JP2000275443A - Light guide plate, surface light source device, and liquid- crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide plate capable of preventing generation of luminescent lines without using a diffusion sheet. SOLUTION: A plurality of grooves 17 of approximately rectangular cross section are formed on one side face 3 of a light guide plate 2 and a plurality of first middle edges 20 and a plurality of second middle edges 21 are formed between both incident surface part side edges 16, 18. Thus, light rays 28, 29 approximately parallel to a light ray 24 impinging on the incident surface part side edge 18 of a lower surface 6 impinge on the second middle edges 21, and light rays 30, 31 approximately parallel to a light ray 23 impinging on the incident surface part side edges 16 of an upper surface 8 impinge on the first middle edges 20, so that light rays 23a, 24a, 28a, 29a, 30a, 31a of light brightness level are densely emitted near the fluorescent lamp 4 side of the light guide plate 2, with the emitted light rays affecting one another and reducing variations in brightness curve so as to make luminescent lines inconspicuous.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device used for a portable personal computer or the like, a surface light source device for illuminating a liquid crystal display panel of the liquid crystal display device, and a light guide plate constituting the surface light source device. .

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 13, a liquid crystal display device used for a portable personal computer or the like has a thin light guide plate 40 made of a light transmitting resin material such as polymethyl methacrylate (PMMA). And a light source (for example, a fluorescent lamp) 4 arranged to face the side surface 41 of the light guide plate 40.
2 and a reflection sheet 44 disposed on the lower surface 43 side of the light guide plate 40. Then, the surface light source device 45 constituting the liquid crystal display device takes in the light emitted from the light source 42 into the inside of the light guide plate 40 from the side surface 41 of the light guide plate 40, and takes the taken-in light into the upper surface of the light guide plate 40 (emission surface). The light is emitted from the surface (surface) 46 via a diffusion sheet 48 in a planar shape, and illuminates a liquid crystal display panel (not shown) disposed opposite to the upper surface 46 of the light guide plate 40.

In recent years, a surface light source device 45 constituting a liquid crystal display device as shown in FIG. 13 has a light guide plate as a basic component thereof in response to demands for miniaturization and weight reduction and improvement of display quality. 40 are variously devised.

For example, a surface light source device 45 shown in FIG.
Is formed at a fine pitch on the side surface 41 of the light guide plate 40 facing the light source 42 at a fine pitch so as to extend in the longitudinal direction of the side surface 41 at a fine pitch. Increasing the amount of light, the light guide plate 40
The amount of light emitted from the upper surface (emission surface) 46 of the light emitting device is increased to achieve high brightness (Japanese Patent Laid-Open No. 8-152262).
No. 5).

[0005] A surface light source device 50 shown in FIG.
A convex portion 54 having a substantially triangular cross section extending in a direction orthogonal to the longitudinal direction of the side surface 53 is continuously formed along the longitudinal direction of the side surface 53, and the light diffused by the convex portion 54 is taken into the light guide plate 52. The emitted light is emitted through the semi-transmissive diffusion sheet 56 arranged on the emission surface 55 of the light guide plate 52, thereby preventing the appearance of a bright line on the light source side end emission surface 55 of the light guide plate 52. In addition, the display quality is improved (see Japanese Patent Application Laid-Open No. 9-145936).

The bright line is a line of bright light generated several lines near the light source side end of the light exit surface 55 of the light guide plate 52.
Emission surface (upper surface) 55 and reflection surface (lower surface) 57 of light guide plate 52
Caused by light incident from the edge on the light source side. When the liquid crystal display panel (not shown) is illuminated by using the light guide plate 52 in which the bright line is generated, the brightness around the bright line is low, so that it becomes difficult to read the display image of the liquid crystal display panel around the bright line. Therefore, in the conventional surface light source device, the one that cannot prevent the generation of the bright line is used while avoiding the portion of the light guide plate where the bright line is generated. It is known that the ratio of the area of the exit surface excluding the emission line generating portion) is small.
For this reason, the second conventional example shown in FIG.
The light guide plate 52 can be downsized, and can meet the demands for downsizing, weight reduction and display quality improvement.

[0007]

However, as described above, in the second conventional example, the projection 54 formed on the light source side surface 53 of the light guide plate 52 and the diffusion sheet disposed on the emission surface 55 of the light guide plate 52. Since the light is diffused twice with the light guide 56 to prevent the appearance of bright lines on the light source side emission surface 55 of the light guide plate 52, when the diffusion sheet 56 is removed and used, The effect of preventing the generation of bright lines was insufficient. Therefore, even when the diffusion sheet 56 is not disposed on the emission surface 55 of the light guide plate 52, the light guide plate 52, the surface light source device 50 including the light guide plate 52, and the surface light source including the light guide plate 52 can effectively make the bright lines inconspicuous. It has been desired to provide a liquid crystal display device including the device 50.

The first conventional example shown in FIG. 13 can meet the demand for improvement of display quality in that high brightness can be achieved. No ingenuity has been achieved. Therefore, in order to make the bright lines inconspicuous in the first conventional example, the diffusion sheet 48 must be used at least as in the second conventional example.

Accordingly, an object of the present invention is to provide a light guide plate which can meet the above-mentioned demands, a surface light source device provided with the light guide plate, and a liquid crystal display device provided with the surface light source device. .

[0010]

According to a first aspect of the present invention, there is provided a light incident surface for receiving light, an exit surface for emitting light in a plane substantially perpendicular to the light incident surface, and a side opposite to the light exit surface. And a reflective surface portion substantially orthogonal to the light incident surface portion,
The present invention relates to a light guide plate formed entirely in a thin plate shape.
In the invention according to claim 1, the light incident surface portion has a first intermediate edge having substantially the same shape as the light incident surface portion side edge of the emission surface portion, and a substantially same shape as the light incident surface portion side edge of the reflection surface portion. At least one pair of the second intermediate edge is formed along the thickness direction of the light guide plate.

According to the first aspect of the present invention, light substantially parallel to light entering the light guide plate from the light incident surface side edge of the light exit surface portion enters the light guide plate from the first intermediate edge. At the same time, light that is substantially parallel to light that enters the light guide plate from the light incident surface side edge of the reflection surface portion enters the light guide plate from the second intermediate edge. As a result, a plurality of lights having a high luminance level are emitted from the vicinity of the light-incident surface side of the light-exiting surface portion, and the emitted lights affect each other to make the luminance level uniform, so that the bright line becomes inconspicuous. Therefore, according to the light guide plate of the present invention, it is possible to effectively use the entire area of the emission surface as a planar light source without using a diffusion sheet.

According to a second aspect of the present invention, there is provided a light incident surface portion for receiving light, an exit surface portion for emitting light in a planar shape substantially perpendicular to the light incident surface portion, and the light incident surface portion being located on the opposite side of the light exit surface portion. The present invention relates to a light guide plate including a reflection surface portion substantially orthogonal to a light surface portion and formed entirely in a thin plate shape. In the invention according to claim 2, the light incident surface portion is substantially parallel to a plane substantially perpendicular to the light exit surface portion, and substantially parallel to the light incident surface portion side edge of the light exit surface portion. At least one groove having a substantially rectangular cross section having a bottom surface is formed.

According to the second aspect of the present invention, the edge of the groove having a substantially rectangular cross section has the same shape as the light incident surface side edge of the light exit surface portion or the light incident surface side edge of the reflection surface portion. The edges have substantially the same shape, and function as the first intermediate edge or the second intermediate edge of the first aspect. Further, according to the invention of claim 2, the bottom surface of the groove is parallel to the plane of the light incident surface portion,
The bottom surface and the flat surface function as a light incident surface, and a light incident area approximately equal to that when no groove is formed in the light incident surface portion can be secured. Therefore, it is possible to prevent the generation of a bright line without significantly lowering the light incident efficiency.

According to a third aspect of the present invention, there is provided a light-entering surface portion for receiving light, an emission surface portion for emitting light in a plane substantially perpendicular to the light-entering surface portion, The present invention relates to a light guide plate including a reflection surface portion substantially orthogonal to a light surface portion and formed entirely in a thin plate shape. Further, in the invention according to claim 3, the light incident surface portion has a top surface substantially parallel to an edge portion between the light incident surface portion and the reflection surface portion on a plane substantially orthogonal to the incident light. It is characterized in that at least one rectangular projection is formed.

According to the third aspect of the present invention, the edge of the projection having a substantially rectangular cross section has the same shape as the light incident surface side edge of the light emitting surface or the light incident surface side edge of the reflective surface portion. The edges have substantially the same shape, and function as the first intermediate edge or the second intermediate edge of the first aspect. According to the third aspect of the present invention, the top surface of the projection is parallel to the plane of the light incident surface portion, and the top surface and the flat surface function as a light incident surface, and are substantially equivalent to the case where no projection is formed on the light incident surface portion. Since the light incident area can be secured, it is possible to prevent the generation of the bright line without significantly lowering the light incident efficiency.

