JPH0444375B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a cathode assembly used in a cathode ray tube.

In cathode ray tubes, such as color picture tubes, a fast-acting cathode assembly is used in order to speed up the time it takes for an image to appear on a fluorescent surface after the power is turned on.

First, an example of such a rapid-acting cathode structure will be explained with reference to FIG. First, a disk-shaped base metal 11 is press-fitted into the upper end of a cathode sleeve 12 made of a nichrome alloy, and three supporting members 13 are fixed at 120° intervals near the open end 15 at the lower end of this cathode sleeve 12. The cathode sleeve 12 is then heat treated for 30 minutes at about 1000° C. in a water-added hydrogen atmosphere with a dew point of 20° C., for example, to blacken the cathode sleeve 12. Next, the support member 13 is fixed to the upper end ₁₄₁ of the cathode support tube 14 so that the cathode sleeve 12 and the cathode support tube 14 have the same axis, thereby completing the cathode structure.

At present, the cathode structure having the above-mentioned structure is used in a color picture tube, and each cathode structure has, for example,
It requires 1.26W of heater power and the image output time is about 4 seconds. By the way, in energy-saving color picture tubes, the diameter of the net has recently become smaller in order to save deflection power, and it is necessary to minimize the temperature rise around the cathode structure, which requires low heater power consumption. It has become like that. In this case, if the heater power consumption is simply reduced, the image output time will be delayed, and the temperature of the base metal 11 and the thermionic emissive material layer deposited thereon will be lowered, the emission of thermionic electrons will be reduced, and the cathode The structure will no longer be able to function normally. That is, the problem here is how to speed up the image output time while maintaining the temperature of the cathode structure, especially the basic metal 11.

In general, the following relationship exists between the image output time, the power consumption of the heater, and the heat capacity of the so-called cathode made of the cathode sleeve 12 and the basic metal 11.

t=kCth/Ph where t: image output time, Cth: heat capacity, Ph: heater power, k: proportionality constant.

As can be seen from this equation, in order to speed up the image output time, it is necessary to reduce the heat capacity of the cathode body or to effectively utilize the heat from the heater. Among these, the heat capacity can be reduced by making the shape of the cathode body smaller, that is, by making the outer diameter of the basic metal 11 and the cathode sleeve 12 smaller, and by making the wall thickness thinner. Further, to effectively utilize the heat from the heater means to effectively capture radiant heat energy, and the first conventional example is a cathode assembly as shown in FIG.
Cathode sleeve 12 to prevent heat radiation from 5
This can be done by increasing the length of the cathode sleeve 12 or by blackening the inner surface of the cathode sleeve 12 to increase heat absorption. In addition, in order to maintain the temperature of the base metal at the desired operating temperature with low heater input power, the cathode structure must be made smaller and the heat radiation from the outer surface of the cathode sleeve 12 must be reduced in order to reduce the heat radiation area of the cathode. It is necessary to. Cathode sleeve 12
In order to reduce heat radiation on the outer surface and increase heat absorption on the inner surface, the inner surface of the cathode sleeve 12 is made of a chromium alloy, the outer surface is made of nickel metal, and only the inner surface is blackened in a moisture-added hydrogen atmosphere with a dew point of 20°C. It is possible by However, when such a material is used, the disadvantage is that during operation of the cathode assembly, the heat radiation characteristics of the nickel metal surface, that is, the outer surface of the cathode sleeve 12, gradually change and the basic metal temperature decreases. be. Furthermore, since nickel metal has higher thermal conductivity than nichrome alloy, it has the disadvantage that heat is easily radiated through the support member, lowering the temperature of the base metal.

Next, a method for determining the thermal peak portion necessary for explaining the present invention will be explained with reference to FIG. 2. For example, a heater 16 is installed in the cathode sleeve 12 of the cathode assembly as shown in FIG.
A current is applied to the heater 16, and the radiant energy on the surface of the cathode sleeve 12 is transferred to the cathode support tube 1.
4 is provided with a slit hole, and as a result of measurement using a radiation thermometer from this slit hole, a curve 17 as shown in FIG. 2b is obtained. A point 19 on the cathode sleeve 12 corresponding to the highest value 18 of this curve 17
is called the heat radiation peak part.

Next, the cathode structure of the previous application filed by the present inventors will be explained with reference to FIG. 3, which improves the above-mentioned drawbacks.

First, a disk-shaped basic metal 21 is press-fitted and fixed to one end of a cylindrical reflecting member 25 of a desired length that can be attached to the outer periphery of the upper end of the cathode sleeve 22, which is open at both ends. The reflective member 25 is attached to surround the outer wall near the upper end of the cathode sleeve 22. Next, the cathode sleeve 22 and the cylindrical reflecting member 25 are fixed at a fixing point 26 by means such as welding.

Also, at the other end of the cathode sleeve 22, there are three
One end of the book support member 23 is welded and the dew point
A heat treatment is performed at approximately 1000° C. for 30 minutes in a hydrated hydrogen atmosphere at 20° C., and the cathode sleeve 22 is covered with chromium oxide to blacken the surface. Next, the other end of the support member 23 is fixed to the shoulder, ie, the upper end 24 ₁ of the cathode support tube 24 made of a cylindrical reflective member. in this case,
As can be seen from the figure, the cathode sleeve 22 and the support member 23 form an acute angle, and the cathode sleeve 23 and the cathode support tube 24 have the same axis.

By arranging the cylindrical reflecting member 25 around the outer periphery of the cathode sleeve 22 in this manner, it is possible to substantially reduce heat radiation from the outer surface of the cathode sleeve 22. Although the presence of the cylindrical reflection member 25 is a disadvantageous factor in increasing heat capacity and speeding up the image output time, the cylindrical reflection member 25 differs from other parts of the cathode structure in that it has mechanical strength and thermal shock strength. The increase in heat capacity does not pose much of a problem in practice, since it can be made thinner without worrying about heat capacity.

Note that the crystal growth that occurs in the cylindrical reflection member 25 during operation is limited to the range from the lower end of the base metal 21 to the fixed point 26 between the cylindrical reflection member 25 and the cathode sleeve 22. Therefore, the fixing point 26 should be placed as close to the base metal 21 as possible, within half the length of the cylindrical reflective member 25 or 0.5 mm from the upper end surface of the base metal 21.
By setting the value within the range, crystal growth can be partially suppressed, thereby almost eliminating changes in thermal conductivity over time and extending the life of the cathode structure. Further, in this example, the cylindrical reflecting member 25
As can be seen from its structure, the cylindrical reflecting member 25 does not play the role of a heat dam, but is merely a heat reflecting plate, and the crystal growth of this cylindrical reflecting member 25 does not contribute to heat conduction, so that the cathode temperature does not rise.

Next, the relationship between the heat radiation peak portion of the cathode sleeve 22 and the cathode support cylinder 24 will be described.

Generally, the cathode sleeve 22 is made of a nichrome alloy as described above, and is blackened by heat treatment in a water-added hydrogen atmosphere with a dew point of 20°C, but this blackening is caused by the formation of chromium oxide on the surface of the cathode sleeve 22. This is because The heat radiation from the blackened cathode sleeve therefore corresponds to the heat radiation from a bad conductor. Thermal radiation from this poor conductor has a nearly uniform value up to 60° from the perpendicular in plane angle, but sharply decreases when the angle exceeds 60°. This is explained by E. Schmid and E.
Eckert Forsch Gebiete Ingenieurw 6175
(1935).

That is, in this example, the cylindrical reflecting member 2 is
5 and the cathode support cylinder 24. That is, the thermal radiation peak portion 29 corresponding to the maximum value 28 of the thermal radiation energy curve 27 of the cathode sleeve 22 shown in FIG. 4 and the upper end portion 2 of the cathode support tube 24
_4. The length of the cylindrical reflective member is determined so that the angle θ ₁ between the straight line 30 connecting the inner edge of the opening of 1 and the cathode sleeve 22 is 30° or less, so that the heat radiation from the cathode sleeve 22 is directed almost toward the cathode support tube 24. It was designed so that it could be directed towards.

However, the disadvantages of the conventional example described above and the cathode sleeve 12 in FIGS. 1 and 3 in the prior application,
22 and the base metals 11, 21 are fixed, the cathode sleeves 12, 22 are oxidized. As mentioned above, this condition is such that the reducing agent Mg contained in the basic metals 11 and 21 diffuses and disappears from the surface, and the MgO
This results in the formation of oxides such as and loss of reducibility. As a result, a depletion zone of about 12 μm from the surface occurs.
The average concentration of Mg is initially 0.03% but becomes about 0.01%. Since the cathode structure in this state deteriorates the emission characteristics immediately after the tube is manufactured, in the previous example, the surface of the base metals 11 and 21 was ground down by about 10 to 20 μm. However, by adding this cutting process, stress strain is left on the basic metal surface, and when this strain is released, a fine grain layer is created during the exhaust process where the oxygen partial pressure is high, preventing the long-term reduction action. .

Therefore, even though it is hydrogen treatment, high temperature treatment is not suitable for use as a cathode substrate. However, a temperature of about 1000° C. is required to coat the chromium in the nickel-chromium alloy on the surface as chromium oxide, and there is a problem that the processing temperatures of the cathode sleeve and the base metal are inconsistent.

An object of the present invention is to solve this contradiction and provide a method for manufacturing a cathode assembly that can improve initial electron emission characteristics and long-term electron emission characteristics.

Next, FIG. 5 shows the structure of an example of the cathode structure to which the present invention is applied, and FIGS. 6 to 1 show the manufacturing method thereof.
It is shown in Figure 1 and its characteristics will be explained.

First, as shown in Fig. 6, the cathode sleeve 32 with both ends open is heat treated at 1000°C for 30 minutes in a water-added hydrogen atmosphere with a dew point of 20°C, and the cathode sleeve 32 is covered with chromium oxide to blacken the surface. do. In addition, a seventh device that can be attached to the outer periphery of this cathode sleeve 32
As shown in the figure, a cylindrical reflecting member 35 of a predetermined length is prepared, and as shown in FIG.
A disk-shaped base metal 31 that can be mounted inside near the upper end of the base metal 31 is brightly annealed under appropriate conditions.

As shown in FIG. 9, the assembly is carried out by placing a blackened cathode sleeve 32 inside a cylindrical reflective member 35, and inserting a disk-shaped base metal 31 whose diameter is slightly smaller than the inner diameter of this cathode sleeve 32. The upper ends of the cathode sleeve 32 and the cylindrical reflective member 35 are held substantially aligned on the upper surface of the base metal 31, and then a compression punch 61 is inserted into the cathode sleeve 32 to apply pressure between the upper surface of the base metal 31 and By applying P and making the base metal 31 bulge, the diameter is increased and the base metal 31 and the cathode sleeve 32 are fitted together as shown in FIG.
2 ₁ is formed and brought into close contact with the cylindrical reflecting member 35 via this bulged portion 32 ₁ . Next, a laser beam 60 is used to weld the overlapping portion of the cylindrical reflecting member 35, the cathode sleeve 32, and the base metal 31. In this case, since the surface of the cathode sleeve 32 is made of chromium oxide, conventional resistance welding is not possible, and a welding method using laser light is appropriate. Next, three supporting members 3 are attached to the other end of the cathode sleeve 32 at 120° intervals.
3 is welded using a laser beam 60 for the same reason as described above.

Next, the other end of the support member 33 is fixed to the shoulder, ie, the upper end ₃₄₁ , of the cathode support tube 34 made of a reflective member, to obtain a cathode assembly as shown in FIG. At this time,
As shown in the figure, the cathode sleeve 32 and the support member 33 form an acute angle, and the cathode sleeve 32 and the cathode support tube 34 are coaxial.

Also, a heat reflection peak portion 39 similar to that in FIG.
The angle θ ₁ between the cathode sleeve 32 and the straight line 40 connecting the opening edge of the upper end 34 ₁ of the cathode support cylinder 34 is
The length of the cylindrical reflecting member 35 is determined so that it is 30 degrees or less.

The main point of the cathode assembly of the present invention produced by such a manufacturing method is the cross-sectional portion near the welding point 36 shown in FIG. That is, the cylindrical reflective member 35, the cathode sleeve 32, and the base metal 31 are overlapped, and the base metal 31 is bulged by applying pressure, thereby forming a gap 37 between the cathode sleeve 32 and the base metal 31, and a gap 37 between the cathode sleeve 32 and the cylindrical reflective member 35. The gap 38 is eliminated, and then welding is performed using a laser beam 60. This necessity is, for example, due to the cathode sleeve 32 and the cylindrical reflective member 35.
Both have a thickness of about 10 to 30 μm, and are extremely easily deformed. Considering the burrs of the cut, etc., it is difficult to suppress the degree of fit between the two to 10 μm or less. Unlike resistance welding, laser beam welding melts from the input direction of the laser beam, forming a mortar-shaped nugget. At this time, if there is a gap 38, the cylindrical reflective member 35 will first melt and fall into the gap 38, creating a hole in the cylindrical reflective member 35, or
Or create an extremely thin section around the melting point. This also applies to the gap 37.

Therefore, it is desirable to eliminate the gaps 38 and 37 as much as possible when welding using laser light. Therefore, in the method for manufacturing a cathode structure of the present invention, the base metal 3
1 was expanded under pressure, making it possible to eliminate gaps.

Next, a second embodiment of the present invention will be described with reference to FIG.

First, the cathode sleeve 42 with both ends open is oxidized in a moisture-adding hydrogen furnace. Further, a cylindrical reflecting member 45 of a required length that can be inserted into the outer periphery of this cathode sleeve 42 is prepared. Next, the cathode sleeve 42 and the cylindrical reflection member 45 are combined, a disk-shaped base metal 41 that has been brightly fired in advance is placed inside, and the base metal 41 is processed to bulge based on the upper surface, and the cathode sleeve 42 and The cylindrical reflecting member 45 is brought into close contact with each other. Next, this close contact portion 46 is exposed to the cylindrical reflecting member 45 using a laser beam.
Weld from the side. If the close contact parts are welded in this way, there will be no hole in the cylindrical reflecting member 45.

Next, a support part 44c and a cathode are formed by making a notch in the lower end of the cathode support tube 44 made of a reflective member fixed to a substrate 47 made of ceramics or the like via bulges 44a and 44b, and bending it inward. The sleeve 42 is welded with a laser beam at a welding point 42a. In this case, the cathode sleeve 42 and the cathode support cylinder 44 are fixed so as to have the same axis to form a cathode assembly. In the cathode assembly described above, the cylindrical reflective member is arranged so that the angle θ ₂ formed by the line 50 connecting the thermal radiation peak portion 49 and the upper edge 44 ₁ of the cathode support cylinder 44 in the longitudinal direction of the cathode sleeve 42 is 30° or less. 45 and its relative position with the cathode support cylinder 44 are determined.

The most important points of the present invention are the first embodiment and the second embodiment.
In both embodiments, the base metal, which is the basis of the cathode, is not exposed to excessive processing temperatures. That is, the base metal contains reducing agents such as Mg and Si, but when these are treated at high temperatures, they diffuse and evaporate, creating a layer on the surface of the base metal in which the reducing agent has disappeared. Raising the base metal to a high temperature causes Mg to be depleted on the surface, and this Mg is oxidized in a hydrogen stream containing water and deposits as magnesium oxide on the surface. This deposited magnesium oxide forms a composite oxide layer with barium oxide, and this composite oxide layer increases with the operating time of the cathode, causing deterioration of the cathode. Therefore, it is not preferable to form a thick unnecessary magnesium oxide layer in the initial stage.

Furthermore, the base metal needs to undergo some grain growth before applying CO ₃ , which is an electron radioactive material (Ba, Sr, Ca). The reason for this is that the electron radioactive material decomposes and generates CO ₂ , and this oxygen diffuses into the base metal, combines with Mg, Si, etc. contained in the base metal to form an oxide, and combines with BaO to form a composite. Creates an oxide layer. Since this composite oxide layer precipitates at the grain boundaries of the base metal, the electron radioactive material is applied in a state where the grains have not grown, that is, as the base metal is rolled, and decomposed during tube manufacture.
When oxygen diffuses into these fine grains due to _CO2 , it creates a fine network of grain boundaries, covering the surface of the base metal,
This grain boundary is clogged with composite oxide, and this grain boundary is metal.
Since Mg and Si are difficult to diffuse, they are difficult to react with (Ba, Sr, Ca)O, which is an electron emitting substance, resulting in a decrease in electron emission. For this reason, it is necessary to allow grain growth of the base metal to such an extent that the reducing agent does not disappear from the surface due to evaporation.

In the present invention, the base metal is heat-treated in advance under appropriate conditions to cause grain growth, and then welded with laser light, so the base metal is in an ideal state.
After that, an electron radioactive substance material is applied and an exhaust activation process is completed.

As explained above, according to the present invention, a cylindrical reflecting member and a cathode sleeve are fitted together so that their tips are in the same position, and a base metal is inserted inside the member, and this base metal is radially moved. Since the base metal, the cathode sleeve, and the cylindrical reflective member are brought into close contact with each other by bulging, and laser welding is performed from the outside of the cylindrical reflective member, a reliable and stable welding state can be obtained. In particular, even if you use a blackened cathode sleeve, or a cathode sleeve or cylindrical reflective member that has dimensions that will leave gaps when they are fitted, sufficient welding strength will be achieved because the laser welding eliminates the gaps between each other. Can be assembled. Furthermore, automation of the production line is also easily possible.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a conventional cathode structure;
FIG. 2 is a diagram explaining the heat radiation peak part, a
The figure is a cross-sectional view showing a state in which a heater is installed in a cathode sleeve to which a base metal is fixed, figure b is a curve diagram showing changes in thermal radiation energy corresponding to figure a, and figure 3 is an example of the cathode structure of the earlier application. FIG. 4 is a diagram illustrating the heat radiation peak portion of the example shown in FIG. 3, FIG. FIG. 5 is a partially cutaway side view showing the first embodiment of the cathode structure of the present invention, and FIGS. 6 to 11 are diagrams showing the main points of the manufacturing process. FIG. 6 is a cross-sectional view of a blackened cathode sleeve, FIG. 7 is a cross-sectional view of a cylindrical reflective member, FIG. 8 is a cross-sectional view of a base metal, and FIG. 9 is a cross-sectional view of a blackened cathode sleeve. Figure 10 is a sectional view showing the process of assembling the sleeve and the cylindrical reflective member and applying pressure to the base metal with a punch. FIG. 11 is an explanatory view showing the step of fixing the support member, and FIG. 12 is a partially cutaway side view showing the second embodiment of the present invention. 11, 21, 31, 41...Base metal, 12,
22, 32, 42... cathode sleeve, 25, 3
5, 45... Cylindrical reflective member, 19, 29, 39,
49...Heat radiation peak part.

Claims (1)

[Claims] 1 A cylindrical reflective member of a predetermined length, a cathode sleeve that is internally housed in the cylindrical reflective member and has an upper end at approximately the same position as the upper end of the cylindrical reflective member, and is inserted and fixed near the upper end of the cathode sleeve. In the method of manufacturing a cathode structure having a disc-shaped base metal, the cathode sleeve is blackened in a water-added hydrogen atmosphere, and then the cylindrical reflective member is attached to the cathode sleeve so that the upper end thereof is approximately a step of inserting the base metal inside the upper end portion of the cathode sleeve while arranging the base metal so that they are in the same position;
the base metal by bulging the base metal in the radial direction;
A step of bringing the cathode sleeve and the upper end of the cylindrical reflective member into close contact with each other, and welding and fixing the cylindrical reflective member, the cathode sleeve, and the base metal by applying laser light from the outside of the cylindrical reflective member corresponding to the bulge. A method for manufacturing a cathode assembly, comprising the steps of: