JP2008108580A - Electrode for cold-cathode fluorescent lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bottomed cylindrical electrode for a cold cathode fluorescent lamp, wherein coarsening of crystal grains called secondary recrystallization is prevented even under an environment in which high temperature heat history is applied, to enhance a product life, and to further enhance discharge characteristics for realizing high luminance and low power consumption. <P>SOLUTION: This electrode for the cold cathode fluorescent lamp provides a metallic structure in which metal carbide and pores are dispersed in the matrix of Mo and W, and the amount of the metal carbide is 1-50 vol.% and its density ratio is 80-96%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cold cathode fluorescent lamp used for an illumination light source, a backlight of a personal computer monitor, a liquid crystal television, a liquid crystal display for a car navigation system, and the like. It is about.

  As shown in FIG. 1, the cold cathode fluorescent lamp has a structure in which electrodes 3 connected to the outside by terminals 2 are arranged at both ends in a glass tube 1. 4 and a sealed gas 5 composed of a rare gas and a small amount of mercury are sealed. A high electric field is applied to the electrodes 3 at both ends to generate a glow discharge in a low-pressure mercury vapor. The mercury excited by the discharge generates ultraviolet rays, and the ultraviolet rays on the inner surface of the glass tube 1 are excited by the ultraviolet rays. To emit light. In recent years, the electrodes used here are formed in a bottomed cylindrical shape capable of obtaining a hollow cathode effect. In this case, the terminal 2 is bonded to the bottom of the bottomed cylindrical electrode 3 by brazing or the like.

  In recent years, cold cathode lamps with such a structure have been used as a light source for backlights of liquid crystal displays, and recently, they are also applied to liquid crystal displays for liquid crystal televisions and car navigation systems, and the demand for them is increasing. Is expanding. Furthermore, the number of cold cathode fluorescent lamps used in one product is approximately one for a liquid crystal display or the like of 15 inches or less, but a plurality of cold cathodes cannot be obtained because the required brightness cannot be obtained for large monitors and televisions. A fluorescent lamp is used. For this reason, demand is growing rapidly.

Although it is a cold cathode fluorescent lamp whose demand is expanding as described above, the following matters are required for the cold cathode fluorescent lamp and the electrodes used therefor in order to improve the performance of liquid crystal displays and the like.
(1) Due to the demand for thinner and lighter products, cold cathode fluorescent lamps are also required to have a smaller diameter, and with this, electrodes are required to be further reduced in size. Is required to be excellent.
(2) Low power consumption is required for liquid crystal displays and the like, and high efficiency of cold cathode fluorescent lamps is required. In addition to the progress of miniaturization since the lamp brightness increases almost inversely with the lamp inner diameter, the electrode is made of a material having a higher electron emission property, that is, a material having a low work function and a low cathode fall voltage. Application is required.
(3) A liquid crystal display or the like requires one inverter per lamp. For this reason, if the brightness of the cold cathode fluorescent lamp is increased, the number of lamps used per liquid crystal display can be reduced and the cost can be reduced at the same time. From this point of view, it is required to increase the brightness of the cold cathode fluorescent lamp, and the electrode is required to be applied with a material having a low cathode effect voltage.
(4) Since the product life of the liquid crystal display is mainly caused by the life of the cold cathode fluorescent lamp, the cold cathode fluorescent lamp is required to have a longer life. For this reason, application of a material that is difficult to be sputtered is desired as the electrode.
(5) In liquid crystal displays and the like, the competition among manufacturers is intense, and even if the characteristics (1) to (4) are satisfied, they cannot be realized as a product at a high cost. It is desired.

  As an electrode material for a cold cathode fluorescent lamp, nickel that has been conventionally easy to process and has been inexpensive has been used. However, with a nickel electrode, if the discharge current is increased in order to increase the amount of electron emission for higher brightness, The nickel electrode is sputtered by the gas ions in the tube, and there is a problem that the life of the electrode is severely shortened. Further, the increase in the discharge current causes an increase in power consumption, and from this, the application to an electrode made of a material having a lower cathode fall voltage, which is changed to nickel, is demanded.

