JP2002358922A - Cold cathode discharge tube and manufacturing method of same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a cold cathode discharge tube by connecting electrodes made of sputtering resistant metal with internal lead at a temperature with no harmful overheat effect. SOLUTION: A cold cathode discharge tube is equipped with electrode assemblies (20) composed of metal leads (11) and electrodes (3) fixed to the leads (11), a glass tube (7) filled up with gas for discharge and fitted with the electrode assemblies (20) at both ends, and a fluorescent film coated on the inside surface of the glass tube (7) and giving off visible light on irradiation of ultraviolet rays generated by discharge of the electrodes (3). A sputtering resistant electrode (3) is made of tantalum, titanium, or niobium, or an alloy of two or more of these metals. Further, in order to protect a welding electrode (17) or glass beads (2) from damage, the electrodes (3) and the leads (11) are bonded with a metal film (1) with a lower fusing point than that of the metal composing the electrodes (3).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cold cathode discharge tube,
In particular, the present invention relates to a cold cathode discharge tube having an electrode made of a high melting point metal.

[0002]

2. Description of the Related Art A cold-cathode discharge tube in which a pair of electrodes are opposed to each other inside a glass tube filled with a rare gas and mercury vapor and a fluorescent film is coated on the inner wall of the glass tube has been conventionally used in a liquid crystal display. Widely used as a light source for backlights. One end of a lead is connected to a pair of electrodes of the cold cathode discharge tube, and the other end of the lead is led out from both ends of the glass tube. When a voltage is applied between the pair of electrodes, electrons are emitted from one of the electrodes, and the electrons collide with mercury atoms in the glass tube to generate ultraviolet rays. This ultraviolet light is wavelength-converted to visible light by a fluorescent film formed on the inner wall of the glass tube.

A conventional cold cathode discharge tube (40) shown in FIG. 3 has a pair of electrode assemblies (20) each having an electrode (3), and the electrode assembly (20) is fixed at both ends and discharges inside. Glass tube (7) filled with a working gas, an external lead (8) connected to the lead-out part (28) of the lead (11) outside the glass tube (7), and a glass tube (7)
And a fluorescent film (9) coated on the inner surface (7a). When a voltage is applied between the pair of electrodes (3), electrons are emitted from one of the electrodes (3), and the electrons collide with mercury atoms in the glass tube (7) to generate ultraviolet rays. This ultraviolet ray is a glass tube (7)
The wavelength is converted into visible light by the fluorescent film (9) formed on the inner wall of the glass tube, and the visible light is emitted to the outside of the glass tube (7).

In manufacturing the cold cathode discharge tube (40), first, a lead lead (14) made of nickel having excellent solderability and an internal lead (15) made of tungsten having excellent glass fusing property are provided.
Then, a lead (11) shown in FIG. The diameters of the lead-out lead (14) and the inner lead (15) are substantially equal. Next, as shown in FIG. 4B, the internal lead (1) of the lead (11) is inserted into the hole (2a) of the glass bead (2) formed in a cylindrical shape.
5) is inserted, and the glass beads (2) are fused to the internal leads (15) with the protruding portions (11a) protruding from the glass beads (2). Then, as shown in FIG. 4 (c), the electrode (3) is pressed against the tip (11b) of the protruding portion (11a) by the chromium copper welding electrode (17), and electricity is supplied to the tungsten internal lead. (1
5) and the outer bottom surface (3a) of the nickel electrode (3) are joined by resistance welding to form an electrode assembly (20). After that, the electrode assemblies (20) are arranged at both ends of the cylindrical glass tube (7),
After filling the glass tube (7) with a discharge gas containing a rare gas and mercury vapor, the glass beads (2) are fused to the glass tube (7), and as shown in FIG. 3) and buried part (29)
Is sealed in the glass tube (7) and the lead-out section including the joint (16)
(28) is led out of the glass tube (7). In the derivation unit (28),
The external lead (8) is connected by solder (13) and the external lead
By cutting off the lead-out portion (28) protruding from (8), the cold cathode discharge tube (40) shown in FIG. 3 is formed.

When an electric current is applied to the electrode (3) of the cold cathode fluorescent discharge tube to turn on the cold cathode fluorescent discharge tube, sputtering in which ions and the like collide with the electrode (3) occurs, and the electrode metal is formed by sputtering. The atoms or molecules are released from the electrode (3) into the discharge tube. The atoms or molecules of the electrode metal combine with mercury filled in the discharge tube to form mercury amalgam, so that the mercury in the discharge tube is consumed and the life of the discharge tube (lamp life) is reduced. Therefore, the length of the lamp life largely depends on the consumption rate of the mercury vapor filled in the discharge tube. For example, there is a strong demand for high brightness in cold cathode fluorescent discharge tubes used for televisions and monitors, and the operating current (tube current)
However, if a large current is applied to the electrode, the amount of sputtering of the electrode increases, and the total amount of atoms or molecules of the electrode metal released from the electrode into the discharge tube increases. The life is shortened by the current.

[0006]

Conventionally, for example, an electrode
(3) was formed of nickel, but since nickel is rapidly consumed by sputtering, if the electrode (3) is formed of a sputtering resistant metal such as niobium having a low sputtering rate, the pressure of the rare gas is set to a high level. Without,
Even if the current density is set high and the brightness is increased, advantages such as the ability to suppress the sputtering of the electrode metal and the extension of the lamp life can be obtained.

[0007] When the electrode (3) made of a sputter-resistant metal and the internal lead (15) are connected by an electric welding method, the electrode
In order to melt the niobium of (3) and the tungsten of the internal lead (15), it is necessary to apply a large electric current and heat to a high temperature. When the niobium generates heat by passing a large current enough to melt the niobium sufficiently, the welding electrode made of chromium copper
(17) not only melts, but also melts and deforms the glass beads (2) attached to the inner lead (15), so that the inner lead (15) and the electrode (3) are substantially joined. Could not.

Accordingly, an object of the present invention is to provide a cold cathode discharge tube capable of joining an electrode formed of a metal having sputter resistance to an internal lead at a temperature that does not cause overheating, and a method of manufacturing the same.

[0009]

A cold cathode discharge tube according to the present invention comprises an electrode assembly (20) having a metal lead (11) and an electrode (3) fixed to the lead (11); A glass tube (7) having an assembly (20) fixed at both ends and filled with a discharge gas therein, and an electrode (3) coated inside the glass tube (7).
And a fluorescent film (9) that emits visible light in response to irradiation of ultraviolet rays generated by the discharge. When the electrode (3) is formed of one or more metals of tantalum, titanium or niobium or alloys thereof, the sputtering resistance is improved, so that even if the tube current density is set higher, the electrode (3) Metal consumption rate can be suppressed. Also,
Metal film (1) having a melting point lower than the melting point of the metal forming electrode (3)
When the electrode (3) and the lead (11) are joined together, a relatively small current flows during energization, so that only the metal film (1) melts, for example, the welding electrode (17) or glass beads.
The electrode (3) and the lead (11) can be reliably welded without damaging the components such as (2) due to overheating.

In an embodiment of the present invention, nickel, copper,
By forming the metal film (1) with a thickness of 2 to 100 μm using iron, aluminum, gold, silver or an alloy thereof, the lead (11) and the electrode (3) can be fused well. Even if the thickness of the fusion metal (1) exceeds 100 μm, the fusion effect does not change to 100 μm, resulting in excessive quality, waste of material to be used, and the thickness of the fusion metal (1) being less than 2 μm. This can cause poor bonding.

In the embodiment of the present invention, the lead (1
1) is composed of a lead lead (14) made of nickel and an internal lead (15) made of tungsten, and the electrode (3) is joined to the internal lead (15) via the metal film (1), and the metal film A glass tube (7) is fused to the surface of the inner lead (15) not covered by (1). The glass beads (2) are in close contact with the tungsten internal lead (15) having excellent glass fusing properties.

According to the method of manufacturing a cold cathode discharge tube of the present invention, a lead (1) formed by joining a lead-out lead (14) and an internal lead (15) is provided.
1) preparing and metal film on the end of the internal lead (15)
Join (1) and internal lead outside metal film (1)
A step of fusing glass beads (2) to (15) and bonding an electrode (3) to an end of an internal lead (15) via a metal film (1) to form an electrode assembly (20) And fusing the electrode assembly (20) to the glass tube (7).

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a cold cathode discharge tube and a method of manufacturing the same according to the present invention will be described below with reference to FIGS. 1 and 2, the same parts as those shown in FIGS. 3 and 4 are denoted by the same reference numerals, and description thereof will be omitted. The cold cathode discharge tube according to the present invention shown in FIG. 1 has the following structural features. (1) The cup-shaped electrode (3) is formed of niobium. (2) The end (11b) of the internal lead (15) made of tungsten and the electrode (3) are joined by a metal film (1) made of nickel. (3) A metal film (1) is formed on the internal lead (15) with a thickness of about 20 μm.

The lead (11) is a lead lead (1) made of nickel.
4) Tungsten internal lead with excellent glass fusing property
(15), and the electrode (3) is bonded to the internal lead (15) via the metal film (1). Metal film (1) of internal lead (15)
The glass beads (2) are adhered to the surface not coated with the glass beads, and the glass tube (7) is fused to the glass beads (2).

When manufacturing the cold cathode discharge tube according to the present invention, as shown in FIG.
Prepare (11). Next, as shown in FIG. 2B, the glass beads (2) are fused to the internal leads (15), and a metal film (1) made of nickel is formed at the end of the internal leads (15). The metal film (1) is formed by various methods such as electroplating, resistance welding, and bonding with a metal brazing material such as solder.
5) can be fixed by joining. The metal film (1) may have a structure firmly fixed to the internal lead (15). However, after temporarily bonding the metal film (1) with a low adhesive force, the metal film (1) is firmly fused (welded) in the next step shown in FIG. ). Either the internal lead (15) of the glass beads (2) or the metal film (1) may be formed first. Subsequently, as shown in FIG. 2 (c), a current is applied while pressing the electrode (3) against the internal lead (15) via the metal film (1) by the welding electrode (17) made of chromium copper, The metal film (1) is securely fused to both the end of the internal lead (15) and the electrode (3) to form the electrode assembly (20). Thereafter, the electrode assembly (20) is fused to the glass tube (7).

In this embodiment, since the electrode (3) is formed of niobium having high sputtering resistance, the sputtering of the electrode (3) can be suppressed even if the tube current density is set to be high. Further, when the electrode (3) and the lead (11) are joined by a metal film (1) having a melting point of, for example, 400 ° C. or lower than the melting point of the metal forming the electrode (3), a relatively small current flows when energized. By flowing, the electrode (3) and the lead (11) can be reliably welded without melting only the metal film (1) and damaging the welding electrode (17) or the glass beads (2). In the embodiment of the present invention, even if the thickness of the fusion metal (1) exceeds 100 μm, the fusion effect does not change to 100 μm,
If the thickness of the fusion metal (1) is less than 2 μm, the quality of the material to be used becomes excessive, the material to be used is wasted, and the bonding failure is caused.

The above embodiment of the present invention can be modified. Although the example in which the electrode (3) is formed of niobium is shown,
The electrode (3) can be formed of one or more metals of niobium, tantalum, titanium, or an alloy thereof to improve the sputtering resistance. Also, not limited to nickel, nickel, copper, iron, aluminum,
By forming the metal film (1) with a thickness of 2 to 100 μm from gold or silver or an alloy thereof, the lead (11) and the electrode (3) can be fused well. Incidentally, the melting points of the respective substances are as follows. Part name Substance Melting point (° C) Metal film forming metal: Nickel: 1455 Copper: 1033 Aluminum: 569 Gold: 1063 Silver: 961 Leading lead: Tungsten: 3380 Electrode forming metal Tantalum: 2850 Titanium: 1800 Niobium: 1950 Glass beads Glass: 550

[0018]

As described above, in the present invention, since the electrode formed of a metal having a low sputtering rate is formed, the pressure of the rare gas is not set to a high level even if the current density is set high. Advantages such as suppression of electrode sputtering, prevention of mercury consumption, and extension of lamp life can be obtained. Further, since a metal film is not formed at the glass bead joining portion of the internal lead, the glass beads can be fused to the lead-out lead while maintaining sufficient airtightness. Furthermore, a discharge tube of a metal electrode having a low sputtering rate can be manufactured only by controlling the conduction current without changing the structure of the welding device and the electrodes used.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a cold cathode discharge tube according to the present invention.

FIG. 2 is a process diagram showing a manufacturing process of a cold cathode discharge tube according to the present invention.

FIG. 3 is a sectional view of a conventional cold cathode discharge tube.

FIG. 4 is a process diagram showing a manufacturing process of a conventional cold cathode discharge tube.

[Explanation of symbols]

(1) ・ ・ Metal film, (3) ・ ・ Electrode, (7) ・ ・ Glass tube,
(9) ・ ・ Fluorescent film, (11) ・ ・ Lead, (14) ・ ・ Derived lead, (15) ・ ・ Internal lead, (20) ・ ・ Electrode assembly,

Claims (4)

[Claims] An electrode assembly comprising a metal lead and an electrode fixed to the lead; a glass tube having the electrode assembly fixed at both ends and filled with a discharge gas therein;
A fluorescent film, which is coated inside the glass tube and emits visible light when irradiated with ultraviolet rays generated by the discharge of the electrode, comprising: a tantalum, titanium, niobium, or alloy thereof.
A cold cathode discharge tube, wherein the electrode is formed of one or more kinds of metals, and the electrode and the lead are joined by a metal film having a melting point lower than the melting point of the metal forming the electrode. 2. The metal film is made of nickel, copper, iron, aluminum, gold or silver or an alloy thereof to form a metal film.
2. The cold cathode discharge tube according to claim 1, wherein the cold cathode discharge tube has a thickness of 00 μm. 3. The lead according to claim 1, wherein the lead is composed of a lead lead made of nickel and an internal lead made of tungsten, and the electrode is joined to the internal lead via the metal film, and is not covered with the metal film. The cold cathode discharge tube according to claim 1, wherein the glass tube is fused to a surface. 4. A step of preparing a lead by joining a lead-out lead and an internal lead; bonding a metal film to an end of the internal lead, and attaching glass beads to the internal lead outside the metal film. Fusing, bonding an electrode to an end of the internal lead via the metal film to form an electrode assembly, and fusing the electrode assembly to a glass tube. A method for producing a cold cathode discharge tube.