JP2002352704A - Manufacturing method of cold cathode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a cold cathode having superior mechanical strength, stable behavior of light emission and long service life. SOLUTION: This is a manufacturing method of a cold cathode for a discharge tube, which has a cold cathode at the tip of a lead sealed through the edge of a glass tube containing rare gas and mercury and has a processes of producing a mixed powder of titanium hydride powder and a high-melting point metal powder, and manufacturing a formed body with the mixed powder, and also sintering the formed body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold cathode in a thin tube type cold cathode discharge tube, and more particularly to a method for manufacturing a small-sized cold cathode having excellent mechanical strength, long life, and stable light emission behavior.

[0002]

2. Description of the Related Art In recent years, cold-cathode discharge tubes have been used as backlight light sources for liquid crystal displays, films with lenses, strobes for digital cameras, and the like. This type of cold cathode discharge tube is desired to have low heat generation, low power consumption, high efficiency, long life, small size and the like. In particular, a thin tube type having an outer diameter of 2 mm or less and a length of 50 mm or less has been developed for use in a flash of a digital camera in recent years. Miniaturization is expected to progress further. Accordingly, the size of the cold cathode sealed at the end of the cold cathode discharge tube also needs to be reduced.
Development of cold cathodes having a length of 1 m or less and a length of 1 mm or less is also in progress.

[0003] Usually, when a predetermined voltage is applied to a cold cathode, a cold cathode discharge tube emits secondary electrons from the cold cathode by ions of the initial plasma generated, and a glass in which mercury or a rare gas is sealed in advance. Discharge starts in the tube. The mercury atoms or rare gas atoms excited by the electron energy associated with the discharge emit ultraviolet rays, and the ultraviolet rays are converted into visible light by a phosphor layer applied to the inner surface of the glass tube, and the visible light is converted. appear.

As the cold cathode, a porous sintered body made of a single refractory metal such as tungsten having a cylindrical shape has been generally used. However, from the viewpoint of improving luminous efficiency, titanium and a refractory metal have recently been used. For example, a porous sintered body of an alloy composed of niobium has attracted attention.

The cold cathode discharge tube is joined by inserting the above porous sintered body into a tungsten wire, a Kovar wire, or a Dumet wire and caulking. After that, the cold cathode is impregnated with an electron-emitting substance, sealed at the end of the glass tube, and sealed with a rare gas such as mercury or xenon gas in the glass tube. As the electron emitting material, barium compounds, yttrium compounds, lanthanum compounds, and the like are mainly used.

[0006] In order to produce a porous sintered body of an alloy composed of titanium and a high melting point metal, a titanium powder and a high melting point metal powder are mixed, filled in a mold, pressed, and then pressed. Means for sintering are common.

[0007]

However, in producing a small-sized porous sintered body having an outer diameter of 1 mm or less and a length of 1 mm or less made of titanium and a high melting point metal, the following problems arise. . That is, the titanium particles, because of poor fluidity, is difficult to fill the mold, kneaded with a resinous binder, by compounding, the fluidity to the mold is improved, When pressurized and compressed, the titanium particles themselves are extensible, so the pressurized pressure is lost due to friction with the mold and does not propagate uniformly throughout, and the mechanical strength of the compact and the subsequent sintered compact Is inferior. As a result, it collapses when swaging to a tungsten wire or a Kovar wire. In addition, for the same reason, there are manufacturing problems such as variations in the density, size, and shape of the sintered body, and it has been difficult to provide a small-sized cold cathode discharge tube.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing a small-sized cold cathode having excellent mechanical strength, long life, and stable light emission behavior. .

[0009]

In order to achieve the above object, a method of manufacturing a cold cathode according to the present invention comprises the steps of: providing a cold cathode at the end of an introduction wire sealed at the end of a glass tube filled with a rare gas or mercury; A method for producing a cold cathode in a cold cathode discharge tube comprising: a step of mixing a powder of titanium hydride and a powder of a high melting point metal to produce a mixed powder; It is characterized by including a step of producing and a step of producing a cold cathode by sintering the compact.

[0010] The method for producing a cold cathode according to the present invention comprises:
Preferably, the powder of the refractory metal is niobium, tungsten, molybdenum, tantalum or zirconium.

(Function) The present inventor uses titanium hydride particles instead of titanium when producing a fine porous sintered body made of an alloy of titanium and a high melting point metal as a cold cathode. It has been found that it is possible to provide a small-sized cold cathode having excellent mechanical strength, long life and stable light emission behavior. The reason is that titanium hydride is usually brittle compared to titanium, so that it is easy to form fine particles, and several μm to several tens μm
Particles can be produced and a compound with excellent fluidity can be formed.In addition, titanium hydride particles have a higher hardness than titanium, and the pressing pressure for compression is uniform throughout. Due to the propagation, it is possible to produce a molded body having a uniform mechanical strength and high mechanical strength, and as a result, the mechanical strength of the sintered body is also improved. Therefore, even when a force is applied when crimping to a tungsten wire or a Kovar wire, the wire does not collapse. For the same reason, there is no variation in the density, size and shape of the sintered body.

Here, titanium hydride is a hydride of titanium, and is a titanium compound represented by TiH _{2 in} a chemical formula. Titanium hydride is heated at 400 to 500 ° C. in a vacuum to release hydrogen and change to titanium. Therefore, even if titanium hydride is used as a raw material powder, a cold cathode as a sintered body after sintering is used. Has no effect on the composition of

Further, since the vacancy state of the cold cathode, which is a sintered body produced, is uniform and can be impregnated with a large amount of an electron emitting material, the luminescent life is long, and the luminous behavior such as brightness, starting voltage, color temperature and the like is also high. It was confirmed by the present inventor that it was stable.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing the structure of a cold cathode discharge tube. The cold cathode 1 is crimped and joined to the tip of the lead wire of the tungsten wire 2 sealed at the end of the thin glass tube 3. The length of the glass tube is, for example, 40 mm, and the diameter is 4 mm. Xenon gas is sealed in the glass tube 3. Reference numeral 4 in FIG. 1 denotes glass for sealing, and the material is the same as that of the glass tube 3. FIG. 2 is a schematic cross-sectional view showing the structure of the cold cathode 1. The cold cathode 1 is made of a cylindrical porous sintered body having a through hole made of titanium and a high melting point metal, and has an outer diameter of 1 mm, an inner diameter of 0.5 mm, The length is 1 mm. The tungsten wire 2 is passed through this penetrated hole, and is joined to the tungsten wire 2 by caulking. FIG. 3 is a flowchart showing the manufacturing method of the present invention, and FIG. 4 shows a processing temperature profile in the sintering step.

In the method of manufacturing a cold cathode according to the present invention, first, a powder of titanium hydride and a powder of a high melting point metal are mixed to prepare a mixed powder. At this time, a binder made of an organic polymer compound and an organic solvent are put into the mixed powder, mixed using a stirrer, and then compounded (granulated) by, for example, a spray drier method to improve fluidity. The filling into the mold is performed smoothly. Then, after filling the mold, a certain pressure is applied to produce a molded body, and then sintered in a vacuum furnace. At this time, the sintering step includes, as shown in FIG. 4, three steps of a debinding step, a dehydrogenation step, a step of melting the powder and bonding the powder to each other. Thus, a cold cathode is manufactured.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of the present invention will be described below with reference to FIGS. (Example 1) First, as shown in the flow chart of the manufacturing method in FIG. 3, powders of titanium hydride and niobium, which are raw material powders, were weighed so that the weight ratio becomes titanium hydride: niobium = 80: 20. Mix. Specifically, titanium hydride 2
40 g and niobium 60 g were mixed to prepare a mixed powder.
At this time, the average particle size of titanium hydride and niobium was 20 μm, respectively. This mixed powder is put into 1000 g of acetone in which 20 g of a binder BL-S (manufactured by Sekisui Chemical) made of an organic polymer compound is dissolved, and mixed using a stirrer.
A slurry was prepared. Then, using this slurry,
A compound (granules) having a particle size of about 50 μm was prepared by a spray drier method. Subsequently, the compound was filled in a mold, and subjected to press working by applying a pressure of 5 ton / cm ² to obtain a cylindrical outer diameter of 1.05 having a through hole.
Approximately 1,000 compacts having a diameter of 0.504 mm and a length of 1.07 mm were produced.

Thereafter, the above-mentioned compact was placed in a vacuum furnace, and a sintering step having a heating pattern as shown in FIG. 4 was performed. At this time, the range indicated by 11 in FIG. 4 is a step for debinding, 12 is a step for dehydrogenating titanium hydride, 13 is a step of melting titanium and niobium powder, and And a step for producing a porous sintered body. Both processes have a vacuum of 2 × 10
It is ^-5 Torr, 11 steps are temperature 400 ° C., holding time 1 hour, 12 steps a temperature 600 ° C., holding time 1 hour, 13 steps and a temperature of 1100 ° C., holding time 2 hours. In this way, as shown in FIG. 2, an outer diameter of 1 mm, an inner diameter of 0.5 mm, and a length of 1 mm are made of titanium and niobium.
The cold cathode 1 which was a cylindrical porous sintered body having a through hole was produced.

Here, the porosity of the cold cathode 1 is controlled by the pressure during press working and the temperature and time during the sintering step.
The porosity is desirably 20 to 30%. The reason is that if the porosity exceeds 30%, the mechanical strength decreases, and furthermore, the electron emitting material impregnated in the cold cathode 1 is excessively evaporated and becomes early, so that the life as the cold cathode is shortened. Conversely, if the porosity is less than 20%, the electron emitting material cannot be impregnated from the outside, and the supply of the electron emitting material to the cold cathode surface during operation is hindered, so that the electron emission characteristics deteriorate. Because you do. The porosity of the cold cathode of the first embodiment is about 2
It was 2-26%. Further, although the shape of the cold cathode of this embodiment is cylindrical, the shape is not limited to this, and the dimensions are not limited to this. Further, the shape of the glass tube is not limited to a straight tube type.

Example 2 In the same manner as in Example 1, as shown in the flow chart of the manufacturing method in FIG. 3, the raw material powders of titanium hydride and zirconium were mixed at a weight ratio of titanium hydride: zirconium = Measure to 80:20 and mix. Specifically, 240 g of titanium hydride,
A mixed powder was prepared by mixing 60 g of zirconium. At this time, the average particle diameters of titanium hydride and zirconium were each 20 μm. This mixed powder was put into 1000 g of acetone in which 20 g of a binder BL-S (manufactured by Sekisui Chemical) composed of an organic polymer compound was dissolved, and mixed with a stirrer to prepare a slurry. Next, using this slurry, a compound (granules) having a particle size of about 50 μm was prepared by a spray drier method. Subsequently, the compound was filled in a mold, and subjected to press working by applying a pressure of 5 ton / cm ² to obtain a cylindrical outer diameter having a through hole.
Approximately 1,000 compacts having a size of 04 mm, an inner diameter of 0.503 mm, and a length of 1.06 mm were produced.

Thereafter, the above-mentioned compact was placed in a vacuum furnace, and a step of sintering having a heating pattern as shown in FIG. 4 was performed. In all of the steps, the degree of vacuum was 2 × 10 ⁻⁵ Torr, and the eleventh step was a temperature of 400 ° C., a holding time of 1 hour,
Step 2 was performed at a temperature of 600 ° C. and a holding time of 1 hour, and step 13 was performed at a temperature of 1200 ° C. and a holding time of 2 hours. In this way, as shown in FIG.
A cold cathode 1 which was a cylindrical porous sintered body having a through hole and made of titanium and zirconium having a length of 1 mm was produced. The porosity of the cold cathode obtained in Example 2 was about 22 to 26% as in Example 1.

(Comparative Example 1) In the same manner as in Example 1 except that titanium powder was used as the raw material powder instead of titanium hydride powder, the weight ratio of titanium and niobium powders was changed to titanium: Measure and mix so that niobium = 80: 20. Specifically, 240 g of titanium, 6 of niobium
0 g was mixed to prepare a mixed powder. At this time, the average particle diameters of titanium and niobium were each 20 μm. This mixed powder is used as a binder BL-S made of an organic polymer compound.
20 g of (manufactured by Sekisui Chemical) was placed in 1000 g of dissolved acetone and mixed with a stirrer to prepare a slurry. Next, using this slurry, a compound (granules) having a particle size of about 50 μm was prepared by a spray drier method. Subsequently, the compound was filled in a mold, and subjected to press working by applying a pressure of 5 ton / cm ² to form a cylindrical outer diameter of 1.05 mm and an inner diameter of 0.504 having a through hole.
Approximately 1,000 compacts having a length of 1.07 mm and a length of 1.07 mm were produced.

Thereafter, as in the first embodiment,
Into a vacuum furnace and observe the heating pattern shown in FIG.
A sintering process was performed. Both processes have a vacuum of 2 ×
10 ^-FiveTorr, and the eleventh step was performed at a temperature of 400 ° C.
Hold time 1 hour, process 12 is temperature 600 ° C, hold time
1 hour, 13 steps: temperature 1100 ° C, holding time 2 hours
And Thus, an outer diameter of 1 m as shown in FIG.
m, inner diameter 0.5mm, length 1mm from titanium and niobium
Is a cylindrical porous sintered body having a through hole
A cold cathode 1 was produced. In addition, the cold cathode obtained in this comparative example
Porosity is about 22 to 26% as in Example 1.
Was.

(Comparative Example 2) In the same manner as in Example 2 except that titanium hydride powder was used as the raw material powder in place of titanium hydride powder, the raw material powder of titanium and zirconium powder was mixed in a weight ratio of titanium: Measure and mix so that zirconium = 80: 20. Specifically, titanium 240
g and 60 g of zirconium were mixed to prepare a mixed powder. At this time, the average particle diameters of titanium and zirconium were respectively 20 μm. This mixed powder was put into 1000 g of acetone in which 20 g of a binder BL-S (manufactured by Sekisui Chemical) composed of an organic polymer compound was dissolved, and mixed with a stirrer to prepare a slurry. Next, using this slurry, a compound (granules) having a particle size of about 50 μm was prepared by a spray drier method. Subsequently, the compound was filled in a mold, and subjected to press working by applying a pressure of 5 ton / cm ² to obtain a cylindrical outer diameter having a through hole.
Approximately 1,000 compacts having a size of 04 mm, an inner diameter of 0.503 mm, and a length of 1.06 mm were produced.

Thereafter, the above-mentioned compact was placed in a vacuum furnace, and as in Example 2, the above-mentioned compact was placed in a vacuum furnace, and a sintering process having a heating pattern as shown in FIG. 4 was performed. . In each step, the degree of vacuum was 2 × 10 ⁻⁵ Torr, and in step 11, the temperature was 400 ° C., the holding time was 1 hour,
Is a temperature of 600 ° C. and a holding time of 1 hour, and a step 13 is a temperature of 1200 ° C. and a holding time of 2 hours. In this manner, a cold cathode 1 which is a cylindrical porous sintered body having a through hole and made of titanium and zirconium having an outer diameter of 1 mm, an inner diameter of 0.5 mm, and a length of 1 mm as shown in FIG. 2 is produced. did. Further, the porosity of the cold cathode obtained in this comparative example was about 22 to 26% as in Example 2.

With respect to the cathodes obtained in Example 1, Example 2, Comparative Example 1 and Comparative Example 2 as described above, 10 cathodes indiscriminately extracted from each Example and Comparative Example were added from the side. Measurement of strength at the time of pressing and breaking (Evaluation criteria: 3.0 Kgf or more, when crimping to a tungsten wire, pass if not broken)
Dimension and density variations (Evaluation criteria: outer diameter 1 ±
0.05mm, inner diameter 0.5 ± 0.05mm, length 1 ±
After the measurement, a tungsten cathode was used to separate tungsten from the cold cathode of each of the examples and comparative examples. A cold-cathode discharge tube in which a cold cathode which was not broken at this time was sealed with a wire was produced, and a light-emitting life (evaluation standard: light emission every 20 seconds, and light emission up to 3000 times is considered to be acceptable), starting. Voltage (Evaluation criteria: Pass if 240 V or less; pass; lower value has better characteristics),
The color temperature (evaluation standard: acceptable if it is in the range of 6000 to 6800 K. The higher the value, the better) was measured. In addition, the cold cathodes of Example 1 and Example 2 could be caulked without disintegration, but 50 cold cathodes of Comparative Example 1 and Comparative Example 2 were extracted. Forty pieces collapsed during swaging. Table 1 shows the results of Example 2 in Examples 1 and 2, Table 3 shows the results of Comparative Example 1, and Table 4 shows the results of Comparative Example 2.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

[Table 4]

As can be seen from Tables 1 to 4, all of the cold cathodes obtained in Examples 1 and 2 had a breaking strength,
It has excellent characteristics in the evaluation items of dimensional and density variations, emission life, starting voltage, color temperature,
It was confirmed that the variation in the characteristics was small.

[0032]

As described above, in the method for manufacturing a cold cathode according to the present invention, a compact is produced by mixing a powder of titanium hydride and a powder of a high melting point metal and then sintering the compact. Thus, by producing a porous cold cathode made of titanium and a high melting point metal, it is possible to provide a small cold cathode having excellent mechanical strength, long life, and stable light emission behavior.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the structure of a cold cathode discharge tube.

FIG. 2 is a schematic sectional view showing a structure of a cold cathode.

FIG. 3 is a flowchart showing a method for manufacturing a cold cathode according to one embodiment of the present invention.

FIG. 4 is a processing temperature profile of a sintering step in the method for manufacturing a cold cathode according to one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Cold cathode 2 Tungsten wire 3 Glass tube 4 Glass for sealing 11 Debinding step 12 Dehydrogenation step 13 Melting between powders and combining powders with each other

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Atsushi Sato 6-11-12 Tanashi-cho, Nishi-Tokyo, Tokyo Within Citizen Watch Co., Ltd. (72) Inventor Shizue Ito 6-Chome, Tanashi-cho, Nishi-Tokyo, Tokyo 1-12 Citizen Watch Co., Ltd. (72) Inventor Yoshiro Hirai 6-12 Tanashi-cho, Nishi-Tokyo, Tokyo 1-12 Citizen Watch Co., Ltd. F-term (reference) 5C015 EE06

Claims (3)

[Claims] 1. A method for producing a cold cathode in a cold cathode discharge tube having a cold cathode at the end of a lead wire sealed at the end of a glass tube filled with a rare gas or mercury, comprising the steps of: A method for manufacturing a cold cathode, comprising: a step of mixing a powder and a powder of a high melting point metal to form a mixed powder; a step of forming a mixed powder to form a molded body; and a step of sintering the molded body. 2. The method according to claim 1, wherein the powder of the refractory metal is niobium, tungsten, molybdenum, tantalum, or zirconium. 3. The method according to claim 1, wherein the step of sintering the compact includes a step of debinding, a step of dehydrogenating, and a step of melting the powder and bonding the powder to each other. 3. The method for producing a cold cathode according to item 1.