JPH1064320A - Surface light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device increasing surface brightness and widening the angle of visibility. SOLUTION: In a surface light source device in which a light source 1 such as a fluorescent lamp is arranged on the incident light surface 5 of a transparent substrate 2 and light incident from the light source 1 is made outgoing from an outgoing light surface 4 to emit light, incident light scatter reflecting structure which is an ellipsoidal or square aggregate in which the ratio of the rough surface part to an optical flat surface is gradually varies with the distance from the light source 1 and the area is increased as the rough surface part is separated from the light source 1, and the major axis if it is an ellipse or the long side if it is a rectangle is arranged almost in parallel to the proceeding direction of the incident light is formed on the surface opposite to the outgoing light surface 4.

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. This incident scattering / reflecting structure is provided with a comparative diffuser comprising a dot-like reflection pattern for diffusing light on the rear surface of the transparent substrate, as shown in, for example, Japanese Patent Publication No. 07-00915,
This reflection pattern is distributed at 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.

[0004]

At the same time, these light source devices are required to be able to recognize display contents not only from the front but also from an oblique direction, that is, to have a wide viewing angle.

Therefore, in such a surface light source device, it is important to adjust the area ratio between the rough surface and the smooth surface to make the luminance distribution uniform and to widen the viewing angle. Conventionally, the amount of light emitted from the light-transmitting substrate and the luminance have been studied, but the viewing angle of the light emitted from the light-transmitting substrate has hardly been studied.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional example.
It is an object of the present invention to provide a surface light source device capable of obtaining a wider viewing angle by increasing light use efficiency.

[0007]

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 light-transmitting substrate and a primary light source disposed on one end surface of the light-transmitting substrate, wherein at least one of the front and rear surfaces of the light-transmitting substrate has an incident light scattering / reflecting structure. In the incident light scattering / reflecting structure, the ratio of the rough surface portion to the optical flat portion changes as the distance from the primary light source increases, and the rough surface portion increases in area as the distance from the primary light source increases. It is a quadrangle aggregate, and a major axis of the ellipse or a long side of the rectangle is arranged substantially parallel to a traveling direction of incident light from the primary light source.

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:
Each is about 1.5 or more.

[0009]

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

As shown in FIG. 1, in the surface light source device of the present embodiment, at least one side surface of a transparent substrate (light-transmitting substrate) 2 is an incident light surface 5 and one surface orthogonal thereto is an outgoing light surface 4.
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 reflective film 3 installed on a surface other than the input / output light surfaces 4 and 5, and A light-scattering / reflecting structure (FIG. 2) having a pattern for forming a rough surface portion is provided on at least one of the outgoing light surface 4 of the transparent substrate 2 or a surface on the opposite side thereof. As shown in FIG. 3, a polygonal shape or an elliptical shape is made into a single shape, and is characterized by being an aggregate thereof.

In this surface light source device, incident light incident from an incident light surface 5 travels in the transparent substrate 2 and is scattered by an incident light scattering / reflecting structure 7 shown in FIG.
Is emitted. In the surface light source device of this embodiment, the distribution of the emission angle of the emitted light is wider than that of the conventional surface light source device, and the light utilization efficiency in the side direction of the surface light source device is high, so that a wide viewing angle can be obtained. Features.

The details will be described below with reference to the drawings.

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

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 concave portions 8 is a polygonal shape whose shape increases as the distance from the light source 1 increases.

The light-transmitting substrate 2 of the present embodiment is made of, for example, a transparent resin such as poly (methyl methacrylate) (PMMA), polycarbonate (PC), and the like. It is about 4 to 1.6. Therefore, light that has entered the outgoing light surface 4 at an incident angle larger than the critical angle is reflected at the light transmitting substrate-air interface and does not exit the outgoing light surface 4.

Here, in order to radiate light from the outgoing light surface 4, at least one of the outgoing light surface 4 and the opposite surface of the transparent substrate 2 is roughened to scatter and reflect the incident light. Is formed. With such a structure, incident light enters the outgoing light surface 4 at an incident angle smaller than the critical angle with respect to the outgoing light surface 4, and is emitted from the transparent substrate 2 through the outgoing light surface 4 to improve the performance as a surface light source. Demonstrate.

On the front surface (or the 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 means that the shape of the polygonal or elliptical dot pattern forming the rough surface is determined according to the distance from the primary light source 1 according to a certain rule. An aggregate that is arranged so that its area changes.

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 / reflecting structure 7, so that the incident light has a certain angular distribution. Light. 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.

