JPH09311223A - Surface light source - Google Patents

Abstract

(57) An object of the present invention is to provide a surface light source device having high surface brightness and uniform surface brightness. A surface light source device in which a light source such as a fluorescent lamp is disposed on a side of an incident light surface of a transparent substrate and light emitted from the light source is emitted from an emission light surface to emit light.
The ratio of the rough surface portion to the optical flat surface portion changes on the surface opposite to the outgoing light surface 4 of the light source 1, and the area increases as the rough surface portion separates from the light source 1. And has a major axis in the case of an ellipse, and a long side in the case of a quadrangle, which is arranged in a direction substantially orthogonal to the traveling direction of the incident 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 device used as various surface light sources such as a liquid crystal backlight, a lighting signboard, and a lighting body.

[0002]

2. Description of the Related Art A light source device used for various surface light sources is composed of a transparent substrate and a light source device installed in parallel with an incident end face of the transparent substrate.
It comprises a secondary light source and an incident light scattering / reflecting structure provided on the transparent substrate to scatter and reflect the incident light. In this incident scattering reflection structure, for example, as shown in Japanese Patent Publication No. 07-009515, a comparison diffusion means 5 composed of a dot-shaped reflection pattern for diffusing light is provided on the rear surface of a transparent substrate, and this reflection pattern is It is distributed with a density that is inversely proportional to the distance from the primary light source and its illuminance.

In addition to these shapes, an incident light scattering / reflecting structure having a V-shaped groove in the traveling direction of incident light or a direction perpendicular thereto, or a circular or polygonal unevenness (instead of screen printing) Hereinafter, an incident light scattering / reflecting structure composed of a rough surface is also used. Also in these cases, the in-plane luminance is made uniform by the area ratio between the rough surface portion and the smooth surface in an arbitrary region.

The performance required for such a surface light source device is the uniformity of the light emission brightness and the brightness over substantially the entire area of the display surface. In a light source device which is practically used, these performances are improved. It is designed for such an incident light scattering reflection structure.

[0005]

In such a light source device, since it is important to increase the surface brightness and make it uniform as described above, it is necessary to form a rough surface on a transparent substrate as in the conventional case. In the light-scattering / reflecting structure, by adjusting the area ratio of the optical plane portion and the rough surface portion in an arbitrary region, the amount of emitted light emitted from the region is adjusted, and the surface brightness is made uniform.

In such a case, the amount of light emitted from the transparent substrate depends on the area amount of the rough surface portion and is controlled. Therefore, the light source device must be designed in a state where both performances are balanced.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above conventional example, and an object of the present invention is to provide a surface light source device having a high surface brightness and a uniform surface brightness.

Another object of the present invention is to provide a surface light source device capable of increasing the utilization efficiency of incident light from a light source and increasing the emission brightness.

[0009]

To achieve the above object, a surface light source device according to the present invention has the following arrangement. That is, a surface light source device comprising a translucent substrate and a primary light source disposed on one end surface of the translucent substrate, wherein an incident light scattering / reflecting structure is provided on at least one of the front and rear surfaces of the translucent substrate. In the incident light scattering / reflecting structure, the ratio of the rough surface portion and the optical flat surface portion changes as the distance from the primary light source increases, and the rough surface portion has an elliptical shape whose area increases as the distance from the primary light source increases. It is an aggregate of quadrangles, and the major axis of the ellipse or the long side of the quadrangle is arranged in a direction substantially orthogonal to the traveling direction of incident light.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

In the surface light source device of this embodiment, as shown in FIG. 1, at least one side surface of a transparent substrate (transparent substrate) 2 is an incident light surface 5, and one surface orthogonal thereto is an emission light surface 4.
And a primary light source 1 such as a fluorescent lamp or a cold cathode tube installed substantially parallel to the incident light surface 5 of the transparent substrate 2, a reflection film 3 installed on a surface other than the incident and outgoing light surfaces 4 and 5, and The transparent substrate 2 is provided with a light-scattering / reflecting structure (FIG. 2) having a pattern for forming a rough surface portion on at least one of the outgoing light surface 4 and the opposite surface thereof, and the pattern of the light-scattering / reflecting structure is As shown in FIG. 3, the polygonal shape is a single shape,
It is characterized by being the aggregate.

