JP2000063171A - Polycrystalline mgo vapor depositing material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To scarcely cause splash and form an MgO film to be formed into an almost uniform thickness even by depositing a vapor by an electron beam vapor deposition method. SOLUTION: This MgO vapor depositing material comprises a sintered compact pellet of a polycrystalline MgO having >=99.90% of MgO purity, especially <=30 ppm content of carbon and >=98% relative density. Furthermore, contents of impurities contained in the sintered compact pellet of the polycrystalline MgO are respectively <=150 ppm each of Si and Al impurities expressed in terms of element concentrations, <=200 ppm of Ca impurity expressed in terms of the element concentration, <=50 ppm of Fe impurity expressed in terms of the element concentration, <=10 ppm each of Cr, V and Ni impurities expressed in terms of the element concentrations, <=20 ppm each of Na and K impurities expressed in terms of the element concentrations and <=150 ppm of Zr impurity expressed in terms of the element concentration.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polycrystalline M suitable for forming an MgO film of an AC type plasma display panel.
It relates to a gO vapor deposition material.

[0002]

2. Description of the Related Art In recent years, liquid crystal (Liquid Crystal)
R & D and commercialization of various flat displays including Al Display (LCD) are remarkable.
Its production is also increasing rapidly. The development and commercialization of color plasma display panels (PDPs) have also become active recently. PDPs tend to be large in size and are at the shortest distance from large-screen wall-mounted TVs for high-definition televisions, and trial production of PDPs with a diagonal size of 40 inches is already underway. PDPs are classified into an AC type in which a metal electrode is covered with a glass dielectric material and a DC type in which a metal electrode is exposed in a discharge space in terms of an electrode structure.

At the beginning of the development of this AC type PDP, since the glass dielectric layer was exposed in the discharge space, it was directly exposed to a discharge, and the surface of the dielectric layer was changed by the sputtering of ion bombardment, so that the discharge starting voltage was increased. It was rising. Therefore, attempts have been made to use various oxides having high heat of sublimation as protective films for this dielectric layer. This protective film plays an important role because it is in direct contact with the discharge gas. That is, the characteristics required for the protective film are low discharge voltage, sputtering resistance during discharge, fast discharge response, and insulation. MgO is used for the protective film as a material satisfying these conditions. This protective film made of MgO protects the surface of the dielectric layer from sputtering during discharge,
Plays an important role in extending the life of the.

Currently, as the protective film of the AC type PDP,
An MgO film formed by an electron beam evaporation method using a crushed single crystal MgO as an evaporation material is known. The MgO film formed by this electron beam evaporation method can be formed at a high speed of 1000 angstroms / minute or more. Regarding the crystal orientation of the formed MgO film, the film oriented to the (111) plane can be driven with the lowest sustaining voltage, and further exists in the film (11
1) It is said that the emission ratio of secondary electrons increases and the drive voltage decreases as the amount of planes increases. The above single crystal Mg
The crushed product of O is obtained by melting MgO clinker having a purity of 98% or more or light-baked MgO (MgO sintered at 1000 ° C. or less) in an electric furnace (arc furnace), that is, after forming an ingot by electrofusion, It is manufactured by crushing and taking out a single crystal part from this ingot.

[0005]

However, in the electron beam evaporation method using the conventional crushed single crystal MgO as an evaporation material, the single crystal MgO is produced by arc melting with a carbon electrode rod. Amount of carbon is 100p
It exists above pm, and there is a considerable amount of carbon in the film deposited by electron beam. If a large amount of carbon is present in the MgO film, during plasma discharge, the electric charges existing in the vicinity of the film surface layer are easily incorporated (trapped) into the film, the frequency of electron collisions decreases, and the emission coefficient of secondary electrons decreases. There was a problem that the discharge voltage had to be increased. Also, in order to locally apply high energy to the vapor deposition material,
There is a problem that vapor deposition of fine powder is scattered (splash) and vapor deposition efficiency is reduced. It is believed that increasing the size of the vapor deposition material is effective in preventing this splash, but as a manufacturing process for single crystal MgO, it is left to stand for a long time after electric melting and then the large ingot is cooled. Then, there is a step of crushing the single crystal portion from the ingot and taking it out, and sizing. At that time, the freshly crushed surface has high activity, and moisture and carbon dioxide in the atmosphere adhere for a long time, so these moisture and carbon dioxide are considerably released in the degassing step before vapor deposition. Deaeration requires a considerable amount of time and is regarded as a problem in improving productivity. The current particle size of the crushed product is 1 to 5 m
It was difficult to stably secure particles larger than m with good yield. Further, in the electron beam evaporation method using the conventional crushed single crystal MgO as an evaporation material, it is difficult to uniformly form an MgO film on a large-area glass dielectric layer, which causes a problem in film thickness distribution. there were. As a result, MgO
When the glass dielectric layer on which the film is formed is incorporated into the PDP, there is a problem that the electrical characteristics such as the discharge starting voltage and the sustaining voltage become higher or change.

On the other hand, MgO clinker and light burned MgO often use MgCl2 obtained from seawater as a raw material, and MgCl2 contains a relatively large amount of Ca, Si and Fe.
Since such impurities are included in the single crystal M
Remains in gO. Further, in the ingot in the manufacturing process of the single crystal MgO, the amount of impurities continuously increases from the center of the ingot toward the surface portion. Therefore, the purity of the product varies very easily depending on how the single crystal portion is taken out. Therefore, there is a problem in that the stability and reliability of the purity of single crystal MgO are lacking.

In order to solve these points, single crystal MgO
Alternatively, a method of using polycrystalline MgO may be considered. However, high density polycrystalline MgO that has been densified by adding various sintering aids has a problem that defects are structurally present in the crystal grain boundaries, and that the higher the purity, the lower the density. It was On the other hand, a structure having few interatomic bond energies with few defects has a large amount of protrusion when the electron beam is irradiated during vapor deposition, unless the electrons of considerably high energy collide with each other and the Mg and O atoms are hard to pop out. Since it is small, the power of the electron beam must be increased to increase the film forming speed, which is a limit. As a result, when the MgO film is formed on the glass dielectric layer by the electron beam evaporation method using these polycrystalline MgO evaporation materials, the crystal orientation (11
1) The amount of orientation to the plane is reduced, and this glass dielectric layer is PD
Since the electrical characteristics when incorporated into P deteriorate, polycrystalline M
gO could not be used as a vapor deposition material.

An object of the present invention is to provide a polycrystalline MgO vapor deposition material capable of forming a film uniformly at a high speed without causing a splash even when vapor-deposited by an electron beam vapor deposition method. Another object of the present invention is to provide a polycrystalline MgO vapor deposition material capable of improving the film characteristics of the formed MgO film.

[0009]

The invention according to claim 1 is
MgO purity is 99.90% or more and carbon content is 30 pp
m or less and a relative density of 98% or more of polycrystalline Mg
It is a polycrystalline MgO vapor deposition material composed of sintered pellets of O. In the polycrystalline MgO vapor deposition material described in claim 1, a high-purity and high-density polycrystalline MgO vapor deposition material is used.
When a MgO film such as a C-type PDP is formed, a splash is extremely small and a stable film can be formed at high speed. Moreover, since the film thickness distribution can be improved, it is possible to obtain an MgO film having a substantially uniform film quality.

The invention according to claim 2 is the invention according to claim 1, further comprising impurities of Si and Al contained in the sintered pellets of polycrystalline MgO in an element concentration of 1 respectively.
It is less than 50 ppm, and Ca impurities are 20 in elemental concentration.
0ppm or less, Fe impurity is 50p in elemental concentration
pm or less, Cr, V, and Ni impurities are each 10 ppm or less in element concentration, Na and K impurities are each 20 ppm or less in element concentration, and Zr impurity concentration is 150 ppm or less. . In the polycrystalline MgO vapor deposition material according to the second aspect, impurities contained in the formed MgO film are extremely small, so that the film characteristics of the MgO film are improved.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described in detail. The polycrystalline MgO vapor deposition material of the present invention has a MgO purity of 99.90% or higher, particularly a carbon amount of 30 ppm or lower, and a relative density of 98% or higher. .

Impurities (Si, Al, Ca, Fe, Cr, V, Ni, N contained in the polycrystalline MgO sintered pellets)
The total content of a, K, C, and Zr) is 850 ppm.
The following is preferable. The individual contents of the above impurities are as follows.
It is less than 50 ppm, and Ca impurities are 20 in elemental concentration.
0ppm or less, Fe impurity is 50p in elemental concentration
pm or less, impurities of Cr, V, and Ni are each 10 ppm or less in element concentration, impurities of Na and K are each 20 ppm or less in element concentration, and impurities of Zr are 150 ppm or less in element concentration. preferable. When each of the above impurities exceeds the above values in elemental concentration, Mg
When a glass substrate formed by depositing an O vapor deposition material by an electron beam vapor deposition method is incorporated into a panel, the quality of the film varies, so that the electrical characteristics, for example, the driving voltage becomes high or unstable. is there.

[0013]

EXAMPLES Hereinafter, the present invention will be described with reference to Examples and Comparative Examples.
The present invention will be described in more detail, but the present invention is not limited to the following examples unless it exceeds the gist. <Example 1> First, MgO powder (MJ-3 manufactured by Iwatani Chemical Co., Ltd.)
0, purity 99.9%, average particle size 0.3 μm, polyethylene glycol as a binder (Sanyo Chemical Co., Ltd. P
EG-200) 1% by weight, and a slurry containing ethanol as a dispersion medium has a concentration of 72% by weight (viscosity 400 cps).
Adjusted to. This slurry was then ball milled (diameter 1
Wet-mix for 20 hours with a 0 mm resin ball) and then spray-dry with a spray dryer to obtain an average particle size of 80μ.
A granulated powder of m was obtained. The conditions for spray drying are as follows: the atomizer (high-speed rotating disk) rotation speed is set to 10,000 rpm,
The heating gas inlet and outlet temperatures are 100 ° C and 6 respectively.
It was set to 0 ° C. Next, the obtained granulated powder was filled in a thin-walled cylindrical container (internal diameter 155 mm, height 8 mm) of a CIP molding apparatus, and CIP molding was performed at 1500 Kg / cm ² . Further, this molded body was sintered in two steps, that is, placed in an electric furnace and primary sintered in the atmosphere at 1300 ° C. for 2 hours, and then at 1650 ° C. for 2 hours.
Second time fired. The rate of temperature rise from primary sintering to secondary sintering is 30 ° C./hour, and the rate of temperature decrease after completion of secondary sintering is 5
It was 0 ° C./hour. The disc of this sintered body was referred to as Example 1.

Example 2 A slurry prepared in the same manner as in Example 1 was wet-mixed for 24 hours in a ball mill using the same balls as in Example 1 and then spray-dried by a spray dryer to obtain an average particle size of 200 μm. Granulated powder of was obtained. This granulated powder is used as a mold for a uniaxial press (inner diameter: 6 mm, depth: 3 m).
m) and were uniaxially press molded at 1000 Kg / cm ² . Except for the above, it was manufactured in the same manner as in Example 1. This sintered pellet was used as Example 2.

Example 3 A slurry prepared in the same manner as in Example 1 was wet-mixed for 24 hours in a ball mill using the same balls as in Example 1 and then spray-dried with a spray dryer to obtain an average particle size of 150 μm. Granulated powder of was obtained. This granulated powder is put into a thin-walled cylindrical container (inner diameter 15
5 mm, height 8 mm), 1500 kg / cm ²
CIP molding was carried out. Except for the above, it was manufactured in the same manner as in Example 1. This sintered disc was used as Example 3. <Example 4> The slurry prepared in the same manner as in Example 1 was wet-mixed for 1 hour with a stirring mill (using a ZrO2 ball having a diameter of 2 mm), and then spray-dried with a spray dryer to form an average particle size of 200 µm. A powder was obtained. This granulated powder was filled in a mold (inner diameter: 6 mm, depth: 3 mm) of a uniaxial pressing device and uniaxially press-molded at 1000 Kg / cm ² . Except for the above, it was manufactured in the same manner as in Example 1. This sintered pellet was used as Example 4.

<Example 5> The slurry prepared in the same manner as in Example 1 was wet-mixed for 1 hour in a stirring mill using the same balls as in Example 5, and then spray-dried by a spray dryer to obtain an average particle size. A granulated powder of 150 μm was obtained. This granulated powder was filled in a mold (inner diameter 6 mm, depth 3 mm) of a uniaxial pressing device and uniaxially press-molded at 1000 Kg / cm ² .
Except for the above, it was manufactured in the same manner as in Example 1. This sintered pellet was used as Example 5.

Comparative Example 1 A slurry prepared in the same manner as in Example 1 was wet-mixed for 48 hours in a ball mill using the same balls as in Example 1 and then spray-dried by a spray dryer to obtain an average particle size of 70 μm. Granulated powder of was obtained. Next, the obtained granulated powder was filled in a thin-walled cylindrical container (internal diameter 155 mm, height 8 mm) of a CIP molding apparatus, and 1500 kg /
CIP molding was performed at cm ² . Further, this molded body was placed in an electric furnace and sintered in the atmosphere at 1650 ° C. for 3 hours. This sintered disc was used as Comparative Example 1. <Comparative Example 2> The slurry prepared in the same manner as in Example 1 was wet-mixed for 8 hours with a stirring mill (using a ZrO2 ball having a diameter of 3 mm), and then with a spray drier, an average particle diameter of 40 μm.
The granulated powder of m was filled in a mold (inner diameter: 6 mm, depth: 3 mm) of a uniaxial press machine and uniaxially press molded at 1000 Kg / cm ² . Sintering was performed as in Comparative Example 1. This sintered pellet was used as Comparative Example 2. <Comparative Example 3> Single crystal MgO produced by commercial electrofusion
The crushed product (purity 99.3%) was used as Comparative Example 3. The crushed product had a diameter of 3 to 5 mm.

