JPH0436950A - Cold cathode fluorescent lamp - Google Patents

Abstract

PURPOSE:To provide a uniform brightness by coating a cylindrical anode with a fluores cent substance over its inner surface, locating a wire-shaped cathode inside the cylindri cal anode, and thereby utilizing ultraviolet rays emitted from neg. glow discharge for energization of the fluorescent substance. CONSTITUTION:Electric discharge is generated by impressing a voltage between an anode 2 and a cathode 4. Because a fluorescent substance film 3 on the anode 2 is charged electrically by this electric discharging, a discharge pause period is provided for canceling it, and voltage is impressed intermittently. When cancel of electric charges on the fluorescent substance film 3 is to be made actively, reverse direction voltage is impressed during the missing periods of this intermittent impression of the voltage. If sufficient discharge current is allowed to flow, neg. glow spreads over the surface of the cathode 4 and its surrounding, and ultraviolet ray emission from the neg. glow is made uniformly form the whole discharge bulb. Thus the fluorescent substance is energized effectively, and efficient light emission is made. Even in a small-sized cold cathode fluorescent lamp. therefore, a vigorous ultraviolet ray emission from the neg. glow, which takes place in the neighborhood of the cathode located on the center axis of a cylindrical anode, can be obtained uniformly form the whole discharge tube, to allow achieving a small-sized cold cathode fluorescent lamp equipped with high brightness.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a cold cathode fluorescent lamp, and more particularly to a cold cathode fluorescent lamp with improved brightness.

BACKGROUND OF THE INVENTION In recent years, cold cathode fluorescent lamps, which are characterized by long life, have been used as light emitting elements for backlight I of liquid crystal display devices and large outdoor display devices. With the miniaturization of liquid crystal display devices and the increase in resolution of large display devices, these cold cathode fluorescent lamps are
It is desired that the device be made smaller and its luminance improved.

Figure 3 shows the structure of a conventional cold cathode fluorescent lamp. As shown in FIG. 3, the discharge tube is composed of a glass tube 1, a glass plate 5 provided with an anode 2 and a cathode 4, and a gas that generates ultraviolet rays by discharge is filled inside the glass plate 5. The ultraviolet light generated by the discharge excites the phosphor 3 coated on the inner surface of the glass tube 1, and emits visible light unique to the phosphor.

Problems to be Solved by the Invention However, when such conventional cold cathode fluorescent lamps are miniaturized, not only are they unable to obtain sufficiently bright luminance (
It became clear that this meant that the luminance of the emitted light became non-uniform.

Generally, in cold cathode discharge, as shown in FIG.
Negative glow 6° Crooks dark area 7 towards the anode 2
．． A positive column 8 is formed.

In the cold cathode fluorescent lamp having the structure shown in Fig. 3, the discharge length becomes shorter as the lamp is made smaller, the positive column 8 decreases, and the negative glow 6 becomes smaller.
The Crookes dark region 7 now occupies the entire tube. At this time, only the negative glow 6 contributes to the light emission, and the light emission from the Crookes dark area 7, which occupies a large proportion in the tube axis direction, is small. Therefore, not only the negative glow 6 in the vicinity of the electrode is bright, but also the excitation efficiency of the phosphor as a whole is lowered, resulting in a reduction in brightness.

The present invention has been made to solve the above problems, and provides a high-intensity compact cold cathode fluorescent lamp with uniform brightness by efficiently utilizing ultraviolet light emission from negative glow discharge for excitation of phosphors.

Means for Solving the Problems Section E In order to solve the problems, the present invention comprises a cylindrical anode, a linear cathode, and a phosphor, and the inner surface of the cylindrical anode is coated with the phosphor, The linear cathode is provided inside the cylindrical anode.

Effect: With this configuration, in a compact cold cathode fluorescent lamp, it is possible to uniformly obtain strong ultraviolet light emission from the negative glow generated near the cathode installed inside the cylindrical anode from the entire discharge tube. , the phosphor is efficiently excited and emitted light.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a partially cutaway side view of a cold cathode fluorescent lamp embodying the present invention. FIG. 2 is an old sectional view taken in a direction perpendicular to the tube axis. In FIG. 1, a cylindrical anode 2 is made of a transparent conductive film made of indium/tin oxide or the like, and is formed on the glass tube 1 from its inner surface to its outer end. A phosphor film 3 is formed by coating on the anode 2. A linear cathode 4 passes along the central axis of the glass tube 1 through glass plates 5 which are hermetically bonded to both ends of the glass tube 1 and is supported in an airtight manner thereby. The gas used is a gas that generates ultraviolet rays when discharged. As for the phosphor and gas filler, those used in current fluorescent lamps can be used.

Discharge is generated by applying a voltage between the anode 2 and the cathode 4. Since the phosphor film 3 of the anode 21 is charged by the discharge,
A discharge stop period is provided to erase this, and voltage is applied intermittently. When attempting to actively erase the charge on the phosphor film 3, a voltage in the opposite direction is applied during the intermittent period.

If a sufficient discharge current is passed, the negative glow will spread around the entire surface of the cathode 4, and the ultraviolet light emitted from the negative glow will be emitted uniformly from the entire discharge tube, efficiently exciting the phosphor and emitting light.

According to this example, even in a compact cold cathode fluorescent lamp, it is possible to uniformly obtain strong ultraviolet light emission from the negative glow generated near the cathode installed at the central axis of the cylindrical anode from the entire discharge tube. This means that a high-intensity compact cold cathode fluorescent lamp can be realized.

In this example, a case where a cylindrical anode and a circular linear cathode were used for the cross-sectional shape was shown, but the point is that if the linear cathode is placed approximately on the central axis of the discharge tube, any cross-sectional shape can be obtained. The effect can also be achieved with elliptical, rectangular anodes and cathodes.

Effects of the Invention As explained in 7-1, according to the present invention, even in a small cold cathode fluorescent lamp, strong ultraviolet rays are generated from the negative glow generated in the vicinity of the cathode installed at the central axis of the cylindrical anode. Luminescence,
Uniformly obtained from the entire discharge tube, it efficiently excites and excites the phosphor.
This enabled the realization of compact, high-brightness cold cathode fluorescent lamps with uniform brightness.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway side view of a cold cathode fluorescent lamp according to an embodiment of the present invention, Fig. 2 is a cross-sectional view of this embodiment when cut in a direction intersecting the tube axis direction, and Fig. 3 is a conventional one. FIG. 4 is a partially cutaway side view of the cold cathode fluorescent lamp shown in FIG. 4, which shows the discharge form formed in the discharge space during gas discharge. 1...Glass tube, 2...Anode, 3...
...phosphor film, 4 ... cathode, 5 ...
・Glass plate. Name of agent: Patent attorney Shigetaka Awano Name: Area

Claims (1)

[Claims] A cylindrical anode, a phosphor film formed on the inner surface of the cylindrical anode, and the linear cathode arranged in the tube axis direction of the cylindrical anode, the cylindrical anode and the cathode. A cold cathode fluorescent lamp with a gas that emits ultraviolet light when discharged between the lamp and the lamp.