JP5395345B2 - Method for producing aluminum-doped zinc oxide transparent conductive film using aerosol - Google Patents

Description

  The present invention relates to a method for producing an aluminum-doped zinc oxide transparent conductive film useful as a transparent conductive film.

  Transparent conductive films are used as transparent electrodes for liquid crystal displays such as solar cells, OA devices and mobile phones, and flat panel displays as thin film materials having transparency to light and moderate conductivity. The transparent conductive film is generally manufactured from a transparent conductive material such as tin-doped indium oxide (ITO), antimony-doped tin oxide (ATO), fluorine-doped tin oxide (FTO), or aluminum-doped zinc oxide (AZO). Among these, since the ITO transparent conductive film can realize relatively high conductivity, it is used in a high range. However, indium contained in ITO is a rare element and expensive. Moreover, the transparent conductive film manufactured from ATO or FTO is generally low in transparency and insufficient in conductivity.

  Therefore, recently, an aluminum-doped zinc oxide (AZO) transparent conductive film having low cost, high transparency, high conductivity and chemical stability has attracted attention. As with other transparent conductive films, this AZO transparent conductive film can be obtained by physical vapor deposition such as ion plating and sputtering, chemical vapor deposition by thermal decomposition of raw material gas having high vapor pressure, coating method, etc. Can be obtained.

  For example, a method of manufacturing an AZO transparent conductive film by sputtering using a high-density AZO sintered body as a target is known (Patent Document 1). With this manufacturing method, a transparent conductive film having high conductivity and excellent transparency can be manufactured. However, the sputtering method generally requires high vacuum conditions, is not suitable for manufacturing a large-area film, and requires a large apparatus.

In addition, a coating material in which fine particles such as AZO are dispersed in a dispersion mainly composed of water and a soluble liquid is applied onto a support and dried to form a fine particle-containing layer, and then the fine particle-containing layer is compressed. A method for producing a transparent conductive film for forming a compressed layer of fine particles (Patent Document 2) has been reported. This manufacturing method is simple, has high productivity, and can manufacture a transparent conductive film at low cost. However, it is difficult to obtain a transparent conductive film having high conductivity as required for a transparent electrode or the like.
JP-A-7-258836 JP 2001-321717 A

  The present invention has been made in view of the above circumstances, and its object is to provide a transparent conductive film having high conductivity and transparency without impairing the conductivity of the aluminum-doped zinc oxide fine particles used as a raw material. An object of the present invention is to provide a method for producing a transparent conductive film that can be produced simply and efficiently at low cost.

  The present inventors have obtained the knowledge that a transparent conductive film having excellent conductivity can be easily produced by using an aerosol obtained by mixing a carrier gas with aluminum-doped zinc oxide fine particles. In particular, it has been found that a transparent conductive film having excellent conductivity can be produced by having a specific particle diameter and the aluminum doping amount within a specific range, and the present invention is completed based on such knowledge. It came to.

That is, the present invention provides an aluminum dope that contains aluminum atoms in an atomic ratio of 0.001 to 0.04 with respect to zinc atoms and has a 50% average particle diameter of 0.5 to 3.0 μm on a volume basis. forming a transparent conductive film made of the mixed carrier gas to form an aerosol (I), and the aerosol is sprayed from a nozzle onto the substrate to collide with the substrate in the zinc oxide fine particles (II) It is related with the manufacturing method of the aluminum dope zinc oxide transparent conductive film using the aerosol characterized by including.

  According to the present invention, it is possible to easily and efficiently produce a transparent conductive film having high conductivity and transparency without impairing the conductivity of the aluminum-doped zinc oxide fine particles used as a raw material.

  The method for producing an aluminum-doped zinc oxide (hereinafter also referred to as “AZO”) transparent conductive film using the aerosol of the present invention comprises the step (I) of forming an aerosol by mixing AZO fine particles with a carrier gas, and the aerosol And a step (II) of forming a transparent conductive film made of the fine particles on the substrate by spraying from a nozzle and colliding with the substrate.

  The method for producing an AZO transparent conductive film using the aerosol of the present invention can be performed according to a so-called aerosol deposition method.

  As the AZO fine particles used in the present invention, AZO fine particles produced by a production method such as a gas phase method, a liquid phase method, or a solid phase method can be used. As a method for producing AZO fine particles by a vapor phase method, for example, an evaporation condensation method in which zinc oxide and aluminum oxide as raw materials are heated and evaporated, and agglomerated in an inert atmosphere gas such as argon and helium to produce fine particles, Examples of the gas phase reaction method include high-vapor pressure zinc and aluminum chlorides, volatile oxychlorides, alkoxides, organic compounds and the like as raw material compounds, and thermal decomposition at high temperatures.

  Examples of the method for producing AZO fine particles by the liquid phase method include, for example, a chemical precipitation method in which solid particles are precipitated by a chemical reaction from an aqueous solution of a zinc salt and an aluminum salt or a metal alkoxide, and a fine particle obtained by hydrolysis and polycondensation reaction of a metal alkoxide. There are obtained alkoxide methods, hydrothermal synthesis methods utilizing hydrothermal conditions of high temperature and pressure, and the like.

  Examples of the method for producing AZO fine particles by the solid phase method include a method in which raw material metal oxide powders are mixed and dispersed, then fired and further pulverized to produce fine particles. Specifically, a method of obtaining AZO fine particles by dispersing zinc oxide and aluminum oxide in a medium such as water and then removing the medium, followed by firing and grinding. The particle diameter of zinc oxide used at this time is preferably about 0.6 μm, and the particle diameter of aluminum oxide is preferably about 0.1 μm.

  Here, the particle diameter of zinc oxide or aluminum oxide refers to a 50% average particle diameter based on volume, and a measured value by a measuring method described later can be adopted.

  The firing temperature when firing the AZO fine particles in the solid phase method is preferably 800 to 1200 ° C, more preferably 850 to 1050 ° C. By using, for example, AZO fine particles obtained by firing at a temperature in this range for 1 to 3 hours, preferably about 2 hours, an AZO transparent conductive film having excellent conductivity can be formed.

  Aluminum atoms in the AZO fine particles are 0.001 to 0.04 in terms of atomic ratio with respect to zinc atoms, and preferably 0.005 to 0.015. If the doping amount of aluminum atoms is within this range, an AZO transparent conductive film having excellent conductivity can be formed.

Further, the average particle size of the AZO fine particles is such that the 50% average particle size on a volume basis is 0.5 to 3.0 μm , preferably 1.0 to 1.5 μm. When the average particle diameter is within this range, an AZO transparent conductive film having excellent conductivity and film hardness can be formed. The average particle diameter can be adjusted by, for example, a method of adjusting by pulverization during the production of AZO fine particles, a method of classifying the produced AZO fine particles, or the like.

  Here, the volume-based 50% average particle diameter of the AZO fine particles is a median diameter (D50) of a volume-based particle size distribution measured by a laser diffraction scattering method. For example, a microtrack particle size distribution measuring apparatus manufactured by Nikkiso Co., Ltd. Can be measured.

  It is preferable that the AZO fine particles have high conductivity because they have excellent conductivity in the obtained transparent conductive film.

  In the step (I) of the present invention, examples of the method for mixing the AZO fine particles and the carrier gas include a method using an aerosol generator. As a mixing method using an aerosol generator, specifically, a carrier gas is introduced into an aerosol generator containing AZO fine particles, the AZO fine particles are rolled up, and the AZO fine particles and the carrier gas are mixed to form an aerosol. A method for deriving the generated aerosol can be illustrated. The capacity of the aerosol generator, the amount of carrier gas introduced into the aerosol generator, and the amount derived from the aerosol generation container can be appropriately selected so that an aerosol of stable AZO fine particles can be formed. Specifically, examples of the introduction / extraction amount of the carrier gas include 6 to 15 L / min. Here, the aerosol is one in which AZO fine particles are dispersed in a carrier gas.

  The carrier gas is preferably one that does not affect the performance of the AZO fine particles or the formed transparent conductive film. Specifically, for example, nitrogen, helium, argon, dry air, or the like can be used. These carrier gases can be used alone or in admixture of two or more.

  The step (I) preferably includes a step of suppressing aggregation of the AZO fine particles loaded in the aerosol generator. Examples of the step of suppressing aggregation of the AZO fine particles include a step of stimulating the AZO fine particles by vibration, electric field, heating or the like. By giving such a stimulus, it is possible to form an aerosol in which the particle diameter of the AZO fine particles is maintained within a certain range.

  Furthermore, in step (I), the formed aerosol may be classified using a classifier, and may be crushed using a crusher. As a result, the AZO fine particles contained in the aerosol have a particle size and particle size distribution effective for the formation of the transparent conductive film, and a stable conductive film is formed by supplying a stable aerosol. can do.

[Step (II)]
Step (II) in the method for producing an AZO transparent conductive film of the present invention is a method of forming the transparent conductive film by spraying the aerosol formed in the step (I) from a nozzle and causing the aerosol to collide with the substrate. For example, a film forming apparatus including a nozzle and a substrate mounting unit can be used.

  The nozzle is not particularly limited as long as it can form a uniform transparent conductive film, and a Laval nozzle is preferable from the viewpoint that a predetermined injection speed can be easily obtained. The opening shape of the nozzle is not limited to a circle, but may be a slit shape corresponding to the width direction of the substrate. When the nozzle opening is circular, for example, when the injection speed is 500 to 700 m / sec, it is preferable that the nozzle has a diameter in the range of 0.5 to 1 mm.

  Two or more nozzles may be provided instead of only one. When a plurality of nozzles are installed, the plurality of nozzles may be provided by branching from one aerosol generator, but each nozzle may be provided corresponding to one aerosol generator. A film forming apparatus provided with a plurality of nozzles is preferable in that film formation can be performed at a high speed and a large-area transparent conductive film can be easily manufactured.

  The substrate on which the transparent conductive film is formed by the collision of the aerosol sprayed from such a nozzle is preferably arranged with a distance from the nozzle of, for example, 0.5 to 30 mm, and keeps an interval of 10 to 20 mm. More preferably, it is arranged. By adjusting the distance between the substrate and the nozzle within this range, it is easy to adjust the collision speed of the aerosol to the substrate, and the transparent conductive film is formed by particles that recoil from the substrate without being involved in the formation of the transparent conductive film. Inhibition can be suppressed.

  Examples of the material of the substrate include glass, ceramic, quartz, sapphire, a silicon wafer, and plastic.

  As the means for placing the substrate, the position on the substrate where the aerosol collides is sequentially moved, and the AZO fine particles in the aerosol sequentially adhere to or react with the new surface of the substrate, and the transparent conductive film is formed on the substrate. Are preferably provided with relative scanning means for relatively scanning the aerosol ejected from the nozzle and the substrate. Specifically, as the relative scanning unit, a substrate mounting table that moves in a certain direction (X direction) and a moving unit that moves the nozzle in a direction perpendicular to the moving direction of the mounting table (Y direction). Can be mentioned. By the relative movement of the nozzle and the substrate, continuous production of a transparent conductive film and production of a large area can be facilitated efficiently.

  The spray speed of the aerosol from the nozzle is not particularly limited, and is appropriately selected according to the spray amount of the aerosol, the nozzle shape, the distance between the nozzle and the substrate, the scanning speed of the nozzle and / or the substrate, the formed film thickness, etc. can do. A preferable injection speed is in the range of 100 to 1,000 m / sec, and more preferably in the range of 500 to 700 m / sec. Within this range, a dense, transparent and highly conductive transparent conductive film can be formed.

  The angle between the aerosol injection direction and the substrate surface is not particularly limited, but the angle formed between the aerosol injection direction and the substrate surface is in the range of 0 ° to 10 ° with respect to the vertical direction of the substrate surface. And more preferably perpendicular to the substrate.

  The inside of the film forming apparatus when forming the transparent conductive film on the substrate is preferably set to a predetermined atmosphere. For example, it is adjusted to about 1,000 to 50,000 Pa and about 20 ° C. When the pressure in the film forming apparatus is within the above range, it is possible to continuously produce a transparent conductive film having high conductivity and film hardness.

  Although the film thickness of the transparent conductive film formed in process (II) is not specifically limited, The range of 150-250 nm is preferable from having the outstanding transparency, electroconductivity, and film | membrane hardness.

  The film thickness of the transparent conductive film is determined by measuring the thickness of the substrate before and after the formation of the transparent conductive film using a stylus type surface shape measuring instrument (DEKTAK8: manufactured by Veeco), and obtaining a value obtained from the difference. Can do.

  Furthermore, it is also possible to add a step of performing resistance heating to the AZO transparent conductive film formed by the step (II). The resistance heating is a heating method using Joule heat generated by passing a current through the resistor, and can be performed by, for example, an electric furnace. The heating temperature is preferably 500 to 1500 ° C.

  As an example of an AZO transparent conductive film manufacturing apparatus to which the AZO transparent conductive film manufacturing method of the present invention is applied, the one shown in FIG. 1 can be exemplified. The transparent conductive film manufacturing apparatus shown in FIG. 1 mainly includes an aerosol generator 3 and a film forming apparatus 6.

  The aerosol generator 3 is connected to a gas cylinder 1 for storing a carrier gas via a gas conveying pipe 2 connected to the bottom, and when a predetermined amount of carrier gas is supplied from the gas cylinder to the aerosol generator 3, it is loaded inside. The transparent conductive material fine particles P to be mixed with the carrier gas form an aerosol. Further, a carrier tube 4 is connected to the upper part of the aerosol generator, and the aerosol formed in the aerosol generator is led out from the carrier tube 4.

  In such an aerosol generator 3, a vibration device and an electric field generator for stimulating the AZO fine particles as necessary in order to suppress aggregation of the AZO fine particles loaded therein and maintain the particle diameter within a certain range. A heating device or the like may be provided. Further, the aerosol generator 3 and the transport pipe 4 are provided with a classifier for removing AZO fine particles having a particle diameter equal to or larger than a predetermined particle diameter contained in the formed aerosol, and particles having a predetermined particle diameter or larger. A crusher for crushing AZO fine particles having a diameter may be provided.

  In the film forming apparatus 6, a nozzle 5 for injecting aerosol supplied through the transport pipe 4 is provided at the tip of the transport pipe 4. The shape of the opening of the nozzle 5 may be a slit having the same width as the stage or a circular opening. Although only one nozzle is illustrated, a plurality of nozzles may be provided.

  In the film forming apparatus 6, a stage (mounting table) 8 is provided that supports a substrate 7 on which a transparent conductive film is formed, for example, connected to a suction apparatus (not shown) and supported by a suction force. The stage has an XY direction moving mechanism so that aerosol sprayed from the nozzle collides with a new surface of the substrate on the stage.

  On the other hand, the nozzle may be provided with a moving mechanism capable of injecting aerosol so as to collide with a new surface of the substrate supported by the stage, instead of the moving mechanism of the stage. For example, the slit-shaped nozzle is moved so as to scan in the X direction to spray aerosol, and a transparent conductive film is formed on the substrate on the fixed stage, or the circular nozzle is moved in the X direction so as to scan in the X direction. The transparent conductive film may be formed on the stage by reciprocally moving the stage in the Y direction.

  The film forming apparatus 6 is provided with a vacuum pump 9 and a temperature control device (not shown) as required, and the inside can be set to atmospheric pressure or reduced pressure and set to a desired temperature. In addition, a transport unit that automatically transports the substrate into the film forming apparatus may be provided so that the substrate is automatically carried into and out of the apparatus.

  The transparent conductive film obtained by the method for producing an AZO transparent conductive film of the present invention is dense, highly conductive and transparent, and includes liquid crystal displays such as solar cells, OA devices and mobile phones, flat panel displays, etc. It is suitable for the electrode member.

  Below, the manufacturing method of the AZO transparent conductive film of this invention is demonstrated concretely in detail, However, The technical scope of this invention is not limited to these.

[Production Examples 1 to 6] Preparation of AZO fine particles Zinc oxide fine particles having an average particle size of 0.6 µm and aluminum oxide fine particles having an average particle size of 0.1 µm were dispersed in 4500 g of water at a mass shown in Table 1. Water was removed by distillation under reduced pressure, followed by firing in the atmosphere at 870 ° C. for 2 hours, and the resulting fired product was pulverized with a ball mill to obtain AZO fine particles (1 to 6).

  About the obtained AZO microparticles | fine-particles, the 50% average particle diameter by a volume reference was measured using the Nikkiso Co., Ltd microtrac particle size distribution measuring apparatus. The results are shown in Table 1.

  The conductivity of the AZO fine particles was measured by the following method. 0.2 g of AZO fine particles and 0.02 g of sintering aid (10 mass% polyvinyl alcohol aqueous solution) are mixed, pressed at 10 MPa, molded, fired at 1200 ° C. for 2 hours, and pellets for measurement (diameter 8 mm, thickness 0) 8 mm). Using a 2400 source meter (manufactured by Caseley Co., Ltd.), the conductivity of the measurement pellets was measured by a four-end needle method in accordance with JIS K 7194. The results are shown in Table 1.

[Examples 1 to 6] Preparation of Transparent Conductive Film Using the obtained AZO fine particles, a transparent conductive film was prepared using the transparent conductive film manufacturing apparatus shown in FIG. The aerosol generator was charged with AZO fine particles, and while the aerosol generator was vibrated by a vibration device, nitrogen gas was introduced into the aerosol generator as a carrier gas at 10 L / min to generate an aerosol. This aerosol is injected into a film forming apparatus adjusted to 10,000 Pa and 20 ° C. at a speed of 600 m / sec from a Laval nozzle having a diameter of 0.8 mm, on a 26 mm × 76 mm sapphire substrate arranged 15 mm from the nozzle. A transparent conductive film was formed by vertical collision. The transparent conductive film was heated at 1200 ° C. for 2 hours using an electric furnace to obtain an AZO transparent conductive film.

[Conductivity]
The conductivity of the obtained AZO transparent conductive film was measured by a four-end needle method according to JIS K 7194 using a 2400 source meter (manufactured by Caseley). The results are shown in Table 2.

[transparency]
The transmittance of the obtained AZO transparent conductive film was measured with a Shimadzu automatic spectrophotometer UV-3100PC (manufactured by Shimadzu Corporation) using light having a wavelength of 550 nm. The results are shown in Table 2.

  From the results, the AZO transparent conductive film is excellent in conductivity and transparency, and is suitable for a transparent electrode of a liquid crystal display.

It is a figure which shows the schematic block diagram of an example of the transparent conducting production apparatus to which the manufacturing method of the AZO transparent conductive film of this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Carrier gas cylinder 3 Aerosol generator 5 Nozzle 6 Film-forming apparatus 7 Substrate 9 Vacuum pump P Transparent conductive material fine particles

Claims (4)

Carrier gas to aluminum-doped zinc oxide fine particles containing aluminum atoms in the range of 0.001 to 0.04 in terms of atomic ratio with respect to zinc atoms and having a 50% average particle diameter of 0.5 to 3.0 μm on a volume basis are mixed and wherein the step of forming an aerosol (I), and then injecting the aerosol from a nozzle comprising the step (II) to form a transparent conductive film made of the fine particles on the substrate to collide the substrate The manufacturing method of the aluminum dope zinc oxide transparent conductive film using the aerosol to do. The method for producing an aluminum-doped zinc oxide transparent conductive film using an aerosol according to claim 1 , wherein in the step (II), the aerosol is injected from the nozzle at an injection speed of 500 to 700 m / sec . The method for producing an aluminum-doped zinc oxide transparent conductive film using an aerosol according to claim 1 or 2 , wherein the nozzle has a diameter of 0.5 to 1 mm in the step (II) .   4. The aluminum dope using the aerosol according to claim 1, wherein in the step (II), the aerosol is caused to collide with the substrate disposed at a distance of 0.5 to 30 mm from the nozzle. 5. A method for producing a zinc oxide transparent conductive film.

Images