Lighting equipment

Abstract

To realize a lighting device which is thin, has a small orientation angle, and achieves low leakage of light, and to realize a lighting device which enables easy control of a light beam.SOLUTION: In a lighting device, LEDs 40 are disposed on side surfaces of a light guide plate 23 and a prism sheet 24 is disposed on a major surface of the light guide plate 23. A first louver 50 extending a first direction and a second louver 60 extending in a direction perpendicular to the first direction are laminated on the prism sheet 24. Further, a liquid crystal lens is disposed on the second louver as necessary.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a lighting device that is thin, has a small light distribution angle, and can reduce light leakage to the surrounding area. [Background technology]

[0002] There is a demand for projecting collimated light onto each seat in an airplane or train. In addition, in automobiles and the like, there are cases where it is desired to emit light at a different angle depending on the purpose. On the other hand, there are cases where it is desired to emit light from a light source at a different angle. In such cases, there are various means, such as changing the angle of the light source, placing a reflector on the light emitted from the light source to change the emission angle, or placing a lens on the light emitted from the light source to change the emission angle.

[0003] There is also a demand for changing the light distribution characteristics of the emitted light by placing a lens on the exit surface of the lighting device. In such cases, the focal length can be easily changed by using a liquid crystal lens. In addition, the function of a liquid crystal lens can be flexibly changed according to the application.

[0004] Patent Document 1 describes a configuration in which a refracting means for changing the angle of emitted light is placed on a direct light source, and describes the use of a lens, a prism, a liquid lens, a liquid crystal lens, or the like as the refracting means.

[0005] Patent Document 2 describes a configuration in which a liquid crystal lens is used in various optical devices. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2012-069409 [Patent Document 2] WO2012 / 099127 A1 Summary of the Invention [Problem to be solved by the invention]

[0007] For example, when a lighting device is used as a spotlight, a light source with high directivity, i.e., a small light distribution angle, is required. Conventionally, such light sources have been configured to form parallel light using a parabolic mirror. However, such light sources require depth, and it is difficult to make the light source itself small or thin.

[0008] On the other hand, when a thin lighting device is used, it is difficult to reduce the light distribution angle, and there is also a problem that light leakage having a very large emission angle occurs.

[0009] An object of the present invention is to realize a lighting device that is thin, has a small light distribution angle, and has little light leakage. Another object of the present invention is to realize a lighting device that has a liquid crystal lens disposed on the exit surface and can accurately control the exit light by the liquid crystal lens. [Means for solving the problem]

[0010] The present invention is intended to solve the above problems, and the main specific means are as follows.

[0011] (1) A lighting device having LEDs arranged on a side of a light guide plate and a prism sheet arranged on a main surface of the light guide plate, characterized in that a first louver extending in a first direction and a second louver extending perpendicular to the first direction are stacked on top of the prism sheet.

[0012] (2) The lighting device according to (1), further comprising a liquid crystal lens disposed on the prism sheet.

[0013] (3) A lighting device comprising LEDs arranged on a side of a light guide plate and a prism sheet arranged on a main surface of the light guide plate, characterized in that a first louver extending in a first direction and a second louver extending perpendicular to the first direction are formed on the prism sheet so as to intersect on the same plane.

[0014] (4) A lighting device comprising an LED arranged on a side of a light guide plate and a prism sheet arranged on a main surface of the light guide plate, characterized in that a louver having a honeycomb structure when viewed in a plane is arranged on top of the prism sheet. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a plan view showing an illumination device that irradiates collimated light using a parabolic mirror. [Diagram 2] XX cross-sectional view of FIG. [Diagram 3] FIG. 2 is an exploded perspective view of a side light type lighting device. [Figure 4] FIG. [Diagram 5] 4 is a graph showing the light distribution characteristics of the lighting device of FIG. 3. [Figure 6] FIG. 2 is an exploded perspective view of the lighting device according to the first embodiment. [Figure 7] 7 is a graph showing the light distribution characteristics of the lighting device of FIG. 6. [Figure 8] FIG. 2 is a plan view of the first louver and the second louver. [Figure 9] FIG. [Figure 10] FIG. 11 is a cross-sectional view of another example louver. [Figure 11] 13 is a cross-sectional view of a louver according to yet another example. [Figure 12] FIG. 2 is a perspective view of an integrated cross louver. [Figure 13] FIG. 2 is a side view of an integrated cross louver. [Figure 14] FIG. 13 is a perspective view of another example integrated cross louver. [Figure 15] FIG. 13 is a side view of another example integrated cross louver. [Figure 16] FIG. 2 is a plan view of the first louver and the second louver in which no transparent resin is present. [Figure 17] 17 is a cross-sectional view taken along CC in FIG. 16. [Figure 18]FIG. 2 is a perspective view of a lattice-shaped cross louver. [Figure 19] FIG. 2 is a plan view of a cross louver having a honeycomb structure. [Figure 20] FIG. 4 is a detailed view of the prism sheet. [Figure 21] 3 shows an example of the arrangement of first and second louvers in the first embodiment. [Figure 22] FIG. 11 is an exploded perspective view of the lighting device according to the second embodiment. [Diagram 23] 13 is a configuration example of a convex lens made of a liquid crystal lens. [Figure 24] FIG. 1 is a perspective view of a two-piece liquid crystal lens. [Diagram 25] 13 is a configuration example of a concave lens made of a liquid crystal lens. [Figure 26] This is an example of deflecting a light beam using a liquid crystal lens. [Figure 27] Another example of deflecting a light beam by a liquid crystal lens. [Figure 28] 1 is a cross-sectional view of a liquid crystal lens according to a first example. [Figure 29] 3 is a plan view of a first electrode and a second electrode of a liquid crystal lens according to a first example. FIG. [Diagram 30] FIG. 4 is a cross-sectional view of a liquid crystal lens according to a second example. [Diagram 31] 11 is a plan view of a first electrode and a second electrode of a liquid crystal lens according to a second example. FIG. [Diagram 32] FIG. 11 is a cross-sectional view of a liquid crystal lens according to a third example. [Diagram 33] FIG. 11 is a plan view of a first electrode and a second electrode of a liquid crystal lens according to a third example. [Diagram 34] FIG. 11 is a cross-sectional view of a liquid crystal lens according to a fourth example. [Diagram 35] FIG. 11 is a plan view of a first electrode and a second electrode of a liquid crystal lens according to a fourth example. [Diagram 36] FIG. 11 is a cross-sectional view showing the use of two liquid crystal lenses. [Figure 37] FIG. 11 is a cross-sectional view showing the use of four liquid crystal lenses. [Figure 38]1 is a cross-sectional view of a liquid crystal lens configured using one liquid crystal lens and one polarizing plate. [Figure 39] 2 is a perspective view showing the arrangement of a first electrode and a second electrode in a liquid crystal lens. FIG. [Diagram 40] 23 is a plan view of the lighting device of FIG. 22, showing only the LED array and the first electrode and the second electrode of the liquid crystal lens. [Diagram 41] 23 is a plan view of another example of the lighting device of FIG. 22, in which only the LED array and the first electrode and the second electrode of the liquid crystal lens are extracted. [Diagram 42] 23 is a plan view of still another example of the lighting device of FIG. 22, in which only the LED array and the first and second electrodes of two pairs of liquid crystal lenses are extracted. FIG. [Diagram 43] FIG. 2 is a plan view showing a state in which the liquid crystal lens is divided in a plane. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] 1 and 2 are examples of an illumination device 2000 used in a spotlight that emits collimated light. In order to obtain such collimated light, a so-called parabolic mirror 1 as shown in FIG. 1 and FIG. 2 has been used conventionally. FIG. 1 is a plan view of an illumination device 2000 using a parabolic mirror 1, and FIG. 2 is a cross-sectional view of the illumination device 2000. In FIG. 1, an LED 2 is disposed in the center of the parabolic mirror 1. The LED 2 is disposed, for example, on an LED substrate 3. The LED 2 uses a high-brightness LED, which becomes hot, and is disposed on a heat sink 4. In FIG. 1, a part of the heat sink 4 is visible on the back of the parabolic mirror 1.

[0017] FIG. 2 is a cross-sectional view taken along line XX in FIG. 1. In FIG. 2, an LED 2 is disposed on the bottom surface of a parabolic mirror 1. The light emitted from the LED 2 is reflected by the parabolic mirror 1, except for the light that goes straight up, and becomes light parallel to the optical axis. However, in order for the parabolic mirror 1 to function adequately, a height h1 of the parabolic mirror 1 is required. To obtain a light distribution angle of about 12 degrees, the height h1 of the parabolic mirror needs to be about 60 mm. In reality, the height h2 of the heat sink, for example about 20 mm, is added to this, so the thickness of the entire lighting device needs to be 80 mm or more.

[0018] The object of the present invention is to realize a thin lighting device that emits collimated light and also to realize a lighting device that can control the light distribution angle of the light emitted from the lighting device or the exit angle from the exit surface. The present invention will be described in detail below using examples. EXAMPLES

[0019] Fig. 3 is an exploded perspective view of a lighting device 1000 related to the first embodiment. Fig. 3 shows a so-called side light type light source in which an LED array 40 is arranged on the side surface of a light guide plate 23, and the entire light source can be made thin. Even the light guide plate 23, which is the thickest of the optical components in Fig. 3, has a thickness of about 2 mm.

[0020] In Fig. 3, LED arrays 40 are arranged on two opposing side surfaces of light guide plate 23. LED array 40 has a configuration in which a plurality of LEDs 41 mounted on an LED substrate 42 are arranged in the y direction. Light guide plate 23 serves to direct light from LED array 40 incident from the side surface toward the main surface of light guide plate 23. A reflective sheet 22 is arranged below light guide plate 23. Reflective sheet 22 reflects light traveling downward from light guide plate 23 to an upward direction.

[0021] The LED array 40, optical components, etc. are housed in an outer frame 20 made of, for example, metal, and a resin frame 21 is used to fix the optical components, etc. in the outer frame 20. A prism sheet 24 for collimating the light emitted from the light guide plate 23 in the optical axis direction is disposed on top of the light guide plate 23. A spacer 25 is disposed around the upper periphery of the prism sheet 24, and a light-shielding tape 26 for defining an emission surface 31 is disposed on top of the spacer 25. A transparent cover 30 is then disposed on top of the light-shielding tape 26.

[0022] In Fig. 3, collimated light 32 is emitted from the exit surface 31 of the transparent cover 30, but in addition to the collimated light 32 shown by a parallelogram, there is also leakage light shown by Lx and Ly. The presence of this leakage light causes the outline of the irradiated light to become blurred. In addition, when a refracting means is disposed on the exit surface 31 to converge, diverge, or change the direction of the emitted light, it is difficult to control this leakage light.

[0023] FIG. 4 shows a light distribution curve of light emitted from lighting device 1000. In FIG. 4, the light emitted from the exit surface of lighting device 1000 can be represented by a light distribution curve shown in an ellipse. In FIG. 4, the length of the arrow represents the light intensity, and the polar angle θ of the arrow represents the direction of the light. In FIG. 4, the light intensity is greatest on the optical axis, i.e., when θ is zero. As the polar angle increases, the light intensity decreases. The light distribution curve shown in FIG. 4 differs depending on the x direction and y direction shown in FIG. 3.

[0024] FIG. 5 shows the light distribution angle characteristic for the lighting device shown in FIG. 3. That is, FIG. 5 shows the light distribution curve shown in FIG. 4, divided into the x direction and the y direction in FIG. 3, with the horizontal axis representing the angle and the vertical axis representing the light intensity. The horizontal axis of FIG. 5 is the polar angle (degrees), and the vertical axis is the relative intensity when the light intensity on the optical axis (polar angle is zero) is set to 1. In FIG. 5, the light intensity forms a smooth curve like a normal distribution up to a polar angle of about 20 degrees, but when the polar angle exceeds 20 degrees, the distribution deviates significantly from the normal distribution. This region corresponds to the leakage light Lx and Ly. In the light distribution curve of Fig. 4, the left side with respect to the optical axis (θ=0°) is the light distribution curve in the x direction, which corresponds to the Lx curve in Fig. 5, and the right side is the light distribution curve in the y direction, which corresponds to the Ly curve in Fig. 5. When the y direction polar angle θ1 and the x direction polar angle θ2 are both 30°, the light intensity in the y direction is greater than the light intensity in the x direction.

[0025] As shown in Fig. 5, the distribution of the leak light is different in the x direction and the y direction. This is because the LED array is arranged in the y direction. In any case, since the leak light Lx and Ly are not collimated light, when the lighting device is used as a floodlight, the outline of the spot becomes blurred. In addition, when a refracting means is arranged on the exit surface 31 of the lighting device 1000 to refract or deflect the exit light, it is difficult to control the leak light Lx and Ly.

[0026] Fig. 6 is an exploded perspective view of a lighting device 1000 according to a first embodiment of the present invention which solves the above problems. In Fig. 6, the configuration from the reflective sheet 22 to the prism sheet 24 is the same as the configuration described in Fig. 5. A feature of Fig. 6 is that cross louvers 50, 60 are disposed between the prism sheet 24 and the transparent cover 30. The cross louvers are a first louver 50 whose louver blades extend in the x direction and a second louver 60 whose louver blades extend in the y direction, which are overlapped and perpendicular to each other.

[0027] The first louver 50 blocks light leakage in the y direction, and the second louver blocks light leakage in the x direction. As a result, it is possible to obtain light distribution characteristics with no light leakage in either the x or y direction. The cross louver may be formed by overlapping the first louver 50 and the second louver 60, or may be an integrated type. The height of the louvers may be different between the first louver 50 and the second louver 60, as necessary.

[0028] FIG. 7 is a graph showing the orientation angle characteristics of the lighting device of FIG. 6. The horizontal and vertical axes of FIG. 7 are the same as those explained in FIG. 5. Comparing FIG. 7 with FIG. 6, firstly, the orientation characteristics have been improved. In other words, when compared at the same polar angle, the relative intensity is smaller in FIG. 7 than in FIG. 6. In other words, the light directivity has been improved.

[0029] The second feature of Fig. 7 is that there is no leakage light Lx and Ly from the lighting device 1000 in Fig. 5. Furthermore, the third feature of Fig. 7 is that there is no difference in the orientation characteristics in the x direction and the y direction. In other words, the orientation characteristics in the x direction and the y direction are represented by the same line. Therefore, the lighting device 1000 in Fig. 6 can provide uniform light with excellent directionality and no blurring in the beam spot.

[0030] 8 is a plan view of the first louver 50 and the second louver 60. The louver blades 70 of the first louver 50 extend in the x direction, and the louver blades 70 of the second louver 60 extend in the y direction. Transparent resin 71 exists between the louver blades 70, and maintains the shapes of the first louver 50 and the second louver 60.

[0031] Fig. 9 is a cross-sectional view taken along line AA of louver 60 in Fig. 8. In Fig. 9, the pitch p of louver blade 70 is, for example, 0.1 mm, the thickness b of louver blade 70 is 0.0185 mm, and the height t of louver blade 70 is 0.7 mm. Louver blade 70 is formed, for example, from black silicone rubber, and most of the light incident on louver blade 70 is absorbed. On the other hand, transparent resin 71 is formed, for example, from transparent silicone rubber with high transmittance.

[0032] Figure 9 shows the path of light in louver 60. Arrows LL in Figure 9 indicate the path of light. Light entering louver 60 is refracted according to the refractive index of transparent resin 71 inside louver 60. The distribution angle θ of light exiting louver 60 can be expressed by Equation 1, where n is the refractive index of transparent resin 71 with respect to air, t is the height of the louver, and a is the width between the louver blades.

[0033] θ=2sin -1 {nsin(tan -1 (a / t))} (Formula 1) 10 shows a case where the cross-sectional shape of the louver blade 70 is triangular instead of rectangular. This can be used when it is desired to adjust the light distribution angle without changing the outer shape of the louver. Note that the cross-sectional shape of the louver blade 70 is not limited to a triangle, and may be a trapezoid, etc.

[0034] Fig. 11 shows an example in which louver covers 72 made of transparent resin are installed on the top and bottom surfaces of the louver. This is used when the mechanical strength of the louver is required. The louver cover 72 is formed of, for example, polycarbonate, and has a thickness of, for example, about 0.2 mm. The other configuration of Fig. 11 is the same as that of Fig. 9.

[0035] The cross louvers can also be formed as an integral unit. Fig. 12 is a perspective view of an integral cross louver 80. In Fig. 12, the first and second louvers are formed as an integral unit, and the rest is the same as that described in Figs. 8 and 9. That is, the lower louver has louver blades 70 that extend in the x direction, and the upper louver has louver blades 70 that extend in the y direction. Transparent resin 71 exists between the louver blades 70.

[0036] Figure 13 is a side view of Figure 12 viewed from direction A. The basic structure of the upper and lower louvers is the same as that explained in Figure 8. In Figure 13, the height of the lower louver is t1 and the height of the upper louver is t2. t1 and t2 may be the same. To change the light distribution angle in the x direction and the light distribution angle in the y direction, simply change t1 and t2.

[0037] Fig. 14 shows a case where louver covers 72 are formed above and below the cross louvers. Louver covers 72 are used when the mechanical strength of the cross louvers is required. Fig. 15 is a side view of Fig. 14 as viewed from direction B. Louver cover 72 is made of, for example, polycarbonate, and has a thickness tc of, for example, about 0.2 mm. The other configurations of Fig. 15 are the same as those described in Fig. 13.

[0038] The louvers described in Figures 8 to 15 have a configuration in which transparent resin 71 exists between louver blades 70. If the refractive index n of transparent resin 71 is large, the light distribution angle also becomes large. If there is space between louver blades 70, the light distribution angle can be made smaller. Figures 16 and 17 are examples. In Figure 16, the left side is a plan view of first louver 50, and the right side is a plan view of second louver 60. The first louver 50 and second louver 60 have the same structure, just rotated by 90 degrees.

[0039] In Fig. 16, louver blades 70 may be made of black resin or metal. There is a space 75 between each louver blade 70, and no resin is present. Louver frames 73 are present to prevent louver blades 70 from coming apart. Louver frames 73 may be formed, for example, from polycarbonate having a thickness of about 0.2 mm, or may be formed from metal. In Fig. 16, louver frames 73 are formed only in the vertical direction, but louver frames 73 may be formed around the entire circumference.

[0040] Figure 17 is a cross-sectional view taken along line CC of Figure 16. Arrow LL in Figure 17 indicates the path of light. In Figure 17, there is space between the louver blades 70, so no refraction occurs. The light distribution angle θ of light emitted from the louver 60 can be expressed by (Equation 2). Comparing Figure 9 and Figure 17, in Figure 17, the light distribution angle θ can be reduced by the amount of the refractive index n.

[0041] θ=2sin-1{sin(tan-1(a / t))} (Equation 2) FIG. 18 is a perspective view of a case where cross louvers 80 are formed as a single unit. FIG. 18 shows a configuration in which louver blades 70 are arranged in a lattice pattern on the same plane to achieve the function of a cross louver with a single sheet. In FIG. 18, there is a space 75 within each lattice. The lattice in FIG. 18 can be formed from metal or black resin, as explained in FIG. 16, and the thickness, height, pitch, etc. of the louver blades 70 can be changed according to the required orientation angle. For example, the height t of the louver, the width a of the space, the thickness b of the louver blades, etc. can be determined with reference to FIG. 9.

[0042] Furthermore, if the shape of the lattice in Fig. 18 is unstable as is, a louver frame 73 made of polycarbonate or the like can be arranged as explained in Fig. 16. The light path or light distribution angle within each lattice in Fig. 18 is as explained in Fig. 17. The light path can be expressed by (Equation 2). Incidentally, although there is space 75 within each lattice in Fig. 18, each lattice may be filled with transparent resin. The light path in this case is expressed by (Equation 1).

[0043] Fig. 19 is a plan view showing an example in which louver 90 is configured with a honeycomb structure. In Fig. 19, the honeycomb structure is formed of louver blades 70 made of black resin or metal, and each cell is a space 75. The collimating effect is the same as (Equation 2). The honeycomb structure is flat, and the same configuration is repeated every 60 degrees of rotation, so there is an advantage that assembly errors in the rotation direction of the louver are unlikely to occur. Another advantage is that moire due to interference with prism sheet 24, which will be explained later, is unlikely to occur.

[0044] The honeycomb structure in Fig. 19 can be made of metal or black resin, similar to that described in Fig. 16, and the thickness, height, pitch, etc. of the louver blades 70 can be changed according to the required orientation angle. For example, the height t of the louvers, the width a of the space, the thickness b of the louver blades 70, etc. can be determined with reference to Fig. 9.

