JP2002289023A - Lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting device as a backlight of a liquid crystal display which achieves uniformity of luminance distribution for light emitted from an exit face of a light guide even if a light emitting diode is used as a light source. SOLUTION: A refractive condensing plate 33 is arranged between two light emitting diodes 12a, 12b and an incident face 29 of a light guide 27. This refractive condensing plate 33 refracts and condenses the lights planar-radially emitted from each of the two light emitting diodes 12a, 12b, respectively, thus making them into a parallel pencil to be incident toward the incident face 29 of the light guide 27.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device,
In particular, the present invention relates to a lighting device that converts light emitted from a point light source such as a light emitting diode into a surface light source.

[0002]

2. Description of the Related Art In a liquid crystal display device, since the liquid crystal display panel itself does not have a self-luminous ability, an illuminating device is arranged as a backlight on the back side of the liquid crystal display panel.
FIG. 6 shows a side view of a part of such a conventional liquid crystal display device, and FIG. 7 shows a plan view of the illumination device shown in FIG.

This liquid crystal display device comprises a liquid crystal display panel 1 and
And a lighting device 6 disposed on the back surface opposite to the observing surface. In the liquid crystal display panel 1, a lower glass substrate 2 and an upper glass substrate 3 are bonded together via a substantially rectangular frame-shaped sealing material (not shown), and the lower glass substrate 2, the upper glass substrate 3, A liquid crystal (not shown) is sealed in a region surrounded by the material, and an upper polarizing plate 4 is attached to an upper surface of the upper glass substrate 2, and a lower polarizing plate 5 is mounted on a lower surface of the lower glass substrate 3. It has a stuck structure.

The lighting device 6 arranged on the back side of the liquid crystal display panel 1 includes a light guide 7 and a light source (12) provided on the back side of the liquid crystal display panel 1. The light guide 7 has a planar rectangular shape, and a surface facing the liquid crystal display panel 1 on the observation side is an emission surface 8, one end surface is an incidence surface 9 on which light is incident, and the light guide 7 is The rear surface on the back side is formed as an inclined surface 10 that is inclined so that the thickness gradually decreases from the incident surface 9 side to the other end surface side. A reflection plate 11 is attached to the inclined surface 10 of the light guide 7. Two light emitting diodes 12 constituting a light source are provided at two predetermined positions on the incident surface 9 side of the light guide 7.

[0005] Then, as shown by arrows in FIG.
The light emitted from each of the two light emitting diodes 12 in a plane radial shape is incident on the incident surface 9 of the light guide 7, spreads while being reflected by the reflection plate 11, is emitted from the emission surface 8 of the light guide 7, and is displayed on the liquid crystal display. The light is incident on the back surface of the panel 1 and illuminates the liquid crystal display panel 1 from the back surface side.

[0006]

In the above-mentioned conventional liquid crystal display device, as shown by arrows in FIG.
Since the light emitted from each of the two light emitting diodes 12 in a plane radial shape is made incident on the incident surface 9 of the light guide 7, FIG.
, The brightness of the area indicated by the reference symbol A is determined by the brightness of the single light emitting diode 12, and the brightness of the area indicated by the reference symbol B is determined by the total brightness of the two light emitting diodes 12. There is a problem that luminance unevenness occurs in the emitted light, and eventually display unevenness occurs on the liquid crystal display panel 1. An object of the present invention is to use a point light source such as a light emitting diode as a light source,
The purpose is to make the luminance distribution of light emitted from the emission surface of the light guide uniform.

[0007]

According to a first aspect of the present invention, there is provided an input surface having one end surface on which light is incident, and an exit surface for guiding the incident light and emitting the light in a predetermined direction. A light guide having the light exit surface as a surface, a point light source disposed opposite to the light incident surface of the light guide, and a light source provided between the point light source and the light incident surface of the light guide; And a refraction light collector for condensing light from a light source and making the light incident on the incident surface. The invention according to claim 2 is characterized in that the refraction light collector is adhered to the incident surface of the light guide via a transparent adhesive. The invention according to claim 3 is characterized in that light scattering means is arranged between the incident surface of the light guide plate and the point light source. The invention according to claim 4 is characterized in that the light scattering means comprises a layer of an adhesive and light scattering fine particles dispersed therein. Claim 5
The invention described in (1) is characterized in that the refraction condensing plate is integrally formed on an incident surface of the light guide. The invention according to claim 6 is characterized in that the refraction light collector has a Fresnel lens-shaped refraction surface. The invention according to claim 7 is characterized in that the refraction light collector having the Fresnel lens-shaped refraction surface has a plurality of focal points, and the point light sources are arranged at positions corresponding to the respective focal points. Things. According to the present invention, a refraction light collector for condensing light from the point light source and making the light incident on the light incident surface is provided between the point light source and the incident surface of the light guide. Radially emitted light is condensed, so that even if a point light source such as a light emitting diode is used as the light source, the luminance distribution of the light emitted from the emission surface of the light guide can be made uniform.

