Transmissive liquid crystal diffraction element

Abstract

Provided is a transmissive liquid crystal diffraction element capable of diffracting different polarized light in the same direction with high diffraction efficiency. The transmissive liquid crystal diffraction element includes a first optical anisotropic layer and a second optical anisotropic layer each having a liquid crystal alignment pattern in which the orientation of an optical axis derived from a liquid crystal compound changes while continuously rotating along at least one direction in the plane. 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. If the length of the orientation of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern that rotates 180° in the plane is taken as one period, one period of the liquid crystal alignment pattern of the first optical anisotropic layer is the same as one period of the liquid crystal alignment pattern of the second optical anisotropic layer.

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 using a liquid crystal compound is proposed.

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

[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] In polarized light diffraction elements using liquid crystal compounds, the direction of bending varies depending on the polarization of the light. Specifically, right-handed and left-handed circularly polarized light incident on the polarized light diffraction element bends and separates in opposite directions. Therefore, regardless of the polarization of the light, it is impossible to diffract the light in a predetermined direction.

[0010] The objective of this invention is to provide a transmissive liquid crystal diffraction element capable of diffracting different polarized light in the same direction.

[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 comprising a first optical anisotropic layer and a second optical anisotropic layer, each having a liquid crystal alignment pattern having an optical axis originating from a liquid crystal compound whose orientation changes while continuously rotating along at least one direction in the plane.

[0014] 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.

[0015] If the length of the orientation of the optical axis originating from the liquid crystal compound in the liquid crystal alignment pattern rotated 180° in the plane is taken as one period, then one period of the liquid crystal alignment pattern of the first optical anisotropy layer is the same as one period of the liquid crystal alignment pattern of the second optical anisotropy layer.

[0016] [2] According to the transmissive liquid crystal diffraction element described in [1], wherein,

[0017] In the first and second optical anisotropic layers, the liquid crystal compound is twisted and oriented in the thickness direction.

[0018] The twist angle of the twist orientation is less than 360°.

[0019] The twisting direction of the liquid crystal compound in the first optical anisotropic layer is opposite to that of the liquid crystal compound in the second optical anisotropic layer.

[0020] [3] According to the transmission-type liquid crystal diffraction element described in [1] or [2], wherein,

[0021] The liquid crystal compound is either rod-shaped or disc-shaped.

[0022] [4] The transmissive liquid crystal diffraction element according to any one of [1] to [3], wherein,

[0023] At least one of the first optical anisotropic layer and the second optical anisotropic layer has a structure in which a rod-shaped liquid crystal layer oriented in a liquid crystal alignment pattern and a disk-shaped liquid crystal layer oriented in a liquid crystal alignment pattern are alternately stacked.

[0024] [5] According to the transmissive liquid crystal diffraction element described in [1], wherein,

[0025] At least one of the first optical anisotropic layer and the second optical anisotropic layer is formed by stacking multiple liquid crystal layers with liquid crystal compounds twisted and oriented in the thickness direction.

[0026] The twist angle of the twisted orientation in each liquid crystal layer is less than 360°.

[0027] In multiple liquid crystal layers, the twisting direction of the liquid crystal compound is alternating in the stacking direction.

[0028] [6] According to the transmissive liquid crystal diffraction element described in [5], wherein,

[0029] At least one of the liquid crystal layers has a structure in which a rod-shaped liquid crystal layer oriented in a liquid crystal alignment pattern and a disk-shaped liquid crystal layer oriented in a liquid crystal alignment pattern are alternately stacked.

[0030] [7] The transmissive liquid crystal diffraction element according to any one of [1] to [6] has a phase difference layer disposed between the first optical anisotropic layer and the second optical anisotropic layer.

[0031] [8] According to the transmissive liquid crystal diffraction element described in [7], wherein,

[0032] The Nz value of the phase difference layer is 0.1 to 1.1.

[0033] [9] The transmissive liquid crystal diffraction element according to any one of [1] to [8] has a λ / 4 plate disposed on at least one of the side of the first optical anisotropy layer opposite to the second optical anisotropy layer and the side of the second optical anisotropy layer opposite to the first optical anisotropy layer.

[0034] Invention Effects

[0035] According to the present invention, a transmission-type liquid crystal diffraction element with high diffraction efficiency can be provided, which can diffract different polarized light in the same direction. 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 2 The front view of the optical anisotropic layer shown.

[0039] Figure 4 Yes 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 It is a conceptual representation Figure 8 The diagram shows the optical anisotropy layer of the transmissive liquid crystal diffraction element.

[0045] Figure 10 This is a diagram that conceptually illustrates another example of the transmissive liquid crystal diffraction element of the present invention.

[0046] Figure 11 This is a diagram that conceptually illustrates another example of the optical anisotropy layer of the transmissive liquid crystal diffraction element of the present invention.

[0047] Figure 12 This is a diagram that conceptually illustrates another example of the transmissive liquid crystal diffraction element of the present invention.

[0048] Figure 13 It is a conceptual representation Figure 12 A diagram showing another example of the liquid crystal layer in a liquid crystal diffraction element.

[0049] Figure 14 This is a diagram that conceptually illustrates another example of the transmissive liquid crystal diffraction element of the present invention.

[0050] Figure 15 This is a diagram that conceptually illustrates another example of the transmissive liquid crystal diffraction element of the present invention.

[0051] Figure 16 This is a diagram that conceptually illustrates another example of the transmissive liquid crystal diffraction element of the present invention.

[0052] Figure 17 This is a diagram that conceptually illustrates another example of the transmissive liquid crystal diffraction element of the present invention.

[0053] Figure 18 This is a diagram that conceptually illustrates another example of the transmissive liquid crystal diffraction element of the present invention.

[0054] Figure 19 This is a diagram that conceptually illustrates another example of the transmissive liquid crystal diffraction element of the present invention. Detailed Implementation

[0055] 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.

[0056] 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.

[0057] In this specification, "(meth)acrylate" is used to mean "any one or both of acrylate and methacrylate".

[0058] In this specification, terms such as "same" and "equal" include the range of errors that are generally permissible in the technical field.

[0059] [Transmission-type liquid crystal diffraction element]

[0060] The liquid crystal diffraction element of the present invention comprises a first optical anisotropic layer and a second optical anisotropic layer having a liquid crystal alignment pattern having an optical axis derived from a liquid crystal compound whose orientation changes continuously while rotating along at least one in-plane direction.

[0061] 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.

[0062] If the length of the orientation of the optical axis originating from the liquid crystal compound in the liquid crystal alignment pattern rotated 180° in the plane is taken as one period, then one period of the liquid crystal alignment pattern of the first optical anisotropy layer is the same as one period of the liquid crystal alignment pattern of the second optical anisotropy layer.

[0063] Figure 1 The present invention conceptually illustrates an example of a transmissive liquid crystal diffraction element.

[0064] Figure 1 The transmissive liquid crystal diffraction element 10 shown has a first optical anisotropic layer 36a and a second optical anisotropic layer 36b stacked 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, the first optical anisotropic layer 36a and the second optical anisotropic layer 36b are only conceptually shown as having liquid crystal compound 40 (molecules of the liquid crystal compound) on their surfaces. However, as... Figure 2 As shown conceptually, the first optical anisotropy layer 36a and the second optical anisotropy layer 36b have a structure in which liquid crystal compound 40 is stacked in the thickness direction, and the optical axes of the liquid crystal compound 40 stacked in the thickness direction are oriented in the same direction.

[0065] like Figure 1 As shown, a first optical anisotropic layer 36a and a second optical anisotropic layer 36b are stacked in the thickness direction.

[0066] The first optical anisotropy layer 36a and the second optical anisotropy layer 36b have a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while rotating continuously along at least one direction in the plane.

[0067] The first optical anisotropic layer 36a and the second optical anisotropic layer 36b, having the aforementioned liquid crystal alignment pattern, enable the diffraction of transmitted light. Regarding the diffraction angle, if one period (hereinafter also referred to as one period of the liquid crystal alignment pattern) is defined as the length of a 180° in-plane rotation of the orientation of the optical axis originating from the liquid crystal compound within the liquid crystal alignment pattern, then the angle depends on the length of this one period. Therefore, by adjusting one period of the liquid crystal alignment pattern, the diffraction angle can be adjusted.

[0068] 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. 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. The transmissive liquid crystal diffraction element of the present invention, having the above structure, transmits and diffracts light incident obliquely onto the main surface. At this time, right-hand circularly polarized light and left-hand circularly polarized light can be diffracted in the same direction. That is, the transmissive liquid crystal diffraction element 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.

[0069] (Optical anisotropic layer)

[0070] use Figure 2 and Figure 3 The first optical anisotropy layer 36a and the second optical anisotropy layer 36b will be described. Furthermore, the optical axes in the liquid crystal alignment pattern of the first optical anisotropy layer 36a and the second optical anisotropy layer 36b have opposite rotation directions, but otherwise have the same structure. Therefore, without needing to distinguish between the first optical anisotropy layer 36a and the second optical anisotropy layer 36b, they will be described together as optical anisotropy layer 36.

[0071] Figure 2 and Figure 3 The example shown is an optically anisotropic layer, which is formed by fixing a liquid crystal phase that aligns a liquid crystal compound, and has an optically anisotropic layer having a liquid crystal alignment pattern in which the orientation of the optical axis originating from the liquid crystal compound changes while rotating continuously along at least one direction in the plane. Figure 2 and Figure 3 In the example shown, in the optical anisotropy layer, the rotation direction of the optical axis in the liquid crystal alignment pattern is... Figure 1 The first optical anisotropy layer 36a is the same.

[0072] exist Figure 2In the example shown, the optical anisotropic layer 36 is stacked on the alignment film 32 stacked on the support 30.

[0073] Furthermore, when the first optical anisotropic layer and the second optical anisotropic layer are stacked as a transmissive liquid crystal diffraction element, such as Figure 2 As shown in the example, the optical anisotropic layer can be laminated on the support 30 and the alignment film 32. Alternatively, the optical anisotropic layer can be laminated, for example, with the support 30 removed and only the alignment film 32 and the optical anisotropic layer laminated. Alternatively, the optical anisotropic layer can be laminated, for example, with the support 30 and the alignment film 32 removed and only the optical anisotropic layer laminated.

[0074] <Support>

[0075] The support 30 supports the orientation film 32 and the optical anisotropy layer 36.

[0076] Regarding the support 30, as long as it can support the alignment film 32 and the optical anisotropy layer 36, various sheet-like materials (thin films, plate-like materials) can be used.

[0077] Furthermore, the emissivity 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.

[0078] There are no particular restrictions 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.

[0079] 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.

[0080] The support 30 can be a single layer or multiple layers.

[0081] Examples of single-layer supports 30 include supports 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.

[0082] <Orientation film>

[0083] An orientation film 32 is formed on the surface of the support 30.

[0084] 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.

[0085] Although described later, 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 continuously while rotating along one direction within the plane. Therefore, an alignment film 32 is formed so that the optical anisotropic layer 36 can form the liquid crystal alignment pattern.

[0086] In the following description, "orientation rotation of optical axis 40A" will also be referred to as "rotation of optical axis 40A".

[0087] The orientation film 32 can utilize various known films.

[0088] Examples include triboelectric films containing organic compounds such as polymers, tilted vapor-deposited films of inorganic compounds, films with microgrooves, and films obtained by accumulating LB (Langmuir-Blodgett) films formed by organic compounds such as ω-trisanoic acid, dioctadecylmethylammonium chloride, and methyl stearate through the Langmuir-Blodgett process.

[0089] The orientation film 32 based on friction treatment can be formed by repeatedly rubbing the surface of the polymer layer with paper or cloth in a constant direction.

[0090] As the material used in the alignment film 32, polyimide, polyvinyl alcohol, polymers with polymerizable groups as described in Japanese Patent Application Publication No. 9-152509, and materials for forming the alignment film 32 as described in Japanese Patent Application Publication Nos. 2005-97377, 2005-99228, and 2005-128503 are preferred.

[0091] In the optical anisotropic layer, the alignment film 32 can preferably be a so-called optical alignment film, which is formed by irradiating the optical alignment material with polarized or unpolarized light. That is, in the optical anisotropic layer, the alignment film 32 can preferably be an alignment film formed by coating the support 30 with an optical alignment material.

[0092] Regarding the irradiation of polarized light, it can be performed vertically or obliquely relative to the photo-alignment film; regarding the irradiation of unpolarized light, it can be performed obliquely relative to the photo-alignment film.

[0093] 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 2007-15643. Azo compounds described in Japanese Patent Publication No. 9, 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. Maleimide and / or alkenyl-substituted nadicimide compounds having photooriented units, 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, and... Compounds capable of photodimerization, 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, are preferred examples.

[0094] Among them, azo compounds, photocrosslinked polyimides, photocrosslinked polyamides, photocrosslinked polyesters, cinnamic acid ester compounds and chalcone compounds can be preferentially utilized.

[0095] 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 to obtain the required alignment function, it is acceptable.

[0096] The thickness of the orientation film 32 is preferably 0.01 to 5 μm, more preferably 0.05 to 2 μm.

[0097] There are no limitations on the method for forming the alignment film 32, and various known methods corresponding to the materials used to form the alignment film 32 can be used. As an example, the following method can be illustrated: after coating the alignment film 32 onto the surface of the support 30 and drying it, the alignment film 32 is exposed to a laser beam to form an alignment pattern.

[0098] Figure 4 The image shows an example of an exposure apparatus that exposes an alignment film 32 to form an alignment pattern.

[0099] Figure 4 The exposure apparatus 60 shown includes: a light source 64, which includes a laser 62; a λ / 2 plate 65, which changes the polarization direction of the laser beam M emitted by the laser 62; a polarization beam splitter 68, which separates the laser beam M emitted by the laser 62 into two beams, MA and MB; mirrors 70A and 70B, which are respectively disposed on the optical paths of the two separated beams MA and MB; and λ / 4 plates 72A and 72B.

[0100] In addition, light source 64 emits linearly polarized light P O The λ / 4 plate 72A will linearly polarize light P. O (Light ray MA) is converted into right-hand circularly polarized light P. R λ / 4 plate 72B will linearly polarize light P O (Light MB) is converted into left-handed circularly polarized light P. L .

[0101] A support 30 having an alignment film 32 before the alignment pattern is formed is placed in the exposure section, so that two 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.

[0102] Due to the interference at this time, the polarization state of the light illuminating the alignment film 32 changes periodically in the form of interference fringes. Thus, an alignment film with an alignment pattern having a periodically changing alignment state can be obtained (hereinafter also referred to as a patterned alignment film).

[0103] 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, the length of one cycle in which the optical axis 40A rotates 180° in one direction can be adjusted in the alignment pattern in which the optical axis 40A originating from the liquid crystal compound 40 rotates continuously in one direction.

[0104] 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.

[0105] Furthermore, by rotating the optical axes of the λ / 4 plates 72A and 72B by 90° respectively, the rotation direction of the optical axis 40A can be reversed.

[0106] As described above, the patterned alignment film has an alignment pattern that aligns the liquid crystal compound, 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 continuously rotating along at least one in-plane direction. If the patterned alignment film uses the axis along the orientation of the liquid crystal compound as its alignment axis, it can be said that the patterned alignment film has an alignment pattern in which the orientation of the alignment axis changes while continuously rotating along at least one in-plane direction. The alignment axis of the patterned alignment film can be detected by measuring absorption anisotropy. For example, while rotating linearly polarized light and irradiating it onto the patterned alignment film, the direction in which the light intensity reaches its maximum or minimum is gradually changed along one in-plane direction, and this is observed.

[0107] Furthermore, in this invention, the orientation film 32 is provided as a preferred embodiment, but is not a necessary component.

[0108] For example, the structure can also be configured such that an alignment pattern is formed on the support 30 by means of rubbing the support 30, processing the support 30 with a laser beam, etc., so that the optical anisotropy layer has a liquid crystal alignment pattern in which the orientation of the optical axis 40A of the liquid crystal compound 40 changes continuously while rotating along at least one direction in the plane. That is, in the present invention, the support 30 can function as an alignment film.

[0109] <Optical Anisotropic Layer>

[0110] An optical anisotropic layer 36 is formed on the surface of the alignment film 32.

[0111] 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 whose orientation, originating from the optical axis of the liquid crystal compound, changes continuously while rotating along at least one direction in the plane.

[0112] like Figure 2 As shown conceptually, in the optical anisotropic layer 36, the liquid crystal compound 40 does not twist and rotate in a spiral shape in the thickness direction, but the liquid crystal compounds 40 at the same position in the surface direction are oriented in such a way that their optical axes 40A are oriented in the same way.

[0113] <<Methods for forming optical anisotropic layers>>

[0114] An optically anisotropic layer can be formed by fixing a liquid crystal phase with a liquid crystal alignment pattern, the orientation of which is derived from the optical axis of the liquid crystal compound and changes while rotating continuously in at least one direction in the plane, into a layer.

[0115] Regarding the structure with a fixed liquid crystal phase, any structure that becomes a liquid crystal phase and maintains the orientation of the liquid crystal compound is acceptable. Typically, it is preferable to set the polymerizable liquid crystal compound to an orientation state along the liquid crystal orientation pattern, and then polymerize and cure it by ultraviolet irradiation, heating, etc., to form a non-flowing layer, and at the same time change it into a structure that will not change its orientation morphology due to external magnetic field or external force.

[0116] Furthermore, in structures where a liquid crystal phase is fixed, it is sufficient to maintain the optical properties of the liquid crystal phase; in optically anisotropic layers, the liquid crystal compound 40 may not exhibit liquid crystal properties. For example, polymerizable liquid crystal compounds can be polymerized through a curing reaction to reduce their molecular weight and thus not exhibit liquid crystal properties.

[0117] As an example of a material used to form an optically anisotropic layer with a fixed liquid crystal phase, a liquid crystal composition comprising a liquid crystal compound can be cited. The liquid crystal compound is preferably a polymerizable liquid crystal compound.

[0118] Furthermore, the liquid crystal composition used to form the optical anisotropic layer may also contain surfactants, polymerization initiators, etc.

[0119] --Polymerizable liquid crystal compounds--

[0120] Polymerizable liquid crystal compounds can be rod-shaped or disc-shaped.

[0121] Examples of rod-shaped polymerizable liquid crystal compounds that form optically anisotropic layers include rod-shaped nematic liquid crystal compounds. Among these rod-shaped nematic liquid crystal compounds, imine derivatives, azo derivatives, cyanobiphenyl derivatives, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexane derivatives, cyano-substituted phenylpyrimidine derivatives, alkoxy-substituted phenylpyrimidine derivatives, phenyl dioxane derivatives, diphenylacetylene derivatives, and alkenylcyclohexylbenzylnitrile derivatives are preferred. Not only low-molecular-weight liquid crystal compounds but also high-molecular-weight liquid crystal compounds can be used.

[0122] Polymerizable liquid crystal compounds are obtained by introducing polymerizable groups into a liquid crystal compound. Examples of polymerizable groups include unsaturated polymerizable groups, epoxy groups, and acridine groups, with unsaturated polymerizable groups being preferred, and olefinically unsaturated polymerizable groups being more preferred. Polymerizable groups can be introduced into the molecule of the liquid crystal compound by various methods. The number of polymerizable groups in the polymerizable liquid crystal compound is preferably 1 to 6, more preferably 1 to 3.

[0123] 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, 6-16616, 7-110,469, 11-80081, 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.

[0124] Furthermore, as polymeric 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. Moreover, as the aforementioned polymeric liquid crystal compounds, polymers obtained by introducing liquid crystal-like mesicrystal groups into the main chain or side chain, or both the main chain and side chain, polymeric cholesterol-type liquid crystals obtained by introducing cholesterol groups into the side chain, liquid crystal polymers disclosed in Japanese Patent Application Publication No. 9-133810, and liquid crystal polymers disclosed in Japanese Patent Application Publication No. 11-293252, etc., can be used.

[0125] --Disc-shaped liquid crystal compound--

[0126] As a disc-shaped liquid crystal compound, compounds described in Japanese Patent Application Publication No. 2007-108732 and Japanese Patent Application Publication No. 2010-244038 are preferred.

[0127] Furthermore, relative to the mass of the solid components of the liquid crystal composition (mass after solvent removal), the amount of polymerizable liquid crystal compound added to the liquid crystal composition is preferably 75 to 99.9% by mass, more preferably 80 to 99% by mass, and even more preferably 85 to 90% by mass.

[0128] --surfactants--

[0129] Liquid crystal compositions used in forming optically anisotropic layers may contain surfactants.

[0130] The surfactant is preferably a compound that can stably or rapidly function as an orientation control agent that helps the orientation of the liquid crystal compound. Examples of surfactants include silicone surfactants and fluorinated surfactants, with fluorinated surfactants being a preferred example.

[0131] 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. 2005-99248, 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.

[0132] In addition, a single surfactant can be used alone, or two or more surfactants can be used in combination.

[0133] As a fluorinated surfactant, the compounds described in paragraphs

[0082] to

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

[0134] The amount of surfactant added to the liquid crystal composition is preferably 0.01 to 10% by mass, more preferably 0.01 to 5% by mass, and even more preferably 0.02 to 1% by mass, relative to the total mass of the liquid crystal compound.

[0135] --Polymerization Initiator--

[0136] When the liquid crystal composition contains a polymerizable compound, it is preferable to include a polymerization initiator. In the case of polymerization by ultraviolet irradiation, the polymerization initiator used is preferably a photopolymerization initiator capable of initiating polymerization by ultraviolet irradiation.

[0137] 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 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).

[0138] The content of photopolymerization initiator in the liquid crystal composition is preferably 0.1 to 20% by mass, more preferably 0.5 to 12% by mass, relative to the content of the liquid crystal compound.

[0139] --Cross-linking agent--

[0140] 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.

[0141] 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 (meth)acrylate and ethylene glycol diglycidyl ether; acridine compounds such as 2,2-dimethylolbutanol-tris[3-(1-acrylidinyl)propionate] and 4,4-bis(ethyleneiminocarbonylamino)diphenylmethane; isocyanate compounds such as hexamethylene diisocyanate and biuret-type isocyanate; polyoxazoline compounds with oxazoline groups on the side chain; and alkoxysilane compounds such as vinyltrimethoxysilane and N-(2-aminoethyl)3-aminopropyltrimethoxysilane. Furthermore, known catalysts can be used according to the reactivity of the crosslinking agent, which can improve film strength and durability, as well as productivity. One catalyst can be used alone, or two or more catalysts can be used simultaneously.

[0142] The content of the crosslinking agent relative to the solid component mass of the liquid crystal composition is preferably 3 to 20% by mass, more preferably 5 to 15% by mass. If the content of the crosslinking agent is within the above range, it is easy to obtain the effect of increased crosslinking density, and the stability of the liquid crystal phase is further improved.

[0143] --Other Additives--

[0144] In the liquid crystal composition, polymerization inhibitors, antioxidants, ultraviolet absorbers, light stabilizers, colorants, and metal oxide particles can be further added as needed, without reducing optical performance, etc.

[0145] When forming an optically anisotropic layer, the liquid crystal composition is preferably used in liquid form.

[0146] The liquid crystal composition may contain a solvent. There are no limitations on the solvent, and it can be appropriately selected according to the purpose, but organic solvents are preferred.

[0147] 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 solvents can be used individually or simultaneously. Among them, ketones are preferred, considering the environmental impact.

[0148] Preferably, when forming the optical anisotropic layer, a liquid crystal composition is coated on the forming surface of the optical anisotropic layer, the liquid crystal compound is oriented into a liquid crystal phase with a predetermined liquid crystal orientation pattern, and then the liquid crystal compound is cured to serve as the optical anisotropic layer.

[0149] 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.

[0150] The coating of liquid crystal compositions can be achieved using all known methods that can uniformly coat liquid onto sheets, such as inkjet printing and roll printing, spin coating, bar coating, and spray coating.

[0151] The coated liquid crystal composition is dried and / or heated as needed, and then cured to form an optically anisotropic layer. During the drying and / or heating process, the liquid crystal compounds in the liquid crystal composition only need to be oriented according to a predetermined liquid crystal orientation pattern. When heating is performed, the heating temperature is preferably below 200°C, more preferably below 130°C.

[0152] 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 irradiation. The irradiation energy is preferably 20 mJ / cm². 2 ~50J / cm 2 More preferably 50mJ / cm 2 ~1500mJ / cm 2To promote the photopolymerization reaction, light irradiation can be carried out under heating conditions or in a nitrogen atmosphere. The wavelength of the ultraviolet light used for irradiation is preferably 250–430 nm.

[0153] If necessary, the polymerized liquid crystal composition can be further activated to align the liquid crystal layers. Activation can be performed using corona treatment or plasma treatment. This improves the wettability of the surface before liquid crystal coating and also improves the orientation of the liquid crystal molecules in horizontal alignment. The discharge amount in the corona treatment is preferably 10–500 W / m. 2 / min. As a manufacturing apparatus, the apparatus described in Republished Patent No. WO14 / 054437 is preferred. For example, a discharge method in atmospheric air based on a corona treatment machine manufactured by KASUGA DENKI, Inc. can be used. For plasma processing, for example, a discharge method in atmospheric air or inert gas atmospheres such as nitrogen or argon can be used using a plasma discharge machine manufactured by Sekisui Chemical Co., Ltd.

[0154] There is no limitation on 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.

[0155] <<Liquid Crystal Alignment Pattern of Optical Anisotropic Layer>>

[0156] As previously described, 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 continuously while rotating in one direction within the plane of the optical anisotropy layer.

[0157] Furthermore, the optical axis 40A derived from the liquid crystal compound 40 refers to 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 of the rod. 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".

[0158] Figure 3 The diagram shows a conceptual top view of the optical anisotropy layer 36.

[0159] Additionally, a top view refers to... Figure 2 The image of the optically anisotropic layer viewed from above is the image of the optically anisotropic layer viewed from the thickness direction (= the stacking direction of each layer (film)).

[0160] Furthermore, in Figure 3In order to facilitate understanding of the structure of the optical anisotropic layer (optical anisotropic layer 36), liquid crystal compound 40 refers only to the liquid crystal compound 40 on the surface of the alignment film 32.

[0161] 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. This liquid crystal alignment pattern, according to the alignment pattern formed on the underlying alignment film 32, changes the orientation of the optical axis 40A continuously while rotating along 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 optical axis 40A of the liquid crystal compound 40 has a liquid crystal alignment pattern that changes continuously while rotating clockwise along the alignment axis D.

[0162] 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).

[0163] In the following description, for convenience, the direction orthogonal to the alignment axis D is referred to as the Y direction. That is, the arrow Y direction refers to a direction orthogonal to the orientation of the optical axis 40A of the liquid crystal compound 40, which changes while continuously rotating within the plane of the optical anisotropy layer. Therefore, in Figure 1 , Figure 2 And as will be discussed later Figure 5 , Figure 6 In this case, the Y direction becomes the direction orthogonal to the plane of the paper.

[0164] Specifically, the orientation of the optical axis 40A of the liquid crystal compound 40 changes continuously while rotating along the arrangement axis D (a specified direction). This means that the angle formed by 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 formed by the optical axis 40A and the arrangement axis D changes from θ to θ+180° or θ-180°.

[0165] Furthermore, the angle difference between the optical axes 40A of adjacent liquid crystal compounds 40 in the direction of the arrangement axis D is preferably 45° or less, more preferably 15° or less, and even more preferably a smaller angle.

[0166] Furthermore, in this invention, the liquid crystal compound rotates toward an angle that decreases in the direction formed by the optical axes 40A of the liquid crystal compounds 40 adjacent to each other in the alignment axis D. Therefore, in Figure 2 and Figure 3 In the optical anisotropic 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.

[0167] On the other hand, in the liquid crystal compound 40 that forms the optical anisotropic layer 36, the orientation of the optical axis 40A is equal 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.

[0168] In other words, in the liquid crystal compound 40 that forms the optical anisotropic layer 36, the angle formed by the optical axis 40A of the liquid crystal compound 40 and the alignment axis D in the Y direction is equal.

[0169] In the optical anisotropic layer 36, among the liquid crystal compounds 40 arranged in the Y direction, the angle formed by 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 formed by the optical axis 40A and the arrangement axis D is equal is designated as region R.

[0170] At this point, the in-plane retardation (Re) value in each region R is preferably substantially half the wavelength, i.e., λ / 2. This is the condition for converting right-handed circularly polarized light into left-handed circularly polarized light, and vice versa. Their in-plane retardation is calculated based on the product of the refractive index difference Δn of the accompanying region R and the thickness of the optical anisotropic layer. Here, the refractive index difference of the accompanying region R in the optical anisotropic layer refers to the refractive index difference defined by the difference between the refractive index in the slow axis direction of region R and the refractive index in the direction orthogonal to the slow axis direction. That is, the refractive index difference Δn of the accompanying region R is equal to the difference between the refractive index of the liquid crystal compound 40 in the direction of the optical axis 40A and the refractive index of the liquid crystal compound 40 in the direction perpendicular to the optical axis 40A in the plane of region R. In other words, the refractive index difference Δn is equal to the refractive index difference of the liquid crystal compound 40.

[0171] 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 by continuous rotation of the in-plane optical axis 40A is set as the length Λ of one cycle in the liquid crystal alignment pattern.

[0172] 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 along the alignment axis D 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".

[0173] In the liquid crystal alignment pattern of the optical anisotropic layer 36, one cycle Λ is repeated in one direction that changes continuously by rotating along the alignment axis D, i.e., the orientation of the optical axis 40A.

