Light splitting system

Abstract

The invention provides a spectroscopic system which can be miniaturized. A spectroscopic system includes an optical element having a prism and a liquid crystal diffraction element disposed on a first surface of the prism directly or via another layer, the prism having a second surface inclined with respect to the first surface, the inclination angle of the second surface being 4 DEG or more, the liquid crystal diffraction element having a cholesteric liquid crystal layer, and the cholesteric liquid crystal layer being disposed on the liquid crystal diffraction element. The cholesteric liquid crystal layer has a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating in at least one in-plane direction, and the length of one cycle is 0.1-1.4 [mu] m when the length of the orientation of the optical axis in the liquid crystal alignment pattern rotated by 180 DEG is set as one cycle. The spectroscopic system causes light to be spectroscopic to enter from the liquid crystal diffraction element side, reflects the incident light by the liquid crystal diffraction element, totally reflects the reflected light on a surface of the liquid crystal diffraction element opposite to the prism side, causes the totally reflected light to enter the prism, and emits the spectroscopic light from the second surface.

Description

Technical Field

[0001] The invention relates to a light splitting system. Background Art

[0002] An optical element is proposed, which has a cholesteric liquid crystal layer, wherein the cholesteric liquid crystal layer is formed by fixing a cholesteric liquid crystal phase having a helical structure in which liquid crystal compounds are spirally rotated and stacked, and has a liquid crystal orientation pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating in at least one direction in a plane. Since such a cholesteric liquid crystal layer having a liquid crystal orientation pattern in a plane reflects incident light in a direction different from that of specular reflection, it is proposed to use it as a diffraction element.

[0003] Patent document 1 describes an optical element formed by stacking multiple layers of cholesteric liquid crystal layers formed by fixing a cholesteric liquid crystal phase, the optical element having a plurality of cholesteric liquid crystal layers having different selective reflection center wavelengths, the cholesteric liquid crystal layers having a liquid crystal orientation pattern in which the direction of an optical axis derived from a liquid crystal compound changes while continuously rotating in at least one direction within a plane, and when the length of a rotation of 180° in a direction in which the direction of an optical axis derived from a liquid crystal compound changes while continuously rotating in the liquid crystal orientation pattern of the cholesteric liquid crystal layer is set to 1 period, in the plurality of cholesteric liquid crystal layers having different selective reflection center wavelengths, the arrangement of the lengths of the selective reflection center wavelengths is consistent with the arrangement of the lengths of 1 period.

[0004] Previous technical literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2019 / 131966 Summary of the invention

[0007] Technical issues to be solved by the invention

[0008] As described in Patent Document 1, the diffraction angle of a cholesteric liquid crystal layer having a liquid crystal orientation pattern depends on the wavelength of incident light. Therefore, a cholesteric liquid crystal layer having such a liquid crystal orientation pattern may be used as a light-splitting component.

[0009] However, since the cholesteric liquid crystal layer reflects light, the light incident on the cholesteric liquid crystal layer and split is emitted to the incident side. Therefore, in the case of utilizing the split light, for example, in the case of separately detecting the split light, it is necessary to arrange the detector for detecting the split light on the incident side of the cholesteric liquid crystal layer. Therefore, it is considered difficult to achieve miniaturization as a splitting system.

[0010] An object of the present invention is to solve the problems of the prior art and to provide a spectroscopic system that can be miniaturized.

[0011] Means for solving technical problems

[0012] In order to solve the problem, the present invention has the following structure.

[0013] [1] A spectroscopic system comprising an optical element, wherein:

[0014] The optical element comprises a prism and a liquid crystal diffraction element arranged on a first surface of the prism directly or via another layer.

[0015] The prism has a second surface inclined relative to the first surface,

[0016] The inclination angle of the second surface relative to the first surface is 4° or more,

[0017] The liquid crystal diffraction element has a cholesteric liquid crystal layer formed by fixing a cholesteric liquid crystal phase.

[0018] The cholesteric liquid crystal layer has a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating in at least one direction in the plane.

[0019] When the length of the direction of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern rotated by 180° is defined as one period, the length of one period is 0.1 to 1.4 μm.

[0020] The spectroscopic system allows the light of the spectroscopic object to be incident from the liquid crystal diffraction element side, uses the liquid crystal diffraction element to reflect the incident light, causes the reflected light to be totally reflected on the surface of the liquid crystal diffraction element on the side opposite to the prism side, causes the totally reflected light to be incident on the prism, and emits the spectroscopic light from the second surface.

[0021] [2] The spectroscopic system according to [1], wherein the liquid crystal diffraction element has a cholesteric liquid crystal layer having a helical structure with twisting directions different from each other.

[0022] [3] The spectroscopic system according to [1] or [2], wherein the inclination angle of the second surface of the prism relative to the first surface is 4° to 5°.

[0023] [4] The spectroscopic system according to [3], wherein, when the wavelength of the light to be spectroscopically detected is λ, the wavelength λ and one period Λ of the liquid crystal orientation pattern satisfy the relationship of equation (1).

[0024] Formula (1) 0.44≤λ / Λ≤1.51

[0025] Effects of the Invention

[0026] According to the present invention, a spectroscopic system that can be miniaturized can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a diagram conceptually showing the optical elements included in the spectroscopic system of the present invention.

[0028] Figure 2 This is a diagram conceptually showing a liquid crystal diffraction element included in the optical element of the present invention.

[0029] Figure 3 It is a magnified representation Figure 2 A top view of a portion of a cholesteric liquid crystal layer of a liquid crystal diffraction element is shown.

[0030] Figure 4 This is a conceptual diagram for explaining the function of the cholesteric liquid crystal layer.

[0031] Figure 5 This is a conceptual diagram of an example of an exposure device for exposing an alignment film for forming a cholesteric liquid crystal layer.

[0032] Figure 6 This is a diagram conceptually showing another example of an optical element included in the spectroscopic system of the present invention.

[0033] Figure 7 It is a conceptual representation of Figure 6 A diagram of another example of a spectroscopic system of an optical element shown.

[0034] Figure 8 This is a diagram conceptually showing another example of an optical element included in the spectroscopic system of the present invention.

[0035] Fig. 9 It is a conceptual representation of Figure 8 A diagram of another example of a spectroscopic system of an optical element shown.

[0036] Fig.10 This is a diagram conceptually showing another example of an optical element included in the spectroscopic system of the present invention.

[0037] Fig.11 It is a diagram for explaining the angle of light incident on an optical element at each position.

[0038] Fig.12 This is a diagram for explaining spectroscopy by a conventional cholesteric liquid crystal layer. DETAILED DESCRIPTION

[0039] Hereinafter, the spectroscopic system of the present invention will be described in detail based on the preferred embodiments shown in the drawings.

[0040] In the present specification, a numerical range expressed using "to" means a range including the numerical values ​​described before and after "to" as the lower limit and the upper limit.

[0041] In this specification, "(meth)acrylate" is used to mean "one or both of acrylate and methacrylate".

[0042] [Spectral system]

[0043] The optical splitting system of the present invention comprises an optical element, wherein:

[0044] The optical element comprises a prism and a liquid crystal diffraction element arranged on a first surface of the prism directly or via another layer.

[0045] The prism has a second surface inclined relative to the first surface,

[0046] The inclination angle of the second surface relative to the first surface is 4° or more,

[0047] The liquid crystal diffraction element has a cholesteric liquid crystal layer formed by fixing a cholesteric liquid crystal phase.

[0048] The cholesteric liquid crystal layer has a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating in at least one direction in the plane.

[0049] When the length of the direction of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern rotated by 180° is defined as one period, the length of one period is 0.1 to 1.4 μm.

[0050] The spectroscopic system allows the light of the spectroscopic object to be incident from the liquid crystal diffraction element side, and uses the liquid crystal diffraction element to reflect the incident light, so that the reflected light is totally reflected on the surface of the liquid crystal diffraction element on the side opposite to the prism side, and the totally reflected light is incident on the prism, and the spectroscopic light is emitted from the second surface.

[0051] Figure 1 2 is a diagram conceptually showing an optical element included in the spectroscopic system of the present invention.

[0052] Figure 1 The optical element 100 shown has a prism 102 and a liquid crystal diffraction element 10 .

[0053] <Prism>

[0054] exist Figure 1In the example shown, the prism 102 is a triangular prism with a right triangle cross section, and the liquid crystal diffraction element 10 is arranged on one of the side surfaces, namely the first surface 102a. In addition, in the prism 102, the other side surface, namely the second surface 102b, is inclined relative to the first surface 102a, and the inclination angle relative to the first surface 102a is 4° or more. In addition, the remaining side surface (third surface) of the prism 102 is perpendicular to the first surface 102a.

[0055] The prism 102 emits light incident from the first surface 102a on which the liquid crystal diffraction element 10 is arranged from the second surface 102b. Therefore, the prism 102 is made of a material that transmits the split light. The transmittance of the prism 102 with respect to the split light is preferably 50% or more, more preferably 70% or more, and further preferably 85% or more.

[0056] The size of the prism 102 is not limited and may be appropriately set according to the material of the prism 102 , the purpose of the optical element 100 (spectrometric system), the required spectroscopic performance, the spot diameter of the light to be spectroscopically detected, and the like.

[0057] As a material of the prism 102 , glass, a synthetic resin such as a plastic resin or a thermosetting resin, or the like can be used.

[0058] <Liquid crystal diffraction element>

[0059] The liquid crystal diffraction element 10 is disposed on the first surface 102 a of the prism 102 directly or via another layer.

[0060] Figure 2 2 is a diagram conceptually showing an example of the liquid crystal diffraction element 10 . Figure 3 FIG. 2 shows a top view of a cholesteric liquid crystal layer of the liquid crystal diffraction element 10. Figure 2 , i.e., a diagram showing the cholesteric liquid crystal layer observed from above, i.e., a diagram showing the cholesteric liquid crystal layer observed from the thickness direction (= the stacking direction of each layer (film)). Figure 3 In order to clearly show the structure of the cholesteric liquid crystal layer, the liquid crystal compound 40 is shown only on the surface.

[0061] Figure 2The liquid crystal diffraction element 10 shown has a cholesteric liquid crystal layer 34, an orientation film 32, and a support 30. In addition, the liquid crystal diffraction element 10 provided on the first surface 102a of the prism 102 as the optical element 100 may be in a state where the cholesteric liquid crystal layer 34 is laminated on the support 30 and the orientation film 32. Alternatively, the liquid crystal diffraction element 10 may be in a state where, for example, the support 30 is peeled off and only the orientation film 32 and the cholesteric liquid crystal layer 34 are laminated. Furthermore, the liquid crystal diffraction element 10 may be in a state where only the cholesteric liquid crystal layer 34 is laminated after the support 30 and the orientation film 32 are peeled off. Furthermore, for example, in the case where the liquid crystal diffraction element 10 has a structure of the support 30, the orientation film 32, and the cholesteric liquid crystal layer 34, the liquid crystal diffraction element 10 may be arranged with the support 30 side facing the prism 102, or may be arranged with the cholesteric liquid crystal layer 34 side facing the prism 102.

[0062] [Cholesteric liquid crystal layer]

[0063] The cholesteric liquid crystal layer 34 is a layer formed by fixing a cholesterically oriented liquid crystal phase (cholesteric liquid crystal phase). As is known to all, the cholesteric liquid crystal layer has a spiral structure in which a liquid crystal compound is spirally rotated and stacked in the thickness direction, and the structure in which the liquid crystal compound is spirally rotated once (rotated 360°) and stacked is a spiral pitch (spiral pitch), and the liquid crystal compound rotating in a spiral has a structure in which multiple pitches are stacked.

[0064] The cholesteric liquid crystal layer reflects right circularly polarized light or left circularly polarized light in a specific wavelength range, depending on the length of the helical pitch and the turning direction (handedness) of the helix of the liquid crystal compound, and transmits the rest of the light.

[0065] Here, in the present invention, the cholesteric liquid crystal layer 34 has a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating in at least one direction in the plane.

[0066] In addition, the optical axis 40A derived from the liquid crystal compound 40 is an axis having the highest refractive index in the liquid crystal compound 40, which is a so-called slow axis. For example, when the liquid crystal compound 40 is a rod-shaped liquid crystal compound, the optical axis 40A is along the long axis direction of the rod shape. On the other hand, when the liquid crystal compound 40 is a disc-shaped liquid crystal compound, the optical axis 40A of the liquid crystal compound 40 refers to an axis parallel to the normal direction of the disc surface of the disc-shaped liquid crystal compound. In the following description, the optical axis 40A derived from the liquid crystal compound 40 is also referred to as "optical axis 40A of the liquid crystal compound 40" or "optical axis 40A".

[0067] like Figure 3As shown, in the top view (XY plane) of the cholesteric liquid crystal layer 34, the liquid crystal compound 40 is arranged along a plurality of arrangement axes D in the XY plane, and on each arrangement axis D, the direction of the optical axis 40A of the liquid crystal compound 40 changes while continuously rotating along one direction in the plane along the arrangement axis D. Figure 3 In the region shown, for convenience of explanation, it is assumed that the arrangement axis D is oriented in the X direction. Also, in the Y direction, the liquid crystal compounds 40 having the same orientation of the optical axes 40A are aligned at equal intervals.

[0068] In addition, “the orientation of the optical axis 40A of the liquid crystal compound 40 changes while continuously rotating in one direction in the plane along the arrangement axis D” means that the angle formed by the optical axis 40A of the liquid crystal compound 40 and the arrangement axis D varies depending on the position in the direction of the arrangement axis D, and the angle formed by the optical axis 40A and the arrangement axis D gradually changes from θ to θ+180° or θ-180° along the arrangement axis D. That is, Figure 3 As shown, the optical axes 40A of the plurality of liquid crystal compounds 40 arranged along the arrangement axis D change while being rotated along the arrangement axis D by a predetermined angle.

[0069] The difference in angle between the optical axes 40A of the liquid crystal compounds 40 adjacent to each other in the arrangement axis D direction is preferably 45° or less, more preferably 15° or less, and still more preferably a smaller angle.

[0070] Furthermore, in the present invention, it is assumed that the rotation direction of the optical axis 40A of the liquid crystal compound in the direction of the arrangement axis D is the direction in which the liquid crystal compound 40 (optical axis 40A) rotates in a direction in which the angle formed by the optical axes 40A of the liquid crystal compounds 40 adjacent to each other in the direction of the arrangement axis D becomes smaller. Figure 2 and Figure 3 In the optically anisotropic layer shown, the optical axis 40A of the liquid crystal compound 40 is rotated rightward (clockwise) along the arrow direction of the alignment axis D.

[0071] In the cholesteric liquid crystal layer 34, in the liquid crystal orientation pattern of this liquid crystal compound 40, in the direction of the arrangement axis D where the in-plane optical axis 40A changes by continuous rotation, the length (distance) of rotating the optical axis 40A of the liquid crystal compound 40 by 180° is set as the length Λ of one period in the liquid crystal orientation pattern.

[0072] That is, the distance between the centers of the two liquid crystal compounds 40 in the direction of the arrangement axis D, which have the same angle with respect to the direction of the arrangement axis D, is set to the length Λ of one period. Figure 3As shown, the distance between the centers of the two liquid crystal compounds 40 whose arrangement axis D direction coincides with the direction of the optical axis 40A is defined as the length of one period Λ. In the following description, the length of one period Λ is also referred to as "one period Λ".

[0073] The liquid crystal alignment pattern of the cholesteric liquid crystal layer 34 repeats the one period Λ in one direction in which the orientation of the arrangement axis D, that is, the optical axis 40A, changes while continuously rotating.

[0074] Next, the effect of diffraction by the cholesteric liquid crystal layer will be described.

[0075] In the conventional cholesteric liquid crystal layer, the helical axis derived from the cholesteric liquid crystal phase is perpendicular to the main surface (XY plane), and its reflection plane is a plane parallel to the main surface (XY plane). The cholesteric liquid crystal phase has mirror reflectivity, so for example, when light is incident on the conventional cholesteric liquid crystal layer from the normal direction, the light is reflected along the normal direction.

[0076] On the other hand, the cholesteric liquid crystal layer 34 having the liquid crystal alignment pattern reflects the incident light while tilting in the direction of the arrangement axis D.

[0077] As an example, assuming that the cholesteric liquid crystal layer 34 selectively reflects right-handed circularly polarized red light, when light enters the cholesteric liquid crystal layer 34, the cholesteric liquid crystal layer 34 reflects only the right-handed circularly polarized red light and transmits other light.

[0078] In the cholesteric liquid crystal layer 34, the optical axis 40A of the liquid crystal compound 40 changes while rotating in the direction of the alignment axis D (one direction). The liquid crystal alignment pattern formed on the cholesteric liquid crystal layer 34 is a periodic pattern in the direction of the alignment axis D. Therefore, Figure 4 As shown, the right-handed circularly polarized light R of the red light vertically incident on the cholesteric liquid crystal layer 34 R The reflected red light is reflected (diffracted) in a direction (azimuth) corresponding to the period of the liquid crystal orientation pattern, and the right-handed circularly polarized light R R The light is reflected (diffracted) in a direction tilted toward the direction (azimuth) of the arrangement axis D with respect to the XY plane (the main surface of the cholesteric liquid crystal layer).

[0079] Therefore, in the cholesteric liquid crystal layer 34 , by appropriately setting the direction of the arrangement axis D, which is one direction in which the optical axis 40A rotates, the reflection direction (reflection azimuth) of light can be adjusted.

[0080] Furthermore, when circularly polarized light having the same wavelength and the same rotation direction is reflected, the reflection direction of the circularly polarized light can be reversed by reversing the rotation direction of the optical axis 40A of the liquid crystal compound 40 oriented in the arrangement axis D direction.

[0081] For example, in Figure 2 and Figure 3 In the embodiment, the rotation direction of the optical axis 40A toward the arrangement axis D is clockwise and some circularly polarized light is reflected while tilted toward the arrangement axis D. However, by setting it to the counterclockwise direction, some circularly polarized light is reflected while tilted toward the direction opposite to the arrangement axis D.

[0082] Furthermore, in the cholesteric liquid crystal layer having the same liquid crystal alignment pattern, the reflection direction is reversed according to the rotation direction of the helix of the liquid crystal compound 40 , that is, the rotation direction of the reflected circularly polarized light.

[0083] For example, when the spiral rotation direction is right-handed, right-handed circularly polarized light is selectively reflected, and the liquid crystal alignment pattern having the optical axis 40A rotating clockwise along the arrangement axis D direction causes the right-handed circularly polarized light to be tilted in the arrangement axis D direction and reflected.

[0084] Furthermore, for example, when the rotation direction of the spiral is a left twist, left-handed circularly polarized light is selectively reflected, and the liquid crystal layer having a liquid crystal orientation pattern in which the optical axis 40A rotates clockwise along the arrangement axis D direction causes the left-handed circularly polarized light to be tilted in the direction opposite to the arrangement axis D direction and reflected.

[0085] In the cholesteric liquid crystal layer 34 having a liquid crystal alignment pattern, the shorter the period Λ is, the larger the angle of the reflected light relative to the incident light is. In other words, the shorter the period Λ is, the more the reflected light is inclined relative to the incident light.

[0086] The angle of diffraction based on the cholesteric liquid crystal layer 34 having such a liquid crystal orientation pattern varies depending on the wavelength of light. Specifically, the longer the wavelength of light, the larger the angle of the reflected light relative to the incident light. Thus, the cholesteric liquid crystal layer 34 can perform light separation by diffracting (reflecting) the incident light at different angles depending on the wavelength.

[0087] Here, in the present invention, the surface of the liquid crystal diffraction element 10 on the side opposite to the prism 102 is used as the total reflection surface 11, and the light reflected and diffracted by the liquid crystal diffraction element 10 (cholesteric liquid crystal layer 34) is totally reflected by the total reflection surface 11. In other words, the liquid crystal diffraction element 10 (cholesteric liquid crystal layer 34) reflects and diffracts the incident light at an angle that causes total reflection on the surface of the liquid crystal diffraction element 10 on the side opposite to the prism 102. That is, the liquid crystal diffraction element 10 (cholesteric liquid crystal layer 34) reflects the incident light at a larger diffraction angle in order to cause total reflection.

[0088] The angle (critical angle) at which total reflection is generated is determined by the refractive index of the medium sandwiching the total reflection surface 11 of the liquid crystal diffraction element 10. That is, when the total reflection surface 11 side of the liquid crystal diffraction element 10 is the cholesteric liquid crystal layer 34 and the liquid crystal diffraction element 10 is in contact with air, the angle at which total reflection is generated is determined by the refractive index of the cholesteric liquid crystal layer 34 and the refractive index of air. Furthermore, when the total reflection surface 11 side of the liquid crystal diffraction element 10 is the support 30, the angle at which total reflection is generated is determined by the refractive index of the support 30 and the refractive index of air.

[0089] Therefore, the diffraction angle of light by the liquid crystal diffraction element 10 (cholesteric liquid crystal layer 34 ) can be appropriately set to produce total reflection according to the refractive index of the layer on the total reflection surface 11 side of the liquid crystal diffraction element 10 .

[0090] The refractive index n of the cholesteric liquid crystal layer and the support described later formed using a common liquid crystal material is about 1.45 to 1.8. Therefore, the angle (critical angle φ) at which total reflection occurs on the total reflection surface 11 when it is an air interface becomes about 34° to 44° from sinφ=1 / n.

[0091] As described above, the diffraction angle based on the cholesteric liquid crystal layer 34 is basically determined by the length of one period Λ of the liquid crystal orientation pattern. From the viewpoint that the cholesteric liquid crystal layer 34 reflects light vertically incident on the cholesteric liquid crystal layer 34 at an angle that causes total reflection on the total reflection surface 11, the length of one period Λ is set to 0.1 to 1.4 μm. The length of one period Λ is preferably 0.2 to 1.2 μm, and more preferably 0.3 to 1 μm.

[0092] Furthermore, as described above, in the present invention, the cholesteric liquid crystal layer performs spectroscopy by reflecting and diffracting the incident light of the spectroscopy target. That is, the cholesteric liquid crystal layer needs to reflect the light of the spectroscopy target with a certain degree of wide bandwidth. On the other hand, a conventional cholesteric liquid crystal layer has wavelength selective reflectivity and is a layer that reflects light in a narrow band.

[0093] Therefore, in the present invention, in order to expand the reflection wavelength region, the cholesteric liquid crystal layer is preferably a structure in which the helical pitch changes in the thickness direction. The cholesteric liquid crystal layer has a structure in which the helical pitch changes in the thickness direction, so that the reflection wavelength region of the cholesteric liquid crystal layer can be expanded. In addition, in order to expand the reflection wavelength region, it is also preferred to increase the birefringence (Δn) of the liquid crystal.

[0094] In the stripe pattern of light and dark portions observed when a cross section is observed using a scanning electron microscope (SEM), the cholesteric liquid crystal layer in which the helical pitch varies in the thickness direction has different intervals between the light and dark portions in the thickness direction.

[0095] Alternatively, in the present invention, the liquid crystal diffraction element may also be configured to have a structure of multiple cholesteric liquid crystal layers with different helical pitches. In this case, each of the multiple cholesteric liquid crystal layers has a liquid crystal orientation pattern, and the light of the selective reflection wavelength in the incident light of the spectral object is reflected and diffracted at an angle that allows total reflection on the total reflection surface. At this time, by making the diffraction angles of each cholesteric liquid crystal layer different, each cholesteric liquid crystal layer can reflect light at different angles (directions), thereby spectrally ...

[0096] <<Method for forming a cholesteric liquid crystal layer>>

[0097] The cholesteric liquid crystal layer can be formed by fixing a cholesteric liquid crystal phase in a layered state.

[0098] The structure formed by fixing the cholesteric liquid crystal phase only needs to be a structure that maintains the orientation of the liquid crystal compound that forms the cholesteric liquid crystal phase. Typically, the following structure is preferred: the polymerizable liquid crystal compound is set to an oriented state of the cholesteric liquid crystal phase, and then polymerized and cured by ultraviolet irradiation, heating, etc. to form a layer without fluidity, and at the same time, the state is changed to a state where the orientation morphology will not change due to an external field or external force.

[0099] In the structure formed by fixing the cholesteric liquid crystal phase, the liquid crystal compound 40 may not exhibit liquid crystallinity in the cholesteric liquid crystal layer as long as the optical properties of the cholesteric liquid crystal phase are maintained. For example, the polymerizable liquid crystal compound may lose its liquid crystallinity by increasing its molecular weight through a curing reaction.

[0100] As a material for forming a cholesteric liquid crystal layer in which a cholesteric liquid crystal phase is fixed, a liquid crystal composition containing a liquid crystal compound is given as an example. The liquid crystal compound is preferably a polymerizable liquid crystal compound.

[0101] Furthermore, the liquid crystal composition used for forming the cholesteric liquid crystal layer may further contain a surfactant and a chiral agent.

[0102] --Polymerizable Liquid Crystalline Compounds--

[0103] The polymerizable liquid crystal compound may be a rod-like liquid crystal compound or a disc-like liquid crystal compound.

[0104] Examples of rod-shaped polymerizable liquid crystal compounds that form a cholesteric liquid crystal phase include rod-shaped nematic liquid crystal compounds. As rod-shaped nematic liquid crystal compounds, preferably used are azomethines, azoxyls, cyanobiphenyls, cyanophenyl esters, benzoates, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolans, and alkenylcyclohexylbenzonitriles. Not only low molecular weight liquid crystal compounds but also high molecular weight liquid crystal compounds can be used.

[0105] The polymerizable liquid crystal compound is obtained by introducing a polymerizable group into a liquid crystal compound. Examples of the polymerizable group include an unsaturated polymerizable group, an epoxy group, and an aziridine group, preferably an unsaturated polymerizable group, and more preferably an ethylenically unsaturated polymerizable group. The polymerizable group can be introduced into the molecule of the liquid crystal compound by various methods. The number of polymerizable groups possessed by the polymerizable liquid crystal compound is preferably 1 to 6, and more preferably 1 to 3.

[0106] Examples of polymerizable liquid crystal compounds include compounds described in Makromol.Chem., Vol. 190, p. 2255 (1989), Advanced Materials, Vol. 5, p. 107 (1993), U.S. Pat. No. 4,683,327, U.S. Pat. No. 5,622,648, U.S. Pat. No. 5,770,107, International Publication No. 95 / 22586, International Publication No. 95 / 24455, International Publication No. 97 / 00600, International Publication No. 98 / 23580, International Publication No. 98 / 52905, Japanese Patent Application Publication No. 1-272551, Japanese Patent Application Publication No. 6-016616, Japanese Patent Application Publication No. 7-110469, Japanese Patent Application Publication No. 11-080081 and Japanese Patent Application Publication No. 2001-328973. Two or more polymerizable liquid crystal compounds may be used simultaneously. When two or more polymerizable liquid crystal compounds are used simultaneously, the alignment temperature can be lowered.

[0107] Furthermore, as polymerizable liquid crystal compounds other than the above, cyclic organopolysiloxane compounds having a cholesteric phase as disclosed in Japanese Patent Laid-Open No. 57-165480 can be used. Furthermore, as the above-mentioned polymer liquid crystal compounds, polymers having a mesogen group showing liquid crystal introduced into the main chain, the side chain, or both the main chain and the side chain, polymer cholesteric liquid crystals having a cholesteric group introduced into the side chain, liquid crystal polymers as disclosed in Japanese Patent Laid-Open No. 9-133810, and liquid crystal polymers as disclosed in Japanese Patent Laid-Open No. 11-293252 can be used.

[0108] --Disc-like Liquid Crystalline Compounds--

[0109] As the discotic liquid crystal compound, for example, the discotic liquid crystal compounds described in Japanese Patent Application Laid-Open No. 2007-108732 or Japanese Patent Application Laid-Open No. 2010-244038 can be preferably used.

[0110] The amount of the 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, relative to the solid content mass of the liquid crystal composition (mass after removing the solvent).

[0111] --Surfactant--

[0112] The liquid crystal composition used in forming the cholesteric liquid crystal layer may contain a surfactant.

[0113] The surfactant is preferably a compound that can function as an alignment control agent that helps to orient the cholesteric liquid crystal phase stably or quickly. Examples of the surfactant include silicone surfactants and fluorine surfactants, and preferably fluorine surfactants are used.

[0114] Specific examples of surfactants include compounds described in paragraphs

[0082] to

[0090] of JP-A-2014-119605, compounds described in paragraphs

[0031] to

[0034] of JP-A-2012-203237, compounds exemplified in paragraphs

[0092] and

[0093] of JP-A-2005-099248, compounds exemplified in paragraphs

[0076] to

[0078] and

[0082] to

[0085] of JP-A-2002-129162, and fluoro(meth)acrylate polymers described in paragraphs

[0018] to

[0043] of JP-A-2007-272185, and the like.

[0115] The surfactant may be used alone or in combination of two or more.

[0116] As the fluorine-based surfactant, compounds described in paragraphs

[0082] to

[0090] of JP-A-2014-119605 are preferred.

[0117] The amount of the surfactant added in 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.

[0118] Examples of the surfactant include the compounds shown below, but are not limited thereto.

[0119] [Chemical formula 1]

[0120]

[0121] [Chemical formula 2]

[0122]

[0123] [Chemical formula 3]

[0124]

[0125] [Chemical formula 4]

[0126]

[0127] [Chemical formula 5]

[0128]

[0129] [Chemical formula 6]

[0130]

[0131] [Chemical formula 7]

[0132]

[0133] [Chemical formula 8]

[0134]

[0135] [Chemical formula 9]

[0136]

[0137] [Chemical formula 10]

[0138]

[0139] [Chemical formula 11]

[0140]

[0141] [Chemical formula 12]

[0142]

[0143] [Chemical formula 13]

[0144]

[0145] [Chemical formula 14]

[0146]

[0147] [Chemical formula 15]

[0148]

[0149] [Chemical formula 16]

[0150]

[0151] [Chemical formula 17]

[0152]

[0153] [Chemical formula 18]

[0154]

[0155] [Chemical formula 19]

[0156]

[0157] [Chemical formula 20]

[0158]

[0159] [Chemical formula 21]

[0160]

[0161] --Chiral Reagents (Optically Active Compounds)--

[0162] A chiral agent has the function of inducing a helical structure of a cholesteric liquid crystal phase. Since the twisting direction or helical period of the helix induced by the compound is different, the chiral agent can be selected according to the purpose.

[0163] There are no particular restrictions on the chiral agent, and known compounds (for example, recorded in Handbook of Liquid Crystal Devices, Chapter 3, Item 4-3, TN (twisted nematic), STN (Super Twisted Nematic) Chiral Agents, page 199, compiled by the 142nd Committee of the Japan Society for the Promotion of Science, recorded in 1989), isosorbide and isomannide derivatives, etc. can be used.

[0164] Chiral agents usually contain asymmetric carbon atoms, but axially asymmetric compounds or surface asymmetric compounds that do not contain asymmetric carbon atoms can also be used as chiral agents. In the example of axially asymmetric compounds or surface asymmetric compounds, binaphthyl, helicene, p-xylene dimer and their derivatives are included. Chiral agents can have polymerizable groups. In the case where both chiral agents and liquid crystal compounds have polymerizable groups, a polymer having repeating units derived from polymerizable liquid crystal compounds and repeating units derived from chiral agents can be formed by polymerization reaction of polymerizable chiral agents and polymerizable liquid crystal compounds. In this way, the polymerizable group possessed by the polymerizable chiral agent is preferably the same group as the polymerizable group possessed by the polymerizable liquid crystal compound. Therefore, the polymerizable group of the chiral agent is also preferably an unsaturated polymerizable group, an epoxy group or an aziridine group, more preferably an unsaturated polymerizable group, and further preferably an olefinic unsaturated polymerizable group.

[0165] Furthermore, the chiral agent may also be a liquid crystal compound.

[0166] When the chiral agent has a photoisomerizable group, it is preferred that a pattern of a desired reflection wavelength corresponding to the emission wavelength can be formed by irradiating a photomask with activating light or the like after coating and orientation. The photoisomerizable group is preferably an isomerization site of a compound showing photochromicity, an azo group, an oxyazolyl group, or a cinnamoyl group. As specific compounds, compounds described in Japanese Patent Application Publication No. 2002-080478, Japanese Patent Application Publication No. 2002-080851, Japanese Patent Application Publication No. 2002-179668, Japanese Patent Application Publication No. 2002-179669, Japanese Patent Application Publication No. 2002-179670, Japanese Patent Application Publication No. 2002-179681, Japanese Patent Application Publication No. 2002-179682, Japanese Patent Application Publication No. 2002-338575, Japanese Patent Application Publication No. 2002-338668, Japanese Patent Application Publication No. 2003-313189, and Japanese Patent Application Publication No. 2003-313292 can be used.

[0167] The content of the chiral agent in the liquid crystal composition is preferably 0.01 to 200 mol %, more preferably 1 to 30 mol %, based on the molar amount of the liquid crystal compound.

[0168] --Polymerization Initiator--

[0169] When the liquid crystal composition contains a polymerizable compound, it preferably contains a polymerization initiator. In the embodiment in which the polymerization reaction is carried out by ultraviolet irradiation, the polymerization initiator used is preferably a photopolymerization initiator that can initiate the polymerization reaction by ultraviolet irradiation.

[0170] Examples of photopolymerization initiators include α-carbonyl compounds (described in U.S. Pat. No. 2,367,661 and U.S. Pat. No. 2,367,670), acyloin ethers (described in U.S. Pat. No. 2,448,828), α-hydrocarbon-substituted aromatic acyloin compounds (described in U.S. Pat. No. 2,722,512), polynuclear quinone compounds (described in U.S. Pat. No. 3,046,127 and U.S. Pat. No. 2,951,758), a combination of a triaryl imidazole dimer and p-aminophenyl ketone (described in U.S. Pat. No. 3,549,367), acridine and phenazine compounds (described in Japanese Patent Application Laid-Open No. 60-105667 and U.S. Pat. No. 4,239,850), and oxadiazole compounds (described in U.S. Pat. No. 4,212,970).

[0171] The content of the photopolymerization initiator in the liquid crystal composition is preferably 0.1 to 20% by mass, more preferably 0.5 to 12% by mass, based on the content of the liquid crystal compound.

[0172] --Crosslinking agent--

[0173] The liquid crystal composition may optionally contain a crosslinking agent in order to improve the film strength and durability after curing. As the crosslinking agent, a crosslinking agent that is cured by ultraviolet rays, heat, moisture, etc. can be preferably used.

[0174] There is no particular limitation on the crosslinking agent, and it can be appropriately selected according to the purpose. For example, multifunctional acrylate compounds such as trimethylolpropane tri(meth)acrylate and pentaerythritol tri(meth)acrylate can be cited; epoxy compounds such as (meth)acrylate glycidyl and ethylene glycol diglycidyl ether; aziridine compounds such as 2,2-bishydroxymethylbutanol-tri[3-(1-aziridine)propionate] and 4,4-bis(ethyleneiminocarbonylamino)diphenylmethane; isocyanate compounds such as hexamethylene diisocyanate and biuret type isocyanate; polyoxazoline compounds having an oxazoline group on the side chain; and alkoxysilane compounds such as vinyltrimethoxysilane and N-(2-aminoethyl)3-aminopropyltrimethoxysilane. In addition, a known catalyst can be used according to the reactivity of the crosslinking agent, so that in addition to improving the film strength and durability, the productivity can also be improved. These may be used alone or in combination of two or more.

[0175] The content of the crosslinking agent is preferably 3 to 20% by mass, more preferably 5 to 15% by mass, relative to the solid content of the liquid crystal composition. When the content of the crosslinking agent is within the above range, the effect of increasing the crosslinking density is easily obtained, and the stability of the cholesteric liquid crystal phase is further improved.

[0176] --Other additives--

[0177] A polymerization inhibitor, an antioxidant, an ultraviolet absorber, a light stabilizer, a colorant, metal oxide fine particles, and the like may be further added to the liquid crystal composition as necessary within a range that does not deteriorate optical properties.

[0178] In forming the cholesteric liquid crystal layer, a liquid crystal composition is preferably used as the liquid.

[0179] The liquid crystal composition may contain a solvent. The solvent is not limited and can be appropriately selected according to the purpose, but is preferably an organic solvent.

[0180] The organic solvent is not limited and can be appropriately selected according to the purpose. For example, ketones, alkyl halides, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters and ethers can be mentioned. These can be used alone or in combination of two or more. Among these, ketones are preferred in consideration of the burden on the environment.

[0181] When forming the cholesteric liquid crystal layer, it is preferred that the liquid crystal composition is applied on the surface on which the cholesteric liquid crystal layer is to be formed, the liquid crystal compound is aligned in a cholesteric liquid crystal phase, and then the liquid crystal compound is cured to form the cholesteric liquid crystal layer.

[0182] That is, when a cholesteric liquid crystal layer is formed on the orientation film 32 described later, it is preferred to apply a liquid crystal composition to the orientation film 32, orient the liquid crystal compound to a cholesteric liquid crystal phase, and then solidify the liquid crystal compound to form a cholesteric liquid crystal layer having a fixed cholesteric liquid crystal phase.

[0183] The liquid crystal composition can be applied by any known method that can uniformly apply a liquid to a sheet-like object, such as a printing method such as inkjet printing and roll printing, and a method such as spin coating, bar coating, and spray coating.

[0184] The applied liquid crystal composition is dried and / or heated as needed, and then cured to form a cholesteric liquid crystal layer. In the drying and / or heating process, the liquid crystal compound in the liquid crystal composition is oriented to a cholesteric liquid crystal phase. When heating is performed, the heating temperature is preferably 200° C. or less, more preferably 130° C. or less.

[0185] The aligned liquid crystal compound is further polymerized as required. The polymerization may be either thermal polymerization or photopolymerization by light irradiation, but photopolymerization is preferred. Ultraviolet rays are preferably used for light irradiation. The irradiation energy is preferably 20 mJ / cm 2 ~50J / cm 2 , more preferably 50 to 1500 mJ / cm 2In order to promote the photopolymerization reaction, light irradiation may be performed under heating conditions or in a nitrogen atmosphere. The wavelength of the ultraviolet rays to be irradiated is preferably 250 to 430 nm.

[0186] Furthermore, as a method for forming a cholesteric liquid crystal layer, the following method is also preferably used: using a composition containing a discotic liquid crystal compound to form a tilted liquid crystal layer in which the molecular axes of the discotic liquid crystal compound are tilted relative to a surface; and forming a cholesteric liquid crystal layer using a composition containing a liquid crystal compound on the tilted liquid crystal layer.

[0187] The method of forming a cholesteric liquid crystal layer using such a tilted liquid crystal layer is described in paragraphs

[0049] to

[0194] of International Publication No. 2019 / 181247.

[0188] The thickness of the cholesteric liquid crystal layer is not limited and may be appropriately set according to the application of the liquid crystal diffraction element, the light reflectivity required for the cholesteric liquid crystal layer, the material forming the cholesteric liquid crystal layer, and the like.

[0189] Furthermore, the cholesteric liquid crystal layer in which the helical pitch changes in the thickness direction can be formed in the following manner: using a chiral reagent that produces reflux isomerization, dimerization, isomerization and dimerization, etc. by irradiation with light so as to change the helical twisting power (HTP), and irradiating light of a wavelength that changes the HTP of the chiral reagent before curing the liquid crystal composition that forms the cholesteric liquid crystal layer or when curing the liquid crystal composition.

[0190] For example, by using a chiral agent whose HTP decreases due to the irradiation of light, the HTP of the chiral agent will decrease due to the irradiation of light. Here, the irradiated light is absorbed by the material forming the cholesteric liquid crystal layer. Therefore, for example, when irradiating light from above, the irradiation amount of light gradually decreases from the top to the bottom. That is, the reduction amount of the HTP of the chiral agent gradually decreases from the top to the bottom. Therefore, above where the HTP is greatly reduced, the helical pitch becomes longer due to the small induction of the helix, and below where the reduction of HTP is small, the helix pitch becomes shorter because the chiral agent induces the helix by the HTP originally possessed. Thus, a cholesteric liquid crystal layer in which the helical pitch changes in the thickness direction can be formed.

[0191] This light irradiation may be performed before the exposure for curing the cholesteric liquid crystal layer or simultaneously with the exposure for curing. Furthermore, the wavelength of the light for changing the HTP of the chiral agent may be the same as or different from the wavelength of the light for curing the cholesteric liquid crystal layer.

[0192] 〔Support〕

[0193] The support 30 supports the alignment film 32 and the cholesteric liquid crystal layer 34 .

[0194] As long as the support 30 can support the alignment film 32 and the cholesteric liquid crystal layer 34 , various sheet-like objects (films, plates) can be used.

[0195] The transmittance of the support 30 with respect to the dispersed light is preferably 50% or more, more preferably 70% or more, and even more preferably 85% or more.

[0196] The thickness of the support 30 is not limited, and may be appropriately set to a thickness capable of maintaining the alignment film 32 and the cholesteric liquid crystal layer 34 according to the application of the optical element 100 and the material of the support 30 .

[0197] The thickness of the support 30 is preferably 1 to 1000 μm, more preferably 3 to 250 μm, and further preferably 5 to 150 μm.

[0198] The support body 30 may be a single layer or a multi-layer.

[0199] As the support body 30 in the case of a single layer, there can be exemplified a support body 30 made of glass, triacetyl cellulose (TAC), polyethylene terephthalate (PET), polycarbonate, polyvinyl chloride, acrylic acid, polyolefin, etc. As an example of the support body 30 in the case of a multilayer, there can be exemplified a support body including any of the above-mentioned single-layer supports as a substrate, and a support body having another layer provided on the surface of the substrate.

[0200] 〔Oriented film〕

[0201] An alignment film 32 is formed on the surface of the support 30 .

[0202] The alignment film 32 is an alignment film for aligning the liquid crystal compound 40 in a predetermined liquid crystal alignment pattern when forming the cholesteric liquid crystal layer 34 .

[0203] As described above, in the present invention, the cholesteric liquid crystal layer 34 has a liquid crystal alignment pattern in which the direction of the optical axis 40A derived from the liquid crystal compound 40 changes while continuously rotating in one direction in the plane (see Figure 3 ). Therefore, the alignment film 32 is formed in a form that enables the cholesteric liquid crystal layer 34 to form the liquid crystal alignment pattern.

[0204] In the following description, “the rotation of the direction of the optical axis 40A” is also simply referred to as “the rotation of the optical axis 40A”.

[0205] As the alignment film 32 , various known photo-alignment films can be used.

[0206] For example, there can be cited friction-treated films composed of organic compounds such as polymers, oblique vapor-deposited films of inorganic compounds, films having microgrooves, and films formed by accumulating LB (Langmuir-Blodgett) films based on the Langmuir-Blodgett method of organic compounds such as ω-tricosanoic acid, dioctadecylmethylammonium chloride and methyl stearate.

[0207] The alignment film 32 formed by the rubbing treatment can be formed by rubbing the surface of the polymer layer with paper or cloth a plurality of times in a predetermined direction.

[0208] The material used for the alignment film 32 is preferably polyimide, polyvinyl alcohol, a polymer having a polymerizable group described in Japanese Patent Application Publication No. 9-152509, or a material used for forming the alignment film 32 described in Japanese Patent Application Publication No. 2005-097377, Japanese Patent Application Publication No. 2005-099228, or Japanese Patent Application Publication No. 2005-128503.

[0209] In the liquid crystal diffraction element, the alignment film 32 is preferably a so-called photo-alignment film formed by irradiating a photo-alignment material with polarized light or non-polarized light to form the alignment film 32. That is, in the liquid crystal diffraction element, as the alignment film 32, a photo-alignment film formed by coating a photo-alignment material on the support 30 is preferably used.

[0210] Irradiation with polarized light can be performed from a vertical direction or an oblique direction with respect to the photo-alignment film, and irradiation with unpolarized light can be performed from an oblique direction with respect to the photo-alignment film.

[0211] Examples of the photo-alignment material that can be used in the alignment film of the present invention include Japanese Patent Application Laid-Open Nos. 2006-285197, 2007-076839, 2007-138138, 2007-094071, 2007-121721, 2007-140465, and 2007-156 The azo compounds described in Japanese Patent Publication No. 439, Japanese Patent Publication No. 2007-133184, Japanese Patent Publication No. 2009-109831, Japanese Patent No. 3883848 and Japanese Patent No. 4151746, the aromatic ester compounds described in Japanese Patent Publication No. 2002-229039, the aromatic ester compounds described in Japanese Patent Publication No. 2002-265541 and Japanese Patent Publication No. 2002-317013 Maleimide and / or alkenyl-substituted nadic imide compounds having photo-alignment units described in Japanese Patent Nos. 4205195 and 4205198, photo-crosslinkable silane derivatives described in Japanese Patent Nos. 2003-520878, 2004-529220, and 4162850, photo-crosslinkable polyimides, photo-crosslinkable polyamides, and photo-crosslinkable polyesters Preferred examples include compounds capable of photodimerization described in JP-A-9-118717, JP-A-10-506420, JP-A-2003-505561, International Publication No. 2010 / 150748, JP-A-2013-177561, and JP-A-2014-012823, in particular cinnamate compounds, chalcone compounds, and coumarin compounds.

[0212] Among them, it is preferable to use an azo compound, a photo-crosslinkable polyimide, a photo-crosslinkable polyamide, a photo-crosslinkable polyester, a cinnamate compound, and a chalcone compound.

[0213] The thickness of the alignment film 32 is not limited, and may be appropriately set according to the material forming the alignment film 32 so as to obtain a desired alignment function.

[0214] The thickness of the alignment film 32 is preferably 0.01 to 5 μm, more preferably 0.05 to 2 μm.

[0215] The method for forming the alignment film 32 is not limited, and various known methods can be used according to the material for forming the alignment film 32. As an example, a method can be exemplified in which the alignment film 32 is applied to the surface of the support 30 and dried, and then the alignment film 32 is exposed to a laser beam to form an alignment pattern.

[0216] Figure 5 FIG. 1 conceptually shows an example of an exposure device for exposing an alignment film to form an alignment pattern.

[0217] Figure 5 The exposure device 60 shown includes: a light source 64 provided with a laser 62; a λ / 2 plate 65 for changing the polarization direction of the laser beam M emitted by the laser 62; a beam splitter 68 for separating the laser beam M emitted by the laser 62 into two light beams, namely, light beams MA and MB; reflectors 70A and 70B respectively arranged on the optical paths of the two separated light beams MA and MB; and λ / 4 plates 72A and 72B.

[0218] In addition, the light source 64 emits linearly polarized light P O The λ / 4 plate 72A converts the linearly polarized light P O (Light MA) is converted into right-handed circularly polarized light P R , the λ / 4 plate 72B converts the linearly polarized light P O (Light MB) is converted into left-handed circularly polarized light P L .

[0219] The support 30 having the alignment film 32 before the alignment pattern is formed is placed in the exposure section, and two light beams MA and MB are made to intersect and interfere on the alignment film 32, and then the interference light is irradiated onto the alignment film 32 for exposure.

[0220] Due to the interference at this time, the polarization state of the light irradiated on the alignment film 32 changes periodically in the form of interference fringes. Thus, an alignment film having an alignment pattern in which the alignment state changes periodically (hereinafter also referred to as a pattern alignment film) can be obtained.

[0221] In the exposure device 60, the period of the alignment pattern can be adjusted by changing the cross angle α of the two light beams MA and MB. That is, in the exposure device 60, by adjusting the cross angle α, in the alignment pattern in which the optical axis 40A originating from the liquid crystal compound 40 rotates continuously in one direction, the length of one period in which the optical axis 40A is rotated 180° in one direction can be adjusted.

[0222] By forming a cholesteric liquid crystal layer on the alignment film 32 having such an alignment pattern in which the alignment state periodically changes, a cholesteric liquid crystal layer having a liquid crystal alignment pattern in which the optical axis 40A derived from the liquid crystal compound 40 continuously rotates in one direction can be formed.

[0223] Furthermore, the rotation direction of the optical axis 40A can be reversed by rotating the optical axes of the λ / 4 plates 72A and 72B by 90° respectively.

[0224] As described above, the patterned orientation film has an orientation pattern, and the orientation pattern orients the liquid crystal compound so as to become a liquid crystal orientation pattern in which the direction of the optical axis of the liquid crystal compound in the cholesteric liquid crystal layer formed on the patterned orientation film changes while rotating continuously in at least one direction in the plane. It can be said that if the axis of the patterned orientation film along the direction in which the liquid crystal compound is oriented is set as the orientation axis, the patterned orientation film has an orientation pattern in which the direction of the orientation axis changes while rotating continuously in at least one direction in the plane. The orientation axis of the patterned orientation film can be detected by measuring the absorption anisotropy. For example, when linearly polarized light is irradiated onto the patterned orientation film while rotating and the amount of light transmitted through the patterned orientation film is measured, it is observed that the direction in which the amount of light becomes maximum or minimum gradually changes along one direction in the plane.

[0225] In the present invention, the alignment film is provided in a preferred embodiment and is not an essential constituent element.

[0226] For example, an orientation pattern can be formed on the support by a method of rubbing the support, processing the support with a laser beam, etc., so that the cholesteric liquid crystal layer can have a structure in which the orientation of the optical axis 40A originating from the liquid crystal compound 40 changes while continuously rotating in at least one direction in the plane. That is, in the present invention, the support can also function as an orientation film.

[0227] <Function of the Spectroscopic System>

[0228] The operation of the spectroscopic system including the optical element 100 described above will be described.

[0229] like Figure 1 As shown, the spectroscopic system makes the light I0 of the spectroscopic object incident on the optical element 100 from the liquid crystal diffraction element 10 side. In the illustrated example, the light I0 is incident on the liquid crystal diffraction element 10 from a direction substantially perpendicular to the main surface (total reflection surface 11) of the liquid crystal diffraction element 10. The incident light I0 is reflected and diffracted in the cholesteric liquid crystal layer 34 of the liquid crystal diffraction element 10. And, at this time, since the diffraction angle is different according to the wavelength, it is spectroscopic. In the illustrated example, for the sake of simplicity, the case where the spectroscopic light is split into three lights I1, I2, and I3 shown by the arrows is described. And, in the illustrated example, the light I0 is diffracted in the azimuth direction of the second surface 102b side.

[0230] The split light I1, I2, I3 is reflected toward the surface of the liquid crystal diffraction element 10 on the side where the light I0 is incident (i.e., the total reflection surface 11). At this time, the light I1, I2, I3 is reflected by the liquid crystal diffraction element 10 (cholesteric liquid crystal layer 34) at a larger diffraction angle. Therefore, the light I1, I2, I3 is incident at an angle that produces total reflection on the total reflection surface 11 and is totally reflected. The totally reflected light I1, I2, I3 travels toward the surface on the prism 102 side of the liquid crystal diffraction element 10. The totally reflected light I1, I2, I3 is incident on the prism 102 side of the liquid crystal diffraction element 10 at a larger incident angle, but because the difference in refractive index between the liquid crystal diffraction element 10 and the prism 102 is small, it is not totally reflected at the interface between the liquid crystal diffraction element 10 and the prism 102 but is incident into the prism 102.

[0231] The light I1, I2, I3 incident on the prism 102 travels in the prism 102 and is incident on the second surface 102b. Here, the second surface 102b is inclined at more than 4° relative to the first surface 102a. Therefore, the incident angle of the light I1, I2, I3 relative to the second surface 102b is smaller than the angle of total reflection (critical angle). Therefore, the light I1, I2, I3 is emitted from the second surface 102b. That is, in the optical element 100, the split light I1, I2, I3 can be emitted from the surface side opposite to the surface (total reflection surface 11) on which the light I0 of the split object is incident.

[0232] As described above, when a cholesteric liquid crystal layer having a liquid crystal orientation pattern is used as a light splitting component, Fig.12 As shown, the light I1, I2, and I3 incident on the cholesteric liquid crystal layer and split are emitted to the incident side. Therefore, it is necessary to arrange a detector for detecting the split light on the light incident side of the cholesteric liquid crystal layer. In this case, there is a limitation that the detector needs to be arranged so as not to block the optical path of the incident light, so it is considered difficult to achieve miniaturization as a spectroscopic system.

[0233] In contrast, the spectroscopic system of the present invention has an optical element as a spectroscopic optical element, the optical element having a prism and a liquid crystal diffraction element having a cholesteric liquid crystal layer having a liquid crystal orientation pattern, the second surface having an inclination angle of 4° or more relative to the first surface having the liquid crystal diffraction element, and the length of one period of the liquid crystal orientation pattern of the cholesteric liquid crystal layer being 0.1 to 1.4 μm. Thus, the spectroscopic system of the present invention can make the light of the spectroscopic object incident from the liquid crystal diffraction element side, reflect the incident light by the liquid crystal diffraction element, make the reflected light totally reflected on the total reflection surface of the liquid crystal diffraction element on the side opposite to the prism side, make the totally reflected light incident on the prism, and emit the spectroscopic light from the second surface. That is, the spectroscopic system can emit the spectroscopic light from the side opposite to the side of the surface on which the light of the spectroscopic object is incident on the optical element. Therefore, for example, when detecting the dispersed light, the detector for detecting the dispersed light can be arranged on the surface side opposite to the incident side, so there are few restrictions on the arrangement of the detector and the spectroscopic system can be miniaturized.

[0234] Here, when the cholesteric liquid crystal layer (liquid crystal diffraction element) having a liquid crystal orientation pattern with a length of 0.1 to 1.4 μm in one period is not in contact with the prism, that is, when the cholesteric liquid crystal layer (liquid crystal diffraction element) capable of reflecting and diffracting the incident light at an angle that causes total reflection on one surface of the liquid crystal diffraction element is not in contact with the prism, the light totally reflected on one main surface of the liquid crystal diffraction element reaches the other main surface of the liquid crystal diffraction element, but because total reflection is also generated on the other main surface, total reflection is repeated on the two main surfaces of the liquid crystal diffraction element, and the light split from the liquid crystal diffraction element cannot be emitted from the main surface. Therefore, such a cholesteric liquid crystal layer alone cannot be used as a splitting component.

[0235] In contrast, the present invention arranges a cholesteric liquid crystal layer (liquid crystal diffraction element) having a liquid crystal orientation pattern with a period length of 0.1 to 1.4 μm and capable of reflecting and diffracting the incident light at an angle causing total reflection on the total reflection surface of the liquid crystal diffraction element, directly or via other layers in contact with the first surface of the prism. The present invention can extract light that is dispersed by the cholesteric liquid crystal layer and totally reflected on the total reflection surface, and can be used as a spectroscopic component.

[0236] Here, from the viewpoint of allowing the light split and totally reflected by the cholesteric liquid crystal layer (liquid crystal diffraction element) to be emitted to the outside from the second surface of the prism, the inclination angle of the second surface relative to the first surface of the prism is preferably 4° to 75, more preferably 10° to 70°, and further preferably 20° to 60°.

[0237] Furthermore, from the perspective of reflecting and diffracting the incident light at an angle that produces total reflection on the total reflection surface of the liquid crystal diffraction element, the length of one period of the liquid crystal orientation pattern of the cholesteric liquid crystal layer is preferably 0.2 to 1.2 μm, more preferably 0.3 to 1 μm, and further preferably 0.4 to 1 μm.

[0238] Furthermore, when the wavelength of the light to be dispersed is λ, it is preferable that the wavelength λ and one period Λ of the liquid crystal alignment pattern satisfy the relationship of formula (1).

[0239] Formula (1) 0.44≤λ / Λ≤1.51

[0240] Here, the wavelength λ of the light to be spectroscopically analyzed refers to the central wavelength in the bandwidth of the light to be spectroscopically analyzed.

[0241] By satisfying the relationship of the above-mentioned formula (1) by the wavelength λ of the light of the spectral object and one period Λ of the liquid crystal orientation pattern, it is possible to obtain the conditions that the incident light is totally reflected on the total reflection surface 11 (the diffracted light will not be emitted from the total reflection surface 11 even if it returns to the total reflection surface 11) and is not totally reflected on the second surface of the prism.

[0242] And, in Figure 1 In the example shown, the spectroscopic system is configured to allow the light of the spectroscopic object to be incident on the optical element 100 from a direction substantially perpendicular to the main surface (total reflection surface 11) of the liquid crystal diffraction element 10, but the present invention is not limited thereto. The spectroscopic system may be configured to allow the light of the spectroscopic object to be incident on the optical element 100 from a direction inclined relative to the perpendicular line of the main surface of the liquid crystal diffraction element 10.

[0243] By increasing the angle of the perpendicular to the main surface of the liquid crystal diffraction element when the light of the spectroscopic object is incident on the optical element (hereinafter also referred to as the incident angle), the angle of the light reflected and diffracted by the cholesteric liquid crystal layer and spectroscopically reflected on the total reflection surface can be adjusted.

[0244] The incident angle of the light to be spectroscopically analyzed is preferably from -45° to 45°, more preferably from -40° to 40°, and still more preferably from -30° to 30°.

[0245] And, in Figure 1 In the example shown, the shape of the prism 102 is a triangular prism with a right-angled triangle cross section, but the shape is not limited thereto. The shape of the prism 102 can be any structure as long as it has a first surface on which a liquid crystal diffraction element is disposed and a second surface inclined at 4° or more relative to the first surface. For example, the cross-sectional shape of the prism 102 can be a polygonal shape such as a quadrilateral or a pentagon. Furthermore, the prism 102 can have a curved surface.

[0246] Here, in Figure 2In the example shown, the liquid crystal diffraction element 10 is configured to have a structure having one cholesteric liquid crystal layer 34, but is not limited thereto. The liquid crystal diffraction element may have two or more cholesteric liquid crystal layers having a liquid crystal orientation pattern. Furthermore, the liquid crystal diffraction element may be configured to have a structure having cholesteric liquid crystal layers having helical structures with twisting directions different from each other.

[0247] Furthermore, the liquid crystal diffraction element can be directly disposed in contact with the prism by forming an alignment film and an optical anisotropic layer on one side of the prism. Furthermore, the liquid crystal diffraction element can be directly disposed in contact with one side of the prism by alignment treatment, liquid crystal coating, polymerization, and the like.

[0248] Alternatively, the liquid crystal diffraction element can be attached to one side of the prism using an adhesive such as an optically transparent adhesive (OCA), an optically transparent double-sided tape, and an ultraviolet curing resin. Furthermore, the liquid crystal diffraction element can be directly attached to one side of the prism by a surface treatment such as a plasma treatment to enhance the adhesion. If necessary, an anti-reflection film or the like can be provided between the prism and the liquid crystal diffraction element.

[0249] Figure 6 This is a diagram conceptually showing another example of an optical element included in the spectroscopic system of the present invention.

[0250] Figure 6 The optical element 100b shown in FIG. 1 includes a prism 102 and a liquid crystal diffraction element 10b. The prism 102 has a Figure 1 The prism 102 of the optical element shown has the same structure, so its description is omitted.

[0251] The liquid crystal diffraction element 10b includes a cholesteric liquid crystal layer 34R and a cholesteric liquid crystal layer 34L. Although not shown in the figure, the liquid crystal diffraction element 10b may include a support and / or an alignment film.

[0252] As is well known, the cholesteric liquid crystal layer has a circularly polarized light selective reflectivity that reflects right-handed circularly polarized light or left-handed circularly polarized light according to the rotation direction (handedness) of the helix based on the liquid crystal compound. The cholesteric liquid crystal layer 34R of the liquid crystal diffraction element 10b is a cholesteric liquid crystal layer that reflects right-handed circularly polarized light, and the cholesteric liquid crystal layer 34L is a cholesteric liquid crystal layer that reflects left-handed circularly polarized light.

