JPS63206701A - Light diffusion device - Google Patents

Abstract

PURPOSE:To use light from a wire-shaped light source such as fluorescent light to realize the brightness uniform over the entire part by using the surface on the thick side of the wedge of a thin type wedge-like photoconductor consisting of a transparent medium having a specific refractive index as a light incident face and one of the slopes thereof as a reflection face. CONSTITUTION:The surface P5 on the thick side of the wedge of the wedge-like photoconductor 10 having such a shape in which the thickness of the photoconductor 2 decreases on progression of rays is used as the incident face, to which the light is entered from the wire-shaped light source 1. One plane P2 of the slopes having the max. area of the photoconductor 10 is used as the reflection face 2b, then the incident ray changes the progressing direction thereof gradually at every repetition of total reflection on progression of the incident ray. The incident ray exceeds the critical angle of the total reflection in some stage and eventually emits to the outside world from an exit side boundary face 2a. The refractive index (n) of the medium 2 is so determined as to satisfy the conditions 1.25<=n<=1.4 and such medium is combined with the shape of the photoconductor 10 so that the exit positions of respective modes are uniformly dispersed. Furthermore, a light diffusion plate 4 is disposed on the exit side.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light diffuser. This type of light diffuser is used as a surface light source to uniformly illuminate a relatively wide area by receiving light from a light source, and in practical use, for example, it can be used as a single stage for illuminating display devices such as advertising lights. , especially in f& near, it is used as a backside illumination means of a liquid crystal display device.

[Prior art and IFI problem 1] Conventionally, when fluorescent lights are used for indoor lighting, advertising billboards outdoors at night, etc., several FFL lights are arranged in parallel and the milk is placed on top of the light diffusion of the board 1. It is common practice to convert the light emitted from a linear light source into a pseudo surface light source by arranging a plate-like object.

However, with the conventional method, the light source flux that is uniform all around the circumference of the fluorescent lamp is forcibly taken out in a plane at a certain position, so the brightness distribution in the plane part where the light diffusion plate is placed is sometimes unsightly and uneven. This visually creates an outline of the fluorescent lamp, which is one cause of detracting from the aesthetic appearance of the lighting device. In order to avoid such non-uniformity, the light diffusion plate and the fluorescent lamp must be placed at a considerable distance, which poses a problem from the perspective of space saving.

Recently, there has been an increasing demand for a relatively small planar light source having a uniform luminance of 4i for back illumination of liquid crystal displays of liquid crystal televisions, portable personal computers, word processors, and the like. To deal with this, there are currently EL (electroluminescence) and direct backlights in which a fluorescent lamp is placed directly below and the brightness distribution is adjusted using a light-shielding filter, etc., but these have low durability, cost, etc.
The reality is that they have advantages and disadvantages in terms of performance, etc., and there are many practical problems.

[L stage for solving problems] The first aspect of the present invention is that in view of the problems of the prior art described in L, it is possible to use an inexpensive light source such as a fluorescent lamp, and it is compact and achieves uniform brightness over the entire surface. It is an object of the present invention to provide a light diffuser which can be used in a variety of ways, and further has less light loss.

The object is to provide a light diffuser using a light guide made of an optically transparent medium, the light guide comprising:
Two planes P1 and P2, one of which is closer than the other, with at least the maximum area, and a substantially triangular shape corresponding to both sides of P1 and P2! Two planes P with approximately f rows in r
3, P4, and a rectangular 1' 11riP5 corresponding to one end surface of the 2f planes P1 and P2.

Moreover, the plane P5 is the light incident surface, and the plane P1 and P2 are
This is achieved by a light diffuser in which one of the following is a reflecting surface, and the refractive index n of the medium satisfies the following: 1.25≦n≦1.4.

[Effect] According to the light diffuser as above.

■Since the refractive index n is in the range of 1.25≦n≦1.4,
When the light from the fluorescent lamp is made incident from the plane P5, the light is reflected by the reflecting surface and is diffused almost evenly regardless of whether it is near or far from the plane P5.

■ By using the shape composed of at least the planes P1 to P5 as one structural unit, the idea of the present invention can be applied in various variations. For example, the shape of the light guide further faces the plane P5. In a typical case where the whole has a thin wedge shape with a plane P6 having a small area, or the two wedge-shaped light guides are integrated with each other on the plane P6, and the integrated It is also possible to construct a light diffuser or the like in which the entire light guide has a substantially arch shape.

(2) By using a diffuser plate together with the light guide, a planar light source with extremely uniform brightness can be provided.

It has the following advantages.

[Example] Hereinafter, a light diffuser according to the present invention will be described in detail based on a specific example.

First, the basic concept of the light diffuser of the present invention is explained in Fig. 4 (a).
), (b), and (C).

In FIGS. 4(a) to (c), 1 is a linear light source such as a fluorescent lamp, 2 is a light guide made of glass or the like, and 3 is a light beam propagating through the light guide 2. In FIG. When light from a light source such as a fluorescent lamp is made to enter the light guide 2 which is optically transparent and has a higher refractive index than the outside world,
The light ray 3 travels inside the light guide 2 while repeating total reflection, and at this time, in the case of natural beam light such as that of a fluorescent lamp, the number of modes of the emitted light ray is in fact infinite. ,
Each beam propagates under total reflection conditions depending on its incident angle and position (see Figure 4 (a)). Therefore, the shape of the model is such that the thickness of the light guide 2 becomes thinner as the light rays progress. to the light guide 2, and the light beam exit surface 2a
When the plane 2b on the opposite side is processed to a reflective mirror surface, the light rays 3 of each mode gradually change their traveling direction each time they undergo total reflection, and at a certain stage they exceed the critical angle of total reflection and are reflected from the output side interface 2a. The exit position l of the light ray of each mode when it goes out to the outside world or becomes a bar (see Figure 4 (b)) is a function of the incident point and the shape and refractive index of the light guide. It is determined uniquely within the error range caused by disturbance factors (nonuniform internal refractive index distribution, impurities, visible absorption of the light guide material, scattering due to structural irregularities at the interface, individual differences in light source characteristics, etc.).

Therefore, the fluorescent lamp 1 The basic concept of the present invention is to convert the light from linear light sources such as
reference).

In other words, the present invention allows light from a linear light source such as a fluorescent lamp to enter an optically transparent light guide having a refractive index and shape based on the unemit IJ, thereby causing total reflection within the light guide. A light diffuser that can be used as a planar light source and has a uniform output ray mode density over a wide area by gradually emitting and diffusing the light rays of each mode as they progress through the interface of the incident surface. It provides:

Based on the above concept, (<In order to realize the light diffuser, the present inventors conducted luminance component 41 analysis and experimental prototype evaluation in parallel.

5(a) to 5(h) are examples of computer-based ray tracing simulation results, assuming the gravel-like light guide shown in FIG. 4(b), with an internal refraction radius of 1. 00 to 2
．． This is the output of the brightness distribution analysis results when the brightness is changed up to 42. In other words, the brightness at the distance from the light source (horizontal axis) (
FIG. According to this, the ideal internal refractive index for achieving uniform brightness distribution is 1.25.
1t in the range of 1.4 was expected.

Therefore, those who have not yet emitted 1jI created a light guide with a shape as shown in Figure 4(b) using a material with a refractive index in this range (e.g., water n = 1.333), and calculated the H degree distribution. When we conducted actual measurements, we obtained results that roughly matched the calculation analysis.

FIG. 6 is a diagram showing an example of the experimental results.

Width 100mm, length 360mm, thickness 20mm to 4
We created a gravel-like aquarium that varies up to mm, and the difference in the refractive index of the transparent material sealed inside the air...
・・・・・・・・・・・・n=1. oθ Fluorine-based inert liquid (Fluorinert, manufactured by Sumitomo 3-M)...n+1.276 Water...................................................................................
. . . The difference in brightness distribution on the light exit surface was actually measured based on the n signature of 1.333. In the figure, the vertical axis is the luminance (n't), and the Ja axis is the light source (BW
This is the distance from the thermal electrode tube (diameter: 17.5 mm).

As can be seen from Figure 6, even in the actually prototyped light guide, the refractive index range (1
, 25≦n≦1.4).

It has been confirmed that substantially good uniformity of light emission can be achieved by using a Fu, So-based inert liquid.

In addition, the present inventors further carried out prototype experiments as described above.

Continuing the analysis, we found that the low refraction region (n = 1.2 or less)
In the high refractive region (nmi 1.4 or higher), no matter how much you change the shape (thickness, etc.) of the wedge-shaped light guide, it is impossible to eliminate the large bias in the brightness distribution, making it difficult to use it as a single-planar light source. It turned out that there was a problem with the throat.

That is, in the present invention, the internal refractive index n is 1.25.
It has been concluded that a patterned light guide in the range of ≦n≦1,4 is effective as a light diffuser for a so-called edge-light incident type planar light source.

FIG. 1 is a schematic perspective view showing an embodiment of a light guide of a light diffuser according to the present invention, which was manufactured based on the above conclusion.

In the figure, the light guide 10 is entirely made of a thin gravel-like transparent body composed of planes P1 to P6. plane P
1 and P2 are 2t planes which have the maximum surface precision and one force is closer to each other than the other, and one of these planes becomes a light emitting surface and the other becomes a reflecting surface. ft1iP3,
P4 is a substantially triangular plane that is substantially parallel to each other and corresponds to both a-planes of the two planes Pi and P2, and serves as a side surface of the light diffuser. Plane P5 is a rectangular plane corresponding to one end surface of 2ftl'1iP1, P2, and light from the fluorescent lamp is introduced into the vicinity of this plane P5.
It is a plane with a small area that faces the plane 5.

Inside the light guide shown in Figure 1, the refractive index n is 1.25≦n≦
! , 4, and media with such refractive indexes include water (n=1.333), diethyl ether (n=1.3538), and potassium iodide aqueous solution (saturation point Since n=1.456, dilute it with water appropriately).

The light incident from the plane P5 is guided by the light reflection layer formed on the plane PI while being reflected inside the light guide lO as shown in 41fl(c), and the light is reflected even in parts far away from the plane P5. will be sufficiently diffused. In this case, the wedge shape can have various shapes, but the angle of the model can be determined by determining the length 11 of planes P1 and P2, the height 2 of plane P5, and the height 13 of plane P6. In the case of this embodiment, since the shape is wedge-shaped, the angle of the pattern is approximately determined by the ratio of 11/intersection 2. The ratio between l and 12 is determined by the intensity of the light source used, the reflectance of the light reflection layer formed on the f-plane PI, the incident angle conditions of the light source such as a fluorescent lamp, and the design of the device in which the diffuser is used. It is determined by the constraints of L, etc., but in the normal case, the ratio r = Imperial l/Bun2.

It has been confirmed through experiments that r is preferably in the range of 10 to 30.

Fig. 2(a) is a perspective view of the light guide lO shown in Fig. 1 with a light diffuser installed in 4R, and Fig. 2(b) is a perspective view of the light guide lO shown in Fig. 1.
FIG.

In the figure, 11 is a diffusion plate, 12 is a fluorescent lamp provided close to the plane P5, and 13 is a reflector 1 of the fluorescent lamp.
14 is the lower surface of the light guide lO (plane PI in the ftS1 diagram)
) is a light-reflecting layer formed on. The light guide IO has a light guide case 20 made of acrylic resin having a shape as shown in FIG. 1, and a medium 21 (water!'g) having a refractive index n of 1.25 to 1.4 is sealed therein. The light-reflecting layer 14 is formed, for example, by vacuum-depositing or plating a metal such as aluminum grass on the plane PL. Further, the light reflective layer 14 may be formed by pasting a metal vapor-deposited tape having light reflective properties on the plane PI, and the thickness of the light reflective layer 14 is not particularly limited as long as it has sufficient light reflective ability. There isn't.

A commercially available fluorescent lamp 12 is sufficient, and its straightness 110 is 1/2.12 with respect to the height fL2 of the plane P5.
It is desirable to set the value to about <D<3/2.vertical 2 in order to equalize the brightness of the diffused light of the diffuser and in terms of device design.

The diffuser plate 11 may be of any material as long as it diffuses light with little loss of light quantity, and a ground glass plate, a milky white glass plate, a milky white resin, or the like can be used. In addition, in FIG. 2, for the sake of explanation, a case is shown in which the light guide lO and the diffuser plate 11 are configured to be separated from each other, but if they are optically separated, the light guide lO The diffuser plate 11 may be in direct contact with one surface thereof.

FIG. 3 is a perspective view showing another embodiment of the light guide according to the light diffuser of the present invention. In this embodiment, the two wedge-shaped light guides 10 shown in FIG.
30.3 in FIG.
Light from the linear light source is made to enter from both sides indicated by 1.

In this embodiment, the horizontal length L in the figure can be increased, and it can be used as a surface light source with a relatively large area. In this case, if one area is the same, compared to a wedge-shaped light guide, light is incident from both sides, and the brightness of the light is higher.

Additionally, once the mold is made, alignment, etc. is done inside the cylinder, compared to arranging wedge-shaped light guides in two rows as shown in Figure fJS1, which reduces costs in manufacturing large-area surface light sources. There are advantages.

[Effect of ffi ljj] As described below, according to the light diffuser of the present invention, in a light diffuser configured to allow light from a linear light source such as a fluorescent lamp to enter from one end surface, the conventional configuration is It becomes possible to provide a surface light source with uniform light brightness near and far from the incident surface. Further, the uniformity can be further improved by using a diffuser plate in combination with the diffuser according to the present invention.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of a light guide of a light diffuser according to the present invention. FIGS. 2(a) and 2(b) are perspective views each showing an example of the configuration of a light diffuser according to the present invention. , is a cross-sectional view. FIG. 3 is a perspective view showing another embodiment of the light guide of the light diffuser. FIGS. 4(a), 4(b), and 4(c) are diagrams for explaining the basic concept of the light diffuser 11, respectively. Figures 5(a) to 5(h) are diagrams showing the results of luminance distribution analysis when the refractive index inside the light guide was changed from 1.00 to 2.42, respectively, and the luminance at a distance from the light source. FIG. FIG. 6 is a diagram showing an example of the results of an experiment in which changes in brightness due to changes in the refractive index of the medium of the light guide according to the present invention were determined. 1O2-shaped light guide 11: Diffusion plate 12: Fluorescent lamp (linear light source) 13: Reflector 14: Light reflecting layer 20: Light guide case 21: Light guide case 30.31: Light incidence surface 40: Arch-shaped light guide agent Patent attorney Sekihira Yamashita Figure 1 Figure 10 (b) (c) Figure 6 tgl is ferlilifl (cm) ``T'&;d?111i1-g-'; (self ff1) September 22, 1988 [■ 4￥ Fraud Office Commissioner Kunio Ogawa 1, 1 Display of listings Patent Application No. 1982-39247 2, Name of invention Light diffuser 3, Person making amendments, 11 cases Relationship with Patent Applicant Address Tokyo TFJ O〆Kyobashi 2-chome [No. 13-19 Name]
(603) Mitsubishi Rayon Co., Ltd. 4, Agent Address: 1113 Toranomon 5-chome & 1 Toranomon 40, Minato-ku, Tokyo
Mori Building Name (6538) Patent Attorney Johei Yamashita-'-7+;・j

Claims (4)

[Claims] (1) A light diffuser equipped with a light guide made of an optically transparent medium, wherein the light guide has two planes P1 having at least a maximum area and one closer to each other than the other; P2 and the two planes P
1. It has a shape composed of two substantially triangular planes P3 and P4 that are substantially parallel to each other and correspond to both side surfaces of P2, and a rectangular plane P5 that corresponds to one end surface of the two planes P1 and P2. In addition, the plane P5 is a light incident surface, and either P1 or P2 is a reflective surface, and the refractive index n of the medium satisfies 1.25≦n≦1.4. Features a light diffuser. (2) The light according to claim 1, wherein the light guide further has a plane P6 having a small area opposite to the plane P5, and the entire plane has a thin wedge shape. Diffuser. (3) Claims characterized in that the two wedge-shaped light guides are each integrated with each other on the plane P6, and the entire integrated light guide has a substantially arch-like shape. The light diffuser according to item 1. (4) The light diffuser according to claim 1, characterized in that a light diffuser plate is also used.