JPH07201217A - Sheet-like light source element - Google Patents

Abstract

PURPOSE:To provide a sheet-like light source element of omnidirectional type of which luminousity in the normal direction is enhanced, by placing a plurality of superposed fine multiprisms on the light incident face of a light conductor of which opposed ends are incident faces. CONSTITUTION:Both side ends of light conductor 3 is used as light inc.ident faces, and on both ends, a light source 5 having a coiled silver deposited film 6 is arranged. At the rear face of the conductor 3, a light reflection layer 4 is arranged while mat treatment is applied to a light emitting face 7. On the side of the face 7, two sheets of multiprisms 1 composed of fine prisms 2 of which top angle is at 80 to 115 degrees are placed in a superposed manner. The prism axes of the multiprisms 1 are substantially parallel to each other, while each prism axis is set to cross the incident light from light incident faces substantially, and the projection of each prism 2 of the multiprism 1 is set to face in the same direction. It is thus possible to obtain a sheet-like light source element of ominidirectional type of which luminousity in the normal direction is enhanced by the distribution control and direction control of emitted light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface light source element,
In particular, the present invention relates to a surface light source element suitable for back lighting means such as liquid crystal display devices.

[0002]

2. Description of the Related Art Conventionally, an edge light type flat light source has been used for back lighting of a liquid crystal display device or the like. Generally, such an edge light type flat light source is often a type in which a light diffusing function is provided on the emission plane, and the pattern of the emitted light is omnidirectional, or the distribution of the emitted light is quite wide. In addition, the brightness in the normal (front) direction is low, and the brightness is insufficient for a color liquid crystal display in which a sharpness is required. On the other hand, on the non-directional light emitting surface with a wide outgoing light distribution,
One multi-prism sheet with an apex angle of 85-110 ° or two prism sheets with prism axes orthogonal to each other is placed, and the distribution angle is narrowed a little by using the light focusing function of the prism. A surface light source element having enhanced luminance in the line direction (front direction) has been implemented.

[0003]

As a surface light source element utilizing the light focusing function of a prism, a surface light source element utilizing a multi-prism sheet having an apex angle of 85 to 110 ° (US Pat. No. 4,791,540). There is a surface light source element (U.S. Pat. No. 4,542,449, Japanese Patent Publication No. 1-37801) that uses a light focusing function by making two multi-prism axes orthogonal to each other. However, in this conventional surface light source element, the brightness rises only about 1.8 to 2.3 times the omnidirectional normal direction luminance.

On the other hand, the surface light source element which makes the light emitted from the light guide directionally emitted obliquely in the traveling direction of the light and changes the emission angle to a normal line or a direction close to the normal line by using a multi-prism. Have also been proposed (JP-A 2-17, JP-A 2-84, and US Pat. No. 5,126,882). However, even with this type of surface light source element, there is a limit to the increase in the luminance of about 3 to 3.5 times the luminance in the normal direction of the omnidirectional type.

The present invention has been made on the basis of the background described above, and an object thereof is to further enhance the non-directional type normal direction luminance by controlling the distribution of emitted light and the directionality control. It is to provide a surface light source element.

[0006]

The above-mentioned problems can be solved by the present invention. That is, in the surface light source element according to the present invention, at least one side end surface is a light incident surface, and one surface that emits light incident from the light incident surface obliquely in the traveling direction of light is a light emitting surface, The multi-prism is composed of a light guide body having a light-reflecting layer on the surface opposite to the light emitting surface, and a plurality of multi-prisms having an apex angle of 80 ° to 115 °, which are arranged to overlap each other on the light-emitting surface side. The prism axis of the multi-prism is substantially parallel to the prism axes of the other multi-prisms, each of the prism axes of the multi-prism is substantially orthogonal to the light incident from the light incident surface, and It is characterized in that the convex portions are arranged so as to face in the same direction.

According to another aspect of the surface light source element of the present invention, at least one side end surface is used as a light incident surface, and one surface that emits light incident from the light incident surface obliquely in the traveling direction of the light. As a light emitting surface, a light guide body provided with a light reflecting layer on the surface opposite to the light emitting surface, and a plurality of multi-prisms having an apex angle of 80 ° to 115 °, which are arranged to overlap with each other on the light emitting surface side, The multi-prism is such that the prism axis of one multi-prism is substantially parallel to the prism axis of the other multi-prism, and
Each of the prism axes of the multi-prism is substantially orthogonal to the light incident from the light incident surface, and each of the multi-prisms sequentially changes the emitting direction of the obliquely emitted light emitted from the light emitting surface to sequentially increase the front brightness. It is characterized by having a function of improving.

