JP2008091074A - Vapor deposition material for plasma display panel protective film excellent in humidity-proofing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sintered body in which humidity-proofing of a vapor deposition material for a PDP composed of oxides of elements belonging to group 2A of the periodic table is improved, which is used as a target material for forming a protective membrane on a substrate by using an electron beam vapor deposition method, and in which without reducing density and sputtering resistance of the obtained protective membrane, superior membrane characteristics, for example, discharge characteristics or the like when used as the protective membrane for the PDP is enabled to be improved, and provide its manufacturing method, and the protective membrane for the PDP obtained by having this sintered body as the target material. <P>SOLUTION: The vapor deposition material for a PDP protective membrane is the sintered body in which relative density composed of the oxides of the elements belonging to the group 2A of the periodic table is ≥90% and which has the average particle diameter of ≥100 μm. Moreover, this is the vapor deposition material for the PDP protective membrane composed of their oxide simple substance, a mixture, or a solid solution obtained by combining two or more of them, and furthermore this is surface-treated by an organic silicate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention provides, for example, a deposition source when a protective film for a plasma display panel (hereinafter also referred to as “PDP”) is manufactured using a vacuum deposition method such as an electron beam deposition method, an ion plating method, or a sputtering method. The present invention relates to a vapor deposition material for a PDP protective film having excellent moisture resistance and a method for producing the same, and a PDP protective film obtained using the vapor deposition material.

  Development of a PDP using the discharge light emission phenomenon is being promoted as a flat display that is easily increased in size. PDPs are roughly classified into a direct current type (DC type) in which a metal electrode is exposed in a discharge space and an alternating current type (AC type) in which the metal electrode is covered with a dielectric because of the difference in electrode structure.

  In the AC type PDP, a protective film is generally formed on the dielectric in order to prevent the surface of the dielectric layer from being altered due to ion bombardment sputtering to increase the discharge voltage. This protective film is required to have a low discharge voltage and excellent sputtering resistance.

  Conventionally, a magnesium oxide (hereinafter sometimes referred to as “MgO”) film has been used as a protective film that satisfies this requirement. Since the MgO film is an insulator having excellent sputtering resistance and a high secondary electron emission coefficient, the discharge start voltage can be lowered, contributing to the extension of the life of the PDP.

  Currently, a protective film for PDP is generally formed on a dielectric by an electron beam evaporation method using MgO as a target material. However, further power saving of the PDP is required, and in order to solve this problem, it is necessary to further lower the discharge start voltage, which has a lower discharge voltage than the conventional one, and the secondary electron emission coefficient is low. It is necessary to develop high materials.

  For example, Patent Document 1 describes that in order to obtain a practically low discharge voltage, the PDP protective film in contact with the discharge gas is preferably a substance having a secondary electron emission coefficient as high as possible. MgP is mainly used for the PDP protective film, but the oxides of elements belonging to Group 2A of the periodic table, mixtures of combinations thereof, or solid solutions have higher secondary electron emission coefficients. The use of these materials can be expected to improve the discharge voltage characteristics of the PDP. However, oxides of elements belonging to Group 2A of the periodic table other than MgO tend to react with moisture in the atmosphere to form hydroxides, and are difficult to be put into practical use because they are difficult to form good oxide thin films. is there. Therefore, when a PDP protective film made of an oxide of an element belonging to Group 2A of the periodic table in contact with the discharge gas is formed by a vacuum deposition method, an element belonging to Group 2A of the periodic table of the deposition source is formed inside the deposition apparatus immediately before the deposition. It is necessary that the oxide of the element belonging to Group 2A of the periodic table is dissociated into oxide and water, and the dissociation pressure of water exceeds the degree of vacuum in the deposition apparatus. A method of forming a protective layer made of an oxide of an element belonging to Group 2A of the periodic table by heating at a temperature higher than that required and then higher than a temperature required for vapor deposition is proposed. However, this has not led to improvement in moisture resistance of the PDP protective film deposition material itself.

  Patent Document 2 describes that a PDP device having a low driving voltage and good moisture resistance is provided. Since the discharge voltage is determined by the material of the discharge surface, a material with a low discharge voltage is preferable, and it is necessary to be resistant to sputtering. From this point of view, for example, mixed oxides such as MgO, MgO, CaO, and BaO are used as conventional discharge surface materials. These dielectric materials forming the discharge surface are preferable because the discharge voltage is relatively low and the sputtering resistance is good. However, since the above materials have poor moisture resistance, it is necessary to pay attention to the atmosphere during the process. In addition, the formed protective film has high reactivity with carbon dioxide gas and water and is chemically active, so it adsorbs water and carbon dioxide gas and changes to magnesium hydroxide or magnesium carbonate over time. What is satisfactory is not obtained.

  Patent Document 3 discloses a MgO sintered body having a relative density of 95% or more, and 0% alkaline earth metal oxide particles in an MgO matrix having crystal grains having an average crystal grain size of 0.3 to 100 μm. An MgO vapor deposition material dispersed in a volume of 5 to 50% by volume is disclosed. However, it does not improve the moisture resistance of the vapor deposition material itself of the oxide of the element belonging to Group 2A of the periodic table, and is not yet satisfactory.

JP 05-211031 A JP 05-290743 A JP 2000-290062 JP

The subject of this invention is improving the moisture resistance of the vapor deposition material for PDP which consists of an oxide of the element which belongs to periodic table 2A group.
For example, a sintered body used as a target material for forming a protective film on a substrate using an electron beam evaporation method, without reducing the density and sputter resistance of the obtained protective film, Sintered body capable of improving excellent film characteristics, for example, discharge characteristics when used as a protective film for PDP, its manufacturing method, and protective film for PDP obtained using this sintered body as a target material Is to provide.

  In order to obtain a low discharge voltage, the protective layer in contact with the discharge gas is preferably a substance having a secondary electron emission coefficient as high as possible. MgO is stable and has a relatively high secondary electron emission coefficient, but the oxides of elements belonging to Group 2A of the periodic table other than MgO, and mixtures or solid solutions of combinations of two or more thereof are higher. It has a secondary electron emission coefficient, and by using these, it is possible to improve the driving voltage and the life due to the driving voltage. However, oxides of elements belonging to Group 2A of the periodic table other than MgO are likely to react with moisture in the atmosphere to form hydroxides, and when this deposition material is formed, there are the following problems.

  First, it is difficult to uniformly form an oxide film on a large-area glass dielectric layer, and the film thickness distribution is not uniform. When a glass dielectric layer formed with an oxide film with insufficient film thickness uniformity is incorporated in a PDP, problems such as an increase in electric characteristics, for example, an increase or fluctuation in discharge start voltage or drive voltage, occur.

  Secondly, oxides of elements belonging to Group 2A of the periodic table, which are raw materials for the PDP protective film deposition material, have a large amount of occluded gas and moisture. For this reason, when a vapor deposition material is installed in a decompression device, there is a problem that it takes a long time from the start of decompression until the degree of vacuum at which vapor deposition is possible. In addition, the gas occluded in the vapor deposition material during heating by electron beam vapor deposition, etc., destabilizes the vapor deposition operation conditions, and the substrate is contaminated by the gas desorbed under reduced pressure, resulting in clean protection. There is a problem that a film cannot be formed.

  Third, the protective film formed from the oxides of elements belonging to Group 2A of the periodic table as a deposition material has high reactivity with carbon dioxide and water and is chemically active, so it adsorbs water and carbon dioxide. Changes over time to magnesium hydroxide or magnesium carbonate. Therefore, handling is complicated, for example, in the manufacturing process, it is necessary to strictly control the process time exposed to the atmosphere.

Conventionally, MgO is used as the deposition material for the PDP protective film. However, as the performance of the PDP increases, the technical level required by the PDP manufacturer increases, and further improvement of the deposition material for the PDP protective film is desired. . For example, in the PDP, high xenon is achieved to improve the light emission efficiency, and accordingly, the discharge voltage increases and the power consumption increases. Lowering the power consumption of PDP is the biggest problem at present, and for that purpose, a protective film material having a low discharge voltage is being developed.
When an oxide of an element belonging to Group 2A of the periodic table having a high secondary electron emission coefficient is used for the vapor deposition material, the band gap decreases in the order of MgO>CaO>SrO> BaO, and the discharge voltage decreases. However, in this order, the stability in the atmosphere (reactivity with moisture-resistant CO ₂ ) also decreases, and there is a need to solve the problem that it has not reached a practical level.

  In order to achieve the above object, the present inventors use an electromelted product having a low surface reactivity as a starting material for a sintered body used as a target material for an electron beam evaporation method and a PDP protective film. Moisture resistance was improved by surface treatment of the vapor deposition material itself.

For example, a PDP protective film deposition material having a relative density of 90% or more of an oxide of an element belonging to Group 2A of the periodic table and an average particle diameter of 100 μm or more. The oxide of the element to which it belongs is preferably a vapor deposition material for a PDP protective film, which is magnesium oxide, calcium oxide, strontium oxide, or barium oxide.
Moreover, the vapor deposition material for PDP protective film which consists of those oxide single-piece | units, and the mixture or solid solution by those 2 or more combinations may be sufficient, Furthermore, 80 weight% or more of the oxide of the element which belongs to 2A group of a periodic table is sufficient. A vapor deposition material for a PDP protective film, which is an electrofused product, is preferable.
Further, the surface of the PDP protective film deposition material is treated with an organic silicate, and the organic silicate is formed of tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, tetraethoxysilane, methyltrimethylsilane. The vapor deposition material for PDP protective film which is ethoxysilane and dimethyldiethoxysilane was invented.

  Based on the above knowledge, the present inventors have used an oxide simple substance of an element belonging to Group 2A of the periodic table, a mixture of two or more combinations thereof, or a starting material for a sintered body made of a solid solution. It is preferable to use a melted pulverized product, and it is more preferable to surface-treat the sintered body with an organic silicate. By improving the moisture resistance characteristics of the vapor deposition material itself, satisfactory characteristics as a PDP protective film can be obtained. The conclusion was reached.

  The vapor deposition material of the present invention can lower the discharge start voltage by containing an oxide of an element belonging to Group 2A of the periodic table having a high secondary electron emission coefficient, and the operating voltage of the PDP is the protective layer. Since it depends on the secondary electron emission coefficient, it can be lowered. These oxides of elements belonging to Group 2A of the periodic table have a problem that they have low moisture resistance, adsorb moisture in the atmosphere, easily change in quality, and result in unstable discharge characteristics. The inventive vapor deposition material has improved this problem.

  In the present invention, elemental oxides other than fused MgO and MgO belonging to Group 2A of the periodic table are used in addition to conventionally used synthetic MgO.

  The oxides of elements belonging to Group 2A of the periodic table have lower melting points in the order of MgO, CaO, SrO, and BaO, and the reactivity with water increases, but the secondary electron emission coefficient tends to increase. In consideration of this point, MgO is most excellent in the reactivity (moisture resistance) with water. However, in order to improve the electrical characteristics of the PDP and reduce the power consumption, it belongs to the 2A group of these periodic tables. It is conceivable to improve moisture resistance so that oxide materials of elements other than MgO can be used stably.

  Therefore, because the moisture resistance is poorer than that of MgO, the content of oxides of elements other than MgO belonging to Group 2A of the periodic table is not reduced, but the high secondary electron emission coefficient is utilized to actively As described below, while increasing the content, by defining physical properties, an oxide vapor deposition material of an element belonging to Group 2A of the periodic table superior to the conventional vapor deposition material for PDP protective film as a target material is obtained. Can do.

  Furthermore, when the surface of the obtained vapor deposition material itself is surface-treated with an organic silicate or the like, the moisture resistance can be further improved.

  Here, the raw material of the deposition material for the PDP protective film includes one or more components selected from the group of oxides consisting of elements belonging to Group 2A of the periodic table, Be, Mg, Ca, Sr, Ba, and Ra. . An oxide made of Mg, Ca, Sr, and Ba is preferable.

  These oxide raw materials for elements belonging to Group 2A of the periodic table can be used as they are, but the moisture resistance can be improved by using an electromelted product obtained by electromelting.

  In some cases, the mixing ratio can be adjusted depending on the balance between the secondary electron emission coefficient and moisture resistance.

For example, although it is inferior to MgO in moisture resistance, since the secondary electron emission coefficient is superior to MgO, in order to actively use CaO,
As raw materials for vapor deposition materials, 60% by mass of MgO obtained by electrofusion to improve moisture resistance and synthetic CaO to improve secondary electron emission coefficient
40% by mass mixed,
60% by mass of MgO obtained by electromelting to improve moisture resistance, 30% by mass of synthetic CaO to improve secondary electron emission coefficient, and fused CaO obtained by electromelting to improve moisture resistance
Use mixed with 10% by mass,
60% by mass of MgO obtained by electromelting to improve moisture resistance, 20% by mass of synthetic CaO to improve secondary electron emission coefficient, and fused CaO obtained by electrofusion to improve moisture resistance
Used by mixing with 20% by mass,
60% by mass of MgO obtained by electromelting to improve moisture resistance, 10% by mass of synthetic CaO to improve secondary electron emission coefficient, and fused CaO obtained by electromelting to improve moisture resistance
Used by mixing with 30% by mass,
60% by mass of MgO obtained by electromelting to improve moisture resistance, fused CaO obtained by electrofusion to improve secondary electron emission coefficient and moisture resistance
Used by mixing with 40% by mass,
Thus, a vapor deposition material can be produced.

The vapor deposition material containing an electromelted product as a raw material for the vapor deposition material is excellent in moisture resistance as compared with a 100% by mass synthetic raw material.
In order to improve moisture resistance, it is necessary to contain 60% by mass or more of an electromelted product as a raw material for the vapor deposition material. Preferably, the total content of the electromelted product is 80% by mass or more, more preferably electromelting. 100% by mass of the product.

  Further, in order to improve the deposition rate without reducing the density of the protective film after film formation, the relative density of the sintered body needs to be 90% or more, preferably 95% or more, More preferably, it is 98% or more, and the average particle diameter needs to be 100 μm or more.

The sintered body of the present invention can be manufactured as follows.
First, the CaO powder manufactured by the electromelting method is mixed with the MgO powder manufactured by the electromelting method at a predetermined ratio. For mixing, a nylon ball (diameter 10 to 20 mm) with an iron core is put in an alcohol solvent for 10 to 30 hours in a pot mill and pulverized and mixed.
Elements belonging to Group 2A of the periodic table used as raw materials can be used in the form of oxides, nitrates, carbonates, sulfates, hydroxides, sulfites, halides, and the like. After natural drying, it is ignited at 100 to 130 ° C. with a hot air dryer.

  Next, a binder is mixed with the raw material prepared by wet pulverization and drying. This mixing process is implemented using a power kneader, a stirring mill, etc., for example. Although it does not specifically limit as a binder, For example, polyethyleneglycol, CMC, PVA, polyvinyl butyral, etc. are used. The addition amount of the binder is preferably 1 to 10% by mass with respect to the total amount of the mixed powder.

  Subsequently, the powder particle which added and mixed the binder is granulated. First, the powder to which the binder has been added and dried is dried and granulated using a crusher or the like to obtain a granular powder. Granule powder may be obtained using a spray dryer. Since granular powder is excellent in fluidity | liquidity, the filling property to the metal mold | die in the subsequent shaping | molding process improves. The average particle size of the granular powder is preferably 0.8 mm or less.

  Next, the obtained granular powder is put into a predetermined mold and molded. For example, a uniaxial press machine or the like can be used for molding. The molding pressure is preferably set to 100 to 300 MPa, for example, in order to adjust the relative density of the obtained molded body. A more preferable molding pressure is 150 to 250 MPa.

Next, the obtained molded body is fired to obtain the sintered body of the present invention. The firing atmosphere is preferably a gas furnace in the air, the firing temperature is set to 1500 to 1700 ° C., and the firing time is preferably set to 3 to 5 hours.
The obtained sintered body can be used as a target material for forming a protective film for PDP.

  The obtained vapor deposition material can be further surface-treated with an organic silicate to improve the moisture resistance of the sintered body. As the organic silicate, tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane and the like can be used, and methyltrimethoxysilane is preferable.

  The obtained sintered body is filled so as to occupy 40 to 80% by volume with respect to the container that can be sealed. Thereto, 100 to 1000 ppm of organic silicate is added and allowed to stand for 1 to 30 hours. The sealed container is preferably maintained at 20 to 200 ° C. More preferably, it is maintained at a temperature equal to or higher than the boiling point of the organic silicate. By standing still, since the organic silicate layer is adsorbed on the surface of the vapor deposition material in the gas phase, the surface treatment can be performed without causing edge chipping or cracking due to collision between the sintered bodies.

  Examples of the film forming method using the sintered body as a target material include an electron beam evaporation method, an ion irradiation evaporation method, and a vacuum evaporation method such as a sputtering method, and an electron beam evaporation material is particularly preferable.

  EXAMPLES The present invention will be specifically described with reference to examples, but the present invention is not limited to the following examples.

Example 1 Production of a sintered body made of an oxide of an element belonging to Group 2A of the periodic table [Example 1]
60% by weight of MgO powder produced by the electromelting method and 40% by weight of CaO powder produced by the electromelting method were pulverized in a pot mill for 24 hours in an alcohol solvent with iron core-containing nylon balls (diameter: about 15 mm).
After natural drying, it is ignited at 120 ° C. with a hot air dryer, then PK type power kneader (Dalton), 5 minutes at 250 rpm, 6% by weight of binder (trade name: Metroles, Shin-Etsu Chemical) is added. While granulating.
Next, the granulated powder was molded by a press machine (manufactured by Ebara Seiki) at a molding pressure of 200 MPa, and then fired in the gas furnace at 1650 ° C. for 4 hours in the atmosphere to obtain a sintered body of 5 mm × 3 mm × 2 mm. Table 1 shows the evaluation of moisture resistance of the sintered body.

  For the evaluation of moisture resistance, the sintered body was weighed, left to stand in a constant temperature and humidity chamber at a temperature of 40 ° C. and a relative humidity of 85% RH for 24 hours, and the weight of the sintered body after standing was measured. Relative evaluation of moisture resistance was performed from the increase rate.

[Example 2]
The mixing ratio of the MgO powder produced by the electromelting method, the CaO powder produced by the electrofusion method, and the commercially available synthetic CaO powder was determined as follows: electrofused MgO: electrofused CaO: synthetic CaO = 60: 30: 10 (mass ratio) A sintered body was produced in the same manner as in Example 1 except that. Table 1 shows the evaluation of moisture resistance of the sintered body.

[Example 3]
The mixing ratio of the MgO powder produced by the electromelting method, the CaO powder produced by the electrofusion method, and the commercially available synthetic CaO powder is defined as: fused MgO: electrofused CaO: synthetic CaO = 60: 20: 20 (mass ratio) A sintered body was produced in the same manner as in Example 1 except that. Table 1 shows the evaluation of moisture resistance of the sintered body.

[Example 4]
The mixing ratio of the MgO powder produced by the electromelting method, the CaO powder produced by the electrofusion method, and the commercially available synthetic CaO powder is defined as: fused MgO: electrofused CaO: synthetic CaO = 60: 10: 30 (mass ratio A sintered body was produced in the same manner as in Example 1 except that. Table 1 shows the evaluation of moisture resistance of the sintered body.

[Comparative Example 1]
Sintering in the same manner as in Example 1 except that the mixing ratio of the MgO powder produced by the electromelting method and the commercially available synthetic CaO powder is electrofused MgO: synthetic CaO = 60: 40 (mass ratio). The body was made. Table 1 shows the evaluation of moisture resistance of the sintered body.

[Comparative Example 2]
Except that the mixing ratio of MgO powder produced by the electromelting method and commercially available SrCO ₃ powder in terms of oxide was changed to electrofused MgO: synthetic SrO = 60: 40 (mass ratio), the same as in Example 1. A sintered body was produced. Table 1 shows the evaluation of moisture resistance of the sintered body.

[Comparative Example 4]
Except that the mixing ratio of MgO powder produced by the electromelting method and commercially available BaCO ₃ powder in terms of oxide was changed to electrofused MgO: synthetic BaO = 60: 40 (mass ratio), the same as in Example 1. A sintered body was produced. Table 1 shows the evaluation of moisture resistance of the sintered body.

Surface treatment of sintered body [Examples 5 to 11]
The sintered bodies obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were further surface-treated with an organic silicate (methyltrimethoxysilane) to obtain Examples 5 to 11.

  It filled so that 40-80 volume% might be occupied with respect to the container which can seal the sintered compact to surface-treat. Thereto, 500 ppm of organic silicate was added, allowed to stand, and allowed to stand at 120 ° C. for 20 hours. Since the organic silicate (methyltrimethoxysilane) is adsorbed on the surface of the sintered body by leaving the sealed container stationary, the surface treatment should be performed without causing edge breaks or cracks due to collision between the sintered bodies. I was able to. Table 2 shows the evaluation of moisture resistance of these sintered bodies.

◎：吸湿性 極小、○：吸湿性
小、×：吸湿性 大

◎: Extremely hygroscopic, ○: Small hygroscopic, ×: High hygroscopic

◎：吸湿性 極小、○：吸湿性
小、×：吸湿性 大

◎: Extremely hygroscopic, ○: Small hygroscopic, ×: High hygroscopic

From the results shown in Table 1, the sintered body in which the content of the single crystal CaO powder produced by the electrofusion method is increased and the content of the commercially available CaO powder is decreased has improved moisture resistance and PDP protection. A uniform oxide film can be produced as a film deposition material and can be suitably used.
Further, it is effective to reduce the power consumption of the PDP protective film itself by containing a large amount of the oxide component of the element belonging to Group 2A of the periodic table having a higher secondary electron emission coefficient than MgO.

  Moreover, as shown in Table 1, in Comparative Examples 1 to 3, when a commercially available product other than the electrofused product is used as a raw material of the sintered body, the moisture resistance is reduced as compared with the sintered bodies of Examples 1 to 4. As can be seen from Table 2, moisture resistance can be improved by surface treatment with an organic silicate.

Claims (6)

A vapor deposition material for a protective film of a plasma display panel, which is a sintered body having a relative density of 90% or more and comprising an oxide of an element belonging to Group 2A of the periodic table and having an average particle diameter of 100 × 10 ⁻⁶ m or more. The vapor deposition material for a plasma display panel protective film according to claim 1, wherein the oxide of an element belonging to Group 2A of the periodic table is magnesium oxide, calcium oxide, strontium oxide, or barium oxide. The vapor deposition material for a plasma display panel protective film according to claim 1 or 2, comprising an oxide of an element belonging to Group 2A of the periodic table, a mixture of two or more of them, or a solid solution. The vapor deposition material for a plasma display panel protective film according to any one of claims 1 to 3, wherein 80 mass% or more of the oxide of an element belonging to Group 2A of the periodic table is an electromelted product. 5. The plasma display panel protective film deposition material according to any one of claims 1 to 4, wherein the surface treatment is performed with an organic silicate. The vapor deposition material for a plasma display panel protective film according to claim 5, wherein the organic silicate is tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, tetraethoxysilane, methyltriethoxysilane, or dimethyldiethoxysilane.