JP2002279812A - Surface light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source enabled to emit a light with almost uniform strength from whole part of a light guide plate. SOLUTION: A refraction surface 12 which makes the light emitted from a light source part 20 is incident on a light guide plate 10 by refracting the light in such a direction that the angle between the refracted light and a normal line of a front surface 10b of a light guide plate 10 becomes smaller, is mounted to an end surface of incidence 10a of the light guide plate 10 composed of the end surface of incidence 10a into which the light is incident, the front surface 10b from which, the light of incidence is emitted, and a back surface 10c facing the front surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art As a surface light source used as a light source of a liquid crystal display device, there is a surface light source which guides light emitted from a light source section by a light guide plate and emits the light from the front surface thereof.

FIG. 11 is a side view showing a conventional surface light source device. The surface light source includes an incident end surface 1a on which light is incident, a front surface 1b from which the incident light is emitted, and a rear surface 1c opposed to the front surface 1b. And a light source unit 3 arranged to face the incident end face 1a of the light guide plate 1.

The light guide plate 1 has a front surface 1b, which is an emission surface, formed as a flat surface, and a rear surface 1c formed as an inclined surface inclined so as to approach the front surface 1b from the incident end surface 1a toward the other end. It is formed of a wedge-shaped transparent plate (for example, an acrylic resin plate), and a reflection film 2 is provided on the entire rear surface 1 c of the light guide plate 1.

The light source unit 3 includes, for example, a cold cathode tube 4 having a length extending over the entire length of the incident end face 1a of the light guide plate 1.
And a reflector 5 that reflects light emitted from the cold cathode tube 4 toward the incident end face 1a of the light guide plate 1.

In this surface light source, light emitted from the light source unit 3 and incident on the light guide plate 1 from the incident end face 1a is, as shown by an arrow in FIG. 11, divided into the front surface 1b of the light guide plate and the outside air (air). Is reflected in the longitudinal direction of the light guide plate 1 by repetition of total reflection at the interface of the light guide plate and reflection at the reflection film 2 provided on the rear surface 1c of the light guide plate, and is totally reflected at the interface between the front surface 1b of the light guide plate and the outside air. Light incident at an incident angle smaller than the critical angle (near perpendicular) is emitted from the light guide plate front surface 1b.

[0007]

However, in the conventional surface light source shown in FIG. 11, the light incident on the light guide plate 1 from the incident end face 1a and guided through the light guide plate 1 is the light guide plate front surface 1b. Most of the light traveling toward the region near the incident end face of the light guide plate is incident on the interface between the light guide plate front surface 1b and the outside air at an incident angle larger than the critical angle for total reflection and is totally reflected. The intensity of light emitted from the region near the end face is lower than the intensity of light emitted from other regions, and therefore, the intensity distribution of the emitted light is uneven.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a surface light source capable of emitting light of substantially uniform intensity from the entire front surface of a light guide plate.

[0009]

A surface light source according to the present invention comprises: a light guide plate having an incident end surface on which light is incident, a front surface from which the incident light is emitted, and a rear surface facing the front surface; A light source unit disposed opposite the incident end face, and the incident end face of the light guide plate is refracted in a direction in which the angle of light emitted from the light source unit with respect to the normal to the front surface of the light guide plate becomes smaller. It is characterized in that a refraction surface for entering the light guide plate is provided.

According to this surface light source, the light is emitted from the light source unit,
The light incident on the light guide plate from the incident end face is refracted by the refraction surface provided on the incident end face in a direction in which the angle with respect to the normal to the front surface of the light guide plate becomes smaller and enters the light guide plate. The light that is incident from the incident end face and is guided through the light guide plate is also incident on the area near the incident end face on the front face of the light guide plate at an incident angle smaller than the critical angle for total reflection, and the area near the incident end face on the front face of the light guide plate. Therefore, a sufficient amount of light can be emitted from the light guide plate, and therefore, light with substantially uniform intensity can be emitted from the entire front surface of the light guide plate.

Another surface light source of the present invention is a light guide plate comprising an incident end face on which light is incident, a front face from which the incident light is emitted, and a rear face opposite to the front face, and an incident end face of the light guide plate. And a light source section arranged to face the
At least one of the front surface and the rear surface of the light guide plate at the incident end surface side, the light emitted from the light source unit, and the light incident on the light guide plate from the incident end surface with respect to the normal to the front surface of the light guide plate A refracting surface for refracting light in a direction in which the angle becomes smaller is formed.

