JPH03189679A - Surface light source device - Google Patents

Abstract

PURPOSE:To obtain equal surface brightness by a comparatively thin light guiding layer by providing an embossing pattern discontinuously having one or more slopes to each mesh respectively on the one side of the transparent light guiding layer. CONSTITUTION:The surface light source device is provided with the embossing pattern discontinuously having one or more slopes to each mesh with 0.1-1mm pitch formed on at least one side of the transparent light guiding layer 2 in order to enhance the efficiency of the reflection and diffusion of light and improve the surface brightness. Thus, light made incident on the layer 2 from a light incident surface advances in the layer 2 while it is repetitively reflected on the slope of each mesh or totally reflected and efficiently scattered. As a result, the surface light source with high accuracy is obtained by the comparatively thin light guiding layer. By forming a pattern that the projecting area of the mesh is gradually expanded with a distance from the light source, the distribution of brightness is adjusted and the uniform surface light source without irregularities is obtained.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a planar light source device used for illumination, etc., particularly for uniformly illuminating a relatively wide area by receiving light from a point light source or a linear light source. A lighting device used as a planar light source for lighting, for example, a planar light source device used as a display lighting panel for advertisements or as backside illumination of a transmissive liquid crystal display device. The present invention relates to a planar light source device with a small amount of light.

[Conventional technology]

Conventionally, when fluorescent lamps are used for indoor lighting, advertising billboards outdoors at night, etc., a linear light source is created by placing several fluorescent lamps in parallel and placing a light-diffusing plate-like object such as a breast plate on top of the fluorescent lamps. It is common practice to convert the light emitted from a fluorescent lamp into a pseudo surface light source, but in this conventional method, the light source flux that is uniform all around the fluorescent lamp is forcibly converted into a flat light source at a certain position. As a result, the brightness distribution on the flat area where the light diffusion plate is placed sometimes becomes unsightly and uneven, which visually becomes the outline of the fluorescent lamp, which is one reason why it spoils the aesthetic appearance of the lighting device. Therefore, the light diffusion plate and the fluorescent lamp must be placed at a considerable distance, which poses a problem from the viewpoint of space saving.

Furthermore, recently there has been an increasing demand for relatively small planar light sources with uniform brightness distribution for use in back lighting of liquid crystal televisions, portable personal computers, and liquid crystal displays.

To deal with this, there are currently EL (electroluminescence) and direct type backlights in which a fluorescent lamp is placed directly below and the brightness distribution is adjusted using a light-shielding filter, etc., but they are not durable and are used as diffused lighting. Since it is not possible to obtain a transparent light that fully satisfies the above, there have been proposals to use two transparent light guide plates to guide light from their side edges, thereby providing diffused illumination of the surface. This has already been done and put into practical use in some areas.

[Problem to be solved by the invention]

However, when using a single transparent light guide plate in the past, it has a low light diffusivity and low brightness. It is necessary to efficiently scatter light and increase brightness by printing a pattern, and these improvement methods have their limits and are not satisfactory considering the complicated processing required for a planar light source device. In order to achieve surface brightness, it is necessary to increase the thickness of the transparent light guide layer considerably, which is a problem because it cannot meet the demand for smaller and lighter devices.

The present invention aims to solve these conventional problems, and it is possible to obtain a luminance equal to or higher than that of the conventional one in an extremely thin transparent light guiding layer.1. It is an object of the present invention to provide a planar light source device that can be made smaller, lighter, and has a simpler structure, easier manufacture, and lower cost.

[Means to solve the problem]

In the present invention, a light-diffusing layer, a transparent light-guiding layer, and a reflective layer are sequentially laminated from the viewing direction, and each of the transparent light-guiding layers has a grid pattern of 0.1 to 1.0 am on at least one side. The transparent light guiding layer has an embossed pattern having one or more discontinuous slopes, and a light source and a reflective layer for the light source are installed on at least one edge of the transparent light guide layer, and if necessary, the grid is This is a planar light source device characterized by an embossed pattern whose projected area gradually increases with distance from the light source.

[For production]

In the planar light source device of the present invention, the reflection and diffusion efficiency of light is increased,
In order to improve surface brightness, an embossed pattern having one or more discontinuous slopes is provided on at least one side of the transparent light guide layer in a pinch 0.1 to 1 fl lattice. The light incident on the transparent light guide layer reaches the slopes or sides of each grid, and has a refractive index lower than that of the transparent light guide layer that exists between the transparent light guide layer and the reflective layer or light diffusion layer. Due to the small amount of air and the adhesive layer, depending on the angle of incidence, it repeats transmission or total reflection while efficiently scattering within the transparent light guide layer, resulting in a relatively thin light guide layer with a high brightness surface. A light source can be obtained, and by applying a pattern in which the projected area of the lattice is gradually expanded with respect to the distance from the light source, the brightness distribution within the effective light emitting surface can be adjusted, resulting in a uniform and even unevenness. A planar light source is obtained.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1 and 2. A light diffusing layer 1 is provided over the tubular light source 4.
A transparent light-guiding layer 2 and a reflective layer 3 are sequentially laminated under the layer.

The light diffusing layer 1 is generally made of acrylic resin or acrylic resin because it further uniformly diffuses the light emitted from the transparent light guiding layer 2 over the entire surface and requires a white surface light source for illuminating the back side of a liquid crystal display or the like. A milky white sheet or plate made of polycarbonate resin containing an appropriate light diffusing agent is used.

In this case, depending on the type and amount of light diffusing agent contained,
It is desirable to select a material suitable for the required characteristics of the device, since the diffusion effect may be reduced and the transmittance may be low, resulting in a reduction in surface brightness.

Furthermore, as the transparent light guiding layer 2, for example, 260×17
0x4m (thickness) or 5 dragon acrylic resin plate (Acrylite (product name), Mitsubishi Rayon side type) with a second layer on both sides.
An embossed pattern 21 having a concave square pyramid pattern with a pitch of 0.51 m and a slope angle of 45° as shown in FIG. A was formed on the entire surface.

In this case, if the pattern pinch was 0.11 m or less, the pattern groove depth became small, reflection and diffusion efficiency decreased, and as shown in Table 1, sufficient brightness could not be obtained.

In addition, when the pitch is 1 dragon or more, the number of slopes decreases, and as shown in Table 1, the brightness decreases as well, and because the pitch is rough, the pattern is transmitted through the light control layer and the light diffusion layer, resulting in a poor appearance. Since there is a problem that unevenness occurs, the pitch is 0.1 to 1.01, preferably 0.4.
A range of ~0.61 is good.

Regarding the slope angle, as shown in Table 1, reflection and diffusion efficiency is low at 18° or 85°, and sufficient brightness cannot be obtained.
0'' is appropriate.

In the margin below, transparent light guide N2 is made of glass, epoxy resin,
Thermosetting resins such as silicone resins, thermoplastic resins such as acrylic resins, polycarbonate resins, polyolefin resins such as polypropylene polyethylene, etc. are acceptable, but from the viewpoint of transmittance, processability, and heat resistance, acrylic resins, polycarbonate resins, or silicone are suitable. Rubber or a polymer alloy thereof is preferable.

Furthermore, the embossed pattern can be applied to the transparent light guide layer 2 by any method, for example, by direct machining, or in the case of thermoplastic resin, the embossed pattern can be applied to the transparent light guide layer 2 in advance by forming a roll or another member such as a plate of steel. It can also be easily obtained by transferring the provided pattern by hot pressing, or by injection molding or casting using a mold having the pattern.

Furthermore, the reflective layer 3 may be, for example, an aluminum vapor-deposited sheet or a synthetic resin plate such as PET acrylic or ABS containing a diffusing agent, but "tetraite", which is made by vapor-depositing silver on a PET substrate and then top-coating it, may be used. (Product name,
A sheet manufactured by Tokyo Oike Sangyo ■ was used.

4 in the figure is a light source, which has a tube diameter of φ61m and an effective light emission length of 260m.
Two 3-wavelength cold cathode tubes (manufactured by Stanley Electric) having a tube current of 5a+A and a tube brightness of 7000 nits were installed so as to face each other in the long side direction. 5 is a reflective layer for the light source, which is provided to reduce the loss of light emitted from the light source 4 (and to provide directionality so that the light is efficiently guided to the incident end face of the transparent light guiding layer 2). , the same member as the reflective layer 3 was used.

Each layer is laminated and the outer periphery of the illumination surface is used as an adhesive margin using double-sided adhesive tape, adhesive, melting, molding, or other fixing means such as fitting into a frame, and the light source 4 is used to reduce light loss. It is preferable to attach a reflective sheet (not shown) similar to the reflective layer 3 to the edge portion where the reflective layer 3 is not installed, and in any case, it is preferable to use a configuration in which each part is fixed together or assembled together.

In the planar light source device according to this embodiment, the power supply voltage is 12
When the light source was turned on via an inverter at V, as shown in Table 1, a surface brightness of 650 nits was obtained at 5 mm thickness, and 600 nits even at 4 mm thickness.

In addition, as Comparative Example 1, when the transparent light guide layer 2 was replaced with a 4-fi thick acrylic flat plate (no treatment), the brightness was 150 nits.
As Comparative Example 2, the pitch was 0.5 m and the slope angle was 4.
When a 5n thick acrylic plate with a 5° hairline pattern on both sides is used as a transparent light guiding layer, the brightness is 400 nits.
Therefore, by using the lattice and quadrangular pyramid embossed pattern of the present invention, the diffusion efficiency is higher than the conventional hairline pattern, the surface brightness is increased, and a thinner light guiding layer can achieve higher brightness than the conventional one. I was able to do that.

In addition, as shown in Comparative Examples 3, 4, and 5.6, a pinch of 0.05°21cm was applied to an acrylic plate with a thickness of 41cm at a slope angle of 45''.
In this case, the slope angle is 18° with a pinch of 0.5.
, the brightness when set at 85° is 470 and 40, respectively.
The light diffusion efficiency was low at 0,420,440 nits, and a sufficient reflection and diffusion effect by the quadrangular pyramidal embossed pattern could not be obtained.

Note that the embossed pattern 21 may be a convex quadrangular pyramid pattern as shown in FIG. A chevron or valley pattern with
Is it an embossed pattern in which the combination of slopes is discontinuously formed so that it does not form a hairline shape, including the vertical plane?
12 can be optionally used, and not only on both sides, but also on one side, either the front side or the back side.

In this case, it is considered that the slope angle α of the slope is selected in the range of 20 to 80'', and that the lattice is not limited to square, but is formed by a combination of slopes in polygonal lattice including triangles.

The specific examples shown in FIGS. 4 to 6 are other examples of the embossed pattern formed on the transparent light guiding layer 2. In the example shown in FIG. 4, the slope angles in four directions are changed. The top of the quadrangular pyramid may be a convex shape that protrudes, or concavely concave, or a mixture of these may be partially juxtaposed, but preferably it is a concave shape. Good.

In the example shown in Fig. 5, the pitch is changed sequentially, and in the example shown in Fig. 6, each grid is arranged in a staggered manner, and the shape arrangement of the square pyramids is varied in various ways. It is also possible to arrange triangular pyramids in each lattice as shown in the example, or to use an embossed pattern 2 with one or two slopes in each lattice as shown in the examples in Figures 8 and 9. be considered.

The transparent light guide layer 2 has an embossed surface on the back side facing the reflective layer 3, and fills an adhesive between the transparent light guide layer 2 and the reflective layer 113. An air layer may be provided in between (and it is also possible to provide a transparent light guide layer 2 in which embossed patterns with different pitches are formed on both the front and back surfaces).

Furthermore, as a result of various studies regarding the embossed pattern 2 of the transparent light guiding layer 2, the arrangement was made such that the projected area of each embossed pattern gradually increases with respect to the distance from the light source, as shown in FIG. By doing so, a planar light source device having a uniform luminance distribution without unevenness within the effective light emitting area was obtained.

The size and area of each emboss is at most 0.1
Although it does not exceed that of a grid with a specified pitch in the range of ~1.0 fl, it is desirable that it be as large as possible in order to obtain high brightness, and there are no restrictions on the small power value.

The rate of change in the area of the emboss between the maximum and minimum values can be set arbitrarily, but the illuminance at a certain point is inversely proportional to the square of the distance between that point and the light source, and the intensity of light is attenuated in a transparent medium. As a result of various tests, when the embossed shape is square as shown in Figure 10, -side length Y
For the distance X from the light source, Y = a + b l nxf
tl (where a.

b is a value determined by the light diffusion layer 1 reflection layer, light source, reflection layer for light source, and the maximum and minimum areas of the pinch and embossment. )'' Since a good brightness distribution can be obtained by arranging the embossing in sequence, it is desirable to arrange the pattern roughly in accordance with the open pattern.

In Example 3, the transparent light guide layer 2 is 260×17
On one side of a 0 x 5 mm (thickness) acrylic resin plate [Acrylite (trade name), manufactured by Mitsubishi Rayon ■], a concave square pyramid as shown in Fig. 10 was placed symmetrically with 0.5 Tsuru Pifti,
Emboss E with a slope angle of 45° and the longest vertical distance from the light sources at both ends in terms of the length of the − side. O, '380 am is the maximum value, and that of the embossed E1 closest to the light source is 0.21
0■l, that of each embossment of E7-1 to Et between them, and Y = 0.184 + 0.1441, the embossed pattern 21 provided almost in accordance with the lX formula was used. 11 reflective layer 3 light source 4. All the light source reflective layers 5 are the same as those described above, and T! i
When two light sources were turned on via an inverter with a source voltage of 12V, as shown in Table 2, an extremely uniform surface light source with no unevenness in luminance distribution within the effective light emitting surface was produced at 700 nm.
It was obtained at a height of 1 degree.

Margin Table 2 below Also, as Comparative Example 7, a similar acrylic board was pinched 0.
Comparing the brightness and brightness distribution of Comparative Example 7 with a concave quadrangular pyramid pattern with a diameter of 5 mm and a slope angle of 45@ uniformly formed over the entire surface, the brightness and unevenness of Comparative Example 7 was as large as 35%, and the brightness was also 600 nits.
On the other hand, in Example 3, in which the embossed pattern was patterned with a difference in projected area, the light path traveling inside the transparent light guiding layer was controlled by the pattern, and a large amount of light near the light source was transmitted through the inside of the light guiding layer. As a result, the brightness distribution is corrected over the entire light emitting surface, making it even and uniform, reducing light loss near the light source, and achieving high brightness. Ta.

Y=a+blnX (max +++in) Light source unevenness=X100 (%) Furthermore, as Example 4, a=0.0 in the il1 formula
08°b -0,044, and one side of the maximum emboss is 0
．． Although the brightness and brightness distribution in the case of 200 Dragon (X-80) are uniform in distribution, the total projected area of the embossing on the entire light emitting surface becomes smaller, so the amount of light emitted from the light emitting surface decreases. The brightness is not necessarily high at 450 nits.

Therefore, in order to obtain high brightness, it is desirable to increase the area of each emboss, but on the other hand, by appropriately setting this area, it is possible to obtain brightness according to the purpose.

Furthermore, the embossed pattern is not limited to the square pyramid pattern shown in FIG. 10, but can also be a polygonal pyramid pattern as shown in FIG. You can.

In addition, the projected area of each emboss does not necessarily have to change all sequentially, but can be changed partially in blocks of several blocks within a range that does not affect the brightness distribution, as shown in Figure 13. It may be something that you continue to do.

In this case, the slope angle α of the embossing may be selected from a range of 20 to 80 @.Furthermore, in some cases where only one of the light sources is used, a pattern arrangement as shown in FIG. 11 may be used.

Furthermore, the pattern is not limited to the entire surface of the light emitting surface, but may be partially patterned only in the portion necessary as a light source.

In the example in Figure 14, the slope angle of the embossing is changed every other
In addition, the depth is arranged so that all the embossments are constant, the example in Fig. 15 has an slope angle that increases as it gets closer to the light source, the example in Fig. 16 has a mixture of convex embossments, and the example in Fig. 17. The example shown in Figure 18 is an arrangement of embossments arranged in a grid, the example shown in Figure 18 is an arrangement of polygonal pyramids other than square pyramids, and the example of triangular pyramids, the example shown in Figure 19 is an example in which the pinch of the embossing is changed sequentially, and the example shown in Figure 20 is an example in which the embossments are arranged in a grid pattern. It is a mixture of various polygonal pyramids, and consideration is given to using these examples in whole or in part.

〔Effect of the invention〕

In the present invention, the transparent light guide layer has a pitch of 0.
By providing an embossed pattern having at least one or more discontinuous slopes on each grid of 1 to 1.0 cranes, the light incident on the transparent light guide plate from the light incident surface is transmitted through the slopes of each quadrangular pyramid. Or, due to the air layer or adhesive layer with a lower refractive index than the light guide plate that exists between the light guide plate and the reflector or light diffusing plate on the sides, the light guide plate repeats transmission or total reflection depending on the incident angle. Since the light guide layer can travel while scattering efficiently, it is possible to obtain the same surface brightness with a relatively thinner light guiding layer than before, and furthermore, the projected area of these embossed patterns can be gradually adjusted with respect to the distance from the light source. By enlarging it, it is possible to make the luminance distribution within the effective light emitting surface uniform without using a separate member for dimming, and as a result, while having the function of a planar light source,
It is possible to make the entire device thinner and lighter.

[Brief explanation of drawings]

FIG. 1A shows a planar light source device according to an embodiment of the present invention.
Figure 1B is a longitudinal cross-sectional view, Figure 2A-B is a perspective view explaining assembly.
are an enlarged plan view and a cross-sectional view of a transparent light guide plate, FIG. 3A-B
8A is an enlarged plan view and a sectional view of another example of a transparent light guide plate, FIGS. 4 to 7 are enlarged plan views of another example of a transparent light guide plate, and FIG. Enlarged plan view of example, No. 8
Figure B is a longitudinal sectional view taken along line I-1 of Figure 8A, Figure 9A
is an enlarged plan view showing two slopes in the grid, and FIG. 9B is a longitudinal sectional view taken along the line ff-ff of FIG. 9A. Figure 10 is an overall view of the embossed projected area change pattern when two light sources are used, Figure 11A is an enlarged plan view of the same pattern when one light source is used, and Figure 11B is a vertical cross-sectional view of Figure 11A. ,
FIG. 120A is an enlarged plan view of another example of the same pattern,
Figure B is a longitudinal cross-sectional view of Figure 12A, Figure 13A is an enlarged plan view when changes in the embossed projected area are partially blocked, Figure 13B is a longitudinal cross-sectional view of Figure 13A, 14-16
FIGS. 17A and 20B are a plan view and a vertical sectional view of a part of another example, and FIGS. 17 to 20 are a plan view of a part of another example of the transparent light guide plate. DESCRIPTION OF SYMBOLS 1... Light diffusing layer, 2... Transparent light guide layer, 3... Reflective layer, 4... Light source, 5... Reflective layer for light source.

Claims (3)

[Claims] (1) A light-diffusing layer, a transparent light-guiding layer, and a reflective layer are sequentially laminated from the viewing direction, and at least one of the grids with a pitch of 0.1 to 1.0 mm is formed on at least one side of the transparent light-guiding layer. A planar light source device comprising an embossed pattern having one or more discontinuous slopes, and a light source and a light source reflective layer disposed at the edge of a transparent light guiding layer. (2) A light diffusing layer, a transparent light guide layer, and a reflective layer are sequentially laminated from the viewing direction, and a light source and a reflective layer for the light source are installed on at least one edge of the transparent light guide layer, and the transparent light guide A planar light source device characterized in that at least one side of the layer is provided with an embossed pattern in which convex or concave square pyramids with a slope angle of 20 to 80 degrees are formed in each grid with a pitch of 0.1 to 1.0 mm. . (3) The planar light source device according to claim 1 or 2, wherein the embossed pattern gradually increases the projected area of each grid pattern as the vertical distance from the light source increases.