JP3137960B2 - Electron emission material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various discharge lamps such as fluorescent lamps, cathode ray tube electrodes, plasma displays, and the like.
The present invention relates to an electron emission material that can be used for an electrode of a fluorescent display tube or the like.

[0002]

2. Description of the Related Art In recent years, social demands for energy saving and resource saving have been increasing, and in response to this, energy saving of light sources and displays for general lighting has been actively promoted. For example, the replacement of incandescent light bulbs with bulb-type fluorescent lamps with higher energy efficiency and longer life, and the replacement of cathode ray tubes with liquid crystal displays with lower energy consumption are progressing rapidly. Along with that,
Fluorescent lamps are rapidly being used for light bulb-type fluorescent lamps and as backlight light sources for liquid crystal displays. Similarly, for cathode ray tubes such as cathode ray tubes, plasma displays, and fluorescent display tubes, there is a demand for electrodes having high energy efficiency and capable of saving energy.

Conventionally, BaO has been used as an electrode of a fluorescent lamp.
Oxide electrodes containing as a main component are generally used. Such an electrode is described in, for example, JP-A-59-75553. However, an oxide electrode containing BaO as a main component has good electron emission properties, but has high specific resistance. Therefore, when a large electron emission current is to be obtained, the temperature becomes high. As a result, the vapor pressure increases and the amount of evaporation increases, resulting in a problem that the life is shortened. Also, B
In the case of an oxide electrode containing aO as a main component, it is necessary to apply a current to a tungsten coil coated with a carbonate of Ba to convert the carbonate into an oxide, and to perform decarboxylation at that time. However, when this electrode is applied to a fluorescent lamp having a thin tube, decarboxylation tends to be insufficient, and as a result, carbon dioxide gas remains in the lamp bulb, causing unstable discharge or an extremely high luminance maintenance ratio. The problem is that it becomes worse.

Further, US Pat. No. 2,686,274 describes a rod-shaped electrode obtained by reducing a ceramic such as Ba ₂ TiO ₄ into a semiconductor. The electrode has problems that it is susceptible to thermal shock, easily deteriorated by sputtering with Hg ions or rare gas ions, and has a small usable current density.

With respect to such a conventional fluorescent lamp electrode, the present inventors have proposed an electrode having a structure in which a ceramic semiconductor is housed in a cylindrical container having one end opened and one end closed. Various improvements have been made to the electrodes and to the discharge lamp using the electrodes (Japanese Patent Publication No.
No. 103627, Japanese Patent No. 2628312, Japanese Patent No. 2773174, Japanese Patent No. 2754647, Japanese Unexamined Patent Application Publication No.
-43546, JP-A-6-267404,
JP-A-9-129177, JP-A-10-1218
9, JP-A-6-302298, JP-A-7-302
No. 142031, JP-A-7-262983,
JP-A-10-3879). These electrodes have characteristics that they have good sputtering resistance and are hard to evaporate, so they are hardly deteriorated and have a long life. However, further improvements in sputtering resistance and resistance to evaporation are desired.

In addition to electrodes for discharge lamps such as fluorescent lamps, various electrodes utilizing discharge by hot cathode operation or cold cathode operation, for example, electrodes used in cathode ray tubes, electron microscopes, plasma displays, field emission displays, etc. However, there is a problem of deterioration due to evaporation and ion sputtering, and improvement of the life is desired.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electron-emitting material which has less evaporation during discharge and has high resistance to ion sputtering.

[0008]

The above object is achieved by the following (1).
The present invention of (8) is achieved. (1) An oxynitride perovskite containing, as metal element components, a first component composed of at least one of Ba, Sr and Ca and a second component composed of at least one of Ta, Zr, Nb, Ti and Hf. Electron emitting material. (2) When the first component is represented by M ^I and the second component is represented by M ^II , M ^I M ^{II is used} as the oxynitride perovskite.
The electron-emitting material according to the above (1), comprising an O ₂ N-type crystal. (3) When the molar ratio of the first component is X and the molar ratio of the second component is Y with respect to the sum of the first component and the second component, 0.8 ≦ X / Y ≦ 1.5. The electron-emitting material according to (1) or (2) above. (4) The electron-emitting material according to any one of the above (1) to (3), wherein a part of the second component is contained as a carbide and / or a nitride. (5) Element M (M is Mg, Sc, Y, La, V, C
at least one of r, Mo, W, Fe, Ni and Al
(1) to (4) containing (a) as a metal element component.
Any of the electron emission materials. (6) The electron-emitting material according to (5), containing the element M in an amount of more than 0% by mass and 10% by mass or less in terms of oxide. (7) a first component M ^I, when the second component expressed respectively _{^{M II, M I 4 M II}} 2 O 9 type crystals, M ^I M ^II ₂ O ₆ type crystals, M ^I M ^II O ₃ type _{^{crystal, M I 5 M II 4 O}} 15 type _{^{crystal, M I 7 M II 6 O}} 22 type crystals and M ^I ₆ M ^II M ^II ₄ above comprising at least one O ₁₈ type crystal (1) to (6) Any of the electron emission materials. (8) The specific resistance at room temperature is 10 ^-6 ~10 ³ Ωm (1) any of the electron-emitting material to (7).

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The oxynitride contained in the electron-emitting material of the present invention has a low vapor pressure and a low electric resistance. For this reason, a larger electron emission current can flow than the conventional electrode material containing BaO as a main component, and electrode deterioration due to evaporation is small. Also,
Electrode deterioration is reduced as compared with the electrode composed of a Ba-Zr-Ta-based composite oxide described in Japanese Patent Application Laid-Open No. 9-129177 by the present applicant. Therefore,
When applied to an electrode that performs hot cathode operation, higher brightness is obtained than a conventional electrode, and the electrode life is significantly prolonged.

In addition, the oxynitride is hardly consumed even by ion sputtering. Therefore, even in a cold cathode operation in which ion sputtering is intensified due to a large cathode drop voltage, wear is small and a long life is realized.

The oxynitride having a perovskite structure is disclosed in Journal of Materials Science, 29, (1994), pp4
686-4693. In this document, the oxynitride is manufactured by baking at 1000 ° C. in an ammonia gas flow, but the oxynitride thus manufactured is evaluated only as a dielectric.
Since oxynitride is a stable compound even in a reducing atmosphere, it is suitable for a multilayer ceramic capacitor having an internal electrode made of a base metal.

Japanese Patent Application Laid-Open No. 63-252920 (corresponding to US Pat. No. 4,964,016) discloses a conductive perovskite represented by the formula AB (O, N) _3. I have. In the above formula, the element A is IA
A metal selected from the group IV and IIA metals, yttrium and lanthanoids, wherein the element B is a group IVA to I
Shows a metal selected from Group B transition metals. In that publication,
This conductive perovskite is manufactured by firing a mixed oxide of metal A and metal B at about 700 to 900 ° C. in an ammonia gas flow. This publication proposes to use this conductive perovskite for the electrodes of a ceramic capacitor, and there is no description or suggestion that the invention is applied to an electron emission material. The composition of the conductive perovskite described in the publication overlaps with the composition of the oxynitride contained in the electron-emitting material of the present invention.
However, this publication does not specifically disclose oxynitride perovskites having the composition defined by the present invention. Further, when the composition limited in the present invention is used and baked in an ammonia gas stream under the conditions described in the publication, the specific resistance becomes too high, so that favorable characteristics as an electron-emitting material cannot be obtained.

As described above, an oxynitride having a perovskite structure itself is known, but the use of the oxynitride as an electron-emitting material is a completely new proposal by the present inventors. It has not been known at all that the above effects are realized when an object is used for an electrode. That is, the oxynitride contained in the electron emission material of the present invention,
It has not been known as an electron emission material.

Hereinafter, the electron emitting material of the present invention will be described in detail.

Electron Emitting Material The electron emitting material of the present invention comprises a first component comprising at least one of Ba, Sr and Ca, Ta, Zr, Nb and Tb.
a second component comprising at least one of i and Hf;
Included as metal element component. The first component is a low work function electron emission component. The second component is a component necessary for lowering the resistance and increasing the melting point of the electron-emitting material. A preferred element of the first component is Ba, and Ba is 5% of the first component.
It preferably accounts for 0 to 100 atomic%, especially 70 to 100 atomic%. Preferred elements of the second component are Ta and / or Zr, especially Ta, where Ta is 5% of the second component.
It preferably accounts for 0 to 100 atomic%, especially 70 to 100 atomic%.

The electron emission material of the present invention contains an oxynitride having a perovskite structure, that is, an oxynitride perovskite (oxynitride perovskite).
When the first component is represented by M ^I and the second component is represented by M ^II , the oxynitride preferably contains at least M ^I M ^II O ₂ N type crystal. In this crystal,
The ratio of oxygen to nitrogen is not limited to 2: 1. The actual product, by defects of oxygen and nitrogen is present, M ^I M
^II O ₂₊ δN _1- δ '. Where δ
And δ ′ are preferably −0.5 to 0.95, more preferably 0 to 0.7. When δ and δ ′ are in such ranges, the effect of suppressing evaporation and evaporation of the electron-emitting material is enhanced. Note that M ^I M
^II O ₂ N type crystal can also be represented as ^{M I M II (O, N} ) 3 type crystal.

The electron-emitting material of the present invention may contain an oxide in addition to the oxynitride perovskite. As the oxide for ^{_{example, M I 4 M II 2 O}} 9 type crystals, M ^I
M ^II ₂ O ₆ type crystals, M ^I M ^II O ₃ type ^{_{crystal, M I 5 M II 4 O}} 15 type ^{_{crystal, M I 7 M II 6 O}} 22 type crystals and ^{_{M I 6 M II M II 4}} O 18 type At least one kind of composite oxide such as a crystal is used. ^{_{Incidentally, M I 6 M II M II}} 4 The O ₁₈ type crystal, for example, Ba ₆ Z
rTa ₄ O ₁₈ is mentioned.

The electron-emitting material, in addition to the oxynitride, the carbide and / or nitride, may especially contain M ^II carbide such as TaC. This carbide or nitride is contained as a result of part of the second component becoming carbide or nitride in the process of producing the electron-emitting material, as described later. Since these carbides and nitrides are substances having a high melting point and high conductivity, even if they are contained, the electron emission characteristics and the sputtering resistance are not impaired at all. In the second component, for example, Ta is likely to be carbide, and Zr is likely to be nitride.

The presence of each crystal in the electron-emitting material depends on the X-ray
We can confirm by occasion. Electron emitting material of the present invention
Is shown in FIG. As shown in FIG.
The pattern is substantially M, except for TaC.^IM^IIO_TwoN type
It is an electron-emitting material composed of a single crystal phase. Departure
Ming's electron-emitting material is M^IM^IIO_TwoN-type crystal as the main component
Preferably, it consists essentially of this crystal only.
More preferably. However, as described above,
There is no problem even if a substance and / or nitride is contained.
Note that M^IM^IIO_TwoThe fact that the N-type crystal is the main component means that the
The maximum peak intensity of each crystal in the fold pattern
When compared, M^IM^IIO_TwoMaximum peak strength of crystals other than N
Degree M^IM^IIO_Two50% or less of the maximum peak intensity of N-type crystal
Lower, preferably 30% or less. However
And, for example, BaZrO_ThreeAnd Ba_FiveTa _FourO_FifteenAnd like
Two or more acids whose peak positions are almost identical
The second largest pin
Using the strength of the^IM^{I I}O_TwoMaximum peak of N-type crystal
Compare with.

In the electron-emitting material, when the molar ratio of the first component is X and the molar ratio of the second component is Y with respect to the total of the first component and the second component, preferably 0.8 ≦ X / Y ≦ 1.5, more preferably 0.9 ≦ X / Y ≦ 1.2. If X / Y is too small, the first component will be depleted early due to discharge, and the sputtering resistance will be insufficient. On the other hand, if X / Y is too large, the electron-emitting material is likely to be evaporated and scattered by sputtering during discharge. Therefore, in any case, for example, when the present invention is applied to a discharge lamp, the brightness is easily reduced due to blackening of the tube wall.

The electron emission material may contain a metal element component other than the first component and the second component. As such a metal element component, an element M (M is Mg, Sc,
Y, La, V, Cr, Mo, W, Fe, Ni and Al
At least one). The element M is added as needed to improve sinterability. The content of the element M in the electron emission material is preferably 1 in terms of oxide.
0 mass% or less, more preferably 5 mass% or less. If the content of the element M is too large, the melting point of the electron-emitting material becomes low, so that the vapor pressure at the time of high temperature use becomes high and the life is shortened. On the other hand, the content of the element M is preferably 0.5% by mass or more in order to sufficiently exert the effect of the addition of the element M. Here, the content in terms of oxide means an oxide having a stoichiometric composition, that is, MgO, Sc ₂
O ₃ , Y ₂ O ₃ , La ₂ O ₃ , V ₂ O ₅ , Cr ₂ O ₃ , MoO ₃ ,
It is the content calculated in terms of WO ₃ , Fe ₂ O ₃ , NiO and Al ₂ O ₃ .

The element M is substituted with a part of M ^I or a part of M ^{II in} the oxynitride, or is not substituted, and is substituted with the oxynitride as an oxide, nitride, carbide, or the like. It is in a mixed state. The fact that a part of M ^I or a part of M ^{II in} the oxynitride crystal is replaced with another metal element can be confirmed by a shift of a peak in X-ray diffraction and a change in a peak intensity ratio. it can.

The resistivity at room temperature of the electron-emitting material of the present invention is usually so 10 ^-6 to 10 ³ [Omega] m, not a dielectric. And operating temperature (usually 900-1 for hot cathode)
At about 400 ° C. and about 700 to 1000 ° C. for a cold cathode), it shows excellent performance as an electron-emitting material. That is, even when the temperature becomes high due to the flow of a large discharge current, the consumption is small because the vapor pressure is low.

Method for Producing Electron Emitting Material The electron emitting material of the present invention can be produced by using a conventionally known method for producing an oxynitride. That is,
Journal of Materials Science, 29, (1994), pp4686-
As shown in 4693, the above-mentioned oxynitride can be obtained by mixing raw material compounds such as oxides and carbonates, followed by firing in an ammonia stream. However, as described above, the Journal of Materials Science, 29, (199
4), since the specific resistance becomes too high when firing under the conditions described in pp4686-4693, when firing in an ammonia stream, the firing temperature is preferably 1100 ° C or higher, more preferably 1200 ° C or higher. And In order to prevent the object to be fired from melting, the firing temperature is preferably set to 2000 ° C.
Or less, more preferably 1700 ° C. or less.

However, when calcination is performed in an ammonia gas stream, since strongly alkaline ammonia is contained in the exhaust gas, it is necessary to pay attention to the corrosion resistance of the manufacturing apparatus. It is necessary to arrange a trap using sulfuric acid or the like at the exhaust port.
Therefore, it is not suitable for mass production, and equipment costs increase.

Therefore, the present inventors have searched for a production method capable of producing oxynitride perovskite without using an ammonia gas flow, and as a result, it has been found that at least the material to be fired containing the raw material powder and carbon are placed in close proximity to each other. It has been found that calcination in an atmosphere containing nitrogen gas can produce oxynitride perovskite. In this method, since a stable and easy-to-use nitrogen gas can be used, the problem of the method using the ammonia gas flow is solved. This method is completely novel as a method for producing oxynitride perovskite, and is the method proposed by the present inventors for the first time. In addition,
The material to be fired in this method may be the raw material powder itself, a coating film containing the raw material powder, or a molded product of the raw material powder. In addition, the raw material powder in this case may be an oxide and / or a starting material that generates an oxide by firing, or may be an intermediate product obtained by firing this to generate a composite oxide.

In this method, the means for arranging the object to be fired and the carbon in close proximity is not particularly limited. For example, a firing furnace at least partially composed of carbon may be used, or a bulk, granular, The object to be fired is baked in a state in which powdered carbon is put, or the object to be fired is mixed with granular or powdered carbon and fired, or the object to be fired is at least partially made of carbon. Or firing in
More than one species may be used in combination. Among these, it is easy to make the raw material powder in the object to be fired substantially uniformly contact the carbon, and the object to be fired is easily exposed to a nitrogen gas stream. A method in which powdered carbon is mixed and fired is preferred. However, when baking a relatively thin coating film, the carbon powder need not be dispersed in the coating film. When the coating film is thin, sufficient carbon can be supplied from the firing furnace or container to the raw material powder in the coating film, and when the carbon powder is dispersed in the thin coating film, the carbon powder becomes denser and flatter. This is because there is a possibility that it may have an effect on the operation.

Examples of the furnace at least partially composed of carbon include, for example, a furnace composed of carbon at least part of a heat insulating material. In an electric furnace, only a heating element or a heating element and a heating element are used. A furnace in which the heat insulating material is made of carbon is used. As the container made of carbon, a container having at least one open end is used so as not to hinder the contact of the nitrogen gas with the object to be fired.

Further, a carbon compound can be used instead of simple carbon. For example, usually, a molded article or a coating film contains a binder made of an organic compound.However, it is also possible to form oxynitride by supplying carbon from the binder by insufficiently removing the binder during firing. it can. The oxynitride can also be generated by putting an organic compound in the raw material powder or by putting an organic compound in a furnace and firing. However, a method using carbon alone is more preferable because oxynitride can be manufactured stably and there is no fear that the characteristics of the electron-emitting material are deteriorated due to the residual organic compound.

Hereinafter, a method for obtaining the electron emitting material of the present invention as a powder or a sintered body will be described in detail.

Production Method 1 of Sintered Body (Powder) In obtaining the electron-emitting material of the present invention as a powder or a sintered body, oxynitride may be formed under the above-mentioned conditions, and other steps are not particularly limited. Instead, for example, the methods shown in FIGS. 1, 2 and 3 can be used. First, each step shown in FIG. 1 will be described.

[0032] In the weighing step weighing process, weighed in accordance with the final composition of the starting material.
As a compound used as a starting material, an oxide and / or a compound which becomes an oxide upon firing, for example, a carbonate, an oxalate, or the like may be used. Usually, BaCO ₃ , SrCO ₃ and It is preferable to use CaCO _3, and the compound containing the second component includes Ta ₂ O ₅ ,
It is preferable to use ZrO ₂ , Nb ₂ O ₅ , TiO ₂ and HfO ₂ . Further, as a starting material of the element M,
MgCO ₃ , Sc ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ , V ₂ O ₅ , C
r ₂ O ₃ , MoO ₃ , WO ₃ , Fe ₂ O ₃ , NiO and Al
It is preferable to use ₂ O ₃ .

Mixing Step In the mixing step, the weighed starting materials are mixed to obtain a raw material powder. For mixing, a method such as a ball mill method, a friction mill method, and a coprecipitation method can be used. After mixing, drying is performed by a dehydration heating drying method or a freeze drying method.

In this mixing step, carbon is added to the starting materials as required. Carbon may be wet-mixed simultaneously with the mixing of the starting materials, or may be added after the starting materials are mixed and then dry-mixed. Carbon has a relatively small specific gravity,
Since it is difficult to disperse in a dispersion medium, a dispersant is added as needed when performing wet mixing. The dispersion medium may be aqueous or organic, but considering the load on the environment,
It is preferable to use an aqueous type.

The amount of carbon added is preferably 50% by mass or less, more preferably 20% by mass or less, based on the starting materials. If the addition amount is too large, a large amount of carbides and nitrides that do not contribute to electron emission tends to be generated, which is not preferable. In addition, it is not preferable because a large amount of carbon remains after firing and is likely to evaporate and gasify when used as an electron-emitting material. On the other hand, in the case where the container made of carbon and the furnace material containing carbon are not used, if the added amount of carbon is too small, it becomes difficult to generate oxynitride. Therefore, in this case, the added amount of carbon is preferably 1% by mass or more, more preferably 2% by mass, based on the starting material. The type of carbon is not particularly limited, and may be any of graphite, amorphous carbon, and the like. The average particle size of carbon in the mixture is preferably 1 mm or less, more preferably 500 μm or less. If the average particle size is too large, it is difficult to uniformly disperse in the mixture, and it is difficult to react, so that it tends to remain after firing. It is preferable that the average particle size of the carbon powder is small, but if the average particle size is too small, it becomes difficult to handle and disperse.
μm or more. In addition, a dispersant may be used to improve the dispersibility of the carbon powder.

Oxynitride Generation Step In the oxynitride generation step, the raw material powder is fired in an atmosphere containing nitrogen gas, preferably in a nitrogen stream, to obtain an electron emission material containing oxynitride perovskite. At this time, as described above, a furnace or a vessel at least partially composed of carbon is used, carbon is disposed in the furnace, or both are used as necessary. The firing temperature is preferably 800
-2000 ° C, more preferably 1100-1700 ° C. If the firing temperature is too low, oxynitrides are less likely to be generated, and if the firing temperature is too high, the amount of carbides and nitrides generated increases, and in any case, the performance as an electron-emitting material tends to be insufficient. If the firing temperature is too high, the object to be fired may be melted. The firing time (temperature holding time) may be generally about 0.5 to 5 hours. This baking may be performed in a powder state, or may be performed in a state in which the powder is molded for easy handling. By this firing, an oxynitride having a perovskite structure is generated. At this time, in addition to the oxynitride, the second
Component carbides and / or nitrides may also be formed at the same time, and carbides are particularly likely to be formed.

The carbon powder mixed with the raw material powder is
Since it is consumed by reacting by firing in a nitrogen gas-containing atmosphere, it does not substantially remain in the fired body if the mixing amount is appropriate. Therefore, it is not necessary to remove the carbon powder from the electron-emitting material after firing. However, for example, when a relatively large amount of carbon powder having a large particle diameter is used, the removal operation may be performed as necessary.

As the nitrogen gas-containing atmosphere, nitrogen 1
It is most preferable that the content be 00%, but an inert gas such as Ar, a reducing gas such as CO or H _2, or a gas containing carbon as a component (for example, benzene or carbon monoxide) may be contained. . However, even in that case, nitrogen is 50% of the whole
It is preferable to occupy the above. A gas containing carbon as a constituent component is generally more difficult to handle than nitrogen, and it is difficult to stably generate an oxynitride perovskite.

When firing in a nitrogen stream, the flow rate of nitrogen gas per unit area in the vicinity of the object to be fired, that is, the nitrogen gas per unit area in the space near the object to be fired in a section perpendicular to the direction of flow of the nitrogen gas flow The gas flow rate is 0.0
It is preferably at least 001 m / s, particularly preferably at least 0.001 m / s. By supplying nitrogen gas to the object to be fired at such a flow rate, oxynitride can be easily and quickly generated in the object to be fired. The flow rate may be set within a range in which the material to be fired is not scattered, and there is no specific upper limit, but it is not usually necessary to set the flow rate to more than 5 m / s.

Since the oxynitride is easily decomposed when heated in an atmosphere containing oxygen gas, it is preferable to keep the firing atmosphere at a low oxygen partial pressure. Since the ease of decomposition of the oxynitride varies depending on the heating temperature, the oxygen partial pressure may be appropriately controlled according to the firing temperature, but preferably 5.0.
× 10 ³ Pa (0.05 atm) or less, more preferably 1.
The pressure is 0 × 10 ³ Pa (0.01 atm) or less, more preferably 0.1 × 10 ³ Pa (0.001 atm) or less. The preferable lower limit of the oxygen partial pressure is not particularly limited, and the oxygen partial pressure may be zero. However, when a normal firing apparatus is used, the oxygen partial pressure in the firing atmosphere is generally 0.1 Pa or more.

Pulverizing Step In the pulverizing step, the electron emitting material obtained in the oxynitride forming step is pulverized to obtain an electron emitting material powder. In this grinding,
A ball mill or airflow pulverization may be used. By providing the pulverizing step, the particle size of the electron-emitting material can be reduced and the particle size distribution can be narrowed, so that the electron-emitting property can be improved and its variation can be reduced. Therefore, it is preferable to provide a pulverizing step. When a sintered body is finally obtained, the process proceeds to the next forming step.

After the pulverization, a granulation step is provided if necessary.
In the granulation step, the pulverized powder is granulated using an aqueous solution containing an organic binder such as polyvinyl alcohol (PVA), polyethylene glycol (PEG), and polyethylene oxide (PEO). Granulation means is not particularly limited, for example, spray drying method, extrusion granulation method, tumbling granulation method, mortar,
A method using a pestle or the like can be used.

Molding Step In the molding step, a compact having the desired electrode shape is obtained by compression molding.

Sintering Step In the sintering step, the compact is fired to obtain a sintered body (electrode). In the sintering step, in order to prevent the decomposition of the already generated oxynitride, the sintering is performed in a nitrogen gas-containing atmosphere as in the oxynitride forming step. However, in this sintering step, it is not necessary to dispose carbon close to the molded object to be fired. The nitrogen gas-containing atmosphere at this time is the same as the nitrogen gas-containing atmosphere described in the description of the oxynitride generation step.
The same applies to the oxygen partial pressure. The firing temperature is preferably 800 to 2000 ° C, more preferably 1100 to 2000.
Perform at 1700 ° C. If the firing temperature is too low, the density of the sintered body tends to be insufficient, and if the firing temperature is too high, a compositional deviation occurs or it tends to react with the setter. The firing time may usually be about 0.5 to 5 hours.

In the method shown in FIG. 1, a sintering step may also serve as an oxynitride generation step by providing a molding step immediately after the mixing step. However, when carbon powder is mixed with the starting material in such a configuration, the carbon powder is present in the compact. Therefore, carbon in the compact may react when the compact is sintered, and the dimensional accuracy and density of the sintered compact may be affected by the consumption of carbon. On the other hand, in the method of FIG. 1, since the carbon is consumed in the oxynitride generation step and then molded, there is no need to worry about the influence of carbon consumption when sintering the compact.

The method shown in FIG. 2 is different from the method shown in FIG. 1 in that a composite oxide forming step is provided before the oxynitride forming step, and the oxynitride forming step also serves as a sintering step. It is different from the method shown in When the oxynitride is directly produced by a relatively high-temperature heat treatment using a starting material containing a highly reactive material such as BaCO ₃ as in the above-mentioned production method 1, a furnace material such as a zirconia setter is used during firing. May react with the starting materials. If the furnace material reacts with the starting material during firing, the furnace material may be consumed or the characteristics and shape (in the case of a molded body) of the electron-emitting material may be affected. On the other hand, if a composite oxide generation step of generating a composite oxide by heat treatment at a relatively low temperature is provided before the oxynitride generation step, occurrence of such a problem can be suppressed. Hereinafter, each step shown in FIG. 2 will be described.

[0047] performed in the same manner as the weighing process shown in weighing Scheme 1.

Mixing Step The mixing step is performed in the same manner as in the mixing step shown in FIG. 1 except that carbon is not mixed.

The composite oxide producing step The raw material powder is calcined in an oxidizing atmosphere such as in air to obtain M ^I ₅
An intermediate product containing a complex oxide such as M ^II ₄ O ₁₅ is produced. Examples of the composite oxide contained in the intermediate product include at least one of the composite oxides that can be included in the electron-emitting material of the present invention. It is preferable that the intermediate product obtained by this calcination is substantially composed of only the composite oxide. The firing temperature is preferably 800
To 1700 ° C, more preferably 800 to 1500 ° C, still more preferably 900 to 1300 ° C. If the firing temperature is too low, M ^I ₅ M ^II ₄ O composite oxide such as ₁₅ is hardly generated. On the other hand, if the firing temperature is too high, sintering proceeds and it becomes difficult to grind, and the composite oxide may be melted or decomposed. The firing time may be about 0.5 to 5 hours. This baking may be performed in a powder state, or may be performed in a state in which the powder is molded for easy handling. Note that the composite oxide generation step may be performed in a reducing atmosphere. The above-mentioned composite oxide can be produced even by firing in a reducing atmosphere. However, since it is necessary to control the atmosphere in order to obtain a reducing atmosphere, and since the performance of the finally obtained electron-emitting material does not depend on the firing atmosphere in the composite oxide generation step, firing is usually performed in air. Is preferred.

Pulverization Step The pulverization step is performed in the same manner as in the pulverization step shown in FIG. At this time, as in the mixing step shown in FIG. 1, carbon is mixed if necessary.

Molding step The molding step is performed in the same manner as in the molding step shown in FIG.

Oxynitride Generation Step The material is fired under the same conditions as in the oxynitride generation step shown in FIG. 1 to obtain a sintered body of an electron emission material containing oxynitride.

Method 3 for Producing Sintered Body (Powder) The method shown in FIG. 3 is the same as the method shown in FIG. 2 in that a composite oxide forming step is provided before the oxynitride forming step. However, in the method of FIG. 2, the oxynitride generation step also serves as a sintering step, whereas in the method of FIG. Is different from the method of FIG. 2 in that a sintered body is obtained by molding and firing. When carbon is added in the pulverization step in the method of FIG. 2, the carbon in the compact reacts when the compact is sintered, so that the dimensional accuracy and density of the sintered compact may be affected by the consumption of carbon. is there. On the other hand, in the method of FIG. 3, since the carbon is consumed in the oxynitride generation step and then molded, there is no need to worry about the influence of carbon consumption when sintering the compact. Hereinafter, each step will be described.

[0054] performed in the same manner as the weighing process shown in weighing process diagram 2.

Mixing Step The mixing step is performed in the same manner as in the mixing step shown in FIG.

Composite Oxide Generation Step A composite oxide is generated in the same manner as in the composite oxide generation step shown in FIG.

First crushing step The first crushing step is performed in the same manner as in the crushing step shown in FIG.

Oxynitride Generation Step An oxynitride-containing electron-emitting material is obtained in the same manner as in the oxynitride generation step shown in FIG. The firing in this step may be performed in a powder state, or may be performed in a state in which the powder is molded for easy handling.

Second Pulverization Step The same procedure as in the first pulverization step is performed except that carbon is not mixed, to obtain a powder of an electron-emitting material.

Molding step The molding step is performed in the same manner as the molding step shown in FIG.

Sintering Step As in the sintering step shown in FIG. 1, the compact is fired under conditions that prevent the decomposition of the oxynitride to obtain a sintered body.

The powder of the electron emitting material can be used for a so-called thick film method. In the thick-film method, a powder of the electron-emitting material is mixed with an aqueous or organic dispersion medium to form a slurry, which is applied to the surface of a tungsten filament or the like, and then heat-treated to form a film made of the electron-emitting material particles. obtain. At this time, a binder is added to the slurry as necessary, and the coating is dried and the binder is removed by a subsequent heat treatment.

Electrodes The electron-emitting material of the present invention is suitable for electrodes for various discharge lamps such as fluorescent lamps. In that case, it can be used both as an electrode for hot cathode operation and as an electrode for cold cathode operation. For example, the electrode proposed by the present inventors, that is, as shown in FIG. 6, an electrode having a structure in which granules 2 made of a ceramic semiconductor are accommodated in a cylindrical container 1 having one end open and one end closed. In the above, the electron-emitting material of the present invention can be used as the ceramic semiconductor, and the electron-emitting material of the present invention can also be used for the cylindrical container 1. In addition to the structure shown in FIG. 6, an electrode may be formed by forming the electron-emitting material of the present invention into a rod-shaped sintered body and inserting the sintered body into a hollow portion of a tungsten coil and fixing the same. .

When the electron-emitting material of the present invention is used as a film, for example, an electron-emitting material film is formed on the surface of a base material such as a linear body (coil-shaped or double-coiled filament) or a plate-shaped body. To form an electrode. As the base material, for example, W, Mo, Ta, Ni, Zr, T
i, etc., or an alloy containing at least one of them, or ZrO ₂ , Al ₂ O ₃ , MgO, A
Ceramics such as 1N and Si ₃ N ₄ or ceramics containing at least one of these (SIALON or the like) can be used. In addition, a coating film containing an oxynitride-containing powder or a raw material powder in which oxynitride is generated by firing and a coating film containing a conductive material are laminated by a printing method or a sheet method, and this is fired. To form a stacked electrode.

When the electron-emitting material of the present invention is used as a film, the thickness of the film is usually about 5 to 1000 μm. The average particle size of the electron emitting material particles in the electron emitting material film is preferably 0.05 to 20 μm, and more preferably 0.1 to 10 μm. In order to further reduce the average particle size in the film, fine particles that are difficult to handle must be used. In addition, such fine particles are likely to aggregate into secondary particles, so that the particle size distribution is widened and it is difficult to form a uniform coating film. On the other hand, if the average particle size in the film is too large, the particles of the electron-emitting material tend to fall off, and the workability during coating is also poor, and the electron-emitting properties are also poor.

The electron-emitting material of the present invention can be used not only for electrodes for various discharge lamps such as fluorescent lamps, but also for electrodes for electron guns of cathode ray tubes, electrodes for plasma displays, electrodes for field emission displays, electrodes for fluorescent display tubes, electron microscopes, It can also be used as an electron emission material such as an electrode. In each of these cases, the effect of the present invention, that is, the longevity of the electrode and the improvement of the characteristics are realized.

[0067] The discharge lamp Figure 7 shows a configuration example of a discharge lamp of hot cathode operation having an electrode shown in FIG. It should be noted that only the vicinity of the pipe end is shown in FIG. This discharge lamp has a structure that can be made thin.

This discharge lamp is coated with a phosphor on its inner surface,
It has a hermetically sealed valve 9. A rare gas (at least one of He, Ne, Ar, Kr, and Xe) is sealed in the valve 9. Usually, the pressure of the rare gas in the valve 9 is preferably 1330 to 22600 Pa. By setting the pressure of the rare gas in this range, high brightness and long life can be achieved.

The lead wire 5 is inserted through the end of the valve 9. An enlarged lead wire portion 6 is formed at an end of the lead wire 5 present in the bulb 9. A conductive pipe 7 is connected to the lead wire enlarging portion 6. If the lead wire 5 can be connected to the conductive pipe 7 by other means, the lead wire enlarged portion 6 may not be provided. The conductive pipe 7 may be made of a material having a high electric conductivity, but a material that emits little gas in a vacuum.
For example, if Ni is used, the generation of gas containing impurities during the manufacture of the discharge lamp is suppressed, and stable discharge is possible.
preferable. However, the conductive pipe 7 may be made of ceramics. The container 1 is disposed in contact with the conductive pipe 7, and the electron emitting material 2 is filled in the container 1. Further, a metal pipe 4 filled with a mercury dispenser material 3 is disposed between the container 1 and the lead wire enlarging portion 6 in the conductive pipe 7. The metal pipe 4
It is a tubular body having both ends opened, and may be made of a metal such as Ni. A slit-shaped opening (not shown) is formed in a portion of the conductive pipe 7 surrounding the metal pipe 4. Mercury in the mercury dispenser material 3 is converted into steam by high-frequency heating or the like on the metal pipe 4, passes between the metal pipe 4 and the lead wire enlarging portion 6 and between the metal pipe 4 and the container 1, and passes through the opening. Released into the discharge space 10. The opening is not limited to the slit shape, and may have any shape as long as the opening can release mercury vapor and does not hinder the holding of the container 1. Further, it is not essential to provide the mercury dispenser material 3, and it may be configured to supply mercury into the bulb during the sealing process.

FIG. 8 shows an example of the configuration of a discharge lamp operating in the cold cathode mode. It should be noted that only the vicinity of the pipe end is shown in FIG. Conventionally, it is common to use a metal tubular body made of Ni or the like for the cold cathode. When an emitter is used, the tubular body is used as an electrode substrate, and the peripheral surface is made of, for example, BaO. The coating film of the emitter is provided. When the present invention is applied to a cold cathode discharge lamp, instead of the conventional emitter coating,
What is necessary is just to provide a coating film containing the above-mentioned electron emission material on the surface of the electrode substrate. As a constituent material of the electrode substrate, in addition to Ni, for example, a high melting point metal such as W, Ti, Zr, Mo, and Ta, or an alloy containing at least one of these can be preferably used.

This discharge lamp shown in FIG. 8 has a phosphor 9 on its inner surface.
A is applied and has a hermetically sealed valve 9. A rare gas is sealed in the valve 9. A lead wire 5 is inserted through an end of the bulb 9. The end of the lead wire 5 present in the valve 9 has a stem 9 for closing the valve end.
An internal introduction line 6A is provided through B. A conductive pipe 7 serving as an electrode substrate is connected to the internal introduction line 6A. On the inner peripheral surface of the conductive pipe 7, an electron emission material film 2A is formed. This discharge lamp has a structure in which mercury is supplied into a bulb during a sealing process.

The electrode using the electron-emitting material of the present invention can be applied not only to the discharge lamp having the above structure. For example, the invention can be applied to various types of discharge lamps already proposed by the present inventors in the above publications.

[0073]

Example 1 An electrode sample having a structure in which granules 2 made of ceramic semiconductor were accommodated in a cylindrical container 1 having one end open and one end closed as shown in FIG. 6 was prepared by the method shown in FIG. Utilized and produced by the following procedure.

First, Ba was selected as the first component, and Ta and Zr were selected as the second component.
aCO ₃ , Ta ₂ O ₅ and ZrO ₂ were prepared.

Next, the starting materials were weighed so that the ratio of Ba, Ta and Zr was as shown in Table 1, and wet-mixed by a ball mill for 20 hours.

Next, after the mixture was dried, the average particle size was 5
0 μm carbon powder was added in an amount of 5% by mass based on the starting material, dry-mixed, and molded at a pressure of 10 MPa. In the obtained molded body,
An oxynitride generation treatment was performed. In this treatment, the molded body is placed in a carbon container having an open upper surface, a gap is provided between the container and the container, and a carbon lid is placed thereon.
It was baked at 0 ° C. for 2 hours. Nitrogen gas was supplied such that the flow rate of nitrogen gas per unit area in a section perpendicular to the direction of flow of the nitrogen gas in the space near the compact in the furnace was 0.01 m / s. The oxygen partial pressure in the firing atmosphere is 2
0 Pa (0.0002 atm) was set. The obtained electron-emitting material was wet-pulverized by a ball mill for 20 hours, dried, added with an aqueous solution containing polyvinyl alcohol, and granulated using a mortar and pestle to form granules.

Next, the granules are molded at a pressure of 200 MPa, and a cylindrical molded body having one end open and the other end closed (density 3.
69 g / cm ³ ) was obtained. After filling the above-mentioned granules into this molded body, it was placed in an electric furnace equipped with a carbon heating element and a carbon heat insulating material and fired at 1600 ° C. for 2 hours in a nitrogen stream to obtain an electrode sample shown in Table 1. The nitrogen gas flow rate and the oxygen partial pressure during the firing were the same as those in the above-mentioned oxynitride generation treatment. The dimensions of each sample were 2.3 mm in outer diameter, 1.7 mm in inner diameter (diameter of the granule storage section), and 1.7 mm in length.
The density of the container was 8.2 g / cm ³ , which was 90% or more of the theoretical density obtained from the crystal structure. In these samples, the composition ratio of the metal element component was almost the same as the composition ratio in the starting material. Table 1 shows X / Y of each sample. The composition ratio of the metal element components was measured by X-ray fluorescence analysis.

Further, Japanese Patent Application Laid-Open No.
Based on the method described in Japanese Patent No. 9177, a comparative electrode sample was prepared in the following procedure. First, after the mixture of the starting materials is molded at a pressure of 100 MPa, the mixture is
It was baked at 0 ° C. for 2 hours. The obtained fired body was wet-pulverized, dried and granulated in the same manner as above to obtain granules, and the granules were compression-molded to obtain a molded body. The compact filled with the granules was completely buried in carbon powder, and calcined at 1600 ° C. for 2 hours while flowing a nitrogen gas. Nitrogen gas was supplied such that the flow rate of nitrogen gas per unit area in a section perpendicular to the direction of flow of the nitrogen gas in the space near the compact in the furnace was 0.00005 m / s. The oxygen partial pressure in the firing atmosphere was 20 Pa (0.0002 atm).
And

X-ray diffraction was performed on these electrode samples. As a result, as shown in FIG. 4, a sample that had undergone an oxynitride forming step, that is, a sample that had been mixed with carbon powder and fired in a nitrogen gas stream was obtained, for example, as shown in FIG. a peak and a peak of the second component carbide oxynitride perovskite such (M ^I M ^II O ₂ N type crystals) were observed. FIG. 4 is an X-ray diffraction pattern of Sample No. 4 shown in Table 1. In FIG. 4, it can be seen that oxynitride perovskite has a single phase except for carbides. In Comparative Sample contrast, oxynitride perovskite without generating only oxides and carbides mainly of M ^I ₅ M ^II ₄ O ₁₅ type crystal (TaC) was confirmed to be produced.

These electrode samples were used for the entire length of the bulb.
00mm, outer diameter 5mm, filling gas Ar, filling pressure 9.3kP
a, enclosure Hg, drive power frequency 30kHz, lamp current 3
It was incorporated in a 0 mA discharge lamp and a continuous lighting test was performed. Although the operating temperature at this time was about 1100 ° C., each sample showed a stable hot cathode operation between 900 ° C. and 1400 ° C.

Table 1 shows the luminance maintenance ratio of the discharge lamp incorporating each sample. This luminance maintenance ratio is a ratio of the luminance after continuous lighting for 3000 hours to the initial value when the luminance after continuous lighting for 100 hours is set to an initial value (100%). The luminance of the discharge lamp was determined by measuring the surface luminance of the bulb with a luminance meter at a position 5 mm closer to the longitudinal center of the bulb from the electrode tip.

[0082]

[Table 1]

As shown in Table 1, when the sample of the present invention containing oxynitride perovskite was used, the luminance retention ratio was higher than when the comparative sample made of oxide was used. In the discharge lamp using the comparative sample, blackening of the bulb tube wall was observed, and it was confirmed that the electron emission material was consumed by evaporation and sputtering of the electron emission material.

Example 2 BaCO ₃ and Ta ₂ O ₅ were used as starting materials,
An electrode sample was prepared in the same manner as in Example 1, except that the ratio of Ta and Ta was as shown in Table 2.
When X-ray diffraction was performed on these electrode samples,
M ^I M ^II O ₂ N type crystal peak and the peak of the carbide of the second component were observed, except carbides, it was confirmed that a single phase of oxynitride perovskite.

These electrode samples were assembled into a discharge lamp in the same manner as in Example 1, and the same continuous lighting test as in Example 1 was performed. Table 2 shows the results.

[0086]

[Table 2]

From Table 2, it can be seen that when X / Y is in the range of 0.8 to 1.5, a high luminance maintenance ratio can be obtained.

Example 3 An electrode sample was prepared in the same manner as in Example 1 except that the first component and the second component were combined as shown in Table 3.
When X-ray diffraction was performed on these electrode samples,
M ^I M ^II O ₂ peak of the N-type crystal and the peak of the second component carbide was observed, except carbides, it was confirmed that a single phase of oxynitride perovskite.

These electrode samples were assembled into a discharge lamp in the same manner as in Example 1, and the same continuous lighting test as in Example 1 was performed. Table 3 shows the results. In Table 3, Sample Nos. 4 and 8 are also shown for comparison.

[0090]

[Table 3]

From Table 3, the combination of Ba and Ta,
In addition, it can be seen that a sufficient luminance maintenance ratio is realized even in a combination other than the combination of these and Zr.

Example 4 An electrode sample was prepared in the same manner as in Sample No. 4 of Table 1, except that an oxide of the element M shown in Table 4 was mixed with the starting material. When for these electrodes samples were subjected to X-ray diffraction, observed and M ^I M ^II O ₂ peak of the N-type crystals and peaks of the second component carbide, it was confirmed that oxynitride perovskite is generated Was.

These electrode samples were assembled into a discharge lamp in the same manner as in Example 1, and the same continuous lighting test as in Example 1 was performed. Table 4 shows the results. Table 4 also shows Sample No. 4 for comparison.

[0094]

[Table 4]

Table 4 shows that a sufficient luminance retention ratio can be obtained even when the compound of the element M is included. However, when the content of the M compound exceeds 10% by mass,
A decrease in the luminance maintenance ratio is observed.

Example 5 In the mixing step, the amount of carbon powder added was 1 to the starting material.
An electrode sample was prepared in the same manner as in Sample No. 4 except that the amount was set to 5% by mass and the firing time in the oxynitride generation treatment was set to 5 hours. FIG. 5 shows an X-ray diffraction pattern of this sample. As shown in the figure, the sample, oxynitride perovskite _{^{(M I M I I O 2}} N type crystal)
In addition, the composite oxide ^{_{(M I 5 M II 4 O}} 15 type crystals) were present. However, the maximum peak intensity of M ^I ₅ M ^II ₄ O ₁₅ type crystal was 50% or less of the maximum peak intensity of M ^I M ^II O ₂ N type crystals. A continuous lighting test was performed by incorporating this electrode sample into a discharge lamp, and the luminance maintenance ratio was measured.
% And a sufficiently high value were obtained.

In Examples 1 to 5, the samples of the present invention all had a specific resistance at room temperature of 10 ^-6 to 10.
It was in the range of ³ Ωm.

[0098]

The electron-emitting material of the present invention has good electron-emitting characteristics, less evaporation at high temperatures, and
Low consumption during ion sputtering. Therefore, for example, when applied to an electrode of a discharge lamp, a discharge lamp with less blackening of the tube wall and a long life is realized.

[Brief description of the drawings]

FIG. 1 is a flowchart showing steps in producing the electron-emitting material of the present invention as a powder or a sintered body.

FIG. 2 is a flowchart showing steps in producing the electron emission material of the present invention as a sintered body.

FIG. 3 is a flowchart showing steps in producing the electron emission material of the present invention as a powder or a sintered body.

FIG. 4 is an X-ray diffraction pattern of the electron-emitting material of the present invention.

FIG. 5 is an X-ray diffraction pattern of the electron-emitting material of the present invention.

FIG. 6 is a cross-sectional view illustrating a configuration example of an electrode.

FIG. 7 is a cross-sectional view illustrating a configuration example of a discharge lamp that operates with a hot cathode.

FIG. 8 is a cross-sectional view showing a configuration example of a discharge lamp of a cold cathode operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Container 2 Electron emission material 2A Electron emission material film 3 Mercury dispenser material 4 Metal pipe 5 Lead wire 6 Lead wire enlargement part 6A Internal introduction wire 7 Conductive pipe 9 Valve 9A Phosphor 9B Stem 10 Discharge space

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Matsuoka Dai 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside TDC Corporation (72) Inventor Masatada Yodogawa 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDD Inside (72) Inventor Taku Harada 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation (56) References JP-A-63-252920 (JP, A) JP-A-7-153373 (JP) , A) JP-A-10-302714 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 1/02-1/44 H01J 9/02-9/18 H01J 61/06 -61/09

Claims (8)

(57) [Claims] 1. A first component comprising at least one of Ba, Sr and Ca, Ta, Zr, Nb, Ti and H
An electron emission material containing an oxynitride perovskite containing at least one of f and a second component as a metal element component. 2. When the first component is represented by M ^I and the second component is represented by M ^II , M is defined as the oxynitride perovskite.
^I M ^II O ₂ N type electron-emitting material according to claim 1 comprising crystals. 3. When the molar ratio of the first component is X and the molar ratio of the second component is Y with respect to the total of the first component and the second component, 0.8 ≦ X / Y ≦ 1. The electron-emitting material according to claim 1 or 2, wherein 4. The electron-emitting material according to claim 1, wherein a part of the second component is contained as a carbide and / or a nitride. 5. An element M (M is Mg, Sc, Y, La,
The electron-emitting material according to any one of claims 1 to 4, further comprising at least one of V, Cr, Mo, W, Fe, Ni, and Al) as a metal element component. 6. The method according to claim 1, wherein said element M is more than 0% by mass in terms of oxide.
The electron-emitting material according to claim 5, which contains 0% by mass or less. 7. The first component M ^I, when the second component expressed respectively _{^{M II, M I 4 M II}} 2 O 9 type crystals, M ^I M ^II ₂ O ₆ type crystals, M ^I M ^II O ₃ type _{^{crystal, M I 5 M II 4 O}} 15 type crystal, according to claim 6 comprising at least one M ^I ₇ M ^II ₆ O ₂₂ type crystals and _{^{M I 6 M II M II 4}} O 18 type crystals Any electron emitting material. 8. A resistivity 10 ^-6 to 10 ³ [Omega] m at room temperature
The electron-emitting material according to claim 1, wherein: