JP3314728B2 - Polycrystalline MgO deposited material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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 crystals (Liquid Crystal) have been developed.
al Display (LCD), and other R & D and practical application of various flat displays are remarkable.
Its production is also increasing rapidly. Recently, color plasma display panels (PDPs) have been actively developed and put into practical use. PDPs are easy to increase in size, are at the shortest distance from large screen wall-mounted televisions for high-definition televisions, and prototypes of 40-inch diagonal PDPs have already been developed. PDPs are classified into an AC type in which a metal electrode is covered with a glass dielectric material in terms of an electrode structure, and a DC type in which a metal electrode is exposed in a discharge space.

At the beginning of the development of the AC type PDP, since the glass dielectric layer was exposed to the discharge space, the glass dielectric layer was directly exposed to the discharge, and the surface of the dielectric layer was changed by ion bombardment, and the discharge starting voltage was lowered. Was rising. For this reason, attempts have been made to use various oxides having high sublimation heat as protective films for the 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 a low discharge voltage, resistance to sputtering during discharge, fast discharge responsiveness, and insulation. MgO is used for the protective film as a material satisfying these conditions. The protective film made of MgO protects the surface of the dielectric layer from sputtering at the time of discharge, and is used for PDP.
It plays an important role in prolonging the service life.

At present, as the above protective film of 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 the electron beam evaporation method can be formed at a high speed of 1000 Å / min or more. The crystal orientation of the formed MgO film is such that a film oriented in the (111) plane can be driven at the lowest sustaining voltage, and furthermore, exists in the film (11
1) It is said that as the amount of the surface increases, the emission ratio of secondary electrons increases and the driving voltage also decreases. The single crystal Mg
The crushed product of O is obtained by melting MgO clinker having a purity of 98% or more or lightly burned MgO (MgO sintered at 1000 ° C. or less) in an electric furnace (arc furnace), that is, into an ingot by electromelting. It is manufactured by crushing and extracting a single crystal part from this ingot.

[0005]

However, in the conventional electron beam evaporation method using a crushed product of single crystal MgO as a deposition material, single crystal MgO is produced by arc melting using a carbon electrode rod. Of carbon is 100p
pm or more, and a considerable amount of carbon is also present in the film deposited by electron beam. When carbon is considerably present in the MgO film, during plasma discharge, charges existing in the vicinity of the film surface layer are easily taken into the film (easy to be trapped), so that the frequency of collision of electrons decreases, and the emission coefficient of secondary electrons decreases. However, there is a problem that the discharge voltage must be increased. Also, to give high energy locally to the deposition material,
There was a problem that the vapor deposition material of the fine powder was scattered (splash) and the vapor deposition efficiency was reduced. It is thought that increasing the size of the vapor deposition material is effective in preventing the generation of this splash. However, as a manufacturing process, single-crystal MgO is allowed to stand naturally for a long time after electric melting, and then cools the large ingot. Further, there is a step of crushing and taking out a single crystal portion from the ingot, and sizing. At that time, the fresh crushed surface has high activity, and moisture and carbon dioxide in the atmosphere adhere over a long period of time. However, it takes a considerable amount of time to degas, and this is regarded as a problem in improving productivity. The current particle size is 1-5m
It has been difficult to stably secure particles larger than m with good yield. In the conventional electron beam evaporation method using a crushed single crystal MgO product as an evaporation material, it is difficult to uniformly form an MgO film on a large-area glass dielectric layer, and there is a problem in film thickness distribution. there were. As a result, MgO
When a glass dielectric layer on which a film is formed is incorporated into a PDP, there is a problem that electrical characteristics, for example, a discharge starting voltage and a sustaining voltage are increased or changed.

On the other hand, MgO clinker and lightly burned MgO often use MgCl2 obtained from seawater as a raw material, and this MgCl2 contains a relatively large amount of Ca, Si, Fe.
And the like, these impurities are contained in the single crystal M
Remains in gO. Further, in the ingot in the production process of the single crystal MgO, the impurity amount 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. As a result, there is a problem that the stability and reliability of the purity of the single crystal MgO are lacking.

In order to solve these problems, a single crystal MgO
Alternatively, a method using polycrystalline MgO may be considered. However, high-density polycrystalline MgO densified by the addition of various sintering aids has a problem that defects are systematically present at crystal grain boundaries, and a problem that the density is lowered when the purity is increased. Was. On the other hand, a structure with few defects and high interatomic bond energy, when irradiating an electron beam during deposition, if electrons with high energy do not collide, the bond is broken off and atoms of Mg and O are difficult to fly out, and the amount of protrusion is small. Since there is little, there is a limit to increasing the film formation rate because the power of the electron beam must be increased. As a result, when an MgO film is formed on a glass dielectric layer by an electron beam evaporation method using these polycrystalline MgO evaporation materials, the crystal orientation (11
1) The amount of orientation on the surface is reduced, and this glass dielectric layer is
Since the electrical characteristics when incorporated in P are reduced, the 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 that can form a film at high speed and uniformly without generating a splash even when vapor deposition is performed by an electron beam vapor deposition method. Another object of the present invention is to provide a polycrystalline MgO vapor deposition material that can improve the film characteristics of a formed MgO film.

[0009]

The invention according to claim 1 is
MgO purity of 99.90% or more and carbon content of 30pp
m and a relative density of 98% or more
This is a polycrystalline MgO vapor deposition material made of a sintered pellet of O. In the polycrystalline MgO vapor deposition material according to the first aspect, the high purity and high density polycrystalline MgO vapor deposition material
When an MgO film such as a C-type PDP is formed, a stable film can be formed at high speed with little splash. Further, since the film thickness distribution can be improved, an MgO film having substantially uniform film quality can be obtained.

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

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 more, in particular, a carbon content of 30 ppm or less, and a relative density of 98% or more. .

The impurities (Si, Al, Ca, Fe, Cr, V, Ni, N) contained in the sintered pellet of polycrystalline MgO
a, K, C, and Zr) in total 850 ppm
The following are preferred. The individual content of the above impurities is such that the impurities of Si and Al are each 1 elemental concentration.
50 ppm or less, and the impurity of Ca is 20
0 ppm or less, and the impurity of Fe is 50 p in element concentration.
pm or less, the impurities of Cr, V and Ni are each 10 ppm or less in element concentration, the impurities of Na and K are each 20 ppm or less in element concentration, and the impurity of Zr is 150 ppm or less in element concentration. preferable. When each of the above impurities exceeds the above value in element concentration, Mg
When a glass substrate on which an O vapor deposition material is formed by an electron beam vapor deposition method is incorporated into a panel, there is a problem that electric characteristics, for example, a driving voltage becomes high or becomes unstable due to variations in film quality. is there.

[0013]

EXAMPLES Hereinafter, the present invention will be described with reference to Examples and Comparative Examples.
The present invention will be described more specifically, 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 (Pan manufactured by Sanyo Chemical Co., Ltd.)
EG-200) was added at 1% by weight, and a slurry containing ethanol as a dispersion medium was concentrated at a concentration of 72% by weight (viscosity: 400 cps).
Was adjusted. Next, this slurry was ball milled (diameter 1
(Using a 0 mm resin ball) for 20 hours and then spray-drying with a spray dryer to obtain an average particle size of 80 μm.
m of granulated powder was obtained. The spray drying conditions were as follows: the rotation speed of the atomizer (high-speed rotating disk) was set to 10,000 rpm,
The inlet and outlet temperatures of the heated gas are 100 ° C and 6 ° C, respectively.
It was set to 0 ° C. Next, the obtained granulated powder was filled into a thin-walled cylindrical container (inner diameter: 155 mm, height: 8 mm) of a CIP molding apparatus, and was subjected to CIP molding at 1500 kg / cm ² . Further, the compact was sintered in two steps, that is, put in an electric furnace and primary-sintered at 1300 ° C. for 2 hours in the air.
Time was secondary sintering. The rate of temperature rise from primary sintering to secondary sintering is 30 ° C./hour, and the rate of temperature decrease after secondary sintering is 5
It was 0 ° C./hour. This sintered disk was designated 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 with a spray dryer to obtain an average particle size of 200 μm. Was obtained. The granulated powder is placed in a uniaxial pressing machine mold (inner diameter 6 mm, depth 3 m).
m), 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 2.

Example 3 The 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. Was obtained. This granulated powder is transferred to a thin cylindrical container (with an inner diameter of 15
5 mm, height 8 mm) and 1500 kg / cm ²
Was CIP molded. Except for the above, it was produced in the same manner as in Example 1. This sintered disk was named Example 3. Example 4 A slurry prepared in the same manner as in Example 1 was wet-mixed for 1 hour in a stirring mill (using ZrO2 balls having a diameter of 2 mm), and then spray-dried with a spray dryer to form granules having an average particle size of 200 μm. A powder was obtained. This granulated powder was filled into a mold of a uniaxial press device (inner diameter: 6 mm, depth: 3 mm), and subjected to uniaxial press molding 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 with a spray dryer to obtain an average particle size. A granulated powder of 150 μm was obtained. This granulated powder was filled into a mold of a uniaxial press device (inner diameter: 6 mm, depth: 3 mm), and subjected to uniaxial press molding 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 with a spray dryer to obtain an average particle size of 70 μm. Was obtained. Next, the obtained granulated powder is filled in a thin-walled cylindrical container (inner diameter: 155 mm, height: 8 mm) of a CIP molding machine, and 1500 kg /
CIP was performed in cm ² . The compact was placed in an electric furnace and sintered at 1650 ° C. for 3 hours in the atmosphere. This sintered disk was used as Comparative Example 1. <Comparative Example 2> The slurry prepared in the same manner as in Example 1 was wet-mixed in a stirring mill (using a ZrO2 ball having a diameter of 3 mm) for 8 hours, and then the average particle size was 40 µm using a spray dryer.
m of the granulated powder was charged into a mold of a uniaxial press device (inner diameter 6 mm, depth 3 mm), and subjected to uniaxial press molding at 1000 kg / cm ² . Sintering was performed in the same manner as in Comparative Example 1. This sintered body pellet was used as Comparative Example 2. Comparative Example 3 Commercially available single crystal MgO produced by electrofusion
A crushed product having a purity of 99.3% was used as Comparative Example 3. The diameter of this crushed product was 3 to 5 mm.

<Comparison Test and Evaluation> (a) Measurement of Relative Density The purity and relative density of the discs, pellets and crushed products of the sintered bodies obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were measured, respectively. Table 1 shows the results. The purity was calculated from the analysis value of impurities, and the relative density was measured in toluene by Archimedes method. Table 1 also shows the conditions for producing the discs and pellets of the sintered bodies of Examples 1 to 5 and Comparative Examples 1 to 3, namely, 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 apparent from Table 1, in Examples 1 to 5, no impurities were mixed in the production process, and the purity of the MgO sintered body was all at least 99.90% corresponding to the starting material MgO powder. And the relative density was reduced to 99% or more. On the other hand, in Comparative Example 2, impurities were mixed in the production process due to inappropriate mixing time and media diameter in a ball mill or a stirring mill. 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 and 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 emissions
ion spectrochemical analysis
sis). Table 2 shows the results.

[0022]

[Table 2]

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

(C) Characteristic test of the formed MgO film and its discharge test The sintered pellets of Examples 2, 4 and 5, the sintered pellet of Comparative Example 2, and the single crystal MgO of Comparative Example 3 were crushed. With the goods
Five types of TEG (Test Element Group) substrates were manufactured by forming films on a glass substrate by an electron beam evaporation method. The TEG substrate is composed of a 3 mm-thick glass substrate (Corning # 7059 glass) on which a base electrode made of an InSn composite oxide film is formed by photolithography.
After forming a glass layer having a thickness of 1 μm and a width of 100 μm at intervals of 0 μm, and forming a glass layer having a thickness of 3 μm by reactive DC sputtering so as to cover these base electrodes, the above-mentioned electron beam evaporation method was performed under the same film forming conditions. It was formed 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 determined by using a He-Ne laser (wavelength: 6238 angstroms), performing ellipsometry at one wavelength and two incident angles (55, 70) on the film, and using analysis software. Next, the discharge starting voltage of the MgO film was measured by the following method. Five types of TEG substrates are replaced by N
e-5% Xe Placed on a heated sample table placed in a 500 Torr vacuum bell jar, connected to the base electrode to a pulse power source, and controlled the TEG substrate to a constant temperature while measuring with a thermocouple, and increased the power source voltage. The voltage at which discharge was started was measured. The pulse power supply is variable in the range of 0 to 300 V, and has a frequency of 66 Hz and a pulse width of 10 μs.
c pulse is generated. Table 3 shows the refractive index and the firing voltage of the MgO film.

[0026]

[Table 3]

As apparent from Table 3, Comparative Examples 2 and 3
Had refractive indexes of 1.65 and 1.68,
In Examples 2, 4 and 5, the refractive index was improved to 1.7 or more. Further, it was found that the discharge starting voltage was lower by about 10 to 20 V in Examples 2, 4 and 5 than in Comparative Examples 2 and 3.
Further, the film forming rate of the example was about three times the value of the comparative example. This is because the single crystal MgO crushed product of Comparative Example 3 has an orientation when irradiated with an electron beam, but the polycrystalline M
This is because the sintered body pellet of gO has no orientation, so that 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 in a PDP, the sputter resistance was good and the driving voltage was lowered.

(D) Film Thickness Distribution of MgO Film The sintered pellet of Example 2, the sintered pellet of Comparative Example 2, and the crushed single crystal MgO of Comparative Example 3 were subjected to electron beam evaporation in the same manner as described above. To form a film on a glass substrate. The film thickness distribution of this MgO film was measured by an ellipsometer using a He—Ne laser (6328 Å). Table 4 shows the results. In Table 4, the thickness of each part is shown as a ratio to the thickness of 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 of each part was shown by a ratio to this.

[0029]

[Table 4]

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

[0031]

As described above, according to the present invention, a polycrystalline MgO vapor-deposited material having a MgO purity of 99.90% or more, particularly a carbon content of 30 ppm or less and a relative density of 98% or more is obtained. Since it is composed of sintered pellets of polycrystalline MgO, using this high-purity and high-density polycrystalline MgO vapor-deposited material to form an MgO film such as an AC-type PDP can efficiently form a film with little splash and substantially An MgO film having a uniform thickness can be obtained. As a result, even if the film area of the MgO film is large, the film can be formed substantially uniformly.
When incorporated in the DP, the discharge starting voltage and the driving 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 pellets of polycrystalline MgO are each added at an element concentration of 15%.
0 ppm or less, Ca impurity is 200pp
m, the impurity of Fe is 50 ppm or less in elemental concentration, and the impurities of Cr, V and Ni are each 1 elemental in concentration.
0 ppm or less, Na and K impurities at an element concentration of 20 ppm or less, and Zr impurity at an element concentration of 15 ppm or less.
If the content is set to 0 ppm or less, impurities contained in the formed MgO film become extremely small, so that the film characteristics of the MgO film are improved.

Further, a slurry having a concentration of 45 to 57% by weight is prepared by mixing MgO powder having a purity of 99.90% or more and an average particle size of 0.1 to 3 μm, a binder and an organic solvent,
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, molded at a predetermined pressure, and sintered at a predetermined temperature. For example, polycrystalline MgO having a MgO purity of 99.90% or more, in particular, a polycrystalline MgO sintered body pellet having a carbon content of 30 ppm or less and a relative density of 98% or more.
An evaporation material can be obtained.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 35/053 H01J 11/02

Claims (2)

(57) [Claims] 1. A polycrystalline MgO comprising a sintered pellet of MgO having a 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. The method according to claim 1, wherein the impurities of Si and Al contained in the polycrystalline MgO sintered pellets have an element concentration of 150% respectively.
ppm or less, and the impurity of Ca is 200 p
pm or less, and the impurity of Fe is 50 ppm in elemental concentration.
The impurities of Cr, V and Ni are each 10 ppm or less in element concentration, the impurities of Na and K are each 20 ppm or less in element concentration, and the impurity concentration of Zr is 150 ppm or less in Zr. Polycrystalline M
gO vapor deposition material.