JPWO2005069349A1 - Discharge electrode, discharge lamp, discharge electrode manufacturing method and manufacturing apparatus - Google Patents

Abstract

Not only the bonding strength between the cup material of the electrode of the cold cathode fluorescent tube as the backlight of the liquid crystal panel and the connection (lead) wire, but also excellent characteristics as an electrode of the cold cathode fluorescent tube are imparted. One or more refractory metals such as Mo, W, Ta, Nb, or a small amount of Ni, Cu, etc. having a function of improving the workability of the refractory metal in the warm state and a function of adjusting crystal grain growth. In the electrode of a cold cathode fluorescent tube made of one or more refractory metals to which various alloy materials are added, or these single crystal metals, the cup part or the lead wire part (rod) and the cup part are warm or heat It is a discharge electrode integrally formed by pressing, extruding, ironing or the like.

Description

  The present invention relates to a discharge electrode, a discharge lamp, a method for manufacturing a discharge electrode, and a manufacturing apparatus suitable for a backlight used as a light source that transmits a liquid crystal panel, particularly a cold cathode fluorescent tube (CCFL).

  The electrode of the cold cathode fluorescent tube is called a cup because of its form. In order to cause the cold cathode fluorescent tube to emit light, a high-voltage AC power supply is loaded on the cup, so that the cup is likely to generate heat.

  For this reason, as described in Patent Document 1, instead of the conventional Ni, the cup material, including the lead-in wire, has good thermal conductivity in terms of material, withstands high temperatures, and even at high temperatures. It is desirable to use a refractory metal such as W, Nb, Ta, or Mo that is not affected by current-carrying characteristics and has good sputtering resistance.

Further, in Patent Document 2, these refractory materials to which a small amount of Ni is added in order to make the cup portion and the wiring portion into an integral structure from the need to increase the strength and thermal conductivity of the cup portion and the wiring portion are conventionally used. Instead of drawing, it is disclosed that this powder is injection-molded, and further discharge characteristics are improved by adding oxides such as La ₂ O ₃ , Y ₂ O ₃ , ZrO ₂ , and CeO ₂ . .

Furthermore, Patent Document 3 and Non-Patent Document 1 disclose that a press mold is used to increase the strength and minimize the size as a manufacturing method with such an electrode.
JP 2003-151696 A JP 2003-242927 A JP 2003-59445 A Press die selection book “Compression die” by Hirokazu Yamamoto

  Backlights described in the above patent documents, in particular, use of a metal having excellent spatter resistance as an electrode material for a cold cathode fluorescent tube (CCFL), formation of a refractory metal cup portion, cup portion and wiring portion It is considered that it is significant from the viewpoint of the required characteristics of the electrode to form an integral structure so that the joint portion with the electrode becomes a fine crystal wire of the same quality and to press work the electrode material.

  However, the press working described in Patent Document 3 is an ordinary metal working method using the metal mold described in Non-Patent Document 1 as it is. In plastic processing that requires large deformation, cracks occur and this is impossible in reality.

  In any case, the electrode of the conventional cold cathode fluorescent tube (CCFL) has a large electrode resistance, a severe cathode voltage drop, a low luminous efficiency in terms of luminance and power consumption, and difficult to plastically process a refractory metal, Since the cup portion and the rod portion are joined by welding or the like, there are many problems to be improved such as poor mechanical strength against bending and pulling of the joint portion.

  The problems to be solved by the present invention are, in particular, plastic processing of a refractory metal having excellent characteristics as an electrode, and a cold cathode fluorescent tube free from defects such as cracks using a refractory metal material as a backlight of a liquid crystal panel. In addition to improving the bonding strength between the production of the electrode cup material and the connection between the cup material and the connection (lead) wire, it is intended to impart excellent characteristics as an electrode of a cold cathode fluorescent tube.

  The present invention is a small amount of Ni having one or more refractory metals such as Mo, W, Ta, Nb, or a function of improving the workability of the refractory metal in the warm state and a function of adjusting grain growth. In the electrode of a cold cathode fluorescent tube made of one or more refractory metals to which an alloy material such as Cu is added, or made of these single crystal metals, the cup portion or the lead wire portion (rod) and the cup portion This is a discharge electrode formed by subjecting the integrally formed body to warm or hot processing by pressing, extruding, ironing or the like.

