JP2002025499A - Cold cathode fluorescent lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tubular type cold cathode fluorescent lamp which can more effectively reduce cathode voltage drop and in which backlight unit is subjected to thinning of wall, weight saving and prolonging of life its time. SOLUTION: For the cold cathode florescent lamp, having a glass tube 1 on the inner wall surface of which a phosphor layer is provided, and in which a rare gas and mercury are soled hermetically, a pair of lead-in wires 6 hermetically introduced in opposed relation to both end parts within the glass tube 1, and a cold cathode 5 hermetically installed in electrical connection with respective opposing tip parts of the lead-in wires 6, the cold cathode 5 is equipped with a metallic cylindrical body 5a formed of molybdenum, tantalum or an alloy thereof, having openings in the surfaces which mutually face opposite to each other and irregularities, processed at least at its side inner wall surface and an emitter layer 5b carried on the irregular surface of the side inner wall of the cylindrical body 5a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold-cathode fluorescent lamp, and more particularly, to a thin-tube cold-cathode fluorescent lamp with high efficiency, small size, and long life.

[0002]

2. Description of the Related Art For example, liquid crystal display devices such as liquid crystal displays, word processors, personal computers, etc., have been developed to have higher performance or higher efficiency, more functions, smaller size, longer life, etc., with the expansion or spread of applications. Is required. In response to such a demand, a cold cathode fluorescent lamp (cold cathode low-pressure discharge lamp) as a light source for a backlight is inevitably required to have a higher efficiency and a longer life. .

FIGS. 3 (a) and 3 (b) show a schematic configuration of a cold cathode fluorescent lamp conventionally used as a light source for a backlight. FIG. 3 (a) is an overall sectional view, and FIG.
(B) is an enlarged sectional view of a cold cathode sealing region. FIG.
In (a) and (b), reference numeral 1 denotes a glass tube (glass bulb) in which a phosphor layer 2 that emits light upon stimulation by ultraviolet rays is provided on an inner wall surface and a rare gas such as neon or argon and mercury are enclosed as a discharge medium. Reference numerals 3, 3 denote a pair of lead-ins which are sealed and introduced in opposition to both ends of the glass tube 1.
Are cold cathodes which are electrically connected to the leading ends of the introduction wires 3 and 3 and are sealed in the glass tube 1 respectively.

The glass tube 1 has an inner diameter of 1.2 to 4.
The length is about 8 mm and the length is about 40 to 800 mm. Also,
In the glass tube 1, for example, 0.5 to 2.0 mg /
cm ³Of mercury and rare of about 60 to 150 Torr
Gas is enclosed as a discharge medium.

Further, in the above configuration, the cold cathode 4 is
For example, the inner diameter is about 0.6 to 1.7 mm, and the wall thickness is 0.1 to
It comprises a cylindrical body (for example, a nickel cylindrical body) 4a having a length of about 0.2 mm and a length of about 2 to 3 mm, and an emitter layer 4b applied and baked on the inner and outer surfaces of the side wall of the cylindrical body 4a. These cold cathodes 4 are connected to a pair of lead wires 3 sealed and introduced into a reduced diameter portion of a cylindrical body 4 a as a constituent member.
Are inserted and fitted, are electrically connected by spot welding or the like, and are mechanically joined and fixed.

That is, the cold cathodes 4,
4, a required voltage is applied to the cold cathodes 4 so that the cold cathodes 4 and 4 function as discharge electrodes. The emitter layer 4b is generally formed of a material mainly composed of an electron-emitting substance such as a barium compound, an yttrium compound, and a lanthanum compound. When a current is applied to the pair of cold cathodes 4 and 4 carrying the emitter layer 4b through the introduction lines 3 and 3, ultraviolet rays are radiated.
Thus, the light is converted into visible light to function as a cold cathode fluorescent lamp.

[0007]

The structure of the cold cathode (discharge electrode) 4 is one of the factors regulating the performance, such as the improvement of the luminous efficiency of the cold cathode fluorescent lamp. For example, reducing the size of the glass tube 1 necessarily involves downsizing the cold cathode 4 to be enclosed. The miniaturization of the cold cathode 4 reduces the surface area of the electrode, so that abnormal glow discharge and sputtering are likely to occur, for example, because the amount of the carried emitter is also greatly restricted.

That is, a negative glow discharge during lamp operation tends to sputter the emitter layer 4b and reduce the emitter function (increase the cathode drop voltage). The negative glow discharge or the like causes the mercury to be sputtered on the inner wall surface of the glass tube in the vicinity of the cold cathode 4, resulting in rapid consumption of the mercury, resulting in a reduction in luminous efficiency and life.

The emitter layer 4b comprises a cylindrical body 4
The paste of the emitter particles is applied to the inner and outer surfaces of the side wall a, and then formed by heating with an electric furnace or a laser beam. And this emitter layer 4b
A configuration is adopted in which the emitter particles are in contact with the inner and outer surfaces of the side wall of the relatively flat cylindrical body 4a with a very small contact surface. Therefore, in the cold cathode 4, the contact between the cylindrical body 4a and the emitter particles is insufficient, and it is difficult to sufficiently secure the transfer of electrons. As a result, the function as the emitter is not sufficiently performed. However, due to the increased amount of mercury consumption, it is not possible to cope with higher performance, smaller size, and longer life of liquid crystal display devices.

Further, the cold cathode fluorescent lamp employs a structure in which a thin glass tube 1 is used as an arc tube main body, and a nickel cylindrical body 4a having a smaller diameter is sealed in the arc tube main body 1. Therefore, there are various problems in operations such as sealing and exhaust in the manufacturing process. In consideration of these problems, attempts have been made to improve the brightness and extend the life of the device by changing the filling gas, improving the electrode structure, and providing a protective film on the phosphor layer 2 (Japanese Patent Laid-Open No. Hei 5 (1993) -107). -290808). However, a cold cathode fluorescent lamp capable of coping with the high performance, miniaturization, and long life of the liquid crystal display device has not yet been developed.

The present invention has been made in view of the above circumstances, and can more effectively reduce the cathode drop voltage.
It is an object of the present invention to provide a thin-tube cold-cathode fluorescent lamp in which a backlight unit is thin, lightweight, and has a long life.

According to the first aspect of the present invention, there is provided a glass tube in which a phosphor layer is provided on an inner wall surface and in which a rare gas and mercury are sealed, and a pair of sealed and introduced opposed to both ends in the glass tube. An introduction wire and a cold cathode fluorescent lamp having a cold cathode which is sealed by being electrically connected to each of the opposite end portions of the introduction wire, wherein the cold cathodes are open at surfaces facing each other, and have at least an inner side. A cold-cathode fluorescent lamp characterized by comprising a metal cylinder made of molybdenum or tantalum or an alloy thereof, the wall of which has been processed into irregularities, and an emitter layer carried on the irregular inner side wall of the cylinder. is there.

According to a second aspect of the present invention, in the cold cathode fluorescent lamp according to the first aspect, the emitter layer contains at least one kind of alkaline earth metal element.

That is, the first and second aspects of the present invention provide a cold cathode fluorescent lamp in which a rare gas and mercury are sealed as a discharge medium in a glass tube and a pair of cold cathodes are sealed at both ends of the glass tube. The cold cathode has a main body made of a metal cylinder such as molybdenum or tantalum whose surfaces facing each other are open, and the inner wall surfaces of which are roughened,
The essential point is that sufficient contact is ensured on the rough surface (inside uneven surface) of the cylindrical body, and the emitter layer is formed and supported.

In the first and second aspects of the present invention,
The glass tube generally has an inner diameter of about 1.2 to 4.8 mm,
The length is about 40 to 800 mm, and inside the glass tube 1,
As a discharge medium, for example, 0.5 to 2.5 mg / cm ³
Mercury and rare gases such as neon and argon 60
A rare gas of about 150 torr is sealed.

In the first and second aspects of the present invention,
The cold cathode is, for example, a tantalum-based or molybdenum-based metal having an inner diameter of about 0.6 to 1.7 mm, a thickness of about 0.1 to 0.2 mm, a length of about 2 to 4 mm, and an uneven inner wall surface. It is composed of a cylindrical body and an emitter layer applied and baked on the uneven surface of the inner wall on the side of the cylindrical body. And while this cold cathode is electrically connected to the metal cylinder,
The required electric power is applied from the outside via the lead-in which seals and leads the end of the glass tube.

Here, the cylindrical body is made of molybdenum, tantalum or an alloy thereof which is excellent in durability, and at least the side inner wall surface is made uneven by machining.
The surface area is enlarged. The side wall surface is made uneven and the amount of emitters is increased, so that the consumption of the cylindrical body by sputtering is reduced, while the contact surface of the supported emitter particles is secured, and the consumption of the emitter by sputtering is not reduced. The configuration to suppress is adopted.

The above-mentioned uneven surface can be formed by, for example, an etching process or a polishing process. Generally, the uneven surface is almost uniformly dispersed in a spot shape. Alternatively, an annular or spiral groove along the inner wall surface may be used. The emitter layer supported and formed on the inner wall surface of the roughened cylindrical body is formed mainly of an electron-emitting substance such as a barium compound, an yttrium compound, and a lanthanum compound.

In any case, since the material of the cylindrical body, the unevenness of the inner wall surface, and the supporting and forming of the emitter layer on the uneven inner wall surface, the consumption of the emitter due to the spatter at the time of lamp operation is reduced. Consumption of mercury in the glass tube is suppressed / reduced by the consumption of the cylindrical body itself due to spattering and in conjunction with the spattering, so that it functions as a cold cathode fluorescent lamp which can sufficiently cope with high performance, miniaturization and long life.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described below with reference to FIGS.

FIG. 1 is an enlarged sectional view showing the structure of a main part of a cold cathode fluorescent lamp according to an embodiment. In FIG. 1, reference numeral 1 denotes a glass tube provided with a phosphor layer 2 on its inner wall surface, which emits light when stimulated by ultraviolet rays, and in which a rare gas and mercury are sealed.
Are a pair of cold cathodes (discharge electrodes) respectively sealed opposite to both ends of the glass tube 1.

Here, the glass tube 1 has, for example, an outer diameter of 2.
It has a diameter of 6 mm, an inner diameter of 2.0 mm, and a length of 220 mm, and contains, for example, about 2.5 mg / cm ³ of mercury and about 80 Torr of rare gas such as neon or argon.
The cold cathode 5 has an outer diameter of 0.9 mm, an inner diameter of 0.6 mm,
A cylindrical member 5a made of tantalum metal having a length of 2.8 mm and having at least a side inner wall surface processed to be uneven,
Emitter layer 5 carried and formed on inner wall irregularity processing surface a
b.

The inner wall surface irregularities of the cylindrical body 5a are:
For example, the diameter is reduced in a ring shape at intervals of about 0.1 mm. However, the diameter may be reduced, for example, by baking / coating tantalum particles or molybdenum particles, etching, or the like. Further, the emitter layer 5b
Is formed mainly of an electron-emitting substance such as a barium compound, an yttrium compound or a lanthanum compound.

Further, the cold cathode 5 is connected to the glass tube 1.
The leading end of the lead-in wire 6 sealed and led out at the end of the cylindrical body 5
The outer peripheral portion is inserted or fitted into the reduced-diameter portion a, and the outer peripheral portion is joined by spot welding or the like, so that electrical connection as well as mechanical fixing is performed. That is, when a current is applied to the pair of cold cathodes 5 through the introduction line 6, ultraviolet rays are radiated by the current supply, and the ultraviolet rays are converted into visible light by the phosphor layer 2 to function as a required light source. I have.

A continuous lighting test was conducted on the cold cathode fluorescent lamp having the above-described structure under a condition of a lamp current of 5 mA. Was found to be excellent. In other words, in the cold cathode fluorescent lamp according to the embodiment, since the sealed / provided cold cathode 5 has good emitter carrying properties and sputtering resistance, the increase in the tube voltage during long-time operation is increased. These problems have been resolved, and electrons are efficiently exchanged by the emitter.

Further, a number of cold cathode fluorescent lamps having the above-described configuration were prepared, and continuous lighting was performed under the condition of a lamp current of 5 mA, and the amount of mercury consumed was checked at every fixed lighting time. That is, a plurality of the cold cathode fluorescent lamps are destroyed every time a fixed lighting time elapses, and the amount of mercury consumed (average value) is calculated from the amount of mercury attached to the surface of the phosphor layer 2 by sputtering or the like.
Was measured, and the result was as shown by curve A in FIG.

For comparison, a conventional cold cathode fluorescent lamp (FIG. 3)
2), the result of examining the relationship between the lighting time and the amount of mercury consumed is also shown by the curve a in FIG. That is, in the configuration of the cold cathode fluorescent lamp, the cold cathode is constituted by a nickel cylinder and an emitter layer formed by coating and baking the inner and outer surfaces of the side wall of the cylinder 4a, except that the cold cathode is sealed and provided. Cold cathode fluorescent lamp of the same standard (see Fig. 3)
Was measured under the same conditions as above, and the amount of mercury consumed (average value) was as shown by a curve a in FIG.

As can be seen from the above embodiment, the cold cathode fluorescent lamp according to the present invention has a more stable behavior thermally in the discharge space because the cold cathode constituent base material is a cylindrical body made of tantalum. Present. In addition, since the supporting / forming surface of the emitter is formed on the uneven inner wall surface of the cylindrical body, the amount of the supported emitter is increased, so that the sputtering of the emitter during lighting is prevented or reduced. The prevention and reduction of the sputtering of the emitter suppresses the consumption of mercury and extends the life.

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the invention. For example, the diameter and length of the glass tube constituting the arc tube, the interval between the cold cathodes, and the shape and size of the cold cathode material (for example, molybdenum, tantalum-based alloy or molybdenum-based alloy) can be appropriately changed and set.

[0030]

According to the first and second aspects of the present invention, since the sputtering resistance of the emitter layer in the cold cathode is improved and the consumption of the emitter is suppressed, a small-sized and long-life cold cathode fluorescent lamp can be provided. Provided. In particular, in the structure of the cold cathode, the cylindrical body supporting the emitter layer is made of molybdenum, tantalum, or an alloy thereof, thereby extending the life of the cold cathode itself. Will be encouraged.

Further, the improvement of the sputtering resistance of the emitter layer contributes to the effect of reducing the tube voltage (cathode drop voltage) and the suppression and reduction of the amount of consumption of mercury. It also leads to higher efficiency. Therefore, a cold cathode fluorescent lamp suitable for a liquid crystal backlight, which is required to have a small size, high efficiency, a long life, and the like, is provided.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view showing a configuration of a main part of a cold cathode fluorescent lamp according to an embodiment.

FIG. 2 is a characteristic diagram showing a comparison between the lighting time and the amount of mercury consumption for the cold cathode fluorescent lamp according to the example and the conventional cold cathode fluorescent lamp.

3A and 3B schematically show the configuration of a conventional cold cathode fluorescent lamp, in which FIG. 3A is an overall sectional view, and FIG. 3B is an enlarged sectional view of a cold cathode sealing region.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Glass tube 2 ... Phosphor layer 3,6 ... Introduction line 4,5 ... Cold cathode 4a ... Nickel cylinder 4b, 5b ... Emitter layer 5a ... Tantalum cylinder

Claims (2)

[Claims] A glass tube in which a phosphor layer is provided on an inner wall surface and in which a rare gas and mercury are sealed; a pair of introduction lines sealed and introduced opposite to both ends in the glass tube; A cold cathode fluorescent lamp having a cold cathode that is electrically connected to and sealed at the opposite end of the introduction wire, wherein the cold cathodes are open at opposing surfaces, and at least the side inner wall surface has irregularities. A cold-cathode fluorescent lamp comprising: a processed metal cylinder made of molybdenum, tantalum or an alloy thereof; and an emitter layer formed and supported on the uneven inner side wall of the cylinder. 2. The cold cathode fluorescent lamp according to claim 1, wherein the emitter layer contains at least one kind of an alkaline earth metal element.