Optical element

Abstract

Provided is an optical element that has good orientation of liquid crystal molecules and that is capable of sufficiently exhibiting the performance of the optical element. The optical element comprises a pattern layer and a liquid crystal layer. The pattern layer has a first surface and a second surface on the opposite side from the first surface. The liquid crystal layer is formed on the first surface of the pattern layer. The pattern layer has, in the first surface, a plurality of domains arranged in the first direction. The domains form a domain unit that is a collection of a prescribed number of domains. The plurality of domains have, in each of the domains, a plurality of recesses arranged in the second direction orthogonal to the first direction. The shortest distance D1 between adjacent recesses in any domain is the same in all the domains. The distance D2 between adjacent recesses in any domain in a direction parallel to the second direction increases as the absolute value of θn of the domain increases.

Description

Optical elements

[0001] The present disclosure relates to optical elements.

[0002] 2. Description of the Related Art There are technical fields in which optical elements are used to change the polarization state of light or the traveling direction of light.

[0003] The optical element described above is used in, for example, a light control device. Furthermore, in recent years, development of devices equipped with optical sensors has progressed in the fields of personal authentication and autonomous vehicle driving. Examples of devices equipped with optical sensors include face authentication devices and LiDAR (light detection and ranging). Optical elements may also be used in such devices equipped with optical sensors. Furthermore, display devices for displaying virtual reality (VR), augmented reality (AR), and mixed reality (MR) have been released in recent years. In this specification, technology for displaying non-existent reality, such as VR, AR, and MR, is referred to as "cross reality (XR)." Optical elements may also be used in display devices for cross reality.

[0004] Known optical element configurations include a configuration in which a liquid crystal layer is provided on a pattern layer having a predetermined pattern (Patent Documents 1 to 3).

[0005] International Publication No. 2018 / 038260 Patent Publication No. 2019-536100 Patent Publication No. 2022-147451

[0006] The pattern layer of the optical element disclosed in Patent Documents 1 and 2 has a structure in which the angle of the pattern of the pattern layer changes stepwise, and a gap is provided between adjacent patterns. The optical element disclosed in Patent Documents 1 and 2 has a problem in that the pattern is divided by the gap, and therefore liquid crystal molecules are difficult to align in the gap portion.

[0007] The pattern layer of the optical element shown in Figure 9 of Patent Document 3 has a configuration in which a semicircular pattern is formed. In the pattern of Patent Document 3, the semicircular pattern is not interrupted midway and the pattern angle changes continuously. For this reason, the pattern of Patent Document 3 makes it easy for liquid crystal molecules to align within the semicircular pattern. However, the pattern of Patent Document 3 has large individual recesses, making it difficult to stably form the pattern layer. This is because, when the pattern layer is formed by molding, smaller individual recesses make it easier to peel the pattern layer from the molding plate.

[0008] In order to solve the above problem, it is conceivable to modify the optical elements of Patent Documents 1 and 2 so that the gaps between adjacent patterns are eliminated and the adjacent patterns are in contact with each other. An optical element modified as described above will have many contact portions where the angle of the patterns changes. The inventors' investigations have found that optical elements with many such contact portions are prone to poor alignment of liquid crystal molecules at the contact portions, making it difficult for the optical element to exhibit sufficient performance.

[0009] The inventors have studied the pattern of the pattern layer to facilitate alignment of the liquid crystal molecules, and as a result have completed an optical element that has good alignment of the liquid crystal molecules and can provide sufficient performance as an optical element.

[0010] The present disclosure provides the following optical element <1>. <1> An optical element having a pattern layer and a liquid crystal layer, wherein the pattern layer has a first surface and a second surface opposite to the first surface, the liquid crystal layer is formed on the first surface of the pattern layer, the pattern layer has a plurality of domains arranged in a first direction in the first surface, the domains form domain units each formed by a collection of a predetermined number of domains, the plurality of domains have, within each domain, a plurality of recesses arranged in a second direction perpendicular to the first direction, adjacent domains are in contact with each other, when the angle formed between the extension direction of the recesses and the first direction in a domain located n-th from one end of the domain unit in the first direction is defined as θn, θn changes stepwise from the one end to the other end of the domain unit in the first direction within a range of more than -90.0 degrees to less than +90.0 degrees, when the shortest distance between adjacent recesses in any domain is defined as D1, D1 is the same in all domains, An optical element, wherein when the distance between adjacent recesses in any domain in a direction parallel to the second direction is defined as D2, D2 in each domain increases as the absolute value of θn of the domain increases.

[0011] The optical element of the present disclosure has good alignment of liquid crystal molecules and can fully exhibit its performance as an optical element.

[0012] Fig. 1 is a cross-sectional view showing an embodiment of an optical element according to the present disclosure; Fig. 2 is a plan view showing an embodiment of a first surface of a pattern layer of the optical element according to the present disclosure; Fig. 3 is a view for explaining θn; Fig. 4 is a view for explaining L1; Fig. 5 is a view for explaining D1 and D2; Fig. 6 is a plan view showing an embodiment of Y-connected recesses; Fig. 7 is a plan view showing an embodiment of a first surface of a pattern layer of an optical element corresponding to a comparative example;

[0013] An embodiment of an optical element according to the present disclosure will be described below. [Optical Element] The optical element according to the present disclosure is an optical element having a pattern layer and a liquid crystal layer, wherein the pattern layer has a first surface and a second surface opposite to the first surface, the liquid crystal layer is formed on the first surface of the pattern layer, the pattern layer has a plurality of domains arranged in a first direction within the first surface, the domains form domain units each comprising a predetermined number of domains, each of the plurality of domains has a plurality of recesses arranged in a second direction perpendicular to the first direction, adjacent domains are in contact with each other, and when the angle formed between the extension direction of the recesses and the first direction in the n-th domain from one end of the domain unit in the first direction is defined as θn, θn changes stepwise from the one end to the other end of the domain unit in the first direction within a range of more than −90.0 degrees to less than +90.0 degrees, When the shortest distance between adjacent recesses in any domain is defined as D1, D1 is the same in all domains, and when the distance between adjacent recesses in any domain in a direction parallel to the second direction is defined as D2, D2 in each domain increases as the absolute value of θn of the domain increases.

[0014] FIG. 1 is a cross-sectional view showing one embodiment of an optical element of the present disclosure. The optical element 100 of FIG. 1 has a patterned layer 20 and a liquid crystal layer 30. In FIG. 1, the patterned layer 20 has a first surface 20a and a second surface 20b opposite the first surface. In FIG. 1, the liquid crystal layer 30 is formed on the first surface 20a of the patterned layer 20. In FIG. 1, the patterned layer 20 has a plurality of recesses 21 on the first surface 20a. The optical element 100 of FIG. 1 has a substrate 10 on the side of the patterned layer 20 opposite the liquid crystal layer 30. In FIG. 1, the symbol d indicates the depth of the recesses. In FIG. 1, the symbol t1 indicates the thickness of the patterned layer at a location that does not have a recess. In FIG. 1, the symbol t2 indicates the thickness of the patterned layer below the recess. In FIG. 1, the symbol t3 indicates the thickness of the liquid crystal layer formed at a location that does not have a recess. FIG. 1 is a schematic cross-sectional view. That is, the scale of each layer constituting the optical element 100 and the scale of the recessed portion on the first surface are schematic for ease of illustration and differ from the actual scale. The same applies to figures other than FIG.

[0015] <Patterned Layer> The patterned layer has a first surface and a second surface opposite to the first surface. A liquid crystal layer is formed on the first surface of the patterned layer. The presence of the patterned layer makes it easier to align the liquid crystal molecules in the liquid crystal layer in a predetermined direction.

[0016] The liquid crystal layer 30 is disposed in the recesses 21 of the pattern layer. The shape of the second surface 20b 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, it is preferable that the second surface of the pattern layer is flat.

[0017] <<Configurations 1 to 3>> The optical element of the present disclosure is required to satisfy the following configurations 1 to 3. Configuration 1: The pattern layer has a plurality of domains arranged in a first direction in a first plane. Configuration 2: The domains form a domain unit in which a predetermined number of domains are assembled. Configuration 3: Each of the plurality of domains has a plurality of recesses arranged in a second direction perpendicular to the first direction.

[0018] Configurations 1 to 3 allow a predetermined arrangement pattern of recesses to be formed from one end of the domain unit to the other end. Furthermore, configurations 1 to 3 make it easier to prevent the individual recesses of the pattern layer from becoming too large, making it easier to stably form the pattern layer. Furthermore, stabilizing the pattern layer makes it easier to align the liquid crystal molecules on the pattern layer, and the performance of the optical element can be stably demonstrated. When forming the pattern layer by shaping, the smaller the individual recesses of the pattern layer, the easier it is to peel the pattern layer from the shaping plate. Therefore, configurations 1 to 3 allow for the stable formation of the pattern layer. While the number of domain units may be only one, it is preferable to have two or more in the first direction.

[0019] FIG. 2 is a plan view showing one embodiment of the first surface of the pattern layer. In FIG. 2, the pattern layer 20 has a plurality of domains arranged in a first direction A1 within the first surface. Reference numerals 23a to 23e denote individual domains. In FIG. 2, the domains form domain units 23, each of which is a collection of a predetermined number of domains. FIG. 2 shows one domain unit 23 in the first direction. In FIG. 2, each of the domains has a plurality of recesses 21 arranged in a second direction A2 perpendicular to the first direction A1. In FIG. 2, adjacent domains are in contact with each other. For example, domain 23a and domain 23b are in contact with each other. In FIG. 2, a boundary 25 is disposed at the end of the domain unit 23 in the first direction A1. It is preferable to have another domain unit (not shown) on the opposite side of the boundary 25 from the domain unit 23.

[0020] <Configuration 4> The optical element of the present disclosure is required to satisfy the following configuration 4. Configuration 4: In the pattern layer, adjacent domains are in contact with each other.

[0021] The contact between adjacent domains makes it easier to align liquid crystal molecules at the domain boundaries. As long as the effects of the present disclosure are not impaired, some regions of the pattern layer may have regions where adjacent domains do not contact each other.

[0022] Furthermore, when adjacent domains are in contact with each other and satisfy the following configurations 6 and 7, the degree of contact between the edges of the recesses of the adjacent domains varies along the second direction (the "variation in contact" will be described later). Therefore, whether the adjacent domains are in contact with each other can be determined based on whether the degree of contact between the edges of the recesses of the adjacent domains varies along the second direction.

[0023] The number of domains forming the domain unit is preferably 4 or more and 359 or less. By setting the number of domains forming the domain unit to 4 or more, it is possible to prevent the angle of the recesses between adjacent domains from changing suddenly, thereby facilitating the alignment of liquid crystal molecules. Furthermore, by setting the number of domains forming the domain unit to 4 or more, it is possible to easily align liquid crystal molecules in the Y-shaped recesses described below. By setting the number of domains forming the domain unit to 359 or less, it is possible to easily reduce the number of contact points between the recesses, thereby facilitating the alignment of liquid crystal molecules. Furthermore, by setting the number of domains forming the domain unit to 359 or less, it is possible to easily increase the length of each recess in the extension direction, thereby facilitating the alignment of liquid crystal molecules. The number of domains forming the domain unit is more preferably 6 or more and 200 or less, more preferably 10 or more and 100 or less, and even more preferably 15 or more and 50 or less.

[0024] In the configuration elements described herein, when multiple upper limit and lower limit options are shown, it is assumed that the range described is a combination of one selected from the upper limit options and one selected from the lower limit options. For example, examples of ranges for the number of domains forming the above domain unit include 4 to 359, 4 to 200, 4 to 100, 4 to 50, 6 to 359, 6 to 200, 6 to 100, 6 to 50, 10 to 359, 10 to 200, 10 to 100, 10 to 50, 15 to 359, 15 to 200, 15 to 100, and 15 to 50.

[0025] The domain width can be adjusted appropriately depending on the purpose. Furthermore, the domains forming one domain unit may have the same or different domain widths. The domain width is the length of the domain in the first direction. As described above, the domain width is not particularly limited, but is usually 1.1 nm or more and 2000 μm or less.

[0026] <<Configuration 5>> The optical element of the present disclosure is required to satisfy the following configuration 5. Configuration 5: When the angle formed between the extension direction of a recess and the first direction in a domain located at the nth position from one end of the domain unit in the first direction is defined as θn, θn changes stepwise from one end to the other end of the domain unit in the first direction in a range from more than −90.0 degrees to less than +90.0 degrees.

[0027] 2, the domain unit 23 is formed from a plurality of domains arranged in a first direction. In configuration 5, "one end of the domain unit in the first direction" means one end of the plurality of domains arranged in the first direction. Although the ends exist on both sides, either side may be used as the reference "one end."

[0028] FIG. 3 is a diagram illustrating θn. In FIG. 3, a domain unit 23 is formed by five domains 23a to 23e. While each domain would normally have multiple recesses 21, FIG. 3 shows only one recess in each domain for ease of explanation. In FIG. 3, the angle between the extension direction of the recess in domain 23a and the first direction is θ1, the angle between the extension direction of the recess in domain 23b and the first direction is θ2, the angle between the extension direction of the recess in domain 23c and the first direction is θ3, the angle between the extension direction of the recess in domain 23d and the first direction is θ4, and the angle between the extension direction of the recess in domain 23e and the first direction is θ5. Because θ3 is 0 degrees, it is represented by a straight line. In FIG. 3, the angle changes stepwise from θ1 at one end to θ5 at the other end.

[0029] Satisfying configuration 5 means that the recesses are arranged in a semicircular or arc shape in one domain unit formed by a group of multiple domains. Therefore, by satisfying configuration 5, the liquid crystal in the liquid crystal layer is also likely to be oriented in a circular or arc shape along the arrangement of the recesses. The liquid crystal layer oriented in a circular or arc shape exhibits the effect of diffracting transmitted light.

[0030] In principle, the angle between the extension direction of the recess and the first direction within the same domain is the same regardless of which recess is selected. However, if distortion occurs in the recess, the angle may differ slightly between individual recesses. For this reason, in this specification, the angle θn between the extension direction of the recess and the first direction within the nth domain is calculated as follows: (a1) Select any 10 recesses within the nth domain. (a2) Calculate the angle between the extension direction of each recess and the first direction. The average of the angles formed at 10 locations is defined as θn.

[0031] When the angle between the extension direction of the recessed portion and the first direction in the domain located at the n+1th position from one end of the domain unit in the first direction is defined as θn+1, the absolute value of the difference between θ and θn+1 is preferably 0.5 degrees or more and 36.0 degrees or less. By setting the absolute value to 36.0 degrees or less, it is possible to prevent the angle of the recessed portions from changing suddenly between adjacent domains, thereby facilitating the alignment of the liquid crystal molecules. Furthermore, by setting the absolute value to 36.0 degrees or less, it is possible to easily align the liquid crystal molecules in the Y-shaped bonded recessed portions described below. By setting the absolute value to 0.5 degrees or more, it is possible to easily reduce the number of contact points between the recessed portions, thereby facilitating the alignment of the liquid crystal molecules. The absolute value is more preferably 0.9 degrees or more and 30.0 degrees or less, even more preferably 1.8 degrees or more and 18.0 degrees or less, and even more preferably 3.6 degrees or more and 12.0 degrees or less.

[0032] A domain unit includes multiple domains. Therefore, multiple absolute values ​​can be calculated from one domain unit. For example, in FIG. 3, four absolute values ​​can be calculated. It is preferable that all of the absolute values ​​are the same in one domain unit. By making all of the absolute values ​​the same, it becomes easier to uniformize the alignment of the liquid crystal molecules in the plane. In order to make all of the absolute values ​​the same in one domain unit, the angle change of θn when moving from one end of the domain unit to the other end can be made uniform.

