JPH03211522A - Display device - Google Patents

Abstract

PURPOSE:To operate the display device without increasing a discharge start voltage even if an ambient temp. is low by providing a heating control means which heats a cold cathode ray tube up to the temp. of the prescribed discharge start voltage. CONSTITUTION:The heating control section 5 which heats the cathode ray tube 3 up to the temp. of the prescribed discharge start voltage is provided near this cathode ray tube 3. The heating control section 5 consists of a heater 5a for heating the cold cathode ray tube 3 and a temp. controller 5b which detects the ambient temp. and turns on the power source of the heater 5a when the ambient temp. falls down to a prescribed temp. or below. The temp. controller 5b operates and the heater 5 is automatically energized when the ambient temp. of the cathode ray tube 3 falls to the specified temp. or below. The cold cathode ray tube 3 is then heated to attain the temp. at which the discharge is possible. The cathode ray tube 3 can maintain the discharge operation in this way even if the ambient temp. falls. The cathode ray tube is thus usable as the light source of the display device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a display device, and particularly to a display device K such as a liquid crystal display device that requires a backlight source.

[Conventional technology]

A time-division type or active matrix type liquid crystal display device can provide a clear display by using a light source that illuminates the back side of a liquid crystal display element.

As a light source for this liquid crystal display element, Japanese Patent Application Laid-Open No. 51-880
There are techniques disclosed in Japanese Patent No. 42 and Japanese Patent Application Laid-Open No. 1-57240. As shown in FIG. 2, this technology uses a cold cathode ray tube 3 as a light source at one end of a transparent plate for light guide (hereinafter referred to as light guide plate 2) corresponding to the size of the display section, that is, the liquid crystal display element 1. The reflection plate 40 provided on the lower surface of the light guide plate 2 has a reflective effect, and the reflection from the cold cathode ray tube 3 to the light guide plate 2
The light passing through the interior is converted into a surface light source to uniformly illuminate the back surface of the liquid crystal display element 1.

[Problem to be solved by the invention]

With the above conventional technology, a uniform surface light source with high brightness can be obtained for the large liquid crystal display element IK, but the cold cathode ray tube 3 used as the light source operates at a low temperature under a predetermined operating voltage. I can't do it.

FIG. 3 is a diagram showing the relationship between the ambient temperature of the cold cathode ray tube 3 and the operating voltage, that is, the discharge starting voltage.

As shown in this diagram, the discharge starting voltage of the cold cathode ray tube is
As the ambient temperature decreases, it is necessary to increase the voltage, so for example, in a cold cathode ray tube whose discharge starting voltage is set to about 250V, it is impossible to discharge when the ambient temperature falls below 5℃, and the liquid crystal display The display of element 1 cannot be clearly seen.

Further, if the discharge starting voltage is set high so that the cold cathode ray tube operates even when the ambient temperature is low, an overvoltage will occur when the ambient temperature is room temperature, and the life of the cold cathode ray tube will be shortened.

An object of the present invention is to provide a display device such as a liquid crystal display device using a cathode ray tube as a light source, which can operate without increasing the firing voltage even when the ambient temperature is low.

[Means to solve the problem]

The above object is to provide a display device that converts the light of a cold cathode ray tube into a surface light source to illuminate a display section, in which the device is provided with a heating control means for heating the cold cathode ray tube to a temperature of a predetermined discharge starting voltage. This is achieved by

[Effect]

When the ambient temperature drops, the heating control means heats the cold cathode ray tube to increase the temperature of the cold cathode ray tube. From this point K, discharge is performed at the set discharge starting voltage. Therefore, cold cathode ray tubes can be used as light sources for display devices such as liquid crystal displays even at low ambient temperatures.

〔Example〕

An embodiment of the present invention will be briefly described below with reference to FIG. Note that the same or equivalent members as in FIG. 2 are given the same reference numerals, and their explanations will be omitted.

As shown in the figure, a heating control section 5 is provided near the cathode ray tube 3 to heat the cathode ray tube 3 to a temperature of a predetermined discharge starting voltage. The heating control unit 5 detects the cold cathode ray tube 3t, the heater 5a that heats it, and the ambient temperature, and turns off the power to the heater 5a when the ambient temperature reaches a predetermined temperature, that is, a temperature below the discharge starting voltage of the cold cathode ray tube 3. It consists of a temperature controller 5b to be switched on, for example a bimetallic thermostat.

It is preferable to provide such a heating control section 5 in a display device, and when the ambient temperature of the cold cathode ray tube 3 is below a certain temperature, for example, 5.
When the temperature reaches .degree. C. or lower, the temperature controller 5b operates, and the cold cathode ray tube 3 is automatically heated to the temperature at which it can be discharged.

Therefore, the cathode ray tube 3 can maintain its discharge operation even when the ambient temperature drops, and can be used as a light source for a display device.

Note that the present invention is not limited to the liquid crystal display element of the above embodiment, but is applicable to all display devices having a display section requiring a surface light source.

〔Effect of the invention〕

According to the present invention, the cold cathode ray tube of the light source can be operated even at low ambient temperatures, thereby expanding the field of use of the display device. Furthermore, since there is no need to increase the discharge starting voltage, there is no fear that the life of the cold cathode ray tube will be shortened.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of an embodiment of a display device according to the present invention, FIG. 2 is a sectional view of a main part of a conventional display device, and FIG. 3 is a diagram showing the firing voltage of a cold cathode ray tube with respect to ambient temperature It is a characteristic line diagram. l...Liquid crystal display element, 2...Transparent plate, 3...
- Cold cathode ray tube, 4...Reflector, 5...Heating control section, 5a...Heater, 5b...Temperature controller. Figure ■ Figure 5: Force A, Foreign Affairs, J Oir Part, Figure Figure 8, Temperature C

Claims (1)

[Claims] 1. A display device that converts light from a cold cathode ray tube into a surface light source to illuminate a display section, comprising heating control means for heating the cold cathode ray tube to a temperature at which it can operate at a predetermined discharge starting voltage. A display device characterized by: