JP2000194273A - Light guide plate and backlighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a light guide plate capable of attaining a sufficient luminescence area even in the case of a small-sized thin plate and having enhanced strength as compared with the conventional wedge-shaped one by forming plural inclined parts at the under surface of a plate from the light incidence side toward the opposite side. SOLUTION: The light guide plate 1 is obtained by injection-molding a synthetic resin such as an acrylic resin or a polycarbonate and has a nearly rectangular cross section and plural inclined parts at the under surface. The inclined parts are continuously formed along the traveling direction of light at a uniform width and the same angle of inclination. When light is incident from a light source 2 on the light guide plate 1, the traveling direction of light reflected by the upper surface of the plate 1 is changed whenever the light is reflected by an inclined surface, the incident angle to the upper surface is gradually reduced and light emerges gradually from the upper surface. The conventional effect is therefore produced while reducing the thickness of the light guide plate 1.

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 for emitting light incident from the side surface from the upper surface and a backlight device using the same, and is particularly suitable for thinning.

[0002]

2. Description of the Related Art Conventionally, as a light guide plate used in a liquid crystal backlight device, for example, a light guide plate described in Japanese Patent Application Laid-Open No. 9-274807 is known. Such a conventional light guide plate is shown in FIGS. In the figure, 11 is a light guide plate, 1
2 is a fluorescent lamp. The light guide plate 11 is injection-molded with a synthetic resin such as an acrylic resin or a polycarbonate. In addition, it usually has a wedge shape in which the lower surface approaches the upper surface as the distance from the incident side surface increases.

[0003] In such a light guide plate, light incident from the side surface travels inside the light guide plate while being repeatedly reflected between the upper surface and the lower surface. At this time, since the lower surface is inclined toward the upper surface as described above, the angle of incidence of light on the upper surface gradually decreases as the distance from the light source increases. Therefore, the light incident on the light guide plate 11 gradually exits from the upper surface while traveling in the light guide plate 11. Thereby, the upper surface of the light guide plate 1 emits surface light, and functions as a backlight device.

[0004]

As described above, such a light guide plate is often used for a liquid crystal backlight. However, recently, with the miniaturization of portable information terminals and mobile phones equipped with a liquid crystal display device, it has been desired that the light guide plate is also reduced in size and thickness. However, in the case where the conventional wedge shape is used to reduce the thickness, if the same light emitting area is to be realized, the inclination angle of the lower surface becomes gentler than before. As described above, when the inclination of the lower surface becomes gentle, the incident angle with respect to the upper surface does not change so much even if the light travels inside the light guide plate, and therefore, only a small amount of light can be emitted from the upper surface. On the other hand, if the lower surface of the light guide plate is inclined at the same angle as in the related art, a sufficient light emitting area cannot be obtained.

Further, when the light guide plate is reduced in size and thickness, in the conventional wedge shape, the thickness of the end portion opposite to the incident surface becomes extremely thin, so that sufficient strength cannot be obtained, and breakage or shape change occurs. Cheap. In particular, there is a problem that defects are liable to occur in a manufacturing process such as injection molding and the production yield is significantly deteriorated.

Accordingly, an object of the present invention is to provide a light guide plate and a backlight device which can realize a sufficient light emitting area even when the device is small and thin, and can improve the strength as compared with the conventional wedge shape. Things.

[0007]

In order to solve the above problems,
The present invention has the following features.

According to a first aspect of the present invention, in a light guide plate for emitting light incident from a side surface from an upper surface, a lower surface is formed substantially parallel to the upper surface, and the lower surface is formed on the lower surface as viewed from the light incident surface side. The inclined part gradually inclined toward the top surface
It is characterized in that a plurality are formed from the light incident part side to the opposite end part.

A second aspect of the present invention is characterized in that, in the first aspect, each of the inclined portions has the same shape as each other.

According to a third aspect of the present invention, in the first aspect, the inclination angle of the inclined portion gradually increases as the distance from the light incident portion side increases.

According to a fourth aspect of the present invention, in the third aspect, the density of the inclined portion is gradually increased as the distance from the light incident portion side increases.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, a projection protruding toward the upper surface is formed in the inclined portion.

According to a sixth aspect of the present invention, in the fifth aspect, the density of the protrusion gradually increases with increasing distance from the light incident portion side.

The invention according to claim 7 is the invention according to claims 1 to 6 above.
Is a backlight device adopting as a light guide plate for surface emission.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described below with reference to FIGS.

In FIG. 1, reference numeral 1 denotes a light guide plate, which is injection-molded with a synthetic resin such as an acrylic resin or a polycarbonate, similarly to the above-mentioned conventional example. The light guide plate 1 has a substantially rectangular cross section, and has a plurality of inclined portions 1a formed on the lower surface. Such an inclined portion 1a is formed continuously with a constant width along the traveling direction of light as shown in FIG. Also,
The inclination angles θ of the inclined portions 1a are all set to be the same.

In FIG. 1, the end of the inclined portion 1a and the starting end of the next inclined portion 1a are connected by a vertical plane. Instead, the inclined end is inclined toward the starting end of the next inclined portion 1a. You may make it connect both on the surface which did. With this configuration, the light guide plate can be easily peeled from the mold during injection molding, and the molding performance is improved.

FIG. 3 shows an example of dimensions of the light guide plate 1.
The thickness of the light incident side surface of the light guide plate 1 is 1 mm. Inclined part 1
If the inclination angle of the light guide plate 1 is set to θ = 2.77 deg. and the width of the inclined portion 1a in the light traveling direction is set to 6.2 mm, the thickness of the thinnest portion of the light guide plate 1 (the end of each inclined portion) is 0.1 mm. 7 mm. Therefore, the decrease in thickness due to the inclined portion 1a is 30%.
The degree of mechanical strength can be suppressed.

FIG. 4 shows a traveling state of light when light from the light source 2 enters the light guide plate 1. As shown in the figure,
The traveling direction of the light reflected on the upper surface of the light guide plate 1 is changed each time the light is reflected on the inclined surface 1a, whereby the incident angle with respect to the upper surface is gradually reduced and the light is gradually emitted from the upper surface. . Therefore, according to such an embodiment,
The same effect as that of the above-described conventional example can be achieved while reducing the thickness of the light guide plate 1.

For reference, FIG. 5 shows an example in which a conventional wedge-shaped light guide plate having the same dimensions is formed. As can be seen from the figure, when the conventional light guide plate is formed with the same dimensions,
Compared to the light guide plate of the present embodiment, only a light emitting area of substantially half can be realized. Moreover, the thickness of the end portion of the light guide plate is extremely small, and there is a possibility that the light guide plate may be damaged by a small external pressure.

In this embodiment, as the light guide plate becomes thinner, it becomes more difficult for the light of the fluorescent lamp to enter the light guide plate.
In the embodiment of FIG. 1, in order to eliminate such inconvenience, the reflective cover 3 is arranged around the fluorescent lamp 2 to increase the efficiency of light incident on the light guide plate 1 from the fluorescent lamp 2.

In this embodiment, the fluorescent lamp 2 is used as a light source.
(Light Emission Diode) may be used. In this case, the red, blue, and green LEDs may be sequentially arranged on the incident side surface of the light guide plate 1, or the light of these three LEDs may be distributed by a number of optical fibers to be incident from the side surface of the light guide plate 1. You may do it.

By the way, when the inclined portion 1a is formed in the same shape as in the above embodiment, there is an effect that the light guide plate 1 is unlikely to be warped with time, but on the other hand, the light reflection on the lower surface is caused. Therefore, the intensity distribution of the light emitted from the upper surface of the light guide plate 1 tends to be uneven. That is, light emission at the center of the upper surface of the light guide plate 1 or at a position slightly closer to the end from the center is reduced.

This inconvenience is usually solved by silk-printing a matrix-shaped irregular reflection dot pattern on the lower surface of the light guide plate 1 while adjusting the dot density.

However, such a problem can also be solved by adjusting the inclination angle and width of the inclined portion 1a in the above embodiment. Hereinafter, various embodiments capable of solving such a problem will be described with reference to the drawings.

FIG. 6 shows an example in which the width of the inclined portion 1a is gradually reduced as the distance from the light source increases. In this case, the angle of the slope 1a gradually increases as the width of the slope decreases. The dimensions of the inclined portion on the closest side of the fluorescent lamp 2 are the same as those in the above embodiment. Therefore, the minimum dimension of the thickness of the light guide plate (the thickness at the end of each inclined portion) is 0.7 mm as in the above embodiment.

According to this embodiment, the fluorescent lamp 2
As the distance from the light guide plate 1 increases, the light enters the upper surface at an incident angle smaller than that in the above embodiment, so that the light reaching the end of the light guide plate 1 in the above embodiment is The light can be emitted at the central portion or at a slightly end side from the central portion.

FIG. 7 shows an example in which a projection is further provided on the inclined portion 1a in the embodiment of FIG. Such protrusions
Although it is formed as a groove shape parallel to the longitudinal direction of the fluorescent lamp 2 when viewed from the lower surface of the light guide plate 1, it may be formed as a plurality of depressions arranged in parallel to the longitudinal direction of the fluorescent lamp 2 instead. . Further, the number of such protrusions is provided so that the number increases as the distance from the fluorescent lamp 2 increases.

According to this configuration, since the light is reflected by the projection, the angle of incidence of the light on the upper surface of the light guide plate becomes smaller than that in the embodiment of FIG. 3, and the light is emitted from the upper surface of the light guide plate. It is easy to be.

FIG. 8 shows the embodiment of FIG.
This is an example in which a protrusion similar to the above is further provided on the inclined portion 1a. According to such a configuration, as in the case of FIG. 7, the light is reflected by the projection, so that the incident angle of light on the upper surface of the light guide plate is smaller than that of the embodiment of FIG. Light is easily emitted from the upper surface.

Although various embodiments according to the present invention have been described above, the present invention is not limited to these embodiments. For example, in the above embodiment, the inclined portion 1a
Are formed continuously, but a flat portion parallel to the upper surface of the light guide plate may be provided between the adjacent inclined portions. Further, the dimensions described in the above embodiment are merely examples, and various design dimensions can be adopted according to the shape, dimensions, number of arrangements, and the like of the inclined portions.

Further, in the embodiment shown in FIG. 6, the width and the inclination angle of the inclined portion are both changed so that the reduction in the thickness of the light guide plate caused by each inclined portion is made to coincide with each other.
A shape that changes only the width of the inclined portion with the same inclination angle, a shape that changes the angle of the inclined portion with a constant width, or a decrease in the thickness of the light guide plate due to each inclined portion, A shape that adjusts both the tilt angle and the width may be employed.

In any case, the inclination angle and width of each inclined portion and the arrangement of the protrusions formed on each inclined portion are set so that the intensity distribution of light emitted from the upper surface of the light guide plate becomes uniform. To do.

Although the present invention is suitable for use in a liquid crystal backlight device, it goes without saying that the present invention can be used for other backlight devices.

[0035]

According to the light guide plate of the present invention, a sufficient light emitting area can be realized even when the light guide plate is small and thin, and the strength can be remarkably improved as compared with the conventional wedge shape.

[Brief description of the drawings]

FIG. 1 is a perspective view according to a first embodiment.

FIG. 2 is a bottom view of the light guide plate according to the first embodiment.

FIG. 3 is a side view of the light guide plate according to the first embodiment.

FIG. 4 is a diagram showing a state of light inside the light guide plate according to the first embodiment.

FIG. 5 is a reference diagram showing the effect of the first embodiment.

FIG. 6 is a side view of a light guide plate according to a second embodiment.

FIG. 7 is a side view of a light guide plate according to a third embodiment.

FIG. 8 is a side view of a light guide plate according to a fourth embodiment.

FIG. 9 is a perspective view showing a conventional example.

FIG. 10 is a side view of a light guide plate according to a conventional example.

[Explanation of symbols]

 Reference Signs List 1 light guide plate 1a inclined portion 2 fluorescent lamp 3 reflective cover

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02F 1/1335 530 G02F 1/1335 530 (72) Inventor Hidetoshi Ito 2-5 Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd. F term (reference) 2H038 AA55 BA01 2H091 FA23Z FA24Z FA42Z FA45Z FB02 FD01 FD03 LA11 LA16 5G435 AA06 AA18 BB03 BB04 BB12 BB15 DD11 EE27 FF08 GG24 LL07

Claims (7)

[Claims] 1. A light guide plate for emitting light incident from a side surface from an upper surface, wherein a lower surface is formed substantially parallel to the upper surface, and the lower surface is gradually formed toward the upper surface when viewed from the light incident surface side. A light guide plate, wherein a plurality of inclined portions are formed from a light incident portion side to an opposite end portion. 2. The light guide plate according to claim 1, wherein the inclined portions have the same shape. 3. The light guide plate according to claim 1, wherein the angle of the inclined portion gradually increases as the distance from the light incident portion increases. 4. The light guide plate according to claim 3, wherein the density of the inclined portion gradually increases as the distance from the light incident portion side increases. 5. The light guide plate according to claim 1, wherein a protrusion protruding toward the upper surface is formed on the inclined portion. 6. The light guide plate according to claim 5, wherein a density of the protrusion gradually increases as the distance from the light incident portion increases. 7. A backlight device employing the above-mentioned claims 1 to 6 as a light guide plate for surface light emission.