JP2002197916A - Surface light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a side light surface light source equipped with a solid light emitting element such as LEDs capable of emitting light having almost uniform brightness distribution from the front of a light guide plate. SOLUTION: A diffusion layer 12 is installed in an incident end surface of the light guide plate 11, light outgoing from the solid light emitting element 10 is diffused with the diffusion layer 12, and made incident from almost the whole region of an incident end surface 11a of the light guide plate 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a surface light source used for a liquid crystal display device or the like.

[0002]

2. Description of the Related Art As a surface light source used in a liquid crystal display device or the like, there is a so-called sidelight type.

FIGS. 10 and 11 are a plan view and a side view showing a conventional sidelight type surface light source. The surface light source has an incident end face 1a for taking in light.
A cold cathode tube 2 having a length extending over the entire length of the incident end surface 1a and a light emitted from the cold cathode tube 2 being opposed to the incident end surface 1a of the light guide plate 1 for guiding light incident from the front surface and emitting the light from the front surface. The reflector 3 which reflects toward the incident end face 1a is arranged.

FIG. 12 is a plan view showing another conventional side light type surface light source. The surface light source is formed of an LED (light emitting diode) or the like facing the incident end face 1a of the light guide plate 1. A plurality (two in the figure) of solid-state light-emitting elements 4
Are arranged at appropriate intervals along the length direction of the incident end face 1a.

[0005]

However, the conventional surface light source shown in FIG. 10 and FIG.
a, the light emitted from the cathode tube 2 is made to enter the light guide plate 1 from almost the entire incident end face 1a of the light guide plate 1 and the front surface of the light guide plate 1 Can emit light having a substantially uniform luminance distribution from the light source, but on the other hand, since the life of the cold cathode fluorescent lamp 3 is short, the cold cathode fluorescent lamp 3 must be replaced frequently, so that the maintenance cost increases. Have a problem.

On the other hand, in the conventional surface light source shown in FIG. 12, since the life of the solid state light emitting element 4 such as an LED is semi-permanent, the light emitting element 4 need not be replaced. Since the light incident on the light guide plate 1 is light emitted from a plurality of solid state light emitting elements 4 arranged at appropriate intervals along the length direction of the incident end face 1a of the light guide plate 1, the incident end face 1
a does not evenly spread over the entire area of the light guide plate 1, and therefore, among the light emitted from the front surface of the light guide plate 1, the brightness of the light emitted from the region shown by the parallel diagonal lines in FIG. There is a problem in that emitted light having a low and almost uniform luminance distribution cannot be obtained.

The number of the solid state light emitting devices 4 is increased,
If the light emitting elements 4 are arranged at a close interval along the length direction of the incident end face 1a of the light guide plate 1, light is incident on the light guide plate 1 from almost the entire area of the incident end face 1a, and the light guide plate 1
Although light with a substantially uniform luminance distribution can be emitted from the front surface of the light emitting element, increasing the number of light emitting elements increases the cost of the surface light source and increases power consumption.

The present invention provides a sidelight-type surface light source having a solid-state light-emitting element capable of emitting light having a substantially uniform luminance distribution from the front surface of a light guide plate with a small number of light-emitting elements. It is intended for.

[0009]

A surface light source according to the present invention has at least one solid-state light emitting element and an incident end face for receiving light emitted from the light emitting element, and guides light incident from the incident end face. A light guide plate for emitting light from the front surface; and a diffusion layer provided on an incident end face of the light guide plate and diffusing outgoing light from the light emitting element and entering the light guide plate from the incident end face. Things.

[0010] Since the surface light source is provided with a diffusion layer on the incident end face of the light guide plate, the light emitted from the light emitting element is diffused by the diffusion layer so that the light guide plate is diffused from almost the entire area of the incident end face. The light can be incident, and therefore, light having a substantially uniform luminance distribution can be emitted from the front surface of the light guide plate with a small number of light emitting elements.

According to another aspect of the present invention, there is provided a surface light source having at least one solid-state light-emitting element and an incident end face for receiving light emitted from the light-emitting element. The light guide plate that emits light and the plurality of light guide fibers are densely arranged in parallel with each other, one end of which is an incident surface substantially perpendicular to the length direction of the light guide fibers, and the other end is the light guide fiber. A light guide fiber assembly that is a horizontally long emission surface inclined with respect to the length direction, and guides the incident light from the incident surface by the plurality of light guide fibers and emits the light from the horizontally long emission surface, The light guide fiber assembly is arranged so that the horizontally long exit surface faces the incident end face of the light guide plate, and the light emitting element is arranged to face the incident surface of the light guide fiber assembly. It is characterized by the following.

In this surface light source, the light emitted from the solid state light emitting element is guided by a plurality of light guide fibers of the light guide fiber assembly, and is incident on the light guide plate from almost the entire area of the incident end face. Since the light-emitting element may be disposed so as to face an incident surface having a smaller area than the horizontally long exit surface of the light-guiding fiber assembly, the number of light-emitting elements is small and almost uniform from the front surface of the light guide plate. It is possible to emit light with an appropriate luminance distribution.

Further, another surface light source of the present invention has at least one solid state light emitting element and an incident end face for taking in the light emitted from the light emitting element, and diffuses and guides the light incident from the incident end face. And a diffused light guide plate that emits light from the front side.

In the surface light source, the diffusion light guide plate diffuses the light incident from the incident end face and guides the light to the entire light guide plate,
Since the light is emitted from the front, with a small number of light emitting elements,
Light having a substantially uniform luminance distribution can be emitted from the front surface of the diffusion light guide plate.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, a surface light source according to the present invention is provided with a diffusion layer on an incident end face of a light guide plate, and diffuses outgoing light from a solid-state light-emitting device by the diffusion layer so that the light guide plate receives the light. By allowing light to enter from almost the entire area of the incident end face, light with a substantially uniform luminance distribution can be emitted from the front surface of the light guide plate with a small number of light emitting elements.

In this surface light source, the diffusion layer has at least one fiber layer in which a plurality of transparent fibers are arranged in parallel, and each of the transparent fibers in the fiber layer has a different refractive index from the transparent fiber. Or a scattering film in which light scattering particles having a different light refractive index from the base material are dispersed in a transparent base material.

In this surface light source, the solid state light emitting device may be disposed so as to face the outer surface of the diffusion layer provided on the incident end face of the light guide plate. It is preferable that a reflection plate is disposed on the side, and the solid state light emitting device is disposed on a side of a space between the diffusion layer and the reflection plate so as to face the space.

In another surface light source of the present invention, a plurality of light guide fibers are densely arranged in parallel with each other, and one end of the light guide fibers is formed as an incident surface substantially perpendicular to the length direction of the light guide fibers. The other end is a horizontally long exit surface inclined with respect to the length direction of the light guide fiber, and a guide for guiding incident light from the incident surface by the plurality of light guide fibers and exiting from the horizontally long exit surface. The solid-state light-emitting element, wherein the optical fiber aggregate is arranged such that the oblong emission surface faces the incident end face of the light guide plate, and the solid-state light-emitting element is arranged so as to oppose the incident surface of the light guide fiber assembly. From the front surface of the light guide plate with a small number of light-emitting elements, and the light emitted from the light guide fiber is made to enter the light guide plate through the light guide fiber aggregate from almost the entire area of the incident end face. Can be emitted

Still another aspect of the present invention is a surface light source, comprising: a light guide plate that receives light emitted from a solid state light emitting element from an incident end face and emits light from the front face by diffusing light incident from the incident end face to guide the light. By using a diffused light guide plate that emits light from a light source, light with a substantially uniform luminance distribution can be emitted from the front surface of the diffused light guide plate with a small number of light emitting elements.

[0020]

1 to 3 show a first embodiment of the present invention. FIG. 1 is a plan view of a surface light source, and FIG. 2 is a side view of the surface light source.

As shown in FIGS. 1 and 2, the surface light source of this embodiment has at least one solid-state light-emitting element 10 and an incident end face 11a for receiving light emitted from the light-emitting element 10. The light guide plate 11 includes a light guide plate 11 that guides light incident from the end face 11a and emits the light from the front face, and a diffusion layer 12 that is provided on the entire incident end face 11a of the light guide plate 11.

Although the structure of the solid-state light-emitting element 10 is not shown, an LED (light-emitting diode) is molded with a transparent resin having light scattering properties. It is set according to the use of the light source.

That is, the solid-state light-emitting element 10 may be one that emits colored light or one that emits white light. The solid-state light-emitting element 10 that emits colored light includes an LED that emits colored light of a predetermined color. A solid-state light-emitting element 1 configured to be molded with the transparent resin and emitting white light;
No. 0 has a configuration in which a red LED that emits red light, a green LED that emits green light, and a blue LED that emits blue light are arranged side by side, and these LEDs are molded with the transparent resin.

The light guide plate 11 has a front surface formed as a flat surface, and a rear surface formed as an inclined surface inclined from one end to the other end so as to approach the front surface. The end face having the larger width between the front and rear faces of both end faces is the incident end face 11a, and the entire front face is the emission face of the light incident from the incident end face 11a. .

The light guide plate 11 guides the light incident from the incident end face 11a by repeating total reflection at the interface between the front and rear surfaces of the light guide plate 11 and the air layer which is the outside air, and emits the light from the entire front surface. I do.

On the other hand, the diffusion layer 12 provided on the incident end face 11a of the light guide plate 11 diffuses the light emitted from the solid-state light emitting element 10 so that the light guide plate 11 has the incident end face 11a.
From.

FIG. 3 is an enlarged sectional view of the diffusion layer 12 in which hatching is omitted, and the diffusion layer 1 shown in FIG.
2 is a roughened film 13 in which one surface of the transparent resin film is roughened.

The diffusion layer 12 shown in FIG. 3B is formed by forming a plurality of transparent fibers (for example, glass fibers) 15 having a diameter of several μm to several tens μm by the length of the incident end face 11 a of the light guide plate 11. At least one fiber layer (two layers in the figure) arranged in parallel along a direction substantially orthogonal to the direction, and each transparent fiber 15 of the fiber layer has a different light refraction from the transparent fiber 15. It is composed of a fiber-containing film 14 bonded by a transparent resin 16 having a specific modulus.

The diffusion layer 12 shown in FIG. 3 (c) has a transparent base 18 made of a resin and a transparent base 18 made of a transparent resin or glass having a light refractive index different from that of the base 18.
It is composed of a scattering particle dispersion film 17 in which light scattering particles 19 having a diameter of about several tens of μm are dispersed.

In FIGS. 1 and 2, the diffusion layer 12 is shown slightly separated from the incident end face 11a of the light guide plate 11. However, the diffusion layer 12 is made of a transparent adhesive or a double-sided adhesive tape (not shown). The incident end face 11 of the light guide plate 11
a.

The solid-state light-emitting device 10 includes a light guide plate 1
It is arranged slightly apart from the diffusion layer 12 provided on the one incident end face 11 a and opposed to the outer surface of the diffusion layer 12.

The number of the solid-state light-emitting elements 10 and the position of the solid-state light-emitting elements 10 are determined by the length of the diffused light emission area when light enters the diffusion layer 12 from one point on its outer surface, and the incident end face 11 a of the light guide plate 11. The length may be selected according to the length. For example, when the length of the diffused light emission region is about half the length of the incident end face 11a of the light guide plate 11, as shown in FIG. The two solid-state light-emitting elements 10 may be arranged so as to correspond to the vicinity of two division points where the incident end face 11a of the light guide plate 11 is substantially equally divided into three in the length direction.

When the length of the diffused light emitting region is about one third of the length of the incident end face 11a of the light guide plate 11, the three solid state light emitting devices 10 What is necessary is just to arrange | position corresponding to the vicinity of each of three division | segmentation which divided the end surface 11a into four substantially equally in the length direction, and the length of the said diffused light emission area | region is the same as the length of the entrance end surface 11a of the said light guide plate 11. When the distance is equal to or greater than one degree, one solid-state light-emitting element 10 may be arranged so as to correspond to the vicinity of the center in the length direction of the incident end face 11a of the light guide plate 11.

This surface light source is provided with a diffusion layer 12 on the incident end face 11a of the light guide plate 11, and the solid-state light emitting element 10 is arranged so as to face the outer surface of the diffusion layer 12.
The light emitted from the light emitting element 10 can be diffused by the diffusion layer 12 and can be made to enter the light guide plate 11 from almost the entire area of the incident end face 11a. Light with a substantially uniform luminance distribution can be emitted.

In the surface light source of this embodiment, the diffusion layer 12 is preferably composed of the fiber-containing film 14 shown in FIG. 3B or the scattering particle dispersion film 17 shown in FIG. Since the fiber-containing film 14 or the scattering particle dispersion film 17 has a higher transmittance than the roughened film 13 shown in FIG. 3A, it diffuses the light emitted from the light-emitting element 10 and The diffused light can be efficiently incident on the light guide plate 11.

FIGS. 4 to 6 are plan views of surface light sources showing second to fourth embodiments of the present invention. The surface light sources of these embodiments are provided on an incident end face 11a of a light guide plate 11. FIG. A reflector 20 is disposed so as to face the outer surface of the diffusion layer 12, and the solid-state light-emitting element 10 is disposed on the side of the space between the diffusion layer 12 and the reflector 20 so as to face the space. is there.

The surface light sources of the second to fourth embodiments are different from the surface light source of the first embodiment in that the solid light emitting device 10 and the arrangement position of the solid-state light emitting element 10 are different. Same as light source.

In the surface light sources of the second and third embodiments shown in FIGS. 4 and 5, the reflecting plate 20 has one end approaching or abutting on one end of the diffusion layer 12 and has one end. From the outer surface of the diffusion layer 12 to the other end side.
The solid-state light-emitting device 10 is disposed on the wide end side of a space that increases from one end side to the other end side between 0 and 0 and faces the space.

The surface light source according to the second embodiment shown in FIG. 4 has one solid-state light emitting element 10 arranged opposite to the space, and the reflecting plate 2 with respect to the outer surface of the diffusion layer 12.
The inclination angle of 0 is set so as to secure an arrangement space for one solid-state light emitting element 10 on the wide end side of the space.

The surface light source of the third embodiment shown in FIG. 5 has two solid state light emitting devices 10 arranged in the width direction of the space so as to face the space.
The inclination angle of the reflection plate 20 with respect to the outer surface of the two is set so as to secure a space for arranging the two solid-state light emitting elements 10 on the wide end side of the space.

On the other hand, in the surface light source of the fourth embodiment shown in FIG. 6, the reflecting plate 20 is arranged substantially parallel to the outer surface of the diffusion layer 12 so as to be separated from the outer surface of the diffusion layer 12. 1
The solid-state light-emitting elements 10 are arranged one by one at both ends of a space between the reflector 2 and the reflector 20 so as to face the space.

According to the surface light sources of the second to fourth embodiments, of the light emitted from the solid-state
Is directly incident on the diffusion layer 12, and the light traveling toward the reflector 20 is reflected by the reflector 20 to form the diffusion layer 1.
2, the light emitted from the light emitting element 10 can efficiently enter the diffusion layer 12 from almost the entire area of the diffusion layer 12, and is thus diffused by the diffusion layer 12. The luminance distribution of light incident on the light guide plate 11 from almost the entire area of the incident end face 11a can be made substantially uniform, and light with a more uniform luminance distribution can be emitted from the front surface of the light guide plate 11.

FIG. 7 is a plan view of a surface light source according to a fifth embodiment of the present invention. The surface light source according to this embodiment guides at least one solid-state light emitting element 10 and light incident from an incident end face 11a. A light guide plate 11 that emits light from the front surface, and a light guide fiber assembly 21 that guides light emitted from the light emitting element 10 and makes the light guide plate 11 enter the light guide plate 11 from an incident end face 11a. The solid state light emitting device 10 and the light guide plate 11
Is the same as that of the first embodiment.

The light guide fiber aggregate 21 has a diameter of several tens μm.
a plurality of light-guiding fibers (for example, glass fibers) having a length of m to several hundred μm
22 are densely arranged in parallel with each other, and one end of which is substantially perpendicular to the length direction of the light guide fiber 22.
a, the other end of which is a horizontally long exit surface 21b inclined with respect to the length direction of the light guide fiber 22, and the incident light from the incident surface 21a is
And exits from the horizontally long exit surface 21b.

In this light guide fiber assembly 21, a predetermined number of light guide fibers 22 are densely arranged in parallel to each other to form a light guide fiber bundle having a square rod shape, and one end of the light guide fiber bundle is formed. The incident surface 21a is formed by being cut substantially perpendicularly to the length direction of the light guide fiber 22, and the other end is cut obliquely with respect to the length direction of the light guide fiber 22 to form the horizontal oblong. Exit surface 21
b, and the number of light guide fibers of the light guide fiber bundle and the inclination angle of the horizontally long exit surface 21b are determined by the width and length of the exit surface 21b being the incident end surface of the light guide plate 11. 11a is set to be substantially equal to the width and length.

The light guide fiber assembly 21 is arranged such that the horizontally long exit surface 21b is formed on the incident end surface 11a of the light guide plate 11.
The solid-state light emitting device 10
Are disposed so as to face the incident surface 21a of the light guide fiber assembly 21.

In this embodiment, the light guide fiber assembly 2
One solid state light emitting element 10 is opposed to one incident surface 21a.
However, the number of the solid-state light emitting elements 10 is such that the light guide fiber aggregate 21 receives light from almost the entire area of the light incident surface 21 a in accordance with the area of the incident surface 21 a of the light guide fiber aggregate 21. What is necessary is just to select so that it may be made incident.

In this embodiment, the reflectors 23 are disposed on the rear surface (the surface opposite to the horizontally long exit surface 21b) and the front and rear surfaces of the light guide fiber assembly 21 (front and rear surface reflection plates). Is not shown).

The surface light source converts the light emitted from the solid state light emitting element 10 into a plurality of light guide fibers 2 of the light guide fiber aggregate 21.
The light-emitting element 10 has an area smaller than that of the horizontally long exit surface 21b of the light-guiding fiber assembly 21. The light guide plate 11 can be disposed with a small number of light emitting elements because it is sufficient to dispose the light guide plate 11 so as to face the small incident surface 21a.
Can emit light having a substantially uniform luminance distribution from the front surface of the light emitting element.

Further, in this embodiment, since the reflection plates 23 are disposed on the rear surface and the front and rear surfaces of the light guide fiber assembly 21, each light guide fiber 22 is guided while the light guide fiber assembly 21 is guided. The light leaking out from the rear surface and the front and rear surfaces of the light guide fiber assembly 21 is reflected by the reflection plate 23 and is incident on the light guide fiber assembly 21 from the rear surface and the front and rear surfaces. Of the light incident on the light guide plate 11 from almost the entire area of the light incident surface 11a of the light guide plate 11. The brightness distribution can be made substantially uniform, and light with a more uniform brightness distribution can be emitted from the front surface of the light guide plate 11.

The light-guiding fiber assembly 21 used in this embodiment is a single-material light-guiding fiber (eg, glass fiber).
22, the light guide fiber aggregate 2
1 may be an optical fiber in which the outer periphery of a core material is densely covered with a clad material having a different refractive index from the core material. In this case, leakage to the rear surface and the front and rear surfaces of the light guide fiber aggregate may be performed. Since there is almost no light, there is no need to provide the reflection plate 23.

FIG. 8 is a plan view of a surface light source according to a sixth embodiment of the present invention. The surface light source of this embodiment includes at least one solid state light emitting element 10 and light emitted from the light emitting element 10. An input end face 24a for receiving the light,
and a diffused light guide plate 24 that diffuses and guides the light incident from a and emits the light from the front surface. The solid state light emitting device 10 is the same as that of the first embodiment.

The diffusion light guide plate 24 is, for example, a scattering particle dispersion plate in which light scattering particles having a different light refractive index from the base material are dispersed in a transparent base material such as an acrylic resin.

The diffusion light guide plate 24 has a wedge plate shape in which the front surface is formed as a flat surface and the rear surface is formed as an inclined surface inclined from one end to the other end so as to approach the front surface. The end face having the larger width between the front and rear faces of the both end faces is defined as the incident end face 24a, and the entire front face is defined as the emission face of the light incident from the incident end face 24a.

The solid-state light-emitting element 10 is arranged at a certain distance from the incident end face 24a of the diffused light guide plate 24 and opposed to the incident end face 24a of the diffused light guide plate 24.

In this embodiment, as shown in FIG. 8, the two solid-state light-emitting elements 10 are divided into two equally dividing the incident end face 24a of the diffused light guide plate 24 into three in the longitudinal direction. It is arranged corresponding to each vicinity.

According to this surface light source, the diffusion light guide plate 24
However, since the light incident from the incident end face 24a is diffused and guided to the entire light guide plate, and the light is emitted from the front surface, it is not necessary to make the diffuse light guide plate 24 have light incident from almost the entirety of the incident end face 24a. Therefore, light with a substantially uniform luminance distribution can be emitted from the front surface of the diffusion light guide plate 24 with a small number of light emitting elements.

FIG. 9 is a side view of a surface light source according to a seventh embodiment of the present invention. The surface light source of this embodiment includes at least one solid-state light emitting element 10 and light emitted from the light emitting element 10. An input end face 25a for receiving the light,
a light guide plate 25 for guiding light incident from a and exiting from the front
A reflection film 26 provided on the front surface of the light guide plate 25;
A diffusion layer 12 provided on an incident end face 25a of the light guide plate 25 to diffuse light emitted from the light emitting element 10 and to enter the light guide plate 25 from the incident end face 25a; and a diffusion layer 12 disposed in front of the light guide plate 25. And a prism sheet 27.

The solid state light emitting device 10 and the diffusion layer 12
Is the same as that of the first embodiment. In this embodiment, the two solid-state light-emitting elements 10 are divided into two by substantially equally dividing the incident end face 25a of the light guide plate 25 in the length direction into three. It is arranged corresponding to each point.

The light guide plate 25 is a transparent plate made of an acrylic resin or the like. One end surface of the light guide plate 25 is an incident end surface 25a, and the front surface of the light guide plate 25 is gradually reduced from the incident end surface 25a side to the other end side. It is formed as a step-shaped surface comprising a step surface and a plurality of step surfaces connecting these step surfaces, and each of the plurality of step surfaces is an elongated emission surface 25b for emitting light incident from the incident end surface 25a. ing.

The reflection film 26 is provided over substantially the entire area between the plurality of elongated emission surfaces 25b on the front surface of the light guide plate 25 (on the plurality of step surfaces of the stepped surface).

The light guide plate 25 reflects the light incident from the incident end face 25a on the reflection film 26 on a plurality of step surfaces on the front surface (stepped surface) of the light guide plate as shown by solid arrows in FIG. The light is guided by repetition of reflection and total reflection at the interface between the rear surface of the light guide plate and the air layer, which is the outside air, and the light is emitted from a plurality of elongated emission surfaces (step surfaces having stair-like surfaces) 25b on the front surface of the light guide plate.

Further, a region between the plurality of elongated emission surfaces 25b on the front surface of the light guide plate 25 (on a plurality of steps of the step-shaped surface).
Reflective film 2 provided over substantially the entire area of each
6 reflects the light incident from the front side of the light guide plate 25 as shown by the dashed arrow in FIG.

On the other hand, the prism sheet 27 disposed on the front side of the light guide plate 25 is a molded product of an acrylic resin or the like, the front surface of which is formed as a flat surface, and the rear surface of the prism sheet 27 is formed of a plurality of elongated members of the light guide plate 25. The length direction of the light exit surface 25b (the light guide plate 25)
(In the width direction) are formed at predetermined pitches.

Note that the plurality of prism portions 27a are provided at a predetermined interval, and the prism sheet 27a is provided.
The area between the prism portions 27a on the rear surface is a gentle inclined surface having a small inclination angle with respect to the front surface of the prism sheet 27.

The prism sheet 27 is provided on the light guide plate 2.
5, the light emitted from the plurality of elongated emission surfaces 25a is refracted in the front direction and emitted, and the light incident from the front is transmitted and emitted to the rear.

That is, the prism sheet 27 transfers the light emitted from the plurality of elongated emission surfaces 25a of the light guide plate 25 to the plurality of prism portions 27a on one side (guide) as indicated by solid arrows in the drawing. Elongated exit surface 25b of light plate 25
From the front side of the prism sheet 27, and the light is emitted from the front side of the prism sheet 27 and is incident from the front side by total reflection at the interface between the other side surface of the prism portion 27a and the air layer as the outside air. The light thus emitted is emitted rearward from a region between the plurality of prism portions 27a on the rear surface of the prism sheet 27 and between the respective prism portions 27a, as indicated by the dashed arrows in the drawing.

The light incident from the front side of the prism sheet 27 and emitted to the rear side is reflected by the reflection films 26 provided on the front surface of the light guide plate 25 between the plurality of elongated emission surfaces 25a. Is done.

The light guide plate 25 is provided on the prism sheet 27 in such a manner that each of the reflection films 26 provided on the front surface of the light guide plate 25 between a plurality of elongated emission surfaces 25a is provided.
Is inclined so that the virtual line passing through the leading edge of the prism sheet 27 is substantially parallel to the virtual line passing through the top of each prism portion 27a on the rear surface of the prism sheet 27. It is arranged as close as possible to the top of the prism part 26a.

The plurality of prism portions 27a on the rear surface of the prism sheet 27 are provided at a pitch smaller than the pitch of the plurality of elongated emission surfaces 25b of the light guide plate 25. Are always opposed to at least one prism portion 27a of the prism sheet 27.

Therefore, the light emitted from the plurality of elongated emission surfaces 25b of the light guide plate 25 enters the plurality of prism portions 27a of the prism sheet 27 from one side thereof with almost no loss, and The light is refracted by total reflection at the interface between the other side surface and the outside air, and efficiently exits to the front side of the prism sheet 27.

That is, in the surface light source, a plurality of elongated emission surfaces 25b are formed on the front surface of the light guide plate 25 along the direction substantially parallel to the incident end surface 25a of the light guide plate 25 at intervals. The plurality of elongated emission surfaces 25 on the front surface of
The light incident on the light guide plate 25 from the incident end surface 25a is emitted from the plurality of elongated emission surfaces 25b on the front surface of the light guide plate 25 by providing the reflection film 26 over substantially the entire region in the region between the light guide plates 25. Most of the light incident on the light guide plate 25 from the front side is reflected by the reflection film 26 provided in the region between the plurality of elongated emission surfaces 25b.

In this embodiment, the front surface of the light guide plate 25 is formed as a step-like surface, so that the plurality of step surfaces are respectively formed as elongated emission surfaces 25b, and the region between these elongated emission surfaces 25b ( A reflection film 26 is provided on substantially the entire area of each of the plurality of step surfaces of the stepped surface, and the prism sheet 2 is provided in front of the light guide plate 25.
7 is disposed, the front direction (the prism sheet 27)
Reflection film 2 when viewed from the direction near the normal to the front surface of
6, the light reflected from the plurality of elongated light exit surfaces 25b of the light guide plate 25 is reflected by the prism sheet 2.
7, and can be emitted to the front side.

This surface light source mainly performs reflection display using external light which is light of the environment under an environment of sufficient brightness, and when the external light of sufficient brightness cannot be obtained, This is used in a reflective / transmissive liquid crystal display device that emits light from a surface light source and performs transmissive display. A front surface of the prism sheet 27 is opposed to a rear surface of the liquid crystal display device behind a liquid crystal display device (not shown). Be placed.

In FIG. 9, the stepped surface of the light guide plate 25 and the prism portion 27a of the prism sheet 27 are shown.
Is greatly exaggerated, the prism sheet 2
The plurality of prism portions 16 are formed at a pitch substantially equal to or several times to several tens times the pixel pitch of the liquid crystal display element (about 100 μm), and the plurality of elongated emission surfaces 25 b of the light guide plate 25 are The prism sheet 27 is formed at a pitch slightly larger than the pitch of the prism portions 27a.

The surface light source of this embodiment has the diffusion layer 12 provided on the incident end face 25a of the light guide plate 25, and the solid-state light emitting element 10 is arranged so as to face the outer surface of the diffusion layer 12. Similarly to the surface light source of the first embodiment described above, light emitted from the light emitting element 10 can be diffused by the diffusion layer 12 and can be made to enter the light guide plate 25 from almost the entire area of the incident end face 25a, Therefore, with a small number of light emitting elements, light having a substantially uniform luminance distribution can be emitted from the plurality of elongated emission surfaces 25b on the front surface of the light guide plate 25.

In this embodiment, the reflection film 26 is provided in the region (on the plurality of steps of the step-shaped surface) between the plurality of elongated emission surfaces 25b on the front surface of the light guide plate 25. The film 26 may be provided on the entire rear surface of the light guide plate 25.

In this embodiment, the solid-state light-emitting element 10 is arranged so as to face the outer surface of the diffusion layer 12 provided on the incident end face 25a of the light guide plate 25, but the solid-state light-emitting element 10 shown in FIGS. As in the second to fourth embodiments, a reflection plate 20 is disposed so as to face the outer surface of the diffusion layer 12, and the space is provided between the diffusion layer 12 and the reflection plate 20 on the side of the space. The solid state light emitting devices 10 may be arranged to face each other.

Further, in this embodiment, the diffusion layer 12 is provided on the incident end face 25a of the light guide plate 25. However, instead of the diffusion layer 12, a light guide is provided as in the fifth embodiment shown in FIG. A fiber assembly 21 may be provided, and the solid-state light emitting element 10 may be disposed so as to face the incident surface 21a of the light guide fiber assembly 21. Further, the light guide plate 25 may be a diffusion light guide plate, and the diffusion layer 12 or The light guide fiber aggregate 21 may be omitted.

The solid-state light-emitting device 10 is not limited to an LED, but may be an EL (electroluminescence) device. Further, the surface light source of the present invention can be widely used not only for the liquid crystal display device but also for other uses.

[0081]

According to the surface light source of the present invention, a diffusion layer is provided on the incident end face of the light guide plate, and the light emitted from the solid-state light emitting element is diffused by the diffusion layer so as to be incident on the light guide plate from almost the entire area of the incident end face. With this configuration, it is possible to emit light having a substantially uniform luminance distribution from the front surface of the light guide plate with a small number of light emitting elements.

In this surface light source, the diffusion layer has at least one fiber layer in which a plurality of transparent fibers are arranged in parallel, and each of the transparent fibers in the fiber layer has a light refractive index different from that of the transparent fibers. A fiber-containing film bonded by a transparent resin having, or a transparent particle, preferably a film composed of a scattering particle dispersion film in which light scattering particles having a different light refractive index from the substrate are dispersed in the transparent substrate. Since the film or the scattering particle dispersion film has a high transmittance, the light emitted from the light emitting element can be diffused and the diffused light can be efficiently incident on the light guide plate.

In this surface light source, the solid state light emitting device may be disposed so as to face the outer surface of the diffusion layer provided on the incident end face of the light guide plate. It is preferable to arrange a reflection plate, and to arrange the solid-state light-emitting element on a side of a space between the diffusion layer and the reflection plate so as to face the space. The luminance distribution of the light diffused by the layer and incident on the light guide plate from almost the entire area of the incident end face can be made substantially uniform, and light with a more uniform luminance distribution can be emitted from the front surface of the light guide plate.

According to another surface light source of the present invention, a plurality of light guide fibers are densely arranged in parallel with each other, and one end thereof is an incident surface substantially perpendicular to the length direction of the light guide fibers. The other end is a horizontally long exit surface inclined with respect to the length direction of the light guide fiber, and a guide for guiding incident light from the incident surface by the plurality of light guide fibers and exiting from the horizontally long exit surface. The solid-state light-emitting element, wherein the optical fiber aggregate is arranged such that the oblong emission surface faces the incident end face of the light guide plate, and the solid-state light-emitting element is arranged so as to oppose the incident surface of the light guide fiber assembly. From the front surface of the light guide plate with a small number of light-emitting elements, because the light emitted from the light guide plate is made to enter the light guide plate through the light guide fiber aggregate from almost the entire area of the incident end face. It is possible to emit light with an appropriate luminance distribution.

