JP3348421B2 - Lighting method of light transmission type liquid crystal display device - Google Patents

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 for a liquid crystal display device using a light transmission type liquid crystal display element.

[0002]

2. Description of the Related Art A light-transmissive liquid crystal display element of this type uses a color liquid crystal display panel for displaying an image in a viewfinder of a video camera, for example. A flat light emitting cold cathode fluorescent lamp is used as a back lighting device on the back side of the color liquid crystal display panel. The cold-cathode fluorescent lamp itself is configured to be in a plane emission state so that no other member such as diffusing light is required for illuminating the flat member. .

[Problems to be solved by the invention]

In the view finder, since the color liquid crystal panel is viewed through an eyepiece having a predetermined magnification, the black spot defect and the attached dust of the cold cathode fluorescent lamp, which is the back illumination, can be seen as it is. Since black dots are scattered in a display image and cannot be seen clearly, a certain standard is specifically provided for black spot defects. The standard of the black spot defect in the cold cathode fluorescent lamp is such that the size of the black spot is very strict, for example, φ0.1 mm or less, so that the yield of the cold cathode fluorescent lamp meeting the standard is poor and the cost is increased. Have a point.

[0004] Further, the cold cathode fluorescent discharge lamp shows a phenomenon that the lighting performance becomes extremely poor when left in the dark for a long time. This is generally called a dark lighting delay. As measures to avoid this, a lighting assist light bulb, an LED, or the like is attached, or an auxiliary electrode is provided inside the lamp to increase the lighting performance.

[0005] However, there is a problem that mounting the bulb or LED is expensive, and the auxiliary electrode has a problem that the lighting performance is deteriorated when an impurity gas such as chlorine gas enters. ing.

[0006] Therefore, in the conventional example, the back lighting and
The flat cold-cathode fluorescent lamp used in the conventional method has a problem that must be solved to eliminate a display that is difficult to see due to a black spot defect.

[0007]

As a specific means for solving the problems of the prior art, the present invention provides at least a liquid crystal display panel.
Of a liquid crystal display device having a panel and a flat cold cathode fluorescent lamp
A lighting method, between the liquid crystal display panel and the flat cold cathode fluorescent lamps, flat-type cold cathode fluorescent lamp substantially 1-2
mm and a transmittance close to 90 to 95%
A diffuser plate with high transmittance is provided to reduce the illumination
Black spot defects and so as not to please flat type cold cathode fluorescent lamp
It is an object of the present invention to provide a method of illuminating a light-transmitting liquid crystal display element, which comprises back-illuminating a liquid crystal display panel by diffusing light so as to solve the problem .

[0008]

The flat cold-cathode fluorescent lamp is located between the liquid crystal display panel and the flat cold-cathode fluorescent lamp by approximately 1 to 2 mm.
By disposing a diffusion plate having a high transmittance of approximately 90 to 95% with a gap, the black spot defect of the back lighting device can be sufficiently diffused without lowering the illuminance , and can be enlarged by a lens. Also, the black spot defect becomes inconspicuous and the screen looks beautiful.

[0009]

FIG. 1 shows a viewfinder 1 of a video camera, in which a liquid crystal display panel 2 and a flat type back panel are shown. A cold cathode fluorescent lamp 3 serving as an illumination device and 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-transmitting 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 diffusion plate 5 is provided between the liquid crystal display panel 2 and the cold cathode fluorescent lamps 3 to illuminate the liquid crystal display panel 2 from the back side by diffusing light from the cold cathode fluorescent lamps 3. The user can see an image or a screen of the liquid crystal display panel 2 through the eyepiece 6.

The diffuser plate 5 used in this case has a relatively low diffusivity and a high transmittance. For example, a diffuser having a transmittance of about 90 to 95% is used. Does not decrease so much as a backlight.

Further, as shown in FIG. 2, if the diffusion plate 5 is disposed at an interval of about 1 to 2 mm with respect to the cold cathode fluorescent lamp 3, the cold cathode fluorescent lamp 3
Black spot defects and the like become almost inconspicuous. In particular,
Beyond the standard of black spot defects (φ0.1 mm or less) in the conventional example, for example, even if it is about φ0.3 mm, it can be almost ignored.

Further, the liquid crystal display panel 2 has a frame 2a on the outer peripheral surface thereof.
They are 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. This is because if the interval is increased, the cold cathode fluorescent lamp 3 must be enlarged as shown by the imaginary line, and the viewfinder 1
This is due to reasons such as being arranged in a restricted space inside.

Therefore, under these restrictions, a thin diffusion plate 5 having a thickness of about 100 to 500 μm is used, and the diffusion plate 5 from the liquid crystal display panel 2 to the cold cathode fluorescent lamp 3 is 10 to 1 μm.
When the thickness is set to about 5 mm, the black spot defect can be diffused without significantly lowering the luminous efficiency of the cold cathode fluorescent lamp 3. Further, depending on the diffusion plate used, sufficient diffusion is possible without leaving any gap.

The specific structure of the cold cathode fluorescent lamp 3 is as follows.
This is as shown in FIG. That is, glass stems 11 and 12 are attached to both ends of a flat glass bulb 10, and anode electrodes 13 and cathode electrodes 14 and auxiliary electrodes 15 and 16 are attached through the stems, respectively.
A fluorescent substance 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 delay in lighting of the cold cathode fluorescent lamp 3 in the dark, an emitter material 18 is applied to the inside of the lamp and to a predetermined position excluding the main electrodes of the anode electrode 13 and the cathode electrode 14. And so on.

This coating position is preferably near the anode electrode 13, but can also be applied near the cathode electrode 14 or the auxiliary electrodes 15 and 16.
7 can be arranged in a mixed state.

The emitter material 18 is a material having a function of reducing the cathode drop voltage. For example, a metal such as calcium, strontium, barium, cesium, or an oxide or a carbonate is used. Generally, the stems 11 and 12 are in the form of carbonates that are stable as a substance.
It is applied to the inside of the lamp and the auxiliary electrodes 15 and 16 and is heated during the manufacture of the lamp and brought into a state close to a vacuum, thereby releasing carbon dioxide gas and existing as an oxide.

If the position of the emitter material 18 is, for example, inside the stem 11 to which the anode electrode 13 is attached, as shown in FIG. 4, the glass of the stem 11 is an insulator, but equivalently. Considering, the emitter material 18 is connected to the atmosphere (GND) via a very small capacitor C and a very large resistor R.

In the initial stage of lighting of the cold cathode fluorescent lamp 3 (still before discharge occurs 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. As a result, electrons are emitted from the emitter material and a weak discharge occurs between the emitter material and the anode electrode. This weak discharge becomes seed discharge, 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 turned on in this manner, the voltage between the anode and the cathode usually drops to about 700 V.
8 hardly occurs. Therefore, since the collision of the cations with the emitter material is reduced, the emitter material 18 remains without being lost.

As described above, in the present invention, the emitter material 18 is provided at a predetermined position in the lamp in order to avoid the lighting delay phenomenon in the dark, and functions only at the very beginning of the discharge. It is.

For the purpose of comparing the product of the present invention with the conventional example, the results of an experiment of dark lighting delay for 100 lamps were as follows. Measurement conditions:-Dark room temperature: 60 hours or more-Immediate lighting with the SGX-3120HI inverter-Experimental results:-Lighting of the product of the present invention: 92%-Lighting of the conventional product: 40%

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

[0027]

As described above, the method for illuminating a light-transmitting liquid crystal display device according to the present invention can be applied to at least a liquid crystal display panel.
Of a liquid crystal display device having a display panel and a flat cold cathode fluorescent lamp.
A flat cold-cathode fluorescent lamp between the liquid crystal display panel and the flat cold-cathode fluorescent lamp by about 1 to 2 m.
high transmittance of approximately 90 to 95% with a gap close to m
Dispersion plate with transmittance is provided to reduce the illuminance.
To avoid black spot defects in flat cold cathode fluorescent lamps.
By illuminating the liquid crystal display panel by back-lighting by diffusing the light to eliminate it, the black spot defects present in the flat-type cold cathode fluorescent lamp are diffused by the diffused light so as not to appear on the liquid crystal display panel. Not only does this look beautiful, but it can be used even when 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 can be improved.

[0028]

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a viewfinder employing an illumination method for a light transmission type liquid crystal display element according to the present invention.

FIG. 2 is an explanatory view schematically showing the principle of the illumination method.

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 View finder 2 Liquid crystal display panel 2a Frame 3 Cold cathode fluorescent lamp 4 Drive circuit 5 Diffusion 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 (1)

(57) [Claims] At least a liquid crystal display panel and a flat cold cathode
A method for illuminating a liquid crystal display device having a fluorescent lamp.
Te, between the liquid crystal display panel and the flat cold cathode fluorescent lamp,
A gap close to the flat cold cathode fluorescent lamp and approximately 1 to 2 mm
A diffusion plate having a high transmittance of about 90 to 95% is provided so that the illuminance is not reduced by the diffusion plate.
A method for illuminating a light-transmissive liquid crystal display element, wherein light is diffused to eliminate black spot defects of a flat cold cathode fluorescent lamp to back-illuminate a liquid crystal display panel.