JP2006210137A - Method of manufacturing getter material, method of manufacturing evaporation type getter device using it, as well as method of manufacturing electronic tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method in which vaporization amount of getter components becomes possible to appropriately control without excess or deficiency in a stable state, and furthermore, the time from heating initiation until the getter components start evaporation is short, and a getter material and an evaporation type getter device with excellent responsiveness can be obtained. <P>SOLUTION: This is the getter material which is constituted of a compact blend composed of Ba-Al alloy powder and Ni powder, and when this getter material is heated in vacuum or in inert gas, the temperature in which the compact blend starts exothermic reaction is in the range of 750°C or more and 900°C or less. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention adsorbs unnecessary gas components inside an electron tube such as a cathode ray tube (CRT), and a method for producing a getter material used for realizing a vacuum state necessary for the electron tube, and an evaporative getter device using the method. The present invention relates to a manufacturing method and a manufacturing method of an electron tube.

When an electron tube such as a cathode ray tube (CRT) is operated with insufficient evacuation, the characteristics are adversely affected. For this reason, a getter device is provided in the electron tube for sufficiently removing unnecessary gas and realizing a high vacuum. Recently, for example, in the field of consumer televisions, large televisions of about 32 inches to 37 inches have become widespread, and CRTs used for such large televisions are also becoming larger. When such a large electron tube is used, the number of components in the tube and the volume of the tube increase, and at the same time the tube volume increases. Therefore, the components in the electron tube including the residual gas in the tube after the evacuation by the exhaust pump in the electron tube manufacturing process and the vacuum vessel are included. It is becoming more and more important to improve the characteristics and stability of getter devices for adsorbing unnecessary gases released from the gas and maintaining a high vacuum inside the electron tube.
Specifically, a getter material composed of a mixture of BaAl alloy powder mainly containing Ba and Al and Ni powder is used, and the getter material is an alloy mainly containing Fe or Ni, such as steel or Ni alloy. An evaporation type getter device filled in a metal container made of stainless steel or the like is equipped for impurity gas adsorption in an electron tube typified by a CRT.

In this getter device, when the temperature is raised by heating a getter material composed of a mixture of Ba-Al alloy powder and Ni powder, an exothermic reaction is started in which the Al component and Ni component combine at a certain temperature. Then, the Ba component in the getter material evaporates (getter flash), and the impurity gas adsorption function is exhibited by this Ba component. As a result, the degree of vacuum in the electron tube is maintained at a predetermined value.
Thus, the evaporative getter device equipped in the electron tube is required to evaporate a certain amount of Ba in order to adsorb the impurity gas in the electron tube and increase the degree of vacuum. That is, when the amount of Ba evaporation is small, a predetermined degree of vacuum required for the electron tube cannot be obtained. Conversely, if the amount of evaporated Ba is excessive, the amount of Ba adhering to the components such as the inner wall of the electron tube becomes excessive, which may cause abnormal discharge or drop off from the tube wall and other parts in the electron tube. Adhering to the surface may cause problems in the normal operation of the electron tube. Therefore, it is important to control the amount of Ba evaporation within a certain range required for the electron tube. As such an evaporative getter device, a device using Ba-Al alloy powder and Ni powder as disclosed in JP-A-10-27541 (Patent Document 1) is known.

Japanese Patent Laid-Open No. 10-27541

However, in the conventional getter material, it has not been understood at all that the exothermic reaction start temperature of the getter material greatly affects the Ba evaporation amount, and the clear range of the exothermic reaction start temperature has not been determined. For this reason, the variation in the exothermic reaction of the getter material becomes large, and there is a problem that the amount of Ba evaporation cannot be controlled sufficiently. Further, the getter material is generally used by filling a metal container having an opening surface for Ba evaporation called gettering, but if the exothermic reaction start temperature of the getter material is too high, the metal container itself is thermally deformed or melted. There is also a problem that the evaporation of Ba cannot be continued in a stable state.
As a method for evaporating Ba from a getter device installed in an electron tube, generally, a getter material installed in the electron tube is applied with a high-frequency magnetic field by a constant high-frequency power in a non-contact state from outside the electron tube. A method of heating the material is employed. According to this heating method, the getter material can be heated in the electron tube sealed in a vacuum state with less influence on parts other than the getter device, and rapid heating is easy and the process time is short in the production of the electron tube. There is an advantage that it can be done.
However, in the heating method by applying a high frequency magnetic field, the metal container filled with the getter material is also heated when the getter material is heated. At this time, in the conventional getter device, since the relationship between the specification of the metal container and the high-frequency heating condition is not considered at all, the following problems have also occurred. That is, when the heating rate of the high frequency power to the metal container is significantly larger than the heating rate for the getter material, the temperature rise of the metal container becomes significantly larger than the temperature rise of the getter material, and before the exothermic reaction of the getter material starts. As a result of the container being deformed or melted, it becomes difficult to evaporate the getter component in a stable state, and the temperature rise of the getter material itself is slowed down, and the heating evaporation process time of the getter material is reduced. If the length is not long, the amount of Ba evaporation until a predetermined degree of vacuum is obtained in the electron tube cannot be obtained (the amount of Ba evaporation with respect to the heating time and the responsiveness until a predetermined degree of vacuum is reduced), which becomes a bottleneck in the electron tube production process. . On the other hand, if the heating and evaporating process time is shortened, there is a problem that the amount of Ba evaporation becomes insufficient and it is difficult to obtain the degree of vacuum necessary for the electron tube.

The method for producing a getter material according to the present invention is a method for producing a getter material composed of a compact mixture composed of Ba-Al alloy powder and Ni powder, and the getter material is heated in vacuum or in an inert gas. In this case, a getter material having a temperature at which the green compact starts an exothermic reaction is in the range of 750 ° C. to 900 ° C. is used.
The average particle size of the Ni powder is preferably 10 μm or less. In the Ni powder, the proportion of Ni powder having a particle size of 20 μm or more is preferably 10% by mass or less.
Moreover, it is preferable that the said compacting body is a compacting body which pressure-molded the mixture of the said Ba-Al alloy powder and Ni powder with the pressure of 400 Mpa or more. Moreover, it is preferable that the electrical resistivity of the said compacting body is 20 m (ohm) -cm or less.
In addition, a method of manufacturing an evaporation type getter device according to the present invention is characterized in that a getter material as described above is filled in a metal container.

Further, the metal container is made of any one of Fe, Ni, Fe alloy and Ni alloy, the thickness of the metal container is tcm, and the frequency of the heating AC magnetic field used for evaporating Ba from the getter material is set. It is preferable that the thickness t and the alternating magnetic field frequency f of the metal container satisfy the relational expression t ≦ 12.7 / (f) ^1/2 when fHz is set.
It is also possible to manufacture an electron tube using the evaporative getter device as described above.

According to the present invention, the amount of evaporation of the getter component can be appropriately controlled in a stable state, and the time from the start of heating to the start of evaporation of the getter component is short (the amount of Ba evaporation relative to the heating time and It is an object of the present invention to provide a method for manufacturing a getter material having excellent responsiveness (until a predetermined degree of vacuum is obtained), a method for manufacturing an evaporation type getter device using the method, and a method for manufacturing an electron tube.
In addition, the metal container filled with the getter material is not deformed or melted, the heat evaporation process time of the getter material can be shortened, and the time for the electron tube to obtain a predetermined degree of vacuum is short. It is also possible to provide an electron tube manufacturing method using the same.

In order to achieve the above object, the present inventors prepare raw material powders having various particle sizes, prepare getter materials at various molding pressures, and fill the getter materials into metal containers having various thicknesses. Assembling the getter device, the conditions such as the exothermic reaction start temperature of the getter material are large and small in the amount of evaporation of the getter component, its controllability and stability, and the responsiveness indicated by the heating time until the getter component starts to evaporate. A comparative study was conducted on the effects on quality and on the presence or absence of deformation and melting of the metal container. As a result, in particular, the raw material powder having a predetermined fine particle diameter is molded at a predetermined molding pressure, and the exothermic reaction start temperature of the green compact mixture is regulated within a predetermined range so that the evaporation amount of the getter component is stabilized. It has been found that it is possible to appropriately control, and that a getter material and an evaporation type getter device having a short response time from the start of heating to the start of evaporation of the getter component and having excellent responsiveness can be obtained for the first time.

Further, the thickness of a metal container composed of an alloy mainly composed of Fe, Ni, etc., which fills the getter material, such as steel, Ni alloy, stainless steel, etc. and for heating used to evaporate Ba from the getter in the electron tube When both are adjusted so that the frequency of the high frequency is in a fixed relationship, the metal container will not be deformed or melted, the heating evaporation process time of the getter material can be shortened, and the electron tube can obtain a predetermined degree of vacuum. It was found that an evaporative getter device with a short time and excellent response was obtained for the first time. The present invention has been completed based on the above findings.
That is, the getter material according to the present invention is a getter material composed of a powder mixture composed of Ba—Al alloy powder and Ni powder, and when this getter material is heated in vacuum or in an inert gas. The temperature at which the powder mixture starts an exothermic reaction is in the range of 750 ° C. to 900 ° C.

The Ba—Al alloy powder constituting the getter material is not limited to BaAl ₄ powder, and basically a Ni—Al alloy is formed by an exothermic reaction between a Ni component and an Al component. Any raw material that evaporates Ba as a getter component can be used. Such an exothermic reaction is likely to occur when Ba—Al alloy and Ni are mixed and heated as a fine powder. Here, Ni powder having a particle size of 10 μm or less can be easily obtained as carbonyl nickel. On the other hand, Ba—Al alloy powder is manufactured by a method of pulverizing a molten alloy lump. At that time, especially BaAl ₄ which is an intermetallic compound becomes brittle, so that the pulverization operation becomes easy. From the viewpoint of pulverization, it is not necessary to be a BaAl ₄ compound having a strictly stoichiometric composition in practical use. The composition in the vicinity of BaAl ₄ , that is, the Al mass ratio is the same from the Al amount in the composition of BaAl ₄ + 10%. A composition between BaAl ₂ that is an intermetallic compound, more specifically, Ba—Al alloy powder in which the Al content in the Ba—Al alloy is 27 to 50% by mass can be suitably used.
In the above getter material, when the getter material composed of a powder mixture of BaAl ₄ alloy powder mainly containing Ba and Al and Ni powder is heated and the temperature rises, the following exothermic reaction formula (1) is followed. Simultaneously with the combination of the Ni component and the Al component, the Ba component evaporates and adsorbs impurities, thereby exhibiting a function as an evaporation type getter.
BaAl ₄ + 4Ni → 4NiAl + Ba (1)

As is apparent from the exothermic reaction formula of the getter material, the mass ratio of the BaAl ₄ alloy powder to the Ni powder in the getter material generally takes a value close to 50%: 50%. Ni other in an exothermic reaction of the getter material: Al ratio of 1: 1 or cause the alloy composition except, or residual becomes different composition ratios alloys and BaAl ₄ without Ba in BaAl is completely evaporated This is a getter device that uses the same amount of getter material depending on conditions such as the state of the getter material, the state of the getter device in which the getter material is put in a metal container, and the temperature and time applied to the getter material. However, the amount of evaporation of Ba is greatly different.
In the getter material according to the present invention, when the getter material composed of the powder mixture is heated in vacuum or in an inert gas, the temperature at which the powder mixture starts an exothermic reaction is 750 ° C. or more and 900 ° C. or less. Specified in range. When the exothermic reaction start temperature is less than 750 ° C., the getter component Ba tends to be excessively evaporated at a low temperature, making it difficult to control the evaporation amount of Ba, and to react easily in the atmosphere. Therefore, deterioration due to oxidation or the like is easily caused even by a low-temperature heating operation required for the assembly process of the electron tube.

On the other hand, when the exothermic reaction start temperature is excessively high so as to exceed 900 ° C., the amount of heating energy that must be added to the getter material becomes large, so even if heating is started, the time until the reaction start temperature is reached. In this case, it is difficult to control the evaporation amount itself and the response time until a predetermined degree of vacuum is obtained in the electron tube is delayed. Become. Therefore, the exothermic reaction start temperature is defined in the range of 750 ° C. or higher and 900 ° C. or lower.
If the particle size of the BaAl ₄ alloy powder and Ni powder mixed when preparing the getter material is set to a very fine region of about 1 μm or less, the exothermic reaction start temperature itself is lowered to less than 700 ° C. and the getter component is evaporated. It is possible to increase the amount. However, as described above, the Ba-Al alloy powder has a property of being easily deteriorated by a reaction such as oxidation in the atmosphere, and the getter device including the Ba-Al alloy powder is attached to the electron tube in the electron tube manufacturing process. In practice, it is extremely difficult to prevent deterioration due to exposure to the atmosphere during the process until evacuation. Furthermore, CRTs (cathode ray tubes such as cathode ray tubes) may be exposed to high temperatures in the glass frit process between the face part and the funnel part before evacuation depending on the attachment part of the getter device.

At this time, since a Ba—Al alloy such as BaAl ₄ is active, a certain degree of deterioration due to oxidation is inevitable. In particular, when the particle diameter of the Ba—Al alloy powder is an extremely fine region of about 1 μm or less, the deterioration phenomenon becomes noticeable rapidly, and the getter performance is greatly reduced. Therefore, it is desirable to adjust the BaAl ₄ alloy powder so that a fine powder having a particle size of less than 1 μm is 10% or less by mass ratio in the BaAl ₄ raw material. On the other hand, since Ni powder is less susceptible to oxidative degradation than BaAl ₄ , it is not necessary to limit the lower limit of particle size.
According to the getter material according to the above configuration, since the temperature at which the compacting mixture starts an exothermic reaction is defined in the range of 750 ° C. or more and 900 ° C. or less, the amount of evaporation of the getter component is stable without excess or deficiency. Thus, it is possible to appropriately control, and it is possible to obtain a getter material and an evaporation type getter device which have a short response time from the start of heating to the start of evaporation of the getter component and have excellent responsiveness. In addition, the metal container filled with the getter material is not deformed or melted, the heat evaporation process time of the getter material can be shortened, and the time required for the electron tube to obtain a predetermined vacuum degree is short, and the responsive evaporation getter device is excellent. Is obtained.

An electron tube such as a cathode ray tube (CRT) using the evaporative getter absorbs unnecessary gas remaining inside the electron tube main body and unnecessary gas generated from each part including the vacuum vessel constituting the electron tube in the electron tube. In order to increase the degree of vacuum, it is necessary to evaporate a certain amount of Ba as a getter component (gas adsorption component). Here, when the amount of Ba evaporation is small, the degree of vacuum required for the electron tube cannot be obtained. On the contrary, if the amount of evaporated Ba becomes excessive, the amount of Ba adhering to the inner wall of the electron tube becomes excessive, which may cause abnormal discharge, or some of the deposits may fall off from the tube wall and other parts in the electron tube. It may cause a malfunction in the normal operation of the electron tube. Therefore, it is important to control the Ba evaporation amount within a certain range required for the electron tube.
On the other hand, in the conventional getter material, since an appropriate range of the exothermic reaction start temperature has not been determined, the variation in the exothermic reaction is large, and it is difficult to sufficiently control the Ba evaporation amount. Furthermore, the getter material is used by filling a metal container having an opening surface for Ba evaporation called gettering. However, if the start temperature of the exothermic reaction of the getter material is too high, the metal container will be thermally deformed or melted. There was also a problem.

The getter material is formed as a powder mixture obtained by compression molding a mixture of Ba—Al alloy powder such as BaAl ₄ and Ni powder, and the exothermic reaction start temperature of the powder mixture is a getter material. It varies depending on the composition ratio between the Ba—Al alloy powder such as BaAl ₄ in the material and the Ni powder, the particle size of each raw material powder, the molding pressure when compression molding the raw material mixture, and the like. This exothermic reaction start temperature is considered to be appropriate to be low so that the heating time of the getter is short and the problem of melting of the metal container is reduced. However, in actual getters, in order to control the amount of Ba evaporation, The relationship with the reaction start temperature was not clarified.
On the other hand, the getter material according to the present invention and the getter device using the getter material are an exothermic reaction in an evaporation type getter using a getter material made of a mixture of Ba—Al alloy powder such as BaAl ₄ and Ni powder. By setting the start temperature in the range of 750 ° C. or more and 900 ° C. or less, it is found that the time from the start of heating by the high frequency magnetic field of the getter to the start of evaporation of the Ba component is short, and the Ba evaporation amount falls within a stable range. And completed based on that knowledge.

The exothermic reaction start temperature of the getter material used in the getter device is shifted to the lower temperature side when the particle size of Ba-Al alloy powder such as BaAl ₄ and Ni powder is made finer, and conversely, when the particle size is increased, the higher temperature side. Move on. This is because the heat generation start temperature shifts to the low temperature side because the contact area between the Ba—Al alloy powder and the Ni powder increases due to the refinement of the raw material powder. When both the particle diameters of Ba—Al alloy powder such as BaAl ₄ and Ni powder are set to 10 μm or less, it is possible to produce a getter material having an exothermic reaction start temperature of 750 ° C. or less than 700 ° C. However, since Ba—Al alloy powders such as BaAl ₄ are inherently chemically active raw materials, with powders of 1 μm or less, oxidation or the like may occur even in an atmosphere environment (in the atmosphere) where electron tube components are exposed in the electron tube production process. There is a drawback that the characteristics easily fluctuate and deteriorate.
Therefore, in the present invention, in order to maintain more stable characteristics within the range of the manufacturing process conditions of the electron tube equipped with the getter device as the particle diameter of the Ba—Al alloy powder, the average particle diameter is 44 μm or less (however, BaAl ₄ or the like In the case of Ba-Al alloy, a fine powder having a particle size of less than 1 μm is preferably within a range not exceeding 10% by mass in the BaAl ₄ raw material powder) or an average particle size in the range of several tens to 150 μm (maximum particle size) It was found that a sufficient amount of Ba evaporation can be stably obtained in the exothermic reaction start temperature range of 750 ° C. or more and 900 ° C. or less by setting the value to a range not exceeding 300 μm.

On the other hand, Ni powder has more stable characteristics in an electron tube manufacturing environment than Ba—Al alloy powder such as BaAl ₄ and is less deteriorated by oxidation. Therefore, there is no problem even if the powder particle size is reduced. However, it has also been found that a particle size of 10 μm or less is desirable in order to increase the contact area with the Ba—Al alloy powder and improve the reactivity. It has also been found that when the mixing ratio (mass ratio) of Ni powder and BaAl ₄ powder is 48:52 to 56:44, the amount of Ba evaporation is maximized. When using the BaAl alloy powder slightly shifted the composition from BaAl _4, it is preferable to set the Al mixing ratio for Ni and approximately the same range as the above BaAl ₄ alloy.
Further, considering the contact area between the BaAl powder and the Ni powder, the Ba—Al alloy powder having an absolute particle size of 1 μm or less is a powder having a mass ratio of less than 10%, and the maximum particle size The diameter is preferably 300 μm or less. On the other hand, the Ni powder preferably has a maximum particle size of 20 μm or less and an average particle size of 10 μm or less.
Furthermore, in the Ni powder of the getter material, the proportion of Ni powder having a particle size of 20 μm or more is preferably 10% by mass or less. If the particle size of the Ni powder is excessively large, the contact area between the Ba—Al alloy powder and the Ni powder becomes small, so the exothermic reaction start temperature becomes high and the amount of Ba evaporation tends to be insufficient. Accordingly, the proportion of Ni powder having a particle size of 20 μm or more in the Ni powder raw material powder is preferably 10% by mass or less.

In the getter material, the powder mixture is preferably a powder compact obtained by pressure-molding a mixture of the Ba—Al alloy powder and Ni powder at a pressure of 400 MPa or more.
When a compact mixture of the same BaAl ₄ alloy powder and Ni powder is produced as a getter material by pressure molding, this getter material has an exothermic reaction start temperature that suddenly rises below a certain molding pressure. Has also been found to have a relatively stable exothermic reaction initiation temperature. In the getter material manufactured by the pressure molding method using BaAl ₄ powder having a practical particle size of 44 μm or less or a range of several tens to 150 μm and Ni powder of 10 μm or less as raw materials, a molding pressure of 400 MPa or more is applied. By doing so, an exothermic reaction start temperature within the desired range can be obtained. However, when the particle size of the Ni powder is set to 10 to 20 μm, the exothermic reaction start temperature of 750 ° C. to 900 ° C. at which the exothermic reaction start temperature rises and a stable Ba evaporation amount is obtained at a molding pressure of less than 1000 MPa. It was not obtained. In other words, in order to obtain an appropriate amount of Ba evaporation, it is important to appropriately adjust the molding pressure according to the particle size of the raw material powder of the getter material as described above.

The evaporative getter device according to the present invention is configured by filling a metal container with the getter material as the compression molded body.
It is important that the getter material is filled in a pressed state in a metal container so that no gap is formed between the metal container and the filled getter material. When play is formed between the getter material and the metal container, there is a high risk that all or part of the getter material, which is a compression-molded body of the metal powder, is dropped from the metal container. Even if a small amount of getter material falls off, it may cause abnormal discharge or cause clogging in the hole of the shadow mask of the CRT, leading to deterioration of the performance of the electron tube.
The operation of evaporating Ba from the getter device installed in the electron tube is generally a method of heating the getter device installed in the electron tube by applying a high-frequency magnetic field by a constant high-frequency power in a non-contact manner from outside the electron tube. Is adopted. According to this method, in the electron tube sealed in a vacuum state, only the getter device can be heated by reducing and reducing the thermal influence on the parts other than the getter device, rapid heating is easy, and the process time in the production of the electron tube Has the advantage of being short.
However, when the getter material is heated by a heating method by applying a high frequency magnetic field, not only the getter material but also the metal container filled with the getter material is heated at the same time. In this regard, in the conventional getter device, since the attention is not paid to the mutual relationship between the metal container and the heating high-frequency condition, the following problems have occurred. That is, when the heating rate of the metal container by the high frequency power is significantly higher than the heating rate of the getter material, the temperature rise of the metal container becomes significantly larger than the temperature rise of the getter material, and the exothermic reaction of the getter material starts. There is a problem that the Ba evaporation is hindered by deformation or melting of the metal container before being performed. Further, the temperature rise of the getter material is slow, and there has been a problem that the heat evaporation process time of the getter material becomes long.

With respect to these problems, in the present invention, the thickness of a metal container made of an alloy mainly composed of Fe, Ni, or the like filled with a getter material, for example, steel, Ni alloy, stainless steel, etc. By adjusting the two so that there is a fixed relationship, the metal container will not be deformed or melted, the heat evaporation process time of the getter material can be shortened, and the time until the electron tube obtains a predetermined vacuum degree is shortened An evaporative getter device with excellent responsiveness is obtained.
That is, the evaporative getter device according to the present invention is filled with a getter material composed of a powder mixture of BaAl alloy powder and Ni powder in a metal container composed of any of Fe, Ni, Fe alloy and Ni alloy. In the evaporative getter apparatus, when the plate thickness of the metal container is tcm and the frequency of the heating AC magnetic field used for heating the getter material and evaporating the Ba component from the getter material is fHz, the metal container The thickness t and the AC magnetic field frequency f satisfy the relational expression t ≦ 12.7 / (f) ^1/2 .
When a getter device composed of a getter material and a metal container filled with the getter device is heated by applying a high-frequency magnetic field generated by applying high-frequency power to a magnetic field generating coil, the thermal energy input by the high-frequency power Will be added to the getter material and the metal container, respectively.
Fe, Fe-base alloy, Ni, Ni-base alloy, Fe or Ni and Fe and Ni, Fe, Ni, Cr have melting points sufficiently higher than the exothermic reaction temperature of the getter material and excellent structural strength and heat resistance. , And an alloy material composed of at least one element selected from Mn. As the alloy material, for example, stainless steel (stainless steel) can be suitably employed. In particular, as stainless steel, an alloy material in which the amount of components such as Cr, Ni, and Mn contained in the alloy in addition to Fe is several mass% to several tens mass% is used. Also, an alloy material to which about 1 to 5% by mass of Cr, Mn, Ni (only addition to Fe), Fe (only addition to Ni), etc. is added for the purpose of increasing the structural strength and heat resistance of Fe and Ni, For example, chrome steel can be used.

When high frequency power is applied to a metal container formed of these metal materials using a high frequency magnetic field generating coil, the frequency (fHz) of the high frequency power and the thickness (tcm) of the metal container are expressed by the following relational expression (2). Is set within a range that satisfies the above, the high-frequency power is applied to the getter material filled in the metal container, a sufficient temperature rise rate is obtained, and Ba evaporation is efficiently performed without causing deformation or melting of the metal container. It has been found that the amount can be secured.
t ≦ 12.7 / (f) ^1/2 (2)
In the above high frequency magnetic field generator, when the plate thickness (tcm) at a certain frequency (fHz) is larger than the value calculated by the above relational expression, the high frequency power is concentrated in the metal container and is added to the getter material. Therefore, it is difficult to obtain a desired Ba evaporation amount by high-frequency heating in a short time. If the heating power is further increased at this point, or if the heating is continued for a longer time, the metal container is heated until it exceeds the secondary recrystallization temperature of its constituent material, causing deformation, Furthermore, since the temperature rises and the metal container is melted, the characteristics of the electron tube are adversely affected anyway.

Here, as schematically shown in FIG. 1, the metal container (gettering) 2 is formed into a bottomed cylindrical shape having a protrusion formed in the center by drawing a metal flat plate, and has an outer side wall having a thickness t1. 2a, a bottom wall 2b having a thickness of t2, an inner side surface 2c having a thickness of t3, and a central top wall 2d having a thickness of t4. However, in the order of the magnitude affected by heat by high frequency heating, the first position is the outer side wall 2a and the second position is the bottom wall 2b. Therefore, it is necessary to reduce the thickness so that at least the thickness t1 of the outer side wall 2a and the thickness t2 of the bottom wall 2b are equal to or less than the plate thickness (tcm) calculated by the relational expression (2). In addition, in order to make the heat capacity of each part of the metal container (gettering) 2 uniform and to make the heat effect by the high frequency heating uniform in the whole container, all the thicknesses t1, t2, t3, t4 of each part in the metal container 2 are all included. Is more preferably reduced to be equal to or less than the plate thickness (tcm) calculated by the relational expression (2).
The electrical resistance of the getter material obtained by press-molding a mixture of Ba—Al alloy powder such as BaAl ₄ and Ni powder is higher than the specific electrical resistivity of Ba—Al alloy such as BaAl ₄ and Ni. On the other hand, the electrical resistance of the metal container is equal to the intrinsic electrical resistivity of the metal material constituting the container.

In the getter material or the evaporative getter device according to the present invention, it is preferable that the electric resistivity of the green compact is 20 mΩ-cm or less. That is, when the electrical resistivity of the getter material obtained by press-molding a mixture of Ba—Al alloy powder such as BaAl ₄ and Ni powder is excessive so as to exceed 20 mΩ-cm, a commonly used Ba evaporation section is used. Since the efficiency of high-frequency heating is extremely deteriorated in a getter device having a diameter of 10 mm to several tens of millimeters (the short diameter of an ellipse such as an ellipse whose outer shape is not circular), the electrical resistivity of the getter material used in the getter device is 20 mΩ. -Cm or less is desirable. The electrical resistivity of the getter material can be adjusted by appropriately combining raw material powders having different electrical resistances and particle sizes and controlling the molding pressure. When the particle size of the raw material powder is excessively refined, the electrical resistivity of the getter material increases and high-frequency heating becomes difficult. Therefore, it is important to use Ba—Al alloy powder and Ni powder having the above-mentioned particle size range or average particle size.
The electron tube manufacturing method according to the present invention is characterized in that the evaporative getter device configured as described above is mounted. According to the electron tube of the present invention, even in the case of a large electron tube, sufficient getter material can be scattered in a stable state, which greatly contributes to improving the quality and reliability of the large electron tube.

Next, an embodiment of a method for manufacturing a getter material according to the present invention will be specifically described with reference to the following examples and comparative examples.
(Examples 1-4 and Comparative Example 1)
BaAl ₄ composition having an average particle diameter of 5 μm and a ratio of having a particle diameter of 20 μm or more is 54% by mass of Ni powder, and the remaining is a particle diameter of 44 μm or less and the average particle diameter is 31 μm. A mixture consisting of the above alloy powders was prepared as a raw material for the getter material for each example and comparative example. The average particle size and the maximum particle size of each powder constituting the getter material were determined by particle size distribution measurement using a sieving method and particle size distribution measurement using a laser scattering diffraction method.
Next, the getter materials 3 according to Examples 1 to 4 and Comparative Example 1 made of each of the powder compacts were prepared by changing the molding pressure and molding the raw materials of the prepared getter materials as shown in Table 1, respectively. Prepared. The exothermic reaction start temperature of the getter material 3 according to each of these examples and comparative examples was measured by a method of increasing the temperature from room temperature at a rate of 10 ° C./min using a differential thermogravimetric analyzer (DTA). The exothermic reaction start temperature of each getter material could be easily measured as the heating temperature corresponding to the peak of the calorific value formed by the rapid increase in the calorific value of the getter material during the overheating operation. A getter material having an exothermic reaction start temperature outside the range specified in the present invention was used as Comparative Example 1.

Next, as shown in FIG. 1, 1.1 g of getter material 3 is filled into a metal container 2 made of SUS304 having thicknesses t1 and t2 of the outer peripheral side wall 2a and the bottom wall 2b of 0.02 cm, and an exothermic reaction start temperature is set. The getter material 3 was molded and pressure-bonded to the metal container 2 with the same pressing force as the molding pressure used at the time of measurement to prepare getter devices 1 according to Examples 1 to 4 and Comparative Example 1. FIG. 1 is a cross-sectional view schematically showing a cross-sectional structure of a getter device 1 according to each example and comparative example. Each getter device 1 includes a metal container 2 made of SUS304 formed by drawing and the metal container 2. And a getter material 3 filled in the concave portion by pressure bonding.
The time from the start of heating to the start of Ba evaporation and the Ba evaporation after heating for 30 seconds when the getter device 1 according to each of the examples and comparative examples prepared as described above is heated with a high-frequency magnetic field having a frequency of 300 kHz and a constant intensity. The amount was measured. The Ba evaporation amount was obtained from the difference in weight of the getter material before and after evaporation. Table 1 summarizes the measurement results of the Ba evaporation amount together with the molding pressure.

As is clear from the results shown in Table 1 above, in the getter devices according to Examples 1 to 4 in which the exothermic reaction start temperature of the getter material composed of each compact mixture is defined within a predetermined range of 782 ° C. to 883 ° C. The amount of evaporation of Ba after heating for 30 seconds was large, and the value was stable, and it was confirmed that excellent evaporation characteristics of the getter component were exhibited. Also, the time from the start of heating to the start of Ba evaporation was as short as 9 seconds, and excellent responsiveness was demonstrated.
On the other hand, in the getter device according to the comparative example 1 filled with the getter material prepared so that the exothermic reaction start temperature of the getter material exceeds 900 ° C., the Ba evaporation amount is compared with the other examples. It was found that the time from the start of heating to the start of Ba evaporation was relatively long, exceeding 11 seconds, and the responsiveness was poor.

On the other hand, in addition to the above comparative example, the BaAl ₄ alloy powder is further finely pulverized so that the average particle size is 10 μm or less, whereby the exothermic reaction start temperature is lowered from 750 ° C., and is defined as 700 to 740 ° C. Was also prepared. Similarly, when the getter device filled with these getter materials was measured for the amount of Ba evaporation after heating for 30 seconds, the amount of Ba evaporation was sufficient and stable in all cases. However, in the getter device using this getter material, the getter material is rapidly deteriorated in the atmosphere. Therefore, the deterioration due to oxidation proceeds rapidly in the process of mounting and fixing the getter device in the electron tube. The amount of Ba evaporation could not be obtained. Therefore, it can be said that the practical exothermic reaction start temperature of the getter material is more preferably 750 ° C. or higher.

(Example 5)
Example 5 shows an example in which three types of raw material mixtures having different particle size distributions are pressure-molded at a molding pressure of 800 to 1500 MPa to prepare the getter materials of Samples 1 to 3.
That is, the raw material mixture for sample 1 is 53% by mass of Ni powder having an average particle size of 6.5 μm and a particle size ratio of 20 μm or more of 5% by mass, the balance being the maximum particle size of 150 μm and the average particle size of 77 μm. A mixture consisting of an alloy powder of the BaAl ₄ composition was prepared as a raw material for the getter material.
Further, as the raw material mixture for Sample 2, 53% by mass of Ni powder having an average particle size of 13 μm and a particle size ratio of 20 μm or more of 8% by mass, and the balance having a maximum particle size of 150 μm and an average particle size of 77 μm A mixture composed of an alloy powder having a certain BaAl ₄ composition was prepared as a raw material for the getter material.
Further, as a raw material mixture for Sample 3, BaAl ₄ having an average particle size of 8 μm, a particle size ratio of 20 μm or more of 13% by mass of Ni powder, 53% by mass of Ni powder, and the balance having a maximum particle size of 150 μm and an average particle size of 77 μm. A mixture consisting of alloy powders of composition was prepared as a raw material for the getter material.

The getter material for each sample thus prepared was molded at a molding pressure of 800 MPa to 1500 MPa as shown in FIG. 2 to prepare a getter material for each sample, and each getter material was the same as in Example 1. The exothermic reaction start temperature was measured, and the measurement result is shown in FIG.
As is clear from the results shown in FIG. 2, the getter material according to Sample 1 has a reaction start temperature in the range of 860 to 880 ° C. in the molding pressure range of 800 MPa to 1500 MPa, and a suitable amount of evaporation of the getter component is expected. it can. On the other hand, in the getter material according to Samples 1 and 2, when the molding pressure is processed in a low pressure range of 800 to 900 MPa, the exothermic reaction start temperature suddenly increases, and sufficient getter component evaporation cannot be expected. There was found. Even in this case, if the molding pressure is 1000 to 1200 MPa, a predetermined exothermic reaction start temperature is obtained. Therefore, a suitable reaction start temperature can be obtained by adjusting the particle size of the raw material powder of the getter material and the molding pressure.

(Example 6)
Example 6 shows an example in which a finer mixture of Ni powder and Ba—Al alloy powder than that in Example 5 is used as a raw material for the getter material. That is, 53% by mass of Ni powder having an average particle size of 4.5 μm and a particle size ratio of 20 μm or more being 2% by mass, and 35% by mass of BaAl ₄ composition alloy powder having an average particle size of 44 μm as the balance. A mixture composed of an alloy powder having a BaAl ₂ composition with a balance of 70 to 44 μm in particle size was prepared as a raw material for the getter material. Next, as shown in FIG. 3, getter materials obtained by press molding are prepared by changing the molding pressure in the range of 300 to 800 MPa, and the exothermic reaction start temperatures of the respective getter materials are the same as in Example 1. And measured. The measurement results are shown in FIG.
As is clear from the results shown in FIG. 3, the getter material according to Example 6 has a reaction start temperature in the range of 800 to 900 ° C. within a molding pressure range of 400 MPa to 800 MPa, and a suitable getter component evaporation amount. It is clear that it is obtained. On the other hand, it has been found that when the molding pressure is less than 400 MPa, the exothermic reaction start temperature rapidly increases, and sufficient getter component evaporation cannot be expected.

(Examples 7-9 and Comparative Examples 2-4)
While preparing three types of getter raw material mixtures with different particle size distributions, prepare two types of metal containers with different plate thicknesses, filling each metal container with each getter raw material mixture, and press-bonding them at a predetermined pressure. A getter device according to an example and a comparative example was created, and the characteristics were compared.
That is, 54% by mass of Ni powder having an average particle size of 4.5 μm and a particle size ratio of 20 μm or more of 2% by mass, and 35% by mass of alloy powder of BaAl ₄ composition having an average particle size of 44 μm or less. A mixture consisting of an alloy powder having a BaAl ₄ composition with the remaining particle size of 53 to 44 μm was prepared as the first raw material of the getter material (Example 7 and Comparative Example 2).
Further, Ni powder having an average particle size of 4 μm and a particle size ratio of 20 μm or more of 3% by mass is 50% by mass, BaAl ₄ composition alloy powder having an average particle size of 44 μm or less is 10% by mass, and the balance is the particle size A mixture of 44 to 53 μm BaAl ₄ composition alloy powder was prepared as a second raw material of the getter material (Example 8 and Comparative Example 3).
Furthermore, 54% by mass of Ni powder having a particle size of 3 to 10 μm, 10% by mass of alloy powder of BaAl ₄ composition having an average particle size of 44 μm or less, and the rest of the alloy powder having a BaAl ₄ composition having a particle size of 53 to 44 μm. As a third raw material of the getter material, Example 9 and Comparative Example 4 were prepared.

On the other hand, two types of SUS316 metal containers 2 having the shape shown in FIG. 1 and having a thickness t of 0.02 cm or 0.025 cm at all portions including the outer side wall 2a and the low wall 2b were prepared.
Then, 1.1 g of the above first to third raw materials are filled in a thin SUS316 metal container 2 having a thickness t of 0.02 cm, and pressure molding is performed at a molding pressure of 1000 MPa, respectively, according to Examples 7 to 9. A getter device was manufactured.
On the other hand, 1.1 g of the above first to third raw materials are filled into a thick SUS316 metal container 2 having a thickness t of 0.025 cm, and pressure molding is performed at a molding pressure of 1000 MPa, respectively, according to Comparative Examples 2 to 4. A getter device was manufactured.

From the heating start time to the Ba evaporation start time when the heating high frequency magnetic field having the same intensity and the frequency of 330 kHz is applied to the getter device according to each of the examples and comparative examples manufactured as described above. The required time and the amount of Ba evaporation after heating for 30 seconds were measured, and the results shown in FIG. 4 were obtained. Here, when the plate thickness t of the corresponding metal container is calculated by substituting the frequency 330 kHz of the heating high frequency into the relational expression of t ≦ 12.7 / (f) ^1/2 that is the equation (2), t ≦ 0. 0221 (cm). That is, the specifications of the getter devices according to Examples 7 to 8 having the thin metal container 2 with the plate thickness t of 0.02 cm satisfy the relational expression (2), while the plate thickness t is 0.025 cm. The specifications of the getter devices according to Comparative Examples 2 to 4 having the thick metal container 2 do not satisfy the relational expression (2).
As is clear from the results shown in FIG. 4, in the getter devices according to Examples 7 to 8 using the thin metal container 2, a sufficient temperature rise rate is obtained by effectively adding high-frequency power to the getter material in the metal container. Therefore, the amount of evaporation of Ba after heating for 30 seconds is sufficient, and the required time from the heating start time to the Ba evaporation start time is less than 10 seconds, and excellent responsiveness is realized.
On the other hand, in the getter devices according to Comparative Examples 2 to 4 using the thick metal container 2, the metal container is deprived of heat and the temperature rise of the getter material is delayed, so that the amount of evaporation of Ba after heating for 30 seconds is insufficient. In addition, the required time from the heating start time to the Ba evaporation start time was over 11 seconds, and it was reconfirmed that the responsiveness was inferior.

(Examples 10-11 and Comparative Examples 5-6)
In this example, Example 7-9 was examined by changing the frequency at the time of high-frequency heating.
54% by mass of Ni powder having an average particle size of 4.5 μm and a particle size portion of less than 2% of 20 μm or more, 35% by mass of BaAl ₄ composition alloy powder having an average particle size of 44 μm or less, and the balance being 44 to 53 μm BaAl ₄ A getter material is obtained by the following method from 1.1 g of a mixture of alloy powders having a composition as a raw material for the getter material. That is, a low carbon steel plate container having a thickness of 0.015 cm was filled and formed into a getter by forming at a forming pressure of 800 MPa into a low carbon steel plate container having a thickness of 0.022 cm. A comparative example 6 was obtained by molding at 800 MPa to obtain a getter. When Example 10 and Comparative Example 5 were heated at a high frequency of 500 kHz and the high frequency power was set so that the time from the start of heating to Ba evaporation was 9.5 seconds for the getter of Example 10, 228 mg of Ba evaporation was obtained. On the other hand, when the getter of Comparative Example 6 was heated with the same high-frequency heating power, 11.6 seconds were required until Ba evaporation after the start of heating, and the amount of Ba evaporation after 30 seconds of heating was 182 mg. When the frequency at this time is applied to the equation of t ≦ 12.7 / (f) ^1/2 , t ≦ 0.018 (cm).

Next, 1.1 g of the same getter material as in Example 10 was used, and the getter was obtained as Example 11 and Comparative Example 6 by the following method. That is, a ferritic stainless steel sheet steel plate container having a thickness of 0.02 cm was filled, and a getter formed by forming at a molding pressure of 1000 MPa was filled into a ferritic stainless steel sheet steel container having a thickness of 0.03 cm. Then, a getter formed by molding at a molding pressure of 1000 MPa was used as Comparative Example 7. When Example 11 and Comparative Example 7 were heated at a high frequency of 250 kHz and the high frequency power was set so that the time from the start of heating to Ba evaporation was 9.6 seconds for the getter of Example 11, the heating was performed for 30 seconds. An amount of Ba evaporation of 230 mg was obtained. On the other hand, in Comparative Example 7 with the same high-frequency heating power, it took 11.7 seconds from the start of heating to Ba evaporation, and the amount of Ba evaporation by heating for 30 seconds was 177 mg. When calculated by the equation of t ≦ 12.7 / (f) ^1/2 at 250 kHz, t ≦ 0.0254 (cm).
Each high-frequency heating was performed after the getter was attached to the electron gun and mounted in the electron tube.

Sectional drawing which shows typically one Embodiment of the getter apparatus formed by filling the getter material which concerns on this invention in the metal container. Graph showing an example of the relationship between the molding pressure of the getter raw material powder and the starting temperature of the exothermic reaction Graph showing an example of the relationship between the molding pressure of getter raw material powder and the start temperature of its exothermic reaction when other raw material powders with different specifications are used The graph which shows an example of the relationship between the time from the start of heating of the getter material until the Ba component starts to evaporate and the evaporation amount of the Ba component when heated for 30 seconds

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Evaporative getter apparatus 2 ... Metal container 2a ... Outer side wall 2b of metal container ... Bottom wall 2c of metal container ... Inner side wall 2d of metal container ... Center top wall 3 of metal container ... Getter material

Claims (9)

In a method for producing a getter material comprising a powder mixture comprising Ba-Al alloy powder and Ni powder, the powder mixture generates heat when the getter material is heated in vacuum or in an inert gas. A method for producing a getter material, wherein a getter material having a temperature at which a reaction is started is in a range of 750 ° C to 900 ° C. The method for producing a getter material according to claim 1, wherein the Ni powder has an average particle size of 10 μm or less. The method for producing a getter material according to any one of claims 1 and 2, wherein a ratio of Ni powder having a particle size of 20 µm or more in the Ni powder is 10 mass% or less. 4. The powder compact according to claim 1, wherein the powder compact is a compact formed by pressing the mixture of the Ba—Al alloy powder and Ni powder at a pressure of 400 MPa or more. 5. 2. A method for producing a getter material according to item 1. 5. The method for producing a getter material according to claim 4, wherein an electrical resistivity of the green compact is 20 mΩ-cm or less. A method for manufacturing an evaporation type getter device, wherein the getter material according to any one of claims 1 to 5 is filled in a metal container. 7. The method of manufacturing an evaporation type getter device according to claim 6, wherein the metal container is composed of any one of Fe, Ni, an Fe alloy, and a Ni alloy, the plate thickness of the metal container is tcm, and Ba is obtained from the getter material. When the frequency of the heating AC magnetic field used for evaporation is fHz, the plate thickness t of the metal container and the AC magnetic field frequency f satisfy the relational expression t ≦ 12.7 / (f) ^1/2. A method for manufacturing an evaporative getter device. In a method for manufacturing an evaporation type getter device in which a metal container composed of any one of Fe, Ni, Fe alloy and Ni alloy is filled with a getter material made of a compacted mixture of Ba-Al alloy powder and Ni powder. When the plate thickness of the metal container is tcm and the frequency of the heating AC magnetic field used for heating the getter material to evaporate the Ba component from the getter material is fHz, the plate thickness t of the metal container and the AC magnetic field A method of manufacturing an evaporation type getter device, wherein the frequency f satisfies the relational expression t ≦ 12.7 / (f) ^1/2 . 9. A method of manufacturing an electron tube comprising the evaporative getter device according to claim 6, wherein the evaporative getter device is attached.

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