JP2005263591A - Protective film material for plasma display panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a protective film material for a plasma display panel by which a magnesium oxide sintered compact having ≥85% relative density is obtained by sintering at a low temperature (1,350-1,450°C). <P>SOLUTION: Tin oxide is mixed with magnesium oxide as an additive. The magnesium oxide sintered compact having 80-90% relative density is obtained by sintering at the low temperature (1,350-1,450°C) while controlling the concentration of tin oxide to be added to ≥0.05 mol% and ≤1.00 mol%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a deposition material suitable for forming a magnesium oxide (hereinafter abbreviated as MgO) film used for protecting a dielectric layer of a plasma display panel from electric discharge.

  In recent years, plasma display panels (hereinafter abbreviated as PDPs) have been attracting attention as self-luminous thin displays. The PDP is close to the principle of a domestic fluorescent lamp which is a kind of bipolar tube. An inert gas such as argon or neon is sealed between two adjacent glass plates formed with a transparent electrode, and plasma discharge is caused to excite the gas to emit visible light from the phosphor. Due to its structure, the PDP can have a larger screen than other displays, and has characteristics such as a high response speed and a wide viewing angle.

  There are two types of PDPs, AC type and DC type, classified according to how voltage is applied during discharge. Both types have a structure in which the discharge space is sandwiched between two glass plates. In the DC type, the electrode is exposed to the discharge space, and in the AC type, the electrode is insulated by a dielectric layer. Different. In the AC type, which is becoming the mainstream of recent products, since the dielectric layer was exposed to the discharge space in the early stages of development, the surface of the dielectric layer was changed by ion bombardment sputtering, and the discharge start voltage in the discharge space increased. Was. In order to suppress an increase in the discharge start voltage, a protective film made of an oxide of alkali metal or alkaline earth metal, MgO or the like is provided on the surface of the dielectric layer. As the protective film, MgO is the most excellent, which makes it possible to extend the life of the PDP.

  In manufacturing a PDP, how to stably form the MgO protective film is a major point. In general, the MgO protective film is formed on a dielectric layer by ion beam evaporation or electron beam evaporation. In these vapor deposition methods, single crystal MgO is mainly used as a vapor deposition material. This single crystal MgO is melted by electrofusion and then cooled, and the single crystal portion is taken out and pulverized. This electromelting method requires high energy to bring MgO to a high temperature. Further, since this single crystal MgO has a high melting point, it is necessary to sinter the single crystal MgO at a high temperature in order to form a sintered body made of single crystal MgO.

  In order to produce a sintered body of single crystal MgO, there are problems that require furnace equipment that can withstand high temperatures and problems that require enormous energy for sintering.

  Conventionally, there is a patent that employs a method using polycrystalline MgO as a method for solving the physical property problems of single crystal MgO (see, for example, Patent Document 1). In this patent, in order to solve the problem that the purity of the product fluctuates very easily by the method of collecting single crystal MgO, and the stability and reliability of the purity of single crystal MgO are not solved, polycrystalline MgO is used. The method of using is adopted. First, 1.5% by weight of polyethylene glycol as a binder is added to MgO powder (purity 99.98%, average particle size 0.2 μm), and a chiller having ethanol as a dispersion medium has a concentration of 53% by weight (viscosity 100 cps). The chiller was wet mixed in a ball mill (using a resin ball having a diameter of 10 mm) for 24 hours and then granulated with a spray dryer (drying tower temperature: 100 ° C.) to produce an average particle size of 100 μm. Grain powder is obtained, filled into a rubber mold and CIP molded at 1000 Kg / cm to obtain a cylindrical molded body having an outer shape and height of 10 mm and 5 mm, and sintered at 1650 ° C. in the atmosphere. ing. This is shown in Table 2 as Example 1, and in addition, as an Example, Table 2 shows examples when the sintering temperature is variously changed.

Japanese Patent No. 3333184

  In the invention of the above-mentioned Patent Document 1, a means of using polycrystalline MgO is adopted in order to solve the physical property problem of single crystal MgO, but the sintering temperature of the sintered body is 1650 ° C or the like. It is not intended to lower the sintering temperature. The problem to be solved by the present invention is to sinter an MgO sintered body whose relative density does not fall below 85% at a low temperature. The reason why the relative density is not lower than 85% is that, when a sintered body is generally used as a vapor deposition material, it is possible to stably deposit by increasing the density to a certain level or higher. .

  In order to solve the above-described problems, the present invention sinters MgO sintered bodies at a low temperature (1350 ° C. to 1450 ° C.) without deteriorating the discharge characteristics of the plasma display panel and having a relative density of less than 85%. The present inventors have studied a vapor-deposited material of an MgO composite material sintered body that can be obtained, and have reached the present invention.

  The present invention is a vapor deposition material for forming a magnesium oxide protective film used in a plasma display panel, and the relative density (density ratio with respect to single crystal magnesium oxide) of a composite material in which an additive is mixed in magnesium oxide is 85%. It is characterized by not falling below.

  Further, the present invention is characterized in that the additive mixed into the magnesium oxide is tin oxide.

  In addition, the present invention is characterized in that the addition concentration of tin oxide mixed in magnesium oxide is 0.05 mol% or more and 1.00 mol% or less.

Further, the present invention is characterized in that the additive mixed into the magnesium oxide is In ₂ O ₃ or Eu ₂ O ₃ .

  According to the present invention, an MgO fired body that has conventionally required firing at a high temperature (1500 ° C. or higher) is fired at a low temperature (1350 ° C. to 1450 ° C.) without adversely affecting the deposition rate and the secondary electron emission coefficient. Made it possible. Therefore, the equipment of the firing furnace can be simplified, and the energy required for firing can be reduced.

As a method for lowering the firing temperature of the MgO fired body, it is effective to use a raw material having a high surface activity and to add impurities. In the present invention, fine powder MgO prepared by thermally decomposing Mg (OH) ₂ with respect to the former is used as a raw material. Further, tin oxide, In ₂ O ₃ , or Eu ₂ O ₃ is added to the latter. These impurities are selected as substances that do not affect the deposition rate and the secondary electron emission coefficient of the deposited film when the fired body is used as a deposition material for forming a protective film of PDP.

FIG. 1 is a flowchart showing a process for producing a protective film material for a plasma display panel according to the present invention.
Hereafter, each process is demonstrated in detail with reference to the flowchart of FIG.
In the present invention, tin oxide is mixed in magnesium oxide as an additive. The concentration of tin oxide added is in the range of 0.05 mol% to 1.00 mol%.

Mg (OH) ₂ obtained by hydroxylating magnesium metal in pure water is decomposed by heating to produce MgO powder having a purity of 99.9% or more (S101). 0.05 mol% to 1.00 mol% of stannic oxide (SnO ₂ ) is added to the MgO powder (S102).
An organic binder is added to the mixture in a 2% to 8% weight ratio. A solvent is added to the mixture so that the amount of oxide is 40 to 60% by weight, and these are mixed and dispersed to prepare a slurry having a MgO average particle size of 0.2 to 0.3 microns. (S103). Polyethylene glycol or the like is used for the binder, and ethanol or the like is used for the solvent.

  In the above process, a ball mill pot and balls having a diameter of 10 to 30 mm are used and mixed for about 20 hours.

  After mixing, the mixture is spray-dried, or the slurry is placed in an open top container and dried, and then pulverized and classified to prepare granulated powder of 40 to 300 microns (S104).

This granulated powder is molded at a molding pressure of 500 to 3000 kg / cm ² with a uniaxial press to produce a molded body having a diameter of 6 to 7 mm and a thickness of 2 to 4 mm (S105).

  The molded body is fired at a firing temperature of 1350 ° C. for 2 hours at atmospheric pressure to produce a fired body as an MgO composite material (S106).

  Table 1 shows the firing density that varies depending on the concentration of tin oxide added and the firing temperature. As shown in Table 1, by setting the amount of tin oxide added to be 0.05 mol% to 1.00 mol%, the fired body (ratio to the density of single crystal MgO) should not fall below 85% relative density. And it turns out that a calcination temperature can be made into 1350 to 1450 degreeC. Even if the addition amount of tin oxide is 1.00 mol% or more, the firing temperature cannot be lowered.

  The relative density of the fired body is closely related to the vapor deposition rate, and decreases when it is 85% or less. From the viewpoint of the deposition rate, 90 ± 3% is preferable.

The amount of addition when In ₂ O ₃ and Eu ₂ O ₃ are added as additives is preferably 0.05 mol% to 0.50 mol%.

  The protective film material for a plasma display panel according to the present invention can be applied not only to electron beam evaporation but also to ion beam evaporation.

Further, by adopting In ₂ O ₃ or Eu ₂ O ₃ as an additive instead of tin oxide, the same result as that of tin oxide can be obtained.

It is a flowchart which shows the formation process of the protective film material for plasma display panels which concerns on this invention.

Claims (4)

A magnesium oxide protective film material used for a plasma display panel,
A protective film material for a plasma display panel, wherein a relative density of a composite material in which an additive is mixed with magnesium oxide with respect to a magnesium oxide single crystal does not fall below 85%.   The protective film material for a plasma display panel according to claim 1, wherein the additive is tin oxide.   3. The protective film material for a plasma display panel according to claim 2, wherein an addition concentration of the tin oxide is 0.05 mol% or more and 1.00 mol% or less. The protective film material for a plasma display panel according to claim 1, wherein the additive is In ₂ O ₃ or Eu ₂ O ₃ .

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