  Also, a material layer having a lower work function than nickel on the inner peripheral surface of a bottomed cylindrical nickel electrode to increase the amount of emitted electrons has been proposed (see, for example, Patent Documents 1 and 2). . However, such an electrode requires a process of coating a material layer having a low work function, and is easily worn out because the electrode base material is nickel. Recently, it has been commercialized by increasing the bottom thickness. Although these have appeared, they do not satisfy all of the above requirements.

  Furthermore, attempts have been made to apply molybdenum or tungsten to the electrode material as a high melting point metal that has a low work function and is difficult to be sputtered. Specifically, an electrode for a cold cathode fluorescent lamp using molybdenum as an electrode material is formed from a molybdenum rolled plate by punching-deep drawing into a bottomed cylindrical shape, which has a higher melting point and discharge characteristics than nickel. In order to be excellent, the above requirements (1) to (5) are satisfied.

  However, the rolled sheet of molybdenum is easily anisotropic and has poor ductility, so that it is difficult to perform plastic working, and further, the material yield is low, resulting in high costs. It does not meet. Further, only a ratio of the thickness of the cylindrical portion and the bottom portion of about 1: 2 can be obtained due to the limitation of the modeling method, and the design freedom of the shape is limited. In addition, application of tungsten to an electrode is difficult because of the fact that tungsten is hard and has poor ductility, so that deep drawing cannot be performed, and the mass production has not actually been achieved.

JP-A-10-144255 JP 2002-289138 A

  In recent years, in liquid crystal displays and the like, the demands of the above (1) to (5), that is, downsizing, high luminance, and low power consumption are increasing, and an electrode material having excellent discharge characteristics is desired. .

  By the way, in order to investigate the discharge characteristics of the above molybdenum and tungsten, a discharge test was performed by creating a bottomed cylindrical electrode having one end opened with the above molybdenum or tungsten rolled plate at the test sample level. Some of the electrodes showed large fracture holes considered to be due to sputtering at the bottom. As a result of investigating the cause, molybdenum and tungsten are refractory metals. However, in a bottomed cylindrical electrode with one open end, mercury vapor is difficult to reach the bottom of the electrode, resulting in a rare gas discharge and high temperature heat. A history was added, and this high-temperature thermal history caused crystal grain coarsening called secondary recrystallization, and in the electrode having such coarse crystal grains, when the discharge current increased, Despite the use of a melting point metal, it was found that the material was easily scattered by sputtering and the above destruction occurred.

  Therefore, the present invention prevents the coarsening of crystal grains, which is called secondary recrystallization even in an environment where a high temperature thermal history is applied, thereby improving the product life and further increasing the brightness and power consumption. It is an object of the present invention to provide a bottomed cylindrical cold cathode fluorescent lamp electrode having improved discharge characteristics.

  The electrode for a cold cathode fluorescent lamp of the present invention exhibits a metal structure in which metal carbide and pores are dispersed in a Mo or W base, the amount of the metal carbide is 1 to 50% by volume, and the density ratio is 80 to 80%. It is characterized by 96%. In another aspect of the cold cathode fluorescent lamp electrode of the present invention, metal carbides and pores are dispersed in a patchy texture matrix composed of a Mo alloy phase containing W and a W alloy phase containing Mo. It exhibits a metal structure, and the amount of Mo and W is a volume ratio of Mo: W = 10: 90 to 90:10, the amount of the metal carbide is 1 to 50% by volume, and the density ratio is 80. It is characterized by -96%.

  Furthermore, the electrode for the cold cathode fluorescent lamp of the present invention preferably further contains 5% by mass or less of Ni, the average crystal grain size is 3 to 10 μm, and the maximum crystal grain size is 20 μm or less. It is preferable.

  According to the electrode for a cold cathode fluorescent lamp of the present invention, the work function of the base of Mo or W, or the base of a patchy tissue composed of the Mo alloy phase containing W and the W alloy phase containing Mo is obtained. By forming a metal structure in which small metal carbides are dispersed, the discharge characteristics are further improved, and even in an environment where high-temperature thermal history is applied, coarsening of crystal grains, which is called secondary recrystallization, is suppressed. Sputtering due to an increase in current can be prevented, and thereby the product life of the electrode can be improved.

  In the electrode for the cold cathode fluorescent lamp of the present invention, the discharge characteristics of the electrode are ensured by using molybdenum or tungsten having a low work function and a high melting point as a base, and a stable metal carbide having a lower work function and a base is used. Dispersion in the electrode can further improve the discharge characteristics of the electrode and can suppress secondary recrystallization of crystal grains due to the pinning effect of the metal carbide dispersed in the matrix.

  An electrode for a cold cathode fluorescent lamp exhibiting such a metal structure can be obtained by sintering raw material powder obtained by mixing carbide powder with molybdenum powder or tungsten powder having a low work function and a high melting point. In addition, the cold cathode fluorescent lamp electrode obtained by sintering the raw material powder is a surface having pores and irregularities derived from the raw material being a metal powder, and is formed by punching from a rolled plate-deep drawing As a result, the ionization effect is increased. Moreover, since the pores remaining in the base suppress the coarsening of the crystal grains by the pinning effect, the effect of preventing the secondary recrystallization of the crystal grains can be obtained. However, when the density ratio exceeds 96%, the pores remaining in the sintered body are scarce, and the effect of improving the ionization effect is poor due to the increase of independent pores, and secondary recrystallization of each phase by the pores. The effect to prevent becomes poor, and it becomes close to that formed by punching from a rolled plate-deep drawing. On the other hand, when the density ratio is less than 80%, the mechanical strength of the electrode is remarkably weakened, and breakage easily occurs during handling in the subsequent lamp manufacturing process. Therefore, the density ratio of the cold cathode fluorescent lamp electrode is desirably 80 to 96%.

  When the dispersion amount of the metal carbide is less than 1% by volume, the improvement of discharge characteristics is poor and the effect of suppressing the growth of crystal grains due to the pinning effect is poor. On the other hand, when the amount of the metal carbide exceeds 50% by volume, the molybdenum powder and tungsten powder forming the matrix are inhibited from diffusion bonding by sintering, and the density of the electrode is remarkably lowered.

  As described above, in the cold cathode fluorescent lamp electrode of the present invention, the metal carbide is dispersed in the matrix to suppress the secondary recrystallization of the crystal grains. Therefore, it is preferable to use a powder having a particle size of 10 μm or less as a raw material powder. On the other hand, the powder having a particle size of less than 1 μm is likely to bite into the gaps in the mold. Accordingly, the particle size of the raw material powder is suitably in the range of 1 to 10 μm. When such raw material powder is used, the base crystal grains obtained after sintering are fine crystal grains having an average crystal grain size of 3 to 10 μm and a maximum crystal grain size of 20 μm or less. Since the metal carbide suppresses and maintains secondary recrystallization due to the pinning effect, excellent discharge characteristics can be maintained for a longer time.

  Furthermore, in the present invention, a mixed powder of molybdenum powder and tungsten powder is used as a raw material powder, and the base is a mottled structure of a Mo alloy phase containing W and a Mo alloy phase containing W. It is more preferable because secondary recrystallization of grains can be prevented. At this time, the amount of Mo and W is preferably a volume ratio of Mo: W = 10: 90 to 90:10. This is because when the amounts of Mo and W deviate from this range, either one of the alloy phases becomes excessive, and the effect of suppressing the secondary recrystallization of crystal grains by the other alloy phase becomes poor.

  Further, the metal carbide in the present invention includes titanium carbide (work function: 3.5 eV), molybdenum carbide (work function: 3.5 eV) lower than the base molybdenum (work function: 4.2 eV), tungsten (work function: 4.5 eV). Work function: 3.8 eV), tungsten carbide (work function: 3.7 eV), vanadium carbide (work function: 3.8 eV), zirconium carbide (work function: 3.4 eV), niobium carbide (work function: 3.8 eV) ), Tantalum carbide (work function: 3.8 eV), and hafnium carbide (work function: 3.4 eV). Among these, titanium carbide having excellent stability is preferable.

  In the present invention, it is preferable to contain a small amount of nickel having a low melting point because the sintering temperature can be reduced without significantly reducing the life of the electrode and the discharge characteristics of the electrode. It is convenient to add nickel to molybdenum powder and / or tungsten powder in the form of nickel powder. That is, since Ni added in the form of nickel powder has a lower melting point than Mo and W, it melts during sintering and wets the surface of molybdenum powder and tungsten powder to activate the surface to form a neck between the powders, Promote growth. As the added amount of nickel powder increases, sintering becomes possible at a low temperature, and even if the sintering temperature is lowered to about 1450 ° C. by addition of about 0.4 mass%, an electrode having a density ratio of 80% or more can be obtained. As a result, the thermal energy consumed in the sintering process can be reduced, and the wear of the furnace can be suppressed. However, when the amount of Ni in the cold cathode fluorescent lamp electrode exceeds 5% by mass, a portion with a high Ni concentration (Ni-rich phase) appears on the electrode surface, and the area of molybdenum and tungsten decreases, resulting in electron emission. Sex is reduced. Therefore, the amount of Ni in the cold cathode fluorescent lamp electrode needs to exceed 0 and not more than 5% by mass.

  In addition, the cold cathode fluorescent lamp electrode of the present invention can be produced by a conventionally known method. For example, a mold using a raw material in which a raw material powder is provided with a larger amount of binder or the like than that provided by a normal pressing method is used. It can manufacture suitably by the method to shape | mold. Hereinafter, the manufacturing process by this method will be specifically described.

  In the manufacturing method as described above, since it is required to flow a metal powder composed of molybdenum powder and tungsten powder in the gap between the molds using a minute mold, the porosity is higher than the porosity when tapping the metal powder. It is preferable to add a binder to the metal powder and knead. The amount of the binder added is preferably 40% by volume or more. If the amount of the binder is less than 40% by volume, the fluidity of the raw material becomes insufficient and uniform metal powder filling cannot be performed. On the other hand, if the binder is added in excess of 60% by volume, the subsequent debinding process takes a long time and causes an increase in production cost. In addition, since the molded body contains an excessive amount of binder, the metal powder cannot be uniformly filled, and shape stability in the debinding process and the sintering process is impaired, and the mold is likely to be deformed. Therefore, it is preferable that the addition amount of a binder is 40-60 volume%.

  Such a binder is more preferably composed of a thermoplastic resin and a wax. The thermoplastic resin is used for imparting plasticity to the raw material, and polystyrene, polyethylene, polypropylene, polyacetal, polyethylene vinyl acetate, and the like are used. Wax prevents metal contact between raw materials, especially metal powder and molds (including dies and punches) to achieve uniform flow of metal powder during pressure molding, and molded body and mold during extraction It is added in order to reduce the friction between them and facilitate extraction, and paraffin wax, urethane wax, carnauba wax and the like are used. The thermoplastic resin and wax having such an action are suitable binders when configured in the range of 20:80 to 60:40.

  The raw material M is obtained by adding and kneading the binder to the metal powder composed of the molybdenum powder and / or the tungsten powder. This raw material M is formed by a mold shown in FIGS. First, after a predetermined amount of raw material M is filled in the die hole 14a of the die 14 (FIG. 2 (a)), the raw material in the die hole 14a is formed into an electrode shape as shown in FIGS. 2 (b) and 2 (c). The first punch 11 that forms the bottom of the molded body, the second punch 12 that forms the inner diameter part of the electrode-shaped molded body, and the third punch 13 that pressurizes the open end surface of the electrode-shaped molded body. 11 is fixed to the die 14, and the second punch 12 is pressed to be pushed into the raw material, and the third punch 13 is molded while applying a back pressure to the raw material. In order to extract the obtained electrode shape molded body 15, first, the first punch 11, the second punch 12, and the third punch 13 are extracted together with the electrode shape molded body 15 from the die 14 (FIG. 2D). Next, the second punch 12 is extracted upward from the electrode-shaped molded body 15 (e). Next, the second and third punches 12 and 13 are raised and separated from the electrode-shaped molded body 15 (f). In addition, although what was described in FIG.2 (b), (c) is shaping | molding by back extrusion, you may raise the 1st punch 11 and it may carry out forward extrusion. However, in any case, if the third punch 13 is formed while applying back pressure to the raw material, the height of the end of the electrode-shaped formed body can be formed uniformly, and the density of the raw material becomes uniform in the formed body. preferable.

  In the above molding step, since the raw material needs to flow and fill the gaps in the minute mold, the raw material is heated to a temperature equal to or higher than the softening point of the thermoplastic resin contained in the binder prior to pressurization. There is a need. If the temperature is not heated, or even if heated, the temperature does not reach the softening point of the thermoplastic resin, the flowability of the raw material is poor, and the raw material cannot be uniformly and densely filled in the gaps of the minute mold. Moreover, it is more preferable to heat to a temperature equal to or higher than the melting point of the thermoplastic resin that maximizes the fluidity of the raw material. This heating may be performed after a raw material is filled in the mold by installing a heater inside the mold, or the raw material may be heated and supplied in advance.

  The raw material may be supplied as a granulated powder of a certain size so as to be handled by a general stamping method using a filling method using a powder supply device such as a feeder (powder box). However, since the mold cavity of the mold for forming the target cold cathode fluorescent lamp electrode is very small, it is uniform and dense when granulated to a powder size suitable for a powder feeder used in a general mold method. It is difficult to fill the granulated powder. On the other hand, when the particle size of the granulated powder is reduced, the fluidity of the raw material powder is lowered, and it is difficult to adjust the granulated powder to a suitable size. For this reason, as shown in FIG. 2 (a), the raw material is packed in a single pellet of a size that fits into the mold cavity, and the raw material is supplied in pellet units. preferable. Moreover, when supplying a raw material by a pellet unit, since supply is easy even if it heats a raw material previously, it is preferable also from this point.

  Since the electrode-shaped molded body obtained as described above contains 40-60% by volume of the binder component, the electrode-shaped molded body is heated to the thermal decomposition temperature of the binder component in order to remove the binder component. Do. The binder is composed of a thermoplastic resin and a wax. However, if the temperature rise rate near the thermal decomposition temperature of the thermoplastic resin and the wax is high, the thermoplastic resin and the wax are rapidly gasified to expand and cause the molded product to lose its shape. Therefore, it is necessary to slowly increase the temperature at least near the thermal decomposition temperature of the thermoplastic resin and wax. From this point of view, the debinding step is temporarily held near the sublimation temperature of the wax as the first stage to remove the wax content in the binder component, and then held again near the thermal decomposition temperature of the thermoplastic resin as the second stage. It is preferable to use a two-stage heating and holding step for removing the thermoplastic resin component. Further, in order to gradually generate gas accompanying thermal decomposition, it is preferable to mix and use a plurality of thermoplastic resins and waxes having different thermal decomposition temperatures.

  However, when all the binder components are removed in this step, the metal powders such as the corners fall off because the bonding between the metal powders has not started at that time. Therefore, a very small part of the binder component needs to remain. The remaining binder component remains in the sintered body as will be described later, and C contained in the remaining binder component becomes a contained component. Therefore, by measuring the C content, the amount of the remaining binder can be identified. When the amount of C remaining in the sintered body is less than 0.01% by mass, the remaining binder component is insufficient and the metal powder falls off. For this reason, it is necessary to make a binder component remain so that C amount in a sintered compact may be 0.01 mass% or more. On the other hand, as will be described later, the upper limit of the amount of C in the sintered body needs to be 0.5% by mass. Such adjustment of the amount of C can be controlled, for example, by adjusting the holding time in the two-stage heating and holding process, and is achieved by setting the holding time in each stage to a range of 30 to 180 minutes. can do.

  In the electrode-shaped molded body after the binder is removed, the metal powders are not yet diffused and are not metallicly bonded, and are extremely brittle. Therefore, sintering is performed in order to diffusely bond metal powders in a metallic manner. The sintering temperature is suitably 1500 ° C. or higher. In the embodiment containing Ni, the sintering temperature is preferably 1450 ° C. or higher. In the sintering process, since the metal powder is fine and has less unevenness as described above, the contact area of the metal powder is large, so that densification by sintering is likely to proceed, and the density ratio is increased at the above temperature. A dense sintered body of 80% or more can be obtained. However, if the sintering temperature is below the lower limit of the above temperature range, densification by sintering does not proceed, and only a sintered body with low density and low strength can be obtained. On the other hand, if the sintering temperature exceeds 1800 ° C., the furnace becomes extremely worn out, so the upper limit of the sintering temperature is preferably set to the above temperature. Sintering atmosphere contains oxygen or carbon, which oxidizes or carbonizes the metal powder surface, making sintering difficult to proceed. If hydrogen is contained, molybdenum powder absorbs hydrogen and expands, so it is inert. It is necessary to use gas or a vacuum atmosphere (reduced pressure atmosphere). Further, in a reduced pressure atmosphere, in the case of a reduced pressure atmosphere having a pressure of 1 MPa or more, it is necessary to introduce an inert gas as a carrier gas to avoid the above problems.

  Molybdenum powder, tungsten powder, metal carbide powder and nickel powder having particle sizes shown in Tables 1 and 2 were prepared. A binder prepared by mixing polyacetal (softening point: 110 ° C., melting point: 180 ° C.) and paraffin wax (softening point: 39 ° C., melting point 61 ° C.) in a ratio of 4: 6 was prepared. These were blended and kneaded in the proportions shown in Table 1 or 2 to prepare raw materials, which were formed into pellets. The pellets were heated to 200 ° C. and supplied to a mold heated in advance to 140 ° C. to perform compacting. After cooling to 40 ° C., extraction was performed to produce an electrode-shaped compact. The obtained green compact was heated to 250 ° C. and held for 60 minutes, then further heated and held at 450 ° C. for 60 to 120 minutes for debinding. Next, sintering was carried out by maintaining the temperature shown in Tables 1 and 2 for 60 minutes in an argon gas atmosphere. About the obtained electrode shape molded object, the elemental analysis by EPMA, the density ratio, and the average crystal grain diameter by a cross-sectional light micrograph were measured. In addition, a cold cathode fluorescent lamp was assembled using the obtained electrode shape molding, and the discharge voltage required to obtain a discharge current of 6 mA was measured under a distance between electrodes: 100 mm and a pressure of enclosed argon gas: 100 torr. Went. Further, the amount of spatter (amount of wear) after sputter discharge was continuously applied to the electrodes for 5 hours under the argon gas pressure of 0.07 torr using the electrode-shaped compact with a discharge voltage of DC 3 kV, a discharge current of 10 mA, and a distance between the electrodes of 50 mm. ) Was measured, and the index was set to 100 when the electrode was made of 100% molybdenum. The sputter index is an index indicating that the lower the sputtering index, the less the sputtering and the better the electrode. These results are also shown in Table 1 and Table 2.

  Further, Sample Nos. 11 and 08 of the obtained electrode shape molded body were held at 1400 ° C. in an argon gas atmosphere for 60 minutes to conduct a crystal grain growth test. These cross-sectional optical micrographs are shown in FIGS. In addition, (a) is a thing before a crystal grain growth test, (b) is a thing after a crystal grain growth test.

  Samples of sample numbers 01 to 21 in Table 1 are examples in which the influence of the content of metal carbide (TiC) was examined. In sample numbers 01 and 08 containing no TiC, the maximum crystal grain size was 25 μm, the discharge voltage was a large value exceeding 430 V, and the sputtering index was a large value exceeding 80. On the other hand, Sample Nos. 02 to 06 and 09 to 13 containing 1% by volume or more of TiC have a maximum crystal grain size as small as 10 μm or less, a discharge voltage is a good value lower than about 400 V, and a sputtering index is also lower than about 70. It was a good value. However, in sample numbers 07 and 14 containing TiC exceeding 50% by volume, the maximum crystal grain size is as small as 4 μm, but the density ratio is less than 80% and densification has not progressed. The index shows a remarkable increasing trend. Further, from FIGS. 3 and 4, no growth of crystal grain size was observed in Sample No. 11 of the present invention, whereas growth of crystal grain size was observed in Sample No. 08. From these results, when TiC is dispersed, it is effective for lowering the discharge voltage and sputtering index, and is effective for preventing secondary recrystallization of crystal grains, and the amount of TiC dispersed is in the range of 1 to 50% by volume. It was confirmed that those effects were great.

  Samples Nos. 15 to 21 in Table 1 examined the influence of the content of metal carbide (TiC) when a mixture of tungsten powder and molybdenum powder was given (Mo: W = 50: 50 (volume ratio)). It is an example. Sample No. 15 containing no TiC has a mottled structure of a W phase containing Mo and a Mo phase containing W, and the base is a single-phase sample (sample No. 01) containing only tungsten or a single-phase containing only molybdenum. The maximum crystal grain size is suppressed to be smaller than that of the sample (sample number 08), and the discharge voltage and the sputtering index are also good values. When TiC is dispersed in such a base of the sample number 15 by 1% by volume or more, the maximum crystal grain size is further reduced, and the discharge voltage and the sputtering index are also reduced to smaller values. However, in the sample of Sample No. 21 containing TiC in excess of 50% by volume, the density ratio is less than 80% and densification has not progressed. As a result, the discharge voltage and the sputtering index tend to increase significantly. From these results, even in the mottled structure of the Mo phase containing Mo and the Mo phase containing W, the inclusion of 1 to 50% by volume of TiC has the effect of refining crystal grains and reducing the discharge voltage and sputtering index. It was confirmed.

  Samples Nos. 11, 18 and 22-29 in Table 1 are examples in which the influence of the content ratio of tungsten powder and molybdenum powder in the case of containing 10% by volume of TiC was examined. In sample number 22 with Mo: W = 5: 95, densification did not proceed at a sintering temperature of 1800 ° C., the density ratio was less than 80%, and the discharge voltage was a value exceeding 400V. On the other hand, in Sample Nos. 18 and 23 to 29 in the range of Mo: W = 10: 90 to 90:10 (volume ratio), the density ratio is improved by over 80%, the discharge voltage is reduced, and the sputtering index. The discharge characteristics are improved. However, in Sample No. 29 exceeding Mo: W = 90: 10 (volume ratio), the amount of Mo is increased and the discharge characteristics are the same as those of Sample No. 11 not containing W, and the effect of improving the discharge characteristics is not seen. From these facts, when tungsten powder and molybdenum powder are mixed to form a patchy structure, the ratio of Mo and W does not become a patchy structure within the range of Mo: W = 10: 90 to 90:10 (volume ratio). It was confirmed that the discharge characteristics were further improved.

  Sample Nos. 11 and 30 to 36 in Table 1 are examples in which the influence of the type of metal carbide was examined. As shown in Table 1, the metal carbide exhibits the same and good characteristics in density ratio, maximum crystal grain size, discharge voltage, and sputtering index in any of TiC, MoC, WC, ZrC, VC, TaC, NbC, and HfC. It was confirmed.

  Samples Nos. 04, 11, 18 and 37 to 51 in Table 2 are examples in which the influence of the Ni content was examined. Samples 04, 11 and 18 that do not contain nickel powder also have good characteristics, but if Ni is contained as in sample numbers 37 to 40, 42 to 45, and 47 to 50, firing is not possible. It was shown that the density ratio, the maximum crystal grain size, the discharge voltage, and the sputtering index were good even when the sintering temperature was lowered (1600 ° C. in the case of W and 1450 ° C. in the case of containing Mo). On the other hand, in the samples of Sample Nos. 41, 46 and 51 in which the Ni content exceeds 5.0% by mass, the maximum crystal grain size exceeds 20 μm, and the increase in the discharge voltage and the sputtering index becomes remarkable. From these results, when the Ni content is 5.0% by mass or less, even if the sintering temperature is lowered, the densification sufficiently proceeds and the density ratio becomes 80% or more, and good discharge characteristics are exhibited. It was confirmed that

  Sample Nos. 11 and 52 to 56 in Table 2 are examples in which the influence of the density ratio was examined. In Sample No. 52, which has a sintering temperature of 1400 ° C., the density ratio was 71%, and the discharge voltage was as large as 412V. On the other hand, in sample numbers 21 to 23 where the sintering temperature exceeds 1550 ° C., the density ratio is 80 to 96%, the discharge voltage is less than 400V, and the sputtering index is less than 80. ing. However, in Sample No. 56, the density ratio was 98%, the maximum crystal grain size was coarsened to 40 μm, the discharge voltage exceeded 400 V, and the sputtering index exceeded 80. From these results, it was confirmed that good discharge characteristics were exhibited when the density ratio was in the range of 80 to 96%.

  Samples Nos. 04, 11, 18 and 57 to 68 in Table 2 are examples in which the influence of the particle size of molybdenum powder and tungsten powder was examined. Samples Nos. 04 and 57 to 59 having a particle size of 10 μm or less (examples of tungsten), Nos. 11 and 61 to 63 (examples of molybdenum), Nos. 18 and 65 to 67 (of tungsten and molybdenum) In the example of patchy structure, the density ratio, maximum crystal grain size, discharge voltage, and sputtering index are good, whereas in sample numbers 60, 64, and 68 with grain sizes exceeding 10 μm, the maximum crystal grain size is 20 μm. As the discharge voltage increases, the sputtering index also increases. From these results, it was confirmed that the particle diameters of the molybdenum powder and tungsten powder were 10 μm or less, fine crystal grains were obtained, and good discharge characteristics were exhibited.

It is sectional drawing which shows the structure of a cold cathode ray lamp. It is sectional drawing which shows the filling process, pressure forming process, and extraction process which manufacture suitably the electrode for cold cathode ray lamps of this invention. It is a cross-sectional light micrograph of the electrode for cold cathode ray lamps of this invention, (a) is a thing before a crystal grain growth test, (b) is a thing after a crystal grain growth test. It is a cross-sectional light micrograph of the electrode for the conventional cold cathode ray lamp, (a) is a thing before a crystal grain growth test, (b) is a thing after a crystal grain growth test.

Explanation of symbols

  11 ... 1st punch, 12 ... 2nd punch, 13 ... 3rd punch, 14 ... Die

Claims (5)

  A cold cathode characterized by presenting a metal structure in which metal carbide and pores are dispersed in a Mo or W base, wherein the amount of the metal carbide is 1 to 50% by volume and the density ratio is 80 to 96%. Fluorescent lamp electrode.   In the base of a mottled structure composed of a Mo alloy phase containing W and a W alloy phase containing Mo, a metal structure in which metal carbides and pores are dispersed is exhibited. : W = 10: 90 to 90:10, the amount of the metal carbide is 1 to 50% by volume, and the density ratio is 80 to 96%.   The cold cathode fluorescent lamp electrode according to claim 1, further comprising 5 mass% or less of Ni.   The metal carbide is at least one of titanium carbide, molybdenum carbide, tungsten carbide, vanadium carbide, zirconium carbide, niobium carbide, tantalum carbide, and hafnium carbide. The electrode for cold cathode fluorescent lamps as described.   5. The cold cathode fluorescent lamp electrode according to claim 1, wherein the average crystal grain size is 3 to 10 μm, and the maximum crystal grain size is 20 μm or less.

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