JP2003173713A - Illumination device and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an illumination device that is capable of improving lighting efficiency and has a simple structure. <P>SOLUTION: The illumination device comprises a second light-guide plate 2B that is a separate body from a first light-guide plate 2A, and this light-guide plate 2B comprises a light-radiating face 26 and a light-reflecting face 25 respectively extending in a second direction, a pair of end faces 24 positioned at both ends in the second direction, and a light incident face 24a that is provided at least at one of these pair of end faces 24 and receives the light from a light source 3 so as to enable the light from the light source 3 to go toward the light reflecting face 25. At least a part of the light-radiating face 26 is made a curvature that is bent so that the thickness of the portion of this second light-guide plate 2B becomes the smaller the more it is separated from the first light-guide plate 2A, and the light reflected by this curvature enters into the first side face 22a of the first light-guide plate 2A through the light-radiating face 26. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminating device suitable for illuminating a desired planar area such as illuminating a liquid crystal panel, and a liquid crystal display device provided with this illuminating device.

[0002]

2. Description of the Related Art An example of a conventional liquid crystal display device is shown in FIG.
Shown in (a) and (b). The illustrated liquid crystal display device is a front light type reflective liquid crystal display device. This liquid crystal display device includes a liquid crystal panel 8 having a reflection plate 80 on a back surface thereof, a light guide plate 9 arranged in front of the liquid crystal panel 8,
And a light source 7. The light guide plate 9 has a substantially rectangular flat plate shape and is made of transparent synthetic resin. Side surface 9 of this light guide plate 9
At 0c, a light incident surface portion 92 that faces the light source 7 is provided. The side surface 90d of the light guide plate 9 is provided with a plurality of recesses 93 each forming a pair of V-shaped wall surfaces 93a. The surface 90 a of the light guide plate 9 has a plurality of convex portions 91.
It has an uneven surface. Each convex portion 91 has two types of inclined surfaces 91a and 91b having different inclination directions.

In the liquid crystal display device having the above structure, the light emitted from the light source 7 enters the light guide plate 9 through the light incident surface portion 92 and advances toward the side surface 90d. Of these lights, the light that reaches the wall surface 93a of each recess 93 is reflected and travels toward the side surface 90e of the light guide plate 9. In the traveling process of the light, the light that reaches the inclined surface 91a of the convex portion 91 is reflected so that the traveling direction thereof is rapidly changed, and enters the back surface 90b of the light guide plate 9. When the incident angle of light on the back surface 90b is smaller than a predetermined critical angle for total reflection specified by the material of the light guide plate 9, this light is directly emitted to the outside of the light guide plate 9. As a result, the liquid crystal panel 8
Is illuminated.

[0004]

However, the above-mentioned conventional device has the following problems.

That is, as the light source 7, for example, LE
Although the D light source is used, the light emitted from the light source 7 has a constant spread angle not only in the width direction of the light guide plate 9 but also in the thickness direction of the light guide plate 9 (the vertical direction in FIG. 7A). There is. Therefore, of the light that has traveled into the light guide plate 9, the proportion of the light that enters the front and back surfaces 90a and 90b of the light guide plate 9 at a small incident angle is relatively large. On the other hand,
When light enters the front and back surfaces 90a and 90b of the light guide plate 9,
If the incident angle is smaller than a predetermined critical angle for total reflection, this light leaks to the outside of the light guide plate 9 as it is. Therefore, in the conventional case, the back surface 90b is formed by the inclined surface 91a.
The ratio of light that leaks to the outside from a portion other than the back surface 90b of the light guide plate 9 in a route different from the route reflected toward is high, resulting in poor illumination efficiency. If the illumination efficiency is poor, the display screen of the liquid crystal panel 8 will be dark and the quality of the image will be poor.

The present invention has been conceived under such circumstances, and an object thereof is to provide a lighting device having a simple structure capable of increasing the lighting efficiency. Another object of the present invention is to provide a liquid crystal display device capable of obtaining a bright display screen.

[0007]

DISCLOSURE OF THE INVENTION In order to solve the above problems, the present invention takes the following technical means.

