JPH0423273Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial field of application This invention is a surface illumination device used for display devices such as illuminated signboards, display displays, etc., and more specifically, a light source is provided on the end surface of a light-transmitting light guide plate. The present invention relates to an illumination device that is arranged to face the light guide plate and uniformly scatters light rays incident from the light source into the plate through the end face of the light guide plate from the plate surface to constitute a secondary surface light source.

Prior Art and Problems The basic structure of this type of area illumination device is that, as shown in Utility Model Application Publication No. 57-201588, a light source is emitted from the end face of a light guide plate with good light transmittance such as a transparent acrylic plate. By forming a light scattering surface with fine irregularities on one side and closely or closely disposing a reflective layer on the other side, the light rays inside the plate are transmitted through the plate. It is designed to reflect and diffuse light to emit a bright light.

However, with this structure, in practice,
In the area close to the light source, a large amount of light is emitted from the plate surface and shines brightly, whereas in the area close to the light source, most of the light rays are dissipated and consumed outside, so they propagate within the light guide plate and reach far away. As a result, the absolute amount of light rays gradually becomes insufficient, and as the distance from the light source increases, the external scattered light becomes weaker and darker, resulting in the essential drawback that uniform illumination over the entire surface cannot be obtained.

In order to improve these drawbacks, the following proposals have been made in the past.

As shown in Utility Model Publication No. 58-46447, transparent fine particles for light scattering are dispersed within the light guide plate to give a light scattering effect, but the amount of dispersed transparent fine particles is small in the area near the light source. , a method that attempts to equalize the illuminance of the board surface over the entire surface by increasing it as the distance increases.

Utility Model No. 56-93772, or Utility Model 58-
As shown in No. 25410, the light scattering surface having fine irregularities formed on the light guide plate has a smaller number of irregularities per unit area as it approaches the light source, and increases as it moves away from the light source. A method for making the illuminance of the light guide plate uniform over the entire surface.

However, in the above method, it is actually extremely difficult to control the change in the dispersion density of the transparent fine particles in a preferable manner at the stage of manufacturing the light guide plate, and the method lacks industrial practicality. In addition, in areas where transparent fine particles are roughly arranged near the light source, reflected and scattered light appears from each fine particle in a scattered manner, resulting in a tendency for a large number of bright spots to become visible unevenly. There were some shortcomings.

In addition, when using the above method, Utility Model Publication No. 56-93772 and Utility Model Publication No. 58
If the display member is a display device that has a display part that is partially translucent, as in the case of No. 25410, it is sufficient to concentrate and radiate the luminescence only in that part. This can be conveniently solved by additionally forming a light scattering surface with increased unevenness density at corresponding locations on the display part located far from the light source, but it is necessary to uniformly irradiate the entire surface of the light guide plate with light. In this case, most of the internally introduced light is still emitted close to the light source,
The absolute amount of light reaching the area far from the light source tends to be insufficient, so no matter how much you increase the unevenness density and increase the ratio of reflected and scattered light to the amount of arriving light, the scattered light will be weak in areas far from the light source. Become,
It was difficult to obtain uniform illuminance over the entire surface. However, it is also possible to suppress the amount of light scattering to the outside by making the uneven surface in the area near the light source extremely rough, but in this case, as in the previous case, the uneven surface in the area close to the light source may be made extremely rough. This results in scattered or linear unevenness in the light scattering portions, making it difficult to achieve a desirable uniform illumination condition over the entire board surface.

In view of the background of the conventional technology described above, this idea was developed to provide uniform illuminance over the entire surface regardless of distance from the light source, with less difficulty in manufacturing, and to easily adjust and control the brightness of each part. The object of the present invention is to provide an improved surface illumination device that provides improved lighting.

Means for Solving the Problems This invention consists of arranging a plurality of transparent light guide plates behind a light diffusion plate, each having a light control scattering surface that increases the degree of light diffusion as the distance from the light source increases. The light from the light source is not directly incident on or irradiated with the light diffusing plate, so that uniform illuminance can be obtained over the entire surface exclusively by the light control effect of the light guide plate and the uniformizing effect of the diffuser plate. It has been devised.

Therefore, this invention includes a light diffusing plate, at least one or more light guide plates arranged on the back side of the light diffusing plate, a reflecting plate arranged on the back side of the light guide plate, and the light guide plate. a light source disposed facing the end surface of the diffuser plate, and a light shielding plate that blocks the light from the light source from entering through the end surface of the diffuser plate,
and each of the plurality of light guide plates is provided with a light control scattering surface made of an uneven rough surface or a diffusive coating layer in such a manner that the light guide plate group as a whole gradually increases the diffusion ratio of light to the amount of arriving light as the light guide plate group as a whole moves away from the light source. The gist of the present invention is a surface illumination device characterized in that: is formed.

Embodiments Hereinafter, this invention will be further explained in detail based on illustrated embodiments.

In Figures 1 and 2, 1a and 1b are two light guide plates that are closely laminated in parallel or arranged with a slight gap between them, and 2 is a reflective plate placed on the back side of the rear light guide plate 1b. 3 is a light diffusing plate disposed on the front side of the front light guide plate 1a; 4 is a translucent display layer disposed to cover the entire front surface of the light diffusing plate; 5 is an end surface of the light guide plates 1a, 1b; A light source 7 consisting of a fluorescent lamp or the like is placed facing the diffuser plate 3, and is placed in such a way as to prevent the light from the light source 5 from directly entering and irradiating the end face and end portion of the diffuser plate 3. It is a light shielding plate made of metal or opaque or translucent synthetic resin and having an L-shaped cross section.

The light guide plates 1a and 1b have a thickness of 2 to 20 mm, preferably 4 mm.
It consists of a transparent plate of about 7 mm with good light transmittance, such as polymethyl methacrylate or polystyrene, and each has a light control plate with a finely uneven surface on one side, as shown in Figure 2. A scattering surface 6 is formed. The scattering surface 6 is formed into a hairline shape by sanding as shown in FIGS. 3A and 3B, or into a matte finish by sandblasting, etching, etc. as shown in FIG. 3C. Alternatively, it may be formed as a diffusible coating layer by applying matte ink, white ink, etc., or as a coating layer having substantially fine irregularities by a known so-called pseudo-etching technique. As shown in FIGS. 2 and 3, the scattering surfaces 6 and 6 for dimming increase the density of the unevenness as they move away from the light source 5, and gradually reduce the number of unevenness per unit area. It is formed to increase. Therefore, the light incident from the end surfaces of the light guide plates 1a and 1b is diffusely emitted from the plate surfaces in such a manner that the ratio of the amount of reflected and scattered light to the amount of light that reaches the plate increases as the distance from the light source 5 increases. There is. As a result, in the overall evaluation of both light guide plates 1a and 1b combined, the diffusion ratio of light to the amount of light reached gradually increases as the distance from the light source 5 increases.

The light-adjusting scattering surface 6 on each light guide plate 1a, 1b may be formed in such a manner that it extends to the end closest to the light source 5, as shown in FIG. As shown in FIG. 3, it may be formed only in other parts except for the area near the light source 5. Furthermore, it is preferable to use a combination of a plurality of light guide plates in which the light control scattering surfaces 6 are formed in different ways. For example, the front light guide plate 1a may have a light control scattering surface 6 as shown in FIG. The light guide plate 1b has a smooth surface on both sides of the lower part and a light control scattering surface 6 formed only on the upper part, so that the guided light incident from the end face can reach a part far from the light source 5 without attenuating it. After guiding, it is preferable to scatter the introduced light predominantly from the rear light guide plate 1b to compensate for the insufficient amount of irradiation light on the front light guide plate 1a.

In addition, if a low refractive index layer made of a material with a relatively smaller refractive index than that of the light guide plate is formed on the back side of the light guide plate, the light entering the plate will not be attenuated to a further distance. This is desirable in that it can lead to Examples of materials for forming such a low refractive index layer include those disclosed in Utility Model Application Publication No. 59-94386 and Japanese Utility Model Application Publication No. 1983-
According to the disclosure of No. 29839, silicone, fluorine resin, etc. can be suitably used.

The reflecting plate 2 is, for example, a mirror plate with an aluminum vapor deposited layer formed on one side of a resin plate, or a white synthetic resin plate, and serves to increase the lighting effect. However, this reflector 2 is
This may be replaced by directly forming a high reflectivity material layer such as an aluminum vapor deposited layer on the back surface of the rear light guide plate 1b.

The light diffusing plate 3 has the function of making the illumination state uniform over the entire surface by entering the light emitted from the light guide plates 1a and 1b from the back side and further diffusing and transmitting it. In this method, the same transparent plate as the light guide plate is used as the carrier 3a, and the diffusion layer 3b is formed by coating the surface of the transparent plate with a diffusive paint, particularly preferably with white fluorescent ink, or by integrating the lamination of opalescent plates. Although it is assumed that the light diffusing plate is integrally formed, the light diffusing plate itself may be formed of a single translucent opalescent plate or the like. When the carrier 3a is composed of a light-guiding transparent plate, the light-guiding plate 1 is also formed on the back surface of the carrier 3a.
Similar to a and 1b, it is also recommended to form a scattering surface for light control.

The display layer 4 is light-transmissive, and is made of a transparent synthetic resin film or thin plate on which desired characters, designs, etc. are printed or drawn using transparent ink.

The light shielding plate 7 prevents the lower part of the light diffusing plate 3 from shining brightly due to the temperature due to the light directly from the light source 5. Therefore, in addition to the illustrated example, for example, the end surface of the diffusing plate 6 may be coated with opaque paint. It is also permissible to form it as a coating layer.

FIG. 4 shows an example of a display device constructed using the above-mentioned surface illumination device. In the same figure, a plurality of light guide plates 1a, 1b, a reflection plate 2, a light diffusion plate 3, and a display layer 4 are stacked one on top of the other, and the peripheral edge portions on three sides are connected to a peripheral frame 8 through a reflective film 10. At the same time, the remaining edge part is connected and fixed in an inserted state in the base box 9 which houses the light source 5 inside with the arrangement of the light shielding plate 7, thereby creating a stand-type structure. The display device is configured as a signboard display device in a flat state.

By the way, in the above-mentioned surface illumination device, when the light source 5 is turned on, it undergoes total reflection within those plates and reaches a long distance, but in the process, it sequentially hits the light control scattering surface 6 and is scattered, causing the reflection plate The light is emitted from behind toward the light diffusing plate 3 along with the light reflected by the light diffusing plate 3 .
Moreover, at this time, the presence of the plurality of light guide plates 1a and 1b and their light control scattering surfaces 6 and 6 are formed in a manner that gradually increases the diffusion ratio of light to the amount of arriving light as the distance from the light source 5 increases. By doing so, the amounts of light irradiated toward the light diffusing plate 3 are mutually complemented and made uniform over the entire surface. Therefore, the amount of light that is further diffused by the light diffusing plate 3 and irradiated onto the display layer 4 is:
Regardless of the distance from the light source 5, the illumination is uniform over the entire surface, and a desirable illumination state without uneven illumination is realized.

FIGS. 5 and 6 show other embodiments. That is, in this embodiment, three light guide plates 1c, 1
d and 1e are used, and the formation areas of the light control scattering surfaces 6a, 6b, and 6c are sequentially changed in a stepwise manner. That is, as shown in FIG. 6, on the front light guide plate 1c, a light control scattering surface 6a is formed in a substantially uniform state only in the upper 3/4 part of the entire height direction, and the light guide plate 1c in the middle is formed in a substantially uniform state. A light control scattering surface 6b is also formed in the upper 2/4 area of the light plate 1d.
Furthermore, the rear light guide plate 1e is provided with a light control scattering surface 6c only in the upper 1/4 portion. Therefore, these light guide plates 1c, 1
In the state where d and 1e are superimposed in parallel,
The number of overlapping areas of the light control scattering surfaces 6a, 6b, and 6c increases as the distance from the light source 5 increases, and as the distance from the light source increases, the overall light guide plate group The light diffusion ratio with respect to the amount of light reached by the light diffusing plate 3 is gradually increased, and the amount of light irradiated toward the light diffusing plate 3 can be made substantially uniform over the entire surface. In the case of this embodiment, the boundary between the dimming scattering surfaces 6a, 6b, and 6c is blurred as shown in the figure so that the boundary is not imaged through the light diffusing plate 3. is desirable.

Effects of the invention As mentioned above, this invention has a plurality of light guide plates arranged behind the light diffusing plate with their end faces facing the light source, and each of these light guide plates has a Since the light control scattering surface is formed in such a manner that the diffusion ratio of light to the amount of light reached gradually increases as the light guide plate moves away from the light source, other light guide plates are used in areas far from the light source where the amount of light guided by one light guide plate is insufficient. The light guide plate can guide the incident light to the relevant part and radiate it, and the amount of light radiated from behind towards the diffuser plate can be adjusted depending on the distance from the light source. It can be assumed that it is almost uniform regardless of the Moreover, since this irradiated light is further diffused by the front diffuser plate before being irradiated, local non-uniformity in light brightness can be eliminated.
In addition, the presence of a light shielding plate on the end face of the diffuser plate prevents the light from the light source from being directly irradiated, so only the part of the diffuser plate close to the light source does not shine excessively brightly. With the synergistic effect described above, the entire front surface of the lighting device can be illuminated with uniform illuminance.

Moreover, since the above-mentioned uniformity control of the irradiated light amount is performed by the light guide plate having a light control scattering surface that changes the degree of light diffusion according to the distance from the light source, it is possible to By adjusting the relative arrangement position of the light guide plate with respect to the plate, it is possible to easily visually confirm the state in which uniform illuminance is obtained over the entire surface and find the most preferable design mode, which facilitates design and manufacture. Furthermore, by disposing a reflecting plate on the back side of the light guide plate to increase the illuminance, it is possible to efficiently irradiate the front side with the amount of light emitted from the light source and obtain a sufficiently bright illumination state.

Therefore, according to the area lighting device according to this invention,
A secondary surface light source having a wide irradiation area and having uniform brightness over the entire area can be provided, which is very convenient for constructing display devices such as ultra-thin illuminated signboards, displays, etc.

[Brief explanation of the drawing]

The drawings show an embodiment of this invention, and FIG. 1 is a longitudinal sectional view of the embodiment with the constituent members slightly separated, FIG. 2 is a perspective view of the same, and FIG. , C are front views showing various formation states of the light control scattering surface of the light guide plate, FIG. 4 is a vertical cross-sectional view of a display device showing a practical example of the surface illumination device of this invention, and FIG. 5 is a diagram showing another implementation. A perspective view of the part corresponding to FIG. 2 showing an example, No. 6
Figures A, B, and C are front views of the light guide plate. 1a, 1b, 1c, 1d, 1e...light guide plate, 2
... Reflection plate, 3 ... Light diffusion plate, 4 ... Display layer, 5
...Light source, 6, 6a, 6b, 6c... Dimming scattering surface, 7... Light shielding plate.

Claims (1)

[Claims for Utility Model Registration] (1) A light diffusing plate, a plurality of light guide plates disposed on the back side thereof, a reflecting plate disposed on the back side of the light guide plate group, and the light guide plate group a light source disposed facing the end surface of the light guide plate, and a light shielding plate that blocks the light from the light source from entering the end face of the diffuser plate, and each of the plurality of light guide plates includes: The entire light guide plate group is characterized in that a light control scattering surface made of an uneven rough surface or a diffusive coating layer is formed in such a manner that the diffusion ratio of light to the amount of arriving light gradually increases as the light guide plate group moves away from the light source. surface lighting device. (2) The light control scattering surfaces of the plurality of light guide plates are made of finely uneven rough surfaces, and the density of the unevenness on each light guide plate increases as it moves away from the light source, thereby reducing the amount of reflected and scattered light that reaches the light source. A surface illumination device according to claim 1, which is configured to gradually increase the ratio of light. (3) The formation areas of the light control scattering surfaces of the plurality of light guide plates are provided in stages with different formation areas in each light guide plate so that the number of overlapping areas increases as the distance from the light source increases. A surface lighting device according to claim 1 of the utility model registration claim.