JPH0736348Y2 - Light guide plate device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a light guide plate device used as a backlight of a liquid crystal color television, a color word processor, a personal computer, a backlight of a signboard, or an interior lighting fixture.

(Prior Art) FIG. 14 shows a conventional light guide plate device, 1 is a light guide plate, and
The acrylic plate 2 having a thickness of 4 mm and the acrylic plate 3 having a thickness of 2 mm are superposed on each other, and one surface of the light guide plate 1 is a light emitting surface 4 and the other surface is a light shielding surface 5. One light diffusing member 6 made of, for example, a polycarbonate film is attached to the light-dissipating surface 4, a white polyethylene sheet 7 is attached to the light-shielding surface 5 to prevent light leakage, and the light-shielding surface 5 is scratched or printed. The irregular reflection portion 9 for irregularly reflecting the light
Are provided in a scattered manner. A light source 10 such as a lamp is provided at both ends of the light guide plate 1, and a cover 11 made of a vinyl chloride film having a thickness of about 0.5 mm is provided so that the light from the light source 10 is guided from the side end surface of the light guide plate 1. 1, the incident light is repeatedly reflected between the light-shielding surface 5 and the light-dissipating surface 4, and is diffusely reflected by the irregular reflection part 9, and the irregularly-reflected light is emitted from the light-dissipating surface 4 and The side was made to emit light.

There is also a light guide plate device in which the light guide plate 1 is formed of one acrylic plate.

However, regardless of whether the light guide plate 1 is a single acrylic plate or a laminate of two acrylic plates, the light guide plate 1 is repeated for the reason that light is repeatedly reflected between the light diffusion surface 4 and the light shielding surface 5. There is a drawback that the device loses a large amount of light before it emits surface light, and the light emission brightness on the side of the light emitting surface 4 does not increase so much. Therefore, it cannot be applied to a color liquid crystal that requires a high brightness backlight. . Also, in general,
In the light emitting surface 4, the brightness is high in the portion close to the light source 10, that is, the side end surface, but as the distance from the light source 10 tends to decrease, the brightness in the light emitting surface 4 becomes uneven.

JP-A-57-128 discloses a light guide plate device capable of obtaining uniform brightness.
Japanese Unexamined Patent Publication No. 383 discloses a surface lighting device in which the irregular reflection area is formed so as to become larger as the distance from the light source increases.

On the other hand, in addition to the uniformity of brightness, there is a demand for weight reduction of the light guide plate device. As a means for reducing the volume of the light guide plate to reduce its weight and to secure a certain level of brightness, Japanese Utility Model Laid-Open No. 62-65676 discloses an illuminated display device in which light sources are arranged on both sides, with a symmetrical central portion. There is disclosed a light guide plate that is thin.

(Problems to be solved by the invention) However, when a light guide plate having a thin central portion is used, the intensity of light varying from the end face to the central portion is slightly different from that when a flat light guide plate is used. Therefore, the degree of a so-called gradation pattern in which the area of the irregular reflection portion for satisfying the uniformity of luminance on the light emitting surface gradually increases (hereinafter, referred to as “the inclination of the gradation pattern of the irregular reflection portion”) is the center of the light guide plate. It is necessary to appropriately select it according to the degree of the downward inclination toward the portion (hereinafter, referred to as “the downward inclination of the light guide plate”). This selection work is complicated by the fact that the inclination of the descending inclination of the light guide plate and the brightness required for the final product (for example, the brightness required for the applied products such as interior devices and color LCD TVs) vary. It will be On the other hand, since the irregular reflection part is generally formed by directly printing on the light-shielding surface of the light guide plate with ink mixed with glass beads or the like, when a light guide plate composed of one sheet is used, a large number of trials are performed. It is not realistic because the light guide plate is wasted because the work is created and the right one is selected.

In view of the above problems, the present invention provides a light guide plate device which can easily and quickly meet a wide variety of requirements such as product size and brightness, which are lightweight, have high brightness, and have excellent brightness uniformity. To do.

(Means for Solving the Problem) The technical means of the present invention for solving this technical problem is provided with a light guide plate 15 having one surface as a light-dissipating surface 16 and the other surface as a light-shielding surface 17. In the light guide plate device, the light is incident from both end faces 18 of the light guide plate 15 and is diffused from the light diffuser face 16 of the light guide plate 15 so that the light diffuser face 16 side emits light.
15 is formed by superimposing a first plate member 19 on the side of the light-dissipating surface 16 and a second plate member 20 on the side of the light-shielding surface 17, and the first plate member 19 is the end surface on both sides.
The light-emitting surface 16 of the first plate member 19 is inclined downward from both ends toward the center so that the light-emitting surface 16 of the first plate member 19 is frosted so that the thickness gradually decreases from 18 to the central portion. Is
A diffuse reflection part 26 that diffuses light is provided on the light shield surface 17 side of the second plate member 20, and the ratio of the diffuse reflection part 26 to the light shield surface 17 gradually increases from the side closer to the light source 24 to the side far from the light source 24. It is characterized in that it is formed as follows.

(Operation) As shown in FIG. 12, the light from the light source 24 is emitted from both end surfaces 18 of the first plate member 19 and the second plate member 20 constituting the light guide plate 15 to the first plate member 19.
And a part of this light reaches the light emitting surface 16 directly without being reflected by the light shielding surface 17, and another part of the light reaches the light emitting surface 16 after being reflected by the light shielding surface 17. The light emitted from the light emitting surface 16 to the outside of the light guide plate 15 while being irregularly refracted here and emitted from the light emitting surface 16 is emitted to the outside through the two light diffusing members 23, and the light is diffused during this time. Light guide plate by member 23
The light emitted from 15 is diffused, and the light emitting surface 16 side of the light guide plate 15 emits light uniformly over the entire surface.

Further, a part of the light from the light source 24 is diffusely reflected by the diffuse reflection portion 26, and the reflected light is emitted from the light emitting surface 16 of the first plate member 19, and as a result, the light emitting surface 16 of the light guide plate 15 emits light. In this case, since the ratio of the irregular reflection portion 26 to the light-shielding surface 17 gradually increases from the side closer to the light source 24 to the side farther from the side, the light emission on the side closer to the light source 24 is suppressed and the light emission on the side farther increases. Therefore, the light emission from the light emitting surface 16 of the light guide plate 15 can be made more uniform regardless of the distance from the light source 24, and the uneven light emission from the light emitting surface 16 can be effectively prevented.

In order to effectively obtain the above effect in the light guide plate device of the present invention, it is necessary to select and set the inclination of the gradation pattern of the diffuse reflection part 26 that is appropriate according to the inclination of the descending inclination of the first plate member 19. The light guide plate 15 of the present invention is formed by stacking the first plate material 19 and the second plate material 20, and the irregular reflection portion 26 is provided on the second plate material 20, so that the irregular reflection portion 26 having various gradation pattern inclinations is printed. An appropriate one may be selected from the second plate materials 20. Therefore, it is possible to easily and promptly provide a light guide plate device having a configuration capable of effectively exerting the effects of the present invention without performing a complicated selection work despite the variety of the first plate members 19.

If the circular arc portion 16a is not provided in the center of the light emitting surface 16 and this portion is bent into a V shape, the light guide surface 15 of the light guide plate 15 on the side of the light emitting surface 16 corresponds to the bent portion. Although a dark line is generated at the center, in the embodiment, since the arc portion 16a is provided at the center of the light diffusion surface 16, it is possible to effectively prevent the above dark line from being generated by the arc portion 16a.

(Embodiment) Hereinafter, the present invention will be described with reference to the illustrated embodiment.
In FIG. 3 to FIG. 3, 15 is a light guide plate, one surface of which is a light emitting surface.
16 and the other surface is a light shielding surface 17. This light guide plate 15
Is the first plate member 19 on the side of the light emitting surface 16 and the second plate member on the side of the light shielding surface 17
20 and 20 are superposed on each other, and the plate members 19 and 20 are each made of a transparent acrylic plate.

Reference numeral 21 denotes a light-shielding member, which is formed by sticking a silver vapor-deposited film having a thickness of about 0.1 mm to an inner surface of a polyethylene film having a thickness of about 0.25 mm, and the light-shielding surface 17 and the light-shielding end surface 22 of the light guide plate 15 are provided so as not to leak light. Affixed to.

Reference numeral 23 denotes a light diffusing member, which is made of a polycarbonate film that diffuses light, and two light diffusing members are arranged on the light diffusing surface 16 side so as to cover the light diffusing surface 16 of the light guide plate 15. It is formed on a rough surface that is rough to allow strong diffusion.

24 is a light source, which is composed of a cold cathode tube lamp, and a light guide plate 15
Two light sources 24 are arranged outside both end faces 18 of the light source 24 so that the light from the light source 24 enters the light guide plate 15 from both end faces 18 of the light guide plate 15. 25 is a light-shielding cover, which is made by sticking a silver vapor deposition film with a thickness of about 0.1 mm on the inner surface of the vinyl chloride film,
Both end surfaces of the light guide plate 15 so that the light from the light source 24 does not leak outside
18 It covers the outer periphery of the light source 24 outside.

As shown in FIGS. 4 to 6, the first plate member 19 of the light guide plate 15 is formed so as to be gradually thinned from both side end faces 18 toward the center portion, and both side end portions have a wall thickness of about 10 mm. The thickness of the central portion is 1.5 mm or less, and the light emitting surface 16 of the first plate member 19 (light guide plate 15) is inclined downward from both ends toward the center, and the arc surface 16a is formed in the center of the light emitting surface 16. Is provided. The light-spreading surface 16 of the first plate member 19 (light guide plate 15) is matt-processed or matt-processed with sandpaper, etc.
Has a gloss buff finish.

The second plate member 20 is a thin plate having a thickness of about 2 mm.
On the light-shielding surface 17 side of 0 (light guide plate 15), spot-like irregular reflection portions 26 that irregularly reflect light are provided in a scattered manner. This diffuse reflection part
Reference numeral 26 is an ink containing, for example, glass beads, which is formed by screen-printing a spot pattern on the light shielding surface 17 of the second plate member 20. The size of the irregular reflection part 26 is set to be a gradation pattern in which the size is increased in proportion to the distance from the light source 24. That is, the irregular reflection portion 26 at the end portion of the second plate member 20 on the light source 26 side is small, and the irregular reflection portion 26 at the central portion side of the second plate member 20 is gradually increased, and the ratio of the irregular reflection portion 26 to the light shielding surface 17 is the light source 24. It gradually increases from the side closer to to the side farther from. Here, since the brightness unevenness of the light emitting surface 16 is different when the inclination of the gradation pattern is different,
The inclination of the gradation pattern of the diffuse reflection unit 26 is appropriately selected according to the inclination of the descending inclination of the plate material 19, the brightness required for the light guide plate device, and the like. Both end surfaces 18 of the second plate member 20 have a gloss puff finish similar to the first plate member 19.

Next, the result of comparison between the embodiment of the present invention shown in FIGS. 1 to 3 and 12 and the conventional example shown in FIG. 14 will be described. The light guide plate devices of the present invention and the conventional example are compared with each other in that the overall thickness, size, number of light sources 24, and light intensity are the same. FIG. 11 shows the luminance measured at 9 points on the effective light emitting surface of the light guide plate device in the embodiment of the present invention,
The parentheses in FIG. 11 indicate the conventional brightness. The average luminance and the degree of luminance unevenness (minimum luminance / maximum luminance × 100) at each point on the effective light emitting surface of the light guide plate device of the present invention and the conventional example are as shown in the table below.

As shown in FIG. 11 and the table above, in the case of the embodiment of the present invention, the luminance is higher over the entire light emitting surface and the luminance unevenness is smaller than the conventional one. Regarding the weight, in the case of the present invention, the weight of the entire device is 480 g, whereas in the conventional example, the weight is 700 g, which is about 2/3.

As described above, according to the configuration of the present invention, it is possible to reduce the weight of the light guide plate and significantly increase the light emission brightness on the light-emitting surface side, and to make the brightness uniform regardless of the distance from the light source. You can However, in order to effectively bring out the effect of the present invention, it is necessary to select the inclination of the gradation pattern of the diffuse reflection part 26 that is suitable for the inclination of the descending inclination of the first plate member 19. For the reason, it is possible to select easily and quickly without creating many prototypes. That is, according to the present invention, the second diffuser reflection portion having various gradient pattern inclinations is printed.
If a test pattern of a plate material is prepared in advance and the second plate material of the test pattern is sequentially combined with the sample of the first plate material, it is possible to find an appropriate pattern of the irregular reflection portion without wastefully creating the first plate material. Therefore, productivity can be improved and product cost can be reduced.

In the present invention, the shape pattern of the irregular reflection part is
The dot pattern is not limited to the one shown. For example,
FIG. 13 shows another embodiment, in which the light shielding surface 17 of the second plate member 20 is provided.
The irregular reflection portion 26 provided on the side is formed into a linear shape, and the irregular reflection portion 26 is formed.
A large number of 26 are provided in parallel on the side of the light shielding surface 17
The number of 26 is gradually increased in proportion to the distance from the light source 24. That is, the interval between the adjacent irregular reflection portions 26 on the light source 24 side of the second plate member 19 is large, and the interval on the central portion side of the second plate member 20 is gradually reduced, whereby the ratio of the irregular reflection unit 26 to the light shielding surface 17 is reduced. It gradually increases from the side closer to the light source 24 to the side farther from it.

(Effect of the Invention) In the light guide plate device of the present invention, the light guide plate is composed of the first plate material and the second plate material, and the light emitting surface of the light emitting surface is gradually thinned toward the center part. Since it is inclined downward from both end sides toward the center, it is possible to reduce the weight and to reduce the repetition of light reflection in the first plate member, thereby substantially uniforming the brightness of the entire light emitting surface and increasing the brightness. Brightness can be achieved. Furthermore, since the light-dissipating surface is matte-finished, it is possible to achieve more uniform brightness and higher brightness.

Further, since the diffuse reflection portion provided on the light-shielding surface side gradually increases in proportion to the light-shielding surface from the side closer to the light source, it suppresses light emission on the side closer to the light source and is farther from the light source. The light emission on the side is increased, the uniformity of the brightness is further enhanced, and the uneven light emission on the light-emitting surface can be effectively prevented.

On the other hand, there are various types of the first plate material depending on the inclination of the descending inclination of the first plate material, the degree of the matte processing, etc., and the gradient pattern of the diffuse reflection part which can effectively bring out the effect of the present invention is different, but the guide of the present invention is different. Since the light plate is formed by superimposing the first plate material and the second plate material, and the diffuse reflection portion is provided on the second plate material, the kind of the second plate material can be appropriately changed without performing a complicated inclination selection setting operation. A light guide plate device capable of effectively and effectively exhibiting the effects of the present invention can be manufactured easily without waste by simply selecting.

[Brief description of drawings]

1 to 12 show an embodiment of the present invention, wherein FIG. 1 is a front view, FIG. 2 is a side sectional view, FIG. 3 is a bottom view, and FIG. 4 is a front view of a first plate member, FIG. 5 is the same side view, FIG. 6 is the same bottom view, FIG. 7 is the front view of the second plate, FIG. 8 is the same side view, FIG. 9 is the same bottom view, and FIG. 10 is the same rear view. FIG. 11 is a front view showing the results of measuring the luminance of the present invention and the conventional device, and FIG. 12 is a sectional view for explaining the operation. FIG. 13 is a rear view of the second plate member showing another embodiment. FIG. 14 is a sectional view showing a conventional example. 15 …… Light guide plate, 16 …… Light-dissipating surface, 17 …… Light-shielding surface, 24 ……
Light source, 26 ... Diffuse reflection part.

Claims (1)

[Scope of utility model registration request] 1. A light guide plate (15), one surface of which is a light-dissipating surface (16) and the other surface of which is a light-shielding surface (17), and the light from a light source (24) is supplied to both end surfaces of the light guide plate (15). The light enters from (18) and is diffused from the light emitting surface (16) of the light guide plate (15), and the light emitting surface (16)
In the light guide plate device in which the side is made to emit light, the light guide plate (15) is provided with a first plate member (1
9) and the second plate member (20) on the side of the light shielding surface (17) are superposed, so that the first plate member (19) is gradually thinned from the both end faces (18) toward the central portion. The light-dissipating surface (16) of the first plate member (19) is inclined downward from both ends toward the center, and the light-dissipating surface (16) of the first plate member (19) is matte-treated to form the second plate member. A diffuse reflection portion (26) that diffusely reflects light is provided on the light shielding surface (17) side of the (20), and the diffuse reflection portion (26)
Is a light-shielding surface (1
A light guide plate device, characterized in that the ratio to 7) is gradually increased.