JPH10283989A - Cold cathode discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce consumed power, and enhance luminous efficiency by confrontation-arranging an electrode made of a high melting point metal-made electrode stem whose sharp head portion is formed facing to a discharge space and a high melting point metal-made wire, closely sticking winding the wire coil-like on the sharp head portion so as to form a hollow portion inside to be an opening-shape facing to the discharge space. SOLUTION: The tip portion of an electrode stem 6 made of high melting point metal such as tungsten or the like having stable degassing action is sharpened facing to a discharge space, and a wire made of the high melting point metal such as the tungsten or the like is closely sticking wound loosely on the electrode stem 6 as a primary coil 7a. Further thereon, the same wire is densely wound closely sticking to the primary coil 7a as a secondary coil 7b so as to form a hollow portion 8 to be an opening shape facing to the discharge space. The sharp head shape angle θ of the electrode stem 6 is set to 30 deg.<=θ<=60 deg. so as to be set in such a range where a hollow electrode effect is easily produced so that stable characteristics are maintained without causing any change of the sharp head shape in long time lighting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small-sized cold cathode discharge lamp used for a small fluorescent lamp for a backlight of a liquid crystal panel, a germicidal lamp, and the like, and relates to an improvement in an electrode structure thereof.

[0002]

2. Description of the Related Art In recent years, as an electrode structure of a small-sized cold-cathode discharge lamp used for a small fluorescent lamp and a germicidal lamp for a backlight of a liquid crystal panel, as disclosed in Japanese Patent Application Laid-Open No. 5-110443, a cylindrical shape is used. Powder sintered body is heated,
There are a cylindrical molded electrode that releases mercury contained in a powder sintered body, and a discharge lamp that uses a hollow electrode made of a high melting point metal disclosed in JP-A-6-52827. The hollow electrode (hollow cathode) is formed by winding a high melting point wire in a coil shape to form a cylindrical structure as a whole, or by forming a high melting point metal into a sleeve shape to form a hollow portion formed inside the discharge space. It has a structure that opens toward

[0003]

However, although the electrode has a function of suppressing the occurrence of abnormal glow discharge from the end face of the cylindrical electrode or the end face of the high melting point wire to some extent, the lamp current increases. Then, there is a problem that the discharge from the end face shifts from a normal glow discharge to an abnormal glow discharge. In addition, when the lamp power is increased to several W to 10 W or more, and application to a small-sized cold cathode discharge lamp with a large brightness is performed, the scattering of electrode materials due to ion bombardment is large, and the blackening phenomenon occurs on the inner wall of the lamp at an early stage. Appears, and there is a problem that light quantity decay is rapid during the service life.

[0004] Further, since the high electron density portion is the end face of the cylindrical electrode or the end face of the high melting point wire, abnormal glow discharge is likely to occur from the end face, and the outer surface of the cylindrical shaped electrode or hollow electrode is damaged. There is also a problem that a glow discharge is generated which causes the discharge to become unstable and the electrode material is beaten out and adhered to the tube wall to cause blackening.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in a conventional small-sized cold cathode discharge lamp using a cylindrical shaped electrode or a hollow electrode. By forming it on the pointed tip, that is, on the central axis of the electrode, even if the current is increased, the hollow electrode effect due to cumulative ionization is effectively generated, the cathode drop voltage that does not contribute to light emission is reduced, power consumption is reduced, and light emission is reduced. The purpose of the present invention is to provide a small-sized cold-cathode discharge lamp that has a long life and excellent lamp characteristics without increasing the efficiency, generating no abnormal glow discharge, and preventing the glow discharge from covering the outer surface of the electrode. And

[0006]

In order to solve the above-mentioned problems, according to the first aspect of the present invention, electrodes arranged opposite to a discharge space are sealed at both ends of a bulb, and at least mercury and diluent are contained therein. This electrode is composed of a refractory metal electrode rod with a pointed head toward the discharge space, and a high-melting point metal wire. It is characterized in that it is wound to form a hollow portion inside and is opened toward the discharge space.

[0007]

Next, an embodiment will be described. FIG. 1 is a configuration diagram showing one embodiment of a small-sized cold cathode discharge lamp according to the present invention. The quartz glass light emitting bulb 1 surrounding the discharge space has an outer diameter of 10 mm and a thickness of 1 mm.
The electrodes 2 are arranged opposite to each other and sealed at both ends of the arc tube bulb 1, and a predetermined amount of rare gas such as argon and mercury are sealed therein. Further, sealing portions 3 are formed at both ends, and the electrodes 2 and the external lead rods 5 are welded and sealed to the molybdenum foil 4.

FIG. 2 is a sectional view showing an electrode structure according to the present invention. The tip of the electrode core bar 6 made of a refractory metal such as tungsten having a stable degassing action and having a diameter of 1.7 mm and a total length of 15.4 mm is pointed toward the discharge space. As a primary coil 7a, a metal φ0.8 mm wire is closely contacted with the electrode core 6 and sparsely wound thereon, and further, the wire is further wound on the secondary coil 7b.
A hollow portion 8 is formed by closely contacting the primary coil 7a and tightly wound to form a shape that opens toward the discharge space.

The angle θ of the pointed shape of the electrode core rod 6 is 30 °.
.Ltoreq..theta..ltoreq.60.degree. Is the range in which the hollow electrode effect is most likely to occur, has sufficient mechanical strength, does not change the peak shape even during long-time operation, and can maintain stable discharge and lamp characteristics.

[0010]

As described above, according to the present invention, the hollow electrode effect of forming a high electron density portion due to the cumulative ionization at the center axis of the electrode occurs, and the cathode drop voltage that does not contribute to light emission is reduced, and therefore, the consumption voltage is reduced. There is an advantage that the power is reduced and the luminous efficiency is improved. Further, since a high electron density portion is formed concentrated on the central axis of the electrode, even if the output of the arc tube is increased, it is possible to sufficiently cope with the supply of the increased current, and high luminance can be achieved. Since the high electron density portion can sufficiently cope with an increase in the lamp current, it is possible to easily increase the output of the cold cathode discharge lamp.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a small-sized cold cathode discharge lamp according to the present invention.

FIG. 2 is a sectional view of an electrode structure according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Arc tube 2 Electrode 3 Sealing part 4 Molybdenum foil 5 External lead rod 6 Electrode core rod 7a Primary coil 7b Secondary coil 8 Hollow part

Claims (3)

[Claims] 1. An electrode disposed opposite to a discharge space at both ends of a bulb is sealed, and at least mercury and a rare gas are sealed therein. The electrode has a pointed head toward the discharge space. An electrode core rod made of a high melting point metal and a wire made of a high melting point metal, the wire is closely wound around the pointed tip in a coil shape to form a hollow portion inside, and has a shape opened toward the discharge space. A cold cathode discharge lamp characterized in that: 2. The cold-melting metal wire according to claim 1, wherein said high-melting-point metal electrode rod is made of tungsten, the peak angle is made 30 ° ≦ θ ≦ 60 °, and said high-melting-point metal wire is made of tungsten. Cathode discharge lamp. 3. The method according to claim 1, wherein the refractory metal wire is wound twice around the sharp tip of the refractory metal electrode rod, the inner coil is loosely wound, and the outer coil is densely wound. The cold cathode discharge lamp according to claim 1 or 2, wherein: