JP2008034241A - Backlight - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight without causing luminance irregularity in the vicinity of light entering surface. <P>SOLUTION: This backlight is provided with: a first light guide plate 12 and a second light guide plate 14 arranged to face side surfaces thereof to each other; a prism sheet 16 and a reflective sheet 18 arranged on the upper surface side and the undersurface side of the first light guide plate, respectively; and a light emitting diode 20 used as a light source. The second light guide plate 14 includes: a second light entering surface 14a entering light of the light emitting diode 20; a second light emitting surface 14b emitting the light entered from the second light entering surface 14a to the first light guide plate 12; and second grooves 14c formed on a surface facing to the second light emitting surface 14b. The first light guide plate 12 includes: a first light entering surface 12a entering the light emitted from the second light emitting surface 14b; a first light emitting surface 12b emitting the light entered from the first light entering surface 12a; and first grooves formed on a surface facing to the first light emitting surface 12b. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a backlight which is a surface light emitting device disposed on the back of a transmissive or transflective liquid crystal display panel, and in particular, a light source is disposed on a light incident surface which is an end surface of a light guide plate having a substantially rectangular parallelepiped shape. The present invention relates to a structure of a backlight that spreads light incident from an incident surface over the entire surface and emits the light from a light exit surface.

  In the following description in this specification, “upper surface side” means the side from which the backlight emits light and emits light, and “lower surface side” means that the backlight on the side opposite to the upper surface side does not emit light. Means side.

As a backlight which is a surface light emitting element of a backlight unit of a liquid crystal display panel, for example, there is one proposed in Patent Document 1.
In the backlight of the above-mentioned Patent Document 1, as illustrated in FIG. 1 of Patent Document 1, a light guide plate (first element: 50), a prism sheet (second element: 51), A reflection sheet (reflection surface: 13) and a light source (linear light source: 14) are provided.

In the backlight of Patent Document 1, a light source including a linear light source is disposed on a light incident surface that is an end surface of a light guide plate having a substantially rectangular parallelepiped shape. Further, the prism sheet is disposed on the light emitting surface side that is the upper surface side of the light guide plate. The prism of the prism sheet is disposed so as to face the light emitting surface of the light guide plate. Further, the reflection sheet is arranged on the lower surface side opposite to the prism sheet arrangement surface on the back surface of the light guide plate.
In addition, the light source arrange | positioned so that the light-incidence surface of the light-guide plate in patent document 1 may be comprised from cold cathode tubes, such as a fluorescent tube.

The cold cathode tube made of a fluorescent tube used as the light source of the backlight of this cited document 1 consumes a large amount of power.
For this reason, when a cold cathode tube made of a fluorescent tube is applied as a backlight for a liquid crystal display panel mounted on a portable electronic device, there is a drawback that the duration of the power source battery of the portable electronic device is shortened. .

Therefore, in order to increase the duration of the power battery in the portable electronic device, a backlight using a light-emitting diode with low power consumption as a light source instead of a fluorescent tube has been proposed.
As a backlight using a light emitting diode as a light source, for example, there is one proposed in Patent Document 2.

In the backlight described in Patent Document 2, as shown in FIG. 1 in Patent Document 2, a prism sheet is disposed on the upper surface side that is the light emitting surface of the light guide plate. The prism of this prism sheet is disposed so as to face the light exit surface of the light guide plate. In addition, a reflection sheet is disposed on the lower surface side of the back surface of the light guide plate.
Furthermore, a light emitting diode is disposed as a light source at a position facing the light incident surface of the end surface of the light guide plate.

Japanese Patent Laid-Open No. 2-17 (the specification, page 4, upper left column, line 1 to page, lower left column, second line, and FIG. 1) Japanese Patent Laying-Open No. 2005-317474 (paragraphs 0013 to 0017 and FIGS. 1 and 4)

In Patent Document 2, in order to eliminate luminance unevenness in the vicinity of the light incident surface, which is the end surface of the light guide plate on which the light emitting diodes are disposed, as shown in FIG. A light scattering region is provided on the light incident surface side of the reflection sheet disposed on the surface.
The light scattering region is disposed so as to face the back surface on the lower surface side of the light guide plate. The light scattering region is formed of a matte white scattering surface formed by a printing method.

By providing the light scattering region along the light incident surface side of the reflection sheet, the light entering the light guide plate from the light emitting diode and radiating from the light guide plate is scattered in the light scattering region and returned to the light guide plate again. . For this reason, in the backlight in Patent Document 2, the luminance unevenness in the vicinity of the light incident surface on which the light from the light emitting diode is incident is improved to some extent.
However, even if a light scattering region composed of a white scattering surface is provided on the reflective sheet, the backlight still has uneven brightness.

  In the backlight in Patent Document 2, it is presumed that the luminance unevenness in the vicinity of the light incident surface of the light guide plate is not eliminated for the following reason.

That is, in the region near the light incident surface of the light guide plate, there is little light emitted from the lower surface side of the light guide plate toward the light scattering region formed of the white scattering surface.
Therefore, in the light scattering region composed of the white scattering surface, the amount of scattered light that is scattered and incident again on the light guide plate and contributes to improving the luminance of the backlight is reduced. As a result, sufficient scattered light is not obtained to eliminate luminance unevenness in the vicinity of the light incident surface of the light guide plate.

  For this reason, in the backlight of Patent Document 2, uneven luminance still occurs in the region between the light emitting diodes near the light incident surface of the light guide plate.

  An object of the present invention is to solve the above-described problems and provide a backlight excellent in in-plane luminance uniformity without luminance unevenness in the vicinity of a light incident surface in a light guide plate.

In order to achieve the above object, the following means are employed in the backlight of the present invention.
In the backlight of the present invention, the first light guide plate and the second light guide plate which have a substantially rectangular parallelepiped shape and are arranged so that the respective side surfaces face each other, and the prism which is disposed on the upper surface side of the first light guide plate A sheet, a reflective sheet disposed on the lower surface side of the first light guide plate, and a light emitting diode serving as a light source. The second light guide plate includes a second light incident surface on which light emitted from the light emitting diode is incident; A second light emitting surface for emitting the light incident from the second light incident surface to the first light guide plate, and a second groove provided on a surface facing the second light emitting surface. The first light guide plate has a first light incident surface on which light emitted from the second light emitting surface of the second light guide plate is incident, and a first light incident surface that emits light incident from the first light incident surface. A first light exit surface, and a first groove provided on a surface opposite to the first light exit surface; The prism sheet has a prism for correcting the directivity of the light emitted from the first light exit surface, and the reflection sheet reflects the light emitted from the first light guide plate back to the first light guide plate. It has a surface.

  The second light guide plate in the backlight of the present invention is characterized in that light emitting diodes are arranged on two opposite sides.

  A bent pattern is provided on the first light incident surface of the first light guide plate of the backlight of the present invention.

  A bent sheet is provided between the first light incident surface of the first light guide plate and the second light output surface of the second light guide plate of the backlight of the present invention.

  The light reflecting member is disposed so as to face the second groove in the second light guide plate of the backlight of the present invention.

  The second light guide plate in the backlight of the present invention is arranged on two opposing sides of the first light guide plate.

  The backlight of the present invention is characterized in that a holder surrounding the first light guide plate, the second light guide plate, the prism sheet, and the reflection sheet is provided.

  In the backlight of the present invention, the first light guide plate and the second light guide plate which have a substantially rectangular parallelepiped shape and are arranged so that the respective side surfaces face each other, and the prism which is disposed on the upper surface side of the first light guide plate A sheet, a reflective sheet disposed on the lower surface side of the first light guide plate, and a light emitting diode serving as a light source. The second light guide plate includes a second light incident surface on which light emitted from the light emitting diode is incident; A second light emitting surface for emitting the light incident from the second light incident surface to the first light guide plate, and a second groove provided on a surface facing the second light emitting surface. The first light guide plate has a first light incident surface on which light emitted from the second light output surface of the second light guide plate is incident, and a first light incident surface that emits light incident from the first light incident surface. 1 light exit surface and a first groove provided on a surface opposite to the first light exit surface The prism sheet has a prism that corrects the directivity of light emitted from the first light exit surface, and the reflection sheet has a reflection surface that returns light emitted from the first light guide plate to the first light guide plate. is doing.

In the backlight of the present invention, two light guide plates, a first light guide plate and a second light guide plate, are provided. And the light emitting diode which is a light source is arrange | positioned so that the 2nd light-incidence surface in a 2nd light-guide plate may be opposed. Light from the light emitting diode is incident on the second light guide plate. Further, in the second light guide plate, light from the light emitting diode incident on the second light incident surface is repeatedly reflected and scattered inside the second light guide plate.
As a result, the light emitted from the light emitting diode incident from the second light incident surface is propagated to the entire surface of the second light guide plate. As a result, in the backlight of the present invention, linear and uniform luminance light can be emitted from the second light exit surface of the second light guide plate.

Furthermore, in the backlight of the present invention, the light from the second light exit surface of the second light guide plate that is linear and has uniform luminance is used as the first light in the first light guide plate. Incident light is incident on the incident surface.
In the first light guide plate, the light incident from the first light incident surface is propagated to the entire surface of the first light guide plate by repeatedly reflecting and scattering inside the first light guide plate. . Light that is linearly incident from the second light guide plate and whose luminance is uniform is spread over the entire surface of the first light guide plate, and emitted from the first light exit surface of the first light guide plate toward the prism sheet. is doing. In the prism sheet, the directivity of the light emitted from the first light guide plate is corrected, and the directivity of the light is controlled to be substantially perpendicular to the light emitting surface of the backlight.

That is, in the backlight of the present invention, linear and uniform luminance light emitted from the second light guide plate is incident on the first light incident surface of the first light guide plate. That is, in Patent Document 2, light from a plurality of light emitting diodes arranged at a predetermined interval is incident on the first light incident surface of the first light guide plate. In this backlight, light with uniform luminance is incident on the entire first light incident surface.
Therefore, in the backlight of the present invention, luminance unevenness does not occur in the region between the light emitting diodes near the first light incident surface of the first light guide plate, and there is no luminance unevenness. A backlight with excellent luminance uniformity can be provided.

  Hereinafter, the structure of the backlight according to the best embodiment of the present invention will be described in detail with reference to the drawings.

[Description of First Embodiment: FIGS. 1 and 2]
First, the structure of the backlight according to the first embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 1 is a plan view showing a backlight according to the first embodiment of the present invention. FIG. 2 is a side view showing the backlight according to the first embodiment of the present invention and in a partially broken state. Here, the side view of FIG. 2 illustrates the backlight structure as viewed in the direction of the arrow, broken along the line AA in FIG.

  In the description of the following embodiments in the present specification, the length direction of the first light incident surface 12a (the width direction of the first light guide plate 12) in the first light guide plate 12 is defined as the X-axis direction. The length direction of the second light incident surface 14a in the second light guide plate 14 (the width direction of the second light guide plate 14) is defined as the Z-axis direction, and as shown in FIG. In the following description, the thickness direction of the light guide plate 12 is defined as the Y-axis direction.

[Description of overall backlight configuration]
First, the overall configuration of the backlight according to the first embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2.
As shown in FIGS. 1 and 2, the backlight 10 according to the present invention includes two light guide plates, a first light guide plate 12 and a second light guide plate 14.

A light emitting diode 20 that emits light toward the second light guide plate 14 is disposed on the second light guide plate 14 so as to face the second light incident surface 14a.
In the second light guide plate 14, the light incident from the light emitting diode 20 is repeatedly reflected and scattered inside the second light guide plate 14 by the second groove 14 c, and is spread over the entire surface.

