JP3990406B2 - Cold cathode fluorescent lamp, electrode, and electrode unit - Google Patents

Description

  The present invention relates to a cold cathode fluorescent lamp, and electrodes and electrode units that constitute a part of the cold cathode fluorescent lamp, and more particularly to an electrode structure of the cold cathode fluorescent lamp.

  In recent years, cold cathode fluorescent lamps are widely used in backlights of liquid crystal panels because of their small size, low power consumption, and long life. In general, a cold cathode fluorescent lamp has a structure in which a pair of electrodes are arranged opposite to each other inside a glass tube filled with a rare gas such as argon and mercury gas, and a lead wire 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 via the lead wire, electrons are emitted from one electrode, collide with mercury atoms, and ultraviolet rays are generated. Ultraviolet rays are converted into visible light by a fluorescent film formed on the surface of the glass tube, and visible light is emitted from the inside of the glass tube. Therefore, the lifetime of the cold cathode fluorescent lamp greatly depends on the consumption of mercury gas.

  The electrodes are usually made of nickel. For example, nickel is 99.7%, manganese is 0.1%, iron is 0.1%, and other impurities (carbon, silicon, copper, sulfur) are 0.1%. . Nickel contains a trace amount of cobalt of about 0.01%. In addition, the above mixing ratio is weight%. When nickel receives an impact of 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 take in mercury gas and become amalgam, the effective amount of mercury gas is reduced. As a result, mercury gas is consumed, leading to a reduction in the lifetime of the cold cathode fluorescent lamp.

Thus, in recent years, a technique for extending the life of a cold cathode fluorescent lamp by using an electrode having good sputtering resistance has been studied. Specifically, a cup electrode technique using molybdenum (Mo), niobium (Nb), etc., which has a lower work function and superior sputtering resistance compared to nickel is disclosed (for example, Patent Documents 1 and 2). reference).
Japanese Patent Laid-Open No. 2002-358992 JP 2003-187740 A

  However, cold cathode fluorescent lamps using these metals have the following problems. First, an electrode using a refractory metal such as molybdenum or niobium has a problem that the surface is oxidized when encapsulated in a glass tube. Specifically, in the manufacturing process of the cold cathode fluorescent lamp, after placing an electrode at the end of the glass tube, the sealing glass (bead glass) at one end of the glass tube is removed with a gas burner or the like in the atmosphere. Seal and seal hermetically by welding to a glass tube. However, heat at the time of melting the bead glass is transmitted to the electrode, and the electrode surface is oxidized by the heat. When the surface of the electrode is oxidized, the spatter resistance is lowered, so that the spatter resistance is not utilized. Moreover, since molybdenum and niobium are not easily reduced once oxidized, it is difficult to reduce them in an atmosphere of hydrogen gas or the like in a subsequent process.

  Second, since molybdenum and niobium are refractory metals, sufficient bonding strength cannot be obtained unless very high heat is applied when welding the lead wire to the electrode. In particular, the melting point of molybdenum is about 3400 ° C., which is considerably higher than the melting point of Kovar (about 1550 ° C.) that is often used as a lead wire. Therefore, it is necessary to sufficiently melt the lead wire and bond it to the electrode. However, since the molybdenum electrode hardly melts, there is a possibility that sufficient bonding strength cannot be obtained as a result. Further, if a temperature at which the molybdenum electrode is sufficiently melted is applied, an excessively high temperature is applied to the lead wire, making bonding difficult. In addition, when a lead wire with a double structure filled with copper is used inside the outer tube made of Kovar, the melting point of copper is even lower at about 1080 ° C, so the internal copper melts first and flows out during welding. There is also a problem of end. Copper is used as a heat dissipation means to release the heat generated by the electrode to the outside of the glass tube when the lamp is used. However, 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 dissipation performance. Leads to.

  Thirdly, molybdenum and niobium are generally expensive, and electrodes based on these are likely to be costly compared to nickel electrodes.

  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 includes a glass tube in which at least a rare gas and a mercury gas are sealed in an airtightly sealed internal space, and a phosphor layer is formed on the inner wall surface, and is disposed in the internal space. A pair of cylindrical electrodes, one end is joined to the bottom surface, and the other end is drawn out of the glass tube. Lead wires. The cylindrical electrode is made of a material having nickel or a nickel alloy as a base material to which titanium is added. The mixing ratio of titanium is 0.01 to 1.55% by weight.

Titanium added to a material based on nickel or a nickel alloy has the property of taking oxygen from the outside and easily segregating at the grain boundaries in the form of oxides. Sputtering tends to occur selectively from crystal grain boundaries where the bonding force between the grains is weak. Therefore, strengthening the bonds between grains at the grain boundaries with titanium improves the sputtering resistance. Since the cold cathode fluorescent lamp of the present invention is based on nickel or a nickel alloy having a low melting point, heating at the time of joining with the lead wire can be performed at a low temperature, and the manufacturability is improved. Furthermore, since the cold cathode fluorescent lamp of the present invention uses nickel or a nickel alloy as a base material, the processability to a cylindrical electrode is good, and it is also effective in suppressing material costs.

  The lead wire may have a two-layer structure in which an outer peripheral portion is formed of a conductor and is filled with copper or a copper alloy.

The electrode of the present invention is a cylindrical electrode used for a cold cathode fluorescent lamp, having a bottom surface at one end and an opening at the other end, made of nickel or a nickel alloy as a base material, and added with titanium. It is made of material. The mixing ratio of titanium is 0.01 to 1.55% by weight.

  The electrode unit of the present invention has the above electrode and a lead wire having one end joined to the bottom surface of the electrode.

  The lead wire may have a two-layer structure in which an outer peripheral portion is formed of a conductor and is filled with copper or a copper alloy.

  As described above, the cold cathode fluorescent lamp of the present invention has a material with improved bonding strength of nickel crystal grain boundaries, so that the spatter resistance superior to that of conventional nickel materials is realized. Moreover, it is excellent in manufacturability and economy, and the object of the present invention can be sufficiently achieved.

  Hereinafter, a first embodiment of a cold cathode fluorescent lamp of the present invention will be described in detail with reference to the drawings. The cold cathode fluorescent lamp of the present invention is suitable for use as a backlight of a liquid crystal panel, but can also be applied to cold cathode fluorescent lamps for other uses. FIG. 1 is a sectional view showing a schematic structure of a first embodiment of a cold cathode lamp.

  The cold cathode fluorescent lamp 1 is configured such that both ends of a glass tube 2 made of borosilicate glass are hermetically sealed with sealing glass (bead glass 3). The outer diameter of the glass tube 2 is in the range of 1.5 to 6.0 mm, preferably in the range of 1.5 to 5.0 mm. The material of the glass tube 2 may be lead glass, soda glass, low lead glass, or the like.

  The inner wall surface 4 of the glass tube 2 is provided with a phosphor layer (not shown) over almost the entire length thereof. The phosphor constituting the phosphor layer can be appropriately selected from existing or new phosphors such as halophosphate phosphors and rare earth phosphors according to the purpose and application of the cold cathode fluorescent lamp 1. Furthermore, the phosphor layer can be composed of a phosphor in which two or more kinds of phosphors are mixed.

  A predetermined amount of rare gas such as argon, xenon, neon and mercury is sealed in the internal space 5 of the glass tube 2 surrounded by the inner wall surface 4, and the internal pressure is reduced to about several tenths of atmospheric pressure. Yes.

  A pair of electrode units 6 are provided at both longitudinal ends of the glass tube 2. Each electrode unit 6 includes a cylindrical electrode 7 and a lead wire 9 bonded to the bottom surface portion 8 of the cylindrical electrode 7. The cylindrical electrode 7 of each electrode unit 6 has an opening 10 of the cylindrical electrode 7 and an opening 10 of the other electrode unit 6 at a position slightly inside the longitudinal end of the internal space 5 of the glass tube 2. They are arranged so that they face each other. One end of each lead wire 9 is welded to the bottom surface portion 8 of the corresponding cylindrical electrode 7, and the other end penetrates the bead glass 3 and is drawn out of the glass tube 2. The lead wire 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. The cylindrical electrode 7 constituting the electrode unit 6 includes a cylindrical portion 23 that is open as one opening portion 10 in the longitudinal direction and is closed by the bottom surface portion 8 on the other side. The cylindrical electrode 7 is formed by pressing 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 material to which a metal having a deoxidizing action (hereinafter referred to as an additive substance) is added using nickel or a nickel alloy as a base material. Additive materials include titanium, zirconium, and hafnium. The mixing ratio of titanium is preferably 0.01 to 2.0% by weight, the mixing ratio of zirconium is preferably 0.05 to 1.1% by weight, and the mixing ratio of hafnium is preferably 0.05 to 1.1% by weight. . The upper limit of each mixing ratio mainly depends on the manufacturability of the cylindrical electrode 7. That is, when the mixing ratio is higher than this, the material becomes hard and it becomes difficult to press-mold into a cylindrical shape. Although the lower limit of each mixing ratio will be described in detail later, it was set from the viewpoint that sufficient anti-sputtering performance can be obtained.

  The composition of one example was nickel 99.7%, titanium 0.05%, manganese 0.15%, and other impurities (carbon, silicon, copper, sulfur, magnesium, iron) 0.1%. . Nickel contains a trace amount of cobalt of about 0.01%.

  Here, the reason why the sputtering resistance of the cylindrical electrode 7 is improved by mixing these metals will be described with reference to FIG. Hereinafter, titanium will be described as an example, but the same applies to zirconium and hafnium. Nickel or a nickel alloy generally has a polycrystalline structure, and a grain boundary B is formed at the boundary surface of the crystal G. Since the crystal grain boundary B is weakly connected with each other, the crystal grain boundary B is easily affected by sputtering. Sputtering mainly occurs from the crystal grain boundary B and gradually spreads inside the crystal G. Also in the case of molybdenum or niobium, when it is oxidized, sputtering proceeds remarkably from the grain boundary B. As described above, since these substances are not easily reduced once oxidized, it is difficult to recover the sputtering resistance.

  In contrast, the present invention utilizes the deoxygenation characteristics of titanium. That is, the additive to nickel tends to segregate at the grain boundary B, and titanium is no exception. Then, by sufficiently segregating titanium to the crystal grain boundary B and taking in oxygen from the outside, the bonding force between the crystals at the crystal grain boundary B is improved, and the sputter resistance of the electrode is improved. The minimum value of the mixing ratio described above is a necessary amount for a sufficient amount of titanium to be distributed at the grain boundaries B for improving the sputtering resistance performance.

  Here, in order to verify how much the sputter resistance performance has improved, a sample was prepared and the sputter performance was confirmed. In the test, titanium, zirconium, and hafnium were separately added to nickel, and a plurality of samples with different addition amounts (% by weight) were prepared to evaluate the spatter resistance and workability. Evaluation was made as a relative comparison with pure nickel. Since the sputter resistance of pure nickel is not very good, it was marked as Δ, and because workability was good, it was marked as ◎. The spatter resistance was determined by visually observing the spatter amount of the electrode, and marked as ◎, ○, Δ in order of increasing spatter amount. The workability was determined by taking into consideration the moldability of the cup-shaped electrode in consideration of the accuracy of the molded shape, the presence or absence of defects, etc. A cross mark of workability is a state having only a workability that is not suitable for practical use. In addition, a sample with a sputtering resistance Δ was not adopted because it has no merit compared with pure nickel. Thus, each sample was evaluated and the result shown in Table 1 was obtained. Samples having both good sputtering resistance and workability were Nos. 2 to 5, 8, 11, and 12 (shown by shading in the table). As described above, it was confirmed that the sputtering resistance performance of the electrode in which titanium, zirconium, and hafnium were added to nickel as additive materials was greatly improved compared to the conventional nickel-made electrode (without additive materials). The sample to which 0.05% by weight of titanium was added had extremely good spatter resistance and workability.

  The cold cathode fluorescent lamp of the present invention not only has improved spatter resistance as described above, but also can improve manufacturability. Since the cylindrical electrode 7 is made of nickel or a nickel alloy as a base material and the mixing ratio of the additive substances is small, the melting point is substantially equal to the melting point of nickel (1455 ° C.). This is almost the same as the melting point (1550 ° C.) of Kovar, which is the material of the lead wire 9, so when the lead wire 9 is welded and fixed to the cylindrical electrode 7, both soften to the same extent, It melts into each other and forms an alloy layer between them to secure it firmly. On the other hand, in the case of an electrode made of a refractory metal such as molybdenum or niobium, there is no choice but to melt and fix the lead wire 9 and there is a tendency for restrictions in terms of adhesion strength and adhesion procedure. The present invention can solve such problems at the same time. Furthermore, since the cold cathode fluorescent lamp of the present invention has a small mixing ratio of the additive substances, the influence on the cost can be minimized. That is, most of the cold cathode fluorescent lamp of the present invention is made of nickel or a nickel alloy, so that it is possible to provide an economical cold cathode fluorescent lamp without much difference in cost from the nickel or nickel alloy electrode.

  Next, a second embodiment of the cold cathode fluorescent lamp of the present invention will be described. The cold cathode fluorescent lamp of this embodiment has a different configuration of the lead tube, and the other parts are the same as those of the first embodiment. Therefore, only the configuration of the lead tube will be described, and the description of the same components as those in the first embodiment will be omitted.

  As shown in FIG. 4, in the lead wire 9b constituting the electrode unit 6b included in the cold cathode fluorescent lamp of this example, the inner part 32 made of copper (Cu) or a copper alloy is inserted into the outer part 33 made of Kovar. Has a multilayer structure (two-layer structure). The inner portion 32 is provided for radiating heat generated from the electrodes. At the tip of the multilayer structure portion, a jumet 34 in which a nickel iron alloy is covered with copper is coupled, and the multi-structure portion is connected to a power supply device (not shown) via the jumet 34.

  As in the first embodiment, the cylindrical electrode 7 is made of a material to which nickel or a nickel alloy is used as a base material and a metal having a deoxidizing action such as titanium, zirconium, hafnium, or the like is added. Accordingly, the sputter resistance is exactly the same as in the first embodiment. Further, the melting point of the cylindrical electrode 7 is about the same as that of nickel, and an excessively high temperature is not required for joining the lead wire 9b. Therefore, the inner portion 32 of the lead wire 9b is overheated by heat during welding, and the copper Is likely to blow out to the outside. For this reason, the heat dissipation of the lead wire 9b is sufficiently ensured.

  While the present invention has been described with reference to the embodiments, the present invention is not limited to the above embodiments, and various modifications can be made. For example, titanium, zirconium, and hafnium are listed as additive substances, but a plurality of these may be used in combination.

  Moreover, since the part which is easy to be sputtered is the part on the bottom face part 8 side of the cylindrical part 23 of the cylindrical electrode, a metal having a deoxidizing action may be mixed only in this part, and the mixing ratio in this part is set. May be raised.

1 is a schematic cross-sectional view showing a first embodiment of a cold cathode fluorescent lamp of the present invention. It is an expansion perspective view of the electrode unit shown in FIG. It is a conceptual diagram of the metal structure for demonstrating the sputter | spatter resistance improvement effect of this invention. It is typical sectional drawing which shows 2nd Embodiment of the cold cathode fluorescent lamp of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cold cathode fluorescent lamp 2 Glass tube 3 Bead glass 4 Inner wall surface 5 Internal space 6, 6b Electrode unit 7 Cylindrical electrode 8 Bottom part 9, 9b Lead wire 23 Cylindrical part

Claims (7)

A glass tube in which at least rare gas and mercury gas are sealed in an airtightly sealed internal space, and a phosphor layer is formed on the inner wall surface;
A pair of cylindrical electrodes disposed in the internal space, having a bottom portion at one end and an opening at the other end, the openings being disposed to face each other;
A lead wire having one end joined to the bottom surface and the other end drawn out of the glass tube;
Have
The cylindrical electrode has a base material made of nickel or a nickel alloy, and is formed of a material to which titanium is added ,
The titanium mixing ratio is 0.01 to 1.55% by weight.
Cold cathode fluorescent lamp.   The cold cathode fluorescent lamp according to claim 1, wherein the titanium is segregated in the form of an oxide at a grain boundary of the base material. The lead wire is outer peripheral portion is formed of a conductive material, having a two-layer structure in which copper or copper alloy is filled in the cold cathode fluorescent lamp according to claim 1 or 2. A cylindrical electrode used in a cold cathode fluorescent lamp,
A bottom part is provided at one end, an opening is provided at the other end, and the base is nickel or a nickel alloy, and is formed of a material to which titanium is added ,
The titanium mixing ratio is 0.01 to 1.55% by weight.
electrode. The electrode according to claim 4 , wherein the titanium is segregated in the form of an oxide at a grain boundary of the base material. An electrode according to claim 4 or 5 , and
A lead wire having one end bonded to the bottom surface of the electrode;
An electrode unit. The electrode unit according to claim 6 , wherein the lead wire has a two-layer structure in which an outer peripheral portion is formed of a conductor and is filled with copper or a copper alloy.

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