[0008]

FIG. 1 is a side view of a main part of a liquid crystal display device according to a first embodiment of the present invention, and FIG.
2 is a plan view of the lighting device shown in FIG.

This liquid crystal display device has a liquid crystal display panel 21.
And an illumination device 26 disposed on the back surface opposite to the observation surface. Liquid crystal display panel 21
Is formed by bonding a lower glass substrate 22 and an upper glass substrate 23 via a substantially rectangular frame-shaped sealing material (not shown), and
A liquid crystal (not shown) is sealed in a region surrounded by the sealing material, and an upper polarizing plate 24 is attached to an upper surface of the upper glass substrate 22, and a lower polarizing plate is attached to a lower surface of the lower glass substrate 23. 25 is attached.

The lighting device 26 disposed on the back side of the liquid crystal display panel 21 includes a light guide 27 and a light source 32 provided on the back side of the liquid crystal display panel 21. Light guide 27
Is formed of a planar rectangular wedge-shaped transparent plate, the surface facing the liquid crystal display panel 21 on the observation side is defined as an emission surface 28, and one end surface is defined as an incident surface 29 on which light is incident. The rear surface on the back side with respect to the front surface has an inclined surface 30 which is inclined such that the thickness gradually decreases from the incident surface 29 side to the other end surface side. A reflection plate 31 is attached to the inclined surface 30 of the light guide 27. Light guide 2
7, a light source 32 is disposed so as to face the entrance surface 29,
The light source 32 includes two light emitting diodes 32 arranged at a predetermined interval in the length direction of the light incident surface 29 of the light guide.
a and 32b.

A refracting light collector 33 is provided between a light source 32 composed of two light emitting diodes 32a and 32b and an incident surface 29 of the light guide 27. The refraction light condensing plate 33 has a flat surface 34 facing the incident surface 29 of the light guide 27, and a Fresnel lens-like refracting surface 35 having a plurality of focal points is formed on the surface facing the light source 32. . Each of the light emitting diodes 32a and 32b of the light source 32 is disposed at a position corresponding to the focal point of each of the Fresnel lens-shaped refraction surfaces 35.

Then, as shown by an arrow in FIG.
Light emitted radially from the two light emitting diodes 32a and 32b is incident on each Fresnel lens-shaped refracting surface 35 of the refracting and condensing plate 33, and each refracting surface 35 (interface with air).
Is refracted into parallel light. The parallel light is emitted from the flat surface 34 of the refraction light collector 33, enters the incident surface 29 of the light guide 27, is guided while being reflected by the reflector 31, and is emitted from the emission surface 28 of the light guide 27. To illuminate the liquid crystal display panel 21 from the back.

As described above, in the illuminating device 26 of the liquid crystal display device, the refraction light collecting plate 33 provided between the light source 32 and the light incident surface 29 of the light guide 27 causes the light emitting diodes 12a and 12b to radiate in a plane radial manner. The emitted light is refracted and condensed to be parallel light, and this parallel light is converted into an incident surface 29
To the light emitting diode 1 which is a point light source.
Even with the use of 2a and 12b, the luminance distribution of the light emitted from the emission surface 28 of the light guide 27 can be made uniform. Therefore, in the liquid crystal display device including the illumination device 26, the luminance distribution of light emitted from the surface of the liquid crystal display panel 21 can be made uniform, and the display quality can be improved.

In the above embodiment, the refraction light collector 33 is used.
Is provided at an appropriate position between the light source 32 and the incident surface 29 of the light guide 27, but the present invention is not limited to this. For example, as in the second embodiment of the present invention shown in FIG.
7 may be in close contact with the entrance surface 29. Also,
A light diffusion layer may be arranged between the refraction light collector 33 and the incident surface 29 of the light guide 27. When the refraction light collector 33 is brought into close contact with the incident surface 29 of the light guide 27, the flat surface 34 of the refraction light collector 33 is attached to the incident surface 29 of the light guide 27 via a transparent adhesive 36. Further, the refraction light collector 33 and the light guide 2
When the light diffusion layer is disposed between the light diffusion layer and the light incident surface 29, the light diffusion layer can be formed by dispersing light scattering fine particles (not shown) in the adhesive. Due to the light scattering effect of the fine particles for use, the luminance distribution of the light emitted from the emission surface 28 of the light guide 27 can be made more uniform.

Further, as in a third embodiment of the present invention shown in FIG. 4, a refraction light collecting plate is integrally formed on the incident surface 29 of the light guide 6, and the incident surface of the light guide 27 is formed as a Fresnel lens. The refraction-light-condensing entrance surface 37 may be a surface. In this case, the transmittance as a whole is improved, the number of parts is reduced, and the cost can be reduced.

FIG. 5 is a schematic side view of a main part of a transflective liquid crystal display device according to a fourth embodiment of the present invention. In this figure, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted as appropriate. In this liquid crystal display device, an illuminating device 41 having a reflection function is arranged on the back side of the liquid crystal display panel 21. The illuminating device 41 is disposed so as to face a prism sheet 42 provided on the back side of the liquid crystal display panel 21, a light guide 43 provided on the back side of the prism sheet 42, and a predetermined one end face of the light guide 43. And a light source 32 disposed so as to face the refracting light collecting plate 33, the Fresnel lens-shaped refracting surface 35 of the refracting light collecting plate 33, and the like.

The light guide 43 is formed in an incident surface 44 having one end surface on which light from the light source 32 is incident, and in a step-like shape that becomes gradually thinner from the incident surface 44 of the one end surface toward the other end surface. The stepped surface is composed of a surface facing the liquid crystal display panel 21 and a flat back surface facing the surface, and the stepped surface has a plurality of step surfaces 4 parallel to the back surface.
5 and an emission surface 46 composed of a step surface perpendicular to these step surfaces 45. On the upper surface of each step surface 45, a reflection film 47 made of an aluminum vapor deposition film or the like is provided, and on the back surface of the light guide 43, a reflection plate 48 is attached.
Then, the light guide 43 has its surface covered with the liquid crystal display panel 21.
Is disposed on the back side of the liquid crystal display panel 21.

The prism sheet 42 is used for the liquid crystal display panel 2.
One surface is formed as a flat surface, and a plurality of triangular cross-section projections 51 are formed at a constant pitch on the back surface opposite to the front surface. With this shape, the protrusion 51
An interface between one side surface and air forms a first optical interface 52, an interface between the other side surface of the protruding portion 51 and air forms a second optical interface 53, and furthermore, each protruding portion 51 The interface between the back surface of the prism sheet 42 and the air between them forms a third optical interface 54. And the prism sheet 42
The projection 51 is disposed on the light guide 43 with the apex of the projection 51 approaching or in contact with the reflection film 47. Note that the pitch of the projecting portions 51 of the prism sheet 42 is substantially the same as the pixel pitch of the liquid crystal display panel 21 or is a fraction of the pixel pitch. Further, the pitch of the step surface 45 of the light guide 43 is slightly larger than the pitch of the protruding portions 51 of the prism sheet 42.

When the liquid crystal display device is used as a transmission type, two light emitting diodes 32 of a light source 32 are used.
a and 32b are turned on. Then, the light emitted from the two light emitting diodes 32a and 32b in a plane radial shape is refracted and condensed by the refraction light condensing plate 33 to become parallel light, and the light guide 4
No. 3 is incident on the incident surface 44. This incident light is reflected by the reflection film 4.
The light travels in the light guide 43 in the lateral direction while being reflected by the reflector 7 and the reflection plate 48, and is emitted from each emission surface 46 as shown by a solid arrow in FIG. 5. The emitted light enters the first optical interface 52 of the prism sheet 42, is totally reflected by the second optical interface 53, is emitted from the front surface of the prism sheet 42, is incident on the back surface of the liquid crystal display panel 21, The display panel 21 is illuminated from the back, and an image corresponding to the display drive of the liquid crystal display panel 21 is observed.

