JPH11232921A - Surface light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source required a thin light guide plate with respect to a large irradiation area, capable of securing a required light quantity without using a large-sized light source, facilitating handling and manufacturing, and is suitable for an indoor LED lighting system. SOLUTION: Light from a light source module plane-like is once incident on the end face of a bar-like light guide plate 2, the light is further incident from the side face of the bar-like light guide plate 2 on a planar light guide plate 10 bonded by a transparent resin having a thickness thinner than the same, and the light is extracted from the planar light guide plate 10. Thereby, even if the planar light guide 10 becomes thin and large-sized, the light module itself will not become large for securing the required light amount.

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 used for an LCD backlight or the like is shown in a perspective view of FIG. 13 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] 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]

By the way, at present, there is a demand for the development of a new type of indoor lighting device (future light) which is energy-efficient and durable and durable. There is a plan to reduce power consumption to approximately 1/8 of incandescent lamps and approximately 1/2 of fluorescent lamps by using them as appliances, and to increase the service life.

Therefore, in order to realize such a concept, the use of the above-described surface light source device using LEDs in the field of lighting such as indoors was examined. However, a surface light source device used for an LCD backlight or the like has a size of at most about 6 inches (15.2 cm). In contrast, with general indoor lighting fixtures,
The surface light source must be capable of uniformly illuminating a wide range, and a size of several meters (m) is required. 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.

[0007] The above-mentioned conventional light guide plate with a diffusion pattern is prepared by raising a metal mold based on an original master on which a pattern is formed by etching or the like, and then manufacturing it by injection molding, or printing diffuse reflection ink dots on the light guide plate. Since it can be manufactured by a mold,
The emission pattern is integrated with the light guide plate. On the other hand, when the light guide plate has a large area of several meters in size,
A large mold is required, and it is difficult to manufacture such a mold and to print a pattern on the large light guide plate itself with high accuracy.

Further, from the viewpoint of easy handling of the apparatus, it is desirable that the thickness of the light guide plate is thin. However, in the conventional method of taking in light from the end face of the light guide plate, when the thickness of the light guide plate is reduced, the height of the light source also needs to be reduced. Since the amount of light required for the illumination device depends on the size of the irradiation area, the required amount of light itself does not change even if the light guide plate becomes thin. Therefore, when thinning the light guide plate,
In order to secure a necessary light quantity, the light source has to be formed in a horizontally long form along the end surface of the light guide plate. However, this method is effective when the irradiation area is small, but when the irradiation area increases, the width of the light source also increases, and handling becomes troublesome. For example, assuming that an area of 1 m square can be covered by a light source of 10 cm width, a large light source of 90 cm width, which is nine times larger than that, is naturally required to cover an area of 3 m square.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem. Light is once incident on a thick light guide plate end face, and light guided in the light guide plate is transmitted to a thinner light guide plate. By adopting the method of propagating, a thin light guide plate can be used for a large irradiation area, and the necessary light amount can be secured without using a large light source. An object is to provide a surface light source device suitable for the device.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, 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, wherein the rod-shaped light guide plate and the light guide plate are provided. A light guide plate having a smaller thickness than the light guide plate, and a light source arranged so that light is incident from a narrow end face of the rod-shaped light guide plate, and one side surface of the rod-shaped light guide plate and the planar light guide plate. The surface of the light guide plate is bonded with a transparent resin. In this configuration, light from a light source is incident from the narrow end face of the rod-shaped light guide plate, and light introduced into the rod-shaped light guide plate is transmitted from one side to a thinner planar light guide plate through a transparent resin. Light is extracted from the light guide plate having a thin planar shape. As described above, since the light from the light source is once introduced into the rod-shaped light guide plate, even if the thin planar light guide plate becomes large in size, the light source itself does not become large in order to secure a necessary light amount. .

Further, 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 shape, and is formed integrally with a rod portion and one side surface of the rod portion. The light guide plate includes a light guide plate having a thin planar portion, and a light source arranged so that light is incident from an end face of the rod portion. In this configuration, the light guide plate of the rod portion and the light guide plate of the planar portion are integrally formed, and the same operation as described above can be obtained.

The planar light guide plate may be rectangular, and the rod-shaped light guide plate may be arranged diagonally to the planar light guide plate. Light that is incident on the narrow end face of the rod-shaped light guide plate from the light source and further propagates from the rod-shaped light guide plate to the planar light guide plate has a predetermined angle with respect to the light traveling direction. Since there are many, the above configuration enables light to reach the entire planar light guide plate, and is particularly effective for a large-sized light guide plate.

Further, the planar light guide plate is rectangular, the light source is located at four corners thereof, and the rod-shaped light guide plate is centered on the diagonal line with respect to the planar light guide plate. It may be arranged to face. With this configuration, an operation equivalent to the above can be obtained.

Further, the planar light guide plate is rectangular, the light source is located at one corner thereof, and the bar-shaped light guide plate is provided with the one corner portion relative to the planar light guide plate. They may be arranged along both sides sandwiching them. With this configuration, an operation equivalent to the above can be obtained.

The planar light guide plate is rectangular, and the light source is located at a pair of diagonal corners,
In addition, the rod-shaped light guide plate may be disposed so as to be directed to another diagonal corner of the planar light guide plate. With this configuration, an operation equivalent to the above can be obtained.

[0016]

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 type lighting device according to an embodiment of the surface light source device of the present invention,
FIGS. 2A and 2B are enlarged views of a portion A and a portion B in FIG.
The light guide illumination device 1 includes a rod-shaped light guide plate 2, a point or linear light source module 3 arranged so that light is incident on the rod-shaped light guide plate 2, and a rod-shaped light guide plate 2. It is composed of a rectangular, planar, transparent resin sheet 8 into which light is introduced and having a smaller thickness, and a diffuse reflection plate 9 provided on one surface of the transparent resin sheet 8. The transparent resin sheet 8 forms a planar light guide plate 10 together with the diffuse reflection plate 9. The light source module 3 is arranged so that light is incident from one end face (narrow end face) in the length direction of the rod-shaped light guide plate 2. Also,
One side surface of the rod-shaped light guide plate 2 and the surface of the transparent resin sheet 8
By being bonded with a transparent resin (resin 14 in FIG. 3), they are optically and physically coupled.

The rod-shaped light guide plate 2 is made of a transparent acrylic resin, glass, or the like, and has a size of, for example, 12.5 × 12.5 × 1.
000mm ones are connected, and from the directivity of light,
It is arranged diagonally with respect to the rectangular light guide plate 10. A transmissive diffusion plate 11 is interposed at the connecting position of the light guide plate 2, and a total reflection seal 13 is attached around the light diffusion plate 11 to prevent light leakage. The size of the transmission type diffusion plate 11 is smaller than the cross-sectional area of the rod-shaped light guide plate 2. As the light source module 3, an LED module (for example, 36 × 36) composed of LEDs that mix white or three colors of R, G, and B may be used. Its size is about 17.7 × 17.7 mm. Further, an LED that emits white light by enclosing an LED that emits ultraviolet light in a fluorescent tube may be used.

The transparent resin sheet 8 is made of an acrylic resin or the like, and the thickness of the planar light guide plate 10 including the diffuse reflection plate 9 is 3
mm, size is 2m × 2 for indoor lighting, for example.
It has a large size of m. The light guide lighting device 1 is installed on a ceiling in a room and used for indoor lighting, and can also be used as a signboard. In the case of installation on a ceiling in a room for indoor lighting, the upper surface of the diffuse reflection plate 9 may be fixed to the ceiling surface.

FIG. 3 is a sectional view of the planar light guide plate 10.
One side of the rod-shaped light guide plate 2 is bonded with a transparent resin 14 to the surface of the transparent resin sheet 8 of the planar light guide plate 10. The transparent resin sheet 8 is provided with a pressure-sensitive adhesive 15 formed in a pattern having a light diffusing action so that light is emitted as uniformly as possible from the entire surface of the transparent resin sheet 8.
Instead of the adhesive 15, a light-transmitting double-sided adhesive tape may be used. FIGS. 4A and 4B are a side view and a bottom view schematically showing emission of light rays. Here, only one rod-shaped light guide plate 2 is shown. A diffuse reflection plate 16 is arranged at the outermost end of the light guide plate 2. The light diffusivity of the adhesive 15 is determined by mixing a diffusion paint with a transparent adhesive (resin).
It can be obtained by using a material having a diffusive property for the pressure-sensitive adhesive itself, or by utilizing the light emission at the end face of the pressure-sensitive adhesive.

The light introduced into the rod-shaped light guide plate 2 is guided while being totally reflected in the light guide plate 2, and leaks little by little from a portion adhered to the thin planar light guide plate 10, whereby the light guide plate is It spreads to ten. Specifically, light f passing through a bonding portion (resin 14) with the transparent resin sheet 8 at a perpendicular portion of the side surface of the light guide plate 2 is incident on the planar light guide plate 10 (details will be described later). Although the probability of incidence from the rod-shaped light guide plate 2 to the thin planar light guide plate 10 is not so high, since light transmitted through the rod-shaped light guide plate 2 is guided by total reflection, it is necessary to take a sufficiently long distance. If the directivity is changed halfway, the efficiency can be improved. This will be described with reference to FIG.

FIG. 5 shows the propagation of light rays in the rod-shaped light guide plate 2 (assuming that the light source is at the center). In the same figure, light reflected many times at the same place does not enter the planar light guide plate 10 as shown in FIG. Therefore, in this embodiment, the transmission type diffusion plate 11 is provided between the connected light guide plates 2.
By changing the directivity of the remaining light,
It is assumed that light easily enters the light guide plate 10.

The mechanism for extracting light from the light exit surface of the light guide illumination device 1 after being incident on the planar light guide plate 10 is basically the same as that described in the above-mentioned prior art. The light introduced into the light plate 10 is totally reflected in the light guide plate 10 and, when entering a diffusion pattern made of the adhesive 15, is diffusely reflected and directed toward the light emitting surface at an angle smaller than the critical angle of total reflection. The reflected light is emitted to the outside. In addition, the refractive index n1 of the rod-shaped light guide plate 2 and the refractive index n2 of the resin 14 to be bonded are shown.
And the refractive index n3 of the planar light guide plate 10 is such that n1 ≦
It is desirable that n2 ≦ n3 to improve the emission efficiency.

FIG. 6 shows the state of light incident on the planar light guide plate 10 from the rod-shaped light guide plate 2. The refractive index of the light guide plate 2 is √
If it is set to about 2, the rod-shaped light guide plate 2 to the planar light guide plate 10
Only light having an inclination of approximately 45 ° with respect to the traveling direction exists. Further, even if light is reflected on the end face side opposite to the light source, the directivity is biased because the light emitted first is stronger.

In order to allow the light to reach the entire rectangular planar light guide plate 10, it is necessary to dispose the rod-shaped light guide plate 2 in consideration of this characteristic. Required. Such various embodiments are shown in FIGS.
(D). (A) is of the same type as that of the above embodiment, in which the rod-shaped light guide plate 2 is arranged diagonally to the planar light guide plate 10. 2B, the light source module 3 is located at four corners of the planar light guide plate 10, and the rod-shaped light guide plate 2 is disposed so as to face the center of the planar light guide plate 10 on a diagonal line thereof. Things.
3C, the light source module 3 is located at one corner of the planar light guide plate 10 and the rod-shaped light guide plate 2 is arranged along both sides sandwiching one corner with respect to the planar light guide plate 10. It is arranged in. (D), the light source module 3 is located at a pair of diagonal corners of the planar light guide plate 10, and the rod-shaped light guide plate 2 is positioned at another diagonal position with respect to the planar light guide plate 10. Are arranged so as to be directed toward the corner portions.

