JPH11224520A - Surface light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce light loss in a boundary part when light conductive plates divided into a plural parts are combined, obtain a large light conductive plate, and apply to an LED(light emitting diode) room lighting system in a surface light source device. SOLUTION: Edge surfaces of a plurality of light conductive plates 21, 22 are combined so that light incident to one light conductive plate 21 from a light source 3 is propagated to the other light conductive plate 22 without practically generating total reflection on the boundary edge surface. Light loss on the boundary surface is reduced as much as possible, a large light conductive plate can be obtained by combining a plurality of light conductive plates, and the light conductive plate obtained is suitable for a lighting system, and it is easy to handle for transportation and setting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface light source device which spreads and emits light from a point or linear light source in a planar manner, and more particularly to a technique applicable to indoor lighting.

[0002]

2. Description of the Related Art Conventionally, as a light source of this type of surface light source device, an LED which is a solid-state light emitting device using a semiconductor has been widely used. It has the feature that it has a long life, and is used for electronic bulletin boards and liquid crystal (LCD) backlights of various devices. Originally, a surface light source device using an LED, which is a point light source, as a light source is converted into a surface light source by using a light guide plate.

A conventional surface light source device is shown in a perspective view of FIG. 11 and a sectional view of FIG. The surface light source device 100 includes a light guide plate 2 for confining light, a light emitting unit 3, and a reflection plate 4. The light guide plate 2 is formed of a transparent resin having a large refractive index such as a polycarbonate resin or a methacryl resin, and a diffusion pattern P is formed on the lower surface of the light guide plate 2 by uneven processing or dot printing of a diffuse reflection ink. I have. The light emitting section 3 is a circuit board 3a on which a plurality of so-called point light sources 3b such as light emitting diodes (LEDs) are mounted, and faces a side surface (light incident surface 7) of the light guide plate 2. The reflection plate 4 is formed of, for example, a white resin sheet having a high reflectance, and has both sides adhered to the lower surface of the light guide plate 2 by a double-sided tape 12.

[0004] Thus, as shown in FIG.
The light f emitted from the light guide surface 2 from the light incident surface 7 to the inside of the light guide plate 2 is confined inside the light guide plate 2 by being totally reflected inside the light guide plate 2. When the light f inside the light guide plate 2 enters the diffusion pattern P, the light f is diffused and reflected, and the light exit surface 6
The light f reflected toward the light at an angle smaller than the critical angle of total reflection is extracted from the light exit surface 6 to the outside. Further, the light f transmitted through a portion of the lower surface of the light guide plate 2 where the diffusion pattern P does not exist is reflected by the reflection plate 4 and again.
Since the light returns to the inside, loss of light quantity from the lower surface of the light guide plate 2 is prevented.

[0005]

Incidentally, it has been considered to use such a surface light source device in the field of lighting such as indoors. Specifically, there is a demand for the development of a new type of indoor lighting device (future light) that is energy-efficient and durable and durable.
The idea is to use D as an indoor lighting fixture to reduce power consumption to approximately 1/8 of incandescent lamps and approximately 1/2 of fluorescent lamps, and to increase the service life.

However, as described above, the liquid crystal (L
A surface light source device used for a backlight of a CD) has a size of at most about 6 inches (15.2 cm). On the other hand, general indoor lighting fixtures need to be surface light sources that can uniformly illuminate a wide area, and require a size of several meters (m). That is, in the case of indoor lighting, the size of the light guide plate is ten times or more the size of a conventional backlight.
Thus, a light guide plate having a large area of several meters in size is difficult to handle in terms of transportation and installation. In order to improve this, there is a method of dividing the light guide plate. In such a case, a boundary between the divided light guide plates is generated, so that when light propagates between the light guide plates, light leakage and total reflection cause light loss. Tends to occur.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and is intended to obtain a large-sized light guide plate by combining a plurality of light guide plates divided into a size that is easy to handle for transportation and installation. An object of the present invention is to provide a surface light source device which can minimize light loss at the boundary portion and is particularly suitable for an indoor LED lighting device.

[0008]

In order to achieve the above object, the present invention provides a surface light source device which spreads and emits light from a point or linear light source in a planar manner, comprising a plurality of light guide plates,
A light source installed so that light is incident from an end face of the one light guide plate, a light reflecting means provided on at least one surface of the light guide plate, and a diffusion pattern member for extracting light from the light guide plate. The light incident on one of the light guide plates from the light source is transmitted to the other light guide plate without substantially total reflection at the boundary between the end surfaces of the plurality of light guide plates. It is combined with In this configuration, since the total reflection at the boundary surface where the plurality of light guide plates are connected to each other at the end surfaces is reduced, light loss at the boundary surface can be reduced as much as possible. Since a large-sized light guide plate is obtained by combining a plurality of light guide plates, it is easy to handle for transportation and installation.

Further, the present invention is directed to a surface light source device which spreads and emits light from a point light source in a planar manner so that light is incident from a plurality of light guide plates and end faces of the one light guide plate. An installed light source, light reflecting means provided on at least one surface of the light guide plate, and a diffusion pattern member for extracting light from the light guide plate, and an end face between the light guide plates has a normal vector. Is a surface having an angle equal to or smaller than the total reflection angle with respect to radiation centered on the light source, or a surface that hardly intersects with the radiation. In this configuration, despite the use of a point light source, total reflection at a boundary surface where a plurality of light guide plates are coupled at end surfaces is reduced,
An operation equivalent to the above is obtained.

[0010] The end surface of the light guide plate on the light source side among the end surfaces between the light guide plates may be a diffusion surface.

Further, the space between the light guide plates may be filled with a transparent medium.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic external view of a light guide lighting device according to a first embodiment of the surface light source device of the present invention, FIG. 2 is an enlarged view of a portion A in FIG. 1, and FIG. 3 is a cross-sectional view of the light guide lighting device. . The light guide illumination device 1 is installed such that light is incident from the end face (light incident surface 7) of one of the light guide plates 21 and 22 made of a transparent acrylic resin or the like divided into a plurality. Point or linear light source 3 and light guide plate 2
And a sheet-like or thin-plate-like reflecting plate 4 (light reflecting means) provided on the non-emission side surfaces of the first and second non-emitting sides. The light guide plates 21 and 22 have their end faces connected to each other. The reflection plate 4 can be attached to the light guide plate 2 with a dot-shaped adhesive 5 made of an epoxy resin or the like having a light diffusion effect. The dot-shaped adhesive 5 is used as the light guide plates 21 and 22 of the reflection plate 4.
And a diffusion pattern is formed such that light is uniformly emitted from the light emitting surface 6.

As the light source 3, an LED array that mixes white or three colors of R, G, and B may be used. Further, an LED that emits white light by enclosing an LED that emits ultraviolet light in a fluorescent tube may be used. In addition, the light guide type lighting device 1 is used by being attached to a ceiling in a room or used for a signboard.
In particular, future LED interior lighting devices have advantages such as energy saving, long service life, small size and light weight, and high speed of turning on and off. When sticking to the ceiling in the room, the reflection plate 4 may be fixed to the ceiling surface.

FIGS. 4A and 4B show the divided light guide plate 2.
It is a top view which shows the form of 1,22. Divided light guide plate 2
When 1 and 22 are simply joined, it is extremely difficult to bring them into complete close contact, so that total reflection occurs at the interface. Therefore, in the present embodiment, the light guide plate 21,
The boundary end surface 23 connecting the two 22 is substantially perpendicular to the light beam. As a result, total reflection which is likely to occur at the boundary surface is reduced, and the overall efficiency is improved.

The shape of the boundary end face 23 shown in FIG.
It is composed of only a plane substantially perpendicular to the radiation extended from the light source 3 and a plane substantially parallel to the radiation. That is, the light guide plate 21,
The end face between the 22 has a normal vector at an angle equal to or smaller than the total reflection angle with respect to the radiation from the light source 3.
With this configuration, even when the light emitted from the light source 3 reaches the boundary end face 23, it always propagates without being reflected, since it always hits the boundary face almost vertically. Boundary end face 2 shown in FIG.
The shape of 3 is constituted only by a surface substantially perpendicular to the radiation extended from the light source 3. That is, the light guide plates 21 and
The end face between the two has a normal vector substantially perpendicular to the radiation from the light source 3. In this example, the boundary end surface 23 is a substantially vertical surface, but an effect can be obtained as long as the angle does not cause total reflection. In the case of a point light source, the diffusion pattern by the adhesive 5 (shown by a broken line) is concentric as shown in FIG.