On the other hand, when this liquid crystal display device is used as a reflection type, external light is used without turning on the light source 32. That is, external light incident from the surface on the observation side of the liquid crystal display panel 21 passes through the liquid crystal display panel 21. This transmitted light is, for example, as shown by a dotted arrow in FIG.
The light passes through the prism sheet 42 and is reflected by the reflection film 47. The reflected light passes through the prism sheet 42 and is incident on the back surface of the liquid crystal display panel 21, passes through the liquid crystal display panel 21 again, and exits to the observation side. An image corresponding to the display drive is observed.

As described above, in the illumination device 41 of the liquid crystal display device, the light emitted from the light source 32 in a plane radial manner by the refraction light collecting plate 33 provided between the light source 32 and the incident surface 44 of the light guide 43. Is refracted and condensed to form parallel light, and the parallel light is made incident on the incident surface 44 of the light guide 43.
Even if a and 32b are used, the luminance distribution of light emitted from the exit surface 46 of the light guide 43 can be made uniform, and the luminance distribution of light emitted from the surface of the prism sheet 42 can be made uniform. Can be. Therefore, in the liquid crystal display device including the illumination device 41, the luminance distribution of the light emitted from the surface of the liquid crystal display panel 21 can be made uniform, and the display quality can be improved.

In the lighting device 41 shown in FIG.
The flat surface 44 of the refraction light collector 33 is changed to the incident surface 44 of the light guide 43.
The light guide 43 may be made to adhere closely or through a transparent adhesive, or the incident surface of the light guide 43 may be a refracting condensing incident surface formed of a Fresnel lens-like refracting surface.

[0023]

As described above, according to the present invention, between the point light source and the incident surface of the light guide, the refraction light collecting plate for condensing light from the point light source and making the light incident on the incident surface is provided. The light emitted from the point light source in a plane radial manner is condensed, so that even if a point light source such as a light emitting diode is used as the light source, the luminance distribution of the light emitted from the light emitting surface of the light guide is uniform. Can be .

[Brief description of the drawings]

FIG. 1 is a side view of a main part of a liquid crystal display device according to a first embodiment of the invention.

FIG. 2 is a plan view of the lighting device shown in FIG.

FIG. 3 is a plan view similar to FIG. 2 of a lighting device according to a second embodiment of the present invention.

FIG. 4 is a plan view similar to FIG. 2 of a lighting device according to a third embodiment of the present invention.

FIG. 5 is a schematic side view of a main part of a transflective liquid crystal display device according to a fourth embodiment of the invention.

FIG. 6 is a side view of a part of an example of a conventional liquid crystal display device.

FIG. 7 is a plan view of the lighting device shown in FIG. 6;

DESCRIPTION OF SYMBOLS 21 Liquid crystal display panel 26 Illumination device 27 Light guide 28 Outgoing surface 29 Incident surface 31 Reflector 32 Light source 32a, 32b Light emitting diode 33 Refraction light collector 35 Fresnel lens refraction surface 36 Transparent adhesive 37 Refraction Focusing entrance surface

Claims (8)

[Claims] A light guide having one end surface on which light is incident, an exit surface for guiding the incident light and emitting the light in a predetermined direction, and a light guide having the exit surface as a surface; A point light source disposed opposite to the light incident surface of the light guide, and provided between the point light source and the light incident surface of the light guide, for condensing light from the point light source and entering the light incident surface; An illumination device comprising: a refracting light-collecting plate for causing the illumination device to emit light. 2. The illuminating device according to claim 1, wherein the refraction light collector is attached to a light incident surface of the light guide via a transparent adhesive. 3. The lighting device according to claim 1, wherein a light scattering means is arranged between the incident surface of the light guide plate and the point light source. 4. The illumination device according to claim 3, wherein said light scattering means comprises a layer of an adhesive and light scattering fine particles dispersed therein. 5. The illumination device according to claim 1, wherein the refraction light collector is integrally formed on an incident surface of the light guide. 6. The illumination device according to claim 1, wherein the refraction light collector has a Fresnel lens-shaped refraction surface. 7. The refracting light-condensing plate having the Fresnel lens-shaped refracting surface has a plurality of focal points, and the point light sources are arranged at positions corresponding to the respective focal points. Lighting equipment. 8. The lighting device according to claim 1, wherein said point light source is a light emitting diode.