Optical element and lighting device including the optical element

Abstract

This optical element comprises a first liquid crystal cell, a second liquid crystal cell, a third liquid crystal cell, and a fourth liquid crystal cell, which are disposed in order so as to overlap each other. The first, second, third, and fourth liquid crystal cells each include a plurality of first electrodes arranged like stripes and extending in a first extension direction, a first orientation film located on the plurality of first electrodes, a liquid crystal layer located on the first orientation film, a second orientation film located on the liquid crystal layer, and a plurality of second electrodes located on the second orientation film, arranged like stripes, extending in a second extension direction, and intersecting the plurality of first electrodes. Further detailed structures are described in the description.

Description

Technical Field

[0001] One embodiment of the present invention relates to an optical element and a lighting device including the optical element. For example, one embodiment of the present invention relates to a lighting device including a light source and an optical element capable of arbitrarily controlling the irradiation area of light from the light source.

Background Art

[0002] In recent years, lighting devices have been developed that can control the irradiation area and irradiation distance of a light source by controlling the light emitted from the light source using an optical element including liquid crystal. For example, Patent Document 1 discloses an optical element having a liquid crystal layer and a pair of comb-shaped electrodes. By forming a potential difference between the pair of comb-shaped electrodes, the alignment of liquid crystal molecules in the liquid crystal layer changes, and a refractive index distribution is formed in the liquid crystal layer. By appropriately controlling this refractive index distribution, the liquid crystal layer functions as a lens.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] One embodiment of the present invention aims to provide an optical element capable of changing the light distribution state of light incident from a light source, and a lighting device including the optical element. Alternatively, one embodiment of the present invention aims to provide an optical element capable of changing the light distribution state while suppressing the coloration of the emitted light as much as possible, and a lighting device including the optical element.

Means for Solving the Problems

[0005] One embodiment of the present invention is an optical element including a first liquid crystal cell, a second liquid crystal cell, a third liquid crystal cell, and a fourth liquid crystal cell arranged in order so as to overlap each other. Each of the first liquid crystal cell, the second liquid crystal cell, the third liquid crystal cell, and the fourth liquid crystal cell is arranged in a stripe shape and includes a plurality of first electrodes extending in a first stretching direction, a first alignment film on the plurality of first electrodes, a liquid crystal layer on the first alignment film, a second alignment film on the liquid crystal layer, and a plurality of second electrodes located on the second alignment film and arranged in a stripe shape and extending in a second stretching direction intersecting the first stretching direction. In each of the first liquid crystal cell, the second liquid crystal cell, the third liquid crystal cell, and the fourth liquid crystal cell, the first alignment film and the second alignment film are configured such that in a situation where no voltage is applied to the plurality of first electrodes and the plurality of second electrodes, the liquid crystal molecules contained in the liquid crystal layer are oriented in a first alignment direction and a second alignment direction intersecting each other, respectively. The angle between the first stretching direction and the first alignment direction is within 10°, and the angle between the second stretching direction and the second alignment direction is within 10°. The first stretching direction of the first liquid crystal cell forms an angle of 0° or more and 10° or less with respect to the first stretching direction of the second liquid crystal cell, and forms an angle of 80° or more and 90° or less with respect to the first stretching direction of the third liquid crystal cell and the fourth liquid crystal cell.

[0006] One embodiment of the present invention is an optical element including a first liquid crystal cell, a second liquid crystal cell, a third liquid crystal cell, and a fourth liquid crystal cell arranged in order so as to overlap each other. Each of the first liquid crystal cell, the second liquid crystal cell, the third liquid crystal cell, and the fourth liquid crystal cell is arranged in a stripe shape and includes a plurality of first electrodes extending in a first stretching direction, a first alignment film on the plurality of first electrodes, a liquid crystal layer on the first alignment film, a second alignment film on the liquid crystal layer, and a plurality of second electrodes located on the second alignment film and arranged in a stripe shape and extending in a second stretching direction intersecting the first stretching direction. In each of the first liquid crystal cell, the second liquid crystal cell, the third liquid crystal cell, and the fourth liquid crystal cell, the first alignment film and the second alignment film are configured to orient liquid crystal molecules contained in the liquid crystal layer in a first alignment direction and a second alignment direction intersecting each other in a situation where no voltage is applied to the plurality of first electrodes and the plurality of second electrodes. In at least one of the first liquid crystal cell, the second liquid crystal cell, the third liquid crystal cell, and the fourth liquid crystal cell, the angle between the first stretching direction and the first alignment direction is within 10°, and the angle between the second stretching direction and the second alignment direction is within 10°. In the liquid crystal cells other than the at least one liquid crystal cell, the angle between the first stretching direction and the first alignment direction is 80° or more and 90° or less, and the angle between the second stretching direction and the second alignment direction is 80° or more and 90° or less.

Brief Description of Drawings

[0007]

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Embodiments for Carrying Out the Invention

[0008] Hereinafter, each embodiment of the present invention will be described with reference to the drawings and the like. However, the present invention can be implemented in various forms without departing from the gist thereof, and is not to be construed as being limited to the description of the embodiments exemplified below.

[0009] For the sake of clearer explanation, the drawings may schematically represent the width, thickness, shape, etc. of each part as compared with the actual aspect, but this is merely an example and does not limit the interpretation of the present invention. In this specification and each figure, elements having the same functions as those described with respect to the previously shown figures may be denoted by the same reference numerals, and redundant explanations may be omitted. This reference numeral is used when collectively representing the same or similar plurality of structures, and a hyphen and a natural number are added after the reference numeral when individually representing them.

[0010] In this specification and the claims, when expressing the aspect of arranging one structure on another structure, when simply described as "on", unless otherwise specified, it includes both the case of arranging another structure directly on one structure in contact therewith and the case of arranging another structure above one structure via yet another structure.

[0011] In this specification and the claims, the expression "a certain structure is exposed from another structure" means an aspect in which a part of a certain structure is not covered by another structure, and the portion not covered by this other structure also includes an aspect in which it is covered by yet another structure. Further, the aspect represented by this expression also includes an aspect in which a certain structure is not in contact with another structure.

[0012] <First Embodiment> In this embodiment, a lighting device 100 including an optical element 110, which is one of the embodiments of the present invention, will be described.

[0013] 1. Overall Structure FIG. 1 shows a schematic exploded perspective view of the lighting device 100. As shown in FIG. 1, the lighting device 100 basically includes a light source 102 and an optical element 110 that overlaps the light source 102. The light source 102 is configured to irradiate light onto the optical element 110 and includes one or more light-emitting elements (not shown). Examples of the light-emitting elements include organic or inorganic light-emitting diodes (LEDs). An organic LED is a light-emitting element in which a light-emitting organic compound is sandwiched between a pair of electrodes, and an inorganic LED is a light-emitting element in which an inorganic light-emitting material such as aluminum gallium arsenide, gallium arsenide phosphide, indium gallium nitride, gallium nitride, aluminum gallium nitride, or gallium phosphide is sandwiched between a pair of electrodes. The light source 102 is preferably configured such that collimated light with relatively high directivity irradiates the optical element 110.

[0014] The optical element 110 includes a plurality of liquid crystal cells 120 that overlap the light source 102 and overlap each other. There is no restriction on the number of the plurality of liquid crystal cells 120, but it is preferable that two, four, or more liquid crystal cells 120 are included in one optical element 110. Adjacent liquid crystal cells 120 are bonded together by a light-transmissive adhesive layer (not shown in FIG. 1). Although details will be described later, each liquid crystal cell 120 is composed of a pair of substrates and structures such as electrodes and a liquid crystal layer provided therebetween, and has a function of diffusing light from the light source 102. Hereinafter, the main surface formed by the substrate is defined as the xy plane, and the direction perpendicular to the xy plane is defined as the z direction. Therefore, the optical element 110 overlaps the light source 102 in the z direction, and the plurality of liquid crystal cells 120 also overlap each other in the z direction. In the following description, a mode in which the first liquid crystal cell 120-1, the second liquid crystal cell 120-2, the third liquid crystal cell 120-3, and the fourth liquid crystal cell 120-4 are arranged in this order from the light source 102 side will be used for explanation.

[0015] 2. Liquid Crystal Cell FIG. 2A and FIG. 2B show schematic top views of the liquid crystal cell 120 as seen from the light source 102 side. In FIG. 2A, the counter substrate 124 among the pair of substrates (substrate 122 and counter substrate 124) is omitted. FIG. 3A and FIG. 3B are schematic views of end faces along the chain lines A-A' and B-B' in FIGS. 2A and 2B, respectively.

[0016] As can be understood from these figures, each liquid crystal cell 120 includes a plurality of first electrodes 130 provided on the substrate 122, a first alignment film 140 on the plurality of first electrodes 130, a liquid crystal layer 128 on the first alignment film 140, a second alignment film 142 on the liquid crystal layer 128, a plurality of second electrodes 132 on the second alignment film 142, and a counter substrate 124 on the plurality of second electrodes 132.

[0017] (1) Substrate and counter substrate The substrate 122 and the counter substrate 124 are joined to each other via a sealing material 126 provided in a frame shape, and each functions as a base material for supporting a plurality of first electrodes 130 and a plurality of second electrodes 132, and seals the liquid crystal layer 128. The substrate 122 and the counter substrate 124 preferably include a material having a high transmittance to the light from the light emitting element 114 in order to transmit the light from the light source 102 and exhibit an illumination function. Therefore, for example, it is preferable to configure the substrate 122 and the counter substrate 124 to include glass, quartz, or a polymer material such as polyimide, polycarbonate, polyester, or acrylic resin. The substrate 122 and the counter substrate 124 may be configured to have a strength that does not deform due to an external force, or may be configured to elastically deform. As shown in FIG. 1, the substrate 122 and the counter substrate 124 may be joined such that a part of the main surface of the substrate 122 is exposed from the counter substrate 124 toward the light source 102 side, and a part of the main surface of the counter substrate 124 is exposed from the substrate 122 to the side opposite to the light source 102.

[0018] (2) First electrode and second electrode As shown in FIGS. 3A and 3B, a plurality of first electrodes 130 are provided on the substrate 122 so as to be in contact with the substrate 122 or via an undercoat (not shown). The undercoat can be formed by one or more films containing a silicon-containing inorganic compound such as silicon nitride or silicon oxide. In order to impart high light transmittance to the liquid crystal cell 120, the first electrode 130 is preferably formed of a conductive oxide that exhibits a high transmittance to visible light, such as indium-tin oxide (ITO) or indium-zinc oxide (IZO). Alternatively, the first electrode 130 may be constituted by a mesh-shaped metal thin film having a plurality of openings so that light from the light source 102 can pass through. As understood from FIG. 2A, the plurality of first electrodes 130 extend in the same direction as each other and are arranged in a stripe shape. The length of each first electrode 130 (the length in the extending direction of the first electrode 130) depends on the size of the optical element 110, but may be selected, for example, from the range of 5 cm or more and 15 cm or less, or 1 cm or more and 10 cm or less. The interval between two adjacent first electrodes 130 may be selected, for example, from the range of 1 μm or more and 30 μm, or 3 μm or more and 20 μm.

[0019] Similarly, a plurality of second electrodes 132 are also provided directly on the counter substrate 124 (under the counter substrate 124 in FIGS. 3A and 3B; the same applies hereinafter) or via an undercoat. In order to impart high light transmittance to the liquid crystal cell 120, the second electrode 132 is also preferably formed of a conductive oxide that exhibits a high transmittance to visible light, such as ITO or IZO, or is constituted by a mesh-shaped metal thin film having a plurality of openings. As shown from FIG. 2A to FIG. 3B, the plurality of second electrodes 132 also extend in the same direction as each other and are arranged in a stripe shape. The length of each second electrode 132 (the length in the extending direction of the second electrode 132) may also be selected from the range of 5 cm or more and 15 cm or less, or 1 cm or more and 10 cm or less. Also, the interval between two adjacent second electrodes 132 may be selected, for example, from the range of 1 μm or more and 30 μm, or 3 μm or more and 20 μm.

[0020] Here, the plurality of first electrodes 130 and the second electrodes 132 are provided so as to intersect each other. The extending direction of the first electrode 130 and the extending direction of the second electrode 132 may be perpendicular to each other, but it is preferable that these directions are not completely perpendicular. For example, the angle formed by the extending direction of the first electrode 130 and the extending direction of the second electrode 132 may be set in the range of 80° or more and less than 90°. In this way, by shifting the extending direction of the second electrode 132 from perpendicular to the extending direction of the first electrode 130, the interference of light by the first electrode 130 and the second electrode 132 can be suppressed, and the problems of unintended coloring or mottling occurring in the light from the light source 102 can be prevented.

[0021] A pulsed alternating voltage (alternating rectangular wave) is applied to the plurality of first electrodes 130. However, the alternating voltage is applied so that the phase is reversed between two adjacent first electrodes 130. Similarly, a pulsed alternating voltage is also applied to the plurality of second electrodes 132 so that the phase is reversed between two adjacent second electrodes 132. Further, the first electrode 130 and the second electrode 132 are configured so as to be driven independently. Therefore, it is also possible to apply an alternating voltage only to the first electrode 130 and not apply a voltage or supply a constant voltage to the second electrode 132, and vice versa.

[0022] As shown in FIG. 3A, every other one of the plurality of first electrodes 130 is connected to a first wiring 134-1, and the remaining first electrodes 130 are also connected to a second wiring 134-2 different from the first wiring 134-1 (see FIG. 2A). The first wiring 134-1 and the second wiring 134-2 are respectively exposed from the opposing substrate 124 on the substrate 122 to form terminals 136-1 and 136-2. An AC voltage is applied from an external circuit (not shown) via these terminals 136-1 and 136-2. Similarly, every other one of the plurality of second electrodes 132 is connected to a third wiring 134-3, and the remaining second electrodes 132 are also connected to a fourth wiring 134-4 different from the third wiring 134-3 (FIG. 3B). The third wiring 134-3 and the fourth wiring 134-4 are exposed from the substrate 122 on the opposing substrate 124 to form terminals 136-3 and 136-4 respectively, and an AC voltage is applied from an external circuit (not shown) via these terminals 136-3 and 136-4. With such a configuration, the plurality of first electrodes 130 on the substrate 122 side and the plurality of second electrodes 132 on the opposing substrate 124 side can be driven independently. Furthermore, the first liquid crystal cell 120-1 to the fourth liquid crystal cell 120-4 can also be driven independently of each other.

[0023] (3) Liquid crystal layer, first alignment film, and second alignment film The liquid crystal layer 128 contains liquid crystal molecules. The structure of the liquid crystal molecules is not limited. Therefore, the liquid crystal molecules may be nematic liquid crystals or smectic liquid crystals. As the liquid crystal molecules, positive liquid crystals in which the dielectric constant in the major axis direction is larger than the dielectric constant in the direction perpendicular to the major axis are used. The liquid crystal layer 128 is sealed in a space formed by the substrate 122, the opposing substrate 124, and the sealing material 126 so as to be sandwiched between the first alignment film 140 and the second alignment film 142.

[0024] The thickness of the liquid crystal layer 128, that is, the distance between the first alignment film 140 and the second alignment film 142 is also arbitrary, but it is preferably larger than the pitch of the first electrode 130 and the second electrode 132. For example, the thickness of the liquid crystal layer 128 is preferably set to be 2 times or more and 10 times or less, 2 times or more and 5 times or less, or 2 times or more and 3 times or less with respect to the pitch of the first electrode 130 or the second electrode 132. Specifically, the thickness of the liquid crystal layer 128 may be selected from the range of, for example, 10 μm or more and 60 μm or less, or 10 μm or more and 50 μm or less. Although not shown, spacers for maintaining this thickness over the entire liquid crystal cell 120 may be provided in the liquid crystal layer 128. Note that when the thickness of the liquid crystal layer 128 described above is adopted in the liquid crystal display device, high responsiveness required for displaying a moving image cannot be obtained, and it becomes difficult to exhibit the functions as a liquid crystal display device.

[0025] The first alignment film 140 and the second alignment film 142 contain polymers such as polyimide and polyester, and sandwich the liquid crystal layer 128. The first alignment film 140 is configured to align the liquid crystal molecules contained in the liquid crystal layer 128 in a certain direction in a situation where no potential difference occurs between adjacent first electrodes 130. Similarly, the second alignment film 142 is also configured to align the liquid crystal molecules contained in the liquid crystal layer 128 in a certain direction in a situation where no potential difference occurs between adjacent second electrodes 132. Hereinafter, the direction in which the first alignment film 140 and the second alignment film 142 align the liquid crystal molecules in the non-electric field state is referred to as the alignment direction. The alignment direction may be imparted, for example, by a rubbing process. Alternatively, the alignment direction may be imparted to the first alignment film 140 and the second alignment film 142 by photo-alignment. Photo-alignment is a rubbing-free alignment process using light. For example, polarized light in the ultraviolet region is irradiated onto an alignment film that has not been rubbed from a predetermined direction. This causes a photoreaction in the alignment film, introduces anisotropy on the surface of the alignment film, and imparts liquid crystal alignment control ability.

[0026] Here, as shown in FIG. 4, the first alignment film 140 and the second alignment film 142 are configured such that their alignment directions are orthogonal to each other, or the angle formed therebetween is 80° or more and 90° or less (see white arrows 144 and 146 in FIG. 4).