The mechanism for extracting light from the light exit surface 6 of the light guide type illuminating device 1 having the above configuration is basically the same as that described in the above-mentioned prior art.
1 is totally reflected in the light guide plate 21 and is incident on the dot-like adhesive 5 forming a diffusion pattern.
The light f (FIG. 3) that is diffusely reflected at the light emitting surface 6 and reflected at an angle smaller than the critical angle of total reflection toward the light emitting surface 6 is extracted from the light emitting surface 6 to the outside. Further, the light introduced into the light guide plate 21 is propagated to the light guide plate 22 via the boundary end face 23, and is also extracted outside from the light exit surface 6 of the light guide plate 22. Since light passes through the boundary surface almost vertically at the boundary end surface 23, light loss here is reduced.

The refractive index of the pressure-sensitive adhesive 5 is preferably equal to or higher than the refractive index of the light guide plate 2. Since the diffusion pattern by the adhesive 5 can be produced by printing on the sheet-like or thin-plate-like reflection plate 4, it is possible to produce a large-area pattern which was impossible with the conventional configuration / method. An arbitrary color may be applied to the pattern of the adhesive 5. The light guide plates 21 and 22 can be combined to have a size of, for example, 2 m × 2 m.

FIG. 5 is a plan view of a light guide type illumination device according to a second embodiment. In this embodiment, the light guide plates 21 and 22 are used.
By forming the diffusion surface 24 on the boundary end surface 23, total reflection at the boundary end surface 23 is prevented. Diffusing surface 24
May be formed by making the end surface of the light guide plate 21 an uneven surface, or by applying a paint having a diffusion effect. Light guide plate 2
A diffusion pattern with a reflector (shown by a dashed line) is provided on the non-emission surfaces of the light guide plates 1 and 22, and the light guide plate 21 side shows the pattern of FIG. Nine patterns are used. The pattern of FIG. 9 may be basically used for the light guide plate 22 side. With this configuration, the light guide plate 21
At the same time as the light exits from the exit surface, the light incident on the diffusion surface 24 at the end surface becomes the diffused light, propagates and enters the light guide plate 22, and exits from the exit surface of the light guide plate 22.

FIGS. 6 (a) and 6 (b) are a plan view and a side view of a light guide type illumination device according to a third embodiment. In this embodiment, the boundary end face 23 between the light guide plates 21 and 22 is
By embedding with (adhesive), total reflection at the boundary end face 23 is prevented. It is desirable that the refractive index (n2) of the transparent resin 25 be substantially equal to or slightly larger than the refractive index (n1) of the light guide plates 21 and 22 (n1 ≦ n2). In addition, swelling or protrusion of the resin to be embedded is expected. On the surfaces of the light guide plates 21 and 22, a reflective plate or a diffuser plate with a pattern is provided (not shown). If such protrusions are present, they are lifted up, which hinders the uniformity of luminance. Resulting in. Therefore, as shown in the drawing, the thickness of the light guide plates 21 and 22 is slightly reduced at the boundary so that even if the transparent resin 25 protrudes,
It is not to be higher than the surfaces of 1, 22. Instead of the transparent resin 25, a double-sided tape may be used. Also,
In the case of a point light source, the pattern of the reflection plate or the diffusion plate
In the case of a linear light source, the one shown in FIG. 9 is used.

FIG. 7 shows a light guide plate 2 according to the third embodiment.
FIG. 4 is a view showing a method of assembling the light guide plates 1 and 22 with an adhesive tape previously applied to one end face of one of the light guide plates 21 and 22;
6 and a plurality of light guide plates 21 and
2 are combined. FIG. 8 shows a light guide plate 2 divided into a plurality of parts.
FIG. 8 is a view showing another method of assembling the light guide plates 21 and 22 with a light guide plate 21,
By sticking 22, the plurality of light guide plates 21 and 22 are combined and fixed.

FIGS. 9 and 10 show that the light source 3 is a linear light source (LE).
FIG. 7 is a schematic diagram of a diffusion pattern in the case of a D module) and in the case of a point light source. A pattern of the adhesive 5 can be provided on the reflection plate 4 side to form a diffusion reflection plate, and both are formed so as to improve light use efficiency and uniformity. The diffusion pattern P shown in FIG. 9 is a linear pattern parallel to the linear light source 3, and is coarser as it is closer to the light source and denser as it is farther, and the pattern width and the shortest pattern pitch are all the pattern P. Of about 300 μm (200 to 500 μm).
It may be in the range of μm or more or less).

The diffusion pattern shown in FIG. 10 is concentric with the point light source 3 as the center. The minimum pattern size and the minimum inter-pattern distance are the same as described above, and are, for example, about 300 μm. By providing a pattern of the pressure-sensitive adhesive 5 on the reflection plate 4 side, a pattern may be formed on a sheet or a thin plate, so that a large-area pattern can be easily formed. The diffuse reflection plate is attached to the light guide plate with an adhesive.

The present invention is not limited to the configuration of the above-described embodiment, but can be variously modified. In short, the light guide plate divided into a plurality is connected by end faces, and the boundary surfaces thereof are equivalently adhered. By adopting a configuration capable of obtaining a light propagation action equivalent to that described above, it is possible to manufacture a light guide plate having a large area with a small light loss at the coupling surface, which is suitable for a lighting device. Although not shown above, by providing a transparent plate having a diffusion effect on the surface on the emission side of the light guide plate divided into a plurality of parts, the emitted light can be made uniform and the light guide plate can be protected. be able to. Also,
The reflection plate itself may be a combination of a plurality of parts.

[0024]

As described above, according to the present invention, when light is propagated from one light guide plate formed by joining the end faces of a plurality of light guide plates to the other light guide plate, the light is substantially converged at those boundary surfaces. Since no total reflection occurs, light loss at the interface is reduced. In addition, since a large-sized light guide plate can be obtained by combining a plurality of light guide plates, it is easy to handle in transportation and installation, and is suitable for an indoor LED lighting device. Also, even in the case of a point light source, the end face between the light guide plates is a surface whose normal vector is at an angle equal to or less than the total reflection angle with respect to the radiation centered on the light source, or a surface that hardly intersects the radiation By doing so, an operation equivalent to the above can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic external view of a light guide illumination device according to a first embodiment of a surface light source device of the present invention.

FIG. 2 is an enlarged view of a portion A in FIG.

FIG. 3 is a cross-sectional view of the light guide type illumination device.

FIGS. 4A and 4B are plan views showing forms of a divided light guide plate.

FIG. 5 is a plan view of a light guide illumination device according to a second embodiment.

FIGS. 6A and 6B are a plan view and a side view of a light guide lighting device according to a third embodiment.

FIG. 7 is a view illustrating a method of assembling a light guide plate according to a third embodiment.

FIG. 8 is a view showing another method of assembling a plurality of divided light guide plates.

FIG. 9 is a schematic diagram of a diffusion pattern when the light source is a line light source.

FIG. 10 is a schematic diagram of a diffusion pattern when a light source is a point light source.

FIG. 11 is a perspective view of a conventional surface light source device.

FIG. 12 is a cross-sectional view of a conventional surface light source device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light guide type illumination device 21, 22 Light guide plate 3 Light source 4 Reflector (light reflection means) 5 Adhesive (diffusion pattern member) 6 Light emission surface 23 Boundary end surface

Claims (4)

[Claims] 1. A surface light source device which spreads and emits light from a point or linear light source in a planar manner, comprising: a plurality of light guide plates; and a light guide plate provided so that light is incident from an end face of the one light guide plate. A light reflecting means provided on at least one surface of the light guide plate; and a diffusion pattern member for extracting light from the light guide plate. A surface light source device, wherein light incident on one of the light guide plates is coupled to the other light guide plate so as to be propagated without substantially total reflection at their boundary surfaces. 2. A surface light source device which spreads and emits light from a point light source in a planar manner, comprising: a plurality of light guide plates; and a light source installed so that light is incident from an end face of the one light guide plate. And a light reflecting means provided on at least one surface of the light guide plate; and a diffusion pattern member for extracting light from the light guide plate. An end face between the light guide plates has a normal vector centered on the light source. A surface light source device characterized in that the surface has an angle equal to or smaller than the total reflection angle with respect to the radiation, or the surface hardly intersects with the radiation. 3. The surface light source device according to claim 1, wherein the end surface of the light guide plate on the light source side among the end surfaces between the light guide plates is a diffusion surface. 4. The surface light source device according to claim 1, wherein a space between the light guide plates is filled with a transparent medium.