JP2001228475A - Surface light source device and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the uncomfortable feeling of a display image caused by the luminance unevenness changing in the time of lighting by one light emitting diode, and lighting by other light emitting diodes, when plural kinds of the light emitting diodes compose a primary light source by applying a surface light source device and a display device to a liquid crystal display device of a portable telephone, e.g. SOLUTION: A plurality of dot light source 18As and 18B are closely disposed so that optical paths in which the illuminating light propagate the inside of a light transmission plate 16 may overlap when viewing from a light-emitting surface 16B side of the light transmission plate 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a surface light source device and a display device, and can be applied to, for example, a liquid crystal display device of a portable telephone. The present invention, when viewed from the emission surface side of the light guide plate, by arranging a plurality of point-like light sources in close proximity such that the optical paths through which the illumination light propagates in the light guide plate overlap,
Even when a primary light source is composed of a plurality of types of light emitting diodes, it is possible to prevent a sense of incongruity in a displayed image due to a change in luminance unevenness between when one light emitting diode is turned on and when another light emitting diode is turned on. To be able to

[0002]

2. Description of the Related Art Conventionally, in a liquid crystal display device used for a cellular phone or the like, a liquid crystal display panel is illuminated by a surface light source device. FIG. 5 is an exploded perspective view showing this type of liquid crystal display device. In the liquid crystal display device 1, a surface light source device 3 is disposed on the back of a liquid crystal display panel 2, and the surface light source device 3 is configured by sequentially stacking a reflection sheet 5 and a light guide plate 6.

As shown in FIG. 6, a cross section is shown in FIG. 6. The light guide plate 6 is formed in a flat plate shape by injection molding a transparent member, for example, acrylic (PMMA resin). Is done. In the surface light source device 3, the light emitting diode 8 is disposed so as to face the incident surface 6D.

The surface light source device 3 causes the illumination light emitted from the light emitting diode 8 to enter the light guide plate 6 from the incident surface 6D and repeats reflection between the back surface 6A and the emission surface 6B while propagating the illumination light. The illumination light is emitted from the emission surface 6B. The reflection sheet 5 is a white sheet material, and reflects the illumination light leaking from the back surface 6A and re-enters the light guide plate 6, thereby improving the utilization efficiency of the illumination light. Thus, the surface light source device 3 is configured to emit light from the emission surface 6B by the illumination light of the primary light source by the point light source to form a surface light source.

In the surface light source device 3 according to such an emission principle, a light scattering pattern for promoting the emission of illumination light is formed on the light guide plate 6 in order to make the distribution of the amount of light emitted from the emission surface 6B uniform. You. That is, the light scattering pattern is partially roughened into, for example, a circular shape by a suitable surface roughening treatment such as mat surface treatment, etching to a corresponding mold, electric discharge machining, or the like. It is formed as a surface. By changing the size of the light scattering pattern, the pitch at which the light scattering pattern is arranged, and the like, the light scattering pattern is appropriately adjusted in area according to a portion where the light scattering pattern is formed per unit area. You. Thus, in the surface light source device, the illumination light emitted from the emission surface 6B has a uniform light amount over the entire emission surface. In the light guide plate 6,
By changing the degree of roughness according to each part instead of the light scattering pattern and making the entire exit surface or the entire back surface rough, the amount of emitted light can be made uniform.

[0006]

By the way, in the above-mentioned liquid crystal display device using a light emitting diode as a primary light source, a plurality of light emitting diodes having different emission colors (for example, two types of light emitting diodes each emitting green or red light). There is a need in the market for changing the driving of these light emitting diodes to change the color of the illumination light supplied to the liquid crystal display panel.

However, when a surface light source device is manufactured using light emitting diodes having different emission colors, the uniformity of the illumination light supplied to the liquid crystal display panel 2 changes for each color when the color of the illumination light is switched. Therefore, there is a problem that a sense of discomfort occurs in the displayed image.

That is, taking a case where a surface light source device is produced by using two kinds of light emitting diodes as an example, as shown in FIG. 7, two kinds of light emitting diodes 8 are arranged along an incident surface 6D.
It is conceivable to arrange A and 8B. However, when the light emitting diodes 8A and 8B are arranged in this manner, the distribution of the illumination light due to the light scattering pattern formed on the light guide plate 6 is different between the illumination light emitted from the light emitting diode 8A and the illumination light emitted from the light emitting diode 8B. And will be very different. In FIG. 7, the distribution of the illumination light is schematically illustrated by indicating the spread of the illumination light emitted from each of the light emitting diodes 8A and 8B by reference numerals A and B.

