JPH04204415A - Illuminating method for liquid crystal display device - Google Patents

Abstract

PURPOSE:To eliminate the difficulty in reading of a liquid crystal display device at the time of starting driving by controlling the lighting circuit of a fluorescent discharge lamp with the flickering signals of an external illuminating device and controlling the lighting circuit of incandescent lamps with the output of a temp. sensor provided near the electrode of the fluorescent discharge lamp. CONSTITUTION:The fluorescent discharge lamp 3 and the incandescent lamps 41 to 46 are prepd. in a lamp housing 2 as the illuminating device of the liquid crystal display device 1. The incandescent lamps 41 to 46 are simultaneously lighted as well by the output of the temp. sensor 6 which measures the temp. of the fluorescent discharge lamp 3 at the time of low-temp. start. The low-temp. electrode part which is the factor for a decrease in the illuminance of the fluorescent discharge lamp 3 is, therefore, rapidly warmed by the incandescent lamps 41 to 46 and the lighting on and off of the incandescent lamps 41 to 46 are controlled while the heating of the fluorescent discharge lamp 3 is continued up to the optimum temp. by the sensor 6 provided in the position where the sensor is hardly affected by the heat of the incandescent lamps 41 to 46. Then, the brightness of the fluorescent discharge lamp 3 is compensated by the incandescent lamps 41 to 46 which are not so much affected by the ambient temp. at the time of the low temp. at which the brightness of the fluorescent discharge lamp decreases. The failure in reading of the meter board of an automobile at the time of starting the driving is obviated in this way.

Description

[Detailed description of the invention] [! ! Business field of use]

The present invention relates to a method for illuminating a liquid crystal display device used, for example, in an automobile instrument panel.

[Conventional technology]

FIG. 4 shows an example of a conventional illumination method for this type of liquid crystal display grzet, in which the liquid crystal display device 91 is illuminated from the back with a light source and illuminated with transmitted light.
Since the liquid crystal display device 91 is provided with a multicolor display function, a fluorescent discharge lamp 82 having excellent color rendering properties is used as a light source. Further, Japanese Utility Model Publication No. 81-59141 discloses a lighting device in which an incandescent lamp is attached to a fluorescent lamp, which is turned on by a temperature sensor when the temperature is low and by a lighting switch. In this configuration, the incandescent bulb serves as a compensation light source and a heater to compensate for the lack of illuminance of the fluorescent lamp during daytime low temperatures.

[Problem to be solved by the invention]

However, in the conventional lighting method described above, the brightness of the fluorescent discharge lamp 92 decreases significantly in cold weather such as winter, so the heater 9 for increasing the temperature of the discharge lamp is
3, and along with this, a temperature sensor 94, a heater control circuit (not shown), etc. for controlling the heater 93 for humidifying the electric blind lamp are also required, which makes the structure complicated in terms of configuration and control. The problem is that even if the above-mentioned device is provided, its effect is not exhibited until the temperature of the heater 93 for raising the temperature of the discharge lamp reaches a constant temperature. At the beginning, there was a problem in that it was difficult to read the liquid crystal display device 91, and solving these problems became an issue. In the content of Japanese Utility Model Application Publication No. 61-59141, there is an example in which an incandescent light bulb compensates for the lack of illuminance of a fluorescent lamp during daytime low temperatures and acts as a heater, but the specific structure of these is not shown. First, it is unclear whether temperature control is being performed effectively.

[Means to solve the problem]

As a specific means for solving the above-mentioned conventional problems, the present invention provides an illumination method for performing transmitted light illumination using a light source provided on the back surface of a liquid crystal display device, wherein the light source comprises:
A fluorescent discharge lamp provided with a temperature sensor and connected to an independent lighting circuit, and an incandescent light bulb connected to at least two systems of lighting circuits separate from the fluorescent discharge lamp are housed in one housing. arranged and thermally coupled, the lighting circuit for the fluorescent discharge lamp is controlled by a flashing signal from an external lighting device, and at least one line of the lighting circuit for the incandescent lamp is located near the electrode of the fluorescent discharge tube. By providing an illumination method for a liquid crystal display device, which is characterized in that the lighting method is controlled by the output of the temperature sensor provided in the central portion of the fluorescent discharge lamp in the longitudinal direction, the display device can be read immediately after the start of operation. The present invention is intended to solve the above-mentioned conventional problems by making it possible to provide without excessive cost increase.

【Example】

Next, the present invention will be explained in detail based on an embodiment shown in the drawings. What is indicated by the reference numeral 1 in FIGS. 1 and 2 is a liquid crystal display device which is, for example, a meter for an automobile. ~4
6 is housed in an integrated lamp housing 2, which serves as a lighting device, and these fluorescent discharge lamps 3 and incandescent bulbs 41 to 4
6 is configured to be in an operating state regardless of day or night by turning on the ignition switch SW. In this embodiment, an example will be described in which the fluorescent discharge lamp 3 is one and the incandescent lamps 41 to 46 are six, but the present invention is not limited to this. It can be freely changed depending on the area of the liquid crystal display device 1 and the like. Here, according to the present invention, the fluorescent discharge lamp 3 has a lighting circuit 51.
A temperature sensor 6, such as a thermistor, for detecting the temperature of the fluorescent discharge lamp 3 is attached to the longitudinal center of the fluorescent discharge lamp 3.
- 46 are incandescent lamps 41 - 44 provided near the three electrodes of the fluorescent discharge lamp are connected to the lighting circuit 52, and the incandescent lamp 45
．． 46t is connected to the lighting circuit 53 as shown in FIG. 3, forming two series. In addition, a temperature control circuit 7 that closes the circuit at 15° C. and opens the circuit at 25° C., for example, is connected to the temperature sensor 6, and the lighting circuit 52 of the incandescent bulbs 41 to 44 uses this temperature control circuit 7. It is connected to the power supply E through the power supply. Further, the lighting circuit 51 of the fluorescent discharge lamp 3 and the incandescent lamp 45
．． The lighting circuit 53 of 46 is connected to the power source E through a day/night control circuit 8 that closes the circuit in response to a turn-off signal from an external lighting device such as a small lamp or headlamp of an automobile, and opens the circuit in response to a turn-on signal. It has become. Next, the operation of the lighting device of the present invention as described above will be explained. First, when starting operation in the daytime and when the ambient temperature is extremely low, the temperature control circuit 7
and the day/night control circuit 8 are all closed, so all of the lighting circuits 51, 52, 53 are connected to the power source E, and the fluorescent discharge lamp 3 and the incandescent bulbs 41 to 46 are connected to the power source E.
All of them are lit. Therefore, the ambient temperature is extremely low and the fluorescent discharge lamp 3
Although the brightness of the liquid crystal display device 1 is reduced, the lack of brightness is compensated by the lighting of the six incandescent bulbs 41 to 46, and the liquid crystal display device 1 becomes readable. When the operation is continued in this state, since the fluorescent discharge lamp 3 and the incandescent bulbs 41 to 46 are disposed in the integrated lamp housing 2, the radiant heat from the incandescent bulbs 41 to 46 causes the fluorescent discharge lamp to is heated to cause a temperature rise, and when the temperature sensor 6 detects that the temperature has reached a constant temperature, the temperature control circuit 7 is opened. As a result, the lighting circuit 5 connected to the temperature control circuit 7
2 is opened and the incandescent bulbs 41 to 44 are turned off, but at this time the luminance of the fluorescent discharge lamp 3 has been recovered, so reading of the liquid crystal display device 1 is not hindered, and excessive It also prevents temperature rise. Next, the operation at night will be explained. At this time, the day/night control circuit 8 is open, so the fluorescent discharge lamp 3 and the incandescent bulbs 45 and 48 are not turned on, and only the incandescent bulbs 41 to 44 are turned on from the beginning. will be lit.
At this time, for example, if the operating power source of the temperature sensor 6 or the temperature control circuit 7 is configured to be connected to the power source E via the day/night control circuit 8, the operation of the temperature control circuit 7 can be stopped. Therefore, even if the ambient temperature rises, the incandescent bulbs 41 to 44 will not be turned off, and the liquid crystal display device 1 will continue to be illuminated by the incandescent bulbs 41 to 44, which is a combination of the above operations. is Table 1 shown on the next page. ■''

[Incidentally, the reason for lighting only with incandescent bulbs 41 to 44 at night is that there is generally a strong demand for dimming at night, so incandescent bulbs 41 to 44 are used, which are easier to dim by changing the pulse duty ratio, for example. Therefore, we have taken measures to meet this demand, and when there is no need for dimming, it is possible to use the same configuration as in the daytime. In addition, in order to cope with a further rise in ambient temperature during the daytime, for example in the summer, a second temperature control circuit 9 which opens at 40° C., for example, is added to the side of the lighting open circuit 53, and when the temperature exceeds the above temperature, all It is also possible to configure the incandescent lamps 41 to 46 to turn off, and the point is to provide a method for compensating for the lack of brightness of a fluorescent discharge lamp by using an incandescent lamp that is not affected by the ambient temperature at low temperatures, which is the gist of the present invention. If so, you are free to adopt any control method. Effects of the Invention As explained above, according to the present invention, a fluorescent discharge lamp and an incandescent lamp are provided in an integrated lamp housing as a lighting device for a liquid crystal display device, and the temperature of the fluorescent discharge lamp is measured when starting at a low temperature. By using a control method that simultaneously turns on the incandescent bulb using the output of the temperature sensor, the incandescent bulb can quickly warm up the low-temperature electrode part, which is the cause of the decrease in illuminance in fluorescent discharge lamps, and also reduce the heat generated by the incandescent bulb. The sensor installed in a position that is less susceptible to the effects of ambient temperature makes it possible to control the incandescent bulbs to turn on and off while continuing to heat the fluorescent discharge lamp to the optimum temperature. This compensates for the brightness of incandescent light bulbs, which is effective in solving problems such as the inability to read the instrument panel of a car at the start of driving. In addition, with the above configuration, the fluorescent discharge lamp is heated by an incandescent bulb, so there is no need to provide a heater, which simplifies the configuration and reduces costs.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view showing an embodiment of the illumination method for a liquid crystal display device according to the present invention, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1, and FIG. 4 is a wiring diagram showing the connection state of the same embodiment, and FIG. 4 is a sectional view showing a conventional example. 1.....Liquid crystal display device 2.....
・Lamp housing 3------Fluorescent discharge lamp
41-46...Baketsu light bulbs 51-53...
・・・・・・Lighting circuit

Claims (2)

[Claims] (1) In a lighting method in which transmitted light illumination is performed using a light source provided on the back of a liquid crystal display device, the light source includes a fluorescent discharge lamp provided with a temperature sensor and connected to an independent lighting circuit, and the fluorescent discharge lamp. An incandescent light bulb connected to at least two systems of lighting circuits separate from the fluorescent discharge lamp is disposed in an integrated lamp housing and is thermally coupled, and the lighting circuit of the fluorescent discharge lamp is connected to an external lighting circuit. Controlled by a blinking signal of the device, at least one series of the lighting circuit for the incandescent lamp is provided near the electrode of the fluorescent discharge tube, and is controlled by the output of the temperature sensor provided in the longitudinal center of the fluorescent discharge lamp. A lighting method for a liquid crystal display device, characterized in that: (2) A series of lighting circuits for the incandescent light bulb are controlled by the blinking signal.
1) A method for illuminating a liquid crystal display device according to item 1).