JP2001215338A - Light transmission plate, side light type surface light source device, and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the luminance unevenness with simple constitution at the time of applying to a reflection type liquid crystal display device of a front light type and using a point light source of a light emitting diode etc. for the primary light source especially, for a light transmission plate, a side light type surface light source device and a display device. SOLUTION: Projected lines 14E or grooves are formed in the light transmission plate 19 so that the illuminating light may make incident on the light transmission plate 14 from a corner, and, moreover, at least each projected line 14E or each groove and the optical path of the illuminating light going straight on from the corner may cross at right angles in the nearly central region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide plate, a side light type surface light source device and a display device, and more particularly, to a front light type reflection type liquid crystal display device.
The present invention is directed to a reflection type display by a so-called front light system, in which illumination light is incident on a light guide plate from a corner, and furthermore, a ridge or a groove is formed in the light guide plate so as to cross an optical path of the illumination light from the corner. Apply to the device,
Even when a point light source such as a light emitting diode is used as the primary light source, it is possible to prevent luminance unevenness with a simple configuration.

[0002]

2. Description of the Related Art In recent years, a reflection type liquid crystal display device which has been considered to be applied to a portable information communication device such as a portable telephone is used even in a dim place or at night by supplementing the amount of extraneous light with an auxiliary light source. Is required. In such a liquid crystal display device, various types of auxiliary light supply methods have been proposed, including a so-called front light type in which auxiliary light is supplied from the front side of the liquid crystal display panel to form a display image. ing.

FIG. 10 is a sectional view showing an example of a reflection type liquid crystal display device according to the front light system. In the liquid crystal display device 1, a side light type surface light source device 2 according to a front light method is disposed on the surface of a liquid crystal display panel 3, and the side light type surface light source device 2 supplies auxiliary light to the liquid crystal display panel 3.

That is, in the front light type side light type surface light source device 2, a light guide plate 4 is disposed on a display surface side of a reflection type liquid crystal display panel 3, and a primary light source 5 is disposed on a side of the light guide plate 4. You. Here, the primary light source 5 is formed, for example, by surrounding the periphery of a fluorescent lamp 6 with a reflector 7, and irradiates the illumination light L to an end surface (hereinafter referred to as an incident surface) 4 </ b> A of the light guide plate 4 from the opening side of the reflector 7.

The light guide plate 4 is formed in a flat plate shape by injection molding a transparent member, for example, acrylic (PMMA resin). The light guide plate 4 has a surface (hereinafter referred to as an emission surface) 4B on the liquid crystal display panel side and an opposite surface to the emission surface 4B. The illumination light L incident from the incident surface 4A propagates while being repeatedly reflected by a surface 4C (hereinafter referred to as a surface).

Further, the light guide plate 4 is formed with a large number of ridges 4E having a rectangular cross section on the exit surface 4B so as to extend in a direction substantially perpendicular to the paper surface. Then, the illumination light L incident on the ridge 4E is bent by a surface 4F substantially perpendicular to the emission surface 4B and emitted to the liquid crystal display panel 3. Here, the ridge means a linear projection, and is usually formed slightly inclined from a direction perpendicular to the paper so as not to generate moire fringes due to interference with pixels of the liquid crystal display panel 3.

Thus, the side light type surface light source device 2
Supplies external light to the liquid crystal display panel 3 through the light guide plate 4. Further, when the amount of extraneous light is insufficient, the primary light source 5 is turned on to supply the illumination light L from the primary light source 5 to the liquid crystal display panel 3.

[0008]

By the way, in the reflection type liquid crystal display device 1 described above with reference to FIG. 10, by using a light emitting diode as the primary light source 5, the power consumption is reduced to be applied to the liquid crystal display device of portable equipment. It is possible to do.

However, when a light emitting diode is simply disposed in place of the fluorescent lamp 6, a light emitting diode which is a point light source is used in place of the fluorescent lamp 6 which is a rod-shaped light source. Uneven distribution occurs in the light distribution. As a result, in the liquid crystal display device 1, the amount of the auxiliary light supplied to the liquid crystal display panel 3 becomes non-uniform, and there is a problem that the display screen due to the auxiliary light may have uneven brightness.

As one method for solving this problem, a method is considered in which illumination light emitted from a light emitting diode is converted into a linear light source by a light guide and incident on a light guide plate.
That is, as shown in FIG. 11, for example, the light guide 8 which is a transparent rod-shaped member having a wedge-shaped cross section is connected to the light incident surface 4 of the light guide plate 4.
A, and the illumination light of the light emitting diode 9 enters from the base of the light guide 8. In this case, as shown in FIG. 12, in order to make the amount of light emitted from the light guide plate 4 uniform, the pitch of the ridges 4E is increased as the distance from the light guide plate 4 and the entrance surface of the light guide 8 increases. It is also conceivable to configure the light guide plate 4.

However, in the case of this method, the light guide 8
However, there is a problem that the overall configuration is complicated by the arrangement of, and a problem that the loss of illumination light is increased by the complicated configuration.

The present invention has been made in consideration of the above points, and is applied to a reflection type liquid crystal display device using a so-called front light system. Even when a point light source such as a light emitting diode is used as a primary light source, the present invention is simple. An object of the present invention is to propose a light guide plate, a sidelight type surface light source device, and a liquid crystal display device that can prevent luminance unevenness by the configuration.

[0013]

According to a first aspect of the present invention, there is provided a liquid crystal display panel, wherein illumination light emitted from a predetermined primary light source is supplied to the liquid crystal display panel. In the light guide plate of the side light type surface light source device to be formed, a corner viewed from the front side is formed by obliquely cutting off to form an incident surface on which illumination light from the point light source is incident, and the surface on the liquid crystal display panel side or Protrusions or grooves for emitting illumination light toward the liquid crystal panel are repeatedly formed on the surface opposite to the liquid crystal display panel so as to cross the optical path of the illumination light from the incident surface.

According to the second aspect of the present invention, the protrusions or grooves are formed in an arc shape with the corner of the incident surface substantially at the center when viewed from the front side.

In the invention according to claim 3, the incident surface is formed at each of the first corner and the second corner at both ends of one side as viewed from the front side, and the ridge or groove is formed at the first corner. A first group that emits illumination light from the incident surface formed at the corner of the first group toward the liquid crystal panel, and an entrance surface formed at the second corner intersecting the ridges or grooves of the first group. And the second group that emits the illumination light from the liquid crystal panel toward the liquid crystal panel.

According to a fourth aspect of the present invention, a side light type surface light source device is configured using the light guide plate according to the first, second or third aspect.

According to the fifth aspect of the present invention, the fourth aspect of the present invention is provided.
The liquid crystal display panel is illuminated by the side light type surface light source device described in (1) to constitute a display device.

According to the first aspect of the present invention, there is provided a light guide plate of a side light type surface light source device which is arranged on a surface of a liquid crystal display panel and supplies illumination light emitted from a predetermined primary light source to the liquid crystal display panel. When the light guide plate is formed in a rectangular shape, for example, when the light guide plate is formed in a rectangular shape, the corner as viewed from the front surface side is formed in a shape cut off obliquely to form an incident surface on which the illumination light from the point light source enters.
If the illumination light can be supplied within the range of degrees, the illumination light can be supplied without causing a significant difference in brightness between parts of the light guide plate. On the other hand, when the incident surface is formed along one side according to the conventional configuration, even if the illumination light can be supplied in a range of about 180 degrees from the point light source, the medium having a low refractive index generally has a low refractive index. Light incident on a high medium travels so that the angle of refraction becomes smaller than the angle of incidence at the interface, so even a point light source that can supply illumination light over a wide range,
Since the illumination light can be incident on the light guide plate only within a narrower range, the illumination light cannot be supplied to each part of the light guide plate without leakage. Thus, according to the configuration of the first aspect, the illumination light can be uniformly supplied to each part of the light guide plate as much as the angle at which the illumination light is to be supplied is reduced, and the illumination light from the point light source is converted to the rod-like light source. It is possible to prevent the bias of the illuminating light propagating inside the light guide plate by directly illuminating the illuminating light from the incident surface without employing a configuration for converting the illuminating light into the illuminating light. As a result, on the surface on the liquid crystal display panel side or on the surface opposite to the liquid crystal display panel side, ridges or grooves for emitting illumination light toward the liquid crystal panel are repeated so as to cross the optical path of the illumination light from the incident surface. With this configuration, even when a point light source such as a light emitting diode is used as the primary light source, it is possible to prevent luminance unevenness with a simple configuration.

According to the second aspect of the present invention, the ridges or grooves are formed in an arc shape with the corner of the incident surface substantially at the center when viewed from the surface side, so that the light propagates so as to spread out from the incident surface. With respect to the illuminating light, ridges or grooves can be arranged at each part so as to be substantially orthogonal to the optical path of the illuminating light, and by adjusting these ridges or grooves, the light amount distribution of the emitted light amount can be made even more uniform. Can be

According to the third aspect of the present invention, the incident surface is
First and second corners at both ends of one side as viewed from the front side
Of the illumination light propagating inside the light guide plate in the case where the light quantity is insufficient, and reducing the bias of the illumination light propagating inside. Can be. Thereby, the ridges or grooves intersect with the first group that emits illumination light from the incident surface formed at the first corner toward the liquid crystal panel, and the first group of ridges or grooves, Illumination light from the incident surface formed at the second corner is formed by the second group that emits the light toward the liquid crystal panel, so that luminance unevenness can be prevented with a simple configuration.

Further, according to the structure of claim 4, claim 1, claim 1,
By configuring the side light type surface light source device using the light guide plate according to claim 2 or 3, high-quality auxiliary light can be supplied to the reflection type liquid crystal display device by the front light method.

According to a fifth aspect of the present invention, a liquid crystal display panel is illuminated by the side light type surface light source device according to the fourth aspect of the present invention to constitute a display device. An image can be formed.

[0023]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that some parts of the drawings are exaggerated for ease of understanding.

(1) First Embodiment (1-1) Configuration of First Embodiment FIG. 1 is an exploded perspective view showing a liquid crystal display device according to a first embodiment of the present invention. . The liquid crystal display device 11 is applied to, for example, a mobile phone. In the configuration shown in FIG. 1, the same configuration as the configuration described above with reference to FIG.
Corresponding reference numerals are attached and duplicate descriptions are omitted.

In the liquid crystal display device 11, auxiliary light is supplied to the liquid crystal display panel 3 by the side light type surface light source device 12. Here, in the sidelight type surface light source device 12, the light guide plate 14 is a transparent plate-like member formed by injection molding a transparent resin such as acrylic (PMMA resin) or a cycloolefin-based polymer. It is made into a flat plate shape by thickness. Further, the light guide plate 14
When viewed from the front surface 14C side, the whole is formed in a rectangular shape, and one corner as viewed from the front surface 14C side is formed by a shape cut off by a flat surface, and is formed as if by a large chamfered shape.

Here, the portion having the cut-off shape is set so that the surface 14C side is cut off more largely than the emission surface 14B side. As a result, the light guide plate 14 has an obliquely inclined surface (hereinafter referred to as a slope) 14D formed at the corner, and the portion on the exit surface 14B side facing the slope 14D is set as the incident surface. Thereby, the light guide plate 14 receives the illumination light of the primary light source by the light emitting diode 15 from the corner viewed from the emission surface 14B side, reflects the illumination light on the inclined surface 14D, and reflects the illumination light reflected on the inclined surface 14D. Is repeatedly reflected and propagated on the exit surface 14B and the surface 14C. Thus, the light emitting diode 15 is arranged so as to be inclined in the direction in which the slope 14D extends when viewed from the surface 14C side.

Further, the light guide plate 14 has a ridge 1 on the surface 14C.
4E is created. Here, the ridges 14E are denoted by reference numerals B and C.
, The pair of slopes 14F and 14
G is directly connected, and the slope 14F on the side farther from the slope 14D is formed to rise at a larger angle than the slope 14G on the side closer to the slope 14D. As a result, the light guide plate 14 reflects the illumination light L coming from the slope 14D side on the slope 14F farther from the slope 14D and emits it toward the liquid crystal display panel 3, as shown in a cross section in FIG. It has been made like that. The slope 14G has a gentle slope, and the illumination light reflected by the slope 14G exceeds the critical angle, so that the emission surface 14B of the light guide plate 14
It is preferable to prevent the light from being emitted from the light source. Ideally, the inclination angles of the slopes 14F and 14G are adjusted so that only the illumination light reflected by the slope 14F is emitted from the emission face 14B.

The light guide plate 14 is configured such that the repetition pitch P of the ridges 14E gradually decreases as the distance from the slope 14D increases, so that the illuminating light incident from the corner can be uniformly distributed to the liquid crystal display panel 3 by the light amount distribution. It is designed to be able to emit light toward. In addition, since the repetition pitch P becomes shorter as the distance from the inclined surface 14D increases, the protruding ridge 14E is repeated with a flat surface disposed therebetween on the side closer to the incident surface.
On the side far from the incident surface, the ridges 14E are arranged on the surface 14C so as to be directly connected.

In this manner, the illumination light is applied to the liquid crystal display panel 3.
The ridge 14E that is emitted toward the surface is arranged linearly so as to be substantially parallel to the direction in which the slope 14D extends when viewed from the surface 14C side.

(1-2) Operation of First Embodiment In the above configuration, in the liquid crystal display device 11 (FIG. 1), extraneous light passes through the light guide plate 14 of the sidelight type surface light source device 12. Incident on the liquid crystal display panel 3, and the light reflected by the liquid crystal display panel 3 passes through the light guide plate 14 and is emitted. Accordingly, when the amount of the external light is sufficient, the display image on the liquid crystal display panel 3 is provided to the user by the external light.

On the other hand, when the amount of extraneous light is insufficient, the lighting of the light emitting diode 15 causes the illuminating light of the light emitting diode 15 to pass through the light guide plate 14 of the sidelight type surface light source device 12 so that the liquid crystal display panel 3 The light reflected by the liquid crystal display panel 3 is transmitted through the light guide plate 14 and emitted. Thus, when the amount of extraneous light is insufficient, the display image on the liquid crystal display panel 3 is provided to the user by supplementing the amount of light with the sidelight type surface light source device 12.

In the side light type surface light source device 12 that emits auxiliary light to the liquid crystal display panel 3 as described above,
At one corner as viewed from the front surface 14C side, the illumination light of the primary light source is emitted from the light emitting diode 15, and this illumination light enters the light guide plate 14 from the emission surface 14B side of the light guide plate 14 and is reflected by the slope 14D. The optical path is bent. In the sidelight type surface light source device 12, the illumination light propagates inside the light guide plate 14 while being repeatedly reflected between the surface 14C and the emission surface 14B, and the slope 14F of the ridge 14E formed on the light guide plate 14 is formed. The component reflected by the light and entering the emission surface 14B at a predetermined angle equal to or smaller than the critical angle is output from the emission surface 14B.
And is supplied to the liquid crystal display panel 3 (FIG. 2). Thus, in the sidelight type surface light source device 12, it is possible to supply auxiliary light from the front surface side of the liquid crystal display panel 3.

Thus, the illumination light is supplied to the liquid crystal display panel 3.
In the side light type surface light source device 12, the slope 14D formed at the corner of the light guide plate 14
When the propagation of the illumination light in a plane parallel to the emission surface 14B is reflected by the light guide plate 14 and propagated inside the light guide plate 14, the light emitting diode 15
By supplying the illumination light within a range of an angle of about 90 degrees, the illumination light can be supplied to each part of the light guide plate 14 without leakage.
On the other hand, in the light guide plate 4 according to the conventional configuration as described above with reference to FIG.
In the end, when the light emitting diodes are directly arranged on the incident surface 4A, even if the illumination light can be supplied at an angle of about 180 degrees from each light emitting diode, the light leaks to each part of the light guide plate 14. And cannot supply illumination light.

In practice, in the light emitting diode, the illumination light can be emitted with a uniform amount of light in almost every direction in the range of about 90 degrees due to the setting of the package shape and the like. At an angle of 180 degrees, it becomes difficult to supply illumination light with a practically sufficiently uniform light amount due to the critical angle of the light guide plate 4 and the like. Thereby, when creating the incident surface 4A along one side,
It is necessary to convert the illumination light from the point light source to the illumination light from the rod-shaped light source and to enter the light guide plate 4 by employing a configuration such as a light guide. On the other hand, the surface light source device 12 can supply the illumination light to each part of the light guide plate 14 with a substantially uniform light amount by supplying the illumination light in the range of 90 degrees as described above. And the illumination light can be supplied to the light guide plate 14.

