JPH06250025A - Light diffusing device - Google Patents

Abstract

PURPOSE:To provide the light diffusing device with which more uniform surface illuminance than heretofore is obtainable and which is of a more groove type. CONSTITUTION:This light diffusing device is provided with a transparent light transmission plate 2 on a light reflection plate 5 and is provided with light sources 1 on one side of both sides of the light transmission plate side faces. The device is so constituted that the light from the light sources 1 is irregularly reflected by the rear surface of the light transmission plate 2 and is dispersed to the surface of the light transmission 2 to obtain the uniform illuminance. The rear surface of the light transmission plate 2 is provided with plural pieces of grooves 3 having an angle in the 45 to 135 deg. range to the direction of the light from the light sources 1 and the spacings between these groove 3 and the grooves 3 are made successively coaser to denser from the light sources 1 to the arrival point of the light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light from a light source provided on the side surface of a light guide plate, which is diffusely reflected on the lower surface of the light guide plate and dispersed on the surface of the light guide plate to obtain a uniform illuminance. Regarding the improvement of the diffuser.

[0002]

2. Description of the Related Art Conventionally, a light-transmitting transparent light guide plate is provided on a light reflecting plate, that is, in contact with or close to the light reflecting plate, and a light source is provided on one side or both sides of the side surface of the light guiding plate. As a light diffusing device in which light from a light source is diffusely reflected on the lower surface of the light guide plate and is dispersed on the surface of the light guide plate to obtain uniform illuminance, various types of light diffusing devices are known. .

[0003]

However, the conventionally known device has problems such as low illuminance, uneven light on the surface of the light guide plate, and the like. Further, the device should be thinner and smaller. Was also requested. An object of the present invention is to provide an improved light diffusing device that solves these problems.

[0004]

The present invention will be described in brief. The present invention relates to a light diffusing device, in which a light-transmissive transparent light guide plate is provided on a light reflecting plate, and In a light diffusing device in which a light source is provided on one side or both sides, light from the light source is diffusely reflected on the lower surface of the light guide plate and is dispersed on the surface of the light guide plate to obtain uniform illuminance. A plurality of grooves that form an angle in the range of 45 to 135 degrees with respect to the direction are provided on the lower surface of the light guide plate, and the distance between the grooves is
The feature is that the density is gradually increased from the light source to the arrival point of light.

Each constituent element of the present invention will be specifically described below. As the material of the light reflection plate and the light guide plate used in the device of the present invention, conventionally known materials are used. For example, as the light reflection plate, a metal film, foil or mirror surface provided on the surface of plastic or glass, other white paper, metal foil,
Examples thereof include the plate itself, or those obtained by coating the surface of these with a white pigment such as titanium white.

As the light guide plate, glass or plastic is used, and plastic is preferable from the viewpoint of light weight and easy processing. Examples of plastics include (meth) acrylic resins and polycarbonate resins. The surface of the light guide plate may be a smooth surface or may be subjected to a light diffusing treatment as in the conventional case.

A conventionally known visible light source may be used as the light source, but in the present invention, it is particularly preferable to use a visible LED.

Nothing needs to be placed on the light guide plate,
A protective plate or a conventionally known milky white light diffusing sheet may be provided.

The features of the present invention are, as described above, the groove provided on the lower surface of the light guide plate and the arrangement thereof. First, the cross-sectional shape of the groove may be arbitrary, but a triangle is preferable, and one or both of two sides in the light guide surface of the triangle may be bulged or dented. . The height of the groove (the deepest part in the light guide plate) may be 0.05 mm or less.
The maximum cross-sectional area of the groove may be 0.0025 cm ² .
Further, the shape of the groove in the longitudinal direction may be linear, curved, or a combination thereof, and may be, for example, mesh or zigzag. Then, the angle may fall within the range of 45 to 135 degrees with respect to the direction of light. This angle is for each groove,
In the case of a curved line, the cutting line may be assumed, but the angle of the line of the entire groove may be used.

Next, in the present specification, the "interval between the grooves" means the highest part of the adjacent grooves (the deepest part in the light guide plate).
It means the length of time. The present invention is characterized in that the distance between the grooves is gradually increased from the light source to the arrival point of the light in order from sparse to dense. The interval between the grooves will be specifically described below with reference to the drawings. When the distance between the grooves on the lower surface of the light guide plate is changed according to a certain standard, the distance from the light arrival point on the coordinate is on the Y axis, and the number of grooves starting from the light arrival point is on the X axis. Then, an example of a parabolic curve resulting from the relationship between the two is given. However, the present invention is not limited to these. The coordinate diagram in FIG. 2 is represented by the following equation (Equation 1):

[0011]

## EQU1 ## Y = 0.02X ² + 0.01X + 0

In the above equation (Equation 1), Y represents the distance from the light reaching point to the groove, and X represents the number of grooves. Next, FIG. 3 shows a coordinate diagram when the change in the groove spacing becomes significantly larger than that in FIG. It is used when the distance from the light source to the light arrival point becomes large. FIG. 4 is a diagram showing an example of coordinates when the light source is placed only on one side of the light guide plate. Used when the distance from the light source to the light arrival point is relatively short.

The groove described above may be manufactured by a conventional method. For example, it may be cast-molded at the time of manufacturing the light guide plate. Alternatively, the grooves may be formed by machining after forming the light guide plate. In particular, a groove having an acute angle can be manufactured more accurately by machining such as cutting.

[0014]

The action of the groove in the device of the present invention is shown in a schematic view in FIG. 1 as a typical example. In FIG. 1, 1 is a light source, 2
Is a light-transmissive transparent plate, 3 is a light refraction diffusion groove layer, 4 is a transparent surface or a cloudy surface layer (light emitting surface), 5 is a light reflection plate, 6 is a milky white light diffusion sheet, and 7 is an electrode terminal. 2, 3, and 4 are collectively referred to as a light guide plate in this specification. Light 11 incident on the light guide plate from the light source 1 is reflected by the lower surface 3 of 2 at angles 12 and 13. The reflected light of 12 and 13 is guided to the surface of 4, but a part of the light is reflected by the surface of 4 and becomes 12 'and 13', which is reflected and refracted by the surface of 3 or 5, and is reflected by the surface of 4. The light is diffused to the surface of 4 with a uniform illuminance. In order to make the diffused light even more uniform, 6 may be provided as necessary as described above.

[0015]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 The shape of the groove was set to the shape shown in FIG. 5 (schematic plan view, the same applies hereinafter), and the distance between the grooves was set as shown in FIG. The machining groove shape is a V-shaped groove with an angle of 30 degrees and a depth of 0.05 mm. The distance between the grooves is 0.4 mm from the light arrival point toward the light source.
When processed with a straight line of 90 degrees with respect to the traveling direction of light by increasing by 0.01 mm, the light entering from the light sources on both sides of the light guide plate is reflected by the processed groove and We were able to extract high-quality light with minimal unevenness.

Example 2 When the groove was formed into the shape shown in FIG. 6 and the arc-shaped groove with the light source inside was processed at the same groove angle, depth and interval as in Example 1, Almost the same results were obtained.

Example 3 The groove was shaped as shown in FIG. 7, and the groove angle, depth, and spacing were the same as in Example 1, and the groove having an inclination of 45 degrees with respect to the light traveling direction was processed. In this case, it was almost the same as that of Example 1, but the result was that there was much unevenness in light and dark.

Example 4 The shape of the groove was set as shown in FIG. 8, and on the machined surface of Example 3,
When the groove with the same shape is applied exactly 90 degrees in the opposite direction to the processed groove, it is brighter than other examples in the place near the light source, but darker in the place far from the light source. It was

[0020]

By using the device of the present invention, the thickness can be reduced to 3 mm or less from the conventional example of 7 mm or more, and the number of light sources can be reduced, so that the power consumption is reduced. Great economic effect. In particular, when illuminating the back surface of a photographic panel used for advertising, it is advantageous in that the installation place can be thin and small.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing the action of grooves in the device of the present invention.

FIG. 2 is a coordinate diagram showing an example of an interval between grooves in the device of the present invention.

FIG. 3 is a coordinate diagram showing an example of a gap between grooves in the device of the present invention.

FIG. 4 is a coordinate diagram showing an example of an interval between grooves in the device of the present invention.

FIG. 5 is a schematic plan view showing an example of the shape of a groove in the device of the present invention.

FIG. 6 is a schematic plan view showing an example of the shape of a groove in the device of the present invention.

FIG. 7 is a schematic plan view showing an example of the shape of a groove in the device of the present invention.

FIG. 8 is a schematic plan view showing an example of the shape of a groove in the device of the present invention.

[Explanation of symbols]

1: Light source, 2: Light-transmissive transparent plate, 3: Light refraction diffusion groove layer, 4: Light emitting surface, 5: Light reflection plate, 6: Milky white light diffusion sheet, 7: Electrode terminal

Claims (1)

[Claims] 1. A light-transmissive transparent light guide plate is provided on a light reflection plate, and a light source is provided on one side or both sides of a side surface of the light guide plate. Light from the light source is diffusely reflected on the lower surface of the light guide plate, In a light diffusing device dispersed on the surface of a light guide plate so as to obtain a uniform illuminance, 45 to 1 with respect to the direction of light from a light source.
A light diffusing device characterized in that a plurality of grooves forming an angle in the range of 35 degrees are provided on the lower surface of the light guide plate, and the distance between the grooves is gradually sparsely and densely from the light source to the arrival point of light. .