  The term “warm” as used in the processing temperature in the present invention means a temperature that is not lower than the ductile brittle transition temperature and lower than the recrystallization temperature, and in a high melting point metal such as Mo, W, Ta, and Nb, a temperature range of 100 to 1000 ° C. Say. When this processing temperature range is below this temperature, processing such as pressing, extrusion, and ironing becomes difficult, cracks occur, and it becomes impossible to manufacture a very small electrode member. Further, when the processing temperature exceeds this warm region, recrystallization occurs, and the performance of mechanical properties such as bending strength as an electrode material is deteriorated.

  In the cold cathode fluorescent tube electrode according to the present invention, the crystal structure is a cup portion or a fiber shape in which the cup portion and the rod are common, that is, the tissue crystal growth direction is the length direction of the electrode, and has a high aspect ratio of 2 or more. In addition to excellent mechanical strength, heat dissipation, and energization effect, it can be a minimal electrode having excellent hollow cathode effect characteristics as an electrode of a cold cathode fluorescent tube.

  If the aspect ratio is smaller than 2, cracks are likely to occur inside due to the thermal history, and deformation easily occurs, so the aspect ratio needs to be 2 or more.

  When the material of the electrode of the present invention is a single crystal, the ductile brittle transition temperature is significantly lower than that of a polycrystalline material, and not only the processing temperature can be lowered but also the electrical resistance can be lowered.

  Since the life of the cup-type discharge electrode is determined by electrode wear rather than by sputtering of the electrode material at the bottom of the cup, at least the thickness of the bottom of the cup needs to be equal to or greater than the thickness of the cup side periphery.

  Since the ratio of the thickness of the bottom part of the cup part to the thickness of the cup side peripheral part is 1 or more, the electrode of the present invention can suppress a decrease in life due to sputtering of the electrode.

  The electrode of the present invention has an increased hollowness such as the shape of the inner bottom of the cup, the shape of the outer edge, and the wall thickness, and can have an uneven shape only on the inner surface of the electrode or on the outer and inner surfaces. In addition, it is a shape body having an excellent γ action, and furthermore, a so-called fin having an uneven surface shape for heat dissipation can be formed on the outer surface of the rod. It is possible to prevent a decrease in transparency of the fluorescent tube due to metal sputtering. In addition, so-called fins having a concavo-convex shape can be formed on the outer surface of the cup portion in order to increase the electron emission efficiency, and this is a minimal electrode with improved characteristics as an electrode of a cold cathode fluorescent tube.

Since the discharge electrode member according to the present invention processes a high-hardness refractory metal in the warm region or the hot region, it is applied to a press member such as a punch or die with high thermal conductivity and high hardness. High strength heat resistant ceramics or carbide or cermet having releasability from the workpiece can be used, for example, Si ₃ N ₄ , SiC, WC-Ni carbide, WC-TiC-TaC ultra A mold made of a cermet such as a so-called binderless carbide, Mo ₂ NiB ₂ or the like is used.

  Also, during warm pressing, the electrode of the cold cathode fluorescent tube needs to have a flat end face of the cup part or the end face of the rod part. In addition, it is preferable to provide a function that responds to an increase in the flow amount of the material in a fixed or variable manner.

The present invention has the following effects.

1. The discharge electrode of the present invention has no cracks inside or on the surface, the electrode has a uniform crystal structure, excellent mechanical strength, uniform electrical resistance, no partial abnormal heat generation, and long life. Can be achieved.

2. Since the length direction of the electrode and the crystal elongation direction are the same, the mechanical strength is high.

3. Since the cup part or the cup part and the rod part are integrally formed, the manufacturing cost is reduced.

4). Organizational factors that hinder electron emission such as interfaces and segregation on the electrode surface are reduced.

5. The machining shape freedom increases considerably, the γ action becomes smooth, the hollow cathode effect increases, and the luminance and luminous efficiency are improved.

6). The sustaining voltage is lowered and the luminance is improved.

7). The electrode of the present invention is manufactured not by punching a plate material with a punching die and molding it by pressing as in the prior art, but by directly manufacturing an approximately large cylindrical material by press molding. Manufacturing costs can be reduced.

  Hereinafter, an embodiment in which the embodiment of the present invention is applied to an electrode of a cold cathode fluorescent tube (CCFL) having a diameter of 2.2 mm as a backlight of a liquid crystal panel will be described.

  FIG. 1 shows a sample 1 as a starting material 1 which was tempered at 100 to 1500 ° C. and heated to 300 ° C. after pure Mo having a diameter of 2.2 mm and a length of 2.4 mm. FIG. 2 shows a configuration of a press 10 for warm-pressing the sample 1 shown in FIG.

The press machine 10 includes a WC-Ni carbide die 13 having a molding space 11 and a rod portion molding space 12 that match the outer surface of the cup portion, and a molding space 11 that matches the outer surface of the cup portion of the die 13. A punch 14 entering the The punch 14 is prepared in a shape in which the outer diameter is matched with the inner diameter of the cup portion and the lower surface is matched with the inner bottom surface of the molding cup portion. Reference numeral 15 denotes a mold material for flattening the upper end surface of the cup portion of the molded electrode. When the mold 13 is made of ceramics such as Si ₃ N ₄ or SiC, the wear resistance is improved. When carbide is used, it has high toughness and can withstand high processing pressure. When a cermet such as Mo ₂ NiP ₂ is used, it has better wear resistance than cemented carbide and can withstand the processing pressure than ceramics.

  Reference numerals 16 and 17 denote spring materials attached to the upper and lower base materials 18 and 19 of the warm press machine 10, respectively. By pressing the upper base material 18 against the lower base material 19, the molding material 1 becomes the mold 13. When the punch 14 enters the inside, it counteracts a fixed or variable resistance against an increase in the flow rate of the material into the mold, and helps uniform deformation. In particular, the spring material 17 attached to the upper base 18 acts on the rear extrusion control plate 15 and has a function of flattening the upper end surface of the molded cup member 101 (FIG. 3).

  Reference numerals 20 and 21 denote pressure adjusting screws, reference numerals 22 and 23 denote heaters (for example, sheathed heaters), and the spring material 16 has a function of flattening the lower end surface of the rod via the front push-out control pin 30. Further, the rods and cups are arbitrarily controlled by controlling the pressures of the spring members 16 and 17 by appropriate amounts. 24-27 are heat insulating materials.

  FIG. 3 shows an electrode 100 formed by a press machine, 101 denotes a cup portion, 102 denotes a rod, and the sizes are a cup portion outer diameter of 2.2 mm, a cup portion inner diameter of 1.8 mm, and a cup portion length. It is 4.9 mm, cup bottom thickness 0.4 mm, depth 4.5 mm, rod length 3 mm, and rod diameter 0.9 mm.

  This press machine 10 was formed at a punch lowering speed of 0.1 mm / s to 20 m / s while maintaining the processing temperature of the processing material 1 at 300 ° C. by the heaters 22 and 23 incorporated in the mold. An electrode 100 having the appearance shown in FIG. As shown in the figure, the cup portion 101 and the current-carrying rod 102 are integrally formed, and the inner surface that affects the discharge function and the discharge function is formed as a smooth surface having a desired size.

  The electrode 100 obtained in this way has an internal crystal structure as shown in FIG. This crystal structure has a fiber shape in which each crystal shown in FIG. 4 has a high aspect ratio of 2 or more.

Table 1 shows the characteristics of the electrode of the present invention thus obtained, an electrode manufactured by a conventional manufacturing method as a comparative example, and a discharge lamp using them.

As is clear from Table 1, in the cold (room temperature) press of the comparative example, the material cracked and the electrode itself could not be manufactured. For this reason, neither measurement of relative density, thermal conductivity, electrical resistivity, or bending strength of the welded part nor manufacture of the lamp could be performed.

  In addition, in the case of the injection molding of the comparative example, it is difficult to sinter high-purity Mo material, and it is necessary to add an active metal such as Ni as a sintering accelerator. Could not be manufactured. Also, the sintered body has many pores, and when energized, the gas in the pores is released, the secondary electrons collide with it, and the number of secondary electrons reaching the phosphor is reduced, so that the luminous efficiency and luminance are reduced. Or gas leakage occurred from the electrode sealing portion of the lamp.

