JP2010143798A - Sintered magnesium oxide and method for producing the same - Google Patents

Abstract

[PROBLEMS] To form a film using a magnesium oxide sintered body as a vapor deposition material at a high film formation rate and to suppress the occurrence of splash during the film formation, and to protect the obtained vapor deposition film for PDP. Provided is a magnesium oxide sintered body capable of lowering a discharge start voltage when used as a film.
SOLUTION: Magnesium oxide, 9-50 mass% of oxide of Group 2A element of periodic table other than magnesium, and 1-10000 ppm of oxide of Group 3B, Group 3A or Group 4A element of periodic table A magnesium oxide sintered body characterized by the above.
[Selection figure] None

Description

  The present invention relates to a magnesium oxide sintered body suitable as a vapor deposition material capable of forming a protective film in a plasma display panel (hereinafter referred to as PDP), and a method for producing the same.

  The PDP is a display device in which a large number of minute discharge spaces are provided in the gap between two glass substrates. For example, in a matrix display type PDP, a large number of electrodes are arranged in a grid pattern, and an image is displayed by selectively causing discharge cells at intersections of the electrodes to emit light. In a typical surface discharge AC type PDP, the display electrode of the front plate is covered with a dielectric layer, and a protective film is formed on the dielectric layer. The protective film has a function to prevent the dielectric layer surface from changing due to direct exposure of the dielectric layer to the discharge and increasing the discharge start voltage, and has a characteristic that it does not change due to ion bombardment sputtering. It is a layer to show.

  Currently, a protective film for PDP is generally formed on a dielectric layer by an electron beam evaporation method using a sintered body such as magnesium oxide as a target material. However, it is required to further lower the discharge start voltage in order to further reduce the power consumption of the PDP, and as a protective film for the PDP, a material having a low discharge start voltage, a high secondary electron emission coefficient, and strong against sputtering. Is required.

  From such a viewpoint, as a material constituting the protective film, a sintered body made of a mixed oxide of magnesium oxide and calcium oxide, barium oxide or the like is proposed in addition to magnesium oxide (Patent Documents 1 and 2). See). These protective film materials are preferable because the discharge start voltage is relatively low and the sputtering resistance is good.

  However, the protective film material based on the mixed oxide has a problem that the strength is low, and there is a problem that a projection portion of the sintered body is destroyed by a thermal shock at the time of vapor deposition, and splash (bumping) is likely to occur. In order to improve the strength, there is a method of adjusting the relative density of the oxide to 95% or more. However, the vapor deposition material having a high relative density has a problem that the film formation rate is reduced.

  In Patent Document 1, a magnesium oxide sintered body having a relative density of 95% or more and having crystal grains having a crystal grain size of 0.3 to 100 μm is oxidized in an alkaline earth metal such as calcium or barium. A vapor deposition material in which 0.5 to 50% by volume of particles are dispersed has been reported, but since this vapor deposition material has a high relative density, the film formation rate is slow and the energy efficiency during film formation is not satisfactory. .

Patent Document 2 describes a vapor deposition material made of a sintered body of magnesium oxide, an oxide of an alkaline earth metal such as calcium or barium, and an oxide of a metal such as aluminum or zirconium. It is described that the content is 0.005 mol% or more and the total amount is 6 mol% or less in terms of metal element amount. Since this vapor deposition material has a low content of metal oxides other than magnesium oxide, it is not sufficient to lower the discharge start voltage. In addition, since the relative density is high, there is also a drawback that the film forming speed is slow.
Japanese Patent No. 3893793 Japanese Patent Laying-Open No. 2005-330574

  Therefore, the present invention has a high film forming speed when forming a film using a magnesium oxide sintered body as a vapor deposition material, and can suppress the occurrence of splash during the film formation. To provide a magnesium oxide sintered body capable of lowering a discharge start voltage when used as a protective film, a vapor deposition material for a protective film of a PDP using the same, and a method for producing the sintered body With the goal.

  When this inventor examined, the composition of a magnesium oxide sintered compact was set to magnesium oxide, the oxide of 2A group element of the periodic table other than magnesium, and the periodic table 3B group 3A group 4A element element. By adjusting each oxide to contain a specific amount, the film formation rate is high when the magnesium oxide sintered body is used as a vapor deposition material, and the occurrence of splash during film formation can be suppressed. Furthermore, the inventors have found that the discharge starting voltage can be lowered when the obtained deposited film is used as a protective film for PDP, and the present invention has been completed.

  That is, the magnesium oxide sintered body of the present invention is composed of magnesium oxide, 9-50% by mass of Group 2A element oxide other than magnesium, and oxidation of Group 3B, Group 3A or Group 4A elements of the Periodic Table. It is characterized by containing 1 to 10,000 ppm of the product.

  The magnesium oxide sintered body includes magnesium oxide powder, carbonate powder or hydroxide powder of Group 2A elements of the periodic table other than magnesium, oxide powder of Group 3B, Group 3A or Group 4A of the periodic table, And a step of preparing a mixture by mixing a binder, a step of granulating the mixture and drying to obtain a granulated powder, a step of forming the granulated powder in a mold to form a molded body, and It can be manufactured by a method including a step of sintering the molded body.

  According to the magnesium oxide sintered body of the present invention, when forming a film using this as a vapor deposition material, the film formation speed is high, and it is possible to suppress the occurrence of splash during film formation, and the obtained vapor deposition film Is used as a protective film for PDP, the discharge start voltage can be lowered.

  The magnesium oxide sintered body of the present invention is mainly composed of magnesium oxide as a constituent component, and further includes an oxide of Group 2A element of the periodic table other than magnesium, and Group 3B, Group 3A or Group 4A element of the periodic table. Containing oxides. A sintered body is manufactured by heating a powder aggregate at a temperature lower than the melting point and connecting the powders by solid phase diffusion of the powder, growth of the neck portion, movement of crystal grain boundaries, etc. It refers to a dense compact.

  Examples of Group 2A elements of the periodic table other than magnesium include calcium, beryllium, strontium, barium, and radium. Only one of these may be used, or two or more may be used in combination. Among these, calcium is preferable because it has a small band gap and a high effect of reducing the discharge start voltage.

  In the magnesium oxide sintered body of the present invention, the content of oxides of Group 2A elements of the periodic table other than magnesium is 9 to 50% by mass. If it is less than 9% by mass, the low voltage effect is insufficient, and if it exceeds 50% by mass, the strength of the sintered body rapidly decreases and splash occurs. Preferably it is 12-35 mass%.

  Periodic Table Group 3B, Group 3A or Group 4A elements include boron, aluminum, gallium, indium, thallium, scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium Holmium, erbium, thulium, ytterbium, lutetium, titanium, zirconium, and hafnium. Only one of these may be used, or two or more may be used in combination. Of these, aluminum, scandium, zirconium, cesium, or yttrium is preferable because of its high splash suppression effect, and aluminum is particularly preferable.

  In the magnesium oxide sintered body of the present invention, the content of oxides of Group 3B, 3A or 4A elements of the periodic table is 1 to 10000 ppm by mass. If it is less than 1 ppm, the strength is not sufficient and splash is generated. If it exceeds 10000 ppm, the effect of reducing the discharge start voltage is inhibited by the addition of an oxide of a Group 2A element of the periodic table other than magnesium. Preferably it is 50-5000 ppm.

  The magnesium oxide sintered body according to the present invention is a three-component system having a specific component ratio. Therefore, the strength of the sintered body is improved as compared with the conventional sintered body. Is suppressed, and it becomes possible to prevent occurrence of splash and scattering of fragments.

  The magnesium oxide sintered body of the present invention has a relative density of less than 95%. If the relative density is 95% or more, the deposition material temperature cannot be kept high at the time of deposition using a vacuum deposition method such as an electron beam deposition method, an ion plating method, or a sputtering method, and sufficient film formation is performed. I can't get the speed. Conventionally, the strength of the sintered body has been increased by adjusting the relative density of the magnesium oxide sintered body to 95% or more so that splash is less likely to occur during vapor deposition. Even if the relative density is less than 95% in the aggregate, splash is unlikely to occur during vapor deposition. The lower limit of the relative density is preferably 80% or more.

  Next, a method for producing the magnesium oxide sintered body of the present invention will be described.

  The magnesium oxide sintered body of the present invention includes magnesium oxide powder, carbonate powder or hydroxide powder of Group 2A elements of the periodic table other than magnesium, oxide of Group 3B, Group 3A or Group 4A of the periodic table A step of mixing a powder and a binder to prepare a mixture, a step of granulating the mixture and drying to obtain a granulated powder, a step of forming the granulated powder in a mold to form a molded body, And it can manufacture by passing through the process of sintering the said molded object.

  Specifically, the average particle size of the magnesium oxide raw material powder having high purity (for example, purity of 99.9% or more) is adjusted to about 0.1 to 10 μm, preferably about 0.2 to 2 μm.

  Separately, the average particle diameter of carbonate powder or hydroxide powder of Group 2A element of the periodic table other than magnesium having high purity (for example, purity of 99% or more, preferably purity of 99.9% or more) is 1.5. It is adjusted to about ˜30 μm, preferably 3 to 20 μm. Conventionally, in order to improve the relative density of the sintered body, a calcium oxide raw material powder that is a Group 2A element of the periodic table other than magnesium is used with an average particle diameter of less than 1.5 μm to increase the molding density. However, in the sintered body of the present invention, since the occurrence of splash can be suppressed even if the relative density is relatively low, the average particle size is 1.5 μm or more as the raw material powder of Group 2A elements of the periodic table other than magnesium. A thing can be used conveniently.

  Separately, oxide powders of Group 3B, Group 3A or Group 4A of the periodic table having high purity (for example, purity of 99% or more, preferably purity of 99.9% or more) are prepared.

  These oxide powders are mixed in a predetermined weight ratio, and an appropriate amount of a resin binder solution is added, and after sufficient mixing, granulation is performed. For granulation, a rolling granulation method, a spray granulation method, or the like can be used. The obtained granulated body is dried and then put into a predetermined mold and molded. For example, a uniaxial press machine or the like can be used. The mold pressure is preferably set to, for example, 50 to 600 MPa in order to adjust the relative density of the obtained molded body.

  Next, the obtained molded body is fired to obtain the magnesium oxide sintered body of the present invention. This firing is preferably set to firing temperature: 1300 to 1800 ° C. and firing time: 0.5 to 20 hours. For firing, an electric furnace, a gas furnace, or the like can be used.

  It does not specifically limit as said resin binder, For example, the binder which consists of CMC (carboxymethylcellulose), PVA (polyvinyl alcohol), an acrylic resin, a vinyl acetate resin etc. can be used. The amount used is about 1 to 10 parts by weight in solid content with respect to 100 parts by weight of the total amount of powder converted to oxide. The binder concentration is preferably about 5% to 50%.

  The magnesium oxide sintered body of the present invention is suitable as a vapor deposition material used as a film forming material when a protective film of a plasma display panel is formed by a vacuum vapor deposition method such as an electron beam vapor deposition method, an ion plating method, or a sputtering method. Can be used. When the magnesium oxide sintered body of the present invention is used, it is possible to form a protective film that is excellent in film performance, while being excellent in energy efficiency during vapor deposition and hardly generating splash.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1
89.9 g of magnesium oxide powder having a purity of 99.9% or more and an average particle diameter (D ₅₀ ) of 0.5 μm, and calcium carbonate powder having a purity of 99.99% or more and an average particle diameter (D ₅₀ ) of 18.95 μm (Kanto Chemical Reagents: calcium carbonate 4N) (17.85 g, 10 wt% in terms of calcium oxide) was added, and aluminum oxide powder with a purity of 99.99% or more and an average particle size (D ₅₀ ) of 0.692 μm (manufactured by Sumitomo Chemical Co., Ltd.) 20 g of an acrylic resin binder solution having a concentration of 30% was added to and mixed with 0.01 g (100 ppm) of [alpha-alumina: AKP-3000]. Then, after granulation and drying, it was formed into a cylindrical shape having a diameter of 8 mm and a thickness of 5 mm by press molding (molding pressure: 200 MPa), and fired at 1450 ° C. for 8 hours in an electric furnace.

  The purity and average particle size of oxides, hydroxides and carbonates used as raw materials were measured by the following methods.

(Measurement of purity of oxide, hydroxide and carbonate)
The purity of magnesium oxide, calcium carbonate, and aluminum oxide was calculated as a value obtained by subtracting the total amount of impurities measured from 100% by mass.

  For each impurity amount (Si, Al, Ca, Mg, Fe, V, Cr, Mn, Ni, Zn, B, Zr, Cu, Na, K, Cl), an ICP emission analyzer (manufactured by Agilent: 4500) is used. The sample was dissolved in acid and then measured.

(Measurement method of average particle diameter of oxide, hydroxide and carbonate)
Measurement was performed using a laser diffraction / scattering particle size distribution analyzer (trade name: HIRA, Nikkiso Co., Ltd.).

  About the magnesium oxide sintered compact containing the calcium oxide and aluminum oxide obtained by the above, the bulk density and the relative density were computed with the following method.

(Calculation method for bulk density of sintered body)
The bulk density of the sintered body was determined by the Archimedes method.

(Calculation method of relative density of sintered body)
The relative density of the sintered body was determined by the Archimedes method. However, the theoretical density of magnesium oxide was calculated as 3.58 g / cc, the theoretical density of calcium oxide as 3.37 g / cc, and the theoretical density of aluminum oxide as 3.99 g / cc.

After 10 g of the obtained magnesium oxide sintered body was filled in a hearth as a vapor deposition material, vapor deposition was performed on a metal substrate at an output of 4 kV and 15 mA for 15 minutes using an electron beam vapor deposition apparatus. At the time of film formation, the state of occurrence of splash was visually observed from the viewport, and further, the surface of the thin film was observed after film formation, and was evaluated according to the following four criteria.
A: Neither splash nor deposit of vapor deposition material on the film surface was observed.
○: Splash is not observed, but it is confirmed that vapor deposition material fragments adhere to the film surface.
Δ: Splash observed.
X: Many splashes observed.

  Furthermore, after the film formation was completed, the vapor deposition material remaining in the hearth was collected, the weight was measured, and the evaporation amount in the vapor deposition step was calculated.

  The results are shown in Table 1.

(Example 2)
A magnesium oxide sintered body was produced and evaluated in the same manner as in Example 1 except that the aluminum oxide was changed to 500 ppm.

(Example 3)
A magnesium oxide sintered body was produced and evaluated in the same manner as in Example 1 except that the aluminum oxide was changed to 1000 ppm.

Example 4
A magnesium oxide sintered body was produced and evaluated in the same manner as in Example 1 except that calcium oxide and aluminum oxide were changed to 20 wt% and 1000 ppm, respectively.

(Example 5)
A magnesium oxide sintered body was produced and evaluated in the same manner as in Example 1 except that calcium oxide and aluminum oxide were changed to 30 wt% and 1000 ppm, respectively.

(Example 6)
A magnesium oxide sintered body was produced and evaluated in the same manner as in Example 1 except that calcium oxide and aluminum oxide were changed to 40 wt% and 1000 ppm, respectively.

(Example 7)
Magnesium oxide baked in the same manner as in Example 1 except that calcium carbonate powder having a purity of 99.99% or more and an average particle diameter (D ₅₀ ) of 4.63 μm was used as the raw material and the calcium oxide was changed to 10 wt%. A knot was produced and evaluated.

(Example 8)
Magnesium oxide baked in the same manner as in Example 1 except that calcium carbonate powder having a purity of 99.99% or more and an average particle diameter (D ₅₀ ) of 28.72 μm was used as a raw material and calcium oxide was changed to 10 wt%. A knot was produced and evaluated.

Example 9
Other than using calcium hydroxide powder as raw material, using calcium hydroxide powder with a purity of 99.9% or more and an average particle diameter (D ₅₀ ) of 6.34 μm, so that the calcium oxide is 10 wt%. Manufactured the magnesium oxide sintered compact similarly to Example 1, and evaluated.

(Example 10)
Example 1 with the exception of using yttrium oxide powder having a purity of 99.9% or more and an average particle diameter (D ₅₀ ) of 30.51 μm without using aluminum oxide powder as a raw material, and changing to 500 ppm. Similarly, a magnesium oxide sintered body was produced and evaluated.

(Example 11)
Example 1 is the same as Example 1 except that zirconium oxide powder having a purity of 99.9% or more and an average particle diameter (D ₅₀ ) of 0.581 μm was used without using aluminum oxide powder as a raw material, and was changed to 500 ppm. Similarly, a magnesium oxide sintered body was produced and evaluated.

Example 12
Example 1 is the same as Example 1 except that cerium oxide powder having a purity of 99.9% or more and an average particle diameter (D ₅₀ ) of 6.676 μm was used without using aluminum oxide powder as a raw material, and was changed to 500 ppm. Similarly, a magnesium oxide sintered body was produced and evaluated.

(Example 13)
Example 1 with the exception of using scandium oxide powder having a purity of 99.9% or more and an average particle diameter (D ₅₀ ) of 15.59 μm without using aluminum oxide powder as a raw material, and changing the concentration to 500 ppm. Similarly, a magnesium oxide sintered body was produced and evaluated.

(Comparative Example 1)
A magnesium oxide sintered body was produced and evaluated in the same manner as in Example 1 except that aluminum oxide powder was not used as a raw material.

(Comparative Example 2)
A magnesium oxide sintered body was used in the same manner as in Example 1 except that calcium carbonate powder having a purity of 99.99% or more and an average particle diameter (D ₅₀ ) of 0.28 μm was used as a raw material, and aluminum oxide powder was not used. Manufactured and evaluated.

(Comparative Example 3)
A magnesium oxide sintered body was produced and evaluated in the same manner as in Example 1 except that aluminum oxide powder was not used as a raw material and calcium oxide was changed to 20 wt%.

(Comparative Example 4)
Other than the fact that calcium carbonate powder with a purity of 99.99% or more and an average particle size (D ₅₀ ) of 0.28 μm was used as the raw material, calcium oxide was changed to 20 wt%, and aluminum oxide powder was not used. Manufactured the magnesium oxide sintered compact similarly to Example 1, and evaluated.

(Comparative Example 5)
A magnesium oxide sintered body was produced and evaluated in the same manner as in Example 1 except that the calcium oxide was changed to 30 wt% and aluminum oxide powder was not used as a raw material.

(Comparative Example 6)
A magnesium oxide sintered body was produced and evaluated in the same manner as in Example 1 except that the calcium oxide was changed to 40 wt% and aluminum oxide powder was not used as a raw material.

表１より、実施例１〜１３の酸化マグネシウム焼結体は蒸発量が多く、すなわち成膜時のエネルギー効率が良好であり、かつ、成膜時のスプラッシュ発生が抑止されていることが分かる。

From Table 1, it can be seen that the magnesium oxide sintered bodies of Examples 1 to 13 have a large amount of evaporation, that is, energy efficiency at the time of film formation is good, and the occurrence of splash at the time of film formation is suppressed.

Claims (9)

  It contains 9 to 50 mass% of oxides of Group 2A elements of the periodic table other than magnesium oxide and magnesium, and 1 to 10,000 ppm of oxides of Group 3B, Group 3A or Group 4A elements of the periodic table, and the relative density is 95 Magnesium oxide sintered body characterized by being less than%.   The content of Group 2A group oxide other than magnesium is 12 to 35% by mass, and the content of Group 3B, Group 3A or Group 4A oxide of the periodic table is 50 to 5000 ppm. The magnesium oxide sintered body according to claim 1.   The Group 2A element of the periodic table other than magnesium is one or more selected from the group consisting of calcium, beryllium, strontium, barium and radium, and the Periodic Table Group 3B, Group 3A or Group Group 4A elements are boron, aluminum, gallium, indium, thallium, scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, titanium The magnesium oxide sintered body according to claim 1 or 2, which is one kind or two or more kinds selected from the group consisting of zirconium, hafnium, and hafnium.   The group 2A element of the periodic table other than magnesium is calcium, and the group 3B, group 3A or group 4A of the periodic table is selected from the group consisting of aluminum, scandium, cerium, zirconium and yttrium. Or the magnesium oxide sintered compact of Claim 1 or 2 which is 2 or more types.   The magnesium oxide sintered body according to any one of claims 1 to 4, wherein the relative density is 80% or more.   The vapor deposition material for protective films of a plasma display panel which consists of a magnesium oxide sintered compact in any one of Claims 1-5. A method for producing a magnesium oxide sintered body according to any one of claims 1 to 5,
Mixture of magnesium oxide powder, carbonate powder or hydroxide powder of Group 2A element of periodic table other than magnesium, oxide powder of Group 3B, Group 3A or Group 4A element of periodic table, and binder The step of preparing,
Granulating the mixture and drying to obtain a granulated powder;
Forming the granulated powder in a mold to form a molded body, and
The manufacturing method of a magnesium oxide sintered compact including the process of sintering the said molded object.   The manufacturing method according to claim 7, wherein the carbonate powder or hydroxide powder of Group 2A elements of the periodic table other than magnesium has an average particle size of 1.5 to 30 µm. The manufacturing method according to claim 7, wherein the carbonate powder or hydroxide powder of Group 2A elements of the periodic table other than magnesium has an average particle diameter of 3 to 20 µm.