From the second light emitting surface 14b that emits light on the second light guide plate 14, the length in the X-axis direction of the first light guide plate 12, that is, the first light incident surface of the first light guide plate 12 is shown. Light having a linear and uniform luminance with a length substantially equal to the length of 12a is emitted.
The second light exit surface 14b of the second light guide plate 14 is provided with the first light incident surface 12a of the first light guide plate 12 on which light from the second light guide plate 14 is incident, with a gap (air). Layer).

In the first light guide plate 12, linear and uniform luminance light incident from the second light guide plate 14 is reflected inside the first light guide plate 12 by the first groove 12c. And it spreads over the entire surface by repeating scattering.
The dimensions in the X-axis direction of the second light exit surface 14b of the second light guide plate 14 and the first light incident surface 12a of the first light guide plate 12 are substantially the same length.
Furthermore, the second light output surface 14b and the first light incident surface 12a are opposed to each other through a gap having a predetermined dimension, and the second light guide plate 14 and the first light guide plate 14 are substantially parallel to each other. An optical plate 12 is provided.

Furthermore, the backlight 10 of the present invention includes a prism sheet 16 disposed on the first light emitting surface 12b side that emits light on the upper surface side of the first light guide plate 12, and a lower surface side of the first light guide plate 12. The reflection sheet 18 disposed on the first groove 12c side is provided.
Then, the light emitted from the backlight 10 is liquid crystal by disposing the transmissive or transflective liquid crystal display panel (not shown) opposite to the upper surface of the prism sheet 16 that emits light. The light is incident on the display panel to improve display contrast in the liquid crystal display panel.

Further, the backlight 10 of the present invention includes a holder 24 provided so as to surround the prism sheet 16, the first light guide plate 12, the second light guide plate 14, the light emitting diode 20, and the reflection sheet 18.
That is, as shown in FIG. 2, the reflection sheet 18, the first light guide plate 12, the second light guide plate 14, the light emitting diode 20, and the prism sheet 16 are accommodated in the holder 24 to constitute the backlight 10. ing.

[Description of Light-Emitting Diode 20]
Next, the light emitting diode 20 will be described with reference to FIG. In the light emitting diode 20, when a voltage is applied in the forward direction of the pn junction using the pn junction in the semiconductor, electrons existing in the n region are combined with holes existing in the p region to cause recombination light emission. It is a semiconductor element that converts current directly into light using recombination light emission.
The light emitting diode 20 is disposed so as to face the second light incident surface 14 a parallel to the Z-axis direction of the second light guide plate 14. As the light emitting diode 20, a light emitting diode that emits a white color is used.

[Description of Second Light Guide Plate 14]
Next, the structure of the second light guide plate 14 will be described in detail with reference to FIGS. The second light guide plate 14 on which the light from the light emitting diode 20 is incident has a substantially rectangular parallelepiped outer shape having six surfaces intersecting each other.
The second light guide plate 14 includes a second light incident surface 14a on which light emitted from the light emitting diode 20 as a light source is incident, and light incident from the second light incident surface 14a. The second light emitting surface 14b that emits toward the first light incident surface 12a and the second groove 14c provided so as to face the second light emitting surface 14b.

Here, the second light guide plate 14 repeatedly reflects and scatters the light from the light emitting diode 20 incident from the second light incident surface 14 a inside the second light guide plate 14, Spread over the entire surface of the light guide plate 14.
Then, the second light guide surface 12b plays a role of emitting light having a linear and uniform brightness toward the first light incident surface 12a of the first light guide plate 12 from the second light output surface 14b. The light plate 14 has.

The second light guide plate 14 is made of a translucent resin material such as polymethyl methacrylate (PMMA) or polycarbonate (PC).
Then, the second light guide plate 14 can be formed by injection molding using these translucent resin materials.

The 2nd groove 14c provided in the surface facing the 2nd light-projection surface 14b in the 2nd light-guide plate 14 has a sawtooth-shaped pattern shape.
As shown in FIG. 2, the ridgeline of the second groove 14c formed of a sawtooth pattern is disposed so as to be parallel to the Y-axis direction.

The second groove 14c provided in the second light guide plate 14 repeats the light from the light emitting diode 20 that enters the second light guide plate 14 from the second light incident surface 14a by a sawtooth pattern. It has a role of reflecting and scattering and propagating it throughout the second light guide plate 14.
The second light guide plate 14 is finally linear and uniform from the entire surface of the second light emitting surface 14b toward the first light incident surface 12a of the first light guide plate 12. The light having the brightness is emitted in the Z-axis direction.

[Description of First Light Guide Plate 12]
Next, the configuration of the first light guide plate 12 will be described in detail with reference to FIGS. 1 and 2. The first light guide plate 12 disposed so as to face the second light emitting surface 14b of the second light guide plate 14 also has a substantially rectangular parallelepiped outer shape having six surfaces intersecting each other.
The first light guide plate 12 includes a first light incident surface 12a on which the linear light emitted from the second light exit surface 14b of the second light guide plate 14 is incident, and the first light incident surface. The first light emitting surface 12b that emits the light incident from 12a toward the prism sheet 16 on the upper surface side, and the first groove 12c provided on the back surface facing the first light emitting surface 12b.

The first light incident surface 12a of the first light guide plate 12 is disposed to face the second light output surface 14b of the second light guide plate 14 with a gap (air layer) having a predetermined dimension.
Moreover, in order to make the linear light which radiate | emits light from the 2nd light-projection surface 14b in the 1st light-guide plate 12 inject into the 1st light-guide plate 12 efficiently, the 1st light-incidence surface 12a is 2nd. It arrange | positions so that it may become substantially parallel to the light-projection surface 14b. Light with uniform brightness is incident on the entire first light incident surface 12a from the second light emitting surface 14b of the second light guide plate 12.

Here, the first light guide plate 12 transmits the linear light from the second light guide plate 14 incident from the first light incident surface 12 a to the second groove inside the first light guide plate 12. The light is repeatedly reflected and scattered by 14 c and spread over the entire surface of the first light guide plate 12.
The first light guide plate 12 has a role of emitting light from the first light emitting surface 12 b toward the prism sheet 16.

  That is, in the first light guide plate 12, the second light output surface 14b of the second light guide plate 14 receives linear light emitted in the Z-axis direction, and the entire surface of the first light output surface 12b. To emit light in the Y-axis direction.

As with the second light guide plate 14, the first light guide plate 12 is made of a resin material having translucency such as a resin material such as polymethyl methacrylate (PMMA) or polycarbonate (PC).
Then, the first light guide plate 12 can be formed by injection molding using these translucent resin materials.

The first groove 12c having a role of repeatedly reflecting and scattering light incident on the first light guide plate 12 from the second light guide plate 14 and propagating it to the entire surface of the first light guide plate 12 is the second groove 12c. Similar to the groove 14c, a saw-tooth pattern is formed.
The ridgeline of the first groove 12c having a sawtooth pattern shape is disposed so as to be parallel to the X-axis direction.

The first groove 12c provided on the lower surface side of the first light guide plate 12 repeatedly reflects and scatters light incident on the first light guide plate 12 from the first light incident surface 12a by a sawtooth pattern. Thus, it has a role of propagating to the entire area inside the first light guide plate 12.
Then, the first light guide plate 12 finally emits light with less luminance variation from the entire surface of the first light output surface 12b toward the prism sheet 16 over the entire surface region of the first light guide plate 12. To do.

[Description of prism sheet]
Next, the configuration of the prism sheet 16 will be described in detail with reference to FIGS. 1 and 2.
The prism sheet 16 disposed on the upper surface side of the first light guide plate 12 has a role of correcting the directivity of light emitted from the first light exit surface 12 b of the first light guide plate 12. That is, the prism sheet 16 has a role of controlling the directivity of light so as to be substantially perpendicular to the light emitting surface of the backlight 10 when light is emitted from the prism sheet 16.

  In order to play a role of correcting the directivity of the light, the prism sheet 16 is provided with a prism having a triangular cross section on the side of the first light guide plate 12 facing the first light exit surface 12b. ing.

The prism formed on the prism sheet 16 has a triangular shape with a prism apex angle of 60 degrees to 70 degrees.
And the ridgeline of the triangular prism top part in the prism sheet 16 is arrange | positioned so that it may become parallel to a X-axis, as shown in FIG. In the plan view of FIG. 1, only the ridge line at the top of the prism in the prism sheet 16 is shown by a broken line.

The arrangement pitch dimension of the top ridge lines of the prism provided on the lower surface side of the prism sheet 16, that is, the surface side facing the first light emitting surface 12b is preferably in the range of 50 μm to 100 μm.
When the arrangement pitch dimension of the prism top ridge lines exceeds 100 μm, the top ridge lines of the prisms in the prism sheet 16 are observed when the backlight 10 emits light, which is not preferable because the visibility decreases.
Furthermore, the lower limit value of the arrangement pitch dimension of the prism apexes is determined from manufacturing restrictions in the prism sheet 16. That is, it is difficult to manufacture a prism having a fine pitch dimension with a ridge line of less than 50 μm with stable quality.

The prism sheet 16 is made of a translucent resin material such as polymethyl methacrylate resin, polycarbonate resin, or polyester resin.
And prism sheet 16 which has a prism on one side can be formed by injection molding using these translucent resin materials.

[Description of reflective sheet]
Next, the configuration of the reflection sheet 18 will be described in detail with reference to FIG. The reflection sheet 18 disposed so as to face the first groove 12c formed on the back surface on the lower surface side of the first light guide plate 12 allows light emitted from the first groove 12c to be reflected on the reflection surface of the reflection sheet 18. A role of returning to the first light guide plate 12 is provided.
That is, the reflection sheet 18 has a role of increasing the light use efficiency and improving the light emission luminance of the backlight 10.

For this purpose, the reflection surface of the reflection sheet 18 provided on the surface facing the first groove 12c is disposed so as to face the entire surface of the first light guide plate 12 in the first groove 12c formation region.
That is, the planar shape of the reflection sheet 18 is approximately the same as the planar shape of the first light guide plate 12. The reflection sheet 18 and the first light guide plate 12 are disposed so as to overlap with each other in substantially the same shape in a plan view.

In FIG. 2, the reflection sheet 18 is disposed only on the surface facing the first groove 12c.
However, the reflection sheet 18 may be provided so as to face the two side surfaces parallel to the Z axis of the first light guide plate 12 and the first light incident surface 12a and to face the side surfaces parallel to the X axis. Good. At this time, the reflection surface of the reflection sheet 18 is disposed on the surface facing the first light guide plate 12.

Thus, in addition to the surface facing the first groove 12c, the reflective sheet 18 is disposed so as to also face the side surface of the first light guide plate 12, thereby providing three side surface portions. The light emitted from can be returned to the first light guide plate 12 again.
Therefore, by providing the reflection sheet 18 on the side surface portion other than the surface facing the first groove 12c, the light use efficiency is increased, and the light emission luminance of the backlight 10 can be improved. Play.

  In order to bring back the light emitted from the first light guide plate 12 back to the first light guide plate 12 and exhibit the effect of increasing the light use efficiency, the reflection sheet 18 is made of aluminum (Al) or silver on the surface of the resin film. A thin film having a high surface reflectance such as (Ag) is formed by a vacuum deposition method or a plating method to form a reflecting surface.

Alternatively, instead of forming a thin film having a high surface reflectance on the resin film, a white polyethylene terephthalate (PET) resin film that irregularly reflects light on the surface can also be used as the reflection sheet 18.
Also in the reflection sheet 18 made of the above-described white polyethylene terephthalate, light is diffusely reflected on the surface of the reflection sheet 18, and light emitted from the first light guide plate 12 toward the reflection sheet 18 is converted into the first light guide plate 12. The function to return to is provided.

[Description of operation]
Next, the operation of the backlight according to the first embodiment of the present invention based on the above configuration will be described.
In the backlight 10 of the present invention, two light guide plates, a first light guide plate 12 and a second light guide plate 14, are provided. Then, a light emitting diode 20 as a light source is disposed so as to face the second light incident surface 14 a of the second light guide plate 14. The light from the light emitting portion of the light emitting diode 20 is incident on the first light incident surface 12 a of the second light guide plate 14. Then, the light is repeatedly reflected and scattered inside the second light guide plate 14 by the second groove 14 c, and the light from the light emitting diode 20 is propagated to the entire surface of the second light guide plate 14.
As a result, in the backlight of the present invention, linear and uniform luminance light can be emitted from the second light emitting surface 14 b of the second light guide plate 14.

Furthermore, in the backlight 10 according to the first embodiment of the present invention, the light having a linear and uniform luminance emitted from the second light emitting surface 14b of the second light guide plate 14 is the first. Is incident on the light guide plate 12.
Then, in the first light guide plate 12, the light incident from the first light incident surface 12a of the first light guide plate 12 is repeated inside the first light guide plate 12 by the first groove 12c. The light from the second light guide plate 14 is propagated to the entire surface of the first light guide plate 12 by being reflected and scattered. Light having a linear and uniform brightness incident from the second light guide plate 14 is spread over the entire surface of the first light guide plate 12. As a result, in the backlight 10 of the present invention, light is emitted from the first light emission surface 12 b of the first light guide plate 12 toward the prism sheet 16.
In the prism sheet 16, the directivity of light emitted from the first light guide plate 12 is corrected, and the directivity of light is controlled to be substantially perpendicular to the light emitting surface of the backlight 10 before being emitted. ing. In addition, the light emitted from the first groove 12c on the lower surface side of the first light guide plate 12 to the outside of the first light guide plate 12 is reflected by the reflection surface provided on the surface of the reflection sheet 18, and again the first light is emitted. The light is incident on the light guide plate 12.

Therefore, in the backlight 10 according to the first embodiment of the present invention, the light is emitted from the second light emitting surface 14b of the second light guide plate 14 in the vicinity of the first light incident surface 12a of the first light guide plate 12. Linear light with uniform luminance is incident. That is, in Patent Document 2, light from a plurality of light emitting diodes arranged at a predetermined interval is incident on the first light incident surface 12a of the first light guide plate 12. In the backlight of the present invention, light with uniform luminance is incident on the entire first light incident surface 12a.
For this reason, in the backlight of the present invention, as shown in Patent Document 2, luminance unevenness is present in a region between the light emitting diode 20 and the light emitting diode 20 in the vicinity of the first light incident surface 12a of the first light guide plate 12. Will not occur. Therefore, in the embodiment of the present invention, it is possible to provide the backlight 10 having excellent in-plane luminance uniformity.

[Explanation of Second Embodiment: FIG. 3]
Next, the structure of the backlight according to the second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 3 is a plan view showing the first light guide plate, the second light guide plate, and the light emitting diode in the backlight according to the second embodiment of the present invention.

The structural difference between the backlight in the second embodiment and the backlight in the first embodiment is that one light emitting diode 20 as a light source is provided in the first embodiment. In the second embodiment, two light emitting diodes 20 and 20 are disposed on the second light incident surfaces 14a and 14a of the second light guide plate 14, respectively.
The configuration of the backlight other than this difference is the same between the first embodiment and the second embodiment.

In the following description of the structure of the backlight in the second embodiment, differences from the first embodiment will be mainly described, and the same structure will be described in detail in the first embodiment and the second embodiment. The description will be omitted or simplified.
In the first embodiment and the second embodiment, the same components in the backlight are denoted by the same reference numerals.

As shown in FIG. 3, the second light guide plate 14 in the second light guide plate 14 has a role of allowing linear and uniform luminance light to enter the first light incident surface 12 a of the first light guide plate 12. Unlike the first embodiment, two light emitting diodes 20 and 20 are disposed on the light incident surfaces 14a and 14a as light sources, respectively.
The two second light incident surfaces 14a and 14a are two opposing side portions of the second light guide plate 14 having a substantially rectangular parallelepiped shape having six surfaces intersecting each other.

That is, in the backlight according to the second embodiment, the light emitting diodes 20 and 20 are disposed on the second light incident surfaces 14a and 14a of the second light guide plate 14 facing each other.
It is preferable to use the two light emitting diodes 20 and 20 having uniform light emission characteristics. As the light emitting diode 20, a light emitting diode that emits a white color is used.

In the first embodiment, the second groove 14c having a saw-tooth pattern provided on the second light guide plate 14 has been described in the embodiment having a structure in which the groove inclination angles are aligned in one direction.
In contrast, in the second groove 14c in the second embodiment, unlike the first embodiment, a groove inclination angle having a sawtooth pattern is provided so as to face the respective light emitting diodes 20 and 20. .

That is, the inclined surface of the second groove 14c in the upper half of the paper surface in FIG. 3 rotates the base line parallel to the X axis in the counterclockwise direction. Further, the inclined surface of the second groove 14c in the lower half of the paper surface in FIG. 3 rotates the base line parallel to the X axis in the clockwise direction.
As described above, the inclined surface of the second groove 14c provided in the second light guide plate 14 in the second embodiment of the present invention is substantially the center position in the X-axis direction of the second light guide plate 14, and the inclination angle is inclined. The directions are opposite to each other.
Further, the ridgeline of the second groove 14c having a triangular cross section is arranged so as to be parallel to the Y-axis direction perpendicular to the paper surface of FIG.

The light from the light emitting diodes 20 and 20 incident from the two second light incident surfaces 14a and 14a facing each other in the second light guide plate 14 is caused to enter the second light guide plate 14 by the second groove 14c. Then, the light is repeatedly reflected and scattered, and propagated to the entire area of the second light guide plate 14.
As a result, linear and uniform luminance light can be emitted from the second light emitting surface 14b of the second light guide plate 14 in the second embodiment of the present invention.

In the backlight according to the second embodiment, light having a linear and uniform luminance is transmitted from the second light exit surface 14 b of the second light guide plate 14 to the first light guide plate 12. The light is incident on the light incident surface 12a. For this reason, the luminance unevenness generated by the backlight of Patent Document 2 in the region near the first light incident surface 12a does not occur in the second embodiment. For this reason, in the second embodiment, it is possible to provide the backlight 10 having excellent in-plane luminance uniformity.
Moreover, in the backlight according to the second embodiment, the light emitted from the two light emitting diodes 20 and 20 can be emitted from the first light emitting surface 12b of the first light guide plate 12 with a light amount added. it can.
Therefore, compared with the backlight of the first embodiment described with reference to FIGS. 1 and 2, the backlight of the second embodiment has an effect that the emission luminance can be increased.

Or if the brightness | luminance requested | required as the backlight 10 is the same brightness as 1st Embodiment, the backlight 10 in 2nd Embodiment can make a light emission area larger than 1st Embodiment.
Therefore, the backlight according to the second embodiment of the present invention in which the two light emitting diodes 20 and 20 are respectively disposed on the second light incident surfaces 14a and 14a of the second light guide plate 14 has a large display area. It has the effect that it becomes possible to implement | achieve the backlight element of the liquid crystal display panel which has.

Furthermore, in the backlight of the second embodiment, the inclined surface of the second groove 14c in the second light guide plate 14 is set so as to face the light emitting diodes 20 and 20, respectively. For this reason, the light incident on the second light guide plate 14 from the light emitting diode 20 can be efficiently emitted from the second light exit surface 14b.
Therefore, in the second embodiment, it is possible to exhibit the effect that the light use efficiency is improved and the light emission luminance of the backlight 10 is increased.

Further, in the backlight according to the second embodiment of the present invention, from the two second light incident surfaces 14a and 14a facing each other at both ends in the longitudinal direction (X-axis direction) of the second light guide plate 14, respectively. Light from the light emitting diodes 20 and 20 is incident.
Therefore, in the second embodiment, it is possible to improve the luminance uniformity in the X-axis direction of the light emitted from the second light guide plate 14.

Therefore, in the second embodiment, light with high luminance uniformity in the X-axis direction is incident on the first light guide plate 12 from the second light exit surface 14 b of the second light guide plate 14.
As a result, the second embodiment of the present invention described with reference to FIG. 3 also has an effect that the in-plane uniformity of the emission luminance in the backlight 10 can be further improved.

[Description of Third Embodiment: FIG. 4]
Next, the structure of the backlight according to the third embodiment of the present invention will be described in detail with reference to FIG.
FIG. 4 is a plan view showing a first light guide plate, a second light guide plate, and a light emitting diode in the backlight according to the third embodiment of the present invention.

The difference in structure between the backlight in the third embodiment and the backlight in the second embodiment is that the first light incident surface 12a in the first light guide plate 12 is flat in the second embodiment. In contrast to the shape, in the third embodiment, a bent pattern 12 d is provided on the first light incident surface 12 a of the first light guide plate 12.
The structure of the backlight other than this difference is the same in the second embodiment and the third embodiment.

In the description of the backlight in the third embodiment below, the difference from the second embodiment will be mainly described, and the same structure in the second embodiment and the third embodiment will be described in detail. The explanation is omitted or simplified.
In the second embodiment and the third embodiment, the same components in the backlight are denoted by the same reference numerals.

As shown in FIG. 4, two second light guide plates 14 in the second light guide plate 14 have a role of causing light having a linear and uniform luminance to enter the first light incident surface 12 a of the first light guide plate 12. As with the backlight of the second embodiment, light emitting diodes 20 and 20 are disposed on the light incident surfaces 14a and 14a as light sources, respectively.
The two second light incident surfaces 14a and 14a are two opposing side portions of the second light guide plate 14 having a substantially rectangular parallelepiped shape having six surfaces intersecting each other.

As shown in FIG. 4, the light emitting diodes 20 and 20 are disposed on the second light incident surfaces 14 a and 14 a opposite to the two surfaces of the second light guide plate 14, respectively.
It is preferable to use the two light emitting diodes 20 and 20 having uniform light emission characteristics. As the light emitting diode 20, a light emitting diode that emits a white color is used.

Similar to the second embodiment, the second light guide plate 14 is provided with a second groove 14c having a sawtooth pattern on the surface facing the second light emitting surface 14b.
As in the second embodiment, the inclination angle of the second groove 14c is substantially the center position in the X-axis direction of the second light guide plate 14 so that the inclination angle inclination directions are opposite to each other. Yes. Further, the ridgeline of the second groove 14c having a triangular cross-sectional shape is disposed so as to be parallel to the Y-axis direction perpendicular to the paper surface of FIG.

The light from the light emitting diodes 20 and 20 incident from the two second light incident surfaces 14a and 14a facing each other in the second light guide plate 14 is caused by the second groove 14c in the second light guide plate 14. The light is repeatedly reflected and scattered and propagated to the entire area of the second light guide plate 14.
As a result, in the third embodiment of the present invention, light having a linear and uniform luminance is transmitted from the second light exit surface 14 b of the second light guide plate 14 to the first light guide plate 12. The light is incident on the first light incident surface 12a. For this reason, the luminance unevenness generated in the backlight of Patent Document 2 in the region near the first light incident surface 12a does not occur in the third embodiment. For this reason, in 3rd Embodiment, the backlight 10 excellent in the uniformity of in-plane brightness | luminance can be provided.
Further, since the two light emitting diodes 20 are used as the light source, in the third embodiment, the light emission luminance of the backlight 10 can be increased and the luminance uniformity in the X-axis direction is improved. be able to.

Furthermore, in the backlight according to the third embodiment, the first light incident surface 12a of the first light guide plate 12 facing the second light exit surface 14b of the second light guide plate 14 has a prism shape. A bent pattern 12d is provided.
The bent pattern 12d provided on the first light incident surface 12a of the first light guide plate 12 is disposed so that the prism shape faces the second light emitting surface 12b.

The bent pattern 12d basically has the same structure as the prism provided on the prism sheet 16 (see FIGS. 1 and 2).
That is, the prism shape of the bent pattern 12d facing the second light exit surface 12b has a triangular shape with a prism apex angle of 60 degrees to 70 degrees. Further, as shown in FIG. 4, the ridge line of the triangular prism top portion is arranged so as to be parallel to the Y axis perpendicular to the paper surface.

  In the bent pattern 12d provided on the first light incident surface 12a, it is preferable that the arrangement pitch dimension of the prism-shaped top ridge line is in a pitch dimension range of 50 μm to 100 μm, similar to the prism sheet 16 described above.

The bent pattern 12d can be formed simultaneously when the first light guide plate 12 is formed by injection molding using a mold.
That is, a bent pattern 12d and a reverse pattern shape may be formed in an injection mold, and a translucent resin material such as polymethyl methacrylate or polycarbonate may be melted and filled in the mold.

In the backlight according to the third embodiment of the present invention, the bent pattern 12d formed on the first light incident surface 12a of the first light guide plate 12 is from the second light output surface 14b of the second light guide plate 14. It has a function of correcting the directivity of the emitted linear light.
That is, the bent pattern 12d having a prism shape has a function of controlling the directivity of light emitted from the second light exit surface 14b of the second light guide plate 14 so as to be substantially perpendicular to the X axis. ing.

Therefore, light in a direction perpendicular to the side parallel to the X axis of the first light guide plate 12 is incident on the first light guide plate 12 due to the prism shape of the bent pattern 12d.
For this reason, in the backlight according to the third embodiment of the present invention, light with uniform light directivity can be incident on the first light guide plate 12.
As a result, the third embodiment shown in FIG. 4 has an effect that the in-plane uniformity of the light emission luminance in the backlight is further improved.

Furthermore, the bent pattern 12d in the third embodiment described above with reference to FIG. 4 may be applied to the backlight 10 in the first embodiment of the present invention described with reference to FIGS. .
That is, in the backlight in which one light emitting diode 20 is disposed on the second light incident surface 14a of the second light guide plate 14, the light from the second light output surface 14b is incident on the first light guide plate 12. A bent pattern 12d as shown in FIG. 4 may be formed on the first light incident surface 12a so as to face the second light emitting surface 14b.

As described above, by providing the backlight of the first embodiment described with reference to FIGS. 1 and 2 with the bent pattern 12d, the first light guide plate 12 has light with uniform light directivity. Can be incident.
As a result, by providing the bent pattern 12d on the first light guide plate 12, the backlight of the first embodiment has an effect of improving the uniformity of in-plane luminance.

Furthermore, the bent pattern 12d in the third embodiment described with reference to FIG. 4 may be applied to the backlight in the second embodiment of the present invention described with reference to FIG.
That is, the light-emitting diodes 20 and 20 are disposed so as to face the two second light incident surfaces 14a and 14a of the second light guide plate 14, respectively, and light from the second light emitting surface 14b is incident. The bent pattern 12d described with reference to FIG. 4 may be formed on the first light incident surface 12a of the first light guide plate 12 so as to face the second light emitting surface 14b.

As described above, by providing the backlight 12 according to the second embodiment described with reference to FIG. 3 with the bent pattern 12d, light having uniform directivity can be incident on the first light guide plate 12. .
As a result, by providing the bent pattern 12d on the first light guide plate 12, in the backlight of the second embodiment, it is possible to exert an effect of improving the uniformity of in-plane luminance.

[Explanation of Fourth Embodiment: FIG. 5]
Next, a backlight structure according to the fourth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 5 is a plan view showing a first light guide plate, a second light guide plate, and a light emitting diode in a backlight according to a fourth embodiment of the present invention.

The difference in structure between the backlight in the fourth embodiment and the backlight in the third embodiment is that the bent pattern 12d is formed on the first light incident surface 12a of the first light guide plate 12 in the third embodiment. In contrast, in the fourth embodiment, the first light incident surface 12a of the first light guide plate 12 is flat, and the first light incident surface 12a and the second light emitting surface 14b are formed. It is the point which arrange | positions the bending sheet | seat 22 between.
The structure of the backlight other than this difference is the same between the third embodiment and the fourth embodiment.

In the description of the backlight in the following fourth embodiment, the difference from the third embodiment will be mainly described, and the same structure in the third embodiment and the fourth embodiment will be described in detail. The description will be omitted or simplified.
Furthermore, in the third embodiment and the fourth embodiment, the same components in the backlight are denoted by the same reference numerals.

As shown in FIG. 5, two second light guide plates 14 in the second light guide plate 14 having a role of allowing light having a linear and uniform luminance to enter the first light incident surface 12 a of the first light guide plate 12. As in the third embodiment, light emitting diodes 20 and 20 are disposed on the light incident surfaces 14a and 14a as light sources, respectively.
The two second light incident surfaces 14a and 14a are two opposing side portions of the second light guide plate 14 having a substantially rectangular parallelepiped shape having six surfaces intersecting each other.

As shown in FIG. 5, light emitting diodes 20 and 20 are disposed on the second light incident surfaces 14 a and 14 a, respectively, facing the two surfaces of the second light guide plate 14.
It is preferable to use the two light emitting diodes 20 and 20 having uniform light emission characteristics. As the light emitting diode 20, a light emitting diode that emits a white color is used.

Further, the second light guide plate 14 is provided with a second groove 14c having a sawtooth pattern on the surface facing the second light emitting surface 14b, as in the second and third embodiments. .
As in the second and third embodiments, the inclination angle of the second groove 14c is substantially the center position in the X-axis direction of the second light guide plate 14, and the inclination angle inclination directions are opposite to each other. Try to be in the direction. Further, the ridgeline of the second groove 14c having a triangular cross-sectional shape is disposed so as to be parallel to the Y-axis direction perpendicular to the paper surface of FIG.

The light from the light emitting diodes 20 and 20 incident from the two second light incident surfaces 14a and 14a facing each other in the second light guide plate 14 is caused by the second groove 14c in the second light guide plate 14. The light is repeatedly reflected and scattered and propagated to the entire area of the second light guide plate 14.
As a result, in the fourth embodiment of the present invention, linear and uniform luminance light can be emitted from the second light emitting surface 14b of the second light guide plate 14. As a result, in the fourth embodiment of the present invention, light having a linear and uniform luminance is transmitted from the second light exit surface 14 b of the second light guide plate 14 to the first light guide plate 12. The light is incident on the first light incident surface 12a. For this reason, the luminance unevenness generated in the backlight of Patent Document 2 in the region near the first light incident surface 12a does not occur in the fourth embodiment. For this reason, in the fourth embodiment, it is possible to provide the backlight 10 having excellent in-plane luminance uniformity.
In addition, since the two light emitting diodes 20 are used as the light source, in the fourth embodiment, it is possible to increase the light emission luminance of the backlight 10 and to improve the uniformity of the luminance in the X-axis direction. be able to.

Furthermore, in the backlight according to the fourth embodiment, a bent sheet 22 is disposed between the second light emitting surface 14b and the first light incident surface 12a.
The bent sheet 22 includes a prism on one surface side. The second light guide plate 14 is disposed on the second light exit surface 14b side so that the prism shape of the bent sheet 22 faces.

The bent sheet 22 basically has the same structure as the prism sheet 16 described with reference to FIGS. 1 and 2.
That is, the prism in the bent sheet 22 disposed so as to face the second light exit surface 12b has a triangular shape with a prism apex angle of 60 degrees to 70 degrees. Further, as shown in FIG. 5, the ridge line of the triangular prism top is arranged so as to be parallel to the Y axis perpendicular to the paper surface.

  As for the prism provided in the bending sheet 22, the arrangement pitch dimension of the top ridge line of the prism is preferably in the range of 50 μm to 100 μm, similarly to the prism sheet 16 described with reference to FIGS. 1 and 2.

Similar to the prism sheet 16, the bent sheet 22 is made of a resin material having translucency such as polymethyl methacrylate resin, polycarbonate resin, or polyester resin.
And the bending sheet | seat 22 can be formed with these translucent resins by the injection molding method using a metal mold | die.

In the backlight according to the fourth embodiment, the bent sheet 22 disposed between the first light incident surface 12a of the first light guide plate 12 and the second light output surface 14b of the second light guide plate 14. Has a role of correcting the directivity of the light emitted from the second light emitting surface 14 b of the second light guide plate 14.
That is, the bent sheet 22 having a prism controls the directivity of the light emitted from the second light emitting surface 14b so as to be substantially perpendicular to the first light incident surface 12a parallel to the X-axis direction. It has a function.

Accordingly, in the fourth embodiment in which the bent sheet 22 is disposed between the first light guide plate 12 and the second light guide plate 14, the right angle is perpendicular to the first light incident surface 12a parallel to the X-axis direction. Light is incident on the first light guide plate 12.
For this reason, in the backlight according to the fourth embodiment of the present invention, light with uniform light directivity can be incident on the first light guide plate 12. As a result, the structure shown in FIG. 5 has an effect that the in-plane uniformity of the light emission luminance in the backlight is further improved.

Moreover, you may apply the bending sheet | seat 22 in 4th Embodiment demonstrated using FIG. 5 above to the backlight 10 in 1st Embodiment of this invention demonstrated using FIG. 1 and FIG.
That is, in the backlight in which one light emitting diode 20 is disposed on the second light incident surface 14a of the second light guide plate 14, the second light emitting surface 14b and the light from the second light emitting surface 14b. Alternatively, the bent sheet 22 may be disposed between the first light incident surface 12a on which the light is incident. The prism of the bent sheet 22 is disposed so as to face the second light exit surface 14 b of the second light guide plate 14.

By arranging the bent sheet 22 in the backlight according to the first embodiment described with reference to FIGS. 1 and 2, light is incident on the first light incident surface 12 a of the first light guide plate 12. Light with uniform directivity can be incident.
As a result, by providing the bent sheet 22 having a prism, the backlight of the first embodiment has an effect that the in-plane luminance uniformity is good.

Furthermore, you may apply the bending sheet | seat 22 in 4th Embodiment demonstrated using FIG. 5 to the backlight in the 2nd Embodiment of this invention demonstrated using FIG.
In other words, the light emitting diodes 20 and 20 are arranged so as to face the two second light incident surfaces 14a and 14a of the second light guide plate 14, respectively, and the second light emitting surface 14b and the first light guide surface 14a. You may employ | adopt the structure which arrange | positions the bending sheet | seat 22 demonstrated using FIG. 5 between the 1st light-incidence surfaces 12a in the optical plate 12. FIG.

As described above, by arranging the bent sheet 22 in the backlight according to the second embodiment described with reference to FIG. 3, light having uniform directivity is incident on the first light guide plate 12. Can do.
As a result, by providing the bent sheet 22 between the first light guide plate 12 and the second light guide plate 14, in the backlight according to the second embodiment, the uniformity of in-plane luminance is improved. Can be achieved.

[Explanation of Fifth Embodiment: FIG. 6]
Next, the structure of the backlight according to the fifth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 6 is a plan view showing a first light guide plate, a second light guide plate, and a light emitting diode in a backlight according to a fifth embodiment of the present invention.

The structural difference between the backlight in the fifth embodiment and the backlight in the second embodiment is that the second light guide plate 14 in the fifth embodiment has a position facing the second groove 14c. The light reflecting member 26 is disposed on the surface.
The structure of the backlight other than this difference is the same in the second embodiment and the fifth embodiment.

