JP5418747B2 - ZnO vapor deposition material, method for producing the same, and method for forming the ZnO film - Google Patents

Description

The present invention relates to a transparent conductive film or gas and water vapor resistant film used for, for example, a solar cell, a transparent electrode of a transparent piezoelectric sensor of a liquid crystal display device, an electroluminescence display device or a touch panel device, or a gas and water vapor resistant film, Used to form films used in active matrix drive devices, antistatic conductive film coatings, gas sensors, electromagnetic shielding panels, piezoelectric devices, photoelectric conversion devices, light-emitting devices, thin-film secondary batteries, etc. that constitute display devices The present invention relates to a ZnO vapor deposition material, a method for producing the same, and a method for forming a ZnO film formed by the ZnO vapor deposition material.

  In recent years, a transparent conductive film is indispensable when manufacturing photoelectric conversion devices such as solar cells. An ITO film (indium oxide film doped with tin) is known as a conventional transparent conductive film. The ITO film has the advantages of excellent transparency and low resistance.

  On the other hand, cost reduction is required for solar cells, liquid crystal display devices, and the like. However, since indium is expensive, when an ITO film is used as the transparent conductive film, the solar cell inevitably has a problem of high cost. In addition, solar cells and the like are manufactured by forming amorphous silicon on a transparent conductive film by a plasma CVD method or the like. At that time, if the transparent conductive film is an ITO film, hydrogen plasma at the time of plasma CVD There was also a problem that the ITO film deteriorated.

In order to eliminate these points, it has been proposed to use a zinc oxide-based film doped with a conductive active element such as Al, B, and Si, which can be manufactured at low cost, as a transparent conductive film such as a solar cell. A zinc oxide-based sputtering target for forming a zinc oxide-based film by sputtering has been proposed (for example, Patent Document 1). According to this zinc oxide-based sputtering target, an extremely low resistance zinc oxide-based sintered body can be obtained by containing a predetermined amount of the conductive active element with respect to zinc. It is said that the higher the dispersibility, the higher the sintered density and the higher the conductivity.
JP-A-6-2130

  However, if sputtering is performed while applying a high voltage to form a high-speed film using a conventional zinc oxide sputtering target, abnormal discharge is likely to occur, the discharge state is unstable and the target is consumed unevenly, There was a problem that it was difficult to obtain a low-resistance film due to composition shift in the obtained film. On the other hand, when the input power is reduced and the voltage is lowered, the film formation rate is reduced, and the film formation efficiency of the zinc oxide film is greatly reduced.

  Further, since the conventional target material has low evaporation efficiency and film formation efficiency, the life of the target material replacement cycle is short, and a target material with high evaporation efficiency and film formation efficiency is required to increase productivity. If the film formation rate is low, the film density is lowered, and there is a possibility that problems such as a decrease in refractive index, a decrease in sputtering resistance, a discharge characteristic, and a deterioration in insulation properties may occur.

  The present invention solves the above-mentioned conventional problems, can form a film having a high conductivity approaching that of an ITO film at a high speed, and can form a conductive film having excellent permeability and denseness. A ZnO vapor deposition material and a ZnO film using the same are provided. In addition, the present invention provides a ZnO vapor deposition material that has a large amount of evaporation per unit energy and can improve the deposition rate, and a ZnO film using the same.

This invention relates to the ZnO vapor deposition material which solved the said subject with the following structures.
[1] A ZnO vapor deposition material used for forming a transparent conductive film, which contains Ce and Al, has a Ce content higher than an Al content, and a Ce content in a range of 0.1 to 14.9% by mass. And a ZnO porous sintered body in which the Al content is in the range of 0.1 to 10% by mass, and the total content of Ce and Al is in the range of 0.2 to 15% by mass. A ZnO vapor deposition material characterized in that the bonded body has a porosity of 3 to 50% and has pores having an average pore diameter of 0.1 to 500 µm .
[2] The ZnO vapor deposition material according to [1], wherein the ZnO porous sintered body is a sintered body of particles having an average crystal grain size in the range of 1 to 500 μm.

  In the ZnO vapor deposition material of the present invention, the ZnO porous sintered body contains a predetermined amount of two elements of Ce and Al at a specific ratio. By using this ZnO vapor deposition material, ZnO having high conductivity approaching the ITO film is obtained. A membrane can be obtained. Specifically, preferably, when the total content of Ce and Al is in the range of 0.2 to 15% by mass, excellent effects in the conductive characteristics and the spectral characteristics can be obtained.

  Moreover, since the ZnO porous sintered body has a porosity of 3 to 50% in the ZnO vapor deposition material of the present invention, the specific surface area inside the vapor deposition material is large, and the evaporation rate of the vapor deposition material can be increased. Specifically, it is possible to obtain an evaporation rate about 1.1 to 2 times that of a conventional ZnO vapor deposition material.

  Furthermore, the ZnO vapor deposition material of the present invention can increase the evaporation rate when the ZnO porous sintered body has pores having an average pore diameter of 0.1 to 500 μm. In addition, since the ZnO porous sintered body is a sintered body of particles having an average crystal grain size of 1 to 500 μm, the specific surface area inside the deposition material can be increased, and the evaporation rate of the deposition material can be increased. The formed ZnO film has excellent film characteristics.

  Further, in the ZnO vapor deposition material of the present invention, the ZnO porous sintered body may be a polycrystalline body or a single crystal body, and an ITO film containing two elements of Ce and Al at a specific ratio in a predetermined ratio. Thus, a ZnO film having high conductivity approaching the above can be obtained.

Moreover, this invention relates to the manufacturing method which solved the said subject with the following structures.
[3] (I) ZnO powder with a purity of 98% or more, CeO ₂ powder in such an amount that the Ce content in the ZnO vapor deposition material becomes 0.1 to 14.9% by mass, and the Al content in the ZnO vapor deposition material A step of preparing a slurry having a concentration of 30 to 75% by mass by mixing Al ₂ O ₃ powder in an amount of 0.1 to 10% by mass, a binder, and an organic solvent, and (II) A step of obtaining a gas-containing slurry by blowing gas; (III) a step of obtaining a porous granulated powder having an average particle size of 50 to 300 μm by spray drying the gas-containing slurry; and (IV) the porous granulation. A step of obtaining a porous molded body by molding a powder, and (V) a step of obtaining a ZnO porous sintered body by sintering the porous molded body at a predetermined temperature, including Ce and Al, Ce content is higher than Al content, Ce content is in the range of 0.1 to 14.9% by mass, and Al content is 0.1 to 10 It consists of a ZnO porous sintered body having a total content of Ce and Al in the range of 0.2 to 15% by mass, and the sintered body has a porosity of 3 to 50%. And producing a ZnO vapor deposition material having pores with an average pore diameter of 0.1 to 500 μm .
[4] In the production method of [3], instead of the steps (II) and (III), (II-2) a step of obtaining a foaming agent-containing slurry by mixing a foaming agent into the raw material powder or slurry; III-2) A method for producing a ZnO vapor deposition material comprising a step of foaming the foaming agent-containing slurry while spray drying to obtain a porous granulated powder having an average particle size of 50 to 300 μm.
[5] In the production method of [3] , instead of the steps (II) to (V), (II-3) an additive-containing slurry in which an additive that volatilizes and decomposes upon firing is mixed into the raw material powder or slurry. And (III-3) spray-drying the additive-containing slurry to obtain a granulated powder having an average particle size of 50 to 300 μm, and (IV-3) molding the granulated powder to form it. And (V-3) a method for producing a ZnO vapor-deposited material, comprising: (V-3) sintering while volatilizing and decomposing the additive to obtain a ZnO porous sintered body.
[6] In the method of [3] to [5] above, in the step (I), the purity is 98% or more, the average particle size is 10 to 500 μm, and the particle size distribution is ± 10% of the average particle size. ZnO powder, CeO ₂ powder, and Al ₂ O ₃ powder contained in the range of ZnO are mixed, and these powders, a binder, and an organic solvent are mixed to prepare a slurry having a concentration of 30 to 75% by mass. A method for producing a vapor deposition material.

  According to the production method of the present invention, a ZnO vapor deposition material having a large evaporation amount and excellent film formability and denseness can be produced relatively easily by the production steps (I) to (V). In particular, (II) a step of obtaining a gas-containing slurry by blowing a gas into the slurry, or (II-2) a step of obtaining a blowing agent-containing slurry by mixing a foaming agent into the raw material powder or slurry, or (II-2) A ZnO vapor deposition material having a predetermined porosity, pores having an average pore diameter, and an average crystal grain size is manufactured relatively easily by a step of mixing a foaming agent into raw material powder or slurry to obtain a foaming agent-containing slurry. Can do.

  Further, the production method of the present invention uses a powder having an average particle size of 10 to 500 μm and a particle size distribution within a range of ± 10% of the average particle size, so that fine particles are substantially between the particles. Since it does not enter, a porous molded body having a porosity of 3 to 50% can be easily obtained.

Furthermore, the present invention relates to the production of the following ZnO films.
[7] A ZnO vapor deposition material according to [1] or [2] above or a ZnO vapor deposition material produced by the method according to any one of [3] to [6] above as an electron beam. A method of forming a ZnO film by vapor deposition, ion plating, sputtering, or plasma vapor deposition.

  The ZnO vapor deposition material of the present invention can be widely used in vacuum film forming methods such as electron beam vapor deposition, ion plating, sputtering, or plasma vapor deposition. Further, by using the ZnO vapor deposition material of the present invention, for example, when the film is formed at the same film formation rate as in the conventional electron beam evaporation method, the filament exchange frequency can be reduced, and the film formation rate can be increased. Thus, the manufacturing time can be shortened.

  Since the ZnO vapor deposition material of the present invention contains Ce and Al as additive elements, a crystal distorted by Ce having an ionic radius larger than Zn is recovered and matched by adding Al having a small ionic radius, so that the transmittance is high. A ZnO film is formed, and a highly durable ZnO film having excellent denseness can be formed. In addition, a film having excellent moisture resistance, gas and water vapor barrier properties can be obtained.

  Furthermore, the ZnO vapor deposition material of the present invention has a predetermined range of porosity, and preferably the pores have a specific range of average pore diameter, and the particles have a specific range of average crystal grain size, The specific surface area can be increased, the evaporation rate can be increased, and the ZnO film can be formed with good film formation efficiency. Moreover, the ZnO film formed by the ZnO vapor deposition material of the present invention is dense, has high conductivity, and is excellent in durability of the film.