According to a fourth aspect of the present invention, there is provided the light guide plate according to any one of the first to third aspects, and a light source disposed at a portion of the light guide plate facing the light incident surface. And a surface light source device.

Since the surface light source device having such a configuration includes a light guide plate capable of preventing the generation of bright lines, it is possible to reduce the size and weight of the light guide plate and to improve display quality. Becomes possible.

According to a fifth aspect of the present invention, there is provided the light guide plate according to the second aspect, and a light source provided on a center line bisecting the light guide plate in a thickness direction and at a position facing the light incident surface portion of the light guide plate. This is a surface light source device. The light guide plate has a dimension from the light incident surface portion side edge of the light emitting surface portion to the groove, the groove width dimension, a dimension between the grooves, and the light incident surface portion side edge of the reflection surface portion. It is characterized in that the dimensions up to the groove are substantially the same.

According to the present invention having such a configuration, light that is substantially parallel to light incident at an equal interval from the light incident surface side edge of the light exit surface portion is incident from the edge of the groove. Further, light that is substantially parallel to light incident from the light incident surface portion side edge of the reflection surface portion and is equally spaced is incident from an edge of the groove. As a result, light having the same brightness level is emitted from the emission surface at substantially equal intervals, and the bright line becomes less noticeable.

According to a sixth aspect of the present invention, there is provided the light guide plate according to the third aspect, and a light source provided at a position on a center line bisecting the light guide plate in a thickness direction and facing the light entrance surface of the light guide plate. This is a surface light source device. The light guide plate has a dimension from the light incident surface portion side edge to the protrusion of the emission surface portion, the protrusion width dimension, a size between the protrusions, and the light incident surface portion side edge of the reflection surface portion. It is characterized in that the dimensions up to the projection are substantially the same.

According to the present invention having such a configuration, light at an equal interval in parallel with light incident from the light entrance surface side edge of the exit surface portion is incident from the edge of the projection. Further, light that is parallel to light incident from the edge of the reflection surface portion on the light incident surface portion and is equally spaced is incident from the edge of the protrusion. As a result, light having the same brightness level is emitted from the emission surface at substantially equal intervals, and the bright line becomes less noticeable.

According to a seventh aspect of the present invention, the light guide plate is formed symmetrically with respect to a center line that bisects the light guide plate in the thickness direction. The present invention relates to the surface light source device described in the above section.

According to the present invention having such a configuration, the light incident from the light incident surface side edge of the light exit surface, the incident light substantially parallel to the light, and the light incident surface side of the reflective surface are provided. Since the light incident from the edge and the incident light substantially parallel to this light are repeatedly emitted and totally reflected symmetrically with respect to a center line bisecting the light guide plate in the thickness direction, for example, only the reflection surface portion It is easier to prevent the generation of bright lines as compared with the case where a light guide plate having a wedge shape is used by tilting the light guide plate. That is, the light guide plate in which only the reflection surface portion is inclined and formed into a wedge shape has an output light component of light incident from the light entrance surface side edge of the output surface portion and an output light component of light incident from the light entrance surface side edge of the reflection surface portion. Since the interval becomes narrower than in the case of the present invention and the luminance level between these emitted light components becomes too high, it becomes more difficult to prevent the occurrence of a bright line than in the present invention.

According to an eighth aspect of the present invention, the surface light source device according to any one of the fourth to seventh aspects is disposed so as to face an emission surface portion of the light guide plate constituting the surface light source device. A liquid crystal display device comprising a liquid crystal display panel.

According to the eighth aspect of the present invention, since the surface light source device is reduced in size and weight and the display quality is improved, the overall size of the liquid crystal display device can be reduced. The weight can be reduced, and the display quality of the liquid crystal display device can be improved.

[0026]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) As shown in FIGS. 1 and 2, a surface light source device 1 according to
The light guide plate 2 has a thin plate shape and is formed of a light-transmitting resin material such as the above. A rod-shaped fluorescent lamp (light source) 4 faces one side surface (light incident surface portion) 3 of the light guide plate 2. Are arranged as follows. In the surface light source device 1, the fluorescent lamp 4 is accommodated in a reflective member 5 that opens toward one side surface 3 of the light guide plate 2, and the light emitted from the fluorescent lamp 4 is reflected by the reflective member 5. The light emitted from the fluorescent lamp 4 is incident on the entire surface of the one side surface 3 of the light guide plate 2. In the surface light source device 1, a reflection sheet 7 facing the lower surface 6 of the light guide plate 2 is arranged on the lower surface (reflection surface portion) 6 side of the light guide plate 2. Further, the surface light source device 1
On the upper surface (emission surface portion) 8 of the light guide plate 2, a downward facing prism sheet 10 is disposed so as to face the upper surface 8 of the light guide plate 2. A liquid crystal display panel 11 is arranged on the upper surface 8 side of the prism sheet 10 so as to face the prism sheet 10. The liquid crystal display panel 11 and the surface light source device 1 constitute a liquid crystal display device 12. It has become so. In addition, all the side surfaces 13, 14, and 15 except one side surface 3 of the light guide plate 2 face a not-shown highly reflective frame or the like.

As shown in FIGS. 1 to 5, the light guide plate 2 is formed such that the upper surface 8 and the lower surface 6 are substantially perpendicular to one side surface 3, respectively. On one side surface 3 of the light guide plate 2, a groove 17 having a substantially rectangular cross section extending in a direction substantially parallel to one side surface edge (the light incident surface portion side edge of the upper surface) 16 of the upper surface 8 is provided. 2 are formed along the thickness direction. Here, as shown in FIG. 3, the one side surface 3 has a dimension L1 of a plane 3a from the light entrance surface side edge 16 of the upper surface 8 to the groove 17, a width dimension L2 of the groove 17, a groove 17,
17, the dimension L3 of the plane 3b from the one side surface edge (edge of the lower surface of the light incident surface portion) 18 of the lower surface 6 to the groove 17 is substantially the same. Further, the light guide plate 2 is formed so as to be vertically symmetric with respect to the center line C in the thickness direction.

As described above, a groove 17 having a substantially rectangular cross section is formed on one side surface 3 of the light guide plate 2, so that the light incident surface portion side edge 16 of the upper surface 8 and the light incident surface portion side of the lower surface 6 are formed. Between the edge 18 and the light incident surface side edge 16 of the upper surface 8
A plurality of first intermediate edges 20 having substantially the same shape as the first and second intermediate edges 21 having substantially the same shape as the light incident surface side edge 18 of the lower surface 6 are formed alternately. The light guide plate 2
Are formed by injection molding, and the light-incident surface-side edge 16 of the upper surface 8, the light-incident surface-side edge 18 of the lower surface 6, the first intermediate edge 20, and the second intermediate edge 21 are formed from the relationship of transferability. The corner R dimensions are substantially the same.

The surface light source device 1 according to the present embodiment having the above-described configuration transmits the light emitted from the fluorescent lamp 4 to the light guide plate 2.
The light is introduced into the light guide plate 2 from one side surface 3 of the light guide plate 2 and propagated while repeatedly causing total reflection inside the light guide plate 2. By emitting the light to the outside, the fluorescent lamp 4
Is emitted from the entire upper surface 8 of the light guide plate 2 in a planar manner. The surface light source device 1 illuminates the liquid crystal display panel 11 via a downwardly facing prism sheet 10 disposed on the upper surface 8 of the light guide plate 2. The prism sheet 10 is formed of a translucent material such as polycarbonate, and has a projection 22 having a substantially triangular cross section over the entire lower surface (the surface facing the upper surface 8 of the light guide plate 2). The protrusions 22 of the prism sheet 10 extend in a direction substantially parallel to the light incident surface (one side surface 3) of the light guide plate 2, and are formed continuously toward the other side surface 14 of the light guide plate 2. The light guide plate 2 functions as a prism that corrects the direction of light emitted from the upper surface 8 of the light guide plate 2 in a direction orthogonal to the upper surface 8.

Here, generally, the surface light source device includes a frame or the like on one of the upper surface 8 and the lower surface 6 of the light guide plate 2 in order to prevent light from entering the light guide plate 2 from a portion other than the one side surface 3. Surface contact is made along the edge on the side surface 3 side. However, due to the transferability when the light guide plate 2 is injection-molded, the incident surface side edge 16 of the upper surface 8 and the incident surface side edge 18 of the lower surface of the light guide plate 2 are rounded. The light emitted from the fluorescent lamp wraps around the two incident surface side edges 16 and 18, and light also enters from both the incident surface side edges 16 and 18. The light incident from both the incident surface side edges 16 and 18 behaves differently from the light incident from the one side surface 3,
It causes the emission line.

That is, as shown in FIG. 6, the light 23, 24 incident from both the light incident surface side edges 18, 16 has a larger inclination angle θ with respect to the upper surface 8 than the light incident from one side surface 3, so that the light is guided. The light is easily emitted from the upper surface 8 of the light plate 2 near the fluorescent lamp 4. In the figure, arrows 23a, 24a, and 24b indicate light 23, 24 incident on light incident surface side edges 16, 18, respectively.
24 outgoing light components. In such a case, as shown in the brightness curve of FIG. 6, the upper surface 8 of the light guide plate 2 near the fluorescent lamp 4 has high brightness levels (bright lines) 2 at substantially constant intervals.
5, 26 and 27 occur. In addition, the light 23, 24 incident from the light incident surface side edges 18, 16 decreases in the amount of emitted light as it goes away from one side surface (light incident surface) 3 of the light guide plate 2, so that the fluorescence of the light guide plate 2 is reduced. When it is away from the vicinity of the lamp 4, no bright line is generated.

However, in the surface light source device 1 according to the present embodiment, as described above, a plurality of grooves 17 having a substantially rectangular cross section are formed on one side surface 3 of the light guide plate 2, and both light incident surface side edges 1 are formed.
First intermediate edge 20 and second intermediate edge 2 between 6, 18
7, a plurality of lights 28 and 29 substantially parallel to the light 24 incident from the light incident surface side edge 18 of the lower surface 6 enter from the second intermediate edge 21 and the upper surface as shown in FIG. Light 23 incident from the light incident surface side edge 16 of FIG.
Light 30 and 31 which are substantially parallel to the incident light from the first intermediate edge 20, and light beams 23 a, 24 a, 28 a, 29 a, 30 a and 31 a having a high luminance level are provided near the fluorescent lamp 4 side of the light guide plate 2.
Are emitted densely, and the respective emitted lights influence each other, so that the change in the brightness curve is reduced and the bright line becomes inconspicuous.

Further, the surface light source device 1 of the present embodiment is similar to that of FIG.
As shown in FIG. 1, one side surface 3 of the light guide plate 2 is a plane substantially orthogonal to the upper surface 8 as an emission surface, and a substantially rectangular groove 17 is formed in this plane. Flat portions (3a, 3b, 3c) of side surface 3 and bottom surface 17 of groove 17
a are substantially parallel to each other, and the plane portions (3a, 3b, 3c) and the bottom surface 17a of the groove 17 serve as a light incident surface. Therefore, the surface light source device 1 of the present embodiment has the groove 1 on one side surface 3 of the light guide plate 2.
Compared to the case of FIG. 6 in which 7 is not formed, the area of the light incident surface is substantially the same, and the generation of the bright line can be prevented without significantly lowering the light incident efficiency.

Here, the surface light source device 1 according to the present embodiment
As an example of the design, the thickness of the light guide plate 2 is 2 to 3 mm.
In the case of, L1, L2, L3, and L4 in FIG.
0.5 mm, each edge 16, 18, 20, 21 has a corner R shape of 0.02 to 0.1 mm, and the depth D of the groove 17 is about 0.02 to 0.1 mm. As described above, it is possible to effectively prevent the generation of the bright line without significantly lowering the light entrance efficiency.

As described above, in the present embodiment, the light guide plate 2
Of light 2 incident from the upper and lower light entrance surface side edges 16 and 18
The bright lines originating from the first and second intermediate edges 20 and 21 are reflected by the light beams 30, 31, 28 and 2,
9, the light guide plate 2, the reflection sheet 7, and the prism sheet 10 can be reduced in size because the entire upper surface 8 of the light guide plate 2 can be effectively used as a surface light source.
The weight can be reduced, and the display quality can be improved.

(Second Embodiment) As shown in FIG. 8, a surface light source device 1 according to a second embodiment of the present invention has a cross section instead of the groove 17 of the first embodiment. A plurality of substantially rectangular projections 32 are formed on one side surface 3 of the light guide plate 2. The protrusions 32 extend in a direction substantially parallel to the light entrance surface side edge 16 of the upper surface 8 and are formed at regular intervals along the thickness direction of the light guide plate 2. here,
One side surface 3 of the light guide plate 2 has a dimension L1 of a plane 3a from the light entrance surface side edge 16 of the upper surface 8 to the projection 32, and the projection 3
2, the dimension L3 of the plane 3b between the projections 32, 32, and the dimension L4 of the plane 3c from the light incident surface side edge 18 of the lower surface 6 to the projection 32 are formed to be substantially the same. The light guide plate 2 is formed so as to be vertically symmetrical with respect to a center line C in the thickness direction of the light guide plate 2. In addition, protrusion 3
2 is the depth D of the groove 17 of the first embodiment.
The dimensions are substantially the same as

As described above, the surface light source device 1 according to the present embodiment, in which the protrusion 32 having a substantially rectangular cross section is formed on one side surface 3 of the light guide plate 2, is similar to the first embodiment. A first intermediate edge 20 having substantially the same shape as the light incident surface portion side edge 16 of the upper surface 8 and a light incident surface of the lower surface 6 between the light incident surface portion side edge 16 of the upper surface 8 and the light incident surface side edge 18 of the lower surface 6. A plurality of light-surface-side edges 18 and second intermediate edges 21 having substantially the same shape are alternately formed. The light guide plate 2 of this embodiment is formed by injection molding as in the case of the first embodiment. 6, the light incident surface side edge 18,
The first intermediate edge 20 and the second intermediate edge 21 have substantially the same corner R dimension. Then, the top surface 32a of the projection 32 having a rectangular cross section and the flat portion (3a, 3
b, 3c) are positioned substantially parallel to each other, and the top surface 32a and the plane portions (3a, 3b, 3c) function as light incident surfaces.

In the surface light source device 1 of this embodiment having the above-described configuration, similarly to the first embodiment, the light substantially parallel to the light incident from the light incident surface side edge 18 of the lower surface 6 is formed. Light that is incident from the second intermediate edge 21 and that is substantially parallel to the light incident from the light incident surface side edge 16 of the upper surface 8 is incident from the first intermediate edge 20, and the luminance level is set near the fluorescent lamp 4 side of the light guide plate 2. Will be emitted densely, each emitted light will affect each other and the change in the brightness curve will be reduced,
The bright line becomes inconspicuous (see FIG. 7). Therefore, the surface light source device 1 of the present embodiment can obtain the same effects as those of the first embodiment.

(Third Embodiment) As shown in FIG. 9, a surface light source device 1 according to a third embodiment of the present invention replaces the rectangular projections 32 of the second embodiment. In addition, a plurality of protrusions 33 having a substantially semicircular cross section are formed on one side surface 3 of the light guide plate 2. The protrusions 33 extend in a direction substantially parallel to the light incident surface side edge 16 of the upper surface 8, are formed at a constant interval L along the thickness direction of the light guide plate 2, and are formed from the protrusions 33. The dimension L1 from the projection 33 to the light entrance surface side edge 18 of the upper surface 8 and the dimension L4 from the projection 33 to the light entrance surface side edge 18 of the lower surface 6 are formed to be equal to the dimension L between the projections 33. As a result, one side surface 3 of the light guide plate 2 is vertically symmetrical with respect to the center line C in the thickness direction of the light guide plate 2.

In the surface light source device 1 according to the present embodiment configured as described above, the protrusion 33 having a substantially semicircular cross section formed on one side surface 3 of the light guide plate 2 is provided on the light incident surface side edge of the upper surface 8. 16 and a second intermediate edge 21 having substantially the same shape as the light incident surface side edge 18 of the lower surface 6.
And the shape is combined. As a result, the surface light source device 1 of the present embodiment has the light entrance surface side edge 1 of the upper surface 8.
The first intermediate edge 2 having substantially the same shape as the light incident surface portion side edge 16 of the upper surface 8 between the light incident surface portion side edge 18 of the lower surface 6 and the lower surface 6.
0 and a plurality of second intermediate edges 21 having substantially the same shape as the light incident surface side edge 18 of the lower surface 6 are formed alternately. Note that the light guide plate 2 of the present embodiment includes the first and second light guide plates.
In the same manner as in the embodiment, it is formed by injection molding.
6 and the lower surface 6 of the light incident surface portion side edge 18 are formed to have substantially the same corner R dimension, and the projection 33 is formed on both light incident surface portion side edges 1.
The radii have substantially the same dimensions as the corners R of the sixth and the eighth corners.

The surface light source device 1 of the present embodiment having the above-described structure is similar to the first and second embodiments.
The light substantially parallel to the light incident from the light incident surface side edge 18 of the lower surface 6 is incident from the protrusion 33, and the light substantially parallel to the light incident from the light incident surface side edge 16 of the upper surface 8 is incident from the protrusion 33. Light rays having a high luminance level are densely emitted near the fluorescent lamp side of the light guide plate 2, and the emitted light influences each other, so that the change in the luminance curve is reduced and the bright line becomes inconspicuous. Therefore, the surface light source device 1 of the present embodiment can obtain the same effects as those of the first and second embodiments.

(Fourth Embodiment) In each of the above embodiments, one side surface 3 and the upper surface 8 are orthogonal to each other, and
And the lower surface 6 are perpendicular to each other. However, the present invention is not limited to this. As shown in FIGS. 10 and 11, the intersection angle φ1 between the one side surface 3 and the upper surface 8 and the intersection angle φ2 between the one side surface 3 and the lower surface 6 are determined. As shown in FIG. 12, the intersection angle φ3 between the one side surface 3 and the lower surface 6 is made slightly smaller than 90 degrees, and the light guide plate 2 becomes thinner as the distance from the fluorescent lamp 4 increases. Thus, the light guide plate 2 may be formed in a wedge shape.

However, the embodiment shown in FIGS. 10 and 11 is more preferable than the embodiment shown in FIG. 12 because it has a greater effect of preventing bright lines from occurring than the embodiment shown in FIG.
The present embodiment shown in FIG. 10 and FIG.
Is formed symmetrically with respect to a center line C that bisects the sheet in the thickness direction. The center of the fluorescent lamp 4 is the light guide plate 2.
Are arranged on a center line C that bisects the sheet in the thickness direction.

That is, in the case shown in FIG. 12, the outgoing light component 24a of the incident light 24 from the light incident surface side edge 18 of the lower surface 6
The distance from the light incident surface side edge 16 of the upper surface 8 to the outgoing light component 23a of the incident light 23 is shorter than in the case shown in FIG. 11, and the outgoing light components 24a, 24a,
This is because the luminance level between the light-emitting portions 23a is increased, and thus, luminance unevenness is likely to occur between the light-incident surface side edge 16 of the upper surface 8 and the light-emitting component 24a and between the light-emitting components 24a and 23a.

Here, in the present invention, the expression that the upper surface 8 is substantially perpendicular to the one side surface 3 means that the intersection angle φ1 between the one side surface 3 and the upper surface 8 is slightly smaller than 90 degrees as in this embodiment. This also includes the case where the intersection angles φ2 and φ3 between the one side surface 3 and the lower surface 6 are slightly smaller than 90 degrees.

It should be noted that the present invention is not limited to the above-described embodiments, and that the grooves 17 and the projections 32 and 33 are formed at an irregular pitch, the width dimension of the groove 17 and the width of the projection 32 are not limited. The dimensions may be changed as appropriate. Also, the groove 17 and the projection 3
The number of 2, 33 can be appropriately changed according to design conditions and the like. The cross-sectional shape of the groove 17 and the projection 32 is
Any shape may be used as long as an intermediate edge having substantially the same shape as the light incident surface portion side edge 16 and the light incident surface portion side edge 18 of the lower surface 6 is formed, for example, a trapezoidal shape. That is, in carrying out the present invention, the specific form can be appropriately changed within a range that does not impair the object of the present invention, depending on the degree of the bright line generated near the light incident surface portion and the allowable range thereof. . Further, in each of the above-described embodiments, the configuration in which the fluorescent lamp 4 is arranged so as to face the one side surface 3 is shown. However, the present invention is not limited to this, and the fluorescent lamp 4 may be appropriately arranged so as to face the other side surfaces 13, 14 and 15. The lamps 4 are arranged and these side surfaces 13, 1
By forming the groove 17 and the projections 32 and 33 in the fourth and fourth surfaces 15, the generation of bright lines near each side surface may be prevented.

[0048]

As described above, the light guide plate of the present invention has the first intermediate edge having substantially the same shape as the light incident surface side edge of the light exit surface portion, and the light guide plate having the substantially same shape as the light incident surface portion side edge of the reflection surface portion. Since at least one pair of the second intermediate edge and the light incident surface portion are formed on the light incident surface portion, light substantially parallel to light incident on the light incident surface portion side edge of the light exit surface portion into the inside of the light guide plate is transmitted from the first intermediate edge to the inside of the light guide plate. And light substantially parallel to the light entering the inside of the light guide plate from the light incident surface side edge of the reflection surface portion enters the light guide plate inside from the second intermediate edge. As a result, in the light guide plate of the present invention, a plurality of lights having a high luminance level are emitted from the vicinity of the light incident surface side of the light outgoing surface portion, and these emitted lights influence each other to make the luminance level uniform, so that the bright line is conspicuous. Disappears. Therefore, the light guide plate of the present invention can effectively use the entire area of the emission surface as a planar light source without using a diffusion sheet, and can eliminate an unused area of the emission surface. It is possible to reduce the weight and weight and improve the display quality. Further, the surface light source device and the liquid crystal display device using such a light guide plate can be reduced in size and weight and improved in display quality.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a surface light source device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the surface light source device taken along line AA of FIG. FIG. 2A is an overall sectional view, and FIG.
FIG. 2B is an enlarged sectional view of a portion B in FIG.

FIG. 3 is an enlarged view of a light incident surface of the light guide plate according to the first embodiment of the present invention.

FIG. 4 is an external perspective view of the light guide plate.

FIG. 5 is an enlarged view of a portion E in FIG. 4;

FIG. 6 is a light emission state diagram of a light guide plate that easily generates a bright line.

FIG. 7 is a light emission state diagram of the light guide plate according to the first embodiment of the present invention.

FIG. 8 is an enlarged view of a light incident surface of a light guide plate according to a second embodiment of the present invention.

FIG. 9 is an enlarged view of a light incident surface of a light guide plate according to a third embodiment of the present invention.

FIG. 10 is a sectional view of a surface light source device according to a fourth embodiment of the present invention.

FIG. 11 is a light emission state diagram of the same surface light source device.

FIG. 12 is a light emission state diagram showing another example of the same surface light source device.

FIG. 13 is a sectional view of a surface light source device showing a first conventional example.

FIG. 14 is a surface light source device showing a second conventional example. FIG.
4A is a plan view, and FIG. 14B is a side view.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Surface light source device, 2 ... Light guide plate, 3 ... One side surface (light entrance surface), 3a, 3b, 3c ... Plane, 4 ... Fluorescent lamp (light source), 6 ... Lower surface (reflection surface part) ), 8 ... top surface (outgoing surface portion), 11 ... liquid crystal display panel, 12 ... liquid crystal display device, 16, 17 ... groove, 17a ... bottom surface, 18 ...
... Light incident surface side edge, 20... First intermediate edge, 21.
... Second intermediate edge, 32, 33... Protrusion, 32a.

Claims (8)

[Claims] A light-receiving surface for receiving light; an emission surface for emitting light in a plane substantially perpendicular to the light-entering surface; and a light-receiving surface located opposite to the light-emitting surface and substantially perpendicular to the light-receiving surface. A light guide plate, the entire surface of which is formed in a thin plate shape, wherein the light incident surface portion has a first intermediate edge having substantially the same shape as a light incident surface side edge of the light exit surface portion, and a light incident surface of the reflection surface portion. A light guide plate, wherein at least one pair of a light surface side edge and a second intermediate edge having substantially the same shape is formed along the thickness direction of the light guide plate. 2. A light incident surface portion for receiving light, an emission surface portion for emitting light in a plane substantially perpendicular to the light incident surface portion, and located on a side opposite to the light exit surface portion and substantially perpendicular to the light incident surface portion. A light guide plate having a thin plate shape as a whole, wherein the light incident surface is substantially parallel to the plane and substantially parallel to the light exit surface, and the light incident on the light exit surface. A light guide plate, wherein at least one groove having a substantially rectangular cross section having a bottom surface substantially parallel to a surface side edge is formed. 3. A light-entering surface for taking in light, an output surface for emitting light in a plane substantially perpendicular to the light-entering surface, and an opposite side of the light-exiting surface and substantially perpendicular to the light-entering surface. A light guide plate having a thin plate shape as a whole, wherein the light incident surface is substantially parallel to the plane and substantially parallel to the light exit surface, and the light incident on the light exit surface. A light guide plate, wherein one or more protrusions having a substantially rectangular cross section having a top surface substantially parallel to a surface side edge are formed. 4. A surface light source device comprising: the light guide plate according to claim 1; and a light source disposed at a portion of the light guide plate facing the light incident surface. . 5. A surface light source device comprising: the light guide plate according to claim 2; and a light source at a position on a center line that bisects the light guide plate in a thickness direction and at a position facing the light incident surface portion of the light guide plate. The light guide plate may have a dimension from the light incident surface portion side edge of the light emitting surface portion to the groove, the groove width dimension, a dimension between the grooves, and the light incident surface portion side edge of the reflection surface portion. A surface light source device characterized in that dimensions up to a groove are substantially the same. 6. A surface light source device comprising: the light guide plate according to claim 3; and a light source at a position on a center line that bisects the light guide plate in a thickness direction and at a position facing the light incident surface portion of the light guide plate. The light guide plate may have a dimension from the light incident surface portion side edge of the light emitting surface portion to the protrusion, a width of the protrusion, a dimension between the protrusions, and the light incident surface portion side edge of the reflective surface portion. A surface light source device characterized in that dimensions up to a protrusion are substantially the same. 7. The surface according to claim 4, wherein the light guide plate is formed symmetrically with respect to a center line bisecting the light guide plate in the thickness direction. Light source device. 8. The surface light source device according to any one of claims 4 to 7, and a liquid crystal display panel arranged to face an emission surface of the light guide plate constituting the surface light source device. A liquid crystal display device comprising: