JPS61158367A - Lighting apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Higashijou 1 Field This invention relates to a lighting device used as a backlight for a passive display device such as a color liquid crystal display.

B0 Summary of the Invention This invention consists of a tubular light source, a linear Fresnel prism plate having a serrated cross section on the - side, and a plane mirror serving as a reflecting mirror, and the linear Fresnel prism and plane mirror are arranged in a V-shape. A tubular light source is arranged in a V-shaped opening, and the mirror image of the light source generated by the plane mirror increases the light utilization rate and increases brightness, and the plane mirror and the linear Fresnel prism plate are arranged closer to each other as they move away from the light source. By doing so, the brightness of the reflective surface is made almost uniform and unevenness in brightness is eliminated.

C. Passive type that modulates natural light or light emitted from other illumination sources and displays patterns by controlling the transmittance or reflectance of light without emitting light itself, like a ventral plate liquid crystal display device. (Non-emissive) display devices are widely used in portable electronic devices such as calculators and watches because of their low power consumption, but the problem is that the display becomes difficult to see in dark surroundings unless a lighting device is provided. was there. In particular, since the display mode of most liquid crystal display devices utilizes the optical anisotropy of liquid crystal, it is essential to stack polarizing plates, and this polarizing plate makes it difficult to control the illumination light. Approximately 50% of the amount will be cut.

In addition, in a liquid crystal display device using a color filter, the amount of light is further reduced due to colorization, and therefore, when used indoors in general, it is essential to attach a lighting means to the display device. However, when relying only on the illumination of the light source attached to the interior, when used in an environment such as outdoors in the daytime, it is necessary to increase the brightness of the display device so as not to lose the brightness of the surroundings. In this case, the power consumption of the light source becomes too large and the low power consumption characteristics of the liquid crystal display device are impaired. Therefore, in order to take advantage of the low power consumption characteristics, a light guide has been proposed that takes in ambient light to illuminate the liquid crystal display device from the back when the surroundings are bright, and illuminates the liquid crystal display device from an internal light source when the surroundings are dark.

Conventionally, backlights used as this type of internal illumination means use an incandescent miniature light bulb or a fluorescent lamp as a light source 1, and adjust the brightness of the illumination surface between the light source 1 and the display panel 2, as shown in FIG. By installing a diffuse transmitting plate 3 made of opalescent glass or a synthetic resin plate that has a uniform light scattering effect over the entire surface, and reflecting the light from the light source on the back side of the light source 1 and guiding it to the front. The structure is such that a reflection plate 4 made of a specular reflection plate or a light-scattering acrylic plate is installed to improve the efficiency of light utilization. In such a backlight, in order to reduce unevenness in brightness, the light M
Since the distance between l and the diffuse transmission plate 3 cannot be made too small,
The disadvantage was that the depth was large.

Conventionally, as shown in FIG. 5, an edge light 5 is installed between the light filter and the display panel 2, and the light incident from the light source 1 through the A side of the edge light 5 has a roughened surface.
It has also been proposed that after being diffusely reflected by a surface, the light is irradiated via the 0 surface to a display panel 2 disposed close to the B surface. However, in this method, the brightness of the roughened surface B becomes darker as the distance from the light source increases, and the brightness of the illuminated surface cannot be made uniform, resulting in uneven illumination.

D1 Problems to be Solved by the Invention This invention solves the above-mentioned problems of conventional illumination unevenness and depth, and provides a thin illumination that has uniform brightness and can provide a bright display without uneven illumination. The aim is to provide the equipment.

Means for Solving the E0 Problem This invention has been made to solve the above-mentioned problems, and includes a tubular light source 10, a linear Fresnel prism plate 11, and a plane mirror 12. 11 and a plane mirror 12 are arranged in a V-shape with one end touching each other and the other end separated so as to form an acute angle,
The device is characterized in that a tubular light source 10 is installed at the opening position of the V-shape.

F0 effect This invention has the above-mentioned configuration, and combines a linear Fresnel prism plate, a reflecting mirror, and a naro plane mirror, so that a mirror image of the tubular light source is generated by the plane mirror, which is similar to the case where a light source with a tube diameter twice as large is used. It is possible to increase the utilization efficiency of light and to make the illumination device thin and bright without increasing the depth of the illumination device.
By arranging the light source in a V-shaped opening position, the brightness of the reflective surface on the light source side and the side far from the light source is almost uniformly averaged, and the brightness on the display surface is It can eliminate uneven brightness.

G. Examples Hereinafter, the present invention will be explained in detail with reference to examples shown in the drawings.

Overall Configuration of the Illumination Device> Figure 1 In FIG. 1 showing the illumination device of the present invention, 10 is a tubular light source, 11 is a linear Fresnel prism plate, and 12 is a plane mirror. The plate 11 and the plane mirror 12 are arranged in a V-shape with one end touching and the other end separated, forming an acute angle of θ=30° C. or less, and the tubular light source 10 is placed close to the opening position separated from each other. It is placed.

13 is a color liquid crystal display panel placed in front of the linear Fresnel prism plate 11.

Explanation of tubular light source>...Figure 1 The tubular light source 10 may include a cold cathode fluorescent discharge tube, a hot cathode fluorescent discharge tube (fluorescent lamp), a discharge tube such as a neon tube, or an incandescent light bulb having a linear filament. In particular, a hot cathode fluorescent discharge tube is preferably used in terms of luminous efficiency and luminous color.

<Description of Linear Fresnel Prism Plate> Fig. 2 The linear Fresnel prism plate 11 is a flat prism with a straight side on the negative side and a serrated cross section on the other side, and faces the tubular light source 10 side. One slope of the sawtooth is the entrance surface 11A, the other side of the sawtooth is the reflection surface 11B, and the other straight surface is the exit surface 11C.
It is said that

The incidence surface 11A and the reflection surface 11B are repeated at a sufficiently fine period compared to the size of the illumination surface.

The angle of the incident surface 11A is the light L1 from the tubular light source 10.
The reflecting surface 11 is set so that it receives almost vertically.
The angle B is such that the light L2 incident from the incident surface 11A is directed to the exit surface 1.
The setting is such that the light comes out almost vertically from 1C. That is, if the incident angle α1 of the light from the tubular light source 10 is 70° with respect to the perpendicular S, then the angle α2 between the incident surface 11A and the perpendicular S is 20°, and the angle α between the reflective surface 11B and the perpendicular S.

is set to 35°. The linear Fresnel prism plate 11
When acrylic resin (refractive index n=1,491) is used as the material, the critical angle is approximately 42 degrees, so that the reflection at the reflecting surface 11B can be total reflection.

In addition, if the display panel 13 illuminated by the above-mentioned illumination device is visually dependent like a liquid crystal display as in this embodiment, it is also possible to match the direction of the emitted light a to the optimal visual direction of the display element. be.

Function of lighting device〉...Figure 3 Next, the operation of the above lighting device will be explained with reference to FIG.

FIG. 3(1) shows a case where the plane mirror 12 of the present invention is used, and FIG. 3(n) shows a case where the conventional plane mirror shown in FIG. 5 is not used.

Tubular light [10 diameters, 1 linear Fresnel prism plate]
If the width of 1 is W, if the plane mirror of (II) is not used, and the angle of the incident surface 11A is set to be arceos (W/D), the mirror image 101 by the reflecting surface 11B of the tubular light [10 is It appears to be stretched by W/D times in a sagging pattern, so the average brightness is D/W of the surface brightness of the tubular light source 10.
Double. On the other hand, when the plane mirror 12 of the present invention shown in (1) is used, the plane mirror 12 produces a mirror image 10゛ of the tubular light source 10, so the angle of the incident surface 11A is
/2D), it is the same as using a light source with twice the tube diameter. Therefore, the mirror image 10' of the tubular light source is stretched by a factor of W/2D, and the average brightness is 2D/W times that of the tubular light [10]. In this way, when the plane mirror 12 is used as in the present invention, the usable luminous flux is doubled and the brightness is doubled up to the same depth*.

As described above, according to the present invention, since a wide screen can be illuminated with a shallow depth, the angle θ between the linear Fournel prism plate 11 and the plane mirror 12 can be made as small as 30" or less. , it becomes possible to make the lighting device thinner.

In addition, when a fluorescent discharge tube is used as the tubular light source 10, the light distribution of the phosphor layer is close to a completely diffused surface, so the luminance of the tube surface is hardly dependent on the angle formed by the line of sight on the tube surface and is almost uniform. It is considered the same as a band-shaped light source with a luminance of . Therefore, in the state shown in FIG. 3, stripes with slightly uniform brightness are observed, and the entire display panel 13 is irradiated with almost uniform brightness, making it possible to reduce unevenness in brightness. If the above-mentioned cotton becomes a problem, there will be no problem if a diffuser-transmitting plate is installed on the surface of the light source.* Of the light emitted from the tubular light source 10,
Since light that does not reach the linear Fournel prism plate 11 or the plane mirror 12 does not contribute to illumination, a reflective layer is provided on a part of the inner or outer wall of the light source, or a gutter-shaped reflecting mirror is provided close to the outer wall of the light source. , the intensity of light in the required direction can be increased, and using this method, the brightness can be improved by 30-70%.

As is clear from the above explanation, according to the lighting device according to the present invention, the linear Fournel prism plate and the plane mirror serving as the reflecting mirror are arranged in a V-shape, and the V-shape is By arranging a tubular light source in the opening, it is possible to increase the utilization rate of the light from the light source, and the luminous flux that can be used remains the same as when the plane mirror is not arranged, which increases the brightness. can be doubled in size. Therefore, the illumination device can be made thinner and brighter, and by arranging the linear Fresnel prism plate and the plane mirror closer to each other as they move away from the light source, the brightness can be made almost uniform, and uneven illumination can be prevented. It has various effects such as reducing

[Brief explanation of the drawing]

FIG. 1 is a side view showing an embodiment of the present invention, FIG. 2 is a sectional view of a linear Fresnel prism plate used in this invention, and FIG.
Figure (1) is a drawing showing the action of this invention device, and Figure 3 (I
f) is a drawing showing the operation of the conventional device, and FIGS. 4 and 5 are schematic diagrams showing the conventional example. 100. Tubular light source 110. Linear Fresnel prism plate 120. plane mirror 1300 display panel

Claims (1)

[Claims] (1) A tubular light source, a linear Fresnel prism plate, and a plane mirror are provided.
1. A lighting device characterized in that the lighting device is arranged in a V-shape, and a tubular light source is installed at an opening position of the V-shape.