JPH0113188B2 - - Google Patents

Description

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

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

First, an example of a fast-acting indirectly heated cathode structure will be explained with reference to FIG. That is, 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 to the lower end of this cathode sleeve 12 at intervals of 120 degrees. Approx. 1000 in a hydrated hydrogen atmosphere at 20℃
℃ for 30 minutes, and the cathode sleeve 12
to blacken. Next, the support member 13 is attached to the cathode support tube 14.
The cathode sleeve 12 and the cathode support tube 14 are fixed to the _upper end 141 of the cathode so as to be coaxial, thereby completing the indirectly heated cathode assembly.

At present, the indirectly heated cathode assembly having the above-described structure is used in color picture tubes, and each indirectly heated cathode assembly requires a heater power of, for example, 1.26 W, and the image output time is approximately 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, so it is necessary to minimize the temperature rise around the indirectly heated cathode structure. It has become required.
In this case, if you simply reduce the heater power consumption,
First, the image output time is delayed, and the temperature of the base metal 11 and the thermionic emissive material layer deposited thereon is lowered, the emission of thermionic electrons is reduced, and normal operation as an indirectly heated cathode structure is no longer possible. It disappears. That is,
The problem here is how to speed up the image output time while maintaining the temperature of the indirectly heated cathode structure, especially the base metal 11.

In general, there is a relationship as shown below between the image output time, the power consumption of the heater, and the heat capacity of the so-called cathode body consisting of the cathode sleeve 12 and the base metal 11.

t=kCth/Ph However, t: Image output time, Cth: Heat capacity, Ph: Heater power, k: Proportionality constant As can be seen from this equation, to speed up the image output time, either reduce the heat capacity of the cathode body, or It is necessary to make effective use of the heat from the 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 base metal 11 and the cathode sleeve 12 smaller, and by making the wall thickness thinner. In addition, to effectively capture heat from the heater, in an indirectly heated cathode structure as shown in FIG. 1, the length of the cathode sleeve 12 is 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. Also, due to the low heater input power, the base metal 1
In order to maintain the temperature of the cathode sleeve 12 at a desired operating temperature, it is necessary to downsize the indirectly heated cathode assembly and to reduce heat radiation on the outer surface of the cathode sleeve 12. Among these, to reduce heat radiation on the outer surface of the cathode sleeve 12 and increase heat absorption on the inner surface, the inner surface of the cathode sleeve 12 is made of chromium metal, the outer surface is made of nickel metal, and the inner surface is heated in a moisture-added hydrogen atmosphere with a dew point of 20°C. This is possible by only applying blackening treatment.
However, when such a material is used, chromium metal gradually diffuses into the nickel metal while the indirectly heated cathode assembly is operated, and the heat on the nickel metal surface, that is, the outer surface of the cathode sleeve 12, is absorbed. It has the disadvantage of changing the radiation characteristics and lowering the base metal temperature. Furthermore, since nickel metal has a higher thermal conductivity than nichrome alloy, it has the disadvantage that heat is easily radiated through the support member 13 and the temperature of the base metal 11 becomes lower.

Next, a method for determining the thermal peak portion of an indirectly heated cathode assembly having such a structure will be explained with reference to FIG.

For example, a heater 16 is installed in the cathode sleeve 12 of an indirectly heated cathode structure as shown in FIG. As a result of measurement using a radiation thermometer from this slit hole, a curve 17 as shown in FIG. 2b was obtained.
Suppose we get . A point 19 on the cathode sleeve 12 corresponding to the maximum value 18 of the radiation temperature of this curve 17 is referred to as a thermal radiation peak portion.

Next, the indirectly heated cathode structure previously filed by the present inventors will be explained with reference to FIG.

First, a cylindrical reflecting member 25 of a predetermined length is provided on the outer periphery of the upper end of the cathode sleeve 22 with both ends open, and a circular base metal 21 is press-fitted and fixed to the upper end of this cylindrical reflecting member 25. A 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. In addition, at the other end of the cathode sleeve 22, there are three supporting members 2 at 120° intervals.
One end of the cathode sleeve 22 is welded and heat treated at about 1000° C. for 30 minutes in a water-added hydrogen atmosphere with a dew point of 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 connected to the shoulder, that is, the upper end 2 of the cathode support tube 24 made of a reflective member.
4 Fixed to ₁ . 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 22 and the cathode support cylinder 24 have the same axis.

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

Next, the relationship between the heat radiation peak portion of the cathode sleeve 22 and the cylindrical reflecting member 25 will be described.

As mentioned above, the cathode sleeve 22 is made of a nichrome alloy 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 oxides on the surface of the cathode sleeve 22. This is because there is. The heat radiation from the blackened cathode sleeve therefore corresponds to the heat radiation from a bad conductor. The thermal radiation from this poor conductor is almost uniform up to a plane angle of 60° from the perpendicular, but it decreases rapidly when the plane angle exceeds 60°.
Forsch Gebiete Ingenieurw6175 (1935).

The prior application makes use of the above properties to provide a positional relationship between the cylindrical reflecting member 25 and the cathode support tube 24 made of the reflecting member. That is, as shown in FIG. 4, the radiant energy curve 27 of the cathode sleeve 22
The cylindrical reflecting member is arranged so that the angle θ formed by the cathode sleeve 22 and _the straight line 30 connecting the thermal radiation peak portion 29 corresponding to the maximum value 28 of The length of the cathode sleeve 22 is determined so that the radiation from the cathode sleeve 22 is approximately equal to the length of the cathode support tube 2.
It is designed to be oriented in four directions.

By adopting such a structure, it has become possible to improve the speed of the indirectly heated cathode structure compared to the conventional structure, but there is one problem similar to the conventional structure. I understood.

That is, the cathode sleeve 1 shown in FIGS. 1 and 3
2, 22 and the base metals 11, 21 are fixed, and then the cathode sleeves 12, 22 are oxidized. This condition is as described above because the treatment is carried out in a water-added hydrogen furnace at 1000°C. The reducing agent contained, such as Mg, diffuses and disappears from the surface, or
As a result, it becomes an oxide such as MgO and loses its reducibility. This value causes a depletion zone of about 12 μm from the surface, and the average concentration of Mg is 0.01%, which was initially 0.03%.
It will be about. In an indirectly heated cathode structure having a base metal in such a state, the surface of the base metal is
Approximately 20 μm had been removed. However, by adding this cutting process, stress strain is left on the base metal surface, and when this strain is released, a fine grain layer is generated during the exhaust process where the oxygen partial pressure is high, which hinders the reduction action for a long period of time. do.

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

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a cathode structure that can solve the above-mentioned contradictions and improve initial electron emission characteristics and long-term electron emission characteristics.

Next, an embodiment of the method for manufacturing a cathode structure according to the present invention will be described with reference to FIGS. 5 to 11.

First, nickel of a predetermined length as shown in Fig.
A cathode sleeve material 32 ₁ made of a chromium alloy is prepared, and this cathode sleeve material 32 ₁ is heat treated at 1000°C for 30 minutes in a water-added hydrogen atmosphere with a dew point of 20°C, resulting in chromium oxidation on the surface as shown in Figure 6. A cylindrical blackened cathode sleeve 32 is formed with a blackened layer 32a made of a material. In the following figures, the blackening layer 32a is omitted.

On the other hand, as shown in FIG. 7, a cylindrical reflecting member 35 of a predetermined length having an inner diameter slightly larger than the outer diameter of the cylindrical blackened cathode sleeve 32 is prepared, and the upper end of this cylindrical reflecting member 35 is bent inwardly. An outer bent part ₃₅₂ is formed at the lower end of the bent part ₃₅₁ .

Furthermore, a disk-shaped base metal 31 as shown in FIG. 8 is prepared, and the base metal 31 is formed so that its outer diameter is slightly smaller than the inner diameter of the cathode sleeve 32, and bright annealed.

FIG. 9 shows a method for assembling these. First, the cylindrical blackened cathode sleeve 3 is attached to the cylindrical reflective member 35 from the outer bent portion 35 ₂ of the lower end thereof.
Insert 2. At this time, the cylindrical blackened cathode sleeve 3
2 is an inner bent portion 35 ₁ of the cylindrical reflecting member 35;
Hold it so that it touches the bottom surface of the Next, insert the disk-shaped base metal 31 into the cylindrical blackened cathode sleeve 32, and press the press stand 51 so that the tip of the inner bent portion ₃₅₁ of the cylindrical reflection member 35 and the surface of the base metal 31 are on the same plane. The punch 52 for compressing the base metal 31 is inserted into the cylindrical blackened cathode sleeve 32 and pressure is applied in the direction of the arrow 53 to bulge the base metal 31 as shown in FIG. and a cylindrical blackened cathode sleeve 32 and a cylindrical reflective member 3
5 is fitted.

Next, the base metal 31, the cylindrical blackened cathode sleeve 3
2. Weld the close contact points 36 ₁ of the cylindrical reflective member 35 at a plurality of welding points 36 using the laser beam 54 .
The laser beam 54 is used for this welding because the surface of the cylindrical blackened cathode sleeve 32 is made of chromium oxide and cannot be fixed by conventional resistance welding.

Next, as shown in FIG.
One end of No. 3 is welded using a laser beam for the same reason. And this support member 33
The other end is fixed to the shoulder or upper end 34 ₁ of the cathode support tube 34 made of a reflective member. In this case, as shown in the figure, the cylindrical blackening cathode sleeve 32 and the support member 33 form an acute angle, and the cylindrical blackening cathode sleeve 32 and the cathode support tube 34 have the same axis. In addition, a straight line 4 connecting the heat radiation peak portion 39 and the opening edge of the upper end portion 34 ₁ of the cathode support cylinder 34
0 and the cylindrical blackened cathode sleeve 32 (θ)
The length of the cylindrical reflecting member 35 is determined so that the angle is 30° or less.

The first point of the embodiment described above lies in the structure of the cylindrical reflecting member 35. That is, when the cylindrical blackened cathode sleeve 32 and the base metal 31 are overlapped and compressed in the process shown in FIG. It is extremely difficult to put both of them on the same surface. In order to improve this accuracy, in this embodiment, an inner bent portion 35 ₁ is provided at the upper end of the cylindrical reflecting member 35, and an outer bent portion 35 ₂ is provided at the lower end.
The first reason for providing the double bent portions 35 ₁ and 35 ₂ is that the cylindrical blackened cathode sleeve 32 has the inner bent portion 3.
5 ₁ and this cylindrical blackened cathode sleeve 32
can be prevented from protruding beyond the upper surfaces of the cylindrical reflecting member 35 and the base metal 31. In addition, while maintaining good roundness of the cylindrical reflective member by the outer bent portion 35 ₂ , the cylindrical blackened cathode sleeve 32 is moved using the bent portion 35 ₂ as a guide and the cylindrical blackened cathode sleeve 32 as a guide. can be easily inserted. Furthermore, when compressing the base metal 31, the upper end can be pressed against the press table 51 by holding the outer bent portion with a jig so that the cylindrical reflective member 35 does not lift up.

The second point of this embodiment is the cross section of the welding point 36. That is, the cylindrical reflective member 35, the cylindrical blackened cathode sleeve 32, and the base metal 31 are stacked one on top of the other, and as shown in FIG. After eliminating the gaps between the cylindrical blackened cathode sleeve 32 and the base metal 31 and the cylindrical reflective member 35, the three are welded together using laser light.
This is because the cylindrical blackened cathode sleeve 32 and the cylindrical reflective member 35 have a thickness of about 10 to 30 μm, and are extremely easy to deform.
It is difficult to keep the degree of fit below 10 μm. Unlike resistance welding, laser beam welding melts from the input direction of the laser beam, forming a cone-shaped nugget. At this time, if there is a gap at the welding position, the reflective member 35 having a cylindrical tip melts first and falls into the gap, creating a hole in the cylindrical reflective member 35 or creating an extremely thin portion around the melting point. This also applies to the gap between the cylindrical blackened cathode sleeve 32 and the base metal 31. Therefore, it is desirable to eliminate gaps as much as possible when welding with laser light, but in this example, due to the bulge of the base metal, it was possible to eliminate the defective gaps during welding with laser light.

In the embodiment described above, the cylindrical reflecting member 35
The inner and outer bent portions 35 ₁ and _{35 2} are provided at the upper and lower ends of the cylindrical blackened cathode sleeve 32 and the blackened surface layer of this sleeve, Cr ₂ O, as described above. This has the effect of preventing the _three layers from coming out on the same surface as the base metal. That is, a ternary carbonate, which is an electron emitting material (not shown), is coated on the base metal 31 like a normal cathode structure, and this ternary carbonate becomes an oxide in the exhaust activation process of a cathode ray tube, etc. , this oxide reacts with Cr ₂ O ₃ (chromium oxide) and evaporates. This evaporation may not be a problem if the base metal has a large diameter, but if the diameter is small, the effective area will be reduced, so the cylindrical cathode sleeve containing chromium should not be exposed to the area where the ternary carbonate of the base metal is applied. This is because it is desirable.

The aforementioned cylindrical reflective member 35 and bent portion 35
₁ and 35 ₂ can be made by cutting the straight cylindrical body using an appropriate method, but the plate body is cut out into a cap shape, the bent part 35 ₂ is formed by edge cutting, and then the bent part 35 2 is formed by cutting out the bottom plate. 35 There is also a way to remove ₁ . in this case,
Depending on the manufacturing method, it is of course possible to create a substantially similar structure even if the inner bent portion 35 ₁ of the cylindrical reflecting member 35 is removed.

In addition, when the bent portion 35 ₁ of the cylindrical reflective member 35 is omitted and the bent portion 35 ₂ is provided, the cylindrical reflective member 3
When inserting the cylindrical blackening sleeve 32 into the cylindrical blackening sleeve 32 and inserting the base metal inside, and compressing and expanding the base metal with a punch, the bent portion ₃₅₂ of the cylindrical reflective member 35 maintains the roundness almost and the insertion is easy. The bent portion 35 ₁ is not necessarily necessary because a holding jig is brought into contact with the end of the cylindrical blackened cathode sleeve 32 in order to prevent floating. However, if both bent portions 35 ₁ or 35 ₂ are missing, it is difficult to maintain the roundness of the cylindrical reflective member 35, making it difficult to insert the cylindrical blackened cathode sleeve 32, and the difference in outer diameter between the two is 50 μm. and 25μm on one side
It is almost impossible to create such a suppressing mechanism in a mass-produced machine, and therefore the cylindrical reflecting member 35 requires an outer bent portion ₃₅₂ .

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

First, a cathode sleeve member with both ends open is oxidized in a hydrogen furnace with water added to form a cylindrical blackened cathode sleeve 42. Next, a cylindrical reflecting member 45 that can be attached to the outer periphery of the cylindrical blackened cathode sleeve 42 and has an inner bent portion 45 ₁ at the upper end and an outer bent portion 45 ₂ at the lower end is prepared. Next, a disk-shaped base metal 41 that has been brightly annealed in advance is put in a combination of these two, and the base metal 41 is pressurized with the upper surface as a reference to bulge in the radial direction, and this base metal 41 and a cylindrical blackened cathode are formed. The sleeve 42 and the cylindrical reflecting member 45 are brought into close contact with each other. Next, by welding this close contact portion 46 ₁ through the welding point 46 with a laser beam, the cylindrical reflective member 4
5 can be welded and fixed well without making any holes.

Next, a supporting portion 44c and a cylinder are formed by cutting in the lower end of the cathode supporting cylinder 44 made of a reflective member that is fixed in advance to a substrate 47 such as ceramics via bulging portions 44a and 44b and bending it inward. The blackened cathode sleeve 42 is welded with a laser beam at a welding point 42a. In this way, the cylindrical blackened cathode sleeve 42 and the cathode support cylinder 44 are fixed so as to have the same axis, and the cathode assembly is completed.

In the embodiment described above, the length of the cylindrical reflecting member 45 and the relative position with respect to the cathode support tube 44 are adjusted so that the angle ( _θ ) between the heat radiation peak portion 49 and the upper edge 441 of the cathode support tube 44 is 30 degrees or less. Of course, it is necessary to decide.

The most important thing in the manufacturing process of the two embodiments described above is not to expose the base metal, which is the basis of the cathode structure, to excessive processing temperatures. In other words, the base metal contains reducing agents such as Mg and Si, but
When this is treated at high temperature, the reducing agent diffuses and evaporates, creating a layer on the surface in which the reducing agent has disappeared.

That is, heating 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 becomes a composite oxide layer with barium oxide, which increases with the operating time of the cathode assembly, causing deterioration. 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 (Ba, Sr, Ca), which is an electron radioactive material. The reason for this is that the electron radioactive material decomposes and generates CO ₂ , and this oxygen diffuses into the base metal and is contained in the base metal.
It combines with Mg, Si, etc. to form an oxide, and combines with BaO to form a composite oxide layer. This composite oxide layer precipitates at the grain boundaries of the base metal, so the grains do not grow. In other words, the electron radioactive material is applied to the base metal after rolling, and oxygen is removed by the CO ₂ decomposed during tube manufacture. However, when it diffuses into these fine grains, it creates fine mesh grain boundaries that cover the surface of the base metal, and these grain boundaries are clogged with composite oxides, and these grain boundaries are
Since Mg and Si are difficult to diffuse, they are difficult to react with (Ba, Sr, Ca)O, which is an electron radioactive 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. Therefore, the base metal of the present invention is heat-treated in advance under appropriate conditions to allow grain growth, and then the electron radioactive substance material is applied to the base metal in an ideal state for laser beam welding, and then the exhaust gas is applied. Of course, it is necessary to complete the process through an activation process.

As described above, the present invention allows the cylindrical reflective member having a predetermined thermal radiation peak, the cylindrical blackened cathode sleeve, and the base metal to be assembled so that the upper end of the cylindrical blackened cathode sleeve does not protrude from the upper surface of the base metal. Moreover, it can be assembled after blackening only the cylindrical cathode sleeve. During this assembly, the base metal, the cylindrical blackened cathode sleeve, and the cylindrical reflective member are welded and fixed using laser light after the base metal is bulged in the radial direction, resulting in a cathode structure with extremely good characteristics, which makes it suitable for industrial use. The value is great.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway side view showing an example of a conventional cathode assembly, Fig. 2 is a diagram illustrating the heat radiation peak portion of the cathode assembly shown in Fig. 1, and Fig. a shows a heater built into the cathode sleeve. FIG. 3 is a partially cutaway side view of the cathode structure of the earlier application,
FIG. 4 is a diagram explaining the heat radiation peak part of the cathode assembly in FIG. Curve diagram showing changes in energy, 5th
Figures 11 to 11 are diagrams showing an embodiment of the method for manufacturing a cathode structure of the present invention, in which Figure 5 is a perspective view showing a cylindrical cathode sleeve material, and Figure 6 is a cylindrical blackened cathode sleeve. 7 is a sectional view showing a cylindrical reflecting member, FIG. 8 is a perspective view of the base metal, FIG. 9 is an explanatory sectional view showing the process of expanding the base metal in the radial direction, and FIG. 10 11 is a partially cutaway side view for explanation showing the welding and fixing process using a laser beam, FIG. 11 is a partially cutaway side view for explanation of the completed cathode structure, and FIG.
The figure is a partially cutaway explanatory side view showing another embodiment of the present invention. 11,21,31,41...Base metal, 12,2
2, 32, 42... Cylindrical blackened cathode sleeve, 1
3, 23, 33, 43...support member, 14, 24,
34, 44...Cathode support cylinder, 19, 29, 39, 4
9...Heat radiation peak portion, 51...Press table, 52...Punch, 53...Laser light.

Claims (1)

[Claims] 1. Inserting a cylindrical blackened cathode sleeve into a cylindrical reflective member having a predetermined length and having at least an outer bent portion at its lower end; and the cylindrical reflective member and the cylindrical blackened cathode sleeve. inserting a disc-shaped base metal having a diameter smaller than the inner diameter of the cylindrical blackened cathode sleeve so that its surface is located at the upper end;
a step of providing a restraining mechanism on the outer bent portion of the cylindrical reflective member to pressurize the base metal to bulge together with the cylindrical blackened cathode sleeve and fit onto the cylindrical reflective member via the fitting portion; . A method for manufacturing a cathode assembly, comprising the steps of: welding and fixing the fitting portion using a laser beam.