In this surface light source device, the incident light incident from the incident light surface 5 travels in the transparent substrate 2, is scattered by the incident light scattering / reflecting structure shown in FIG. 2, and is emitted from the outgoing light surface 4 as outgoing light. To be done. In the surface light source device of this embodiment, the distribution of the emission angle of the emitted light is narrower than that of the conventional surface light source device, and the utilization efficiency of light in the front direction of the surface light source device is high, so that the intensity of the light source is not increased. The feature is that emitted light with high brightness can be obtained.

A detailed description will be given below with reference to the drawings.

FIG. 1 is an external perspective view showing the external shape of the surface light source device of this embodiment.

In the figure, a long primary light source 1 such as a fluorescent lamp is driven to emit light by power supply from a DC power source 10, and the emitted light passes through an incident light surface 5 to a transparent substrate 2
It is incident inside. Further, a reflector (reflecting plate) 6 is provided around the light source 1 other than the incident light surface 5, and the light emitted from the light source 1 is reflected to the incident light surface 5 side so that the light source 1 1 increases the irradiation efficiency. The light thus incident on the transparent substrate 2 travels straight through the transparent substrate 2, is reflected by the reflection film 3 and the light scattering / reflection structure, and is emitted from the emission light surface 4.

FIG. 2 is a view for explaining the incident light scattering / reflecting structure 7 in the present embodiment, and is a view taken along the line AA ′ in FIG.

On the opposite side of the outgoing light surface 4 of the transparent substrate 2, that is,
As shown in FIG. 2, a concave portion (dot pattern) 8 for scattering incident light is provided on the reflective film 3 side. FIG. 3 shows the shape of the recess 8 in a top view.
(A) and (b). That is, the shape of these recesses 8 is a polygonal shape whose shape increases as the distance from the light source 1 increases.

The transparent substrate 2 of the present embodiment is made of a transparent resin such as poly (methyl methacrylate) (PMMA) or polycarbonate (PC), and the refractive index of light with respect to air is about 1. It is about 4 to 1.6. Therefore, the light incident on the outgoing light surface 4 at an incident angle larger than the critical angle is reflected by the transparent substrate-air interface and does not exit from the outgoing light surface.

Here, in order to emit the light from the outgoing light surface 4, at least one of the outgoing light surface 4 of the transparent substrate 2 or the opposite surface is roughened so that the incident light is scattered and reflected. In order to form an incident light scattering reflection structure of With such a structure, the incident light is transmitted through the outgoing light surface 4
On the other hand, the light enters the outgoing light surface 4 at an incident angle smaller than the critical angle, and exits from the transparent substrate 2 through the outgoing light surface 4 to exhibit the performance as a surface light source.

On the front surface (or back surface) of the transparent substrate 2,
In order to make the luminance uniform, a dot pattern 8 combining a rough surface and a smooth surface is formed, and light is reflected on the smooth surface (9 in FIG. 2) and light is reflected on the rough surface (the concave portion 8 in FIG. 2). Scattered. Then, the area ratio of the smooth surface / rough surface in an arbitrary region on the emission light surface 4 of the transparent substrate 2 is changed according to the position on the transparent substrate 2 and the distance from the primary light source 1. Thereby, uniformity of the in-plane luminance on the emission light surface 4 is achieved.

The dot pattern referred to here is that the area of each polygonal dot pattern forming the rough surface changes according to the distance from the primary light source 1 according to a certain rule. It is an aggregate that is arranged to do.

Further, since the light incident from the primary light source 1 through the incident light surface 5 of the transparent substrate 2 is scattered in each direction by the rough surface portion of the incident light scattering reflection structure, the incident light is angled in various directions. The light has a distribution width of. Of the reflected light, the light incident on the outgoing light surface 4 at an angle smaller than the critical angle is emitted from the outgoing light surface 4 and shines the outgoing light surface 4 of the panel of the surface display device.

The inventors of the present invention have found that the distribution width of the angle of the scattered light depends on each shape of the dot pattern of the incident light scattering reflection structure that scatters the incident light, and in particular, the length of the dot with respect to the traveling direction of the incident light. It was found that It has been noted that this makes it possible to increase the distribution of the reflected light, of which the incident angle on the outgoing light surface 4 is small, and to create a surface light source having high brightness in the front direction of the light source device.

The dot pattern of this embodiment is shown in FIG.
As shown in (a) and (b), it is an aggregation of elliptical or polygonal dot patterns in which the area of the single dot pattern 8 increases as the distance from the primary light source 1 increases. Each of these dot patterns 8 has a shape in which the length in the direction in which the incident light from the primary light source 1 travels (the direction from top to bottom in FIG. 3) is shorter than the length in the direction orthogonal thereto ( (See FIG. 3).

The shape of each of these dot patterns is as follows.
In the case of an ellipse, the ratio of the major axis to the minor axis, and in the case of a quadrangle, the ratio of the length of the major side to the minor side is preferably about "1.5" or more, and more preferably, The ratio is about “2.0” or more and “10.0” or less.

When the ratio of the long side to the short side of these dot patterns is "1.5" or less, the effect of increasing the distribution of the light is small because the incident angle of the light with respect to the outgoing light surface 4 is small. A ratio of "1.5" or more is required to make the light emitting surface 4 have high brightness. Also, this ratio is "10.0"
In the above case, the polygon which is the shape of the dot pattern becomes elongated and it is difficult to form a dot pattern for uniformization by preventing a single dot from overlapping adjacent dots.

Further, this ratio does not necessarily have to be the same over the entire dot pattern, and may be changed for each dot pattern. Further, the ratio between the vicinity of the incident light surface 5 and the end of the transparent substrate 2 may be different.

In this case, the size of the elliptical shape (quadrangular shape) of the dot pattern 8 is such that the major axis (long side) is 50 μm to 600 μm.
The range of μm is preferable, and the length of the short diameter (short side) is 5 μm to
300 μm (major axis / minor axis (long side / short side) ratio is 2.0
~ 10.0) is preferable.

Further, the shape of the rough surface formed according to these dot patterns needs to have a surface roughness sufficient to scatter incident light. For that purpose, the surface roughness of the rough surface is required. Is preferably 1 μm or more in Rz which is a parameter defined by JIS B0601.

Next, a specific example in the embodiment of the present invention will be described. [Embodiments 1, 2 and Comparative Example 1] (Preparation of Transparent Substrate 2) In this embodiment, 122 mm ×
An elliptical dot pattern 8 having a ratio of the major axis to the minor axis of 1.0 to 10.0 is formed on the cavity surface of a light guide plate mold of 91 mm × 3 mm (thickness) from the primary light source 1. Using a mold formed so that its area increases with distance, polymethyl methacrylate (PMM) is placed in the mold.
A) was injection molded to form a transparent substrate 2. (Measurement of Luminance) The reflection film 3 is arranged on the transparent substrate 2 made of PMMA thus formed other than the incident / emission light surfaces 4 and 5.
A surface light source device was prepared by making light from the cold cathode tube 1 and a reflector 6 wound around the cold cathode tube 1 incident from an incident light surface 5.

The luminance of the light emitted from the emission surface 4 of this surface light source device is measured by a luminance meter (BM-made by Topcom Co., Ltd.).
7), the angle distribution of the outgoing light was measured while changing the angle of the luminance meter with respect to the outgoing light surface 4. The result is shown in FIG.
The “half width” in FIG. 4 is 50% of the maximum luminance value.
It is a value indicating the range of the angle formed by the emitted light having a luminance of at least%.

FIG. 4 shows a comparative example between the case where circular dots are used and the case where the elliptical dot pattern of this embodiment is used. The elliptical shape of this embodiment is more average. It can be seen that the brightness is increased by about 600 to 750 (cd / square m).

FIG. 5 shows a distribution example of the brightness and the angle of the emitted light when the dot shape is circular, and FIG. 6 shows a distribution example of the brightness and the angle of the emitted light in [Example 1]. [Embodiments 3 and 4 and Comparative Example 2] (Preparation of Transparent Substrate 2) In this embodiment, 122 mm ×
On a cavity surface of a light guide plate mold of 91 mm × 3 mm (thickness), a square dot pattern 8 having a ratio of a long side to a short side of 1.0 to 2.0 is placed at a distance from the primary light source 1. In accordance with the above, a mold formed so as to increase its area is used, and polymethyl methacrylate (PMM
A) was injection molded to form a transparent substrate 2. (Measurement of Luminance) A surface light source device was prepared in the same manner as in the first and second embodiments and the comparative example, and the emission luminance was measured.

FIG. 7 shows a comparative example of the case where square dots are used and the case where the square dot pattern of the present embodiment is used. About 500 (cd / square meter) higher,
It can be seen that the full width at half maximum is also decreasing with it.

FIG. 8 shows a distribution example of the angle of the emitted light and its luminance ratio in the comparative example of FIG. 7, and FIG. 9 shows a distribution example of the angle of the emitted light and its luminance ratio in the present embodiment. ing.

As described above, according to this embodiment, a light source device capable of maintaining the uniformity of in-plane brightness and further improving the emission brightness is obtained.

[0037]

As described above, according to the present invention, the surface luminance can be increased and the surface luminance can be made uniform.

Further, according to the present invention, there is an effect that the utilization efficiency of the incident light from the light source can be increased and the emission brightness can be increased.

[0039]

[Brief description of drawings]

FIG. 1 is an external perspective view illustrating a shape of a light source device according to an embodiment.

FIG. 2 is a sectional view taken along the line A-A 'in FIG.

3A and 3B are top views showing the arrangement of dot patterns provided on the transparent substrate of the light source device according to the present embodiment, where FIG. 3A shows a case where the dot pattern is elliptical, and FIG. 3B shows a square dot pattern. Shows the case.

FIG. 4 is a diagram showing a comparative example of the surface light source device of the present embodiment and a light source device to be compared.

FIG. 5 is a diagram showing an example of distribution of luminance and angle of emitted light when a dot pattern has a circular shape;

FIG. 6 is a diagram showing an example of a distribution of brightness and angle of emitted light in the first embodiment.

FIG. 7 is a diagram comparing the characteristics with the third and fourth embodiments and the comparative example 2.

FIG. 8 is a diagram illustrating an example of distribution of luminance and angle of emitted light when a dot pattern has a square shape.

FIG. 9 is a diagram showing a distribution example of luminance and angles of emitted light in the third embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light source (fluorescent lamp, cold cathode tube) 2 transparent substrate 3 reflective film 4 outgoing light surface 5 incident light surface 6 reflector 7 incident light scattering / reflecting structure 8 dot pattern (recess) 10 DC power supply

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigenkuni Dewa 4-chome, Nihombashi Muromachi, Chuo-ku, Tokyo 8F, Yuka Denshi Co., Ltd. (72) Inventor Kunihiko Kurokawa Nihonbashi Muromachi, Chuo-ku, Tokyo 4th, 1st and 5th, same building 8F Yuka Denshi Co., Ltd.

Claims (3)

[Claims] 1. A surface light source device comprising a translucent substrate and a primary light source disposed on one end surface of the translucent substrate, wherein an incident light scattering reflection structure is provided on at least one of the front and rear surfaces of the translucent substrate. In the incident light scattering / reflecting structure, the ratio of the rough surface portion to the optical flat surface portion changes as the distance from the primary light source increases, and the area of the rough surface portion increases as the distance from the primary light source increases. A surface light source device, which is an aggregate of ellipses or quadrangles, and in which the major axis of the ellipse or the long sides of the quadrangle are arranged in a direction substantially orthogonal to the traveling direction of incident light. 2. When the rough surface portion has an elliptical shape, the ratio of the major axis to the minor axis is, and when the rough surface portion is a quadrangle, the ratio of the long side to the short side is:
2. The method according to claim 1, wherein each of them is about 1.5 or more.
A surface light source device according to claim 1. 3. The surface light source device according to claim 1, wherein a surface for light reflection is provided on a surface other than the incident light surface and the emission light surface of the transparent substrate.