Optical element and manufacturing method for optical element

Abstract

To improve the orientation of liquid crystal molecules of a liquid crystal layer in an optical element including a liquid crystal layer on a pattern layer.SOLUTION: Provided is an optical element including a pattern layer and a first liquid crystal layer, wherein the pattern layer has a first plane and a second plane on the side reverse from the first plane. The first plane includes a first pattern region where recesses are arranged in a prescribed pattern, and the prescribed pattern in the first pattern region has a first pitch. The first liquid crystal layer includes a region which is located on the first plane side of the pattern layer, and in which liquid crystal molecules are oriented with a second pitch in plane. A second liquid crystal layer is included between the pattern layer and the first liquid crystal layer, in which liquid crystal molecules are oriented in spiral form in the thickness direction. The thickness of the second liquid crystal layer is 50 nm or greater, and the first pitch of the pattern layer and the second pitch of the first liquid crystal layer appropriately match each other.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an optical element and a method for manufacturing the optical element.

Background Art

[0002] There is a technical field in which optical elements are used to change the polarization state of light or the traveling direction of light.

[0003] The above-described optical element is used, for example, in a dimming device. In recent years, in personal authentication and vehicle autonomous driving, the development of devices equipped with optical sensors has been progressing. Examples of devices equipped with optical sensors include face recognition devices, LiDAR (light detection and ranging), and the like. Optical elements may also be used in such devices equipped with optical sensors. In recent years, display devices for displaying virtual reality (VR: Virtual Reality), augmented reality (AR: Augmented Reality), and mixed reality (MR: Mixed Reality) have been put on the market. In this specification, technologies for displaying things that do not exist in reality such as VR, AR, and MR are referred to as "cross-reality (XR: X Reality)". Optical elements may also be used in display devices for cross-reality.

[0004] As a configuration of an optical element, a configuration including a liquid crystal layer on a pattern layer having a predetermined pattern is known (Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In Patent Documents 1 and 2, a pattern layer having a predetermined pattern has a role of facilitating the alignment of liquid crystal molecules in a liquid crystal layer. However, when a liquid crystal layer is formed on a pattern layer having a predetermined pattern as in Patent Documents 1 and 2, cases where the alignment of liquid crystal molecules in the liquid crystal layer is insufficient frequently occurred. In particular, when the pitch of the pattern of the pattern layer is short, the frequency of insufficient alignment of liquid crystal molecules in the liquid crystal layer increases.

Means for Solving the Problems

[0007] The present disclosure aims to provide an optical element having a liquid crystal layer on a pattern layer, which can improve the alignment of liquid crystal molecules in the liquid crystal layer. The present disclosure aims to provide a method for efficiently manufacturing the optical element.

[0008] The present disclosure provides the following optical elements and manufacturing methods of the optical elements in [1] and [2]. [1] An optical element having a pattern layer and a first liquid crystal layer, wherein the pattern layer has a first surface and a second surface opposite to the first surface, the first surface has a first pattern region in which recesses are arranged in a predetermined pattern, and the predetermined pattern of the first pattern region has a first pitch, the first liquid crystal layer is disposed on the first surface side of the pattern layer and has a region in which liquid crystal molecules are aligned with a second pitch in the plane, a second liquid crystal layer in which liquid crystal molecules are spirally aligned in the thickness direction is provided between the pattern layer and the first liquid crystal layer, and the second liquid crystal layer has a thickness of 50 nm or more, an optical element in which the first pitch of the pattern layer and the second pitch of the first liquid crystal layer substantially coincide. [2] A method for manufacturing the optical element according to [1], which includes the following first to fourth steps. First step: A step of applying a coating liquid for forming a pattern layer containing a resin on a substrate to form a layer containing the resin. Second step: A step of forming a pattern layer by shaping a layer containing a resin using a plate having a shape complementary to the surface shape of the first surface of the pattern layer. Third step: A step of forming a second liquid crystal layer by applying a coating liquid for forming a second liquid crystal layer on the pattern layer. Fourth step: A step of forming a first liquid crystal layer by applying a coating liquid for forming a first liquid crystal layer on the second liquid crystal layer.

Advantages of the Invention

[0009] The optical element of the present disclosure can improve the alignment of liquid crystal molecules in the liquid crystal layer in an optical element having a liquid crystal layer on a pattern layer. The manufacturing method of the optical element of the present disclosure can efficiently manufacture an optical element having the above-described characteristics.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the optical element of the present disclosure will be described.

[0012] [Optical Element] The optical element of the present disclosure has a pattern layer and a first liquid crystal layer, wherein the pattern layer has a first surface and a second surface opposite to the first surface, the first surface has a first pattern region in which recesses are arranged in a predetermined pattern, and the predetermined pattern of the first pattern region has a first pitch, the first liquid crystal layer is disposed on the first surface side of the pattern layer and has a region in which liquid crystal molecules are oriented with a second pitch in the plane, a second liquid crystal layer in which liquid crystal molecules are spirally oriented in the thickness direction is provided between the pattern layer and the first liquid crystal layer, and the second liquid crystal layer has a thickness of 50 nm or more, and the first pitch of the pattern layer substantially coincides with the second pitch of the first liquid crystal layer.

[0013] FIG. 1 is a cross-sectional view showing an embodiment of the optical element of the present disclosure. The optical element 100 in FIG. 1 has a pattern layer 10 and a first liquid crystal layer 30. In FIG. 1, the pattern layer 10 has a first surface 10a and a second surface 10b opposite to the first surface. In FIG. 1, the first liquid crystal layer 30 is formed on the first surface 20a side of the pattern layer 10. In FIG. 1, the pattern layer 10 has a plurality of recesses on the first surface 10a. In FIG. 1, the pattern layer 10 has a first pattern region R1 in which the recesses are arranged with a first pitch P1 and a first' pattern region R1' in which the recesses are arranged with a first' pitch P1'. In FIG. 1, the first liquid crystal layer 30 has a region in which liquid crystal molecules are arranged with a second pitch P2 and a region in which liquid crystal molecules are arranged with a second' pitch P2'. In FIG. 1, a second liquid crystal layer 20 is disposed between the pattern layer 10 and the first liquid crystal layer. In FIG. 1, the first pitch P1 of the pattern layer and the second pitch P2 of the first liquid crystal layer are substantially the same (although the positions of both pitches are shifted in the left - right direction of FIG. 1, the lengths of the pitches are substantially the same). In FIG. 1, the first' pitch P1' of the pattern layer and the second' pitch P2' of the first liquid crystal layer are substantially the same (although the positions of both pitches are shifted in the left - right direction of FIG. 1, the lengths of the pitches are substantially the same). In FIG. 1, the first' pitch P1' is different from the first pitch P1. In FIG. 1, the second' pitch P2' is different from the second pitch P2. In FIG. 1, the diagonal broken line of the second liquid crystal layer 20 is a line connecting locations where the alignment directions of the molecules in the second liquid crystal layer are the same (actually, in the second liquid crystal layer, an infinite number of locations where the alignment directions of the molecules are the same are formed (see FIG. 7). In FIG. 1, a broken line is drawn every time the alignment direction of the molecules changes by 180 degrees). FIG. 1 is a schematic cross - sectional view. That is, the scales of the respective layers constituting the optical element 100 are schematized for easy illustration and are different from the actual scales. The same applies to the figures other than FIG. 1.

[0014] <Stacked structure> The optical element of the present disclosure has a pattern layer, a second liquid crystal layer, and a first liquid crystal layer. Preferably, in the thickness direction, the optical element of the present disclosure has the pattern layer, the second liquid crystal layer, and the first liquid crystal layer in this order. Preferably, in the thickness direction, the first surface of the pattern layer is in contact with the second liquid crystal layer, and the second liquid crystal layer is in contact with the first liquid crystal layer.

[0015] The optical element of the present disclosure may have other layers other than the pattern layer, the second liquid crystal layer, and the first liquid crystal layer. Examples of the other layers include a substrate, an antistatic layer, etc. The substrate and the antistatic layer are preferably disposed on the side opposite to the second liquid crystal layer of the pattern layer. A primer layer for enhancing the adhesion of the pattern layer may be provided between the substrate and the pattern layer. Examples of the laminated structure of the optical element of the present disclosure include the following (1) to (4). In the following (1) to (4), " / " indicates the interface of the layer. (1) Pattern layer / Second liquid crystal layer / First liquid crystal layer (2) Substrate / Pattern layer / Second liquid crystal layer / First liquid crystal layer (3) Antistatic layer / Pattern layer / Second liquid crystal layer / First liquid crystal layer (4) Antistatic layer / Substrate / Pattern layer / Second liquid crystal layer / First liquid crystal layer

[0016] Since the optical element of the present disclosure has a second liquid crystal layer in which liquid crystal molecules are helically aligned in the thickness direction between the pattern layer and the first liquid crystal layer, the alignment of the liquid crystal molecules in the first liquid crystal layer can be improved. The reason is considered as follows.

[0017] The liquid crystal layer can be formed, for example, in the following steps S1 to S3. S1: Prepare a coating solution in which liquid crystal molecules are dissolved in a solvent. S2: Apply the coating solution to an alignment layer such as a pattern layer and dry it. S3: Volatilize the solvent of the coating solution to form a liquid crystal layer. The coating solution in S1 is usually a dilute solution. The liquid crystal molecules in the dilute solution are random and not aligned. In S2, as the solvent of the coating solution gradually volatilizes, the coating solution becomes a concentrated solution. In the concentrated solution, the liquid crystal molecules partially form a liquid crystal phase. Then, when the solvent of the concentrated solution volatilizes, the liquid crystal phase partially formed in S2 aligns on the alignment layer, and a liquid crystal layer in which the liquid crystal molecules are aligned is formed. FIG. 2 is an image diagram showing an embodiment of the state of liquid crystal molecules in S1 to S3 when liquid crystal molecules that are not helically aligned in the thickness direction are used as the liquid crystal molecules constituting the liquid crystal layer. FIG. 3 is an image diagram showing an embodiment of the state of liquid crystal molecules in S1 to S3 when liquid crystal molecules that are helically aligned in the thickness direction are used as the liquid crystal molecules constituting the liquid crystal layer. In the stage of S1, the directions of the liquid crystal molecules are completely random in both FIGS. 2 and 3. As shown in FIG. 3, the liquid crystal molecules that are helically oriented in the thickness direction not only partially form a liquid crystal phase under the influence of the chiral agent at the stage of S2, but also form a helical layer structure. Therefore, when using liquid crystal molecules that are helically oriented in the thickness direction, in S3, a liquid crystal layer in which the liquid crystal molecules are oriented is quickly formed. On the other hand, as shown in FIG. 2, since the liquid crystal molecules that are not helically oriented in the thickness direction do not form a layer structure at the stage of S2, it is difficult to quickly form a liquid crystal layer in which the liquid crystal molecules are oriented in S3. S3-1 in FIG. 2 shows the initial stage of orientation, and S3-2 shows the stage where the orientation is completed. The liquid crystal composition showing the characteristics of FIG. 2 is, for example, a nematic liquid crystal compound with homeotropic alignment. The liquid crystal compound showing the characteristics of FIG. 3 is, for example, a liquid crystal composition obtained by adding a chiral agent to a nematic liquid crystal compound. As described above, compared with the liquid crystal molecules that are not helically oriented in the thickness direction, the liquid crystal molecules that are helically oriented in the thickness direction can more easily and quickly orient the liquid crystal molecules when forming a liquid crystal layer. And the liquid crystal layer in which the liquid crystal molecules are helically oriented in the thickness direction can easily improve the orientation property of other liquid crystal layers formed on the liquid crystal layer. Therefore, the optical element of the present disclosure has a second liquid crystal layer in which the liquid crystal molecules are helically oriented in the thickness direction between the pattern layer and the first liquid crystal layer, so that the orientation property of the liquid crystal molecules in the first liquid crystal layer can be improved (however, the second liquid crystal layer needs to have a thickness of 50 nm or more). Furthermore, the optical element of the present disclosure can make the orientation pitch of the liquid crystal molecules in the first liquid crystal layer substantially the same as the pitch of the pattern in the pattern layer. The shorter the pitch of the pattern in the pattern layer, the more difficult it is for the liquid crystal molecules to align along the pattern. However, the liquid crystal molecules that are helically oriented in the thickness direction can easily and quickly align following the pattern even when the pitch of the pattern in the pattern layer is short. Therefore, when the pitch of the pattern in the pattern layer is short, the effect of the optical element of the present disclosure is particularly effective.

[0018] <Pattern layer> The pattern layer has a first surface and a second surface opposite to the first surface. On the first surface of the pattern layer, recesses are arranged in a predetermined pattern. The shape on the second surface side of the pattern layer is not particularly limited. In order to improve the adhesion between the second surface side of the pattern layer and other members such as a substrate, the second surface of the pattern layer is preferably flat.

[0019] The first surface of the pattern layer has a first pattern region in which recesses are arranged in a predetermined pattern, and the predetermined pattern of the first pattern region has a first pitch. The entire surface of the first surface of the pattern layer may be the first pattern region. The first surface of the pattern layer may further have a region other than the first pattern region. For example, as shown in FIG. 1, the first surface of the pattern layer has a first' pattern region in which recesses are arranged in a predetermined pattern, and the predetermined pattern of the first' pattern region may have a first' pitch. In this case, the first' pitch and the first pitch are assumed to be different.

[0020] In this specification, the pitch of the recesses arranged in a predetermined pattern means the distance until the direction of the recesses rotates 180 degrees. P1 in FIG. 4(a) and P1 in FIG. 4(b) respectively indicate the pitch of the recesses arranged in a predetermined pattern. The "direction of the recesses" serving as a criterion for determining the pitch can be determined by the direction of the tangent line drawn on the planar shape of the recesses.

[0021] The first pattern region and the first' pattern region may form a predetermined pattern by the planar shape of a single recess as shown in FIG. 4(a). Further, the first pattern region of the pattern layer may form a predetermined pattern by the planar shape connecting a plurality of recesses as shown in FIG. 4(b). Both FIG. 4(a) and FIG. 4(b) form an arc-shaped pattern. When forming a predetermined pattern by the planar shape connecting a plurality of recesses as shown in FIG. 4(b), adjacent recesses may have a slight interval.

[0022] The optical element of the present disclosure preferably has the following first configuration. <First Configuration> The first pattern region of the pattern layer has a plurality of domains arranged in a first direction, and each of the plurality of domains has a plurality of recesses arranged in a second direction orthogonal to the first direction within each domain. The domains form a domain unit in which a predetermined number of domains are aggregated, and the predetermined pattern is formed by a planar shape connecting the recesses at one end in the first direction of the domain unit to the recesses at the other end.

[0023] The first configuration will be described with reference to FIG. 5. FIG. 5 is a plan view of the pattern layer in plan view. In FIG. 5, reference numerals 13a to 13e denote a plurality of domains arranged in the first direction. In FIG. 5, reference symbol A1 indicates the first direction, and reference symbol A2 indicates the second direction orthogonal to the first direction. In FIG. 5, the domains form a domain unit 13 in which a predetermined number of domains are aggregated. In FIG. 5, the number of domains constituting the domain unit is 5 in each case, but the number of domains constituting the domain unit is not limited to 5. In FIG. 5, the plurality of domains each have a plurality of recesses 11 arranged in a second direction orthogonal to the first direction within each domain.

[0024] The recesses of adjacent domains may be arranged with a gap as shown in FIG. 5, or may be arranged in contact with each other.

[0025] When having a first' pattern region in addition to the first pattern region, it is preferable to have the following first' configuration. <First' configuration> The first' pattern region of the pattern layer has a plurality of domains arranged in a first direction, and each of the plurality of domains has a plurality of recesses arranged in a second direction orthogonal to the first direction within each domain. The domains form a domain unit in which a predetermined number of domains are aggregated, and the predetermined pattern is formed by a planar shape connecting the recesses at one end in the first direction of the domain unit to the recesses at the other end.

[0026] The number of domains forming one domain unit is not particularly limited, but is preferably 3 or more and 179 or less, more preferably 4 or more and 150 or less, still more preferably 5 or more and 100 or less, and even more preferably 10 or more and 50 or less. By setting the number of domains forming the domain unit within the above range, it is possible to suppress a sharp change in the angle of the concave portion between adjacent domains, and it is easy to increase the length of each concave portion in the extending direction, so that the alignment property of the second liquid crystal layer can be more easily improved.

[0027] When the optical element of the present disclosure satisfies the first configuration, it preferably further has the following second configuration. <Second Configuration> The plurality of concave portions included in the same domain of the first pattern region have congruent or similar planar shapes of the concave portions.

[0028] When the optical element of the present disclosure satisfies the first' configuration, it preferably further has the following second' configuration. <Second' Configuration> The plurality of concave portions included in the same domain of the first' pattern region have congruent or similar planar shapes of the concave portions.

[0029] In this specification, "congruent" means that when the concave portion is moved in the second direction, the planar shape of the concave portion completely coincides. "Similar" means that when the concave portion is moved in the second direction, the coincidence rate of the area of the planar shape of the concave portion is 90% or more. The coincidence rate of the area is preferably 95% or more, more preferably 97% or more, and even more preferably 99% or more.

[0030] In the first pattern region of the optical element of the present disclosure, the concave portions are preferably arranged such that the direction of the concave portions changes stepwise along one direction in the plane. In FIGS. 4(a) and (b), the direction of the concave portions changes stepwise in the left-right direction of the drawing. Also, in FIG. 6, the directions of the three concave portions 11 change stepwise along the A1 direction in the figure. In this specification, it can be said that "the direction of the concave portion" = "the direction of the tangent line to the outer frame of the concave portion". In the first pattern region, the predetermined pattern formed by the concave portions varies depending on the function imparted by the optical element, and thus cannot be generally stated. As an embodiment of the predetermined pattern formed by the concave portions in the first pattern region, a circular or arc-shaped pattern can be mentioned. Arranging the concave portions in a circular or arc shape in the first pattern region means that the direction of the concave portions changes stepwise along one direction in the plane in the first pattern region.

[0031] When the direction of the concave portions changes stepwise along a predetermined direction in the plane in the first pattern region of the pattern layer, the direction of the liquid crystal molecules in the first liquid crystal layer in the region corresponding to the first pattern region can also change stepwise along the predetermined direction in the plane. Functions exhibited by the stepwise change in the direction of the liquid crystal molecules in the first liquid crystal layer along one direction in the plane include the following functions (X1) to (X2). (X1) When circularly polarized light is incident as incident light, a function of diffracting the incident light and inverting the phase of the incident light. (X2) When natural light or linearly polarized light is incident as incident light, a function of diffracting the incident light and separating it into right-circularly polarized light and left-circularly polarized light.

[0032] When the optical element of the present disclosure has a first' pattern region, in the first' pattern region, the concave portions are preferably arranged such that the direction of the concave portions changes stepwise along one direction in the plane.

[0033] In the first pattern region of the pattern layer, the first pitch cannot be generally stated because it varies depending on the intended optical characteristics. The upper limit of the first pitch is, for example, 10000 μm or less, preferably 1000 μm or less, more preferably 100 μm or less, and even more preferably 10 μm or less. In the optical element of the present disclosure, the upper limit of the first pitch is particularly preferably 5 μm or less (5000 nm or less). As the pitch of the pattern in the pattern layer becomes shorter, the liquid crystal molecules tend to be less likely to be aligned along the pattern. However, since the optical element of the present disclosure has a second liquid crystal layer in which the liquid crystal molecules are helically aligned in the thickness direction between the pattern layer and the first liquid crystal layer, even when the first pitch is 5000 nm or less, it is easy to improve the alignment property of the first liquid crystal layer. The lower limit of the first pitch is, for example, 100 nm or more, preferably 200 nm or more, and more preferably 300 nm or more. When the target wavelength of the diffracted light is in the visible light region and in cases other than reflective diffraction elements using cholesteric liquid crystal or the like as the liquid crystal of the first liquid crystal layer, the lower limit of the first pitch is preferably 400 nm or more.

[0034] When the optical element of the present disclosure has a first' pattern region, the embodiments of the range of the first' pitch are the same as the embodiments of the range of the first pitch described above. It should be noted that the first' pitch and the first pitch are different from each other.

[0035] In this specification, the conditions calculated or determined from the planar shape of the pattern layer such as the first pitch, the first' pitch, and the planar shape of the concave portion in plan view are calculated or determined from a photograph taken of the first surface of the pattern layer with a scanning electron microscope. The scanning electron microscope is preferably imaged under the following conditions. Examples of the scanning electron microscope include the product name "SU8000" of Hitachi High-Technologies Corporation. <Imaging conditions> ·Acceleration voltage: 5.0 kV ·Emission current: 5.0 μA ·Probe current: High ·Detector: SE(U) ·WD: 8 mm ·Condenser lens 1: 5.0 ·Condenser lens 2: 1.0 ·Tilt function of the material table: Enter tilt angle "0.0"

[0036] 《Concave part》 The planar shape of each concave part preferably satisfies the following (Y1) to (Y3). By satisfying the following (Y1) to (Y3), the pattern layer can be more easily peeled off from the shaping plate, so that the pattern layer can be more stably formed. Each concave part in Fig. 4 satisfies the following (Y1) to (Y3). (Y1) It has a first line and a second line which are a pair of parallel lines. (Y2) It has a line connecting the ends on the same side of the first line and the second line. (Y3) The length of the first line and the second line > the length of the line connecting the ends of (Y2)

[0037] The first line and the second line of the above (Y1) may be straight lines or curves such as arcs. The first line and the second line of the above (Y1) only need to be substantially parallel. Substantially parallel means that the angle formed by the first line and the second line is 3.0 degrees or less. The angle formed by the first line and the second line is preferably 1.0 degree or less, and more preferably 0.5 degree or less. The first line and the second line of the above (Y1) preferably have substantially equal lengths. Substantially equal lengths means that the ratio of the length of the first line to the length of the second line is 0.80 or more and 1.20 or less. The ratio is preferably 0.90 or more and 1.10 or less, and more preferably 0.95 or more and 1.05 or less.

[0038] The length of each concave part in the pitch direction is not particularly limited. The length of each concave part in the pitch direction is determined by the pitch length and the number of divisions of the concave part in the pitch direction. In the case of Fig. 4, the length of each concave part in the left-right direction corresponds to the length of each concave part in the pitch direction.

[0039] The width of each recess is not particularly limited. However, when the width of the recess is 1 nm or less, when the liquid crystal molecules aggregate and increase in size, it may be difficult for the liquid crystal molecules to enter the recess, and the alignment may deteriorate. Therefore, the size of the opening of the recess is preferably 1 nm or more. Note that even if the width of the deepest part of the recess is 1 nm or less, it is difficult to deteriorate the alignment property of the liquid crystal molecules. When the width of the recess is 2000 nm or more, the liquid crystal alignment regulating force hardly works. Therefore, the width of the recess is preferably 1 nm or more and 2000 nm or less, more preferably 5 nm or more and 1000 nm or less, and even more preferably 15 nm or more and 500 nm or less. In the case of FIG. 4, the length of the line connecting the ends of (Y2) corresponds to the width of each recess.

[0040] The depth of each recess is not particularly limited, but is preferably 2 nm or more and 200 nm or less, more preferably 10 nm or more and 100 nm or less, and even more preferably 15 nm or more and 50 nm or less. In this specification, the depth of the recess means the average value of 18 locations excluding the minimum value and the maximum value from the depths of 20 arbitrarily extracted recesses. By setting the depth of the recess to 2 nm or more, the second liquid crystal layer can be more easily aligned along the recess. By setting the depth of the recess to 200 nm or less, the pattern layer can be more easily peeled off from the shaping plate, so that the pattern layer can be more stably formed.

[0041] The depth of each recess shall be calculated from a photograph obtained by imaging a vertical cross-section of the optical element with a scanning electron microscope. The depth of each recess shall be the maximum value of the depths of the individual recesses. The imaging conditions of the scanning electron microscope are preferably imaging under the following conditions. Examples of the scanning electron microscope include the product name "SU8000" of Hitachi High-Technologies Corporation. <Imaging Conditions> ·Acceleration voltage: 5.0 kV ·Emission current: 5.0 μA ·Probe current: High ·Detector: SE(U) ·WD: 8 mm ·Condenser lens 1: 5.0 · Condenser lens 2:1.0 · Tilt function of the material stage: Enter tilt angle "0.0"

[0042] The depth of each recess is preferably substantially the same. Substantially the same depth means that D1 / D2 calculated by the following (1) and (2) is 1.3 or less. D1 / D2 is preferably 1.2 or less, more preferably 1.1 or less. (1) Regarding the depths of 18 recesses obtained by excluding the minimum value and the maximum value from the depths of 20 randomly selected recesses, let the depth of the deepest recess be D1 and the depth of the shallowest recess be D2. (2) Calculate D1 / D2.

[0043] The pattern layer may have a thickness below the recess. In FIG. 1, reference numeral t1 indicates the thickness of the pattern layer below the recess. The average value of the thickness below the recess is preferably 0.5 μm or more and 20 μm or less, more preferably 1 μm or more and 15 μm or less, still more preferably 2 μm or more and 7 μm or less. By setting t1 to 0.5 μm or more, it is easy to control the curing when forming the pattern layer, and it is easy to coat the second liquid crystal layer on the pattern layer. By setting t1 to 20 μm or less, it is easy to suppress the occurrence of curl. The average value of the thickness below the recess means the average value of the thicknesses of 18 locations obtained by excluding the maximum value and the minimum value from the thicknesses of 20 arbitrary locations in the cross-sectional photograph of the optical element.

[0044] 《Material of the pattern layer》 The pattern layer preferably contains a resin. The ratio of the resin in the pattern layer is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more based on the total solid content of the pattern layer.

[0045] ― Resin ― Examples of the resin of the pattern layer include thermoplastic resins and cured products of curable resin compositions. Among these, the cured product of the curable resin composition is preferred in order to improve the strength. The proportion of the cured product of the curable resin composition is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 90% by mass or more based on the total solid content of the pattern layer.

[0046] Examples of the cured product of the curable resin composition include cured products of thermosetting resin compositions and cured products of radiation-curable resin compositions. Among these, the cured product of the radiation-curable resin composition is preferred.

[0047] The radiation-curable resin composition is a composition containing a compound having a radiation-curable functional group (hereinafter also referred to as "radiation-curable compound"). Examples of the radiation-curable functional group include ethylenically unsaturated bond groups such as (meth)acryloyl group, vinyl group, allyl group, and epoxy group, oxetanyl group, etc. As the radiation-curable resin, a compound having an ethylenically unsaturated bond group is preferred. Also, from the viewpoint of suppressing damage to the pattern layer during the process of manufacturing an optical element, as the radiation-curable resin, a compound having two or more ethylenically unsaturated bond groups is more preferred. Among them, a polyfunctional (meth)acrylate-based compound having two or more ethylenically unsaturated bond groups is still more preferred. As the polyfunctional (meth)acrylate-based compound, either a monomer or an oligomer can be used. The radiation refers to those having energy quanta capable of polymerizing or crosslinking molecules among electromagnetic waves or charged particle beams. Usually, ultraviolet rays (UV) or electron beams (EB) are used, but other electromagnetic waves such as X-rays, γ-rays, and charged particle beams such as α-rays and ion beams can also be used.

[0048] Among polyfunctional (meth)acrylate compounds, examples of bifunctional (meth)acrylate monomers include ethylene glycol di(meth)acrylate, bisphenol A tetraethoxydiacrylate, bisphenol A tetrapropoxydiacrylate, 1,6 - hexanediol diacrylate, and the like. Examples of trifunctional or higher (meth)acrylate monomers include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol tetra(meth)acrylate, isocyanuric acid - modified tri(meth)acrylate, and the like. The above (meth)acrylate monomers may be those in which a part of the molecular skeleton is modified, and those modified with ethylene oxide, propylene oxide, caprolactone, isocyanuric acid, alkyl, cyclic alkyl, aromatic, bisphenol, etc. can also be used.

[0049] Examples of polyfunctional (meth)acrylate oligomers include acrylate - based polymers such as urethane (meth)acrylate, epoxy (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, and the like. Urethane (meth)acrylate is obtained, for example, by the reaction of a polyhydric alcohol, an organic diisocyanate, and hydroxy(meth)acrylate. Preferred epoxy (meth)acrylates are (meth)acrylates obtained by reacting trifunctional or higher aromatic epoxy resins, alicyclic epoxy resins, aliphatic epoxy resins, etc. with (meth)acrylic acid, (meth)acrylates obtained by reacting bifunctional or higher aromatic epoxy resins, alicyclic epoxy resins, aliphatic epoxy resins, etc. with polybasic acids and (meth)acrylic acid, and (meth)acrylates obtained by reacting bifunctional or higher aromatic epoxy resins, alicyclic epoxy resins, aliphatic epoxy resins, etc. with phenols and (meth)acrylic acid. The above-mentioned radiation-curable resin can be used alone or in combination of two or more kinds. When the difference between the average refractive index of the resin in the pattern layer and the average refractive index of the liquid crystal in the second liquid crystal layer increases, the interface reflection increases. Therefore, the difference between the average refractive index of the resin in the pattern layer and the average refractive index of the liquid crystal in the second liquid crystal layer is preferably 0.97 or more and 1.03 or less, and more preferably 0.99 or more and 1.01 or less.

[0050] When the radiation-curable resin is an ultraviolet-curable resin, the coating liquid for forming the resin layer preferably contains additives such as a photopolymerization initiator and a photopolymerization accelerator. Examples of the photopolymerization initiator include one or more selected from acetophenone, benzophenone, α-hydroxyalkylphenone, Michler's ketone, benzoin, benzyldimethylketal, benzoyl benzoate, α-acyl oxime ester, thioxanthones, and the like. In addition, the photopolymerization accelerator can reduce the polymerization inhibition by air during curing and increase the curing rate. Examples thereof include one or more selected from isoamyl p-dimethylaminobenzoate, ethyl p-dimethylaminobenzoate, and the like.

[0051] The pattern layer may contain additives such as a refractive index adjuster, an antioxidant, an ultraviolet absorber, a light stabilizer, and an antistatic agent within a range that does not inhibit the effects of the present disclosure.

[0052] 《Method for forming pattern layer》 The pattern layer can be formed, for example, by shaping the pattern layer before shaping using a plate having a shape complementary to the surface shape of the first surface. More specifically, the pattern layer can be formed, for example, by the following steps 1 and 2.

[0053] Step 1: A step of applying a coating liquid for forming a pattern layer containing a resin on a substrate to form a layer containing the resin. Step 2: A step of shaping the layer containing the resin using a plate having a shape complementary to the surface shape of the first surface of the pattern layer.

[0054] When the coating liquid for forming the pattern layer contains a solvent, it is preferable to dry the solvent in Step 1.

[0055] When a curable resin is used as the resin, it is preferable to use, as the coating liquid for forming the pattern layer in Step 1, a coating liquid for forming a pattern layer containing a curable resin composition. That is, when a curable resin is used as the resin, it is preferable that the curable resin in the coating liquid in Step 1 is in an uncured state. When using, as the coating liquid for forming the pattern layer in Step 1, a coating liquid for forming a pattern layer containing a radiation-curable resin composition, it is preferable to irradiate radiation simultaneously with shaping in Step 2 to cure the radiation-curable resin composition contained in the shaped layer.

[0056] When there is another layer such as a primer layer between the substrate and the pattern layer, it is preferable to perform a step of forming another layer on the substrate before Step 1.

[0057] The plate used in Step 2 can be produced by general means such as laser lithography, electron beam lithography, and FIB (Focused Ion Beam). The concavo-convex shape formed on the surface of the plate can be designed with general simulation software. Further, it is also preferable to produce a large number of replicated plates of the plate produced by the above-described means, arrange the large number of replicated plates side by side, and use them as a multi-sided plate. Replication of the plate can be carried out by general means such as electroforming. Examples of the shape of the plate include a flat plate shape and a cylindrical shape. A cylindrical plate can be processed in a roll-to-roll manner and is preferable in terms of excellent productivity.

[0058] <Second liquid crystal layer> The optical element of the present disclosure needs to have a second liquid crystal layer in which liquid crystal molecules are helically aligned in the thickness direction between the pattern layer and the first liquid crystal layer. The second liquid crystal layer needs to have a thickness of 50 nm or more.

[0059] As described above, liquid crystal molecules that are helically oriented in the thickness direction can be easily and rapidly oriented when forming the liquid crystal layer. And a liquid crystal layer in which liquid crystal molecules are helically oriented in the thickness direction can easily improve the alignment property of another liquid crystal layer formed on the liquid crystal layer. Therefore, the optical element of the present disclosure has a second liquid crystal layer in which liquid crystal molecules are helically oriented in the thickness direction between the pattern layer and the first liquid crystal layer, so that the alignment property of the liquid crystal molecules in the first liquid crystal layer can be improved. However, when the thickness of the second liquid crystal layer is thin, there is a tendency that liquid crystal molecules are less likely to be helically oriented in the thickness direction. For this reason, the thickness of the second liquid crystal layer needs to be 50 nm or more.

[0060] The second liquid crystal layer has a layered structure in which a large number of rod-shaped molecules overlap. In each layer, the respective liquid crystal molecules are arranged in a certain direction, and the mutually adjacent layers are stacked such that the arrangement directions of the liquid crystal molecules are helically oriented. The twist direction of the helix has a right direction and a left direction, and can be selected according to the purpose. As described above, the second liquid crystal layer has a layered structure in which a large number of rod-shaped molecules overlap. Among the multiple layers constituting the second liquid crystal layer, the liquid crystal molecules in the layer located on the pattern layer side are arranged along the direction of the recess. Also, the period of the helix (the length in the thickness direction until the twist angle of the helix changes by 360 degrees) is substantially the same at any location in the plane of the second liquid crystal layer. For this reason, an alignment pattern having a pitch corresponding to the pitch of the recesses of the pattern layer is formed in the plane direction in each layer constituting the second liquid crystal layer. The alignment pitch of the second liquid crystal layer means the length until the arrangement direction of the liquid crystal molecules rotates 180 degrees in the plane direction. An alignment pattern having a pitch corresponding to the pitch of the recesses of the pattern layer is formed in the second liquid crystal layer. For this reason, the first liquid crystal layer disposed on the second liquid crystal layer is likely to be aligned following the alignment pattern of the second liquid crystal layer. Also, since the alignment pitch of the first liquid crystal layer follows the alignment pitch of the second liquid crystal layer, it follows the pitch of the pattern. FIG. 7 is an image diagram of the alignment state of liquid crystal molecules in the second liquid crystal layer 20. In FIG. 7, there is a layered structure in which a large number of rod-shaped molecules overlap. Within each layer, the respective liquid crystal molecules are arranged in a certain direction, and the mutually adjacent layers are stacked such that the alignment directions of the liquid crystal molecules are helically oriented. In FIG. 7, reference sign P indicates the length (the alignment pitch of the second liquid crystal layer) until the alignment direction of the liquid crystal molecules rotates 180 degrees in the plane direction. In addition, in FIG. 7, the unevenness on the pattern layer side of the second liquid crystal layer is omitted.

[0061] The second liquid crystal layer can be formed, for example, from a liquid crystal composition in which a chiral agent is added to a nematic liquid crystal compound. The period of the helix of the second liquid crystal layer can be adjusted, for example, by the type of chiral agent and the concentration of the chiral agent. As the chiral agent and the rod-shaped liquid crystal compound constituting the nematic liquid crystal compound, general-purpose materials can be used.

[0062] Since the twisting direction or the helical pitch of the helix induced by the compound is different for different chiral agents, it may be selected according to the purpose. The chiral agent is not particularly limited, and examples include general-purpose compounds such as isosorbide, isomannide derivatives, binaphthyl, helicene, and paracyclophane.

[0063] Examples of the rod-shaped liquid crystal compound include the same ones as those exemplified for the first liquid crystal layer.

[0064] The second liquid crystal layer can be formed, for example, by applying a coating liquid for forming the second liquid crystal layer containing a liquid crystal compound onto the first surface of the pattern layer, and then drying and curing it as necessary.

[0065] The second liquid crystal layer is preferably formed over the entire first surface of the pattern layer. That is, it is preferable to form the second liquid crystal layer also at locations on the first surface of the pattern layer that do not have recesses (FIG. 1).

[0066] The second liquid crystal layer is required to have a thickness of 50 nm or more. The second liquid crystal layer preferably has a thickness of 75 nm or more, and more preferably 100 nm or more. As the number of repetitions of the spiral period in the second liquid crystal layer increases, the regular structure within the layer becomes more likely to collapse. For this reason, if the thickness of the second liquid crystal layer is too thick, the in-plane orientation may be disrupted. Therefore, the second liquid crystal layer preferably has a thickness of 1000 nm or less, more preferably 950 nm or less, and even more preferably 900 nm or less. As described later, when the second liquid crystal layer has selective reflectivity, it is preferable to adjust the thickness according to the selective wavelength.

[0067] In the constituent elements shown in this specification, when a plurality of options for the upper limit and a plurality of options for the lower limit of a numerical value are shown respectively, it is assumed that embodiments within the range combined by selecting one from the options for the upper limit and one from the options for the lower limit are described. For example, as embodiments of the thickness range of the second liquid crystal layer described above, there are 50 nm or more and 1000 nm or less, 50 nm or more and 950 nm or less, 50 nm or more and 900 nm or less, 75 nm or more and 1000 nm or less, 75 nm or more and 950 nm or less, 75 nm or more and 900 nm or less, 100 nm or more and 1000 nm or less, 100 nm or more and 950 nm or less, 100 nm or more and 900 nm or less.

[0068] In this specification, the thickness of the second liquid crystal layer is calculated by the following (1) to (3). (1) At locations corresponding to the locations having the concave portions of the pattern layer, the thickness of the second liquid crystal layer is measured at arbitrarily 10 locations. The thickness is measured from the cross-sectional photograph of the optical element. The average value of 8 locations excluding the minimum value and the maximum value is taken as the thickness of the second liquid crystal layer at the location having the concave portion. (2) At locations corresponding to the locations having no concave portions of the pattern layer, the thickness of the second liquid crystal layer is measured at arbitrarily 10 locations. The thickness is measured from the cross-sectional photograph of the optical element. The average value of 8 locations excluding the minimum value and the maximum value is taken as the thickness of the second liquid crystal layer at the location having no concave portion. (3) The average value of the thickness of the second liquid crystal layer at the location with the recess calculated in (1) above and the thickness of the second liquid crystal layer at the location without the recess calculated in (2) above is taken as the thickness of the second liquid crystal layer.

[0069] It is preferable that the second liquid crystal layer satisfies the following third configuration. <Third Configuration> The second liquid crystal layer has a twist angle of the helix of 360 degrees or more and has selective reflectivity that reflects circularly polarized light in a specific wavelength range.

[0070] The fact that the twist angle of the helix is 360 degrees or more means that the second liquid crystal layer has a predetermined thickness. Therefore, by having the third configuration, it is easy to improve the alignment property of the second liquid crystal layer. Also, due to the twist angle of the helix being 360 degrees or more, selective reflectivity that reflects specific circularly polarized light in a specific wavelength range can be imparted to the second liquid crystal layer.

[0071] Assuming that the selective wavelength is λ (nm), the helical pitch width at the selective wavelength λ is P (nm), the average refractive index of the liquid crystal layer is n, and the thickness is d (nm), the twist angle of the helix (degrees) can be calculated by the following formula (1). In the following formula (1), P = λ / n. The helical pitch width P may be calculated from the pitch of the shading when observing the cross section with STEM. Twist angle = d / P × 360 (1)

[0072] The average refractive index of the liquid crystal layer can be measured by the following methods C1 to C3 using, for example, the formula for the reflectivity of normal incidence by Fresnel. However, since diffraction occurs in the region having an alignment pitch in the plane direction, the refractive index cannot be measured. Therefore, a measurement sample having no alignment pitch in the plane direction is prepared, and the average refractive index of the liquid crystal layer is measured using the sample. C1: Light inclined 5 degrees from the perpendicular is incident on the liquid crystal layer, and the reflectivity is measured at an angle in the specular reflection direction. The incident light is linearly polarized light parallel to the slow axis of the second liquid crystal layer. Then, from the reflectivity in the slow axis direction obtained, the refractive index (Nx*) is calculated using the following formula. Reflectivity in the slow axis direction = ((1 - Nx*) / (1 + Nx*)) 2 C2: For the liquid crystal layer, light inclined 5 degrees from the perpendicular is incident, and the reflectivity is measured at an angle in the specular reflection direction. The incident light is linearly polarized light parallel to the slow axis of the second liquid crystal layer. Then, from the obtained reflectivity in the slow axis direction, the refractive index (Ny*) is calculated using the following formula. Reflectivity in the slow axis direction = ((1 - Ny*) / (1 + Ny*)) 2 C3: Adjust the values of the three-dimensional refractive index (Nx, Ny, Nz) calculated from a phase difference measuring device (product name: "KOBRA" manufactured by Oji Scientific Instruments Co., Ltd.) so that they match the in-plane refractive indices Nx* and Ny* of C1 and C2. Then, take "(Nx + Ny + Nz) / 3" as the average refractive index.

[0073] When the third configuration is satisfied, it is preferable to further satisfy the following third-1 configuration. <Third-1 configuration> The wavelength selectively reflected by the second liquid crystal layer is 380 nm or less.

[0074] By satisfying the third-1 configuration, it is easy to suppress the imparting of color to the optical element. In the third-1 configuration, it is more preferable that the wavelength selectively reflected by the second liquid crystal layer is 360 nm or less, and even more preferably 340 nm or less. In the third-1 configuration, it is preferable that the lower limit of the wavelength selectively reflected by the second liquid crystal layer is 150 nm or more.

[0075] When the third configuration is satisfied, it is preferable to further satisfy the following third-2 configuration. <Third-2 configuration> The wavelength selectively reflected by the second liquid crystal layer is 850 nm or more and 5000 nm or less.

[0076] In the third-2 configuration, by setting the wavelength selectively reflected by the second liquid crystal layer to 850 nm or more, it is easy to suppress the imparting of color to the optical element. As the wavelength of selective reflection increases, the length until the twist angle of the helix rotates 360 degrees becomes longer. Therefore, it becomes difficult to maintain the state of S2 in FIG. 3, and the alignment stability of the liquid crystal molecules tends to decrease. For this reason, in the configuration of 3-2, by setting the wavelength selectively reflected by the second liquid crystal layer to 5000 nm or less, it is easier to improve the alignment property of the second liquid crystal layer. In the configuration of 3-2, the lower limit of the wavelength selectively reflected by the second liquid crystal layer is more preferably 870 nm or more, and even more preferably 900 nm or more. In the configuration of 3-2, the upper limit of the wavelength selectively reflected by the second liquid crystal layer is more preferably 4500 nm or less, even more preferably 4000 nm or less, and even more preferably 3500 nm or less.

[0077] As described above, the more the number of repetitions of the helix period increases, the more likely the regular structure in the second liquid crystal layer is to collapse. Also, the shorter the selective wavelength of the second liquid crystal layer, the shorter the helix period, and the longer the selective wavelength of the second liquid crystal layer, the longer the helix period. For this reason, when the second liquid crystal layer satisfies the third configuration, it is preferable to adjust the thickness of the second liquid crystal layer according to the selective wavelength. For example, it is preferable to satisfy the following configuration of 3-3 or 3-4. <Configuration of 3-3> The wavelength selectively reflected by the second liquid crystal layer is 250 nm or less, and the thickness of the second liquid crystal layer is 50 nm or more and 200 nm or less. <Configuration of 3-4> The wavelength selectively reflected by the second liquid crystal layer is 850 nm or more and 1000 nm or less, and the thickness of the second liquid crystal layer is 50 nm or more and 500 nm or less.

[0078] The interface between the second liquid crystal layer and the first liquid crystal layer can be determined, for example, by the following operations (B1) to (B4). The degree of dyeing of the first liquid crystal layer and the second liquid crystal layer is different. Therefore, the interface with different degrees of dyeing can be determined as the interface between the second liquid crystal layer and the first liquid crystal layer. In addition, the degree to which the sample is dyed also varies depending on the direction of the alignment of the liquid crystal molecules. Therefore, by the operations (B1) to (B4) below, the second pitch, etc. of the first liquid crystal layer can also be determined. (B1) Prepare a cut sample by cutting the optical element into strip shapes. Embed the cut sample with a thermosetting resin to prepare an embedded sample. (B2) Use a microtome to cut the embedded sample to prepare an ultra-thin section sample. The cutting described above is performed so that a vertical cross-section in the thickness direction of the optical element is exposed. The conditions of the microtome are as follows: use a diamond knife as the knife and set the set section thickness to 80 nm. (B3) Stain the ultra-thin section sample by immersing it in an osmium tetroxide solution for 30 minutes and a ruthenium tetroxide solution for 5 minutes. (B4) Observe the stained sample by STEM under the following conditions. <STEM conditions> · Equipment (manufactured by Hitachi High-Technologies Corporation, product number: S-4800 TYPE1) · Acceleration voltage: 30.0 kv · Emission current: 10 μA · W.D: 8 mm · Detector: TE

[0079] <First liquid crystal layer> In the optical element of the present disclosure, the first liquid crystal layer is formed on the second liquid crystal layer. The first liquid crystal layer can be formed, for example, by applying a coating liquid for forming the first liquid crystal layer containing a liquid crystal compound on the second liquid crystal layer and then drying and curing it as necessary. The first liquid crystal layer is preferably formed over the entire surface on the second liquid crystal layer.

[0080] In the optical element of the present disclosure, the first liquid crystal layer needs to be disposed on the first surface side of the pattern layer and have a region in which liquid crystal molecules are aligned with a second pitch in the plane. Further, in the optical element of the present disclosure, the first pitch of the pattern layer and the second pitch of the first liquid crystal layer need to be substantially the same. As described above, an alignment pattern having a pitch corresponding to the pitch of the concave portions of the pattern layer is formed in the second liquid crystal layer. Therefore, the first liquid crystal layer disposed on the second liquid crystal layer is likely to be aligned following the alignment pattern of the second liquid crystal layer. Further, since the alignment pitch of the first liquid crystal layer follows the alignment pitch of the second liquid crystal layer, it follows the pitch of the pattern. Therefore, in the optical element of the present disclosure, the first liquid crystal layer comes to have a region in which liquid crystal molecules are aligned with a second pitch in the plane, and further, the first pitch of the pattern layer and the second pitch of the first liquid crystal layer are substantially the same.

[0081] In this specification, the alignment pitch of the liquid crystal molecules in the first liquid crystal layer such as the second pitch and the second' pitch means the length until the alignment direction of the liquid crystal molecules rotates 180 degrees in the plane direction.

[0082] In this specification, the fact that the first pitch of the pattern layer and the second pitch of the first liquid crystal layer are substantially the same means that the first pitch / second pitch is 0.97 or more and 1.03 or less. The first pitch / second pitch is preferably 0.98 or more and 1.02 or less, and more preferably 0.99 or more and 1.01 or less. In this specification, the fact that the first' pitch of the pattern layer and the second' pitch of the first liquid crystal layer are substantially the same means that the first' pitch / second' pitch is 0.97 or more and 1.03 or less. The first' pitch / second' pitch is preferably 0.98 or more and 1.02 or less, and more preferably 0.99 or more and 1.01 or less.

[0083] In FIG. 1, the first pitch P1 of the pattern layer and the second pitch P2 of the first liquid crystal layer are displaced in the left-right direction of FIG. 1. Thus, the first pitch P1 of the pattern layer and the second pitch P2 of the first liquid crystal layer may be displaced when viewed in plan view. Also, the first pitch P1 of the pattern layer and the second pitch P2 of the first liquid crystal layer may coincide without displacement when viewed in plan view. In FIG. 1, the first' pitch P1' of the pattern layer and the second' pitch P2' of the first liquid crystal layer are displaced in the left-right direction of FIG. 1. Thus, the first' pitch P1' of the pattern layer and the second' pitch P2' of the first liquid crystal layer may be displaced when viewed in plan view. Also, the first' pitch P1' of the pattern layer and the second' pitch P2' of the first liquid crystal layer may coincide without displacement when viewed in plan view.

[0084] Since the optical element of the present disclosure has a second liquid crystal layer between the pattern layer and the first liquid crystal layer, it is easy to improve the alignment property of the first liquid crystal layer. The alignment property of the first liquid crystal layer can be evaluated, for example, by the method described in the examples.

[0085] Examples of the liquid crystal compound of the first liquid crystal layer include one or more selected from rod-shaped liquid crystal compounds such as nematic liquid crystal compounds and smectic liquid crystal compounds, cholesteric liquid crystal compounds, and discotic liquid crystal compounds (disc-shaped liquid crystal compounds). The first liquid crystal layer may further contain a chiral agent in addition to the liquid crystal compound. For example, a liquid crystal layer containing a nematic liquid crystal compound and a chiral agent has an alignment in which the direction of the molecules of the liquid crystal compound rotates when the liquid crystal layer is viewed in plan view. However, it is not necessary for the direction of the molecules of the liquid crystal compound to rotate 360 degrees, and a rotation of less than 360 degrees may be sufficient.

[0086] The first liquid crystal layer is preferably a homogeneously aligned liquid crystal layer in order to easily impart a predetermined in-plane retardation to the first liquid crystal layer. For this reason, a rod-shaped liquid crystal compound is preferable as the liquid crystal compound of the first liquid crystal layer.

[0087] The liquid crystal compound is preferably a rod-shaped liquid crystal compound. The rod-shaped liquid crystal compound is not particularly limited, and examples thereof include the compounds shown in the following (1) to (28).

[0088] [Chemical formula]

[0089] [Chemical formula]

[0090] [Chemical formula]

[0091] [Chemical formula]

[0092] Among the liquid crystal compounds, a polymerizable rod-shaped liquid crystal material is preferred. Examples of the polymerizable functional group of the polymerizable rod-shaped liquid crystal material include those that polymerize by the action of ionizing radiation such as ultraviolet rays and electron beams, or heat. Specific examples include radical polymerizable functional groups. Examples of the radical polymerizable functional group include a functional group having at least one addition-polymerizable ethylenically unsaturated double bond, and more specifically, a vinyl group, an acrylate group (a general term including an acryloyl group, a methacryloyl group, an acryloyloxy group, and a methacryloyloxy group), with or without a substituent, and the like.

[0093] The first liquid crystal layer may have positive wavelength dispersibility or negative wavelength dispersion. Negative wavelength dispersibility is a characteristic in which the retardation imparted to the transmitted light increases as the wavelength of the transmitted light becomes longer. Positive wavelength dispersibility is a characteristic in which the retardation imparted to the transmitted light decreases as the wavelength of the transmitted light becomes longer. In this specification, when the in-plane retardation at a wavelength of 450 nm is defined as Re450 and the in-plane retardation at a wavelength of 550 nm is defined as Re550, the characteristic where Re450 < Re550 is referred to as negative wavelength dispersibility. In this specification, the characteristic where Re450 > Re550 is referred to as positive wavelength dispersibility.

[0094] The birefringence of the liquid crystal in the first liquid crystal layer is preferably 0.10 or more and 0.30 or less, and more preferably 0.15 or more and 0.26 or less. The larger the birefringence of the liquid crystal, the more preferable it is because the same optical performance can be obtained even if the thickness of the liquid crystal layer is reduced. However, as the birefringence of the liquid crystal increases, it is necessary to add a unit that is vulnerable to ultraviolet light, such as an aromatic ring like a benzene ring, to the liquid crystal molecular structure. For this reason, the birefringence of the liquid crystal in the first liquid crystal layer is preferably 0.30 or less. The birefringence of the liquid crystal can be calculated by dividing the in-plane retardation measured in an area without a pattern pitch by the thickness. The in-plane retardation can be measured, for example, with "Model No.: KOBRA-WR" manufactured by Oji Scientific Instruments Co., Ltd., and the thickness can be measured from a cross-sectional SEM.

[0095] The optical element of the present disclosure preferably has the following fourth configuration. <Fourth Configuration> The first surface further has a first' pattern region in which recesses are arranged in a predetermined pattern. The predetermined pattern of the first' pattern region has a first' pitch, and the first' pitch is different from the first pitch. The first liquid crystal layer further has a region in which liquid crystal molecules are aligned with a second' pitch in the plane, and the second' pitch is different from the second pitch. The first' pitch of the pattern layer and the second' pitch of the first liquid crystal layer are substantially the same.

[0096] Liquid crystal layers with different pitches can exhibit different optical properties. Therefore, by having the fourth configuration, the optical element can exhibit different optical properties in the plane. For example, by having the fourth configuration, the optical element can change the angle of diffracted light in the plane.

[0097] <Substrate> The optical element of the present disclosure may have a substrate.

[0098] As the material constituting the substrate, various materials can be used, but materials with good mechanical properties, optical properties, stability, and processability are preferred. Such materials include polymer resins having an alicyclic structure, methacrylic resins, polycarbonate resins, polystyrene resins, acrylonitrile-styrene copolymers, methyl methacrylate-styrene copolymers, ABS resins, polyethersulfone, triacetyl cellulose, polyethylene terephthalate, epoxy acrylate, urethane acrylate, etc.; resins; glass; etc. Resins are preferred. That is, the substrate is preferably a resin substrate. The in-plane retardation of the substrate is preferably 20 nm or less, more preferably 5 nm or less, still more preferably 3 nm or less, even more preferably 1 nm or less, and most preferably 0 nm. In this specification, the wavelength of light serving as the reference for refractive index and retardation is 550 nm unless otherwise specified.

[0099] The thickness of the substrate can be appropriately adjusted within the range of 5 μm or more and 1000 μm or less. The thickness of the substrate can be measured with a film thickness measuring instrument. Examples of the film thickness measuring instrument include Mitutoyo's Digimatic standard outside micrometer (product number: MDC-25SX). The thickness of the substrate may be the average value obtained by measuring any 10 points and falling within the above numerical values.

[0100] The substrate preferably has a total light transmittance of 70% or more, more preferably 80% or more, and still more preferably 85% or more in accordance with JIS K7361-1:1997. The substrate preferably has a haze of 10% or less, more preferably 5% or less, and even more preferably 3% or less in accordance with JIS K7136:2000.

[0101] In order to suppress the refraction of light at the interface between the substrate and the pattern layer, it is preferable that the refractive index of the pattern layer and the refractive index of the substrate be close in value. Specifically, the refractive index of the pattern layer / the refractive index of the substrate is preferably 0.97 or more and 1.03 or less, more preferably 0.99 or more and 1.01 or less.

[0102] <Retardation> The optical element preferably has an average value of the in-plane retardation within a predetermined range. When the wavelength to be controlled is λ [nm], the in-plane retardation of the optical element is preferably (λ / 2) × 0.95 or more and (λ / 2) × 1.05 or less, preferably (λ / 2) × 0.97 or more and (λ / 2) × 1.03 or less, and more preferably (λ / 2) × 0.99 or more and (λ / 2) × 1.01 or less. The retardation of the optical element can be adjusted by the first liquid crystal layer alone or by the first liquid crystal layer and the second liquid crystal layer. By setting the average value of the in-plane retardation of the optical element within the above range, when the optical element is used as a diffractive optical element, for example, the following actions can be exhibited. (1) When circularly polarized light is incident on the diffractive optical element, the light can be diffracted and the phase of the light can be inverted. (2) When natural light or linearly polarized light is incident on the diffractive optical element, the light can be diffracted and polarized and separated into right-circularly polarized light and left-circularly polarized light.

[0103] The in-plane retardation of the optical element means the average value of five in-plane retardations excluding the maximum value and the minimum value from any ten in-plane retardations. Examples of the measuring device for the in-plane retardation include the product named "AxoStep" manufactured by AXOMETRICS and the two-dimensional birefringence evaluation system (product name: WPA-Micro) of Photonic Lattice. The former product is suitable for measuring a wide area, and the latter product is suitable for measuring a narrow area.

[0104] In the second liquid crystal layer, since the liquid crystal molecules are helically aligned in the thickness direction, the in-plane retardation becomes small. In particular, when the twist angle is 360 degrees or more, the second liquid crystal layer substantially has no in-plane retardation. Therefore, it is preferable to adjust the in-plane retardation of the optical element with the first liquid crystal layer. The in-plane retardation of the first liquid crystal layer is preferably, for example, an in-plane retardation of half of the incident light wavelength in order to obtain diffracted light. For example, an in-plane retardation of 266 nm is required to generate diffracted light with respect to a green laser of 532 nm. When part or all of the first liquid crystal layer is twisted by a chiral agent or the like, it is difficult to measure with a normal measuring device. When at least part of the liquid crystal layer is twisted, the twist angle and the in-plane retardation can be calculated from the total thickness calculated from a cross-sectional SEM and the Mueller matrix calculated from the product name "AXOSCAN" manufactured by AXOMETRICS. However, even with the above-described method, it cannot be measured in an area having an alignment pitch in the plane direction. Therefore, a measurement sample having no alignment pitch in the plane direction is prepared, and the in-plane retardation is measured using the sample. The in-plane retardation of the first liquid crystal layer cannot be generally stated because it varies depending on the wavelength that controls diffraction. In order to control a wavelength equal to or longer than visible light, the in-plane retardation of the first liquid crystal layer is preferably 200 nm or more. In order to control a wavelength equal to or longer than infrared light, the in-plane retardation of the first liquid crystal layer is preferably 400 nm or more, more preferably 1000 nm or more, and still more preferably 1500 nm or more. The upper limit of the in-plane retardation of the first liquid crystal layer is about 5000 nm. In the case of applications that do not require diffraction, since it is not necessary to have a retardation value of half of the incident light wavelength, the in-plane retardation of the first liquid crystal layer can be changed according to the design. The in-plane retardation of the second liquid crystal layer is preferably substantially 0 nm. In this specification, "the in-plane retardation is substantially 0 nm" means that the in-plane retardation is 10 nm or less, preferably 5 nm or less, more preferably 1 nm or less, and most preferably 0 nm. However, when designing the wavelength of selective reflection to be 850 nm or more and 5000 nm or less, since it is necessary to increase the thickness of the liquid crystal layer in order to make the in-plane retardation of the second liquid crystal layer 0 nm, the liquid crystal alignment is likely to deteriorate. Therefore, when designing the wavelength of selective reflection to be 850 nm or more and 5000 nm or less, it is preferable that the in-plane retardation of the second liquid crystal layer is not 0 nm. On the other hand, when the wavelength of selective reflection of the second liquid crystal layer is less than 850 nm, the in-plane retardation of the second liquid crystal layer is preferably substantially 0 nm.

[0105] When the in-plane retardation of the first liquid crystal layer is defined as λ1 [nm] and the wavelength selectively reflected by the second liquid crystal layer is defined as λ2 [nm], the optical element of the present disclosure preferably satisfies the following formula (2). 2λ1≠λ2 (2)

[0106] By satisfying the above formula (2), the amount of light of the wavelength controlled by the first liquid crystal layer can be increased. In order to more easily exhibit the above-described effects, the absolute value of the difference between 2λ1 and λ2 is preferably 50 nm or more, more preferably 100 nm or more, and even more preferably 150 nm or more.

[0107] <Use> The optical element of the present disclosure can be used, for example, as a diffractive optical element. Further, the optical element of the present disclosure can also be used as a member of a light control device. The light transmitted through the diffractive optical element can be adjusted within a range of a predetermined diffraction angle. Therefore, for example, by using a diffractive optical element, the irradiation range of light can be widened or narrowed. Further, by causing the light transmitted through the diffractive optical element to interfere with each other, the actions of a lens, a prism, and the like can also be caused. Due to the above-described operation, the diffractive optical element can be used, for example, as a member of devices such as cross-reality, optical sensors, and laser projectors.

[0108] When the alignment pitch of the liquid crystal molecules in the first liquid crystal layer is x [nm], the wavelength of light is λ [nm], and the incident angle of light is θ0, the diffraction angle θ of the diffractive optical element can be expressed by the following formula. θ and θ0 are angles when the perpendicular direction to the plane of the diffractive optical element is 0 degrees. In the following formula, θ0 is the case in the plus direction from the perpendicular direction. The plus or minus sign is attached because there are cases of diffraction in the plus direction and diffraction in the minus direction with respect to the perpendicular direction depending on the rotation direction of the circularly polarized light that is the incident light. sinθ = ±(λ / x) + sinθ0

[0109] For example, when the incident angle θ0 is fixed at 0 degrees and the wavelength of light is fixed at 1550 nm, the relationship between the pitch and the diffraction angle is as shown in Table 1 below. [Table 1]

[0110] The diffraction angle in Table 1 is the angle when there is one diffractive optical element. If the polarization state is the same, when the number of diffractive optical elements is increased, the diffraction angle increases by a multiple of the number of diffractive optical elements. When the diffraction angle at an arbitrary pitch is θ (degrees) and the number of diffractive optical elements is n, the diffraction angle can be expressed as 2 n-1 ×θ (degrees).

[0111] [Method for manufacturing an optical element] The optical element of the present disclosure described above can be manufactured, for example, in the following first to fourth steps. First step: A step of applying a coating liquid for forming a pattern layer containing a resin on a substrate to form a layer containing a resin. Second step: A step of forming a pattern layer by shaping the layer containing a resin using a plate having a shape complementary to the surface shape of the first surface of the pattern layer. The third step: A step of applying a coating liquid for forming a second liquid crystal layer on the pattern layer to form a second liquid crystal layer. The fourth step: A step of applying a coating liquid for forming a first liquid crystal layer on the second liquid crystal layer to form a first liquid crystal layer.

[0112] The method for manufacturing an optical element of the present disclosure does not necessarily need to continuously perform the first to fourth steps in one line. For example, after the second step, the laminate may be wound up, and the third to fourth steps may be performed after moving the wound-up laminate to another line. However, when the first to fourth steps are not continuously performed in one line, the yield of the optical element tends to decrease. Therefore, in the method for manufacturing an optical element of the present disclosure, it is preferable to continuously perform the first to fourth steps in one line.

[0113] The present disclosure includes the following [1] to

[17] . [1] An optical element having a pattern layer and a first liquid crystal layer, The pattern layer has a first surface and a second surface opposite to the first surface, The first surface has a first pattern region in which recesses are arranged in a predetermined pattern, and the predetermined pattern of the first pattern region has a first pitch, The first liquid crystal layer is disposed on the first surface side of the pattern layer and has a region in which liquid crystal molecules are oriented with a second pitch in the plane, Between the pattern layer and the first liquid crystal layer, there is a second liquid crystal layer in which liquid crystal molecules are helically oriented in the thickness direction, and the second liquid crystal layer has a thickness of 50 nm or more, An optical element in which the first pitch of the pattern layer and the second pitch of the first liquid crystal layer substantially coincide. [2] The optical element according to [1], wherein the second liquid crystal layer has a thickness of 50 nm or more and 1000 nm or less. [3] The optical element according to [1], wherein the second liquid crystal layer has a twist angle of the helix of 360 degrees or more and has selective reflectivity for reflecting circularly polarized light in a specific wavelength range. [4] The optical element according to [3], wherein the wavelength selectively reflected by the second liquid crystal layer is 380 nm or less. [5] The optical element according to [3], wherein the wavelength selectively reflected by the second liquid crystal layer is 850 nm or more and 5000 nm or less. [6] The optical element according to [3], wherein the wavelength selectively reflected by the second liquid crystal layer is 250 nm or less, and the thickness of the second liquid crystal layer is 50 nm or more and 200 nm or less. [7] The optical element according to [3], wherein the wavelength selectively reflected by the second liquid crystal layer is 850 nm or more and 1000 nm or less, and the thickness of the second liquid crystal layer is 50 nm or more and 500 nm or less. [8] The optical element according to any one of [1] to [7], wherein the first liquid crystal layer is a homogeneously aligned liquid crystal layer. [9] The optical element according to any one of [1] to [8], wherein in the first pattern region of the pattern layer, the predetermined pattern is formed by the planar shape of a single recess.

[10] The optical element according to any one of [1] to [8], wherein in the first pattern region of the pattern layer, the predetermined pattern is formed by the planar shape connecting a plurality of recesses.

[11] The first pattern region of the pattern layer has a plurality of domains arranged in a first direction, each of the plurality of domains has a plurality of recesses arranged in a second direction orthogonal to the first direction within each domain, the domains form a domain unit in which a predetermined number of domains are aggregated, The optical element according to any one of [1] to [8], wherein the predetermined pattern is formed by the planar shape connecting the recesses at one end in the first direction of the domain unit to the recesses at the other end.

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

[11] , wherein in the first pattern region of the pattern layer, the predetermined pattern is a circular or arc-shaped pattern.

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

[12] , wherein the first pitch is 5000 nm or less.

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

[13] , wherein the in-plane retardation of the first liquid crystal layer is 200 nm or more, and the in-plane retardation of the second liquid crystal layer is substantially 0 nm.

[15] The optical element according to any one of [3] to [7], which satisfies the following formula (2) when the in-plane retardation of the first liquid crystal layer is defined as λ1 [nm] and the wavelength selectively reflected by the second liquid crystal layer is defined as λ2 [nm]. 2λ1≠λ2 (2)

[16] The first surface further has a first' pattern region in which recesses are arranged in a predetermined pattern. The predetermined pattern of the first' pattern region has a first' pitch, and the first' pitch is different from the first pitch. The first liquid crystal layer further has a region in which liquid crystal molecules are aligned with a second' pitch in the plane, and the second' pitch is different from the second pitch. The optical element according to any one of [1] to

[15] , wherein the first' pitch of the pattern layer substantially coincides with the second' pitch of the first liquid crystal layer.

[17] A method for manufacturing the optical element according to [1], comprising the following first to fourth steps. First step: A step of applying a coating liquid for forming a pattern layer containing a resin on a substrate to form a layer containing a resin. Second step: A step of forming a pattern layer by shaping the layer containing a resin using a plate having a shape complementary to the surface shape of the first surface of the pattern layer. Third step: A step of applying a coating liquid for forming a second liquid crystal layer on the pattern layer to form a second liquid crystal layer. Fourth step: A step of applying a coating liquid for forming a first liquid crystal layer on the second liquid crystal layer to form a first liquid crystal layer.

Example

[0114] Next, the present disclosure will be described in more detail with reference to examples, but the present disclosure is not limited to these examples in any way. Note that "parts" and "%" are based on mass unless otherwise specified.

[0115] 1. Measurement and evaluation Regarding the optical elements of the examples and comparative examples, the following measurements and evaluations were carried out. The atmosphere during each measurement and evaluation was set to a temperature of 23 ± 5°C and a relative humidity of 40% or more and 65% or less. Before the start of each measurement and evaluation, the target sample was exposed to the above atmosphere for 30 minutes or more and 60 minutes or less, and then the measurement and evaluation were carried out.

[0116] 1-1. Planar shape of the pattern layer The first surface of the pattern layer of the intermediate of the optical element of the examples and comparative examples was imaged using a scanning electron microscope (Hitachi High-Technologies Corporation, trade name "SU8000"). The imaging conditions were as follows. The intermediate means a laminate having a primer layer and a pattern layer on a substrate. Based on the taken photograph, the first pitch of the first pattern region was measured. The results are shown in Table 2. <Imaging conditions> · Acceleration voltage: 5.0 kV · Emission current: 5.0 uA · Probe current: High · Detector: SE(U) · WD: 8 mm · Condenser lens 1: 5.0 · Condenser lens 2: 1.0 · Tilt function of the specimen stage: Input tilt angle "0.0"

[0117] 1-2. Alignment pitch of the first liquid crystal layer (second pitch) Based on the operations in (B1) to (B4) of the specification text, the second pitch of the first liquid crystal layer of the optical elements of the examples and comparative examples was measured. In Comparative Examples 1 and 2, since the alignment of the first liquid crystal layer was insufficient, the second pitch of the first liquid crystal layer could not be detected.

[0118] 1-3. Alignment Regarding the optical elements of the examples and comparative examples, the alignment of the first liquid crystal layer was evaluated according to the following criteria. A polarizing microscope was used for the evaluation. The results are shown in Table 2. The observation region was 25 μm × 25 μm. It can be said that the less the schlieren structure, the better the alignment of the liquid crystal molecules. A: Those with 6 or fewer schlieren structures excluding those caused by dust. A: Those in which the number of Schlieren structures is 7 or more and 12 or less, excluding those caused by dust. B: Those in which the number of Schlieren structures is 13 or more and 19 or less, excluding those caused by dust. C: Those in which the number of Schlieren structures is 20 or more, excluding those caused by dust.

[0119] 1-4. Color and taste Under the illumination of a fluorescent lamp, the optical elements of the examples and comparative examples were visually observed. Table 2 shows the results of observation from the front direction and at an angle of 45 degrees.

[0120] 2. Plate production <Shape design by simulation> Using a simulation tool, the pattern on the first surface of the pattern layer was designed. The first surface was made to have a first pattern region in which the concave portions were arranged in a predetermined pattern. As shown in FIG. 5, the concave portions were arranged so that the planar shape connecting the plurality of concave portions became an arc-shaped pattern. In FIG. 5, there are two arc-shaped patterns in the first direction A1 and one arc-shaped pattern in the second direction A2. However, in both the first direction A1 and the second direction A2, the number of repetitions of the arc-shaped pattern was increased until it became a sufficient number. The first pitch P1 of the first pattern region was set to 2500 nm. One arc-shaped pattern was formed by a plurality of concave portions. The plurality of concave portions were formed such that the direction of the concave portions fluctuated by 0.5 degrees each. The interval between the individual concave portions was set to 25 nm. The width of each concave portion was 25 nm, and the depth of each concave portion was 30 nm. <Plate production using the above data> Using a 6-inch square synthetic quartz plate, a quartz master mold having the surface shape designed by simulation was produced by an electron beam lithography process using an electron beam drawing apparatus and a dry etching apparatus. Next, after pouring an ultraviolet curable resin into the master mold, a transparent substrate was placed on top of the ultraviolet curable resin. Then, ultraviolet light was irradiated to cure the resin. Subsequently, the transparent substrate and the resin were peeled off from the master mold to obtain a resin plate having a shape complementary to that of the master mold. Next, by electroforming, a replica mold of the master mold, which is a mold having a shape complementary to that of the resin plate, was obtained. A plurality of the replica molds were produced. The plurality of replica molds were wound around a roll to produce a roll-shaped plate used in the examples.

[0121] 3. Fabrication of Optical Element [Example 1] A primer layer with the following formulation was applied and dried on a substrate (cycloolefin polymer with a thickness of 40 μm, trade name "Zeonoa" by Nippon Zeon Co., Ltd.) to form a primer layer with a thickness of 0.5 μm. Next, a coating liquid for forming a pattern layer with the following formulation was applied and dried on the primer layer to form a layer containing uncured resin. Next, using the roll-shaped plate prepared in "2" above, the layer containing uncured resin was shaped, and at the same time, ultraviolet light was irradiated from the substrate side (integrated light quantity: 500 mJ / cm 2 ) to cure the shaped layer containing resin. Subsequently, the shaped layer was peeled off from the plate to obtain a laminate having a primer layer and a pattern layer on the substrate. Next, a second coating liquid for forming a liquid crystal layer was applied and dried on the pattern layer, and then ultraviolet light was irradiated (integrated light quantity: 150 mJ / cm 2 ) to form a second liquid crystal layer (thickness: 300 nm, selective reflection wavelength: 350 nm, twist angle: 360 degrees or more). Next, a first coating liquid for forming a liquid crystal layer was applied and dried on the second liquid crystal layer, and then ultraviolet light was irradiated (integrated light quantity: 150 mJ / cm 2 ) to form a first liquid crystal layer. For the first liquid crystal layer, a liquid crystal with an in-plane birefringence (Δn) of 0.17 was used, and the film thickness was adjusted so that the in-plane retardation at a wavelength of 532 nm was 266 nm. The first liquid crystal layer with the above film thickness was formed by two coatings. Through the above steps, the optical element of Example 1 was obtained. The optical element of Example 1 was produced by continuously performing a series of steps in a roll-to-roll manner.

[0122] <Coating liquid for forming primer layer> · Polyolefin resin: 70 parts by mass (Manufactured by Mitsubishi Chemical Corporation, trade name: Surflen P-1000) · Silica-based lubricant: 5 parts by mass (Manufactured by CIK Nanotech Co., Ltd., trade name: SIRMIBK15WT%-E65) · Methyl ethyl ketone: 25 parts by mass

[0123] <Coating liquid for forming pattern layer> · Pentaerythritol triacrylate: 96 parts by mass (Manufactured by Nippon Kayaku Co., Ltd., trade name: PET-30) · Photoinitiator: 4 parts by mass (Manufactured by IGM, trade name: Omnirad184)

[0124] <Coating liquid for forming the second liquid crystal layer> · Rod-shaped liquid crystal molecules: 10 parts by mass (Liquid crystal manufactured by Tokyo Chemical Industry Co., Ltd. (CAS RN: 132900-75-5, product code: D5936)) · Photoinitiator: 0.4 parts by mass (Manufactured by IGM, trade name: Omnirad184) · Chiral agent: 0.5 parts by mass (Paricolor LC756 (trade name) manufactured by BASF) · Methyl ethyl ketone: 49.1 parts by mass · Cyclohexanone: 40.0 parts by mass

[0125] <Coating liquid for forming the first liquid crystal layer> · Rod-shaped liquid crystal molecules: 10 parts by mass (A 7:3 mixture of liquid crystal manufactured by Tokyo Chemical Industry Co., Ltd. (CAS RN: 132900-75-5, product code: D5936) and liquid crystal manufactured by BASF (Paricolor LC1057 (trade name)). In-plane birefringence (Δn) = 0.17) · Photoinitiator: 0.4 parts by mass (Manufactured by IGM, trade name: Omnirad184) · Methyl ethyl ketone: 89.6 parts by mass

[0126] [Examples 2 to 12], [Comparative Example 1] Optical elements of Examples 2 to 12 and Comparative Example 1 were obtained in the same manner as in Example 1, except that the thickness of the second liquid crystal layer and the selective reflection wavelength of the second liquid crystal layer were changed to the values shown in Table 2. The selective reflection wavelength of the second liquid crystal layer was adjusted by the amount of the chiral agent. Note that the selective wavelength of those with a twist angle of less than 360 degrees in the second liquid crystal layer was described as the selective wavelength assumed when the twist angle was 360 degrees or more.

[0127] [Comparative Example 2] An optical element of Comparative Example 2 was obtained in the same manner as in Example 1, except that the first liquid crystal layer was formed without interposing the second liquid crystal layer on the pattern layer.

[0128]

Table 2

[0129] As shown in Table 2, it can be confirmed that the optical elements of the examples can improve the alignment of the liquid crystal molecules in the liquid crystal layer in an optical element having a liquid crystal layer on the pattern layer.

Explanation of symbols

[0130] 10: Pattern layer 10a: First surface 10b: Second surface 11: Concave portion 13: Domain unit 13a, 13b, 13c, 13d, 13e: Domains 20: Second liquid crystal layer 30: First liquid crystal layer 100: Optical element P1: First pitch P2: Second pitch P1’: First’ pitch P2’: Second’ pitch R1: First pattern region R1’: First’ pattern region

Claims

1. An optical element having a pattern layer and a first liquid crystal layer, wherein the pattern layer has a first surface and a second surface opposite to the first surface, the first surface has a first pattern region in which recesses are arranged in a predetermined pattern, and the predetermined pattern in the first pattern region has a first pitch, the first liquid crystal layer is disposed on the first surface side of the pattern layer and has a region in which liquid crystal molecules are aligned with a second pitch in the plane, a second liquid crystal layer in which liquid crystal molecules are spirally aligned in the thickness direction is provided between the pattern layer and the first liquid crystal layer, and the second liquid crystal layer has a thickness of 50 nm or more, an optical element in which the first pitch of the pattern layer substantially coincides with the second pitch of the first liquid crystal layer.

2. The optical element according to claim 1, wherein the second liquid crystal layer has a thickness of 50 nm or more and 1000 nm or less.

3. The optical element according to claim 1, wherein the second liquid crystal layer has a twist angle of the helix of 360 degrees or more and has selective reflectivity for reflecting circularly polarized light in a specific wavelength range.

4. The optical element according to claim 3, wherein the wavelength selectively reflected by the second liquid crystal layer is 380 nm or less.

5. The optical element according to claim 3, wherein the wavelength selectively reflected by the second liquid crystal layer is 850 nm or more and 5000 nm or less.

6. The optical element according to claim 3, wherein the wavelength selectively reflected by the second liquid crystal layer is 250 nm or less, and the thickness of the second liquid crystal layer is 50 nm or more and 200 nm or less.

7. The optical element according to claim 3, wherein the wavelength selectively reflected by the second liquid crystal layer is 850 nm or more and 1000 nm or less, and the thickness of the second liquid crystal layer is 50 nm or more and 500 nm or less.

8. The optical element according to claim 1, wherein the first liquid crystal layer is a homogeneously aligned liquid crystal layer.

9. The optical element according to claim 1, wherein the predetermined pattern is formed by the planar shape of a single recess in the first pattern region of the pattern layer.

10. The optical element according to claim 1, wherein the predetermined pattern is formed by the planar shape connecting a plurality of recesses in the first pattern region of the pattern layer.

11. The first pattern region of the pattern layer has a plurality of domains arranged in a first direction, each of the plurality of domains has a plurality of recesses arranged in a second direction orthogonal to the first direction within each domain. The domain forms a domain unit in which a predetermined number of domains are aggregated, The optical element according to claim 1, wherein the predetermined pattern is formed by a planar shape connecting recesses at one end in a first direction of the domain unit to recesses at the other end.

12. The optical element according to claim 1, wherein in the first pattern region of the pattern layer, the predetermined pattern is a circular or arc-shaped pattern.

13. The optical element according to claim 1, wherein the first pitch is 5000 nm or less.

14. The optical element according to claim 1, wherein the in-plane retardation of the first liquid crystal layer is 200 nm or more, and the in-plane retardation of the second liquid crystal layer is substantially 0 nm.

15. The optical element according to claim 3, which satisfies the following formula (2) when the in-plane retardation of the first liquid crystal layer is defined as λ1 [nm] and the wavelength selectively reflected by the second liquid crystal layer is defined as λ2 [nm]. 2λ1≠λ2 (2)

16. The first surface further has a first' pattern region in which recesses are arranged in a predetermined pattern, the predetermined pattern of the first' pattern region has a first' pitch, and the first' pitch is different from the first pitch, The first liquid crystal layer further has a region in which liquid crystal molecules are aligned in a second' pitch in the plane, and the second' pitch is different from the second pitch, The optical element according to claim 1, wherein the first' pitch of the pattern layer substantially coincides with the second' pitch of the first liquid crystal layer.

17. A method for manufacturing the optical element according to claim 1, comprising the following first to fourth steps. First step: A step of applying a coating liquid for forming a pattern layer containing a resin on a substrate to form a layer containing a resin. Second step: A step of forming a pattern layer by shaping the layer containing a resin using a plate having a shape complementary to the surface shape of the first surface of the pattern layer. Third step: A step of applying a coating liquid for forming a second liquid crystal layer on the pattern layer to form a second liquid crystal layer. Fourth step: A step of applying a coating liquid for forming a first liquid crystal layer on the second liquid crystal layer to form a first liquid crystal layer.

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