JPH0393104A - Surface light emitting device - Google Patents

Abstract

PURPOSE:To obtain uniform luminescence by using light sources with irregular intensity distribution, arranging the long direction of a light conducting plate in the direction with high intensity from light entering end faces, and gradually tilting the back face of the light conducting plate in the short direction to make the thickness thin. CONSTITUTION:Filaments 9b and 10b of light sources 9 and 10 are arranged perpendicularly to the long direction of a light conducting plate 11. The light conducting plate 11 made of light conducting acrylic acid, for example, and having light entering end faces 11a and 11j fed with the nearly semi-circular light surrounding the light sources 9 and 10 respectively is gradually tilted in a curve shape on its back face as it is separated from light sources 9 and 10 to make the thickness thin, and a scattering/reflecting layer 11b is provided on this back face. The light fed through the light entering end face 11a or 11j enters the light conducting plate 11, and it is irregularly reflected on the scattering/reflecting layer 11b and radiated on the opposite plate face 11c. The light quantity on the whole face of a liquid crystal display panel 4 can be made nearly equal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a surface emitting device for backlighting, for example, a liquid crystal display panel. [Prior Art] A conventional surface emitting device is disclosed in, for example, Japanese Utility Model Application Publication No. 62-69281. As shown in FIG. 6, this disclosed device includes a light guide plate 1, incandescent lamps 2a, 2b provided near the flat end surface thereof, and the light guide plate 1 and the incandescent lamps 2a, 2b. The light from the incandescent lamps 2a and 2b is introduced into the light guide plate 1, and the light is reflected by a scattering reflection layer (not shown) provided on the back surface of the light guide plate 1. The light is scattered and reflected and radiated from the surface of the light guide plate 1. This makes it possible to illuminate, for example, a liquid crystal display panel (not shown) provided in front of the light guide plate 1. [Problems to be Solved by the Invention] Since the conventional surface light emitting device is as described above, for example, as shown in FIG. When the light bulb 2a is installed, the brightness distribution of the incandescent light bulb 2a becomes an ellipse as shown in the figure (showing that the light intensity is the same on the dotted line). The amount of incident light is large in the area close to the light bulb 2a, and the amount of incident light is small in the area far away from the light bulb 2a.In the end, the distribution of the amount of incident light becomes elliptical as shown in the figure. In addition, as shown in FIG. 8, incandescent light bulbs 2a and 2b
Light whose incident angle exceeds the Brewster angle of the light guide plate 1 is only partially incident on the light guide plate 1 because the reflectance of the light guide plate 1 increases rapidly, and the amount of incident light decreases. For this reason, the light emitted from the surface of the light guide plate l is strong near the incandescent light bulb 2a, and weak in areas far away, making it impossible to obtain uniform surface light emission. In addition, the flat light guide plate 1 has the problem that it becomes darker as it moves away from the light source, making it impossible to obtain uniform brightness over the entire light guide plate 1. The present invention was made in order to solve the above-mentioned problems, and aims to provide a surface emitting device that can emit light with uniform intensity regardless of location. [Means for Solving the Problems] A surface emitting device according to the present invention includes a light source with a brightness distribution of strength and weakness, a large light end face formed to surround the light source, and a light source that is separated from the light source in a direction where the brightness of the light source is low. a scattering reflection layer provided on the back surface which is gradually inclined in a curved shape according to the above, and a light guide plate having a flat surface for light emission and disposed so that the direction of the light source having less brightness is the transverse direction. It is something. [Function] In the surface emitting device of the present invention, the light from the light source that enters into the light guide plate from the light input end surface is mainly caused by the action of the filament direction and the light input end surface, and the light guide plate portion that is close to the light source and the light guide plate that is farther from the light source. The parts are uniform in the longitudinal direction. In addition, by gradually inclining the back surface of the light guide plate and making the plate thinner as it moves away from the light source, it becomes uniform in the transverse direction, allowing light to reach uniformly over the entire surface of the light guide plate.
Light can be emitted uniformly from the surface of the light guide plate. [Example] An example of the present invention will be described below with reference to the drawings. Figure 1 (A) and Figure 1 (B) are the I-1 line, ■1■
A sectional view and a side sectional view of the surface emitting device according to the present invention taken along the line are shown, and FIG. 2 is an enlarged sectional view of the main part of FIG. (not shown) is formed by a transparent electrode (not shown), and a control circuit (@
This is a liquid crystal display panel that turns on and off a predetermined display pattern based on a signal (not shown), and has first and second glass plates 4a and 4b that sandwich a liquid crystal material (not shown). 4a' is a terminal section in which terminals of transparent electrodes are arranged on the lth glass@4a; 5a to 5h are leads electrically connected to each transparent electrode of the terminal section 4a' of the liquid crystal display panel 4; Each lead, for example, a clamping part 5c' of the lead 5c clamps a terminal part 4al of the first glass plate 4a. Reference numeral 7 denotes a colored light-transmitting filter plate disposed on the back side of the liquid crystal display panel 4, that is, on the second glass plate 4b side, and that colors the light. Reference numeral 8 denotes a print to which the leads 5a to 5h of the liquid crystal display panel 4 are soldered. Board 9.10 is a printed circuit board 8 with leads 9a. 10a (not shown) is a light source consisting of a soldered incandescent bulb; 9b. 10b is a light source 9.
It is a filament of IO, and in FIG. A light guide plate made of a light guide material such as acrylic resin and having light incident end surfaces 11a and IIJ through which light enters, the back surface is gradually inclined in a curved shape as the distance from the light source 9.lO increases, and the plate thickness is made thinner. A scattering/reflection layer 1lb such as a white paint film is provided on the back surface of this layer.Thereby, the light incident from the light incident end face 11a or 11j enters the light guide plate 11, is diffusely reflected by the scattering/reflection layer 1lb, and reaches the opposing plate. The light is emitted from the surface 11c.Furthermore, a cross section taken along the line Vl-Vl in FIG. 4(A) and FIG. 4(^) is shown in FIG. Stability is improved by providing a rib Fig as shown in Fig. 4(A).
can be fitted onto the printed circuit board 8 and fixed. On the other hand, the legs 12a of the reflection frame 12 are soldered to the printed circuit board 8, and the light sources 9 and 10 are surrounded by light source surrounding parts 12b and 12c, and the three end faces lid and lid of the light guide plate 11 are
A reflective frame made of, for example, an aluminum plate holds the light guide plate l1 in close contact with the light guide plate llf, and these light sources 9 and 10, the light guide plate 11#, and the reflective frame 12 constitute a surface emitting device l3. Next, the operation of a surface emitting device according to an embodiment of the present invention will be explained. The light sources 9 and 10 are arranged in the lateral direction of the light guide plate 11 (as shown in FIG. 1(A) As shown in Figure 3, the luminance distribution of the light sources 9 and 10 is such that the longitudinal direction of the light guide plate l1 is the long axis and the short axis is the short axis. It looks like an ellipse with a direction. Therefore,
Among the light incident end faces 11a (1.1j) of the light guide plate 11, the brightness of the light source 9 (10) is weak in the direction parallel to the filament 9b (10b) of the light source 9 (10).
), the brightness of the light source 9 (10) becomes stronger in the direction perpendicular to the filament 9b (10b). However, light guide plate 1
The light entrance end surface 11a (llj) of the light guide plate 1l surrounds the light source 9 (10) in a substantially semicircular manner, and the light from the light source 9 (10) always approaches the light entrance end surface 11a (llj) of the light guide plate 1l. Since the light is incident in the normal direction, it is incident without exceeding the Brewster angle at the human light end face 11a (llj), and a part of it is reflected by the surface of the reflection frame l2, and most of the light is reflected from the light source 9 (10). Almost the same incidence efficiency is obtained for all angles. As a result,
As shown in the figure 0, the light source 9 (
10) The difference in brightness is extremely small between areas near and far away. This difference is, for example, as shown in FIG.
c) can be eliminated by appropriately designing the shape. For example, in the embodiment, the reflective surface 12b of the light source surrounding portion 12b
' is the part far from the light source 9 in the longitudinal direction of the light guide plate 1l, and 45
The amount of light is supplemented by incorporating reflected light by arranging it at an angle of 6. As described above, the light incident end face 11a of the light guide plate 11. Since the light incident from 11j can be made almost uniform in the amount of light in any part due to the reflected light, the light entering end face 11a, ll
The light incident from the light guide plate 11 propagates uniformly throughout the light guide plate 11, and then the scattering reflection layer 1lb spreads the light source 9.10 so that the closer it is to the light source 9.10, the weaker the irradiation to the liquid crystal display panel 4 becomes. 9. By looking at the liquid crystal display panel 4 at an angle from 9.10, the irradiation on the liquid crystal display panel 4 is strengthened so that it is scattered and reflected, making the amount of light on the entire surface almost equal. As a result, the brightness distribution at each point on the plate surface 11c of the light guide plate 11 becomes uniform as shown in FIG. do. Next, the emitted light is colored and made uniform by passing through the filter plate 7, and then is applied to the liquid crystal display panel 4.
illuminate. In this way, the plate surface 11c of the light guide plate l1 becomes a uniform light emitting surface, and the liquid crystal display panel 4 can be uniformly illuminated. By the way, in this embodiment, since the light sources 9 and 1O are arranged on the back side of the terminal section 48' of the liquid crystal display panel 4,
Light source 9.10 and light source enclosure 12b. 12c (for example, position E shown in FIG. 1), the area occupied by the device can be reduced. Furthermore, in this embodiment, the leads 5a to 5h
Since the first glass plate 4a connected to the front panel is placed on the outside and the second glass plate 4b is placed on the side of the surface emitting device 13, the light source surrounding portions 12b, 12c of the reflection frame l2 and the sandwiching portions of the leads 5a to 5b, for example, 50', thereby making it difficult for short circuits between the leads 5a to 5h caused by the reflective frame 12 to occur when the reflective frame l2 is conductive. In the above embodiment, the case of illuminating a liquid crystal display panel has been described, but it goes without saying that the present invention can also be used for displaying other translucent display panels or simply as a lighting device. Further, in the embodiment, an example has been described in which the lips llg are provided on the longitudinal side surfaces 11d and llf of the light guide plate l1, but they may be formed in a lattice shape instead of a plate shape. In addition, although the printed circuit board 8 is supported by the claw portion 11h provided on the lip llg, a claw portion is provided on the reflective frame 12 instead of on the light guide plate 11, and the light guide plate l1 is fitted into this claw portion and supported. You may also do this. Furthermore, the rib Ilg may be provided in a thin walled portion at the outer end of the light guide plate 1l, as shown in FIG. In this case, ribllg
Since the area provided with this does not serve as a scattering/reflection surface, the effective surface emitting area becomes smaller. Furthermore, the rib llg is plate surface 11
c may be provided at any angle, and the scattering/reflection layer 1lb and the end face 11a can be set independently of the ribs so as to improve the light guiding characteristics, so that the same effect as in the above embodiment can be obtained. [Effects of the Invention] As described above, according to the present invention, a light source with a brightness distribution of strength and weakness is used, a light entrance end surface is formed to surround this light source, and a light guide plate is directed in a direction where the brightness of this light source is low. By rearranging the width direction of the light guide plate, and gradually making the back surface of the light guide plate thinner as it moves away from the light source, we also provided a light scattering layer on the back surface of the light guide plate. The intensity of the light from the light source that enters from the light input end surface becomes uniform, and it is also distributed uniformly throughout the light guide plate, so that surface light is emitted uniformly from the entire mask of the light guide plate, making it suitable for back illumination of liquid crystal display panels. It is.

[Brief explanation of drawings]

FIG. 1(^) is a sectional view taken along line I-I in FIG. 1(B) of a surface emitting device according to an embodiment of the present invention, and FIG. Side sectional view along ■-■ line, 2nd
The figure is an enlarged sectional view of the main part of FIG. 1 (A), FIG. 3 is an explanatory diagram showing the luminance distribution of the light source light, FIG. ) is Vl-Vl in Figure 4(A)
5 is a perspective view showing another embodiment of the light guide plate, FIG. 6 is a partially exploded perspective view of a conventional surface emitting device,
FIG. 7 is an explanatory diagram showing the luminance distribution of the light source light in the conventional example;
The figure is an explanatory diagram showing how light from a light source enters a light guide plate in a conventional example. In the figure, 8... printed circuit board, 9, IO... light source, 1
1...Light guide plate, lla, Ilj...Light entrance end surface,
llb...scattering reflection layer, llc...plate surface. In addition, the same symbols in the figures indicate the same or equivalent parts. Fig. 2 ll Fig. 3 Fig. 4 (A no 11j (B no 5 Fig. 6 Fig. 8? Fig. 8 Procedure amendment (spontaneous) 1990 2 1Ee7 2. Name of the invention Surface emitting device 3 .Representative of the person making the amendment: Kishinoya 5. Column 6. “Detailed Description of the Invention” of the specification to be amended 6. Contents of the amendment (1) “Leads 5a to 5bJ” on page 10, line 5 of the specification Correct as “lead 5a to 5h”.

Claims (1)

[Claims] A light source with a brightness distribution of strength and weakness, a light entrance end face formed to surround the light source, a back surface that is gradually inclined in a curved shape as it moves away from the light source in a direction where the brightness of the light source is low, and a back surface provided on the back surface. It has a scattering reflection layer for reflecting a part of the light incident from the light input end face, and a flat surface for emitting almost all of the light to the outside, and the direction in which the light source has less brightness is the short side. A surface emitting device including a light guide plate arranged in the same direction as the light guide plate.