JP2005162543A - Method for forming metal oxide thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a dense metal oxide thin film small in film thickness variation on a substrate such as a plastic film low in heat resistance in a short period of time at a temperature lower than the heat-resistant temperature of the substrate. <P>SOLUTION: A metal oxide thin film formed by using a metal alkoxide expressed by R"<SB>m</SB>Me(OR')<SB>n</SB>as a source material, wherein Me is the center metal, R' represents a hydrocarbon group, R" represents a hydrocarbon group or halogen, and n>0, and having an inner structure with ≥0.05 mixing ratio of OH is subjected to spraying with an alkali mixture gas containing one or more kinds of alkali gas and diluted with a carrier gas. This induces condensation reaction in OH groups in the metal oxide thin film and promotes to changes into a metal oxide coupling so as to obtain a dense metal oxide thin film having little change in the film thickness at a low temperature in a short period of time. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a metal oxide thin film obtained from an organometallic compound.

  By forming a metal oxide thin film on the substrate surface, a photocatalytic function, a hard coat function, a gas barrier function or a conductive function can be imparted.

  Known methods for forming a metal oxide thin film on the surface of a substrate include a CVD method, a vapor deposition method, a sputtering method, and a sol-gel method using a solution, which are film formation methods based on a gas phase reaction.

  Among these film forming methods, the vapor deposition method and the sputtering method are vacuum type film forming methods, so that the film forming apparatus to be used requires large equipment such as a processing chamber and a vacuum pump, and complicated work under high pressure reduction. There is a problem.

On the other hand, the sol-gel method does not require a large facility such as a processing chamber or a vacuum pump and a highly decompressed environment, and has an advantage in that a film can be formed with a simple facility (see, for example, Patent Document 1).
JP-A-10-176118

  However, a metal oxide obtained from an organometallic compound by a sol-gel method requires high-temperature and long-time heat treatment in order to remove impurities and unreacted portions in the film after film formation. For this reason, the base material which can be used is limited and there exists a problem that it is difficult to form a metal oxide thin film of favorable film quality on a base material with low heat resistance, such as a plastic film.

  The present invention has been made in view of such circumstances, and does not require a large facility such as a processing chamber or a vacuum pump and a highly decompressed environment, and a metal oxide thin film is formed on the surface of a substrate having low heat resistance such as a plastic film. An object of the present invention is to provide a method for manufacturing a metal oxide thin film that can be formed at a low temperature in a short time.

The method for producing a metal oxide thin film of the present invention is as follows: R ″ _m Me (OR ′) _n (Me is a central metal, R ′ is a hydrocarbon group, R ″ is a hydrocarbon group and halogen or H, n> 0) A metal oxide thin film formed using the metal alkoxide shown as a raw material, an alkali mixed gas containing at least one kind of alkaline gas and diluted with a carrier gas, or the alkali mixed gas and moisture It is characterized by spraying a mixed gas with the containing gas.

  As described above, after the metal oxide thin film is formed, the alkali mixed gas is sprayed to cause the OH groups in the metal oxide thin film to undergo a condensation reaction, thereby promoting the change to the metal-oxygen bond. Therefore, it is possible to produce a dense thin film with little change in film thickness at a low temperature in a short time.

  In the method for producing a metal oxide thin film of the present invention, the internal structure of the metal oxide thin film before the alkali mixed gas spray treatment is a peak intensity ratio between a Me—OH bond and a Me—O—Me bond in FT-IR measurement. It is preferable that the OH mixture ratio [OH mixture ratio = (Me-OH intensity) / (Me-O-Me intensity)] calculated from the above is 0.05 or more.

  In the method for producing a metal oxide thin film of the present invention, the concentration of the alkali mixed gas is preferably 10 ppm or more and 1% or less.

  In the method for producing a metal oxide thin film of the present invention, a plasma CVD method is preferable as a method for forming a metal oxide thin film using the metal alkoxide as a raw material. Further, silicon oxide is preferable as the metal oxide thin film.

The alkali mixed gas used in the method for producing a metal oxide thin film of the present invention is preferably a mixed gas containing NH ₃ .

  Next, the present invention will be described in detail.

  The metal thin film production method of the present invention is characterized by including a treatment of spraying an alkali mixed gas onto a metal oxide thin film obtained from a metal alkoxide. Specifically, as shown in FIG. 1, a metal oxide film is formed on a substrate from an organometallic compound in a metal thin film deposition zone 1, and subsequently, a metal is deposited in an alkaline mixed gas spray zone 2. It is characterized by comprising a process in which OH groups in an oxide thin film are subjected to a condensation reaction to promote a change to a metal-oxygen bond.

  In the present invention, examples of the metal oxide obtained from the metal alkoxide include silicon oxide, titanium oxide, zirconium oxide, aluminum oxide, hafnium oxide, magnesium oxide, yttrium oxide, scandium oxide, tin oxide, indium oxide, antimony oxide, Examples include a single substance such as zinc oxide, lanthanum oxide, or tantalum oxide, or a mixture of two or more kinds. In particular, silicon oxide is widely used among metal oxides from the viewpoint of application fields as optical and electrical materials.

The metal alkoxide used in the present invention is represented by R ″ _m Me (OR ′) _n (Me is a central metal, R ′ is a hydrocarbon group, R ″ is a hydrocarbon group and halogen or H, n> 0). Is. Such raw materials may be used alone or in combination of two or more.

Examples of the metal alkoxide of silicon oxide include tetramethoxysilane; Si (OCH ₃ ) ₄ , tetraethoxysilane; Si (OC ₂ H ₅ ) ₄ , methyltrimethoxysilane; (C
H ₃ ) Si (OCH ₃ ) ₃ , dimethyldimethoxysilane; (CH ₃ ) ₂ Si (OCH ₃ ) _{2 and the} like.

  Examples of the method for forming a metal oxide thin film used in the present invention include a sol-gel method, a spray method, a plasma CVD method, and the like. The metal oxide thin film formed by these methods has an OH mixture ratio [OH mixture ratio = (Me−] calculated from the peak intensity ratio of the Me—OH bond and the Me—O—Me bond in the FT-IR measurement. It is preferable to have an internal structure in which (OH strength) / (Me-O-Me strength)] is 0.05 or more. Among them, a metal oxide thin film formed by a plasma CVD method is particularly preferable because of excellent mechanical performance, optical performance, appearance, and the like.

  Here, since the film thickness of the metal oxide thin film having the film internal structure as described above changes with time, conventionally, curing at a high temperature is necessary. For this reason, a plastic film with low heat resistance requires long-term curing at a low temperature below the heat resistance temperature of the substrate.

The cause of the change in the film thickness is considered to be that the residual OH groups present in the film are condensed with each other over time, and the film is contracted. Therefore, it is possible to stabilize the film thickness by carrying out this reaction after film formation. In the present invention, alkali mixed gas spraying is adopted as a specific method for promoting the reaction. In addition, it is thought that the process by alkali mixed gas is the method using the condensation reaction acceleration | stimulation catalytic action of an alkali.

  The alkali mixed gas used in the present invention is a mixed gas obtained by blending one or more kinds of alkaline gases and diluted with a carrier gas, or a gas containing the alkali mixed gas and moisture. In addition, the concentration range of the alkali mixed gas is preferably 10 ppm or more and 1% or less as a condition not causing the condensation reaction promoting effect and film deterioration.

Examples of the alkaline gas include NH ₃ , primary, secondary and tertiary alkylamines,
Examples include arylamines, alcoholamines alone, or a mixture of two or more. Examples of the amine include methylamine, dimethylamine, trimethylamine, n-butylamine, n-propylamine, tetramethylammonium hydroxide, piperidine or 2-methoxyethylamine. Of these alkaline gases, NH ₃ is particularly preferable from the viewpoints of vaporization, reactivity, and simplicity.

  Examples of the carrier gas for diluting the alkaline gas include noble gases such as helium, neon, argon, and xenon, nitrogen, oxygen, carbon dioxide, and air. These may be used alone or in combination of two or more. Note that these carrier gases may contain moisture.

  The base material for film formation is not particularly limited, and examples thereof include plastics, silicon wafers, and glass substrates. For plastics, polyethylene, polypropylene, polystyrene, polycarbonate, polyethylene terephthalate, polyethylene naphthalate, polyethyl methacrylate, polytetrafluoroethylene, norbornene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyether ketone, polyimide, polyamide, Examples include acrylic resin, diacetyl cellulose, triacetyl cellulose, regenerated cellulose, and alkali-treated triacetyl cellulose. Examples of these shapes include a plate shape and a film shape, but are not particularly limited.

  In the method for producing a metal oxide thin film of the present invention, the use of an alkali mixed gas can suppress a change with time of the film thickness after the metal oxide film is formed, so that the film thickness can be easily controlled. Furthermore, since no curing process is required, the change in film thickness can be reduced even if the substrate is a plastic film having low heat resistance.

  According to the present invention, since a metal oxide thin film formed using a metal alkoxide as a raw material is post-treated with an alkali mixed gas (or a mixed gas of an alkali mixed gas and moisture-containing gas), plastic A dense metal oxide thin film with little change in film thickness can be obtained in a short time at a temperature lower than the heat resistant temperature of the substrate, compared to a substrate having low heat resistance such as a film. Thereby, it is possible to impart functions such as optical properties, photocatalytic properties, hard coat properties, gas barrier properties, or conductivity to the substrate surface. Among them, as the optical characteristic function, for example, a light transmission function, an antireflection function, a reflection function, or a selective reflection function can be performed, and products for various applications utilizing these performances can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, in the metal oxide thin film deposition zone 1, the present invention provides R ″ _m Me (O
R ′) _n (Me is a central metal, R ′ is a hydrocarbon group, R ″ is a hydrocarbon group and halogen or H, n> 0) as a raw material, and a metal oxide on the substrate surface A thin film is formed, and in succession, in the alkali mixed gas spray zone 2, an alkali gas (for example, NH ₃₎ is applied to the metal oxide thin film formed in the metal oxide thin film formation zone 1. ) By condensing OH groups in the metal oxide thin film by spraying an alkali mixed gas containing one or more types and diluted with a carrier gas (or a mixed gas of the alkali mixed gas and water-containing gas). It is a method for producing a metal oxide thin film characterized by performing a process of reacting to promote a change to a metal-oxygen bond.

  In this metal oxide thin film manufacturing method, the internal structure of the metal oxide thin film before the alkali mixed gas spray treatment is calculated from the peak intensity ratio of the Me—OH bond and the Me—O—Me bond in the FT-IR measurement. The OH mixture ratio [OH mixture ratio = (Me-OH strength) / (Me-O-Me strength)] is preferably 0.05 or more.

  As a specific example of the film forming apparatus used in the metal oxide thin film forming zone 1, for example, as shown in FIG. A curved surface electrode 12 and a power source 13 for applying a pulsed electric field between the roll electrode 11 and the curved surface electrode 12 facing each other are provided, and between the roll electrode 11 and the curved surface electrode 12 by applying the pulsed electric field by the power source 13 And a plasma CVD apparatus for generating a plasma to treat the surface of the substrate S.

  Moreover, as a specific example of the spray processing apparatus used for the alkali mixed gas spray zone 2, for example, as shown in FIG. 3, a flat plate 21 for transporting a substrate and a flat plate 22 arranged to face the flat plate 21 in parallel. And an air supply nozzle 23 that supplies an alkali mixed gas between the pair of flat plates 21 and 22 and an exhaust nozzle 24 that exhausts air between the flat plates 21 and 22.

  Examples of the present invention will be described below together with comparative examples.

<Example 1>
A metal oxide thin film was prepared under the following conditions.

  A gas in which tetramethoxysilane, which is a metal alkoxide, nitrogen, and oxygen were mixed in a volume ratio of 40: 20: 0.2 on a polyethylene terephthalate film (hereinafter referred to as PET film) having a thickness of 75 μm was used. A silicon oxide film having a thickness of 100 nm was formed by plasma CVD. However, plasma CVD was performed under the following conditions.

-Film formation conditions by plasma CVD-
[Equipment configuration / deposition conditions]
In the plasma CVD apparatus shown in FIG. 2, roll electrodes 11 (diameter 400 mm, length 1080 mm, surface: solid dielectric (TiO ₂ : 20 wt%, Al ₂ O ₃ : 80 wt%, thickness 1 mm) facing each other are sprayed. ) And a curved electrode (curvature radius 202 mm, diameter 100 mm, length 810 mm, surface: solid dielectric (TiO ₂ : 20 wt%, Al ₂ O ₃ : 80 wt%, thickness 1)
mm) was 2 mm, and the substrate S (PET substrate) was placed in close contact with the discharge surface of the roll electrode 11.

Next, after the inside of the container 10 is evacuated to 1.33 kPa (10 Torr) by a vacuum pump, the above-mentioned mixed gas is introduced to 101.3 kPa (760 Torr) through a gas inlet mass flow controller (flow rate: 50 slm). In this state, the substrate S was conveyed at a traveling speed of 0.5 m / min, and the roll electrode 11 was rotated in the same direction at the same speed. The roll electrode 11 and the curved electrode 12 were both maintained at 60 ° C.

Then, a rising speed of 5 μsec, a discharge voltage of 17 kV (electric field intensity of 85 kV / cm, discharge current density of 0.03 mA / cm ²⁾ between the roll electrode 11 and the curved electrode 12 from the power source 13.
), A pulse electric field having a frequency of 4 kHz was applied, plasma was generated between the roll electrode 11 and the curved surface electrode 12, and a plasma CVD film was formed on the surface of the PET substrate.

In addition, about silicon oxide formed into a film on PET base material, it measures using a FT-IR (Bio-rad FTS135) (700-4000cm < ^-1 >), and it belongs to SiOH of 940cm < ^-1 > vicinity. It is confirmed that the OH mixing ratio, which is the intensity ratio of the absorption peak attributed to SiOSi in the vicinity of 1050 to 1080 cm ⁻¹ , is 0.05 or more.

-Alkaline mixed gas treatment-
Next, with respect to the PET base material with a silicon oxide film having an OH mixture ratio of 0.05 or more after the plasma CVD film formation, the spray processing apparatus of FIG. 3 (the alkali mixed gas spray processing zone 2 of FIG. ), Gas spraying was performed on the silicon oxide film under the following conditions using NH ₃ (500 ppm) diluted with nitrogen gas as the alkaline gas.

[Device configuration]
First, in the spray processing apparatus of FIG. 3, the distance between the flat plate 21 and the flat plate 22 is set to 2 mm, the surface temperature of the flat plate 21 is 70 ° C., and the supply nozzle 3 and the exhaust nozzle 24 having a width of 150 mm are heated. By adjusting the temperature, the temperature of the alkali mixed gas supplied from the air supply nozzle 23 was set to 50 ° C.

[Gas conditions]
The alkali mixed gas used for the spraying treatment was NH ₃ diluted with nitrogen gas, the NH ₃ concentration was 500 ppm, and the gas temperature was 50 ° C.

[Spray treatment conditions]
The base film was run at a running speed of 1 m / min in a state where the PET film S with silicon oxide film was in close contact with the flat plate 21 of the spray treatment apparatus of FIG. Further, 20 ml of the alkali mixed gas was introduced from the air supply nozzle 23, and 30 slm was exhausted by the exhaust nozzle 24, so that the silicon oxide film was sprayed.

  The sample (PET substrate with a silicon oxide film) obtained by the above treatment was evaluated by the following method. The evaluation results are shown in Table 1 below.

<Evaluation method>
A PET base material with a silicon oxide film produced by the above process was cut into 5 cm square, and the back surface was roughened with # 400 sandpaper, and then painted with black ink to a size of about 2 cm in diameter to produce a sample. With respect to this back-treated sample, a reflectance spectrum with a wavelength of 380 to 780 nm was measured using a spectrophotometer (manufactured by Shimadzu Corporation, model “UV-3101PC”). The reflectance spectrum was analyzed with optical characteristic calculation software (JA Woollam V.A.S.E. for Windows (R)) to calculate the initial film thickness. Furthermore, after leaving this sample at 90 ° C. for 3 days (72 hours), the film thickness was measured using the above-described method, and the film thickness change rate was obtained from the measurement result by the following formula.

Film thickness change rate (%) = [(1− (film thickness after aging / initial film thickness)] × 100
<Example 2>
In Example 1, it was made the same as Example 1 except having set the density | concentration of the alkali mixed gas used by a gas spray process to 5 ppm.

  The same evaluation as Example 1 was performed about the obtained sample (PET base material with a silicon oxide film). The evaluation results are shown in Table 1 below.

<Example 3>
By adding 100 parts by weight of tetraethoxysilane, which is an organometallic compound, to 1300 parts by weight of isopropyl alcohol, with stirring, 55 parts by weight of 0.36% hydrochloric acid and stirring at 25 ° C. for 2 hours A coating solution was obtained. The obtained coating solution was coated on a 75 μm-thick PET film while adjusting the thickness to 150 nm under a condition of 400 rpm and 30 seconds with a spin coater to obtain a silicon oxide film. The same alkali mixed gas spraying process as that in Example 1 was performed on the silicon oxide film after film formation.

  The same evaluation as Example 1 was performed about the obtained sample (PET base material with a silicon oxide film). The evaluation results are shown in Table 1 below.

<Example 4>
In Example 1, it was set as the same as Example 1 except having used the gas which volatilizes naturally from the 0.1 wt% ammonia water for alkali mixed gas spraying process.

  The same evaluation as Example 1 was performed about the obtained sample (PET base material with a silicon oxide film). The evaluation results are shown in Table 1 below.

<Comparative Example 1>
In Example 1, it was set as the same as Example 1 except not having performed alkali mixed gas spraying processing.

  The same evaluation as Example 1 was performed about the obtained sample (PET base material with a silicon oxide film). The evaluation results are shown in Table 1 below.

<Comparative example 2>
In Example 1, it replaced with the alkali mixed gas spray process, and it was the same as Example 1 except having performed heat processing for 10 minutes at 90 degreeC.

  The same evaluation as Example 1 was performed about the obtained sample (PET base material with a silicon oxide film). The evaluation results are shown in Table 1 below.

  The present invention provides an optical function such as light transmission, antireflection / reflection or selective reflection, a photocatalytic function, a hard coat function, a gas barrier function, or a conductive function on the surface of a substrate having low heat resistance such as a plastic film. It can be used effectively to give the function of.

It is a block diagram which shows an example of the preparation methods of the metal oxide thin film of this invention. It is a figure which shows typically an example of the film-forming apparatus used for the metal oxide thin film film-forming zone of FIG. It is a figure which shows typically an example of the spray processing apparatus used for the alkali mixed gas spray zone of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal oxide thin film film-forming zone 2 Alkali mixed gas spray zone 10 Container 11 Roll electrode 12 Curved electrode 13 Power supply 21,22 Flat plate 23 Supply nozzle 24 Exhaust nozzle S Substrate

Claims (6)

R ″ _m Me (OR ′) _n (Me is a central metal, R ′ is a hydrocarbon group, R ″ is a hydrocarbon group and halogen or H, and n> 0). The metal oxide thin film is sprayed with an alkali mixed gas containing one or more kinds of alkali gas and diluted with a carrier gas, or a mixed gas of the alkali mixed gas and a gas containing moisture. A method for producing a metal oxide thin film. The internal structure of the metal oxide thin film before the alkali mixed gas spraying treatment is FT-IR measurement, and the OH mixture calculated from the peak intensity ratio of the Me—OH bond and the Me—O—Me bond by the following formula The method for producing a metal oxide thin film according to claim 1, wherein the ratio is 0.05 or more.
OH mixing ratio = (Me-OH strength) / (Me-O-Me strength)   The method for producing a metal oxide thin film according to claim 1, wherein the concentration of the alkali mixed gas is 10 ppm or more and 1% or less.   The method for producing a metal oxide thin film according to any one of claims 1 to 3, wherein a film forming method of the metal oxide thin film using the metal alkoxide as a raw material is a plasma CVD method.   The method for producing a metal oxide thin film according to claim 1, wherein the metal oxide thin film is silicon oxide. The method for producing a metal oxide thin film according to claim 1, wherein the alkali mixed gas is a mixed gas containing NH ₃ .

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