By the way, the illumination light incident from the corner of the light guide plate 14 propagates inside the light guide plate 14 so as to spread from the corner. Thereby, in the light guide plate 14, the ridges 14E are repeatedly formed so as to cross the optical path of the illumination light so as to correspond to the incidence of the illumination light from this corner. Thereby, the light guide plate 1
Illumination light propagating inside 4 is reflected by the slope 14F of each ridge 14E and supplied to the liquid crystal display panel 3.

As described above, the illumination light supplied to the liquid crystal display panel 3 is prevented from being extremely deviated in the amount of light and propagates inside the light guide plate 14, so that the illumination light is substantially uniform with respect to the liquid crystal display panel 3. The light is emitted according to the light amount distribution. Thus, in the liquid crystal display device 11, luminance unevenness can be prevented with a simple configuration.

(1-3) Effects of the First Embodiment According to the above configuration, the illumination light is incident from the corner of the light guide plate, so that it is applied to a reflection type display device using a so-called front light system. Even when a light-emitting diode is used as the primary light source, luminance unevenness can be prevented with a simple configuration.

(2) Second Embodiment FIG. 3 is a plan view showing a light guide plate applied to a liquid crystal display device according to a second embodiment of the present invention as viewed from the front side. In this light guide plate, when viewed from the front side, a ridge is formed in an arc shape having a center set substantially at a corner set on the incident surface.

That is, the illumination light incident from the corner propagates inside the light guide plate so as to spread from the corner. Therefore, when the ridge is formed linearly as in the first embodiment, the illumination light enters obliquely with respect to the ridge as approaching the side surface of the light guide plate.
There is a possibility that the illumination light cannot be emitted at an angle effective for illuminating the illumination light. In addition, the pitch of the ridge becomes larger as approaching the side surface because the illumination light enters obliquely with respect to the ridge (that is, the traveling direction of the illumination light becomes an angle θ with respect to the direction orthogonal to the ridge). When the illumination light travels smoothly with respect to the ridge with only a shift, if the effective pitch P1 of the ridge with respect to the illumination light is the actual processing pitch P0,
P1 = P0 / cos θ (0 degree <θ <90 degrees), whereby the amount of auxiliary light may decrease near the side surface.

However, if the ridge is formed by an arc shape having a corner substantially at the center as in this embodiment,
Protrusions can be formed so that the optical path of the illumination light traveling straight from the incident surface and each part are orthogonal to each other. Therefore, the oblique incidence of the illumination light on the ridge can be prevented, and most of the emitted light can be effective for illuminating the liquid crystal display panel 3, thereby further improving the efficiency as compared with the first embodiment. Auxiliary light can be supplied with a good and uniform light amount distribution.

In particular, when a ridge is formed by an arc shape having a corner substantially at the center as in this embodiment, this arc shape is made to be an elliptical arc shape.
The pitch of the ridges can be varied between the long side and the short side of the light guide plate, whereby the amount of emitted light can be finely adjusted. Accordingly, as compared with the case of the first embodiment, it is possible to further uniform the amount of emitted light and form a high-quality display image.

Further, as described above with reference to FIGS. 11 and 12, when a linear ridge is formed by being inclined obliquely in one direction in order to prevent moire due to interference with the liquid crystal display panel, it propagates inside the light guide plate. In the illumination light, the traveling direction gradually tilts obliquely due to the reflection on the ridge. As a result, the amount of emitted light at the portion along the side surface is significantly changed as compared with the other portions along the side surface toward the end surface opposite to the incident surface. That is, on the side where the illuminating light propagates obliquely and the illuminating light gradually moves away from the side surface (in the example shown in FIGS. 11 and 12, the area on the left side of the broken line in the drawings), the amount of emitted light decreases. I do.

In this embodiment, however, the ridges are formed in an arc shape having a corner substantially at the center, so that the ridges are formed obliquely in one direction. Can be effectively prevented from tilting the traveling direction of the illumination light propagating through
As a result, it is possible to prevent such a change in the amount of emitted light along the side surface.

According to the structure shown in FIG. 3, the ridge is formed in an arc shape with the corner substantially at the center, so that
Further, the auxiliary light can be supplied with a more uniform light amount distribution, and a higher quality display image can be formed accordingly.

