JPH02245787A - light source device - Google Patents

Abstract

PURPOSE:To obtain a surface light source ensuring uniform, high brightness on an entire screen by forming one side of a transparent substrate into a curved surface, providing the thinnest part on the central part between light sources, forming the other surface into a flat surface, the central part between light sources into a mirror, and making the remaining parts coarse. CONSTITUTION:In a light source device where light sources are arranged on both edge surface parts of the transparent substrate 4A, the surface of an observer side of the transparent substrate 4A is constituted of an inclined and curved surface 4b. The coarse, surface is formed on one side of the transparent substrate 4A, the inclined and curved surface 4b in order to diffuse an incident light beam. The other flat surface of the transparent substrate 4A is formed into a stripe shaped mirror of the prescribed width over the center of the light sources 4B, and remaining parts are made coarse. A high-brightness reflecting layer is provided by facing to a flat surface part 4a. Therefore, a large-sized, high-brightness surface light source can be attained, so that uniformed brightness can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light source device, and relates to a technique that is effective when applied to a light source device such as a liquid crystal display device that requires a surface light source.

[Conventional technology]

A conventional planar light source device is described in Japanese Patent Publication No. 58-17957. As shown in FIG. 7, a light source 4B is placed on one end surface of the transparent substrate 4A, and the transparent substrate 4B is
A is made of a material with good light transmission, one surface 4a facing the viewer is a smooth surface, and the other surface 4b facing the viewer is a rough surface. The rough surface 4b is configured to diffuse the light from the light source 4B and reflect the light from the light source 4B onto the smooth surface 4a. The transparent substrate 4A has an inclined plane so that the thickness decreases as the distance from the light source 4B increases.

[Problem to be solved by the invention]

In the above conventional technology, the thickness of the transparent substrate decreases as X increases, as shown in FIG. (a) For a planar light source with a relatively small area, a single fluorescent tube is used as shown in Figure 7, and (b) For a large area, a single fluorescent tube is used as a planar light source. By adopting the two-story structure shown in FIG. 8, a large-area, high-intensity surface light source can be obtained. However, in the case of (a), these conventional technologies have difficulty in dealing with high brightness and large areas even though they are thin and lightweight.In the case of (b), it is difficult to deal with high brightness and large areas. Even though it is a surface light source, it has been difficult to realize it in terms of thinness and weight reduction.The purpose of the present invention is to provide a light source with a large area, light weight, thinness, and uniform high brightness over the entire screen. The purpose of the present invention is to provide a technology that makes it possible to obtain a surface light source.

[Means to solve the problem]

The above purpose is to observe the transparent substrate in a light source device in which light sources are disposed on both end surfaces of the transparent substrate, so that changes in the amount of light per unit area on the observation surface remote from the light source can be suppressed within a certain level range. The surface on the transparent substrate's side is an inclined curved surface, and one surface of the transparent substrate, which is the inclined curved surface, is formed with a rough surface to diffuse the incident light beam, and the other surface of the transparent substrate, which is the flat surface, is formed between the light sources. This is achieved by forming mirror surfaces in the shape of a toss of a predetermined width across the center, leaving the rest as a rough surface, and providing a reflective layer with high brightness opposite to the flat surface.

[Effect]

According to the above-mentioned means, by arranging the light sources on both sides, a surface light source with a large area and high brightness can be obtained. or,
By providing the inclined curved surface of the transparent substrate on the 89 side, a space is formed between the thinnest part of the transparent substrate and the --shaped diffusion layer on the inclined curved surface. It is possible to prevent non-uniformity in brightness caused by the combination of incident light rays. Furthermore, since the surface of the transparent substrate is roughened except for the end surface where the light source is disposed and the band-shaped portion substantially along the innermost thin portion in the plan view, which is the other surface, the transparent substrate is roughened from the side of the diffusion layer. Non-uniformity in brightness when viewed is eliminated, and a light source with −-like brightness can be obtained. The reason why the band-shaped portion of the flat portion is not roughened and is made into a mirror surface is to prevent the brightness of the central portion from becoming too high by allowing light to escape from this portion to the outside of the substrate. The light emitted from the mirror surface is reflected by the reflector and enters the transparent substrate again, but at this time, light loss occurs, resulting in lower brightness in the central area.

〔Example〕

Hereinafter, the structure of the present invention will be described together with an embodiment in which the present invention is applied to a light source device of a liquid crystal display device. In addition, in all the times for explaining the example.

Components having the same function are given the same reference numerals, and repeated explanations thereof will be omitted.

A liquid crystal display device and its light source device according to an embodiment of the present invention are shown in FIG. 1 (cross-sectional view) and FIG. 2 (exploded perspective view).

As shown in FIGS. 1 and 2, the liquid crystal display device includes a liquid crystal display panel 3 and a light source device v14 inside defined by a lower frame (mold case) 1 and an upper frame (cover) 2. Each is set up separately.

The lower frame 1 has a rectangular shape and is made of, for example, a resin material. The upper frame 2 has a rectangular shape that fits into the lower frame 1. The upper frame 2 is provided with an opening 2A in the center.

The opening 2A is configured to expose the liquid crystal panel 3. The upper frame 2 is made of, for example, a metal material such as iron or an aluminum alloy, or a resin material.

The liquid crystal display panel 3 is not shown in detail, but it is driven by a dot matrix type time division method, or a T.
It is composed of components driven by PT. In the liquid crystal display panel 3, a liquid crystal section 3A is provided in a gap between a lower transparent glass substrate 3B and an upper transparent glass substrate 3C. The liquid crystal section 3A is filled with liquid crystal that is regulated by alignment films formed on the inner (liquid crystal side) surfaces of the lower transparent glass substrate 3B and the upper transparent glass substrate 3C, respectively. This liquid crystal section 3
A twisted nematic type liquid crystal is used as the liquid crystal for A. The liquid crystal of the liquid crystal section 3A is configured such that the lighting display is controlled by a scanning electrode formed on the inner surface of the lower transparent glass substrate 3B and a display electrode formed on the inner surface of the upper glass substrate 3C. . A polarizing plate 3D is provided on the outer surface of the lower transparent glass substrate 3B, and a polarizing plate 3E is provided on the outer surface of the upper transparent glass substrate 3C.

The display electrodes are as shown in FIG. Since the display electrode is divided into upper and lower halves, segment driver circuits 5B and 5C are provided.

Each of the segment driver circuits 5B and 5C is composed of a wiring board (eg, made of glass epoxy resin) on which a semiconductor device for segment drivers is mounted.

The scanning electrodes are driven by a common driver circuit 5A detachably attached to the bottom of the lower frame 1. This common driver circuit 5A is the segment driver circuit 5B.
Similarly to 5C and 5C, it is composed of a wiring board on which a semiconductor device is mounted.

The segment driver circuits 5B and 5C and the common driver circuit 5A are each driven by a liquid crystal (LCD) driving power supply circuit and a timing generation circuit. The liquid crystal drive circuit 5D similarly includes a wiring board on which a semiconductor device and passive elements such as resistors and capacitors are mounted.

As shown in FIGS. 1 to 3, the light source device 4 mainly includes a transparent substrate 4A, a light source 4B, a light source reflector 4C1, a transparent substrate reflector 4D, and an inverter power supply circuit 4E. Note that 4E may not be built into the liquid crystal module.

As shown in detail in FIG. 4 (a perspective view of the transparent substrate viewed from diagonally above), the transparent substrate 4A is made of a rectangular transparent material that is transparent to light.

The transparent substrate 4A is made of acrylic resin with a light transmittance of about 90 to 95%. Further, the transparent substrate 4A may be made of a transparent glass material. In this embodiment, the transparent substrate 4A
The width direction dimension W is 250 (m++) and the length direction is 16
0(m+).

The surface 4b of the transparent substrate 4A on the diffuser plate 6 side is formed of an inclined curved surface so that the light incident on the diffuser plate does not decrease significantly even when the transparent substrate 4A is away from the light source. In other words, the transparent substrate 4A becomes thinner as it moves away from the light source 4B (dimensions H to h
It is composed of continuous inclined curved surfaces such as This inclined curved surface 4b can be substantially expressed by the following equation.

0≦X≦(L/2-d) Yz=h... (2)L
/2-d≦X≦L/2 However, Yi, Yz: Distance in H or h direction
5-31111 d=0.5-1. O, O @ (In the range L/2≦X≦L, Yz, Yz becomes a line-symmetrical curve with respect to X=L/2.) By appropriately selecting the curved surface 4b as described above, theoretically It should be possible to obtain uniform surface brightness, but in reality there are manufacturing errors, and in order to make the brightness more uniform, which has the drawback of impairing the uniformity of brightness due to slight changes in the curved surface. Not only optimizes the curved surface 4b, but also the entire surface of the transparent substrate,
It is effective to roughen the surface except for the two end faces facing the light source 4B. This rough surface has substantially the same roughness as a surface formed by filing with, for example, a No. 20 to No. 400 file. In addition, when molding a transparent substrate by injection molding, forming a matte surface makes it easier to control the degree of roughness (mat pitch and groove depth), and has excellent moldability, which is preferable in terms of processability. However, even in this case, the brightness distribution is still affected by manufacturing errors.
In order to suppress variations in the brightness distribution due to manufacturing errors, a curved surface is set in advance so that the brightness is high in the center, and the high brightness in the center is made uniform by the following means.

FIG. 5 shows an example of a transparent substrate 4A that provides this means. FIG. 5 is a diagram of the transparent substrate 4A and the light source section 4B viewed from the plane section 4a side. The hatched portion in FIG. 1 is a roughened portion. It is. In other words, 2Q across the center line from the flat part 4a
A non-roughened mirror-like area is formed with a width of . The light diffused in the transparent substrate passes through the mirror surface portion and heads toward the reflection plate 4D.

This light is reflected by the reflector plate 4D and passes through the mirror surface and enters the transparent substrate 4A again, but a loss of light occurs during reflection and incidence, and as a result, the light is lost in the central part of the diffuser plate 4D.
It is possible to reduce the amount of light directed to the side, and it is possible to make the in-plane luminance distribution uniform.

In this case, the width 212 of the mirror surface portion may be approximately equal to the width 2d of the flat portion near the center of the curved surface portion 4b.

Figure 6 shows how the in-plane luminance distribution is made almost uniform by providing a mirror surface part with a width of 212 = 8 mm on the 4a side.
The in-plane luminance distribution in the figure is the result of measurement from above the diffuser plate 6. d, H in FIG.

L and h are the same as the definition in the first formula, and each is 4.0
mm, 7.0++a, 160+am, 1.6mm
It is.

Also, for the curved surface 4b in FIG. 6, n=
It is represented by a curved surface in the case of 2.3.

Also, d=ffi.

The light source 4B uses a cold cathode ray tube having a length of about 270 (m+a), for example. This cold cathode ray tube is driven by an inverter power supply circuit 4E attached to the bottom of the lower frame 1. This inverter power supply circuit 4E has, for example, 5 to 3
0 (V) DC power supply at 300 to 400 V for 30 to 50
(KHz) AC power.

The inverter power supply circuit 4E is constructed of a wiring board on which semiconductor devices and the like are mounted, similar to the circuits 5A to 5D.

The light source reflector 4C efficiently reflects the light from the light source 4B to the transparent substrate 4.
In order to be able to reflect in the A direction, the light source 4B is covered except for a part, and the cross section is configured in a U-shape or a U-shape.

This light source reflector 4C is made of, for example, an aluminum plate coated with white paint (acrylic resin paint) on the surface (surface on the light @ 4B side), and in particular, the brightness value of the white paint is 9.
4 or more is desirable (however, the L medium value is based on CIE's ULCS
It is the brightness index in the color system. ) The reflecting plate 4D is formed on the flat surface 4a of the transparent substrate 4A so as to efficiently reflect the light from the light source 4B toward the liquid crystal panel 3 side. This substrate reflecting plate 4D is made of the same material as the light source reflecting plate 4C, for example, and in this case as well, the higher the medium brightness value of the reflecting plate, the better, and preferably 94 or more.

A light diffusing plate 6 is provided between the liquid crystal panel 3 and the transparent substrate 4A of the light source device 4. This acrylic resin preferably has a plate thickness of 0.5 to 3.0 m and is roughened on both sides.

A plurality of light sources 4B of the present invention may be arranged at each end, or may be composed of LEDs.

In the above explanation, the inclined curved surface 4b is expressed by an exponential function, but it may be approximately an exponential function, and even if it is constructed by a combination of planes in consideration of manufacturing margin, there is no substantial effect. can be obtained.

Since the light source device 4 of the present invention can obtain high luminance, the liquid crystal display panel 3 of the liquid crystal display device can be operated in a super twisted nematic type white & black mode (
This is effective when the light transmittance is low.

Further, the present invention is not limited to liquid crystal display elements, but can be applied to all light source devices that require a surface light source, such as light source devices for measuring instruments.

〔Effect of the invention〕

According to the present invention, a surface light source with high brightness and uniform brightness can be obtained.

[Brief explanation of drawings]

1 is a cross-sectional view of a light source device according to an embodiment of the present invention used in a liquid crystal display element; FIG. 2 is an exploded perspective view of an embodiment of the present invention shown in FIG. 1; The figure is a rear perspective view of a liquid crystal display device which is an embodiment of the present invention, FIG. 4 is a perspective view showing main parts of a light source device which is an embodiment of the present invention, and FIG. 6 is a diagram showing a luminance distribution of a light source device according to the present invention, and FIGS. 7 and 8 are cross-sectional views showing conventional light source devices, respectively. 3...Liquid crystal display panel, 3A...Liquid crystal section, 4...
Light source device, 4A...Transparent substrate, 4B...Light source, 4C
...Reflector for light source, 4D...Reflector for board, 4E.
... Inverter power supply circuit, 4a... Plan view, 4b...
・Curved surface part. Meienba q set middle, χ (Chikuml funeral 7th figure 8A

Claims (1)

[Claims] 1. One surface of a transparent substrate having light transmittance is a rough surface,
In a light source device in which a reflecting plate is provided on the opposite surface side and light sources are arranged on both end surfaces of the transparent substrate, the one surface of the transparent substrate has a thick wall in the center between the light sources. It is composed of a combination of an inclined curved surface or a flat surface having the thinnest part, the other surface side is a flat surface, the central part between the light sources is a mirror surface, and the rest of the other surface side is roughened. Characteristic light source device. 2. The light source according to claim 1, wherein the inclined curved surface of the transparent substrate is expressed by an exponential function of the distance from each light source, and is symmetrical with respect to the center of each light source. Device. 3. The one surface of the thinnest wall portion in the central portion is substantially flat, and the mirror surface portion of the other surface is formed substantially opposite to the plane of the thinnest wall portion. The light source device according to claim 1, characterized in that: 4. The light source device according to claim 1, further comprising a light diffusing surface on the one surface side. 5. Each of the light source devices according to claims 1 to 4, wherein a liquid crystal display panel is disposed on the one surface side of the transparent substrate, and the light source device is used for liquid crystal display. . 6. Each of the light source devices according to claims 1 to 5, wherein a plurality of light sources are arranged on one end surface portion of the transparent substrate.