JP2003226956A - MgO VAPOR DEPOSITION MATERIAL AND PRODUCTION METHOD THEREFOR - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electron beam vapor deposition method, in which splash is hard to occur even on vapor deposition and the film properties of an MgO film to be deposited is improved. <P>SOLUTION: The vapor deposition material consists of polycrystals having an MgO purity of ≥99.0% and a relative density of ≥90.0%, and having a sulfur S content of 0.01 to 50 ppm. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a MgO vapor deposition material and a method for manufacturing the same, and more particularly to a technique suitable for forming a MgO film in an AC type plasma display panel.

[0002]

2. Description of the Related Art Conventionally, since MgO has excellent heat resistance, it has been mainly used as a heat-resistant material such as a crucible or a refractory brick, and it has been attempted to add a sintering aid to increase its mechanical strength. There is. As such a technique, for example, those described in Patent Documents 1 to 3 are known.

[0003]

[Patent Document 1] Japanese Patent Laid-Open No. 07-133149

[Patent Document 2] Japanese Patent No. 2961389

[Patent Document 3] Japanese Patent Publication No. 07-102988

[Patent Document 4] Japanese Unexamined Patent Application Publication No. 11-213875

[Patent Document 5] Japanese Patent Laid-Open No. 05-311412

[Patent Document 6] Japanese Patent Laid-Open No. 10-291854

[Patent Document 7] Japanese Unexamined Patent Publication No. 10-297955

[Patent Document 8] Japanese Patent Laid-Open No. 10-297956

[Patent Document 9] Japanese Patent Laid-Open No. 11-29857

[Patent Document 10] Japanese Patent Laid-Open No. 11-29355

[Patent Document 11] Japanese Patent Laid-Open No. 2000-63171

[Patent Document 12] Japanese Patent Laid-Open No. 09-235667

[Non-Patent Document 1] IEICE Trans. Electron., Vol.E82-C,
No.10, p.1804-1807, (1999)

In recent years, liquid crystal (Liquid Crystal Display: L)
CDs and other flat displays (Flat
Research and development and commercialization of Panel Display) are remarkable, and their production is also increasing rapidly. The development and practical use of color plasma display panels (PDPs) have also become active recently. PDP
Is easy to increase in size, is the shortest distance from a large-screen wall-mounted TV for high-definition, and is already a 60-inch diagonal PDP.
In the PDP, an AC type in which a metal electrode is covered with a glass dielectric material is predominant among PDPs in terms of an electrode structure.

In this AC type PDP, the surface of the glass dielectric layer is coated with a protective film having high heat of sublimation so that the surface of the glass dielectric layer is not changed by the ion bombardment sputtering and the discharge starting voltage does not rise. Since this protective film is in direct contact with the discharge gas, it plays a plurality of important roles in addition to the sputtering resistance. That is, the characteristics required for the protective film include sputtering resistance during discharge, high secondary electron emission ability (providing a low discharge voltage), insulation, and light transmission. As a material satisfying these conditions, MgO is generally used as an evaporation material, and an MgO film formed by an electron beam evaporation method or an ion plating method is used. This MgO protective film is
As described above, by protecting the surface of the dielectric layer from sputtering during discharge, it plays an important role in extending the life of the PDP, and it is known that the higher the film density of the protective film, the better the sputter resistance. (Non-patent document 1).

Further, as this protective film material (vapor deposition material), MgO single crystal and MgO polycrystal are known. Such techniques include those described in Patent Documents 6 to 11, for example. Further, in the technique described in Patent Document 4, the secondary electron emission efficiency of the protective film is improved by reducing the negative element component such as sulfur, and the display performance such as the discharge start delay of the light emitting cell and the writing operation failure is improved. It says that the problems can be improved. Here, as a method for removing the negative element component such as sulfur, after crystal growth (after pellet production), before the protective film formation, about 1.33 × 10 ⁻¹ Pa (10 ⁻³ to
rr) 1400 in the following high vacuum or atmosphere containing oxygen
Although it is proposed that the heat treatment needs to be performed at a temperature of not less than 0 ° C., the removal efficiency of sulfur was low in the above method in the case of the polycrystal and the single crystal obtained by the electrofusion method with the relative density of 90% or more.

The above-mentioned MgO polycrystal is generally produced by granulating, molding and firing MgO powder having an arbitrary purity and impurity composition obtained by a seawater method or a vapor phase method. On the other hand, single crystal Mg
O is generally obtained by melting MgO clinker having a purity of 98% or more or lightly burned MgO (sintered at 1000 ° C. or less) in an electric arc furnace (arc furnace), that is, after forming an ingot by electric melting, It is manufactured by taking out a single crystal part from this ingot and crushing it. MgO powder and M used as raw materials for producing these
The gO clinker and light burned MgO generally contain a sulfur S component as an impurity because of its manufacturing principle and the high reactivity specific to MgO.

[0008]

The electron beam evaporation method,
It has been found that the amount of impurity sulfur S released from the MgO vapor deposition material at the time of film formation by the ion plating method or the like has an adverse effect on the degree of splashing (splash) of the vapor deposition material. That is, as the amount of impurity sulfur S increases, the degree of splash generation increases, and if the splash level is large, the use efficiency of the amount of vapor deposition material that can be used for film formation decreases, resulting in an increase in material cost. there were. Further, if the amount of impurity sulfur S is large, it becomes difficult to control the crystal orientation and the fine structure of the obtained film, and further the dense deposition of the MgO film component on the substrate is hindered, resulting in a decrease in the film density. There was a problem of doing. When the MgO film density is lowered, problems such as a lowered refractive index, a lowered sputter resistance, a deteriorated discharge characteristic and an insulating property may occur.

Here, as the target material used in the sputtering method, the technique described in the above Patent Document 12 is known. When creating a target material used in the sputtering method, it is necessary to make this target material as dense as possible. On the other hand, when creating a vapor deposition material used in the electron beam vapor deposition method, the range of density required for the vapor deposition material is not so precise from the results of degassing measurement and film formation evaluation from this vapor deposition material. The inventors of the present application have confirmed that there is no need to manufacture the vapor deposition material, and the allowable range of the density of the vapor deposition material is relatively wide.

Further, although the target material and the vapor deposition material are not so different in terms of microstructure, there are great differences in terms of macro. That is, in the sputtering method, the target material is formed in a relatively large plate shape such as a disc or a square plate, whereas in the electron beam evaporation material, the evaporation material is formed in a small pellet shape. In the sputtering method in which cations such as argon knock out the film-forming material that is the target material at the atomic level and deposit it on the substrate, the target material is formed into a plate shape that is relatively larger than the film-forming target such as the substrate. This is to make the thickness distribution of the film obtained from the target material uniform.

On the other hand, in the electron beam method of depositing on the substrate by heating in the vapor phase by heating with an electron beam, the evaporation material is formed into small pellets by forming the evaporation material into a crucible of an electron beam evaporation apparatus. This is because it is sequentially supplied to. Further, in the electron beam evaporation method, there is an optimum size range at the time of evaporation from the viewpoint of the phenomenon called splash called the electron beam evaporation method and the film formation rate.

As described above, since the film forming mechanism of the sputtering method is different from that of the electron beam evaporation method, the film forming conditions are completely different and the obtained film quality is also different. That is, in the sputtering method, the composition of the obtained film is different depending on whether the target material is easily sputtered (sputter resistance), whereas in the electron beam evaporation method, whether the vapor deposition material is likely to be in a vapor phase state or not. The composition of the film varies depending on (vapor pressure). As a result, the composition of the film obtained from the target material and the vapor deposition material having exactly the same composition is different, and the amount of impurities taken into the film is also different.

Further, it is usually necessary to form the target material into a plate shape by sintering or the like and then grind it so that its surface roughness becomes about 1 μm or less using a surface grinder or the like. This is because if there is a sharp portion in the target material, electrons tend to collect in that portion, the collision of argon ions concentrates, and a phenomenon called arcing occurs, resulting in a non-uniform film quality. This is to remove the pointed portion of. On the other hand, in the case of the vapor deposition material, the film formation rate can be increased by increasing the surface roughness of the vapor deposition material. Although this mechanism is unknown, it is considered that the increase in the evaporation area of the vapor deposition material is a major factor.

Therefore, the target material and the vapor deposition material are not similar to each other, and the fact that the conditions such as composition and shape are similar to each other means that the respective technologies are applied to the respective fields. It cannot be said.

The present invention has been made in view of the above circumstances, and aims to achieve the following objects. 1. To reduce the splash in the vapor deposition material. 2. Optimize the amount of sulfur S in the vapor deposition material. 3. To prevent a decrease in the film density of MgO. 4. Light transmission, spatter resistance, discharge characteristics,
To prevent deterioration of insulation.

[0016]

In the MgO vapor deposition material of the present invention, the MgO purity is 99.0% or more, the relative density is 90.0% or more, and the average sulfur S content is 0.01-5.
The above-mentioned problem was solved by making it a 0 ppm polycrystal pellet. In the present invention, it is also preferable that the polycrystalline pellet has a granular portion having a low sulfur S content and a grain boundary portion having a higher sulfur S content than the granular portion. The present invention also relates to sulfur S in the granular portion and the grain boundary portion.
It is also possible that the ratio of the contents of is greater than 5. In the method for producing a MgO vapor deposition material of the present invention, the above-mentioned problems are solved by using MgO powder having a sulfur S content of 0.01 to 50 ppm as a raw material to form polycrystalline pellets by a sintering method. In the present invention, it is desirable that the polycrystalline pellet be formed with a granular portion having a low sulfur S content and a grain boundary portion having a higher sulfur S content than the granular portion. The ratio of the content of sulfur S in the granular portion and the grain boundary portion of the present invention can be made larger than 5.

In the MgO vapor deposition material of the present invention, MgO
The purity is 99.0% or more, the relative density is 90.0% or more, and the sulfur S content is 0.01 to 50 ppm. AC type PD by Ting method
When a protective film of MgO such as P is formed, the degree of generation of splash is reduced, and the film characteristics can be improved as a protective film. This is considered to be because the gasification component is reduced and the splash is reduced by setting as described above. Here, the film characteristics include MgO film density, film thickness distribution, refractive index, spatter resistance, discharge characteristics (discharge voltage, discharge response, etc.), and insulation.

Here, when the sulfur S content is set to be less than 0.01 ppm, the strength of the vapor deposition material is insufficient, which is not preferable, and when the sulfur S content is set to be more than 50 ppm. During the film formation by the electron beam evaporation method, the ion plating method, etc., the occurrence of splash of the evaporation material increases, and as a result, the efficiency of the amount of the evaporation material that can be used for film formation decreases, resulting in As the cost increases, it becomes difficult to control the crystal orientation and the fine structure of the obtained film, and further, the dense deposition of the MgO film component on the substrate is hindered, resulting in a decrease in the film density. Therefore, it is not preferable.

In the MgO vapor deposition material of the present invention, MgO
With a purity of 99.0% or more and a relative density of 90.0% or more, and a sulfur S content average value of 0.01 to 50 ppm, a polycrystalline pellet having a degree of generation of splash as compared with a single crystal pellet is obtained. Can be reduced and the film characteristics can be improved as a protective film. This is based on the following knowledge obtained by the inventor of the present application. Splash particles from the single crystal MgO are flaky, which is presumed to be due to cleavage at the crystal plane. On the other hand, polycrystalline Mg
In O, the shape is irregular, which is presumed to be due to the progress of fracture at grain boundaries. Furthermore, since polycrystals are more brittle than single crystals, even if microcracks occur in the material, they will not immediately become splashes.
That is, it is considered that the polycrystalline MgO pellets can reduce the frequency of division of the pellets as compared with the single crystal MgO.

According to the present invention, the polycrystal has a granular portion (crystal grain portion) having a low sulfur S content and a grain boundary portion having a higher sulfur S content than the granular portion, whereby the splash of The degree of occurrence can be reduced and the film characteristics can be improved as a protective film. This is based on the following knowledge obtained by the inventor of the present application. From the results of various analyzes such as Examples described later, in the single crystal pellet, sulfur S, which is a gasification component, is present in the inside substantially uniformly. On the other hand, in the polycrystalline pellet, it was found that sulfur S, which is a gasification component, is unevenly distributed on the surface of the granular portion (grain boundary portion) and the surface of the pellet. In other words, when sulfur as one of the gasification components that cause gasification and volume expansion when heated is unevenly distributed inside the material, this gasification component causes volume expansion due to heating during ion beam deposition. Then
It is considered that this volume expansion causes microcracks in the pellets, and the microcracks trigger the splash.

However, since polycrystals are more brittle than single crystals, even if microcracks occur in the material, the splash does not immediately occur. Further, in that case, it is expected that the splash will be further less likely to occur because a path through which the gasification component escapes is formed. Therefore, it is considered that the polycrystal has a smaller splash amount than the single crystal.

The ratio of the content of sulfur S in the granular portion and the grain boundary portion of the present invention may be made larger than 5.
It has been found to be effective in further suppressing the splash.

Further, as described above, the ratio of the content of sulfur S in the granular portion and the grain boundary portion is preferably set to be larger than 5. Here, when the ratio of the content of sulfur S in both of the above parts is made smaller than 5, the amount of sulfur S which is a gasification component in the granular portion becomes too large, so that the sulfur S in the granular portion and the grain boundary portion is increased. This is not preferable because the difference in the content becomes small and the merit due to uneven distribution of the gasification component, that is, the merit that the gasification component escapes at the grain boundary portion during heating and the splash is reduced is reduced. Further, the sulfur content of the entire pellet increases, and the splash cannot be reduced, which is not preferable.

Further, in the present invention, the content of sulfur S in the granular portion of MgO is less than 0.01 element%, and the content of sulfur S in the grain boundary portion is about 0.03 element%. Can be here,
The values of the grain portion and the grain boundary portion are T of the polycrystalline body cross section.
It is obtained by composition analysis by EM-EDX (morphological observation with a transmission electron microscope). For reference, the existence form of sulfur S is ESCA (Electron Spectroscopy for
Chemical Analysis or XPS; X-ray Photoelectro
n Spectroscopy) was performed on the outermost surface of the sample and the interior sputter-etched with argon ions. Here, the ESCA analysis is to irradiate a sample with X-rays and measure the electron energy emitted at that time. Further, the average content of sulfur S contained in the sample is determined by the high-frequency melting of the sample, and the SO ₂ released at that time.
It was measured by the amount of infrared absorption of gas.

Here, the thickness of the grain boundary portion is 1 to 200 nm.
It is preferable that the degree is set. As a result, when heating,
When the sulfur S, which is a gasification component, expands in volume, there is a path for the gasification component to quickly escape to the outside of the pellets, so that splashing can be further suppressed. At this time, when the thickness of the grain boundary portion is set to be thinner than about 1 nm, the grain boundary portion having a relatively high concentration of sulfur S, which is a gasification component, cannot be sufficiently formed, so that the gasification component is not heated during heating. It is not preferable because it cannot be released promptly and the splash level increases. Further, when the thickness of the grain boundary portion is set to be thicker than about 200 nm,
Since the content of sulfur S, which is a gasification component, is too large, the splash degree increases, which is not preferable.

Further, in the present invention, the average crystal grain size of the polycrystalline pellets made of the MgO sintered body is 1 to 50.
It is 0 μm, and it is possible to have rounded pores having an average inner diameter of 10 μm or less in the crystal grains of the sintered body pellet. In this MgO vapor deposition material, since the sintered pellet of polycrystalline MgO has a fine crystal structure and it is possible to reduce the occurrence of defects in the crystal grain boundaries, the formed MgO film has excellent film characteristics. Have.

Further, according to the present invention, Si contained in a polycrystalline pellet made of a sintered body of polycrystalline MgO has an element concentration of 5000 ppm or less, an Al impurity has an element concentration of 300 ppm or less, and Ca of Ca Impurity is 2000 ppm or less in elemental concentration, Fe impurity is 400 ppm or less in elemental concentration, Cr, V and Ni impurities are 50 ppm or less in elemental concentration respectively, and Na and K impurities are 30 ppm in elemental concentration respectively. And the impurity of C is 300 ppm or less in element concentration,
It is possible that the Zr impurities have an element concentration of 150 ppm or less. In this MgO vapor deposition material, the formed Mg
Since the impurities contained in the O film are extremely small, this M
The film characteristics of the gO film can be further improved.

In the method for producing a MgO vapor deposition material according to the present invention, the MgO vapor deposition material as described above can be produced by using MgO powder having a sulfur S content of 0.01 to 50 ppm as a raw material.

In the present invention, the purity is 99.0% or more, the relative density is 90.0% or more, and the sulfur S content is 0.0.
MgO having an average particle size of 0.1 to 5 μm at 1 to 50 ppm
Using the powder as a raw material, mixing the powder, the binder and the organic solvent to prepare a slurry having a concentration of 45 to 75% by weight, and spray drying the slurry to obtain an average particle size of 5
The method may include a step of obtaining a granulated powder having a particle size of 0 to 300 μm, a step of putting the granulated powder in a predetermined mold and molding at a predetermined pressure, and a step of sintering the compact at a predetermined temperature. . The step of obtaining the granulated powder may be a general rolling granulation method.

At this time, as desulfurization treatment for the raw material powder MgO, the MgO powder and water are allowed to act on each other to form Mg (OH) ₂
After preparing a solution and separating sulfur S component as MgSO ₄ , it is baked in the atmosphere to remove water. Thereby, the average value of sulfur S content is 0.01 to 50 ppm
The desulfurized MgO powder can be produced. here,
The average value of sulfur S content means the average content of sulfur S in the whole pellet, and is different from the respective sulfur S content in the granular portion and the grain boundary portion.

When a polycrystalline MgO vapor deposition material is produced by this method, the above MgO purity is 99.0% or more, the relative density is 90% or more, and the sulfur S content is 0.01 to 50 ppm. It is possible to obtain a MgO vapor deposition material composed of polycrystalline pellets of the body.

Further, 750 to 2000 kg of granulated powder
/ Cm is preferable to CIP molding or granulating the powder to uniaxial pressing at a pressure of 1000～3000Kg / cm ² at a ^second pressure, also the compact 1250-135
After primary sintering at a temperature of 0 ° C., the temperature is raised to 1500 to 17
Secondary sintering is preferably performed at a temperature of 00 ° C.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION The first embodiment of the MgO vapor deposition material and the method for producing the same according to the present invention will be described in detail below.

The MgO vapor deposition material of this embodiment has a sulfur S content of 0.01 to 50 ppm and a MgO purity of 9%.
9.0% or more, more preferably 99.5% or more, 9
It is composed of polycrystalline MgO sintered pellets having a relative density of 9.9% or more and a relative density of 90% or more, more preferably 97% or more and 98% or more. The average grain size of the sintered pellets is 1 to 500 μm, and the polycrystalline pellets of the sintered body have rounded pores with an average inner diameter of 10 μm or less.

Here, when the sulfur S content is set lower than 0.01 ppm, the strength of the vapor deposition material is insufficient, which is not preferable, and when the sulfur S content is set higher than 50 ppm, the electron When a film is formed by the beam evaporation method or the ion plating method, the degree of generation of splash of the evaporation material is increased, and as a result, the usage efficiency of the amount of the evaporation material that can be used for film formation is reduced, resulting in a material cost reduction. Since the crystal orientation and the fine structure of the obtained film are difficult to control, and the dense volume of the MgO film component on the substrate is obstructed as a result, the film density decreases as a result. Not preferable.

The average crystal grain size of the polycrystalline pellets made of a sintered body is set to 1 to 500 μm because the MgO structure can be controlled within this grain size range. In addition, the average inner diameter of the pores in the crystal grains of the sintered pellet is 10 μm.
The reason for this is that it is difficult to control the structure of MgO when the thickness exceeds 10 μm.

The polycrystalline pellet made of a sintered body is a granular portion (crystal grain portion) in which the polycrystalline body has a low sulfur S content.
And a grain boundary portion having a higher sulfur S content than the grain portion around the grain portion (crystal grain portion). Specifically, the sulfur S content is 0.000001 to 0.0, respectively, in the granular portion.
The content of sulfur S in the grain boundary portion is preferably about 0.01 to 0.1 element%.

Here, when the content of sulfur S in the granular portion is not set in the range of about 0.000001 to 0.005 element%, the average amount of sulfur S becomes large and the splash is extremely severe. And the desulfurization treatment of the raw material becomes extremely long, resulting in an increase in manufacturing cost, which is not preferable. Further, if the content of sulfur S in the grain boundary portion is not set in the range of about 0.01 to 0.1 element%, the effect of reducing the splash becomes insufficient, which is not preferable.

Further, as described above, it is preferable that the ratio of the content of sulfur S in the granular portion and the grain boundary portion is set to be larger than 5. Here, when the ratio of the content of sulfur S in both of the above parts is set to be less than 5,
Since the sulfur S, which is the gasification component in the granular portion, becomes too large, the difference in the sulfur content between the granular portion and the grain boundary portion becomes small, and the merit due to uneven distribution of the gasification component,
It is not preferable because a pass through which the gasification component escapes is formed in the grain boundary portion during heating, and the advantage of reducing splash is reduced. Further, the sulfur content of the entire pellet increases, and the splash cannot be reduced, which is not preferable. In addition, when the ratio of the sulfur S content is made smaller than the above value and the average of the sulfur S content is not made small, the swelling of the gasification component considered to occur along the grain boundary portion outside the pellet Could be blocked,
Microcracks may be generated due to the volume expansion of the gasification component, which may increase the degree of splash generation, which is not preferable.

The thickness of the grain boundary portion is 1 to 200 nm.
It is preferable that the degree is set. At this time, when the thickness of the grain boundary portion is set to be thinner than about 1 nm, the grain boundary portion having a relatively high concentration of sulfur S, which is a gasification component, cannot be sufficiently formed, so that the gasification component is not heated during heating. It is not preferable because it cannot be released promptly and the splash level increases. The thickness of the grain boundary portion is 200 nm
When it is set to be thinner than the above range, the content of sulfur S, which is a gasification component, is too large, and the splash degree increases, which is not preferable.

Impurities (Si, Al, Ca, Fe, Cr, V, Ni, N contained in the sintered pellet of polycrystalline MgO
The total content of a, K, C and Zr) is 10,000 pp
It is preferably m or less. In addition, the individual contents of the above impurities are as follows:
1 is an element concentration of 300 ppm or less, Ca impurities are an element concentration of 2000 ppm or less, Fe impurities are an element concentration of 400 ppm or less, Cr, V and N
The impurity concentration of i is 50 ppm or less, and the impurity concentration of Na and K is 30 pp.
It is preferable that the impurity concentration of C is m or less, the impurity concentration of C is 300 ppm or less in element concentration, and the impurity concentration of Zr is 150 ppm or less in element concentration. When each of the above impurities exceeds the above value in elemental concentration, when a glass substrate on which a MgO vapor deposition material is formed by an electron beam vapor deposition method is incorporated into a panel, variations in film quality occur, and therefore electrical characteristics such as driving There is a problem that the voltage becomes high or becomes unstable.

A method of manufacturing the MgO vapor deposition material thus configured will be described.

First, desulfurization M having a sulfur S content of 0.01 to 50 ppm is prepared from MgO powder having a purity of 99.0% or more.
Make gO powder. Here, the MgO powder and water are allowed to act to prepare a Mg (OH) ₂ solution, and the sulfur S component is added to the M
After being separated as gSO ₄ , it is baked in the air to remove water, and thus desulfurized MgO powder having a small amount of sulfur component is obtained.

The sulfur S content is 0.01 to 50 ppm
Then, the desulfurized MgO powder, the binder and the organic solvent are mixed to prepare a slurry having a concentration of 45 to 75% by weight. The concentration of the slurry is limited to 45 to 75% by weight because when it exceeds 75% by weight, there is a problem that stable granulation is difficult because the above slurry is a non-aqueous system.
It is because a dense MgO sintered body having a uniform structure cannot be obtained when the amount is less than 1. That is, when the slurry concentration is limited to the above range, the viscosity of the slurry is 200 to 1000 cps.
Therefore, the granulation of the powder by the spray dryer can be stably carried out, and further, the density of the molded body becomes high, and the dense sintered body can be manufactured.

The average particle size of the desulfurized MgO powder is 0.1.
It is preferably in the range of ˜5 μm. The average particle size of the MgO powder was limited to 0.1 to 5 μm because it was 0.1 μm.
If it is less than 5, the powder will be too fine and agglomerate, resulting in poor handling of the powder and making it difficult to prepare a high-concentration slurry of 45% by weight or more. If it exceeds 5 μm, it will be difficult to control the fine structure. , Because a dense sintered body pellet cannot be obtained. Further, if the average particle size of the MgO powder is limited to the above range, there is an advantage that desired sintered body pellets can be obtained without using a sintering aid. It is preferable to use polyethylene glycol or polyvinyl butyral as the binder and ethanol or propanol as the organic solvent. Binder is 0.2 to 2.5% by weight
It is preferable to add.

The wet mixing of the MgO powder, the binder and the organic solvent, especially the wet mixing of the MgO powder and the organic solvent as the dispersion medium is carried out by a wet ball mill or a stirring mill. In the wet ball mill, when using ZrO ₂ balls, a large number of ZrO ₂ balls having a diameter of 5 to 10 mm are used for wet mixing for 8 to 24 hours, preferably 20 to 24 hours. The diameter of the ZrO ₂ ball is 5-10 m
The reason why it is limited to m is that the mixing is insufficient if it is less than 5 mm, and there is a problem that impurities increase if it exceeds 10 mm. Further, the reason that the mixing time is as long as 24 hours at the longest is that the generation of impurities is small even after continuous mixing for a long time. On the other hand, in a wet ball mill, when resin balls containing an iron core are used, the diameter is 10 to 15 m.
It is preferable to use m balls.

In the stirring mill, ZrO _{2 having} a diameter of 1 to 3 mm is used.
It is wet-mixed for 0.5 to 1 hour using a ball. Z
The reason why the diameter of the rO ₂ ball is limited to 1 to 3 mm is
This is because if it is less than 1 mm, the mixing becomes insufficient.
This is because there is a problem that impurities increase when the thickness exceeds mm. The reason why the mixing time is as short as 1 hour at the longest is that if it exceeds 1 hour, not only the mixing of the raw materials but also the work of crushing is performed, which causes the generation of impurities, and the mixing time of 1 hour is sufficient. . In addition, mixing powder and binder liquid /
Granulation may be carried out by a general rolling granulation method. In this case, there is an advantage that the process is simplified because there is no need to separate the ball and the like after the process.

Next, the above slurry is spray-dried to obtain a granulated powder having an average particle size of 50 to 300 μm, preferably 50 to 200 μm, and the granulated powder is put into a predetermined mold and molded at a predetermined pressure. To do. Here, the average particle size is 50 to 300 μm.
The reason why it is limited to m is that if it is less than 50 μm, the moldability is poor, and if it exceeds 300 μm, the density of the molded product is low and the strength is low. The spray drying is preferably carried out using a spray dryer, and the predetermined mold is a uniaxial press machine or a cold isostatic molding machine (CIP (Co
ld Isostatic Press) molding equipment) is used. With a uniaxial press, the granulated powder is 750-2000 kg / cm
^2, preferably uniaxial pressing at a pressure of 1000~1500kg / cm ^2, the CIP molding apparatus, granulated powder 1000~3000kg / cm ^2, preferably 150
CIP molding is performed at a pressure of 0 to 2000 kg / cm ² .
The pressure is limited to the above range in order to increase the density of the molded body, prevent deformation after sintering, and make post-processing unnecessary.

Further, the compact is sintered. It is preferable to degrease the molded body at a temperature of 350 to 620 ° C. before sintering. This degreasing treatment is performed in order to prevent color unevenness after sintering of the molded body, and it is preferable to perform the degreasing treatment sufficiently for a long time. Sintering is carried out at a temperature of 1250 to 1350 ° C. for 1 to 5 hours, followed by further heating to 1500 to 17
It is performed by two-stage sintering consisting of secondary sintering performed at a temperature of 00 ° C. for 1 to 10 hours.

When the temperature of the molded body is raised for the primary sintering, the sintering starts at 1200 ° C. and progresses considerably at 1350 ° C. By performing primary sintering at this temperature, even if the grain size is large, there is no unevenness in sintering between the surface and the inside (difference in microstructure), and by performing secondary sintering at a temperature of 1500 to 1700 ° C. Sintered pellets having a density close to 100% are obtained. This sintered body pellet has a few pores, but these pores are not in the grain boundaries that affect the characteristics of the MgO sintered body, but in the crystal grains that hardly affect the characteristics of the MgO sintered body. Exists. As a result, when the MgO sintered body pellets having the sulfur S content of the present invention were formed into a film on the plasma display panel, the splash was small,
An MgO film having good film characteristics can be obtained.

Further, in the case of sintering a compact having a large shape, further densification can be achieved by slowing the temperature rising rate during the two-step sintering to 20 to 30 ° C./hour. Further, in the sintering at normal pressure, if the sintering temperature is less than 1500 ° C., the densification cannot be sufficiently performed, but the sintering temperature is 1500.
Since it is possible to obtain a high-density sintered body at a temperature of ℃ or higher, hot isostatic pressing (HIP (Hot Isostatic Press
) Method and hot pressing method, etc.

In the MgO vapor deposition material and the method for producing the same according to this embodiment, the MgO purity is 99.0% or more, the relative density is 90.0% or more, and the sulfur S content average value is 0.0.
By making it 1 to 50 ppm of polycrystalline pellets,
When the MgO vapor deposition material is used to form a MgO protective film such as an AC type PDP by an electron beam vapor deposition method or an ion plating method, the occurrence of splash is reduced as compared with a single crystal pellet. The film characteristics can be improved also as a protective film. This is considered to be because the gasification component is reduced and the splash is reduced by setting as described above.

This prevents an increase in the occurrence of splash of the vapor deposition material during the film formation by the electron beam vapor deposition method or the ion plating method, and as a result, the use of the vapor deposition material amount which can be used for the film formation. It is possible to prevent a decrease in efficiency and, as a result, to reduce the material cost, prevent the control of the crystal orientation and the fine structure of the obtained film from becoming difficult, and further to make the MgO film component dense on the substrate. As a result, the film density can be prevented from being lowered.

Further, in the MgO vapor deposition material of the present embodiment, the splash particles from the single-crystal MgO are in the form of flakes which are presumed to be due to the cleavage at the crystal plane, while the polycrystalline MgO is used. Then, this is presumed to be due to the progress of fracture at the grain boundaries, and it is considered that the splash is reduced because the shape is irregular. further,
Since polycrystals are more brittle than single crystals, even if microcracks occur in the material, they do not immediately become splashes. That is, in the polycrystalline MgO pellets compared to single crystal MgO, the pellets themselves are divided. It is considered that the splash can be reduced by reducing the frequency of damage.

In this embodiment, the polycrystal is sulfur S.
By having a granular portion having a low content (crystal grain portion) and a grain boundary portion having a higher sulfur S content than the granular portion, the generation degree of splash is reduced and the film characteristics are improved even as a protective film. be able to. From the results of various analyses, it can be seen that the sulfur S, which is a gasification component, is almost uniformly present inside the single crystal pellet, whereas the sulfur S, which is a gasification component, is almost uniformly present inside the polycrystalline pellet. It is thought that this is due to uneven distribution on the boundary surface) and the pellet surface.

That is, inside the material, one of the gasification components that causes gasification and volume expansion when heated is
Due to the uneven distribution of sulfur S as a component, even if this gasified component expands in volume by heating during electron beam evaporation, microcracks of the pellets generated by this volume expansion are generated along the grain boundary part. It is considered that it is possible to reduce that the microcracks directly trigger the splash.

Furthermore, since polycrystals have higher brittleness than single crystals, even if microcracks occur in the material, the splash does not immediately occur. Further, in that case, it is expected that the splash will be further less likely to occur because a path through which the gasification component escapes is formed. Therefore, it is considered that the polycrystal has a smaller splash amount than the single crystal.

In this embodiment, by setting the ratio of the content of sulfur S in the granular portion and the grain boundary portion as described above, the sulfur in the granular portion and the grain boundary portion is set as described above. The ratio of the S content can be set, and not only the brittleness of the material but also the sulfur S content as a gasification component that triggers the splash can be reduced, which is effective for further suppressing the splash. is there.

Further, the thickness of the grain boundary portion is 1 to 200 nm.
By setting the degree to a certain extent, when the sulfur S, which is a gasification component, expands in volume during heating, there is a path for the gasification component to quickly escape to the outside of the pellets, so that it is possible to further prevent splashing. At this time, when the thickness of the grain boundary portion is set to be thinner than about 1 nm, the grain boundary portion having a relatively high concentration of sulfur S, which is a gasification component, cannot be sufficiently formed, so that the gasification component is not heated during heating. It is not preferable because it cannot be released promptly and the splash level increases. The thickness of the grain boundary portion is 200n
When it is set to be thinner than about m, the content of sulfur S, which is a gasification component, is too large, so that the splash degree increases, which is not preferable.

The second embodiment of the MgO vapor deposition material and the method for producing the same according to the present invention will be described in detail below.

Also in this embodiment, as in the first embodiment, the sulfur S content is set to 0.01 to 50 ppm,
After electrolysis of desulfurized MgO powder having a purity of 99.0% or more and gradual cooling into an ingot, the single crystal part is taken out from the ingot and crushed, and the center diameter is about 5 m with a diameter of about 2 to 8 mm.
m plate-shaped single crystal pellets are prepared. As a result, similar to the first embodiment, the sulfur S content of this embodiment is M
When gO single crystal pellets are deposited on a plasma display panel, Mg with less splash and good film properties is formed.
An O film can be obtained.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist.

First, a commercially available MgO powder / clinker was subjected to high frequency melting, and the sulfur S content was measured by the infrared absorption amount of SO ₂ gas released at that time. In addition, atomic absorption and ICP (Inductiveli Coupled Plasme emission pect)
The MgO purity was measured by rochemical analysis (inductively coupled plasma analysis method). Here, in the case of a clinker, it was pulverized into powder. Also, the MgO purity is ICP
Major impurity metal elements (Al, Si, F
e, Ca, Ni, Na, K, Zr, Cr, V, C) amount is shown as a value subtracted from 100%. The results are shown in Table 1.

By reacting these powders with water, Mg (O
H) ₂ solution is prepared, and after separating sulfur S component as MgSO ₄ , it is baked in the air to remove water,
A desulfurized MgO powder having a small amount of sulfur component was obtained. Table 1 also shows the amount of sulfur in each desulfurized MgO powder.

[0065]

[Table 1]

<Examples 1 to 4> 1% by weight of polyethylene glycol as a binder was added to desulfurized MgO powder (average particle size 0.3 μm) subjected to the desulfurization treatment shown in Table 1, and methanol denatured alcohol was added. A slurry containing the above as a dispersion medium was prepared to have a concentration of 30% by weight. Then, this slurry was wet-mixed for 24 hours with a ball mill (using a nylon-coated steel ball having a diameter of 5 to 20 mm), and then the dispersion medium was vaporized at 80 ° C. with a vacuum dryer, and subsequently crushed by a dry method. A granulated powder having an average particle size of 200 μm was obtained. Next, the obtained granulated powder is uniaxially molded by a press machine,
1000 kg / cm ² at an outer diameter 6.7Mmfai, thickness 2.
It was molded to 0 mm. Further, this molded body was placed in an electric furnace and subjected to primary calcination in the atmosphere at 1300 ° C. for 1 hour and then secondary calcination at 1650 ° C. for 3 hours. The obtained polycrystalline sintered body pellet has an outer diameter of 5.0 ± 0.5 mmφ and a thickness of 1.6 ± 0.2 m.
It was m. The disks of this sintered body were referred to as Examples 1 to 4.

Example 5 The desulfurized MgO powder subjected to the desulfurization treatment shown in Table 1 was electromelted and gradually cooled to form an ingot, and the single crystal part was taken out from the ingot and crushed, A plate-like single crystal pellet having a diameter of 2 to 8 mm and a center diameter of about 5 mm was obtained, and this was set as Example 5.

<Comparative Examples 1 to 4> M before the desulfurization treatment
Polycrystalline sintered body pellets were obtained in the same manner as in Examples 1 to 4 using gO powder, and were used as Comparative Examples 1 to 4.

Comparative Example 5 MgO Before Desulfurization Treatment
A plate-like single crystal pellet was obtained in the same manner as in Example 5 using the powder, and this was used as Comparative Example 5.

<Comparative Test and Evaluation> (a) Measurement of Relative Density and Sulfur Content The relative densities of the pellets obtained in Examples 1 to 5 and Comparative Examples 1 to 5 were measured in toluene by the Archimedes method. Moreover, the amount of sulfur in the MgO pellets was measured in the same manner as the MgO powder. The results are shown in Table 2.

(B) Splash evaluation The splash test of the MgO vapor deposition material was carried out by depositing the hemispherical hearth (diameter 50 mm, depth 25 mm) of the electron beam vapor deposition apparatus in Examples 1-5 and Comparative Examples 1-5. The material is charged and the ultimate vacuum is 2.66 × 10 ⁻⁴ Pa (2.0 × 1
0 ^-6 Torr), _{O 2} partial pressure 1.33 × ¹⁰ -2 Pa
The accelerating voltage is 1 with the atmosphere of (1.0 × 10 ⁻⁴ Torr).
The MgO vapor deposition material was heated by irradiating it with an electron beam of 0 kV and a beam scan area of about 40 mmφ. In addition,
The electron beam current amount was held at 90 mA for 10 min, the state of the hearth at that time was directly observed with a digital video camera, and the number of scattered particles was counted to evaluate.
The results are shown in Table 2.

(C) Evaluation of Sputtering Resistance Using the MgO vapor deposition materials obtained in Examples 1 to 5 and Comparative Examples 1 to 5, an ultimate vacuum degree was obtained on a silicon wafer with a thermal oxide film having a film thickness of 1000Å. 2.66 x 10 ^-4 Pa
(2.0 × 10 ⁻⁶ Torr), O ₂ partial pressure 1.33 × 10
^-2 Pa (1.0 x 10 ^-4 Torr), substrate temperature 200
At a temperature of 400 ° C, a distance between the MgO vapor deposition material and the substrate of 400 mm, and a film forming rate of 15 Å / sec.
A thin film was obtained. This MgO thin film was etched from the film surface with Ar ions (2 kV), and the sputtering resistance was evaluated by the value Sp obtained by dividing the film thickness by the time until the entire film was etched. Here, the time for etching the entire film is the time until the element amount curves of Mg of the film component and Si of the substrate component intersect. Further, it is indicated that the smaller the Sp value, the better the spatter resistance. The results are shown in Table 2.

[0073]

[Table 2]

From these results, MgO of Examples 1-5
When the vapor deposition material is used, the splash is as small as one digit, and the Sp value is 11.0 or less, whereas when the MgO vapor deposition material of Comparative Examples 1 to 5 is used, the splash is two digits. And the Sp value is 11.0 or more, which shows that the sputter resistance is lowered.

(D) Hardness of single crystal and polycrystal (brittleness of material) Vickers hardness of Example 3 which is a polycrystal pellet by comparative sintering method and Example 5 which is a monocrystal pellet by electrofusion method (Hv) and fracture toughness (K _IC ) were measured.
The Vickers hardness (Hv) was 608 ± 35 and 698 ± 51 (measured value) in Example 3 and Example 5, respectively.
In Example 5, which is a single crystal, it is as high as about 15%, while the fracture toughness (K _IC ) is 1.91 MPa.
In Example 5, which is a single crystal with m ^1/2 and 1.26 Mpa · m ^1/2 (measured value), it is as low as 34%, and once microcracks are generated, they propagate immediately and the vapor deposition material fragments scatter (splash). It is thought to occur easily.

(E) Splash Comparison Test Based on Crystalline Similar to the splash evaluation in (b) above, a splash test was carried out on polycrystalline pellets of Example 3 and single crystal pellets of Example 5. The splash evaluation here is almost the same as the content described above, but the value when the electron beam current value was sequentially increased to 30 to 240 mA and each current value was held for 1 min was shown. The result is shown in FIG.

From the result of FIG. 1, compared with the single crystal pellet,
It can be seen that splash generation is less than half in Example 3 which is a polycrystalline pellet. In addition, the splash particles at this time were examined. The result is shown in FIG.

According to FIG. 2, the splash grains from the single crystal were flaky, and it is presumed that this was because cleavage occurred at the crystal plane. On the other hand, the polycrystal has an irregular shape, which is presumed to be due to the progress of fracture at the grain boundaries. It is considered that the single crystal has gasification components uniformly inside, while the polycrystal is unevenly distributed at the surface / grain interface (various analysis results), and the volume expansion due to heating of the gasification components inside the material triggers the splash. To be However, since polycrystals are more brittle than single crystals, even if microcracks occur in the material, the splash does not immediately occur. Further, in that case, it is expected that the splash will be further less likely to occur because a path through which the gasification component escapes is formed. Therefore, it is considered that the polycrystal had a smaller splash amount than the single crystal (Table 2, FIG. 1). As described above, the brittleness of the material is also important, but Table 2 shows that the reduction of the amount of gasification component that triggers the splash is more effective by further suppressing the splash.

(F) Evaluation of Uneven Distribution of Gasification Component (Sulfur S) Next, in the polycrystalline pellet of Example 4, the following composition and morphology were applied to the grain / grain boundary portion, the outermost surface, and the whole. An analysis was done.

1. Grain boundary / grain part analysis: TEM-EDX
(Transmission electron microscope morphological observation) analysis point 30 nm
It was done with φ. 2. Outermost surface analysis; evaluated by ESCA. Analysis of the surface after cleaning the sample surface by sputter etching (etching of about 0.5 nm from the outermost surface) for 0.5 minutes with argon ions. The analysis depth is about 0.5-5 nm. 3. Overall analysis: The whole sample was subjected to high frequency melting, and measured by the infrared absorption amount of SO ₂ gas released at that time. The results are shown in Tables 3 and 4 and FIG. FIG. 3 is a cross-sectional TEM photograph of a sample, and in the figure, reference numerals 1 to 1
5 indicates a measurement point, and points 1 to 3 are grain boundary portions,
The points 4 and 5 are located in the crystal grain portion (granular portion). In addition, points 1 to 5 are indicated by # 1 to # 5 in the table.

[0081]

[Table 3]

[Table 4]

<Results> It was confirmed that 0.03 element% of sulfur S was unevenly distributed in the grain boundary portion, but the concentration was too low in the grain portion and was below the detection limit at which it could not be directly detected. Since sulfur S on the outermost surface of the polycrystal is present in the form of sulfate in an amount of 0.9 element%, it is presumed that the same is true at the grain boundaries. On the other hand, in the infrared absorption analysis, sulfur S is 20 ppm (0.
002 wt%), the estimated sulfur content is 0.0
Since the content is 0016 element% or less, it is understood that an extremely large amount of S is present in the grain boundary and the content ratio of sulfur in the grain portion and the grain boundary portion is 18 times or more.

As described above, from the results of Tables 3 and 4, almost no gasification component is present in the crystal grain portion (granular portion), and most of the gasification component is unevenly distributed in the grain boundary portion. I understand.

[0084]

According to the MgO vapor deposition material of the present invention, MgO
The purity is 99.0% or more, the relative density is 90.0% or more, and the sulfur S content is 0.01 to 50 ppm. AC type PD by Ting method
When a MgO protective film such as P is formed, the degree of occurrence of splash is reduced, and the protective film has a MgO film density of
It is possible to improve film characteristics such as film thickness distribution, light transmission, sputtering resistance, discharge characteristics (discharge voltage, discharge response, etc.), and insulation. Moreover, in the manufacturing method of the MgO vapor deposition material of this invention, sulfur S content is 0.01-5.
By using 0 ppm MgO powder as a raw material,
It is possible to manufacture the MgO vapor deposition material as described above.

[Brief description of drawings]

FIG. 1 shows the results of a splash test in Examples of a MgO vapor deposition material and a method for manufacturing the same according to the present invention, and is a graph of the number of splash particles with respect to an electron beam current value.

FIG. 2 shows results of a splash test in Examples of the MgO vapor deposition material and the method for producing the same according to the present invention, and is images of splash pieces in single crystals and polycrystals.

FIG. 3 shows the results of uneven distribution of gasification components in the examples of the MgO vapor deposition material and the method for producing the same according to the present invention, and shows the positions of measurement points in a TEM photograph of a sample cross section.

[Explanation of symbols]

1-5 measurement points

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Ginjiro Toyoguchi             1002-14 Mukoyama, Naka-machi, Naka-gun, Ibaraki Prefecture             Terari Co., Ltd.             Inside (72) Inventor Shoro Kuromitsu             1002-14 Mukoyama, Naka-machi, Naka-gun, Ibaraki Prefecture             Terari Co., Ltd.             Inside F-term (reference) 4K029 AA09 BA43 BC05 BC08 BD00                       CA01 CA03 DB05 DB08 DB21                       DD03                 5C027 AA07                 5C040 GE09

Claims (6)

[Claims] 1. The MgO purity is 99.0% or more, the relative density is 90.0% or more, and the sulfur S content average value is 0.01.
A MgO vapor deposition material characterized in that it is a polycrystalline pellet of ˜50 ppm. 2. The Mg according to claim 1, wherein the polycrystalline pellet has a granular portion having a low sulfur S content and a grain boundary portion having a higher sulfur S content than the granular portion.
O vapor deposition material. 3. The MgO vapor deposition material according to claim 2, wherein the ratio of the content of sulfur S in the granular portion and the grain boundary portion is larger than 5. 4. MgO powder having a purity of 99.0% or more and a sulfur S content of 0.01 to 50 ppm is used as a raw material to form polycrystalline pellets by a sintering method.
Manufacturing method of vapor deposition material. 5. The MgO according to claim 4, wherein the polycrystalline pellet is formed with a granular portion having a low sulfur S content and a grain boundary portion having a higher sulfur S content than the granular portion. Manufacturing method of vapor deposition material. 6. The method for producing a MgO vapor deposition material according to claim 5, wherein the ratio of the content of sulfur S in the granular portion and the grain boundary portion is made larger than 5.