JPH0686195A - Method and device for illuminating light transmission type liquid crystal display element - Google Patents

Abstract

PURPOSE:To enable the use of the defect of a black point by relaxing the specification of the defect of the black point by arranging a diffusion plate between a liquid crystal display panel and a flat type cold cathode fluorescent lamp and performing the back illumination for the liquid crystal display panel by diffusing the light of the flat type cold cathode fluorescent lamp. CONSTITUTION:Within the view finder 1 of a video camera, a liquid crystal display panel 2 and driving circuit 4, etc., for driving a cold cathode fluorescent lamp 3 to be a flat type back illuminator and the liquid crystal display panel 2, etc., are provided. In this case, the liquid crystal display panel 2 is composed of color or black and white liquid crystal display elements of light transmission type and projects the video photographed by the video camera or the reproduced images from photographed tapes. A diffusion plate 5 is arranged between the liquid crystal display panel 2 and the cold cathode fluorescent lamp 3, the liquid crystal display panel 2 is illuminated from the back side by diffusing the light from the cold cathode fluorescent lamp 3, and the video or screen of the liquid crystal display panel 2 can be seen via an eyepiece 6. At the inside of the lamp, emitter material is arranged by an application, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a back lighting method in a liquid crystal display device using a light transmissive liquid crystal display element and a lighting device including a flat cold cathode fluorescent lamp used for the lighting.

[0002]

2. Description of the Related Art In this type of light-transmissive liquid crystal display element, a color liquid crystal display panel is used for image display in a viewfinder of a video camera, for example. A flat-emission type cold cathode fluorescent lamp is used as a back lighting device on the back side of the color liquid crystal display panel. This cold cathode fluorescent lamp is configured so that it does not require the interposition of another member for diffusing light when illuminating the flat plate-shaped member by itself becoming a surface emitting state. .

[Problems to be Solved by the Invention]

In the viewfinder, since the color liquid crystal panel is viewed through the eyepiece having a predetermined magnification, the black spot defect of the cold cathode fluorescent lamp, which is the back illumination, and the attached dust can be seen as it is. Since black dots are scattered in the displayed image so that they cannot be seen neatly, a certain standard is provided especially for black dot defects. The standard of the black spot defect in the cold cathode fluorescent lamp is very strict, for example, the size of the black spot is 0.1 mm or less, so that the yield of the cold cathode fluorescent lamp which meets the standard is poor and the cost is increased. Have a point.

Further, the cold cathode fluorescent discharge lamp exhibits a phenomenon in which the lighting performance is extremely deteriorated when left in the dark for a long time. This is generally called a lighting delay in the dark. As a measure for avoiding this, a light bulb for assisting lighting, an LED, or the like is attached, or an auxiliary electrode is provided inside the lamp to improve lighting performance.

However, there is a problem that mounting of the light bulb or the LED is expensive, and the auxiliary electrode has a problem that lighting performance is deteriorated if impure gas such as chlorine gas enters. ing.

Therefore, the conventional example has a problem that it is necessary to solve the difficult-to-see display due to the black spot defect in the cold cathode fluorescent lamp and to solve the lighting delay in the dark with a simple structure.

[0007]

As a concrete means for solving the above-mentioned problems of the conventional example, the present invention provides a flat cold cathode by disposing a diffusion plate between a liquid crystal display panel and a flat cold cathode fluorescent lamp. A cold cathode fluorescent lamp used as a backlight of a liquid crystal display panel, as well as a method for illuminating a light-transmitting liquid crystal display element, characterized in that the light of a fluorescent lamp is diffused to back illuminate a liquid crystal display panel. The present invention provides an illuminating device characterized in that a substance having an action of reducing a cathode drop voltage is disposed in a portion other than a main electrode inside the lamp, wherein the diffusion plate is provided between the cold cathode fluorescent lamp and In the lighting device, the substance is an emitter substance which is disposed with a predetermined gap and has a function of further reducing the cathode drop voltage.

[0008]

By providing the diffusion plate between the liquid crystal display panel and the cold cathode fluorescent lamp, the black spot defects of the back lighting device are sufficiently diffused, and the black spot defects are conspicuous even when enlarged by the lens. The screen disappears and the screen looks beautiful.
Further, by disposing the emitter material inside the cold cathode fluorescent lamp by means such as coating, a discharge phenomenon occurs between the emitter material and the anode electrode in the initial stage of lighting, so that the lighting delay phenomenon in the dark is eliminated.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail with reference to the illustrated embodiment. FIG. 1 shows a viewfinder 1 of a video camera. In the viewfinder 1, a liquid crystal display panel 2 and a flat back panel are provided. A cold cathode fluorescent lamp 3 serving as an illuminating device, a drive circuit 4 for driving the liquid crystal panel 2 and the like are provided.

The liquid crystal display panel 2 is composed of a light-transmissive color or black and white liquid crystal display element, and displays an image photographed by a video camera or a reproduced image from a photographed tape.

A diffusing plate 5 is provided between the liquid crystal display panel 2 and the cold cathode fluorescent lamp 3 to diffuse the light from the cold cathode fluorescent lamp 3 to illuminate the liquid crystal display panel 2 from the rear side. The image or screen of the liquid crystal display panel 2 can be viewed through the eyepiece lens 6.

The diffuser plate 5 used in this case has a relatively low diffusivity and a high transmittance, for example, a transmittance of about 90 to 95%, so that the cold cathode fluorescent lamp 3 is used. Illumination as a backlight does not decrease so much.

Further, as shown in FIG. 2, if the diffuser plate 5 is arranged at an interval of about 1 to 2 mm with respect to the cold cathode fluorescent lamp 3, the cold cathode fluorescent lamp 3 is caused by a light diffusion phenomenon.
The black spot defects and the like in are almost inconspicuous. In particular,
Even if it exceeds the standard of the black spot defect (φ 0.1 mm or less) in the conventional example, for example, about φ 0.3 mm, it can be almost ignored.

Further, the liquid crystal display panel 2 is provided with a frame 2a on the outer peripheral surface thereof, and is approximately 0 to 0.5 with the diffusion plate 5.
It is arranged with an interval of about mm. The distance between the liquid crystal display panel 2 and the cold cathode fluorescent lamp 3 cannot be so large. Because, if the distance is increased, the cold cathode fluorescent lamp 3 must be increased as indicated by the phantom line, and the viewfinder 1
This is due to reasons such as the arrangement in a restricted space inside.

Therefore, within these restrictions, the diffuser plate 5 having a thin thickness of about 100 to 500 .mu.m is used, and the liquid crystal display panel 2 to the cold cathode fluorescent lamp 3 has a thickness of 10 to 1.
If the thickness is set to about 5 mm, the luminous efficiency of the cold cathode fluorescent lamp 3 is not lowered so much and the black spot defects can be diffused. Also, depending on the diffuser plate used, sufficient diffusion is possible without opening any gaps.

The specific structure of the cold cathode fluorescent lamp 3 is as follows.
This is as shown in FIG. That is, the glass stems 11 and 12 are attached to both ends of the flat glass bulb 10, and the anode electrodes 13 and the cathode electrodes 14 and the auxiliary electrodes 15 and 16 are attached to penetrate the stems, respectively.
A phosphor 17 is applied to the inner surface of the bulb 10, and an inert gas such as argon gas is sealed inside.

In order to eliminate such a lighting delay in the dark of the cold cathode fluorescent lamp 3, the emitter material 18 is applied inside the lamp at a predetermined position excluding the main electrodes of the anode electrode 13 and the cathode electrode 14. And the like.

This coating position is preferably in the vicinity of the anode electrode 13, but can be applied in the vicinity of the cathode electrode 14 or the auxiliary electrodes 15 and 16, and the phosphor 1 can be applied.
It can be arranged in a mixed state with 7.

The emitter material 18 is a material having a function of reducing the cathode drop voltage, and for example, a metallic material such as calcium, strontium, barium or cesium, or an oxide or a carbonate thereof is used. In general, the stems 11, 12 are in the form of stable carbonates as substances.
The carbon dioxide gas is released and exists as an oxide by being applied and placed on the inside of the lamp and the auxiliary electrodes 15 and 16 and being heated during the manufacture of the lamp and being in a state close to a vacuum.

If the emitter material 18 is disposed inside the stem 11 to which the anode electrode 13 is attached, the glass of the stem 11 is an insulator as shown in FIG. Considering that, the emitter material 18 is connected to the atmosphere (GND) through a very small capacitor C and a very large resistance R.

At the initial lighting of the cold cathode fluorescent lamp 3 (before discharge between the anode and the cathode),
For example, in the case of the SGX 3120 (trade name) inverter, a voltage of 2.5 KV is applied to the anode electrode 13 at the pulse peak.

Since the anode electrode 13 and the emitter material 18 are close to each other, the potential gradient is large. Therefore, electrons are emitted from the emitter material and a weak discharge occurs between the emitter material and the anode electrode. This weak discharge becomes a seed discharge, a discharge (main discharge) starts between the anode electrode 13 and the cathode electrode 14, and the cold cathode fluorescent lamp 3 is turned on.

When the cold cathode fluorescent lamp 3 is lit in this manner, the voltage between the anode and the cathode usually drops to about 700 V, so that the anode electrode 13 and the emitter material 1
The discharge between 8 and 8 hardly occurs. Therefore, the collision of cations with the emitter material is reduced, and the emitter material 18 remains without being lost.

As described above, in the present invention, in order to avoid the lighting delay phenomenon in the dark, the emitter material 18 is made to exist at a predetermined position in the lamp, and it functions only at the very initial stage of discharge. Of.

Then, in order to actually compare the product of the present invention with the conventional example, the results of the dark lighting delay experiment for 100 lamps each were as follows. Measurement conditions: -Normal temperature darkness: 60 hours or more-Simultaneous lighting with SGX / 3120HI inverter, experimental results: -Lighting establishment of the product of the present invention: 92% -Establishment of lighting of the conventional product: 40%

As is clear from the above experimental results, it was confirmed that the cold cathode fluorescent lamp according to the present invention has almost no dark lighting delay phenomenon and is quickly lit.

[0027]

As described above, the method for illuminating the light-transmitting liquid crystal display device according to the present invention includes a diffuser plate disposed between a liquid crystal display panel and a flat cold cathode fluorescent lamp to provide a flat cold cathode. By diffusing the light of the fluorescent lamp to back illuminate the liquid crystal display panel, the black spot defects existing in the flat cold cathode fluorescent lamp are diffused by the diffused light so that they do not appear on the liquid crystal display panel. Not only does the display screen look neat, but it can be used even if the black spot defect greatly exceeds the conventional standard, so that the standard can be relaxed and the yield of flat cold cathode fluorescent lamps is improved. Play.

Further, the lighting device according to the present invention is a cold cathode fluorescent lamp used as a backlight of a liquid crystal display panel, and a substance having a function of reducing a cathode drop voltage in a portion other than a main electrode inside the lamp. By arranging the above-mentioned structure, there is an excellent effect that the lighting delay in the dark can be avoided while the structure is simple and inexpensive.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a viewfinder adopting a method of illuminating a light transmission type liquid crystal display device according to the present invention.

FIG. 2 is an explanatory diagram showing an outline of a principle of the illumination method.

FIG. 3 is a schematic cross-sectional view of a cold cathode fluorescent lamp of a lighting device according to the present invention.

FIG. 4 is an explanatory diagram showing a lighting principle of the cold cathode fluorescent lamp.

[Explanation of symbols] 1 viewfinder 2 liquid crystal display panel 2a frame 3 cold cathode fluorescent lamp 4 driving circuit 5 diffuser plate 6 eyepiece 10 glass bulb 11, 12 glass stem 13 anode electrode 14 cathode electrode 15, 16 auxiliary Electrode 17 Phosphor 18 Emitter material

Claims (4)

[Claims] 1. A diffuser plate is disposed between a liquid crystal display panel and a flat cold cathode fluorescent lamp to diffuse the light of the flat cold cathode fluorescent lamp to back illuminate the liquid crystal display panel. A method of illuminating a light-transmissive liquid crystal display device characterized. 2. The method for illuminating a light-transmissive liquid crystal display device according to claim 1, wherein the diffuser plate is disposed with a predetermined gap between the diffuser plate and the flat cold cathode fluorescent lamp. 3. A cold cathode fluorescent lamp used as a backlight of a liquid crystal display panel, characterized in that a substance having an action of reducing a cathode drop voltage is arranged in a portion other than a main electrode inside the lamp. Lighting equipment. 4. The lighting device according to claim 3, wherein the substance having a function of reducing the cathode drop voltage is an emitter substance.