In the following description of the backlight structure in the fifth embodiment, differences from the second embodiment will be mainly described, and the details of the same structure in the second embodiment and the fifth embodiment will be described. The description will be omitted or simplified.
In the second embodiment and the fifth embodiment, the same components in the backlight are denoted by the same reference numerals.

As shown in FIG. 6, the two second light guide plates 14 in the second light guide plate 14 have a role of causing linear and uniform light to enter the first light incident surface 12 a of the first light guide plate 12. As in the second embodiment, light emitting diodes 20 and 20 are disposed on the light incident surfaces 14a and 14a as light sources, respectively.
The two second light incident surfaces 14a and 14a are two opposing side portions of the second light guide plate 14 having a substantially rectangular parallelepiped shape having six surfaces intersecting each other.

As shown in FIG. 6, light emitting diodes 20 and 20 are disposed on the second light incident surfaces 14 a and 14 a opposite to the two surfaces of the second light guide plate 14, respectively.
It is preferable to use the two light emitting diodes 20 and 20 having uniform light emission characteristics. As the light emitting diode 20, a light emitting diode that emits a white color is used.

Further, the second light guide plate 14 of the backlight according to the fifth embodiment has a saw blade on the surface facing the second light exit surface 14b, as in the second, third, and fourth embodiments. A second groove 14c having a pattern is provided.
The inclination angle of the second groove 14c is substantially the center position in the X-axis direction of the second light guide plate 14 as in the second embodiment, the third embodiment, and the fourth embodiment. The inclination angle inclination directions are opposite to each other. Further, the ridgeline of the second groove 14c having a triangular cross-sectional shape is arranged so as to be parallel to the Y-axis direction perpendicular to the paper surface of FIG.

The light from the light emitting diodes 20 and 20 incident from the two second light incident surfaces 14a and 14a facing each other in the second light guide plate 14 is caused by the second groove 14c in the second light guide plate 14. The light is repeatedly reflected and scattered and propagated to the entire area of the second light guide plate 14.
Thus, in the fifth embodiment of the present invention, it is possible to emit linear and uniform luminance light from the second light emitting surface 14b of the second light guide plate 14. . As a result, in the fifth embodiment of the present invention, light having a linear and uniform luminance is transmitted from the second light exit surface 14b of the second light guide plate 14 to the first light guide plate 12. The light is incident on the first light incident surface 12a. For this reason, the luminance unevenness generated in the backlight of Patent Document 2 in the region near the first light incident surface 12a does not occur in the fifth embodiment. For this reason, in the fifth embodiment, it is possible to provide the backlight 10 having excellent in-plane luminance uniformity.
In addition, since the two light emitting diodes 20 are used as the light source, in the fifth embodiment, it is possible to increase the light emission luminance of the backlight 10 and to improve the uniformity of the luminance in the X-axis direction. be able to.

Further, in the backlight according to the fifth embodiment, the light reflecting member 26 having a reflecting surface on one surface side at a position facing the second groove 14c having a sawtooth pattern in the second light guide plate 14. Is arranged. The light reflecting member 26 has a function of returning the light emitted from the second groove 14 c to the second light guide plate 14.
The reflecting surface formed on the light reflecting member 26 is disposed so as to face the second groove 14c. Here, the second light guide plate 14 and the light reflecting member 26 have substantially the same dimension in the X-axis direction.

The light reflecting member 26 basically has the same structure as the reflecting sheet 18 described with reference to FIG.
That is, the light reflecting member 26 is formed as a reflecting surface by forming a thin film having a high surface reflectance such as aluminum (Al) or silver (Ag) on the resin film surface by a vacuum deposition method or a plating method.

Alternatively, a white polyethylene terephthalate (PET) resin film that irregularly reflects light on the surface can be used as the light reflecting member 26 instead of the resin film on which a thin film having a high surface reflectance is formed.
Also in the light reflecting member 26 made of such white polyethylene terephthalate, the light is diffusely reflected on the surface of the light reflecting member 26 and the light emitted from the second light guide plate 14 toward the light reflecting member 26 is second. A function of returning to the light guide plate 14 is provided.

In the fifth embodiment of the present invention, by arranging the light reflecting member 26, the light emitted from the second groove 14 c in the second light guide plate 14 is again introduced into the second light guide plate 14. Can be returned.
As a result, in the backlight according to the fifth embodiment of the present invention, the utilization efficiency of the light emitted from the light emitting diode 20 can be improved, and the light emission luminance of the backlight can be increased.

In the embodiment described above with reference to FIG. 6, the light reflecting member 26 has been described as an example in which the light reflecting member 26 is disposed at a position facing the second groove 14 c.
However, the light reflecting member 26 can also be disposed on the upper surface and the lower surface made of the XZ plane in the second light guide plate 14.

Thus, if the light reflecting member 26 is disposed so as to face the three surfaces excluding the second light emitting surface 14b and the two second light incident surfaces 14a, 14a in the second light guide plate 14. The effects described below can be obtained.
That is, not only the light emitted from the second groove 14 c of the second light guide plate 14 but also the light emitted from the upper surface and the lower surface of the second light guide plate 14 is again returned to the second light guide plate 26 by the light reflecting member 26. 14 can be returned. Therefore, by disposing the reflecting surface of the light reflecting member 26 so as to face the three surfaces of the second light guide plate 14, the light utilization efficiency can be further improved and the luminance of the backlight can be increased. Has an effect.

Furthermore, the light reflecting member 26 disposed so as to face the second groove 14c is also applied to the backlights in the first, second, third, and fourth embodiments described so far. Can do.
Also in the backlights in the first, second, third, and fourth embodiments, the light reflecting member 26 is disposed so as to face the second groove 14 c provided in the second light guide plate 14. The light emitted from the second groove 14 c in the second light guide plate 14 can be returned to the inside of the second light guide plate 14 again. For this reason, in the first, second, third, and fourth embodiments, there is an effect that the light use efficiency is improved and the luminance of the backlight can be increased.

Furthermore, in the first to fourth embodiments, the light reflecting member 26 has an upper surface formed of an XZ plane in the second light guide plate 14 in addition to the surface facing the second groove 14c. You may employ | adopt the structure arrange | positioned also in a lower surface.
As described above, the light reflecting member 26 is disposed so as to face the three surfaces of the second light guide plate 14 excluding the second light emitting surface 14b and the two second light incident surfaces 14a and 14a. The following effects can be obtained. That is, the light emitted from the three surfaces excluding the second light incident surface 14a and the second light emitting surface 14b can be returned to the second light guide plate 14 again. As a result, in the first to fourth embodiments, the light utilization efficiency is further increased, and the luminance of the backlight can be improved.

Further, in the backlight of the fifth embodiment, a configuration in which the bent pattern 12d is formed on the first light guide plate 12 as in the configuration of the third embodiment described above with reference to FIG. Good. As described above, when the configuration in which the bent pattern 12d is provided on the first light guide plate 12 in the backlight of the fifth embodiment, the first light incident surface 12a parallel to the X-axis direction is perpendicular to the first light incident surface 12a. The light emitted from the second light guide plate 14 can be incident on the first light guide plate 12.
As a result, also in the backlight of the fifth embodiment, it is possible to cause the light having uniform directivity to be incident on the first light incident surface 12a of the first light guide plate 12 by the bent pattern 12d. Therefore, in the fifth embodiment of the present invention, it is possible to further improve the in-plane uniformity of emission luminance in the backlight.

Furthermore, in the backlight according to the fifth embodiment, the light incident surface 12a and the second light guide plate 14 of the first light guide plate 12 are configured as in the configuration of the fourth embodiment described above with reference to FIG. A configuration in which the bent sheet 22 is disposed between the second light exit surface 14b in FIG. As described above, when the configuration in which the bent sheet 22 is disposed between the first light guide plate 12 and the second light guide plate 14 in the backlight of the fifth embodiment, the first parallel to the X-axis direction is adopted. Light emitted from the second light guide plate 14 can be incident on the first light guide plate 12 at a right angle to the light incident surface 12a.
As a result, also in the backlight according to the fifth embodiment, the bent sheet 22 makes it possible to make the light with uniform directivity incident on the first light guide plate 12. Therefore, in the fifth embodiment of the present invention, it is possible to further improve the in-plane uniformity of emission luminance in the backlight.

[Explanation of Sixth Embodiment: FIG. 7]
Next, a backlight structure according to the sixth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 7 is a plan view showing a first light guide plate, a second light guide plate, and a light emitting diode in a backlight according to a sixth embodiment of the present invention.

The structural difference between the backlight in the sixth embodiment and the backlight in the first embodiment is that the planar shape of the second light guide plate 14 is rectangular in the first embodiment. On the other hand, in the sixth embodiment, the planar shape of the second light guide plate 14 is a wedge shape.
The structure of the backlight other than this difference is the same between the sixth embodiment and the first embodiment.

In the description of the backlight structure in the sixth embodiment below, the difference from the first embodiment will be mainly described, and the same structure in the first embodiment and the sixth embodiment will be described in detail. The explanation is omitted or simplified.
In the first embodiment and the sixth embodiment, the same reference numerals are given to the same components in the backlight.

As shown in FIG. 7, the second light in the second light guide plate 14 having the role of making light having a linear and uniform luminance incident on the first light incident surface 12 a in the first light guide plate 12. One light emitting diode 20 is disposed on the incident surface 14a.
As the light emitting diode 20, a light emitting diode that emits white color is used.

In the backlight according to the sixth embodiment, the second light guide plate 14 is provided with a second groove 14c having a sawtooth pattern on the surface facing the second light emitting surface 14b.
Further, the ridge line formed of the sawtooth pattern of the second groove 14c is arranged so as to be parallel to the Y-axis direction perpendicular to the paper surface of FIG.

The second groove 14c provided on the second light guide plate 14 repeatedly reflects and scatters light incident on the second light guide plate 14 from the second light incident surface 14a in a sawtooth pattern. And has a role of propagating throughout the second light guide plate 14.
The second light guide plate 14 emits light having a linear and uniform luminance from the entire surface of the second light emitting surface 14b toward the first light incident surface 12a of the first light guide plate 12. To do. As a result, in the sixth embodiment of the present invention, light having a linear and uniform luminance is transmitted from the second light exit surface 14 b of the second light guide plate 14 to the first light guide plate 12. The light is incident on the first light incident surface 12a. For this reason, the luminance unevenness generated in the backlight of Patent Document 2 in the region near the first light incident surface 12a does not occur in the sixth embodiment. For this reason, in the sixth embodiment, it is possible to obtain the backlight 10 having excellent in-plane luminance uniformity.

Further, in the second light guide plate 14 of the backlight according to the sixth embodiment of the present invention, the dimension (width dimension) in the Z-axis direction on the second light incident surface 14a side on which the light from the light emitting diode 20 is incident, The dimension (width dimension) in the Z-axis direction on the side facing the second light incident surface 14a is different.
That is, the dimension in the Z-axis direction on the second light incident surface 14a side is made larger than the dimension in the Z-axis direction on the side facing the second light incident surface 14a, and the planar shape of the second light guide plate 14 is made. Use a wedge shape. The inclination angle of the second groove 14c surface with respect to the X-axis for forming the wedge shape is about 0.5 to 2 degrees.

When the surface of the second groove 14c is inclined with respect to the X-axis in this way, the light from the light emitting diode 20 incident on the second light guide plate 14 from the second light incident surface 14a is efficiently reflected by the second light. The light can be emitted from the emission surface 14b.
As a result, in the sixth embodiment of the present invention, there is an effect that it is possible to obtain the backlight 10 in which the light use efficiency is improved and the luminance is further improved.

Further, in the sixth embodiment described with reference to FIG. 7, at a position facing the second groove 14 c, or a position facing the upper surface and the lower surface made of the XZ plane in the second light guide plate 14, You may employ | adopt the structure which arrange | positions the light reflection member 26 with a reflective surface in 5th Embodiment demonstrated using FIG.
In the backlight according to the sixth embodiment, the light reflecting member 26 is disposed at a position facing the second groove 14c, or a position facing the four surfaces excluding the second light emitting surface 14b and the second light incident surface 14a. By providing the light, the light use efficiency can be improved and the light emission luminance of the backlight can be increased.

Further, in the backlight of the sixth embodiment, a configuration in which the bent pattern 12d is formed on the first light guide plate 12 as in the configuration of the third embodiment described above with reference to FIG. Good. As described above, when the configuration in which the bent pattern 12d is provided on the first light guide plate 12 in the backlight of the sixth embodiment, the first light incident surface 12a parallel to the X-axis direction is perpendicular to the first light incident surface 12a. The light emitted from the second light guide plate 14 can be incident on the first light guide plate 12.
As a result, also in the backlight of the sixth embodiment, the light having uniform directivity can be incident on the first light incident surface 12a of the first light guide plate 12 by the bent pattern 12d. Therefore, in the sixth embodiment of the present invention, it is possible to further improve the in-plane uniformity of emission luminance in the backlight.

Furthermore, in the backlight according to the sixth embodiment, the light incident surface 12a and the second light guide plate 14 in the first light guide plate 12 as in the configuration of the fourth embodiment described above with reference to FIG. A configuration in which the bent sheet 22 is disposed between the second light exit surface 14b in FIG. As described above, when the configuration in which the bent sheet 22 is disposed between the first light guide plate 12 and the second light guide plate 14 in the backlight of the sixth embodiment, the first parallel to the X-axis direction is adopted. Light emitted from the second light guide plate 14 can be incident on the first light guide plate 12 at a right angle to the light incident surface 12a.
As a result, also in the backlight according to the sixth embodiment, the bent sheet 22 allows light having uniform directivity to be incident on the first light guide plate 12. Therefore, in the sixth embodiment of the present invention, the effect that the in-plane uniformity of the light emission luminance in the backlight can be further improved can be exhibited.

[Description of Seventh Embodiment: FIG. 8]
Next, the structure of the seventh embodiment of the backlight of the present invention will be described in detail with reference to FIG.
FIG. 8 is a plan view showing a first light guide plate, a second light guide plate, and a light emitting diode in a backlight according to a seventh embodiment of the present invention.

The structural difference between the backlight in the seventh embodiment and the backlight in the second embodiment is that the planar shape of the second light guide plate 14 is rectangular in the second embodiment. On the other hand, in the seventh embodiment, the planar shape of the second light guide plate 14 is a shape in which two wedges are brought into contact with each other and the surface of the second groove 14c is inclined.
The structure of the backlight other than this difference is the same between the seventh embodiment and the second embodiment.

In the description of the backlight structure in the seventh embodiment below, the description will focus on the differences from the second embodiment, and the same structures in the second embodiment and the seventh embodiment will be described in detail. The explanation is omitted or simplified.
In the second embodiment and the seventh embodiment, the same components in the backlight are denoted by the same reference numerals.

As shown in FIG. 8, the two second light guide plates 14 in the second light guide plate 14 have a role of causing linear and uniform light to enter the first light incident surface 12 a of the first light guide plate 12. Light emitting diodes 20 and 20 are disposed as light sources on the two light incident surfaces 14a and 14a, respectively.
The two second light incident surfaces 14a and 14a are two opposing side portions of the second light guide plate 14 having a substantially rectangular parallelepiped shape having six surfaces intersecting each other.

That is, in the backlight according to the seventh embodiment, the light emitting diodes 20 and 20 are disposed on the second light incident surfaces 14 a and 14 a of the second light guide plate 14 facing each other.
It is preferable to use the two light emitting diodes 20 and 20 having uniform light emission characteristics. As the light emitting diode 20, a light emitting diode that emits a white color is used.

The second light guide plate 14 is provided with a second groove 14c having a sawtooth pattern on the surface facing the second light emitting surface 14b. The light from the light emitting diodes 20 and 20 incident from the two second light incident surfaces 14a and 14a facing each other in the second light guide plate 14 is caused by the second groove 14c in the second light guide plate 14. The light is repeatedly reflected and scattered and propagated to the entire area of the second light guide plate 14.
As a result, in the seventh embodiment of the present invention, it is possible to emit linear and uniform light from the second light emitting surface 14b of the second light guide plate 14. As a result, in the seventh embodiment of the present invention, light having a linear and uniform luminance is transmitted from the second light exit surface 14b of the second light guide plate 14 to the first light guide plate 12. The light is incident on the first light incident surface 12a. For this reason, the luminance unevenness generated in the backlight of Patent Document 2 in the region near the first light incident surface 12a does not occur in the seventh embodiment. For this reason, in the seventh embodiment, it is possible to obtain the backlight 10 having excellent in-plane luminance uniformity.
Further, since the two light emitting diodes 20 are used as the light source, in the seventh embodiment, the light emission luminance of the backlight 10 can be increased and the luminance uniformity in the X-axis direction is improved. be able to.

  Furthermore, in the seventh embodiment, the dimension in the Z-axis direction on the two second light incident surfaces 14a, 14a side of the second light guide plate 14 is set to the intermediate position in the X-axis direction of the second light guide plate. The size of the second light guide plate 14 is made larger than the respective dimensions, and the planar shape of the second light guide plate 14 is made such that two wedges are brought into contact with each other.

That is, the second groove 14c is configured such that the inclination of the surface of the second groove 14c is opposite to that of the upper half and the lower half of FIG. Yes.
The inclination angle of the second groove 14c surface with respect to the X axis for making the wedge shape is about 0.5 to 2 degrees, respectively. Further, the ridge line of the second groove 14c is disposed so as to be parallel to the Y-axis direction perpendicular to the paper surface of FIG.

As described above, when the second groove 14c surface is inclined in the opposite direction between the upper half and the lower half with the intermediate position in the X-axis direction as a boundary, the second light guide plate 14 extends from the second light incident surfaces 14a, 14a. Light incident on the inside can be efficiently emitted from the second light exit surface 14b.
Therefore, the seventh embodiment described with reference to FIG. 8 has the effect of improving the light use efficiency and obtaining the backlight 10 with higher emission luminance.

Further, in the seventh embodiment, the position facing the second groove 14c, or the position facing the upper surface and the lower surface made of the XZ plane in the second light guide plate 14 has been described with reference to FIG. You may employ | adopt the structure which arrange | positions the light reflection member 26 in 5th Embodiment.
In the seventh embodiment, the light reflecting member 26 is disposed at a position facing the second groove 14c or at a position facing three surfaces excluding the second light emitting surface 14b and the two light incident surfaces 14a. By doing so, the light radiate | emitted from the 2nd groove 14c and the upper surface and lower surface of the 2nd light-guide plate 14 can be returned in the 2nd light-guide plate 14 inside.
As described above, also in the seventh embodiment, by arranging the light reflecting member 26, the light use efficiency can be improved, and the light emission luminance of the backlight can be increased.

Further, in the backlight of the seventh embodiment, a configuration in which the bent pattern 12d is formed on the first light guide plate 12 as in the configuration of the third embodiment described above with reference to FIG. Good. As described above, when the configuration in which the bent pattern 12d is provided on the first light guide plate 12 in the backlight according to the seventh embodiment, the first light incident surface 12a parallel to the X-axis direction is perpendicular to the first light incident surface 12a. The light emitted from the second light guide plate 14 can be incident on the first light guide plate 12.
As a result, also in the backlight of the seventh embodiment, the light having uniform directivity can be incident on the first light incident surface 12a of the first light guide plate 12 by the bent pattern 12d. Therefore, in the seventh embodiment of the present invention, it is possible to further improve the in-plane uniformity of emission luminance in the backlight.

Furthermore, in the backlight of the seventh embodiment, the light incident surface 12a and the second light guide plate 14 of the first light guide plate 12 are configured as in the configuration of the fourth embodiment described above with reference to FIG. A configuration in which the bent sheet 22 is disposed between the second light exit surface 14b in FIG. As described above, when the configuration in which the bent sheet 22 is disposed between the first light guide plate 12 and the second light guide plate 14 in the backlight according to the seventh embodiment, the first parallel to the X-axis direction is adopted. Light emitted from the second light guide plate 14 can be incident on the first light guide plate 12 at a right angle to the light incident surface 12a.
As a result, also in the backlight of the seventh embodiment, the bent sheet 22 makes it possible to make the light with uniform directivity incident on the first light guide plate 12. Therefore, in the seventh embodiment of the present invention, the effect that the in-plane uniformity of the light emission luminance in the backlight can be further improved can be exhibited.

[Explanation of Eighth Embodiment: FIGS. 9 and 10]
Next, the structure of the eighth embodiment of the backlight of the present invention will be described in detail with reference to FIGS.
FIG. 9 is a plan view showing a first light guide plate, a second light guide plate, and a light emitting diode in a backlight according to an eighth embodiment of the present invention. FIG. 10 is a side view showing the first light guide plate and the second light guide plate in the backlight according to the eighth embodiment of the present invention.

The structural differences between the backlight in the eighth embodiment and the backlight in the second embodiment are as follows. In the second embodiment, the side surface of the first light guide plate 12 is as shown in FIG. Whereas there is one second light guide plate 14 disposed so as to face the first light incident surface 12a to be provided, the backlight in the eighth embodiment is shown in the plan view of FIG. As described above, the two second light guide plates 14 and 14 are disposed on the first light incident surfaces 12a and 12a formed of two opposing side surfaces of the first light guide plate 12, respectively.
The structure of the backlight other than this difference is the same between the eighth embodiment and the second embodiment.

In the following description of the structure of the backlight in the eighth embodiment, differences from the second embodiment will be mainly described, and the details of the same structure in the second embodiment and the eighth embodiment will be described. The description will be omitted or simplified.
In the second embodiment and the eighth embodiment, the same components in the backlight are denoted by the same reference numerals.

As shown in FIGS. 9 and 10, the first light incident surfaces 12a and 12a, which are two opposing side surfaces of the first light guide plate 12, have a role of causing light having linear and uniform luminance to enter each other. The 2nd light guide plates 14 and 14 which have are arrange | positioned.
The two first light incident surfaces 12a and 12a in the first light guide plate 12 are two opposite side surfaces of the first light guide plate 12 having a substantially rectangular parallelepiped shape having six surfaces intersecting each other. .

Further, two light emitting diodes 20 and 20 are disposed on the two second light guide plates 14 and 14 as light sources, respectively.
In the backlight according to the eighth embodiment, the light emitting diodes 20 and 20 are disposed on the second light incident surfaces 14a and 14a of the second light guide plates 14 and 14 facing each other.

That is, the backlight 10 according to the eighth embodiment includes two second light guide plates 14 and 14 and four light emitting diodes 20, 20, 20, and 20, as shown in FIG. .
As these four light emitting diodes 20, it is preferable to use those having uniform light emitting characteristics. As the light emitting diode 20, a light emitting diode that emits a white color is used.

Further, the two second light guide plates 14 and 14 are provided with a second groove 14c having a sawtooth pattern.
The second groove 14c provided on the two first light incident surfaces 12a of the first light guide plate 12 on the opposite side of the surface facing each other is set so that the groove inclination angle faces the respective light emitting diodes 20 and 20. Set.

That is, the inclined surface of the upper half second groove 14c on the left side in FIG. 9 rotates the base line parallel to the X axis in the counterclockwise direction. Further, the inclined surface of the lower half second groove 14 on the left side in FIG. 9 is configured to rotate a base line parallel to the X axis in the clockwise direction.
Further, the inclined surface of the upper half second groove 14c on the right side in FIG. 9 rotates the base line parallel to the X axis in the clockwise direction. Furthermore, the inclined surface of the second groove 14 in the lower half on the right side in FIG. 9 is configured to rotate the base line parallel to the X axis in the counterclockwise direction.

The ridgeline of the second groove 14c having a triangular cross-sectional shape is disposed so as to be parallel to the Y-axis direction as shown in FIG.
The light from the light emitting diode 20 incident from the two second light incident surfaces 14a facing each other of the second light guide plate 14 is repeatedly reflected and reflected inside the second light guide plate 14 by the second groove 14c. The light is scattered and propagated to the entire surface of the second light guide plate 14.
In the backlight according to the eighth embodiment of the present invention, linear and uniform from the two second light guide plates 14 toward the two first light incident surfaces 12a of the first light guide plate 12. Luminance light can be emitted. In the backlight according to the eighth embodiment, light having a linear and uniform luminance is transmitted from the second light exit surface 14 b of the second light guide plate 14 to the first light guide plate 12. The light is incident on the light incident surface 12a. For this reason, the luminance unevenness generated in the backlight of Patent Document 2 in the region near the first light incident surface 12a does not occur in the second embodiment. For this reason, in the eighth embodiment, it is possible to provide the backlight 10 having excellent in-plane luminance uniformity.

Furthermore, in the eighth embodiment, the inclined surfaces of the second grooves 14c in the two second light guide plates 14 and 14 are set so as to face the light emitting diodes 20 and 20, respectively, as shown in FIG. ing. As a result, light incident on the second light guide plate 14 from the light emitting diode 20 can be efficiently emitted from the second light exit surface 14b.
Therefore, in the eighth embodiment, the light use efficiency is improved, and the light emission luminance of the backlight 10 is increased.

Furthermore, the pattern shape of the first groove 12c having a sawtooth pattern provided on the back surface on the lower surface side of the first light guide plate 12 is also different between the eighth embodiment and the second (first) embodiment. It is
That is, in the light guide plate 12 of the second (first) embodiment shown in FIG. 2, the first groove 12c provided on the first light guide plate 12 is arranged so that the inclination angles of the groove inclined surfaces are aligned in one direction. A pattern was formed. On the other hand, in the first groove 12c in the eighth embodiment, the angle of the groove inclined surface is set so as to face each of the second light guide plates 14 and 14, as shown in FIG. .

  In the backlight according to the eighth embodiment, the inclined surface of the first groove 12c in the left half of the sheet of FIG. 10 rotates the base line parallel to the Z axis in the counterclockwise direction. Further, the inclined surface of the first groove 12c in the right half of the sheet of FIG. 10 is configured to rotate the base line parallel to the Z axis in the clockwise direction.

As described above, in the backlight according to the eighth embodiment described with reference to FIGS. 9 and 10, the inclined surface of the first groove 12 c formed of the sawtooth pattern in the first light guide plate 12 is set to the second surface. It is set so as to face the light guide plate 14. As a result, the light that is emitted from the two second light guide plates 14 and 14 disposed opposite to the two side surfaces of the first light guide plate 12 and incident on the first light guide plate 12 is efficiently converted into the first light. The light can be emitted from the emission surface 12b.
Therefore, in the eighth embodiment of the present invention, the light use efficiency can be increased, and the light emission luminance in the backlight 10 can be further improved.

The backlight of the eighth embodiment described with reference to FIGS. 9 and 10 has a structure that is particularly suitable for backlighting a liquid crystal display panel having a large display area.
The first light guide plate 12 is linear and uniform from the second light guide plates 14 and 14 toward the two first light incident surfaces 12a and 12a that intersect the long side surfaces parallel to the Z-axis direction of the first light guide plate 12, respectively. Light with a reduced brightness is incident.
For this reason, even if the backlight 10 in the eighth embodiment is applied for backlighting a liquid crystal display panel having a large display area, luminance unevenness does not occur in a wide area, and the in-plane uniformity of light emission luminance is excellent. In addition, it is possible to provide a backlight with high emission luminance.

Furthermore, in the backlight according to the eighth embodiment, a position facing the two second grooves 14c and 14c, or an upper surface and a lower surface, which are XZ surfaces of the second light guide plate 14, are shown in FIG. You may employ | adopt the structure which arrange | positions the light reflection member 26 in 5th Embodiment demonstrated using FIG.
As described above, in the backlight according to the eighth embodiment, by arranging the light reflecting portion member 26, the light emitted from the upper surface and the lower surface of the second groove 14c or the second light guide plate 14 is again generated. It is possible to return to the inside of the two light guide plates 14.

  Therefore, in the backlight according to the eighth embodiment described with reference to FIGS. 9 and 10, the position facing the second groove 14c, or the second light emitting surface 14b and the two second light incident surfaces. By disposing the light reflecting member 26 at a position facing the three surfaces except 14a, the light use efficiency can be improved and the luminance of the backlight can be increased also in the eighth embodiment.

In the backlight of the eighth embodiment, a configuration in which the bent pattern 12d is formed on the first light guide plate 12 as in the configuration of the third embodiment described above with reference to FIG. Good. As described above, when the configuration in which the bent pattern 12d is provided on the first light guide plate 12 in the backlight according to the eighth embodiment, the first light incident surface 12a parallel to the X-axis direction is perpendicular to the first light incident surface 12a. The light emitted from the second light guide plate 14 can be incident on the first light guide plate 12.
As a result, also in the backlight according to the eighth embodiment, the light having uniform directivity can be incident on the first light incident surface 12a of the first light guide plate 12 by the bent pattern 12d. Therefore, in the eighth embodiment of the present invention, it is possible to further improve the in-plane uniformity of the light emission luminance in the backlight.

Furthermore, in the backlight of the eighth embodiment, the light incident surface 12a and the second light guide plate 14 of the first light guide plate 12 are configured as in the configuration of the fourth embodiment described above with reference to FIG. A configuration in which the bent sheet 22 is disposed between the second light exit surface 14b in FIG. As described above, when the configuration in which the bent sheet 22 is disposed between the first light guide plate 12 and the second light guide plate 14 in the backlight according to the eighth embodiment, the first parallel to the X-axis direction is adopted. Light emitted from the second light guide plate 14 can be incident on the first light guide plate 12 at a right angle to the light incident surface 12a.
As a result, also in the backlight according to the eighth embodiment, the bent sheet 22 allows light having uniform directivity to be incident on the first light guide plate 12. Therefore, in the eighth embodiment of the present invention, the effect that the in-plane uniformity of the light emission luminance in the backlight can be further improved can be exhibited.

Further, the planar shape of the two second light guide plates 14 in the eighth embodiment of the present invention is a shape in which two wedges are abutted as in the seventh embodiment described with reference to FIG. Thus, the surface of the second groove 14c having a sawtooth pattern may be inclined.
In this way, the second groove 14c surface is inclined in the opposite direction in the upper half and the lower half with the intermediate position in the X-axis direction as the boundary, like the second light guide plate 14 in the seventh embodiment. Then, light incident from the second light incident surface 14a can be efficiently emitted from the second light emitting surface 14b. Therefore, in the eighth embodiment of the present invention, it is possible to obtain the backlight 10 in which the light use efficiency is increased and the light emission luminance is further improved.

In the eighth embodiment, the two second light guide plates 14 arranged on the opposing side surfaces of the first light guide plate 12 are substantially rectangular parallelepiped as in the first embodiment described with reference to FIG. A structure in which one light emitting diode 20 is disposed on one second light incident surface 14a of the second light guide plate 14 having a shape, or a wedge shape as in the sixth embodiment described with reference to FIG. A structure may be adopted in which one light emitting diode 20 is disposed on one second light incident surface 14a of the second light guide plate 14 that is provided.
Even when such a structure of the second light guide plate 14 and the structure of the light emitting diode 20 is provided, substantially the same effect as that of the eighth embodiment described above can be obtained.

Next, a modification that modifies the eighth embodiment of the present invention in which a total of four light emitting diodes 20 are disposed will be described. As a modified example of the eighth embodiment, two first light incident surfaces 12a and 12a in the first light guide plate 12 have two roles of causing light having a linear and uniform luminance to enter. In this structure, one light emitting diode 20 is disposed on each of the second light incident surfaces 14 a and 14 a of the two light guide plates 14.
That is, in the modification of the eighth embodiment, two second light guide plates 14 and 14 and two light emitting diodes 20 and 20 are provided.

In the modification of the eighth embodiment, since there are two light emitting diodes 20, the light emission luminance is slightly lower than that of the backlight having four light emitting diodes 20 shown in FIGS. 9 and 10. Become.
However, when the number of the light emitting diodes 20 is reduced by half, the power consumption of the backlight can be reduced, and the effect that the duration of the power supply battery in the portable electronic device can be greatly extended can be exhibited.

When the backlight structure in the modification of the eighth embodiment is employed, preferably, the two light emitting diodes 20 are arranged on the diagonal line of the first light guide plate 12 having a rectangular planar shape.
As described above, when the two light emitting diodes 20 are arranged on the diagonal line, the luminance unevenness is not generated and the in-plane uniformity of the light emission luminance is improved. The backlight according to the modified example of the eighth embodiment Demonstrate.

[Explanation of Ninth Embodiment: FIG. 11]
Next, the structure of the ninth embodiment of the backlight of the present invention will be described in detail with reference to FIGS.
FIG. 11 is a side view showing the first light guide plate and the second light guide plate in the backlight according to the ninth embodiment of the present invention.

The difference in structure between the backlight in the ninth embodiment and the backlight in the eighth embodiment is that the side shape of the first light guide plate 12 in the eighth embodiment is as shown in FIG. In contrast to the rectangular shape, in the ninth embodiment, the side surface shape of the first light guide plate 14 is a shape that is a combination of two wedges as shown in FIG. It is a point which inclines the groove 12c surface.
The structure of the backlight other than this difference is the same between the ninth embodiment and the eighth embodiment.

In the following description of the structure of the backlight in the ninth embodiment, differences from the eighth embodiment will be mainly described, and the same structures in the eighth embodiment and the ninth embodiment will be described in detail. The explanation is omitted or simplified.
In the eighth embodiment and the ninth embodiment, the same components in the backlight are denoted by the same reference numerals.

As shown in FIG. 9 and FIG. 11, the first light incident surfaces 12 a and 12 a, which are two opposite side surfaces of the first light guide plate 12, have a role of making light having a linear and uniform luminance enter each. Second light guide plates 14 and 14 are provided.
The two first light incident surfaces 12a and 12a in the first light guide plate 12 are two opposite side surfaces of the first light guide plate 12 having a substantially rectangular parallelepiped shape having six surfaces intersecting each other. .

In addition, two light emitting diodes 20 and 20 are disposed as light sources on the two second light guide plates 14 and 14, respectively.
In the backlight according to the ninth embodiment, light emitting diodes 20 and 20 are disposed on the second light incident surfaces 14a and 14a of the second light guide plates 14 and 14 facing each other.

That is, the backlight 10 of the ninth embodiment includes two second light guide plates 14 and 14 and four light emitting diodes 20, 20, 20, and 20, as shown in FIG.
As these four light emitting diodes 20, those having uniform light emission characteristics are preferably used. Further, as the light emitting diode 20, a light emitting diode that emits a white color is used.

Furthermore, the two second light guide plates 14 are provided with a second groove 14c having a sawtooth pattern.
The second groove 14c provided on the two first light incident surfaces 12a of the first light guide plate 12 on the opposite side of the surface facing each other is set so that the groove inclination angle faces the respective light emitting diodes 20 and 20. Set.

That is, the inclined surface of the upper half second groove 14c on the left side in FIG. 9 rotates the base line parallel to the X axis in the counterclockwise direction. Further, the inclined surface of the lower half second groove 14 on the left side in FIG. 9 is configured to rotate a base line parallel to the X axis in the clockwise direction.
Further, the inclined surface of the upper half second groove 14c on the right side in FIG. 9 rotates the base line parallel to the X axis in the clockwise direction. Furthermore, the inclined surface of the second groove 14 in the lower half on the right side in FIG. 9 is configured to rotate the base line parallel to the X axis in the counterclockwise direction.

The ridgeline of the second groove 14c having a triangular cross-sectional shape is disposed so as to be parallel to the Y-axis direction as shown in FIG.
The light from the light emitting diode 20 that is incident from the two second light incident surfaces 14a facing each other of the second light guide plate 14 is repeatedly transmitted by the second groove 14c inside the second light guide plate 14. The light is reflected and scattered and propagated to the entire area of the second light guide plate 14.

In the backlight according to the ninth embodiment of the present invention, linear and uniform from the two second light guide plates 14 toward the two first light incident surfaces 12a of the first light guide plate 12. It is possible to emit light with high brightness. In the backlight according to the ninth embodiment, light having a linear and uniform luminance is transmitted from the second light exit surface 14 b of the second light guide plate 14 to the first light guide plate 12. The light is incident on the light incident surface 12a. For this reason, the luminance unevenness generated in the backlight of Patent Document 2 in the region near the first light incident surface 12a does not occur in the second embodiment.
For this reason, in the ninth embodiment, it is possible to provide the backlight 10 having excellent in-plane luminance uniformity.

In the backlight of the ninth embodiment, the inclined surfaces of the second grooves 14c in the two second light guide plates 14 are set so as to face the light emitting diodes 20 as shown in FIG. As a result, light incident on the second light guide plate 14 from the light emitting diode 20 can be efficiently emitted from the second light exit surface 14b.
As a result, in the ninth embodiment, the light use efficiency is improved, and the light emission luminance of the backlight 10 is increased.

In the backlight of the ninth embodiment, the side shape of the first light guide plate 12 is different from that of the eighth embodiment shown in FIG.
That is, as shown in FIG. 11, the side shape of the first light guide plate 12 is the dimension in the Y-axis direction on the two first light incident surfaces 12 a and 12 a side, and the Z-axis direction of the first light guide plate 12. The first groove 12c surface is inclined so that the side surface shape of the first light guide plate 12 is a combination of two wedges butted together.
The inclination angle of the first groove 12c surface with respect to the Z-axis for obtaining the wedge shape is about 0.5 to 2 degrees, respectively.

When the surface of the first groove 12c is inclined in this way, the light incident on the first light guide plate 12 from the first light incident surfaces 12a and 12a is efficiently emitted from the first light emitting surface 12b. Can do.
Therefore, in the ninth embodiment, there is an effect that the light use efficiency is improved and the backlight 10 having higher light emission luminance can be obtained.

Furthermore, in the ninth embodiment, the fifth embodiment described with reference to FIG. 6 is provided on the position facing the second groove 14c or on the upper and lower surfaces which are the XZ plane of the second light guide plate 14. You may employ | adopt the structure which arrange | positions the light reflection member 26 in a form.
Thus, in the ninth embodiment, by arranging the light reflecting member 26, the light emitted from the upper surface and the lower surface of the second groove 14c and the second light guide plate 14 is transmitted to the second light guide plate. 14 can be returned to the inside.

  As described above, in the backlight 10 of the ninth embodiment described with reference to FIGS. 9 and 11, the second groove 14c is opposed to the surface, or the second light emitting surface 14b and the two second light emitting surfaces 14b. By disposing the light reflecting member 26 at positions facing the three surfaces other than the light incident surface 14b, the light use efficiency can be improved and the light emission luminance of the backlight can be increased.

In the backlight of the ninth embodiment, a configuration in which the bent pattern 12d is formed on the first light guide plate 12 as in the configuration of the third embodiment described above with reference to FIG. Good. As described above, when the configuration in which the first light guide plate 12 in the backlight of the ninth embodiment is provided with the bent pattern 12d, the first light incident surface 12a parallel to the X-axis direction is perpendicular to the first light incident surface 12a. The light emitted from the second light guide plate 14 can be incident on the first light guide plate 12.
As a result, also in the backlight of the ninth embodiment, the light having uniform directivity can be incident on the first light incident surface 12a of the first light guide plate 12 by the bent pattern 12d. Therefore, in the ninth embodiment of the present invention, it is possible to further improve the in-plane uniformity of emission luminance in the backlight.

Furthermore, in the backlight of the ninth embodiment, the light incident surface 12a and the second light guide plate 14 of the first light guide plate 12 are the same as the configuration of the fourth embodiment described above with reference to FIG. A configuration in which the bent sheet 22 is disposed between the second light exit surface 14b in FIG. As described above, when the configuration in which the bent sheet 22 is disposed between the first light guide plate 12 and the second light guide plate 14 in the backlight of the ninth embodiment, the first parallel to the X-axis direction is adopted. Light emitted from the second light guide plate 14 can be incident on the first light guide plate 12 at a right angle to the light incident surface 12a.
As a result, also in the backlight of the ninth embodiment, the bent sheet 22 allows light having uniform directivity to enter the first light guide plate 12. Therefore, in the ninth embodiment of the present invention, the effect that the in-plane uniformity of the emission luminance in the backlight can be further improved can be exhibited.

Further, in the ninth embodiment, the two second light guide plates 14 arranged on the opposite side surfaces of the first light guide plate 12 are substantially rectangular parallelepiped as in the first embodiment described with reference to FIG. A structure in which one light emitting diode 20 is disposed on one second light incident surface 14a of the second light guide plate 14 having a shape, or a wedge shape as in the sixth embodiment described with reference to FIG. A structure may be adopted in which one light emitting diode 20 is disposed on one second light incident surface 14a of the second light guide plate 14 that is provided.
Even when such a structure of the second light guide plate 14 and an arrangement structure of the light emitting diode 20 are adopted, substantially the same effects as those of the ninth embodiment described above can be obtained.

Next, a modification that modifies the ninth embodiment of the present invention in which a total of four light emitting diodes 20 are arranged will be described. As a modified example of the ninth embodiment, two first light incident surfaces 12a and 12a in the first light guide plate 12 have two roles of causing light having a linear and uniform luminance to enter. In this structure, one light emitting diode 20 is disposed on each of the second light incident surfaces 14 a and 14 a of the two light guide plates 14.
That is, in the modification of the ninth embodiment, two second light guide plates 14 and 14 and two light emitting diodes 20 and 20 are provided.

In the modification of the ninth embodiment, since there are two light emitting diodes 20, the light emitting diodes 20 are slightly compared with the backlight including the four light emitting diodes 20 in the ninth embodiment shown in FIGS. 9 and 11. , The emission luminance is lowered.
However, since the number of the light emitting diodes 20 is halved, the power consumption of the backlight can be halved and the duration of the power battery of the portable electronic device can be greatly extended. Play.

When adopting the backlight structure in the modification of the ninth embodiment, preferably, the two light emitting diodes 20 are arranged on the diagonal line of the first light guide plate 12 having a rectangular planar shape.
As described above, when the two light emitting diodes 20 are arranged on the diagonal line, the luminance unevenness is not generated and the in-plane uniformity of the light emission luminance is improved. The backlight according to the modification of the ninth embodiment Demonstrate.

[Description of the fixing structure of the reflection sheet and light guide plate to the holder]
Next, the fixing structure of the reflection sheet 18, the first light guide plate 12, and the second light guide plate 14 to the holder 24 will be described in detail with reference to FIGS. 1 and 2.
One of the holders 24 has a square tube shape with one opening and the other bottomed. The holder 24 is made of a resin material.

The reflection sheet 18 is fixed to the holder 24 by sticking the reflection sheet 18 to the bottom surface of the holder 24 using a double-sided tape having a thickness of about 0.03 mm.
The first light guide plate 12 is fixed to the holder 24 by forming a claw (not shown) in the first light guide plate 12 and forming a groove (not shown) in the holder 24 to engage with the claw. And by engaging the claw and the groove.

The second light guide plate 14 is fixed to the holder 24 in the Y-axis direction between the second light exit surface 14b of the second light guide plate 14 and the first light incident surface 12a of the first light guide plate 12. Use double-sided tape to match the height.
Further, the prism sheet 16 is placed on the first light emitting surface 12b of the first light guide plate 12, and the peripheral edge of the prism sheet 16 is formed by a rim sheet (not shown) from the light emitting surface side of the prism sheet 16. , Fix to press.

It is a top view which shows the backlight in embodiment of this invention. It is the side view which showed the backlight in embodiment of this invention, and fractured | ruptured partially. It is a top view which shows the 1st light guide plate, the 2nd light guide plate, and a light emitting diode among the backlights in embodiment of this invention. It is a top view which shows the 1st light guide plate, the 2nd light guide plate, and a light emitting diode among the backlights in embodiment of this invention. It is a top view which shows the 1st light guide plate, the 2nd light guide plate, and a light emitting diode among the backlights in embodiment of this invention. It is a top view which shows the 1st light guide plate, the 2nd light guide plate, and a light emitting diode among the backlights in embodiment of this invention. It is a top view which shows the 1st light guide plate, the 2nd light guide plate, and a light emitting diode among the backlights in embodiment of this invention. It is a top view which shows the 1st light guide plate, the 2nd light guide plate, and a light emitting diode among the backlights in embodiment of this invention. It is a top view which shows the 1st light guide plate, the 2nd light guide plate, and a light emitting diode among the backlights in embodiment of this invention. It is a side view which shows the backlight in embodiment of this invention. It is a side view which shows the backlight in embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Backlight 12 1st light-guide plate 14 2nd light-guide plate 16 Prism sheet 18 Reflective sheet 20 Light emitting diode 22 Bending sheet 24 Holder 26 Light reflection member

Claims (7)

A first light guide plate and a second light guide plate that have a substantially rectangular parallelepiped shape and are disposed so that the side surfaces face each other, a prism sheet disposed on the upper surface side of the first light guide plate, and the first light guide plate A reflection sheet disposed on the lower surface side of the light plate, and a light emitting diode as a light source,
The second light guide plate has a second light incident surface on which light emitted from the light emitting diode is incident, and a second light that is incident on the second light incident surface and is emitted to the first light guide plate. A light exit surface, and a second groove provided on a surface facing the second light exit surface,
The first light guide plate emits a first light incident surface on which light emitted from the second light exit surface of the second light guide plate is incident, and light incident from the first light incident surface. A first light exit surface and a first groove provided on a surface facing the first light exit surface;
The prism sheet has a prism that corrects the directivity of light emitted from the first light exit surface;
The reflection sheet has a reflection surface that returns light emitted from the first light guide plate to the first light guide plate. The backlight according to claim 1, wherein the second light guide plate has the light emitting diodes disposed on two opposite sides. The backlight according to claim 1, wherein a bent pattern is provided on the first light incident surface of the first light guide plate. The bent sheet is disposed between the first light incident surface of the first light guide plate and the second light output surface of the second light guide plate. The backlight according to any one of 2. The backlight according to claim 1, wherein a light reflecting member is disposed so as to face the second groove of the second light guide plate. The backlight according to any one of claims 1 to 5, wherein the second light guide plate is disposed on two opposing sides of the first light guide plate. The backlight according to claim 1, further comprising a holder that surrounds the first light guide plate, the second light guide plate, the prism sheet, and the reflection sheet.

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