[0008]

The surface light source element having the above structure according to the present invention operates and operates as follows. For example, the side end surface of 1 is a light incident surface, and the surface 1 of which light incident from the light incident surface is obliquely emitted in the traveling direction of the light is a light emitting surface, and light is reflected on the surface opposite to the light emitting surface. It is composed of a light guide having a layer and two multi-prisms having an apex angle of 90 °, which are arranged so as to be overlapped with each other on the light exit surface side. These multi-prisms have one prism axis of another multi-prism. It is assumed that the surface light source element is substantially parallel to the prism axis of the multi-prism and each of the prism axes of the multi-prism is substantially orthogonal to the light incident from the light incident surface.

In the surface light source element according to the present invention as described above, for example, the intensity at which the light guide has an angle distribution width of the outgoing light of about 40 degrees in a half value width in an oblique direction of about 60 degrees in the traveling direction of the incident light. It is assumed that light having the directivity of is emitted. The light emitted by the first multi-prism mounted on the light emitting surface of the light guide has a distribution width of about 20 ° and 1/2, and the emission angle of the light is about 30 °. This is theoretically proved that light incident on a multi-prism with an apex angle of 90 degrees at an incident angle of about 60 degrees exits at about 30 degrees even if calculated by Snell's law. The light from the first multi-prism is incident on the second multi-prism at an incident angle of 30 °,
The light emitted from the multi-prism has a distribution width of about 2
It is 0 °, the emission angle of the light is about 0 ° (normal direction), and the half-value width of the emission angle distribution hardly changes.

As can be understood from the above example, and as schematically illustrated in FIG. 7, each of the multi-prisms 1 sequentially changes the emitting direction of the obliquely emitted light emitted from the light emitting surface to sequentially change the front luminance. Has the function of improving.

[0011]

The present invention will be specifically described with reference to the following examples. [Evaluation example] Matte-shaped light guide with a thickness of 5 mm (Acrylite fine mat colorless transparent product manufactured by Mitsubishi Rayon, 100
X 110 mm (effective surface size 90 x 110 mm) is prepared, and a PET film is silver-deposited on the end faces of two sides of 100 mm (hereinafter PE) so that the matte surface becomes the emitting surface.
(Abbreviated as T-Ag) was adhered by adhesion processing, and PET-Ag was taped to the plane surface of the light guide to form a reflection surface.

PET-Ag is attached to the end faces of the two sides of 110 mm.
Wrap around with cold cathode tube (KC130T4 manufactured by Matsushita Electric Industrial Co., Ltd.
E72, 4 mmφ × 130 mm) was installed as a light source lamp. Inverter (TDK CXA-M
It was connected to a DC power supply via 10 L) and 12V DC was applied to light. In the following experiments and comparative experiments, the positional relationship between the light source lamp and the light guide and the lighting conditions are the same. The measuring method for evaluation is performed as follows, and is the same in the following experiments and comparative experiments.

A panel to be measured is placed on a measuring table, and a black paper having a pinhole of 3 mmφ is fixed at the center of the panel to be measured, which is prepared so as to rotate at the center of the panel and a rotation axis parallel to the lamp axis. , Adjust the distance so that the measurement circle of the luminance meter is 8-9 mm. All of these measurements are performed in a dark room, and the aging time of the lamp is measured after 30 minutes or more have elapsed.

Luminance was measured under different experimental conditions as follows. Experiment 1: Nothing was placed on the exit surface of the light guide. Experiment-2: A vertical angle of 90 ° pitch 0.05 on the exit surface of the light guide
A mm multi-prism is mounted with its apex angle outward and its prism axis parallel to the lamp axis. Experiment-3: (corresponding to the example of the present invention) On the panel of Experiment-2, one multi-prism is further placed with the prism axis parallel to the lamp axis and the apex angle facing outward. Experiment-4: (corresponding to US Pat. No. 4,542,449) The panel of Experiment-2 was further provided with one multi-prism with the prism axis orthogonal to the lamp axis and the apex angle facing outward. Place it.

Comparison-1: One diffusion film (manufactured by Kimoto Co., Ltd.) is placed on the exit surface of the light guide. Comparison-2: A multi-prism having a vertical angle of 90 degrees and a pitch of 0.05 mm is placed on the diffusion film of Comparative-1 with the vertical angle facing outward and the prism axis parallel to the lamp axis. Comparison-3: A single multi-prism is further placed on the panel of Comparison-2 with the prism axis parallel to the lamp axis and the apex angle facing outward. Comparison-4: (corresponding to US Pat. No. 4,542,449) The second multi-prism of the panel of Comparison-3 is mounted with the prism axis orthogonal to the lamp axis and the apex angle facing outward. Place.

The measurement results are shown in Tables 1 and 2. here,
Align the optical axis of the measuring instrument in the direction perpendicular to the surface of the object to be measured, and use this as the normal direction. On the other hand, the angle when rotated to the left is displayed as (-), and when rotated to the right (+) ) To display.
Table 2 shows the absolute value of the numerical value read by the luminance meter (not the luminance but a value close to the luminous intensity). Further, in Table 1, the ratio is calculated at the same time and the maximum value is displayed as 1.00.

[0017]

[Table 1]

[0018]

[Table 2]

As can be seen from the measurement results, the surface light source according to the present invention achieves high brightness by condensing light in a specific direction such as the front direction (normal direction).

[Configuration Example] The present invention can have various configurations within the scope of the invention. FIG. 1 shows an example of assembling the surface light source element according to the present invention. In this example, the light guide 3
The end surface on the second side is used as a light incident surface, and the light source 5 is wound around the end surface with a silver vapor deposition film 6 or the like. The light reflecting layer 4 is provided on the back surface of the light guide, and the light emitting surface 7 is matted. This processing can be changed to formation of fine lenses or prisms, application of a scattering material by screen printing, etc. as long as light is emitted obliquely from the light emitting surface.

On the light emitting surface side, two multi-prisms 1 each having a vertical angle of 80 ° to 115 ° and on which a large number of fine prisms 2 are formed are placed in an overlapping manner. In these multi-prisms 1, the prism axis of the first multi-prism 1 is substantially parallel to the prism axis of the second multi-prism 1, and each of the prism axes of these multi-prisms 1 is from the light incident surface. The projections 2 of the multi-prism 1 are arranged so as to be substantially orthogonal to the incident light and to face the same direction.

The present invention is not limited to the above example, and various modifications can be made. For example, the number of light sources may be one, and as shown in FIG. As a result, the light source can be saved and the power consumption can be reduced. Further, as shown in FIG. 3, the apex angle may be directed inward. By making the convex portion of the multi-prism face inward, mechanical damage to the convex portion of the multi-prism can be prevented. Furthermore, as shown in FIG. 4, two or more and three multi-prisms can be mounted. By using more multi-prisms in this way, it is possible to freely change the design of the light collecting direction.

In the present invention, the function of the present invention for improving the front brightness by sequentially changing the emission direction of the oblique emission light emitted from the light emission surface by each of the multi-prism sheets to the plurality of multi-prism sheets is not impaired. As long as it is possible to arrange various optical members. For example, as shown in FIG. 5, the transparent scattering sheet 8 may be arranged between the light exit surface and the multi-prism 1, and as shown in FIG. 6, the transparent scattering sheet 8 may be arranged between the multi-prisms 1. it can. Further, a plurality of prism sheets having different angles can be placed on the light emitting surface.

[0024]

According to the present invention, it is possible to provide an omnidirectional surface light source element having a higher luminance in the normal direction by controlling the distribution and directionality of emitted light. It is possible to achieve high brightness by reducing power consumption as much as possible. In addition, depending on the application, when the output angle distribution is closer to parallel light, it is possible to achieve this object by using a diffused light source when focusing is desired.

[Brief description of drawings]

FIG. 1 is an assembled perspective view of an example of a surface light source element according to the present invention.

FIG. 2 is a perspective view of an example of a light guide that can be used in the surface light source element according to the present invention.

FIG. 3 is a sectional view of an example of a surface light source element according to the present invention.

FIG. 4 is a sectional view of an example of a surface light source element according to the present invention.

FIG. 5 is a sectional view of an example of a surface light source element according to the present invention.

FIG. 6 is a sectional view of an example of a surface light source element according to the present invention.

FIG. 7 is a schematic view for explaining the function of the surface light source element according to the present invention.

[Explanation of symbols]

 1 Multi Prism 2 Prism 3 Light Guide 4 Light Reflecting Layer 5 Light Source 6 Reflecting Film 7 Light Emitting Surface 8 Scattering Sheet

Claims (2)

[Claims] 1. At least one side end surface is a light incident surface,
A light guide body having a light emitting surface on one surface for obliquely emitting light incident from the light incident surface toward a traveling direction of the light, and a light reflecting layer on a surface opposite to the light emitting surface; A plurality of apex angles of 80 ° to 1 arranged so as to be stacked on the light emitting surface side
15 ° multi-prism, wherein the multi-prism has a prism axis of one of the multi-prisms substantially parallel to a prism axis of the other multi-prism, and each of the prism axes of the multi-prism has the optical axis. A surface light source element, wherein the multi-prisms are arranged so as to be substantially orthogonal to the light incident from the incident surface and the respective convex portions of the multi-prisms are oriented in the same direction. 2. At least one side end surface is a light incident surface,
A light guide body having a light emitting surface on one surface for obliquely emitting light incident from the light incident surface toward a traveling direction of the light, and a light reflecting layer on a surface opposite to the light emitting surface; A plurality of apex angles of 80 ° to 1 arranged so as to be stacked on the light emitting surface side
15 ° multi-prism, wherein the multi-prism has a prism axis of one of the multi-prisms substantially parallel to a prism axis of the other multi-prism, and each of the prism axes of the multi-prism has the optical axis. The multi-prisms are substantially orthogonal to the light incident from the incident surface, and each of the multi-prisms has a function of sequentially changing the emission direction of obliquely emitted light emitted from the light emitting surface to improve the front brightness. Surface light source element.