JP2003031142A - Cathode structure and color picture tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cathode structure of which, every problems of prevention of evaporation of chrome, improvement of thermal efficiency, and cost reduction, are solved, and to provide a color picture tube to which, the above cathode structure with high reliability is mounted. SOLUTION: A cathode sleeve 13 of the cathode structure is formed into double cylinder structure. An inner cylinder 13A is made of Nicrome alloy blackened by wet hydrogen treatment. An outer cylinder 13B is made of nickel of which, the surface has white metallic luster. The volume of heat released from the outer surface of the cathode sleeve 13 to the circumferential space is small because of low heat radiation rate. Nickel does not evaporate at high temperature. The cathode structure 10 solves all problems of prevention of evaporation of chrome, improvement of thermal efficiency, and cost reduction.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a cathode assembly for a color cathode ray tube and a color cathode ray tube.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional cathode assembly 30.
A partial cross-sectional view of (JP 2001-6521 A) is shown. The cup 32 accommodating the cathode pellet 31 is fitted into the tip of the cathode sleeve 33, and the periphery thereof is resistance welded to form the cathode pellet 31, the cup 32, and the cathode sleeve 3.
Integrate 3. After that, the heater 34 is inserted from below the cathode sleeve 33.

The material of the cup 32 and the cathode sleeve 33 is a nichrome alloy of 80% nickel and 20% chromium, and the surface thereof has a usual white metallic luster. The nichrome alloy is used for the cathode sleeve 33 because it has high mechanical strength, good heat resistance, and poor heat conduction.
(If the heat conduction is good, the heat will escape to the lower side of the cathode sleeve, and the condition will be poor.)

After the cathode structure 30 is mounted on a color cathode ray tube, decomposition is performed at 1020 ° C. for 5 minutes based on the electron emission surface temperature of the cathode pellet 31, 1080 ° C.-1.
It is heat activated for 5 minutes and put to practical use. The temperature of the heater 34 and the temperature of the cathode sleeve 33 during disassembly are 1 each
160 ° C., 1120 ° C., heater 34 temperature at the time of thermal activation, cathode sleeve 33 temperature are 1220 ° C.,
It is 1180 ° C.

In practical use, the cathode pellet 31 has an electron emission surface temperature of 780 ° C., the heater 34 has a temperature of 920 ° C., and the cathode sleeve 33 has a temperature of 880 ° C. The cathode structure 30 is used at this practical temperature for up to 30,000 hours.

The lower the temperature of the heater 34, the higher the reliability of the cathode assembly 30, and therefore the cathode pellet 31.
Efforts are constantly being made to lower the temperature of the heater 34 while maintaining that temperature. Eg cathode sleeve 3
There is a method of changing the inner surface of 3 from metallic luster to black so that the radiant heat from the heater 34 is well absorbed by the cathode sleeve 33.

According to Japanese Patent Laid-Open No. 7-153384,
When a nichrome alloy cathode sleeve is heat-treated in wet hydrogen, chromium in the nichrome alloy oxidizes and turns black, the inner and outer surfaces of the cathode sleeve turn black, and the heat emissivity (heat absorptivity) increases from 20% to 80% Get higher

As another blackening method, there is a method in which tungsten fine powder mixed with an organic solvent is applied to the inner surface of the cathode sleeve and baked.

[0009]

When the surface of the nichrome alloy cathode sleeve has a white metallic luster (no surface treatment is applied), chromium in the nichrome alloy selectively evaporates from the surface during heating. Then, it adheres to the surrounding electrodes and contaminates. This contamination is remarkable at the time of decomposition and activation in which the temperature of the cathode sleeve becomes higher than in practical use. However, since the white metal luster surface has a low thermal emissivity of 20%, there is an advantage that heat cannot easily escape from the cathode sleeve to the peripheral space during practical use.

When the inner and outer surfaces of the cathode sleeve are blackened by the wet hydrogen treatment, heat from the heater is easily absorbed on the inner surface of the cathode sleeve, and chromium is not evaporated on the outer surface of the cathode sleeve, so that contamination can be avoided. However, since the heat emissivity of the outer surface of the cathode sleeve is as high as 80%, heat easily escapes from the cathode sleeve to the surrounding space, and the thermal efficiency is not necessarily improved.

In the method of baking fine tungsten powder on the inner surface of the cathode sleeve, the heat absorption from the heater is good and the heat radiation from the outer surface of the cathode sleeve is small, so the thermal efficiency is good, but the manufacturing process is very time-consuming and costly. Moreover, evaporation of chromium is inevitable.

As described above, in the conventional cathode sleeve structure, it was not possible to satisfy all of the problems of evaporation of chromium, improvement of thermal efficiency and cost problems.

[0013]

In the cathode assembly of the present invention, the cathode sleeve is a double cylinder. The inner cylinder (inner cylinder) is made of nichrome alloy, and the inner and outer surfaces are blackened by wet hydrogen treatment. The inner cylinder uses a nichrome alloy, so it has good heat resistance. Since the inner surface of the inner cylinder is blackened, the heat absorption rate of the heater is 80%. Further, since blackening is performed by wet hydrogen treatment, mass productivity is good. However, since the wet hydrogen treatment is performed, the outer surface of the inner cylinder, which is not desired to be blackened, is also blackened. This drawback can be overcome by covering the outer cylinder.

Since the outer cylinder is made of nickel and the surface is not specially treated, it has a white metallic luster. Since nickel is used for the outer cylinder, it does not evaporate like chromium and does not contaminate the peripheral electrodes even at high temperatures. Since the outer cylinder has a white metallic luster and the thermal emissivity is as low as 20%, less heat is radiated from the outer surface of the cathode sleeve and less heat escapes to the surrounding space. Therefore, thermal efficiency is high.

In this way, the cathode structure of the present invention can satisfy all of chromium evaporation prevention, thermal efficiency improvement, and cost problems. Then, by mounting the cathode structure of the present invention, a highly reliable color cathode ray tube related to the cathode structure can be realized.

According to a first aspect of the present invention, in a cathode structure in which a heater is inserted in a substantially cylindrical cathode sleeve, the cathode sleeve is a double cylinder including an inner cylinder and an outer cylinder in close contact with each other. At least the inner surface of which is blackened, and at least the outer surface of the outer cylinder has a metallic luster.

A second aspect of the present invention is the cathode structure according to the first aspect, characterized in that the material of the inner cylinder is a nichrome alloy and the material of the outer cylinder is nickel.

The invention according to claim 3 is the cathode assembly according to claim 1, wherein the inner cylinder is blackened by a heat treatment in wet hydrogen.

The invention according to claim 4 is a color cathode ray tube equipped with any one of the cathode structures according to claims 1 to 3.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a partial cross-sectional view of an embodiment 10 of the cathode assembly according to the present invention. Cathode pellet 11
A cup 12 accommodating therein is fitted into the tip of the cathode sleeve 13. The cathode sleeve 13 is a partially double cylinder, and the inner cylinder 13A is made of blackened nichrome alloy (80% nickel, 20% chromium, thickness 20 μm), the outer cylinder 1
3B is made of nickel with a white metallic luster (thickness 20 μm). The outer cylinder 13B is necessary only for the upper portion heated by the heater 14. Example 1 of the cathode structure of the present invention
The approximate size of 0 is that the diameter is 1.5 mm at the top and 2.5 m at the bottom.
m, inner cylinder 13A total length 8 mm, outer cylinder 13B total length 5 mm
Is.

FIG. 2 shows an embodiment 1 of the cathode assembly of the present invention.
The manufacturing method of the cathode sleeve 13 of 0 is shown. As shown in FIG. 2 (a), an inner cylinder 13A made of a nichrome alloy, which has been previously heat-treated in wet hydrogen to form a blackened film of chromium oxide on the surface thereof, is made of nickel which shows white metallic luster without surface treatment. Cover the outer cylinder 13B closely. At this time, the outer cylinder 13
If B is heated and expanded, that is, a shrink fitting method is used, it is easy to cover. As a result, the double cylindrical cathode sleeve 13 shown in FIG. 2B is completed. Since the inner cylinder 13A is blackened by wet hydrogen treatment, mass productivity is good.

Embodiment 1 of the cathode assembly of the present invention shown in FIG.
For 0, the cup 12 containing the cathode pellet 11 was fitted into the tip of the cathode sleeve 13 made by the manufacturing method of FIG. 2, and the periphery thereof was fixed by resistance welding or laser welding, and the heater 14 was inserted from below. able to make.

The cathode pellet 11 is obtained by mixing nickel powder, scandium oxide powder, and barium-strontium-calcium coprecipitated carbonate powder and cutting it out from a sintered body which is hot isostatically pressed and has a dimension of diameter. 1.1m
m and the thickness is 0.22 mm.

The cup 12 has an inner diameter of 1.1 mm and a depth of 0.2.
mm Nichrome alloy with a wall thickness of 50 μm (80% nickel,
20% chrome).

The tenth embodiment of the cathode assembly of the present invention is
After being mounted on a color cathode ray tube by a conventional manufacturing method, the temperature of the electron emission surface of the cathode pellet 11 is set to 1020 as a reference.
Decompose at 5 ° C for 5 minutes and heat activate at 1080 ° C for 15 minutes.

The inner surface of the conventional cathode sleeve has a white metallic luster, but the inner surface of the cathode sleeve 13 of the present invention is blackened, so that the heat absorption rate is 20% to 80% of the conventional one.
It is high. On the other hand, the outer cylinder 13B is made of nickel and the surface is not specially treated, so that it has a white metallic luster.
Since the outer cylinder has a white metallic luster and the heat emissivity is as low as 20%, the heat radiation from the outer surface of the cathode sleeve is small and the heat escaping to the surrounding space is small. Therefore, the temperature of the heater 14 and the temperature of the cathode sleeve 13 can be lowered by 30 ° C. from the conventional temperature, and the temperature of the heater and the temperature of the cathode sleeve at the time of disassembly are 113 respectively.
0 ° C., 1090 ° C., the heater temperature at the time of thermal activation, and the cathode sleeve temperature are 1190 ° C. and 1150 ° C., respectively.

Further, the heater 14 necessary for maintaining the electron emission surface temperature of the cathode pellet 11 of 780 ° C. in practical use.
Temperature is 890 ° C, and the temperature of the cathode sleeve 13 is about 8
It is 50 ° C. These temperatures are 30 ° C lower than before. The cathode structure 10 is used at this practical temperature for up to 30,000 hours.

Further, since the outer cylinder 13B is made of nickel, it does not evaporate like chromium and does not contaminate the peripheral electrodes even when it is heated to a high temperature during decomposition and thermal activation.

[0029]

According to the cathode structure of the present invention, the cathode sleeve is a double cylinder. The inner cylinder is made of Nichrome alloy and the inner and outer surfaces are blackened by wet hydrogen treatment. The inner cylinder is a nichrome alloy, so it has good heat resistance. Since the inner surface of the inner cylinder is blackened, the heat absorption rate of the heater is 80%. Further, since blackening is performed by wet hydrogen treatment, mass productivity is good.

The outer cylinder is made of nickel and the surface has a white metallic luster. Since the outer cylinder is nickel, it does not evaporate and does not contaminate the peripheral electrodes like chromium does. Since the outer cylinder has a white metallic luster and the thermal emissivity is as low as 20%, less heat is radiated from the outer surface of the cathode sleeve and less heat escapes to the surrounding space. Therefore, thermal efficiency is high.

In this way, the cathode structure of the present invention can satisfy all of chromium evaporation prevention, thermal efficiency improvement, and cost problems. Then, by mounting the cathode structure of the present invention, a highly reliable color cathode ray tube related to the cathode structure can be realized.

[Brief description of drawings]

FIG. 1 is a partial sectional view of a cathode assembly according to the present invention.

FIG. 2 is an explanatory view of a method for manufacturing a cathode sleeve of the cathode assembly of the present invention.

FIG. 3 is a partial sectional view of a conventional cathode assembly.

[Explanation of symbols]

10 Cathode structure 11 cathode pellets 12 cups 13 cathode sleeve 13A inner cylinder 13B outer cylinder 14 heater 30 cathode structure 31 cathode pellet 32 cups 33 cathode sleeve 34 heater

Claims (4)

[Claims] 1. A cathode structure in which a heater is inserted into a substantially cylindrical cathode sleeve, which is a double cylinder composed of an inner cylinder and an outer cylinder in which the cathode sleeve is in close contact, and at least the inner surface of the inner cylinder is blackened. The cathode assembly is characterized in that at least the outer surface of the outer cylinder has a metallic luster. 2. The cathode assembly according to claim 1, wherein the material of the inner cylinder is a nichrome alloy, and the material of the outer cylinder is nickel. 3. The cathode assembly according to claim 1, wherein the inner cylinder is blackened by a heat treatment in wet hydrogen. 4. A color cathode ray tube equipped with any one of the cathode structures according to claim 1.