[0033] The absolute value of the difference between θ and θn+1 can be determined, for example, by the number of domains that form the domain unit. Specifically, when the number of domains that form the domain unit is x, the absolute value of the difference can be "180 degrees / (x+1)". The minimum value of θn is greater than -90.0 degrees, and the maximum value of θn is less than +90.0 degrees. When the absolute value of the difference is fixed at "180 degrees / (x+1)", the minimum and maximum values ​​can be expressed by the following formulas. Minimum value of θn = -{180 degrees / (x+1)} x {(x-1) / 2} Maximum value of θn = +{180 degrees / (x+1)} x {(x-1) / 2}

[0034] In this specification, the conditions calculated or determined from the planar shape of the pattern layer, such as θn, L1, D1, D2 and pitch, are calculated or determined from a photograph of the first surface of the pattern layer taken with a scanning electron microscope.

[0035] <<Configurations 6 and 7>> The optical element of the present disclosure is required to satisfy the following configurations 6 and 7. Configuration 6: When the shortest distance between adjacent recesses in any domain is defined as D1, D1 is the same in all domains. Configuration 7: When the distance between adjacent recesses in any domain in a direction parallel to the second direction is defined as D2, D2 in each domain increases as the absolute value of θn of the domain increases.

[0036] Each of the multiple domains has multiple recesses arranged in a second direction perpendicular to the first direction. D1 in configuration 6 is the distance between adjacent recesses in the second direction in any domain, and indicates the shortest distance. D2 in configuration 7 is the distance between adjacent recesses in the second direction in any domain, and indicates the distance in a direction parallel to the second direction. The "distance in a parallel direction" in configuration 7 is measured at the midpoint of the extension direction of the recesses.

[0037] FIG. 5 is a diagram for explaining D1 and D2. In FIG. 5, a portion of the domain unit is enlarged to facilitate explanation of D1 and D2. In FIG. 5, D1-a indicates the shortest distance between adjacent recesses in domain 23a, D1-b indicates the shortest distance between adjacent recesses in domain 23b, and D1-c indicates the shortest distance between adjacent recesses in domain 23c. In FIG. 5, the lengths of D1-a, D1-b, and D1-c are equal to the length of a perpendicular line to the outer frame line of the planar view shape of adjacent recesses. In FIG. 5, D2-a indicates the distance in a direction parallel to the second direction between adjacent recesses in domain 23a, D2-b indicates the distance in a direction parallel to the second direction between adjacent recesses in domain 23b, and D2-c indicates the distance in a direction parallel to the second direction between adjacent recesses in domain 23c. In Fig. 5, the absolute values ​​of θn of each domain have the following relationship: absolute value of θn of domain 23a > absolute value of θn of domain 23b > absolute value of θn of domain 23c. Therefore, in Fig. 5, the relationship is D2-a > D2-b > D2-c. Note that in domains in which the extension direction of the recesses is parallel to the first direction, D1 and D2 are substantially the same. In Fig. 5, D1-c and D2-c are the same.

[0038] By satisfying the features 6 and 7, the degree of contact between the recessed portion edges of adjacent domains varies along the second direction (FIGS. 2 and 4). For example, in FIG. 4, the degree of contact between the recessed portion edges of domain 23c and domain 23b varies along the second direction from a large amount of contact to a small amount of contact to no contact at all. Similarly, the degree of contact between the recessed portion edges of domain 23b and domain 23a varies along the second direction from a large amount of contact to a small amount of contact to no contact at all.

[0039] As described above, by satisfying the features 6 and 7, the degree of contact between the recessed portion edges of adjacent domains varies along the second direction. When the degree of contact between the recessed portion edges of adjacent domains varies along the second direction, it becomes easier to align liquid crystal molecules for the following reasons (1) and (2): (1) The proportion of contact between the recessed portion edges of adjacent domains can be reduced. Furthermore, among contacting recesses, the proportion of recesses whose edges are in complete contact can be reduced (the more complete the contact between the recessed portion edges, the more likely it is that poor alignment of liquid crystal molecules will occur). Therefore, it becomes easier to suppress poor alignment of liquid crystal molecules due to contact between the recessed portion edges of adjacent domains. (2) By satisfying the features 6 and 7, recesses that do not contact the recessed portion edges of adjacent domains at all are formed. Because the above feature 4 allows adjacent domains to be in contact, the spacing between the recessed portions of adjacent domains can be shortened at locations where the recessed portion edges do not contact. Therefore, it becomes easier to improve the alignment of liquid crystal molecules at domain boundaries even at locations where the recessed portion edges do not contact.

[0040] FIG. 7 is a plan view showing the arrangement pattern of recesses of an optical element corresponding to a comparative example that does not satisfy the configurations 6 and 7. In the optical element of FIG. 7, the ends of the recesses of adjacent domains are in contact with each other in the same manner in the second direction. That is, in the optical element of FIG. 7, the degree of contact between the ends of the recesses of adjacent domains does not vary along the second direction. The optical element of FIG. 7 is prone to poor alignment of the liquid crystal molecules, making it difficult to improve the alignment of the liquid crystal molecules. Furthermore, in the optical element of FIG. 7, D1 in the domains at both ends is small, making it difficult to peel the pattern layer from the shaping plate, and the pattern layer cannot be stably formed.

[0041] The range of D1 is not particularly limited, but is preferably 5 nm or more and 75 nm or less, more preferably 12 nm or more and 55 nm or less, and even more preferably 20 nm or more and 40 nm or less. D1 corresponds to the distance between adjacent recesses in each domain.

[0042] The range of D2 is not particularly limited, but is preferably 5 nm or more and 10,000 nm or less, more preferably 12 nm or more and 5,000 nm or less, and even more preferably 20 nm or more and 1,000 nm or less.

[0043] In configuration 6, "D1 is the same in all domains" is not limited to being completely the same, but includes "substantially the same." In this specification, if the ratio of the largest D1 to the smallest D1 (largest D1 / smallest D1) is 1.1 or less, "D1 is the same in all domains."

[0044] In configuration 7, the absolute value of the difference in D2 between adjacent domains depends, in principle, on the absolute value of the difference between θ and θn+1. The larger the absolute value of the difference between θ and θn+1, the larger the absolute value of the difference in D2 between adjacent domains can be. When the planar shape of the recess is substantially quadrangular and configurations 5 and 6 are satisfied, configuration 7 is automatically satisfied.

[0045] In principle, the shortest distance between adjacent recesses within the same domain is the same regardless of which recesses are selected. However, if distortion occurs in the recesses, the shortest distance may differ slightly depending on the combination of adjacent recesses. For this reason, in this specification, the shortest distance D1 between adjacent recesses within an arbitrary domain is calculated as follows: (c1) Select any 10 pairs of adjacent recesses within an arbitrary domain. (c2) Calculate the shortest distance between each pair of recesses. The average of the 10 shortest distances is defined as D1.

[0046] In principle, the distance between adjacent recesses in the same domain in the direction parallel to the second direction is the same regardless of which recesses are selected. However, if distortion occurs in the recesses, the shortest distance may vary slightly depending on the combination of adjacent recesses. For this reason, in this specification, the distance D2 between adjacent recesses in an arbitrary domain in the direction parallel to the second direction is calculated as follows: (d1) Select any 10 pairs of adjacent recesses in an arbitrary domain. (d2) Calculate the distance between each pair of recesses in the direction parallel to the second direction. The average of the 10 distances is defined as D2.

[0047] The optical element of the present disclosure may satisfy the following configuration 8. Configuration 8: When the length of a recess in an extension direction in any domain is defined as L1, L1 in each domain increases as the absolute value of θn of the domain increases.

[0048] 4 is a diagram illustrating the length L1 of the recess in the extension direction. In FIG. 4, a portion of the domain unit is shown enlarged to facilitate the explanation of L1. In FIG. 4, L1-a indicates the length of the recess in the extension direction within domain 23a, L1-b indicates the length of the recess in the extension direction within domain 23b, and L1-c indicates the length of the recess in the extension direction within domain 23c. In FIG. 4, the relationship is L1-a > L1-b > L1-c.

[0049] By satisfying configuration 8, it is possible to reduce the number of contact points between the recesses, thereby making it easier to align the liquid crystal molecules. The length of L1 in each domain does not need to be correlated with the magnitude of the absolute value of θn of the domain. In other words, the optical element of the present disclosure does not need to satisfy configuration 8.

[0050] The number of contact points between recesses can also be reduced by using a configuration opposite to configuration 8. The configuration opposite to configuration 8 is a configuration in which "when the length of a recess in an extension direction within an arbitrary domain is defined as L1, L1 in each domain becomes shorter as the absolute value of θn of the domain increases." However, a configuration opposite to configuration 8 makes it difficult to stably form a patterned layer, making it difficult for liquid crystal molecules on the patterned layer to align. This is because, when a patterned layer is formed by shaping, shorter recesses with small θn make it easier to peel the patterned layer from the shaping plate. Furthermore, when forming a liquid crystal layer on a patterned layer, shorter recesses with small θn make it easier to fill the recesses with liquid crystal and to easily remove any trapped air bubbles. In other words, configuration 8 is also superior in that it makes it easier to stably form a patterned layer and therefore easier to align liquid crystal molecules on the patterned layer.

[0051] In principle, the length of recesses in the extension direction within the same domain is the same regardless of which recesses are selected. However, if distortion occurs in the recesses, the length may vary slightly between individual recesses. For this reason, in this specification, the length L1 of recesses in the extension direction within an arbitrary domain is calculated as follows: (b1) Select any 10 recesses within any domain. (b2) Calculate the length of each recess in the extension direction. The average length of the 10 recesses is defined as L1.

[0052] <<Recess>> The recess is not particularly limited as long as it satisfies the above-mentioned features 3 and 5 to 7.

[0053] The planar shapes of multiple recesses included in the same domain are preferably congruent or similar to each other. This configuration makes it easier to peel the pattern layer from the shaping plate, thereby facilitating more stable formation of the pattern layer. "Congruent" means that the planar shapes of the recesses completely match when the recesses are moved in the second direction. "Similar" means that the area of ​​the planar shapes of the recesses matches 90% or more when the recesses are moved in the second direction. The area match is preferably 95% or more, more preferably 97% or more, and even more preferably 99% or more. When forming recesses using electron beam lithography or the like, the ends of the recesses may be distorted. Furthermore, when combined recesses, as described below, are formed, the shape of the vicinity of the combined portion may differ from that of the independent recesses. Therefore, when the length L1 of the recess in the extension direction is taken as 100%, congruent or similar is determined excluding 10% of both ends.

[0054] The planar shape of the recess preferably satisfies the following (1) to (3). By satisfying the following (1) to (3), the pattern layer can be more easily peeled from the shaping plate, and the pattern layer can be more stably formed. (1) A pair of parallel lines, a first line and a second line, is provided. (2) A line connecting the ends of the first line and the second line on the same side is provided. (3) The length of the first line and the second line is greater than the length of the line connecting the ends of the line (2).

[0055] The extension direction of the first line and the second line in (1) above can be regarded as the extension direction of the recess. If the first line and the second line are arcs, the direction of the tangent to the midpoint of the arc can be regarded as the extension direction of the recess.

[0056] The first and second lines in (1) above may be straight lines or curved lines such as arcs, but are preferably straight lines. Making the first and second lines straight makes it easier to adjust the above-mentioned configurations 6 and 7. Making the first and second lines straight also makes it easier to adjust the degree to which the ends of the recesses of adjacent domains contact each other along the second direction. The straight lines may be slightly distorted.

[0057] The first line and the second line in (1) above may be substantially parallel. "Substantially parallel" means that the angle between the first line and the second line is 3.0 degrees or less. The angle between the first line and the second line is preferably 1.0 degrees or less, and more preferably 0.5 degrees or less.

[0058] The first and second lines in (1) above 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 to 1.20. The ratio is preferably 0.90 to 1.10, and more preferably 0.95 to 1.05.

[0059] The recess is preferably substantially rectangular. When recesses are formed by electron beam lithography or the like, slight distortion may occur. Therefore, even when recesses having a rectangular shape in plan view are formed, slight distortion may occur in two pairs of opposite sides constituting the rectangle. Distortion is particularly likely to occur in the shorter sides. A substantially rectangular shape is a rectangle that allows slight distortion. In this specification, a substantially rectangular shape means one in which the area matching rate in the following formula is 95% or more and 105% or less. In the formula below, the "plan view shape of the recess after distortion correction" means "a plan view shape in which the portions of the distorted lines are corrected with straight lines that average the distortion." Area matching rate (%) = (area of ​​the actual plan view shape of the recess / area of ​​the plan view shape of the recess after distortion correction) × 100

[0060] The length of the recess in the extension direction is not particularly limited, but is preferably 1.1 nm or more and 7000 μm or less, more preferably 10 nm or more and 6000 μm or less, and even more preferably 15 nm or more and 5000 μm or less. The length of the recess in the extension direction means the length of the recess in the major axis direction.

[0061] The approximate value of the length of the recess in the extension direction can be calculated from the following formula: Approximate value of length of recess in the extension direction=x / cos θn (In the formula, "x" means the width of the domain including the recess whose length is to be calculated, and "θn" means θn as defined in this specification.)

[0062] The length of the recess in the direction perpendicular to the extension direction is not particularly limited, but is preferably 5 nm or more and 75 nm or less, more preferably 12 nm or more and 55 nm or less, and even more preferably 20 nm or more and 40 nm or less. The length of the recess in the direction perpendicular to the extension direction means the length of the minor axis of the recess. By making the length of the minor axis of the recess 5 nm or more, it becomes easier to peel the pattern layer from the shaping plate, making it easier to form the pattern layer more stably. By making the length of the minor axis of the recess 75 nm or less, it becomes easier to suppress a decrease in the alignment of the liquid crystal molecules. In this specification, the length of the minor axis of the recess means the average value of the uniaxial lengths of 10 recesses selected at random.

[0063] The depth of the recesses 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 recesses means the average value of the maximum depths of 10 recesses selected at random. By making the depth of the recesses 2 nm or more, it is possible to more easily align the liquid crystal molecules along the recesses. By making the depth of the recesses 200 nm or less, it is easier to peel the pattern layer from the shaping plate, making it easier to form the pattern layer more stably.

[0064] The depth of the recess is calculated from a photograph of a vertical cross section of the optical element taken with a scanning electron microscope.

[0065] It is preferable that the depth of the recesses in each domain is substantially the same. Furthermore, it is preferable that the depths of the recesses in different domains are also substantially the same. "Substantially the same depth" means that the ratio of the depth of the deepest recess to the depth of the shallowest recess is 1.3 or less. This ratio is preferably 1.2 or less, and more preferably 1.1 or less.

[0066] The optical element of the present disclosure preferably has, as recesses, bonding recesses that contact the recesses of adjacent domains and non-bonding recesses that do not contact the recesses of adjacent domains. The bonding recesses preferably have bilateral bonding recesses that contact the recesses on both sides of adjacent domains, and unilateral bonding recesses that contact the recesses on one side of adjacent domains. By configuring adjacent domains to be in contact with each other and by having bonding recesses and non-bonding recesses, it is possible to easily improve the alignment of liquid crystal molecules.

[0067] The bonding recess may be a bonding recess formed by bonding recesses of adjacent domains one by one.

[0068] -Y Bond- Furthermore, the bonding recess may be a bonding recess formed by bonding two recesses in one adjacent domain to one recess in the other adjacent domain. In this specification, the bonding between two recesses in one adjacent domain to one recess in the other adjacent domain is referred to as a "Y bond."

[0069] 6 is a plan view showing an embodiment of Y-connected recesses. In FIG. 6, dotted lines indicate domain boundaries. In FIG. 6, two recesses in the left domain and one recess in the right domain form a Y-connection.

[0070] It is preferable that the Y-shaped bond is formed between domains that satisfy the following relationship. By satisfying the following relationship, the pattern layer can be more easily peeled from the shaping plate, and the pattern layer can be more stably formed. <Preferred domain relationship> Absolute value of θn of the domain on the side having two recesses < Absolute value of θn of the domain on the side having one recess

[0071] <<Boundary>> The optical element of the present disclosure preferably has a plurality of domain units in the first direction. For example, in FIG. 2, it is preferable to have another domain unit (not shown) on the opposite side of the domain unit 23 of the boundary 25. A boundary 25 may be provided between each domain unit. For example, a convex portion parallel to the second direction is disposed in the boundary. Since liquid crystal is difficult to align in the convex portion, the presence of a convex portion in the boundary makes it easier to clearly distinguish the domain units. Reference numeral 25-2 in FIG. 2 denotes a convex portion. As shown in FIG. 2, the boundary may have a plurality of convex portions.

[0072] The width of the convex portion at the boundary is preferably more than 0 nm and not more than 100 nm, more preferably 2 nm or more and 75 nm or less, and even more preferably 4 nm or more and 50 nm or less.

[0073] <<Pitch>> The pitch of the recesses in the first direction cannot be generalized because it varies depending on the desired optical properties. However, it is preferably 0.4 μm or more and 10,000 μm or less, more preferably 0.7 μm or more and 8,000 μm or less, and even more preferably 1.0 μm or more and 6,000 μm or less. A pitch of 0.4 μm or more is preferable because it facilitates alignment of liquid crystal molecules and facilitates obtaining optical properties for blue (wavelength 450 nm), which is on the short wavelength side of the visible light range. In this specification, the pitch of the recesses in the first direction means "the distance between recesses that correspond to each other in adjacent domain units." For example, in FIG. 3, P1 corresponds to the pitch of the recesses in the first direction. In this specification, the term "pitch" means "the pitch of the recesses in the first direction" unless otherwise specified.

[0074] In the optical element of the present disclosure, the number of Y-shaped bonds calculated by the following (1) to (3) is preferably 2 or more. (1) The first surface of the pattern layer is imaged using a scanning electron microscope. The imaging conditions are preferably the same as those for imaging the planar view shape in the examples. (2) At any point in the captured photograph, the planar view shape of the recesses in a square region, each side of which has a length equal to the pitch, is observed, and the number of Y-shaped bonds is counted. (3) The number of Y-shaped bonds is counted at 10 points, and the average value of the 10 points is taken as the number of Y-shaped bonds.

[0075] By setting the number of Y-shaped bonds to 2 or more, the pattern layer can be more easily peeled from the shaping plate, making it easier to form the pattern layer more stably. The number of Y-shaped bonds is more preferably 3 or more, and even more preferably 5 or more. If the number of Y-shaped bonds is too large, the number of bonding portions increases, making it easier for the alignment of the liquid crystal molecules to decrease. Therefore, the number of Y-shaped bonds is preferably 1000 or less, more preferably 500 or less, and even more preferably 100 or less.

[0076] The pattern layer may have a thickness below the recesses. In FIG. 1, the symbol t2 indicates the thickness of the pattern layer below the recesses. The average thickness below the recesses is preferably 0.5 μm or more and 20 μm or less, more preferably 1 μm or more and 15 μm or less, and even more preferably 2 μm or more and 7 μm or less. By setting t2 to 0.5 μm or more, it is possible to easily control the curing when forming the pattern layer and to easily coat a liquid crystal layer on the pattern layer. By setting t2 to 20 μm or less, it is possible to easily suppress the occurrence of curl. The average thickness below the recesses means the average value of the thicknesses at five arbitrary seven locations in a cross-sectional photograph of the optical element, excluding the maximum and minimum values. The depth d of the recesses and t2 preferably satisfy the relationship d / t2≦0.1. By satisfying this relationship, it is possible to easily suppress cohesive failure of the resin in the pattern layer when peeling the pattern layer from the shaping plate.

[0077] <<Material of Pattern Layer>> The pattern layer preferably contains a resin. The proportion of the resin in the pattern layer is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more, based on the total solid content of the pattern layer.

[0078] Resin: Examples of resins for the pattern layer include thermoplastic resins and cured products of curable resin compositions. Among these, cured products of curable resin compositions are preferred in order to improve strength. The proportion of the cured product of the curable resin composition relative to the total solid content of the pattern layer is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more.

[0079] Examples of the cured product of the curable resin composition include a cured product of a heat-curable resin composition and a cured product of an ionizing radiation-curable resin composition, and among these, a cured product of an ionizing radiation-curable resin composition is preferred.

[0080] The ionizing radiation curable resin composition is a composition containing a compound having an ionizing radiation curable functional group (hereinafter also referred to as "ionizing radiation curable compound"). Examples of the ionizing radiation curable functional group include ethylenically unsaturated bond groups such as (meth)acryloyl groups, vinyl groups, and allyl groups, as well as epoxy groups and oxetanyl groups. The ionizing radiation curable resin is preferably a compound having an ethylenically unsaturated bond group. Furthermore, from the viewpoint of preventing damage to the pattern layer during the manufacturing process of the optical element, the ionizing radiation curable resin is more preferably a compound having two or more ethylenically unsaturated bond groups, and among these, a polyfunctional (meth)acrylate compound having two or more ethylenically unsaturated bond groups is even more preferred. The polyfunctional (meth)acrylate compound can be either a monomer or an oligomer. Ionizing radiation refers to electromagnetic waves or charged particle beams that have an energy quantum capable of polymerizing or crosslinking molecules. Usually, ultraviolet (UV) rays or electron beams (EB) are used, but other types of electromagnetic waves such as X-rays and gamma rays, and charged particle beams such as alpha rays and ion beams can also be used.

[0081] Among the polyfunctional (meth)acrylate compounds, examples of bifunctional (meth)acrylate monomers include ethylene glycol di(meth)acrylate, bisphenol A tetraethoxydiacrylate, bisphenol A tetrapropoxydiacrylate, and 1,6-hexanediol diacrylate. Examples of trifunctional or higher functional (meth)acrylate monomers include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol tetra(meth)acrylate, and isocyanuric acid-modified tri(meth)acrylate. The above (meth)acrylate monomers may have a portion of their molecular skeleton modified, and those modified with ethylene oxide, propylene oxide, caprolactone, isocyanuric acid, alkyl, cyclic alkyl, aromatic, bisphenol, or the like can also be used.

[0082] Examples of polyfunctional (meth)acrylate oligomers include acrylate polymers such as urethane (meth)acrylate, epoxy (meth)acrylate, polyester (meth)acrylate, and polyether (meth)acrylate. Urethane (meth)acrylates can be obtained, for example, by reacting a polyhydric alcohol and an organic diisocyanate with a hydroxy (meth)acrylate. Preferred epoxy (meth)acrylates include (meth)acrylates obtained by reacting a trifunctional or higher aromatic epoxy resin, alicyclic epoxy resin, aliphatic epoxy resin, or the like with (meth)acrylic acid; (meth)acrylates obtained by reacting a bifunctional or higher aromatic epoxy resin, alicyclic epoxy resin, aliphatic epoxy resin, or the like with a polybasic acid and (meth)acrylic acid; and (meth)acrylates obtained by reacting a bifunctional or higher aromatic epoxy resin, alicyclic epoxy resin, aliphatic epoxy resin, or the like with a phenol and (meth)acrylic acid. The above-mentioned ionizing radiation curable resins can be used alone or in combination of two or more.

[0083] When the ionizing radiation-curable resin is an ultraviolet-curable resin, the resin layer-forming coating liquid 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, benzyl dimethyl ketal, benzoyl benzoate, α-acyloxime ester, thioxanthones, etc. The photopolymerization accelerator can reduce polymerization inhibition by air during curing and increase the curing rate, and examples thereof include one or more selected from p-dimethylaminobenzoic acid isoamyl ester, p-dimethylaminobenzoic acid ethyl ester, etc.

[0084] The pattern layer may contain additives such as a refractive index adjuster, an antioxidant, an ultraviolet absorber, a light stabilizer, and an antistatic agent, as long as the effects of the present disclosure are not impaired.

[0085] <<Method for forming pattern layer>> The pattern layer can be formed, for example, by shaping the unshaped pattern layer 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.

[0086] Step 1: A step of applying a resin-containing pattern layer-forming coating liquid onto a substrate to form a resin-containing layer. Step 2: A step of shaping the resin-containing layer using a plate having a shape complementary to the surface shape of the first surface of the pattern layer.

[0087] When the coating liquid for forming a pattern layer contains a solvent, it is preferable to dry the solvent in step 1.

[0088] When a curable resin is used as the resin, it is preferable to use a pattern layer-forming coating liquid containing a curable resin composition as the pattern layer-forming coating liquid in step 1. 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 a pattern layer-forming coating liquid containing an ionizing radiation-curable resin composition is used as the pattern layer-forming coating liquid in step 1, it is preferable to irradiate with ionizing radiation simultaneously with the shaping in step 2, and cure the ionizing radiation-curable resin composition contained in the shaped layer.

[0089] When another layer such as a primer layer is present between the substrate and the pattern layer, it is preferable to carry out a step of forming the other layer on the substrate before step 1.

[0090] The plate used in step 2 can be fabricated by general-purpose means such as laser lithography, electron beam lithography, or FIB (Focused Ion Beam). The concave-convex shape formed on the surface of the plate can be designed using general-purpose simulation software. It is also preferable to create multiple copies of the plate fabricated by the above-described means and then arrange these copies to form a multi-faceted plate. The plate can be replicated by general-purpose means such as electroforming. Examples of plate shapes include flat and cylindrical. Cylindrical plates are preferred because they can be processed by roll-to-roll and offer excellent productivity. The aforementioned Y-shaped connecting recesses, etc., may be provided at the time of design using simulation software. Furthermore, during the process of forming the concave-convex shape using general-purpose means such as electron beam lithography, closely spaced recesses may be joined together. In this way, connecting recesses may be provided during the process of forming the concave-convex shape (those skilled in the art can adjust the number of connecting recesses taking into account the exposure accuracy and the spacing between adjacent recesses).

[0091] <Liquid Crystal Layer> In the optical element of the present disclosure, the liquid crystal layer is formed on the first surface of the patterned layer. The liquid crystal layer can be formed, for example, by applying a liquid crystal layer-forming coating liquid containing a liquid crystal compound onto the patterned layer, and then drying and curing the liquid crystal layer as necessary.

[0092] Examples of the liquid crystal compound 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 (disk-shaped liquid crystal compounds). The 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 liquid crystal compound molecules rotates when the liquid crystal layer is viewed in a plane. However, the direction of the liquid crystal compound molecules does not need to rotate 360 ​​degrees, and may be rotated by less than 360 degrees. Furthermore, the direction of rotation of the liquid crystal compound molecules may be clockwise or counterclockwise.

[0093] The liquid crystal compound is preferably a rod-shaped liquid crystal compound, and although there is no particular limitation on the rod-shaped liquid crystal compound, examples thereof include the compounds shown in (1) to (17) below.

[0094]

[0095]

[0096] Among liquid crystal compounds, polymerizable rod-shaped liquid crystal materials are preferred. Polymerizable functional groups of polymerizable rod-shaped liquid crystal materials include those that polymerize under the action of ionizing radiation such as ultraviolet light or electron beams, or heat. Specific examples include radically polymerizable functional groups. Examples of radically polymerizable functional groups include functional groups having at least one addition-polymerizable ethylenically unsaturated double bond, and more specific examples include vinyl groups and acrylate groups (a general term including acryloyl groups, methacryloyl groups, acryloyloxy groups, and methacryloyloxy groups), with or without substituents.

[0097] The liquid crystal layer is preferably formed over the entire surface of the first surface of the pattern layer. That is, it is preferable to form the liquid crystal layer also in areas on the first surface of the pattern layer that do not have recesses (FIG. 1). The thickness of the liquid crystal layer may be adjusted according to the desired retardation value.

[0098] The liquid crystal layer may have a single layer structure or a multi-layer structure. In order to reduce the thickness, the liquid crystal layer preferably has a single layer structure. In order to improve the display quality by broadening the bandwidth of the optical element, the liquid crystal layer preferably satisfies the following condition (i) or (ii): (i) The liquid crystal layer has a multi-layer structure and has positive wavelength dispersion or negative wavelength dispersion. (ii) The liquid crystal layer has a single layer structure and has positive wavelength dispersion or negative wavelength dispersion.

[0099] The liquid crystal layer may have positive wavelength dispersion or negative wavelength dispersion. Negative wavelength dispersion is a characteristic in which the retardation imparted to transmitted light increases as the wavelength of transmitted light increases. Positive wavelength dispersion is a characteristic in which the retardation imparted to transmitted light decreases as the wavelength of transmitted light increases. 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, a characteristic in which Re450<Re550 is referred to as negative wavelength dispersion. In this specification, a characteristic in which Re450>Re550 is referred to as positive wavelength dispersion.

[0100] In an optical element having a liquid crystal layer laminated on a patterned layer, the shape of the patterned layer can be confirmed, for example, by the following method (1) or (2). Note that the shape of the patterned layer may be confirmed by a method other than the following methods (1) and (2), as long as the method can easily remove the liquid crystal layer on the patterned layer. (1) According to JIS K5600-5-6:1999, 100 grid-like cuts are made on the surface of the liquid crystal layer at 1 mm intervals. Then, 18 mm Scotch tape (registered trademark) manufactured by Nichiban Co., Ltd. is applied to the cut areas and rubbed with an eraser to firmly adhere the tape to the coating film. The tape is then momentarily peeled off at least 10 times to remove the coating film. If, during the above-described operation, some of the coating film from the grid-like cuts begins to peel off, it is preferable to repeat the above-described operation, focusing on the peeled area. In this way, the shape of the patterned layer can be confirmed by peeling off the liquid crystal layer on the patterned layer. (2) Using a cross-section cutting technique used for cross-sectional observations such as STEM, the optical element is cut as thin as possible and cross-sectional STEM images are taken repeatedly. The cross-sectional STEM images obtained are then stitched together to create a three-dimensional image, allowing the shape of the pattern layer to be confirmed.

[0101] <Substrate> The optical element of the present disclosure may have a substrate.

[0102] Various materials can be used as the material constituting the substrate, but materials with good mechanical properties, optical properties, stability, and processability are preferred. Examples of 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, and urethane acrylate; glass; and the like, with resins being 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, even more preferably 3 nm or less, even more preferably 1 nm or less, and most preferably 0 nm. The wavelength λ of light serving as the reference for the retardation is 550 nm.

[0103] The thickness of the substrate can be adjusted appropriately within the range of 5 μm or more and 1000 μm or less. The thickness of the substrate is measured using a film thickness measuring device. Examples of film thickness measuring devices include a Mitutoyo Digimatic Standard Outside Micrometer (product number: MDC-25SX). The thickness of the substrate may be measured at any 10 points, and the average value thereof may be the above-mentioned value.

[0104] The substrate preferably has a total light transmittance of 70% or more, more preferably 80% or more, and even more preferably 85% or more according to 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 according to JIS K7136:2000.

[0105] In order to suppress 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 are close to each other. 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, and more preferably 0.99 or more and 1.01 or less. The wavelength λ of light that serves as the reference for the refractive index is 550 nm.

[0106] <Other Layers> The optical element of the present disclosure may further include other layers. Examples of other layers include a primer layer for improving adhesion between the substrate and the pattern layer, an antistatic layer, etc. The primer layer is preferably formed between the substrate and the pattern layer. The antistatic layer is preferably formed on the opposite side of the substrate from the pattern layer.

[0107] <Retardation> The optical element may have an average 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, more 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. By setting the average in-plane retardation of the optical element within the above range, the optical element can exhibit, for example, the following effects when used as a diffractive optical element. (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 the light can be separated into right-handed circularly polarized light and left-handed circularly polarized light. The in-plane retardation of an optical element refers to the average value of five in-plane retardations, excluding the maximum and minimum values, from among the seven in-plane retardations in the plane of the optical element. The wavelength λ of light serving as the reference for the retardation is 550 nm. Examples of in-plane retardation measuring devices include the "AxoStep" manufactured by AXOMETRICS and the two-dimensional birefringence evaluation system (product name: WPA-Micro) from Photonic Lattice. The former product is suitable for measuring a wide area, while the latter product is suitable for measuring a narrow area.

[0108] <Applications> The optical element of the present disclosure can be used, for example, as a diffractive optical element. The optical element of the present disclosure can also be used as a component of a light control device. Light transmitted through a diffractive optical element can be adjusted to a predetermined diffraction angle range. Therefore, for example, by using a diffractive optical element, it is possible to widen or narrow the irradiation range of light. Furthermore, by causing the lights transmitted through the diffractive optical element to interfere with each other, it is possible to produce the effects of a lens, a prism, or the like. Due to the above-mentioned effects, the diffractive optical element can be used as a component of devices such as cross reality, optical sensors, and laser projectors.

[0109] The diffraction angle θ of a diffractive optical element is expressed as follows: pitch is x [nm], wavelength of light is λ [nm], and incident angle of light is θ ０ In this case, θ and θ can be expressed by the following equations.０ is the angle when the perpendicular direction to the plane of the diffractive optical element is set to 0 degrees. ０ is the case when the angle is in the positive direction from the perpendicular direction. Depending on the direction of rotation of the circularly polarized incident light, the light may be diffracted in the positive direction or the negative direction relative to the perpendicular direction. For this reason, the ± sign is added to the following formula. As mentioned above, the pitch means the distance between recesses that correspond to each other in adjacent domain units. sin θ = ±(λ / x) + sin θ ０

[0110] For example, the incident angle θ ０ When the angle is fixed to 0 degrees and the wavelength of light is fixed to 1550 nm, the relationship between the pitch and the diffraction angle is as shown in Table 1 below.

[0111] The diffraction angles in Table 1 are angles when there is one diffractive optical element. If the polarization state is the same, increasing the number of diffractive optical elements increases the diffraction angle as a multiplier of the number of diffractive optical elements. If the diffraction angle at an arbitrary pitch is θ (degrees) and the number of diffractive optical elements is n, the diffraction angle is 2 ｎ－１ It can be expressed as ×θ (degrees).

[0112] The present disclosure includes the following items <1> to <11>. <1> An optical element having a pattern layer and a liquid crystal layer, wherein the pattern layer has a first surface and a second surface opposite to the first surface, the liquid crystal layer is formed on the first surface of the pattern layer, the pattern layer has a plurality of domains arranged in a first direction in the first surface, the domains form domain units each formed by a collection of a predetermined number of domains, the plurality of domains have, within each domain, a plurality of recesses arranged in a second direction perpendicular to the first direction, adjacent domains are in contact with each other, when an angle formed between an extension direction of the recesses and the first direction in a domain located n-th from one end of the domain unit in the first direction is defined as θn, θn changes stepwise from the one end to the other end of the domain unit in the first direction within a range of more than −90.0 degrees to less than +90.0 degrees, when a shortest distance between adjacent recesses in any domain is defined as D1, D1 is the same in all domains, An optical element, wherein, when the distance between adjacent recesses in any domain in a direction parallel to the second direction is defined as D2, D2 in each domain increases as the absolute value of θn of the domain increases. <2> The optical element according to <1>, in which the number of domains forming the domain unit is 4 or more and 359 or less. <3> The optical element according to <1> or <2>, in which, when the length in the extension direction of the recesses in any domain is defined as L1, L1 in each domain increases as the absolute value of θn of the domain increases. <4> The optical element according to any of <1> to <3>, in which, when the angle formed between the extension direction of the recesses and the first direction in a domain located n+1-th from one end of the domain unit in the first direction is defined as θn+1, the absolute value of the difference between θ and θn+1 is 0.5 degrees or more and 36.0 degrees or less. <5> The optical element according to any one of <1> to <4>, wherein the recesses include coupling recesses that contact the recesses of adjacent domains and non-coupling recesses that do not contact the recesses of adjacent domains.<6> The optical element according to <5>, wherein the bonding recesses have a double bonding recess that contacts recesses on both sides of adjacent domains, and a single bonding recess that contacts recesses on one side of adjacent domains. <7> The optical element according to <5>, wherein the bonding recesses are formed by bonding two recesses of one adjacent domain to one recess of the other adjacent domain. <8> The optical element according to any one of <1> to <7>, wherein the liquid crystal layer has a single-layer structure. <9> The optical element according to any one of <1> to <7>, wherein the liquid crystal layer has a multi-layer structure. <10> The optical element according to <8>, wherein the liquid crystal layer has positive wavelength dispersion or negative wavelength dispersion. <11> The optical element according to <9>, wherein the liquid crystal layer has positive wavelength dispersion or negative wavelength dispersion.

[0113] Next, the present disclosure will be described in more detail with reference to examples, but the present disclosure is not limited to these examples. Note that "parts" and "%" are based on mass unless otherwise specified.

[0114] 1. Measurement and Evaluation The following measurements and evaluations were carried out on the optical elements of the Examples and Comparative Examples. The atmosphere during each measurement and evaluation was a temperature of 23±5°C and a relative humidity of 40% to 65%. Before starting each measurement and evaluation, the target sample was exposed to the atmosphere for 30 to 60 minutes, and then the measurement and evaluation were carried out.

[0115] 1-1. Planar Shape of Pattern Layer The first surface of the pattern layer of the intermediate of the optical element of the example and comparative example was imaged using a scanning electron microscope (Hitachi High-Technologies Corporation, product name "SU8000"). The imaging conditions were as follows. The intermediate refers to a laminate having a primer layer and a pattern layer on a substrate. Then, based on the captured photograph, θn, L1, the length of the recess in the minor axis direction, D1, D2, the number of Y-shaped bonds, the domain width, and the pitch were measured. θn, L1, the length of the recess in the minor axis direction, D1, D2, and the number of Y-shaped bonds were averaged over 10 locations. The results are shown in Table 3. For comparative examples in which the pattern layer could not be peeled from the plate during pattern layer formation, the results were marked with "-." <Imaging conditions> ・Accelerating voltage: 5.0Kv ・Emission current: 5.0uA ・Probe current: High ・Detector: SE(U) ・WD: 8mm ・Condenser lens 1: 5.0 ・Condenser lens 2: 1.0 ・Tilt function of sample stand: Enter tilt angle "0.0"

[0116] 1-2. Depth of recesses in pattern layer Vertical cross sections of the optical elements of the examples and comparative examples were photographed using a scanning electron microscope (Hitachi High-Technologies Corporation, product name "SU8000"). The photographing conditions were the same as those in 1-1 above. The depth of the recesses in the intermediate body was then measured. The depth of the recesses was taken as the average value of 10 locations. The results are shown in Table 3.

[0117] 1-3. Peelability Peelability was evaluated according to the following criteria. The results are shown in Table 3. A: When the pattern layer was formed, no resin remained on the shaping plate, and the pattern layer was easily peelable from the plate. B: When the pattern layer was formed, a small amount of resin remained on the shaping plate, but the pattern layer was easily peelable from the plate. C: When the pattern layer was formed, some of the resin remained on the shaping plate, and the pattern layer was not easily peelable from the plate. D: When the pattern layer was formed, the shaping plate could not be peeled from the shaped layer.

[0118] 1-4. First Alignment The alignment of the liquid crystal layer was evaluated for the optical elements of the Examples and Comparative Examples according to the following criteria. A polarizing microscope was used for the evaluation. The results are shown in Table 3. When the pitch of the pattern layer is 1 μm, the "observation area 50 times the pitch of the pattern layer" described below is 50 μm x 50 μm. The fewer schlieren textures there are, the better the alignment of the liquid crystal molecules. A: In an observation area 50 times the pitch of the pattern layer, the number of schlieren textures is zero, excluding those caused by dust. B: In an observation area 50 times the pitch of the pattern layer, the number of schlieren textures is between 1 and 9, excluding those caused by dust. C: In an observation area 50 times the pitch of the pattern layer, the number of schlieren textures is 10 or more, excluding those caused by dust.

[0119] 1-5. Second Orientation For the optical elements of the Examples and Comparative Examples, the orientation of the liquid crystal molecules at the points where adjacent recesses are joined was observed and evaluated according to the following criteria. For the observations, a two-dimensional birefringence evaluation system (product name: WPA-Micro) from Photonic Lattice was used. For the second orientation, a narrower area was observed than for the first orientation. A: Where adjacent recesses are joined, the difference between the orientation of the recesses and the orientation of the liquid crystal molecules is less than 3.0 degrees. B: Where adjacent recesses are joined, the difference between the orientation of the recesses and the orientation of the liquid crystal molecules is 3.0 degrees or more and 6.0 degrees or less. C: Where adjacent recesses are joined, the difference between the orientation of the recesses and the orientation of the liquid crystal molecules is more than 6.0 degrees.

[0120] 1-6. Third Orientation For the optical elements of the examples and comparative examples, the orientation of the liquid crystal molecules in areas where adjacent recesses were not bonded was observed and evaluated according to the following criteria. For the observations, a two-dimensional birefringence evaluation system (product name: WPA-Micro) from Photonic Lattice was used. For the third orientation, a narrower area was observed than for the first orientation. A: In areas where adjacent recesses are not bonded, the difference between the orientation of the recesses and the orientation of the liquid crystal molecules is less than 3.0 degrees. B: In areas where adjacent recesses are not bonded, the difference between the orientation of the recesses and the orientation of the liquid crystal molecules is 3.0 degrees or more and 6.0 degrees or less. C: In areas where adjacent recesses are not bonded, the difference between the orientation of the recesses and the orientation of the liquid crystal molecules is more than 6.0 degrees.

[0121] 2. Fabrication of the Plate A simulation tool was used to design the shape of the first surface of the pattern layer. In the simulation, θn, L1, the length of the recess in the minor axis direction, D1, D2, the number of Y-shaped bonds, the domain width, and the domain pitch were set to the values ​​listed in Table 2. Furthermore, multiple domain units were arranged in the first direction, and boundaries were arranged between the domain units. The width of the boundaries was set to be the same as the domain width. The simulation shapes of the examples were simulated to satisfy configurations 1 to 8 of the specification. The recess arrangement pattern of the simulation shape used in the comparative example was a pattern in which the recess ends of adjacent domains all contacted equally in the second direction, as shown in FIG. 7. The recess arrangement pattern of the simulation shape used in the examples was one in which the degree of contact between the recess ends of adjacent domains varied along the second direction. Using a 6-inch square synthetic quartz plate, a quartz master mold having the surface shape designed in the simulation was fabricated by an electron beam lithography process using an electron beam lithography system and a dry etching system. Next, an ultraviolet-curable resin was poured into the master mold, and a transparent substrate was then placed on top of the ultraviolet-curable resin. The resin was then cured by irradiating it with ultraviolet light. The transparent substrate and resin were then peeled off from the master mold to obtain a resin plate having a shape complementary to that of the master mold. Next, electroforming was used to obtain a replica mold of the master mold, which is a mold having a shape complementary to that of the resin plate. Multiple replica molds were produced. Multiple replica molds were wound around a roll to produce a roll-shaped plate used in the examples and comparative examples.

[0122] 3. Fabrication of Optical Element [Example 1] A primer layer having the following formulation was applied to a substrate (a 40 μm thick cycloolefin polymer, Zeon Corporation's trade name "ZEONOR") and dried to form a primer layer having a thickness of 0.5 μm. Next, a pattern layer-forming coating liquid having the following formulation was applied to the primer layer and dried to form a layer containing uncured resin. Next, the roll-shaped plate prepared in "2" above was used to form the layer containing uncured resin, and at the same time, ultraviolet light was irradiated from the substrate side (cumulative light amount: 500 mJ / cm ２), and the layer containing the shaped resin was cured. Next, 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, the following liquid crystal layer-forming coating solution was applied to the pattern layer, dried, and then irradiated with ultraviolet light (integrated light amount: 150 mJ / cm ２ ), a liquid crystal layer was formed. The liquid crystal layer used was a liquid crystal with an in-plane birefringence (Δn) of 0.17, and the film thickness was adjusted so that the in-plane retardation was 266 nm. The liquid crystal layer with the above film thickness was formed by two coating steps. The optical element of Example 1 was obtained by the above process. The optical element of Example 1 was produced by roll-to-roll production.

[0123] <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 Nanotec Co., Ltd., trade name: SIRMIBK15WT%-E65) Methyl ethyl ketone: 25 parts by mass

[0124] <Coating liquid for forming pattern layer> Pentaerythritol triacrylate: 96 parts by mass (manufactured by Nippon Kayaku Co., Ltd., product name: PET-30) Photopolymerization initiator: 4 parts by mass (manufactured by IGM, product name: Omnirad 184)

[0125] <Liquid crystal layer forming coating liquid> Rod-shaped liquid crystal molecules: 10 parts by mass (LC242 (trade name), manufactured by BASF, in-plane birefringence (Δn) = 0.17) Photopolymerization initiator: 0.4 parts by mass (manufactured by IGM, trade name: Omnirad 184) Methyl ethyl ketone: 89.6 parts by mass

[0126] [Examples 2 to 5], [Comparative Examples 1 to 5] Except for changing the plate to that shown in Table 2, laminates having a primer layer and a pattern layer on a substrate, and optical elements were obtained in the same manner as in Example 1.

[0127]

[0128] In Table 2, "one end" means "domain at one end", "center" means "center domain", and "other end" means "domain at the other end".

[0129]

[0130] In Table 3, "one end" means "domain at one end", "center" means "center domain", and "other end" means "domain at the other end".

[0131] As is clear from Table 3, the optical elements of the examples have good alignment of the liquid crystal molecules, and therefore it can be confirmed that the performance of the optical elements can be fully exhibited.

[0132] 10: Substrate 20: Pattern layer 20a: First surface 20b: Second surface 21: Recess 22: Bonding recess 23: Domain unit 23a, 23b, 23c, 23d, 23e, 23f, 23g, 23h: Individual domain 25: Boundary 25-1: Boundary recess 25-2: Convex 30: Liquid crystal layer 100: Optical element A1: First direction A2: Second direction

Claims

1. An optical element having a pattern layer and a liquid crystal layer, wherein the pattern layer has a first surface and a second surface opposite to the first surface, the liquid crystal layer is formed on the first surface of the pattern layer, the pattern layer has a plurality of domains arranged in a first direction within the first surface, the domains form domain units in which a predetermined number of domains are assembled, the plurality of domains have a plurality of recesses arranged in a second direction perpendicular to the first direction within each domain, adjacent domains are in contact with each other, when the angle between the extension direction of the recesses and the first direction in the domain located n-th from one end of the domain unit in the first direction is defined as θn, θn changes stepwise from the one end to the other end of the domain unit in the first direction within a range of more than -90.0 degrees to less than +90.0 degrees, and when the shortest distance between adjacent recesses in any domain is defined as D1, D1 is the same in all domains, An optical element, wherein when the distance between adjacent recesses in any domain in a direction parallel to the second direction is defined as D2, D2 in each domain increases as the absolute value of θn of the domain increases.

2. The optical element according to claim 1, wherein the number of the domains forming the domain unit is 4 or more and 359 or less.

3. The optical element according to claim 1, wherein when the length in the extension direction of the recess in any domain is defined as L1, L1 in each domain becomes longer as the absolute value of θn of the domain becomes larger.

4. The optical element described in claim 1, wherein, when the angle between the extension direction of the recess and the first direction in the domain located n+1th from one end of the domain unit in the first direction is defined as θn+1, the absolute value of the difference between θ and θn+1 is 0.5 degrees or more and 36.0 degrees or less.

5. The optical element according to claim 1, wherein the recesses include a bonding recess that contacts the recesses of an adjacent domain and a non-bonding recess that does not contact the recesses of an adjacent domain.

6. The optical element according to claim 5, wherein the coupling recesses include a double-sided coupling recess that contacts the recesses on both sides of adjacent domains on both sides, and a single-sided coupling recess that contacts the recesses on one side of adjacent domains on both sides.

7. The optical element according to claim 5, wherein the coupling recess comprises a coupling recess in which two recesses in one adjacent domain are coupled to one recess in the other adjacent domain.

8. The optical element according to claim 1, wherein the liquid crystal layer has a single layer structure.

9. The optical element according to claim 1, wherein the liquid crystal layer has a multi-layer structure.

10. The optical element according to claim 8, wherein the liquid crystal layer has positive or negative wavelength dispersion.

11. The optical element according to claim 9, wherein the liquid crystal layer has positive wavelength dispersion or negative wavelength dispersion.

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