JP2020170668A - Light guide member and surface light source device - Google Patents

Abstract

To make a surface light source device thinner.SOLUTION: A light guide member 10 is arranged so as to face a plurality of light sources 5 in a first direction d1. The light guide member 10 comprises a plurality of first portions 20, and a second portion 30. The first portions 20 are provided so as to face the plurality of light sources 5 in the first direction d1 respectively, and comprise reflecting surfaces 22 for reflecting at least a portion of light from the light sources 5. The second portion 30 comprises a first surface 31 and a second surface 32 opposed to each other in the first direction d1, and allows light to be guided in a second direction d2 not parallel to the first direction d1 by allowing at least a portion of light reflected by the first portions 20 to be totally reflected by the first surface 31 and the second surface 32.SELECTED DRAWING: Figure 3

Description

The present invention relates to a light guide member and a surface light source device having a light guide member.

A surface light source device having a light emitting surface that emits light in a planar shape is widely used as a backlight that is incorporated in a liquid crystal display device and illuminates the liquid crystal display panel from the back side (for example, Patent Document 1). Surface light source devices for liquid crystal display devices are roughly classified into a direct type in which a plurality of light sources are arranged directly under the optical member and an edge light type (also called a side light type) in which a plurality of light sources are arranged on the side of the optical member. ) And.

The conventional surface light source device always emits light over the entire surface. Therefore, in a display device having a conventional surface light source device, when displaying black, the light from the surface light source device is blocked. However, the light from the surface light source device cannot be sufficiently blocked and the contrast of the image displayed on the display device deteriorates, and the light to be blocked is also emitted, so that the power consumption of the surface light source device becomes large. There is a problem.

In order to deal with such a problem, local dimming that independently controls the light emission of the surface light source device at each position in the surface is known. By performing local dimming in the surface light source device, it is possible to control so that only the light source corresponding to the portion displaying black is not emitted. Therefore, the contrast of the image displayed on the display device can be improved without blocking the light from the surface light source device. Further, the power consumption in the surface light source device can be reduced.

In the edge light type surface light source device, since the light source is arranged on the side of the optical member to guide the light of one light source in one direction, it is difficult to perform local dimming. On the other hand, in the direct type surface light source device, local dimming can be easily performed by independently controlling the light emission of a plurality of light sources arranged directly under the optical member. Therefore, in order to improve the contrast of the image displayed on the display device and reduce the power consumption in the surface light source device, it is desired to use a direct type surface light source device.

Japanese Patent No. 4959491

By the way, in the direct type surface light source device, a plurality of optical members are arranged below the optical member so as to face the plurality of light sources. With the plurality of optical members, the unevenness of brightness caused by the arrangement of the plurality of light sources can be eliminated, and the in-plane distribution of the amount of light emitted from the surface light source device can be made uniform. In order to make the brightness distribution uniform, it is necessary to separate the optical member from the light source to some extent. Therefore, in the direct type surface light source device, the length between the optical member and the light source becomes long, and it is difficult to reduce the thickness.

The present invention has been made in consideration of the above points, and an object of the present invention is to reduce the thickness of the surface light source device.

The first light guide member of the present invention is a light guide member arranged to face a plurality of light sources in the first direction.
A plurality of first portions provided facing each of the plurality of light sources and having a reflecting surface that reflects at least a part of the light from the light source.
The first surface has a first surface and a second surface facing each other in the first direction, and at least a part of the light reflected by the first portion is totally reflected by the first surface and the second surface. It includes a second portion that guides light in a second direction that is non-parallel to one direction.

In the first light guide member of the present invention
The first portion has an incident side facing the light source.
The reflective surface may be inclined with respect to the incident side surface.

In the first light guide member of the present invention, the inclination angle of the reflecting surface with respect to the incident side surface may become smaller as the distance from the incident side surface increases.

In the first light guide member of the present invention, the reflective surface is a surface provided on the side of the first portion opposite to the side facing the light source and forming a recess that tapers toward the side facing the light source. It may be.

In the first light guide member of the present invention, the outer contour of the reflecting surface may be a square, a regular hexagon, or a circle in a plan view.

In the first light guide member of the present invention, the second surface of the second portion may be connected to the reflection surface of the first portion.

In the first light guide member of the present invention
The first surface is a flat surface and
The second surface may include a portion parallel to the first surface.

In the first light guide member of the present invention, the refractive index of the second portion may be 1.20 or more.

In the first light guide member of the present invention, the second portion may have an emission means for emitting the light being guided.

In the first light guide member of the present invention, the light emitting means may have a higher density as it is separated from the reflecting surface.

In the first light guide member of the present invention, the emission means may be provided on the second surface of the second portion.

In the first light guide member of the present invention, the emitting means may have a concave shape or a convex shape provided on a part of the second surface.

The second light guide member of the present invention is a light guide member arranged to face a plurality of light sources in the first direction.
The one-sided main surface faces the light source and
The main surface on one side and the main surface on the other side facing the first direction are provided.
The other side main surface is provided with a plurality of concave shapes that taper toward the one side main surface so as to be separated from each other.
The portion of the other main surface that forms the concave shape functions as a reflecting surface that reflects at least a part of the light incident from the one side main surface.
The one-side main surface and the other-side main surface guide light in a second direction non-parallel to the first direction by totally reflecting at least a part of the light reflected by the reflection surface.

The surface light source device of the present invention
With any of the light guide members mentioned above,
A plurality of light sources facing the first portion of the light guide member in the first direction are provided.

In the surface light source device of the present invention, the length between the light source and the light guide member in the first direction may be 10 mm or less.

In the surface light source device of the present invention, the length of the reflecting surface along the second direction may be 1 time or more and 20 times or less the length of the light source along the second direction.

In the surface light source device of the present invention, the maximum length between the first surface and the second surface may be 10 times or less the length of the light source along the second direction.

According to the present invention, the surface light source device can be made thinner.

FIG. 1 is a perspective view schematically showing a surface light source device. FIG. 2 is a plan view of the surface light source device of FIG. FIG. 3 is a cross-sectional view of the surface light source device along lines III-III of FIG. FIG. 4 is a perspective view showing one first portion of the light guide member. FIG. 5 is a diagram for explaining the operation of the surface light source device. FIG. 6 is a plan view showing a modified example of the first portion of the light guide member. FIG. 7 is a perspective view of a modified example of the first part. FIG. 8 is a plan view showing another modification of the first portion of the light guide member. FIG. 9 is a perspective view of another modified example of the first portion.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings attached to the present specification, the scale, aspect ratio, etc. are appropriately changed from those of the actual product and exaggerated for the convenience of illustration and comprehension.

It should be noted that the terms such as "parallel", "orthogonal", and "same", and the values of length and angle, etc., which specify the shape and geometric conditions and their degrees as used in the present specification, are strictly defined. Without being bound by the meaning, we will interpret it including the range where similar functions can be expected.

FIG. 1 is a perspective view schematically showing a surface light source device 1. The surface light source device 1 emits light in a planar manner. The surface light source device 1 is incorporated in, for example, a liquid crystal display device and is used as a backlight of the liquid crystal display device. The surface light source device 1 is configured as a direct type surface light source device. The surface light source device 1 includes a plurality of light sources 5 two-dimensionally arranged on a plane substantially parallel to the light emitting surface of the surface light source device 1, and a light guide member 10 arranged to face the plurality of light sources 5 in the first direction d1. And have. The light source 5 is arranged so as to face the one-side main surface 11 described later of the light guide member 10. Further, the light source 5 is arranged at a position facing the reflection surface 22 of the light guide member 10 described later. The first direction d1 is the thickness direction of the surface light source device 1. In the example shown in FIG. 1, the surface of the light guide member 10 opposite to the side facing the light source 5 is the light emitting surface of the surface light source device 1. The surface light source device 1 may further have a diffuser plate or the like not shown in FIG. 1 arranged on the side of the light guide member 10 opposite to the side facing the light source 5. In this case, the surface of the diffuser plate opposite to the side facing the light guide member 10 is the light emitting surface of the surface light source device 1.

The light emission of the plurality of light sources 5 can be independently controlled according to the image displayed on the display device or the like in which the surface light source device 1 is incorporated. That is, the surface light source device 1 can perform local dimming. Therefore, the surface light source device 1 of the present embodiment can improve the contrast of the image displayed on the built-in display device, and can further reduce the power consumption of the surface light source device 1. The light emission of the plurality of light sources 5 is controlled by, for example, a signal from a control unit (not shown).

The light source 5 is arranged at a position corresponding to the grid points of the square grid. The distance between the adjacent light sources 5 is, for example, 100 mm or less. The light source 5 may be configured in various forms such as a point LED (light emitting diode) or an incandescent light bulb. In particular, it is preferable that an LED is used as the light source 5 in order to reduce the thickness of the surface light source device 1. The thickness of such a light source 5 is, for example, 10 μm or more and 5000 μm or less. Further, the light source 5 is, for example, a square or rectangle having a side of 10 μm or more and 5000 μm or less in a plan view, or a circle having a diameter of 10 μm or more and 5000 μm or less.

The light guide member 10 incidents light from the light source 5 and guides the light in the second direction d2, which is non-parallel to the first direction d1. In the illustrated example, the first direction d1 and the second direction d2 are orthogonal to each other. Further, in the illustrated example, the light guide member 10 guides the light from the light source 5 in a plane. In other words, the second direction d2 is an arbitrary direction non-parallel to the first direction d1. The light guide member 10 emits the light guiding the inside from the side opposite to the side facing the light source 5. The light emitted from the light guide member 10 is substantially uniform in a plan view.

The light guide member 10 is arranged so as to face the light source 5 in the first direction d1. In order to reduce the thickness of the surface light source device 1, the length D between the light source 5 and the light guide member 10 in the first direction d1 is 10 mm or less, preferably 1 mm or less. The light guide member 10 is arranged in the entire surface light source device 1. The light guide member 10 is an integrally formed member. Further, the light guide member 10 is, for example, a thermoplastic resin and is formed of a resin having high visible light transmittance. As the resin forming the light guide member 10, an acrylic resin, a polycarbonate resin, and a COP (cycloolefin polymer) can be exemplified.

As shown in FIG. 1, the light guide member 10 has a plate-like outer shape. The light guide member 10 has a main surface 11 on one side and a main surface 12 on the other side facing each other. The one-side main surface 11 and the other-side main surface 12 face the first direction d1. The main surface 11 on one side faces the light source 5. The light guide member 10 extends in a direction non-parallel to the first direction d1, and therefore extends in the second direction d2 as well. As will be described in detail later, the light guide member 10 directs the traveling direction of the light incident inside from the one-side main surface 11 from the first direction d1 to the second direction d2, and further directs the one-side main surface 11 and others. The light is guided in the second direction d2 by total reflection on the side main surface 12.

FIG. 2 shows a plan view of the surface light source device 1. As shown in FIG. 2, the light guide member 10 has a plurality of first portions 20 and a second portion 30 surrounding the first portion 20. In the illustrated example, the light guide member 10 is plane-divided into either the first portion 20 or the second portion 30 along the plate surface thereof. Of these, the first portion 20 has a recess 25 formed on the side opposite to the light source 5. In particular, the first portion 20 has a recess 25 on the side where the light of the light guide member 10 is emitted. The recess 25 has a tapered shape toward the side of the main surface 11 on one side along the first direction d1. The other side main surface 12 in the first portion 20 is formed by surfaces (surface, wall surface) forming the recess 25. The surface forming the recess 25 constitutes a reflective surface 22 that is inclined with respect to the one-side main surface 11 described later. The second portion 30 is a portion of the light guide member 10 that is substantially flat on the incident side and the light emitting side.

The alternate long and short dash line in FIG. 2 indicates an intermediate line between adjacent first portions 20. In the example shown in FIG. 2, the center of the first portion 20 is provided at a position corresponding to the grid points of the square grid. The area surrounded by the middle line of the first portion 20 is a square.

FIG. 3 is a cross-sectional view of the surface light source device 1 along the line III-III of FIG. As shown in FIG. 3, the first portion 20 faces the light source 5 in the first direction d1. The first portion 20 has an incident side surface 21 facing the light source 5 and a reflecting surface 22 capable of reflecting light. That is, the one-side main surface 11 of the light guide member 10 includes the incident side surface 21 in the first portion 20. The other side main surface 12 of the light guide member 10 includes a reflecting surface 22 in the first portion 20. The reflecting surface 22 faces the incident side surface 21 in the first direction d1.

The first portion 20 reflects at least a part of the light from the light source 5 incident on the incident side surface 21 by the reflecting surface 22. The traveling direction of the light reflected by the reflecting surface 22 is changed so that the angle formed with respect to the first direction d1 becomes large, while the angle formed with respect to the second direction d2 becomes small.

The reflecting surface 22 is provided at a position overlapping the light source 5 at least in a plan view so that the light from the light source 5 incident on the incident side surface 21 is incident on the reflecting surface 22. The reflecting surface 22 has a function of reflecting at least a part of light by total reflection based on the difference in refractive index between the first portion 20 and the outside of the first portion 20. According to total reflection, the traveling direction of light can be changed efficiently.

The reflective surface 22 is a part of the surface of the first portion 20 and is an interface between the first portion 20 and the outside of the first portion 20. As in the illustrated example, when the light guide member 10 is a portion having a recess 25 on the light emitting side, the reflecting surface 22 is the first portion 20 and the air outside the first portion 20. Interface. However, not limited to the illustrated example, the portion of the light guide member 10 that is the recess 25 may be flattened with a resin or the like having a refractive index different from that of the first portion 20. When the light guide plate is formed by the light guide member 10 and the filler filled in the recess 25 of the light guide member 10 in this way, the interface between the first portion 20 and the resin becomes the reflective surface 22.

The recess 25 has a shape that tapers toward the light source 5 along the first direction d1. The deepest and deepest portion of the recess 25 is located at a position overlapping the light source 5 in projection in the first direction d1. Then, the depth of the recess 25 becomes shallower as it shifts from the deepest portion in the direction orthogonal to the first direction d1. As described above, the surface of the other side main surface 12 forming the recess 25 forms the reflecting surface 22 that directs the traveling direction of light from the first direction d1 to the second direction d2. Therefore, the reflective surface 22 formed by the recess 25 is inclined with respect to both the first direction d1 and the second direction d2. The recess 25 is a regular polygon centered on an axis extending in the first direction d1 in a plan view and intersecting with the light source 5 so that the light from one light source 5 can be radially spread when observed from the first direction d1. Alternatively, it is preferably circular, and preferably has the shape of a rotating body that tapers further. Specifically, as the shape of the recess 25, a pyramid shape such as a triangular pyramid shape, a quadrangular pyramid shape, a pentagonal pyramid shape, a hexagonal pyramid shape, a conical shape, or the like can be exemplified.

In addition, in this specification, a cone shape is not only a shape formed by connecting a closed curve or a polygonal line on a plane and one point outside the plane by a straight line, but also by connecting by a curve. Also includes shapes.

The incident side surface 21 and the reflecting surface 22 may be adjacent to each other, for example. Further, it is preferable that the length W of the reflecting surface 22 along the second direction d2, in other words, the width of the reflecting surface 22 is wide so that the light incident from the incident side surface 21 can easily enter the reflecting surface 22. .. Specifically, the length W of the reflecting surface 22 along the second direction d2 is preferably 1 time or more and 20 times or less the length of the light source 5 along the second direction d2, and is 2 times or more and 10 times or more. More preferably, it is twice or less.

Here, the length of the light source 5 means the length of only the portion of the light source that emits light, and is the length excluding the border of the portion that emits light.

The reflection on the reflecting surface 22 is preferably total reflection in consideration of the reflection efficiency. Light is totally reflected on the reflecting surface 22 based on the difference in refractive index between the first portion 20 and the outside of the first portion 20, among other things, incident on the reflecting surface 22 at a larger angle of incidence. It is preferable that the refractive index of the first portion 20 is sufficiently larger than the external refractive index of the first portion 20 so that the light can be totally reflected. Specifically, the refractive index of the first portion 20 is preferably 1.20 or more, and more preferably 1.30 or more.

Further, the incident side surface 21 is a flat surface parallel to the second direction d2, and the reflecting surface 22 is inclined with respect to the incident side surface 21. The inclination angle of the reflecting surface 22 with respect to the incident side surface 21 becomes smaller as the distance from the incident side surface 21 increases. At this time, as the distance from the deepest portion of the recess 25 in the second direction d2 increases, the inclination angle of the reflecting surface 22 with respect to the incident side surface 21 becomes smaller. In the vicinity of the deepest portion of the recess 25 just above the center of the light source 5 along the first direction d1, the angle formed by the traveling direction of the light incident on the reflecting surface 22 with respect to the second direction d2 becomes large. In order to totally reflect such light, it is preferable that the inclination angle of the reflecting surface 22 with respect to the incident side surface 21 is large in the vicinity of the deepest portion of the recess 25. On the contrary, in the region separated from the deepest portion of the recess 25 directly above the light source 5 along the first direction d1 in the second direction d2, the traveling direction of the light incident on the reflecting surface 22 is relative to the second direction d2. The angle of formation becomes smaller. In order to totally reflect such light, it is preferable that the inclination angle of the reflecting surface 22 with respect to the incident side surface 21 is small in the region separated from the deepest portion of the recess 25 in the second direction d2.

FIG. 4 shows one first portion 20. As shown in FIGS. 2 and 4, the outer contour of the reflective surface 22 included in the first portion 20, particularly one first portion 20, in other words, the outer surface of the reflective surface 22 forming one recess 25. The contour is circular in plan view. The reflective surface 22 of the first portion 20 is a curved surface in which the inclination angle with respect to the incident side surface 21 decreases from the center of the circle toward the outer circumference.

The second portion 30 guides the light reflected by the first portion 20. The second portion 30 has a first surface 31 and a second surface 32 facing each other in the first direction d1. By reflecting the light on the first surface 31 and the second surface 32, the light can be guided in the second direction d2 in the second portion 30. It is preferable that the first surface 31 and the second surface 32 reflect light by total reflection based on the difference in refractive index between the second portion 30 and the outside of the second portion 30. The light guiding the second portion 30 is emitted from the second surface 32.

The first surface 31 is a surface on the side facing the light source 5, and the second surface 32 is a surface opposite to the side facing the light source 5. The first surface 31 is a flat surface parallel to the second direction d2. That is, the first surface 31 is parallel to the incident side surface 21 of the first portion 20. In the illustrated example, the first surface 31 is connected to the incident side surface 21. The one-side main surface 11 of the light guide member 10 includes an incident side surface 21 in the first portion 20 and a first surface 31 in the second portion 30. Further, the second surface 32 includes a portion parallel to the first surface 31. The second surface 32 is connected to the reflecting surface 22 of the first portion 20. The other side main surface 12 of the light guide member 10 includes a reflecting surface 22 in the first portion 20 and a second surface 32 in the second portion 30.

The maximum length T between the first surface 31 and the second surface 32, in other words, the thickness of the second portion 30, is a light source along the second direction d2 in order to reduce the thickness of the surface light source device 1. The length of 5 is preferably 0.5 times or more and 10 times or less, and more preferably 1 time or more and 5 times or less. In the illustrated example, the thickness of the second portion 30 coincides with the thickness of the light guide member 10.

The reflection on the first surface 31 and the second surface 32 is preferably total reflection in consideration of the reflection efficiency. Above all, a larger angle of incidence so that light can be totally reflected on the first and second surfaces 31 based on the difference in refractive index between the second portion 30 and the outside of the second portion 30. The refractive index of the second portion 30 is sufficiently larger than the external refractive index of the second portion 30 so that the light incident on the first surface 31 and the second surface 32 can be totally reflected. Is preferable. Specifically, the refractive index of the second portion 30 is preferably 1.20 or more, and more preferably 1.30 or more.

