JP2002100319A - Fluorescence discharge tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a high luminance in a high level without reducing a lamp lifetime of a fluorescence discharge tube. SOLUTION: In the fluorescence discharge tube equipped with a glass tube (2) to form a closing space (3), a pair of electrodes (8) arranged within the closing space (3) and fixed at both ends of the glass tube (2), and a fluorescent film (9) formed on the surface of the glass tube (2), because the electrodes (8) are constituted by niobium, titanium, tantalum or metals selected from these alloys of a low sputtering rate, a consumption by sputtering of metal to constitute the electrodes (8) is suppressed and a rare gas is enclosed in the closing space (3) by a lower pressure than that of a traditional rare gas, and the fluorescence discharge tube can be emitted with a high luminance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorescent discharge tube which emits light with high luminance while maintaining a predetermined lamp life.

[0002]

2. Description of the Related Art A pair of electrodes are fixed to both ends of a glass tube (glass bulb) so as to face each other, and a closed space (sealed space) formed inside the glass tube is filled with rare gas and mercury vapor in a sealed state. A cold cathode fluorescent discharge tube in which a fluorescent film is coated on the inner wall of a glass tube is widely used, for example, as a backlight source for a liquid crystal display. A conventional cold cathode discharge tube includes an electrode assembly having a terminal component and a cup-shaped electrode fused to a tip end of the terminal component, and an electrode assembly having an electrode hermetically fixed at both ends and having a discharge inside. Glass tube filled with gas (rare gas, mercury vapor) and glass tube
And (2) a fluorescent film that is formed on the inner wall surface and emits visible light when irradiated with ultraviolet light generated by a discharge between a pair of electrodes. The electrodes are formed of nickel or the like which is excellent in workability.

[0003]

When a current is applied to the electrodes of the cold cathode fluorescent discharge tube to light the cold cathode fluorescent discharge tube,
Sputtering occurs where ions and the like collide with the electrodes,
The atoms or molecules of the electrode metal are released from the electrode into the discharge tube by sputtering. The atoms or molecules of the electrode metal combine with the 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, a cold cathode fluorescent discharge tube used for a television monitor is required to have high brightness, and high brightness can be achieved by increasing an operating current (tube current). 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 inside of the discharge tube increases.

In this case, if the pressure of the rare gas charged in the discharge tube is increased to suppress sputtering, a desired lamp life can be maintained even when a large current is used.
When the pressure of the rare gas is increased, there is a problem that the luminance is reduced as a result. For this reason, conventionally, it has not been possible to achieve high luminance by increasing the current while maintaining a desired lamp life.
SUMMARY OF THE INVENTION An object of the present invention is to provide a fluorescent discharge tube capable of obtaining a desired lamp life and achieving a high level of luminance.

[0005]

According to the present invention, there is provided a fluorescent tube comprising:
A glass tube (2) forming a closed space (3), a pair of electrodes (8) arranged in the closed space (3) and fixed to both ends of the glass tube (2), and a glass tube (2). Fluorescent film formed on the surface (9)
And emits light when a voltage is applied to the pair of electrodes (8). Since the electrode (8) is composed of a metal selected from niobium, titanium, tantalum or an alloy thereof having a low sputtering rate, the consumption of the metal constituting the electrode (8) is suppressed, and the pressure is lower than the conventional rare gas pressure. A rare gas is sealed in the closed space (3) at a pressure of 10 × 10 ³ Pascal or less,
The fluorescent tube of the present invention can emit light with high luminance. In the embodiment of the present invention, even when a current of 5.0 mA or more is applied to the electrode (8), the amount of consumption of the electrode by sputtering is small.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a fluorescent discharge tube according to the present invention applied to a cold cathode fluorescent discharge tube used for a television monitor will be described with reference to FIGS.

The fluorescent discharge tube (1) is an elongated glass tube (glass bulb) forming a substantially cylindrical closed space (3) inside.
(2), a pair of electrode assemblies (4) hermetically fused to both ends of the glass tube (2), and a fluorescent film (5) formed on the inner wall surface of the glass tube (2). I have. An ultraviolet absorbing film composed of a titanium oxide film or the like may be formed on the outer peripheral surface of the glass tube (2). The closed space (3) is filled with a rare gas such as an argon gas and mercury vapor (discharge gas). Electrode assembly (4)
As shown in FIG. 2, a lead portion (6) formed of, for example, nickel, a buried portion (7) formed of, for example, tungsten, and an electrode (8) formed in, for example, a cup shape are provided. I have. Since the lead-out part (6) is fused to one end of the buried part (7) by resistance welding or the like, a bulge (9) is formed between the lead-out part (6) and the buried part (7). The formation of the bulging portion (9) can be suppressed by changing the wire diameter of the two. The lead-out part (6) and the buried part (7) constitute an introduction line. The electrode (8) is fused to the other end of the buried portion (7) by resistance welding or the like. The fluorescent film (5) emits visible light upon irradiation with ultraviolet light generated by the discharge between the electrodes (8).

The lead-out portion of the lead-out portion (6) led out from both ends of the glass tube (2) is connected to external terminals (10) via solder.
Therefore, it is desirable to form the lead-out portion (6) with a metal having good solderability. One end of the buried portion (7) is introduced into the glass tube (2). Tungsten is preferably used as a material for forming the buried portion because it is in good contact with the glass material constituting this kind of glass tube (2).

In this embodiment, the cup electrode (8) welded to the buried portion (7) is formed of niobium (Nb) or a metal material containing niobium as a main component according to the present invention.
Since the metal material containing niobium as a main component may include a metal or the like other than niobium as an alloy or as a composition,
A metal in which the properties of niobium are substantially maintained.

The cup electrode (8) comprises a cylindrical side wall (8a) and a bottom wall (8b) provided at one end of the side wall (8a), and is provided at the other end of the side wall (8a). Has an opening (8c). The electrode (8) described in the present embodiment is not limited to a cup shape, and can be formed in various shapes such as a rod shape, a spiral shape, and a counter electrode shape.

An inner end of a buried portion (7) and a pair of electrodes (8) constituting a pair of electrode assemblies (4) arranged at both ends of the glass tube (2) are closed space (3) of the glass tube (2). The lead-out part (6) is led out of the glass tube (2). In the present embodiment, the pressure of the rare gas filled in the glass tube (2) is set to 4 × 10 ³ Pascal.

In operation, when a voltage is applied between the pair of electrodes (8), electrons are emitted from one of the electrodes (8), and the electrons collide with mercury atoms in the glass tube (2) to emit ultraviolet rays. appear. This ultraviolet light is wavelength-converted into visible light by the fluorescent film (5) formed on the inner wall of the glass tube (2). The electrode (8) formed of niobium harder than nickel is hardly sputtered by collision of mercury and ions even when a relatively large operating current of 6 mA or more is passed.

In experiments conducted by the present inventors, the sputtering rates of titanium and niobium were both 0.4 or less and the sputtering rate of tantalum was 0.6 or less.
Nickel was about 0.7. The sputtering rate S mentioned here, when the high-speed particles jumped out atoms constituting the N _s number of target from N ₁ pieces collided target material, the amount defined in S≡N ₁ / N _s. That is, even if the operating current increases, the total amount of electrode metal atoms or molecules released from the electrode (8) into the glass tube (2) does not increase so much, and the amount of mercury amalgam formed is small. Life can be extended. In the niobium-made electrode (8), even when the operating current is in a large current range of 6 mA or more, the consumption of the electrode (8) by sputtering is small, and the pressure of the rare gas in the glass tube (2) is reduced to 10 × 1.
0 ³ Set Pascal below the low level, it is possible to high level achieve high luminance while maintaining a desired lamp life. For example, when assuring a lamp life of 50,000 hours using an operating current of 6 mA, a gas pressure of at least 6 × 1 in a cold cathode fluorescent tube with a conventional nickel electrode is used.
Although it is necessary to set the gas pressure to 0 ³ Pascal or more, in this embodiment, the gas pressure can be set to 4 × 10 ³ Pascal lower than this. That is, in the present embodiment, if the operating current and the lamp life are maintained under the same conditions as in the past, the pressure of the rare gas in the closed space (3) can be set to a relatively low level, so that the desired lamp life And a cold-cathode fluorescent tube with improved brightness can be realized.

In the above embodiment, the electrode is made of niobium.
Instead of forming (8), it may be formed of an alloy mainly composed of niobium, titanium or tantalum, an alloy mainly composed of titanium or tantalum, or an alloy of a metal selected from niobium, titanium and tantalum. Therefore, in the fluorescent discharge tube of the present invention, the electrode (8) can be formed from niobium, titanium, tantalum or an alloy thereof, but the electrode (8) composed of niobium has the best lamp voltage characteristics. Show characteristics. In order to achieve a high level of brightness while maintaining the lamp life, the pressure of the rare gas in the glass tube (2) should be 10 × 10 ³ Pascal or less, preferably 5 × 10 ³ Pascal.
It is better to set it below Pascal. In order to realize a high-brightness fluorescent discharge tube which is desirable for a cold cathode fluorescent discharge tube for a television monitor, the operating current should be set to 5.0 mA or more, preferably 6.0 mA or more.

[0015]

As described above, according to the present invention, a fluorescent discharge tube which emits light with high luminance can be realized without reducing the life of the fluorescent discharge tube.

[Brief description of the drawings]

FIG. 1 is a sectional view of a fluorescent discharge tube according to the present invention.

FIG. 2 is an exploded perspective view of an electrode assembly used in the fluorescent discharge tube of FIG.

[Explanation of symbols]

(1) Fluorescent discharge tube, (2) Glass tube, (3) Closed space, (4) Electrode assembly, (5) Fluorescent film,
(6) ・ ・ Derivation part, (7) ・ ・ Buried part, (8) ・ ・ Electrode,

Claims (2)

[Claims] A glass tube forming a closed space, a pair of electrodes disposed in the closed space and fixed to both ends of the glass tube, and a fluorescent film formed on a surface of the glass tube. A fluorescent discharge tube that emits light by applying a voltage to the pair of electrodes, wherein the electrodes are made of a metal selected from niobium, titanium, tantalum or an alloy thereof, and are diluted at a pressure of 10 × 10 ³ Pascal or less. A fluorescent discharge tube, wherein gas is sealed in the closed space. 2. The fluorescent discharge tube according to claim 1, wherein a current flowing through the electrode is 5.0 mA or more.