JPS5817957B2 - Hikarikaku Sansouchi - Google Patents

Description

[Detailed description of the invention] Traditionally, light source lamps provide uniform brightness over a wide area.

In order to obtain the desired surface light source, it has been common practice to use a diffuser plate made of opalescent glass or frosted glass, and to irradiate light from behind perpendicularly to the main irradiation surface of the diffuser plate.

However, when light is diffused using the above method, there are two contradictory relationships between the brightness obtained through the diffuser plate and its uniform distribution.

That is, the first problem is that if the distance between the diffuser plate and the light source is increased, the range of uniform brightness becomes wider, but the brightness decreases, and as the distance between the diffuser plate and the light source is decreased, the range of uniform brightness becomes narrower.
The second problem is that increasing the diffusivity of a diffuser plate generally reduces light transmittance and impairs brightness, and conversely, increasing transmittance narrows the area of uniform brightness.

Therefore, in order to obtain a bright, uniform, and wide-area light source using the above method, it is necessary to install a light source with a large W number at a sufficient distance from the diffuser plate, or to install multiple light sources. However, either method consumes a lot of power and increases the size of the structure.

In addition, in the case of the former method, since a sufficient distance in the thickness direction must be maintained, there are many restrictions on the installation and implementation of the device, and it is particularly difficult to use for light tables, wall hangings, embedded advertisements, etc. It was not suitable for thin devices.

Furthermore, in some cases, cooling equipment may have to be added to both systems.

In view of the above, the present invention not only provides a wide, bright and uniform diffusion surface using one or a small number of light source lamps, but also provides an efficient light diffusion device that does not take up the depth of the device. .

An embodiment of the light diffusing device according to the present invention in which an inclined portion is provided on the back surface of the transparent substrate will be briefly described in the second and third drawings.
This device makes the light beam of a light source lamp 1 enter from the end surface 2a of a transparent substrate 2, and applies appropriate light to the opposite observation surface (back surface) of the transparent substrate so that a uniform illuminance distribution is obtained on one side of the transparent substrate, the observation surface side. A scattering process is applied to the transparent substrate, and a scattering reflection plate 3 is provided in contact with this surface, thereby making one side of the transparent substrate a surface light source with uniform illuminance.

Next, each component of this embodiment will be explained in detail.

The transparent plate 2 has an end surface 2a facing the light source lamp 1 and an observation surface side 2.
b is a smooth surface, the cross-sectional shape of the map is a parabola or a straight line cut along the cross-sectional direction with a base line at a certain distance from the end surface 2a, and the back side of the observation surface is exposed to light. The reflected light and the transmitted light distribution with respect to the incident direction are given directivity, and the luminous flux is configured to be reflected as effectively as possible toward the irradiation surface side (the above-mentioned observation surface side).

As a result of conducting various experiments on transparent substrates, we obtained the following data.

First, the luminance of the surface of the substrate. As is clear from FIG. 5, for the cloth, good results were obtained when the cloth was cut diagonally in a straight line from a position corresponding to 1/3 of the end surface on the opposite side from the end surface on the light source side.

Next, regarding the characteristics of the reflected light on the back surface, the absorption components on the back surface should be as small as possible, and the reflected light and transmitted light should be minimized.

It is desirable to perform appropriate surface roughening so that the scattered light distribution has no component that returns in the direction of the light beam.

For this reason, the rough surface itself needs to have directionality.
An example of this is as shown in FIG. 4, where the roughening is done in parallel from the end surface (2) to the end surface (2).

'As shown in FIG. 9, the effect of making the brightness distribution on the front side uniform varies depending on the way the back surface is roughened.

Regarding examples A-E in the same figure, A is Al2O with a diameter of 2μ
For B, use A1□031 powder with a diameter of 10μ, for C, use #300 sandpaper, and for D, use #200 sandpaper to roughen in parallel. , E is a #150 abrasive and is made by sandblasting (therefore, there is no directionality in roughening in this case).

) This is the case when the surface is roughened.

Among these, as is clear from the figure, the remarkable effects in relation to the above are recognized in the cases of B, C, and D, and their optical characteristics are as follows.

When the incident angle of light incident on a surface parallel to the directional rough surface (the direction of the roughness) is 75°, the reflected light distribution has a peak at 75° as shown in Figure 6. , its value is 5-30
and its half width is in the range of 4° to 8°.

Furthermore, the incident angle 4 of the light incident on a surface perpendicular to the rough surface is 75
°, the reflected light distribution has a peak at 75° as shown in Figure 7, its value is in the range of 5 to 30, and its half width is 6°.
~10°.

Next, as the reflection plate 3 that is set in close contact with or in close proximity to the back surface of the transparent substrate, it is desirable to use a diffuser reflection plate that transmits and absorbs as little light as possible.

Figure 8 shows the distribution of reflected light when light is applied to various sheet-shaped reflective materials at an incident angle of 75°, and Figure 10 shows the distribution of reflected light when the sheet-shaped reflective plate is used in combination with the transparent substrate. This figure shows the brightness distribution when

Specifically, ■ is a glass peace screen, W is A28
X is kraft paper, Y is a reflective screen, and Z is an aluminum plate sandblasted with #200 abrasive.

As a result of experimenting with each of these in combination with the transparent substrate,
The reflecting plate 3 has a reflectance of 30 coefficients or more and a half-width of the reflected light distribution of 90° or more (i.e., V, W in the above example).
, X) has been proven to be suitable.

In the apparatus of the present invention configured as described above, the light flux from the light source lamp enters from the end surface 2a of the transparent substrate, part of it travels toward the front surface (observation surface side), another part goes parallel to the surface, and the rest The part advances to the back side and most of it passes through the back side,
The remaining portion is scattered and reflected and travels toward the surface.

Also, most of the light that has passed through this back surface is reflected by the opposing reflector, does not pass through the back surface of the transparent substrate, undergoes repeated scattering and reflection, and is refracted before proceeding to the front side, resulting in such complex reflection, transmission, and refraction. It is thought that because of the movement, a uniform illuminance surface can be obtained on the surface side.

In the above embodiment, a slope is provided on the bottom surface of the transparent substrate and one light source lamp is installed, but the bottom surface may be made parallel to the surface and light source lamps are installed on both end surfaces of the transparent substrate. is also possible.

Furthermore, in order to utilize external light from the rear direction, it is also a gist of the present invention to configure the above-mentioned reflecting plate with a transmissive diffuser plate having special directivity so as to transmit and utilize the external light from the rear direction. It's not the opposite.

In the above explanation, the observation surface (surface) of the substrate is assumed to be a smooth surface, but if a wider uniformity of illuminance on the surface is required, even if the light efficiency is slightly reduced, it is necessary to use light on the surface. In some cases, a process to impart diffusivity may be applied.

Furthermore, for the same purpose, a light diffusing plate may be placed on the observation surface side of the substrate.

The light diffusing device according to the present invention has a simple structure as described above, and uses one tungsten bulb (9V x 0.25A), for example, to provide uniform illuminance (0.5 EV (within 52)
When using a milky-white diffuser plate having a transmittance of 1, it is necessary to install the light source lamp at a distance of 130 mm in the direction perpendicular to the surface of the milky-white diffuser plate. Transparent substrate (approximately 7 mm thick)
It is sufficient to install the above-mentioned tungsten bulb on the end face of the light source, and an extremely flat surface light source device can be obtained.

In addition, since the structure uses the light of the light source lamp effectively, the number of lamps and power consumption can be kept to a minimum.

The above-mentioned advantages of the present invention contribute to improving the performance of various devices that require a uniform surface light source, such as display panels for various instruments, light tables, illuminated signboards, etc., and significantly reducing power consumption.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional light diffusing device, and FIGS. 2 and 3 are an external view and a sectional view of an embodiment of the light diffusing device of the present invention, respectively. FIG. 4 is a perspective view showing the roughened state of the transparent substrate used in the present invention. 5 to 10 are diagrams showing data on various optical properties of the transparent substrate and the reflecting plate. 1...Light source lamp, 2...Transparent substrate,
3...Reflector, 4...Opalescent diffuser.

Claims (1)

[Claims] 1. The back surface of a transparent substrate with good light transmittance is directionally roughened so as to have light reflectivity and transmittance, and the surface of the substrate is in contact with or in close proximity to the back surface of the substrate. hand. In a light diffusing device in which a reflecting plate and a light source are arranged on the side surface of the substrate perpendicular to the direction of the roughening, so that uniform illuminance can be obtained on the surface of the substrate, the rough surface is When the incident angle of light incident on a plane parallel to the direction is 75°, the reflected light distribution has a peak at 75°, its value is between 5 and 30, and its half-width is 4. °
When the angle of incidence of light incident on a plane perpendicular to the direction is 75°, the reflected light distribution has a peak at 75°, and its value is 5 to 30 degrees. A light diffusing device characterized in that the half-width thereof is in the range of 6° to 10°.