JP3303179B2 - Surface light source device - Google Patents

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 using a light guide in which a pattern having a rough surface portion is formed on the lower surface or the entire lower surface has a rough surface portion.

[0002]

2. Description of the Related Art A conventional surface light source device using a light guide has a plate-like light guide 1 made of a transparent material and has a structure shown in FIG. The linear light source 2 disposed, the light diffusing member 3 disposed on the light exit surface 1b side of the light guide 1, and the reflection disposed on the surface 1c opposite to the light exit surface 1b of the light guide 1 And a member 4.

In a conventional surface light source device using a light guide, a large number of rough surface portions 6 are formed on a surface 1c of the light guide 1 on which the reflection member 4 is disposed, as shown in FIG. Either a predetermined pattern is formed by (a minute diffusion portion having a minute area as a rough surface and a diffusion action is provided) or the entire surface 1c is formed as a rough surface portion. Reference numeral 5 denotes a prism sheet provided with a large number of prism-shaped protrusions 7 on the surface.

In the surface light source device shown in FIG. 4, light from a light source 2 is made incident on an incident end face 1a of a light guide 1 and totally reflected by respective inner surfaces of an exit surface 1b and a surface 1c of the light guide 1. End face 1d
In the direction of. Here, the light that has reached the rough surface portion 1c of the light guide 1 is reflected or transmitted while being diffused, and the transmitted light is reflected by the reflection member 4 and returned to the light guide 1. By being diffused in this manner, a part of the light exits from the exit surface 1b, passes through the diffusion member 3 and becomes diffused light, and further passes through the prism sheet 5 to become a surface light source. Here, by appropriately changing the distribution density of the rough surface formed on the surface 1c of the light guide 1 depending on the location, the light quantity distribution on the exit surface 1b of the light exiting from the exit surface 1b of the light guide 1 is improved. The brightness distribution of the diffused light transmitted through the diffusion member 3 is made uniform so as to be uniform.

In the case of a surface light source device of a system in which the entire surface 1c of the light guide is roughened, the shape of the rough surface is changed so that the light emitted from the light emission surface 1b of the light guide is changed. The light amount distribution on the exit surface 1b is made uniform.

[0006]

In the surface light source device shown in FIG. 4, the luminance distribution of the light emitted from the diffusion member 3 can be made uniform by selecting the pattern of the rough surface portion. The ratio of the amount of light emitted from the emission surface 1b of the light guide to the amount of light incident into the light guide 1 is small, and there is a problem in terms of light use efficiency. This means that the light guide surface 1c
The same applies to the case of a surface light source device in which the whole is a rough surface portion.

It is an object of the present invention to provide a surface light source device which is brighter than a conventional surface light source device by determining the shape of the roughness of each rough surface portion (the shape of the unevenness of the rough surface).

[0008]

The surface light source device according to the present invention comprises:
A plate-shaped light guide ing a transparent material, the end face of the light guide and the linear light source of a fluorescent tube or the like disposed near the (incident end surface), the light diffusing disposed on the exit surface side of the light guide A light-guiding member, and a reflecting member arranged on the side opposite to the light-emitting surface of the light guide.
The shape where the lower surface of the body is inclined, the light source side is thick and the other side is thin
And the inclination angle α of the lower surface is within a range of 0 ° <α ≦ 4 °.
In addition, a pattern composed of a large number of minute diffusion portions (rough surfaces) is formed on the surface of the light guide on which the reflection member is disposed, and the cross-sectional shape (roughness of the rough surface) of each rough surface is formed. Is a specific shape, and the average height difference is Δ
H, when the average pitch is P, the following conditions (1) to
It is intended to satisfy (3). That is, first, ΔH / P is set within the following range.

0.1 ≦ ΔH / P ≦ 0.4 (1) The surface light source device of the present invention having the above-described configuration has a surface which is brighter than the conventional surface light source device, as will be described later in detail based on the data of the embodiment. First, in order to obtain a light source , this condition (1)
It is necessary to meet.

In the surface light source device of the present invention , ΔH / P is set within the above range, and the height difference ΔH of the roughness is set within the following range (to satisfy the condition (2)). More desirable.

4.0 μm <ΔH ≦ 10 μm (2) In the surface light source device of the present invention , ΔH / P is set within the above range, and the average pitch P is set within the following range (conditions:
(3) is desirable.

[0012] 25μm ≦ P ≦ 100μm (3) further [Delta] H / P, [Delta] H, a surface light source device was set to be within the respectively following ranges P is most preferred.

0.1 ≦ ΔH / P ≦ 0.4 (1) 4.0 μm <ΔH ≦ 10 μm (2) 25 μm ≦ P ≦ 100 μm (3) The surface light source device of the present invention is made as a result of the following experiment. As a result, it has been found that the above-described configuration is brighter than the conventional surface light source device.

