JPH11283498A - Cold cathode fluorescent lamp and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a getter, which also serves as an electrode, from bringing impure gas into a sealed glass tube by a vacuum heating process in advance to extend the service life. SOLUTION: A coil-shaped electrode 2 is formed from tantalum or alloy of tantalum. The coil-shaped electrode 2 is sealed into a glass tube 4 in a state wherein a vacuum heating process is carried out and adsorptive gas is emitted in advance to manufacture a cold cathode fluorescent lamp 1. With the vacuum heating process carried in advance, a getter, which also serves as the electrode 2, is prevented from bringing impure gas into the sealed glass tube 4. The cold cathode fluorescent lamp 1 whose outside diameter is the order of 2 mm, which is required in a market now, is manufactured in a state in which a life can be extended.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used as a light source for illuminating a liquid crystal display element in a device having a liquid crystal display element as a display section, such as a portable or vehicle-mounted television receiver or a portable computer. The present invention relates to a cold cathode fluorescent lamp that has been used.

[0002]

2. Description of the Related Art FIG. 5 shows an example of the structure of a conventional cold cathode fluorescent lamp 90 of this type.
Both ends of the glass tube 91 coated with are sealed by beads 94 through which a lead wire 93 having a plate-like electrode 92 passes. In the glass tube 91, an inert gas 95, mercury 96
Is enclosed.

The plate electrode 92 is coated with a mercury alloy on one surface and a getter on the other surface. After the glass tube 91 is sealed, the plate electrode 92 is heated at a high frequency. By doing so, mercury 96 is released from the mercury alloy and the getter is activated.

[0004]

However, in the above-mentioned conventional cold cathode fluorescent lamp 90, firstly,
Since the plate-shaped electrode 92 is heated after the sealing is performed, the heat of the plate-shaped electrode 92 is transmitted to the lead-in wire 93 to cause cracks or the like in the bead 94 to cause poor sealing (leakage). As a result, the yield in the production process is reduced.

Secondly, for the purpose of miniaturizing portable equipment, the outer diameter of the cold cathode fluorescent lamp 90 is required to be further reduced (for example, 2 mm). In the configuration (1), it is difficult to reduce the size of the current electrode (for example, 3 mm) or more due to the amount of mercury held in the plate-shaped electrode 92 and the like, and there is a problem that the market cannot be satisfied.

As a solution to the above miniaturization, a cold cathode fluorescent lamp 80 having a tungsten or nickel rod electrode 82 as shown in FIG. 6 has also been proposed. In this case, the supply of the inert gas 95 and the mercury 96 into the glass tube 91 can be performed from the outside immediately before the sealing, but a getter cannot be provided, and hence, the glass tube or the like is later provided. The generated impure gas 87 causes a problem that the lamp life is shortened, and the impure gas 87 also causes a problem in that the discharge meanders and deteriorates the performance, and the performance is insufficient as a substitute.

[0007]

According to the present invention, as a specific means for solving the above-mentioned conventional problems, a coil-shaped electrode is formed of tantalum or a tantalum alloy, and the coil-shaped electrode is previously subjected to a vacuum heat treatment. And performing a sealing step in a bulb in a state where the adsorbed gas is released, and a cold cathode fluorescent lamp manufactured by the above-described manufacturing method. Is to solve the problem.

[0008]

Next, a method for manufacturing a cold cathode fluorescent lamp 1 according to the present invention will be described in detail in the order of steps.
FIG. 1 shows a coiled electrode 2. In the present invention, the coiled electrode 2 is formed in a coil shape using a wire of tantalum (Ta) or a tantalum alloy. At this time,
To manufacture the cold cathode fluorescent lamp 1 having an outer diameter of about 2 mm, it is appropriate that the outer diameter D of the coil electrode 2 is approximately 0.85 mm and the length L is approximately 2.5 mm.

In the present invention, tantalum (Ta) or a tantalum alloy is selected as the coil-shaped electrode 2 because tantalum has a function as a getter. In addition, titanium is used as a metal having a function as a getter. Niobium and zirconia conventionally used as this type of getter are known.

Therefore, the inventors of the present invention conducted a comparative study of the above members in order to achieve the present invention. As a result, when titanium was used as an electrode member, spatter was severe, and so-called blackening phenomenon was remarkably generated, which shortened the lamp life. Met. Niobium has excellent sputter resistance,
The function as a getter was poor and the life of the lamp was shortened.

Although zirconia is excellent in the function as a getter, spatter resistance when used as the coiled electrode 2 is inferior to tantalum, and as a whole result, tantalum is advantageous for lamp life. As a result, the present invention selects tantalum as the electrode member.

Therefore, in the present invention, in order to efficiently perform the function as a getter, the coil-shaped electrode 2 in which the wire is formed into a coil shape so that a large surface area can be obtained with a small volume of tantalum or a tantalum alloy. Is what you do. Therefore, the cross-sectional shape of the wire is arbitrary as long as it meets the above-mentioned purpose and can be processed by a winding machine or the like.

In the present invention, as a subsequent step, the coil-shaped electrode 2 is activated as a getter, and as shown in FIG.
It is stored in the molybdenum boat 11 inside, and is heated by the heater 12 and exhausted by the pump 13. Therefore,
Since the impurity gas absorbed by the coiled electrode 2 is released and activated, the first valve 14 is closed and the second valve 15 is opened when the activation is completed.
An inert gas such as nitrogen is filled from the cylinder 17 during the time.

After the inert gas is filled, the third valve 16 is closed and the quartz tube 10 is kept filled with the inert gas, so that the activation of the coiled electrode 2 is maintained. In this state, it is stored until it is mounted on the cold cathode fluorescent lamp 1. Although not shown, the coil electrode 2 may be provided with the lead wire 3 at the time of activation of the coil electrode 2.

FIG. 3 shows a sealing step of the manufacturing method according to the present invention. One end of the glass tube 4 having a necessary portion coated with the phosphor 4a is a bead 5a through which the lead-in line 3 passes.
Then, the coiled electrode 2 is attached to an end of the introduction wire 3 inside the glass tube 4 by appropriate means such as welding. In addition, the glass tube 4
A bead 5b is attached to the other end of the inside of the glass tube 4 in the same manner as described above so as to penetrate the lead wire 3 to which the coiled electrode 2 is attached.

The bead 5b is partially welded so as to have a gap with the glass tube 4 and is in a so-called temporary fixing state. Further, in the present invention, a bead 5c is attached further outside the bead 5b, and the introduction wire 3 having a mercury holder 6 holding a mercury alloy attached to the bead 5b penetrates the bead 5c. The bead 5c is sealed when the gas in the glass tube 4 is exhausted and the inert gas 7 is sealed (the figure shows the state after the sealing is performed).

Therefore, when the outer bead 5c is sealed, the inside of the glass tube 4 is sealed. In this state, the mercury holder 6 is heated by high frequency or the like, and the mercury vapor 8 is generated. At this time, since the inner bead 5b has a gap with the glass tube in a temporarily fixed state, the generated vaporous mercury 8 passes through the gap and uniformly spreads inside the glass tube 4. Becomes

Thereafter, if the inner bead 5b is welded, a gap between the bead 5a and the bead 5b is obtained by sealing the required amount of the inert gas 7 and the mercury vapor 8 in the glass tube 4. Therefore, by cutting and removing the outside from the bead 5b, the cold cathode fluorescent lamp 1 of the present invention shown in FIG. 4 can be obtained.

Next, the operation and effects of the cold cathode fluorescent lamp 1 of the present invention obtained by the above-described manufacturing method will be described. The comparison was made with respect to a cold cathode fluorescent lamp employing a plate-like electrode (see FIG. 5 of a conventional example). First,
When the life test was confirmed by a life acceleration test by a temperature cycle, the conventional cold cathode fluorescent lamp was 114 cycles, whereas the cold cathode fluorescent lamp 1 of the present invention was 536.
The cycle and the life extension of about 4.7 times were observed.

Considering this factor, since the getter is activated in the state of the prior art after being sealed as a cold-cathode fluorescent lamp, the impure gas which has already been absorbed is temporarily removed from the glass tube. Will be released. At this time, the getter absorbs the impurity gas again, but a part of the impurity gas is combined with mercury, and the effective amount of mercury in the glass tube decreases.

Here, it is said that the life of the cold cathode fluorescent lamp is substantially proportional to the amount of mercury in the glass tube, so the above-mentioned decrease in the amount of mercury leads to a shortened life. In addition, the emission and absorption of the impurity gas contained by the getter itself causes, for example, a shortage in the ability to absorb the impurity gas newly released from a glass tube, a phosphor, etc. This leads to a reduction in the amount and a shortened life.

On the other hand, according to the manufacturing method of the present invention, the getter (coiled electrode 2) is activated before being sealed in the glass tube 4, and the impurity gas is already released. Glass tube 4 associated with heat activation after sealing.
There is no emission of impure gas at the pressure and therefore no reduction of mercury 8. Further, since the impurity gas is not absorbed at the time of sealing in the glass tube 4, the adsorption capability as a getter (coiled electrode 2) is large, and a large amount of impurity gas newly generated after sealing is also absorbed. The life can be extended.

Also, in the present invention, when the mercury 8 is generated in the glass tube 4, heating is performed, and there is a possibility that cracks may be generated as a cause of leakage. However, in the present invention, the mercury holder 6 is attached to the bead 5c, and this bead 5c is cut off when the cold cathode fluorescent lamp 1 is completed. Does not have any effect. Therefore, according to the manufacturing method of the present invention, the cold cathode fluorescent lamp 1 can be manufactured without using a plate-like electrode, and the cold cathode fluorescent lamp 1 having an outer diameter of about 2 mm required in the market can also be manufactured. Becomes

[0024]

As described above, according to the present invention, a coil-shaped electrode is formed of tantalum or a tantalum alloy,
A method of manufacturing a cold cathode fluorescent lamp in which the coil-shaped electrode is subjected to a vacuum heating process in advance and a process of sealing in a bulb in a state where the adsorbed gas is released is performed. It is possible to produce cold cathode fluorescent lamps with an outer diameter of about 2 mm, which is currently demanded in the market, while preventing the getter, which also functions as an electrode, from introducing impurities into the glass tube after shutting down and extending its life. This is extremely effective in improving the performance of this type of cold cathode fluorescent lamp.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of an electrode in a method of manufacturing a cold cathode fluorescent lamp according to the present invention.

FIG. 2 is an explanatory view showing a step of vacuum heat treatment of an electrode in the same manufacturing method.

FIG. 3 is an explanatory view showing a sealing step in the same manufacturing method.

FIG. 4 is a sectional view showing a cold cathode fluorescent lamp formed by the manufacturing method according to the present invention.

FIG. 5 is a sectional view showing a conventional example.

FIG. 6 is a sectional view showing another conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cold cathode fluorescent lamp 2 ... Electrode 3 ... Introduction line 4 ... Glass tube 5a, 5b, 5c ... Bead 6 ... Mercury holder 7 ... Inert gas 8 ... Mercury 10 ... Quartz tube 11 … Molybdenum boat 12… Heater 13… Pump 14… First valve 15… Second valve 16… Third valve

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuhide Yasuda, Fukushima Prefecture Iwaki City, Hirakita Shirato 30-1 Kamiohira

Claims (2)

[Claims] 1. A method of forming a coil-shaped electrode from tantalum or a tantalum alloy, and performing a sealing step in a glass tube in a state in which the coil-shaped electrode is previously subjected to a vacuum heating treatment to release an adsorbed gas. A method for manufacturing a cold cathode fluorescent lamp, characterized by: 2. A cold cathode fluorescent lamp manufactured by the manufacturing method according to claim 1.