FIG. 8 shows an embodiment in which the above-mentioned improvement measures against the bias of the directivity of light are taken. In this example, the planar light guide plate 1 is located in the immediate vicinity of the rod-shaped light guide plate 2.
0, a plurality of minute cuts 17, and this cut 1
The reflective sheet 18 is attached so as to cover the upper surface of the reference numeral 7. With this configuration, reflection occurs at the notch 17 and the directivity of light entering the planar light guide plate 10 can be changed. Light leakage from the cut 17 is prevented by the reflection sheet 18.

FIG. 9 is a schematic view of a diffusion pattern formed on the light guide plate 10 according to an embodiment. The diffusion pattern is a rod-shaped light guide plate 2 for improving the uniformity of emitted light.
The closer, the coarser, the farther, the denser. The minimum pattern size and the minimum inter-pattern distance are both large enough to provide stamp (printing) accuracy of the pattern P, and are, for example, about 300 μm (200 to 500 μm).
, Or more or less).

Next, FIGS. 10 to 12 show examples of simulating the efficiency when light is incident from the rod-shaped light guide plate 2 (A: also referred to as a light guide bar) to the thin planar light guide plate 10 (B). This will be described with reference to FIG. FIG. 10 is a model configuration diagram for that purpose, in which the length of the light guide plate 2 is W, the height of the narrow end face (light guide rod thickness) where light is incident is a, and the thickness of the light guide plate 10 (light guide plate thickness). Is assumed to be b. In FIG. 1, the side surface of the light guide plate 2 is shaped to be joined to the end surface of the light guide plate 10, but the light guide plate 2 as shown in FIGS.
It is the same even if it is in the form of being joined on zero.
FIG. 11 is a diagram mainly showing a traveling direction of light in the rod-shaped light guide plate 2, wherein A is light that could not be incident on the light guide plate 10 from the light guide plate 2, and B was incident on the light guide plate 10 from the light guide plate 2. Indicates light. Of the light that has hit the side surface of the light guide plate 2, if it is a joint portion (S in the drawing) with the light guide plate 10, the light is
0 (B). If it is not the junction with the light guide plate 10 (S 'in the figure), no light enters the light guide plate 10 (A).

FIG. 12 is a characteristic diagram showing the incident efficiency. The horizontal axis represents the ratio of the light guide plate thickness b to the light guide rod thickness a, and the vertical axis represents the efficiency of incidence on the light guide plate. As the ratio of the light guide plate thickness b to the light guide rod thickness a becomes closer to 1, the efficiency increases, but from the viewpoint of easy handling, a thin light guide plate thickness b is desired, and even if the ratio is about 0.1, It is considered practical. In addition, it can be seen that the longer the light guide rod length is, the more efficient the light guide rod thickness a is.

As described above, according to this embodiment, light is once incident on the end face of the thick light guide plate 2 and then propagates to the thin light guide plate. In addition, the required light amount can be secured without increasing the size of the light source, and the handling and manufacturing are easy. In particular, it is effective as a future LED indoor lighting device, and by using the LED as the light source, It also has advantages such as energy saving, long service life, small size and light weight, fast turning on and off.

The present invention is not limited to the configuration of the above embodiment, and various modifications are possible. For example, FIGS. 1 and 3 show a configuration in which the light guide plate 2 is joined on the light guide plate 10, whereas FIG. 11 shows an end face of the light guide plate 10 joined to the side surface of the light guide plate 2. Although such a form is shown, it is functionally equivalent, and may be a form in which both are integrated. That is, the rod-shaped light guide plate 2 and the planar light guide plate 10 may be integrally formed, and may be an integrated light guide plate including a rod-shaped portion and a planar portion. The bar may be along the side edge or diagonally with respect to the plane. Further, by using this surface light source device, a display plate (signboard) for displaying a static image may be formed by devising a pattern formed by the adhesive 15 having a diffusive property for light extraction. It is possible.

[0031]

As described above, according to the present invention, light from a light source is once incident from the narrow end face of the rod-shaped light guide plate, and is further transmitted from one side surface of the rod-shaped light guide plate to the thin planar light guide plate. Even if the thin planar light guide plate becomes large in size, the light source itself does not become large in order to secure the necessary light amount,
In addition, a thin light guide plate may be used for a large irradiation area, handling and manufacturing are easy, and a surface light source device suitable for an indoor LED lighting device can be provided. The same effect can be obtained even when the light guide plate of the rod-shaped portion and the light guide plate of the planar portion are integrally formed.

[Brief description of the drawings]

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

FIGS. 2A and 2B are enlarged views of a portion A and a portion B of FIG.

FIG. 3 is a sectional view of a planar light guide plate.

FIGS. 4A and 4B are a side view and a bottom view schematically showing light emission.

FIG. 5 is a diagram showing a light beam propagation state in a rod-shaped light guide plate.

FIG. 6 is a plan view illustrating a state of light incident on a planar light guide plate from a rod-shaped light guide plate.

FIGS. 7A to 7D are plan views showing various embodiments of the light guide illumination device.

FIG. 8 is a plan view of an embodiment in which an improvement measure is taken against deviation of light directivity.

FIG. 9 is a schematic view of a diffusion pattern formed on a planar light guide plate according to an embodiment.

FIG. 10 is a model configuration diagram for simulating light incidence efficiency.

FIG. 11 is a view mainly showing a traveling direction of light in a rod-shaped light guide plate.

FIG. 12 is a characteristic diagram showing the incident efficiency.

FIG. 13 is a perspective view of a conventional surface light source device.

FIG. 14 is a cross-sectional view of a conventional surface light source device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light guide type illuminating device 2 Rod-shaped light guide plate 3 Light source module (light source) 8 Transparent resin sheet 9 Diffuse reflection plate 10 Planar light guide plate 14 Transparent resin

Claims (6)

[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 rod-shaped light guide plate; a planar light guide plate thinner than the light guide plate; A light source arranged so that light is incident from a narrow end face of the light guide plate, wherein one side surface of the rod-shaped light guide plate and the surface of the planar light guide plate are bonded with a transparent resin. Characteristic surface light source device. 2. A surface light source device which spreads and emits light from a point or linear light source in a planar shape, wherein the rod portion is formed integrally with one side surface of the rod portion, and has a thickness smaller than that of the rod portion. A surface light source device, comprising: a light guide plate including a planar portion; and a light source arranged so that light is incident from an end surface of the rod portion. 3. The planar light guide plate is rectangular, and the rod-shaped light guide plate is disposed diagonally to the planar light guide plate. A surface light source device according to claim 1. 4. The planar light guide plate is rectangular, the light source is located at four corners thereof, and the rod-shaped light guide plate is centered on the diagonal line with respect to the planar light guide plate. The surface light source device according to claim 1, wherein the surface light source device is disposed so as to face. 5. The planar light guide plate is rectangular, the light source is located at one corner thereof, and the rod-shaped light guide plate is provided with the one corner portion with respect to the planar light guide plate. The surface light source device according to claim 1, wherein the surface light source device is arranged along both sides sandwiching the surface light source device. 6. The planar light guide plate is rectangular, the light source is located at a pair of diagonal corners, and the rod-shaped light guide plate is no longer provided with respect to the planar light guide plate. The surface light source device according to claim 1, wherein the surface light source device is arranged so as to face each of the corner portions at one diagonal position.