ILLUMINATION DEVICE

According to one embodiment, an illumination device includes a first projecting portion on a first main surface and a second projecting portion on a second main surface on an opposite side to the first main surface in a first area of a first guide, a third projecting portion on a third main surface opposing the second main surface and a fourth projecting portion on a fourth main surface on an opposite side to the third main surface, in a third area of a second guide, and the first projecting portion and the third projecting portion have a cross sectional shape of a scalene triangle and the second projecting portion and the fourth projecting portion have a cross sectional shape of an isosceles triangle.

FIELD

Embodiments described herein relate generally to an illumination device.

BACKGROUND

An illumination device with a light source element and a light guide has been developed as a surface emitting illumination device.

DETAILED DESCRIPTION

In general, according to one embodiment, an illumination device comprisesa first illumination element comprising a first light source element and a first light guide including a first area and a second area;a second illumination element overlapping the first illumination element and comprising a second light source element and a second light guide including a third area and a fourth area; anda liquid crystal cell overlapping the second illumination element, whereinthe first light guide includes a first side surface and a second side surface,the first light source element is located to oppose the second side surface,the second area is located between the second side surface of the first light guide and the first area,the second light guide includes a third side surface and a fourth side surface,the second light source element is located to oppose the third side surface of the second light guide,the fourth area is located between the fourth side of the second light guide and the third area, the fourth side surface is disposed closer to the second side surface than the first side surface,the first area of the first light guide is provided with a first projecting portion on a first main surface and a second projecting portion on a second main surface on a side opposite to the first main surface,the third area of the second light guide is provided with a third projecting portion on a third main surface on a side opposite to the second main surface and a fourth projecting portion on a fourth main surface on a side opposite to the third main surface,the liquid crystal cell includes a first substrate provided with a first electrode, a second substrate provided with a second electrode, and a liquid crystal layer provided between the first substrate and the second substrate,the first projecting portion and the third projecting portion have a cross-sectional shape of a scalene triangle, andthe second projecting portion and the fourth projecting portion have a cross-sectional shape of an isosceles triangle.

An object of this embodiment is to provide an illumination device which can irradiates light at a desired location.

The embodiments described herein are not general ones, but rather embodiments that illustrate the same or corresponding special technical features of the invention. The following is a detailed description of one embodiment of an illumination device with reference to the drawings.

In this embodiment, a first direction X, a second direction Y and a third direction Z are orthogonal to each other, but may intersect at an angle other than 90 degrees (°). The direction toward the tip of the arrow in the third direction Z is defined as up or above, and the direction opposite to the direction toward the tip of the arrow in the third direction Z is defined as down or below. Note that the first direction X, the second direction Y and the third direction Z may as well be referred to as an X direction, a Y direction and a Z direction, respectively.

With such expressions as “the second member above the first member” and “the second member below the first member”, the second member may be in contact with the first member or may be located away from the first member. In the latter case, a third member may be interposed between the first member and the second member. On the other hand, with such expressions as “the second member on the first member” and “the second member beneath the first member”, the second member is in contact with the first member.

Further, it is assumed that there is an observation position to observe the illumination device on a tip side of the arrow in the third direction Z. Here, viewing from this observation position toward the X-Y plane defined by the first direction X and the second direction Y is referred to as plan view. Viewing a cross-section of the illumination device in the X-Z plane defined by the first direction X and the third direction Z or in the Y-Z plane defined by the second direction Y and the third direction Z is referred to as cross-sectional view.

EMBODIMENTS

FIG.1is an exploded view showing a schematic configuration of an illumination device of this embodiment.FIG.2is a cross-sectional view showing the schematic configuration of the illumination device of the embodiment.

An illumination device ILD comprises a reflective sheet REF, an illumination element IL1, an illumination element IL2, and a liquid crystal lens LNS, which are provided in order along a direction opposite to the third direction Z. Light emitted from the illumination device ILD is emitted downward. The reflective sheet REF and the illumination element IL1, the illumination element IL1and the illumination element IL2, and the illumination element IL2and the liquid crystal lens LNS are provided to oppose each other, respectively.

The illumination element IL1comprises a first light guide LG1and a plurality of first light source elements LSM1. The plurality of light source elements LSM1are provided adjacent to a second side surface LG1s2of the light guide LG1. The side surface LG1s2is a light entry portion where light from the light source elements LSM1enters. On the first side surface LG1s1, which is on a side opposite to the side surface LG1s2, a light source element LSM1is not provided.

The light guide LG1comprises a first main surface LG1aopposing the reflective sheet REF and a second main surface LG1bopposing the light guide LG2. The main surface LG1bis provided on a side opposite to the main surface LG1a. The light guide LG1includes a central portion LG1cin a side parallel to the first direction X. Note that the central portion LG1cmay not be the central part of the parallel sides of the light guide LG1, but may be the central part of the sides of the effective light emitting area in the light guide LG1. The effective light-emitting area is an area where light is emitted from the light guide LG1. This is also the case for the light guide LG2.

Here, the area of the light guide LG1proximate to the side surface LG1s1is designated as a first area AR11and the area of the light guide LG1proximate to the side surface LG1s2is designated as a second area AR12. In the area AR11, a plurality of first projecting portions TV1aare provided on the main surface LG1aand a plurality of second projecting portions TV1bare provided on the main surface LG1b. In the area AR12, the projecting portions TV1aand TV1bare not provided. That is, the projecting portions TV1aand the projecting portions TV1bare not provided on a side surface LG1s2side, where the light source elements LSM1are provided, but they are provided on a side surface LG1s1side, where the light source elements LSM1are not provided.

The area AR11extends from the side surface LG1s1beyond the central portion LG1cto the side surface LG1s2. The area AR12occupies the area from the side surface LG1s2to just front of the central portion LG1c. In other words, the area AR11includes the central portion LG1cand the area AR12does not include the central portion LG1c.

The plurality of projecting portions TV1aare arranged along a direction parallel to the first direction X and each extends along a direction parallel to the second direction Y. The plurality of projecting portions TV1beach extend in a direction parallel to the first direction X and are arranged along a direction parallel to the second direction Y. Each of the projecting portions TV1ahas a triangular prism form, the cross-sectional shape of which is a scalene triangle. Each of the projecting portions TV1bhas a triangular prism form, the cross-sectional shape of which is an isosceles triangle. Details of the cross-sectional shapes of the projecting portions TV1aand the projecting portions TV1bwill be provided later. The projecting portions TV1aand the projecting portions TV1bare formed to be integrated with the light guide LG1as one body.

The illumination element IL2comprises a second light guide LG2and a plurality of second light source elements LSM2. The plurality of light source elements LSM2are provided adjacent to the third side surface LG2s1of the light guide LG2. The side surface LG2s1is the light entry portion where light from the light source elements LSM2enters. The light source elements LSM2are not provided on the fourth side surface LG2s2, which is located on a side opposite to the side surface LG2s1.

InFIGS.1and2, the side surface LG2s2is arranged along the side surface LG1s2in the third direction Z. Note that the configuration is not limited to this, but it suffices if the side surface LG2s2is disposed closer to the side surface LG1s2than to the side surface LG1s1.

The light guide LG2comprises a third main surface LG2aopposing the light guide LG1and a fourth main surface LG2bopposing the liquid crystal lens LNS. The main surface LG2bis provided on a side opposite to the main surface LG2a. In the side of the light guide LG2, parallel to the first direction X, the central portion is designated as LG2c.

The area of the light guide LG2, proximate to the side surface LG2s1is designated as a third area AR21and the area of the light guide LG2, proximate to the side surface LG2s2is designated as a fourth area AR22. In the area AR22, a plurality of third projecting portions TV2aare provided on the main surface LG2aand a plurality of fourth projecting portions TV2bare provided on the main surface LG2b. In the area AR21, the projecting portions TV2aand the projecting portions TV2bare not provided. In other words, the projecting portions TV2aand the projecting portions TV2bare not provided on the side surface LG2s1side, where the light source elements LSM2are provided, but they are provided on the side surface LG2s2side, where the light source elements LSM2are not provided.

The area AR22extends from the side surface LG2s2beyond the central portion LG2cto the side surface LG2s1side. The area AR11occupies the area from the side surface LG2s1to just front of the central portion LG2c. In other words, the area AR22includes the central portion LG2c, whereas the area AR21does not include the central portion LG2c. Note that the area AR21and the area AR12do not overlap each other in plan view.

The plurality of projecting portions TV2aare arranged in a direction parallel to the first direction X and each extends along a direction parallel to the second direction Y. The plurality of projecting portions TV2beach extend in a direction parallel to the first direction X and are arranged along a direction parallel to the second direction Y. Each of the plurality of projecting portions TV2ahas a triangular prism form, the cross-sectional shape of which is a scalene triangle. Each of the plurality of projecting portions TV2bhas a triangular prism form, the cross-sectional shape of which is an isosceles triangle. Details of the cross-sectional shapes of the projecting portions TV2aand the projecting portions TV2bwill be provided later. The projecting portions TV2aand the projecting portions TV2bare formed to be integrated with the light guide LG1as one body.

In the illumination element IL1, light LT1emitted from the light source elements LSM1enters the light guide LG1from the side surface LG1s2. In the area AR12, where the projecting portions TV1aand the projecting portions TV1bare not provided, the light LT1is not emitted to the outside and propagates in the light guide LG1while totally reflecting therein. When the light LT1reaches the area AR11, the reflection angle is changed by the projecting portions TV1aand the projecting portions TV1b, and the light is emitted toward the illumination element IL2at an angle with respect to the third direction Z.

The light LT1entering the illumination element IL2passes through the light guide LG2, enters the liquid crystal lens from a light incident surface LNSa of the liquid crystal lens and exits from a light exit surface LNSb of the liquid crystal lens.

The light LT1incident on the liquid crystal lens LNS passes through the liquid crystal lens LNS as it is when the liquid crystal lens LNS is in the off state, and is emitted downward as light LT1p. When the liquid crystal lens LNS is in the on state, the light LT1is polarized by the liquid crystal lens LNS and is emitted as polarized light LT1c. Details of the configuration and operation of the liquid crystal lens LNS will be provided later.

In the illumination element IL2, light LT2emitted from the light source element LSM2enters the light guide LG2from the side surface LG2s1. In the area AR21, where the projecting portions TV2aand the projecting portions TV2bare not provided, the light LT2is not emitted to the outside and propagates in the light guide LG2while totally reflecting therein. When the light LT2reaches the area AR22, the reflection angle is changed by the projecting portions TV2aand the projecting portions TV2b, and the light is emitted at an angle to the third direction Z toward the liquid crystal lens LNS.

The light LT2entering the liquid crystal lens LNS passes through the liquid crystal lens LNS as it is and is emitted downward as light LT2pwhen the liquid crystal lens LNS is in the off state. When the liquid crystal lens LNS is in the on state, the light LT2is polarized by the liquid crystal lens LNS and is emitted as polarized light LT2c.

The angles at which the light LT1pand the light LT2pare emitted with respect to the third direction Z are designated as an angle Rip and an angle R2p, respectively. When the total of the angles Rip and R2pis referred to as an angle Rp, the angle Rip, then, is the light distribution angle of the light emitted by the illumination device ILD when the liquid crystal lens LNS is in the off state.

Similarly, here, the angles at which the polarized light LT1cand the polarized light LT2care emitted are designated as an angle R1cand an angle R2c, respectively. When the total angle of the angles R1cand R2cis referred to as an angle Rc, then the angle Rc is the light distribution angle of the light emitted from the illumination device ILD when the liquid crystal lens LNS is in the on state.

The angle Rp (=R1p+R2p) is greater than the angle Rc (=R1c+R2c). Further, the angle Rip and the angle R2pare greater than the angle R1cand the angle R2c, respectively. That is, the light LT1pand the light LT2pare emitted further outward, whereas the polarized light LT1cand the polarized light LT2care emitted further inward.

The angle Rip and the angle R2pare each, for example, 45°. The angle R1cand the angle R2care, each, for example, 22°. That is, the angle Rp is 90° and the angle Rc is 44°. Thus, the light distribution angle of the liquid crystal lens LNS in the on state is less than the light distribution angle in the off state.

In the illumination device ILD of this embodiment, the lighting of the light source element LSM1and the light source element LSM2of the illumination element IL1and the illumination element IL2, and the on state and off state of the liquid crystal lens LNS are combined, and thus the illumination light emitted can be controlled to be set in a desired direction.

FIG.3is a schematic cross-sectional view showing an arrangement of the light guide and the projecting portions of the illumination device. The area AR11of the light guide LG1overlaps the area AR22of the light guide LG2in plan view. That is, some of the plurality of projecting portions TV1aand some of the plurality of projecting portions TV2aoverlap each other in plan view near the central portions of the light guides LG1and LG2. In reverse, the area AR12and the area AR21do not overlap each other in plan view.

The region of the area AR11of the light guide LG1, which overlaps the area AR22is designated as an overlapping region OR1, and the region of the area AR22, which overlaps the area AR11is designated as an overlapping region OR2. Light from the light source element LSM1entering from the side surface LG1s2is gradually emitted from a plurality of projecting portions TV1aas it approaches the side surface LG1s1. In order to emit light in the area closer to the side surface LG1s1with respect to the central portion LG1cof the light guide LG1, projecting portions TV1aare necessary as well in the area closer to the light entry side with respect to the central portion LG1c.

The above is also the case for the light guide LG2. Therefore, projecting portions TV2aare necessary as well on the light entry side (the side surface LG2s1side) with respect to the central portion LG2cof the light guide LG2.

At an end portion on the side surface LG1s2side of the area AR11(overlapping OR1), all the incident light is emitted downward, and therefore the luminance of the emitted light is reduced. Similarly, at an end portion on the side surface LG2s1side of the area AR22(overlapping region OR2), the luminance of the emitted light is reduced because all the incident light is emitted to the outside. Therefore, with the overlapping region OR1and the overlapping region OR2thus provided, the reduced luminance can be compensated for with each other. As a result, the luminance of the light emitted from the light guide LG1and the light guide LG2can be made uniform.

FIGS.4A and4Bare schematic enlarged cross-sectional views showing the shape of the projecting portions of the illumination device. In each of the projecting portions TV1aof the light guide LG1, the cross-sectional shape in the X-Z plane is a scalene triangle (seeFIG.4A). Among the edges of the scalene triangle, the edge tangent to the main surface LG1aof the light guide LG1is designated as an edge E1a1. The scalene triangle includes an edge E1a2and an edge E1a3extending from the edge E1a1. The angle formed by the edge E1a1and the edge E1a2is designated as an angle T1a1, the angle formed by the edge E1a1and the edge E1a3is designated as an angle T1a2, and the angle formed by the edge E1a2and the edge E1a3is designated as an angle T1a3.

As shown inFIG.4A, the lengths of the edges E1a1, E1a2, and E1a3are all different from each other.

The angle T1a1should preferably be 90° (90 degrees). That is, the scalene triangle should preferably be a right triangle. When the angle T1a1is 90°, light incident on the projecting portions TV1acan be efficiently reflected, which is desirable. Note here that the configuration is not limited to this, and it suffices if the angle T1a1is close to 90°, for example, in a range between 80° and 90°.

The angle T1a2is an acute angle, for example, 15° (15 degrees). The angle T1a3is an acute angle, for example, 75°. The angle T1a2and the angle T1a3can be determined according to the light distribution angle of the emitted light.

The gap and pitch between each adjacent pair of the projecting portions TV1aare defined as a gap Tg1and a pitch Tp1, respectively. The pitch Tp1is the sum of the length of the edge E1a1and the gap Tg1. When the pitch Tp1is set to a predetermined fixed value, the distribution of the projecting portions TV1acan be controlled by changing the length of the edge E1a1.

In each of the projecting portions TV1bof the light guide LG1, the cross-sectional shape thereon in the Y-Z plane is an isosceles triangle (seeFIG.4b). Among the edges of the isosceles triangle, the edge tangent to the main surface LG1bof the light guide LG1is designated as an edge E1b1. The isosceles triangle includes an edge E1b2and an edge E1b3, which extend from the edge E1b1. The angle formed by the edge E1b1and the edge E1b2is designated as an angle T1b1, the angle formed by the edge E1b1and the edge E1b3is designated as an angle T1b2, and the angle formed by an edge E1b2and an edge E1b3is designated as an angle T1b3.

In the isosceles triangle, the base angle T1b1and angle T1b2are equal to each other. The angle T1b3, which is the vertex angle, may as well be equal to the angle T1b1and the angle T1b2. In other words, the cross-sectional shape of the projecting portions TV1b, which is the isosceles triangle, may as well be an equilateral triangle.

FIGS.5A and5Bare schematic enlarged cross-sectional views each showing the shape of the projecting portions of the illumination device. In each of the projecting portions TV2aof the light guide LG2, the cross-sectional shape thereof in the X-Z plane is an scalene triangle (seeFIG.5A). Among the edges of the scalene triangle, the edge tangent to the main surface LG2aof the light guide LG2is designated as an edge E2a1. The scalene triangle includes an edge E2a2and an edge E2a3, which extend from the edge E2a1. The angle formed by the edge E2a1and the edge E2a2is designated as an angle T2a1, the angle formed by the edge E2a1and the edge E2a3is designated as an angle T2a2, and the angle formed by the edge E2a2and the edge E2a3is designated as an angle T2a3.

As shown inFIG.5A, the lengths of the edge E2a1, the edge E2a2, and the edge E2a3are all different from each other.

The angle T2a1should preferably be 90°. In other words, the scalene triangle should preferably be a right triangle. When the angle T2a1is 90°, light incident on the projecting portion TV2acan be reflected efficiently, which is suitable. However, the configuration is not limited to this, but it suffices if the angle T2a1is close to 90°, for example, between in a range of 80° and 90°.

The angle T2a2is an acute angle, for example, 15°. The angle T2a3is an acute angle, for example, 75°. The angle T2a2and the angle T2a3should be determined according to the light distribution angle of the emitted light.

The gap and pitch between each adjacent pair of the projecting portions TV2aare defined as a gap Tg2and a pitch Tp2, respectively. The pitch Tp2is the sum of the length of the edge E2a1and the gap Tg2. As in the case of the projecting portions TV1a, when the pitch Tp2is set to a predetermined fixed value, the distribution of the projecting portion TV2acan be controlled by changing the length of the edge E2a1.

The cross-sectional shape of each of the projecting portions TV1aof the light guide LG1and the cross-sectional shape of each of the projecting portions TV2aof the light guide LG2are arranged in line symmetrical positions with respect to a direction parallel to the Y-Z plane. In this embodiment, the lengths of the edges E1a1and E2a1, the lengths of the edges E1a2and E2a2, and the lengths of the edges E1a3and E2a3are equal to each other in each case.

The degrees of the angle T1a1and the angle T2a1, those of the angle T1a2and the angle T2a2, and those of the angle T1a3and the angle T2a3are equal to each other in each case.

In each of the projecting portions TV2bof the light guide LG2, the cross-sectional shape thereof in the Y-Z plane is an isosceles triangle (seeFIG.5B). Among the edges of the isosceles triangle, the edge tangent to the main surface LG2bof the light guide LG2is designated as an edge E2b1. The isosceles triangle includes an edge E2b2and an edge E2b3, which extend from the edge E2b1. The angle formed by the edge E2b1and the edge E2b2is designated as an angle T2b1, the angle formed by the edge E2b1and the edge E2b3is designated as an angle T2b2, and the angle formed by the edge E2b2and the edge E2b3is designated as an angle T2b3.

In the isosceles triangle, the base angle T2b1and angle T2b2are equal to each other. The angle T2b3, which is the vertex angle, may as well be equal to the angle T2b1and the angle T2b2. In other words, the cross-sectional shape of the projecting portions TV2b, which is the isosceles triangle, may as well be an equilateral triangle.

Here, the liquid crystal lens LNS will be explained.FIG.6is a perspective view showing a configuration of the liquid crystal lens.

The liquid crystal lens LNS comprises a first liquid crystal cell10, a second liquid crystal cell20, a third liquid crystal cell30, and a fourth liquid crystal cell40. The liquid crystal lens LNS of this embodiment is of a type which comprise two or more liquid crystal cells, and is not limited to the configuration with four liquid crystal cells, as shown in the example inFIG.6.

In the third direction Z, the fourth liquid crystal cell40, the third liquid crystal cell30, the second liquid crystal cell20, and the first liquid crystal cell10overlap in this order.

Light LT1and light LT2emitted from the illumination element IL2pass through the fourth liquid crystal cell40, the third liquid crystal cell30, the second liquid crystal cell20, and the first liquid crystal cell10, in that order. As will be described later, the first liquid crystal cell10, the second liquid crystal cell20, the third liquid crystal cell30, and the fourth liquid crystal cell40are configured to refract part of polarization components of the incident light. With the liquid crystal lens LNS, it is possible to diffuse and focus the light.

FIG.7is an exploded view schematically showing the liquid crystal lens illustrated inFIG.6.

The first liquid crystal cell10comprises a first transparent substrate S11, a second transparent substrate S21, a liquid crystal layer LC1, and a seal SE1. The first transparent substrate S11and the second transparent substrate S21are adhered together by the seal SE1. The liquid crystal layer LC1is held between the first transparent substrate S11and the second transparent substrate S21and sealed by the seal SE1. The effective area AA1, where incident light can be refracted, is formed on an inner side of the region enclosed by the seal SE1.

The first transparent substrate S11includes an extending portion EX1extending outwardly from the second transparent substrate S21along the first direction X and an extending portion EY1extending outwardly from the second transparent substrate S21along the second direction Y. At least one of the extending portion EX1and the extending portion EY1is connected to a flexible wiring substrate F indicated by the dotted line.

The second liquid crystal cell20comprises a first transparent substrate S12, a second transparent substrate S22, a liquid crystal layer LC2, and a seal SE2. The effective area AA2is formed on an inner side of the region enclosed by the seal SE2.

The first transparent substrate S12includes an extending portion EX2and an extending portion EY2. In the third direction Z, the extending portion EX2overlaps the extending portion EX1and the extending portion EY2overlaps the extending portion EY1. A flexible wiring substrate is connected to at least one of the extending portion EX2and the extending portion EY2, but the illustration of the flexible wiring substrate is omitted in the other cells, that is, the second liquid crystal cells20to the fourth liquid crystal cell40.

The third liquid crystal cell30comprises a first transparent substrate S13, a second transparent substrate S23, a liquid crystal layer LC3, and a seal SE3. The effective area AA3is formed on an inner side of the region enclosed by the seal SE3.

The first transparent substrate S13includes an extending portion EX3and an extending portion EY3. In the third direction Z, the extending portion EY3overlaps the extending portion EY2. The extending portion EX3does not overlap the extending portion EX2and is located on the opposite side to the extending portion EX2.

The fourth liquid crystal cell40comprises a first transparent substrate S14, a second transparent substrate S24, a liquid crystal layer LC4, and a seal SE4. The effective area AA4is formed on an inner side of the region enclosed by the seal SE4.

The first transparent substrate S14includes an extending portion EX4and an extending portion EY4. In the third direction Z, the extending portion EX4overlaps the extending portion EX3and the extending portion EY4overlaps the extending portion EY3.

Between the first liquid crystal cell10and the second liquid crystal cell20, a transparent adhesive layer TA12is disposed. The transparent adhesive layer TA12adheres the first transparent substrate S11and the second transparent substrate S22together.

Between the second liquid crystal cell20and the third liquid crystal cell30, a transparent adhesive layer TA23is disposed. The transparent adhesive layer TA23adheres the first transparent substrate S12and the second transparent substrate S23together.

Between the third liquid crystal cell30and the fourth liquid crystal cell40, a transparent adhesive layer TA34is disposed. The transparent adhesive layer TA34adheres the first transparent substrate S13and the second transparent substrate S24together.

The first transparent substrate S11to the first transparent substrate S14are each formed into a square shape and have equivalent sizes. For example, in the first transparent substrate S11, the side SX and the side SY are orthogonal to each other, and the length of the side SX is identical to the length of the side SY.

With the above-described configuration, when the first liquid crystal cell10, the second liquid crystal cell20, the third liquid crystal cell30, and the fourth liquid crystal cell40are adhered to each other, the sides thereof along the first direction X overlap each other, as shown inFIG.6, and the sides thereof along the second direction Y as well overlap each other.

Note that the second substrate, which has a shape substantially the same as that of the area through which light passes (the effective area, which will be described later), may be made square-shaped, and the first substrate may be made to have a polygonal shape other than square-shaped, for example, rectangular-shaped. Further, it is also possible to adopt a configuration in which one of the extending portions of each liquid crystal cell is deleted.

Next, the configuration of each liquid crystal cell will be described more specifically. Note that the following description is directed to, as an example, the first liquid crystal cell10of the plurality of the liquid crystal cells which constitute the liquid crystal lens LNS, but the configuration of each of the other liquid crystal cells from the second liquid crystal cell20to the fourth liquid crystal cell40is approximately the same as that of the first liquid crystal cell10, except for the extending direction of the strip electrodes.

FIG.8is a perspective view schematically showing the first liquid crystal cell10illustrated inFIG.7.

The first liquid crystal cell10comprises, in the effective area AA1, a first strip electrode E11A and a second strip electrode E11B, a first alignment film AL11, a third strip electrode E21A and a fourth strip electrode E21B, and a second alignment film AL21.

The first strip electrode E11A and the second strip electrode E11B are located between the first transparent substrate S11and the first alignment film AL11, are spaced apart from each other and extend in the same direction. The first strip electrode E11A and the second strip electrode E11B may be in contact with the first transparent substrate S11or may have an insulating film interposed between them and the first transparent substrate S11. Further, an insulating film may be interposed between the first strip electrode E11A and the second strip electrode E11B, and the first strip electrode E11A may be located in a layer different from that of the second strip electrode E11B.

There are a plurality of first strip electrodes E11A and a plurality of second strip electrodes E11B, which are aligned in the first direction X and arranged alternately. The plurality of first strip electrodes E11A are electrically connected to each other and configured so that the same voltage is applied thereto. The plurality of second strip electrodes E11B are electrically connected to each other and configured so that the same voltage is applied thereto. However, the voltage applied to the second strip electrode E11B is controlled to be different from the voltage applied to the first strip electrode E11A.

The first alignment film AL11covers the first strip electrodes E11A and the second strip electrodes E11B. The alignment treatment direction AD11of the first alignment film AL11is in the first direction X. Note that the alignment treatment of each alignment film may be a rubbing treatment or a photo-alignment treatment. The alignment treatment direction may as well be referred to as a rubbing direction. Generally, when no voltage is being applied to the liquid crystal layer (initial alignment state), liquid crystal molecules located near the alignment film are initially aligned in a predetermined direction by an alignment restriction force along the alignment treatment direction of the alignment film. That is, in the example presented here, the initial alignment direction of the liquid crystal molecules LM11along the first alignment film AL11is in the first direction X. The alignment direction AD11intersects the first strip electrode E11A and the second strip electrode E11B.

The third strip electrode E21A and the fourth strip electrode E21B are located between the second transparent substrate S21and the second alignment film AL21, are spaced apart from each other and extend in the same direction. The third strip electrode E21A and the fourth strip electrode E21B may be in contact with the second transparent substrate S21or an insulating film may be interposed between them and the second transparent substrate S21. Further, an insulating film may be interposed between the third strip electrode E21A and the fourth strip electrode E21B, and the third strip electrode E21A may be located in a layer different from that of the fourth strip electrode E21B.

There are a plurality of third strip electrodes E21A and a plurality of fourth strip electrodes E21B, which are aligned in the second direction Y and arranged alternately. The plurality of third strip electrodes E21A are electrically connected to each other and configured so that the same voltage is applied thereto. The plurality of fourth strip electrodes E21B are electrically connected to each other and configured so that the same voltage is applied thereto. However, the voltage applied to the fourth strip electrodes E21B is controlled to be different from the voltage applied to the third strip electrodes E21A. The extending direction of the first strip electrodes E11A and the second strip electrodes E11B is orthogonal to the extending direction of the third strip electrodes E21A and the fourth strip electrodes E21B, as will be described in detail later.

The second alignment film AL21covers the third strip electrodes E21A and the fourth strip electrodes E21B. The alignment direction AD21of the second alignment film AL21is in the second direction Y. That is, in the example presented here, the initial alignment direction of the liquid crystal molecules LM21along the second alignment film AL21is in the second direction Y. The alignment direction AD11of the first alignment film AL11and the alignment direction AD21of the second alignment film AL21are orthogonal to each other. The alignment direction AD21intersects the third strip electrodes E21A and the fourth strip electrodes E21B.

The optical activity in the first liquid crystal cell10will now be described with reference toFIGS.9and10. InFIGS.9and10, only the configurations necessary for explanation, such as the liquid crystal molecules LM1in the vicinity of the transparent substrate S11, are illustrated.

FIG.9is a diagram schematically showing the first liquid crystal cell10in an off state (OFF) where no electric field is formed in the liquid crystal layer LC1.

In the liquid crystal layer LC1in the off state, the liquid crystal molecules LM1are initially aligned. In an off state such as this, the liquid crystal layer LC1has a substantially uniform refractive index distribution. Therefore, a polarization component POL1, which is incident light to the first liquid crystal cell10, passes through the liquid crystal layer LC1without substantially being refracted (or diffused).

As shown inFIG.9, the initial alignment directions of the liquid crystal molecules of the liquid crystal layer LC1are crossed at 90° between the transparent substrates S11and S21in the first liquid crystal cell10. The liquid crystal molecules of the liquid crystal layer LC1are aligned in one of the first direction X and the second direction Y on a second transparent substrate S21side. The liquid crystal molecules gradually change their alignment from the one of the directions to the other of the first direction X and the second direction Y as the location is closer toward the first transparent substrate S11. The liquid crystal molecules are aligned in the other direction on a first transparent substrate S11side.

The direction of the polarization component changes in accordance with such a change in the alignment of the liquid crystal layer LC1. More specifically, the polarization component having its polarization axis on this one direction changes its polarization axis to the other direction in the process of passing through the liquid crystal layer LC1. On the other hand, the polarization component having the polarization axis on the other direction changes its polarization axis to the one direction in the process of passing through the liquid crystal layer LC1. Therefore, when viewed in terms of these mutually orthogonal polarization components, their polarization axes are interchanged in the process of passing through the first liquid crystal cell10. Such an effect of changing the direction of the polarization axes may be referred to as optical rotation in the following descriptions.

FIG.10is a diagram schematically showing the first liquid crystal cell10in the on state (ON), where an electric field is formed in the liquid crystal layer LC1.

In the on state, a potential difference is created between the first strip electrodes E11A and the second strip electrodes E11B, and thus an electric field is formed in the liquid crystal layer LC1. For example, when the liquid crystal layer LC1has positive dielectric constant anisotropy, the liquid crystal molecules LM1are aligned so that their long axes are along the electric field. Note here that the range covered by the electric field between the first strip electrodes E11A and the second strip electrodes E11B is mainly about ½ of the thickness of the liquid crystal layer LC1. Therefore, as shown inFIG.10, in the range of the liquid crystal layer LC1, that is close to the first transparent substrate S11, a region in which the liquid crystal molecules LM1are aligned substantially perpendicular to the substrate, a region in which the liquid crystal molecules LM1are aligned diagonally to the substrate, a region in which the liquid crystal molecules LM1are aligned substantially horizontal to the substrate, etc., are formed.

The liquid crystal molecules LM1have a refractive index anisotropy Δn. Therefore, the liquid crystal layer LC1in the on state has a refractive index distribution or retardation distribution according to the alignment state of the liquid crystal molecules LM1. The retardation here is expressed as: Δn·d, where the thickness of the liquid crystal layer LC1is represented by d. Note that in this example, a positive type liquid crystal is used as the liquid crystal layer LC1, but a negative type liquid crystal can as well be adopted by taking the alignment direction, etc. into consideration.

In an on state such as this, the polarization component POL1is diffused under the influence of the refractive index distribution of the liquid crystal layer LC1as it passes through the liquid crystal layer LC1. More specifically, the polarization component having a polarization axis in one of the first direction X and the second direction Y is diffused under the influence of the refractive index distribution of the liquid crystal layer LC1and is rotated in the other direction of the first direction X and the second direction Y. The polarization component having the polarization axis in the other direction is not affected by the refractive index distribution and passes through the liquid crystal layer LC1without being diffused but rotated only in that one direction.

Note thatFIG.10illustrates the case where an electric field is formed by the potential difference between the first strip electrodes E11A and the second strip electrodes E11B, but when diffusing incident light by the first liquid crystal cell10, it is preferable to form an electric field by the potential difference between the third strip electrodes E21A and the fourth strip electrodes E21B as well. With this configuration, the alignment state of not only the liquid crystal molecules in the vicinity of the first transparent substrate S11but also that of the liquid crystal molecules in the vicinity of the second transparent substrate S21can be controlled, and thus a predetermined refractive index distribution can be formed in the liquid crystal layer LC1.

More specifically, the liquid crystal layer LC1on the second transparent substrate S21side also has a refractive index distribution, and thus the polarization component that is rotated in the other direction of the first direction X and the second direction Y in the process of passing through the liquid crystal layer LC1is diffused. In other words, the polarization component diffused on the transparent substrate S11side is further diffused on the transparent substrate S21side and emitted from the first liquid crystal cell10. On the other hand, the polarization component that is rotated in the one of the first direction X and the second direction Y in the process of passing through the liquid crystal layer LC1is emitted from the first liquid crystal cell10without being affected by the refractive index distribution.

Such diffusion and rotation of the polarization components occur in the second liquid crystal cell20as well. That is, the polarization component of light emitted from the light source, which has a polarization axis directed in one of the first direction X and the second direction Y changes the direction of its polarization axis from the one to the other of the first direction X and the second direction Y as it passes through the first liquid crystal cell10. Further, it passes through the second liquid crystal cell20, the component changes the direction of its polarization axis from the other to the one of the directions.

Here, when the liquid crystal molecules parallel to the polarization component have a refractive index distribution in this process, the polarization component is diffused according to the refractive index distribution. Similarly, the polarization component of light emitted from the light source, which has a polarization axis directed in the other one of the first direction X and the second direction Y changes the direction of its polarization axis from the other one to the one of the first direction X and the second direction Y as it passes through the first liquid crystal cell10. Further, as it passes through the second liquid crystal cell20, the direction of the polarization axis is changed from the one to the other one. Further, when the liquid crystal molecules parallel to the polarization component have a refractive index distribution in this process, the polarization component is diffused according to the refractive index distribution.

The same phenomenon occurs in the third liquid crystal cell30and the fourth liquid crystal cell40as well, but these correspond to the first liquid crystal cells and second liquid crystal cells when rotated by 90°, the polarization components that cause the diffusion effect are switched over.

That is, in the configuration in which the first liquid crystal cell10, the second liquid crystal cell20, the third liquid crystal cell30, and the fourth liquid crystal cell40are stacked one on another, for example, the first liquid crystal cell10and the fourth liquid crystal cell40are configured to scatter (diffuse) the polarization component POL1, which is mainly of the p-polarized light, whereas the second liquid crystal cell20and the third liquid crystal30are configured to scatter (diffuse) the polarization component POL2, which is mainly of the s-polarized light.

In this embodiment, the liquid crystal lens LNS with four liquid crystal cells is described, but this embodiment is not limited to this configuration. It suffices if the liquid crystal lens LNS includes at least one liquid crystal cell, but it may include two or more liquid crystal cells.

FIGS.11and12are diagrams each showing illuminance distribution of light emitted from the illumination element.FIGS.11and12show the illuminance distributions in the illumination elements IL2and IL1, respectively.

InFIG.11, the horizontal axis indicates the distance from the central portion LG2cof the light guide LG2in the first direction X, where the position of the central portion LG2cis defined as 0, and the vertical axis indicates the illuminance. As to the horizontal axis, the left end corresponds to the location of the side surface LG2s1and the right end to the side surface LG2s2. The figure illustrates that as the location is closer to the side surface LG2s1, it approaches the light source element LSM2. On the other hand, the closer to the side surface LG2s2, the further away from the light source element LSM2.

At the locations from the side surface LG2s1to the central portion LG1c, the illuminance of the illumination element IL1is substantially zero (0). The illuminance rises sharply near the central portion LG2c, and at the locations from the central portion LG2cto the side surface LG2s2, the illuminance is approximately 5,000 [lx] or higher. The maximum value exists near the location 20 mm away from the central portion LG2cto the side surface LG2s2. The maximum value is approximately 10,000 [lx].

InFIG.12, the horizontal axis indicates the distance from the central portion LG1cof the light guide LG1in the first direction X, where the central portion LG1cis designated as0, and the vertical axis indicates the illuminance. On the horizontal axis, the left end corresponds to the location of the side surface LG1s1and the right end to side the surface LG1s2. It is illustrated that as the location is closer to the side surface LG1s1, it is further away from the light source element LSM1. On the other hand, the closer to the side surface LG1s1, the closer to the light source element LSM1.

The illuminance of the illumination element IL1is substantially zero (0) at the locations from the side surface LG1s2to the central portion LG1c. The illuminance rises sharply around the central portion LG1c, and at the locations from the central portion LG1cto the side surface LG1s1, the illuminance is approximately 5,000 [lx] or higher. The maximum value exists near the location 20 mm away from the central portion LG1cto the side surface LG1s1(which is the location of −20 [mm]). The maximum value is approximately 10,000 [lx].

FIGS.13and14are diagrams each showing the relationship of the normalized luminous intensity of the emitted light to the zenith angle in the illumination elements.FIG.13shows plots for the illumination element IL2andFIG.14are plots for the illumination element IL1. The relationship between the vertex angle θ [° (degree(s))] and the normalized luminous intensity I [a.u.] may as well be referred to as the emission angle distribution.

InFIGS.13and14, the vertex angle on the horizontal axis indicates the angle of the emitted light in the first direction X or the angle of the emitted light in the second direction Y. The angle of the emitted light in the first direction X is the angle between the emitted light from the light source elements and the Y-Z plane. The angle of the emitted light in the second direction Y is the angle between the emitted light from the light source elements and the X-Z plane. In the ideal collimated light, the angle of the emitted light in the first direction X and second direction Y is 0°, but in the actual emitted light, there is a distribution of emission angles.

InFIGS.13and14, the emission angle distribution Px in the first direction X is indicated by a solid line and the emission angle distribution Py in the second direction Y is indicated by a dotted line. As shown inFIG.13, the illumination element IL2exhibits a maximum normalized luminous intensity I at a vertex angle of 45° for the first direction X. For the second direction Y, the normalized luminous intensity I is substantially constant even if the vertex angle θ changes. This is because it is not diffused by the liquid crystal lens LNS.

As shown inFIG.14, for the first direction X, the illumination element IL1exhibits a maximum normalized luminous intensity I at a vertex angle of −45°. For the second direction Y, the normalized luminous intensity I is substantially constant even when the angle θ is changed, as is the case of the illumination element IL2.

Let us return toFIG.2. The light LT1pand the light LT2pcorrespond to the emitted light shown inFIGS.12and11, respectively. The angle Rip and the angle R2pcorrespond to the vertex angles in the first direction X shown inFIGS.14and13, respectively.

By the illumination element IL1and the illumination element IL2, the light LT1and the light LT2are emitted more outwardly as light LT1pand light LT2p, respectively. On the other hand, by the liquid crystal lens LNS in the on state, the light is emitted more inwardly as polarized light LT1cand polarized light LT2c.

As described above, by changing the emission angle, it is possible to illuminate light at a desired location.

FIGS.15,16,17,18,19,20,21,22, and23are diagrams each showing the relationship of the luminous intensity of the emitted light to the angle of the emitted light in this illumination device.FIGS.15,16, and17each show the relationship between the angle (which may as well be referred to as the emission angle) and the luminous intensity of emitted light in the configuration of the illumination device ILD in which the liquid crystal lens LNS is not provided.FIGS.18,19, and20each show the relationship between the angle and the luminous intensity of the emitted light of the illumination device ILD when the liquid crystal lens LNS is in the off state.FIGS.21,22, and23each show the relationship between the angle and the luminous intensity of the emitted light of the illuminator ILD when the liquid crystal lens LNS is in the on state. InFIGS.15to23, the angle [° ] on the horizontal axis is similar to the vertex angle θ inFIGS.13and14. The luminous intensity on the vertical axis is similar to the normalized luminous intensity inFIGS.13and14.

FIGS.15,18, and21show the cases where the illumination element IL1is turned on, that is, the light source elements LSM1are turned on.FIGS.16,19, and22show the cases in which the illumination element IL2is turned on, that is, the light source elements LSM2are turned on.FIGS.17,20, and23show the cases where both the illumination element IL1and the illumination element IL2are turned on, that is, both the light source elements LSM1and the light source elements LSM2are turned on.

As shown inFIG.15, the luminous intensity of the emitted light relating to the illumination element IL1in the configuration without the liquid crystal lens LNS becomes maximum when the emission angle is −45°. Similarly, as shown inFIG.16, the luminous intensity of the emitted light relating to the illumination element IL2becomes maximum when the emission angle is 45°. When both the illumination elements IL1and IL2are turned on, the luminous intensity becomes maximal when the emission angles are at −45° and 45°, as shown inFIG.17.

When the liquid crystal lens LNS is provided but not turned on, the luminous intensity of the emitted light relating to the illumination element IL1becomes maximum when the emission angle is −40°, as shown inFIG.18. Similarly, as shown inFIG.19, the luminous intensity of the emitted light relating to the illumination element IL2becomes maximum when the emission angle is 40°. When both the illumination elements IL1and IL2are turned on, the luminous intensity becomes maximal when the emission angle is at −40° and 40°, as shown inFIG.20. When passing through the liquid crystal lens LNS, the emitted light is refracted, and therefore the emission angle becomes smaller than when the liquid crystal lens LNS is not provided. However, compared to the case where the liquid crystal lens LNS is turned on (which will be described later), the influence on the emission angle is small.

In the case where the liquid crystal lens LNS is turned on, as shown inFIG.21, the luminous intensity of the emitted light relating to the illumination element IL1becomes maximum when the emission angle is −20°. Similarly, as shown inFIG.22, the luminous intensity of the light emitted from the illumination element IL2becomes maximum when the emission angle is 20°.

When the liquid crystal lens LNS is set in the on state, the emission angle of the maximum luminous intensity is smaller than when it is in the off state. This is because, when the liquid crystal lens LNS is in the on state, the light incident on the liquid crystal lens LNS is diffused under the influence of the refractive index distribution of the liquid crystal layer, as described above. With this configuration, the light emitted from the liquid crystal lens LNS can be directed more inwardly.

When both the illumination element IL1and the illumination element IL2are turned on, the luminous intensity becomes maximum when the emission angle is between −5° and 5°, as shown inFIG.23. Since the emitted light from the illumination elements IL1and IL2are combined together, the luminous intensity is substantially constant in a range of the emission angles from −5° to 5°. Thus, when the liquid crystal lens LNS is in the on state and both the illumination element IL1and the illumination element IL2are turned on, light with a constant luminous intensity can be obtained for the emitting surface (irradiation surface).

FIGS.24,25,26, and27each show an example of the application of the illumination device of this embodiment. A vehicle VHC comprises a driver's seat DRV, a passenger's seat PRS, a windshield WSD, a shift lever SLV, a steering wheel WHL, a ceiling CEL, side mirrors SMR and the like. The lighting device ILD is installed in the ceiling CEL of the vehicle VHC.

FIG.24shows an example of the case where the illumination element IL2of the illumination device ILD is set in the on state, that is, only the light source elements LSM2are turned on, and the liquid crystal lens LNS is set in the off state. Spot light is irradiated as the illumination light ILT on the right side and on the outer side of the drawing. The illumination light ILT corresponds to the light LT2p.

FIG.25shows an example of the case where both the illumination elements IL1and IL2of the illumination device ILD are set in the on state, that is, the light source elements LSM1and the light source elements LSM2are turned on and the liquid crystal lens LNS is set in the off state. Spot light is irradiated as the illumination light ILT on both the left and right sides and on the outer side of the drawing. The illumination light ILT corresponds to the light LT1pand the light LT2p. In the example shown inFIG.25, on the outer side of the left and right sides of the drawing, the spot light is irradiated, whereas the inner side is not irradiated with the like, and becomes dark.

FIG.26shows an example of the case where the illumination element IL2of the illumination device ILD is set in the on state, that is, only the light source elements LSM2are turned on, and the liquid crystal lens LNS is set in the on state. The illumination light ILT is irradiated on the right side and on the inner side of the drawing. The illumination light ILT corresponds to the polarized light LT2c.

FIG.27shows an example of the case where both the illumination element IL1and the illumination element IL2of the illumination device ILD are set in the on state, that is, the light source elements LSM1and the light source elements LSM2are turned on, and the liquid crystal lens LNS is set in the on state. The illumination light ILT is irradiated on both the left and right sides and on the inner side of the drawing. The illumination light ILT corresponds to the polarized light LT1cand the polarized light LT2c. In the example shown inFIG.27, the light irradiated on the left and right sides shifted to the inner side, and therefore unlikeFIG.25, the area where the illumination light ILT reaches is entirely irradiated. Further, as described with reference toFIG.23, the luminous intensity is uniform with the illumination light ILT having such a configuration.

In the illumination device ILD of this embodiment, the light guide LG1and the light guide LG2comprise projecting portions TV1aand projecting portions TV1b, and projecting portions TV2aand projecting portions TV2b, respectively, on the side surface side far from the light source element LSM1and the light source element LSM2. The liquid crystal lenses LNS which can diffuse light is provided so as to overlap the illumination element IL1comprising the light guide LG1and the illumination element IL2comprising the light guide LG2.

With the illumination element IL1and the illumination element IL2, it is possible to obtain illumination light with a large light distribution angle. With the liquid crystal lens, it is possible to obtain illumination light with a small light distribution angle. By controlling the turning on and off of the light source elements LSM1and the light source elements LSM2of the illumination element IL1and the illumination element IL2, it is possible to illuminate either or both the left or right side.

According to the above-described embodiments, it is possible to provide an illumination device that can irradiate light at a desired location.

In this disclosure, the light source elements LSM1and the light source elements LSM2are the first light source elements and the second light source elements, respectively. The light guide LG1and the light guide LG2are the first light guide and the second light guide, respectively. The area AR11, The area AR12, the area AR21, and the area AR22are the first area, the second area, the third area, and the fourth area, respectively.

In this disclosure, the side surface LG1s1and the side surface LG1s2of the light guide LG1, and the side surface LG2s1and the side surface LG2s2of the light guide LG2are referred to as the first side surface, the second side surface, the third side surface, and the fourth side surface, respectively. The main surface LG1aand the main surface LG1bof the light guide LG1, and the main surface LG2aand the main surface LG2bof the light guide LG2are referred to as the first main surface, the second main surface, the third main surface, and the fourth main surface, respectively.

In this disclosure, the projecting portions TV1a, the projecting portions TV1b, the projecting portions TV2a, and the projecting portions TV2bare referred to as the first projecting portions, the second projecting portions, the third projecting portions, and the fourth projecting portions, respectively.

Of the edges of the scalene triangle, which is the cross-sectional shape of the projecting portions TV1a, the edge E1a1, the edge E1a2, and the edge E1a3are referred to as the first edge, the second edge, and the third edge, respectively. The angle T1a1formed by the edge E1a1and the edge E1a2, the angle T1a2formed by the edge E1a1and the edge E1a3, and the angle T1a3formed by the edge E1a2and the edge E1a3are referred to as the first angle, the second angle, and the third angle, respectively.

Of the edges of the scalene triangle, which is the cross-sectional shape of the projecting portions TV2a, the edge E2a1, the edge E2a2, and the edge E2a3are the fourth edge, the fifth edge, and the sixth edge, respectively. The angle T2a1formed by the edge E2a1and the edge E2a2, the angle T2a2formed by the edge E2a1and the edge E2a3, and the angle T2a3formed by the edge E2a2and the edge E2a3are the fourth angle, the fifth angle, and the sixth angle, respectively.