According to the present inventors, the distribution width of the angle of the scattered light depends on each shape of the dot pattern of the incident light scattering / reflecting structure 7 for scattering the incident light, and in particular, is substantially parallel to the traveling direction of the incident light. It has been found that it changes depending on the length of the dot.
Further, the present inventors have paid attention to the fact that the surface light source having a wide viewing angle for the emitted light can be created by widening the distribution width of the angle of the scattered light.

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 the dot patterns 8 has a shape in which the length substantially parallel to the direction in which the incident light from the primary light source 1 travels (the direction from top to bottom in FIG. 3) is longer 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 between the long side (major axis) and the short side (minor axis) of these dot patterns is "1.5" or less, the effect of reducing the distribution of the incident angle of light on the emission light surface 4 is small. Therefore, in order to make the emission light surface 4 have high brightness, “1.
A ratio of 5 or more is required.
In the case of 0.0 "or more, the dot or polygonal or elliptical shape of the dot pattern is elongated, and a dot pattern for uniformity is formed so that a single dot does not overlap an adjacent dot. It becomes difficult.

The ratio does not necessarily have to be the same over the entire dot pattern, but 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.

At this time, the size of the elliptical shape (or square shape) of the dot pattern 8 is such that the major axis (long side) is 50 μm to 6 μm.
The range of 00 μm is preferable, and the length of the minor axis (short side) is 5 μm.
m to 300 μm (the ratio of major axis / minor axis (long side / short side) is 2.0 to 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. Is preferably 1 μm or more in Rz which is a parameter specified in JIS B0601, for example.

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 disposed on the PMMA transparent substrate 2 in addition to the input and output light surfaces 4 and 5 and the cold cathode tube 1
Then, light from the reflector 6 wound around the cold cathode tube 1 was incident on the incident light surface 5 to produce a surface light source device.

The luminance of the light emitted from the emission light surface 4 of the surface light source device is measured by a luminance meter (BM-BM, manufactured 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 an example in which a circular dot is used and a comparative example in which the elliptical dot pattern of the present embodiment is used. It can be seen that the value range is increased by about 3 to 4 (deg).

FIG. 5 shows an example of the distribution of the luminance and the angle of the emitted light when the dot shape is circular, and FIG. 6 shows an example of the distribution of the angle of the luminance and 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 an example in which a square dot is used and a comparative example in which the rectangular dot pattern according to the present embodiment is used. It turns out that it is about 3 (deg) higher.

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

As described above, according to the present embodiment, it is possible to obtain a light source device capable of maintaining uniformity of in-plane luminance and further widening the viewing angle.

[0036]

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 distribution of the emission angle of the emitted light is wide and a wide viewing angle can be obtained.

[0038]

[Brief description of the 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 illustrating an arrangement of dot patterns provided on a transparent substrate of the light source device according to the present embodiment. FIG. 3A illustrates a case where the dot pattern is elliptical, and FIG. Is shown.

FIG. 4 is a diagram illustrating a comparative example of the surface light source device according to the first and second embodiments 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 illustrating a distribution example of luminance and an angle of emitted light in the first and second embodiments (elliptical pattern).

FIG. 7 is a diagram comparing characteristics of the third embodiment and a comparative example.

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 an example of distribution of luminance and angle of emitted light in the third and fourth embodiments.

[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

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigekuni Dewa 4-5-1, Nihonbashi-Muromachi, Chuo-ku, Tokyo Inside 8F Yuka Denshi Co., Ltd. (72) Inventor Kunihiko Kurokawa Nihonbashi-Muromachi, Chuo-ku, Tokyo 4F-1-5 joint building 8F Yuka Electronics Co., Ltd.

Claims (4)

[Claims] 1. A surface light source device comprising: a light-transmitting substrate; and a primary light source disposed on one end surface of the light-transmitting substrate, wherein at least one of front and rear surfaces of the light-transmitting substrate has an incident light scattering / reflecting structure. The incident light scattering / reflecting structure has a ratio of a rough surface portion and an optical flat surface portion that changes as the distance from the primary light source increases, and an area of the rough surface portion increases as the distance from the primary light source increases. A surface light source device, wherein the surface light source device is an aggregate of an ellipse or a square, and a major axis or a long side of the ellipse is arranged substantially parallel to a traveling direction of incident light from the primary light source. . 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 2, wherein the ratio is 2.0 or more and 10.0 or less. 4. The surface light source according to claim 1, wherein a light reflecting member is provided on a surface other than the incident light surface and the outgoing light surface of the translucent substrate. apparatus.