JPH03201304A - Luminaire - Google Patents

Abstract

PURPOSE:To enhance the total light emission efficiency of a luminaire by forming the irregular reflection surface of a transparent plate from fine lines of milky white type. CONSTITUTION:An irregular reflection surface 3 is formed on one face of a transparent plate 1 and in this case white fine lines of fixed width are printed thereon by screen printing. The transparent plate 1 is set in a luminaire while being sandwiched between a diffusion plate 4 and a reflection plate 5 and light introduced therein from an end face 20 is allowed to advance white being repeatedly reflected and scattered between the irregular reflection surface 3 and a total reflection surface 6; i.e. because the irregular reflection surface 3 is comprised of a total reflecting portion 10 and an irregular reflecting portion 11 formed of fine lines of milky white type, light is spread over not only near the end face from which the light is introduced but also the whole area of the transparent plate 1 and is allowed to go out of the diffusion plate 4 so that the luminance distribution of illumination light is flat when seen from the side of the diffusion plate 4. Thereby the total light emission efficiency of the luminaire is enhanced and also the luminance distribution of the luminaire is made flat.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention mainly relates to a thin back illumination device for a liquid crystal display incorporated in computers, word processors, and liquid crystal televisions.

[Prior Art] Conventionally, as described in Japanese Patent Laid-Open No. 63-62105, a system has been known in which a diffused reflection surface is formed by milky-white halftone dots on a transparent plate.

[Problems to be Solved by the Invention] However, when such a conventional lighting device is set behind a liquid crystal display and turned on, the luminous efficiency is low, and it is necessary to stack multiple transparent plates in order to increase the luminance of surface emission. As a result, the illumination device becomes thick, and it is difficult to obtain a flat in-plane brightness distribution, which causes unevenness to appear on the liquid crystal screen.

The present invention is intended to solve these conventional problems, and its purpose is to provide a thin lighting device that uses only one thin transparent plate to provide high luminous efficiency and a flat luminance distribution. There is a particular thing.

[Means for Solving the Problems] In order to solve the above problems, the lighting device of the present invention includes (1) a surface in which a light source is arranged adjacent to the light introduction end surface of a transparent plate having a diffused reflection surface on at least one surface! ] A light device, characterized in that the diffused reflection surface of the transparent plate is formed of milky white thin lines.

(2) The thin milky wires are arranged parallel to the light introduction end surface, and the width of each thin wire is increased or decreased depending on the distance from the light source.

(3) The milky-white thin wires are arranged parallel to the light introduction end surface, and the line pitch is increased or decreased according to the distance from the light source while keeping the line width of each thin wire constant. .

[Function 1] In the illumination device described above, the light incident from the light-introducing end face of the transparent plate travels through the transparent plate while being almost totally reflected, and hits the milky-white thin line. The light is diffusely reflected there and exits from the transparent plate. Therefore, the intensity of the emitted light and its distribution change depending on the pattern and arrangement of the thin lines, and the design of the diffused reflection section has a great effect on the illumination quality.

This will be explained in detail while comparing with the conventional technology.

- A backlighting device for a liquid crystal display inside the shell is required to be bright and have uniform brightness. In a so-called edge-light illumination device in which light is incident on the end face of a transparent plate and the light is guided inside the transparent plate to constitute a planar illumination device like the illumination device of the present invention, a diffused reflection surface provided on the transparent plate is used. By increasing the amount of diffused reflection, the total amount of light emitted can be increased, that is, brighter illumination can be obtained. However, if the amount of diffused reflection is increased too much, the brightness will rapidly decrease as the distance from the light source increases, resulting in large brightness unevenness within the light output surface used for illumination.

As a countermeasure against this, the diffused reflection surface should be composed of a diffused reflection part and a total reflection part, and the diffused reflection part and the total reflection part should be delicately arranged so that each part has uniform brightness and at the same time has high overall light output efficiency and bright illumination. .

In the prior art described above, this is realized by forming milky-white halftone dots on a transparent plate, but with this method, it is difficult to increase the area ratio of the diffused reflection part to the total reflection part (hereinafter referred to as area ratio). Light output efficiency tends to be low.

Furthermore, if a manufacturing error occurs with respect to the intended design dimensions of the halftone dots, the above-mentioned area ratio will change by the square of this error, resulting in a lighting device with particularly large variations in brightness unevenness, which is a major drawback.

On the other hand, in the lighting device having the configuration of the present invention, the above-mentioned area ratio can be set in any way by changing only the width of the milky white thin line, so the overall light output efficiency can be increased.
Even if a manufacturing error occurs with respect to the intended design dimensions, the change in the area ratio can be suppressed to an amount proportional to the error, making it possible to realize a lighting device with little variation in brightness.

In recent years, simulation technology such as computer-based ray tracing has been developed, and it has become possible to design optimal optical systems with high precision.The lighting device having the configuration of the present invention is also suitable from the viewpoint of manufacturing the optical system with high precision. be.

[Example 1 An example of the present invention will be described below based on the drawings.
The light source 2 may be arranged in a straight line, etc. The light source 2 is placed adjacent to the end surface 20 of the transparent plate l, and the light beam from the light source 2 is transmitted through the transparent plate l.
guided by. In this case, the transparent plate l is 1.0-5', Om
Although a PMMA resin plate with a uniform thickness of m is used, materials such as polycarbonate, polystyrene, glass, etc. can also be used. A diffused reflection surface 3 is formed on one side of the transparent plate,
In this case, a thin white line with a constant width was printed by silk screen printing. In addition, methods other than printing, such as transparent plate
Methods such as masking and painting white or pasting white tape with adhesive may also be used. The transparent plate 1 is set between a diffuser plate 4 and a reflector plate 5, and the light introduced from the end face 20 travels between the diffuse reflection surface 3 and the total reflection surface 6 while repeating reflection and scattering. As mentioned above, the diffused reflection surface 3 includes the total reflection part IO and the diffused reflection part 1 made of milky white pure cotton.
1, the light spreads not only near the introduction end face but also throughout the entire transparent plate l and exits to the diffuser plate 4 side, so that the luminance distribution of the illumination light seen from the diffuser plate 4 side becomes flat. Ta. Note that arrow A indicates the direction in which light comes out.

As shown in Fig. 10, the luminance distribution can be improved to some extent by the method described in JP-A No. 63-62105, in which the diffused reflection surface is formed with milky white halftone dots, but this method does not improve the overall light output efficiency. In order to achieve this, it is necessary to use a plurality of transparent plates 1 one on top of the other, and the entire lighting device ends up being thick.In contrast, in one embodiment of the lighting device according to the present invention shown in FIG. It is possible to increase the area ratio of the diffuse reflection section 11 to the total reflection section 1O, and the transparent plate 1 is made of only one piece, making it possible to construct a lighting device that is very bright and has a good luminance distribution by being significantly thinner. I was able to do that.

Figure 2 is a graph showing the luminance distribution when the lighting device in Figure 1 is turned on, and the luminance on the top surface of the diffuser m4 in Figure 1 was measured by sweeping the luminance meter at a constant speed from B to C. be. To further supplement the embodiment shown in Fig. 1, the diffusion plate 4
In order to remove narrow-area brightness unevenness and obtain visually uniform illumination, it is necessary to keep the printed line width of thin lines within a certain range. The line width was set to about 0.1 to 0.5 mm for 1.0 mm. Further, when the pitch was 0.5 mm, the line width was set to about 0.05 to 0.25 mm. This is because it is difficult to completely eliminate narrow-area brightness unevenness when the area ratio is less than 10%, and furthermore, if the diffused reflection surface 3 is manufactured under the condition that the line pitch and line width are fixed to certain values, the area This is because when the ratio exceeds 50%, the brightness at the center of the diffuser plate decreases significantly, and brightness unevenness worsens.

The thickness of the printing ink is 17,100 to 77,100 mm, preferably 2/100 to 5/100 mm. The printing ink used was a mixture of acrylic or urethane resin or ultraviolet curing resin with titanium oxide powder, etc., but the printing thickness was 1/100 m.
If it is less than 100 mm, the amount of light that passes through it will increase and the diffused reflection effect will be small. If it exceeds 77100 mm, the adhesion of the print will decrease and it will easily peel off or chip, and at the same time it will be difficult to obtain dimensional accuracy.

FIG. 3 is an explanatory diagram of the pattern of the diffused reflection surface 3 provided on the transparent plate 1 used in FIG. 1. The line width and pitch of the diffuse reflection section 11 and the total reflection section 10 are arranged so that absolute brightness is high and brightness unevenness is reduced. In reality, when the external dimensions and thickness of the transparent plate 1 change, the optimum values for pitch and line width also change, so the dimensions of the transparent plate 1! Fine adjustment is required depending on the acceptable quality of Ia light.

It has been found that when the illumination device using the linear pattern shown in FIG. 3 is used as a backlight for a liquid crystal display, the displayed characters can be visually read easily.

Figures 4 and 5 are pattern diagrams of the diffused reflection surface of an embodiment in which milky-white thin lines are composed of curved lines or curved straight lines, respectively, and are suitable for illumination of displays for displaying images such as figures and pictures. .

FIG. 6 is an explanatory diagram showing an embodiment of the present invention in which the line width of each thin line is increased or decreased according to the distance from the light source, and the diffuser plate is removed for the sake of explanation. Diffuse reflection part 1
By configuring 1 with a thin line near the end face 20 and a wide line at the center of the transparent plate 1, it was possible to obtain a brightness distribution that was even flatter than that of Embodiment 6 in FIG. In this embodiment as well, a PMMA resin plate having a uniform thickness of 1 to 5 mm was used as the transparent plate 1. In this case, the pitch of the thin lines is also constant, for example, 1 mm pitch, and the line width is 0.2 mm near the end surface 20.
mm, and the central part of the transparent plate was set to about 0.85 mm. If the pitch is set to 0.5 mm, the line width will be approximately 0.1 mm near the end face 20, and 0.4 to 0.45 at the center of the transparent plate.
It may be set in mm.

As in the previous embodiment, in this case the pitch is 1. In the case of 0mm, good results were not obtained when the line width was less than 0.05 mm or more than 0.85 mm.

This shows that visual brightness unevenness is not determined simply by line width, but that the ratio of line width to pitch dimension is important, and in reality, this ratio is 5 to 85%, preferably 10 to 80%. % is preferred. Also, the pitch dimension is 0.5
The best results were obtained by setting the distance between about 1.5 mm and 1.5 mm.

Furthermore, although the line width is gradually increased from the thinnest line toward the center of the transparent plate, it is not possible to obtain a uniform luminance distribution by simply increasing or decreasing it at a constant rate. It is necessary to optimize the method of increase/decrease depending on the size and thickness of the transparent plate.

There are cases in which special liquid crystal displays require lighting with slightly higher brightness in the center than in the periphery, but this can be easily accommodated by changing the way the line width is increased or decreased.

Figure 7 is like Figure 6! ]A This is a graph showing the brightness distribution when the light device is turned on, and was measured by attaching a diffuser plate, which is omitted from the figure for the sake of explanation, and sweeping the brightness meter at a constant speed from D to E over the diffuser plate. It is. Compared to FIG. 2, results were obtained in which both the brightness distribution and the absolute brightness were improved.

FIG. 8 is an explanatory diagram showing an embodiment in which light sources are arranged on four end faces of a transparent plate. When using a liquid crystal display with a large light transmission loss, a lighting device as bright as possible is required, but in this example, four rod-shaped light sources 2 were used, so the two-pair type shown in Figure 1 was used. We were able to obtain more than twice as much brightness compared to the example shown above.

FIG. 9 is an explanatory diagram showing an embodiment of the present invention in which the line pitch is increased or decreased according to the distance from the light source while keeping the line width of each thin line constant. Since the pitch is coarse near the light source and the pitch is dense in the area far from the light source, a light brightness distribution of 6, which is equivalent to the result in the example shown in FIG. 6, can be obtained. - When forming a fine line pattern inside the shell by printing, the accuracy of the finished printed width tends to change depending on the width of the fine line due to the influence of the surface tension of the ink.
In this embodiment shown in the figure, since all thin lines of the same width are printed, printing errors are extremely unlikely to occur, and therefore, good results were obtained in that brightness variations were further reduced.

In this embodiment, a PMMA resin plate having a uniform thickness of 1 to 5 mm was used as the transparent plate 1. The line width of the diffuse reflection section 11 is 01 to 0.3 mm, preferably 0.2 to 0.25 m.
It is preferable to set the pitch between m, in which case the pitch is 1
．． A flat brightness was achieved by making it denser or coarser between 50mm and 0.25mm.

[Effects of the Invention 1] As detailed above, in the lighting device of the present invention, (1) the diffused reflection surface of the transparent plate is formed of milky white thin lines. Furthermore, (2) when the milky white thin wires are arranged parallel to the light introduction end surface, the line width of each thin wire is increased or decreased according to the distance from the light source.

(3) The milky white thin wires are arranged parallel to the light introduction end surface, and the pitch between the lines is increased or decreased according to the distance from the light source while keeping the line width of each thin wire constant.

The above configuration has the great effect of being able to provide a lighting device with high overall luminous efficiency and a flat luminance distribution that is thinner than conventional ones, and the variation in illumination quality is much smaller than before. This has the practical effect of being able to do the following.

Furthermore, if the illumination device of the present invention, which is composed of straight, milky-white thin lines, is used as back illumination when displaying characters, etc. on a liquid crystal display, it will have the effect that the displayed characters will be visually very easy to read. ing.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the lighting device of the present invention. FIG. 2 is a graph showing the luminance distribution when the lighting device shown in FIG. 1 is turned on. FIG. 3 is a detailed view of the diffused reflection surface provided on the transparent plate used in the embodiment of FIG. 1, and FIG. 4 is an explanatory diagram of the pattern of the diffused reflection surface, which is composed of milky-white thin lines formed by curved lines. FIG. 5 is an explanatory diagram of a pattern of a diffused reflection surface composed of straight lines formed by bending milky white thin lines. FIG. 6 is an explanatory diagram showing an embodiment of the present invention in which the width of the thin line is increased or decreased depending on the distance from the light source. Figure 7 is the 6th
A graph showing a luminance distribution when the lighting device shown in the figure is turned on. FIG. 8 is an explanatory diagram showing an embodiment of the present invention in which light sources are arranged on four end faces of a transparent plate, and FIG. 9 is an explanatory diagram showing an embodiment of the present invention in which light sources are arranged on the four end faces of a transparent plate, and FIG. FIG. 2 is an explanatory diagram showing an example of the present invention in which the amount is increased or decreased. FIG. 10 is a perspective view showing an example of a conventionally used opening device. Transparent plate Light source diffused reflection surface Diffusion plate Reflector Total reflection plate Total reflection of the diffused reflection surface Diffuse reflection of the diffused reflection surface

Claims (3)

[Claims] (1) In a surface lighting device in which a light source is arranged adjacent to the light introduction end surface of a transparent plate having a diffused reflection surface on at least one surface,
An illumination device characterized in that the diffused reflection surface of the transparent plate is formed of milky white thin lines. (2) The lighting device according to claim 1, wherein the milky white thin wires are arranged parallel to the light introducing end face, and the line width of each thin wire is increased or decreased depending on the distance from the light source. (3) The milky-white thin wires are arranged parallel to the light introduction end surface, and the line pitch is increased or decreased according to the distance from the light source while keeping the line width of each thin wire constant. The lighting device according to claim 1.