Transmissive liquid crystal diffraction element

Abstract

Provided is a transmissive liquid crystal diffraction element capable of diffracting different polarized light in the same direction and having high diffraction efficiency for non-polarized light. The transmissive liquid crystal diffraction element has a first to fourth optically anisotropic layer, the first to fourth optically anisotropic layer has a liquid crystal alignment pattern in which the orientation of an optical axis continuously changes in at least one direction in the in-plane, the optical axis of the first to fourth optically anisotropic layer is twisted in the thickness direction, the direction of rotation of the optical axis in the liquid crystal alignment pattern of the first optically anisotropic layer and the second optically anisotropic layer and the direction of twisting of the optical axis in the thickness direction are opposite, the direction of rotation of the optical axis in the liquid crystal alignment pattern of the third optically anisotropic layer and the fourth optically anisotropic layer and the direction of twisting of the optical axis in the thickness direction are opposite, one period in the liquid crystal alignment pattern of the first optically anisotropic layer and the second optically anisotropic layer and the third optically anisotropic layer and the fourth optically anisotropic layer is the same, respectively, and one period in the liquid crystal alignment pattern of the first optically anisotropic layer and the third optically anisotropic layer is different.

Description

Technical Field

[0001] This invention relates to a transmissive liquid crystal diffraction element that diffracts incident light. Background Technology

[0002] Diffraction elements, as optical components that bend light to control its direction of travel, are used in many optical devices or systems.

[0003] As such a diffraction element, a liquid crystal diffraction element made of a liquid crystal compound is proposed.

[0004] For example, Patent Document 1 describes a polarization diffraction grating comprising a first polarization diffraction grating layer and a second polarization diffraction grating layer. The first polarization diffraction grating layer includes a molecular structure twisted according to a first twist property, such that the relative orientation of each of the molecules in the first polarization diffraction grating layer is rotated by a first twist angle on a first thickness defined between the two sides of the first polarization diffraction grating layer. The second polarization diffraction grating layer is located on the first polarization diffraction grating layer and includes a molecular structure twisted according to a second twist property opposite to the first twist property, such that the relative orientation of each of the molecules in the second polarization diffraction grating layer is rotated by a second twist angle on a second thickness defined between the two sides of the second polarization diffraction grating layer.

[0005] Previous technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2014-089476 Summary of the Invention

[0008] The technical problem to be solved by the invention

[0009] Polarizing diffraction elements made of liquid crystal compounds bend in different directions depending on the polarization of the light. Specifically, right-handed and left-handed circularly polarized light incident on a polarizing diffraction element bends and separates in opposite directions. Therefore, regardless of the polarization of the light, it is impossible to diffract light in a predetermined direction; for unpolarized light, the efficiency of diffracted light in the desired direction is at most 50%.

[0010] The objective of this invention is to provide a transmissive liquid crystal diffraction element that can diffract different polarized light in the same direction and can diffract unpolarized light with high efficiency.

[0011] means for solving technical problems

[0012] To address this issue, the present invention has the following structure.

[0013] [1] A transmissive liquid crystal diffraction element having a first optical anisotropic layer to a fourth optical anisotropic layer, wherein the first optical anisotropic layer to the fourth optical anisotropic layer have a liquid crystal alignment pattern that changes while the orientation of the optical axis of the liquid crystal compound is continuously rotated in at least one in-plane direction.

[0014] In the first to fourth optical anisotropic layers, the optical axis originating from the liquid crystal compound is twisted along the thickness direction.

[0015] The rotation direction of the optical axis in the liquid crystal alignment pattern of the first optical anisotropic layer is opposite to the rotation direction of the optical axis in the liquid crystal alignment pattern of the second optical anisotropic layer.

[0016] The rotation direction of the optical axis in the liquid crystal alignment pattern of the third optical anisotropy layer is opposite to the rotation direction of the optical axis in the liquid crystal alignment pattern of the fourth optical anisotropy layer.

[0017] The twist direction of the optical axis originating from the liquid crystal compound in the thickness direction of the first optical anisotropic layer is opposite to the twist direction of the optical axis originating from the liquid crystal compound in the thickness direction of the second optical anisotropic layer.

[0018] The twist direction of the optical axis originating from the liquid crystal compound in the thickness direction of the third optical anisotropic layer is opposite to the twist direction of the optical axis originating from the liquid crystal compound in the thickness direction of the fourth optical anisotropic layer.

[0019] When the length of 180° in-plane rotation of the optical axis originating from the liquid crystal compound in the liquid crystal alignment pattern is defined as one period, one period in the liquid crystal alignment pattern of the first optical anisotropy layer is the same as one period in the liquid crystal alignment pattern of the second optical anisotropy layer.

[0020] One period in the liquid crystal alignment pattern of the third optical anisotropic layer is the same as one period in the liquid crystal alignment pattern of the fourth optical anisotropic layer.

[0021] One period in the liquid crystal alignment pattern of the first optical anisotropic layer is different from one period in the liquid crystal alignment pattern of the third optical anisotropic layer.

[0022] [2] According to the transmissive liquid crystal diffraction element described in [1], wherein,

[0023] The twist angle of the optical axis originating from the liquid crystal compound in the thickness direction of the first to fourth optical anisotropic layers is less than 360°.

[0024] [3] According to the transmission-type liquid crystal diffraction element described in [1] or [2], wherein,

[0025] The first to fourth optical anisotropic layers have a liquid crystal alignment pattern in a radial pattern.

[0026] [4] The transmissive liquid crystal diffraction element according to any one of [1] to [3], wherein,

[0027] In at least one combination of the combination of the first optical anisotropic layer and the second optical anisotropic layer and the combination of the third optical anisotropic layer and the fourth optical anisotropic layer, one period of the liquid crystal alignment pattern gradually changes along one direction.

[0028] [5] According to the transmission-type liquid crystal diffraction element described in [3] or [4], wherein,

[0029] From the center of the radial liquid crystal alignment pattern toward the outer part, the difference between the reciprocal of one period of the liquid crystal alignment pattern of the first optical anisotropic layer and the reciprocal of one period of the liquid crystal alignment pattern of the third optical anisotropic layer gradually increases.

[0030] [6] The transmissive liquid crystal diffraction element according to any one of [1] to [5], wherein,

[0031] A C-plate is also present between any of the layers from the first to the fourth optical anisotropy layer.

[0032] [7] The transmissive liquid crystal diffraction element according to any one of [1] to [6], wherein,

[0033] In at least one combination of the combination of the first optical anisotropic layer and the second optical anisotropic layer and the combination of the third optical anisotropic layer and the fourth optical anisotropic layer, the liquid crystal compound of one optical anisotropic layer is a rod-shaped liquid crystal compound, and the liquid crystal compound of the other optical anisotropic layer is a disk-shaped liquid crystal compound.

[0034] Invention Effects

[0035] According to the present invention, a transmissive liquid crystal diffraction element is provided that can diffract different polarized light in the same direction and also has high diffraction efficiency for unpolarized light. Attached Figure Description

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

[0037] Figure 2 It is a conceptual representation Figure 1 The diagram shows the optical anisotropy layer of the transmissive liquid crystal diffraction element.

[0038] Figure 3 yes Figure 2The top view of the optical anisotropic layer shown.

[0039] Figure 4 For use in forming Figure 2 A conceptual diagram of an example of an exposure apparatus for exposing an alignment film of an optical anisotropic layer.

[0040] Figure 5 This is a conceptual diagram used to illustrate the role of optical anisotropic layers.

[0041] Figure 6 This is a conceptual diagram used to illustrate the role of optical anisotropic layers.

[0042] Figure 7 It is used for explanation Figure 1 The diagram shows a conceptual representation of the function of a transmissive liquid crystal diffraction element.

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

[0044] Figure 9 This is a diagram that conceptually illustrates another example of the transmissive liquid crystal diffraction element of the present invention.

[0045] Figure 10 This is a top view conceptually illustrating another example of the optical anisotropy layer of the transmissive liquid crystal diffraction element of the present invention.

[0046] Figure 11 For use in forming Figure 10 A conceptual diagram of an example of an exposure apparatus for exposing an alignment film of an optical anisotropic layer.

[0047] Figure 12 This is a front view of the first and second optically anisotropic layers in another example of the transmissive liquid crystal diffraction element of the present invention.

[0048] Figure 13 This is a front view of the third and fourth optical anisotropy layers in another example of the transmissive liquid crystal diffraction element of the present invention.

[0049] Figure 14 This is a diagram that conceptually illustrates the relationship between one period of the first optical anisotropy layer and one period of the third optical anisotropy layer in another example of the transmissive liquid crystal diffraction element of the present invention.

[0050] Figure 15 This is a conceptual diagram illustrating the function of another example of the transmissive liquid crystal diffraction element of the present invention.

[0051] Figure 16This is a conceptual diagram illustrating the function of another example of the transmissive liquid crystal diffraction element of the present invention. Detailed Implementation

[0052] Hereinafter, the transmissive liquid crystal diffraction element of the present invention will be described in detail with reference to the preferred embodiment shown in the accompanying drawings.

[0053] In this specification, the numerical range indicated by “~” refers to the range encompassed by the values ​​recorded before and after “~” as the lower and upper limits.

[0054] In this specification, "(meth)acrylate" is used to mean "any one or both of acrylate and methacrylate".

[0055] In this specification, terms such as "same" and "equal" include the range of errors that are generally permissible in the technical field.

[0056] [Transmission-type liquid crystal diffraction element]

[0057] The liquid crystal diffraction element of the present invention is as follows:

[0058] It has a first optical anisotropic layer to a fourth optical anisotropic layer, wherein the first optical anisotropic layer to the fourth optical anisotropic layer have a liquid crystal alignment pattern that changes while the orientation of the optical axis derived from the liquid crystal compound is continuously rotated in at least one in-plane direction.

[0059] In the first to fourth optical anisotropic layers, the optical axis originating from the liquid crystal compound is twisted along the thickness direction.

[0060] The rotation direction of the optical axis in the liquid crystal alignment pattern of the first optical anisotropic layer is opposite to the rotation direction of the optical axis in the liquid crystal alignment pattern of the second optical anisotropic layer.

[0061] The rotation direction of the optical axis in the liquid crystal alignment pattern of the third optical anisotropy layer is opposite to the rotation direction of the optical axis in the liquid crystal alignment pattern of the fourth optical anisotropy layer.

[0062] The twist direction of the optical axis originating from the liquid crystal compound in the thickness direction of the first optical anisotropic layer is opposite to the twist direction of the optical axis originating from the liquid crystal compound in the thickness direction of the second optical anisotropic layer.

[0063] The twist direction of the optical axis originating from the liquid crystal compound in the thickness direction of the third optical anisotropic layer is opposite to the twist direction of the optical axis originating from the liquid crystal compound in the thickness direction of the fourth optical anisotropic layer.

[0064] When the length of 180° in-plane rotation of the optical axis originating from the liquid crystal compound in the liquid crystal alignment pattern is defined as one period, one period in the liquid crystal alignment pattern of the first optical anisotropy layer is the same as one period in the liquid crystal alignment pattern of the second optical anisotropy layer.

[0065] One period in the liquid crystal alignment pattern of the third optical anisotropic layer is the same as one period in the liquid crystal alignment pattern of the fourth optical anisotropic layer.

[0066] One period in the liquid crystal alignment pattern of the first optical anisotropic layer is different from one period in the liquid crystal alignment pattern of the third optical anisotropic layer.

[0067] Figure 1 The present invention conceptually illustrates an example of a transmissive liquid crystal diffraction element.

[0068] Figure 1 The transmissive liquid crystal diffraction element 10 shown has a first optical anisotropic layer 36a, a second optical anisotropic layer 36b, a third optical anisotropic layer 36c, and a fourth optical anisotropic layer 36d arranged sequentially in the thickness direction. Furthermore, in Figure 1 In order to simplify the accompanying drawings and clearly illustrate the structure of the transmissive liquid crystal diffraction element 10, only a portion of the liquid crystal compound 40 (liquid crystal compound molecules) is conceptually shown in the first optical anisotropy layer 36a to the fourth optical anisotropy layer 36d. However, as in Figure 2 The diagram conceptually shows that the first optical anisotropy layer 36a to the fourth optical anisotropy layer 36d have a structure in which liquid crystal compound 40 is stacked in the thickness direction, and the optical axis of the liquid crystal compound 40 stacked in the thickness direction is oriented in a twisted manner.

[0069] The first optical anisotropy layer 36a to the fourth optical anisotropy layer 36d each have a liquid crystal alignment pattern that changes as the orientation of the optical axis originating from the liquid crystal compound 40 rotates continuously in at least one direction within the plane.

[0070] The first optical anisotropic layer 36a to the fourth optical anisotropic layer 36d are each capable of diffracting transmitted light through the liquid crystal alignment pattern described above. Regarding the diffraction angle based on each optical anisotropic layer, if the length of a 180° in-plane rotation of the orientation of the optical axis originating from the liquid crystal compound 40 in the liquid crystal alignment pattern is defined as one period (hereinafter also referred to as one period of the liquid crystal alignment pattern), then the diffraction angle depends on the length of this one period. Therefore, the diffraction angle of each optical anisotropic layer can be adjusted by adjusting one period of the liquid crystal alignment pattern.

[0071] The diffraction of light based on the optical anisotropic layer with the aforementioned liquid crystal alignment pattern varies depending on the polarization of the light. Specifically, right-handed and left-handed circularly polarized light incident on the optical anisotropic layer are diffracted and separated in opposite directions. The diffraction direction based on the optical anisotropic layer depends on the rotation direction of the optical axis in the liquid crystal alignment pattern.

[0072] Furthermore, the optical axes originating from the liquid crystal compound in each of the first optical anisotropic layer 36a to the fourth optical anisotropic layer 36d are twisted along the thickness direction. As described above, the optical anisotropic layer with the liquid crystal alignment pattern diffracts in different directions depending on the polarized light. In this case, if the optical axis originating from the liquid crystal compound is twisted along the thickness direction, the equiphase surface is tilted relative to the main surface of the optical anisotropic layer. Therefore, depending on the incident angle of the light, one polarized light is easily diffracted while the other polarized light is difficult to diffract. This will be described in detail later. In addition, the equiphase surface is a periodic surface of the liquid crystal compound in the same alignment direction.

[0073] In this invention, the rotation direction of the optical axis in the liquid crystal alignment pattern of the first optical anisotropy layer 36a is opposite to the rotation direction of the optical axis in the liquid crystal alignment pattern of the second optical anisotropy layer 36b. Furthermore, one period of the liquid crystal alignment pattern of the first optical anisotropy layer 36a is the same as one period of the liquid crystal alignment pattern of the second optical anisotropy layer 36b. Also, the twist direction of the optical axis originating from the liquid crystal compound in the thickness direction of the first optical anisotropy layer 36a is opposite to the twist direction of the optical axis originating from the liquid crystal compound in the thickness direction of the second optical anisotropy layer 36b.

[0074] Furthermore, the rotation direction of the optical axis in the liquid crystal alignment pattern of the third optical anisotropy layer 36c is opposite to the rotation direction of the optical axis in the liquid crystal alignment pattern of the fourth optical anisotropy layer 36d. Also, one period of the liquid crystal alignment pattern of the third optical anisotropy layer 36c is the same as one period of the liquid crystal alignment pattern of the fourth optical anisotropy layer 36d. Furthermore, the twist direction of the optical axis originating from the liquid crystal compound in the thickness direction of the third optical anisotropy layer 36c is opposite to the twist direction of the optical axis originating from the liquid crystal compound in the thickness direction of the fourth optical anisotropy layer 36d.

[0075] Furthermore, one period in the liquid crystal alignment pattern of the first optical anisotropic layer 36a (and the second optical anisotropic layer 36b) is different from one period in the liquid crystal alignment pattern of the third optical anisotropic layer 36c (and the fourth optical anisotropic layer 36d).

[0076] exist Figure 1 In the example shown, the rotation direction of the optical axis in the liquid crystal alignment pattern of the first optical anisotropy layer 36a is in Figure 1 When viewed from above, the rotation is clockwise from left to right. On the other hand, the optical axis in the liquid crystal alignment pattern of the second optical anisotropy layer 36b rotates counterclockwise to the left. Furthermore, the twist direction of the optical axis originating from the liquid crystal compound in the thickness direction of the first optical anisotropy layer 36a is... Figure 1 The optical axis of the second optical anisotropy layer 36b is twisted from top to bottom and to the right (clockwise). On the other hand, the optical axis originating from the liquid crystal compound in the thickness direction of the second optical anisotropy layer 36b is twisted to the left (counterclockwise).

[0077] Furthermore, in Figure 1 In the example shown, the rotation direction of the optical axis in the liquid crystal alignment pattern of the third optical anisotropy layer 36c is in Figure 1 When viewed from above, the rotation is clockwise from left to right. On the other hand, the optical axis in the liquid crystal alignment pattern of the fourth optical anisotropy layer 36d rotates counterclockwise to the left. Furthermore, the twist direction of the optical axis originating from the liquid crystal compound in the thickness direction of the third optical anisotropy layer 36c is... Figure 1 The optical axis of the fourth optical anisotropy layer 36d is twisted from top to bottom and to the right (clockwise). On the other hand, the optical axis originating from the liquid crystal compound in the thickness direction of the fourth optical anisotropy layer 36d is twisted to the left (counterclockwise).

[0078] And, as Figure 1 As shown, one period of the liquid crystal alignment pattern of the first optical anisotropic layer 36a is the same as one period of the liquid crystal alignment pattern of the second optical anisotropic layer 36b, one period of the liquid crystal alignment pattern of the third optical anisotropic layer 36c is the same as one period of the liquid crystal alignment pattern of the fourth optical anisotropic layer 36d, and one period of the liquid crystal alignment pattern of the first optical anisotropic layer 36a is different from one period of the liquid crystal alignment pattern of the third optical anisotropic layer 36c.

[0079] The transmissive liquid crystal diffraction element 10 of the present invention, having the above structure, transmits and diffracts incident light. In this case, right-handed and left-handed circularly polarized light can be diffracted in the same direction. That is, the transmissive liquid crystal diffraction element 10 of the present invention can diffract different polarized light in the same direction, thereby realizing a transmissive liquid crystal diffraction element with high diffraction efficiency. This effect will be described in detail later.

[0080] Furthermore, the rotation direction of the optical axis and the twist direction of the optical axis in the thickness direction of the liquid crystal alignment pattern of each optical anisotropy layer are not limited to... Figure 1In the example shown, other combinations are also possible, provided that the optical axes in the liquid crystal alignment patterns of the first optical anisotropy layer 36a and the second optical anisotropy layer 36b rotate in opposite directions and the optical axes in the thickness direction twist in opposite directions, and the optical axes in the liquid crystal alignment patterns of the third optical anisotropy layer 36c and the fourth optical anisotropy layer 36d rotate in opposite directions and the optical axes in the thickness direction twist in opposite directions.

[0081] Furthermore, in Figure 1 In the example shown, the optical axes in the liquid crystal alignment patterns of the first optical anisotropy layer 36a and the third optical anisotropy layer 36c have the same rotation direction and the same twist direction in the thickness direction, and the optical axes in the liquid crystal alignment patterns of the second optical anisotropy layer 36b and the fourth optical anisotropy layer 36d have the same rotation direction and the same twist direction in the thickness direction, but this is not a limitation. For example, it could also be a structure in which the optical axes in the liquid crystal alignment patterns of the first optical anisotropy layer 36a and the fourth optical anisotropy layer 36d have the same rotation direction and the same twist direction in the thickness direction, and the optical axes in the liquid crystal alignment patterns of the second optical anisotropy layer 36b and the third optical anisotropy layer 36c have the same rotation direction and the same twist direction in the thickness direction.

[0082] In this invention, preferably, the rotation direction of the optical axis and the twist direction of the optical axis in the liquid crystal alignment pattern of one of the first optical anisotropic layer 36a and the second optical anisotropic layer 36b, and one of the third optical anisotropic layer 36c and the fourth optical anisotropic layer 36d are the same, and the rotation direction of the optical axis and the twist direction of the optical axis in the liquid crystal alignment pattern of the other of the first optical anisotropic layer 36a and the second optical anisotropic layer 36b, and the other of the third optical anisotropic layer 36c and the fourth optical anisotropic layer 36d are the same.

[0083] Furthermore, it is preferable that the average tilt direction (tilted to the right or left) of the equiphase surfaces is the same across each optical anisotropic layer. When the tilts of the equiphase surfaces of the optical anisotropic layers are opposite, the intensity of the diffracted light (diffraction efficiency) decreases. Moreover, when the normal direction of the substrate surface is set to 0 degrees, the average tilt angle of the equiphase surfaces is preferably 5 to 35 degrees. Here, the average tilt angle refers to the angle obtained by averaging the tilt angles along the thickness direction when the optical anisotropic layers have a tilt angle distribution along the thickness direction.

[0084] Furthermore, in Figure 1In the example shown, the optical anisotropic layers are configured separately, but this is not a limitation; the optical anisotropic layers can also be configured to be in contact with each other. For example, the first optical anisotropic layer 36a and the second optical anisotropic layer 36b can be in contact, the second optical anisotropic layer 36b and the third optical anisotropic layer 36c can be separate, and the third optical anisotropic layer 36c and the fourth optical anisotropic layer 36d can be in contact.

[0085] (Optical anisotropic layer)

[0086] use Figure 2 and Figure 3 The first optical anisotropic layer 36a to the fourth optical anisotropic layer 36d will be described. Furthermore, except for the rotation direction of the optical axis in the liquid crystal alignment pattern, one period of the liquid crystal alignment pattern, and the twist direction of the optical axis in the thickness direction, the first optical anisotropic layer 36a to the fourth optical anisotropic layer 36d have the same structure. Therefore, without needing to distinguish between the first optical anisotropic layer 36a to the fourth optical anisotropic layer 36d, they will all be described as optical anisotropic layer 36.

[0087] Figure 2 and Figure 3 The example shown is an optical anisotropy layer 36 formed by fixing a liquid crystal phase that aligns a liquid crystal compound and having a liquid crystal alignment pattern that changes as the orientation of the optical axis originating from the liquid crystal compound rotates continuously in at least one direction within the plane, and an optical anisotropy layer 36 that is twisted along the thickness direction by the optical axis originating from the liquid crystal compound. Figure 2 and Figure 3 In the example shown, the rotation direction of the optical axis and the twist direction of the optical axis in the thickness direction of the liquid crystal alignment pattern of the optical anisotropy layer 36 are different from those of the optical anisotropy layer 36. Figure 1 The first optical anisotropy layer 36a is the same.

[0088] exist Figure 2 In the example shown, the optical anisotropic layer 36 is stacked on the alignment film 32 stacked on the support 30.

[0089] Furthermore, when the first optical anisotropic layer 36a to the fourth optical anisotropic layer 36d are used as a transmissive liquid crystal diffraction element, such as Figure 2 As shown in the example, the optical anisotropy layer 36 can also be used in a state where it is laminated on the support 30 and the alignment film 32. Alternatively, the optical anisotropy layer 36 can be used, for example, in a state where the support 30 has been peeled off, and only the alignment film 32 and the optical anisotropy layer 36 are laminated. Alternatively, the optical anisotropy layer 36 can be used, for example, in a state where the support 30 and the alignment film 32 have been peeled off, and only the optical anisotropy layer 36 is used.

[0090] <Support>

[0091] The support 30 supports the orientation film 32 and the optical anisotropy layer 36.

[0092] As long as the alignment film 32 and the optical anisotropy layer 36 can be supported, the support 30 can utilize various sheet-like materials (thin films, plates).

[0093] Furthermore, the transmittance of the support 30 relative to the diffracted light is preferably 50% or more, more preferably 70% or more, and even more preferably 85% or more.

[0094] There is no limitation on the thickness of the support 30. As long as the thickness of the support 30 is appropriately set according to the application of the transmissive liquid crystal diffraction element and the forming material of the support 30, it can maintain the thickness of the alignment film 32 and the optical anisotropy layer 36.

[0095] The thickness of the support 30 is preferably 1 to 1000 μm, more preferably 3 to 250 μm, and even more preferably 5 to 150 μm.

[0096] The support 30 can be a single layer or multiple layers.

[0097] Examples of single-layer supports 30 include supports 30 made of glass, triacetyl cellulose (TAC), polyethylene terephthalate (PET), polycarbonate, polyvinyl chloride, acrylic acid, and polyolefins. Examples of multi-layer supports 30 include supports that include any of the aforementioned single-layer supports as a substrate, and supports with other layers disposed on the surface of the substrate.

[0098] <Orientation film>

[0099] An orientation film 32 is formed on the surface of the support 30.

[0100] The alignment film 32 is an alignment film used to align the liquid crystal compound 40 into a predetermined liquid crystal alignment pattern when forming the optical anisotropic layer 36.

[0101] As described above, in this invention, the optical anisotropy layer 36 has an optical axis 40A derived from the liquid crystal compound 40 (see reference). Figure 3 The orientation of the liquid crystal alignment pattern changes as it rotates continuously in one direction within the plane. Therefore, the alignment film 32 is formed so that the optical anisotropic layer 36 can form the liquid crystal alignment pattern.

[0102] In the following description, "orientation rotation of optical axis 40A" will also be referred to as "rotation of optical axis 40A".

[0103] The alignment film 32 can utilize various known alignment films.

[0104] Examples include triboelectric films formed from organic compounds such as polymers, tilted vapor-deposited films of inorganic compounds, films with microgrooves, and films formed by accumulating organic compounds such as ω-trisanoic acid, dioctadecylmethylammonium chloride, and methyl stearate using the Langmuir-Blodgett process.

[0105] The orientation film 32 based on friction treatment can be formed by rubbing the surface of the polymer layer multiple times in a specified direction with paper or cloth.

[0106] The preferred materials used in the alignment film 32 are polyimide, polyvinyl alcohol, polymers with polymerizable groups as described in Japanese Patent Application Publication No. 9-152509, and materials used in the formation of the alignment film 32 as described in Japanese Patent Application Publication Nos. 2005-97377, 2005-99228, and 2005-128503.

[0107] The alignment film 32 is preferably a so-called photoalignment film formed by irradiating polarized or unpolarized light with a material that is photooriented. That is, as the alignment film 32, it is preferable to use a photoalignment film formed by coating a photoalignment material on a support 30.

[0108] Regarding the irradiation of polarized light, it can be performed from a direction perpendicular to or inclined relative to the photo-alignment film; regarding the irradiation of unpolarized light, it can be performed from a direction inclined relative to the photo-alignment film.

[0109] Examples of photoalignment materials that can be used in the alignment film of the present invention include, for example, Japanese Patent Application Publication Nos. 2006-285197, 2007-76839, 2007-138138, 2007-94071, 2007-121721, 2007-140465, and 2007-156. Azo compounds described in Japanese Patent Publication No. 439, Japanese Patent Application Publication No. 2007-133184, Japanese Patent Application Publication No. 2009-109831, Japanese Patent Publication No. 3883848 and Japanese Patent Publication No. 4151746, aromatic ester compounds described in Japanese Patent Application Publication No. 2002-229039, and Japanese Patent Application Publication No. 2002-265541 and Japanese Patent Application Publication No. 2002-317013. Maleimides having photooriented units and / or alkenyl-substituted nadicimide compounds, photocrosslinkable silane derivatives described in Japanese Patent Nos. 4205195 and 4205198, photocrosslinkable polyimides, photocrosslinkable polyamides, and photocrosslinkable polyesters described in Japanese Patent Nos. 2003-520878, 2004-529220, and 4162850. Preferred examples include photodimerizable compounds, particularly cinnamic acid ester compounds, chalcone compounds, and coumarin compounds, as described in Japanese Patent Application Publication Nos. 9-118717, 10-506420, 2003-505561, International Publication No. 2010 / 150748, 2013-177561, and 2014-12823.

[0110] Among them, azo compounds, photocrosslinkable polyimides, photocrosslinkable polyamides, photocrosslinkable polyesters, cinnamic acid ester compounds and chalcone compounds are preferred.

[0111] There is no limitation on the thickness of the alignment film 32. As long as the thickness is appropriately set according to the forming material of the alignment film 32, the required alignment function can be obtained.

[0112] The thickness of the orientation film 32 is preferably 0.01 to 5 μm, more preferably 0.05 to 2 μm.

[0113] There are no limitations on the method of forming the alignment film 32, and various known methods corresponding to the forming materials of the alignment film 32 can be used. As an example, a method can be illustrated by coating the alignment film 32 onto the surface of the support 30 and drying it, and then exposing the alignment film 32 with a laser beam to form an alignment pattern.

[0114] Figure 4 The image shows an example of an exposure apparatus that exposes an alignment film 32 to form an alignment pattern.

[0115] Figure 4 The exposure apparatus 60 shown includes: a light source 64 on which a laser 62 is provided; a λ / 2 plate 65 for changing the polarization direction of the laser beam M emitted from the laser 62; a beam splitter 68 for separating the laser beam M emitted from the laser 62 into two beams, MA and MB; mirrors 70A and 70B respectively disposed on the optical paths of the two separated beams MA and MB; and λ / 4 plates 72A and 72B.

[0116] Additionally, light source 64 emits linearly polarized light P0. Plate 72A (λ / 4) converts the linearly polarized light P0 (ray MA) into right-handed circularly polarized light P... R The λ / 4 plate 72B converts linearly polarized light P0 (ray MB) into left-handed circularly polarized light P L .

[0117] A support 30 having an alignment film 32 before the alignment pattern is formed is disposed in the exposure section, so that two light rays MA and MB cross and interfere on the alignment film 32, and the interference light is irradiated onto the alignment film 32 for exposure.

[0118] Through this interference, the polarization state of the light incident on the alignment film 32 changes periodically in the form of interference fringes. Thus, an alignment film (hereinafter also referred to as a patterned alignment film) with an alignment pattern having a periodically changing alignment state can be obtained.

[0119] In the exposure apparatus 60, the period of the alignment pattern can be adjusted by changing the cross angle α of the two light rays MA and MB. That is, in the exposure apparatus 60, by adjusting the cross angle α, in an alignment pattern in which the optical axis 40A originating from the liquid crystal compound 40 rotates continuously in one direction, the length of one cycle in which the optical axis 40A rotates 180° in the direction in which the optical axis 40A is rotated can be adjusted.

[0120] By forming an optically anisotropic layer on an alignment film 32 having an alignment pattern that periodically changes in such an alignment state, as described later, an optically anisotropic layer 36 having a liquid crystal alignment pattern that continuously rotates in one direction along an optical axis 40A derived from the liquid crystal compound 40 can be formed.

[0121] Furthermore, the rotation direction of optical axis 40A can be reversed by rotating the optical axes of λ / 4 plates 72A and 72B by 90° respectively.

[0122] As described above, the patterned alignment film has an alignment pattern in which the liquid crystal compound is aligned such that the orientation of the optical axis of the liquid crystal compound in the optical anisotropy layer formed on the patterned alignment film changes while rotating continuously in at least one in-plane direction. If the axis along which the liquid crystal compound is aligned is defined as the alignment axis, then the patterned alignment film can be said to have an alignment pattern in which the orientation of the alignment axis changes while rotating continuously in at least one in-plane direction. The alignment axis of the patterned alignment film can be detected by measuring absorption anisotropy. For example, when linearly polarized light is irradiated onto the patterned alignment film while rotating, and the amount of light transmitted through the patterned alignment film is measured, it is observed that the direction in which the light amount becomes maximum or minimum gradually changes in one in-plane direction.

[0123] Furthermore, in this invention, the orientation film 32 is provided in a preferred manner, but is not a necessary component.

[0124] For example, an alignment pattern can be formed on the support 30 by methods such as rubbing the support 30 or processing the support 30 with a laser beam, thereby enabling the optical anisotropy layer to have a liquid crystal alignment pattern that changes as it rotates continuously in at least one in-plane direction, originating from the optical axis 40A of the liquid crystal compound 40. That is, in the present invention, the support 30 can also function as an alignment film.

[0125] <Optical Anisotropic Layer>

[0126] An optical anisotropic layer 36 is formed on the surface of the alignment film 32.

[0127] As described above, the optical anisotropy layer 36 is an optical anisotropy layer formed by fixing a liquid crystal phase that aligns the liquid crystal compound, and is an optical anisotropy layer having a liquid crystal alignment pattern that changes while the orientation of the optical axis originating from the liquid crystal compound is continuously rotated in at least one direction in the plane.

[0128] Furthermore, as in Figure 2 The diagram conceptually illustrates that the optical anisotropic layer 36 has a twisted structure in which liquid crystal compounds 40 are stacked in a rotating manner along the thickness direction. In the example shown, the total twist angle from the liquid crystal compound 40 present on one main surface side of the optical anisotropic layer 36 to the liquid crystal compound 40 present on the other main surface side is less than 360°.

[0129] Thus, the optical anisotropy layer 36 has a liquid crystal alignment pattern that changes while continuously rotating along the orientation of the optical axis 40A along the alignment axis D. Furthermore, if the liquid crystal compound 40 has a twisted structure in the thickness direction, then in a section parallel to the alignment axis D, the equiphase surfaces connecting the liquid crystal compounds 40 in the thickness direction become tilted relative to the main surface of the optical anisotropy layer 36. Because the equiphase surfaces are tilted in this way, the diffraction efficiency decreases depending on the angle of the incident light and the rotation direction of the circularly polarized light, resulting in a situation where virtually no diffraction occurs. For example, in… Figure 2 In the case of the optical anisotropy layer 36 shown, right-handed circularly polarized light incident perpendicularly to the main surface... Figure 2 The light is diffracted in a downward-left direction. On the other hand, left-handed circularly polarized light incident perpendicularly to the main surface is diffracted by the liquid crystal alignment pattern. Figure 2 The light is diffracted in a downward-right direction, but because the equiphase surfaces are tilted in opposite directions, the diffraction effect is not fully utilized, and the light is transmitted as zero-order light without being diffracted.

[0130] Furthermore, if a cross-section parallel to the alignment axis D is observed using a SEM (scanning electron microscope), a stripe pattern of alternating bright and dark areas due to the orientation of the liquid crystal compound can be observed. This tilt of the bright and dark areas can be considered as the tilt of equiphase surfaces.

[0131] The transmissive liquid crystal diffraction element of the present invention utilizes the transmission of zero-order light in each of the first optical anisotropic layer 36a to the fourth optical anisotropic layer 36d, and is configured to diffract right-handed and left-handed circularly polarized light in the same direction. This will be described in detail later.

[0132] <<Methods for forming optical anisotropic layers>>

[0133] The optical anisotropic layer has a liquid crystal orientation pattern that changes as the orientation of the optical axis of the liquid crystal compound rotates continuously in at least one direction within the plane, and can be formed in a layered fixed liquid crystal phase, the liquid crystal phase orientation being a twisted structure in which the liquid crystal compound (optical axis) rotates and stacks in the thickness direction.

[0134] The structure formed by fixing the liquid crystal phase can be any structure that maintains the orientation of the liquid crystal compound in the liquid crystal phase. Typically, the following structure is preferred: based on setting the polymerizable liquid crystal compound in an orientation state along the liquid crystal orientation pattern, it is polymerized and cured by ultraviolet irradiation, heating, etc. to form a non-flowable layer, and at the same time, it is changed to a state in which the orientation morphology will not change due to external field or external force.

[0135] Furthermore, in structures where a liquid crystal phase is fixed, as long as the optical properties of the liquid crystal phase are maintained, the liquid crystal compound 40 may not exhibit liquid crystal properties in optically anisotropic layers. For example, polymerizable liquid crystal compounds can lose their liquid crystal properties by undergoing a curing reaction to increase their molecular weight.

[0136] As an example of materials used in the formation of an optically anisotropic layer formed by fixing a liquid crystal phase, a liquid crystal composition containing a liquid crystal compound can be cited. The liquid crystal compound is preferably a polymerizable liquid crystal compound.

[0137] Furthermore, in order to set the optical anisotropic layer as a structure in which the liquid crystal compound is twisted and oriented in the thickness direction, it is only necessary to contain a chiral reagent in the liquid crystal composition.

[0138] Furthermore, the liquid crystal composition used in the formation of the optical anisotropic layer may also contain surfactants, polymerization initiators, etc.

[0139] --Polymerizable liquid crystal compounds--

[0140] Polymerizable liquid crystal compounds can be rod-shaped or disc-shaped.

[0141] Examples of rod-shaped polymeric liquid crystal compounds that form optically anisotropic layers include rod-shaped nematic liquid crystal compounds. Preferred rod-shaped nematic liquid crystal compounds include those containing methylimine, azo oxides, cyanobiphenyl, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexane, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyl dioxanes, diphenylacetylene, and alkenylcyclohexylbenzonitrile. Not only low-molecular-weight liquid crystal compounds but also high-molecular-weight liquid crystal compounds can be used.

[0142] Polymerizable liquid crystal compounds are obtained by incorporating polymeric groups into a liquid crystal compound. Examples of polymeric groups include unsaturated polymeric groups, epoxy groups, and acridine groups; unsaturated polymeric groups are preferred, and olefinically unsaturated polymeric groups are more preferred. Polymeric groups can be incorporated into the molecules of the liquid crystal compound by various methods. The number of polymeric groups in the polymerizable liquid crystal compound is preferably 1 to 6, more preferably 1 to 3.

[0143] Examples of polymerizable liquid crystal compounds include those described in Makromol. Chem., Vol. 190, pp. 2255 (1989), Advanced Materials, Vol. 5, pp. 107 (1993), U.S. Patent No. 4,683,327, U.S. Patent No. 5,622,648, U.S. Patent No. 5,770,107, International Publications Nos. 95 / 22586, 95 / 24455, 97 / 00600, 98 / 23580, 98 / 52905, Japanese Patent Application Publications Nos. 1-272,551, 6-016,616, 7-110,469, 11-080081, and 2001-328,973. Two or more polymerizable liquid crystal compounds can be used together. Using two or more polymerizable liquid crystal compounds together can lower the orientation temperature.

[0144] Furthermore, as polymerizable liquid crystal compounds other than those mentioned above, cyclic organopolysiloxane compounds having a cholesterol phase, such as those disclosed in Japanese Patent Application Publication No. 57-165480, can be used. In addition, as the aforementioned polymeric liquid crystal compounds, polymers in which the mesopyronic groups for displaying liquid crystals are introduced into the main chain, side chain, or both the main chain and side chain, cholesteric liquid crystals in which cholesterol groups are introduced into the side chains, liquid crystal polymers such as those disclosed in Japanese Patent Application Publication No. 9-133810, and liquid crystal polymers such as those disclosed in Japanese Patent Application Publication No. 11-293252 can be used.

[0145] --Disc-shaped liquid crystal compound--

[0146] As a disc-shaped liquid crystal compound, for example, the disc-shaped liquid crystal compound described in Japanese Patent Application Publication No. 2007-108732 or Japanese Patent Application Publication No. 2010-244038 can be preferred.

[0147] Furthermore, the amount of polymerizable liquid crystal compound added in the liquid crystal composition is preferably 75 to 99.9% by mass relative to the mass of the solid components of the liquid crystal composition (mass after solvent removal), more preferably 80 to 99% by mass, and even more preferably 85 to 90% by mass.

[0148] --Chiral reagents (optically active compounds)--

[0149] Chiral reagents (chiral agents) have the function of inducing twisted structures in liquid crystal phases. Since chiral reagents vary in the direction of helical twisting and the helical twisting power (HTP) induced by the compound, they can be selected according to the purpose.

[0150] There are no particular restrictions on the use of chiral reagents, and well-known compounds can be used (e.g., those described in the Liquid Crystal Device Handbook, Chapter 3, Item 4-3, TN (twisted nematic), STN (Super Twisted Nematic) chiral reagents, page 199, edited by the 142nd Committee of the Japan Society for the Promotion of Science, 1989), isosorbide and isomannitol derivatives, etc.

[0151] Chiral reagents typically contain asymmetric carbon atoms, but axially chiral compounds or planar chiral compounds that do not contain asymmetric carbon atoms can also be used as chiral reagents. Examples of axially chiral compounds or planar chiral compounds include binatene, helicene, p-xylene dimers, and their derivatives. Chiral reagents may also have polymerizable groups. When both the chiral reagent and the liquid crystal compound have polymerizable groups, a polymer having repeating units derived from the polymeric liquid crystal compound and repeating units derived from the chiral reagent can be formed by the polymerization reaction of the polymerizable chiral reagent and the polymeric liquid crystal compound. In this manner, the polymerizable groups possessed by the polymerizable chiral reagent are preferably groups of the same kind as those possessed by the polymeric liquid crystal compound. Therefore, the polymerizable groups of the chiral reagent are preferably unsaturated polymerizable groups, epoxy groups, or acridine groups, more preferably unsaturated polymerizable groups, and even more preferably olefinic unsaturated polymerizable groups.

[0152] Furthermore, the chiral reagent can also be a liquid crystal compound.

[0153] When the chiral reagent has a photoisomerizing group, the desired twisted orientation corresponding to the emission wavelength can be formed by irradiation with a photomask such as activating light after coating and orientation, which is therefore preferred. As the photoisomerizing group, isomerization sites of compounds exhibiting photochromic properties, azo groups, oxyazo groups, or cinnamyl groups are preferred. As specific compounds, the compounds described in Japanese Patent Application Publication Nos. 2002-80478, 2002-80851, 2002-179668, 2002-179669, 2002-179670, 2002-179681, 2002-179682, 2002-338575, 2002-338668, 2003-313189, and 2003-313292 may be used.

[0154] The content of the chiral reagent in the liquid crystal composition relative to the molar content of the liquid crystal compound is preferably 0.01 to 200 mol%, more preferably 1 to 30 mol%.

[0155] --surfactants--

[0156] The liquid crystal composition used to form the optical anisotropic layer may contain a surfactant.

[0157] The surfactant is preferably a compound that can function as an orientation control agent, which helps the liquid crystal compound to orient stably or rapidly. Examples of surfactants include, for example, siloxane-based surfactants and fluorinated surfactants, with fluorinated surfactants being a preferred example.

[0158] Specific examples of surfactants include compounds described in paragraphs

[0082] to

[0090] of Japanese Patent Application Publication No. 2014-119605, compounds described in paragraphs

[0031] to

[0034] of Japanese Patent Application Publication No. 2012-203237, compounds exemplified in paragraphs

[0092] and

[0093] of Japanese Patent Application Publication No. 2005-099248, compounds exemplified in paragraphs

[0076] to

[0078] and

[0082] to

[0085] of Japanese Patent Application Publication No. 2002-129162, and fluoro(meth)acrylate polymers described in paragraphs

[0018] to

[0043] of Japanese Patent Application Publication No. 2007-272185.