According to this surface light source, the light is emitted from the light source unit,
The light incident on the light guide plate from the incident end face has an angle with respect to a normal line of the front face of the light guide plate due to a refraction surface formed at an end of the light guide plate on the incident end face side of at least one of the front face and the rear face. Since the light is refracted in the smaller direction, light incident on the light guide plate from its incident end face and guided through the light guide plate is also incident on the light guide plate front surface in a region near the incident end face at an incident angle smaller than the critical angle for total reflection. When the light is incident, a sufficient amount of light can be emitted from a region near the incident end face of the front surface of the light guide plate, and therefore, light of substantially uniform intensity can be emitted from the entire front surface of the light guide plate.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the surface light source of the present invention refracts the light emitted from the light source section at the incident end face of the light guide plate in a direction in which the angle with respect to the normal to the front surface of the light guide plate becomes smaller. By providing a refraction surface for entering the light guide plate, light of substantially uniform intensity is emitted from the entire front surface of the light guide plate.

In this surface light source, it is preferable that the refraction surface provided on the incident end face of the light guide plate comprises a plurality of prism faces or lens faces arranged in the height direction of the incident end face.

According to another aspect of the present invention, at least one of the front and rear surfaces of the light guide plate emits light from the light source unit at the end on the incident end surface side, and enters the light guide plate from the incident end surface. By forming a refraction surface that refracts light in a direction in which the angle of the front surface of the light guide plate with respect to the normal to the front surface becomes smaller, light of substantially uniform intensity is emitted from the entire front surface of the light guide plate.

In this surface light source, the refracting surface formed on the incident end surface side of at least one of the front surface and the rear surface of the light guide plate is configured such that the light incident surface is incident on the surface on which the refracting surface is formed. The light guide plate preferably has an inclined surface that is obliquely recessed in an inner direction of the light guide plate from an end face toward the other end of the light guide plate.

Also, in any surface light source of the present invention, it is preferable that an optical means for refracting light emitted from the front surface of the light guide plate in a predetermined direction is disposed in front of the front surface of the light guide plate. .

[0018]

1 and 2 show a first embodiment of the present invention. FIG. 1 is a side view of a surface light source, and FIG. 2 is an enlarged side view of a light guide plate of the surface light source on an incident end face side. is there.

As shown in FIGS. 1 and 2, the surface light source of this embodiment includes an incident end face 10a on which light is incident, a front face 10b from which the incident light is emitted, and a rear face 10c facing the front face. The light guide plate 10 includes a light guide plate 10 and a light source unit 20 arranged to face the incident end face 10a of the light guide plate 10.

The light guide plate 10 has a front surface 10 as an emission surface.
b is formed on a flat surface, and the rear surface 10c is
The light guide plate 10 is made of a transparent plate (for example, an acrylic resin) formed on an inclined surface that is inclined so as to approach the front surface 10b from the side a toward the other end.
c is provided with a reflective film 11 made of a vapor-deposited or plated film of a high-reflectance metal such as aluminum over its entire surface.

On the incident end face 10a of the light guide plate 10, light emitted from the light source unit 20 is applied to the front face 1 of the light guide plate 10.
A refracting surface 12 is provided for refracting light in a direction in which the angle with respect to the normal to 0b becomes smaller and entering the light guide plate 10.

The refracting surface 12 is composed of, for example, a plurality of prism faces 12a arranged in the height direction of the incident end face 10a. It is formed in a horizontally long prism shape along the width direction of the optical plate 10).

The light guide plate 10 shown in FIGS.
Sets the incident end face 10a to the plurality of prism faces 12a.
The light guide plate 10 may be formed such that the incident end face is formed as a flat surface and the incident end face is provided with an end face layer on which the refraction surface 12 is formed. In that case, even if the end face layer is molded separately from the light guide plate and is attached to the incident end face of the light guide plate, the incident end face side of the light guide plate is fitted into a mold for forming the refraction surface 12,
It may be formed by injecting a photocurable resin into the mold and curing the resin by light irradiation from the light guide plate side. On the other hand, the light source unit 20 is, for example, a cold cathode tube 21 having a length extending over the entire length of the incident end face 10 a of the light guide plate 10, and directs light emitted from the cold cathode tube 21 to the incident end face 10 a of the light guide plate 10. And a reflector 22 that reflects light.

The surface light source emits light emitted from the light source unit 20 and incident on the light guide plate 10 from its incident end face 10a to the light guide plate front face 10b as shown by arrows in FIGS. The interface between the front surface 10b of the light guide plate and the outside air while being guided in the length direction of the light guide plate 10 by repeating the total reflection at the interface with the outside air (air) and the reflection on the reflection film 11 provided on the rear surface 10c of the light guide plate. Incident on the light guide plate front surface 10b at an incident angle smaller than the total reflection critical angle (closer to the vertical).
Emitted from

In this case, the surface light source of this embodiment is a refraction surface 1 comprising a plurality of prism surfaces 12a arranged on the incident end face 10a of the light guide plate 10 in the height direction of the incident end face 10a.
2, the light emitted from the light source unit 20 and incident on the light guide plate 10 from the incident end face 10a thereof is transmitted to the front surface 10b of the light guide plate 10 by the refraction surface 12 provided on the incident end face 10a. Is refracted in a direction in which the angle becomes smaller with respect to the normal line and enters the light guide plate 10.

Therefore, according to the surface light source, the light is incident on the light guide plate 10 from the incident end face 10a of the light guide plate 10.
The light guided inside 0 is also incident on a region near the incident end face of the light guide plate front surface 10b at an incident angle smaller than the critical angle for total reflection,
A sufficient amount of light can be emitted from a region near the incident end face of the light guide plate front surface 10b.
Can emit light of substantially uniform intensity from the entire front surface of the light emitting element.

As described above, since the surface light source emits light of substantially uniform intensity from the entire front surface of the light guide plate 10, for example, by using the surface light source as a light source of a liquid crystal display device, the brightness of the entire screen is improved. , A liquid crystal display device having a good display quality and uniform display quality can be obtained.

FIG. 3 is a side view of the liquid crystal display device provided with the surface light source of the above embodiment. In this liquid crystal display device, the surface light source of the above embodiment is provided behind the liquid crystal display element 30 and the light guide plate thereof. 10 is a backlight type in which a front surface 10 b of the liquid crystal display 10 is opposed to a rear surface of the liquid crystal display element 30.

The liquid crystal display element 30 may be any of a TN (twisted nematic) type, an STN (super twisted nematic) type, a homogeneous alignment type in which liquid crystal molecules are homogenized in one direction, or a ferroelectric liquid crystal display element. A liquid crystal cell 31 in which transparent electrodes are respectively provided on inner surfaces of a pair of front and rear transparent substrates opposed to each other with a liquid crystal layer interposed therebetween, The cell 31 includes a pair of polarizing plates 32 and 33 disposed on the front and rear surfaces of the cell 31, respectively.

This liquid crystal display device performs reflection display using the external light which is the light of the environment under the environment of sufficient brightness, and when the external light of sufficient brightness cannot be obtained, the surface light source The illumination light is emitted to perform transmissive display using the illumination light. In the case of reflective display using external light, light enters from the front side, which is the display observation side, and passes through the liquid crystal display element 30. Light is reflected by a reflective film 11 provided on a rear surface 10c of the light guide plate 10 of the surface light source as indicated by a dashed arrow in the figure, and the reflected light is transmitted through the liquid crystal display element 30 to the front side. Emit.

In the case of the transmissive display using the illumination light, the illumination light emitted from the surface light source enters the liquid crystal display element 30 from the rear surface as shown by a solid arrow in FIG. Light transmitted through the liquid crystal display element 30 is emitted to the front side.

The surface light source of the above embodiment is a light guide plate 10
Although the reflection film 11 is provided on the rear surface 10c of the light guide plate 10, the reflection film 11 on the rear surface 10c of the light guide plate 10 may be omitted.
Light from the incident end face 10a is totally reflected at the interface between the front surface 10b of the light guide plate and the outside air and the rear surface 10c of the light guide plate.
Light guide plate 10 by repeating total internal reflection at the interface between
The light can be emitted from the front surface 10b of the light guide plate while being guided in the length direction.

The surface light source in which the reflection film 11 on the rear surface 10c of the light guide plate 10 is omitted as described above is not limited to the backlight type liquid crystal display device performing the reflection display and the transmission display shown in FIG. The present invention can be used for a backlight type liquid crystal display device which performs a transmissive display using illumination light from a camera, and a front light type liquid crystal display device.

FIG. 4 is a side view of a front light type liquid crystal display device provided with a surface light source in which the reflection film 11 on the rear surface 10c of the light guide plate 10 is omitted. In addition, the surface light source of the above embodiment is arranged such that the front surface 10b of the light guide plate 10 is opposed to the front surface of the liquid crystal display element 30 and the reflection plate 34 is arranged behind the liquid crystal display element 30. Has become. The liquid crystal display element 30 is the same as that shown in FIG.

This liquid crystal display device performs reflection display using external light which is the light of the environment under an environment of sufficient brightness, and when the external light of sufficient brightness cannot be obtained, the liquid crystal display device transmits from the surface light source. The illumination light is emitted to perform reflection display using the illumination light. In the case of reflection display using external light, light is incident from the front side, which is the display observation side, and the light guide plate 10 of the surface light source is The light transmitted through the liquid crystal display element 30 is reflected by a reflector 34 as shown by a broken arrow in the figure, and the reflected light is transmitted through the liquid crystal display element 30 and the light guide plate 10 of the surface light source. Out to the front side.

In the case of reflection display using the illumination light, the illumination light emitted from the surface light source enters the liquid crystal display element 30 from the front as shown by a solid arrow in FIG. The light transmitted through the liquid crystal display element 30 is reflected by the reflection plate 34, and the reflected light is reflected by the liquid crystal display element 3
0 and the light passes through the light guide plate 10 of the surface light source and is emitted to the front side.

FIG. 5 is a side view of a surface light source according to a second embodiment of the present invention. Polarizing plate 23 for causing the emitted light to enter the light guide plate 10 as linearly polarized light
Is added. The polarizing plate 23 is fitted into an opening of the reflector 22 of the light source unit 20.

The surface light source of this embodiment is provided with the polarizing plate 23 for allowing the light emitted from the light source unit 20 to enter the light guide plate 10 as linearly polarized light. It is possible to emit linearly polarized light having a uniform intensity and a polarization component along the transmission axis (not shown) of the polarizing plate 23.

The surface light source of this embodiment can be used in any of the liquid crystal display devices shown in FIGS. 3 and 4. This surface light source can be used in the backlight type liquid crystal display device shown in FIG. When used, the direction of the transmission axis of the polarizing plate 23 is set so that linearly polarized light having a polarization component along the transmission axis of the rear polarizing plate 33 of the liquid crystal display element 30 is emitted from the front surface of the light guide plate 10. Just set it.

The backlight type liquid crystal display device provided with the surface light source according to this embodiment comprises a liquid crystal display element 30 from the surface light source.
The linearly polarized light of the polarization component along the transmission axis of the rear polarizing plate 33 is emitted, and the light is transmitted through the rear polarizing plate 33 and enters the liquid crystal cell 31. And a display with higher contrast can be obtained.

In the backlight type liquid crystal display device provided with the surface light source of this embodiment, the rear polarizing plate 33 of the liquid crystal display element 30 is omitted, and the linearly polarized light emitted from the surface light source is converted to the liquid crystal. A configuration in which the light enters the cell 31 may be employed.

When the surface light source of this embodiment is used in the front light type liquid crystal display device shown in FIG. 4, the transmission axis of the polarizing plate 23 is oriented from the front of the light guide plate 10 to the liquid crystal display. What is necessary is just to set so that the linearly polarized light of the polarization component along the transmission axis of the front polarizing plate 32 of the element 30 may be emitted.

The front light type liquid crystal display device provided with the surface light source according to this embodiment comprises a liquid crystal display element 3 from the surface light source.
0, a linearly polarized light having a polarization component along the transmission axis of the front polarizing plate 32 is emitted, and the light is transmitted through the front polarizing plate 33 and enters the liquid crystal cell 31. High linearly polarized light is incident, and a display with higher contrast can be obtained.