(3) Third Embodiment FIG. 4, which is shown in comparison with FIG. 1, is an exploded perspective view showing a liquid crystal display device according to a third embodiment of the present invention. The liquid crystal display device 21 supplies auxiliary light to the liquid crystal display panel 3 by the side light type surface light source device 22.

Here, the light guide plate 24 has a shape in which the corners at both ends on the short side as viewed from the surface 24C side are cut off obliquely, and the slope 24D is formed on this portion similarly to the first embodiment. , An incident surface is formed, and a light emitting diode 15 is arranged so as to face the incident surface.

Light emitting diode 1 to these two corners
In order to correspond to the arrangement of No. 5, the light guide plate 24 includes a first group of ridges 14EA each corresponding to one corner-side incident surface, as shown in an enlarged view by a symbol D, and the first group of ridges 14EA. A second group of ridges 14EB that intersect with the ridge 14EA and correspond to the entrance surface on the other corner side is formed. Each of the first group of ridges 14EA and the second group of ridges 14EB is constituted by a pair of slopes 14FA, 14GA and 14FB, 14GB, respectively, similarly to the ridge 14E described above in the first embodiment. It has been made to be.

As shown in the enlarged view of FIG. 5, the first group of ridges 14EA corresponding to one incident surface receives the illumination light L coming from the other incident surface at a large angle. Thus, the illumination light on the other side does not affect the emission toward the liquid crystal display panel 3 or the like, and the illumination light on the one side is
Can be emitted.

As a result, in this embodiment, the amount of auxiliary light supplied to the liquid crystal display panel 3 can be increased by the illumination light from the two light emitting diodes, whereby a bright, high-quality display image without luminance unevenness can be obtained. Can be displayed.

Further, in this embodiment, a group of ridges 1
When the propagation direction of the illumination light is obliquely inclined due to the reflection of 4EA or 14EB, this group of ridges 14EA or 14EB
This inclination is corrected by the reflection of another group of the ridges 14EB or 14EA that intersect with the ridges. This makes it possible to prevent a change in the amount of emitted light as described in the second embodiment with reference to FIGS. 11 and 12, thereby also emitting a high-quality auxiliary light to form a high-quality display image. can do.

According to the structure shown in FIG. 4, the illumination light is made incident from two corners, and furthermore, ridges are formed so as to correspond to the two corners, respectively. As a result, a higher-quality display image can be formed.

(4) Fourth Embodiment FIG. 6 in comparison with FIG. 3 shows a light guide plate applied to a liquid crystal display device according to a fourth embodiment of the present invention as viewed from the front side. It is a top view. In this light guide plate, two corners are set on the incident surface, and two groups of ridges are formed in an arc shape with the two corners set on the incident surface being substantially centered.

According to the structure shown in FIG. 6, the illumination light is made to enter from two corners, and the ridges corresponding to these two corners are formed in an arc shape, so that the above-described second and third corners are formed. The above-described effects can be obtained in combination with the above-described embodiment, whereby higher-quality illumination light can be emitted.

(5) Other Embodiments In the above-described embodiment, a pair of inclined ridges are formed on the surface, and the illuminating light propagating inside the light guide plate is formed by the ridges on the liquid crystal display panel. However, the present invention is not limited to this, and when ridges are formed in various shapes, illumination light propagating inside the light guide plate by grooves instead of ridges is further applied to the liquid crystal display panel. It can be widely applied when emitting light. In this groove,
As shown in FIG. 7, when creating with a triangular cross section,
As shown in FIG. 8, a case in which the object is created by an arc-shaped cross section may be considered.

Further, in the above-described embodiment, the case where the ridge is formed on the surface has been described. However, the present invention is not limited to this, and can be widely applied to the case where the ridge is formed on the emission surface side. In addition to the protrusions formed on the light-exiting surface side in addition to the protrusions described above with reference to FIG. 10, for example, a case in which the protrusions are formed in an obliquely cross-sectional shape as shown in FIG.

Further, in the above-described embodiment, the case where one or two corners of the light guide plate are set as the incident surface has been described. However, the present invention is not limited to this, and three or four corners may be provided. It can be widely applied to the case of setting. In this case, it is conceivable to apply a ridge having a rectangular cross section as described above with reference to FIG.

In the above-described embodiment, a case has been described where a slope is formed by a flat surface at a corner. However, the present invention is not limited to this, and a slope may be formed by a curved surface as needed.

In the above-described embodiment, the case where the illumination light is incident from the exit surface side has been described. However, the present invention is not limited to this. For example, the corner portion of the light guide plate 14 in FIG. The present invention can be widely applied to a case where an incident surface is set on the front surface side, and a case where illumination light is incident from a side surface. In addition, the surface or the emission surface of the light guide plate 14 is vertically cut off at a corner portion of the light guide plate 14,
This notched surface can be used as the incident surface.

In the above embodiment, the case where the light guide plate is formed with a constant thickness has been described. However, the present invention is not limited to this, and can be widely applied to the case where the light guide plate is formed with a wedge-shaped cross section. it can.

In the above-described embodiment, the case where the present invention is applied to a mobile phone has been described. However, the present invention is not limited to this, and can be widely applied to various electronic devices.

[0061]

As described above, according to the present invention, the illuminating light is made to enter the light guide plate from the corner, and the illuminating light traveling straight from the corner is at least substantially at the center of each ridge or groove. By forming ridges or grooves on the light guide plate so as to be orthogonal to the optical path of the light guide plate, it can be applied to a reflection type display device using a so-called front light method, and even when a point light source such as a light emitting diode is used as a primary light source, With such a configuration, luminance unevenness can be prevented.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a light guide plate of the surface light source device applied to the liquid crystal display device of FIG.

FIG. 3 is a plan view showing a light guide plate applied to a liquid crystal display device according to a second embodiment of the present invention.

FIG. 4 is an exploded perspective view showing a liquid crystal display device according to a third embodiment of the present invention in comparison with FIG.

FIG. 5 is a plan view showing a protrusion of the light guide plate of FIG. 5 in detail.

FIG. 6 is a plan view showing a light guide plate applied to a liquid crystal display device according to a fourth embodiment of the present invention in comparison with FIG.

FIG. 7 is a cross-sectional view showing a light guide plate according to a configuration in which grooves are arranged on the surface.

FIG. 8 is a cross-sectional view showing a light guide plate according to a configuration in which a groove having an arc-shaped cross section is arranged on the surface.

FIG. 9 is a cross-sectional view showing a light guide plate according to a configuration in which ridges are arranged on an emission surface.

FIG. 10 is a sectional view showing a conventional liquid crystal display device.

FIG. 11 is a plan view showing a side light type surface light source device in which a light emitting diode is used as a primary light source by using a light guide.

12 is a plan view showing a case where the pitch of the ridge is varied in the configuration of FIG. 11;

[Explanation of symbols]

1, 11, 21 ... Liquid crystal display device, 2, 12, 22 ...
Sidelight type surface light source device, 3 ... LCD panel,
4, 14, 24 ... light guide plate, 14E, 14EA, 14E
B, 24E ... ridge, 9, 15 ... light emitting diode

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09F 9/00 336 F21Y 101: 02 // F21Y 101: 02 G02F 1/1335 530

Claims (5)

[Claims] 1. A light guide plate of a side light type surface light source device which is arranged on a surface of a liquid crystal display panel and supplies illumination light emitted from a predetermined primary light source to the liquid crystal display panel. Is formed in an obliquely cut shape to form an incident surface on which the illumination light from the point light source enters, and the illumination light is provided on a surface on the liquid crystal display panel side or on a surface opposite to the liquid crystal display panel side. A light guide plate, wherein a ridge or a groove for emitting light toward the liquid crystal panel is repeatedly formed so as to cross an optical path of illumination light from the incident surface. 2. The method according to claim 1, wherein the ridge or the groove is viewed from the surface side.
The light guide plate according to claim 1, wherein the light guide plate is formed in an arc shape with the corner of the incident surface substantially at the center. 3. The incident surface is formed at a first corner and a second corner at both ends of one side as viewed from the front side, and the ridge or groove is formed at the first corner. A first group for emitting illumination light from the formed incident surface toward the liquid crystal panel;
And a second group that intersects with the ridges or grooves of the group and emits illumination light from an incident surface formed at the second corner toward the liquid crystal panel. The light guide plate according to claim 1 or 2. 4. A sidelight type surface light source device using the light guide plate according to claim 1, 2 or 3. 5. A display device, wherein a liquid crystal display panel is illuminated by the side light type surface light source device according to claim 4.