[0253] Furthermore, the selective reflection wavelength region of the cholesteric liquid crystal layer 34R and the selective reflection wavelength region of the cholesteric liquid crystal layer 34L overlap and are preferably substantially identical.

[0254] The cholesteric liquid crystal layer 34R and the cholesteric liquid crystal layer 34L are Figure 2 and Figure 3The cholesteric liquid crystal layer 34 shown similarly has a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating in at least one direction in the plane.

[0255] The rotation direction of the optical axis of the liquid crystal compound in the liquid crystal orientation pattern of the cholesteric liquid crystal layer 34R (hereinafter, also referred to as the rotation direction of the liquid crystal orientation pattern) is opposite to the rotation direction of the optical axis of the liquid crystal compound in the liquid crystal orientation pattern of the cholesteric liquid crystal layer 34L. As described above, when the rotation direction of the liquid crystal orientation pattern in the cholesteric liquid crystal layer that selectively reflects right-handed circularly polarized light is the same as the rotation direction of the liquid crystal orientation pattern in the cholesteric liquid crystal layer that selectively reflects left-handed circularly polarized light, the two cholesteric liquid crystal layers reflect and diffract light in opposite directions (opposite azimuth directions) along the arrangement axis D direction. Therefore, by making the rotation direction of the liquid crystal orientation pattern in the cholesteric liquid crystal layer 34R that selectively reflects right-handed circularly polarized light opposite to the rotation direction of the liquid crystal orientation pattern in the cholesteric liquid crystal layer 34L that selectively reflects left-handed circularly polarized light, the two cholesteric liquid crystal layers can reflect and diffract light in the same direction (azimuth direction) along the arrangement axis D direction.

[0256] Furthermore, the length of one period in the liquid crystal orientation pattern of the cholesteric liquid crystal layer 34R is substantially the same as the length of one period in the liquid crystal orientation pattern of the cholesteric liquid crystal layer 34L. As described above, the diffraction angle of light by the cholesteric liquid crystal layer having the liquid crystal orientation pattern changes according to the length of one period of the liquid crystal orientation pattern, and therefore, by making the length of one period in the liquid crystal orientation pattern of the cholesteric liquid crystal layer 34R and the length of one period in the liquid crystal orientation pattern of the cholesteric liquid crystal layer 34L substantially the same, the diffraction angle of light by the cholesteric liquid crystal layer 34R and the diffraction angle of light by the cholesteric liquid crystal layer 34L can be made substantially the same.

[0257] use Figure 6 and Figure 7 The function of the spectroscopic system including the optical element 100b having the liquid crystal diffraction element 10b will be described. Figure 6 In FIG. 1 , for convenience of explanation, among the lights reflected and diffracted by the cholesteric liquid crystal layer 34R and the cholesteric liquid crystal layer 34L, only arrows indicating light of one wavelength are shown. Figure 7 In the figure, for the sake of convenience, illustration of arrows related to reflection in the cholesteric liquid crystal layer, light splitting, and total reflection on the total reflection surface is omitted.

[0258] like Figure 6 As shown, the spectroscopic system makes the light of the spectroscopic object (I R0 and I L0) enters the optical element 100b from the liquid crystal diffraction element 10b side. The right-handed circularly polarized light component I R0 The light is transmitted through the cholesteric liquid crystal layer 34L, and is reflected and split by the cholesteric liquid crystal layer 34R. R1 The light is totally reflected by the surface (total reflection surface 11) of the liquid crystal diffraction element 10b on the side opposite to the prism 102, travels toward the prism 102, enters the prism 102, and is emitted from the second surface 102b of the prism 102. L0 The light is reflected and split by the cholesteric liquid crystal layer 34L. L1 The light is totally reflected by the surface (total reflection surface 11 ) of the liquid crystal diffraction element 10 b opposite to the prism 102 and travels toward the prism 102 . It then passes through the cholesteric liquid crystal layer 34R and enters the prism 102 , and is emitted from the second surface 102 b of the prism 102 .

[0259] Since the length of one period in the liquid crystal alignment pattern of the cholesteric liquid crystal layer 34R is substantially the same as the length of one period in the liquid crystal alignment pattern of the cholesteric liquid crystal layer 34L, the light I of a certain wavelength dispersed by the cholesteric liquid crystal layer 34R is R1 The traveling direction of the light I of the same wavelength split by the cholesteric liquid crystal layer 34L L1 Therefore, the light I emitted from the second surface 102b of the prism 102 is substantially parallel to the direction of travel. R1 Wako I L1 Roughly parallel at each wavelength.

[0260] Thus, an example of a spectroscopic system having an optical element that emits light of a spectroscopic target substantially in parallel for each wavelength is shown. Figure 7 .

[0261] Figure 7 The spectroscopic system 150 shown includes the optical element 100 b , a condenser lens 110 disposed away from the second surface side of the optical element 100 b , and a sensor 112 disposed on the side of the condenser lens 110 opposite to the optical element 100 b side.

[0262] As described above, the optical element 100b separates the right-handed circularly polarized light component and the left-handed circularly polarized light component of the incident unpolarized light I0 to be separated, and emits them from the second surface 102b of the prism 102. Figure 7 As shown, right-handed circularly polarized light I R1 and left-handed circularly polarized light I L1 Emitted parallel to the right circularly polarized light I R1 and left-handed circularly polarized light I L1 Right-handed circularly polarized light of different wavelengths IR2 and left-handed circularly polarized light I L2 Parallel to the right circularly polarized light I R1 and left-handed circularly polarized light I L1 Different angles of emission, and, with these different right-handed circularly polarized light I R3 and left-handed circularly polarized light I L3 Parallel to the right circularly polarized light I R1 and left-handed circularly polarized light I L1 , and right circularly polarized light I R2 and left-handed circularly polarized light I L2 Shooting at different angles.

[0263] The light emitted from the second surface 102 b of the prism 102 is incident on the condenser lens 110 .

[0264] The condenser lens 110 directs the incident right-handed circularly polarized light I R1 and left-handed circularly polarized light I L1 , right circularly polarized light I R2 and left-handed circularly polarized light I L2 , right circularly polarized light I R3 and left-handed circularly polarized light I L3 The light is collected so as to be focused on the detection surface of the sensor 112 .

[0265] The condenser lens 110 is not particularly limited, and a known convex lens or the like can be used.

[0266] The sensor 112 is a detector that detects light by photoelectric conversion, and may be a two-dimensional sensor in which a plurality of pixels are arranged two-dimensionally, or a line sensor in which a plurality of pixels are arranged one-dimensionally (linearly). As the sensor 112, a conventionally known imaging element such as a CCD (Charge-Coupled Device) image sensor or a CMOS (complementary metal oxide semiconductor) image sensor may be used.

[0267] The right-handed circularly polarized light I focused by the focusing lens 110 R1 and left-handed circularly polarized light I L1 , right circularly polarized light I R2 and left-handed circularly polarized light I L2 , and right circularly polarized light I R3 and left-handed circularly polarized light I L3 are incident on the sensor 112. At this time, the right-handed circularly polarized light I R1 and left-handed circularly polarized light I L1 The right-handed circularly polarized light IR2 and left-handed circularly polarized light I L2 The incident light is right-handed circularly polarized I R1 and left-handed circularly polarized light I L1 Different positions (pixels). Moreover, right-handed circularly polarized light I R3 and left-handed circularly polarized light I L3 The incident light is right-handed circularly polarized I R1 and left-handed circularly polarized light I L1 , and right circularly polarized light I R2 and left-handed circularly polarized light I L2 Different positions (pixels).

[0268] Therefore, the spectroscopic system 150 can detect the total light amount of right-handed circularly polarized light and left-handed circularly polarized light for each wavelength in different pixels of the sensor 112. That is, the spectroscopic system 150 can measure the wavelength distribution of the light to be spectroscopically targeted.

[0269] Furthermore, the optical splitter system 150 can be used as a detector for continuously splitting and detecting light beams of overlapping wavelengths to extract optical signals contained in each wavelength in optical wavelength multiplexing communication in which optical signals are simultaneously transmitted to multiple wavelengths for communication.

[0270] Here, Figure 6 and Figure 7 In the spectroscopic system 150 (optical element 100b) shown, the period of the liquid crystal orientation pattern of the cholesteric liquid crystal layer 34R and the period of the liquid crystal orientation pattern of the cholesteric liquid crystal layer 34L possessed by the liquid crystal diffraction element 10b are the same, but it is not limited to this. The period of the liquid crystal orientation pattern of the cholesteric liquid crystal layer 34R and the period of the liquid crystal orientation pattern of the cholesteric liquid crystal layer 34L may be different.

[0271] exist Figure 8 In the embodiment of the present invention, the optical element 100c of the spectroscopic system has a liquid crystal diffraction element 10c instead of the liquid crystal diffraction element 10b, and has the same Figure 6 Therefore, description of the same points as those of the optical element 100b will be omitted, and only the different points will be described.

[0272] The optical element 100c includes a cholesteric liquid crystal layer 34Rb and a cholesteric liquid crystal layer 34Lb. The cholesteric liquid crystal layer 34Rb is a cholesteric liquid crystal layer that reflects right-handed circularly polarized light, and the cholesteric liquid crystal layer 34Lb is a cholesteric liquid crystal layer that reflects left-handed circularly polarized light.

[0273] Furthermore, the selective reflection wavelength region of the cholesteric liquid crystal layer 34Rb overlaps with the selective reflection wavelength region of the cholesteric liquid crystal layer 34Lb, and preferably substantially coincides with each other.

[0274] The cholesteric liquid crystal layer 34Rb and the cholesteric liquid crystal layer 34Lb are Figure 2 and Figure 3 The cholesteric liquid crystal layer 34 shown similarly has a liquid crystal orientation pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating in at least one direction in the plane. Furthermore, the rotation direction of the liquid crystal orientation pattern in the cholesteric liquid crystal layer 34Rb that selectively reflects right circularly polarized light is opposite to the rotation direction of the liquid crystal orientation pattern in the cholesteric liquid crystal layer 34Lb that selectively reflects left circularly polarized light.

[0275] Here, the length of one period in the liquid crystal alignment pattern of the cholesteric liquid crystal layer 34Rb is different from the length of one period in the liquid crystal alignment pattern of the cholesteric liquid crystal layer 34Lb. That is, the diffraction angle of light by the cholesteric liquid crystal layer 34Rb is different from the diffraction angle of light by the cholesteric liquid crystal layer 34Lb.

[0276] use Figure 8 and Fig. 9 The function of the spectroscopic system including the optical element 100c having the liquid crystal diffraction element 10c will be described. Figure 8 In FIG. 1 , for convenience of explanation, among the lights reflected and diffracted by the cholesteric liquid crystal layer 34Rb and the cholesteric liquid crystal layer 34Lb, only arrows indicating light of one wavelength are shown. Fig. 9 In the figure, for the sake of convenience, illustration of arrows related to reflection in the cholesteric liquid crystal layer, light splitting, and total reflection on the total reflection surface is omitted.

[0277] like Figure 8 As shown, the spectroscopic system makes the light of the spectroscopic object (I R0 and I L0 ) enters the optical element 100c from the liquid crystal diffraction element 10c side. The right-handed circularly polarized light component I R0 The light is transmitted through the cholesteric liquid crystal layer 34Lb, and is reflected and split by the cholesteric liquid crystal layer 34Rb. R1 The light is totally reflected by the surface (total reflection surface 11) of the liquid crystal diffraction element 10c on the side opposite to the prism 102, travels toward the prism 102, enters the prism 102, and is emitted from the second surface 102b of the prism 102. L0 The light is reflected and split by the cholesteric liquid crystal layer 34Lb. L1 The light is totally reflected by the surface (total reflection surface 11 ) of the liquid crystal diffraction element 10 c opposite to the prism 102 and travels toward the prism 102 . It then passes through the cholesteric liquid crystal layer 34Rb and enters the prism 102 , and is emitted from the second surface 102 b of the prism 102 .

[0278] Since the length of one period in the liquid crystal alignment pattern of the cholesteric liquid crystal layer 34Rb is different from the length of one period in the liquid crystal alignment pattern of the cholesteric liquid crystal layer 34Lb, the light I of a certain wavelength dispersed by the cholesteric liquid crystal layer 34Rb is R1 The traveling direction of the light I of the same wavelength split by the cholesteric liquid crystal layer 34Lb is L1 Therefore, the light I emitted from the second surface 102b of the prism 102 is not parallel to the direction of travel. R1 Wako I L1 Not parallel at every wavelength.

[0279] In this way, an example of a spectroscopic system having an optical element that emits light of a spectroscopic object in a non-parallel manner for each wavelength is shown. Fig. 9 .

[0280] Fig. 9 The spectroscopic system 150 b shown includes the optical element 100 c , a condenser lens 110 disposed away from the second surface side of the optical element 100 c , and a sensor 112 disposed on the side of the condenser lens 110 opposite to the optical element 100 b side.

[0281] As described above, the optical element 100c separates the right-handed circularly polarized light component and the left-handed circularly polarized light component of the incident unpolarized light I0 to be separated, and emits them from the second surface 102b of the prism 102. Fig. 9 As shown, right-handed circularly polarized light I R1 and left-handed circularly polarized light I L1 It is not emitted in parallel with the right circularly polarized light I R1 and left-handed circularly polarized light I L1 Right-handed circularly polarized light of different wavelengths I R2 and left-handed circularly polarized light I L2 The right-handed circularly polarized light I R3 and left-handed circularly polarized light I L3 Not ejected in parallel.

[0282] The light emitted from the second surface 102 b of the prism 102 is incident on the condenser lens 110 .

[0283] The condenser lens 110 emits the right-handed circularly polarized light I in different directions. R1 , right circularly polarized light I R2 and right circularly polarized light I R3 The condenser lens 110 condenses the left-handed circularly polarized light I L1 , left-handed circularly polarized light I L2 and left-handed circularly polarized light IL3 With the right circularly polarized light I R1 , right circularly polarized light I R2 and right circularly polarized light I R3 The light is focused in different ways at different positions on the detection surface of the sensor 112 .

[0284] Each light beam that has passed through the condenser lens 110 enters a different position (pixel) of the sensor 112. Therefore, the spectroscopic system 150b can detect the amount of light beams having different wavelengths and polarization states at different pixels of the sensor 112. The spectroscopic system 150b of this structure can be used for polarization spectrum imaging, etc.

[0285] In addition, Fig. 9 In the example shown, a structure is used in which one sensor 112 detects each wavelength of right-handed circularly polarized light and each wavelength of left-handed circularly polarized light, but the present invention is not limited to this. A structure may also be used in which different sensors respectively detect each wavelength of right-handed circularly polarized light and each wavelength of left-handed circularly polarized light.

[0286] Here, in Figure 1 In the examples shown in FIG. 1 and FIG. 2 , the liquid crystal diffraction element 10 (cholesteric liquid crystal layer 34 ) diffracts incident light in an azimuth direction toward the second surface 102 b of the prism 102 , but the present invention is not limited thereto.

[0287] Fig.10 This is a diagram conceptually showing another example of an optical element included in the spectroscopic system of the present invention.

[0288] Fig.10 The optical element 100d shown in the figure includes a prism 102, a liquid crystal diffraction element 10d disposed on a first surface 102a of the prism 102, and a reflective layer 104 disposed on a third surface 102c of the prism 102. Fig.10 In FIG. 1 , for convenience of explanation, among the light reflected and diffracted and dispersed by the cholesteric liquid crystal layer, only arrows indicating light of one wavelength are shown.

[0289] In the liquid crystal diffraction element 10d, the azimuth direction of the light reflected and diffracted by the cholesteric liquid crystal layer is opposite to the azimuth direction of the second surface 102b of the prism 102. That is, the cholesteric liquid crystal layer of the liquid crystal diffraction element 10d diffracts the light I0 of the spectroscopic object toward the azimuth direction of the third surface 102c side of the prism 102.

[0290] The light I1 reflected, diffracted and split by the liquid crystal diffraction element 10d (cholesteric liquid crystal layer) is totally reflected on the total reflection surface 11 of the liquid crystal diffraction element 10d and enters the prism 102. The light I1 entering the prism 102 travels in the prism 102 and enters the third surface 102c. Since the reflection layer 104 is arranged on the third surface 102c, the light I1 is reflected by the reflection layer 104, travels toward the second surface 102b side, and is emitted from the second surface 102b.

[0291] In this way, the liquid crystal diffraction element (cholesteric liquid crystal layer) may be configured to diffract incident light in an azimuth direction toward the third surface 102 c on the opposite side to the second surface 102 b of the prism 102 .

[0292] exist Fig.10 In the structure shown, when the third surface 102c is 90° relative to the first surface 102a, the direction of travel of the light that is split by the liquid crystal diffraction element 10d and diffracted toward the third surface 102c side and reflected by the reflective layer 104 and emitted from the second surface 102b is parallel to the direction of travel of the light emitted from the second surface 102b when the liquid crystal diffraction element diffracts the light toward the second surface 102b side.

[0293] The reflective layer 104 is not particularly limited, and a known reflective layer such as a metal layer can be used as appropriate.

[0294] In addition, Fig.10 In the example shown, the reflective layer 104 is provided on the third surface 102c of the prism 102, but the present invention is not limited thereto, and the third surface 102c may totally reflect light.

[0295] Furthermore, in the spectroscopic system of the present invention, the optical element may include components other than the prism and the liquid crystal diffraction element. For example, a phase difference layer may be provided on the first surface of the prism.

[0296] Furthermore, in the above-mentioned example, the spectroscopic system is configured to have an optical element, a focusing lens, and a sensor, but the present invention is not limited thereto. The spectroscopic system of the present invention may be configured to have an optical element and a sensor, for example. In this case, by using a light source with a small beam diameter, it is possible to obtain spectroscopic points separated on the sensor.

[0297] As mentioned above, the spectroscopic system of the present invention has been described in detail, but the present invention is not limited to the above-mentioned example, and various improvements or changes can be made without departing from the scope of the present invention.

[0298] Example

[0299] Below, enumerate embodiment, further feature of the present invention is specifically described.Material, reagent, usage amount, amount of substance, ratio, processing content and processing step etc. shown in following examples can be changed suitably as long as do not depart from the gist of the present invention.Therefore, the scope of the present invention should not be interpreted restrictively by the specific example shown below.

[0300] [Example 1]

[0301] <Fabrication of Liquid Crystal Diffraction Element>

[0302] (Formation of Orientation Film)

[0303] A glass substrate (Corning Incorporated EAGLE) was prepared as a support. The following alignment film forming coating liquid was applied to the support by spin coating. The support having the coating film of the alignment film forming coating liquid was dried on a hot plate at 60° C. for 60 seconds to form an alignment film P-2.

[0304] Coating liquid for forming an alignment film

[0305]

[0306]

[0307] Materials for photo-orientation

[0308] [Chemical formula 22]

[0309]

[0310] (Exposure of Alignment Film)

[0311] use Figure 5 The exposure device shown in the figure exposed the alignment film to form an alignment film P-2 having an alignment pattern. In the exposure device, a device that emits a laser beam with a wavelength (325nm) was used as a laser. The exposure amount based on the interference light was set to 300mJ / cm 2 In addition, the intersection angle (intersection angle α) of the two lights was adjusted so that one period Λ (the length of the optical axis rotated 180°) of the alignment pattern formed by the interference of the two laser beams was 0.7 μm.

[0312] (Formation of Liquid Crystal Layer)

[0313] As a liquid crystal composition for forming a liquid crystal layer, the following composition B-2 was prepared.

[0314] Composition B-2

[0315]

[0316] Rod-like liquid crystal compound L-1 (containing the following structures in the mass ratio shown on the right)

[0317] [Chemical formula 23]

[0318]

[0319] [Chemical formula 24]

[0320]

[0321] [Chemical formula 25]

[0322]

[0323] Chiral reagent Ch-3

[0324] [Chemical formula 26]

[0325]

[0326] The liquid crystal composition B-2 was coated on the orientation film P-2 at 500 rpm using a spin coater for 10 seconds (coating step). Next, the coating of the liquid crystal composition B-2 was heated on a hot plate at 80°C for 3 minutes (180 seconds) (heating step). Next, in a nitrogen environment, a high-pressure mercury lamp was used to expose the liquid crystal composition at 100°C through a 300nm long-wave filter and a 350nm short-wave filter so that the irradiation amount of light measured at a wavelength of 315nm was 9mJ / cm 2 (First exposure step) The first exposure step is to control the structure to have regions with different helical pitches depending on the position in the thickness direction. Then, a high pressure mercury lamp is used at 100°C in a nitrogen environment at 1000 mJ / cm 2 The coating film was exposed to ultraviolet light with a wavelength of 365 nm at an exposure dose of 1000 nm (second exposure step). The second exposure step is to cure the liquid crystal composition to fix the orientation of the liquid crystal compound. In this way, a cholesteric liquid crystal layer was formed.

[0327] Finally, the film thickness of the cholesteric liquid crystal layer is 7 μm, and the period Λ of the liquid crystal orientation pattern is 0.7 μm, which is a right-twisted cholesteric orientation. In the cross-sectional image based on SEM, due to the cholesteric orientation and the liquid crystal orientation pattern in the plane, the cholesteric liquid crystal layer is observed to have inclined light and dark lines relative to the lower interface (interface with the glass substrate). It is observed that the angle of the light and dark lines gradually changes in the thickness direction, and the angle is 15° to 50°, and the structure acts as a broadband reflective diffraction element.

[0328] <Production of optical components>

[0329] The prepared liquid crystal diffraction element is transferred and bonded to the bottom surface of the prepared prism. The prism is an optical glass of the SK2 model of SCHO TT company, and the refractive index at a wavelength of 633nm is 1.605. The prepared prism is a prism with an inclined surface (second surface) on the bottom surface (first surface), and the angle of the inclined surface is 53° relative to the bottom surface. Regarding the bonding direction of the cholesteric liquid crystal layer, the direction of the diffraction vector in the plane of the cholesteric liquid crystal layer (the direction orthogonal to the light and dark lines) is made orthogonal to the direction of the boundary line between the bottom surface and the inclined surface. The cholesteric liquid crystal layer peeled off from the support is directly bonded by a bonding force enhancement surface treatment based on plasma treatment for bonding. In this way, an optical element is produced.

[0330] <Production of Spectroscopic System>

[0331] A spectroscopic system was fabricated using the fabricated optical elements.

[0332] In the spectroscopic system, the collimated light to be spectroscopically targeted is incident on the optical element from the cholesteric liquid crystal layer side. At this time, the incident angle is 30°. The light to be spectroscopically targeted is non-polarized light in the visible light region, and the wavelength is mainly 450 to 650 nm.

[0333] Furthermore, a condenser lens and a line sensor were arranged on the second surface side of the prism of the optical element to produce a spectroscopic system.

[0334] [evaluate]

[0335] In the manufactured spectroscopic system, the light of the spectroscopic object is incident on the optical element. The right-handed circularly polarized light component of the incident spectroscopic object is obliquely reflected and diffracted by the liquid crystal diffraction element, and then is totally reflected on the total reflection surface and then transmitted through the liquid crystal diffraction element to be emitted from the second surface of the prism. In the spectroscopic system, the light of each wavelength emitted from the second surface is collected and detected by a line sensor. As a result, at all wavelengths of the diffracted right-handed circularly polarized light, more than 80% of the light amount at the time of incidence can be detected. And, as shown in FIG. Fig.11 The angles of light traveling within the optical element at each position are shown in Table 1. Fig.11 The θ1 shown is the angle of the incident light relative to the direction perpendicular to the main surface of the liquid crystal diffraction element of the optical element (incident angle). θ2b is the angle of the light incident from the liquid crystal diffraction element to the prism relative to the direction perpendicular to the interface between the liquid crystal diffraction element and the prism. φib is the angle of the light that travels in the prism and reaches the second surface relative to the direction perpendicular to the second surface. φob is the angle of the light emitted from the second surface relative to the direction perpendicular to the second surface. ψob is the angle of the light emitted from the second surface relative to the direction perpendicular to the main surface of the liquid crystal diffraction element of the optical element.

[0336] [Table 1]

[0337]

[0338] [Example 2]

[0339] An optical element was produced in the same manner as in Example 1, except that the cholesteric liquid crystal layer was changed to the following two-layer cholesteric liquid crystal layer, and a spectroscopic system was produced.

[0340] <Fabrication of a double-layer cholesteric liquid crystal layer>

[0341] The double-layer cholesteric liquid crystal layer is produced by laminating a right-twisted cholesteric liquid crystal layer and a left-twisted cholesteric liquid crystal layer.

[0342] In the same manner as in Example 1, a right-twisted cholesteric liquid crystal layer was produced.

[0343] A left-twisted cholesteric liquid crystal layer was produced in the same manner as in Example 1 except that the chiral agent of composition B-2 was changed to Ch-4.

[0344] Chiral reagent Ch-4

[0345] [Chemical formula 27]

[0346]

[0347] Finally, the film thickness of the left-twisted cholesteric liquid crystal layer is 7μm, and one period Λ of the liquid crystal orientation pattern is 0.7μm. In the cross-sectional image based on SEM, due to the cholesteric orientation and the liquid crystal orientation pattern in the plane, the cholesteric liquid crystal layer is observed to have inclined light and dark lines relative to the lower interface (the interface with the glass substrate). It is observed that the angle of the light and dark lines gradually changes in the thickness direction, and the angle is 15° to 50°, and the structure acts as a broadband reflective diffraction element. The direction of the tilt of the light and dark lines is opposite to that of the right-twisted cholesteric liquid crystal layer, which is due to the opposite twist angle.

[0348] The right-twisted and left-twisted cholesteric liquid crystal layers were laminated and bonded. When laminating, the directions of the inclinations of the light and dark lines were aligned, and when bonding the left-twisted cholesteric liquid crystal layer, the directions were reversed by 180°. As described above, the cholesteric liquid crystal layer of Example 2 was manufactured.

[0349] [evaluate]

[0350] The prepared spectroscopic system was evaluated in the same manner as in Example 1. The evaluation results showed that the diffracted right-handed circularly polarized light and left-handed circularly polarized light could be detected with an efficiency of more than 80% at all wavelengths. In addition, the angles of the light traveling in the optical element were the same as in Example 1.

[0351] [Example 3]

[0352] An optical element was produced in the same manner as in Example 2, and a spectroscopic system was produced, except that a prism in which the inclined surface (second surface) had an inclination angle of 35° with respect to the bottom surface (first surface) was used.

[0353] [evaluate]

[0354] The prepared spectroscopic system was evaluated in the same manner as in Example 1. As a result of the evaluation, the diffracted right-handed circularly polarized light and left-handed circularly polarized light were detected with an efficiency of 80% or more at all wavelengths. In addition, the angles of the light traveling in the optical element at each position are shown in Table 2.

[0355] [Table 2]

[0356]

[0357] [Example 4]

[0358] An optical element was produced in the same manner as in Example 2, and a spectroscopic system was produced, except that a prism in which the inclined surface (second surface) had an inclination angle of 70° with respect to the bottom surface (first surface) was used.

[0359] [evaluate]

[0360] The prepared spectroscopic system was evaluated in the same manner as in Example 1. As a result of the evaluation, the diffracted right-handed circularly polarized light and left-handed circularly polarized light could be detected with an efficiency of more than 80% at all wavelengths. In addition, the angles of the light traveling in the optical element at each position are shown in Table 3.

[0361] [Table 3]

[0362]

[0363] [Comparative Example 1]

[0364] An optical element was produced in the same manner as in Example 2, and a spectroscopic system was produced, except that a prism in which the inclined surface (second surface) had an inclination angle of 3° with respect to the bottom surface (first surface) was used.

[0365] [evaluate]

[0366] The prepared spectroscopic system was evaluated in the same manner as in Example 1. As a result, the angle of the light reaching the second surface relative to the second surface was greater than the critical angle, so it was totally reflected on the second surface without being emitted, and did not function as a spectroscopic system. The angles of the light traveling in the optical element at various positions are shown in Table 4.

[0367] [Table 4]

[0368]

[0369] [Example 5]

[0370] The optical element was manufactured in the same manner as in Example 2 except that one period of the liquid crystal orientation pattern of the right-twisted and left-twisted cholesteric liquid crystal layers was changed to 0.43 μm, and the spectroscopic system was manufactured in the same manner as in Example 2 except that the incident angle of the light of the spectroscopic object was set to 0°.

[0371] [evaluate]

[0372] The prepared spectroscopic system was evaluated in the same manner as in Example 1. As a result of the evaluation, the diffracted right-handed circularly polarized light and left-handed circularly polarized light were detected with an efficiency of 80% or more at all wavelengths. In addition, the angles of the light traveling in the optical element at each position are shown in Table 5.

[0373] [Table 5]

[0374]

[0375] [Example 6]

[0376] An optical element was produced in the same manner as in Example 2, except that one period of the liquid crystal alignment pattern of the right-twisted and left-twisted cholesteric liquid crystal layers was changed to 0.8 μm, and a spectroscopic system was produced.

[0377] [evaluate]

[0378] The prepared spectroscopic system was evaluated in the same manner as in Example 1. As a result of the evaluation, the diffracted right-handed circularly polarized light and left-handed circularly polarized light were detected with an efficiency of 80% or more at all wavelengths. In addition, the angles of the light traveling in the optical element at each position are shown in Table 6.

[0379] [Table 6]

[0380]

[0381] [Example 7]

[0382] The optical element was manufactured in the same manner as in Example 2 except that one period of the liquid crystal orientation pattern of the right-twisted and left-twisted cholesteric liquid crystal layers was changed to 1.0 μm, and the spectroscopic system was manufactured in the same manner as in Example 2 except that the incident angle of the light of the spectroscopic object was set to 35°.

[0383] [evaluate]

[0384] The prepared spectroscopic system was evaluated in the same manner as in Example 1. As a result of the evaluation, the diffracted right-handed circularly polarized light and left-handed circularly polarized light were detected with an efficiency of 80% or more at all wavelengths. In addition, the angles of the light traveling in the optical element at various positions are shown in Table 7.

[0385] [Table 7]

[0386]

[0387] [Comparative Example 2]

[0388] An optical element was produced in the same manner as in Example 2, except that one period of the liquid crystal alignment pattern of the right-twisted and left-twisted cholesteric liquid crystal layers was changed to 1.5 μm, and a spectroscopic system was produced.

[0389] [evaluate]

[0390] The prepared spectroscopic system was evaluated in the same manner as in Example 1. As a result, the angle of the light reflected by the liquid crystal diffraction element and returned to the incident side surface was less than the critical angle, so it was not totally reflected on the incident side surface and did not enter the prism, so it did not function as a spectroscopic system. The angles of the light traveling in the optical element at various positions are shown in Table 8.

[0391] [Table 8]

[0392]

[0393] [Example 8]

[0394] As liquid crystal compositions for forming a liquid crystal layer, the following compositions B-3 and B-4 were used, and an optical element having a right-twisted and left-twisted cholesteric liquid crystal layer with a period of 0.43 μm bonded to a liquid crystal orientation pattern was produced in the same manner as in Example 5, and a spectroscopic system was produced in the same manner as in Example 5, except that the incident angle of light of the spectroscopic object was set to 0°.

[0395] Composition B-3 (composition for right-twisted cholesteric liquid crystal layer)

[0396]

[0397] Composition B-4 (composition for left-twisted cholesteric liquid crystal layer)

[0398]

[0399] Surfactant T-1

[0400] [Chemical formula 28]

[0401]

[0402] [evaluate]

[0403] The prepared spectroscopic system was evaluated in the same manner as in Example 1. As a result of the evaluation, the diffracted right-handed circularly polarized light and left-handed circularly polarized light were detected with an efficiency of 85% or more at all wavelengths. Furthermore, the angle of the light traveling in the optical element at each position was the same as that in Table 5.

[0404] [Example 9]

[0405] An optical element having a right-twisted and left-twisted cholesteric liquid crystal layer with a period of 0.43 μm bonded to a liquid crystal orientation pattern was produced in the same manner as in Example 8, except that the surfactant was changed from T-1 to the following T-2, and the spectroscopic system was produced in the same manner as in Example 8, except that the incident angle of the light of the spectroscopic object was set to 0°.

[0406] Surfactant T-2

[0407] [Chemical formula 29]

[0408]

[0409] [evaluate]

[0410] The prepared spectroscopic system was evaluated in the same manner as in Example 1. As a result of the evaluation, the diffracted right-handed circularly polarized light and left-handed circularly polarized light were detected with an efficiency of 85% or more at all wavelengths. Furthermore, the angle of the light traveling in the optical element at each position was the same as that in Table 5.

[0411] From the above results, the effects of the present invention are obvious.

[0412] Explanation of symbols

[0413] 10, 10b~10d-liquid crystal diffraction element, 11-total reflection surface, 30-support body, 32-alignment film, 34-cholesteric liquid crystal layer, 34R, 34Rb-cholesteric liquid crystal layer reflecting right-handed circularly polarized light, 34L, 34Lb-cholesteric liquid crystal layer reflecting left-handed circularly polarized light, 40-liquid crystal compound, 40A-optical axis, 60-exposure device, 62-laser, 64-light source, 65-λ / 2 plate , 68-beam splitter, 70A, 70B-reflecting mirror, 72A, 72B-λ / 4 plate, 100, 100b, 100c-optical element, 102-prism, 102a-first surface, 102b-second surface, 102c-third surface, 104-reflection layer, 110-lens, 112-sensor, 150, 150b-spectrometric system, 200-cholesteric liquid crystal layer, I0-light of the spectroscopic object, I R0 - right-handed circularly polarized light component of the light of the spectral object, I L0 - the left-handed circularly polarized light component of the light to be split, I1, I2, I3 - the light to be split, I R1 ,I R2 ,I R3 -Split right circularly polarized light, I L1 ,I L2 ,I L3 -Split left-handed circularly polarized light, Λ-1 period, D-arrangement axis, R R - right-handed circularly polarized light, M-laser beam, MA, MB-light, P O -Linearly polarized light, P R -Right-handed circularly polarized light, P L -Left-hand circularly polarized light, α-crossing angle.

Claims

1. A spectroscopic system comprising an optical element, wherein: The optical element comprises a prism and a liquid crystal diffraction element disposed on a first surface of the prism directly or via another layer. The prism has a second surface inclined relative to the first surface, The inclination angle of the second surface relative to the first surface is 4° or more, The liquid crystal diffraction element has a cholesteric liquid crystal layer formed by fixing a cholesteric liquid crystal phase. The cholesteric liquid crystal layer has a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating in at least one direction in the plane. When the length of the direction of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern rotated by 180° is defined as one period, the length of the one period is 0.1 to 1.4 μm, The spectroscopic system allows the light of the spectroscopic object to be incident from the side of the liquid crystal diffraction element, and uses the liquid crystal diffraction element to reflect the incident light, so that the reflected light is totally reflected on the surface of the liquid crystal diffraction element on the side opposite to the prism side, and the totally reflected light is incident on the prism, and the spectroscopic light is emitted from the second surface.

2. The optical spectrometer according to claim 1, wherein: The liquid crystal diffraction element includes the cholesteric liquid crystal layer having helical structures with twisting directions different from each other.

3. The optical spectrometer system according to claim 1, wherein: The second surface of the prism has an inclination angle of 4° to 5° with respect to the first surface.

4. The optical splitting system according to claim 3, wherein: When the wavelength of the light to be split is λ, the wavelength λ and one period Λ of the liquid crystal alignment pattern satisfy the relationship of formula (1): Formula (1) 0.44≤λ / Λ≤1.51.

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