[0045] Each cell of the honeycomb louver 90 in Fig. 19 has a space 75, but each cell can also be filled with a transparent resin. In this case, the collimating effect can be expressed by (Equation 1). In addition, to ensure the strength of the louver, a louver cover 72 may be used as necessary.

[0046] In the configuration of Example 1 shown in FIG. 6, an inverted prism sheet 24 is used to collimate light. The inverted prism sheet 24 is a prism sheet with a prism surface facing downward. FIG. 20 is a detailed view of the prism sheet 24. In the prism sheet 24 of FIG. 20, a prism array formed by V-shaped grooves extends in the y direction and is arranged in the x direction. Two prism sheets 24 may be used as necessary. In this case, the extension directions of the prism array are arranged at right angles to each other in the two prism sheets.

[0047] Example dimensions of the prism sheet 24 are as follows: The thickness tp of the prism sheet 24 is, for example, 0.125 mm, the depth Vd of the V groove is, for example, 0.075 mm, the apex angle θp is, for example, 66 degrees, and the pitch pp is, for example, 0.1 mm. The prism sheet 24 in Fig. 20 acts to collect light that tends to spread in the x direction in the direction of the emission surface, i.e., in the z direction.

[0048] When viewed microscopically, the prism sheet 24 shown in Fig. 20 has repeated vertical stripes due to the horizontal pitch pp. This can easily cause interference with, for example, the second louver 60 of Fig. 8, resulting in moire. To prevent this, for example, the second louver 60 can be rotated by φ in the planar direction as shown in Fig. 21. The value of φ can be, for example, 3 to 4 degrees, that is, 3 degrees or more. In this case, the first louver is also rotated by φ in the same manner.

[0049] Although the prism array in the prism sheet in Fig. 20 extends in the y direction, there are also cases where the prism array extends in the x direction. In this case, for example, interference with the first louver 50 in Fig. 8 becomes a problem, but this can be dealt with in the same manner as described above. Note that instead of rotating the louvers 50, 60, the prism sheet may be rotated.

[0050] Incidentally, the louver may also cause interference with the electrodes of the liquid crystal lens, which will be described in Example 2, resulting in moire fringes. In this case, too, moire fringes can be reduced by rotating the extension direction of the louver blades 70 from the extension direction of the electrodes of the liquid crystal lens by 3 to 4 degrees, i.e., 3 degrees or more, in a plan view. Alternatively, as will be described in detail later, moire fringes can be reduced by rotating the extension direction of the electrodes of the liquid crystal lens by a similar angle. EXAMPLES

[0051] FIG. 22 is an exploded perspective view of a lighting device 1000 according to a second embodiment. FIG. 22 differs from FIG. 6 in that a liquid crystal lens 100 is used in place of the transparent cover 30 in FIG. 6. The liquid crystal lens 100 in this specification includes lenses that have not only convergence and divergence but also light deflection properties (changing the direction of travel of light). In FIG. 22, the configuration from the outer frame 20 to the light-shielding tape 26 is the same as in FIG. 6, so a description thereof will be omitted. In other words, light collimated by the cross louvers 50, 60, etc. is incident on the liquid crystal lens 100 in FIG. 22.

[0052] Fig. 23 is a cross-sectional view showing the principle of a liquid crystal lens. In Fig. 23, collimated light is incident from the left side of the liquid crystal layer 300. P in Fig. 3 means the deflection direction of the incident light. The deflection direction of normal light is randomly distributed, but since liquid crystal has anisotropy in the refractive index, Fig. 23 shows the effect on light deflected in the P direction.

[0053] 23, in liquid crystal layer 300, liquid crystal molecules 301 are aligned by electrodes so that the inclination increases toward the periphery of liquid crystal layer 300. Liquid crystal molecules 301 have an elongated shape, and the effective refractive index of liquid crystal molecules 301 in the long axis direction is greater than the effective refractive index of liquid crystal molecules 301 in the short axis direction, so that the refractive index increases toward the periphery of liquid crystal layer 300, forming a convex lens. The dotted line in Fig. 23 is the light wavefront WF, and f is the focus distance of the lens.

[0054] Since liquid crystal has anisotropy in refractive index, to form a lens, a second lens is required that acts on light polarized in a direction perpendicular to the direction of polarization of the light that the first lens acts on. FIG. 24 is an exploded perspective view showing this lens configuration. In FIG. 24, the parallelogram on the left is the wavefront of the light. That is, light polarized in the X and Y directions enters the liquid crystal layer. First liquid crystal lens 110 is a lens that acts on X-polarized light, and second lens 120 is a lens that acts on Y-polarized light.

[0055] 24, the initial alignment directions of liquid crystal molecules 301 differ by 90 degrees between first liquid crystal lens 110 and second liquid crystal lens 120. The initial alignment of liquid crystal molecules 301 is determined by the alignment direction of the alignment film in the liquid crystal lens. That is, in FIG. 24, the alignment directions of the alignment films on the substrates on the light-incident side of the two liquid crystal lenses are perpendicular to each other.

[0056] Fig. 25 shows a case where a concave lens is formed by a liquid crystal lens. In Fig. 25, the wavefront WF is parallel to the liquid crystal layer 300, and light polarized in one direction enters the liquid crystal layer 300 from the left side. In Fig. 25, the liquid crystal molecules 301 in the liquid crystal layer 300 are oriented most strongly near the optical axis by the electrodes, and the orientation angle becomes smaller toward the periphery. With such a lens configuration based on liquid crystal orientation, the wavefront WF of the light that has passed through the liquid crystal layer 300 becomes a curve as shown by the dotted line in Fig. 25, and a concave lens is formed. Note that, in the case of a concave lens, two liquid crystal lenses are still required, as shown in Fig. 24.

[0057] Fig. 26 is a diagram showing the principle of deflecting light to the left by a liquid crystal lens. In Fig. 26, the upper diagram is a cross-sectional view of liquid crystal lens 100. A first electrode 102 is formed on a first substrate 101 of liquid crystal lens 100, a second electrode 104 is formed on a second substrate 103, and a liquid crystal layer 300 is present between the first electrode 102 and the second electrode 104. Liquid crystal layer 300 is sealed with a sealant 105. In Fig. 26, a polarizing plate 250 is used instead of two liquid crystal lenses, so that only one liquid crystal lens is used.

[0058] When a voltage v is applied between the first electrode 102 and the second electrode 104 in Fig. 26 such that the potential difference increases from left to right, as shown in the graph at the bottom of Fig. 26, the orientation angle of the liquid crystal molecules 301 changes from place to place, and the effective birefringence Δn of the liquid crystal layer 300 changes as shown in the graph. With such a configuration of the liquid crystal layer 300, collimated light LL incident on the liquid crystal lens 100 from below is deflected to the left and emitted.

[0059] Fig. 27 is a diagram showing the principle of deflecting light to the right by the liquid crystal lens 100. In Fig. 27, the upper diagram is the same as Fig. 26 except for the way in which the voltage is applied between the first electrode 102 and the second electrode 104. When a voltage v is applied between the first electrode 102 and the second electrode 104 in Fig. 27 such that the potential difference decreases from left to right as shown in the graph in the lower part of Fig. 27, the orientation angle of the liquid crystal molecules 301 changes from place to place, and the effective birefringence Δn of the liquid crystal changes as shown in the graph. With such a configuration of the liquid crystal layer 300, the collimated light LL incident on the liquid crystal lens 100 is deflected to the right.

[0060] Fig. 28 is a cross-sectional view showing a first example of the configuration of an actual liquid crystal lens. In Fig. 28, a first electrode 102 is disposed on a first substrate 101, a second electrode 104 is disposed on a second substrate 103, and a liquid crystal layer 300 is sandwiched between the first substrate 101 and the second substrate 103. An alignment film is formed to cover the first electrode 102 and the second electrode 104, but is omitted in Fig. 28. The same applies to the following figures. The initial alignment direction of liquid crystal molecules 301 is determined by performing an alignment process such as rubbing on the alignment film.

[0061] 28, the initial alignment direction of the liquid crystal molecules 301 on the first substrate 101 side and the initial alignment direction of the liquid crystal molecules 301 on the second substrate 103 side are at an angle of 90 degrees, forming a so-called TN (Twisted Nematic) type liquid crystal lens. The first electrode 102 extends in the x direction, and the second electrode 104 extends in the y direction. However, the liquid crystal lens 100 is not limited to being formed using a TN type liquid crystal.

[0062] The diagram on the left side of Fig. 29 is a plan view of the first electrode 102 formed on the first substrate 101. The diagram on the right side of Fig. 29 is a plan view of the second electrode 104 formed on the second substrate 103. The first electrode 102 extends in the x direction, and the second electrode 104 extends in the y direction. At the intersections of the first electrode 102 and the second electrode 104, the liquid crystal molecules 301 are oriented in accordance with the voltage. In other words, various liquid crystal lens functions can be achieved by varying the method of applying voltage to the first electrode 102 and the second electrode 104.

[0063] FIG. 30 is a cross-sectional view showing a second example of the configuration of an actual liquid crystal lens 100. In FIG. 28, a striped first electrode 102 is arranged on a first substrate 101, a planar second electrode 104 is arranged on a second substrate 103, and a liquid crystal layer 300 is sandwiched between the first substrate 101 and the second substrate 103. The left side of FIG. 31 is a plan view of the first electrode 102 formed on the first substrate 101, and the first electrode extends in the x direction. The right side of FIG. 31 is a plan view of the second electrode 104 formed on the second substrate 103, and the second electrode 104 is planar. In the second example, various liquid crystal lens functions can also be exhibited depending on the voltage applied between the first electrode 102 and the second electrode 104.

[0064] Fig. 32 is a cross-sectional view showing a third example of the configuration of an actual liquid crystal lens 100. In Fig. 32, striped first electrodes 102 are arranged on a first substrate 101, and no electrodes are formed on a second substrate 103. The diagram on the left side of Fig. 33 is a plan view of the first electrodes 102 formed on the first substrate 101, and the first electrodes 102 extend in the x direction. The diagram on the right side of Fig. 33 depicts only the second substrate 103, and no second electrode is present.

[0065] The third example is a liquid crystal lens of the horizontal electric field type, in which the liquid crystal is driven only by the first electrodes 102 formed on the first substrate 101. That is, the liquid crystal molecules 301 are oriented by the potential difference between adjacent stripe-shaped first electrodes 102, thereby forming a lens. By variously changing the voltage between the stripe electrodes of the first electrodes 102, various lenses can be formed.

[0066] Fig. 34 is a cross-sectional view showing a fourth example of the configuration of an actual liquid crystal lens 100. In Fig. 34, a concentric first electrode 102 is arranged on a first substrate 101, a planar second electrode 104 is arranged on a second substrate 102, and a liquid crystal layer 300 is sandwiched between the first substrate 101 and the second substrate 103. The diagram on the left side of Fig. 35 is a plan view of the first electrode 102 formed on the first substrate 100. The first electrode 102 is in the form of concentric circles. An extraction electrode 106 for applying a voltage is connected to each of the circular electrodes.

[0067] 35, lenses of various strengths can be formed by changing the voltage between the first electrode 102 and the second electrode 104. The fourth example has the feature that the first electrode 102 is formed in a concentric circle, so that a circular lens can be easily formed.

[0068] 28 to 35 each show the structure of a single liquid crystal lens. However, since liquid crystal can only control polarized light in one direction, an actual liquid crystal lens must be used in a set of two liquid crystal lenses. Fig. 36 is a cross-sectional view of a first liquid crystal lens 110 and a second liquid crystal lens 120 superimposed with adhesive 200.

[0069] In FIG. 36, the first liquid crystal lens 110 is a TN liquid crystal, and has a configuration in which a first electrode 102 is formed on a first substrate 101, a second electrode 104 is formed on a second substrate 103, and a liquid crystal layer 300 is sandwiched between the first substrate 101 and the second substrate 103. The second liquid crystal lens 120 has the same structure. The first liquid crystal lens and the second liquid crystal lens have the same structure, but the light distribution direction AL of the alignment film of the first substrate 101 in the first liquid crystal lens 110 and the light distribution direction AL of the alignment film of the first substrate 101 in the second liquid crystal lens 120 intersect at 90 degrees. In other words, the first liquid crystal lens 110 acts on polarized light polarized in a first direction of the incident light, and the second liquid crystal lens 120 acts on polarized light polarized in a second direction perpendicular to the first direction of the incident light.

[0070] When two liquid crystal lenses alone do not provide sufficient lens action or deflection action, four liquid crystal lenses may be used. Fig. 37 shows an example in which four liquid crystal lenses are combined with adhesive 200. In Fig. 37, a first liquid crystal lens 110, a second liquid crystal lens 120, a third liquid crystal lens 130, and a fourth liquid crystal lens 140 are layered from the bottom. The configurations of the first liquid crystal lens 110 and the second liquid crystal lens 120 are as described in Fig. 36. The third liquid crystal lens 130 and the fourth liquid crystal lens 140 are the same as the first liquid crystal lens 110 and the second liquid crystal lens 120.

[0071] In Figure 37, the orientation direction AL of the alignment film formed on the first substrate 101 of the first liquid crystal lens 110 and the light distribution direction AL of the alignment film formed on the first substrate 101 of the second liquid crystal lens 120 are perpendicular to each other, and the orientation direction AL of the alignment film formed on the first substrate 101 of the third liquid crystal lens 130 and the light distribution direction AL of the alignment film formed on the first substrate 101 of the fourth liquid crystal lens 140 are perpendicular to each other.

[0072] The alignment directions of the alignment films of the first to fourth liquid crystal lenses can be combined in other ways than those shown in Fig. 37. Also, each liquid crystal lens does not need to be limited to a TN liquid crystal.

[0073] Fig. 38 shows a configuration in which only one liquid crystal lens 100 is required. In Fig. 38, a polarizing plate 250 is attached under the first liquid crystal lens 110. The structure and action of the first liquid crystal lens 110 are as described in Figs. 28 to 31 etc. Since liquid crystal acts only on light polarized in a specific direction, it is necessary for polarized light to be incident on the first liquid crystal lens 110.

[0074] 38, polarized light that can be controlled by liquid crystal is made incident on the first liquid crystal lens 110 by disposing a polarizing plate 250 on the first substrate 101 of the liquid crystal lens 110. However, when the polarizing plate 250 is used, light that is polarized in a direction perpendicular to the transmission axis direction of the polarizing plate 250 cannot be transmitted. Therefore, by using a polarizing reflector that reflects the light that cannot be transmitted through the polarizing plate 250 to the prism sheet side and then reflects it again on the prism sheet side to rotate the polarization axis of the light and reuse it, the light utilization efficiency can be improved.

[0075] Fig. 39 is a perspective view of the liquid crystal lens shown in Fig. 28. On the first substrate 101, first electrodes 102 extend in the y direction and are arranged in the x direction. On the second substrate 103, second electrodes 104 extend in the x direction and are arranged in the y direction. When the first substrate 101 and the second substrate 103 are superimposed, the electrode shape appears to be a grid shape in a plan view.

[0076] Fig. 40 is a plan view of only the electrodes of liquid crystal lens 100 and LED array 40 in the lighting device of Fig. 22. Liquid crystal lens 100 uses the configuration of Fig. 28. The electrodes formed on liquid crystal lens 100 are often made of transparent electrodes such as ITO, but even transparent electrodes do not have 100% transmittance, so regular light and dark patterns occur. This causes interference between this regular light and dark and the cross louvers 50, 60, resulting in moire.

[0077] Fig. 41 is a plan view showing a structure that counters moire. In Fig. 41, the electrodes 102 and 104 in a lattice structure are rotated 45 degrees in a plan view. This makes it possible to suppress moire. Even a rotation angle φ of 3 to 4 degrees has a significant effect on moire.

[0078] Fig. 42 shows an example in which two liquid crystal lenses are used. The lattice-structured electrodes formed on the first liquid crystal lens and the lattice-structured electrodes formed on the second liquid crystal lens overlap at a 45-degree angle in plan view. As a variation of Fig. 42, if the lattice-structured electrodes formed on the first liquid crystal lens are rotated 22.5 degrees in the x direction and the lattice-structured electrodes formed on the second liquid crystal lens are rotated a further 45 degrees, moire can be further improved.

[0079] In this way, by rotating the electrodes formed on liquid crystal lens 100 at various angles, it is possible to prevent interference with cross louvers 50, 60. The liquid crystal lens 100 described above can be applied not only to the liquid crystal lenses shown in Figures 28 and 29, but also to the liquid crystal lenses shown in Figures 30 and 31, and to various other liquid crystal lenses. Note that the same effect can be obtained by rotating the cross louvers 50, 60 in the planar direction, instead of rotating the electrodes of the liquid crystal lens.

[0080] Incidentally, if the first electrode 102 of the first substrate 101 of the liquid crystal lens is a concentric electrode as shown in Figures 34 and 35, moire due to interference with the cross louver is unlikely to occur. In other words, in terms of moire, a liquid crystal lens having a concentric electrode is suitable for combination with a cross louver.

[0081] FIG. 43 is a plan view showing a configuration in which a plurality of regions with different characteristics are formed in a planar direction with respect to the configuration of the liquid crystal lens 100. There are cases where it is desired to change the light emitted from the lighting device to a spot with a luminance distribution, or to change the spot shape, rather than a simple light spot. Such a request can be met by forming a plurality of regions with different characteristics in a planar view in the liquid crystal lens 100. In the regions R1 and R2 in FIG. 43, the shapes of the electrodes constituting the liquid crystal lens are changed, and the characteristics of the liquid crystal lens are changed for each region. In addition, more detailed control can be performed by controlling the voltage applied to the electrodes. [Explanation of symbols]

[0082] REFERENCE SIGNS LIST 1...parabolic mirror, 2...LED, 3...LED substrate, 4...heat sink, 20...outer frame, 21...resin frame, 22...reflective sheet, 23...light guide plate, 24...prism sheet, 25...spacer, 26...light shielding tape, 30...cover, 31...emission area, 32...collimated light, 40...LED array, 41...LED, 42...LED substrate, 50...first louver, 60...second louver, 70...louver blade, 71...transparent resin, 72...louver cover, 73...louver frame, 75...space, 80...cross louver, 90...honeycomb louver, 100...liquid crystal lens, 101...first substrate, 102...first electrode, 103...second substrate, 104...second electrode, 105...sealing material, 106...drawing wire, 110...first liquid crystal lens, 120...second liquid crystal lens, 130...third liquid crystal lens, 140...fourth liquid crystal lens, 200...adhesive, 250...polarizing plate, 1000...illumination device, 2000...illumination device, AL...alignment direction, LL...light, Lx...leakage light, Ly...leakage light, R1...first region, R2...second region, 521...fourth electrode

Claims

1. An illumination device comprising: an LED disposed on a side surface of a light guide plate; the light guide plate having a main surface for emitting light from the LED that is incident from the side surface; and a prism sheet disposed on the main surface of the light guide plate, a first louver extending in a first direction and a second louver extending in a second direction perpendicular to the first direction are stacked on the prism sheet; A liquid crystal lens is disposed on the second louver; the liquid crystal lens comprises a first substrate having a first electrode extending in the first direction, a second substrate having a second electrode extending in the second direction, and a liquid crystal layer disposed between the first substrate and the second substrate; a liquid crystal lens that receives light collimated by the first louver and the second louver;

2. 2. The lighting device of claim 1, wherein the prism sheet has a prism array extending in a third direction, the first direction and the third direction being at least 3 degrees apart, and the second direction and the third direction being at least 3 degrees apart.

3. The lighting device according to claim 1 , wherein a light distribution angle of the first louver is different from a light distribution angle of the second louver.

4. the first louver has a first thickness along an optical axis and the second louver has a second thickness along the optical axis; The illumination device of claim 1 , wherein the first thickness and the second thickness are different.

5. 2. The lighting device of claim 1, wherein the first louver has a first louver blade, the second louver has a second louver blade, and there is space between the first louver blade and the first louver blade, and between the second louver blade and the second louver blade.

6. The lighting device of claim 1, characterized in that the first louver has a first louver blade, the second louver has a second louver blade, and a transparent resin is present between the first louver blade and the first louver blade, and between the second louver blade and the second louver blade.

7. 2. The lighting device according to claim 1, wherein the liquid crystal lens has a first electrode extending in a direction rotated by a first angle from the first direction, the first angle being 3 degrees or more.

8. 8. The lighting device according to claim 7, wherein the liquid crystal lens has a second electrode extending in a direction rotated by the first angle from the second direction.

9. 9. The illumination device of claim 8, wherein the first angle is 22.5 degrees.

10. 9. The illumination device of claim 8, wherein the first angle is 45 degrees.

11. 8. The lighting device according to claim 7, wherein the liquid crystal lens has a second electrode extending in a direction perpendicular to an extending direction of the first electrode.

Images