The refractive index of the first portion 20 and the refractive index of the second portion 30 may be the same. For example, since the first portion 20 and the second portion 30 are integrally molded from the same material, the refractive index of the first portion 20 and the refractive index of the second portion 30 can be made the same. ..

The second portion 30 further has an emitting means 35 for emitting the light guiding the inside thereof from the light guide member 10. The emitting means 35 is provided on the second surface 32 of the second portion 30 in the example shown in FIG. More specifically, the emitting means 35 has a convex shape provided on a part of the second surface 32. By incident on the convex shape, the light can have an angle less than the total reflection angle on the second surface 32. Light having an angle less than the total reflection angle on the second surface 32 is emitted from the second surface 32 without being totally reflected on the second surface 32. On the other hand, since the first surface 31 is not provided with an emitting means such as a convex shape, light is hardly emitted from the first surface 31. That is, by providing the emitting means 35 only on the second surface 32, the light guiding the second portion 30 can be selectively emitted from the second surface 32.

The emitting means 35 is not limited to the illustrated example, and may have a concave shape provided on a part of the second surface 32, for example. When the emitting means 35 has a concave shape, the light incident on the concave shape has an angle less than the total reflection angle, so that the light can be emitted from the second surface 32, similarly to the convex shape described above. Alternatively, the emitting means 35 may be scattered particles or the like included in the second portion 30. By being scattered by the scattered particles, the scattered light can enter the second surface 32 at an angle less than the total reflection angle. Light incident at an angle less than the total reflection angle is emitted from the second surface 32 without being totally reflected on the second surface 32.

By adjusting the distribution of the emitting means 35 along the second direction d2, the distribution of the amount of light emitted from the light guide member 10 along the second direction d2 can be adjusted. In the example shown in FIG. 3, the emitting means 35 has an increased density as it is separated from the reflecting surface 22 of the first portion 20 along the second direction d2. That is, as the distance from the reflecting surface 22 increases, the light is more likely to be emitted. Here, the density of the emitting means 35 is, for example, the ratio of the area where the convex shape is provided per the unit area of the second surface 32 when the emitting means 35 has a convex shape provided on the second surface 32. Means.

Such a light guide member 10 can be formed, for example, by injection molding a transparent resin.

Next, the operations of the light guide member 10 and the surface light source device 1 of the present embodiment will be described with reference to FIG. FIG. 5 is a cross-sectional view showing an example of the path of light from the light source 5 inside the light guide member 10.

Since the first portion 20 of the light guide member 10 faces the light source 5 in the first direction d1, as shown in FIG. 5, the light from the light source 5 is incident on the first portion 20 of the light guide member 10. It is incident from 21. The light incident on the first portion 20 is directed to the reflecting surface 22 facing the incident side surface 21.

A part of the light directed to the reflecting surface 22 may enter the reflecting surface 22 at an angle less than the total reflection angle, as in the light L1 shown in FIG. Such light L1 is not reflected by the reflecting surface 22, but is emitted from the reflecting surface 22.

On the other hand, at least a part of the light incident on the reflecting surface 22 is incident on the reflecting surface 22 at an angle equal to or larger than the total reflection angle as shown by the light L2 shown in FIG. Such light L2 is reflected once or multiple times on the reflecting surface 22. The light reflected by the reflecting surface 22 includes a component directed to the second direction d2, which is non-parallel to the first direction d1. By heading in the second direction d2, the light from the light source 5 is incident on the first portion 20 to the second portion 30 of the light guide member 10.

The light incident on the second portion 30 is reflected by the first surface 31 and the second surface 32, so that the light is guided in the second direction d2. The second surface 32 is provided with a convex emitting means 35. The light incident on the emitting means 35 has an angle less than the total reflection angle on the second surface 32, and is emitted from the second surface 32.

As described above, the light from the light source 5 is guided by the light guide member 10 in the second direction d2, and is emitted from the second surface 32 of the second portion 30. In other words, the light guide member 10 can spread the light from the light source 5 in the second direction d2. By spreading the light in the second direction d2, the in-plane distribution of the amount of light emitted from the surface light source device 1 can be made uniform.

By the way, in the conventional direct type surface light source device, it is necessary to arrange the optical member at a position away from the light source in order to make the brightness of the emitted light uniform. By arranging the optical member at a position away from the light source, the light from the light source can be spread, and the light can be easily incident on the optical member uniformly. By uniformly injecting light into the optical member, it is possible to reduce the unevenness of the brightness of the light emitted from the surface light source device. However, the direction between the light source and the optical member coincides with the thickness direction of the surface light source device. Therefore, if the length between the light source and the optical member is increased in order to make the brightness of the emitted light uniform, the thickness of the entire surface light source device becomes thick.

On the other hand, in the present embodiment, as the optical member, the light guide member 10 facing the light source 5 is arranged in the first direction d1 which is the thickness direction of the surface light source device 1. The light guide member 10 guides the light from the light source 5 in the second direction d2, which is non-parallel to the first direction d1. More specifically, the light from the light source 5 incident from the incident side surface 21 of the first portion 20 is reflected by the reflecting surface 22 and heads toward the second portion 30, and the first surface 31 and the second surface 32 of the second portion 30. By total reflection with and, it is possible to go to the second direction d2. Therefore, the light from the light source 5 can be spread by guiding the inside of the light guide member 10 without increasing the length between the light source 5 and the light guide member 10. As described above, the light guide member 10 of the present embodiment spreads the light from the light source 5 and emits the light emitted from the surface light source device 1 regardless of the length between the light source 5 and the light guide member 10. The unevenness of the brightness of the light can be reduced. That is, the surface light source device 1 can be made thinner by shortening the length D between the light source 5 and the light guide member 10 without impairing the function of the surface light source device 1.

Specifically, the length D between the light source 5 and the light guide member 10 in the first direction d1 is 10 mm or less, preferably 1 mm or less. In this way, the length between the light source 5 and the light guide member 10 can be sufficiently reduced. Therefore, the surface light source device 1 can be made thinner.

Further, the reflecting surface 22 is inclined with respect to the incident side surface 21. Therefore, the light from the light source 5 incident from the incident side surface 21 is easily contained in the component toward the second direction d2 by being reflected by the reflecting surface 22, and can be easily directed to the second portion 30. The light directed to the second portion 30 is guided in the second portion 30. Therefore, even if the length between the light source 5 and the light guide member 10 is reduced, the light from the light source 5 can be spread.

Further, the reflecting surface 22 is inclined with respect to the first direction d1 and the second direction d2 so as to be separated from the light source 5 in the first direction d1 as it is separated from the light source 5 in the second direction d2, and the incident side surface of the reflecting surface 22. The inclination angle with respect to 21 becomes smaller as the distance from the incident side surface 21 increases. As a result, the light incident from the incident side surface 21 can be incident on the reflective surface 22 so that the incident angle is equal to or larger than the total reflection angle without increasing the length of the reflective surface 22 in the first direction d1. .. In other words, the thickness of the light guide member 10 can be reduced while allowing the light from the light source 5 to be reflected by the reflecting surface 22 and guided by the second portion 30. By making the light guide member 10 thinner, the surface light source device 1 can be made thinner.

Further, the length W of the reflecting surface 22 along the second direction d2 is one or more times, preferably twice or more, the length of the light source 5 along the second direction d2. Since the length of the reflecting surface 22 in the second direction d2 is longer than the length of the light source 5 along the second direction d2, the light incident on the first portion 20 of the light guide member 10 from the light source 5 Can be appropriately reflected by the reflecting surface 22. Further, the length W of the reflecting surface 22 in the second direction d2 is 20 times or less, preferably 10 times or less, the length of the light source 5 along the second direction d2. The first portion 20 does not have a function of guiding light to the second direction d2. Since the length of the reflecting surface 22 in the second direction d2 is not too long, the light guide member 10 can easily exert the function of guiding the light to the second direction d2, and the light emitted from the light guide member 10. The unevenness of the brightness of the light can be reduced.

Further, the outer contour of the reflecting surface 22 forming one recess 25 when observed from the first direction d1 is circular in a plan view. In other words, one recess 25 is circular in plan view. Therefore, the light reflected by the reflecting surface 22 goes in the second direction d2 so as to extend from the circle. That is, the light spreads isotropically from a circle in a plan view. The circular shape has a constant length from the center to the periphery. Therefore, the light reflected by the reflecting surface 22 can be uniformly spread in the second direction d2.

Further, the second surface 32 of the second portion 30 is connected to the reflecting surface 22 of the first portion 20. Therefore, it is possible to prevent the light reflected by the reflecting surface 22 from being emitted from the light guide member 10 without being incident on the second portion 30. In other words, the light reflected by the reflecting surface 22 can be easily incident on the second portion 30. That is, the light can be guided by the second portion 30 to reduce the unevenness of brightness from the light guide member 10 and emit the light.

Further, thinning the second portion 30 does not affect the total reflection of light on the first surface 31 and the second surface 32 on the second portion 30. Therefore, the thickness of the second portion 30 can be reduced. Specifically, the maximum length T between the first surface 31 and the second surface 32 is 0.5 times or more and 10 times or less the length of the light source 5 along the second direction d2, preferably. It is 1 times or more and 5 times or less. By thinning the second portion 30, the thickness of the light guide member 10 can be reduced. By making the light guide member 10 thinner, the surface light source device 1 can be made thinner. In addition, the light emitted from the end of the light source 5 in the second direction d2 is incident on the reflecting surface 22 of the first portion 20 at a small incident angle. Light incident at a small incident angle is unlikely to be totally reflected. By making the thickness of the light guide member 10 sufficiently thicker than that of the light source 5, it is possible to increase the angle of incidence of the light emitted from the end portion of the light source 5 in the second direction d2 on the reflecting surface 22. That is, the light from the end portion of the light source 5 in the second direction d2 can be easily totally reflected by the reflecting surface 22.

Further, the first surface 31 is a flat surface, and the second surface 32 includes a portion parallel to the first surface 31. According to such a first surface 31 and a second surface 32, it is easy to continuously totally reflect light on the first surface 31 and the second surface 32. That is, the light can be easily guided in the second portion 30.

Further, the refractive index of the second portion 30 is 1.20 or more, preferably 1.30 or more. Since the refractive index of the second portion 30 is sufficiently large in this way, even if light is incident on the first surface 31 and the second surface 32 at a large angle, it is easy to totally reflect the light. That is, it is possible to easily guide the light in the second portion 30.

Further, the second portion 30 has an emitting means 35. The light emitting means 35 can emit the light guiding the second portion 30. That is, the light from the light source 5 incident on the light guide member 10 can be taken out.

In particular, the light emitting means 35 has a higher density as it is separated from the reflecting surface 22. The reflecting surface 22 faces the light source 5 in the first direction d1. That is, the density of the emitting means 35 increases as the distance from the light source 5 increases. Since the amount of light is larger as it is closer to the light source 5, a sufficient amount of light is emitted even if the number of emitting means 35 is small. On the other hand, the farther away from the light source 5, the smaller the amount of light. Therefore, if the number of emitting means 35 is small, the amount of light emitted is smaller than that at a position closer to the light source 5. Since the number of the emitting means 35 increases as the distance from the light source 5 increases, the emission of light from the second portion 30 in the region separated from the reflecting surface 22 along the second direction d2 is promoted, and the light is separated from the light source 5. It is possible to effectively suppress the decrease in the amount of emitted light as the light source is used.

Such an emitting means 35 is provided on the second surface 32 of the second portion 30. Therefore, the light guiding the second portion 30 can be selectively emitted from the second surface 32. That is, light can be used efficiently. Further, the emitting means 35 has a concave shape or a convex shape provided on a part of the second surface 32. Such an emitting means 35 can be easily formed. Further, since the emitting means 35 is provided on the second surface 32 as a concave shape or a convex shape, the light is easily emitted on the second surface 32.

As described above, the light guide member 10 of the present embodiment is a light guide member arranged to face the plurality of light sources 5 in the first direction d1, and is provided so as to face each of the plurality of light sources 5. It has a plurality of first portions 20 having a reflecting surface 22 that reflects at least a part of the light from the light source 5, and a first surface 31 and a second surface 32 that face each other in the first direction d1. With the second portion 30, which guides the light to the second direction d2, which is non-parallel to the first direction d1, by totally reflecting at least a part of the light reflected by the portion 20 on the first surface 31 and the second surface 32. , Equipped with. According to such a light guide member 10, the light from the light source 5 incident from the incident side surface 21 of the first portion 20 is reflected by the reflecting surface 22 and directed toward the second portion 30, and the first portion 30 of the second portion 30. By total reflection on the surface 31 and the second surface 32, it is possible to move toward the second direction d2. Therefore, even if the length between the light source 5 and the light guide member 10 is shortened, the light from the light source 5 can be spread by guiding the inside of the light guide member 10. That is, by arranging such a light guide member 10 facing the light source 5, the surface light source device 1 can be made thinner.

It is possible to make various changes to the above-described embodiment.

For example, as shown in FIG. 6, the outer contour of the reflecting surface 22 may be square in a plan view. In other words, one recess 25 may be square in a plan view. In this case, the light reflected by the reflecting surface 22 goes in the second direction d2 so as to extend from the square. That is, in the first portion 20, the light isotropically spread from the square shape in a plan view, and the unevenness of the brightness of the light incident on the second portion 30 can be reduced.

FIG. 7 shows the first portion 20 shown in FIG. The reflective surface 22 of the first portion 20 is a convex curved surface in which the inclination angle with respect to the incident side surface 21 decreases from the center of the square toward the peripheral edge.

Further, in the example shown in FIG. 6, the first portion 20 is provided at a position corresponding to the grid points of the square grid. Therefore, the area surrounded by the intermediate line of the first portion 20 is a square. Therefore, the light reflected by the reflecting surface 22 isotropically spread to the intermediate line of the first portion 20. Here, the square is a shape that can be tessellated. Therefore, the entire light guide member 10 can be spread only in the region surrounded by the intermediate line of the same first portion 20. Since the light guide member 10 is formed so as to be spread over the region surrounded by the intermediate line of the first portion 20, the light reflected by the reflecting surface 22 is isotropic in each region of the light guide member 10. Spread to. That is, it is possible to reduce the unevenness of the brightness of the emitted light in the entire light guide member 10.

Alternatively, as shown in FIG. 8, the outer contour of the reflecting surface 22 may be a regular hexagon in a plan view. In other words, one recess 25 may be a regular hexagon in a plan view. In this case, the light reflected by the reflecting surface 22 goes in the second direction d2 so as to extend from the regular hexagon. That is, in the first portion 20, the light isotropically spread from the regular hexagonal shape in a plan view, and the unevenness of the brightness of the light incident on the second portion 30 can be reduced.

FIG. 9 shows the first portion 20 shown in FIG. The reflecting surface 22 of the first portion 20 is a curved surface in which the inclination angle with respect to the incident side surface 21 decreases from the center of the regular hexagon toward each vertex.

Further, in the example shown in FIG. 8, the first portion 20 is provided at a position corresponding to a grid point of a hexagonal lattice corresponding to a regular hexagon. Therefore, the region surrounded by the alternate long and short dash line in FIG. 8 which is the intermediate line of the first portion 20 is a regular hexagon. Therefore, the light reflected by the reflecting surface 22 isotropically spread to the intermediate line of the first portion 20. Here, the regular hexagon is a shape that can be tessellated. Therefore, the entire light guide member 10 can be spread only in the region surrounded by the intermediate line of the same first portion 20. Since the light guide member 10 is formed so as to be spread over the region surrounded by the intermediate line of the first portion 20, the light reflected by the reflecting surface 22 is isotropic in each region of the light guide member 10. Spread to. That is, it is possible to reduce the unevenness of the brightness of the emitted light in the entire light guide member 10.

In particular, the regular hexagon has a smaller ratio of the longest length to the shortest length from the center to the periphery as compared with the square shown in FIG. Specifically, the ratio of the longest length to the shortest length from the center to the periphery of the square is about 1.41, while the longest length to the shortest length from the center to the periphery of a regular hexagon. The ratio of the dimensions is about 1.15. That is, the regular hexagon has a smaller variation in length from the center to the periphery than the square. Therefore, as shown in FIG. 8, since the light guide member 10 is formed so as to tessellate in the region surrounded by the intermediate line of the first portion 20, light is emitted from the entire light guide member 10. It becomes easier to emit light more uniformly. Therefore, the unevenness of the brightness of the light emitted from the light guide member 10 can be further reduced.

Further, in the example shown in FIG. 8, the first portion 20 is provided so as to face the light source 5. In other words, the light source 5 is arranged at a position facing the first portion 20. In this modification, since the center of the first portion 20 is provided at a position corresponding to the lattice points of the hexagonal lattice, the light source 5 also corresponds to the lattice points of the hexagonal lattice so as to face the first portion 20. It is placed in a position.

1 surface light source device 5 light source 10 light guide member 11 one side main surface 12 other side main surface 20 first part 21 incident side surface 22 reflection surface 25 recess 30 second part 31 first surface 32 second surface 35 exit means

Claims (17)

A light guide member arranged facing a plurality of light sources in the first direction.
A plurality of first portions provided facing each of the plurality of light sources and having a reflecting surface that reflects at least a part of the light from the light source.
The first surface has a first surface and a second surface facing each other in the first direction, and at least a part of the light reflected by the first portion is totally reflected by the first surface and the second surface. A light guide member comprising a second portion that guides light in a second direction that is non-parallel to one direction. The first portion has an incident side facing the light source.
The light guide member according to claim 1, wherein the reflecting surface is inclined with respect to the incident side surface. The light guide member according to claim 2, wherein the inclination angle of the reflecting surface with respect to the incident side surface becomes smaller as the distance from the incident side surface increases. Any one of claims 1 to 3, wherein the reflective surface is a surface of the first portion that is provided on a side opposite to the side facing the light source and forms a recess that tapers toward the side facing the light source. The light source member according to item 1. The light guide member according to any one of claims 1 to 4, wherein the outer contour of the reflecting surface is a square, a regular hexagon, or a circle in a plan view. The light guide member according to any one of claims 1 to 5, wherein the second surface of the second portion is connected to the reflection surface of the first portion. The first surface is a flat surface and
The light guide member according to any one of claims 1 to 6, wherein the second surface includes a portion parallel to the first surface. The light guide member according to any one of claims 1 to 7, wherein the refractive index of the second portion is 1.20 or more. The light guide member according to any one of claims 1 to 8, wherein the second portion has an emission means for emitting the light being guided. The light guide member according to claim 9, wherein the light emitting means has a higher density as the distance from the reflecting surface increases. The light guide member according to claim 9 or 10, wherein the light emitting means is provided on the second surface of the second portion. The light guide member according to claim 11, wherein the light emitting means has a concave shape or a convex shape provided on a part of the second surface. A light guide member arranged facing a plurality of light sources in the first direction.
The main surface on one side and the main surface on the other side facing the first direction are provided.
The one-sided main surface faces the light source and
The other side main surface is provided with a plurality of concave shapes that taper toward the one side main surface so as to be separated from each other.
The portion of the other main surface that forms the concave shape functions as a reflecting surface that reflects at least a part of the light incident from the one side main surface.
The one-side main surface and the other-side main surface guide light in a second direction non-parallel to the first direction by totally reflecting at least a part of the light reflected by the reflection surface. Optical member. The light guide member according to any one of claims 1 to 12,
A surface light source device comprising a plurality of light sources facing the first portion of the light guide member in the first direction. The surface light source device according to claim 14, wherein the length between the light source and the light guide member in the first direction is 10 mm or less. The surface light source device according to claim 14 or 15, wherein the length of the reflecting surface along the second direction is 1 time or more and 20 times or less the length of the light source along the second direction. The aspect of any one of claims 14 to 16, wherein the maximum length between the first surface and the second surface is 10 times or less the length of the light source along the second direction. Surface light source device.

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