[0159] In addition, a single surfactant can be used alone, or two or more surfactants can be used in combination.

[0160] As a fluorinated surfactant, the compounds described in paragraphs

[0082] to

[0090] of Japanese Patent Application Publication No. 2014-119605 are preferred.

[0161] The amount of surfactant added to the liquid crystal composition is preferably 0.01 to 10% by mass relative to the total mass of the liquid crystal compound, more preferably 0.01 to 5% by mass, and even more preferably 0.02 to 1% by mass.

[0162] --Polymerization Initiator--

[0163] When the liquid crystal composition contains a polymerizable compound, it is preferable to include a polymerization initiator. In the case of polymerization reaction carried out by ultraviolet irradiation, the polymerization initiator used is preferably a photopolymerization initiator capable of initiating polymerization reaction by ultraviolet irradiation.

[0164] Examples of photopolymerization initiators include α-carbonyl compounds (described in U.S. Patent Nos. 2,367,661 and 2,367,670), azobin ethers (described in U.S. Patent No. 2,448,828), α-hydrocarbon-substituted aromatic azobin compounds (described in U.S. Patent No. 2,722,512), polynucleoquinone compounds (described in U.S. Patent Nos. 3,046,127 and 2,951,758), combinations of triarylimidazolium dimers and p-aminophenyl ketones (described in U.S. Patent No. 3,549,367), acridine and phenazine compounds (described in Japanese Patent Application Publication No. 60-105,667 and U.S. Patent No. 4,239,850), and oxadiazole compounds (described in U.S. Patent No. 4,212,970).

[0165] The content of the photopolymerization initiator in the liquid crystal composition is preferably 0.1 to 20% by mass relative to the content of the liquid crystal compound, and more preferably 0.5 to 12% by mass.

[0166] --Cross-linking agent--

[0167] To improve the strength and durability of the cured film, the liquid crystal composition may contain any crosslinking agent. As a crosslinking agent, a crosslinking agent that is cured by ultraviolet light, heat, or moisture is preferred.

[0168] There are no particular limitations on the crosslinking agent; it can be appropriately selected according to the purpose. Examples include polyfunctional acrylate compounds such as trimethylolpropane tri(meth)acrylate and pentaerythritol tri(meth)acrylate; epoxy compounds such as glycidyl methacrylate and ethylene glycol diglycidyl ether; acridine compounds such as 2,2-dihydroxymethylbutanol-tris[3-(1-acrylidinyl)propionate] and 4,4-bis(ethyleneiminocarbonylamino)diphenylmethane; isocyanate compounds such as hexamethylene diisocyanate and biuret-type isocyanate; polyoxazoline compounds having an oxazoline group on the side chain; and alkoxysilane compounds such as vinyltrimethoxysilane and N-(2-aminoethyl)3-aminopropyltrimethoxysilane. Furthermore, known catalysts can be used depending on the reactivity of the crosslinking agent, which can improve not only film strength and durability but also productivity. One of these can be used alone, or two or more can be used in combination.

[0169] The content of the crosslinking agent is preferably 3 to 20% by mass relative to the solid components of the liquid crystal composition, more preferably 5 to 15% by mass. As long as the content of the crosslinking agent is within the above range, it is easy to obtain the effect of increasing the crosslinking density, thereby further improving the stability of the liquid crystal phase.

[0170] --Other Additives--

[0171] Without reducing optical performance, polymerization inhibitors, antioxidants, ultraviolet absorbers, light stabilizers, colorants, and metal oxide particles can be further added to the liquid crystal composition as needed.

[0172] The liquid crystal composition is preferably used as a liquid when forming an optically anisotropic layer.

[0173] The liquid crystal composition may contain a solvent. There are no limitations on the solvent, which can be appropriately selected according to the purpose, but organic solvents are preferred.

[0174] There are no restrictions on the organic solvents used; they can be appropriately selected according to the purpose. Examples include ketones, haloalkanes, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, and ethers. One or more of these can be used alone or in combination. Among these, ketones are preferred, considering their environmental impact.

[0175] When forming an optically anisotropic layer, it is preferable to coat a liquid crystal composition on the surface of the optically anisotropic layer, align the liquid crystal compound to a liquid crystal phase state with a predetermined liquid crystal alignment pattern, and then cure the liquid crystal compound to form an optically anisotropic layer.

[0176] That is, when an optically anisotropic layer is formed on the alignment film 32, it is preferable to coat the alignment film 32 with a liquid crystal composition, align the liquid crystal compound into a predetermined liquid crystal alignment pattern, and then cure the liquid crystal compound to form an optically anisotropic layer with a fixed liquid crystal phase.

[0177] Regarding the coating of liquid crystal compositions, all known methods capable of uniformly coating liquid onto sheets can be used, including printing methods such as inkjet and roll printing, as well as spin coating, bar coating, and spray coating.

[0178] As needed, the coated liquid crystal composition is dried and / or heated, and then cured to form an optically anisotropic layer. During this drying and / or heating process, the liquid crystal compounds in the liquid crystal composition are oriented according to a predetermined liquid crystal orientation pattern and twisted structure. When heating is performed, the heating temperature is preferably below 200°C, more preferably below 130°C.

[0179] The oriented liquid crystal compound may be further polymerized as needed. Polymerization can be either thermal polymerization or photopolymerization using light irradiation, but photopolymerization is preferred. Ultraviolet light is preferably used for light irradiation. The irradiation energy is preferably 20 mJ / cm². 2 ~50J / cm 2 More preferably 50–1500 mJ / cm 2To promote the photopolymerization reaction, light irradiation can also be carried out under heating conditions or in a nitrogen atmosphere. The wavelength of the irradiated ultraviolet light is preferably 250–430 nm.

[0180] There is no limit to the thickness of the optical anisotropic layer. As long as the thickness is appropriately set according to the application of the optical anisotropic layer, the required light reflectivity of the optical anisotropic layer, and the forming material of the optical anisotropic layer, the thickness that can obtain the required light reflectivity can be achieved.

[0181] <<Liquid Crystal Alignment Pattern of Optical Anisotropic Layer>>

[0182] As described above, the optical anisotropy layer has a liquid crystal alignment pattern in which the orientation of the optical axis 40A derived from the liquid crystal compound 40 changes while rotating continuously in one direction within the plane of the optical anisotropy layer.

[0183] Furthermore, the optical axis 40A derived from the liquid crystal compound 40 is the axis with the highest refractive index in the liquid crystal compound 40, also known as the slow axis. For example, in the case where the liquid crystal compound 40 is a rod-shaped liquid crystal compound, the optical axis 40A is along the long axis direction of the rod shape. In the following description, the optical axis 40A derived from the liquid crystal compound 40 will also be referred to as "optical axis 40A of liquid crystal compound 40" or "optical axis 40A".

[0184] Figure 3 The diagram shows a conceptual top view of the optical anisotropy layer 36.

[0185] Additionally, a top view refers to... Figure 2 The image shown is an optical anisotropic layer 36 viewed from above, which is the image of the optical anisotropic layer 36 viewed from the thickness direction (= the stacking direction of each layer (film)).

[0186] Furthermore, in Figure 3 In the diagram, only the liquid crystal compound 40 on the surface of the alignment film 32 is shown to clearly illustrate the structure of the optical anisotropy layer 36.

[0187] like Figure 3 As shown, on the surface of the alignment film 32, the liquid crystal compound 40 constituting the optical anisotropy layer 36 has a liquid crystal alignment pattern such that, according to the alignment pattern formed on the lower alignment film 32, the orientation of the optical axis 40A changes while continuously rotating in a predetermined direction indicated by arrow D (hereinafter referred to as alignment axis D) within the plane of the optical anisotropy layer. In the example shown, the liquid crystal alignment pattern shows that the optical axis 40A of the liquid crystal compound 40 changes while continuously rotating clockwise along the alignment axis D.

[0188] The liquid crystal compound 40 constituting the optical anisotropic layer 36 is arranged in a two-dimensional configuration on the alignment axis D and in a direction orthogonal to that direction (the alignment axis D direction).

[0189] In the following description, for convenience, the direction orthogonal to the alignment axis D is designated as the Y direction. That is, the arrow Y direction is orthogonal to a direction in which the orientation of the optical axis 40A of the liquid crystal compound 40 changes simultaneously with continuous rotation within the plane of the optical anisotropy layer. Therefore, in Figure 1 , Figure 2 And then Figure 5 , Figure 6 In this case, the Y direction becomes the direction orthogonal to the plane of the paper.

[0190] The orientation of the optical axis 40A of the liquid crystal compound 40 changes as it rotates continuously along the arrangement axis D (a specified direction). Specifically, the angle between the optical axis 40A of the liquid crystal compound 40 arranged along the arrangement axis D and the arrangement axis D varies depending on the position of the arrangement axis D. Along the arrangement axis D, the angle between the optical axis 40A and the arrangement axis D changes sequentially from θ to θ+180° or θ-180°.

[0191] Furthermore, the angle difference between the optical axes 40A of adjacent liquid crystal compounds 40 in the alignment axis D direction is preferably 45° or less, more preferably 15° or less, and even more preferably a smaller angle.

[0192] Furthermore, in this invention, the liquid crystal compound is designed to rotate in a direction in which the angle between the optical axes 40A of the liquid crystal compounds 40 adjacent to each other in the alignment axis D decreases. Therefore, in Figure 2 and Figure 3 In the optical anisotropy layer shown, the optical axis 40A of the liquid crystal compound 40 rotates to the right (clockwise) along the direction of the arrow on the arrangement axis D.

[0193] On the other hand, the liquid crystal compound 40 forming the optical anisotropic layer 36 has the same orientation as the optical axis 40A in the Y direction, which is orthogonal to the alignment axis D direction, i.e., in the Y direction, which is orthogonal to a direction in which the optical axis 40A rotates continuously.

[0194] In other words, in the Y direction, the optical axis 40A of the liquid crystal compound 40 forming the optical anisotropic layer 36 is at the same angle as the alignment axis D.

[0195] In the optical anisotropic layer 36, among the liquid crystal compounds arranged in the Y direction, the angle between the optical axis 40A and the arrangement axis D (a direction in which the optical axis of the liquid crystal compound 40 is rotated) is equal. The region in the Y direction where the liquid crystal compound 40 with the angle between the optical axis 40A and the arrangement axis D is equal is designated as region R.

[0196] At this point, the value of the in-plane retardation (Re) in each region R is preferably half a wavelength, i.e., λ / 2. These in-plane retardations are calculated by multiplying the refractive index difference Δn associated with the refractive index anisotropy of region R by the thickness of the optical anisotropy layer. Here, the refractive index difference associated with the refractive index anisotropy of region R in the optical anisotropy layer is defined as the difference between the refractive index in the slow axis direction within the plane of region R and the refractive index in the direction orthogonal to the slow axis direction. That is, the refractive index difference Δn associated with the refractive index anisotropy of region R is equal to the difference between the refractive index of the liquid crystal compound 40 in the direction of the optical axis 40A and the refractive index of the liquid crystal compound 40 in the direction perpendicular to the optical axis 40A within the plane of region R. In other words, the refractive index difference Δn is equal to the refractive index difference of the liquid crystal compound 40.

[0197] In the optical anisotropy layer 36, in the liquid crystal alignment pattern of this liquid crystal compound 40, the length (distance) of rotating the optical axis 40A of the liquid crystal compound 40 by 180° in the direction of the alignment axis D which changes due to continuous rotation of the in-plane optical axis 40A is set as the length Λ of one cycle in the liquid crystal alignment pattern.

[0198] That is, the distance between the centers of two liquid crystal compounds 40 with equal angles relative to the alignment axis D along the alignment axis D is defined as the length Λ of one period. Specifically, as... Figure 3 As shown, the distance between the centers of two liquid crystal compounds 40 whose alignment axis D is aligned with the optical axis 40A is defined as the length Λ of one period. In the following description, this length Λ of one period will also be referred to as "one period Λ".

[0199] The liquid crystal alignment pattern of the optical anisotropic layer 36 repeats one cycle Λ in one direction that changes as the orientation of the optical axis 40A is continuously rotated in the direction of the alignment axis D.

[0200] If circularly polarized light is incident on this optical anisotropic layer 36, the light is refracted and the direction of the circularly polarized light is reversed.

[0201] exist Figure 5 and Figure 6 This function is conceptually illustrated. Furthermore, in the optical anisotropy layer 36, the product of the refractive index difference of the liquid crystal compound and the thickness of the optical anisotropy layer is set to λ / 2. And, using... Figure 5 and Figure 6 The description is used to explain the function of the liquid crystal alignment pattern of the optical anisotropy layer 36, and is therefore explained as a twisted structure that does not have an optical axis in the thickness direction.

[0202] like Figure 5 As shown, when the product of the refractive index difference of the liquid crystal compound in the optical anisotropic layer 36 and the thickness of the optical anisotropic layer is λ / 2, if the incident light L1, which is left-handed circularly polarized light, is incident on the optical anisotropic layer 36, the incident light L1 is given a phase difference of 180° through the optical anisotropic layer 36, and the transmitted light L2 is converted into right-handed circularly polarized light.

[0203] Furthermore, the liquid crystal alignment pattern formed on the optical anisotropic layer 36 is a periodic pattern along the alignment axis D, therefore the transmitted light L2 travels in a direction different from the direction of travel of the incident light L1. Thus, the incident light L1, which is left-handed circularly polarized, is converted into transmitted light L2, which is right-handed circularly polarized, tilted only at a predetermined angle relative to the incident direction along the alignment axis D. Figure 5 In the example shown, the transmitted light L2 is diffracted to travel in a downward-right direction.

[0204] On the other hand, such as Figure 6 As shown, when the product of the refractive index difference of the liquid crystal compound in the optical anisotropic layer 36 and the thickness of the optical anisotropic layer is λ / 2, if the incident light L4 of right-hand circularly polarized light is incident on the optical anisotropic layer 36, the incident light L4 is given a phase difference of 180° through the optical anisotropic layer 36, and is thus converted into the transmitted light L5 of left-hand circularly polarized light.

[0205] Furthermore, the liquid crystal alignment pattern formed on the optical anisotropic layer 36 is a periodic pattern along the alignment axis D, therefore the transmitted light L5 travels in a direction different from the direction of travel of the incident light L4. At this time, the transmitted light L5 travels in a direction different from the transmitted light L2, that is, in a direction opposite to the direction of the arrow on the alignment axis D relative to the incident direction. Thus, the incident light L4 is converted into transmitted light L5, which is left-handed circularly polarized light tilted at a predetermined angle relative to the incident direction in a direction opposite to the alignment axis D. Figure 6 In the example shown, the transmitted light L5 is diffracted to travel in a downward-left direction.

[0206] As described above, the optical anisotropy layer 36 can adjust the refraction angles of transmitted light L2 and L5 according to the length of one period Λ of the formed liquid crystal alignment pattern. Specifically, with respect to the optical anisotropy layer 36, the shorter the one period Λ of the liquid crystal alignment pattern, the stronger the interference between the light passing through the adjacent liquid crystal compounds 40, and thus the greater the refraction of transmitted light L2 and L5.

[0207] Furthermore, by reversing the rotation direction of the optical axis 40A of the liquid crystal compound 40, which rotates along the alignment axis D, the direction of refraction of transmitted light can be reversed. That is, in Figures 5-6 In the example shown, the optical axis 40A, which is oriented towards the alignment axis D, rotates clockwise. However, by setting this rotation direction to counterclockwise, the direction of refraction of the transmitted light can be reversed. Specifically, in Figure 5 and Figure 6 In the diagram, when the optical axis 40A, oriented towards the alignment axis D, rotates counterclockwise, left-handed circularly polarized light incident on the optical anisotropic layer 36 from the upper side is converted into right-handed circularly polarized light upon transmission through the optical anisotropic layer 36 and diffracted to travel in the lower left direction. Conversely, right-handed circularly polarized light incident on the optical anisotropic layer 36 from the upper side is converted into left-handed circularly polarized light upon transmission through the optical anisotropic layer 36 and diffracted to travel in the lower right direction.

[0208] (The function of a transmission-type liquid crystal diffraction element)

[0209] Next, using Figure 7 The function of the transmissive liquid crystal diffraction element of the present invention, which has a structure having four layers of optically anisotropic layers having such liquid crystal alignment patterns, will be explained.

[0210] As described above, in the transmissive liquid crystal diffraction element 10 of the present invention, a first optical anisotropy layer 36a to a fourth optical anisotropy layer 36d having liquid crystal alignment patterns are arranged sequentially. The rotation directions of the optical axes in the liquid crystal alignment patterns of the first optical anisotropy layer 36a and the second optical anisotropy layer 36b are opposite, and the twist directions of the optical axes in the thickness direction are opposite. Furthermore, the rotation directions of the optical axes in the liquid crystal alignment patterns of the third optical anisotropy layer 36c and the fourth optical anisotropy layer 36d are opposite, and the twist directions of the optical axes in the thickness direction are opposite. In addition, one period of the liquid crystal alignment patterns of the first optical anisotropy layer 36a and the second optical anisotropy layer 36b is the same, one period of the liquid crystal alignment patterns of the third optical anisotropy layer 36c and the fourth optical anisotropy layer 36d is the same, and one period of the liquid crystal alignment patterns of the first optical anisotropy layer 36a and the third optical anisotropy layer 36c is different.

[0211] Here, regarding the first optical anisotropy layer 36a and the second optical anisotropy layer 36b, the same period of the liquid crystal alignment pattern means that, based on the period of the liquid crystal alignment pattern of the first optical anisotropy layer 36a, if the period of the liquid crystal alignment pattern of the second optical anisotropy layer 36b differs by about 0.8 to 1.2, then the effect on the diffraction angle of the light emitted from the second optical anisotropy layer 36b is small.

[0212] Similarly, regarding the third optical anisotropic layer 36c and the fourth optical anisotropic layer 36d, the same period of the liquid crystal alignment pattern means that, based on the period of the liquid crystal alignment pattern of the third optical anisotropic layer 36c, if the period of the liquid crystal alignment pattern of the fourth optical anisotropic layer 36d differs by about 0.8 to 1.2, then the effect on the diffraction angle of the light emitted from the fourth optical anisotropic layer 36d will be small.

[0213] Furthermore, regarding the first optical anisotropic layer 36a and the second optical anisotropic layer 36b, even if there is a difference in one period of the liquid crystal alignment pattern, the difference in one period of the liquid crystal alignment pattern of the third optical anisotropic layer 36c and the fourth optical anisotropic layer 36d is offset by the difference in one period of the liquid crystal alignment pattern of the first optical anisotropic layer 36a and the second optical anisotropic layer 36b, thereby making the diffraction angles of the right-hand circularly polarized light and the left-hand circularly polarized light emitted from the fourth optical anisotropic layer 36d appropriate.

[0214] Furthermore, the direction of the alignment axis D of the liquid crystal alignment pattern in the first optical anisotropic layer 36a is the same as the direction of the alignment axis D of the liquid crystal alignment pattern in the second optical anisotropic layer 36b. Similarly, the direction of the alignment axis D of the liquid crystal alignment pattern in the third optical anisotropic layer 36c is the same as the direction of the alignment axis D of the liquid crystal alignment pattern in the fourth optical anisotropic layer 36d. Moreover, the direction of the alignment axis D of the liquid crystal alignment pattern in the first optical anisotropic layer 36a is the same as the direction of the alignment axis D of the liquid crystal alignment pattern in the third optical anisotropic layer 36c. Figure 7 In the example shown, the direction of the arrangement axis D of any optical anisotropic layer is the left direction in the figure.

[0215] Right-handed circularly polarized light I R and left-handed circularly polarized light I L The following is an example of a transmissive liquid crystal diffraction element 10 with this structure that is incident from the side of the first optical anisotropic layer 36a.

[0216] like Figure 7 As shown, right-handed circularly polarized light I R and left-handed circularly polarized light I L It is incident perpendicularly on the main surface of the first optical anisotropic layer 36a.

[0217] As described above, the optical anisotropy layer causes right-handed circularly polarized light I R and left-handed circularly polarized light I L Diffraction occurs in opposite directions along the arrangement axis D. Figure 7In the example shown, the first optical anisotropy layer 36a causes the incident right-handed circularly polarized light I... R Relative to the incident right-handed circularly polarized light I R The direction of travel is along the arrangement axis D. Figure 7 Diffraction occurs in the left-hand direction. Furthermore, as described above, the diffracted light is converted into left-handed circularly polarized light I. L1 .

[0218] On the other hand, for left-handed circularly polarized light I L The first optical anisotropy layer 36a aims to make the incident left-handed circularly polarized light I L Relative to the incident left-handed circularly polarized light I L The direction of travel is along the arrangement axis D. Figure 7 Diffraction occurs in the right-hand direction. However, as mentioned above, the optical anisotropic layer has a distorted structure, and the equiphase surface is tilted relative to the principal surface of the optical anisotropic layer. Therefore, diffraction in this direction is ineffective, and the incident left-hand circularly polarized light I... L Almost undiffracted, with left-handed circularly polarized light I L (0th light) state towards Figure 7 The first optical anisotropic layer 36a in the downward direction transmission.

[0219] Left-handed circularly polarized light I transmitted through the first optical anisotropy layer 36a L1 and left-handed circularly polarized light I L The incident light is incident on the second optical anisotropy layer 36b. As described above, the rotation direction of the optical axis in the liquid crystal alignment pattern of the second optical anisotropy layer 36b is opposite to that of the first optical anisotropy layer 36a. Therefore, the second optical anisotropy layer 36b diffracts the incident circularly polarized light in a direction opposite to that of the first optical anisotropy layer 36a. That is, it diffracts left-handed circularly polarized light to the left along the alignment axis D.

[0220] like Figure 7 As shown, left-handed circularly polarized light I L1 It is incident on the second optical anisotropy layer 36b in a manner that travels from the upper right to the lower left. Here, for left-handed circularly polarized light I... L1 The second optical anisotropy layer 36b aims to make the incident left-handed circularly polarized light I... L1 Relative to the incident left-handed circularly polarized light I L1 The direction of travel is along the arrangement axis D. Figure 7 Diffraction occurs in the left-hand direction. However, because it is incident on the optical anisotropic layer at an angle to the lower left, it cannot bend further to the left, and the incident left-handed circularly polarized light I... L1 Almost undiffracted, with left-handed circularly polarized light I L1 The second optical anisotropic layer 36b is transmitted to the lower left direction in the state of (0th light).

[0221] On the other hand, the second optical anisotropy layer 36b causes the left-hand circularly polarized light I incident perpendicular to the main surface to... L Relative to the incident left-handed circularly polarized light I L The direction of travel is along the arrangement axis D. Figure 7 The light diffracts in the direction of travel to the left. Furthermore, as described above, the diffracted light is converted into right-handed circularly polarized light I. R1 .

[0222] Since the liquid crystal alignment patterns of the first optical anisotropic layer 36a and the second optical anisotropic layer 36b have the same period, the left-handed circularly polarized light I in the first optical anisotropic layer 36a... L1 The diffraction angle and the right-hand circularly polarized light I in the second optical anisotropy layer 36b R1 The diffraction angles are approximately the same. Therefore, the right-handed circularly polarized light I transmitted through the first optical anisotropic layer 36a and the second optical anisotropic layer 36b... R1 and left-handed circularly polarized light I L1 Proceeding in the same direction (roughly parallel).

[0223] Right-handed circularly polarized light I transmitted through the second optical anisotropy layer 36b R1 and left-handed circularly polarized light I L1 It is incident on the third optical anisotropy layer 36c. At this time, the right-handed circularly polarized light I... R1 and left-handed circularly polarized light I L1 The light is diffracted by the first optical anisotropic layer 36a and the second optical anisotropic layer 36b, therefore the right-handed circularly polarized light I... R1 and left-handed circularly polarized light I L1 It is incident on the third optical anisotropy layer 36c from an inclined direction relative to the main surface of the third optical anisotropy layer 36c.

[0224] The third optical anisotropy layer 36c causes the incident left-handed circularly polarized light I... L1 Relative to the incident left-handed circularly polarized light I L1 The direction of travel is along the arrangement axis D. Figure 7 Diffraction occurs in the right-hand direction. Furthermore, as described above, the diffracted light is converted into right-hand circularly polarized light I. R2 .

[0225] Left-handed circularly polarized light I incident on the third optical anisotropy layer 36c L1 The first optical anisotropic layer 36a is oriented Figure 7 Left-hand diffraction, the third optical anisotropic layer 36c makes the left-hand circularly polarized light I L1The light diffracts in the opposite direction (rightward) to the first optical anisotropy layer 36a. Therefore, the right-handed circularly polarized light I that has passed through the first optical anisotropy layer 36a to the third optical anisotropy layer 36c... R2 Compared to the right-hand circularly polarized light I incident on the transmissive liquid crystal diffraction element 10 R The diffraction angle becomes the difference between the diffraction angle based on the first optical anisotropic layer 36a and the diffraction angle based on the third optical anisotropic layer 36c.

[0226] Here, one period of the liquid crystal alignment pattern of the third optical anisotropic layer 36c is different from one period of the liquid crystal alignment pattern of the first optical anisotropic layer 36a. Therefore, the diffraction angle based on the first optical anisotropic layer 36a is different from the diffraction angle based on the third optical anisotropic layer 36c. Figure 7 In the example shown, one period of the liquid crystal alignment pattern of the third optical anisotropy layer 36c is longer than one period of the liquid crystal alignment pattern of the first optical anisotropy layer 36a. Therefore, the diffraction angle based on the third optical anisotropy layer 36c is smaller than the diffraction angle based on the first optical anisotropy layer 36a. Consequently, the right-handed circularly polarized light I transmitted through the first optical anisotropy layer 36a to the third optical anisotropy layer 36c... R2 exist Figure 7 The middle part is in a state of moving to the lower left, almost perpendicular to the main surface.

[0227] On the other hand, for right-hand circularly polarized light I R1 The third optical anisotropy layer 36c aims to make the incident right-handed circularly polarized light I... R1 Relative to the incident right-handed circularly polarized light I R1 The direction of travel is along the arrangement axis D. Figure 7 Diffraction occurs in the left direction. However, as mentioned above, the optical anisotropic layer has a distorted structure, and the equiphase surface is tilted relative to the principal surface of the optical anisotropic layer. Therefore, diffraction in this direction is ineffective, and the incident right-handed circularly polarized light I... R1 Almost undiffracted, with right-handed circularly polarized light I R1 (0th light) state towards Figure 7 The third optical anisotropic layer 36c is transmitted in the lower left direction.

[0228] Right-handed circularly polarized light I transmitted through the third optical anisotropy layer 36c R2 and right-handed circularly polarized light I R1The incident light is incident on the fourth optical anisotropy layer 36d. As described above, the rotation direction of the optical axis in the liquid crystal alignment pattern of the fourth optical anisotropy layer 36d is opposite to that of the third optical anisotropy layer 36c. Therefore, the fourth optical anisotropy layer 36d diffracts the incident circularly polarized light in a direction opposite to that of the third optical anisotropy layer 36c. That is, it diffracts the right-handed circularly polarized light to the right along the alignment axis D.

[0229] like Figure 7 As shown, right-handed circularly polarized light I R2 The light is incident on the fourth optical anisotropy layer 36d from the upper right to the lower left at an angle approximately perpendicular to the main surface of the fourth optical anisotropy layer 36d. Here, for right-handed circularly polarized light I... R2 The fourth optical anisotropy layer 36d aims to make the incident right-handed circularly polarized light I... R2 Relative to the incident right-handed circularly polarized light I R2 The direction of travel is along the arrangement axis D. Figure 7 The diffraction occurs in the right direction. However, since the equiphase surface is tilted relative to the principal surface of the optical anisotropic layer, diffraction in this direction is ineffective, and the incident right-handed circularly polarized light I... R2 Almost undiffracted, with right-handed circularly polarized light I R2 (0th light) state, and at a position nearly perpendicular to Figure 7 The angle of the main surface is from the upper right to the lower left, transmitting the fourth optical anisotropic layer 36d.

[0230] On the other hand, the fourth optical anisotropy layer 36d causes right-handed circularly polarized light I, which is incident at a large angle from the upper right to the lower left, to... R1 Relative to the incident right-handed circularly polarized light I R1 The direction of travel is along the arrangement axis D. Figure 7 Diffraction occurs in the direction of rightward travel. Furthermore, as described above, the diffracted light is converted into left-handed circularly polarized light I. L2 .

[0231] Right-handed circularly polarized light I incident on the fourth optical anisotropy layer 36d R1 The second optical anisotropic layer 36b is oriented Figure 7 Diffraction in the left-center direction, the fourth optical anisotropic layer 36d makes the right-hand circularly polarized light I R1 The light diffracts in the opposite direction (to the right) to the direction of the second optical anisotropy layer 36b. Therefore, the left-handed circularly polarized light I that has been transmitted through the first optical anisotropy layer 36a to the fourth optical anisotropy layer 36d... L2 Compared to the left-handed circularly polarized light I incident on the transmissive liquid crystal diffraction element 10 LThe diffraction angle becomes the difference between the diffraction angle based on the second optical anisotropic layer 36b and the diffraction angle based on the fourth optical anisotropic layer 36d.

[0232] One period of the liquid crystal alignment pattern of the fourth optical anisotropic layer 36d is different from one period of the liquid crystal alignment pattern of the second optical anisotropic layer 36b. Therefore, the diffraction angle based on the second optical anisotropic layer 36b is different from the diffraction angle based on the fourth optical anisotropic layer 36d. Figure 7 In the example shown, one period of the liquid crystal alignment pattern of the fourth optical anisotropy layer 36d is longer than one period of the liquid crystal alignment pattern of the second optical anisotropy layer 36b. Therefore, the diffraction angle based on the fourth optical anisotropy layer 36d is smaller than the diffraction angle based on the second optical anisotropy layer 36b. Consequently, the left-handed circularly polarized light I transmitted from the first optical anisotropy layer 36a to the fourth optical anisotropy layer 36d... L2 exist Figure 7 The middle part is in a state of moving to the lower left, almost perpendicular to the main surface.

[0233] Furthermore, the liquid crystal alignment patterns of the first optical anisotropic layer 36a and the second optical anisotropic layer 36b have the same period, and the liquid crystal alignment patterns of the third optical anisotropic layer 36c and the fourth optical anisotropic layer 36d have the same period. Therefore, right-handed circularly polarized light I transmitted through the first optical anisotropic layer 36a to the fourth optical anisotropic layer 36d is transmitted. R2 and left-handed circularly polarized light I L2 They are diffracted at approximately the same angle and travel in the same direction (approximately parallel).

[0234] As described above, the transmissive liquid crystal diffraction element of the present invention can diffract different polarized light (right-hand circularly polarized light and left-hand circularly polarized light) in the same direction, thus enabling high-efficiency diffraction of unpolarized light.

[0235] Here, as Figure 7 As shown, even with only the combination of the first optical anisotropic layer 36a and the second optical anisotropic layer 36b, it is possible to make the incident right-handed circularly polarized light I... R and left-handed circularly polarized light I LDiffraction occurs in the same direction. However, in an optical anisotropic layer with a structure where the equiphase surface is tilted relative to the main surface, in order to achieve the condition described above where diffraction does not occur depending on the angle of the incident light and the rotation direction of the circularly polarized light, the diffraction angle in the optical anisotropic layer needs to be increased. Therefore, when only the first optical anisotropic layer 36a and the second optical anisotropic layer 36b are combined, only a transmission-type liquid crystal diffraction element that diffracts at a large diffraction angle can be obtained, and it is not possible to diffract right-handed and left-handed circularly polarized light in the same direction at a small diffraction angle.

[0236] In contrast, the transmissive liquid crystal diffraction element of the present invention has four optical anisotropy layers: a first optical anisotropy layer 36a to a fourth optical anisotropy layer 36d. The combination of the first optical anisotropy layer 36a and the second optical anisotropy layer 36b (hereinafter also referred to as combination 1) causes the incident right-hand circularly polarized light and left-hand circularly polarized light to diffract in the same direction at a large diffraction angle. The combination of the third optical anisotropy layer 36c and the fourth optical anisotropy layer 36d (hereinafter also referred to as combination 2) causes the right-hand circularly polarized light and left-hand circularly polarized light diffracted by combination 1 to diffract in a direction opposite to the diffraction direction based on combination 1 at a large angle. Thus, as a transmissive liquid crystal diffraction element, it is possible to diffract right-hand circularly polarized light and left-hand circularly polarized light in the same direction with a diffraction angle with a small difference between the diffraction angle based on combination 1 and the diffraction angle based on combination 2.

[0237] Here, if one period of the liquid crystal alignment pattern of the first optical anisotropic layer 36a and the second optical anisotropic layer 36b is set as Λ1, and one period of the liquid crystal alignment pattern of the third optical anisotropic layer 36c and the fourth optical anisotropic layer 36d is set as Λ2, then the final diffraction angle of the transmissive liquid crystal diffraction element 10 is determined by the absolute value of Λ1·Λ2 / (Λ1-Λ2).

[0238] Furthermore, the diffraction angle of each individual optical anisotropic layer from the first optical anisotropic layer 36a to the fourth optical anisotropic layer 36d is preferably 50° to 130°, more preferably 60° to 120°, and even more preferably 70° to 110°. By setting the diffraction angle of the optical anisotropic layer within this range, as described above, it is possible to achieve a situation where no diffraction occurs depending on the angle of the incident light and the rotation direction of the circularly polarized light.

[0239] Here, the transmissive liquid crystal diffraction element of the present invention is not limited to a structure having only the first optical anisotropy layer 36a to the fourth optical anisotropy layer 36d. As described above, each optical anisotropy layer 36 of the transmissive liquid crystal diffraction element may be stacked with the support 30 and the alignment film 32, or it may be stacked with the alignment film 32.

[0240] Furthermore, the transmissive liquid crystal diffraction element of the present invention can have other layers. For example, a C-plate can be provided between the optically anisotropic layers. As an example, Figure 8 The transmissive liquid crystal diffraction element 10b shown has a C-plate 38 between the second optical anisotropy layer 36b and the third optical anisotropy layer 36c.

[0241] As described above, the optical anisotropy layer 36 converts incident circularly polarized light into circularly polarized light with the opposite rotation direction. However, sometimes it does not convert into circularly polarized light with the completely opposite direction, but becomes ellipticly polarized light. In a transmissive liquid crystal diffraction element, if the light converted by a certain optical anisotropy layer becomes ellipticly polarized light, the effect of the next optical anisotropy layer may not be accurately obtained, resulting in a decrease in diffraction efficiency.

[0242] Therefore, by setting a structure in which there are C plates 38 between optical anisotropic layers, it is possible to impart a phase difference to the circularly polarized light emitted from a certain optical anisotropic layer, so that it becomes circularly polarized light. Thus, the effect of the next optical anisotropic layer can be accurately obtained, thereby improving the diffraction efficiency.

[0243] Furthermore, even when C-plates are placed between optically anisotropic layers, the C-plates do not affect diffraction. Therefore, as a transmission-type liquid crystal diffraction element, it is possible to achieve the same performance as... Figure 7 The example shown exhibits the same diffraction effect.

[0244] As a phase difference layer, it is sufficient to impart a phase difference to the circularly polarized light emitted from the first optical anisotropic layer 36a, and the C plate and A plate can be used appropriately.

[0245] The thickness retardation of the phase retardation layer can be appropriately set according to the incident angle of the light and the structure of the first optical anisotropy layer 36a, so that the circularly polarized light emitted from the first optical anisotropy layer 36a can be converted into circularly polarized light. As an indicator, Nz = Rth / Re + 0.5 can be used. Here, Rth is the thickness retardation and Re is the in-plane retardation. Nz is preferably 0.1 to 1.1, more preferably 0.8 to 0.2, and even more preferably 0.7 to 0.3.

[0246] Furthermore, in this invention, in at least one combination of the first optical anisotropic layer 36a and the second optical anisotropic layer 36b combination 1 and the third optical anisotropic layer 36c and the fourth optical anisotropic layer 36d combination 2, preferably, the liquid crystal compound of one optical anisotropic layer is a rod-shaped liquid crystal compound, and the liquid crystal compound of the other optical anisotropic layer is a disk-shaped liquid crystal compound.

[0247] Figure 9This is a diagram that conceptually illustrates another example of the transmissive liquid crystal diffraction element of the present invention.

[0248] Figure 9 The transmissive liquid crystal diffraction element 10c shown sequentially comprises a first optical anisotropic layer 36e, a second optical anisotropic layer 36b, a third optical anisotropic layer 36f, and a fourth optical anisotropic layer 36d. Furthermore, in Figure 9 In the accompanying drawings, the structure of the transmissive liquid crystal diffraction element 10c is clearly shown for simplicity, while the liquid crystal compound 40 on the surface of each optical anisotropy layer is only conceptually shown. However, compared with... Figure 1 Similarly, in the examples shown, each optical anisotropic layer has a structure in which liquid crystal compound 40 is stacked in the thickness direction, and has a structure in which the optical axis of the liquid crystal compound 40 stacked in the thickness direction is twisted.

[0249] In the transmissive liquid crystal diffraction element 10c, in the combination 1 of the first optical anisotropic layer 36e and the second optical anisotropic layer 36b, the liquid crystal compound of the first optical anisotropic layer 36e is a disk-shaped liquid crystal compound 40b, and the liquid crystal compound of the second optical anisotropic layer 36b is a rod-shaped liquid crystal compound 40. Furthermore, in the combination 2 of the third optical anisotropic layer 36f and the fourth optical anisotropic layer 36d, the liquid crystal compound of the third optical anisotropic layer 36f is a disk-shaped liquid crystal compound 40b, and the liquid crystal compound of the fourth optical anisotropic layer 36d is a rod-shaped liquid crystal compound 40.

[0250] The second optical anisotropy layer 36b and the fourth optical anisotropy layer 36d respectively have the same characteristics as... Figure 1 The second optical anisotropic layer 36b and the fourth optical anisotropic layer 36d shown have the same structure, so their description is omitted.

[0251] The first optical anisotropic layer 36e, in addition to being formed using a disk-shaped liquid crystal compound 40b, has the same properties as... Figure 1 The structure is the same as that of the first optical anisotropy layer 36a shown. The optical axis of the disk-shaped liquid crystal compound 40b is oriented in a direction perpendicular to the disk surface. Therefore, in the first optical anisotropy layer 36e, the disk-shaped liquid crystal compound 40b is oriented in such a way that the disk surface is perpendicular to the interface of the first optical anisotropy layer 36e.

[0252] The first optical anisotropy layer 36e has a liquid crystal alignment pattern in which the orientation of the optical axis originating from the liquid crystal compound changes continuously as it rotates in at least one in-plane direction, and the rotation direction of the optical axis is opposite to the rotation direction of the optical axis in the liquid crystal alignment pattern of the second optical anisotropy layer 36b. Furthermore, the optical axis originating from the liquid crystal compound in the first optical anisotropy layer 36e is twisted in the thickness direction, and the twisting direction is opposite to the twisting direction of the optical axis in the thickness direction of the second optical anisotropy layer 36b. Also, one period in the liquid crystal alignment pattern of the first optical anisotropy layer 36e is the same as one period in the liquid crystal alignment pattern of the second optical anisotropy layer 36b.

[0253] The third optical anisotropy layer 36f, in addition to being formed using a disk-shaped liquid crystal compound 40b, has the same properties as... Figure 1 The structure is the same as that of the third optical anisotropy layer 36c shown. The optical axis of the disk-shaped liquid crystal compound 40b is oriented perpendicular to the disk surface. Therefore, in the third optical anisotropy layer 36f, the disk-shaped liquid crystal compound 40b is oriented such that the disk surface is perpendicular to the interface of the third optical anisotropy layer 36f.

[0254] The third optical anisotropy layer 36f has a liquid crystal alignment pattern in which the orientation of the optical axis originating from the liquid crystal compound changes continuously as it rotates in at least one in-plane direction, and the rotation direction of the optical axis is opposite to the rotation direction of the optical axis in the liquid crystal alignment pattern of the fourth optical anisotropy layer 36d. Furthermore, the optical axis originating from the liquid crystal compound in the thickness direction of the third optical anisotropy layer 36f is twisted, and its twisting direction is opposite to the twisting direction of the optical axis in the thickness direction of the fourth optical anisotropy layer 36d. Also, one period in the liquid crystal alignment pattern of the third optical anisotropy layer 36f is the same as one period in the liquid crystal alignment pattern of the fourth optical anisotropy layer 36d, but different from one period in the liquid crystal alignment pattern of the first optical anisotropy layer 36e.

[0255] Thus, in at least one of the combinations 1 (first optical anisotropic layer 36a and second optical anisotropic layer 36b) and 2 (third optical anisotropic layer 36c and fourth optical anisotropic layer 36d), by setting the liquid crystal compound of one optical anisotropic layer to be a rod-shaped liquid crystal compound and the liquid crystal compound of the other optical anisotropic layer to be a disk-shaped liquid crystal compound, the thickness retardation Rth in each combination can be made close to zero. Therefore, the change in in-plane retardation Re when light is incident on the transmissive liquid crystal diffraction element from an oblique direction is reduced. Therefore, the incident angle dependence of diffraction performance, such as diffraction efficiency, can be improved. Thus, the diffraction efficiency of the transmissive liquid crystal diffraction element can be further improved.

[0256] Furthermore, in Figure 3In the liquid crystal alignment pattern of the optical anisotropic layer shown, the alignment axis D exists along one direction, and the optical axis 40A of the liquid crystal compound 40 rotates continuously in one direction along the alignment axis D.

[0257] However, the present invention is not limited thereto. Various structures can be used as long as the optical axis 40A of the liquid crystal compound 40 in the optical anisotropic layer rotates continuously in one direction.

[0258] For example, as in Figure 10 The top view conceptually illustrates that the optical anisotropy layer 36 can be a structure with a radial liquid crystal alignment pattern. Figure 10 In the optical anisotropy layer 36 shown, the orientation of the optical axis of the liquid crystal compound 40 changes continuously while rotating along multiple directions from the center of the optical anisotropy layer 36 outward, such as the direction indicated by arrow A1, the direction indicated by arrow A2, the direction indicated by arrow A3, etc. That is, arrows A1, A2, and A3 are arrangement axes.

[0259] And, as Figure 10 As shown, the optical axis of the liquid crystal compound 40 changes as it rotates outward from the center of the optical anisotropic layer 36 in the same direction. Figure 10 The orientation shown is counter-clockwise. Along Figure 10 The rotation direction of the optical axis of each of the arrows A1, A2, and A3 changes from the center outwards, becoming counterclockwise.

[0260] Thus, in a radial pattern of liquid crystal alignment, the lines connecting liquid crystal compounds with optical axes pointing in the same direction are circular, and the circular line segments form a concentric circle pattern.

[0261] Thus, the optical anisotropic layer 36 with a radial liquid crystal alignment pattern can concentrate transmitted light when incident light is diffracted along each alignment axis (A1 to A3, etc.) in an azimuth direction toward the center. Alternatively, it can diffuse transmitted light when incident light is diffracted along each alignment axis (A1 to A3) in an azimuth direction toward the outside. Whether the transmitted light is diffracted along the center or toward the outside depends on the polarization state of the incident light and the rotation direction of the optical axes in the liquid crystal alignment pattern.

[0262] Here, in a single optically anisotropic layer where the liquid crystal alignment pattern has a radial pattern, one type of circularly polarized light is focused, while another type of circularly polarized light is diverged. Therefore, for example, as a focusing lens for focusing unpolarized light, its efficiency is approximately 50%.

[0263] In contrast, in this invention, by setting the liquid crystal alignment pattern of the first to fourth optical anisotropic layers to this radial pattern, right-hand circularly polarized light and left-hand circularly polarized light can be focused or diverged in the same direction. Therefore, even unpolarized light can be made into a lens that focuses or diverges light with high efficiency.

[0264] In the transmissive liquid crystal diffraction element of the present invention, when the liquid crystal alignment pattern of the first optical anisotropic layer to the fourth optical anisotropic layer is set as the above-mentioned radial pattern, in at least one combination of the combination 1 of the first optical anisotropic layer and the second optical anisotropic layer and the combination 2 of the third optical anisotropic layer and the fourth optical anisotropic layer, it is preferable that one period of the liquid crystal alignment pattern gradually changes along one direction.

[0265] Specifically, for example, when one period of the liquid crystal alignment pattern of combination 1 is less than one period of the liquid crystal alignment pattern of combination 2, that is, when the diffraction angle based on combination 1 is greater than the diffraction angle based on combination 2, it is preferable that one period of the liquid crystal alignment pattern of combination 1 gradually decreases from the center of the radial pattern outwards. Alternatively, it is also preferable that one period of the liquid crystal alignment pattern of combination 2 gradually increases from the center of the radial pattern outwards. Alternatively, it is also possible that one period of the liquid crystal alignment pattern of combination 1 gradually decreases from the center of the radial pattern outwards and one period of the liquid crystal alignment pattern of combination 2 gradually increases from the center of the radial pattern outwards. With this structure, from the center of the radial pattern outwards, the diffraction angle based on combination 1 further increases and / or the diffraction angle based on combination 2 further decreases, so the absolute value of the difference between the diffraction angle based on combination 1 and the diffraction angle based on combination 2 increases from the center of the radial pattern outwards. Therefore, light incident near the outer edge of the transmissive liquid crystal diffraction element is diffracted more than light incident near the center, thus enabling it to function more effectively as a condensing lens or a diverging lens.

[0266] When one period of the liquid crystal alignment pattern of combination 1 is greater than one period of the liquid crystal alignment pattern of combination 2, it is preferable that one period of the liquid crystal alignment pattern of combination 1 gradually increases from the center of the radial pattern outward and / or one period of the liquid crystal alignment pattern of combination 2 gradually decreases from the center of the radial pattern outward.

[0267] In this structure, the relationship between one period Λ1 of the liquid crystal alignment pattern of combination 1 (first optical anisotropic layer) and one period Λ2 of the liquid crystal alignment pattern of combination 2 (third optical anisotropic layer) can be represented by the difference of their reciprocals. The difference between the reciprocal (1 / Λ1) of one period of the liquid crystal alignment pattern of combination 1 (first optical anisotropic layer) and the reciprocal (1 / Λ2) of one period of the liquid crystal alignment pattern of combination 2 (third optical anisotropic layer) becomes the reciprocal of the period Λ of the combined element of combination 1 and combination 2. Therefore, by setting Λ to a desired distribution (e.g., gradually decreasing from the center of the radial liquid crystal alignment pattern toward the outer part), the combined element can be used as a focusing or diverging element such as a lens.

[0268] exist Figure 14 A graph showing the relationship between Λ and the position (x) from the center of the optical anisotropic layer is displayed.

[0269] As an example, in Figure 12 A conceptual diagram illustrating the liquid crystal alignment pattern of the first optical anisotropic layer 36a and the second optical anisotropic layer 36b (combination 1) is shown. Figure 13 A conceptual diagram illustrating the liquid crystal alignment pattern of the third optical anisotropic layer 36c and the fourth optical anisotropic layer 36d (combination 2) is shown. Figure 12 and Figure 13 In the image, dashed lines indicate the interval of one cycle of the liquid crystal alignment pattern in the optical anisotropic layer.

[0270] like Figure 12 As shown, one period of the liquid crystal alignment pattern of the first optical anisotropic layer 36a and the second optical anisotropic layer 36b (combination 1) is constant. Furthermore, as... Figure 13 As shown, one period of the liquid crystal alignment pattern of the third optical anisotropic layer 36c and the fourth optical anisotropic layer 36d (combination 2) gradually decreases in size from the center of the radial pattern outwards. Furthermore, Figure 12 and Figure 13 The example shown is an example where one period of the liquid crystal alignment pattern of combination 2 is smaller than one period of the liquid crystal alignment pattern of combination 1.

[0271] use Figure 15 An example of the function of a transmissive liquid crystal diffraction element having a first optical anisotropy layer 36a to a fourth optical anisotropy layer 36d (with such a liquid crystal alignment pattern) will be explained.

[0272] Parallel light from Figure 15The incident light is incident on the side of the first optical anisotropy layer 36a of the transmissive liquid crystal diffraction element 10. The incident parallel light is diffracted outward at a predetermined angle by the assembly 1. At this time, one period of the liquid crystal alignment pattern of the assembly 1 is constant, so the diffraction angle is constant at any position in the plane of the optical anisotropy layer.

[0273] The light diffracted by Assembly 1 is incident on Assembly 2 and diffracted by Assembly 2 at a predetermined angle toward the center. At this time, one period of the liquid crystal alignment pattern in Assembly 2 gradually decreases from the center outwards, therefore the diffraction angle further increases from the center outwards within the plane of the optical anisotropic layer. Thus, as... Figure 15 As shown, the diffracted light is focused.

[0274] In addition, Figure 15 In the example shown, combination 1 is configured to diffract light outwards and combination 2 to diffract light towards the center, but it is not limited to this configuration. Figure 16 As shown, it can also be configured as a structure where combination 1 diffracts light towards the center and combination 2 diffracts light towards the outside. When focusing light using the structure where combination 1 diffracts light towards the center and combination 2 diffracts light towards the outside, it is sufficient to make the diffraction angle based on combination 1 greater than the diffraction angle based on combination 2.

[0275] Here, Figure 2 The optical anisotropic layer 36 shown illustrates a structure in which the optical axis of the liquid crystal compound is parallel to the main surface of the optical anisotropic layer, but is not limited to this. In the optical anisotropic layer, the optical axis of the liquid crystal compound may be tilted toward the main surface of the optical anisotropic layer.

[0276] Furthermore, the structure can also be as follows: at least one of the optical anisotropic layers has a structure in which rod-shaped liquid crystal layers oriented in a liquid crystal alignment pattern and disk-shaped liquid crystal layers oriented in a liquid crystal alignment pattern are alternately stacked. More preferably, all optical anisotropic layers have a structure in which rod-shaped liquid crystal layers and disk-shaped liquid crystal layers are alternately stacked.

[0277] By configuring the optical anisotropic layer as a structure consisting of alternating layers of rod-shaped and disk-shaped liquid crystal layers, the thickness retardation Rth of the optical anisotropic layer can be made close to zero. Consequently, the change in in-plane retardation Re when light is incident on the optical anisotropic layer from an oblique direction is reduced. Therefore, the incident angle dependence of diffraction properties, such as diffraction efficiency, can be improved.

[0278] Furthermore, since the diffracted light is generated at various positions along the thickness direction of the diffracting layer, it is preferable that Rth is close to zero at any position along the thickness direction of the diffracting layer, and preferably that Rth is canceled out at each position along the thickness direction of the diffracting layer. Thus, it is preferable that the Rth of adjacent layers of the alternately stacked rod-shaped liquid crystal layers and disk-shaped liquid crystal layers have a positive-negative relationship, and the absolute value of Rth for each layer is approximately 10 to 200 nm.

[0279] By incorporating this optically anisotropic layer, the diffraction efficiency of transmissive liquid crystal diffraction elements can be further improved.

[0280] Regarding the thickness of each rod-shaped liquid crystal layer and the disk-shaped liquid crystal layer, it is preferable that the total thickness of the rod-shaped liquid crystal layer and the disk-shaped liquid crystal layer is not too large relative to the wavelength of the incident light. The thickness of each rod-shaped liquid crystal layer and the disk-shaped liquid crystal layer is preferably 0.1μm to 5μm, more preferably 0.1μm to 2μm, and even more preferably 0.1μm to 0.5μm.

[0281] Furthermore, in Figure 2 In the example shown, the optical anisotropy layer 36 is configured such that the twist angle per unit length in the twisted structure of the optical axis derived from the liquid crystal compound in the thickness direction is constant, but it is not limited to this. The optical anisotropy layer 36 may also have a gradually changing twist angle per unit length in the twisted structure of the optical axis derived from the liquid crystal compound in the thickness direction.

[0282] The transmissive liquid crystal diffraction element of the present invention has been described in detail above. However, the present invention is not limited to the above examples. Various improvements or modifications can be made without departing from the spirit of the present invention.

[0283] Example

[0284] The following examples illustrate the features of the present invention in further detail. The materials, reagents, dosages, quantities, proportions, processing contents, and processing steps shown in the following examples can be appropriately modified without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be limited by the specific examples shown below.

[0285] [Comparative Example 1]

[0286] <Fabrication of Transmission-Type Liquid Crystal Diffraction Elements>

[0287] (Formation of the orientation film)

[0288] A glass substrate was prepared as a support. The following alignment film forming coating liquid was applied to the support by spin coating. The support with the coating liquid forming the alignment film was dried on a hot plate at 60°C for 60 seconds, thereby forming the alignment film P-2.

[0289] Coating solution for oriented film formation

[0290]

[0291]

[0292] Materials for light orientation

[0293] [Chemical Formula 1]

[0294]

[0295] (Exposure of the alignment film)

[0296] The obtained alignment film was irradiated with P-2 (50 mJ / cm). 2 The orientation film P-2 was exposed using polarized ultraviolet light from an ultra-high pressure mercury lamp.

[0297] use Figure 4 The exposure apparatus shown exposes an alignment film to form an alignment film P-2 with an alignment pattern. A device emitting a laser beam with an emission wavelength of 325 nm is used as the laser in the exposure apparatus. The exposure dose based on interference light is set to 300 mJ / cm². 2 In addition, the cross angle (cross angle α) of the two beams was adjusted so that one period Λ (the length of the optical axis rotated 180°) of the orientation pattern formed by the interference of the two laser beams became 10 μm.

[0298] (Formation of an anisotropic optical layer)

[0299] Composition B-1 was prepared as a liquid crystal composition for forming an optically anisotropic layer.

[0300] Composition B-1

[0301]

[0302] Rod-shaped liquid crystal compound L-1 (containing the following structure in the mass ratio shown on the right)

[0303] [Chemical Formula 2]

[0304]

[0305] Leveling agent T-1

[0306] [Chemical Formula 3]

[0307]

[0308] The optical anisotropic layer is formed by multi-coating composition B-1 onto an alignment film P-2. The process is repeated as follows: first, a first layer of composition B-1 is coated onto the alignment film, and after heating and cooling, it is cured with ultraviolet light to form a liquid crystal immobilization layer. Then, a second layer is coated on top of this liquid crystal immobilization layer, and the process is similarly followed by heating, cooling, and ultraviolet curing.

[0309] First, for the first layer, the following composition B-1 is coated onto the alignment film P-2, and the coating is heated to 80°C on a hot plate. Then, at 80°C, a high-pressure mercury lamp at 300 mJ / cm² is used under a nitrogen atmosphere. 2 The coating was irradiated with ultraviolet light at a wavelength of 365 nm, thereby fixing the orientation of the liquid crystal compound.

[0310] For the second layer and thereafter, layers are overlapped on the liquid crystal immobilization layer, and then heated and cooled under the same conditions as described above, followed by ultraviolet curing to create the liquid crystal immobilization layer. This process of overlapping coating is repeated until the total thickness reaches the desired film thickness, thus forming an optically anisotropic layer.

[0311] Furthermore, for the refractive index difference Δn of the cured layer of composition B-1, the retardation Re(λ) and film thickness of the liquid crystal immobilized layer were measured and determined as follows: Composition B-1 was coated onto a separately prepared support with an alignment film for retardation measurement, and oriented so that the liquid crystal compound was horizontally aligned with the substrate before being immobilized by ultraviolet irradiation. Δn can be calculated by dividing the retardation Re(λ) by the film thickness. λ The delay Re(λ) was measured at the target wavelength using an Axometrix Axoscan sensor, and the film thickness was measured using SEM. In the notation of Re(λ), λ represents the wavelength of the incident light. Hereinafter, the wavelength λ of the incident light is set to 600 nm.

[0312] For the optically anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 600 The thickness, Re(600), eventually reaches 300 nm and becomes periodically oriented. Furthermore, the twist angle in the thickness direction of the optically anisotropic layer is 0°. Moreover, in a cross-sectional image based on SEM, a bright-dark line perpendicular to the lower interface of the optically anisotropic layer (the interface with the glass substrate) is observed. This bright-dark line is observed through a structure formed by stacking liquid crystal compounds oriented in the same direction along the thickness direction.

[0313] One layer of this optical anisotropic layer was used as a transmission-type liquid crystal diffraction element in Comparative Example 1.

[0314] [Comparative Example 2]

[0315] An optical anisotropic layer was fabricated in the same manner as in Comparative Example 1, and then rotated 180 degrees so that the rotation direction of the optical axis originating from the liquid crystal compound, which changes continuously along one in-plane direction, becomes opposite to that of the optical anisotropic layer, and this was used as the optical anisotropic layer of Comparative Example 2.

[0316] The structures of Comparative Example 1 and Comparative Example 2 are shown in Table 1 below. In Table 1, the line count is the number of cycles per 1 mm, obtained by dividing 1000 (μm) by one cycle (μm). Furthermore, the tilt angle refers to the angle between the bright and dark lines observed through the SEM cross-section and the perpendicular line to the main surface.

[0317] [Table 1]

[0318]

[0319] [Example 1]

[0320] (Formation of the first optical anisotropy layer)

[0321] In the formation of the alignment film in Comparative Example 1, one period Λ of the alignment pattern was made 1 μm, and otherwise the alignment film was formed in the same manner as in Comparative Example 1.

[0322] In the formation of the optical anisotropic layer in Comparative Example 1, the following composition B-2 was used instead of composition B-1. Otherwise, the first optical anisotropic layer was formed in the same manner as in Comparative Example 1.

[0323] The following composition B-2 was used as the liquid crystal composition for forming the first optical anisotropic layer.

[0324] Composition B-2

[0325]

[0326]

[0327] Chiral reagent Ch-A

[0328] [Chemical Formula 4]

[0329]

[0330] (Formation of the second optical anisotropic layer)

[0331] The alignment film is rotated 180 degrees in the same way as the first optical anisotropy layer, so that the rotation direction of the optical axis originating from the liquid crystal compound, which changes continuously along one in-plane direction, becomes opposite to that of the first optical anisotropy layer.

[0332] In the formation of the optical anisotropic layer in Comparative Example 1, the following composition B-3 was used instead of composition B-1. Otherwise, the second optical anisotropic layer was formed in the same manner as in Comparative Example 1.

[0333] The following composition B-3 was used as the liquid crystal composition for forming the second optical anisotropic layer.

[0334] Composition B-3

[0335]

[0336] Chiral reagent Ch-B

[0337] [Chemical Formula 5]

[0338]

[0339] (Formation of the third optical anisotropic layer)

[0340] In the formation of the first optical anisotropic layer, one period Λ of the orientation pattern of the orientation film is made to be 1.111 μm. Otherwise, the third optical anisotropic layer is formed in the same manner as the first optical anisotropic layer.

[0341] (Formation of the fourth optical anisotropic layer)

[0342] In the formation of the second optical anisotropic layer, one period Λ of the orientation pattern of the orientation film is made to be 1.111 μm. Otherwise, the fourth optical anisotropic layer is formed in the same manner as the second optical anisotropic layer.

[0343] For the first optical anisotropic layer, the Δn of the liquid crystal was confirmed using polarization microscopy. 600 The thickness = Re(600) eventually becomes 300 nm and becomes periodically oriented. Furthermore, the twist angle in the thickness direction of the first optical anisotropic layer is 80° (right twist). Moreover, in the SEM-based cross-sectional image, bright and dark lines tilted relative to the lower interface of the first optical anisotropic layer (interface with the glass substrate) are observed.

[0344] For the second optical anisotropic layer, the Δn of the liquid crystal was confirmed using polarized light microscopy. 600 The thickness = Re(600) eventually becomes 300 nm and becomes periodically oriented. Furthermore, the twist angle in the thickness direction of the second optical anisotropic layer is -80° (left twist). Also, in the SEM-based cross-sectional image, bright and dark lines tilted relative to the lower interface of the second optical anisotropic layer are observed. The tilt angle at this point is the same as that of the first optical anisotropic layer, and the tilt direction is the same.

[0345] For the third optical anisotropic layer, the Δn of the liquid crystal was confirmed using polarized light microscopy. 600 The thickness = Re(600) eventually becomes 300 nm and becomes periodically oriented. Furthermore, the twist angle in the thickness direction of the third optical anisotropy layer is 80° (right twist). Also, in the SEM-based cross-sectional image, bright and dark lines tilted relative to the lower interface of the third optical anisotropy layer (the interface with the glass substrate) are observed. The tilt angle at this point is different from that of the first optical anisotropy layer, but the tilt direction is the same.

[0346] For the fourth optical anisotropic layer, the Δn of the liquid crystal was confirmed using polarized light microscopy. 600 The thickness = Re(600) eventually becomes 300 nm and becomes periodically oriented. Furthermore, the twist angle in the thickness direction of the fourth optical anisotropic layer is -80° (left twist). Also, in the SEM-based cross-sectional image, bright and dark lines tilted relative to the lower interface of the fourth optical anisotropic layer are observed. The tilt angle at this point is the same as that of the third optical anisotropic layer, and the tilt direction is the same.

[0347] The first to fourth optically anisotropic layers were sequentially stacked to fabricate the transmissive liquid crystal diffraction element of Example 1. The diffraction element is 20 mm square.

[0348] The structure of the transmissive liquid crystal diffraction element of Example 1 is shown in Table 2 below.

[0349] [Table 2]

[0350]

[0351] [Example 2]

[0352] In Example 1, one period of the third and fourth optical anisotropic layers was set to 0.909 μm. Otherwise, a transmissive liquid crystal diffraction element was fabricated in the same manner as in Example 1.

[0353] The structure of the transmissive liquid crystal diffraction element of Example 2 is shown in Table 3 below.

[0354] [Table 3]

[0355]

[0356] [evaluate]

[0357] A straight-through beam of unpolarized light with a wavelength of 600 nm (1 mm in diameter) was incident on the fabricated transmissive liquid crystal diffraction element from the normal direction of the main surface of the transmissive liquid crystal diffraction element (in this embodiment, the main surface of the first optical anisotropic layer side), and the diffraction intensity (diffraction efficiency) of the diffracted light was measured using a power meter. The standard for intensity (diffraction efficiency) is as follows.

[0358] • A: Intensity (diffraction efficiency) is above 90%.

[0359] • B: Intensity (diffraction efficiency) is above 80%.

[0360] • C: Intensity (diffraction efficiency) is above 70%.

[0361] • D: Intensity (diffraction efficiency) is 60% or higher.

[0362] E: Intensity (diffraction efficiency) is 50% or higher.

[0363] • F: Intensity (diffraction efficiency) less than 50%

[0364] The results are shown in Table 4 below.

[0365] [Table 4]

[0366] Comparative Example 1 F Comparative Example 2 F Example 1 A Example 2 A

[0367] As shown in Table 1, in the embodiments of the present invention, even with unpolarized light, a large diffraction efficiency can be obtained. That is, it can be seen that different circularly polarized light can be diffracted in the same direction.

[0368] [Comparative Examples 11-12]

[0369] As an exposure device for alignment films, such as Figure 11 The exposure apparatus shown was used to form a radial orientation pattern using the exposure method described in WO2019 / 189818. Otherwise, a transmissive liquid crystal diffraction element was fabricated in the same manner as Comparative Examples 1 and 2. The size was set to a diameter of 40 mm. This transmissive liquid crystal diffraction element functions as a condenser lens.

[0370] The structures of Comparative Example 1 and Comparative Example 2 are shown in Table 5 below.

[0371] [Table 5]

[0372]

[0373] [Example 11]

[0374] As an exposure device for alignment films, such as Figure 11The exposure apparatus shown was used to form a radial orientation pattern using the exposure method described in WO2019 / 189818. In addition, a first to a fourth optical anisotropic layer were formed in the same manner as in Example 1 to fabricate a transmissive liquid crystal diffraction element. The size was set to a diameter of 40 mm. This transmissive liquid crystal diffraction element functions as a condenser lens.

[0375] The structure of the transmissive liquid crystal diffraction element of Example 11 is shown in Table 6 below.

[0376] [Table 6]

[0377]

[0378] [Example 12]

[0379] As an exposure device for alignment films, such as Figure 11 The exposure apparatus shown, using the exposure method described in WO2019 / 189818, forms a radial orientation pattern with the in-plane rotation direction of each optical anisotropic layer opposite to that of Example 11. Furthermore, the first to fourth optical anisotropic layers are formed in the same manner as in Example 2 to fabricate a transmissive liquid crystal diffraction element. The size is set to a diameter of 40 mm. This transmissive liquid crystal diffraction element functions as a condenser lens.

[0380] The structure of the transmissive liquid crystal diffraction element of Example 12 is shown in Table 7 below.

[0381] [Table 7]

[0382]

[0383] [evaluate]

[0384] A straight-through beam of unpolarized light with a wavelength of 600 nm (40 mm in diameter) was incident on the fabricated transmissive liquid crystal diffraction element from the normal direction of the main surface of the transmissive liquid crystal diffraction element (the main surface of the first optical anisotropic layer side in this embodiment), and the diffraction intensity (diffraction efficiency) of the focused light (first-order diffraction light) using a lens was measured using a power meter. The criteria for intensity (diffraction efficiency) are as follows.

[0385] • A: Intensity (diffraction efficiency) is above 90%.

[0386] • B: Intensity (diffraction efficiency) is above 80%.

[0387] • C: Intensity (diffraction efficiency) is above 70%.

[0388] • D: Intensity (diffraction efficiency) is 60% or higher.

[0389] E: Intensity (diffraction efficiency) is 50% or higher.

[0390] • F: Intensity (diffraction efficiency) less than 50%

[0391] The results are shown in Table 8 below.

[0392] [Table 8]

[0393] Comparative Example 11 F Comparative Example 12 F Example 11 A Example 12 A

[0394] As shown in Table 8, in the comparative examples, due to the polarization dependence, less than half of the diffraction efficiency can be obtained for unpolarized light. In contrast, the embodiments of the present invention achieve a higher diffraction efficiency even for unpolarized light. Furthermore, when the lens is visually observed, unwanted images caused by the diverging light of the -1st order can be observed in the comparative examples, while these are almost not observed in the embodiments, thus enabling the realization of a good lens corresponding to unpolarized light.

[0395] The results above show that the present invention is effective.

[0396] Symbol Explanation

[0397] 10, 10b - Transmissive liquid crystal diffraction element; 30 - Support; 32 - Alignment film; 36 - Optical anisotropy layer; 36a, 36e - First optical anisotropy layer; 36b - Second optical anisotropy layer; 36c, 36f - Third optical anisotropy layer; 36d - Fourth optical anisotropy layer; 38 - C plate; 40 - Liquid crystal compound (rod-shaped liquid crystal compound); 40b - Disk-shaped liquid crystal compound; 40A - Optical axis; 60, 80 - Exposure device; 62, 82 - Laser; 64, 84 - Light source; 65 - λ / 2 plate; 68 - Beam splitter; 70A, 70B, 90A, 90B - Mirrors; 72A, 72B, 96 - λ / 4 plate; 86, 94 - Polarizing beam splitter; 92 - Lens; I R I R1 I R2 - Right-handed circularly polarized light, I L I L1 I L2 - Left-handed circularly polarized light, D, A1, A2, A3 - arrangement axes, R - region, Λ - 1 period, MA, MB - light rays, P O - Linearly polarized light, P R - Right-handed circularly polarized light, P L - Left-handed circularly polarized light, M-laser beam, MP-P polarized light, MS-S polarized light, α-angle, L1, L2, L4, L5-light.

Claims

1. A transmissive liquid crystal diffraction element, comprising: The first to fourth optical anisotropic layers have a liquid crystal alignment pattern that changes as the orientation of the optical axis originating from the liquid crystal compound continuously rotates in at least one in-plane direction. In the first to fourth optical anisotropy layers, the optical axis originating from the liquid crystal compound is twisted along the thickness direction. The rotation direction of the optical axis in the liquid crystal alignment pattern of the first optical anisotropic layer is opposite to the rotation direction of the optical axis in the liquid crystal alignment pattern of the second optical anisotropic layer. The rotation direction of the optical axis in the liquid crystal alignment pattern of the third optical anisotropic layer is opposite to the rotation direction of the optical axis in the liquid crystal alignment pattern of the fourth optical anisotropic layer. The twist direction of the optical axis originating from the liquid crystal compound in the thickness direction of the first optical anisotropic layer is opposite to the twist direction of the optical axis originating from the liquid crystal compound in the thickness direction of the second optical anisotropic layer. The twist direction of the optical axis originating from the liquid crystal compound in the thickness direction of the third optical anisotropic layer is opposite to the twist direction of the optical axis originating from the liquid crystal compound in the thickness direction of the fourth optical anisotropic layer. When the length of a 180° in-plane rotation of the orientation of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern is defined as one period, one period in the liquid crystal alignment pattern of the first optical anisotropy layer is the same as one period in the liquid crystal alignment pattern of the second optical anisotropy layer. One period of the liquid crystal alignment pattern in the third optical anisotropic layer is the same as one period of the liquid crystal alignment pattern in the fourth optical anisotropic layer. One period of the liquid crystal alignment pattern in the first optical anisotropic layer is different from one period of the liquid crystal alignment pattern in the third optical anisotropic layer.

2. The transmissive liquid crystal diffraction element according to claim 1, wherein, The twist angle of the optical axis derived from the liquid crystal compound in the thickness direction of the first to fourth optical anisotropic layers is less than 360°.

3. The transmissive liquid crystal diffraction element according to claim 1 or 2, wherein, The first optical anisotropic layer to the fourth optical anisotropic layer have the liquid crystal alignment pattern radially.

4. The transmissive liquid crystal diffraction element according to claim 1 or 2, wherein, In at least one combination of the combination of the first optical anisotropic layer and the second optical anisotropic layer and the combination of the third optical anisotropic layer and the fourth optical anisotropic layer, one period of the liquid crystal alignment pattern gradually changes along one direction.

5. The transmissive liquid crystal diffraction element according to claim 3, wherein, From the center of the radial liquid crystal alignment pattern toward the outer portion, the difference between the reciprocal of one period of the liquid crystal alignment pattern of the first optical anisotropic layer and the reciprocal of one period of the liquid crystal alignment pattern of the third optical anisotropic layer gradually increases.

6. The transmissive liquid crystal diffraction element according to claim 1 or 2, wherein, A C-plate is also present between any one of the first to fourth optical anisotropic layers.

7. The transmissive liquid crystal diffraction element according to claim 1 or 2, wherein, In at least one combination of the first optical anisotropic layer and the second optical anisotropic layer and the third optical anisotropic layer and the fourth optical anisotropic layer, the liquid crystal compound of one optical anisotropic layer is a rod-shaped liquid crystal compound, and the liquid crystal compound of the other optical anisotropic layer is a disk-shaped liquid crystal compound.

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