That is, if one light emitting diode is driven and the light scattering pattern is designed so that a display screen can be created by supplying illumination light to the liquid crystal display panel 2 with a substantially uniform light amount, the other light emitting diode is driven. In the case of using a diode, it is difficult to design a light scattering pattern so that the distribution of illumination light by both light emitting diodes is the same, such that illumination light cannot be supplied due to a uniform amount of light. When the color of the light is switched, the uniformity of the illumination light supplied to the liquid crystal display panel 2 changes, causing a sense of incongruity.

However, on the other hand, a light emitting diode (hereinafter, referred to as a package) in which two types of chips are sealed in one package.
Also known is a two-color light-emitting diode), which can be used as a primary light source to supply two colors of light from one light-emitting diode.
It is possible to switch the color of the display screen in the liquid crystal display device by switching the color of the illuminating light supplied to the liquid crystal display panel without causing any trouble when using the light emitting diodes of the different types.

However, in the case of a two-color light emitting diode, if the amount of light emission between the two types of light emitting diode chips varies greatly, the liquid crystal display device 1 changes the color of the display screen when the color of the display screen is switched. Although there is a problem that the brightness changes, it is necessary to use a large amount of time and effort for the task of selecting the ones with small variation in the amount of light emission, sealing them in one package, and solving the above-mentioned problem. The disadvantage also arises. Further, the two-color light emitting diode has a drawback that its versatility is poor, and it is not expected that the price can be reduced by the mass production effect.

For these reasons, conventionally, it has been desired to form a surface light source device using two types of light emitting diodes having different emission colors without using two colors of light emitting diodes. That is, when two types of light emitting diodes are used, it is relatively easy to individually select light emitting diodes having substantially the same light emission amount from those already packaged. By creating the device, it is considered that display screens of different colors can be provided with almost the same brightness. Further, such a light emitting diode has a feature that it is more versatile than a light emitting diode of two colors.

The present invention has been made in view of the above points, and even when a primary light source is constituted by a plurality of types of light emitting diodes, it is necessary to light one light emitting diode and another light emitting diode. An object of the present invention is to propose a surface light source device and a liquid crystal display device that can prevent an unnatural feeling of an image due to a change in luminance unevenness.

[0014]

According to a first aspect of the present invention, there is provided a surface light source device for emitting illumination light from a primary light source to a light guide plate to emit light from an emission surface of the light guide plate. The light guide plate is configured such that illumination light from a primary light source incident from a predetermined incident surface is reflected on an inclined surface obliquely inclined with respect to the incident surface and propagates through the light guide plate. The surface facing the surface and / or the emission surface is subjected to processing for promoting emission of the illumination light, and a plurality of point-like light emitters arranged in close proximity to each other are used as the primary light source. Are arranged such that the optical paths through which the illuminating light from the respective light emitters propagates through the light guide plate substantially overlap when viewed from the emission surface side.

In the invention according to a second aspect, in the configuration of the first aspect, the plurality of point-like illuminants are arranged so as to substantially follow the projection of the normal of the inclined surface onto the incident surface.

Further, in the invention of claim 3, claim 1
Alternatively, in the configuration according to claim 2, the incident surface is formed along an arbitrary edge of the light guide plate.

According to the fourth aspect of the present invention, there is provided the first aspect.
Alternatively, in the configuration of claim 2, the incident surface is formed at an arbitrary corner of the light guide plate.

According to a fifth aspect of the present invention, the liquid crystal display panel is illuminated by the surface light source device according to the first, second, third or fourth aspect.

According to the first aspect of the present invention, the emission surface and / or the surface facing the emission surface are processed to promote the emission of the illumination light, so that the illumination light propagating inside the light guide plate is processed. If the distribution changes significantly, the uniformity of the amount of emitted light will change. In this case, the primary light source is a plurality of point-like light sources arranged close to each other, and the primary light sources are arranged such that the optical paths through which the illumination light from each light emitter propagates through the light guide plate substantially overlap when viewed from the emission surface side. Accordingly, in these point light sources, the distribution of the illumination light propagating through the light guide plate can be made substantially equal. As a result, the illumination light from the plurality of point light sources can be emitted with substantially the same luminance distribution, and a sense of discomfort in the displayed image due to the difference in the luminance distribution can be prevented.

According to the second aspect of the present invention, in the configuration of the first aspect, the plurality of point-like illuminants are arranged side by side so as to substantially follow the projection of the normal of the slope onto the incident surface. By disposing the light emitting diodes, it is possible to prevent a sense of discomfort in the displayed image.

According to the third aspect of the present invention, in the configuration of the first or second aspect, the incident surface is formed along an arbitrary edge of the light guide plate, so that the primary surface is formed along one side. In the configuration in which the light sources are arranged, it is possible to prevent a sense of discomfort in the displayed image.

According to the fourth aspect of the present invention, in the configuration of the first or second aspect, the incident surface is formed at an arbitrary corner of the light guide plate, so that the primary light source is arranged at the corner of the light guide plate. With such a configuration, it is possible to prevent a sense of discomfort in the displayed image.

According to a fifth aspect of the present invention, there is provided the first aspect of the present invention.
By illuminating the liquid crystal display panel with the surface light source device according to claim 2, 3, or 4, a high quality display image can be formed.

[0024]

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) Configuration of Embodiment FIG. 1 is an exploded perspective view showing a liquid crystal display device according to an 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 configurations as those described above with reference to FIG. 5 are denoted by the corresponding reference numerals, and redundant description will be omitted.

In the liquid crystal display device 11, the light guide plate 1
Reference numeral 6 denotes a transparent plate-like member formed by injection molding a transparent resin such as acrylic (PMMA resin or the like), cycloolefin-based polymer, or the like. Emission surface 16B which is the surface on the liquid crystal display panel 2 side
As shown in FIG. 2A, the shape of the light guide plate 16 is viewed from the side.
Has a rectangular shape when viewed from the exit surface 16B side. Further, the light guide plate 16 is formed in a shape in which corners at one end on one short side are cut off by a flat surface, and is formed in a shape as if a large chamfer. In FIG. 2A, a rectangular area surrounded by a dotted line is an effective light emitting area actually used for displaying an image.

Here, the cutout portion is set so that the light exit surface 16B side has a shape that is larger than the rear surface 16A side. In this portion, the cut-off shape is formed such that the angle θ1 formed between the ridge line formed at the corner and the short side is approximately 45 degrees. In addition, FIG.
As shown in FIG. 2B by taking a cross section along the line A, the angle θ2 between the obliquely inclined surface (hereinafter referred to as a slope) 16C formed at this corner and the back surface 16A is 45 degrees or more.
A predetermined angle is set within a range of 20 degrees.

The light guide plate 16 has a rear surface 16A opposite to the inclined surface 16C set as an incident surface 16D. As a result, the light guide plate 16 receives the illumination light of the primary light source from the corner as viewed from the exit surface 16B side, and converts the illumination light to the slope 16C.
Reflected by Further, the light guide plate 16 emits the illumination light from the emission surface 16B while the illumination light reflected on the inclined surface 16C is repeatedly reflected and propagated on the emission surface 16B and the back surface 16A.

The light guide plate 16 is thus provided with the light exit surface 16.
In order that the light quantity distribution of the illumination light emitted from B becomes uniform,
A light scattering pattern of a fixed size with the formed density adjusted is formed on the emission surface 16B.

The light guide plate 16 configured as described above (FIG. 1) is housed in a frame (not shown) together with the reflection sheet 5 and arranged at a predetermined position on a wiring board (not shown).
The wiring board is provided with an integrated circuit and the like for driving the liquid crystal display panel 2 required for the mobile phone. When the light guide plate 16 is arranged in this manner, it faces the incident surface 16D of the light guide plate 16. One set of light emitting diodes 18A
And 18B are arranged.

As a result, the surface light source device 13 can switch the color of the illumination light supplied to the liquid crystal display panel 2 by switching the driving of the set of light emitting diodes 18A and 18B.

Here, one set of light emitting diodes 18A and 1
For 8B, a light emitting device having substantially the same amount of emitted light and further having substantially the same directivity is applied. Further, the light emitting diodes 18A and 18B are arranged such that, when viewed from the light exit surface 16B side of the light guide plate 16, the incident surfaces 16D are arranged such that the optical paths of the illumination light that is reflected by the inclined surface 16C and propagates inside the light guide plate 16 overlap. Are arranged side by side so as to be substantially along the projection of the normal to the slope 16C. Thereby, in the surface light source device 13, the distribution of the illumination light propagating inside the light guide plate 16 is not largely different between the light emitting diodes 18A and 18B.

Further, the light emitting diodes 18A and 18B
Adjusts the positional relationship between the light-emitting diodes 18A and 18B according to the position of the chip sealed in the package so that the light-emitting points of the light-emitting diodes 18A and 18B are aligned with the projection when the light-emitting diodes 18A and 18B are arranged in this manner. In addition, as shown in FIG. 1, it is preferable that the inclined surface 16C is arranged to be inclined along the forming direction of the inclined surface 16C.

(2) Operation of Embodiment In the above configuration, in the liquid crystal display device 11 (FIG. 1), the liquid crystal is generated by the illumination light emitted from the surface light source device 13 arranged on the back of the liquid crystal display panel 2. Display panel 2
Is illuminated, so that the display on the liquid crystal display panel 2 can be viewed.

In the surface light source device 13 for illuminating the liquid crystal display panel 2 as described above, the illumination light of the primary light source is emitted from the light emitting diode 18A or 18B at two corners of the light guide plate 16 viewed from the liquid crystal display panel 2 side. After being emitted and entering this light guide plate 16 from the back surface 16A side of the light guide plate 16, the light path is bent by being reflected by the inclined surface 16C.

In the surface light source device 13, the illumination light propagates inside the light guide plate 16 while being repeatedly reflected between the light exit surface 16B and the rear surface 16A, and enters the light exit surface 16B at an incident angle smaller than the critical angle. Illumination light is emitted from the emission surface 16B. As a result, the emission surface 16B of the light guide plate 16 is illuminated by the illumination light emitted from the point light source to form a surface light source, and the illumination light from the surface light source forms the liquid crystal display panel 2.
Is illuminated. Similarly, the illumination light incident on the back surface 16A at an incident angle equal to or smaller than the critical angle is emitted from the back surface 16A, and the illumination light is reflected by the reflection sheet 5 and re-enters the light guide plate 16, and Thereby, the utilization efficiency of the illumination light is improved.

Further, the illumination light propagating inside the light guide plate 16 in this manner is scattered by the light scattering pattern formed on the exit surface 16B, and is promoted to exit from the exit surface 16B. Is emitted.

As described above, the illumination light which enters the light guide plate 16 and is emitted from the light exit surface 16B of the light guide plate 16 is reflected by the inclined surface 16C formed at the corner of the light guide plate 16 so as to be reflected inside the light guide plate 16. 3B, the light-emitting diodes 18A and 18B as shown in FIG.
The displacement of the light-emitting points when the pixels are arranged side by side is corrected, and FIG.
As shown in (A), when the propagation of the illumination light in a plane parallel to the emission surface 16B is observed, the light emitting diode 18A
And 18B, the illumination light can be supplied to the light guide plate 16 at an angle of about 90 degrees, and the illumination light can be supplied to each part of the light guide plate 16 without leakage. In FIG. 3, the spread of the illumination light emitted from the light emitting diodes 18A and 18B is indicated by reference numerals LA and LB, respectively, in comparison with FIG.

As a result, in the surface light source device 13, as compared with the case where the primary light source is arranged along one side as in the case of the conventional configuration described above with reference to FIG. Extreme bias of light can be reduced, and the illumination light can be emitted with a sufficiently uniform emission light amount even if the spectral scattering patterns are not locally densely arranged.

In the surface light source device 13 according to the illumination light emission principle, the light emitting diodes 18A and 18B
, The illumination light is selectively emitted from the light emitting diodes 18A and 18 respectively. Further, by illuminating the liquid crystal display panel 2 with the illumination light, the color of the displayed image is switched. That is, for example, by applying red and green light emitting diodes to the light emitting diodes 18A and 18B, respectively, the color of the display screen is set to red and green, or the light amount of each of the light emitting diodes 18A and 18B is adjusted to a neutral color between them. Can be.

In this case, in the surface light source device 13,
The light emitting diodes 18A and 18B each have a light output amount substantially equal to each other and a light directivity approximately equal to each other. Further, when viewed from the light exit surface 16B side of the light guide plate 16, the light guide diodes 16A and 18B are reflected by the inclined surface 16C. Are arranged substantially along the projection of the normal of the inclined surface 16C to the incident surface 16D so as to overlap the optical paths of the illumination light propagating inside the light-emitting diode 18A.
Illuminating light and the illuminating light from the light emitting diode 18B can make the distribution of the illuminating light propagating inside the light guide plate 16 substantially equal, whereby even when a primary light source is constituted by a plurality of types of light emitting diodes, It is possible to prevent a sense of discomfort in the displayed image.

That is, generally, in a light emitting diode, the largest amount of light is emitted in the front direction of the light emitting surface, and this front direction becomes the main emission direction of the illumination light.
Further, in the light emitting diode, the amount of light emitted in a direction deviated from the front direction changes according to packaging or the like, and in this embodiment, the illumination light propagating inside the light guide plate 16 due to the change in the amount of light. Will be determined.

However, in this embodiment, the slope 16C
The light emitting diodes 18A are arranged close to each other so that the optical paths of the illumination light reflected by the light and propagating inside the light guide plate 16 overlap.
And 18B, the distribution of the illumination light can be made substantially equal in the main emission direction of the illumination light.

Further, by arranging the light emitting diodes 18A and 18B so as to be adjacent to each other along the projection, the illumination light emitted from the light emitting diodes 18A and 18B respectively has an optical path difference until reflected by the slope 16C. The displacement of the light-emitting points due to the arrangement is corrected (see FIG. 3B), whereby the illumination light from each of the light-emitting diodes 18A and 18B is emitted from the light-emitting surface with substantially the same distribution.

Thus, in this embodiment, the distribution of the illumination light is set to be substantially equal in each of the light emitting diodes 18A and 18B, so that even when the illumination light is switched,
It is possible to prevent the distribution of the emitted light amount from changing, and it is possible to eliminate a feeling of strangeness.

(3) Effects of the Embodiment According to the above configuration, a plurality of light emitting diodes are arranged close to each other so that the optical paths of the illumination light propagating in the light guide plate overlap each other. Accordingly, when a primary light source is configured, it is possible to prevent a sense of discomfort in a displayed image.

(4) Other Embodiments In the above-described embodiment, the case where the light emitting diodes are arranged on the short side and both ends of the light guide plate has been described.
The present invention is not limited to this, and as shown in FIG.
The present invention can be widely applied to a case where light emitting diodes are arranged along one side.

In the above-described embodiment, the case where the slope for bending the optical path of the illumination light is formed by a flat surface has been described. However, the present invention is not limited to this, and the slope is formed by a curved surface as necessary. It can be widely applied to cases and the like.

In the above-described embodiment, the case where the illumination light is incident from the back side has been described. However, the present invention is not limited to this, and the light guide plate 16 of FIG. The present invention can be widely applied to a case where an incident surface is set.

In the above-described embodiment, the case where the light scattering pattern is arranged on the emission surface has been described. However, the present invention is not limited to this, and the light scattering pattern may be formed on the back surface. May be created.

Further, in the above-described embodiment, the case has been described in which the light guide plate is subjected to processing for creating a light scattering pattern by roughening processing to promote emission of illumination light, but the present invention is not limited to this. Also, the present invention can be widely applied to a case where a minute dome shape is formed on the surface of the light guide plate and a function of promoting emission of illumination light is added by the dome shape.

Further, in the above-described embodiment, the case where the primary light source is constituted by two kinds of light emitting diodes and the lighting is performed alternately has been described.
The present invention can be widely applied to a case where a primary light source is constituted by more than two types of light emitting diodes, and furthermore, a case where a plurality of light emitting diodes are simultaneously turned on. In this way, for example, when a white primary light source is constituted by red, blue, and green light emitting diodes, it is possible to prevent the color balance from being disturbed at each part of the emission surface 16B, and to achieve a nonuniform color balance. Discomfort can be eliminated. Further, color display can be performed by synchronizing the lighting of the light emitting diode of each color and the opening and closing of the liquid crystal cell. In addition, the same light emitting diode can be used to widen the adjustment range of the light amount.

In the above-described embodiment, the case where the illumination light is incident from the back side has been described. However, the present invention is not limited to this, and the slope formed by cutting off the corner of the light guide plate faces the emission surface. Then, the incident surface may be set at a portion of the exit surface facing the inclined surface. In particular, such an embodiment is suitable for application as a so-called front light that illuminates the reflective liquid crystal display panel from the front side. Also, when applying to a front light, if the size of the reflection type liquid crystal display panel is substantially the same as or slightly larger than the light guide plate, the corners of the light guide plate are cut off and the reflection type liquid crystal display By notching the corner of the panel and locating the light emitting diode at the cut-out portion, the thickness of the display device can be reduced.

Further, in the case where the present invention is applied to a front light as described above, the incident light guide portion may be formed by projecting a portion set as an incident surface from other portions (emission surface). In this case, as described above, the corners of the reflective liquid crystal display panel are cut out, and the incident light guide portion formed to project from the cutout portion is locked to position the reflective liquid crystal display panel and the light guide plate. You may make it match. In such a configuration, if the incident light guide is damaged due to contact with the reflective liquid crystal display panel, the propagation of the incident light may be hindered. It is desirable that at least one of the incident light guide portion side and the reflection type liquid crystal display panel side is subjected to some kind of damage prevention processing so as not to damage the portion that comes into contact with the panel.

In the above-described 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.

Further, in the present invention, the optical paths of the light propagating inside the light guide plate are overlapped, and to realize this, the configuration described in the above embodiment is adopted. This is one of the major features of the present invention. Various technologies related to the surface light source device are applied to the configuration other than the configuration which is a feature of the present invention as long as the effects of the present invention are not impaired or in order to further enhance the effects of the present invention. It is possible.

For example, as a configuration enabling uniform emission of illumination light from the light guide plate, in addition to the shape of the light scattering pattern and the rough surface processing of the light guide plate as exemplified in the above description of the prior art, A light guide plate is formed by mixing fine particles made of a transparent material having a different refractive index from the main material forming the light guide plate to form a light guide plate, or a cross section orthogonal to the longitudinal direction of the back surface or the emission surface of the light guide plate is substantially V-shaped, for example. A configuration in which grooves having a shape are arranged substantially along the main propagation direction of the illumination light propagating in the light guide plate or substantially perpendicular to the main propagation direction can be appropriately adopted. . Also in the present invention, a surface light source device and a liquid crystal display device are configured by laminating various optical members such as a prism sheet and a diffusion sheet conventionally used in a surface light source device on a light guide plate. You can also.

As described above, according to the present invention, a plurality of point-like light sources are arranged close to each other so that the optical paths through which the illuminating light propagates in the light guide plate overlap when viewed from the exit surface side of the light guide plate. By arranging, even when the primary light source is constituted by a plurality of types of light emitting diodes or the like, the brightness unevenness changes between the time of lighting by one light emitting diode and the time of lighting of another light emitting diode. Discomfort can be prevented.

[0059]

[Brief description of the drawings]

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

FIG. 2 is a plan view showing a light guide plate of the surface light source device applied to the liquid crystal display device of FIG. 1 when viewed from an emission surface side, and a cross-sectional view cut along line AA.

FIG. 3 is a plan view and a cross-sectional view showing the vicinity of a slope in detail in comparison with FIG. 2;

FIG. 4 is a plan view showing a light guide plate according to another embodiment of the present invention in comparison with FIG.

FIG. 5 is an exploded perspective view showing a conventional liquid crystal display device.

6 is a cross-sectional view for explaining a surface light source device applied to the liquid crystal display device of FIG.

FIG. 7 is a plan view for explaining a case where a primary light source in the surface light source device of FIG. 6 is constituted by two types of light emitting diodes.

[Explanation of symbols]

1, 11 ... liquid crystal display device, 2 ... liquid crystal display panel,
3, 13 surface light source device, 5 reflection sheet, 6, 16
…… Light guide plate, 6A, 16A …… Back side, 6B, 16B…
Outgoing surface, 6C, 16C... Slope, 6D, 16D... Incident surface, 8, 18,.

Claims (5)

[Claims] 1. A surface light source device for emitting illumination light from a primary light source to a light guide plate and emitting light from an exit surface of the light guide plate, wherein the light guide plate is configured to illuminate the primary light source from a predetermined incident surface. The light is reflected on an inclined surface obliquely inclined with respect to the incident surface and propagates through the light guide plate, and the light exiting surface and / or a surface facing the light exiting surface is provided. A process for promoting emission of the illumination light is performed; a plurality of point-like light emitters arranged in close proximity to each other are used as the primary light source; A surface light source device, wherein an optical path through which light propagates through the light guide plate is disposed so as to substantially overlap when viewed from the emission surface side. 2. The surface light source device according to claim 1, wherein the plurality of point light emitters are arranged so as to substantially follow a projection of a normal of the slope onto the incident surface. 3. The surface light source device according to claim 1, wherein the incident surface is formed along an arbitrary edge of the light guide plate. 4. The surface light source device according to claim 1, wherein the incident surface is formed at an arbitrary corner of the light guide plate. 5. A display device, wherein a liquid crystal display panel is illuminated by the surface light source device according to claim 1, 2, 3, or 4.