[0027] On the one hand, as shown in FIG. 5A, the plurality of first electrodes 130 and the first alignment film 140 may be arranged such that the stretching direction of the plurality of first electrodes 130 and the alignment direction of the first alignment film 140 (see the white arrow 144) are parallel to each other. As shown in FIG. 5B, they may be arranged such that the stretching direction of the plurality of first electrodes 130 is inclined from the alignment direction of the first alignment film 140. In the latter case, the angle formed by the stretching direction of the plurality of first electrodes 130 and the alignment direction of the first alignment film 140 may be selected from the range greater than 0° and less than or equal to 10°, greater than or equal to 1° and less than or equal to 5°, or greater than or equal to 1° and less than or equal to 3°. Since the stretching direction of the plurality of first electrodes 130 is inclined from the alignment direction of the first alignment film 140, the direction in which the liquid crystal molecules twist when a horizontal electric field is generated can be fixed. Therefore, the responsiveness of the liquid crystal molecules is improved, and the disturbance of the refractive index distribution of the liquid crystal layer 128 caused by the variation in the rotation direction of the liquid crystal molecules can be prevented.

[0028] Although not shown, the relationship between the plurality of second electrodes 132 and the second alignment film 142 is the same. That is, the plurality of second electrodes 132 and the second alignment film 142 may be arranged such that the stretching direction of the plurality of second electrodes 132 is parallel to the alignment direction of the second alignment film 142, or may be arranged such that the stretching direction of the plurality of second electrodes 132 is inclined from the alignment direction of the second alignment film 142 within the range greater than 0° and less than or equal to 10°, greater than or equal to 1° and less than or equal to 5°, or greater than or equal to 1° and less than or equal to 3°. As described above, due to the inclination between the stretching direction of the plurality of second electrodes 132 and the alignment direction of the second alignment film 142, the responsiveness of the liquid crystal molecules is improved, and the refractive index distribution of the liquid crystal layer 128 can be precisely controlled. Incidentally, when the angle formed by the stretching direction of the electrode and the alignment direction of the alignment film covering the electrode is in the relationship of 0° to 10° or less, it may be referred to as "the stretching direction of the electrode and the alignment direction of the alignment film are aligned".

[0029] Here, the extending direction of each first electrode 130, when the entire first electrode 130 has a linear shape, is the direction from the intersection with the first wiring or the second wiring to the tip of the first electrode 130. However, as shown in FIG. 5C, each first electrode 130 can have a bent structure including a plurality of straight portions. In this case, a plurality of first electrodes 130 are arranged such that the extending direction of at least one straight portion is inclined within a range greater than 0° and equal to or less than 10°, greater than or equal to 1° and less than or equal to 5°, or greater than or equal to 1° and less than or equal to 3° from the alignment direction of the first alignment film 140. The same applies to the second electrode 132. That is, the extending direction of each second electrode 132, when the entire second electrode 132 has a linear shape, is the direction from the intersection with the third wiring or the fourth wiring to the tip of the second electrode 132. Although not shown, each second electrode 132 can also have a bent structure including a plurality of straight portions. In this case, a plurality of second electrodes 132 are arranged such that the extending direction of at least one straight portion is inclined within a range greater than 0° and equal to or less than 10°, greater than or equal to 1° and less than or equal to 5°, or greater than or equal to 1° and less than or equal to 3° from the alignment direction of the second alignment film 142. In this way, in each of the plurality of first electrodes 130 and the plurality of second electrodes 132, by forming one or more straight portions inclined from the alignment direction of the first alignment film 140 or the second alignment film 142, the rotation direction of the liquid crystal molecules can be regulated, and the refractive index distribution can be precisely controlled.

[0030] In each liquid crystal cell 120, in order to more precisely regulate the rotation direction of the liquid crystal molecules, it is preferable to configure all or at least one of the first electrodes 130 to have a linear side (side 130a in FIG. 6) inclined from the alignment direction of the first alignment film 140 at the tip. In other words, it is preferable to configure all or at least one of the first electrodes 130 such that the tip has an acute angle. By configuring each first electrode 130 in this way, when a potential difference is applied between adjacent first electrodes 130, it is possible to avoid the direction of the lateral electric field becoming perpendicular to the alignment direction of the first alignment film 140 at the tip portion, so that the rotation direction of the liquid crystal can be regulated. The same applies to the second electrode 132.

[0031] 3. Arrangement of a plurality of liquid crystal cells in an optical element The arrangement of the first liquid crystal cell 120-1 to the fourth liquid crystal cell 120-4 in the present embodiment will be described with reference to the schematic end view of FIG. 7. In the following description, the x direction and the y direction in which the extending directions of the first electrode 130 and the second electrode 132, and the alignment directions of the first alignment film 140 and the second alignment film 142 are orthogonal to each other will be used. However, as described above, in each liquid crystal cell 120, the extending direction of the first electrode 130 and the alignment direction of the first alignment film 140 may be parallel or inclined with respect to each other. Similarly, in each liquid crystal cell 120, the extending direction of the second electrode 132 and the alignment direction of the second alignment film 142 may be parallel or inclined with respect to each other. Further, in each liquid crystal cell 120, the alignment directions of the first alignment film 140 and the second alignment film 142 may be orthogonal or may intersect so as to deviate from perpendicularity. Therefore, when referring to one direction in the following description, it includes not only the direction parallel to the said direction, but also the direction inclined within the range of more than 0° and 10° or less, more than 1° and 5° or less, or more than 1° and 3° or less. Also, the direction orthogonal to one direction includes not only the direction perpendicular to the said direction, but also the direction intersecting at an angle of more than 80° and less than 90°, more than 85° and less than 89°, or more than 87° and less than 89°. Similarly, the direction parallel to one direction includes not only the direction parallel to the said direction, but also the direction inclined at an angle within the range of more than 0° and 10° or less, more than 1° and 5° or less, or more than 1° and 3° or less from the said direction.

[0032] As shown in FIG. 7, in the optical element 110, the first liquid crystal cell 120-1 to the fourth liquid crystal cell 120-4 having the same structure are arranged so as to overlap each other, and adjacent liquid crystal cells 120 are joined by an adhesive layer 160 that transmits visible light.

[0033] The first liquid crystal cell 120-1 and the second liquid crystal cell 120-2 have the same arrangement. Specifically, in both the first liquid crystal cell 120-1 and the second liquid crystal cell 120-2, a plurality of first electrodes 130 extend in one direction (here, the y direction), and a plurality of second electrodes 132 extend in a direction intersecting with the said direction (here, the x direction). Therefore, in each of the first liquid crystal cell 120-1 and the second liquid crystal cell 120-2, the alignment directions of the first alignment film 140 and the second alignment film 142 are the y direction and the x direction, respectively. In other words, in each of the first liquid crystal cell 120-1 and the second liquid crystal cell 120-2, the extending directions of the plurality of first electrodes 130 and the plurality of second electrodes 132 are orthogonal to each other and parallel to the alignment directions of the first alignment film 140 and the second alignment film 142, respectively.

[0034] On the other hand, although the third liquid crystal cell 120-3 and the fourth liquid crystal cell 120-4 have the same arrangement as each other, they have an arrangement different from that of the first liquid crystal cell 120-1 or the second liquid crystal cell 120-2. Specifically, in both the third liquid crystal cell 120-3 and the fourth liquid crystal cell 120-4, a plurality of first electrodes 130 extend in the x direction, and a plurality of second electrodes 132 extend in the y direction. Therefore, in each of the third liquid crystal cell 120-3 and the fourth liquid crystal cell 120-4, the alignment directions of the first alignment film 140 and the second alignment film 142 are the x direction and the y direction, respectively. Also in each of the third liquid crystal cell 120-3 and the fourth liquid crystal cell 120-4, the extending directions of the plurality of first electrodes 130 and the plurality of second electrodes 132 are orthogonal to each other and parallel to the alignment directions of the first alignment film 140 and the second alignment film 142, respectively.

[0035] Note that the stretching direction of the first electrode 130 of the first liquid crystal cell 120-1 may be completely parallel to the stretching direction of the first electrode 130 of the second liquid crystal cell 120-2, but the angle formed by these directions may be greater than 0° and 10° or less, 1° or more and 5° or less, or 1° or more and 3° or less. Similarly, the stretching direction of the second electrode 132 of the first liquid crystal cell 120-1 may be completely parallel to the stretching direction of the second electrode 132 of the second liquid crystal cell 120-2, but the angle formed by these directions may be greater than 0° and 10° or less, 1° or more and 5° or less, or 1° or more and 3° or less. Further, the stretching direction of the second electrode 132 of the first liquid crystal cell 120-1 may be completely perpendicular to the stretching direction of the first electrode 130 of the second liquid crystal cell 120-2, but the angle formed by these directions may be 80° or more and less than 90°, 85° or more and 89° or less, or 87° or more and 89° or less. Similarly, the stretching direction of the first electrode 130 of the first liquid crystal cell 120-1 may be completely perpendicular to the stretching direction of the second electrode 132 of the second liquid crystal cell 120-2, but the angle formed by these directions may be 80° or more and less than 90°, 85° or more and 89° or less, or 87° or more and 89° or less. Therefore, between the first liquid crystal cell 120-1 and the second liquid crystal cell 120-2, the stretching directions of the first electrode 130 and the second electrode 132 may be shifted from each other within the xy plane. By forming such a shift, light interference can be suppressed, and the occurrence of uneven illuminance can be prevented. Similar relationships may be established for the stretching directions of the first electrode 130 and the second electrode 132 between the second liquid crystal cell 120-2 and the third liquid crystal cell 120-3, and between the third liquid crystal cell 120-3 and the fourth liquid crystal cell 120-4.

[0036] 4. Light distribution control by optical elements (1) Light diffusion in each liquid crystal cell The above-described optical element 110 diffuses the light emitted from the light source 102 in a certain direction. Therefore, by individually driving the plurality of liquid crystal cells 120, the light from the light source 102 can be changed into an arbitrary shape, and as a result, the light distribution of the lighting device 100 can be controlled to arbitrarily control the shape of the region (hereinafter, irradiation region) where the lighting device 100 irradiates the object. Here, the principle of light diffusion in one liquid crystal cell 120 will be described.

[0037] A. When not driven Schematic end views showing the state of a liquid crystal cell 120 when not driven are shown in FIGS. 8A and 8B. FIG. 8A is a schematic end view seen from the y direction, and FIG. 8B is a schematic end view seen from the x direction. In the following figures, the liquid crystal molecules are represented by white ellipses or circles.

[0038] When the liquid crystal cell 120 is not driven, it means that no voltage is applied to the plurality of first electrodes 130 and the plurality of second electrodes 132, or a constant voltage is applied. In this case, no transverse electric field is generated between the plurality of first electrodes 130 or between the plurality of second electrodes 132. When not driven, since there is no electric field, the liquid crystal molecules are aligned according to the alignment directions of the first alignment film 140 and the second alignment film 142. For this reason, the liquid crystal molecules are aligned along the alignment direction (here, the y direction) of the first alignment film 140 near the substrate 122, and as they approach the counter substrate 124, they rotate about the z direction as the central axis and are twisted by 90°. As a result, when the light emitted from the light source 102 passes through the liquid crystal layer from one substrate to the other substrate, although the polarization component rotates along the twisted state of the liquid crystal molecules (this phenomenon is called optical rotation), since the liquid crystal molecules do not produce a refractive index distribution, phenomena such as diffusion do not occur. Thereby, the shape of the light emitted from the light source 102 is reflected in the shape of the irradiation region. Also, when the light source 102 emits collimated light with relatively high directivity, a relatively narrow region can be selectively irradiated.

[0039] B. When driven One mode during the driving of the liquid crystal cell 120 is a mode in which a pulsed alternating voltage is applied to the plurality of first electrodes 130 and the plurality of second electrodes 132 such that the phases are inverted between adjacent first electrodes 130 and between adjacent second electrodes 132. Within each liquid crystal cell 120, the frequency of the alternating voltage is the same. The alternating voltage may be selected, for example, from the range of 3V or more and 50V or less, or 3V or more and 30V or less. Since the extending directions of the first electrode 130 and the second electrode 132 are orthogonal or intersect in the range of 80° or more and less than 90°, 85° or more and 89° or less, or 87° or more and 89° or less, by applying the alternating voltage, a transverse electric field that is orthogonal to each other or intersects in the range of 80° or more and less than 90° is generated between adjacent first electrodes 130 and between adjacent second electrodes 132. An electric field (longitudinal electric field) is also generated between the first electrode 130 and the second electrode 132, but the thickness of the liquid crystal layer 128 is large compared to the intervals between adjacent first electrodes 130 and between adjacent second electrodes 132. Therefore, the longitudinal electric field is significantly smaller than the transverse electric field and can be ignored, so each liquid crystal molecule is oriented according to the transverse electric field.

[0040] When a horizontal electric field is generated in the liquid crystal layer 128, the liquid crystal molecules on the side of the first electrode 130 are oriented in the direction of the horizontal electric field and are oriented in an upwardly convex arc shape between adjacent first electrodes 130 (FIG. 9A). The same applies to the side of the second electrode 132, and the liquid crystal molecules are oriented in the direction of the horizontal electric field and are oriented in a downwardly convex arc shape between adjacent second electrodes 132 (FIG. 9B). Such a change in the orientation of the liquid crystal molecules causes a refractive index distribution in the liquid crystal layer 128. As a result, as shown in FIG. 10, among the light incident from the counter substrate 124 of the liquid crystal cell 120 into the liquid crystal layer 128, the component (polarization component) 152 parallel to the horizontal electric field formed by the second electrode 132 diffuses, and the other polarization component 154 is transmitted. Here, by driving the liquid crystal cell 120 to form an electric field between adjacent first electrodes 130 and to form an electric field between adjacent second electrodes 132, the liquid crystal molecules near each substrate rotate along the direction of the electric field (for example, in a direction orthogonal to the orientation direction at the time of non-driving). As a result, the alignment state realized at the time of non-driving, that is, the twisted state in which the direction of the liquid crystal molecules gradually rotates as the direction from the substrate 122 to the counter substrate 124 is seen from the z direction, collapses, and both polarization components 152 and 154 do not rotate even when passing through the liquid crystal layer 128. Therefore, the polarization components 152 and 154 are affected by the refractive index distribution of the liquid crystal molecules aligned in the direction matching the direction of each polarization component while maintaining the polarization direction before and after passing through the first liquid crystal cell 120-1. More specifically, the polarization component 152 in the y direction is affected by the refractive index distribution of the liquid crystal molecules on the side of the counter substrate 124 and diffuses in the y direction, but does not change the polarization axis in the x direction. Also, the polarization component 154 in the x direction is affected by the refractive index distribution of the liquid crystal molecules on the side of the substrate 122 and diffuses in the x direction, but does not change the polarization axis in the y direction.

[0041] In another aspect during the driving of the liquid crystal cell 120, a pulsed AC voltage is applied to one of the plurality of first electrodes 130 and the plurality of second electrodes 132, and no voltage or a constant voltage is applied to the other. Even in this case, the AC voltage is applied so that the phase is reversed between adjacent first electrodes 130 or between adjacent second electrodes 132. For example, when a pulsed AC voltage is applied to the plurality of first electrodes 130, on the substrate 122 side, the liquid crystal molecules are oriented in the direction of the horizontal electric field and are oriented in a convex arc shape between adjacent first electrodes 130 (FIG. 11), and a refractive index distribution is generated in the liquid crystal layer 128. Therefore, as shown in FIG. 11, the light incident on the liquid crystal layer 128 from the counter substrate 124 of the liquid crystal cell 120 is not diffused by the liquid crystal layer 128 on the second electrode 132 side. However, due to the refractive index distribution formed in the liquid crystal layer 128 on the first electrode 130 side, the polarization component 154 parallel to the direction of the horizontal electric field on the first electrode 130 side is selectively diffused, and the other polarization component 152 is not diffused. At this time, in the liquid crystal layer 128 on the second electrode 132 side, the orientation during non-driving is maintained and the liquid crystal molecules are oriented in the y direction. Also, on the first electrode 130 side, the liquid crystal molecules take an upwardly convex orientation state along the y direction which is the direction of the horizontal electric field. As a result, the twisted state of the liquid crystal molecules during non-driving is eliminated, and both polarization components 152 and 154 do not rotate even when passing through the liquid crystal layer 128. Therefore, in this aspect, it is possible to selectively diffuse only the polarization component 154 while maintaining the polarization directions of both polarization components 152 and 154.

[0042] Although detailed description is omitted, the same applies when no voltage is applied to the plurality of first electrodes 130 or a constant voltage is applied while a pulsed AC voltage is applied to the plurality of second electrodes 132. In this case, one component of the incident light (here, the polarization component 152) is selectively diffused by the liquid crystal layer 128 on the second electrode 132 side, and the other polarization component 154 is not diffused. Also, both polarization components 152 and 154 do not rotate. Thus, the liquid crystal cell 120 can selectively diffuse one polarization component while maintaining the polarization directions of both polarization components 152 and 154 by forming a horizontal electric field on one of the plurality of first electrodes 130 and the plurality of second electrodes 132.