FIGS. 6 to 8 are side views of surface light sources showing the third to fifth embodiments of the present invention. The surface light sources of these embodiments are the same as those of the first embodiment described above. The front surface 10 b of the light guide plate 10 is provided in front of the front surface 10 b of the light guide plate 10.
The optical means for refracting the light emitted from b in a predetermined direction is arranged.

That is, the surface light source of the third embodiment shown in FIG. 6 is the same as the surface light source of the surface light source plate 10 of the first embodiment.
b, an optical unit 24a including a diffusion plate 25 and a light-collecting plate 26 provided in front of the diffusion plate 25 and having directivity in the front direction is arranged.

The diffusing plate 25 is made of, for example, a transparent resin film into which diffusing particles are mixed. The condensing plate 26 has an elongated isosceles triangular prism along the width direction of the light guide plate 10 on the front surface. The parts are composed of prism sheets that are closely arranged and formed in parallel with each other.

According to the surface light source of this embodiment, the light emitted from the front surface 10b of the light guide plate 10 is diffused by the diffusion plate 25, and the diffused light is diffused by the light collector 26 in the front direction (of the light guide plate 10). Since the light can be condensed and emitted in the direction near the normal line of the front surface 10b), light with more uniform intensity distribution and directivity in the front direction can be emitted.

The surface light source according to the fourth embodiment shown in FIG. 7 has a light refraction plate 27 having directivity in the front direction provided in front of the front surface 10b of the light guide plate 10 of the surface light source according to the first embodiment. The optical means 24b is arranged.

The light refraction plate 27 is provided on the light guide plate 1.
On the rear surface facing the front surface 10b of the light guide plate 10, a prism sheet in which elongated isosceles triangular prism portions along the width direction of the light guide plate 10 are densely arranged and formed parallel to each other.

According to the surface light source of this embodiment, the light emitted from the front surface 10b of the light guide plate 10 can be refracted in the front direction by the light refraction plate 27 and emitted.
Light having uniform intensity distribution and directivity in the front direction can be emitted.

The surface light source of the fifth embodiment shown in FIG. 8 has a directivity obliquely to the front of the front surface 10b of the light guide plate 10 of the surface light source of the first embodiment. The optical means 24c comprising a light refraction plate 28 is provided.

The light refracting plate 28 is formed of a sawtooth-shaped prism sheet on the front surface of which is formed in parallel with each other elongated narrow trapezoidal prisms along the width direction of the light guide plate 10. .

According to the surface light source of this embodiment, light emitted from the front surface 10b of the light guide plate 10 can be refracted by the light refraction plate 28 in the oblique direction with respect to the front direction and emitted. Light with uniform distribution and directivity in oblique directions can be emitted.

In the surface light sources of the third to fifth embodiments, the reflection film 11 is provided on the rear surface 10c of the light guide plate 10, but the reflection film 11 on the rear surface 10c of the light guide plate 10 is omitted. May be.

The surface light sources of the first to fifth embodiments are arranged such that the incident end face 10a of the light guide plate 10 is
The light guide plate 10 is provided with a refraction surface 13 composed of a plurality of horizontally long prism surfaces 12a arranged in the height direction, and the refraction surface provided on the incident end face 10a of the light guide plate 10 transmits light emitted from the light source unit 20 to the light guide plate 10a. If the light is refracted in a direction in which the angle with respect to the normal line of the front surface 10b becomes smaller and is incident on the light guide plate 10, for example, a refracting surface composed of a plurality of horizontally long lens surfaces arranged in the height direction of the incident end face 10a may be used. Further, a refracting surface composed of a plurality of pyramidal prism surfaces or spherical lens surfaces arranged in the height direction and the length direction of the incident end face 10a may be used.

9 and 10 show a sixth embodiment of the present invention. FIG. 9 is a side view of a surface light source, and FIG. 10 is an enlarged side view of a light guide plate of the surface light source on the side of an incident end face. .

In the surface light source of this embodiment, the incident end face 10a of the light guide plate 10 is set to be a substantially vertical surface, and the front end 10b and the rear end face 10c of the light guide plate 10 are respectively connected to the ends on the side of the incident end face 10a from the light source section 20. The light guide plate 10 is provided with refraction surfaces 13 and 14 for refracting light incident on the light guide plate 10 from the incident end face 10a in a direction in which the angle with respect to the normal line of the front surface 10b of the light guide plate 10 becomes smaller. The configuration is the same as the surface light source of the first embodiment.

In the surface light source of this embodiment, the refraction surface 13 formed at the end of the front surface 10b of the light guide plate 10 on the side of the incident end surface 10a is different from the light guide plate front surface 10b from the incident end surface 10a. Light guide plate 1 toward the other end of the
It is composed of an inclined surface that is obliquely recessed in the inner direction of 0,
Further, a refraction surface 14 formed at an end of the rear surface 10c of the light guide plate 10 on the side of the incident end surface 10a is provided on the light guide plate rear surface 10c from the incident end surface 10a toward the other end of the light guide plate 10. 10 is formed of an inclined surface which is obliquely recessed in the inner direction.

The surface light source of this embodiment is provided at the front end 10b and the rear end 10c of the light guide plate 10 on the side of the light incident end face 10a, respectively, from the light incident end face 10a toward the other end of the light guide plate 10. Since the refraction surfaces 13 and 14 are formed as inclined surfaces that are obliquely recessed in the internal direction, the light exits from the light source unit 20 and enters the light guide plate 10 at the incident end face 10 a.
Of the light incident on the front surface 10b and the rear surface 10c of the light guide plate 10 toward the incident end surface 10a side, as shown by arrows in FIGS. The light guide plate 1 is totally reflected at the interface with the outside air,
The light is refracted in a direction in which the angle becomes smaller with respect to the normal line of the front surface 10b of 0.

Therefore, according to the surface light source of this embodiment,
Light incident on the light guide plate 10 from the incident end face 10a and guided through the light guide plate 10 is also incident on a region near the incident end face of the front face 10b of the light guide plate at an incident angle smaller than the critical angle for total reflection. A sufficient amount of light can be emitted from a region near the incident end face of the light plate front surface 10b, and therefore, light with substantially uniform intensity can be emitted from the entire front surface of the light guide plate. Light with substantially uniform intensity can be emitted from the entire front surface of the light guide plate 10.

In this embodiment, the front end 10b and the rear end 10c of the light guide plate 10 are provided at the ends on the incident end face 10a side.
The refraction surfaces 13 and 14 are formed as inclined surfaces that are obliquely recessed inwardly of the light guide plate 10 from the incident end face 10 a toward the other end of the light guide plate 10.
The front surface 10b and the rear surface 10c of the front surface 10b are formed with refraction surfaces formed at the end portions on the side of the incident end surface 10a. As long as the surface is refracted in a direction in which the angle with respect to the normal decreases, the surface may be a curved refraction surface.

In this embodiment, the refraction surfaces 13 and 14 are formed at the front end 10b and the rear end 10c of the light guide plate 10 on the incident end surface 10a side, respectively.
The light refracting surface that refracts light emitted from the light guide plate 10 from the incident end face 10a in a direction in which the angle with respect to the normal line of the front surface 10b of the light guide plate 10 becomes smaller is a front surface 10b and a rear surface of the light guide plate 10 10c may be formed only on one of the surfaces.

Further, the surface light source of this embodiment is a light guide plate 1
Although the reflective film 11 is provided on the rear surface 10c of the light guide plate 10, the reflective film 11 on the rear surface 10c of the light guide plate 10 may be omitted.

The surface light source of this embodiment is shown in FIGS.
In the same manner as the surface light source devices of the third to fifth embodiments shown in FIG. 3, the front surface 1b of the light guide plate 10 is provided in front of the front surface 10b of the light guide plate 10.
Optical means 24a, 24b, 24c for refracting light emitted from Ob in a predetermined direction may be arranged.
This makes it possible to emit light having a uniform intensity distribution and directivity in a predetermined direction.

[0065]

According to the surface light source of the present invention, the light emitted from the light source section is refracted at the incident end face of the light guide plate in a direction in which the angle becomes smaller with respect to the normal to the front surface of the light guide plate, and the light is transmitted to the light guide plate. Since the refraction surface for incidence is provided, light of substantially uniform intensity can be emitted from the entire front surface of the light guide plate.

In this surface light source, the refracting surface provided on the incident end face of the light guide plate preferably comprises a plurality of prism faces or lens faces arranged in the height direction of the incident end face. By providing the surface, the light emitted from the light source unit can be refracted in a direction in which the angle becomes smaller with respect to the normal to the front surface of the light guide plate and can be incident on the light guide plate.

Further, another surface light source of the present invention emits light from a light source at an end of at least one of a front surface and a rear surface of the light guide plate on an incident end surface side, and the light incident on the light guide plate. Since a refraction surface that refracts light incident from an end face in a direction in which an angle becomes smaller with respect to a normal to the front surface of the light guide plate is formed, light of substantially uniform intensity is emitted from the entire front surface of the light guide plate. can do.

In this surface light source, the refracting surface formed on the incident end surface side of at least one of the front surface and the rear surface of the light guide plate is configured such that the incident light is incident on the surface on which the refracting surface is formed. The light guide plate preferably has an inclined surface that is obliquely recessed in the interior direction of the light guide plate from the end surface toward the other end of the light guide plate. By forming such a refraction surface, light is emitted from the light source unit. Then, the light incident on the light guide plate from the incident end face can be refracted in a direction in which the angle becomes smaller with respect to the normal to the front surface of the light guide plate.

Also, any surface light source of the present invention preferably has a structure in which an optical means for refracting light emitted from the front surface of the light guide plate in a predetermined direction is disposed in front of the front surface of the light guide plate. In this manner, light having a uniform intensity distribution and directivity in a predetermined direction can be emitted.

[Brief description of the drawings]

FIG. 1 is a side view of a surface light source according to a first embodiment of the present invention.

FIG. 2 is an enlarged side view of the light guide plate of the surface light source of the first embodiment on the incident end face side.

FIG. 3 is a side view of a backlight type liquid crystal display device including the surface light source according to the first embodiment.

FIG. 4 is a side view of a front light type liquid crystal display device provided with a surface light source in which the reflection film on the rear surface of the light guide plate is omitted from the surface light source of the first embodiment.

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

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

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

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

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

FIG. 10 is an enlarged side view of an incident end face side of a light guide plate of a surface light source according to a sixth embodiment.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Light guide plate 10a ... Incident end surface 10b ... Front surface 10c ... Back surface 11 ... Reflection film 12 ... Refraction surface 12a ... Prism surface 13, 14 ... Refraction surface 20 ... Light source part 24a, 24b, 24c ... Optical means 25 ... Diffusion plate 26 ... Light collectors 27, 28 ... light refractor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) G02F 1/13357 G02F 1/13357 // F21Y 103: 00 F21Y 103: 00

Claims (5)

[Claims] 1. A light guide plate comprising an incident end face on which light is incident, a front face on which the incident light is emitted, and a rear face opposed to the front face, and a light source section disposed to face the incident end face of the light guide plate. A refraction surface is provided on the incident end face of the light guide plate, for refracting light emitted from the light source unit in a direction in which an angle with respect to a normal to the front surface of the light guide plate is reduced and allowing the light to enter the light guide plate. A surface light source characterized in that: 2. A refracting surface provided on an incident end face of a light guide plate,
The surface light source according to claim 1, comprising a plurality of prism surfaces or lens surfaces arranged in the height direction of the incident end surface. 3. A light guide plate comprising an incident end face on which light is incident, a front face on which the incident light is emitted, and a rear face opposite to the front face, and a light source section disposed to face the incident end face of the light guide plate. And at least one of a front surface and a rear surface of the light guide plate, on the incident end surface side end, the light emitted from the light source unit, and the light incident on the light guide plate from the incident end surface is front surface of the light guide plate. A refracting surface for refracting light in a direction in which the angle with respect to the normal line becomes smaller. 4. A refracting surface formed on an incident end surface side of at least one of a front surface and a rear surface of the light guide plate, wherein the refraction surface is formed on the light guide plate from the incident end surface with respect to the surface on which the refraction surface is formed. 4. The surface light source according to claim 3, wherein the surface light source comprises an inclined surface which is obliquely recessed in an inner direction of the light guide plate toward the other end of the light guide plate. 5. 5. The surface according to claim 1, wherein an optical means for refracting light emitted from the front surface of the light guide plate in a predetermined direction is disposed in front of the front surface of the light guide plate. light source.