CN1061462C - Oxide cathode for electron tube - Google Patents

Oxide cathode for electron tube Download PDF

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Publication number
CN1061462C
CN1061462C CN93121498A CN93121498A CN1061462C CN 1061462 C CN1061462 C CN 1061462C CN 93121498 A CN93121498 A CN 93121498A CN 93121498 A CN93121498 A CN 93121498A CN 1061462 C CN1061462 C CN 1061462C
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China
Prior art keywords
oxide
emission material
coated cathode
oxide coated
material layer
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Expired - Fee Related
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CN93121498A
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Chinese (zh)
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CN1099185A (en
Inventor
崔钟书
孙景千
崔龟锡
朱圭楠
李相沅
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Samsung Electronics Co Ltd
Samsung SDI Co Ltd
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Samsung Electron Devices Co Ltd
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Priority claimed from KR1019930021670A external-priority patent/KR950006911A/en
Priority claimed from KR1019930022490A external-priority patent/KR100271484B1/en
Application filed by Samsung Electron Devices Co Ltd filed Critical Samsung Electron Devices Co Ltd
Publication of CN1099185A publication Critical patent/CN1099185A/en
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Publication of CN1061462C publication Critical patent/CN1061462C/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/02—Main electrodes
    • H01J1/13—Solid thermionic cathodes
    • H01J1/14—Solid thermionic cathodes characterised by the material
    • H01J1/144—Solid thermionic cathodes characterised by the material with other metal oxides as an emissive material

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  • Solid Thermionic Cathode (AREA)
  • Discharge Lamp (AREA)

Abstract

In an oxide cathode comprising a metal base, an electron emissive material layer containing at least Ba formed on the metal base, and a means for heating the electron emissive material layer, the electron emissive material layer further comprises at least one of a lanthanum oxide and a terbium oxide, and forms a needle-shaped crystal structure, or the electron emissive material layer further comprises at least one of a lanthanum oxide and a terbium oxide, and the metal base is subject to a heat treatment under vacuum. The oxide cathode has an effect on lengthening the lifetime, and has a manufacturing procedure interchangeable with a conventional one.

Description

The oxide coated cathode of electron tube
The present invention relates to the oxide coated cathode of electron tube (as cathode ray tube or camera tube), more particularly, relate to novel oxide coated cathode with long-life electron tube.
Concerning the electron tube hot cathode of routine, a kind of " oxide coated cathode " arranged, it comprises that being formed on Ni is the alkaline earth carbide layer that forms on the metallic substrates of key component.This alkaline earth metal carbonate is converted into oxide in vacuum, thereby is called as oxide coated cathode.Oxide coated cathode works in lower temperature (700-800 ℃), because its work function is lower.Yet the life-span of oxide coated cathode is shorter.
Fig. 1 is a schematic diagram, has shown the structure of conventional oxide coated cathode.Conventional oxide coated cathode comprise plate-like metallic substrates 2, support metal substrate 2 cylindrical sleeve 3, be used for the heater 4 of heated cathode and be formed on the metallic substrates 2 and making the electron emission material layer 1 that main component is made with alkaline earth oxide.This conventional oxide coated cathode is to make by inserting sleeve 3 and form the electron emission material layer 1 that is mixed and made into by at least two kinds of alkaline earth oxides on the surface of metallic substrates 2 with an end of metallic substrates 2 sealing cylindrical sleeve 3, heater 4.
Metallic substrates 2 is positioned on the sleeve 3, and supports electron emission material layer 1.It is by making such as the refractory metal of nickel (Ni) or platinum (Pt), and comprises reduction elements so that the reduction of alkaline earth oxide.What be used as reduction elements usually is the reducing metal, as tungsten (W), magnesium (Mg), silicon (Si) or zirconium (Zr).The reducing metal use that mutually combines usually.
Support metal substrate 2 and wherein the sleeve 3 of having heaters 4 usually by making such as molybdenum (Mo), tantalum (Ta), tungsten (W) or stainless refractory metal.
The heater 4 that is arranged in sleeve 3 is by metallic substrates 2 heating electron emission material layers 1.It is to be made by the tungsten filament that is covered with aluminium oxide etc.
Launch thermionic electron emission material layer 1 and be formed in alkaline-earth metal oxide layer on the metallic substrates 2.On metallic substrates 2, scribble the suspended matter of the carbon carbon salt of alkaline-earth metal (Ba, Sr, Ca etc.).After coating was in a vacuum by heater 4 heating, alkaline earth metal carbonate was converted into oxide.For example, brium carbonate resolves into barium monoxide:
Subsequently, alkaline earth oxide under 900 to 1000 ℃ high temperature by partial reduction, thereby make it to be activated, to have semi-conductive character.In this activation process, be included in electron emission material layer 1 in the metallic substrates 2, that form to alkaline earth oxide such as the reduction elements of Si or Mg and the interfacial diffusion between the metallic substrates 2, and react with alkaline earth oxide immediately.For example, barium monoxide is reduced element reduction, produces free barium:
The free barium that produces from BaO becomes the oxygen vacancies N-type semiconductor N.Therefore, under 700 to 800 ℃ working temperature, under normal condition, obtained 0.5 to 0.8A/cm 2Emission current.
General oxide coated cathode works in the high temperature more than 750 ℃, so Ba, Sr or Ca are owing to high-vapor-pressure evaporates freely, and electron emission layer reduces when working.In addition, because the reduction of alkaline earth oxide, the boundary zone between electron emission material layer and metallic substrates has formed such as MgO and Ba 2SiO 4The oxide intermediate layer and as the barrier layer.So the barrier layer that forms has stoped reduction elements Mg or Si to diffuse into electron emission layer, thereby can not produce the free barium of q.s, and Ba, Sr or the Ca of evaporation are difficult to be replenished.In addition, electron emission current also is subjected to the high-resistance restriction in intermediate layer.Thereby shortening and other ill effects of cathode life caused in the intermediate layer.On the other hand, too much reduction elements is supplied with and is caused the over reduction of BaO, so can't obtain stable emission current.
As mentioned above, the shortcoming of traditional oxide coated cathode is that its working temperature in use uprises, and make emission effciency reduce to the about 75% of its initial characteristic, and its life-span has been shortened in the consumption of electronic emission material.
Recently picture tube develops to large-screen and high definition direction, so require picture tube that higher brightness and purity are arranged.Therefore, the negative electrode of electron gun electronics emission and life-span of needing high current density will be grown.Yet the conventional general life-span of oxide coated cathode is shorter, so can't satisfy these requirements.
Known a kind of impregnated cathode has high current density and long-life, be make of complicated method and working temperature be 1100 ℃ or higher, this is than the high 300-400 of oxide coated cathode ℃.Therefore, people have carried out the effort that continues, are easy to make and life-span of oxide coated cathode that working temperature is low with prolongation.
In Japan Patent open (Japanese Patent Laid-Open PiiblicationNo.Sho 59-20941), lanthanum is by with LaNi 5And La 2O 3Form be dispersed in the metallic substrates, thereby the intensity that makes metallic substrates can be not weakened and reducing agent wherein is not depleted.British patent (Britain Patent No.1592502) has been announced a kind of electronic emission material that is used for discharge lamp, wherein BeO and Y 2O 3Be added into Ba 2-xSr xCaWO 6(wherein x from 0.0 to 0.5).
At United States Patent (USP) the 4th, in 797, No. 593, at least a rare-earth oxide of from the group of forming by the oxide of Y, La, Ce, Pr, Nd, Sm, Gd, Sc, Dy, Ho, Er and Tm, selecting, be added in the electronic emission material that contains Ba at least, to improve electron emission characteristic.
But above-mentioned negative electrode does not significantly improve the short life of oxide coated cathode.In addition, the manufacture craft of above-mentioned negative electrode is not can be with the exchange of general oxide coated cathode.Particularly need to change the activating process of negative electrode.For example, in above-mentioned United States Patent (USP) (No.4,797,593), with before alkaline earth oxide mixes, rare-earth oxide will be subjected to high-temperature heating treatment under reducing environment.
Consider the problems referred to above of conventional oxide coated cathode, an object of the present invention is to provide a kind of oxide coated cathode, wherein, in the longer time, keep stable electron emission characteristic by suppressing the excessive evaporation of Ba, thereby prolonged the life-span greatly, and manufacture craft can with the exchange of routine.
For realizing this purpose, according to one embodiment of present invention, provide a kind of oxide coated cathode, comprising:
Metallic substrates;
At least comprise the electron emission material layer that is formed on the Ba on the metallic substrates; And
Be used to heat the device of electron emission material layer,
It is characterized in that,
Electron emission material layer further comprises at least a in lanthanum-oxides and the terbium oxide, and its content is the total weight according to electronic emission material, is preferably in percentage by weight and is in 0.0001% to 5% the scope.
According to oxide coated cathode of the present invention, its electron emission material layer is a needle-shaped crystal structure.
In addition, in oxide coated cathode according to another embodiment of the present invention, metallic substrates is the Ni metallic substrates that contains Si and Mg, and it is preferably 10 -6Torr (1.333 * 10 -4Pa) high-temperature process that is subjected to more than 900 ℃ in the Yi Shang vacuum forms.
By below in conjunction with accompanying drawing to the detailed description that most preferred embodiment of the present invention carried out, can have a better understanding to its above-mentioned purpose and other advantages.In the accompanying drawings:
Fig. 1 is a schematic sectional view, shows conventional oxide coated cathode;
Fig. 2 is an enlarged diagram, shows the electron emission material layer of oxide coated cathode according to an embodiment of the invention;
Fig. 3 is a curve chart, and the MIK that shows oxide coated cathode (a) and conventional oxide coated cathode (b) according to an embodiment of the invention is situation over time;
Fig. 4 is a curve chart, shows oxide coated cathode 9a according to another embodiment of the present invention) and the MIK of conventional oxide coated cathode (b) situation over time.
In oxide coated cathode according to the present invention, electron emission material layer on the metallic substrates further comprises lanthanum-oxides and/or terbium oxide, and electron emission material layer forms needle-shaped crystal structure, or metallic substrates is subjected to high-temperature process under vacuum, thereby makes the stable and launch stability of electron emission characteristic can keeping the longer time than routine.
Be added to lanthanum-oxides and/or terbium oxide in the electronic emission material that comprises Ba at least, in electron emission material layer, forming stable BaO after the burin-in process, thereby making negative electrode that stable electron emission characteristic be arranged.
Except the stable electron emission characteristic that stable BaO causes, also considered the suitable supply of reducing metal, to prolong the life-span of oxide coated cathode.This suitable supply of reducing metal can realize by following two kinds of methods.First kind is the needle-shaped crystal structure that forms electron emission material layer, and second kind is the heat treatment of metallic substrates.If electron emission material layer forms acicular crystal, the reducing metal is VELOCITY DIFFUSION suitably, thereby current density is remained on the bigger value in long-time, perhaps, under vacuum, be subjected to heat treatment if contain the metallic substrates of reducing metal, can prevent the excessive supply of reducing metal, thereby keep the stable state of the stable BaO of lanthanum-oxides and/or terbium oxide generation for a long time.In this way, can launch by electronics steady in a long-term, and prolonged the life-span of oxide coated cathode.
In the present invention, available such as (Ba, Sr, Ca) CO 3Three heavy carbonate or such as (Ba, Sr) CO 3Two heavy carbonate make electron emission material layer.For lanthanum-oxides or terbium oxide are added in the electronic emission material, can adopt any lanthanum compound or terbium compound and the lanthanum-oxides and the terbium oxide itself that can convert oxide to through heating.
The contained lanthanum-oxides or the amount of terbium oxide according to the total amount of electronic emission material, are preferably in the scope that percentage by weight is 0.0001%-5% in the electronic emission material.The lanthanum-oxides or the terbium oxide that are lower than percentage by weight 0.0001% can't be realized stable BaO, and can not prolong.On the other hand, can make relatively poor initial transmissions characteristic degradation, thereby reduce the effect of life-saving more than the lanthanum-oxides or the terbium oxide of percentage by weight 5%.
Lanthanum-oxides or terbium oxide, or the two, be comprised in such as co-precipitation three heavy carbonate (Ba, Sr, Ca) CO 3In, as electronic emission material.Co-precipitation three heavy carbonate can be by handle such as Ba (NO 3) 2, Sr (NO 3) 2Or Ca (NO 3) 2Nitride be dissolved in the pure water, and Na 2CO 3Or (NH 4) 2CO 3Be added in the nitride solution with as the carbonate of Ba, Sr and Ca and co-precipitation as sediment.In this manufacturing process, factors such as solution temperature according to such as nitride concentration, pH value, precipitation the time or settling velocity, the carbonate crystal structure of gained is different.According to one embodiment of present invention, should control above-mentioned factor to form needle-shaped crystal structure.In three heavy carbonate electronic emission materials of the acicular crystal of co-precipitation, add lanthanide and/or terbium oxide, maybe can be transformed into the lanthanum compound or the terbium compound of oxide by heating, to produce suspended matter.This suspended matter can with drip, spraying or sputter, be added on the metallic substrates, to provide oxide coated cathode according to an embodiment of the invention.
In oxide coated cathode according to another embodiment of the present invention, metallic substrates is preferably in 1.333 * 10 -4Under the vacuum more than the Pa, be subjected to the heat treated more than 900 ℃.In addition, lanthanum-oxides and/or terbium oxide be comprised in as electronic emission material, such as co-precipitation (Ba, Sr, Ca) CO 3The material of three heavy carbonate in.
Oxide coated cathode of the present invention is inserted and secured in the electron gun, and heater is inserted and secured in the sleeve.After electron gun is enclosed in the cover of electron tube, in vacuum, make the carbonate decomposition of electron emission material layer become oxide by heater.Then, with traditional manufacture craft electron tube is carried out activation processing.
To describe the present invention in detail by following Example, these examples are only represented and the present invention are described, and should not think that the present invention only limits to these concrete examples.
(example 1)
Carbonic acid ammonia is added into Ba (NO 3) 2, Sr (NO 3) 2And Ca (NO 3) 2Mixture solution in, wherein ratio Ba: Sr: Ca is 50: 40: 10, with the Ba, the Sr that form co-precipitation and the carbonate of Ca.At this moment, for forming co-precipitation three heavy carbonate of needle-shaped crystal structure, the tested control of reaction condition is as follows: the concentration of triple nitride is higher than 0.6M; With aqua ammonia pH is controlled at more than 8; And using (NH 4) 2CO 3When making sediment, the temperature of nitride solution is higher than 60 ℃, and sedimentary solution drips with the speed of per minute 30ml.In co-precipitation three heavy carbonate of needle-shaped crystal structure, add 1% La of the electronic emission material weight calculated with oxide 2O 3Then, nitrocellulose and organic solvent are stirred out, to make the suspension of electronic emission material.
The Ni metallic substrates that contains Si and Mg is cleaned.Then, as above the suspension of the electronic emission material of Zhi Zuoing is sprayed onto in the substrate, promptly obtains according to of the present invention one after the drying
The oxide coated cathode of embodiment.(example 2)
Repeat the step identical, just in three bicarbonate solutions of co-precipitation, add 5% Tb with the electronic emission material weight of oxide calculating with example 1 4O 7, to obtain oxide coated cathode according to an embodiment of the invention.(example 3)
Repeat with example 1 in identical step, just in three bicarbonate solutions of co-precipitation, add 0.001% La with the electronic emission material weight of oxide calculating 2O 3, to obtain oxide coated cathode according to an embodiment of the invention.(example 4)
Repeat with example 1 in identical step, just in three bicarbonate solutions of co-precipitation, add 0.001% Tb with the electronic emission material weight of oxide calculating 4O 7, to obtain oxide coated cathode according to an embodiment of the invention.(example 5)
Repeat with example 1 in identical step, just in three bicarbonate solutions of co-precipitation, add 0.01% La with the electronic emission material weight of oxide calculating 2O 3With Tb 4O 7Mixture, to obtain oxide coated cathode according to an embodiment of the invention.(example 6)
The Ni metallic substrates that contains Si and Mg is 1.333 * 10 -4In the vacuum more than the Pa, be subjected to 1000 ℃ heat treated.
In the electronic emission material that co-precipitation three heavy carbonate constitute, add 1% La of the electronic emission material weight calculated with oxide 2O 3Then, nitrocellulose and organic solution are stirred out, to make the suspension of electronic emission material.
Above-mentioned suspension is sprayed on the heat treated metallic substrates, obtains oxide coated cathode according to another embodiment of the present invention after the drying.(example 7)
Repeat with example 6 in identical step, just in three bicarbonate solutions of co-precipitation, add 0.0001% La with the electronic emission material weight of oxide calculating 2O 3, to obtain oxide coated cathode according to another embodiment of the present invention.(example 8)
Identical step in weight and the example 6 just adds 5% La of the electronic emission material weight calculated with oxide in three bicarbonate solutions of co-precipitation 2O 3, to obtain oxide coated cathode according to another embodiment of the present invention.
Fig. 2 is an enlarged diagram, shows the electron emission material layer of the oxide coated cathode of making by example 1.Fig. 2 illustrates, and the electronic emission material of making in example 1 has formed needle-shaped crystal structure.
For estimating the characteristic of oxide coated cathode of the present invention, the oxide coated cathode of as above making is inserted and is installed in the electron gun, and heater is inserted and is contained in the sleeve.After in the cover of electron gun being enclosed electron tube, in vacuum, utilize heater that the carbonate decomposition in the electron emission material layer is become oxide.After this, carry out activation processing with conventional electron tube manufacture craft, and measure its electron emission characteristic.
The initiating electron emission characteristics is assessed with MIK (maximum cathode current), and the latter is the maximum current that negative electrode is launched under constant running status.Life characteristic is assessed with the negative electrode electric current decrease behind the continuous operation certain hour under steady state that is contained in the electron tube.Be that it is assessed with the consistency of MIK in constant period.
Fig. 3 is a curve chart, shows the MIK situation over time of the oxide coated cathode (b) of the oxide coated cathode (a) made by example 1 and routine.As shown in Figure 3, the life-span of oxide coated cathode according to an embodiment of the invention than traditional prolongation 20%.The oxide coated cathode of making according to example 2 to 5 also demonstrated on their life-span same effect.
Fig. 4 is a curve chart, and the MIK that shows the oxide coated cathode (a) made by example 6 and conventional oxide coated cathode (b) is situation over time, as shown in Figure 4, the life-span of oxide coated cathode according to another embodiment of the present invention than the prolongation of routine 20%.The oxide coated cathodes of making according to example 7 and 8 also demonstrate them same effect on the life-span.
As implied above, oxide coated cathode according to the present invention is characterised in that electron emission material layer contains lanthanum-oxides and/or terbium oxide and forms needle-shaped crystal structure, or it is characterized in that electronic emission material contains lanthanum-oxides and/or terbium oxide and metallic substrates and is subjected to heat treatment under vacuum, the effect of life-saving is arranged and the procedure that can replace mutually with conventional procedure is arranged.
Though it has been carried out concrete demonstration and description in conjunction with specific embodiments of the invention, it will be understood by those skilled in the art that, under the prerequisite that does not break away from the scope of the invention that limits as appended claims and spirit, can carry out multiple modification to wherein form and details.

Claims (2)

1. oxide coated cathode comprises:
Metallic substrates;
Be formed on the metallic substrates, comprise the electron emission material layer of Ba at least; And
Be used to heat the device of electron emission material layer,
It is characterized in that,
Electron emission material layer further comprises at least a in lanthanum-oxides and the terbium oxide, and forms needle-shaped crystal structure, and its content is in 0.0001% to 5% the scope for the percentage by weight according to the total weight of electronic emission material.
2. oxide coated cathode as claimed in claim 1 is characterized in that, metallic substrates is the Ni metallic substrates that contains Si and Mg, and it is by 1.333 * 10 -4The heat treatment that is subjected to temperature more than 900 ℃ under the vacuum more than the Pa forms.
CN93121498A 1993-08-20 1993-12-29 Oxide cathode for electron tube Expired - Fee Related CN1061462C (en)

Applications Claiming Priority (12)

Application Number Priority Date Filing Date Title
KR930016231 1993-08-20
KR16231/1993 1993-08-20
KR16231/93 1993-08-20
KR1019930021670A KR950006911A (en) 1993-08-20 1993-10-19 Oxide cathode for electron tube
KR21670/93 1993-10-19
KR21670/1993 1993-10-19
KR930022124 1993-10-23
KR22124/93 1993-10-23
KR22124/1993 1993-10-23
KR22490/1993 1993-10-27
KR1019930022490A KR100271484B1 (en) 1993-10-23 1993-10-27 Oxide cathode
KR22490/93 1993-10-27

Publications (2)

Publication Number Publication Date
CN1099185A CN1099185A (en) 1995-02-22
CN1061462C true CN1061462C (en) 2001-01-31

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CN93121498A Expired - Fee Related CN1061462C (en) 1993-08-20 1993-12-29 Oxide cathode for electron tube

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EP (1) EP0639848B1 (en)
JP (1) JPH0765692A (en)
CN (1) CN1061462C (en)
DE (1) DE69313845T2 (en)
SG (1) SG44617A1 (en)
TW (1) TW259877B (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100200661B1 (en) * 1994-10-12 1999-06-15 손욱 Cathode for electron tube
EP1232511B1 (en) * 2000-09-19 2007-08-15 Koninklijke Philips Electronics N.V. Oxide cathode
JP2007305438A (en) * 2006-05-12 2007-11-22 New Japan Radio Co Ltd Oxide cathode and its manufacturing method, and method of manufacturing carbonate for oxide cathode used for it

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4797593A (en) * 1985-07-19 1989-01-10 Mitsubishi Denki Kabushiki Kaisha Cathode for electron tube

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB182817A (en) * 1921-07-11 1923-08-09 Drahtlose Telegraphie Gmbh Improvements in the cathodes of electric discharge tubes
US1794298A (en) * 1926-09-21 1931-02-24 Gen Electric Thermionic cathode

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4797593A (en) * 1985-07-19 1989-01-10 Mitsubishi Denki Kabushiki Kaisha Cathode for electron tube

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Publication number Publication date
SG44617A1 (en) 1997-12-19
CN1099185A (en) 1995-02-22
DE69313845T2 (en) 1998-04-02
EP0639848B1 (en) 1997-09-10
JPH0765692A (en) 1995-03-10
EP0639848A1 (en) 1995-02-22
TW259877B (en) 1995-10-11
DE69313845D1 (en) 1997-10-16

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