JP4371924B2 - Cold cathode fluorescent lamp, cylindrical electrode and electrode unit - Google Patents

Description

  The present invention relates to a cold cathode fluorescent lamp, and more particularly, to an improvement in an electrode of a cold cathode fluorescent lamp.

  In recent years, with the increase in size and brightness of liquid crystal panels, cup-shaped electrodes using a high melting point sintered metal are used for the electrodes of cold cathode fluorescent lamps that are light sources. Specifically, a cup-shaped electrode using molybdenum (Mo), niobium (Nb) or the like having a low work function and excellent spatter resistance compared to nickel (Ni) is used (see, for example, Patent Document 1). ). However, an electrode using a high melting point sintered metal has the following problems, while having the above advantages. That is, it is necessary to weld a lead wire for applying a voltage to the electrode of the cold cathode fluorescent lamp. However, when the electrode is made of a sintered metal having a high melting point, sufficient bonding strength cannot be obtained unless very high heat is applied when welding one end of the lead wire to the electrode. Furthermore, when a lead wire in which the outer side of a copper or copper alloy wire is covered with Kovar is used, the internal copper may be overheated by the heat at the time of welding to the electrode and blown out to the outside.

Therefore, Patent Document 2 discloses a technique in which the welding temperature is lowered by providing a nickel layer having a melting point lower than that of the electrode material at the tip of the lead wire welded to the electrode.
Japanese Patent Laid-Open No. 2002-358992 JP 2003-187740 A

  In addition to the above problems, electrodes using high melting point sintered metals such as molybdenum (Mo) and niobium (Nb) have another problem that the surface is oxidized when sealed in a glass tube. Specifically, in the manufacturing process of the cold cathode fluorescent lamp, after an electrode is disposed at the end of the glass tube, the end of the glass tube is hermetically sealed with sealing glass (bead glass). However, heat at the time of melting the bead glass is transmitted to the electrode, and the electrode surface is oxidized by the heat. Furthermore, high melting point sintered metals such as molybdenum (Mo) and niobium (Nb) have the property that they are difficult to be reduced once oxidized.

  An object of the present invention is to simultaneously solve the above two problems such as the above-mentioned problem caused by overheating at the time of welding with a lead wire and surface oxidation at the time of encapsulation in a glass tube.

  The cold cathode fluorescent lamp of the present invention is arranged in a glass tube in which at least a rare gas is sealed in an internal space hermetically sealed with a sealing glass and a phosphor layer is formed on an inner wall surface, and the internal space. A cold cathode fluorescent lamp having a cylindrical electrode and a lead wire having one end bonded to the outer surface of the cylindrical electrode and the other end penetrating the sealing glass and drawn out of the glass tube. The electrode has a first metal layer constituting the inner surface, a second metal layer constituting the outer surface, a sintered metal layer provided between the first metal layer and the second metal layer, The first metal layer and the second metal layer are made of a metal that has a lower melting point than the sintered metal forming the sintered metal layer and is easily reduced.

  According to the present invention having the above configuration, the surface oxidation of the sintered metal layer when the cylindrical electrode is sealed in the glass tube is avoided by the first metal layer and the second metal layer, and the oxidation of these metal layers is performed. Will be reduced later. In this sense, the first metal layer and the second metal layer function as a protective layer for the sintered metal layer. Further, the outer surface of the cylindrical electrode to which the lead wire is welded is constituted by a second metal layer having a lower melting point than the sintered metal layer. Therefore, the cylindrical electrode and the lead wire are sufficiently firmly bonded even at a lower welding temperature than when the lead wire is directly welded to the sintered metal layer.

  As is apparent from the above description, the cylindrical electrode only needs to be provided with a sintered metal layer between the inner surface made of the first metal layer and the outer surface made of the second metal layer. The layer structure is not limited. For example, one or more other metal layers are interposed between the first metal layer and the sintered metal layer, or one other metal layer is interposed between the second metal layer and the sintered metal layer. It may be interposed as described above.

  Moreover, even if the cylindrical electrode and the lead wire are previously unitized by a manufacturing process independent of the manufacturing process of the cold cathode fluorescent lamp, in a series of manufacturing processes of the cold cathode fluorescent lamp, A separate cylindrical electrode and a lead wire may be joined and integrated. That is, when the cylindrical electrode is inserted into the glass tube, it is only necessary that the lead wire is bonded to the outer surface of the cylindrical electrode.

  The first metal layer and the second metal layer are inferior in spatter resistance compared to the sintered metal layer, and the first metal layer and the second metal layer are lost with the passage of time. There is no inconvenience even if the binder metal layer is exposed. This is because sintered metal electrodes have the above-mentioned advantages in the first place, but during the operation of the cold cathode fluorescent lamp, they are exposed to heat generation and oxidizing atmosphere that oxidizes the sintered metal layer. Because there is no. From this point of view, it is desirable that the first metal layer and the second metal layer are sputtered after the electrodes are enclosed in the glass tube, and the sintered metal layer is exposed. However, if the metal struck out by sputtering from the first metal layer and the second metal layer becomes excessive, there is a possibility that amalgam is generated by combining with mercury enclosed in the internal space. Therefore, the thickness of the first metal layer constituting the inner surface of the cylindrical electrode that is more easily sputtered during lighting is set to the minimum thickness necessary to achieve the purpose of preventing oxidation of the sintered metal layer. It is desirable. Of course, from the viewpoint of avoiding the occurrence of amalgam, the thickness of the second metal layer is not too thin, but the second metal layer is not only for preventing oxidation of the sintered metal layer, but also for the cylindrical electrode and It also plays another role of firmly joining the lead wire. Therefore, when setting the thickness of the second metal layer, it is necessary to take this viewpoint into consideration. When the above is considered comprehensively, the ratio of the thickness of the first metal layer to the thickness of the sintered metal layer is within the range of 1:45 to 2: 5, and the thickness of the second metal layer and the sintered metal layer. It is desirable that the ratio with the thickness of the material be in the range of 1: 9 to 7:20.

  Without sacrificing the advantages of sintered metal electrodes with low work function and excellent spatter resistance, problems due to surface oxidation during encapsulation of electrodes in glass tubes and overheating during lead wire bonding can be solved simultaneously .

(Embodiment 1)
Hereinafter, an example of an embodiment of a cold cathode fluorescent lamp of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view showing a schematic structure of the cold cathode lamp of this example.

  In the cold cathode fluorescent lamp 1 shown in FIG. 1, 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 3.0 mm. However, 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 enclosed 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 the atmospheric pressure. ing.

  A pair of electrode units 6 is provided at both ends of the glass tube 2 in the longitudinal direction. Each electrode unit 6 includes a cylindrical electrode 7 and a lead wire 9 bonded to the bottom surface 8 of the cylindrical electrode 7. The cylindrical electrode 7 provided in one electrode unit 6 is disposed at a position slightly inside the longitudinal end of the internal space 5 of the glass tube 2 in a direction facing the cylindrical electrode 7 provided in the other electrode unit 6. One end of each lead wire 9 is welded to the bottom surface 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 above is the schematic structure of the cold cathode fluorescent lamp 1 of this example.

  Next, each electrode unit 6 shown in FIG. 1 will be described in more detail with reference to FIGS. FIG. 2 is an enlarged perspective view showing the electrode unit 6 provided in the cold cathode fluorescent lamp 1, and FIG. 3 is an enlarged sectional view.

  As shown in FIG. 2, the cylindrical electrode 7 constituting the electrode unit 6 has a metal plate in a cylindrical shape (cup shape) having an opening 10 in one longitudinal direction and the other closed by a bottom 11. One end face 12 of the lead wire 9 is welded to the bottom face 8 of the cylindrical electrode 7. The metal plate as the material of the cylindrical electrode 7 has a multilayer structure (three-layer structure) in which a sintered metal layer made of molybdenum is laminated between two metal layers made of nickel or a nickel alloy. Here, one of the two metal layers is formed relatively thin compared to the other. Nickel or a nickel alloy has a property that it has a lower melting point than molybdenum and is easily reduced.

When the cylindrical electrode 7 is press-formed from the metal plate, pressure is applied to the metal plate from the metal layer side having the smaller thickness toward the other metal layer side. Therefore, the cylindrical electrode 7 shown in FIG. 2 has a sectional structure as shown in FIG. That is, the inner surface 21 is constituted by the first metal layer 20, and the outer surface 23 is constituted by the second metal layer 22, and the sintered metal layer is interposed between the first metal layer 20 and the second metal layer 22. 24 is provided. As a result, the bottom surface (a part of the outer surface 23) 8 of the cylindrical electrode 7 to which the end surface 12 of the lead wire 9 is welded is constituted by the second metal layer 22, and the thickness (t ₁₎ of the sintered metal layer 24. ) is thin it can be seen than the first metal layer 20 having a thickness (t ₂₎ and a second thickness of the metal layer 22 (t _3).

  However, in the cylindrical electrode 7, the inner surface 21 is formed by the first metal layer 20, the outer surface 23 is formed by the second metal layer 22, and the sintered metal layer 24 is disposed between the metal layers 20 and 22. If so, the same effect can be obtained even with a multilayer structure of four or more layers. Specifically, one or more other metal layers are laminated between the first metal layer 20 and the sintered metal layer 24, or between the second metal layer 22 and the sintered metal layer 24. One or more other metal layers may be laminated.

  The metal constituting the first metal layer 20 and the second metal layer 22 is nickel or nickel as long as it has a lower melting point than the sintered metal constituting the sintered metal layer 24 and is easily reduced. It is not limited to alloys.

  As shown in FIG. 3, in the cylindrical electrode 7 in this example, a part of the sintered metal layer 24 is exposed to the outside at the end face (periphery of the opening 10), and this part is also the first metal. It may be configured to be covered by the layer 20 or / and the second metal layer 22.

  Furthermore, the forming method of the cylindrical electrode 7 is not limited to the above method. For example, the first metal layer 20 and the second metal layer 22 may be formed after the sintered metal plate is pressed into a cylindrical shape. Moreover, after pressing the metal plate by which the metal layer used as the 1st metal layer 20 or the 2nd metal layer 22 is laminated | stacked beforehand on the single side | surface of a sintered metal layer, the 2nd metal layer 22 or the 1st The metal layer 20 may be formed.

(Embodiment 2)
Hereinafter, other examples of the embodiment of the cold cathode fluorescent lamp of the present invention will be described. However, the basic configuration of the example cathode fluorescent lamp of this example is the same as that of the cold cathode fluorescent lamp of Embodiment 1, and only the configuration of the electrode unit is different. Therefore, only the configuration of the electrode unit included in the cold cathode fluorescent lamp of this example will be described, and description of the other configurations will be omitted.

  The difference between the electrode unit included in the cold cathode fluorescent lamp of this example and the electrode unit included in the cold cathode fluorescent lamp of Embodiment 1 is in the lead wire. Specifically, as shown in FIG. 4, the lead wire 31 constituting the electrode unit 30 included in the cold cathode fluorescent lamp of this example is an outer portion in which an inner portion 32 made of copper (Cu) or a copper alloy is made of Kovar. 33 has a multilayer structure (two-layer structure) covered with 33. In addition, about the structure same as the electrode unit 6 with which the cold cathode fluorescent lamp 1 of Embodiment 1 is provided, the same code | symbol is attached | subjected in a figure and description is abbreviate | omitted.

  The lead wire 31 shown in FIG. 4 can be manufactured as follows, for example. First, as shown in FIG. 5A, while rolling a Kovar plate material in the width direction using a roller die 40, the contacting end surfaces in the width direction are welded in an argon gas atmosphere to form a hollow Kovar. The tube 41 is manufactured (Kovar manufacturing process). Next, as shown in FIG. 5 (b), a copper or copper alloy wire 42 is inserted into the internal space of the Kovar tube 41 (wire rod insertion step). Thereafter, as shown in FIG. 5C, the Kovar tube 41 in which the wire 42 is inserted is passed through a rotating swaging die 43 to be drawn. Next, the drawn Kovar tube 41 and the wire 42 are annealed in a hydrogen gas atmosphere. By this annealing step, a metal diffusion layer is formed between the outer peripheral surface of the wire 42 and the inner peripheral surface of the Kovar tube 41, and the adhesion between the Kovar tube 41 and the wire 42 is improved. Further, distortion generated in the Kovar tube 41 by the annealing is also removed. Here, Kovar and copper have good compatibility in the above-mentioned adhesion, and have an advantage that it is difficult to cause a decrease in thermal conductivity due to poor adhesion. After completion of the annealing step, as shown in FIG. 5 (d), the Kovar tube 41 and the wire 42 are drawn through a hole die 44, finished to a predetermined outer diameter, and as shown in FIG. Cut to length.

  As described above, the cylindrical electrode 7 shown in FIG. 4 has the same multilayer structure as the cylindrical electrode 7 shown in FIG. That is, the bottom surface 8 of the cylindrical electrode 7 to which the end surface 12 of the lead wire 31 is welded is constituted by the second metal layer 22 having a lower melting point than the sintered metal layer 24. Therefore, the cylindrical electrode 7 and the lead wire 31 can be sufficiently firmly joined to each other at a welding temperature lower than that when the lead wire 31 is welded to the sintered metal layer 24. There is no inconvenience that the inner part 32 of 31 is overheated and blows out. The point that the surface oxidation of the sintered metal layer 24 is effectively suppressed when the electrode is sealed in the internal space of the glass tube is the same as that of the cylindrical electrode 7 shown in FIG.

It is typical sectional drawing which shows an example of embodiment of the cold cathode fluorescent lamp of this invention. It is an expansion perspective view of the electrode unit shown in FIG. It is an expanded sectional view of the electrode unit shown in FIG. It is an expanded sectional view showing other examples of an electrode unit. (A)-(e) is a schematic diagram which shows an example of the manufacturing process of a lead wire.

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 Electrode unit 7 Cylindrical electrode 8 Bottom surface 9 Lead wire 10 Opening part 11 Bottom 20 First metal layer 21 Inner surface 22 Second metal layer 23 Outer surface 24 Sintered metal layer 30 Electrode unit 31 Lead wire 32 Inner portion 33 Outer portion 40 Roller die 41 Kovar tube 42 Wire rod 43 Die 44 Hole die

Claims (7)

A glass tube in which at least a rare gas is sealed in an internal space hermetically sealed with a sealing glass and a phosphor layer is formed on an inner wall surface, a cylindrical electrode disposed in the internal space, and one end A lead wire joined to the outer surface of the cylindrical electrode, the other end penetrating the sealing glass and drawn out of the glass tube;
The cylindrical electrode includes a first metal layer constituting an inner surface, a second metal layer constituting an outer surface, and a sintered metal provided between the first metal layer and the second metal layer. And having a layer
The first metal layer and the second metal layer are cold cathode fluorescent lamps having a melting point lower than that of the sintered metal forming the sintered metal layer and formed of a metal that is easily reduced ,
The cold cathode fluorescent lamp, wherein the first metal layer and the second metal layer are formed of nickel or a nickel alloy, and the sintered metal layer is formed of molybdenum, niobium, or an alloy thereof . The ratio between the thickness of the first metal layer and the thickness of the sintered metal layer is 1:45 to 2: 5, and the ratio between the thickness of the second metal layer and the thickness of the sintered metal layer is The cold cathode fluorescent lamp according to claim 1, wherein the ratio is 1: 9 to 7:20. The cold cathode fluorescent lamp according to claim 1 or 2 , wherein the lead wire has a multilayer structure in which an inner portion made of copper or a copper alloy is covered with an outer portion made of Kovar. Having a first metal layer forming the inner surface, and a second metal layer constituting the outer surface, and a sintered metal layer provided between their first and second metal layers The first metal layer and the second metal layer are used for a cold cathode fluorescent lamp having a melting point lower than that of the sintered metal forming the sintered metal layer and formed of a metal that is easily reduced. A cylindrical electrode,
A cylindrical electrode in which the first metal layer and the second metal layer are formed of nickel or a nickel alloy, and the sintered metal layer is formed of molybdenum, niobium, or an alloy thereof . The ratio between the thickness of the first metal layer and the thickness of the sintered metal layer is 1:45 to 2: 5, and the ratio between the thickness of the second metal layer and the thickness of the sintered metal layer is It is 1: 9-7: 20, The cylindrical electrode of Claim 4 . An electrode unit comprising the cylindrical electrode according to claim 4 or 5 , and a lead wire having one end joined to an outer surface of the cylindrical electrode. The electrode unit according to claim 6, wherein the lead wire has a multilayer structure in which an inner portion made of copper or a copper alloy is covered with an outer portion made of Kovar.

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