JPH07282612A - Lighting system - Google Patents

Abstract

PURPOSE:To provide the uniformity of brightness by providing a constitution preventing a virtual image of each light source, reflected in a visual field direction from each of a belt-shaped reflecting part, from overlapping with each other beyond an internal diameter of a tubular light source, so as to reduce the number of the belt-shaped reflecting parts. CONSTITUTION:A device comprises a tubular light source 10 and a reflecting member having a plurality of belt-shaped reflecting parts 20... reflecting light of the light source 10, to set up the light source 10 in a central part of the reflecting member. Virtual images 11 to 15 of each light source, reflected in a visual field direction from each belt-shaped reflecting part, are prevented from overlapping with each other beyond an internal diameter of the tubular light source 10. In this way, the number of the belt-shaped reflecting parts can be decreased, also to enable the dimension to shallow in a depth direction of a lower surface of the tubular light source, and outward appearance of a liquid crystal display device, built in lighting system, can be freely designed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a display image quality by arranging it on the back side, back side or top side of a passive display panel found in personal computer devices, liquid crystal television devices, liquid crystal monitor devices and the like. Lighting device for improving.

[0002]

2. Description of the Related Art A liquid crystal display device utilizes optical anisotropy of liquid crystal to transmit or reflect light to control and modulate the transmittance of the light for display. Therefore, since the liquid crystal display device is positioned as a so-called passive device (non-light emitting body), there is a problem that the display becomes difficult to see unless the back lighting means is provided when the surroundings are dark. Further, as described above, almost all liquid crystal display devices use optical anisotropy, so that it is indispensable to stack polarizing plates, and because of this polarizing plate, about 50% of illumination light is used. Will be cut. Especially color
In a liquid crystal display device using a filter, the amount of light is further reduced due to colorization. Therefore, it is an essential requirement to attach a lighting means to the device for general indoor use. Due to the usefulness of liquid crystal display devices, portable information devices such as liquid crystal televisions are mainly used in portable electronic devices.
It has been widely used as a service. Therefore, how to obtain a lighting device with low power consumption, lightness, thinness, shortness, brightness, and uniform brightness distribution is an issue in designing a liquid crystal display device.

JP-A-63-24280 and JP-A-64-5
15 and Japanese Patent Application Laid-Open No. 2-136829, many inventions have been made in the past with respect to the lighting device.

FIG. 3 and FIG. 4 show an illuminating device 40 which has been conventionally used as the illuminating means as a technique. In FIG. 3, a cold cathode or hot cathode fluorescent tube is used as the tubular light source 10, and a light scattering effect is provided between the tubular light source and the liquid crystal display panel in order to make the brightness of the illumination surface uniform over the entire surface. A diffusion plate 30 made of milky white glass, plastic, or the like is provided. Further, as the reflection plate 26 arranged below the fluorescent tube, a mirror surface or plastic or metal having a white light scattering effect is used. Reflector 2
Reference numeral 6 is provided to reflect the light emitted from the light source 10 toward the back surface and guide it to the front surface to improve the light utilization efficiency. On the other hand, the liquid crystal panel 50 is disposed above the diffusion plate 30.

A light quantity adjusting screen may be provided on the lower surface of the diffusion plate 30. Further, a visual adjustment plate having a prism or Fresnel lens may be provided on the upper surface or the lower surface of the diffusion plate 30.

The light emitted from the tubular light source 10 to the lower and side portions is reflected by the reflection plate 26 and enters the diffuser plate, and the light emitted from the light source 10 toward the upper part directly enters the diffuser plate 30. The light that has entered the diffusion plate 30 is diffused in the diffusion plate, and substantially uniform light enters the liquid crystal panel 50 from the entire surface of the diffusion plate.
Light on which an image is formed by the incident side polarization plate, the liquid crystal material, and the emission side polarization plate that configure the liquid crystal panel 50 emerges from the liquid crystal panel 50.

As shown in FIG. 4 which is an explanatory view of the related art, in such an illuminating device 40, the distance between the tubular light source 10 and the diffuser plate 30 cannot be shortened so much in order to reduce the unevenness in brightness, so that the depth is reduced. The illuminating device is not suitable for downsizing and weight reduction, which is an advantage of liquid crystal display devices.

Further, in order to reduce uneven brightness, the diffusion plate 3
As 0, a material having a large light diffusivity must be used, and there is a drawback that the brightness is lowered as a whole. Further, in order to shorten the distance between the tubular light source 1 and the diffuser plate, a luminance uniformizing screen is provided between the tubular light source 1 and the diffuser plate to prevent the luminance from increasing near the tubular light source, or the plate of the tubular light source portion of the diffuser plate. It has been proposed to increase only the thickness, but there is a drawback that the brightness is still lowered.

On the other hand, as shown in the reflection plate 26 of FIG. 3, a large number of strip-shaped reflecting portions 26 are provided and each strip-shaped portion 27 of the strip-shaped reflecting portion 26 becomes closer to the tubular light source 10 as it approaches the tubular light source 10. There is also a case where a parabolic prismatic reflecting mirror is used for the tubular light source 10. For details, see JP-A-63-24280.
It is described in the official gazette. In this case, if the shape of the lighting device 40 changes due to a change in the size of the liquid crystal panel, the strip-shaped portion 2
7 had to be redesigned, and there was a problem that the design of the band-shaped portion 27 was extremely complicated, and the mold for molding the reflection plate 26 was complicated and the life of the mold was short. .

[0010]

Increasing the depth of the illuminating device restricts the external design of the liquid crystal display device and further impairs the thinness which is a characteristic of the liquid crystal display device, thereby reducing the commercial value. . Further, the image quality performance of the liquid crystal display device is determined because it contributes to the uniformity of the brightness of the built-in lighting device, and a means for simultaneously improving the brightness is found in the example of the reflection plate 27 of FIG. As described above, the current situation is that it is very expensive and has not been put to practical use. In view of these, an object of the present invention is to provide an illumination structure that can achieve uniform brightness and improved brightness at the same time at a low cost and with a simple structure.

[0011]

In order to solve the above-mentioned problems, the present invention comprises at least a tubular light source and a reflecting member having a plurality of strip-shaped reflecting portions for reflecting the light of the light source, wherein the light source is In the illuminating device installed in the central portion of the reflecting member, the virtual images of the respective light sources reflected in the visual field direction from the respective reflecting portions do not overlap and exceed the inner diameter of the tubular light source.

[0012]

FIG. 1 shows a virtual image state diagram of a light source in an embodiment of the present invention. Further, FIG. 2 is a state diagram of a luminance diagram showing the state of luminance in FIG. We have repeated experiments to make the luminance incident on the diffusing member or the liquid crystal panel uniform, and in order to increase the light utilization efficiency and increase the luminance by utilizing the total reflection by the reflecting member,
Reflecting member 20 from above tubular light source 10 to behind tubular light source 10
When looking at it, it was found that the virtual image of the tubular light source 10 should be reflected on the front surface of the reflector.

Further, considering the easiness of making the reflecting member 20 which is the above-mentioned drawback, the substantially three-sided mirror reflecting member shown in FIG. 1 can be obtained. At this time, it is preferable to determine the shape of the reflecting member 20 so that the virtual image of the tubular light source 10 can be obtained from the virtual image 11 as shown in the virtual image 15.

Further, it has been found that in the virtual images 11 to 15, the shape of the reflecting plate is determined so that the virtual images partially overlap with each other, whereby it is corrected that the brightness decreases toward the outside of the tubular light source 10.

The shape of the reflecting plate will be determined based on the above experimental results. In FIG. 1, the first end contacting the inner end of the tubular light source 10 which is a fluorescent tube from the open end of the reflecting member 20
A straight line is drawn, and an angle formed by the first straight line and the first inclined surface of the reflecting member 20 is set to an angle 103, and a first parallel line is drawn in parallel with the first straight line in contact with the inner circle below the tubular light source 10.
The point in contact with the first slope of is the inflection point 23. Tubular light source 1
A point parallel to the first straight line passing through the center of 0 and drawing a second parallel line to be in contact with the first slope of the reflecting member 20 is defined as a point 22, and
A first horizontal line passing through the center of the tubular light source 10 is drawn, and an angle formed by the first horizontal line and the second parallel line is an angle 101. Point 2
The first vertical line is drawn from 2, and the angle between the first vertical line and the first slope of the reflecting member 20 is an angle 102. The length in the vertical direction between the open end and the point 22 is defined as the length 104. Point 22
The length of the inflection point 23 in the vertical direction is defined as a length 105.
Let the radius of the inner circle of the tubular light source be the inner radius C. Further, the length in the horizontal direction from the center of the tubular light source 10 to the open end, which is determined by the space of the display device device vacated as the lighting device, is the length A, and the end of the reflecting member 20 from the center of the tubular light source 10. The length in the vertical direction to the part is defined as length B.

When the angle of the reflecting member 20 on the tubular light source side is obtained using the symbols defined as described above, it is as follows.

[0017]

## EQU1 ## (angle 101) + 2 × (angle 102) = 90 degrees

Tan (angle 101) = (length 105) ÷ (length A)

[Equation 3] (Length 104) + (Length 105) = (Length B)

Tan (angle 102) = (inner radius C) ÷ (length 104)

The above equations 1 to 4 are solved to obtain the angle 102.
When the angle 103 is calculated, the reflection part of the reflection member 20 is determined.

Further, in FIG. 1, the angle of the reflecting member 20 needs to be changed like the slope 21 at the position where the virtual image 15 is cut, but at this time, it can be obtained in the same manner as described above.

On the other hand, the smaller the difference in brightness between adjacent measurement points is, the better, but in order to realize this, it is necessary to overlap the brightness curves of the individual virtual images in the vicinity of the apexes. Although the brightness curve becomes gentler as the distance between the vertices of the individual virtual images becomes smaller, the brightness curve can be rounded by the diffusion member 30 to reduce the brightness difference between adjacent measurement points.

FIG. 2 is a diagram showing the brightness curve in FIG. 1, and the virtual image 13 and the virtual image 14 by the tubular light source 10 are circumscribed by the inner tube diameter 106 of the tubular light source 10. The brightness curve at this time is shown by a brightness curve 16. The unevenness on the top of the brightness curve 16 was an amount that could be visually made uniform by the diffusion member 30.

[0022]

In the illumination device of the present invention, the virtual images of the light sources reflected by the reflecting member in the visual field direction do not overlap each other beyond the inner diameter of the tubular light source, so that the number of strip-shaped reflecting portions can be reduced. In addition to being able to do so, the dimension of the lower surface of the tubular light source in the depth direction can be made shallow, so that the external design of the liquid crystal display device incorporating the lighting device can be freely designed, and the thinness which is a characteristic of the liquid crystal display device The product value is improved because it can be obtained. In addition, it is possible to obtain the uniformity of the brightness of the illuminating device and also to simplify the mold of the reflecting member, which leads to a cost reduction effect.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention and a virtual image state diagram of a light source in the embodiment.

FIG. 2 is a brightness state diagram for explaining the uniformization of brightness in FIG.

FIG. 3 is an external perspective view showing a lighting device portion of a conventional liquid crystal display device.

FIG. 4 is a cross-sectional view of a conventional lighting device.

[Explanation of symbols]

 10 tubular light source 11, 12, 13, 14, 15 virtual image 16 brightness curve 20 reflecting member 30 diffusing member

Claims (1)

[Claims] 1. A lighting device comprising at least a tubular light source and a reflecting member having a plurality of strip-shaped reflecting portions for reflecting the light of the light source, wherein the light source is installed in a central portion of the reflecting member. An illuminating device characterized in that virtual images of respective light sources reflected from respective parts in the visual field direction do not overlap each other beyond the inner diameter of the tubular light source.