JPS6368814A - Lighting equipment for liquid crystal display - Google Patents

Abstract

PURPOSE:To reduce the spread of a light beam from a light source and to improve the utilization efficiency of the light by forming a light distribution control plate so that fine projections are formed over the entire surface on the side of a liquid crystal display device. CONSTITUTION:This lighting device has the light source 1 arranged behind a liquid crystal display device 3 and the light distribution control plate 2 made of a transparent material interposed between the liquid crystal display device 3 and light source 1, and the light distribution control plate 2 is formed having fine projections 4 on the entire surface on the side of the liquid crystal display device 3. The fine projections 4 formed on the light distribution control plate 2 reduce the spread of the light beam from the light source 1 to obtain luminous flux crossing the plate surface of the liquid crystal device 3 almost at right angles and the liquid crystal display device 3 has high brightness with the relatively small light source.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field 1] The present invention relates to a lighting device for a liquid crystal display device, and more particularly, to a lighting device for a liquid crystal display device that irradiates light from behind a dot matrix type translucent liquid crystal display device. It is something.

[Background Art 1] In general, a lighting device is known that improves the contrast of a dot matrix type translucent liquid crystal display device by irradiating light from behind the device. As a light source for this type of lighting device, a light source that approximates a point light source or a line light source, such as a fluorescent lamp, is used in terms of luminous efficiency. There is a problem in that the brightness on the surface of the liquid crystal display device becomes uneven due to this. In order to solve this problem, conventionally, as shown in FIG.
As shown in FIG. 10, the light emitted from the light source 1 enters the light guide plate 6 upwardly and radiates forward, and then is diffused and transmitted by the diffuser plate 5. A configuration is used that allows

By the way, the liquid crystal used in the liquid crystal display device 3 generally has a relatively large refractive index, and if the angle of incidence with respect to the plate surface of the liquid crystal display device 3 is large, the light will be totally reflected and will not be transmitted. Considering the utilization efficiency of the emitted light rays, it is desirable to irradiate the plate surface with a light ray that is substantially perpendicular to the plate surface from behind.

However, since the light beams transmitted through the diffuser plate 5 as described above are incident on the liquid crystal display device 3 at all angles, the conventional method of reducing brightness unevenness using the diffuser plate 5 There was a problem in that the utilization efficiency of the light rays emitted from the rays was low.

[Object of the Invention] The present invention has been made in view of the above-mentioned points, and its object is to provide a liquid crystal display using a relatively small light source with high utilization efficiency of light rays emitted from a light source. An object of the present invention is to provide a lighting device for a liquid crystal display device that allows high brightness to be obtained in the device.

[Disclosure 1 of the Invention The lighting device for a liquid crystal display device according to the present invention is a lighting device that irradiates light from behind a dot matrix type translucent liquid crystal display device, and is a lighting device disposed behind the liquid crystal display device. and a light distribution control board made of a transparent material interposed between the liquid crystal display device and the light source, and the light distribution control board has minute protrusions over the entire surface on the liquid crystal display device side. The micro-protrusions formed on the light distribution control board reduce the spread of the light beam from the light source and direct the light beam almost perpendicular to the plate surface of the liquid crystal display device. This is what I did to get it.

(Example 1) As shown in FIG. 1, a light source 1 is provided behind a liquid crystal display device 3, and a light distribution control board 2 is interposed between the liquid crystal display device 3 and the light source 1. As the light source 1, a plurality of small fluorescent lamps are used, and as the liquid crystal display device 3, a dot matrix type transmissive type is used. The fluorescent lamp which is the light source 1 is located behind the liquid crystal display device M3.
They are arranged in rows along the board surface. The light distribution control board 2 is made of a transparent material such as glass and has a shape of t, ? ! -, and a large number of minute protrusions 4 are formed over the entire surface on the liquid crystal display device 3 side. As shown in FIG. 2, the minute protrusions 4 are arranged in a grid pattern with their centers arranged on square lattice points, or
Alternatively, as shown in FIG. 3, the centers may be arranged on a diamond-shaped lattice, α, in a nest of peaks. The arrangement shape of these may be made to correspond to the arrangement shape of each pixel of the liquid crystal display device 3. Further, the surface of the minute protrusions 4 is finished to have gloss. Since each microprotrusion 4 forms a spherical lens and acts as a convex lens, it has the effect of reducing the spread of the light beam from the light source 1. By the way, since each microprotrusion 4 acts as a convex lens, the density of light #I near the center (optical axis) of the microprotrusion 4 becomes larger than that at the periphery, and microscopically, the brightness becomes uneven. will occur. Therefore, the smaller the formation pitch of the microprotrusions 4, the less noticeable the unevenness in brightness becomes, but the smaller the formation pitch, the more difficult it becomes to manufacture, so the formation pitch is set to a limit of three times the number of pixels of the liquid crystal display device 3. . The reason why the formation pitch is set to three times the pixel or less is as follows. In other words, when considering a color liquid crystal display device, one color is determined by the three elements red, green, and blue, and one point is formed by a set of three elements. This is because uneven brightness on the screen is considered not to be a problem as long as the formation pitch is equal to or less than the formation pitch of a set of elements. In addition, for small liquid crystal display devices such as so-called pocket TVs that can be viewed from a short distance, and monochrome liquid crystal display devices, the pixel size is set based on the relationship between the display screen size and the number of pixels, regardless of the resolution of the eye. Since the pixel formation pitch is generally considered to be smaller than the resolution of the human eye, when viewing the liquid crystal display device 3 at close range, the microprotrusions 4 are The formation pitch may be set to 1xx or less. Furthermore, in the case where the pixels are sufficiently smaller than the resolution of the eye, such as in a so-called high-definition television, the formation pitch of the minute protrusions 4 may be set to three times or less that of the pixels of a normal television. Further, the formation pitch of each microprotrusion 4 may be made to match the formation pitch of each pixel of the liquid crystal display device 3, and the optical axis of the microprotrusion 4 may be made to match the center of each pixel of the liquid crystal display device M3. .

The light distribution control board 2 formed as described above has the effect of blurring the image of the light source 1, and has the effect of equalizing the light density over the entire light distribution control board 2 when viewed macroscopically. Therefore, uneven brightness of the liquid crystal display device 3 can be suppressed without using a diffuser plate. In addition, each microprotrusion 4 acts as a convex lens, which has the effect of reducing the spread of the transmitted light beam and refracting the light flux so as to concentrate it on the optical axis side, so that the light flux introduced into the liquid crystal display device 3 The component in the direction perpendicular to the plate surface of the liquid crystal display device 3 increases, and as a result, the brightness of the liquid crystal display device 3 can be increased by efficiently utilizing the light emitted from the light source 1.

In this case, each microprotrusion 4 may be formed into an aspherical surface such as a paraboloid or a truncated cone other than a spherical surface. For example, as shown in FIG. For example, the beam aperture can be made smaller than that in the case where the beam is formed only from spherical surfaces. Furthermore, as shown in FIG. 5, the projection onto the plane orthogonal to the optical axis is elliptical, and the minute protrusion 4 is a spheroid rotated around the long axis of this ellipse, and as shown in FIG. As shown in FIG. 2, it may be a hexagonal pyramid-shaped minute protrusion 4 or the like.

(Example 2) In Example 1, only the light distribution control plate 2 was interposed between the light source 1 and the liquid crystal display device 3, but as shown in FIG. good. That is, the diffusion plate 5 made of flower-colored glass or the like is interposed between the light source 1 and the light distribution control plate 2, and the light rays from the light source 1 are first diffused and then transmitted through the light distribution control plate 2. Even if the light source 1 has a relatively large amount of uneven brightness, the uneven brightness can be suppressed. Here, since the transparent material such as glass that forms the light distribution control plate 2 generally has a lower refractive index than liquid crystal, the component of the light transmitted through the diffuser plate 5 that is totally reflected at the back surface of the light distribution control plate 2 is , is smaller than the total reflection component when the light is directly incident on the liquid crystal display panel 3, and the utilization efficiency of the light rays emitted from the light source 1 does not decrease much even though the diffuser plate 5 is used. Furthermore, since the light beam transmitted through the diffuser plate 5 is diffused in all directions, the light beam incident on the minute protrusion 4 is equivalent to innumerable light sources 1' on the optical axis, as shown in FIG. 4 narrows the beam aperture, so the light beams that have passed through the minute protrusions 4 are focused on the optical axis side as a whole, and as a result, the amount of light that passes through the liquid crystal display device 3 is smaller than when only the diffuser plate 5 is used. This increases the brightness of the liquid crystal display device 3.

[Effects of the Invention] As described above, the present invention is an illumination device that irradiates light from behind a dot matrix type translucent liquid crystal display device, which comprises a light source disposed behind the liquid crystal display device; , has a light distribution control board made of a transparent material interposed between the liquid crystal display device and the light source, and the light distribution control board has minute protrusions protruding over the entire surface of the liquid crystal display device side. The minute protrusions formed on the light distribution control board reduce the beam spread of the light rays from the light source, and when the light rays emitted from the light source are diffused only by the diffuser plate. In comparison, the luminous flux that is almost perpendicular to the plate surface of the liquid crystal display device increases, and as a result, the efficiency of using the light emitted from the light source increases, making it possible to increase the brightness of the liquid crystal display device with a relatively small light source. It has the advantage of being able to

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing Embodiment 1 of the present invention, and FIG. 2 (
a) and (b) are respectively a plan view and a side view showing an example of the light distribution control board used in the above, and FIGS. 3(a) and 3(b) are plane views showing other examples of the light distribution control board used in the above, respectively. 4(a) and 4(b) are a plan view showing still another example of the light distribution control board used in the above, and a side view, and FIG. 4(a), X-X.
A line sectional view, FIGS. 5(a), 5(b), and 5(c) are a plan view, a side view, and a front view showing an example of the same microprotrusions, respectively;
6(a), 6(b), and 6(c) are a plan view, a side view, and a front view showing other examples of the same microprotrusions, respectively, and FIG. 7 is a schematic configuration diagram showing Embodiment 2 of the present invention, and FIG. 8 is an explanatory diagram of the same operation as above, FIG. 9 is a schematic configuration diagram showing a conventional example, and FIG. 10 is a schematic configuration diagram showing another conventional example. 1 is a light source, 2 is a light distribution control board, 3 is a liquid crystal display device, and 4 is a minute protrusion. Agent Patent attorney Ishi 1) Ai 71...Light source 2...Light distribution control board Figure 2 Figure 3 Figure 4 (b) Figure 5 (a) (b) Figure 6 (G) ( b) (C) Procedural amendments to Figures 7, 8, 9, and 10 (voluntary) August 22, 1988

Claims (3)

[Claims] (1) An illumination device that emits light from behind a dot matrix type translucent liquid crystal display device, which is between a light source arranged behind the liquid crystal display device and the liquid crystal display device and the light source. It has a light distribution control board made of an interposed translucent material, and the light distribution control board is formed in a shape in which minute protrusions are protruded over the entire surface on the liquid crystal display side. A lighting device for a liquid crystal display device. (2) The illumination device for a liquid crystal display device according to claim 1, wherein the formation pitch of the microprotrusions is set to be three times or less the formation pitch of each pixel of the liquid crystal display device. (3) The illumination device for a liquid crystal display device according to claim 1, wherein the formation pitch of the microprotrusions is set to 1 mm or less.