JPH06136162A - Formation of thin metal oxide film - Google Patents

Abstract

PURPOSE:To form a metal oxide easily without fail at a relatively low temperature by irradiating the coating film with ultraviolet rays in the course of a process comprising applying a metal alkoxide solution to a substrate and drying and heat-treating the film. CONSTITUTION:A metal alkoxide solution is applied to a substrate and drying and heat-treating the film to hydrolyze and condense the metal alkoxide to form a thin metal oxide film on the substrate. In the course of this process, the coating film is irradiated with ultraviolet rays to obtain the purpose thin metal oxide film. Examples of the metals of the metal alkoxides include silicon titanium zirconium and aluminum and further include tin, vanadium, zinc, calcium lithium, lead and boron. It is desirable to add an organometallic Lewis acid to the metal alkoxide solution in order enable its sol-gel reaction at low temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a metal oxide thin film, and in particular, a metal oxide thin film can be formed at a relatively low temperature. In some cases, the present invention relates to a method for forming a metal oxide thin film.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
As a means for inexpensively forming a metal thin film layer on a plastic film, a method of applying a solution in which metal or metal oxide particles are dispersed in an organic binder, vapor deposition of a metal or metal oxide material such as vacuum deposition or sputtering, etc. The law has been adopted.

However, these conventional techniques require a relatively high vacuum in the latter vapor deposition method, so that the manufacturing cost is high and the mass productivity is difficult. Further, the former method of applying a metal fine particle solution is a method that does not require a vacuum and is relatively inexpensive and excellent in mass productivity. For example, performance such as conductivity is
There were problems such as being inferior to the vapor deposition method. On the other hand, conventionally, a method of forming a metal oxide thin film on a substrate by a sol-gel method utilizing hydrolysis and polycondensation reaction of metal alkoxide is known, but this method is generally the final densification of the sol. Since it requires a heat treatment at about 400 ° C. or higher, it could not be applied as it is to a general plastic film having poor heat resistance.

The present invention has been made in order to solve these problems, and a metal oxide thin film having excellent properties can be easily and surely formed by a sol-gel method even at a relatively low temperature. A metal oxide thin film laminated plastic film useful for various industrial films, optical films, packaging films, etc. can be obtained by industrially forming a metal oxide thin film on the above plastic film. It is an object to provide a method for forming an oxide thin film.

[0005]

Means and Actions for Solving the Problems The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, by performing ultraviolet irradiation during the sol-gel reaction, a sol-gel on a plastic film was obtained. It is possible to form a metal oxide layer by a reaction, and more specifically, a metal alkoxide solution is applied to a substrate, and this coating film is dried and heat-treated to hydrolyze and condense the metal alkoxide to thereby give the substrate. By subjecting the above coating film to UV irradiation in the process of forming a metal oxide thin film thereon, the sol-gel reaction is sufficiently completed even at a relatively low temperature, that is, a low temperature of 40 to 280 ° C. The inventors have found that a metal oxide thin film having a good performance can be strongly obtained on the above substrate, and have completed the present invention.

An important feature of the present invention is that it is exposed to ultraviolet rays before and after drying, heat treatment, or during treatment.
It was newly discovered that it is effective in promoting the formation of an inorganic thin film at a lower temperature or improving the performance of an inorganic thin film. That is, for example, during the drying / heat treatment, or by irradiating ultraviolet rays before and after the heat treatment, the hydrolysis / polycondensation reaction is accelerated, and the temperature of these reactions is accelerated, so that a dense film is easily formed. It will be.

The present invention will be described in more detail below. In the method for forming a metal oxide thin film of the present invention, a metal alkoxide solution is applied to a substrate, and the coating film is dried and heat-treated to hydrolyze the metal alkoxide. In the process of forming a metal oxide thin film on the substrate by condensation, the coating film is subjected to ultraviolet irradiation treatment.

Here, as the substrate on which the metal oxide thin film is formed, a plastic film or other plastic molding can be effectively used. Known materials can be used as the plastic film used in the present invention. For example, polyimide, polyarylate, epoxy resin, phenoxy resin, polyvinyl alcohol, cellulose acetate, polyethylene terephthalate, polynaphthalene terephthalate, polyether sulfone, polysulfone, polycarbonate, polyetheramide, polymethylmethacrylate,
Examples thereof include polystyrene, polyamide, polypropylene, polyethylene, polyvinyl chloride and the like. These plastic films may be a single layer or a composite of two or more kinds, and may be a composite of other materials laminated on one side or both sides for the purpose of improving various functionalities. Further, these plastic films may be appropriately added therein with a thermal property modifier, a mold release agent, an antistatic agent, etc. for improving thermal stability. The film thickness range is usually 2 nm to 1 μm.

In the present invention, the metal alkoxide solution is first applied to the substrate.

In this case, the alkoxy metal used for forming the metal oxide thin film layer is not particularly limited, but for example, silicon, titanium, zirconia, aluminum, etc., or indium, tin, vanadium, zinc, calcium, lithium, lead. , And an alkoxy metal such as boron. Specifically, methoxysilane, ethoxysilane, tetraethoxysilane, isopropoxy titanium, methoxy vanadium, isopropoxy vanadium,
Methoxyzinc, tetraethoxyzirconium, n-propoxyindium, i-propoxyindium, n-propoxytin, tetraethoxyaluminum, etc. may be mentioned, and one of these may be used alone or two or more of them may be used in combination. Can be used.

In the metal alkoxide solution, if necessary, other metal or metal oxide of the same kind or different kind can be used as a metal component in addition to the alkoxy metal.

The above metal alkoxide solution is preferably blended with an organometallic Lewis acid in order to enable a sol-gel reaction at a low temperature.

Examples of the organometallic Lewis acid used here include acetates of metals such as germanium, titanium, aluminum, antimony and tin, other organic acid salts, halides and phosphates. The acid may be an inorganic acid such as hydrochloric acid, acetic acid or nitric acid, which is used alone or as a catalyst, acetic acid, trifluoroacetic acid, p
-Toluenesulfonic acid, organic acid such as methanesulfonic acid,
Also, these are used in combination with acids such as substances generated by heating or light irradiation. The addition amount of the organometallic Lewis acid is preferably 0.001 to 5% by weight.

Further, as catalysts, instead of such acids, monoethanolamine, diethanolamine, triethanolamine, diethylamine, triethylamine, DBU (diazabicycloundecene-1), DB
A bicyclo ring amine such as N (diazabicyclononene) or a base such as ammonia or phosphine can be used.

The above-mentioned components such as metal alkoxide are dissolved or dispersed in a solvent. As the solvent, it is necessary to coat the above-mentioned alkoxy metal and catalyst on a plastic film and then to evaporate them. If a solvent is preferable and does not react with an alkoxy metal or a catalyst and does not dissolve a substrate such as a plastic film, a commonly used solvent can be used. For example, alcohols such as ethyl alcohol, methyl alcohol, isopropyl alcohol, n-propyl alcohol and methoxymethyl alcohol, water, acetic acid esters such as ethyl acetate and methyl acetate, ketones such as acetone and methyl ethyl ketone, ethers such as tetrahydrofuran, and ethylene glycol mono. Ethylene glycol monoalkyl ethers such as ethyl ether, dimethylformamide, dimethylsulfoxide and the like can be mentioned.

As the method for applying the above-mentioned metal alkoxide solution to the substrate, various methods usually used such as spraying, dipping, bar coating, roll coating and spin coating can be used, but as a method for applying a uniform thickness, , Dip or roll coating methods are preferred. Further, a pattern printing method such as an offset or screen printing method can also be adopted.

In the present invention, after the metal alkoxide solution is coated on the substrate in this way, the coating film is dried and heat-treated, and at the same time, ultraviolet irradiation is carried out.

In this case, the drying can be performed at room temperature,
It is preferable to heat, and thereby, the hydrolysis and polycondensation reaction are promoted together with the evaporation of the solvent, and it becomes possible to form a stronger thin film. Therefore, the heat treatment can be carried out at a heating temperature suitable for these purposes or the heat resistance of the plastic film or the like, and is usually 40 ° C. or higher, preferably 50 ° C. to 280 ° C.
And a range in which the substrate has heat resistance.

The UV irradiation may be carried out at any stage before the coating film is dried, during the drying process, after the drying process and during the heat treatment process, and may be carried out not only in one stage but also in two or more stages. Good. The ultraviolet irradiation treatment can be performed by a usual method using a low pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, or the like. In this case, the irradiation may be performed at room temperature or under heating.

The metal oxide thin film obtained as described above is usually formed to have a film thickness of 0.001 to 1 μm.
If the film thickness is thicker than 1 μm, the film is likely to be cracked or peeled. On the other hand, if the thickness is less than 0.001 μm, the characteristics that can be provided for the intended use cannot be obtained in many cases.

The metal oxide thin film may be formed on one side or both sides of a plastic film or the like depending on the application.

Here, the degree of density of the thin film can be controlled by changing the processing conditions such as heating temperature, catalyst, pH, starting material and the like. That is, when treated with a small amount of water and acidity, a dense film is obtained, which has barrier properties,
It is suitable for purposes such as scratch resistance, high conductivity, and high hardness. On the contrary, in the presence of alkali, or a porous thin film obtained by the reaction in the presence of a large number of water,
It is effective for enhancing the easy adhesion and the high adsorption of ink and the like.

The plastic film on which the metal oxide thin film is formed can be further used for various applications such as heat ray reflection and selective absorption as an optical film, as an antireflection multilayer coating (TiO ₂ / SnO ₂ ) of a polarizing film, and the like. It can be used for transparent electrodes for liquid crystal display devices, transparent touch panels, and the like.

[0024]

According to the present invention, a metal oxide thin film can be formed easily and reliably at a relatively low temperature, and is particularly effective for forming a metal oxide thin film on a plastic film.

[0025]

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

2.74 g of isopropoxyindium
(0.009 mol), n-propoxy tin 0.355 g
(0.001 mol) of isopropyl alcohol 100m
It was dissolved in 1 (solution A).

On the other hand, a solution B prepared by dissolving 10 ml (0.01 mol) of concentrated hydrochloric acid in 100 ml of isopropyl alcohol,
A solution C was prepared by dissolving 1.44 ml (0.08 rumo) of water in 800 ml of isopropyl alcohol.

Solution B and then solution C were successively added dropwise to solution A while stirring, and after mixing, the mixture was further stirred at room temperature for 3 hours to obtain a transparent viscous solution.

25 mg of tin acetate was added to 100 ml of this solution.
Add an equal amount of the solution dispersed in isopropyl alcohol,
A clear, viscous solution was obtained.

Then, the obtained viscous solution was treated with a polyethylene terephthalate film (76 mm × 26 mm × 0.1 mm).
mm) was applied by a bar coating method to about 0.2 μm.
This was dried at 100 ° C. for 10 minutes, further heat-treated at 150 ° C. for 10 minutes, and then irradiated with ultraviolet rays from a height of 8 cm for about 10 seconds using a 160 W / cm high pressure mercury lamp. The irradiation energy at this time is 1800 m
It was J / cm ² .

By the above treatment, a laminated sheet having a metal oxide (InO ₂ / SnO ₂ ) thin film with a thickness of about 0.2 μm was obtained on the polyethylene terephthalate film.
The resistance of this thin layer was 2 × 10 ⁵ Ω / mouth.

Claims (3)

[Claims] 1. A substrate is coated with a metal alkoxide solution,
This coating film is dried and heat-treated to hydrolyze and condense the metal alkoxide to form a metal oxide thin film on the substrate, and the coating film is subjected to ultraviolet irradiation treatment. Method for forming oxide thin film. 2. The method of claim 1, wherein the substrate is plastic. 3. The method according to claim 1, wherein the heat treatment temperature is 40 to 280 ° C.