Hereinafter, the present invention will be specifically described together with examples.
[ZnO vapor deposition material]
The ZnO vapor deposition material of the present invention is a ZnO vapor deposition material used for forming a transparent conductive film, which contains Ce and Al, has a Ce content higher than an Al content, and a Ce content of 0.1 to 14. ZnO porous sintered body having a content of 9% by mass and an Al content of 0.1 to 10% by mass, and a total content of Ce and Al of 0.2 to 15% by mass The sintered body has a porosity of 3 to 50% and has pores having an average pore diameter of 0.1 to 500 μm .

  A detailed investigation was conducted on the influence of the ZnO vapor deposition material and the additive species in the ZnO film formed using this vapor deposition material and the content thereof on the conductivity. As a result, the ZnO porous sintered body contained it as an additive element. It was confirmed that the content ratio of the two elements of Ce and Al had a great influence. Based on the above knowledge, the ZnO vapor deposition material according to the present invention contains ZnO as a main component and contains both elements of Ce and Al, thereby expressing and maintaining a large amount of overelectrons that contribute to conductivity, and having high conductivity. This is a ZnO vapor deposition material that can form a ZnO film having the following.

  As the ratio of the two elements of Ce and Al contained in the ZnO porous sintered body is larger within a certain range, the conductivity generally becomes better. Specifically, the content of Ce contained in the ZnO vapor deposition material is suitably 0.1 to 14.9% by mass, and preferably 3 to 6% by mass. When the Ce content is less than the lower limit of 0.1% by mass, the conductivity is remarkably reduced, and when the Ce content exceeds the upper limit of 14.9% by mass, the transmittance is remarkably reduced.

  Moreover, 0.1-10 mass% is suitable for content of Al contained in a ZnO vapor deposition material, and 1-3 mass% is preferable. When the amount of Al is less than the lower limit of 0.1% by mass, the conductivity is remarkably lowered, and when the amount of Al exceeds the upper limit of 10% by mass, a composition shift occurs during vapor deposition.

  The ZnO vapor deposition material of the present invention maintains a dense crystal structure by containing more Ce than Al. When the Ce content is less than the Al content, conductivity and transmittance are lowered. The total content of Ce and Al is preferably in the range of 0.2 to 15% by mass. When the total content of Ce and Al exceeds this range, the specific resistance and transmittance of the ZnO vapor deposition material are significantly reduced.

When these Ce and Al are contained in a trace amount in the ZnO vapor deposition material, they are not present as granular precipitates in the grain boundaries and grains of the ZnO matrix, but are uniformly dispersed in the ZnO vapor deposition material. Yes. In the ZnO vapor deposition material, Ce is present as an oxide such as CeO ₂ or Ce ₂ O ₃ , and Al is considered to be present as Al ₂ O ₃ .

  The ZnO vapor deposition material of the present invention contains trivalent or tetravalent rare earth element Ce as an additive element, and this Ce generates excess carrier electrons with respect to divalent Zn, thereby ensuring high conductivity. can do. In addition, when rare earth elements are added to a ZnO vapor deposition material, they are materials that are unlikely to cause a composition shift during vapor deposition, and a desired composition ratio can be maintained when a film is formed.

  Moreover, according to the ZnO vapor deposition material of this invention, the electroconductivity by oxygen deficiency other than forced injection of a carrier electron is acquired. Normally, oxygen gas is introduced in the vapor deposition method, but generally oxygen is insufficient in the film composition. In forming a transparent conductive film, a method of reducing oxygen resistance by generating oxygen vacancies is employed. However, when a rare earth element is added, there is an advantage that it is easy to control because it has excellent evaporation performance. In addition to this advantage, the ZnO vapor deposition material of the present invention can obtain high conductivity approaching that of ITO by including Al as an additive element.

  The ZnO vapor deposition material of the present invention is composed of a ZnO porous sintered body having a porosity of 3 to 50%. The porosity of the sintered body is suitably from 3 to 50%, preferably from 5 to 30%, more preferably from 10 to 30%, still more preferably from 20 to 30%. When the porosity is less than 3%, the evaporation rate of the vapor deposition material does not increase during the film formation by the electron beam evaporation method or the ion plating method, resulting in a decrease in the film formation rate, resulting in a lower manufacturing cost. Since it increases, it is not preferable. On the other hand, if the porosity exceeds 50%, the strength of the porous sintered body is lowered and it is difficult to obtain sufficient mechanical strength. If the porosity is 10% or more, the evaporation rate can be improved. If the porosity is 20% or more, the evaporation rate is about 2.0 times that of the conventional ZnO evaporation material. A material can be obtained.

  Furthermore, the pores of the ZnO porous sintered body of the present invention preferably have an average pore diameter of 0.1 to 500 μm. When the average pore diameter of the pores is within the above range, the evaporation rate can be further increased. Here, if the pore diameter is less than 0.1 μm, there is no merit of having pores, and if the pore diameter exceeds 500 μm, the strength of the sintered body is reduced. Therefore, it is not preferable.

  In addition, a pore diameter (inner diameter of a pore) means, for example, the largest one among the internal dimensions of pores existing when an evaporation material cross section is observed by an observation means such as SEM. The evaluation method of this pore includes the measurement of the porosity by the substitution method, the measurement of the porosity by the microscopic method, the measurement of the surface area and the pore distribution by gas adsorption, the measurement of the surface area and the pore distribution by the mercury intrusion method, the gas permeation method It is possible to employ surface area measurement by means of, or measurement of pore distribution by the X-ray small angle scattering method.

The shape of the pores is preferably rounded, and finer pores are preferably formed on the surface of the pores in order to improve the evaporation rate. As a method for evaluating pores, the surface area measurement is preferably 5 to 40 m ² / g, and the pore distribution measurement preferably has at least one peak of pore distribution in the range of 1 to 100 μm. . Moreover, it is preferable that the portions (frame portions) other than the pores are substantially sintered. For example, the density of the frame portions of the porous sintered body is preferably 98% or more.

  Further, the particles of the ZnO porous sintered body of the present invention preferably have an average crystal grain size of 1 to 500 μm and have round pores of about 0.1 to 500 μm in the sintered body. Since this ZnO porous sintered body has a fine crystal structure with an average crystal grain size in the above range and can reduce the occurrence of defects at the crystal grain boundaries, the formed ZnO film is made of ZnO. Excellent film characteristics such as film density, film thickness distribution, refractive index, sputtering resistance, discharge characteristics (discharge voltage, discharge response, etc.), insulation, and the like. Here, if the average crystal grain size is less than 1 μm, there is a problem that the film forming rate is lowered, and if the average crystal grain size exceeds 500 μm, the deposition rate of the additive element becomes non-uniform. The average crystal grain size is preferably in the range of 5 to 40 μm, and more preferably in the range of 10 to 30 μm.

  The ZnO vapor deposition material of the present invention is preferably formed into a disk-like or spherical pellet. When this vapor deposition material is spherical, the diameter is suitably 5 to 30 mm, preferably 5 to 15 mm. This is because if the diameter is less than 5 mm, it is too small to cause splash, and if the diameter exceeds 30 mm, it becomes difficult to handle in the actual manufacturing process. When this vapor deposition material is disk shape, the diameter is 5-20 mm, Preferably it is 5-10 mm, and height is 1-10 mm, Preferably 2-5 mm is good. If the diameter is less than 5 mm or the height is less than 1 mm, it is too small to cause splash, and if the diameter exceeds 30 mm or the height exceeds 10 mm, handling becomes difficult in the actual manufacturing process, which is not preferable.

Hereinafter, the manufacturing method of the ZnO vapor deposition material which concerns on this invention is demonstrated.
〔Production method〕
The ZnO vapor deposition material according to the present invention includes a ZnO powder having a purity of 98% or more, a CeO ₂ powder in an amount such that the Ce content in the ZnO vapor deposition material is 0.1 to 14.9% by mass, and the ZnO vapor deposition material. and Al ₂ O ₃ powder in an amount Al content is 0.1 to 10 mass%, and a binder, by mixing the organic solvent, preparing a concentration of 30 to 75 wt% of the slurry, the slurry A step of obtaining a granulated powder having an average particle size of 50 to 300 μm by spray drying, a step of obtaining a porous compact by molding the granulated powder, and sintering the compact at a predetermined temperature to obtain a porous ZnO It can manufacture by the process of obtaining a quality sintered compact.

  The ZnO powder preferably has a purity of 98% or more, and more preferably 98.4% or more. If the purity of the ZnO powder is 98% or more, it is possible to suppress a decrease in conductivity due to the influence of impurities. Moreover, it is preferable that the average particle diameter of ZnO powder exists in the range of 0.1-10 micrometers. If the average particle size of the ZnO powder is less than 0.1 μm, the powder is too fine and agglomerates, so that the handling of the powder tends to be poor, and it is difficult to prepare a high-concentration slurry. It tends to be difficult and difficult to obtain dense pellets. Furthermore, when the average particle diameter of the ZnO powder is adjusted to the above range, there is an advantage that a desired sintered body can be obtained without using a sintering aid.

The CeO ₂ powder is preferably added with cerium oxide particles having a primary particle size of nanoscale when considering the uneven distribution of the Ce powder, the reactivity with the ZnO matrix, and the purity of the Ce compound. The Al ₂ O ₃ powder preferably has an average particle size in the range of 0.01 to 1 μm, particularly preferably in the range of 0.05 to 0.5 μm. Use of Al ₂ O ₃ powder having this average particle size is convenient for uniformly dispersing CeO ₂ powder.

  As the binder, polyethylene glycol, polyvinyl butyral or the like can be used, and the binder is preferably added in an amount of 0.2 to 2.5% by mass. As the organic solvent, ethanol, propanol or the like can be used.

  The raw material powder, a binder, and an organic solvent are mixed to prepare a slurry having a concentration of 30 to 75% by mass, preferably 40 to 65% by mass. If the slurry concentration exceeds 75% by mass, stable granulation is difficult because the slurry is non-aqueous, and if it is less than 30% by mass, a dense ZnO sintered body having a uniform structure is difficult to obtain. When the slurry concentration is adjusted to the above range, the slurry has a viscosity of 200 to 1000 cps, and can be stably granulated with a spray dryer. Further, the density of the molded body is increased and a dense sintered body can be obtained. Can be obtained.

The wet mixing of the raw material powder, the binder and the organic solvent, particularly the wet mixing of the raw material powder and the organic solvent which is the dispersion medium may be performed using a wet ball mill or a stirring mill. When ZrO ₂ balls are used in the wet ball mill, wet mixing is performed using a large number of ZrO ₂ balls having a diameter of 5 to 10 mm for 8 to 24 hours, preferably 20 to 24 hours. If the diameter of the ZrO ₂ ball is less than 5 mm, mixing may be insufficient. If the diameter exceeds 10 mm, impurities may increase, which is not preferable. Even when the mixing time is as long as 24 hours, the generation of impurities due to pulverization is small. On the other hand, in a wet ball mill, when a resin ball with an iron core is used, it is preferable to use a ball having a diameter of 10 to 15 mm.

In the stirring mill, wet mixing is preferably performed for 0.5 to 1 hour using a ZrO ₂ ball having a diameter of 1 to 3 mm. If the diameter of the ZrO ₂ ball is less than 1 mm, mixing tends to be insufficient, and if it exceeds 3 mm, impurities increase, which is not preferable. Further, if the mixing time exceeds 1 hour, it is not preferable because it causes not only mixing of raw materials but also generation of impurities due to pulverization. In addition, if it is 1 hour, it can mix sufficiently. Furthermore, mixing / granulation of the powder and the additive may be performed by a general rolling granulation method. In this case, there is an advantage that the process can be simplified because there is no need to separate the ball and the like after the process.

  The production method of the present invention prepares a gas-containing slurry by blowing gas into the slurry as a first means for obtaining a porous sintered body. This gas blowing and mixing is preferably performed by a mechanical pump, gas pressure blowing, or the like. As the gas, air, insoluble gas, water-insoluble gas or the like can be used.

  The gas-containing slurry is spray dried. This spray drying may be performed using a spray dryer, and may be performed at 150 to 250 ° C. for 3 hours. Since gas is blown into the slurry, the granulated powder obtained by spray drying the slurry becomes porous. By this spray drying, a porous granulated powder having an average particle size of 50 to 300 μm can be obtained.

The manufacturing method of this invention prepares the slurry which mixed the foaming agent as a 2nd means for obtaining a porous sintered compact. As the foaming agent, an organic foaming agent or an inorganic foaming agent can be used. As the organic foaming agent, azodicarbonamide, dinitrosopentamethylenetetramine or the like is used, and as the inorganic foaming agent, carbonate or the like is used. Blowing agents, ZnO powder, CeO ₂ powder, be mixed with Al ₂ O ₃ powder may be added during slurry preparation.

  The foaming agent-containing slurry is spray dried. This spray drying may be performed using a spray dryer, and may be performed at 150 to 250 ° C. for 3 hours. The foaming agent contained in the slurry is foamed and decomposed in this spray drying stage, and the resulting granulated powder is made porous. By this spray drying, a porous granulated powder having an average particle diameter of 50 to 300 μm can be obtained.

  In the production method of the present invention, as a third means for obtaining a porous sintered body, a slurry in which an additive that volatilizes and decomposes at the time of sintering is mixed is prepared. Examples of the additive that can be dissolved in a solvent include butyral, and examples of a system that is soluble in an alcohol solvent include cellulose, polyvinyl, polyester, and polyethylene. Moreover, as what does not melt | dissolve in an alcohol solvent, the starch type | system | group and polystyrene type whose average particle diameter is about several micrometers-about 500 micrometers can be used. It is preferable that about 20% by mass of butyral is mixed into the slurry, or about 20% by mass of starch is mixed into the slurry.

  Since the slurry contains the additive, the additive is volatilized and decomposed during sintering to form pores, so that a porous sintered body can be obtained. Note that the diameter and shape of the pores can be controlled by adjusting the type or amount of the additive. For example, by using a butyral-based additive, pores having a pore diameter on the order of 0.1 μm to 10 μm can be formed. Moreover, when a starch is used, pores having a pore size and shape comparable to the particle size of the starch can be formed. Thus, the starch is easier to control the pore diameter and shape of the pores.

  Specifically, for example, the ZnO vapor deposition material of the present invention is about 1.3 times that of a vapor deposition material using a butyral additive, compared to the evaporation rate of a conventional ZnO vapor deposition material having a relative density of about 98% or more. It is possible to obtain a vapor deposition rate of about 1.5 times, and with a vapor deposition material using a starch having an average particle size of 0.1 to 500 μm, an evaporation rate of about 2 times can be obtained. Therefore, it is possible to obtain such a high film formation rate.

The production method of the present invention prepares a slurry using ZnO powder having a particle size distribution in a predetermined range as a fourth means for obtaining a porous sintered body. Specifically, a ZnO powder having an average particle diameter of 10 to 500 μm and a particle size distribution within a range of ± 10% of the average particle diameter is used. When the particle size distribution of the ZnO powder is out of the range of ± 10% of the average particle size, the porosity is lowered. A more preferable range of the particle size distribution is within a range of ± 5% of the average particle size. Incidentally, the preferred particle size of CeO ₂ powder and Al ₂ O ₃ powder much smaller than the ZnO powder, may be removed because the amount is small as compared with the ZnO powder from the restriction of the particle size distribution.

  A slurry using ZnO powder having a controlled particle size distribution is spray-dried. This spray drying may be performed using a spray dryer, and may be performed at 150 to 250 ° C. for 3 hours. In the slurry to be spray-dried, ZnO powder having an average particle size of 10 to 500 μm and a particle size distribution within a range of ± 10% of the average particle size is used. Therefore, the gap between the ZnO particles is not filled with fine ZnO particles, the gap between the ZnO particles remains as pores, and the granulated powder becomes porous. By this spray drying, a porous granulated powder having an average particle size of 50 to 300 μm can be obtained.

  Next, the slurry is spray-dried to obtain a granulated powder having an average particle size of 50 to 300 μm, and the granulated powder is then pressure-molded. Here, if the average particle size of the granulated powder is less than 50 μm, the moldability is inferior, and if it is more than 300 μm, the density of the molded body is lowered and the strength tends to be insufficient.

As the pressure molding apparatus, a uniaxial press apparatus, a cold isostatic pressing apparatus (CIP (Cold Isostatic Press) molding apparatus) or other apparatuses may be used. Compacting pressure 100~2000kgf / cm ² (9.8~196MPa) are suitable, 100~1000kgf / cm ² (9.8~98MPa) are preferred. By molding at a pressure in the above range, the density of the molded body can be increased, deformation after sintering can be prevented, and post-processing can be eliminated.

  Next, the molded body is sintered. It is preferable to degrease the molded body at a temperature of 350 to 620 ° C. before sintering. This degreasing treatment can prevent color spots after sintering of the molded body. This degreasing treatment is preferably performed sufficiently over time.

  Sintering is performed in air, inert gas, vacuum or reducing gas atmosphere at a temperature of 1000 ° C. or higher, preferably 1200 to 1400 ° C. for 1 to 10 hours, preferably 2 to 5 hours. Sintering is performed at atmospheric pressure, but when performing pressure sintering such as hot press (HP) sintering or hot isostatic press (HIP) sintering, inert gas, vacuum Or it is preferable to carry out for 1 to 5 hours at the temperature of 1000 degreeC or more in reducing gas atmosphere.

A ZnO film is formed on the substrate surface by a vacuum film-forming method using the obtained ZnO vapor deposition material made of a porous sintered body as a target material. Examples of a vacuum film forming method suitable for forming a film using the ZnO vapor deposition material of the present invention include an electron beam vapor deposition method, an ion plating method, a sputtering method, and a plasma vapor deposition method. Since the ZnO film of the present invention formed by these film formation methods uses the ZnO vapor deposition material of the present invention, the specific resistance approaching that of ITO is 3 to 5 × 10 ⁻⁴ Ω · cm. High conductivity and high transmittance with a visible light transmittance of 90% or more can be obtained. Furthermore, the durability of the film is improved by adding a crystal having a ionic radius that is distorted by Ce larger than Zn and recovering and matching it by adding Al having a small ionic radius.

  The production method of the present invention includes a first aspect in which gas is mixed into the slurry, a second aspect in which a slurry containing a foaming agent is prepared, and a third aspect in which a slurry containing an additive that volatilizes and decomposes during firing is prepared. In any of the fourth aspects of preparing a slurry using ZnO powder having a particle size distribution in a predetermined range, the porosity, pore diameter, and pore shape can be easily controlled, so that it has more optimal pores. It becomes possible to manufacture a vapor deposition material. Thereby, even when there are many pore states required depending on the production conditions and the like, it is possible to provide an optimal vapor deposition material corresponding to them.

  Furthermore, since the ZnO vapor deposition material of the present invention is mainly composed of a porous sintered body having a porosity of 5 to 30% and a pore diameter of 0.1 to 500 μm, this ZnO vapor deposition material is used for the electron beam vapor deposition method. Alternatively, the evaporation rate can be improved when a ZnO transparent conductive film is formed by ion plating. In other words, when film formation is performed with the same electron beam energy, the film formation rate can be increased to shorten the working time, thereby increasing the number of manufacturing in a predetermined time, and film formation at a similar film formation rate. In this case, it is possible to reduce the electron beam energy, delay the replacement time of the filament of the electron gun, etc., reduce the number of maintenance times, improve the productivity, and consequently reduce the manufacturing cost.

Examples of the present invention are shown below together with comparative examples. In each example and comparative example, commercially available ZnO powder (purity 99% or more, average particle size 0.3 μm), CeO ₂ powder (purity 99% or more, average particle size 0.3 μm), Al ₂ O ₃ powder (purity) 99% or more, average particle size 0.3 μm) was used. In any case, the slurry was prepared by wet mixing for 24 hours using a ball mill (using a nylon coated steel ball having a diameter of 5 to 20 mm). Further, in any case, a uniaxial molding press was used as a molding device, and the outer diameter was 6.7 mmφ and the thickness was 2.0 mm at a pressure of 100 kgf / cm ² (9.8 MPa). This molded body was put into an electric furnace and fired at 1300 ° C. in the atmosphere for 3 hours to form sintered body pellets.

  In Examples and Comparative Examples, the porosity was measured by a substitution method. The average pore size and crystal grain size were measured by SEM (scanning electron microscope). The evaporation rate was measured with a quartz film thickness monitor installed diagonally above Haas. The specific resistance was measured by a 4-terminal 4-probe method by applying a constant current at 25 ° C. using a product name Loresta (HP type, MCP-T410, probe in series 1.5 mm pitch) at Mitsubishi Chemical Corporation as a measuring instrument. did. Visible light transmittance is measured by using a spectrophotometer U-4000 manufactured by Hitachi, Ltd. as a measuring instrument, and in the visible light wavelength range (380 to 780 nm), the substrate after film formation is placed perpendicular to the measuring light. did.

[Example 1]
To 100 g of raw material powder composed of 91 g of ZnO powder, 6.2 g of CeO ₂ powder and 2.8 g of Al ₂ O ₃ powder, 1% by mass of polyvinyl butyral as a binder is added, and methanol-modified alcohol is added as a dispersion medium to a concentration of 30 A mass% slurry was obtained. Subsequently, this slurry was put into a ball mill, and air was blown in and wet mixed to obtain a gas-containing slurry. This slurry was vaporized with a vacuum dryer at 80 ° C., followed by dry crushing to obtain a porous granulated powder having an average particle size of 200 μm. This granulated powder was pressure-molded and the compact was fired to produce a porous sintered compact pellet (ZnO vapor deposition material). Table 1 shows the porosity, average pore diameter, and average crystal grain size of this sintered body.

[Example 2]
An organic foaming agent and an inorganic foaming agent are added to 100 g of the same raw material powder as in Example 1, 1% by weight of polyvinyl butyral is added as a binder, methanol-modified alcohol is added as a dispersion medium, and a slurry having a concentration of 30% by weight. (Viscosity 200 to 4000 cps). Azodicarbonamide and dinitrosopentamethylenetetramine were used as organic blowing agents, and carbonates were used as inorganic blowing agents. After this foaming agent-containing slurry was placed in a ball mill and wet-mixed, the dispersion medium was vaporized at 80 ° C. in a vacuum dryer, followed by dry crushing to obtain a porous granulated powder having an average particle size of 200 μm. This granulated powder was pressure-molded and the compact was fired to produce a porous sintered compact pellet (ZnO vapor deposition material). Table 1 shows the porosity, average pore diameter, and average crystal grain size of this sintered body.

Example 3
An additive that volatilizes and decomposes during firing is added to 100 g of the same raw material powder as in Example 1, 1% by weight of polyvinyl butyral is added as a binder, methanol-modified alcohol is added as a dispersion medium, and a slurry having a concentration of 30% by weight ( The viscosity was 200 to 4000 cps). Polyvinyl butyral 20% by mass was used as an additive that volatilizes and decomposes during firing. This additive-containing slurry was placed in a ball mill and wet-mixed, and then the dispersion medium was vaporized at 80 ° C. in a vacuum dryer, followed by dry crushing to obtain a granulated powder having an average particle size of 200 μm. The granulated powder was pressure-molded, and the molded body was fired to volatilize and decompose the additive to produce a porous sintered body pellet (ZnO vapor deposition material). Table 1 shows the porosity, average pore diameter, and average crystal grain size of this sintered body.

Example 4
A porous sintered pellet (ZnO vapor deposition material) was produced in the same manner as in Example 3 except that 20% by mass of starch having a particle size of 50 μm was used as an additive that volatilizes and decomposes during firing. Table 1 shows the porosity, average pore diameter, and average crystal grain size of this sintered body.

Example 5
The same raw material powder as in Example 1 was used, and the ZnO powder was sieved to obtain a ZnO powder having an average particle size of 60 μm and a particle size distribution in the range of 55 to 65 μm. To this raw material powder containing ZnO powder, 1% by weight of polyvinyl butyral is added as a binder, 30% by weight of methanol-modified alcohol is added as an organic solvent, and they are mixed to prepare a slurry having a ZnO powder concentration of 30% by weight. did. Next, this slurry was spray-dried to obtain a porous granulated powder having an average particle size of 200 μm. This granulated powder was pressure-molded and the compact was fired to produce a porous sintered compact pellet (ZnO vapor deposition material). Table 1 shows the porosity, average pore diameter, and average crystal grain size of this sintered body.

[Comparative Example 1]
A slurry is prepared in the same manner as in Example 1 except that the same raw material powder as in Example 1 is used, and neither air introduction to the slurry, addition of a foaming agent, nor use of an additive that volatilizes and decomposes during firing is performed. This slurry was spray-dried to obtain a granulated powder having an average particle size of 200 μm. The granulated powder was pressure-molded, and the compact was fired to produce a sintered pellet (ZnO vapor deposition material). Table 1 shows the porosity, average pore diameter, and average crystal grain size of this sintered body.

[Comparative Example 2]
A slurry was prepared in the same manner as in Comparative Example 1 except that 100 g of ZnO powder to which CeO ₂ powder and Al ₂ O ₃ powder were not added was used, and this slurry was spray-dried to obtain a granulated powder having an average particle size of 200 μm. . The granulated powder was pressure-molded, and the compact was fired to produce a sintered pellet (ZnO vapor deposition material). Table 1 shows the porosity, average pore diameter, and average crystal grain size of this sintered body.

[Vapor deposition test]
A vapor deposition test was conducted using the ZnO vapor deposition materials of Examples 1 to 5 and the ZnO vapor deposition materials of Comparative Examples 1 and 2. A sample vapor deposition material is charged in a hearth (diameter 50 mm, depth 25 mm) of an electron beam vapor deposition apparatus, an ultimate vacuum is 2.66 × 10 ⁻⁴ Pa (2.0 × 10 ⁻⁶ Torr), and an O ₂ partial pressure is 1. A ZnO film was formed by adjusting the atmosphere to 33 × 10 ⁻² Pa (1.0 × 10 ⁻⁴ Torr), irradiating an electron beam with an acceleration voltage of 10 kV and a beam scan area of about 40 mmφ, and heating the ZnO vapor deposition material. . The evaporation rate was measured with a quartz film thickness monitor installed diagonally above Haas. The results are shown in Table 1. As shown in Table 1, the vapor deposition rates of Examples 1 to 5 are about 1.1 to 2 times that of Comparative Examples 1 and 2, and the evaporation rate is large.

[Moisture resistance test]
The samples of Examples 1 to 5 and Comparative Examples 1 and 2 were subjected to a moisture resistance test. In the humidity resistance test, the specific resistance of the film at each time was measured up to 2000 hours in an atmosphere of 60% humidity and 90 ° C. The results are shown in Table 2. As shown in Table 2, the resistivity of a ZnO film formed using a ZnO vapor deposition material containing Ce and Al has a specific resistance deterioration rate several times lower than that of an additive-free ZnO film. This indicates that the ZnO film containing Ce and Al is several times more stable.

[Examples 6 to 8]
Porous sintered body pellets (ZnO vapor deposition material) as in Example 1 except that the Ce content was 0.2% by mass, the Al content was 0.1% by mass, and the porosity was 8 to 31%. Manufactured.

[Examples 9 to 11]
A porous sintered body pellet (ZnO vapor deposition material) is produced in the same manner as in Example 1 except that the Ce content is 14.9% by mass, the Al content is 10% by mass, and the porosity is 9-30%. did.

[Comparative Example 3]
A porous sintered body pellet (ZnO vapor deposition material) was produced in the same manner as in Examples 6 to 8, except that the porosity was adjusted to 2%.

[Comparative Example 4]
A porous sintered body pellet (ZnO vapor deposition material) was produced in the same manner as in Examples 9 to 11 except that the porosity was adjusted to 2%.

[Comparative Examples 5 to 8]
A porous sintered pellet (ZnO vapor deposition material) was produced in the same manner as in Example 1 except that the Ce content was 20% by mass, the Al content was 15% by mass, and the porosity was adjusted to 2 to 29%.

  Vapor deposition tests were performed on the samples of Examples 6 to 11 and Comparative Examples 3 to 8. The results are shown in Table 3. As shown in Table 3, the evaporation rate of the ZnO vapor deposition materials of Examples 6 to 11 is faster than that of the comparative example as in Table 1, and the specific resistance is excellent. On the other hand, the evaporation rates of Comparative Examples 2, 3, 4, and 8 having a small porosity are 13.0 to 14.7, which is significantly low. In Comparative Examples 5 to 8 having a large Ce content and Al content, the specific resistance of the ZnO film is remarkably large, and the transmittance is significantly low.

Claims (7)

A ZnO vapor deposition material used for forming a transparent conductive film, which contains Ce and Al, has a Ce content higher than an Al content, and has a Ce content within a range of 0.1 to 14.9% by mass and Al. The ZnO porous sintered body has a content in the range of 0.1 to 10% by mass and a total content of Ce and Al in the range of 0.2 to 15% by mass. A ZnO vapor deposition material having a porosity of 3 to 50% and having pores having an average pore diameter of 0.1 to 500 µm . The ZnO vapor deposition material according to claim 1, wherein the ZnO porous sintered body is a sintered body of particles having an average crystal grain size in the range of 1 to 500 µm. (I) ZnO powder having a purity of 98% or more, CeO ₂ powder in an amount such that the Ce content in the ZnO vapor deposition material is 0.1 to 14.9% by mass, and the Al content in the ZnO vapor deposition material is 0.1. A step of preparing a slurry having a concentration of 30 to 75% by mass by mixing Al ₂ O ₃ powder in an amount of 1 to 10% by mass, a binder, and an organic solvent, and (II) injecting gas into the slurry A step of obtaining a gas-containing slurry, (III) a step of spray-drying the gas-containing slurry to obtain a porous granulated powder having an average particle size of 50 to 300 μm, and (IV) molding the porous granulated powder. A porous molded body, and (V) a step of sintering the porous molded body at a predetermined temperature to obtain a ZnO porous sintered body , containing Ce and Al, and containing Ce Is more than the Al content, the Ce content is in the range of 0.1 to 14.9% by mass, and the Al content is 0.1 to 10% by mass A ZnO porous sintered body having a total content of Ce and Al in the range of 0.2 to 15% by mass, and the sintered body has a porosity of 3 to 50%. A method for producing a ZnO vapor deposition material, comprising producing a ZnO vapor deposition material having pores having an average pore diameter of 0.1 to 500 μm . In the production method of claim 3, in place of the steps (II) and (III), (II-2) a step of mixing a foaming agent into the raw material powder or slurry to obtain a foaming agent-containing slurry, and (III-2) A method for producing a ZnO vapor deposition material, comprising: foaming the foaming agent-containing slurry while spray-drying to obtain a porous granulated powder having an average particle size of 50 to 300 μm. In the manufacturing method of Claim 3 , it replaces with the process of said (II)-(V), (II-3) The process of mixing the additive which volatilizes and decomposes at the time of baking to raw material powder or slurry, and obtaining an additive containing slurry, (III-3) a step of spray-drying the additive-containing slurry to obtain a granulated powder having an average particle size of 50 to 300 μm; and (IV-3) a step of obtaining the molded body by molding the granulated powder. And (V-3) a method for producing a ZnO vapor deposition material, comprising a step of obtaining a ZnO porous sintered body by sintering while the above additive is volatilized and decomposed. 6. The production method according to claim 3, wherein in the step (I), the purity is 98% or more, the average particle size is 10 to 500 μm, and the particle size distribution is within a range of ± 10% of the average particle size. ZnO powder, CeO ₂ powder, and Al ₂ O ₃ powder are mixed, and these powders, a binder, and an organic solvent are mixed to prepare a slurry having a concentration of 30 to 75% by mass. . The ZnO vapor deposition material according to claim 1 or claim 2 or the ZnO vapor deposition material manufactured by the method according to any one of claims 3 to 6 as a target material, an electron beam vapor deposition method, an ion plating method. , A method of forming a ZnO film by sputtering or plasma deposition.