, Chapter 3, Item 4-3, TN (Twisted Nematic), STN (Super Twisted Nematic) Chiral Agents, page 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.

[0262] Furthermore, chiral reagents that undergo reverse isomerization, dimerization, isomerization and dimerization, etc. upon irradiation with light and that reduce the helical twisting power (HTP) can also be appropriately used.

[0263] Chiral agents usually contain asymmetric carbon atoms, but axial chiral compounds or planar chiral compounds that do not contain asymmetric carbon atoms can also be used as chiral agents. In the example of axial asymmetric compounds or surface asymmetric compounds, binaphthyl, helicene, p-xylene dimer and their derivatives are included. Chiral agents can have polymerizable groups. When both chiral agents and liquid crystal compounds have polymerizable groups, a polymer having repeating units derived from polymerizable liquid crystal compounds and repeating units derived from chiral agents can be formed by the polymerization reaction of polymerizable chiral agents and polymerizable liquid crystal compounds. In this way, the polymerizable groups possessed by polymerizable chiral agents are preferably groups of the same type as the polymerizable groups possessed by polymerizable liquid crystal compounds. Therefore, the polymerizable groups of chiral agents are also preferably unsaturated polymerizable groups, epoxy groups or aziridine groups, more preferably unsaturated polymerizable groups, and further preferably ethylenically unsaturated polymerizable groups.

[0264] Also, the chiral agent may be a liquid crystal compound.

[0265] When the chiral agent has a photoisomerizable group, it is preferred that a pattern of a desired reflection wavelength corresponding to the emission wavelength can be formed by irradiating a photomask with activating light or the like after coating and orientation. The photoisomerizable group is preferably an isomerization site of a compound showing photochromicity, an azo group, an oxyazolyl group, or a cinnamoyl group. As specific compounds, compounds described in Japanese Patent Application Publication No. 2002-080478, Japanese Patent Application Publication No. 2002-080851, Japanese Patent Application Publication No. 2002-179668, Japanese Patent Application Publication No. 2002-179669, Japanese Patent Application Publication No. 2002-179670, Japanese Patent Application Publication No. 2002-179681, Japanese Patent Application Publication No. 2002-179682, Japanese Patent Application Publication No. 2002-338575, Japanese Patent Application Publication No. 2002-338668, Japanese Patent Application Publication No. 2003-313189, and Japanese Patent Application Publication No. 2003-313292 can be used.

[0266] The content of the chiral agent in the liquid crystal composition may be appropriately set according to the target helical twist amount in the thickness direction and the type of the chiral agent.

[0267] As described above, in the liquid crystal diffraction element of the present invention, the optically anisotropic layer has 80 continuous dark lines selected as described above, such as Figure 5As conceptually shown in FIG. 1 , the width of the dark line e of the even-numbered bits is narrower than the width of the adjacent dark line o of the odd-numbered bits, and the width of the dark line o of the odd-numbered bits is wider than the width of the adjacent dark line e of the even-numbered bits.

[0268] That is, as described above, in the liquid crystal diffraction element of the present invention, the optically anisotropic layer has a nonlinear liquid crystal alignment pattern in which the rotation of the optical axis of the liquid crystal compound in one period is not constant.

[0269] Such a nonlinear liquid crystal alignment pattern can be formed by appropriately performing the following operations: selection of liquid crystal compounds in the liquid crystal composition forming the optically anisotropic layer, mixing of liquid crystal compounds, selection and adjustment of the addition amount of a chiral agent, mixing of a leveling agent, and the like.

[0270] In addition, a nonlinear liquid crystal orientation pattern can be formed by applying a liquid crystal composition adjusted with these on an orientation film having an orientation pattern corresponding to a conventional linear liquid crystal orientation pattern, drying the liquid crystal composition, and polymerizing the liquid crystal compound as required. Furthermore, after applying the liquid crystal composition, a heat treatment may be performed as required to orient the liquid crystal compound in a spiral shape in the thickness direction.

[0271] Specifically, regarding the liquid crystal compound, the nonlinearity of the liquid crystal alignment pattern can be changed according to the elastic constant of the liquid crystal compound.

[0272] More specifically, the nonlinearity of the liquid crystal orientation pattern can be changed by balancing the elastic constants K11 for ejection deformation, K22 for twisting deformation, and K33 for bending deformation. For example, a nonlinear liquid crystal orientation pattern can be formed when the values ​​of K11 / K33 or K33 / K11 are large, or when the values ​​of K22 / K11 and / or K22 / K33 are small.

[0273] Furthermore, regarding the chiral agent, by adding the chiral agent to the liquid crystal composition for forming the optically anisotropic layer, the liquid crystal compound can be twisted and aligned in the thickness direction.

[0274] By twisting the liquid crystal compound in the thickness direction and 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, the nonlinearity of the liquid crystal orientation pattern can be changed and a nonlinear liquid crystal orientation pattern can be formed.

[0275] The leveling agent can be used to orient the liquid crystal compound in an inclined (pitch) manner with respect to the main surface of the optically anisotropic layer, depending on the type and amount of the leveling agent added.

[0276] By tilting the liquid crystal compound and combining it with a liquid crystal compound having large K11 / K33 or K33 / K11 values ​​or a liquid crystal compound having small K22 / K11 and / or K22 / K33 values, the nonlinearity of the liquid crystal orientation pattern can be changed and a nonlinear liquid crystal orientation pattern can be formed.

[0277] The selection and adjustment of only one of these liquid crystal compounds, chiral agents, and leveling agents may be performed, or the selection and adjustment of all of these liquid crystal compounds, chiral agents, and leveling agents may be performed.

[0278] The liquid crystal diffraction element of the present invention can be combined with various components and appropriately used as an optical element, an optical unit, an optical module, an optical device, and the like.

[0279] For example, at least a portion of the surface of the liquid crystal diffraction element of the present invention may be a curved surface.

[0280] The liquid crystal diffraction element has a curved surface portion, and when the liquid crystal diffraction element is used in a VR image display device such as a head mounted display or AR glasses, the viewing angle can be expanded. In addition, the liquid crystal diffraction element has a curved surface portion, and chromatic aberration is less likely to occur.

[0281] Here, in the liquid crystal diffraction element of the present invention, the method for forming the curved surface portion is not limited, and various known methods for making at least a part of a sheet-like object into a curved surface shape can be used, but the following method is preferably exemplified.

[0282] That is, a substrate is prepared, at least one of which is a curved surface and has an opposing main surface A and a main surface B. The liquid crystal diffraction element of the present invention is attached to the main surface having a curved surface among the main surface A and the main surface B. Thus, an optical unit can be obtained: the optical unit is composed of the substrate and the liquid crystal diffraction element of the present invention, and the liquid crystal diffraction element is set to a curved surface shape along the curved surface of the substrate.

[0283] The substrate is not limited, and can be made of various resin materials, etc., and various known materials that transmit the light diffracted by the liquid crystal diffraction element. In addition, the substrate can be as follows: one main surface has a curved surface and the other main surface is a plane, or both main surfaces have curved surfaces.

[0284] The substrate and the liquid crystal diffraction element may be attached to each other by a known method using OCA (Optical Clear Adhesive) etc. The liquid crystal diffraction element may be attached to one of the main surfaces A and B, or to both main surfaces.

[0285] Furthermore, in the liquid crystal diffraction element of the present invention, the liquid crystal compound of the optically anisotropic layer may not be fixed, but the alignment state of the optically anisotropic layer may be changed as an optical unit combined with an external input mechanism.

[0286] For example, by changing one period of the optically anisotropic layer by an external input mechanism, a variable-focus lens can be realized in the liquid crystal diffraction element having a concentric liquid crystal alignment pattern that functions as a lens.

[0287] As the external input mechanism, various known mechanisms capable of changing the orientation state of the liquid crystal compound can be used in various optical devices having a liquid crystal layer, etc. As an example, an external input mechanism having a pair of substrates sandwiching a liquid crystal diffraction element and a transparent electrode disposed on at least one of the substrates can be illustrated.

[0288] Furthermore, the optical unit having the liquid crystal diffraction element of the present invention and the external input mechanism may also be an optical unit further combined with a liquid crystal unit. In the optical unit, the driving mechanism of the liquid crystal unit may be shared with the external input mechanism that changes the orientation state of the liquid crystal diffraction element of the present invention, or a driving mechanism of the liquid crystal unit or the like may be separately provided.

[0289] Furthermore, the liquid crystal diffraction element of the present invention is also preferably used as an optical unit in combination with a circular polarizing plate.

[0290] By combining the liquid crystal diffraction element of the present invention and a circular polarizer, the desired circularly polarized light can be incident on the liquid crystal diffraction element of the present invention. Furthermore, by combining the liquid crystal diffraction element of the present invention and a circularly polarizer, the circularly polarized light diffracted by the liquid crystal diffraction element of the present invention can also be emitted as linearly polarized light.

[0291] The circular polarizing plate is not limited, and various known circular polarizing plates such as a circular polarizing plate in which a wave plate (retardation plate) such as a quarter wave plate (λ / 4 plate) and a linear polarizer are combined can be used.

[0292] That is, the liquid crystal diffraction element of the present invention can be combined with various components and used as an optical unit.

[0293] Furthermore, the liquid crystal diffraction element of the present invention and the optical unit including the liquid crystal diffraction element of the present invention can be combined with various components to be used as an optical module.

[0294] Furthermore, the liquid crystal diffraction element of the present invention, the optical unit including the liquid crystal diffraction element of the present invention, and the optical module including the liquid crystal diffraction element of the present invention can be used in various optical devices.

[0295] As an optical device including the liquid crystal diffraction element of the present invention, a head mounted display, a VR display device, a sensor, a communication device, etc. can be exemplified.

[0296] The liquid crystal diffraction element of the present invention has been described in detail above, but the present invention is not limited to the above-mentioned examples, and various improvements or changes can be made without departing from the gist of the present invention.

[0297] Example

[0298] The following examples are given to illustrate the characteristics of the present invention in more detail. The materials, reagents, usage amounts, amounts, ratios, processing contents and processing sequences shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention should not be interpreted as restrictive by the specific examples shown below.

[0299] [Comparative Example 1]

[0300] A commercially available liquid crystal lens (manufactured by Edmund Corporation, polarized light direct plane lens, #14-778) was prepared.

[0301] The optical anisotropic layer of the liquid crystal lens was confirmed by polarizing microscope. Figure 7 The concentric circle pattern shown. In addition, in the liquid crystal orientation pattern, it is a liquid crystal orientation pattern as follows: in one cycle of the optical axis of the liquid crystal compound rotating 180°, one cycle at a distance of about 5 mm from the center is 4.0 μm, and one cycle at a distance of 10 mm from the center is 2.0, and the cycle becomes shorter toward the outward direction.

[0302] The average period of 50 periods in one direction rotated from one longest period along the optical axis of the liquid crystal compound was 25 μm.

[0303] The main surface of the liquid crystal lens was observed under crossed Nicols using an optical microscope in a region having one period less than the average period. The observation was performed so that the absorption axis of one polarizer was parallel to one direction of rotation of the optical axis derived from the liquid crystal compound in the liquid crystal lens.

[0304] The absorption axis of the polarizer parallel to the one direction was set as the observation direction, and the observed bright lines and dark lines were searched for dark lines wider than the dark lines on both sides. However, in this liquid crystal lens, the width of the dark lines was almost uniform, and no dark lines wider than the dark lines on both sides were found.

[0305] That is, it was confirmed that the optically anisotropic layer of the liquid crystal lens had a linear liquid crystal alignment pattern.

[0306] [Comparative Example 2]

[0307] <Fabrication of Liquid Crystal Diffraction Element>

[0308] (Support)

[0309] As a support, a glass substrate was prepared.

[0310] (Formation of Orientation Film)

[0311] The following coating liquid for forming an alignment film was applied onto the support by spin coating, and the support on which the coating film of the coating liquid for forming an alignment film was formed was dried on a hot plate at 60° C. for 60 seconds to form an alignment film.

[0312] Coating liquid for forming an alignment film

[0313]

[0314] -Raw material A for photo-orientation

[0315] [Chemical formula 3]

[0316]

[0317] (Exposure of Alignment Film)

[0318] use Fig.13 The exposure device shown exposes the alignment film to light, thereby forming an alignment film P-1 having an alignment pattern.

[0319] The exposure device used a laser beam emitting a wavelength (355 nm) as a laser. The exposure amount based on the interference light was set to 1000 mJ / cm 2 .

[0320] (Formation of Optically Anisotropic Layer)

[0321] <Formation of the first area>

[0322] As a liquid crystal composition for forming the first region of the optically anisotropic layer, the following composition A-1 was prepared.

[0323] Composition A-1

[0324]

[0325] Liquid crystal compound L-1

[0326] [Chemical formula 4]

[0327]

[0328] Chiral reagent C-1

[0329] [Chemical formula 5]

[0330]

[0331] Leveling agent T-1

[0332] [Chemical formula 6]

[0333]

[0334] The first region of the optically anisotropic layer is formed by coating the composition A-1 on the alignment film P-1 in multiple layers. Multilayer coating means that the following treatment is repeatedly performed: first, the first layer of the composition A-1 is coated on the alignment film, and then heated and ultraviolet curing is performed to prepare a liquid crystal fixing layer, and then the second layer and later layers are coated on the liquid crystal fixing layer by overlapping the coating composition, and similarly heated and ultraviolet curing is performed.

[0335] First, in the first layer, the following composition A-1 was applied on the oriented film P-1, and the coated film was heated to 80° C. on a hot plate, and then, a high pressure mercury lamp was used in a nitrogen atmosphere at 300 mJ / cm 2 The coating film was irradiated with ultraviolet rays having a wavelength of 365 nm, thereby fixing the alignment of the liquid crystal compound.

[0336] After the second layer, the coating is overlapped on the liquid crystal fixing layer, and then heated and cured by ultraviolet light under the same conditions as above, thereby producing a liquid crystal fixing layer. In this way, the overlapping coating is repeated until the total thickness reaches the desired film thickness, thereby forming the first region of the optically anisotropic layer.

[0337] In addition, the refractive index difference Δn of the solidified layer of composition A-1 is obtained by measuring the delay value and film thickness of the following liquid crystal fixed layer (solidified layer), which is obtained by coating composition A-1 on a support with an oriented film for delay measurement prepared separately, and irradiating ultraviolet light to fix the liquid crystal compound after the direction is lost on the substrate in a horizontal orientation. Δn can be calculated by dividing the delay value by the film thickness. The delay value is measured at the target wavelength using Axoscan manufactured by Axometrix, and the film thickness is measured using SEM.

[0338] In the first area, the Δn of the liquid crystal was finally confirmed using a polarizing microscope. 550 × thickness (=Re(550)) is 180nm, and has Figure 7 The concentric circle liquid crystal alignment pattern shown.

[0339] In addition, in the liquid crystal orientation pattern of the first region, in one cycle in which the optical axis of the liquid crystal compound rotates 180°, one cycle at a distance of about 5 mm from the center is 4.0 μm, one cycle at a distance of 10 mm from the center is 2.0 μm, and one cycle at a distance of 23 mm from the center is 1.0 μm, which is a liquid crystal orientation pattern in which the period becomes shorter toward the outward direction.

[0340] Furthermore, in the first region, the twist angle of the liquid crystal compound in the thickness direction is 80°.

[0341] Unless otherwise specified, the following is carried out in the same manner as above. 550 × thickness” etc.

[0342] <Formation of the Second Area>

[0343] Composition A-2 was prepared which was identical to composition A-1 except that chiral reagent C-1 was not included.

[0344] The second region of the optically anisotropic layer was formed on the first region in the same manner as the first region except that composition A-2 was used.

[0345] In the second region, the Δn of the liquid crystal was finally confirmed using a polarizing microscope. 550 × thickness (=Re(550)) is 365nm, and has Figure 7 The concentric circle liquid crystal alignment pattern shown.

[0346] In addition, in the liquid crystal orientation pattern of the second region, in one cycle in which the optical axis of the liquid crystal compound rotates 180°, one cycle at a distance of about 5 mm from the center is 4.0 μm, one cycle at a distance of 10 mm from the center is 2.0 μm, and one cycle at a distance of 23 mm from the center is 1.0 μm, which is a liquid crystal orientation pattern in which the period becomes shorter toward the outward direction.

[0347] Furthermore, in the second region, the twist angle of the liquid crystal compound in the thickness direction is 0°.

[0348] <Formation of the third area>

[0349] Composition A-3 was prepared which was the same as composition A-1 except that chiral reagent C-1 was changed to the following chiral reagent C-2 and the content of the chiral reagent was changed to 0.54 parts by mass.

[0350] This composition A-3 was used, except that the third region of the optically anisotropic layer was formed on the second region in the same manner as the first 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.

[0351] Chiral reagent C-2

[0352] [Chemical formula 7]

[0353]

[0354] In the third region, the Δn of the liquid crystal was finally confirmed using a polarizing microscope. 550 × thickness (=Re(550)) is 185nm, and has Figure 7 The concentric circle liquid crystal alignment pattern shown.

[0355] In addition, in the liquid crystal orientation pattern of the third region, in one cycle in which the optical axis of the liquid crystal compound rotates 180°, one cycle at a distance of about 5 mm from the center is 4.0 μm, one cycle at a distance of 10 mm from the center is 2.0 μm, and one cycle at a distance of 23 mm from the center is 1.0 μm, which is a liquid crystal orientation pattern in which the cycle becomes shorter toward the outward direction. That is, in this example, the liquid crystal orientation pattern of each region is the same.

[0356] Furthermore, in the third region, the twist angle of the liquid crystal compound in the thickness direction is -80°.

[0357] The cross section of the optically anisotropic layer was examined by SEM, and as a result, it was confirmed that Fig.10 Light and dark areas shown.

[0358] In the liquid crystal alignment pattern of the produced optically anisotropic layer, the average period among 50 periods, which is the longest period, in one direction rotated along the optical axis of the liquid crystal compound, was 25 μm.

[0359] The main surface of the liquid crystal diffraction element was observed under crossed Nicols by an optical microscope in a region having one period less than the average period. The observation was performed in such a way that the absorption axis of one polarizer was parallel to one direction of rotation of the optical axis of the liquid crystal compound in the liquid crystal diffraction element.

[0360] The absorption axis of the polarizer parallel to the one direction was set as the observation direction, and a dark line wider than the dark lines on both sides was searched among the observed bright lines and dark lines. However, in the liquid crystal diffraction element, the width of the dark lines was almost uniform, and no dark lines wider than the dark lines on both sides were found.

[0361] That is, it was confirmed that the optically anisotropic layer of the liquid crystal diffraction element had a linear liquid crystal alignment pattern.

[0362] [Example 1]

[0363] In the same manner as in Comparative Example 2, an alignment film was formed on a glass substrate and exposed to light, thereby forming an alignment film P-1 having an alignment pattern.

[0364] (Formation of Optically Anisotropic Layer)

[0365] <Formation of the first area>

[0366] As a liquid crystal composition for forming the first region of the optically anisotropic layer, the following composition B-1 was prepared.

[0367] Composition B-1

[0368]

[0369]

[0370] Liquid crystal compound L-2

[0371] [Chemical formula 8]

[0372]

[0373] Leveling agent T-2

[0374] [Chemical formula 9]

[0375]

[0376] The multilayer composition B-1 was applied onto the oriented film P-1 in the same manner as above, thereby forming the first region of the optically anisotropic layer.

[0377] In the first area, the Δn of the liquid crystal was finally confirmed using a polarizing microscope. 550 × thickness (=Re(550)) is 180nm, and has Figure 7 The concentric circle liquid crystal alignment pattern shown.

[0378] In addition, in the liquid crystal orientation pattern of the first region, in one cycle in which the optical axis of the liquid crystal compound rotates 180°, one cycle at a distance of about 5 mm from the center is 4.0 μm, one cycle at a distance of 10 mm from the center is 2.0 μm, and one cycle at a distance of 23 mm from the center is 1.0 μm, which is a liquid crystal orientation pattern in which the period becomes shorter toward the outward direction.

[0379] Furthermore, in the first region, the twist angle of the liquid crystal compound in the thickness direction is 80°.

[0380] <Formation of the Second Area>

[0381] Composition B-2 was prepared which was identical to composition B-1 except that chiral reagent C-1 was not included.

[0382] The second region of the optically anisotropic layer was formed on the first region in the same manner as the first region except that the composition B-2 was used.

[0383] In the second region, the Δn of the liquid crystal was finally confirmed using a polarizing microscope. 550 × thickness (=Re(550)) is 365nm, and has Figure 7 The concentric circle liquid crystal alignment pattern shown.

[0384] In addition, in the liquid crystal orientation pattern of the second region, in one cycle in which the optical axis of the liquid crystal compound rotates 180°, one cycle at a distance of about 5 mm from the center is 4.0 μm, one cycle at a distance of 10 mm from the center is 2.0 μm, and one cycle at a distance of 23 mm from the center is 1.0 μm, which is a liquid crystal orientation pattern in which the period becomes shorter toward the outward direction.

[0385] Furthermore, in the second region, the twist angle of the liquid crystal compound in the thickness direction is 0°.

[0386] <Formation of the third area>

[0387] Composition B-3 was prepared which was the same as composition B-1 except that chiral reagent C-1 was changed to chiral reagent C-2 and the content of the chiral reagent was changed to 0.54 parts by mass.

[0388] This composition B-3 was used, except that the third region of the optically anisotropic layer was formed on the second region in the same manner as the first 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.

[0389] In the third region, the Δn of the liquid crystal was finally confirmed using a polarizing microscope. 550 × thickness (=Re(550)) is 185nm, and has Figure 7 The concentric circle liquid crystal alignment pattern shown.

[0390] In addition, in the liquid crystal orientation pattern of the third region, in one cycle in which the optical axis of the liquid crystal compound rotates 180°, one cycle at a distance of about 5 mm from the center is 4.0 μm, one cycle at a distance of 10 mm from the center is 2.0 μm, and one cycle at a distance of 23 mm from the center is 1.0 μm, which is a liquid crystal orientation pattern in which the cycle becomes shorter toward the outward direction. That is, in this example, the liquid crystal orientation pattern of each region is the same.

[0391] Furthermore, in the third region, the twist angle of the liquid crystal compound in the thickness direction is -80°.

[0392] Furthermore, the cross section of the optically anisotropic layer was confirmed by SEM, and as a result, the following was confirmed: Fig.10 The dark area shown.

[0393] In the liquid crystal alignment pattern of the produced optically anisotropic layer, the average period among 50 periods, which is the longest period, in one direction rotated along the optical axis of the liquid crystal compound, was 25 μm.

[0394] The main surface of the liquid crystal diffraction element was observed under crossed Nicols by an optical microscope in a region having one period less than the average period. The observation was performed in such a way that the absorption axis of one polarizer was parallel to one direction of rotation of the optical axis of the liquid crystal compound in the liquid crystal diffraction element.

[0395] The absorption axis of the polarizer parallel to the one direction was set as the observation direction, and a dark line wider than the dark lines located on both sides was randomly selected from the observed bright lines and dark lines. The randomly selected dark line was set as the first line, and 80 dark lines were selected continuously in the observation direction. The result of confirming the width of each dark line confirmed that the width of the dark line of the even-numbered position was narrower than the width of the dark line of the adjacent odd-numbered position, and the width of the dark line of the odd-numbered position was wider than the width of the dark line of the adjacent even-numbered position.

[0396] That is, it was confirmed that the optically anisotropic layer of the liquid crystal diffraction element had a nonlinear liquid crystal alignment pattern.

[0397] [Example 2]

[0398] In the same manner as in Comparative Example 2, an alignment film was formed on a glass substrate and exposed to light, thereby forming an alignment film P-1 having an alignment pattern.

[0399] (Formation of Optically Anisotropic Layer)

[0400] <Formation of the first area>

[0401] As a liquid crystal composition for forming the first region of the optically anisotropic layer, the following composition C-1 was prepared.

[0402] Composition C-1

[0403]

[0404] Liquid crystal compound L-3

[0405] [Chemical formula 10]

[0406]

[0407] The multilayer composition C-1 was applied onto the oriented film P-1 in the same manner as above, thereby forming the first region of the optically anisotropic layer.

[0408] In the first area, the Δn of the liquid crystal was finally confirmed using a polarizing microscope. 550 × thickness (=Re(550)) is 180nm, and has Figure 7 The concentric circle liquid crystal alignment pattern shown.

[0409] In addition, in the liquid crystal orientation pattern of the first region, in one cycle in which the optical axis of the liquid crystal compound rotates 180°, one cycle at a distance of about 5 mm from the center is 4.0 μm, one cycle at a distance of 10 mm from the center is 2.0 μm, and one cycle at a distance of 23 mm from the center is 1.0 μm, which is a liquid crystal orientation pattern in which the period becomes shorter toward the outward direction.

[0410] Furthermore, in the first region, the twist angle of the liquid crystal compound in the thickness direction is 80°.

[0411] <Formation of the Second Area>

[0412] Composition C-2 was prepared which was identical to composition C-1 except that chiral reagent C-1 was not included.

[0413] The second region of the optically anisotropic layer was formed on the first region in the same manner as the first region except that composition C-2 was used.

[0414] In the second region, the final liquid crystal Δn 550 × thickness (=Re(550)) was 365 nm, and polarizing microscope was used to confirm that Figure 7 The concentric circle liquid crystal alignment pattern shown.

[0415] In addition, in the liquid crystal orientation pattern of the second region, in one cycle in which the optical axis of the liquid crystal compound rotates 180°, one cycle at a distance of about 5 mm from the center is 4.0 μm, one cycle at a distance of 10 mm from the center is 2.0 μm, and one cycle at a distance of 23 mm from the center is 1.0 μm, which is a liquid crystal orientation pattern in which the period becomes shorter toward the outward direction.

[0416] Furthermore, in the second region, the twist angle of the liquid crystal compound in the thickness direction is 0°.

[0417] <Formation of the third area>

[0418] A composition C-3 was prepared which was the same as the composition C-1 except that the chiral reagent C-1 was changed to the chiral reagent C-2 and the content of the chiral reagent was changed to 0.54 parts by mass.

[0419] This composition C-3 was used, except that the third region of the optically anisotropic layer was formed on the second region in the same manner as the first 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.

[0420] In the third region, the final liquid crystal Δn 550 × thickness (=Re(550)) was 185 nm, and polarizing microscope was used to confirm that Figure 7 The concentric circle liquid crystal alignment pattern shown.

[0421] In addition, in the liquid crystal orientation pattern of the third region, in one cycle in which the optical axis of the liquid crystal compound rotates 180°, one cycle at a distance of about 5 mm from the center is 4.0 μm, one cycle at a distance of 10 mm from the center is 2.0 μm, and one cycle at a distance of 23 mm from the center is 1.0 μm, which is a liquid crystal orientation pattern in which the cycle becomes shorter toward the outward direction. That is, in this example, the liquid crystal orientation pattern of each region is the same.

[0422] Furthermore, in the third region, the twist angle of the liquid crystal compound in the thickness direction is -80°.

[0423] The cross section of the optically anisotropic layer was examined by SEM, and as a result, it was confirmed that Fig.10 Light and dark areas shown.

[0424] In the liquid crystal alignment pattern of the produced optically anisotropic layer, the average period among 50 periods, which is the longest period, in one direction rotated along the optical axis of the liquid crystal compound, was 25 μm.

[0425] The main surface of the liquid crystal diffraction element was observed under crossed Nicols by an optical microscope in a region having one period less than the average period. The observation was performed in such a way that the absorption axis of one polarizer was parallel to one direction of rotation of the optical axis of the liquid crystal compound in the liquid crystal diffraction element.

[0426] The absorption axis of the polarizer parallel to the one direction was set as the observation direction, and a dark line wider than the dark lines located on both sides was randomly selected from the observed bright lines and dark lines. The randomly selected dark line was set as the first line, and 80 dark lines were selected continuously in the observation direction. The result of confirming the width of each dark line confirmed that the width of the dark line of the even-numbered position was narrower than the width of the dark line of the adjacent odd-numbered position, and the width of the dark line of the odd-numbered position was wider than the width of the dark line of the adjacent even-numbered position.

[0427] That is, it was confirmed that the optically anisotropic layer of the liquid crystal diffraction element had a nonlinear liquid crystal alignment pattern.

[0428] [Comparative Example 3]

[0429] In the same manner as in Comparative Example 2, an alignment film was formed on a glass substrate, and exposure of the alignment film was performed.

[0430] (Formation of Optically Anisotropic Layer)

[0431] <Formation of the first area>

[0432] In the formation of the second region in Comparative Example 2, the first region of the optically anisotropic layer was formed on the alignment film in the same manner except that the film thickness of the optically anisotropic layer was adjusted.

[0433] In the first area, the Δn of the liquid crystal was finally confirmed using a polarizing microscope. 550 × thickness (=Re(550)) is 275nm, and has Figure 7 The concentric circle liquid crystal alignment pattern shown.

[0434] In addition, in the liquid crystal orientation pattern of the first region, in one cycle in which the optical axis of the liquid crystal compound rotates 180°, one cycle at a distance of about 5 mm from the center is 4.0 μm, one cycle at a distance of 10 mm from the center is 2.0 μm, and one cycle at a distance of 23 mm from the center is 1.0 μm, which is a liquid crystal orientation pattern in which the period becomes shorter toward the outward direction.

[0435] Furthermore, in the first region, the twist angle of the liquid crystal compound in the thickness direction is 0°.

[0436] The cross section of the optically anisotropic layer was examined by SEM, and as a result, it was confirmed that Fig.10 The bright and dark parts of the second area in the center.

[0437] In the liquid crystal alignment pattern of the produced optically anisotropic layer, the average period among 50 periods, which is the longest period, in one direction rotated along the optical axis of the liquid crystal compound, was 25 μm.

[0438] The main surface of the liquid crystal diffraction element was observed under crossed Nicols by an optical microscope in a region having one period less than the average period. The observation was performed in such a way that the absorption axis of one polarizer was parallel to one direction of rotation of the optical axis of the liquid crystal compound in the liquid crystal diffraction element.

[0439] The absorption axis of the polarizer parallel to the one direction was set as the observation direction, and a dark line wider than the dark lines on both sides was searched among the observed bright lines and dark lines. However, in the liquid crystal diffraction element, the width of the dark lines was almost uniform, and no dark lines wider than the dark lines on both sides were found.

[0440] That is, it was confirmed that the optically anisotropic layer of the liquid crystal diffraction element had a linear liquid crystal alignment pattern.

[0441] [Example 3]

[0442] In the same manner as in Example 1, an alignment film was formed on a glass substrate, and exposure of the alignment film was performed.

[0443] (Formation of Optically Anisotropic Layer)

[0444] <Formation of the first area>

[0445] In forming the second region in Example 1, the first region of the optically anisotropic layer was formed on the alignment film in the same manner except that the film thickness of the optically anisotropic layer was adjusted.

[0446] In the first area, the Δn of the liquid crystal was finally confirmed using a polarizing microscope. 550 × thickness (=Re(550)) is 275nm, and has Figure 7 The concentric circle liquid crystal alignment pattern shown.

[0447] In addition, in the liquid crystal orientation pattern of the first region, in one cycle in which the optical axis of the liquid crystal compound rotates 180°, one cycle at a distance of about 5 mm from the center is 4.0 μm, one cycle at a distance of 10 mm from the center is 2.0 μm, and one cycle at a distance of 23 mm from the center is 1.0 μm, which is a liquid crystal orientation pattern in which the period becomes shorter toward the outward direction.

[0448] Furthermore, in the first region, the twist angle of the liquid crystal compound in the thickness direction is 0°.

[0449] Furthermore, the cross section of the optically anisotropic layer was confirmed by SEM, and as a result, the following was confirmed: Fig.10 The bright and dark parts of the second area in the center.

[0450] In the liquid crystal alignment pattern of the produced optically anisotropic layer, the average period among 50 periods, which is the longest period, in one direction rotated along the optical axis of the liquid crystal compound, was 25 μm.

[0451] The main surface of the liquid crystal diffraction element was observed under crossed Nicols by an optical microscope in a region having one period less than the average period. The observation was performed in such a way that the absorption axis of one polarizer was parallel to one direction of rotation of the optical axis of the liquid crystal compound in the liquid crystal diffraction element.

[0452] The absorption axis of the polarizer parallel to the one direction was set as the observation direction, and a dark line wider than the dark lines located on both sides was randomly selected from the observed bright lines and dark lines. The randomly selected dark line was set as the first line, and 80 dark lines were selected continuously in the observation direction. The result of confirming the width of each dark line confirmed that the width of the dark line of the even-numbered position was narrower than the width of the dark line of the adjacent odd-numbered position, and the width of the dark line of the odd-numbered position was wider than the width of the dark line of the adjacent even-numbered position.

[0453] That is, it was confirmed that the optically anisotropic layer of the liquid crystal diffraction element had a nonlinear liquid crystal alignment pattern.

[0454] [Example 4]

[0455] In the same manner as in Example 1, an alignment film was formed on a glass substrate, and exposure of the alignment film was performed.

[0456] (Formation of Optically Anisotropic Layer)

[0457] <Formation of the first area>

[0458] In the formation of the first region in Example 1, 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 the chiral agent C-1 in the composition B-1 was changed.

[0459] In the first area, the Δn of the liquid crystal was finally confirmed using a polarizing microscope. 550 × thickness (=Re(550)) is 180nm, and has Figure 7 The concentric circle liquid crystal alignment pattern shown.

[0460] In addition, in the liquid crystal orientation pattern of the first region, in one cycle in which the optical axis of the liquid crystal compound rotates 180°, one cycle at a distance of about 5 mm from the center is 4.0 μm, one cycle at a distance of 10 mm from the center is 2.0 μm, and one cycle at a distance of 23 mm from the center is 1.0 μm, which is a liquid crystal orientation pattern in which the period becomes shorter toward the outward direction.

[0461] Furthermore, in the first region, the twist angle of the liquid crystal compound in the thickness direction is 85°.

[0462] <Formation of the Second Area>

[0463] In the formation of the first region in Example 1, the second region of the optically anisotropic layer was formed on the first region in the same manner except that the content of the chiral agent C-1 in the composition B-1 and the film thickness were changed.

[0464] In the second region, the Δn of the liquid crystal was finally confirmed using a polarizing microscope. 550× thickness (=Re(550)) is 365nm, and has Figure 7 The concentric circle liquid crystal alignment pattern shown.

[0465] In addition, in the liquid crystal orientation pattern of the second region, in one cycle in which the optical axis of the liquid crystal compound rotates 180°, one cycle at a distance of about 5 mm from the center is 4.0 μm, one cycle at a distance of 10 mm from the center is 2.0 μm, and one cycle at a distance of 23 mm from the center is 1.0 μm, which is a liquid crystal orientation pattern in which the period becomes shorter toward the outward direction.

[0466] Furthermore, in the second region, the twist angle of the liquid crystal compound in the thickness direction was 13°.

[0467] <Formation of the third area>

[0468] In the formation of the third region of Example 1, the content of the chiral agent C-2 of the composition B-3 was changed. In addition, the third region of the optically anisotropic layer was formed on the second region in the same manner, thereby producing a liquid crystal diffraction element having an optically anisotropic layer composed of the first region, the second region and the third region.

[0469] In the third region, the Δn of the liquid crystal was finally confirmed using a polarizing microscope. 550 × thickness (=Re(550)) is 185nm, and has Figure 7 The concentric circle liquid crystal alignment pattern shown.

[0470] In addition, in the liquid crystal orientation pattern of the third region, in one cycle in which the optical axis of the liquid crystal compound rotates 180°, one cycle at a distance of about 5 mm from the center is 4.0 μm, one cycle at a distance of 10 mm from the center is 2.0 μm, and one cycle at a distance of 23 mm from the center is 1.0 μm, which is a liquid crystal orientation pattern in which the cycle becomes shorter toward the outward direction. That is, in this example, the liquid crystal orientation pattern of each region is the same.

[0471] Furthermore, in the third region, the twist angle of the liquid crystal compound in the thickness direction is -73°.

[0472] Furthermore, when a cross section of the optically anisotropic layer was observed using a SEM, a pattern of dark and light portions was observed.

[0473] In the liquid crystal alignment pattern of the produced optically anisotropic layer, the average period among 50 periods, which is the longest period, in one direction rotated along the optical axis of the liquid crystal compound, was 25 μm.

[0474] The main surface of the liquid crystal diffraction element was observed under crossed Nicols by an optical microscope in a region having one period less than the average period. The observation was performed in such a way that the absorption axis of one polarizer was parallel to one direction of rotation of the optical axis of the liquid crystal compound in the liquid crystal diffraction element.

[0475] The absorption axis of the polarizer parallel to the one direction was set as the observation direction, and a dark line wider than the dark lines located on both sides was randomly selected from the observed bright lines and dark lines. The randomly selected dark line was set as the first line, and 80 dark lines were selected continuously in the observation direction. The result of confirming the width of each dark line confirmed that the width of the dark line of the even-numbered position was narrower than the width of the dark line of the adjacent odd-numbered position, and the width of the dark line of the odd-numbered position was wider than the width of the dark line of the adjacent even-numbered position.

[0476] That is, it was confirmed that the optically anisotropic layer of the liquid crystal diffraction element had a nonlinear liquid crystal alignment pattern.

[0477] [evaluate]

[0478] <0th-order light cutoff capability>

[0479] 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 on the liquid crystal lens of Comparative Example 1 and the manufactured liquid crystal diffraction element from the front (in the direction where the angle relative to the normal is 0°) at a position approximately 5 mm away from the center. The light intensity of the incident light and the light intensity of the 0th-order light from the polarized light diffraction element in the outgoing light were measured using a photodetector, and the light amount of the 0th-order light (the light amount of the 0th-order light when the light amount of the incident light is set to 1) was calculated using the following formula.

[0480] Amount of light of 0th order light (A) = Light intensity of 0th order light / Light intensity of incident light

[0481] The average value (0th order LL(A)) of the amount of 0th order light when 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) are incident is calculated.

[0482] Next, in the above evaluation, a circular polarizer (λ / 4 plate: WPQSM05-532 of Thorlabs, linear polarizer: SPF-50C-32 of SIGMAKOKI CO., LTD.) was arranged on the front side of the 0th order light (direction with an angle of 0° relative to the normal) downstream of the liquid crystal lens of Comparative Example 1 and the produced liquid crystal diffraction element. At this time, the circular polarizer was arranged to transmit left-handed circularly polarized light and absorb right-handed circularly polarized light. The right-handed polarized light with an incident 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 respectively, and the light intensity of the incident light and the light intensity of the 0th order light emitted from the circular polarizer were measured with a photodetector, and the light amount of the 0th order light was calculated using the following formula.

[0483] Light intensity of zero-order light (B) = Light intensity of zero-order light / Light intensity of incident light

[0484] The average value (0th order LL(B)) of the amount of 0th order light when 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) are incident is calculated.

[0485] The 0th order LL (A) without a circular polarizer and the 0th order LL (B) with a circular polarizer were compared. As a result, compared with Comparative Examples 1 and 2, in Examples 1, 2, and 4, the cutoff capability of the 0th order light using the circular polarizer was high, and the leakage of the 0th order light from the circular polarizer could be suppressed. Similarly, compared with Comparative Example 3, in Example 3, the cutoff capability of the 0th order light using the circular polarizer was also high.

[0486] The zero-order light leakage was also evaluated similarly at a position about 10 mm from the center of the liquid crystal lens of Comparative Example 1 and the produced liquid crystal diffraction element.

[0487] The 0th order LL (A) without a circular polarizer and the 0th order LL (B) with a circular polarizer were compared. As a result, compared with Comparative Examples 1 and 2, in Examples 1, 2, and 4, the cutoff capability of the 0th order light using the circular polarizer was high, and the leakage of the 0th order light from the circular polarizer could be suppressed. Similarly, compared with Comparative Example 3, in Example 3, the cutoff capability of the 0th order light using the circular polarizer was also high.

[0488] The zero-order light leakage was also evaluated similarly at a position about 23 mm from the center of the produced liquid crystal diffraction element.

[0489] The 0th order LL (A) without a circular polarizer and the 0th order LL (B) with a circular polarizer were compared. As a result, in Example 1, Example 2, and Example 4, the cutoff capability of the 0th order light using the circular polarizer was high compared to Comparative Example 2, and the leakage of the 0th order light from the circular polarizer could be suppressed. Compared with Example 1, in Example 4, the cutoff capability of the 0th order light using the circular polarizer was higher.

[0490] Furthermore, in the polarized light diffraction element manufactured in Example 2, when the incident position of light is changed to 5mm, 10mm, and 23mm from the center of the element, the polarization state of the 0th order light changes according to the incident position of light, and the ellipticity difference εin-ε0 between the incident polarized light and the 0th order light changes. Furthermore, the absolute value Abs(Δε(LH)-Δε(RH)) of the difference between the ellipticity difference Δε(RH) between the incident light and the 0th order light when right-handed polarized light is incident and the difference Δε(LH) between the incident light and the 0th order light when left-handed polarized light is incident increases as the incident position of light moves away from the center of the element (5mm→10mm→23mm). When the 0th order LL(A) when there is no circular polarizer and the 0th order LL(B) when there is a circular polarizer at each incident position of light, the cutoff capability of the 0th order light by the circular polarizer is improved.

[0491] Furthermore, in the liquid crystal diffraction element produced in Example 4, when the incident position of light is changed from the center of the element to 5 mm, 10 mm, and 23 mm, the polarization state of the 0th order light changes according to the incident position of light, and the ellipticity difference εin-ε0 between the incident polarized light and the 0th order light changes. Furthermore, the absolute value Abs(Δε(LH)-Δε(RH)) of the difference between the ellipticity difference Δε(RH) between the incident light and the 0th order light when right-handed polarized light is incident and the difference Δε(LH) between the incident light and the 0th order light when left-handed polarized light is incident increases as the incident position of light moves away from the center of the element (5 mm→10 mm→23 mm). When the 0th order LL (A) when there is no circular polarizer and the 0th order LL (B) when there is a circular polarizer at each incident position of light, the cutoff capability of the 0th order light by the circular polarizer is improved. In Example 4, compared with Example 2, the change in Abs (Δε(LH)-Δε(RH)) when the incident position of the element changes from 10mm→23mm and the change in the cutoff ability of 0th order light using the circular polarizer is large, and the cutoff ability of 0th order light using the circular polarizer at 23mm is high.

[0492] <Liquid crystal orientation pattern>

[0493] The liquid crystal diffraction elements of Examples 1 to 4, the liquid crystal lens of Comparative Example 1, and the liquid crystal diffraction elements of Comparative Examples 2 and 3 were observed with an optical microscope, and the observed images were photographed.

[0494] In the obtained 8-bit (256 grayscale) photographic image, the image was binarized using the average value of the brightest grayscale and the darkest grayscale as a threshold, and the widths of 80 consecutive dark lines were measured in the same manner as before.

[0495] will satisfy the following

[0496] [Average of dark line widths of odd-numbered bits] - [Average of dark line widths of even-numbered bits] >

[0497] ([Standard deviation of dark line widths of odd-numbered bits] + [Standard deviation of dark line widths of even-numbered bits]) / 2

[0498] Set the ones that satisfy the condition to A, and set the ones that do not satisfy the condition to B.

[0499] As a result, Examples 1 to 4 were all A, and Comparative Examples 1 to 3 were all B.

[0500] From the above results, the effects of the present invention are obvious.

[0501] Industrial Applicability

[0502] The present invention can be suitably used in various devices such as optical devices such as head-mounted displays and virtual reality display devices.

[0503] Explanation of symbols

[0504] 10-liquid crystal diffraction element, 30-support, 32-aligned film, 36, 36A, 36B, 36C, 36S, 36Z-optical anisotropic layer, 40-liquid crystal compound, 40A-optical axis, 42-bright part, 44-dark part, 60-exposure device, 62-laser, 64-light source, 65-λ / 2 plate, 68-beam splitter, 70A, 70B, 90A, 90B-reflecting mirror, 72A, 72B, 96-λ / 4 plate, 86, 94-polarization beam splitter, 92-lens, o-dark line (odd digits), e-dark line (even digits), Λ-1 period, D-arrangement axis, R-region, M-laser beam, MA, MB-light, MP-P polarized light, MS-S polarized light, P O -Linearly polarized light, P R -Right-handed circularly polarized light, P L -Left-handed circularly polarized light, α-crossing angle, L1, L4-incident light, L2, L5-transmitted light.

Claims

1. A liquid crystal diffraction element comprising an optically anisotropic layer formed using a liquid crystal composition containing a liquid crystal compound, 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 continuously rotating in at least one direction in a plane. The length of the direction of the optical axis derived from the liquid crystal compound in the liquid crystal orientation pattern rotated by 180° in the plane is defined as one period, the average period of 50 periods along the one direction starting from the longest period of the one period is defined as Λa, and the main surface of the optically anisotropic layer is observed under crossed Nicols with an optical microscope in a region having one period less than the average period Λa, The optically anisotropic layer is arranged in such a manner that the absorption axis of the polarizer constituting the crossed Nicols is parallel to the one direction, the absorption axis of the polarizer parallel to the one direction is used as the observation direction, and among the observed bright lines and dark lines, a dark line having a width wider than the dark lines adjacent to both sides is arbitrarily selected, and when the arbitrarily selected dark line is selected as the first one and 80 dark lines are selected continuously in the observation direction, In the selected 80 continuous dark lines, the dark line width of the even-numbered bits is narrower than the dark line width of the adjacent odd-numbered bits, and the dark line width of the odd-numbered bits is wider than the dark line width of the adjacent even-numbered bits.

2. The liquid crystal diffraction element according to claim 1, wherein: The selected 80 continuous dark lines satisfy the following formula: [Average of dark line widths of odd-numbered bits] - [Average of dark line widths of even-numbered bits] > ([Standard deviation of dark line widths of odd-numbered bits] + [Standard deviation of dark line widths of even-numbered bits]) / 2.

3. The liquid crystal diffraction element according to claim 1 or 2, wherein: The liquid crystal alignment pattern is a concentric circle pattern having one direction in which the direction of the optical axis of the liquid crystal compound changes while continuously rotating in a concentric circle from the inside toward the outside.

Images