[0174] If circularly polarized light enters this optical anisotropy layer 36, the light is refracted and the direction of the circularly polarized light is reversed.

[0175] exist Figure 5 and Figure 6 This function is conceptually illustrated in the diagram. 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 λ / 2.

[0176] 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, enters the optical anisotropic layer 36, the incident light L1 is given a phase difference of 180° by passing through the optical anisotropic layer 36, and the transmitted light L2 is converted into right-handed circularly polarized light.

[0177] 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. As described above, the incident light L1, which is left-handed circularly polarized, is converted into transmitted light L2, which is right-handed circularly polarized and tilted at a constant 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.

[0178] 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 enters the optical anisotropic layer 36, the incident light L4 will be given a phase difference of 180° by passing through the optical anisotropic layer 36 and will be converted into the transmitted light L5 of left-hand circularly polarized light.

[0179] 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. As described above, the incident light L4 is converted into left-handed circularly polarized transmitted light L5, which is tilted at a constant 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.

[0180] As previously described, 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, in the optical anisotropy layer 36, the shorter one period Λ of the liquid crystal alignment pattern, the stronger the interference between the light passing through the adjacent liquid crystal compounds 40, thus enabling the transmitted light L2 and L5 to be refracted significantly.

[0181] 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 refraction direction of the transmitted light can be reversed. That is, in Figure 5 and Figure 6 In the example shown, the rotation direction of the optical axis 40A towards the alignment axis D is clockwise, but by setting this rotation direction to counterclockwise, the refraction direction of the transmitted light can be reversed. Specifically, in Figure 5 and Figure 6 In the diagram, when the optical axis 40A, which is oriented towards the alignment axis D, rotates counterclockwise, left-handed circularly polarized light incident from the upper side of the optical anisotropic layer 36 is converted into right-handed circularly polarized light upon passing through the optical anisotropic layer 36 and is diffracted to travel in the lower left direction. Conversely, right-handed circularly polarized light incident from the upper side of the optical anisotropic layer 36 is converted into left-handed circularly polarized light upon passing through the optical anisotropic layer 36 and is diffracted to travel in the lower right direction.

[0182] (The function of a transmission-type liquid crystal diffraction element)

[0183] Next, using Figure 7 The function of the transmissive liquid crystal diffraction element of the present invention, having a structure having two layers of optically anisotropic layers having such liquid crystal alignment patterns, will be explained. Furthermore, in Figure 7 For illustration purposes, the first optical anisotropy layer 36a and the second optical anisotropy layer 36b are shown separately.

[0184] As previously described, the transmissive liquid crystal diffraction element of the present invention is stacked with a first optical anisotropic layer and a second optical anisotropic layer having liquid crystal alignment patterns, wherein the rotation directions of the optical axes in the liquid crystal alignment patterns of each optical anisotropic layer are opposite. Figure 7 In the first optical anisotropy layer 36a, the optical axis rotates clockwise (right-handed), and the optical axis rotates counterclockwise (left-handed).

[0185] Furthermore, the direction of the alignment axis D of the liquid crystal alignment pattern in the first optical anisotropic layer 36a is consistent with the direction of the alignment axis D of the liquid crystal alignment pattern in the second optical anisotropic layer 36b. Figure 7 In the example shown, the direction of the arrangement axis D is to the left in the figure.

[0186] Furthermore, the length of one period Λ of the liquid crystal alignment pattern in the first optical anisotropic layer 36a is the same as the length of one period Λ of the liquid crystal alignment pattern in the second optical anisotropic layer 36b.

[0187] 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 of this structure that is incident from the side of the first optical anisotropic layer 36a.

[0188] like Figure 7 As shown, right-handed circularly polarized light I R and left-handed circularly polarized light I L The light enters obliquely relative to the main surface of the first optical anisotropy layer 36a. In the example shown, right-handed circularly polarized light I... R and left-handed circularly polarized light I L Along the alignment axis D, light enters the first optical anisotropic layer 36a at the same incident angle, such that light from... Figure 7 Proceed from the upper left to the lower right.

[0189] As mentioned earlier, the optical anisotropic layer enables right-handed circularly polarized light I... R and left-handed circularly polarized light I L Diffraction occurs in opposite directions along the alignment axis D. Figure 7 In 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 The light diffracts in the direction of the lower left. Furthermore, as mentioned earlier, the diffracted light is converted into left-handed circularly polarized light I. L1 .

[0190] 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, due to the angle dependence of diffraction efficiency based on the optical anisotropy layer, the diffraction efficiency decreases in this direction, thus the incident left-hand circularly polarized light I... L Almost not diffracted, while left-handed circularly polarized light I L The original sample is transmitted through the first optical anisotropic layer 36a in the lower right direction of the diagram.

[0191] Left-handed circularly polarized light I transmitted through the first optical anisotropy layer 36a L1 and left-handed circularly polarized light I L The light is incident into the second optical anisotropy layer 36b. As previously described, in the second optical anisotropy layer 36b, the rotation direction of the optical axis in the liquid crystal alignment pattern is opposite to that of the first optical anisotropy layer 36a. Therefore, the second optical anisotropy layer 36b causes the incident circularly polarized light to diffract in the opposite direction to that of the first optical anisotropy layer 36a. That is, it causes left-handed circularly polarized light to diffract to the left along the alignment axis D.

[0192] like Figure 7 As shown, left-handed circularly polarized light I L1 It enters relative to the second optical anisotropy layer 36b, traveling 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, due to the angle dependence of diffraction efficiency based on the optical anisotropy layer, the diffraction efficiency decreases in this direction, thus the incident left-hand circularly polarized light I... L1 Almost not diffracted, while left-handed circularly polarized light I L1 The second optical anisotropic layer 36b is transmitted to the lower left direction as is.

[0193] On the other hand, the second optical anisotropy layer 36b causes the left-hand circularly polarized light I traveling from the upper left to the lower right direction to... L Relative to the incident left-handed circularly polarized light I L The direction of travel, along the arrangement axis D Figure 7 The light diffracts in the direction of the lower left. Furthermore, as mentioned earlier, the diffracted light is converted into right-handed circularly polarized light I. R1 .

[0194] Therefore, as Figure 7 As shown, right-handed circularly polarized light I is incident obliquely into the first optical anisotropy layer 36a and the second optical anisotropy layer 36b. R and left-handed circularly polarized light I L Become left-handed circularly polarized light I L1 and right-handed circularly polarized light I R1 They are emitted in the same direction by diffraction.

[0195] As mentioned earlier, in polarized light diffraction elements using liquid crystal compounds, the direction of bending varies depending on the polarization of the light. Therefore, in conventional polarized light diffraction elements, the incident right-handed and left-handed circularly polarized light bend and separate in opposite directions, and regardless of the polarization of the light, it is impossible to diffract the light in the specified direction.

[0196] In contrast, as described above, the transmissive liquid crystal diffraction element of the present invention enables right-hand circularly polarized light and left-hand circularly polarized light incident obliquely to be diffracted in the same direction and emitted.

[0197] In order to make right-handed circularly polarized light and left-handed circularly polarized light, which are incident from an oblique angle, diffract in the same direction, the incident angle of the light relative to the transmissive liquid crystal diffraction element is preferably 10° to 80°, more preferably 20° to 70°, and even more preferably 40° to 50°.

[0198] Furthermore, in order to achieve the effect of diffracting right-handed and left-handed circularly polarized light incident from an oblique angle in the same direction, the diffraction angles of the first optical anisotropy layer 36a and the second optical anisotropy layer 36b are preferably 50° to 130°, more preferably 60° to 120°, and even more preferably 70° to 110°. Here, the diffraction angle refers to the angle formed by the incident light and the diffracted light.

[0199] If the length of one period of the liquid crystal alignment pattern of the first optical anisotropic layer 36a is set as Λ1, and the length of one period of the liquid crystal alignment pattern of the second optical anisotropic layer 36b is set as Λ2, then Λ1 and Λ2 can be appropriately set according to the desired diffraction angle, etc. The ratio of Λ1 to Λ2 is preferably approximately 0.2 to 5. To make the angle formed by the diffracted light and the diffraction grating surface match the incident angle, the ratio of Λ1 to Λ2 can be set to 1.

[0200] Furthermore, to achieve the effects of the present invention, the incident light is diffracted at a large angle. To separate the 0th-order and 1st-order light by angle and utilize the difference in diffraction efficiency, the angle difference between the 0th-order and 1st-order light is preferably large. Here, "0th-order light" refers to light that does not change direction due to diffraction at the diffraction grating, and "1st-order light" refers to light whose direction changes due to diffraction at the diffraction grating in the direction of +1st or -1st-order diffraction conditions. On the other hand, if the angle difference between the 0th-order and 1st-order light is too large, it deviates from the diffraction conditions for 1st-order light. The ratio of the wavelength λ corresponding to the diffraction angle of the light to the liquid crystal pattern spacing Λ, i.e., λ / Λ, is preferably in the range of 0.1 to 1.9, more preferably in the range of 0.2 to 1.8, and even more preferably in the range of 0.3 to 1.7.

[0201] Furthermore, the transmissive liquid crystal diffraction element is not limited to a structure having only a first optical anisotropy layer 36a and a second optical anisotropy layer 36b. As mentioned above, the first optical anisotropy layer 36a and / or the second optical anisotropy layer 36b of the transmissive liquid crystal diffraction element can be stacked with the support 30 and the alignment film 32, or can be stacked with the alignment film 32.

[0202] Here, when the incident angle and the exit angle of the light relative to the transmissive liquid crystal diffraction element 10 are equal, such as Figure 2 As shown in the example, the first optical anisotropic layer 36a and the second optical anisotropic layer 36b preferably have a structure in which the optical axes of the liquid crystal compounds 40 stacked in the thickness direction are oriented in the same direction. In other words, the optical axes of the liquid crystal compounds 40 present at the same position in the planar direction are preferably oriented in the same direction. That is, the first optical anisotropic layer 36a and the second optical anisotropic layer 36b are preferably oriented in the thickness direction without twisting of the liquid crystal compounds 40. When the incident angle and the exit angle of light relative to the transmissive liquid crystal diffraction element 10 are equal, the diffraction efficiency can be improved by setting the first optical anisotropic layer 36a and the second optical anisotropic layer 36b to a structure in which the liquid crystal compounds 40 are oriented without twisting.

[0203] On the other hand, when the incident angle and exit angle of light relative to the transmissive liquid crystal diffraction element 10 are different, such as Figure 8 As shown in the example, the first optical anisotropic layer 37a and the second optical anisotropic layer 37b are preferably oriented in a twisted manner in the thickness direction of the liquid crystal compound. In the twisted orientation of the first optical anisotropic layer 37a and the second optical anisotropic layer 37b, the twist angle in the thickness direction is less than 360°. That is, the twisted orientation is to the extent that cholesterol-type orientation is not performed.

[0204] Furthermore, the twisting direction of the liquid crystal compound 40 in the first optical anisotropy layer 37a is opposite to the twisting direction of the liquid crystal compound 40 in the second optical anisotropy layer 37b. Figure 8 In the example shown, in the first optical anisotropy layer 37a, the liquid crystal compound 40 is twisted clockwise from the upper side to the lower side in the figure. On the other hand, in the second optical anisotropy layer 37b, the liquid crystal compound 40 is twisted counterclockwise from the upper side to the lower side in the figure.

[0205] And, with Figure 1Similarly, the rotation direction of the optical axis in the liquid crystal alignment pattern of the first optical anisotropy layer 37a is opposite to the rotation direction of the optical axis in the liquid crystal alignment pattern of the second optical anisotropy layer 37b. Furthermore, while the rotation directions of the optical axes in the liquid crystal alignment patterns of the first optical anisotropy layer 37a and the second optical anisotropy layer 37b are opposite, and the twisting directions of the liquid crystal compounds oriented in the thickness direction are opposite, they have the same structure. Therefore, without needing to distinguish between the first optical anisotropy layer 37a and the second optical anisotropy layer 37b, they will be described together as optical anisotropy layer 37.

[0206] Figure 9 The figure shown is a conceptual representation of the optical anisotropy layer 37. Figure 9 In the optical anisotropy layer 37 shown, the liquid crystal compound is twisted and oriented in the thickness direction, and otherwise has the same properties as... Figure 2 The optical anisotropic layer 36 shown has the same structure. That is, if viewed from the thickness direction... Figure 9 The optical anisotropy layer 37 shown is related to Figure 3 Similarly, the example shown has a liquid crystal alignment pattern that changes continuously while rotating along the orientation of the optical axis 40A within the plane of the optical anisotropic layer 37, along the alignment axis D.

[0207] Figure 9 The optical anisotropy layer 37 shown has a twisted structure formed by rotating and stacking liquid crystal compounds 40 in the thickness direction, and the total rotation angle from the liquid crystal compound 40 present on one main surface side of the optical anisotropy layer 37 to the liquid crystal compound 40 present on the other main surface side is less than 360°.

[0208] As described above, the optical anisotropy layer 37 has a liquid crystal alignment pattern that changes continuously while rotating along the orientation of the optical axis 40A along the alignment axis D in the plane, and if the liquid crystal compound 40 has a twisted structure in the thickness direction, then in a section parallel to the alignment axis D, line segments of the liquid crystal compound 40 oriented in the same direction are connected in the thickness direction. Figure 8 The line segments (represented by H1 and H2) are inclined relative to the main surface of the optical anisotropic layer 37. By appropriately adjusting the incident and exit angles of light relative to these line segments H1 and H2, the diffraction efficiency can be improved when the incident and exit angles of light relative to the transmissive liquid crystal diffraction element 10 are different. Specifically, line segments H1 and H2 are preferably parallel, and the incident and exit angles of light are preferably angles approximately at the midpoint of line segments H1 and H2.

[0209] From the viewpoint of diffraction efficiency, it is preferable that line segments H1 and H2 are parallel. Therefore, it is preferable that the twisting direction of the liquid crystal compound 40 in the first optical anisotropic layer 37a is opposite to the twisting direction of the liquid crystal compound 40 in the second optical anisotropic layer 37b, and that the twisting angles are equal.

[0210] As described above, 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 used to form the optical anisotropic layer.

[0211] --Chiral reagents (optically active compounds)--

[0212] Chiral reagents (optically active compounds) have the function of inducing helical structures in liquid crystal phases. The direction of helical twisting and the helical twisting power (HTP) induced by a chiral reagent vary depending on the compound; therefore, selection should be based on the intended purpose.

[0213] There are no particular restrictions on the use of chiral reagents, and well-known compounds can be used (e.g., Liquid Crystal Devices Handbook, Chapter 3, Item 4-3, TN (twisted nematic) and STN (Super Twisted Nematic) as chiral reagents, page 199, edited by Committee 142 of the Japan Society for the Promotion of Science, 1989), isosorbide and isomannitol derivatives, etc.

[0214] Chiral reagents typically contain asymmetric carbon atoms, but axially asymmetric or surface-asymmetric compounds that do not contain asymmetric carbon atoms can also be used as chiral reagents. Examples of axially asymmetric or surface-asymmetric compounds include binatene, helicene, p-xylene dimers, and their derivatives. Chiral reagents can have polymerizable groups. When both the chiral reagent and the liquid crystal compound have polymerizable groups, a polymer having repeating units derived from the polymerizable liquid crystal compound and repeating units derived from the chiral reagent can be formed through the polymerization reaction of the polymerizable chiral reagent and the polymerizable liquid crystal compound. In this manner, the polymerizable groups possessed by the polymerizable chiral reagent are preferably of the same type as those possessed by the polymerizable 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 olefinically unsaturated polymerizable groups.

[0215] Furthermore, the chiral reagent can be a liquid crystal compound.

[0216] When the chiral reagent has a photoisomerizing group, after coating and orientation, irradiation with a photomask such as activating light can form a desired twisted orientation corresponding to the emission wavelength, 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.

[0217] The content of the chiral reagent in the liquid crystal composition is preferably 0.01 to 200 mol% relative to the molar content of the liquid crystal compound, and more preferably 1 to 30 mol%.

[0218] Furthermore, transmissive liquid crystal diffraction elements can have other layers. For example, such as Figure 10 As shown in the example, a phase difference layer 38 can be present between the first optical anisotropic layer 36a and the second optical anisotropic layer 36b.

[0219] As previously described, 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 the first optical anisotropy layer 36a becomes ellipticly polarized light, the effect of the second optical anisotropy layer 36b may not be accurately obtained, resulting in a decrease in diffraction efficiency.

[0220] Therefore, by setting a structure with a phase difference layer 38 between the first optical anisotropic layer 36a and the second optical anisotropic layer 36b, the circularly polarized light emitted from the first optical anisotropic layer 36a can be given a phase difference and become circularly polarized light. Thus, the effect of the second optical anisotropic layer 36b can be accurately obtained, and the diffraction efficiency can be improved.

[0221] Furthermore, even when a phase retardation layer is provided between the first optical anisotropy layer 36a and the second optical anisotropy layer 36b, light only passes through the phase retardation layer 38 when traveling between the first optical anisotropy layer 36a and the second optical anisotropy layer 36b, without affecting diffraction. Therefore, it is also possible to obtain the same... Figure 7The example shown exhibits the same diffraction effect.

[0222] 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.

[0223] The thickness retardation of the phase détente layer can be appropriately set according to the incident angle of the light, the structure of the first optical anisotropy layer 36a, etc., in a way that allows the circularly polarized light emitted from the first optical anisotropy layer 36a to 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.

[0224] Here, Figure 2 The optical anisotropy layer 36 shown and Figure 9 The optical anisotropic layer 37 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.

[0225] and, Figure 3 The optical axis 40A of the liquid crystal compound 40 in the liquid crystal alignment pattern of the optical anisotropic layer shown rotates continuously only along the alignment axis D.

[0226] 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 rotates continuously in one direction in the optical anisotropic layer.

[0227] Preferably, at least one of the first optical anisotropic layer and the second optical anisotropic layer 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, both the first optical anisotropic layer and the second optical anisotropic layer have a structure in which rod-shaped liquid crystal layers and disk-shaped liquid crystal layers are alternately stacked.

[0228] Figure 11 This is a diagram that conceptually illustrates another example of the optical anisotropy layer of the transmissive liquid crystal diffraction element of the present invention.

[0229] Figure 11 The optical anisotropy layer 36c shown alternately comprises a total of four liquid crystal layers 42 formed using rod-shaped liquid crystal compound 40c (hereinafter referred to as rod-shaped liquid crystal layers) and four liquid crystal layers 44 formed using disk-shaped liquid crystal compound 40d (hereinafter referred to as disk-shaped liquid crystal layers). Furthermore, in Figure 11 In this drawing, the structure of the optical anisotropic layer 36c is clearly shown for simplicity, while the rod-shaped liquid crystal layer 42 and the disk-shaped liquid crystal layer 44 are only conceptually shown as liquid crystal compounds on their surfaces. However, the rod-shaped liquid crystal layer 42 and the disk-shaped liquid crystal layer 44 have a structure in which liquid crystal compounds are stacked in the thickness direction, and the optical axes of the liquid crystal compounds stacked in the thickness direction are oriented in the same direction.

[0230] The rod-shaped liquid crystal layer 42 is the following layer, namely, with Figure 2 and Figure 3 Similarly, the example shown is a layer in which the orientation of a liquid crystal alignment pattern is changed by continuously rotating the rod-shaped liquid crystal compound 40c along at least one direction in the plane with its optical axis orientation. Furthermore, the disk-shaped liquid crystal layer 44 is a layer that, with... Figure 2 and Figure 3 Similarly, the example shown is a layer in which the orientation of a liquid crystal alignment pattern is changed by continuously rotating the disc-shaped liquid crystal compound 40d along at least one direction within the plane. Furthermore, as described previously, the optical axis of the rod-shaped liquid crystal compound 40c is oriented along its long axis. On the other hand, the optical axis of the disc-shaped liquid crystal compound 40d is oriented along a direction perpendicular to the disc surface. Therefore, in the disc-shaped liquid crystal layer 44, the disc-shaped liquid crystal compound 40d is oriented in a manner perpendicular to the interface between the disc surface and the disc-shaped liquid crystal layer 44.

[0231] In one optically anisotropic layer 36c, the liquid crystal alignment patterns of each rod-shaped liquid crystal layer 42 and disk-shaped liquid crystal layer 44 have the same period, and the rotation directions of the optical axes in the liquid crystal alignment patterns are the same. Therefore, in Figure 11 In the example shown, the two rod-shaped liquid crystal layers 42 and the two disk-shaped liquid crystal layers 44 serve as an optical anisotropy layer 36c, performing the function of the aforementioned optical anisotropy layer 36.

[0232] By configuring the optical anisotropic layer with alternating layers of rod-shaped liquid crystal layers 42 and disk-shaped liquid crystal layers 44, 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 enters the optical anisotropic layer obliquely is reduced. Therefore, the incident angle dependence of diffraction performance, such as diffraction efficiency, can be improved.

[0233] 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 it is preferable 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 layer and disk-shaped liquid crystal layer is positive and negative, and the absolute value of Rth of each layer is about 10 to 200 nm.

[0234] By incorporating this optically anisotropic layer, the diffraction efficiency of transmissive liquid crystal diffraction elements can be further improved.

[0235] Here, the thickness of each rod-shaped liquid crystal layer 42 and the disk-shaped liquid crystal layer 44 is preferably 0.1 μm to 5 μm, more preferably 0.1 μm to 2 μm, and even more preferably 0.1 μm to 0.5 μm. Furthermore, it is preferable that the combined thickness of the rod-shaped liquid crystal layer 42 and the disk-shaped liquid crystal layer 44 is not too large relative to the wavelength of the incident light.

[0236] In addition, Figure 11 In the example shown, the structure is provided with two rod-shaped liquid crystal layers 42 and two disk-shaped liquid crystal layers 44, but it is not limited to this. It can also be a structure with one rod-shaped liquid crystal layer 42 and one disk-shaped liquid crystal layer 44, or it can have three or more rod-shaped liquid crystal layers 42 and disk-shaped liquid crystal layers 44 respectively.

[0237] By stacking multiple layers of rod-shaped liquid crystal layer 42 and disk-shaped liquid crystal layer 44, and ensuring that the retardation Δn×d (Δn is the refractive index difference of the liquid crystal compound and d is the thickness of the liquid crystal layer) of rod-shaped liquid crystal layer 42 and disk-shaped liquid crystal layer 44 are of the same value, the thickness direction retardation Rth of the optical anisotropic layer can be made closer to zero, which is therefore preferred.

[0238] Furthermore, by changing the values ​​of Δn and thickness d of the rod-shaped liquid crystal layer and the disk-shaped liquid crystal layer, the value of Rth of the optical anisotropy layer can be precisely controlled. In this structure, Rth = ((ne + no) / 2 - no) × d = (ne - no) / 2 × d. However, since ne > no for the rod-shaped liquid crystal layer, Rth > 0, and since ne < no for the disk-shaped liquid crystal layer, Rth < 0. In this invention, the rod-shaped liquid crystal layer and the disk-shaped liquid crystal layer can be stacked alternately, and their ratio can be changed. Therefore, the value of Rth can be precisely controlled between cases where all layers are rod-shaped liquid crystal layers and cases where all layers are disk-shaped liquid crystal layers.

[0239] like Figure 11 As shown, preferably, the rod-shaped liquid crystal compound 40c is oriented with its optical axis (pointing out) parallel to the interface of the rod-shaped liquid crystal layer 42, and the disk-shaped liquid crystal compound 40d is oriented with its disk surface perpendicular to the interface of the disk-shaped liquid crystal layer 44. Thus, within the plane, while continuously maintaining the change in the thickness direction along the slow axis, the refractive index in the thickness direction is averaged by the disk-shaped and rod-shaped liquid crystal compounds, thereby bringing the thickness direction retardation Rth close to zero and further improving the incident angle dependence.

[0240] Furthermore, in the preferred embodiment of the transmissive liquid crystal diffraction element of the present invention, at least one of the first optical anisotropic layer and the second optical anisotropic layer is formed by stacking multiple liquid crystal layers with liquid crystal compounds twisted and oriented in the thickness direction, the twist angle of each liquid crystal layer is less than 360°, and in the multiple liquid crystal layers, the twist direction of the liquid crystal compound is alternating in the stacking direction.

[0241] Figure 12 This is a diagram that conceptually illustrates another example of the transmissive liquid crystal diffraction element of the present invention.

[0242] Figure 12 The transmissive liquid crystal diffraction element shown has: a first optical anisotropic layer 37c having liquid crystal layers 46a and 46b; and a second optical anisotropic layer 37d having liquid crystal layers 48a and 48b.

[0243] and Figure 3 Similarly, in the example shown, the liquid crystal layers 46a and 46b of the first optical anisotropy layer 37a are layers having a liquid crystal alignment pattern in which the orientation of the optical axis of the liquid crystal compound 40 changes continuously while rotating along at least one direction in the plane. Furthermore, in liquid crystal layers 46a and 46b, one period of the liquid crystal alignment pattern is the same, and the rotation direction of the optical axis in the liquid crystal alignment pattern is the same.

[0244] Here, in liquid crystal layers 46a and 46b, the liquid crystal compound 40 is twisted in the thickness direction, but the twisting direction of the liquid crystal compound 40 in liquid crystal layer 46a is opposite to the twisting direction of the liquid crystal compound 40 in liquid crystal layer 46b.

[0245] exist Figure 12 In the example shown, the twisting direction of the liquid crystal compound 40 in liquid crystal layer 46a is a counterclockwise rotation from the top to the bottom in the figure. On the other hand, the twisting direction of the liquid crystal compound 40 in liquid crystal layer 46b is a clockwise rotation from the top to the bottom in the figure.

[0246] That is, the first optical anisotropy layer 37c has liquid crystal layers with different twisting directions of the liquid crystal compound 40 in the thickness direction.

[0247] Similarly, with Figure 3 Similarly, in the example shown, the liquid crystal layers 48a and 48b of the second optical anisotropy layer 37d are layers having a liquid crystal alignment pattern in which the orientation of the optical axis of the liquid crystal compound 40 changes continuously while rotating along at least one direction in the plane. Furthermore, in liquid crystal layers 48a and 48b, one period of the liquid crystal alignment pattern is the same, and the rotation direction of the optical axis in the liquid crystal alignment pattern is the same.

[0248] Furthermore, the rotation direction of the optical axis in the liquid crystal alignment pattern of the liquid crystal layers 48a and 48b of the second optical anisotropy layer 37d is opposite to the rotation direction of the optical axis in the liquid crystal alignment pattern of the liquid crystal layers 46a and 46b of the first optical anisotropy layer 37c.

[0249] Here, in liquid crystal layers 48a and 48b, the liquid crystal compound 40 is twisted in the thickness direction, but the twisting direction of the liquid crystal compound 40 in liquid crystal layer 48a is opposite to that in liquid crystal layer 48b.

[0250] exist Figure 12 In the example shown, the twisting direction of the liquid crystal compound 40 in liquid crystal layer 48a is a counterclockwise rotation from the top to the bottom in the figure. On the other hand, the twisting direction of the liquid crystal compound 40 in liquid crystal layer 48b is a clockwise rotation from the top to the bottom in the figure.

[0251] That is, the second optical anisotropy layer 37d has a liquid crystal layer with different twist directions of the liquid crystal compound 40 in the thickness direction.

[0252] As described above, by configuring the optically anisotropic layer as having liquid crystal layers with different twisting directions of the liquid crystal compound 40 in the thickness direction, the angle dependence and wavelength dependence of diffraction efficiency are improved. In this case, the optimal values ​​of the twist angle (total twist angle in the thickness direction) and the retardation Δn×d of each liquid crystal layer change depending on the refractive index difference Δn of the liquid crystal compound. Therefore, it is sufficient to optimize the twist angle according to each liquid crystal layer. The twist angle is preferably 30–180°. The twist orientation can be achieved by adding the commonly used chiral reagent described above.

[0253] Furthermore, if the Δn of the liquid crystal compound is large, the angle dependence and wavelength dependence are further improved, which is therefore preferred.

[0254] Furthermore, in Figure 12 In the example shown, the optical anisotropy layer is configured as a two-layer structure with stacked liquid crystal layers having different twisting directions, but it is not limited to this. The optical anisotropy layer can have three or more liquid crystal layers with different twisting directions. Alternatively, the optical anisotropy layer can have a liquid crystal layer with an untwisted liquid crystal compound in the thickness direction between two liquid crystal layers with different twisting directions. This further improves the angle dependence and wavelength dependence of the diffraction efficiency.

[0255] Preferably, the non-twisted liquid crystal layer between the twisted-oriented liquid crystal layers has an optical axis direction that is continuously connected (or oriented in the same direction) to the optical axis direction of the liquid crystal compound at each position in the plane with the optical axis direction of the liquid crystal compound at the interface of the adjacent twisted-oriented liquid crystal layer. As described above, the structure in which the optical axes of the liquid crystal compounds are continuously connected between adjacent liquid crystal layers can be fabricated by laminating an upper liquid crystal layer on top of a lower liquid crystal layer.

[0256] In the case where the optical anisotropic layer has a structure in which the twisting directions of the liquid crystal compound 40 in the thickness direction are different, from the viewpoint of symmetry of diffraction performance, the twisting angle per unit length in the thickness direction of each liquid crystal layer is preferably the same. On the other hand, in order to improve the diffraction performance at a certain angle, the twisting angle per unit length in the thickness direction of each liquid crystal layer may also be different.

[0257] The thickness of each liquid crystal layer is preferably 0.1μm to 5μm, more preferably 0.1μm to 2μm, and even more preferably 0.1μm to 0.5μm.

[0258] Similarly, it is preferable that the Rth values ​​of adjacent layers of the alternately stacked rod-shaped liquid crystal layers and disk-shaped liquid crystal layers are positive and negative, and the absolute value of the Rth value of each layer is about 10 to 200 nm.

[0259] Here, as Figure 12 As shown, in the case where the optical anisotropic layer has a structure in which the twisting directions of the liquid crystal compound 40 in the thickness direction are different, it is preferable that at least one of the liquid crystal layers has a structure in which a rod-shaped liquid crystal layer oriented with a liquid crystal alignment pattern and a disk-shaped liquid crystal layer oriented with a liquid crystal alignment pattern are alternately stacked.

[0260] Figure 13 This is a diagram that conceptually illustrates another example of the liquid crystal layer possessed by the optical anisotropy layer of the transmissive liquid crystal diffraction element of the present invention.

[0261] Figure 13 The liquid crystal layer 47 shown alternately comprises a total of four rod-shaped liquid crystal layers 42b formed using rod-shaped liquid crystal compound 40c and disk-shaped liquid crystal layers 44b formed using disk-shaped liquid crystal compound 40d. Furthermore, in Figure 13 In this drawing, the structure of liquid crystal layer 47 is clearly shown for simplicity, while the surface liquid crystal compounds of rod-shaped liquid crystal layer 42b and disk-shaped liquid crystal layer 44b are only conceptually shown. However, rod-shaped liquid crystal layer 42b and disk-shaped liquid crystal layer 44b have a structure formed by stacking liquid crystal compounds in the thickness direction.

[0262] The rod-shaped liquid crystal layer 42b is the following layer, namely, with... Figure 3Similarly, the example shown is a layer in which the orientation of the rod-shaped liquid crystal compound 40c is changed by continuously rotating it along at least one direction in the plane, altering the orientation of its optical axis. Furthermore, the disk-shaped liquid crystal layer 44b is a layer that, with... Figure 3 Similarly, the example shown is a layer in which the liquid crystal alignment pattern of a disk-shaped liquid crystal compound 40d is continuously rotated along at least one direction in the plane while its optical axis orientation is changed.

[0263] In one liquid crystal layer 47, the liquid crystal alignment patterns of each rod-shaped liquid crystal layer 42b and disk-shaped liquid crystal layer 44b have the same period, and the rotation direction of the optical axis in the liquid crystal alignment pattern is the same.

[0264] Here, in Figure 13 In the example shown, from the lower rod-shaped liquid crystal layer 42b towards the upper disk-shaped liquid crystal layer 44b, the length direction of the liquid crystal compound within the layer is integrally twisted and oriented in the thickness direction. Thus, the two rod-shaped liquid crystal layers 42b and the two disk-shaped liquid crystal layers 44b together form a single liquid crystal layer 47, functioning as... Figure 12 The liquid crystal layer shown has the same function. In addition, the length direction of the liquid crystal compound in the disk-shaped liquid crystal layer 44b refers to the length direction of the shape of the disk-shaped liquid crystal compound projected onto the surface (interface) of the disk-shaped liquid crystal layer.

[0265] As described above, when the optical anisotropy layer has a structure in which the twisting directions of the liquid crystal compound 40 in the thickness direction are different, by setting at least one of the liquid crystal layers to a structure in which a rod-shaped liquid crystal layer and a disk-shaped liquid crystal layer are stacked, the incident angle dependence of diffraction performance such as diffraction efficiency can be further improved.

[0266] The thicknesses of the rod-shaped liquid crystal layer 42b and the disk-shaped liquid crystal layer 44b are the same as those of the rod-shaped liquid crystal layer 42 and the disk-shaped liquid crystal layer 44.

[0267] Furthermore, the transmissive liquid crystal diffraction element of the present invention preferably has a λ / 4 plate disposed on at least one of the side of the first optical anisotropy layer opposite to the second optical anisotropy layer and the side of the second optical anisotropy layer opposite to the first optical anisotropy layer.

[0268] Figure 14 This is a diagram that conceptually illustrates another example of the transmissive liquid crystal diffraction element of the present invention.

[0269] Figure 14 The transmissive liquid crystal diffraction element shown has, in sequence, a first λ / 4 plate 50, a first optical anisotropic layer 36a, a second optical anisotropic layer 36b, and a second λ / 4 plate 50. That is, Figure 14The transmissive liquid crystal diffraction element shown has a structure in which a first optical anisotropic layer 36a and a second optical anisotropic layer 36b are sandwiched between λ / 4 plates 50.

[0270] Furthermore, the first optical anisotropy layer 36a and the second optical anisotropy layer 36b have the same characteristics as... Figure 1 The first optical anisotropic layer 36a and the second optical anisotropic layer 36b shown have the same structure, so their description is omitted.

[0271] The first λ / 4 plate 50 and the second λ / 4 plate 50 are conventionally known λ / 4 plates. It is well known that circularly polarized light incident on the λ / 4 plate is converted into linearly polarized light, and linearly polarized light incident on the λ / 4 plate is converted into circularly polarized light. The λ / 4 plate 50 is configured such that its slow axis, relative to the optical axis derived from the liquid crystal compound, is continuously rotated in one in-plane direction and its orientation (alignment axis D direction) changes at 45 degrees or -45 degrees.

[0272] Therefore, in Figure 14 In the example shown, linearly polarized light whose vibration directions are orthogonal to each other can bend in the same direction.

[0273] Specifically, consider an example where s-polarized light and p-polarized light are incident on a transmissive liquid crystal diffraction element from the same direction. First, if the s-polarized light and p-polarized light enter the transmissive liquid crystal diffraction element, they are converted into right-handed and left-handed circularly polarized light, respectively, by the first λ / 4 plate 50. The converted right-handed and left-handed circularly polarized light then pass sequentially through the first optical anisotropic layer 36a and the second optical anisotropic layer 36b. At this time, with... Figure 1 Similarly, in a transmissive liquid crystal diffraction element, light passing through the second optical anisotropy layer 36b is bent in the same direction as left-handed and right-handed circularly polarized light. The bent left-handed and right-handed circularly polarized light enters the second λ / 4 plate 50 and is converted into s-polarized light and p-polarized light. At this time, the s-polarized light and p-polarized light are emitted in the same direction.

[0274] As described above, by setting the transmissive liquid crystal diffraction element to a structure with a λ / 4 plate, linearly polarized light with mutually orthogonal vibration directions is not mixed, but can be bent in the same direction.

[0275] In addition, Figure 14In the example shown, a structure is provided having two λ / 4 plates 50 sandwiching the first optical anisotropic layer 36a and the second optical anisotropic layer 36b, but it is not limited to this. For example, by using a transmissive liquid crystal diffraction element with only the first λ / 4 plate 50 on the side of the first optical anisotropic layer 36a, it is possible to bend incident right-handed and left-handed circularly polarized light, which are linearly polarized light with mutually orthogonal vibration directions, in the same direction. Furthermore, by using a transmissive liquid crystal diffraction element with only the second λ / 4 plate 50 on the side of the second optical anisotropic layer 36b, it is possible to convert incident linearly polarized light with mutually orthogonal vibration directions into right-handed and left-handed circularly polarized light, which are then bent in the same direction.

[0276] There are no limitations on the type of λ / 4 plate; various plates with known λ / 4 functions can be used. Specific examples of λ / 4 plates include those described in U.S. Patent Application Publication No. 2015 / 0277006.

[0277] For example, as a single-layer structure, the λ / 4 plate 26 can be a stretched polymer film or a phase retardation film having an optical anisotropy layer with λ / 4 function disposed on a support. Furthermore, as a multi-layer structure, a broadband λ / 4 plate formed by stacking λ / 4 plates and λ / 2 wavelength plates can be cited.

[0278] There is no particular limitation on the thickness of the λ / 4 plate, but it is preferred to be 1 to 500 μm, more preferably 1 to 50 μm, and even more preferably 1 to 5 μm.

[0279] The λ / 4 plate used in this invention preferably has reverse wavelength dispersion. By having reverse wavelength dispersion, the wavelength dependence can be improved. For example, a λ / 4 plate with reverse wavelength dispersion can be fabricated using a reverse-dispersion liquid crystal material.

[0280] Furthermore, from the viewpoint of improving the dependence on the incident angle, the λ / 4 plate is preferably a wide-viewing-angle λ / 4 plate. A wide-viewing-angle λ / 4 plate refers to a plate with a late band in the thickness direction that is close to zero. Such a wide-viewing-angle λ / 4 plate can be achieved, for example, by stacking a positive A plate and a positive C plate.

[0281] Figure 15 and Figure 16 This is a diagram that conceptually illustrates another example of the transmissive liquid crystal diffraction element of the present invention.

[0282] exist Figure 15 and Figure 16In this structure, both the first and second liquid crystal layers have a right-twisted layer and a left-twisted layer continuously stacked on top of each other. The right-twisted layer and the left-twisted layer have different film thicknesses and different absolute values ​​of their twist angles. This expands the wavelength range from which high diffraction efficiency can be obtained. In a cross-sectional image of the first optical anisotropy layer based on SEM, a horizontally oriented, asymmetrical "V" shape with different lengths and angles is observed, where two lines extend obliquely to the left and right relative to the lower interface of the first optical anisotropy layer. Similarly, a horizontally oriented "V" shape is also observed in the second optical anisotropy layer. This horizontally oriented "V" shape is used to describe a structure in which two liquid crystal layers with liquid crystal compounds oriented in different right-to-left twist directions in the thickness direction are stacked in the thickness direction, and the difference in the thickness and absolute value of the twist angle of the right-twisted layer and the left-twisted layer is used for observation.

[0283] Figure 15 Transmissive liquid crystal diffraction elements can be fabricated by stacking a first liquid crystal layer and a second liquid crystal layer in the same manner, with the first and second liquid crystal layers flipped vertically. On the other hand, Figure 16 Transmissive liquid crystal diffraction elements can be fabricated by stacking the first liquid crystal layer and the second liquid crystal layer in a symmetrical manner with a right twisted layer and a left twisted layer.

[0284] Figure 15 The overlapping method is as follows: the twisted layers in the first liquid crystal layer and the second liquid crystal layer are opposite each other in the same direction, forming horizontal "V" shapes that are asymmetrical to the left and right with the same sharp direction. Figure 16 The overlapping method is as follows: the twisted layers in the first and second liquid crystal layers are opposite each other, forming horizontally asymmetrical "V" shapes with opposite sharp directions. Regardless of the overlapping method, the wavelength range in which high diffraction efficiency can be obtained can be expanded.

[0285] 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 and modifications can be made without departing from the spirit of the present invention.

[0286] Example

[0287] 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.

[0288] [Example 1]

[0289] <Fabrication of Transmission-Type Liquid Crystal Diffraction Elements>

[0290] (Formation of the orientation film)

[0291] 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.

[0292] Coating solution for oriented film formation

[0293]

[0294] Raw materials for photoorientation

[0295] [Chemical Formula 1]

[0296]

[0297] (Exposure of the alignment film)

[0298] 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.

[0299] use Figure 4 The exposure apparatus shown exposes an alignment film, forming an alignment film P-2 with an alignment pattern. A laser 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 Furthermore, the cross angle (cross angle α) of the two beams was adjusted so that one period Λ (the length of 180° rotation of the optical axis) of the orientation pattern formed by the interference of the two laser beams was 1.05 μm.

[0300] (Formation of the first optical anisotropy layer)

[0301] Composition B-1 was prepared as a liquid crystal composition for forming a liquid crystal layer.

[0302] Composition B-1

[0303]

[0304]

[0305] Rod-shaped liquid crystal compound L-1 (containing the following structure in the mass ratio shown on the right)

[0306] [Chemical Formula 2]

[0307]

[0308] Leveling agent T-1

[0309] [Chemical Formula 3]

[0310]

[0311] The first optical anisotropic layer is formed by coating multiple layers of composition B-1 onto an alignment film P-2. The process is repeated as follows: first, the first layer of composition B-1 is coated onto the alignment film, heated, cooled, and then cured under ultraviolet light to form a liquid crystal immobilization layer. Then, for the second layer and thereafter, the liquid crystal immobilization layer is overlapped and coated, and then similarly heated, cooled, and cured under ultraviolet light.

[0312] First, for the first layer, the following composition B-1 is coated onto the alignment film P-2. The coating is heated to 80°C on a hot plate, and 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.

[0313] For the second layer and thereafter, the liquid crystal immobilization layer is overlapped and coated onto the liquid crystal immobilization layer. After heating and cooling under the same conditions as described above, it is cured with ultraviolet light to form the liquid crystal immobilization layer. This overlapping coating process is repeated until the total thickness reaches the desired film thickness, thus forming the first optical anisotropic layer.

[0314] Furthermore, the refractive index difference Δn of the cured layer of liquid crystal composition B-1 was measured and the retardation Re(λ) and film thickness of the liquid crystal immobilized layer were determined. This liquid crystal immobilized layer was obtained by coating liquid crystal composition B-1 onto a separately prepared support with an alignment film for retardation measurement, aligning it so that the orientation of the liquid crystal compound was horizontal with the substrate, and then immobilizing it 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 1550 nm.

[0315] For the first optical anisotropic layer, the Δn of the final liquid crystal was confirmed using polarization microscopy. 1550The thickness = Re(1550) is 775 nm, and it is periodically oriented. Furthermore, the twist angle in the thickness direction of the first optical anisotropic layer is 0°. In a cross-sectional image based on SEM, a bright-dark line perpendicular to the lower interface of the first optical 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 in the thickness direction.

[0316] (Formation of the second optical anisotropic layer)

[0317] An optically anisotropic layer was formed in the same manner as the first optically anisotropic layer, and this was used as the second optically anisotropic layer. Similar to the first optically anisotropic layer, the Δn of the final liquid crystal was confirmed by polarization microscopy. 1550 The thickness = Re(1550) becomes 775 nm and is periodically oriented. Furthermore, the twist angle in the thickness direction of the second optical anisotropic layer is 0°. Also, in the SEM-based cross-sectional image, bright and dark lines perpendicular to the lower interface of the second optical anisotropic layer (the interface with the glass substrate) are observed.

[0318] The second optical anisotropic layer was transferred and bonded to the first optical anisotropic layer using an adhesive. At this time, the second optical anisotropic layer was rotated 180 degrees relative to an axis perpendicular to the main surface and bonded together, with the rotation direction of the optical axis originating from the liquid crystal compound, which changes continuously along one in-plane direction, being reversed from that of the first optical anisotropic layer, and the orientation of the rotation direction in one in-plane direction (alignment axis D) being parallel to that of the first optical anisotropic layer. Thus, a transmissive liquid crystal diffraction element (bending diffraction element) with the first and second optical anisotropic layers stacked together was fabricated.

[0319] The value of λ / Λ of this diffraction element is 1.48 relative to the incident wavelength λ1550nm, which is Λ=1.05μm.

[0320] [Example 2]

[0321] In the formation of the first optical anisotropic layer in Example 1, composition B-1 was changed to composition B-2, and in the formation of the second optical anisotropic layer, composition B-1 was changed to composition B-3, and a transmissive liquid crystal diffraction element was fabricated in the same manner as in Example 1.

[0322] Composition B-2

[0323]

[0324]

[0325] Chiral reagent Ch-A [Chemical Formula 4]

[0326]

[0327] Composition B-3

[0328]

[0329] Chiral reagent Ch-B [Chemical Formula 5]

[0330]

[0331] For the first optical anisotropic layer, the Δn of the final liquid crystal was confirmed using polarization microscopy. 1550 The thickness = Re(1550) becomes 775 nm and is periodically oriented. Furthermore, the twist angle in the thickness direction of the first optical anisotropic layer is 120° (right twist). Moreover, in the SEM-based cross-sectional image, bright and dark lines inclined relative to the lower interface of the first optical anisotropic layer (interface with the glass substrate) are observed.

[0332] For the second optical anisotropic layer, the Δn of the final liquid crystal was confirmed using polarized light microscopy. 1550 The thickness = Re(1550) becomes 775 nm, and it is periodically oriented. Furthermore, the twist angle in the thickness direction of the second optical anisotropic layer is -120° (left twist). Also, in the SEM-based cross-sectional image, bright and dark lines tilted relative to the lower interface (interface with the glass substrate) of the second optical anisotropic layer are observed. The absolute value of this tilt angle is the same as that of the first optical anisotropic layer, but the tilt direction is opposite.

[0333] In the same manner as in Example 1, the second optical anisotropic layer is transferred to the first optical anisotropic layer so that the rotation directions of the optical axes in the liquid crystal alignment pattern are reversed. At this time, the tilted light and dark lines of the first optical anisotropic layer are parallel to the tilted light and dark lines of the second optical anisotropic layer.

[0334] The value of λ / Λ of this diffraction element is 1.48 relative to the incident wavelength λ1550nm, which is Λ=1.05μm.

[0335] [Example 3]

[0336] A C-plate with positive refractive index anisotropy was disposed between the first optical anisotropy layer and the second optical anisotropy layer. Otherwise, a transmissive liquid crystal diffraction element was fabricated in the same manner as in Example 1.

[0337] The positive C-plate is formed by vertically aligning the rod-shaped liquid crystal compound L-1 and then curing it with ultraviolet light. At this time, the thickness retardation (Rth) of the positive C-plate is -390 nm. The positive C-plate is then bonded to the first optical anisotropy layer using an adhesive.

[0338] The value of λ / Λ of this diffraction element is 1.48 relative to the incident wavelength λ1550nm, which is Λ=1.05μm.

[0339] [Comparative Example 1]

[0340] A transmissive liquid crystal diffraction element having only the first optical anisotropy layer of Example 1 was fabricated.

[0341] [evaluate]

[0342] In the fabricated transmissive liquid crystal diffraction element, the azimuth angle is derived from the orientation (alignment axis D direction) of the optical axis of the liquid crystal compound, which changes continuously while rotating along an in-plane direction. A laser beam with a wavelength of 1550 nm is incident at an angle θi from the normal direction of the main surface of the transmissive liquid crystal diffraction element. In the azimuth direction of the incident light, the exit angle θo and intensity (diffraction efficiency) of the refracted light refracted in the direction opposite to the incident direction, and the exit angle θp and intensity (diffraction efficiency) of the refracted light refracted in the direction same as the incident direction, are measured using a power meter. The incident laser beam is assumed to be unpolarized. The criteria for intensity (diffraction efficiency) are as follows.

[0343] •S: Intensity (diffraction efficiency) is above 95%.

[0344] • A: Intensity (diffraction efficiency) is above 92%.

[0345] • B: Intensity (diffraction efficiency) is above 90%.

[0346] • C: Intensity (diffraction efficiency) is above 80%.

[0347] • D: Intensity (diffraction efficiency) is 50% or higher

[0348] • E: Intensity (diffraction efficiency) less than 50%

[0349] The results are shown in Table 1 below.

[0350] [Table 1]

[0351]

[0352] As shown in Table 1, the embodiments of the present invention can significantly bend the angle of incident light. Furthermore, no refracted light was observed refracted in the same direction as the incident light (angle θp), but the intensity (diffraction efficiency) of the refracted light refracted in the opposite direction to the incident light (angle θo) was observed to be over 50%. Therefore, it can be concluded that both the right-hand circularly polarized component and the left-hand circularly polarized component of the incident light can be diffracted in the same direction (angle θo).

[0353] [Example 4]

[0354] The formation and exposure of the alignment film are the same as in Example 1, and the first optical anisotropic layer and the second optical anisotropic layer are formed in the following manner.

[0355] (Preparation of liquid crystal compositions)

[0356] Compositions C-1, C-2, D-1, and D-2 were prepared as liquid crystal compositions for forming liquid crystal layers. The symbol C indicates that the main component of the liquid crystal compound is a rod-shaped compound, and D indicates that the main component of the liquid crystal compound is a disc-shaped compound. Furthermore, 1 indicates right-hand twist, and 2 indicates left-hand twist. That is, composition C-1 is a liquid crystal composition with a rod-shaped liquid crystal compound as the main component and twisted to the right; composition C-2 is a liquid crystal composition with a rod-shaped liquid crystal compound as the main component and twisted to the left; composition D-1 is a liquid crystal composition with a disc-shaped liquid crystal compound as the main component and twisted to the right; and composition D-2 is a liquid crystal composition with a disc-shaped liquid crystal compound as the main component and twisted to the left.

[0357] Composition C-1

[0358]

[0359] Composition C-2

[0360]

[0361] Composition D-1

[0362]

[0363]

[0364] Composition D-2

[0365]

[0366] Disk-shaped liquid crystal compound L-2

[0367] [Chemical Formula 6]

[0368]

[0369] Disk-shaped liquid crystal compound L-3

[0370] [Chemical Formula 7]

[0371]

[0372] Chiral reagent Ch-2

[0373] [Chemical Formula 8]

[0374]

[0375] Chiral reagent Ch-3

[0376] [Chemical Formula 9]

[0377]

[0378] (Formation of the first optical anisotropy layer)

[0379] The first optical anisotropic layer is formed by coating multiple layers of composition C-1 onto an alignment film P-2, and then coating multiple layers of composition C-2 thereon. The liquid crystal layer C-1 is formed by repeating the following process: first, the first layer of composition C-1 is coated onto the alignment film, heated, cooled, and then cured under ultraviolet light to create a liquid crystal immobilization layer. For subsequent layers, layers are overlapped onto this liquid crystal immobilization layer, and then similarly heated, cooled, and cured under ultraviolet light. The process from coating to ultraviolet curing is the same as in Example 1. At this time, a good alignment state is obtained by setting the coating thickness for each overlap coating to approximately 0.4 μm for the thickness of the liquid crystal layer C-1. Therefore, the Δn of the liquid crystal layer C-1... 1550 ×thickness = Re(1550) becomes 930nm.

[0380] On top of this, multiple layers of composition C-2 are coated in the same manner to form a liquid crystal layer C-2. Thus, the Δn of the liquid crystal layer C-2... 1550 ×thickness = Re(1550) becomes 930 nm. Thus, a first optical anisotropic layer was fabricated, consisting of overlapping liquid crystal layers C-1 and C-2. Microscopic examination confirmed periodic orientation. Furthermore, the thickness-direction twist angle of the C-1 portion of the first optical anisotropic layer is 60°, and the thickness-direction twist angle of the C-2 portion is -60°. In a cross-sectional image based on SEM, a horizontally placed "V" shape of light and dark lines was observed relative to the lower interface of the first optical anisotropic layer (the interface with the glass substrate). These light and dark lines were observed through a structure formed by stacking liquid crystal compounds oriented in different thickness-direction twist directions on the right and left sides in the thickness direction.

[0381] (Formation of the second optical anisotropic layer and fabrication of a transmission-type liquid crystal diffraction element)

[0382] An optical anisotropic layer was formed in the same manner as the first optical anisotropic layer, and this was used as the second optical anisotropic layer. The second optical anisotropic layer was transferred and bonded to the first optical anisotropic layer using adhesive. At this time, the second optical anisotropic layer was rotated 180 degrees relative to an axis perpendicular to the main surface and bonded, with the rotation direction of the optical axis derived from the liquid crystal compound, which changes continuously along one in-plane direction, being reversed from that of the first optical anisotropic layer, and the orientation of the rotation direction in one in-plane direction (alignment axis D) being parallel to that of the first optical anisotropic layer. Thus, a transmissive liquid crystal diffraction element with the first and second optical anisotropic layers stacked was fabricated (see reference). Figure 17 ).

[0383] The value of λ / Λ of this diffraction element is 1.48 relative to the incident wavelength λ1550nm, which is Λ=1.05μm.

[0384] [Example 5]

[0385] The formation and exposure of the alignment film are the same as in Example 1, and the first optical anisotropic layer and the second optical anisotropic layer are formed in the following manner.

[0386] (Formation of the first optical anisotropy layer)

[0387] The first optical anisotropic layer is formed by alternately coating multiple layers of composition C-1 and composition D-1 on an alignment film P-2, and then alternately coating multiple layers of composition C-2 and composition D-2 on the same film. First, a rod-shaped liquid crystal layer C-1 is formed by coating, heating, and cooling composition C-1 on the alignment film, followed by UV curing. Then, for the second layer, composition D-1 is overlapped and coated onto the rod-shaped liquid crystal layer C-1, and similarly heated, cooled, and then UV cured to form a disk-shaped liquid crystal layer D-1. Then, the rod-shaped liquid crystal layer C-1 and the disk-shaped liquid crystal layer D-1 are formed alternately. The process from coating to UV curing is the same as in Example 1. Here, a good alignment state is obtained by setting the coating thickness for each overlap coating to approximately 0.4 μm of the liquid crystal layer thickness. Furthermore, the orientation direction of the liquid crystal compound in the rod-shaped liquid crystal layer C-1 (the direction of the long axis of the rod-shaped liquid crystal compound) is parallel to the orientation direction of the liquid crystal compound in the disk-shaped liquid crystal layer D-1 (the direction of the long side of the disk-shaped liquid crystal compound) during the lamination process. Therefore, the late band in the thickness direction cancels out the optical properties. Thus, the overall Δn of the liquid crystal layer having multiple rod-shaped liquid crystal layers C-1 and disk-shaped liquid crystal layers D-1 is... 1550×thickness = Re(1550) becomes 930nm. At this point, Δn 1550 is the birefringence in the in-plane direction.

[0388] Multiple layers of composition C-2 and composition D-2 were alternately coated onto it. This formed a liquid crystal layer having alternating rod-shaped liquid crystal layers C-2 and disk-shaped liquid crystal layers D-2. The overall Δn of the liquid crystal layer... 1550 ×thickness = Re(1550) becomes 930 nm. Thus, a first optically anisotropic layer was fabricated, on which alternating rod-shaped liquid crystal layers C-1 and disk-shaped liquid crystal layers D-1 are superimposed, with alternating rod-shaped liquid crystal layers C-2 and disk-shaped liquid crystal layers D-2. Microscopic examination confirmed periodic orientation. Furthermore, the thickness-direction twist angle of the liquid crystal layer portion of the first optically anisotropic layer where rod-shaped liquid crystal layers C-1 and disk-shaped liquid crystal layers D-1 are alternately stacked is 60°, and the thickness-direction twist angle of the liquid crystal layer portion where rod-shaped liquid crystal layers C-2 and disk-shaped liquid crystal layers D-2 are alternately stacked is -60°.

[0389] Furthermore, in the SEM-based cross-sectional image, a bright-dark line resembling a horizontal "V" shape was observed relative to the lower interface of the first optical anisotropy layer (the interface with the glass substrate). This bright-dark line was observed through a structure formed by stacking liquid crystal compounds oriented in twist directions with different positive and negative thickness directions in the thickness direction.

[0390] (Formation of the second optical anisotropic layer and fabrication of a transmission-type liquid crystal diffraction element)

[0391] An optical anisotropic layer was formed in the same manner as the first optical anisotropic layer, and this was used as the second optical anisotropic layer. The second optical anisotropic layer was transferred and bonded to the first optical anisotropic layer using adhesive. At this time, the second optical anisotropic layer was rotated 180 degrees relative to an axis perpendicular to the main surface and bonded, with the rotation direction of the optical axis derived from the liquid crystal compound, which changes continuously along one in-plane direction, being reversed from that of the first optical anisotropic layer, and the orientation of the rotation direction in one in-plane direction (alignment axis D) being parallel to that of the first optical anisotropic layer. Thus, a transmissive liquid crystal diffraction element with the first and second optical anisotropic layers stacked was fabricated (see reference). Figure 18 ).

[0392] The value of λ / Λ of this diffraction element is 1.48 relative to the incident wavelength λ1550nm, which is Λ=1.05μm.

[0393] [Example 6]

[0394] A λ / 4 plate was bonded to both sides of the transmissive liquid crystal diffraction element of Example 5 using an adhesive material to form the transmissive liquid crystal diffraction element of Example 6 (reference). Figure 19 The slow axes of the two λ / 4 plates were bonded at 45 degrees and -45 degrees respectively, with the azimuth angle relative to the optical axis derived from the liquid crystal compound changing continuously while rotating in one in-plane direction (alignment axis D direction). Furthermore, the λ / 4 plates were fabricated using the method described in the embodiment of WO13 / 137464, and configured as a stacked positive A plate and positive C plate. In this case, the in-plane late band Re(1550) was set to 388 nm, and the late band Rth(1550) in the thickness direction was set to 0 nm.

[0395] The value of λ / Λ of this diffraction element is 1.48 relative to the incident wavelength λ1550nm, which is Λ=1.05μm.

[0396] [Example 7]

[0397] The first optical anisotropic layer and the second optical anisotropic layer in the transmissive liquid crystal diffraction element of Example 6 were formed in the following manner. Otherwise, the transmissive liquid crystal diffraction element of Example 7 was fabricated in the same manner as in Example 6.

[0398] (Preparation of liquid crystal compositions)

[0399] Compositions C-3, C-4, D-3, and D-4 were prepared as liquid crystal compositions for forming liquid crystal layers. The symbol C indicates that the main component of the liquid crystal compound is a rod-shaped compound, and D indicates that the main component of the liquid crystal compound is a disc-shaped compound. Furthermore, 3 indicates right-hand twist, and 4 indicates left-hand twist. That is, composition C-3 is a liquid crystal composition with a rod-shaped liquid crystal compound as the main component and twisted to the right; composition C-4 is a liquid crystal composition with a rod-shaped liquid crystal compound as the main component and twisted to the left; composition D-3 is a liquid crystal composition with a disc-shaped liquid crystal compound as the main component and twisted to the right; and composition D-4 is a liquid crystal composition with a disc-shaped liquid crystal compound as the main component and twisted to the left.

[0400] Composition C-3

[0401]

[0402] Composition C-4

[0403]

[0404]

[0405] Leveling agent T-2

[0406] [Chemical Formula 10]

[0407]

[0408] Composition D-3

[0409]

[0410] Composition D-4

[0411]

[0412]

[0413] Orientation aid J-1

[0414] [Chemical Formula 11]

[0415]

[0416] Orientation aid J-2

[0417] [Chemical Formula 12]

[0418]

[0419] Polymerization initiator I-1

[0420] [Chemical Formula 13]

[0421]

[0422] Leveling agent T-3

[0423] [Chemical Formula 14]

[0424]

[0425] Leveling agent T-4

[0426] [Chemical Formula 15]

[0427]

[0428] (Formation of the first optical anisotropy layer)

[0429] The first optical anisotropic layer is formed by alternately coating multiple layers of composition C-3 and composition D-3 on an alignment film P-2, and then alternately coating multiple layers of composition C-4 and composition D-4 on the same film. First, the first layer of composition C-3 is coated onto the alignment film, and after heating and cooling at 80°C, it is subjected to an optical anisotropic layer with a specific gravity of 800 mJ / cm². 2 After forming a rod-shaped liquid crystal layer C-3 by UV curing, its surface is then treated with 75W / m 2Corona treatment was performed at 800 mJ / cm². For the second layer, composition D-3 was coated on top of the rod-shaped liquid crystal layer C-3. After heating and cooling at 110°C, the coating was applied at 800 mJ / cm². 2 UV curing was performed to form a disk-shaped liquid crystal layer D-3. Then, a curing process was applied to its surface at 75 W / m². 2 The process involved corona treatment at a rate of / min, followed by heat treatment at 120°C. Then, rod-shaped liquid crystal layers C-3 and disk-shaped liquid crystal layers D-3 were alternately and repeatedly formed. At this time, a good alignment state was obtained by setting the coating thickness for each overlap to approximately 0.1 μm. Furthermore, the alignment direction of the liquid crystal compound in rod-shaped liquid crystal layer C-3 (the direction of the long axis of the rod-shaped liquid crystal compound) and the alignment direction of the liquid crystal compound in disk-shaped liquid crystal layer D-3 (the direction of the long side of the disk-shaped liquid crystal compound) were aligned parallel during the layering process, thus canceling out the late band in the thickness direction. Therefore, the overall Δn of the liquid crystal layer with multiple rod-shaped liquid crystal layers C-3 and disk-shaped liquid crystal layers D-3 was achieved. 1550 ×thickness = Re(1550) becomes 930nm. At this point, Δn 1550 is the birefringence in the in-plane direction.

[0430] Multiple layers of composition C-4 and composition D-4 were alternately coated onto it. Thus, a liquid crystal layer was formed having multiple rod-shaped liquid crystal layers C-4 and disk-shaped liquid crystal layers D-4 alternately. The overall Δn of the liquid crystal layer... 1550 ×Thickness = Re(1550) becomes 930 nm. Thus, a first optically anisotropic layer was fabricated, on which alternating rod-shaped liquid crystal layers C-3 and disk-shaped liquid crystal layers D-3 are superimposed, with alternating rod-shaped liquid crystal layers C-4 and disk-shaped liquid crystal layers D-4. Microscopic examination confirmed periodic orientation. Furthermore, the thickness-direction twist angle of the portion of the first optically anisotropic layer where rod-shaped liquid crystal layers C-3 and disk-shaped liquid crystal layers D-3 are alternately stacked is 60°, and the thickness-direction twist angle of the portion where rod-shaped liquid crystal layers C-4 and disk-shaped liquid crystal layers D-4 are alternately stacked is -60°.

[0431] Furthermore, in the SEM-based cross-sectional image, a bright-dark line resembling a horizontal "V" shape was observed relative to the lower interface of the first optical anisotropy layer (the interface with the glass substrate). This bright-dark line was observed through a structure formed by stacking liquid crystal compounds oriented in twist directions with different positive and negative thickness directions in the thickness direction.

[0432] (Formation of the second optical anisotropic layer and fabrication of a transmission-type liquid crystal diffraction element)

[0433] An optical anisotropic layer was formed in the same manner as the first optical anisotropic layer, and this was used as the second optical anisotropic layer. The second optical anisotropic layer was transferred and bonded to the first optical anisotropic layer using an adhesive. At this time, the second optical anisotropic layer was rotated 180 degrees relative to an axis perpendicular to the main surface and bonded together, with the rotation direction of the optical axis derived from the liquid crystal compound, which changes continuously along one in-plane direction, being reversed from that of the first optical anisotropic layer, and the orientation of the rotation direction in one in-plane direction (alignment axis D) being parallel to that of the first optical anisotropic layer. Thus, a transmissive liquid crystal diffraction element with the first and second optical anisotropic layers stacked together was fabricated.

[0434] The value of λ / Λ of this diffraction element is 1.48 relative to the incident wavelength λ1550nm, which is Λ=1.05μm.

[0435] [Example 8]

[0436] In the fabrication of the transmissive liquid crystal diffraction element in Example 7, plasma treatment was performed instead of corona treatment. Otherwise, the transmissive liquid crystal diffraction element was fabricated in the same manner as in Example 7. Regarding the plasma treatment, a Plasma Cleaner PDC-32G manufactured by Harrick Plasma was used to perform plasma treatment on the sample surface for 10 seconds under MED output and reduced pressure conditions. Thus, the transmissive liquid crystal diffraction element was fabricated.

[0437] The value of λ / Λ of this diffraction element is 1.48 relative to the incident wavelength λ1550nm, which is Λ=1.05μm.

[0438] [evaluate]

[0439] In the fabricated transmissive liquid crystal diffraction element, the azimuth angle is derived from the orientation (alignment axis D direction) of the optical axis of the liquid crystal compound, which changes continuously while rotating along one in-plane direction. A laser beam with a wavelength of 1550 nm is incident at an angle θi from the normal direction of the main surface of the transmissive liquid crystal diffraction element. In the azimuth direction of the incident light, the exit angle θo and intensity (diffraction efficiency) of the refracted light refracted in the direction opposite to the incident direction, and the exit angle θp and intensity (diffraction efficiency) of the refracted light refracted in the direction in the same direction as the incident direction, are measured using a power meter. Furthermore, in Examples 11 and 12, right-handed circularly polarized light and left-handed circularly polarized light were incident on the laser beam, respectively. In Example 13, S-polarized light and P-polarized light were incident on the laser beam, respectively. The average intensity of the right-handed circularly polarized light and the left-handed circularly polarized light, or the average intensity of the S-polarized light and the P-polarized light, is used as the evaluated intensity value. The criteria are as follows.

[0440] •SS: Intensity (diffraction efficiency) above 97%

[0441] •S: Intensity (diffraction efficiency) is above 95%.

[0442] • A: Intensity (diffraction efficiency) is above 92%.

[0443] • B: Intensity (diffraction efficiency) is above 90%.

[0444] • C: Intensity (diffraction efficiency) is above 80%.

[0445] • D: Intensity (diffraction efficiency) is 50% or higher

[0446] • E: Intensity (diffraction efficiency) less than 50%

[0447] Furthermore, the polarization retention characteristics were evaluated using the following criteria.

[0448] • A: Right-handed circularly polarized light and left-handed circularly polarized light, or S-polarized light and P-polarized light, are diffracted without mixing.

[0449] •B: Right-handed circularly polarized light and left-handed circularly polarized light, or S-polarized light and P-polarized light, are diffracted with almost no mixing.

[0450] •C: Diffraction occurs when right-handed and left-handed circularly polarized light, or S-polarized and P-polarized light, are mixed.

[0451] The results are shown in Table 2 below.

[0452] [Table 2]

[0453]

[0454] As shown in Table 2, in the embodiments of the present invention, even if the incident angle of the incident light changes from the center (42.6 ± 5 degrees), the diffraction efficiency does not decrease, and the angle of the incident light can be significantly bent. Furthermore, it is observed that no refracted light is observed refracted in the same direction (angle θp) as the incident direction of the light, and all polarized components of the incident light (right-hand circularly polarized light and left-hand circularly polarized light, or S-polarized light and P-polarized light) diffract in the same direction (angle θo). Moreover, diffraction is possible while maintaining the polarization state of the incident light. That is, in Embodiments 4 and 5, when the incident polarized light is right-hand circularly polarized, the diffracted light becomes left-hand circularly polarized, and when the incident polarized light is left-hand circularly polarized, the diffracted light becomes right-hand circularly polarized, and they diffract without mixing. Similarly, in Embodiment 6, when the incident polarized light is S-polarized, the diffracted light becomes S-polarized, and when the incident polarized light is P-polarized, the diffracted light becomes P-polarized, and they diffract without mixing. In particular, Examples 5 and 6 are implemented with high effectiveness.

[0455] [Example 71]

[0456] Based on Example 7, the following examples were prepared and evaluated to confirm the effects of the present invention when the wavelength of the incident light was changed. A transmissive liquid crystal diffraction element was prepared in the same manner as in Example 7, and the wavelength of the incident light was changed as shown in the table below, and the results were evaluated.

[0457] [Table 3]

[0458]

[0459] The λ / Λ value of this diffraction element is 1.45 relative to the incident wavelength λ1520nm, 1.48 relative to the incident wavelength λ1550nm, and 1.5 relative to the incident wavelength λ1580nm, which is Λ = 1.05μm.

[0460] As shown in Table 3, in the embodiments of the present invention, even if the wavelength of the incident light changes (1520–1580 nm), all polarized components of the incident light can be significantly bent with high diffraction efficiency, and diffracted while maintaining the polarization state of the incident light. Furthermore, it is evident that the exit angle varies depending on the wavelength of the incident light, thus functioning as a highly efficient beam splitter with high polarization retention characteristics.

[0461] [Example 72]

[0462] Based on Example 7, the following examples were prepared and evaluated to confirm the effectiveness of the present invention when the wavelength of the incident light was changed. In Example 7, Δn was set to 0.887 μm, and the overall Δn of the liquid crystal layer having multiple rod-shaped liquid crystal layers C-3 and disk-shaped liquid crystal layers D-3 was... 1310 ×Thickness = Re(1310) is set to 786nm, and the overall Δn of the liquid crystal layer consisting of multiple rod-shaped liquid crystal layers C-4 and disk-shaped liquid crystal layers D-4 is calculated. 1310 The thickness (Re(1310)) was set to 786 nm. Furthermore, the concentration of the chiral reagent in each layer was adjusted so that the thickness-direction twist angle of the liquid crystal layer portion where rod-shaped liquid crystal layer C-3 and disk-shaped liquid crystal layer D-3 were alternately stacked was 60°, and the thickness-direction twist angle of the liquid crystal layer portion where rod-shaped liquid crystal layer C-4 and disk-shaped liquid crystal layer D-4 were alternately stacked was -60°. Thus, a transmissive liquid crystal diffraction element was fabricated, and the wavelength of the incident light was changed and evaluated as shown in the table below.

[0463] [Table 4]

[0464]

[0465] The λ / Λ value of this diffraction element is 1.45 relative to the incident wavelength λ1285nm, 1.48 relative to the incident wavelength λ1310nm, and 1.51 relative to the incident wavelength λ1335nm, which is Λ = 0.887μm.

[0466] As shown in Table 4, in the embodiments of the present invention, even if the wavelength of the incident light changes (1285–1335 nm), all polarized components of the incident light can be significantly bent with high diffraction efficiency, and diffracted while maintaining the polarization state of the incident light. Furthermore, it is known that the exit angle varies depending on the wavelength of the incident light, thus functioning as a highly efficient beam splitter with high polarization retention characteristics.

[0467] [Example 9]

[0468] An alignment film was formed in the same manner as in Example 1, and the cross angle (cross angle α) of the two beams was adjusted so that one period Λ (the length of 180° rotation of the optical axis) of the alignment pattern formed by the interference of two laser beams was 1.0 μm. Otherwise, the alignment film was exposed in the same manner. The first optical anisotropic layer and the second optical anisotropic layer were formed in the following manner.

[0469] (Formation of the first optical anisotropy layer)

[0470] As a liquid crystal composition for forming a liquid crystal layer, the film thickness was adjusted in the formation of the first optical anisotropic layer (composition B-1) in Example 1, and the first optical anisotropic layer was formed in the same manner otherwise.

[0471] For the first optical anisotropic layer, the Δn of the final liquid crystal was confirmed using polarization microscopy. 550 The thickness = Re(550) is 280 nm, and it is periodically oriented. Furthermore, the twist angle in the thickness direction of the first optical anisotropic layer is 0°. Moreover, in the cross-sectional image based on SEM, bright and dark lines perpendicular to the lower interface of the first optical anisotropic layer (the interface with the glass substrate) are observed.

[0472] An optical anisotropic layer was formed in the same manner as the first optical anisotropic layer, and this was used as the second optical anisotropic layer. The second optical anisotropic layer was transferred and bonded to the first optical anisotropic layer using an adhesive. At this time, the second optical anisotropic layer was rotated 180 degrees relative to an axis perpendicular to the main surface and bonded together, with the rotation direction of the optical axis derived from the liquid crystal compound, which changes continuously along one in-plane direction, being reversed from that of the first optical anisotropic layer, and the orientation of the rotation direction in one in-plane direction (alignment axis D) being parallel to that of the first optical anisotropic layer. Thus, a transmissive liquid crystal diffraction element with the first and second optical anisotropic layers stacked together was fabricated.

[0473] The λ / Λ value of this diffraction element is 0.45 relative to the incident wavelength λ450nm, 0.53 relative to the incident wavelength λ532nm, and 0.65 relative to the incident wavelength λ650nm, which is Λ = 1.0μm.

[0474] [Comparative Example 2]

[0475] A transmissive liquid crystal diffraction element having only the first optical anisotropy layer of Example 9 was fabricated.

[0476] [evaluate]

[0477] In the fabricated transmissive liquid crystal diffraction element, the azimuth angle is derived from the orientation (alignment axis D direction) of the optical axis of the liquid crystal compound, which changes continuously while rotating along an in-plane direction. Laser beams with wavelengths of 450 nm, 532 nm, and 650 nm are incident at an angle θi from the normal direction of the main surface of the transmissive liquid crystal diffraction element. In the azimuth direction of the incident light, the exit angle θo and intensity (diffraction efficiency) of the refracted light refracted in the direction opposite to the incident direction, and the exit angle θp and intensity (diffraction efficiency) of the light refracted in the direction in the same direction as the incident direction are measured using a power meter. The incident laser beams are used to incident right-handed and left-handed circularly polarized light, and their average value is taken as the intensity (diffraction efficiency). The standard for intensity (diffraction efficiency) is as follows. Furthermore, the evaluation of intensity (diffraction efficiency) is performed using the average intensity (diffraction efficiency) of the refracted light at wavelengths of 450 nm, 532 nm, and 650 nm.

[0478] • S: Intensity (diffraction efficiency) is above 80%.

[0479] • A: Intensity (diffraction efficiency) is 75% or higher.

[0480] • B: Intensity (diffraction efficiency) is above 70%.

[0481] • C: Intensity (diffraction efficiency) is 60% or higher

[0482] • D: Intensity (diffraction efficiency) is 50% or higher

[0483] • E: Intensity (diffraction efficiency) less than 50%

[0484] The results are shown in Table 5 below.

[0485] [Table 5]

[0486]

[0487] As shown in Table 5, in the embodiments of the present invention, high light intensity (diffraction efficiency) is obtained relative to incident light of different wavelengths. Furthermore, high diffraction efficiency is achieved by diffracting all polarized components of the incident light (right-hand circularly polarized light and left-hand circularly polarized light) in the same direction (angle θo). Moreover, the exit angle θp bends the light at different exit angles relative to wavelengths of 450 nm, 532 nm, and 650 nm. That is, it can be seen that the embodiments of the present invention function as a beam-splitting element with high diffraction efficiency.

[0488] [Example 10]

[0489] An alignment film was formed in the same manner as in Example 9, and the alignment film was exposed. A first optical anisotropic layer and a second optical anisotropic layer were formed in the following manner.

[0490] (Formation of the first optical anisotropy layer)

[0491] The first optical anisotropic layer is formed by coating multiple layers of composition B-4 onto alignment film P-2. The manufacturing conditions of heating, cooling, and UV curing are the same as in Example 1. By forming these multiple layers, the Δn of the liquid crystal layer based on composition B-4 increases. 600 The thickness = Re(600) becomes 214 nm, and the twist angle becomes 90 degrees. Furthermore, multiple layers of composition B-5 are coated onto the liquid crystal layer based on composition B-4. By forming these multiple layers, the Δn of the liquid crystal layer based on composition B-5 increases. 600 The thickness = Re(600) becomes 305 nm, and the twist angle becomes -33 degrees. Thus, the first optical anisotropic layer is formed. In the SEM-based cross-sectional image, a horizontally placed "V" shape with different lengths and angles of two lines extending obliquely to the left and right relative to the lower interface (interface with the glass substrate) of the first optical anisotropic layer is observed. This bright and dark line is formed by a structure of liquid crystal compounds stacked in the thickness direction with twist directions oriented in different thickness directions on the right and left, and is observed by the difference in the absolute values ​​of the thickness and twist angle of the right twist layer and the left twist layer.

[0492] Composition B-4

[0493]

[0494]

[0495] Composition B-5

[0496]

[0497] (Formation of the second optical anisotropic layer and fabrication of a transmission-type liquid crystal diffraction element)

[0498] An optical anisotropic layer was formed in the same manner as the first optical anisotropic layer, and this was used as the second optical anisotropic layer. The second optical anisotropic layer was transferred and bonded to the first optical anisotropic layer using an adhesive. At this time, the second optical anisotropic layer was rotated 180 degrees relative to an axis perpendicular to the main surface and bonded together, with the rotation direction of the optical axis derived from the liquid crystal compound, which changes continuously along one in-plane direction, being reversed from that of the first optical anisotropic layer, and the orientation of the rotation direction in one in-plane direction (alignment axis D) being parallel to that of the first optical anisotropic layer. Thus, a transmissive liquid crystal diffraction element with the first and second optical anisotropic layers stacked together was fabricated.

[0499] The λ / Λ value of this diffraction element is 0.45 relative to the incident wavelength λ450nm, 0.53 relative to the incident wavelength λ532nm, 0.65 relative to the incident wavelength λ650nm, and 0.98 relative to the incident wavelength λ980nm, which is Λ = 1.0μm.

[0500] [evaluate]

[0501] In the fabricated transmissive liquid crystal diffraction element, the azimuth angle is derived from the orientation (alignment axis D direction) of the optical axis of the liquid crystal compound, which changes continuously while rotating along an in-plane direction. Laser beams with wavelengths of 450 nm, 532 nm, 650 nm, and 980 nm are incident at an angle θi from the normal direction of the main surface of the transmissive liquid crystal diffraction element. In the azimuth direction of the incident light, the exit angle θo and intensity (diffraction efficiency) of the refracted light refracted in the direction opposite to the incident direction, and the exit angle θp and intensity (diffraction efficiency) of the light refracted in the direction in the same direction as the incident direction are measured using a power meter. The incident laser beams are used to incident right-handed and left-handed circularly polarized light, and their average value is taken as the intensity (diffraction efficiency). The standard for intensity (diffraction efficiency) is as follows. Furthermore, the evaluation of intensity (diffraction efficiency) is performed using the average intensity (diffraction efficiency) of the refracted light at wavelengths of 450 nm, 532 nm, 650 nm, and 980 nm.

[0502] • S: Intensity (diffraction efficiency) is 70% or higher.

[0503] • A: Intensity (diffraction efficiency) is 65% or higher.

[0504] • B: Intensity (diffraction efficiency) is above 60%.

[0505] • C: Intensity (diffraction efficiency) is 50% or higher

[0506] • D: Intensity (diffraction efficiency) is 40% or higher.

[0507] • E: Intensity (diffraction efficiency) less than 40%

[0508] The results are shown in Table 6 below.

[0509] [Table 6]

[0510]

[0511] As shown in Table 6, in the embodiments of the present invention, high light intensity (diffraction efficiency) is obtained relative to incident light of different wavelengths. Furthermore, high diffraction efficiency is achieved by diffracting all polarized components of the incident light (right-hand circularly polarized light and left-hand circularly polarized light) in the same direction (angle θo). Therefore, it functions as a beam-splitting element with high diffraction efficiency relative to wavelengths of 450 nm, 532 nm, 650 nm, and 980 nm, from visible light to infrared.

[0512] [Example 11]

[0513] In Example 10, the cross angle (cross angle α) of the two lights was adjusted so that one period Λ of the orientation pattern was 2.375 μm. Otherwise, the orientation film was exposed in the same manner.

[0514] Furthermore, a composition containing 0.16 parts by mass of chiral reagent Ch-A in composition B-4 is designated as composition B-6. A composition containing 0.07 parts by mass of chiral reagent Ch-B in composition B-5 is designated as composition B-7. The first optical anisotropy layer is formed by coating multiple layers of the following composition B-6 onto the alignment film P-2. The manufacturing conditions of heating, cooling, and UV curing are the same as in Example 1. By forming these multiple layers, the Δn of the liquid crystal layer based on composition B-6... 1400 The thickness = Re(1400) becomes 508 nm, and the twist angle becomes 90 degrees. Furthermore, multiple layers of composition B-7 are coated onto the liquid crystal layer based on composition B-6. By forming these multiple layers, the Δn of the liquid crystal layer based on composition B-7 increases. 1400The thickness = Re(1400) becomes 724 nm, and the twist angle becomes -33 degrees. Thus, the first optical anisotropic layer is formed. In a cross-sectional image based on SEM, a horizontally placed "V" shape with different lengths and angles of two lines extending obliquely to the left and right relative to the lower interface (interface with the glass substrate) of the first optical anisotropic layer is observed. This bright-dark line is formed by a structure of liquid crystal compounds stacked in the thickness direction but oriented in twist directions on the right and left sides, and is observed through the difference in the absolute values ​​of the thickness and twist angle of the right and left twist layers.

[0515] (Formation of the second optical anisotropic layer and fabrication of a transmission-type liquid crystal diffraction element)

[0516] An optical anisotropic layer was formed in the same manner as the first optical anisotropic layer, and this was used as the second optical anisotropic layer. The second optical anisotropic layer was transferred and bonded to the first optical anisotropic layer using an adhesive. At this time, the second optical anisotropic layer was rotated 180 degrees relative to an axis perpendicular to the main surface and bonded together, with the rotation direction of the optical axis derived from the liquid crystal compound, which changes continuously along one in-plane direction, being reversed from that of the first optical anisotropic layer, and the orientation of the rotation direction in one in-plane direction (alignment axis D) being parallel to that of the first optical anisotropic layer. Thus, a transmissive liquid crystal diffraction element with the first and second optical anisotropic layers stacked together was fabricated.

[0517] The λ / Λ value of this diffraction element is 0.40 relative to the incident wavelength λ950nm, 0.59 relative to the incident wavelength λ1400nm, and 1.05 relative to the incident wavelength λ2500nm, which is Λ = 2.375μm.

[0518] [evaluate]

[0519] In the fabricated transmissive liquid crystal diffraction element, the following were measured: the azimuth angle, which is the azimuth originating from the optical axis of the liquid crystal compound, which changes continuously while rotating along an in-plane direction (alignment axis D direction); and the exit angle θo and intensity (diffraction efficiency) of the refracted light refracted at an incident angle θi from the normal direction of the main surface of the transmissive liquid crystal diffraction element in a direction opposite to the incident direction of light with wavelengths of 950 nm, 1400 nm, and 2500 nm; and the exit angle θp and intensity (diffraction efficiency) of the light emitted in the same direction as the incident direction of the light. The intensity was set as the average of the diffraction efficiencies relative to the incident light of right-handed and left-handed circularly polarized light. The criteria for intensity (diffraction efficiency) are as follows.

[0520] • S: Intensity (diffraction efficiency) is 60% or higher.

[0521] • A: Intensity (diffraction efficiency) is 55% or higher.

[0522] • B: Intensity (diffraction efficiency) is 50% or higher.

[0523] • C: Intensity (diffraction efficiency) is 40% or higher

[0524] • D: Intensity (diffraction efficiency) is 30% or higher

[0525] • E: Intensity (diffraction efficiency) less than 30%

[0526] The results are shown in Table 7 below.

[0527] [Table 7]

[0528]

[0529] As shown in Table 7, in the embodiments of the present invention, high light intensity (diffraction efficiency) is obtained relative to incident light of different wavelengths. Furthermore, high diffraction efficiency is achieved by diffracting all polarized components of the incident light (right-hand circularly polarized light and left-hand circularly polarized light) in the same direction (angle θo). Therefore, it functions as a beam-splitting element with high diffraction efficiency in the infrared range of 950 to 2500 nm.

[0530] Based on the above results, the effectiveness of the present invention is clearly evident.

[0531] Industrial availability

[0532] In optical communications and the like, it is preferred for various applications that bend light. Reflective components such as mirrors used for bending light change the direction of light travel in the opposite direction in the direction perpendicular to the reflecting surface, but do not change it in the direction parallel to the reflecting surface. In contrast, the transmissive liquid crystal diffraction element of the present invention does not change the direction of light travel in the direction perpendicular to the main surface, but changes the direction of light travel in the opposite direction in the direction parallel to the main surface. Therefore, in the transmissive liquid crystal diffraction element and the reflective component of the present invention, if the same light bending effect is to be obtained, the orientation of the light-injecting surface differs by 90°. Therefore, in optical communications and the like, where installation space is limited due to miniaturization and thinning, the transmissive liquid crystal diffraction element of the present invention can sometimes be easily configured even in locations where it is difficult to configure a reflective component.

[0533] Furthermore, it is preferred for various applications of splitting light, such as in hyperspectral cameras. Spectroscopic elements, such as diffraction elements, used for splitting light bend light over a wide wavelength range and require high diffraction efficiency. The transmissive liquid crystal diffraction element of the present invention can split incident light over a wide wavelength range with high diffraction efficiency, enabling high-sensitivity light detection in hyperspectral cameras and the like.

[0534] Symbol Explanation

[0535] 10 - Transmissive liquid crystal diffraction element; 30 - Support; 32 - Alignment film; 36, 37, 36c - Optical anisotropic layers; 36a, 37a, 37c - First optical anisotropic layer; 36b, 37b, 37d - Second optical anisotropic layer; 38 - Phase reversal layer; 40 - Liquid crystal compound; 40c - Rod-shaped liquid crystal compound; 40d - Disk-shaped liquid crystal compound; 40A - Optical axis; 42, 42b - Rod-shaped liquid crystal layer; 44, 44b - Disk-shaped liquid crystal layer; 46a, 46b, 47, 48a, 48b - Liquid crystal layer; 50 - λ / 4 plate; 60 - Exposure device; 62 - Laser; 64 - Light source; 65 - λ / 2 plate; 68 - Polarization beam splitter; 70A, 70B - Mirrors; 72A, 72B - λ / 4 plate; I R I R1 - Right-handed circularly polarized light, I L I L1 - Left-handed circularly polarized light, D - alignment axis, R - region, Λ - 1 period, M - laser beam, MA, MB - light rays, P O - Linearly polarized light, P R - Right-handed circularly polarized light, P L - Left-handed circularly polarized light, α-angle, L1, L2, L4, L5-light.

Claims

1. A transmissive liquid crystal diffraction element comprising a first optically anisotropic layer and a second optically anisotropic layer, each having a liquid crystal alignment pattern having an optical axis originating from a liquid crystal compound whose orientation changes while continuously rotating along at least one in-plane 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. If the length of the orientation of the optical axis originating from the liquid crystal compound in the liquid crystal alignment pattern, rotated 180° in-plane, is taken as one period, then one period of the liquid crystal alignment pattern of the first optical anisotropy layer is the same as one period of the liquid crystal alignment pattern of the second optical anisotropy layer. In the first optical anisotropic layer and the second optical anisotropic layer, the liquid crystal compound is twisted and oriented in the thickness direction. The twist angle of the twist orientation is less than 360°. The twisting direction of the liquid crystal compound in the first optical anisotropic layer is opposite to that of the liquid crystal compound in the second optical anisotropic layer.

2. The transmissive liquid crystal diffraction element according to claim 1, wherein, The liquid crystal compound is a rod-shaped liquid crystal compound or a disc-shaped liquid crystal compound.

3. The transmissive liquid crystal diffraction element according to claim 1 or 2, wherein, At least one of the first optical anisotropic layer and the second optical anisotropic layer has a structure in which a rod-shaped liquid crystal layer oriented with the liquid crystal alignment pattern and a disk-shaped liquid crystal layer oriented with the liquid crystal alignment pattern are alternately stacked.

4. The transmissive liquid crystal diffraction element according to claim 1 or 2, having a phase difference layer disposed between the first optical anisotropy layer and the second optical anisotropy layer.

5. The transmissive liquid crystal diffraction element according to claim 4, wherein, The Nz value of the phase difference layer is 0.1 to 1.

1.

6. The transmissive liquid crystal diffraction element according to claim 1 or 2, wherein, A λ / 4 plate having at least one of the sides of the first optical anisotropy layer opposite to the second optical anisotropy layer and the side of the second optical anisotropy layer opposite to the first optical anisotropy layer.

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