When a rough surface is formed on the light guide, for example, as shown in FIG. 5, a method of forming a rough surface by controlling the depth of unevenness of the rough surface to be substantially constant is used. in even Saga substantially constant, and if the pitch P ₁ as (a) in FIG. 5 is small, and if it is slightly larger pitch P ₂ is as (B), the pitch P ₃ as (C) Is large, the luminance may be different or equal.

Similarly, when controlling the depth while keeping the pitch substantially constant, the luminance may be different or equal depending on whether the depth is large or small.

Thus, the brightness of the light emitted from the light emitting surface of the light guide depends not on the depth or pitch of the rough surface, but on the degree of inclination of each uneven shape of the rough surface. It was considered that the brightness would be highest when the condition was within a certain range, and the brightness would decrease even if the degree of tilt became larger or smaller than within a certain range.

The present invention has been made on the basis of the above idea, and is one of the factors representing the rough surface of each rough surface portion of the pattern by the rough surface portion formed on the surface of the light guide on the reflecting member side. The factors affecting the brightness are based on the results of repeated experiments focusing on the unevenness of the rough surface, especially on the degree of inclination of each unevenness, rather than the depth or pitch. Actually, the degree of the inclination is indicated by a parameter (ΔH / P), which is a ratio between the average height difference ΔH of the unevenness of the rough surface and the average pitch P shown in FIG. 2, and the relationship between this and the brightness is obtained by an experiment. Based on the results, the present invention has been made by confirming that the value of ΔH / P within the above range has high brightness.

Next, the results of the experiment will be described. The measured values in the following table are average values measured on the line indicated by A in FIG.

As is clear from the above table, it is understood that the brightness is smaller in the conditions 7, 11, 12, and 16 than in the other conditions . This That These are the greater than the value of [Delta] H / P is less than or compared with other conditions, [Delta] H / P The results are within the following ranges
Under conditions necessary to obtain a bright surface light source device
You can see that there is.

0.1 ≦ ΔH / P ≦ 0.4 Further , if the average height difference ΔH is too large, it is assumed that ΔH / P
Even if P is within the above range, it is not preferable from other points in terms of forming a rough surface, and the effect is not obtained as in the conditions 21 and 22, and even if the value of ΔH is too small, the rough surface may not be formed. Although it is bright as in the conditions 1, 2, and 3, a sufficient effect cannot be obtained. Therefore, ΔH is desirably within the following range.

4.0 μm <ΔH ≦ 10 μm Further, if the value of the average pitch P is too large or too small, it is not preferable for the same reason. Especially the average pitch P
When is small, as can be seen from the above experimental data, although a certain effect can be obtained in terms of brightness, the effect does not become remarkably bright, and even if ΔH / P is set within the above range, the effect is relatively small. Become smaller. Therefore, it is more preferable to set the value of P within the following range.

25 μm ≦ P ≦ 100 μm Particularly when both ΔH and P are out of the above-mentioned range as in the condition 22 , even if the value of ΔH / P is in the above-mentioned range, it is difficult to obtain the effect.

For the above reasons, it is most desirable to set the values of ΔH / P, ΔH, and P to fall within the following ranges.

0.1 ≦ ΔH / P ≦ 0.4 4.0 μm <ΔH ≦ 10 μm 25 μm ≦ P ≦ 100 μm As described above, the surface light source device of the present invention is made of a transparent material and is a plate-shaped light guide. Body, a linear light source such as a fluorescent tube arranged close to the incident end face of the light guide, a light diffusing member arranged on the emission surface side of the light guide, and a surface opposite to the emission surface of the light guide. And a pattern of a large number of minute diffusion portions (rough surface portions) in which a rough surface is formed on the surface of the light guide on the side of the reflection member (surface opposite to the exit surface). When the above-mentioned ΔH / P is defined as a parameter indicating the roughness (roughness) of the rough surface portion, the value is made to fall within the above range.

Further, in the surface light source device of the present invention, it is desirable that the value of the parameter ΔH be within the above-mentioned range or the value of the parameter P be within the above-mentioned range.

In the present invention, it is most desirable that all of the three parameters ΔH / P, ΔH, and P fall within the above ranges.

In the surface light source device according to the present invention, the light guide may not be a plane in which the light exit surface and the surface opposite to the light exit surface are parallel. As shown in FIG. 6, after the laser beam A is incident on the parallel-plane plate-shaped light guide at an angle θ, the light B transmitted through the rough surface portion 6 is emitted at an emission angle ψ. Here, as a result of measuring the emission angle 時 when the incident angle θ of the laser beam A was changed, it was found that it was almost constant. That is, the outgoing angle ほ ぼ is substantially constant regardless of the incident angle θ.

From this, it can be seen that the angle of incidence of light on the rough surface 6 has little effect on the action of the rough surface 6 on the light reaching the rough surface 6.

When several experiments were conducted, the inclination angle α of the surface 1c of the light guide shown in FIG.
In the range of about (0 ° <α ≦ 4 °) , the relationship between the brightness of light emitted from the emission surface 1b of the light guide and the shape of the rough surface portion 6 is such that the emission surface 1b and the surface 1c described above are different. It was confirmed that the relationship was almost the same as that of the parallel light guide 1.

For the above reasons, the present invention can be applied to a surface light source device using a light guide in which the inclination angle α of the lower surface 1c is in the range of 0 ° to 4 ° (0 ° <α ≦ 4 °). .

Also, in the case of a surface light source device in which the entire surface 1c of the light guide is rough, if the shape of the fine irregularities of the rough surface is changed within the above range, The amount of light emitted from the emission surface 1b is larger than in the conventional example.
That is, the roughened surface is formed over substantially the entire surface of the light guide on the reflecting member side, and the roughness of the emitted light is changed by using the roughened surface, such as one in which the roughness is changed so that the luminance distribution of the emitted light becomes uniform. A surface light source device using a light guide having a rough surface for uniformizing the luminance on the surface on the reflection member side, such as a surface light source device for making the luminance uniform, wherein the roughness of the rough surface is ΔH / P. ΔH and P values
Satisfying the above-mentioned conditions belong to the surface light source device of the present invention.

[0032]

Next, an embodiment of the surface light source device of the present invention will be described. FIG. 1 is a view showing an embodiment of the present invention, in which (A) shows a cross section in a direction perpendicular to the length direction of a linear light source,
(B) shows a pattern formed on the lower surface of the light guide.

In FIG. 1, reference numeral 1 denotes a light guide made of a transparent resin or the like, 2 denotes a linear light source such as a cold cathode tube, 3 denotes a diffusion member, 4 denotes a reflection member, and 5 denotes a prism sheet. In FIG. 1 (A), the light guide 2 is drawn so that its lower surface is inclined and has a large slope. 1a side of the thickness t ₁ is 4.0mm, the thickness t ₂ of the opposite surface 1d 1.
5 mm, and the actual value of the inclination θ is small at about 2.7 °. On the lower surface 1c of the light guide of this embodiment, a pattern of a large number of rough surface portions 6 is formed as shown in FIG. The inside of each rough surface portion 6 is formed with minute irregularities having ΔH and P values satisfying the above conditions.
In this pattern, the smallest rough surface portion was D ₁ = 0.6 m.
m, T ₁ = 1.0 mm and the largest one is D _n = 0.9 m
m, T _n = 1.0 mm, and the size is gradually changed.

The pattern shown in FIG.
Is used with a rough surface of ΔH = 7 μm and P = 25 μm, and the luminance distribution of light emitted from the prism sheet 5 when the structure shown in FIG. 1A is extremely uniform and the brightness is
4200 [nt] is about 15% higher than that of the same type of the related art.

In the above embodiment, the rough surface formed on the surface 1c of the light guide 1 is a pattern composed of a large number of rough surfaces 6 as shown in FIG. 1B, but almost the entire surface 1c is a rough surface. ,
Even if the brightness distribution of the light from the emission surface is made uniform by appropriately changing the roughness or the like, the unevenness of the rough surface may satisfy the above condition.

[0036]

The surface light source device using the light guide of the present invention is
The brightness is increased by defining the uneven shape of the roughness of the rough surface portion formed on the lower surface of the light guide.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a surface light source device of the present invention.

FIG. 2 is a view for explaining parameters that define the irregular shape of a rough surface used in the present invention.

FIG. 3 is a diagram showing a luminance measurement position of light emitted from the surface light source device.

FIG. 4 is a diagram showing a configuration of an example of a conventional surface light source device.

FIG. 5 is a diagram showing various uneven shapes having a constant depth in the rough surface of the light guide.

FIG. 6 is a diagram illustrating a relationship between incident light and light emitted from a rough surface in the surface light source device.

FIG. 7 is a diagram showing a cross-sectional shape of a light guide having an inclined surface.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light guide 2 Light source 3 Light diffusing member 4 Reflecting member 5 Prism sheet 6 Pattern of rough surface part provided in light guide

Claims (1)

(57) [Claims] 1. A light guide having a rough surface portion on a lower surface, a light source disposed close to an incident end face of the light guide, a diffusion member disposed on an emission surface side of the light guide, and a lower surface of the light guide. And a reflecting member disposed on the side of the light guide, and the lower surface of the light guide is inclined.
The light guide has a shape that is thick on the light source side and thin on the other side.
When the inclination angle α of the surface is in the range of 0 ° <α ≦ 4 °, the average height difference of the fine unevenness of the rough surface portion of the light guide is ΔH, and the average pitch is P, the rough surface of the rough surface portion The surface light source device characterized in that the state of the unevenness satisfies the following conditions (1) to (3). 0.1 ≦ ΔH / P ≦ 0.4 (1) 4.0 μm <ΔH ≦ 10 μm (2) 25 μm ≦ P ≦ 100 μm (3)