Further, another surface light source according to the present invention provides a light guide plate which takes in light emitted from a solid state light emitting element from an incident end face and emits light from the front face by diffusing light incident from the incident end face to guide the light guide plate. Since the light guide plate is a diffused light guide plate, light with a substantially uniform luminance distribution can be emitted from the front surface of the diffused light guide plate with a small number of light emitting elements.

[Brief description of the drawings]

FIG. 1 is a plan view of a surface light source showing a first embodiment of the present invention.

FIG. 2 is a side view of the surface light source.

FIG. 3 is an enlarged sectional view of the surface light source in which a diffusion layer is not hatched.

FIG. 4 is a plan view of a surface light source according to a second embodiment of the present invention.

FIG. 5 is a plan view of a surface light source according to a third embodiment of the present invention.

FIG. 6 is a plan view of a surface light source according to a fourth embodiment of the present invention.

FIG. 7 is a plan view of a surface light source according to a fifth embodiment of the present invention.

FIG. 8 is a plan view of a surface light source according to a sixth embodiment of the present invention.

FIG. 9 is a side view of a surface light source according to a seventh embodiment of the present invention.

FIG. 10 is a plan view of a conventional surface light source.

FIG. 11 is a side view of the conventional surface light source.

FIG. 12 is a plan view of another conventional surface light source.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Solid-state light emitting element 11 ... Light guide plate 11a ... Incident end face 12 ... Diffusion layer 13 ... Roughened film 14 ... Fiber-containing film 15 ... Transparent fiber 16 ... Transparent resin 17 ... Scattering particle dispersion film 18 ... Base material 19 ... Light scattering Particles 20: Reflector 21: Light guide fiber assembly 21a: Incident surface 21b: Outgoing surface 22: Light guide fiber 23: Reflector 24: Diffusion light guide 24a: Incident end face 25: Light guide plate 25a: Incident end face 25b: Slender emission Surface 26: Reflective film 27: Prism sheet

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) // F21Y 101: 02 F21Y 101: 02

Claims (7)

[Claims] 1. A light guide plate having at least one solid state light emitting element, an incident end face for taking in light emitted from the light emitting element, guiding light incident from the incident end face and emitting the light from the front face, and the light guide plate And a diffusion layer provided on the light incident surface of the light emitting element and diffusing the light emitted from the light emitting element to be incident on the light guide plate from the light incident surface. 2. The diffusion layer has at least one fiber layer in which a plurality of transparent fibers are arranged in parallel, and each transparent fiber of the fiber layer is formed of a transparent resin having a light refractive index different from that of the transparent fibers. The surface light source according to claim 1, wherein the surface light source is made of a fiber-containing film bonded by a polymer. 3. The diffusion layer according to claim 1, wherein the diffusion layer comprises a scattering particle dispersion film in which light scattering particles having a different light refractive index from the substrate are dispersed in a transparent substrate.
Surface light source according to 1. 4. The surface light source according to claim 1, wherein the solid-state light-emitting element is disposed so as to face an outer surface of a diffusion layer provided on an incident end face of the light guide plate. 5. A reflection plate is disposed opposite to an outer surface of a diffusion layer provided on an incident end face of a light guide plate, and is disposed on a side of a space between the diffusion layer and the reflection plate to face the space. Wherein a solid-state light emitting element is arranged.
3. The surface light source according to any one of 3. 6. A light guide plate having at least one solid state light emitting element, an incident end face for taking in light emitted from the light emitting element, guiding light incident from the incident end face and emitting the light from the front face, and a plurality of light guide plates. The light guide fibers are densely arranged in parallel with each other, and one end thereof is an incident surface substantially perpendicular to the length direction of the light guide fiber, and the other end is oblong with the inclination angle with respect to the length direction of the light guide fiber. And a light guide fiber assembly that guides the incident light from the incident surface by the plurality of light guide fibers and emits the light from the horizontally long output surface, wherein the light guide fiber assembly is A surface light source, wherein a horizontally long emission surface is arranged to face an incident end surface of the light guide plate, and the light emitting element is arranged to face an incidence surface of the light guide fiber assembly. 7. A diffused light guide plate having at least one solid state light emitting element, an incident end face for taking in light emitted from the light emitting element, diffusing and guiding light incident from the incident end face, and emitting the light from the front face. A surface light source comprising: