JPH03296018A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent the generation of a delay in the start of the electric discharge of a fluorescent tube and to allow the sure emission of images when a power source is turned on by providing an auxiliary light source and irradiating the fluorescent tube with light. CONSTITUTION:This device has a liquid crystal panel 1 for displaying the images, the fluorescent tube 2 to serve as the light source for the liquid crystal panel 1 and the auxiliary light source 8 for irradiating the fluorescent tube 2 with the light. The liquid crystal panel 1 and the fluorescent tube 2 are driven and an incandescent lamp 8 is driven when a power source is impressed to a driving circuit 6. The incandescent lamp is lighted for a specified period of time and the light of the incandescent lamp 8 falls onto the fluorescent tube 2; therefore, the electric discharge is liable to be generated in the fluorescent tube 2 by a photoelectric effect. The electric discharge is then started immediately and the fluorescent tube is lighted. The delay time at the start of the discharge of the fluorescent tube is shortened in this way and the sure emission of the images is executed when the power source is turned on.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid crystal display device using a liquid crystal panel to display images.

2. Description of the Related Art In recent years, the number of liquid crystal display devices such as color liquid crystal TVs that display TV images using liquid crystal panels has increased, and they have also come to be used in viewfinders of video cameras.

Conventionally, video cameras have been made using this type of liquid crystal panel. The configuration will be explained below.

As shown in the figure, the liquid crystal panel 1 displays images, and is provided with a fluorescent tube that serves as a light source for the liquid crystal panel 1. A diffuser plate 3 is placed between the liquid crystal panel 1 and the fluorescent tube 2, and the fluorescent tube 2
A reflecting plate 4 is arranged behind the. The eyepiece 5 performs focus adjustment and magnification when viewing. The liquid crystal panel 1 and the fluorescent tubes 2 are driven by a drive circuit 6. These liquid crystal panels1. Fluorescent tube 2. The diffuser plate 4 and the drive circuit 6 are housed in a case 7.

The operation of the above configuration will be explained.

When the liquid crystal panel 1 and the fluorescent tubes 2 are driven by the drive circuit 6, the light emitted from the fluorescent tubes 2 is turned into a surface light source by the reflection plate 4 and the diffuser plate 3. The image is then converted into an image and displayed on the LCD panel 1. This image can be enlarged and focused using the eyepiece 5 for viewing.

Problems to be Solved by the Invention In the liquid crystal display device as described above, the fluorescent tube 2 is surrounded by the case 7 and the eyepiece 5, and is turned on in pitch darkness. In view finders, in particular, in order to downsize and extend the lifespan, the fluorescent tube 2 does not have a heater like a normal fluorescent lamp, and when it is turned on, it starts discharging by cold cathode operation. For this reason, it is necessary to start the discharge using only the alternating current voltage applied to the fluorescent tube 2. However, if the fluorescent tube 2 is left unlit for a long period of time while fishing on a boat and is turned on in pitch darkness, it is necessary to There is a discharge start delay phenomenon in which the light does not turn on immediately and the start of discharge is delayed when only the voltage is applied, and in some cases, the start of discharge is delayed for several tens of seconds. That is, the image will not be visible until the fluorescent tube 2 is turned on.

The present invention solves the above problems, and provides a liquid crystal display device that is provided with an auxiliary light source that irradiates light to the fluorescent tubes, shortens the discharge start delay time of the fluorescent tubes, and reliably displays an image when the power is turned on. It is an object.

Means for Solving the Problems In order to achieve the above objects, the present invention provides a liquid crystal panel for displaying images, a fluorescent tube serving as a light source for the liquid crystal panel, and an auxiliary light source for irradiating light to the fluorescent tube. The first means of solving the problem is to have the following. In addition to the first means for solving the problem, a second means for solving the problem is that the auxiliary light source is a light source that does not utilize cold cathode discharge. Furthermore, in addition to the first or second problem-solving means described above, a third problem-solving means is that the auxiliary light source is turned on only for a certain period of time after the power is turned on.

In addition to the first or second problem-solving means, a fourth problem-solving means is that the lighting of the auxiliary light source is controlled by the output of the detection means that detects the lighting of the fluorescent tube. Furthermore, in addition to the first means for solving the problem, a fifth means for solving the problem is that the auxiliary light source is an external light irradiation means for applying external light.

Operation The present invention has the above-mentioned first problem solving means, whereby the fluorescent tube is irradiated with light from the auxiliary light source, thereby giving the fluorescent tube light energy, and the fluorescent tube is easily discharged due to the photoelectric effect. Can be lit immediately. Further, according to the second problem-solving means, the auxiliary light source can be turned on at the same time as the power is turned on, and the fluorescent tube can be immediately turned on by applying light energy to the fluorescent tube.

Furthermore, according to the third problem-solving means, the auxiliary light source emits light while the fluorescent tube is turned on, and the fluorescent tube can be reliably turned on when the power is turned on. Further, according to the fourth problem solving means, the auxiliary light source is turned on until the fluorescent tube is lit, and the fluorescent tube can be reliably lit by the auxiliary light source. Furthermore, the fifth
With the problem solving means, the fluorescent tube is irradiated with external light from the external light irradiation means, and the fluorescent tube can be reliably lit by this external light.

EXAMPLES Hereinafter, examples of the first and second problem solving means of the present invention will be described with reference to FIG. Note that components having the same configuration as those of the conventional example are given the same reference numerals, and description thereof will be omitted.

As shown in the figure, the light bulb 8 is placed on the rear side of the fluorescent tube 2 (reflector 1
4 side) to irradiate light onto the fluorescent tube 2 as an auxiliary light source.

Next, the operation will be explained. When power is applied to the drive circuit 6, the drive circuit 6 controls the liquid crystal panel 1, the fluorescent tubes 2, .
The light bulb 8 is driven. The light bulb 8 is connected between the power supplies of the drive circuit 6. The image on the liquid crystal panel 1 can be viewed through the eyepiece 5 as in the conventional example. If the fluorescent tube 2 causes a delay in the start of discharge when the power is turned on, the light bulb 8 will shine at the same time as the power is turned on even in pitch darkness because the light bulb 8 does not utilize discharge, so the light from the bulb 8 will hit the fluorescent tube 2. . Therefore, the photoelectric effect of the fluorescent tube 2 makes it easier to discharge, and the discharge starts immediately, causing lighting. At this time, the illuminance is only a few lux and the photoelectric effect appears, so the brightness needs to be much lower than the brightness of the fluorescent tube 2. Although this embodiment has been described using the light bulb 8 as the auxiliary light source, any light source may be used as long as it can provide a brightness that produces the photoelectric effect of the fluorescent tube 2 and does not utilize cold cathode discharge. For example, it may be a light emitting diode of a semiconductor optical device.

As described above, according to the liquid crystal display device of the embodiment of the first and second problem solving means, the light bulb 8 is provided as an auxiliary light source that does not utilize cold cathode discharge, and the fluorescent tube 2 is irradiated with light. 2 does not become completely dark, the fluorescent tube 2 easily discharges due to the photoelectric effect, it is possible to prevent the occurrence of a delayed discharge start phenomenon of the fluorescent tube 2, and it is possible to reliably display an image when the power is turned on.

Next, description of the embodiment of the third problem-solving means of the present invention will be omitted.

As shown in the figure, a light bulb 8 is provided on the rear side of the fluorescent tube 2, and serves as an auxiliary light source to irradiate the fluorescent tube 2 with light, and is turned on for a certain period of time after power is turned on by a control circuit 9.

Next, the operation will be explained. When power is applied to the drive circuit 6, the drive circuit 6 drives the liquid crystal panel 1 and the fluorescent tubes 2, and the control circuit 9 drives the light bulb 8, which lights up for a certain period of time. At this time, since the light bulb 8 does not utilize discharge, it lights up as soon as the power is turned on even in pitch darkness, so the light from the light bulb 8 hits the fluorescent tube 2. Therefore, the photoelectric effect of the fluorescent tube 2 makes it easier to discharge, and the fluorescent tube 2 immediately starts discharging and lights up.The illuminance at this time is a few lux, and the photoelectric effect appears.Then, after a certain period of time, the light bulb 8 is turned off, and the image on the liquid crystal panel 1 can be viewed through the eyepiece 5 as described above.The auxiliary light source only needs to be turned on when the power is turned on, and it is not needed after the fluorescent tube 2 is turned on, so the time is short. There is no increase in power consumption, and there is no effect on the screen.

It should be noted that the auxiliary light source may be anything that can provide a brightness that produces the photoelectric effect of a fluorescent tube and does not utilize cold cathode discharge, such as a light emitting diode.

As described above, according to the liquid crystal display device of the embodiment of the third problem solving means, it is possible to prevent the occurrence of the delay in the start of discharge of the fluorescent tube 2, and it is possible to reliably display an image when the power is turned on. Since the auxiliary light source is turned on only for a certain period of time, there is no increase in power and no effect on the image.

Next, an embodiment of the fourth problem-solving means of the present invention will be described with reference to FIG. Components having the same configuration as those in the above embodiment are given the same reference numerals and explanations will be omitted.

As shown in the figure, the light bulb 8 is placed behind the fluorescent tube 2,
Light is irradiated onto the fluorescent tube 2 as an auxiliary light source. Detection means 10
consists of a phototransistor, a photodiode, etc., which are charging conversion elements that detect the lighting of the fluorescent tube 2.
A control circuit 11 is provided which controls lighting of the light bulb 8 based on the output of the detection means 10.

Next, the operation will be explained. When power is applied to the drive circuit 6, the drive circuit 6 drives the liquid crystal panel 1 and the fluorescent tubes 2. At this time, if the fluorescent tube 2 is not lit due to a discharge delay phenomenon, the detection means 10 detects the non-lighting, and the control circuit 11 drives the light bulb 8 to turn on the light bulb 8.

Since the light bulb 8 does not utilize electric discharge, it lights up at the same time as it is driven even in pitch darkness. Therefore, the light from the light bulb 8 hits the fluorescent tube 2, and the photoelectric effect of the fluorescent tube 2 makes it easier to discharge, so that the discharge starts immediately and the lamp turns on.

At this time, the illuminance is several lux, and the charging effect appears, so the brightness of the light bulb 8 is dark and has a large difference from the brightness of the fluorescent tube 2. Based on this difference, the detection means 10 detects the lighting of the fluorescent tube 20, and its output is As a result, the control circuit 11 stops driving the light bulb 8, and the light bulb 8 is turned off. When the fluorescent tube 2 is turned on, the image on the liquid crystal panel 1 can be viewed through the eyepiece 5.

The light bulb 8, which is an auxiliary light source, is turned on only when the fluorescent tube 2 causes a discharge delay phenomenon, and the light bulb 8 is turned on.
As soon as the light hits the fluorescent tube 2, the fluorescent tube 2 is lit and the light bulb 8 is turned off, so the time is very short, there is almost no need for an increase in power, and there is no effect on the screen.

The auxiliary light source may be any source that can provide the brightness that produces the photoelectric effect of a fluorescent tube and does not utilize cold cathode discharge.
For example, it may be a light emitting diode of a semiconductor optical device.

Further, the detection means 10 may be of any type as long as it can detect the lighting of the fluorescent tube 2 (for example, it is also possible to use a method of detecting the current of the fluorescent tube).

In this way, according to the liquid crystal display device of the embodiment of the fourth problem solving means, lighting of the fluorescent tube 2 is detected, and the lighting of the fluorescent tube 2 is detected.
By providing an auxiliary light source and irradiating light between the fluorescent tubes 2 until the fluorescent tubes 2 turn on, the fluorescent tubes 2 are not in a completely dark state and are easily discharged due to the photoelectric effect, causing a delay in the start of discharge of the fluorescent tubes 2. It is possible to prevent this from happening, and the image can be reliably displayed when the power is turned on, and since the auxiliary light source is turned on only when the fluorescent tube 2 causes a discharge delay phenomenon, there is no increase in power and no influence on the image.

Next, an embodiment of the fifth problem-solving means of the present invention will be described with reference to FIG. Components having the same configuration as those in the above embodiment are given the same reference numerals and explanations will be omitted.

As shown in the figure, the external light irradiating means 12 is provided in a part of the case 7, is made of a light-transmissive member, and serves as an auxiliary light source by directing external light onto the fluorescent tube 2.

Next, the operation will be explained. When power is applied to the drive circuit 6, the drive circuit 6 drives the liquid crystal panel 1 and the fluorescent tubes 2. At this time, the fluorescent tube 2 is illuminated with external light by the external light irradiation means 12.

Therefore, the fluorescent tube 2 is in a state where it is easily discharged due to the photoelectric effect, and the discharge starts immediately and the lamp is lit. The reflection plate 4 and diffuser plate 3 of the fluorescent tube 2 serve as a surface light source, which is converted into an image by the liquid crystal panel 1. This image can be viewed through the eyepiece 5.

Since the illuminance of the fluorescent tube 2 at which the photoelectric effect occurs may be several lux, a certain degree of transmittance is sufficient. In addition, the external light irradiation means 1
2, since it is sufficient to expose the fluorescent tube 12 to external light, it is also possible to simply provide holes, slits, etc. in the case 7 to provide appropriate brightness.

Next, another embodiment of the fifth problem-solving means of the present invention will be described with reference to FIG. Components having the same configuration as those in the above embodiment are given the same reference numerals and explanations will be omitted.

As shown in the figure, the optical fiber 13 is provided so as to irradiate external light to the rear side of the fluorescent tube 2 to form an external light irradiation means 12 and serve as an auxiliary light source.

As described above, since the optical path can be freely selected by using the optical fiber 13, external light can be applied only to the rear side of the fluorescent tube 12 (the side opposite to the liquid crystal panel 1). Therefore, since external light does not appear on the 1ft4 liquid crystal panel, its influence on the image can be eliminated, and the color temperature of the image can be determined by the color temperature of the light emitted from the fluorescent tube 2.

As described above, according to the liquid crystal display device of the embodiment of the fifth problem solving means, by providing the external light irradiating means 12 in a part of the case 7 in order to irradiate the fluorescent tube 2 with external light,
The fluorescent tube 2 is not in a completely dark state and is easily discharged due to the photoelectric effect, so that the occurrence of a delayed discharge start phenomenon of the fluorescent tube 2 can be prevented, and an image can be reliably output when the power is turned on. Further, as the external light irradiation means 12, an optical fiber 13, which can freely take the optical path, is used to radiate the fluorescent tube 2.
It is also possible to eliminate the effect on the image by shining external light only on the rear side.

Effects of the Invention As is clear from the above embodiments, according to the present invention, by providing an auxiliary light source and irradiating light onto the fluorescent tube, the fluorescent tube is not in a completely dark state and is easily discharged due to the photoelectric effect.
It is possible to prevent the occurrence of a delayed discharge start phenomenon of fluorescent tubes, and it is possible to reliably display an image when the power is turned on.

[Brief explanation of the drawing]

1 to 5 are cross-sectional views of liquid crystal display devices according to embodiments of the present invention, and FIG. 6 is a cross-sectional view of a conventional liquid crystal display device. 1...Liquid crystal panel, 2...fluorescent tube, 8...bulb diagram (auxiliary light source)

Claims (5)

[Claims] (1) A liquid crystal display device comprising a liquid crystal panel for displaying images, a fluorescent tube serving as a light source for the liquid crystal panel, and an auxiliary light source for irradiating light to the fluorescent tube. (2) The liquid crystal display device according to claim 1, wherein the auxiliary light source is a light source that does not utilize cold cathode discharge. (3) The liquid crystal display device according to claim 1 or 2, wherein the auxiliary light source is turned on only for a certain period of time after power is turned on. (4) The lighting of the auxiliary light source is controlled by the output of a detection means for detecting lighting of a fluorescent tube.
The liquid crystal display device described. (5) The liquid crystal display device according to claim 1, wherein the auxiliary light source serves as external light irradiation means for applying external light.