JP2012072428A - Vapor deposition material for protective film of plasma display panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vapor deposition material for a protective film of a plasma display made of a magnesium oxide sintered body which is excellent in smoothness of the surface of a sintered body and enables a smooth supply.
A deposition material for a protective film of a plasma display comprising a magnesium oxide sintered body containing 2 to 50% by mass of calcium oxide and having a relative density of 95% or more,
Magnesium oxide sintered body has a BET specific surface area of 5 m ² / g or more, a volume-based cumulative 50% particle diameter (D ₅₀ ) by laser diffraction scattering type particle size distribution measurement of 0.1 to 0.5 μm, laser diffraction scattering type The ratio D ₉₀ / D ₁₀ between the volume-based cumulative 10% particle size (D ₁₀ ) and the volume-based cumulative 90% particle size (D ₉₀ ) by particle size distribution measurement is 10 or less, and the purity is 99.5% by mass or more. Deposition material for protective film of plasma display panel using magnesium oxide fine particles as raw material.
[Selection figure] None

Description

  The present invention relates to a protective film deposition material for a plasma display panel (hereinafter referred to as PDP).

  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 the direct exposure of the dielectric layer to the discharge start voltage, and is not changed by 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, a sintered body made of a mixed oxide of magnesium oxide and calcium oxide, barium oxide or the like has been proposed as a material constituting the protective film. These protective film materials have the advantage that the discharge starting voltage is relatively low and the spatter resistance is good, but on the other hand, the strength is low and the protrusions of the sintered body are destroyed by the thermal shock during vapor deposition. There is a problem that splash (sudden boiling) is likely to occur. In order to solve this point, a magnesium oxide sintered body having a relative density of 95% or more and having an average crystal grain size of 0.3 to 100 μm contains alkaline earth metal oxide particles in an amount of 0.1%. A vapor deposition material composed of a magnesium oxide sintered body dispersed in an amount of 5 to 50% by volume has been proposed (see Patent Document 1).

JP 2000-290062 JP

  However, the vapor deposition material proposed in Patent Document 1 has a problem that the vapor deposition material cannot be supplied smoothly because the surface of the sintered body lacks smoothness and large friction occurs.

  This invention is made | formed in view of said subject, and is providing the vapor deposition material for protective films of PDP which is excellent in the smoothness of the surface of a sintered compact, and enables supply of a smooth vapor deposition material.

The present invention is a deposition material for a protective film of a plasma display comprising a magnesium oxide sintered body containing 2 to 50% by mass of calcium oxide and having a relative density of 95% or more,
Magnesium oxide sintered body has a BET specific surface area of 5 m ² / g or more, a volume-based cumulative 50% particle diameter (D ₅₀ ) by laser diffraction scattering type particle size distribution measurement of 0.1 to 0.5 μm, laser diffraction scattering type The ratio D ₉₀ / D ₁₀ between the volume-based cumulative 10% particle size (D ₁₀ ) and the volume-based cumulative 90% particle size (D ₉₀ ) by particle size distribution measurement is 10 or less, and the purity is 99.5% by mass or more. The present invention relates to a vapor deposition material for a protective film of a plasma display panel, using as a raw material magnesium oxide fine particles.

  According to the vapor deposition material for the protective film of the PDP of the present invention, since the surface of the sintered body is excellent, the occurrence of friction is small and the vapor deposition material can be supplied smoothly. In addition, the occurrence of splash at the time of film formation is suppressed, and when the obtained deposited film is used as a protective film for PDP, there is an advantage that the discharge start voltage can be lowered.

  The deposition material for a protective film of the PDP of the present invention is composed of a magnesium oxide sintered body containing 2 to 50% by mass of calcium oxide and having a relative density of 95% or more.

  In the present invention, the magnesium oxide sintered body contains magnesium oxide as a main component (50% by mass or more) as a constituent component, and further contains calcium oxide having a small band gap and a high effect of reducing the discharge start voltage. Here, the sintered body means that the powder aggregates are connected by solid phase diffusion of the powder, growth of the neck portion, movement of crystal grain boundaries, etc. by heating the aggregate of the powder at a temperature lower than the melting point. It refers to a dense molded body manufactured in this way.

  The content of calcium oxide is 2 to 50% by mass in 100% by mass of the magnesium oxide sintered body. Within this range, the discharge start voltage when the deposited film is used as a protective film for PDP can be sufficiently reduced, and sufficient strength is provided to the magnesium oxide sintered body, so Splash generation can be suppressed. The content of calcium oxide is preferably 3 to 20% by mass.

  In the present invention, the relative density of the magnesium oxide sintered body is 95% or more, and since the sintered body has a high strength, breakage due to thermal shock at the time of film formation is suppressed, and the occurrence of splash and fragments It becomes possible to prevent scattering.

  In the present invention, by using magnesium oxide fine particles having specific physical properties as a raw material, not only the occurrence of splash during film formation can be suppressed, but also the smoothness of the sintered body surface is excellent. Therefore, there is little generation of friction, and the vapor deposition material can be supplied smoothly. When the obtained deposited film is used as a protective film for PDP, the discharge start voltage can be lowered.

In the present invention, the magnesium oxide sintered body has a BET specific surface area of 5 m ² / g or more, a volume-based cumulative 50% particle diameter (D ₅₀ ) of 0.1 to 0.5 μm by laser diffraction scattering type particle size distribution measurement, Purity 99. The ratio D ₉₀ / D ₁₀ of the volume-based cumulative 10% particle diameter (D ₁₀ ) and the volume-based cumulative 90% particle diameter (D ₉₀ ) by laser diffraction scattering particle size distribution measurement is 10 or less. One of the raw materials is 5% by mass or more of magnesium oxide fine particles.

In the present specification, the purity refers to the impurity element (Ag, Al, B, Ba, Bi, Cd, Cl, Co, Cr, Cu, Fe, Ga, In, K, Li, Mn, Mo, Na in the target fine particles. , Ni, P, Pb, S, Si, Sr, Tl, V, Zn, Ti, and Zr) are measured, and the total content is subtracted from 100% by mass. In the present specification, high purity means that the purity calculated as described above is 99.5% by mass or more.
Impurity elements to be measured (Ag, Al, B, Ba, Bi, Cd, Co, Cr, Cu, Fe, Ga, In, K, Li, Mn, Mo, Na, Ni, P, Pb, S, Si , Sr, Tl, V, Zn, Ti, and Zr), using an ICP emission spectrometer, the sample was dissolved in acid, then the mass was measured, and the Cl amount was measured using a spectrophotometer. Is dissolved in an acid and the mass is measured.

The BET specific surface area is preferably 20 m ² / g or more, more preferably 40 m ² / g or more, D ₅₀ is preferably 0.2 to 0.4 μm, and D ₉₀ / D ₁₀ is preferably 5 or less. The purity is preferably 99.9% by mass or more.

  The magnesium oxide fine particles preferably have a total content of Fe, Ti, Ni, Cr, Mo and Mn of 500 mass ppm or less. When the total content is 500 ppm by mass or less, the mixing of metal impurities into the protective film deposition material of the plasma display panel is sufficiently small. The total content is more preferably 450 mass ppm or less.

  The magnesium oxide fine particles preferably have a chlorine content of 500 mass ppm or less. When this content is 500 ppm by mass or less, the mixing of chlorine into the protective film deposition material of the plasma display panel is sufficiently small. The content is more preferably 450 ppm by mass or less.

  In the magnesium oxide fine particles, the ratio Dv / Dn of the volume average particle diameter (Dv) to the number average particle diameter (Dn) is preferably 1 to 10, more preferably 1 to 8.

Magnesium oxide particles have a BET specific surface area of 5 m ² / g or more, a volume-based cumulative 50% particle diameter (D ₅₀ ) of 0.1 to 0.5 μm by laser diffraction scattering particle size distribution measurement, and a laser diffraction scattering particle size distribution. The ratio D ₉₀ / D ₁₀ of the volume-based cumulative 10% particle diameter (D ₁₀ ) to the volume-based cumulative 90% particle diameter (D ₉₀ ) by measurement is 10 or less, and water having a purity of 99.5% by mass or more Magnesium oxide fine particles can be obtained by firing. Baking can be performed at 500-1500 degreeC in an atmospheric condition, for example.

Magnesium hydroxide fine particles having the above characteristics are
Preparing a magnesium chloride aqueous solution (A);
A step (B) of obtaining a magnesium hydroxide slurry by reacting an aqueous magnesium chloride solution with an alkaline aqueous solution of 1 to 18 N at a reaction rate of 101 to 210 mol%;
The magnesium hydroxide slurry is maintained at a temperature of 101 to 200 ° C. with stirring to obtain a hydrothermally treated magnesium hydroxide slurry (C); and the hydrothermally treated magnesium hydroxide slurry is filtered, washed and Step of drying to obtain magnesium hydroxide fine particles (D)
It can obtain by the method containing. Here, the reaction rate is a value calculated by assuming that the amount of alkali necessary for all magnesium chloride to become magnesium hydroxide is 100 mol%.

  The magnesium oxide sintered body containing calcium oxide is mixed with a predetermined amount of magnesium oxide fine particles and calcium compound fine particles, and a binder solution and optionally additives such as a dispersant, and then granulated, dried, and predetermined. After being introduced into a mold and molded, it can be obtained by sintering.

Examples of the calcium compound fine particles include calcium oxide, carbonate or hydroxide fine particles, and high purity (for example, a purity of 99% by mass or more, preferably a purity of 99.9% by mass or more) is preferable. . The volume-based cumulative 50% particle diameter (D ₅₀ ) of the calcium compound fine particles measured by laser diffraction scattering type particle size distribution is preferably 0.5 to 30 μm. This is because the smoothness of the surface of the sintered body can be maintained within this range. D ₅₀ is more preferably 1.5 to 20 μm.

  The magnesium oxide fine particles and the calcium compound fine particles can be used in an amount such that the calcium oxide in the magnesium oxide sintered body becomes a desired amount.

  The binder solution is not particularly limited, and for example, a solution such as CMC (carboxymethyl cellulose), PVA (polyvinyl alcohol), acrylic resin, vinyl acetate resin, or the like can be used, but is not limited thereto. The concentration of the binder solution is preferably 5 to 50% by weight. The solvent of a solution is not specifically limited, Ethanol etc. are mentioned. The binder solution is preferably 1 to 10 parts by weight with respect to a total of 100 parts by weight of the oxide-converted fine particles as the resin solid content.

  Granulation can be performed by a rolling granulation method, a spray granulation method, or the like, but is not limited thereto. The obtained granulated body is dried and then put into a predetermined mold and molded. Molding can be performed using a single-screw press machine or the like, but is not limited thereto. The mold pressure is preferably set to 50 to 600 MPa in order to adjust the relative density of the obtained molded body. A magnesium oxide sintered body can be obtained by firing the obtained molded body. Firing can be performed at a firing temperature of 1300 to 1800 ° C. and a firing time of 0.5 to 20 hours. For firing, an electric furnace, a gas furnace, or the like can be used.

  The vapor deposition material which consists of a magnesium oxide sintered compact of this invention is used as a film-forming raw material of the protective film for PDP. The method of film formation is not particularly limited, and a vacuum vapor deposition method such as an electron beam vapor deposition method, an ion plating method, or a sputtering method can be used.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

  The physical properties of the magnesium oxide fine particles and the properties as a vapor deposition material were measured by the following methods.

(1) Impurity mass measurement method Impurity elements (Ag, Al, B, Ba, Bi, Cd, Co, Cr, Cu, Fe, Ga, In, K, Li, Mn, Mo, Na, Ni to be measured) , P, Pb, S, Si, Sr, Tl, V, Zn, Ti and Zr) were dissolved in acid using an ICP emission analyzer (trade name: SPS-5100, manufactured by Seiko Instruments) It was measured.
The amount of Cl was measured using a spectrophotometer (trade name: UV-2550, manufactured by Shimadzu Corporation) after dissolving the sample in acid.

(2) Purity measurement method The purity of magnesium hydroxide, magnesium oxide, and calcium compound was calculated as a value obtained by subtracting the total mass of impurity elements measured by the above-mentioned "impurity amount measurement method" from 100% by mass.

(3) BET specific surface area measuring method The specific surface area was measured by the BET method of the gas adsorption method using a specific surface area measuring device (trade name: Macsorb 1210, manufactured by Mountec Co., Ltd.).

(4) Particle diameter measurement method Using a laser diffraction / scattering particle size distribution measuring device (trade name: MT3300, manufactured by Nikkiso Co., Ltd.), volume-based cumulative 10% particle diameter (D ₁₀ ), volume-based cumulative 50% The particle diameter (D ₅₀ ) and the volume-based cumulative 90% particle diameter (D ₉₀ ) were measured. The volume average particle diameter (Dv) and the number average particle diameter (Dn) were also measured with the above apparatus.

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

(6) Method for calculating 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 3.58 g / cc, the theoretical density of calcium oxide was 3.32 g / cc, and the theoretical density of aluminum oxide was 3.97 g / cc.

After 10 kg of hearth was filled as a vapor deposition material with a magnesium oxide sintered body containing calcium oxide, vapor deposition was performed on the substrate at an output of 18 kV and 900 mA for 15 minutes using an electron beam vapor deposition apparatus. During the film formation, the state of occurrence of splash was visually observed from the viewport. Further, after the film formation, the surface of the thin film was observed and evaluated in three stages based on the following evaluation criteria.
A: Neither splash nor deposit of vapor deposition material on the film surface was observed.
○: Splash was observed, but no deposits of vapor deposition material on the film surface were observed.
X: Many splashes were observed, and deposition material fragments were confirmed to adhere to the film surface.

(Maximum static friction force measurement method)
In order to confirm the frictional force of the sintered body, the vapor deposition material is put into a stainless steel groove whose angle can be changed, and from the angle θ at which the sintered body starts to slide, the force applied to the sintered body is calculated as the maximum static frictional force: F Calculated from the formula.
F (× 10 ⁻³ N) = μ · m · g · cosθ
μ: Static friction coefficient (calculated as μ = tan θ)
m: weight of sintered body g: acceleration of gravity

  The magnesium oxide sintered body was prepared as follows.

[Preparation of magnesium oxide fine particles 1]
A crude magnesium chloride aqueous solution having a purity of 90% by mass or more and a concentration of 3.5 mol / L was prepared. The concentration was adjusted by adding pure water (water purified by passing through an ion exchange resin to have an electric conductivity of 0.1 μS / cm or less) to this magnesium chloride aqueous solution, and a crude magnesium chloride aqueous solution having a concentration of 2.0 mol / L. It was.

  Next, a sodium hydroxide aqueous solution with a concentration of 17.84 mol / L was added to the crude magnesium chloride aqueous solution with a concentration of 2.0 mol / L so as to achieve a reaction rate of 20 mol%. An acrylamide / sodium acrylate copolymer was added in an amount of 500 ppm by mass to the produced magnesium hydroxide, the magnesium hydroxide was coagulated and precipitated, and the supernatant was taken out to obtain an aqueous magnesium chloride solution.

  The concentration of the obtained magnesium chloride aqueous solution was adjusted to obtain a magnesium chloride aqueous solution having a concentration of 2.0 mol / L. This magnesium chloride aqueous solution was reacted with a sodium hydroxide aqueous solution having a concentration of 17.84 mol / L so that the reaction rate was 200 mol% to prepare a magnesium hydroxide slurry having a concentration of 100 g / L.

  The obtained magnesium hydroxide slurry was held with stirring at 150 ° C. for 1 hour using an autoclave, and subjected to hydrothermal treatment (heated stirring treatment). The first magnesium hydroxide slurry subjected to hydrothermal treatment was filtered and washed with water to obtain a first magnesium hydroxide cake. Washing with water was performed by adding 40 times the pure water after mass filtration to the dried magnesium hydroxide.

Next, repulp washing was performed on the obtained first magnesium hydroxide cake. In the repulp washing, first, 40 times pure water was added on a mass basis with respect to the dried magnesium hydroxide of the first magnesium hydroxide cake to obtain a second magnesium hydroxide slurry. Next, the second magnesium hydroxide slurry is stirred at room temperature using a stirrer at a rotation speed of 500 rpm for 1 hour, and the second magnesium hydroxide slurry after the stirring is further filtered using filter paper. Then, with respect to the dried magnesium hydroxide, 20 times as much pure water was added after filtration and washed with water to obtain a second magnesium hydroxide cake. The above-described repulp washing was performed once, and the repulp washing was further repeated 10 times to obtain a high purity magnesium hydroxide cake. The high purity magnesium hydroxide cake was dried to obtain high purity magnesium hydroxide fine particles. The obtained high purity magnesium hydroxide fine particles had the following characteristics.
BET specific surface area: 10.87 m ² / g
Particle size: D ₅₀ 0.47 μm, D ₁₀ 0.18 μm, D ₉₀ 0.84 μm,
Dv / Dn 2.48
Particle size distribution: D ₉₀ / D ₁₀ 4.7
Impurity amount: Cl 307ppm
Total content of Fe, Ti, NI, Cr, Mo and Mn 421ppm
Purity:> 99.9% by mass

  The obtained high-purity magnesium hydroxide fine particles were fired at 1000 ° C. for 1 hour in an air atmosphere to obtain magnesium oxide fine particles 1. The characteristics of the magnesium oxide fine particles 1 are shown in Table 1.

[Preparation of magnesium oxide fine particles 2]
In preparing high purity magnesium hydroxide fine particles, high purity magnesium hydroxide fine particles were obtained with a reaction rate of 105 mol% in a reaction between an aqueous magnesium chloride solution and an aqueous sodium hydroxide solution and a hydrothermal treatment time of 3 hours. Magnesium oxide fine particles 2 were obtained in the same manner as the magnesium oxide fine particles 1 except that the magnesium hydroxide fine particles were calcined at 600 ° C. Table 1 shows the characteristics of the magnesium oxide fine particles 2.
The high purity magnesium hydroxide fine particles had the following characteristics.
BET specific surface area: 17.15 m ² / g
Particle size: D ₅₀ 0.38 μm, D ₁₀ 0.18 μm, D ₉₀ 0.89 μm,
Dv / Dn 2.4
Particle size distribution: D ₉₀ / D ₁₀ 4.9
Impurity amount: Cl 448ppm
Total content of Fe, Ti, NI, Cr, Mo and Mn 10ppm
Purity:> 99.9% by mass

[Preparation of magnesium oxide fine particles 3]
In preparing high purity magnesium hydroxide fine particles, high purity magnesium hydroxide fine particles were obtained with a reaction rate of 150 mol% in a reaction between an aqueous magnesium chloride solution and an aqueous sodium hydroxide solution and a hydrothermal treatment time of 1 hour. Magnesium oxide fine particles 3 were obtained in the same manner as the magnesium oxide fine particles 1 except that the magnesium hydroxide fine particles were calcined at 800 ° C. Table 1 shows the characteristics of the magnesium oxide fine particles 3.
The high purity magnesium hydroxide fine particles had the following characteristics.
BET specific surface area: 12.15 m ² / g
Particle size: D ₅₀ 0.33 μm, D ₁₀ 0.18 μm, D ₉₀ 0.81 μm,
Dv / Dn 2.39
Particle size distribution: D ₉₀ / D ₁₀ 4.5
Impurity amount: Cl 188ppm
Total content of Fe, Ti, NI, Cr, Mo and Mn 10ppm
Purity:> 99.9% by mass

[Preparation of Magnesium Oxide Fine Particles 4]
In the preparation of high purity magnesium hydroxide fine particles, high purity magnesium hydroxide fine particles were obtained with a reaction rate of 95 mol% in a reaction between a magnesium chloride aqueous solution and a sodium hydroxide aqueous solution and a hydrothermal treatment time of 3 hours. Magnesium oxide fine particles 4 were obtained in the same manner as the magnesium oxide fine particles 1 except that the magnesium hydroxide fine particles were calcined at 800 ° C. Table 1 shows the characteristics of the magnesium oxide fine particles 4.

[Preparation of magnesium oxide fine particles 5]
In the preparation of high purity magnesium hydroxide fine particles, high purity magnesium hydroxide fine particles were obtained with a reaction rate of 95 mol% in a reaction between a magnesium chloride aqueous solution and a sodium hydroxide aqueous solution and a hydrothermal treatment time of 2 hours. Magnesium oxide fine particles 5 were obtained in the same manner as the magnesium oxide fine particles 1 except that the magnesium hydroxide fine particles were fired at 1000 ° C. The characteristics of the magnesium oxide fine particles 5 are shown in Table 1.

[Preparation of magnesium oxide fine particles 6]
In preparing high-purity magnesium hydroxide fine particles, high-purity magnesium hydroxide fine particles were obtained with a reaction rate of 90 mol% in a reaction between a magnesium chloride aqueous solution and a sodium hydroxide aqueous solution and a hydrothermal treatment time of 3 hours. Magnesium oxide fine particles 6 were obtained in the same manner as the magnesium oxide fine particles 1 except that the magnesium hydroxide fine particles were fired at 1200 ° C. Table 1 shows the characteristics of the magnesium oxide fine particles 6.

  Preparation of the vapor deposition material which consists of a magnesium oxide sintered compact was performed as follows.

[Example 1]
17.85 g (equivalent to 10% by mass in terms of calcium oxide) of 89.99 g of magnesium oxide fine particles 1 and D ₅₀ 18.95 μm calcium carbonate fine particles (manufactured by Kanto Chemical Reagents: calcium carbonate 4N, purity 99.99% or more) ) Added and mixed. Then, after granulation and drying, it is formed into a 8 mm × 8 mm × 3.5 mm rectangular solid by press molding (molding pressure: 200 MPa), fired in an electric furnace at 1450 ° C. × 8 hours, and calcined with magnesium oxide containing calcium oxide. A bonded body was obtained and used as a vapor deposition material.

[Example 2]
The D ₅₀ of fine calcium carbonate particles of Example 1 was changed to 7.65μm by wet grinding, except for adding 3% by mass of calcium oxide in terms, a similar manner to Example 1, magnesium oxide sintered containing calcium oxide A body was obtained and used as a vapor deposition material.

Example 3
The D ₅₀ of fine calcium carbonate particles of Example 1 was changed to 1.86μm by wet grinding, except for adding 15 wt% calcium oxide conversion, performed in the same manner as in Example 1, magnesium oxide sintered containing calcium oxide A body was obtained and used as a vapor deposition material.

Example 4
In place of the magnesium oxide fine particles 1, magnesium oxide fine particles 2 were used, and the calcium carbonate fine particles of Example 1 were changed in the same manner as in Example 1 except that D ₅₀ was changed to 3.56 μm by wet grinding. The magnesium oxide sintered compact containing this was obtained, and this was made into the vapor deposition material.

Example 5
A magnesium oxide sintered body containing calcium oxide was obtained in the same manner as in Example 1 except that the magnesium oxide fine particles 3 were used in place of the magnesium oxide fine particles 1, and this was used as a vapor deposition material.

[Comparative Examples 1-3]
Using magnesium oxide fine particles 4-6, it carried out similarly to Example 1, the magnesium oxide sintered compact containing a calcium oxide was obtained, and this was made into the vapor deposition material of a comparative example. Comparative Example 2-3, a _{D 50} of fine calcium carbonate particles of Example 1 by wet grinding, respectively, was used was changed to 7.65μm and 1.86μm.

Claims (6)

A vapor deposition material for a protective film of a plasma display comprising a magnesium oxide sintered body containing 2 to 50% by mass of calcium oxide and having a relative density of 95% or more,
Magnesium oxide sintered body has a BET specific surface area of 5 m ² / g or more, a volume-based cumulative 50% particle diameter (D ₅₀ ) by laser diffraction scattering type particle size distribution measurement of 0.1 to 0.5 μm, laser diffraction scattering type The ratio D ₉₀ / D ₁₀ between the volume-based cumulative 10% particle size (D ₁₀ ) and the volume-based cumulative 90% particle size (D ₉₀ ) by particle size distribution measurement is 10 or less, and the purity is 99.5% by mass or more. Deposition material for protective film of plasma display panel using magnesium oxide fine particles as raw material.   The vapor deposition material for a protective film of a plasma display panel according to claim 1, wherein the magnesium oxide sintered body is further made of calcium carbonate and / or calcium hydroxide.   The deposition material for a protective film of a plasma display panel according to claim 1 or 2, wherein the purity of the magnesium oxide fine particles is 99.9 mass% or more.   The evaporation material for a protective film of a plasma display panel according to any one of claims 1 to 3, wherein the total content of Fe, Ti, Ni, Cr, Mo and Mn in the magnesium oxide fine particles is 500 ppm by mass or less.   The vapor deposition material for a protective film of a plasma display panel according to any one of claims 1 to 4, wherein the chlorine content of the magnesium oxide fine particles is 500 mass ppm or less.   The protective film for a plasma display panel according to any one of claims 1 to 5, wherein the ratio Dv / Dn of the volume average particle diameter (Dv) to the number average particle diameter (Dn) of the magnesium oxide fine particles is 1 to 10. Vapor deposition material.