<Comparative Test and Evaluation> (a) Relative Density Measurement Purity and relative density of the sintered discs, pellets and crushed products obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were measured. The results are shown in Table 1. The purity was calculated from the analysis value of impurities, and the relative density was measured by the Archimedes method in toluene. Further, Table 1 describes the manufacturing conditions of the discs and pellets of the sintered bodies of Examples 1 to 5 and Comparative Examples 1 to 3, that is, the mixing treatment of the slurry, the average particle size of the granulated powder, and the sintering conditions of the molded body. .

[0019]

[Table 1]

As is clear from Table 1, in Examples 1 to 5, impurities were not mixed in during the manufacturing process, and the purity of the MgO sintered body was 99.90% or more in all, corresponding to the starting MgO powder. The relative density was densified to 99% or more. On the other hand, in Comparative Example 2, impurities were mixed in the manufacturing process because the time for mixing in a ball mill or a stirring mill and the media diameter were inappropriate. Further, from Examples 1 and 3 and Comparative Examples 1 and 2, it was found that the two-stage sintering was preferable to the one-stage sintering with respect to the relative density.

(B) Analysis of Impurities The impurities contained in the sintered body of Example 3, the sintered body of Comparative Example 2 and the crushed single crystal MgO of Comparative Example 3 were analyzed by atomic absorption and ICP (inductively coupled plasma). Analytical method, Inducti
Very Coupled Plasma Emiss
ion spectrochemical analysis
sis). The results are shown in Table 2.

[0022]

[Table 2]

As is clear from Table 2, in Example 3, the concentration of impurities was less than 25 ppm, while in Comparative Example 2
The concentration of impurities other than Zr was 30 ppm or less, but the concentration of the impurity Zr was 800 ppm, which was considerably high. In Comparative Example 3, the concentration of impurity Ca is 390 ppm.
And showed an extremely high value. This is because the raw material of Comparative Example 3 contained a large amount of Al, Ca and Fe, and particularly contained a large amount of Ca.

(C) Characteristic test of deposited MgO film and its discharge property test Sintered body pellets of Examples 2, 4 and 5, sintered pellets of Comparative Example 2 and crushing of single crystal MgO of Comparative Example 3 To the item
Five types of TEG (Test Element Group) substrates were produced by forming a film on a glass substrate by an electron beam evaporation method. For the TEG substrate, a base electrode made of an InSn composite oxide film is formed by photolithography on a glass substrate (made of Corning # 7059 glass) having a thickness of 3 mm.
After forming a glass layer having a thickness of 1 μm and a width of 100 μm at intervals of 0 μm and having a thickness of 3 μm by reactive DC sputtering so as to cover these base electrodes, the same film forming conditions were applied by the electron beam evaporation method described above. It was made by depositing a 7000 Å thick MgO film. The deposition conditions of the MgO film, an acceleration voltage is 15 KV, the deposition pressure is 1 × 10- ² Pa, the deposition distance was 600 mm.

First, the refractive index of the MgO film was measured. M
The refractive index of the gO film was obtained by performing ellipso measurement on the film with one wavelength and two incident angles (55, 70) using a He-Ne laser (wavelength 6238 angstrom), and was obtained using analysis software. Next, the discharge starting voltage of the MgO film was measured by the following method. 5 types of TEG boards are
e-5% Xe was placed on a heating sample stand placed in a 500 Torr vacuum bell jar, the base electrode was connected to a pulse power source, and the TEG substrate was controlled to a constant temperature while being measured by a thermocouple to raise the power source voltage. Then, the voltage at which the discharge was started was measured. The pulse power supply has a variable voltage in the range of 0 to 300 V and a pulse width of 10 μse at a frequency of 66 Hz.
c pulse is generated. Table 3 shows the refractive index and the discharge start voltage of the MgO film.

[0026]

[Table 3]

As is clear from Table 3, Comparative Examples 2 and 3
In contrast, the refractive indices were 1.65 and 1.68, while
In Examples 2, 4 and 5, the refractive index was improved to 1.7 or more. It was also found that the discharge start voltage was lower in Examples 2, 4 and 5 by about 10 to 20 V than in Comparative Examples 2 and 3.
Further, the film forming rate of the example was about three times that of the comparative example. This is because the single crystal MgO crushed product of Comparative Example 3 has an orientation when hit by an electron beam, but the polycrystalline M of the embodiment is
This is because the sintered pellet of gO has no orientation, and thus efficient film formation is possible. In addition, when the substrate on which the MgO film was formed using Examples 2, 4 and 5 was incorporated into a PDP, the sputtering resistance was good and the driving voltage was also lowered.

(D) Thickness distribution of MgO film The sintered pellets of Example 2 and the sintered pellets of Comparative Example 2 and the crushed single crystal MgO of Comparative Example 3 were subjected to the electron beam evaporation method in the same manner as above. To form a film on a glass substrate. The film thickness distribution of this MgO film was measured by an ellipso of a He—Ne laser (6328 angstrom). The results are shown in Table 4. In Table 4, the film thickness of each part is shown as a ratio to the film thickness at the center of the glass substrate. That is, the film thickness at the center of the glass substrate was set to 1.0, and the film thickness at each part was shown as a ratio to this.

[0029]

[Table 4]

As is clear from Table 4, the reduction rate (variation rate) of Example 2 was smaller than that of Comparative Examples 2 and 3.

[0031]

As described above, according to the present invention, the polycrystalline MgO vapor deposition material has a MgO purity of 99.90% or more, particularly a carbon amount of 30 ppm or less and a relative density of 98% or more. Since it is composed of sintered pellets of polycrystalline MgO, when a MgO film such as AC type PDP is formed by using this high-purity and high-density polycrystalline MgO vapor deposition material, it is possible to efficiently form a film with little splash. An MgO film having a uniform film thickness can be obtained. As a result, even if the MgO film has a large film formation area, it can be formed substantially uniformly.
When incorporated in the DP, the discharge start voltage and the drive voltage can be kept low and constant, and the electrical characteristics of the PDP can be improved.

Further, the impurities of Si and Al contained in the sintered pellet of polycrystalline MgO are each contained in an element concentration of 15
The elemental concentration of Ca impurities is 200 pp below 0 ppm.
m or less, Fe impurities at an elemental concentration of 50 ppm or less, and Cr, V, and Ni impurities at an elemental concentration of 1 respectively.
0 ppm or less, Na and K impurities in elemental concentrations of 20 ppm or less, and Zr impurities in elemental concentration of 15 ppm or less.
If the content is 0 ppm or less, the impurities contained in the formed MgO film are extremely small, so that the film characteristics of the MgO film are improved.

Further, MgO powder having a purity of 99.90% or more and an average particle diameter of 0.1 to 3 μm is mixed with a binder and an organic solvent to prepare a slurry having a concentration of 45 to 57% by weight.
After the slurry is spray-dried to obtain a granulated powder having an average particle size of 50 to 300 μm, the granulated powder is put into a predetermined mold and molded at a predetermined pressure, and the molded body is sintered at a predetermined temperature. For example, the above-mentioned MgO purity is 99.90% or more, and in particular, the polycrystalline MgO made of sintered pellets of polycrystalline MgO having a carbon amount of 30 ppm or less and a relative density of 98% or more.
A vapor deposition material can be obtained.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4G030 AA03 AA04 AA07 AA08 AA17                       AA22 AA27 AA29 AA36 AA37                       AA45 AA60 CA01 GA28 GA29                 4K029 AA09 BA43 BB08 BD00 DB05                       DB17                 5C040 GE07 KA04 KB08 KB19 KB30                       MA24 MA26

Claims (2)

[Claims] 1. A polycrystalline MgO composed of sintered pellets of polycrystalline MgO having a MgO purity of 99.90% or more, a carbon amount of 30 ppm or less, and a relative density of 98% or more.
Evaporation material. 2. Impurities of Si and Al contained in the polycrystalline MgO sintered pellets are contained in elemental concentrations of 150 and 150, respectively.
It is less than ppm and the impurity of Ca is 200p in elemental concentration.
pm or less, Fe impurity is 50 ppm in elemental concentration
The Cr content, the V content, and the Ni content are 10 ppm or less, the Na content and the K content are 20 ppm, and the Zr content is 150 ppm or less. Polycrystalline M
gO vapor deposition material.