[0043] The stretching directions of the first electrode 130 and the second electrode 132, the alignment directions of the first alignment film 140 and the second alignment film 142, and the effects of the presence or absence of driving of the first electrode 130 and the second electrode 132 on the light from the light source 102 incident from the counter substrate 124 side are summarized in Table 1. As shown in Table 1, by appropriately selecting the arrangement of the liquid crystal cell 120 (that is, the stretching directions of the first electrode 130 and the second electrode 132, or the alignment directions of the first alignment film 140 and the second alignment film 142) and the presence or absence of driving of the first electrode 130 and the second electrode 132, the two polarization components can be diffused independently, or the two polarization components can be simultaneously optically rotated. [Table 1]

[0044] (2) Light distribution control by the optical element As described above, the first liquid crystal cell 120-1 to the fourth liquid crystal cell 120-4 can be driven independently, and further, in each liquid crystal cell 120, a plurality of first electrodes 130 and a plurality of second electrodes 132 can be driven independently. Therefore, in the optical element 110 according to the present embodiment, by appropriately driving a plurality of first electrodes 130 and a plurality of second electrodes 132 of the first liquid crystal cell 120-1 to the fourth liquid crystal cell 120-4, the light from the light source 102 can be changed into an arbitrary shape.

[0045] For example, as shown in FIG. 7, assume a case where light from the light source 102 is irradiated from the side of the first liquid crystal cell 120-1 of the optical element 110 and light is extracted from the fourth liquid crystal cell 120-4. At this time, each liquid crystal cell 120 is driven as shown in Table 2. That is, the first electrode 130 and the second electrode 132 of all the liquid crystal cells 120 are driven. In this case, as shown in Table 2, the polarization component in the y direction of the incident light is diffused in the y direction a total of 4 times, once by each of the four liquid crystal cells 120. Similarly, the polarization component in the x direction is also diffused in the x direction a total of 4 times. Therefore, incident light that gives a circular irradiation region can be changed to light that gives a cross-shaped irradiation region. Also, by diffusing each polarization component a large number of times (for example, at least 3 times), the spectral state is scattered accordingly, so that coloring of the light can be prevented. Note that the lengths in the x direction and y direction of the cross shape can be adjusted by appropriately adjusting the AC voltage applied to the first electrode 130 and the second electrode 132. Note that the hyphens in Table 2 mean that the incident light is transmitted without being diffused or optically rotated (the same applies to the following tables) unless otherwise noted.

Table 2

[0046] Alternatively, a part of the four liquid crystal cells 120 may be driven. For example, as shown in Table 3, the first electrodes 130 and the second electrodes 132 of the first liquid crystal cell 120-1, the second liquid crystal cell 120-2, and the fourth liquid crystal cell 120-4 are driven, and the first electrode 130 and the second electrode 132 of the third liquid crystal cell are not driven. In this case, the polarization component in the y direction of the incident light is diffused in the y direction, the y direction, and the x direction by the first liquid crystal cell 120-1, the second liquid crystal cell 120-2, and the fourth liquid crystal cell 120-4, respectively, and the polarization component in the x direction of the incident light is diffused in the x direction, the x direction, and the y direction by the first liquid crystal cell 120-1, the second liquid crystal cell 120-2, and the fourth liquid crystal cell 120-4, respectively. As a result, the irradiation area can be greatly expanded while maintaining the shape of the irradiation area of the light source 102. Further, by diffusing each polarization component a plurality of times (for example, three or more times), coloring of the light can be prevented.

Table 3

[0047] Alternatively, a part of the four liquid crystal cells 120 may be driven as shown in Table 4. In this example, the second electrodes 132 of the first liquid crystal cell 120-1 and the second liquid crystal cell 120-2, and the first electrode 130 of the fourth liquid crystal cell 120-4 are driven. In this case, the polarization component in the y direction of the incident light is diffused in the y direction by the first liquid crystal cell 120-1 and the second liquid crystal cell 120-2, and the polarization component in the x direction of the incident light is diffused in the y direction by the fourth liquid crystal cell 120-4. As a result, the incident light that gives a circular irradiation area can be changed to light that gives a line-shaped irradiation area extended in the y direction.

Table 4

[0048] Alternatively, a part of the four liquid crystal cells 120 may be driven as shown in Table 5. In this example, the first electrodes 130 of the first liquid crystal cell 120-1 and the second liquid crystal cell 120-2, and the second electrode 132 of the fourth liquid crystal cell 120-4 are driven. In this case, the polarization component in the y direction of the incident light is optically rotated by the third liquid crystal cell 120-3 to become an x-polarized component, and further diffused in the x direction by the fourth liquid crystal cell 120-4. On the other hand, the polarization component in the x direction of the incident light is diffused in the x direction by the first liquid crystal cell 120-1 and the second liquid crystal cell 120-2, and further optically rotated by the third liquid crystal cell 120-3 to give a polarization component in the y direction. As a result, the incident light that gives a circular irradiation region can be changed to light that gives a line-shaped irradiation region extended in the x direction. [Table 5]

[0049] As described above, in the lighting device 100 according to the present embodiment, it is possible to change the light incident from the light source 102 into light that gives an irradiation region of an arbitrary shape by the optical element 110. Further, since each polarization component of the incident light can be diffused a plurality of times (for example, three or more times), it is possible to prevent the coloring of the light with a changed light distribution, and the color of the light from the light source 102 can be reproduced. Thus, in the lighting device 100, it is possible to achieve advanced light distribution control without light coloring.

[0050] <Second Embodiment> In this embodiment, an optical element 112 having a structure different from that of the optical element 110 will be described. The description of the configurations that are the same as or similar to those described in the first embodiment may be omitted.

[0051] 1. Structure of Optical Element and Light Distribution Control As described in the first embodiment, the first liquid crystal cell 120-1 to the fourth liquid crystal cell 120-4 included in the optical element 110 have the same structure as each other. Also, in each liquid crystal cell 120, the stretching direction of the plurality of first electrodes 130 and the alignment direction of the first alignment film 140 are parallel or form an angle of 0° or more and 10° or less, and the stretching direction of the plurality of second electrodes 132 and the alignment direction of the second alignment film 142 are also parallel or form an angle of 0° or more and 10° or less.

[0052] On the other hand, among the first liquid crystal cell 120-1 to the fourth liquid crystal cell 120-4 included in the optical element 112, at least one liquid crystal cell has the same configuration as the liquid crystal cell 120 described in the first embodiment, while the others have different structures. As will be described later, in the liquid crystal cell with a different structure, both polarization components of the incident light are optically rotated regardless of whether the optical element 112 is driven or not. Therefore, hereinafter, this liquid crystal cell with a different structure is also referred to as a optically rotatory liquid crystal cell.

[0053] More specifically, as shown in FIG. 12, in the optically rotatory liquid crystal cell 121, the stretching direction of the plurality of first electrodes 130 and the alignment direction of the first alignment film 140 are perpendicular to each other or form an angle of 80° or more and 90° or less, and the stretching direction of the plurality of second electrodes 132 and the alignment direction of the second alignment film 142 are also perpendicular to each other or form an angle of 80° or more and 90° or less (see arrows 148 and 150 in FIG. 12). Similar to the liquid crystal cell 120, in the optically rotatory liquid crystal cell 121, the stretching direction of the first electrode 130 and the stretching direction of the second electrode 132 are perpendicular to each other or form an angle of 80° or more and 90° or less, and the alignment films of the first alignment film 140 and the second alignment film 142 are also perpendicular to each other or form an angle of 80° or more and 90° or less. Note that when the angle formed by the stretching direction of the electrode and the alignment direction of the alignment film covering the electrode is greater than 10°, more preferably, when these angles are in the relationship of 80° to 90°, it may be referred to as "the stretching direction of the electrode intersects with the alignment direction of the alignment film".

[0054] In the optically active liquid crystal cell 121, when not driven, as shown in FIG. 13A, since the liquid crystal molecules are aligned according to the alignment directions of the first alignment film 140 and the second alignment film 142, the alignment direction of the liquid crystal molecules is the alignment direction of the first alignment film 140 (here, the x direction) near the substrate 122, and as it approaches the counter substrate 124, it rotates about the z direction as the central axis, and twists by the difference in the alignment directions between these alignment films (for example, 90° if the alignment directions of both alignment films are orthogonal). As a result, the light emitted from the light source 102 only rotates optically without diffusing when the liquid crystal cell 120 is not driven, so the shape of the light emitted from the light source 102 is reflected in the shape of the irradiation region. Also, when the light source 102 emits collimated light with relatively high directivity, a relatively narrow region can be selectively irradiated.

[0055] On the other hand, for example, when an alternating voltage is applied to the plurality of first electrodes 130 and the plurality of second electrodes 132 to drive the optically active liquid crystal cell 121, similar to the liquid crystal cell 120, the liquid crystal molecules on the first electrode 130 side and the second electrode 132 side are aligned along the direction of the transverse electric field, and are aligned in an arc shape convex upward and convex downward between the first electrodes 130 and between the second electrodes 132, respectively (FIG. 13B). However, at this time, since the liquid crystal molecules hardly rotate in the xy plane, the alignment direction in the xy plane does not change. For this reason, the twist about the z direction of the liquid crystal molecules is maintained. Therefore, among the light incident from the counter substrate 124 to the liquid crystal layer 128 of the liquid crystal cell 120, the polarization component parallel to the transverse electric field formed by the second electrode 132 diffuses in the liquid crystal layer 128 on the second electrode 132 side, then rotates optically in the liquid crystal layer 128, and further diffuses in the liquid crystal layer 128 on the first electrode 130 side. Thus, in the optically active liquid crystal cell 121, diffusion and optical rotation occur simultaneously during driving. Similar to the liquid crystal cell 120, it is also possible to selectively diffuse only one polarization component in one direction by applying an alternating voltage to only one of the first electrode 130 and the second electrode 132. Also, even when an alternating voltage is applied to only one of the first electrode 130 and the second electrode 132, the twist about the z direction of the liquid crystal molecules is maintained, so both polarization components rotate optically.

[0056] There is no restriction on the number of liquid crystal cells 120 included in the optical element 112. For example, as shown in FIG. 14, the third liquid crystal cell 120-3 is a optically active liquid crystal cell 121, and the others may be liquid crystal cells 120. In this case, the stretching direction of the first electrode 130 of the first liquid crystal cell 120-1 forms an angle of 0° or more and 10° or less with respect to the stretching direction of the first electrode 130 of the second liquid crystal cell 120-2, and forms an angle of 80° or more and 90° or less with respect to the stretching direction of the first electrodes 130 of the third liquid crystal cell 120-3 and the fourth liquid crystal cell 120-4. The first liquid crystal cell 120-1 to the fourth liquid crystal cell 120-4 may be arranged accordingly. Note that not only the third liquid crystal cell, but also a configuration in which any one or two of the first liquid crystal cell 120-1, the second liquid crystal cell 120-2, and the fourth liquid crystal cell 120-4 are optically active liquid crystal cells can also be adopted.

[0057] Such a driving method for the optical element 112 may be appropriately determined, and the light from the light source 102 can be changed into various shapes by selecting the driving method. For example, the light from the light source 102 is incident on the optical element 112 from the side of the first liquid crystal cell 120-1, and the optical element 112 is driven as shown in Table 6. That is, the first electrodes 130 and the second electrodes 132 of the first liquid crystal cell 120-1 and the second liquid crystal cell 120-2, and the second electrodes 132 of the third liquid crystal cell 120-3 which is the optically active liquid crystal cell 121 are driven. In this case, the polarization component in the y direction of the incident light is diffused in the y direction without being optically rotated by the first liquid crystal cell 120-1 and the second liquid crystal cell 120-2, and then is optically rotated twice by the third liquid crystal cell 120-3 and the fourth liquid crystal cell 120-4 which function as the optically active liquid crystal cell 121 and returns to the polarization component in the y direction. On the other hand, the polarization component in the x direction is diffused a total of three times in the x direction by the first liquid crystal cell 120-1, the second liquid crystal cell 120-2, and the third liquid crystal cell 120-3 which functions as the optically active liquid crystal cell 121, and is optically rotated twice by the third liquid crystal cell 120-3 and the fourth liquid crystal cell 120-4 and returns to the polarization component in the x direction. Thus, since the polarization components in the x direction and the y direction can be diffused a plurality of times in the x direction and the y direction respectively, the incident light giving a circular irradiation region can be changed into the light giving a cross-shaped irradiation region. Also, since any polarization component is diffused a large number of times (the polarization component in the x direction is at least three times), the coloring of the light can be effectively suppressed.

Table 6

[0058] Alternatively, as shown in Table 7, all of the four liquid crystal cells 120 may be driven. That is, the first electrodes 130 and the second electrodes 132 of all the liquid crystal cells 120 including the third liquid crystal cell 120-3 that functions as the optically active liquid crystal cell 121 may be driven. By such driving, among the incident light, the polarization component in the y direction is diffused in the y direction, the y direction, and the x direction without being optically rotated by the first liquid crystal cell 120-1, the second liquid crystal cell 120-2, and the fourth liquid crystal cell 120-4, respectively, and is optically rotated by the third liquid crystal cell 120-3 (i.e., the optically active liquid crystal cell 121) to become a polarization component in the x direction. On the other hand, the polarization component in the x direction is diffused in the x direction by the first liquid crystal cell 120-1, the second liquid crystal cell 120-2, and the third liquid crystal cell 120-3, is optically rotated by the third liquid crystal cell 120-3, and is further diffused in the y direction by the third liquid crystal cell 120-3 and the fourth liquid crystal cell 120-4. As a result, the incident light can be diffused in the x direction and the y direction while maintaining the circular irradiation region. Also, since any polarization component is diffused a number of times (at least three times), coloring of the light can be effectively suppressed.

Table 7

[0059] Alternatively, the optical element 112 may be driven as shown in Table 8. That is, the second electrodes 132 of the first liquid crystal cell 120-1 and the second liquid crystal cell 120-2 may be driven, and the first electrodes 130 of the third liquid crystal cell 120-3 and the fourth liquid crystal cell 120-4 may be driven. In this case, among the incident light, the polarization component in the y direction is diffused in the y direction without being optically rotated by the first liquid crystal cell 120-1 and the second liquid crystal cell 120-2, and is optically rotated by the third liquid crystal cell 120-3 (i.e., the optically active liquid crystal cell 121) to become a polarization component in the x direction. On the other hand, the polarization component in the x direction is diffused in the y direction by the third liquid crystal cell 120-3 and the fourth liquid crystal cell 120-4, and is optically rotated by the third liquid crystal cell 120-3 to change to a polarization component in the y direction. As a result, the light that gives a circular irradiation region can be changed to light that gives a line-shaped irradiation region in which the incident light is extended in the y direction.

Table 8

[0060] Alternatively, the optical element 112 may be driven as shown in Table 9. That is, the first electrodes 130 of the first liquid crystal cell 120-1 and the second liquid crystal cell 120-2 may be driven, and the second electrodes 132 of the third liquid crystal cell 120-3 and the fourth liquid crystal cell 120-4 may be driven. In this case, the polarization component in the y direction of the incident light diffuses in the x direction without being optically rotated by the fourth liquid crystal cell 120-4, and is optically rotated by the third liquid crystal cell 120-3 (i.e., the optically rotatable liquid crystal cell 121) to become a polarization component in the x direction. On the other hand, the polarization component in the x direction is diffused in the x direction by the first liquid crystal cell 120-1 and the second liquid crystal cell 120-2, diffuses in the x direction by the third liquid crystal cell 120-3, and is optically rotated to change into light having a y component. As a result, the incident light that gives a circular irradiation region can be changed into light that gives a line-shaped irradiation region extended in the x direction. Further, since at least one polarization component (the polarization component in the x direction) is also diffused a plurality of times (at least three times), coloring of the light can be effectively suppressed.

Table 9

[0061] 2. Modification Example 1 The above-described optical element 112 includes three liquid crystal cells 120 and one optically rotatable liquid crystal cell 121, but the structure of the optical element 112 is not limited thereto, and it may include a plurality of optically rotatable liquid crystal cells 121. For example, as shown in FIG. 15, the first liquid crystal cell 120-1 and the second liquid crystal cell 120-2 may be optically rotatable liquid crystal cells 121. In this case, the extending direction of the first electrode 130 of the first liquid crystal cell 120-1 forms an angle of 0° or more and 10° or less with the extending direction of the first electrode 130 of the second liquid crystal cell 120-2, and forms an angle of 80° or more and 90° or less with the extending direction of the first electrode 130 of the third liquid crystal cell 120-3 and the fourth liquid crystal cell 120-4. The first liquid crystal cell 120-1 to the fourth liquid crystal cell 120-4 may be arranged.

[0062] The driving method of the optical element 112 according to the first modification example is also arbitrary, but for example, it may be driven as shown in Table 10. That is, the second electrode 132 of the first liquid crystal cell 120-1, the first electrode 130 of the second liquid crystal cell 120-2, and the first electrodes 130 and second electrodes 132 of the third liquid crystal cell 120-3 and the fourth liquid crystal cell 120-4 may be driven. In this case, the polarization component in the y direction of the incident light is diffused in the y direction by the first liquid crystal cell 120-1, the third liquid crystal cell 120-3, and the fourth liquid crystal cell 120-4, and further rotates twice by the first liquid crystal cell 120-1 and the second liquid crystal cell 120-2, so that a polarization component in the y direction diffused three times in the y direction is given. On the other hand, the polarization component in the x direction is diffused in the x direction by the second liquid crystal cell 120-2, the third liquid crystal cell 120-3, and the fourth liquid crystal cell 120-4, and rotates twice by the first liquid crystal cell 120-1 and the second liquid crystal cell 120-2, so that a polarization component in the x direction diffused three times in the x direction is given. As a result, incident light giving a circular irradiation region can be changed to light giving a cross-shaped irradiation region. Also, since both polarization components are diffused a large number of times (at least three times), coloring of light can be effectively suppressed.

Table 10

[0063] 3. Second Modification Example When using the optically active liquid crystal cell 121 as the first liquid crystal cell 120-1 and the second liquid crystal cell 120-2 as in the first modification example, as shown in FIG. 16, the stretching direction of the first electrode 130 of the first liquid crystal cell 120-1 forms an angle of 0° or more and 10° or less with respect to the stretching direction of the first electrode 130 of the third liquid crystal cell 120-3, and 80° or more and 90° or less with respect to the stretching direction of the first electrode 130 of the second liquid crystal cell 120-2 and the fourth liquid crystal cell 120-4, the first liquid crystal cell 120-1 to the fourth liquid crystal cell 120-4 may be arranged.

[0064] The driving method of the optical element 112 according to the second modification example is also arbitrary. For example, as shown in Table 11, a driving method similar to that of the first modification example may be adopted. That is, the second electrode 132 of the first liquid crystal cell 120-1, the first electrode 130 of the second liquid crystal cell 120-2, and the first electrodes 130 and second electrodes 132 of the third liquid crystal cell 120-3 and the fourth liquid crystal cell 120-4 may be driven. In this case, the polarization component in the y direction of the incident light is diffused in the y direction from the first liquid crystal cell 120-1 to the fourth liquid crystal cell 120-4, and further undergoes two rotations of the polarized light by the first liquid crystal cell 120-1 and the second liquid crystal cell 120-2, so that a polarization component in the y direction diffused four times in the y direction is given. On the other hand, the polarization component in the x direction is diffused in the x direction by the third liquid crystal cell 120-3 and the fourth liquid crystal cell 120-4, and undergoes two rotations of the polarized light by the first liquid crystal cell 120-1 and the second liquid crystal cell 120-2, so that a polarization component in the x direction diffused twice in the x direction is given. As a result, the incident light giving a circular irradiation region can be changed to light giving a cross-shaped irradiation region. Further, since at least one of the polarization components is diffused a large number of times (at least three times), the coloring of the light can be effectively suppressed.

Table 11

[0065] 4. Third Modification Example When using two optically active liquid crystal cells 121 as in the first and second modification examples, as shown in FIG. 17, the optically active liquid crystal cells 121 may be used as the first liquid crystal cell 120-1 and the third liquid crystal cell 120-3. In this case, for example, the stretching direction of the first electrode 130 of the first liquid crystal cell 120-1 forms an angle of 0° or more and 10° or less with the stretching direction of the first electrode 130 of the second liquid crystal cell 120-2, and forms an angle of 80° or more and 90° or less with the stretching direction of the first electrode 130 of the third liquid crystal cell 120-3 and the fourth liquid crystal cell 120-4. The first liquid crystal cell 120-1 to the fourth liquid crystal cell 120-4 may be arranged.

[0066] The driving method of the optical element 112 according to this Modification 3 is also arbitrary. For example, as shown in Table 12, the optical element 112 may be driven. That is, the second electrodes 132 of the first liquid crystal cell 120-1 and the third liquid crystal cell 120-3 may be driven, and the other electrodes may not be driven. In this case, the polarization component in the y direction of the incident light is diffused in the y direction by the first liquid crystal cell 120-1, and further undergoes four rotations of light by the fourth liquid crystal cell 120-4 from the first liquid crystal cell 120-1, so that a polarization component in the y direction diffused once in the y direction is given. On the other hand, the polarization component in the x direction is diffused in the x direction by the third liquid crystal cell 120-3 and undergoes four rotations of light by the fourth liquid crystal cell 120-4 from the first liquid crystal cell 120-1, so that a polarization component in the x direction diffused once in the x direction is given. As a result, the incident light giving a circular irradiation region can be changed to light giving a cross-shaped irradiation region.

Table 12

[0067] 5. Modification 4 When using two optically active liquid crystal cells 121 as in Modifications 1 to 3, as shown in FIG. 18, the optically active liquid crystal cells 121 may be used as the first liquid crystal cell 120-1 and the fourth liquid crystal cell 120-4. In this case, for example, the stretching direction of the first electrode 130 of the first liquid crystal cell 120-1 forms an angle of 0° or more and 10° or less with respect to the stretching direction of the first electrode 130 of the second liquid crystal cell 120-2, and 80° or more and 90° or less with respect to the stretching direction of the first electrode 130 of the third liquid crystal cell 120-3 and the fourth liquid crystal cell 120-4. The first liquid crystal cell 120-1 to the fourth liquid crystal cell 120-4 may be arranged.

[0068] The driving method of the optical element 112 according to this Modification Example 4 is also arbitrary. For example, as shown in Table 13, the optical element 112 may be driven. That is, the first electrode 130 of the third liquid crystal cell 120-3 and the second electrodes 132 of the first liquid crystal cell 120-1, the third liquid crystal cell 120-3, and the fourth liquid crystal cell 120-4 may be driven, and the other electrodes may not be driven. In this case, the polarization component in the y direction of the incident light diffuses in the y direction by the first liquid crystal cell 120-1 and the third liquid crystal cell 120-3, and undergoes three rotations of light by the first liquid crystal cell 120-1, the second liquid crystal cell 120-2, and the fourth liquid crystal cell 120-4, so that a polarization component in the x direction that has diffused twice in the y direction is provided. On the other hand, the polarization component in the x direction diffuses in the x direction by the third liquid crystal cell 120-3 and the fourth liquid crystal cell 120-4, and undergoes three rotations of light by the first liquid crystal cell 120-1, the second liquid crystal cell 120-2, and the fourth liquid crystal cell 120-4, so that a polarization component in the y direction that has diffused twice in the x direction is provided. As a result, the incident light that provides a circular irradiation region can be changed to light that provides a cross-shaped irradiation region.

Table 13

[0069] 6. Modification Example 5 When using the optically active liquid crystal cell 121 as the first liquid crystal cell 120-1 and the fourth liquid crystal cell 120-4 as in Modification Example 4, as shown in FIG. 19, the stretching direction of the first electrode 130 of the first liquid crystal cell 120-1 forms an angle of 0° or more and 10° or less with respect to the stretching direction of the first electrodes 130 of the second liquid crystal cell 120-2, the third liquid crystal cell 120-3, and the fourth liquid crystal cell 120-4. The fourth liquid crystal cell 120-4 may be arranged.

[0070] The driving method of the optical element 112 according to the fifth modification example is also arbitrary. For example, as shown in Table 14, a driving method similar to that of the fourth modification example may be adopted. That is, the first electrode 130 of the third liquid crystal cell 120-3 and the second electrodes 132 of the first liquid crystal cell 120-1, the third liquid crystal cell 120-3, and the fourth liquid crystal cell 120-4 may be driven, and other electrodes may not be driven. In this case, the polarization component in the y direction of the incident light is diffused in the y direction by the first liquid crystal cell 120-1, the third liquid crystal cell 120-3, and the fourth liquid crystal cell 120-4, and is circularly polarized three times by the first liquid crystal cell 120-1, the second liquid crystal cell 120-2, and the fourth liquid crystal cell 120-4. Therefore, a polarization component in the x direction diffused three times in the y direction is given. On the other hand, the polarization component in the x direction is diffused in the x direction by the third liquid crystal cell 120-3 and is circularly polarized three times by the first liquid crystal cell 120-1, the second liquid crystal cell 120-2, and the fourth liquid crystal cell 120-4. Therefore, a polarization component in the y direction diffused once in the x direction is given. As a result, the incident light giving a circular irradiation region can be changed to light giving a cross-shaped irradiation region. In addition, since at least one of the polarization components is diffused a large number of times (at least three times), coloring of the light can be effectively suppressed.

Table 14

[0071] As described above, by using the optical elements 110 and 112 according to the embodiments of the present invention, the light from the light source 102 can be changed to light giving an arbitrary irradiation region. In addition, by appropriately selecting the structures and arrangements of the plurality of liquid crystal cells 120 in the optical elements 110 and 112, coloring of the light with a changed light distribution can be suppressed. Therefore, the lighting device 100 including the optical elements 110 and 112 according to the embodiments of the present invention can function as a lighting device capable of giving various irradiation regions.

[0072] As long as the embodiments described above as embodiments of the present invention do not conflict with each other, they can be implemented in appropriate combinations. Further, based on the display device of each embodiment, those in which a person skilled in the art appropriately adds, deletes, or changes the design of components, or adds, omits, or changes conditions of processes, are also included in the scope of the present invention as long as they have the gist of the present invention.

[0073] Even if there are other effects different from the effects brought about by the aspects of the above-described embodiments, those that are obvious from the description of this specification or can be easily predicted by a person skilled in the art are naturally understood to be brought about by the present invention.

Description of Reference Numerals

[0074] 100: Lighting device, 102: Light source, 110: Optical element, 112: Optical element, 114: Light-emitting element, 120: Liquid crystal cell, 120-1: First liquid crystal cell, 120-2: Second liquid crystal cell, 120-3: Third liquid crystal cell, 120-4: Fourth liquid crystal cell, 121: Twisted nematic liquid crystal cell, 122: Substrate, 124: Counter substrate, 126: Sealing material, 128: Liquid crystal layer, 130: First electrode, 130a: Side, 132: Second electrode, 134-1: First wiring, 134-2: Second wiring, 134-3: Third wiring, 134-4: Fourth wiring, 136-1: Terminal, 136-2: Terminal, 136-3: Terminal, 136-4: Terminal, 140: First alignment film, 142: Second alignment film, 144: Arrow, 146: Arrow, 148: Arrow, 150: Arrow, 152: Polarization component, 154: Polarization component, 160: Adhesive layer

Claims

1. A first liquid crystal cell, a second liquid crystal cell, a third liquid crystal cell, and a fourth liquid crystal cell are provided and arranged in order so as to overlap each other. Each of the first liquid crystal cell, the second liquid crystal cell, the third liquid crystal cell, and the fourth liquid crystal cell has a plurality of first electrodes arranged in a stripe shape and extending in a first stretching direction, a first alignment film on the plurality of first electrodes, a liquid crystal layer on the first alignment film, a second alignment film on the liquid crystal layer, and a plurality of second electrodes which are located on the second alignment film, arranged in a stripe shape, and extend in a second stretching direction intersecting the first stretching direction. In each of the first liquid crystal cell, the second liquid crystal cell, the third liquid crystal cell, and the fourth liquid crystal cell, the first alignment film and the second alignment film are configured such that, in a situation where no voltage is applied to the plurality of first electrodes and the plurality of second electrodes, the liquid crystal molecules contained in the liquid crystal layer are oriented in a first alignment direction and a second alignment direction intersecting each other, respectively. The angle between the first stretching direction and the first alignment direction is within 10°. The angle between the second stretching direction and the second alignment direction is within 10°. The first stretching direction of the first liquid crystal cell forms an angle of 0° or more and 10° or less with respect to the first stretching direction of the second liquid crystal cell, and forms an angle of 80° or more and 90° or less with respect to the first stretching direction of the third liquid crystal cell and the fourth liquid crystal cell. An optical element.

2. In each of the first liquid crystal cell, the second liquid crystal cell, the third liquid crystal cell, and the fourth liquid crystal cell, the plurality of first electrodes are configured such that a first alternating voltage is applied so as to have an opposite phase between adjacent first electrodes. The plurality of second electrodes are configured such that a second alternating voltage is applied so as to have an opposite phase between adjacent second electrodes. The optical element according to claim 1.

3. In at least one of the first liquid crystal cell, the second liquid crystal cell, the third liquid crystal cell, and the fourth liquid crystal cell, each of the plurality of first electrodes and the plurality of second electrodes is bent so as to have a plurality of straight portions. The optical element according to claim 1.

4. In each of the plurality of first electrodes, at least one stretching direction of the plurality of straight portions is inclined from the first alignment direction. The optical element according to claim 3, wherein in each of the plurality of second electrodes, at least one extending direction of the plurality of straight portions is inclined from the second alignment direction.

5. In at least one of the first liquid crystal cell, the second liquid crystal cell, the third liquid crystal cell, and the fourth liquid crystal cell, at least one tip of the plurality of first electrodes has an acute angle, The optical element according to claim 1, wherein at least one tip of the plurality of second electrodes has an acute angle.

6. The optical element according to claim 1, and An illumination device including a light source located above the optical element and disposed on the first liquid crystal cell side.

7. Comprising a first liquid crystal cell, a second liquid crystal cell, a third liquid crystal cell, and a fourth liquid crystal cell arranged in order to overlap each other, Each of the first liquid crystal cell, the second liquid crystal cell, the third liquid crystal cell, and the fourth liquid crystal cell, A plurality of first electrodes arranged in a stripe pattern and extending in a first extending direction, A first alignment film on the plurality of first electrodes, A liquid crystal layer on the first alignment film, A second alignment film on the liquid crystal layer, and Located on the second alignment film, arranged in a stripe pattern, and having a plurality of second electrodes extending in a second extending direction intersecting the first extending direction, In each of the first liquid crystal cell, the second liquid crystal cell, the third liquid crystal cell, and the fourth liquid crystal cell, The first alignment film and the second alignment film are configured to align the liquid crystal molecules contained in the liquid crystal layer in a first alignment direction and a second alignment direction intersecting each other in a situation where no voltage is applied to the plurality of first electrodes and the plurality of second electrodes, In at least one liquid crystal cell of the first liquid crystal cell, the second liquid crystal cell, the third liquid crystal cell, and the fourth liquid crystal cell, The angle between the first extending direction and the first alignment direction is within 10°, The angle between the second extending direction and the second alignment direction is within 10°, In the liquid crystal cells other than the at least one liquid crystal cell, The angle between the first extending direction and the first alignment direction is 80° or more and 90° or less, An optical element in which the angle between the second extending direction and the second alignment direction is 80° or more and 90° or less.

8. The at least one liquid crystal cell includes the first liquid crystal cell, the second liquid crystal cell, and the third liquid crystal cell, The first stretching direction of the first liquid crystal cell forms an angle of 0° or more and 10° or less with respect to the first stretching direction of the second liquid crystal cell, and forms an angle of 80° or more and 90° or less with respect to the first stretching direction of the third liquid crystal cell and the fourth liquid crystal cell. The optical element according to claim 7.

9. The at least one liquid crystal cell includes the third liquid crystal cell and the fourth liquid crystal cell. The first stretching direction of the first liquid crystal cell forms an angle of 0° or more and 10° or less with respect to the first stretching direction of the second liquid crystal cell, and forms an angle of 80° or more and 90° or less with respect to the first stretching direction of the third liquid crystal cell and the fourth liquid crystal cell. The optical element according to claim 7.

10. The at least one liquid crystal cell includes the third liquid crystal cell and the fourth liquid crystal cell. The first stretching direction of the first liquid crystal cell forms an angle of 0° or more and 10° or less with respect to the first stretching direction of the third liquid crystal cell, and forms an angle of 80° or more and 90° or less with respect to the first stretching direction of the second liquid crystal cell and the fourth liquid crystal cell. The optical element according to claim 7.

11. The at least one liquid crystal cell includes the second liquid crystal cell and the fourth liquid crystal cell. The first stretching direction of the first liquid crystal cell forms an angle of 0° or more and 10° or less with respect to the first stretching direction of the second liquid crystal cell, and forms an angle of 80° or more and 90° or less with respect to the first stretching direction of the third liquid crystal cell and the fourth liquid crystal cell. The optical element according to claim 7.

12. The at least one liquid crystal cell includes the second liquid crystal cell and the third liquid crystal cell. The first stretching direction of the first liquid crystal cell forms an angle of 0° or more and 10° or less with respect to the first stretching direction of the second liquid crystal cell, and forms an angle of 80° or more and 90° or less with respect to the first stretching direction of the third liquid crystal cell and the fourth liquid crystal cell. The optical element according to claim 7.

13. The at least one liquid crystal cell includes the second liquid crystal cell and the third liquid crystal cell. The first stretching direction of the first liquid crystal cell forms an angle of 0° or more and 10° or less with respect to the first stretching directions of the second liquid crystal cell, the third liquid crystal cell, and the fourth liquid crystal cell. The optical element according to claim 7.

14. In each of the first liquid crystal cell, the second liquid crystal cell, the third liquid crystal cell, and the fourth liquid crystal cell The plurality of first electrodes are configured such that a first alternating voltage is applied so as to have opposite phases between adjacent first electrodes. The plurality of second electrodes are configured such that a second alternating voltage is applied so as to have opposite phases between adjacent second electrodes. The optical element according to claim 7.

15. In at least one of the first liquid crystal cell, the second liquid crystal cell, the third liquid crystal cell, and the fourth liquid crystal cell, Each of the plurality of first electrodes and the plurality of second electrodes is bent so as to have a plurality of straight portions. The optical element according to claim 7.

16. In each of the plurality of first ones, at least one extending direction of the plurality of straight portions is inclined from the first alignment direction. In each of the plurality of second ones, at least one extending direction of the plurality of straight portions is inclined from the second alignment direction. The optical element according to claim 15.

17. In at least one of the first liquid crystal cell, the second liquid crystal cell, the third liquid crystal cell, and the fourth liquid crystal cell, At least one of the plurality of first electrodes has an acute tip. At least one of the plurality of second electrodes has an acute tip. The optical element according to claim 7.

18. The optical element according to claim 7, and An illumination device including a light source located above the optical element and disposed on the first liquid crystal cell side.

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