An illumination device provided by the first aspect of the present invention comprises a light source and a first light guide plate, and the first light guide plate is spaced in the thickness direction. When the light from the light source travels in the first direction in the first light guide plate, it has front and back surfaces and first and second side surfaces spaced in the first direction. An illuminating device capable of emitting light from the back surface, comprising a second light guide plate that is separate from the first light guide plate, and the second light guide plate is the first light guide plate. Second crossing direction
A light emitting surface and a light reflecting surface extending in the respective directions,
A pair of end faces located at both ends in the second direction, and at least one of the pair of end faces are provided so that light from the light source can travel toward the light reflecting surface. And a light incident surface for receiving light, and at least a part of the light emitting surface is curved such that the thickness of the second light guide plate becomes smaller as it goes away from the first light guide plate. It is a curved surface, and the light reflected by the curved surface is configured to enter the first side surface of the first light guide plate via the light emitting surface.

A plurality of inclined surfaces are formed on the surface of the first light guide plate, and light reaching these plurality of inclined surfaces is reflected toward the back surface of the first light guide plate. Thus, it is possible to adopt a structure in which the back surface emits light.

According to this structure, by utilizing the second light guide plate, the light of the light source is properly guided into the first light guide plate, and the back surface of the first light guide plate is also guided. It is possible to emit light toward a desired illumination area. When the light from the light source travels into the second light guide plate and is reflected by the curved surface portion of the light reflection surface, in the reflected light, in the thickness direction of the first and second light guide plates. It is possible to generate a large amount of light that does not have a large spread angle. Therefore, when the reflected light including such light travels into the first light guide plate, the light is wastefully emitted to the outside from a position other than the back surface of the first light guide plate as compared with the case of the conventional technique. It is possible to reduce the amount of lighting and improve the lighting efficiency.

In a preferred embodiment of the present invention, the curved surface is a paraboloidal surface. When receiving a plurality of light rays starting from a point corresponding to the focal point of the parabolic cylinder surface and then reflecting the light rays, the parabolic cylinder surface has a characteristic that these plurality of light rays form a bundle of rays parallel to the principal axis. Therefore, according to the above configuration, among the light reflected by the light reflecting surface of the second light guide plate, the light that does not have a large spread angle in the thickness direction of the first and second light guide plates is included. It is more preferable to include a large amount to reduce the amount of light that is unduly emitted from a portion other than the back surface of the first light guide plate.

In another preferred embodiment of the present invention, the light exit surface of the second light guide plate is a convex curved surface. According to such a configuration, the light emitting surface plays the same role as the lens surface of the convex lens, and the light traveling from the light emitting surface toward the first light guide plate is
It is possible to more thoroughly suppress the spread of the first and second light guide plates in the thickness direction.

An illumination device provided by the second aspect of the present invention comprises a light source and a light guide plate, and the light guide plate has a front surface and a back surface which are spaced in a thickness direction, and a first light guide plate. A first and a second side surface spaced apart in a direction, and a third and a fourth side surface connected to the first and second side surfaces and spaced apart in a second direction. At least a part of at least one of the fourth side surfaces is a light incident surface for allowing the light from the light source to enter so as to allow the light from the light source to travel toward the first side surface. In the illuminating device, which is capable of emitting the light from the back surface when the light travels in the first direction in the inside, a surface of one side edge including the first side surface of the light guide plate is , The further away from the second side surface in the first direction, It is characterized in that the thickness of one side edge portion of the light guide plate is a curved curved so as to reduce. Also in this case, the curved surface may be a parabolic cylindrical surface.

The illuminating device having such a structure corresponds to the illuminating device provided by the first aspect of the present invention in which the first light guide plate and the second light guide plate are integrated. Has become. Therefore, also in this lighting device, the same effects as those of the lighting device provided by the first aspect of the present invention can be obtained.

A liquid crystal display device provided by the third aspect of the present invention is a liquid crystal display device including a liquid crystal panel and an illuminating device for illuminating the liquid crystal panel. The lighting device provided by the first aspect or the second aspect of the present invention is used.

With such a configuration, since the illumination efficiency of the illumination device is good, the display screen of the liquid crystal panel can be brightened and the quality of the displayed image can be improved with low power consumption.

Other features and advantages of the present invention will become more apparent from the following description of the embodiments of the invention.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings.

1 and 2 show an embodiment of the present invention. The liquid crystal display device A shown in FIG. 1 is a front-light type reflective liquid crystal display device, and includes a liquid crystal panel 1 and a lighting device B. The lighting device B includes first and second light guide plates 2A and 2B and a pair of light sources 3.

The first light guide plate 2A is made of a highly transparent synthetic resin having a substantially rectangular flat plate shape, and has a front surface 20a and a rear surface 20b spaced in the thickness direction, and first to fourth portions.
Side surfaces 22a to 22d. First and second
As shown in FIG. 2, the side surfaces 22a and 22b are spaced from each other in the first direction N1 and extend in the second direction N2 orthogonal thereto. The third and fourth side faces 22c, 22d are spaced from each other in the second direction N2 and extend in the first direction N1. All of the plurality of surfaces of the first light guide plate 2A are smooth surfaces (mirror surfaces) capable of totally reflecting the light received under a constant condition.

The first to fourth side faces 22a to 22d and the back face 20b are all flat. In contrast,
The surface 20a is an uneven surface provided with a plurality of convex portions 21 extending uniformly in the cross section in the second direction N2. Each convex portion 2
1 has a plurality of two kinds of inclined surfaces 21a and 21b inclined with respect to the back surface 20b. When each of the inclined surfaces 21a receives the light traveling from the first side surface 22a to the second side surface 22b, the inclined surface 21a is a surface that reflects the light so that the light is incident on the back surface 20b at a small incident angle. Each inclined surface 21b
Is a surface for totally reflecting this light as much as possible and preventing it from leaking to the outside of the light guide plate 2 when receiving light traveling in the same direction as described above. It is inclined at a relatively gentle angle.

The second light guide plate 2B is made of the same transparent resin as the first light guide plate 2A and is provided adjacent to the first light guide plate 2A. The second light guide plate 2B has a light reflecting surface 25 and a light emitting surface 26 extending in the second direction N2.
And a pair of end faces 24 located at both ends in the second direction N2. Of the plurality of surfaces of the second light guide plate 2B extending in the second direction N2, the portion excluding the light emitting surface 26 is the light reflecting surface 25. The surface of each part of the second light guide plate 2B is also mirror-like, like the first light guide plate 2A.

A part of each end face 24 is a light incident face 24a on which the light source 3 is arranged so as to face it. The light source 3 is, for example, an LED light source, and specific examples thereof include an LED bare chip directly used as a light source, or an LE.
There is a D bare chip resin-packaged in a chip shape using a resin having a light-transmitting property. The light emitted from the light source 3 travels into the second light guide plate 2B via the light incident surface 24a and enters the light reflecting surface 25.

As shown in FIG. 1 (a), the light reflecting surface 25 has a pair of upper and lower flat surface portions 25a spaced apart in the thickness direction, and a curved surface portion 25b connected to these. There is. The curved surface portion 25b is a parabolic pillar surface that is curved so as to reduce the thickness of the second light guide plate 2B as the distance from the first light guide plate 2A increases. More specifically, when the contour line of the curved surface portion 25b is expressed by the orthogonal coordinates of the x and y axes with the point O in the figure as the origin, the contour line is a parabola corresponding to y = 4x ² . Note that the y-axis coincides with the center line C in the thickness direction of the second light guide plate 2B.

As shown in FIG. 2B, a portion of the light reflecting surface 25, which is opposite to the light emitting surface 26, has a pair of mountain-shaped inclined wall surfaces 29a and a surface connecting them. A plurality of concave portions 29, which respectively form 29b, are provided at appropriate intervals in the second direction N2. Each inclined wall 2
When the light emitted from the light source 3 is received by each of the inclined wall surfaces 29a, the inclination angle θ of 9a is an angle at which the light can be totally reflected in the first direction N1 or in a direction substantially parallel thereto.
The plurality of inclined wall surfaces 29a help to efficiently introduce light from the second light guide plate 2B to the first light guide plate 2A.

The light exit surface 26 is the first light guide plate 2A of the first light guide plate 2A.
And faces the side surface 22a. This light emitting surface 2
6 is a convex curved surface having an appropriate radius of curvature R.

The second light guide plate 2B preferably has a structure in which the light reflecting surface 25 is covered by a reflector 40 having a high light reflectance, as shown by the phantom line in FIG. 1 (b). With such a configuration, when the light inside the second light guide plate 2B is transmitted through the light reflecting surface 25, this light can be returned to the inside of the second light guide plate 2B, and the loss of light is reduced. It is suitable for

The liquid crystal panel 1 has a conventionally known structure and has, for example, the following configuration. That is, the liquid crystal panel 1 is one in which a liquid crystal 11 is enclosed between a pair of substrates 10a, 10b made of glass or resin, and a plurality of electrodes 14a, 14b and Alignment films 13a, 1
3b is provided. A polarizing plate 16a is provided on the front surface of the substrate 10a. As a driving method, a simple matrix method (passive driving method) is adopted, and the plurality of electrodes 14a correspond to horizontal electrodes (scanning electrodes), extend in the left-right direction in the figure, and extend in the direction orthogonal to the plane of the drawing. They are arranged in parallel at intervals. The plurality of electrodes 14b correspond to vertical electrodes (signal electrodes), extend in a direction orthogonal to the paper surface, and are arranged in parallel in the left-right direction of the drawing at equal intervals. Liquid crystal 11
Is configured such that a voltage is applied to a portion where the two types of electrodes 14a and 14b intersect and overlap each other, and this portion serves as a dot-shaped pixel. Of course, in the present invention, an active drive system can be adopted as a drive system for the liquid crystal panel.

The substrate 10a is a transparent substrate, and each electrode 14a is a transparent electrode made of an ITO film or the like. On the other hand, each electrode 14b is a metal reflection electrode capable of reflecting light. This liquid crystal panel 1
In the above, when the light traveling from the front surface toward the liquid crystal panel 1 passes through the polarizing plate 16a, the substrate 10a, and the liquid crystal 11, it is reflected by the plurality of electrodes 14b toward the front surface of the liquid crystal panel 1. Has become. Of course, in the present invention, instead of such a structure using the reflective electrode, a structure in which a reflective plate is provided on the back surface of the liquid crystal panel 1 can be adopted. As the liquid crystal panel, one for color display may be used instead of one for monochrome display.

Next, the operation of the liquid crystal display device A having the above structure will be described.

In FIG. 2, when the pair of light sources 3 are driven to turn on, the light emitted from each light source 3 emits light.
Through the second light guide plate 2B. Most of this light reaches the light emitting surface 26 by one total reflection by the light reflecting surface 25 or by repeating total reflection multiple times for each part of the light reflecting surface 25, and reaches the first light guide plate 2A.
The light is emitted toward the first side surface 22a.

Since the curved surface portion 25b of the light reflecting surface 25 is a parabolic cylindrical surface, the curved surface portion 2b is formed due to the characteristics of the parabolic cylindrical surface.
Part of the light reflected by 5b is the second light guide plate 2B.
Traveling in parallel or substantially parallel to the central axis C of the
Will be headed for. Therefore, the light entering the first light guide plate 2A from the second light guide plate 2B does not include many light rays having a large inclination angle with respect to the central axis C. Further, when light is emitted from the light emitting surface 26, since the light emitting surface 26 is a convex curved surface, a light ray having an inclination with respect to the central axis C is refracted so as to approach an angle parallel to the central axis C. To do. Therefore, the first and second light guide plates 2A,
Light concentrated in the thickness direction of 2B travels in the first light guide plate 2A at a high rate.

When the light narrowed in the thickness direction as described above enters the first light guide plate 2A, this light is inclined surface 21.
Except when reflected by a toward the back surface 20b,
The phenomenon that most of them enter the respective parts of the first light guide plate 2A at a small incident angle and leak to the outside as they are is unlikely to occur. As a result, the amount of light emitted from the rear surface 20b toward the liquid crystal panel 1 increases by that amount.

The light is emitted from the rear surface 20b toward the liquid crystal panel 1, as in the prior art. The light is totally reflected by the portions of the front and rear surfaces 20a and 20b of the first light guide plate 2A except the inclined surface 21a. This is done by repeating the light traveling from the first side surface 22a to the second side surface 22b while being totally reflected toward the back surface 20b while reaching the inclined surface 21a in the course of the progress. The light applied to the liquid crystal panel 1 is reflected by the electrodes 14b of the liquid crystal panel 1 toward the front surface of the liquid crystal panel 1, and is transmitted through the first light guide plate 2A in the thickness direction. Therefore, this first light guide plate 2
The image displayed on the liquid crystal panel 1 can be viewed through A. As described above, since the illumination efficiency of the illumination device B is high, the display screen of the liquid crystal panel 1 can be brightened with low power consumption and its image quality can be improved.

The inventors of the present application performed simulations on the lighting device B of the above-described embodiment and the lighting device of the comparative example shown in FIG. The comparative example shown in FIG. 3 is provided with the first light guide plate 2A, the second light guide plate 2E, and the pair of light sources 3. The first light guide plate 2A and each light source 3 are the same as those in the above-described embodiment. It is the same as the one. Second proportional light guide plate 2
E has a rectangular cross section, and is configured differently from the second light guide plate 2B having the parabolic prismatic light reflecting surface and the convex curved light emitting surface of the above embodiment. . The description of specific dimensions of each part of the above-described embodiment and the comparative example is omitted, but the above-described embodiment and the comparative example are different only in the points of the second light guide plate 2E described above. No
All other configurations were the same. The simulation is to analyze the paths of these light rays when a plurality of light rays radially radiating at a constant angle are incident on the second light guide plate 2B and the second light guide plate 2E from each light source 3. did. As an example of such a simulation result, when a total of 400 light beams from the pair of light sources 3 are made incident on each of the second light guide plate 2B and the second light guide plate 2E, in comparison with each other, The number of light rays emitted downward from the back surface 20b of the light guide plate 2A of No. 1 was 185. On the other hand, in the above embodiment, the number is 206. From this simulation result, it will be understood that according to the above-described embodiment, the illumination efficiency can be improved as compared with the related art.

4 to 6 show another embodiment of the present invention. In these figures, the same or similar elements as those in the above embodiment are designated by the same reference numerals as in the above embodiment.

In the illumination device Ba shown in FIG. 4, when the light traveling in the first light guide plate 2A reaches the second side surface 22b,
This light is reflected in the direction of the first side surface 22a. As a means for this, for example, the second side surface 22b is provided with the reflection film 4 made of a vapor deposition film of aluminum or the like. On the surface 20a of the first light guide plate 2A,
When the light traveling from the second side surface 22b toward the first side surface 22a is received, the plurality of inclined surfaces 21 that reflect the light toward the back surface 20b at a small incident angle.
c are formed so as to be arranged alternately with the inclined surfaces 21a.

According to this structure, the second light guide plate 2
Part of the light that has traveled from B to the inside of the first light guide plate 2A is
In addition to being emitted from the back surface 20b when traveling from the side surface 22a to the second side surface 22b, when the remaining light is returned from the second side surface 22b toward the first side surface 22a, This light can be appropriately emitted from the back surface 20b. With this configuration, the returning light can be used for illumination, and the leakage of light from the second side surface 22b can be prevented, so that the illumination efficiency can be further improved. Further, it is also suitable for solving the problem that either one of the vicinity of the first side surface 22a and the vicinity of the second side surface 22b becomes brighter than the other, and making the illuminance of the illumination area uniform. .

In the structure shown in FIG. 4, the light emitting surface 26 of the second light guide plate 2B is made flat, but the present invention can also have such a structure. Further, in the present invention, all the surfaces of the second light guide plate extending in the second direction N2 except the light emitting surface 26 may be formed in a curved shape. The curved surface does not have to be an accurate parabolic cylindrical surface, and can be formed into various curved surfaces within a range in which the effect intended by the present invention can be effectively obtained.

The illumination device Bb shown in FIGS. 5 and 6 has a structure corresponding to that of the first and second light guide plates 2A and 2B of the embodiment shown in FIGS. There is. More specifically, in the lighting device Bb of the present embodiment, one side edge surface 28 including the first side surface 22a of the light guide plate 2 in which the plurality of inclined surfaces 21a and 21b are formed on the surface 20a.
Is formed as a parabolic column surface. The first side surface 22 of the third and fourth side surfaces 22c and 22d of the light guide plate 2
A light incident surface 24a is formed in the vicinity of a, and the light source 3 faces this portion.

According to this structure, when the light emitted from each light source 3 travels into the light guide plate 2 and reaches the surface 28, a part of this light is transmitted through the central axis of the light guide plate 2 in the thickness direction. It is possible to reflect the light so as not to have a large inclination with respect to the light guide plate 2, and it is possible to allow the light that is focused in the thickness direction of the light guide plate 2 to travel toward the second side surface 22b. Therefore, also in the present embodiment, the illumination efficiency can be increased similarly to the above-described embodiments. In this embodiment, since the number of light guide plates is one, it is possible to improve the productivity of the lighting device as compared with the case where two light guide plates are used.

The content of the present invention is not limited to the above-mentioned embodiment. The specific configurations of the respective parts of the illumination device and the liquid crystal display device according to the present invention can be changed in design in various ways.

The liquid crystal display device according to the present invention can be configured as a backlight type transmissive liquid crystal display device instead of the front light type reflective liquid crystal display device. In the case of the backlight system, by making the back surface of the light guide plate that emits light face the back surface of the liquid crystal panel, the light that has entered the liquid crystal panel from the light exit surface of the light guide plate remains It suffices that the light is transmitted to the front side, and it is not necessary to change the basic structure of the lighting device itself. The front surface of the light guide plate in the present invention refers to one of the two surfaces spaced in the thickness direction of the light guide plate, and the back surface refers to the other surface on the opposite side. The upward surface is not always the surface referred to in the present invention.

In the illuminating device according to the present invention, the specific number of light sources is not limited, and for example, it may be configured to use only one light source. Further, the specific type of the light source is not limited, and a light source other than the LED light source can be used.

[Brief description of drawings]

1A and 1B show an embodiment of the present invention, in which FIG. 1A is an enlarged sectional view of a main part, and FIG. 1B is a schematic sectional view of the whole.

2A is a plan view of FIG. 1B, and FIG.
[Fig. 4] is an enlarged cross-sectional view of a II part in (a).

FIG. 3 shows a comparison with the present invention, (a) is a plan view, and (b) is a sectional view thereof.

FIG. 4 is a sectional view showing another embodiment of the present invention.

FIG. 5 is a sectional view showing another embodiment of the present invention.

FIG. 6 is a plan view of FIG.

FIG. 7 shows the prior art, (a) is a sectional view,
(B) is the top view.

[Explanation of symbols]

A liquid crystal display B, Ba, Bb lighting device 1 LCD panel 2 Light guide plate 2A First light guide plate 2B Second light guide plate 3 light sources 20a surface 20b back side 21a inclined surface 22a First side surface 22b Second side 22c Third side surface 22d Fourth side 24 end face 24a light incident surface 25 Light reflection surface 27 Light exit surface

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02F 1/13357 G02F 1/13357 // F21Y 101: 02 F21Y 101: 02 F term (reference) 2H038 AA52 AA55 BA06 2H091 FA08X FA08Z FA23Z FA41X FA41Z FA45Z GA01 LA30

Claims (6)

[Claims] 1. A light source and a first light guide plate, wherein the first light guide plate has front and back surfaces spaced in a thickness direction and a space in the first direction. An illuminating device having first and second side surfaces, wherein when the light from the light source travels in the first direction in the first light guide plate, the light can be emitted from the back surface. And a second light guide plate which is separate from the first light guide plate, and the second light guide plate is respectively provided in a second direction intersecting with the first direction. A light emitting surface and a light reflecting surface which extend, a pair of end surfaces located at both ends in the second direction, and a light provided from at least one of the pair of end surfaces, and directing light from the light source toward the light reflecting surface. And a light incident surface that receives light from the light source so as to be able to proceed, At least a part of the light-exiting surface is a curved surface so that the thickness of the second light guide plate becomes smaller as it goes away from the first light guide plate, and the light reflected by the curved surface becomes light. An illumination device configured to enter the first side surface of the first light guide plate via a light exit surface. 2. The curved surface is a parabolic prismatic surface.
The lighting device according to. 3. The illumination device according to claim 1, wherein a light emitting surface of the second light guide plate is a convex curved surface. 4. The surface of the first light guide plate is formed with a plurality of inclined surfaces, and light reaching these plurality of inclined surfaces is reflected toward the back surface of the first light guide plate. The illuminating device according to claim 1 or 2, wherein the illuminating device is configured to emit to the outside from this back surface. 5. A light source and a light guide plate, wherein the light guide plate has front and back surfaces spaced apart in a thickness direction, and a first light guide plate.
A first side surface and a second side surface that are spaced apart in the second direction, and third and fourth side surfaces that are connected to the first and second side surfaces and are spaced apart in the second direction. A part of at least one of the fourth side surface is a light incident surface for allowing the light from the light source to enter so as to allow the light from the light source to travel toward the first side surface. A lighting device, wherein the light can be emitted from the back surface when the light travels in the first direction in the light plate, the surface of one side edge including the first side surface of the light guide plate. Is a curved surface that is curved such that the thickness of one side edge portion of the light guide plate becomes smaller as it goes away from the second side surface in the first direction. 6. A liquid crystal display device comprising a liquid crystal panel and an illuminating device for illuminating the liquid crystal panel, wherein the illuminating device according to any one of claims 1 to 5 is used as the illuminating device. A liquid crystal display device characterized by being used.