HK1108969A - Cold cathode fluorescent lamp, electrode unit and manufacturing method thereof - Google Patents

Description

Cold cathode fluorescent lamp, electrode unit and method for manufacturing electrode unit

Technical Field

The present invention relates to a cold cathode fluorescent lamp and an electrode unit constituting a part of the cold cathode fluorescent lamp, and particularly to an improvement in an electrode material.

Background

Cold cathode fluorescent lamps have characteristics such as easy miniaturization, low power consumption, and long life, and are widely used in recent years for backlights of liquid crystal panels. In general, a cold cathode fluorescent lamp has the following structure: a pair of electrodes are arranged facing each other in a glass tube filled with a rare gas such as argon and a mercury gas, and a lead is connected to each electrode. The electrodes are formed in a cup shape and are arranged so that the openings of the cups face each other. When a voltage is applied between the electrodes through the lead, electrons are emitted from one of the electrodes, and strike mercury atoms to generate ultraviolet rays. The ultraviolet rays are converted into visible rays through the fluorescent film formed on the surface of the glass tube, thereby emitting the visible rays from the inside of the glass tube. Therefore, the life of the cold cathode fluorescent lamp depends to a large extent on the consumption of mercury gas.

Typical electrodes are made of nickel (Ni) or nickel alloys. An example of the composition of nickel used as the electrode material is as follows: 99.7% of nickel, 0.1% of manganese, 0.1% of iron and 0.1% of other impurities (carbon, silicon, copper and sulfur). Nickel contains a trace amount of cobalt of about 0.01%. In addition, the above mixing ratios are all weight percentages.

Here, when the nickel is hit by argon gas or the like inside the glass tube, nickel atoms are knocked out and scattered. This phenomenon is called sputtering. Since the scattered nickel atoms absorb the mercury gas and become an amalgam, the effective amount of the mercury gas decreases. As a result, mercury gas is consumed, and the life of the cold cathode fluorescent lamp is reduced.

Therefore, in recent years, a technique for extending the life of a cold cathode fluorescent lamp by using an electrode having excellent sputtering resistance has been studied. Specifically, a cup-shaped electrode using molybdenum (Mo), niobium (Nb), or the like, which has a lower work function than nickel and is excellent in sputtering resistance, has been developed (see, for example, japanese patent laid-open nos. 2002-358992 and 2003-187740).

However, the cold cathode fluorescent lamp using the electrode made of molybdenum or niobium has the following problems. First, there is a problem that an electrode using a high melting point metal such as molybdenum or niobium is oxidized at the surface when sealed in a glass tube. Specifically, in the manufacturing process of the cold cathode fluorescent lamp, after the electrodes are disposed at the ends of the glass tube, the sealing glass (bead glass) at one end of the glass tube is baked by gas flame or the like in the atmosphere and is welded to the glass tube, thereby performing hermetic sealing. However, heat generated when the solder glass is melted is transferred to the electrode, and the surface of the electrode is oxidized by the heat. Once the electrode surface is oxidized, its sputtering resistance is significantly reduced, and thus sputtering resistance which is not easily obtained cannot be exerted. Further, molybdenum or niobium is difficult to reduce once oxidized, and therefore, it is difficult to reduce with hydrogen gas or the like in a subsequent step.

Second, since molybdenum or niobium is a high melting point metal, sufficient bonding strength cannot be obtained without applying very high heat when welding a lead to an electrode. In particular, molybdenum has a melting point of about 3400 ℃ which is much higher than the melting point (1550 ℃) of kovar, which is commonly used as a lead. Therefore, it is necessary to sufficiently melt the lead wire to be bonded to the electrode. However, since the molybdenum electrode hardly melts, a sufficient bonding strength may not be obtained as a result. Further, when a temperature at which the molybdenum electrode is sufficiently melted is applied, the temperature of the lead wire is too high, and therefore, bonding may be difficult. In addition, when a lead wire of a double structure in which copper is filled in the inside of an outer tube made of kovar is used, the melting point of copper is lower, about 1080 ℃, and thus the inside copper is melted first and flows out at the time of welding. Copper functions as a heat radiating unit for radiating heat emitted from the electrodes to the outside of the glass tube when the lamp is used, and if copper flows out, a hollow portion not filled with copper is generated inside the outer tube made of kovar, resulting in a decrease in heat radiation performance.

Third, molybdenum and niobium are generally expensive, and are difficult and expensive to roll-form into thin plates or press-form into cup electrodes. Therefore, electrodes made of these high-melting point metals are more likely to cause a cost increase than electrodes made of nickel.

Disclosure of Invention

In view of the above problems, an object of the present invention is to provide a cold cathode fluorescent lamp which is excellent in sputtering resistance and manufacturability and is economical.

The cold cathode fluorescent lamp of the present invention comprises: a glass tube, a pair of cylindrical electrodes, and a lead wire. The glass tube has an inner space hermetically sealed, at least rare gas and mercury gas are sealed in the inner space, and a phosphor layer is formed on an inner wall surface thereof. The cylindrical electrode is disposed in the internal space of the glass tube, and has a bottom surface portion at one end and an opening portion at the other end. Further, the cylindrical electrodes are disposed in the inner space of the glass tube in such a direction that the openings face each other. One end of the lead wire is joined to the bottom surface of the cylindrical electrode, and the other end is led out of the glass tube. In addition, each cylindrical electrode is formed of a metal material obtained by heat-treating a nickel-based metal in which magnesium is dispersed to oxidize the dispersed magnesium. The cylindrical electrode preferably contains 0.005 to 0.15 wt% of magnesium.

The electrode unit of the present invention comprises: a cylindrical electrode having a bottom surface portion formed at one end and an opening portion formed at the other end; and a lead wire bonded to the bottom surface portion of the cylindrical electrode. Wherein the cylindrical electrode is formed of a metal material obtained by subjecting a nickel-based metal in which magnesium is dispersed to a heat treatment to oxidize the dispersed magnesium. The cylindrical electrode preferably contains 0.005 to 0.15 wt% of magnesium.

The method for manufacturing an electrode unit of the present invention includes: a step of oxidizing magnesium by heat-treating a nickel-based metal material in which magnesium is dispersed; processing the metal material subjected to the oxidation treatment into a cylindrical shape having a bottom surface portion formed at one end and an opening portion formed at the other end; and a step of bonding one end of the lead to the bottom surface portion.

The heat treatment is preferably performed in an oxygen atmosphere or a water vapor atmosphere. The heating temperature is preferably 820 ℃ to 1080 ℃. The mixing ratio of magnesium in the metal material is preferably 0.005 to 0.15 wt%.

The objects, features and advantages of the present invention other than those described above will be apparent from the following description and drawings illustrating an example of the present invention.

Drawings

FIG. 1 is a sectional view schematically showing an example of an embodiment of a cold cathode fluorescent lamp according to the present invention;

FIG. 2 is an enlarged perspective view of the electrode unit shown in FIG. 1;

fig. 3 is a sectional view schematically showing another example of the embodiment of the cold cathode fluorescent lamp of the present invention.

Detailed Description

An example of an embodiment of a cold cathode fluorescent lamp according to the present invention will be described in detail below with reference to the drawings. The cold cathode fluorescent lamp in this example is suitable for use as a backlight for a liquid crystal panel, but may be applied to cold cathode fluorescent lamps for other applications. Fig. 1 is a sectional view showing a schematic structure of a cold cathode fluorescent lamp 1 in this example.

The cold cathode fluorescent lamp 1 has the following basic structure: both ends of the glass tube 2 formed of borosilicate glass are hermetically sealed by a sealing glass (solder glass 3). The outer diameter of the glass tube 2 is in the range of 1.5 to 6.0mm, preferably 1.5 to 5.0 mm. The material of the glass tube 2 may be lead glass, soda-lime glass, low-lead glass, or the like.

On the inner wall surface 4 of the glass tube 2, a phosphor layer not shown in the figure is provided almost throughout the entire length thereof. The phosphor constituting the phosphor layer may be selected from existing or new phosphors such as halophosphate phosphors (halophosphate phosphors) and rare earth phosphors, depending on the purpose or application of the cold cathode fluorescent lamp 1. The phosphor layer may be formed of a mixture of two or more phosphors.

A predetermined amount of rare gas such as argon, xenon, neon, or the like and mercury are sealed in an internal space 5 of the glass tube 2 surrounded by the inner wall surface 4, and the internal pressure thereof is reduced to a pressure of several tens of times the atmospheric pressure.

A pair of electrode units 6 are provided at both ends of the glass tube 2 in the longitudinal direction. Each electrode unit 6 is composed of a cylindrical electrode 7 and a lead wire 9 joined to a bottom surface portion 8 of the cylindrical electrode 7. The cylindrical electrodes 7 of the electrode units 6 are arranged slightly inside the longitudinal end of the internal space 5 of the glass tube 2 so that the opening 10 of one cylindrical electrode 7 faces the opening 10 of the other cylindrical electrode 7. One end of each lead wire 9 is soldered to the bottom surface portion 8 of the corresponding cylindrical electrode 7, and the other end thereof is led out to the outside of the glass tube 2 through the solder glass 3. The lead 9 is made of a conductive material such as kovar.

Fig. 2 is an enlarged perspective view showing the electrode unit 6 included in the cold cathode fluorescent lamp 1. One end of the cylindrical electrode 7 constituting the electrode unit 6 in the longitudinal direction is open as an opening 10, and the other end is closed by the bottom surface 8 to form a bottomed cylindrical shape. The cylindrical electrode 7 is obtained by press-working a metal plate into a cylindrical shape (cup shape). One end surface 12 of the lead wire 9 is welded to the bottom surface portion 8 of the cylindrical electrode 7.

The cylindrical electrode 7 is formed of a metal material obtained by heating a nickel-based metal in which magnesium (Mg) is dispersed in an oxygen atmosphere or a water vapor atmosphere to oxidize the dispersed magnesium. The metal material comprises the following components: 99.7% of nickel, 0.025% of magnesium, 0.15% of manganese and 0.1% of other impurities (carbon, silicon, copper, sulfur and iron). Nickel contains a trace amount of cobalt of about 0.01%. The above mixing ratio is a weight percentage.

The method for manufacturing the metal material and the method for manufacturing the cylindrical electrode 7 using the metal material are as follows.

(1) An ingot of the metallic material having the above composition is produced by a melting method.

(2) The ingot was processed into a thin plate shape by hot rolling and cold rolling.

(3) The metal material processed into a thin plate shape is heated in an oxygen atmosphere or a water vapor atmosphere to oxidize magnesium at a surface portion of the metal material. The heating temperature in this case is preferably 820 ℃ to 1080 ℃.

(4) The magnesium-oxidized metal material of the surface portion is cut into a predetermined width.

(5) The metal material cut to a predetermined width is press-worked into a cup shape as shown in fig. 2.

Here, the reason why the sputtering resistance of the cylindrical electrode 7 is improved by forming the cylindrical electrode 7 with the above-described metal material will be described. Nickel or nickel alloys generally have a polycrystalline structure with grain boundaries formed at the grain boundaries of the crystals. The grains are weakly bonded to each other at the grain boundaries and are therefore susceptible to sputtering. As a result, sputtering is mainly generated from the grain boundaries and gradually spreads into the interior of the crystal. Also in the case of molybdenum or niobium, sputtering will spread significantly from the grain boundaries if oxidized.

On the other hand, in the above metal material, the magnesium mixed in the nickel is oxidized (by the above step (3)), whereby the bonding of the grains at the grain boundaries becomes strong. That is, a mixture (additive) in nickel tends to segregate to grain boundaries, and magnesium is no exception. Therefore, the bonding force between the grains at the grain boundaries is improved by oxidizing magnesium segregated to the grain boundaries (by taking oxygen from the outside). As a result, the cylindrical electrode 7 formed of the metal material has excellent sputtering resistance. Since the metal material is manufactured by a melting method, the oxide of magnesium does not exist in the form of particles.

The principle of improving the sputtering resistance of the cylindrical electrode 7 is as described above, and also in the present invention, the manufacturability of the electrode unit 6 is improved. That is, since the cylindrical electrode 7 is made of a nickel-based metal material, its melting point is substantially the same as the melting point (1455 ℃) of nickel, and also substantially the same as the melting point (1550 ℃) of kovar, which is a material of the lead 9. Therefore, when the lead 9 is welded and fixed to the cylindrical electrode 7, the two soften and fuse with each other to the same extent, forming an alloy layer therebetween, and are thereby firmly fixed. On the contrary, when the electrode is formed of a high melting point metal such as molybdenum or niobium, the lead 9 is only melted and fixed, and thus the bonding strength and the bonding process are easily restricted. The present invention can solve the above problems simultaneously. Further, since most of the metal materials are nickel, the cost is not much different from that of the nickel electrode.

Next, another example of the embodiment of the cold cathode fluorescent lamp of the present invention will be described. The structure of the lead wires constituting the electrode unit is different from that of the cold cathode fluorescent lamp shown in fig. 1 in the cold cathode fluorescent lamp of this example. Therefore, only the structure of the lead wire will be described below, and the description of the same components as those of the cold cathode fluorescent lamp shown in fig. 1 will be omitted.

Fig. 3 shows the structure of the lead wire 9b constituting the electrode unit 6b of the cold cathode fluorescent lamp in this example. The lead 9b has a multilayer structure (double-layer structure) as follows: an inner portion 32 made of copper (Cu) or a copper alloy is provided inside an outer portion 33 made of kovar. The inner side 32 serves to dissipate heat generated by the electrodes. A dumet copper-iron-nickel alloy wire 34, which is formed by covering the periphery of an iron-nickel alloy with copper, is joined to the tip of the multilayer structure portion, and is connected to a power supply device (not shown) through the dumet copper-iron-nickel alloy wire 34.

The cylindrical electrode 7 shown in fig. 3 is made of the same metal material as that described above. Therefore, the sputtering resistance is completely the same as that of the cylindrical electrode 7 shown in fig. 1 and 2. Since the melting point of the cylindrical electrode 7 is substantially the same as the melting point of nickel, an excessively high temperature is not required for bonding with the lead 9 b. Therefore, the possibility that the inner side portion 32 of the lead 9b is overheated by heat at the time of welding, causing copper or a copper alloy to be blown out to the outside is reduced. Therefore, the heat dissipation performance of the lead 9b can be sufficiently ensured.

As described above, the cylindrical electrode constituting the cold cathode fluorescent lamp or the electrode unit of the present invention is formed of a metal material obtained by heat-treating a nickel-based metal in which magnesium is dispersed to oxidize the dispersed magnesium. Further, according to the method of manufacturing an electrode unit of the present invention, it is possible to obtain an electrode unit having a cylindrical electrode formed of a metal material obtained by subjecting a nickel-based metal in which magnesium is dispersed to a heat treatment to oxidize the dispersed magnesium. Therefore, the sputtering resistance of the cylindrical electrode can be improved, and the life of the cold cathode fluorescent lamp can be extended.

While the preferred embodiments of the present invention have been illustrated and described in detail, it is to be understood that: various changes and modifications can be made without departing from the spirit and scope of the claims.

Claims (9)

1. A cold cathode fluorescent lamp having:

a glass tube in which at least rare gas and mercury gas are sealed in an inner space hermetically sealed, and a phosphor layer is formed on an inner wall surface thereof;

a pair of cylindrical electrodes disposed in the internal space, each of the cylindrical electrodes having a bottom surface portion at one end and an opening portion at the other end, the cylindrical electrodes being disposed so that the opening portions face each other; and

a lead wire having one end joined to the bottom surface portion and the other end led out to the outside of the glass tube;

wherein the cylindrical electrode is formed of a metal material obtained by subjecting a nickel-based metal in which magnesium is dispersed to a heat treatment to oxidize the dispersed magnesium.

2. The cold cathode fluorescent lamp of claim 1, wherein the cylindrical electrode contains 0.005 to 0.15 weight percent magnesium.

3. An electrode unit having: a cylindrical electrode having a bottom surface portion formed at one end and an opening portion formed at the other end; and a lead wire joined on the bottom surface portion of the cylindrical electrode;

wherein the cylindrical electrode is formed of a metal material obtained by subjecting a nickel-based metal in which magnesium is dispersed to a heat treatment to oxidize the dispersed magnesium.

4. The electrode unit according to claim 3, wherein the magnesium is contained in the cylindrical electrode in an amount of 0.005 to 0.15 wt%.

5. A method of manufacturing an electrode unit, comprising:

a step of subjecting a nickel-based metal material in which magnesium is dispersed to a heat treatment to oxidize the dispersed magnesium;

processing the metal material subjected to the oxidation treatment into a cylindrical shape having a bottom surface portion formed at one end and an opening portion formed at the other end; and

and a step of bonding one end of the lead to the bottom surface portion.

6. The method of manufacturing an electrode unit according to claim 5, wherein the heating treatment is performed in an oxygen atmosphere.

7. The method of manufacturing an electrode unit according to claim 5, wherein the heating treatment is performed in a water vapor atmosphere.

8. The method for manufacturing an electrode unit according to any one of claims 5 to 7, wherein a heating temperature at the time of the heating treatment is 820 ℃ or higher and 1080 ℃ or lower.

9. The method of manufacturing an electrode unit according to any one of claims 5 to 7, wherein a mixing ratio of magnesium in the metal material is 0.005 percent by weight or more and 0.15 percent by weight or less.