  In the welding method of the comparative example, a structure in which crystal grains have grown and a welding defect are seen at the joint between the cup portion and the rod portion, and the mechanical strength against bending and tension is deformed due to the influence of heat generated by energization. , Low production yield and short life.

  Now, looking at the electrode resistance, which is a problem, the present invention is about 1/4 of that of the injection molding of the comparative example, and is smaller than that of the welding of the comparative example. Efficiency was improved. In addition, the heat generation temperature at the electrode portion was lowered, and the decrease in brightness due to sputtering of the electrode material could be suppressed.

  Looking at the bonding strength between the cup part and the rod part, the value of the bending strength of the bonding part of the present invention is 1.5 to 1.7 times that of the comparative example of welding or injection molding. As a result, the production yield at the time of production and the life of the product were improved.

  Further, the thermal conductivity of the electrode of the present invention is about 1.8 times higher than that of the injection-molded one of the comparative example, which is higher than that of welding. The reduction of the brightness was suppressed.

  In addition, when a single crystal material is used as the electrode material, the electrode electrical resistance is reduced, the power consumption is reduced, the luminance is improved, and the heat generation temperature of the electrode is lowered, so that the sputtering of the electrode material is suppressed and the electrode life is reduced and the brightness is reduced. When the reduction is suppressed and processing is performed, the ductile brittle transition temperature is lower than that of the polycrystalline material (for example, high-purity Mo and the transition temperature is 277 ° C.), so that the mold life is improved.

  Furthermore, in the electrode of the present invention, when the ratio of the thickness of the bottom of the cup part to the thickness of the side periphery is 1 or more, the life is determined by electrode consumption due to sputtering at the bottom of the cup part. Extend.

  As shown in FIG. 5, when fins are provided on the outer periphery of the rod portion of the electrode of the present invention, heat dissipation is improved, electrode material spatter is suppressed, electrode life is improved, and lightness deterioration of the light bulb is suppressed, so that the life of the light bulb is reduced. Improved.

  As shown in FIG. 6, when fins are provided on the outer periphery of the cup portion of the electrode of the present invention, thermionic emission efficiency is improved, the brightness of the bulb is improved, and the luminous efficiency is increased.

  When projections are provided on at least one of the cup inner surface or outer surface of the electrode of the present invention as shown in FIGS. 7A to 7C, the electron emission rate is improved and the luminance is improved.

  In this example, the electrode material using Mo was used. However, one or more of W, Ta, and Nb, or the function of improving workability and adjustment of crystal grain growth in warm or hot conditions. The same result was obtained even when one or more kinds of alloy materials having functions were added.

  And when the manufacturing method and manufacturing apparatus of the present invention are used, the bonding strength between the cup portion and the rod portion with high accuracy, high hardness and no defects such as cracks using a refractory metal is high, and the electrode electrical resistance is small. It was possible to produce an electrode having good light emission effect and good thermal conductivity by suppressing the life reduction and lightness reduction due to sputtering.

  As shown in Table 1, the present invention has excellent characteristics as a discharge tube electrode in terms of electrical characteristics, thermal conductivity, and mechanical strength.

  In the first embodiment, an apparatus as shown in FIG. 2 in which the cup part and the rod part can be formed integrally is used, but the rod part forming space 12 of this apparatus is not provided, and the front extrusion control pin 30 is the lower end of the forming space 11. A cup portion as shown in FIG. 9 was manufactured in the same manner as in Example 1 using the apparatus of the present invention as shown in FIG. 8 having the eject pin 31 for ejecting the workpiece.

  The cup part thus obtained had no cracks inside or on the surface, and its crystal structure was investigated. As in Example 1, each crystal had a high density of 2 or more as shown in FIG. It was in the form of a fiber having an aspect ratio.

  Further, by changing the mold used for molding, as shown in FIG. 11, the outer surface and inner surface of the cup portion can be made uneven, and when used as an electrode, it has an excellent hollow cathode effect and an excellent γ An electrode having an action could be obtained.

  The discharge rod electrode is manufactured by discharging the current-carrying rod of the same or different material on the outer bottom surface of the cup obtained in this way, using electron beam welding, laser beam welding, resistance welding, or brazing to discharge the electrode. Although incorporated and used, the same results as in Table 1 of Example 1 were obtained.

  The present invention can be applied to electrodes such as magnetron end hats, projector-light source electrodes, electron guns, halogen bulb members, etc., in addition to the cold cathodes of the fluorescent tubes of backlights of liquid crystal displays cited as examples.

The external shape of the raw material for shaping | molding of the discharge electrode of this invention is shown. The structure of a warm press for forming a material is shown. The external appearance of the discharge electrode after shaping | molding is shown. The crystal structure of the discharge electrode after shaping | molding is shown. The electrode which has a fin in the rod part outer periphery of the electrode of this invention is shown. The electrode which has a fin in the cup part outer periphery of the electrode of this invention is shown. The electrode which has a processus | protrusion in at least one of the cup inner surface or outer surface of the electrode of this invention is shown. The structure of the warm press for shape | molding only a cup part is shown. The external appearance of the cup part after shaping | molding is shown. The crystal structure of the cup part after shaping | molding is shown. The electrode which has a fin in the cup part outer periphery of this invention is shown.

Explanation of symbols

1: Material 10: Press machine 11: Molding space 12: Rod part molding space 13: Mold 14: Punch 15: Back extrusion control plate 16, 17: Spring material 18: Upper base material 19: Lower base material 20, 21: Pressure adjusting screws 22, 23: heaters 24-27: heat insulating material 30: forward pushing control pin 31: eject pin 100: electrode 101: cup member 102: rod

Claims (11)

  A discharge electrode in which a cup part or a cup part and a rod part are formed by molding a refractory metal material warm or by hot forming.   The refractory metal material is made of one or more of Mo, W, Ta, and Nb, or an alloy material having a function of improving workability and adjusting crystal grain growth in warm or hot conditions is added thereto. The discharge electrode according to claim 1, comprising at least one refractory metal.   The discharge electrode according to claim 1 or 2, wherein a warm forming temperature is in a temperature range of 100 to 1300 ° C.   The crystal structure of the electrode having a cup portion or a common cup portion and rod portion is a crystal growth direction of the electrode and forms a fiber shape having an aspect ratio of 2 or more. The discharge electrode according to any one of the above.   The discharge electrode according to any one of claims 1 to 3, wherein the discharge electrode is made of a single crystal.   The discharge electrode according to any one of claims 1 to 5, wherein the ratio of the thickness of the bottom portion to the thickness of the side peripheral portion of the cup portion is 1 or more.   The discharge electrode according to any one of claims 1 to 6, wherein at least one of the rod portion and the cup portion has a fin shape.   The discharge electrode according to claim 1, further comprising a protrusion on the inner surface or the outer surface of the cup portion.   A discharge lamp having discharge electrodes provided at both ends of a glass bulb, wherein the discharge electrode according to any one of claims 1 to 8 is used.   The cup part or the cup part and the rod part are pressed together with a metal mold made of high melting point metal material with high thermal conductivity, high hardness, high strength heat resistant ceramics or carbide or cermet, A method of manufacturing a discharge electrode in which a mold is fixedly or variably associated with an increase in the amount of material flow in a direction opposite to the plastic flow direction of the material.   A molding space that matches the outer surface of the cup part or a mold that has a molding space that matches the outer surface of the cup part and a molding part of the rod part, an outer diameter that matches the inner diameter of the cup part, and a lower surface that is the inner bottom surface of the molding cup part A punch having a combined shape and a cup upper end surface mold material for flattening the upper end surface of the cup portion of the molded electrode or a cup upper end surface mold material for flattening the upper end surface of the cup portion of the molded electrode, and A rod lower end surface mold material for flattening the lower end surface of the rod portion of the molded electrode, and a mold material for flattening the upper end surface of the cup portion or for flattening the upper end surface of the cup portion Discharge electrode manufacturing apparatus comprising a warm or hot press, in which a member that resists variably or variably against the increase in the flow rate of the material into the mold is provided in the mold material and the rod part forming space .