JPS6318825B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides barium-aluminum alloy powder,
There is a getter device in which nickel powder is filled in a getter container made of annular metal and has a U-shaped cross section, and barium can be evaporated by heating.

The getter device is usually heated in an evacuated and sealed vacuum chamber by, for example, high-frequency induction heating to form a getter film of barium on the inner wall of the vacuum chamber. During such processes, the getter device may be subject to undesirable heating. For example, this is the case in the manufacturing process of picture tubes as disclosed in Japanese Patent Publication No. 12031/1983.

According to the technique disclosed in this publication, a getter device is installed inside the picture tube before the panel section and the funnel section that constitute the picture tube are sealed together with frit glass, and then heated at about 400 to 450 degrees Celsius in the atmosphere for 1 hour.
By heating for a period of time, the panel portion and the funnel portion are sealed together via the fritted glass.

In this case, a typical getter material containing a mixed powder of barium-aluminum alloy (BaAl ₄ ) powder and nickel (Ni) powder (mixed weight ratio of approximately 1:1) is heated in the atmosphere at temperatures above 350°C for a long period of time. When exposed, it oxidizes to produce mainly nickel oxide (NiO). If NiO is present in the getter device, NiO and BaAl ₄ react rapidly at high temperatures, so when the getter device is heated to evaporate barium (hereinafter referred to as getta flash), explosive barium is released. This results in the scattering of At this time, if the amount of NiO generated increases further, the metal getter container will also melt and be explosively scattered along with the getter material. For example, in a color picture tube for color television, this type of explosive scattering must be avoided during completion because it can cause the picture tube to withstand poor pressure. For the above reasons, there is a need for a getter device that does not cause any trouble even when exposed to high temperatures in the atmosphere.

For this purpose, a getter device in which the exposed surface of the getter material was coated with organic silane was developed in Japanese Patent Laid-Open No.
A getter device coated with silicon oxide is disclosed in Japanese Patent Application Laid-Open No. 139355/1984.

First, according to JP-A No. 52-84960, a getter device coated with organic silane such as polysiloxane containing alkyl, aryl, aralkyl, alkaryl and hydrogen can withstand heating at 420°C for 1 hour in air. , a technique has been disclosed that can evaporate barium without causing explosive scattering.

However, such getter devices coated with organic silane have the following drawbacks when used. That is, such a getter device mainly emits a large amount of hydrocarbon gas during getter flushing. This released gas is not easily adsorbed by the getter membrane, and the pressure inside the tube remains at about 10 ^-3 Torr for a while after the getter flush.

As is well known, a large amount of residual gas is ionized in a space to which a high voltage is applied, such as in a color picture tube for color television, and is then accelerated and collides with the cathode or anode. It can be easily inferred that due to this so-called sputtering effect, a portion of the electron-emitting substance on the cathode will fly to other undesirable locations, resulting in a significant deterioration of the breakdown voltage characteristics.

Further, in Japanese Patent Application Laid-Open No. 139355/1989, it is disclosed that a getter device in which the exposed surface of the getter material is covered with a silicon oxide layer can withstand heating at 450°C for one hour in the air, and that such a silicon oxide layer However, a technique has been disclosed which is obtained by heating the silicates remaining after immersing the Getter device in a solution of hydrolyzed ethylsilicate in a composition consisting of, for example, methanol, deionized water and nitric acid to 120° C. in vacuo. ing. The getter device thus obtained exhibits considerable protection against high temperature oxidation. That is, when a getter device without a protective coating is heated in the atmosphere at 450°C for 1 hour and then flashed in a vacuum, explosive scattering occurs, and most of the getter container is also scattered. On the other hand, when a getter device whose exposed surface is coated with a silicon oxide layer using the method described above is similarly heated in the atmosphere and then flashed in a vacuum, the degree of explosive scattering is considerably improved. However, only a small amount of the getter material fell off and a partially sintered getter material rose to the outside of the getter container (peel-off phenomenon). However, mild explosive scattering and lifting of the getter material must be completely avoided in electron tubes such as picture tubes. This is because, as mentioned above, these materials significantly deteriorate the withstand voltage characteristics of the electron tube. Explosive scattering causes the scattered particles to fly to undesired locations within the pipe, which not only deteriorates the withstand voltage characteristics but may even cause short circuits. Furthermore, the lifting of the getter material causes the formation of a barium film at undesired locations within the tube, which also causes deterioration of the pressure resistance characteristics. The oxidation of Ni in the Getsuta material is thought to be the cause of such mild but explosive scattering. When the surface of the getter device coated with a silicon oxide layer by the method described above was observed using an electron microscope, it was found that the silicon oxide layer had a porous structure. It is thought that oxygen was supplied to the surface of the getter device through these pores, and a portion of the getter material was oxidized.

In order to eliminate the above-mentioned drawbacks, the inventors have previously filed an application for a getter device in which a boric acid compound is formed on the exposed surface of a getter material. By forming a boric acid compound on the surface of the getter container in this manner, a getter device having high temperature oxidation resistance can be obtained.

Next, a method for manufacturing such a getter device will be described. First, the getter device is immersed in an alcoholic solution of a boric acid compound, dried, and then degassed by vacuum heating. At this time, the boric acid compound is melted, and the surface of the getter device is completely coated with the transparent and dense vitreous boric acid compound. The boric acid compound mentioned here consists essentially of a single substance or a mixture selected from the group consisting of boric anhydride, orthoboric acid, metaboric acid, and tetraboric acid. Almost the same effect can be expected using any of these substances. i.e. in the atmosphere
Even when heated at 450°C for 2 hours, the getter device is hardly oxidized. In addition, almost no nickel oxide (NiO), which causes explosive scattering during barium flashing, is produced. Furthermore, this getter device heated in the atmosphere at 450°C for 2 hours can successfully flash barium in the manufacturing process of electron tubes such as picture tubes.

However, it has been found that the above-mentioned getter device has the following problems. That is, in the manufacturing process of color picture tubes for color television, if the panel part with the getter device installed inside and the funnel part are sealed with frit glass in advance, and then left in a high temperature atmosphere for a long time, the atmosphere The moisture inside is adsorbed by the boric acid compound coating layer. A portion of this adsorbed water is discharged outside the tube in the subsequent exhaust process, but the rest is discharged into the tube in the getter flush process. As is well known, this released moisture reacts with carbon compounds adsorbed on the barium film and is converted into hydrocarbon gas such as methane. This gas is difficult to be adsorbed by the getter film and remains in the tube for some time after the getter flush. The harmfulness of such residual gas is as described above.

The present invention was made in view of the above-mentioned drawbacks and problems, and an object of the present invention is to provide a high-quality getter device that has high temperature oxidation resistance and does not cause any trouble when used. There is.

That is, the present invention forms a boric acid compound-silicon dioxide glassy coating with improved water resistance on at least the exposed surface of the getter material by incorporating a small amount of silicon dioxide into a boric acid compound coating having excellent high-temperature oxidation resistance. It is a getter device.

_{For example , T.J.}
Rocket, W. R. Foster: J. Am. Ceram.
Soc., 48 [2] 78 (1965), etc., and in a B ₂ O ₃ -SiO ₂ mixed system, there is a eutectic point at 2% by weight SiO ₂ and the melting temperature is lowered.

When a boric acid compound mixed with SiO ₂ is applied to at least the exposed surface of the getter material and then heated and melted in a vacuum to form a dense coating, the vacuum treatment temperature is mainly used for sintering the nickel powder in the getter material. Therefore, it is limited.

In other words, the nickel powder used in the Getta device, which has a particle size of several μm, becomes noticeably coarser due to sintering at about 600°C, which reduces the reaction rate with BaAl ₄ during Getta flashing, and as a result, barium evaporates. This is not preferable because it reduces the amount. Therefore, the vacuum treatment temperature is suitably 550°C or lower, preferably 500°C or lower.

In the B ₂ O ₃ -SiO ₂ system phase diagram, the SiO ₂ content that has a melting point of 500°C or less is approximately 7% or less, but when processing time is considered, the practical content is 5% or less. It was hot.

Next, the getter device of the present invention will be explained using the drawings. That is, FIG. 1 is a cross-sectional view of the getter device of the present invention, and in the figure, a getter material 11 containing barium-aluminum alloy powder and nickel powder is filled into a getter container 12 made of annular metal and having a substantially U-shaped cross section. The surfaces of the getter container 12 and the getter material 11 are coated with a boric acid compound coating 1 containing silicon dioxide.
Covered by 3.

Next, the getter device of the present invention will be explained in detail using examples.

Example 1 Mixed powder of BaAl ₄ powder and Ni powder (mixed weight ratio of approximately 1:
1) and a getsuta material with a few percent of germanium nitride-iron powder added to it with an outer diameter of 22 mm, an inner diameter of 15 mm, and a height of
A heat-generating barium getter device with a so-called nitrogen release source, which was filled in a ring-shaped metal getter container made of stainless steel and approximately U-shaped in cross section with a 1.9 mm cross section, was placed in a 10% by weight boric anhydride-methanol solution in which silicon dioxide powder was dispersed. Soak in. As the silicon dioxide powder, a fine powder with a particle size of 0.1 μm was used to facilitate melting, and the amount added was 2% by weight based on boric anhydride. After dipping, it was dried in the atmosphere using an infrared lamp, and further heated in a vacuum at 500°C for 30 minutes to produce a getter device as shown in Figure 1. In this case, the exposed surfaces of the getter container and getter material are covered with a thin, transparent, dense boric acid compound-silicon dioxide coating.

The getter device created in this way was placed in the atmosphere.
After heating at 450°C for 2 hours, it was placed in a vacuum container and subjected to high-frequency induction heating from the outside to perform a getter flash. At this time, when the residual gas in the vacuum container was analyzed using a residual gas analyzer, it was found that there was very little hydrocarbon gas. In addition, when a similar experiment was conducted after heating the Getta device in the atmosphere at 450°C for 2 hours and leaving it in a room with approximately 70% humidity for 24 hours, the increase in hydrocarbon gas was slight. In addition, although flash experiments were conducted using a number of getter devices, no explosive barium scattering or peel-off phenomenon was observed. Furthermore, when the amount and distribution of scattered barium in the formed barium film, the amount of released gas, etc. were measured, it was confirmed that there were no abnormalities at all.

Embodiment 2 FIG. 2 shows an embodiment in which the getter device obtained according to the present invention is applied to a color picture tube. In the figure, a fluorescent film 21 and an aluminum vapor-deposited film 22 are formed on the inner surface of a front glass panel 20, and a shadow mask 23 is attached via a frame 24. Next, the getter device according to the present invention manufactured as shown in (Example 1) is attached to the frame 24 via the support plate 26. Thereafter, the funnel 28 whose inner surface is coated with Aquadag 27 and the glass panel 20 are adhered to each other using fritted glass 29 in a predetermined manner, and both are fixed by heating at approximately 450° C. for 1 hour, and the fluorescent film 21 and this fluorescent The organic material of the optical film 21 and the aluminum deposited film 22 is evaporated. Thereafter, the electron gun is attached to the neck portion 30, and the tube is sealed off through a well-known exhaust process. Next, a getter flash is performed by induction heating using high frequency waves, and the color picture tube is completed through aging of the electron gun, etc. It was confirmed that there were no abnormalities in the electron emission characteristics of the color picture tube thus obtained. Therefore, by using the getter device of the present invention, it is no longer necessary to insert the getter device through the neck portion 30 of the funnel 28, and the diameter of the neck portion 30 can be reduced. This is beneficial when using a smaller, power-saving cathode. Furthermore, since the getter device can be electrically separated from the electron gun, it is possible to prevent undesired surge current from flowing between the getter device and the electron gun. After boric acid anhydride is made into an alcohol solution, it is dried in the atmosphere to mainly change into orthoboric acid. Further, orthoboric acid changes into metaboric acid, tetraboric acid, boric anhydride, etc. depending on heating conditions. Therefore, getter devices were prepared in the same manner as in Example 1 using these various boric acid compounds alone or in mixtures thereof, and getter flushing was performed, and similar effects were obtained.

As shown in the above examples, the present invention has high temperature oxidation resistance because the exposed surface of the getter material containing at least barium-aluminum alloy powder and nickel powder is covered with a coating of a boric acid compound containing silicon dioxide. It is a high-quality getter device that has excellent water resistance and does not cause any problems when used.

[Brief explanation of the drawing]

FIG. 1 is an axial cross-sectional view of a getter device according to the present invention, and FIG. 2 is a partially cut away exploded elevational view showing an embodiment of the getter device of the present invention attached to a color picture tube. 11...Getsuta material, 12...Getsuta container, 13
...boric acid compound coating containing silicon dioxide, 2
0... Glass panel, 21... Fluorescent film, 22...
Aluminum vapor deposited film, 23...Shadow mask,
24...Frame, 25...Getter device, 26...
...Support plate, 27...Aqua Dug, 28...Funnel, 29...Flit glass.

Claims (1)

[Scope of Claims] 1. A getter device in which a getter material containing barium-aluminum alloy powder and nickel powder is filled in a ring-shaped metal getter container with a substantially U-shaped cross section, wherein at least the surface of the getter material is coated with silicon oxide. A getter device characterized by having a coating of a boric acid compound containing. 2. The getter device according to claim 1, wherein the boric acid compound consists essentially of a single substance or a mixture selected from the group consisting of boric anhydride, orthoboric acid, metaboric acid, and tetraboric acid. 3. The getter device according to claim 1, wherein the content of silicon oxide is 5% by weight or less.