JP2018003118A - Method for manufacturing thin film, thin film deposition material, optical thin film and optical member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a method for manufacturing an optical thin film excellent in durability and having a low refractive index, capable of forming the thin film without passing a complicated process; a thin film deposition material; an optical thin film; and an optical member.SOLUTION: The method for manufacturing a thin film comprises the steps of: depositing an object to be deposited by a thin film deposition material and a physical vapor deposition method to form a vapor deposition film; and contacting the vapor deposition film with an acid material to obtain a thin film having an air space. The thin film deposition material includes indium oxide and silicon oxide, and a mixture having an indium oxide of 0.05-0.25 mol to a silicon oxide of 1 mol is used. Silicon monoxide is included as the principal component of the silicon oxide; the refractive index of the thin film is 1.38 or less; and the porosity of the thin film is 8-70%.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for manufacturing a thin film, a thin film forming material, an optical thin film, and an optical member.

  Optical thin films have long been used in various optical devices by applying the light interference phenomenon. It has begun to be used as a permeable film for optical devices such as submarine periscopes, microscopes, and binoculars. In recent years, optical thin films have been used for astronomical telescopes, spectacle lenses, camera lenses, and the like. The optical thin film used in such an optical device includes an antireflection film that prevents reflection of light of a specific wavelength, a bandpass filter that transmits only a specific wavelength, and partially reflects incident light. It is also used in equipment that uses light, such as an optical pickup component such as a beam splitter that transmits light. Recently, optical thin films are also used in optical filters such as near-infrared filters and near-ultraviolet filters for vehicles, and optical thin films are used in a wide range of fields as an indispensable material in the latest electronics field. .

In order to enhance the antireflection effect of the optical thin film, it is effective to form an optical thin film having a refractive index close to the value of the square root of the refractive index of the film on the outermost surface of the film. It is. In order to form such an optical thin film, it is useful to contain air having a refractive index of 1.0 in the thin film, and optical thin films containing air by various methods including the sol-gel method have been proposed. Yes.
For example, Patent Document 1 discloses, in order from the glass substrate side, a first layer mainly composed of silica formed by a vacuum evaporation method, and a second layer of an inorganic oxide film formed by a vacuum evaporation method. An optical element including an antireflection film having a third layer obtained by applying a solution containing hollow silica fine particles and a binder on the second layer and firing the same is described.
Patent Document 2 discloses an inorganic base layer made of an inorganic material, a surface modified layer containing an inorganic oxide such as SiO ₂ , an acrylic resin laminated on the surface modified layer, etc. An antireflection film including an adhesion layer containing a binder and a low refractive index layer in which hollow silica particles are bound by a binder is described.
In Patent Document 3, a mixed liquid in which a sol solution in which magnesium fluoride (MgF ₂ ) fine particles are dispersed and an amorphous silicon oxide-based binder solution is applied to a substrate and heat-treated. _A method for producing an optical thin film in which _two fine particles are bound by an amorphous silicon oxide-based binder and a large number of voids are formed between MgF ₂ fine particles is described.

JP 2006-018095 A JP2015-222450A International Publication No. 2006/030848

However, as described in Patent Documents 1 to 3, when an optical thin film that is the outermost layer is formed by a sol-gel method in which a sol containing fine particles and a binder is bound, the formation of the thin film by the sol-gel method is performed in the atmosphere. Therefore, when the lower layer than the outermost layer is formed in vacuum, there is a problem that foreign matter is easily adsorbed when it is opened to the atmosphere for performing the sol-gel method, and it is necessary to remove the foreign matter. In addition, when an optical thin film that is the outermost layer is formed by the sol-gel method as described in Patent Documents 1 to 3, the change in the viscosity of the sol over time must be strictly controlled in order to precisely control the film thickness. And a thin film must be formed while constantly monitoring the viscosity of the sol, which may complicate the production. Furthermore, when forming an optical thin film that is the outermost layer by the sol-gel method, an excessive amount of sol is required when applying the sol to the film by dip coating, and the sol is applied to the film by the spin coating method. When it does, there also exists a problem that it is difficult to apply | coat to a curved surface with a uniform film thickness. Furthermore, when an optical thin film is formed by the sol-gel method, it is necessary to perform a heat treatment after applying the sol, and an optical thin film is formed on a film formed from a material having low heat resistance, for example, plastic having low heat resistance. There is a problem that it is difficult.
Therefore, one embodiment of the present invention is a method for producing an optical thin film having a low refractive index excellent in durability, a thin film forming material, an optical thin film, and an optical member. The purpose is to provide.

Means for solving the above problems are as follows, and the present invention includes the following forms.
In the first embodiment of the present invention, a thin film forming material is deposited on an object to be deposited by physical vapor deposition to form a vapor deposition film, and the vapor deposition film and an acidic substance are brought into contact with each other to form voids. And using the mixture containing indium oxide and silicon oxide as the thin film forming material, the indium oxide being 0.05 mol or more and 0.25 mol or less with respect to 1 mol of silicon oxide. This is a method for producing a thin film.

  A second embodiment of the present invention is characterized in that it is a mixture containing indium oxide and silicon oxide, and the indium oxide is 0.05 mol or more and 0.25 mol or less with respect to 1 mol of silicon oxide. It is a thin film forming material.

  A third embodiment of the present invention is an optical thin film characterized by containing indium oxide and silicon oxide and having a refractive index of 1.38 or less.

  4th embodiment of this invention is an optical member which has the said optical thin film and a to-be-film-formed object.

  According to the embodiment of the present invention, it is possible to provide a method for producing an optical thin film having a low refractive index excellent in durability, a thin film forming material, an optical thin film, and an optical member.

FIG. 1 is a SEM photograph of the surface of the optical thin film of Example 2 of the present invention. FIG. 2 is a SEM photograph of a cross section of the optical thin film of Example 2 of the present invention. FIG. 3 is a graph showing the relationship between the contact time with an acidic substance for reducing the refractive index of the thin film having voids in Examples to 1.38 or less and the In ₂ O ₃ / SiO molar ratio of the thin film forming material. is there.

  Hereinafter, an optical thin film manufacturing method, a thin film forming material, an optical thin film, and an optical member according to an embodiment of the present disclosure will be described. However, one embodiment described below is an example for embodying the technical idea of the present invention, and the present invention is not limited to the following thin film manufacturing method, thin film forming material, optical thin film, and optical member. . In addition, the content of each component in the composition means the total amount of the plurality of substances present in the composition unless there is a specific notice when there are a plurality of substances corresponding to each component in the composition. .

[Method for producing thin film]
In one embodiment of the present invention, a thin film-forming material is deposited on an object to be deposited by physical vapor deposition to form a vapor deposition film, and the vapor deposition film is contacted with an acidic substance to form a thin film having a void. And a step of using a mixture of indium oxide and silicon oxide, wherein the indium oxide is 0.05 mol or more and 0.25 mol or less with respect to 1 mol of silicon oxide. It is a manufacturing method.

(Thin film forming material)
The thin film forming material used in the manufacturing method of one embodiment of the present invention uses a mixture containing indium oxide and silicon oxide, and the indium oxide is 0.05 mol or more and 0.25 mol or less with respect to 1 mol of silicon oxide. .
By using a mixture containing indium oxide and silicon oxide as a thin film forming material, and indium oxide is 0.05 mol or more and 0.25 mol or less with respect to 1 mol of silicon oxide, indium oxide (I ) (In ₂ O), indium oxide (III) (In ₂ O ₃ ) and silicon dioxide (IV) (SiO ₂ ) can be formed. Since indium (I) oxide is highly soluble in acidic substances, indium oxide (In ₂ O) contained in the deposited film can be removed in a short time by bringing the deposited film into contact with the acidic substance. A thin film having a void satisfying the refractive index of can be formed.
When the molar ratio of indium oxide to 1 mol of silicon oxide in the mixture is less than 0.05 as a thin film forming material, the amount of indium oxide in the thin film forming material is small, and even after contact with an acidic substance after forming a deposited film It becomes difficult to form a thin film having a void satisfying a desired refractive index.
When the molar ratio of indium oxide to 1 mol of silicon oxide in the mixture which is a thin film forming material exceeds 0.25, the amount of indium oxide is too large, and when it is brought into contact with an acidic substance, there are too many voids. May be easily peeled off, which is not preferable.
The mixture used as the thin film forming material is more preferably 0.06 or more and 0.25 or less, more preferably 0.08 or more and 0.23 or less, still more preferably indium oxide with respect to 1 mol of silicon oxide. It is 0.10 or more and 0.22 or less.

Indium oxide used as a raw material for the film forming material is preferably indium oxide (III) (In ₂ O ₃ ).
The silicon oxide used as the raw material for the thin film forming material preferably contains silicon monoxide (SiO) as a main component. Here, “containing silicon monoxide as a main component” in silicon oxide means that at least 50% by mass of silicon monoxide is contained in 100% by mass of silicon oxide used as a raw material for a thin film forming material. The content of silicon monoxide (SiO) in silicon oxide (100% by mass) used as a raw material for the thin film forming material is preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more. Particularly preferred is 99% by mass or more, and most preferred is substantially 100% by mass. “The content of silicon monoxide in silicon oxide is substantially 100% by mass” used as a raw material for the thin film forming material means that the content of substances other than silicon monoxide in silicon oxide is 0.1% by mass or less. It means that.
The physical vapor deposition method in the manufacturing method of one embodiment of the present invention is not limited to the electron beam vapor deposition method. For example, in the case of the electron beam vapor deposition method, silicon monoxide (SiO) has a relatively low temperature. Therefore, the amount of solid foreign matter (splash) adhering to the film-forming object can be reduced because it can become a gas without melting like silicon dioxide (SiO ₂ ) during vapor deposition. Moreover, since silicon monoxide (SiO) can be sublimated together with indium (III) oxide (In ₂ O ₃ ), which is the same sublimable material, a vapor deposition film containing them simultaneously can be formed.
The silicon oxide used as the raw material for the thin film forming material may contain silicon dioxide (SiO ₂ ) as long as solid foreign substances are not increased. The content of silicon dioxide in silicon oxide used as a raw material for the thin film forming material is preferably less than 30% by mass, more preferably less than 20% by mass, still more preferably less than 10% by mass, and particularly preferably 1% by mass. Less than, most preferably less than 0.1% by weight.

As the thin film forming material, indium oxide (III) (In ₂ O ₃ ) and silicon oxide (SiO, SiO ₂ ) are used, and indium oxide is 0.05 mol to 0.25 mol with respect to 1 mol of silicon oxide. It is preferable to mix the raw material mixture into a raw material mixture, press-mold the raw material mixture into a molded product, and then fire and sinter the mixture (sintered body) as the thin film forming material. By using a sintered mixture (sintered body) as the thin film forming material, the thin film forming material is substantially uniformly vaporized by physical vapor deposition, and indium oxide (III) (In ₂ O ₃ ) and its indium oxide ( III) A vapor deposition film in which indium (I) oxide (In ₂ O) generated by thermal decomposition of (In ₂ O ₃ ) and silicon dioxide (SiO ₂ ) is substantially uniformly mixed is substantially evenly formed on the surface of the film. Can be deposited.
The molded product obtained by press-molding the raw material mixture is preferably fired in an inert gas atmosphere. The inert gas atmosphere means an atmosphere containing argon, helium, nitrogen or the like as a main component in the atmosphere. The inert gas atmosphere inevitably contains oxygen as an impurity. In this specification, an inert gas atmosphere is used when the concentration of oxygen contained in the atmosphere is 15% by volume or less. The concentration of oxygen in the inert gas atmosphere is preferably 10% by volume or less, more preferably 5% by volume or less, and still more preferably 1% by volume or less. The solid material obtained by press-molding the raw material mixture can be made to contain as little impurities as possible in the thin film forming material by firing in an inert gas atmosphere.

The temperature at which the raw material mixture is fired to form a sintered body is preferably 500 ° C. or higher and 900 ° C. or lower, more preferably 600 ° C. or higher and 880 ° C. or lower, and further preferably 700 ° C. or higher and 850 ° C. or lower. If the temperature at which the raw material mixture is fired is not more than the upper limit value, indium oxide will not become metal indium by thermal reduction. This metal indium is a liquid at a temperature exceeding the upper limit, and is agglomerated due to its surface tension. By setting it to the upper limit value or less, such aggregation can be avoided, and there is no possibility that the uniformity of the material contained in the mixture is impaired. Furthermore, if the uniformity is not impaired in this way, even when the thin film forming material is vaporized by physical vapor deposition, the uniformity of the vaporized material is not impaired, and indium (I) oxide (In ₂ O) and oxidation A vapor deposition film in which indium (III) (In ₂ O ₃ ) and silicon dioxide (SiO ₂ ) are substantially uniformly mixed can be deposited on the surface of the deposition target.

(Process for forming a deposited film)
In the manufacturing method of one embodiment of the present invention, a thin film forming material is deposited on an object to be deposited by physical vapor deposition to form a vapor deposition film.
Examples of physical vapor deposition include resistance heating vapor deposition, electron beam vapor deposition, ion beam vapor deposition, ion plating, and sputtering. Among them, the physical vapor deposition method is preferably a resistance heating vapor deposition method or an electron beam vapor deposition method, and more preferably an electron beam vapor deposition method. The resistance heating vapor deposition method or the electron beam vapor deposition method can uniformly form a vapor deposition film on a curved surface having a large area or a small curvature radius. Furthermore, since the electron beam evaporation method heats the thin film forming material directly by irradiating an electron beam, it has high thermal efficiency, and even a thin film forming material such as an oxide having a high melting point and low thermal conductivity is efficiently vaporized, A vapor deposition film having a stable composition based on the composition of the thin film forming material can be formed on the deposition object in a short time.
For ion assist, an ion assist beam deposition method including an ion source may be used.

The atmospheric pressure at the time of vapor deposition film formation changes with kinds of physical vapor deposition to be used. When the electron beam evaporation method is used as the physical vapor deposition method, the atmospheric pressure when forming the vapor deposition film on the film formation object is 1.0 × 10 ⁻⁴ Pa or more and 5.0 × 10 ⁻² Pa or less. It is preferable that The atmospheric pressure at the time of forming the vapor deposition film on the deposition target can be controlled, for example, by introducing oxygen into the vapor deposition apparatus.
Moreover, the temperature of the film formation object at the time of vapor deposition film formation becomes like this. Preferably it is 50 to 150 degreeC, More preferably, it is 80 to 120 degreeC. If the temperature of the film formation object at the time of vapor deposition film formation is in the said range, it will be hard to exert a bad influence on the film formation object formed from materials, such as a plastic with low heat resistance.

  In the manufacturing method of one embodiment of the present invention, the film formation object may be formed from glass or optical glass, or may be formed from plastic. Examples of the plastic include polyester, acrylic, polycarbonate, polyamide, polyimide, polyethersulfone, polysulfone, and polyolefin resins. The form of the film-formation object may be, for example, a flat or curved lens-like substrate, or a flexible sheet. Since the manufacturing method of one embodiment of the present invention can form a deposited film even at a relatively low temperature, an optical thin film having a low refractive index is formed even on an object formed from a material having low heat resistance. can do.

(Step of contacting with an acidic substance)
The manufacturing method of one Embodiment of this invention includes the process of making the said vapor deposition film and an acidic substance contact, and obtaining the thin film which has a space | gap.
Using a mixture containing indium oxide and silicon oxide as a thin film forming material, and indium oxide being 0.05 mol or more and 0.25 mol or less with respect to 1 mol of silicon oxide, The formed deposited film contains indium (I) oxide (In ₂ O), indium oxide (III) (In ₂ O ₃ ), and silicon dioxide (IV) (SiO ₂ ). Among these oxides constituting the vapor deposition film, indium (I) oxide (In ₂ O) has high solubility in acidic substances, so that the vapor deposition film is brought into contact with the acidic substance, so that indium (I) oxide is converted. By eluting from the deposited film, a thin film having voids satisfying a desired refractive index can be formed. Of the oxides constituting the deposited film, indium (III) oxide (In ₂ O ₃ ) is also eluted from the thin film depending on the contact time with the acidic substance, and is surrounded by indium (III) oxide (In ₂ O ₃ ). Some of the silicon dioxide (IV) (SiO ₂ ) that has been released may also be detached from the thin film at the same time as indium (III) oxide (In ₂ O ₃ ) is eluted from the thin film. The substance constituting the thin film having voids is mainly silicon dioxide (IV) (SiO ₂ ), and indium (III) oxide (In ₂ O ₃ ) that does not elute is also included.
In the manufacturing method of one embodiment of the present invention, by using the thin film forming material of one embodiment of the present invention, indium (I) oxide (In ₂ O) and indium (III) oxide having high solubility in an acidic substance. A vapor-deposited film containing (In ₂ O ₃ ) and silicon dioxide (IV) (SiO ₂ ) can be formed, and then the vapor-deposited film is brought into contact with an acidic substance without impairing the durability of the thin film. Insoluble (I) oxide (In ₂ O) with high solubility can be eluted first to increase the porosity of the thin film, and by increasing the porosity, the refractive index of the thin film can be lowered, A thin film having a low refractive index can be formed.
Indium oxide (I) (In ₂ O) has a black body color, and absorbs visible light when indium oxide (I) (In ₂ O) remains in the thin film. For example, by measuring the absorptivity {100− (transmittance + reflectance)} of a thin film with a spectrophotometer, when the thin film absorbs visible light, the absorptance of the thin film increases and the absorptance increases. When it is, it can be confirmed that indium (I) oxide (In ₂ O) remains in the thin film.
The thin film obtained by the manufacturing method of one embodiment of the present invention can elute indium oxide (I) (In ₂ O), which is easily eluted, from the deposited film by bringing the deposited film into contact with an acidic substance. By elution of indium (I) oxide (In ₂ O), the porosity is high and the refractive index can be lowered.

(Acid substance)
Examples of acidic substances include hydrochloric acid, sulfuric acid, nitric acid and the like. The acidic substance is preferably hydrochloric acid having high solubility and high ionization degree of indium (I) oxide (In ₂ O) and indium oxide (III) (In ₂ O ₃ ) in the deposited film.

The temperature at which the vapor-deposited film and the acidic substance are brought into contact increases the elution of indium (I) oxide (In ₂ O) and / or indium (III) oxide (In ₂ O ₃ ) in the vapor-deposited film as the temperature increases. And the contact time can be shortened, which is preferable in manufacturing.
On the other hand, if the temperature at which the deposited film is brought into contact with the acidic substance is too high, a heat-resistant and corrosion-resistant container and equipment for ensuring safety are required to withstand the corrosion caused by the acidic substance, which may increase the manufacturing cost. There is.
The temperature at which the deposited film is brought into contact with the acidic substance is preferably 10 ° C. or higher and 100 ° C. or lower, more preferably 20 ° C. or higher and 90 ° C. or lower, further preferably 30 ° C. or higher and 85 ° C. or lower, and still more preferably 40 ° C. or higher. 80 ° C. or lower, particularly preferably 45 ° C. or higher and 75 ° C. or lower.

  The time for contacting the vapor deposition film and the acidic substance varies depending on the contact temperature and the concentration of the acidic substance, and may be a period for obtaining a thin film having a porosity satisfying a desired refractive index. The time for contacting the vapor-deposited film and the acidic substance is preferably 10 seconds or more, more preferably 30 seconds or more, preferably in order to improve the production efficiency and maintain the durability of the thin film and the film formation object. 36 hours or less, more preferably 25 hours or less.

In general, the method of bringing a vapor deposition film into contact with an acidic substance is a method of immersing a film-forming object in which a vapor-deposited film is formed in an acidic solution, or a method in which only a vapor-deposited film formed on a film-forming object is in an acidic solution. And a method of spraying an acidic solution on the vapor deposition film. In the method of immersing the deposited film in an acidic substance, indium oxide (I) (In ₂ O) in the deposited film elutes after a predetermined time has elapsed, and indium oxide (In ₂ O) depends on the concentration of the acidic substance and the contact time with the acidic substance. III) (In ₂ O ₃ ) is also eluted. In the method of spraying the acidic solution onto the deposited film, indium (I) oxide (In ₂ O) is eluted by immersing the deposited film in water after a predetermined time has passed, and the concentration of the acidic substance and the contact between the acidic substance and the deposited film Depending on the time, indium (III) oxide (In ₂ O ₃ ) elutes in water. Indium (I) oxide (In ₂ O) in the deposited film elutes and in some cases indium oxide (III) (In ₂ O ₃ ) elutes, a thin film having voids is obtained.

[Thin film with voids: optical thin film]
The thin film having voids manufactured by the method of one embodiment of the present invention includes indium (III) oxide (In ₂ O ₃ ) and silicon oxide (IV) (SiO ₂ ), and has a refractive index of 1.38. It is the following optical thin film.
The refractive index of the glass or optical glass constituting the film formation is about 1.43 to 1.69, and the refractive index of plastics such as polycarbonate and polymethyl methacrylate resin is about 1.59 to 1.70. . In addition, the refractive index of magnesium fluoride (MgF ₂ ), which is conventionally known as a low refractive material, is 1.38.
The optical thin film according to an embodiment of the present invention has a refractive index of 1.38 or less and is equal to or lower than the refractive index of magnesium fluoride (MgF ₂ ), which is known as a conventional low refractive material, and thus is an object to be deposited. It becomes a value close to the square root (about 1.20 to 1.30) of the refractive index of optical glass or plastic, and the antireflection effect can be enhanced.
The refractive index of the optical thin film of one embodiment of the present invention is based on the examples described later, and the reflection spectrum of the optical thin film is measured with a spectrophotometer and the reflected light intensity is set to 100 when the incident light intensity is 100. Can be measured as a reflectance, and can be calculated from the measured reflectance using a Fresnel coefficient.

The thin film having voids produced by the method of one embodiment of the present invention is preferably an optical thin film having a porosity of 8% or more and 70% or less.
When the porosity of the optical thin film is 8% or more and 70% or less, the refractive index of the thin film can be lowered while maintaining the durability of the thin film.
The thin film having voids produced by the method of one embodiment of the present invention has a porosity of more preferably 10% or more and 68% or less, and further preferably 15% or more and 67% or less. The porosity (total porosity Vp) of the optical thin film can be determined using the Lorenz-Lorenz equation based on examples described later.

(Optical member)
An optical member including an optical thin film and a film formation object according to an embodiment of the present invention includes a disk drive device including an optical pickup component such as an astronomical telescope, a spectacle lens, a camera, a band pass filter, and a beam splitter, It can be used as an optical member for a display device or the like provided with a fine liquid crystal panel. In addition, by applying the optical thin film to the light extraction portion to the outside of the light emitting device, the emission of light from the light emitting device to the outside can be promoted, and the improvement of the light extraction efficiency and the reduction of heat generation can be expected.

  Hereinafter, the present invention will be specifically described by way of examples.

Example 1
(Manufacture of thin film forming materials)
140 g of indium (III) oxide powder (In ₂ O ₃ ) (purity: 99.99 mass%) and 100 g of silicon monoxide powder (SiO) (purity: 99.9 mass%) were put into a 1 L nylon pot. A nylon ball having a diameter of 20 mm (φ20) was added together with these powders, and mixed for 30 minutes while loosening the aggregates to obtain a raw material mixture. The molar ratio of indium oxide to 1 mol of silicon oxide (In ₂ O ₃ / SiO molar ratio) was 0.22. The raw material mixture was taken out of the pot and press-molded to obtain a molded body. This molded body was fired at 800 ° C. for 2 hours in an inert atmosphere (argon (Ar): 99.99% by volume) to obtain a thin film forming material (sintered body) 1.

(Manufacture of evaporated film)
A double-sided polished glass (manufactured by SHOTT AG, BK-7) was used as the film formation. An object to be deposited and the thin film forming material 1 are placed in a vapor deposition apparatus, and an electron beam (JEOL) is applied to the thin film forming material 1 in a state where the pressure in the vapor deposition apparatus is reduced to 1.0 × 10 ⁻⁴ Pa. Irradiated with JEBG-102UH0 manufactured by Co., Ltd., and indium oxide (I) (In ₂ O), indium oxide (III) (In ₂ O ₃ ), and silicon dioxide (SiO ₂ ) are applied to one surface of the film formation object. The vapor deposition film containing was formed. The temperature of the film formation object during film formation was set to 100 ° C., and the control pressure in the vapor deposition apparatus during film formation was set to 2.0 × 10 ⁻² Pa by introducing oxygen.

(Manufacture of thin film having voids)
A hydrochloric acid solution having a concentration of 18% by mass heated to 50 ° C. was used as the acidic solution, and the film-formed material on which the deposited film was formed was immersed in this hydrochloric acid solution, and mainly indium (I) oxide (In ₂ O) was eluted to produce a thin film having voids. The contact time (immersion time) between the vapor-deposited film and the acidic solution was 1 minute, and the refractive index of the obtained thin film having voids was measured by the method described later. A thin film having voids with a contact time (immersion time) with an acidic solution of 1 minute and a refractive index of 1.18 was obtained.
In addition, the deposited film formed by the above-described method is brought into contact (immersion) with each of an acidic solution at 50 ° C. and an acidic solution at 75 ° C., and the refractive index of the thin film is 1.38 or less with the acidic solution at each temperature. The contact (immersion) time with the acidic solution was measured.

(Example 2)
120 g of In ₂ O ₃ powder and 100 g of SiO powder (In ₂ O ₃ / SiO molar ratio was 0.19) were mixed, and a thin film forming material 2 was obtained in the same manner as in Example 1. A thin film having voids was produced in the same manner as in Example 1 except that this thin film forming material 2 was used. The contact time (immersion time) between the vapor-deposited film and the acidic solution was 1 minute, and the refractive index of the obtained thin film having voids was measured by the method described later. A thin film having voids having a contact time (immersion time) with an acidic solution of 1 minute and a refractive index of 1.29 was obtained. An SEM photograph of the surface of the thin film of Example 2 obtained by contacting (immersing) the deposited film with an acidic solution at 50 ° C. for 1 minute is shown in FIG. 1, and an SEM photograph of the cross section of the thin film is shown in FIG.
In addition, the deposited film formed by the above-described method is brought into contact (immersion) with each of an acidic solution at 50 ° C. and an acidic solution at 75 ° C., and the refractive index of the thin film is 1.38 or less with the acidic solution at each temperature. The contact (immersion) time with the acidic solution was measured.

(Example 3)
80 g of In ₂ O ₃ powder and 100 g of SiO powder (In ₂ O ₃ / SiO molar ratio was 0.13) were mixed, and a thin film forming material 3 was obtained in the same manner as in Example 1. A thin film having voids was produced in the same manner as in Example 1 except that this thin film forming material 3 was used. The contact time (immersion time) between the vapor-deposited film and the acidic solution was 1 minute, and the refractive index of the obtained thin film having voids was measured by the method described later. A thin film having voids with a contact time (immersion time) with an acidic solution of 1 minute and a refractive index of 1.35 was obtained.
In addition, the deposited film formed by the above-described method is brought into contact (immersion) with each of an acidic solution at 50 ° C. and an acidic solution at 75 ° C., and the refractive index of the thin film is 1.38 or less with the acidic solution at each temperature. The contact (immersion) time with the acidic solution was measured.

Example 4
60 g of In ₂ O ₃ powder and 100 g of SiO powder (In ₂ O ₃ / SiO molar ratio was 0.10) were mixed, and a thin film forming material 4 was obtained in the same manner as in Example 1. A thin film having voids was produced in the same manner as in Example 1 except that this thin film forming material 4 was used. The contact time (immersion time) between the vapor-deposited film and the acidic solution was 1 minute, and the refractive index of the obtained thin film having voids was measured by the method described later. A thin film having a void having a contact time (immersion time) with an acidic solution of 1 minute and a refractive index of 1.45 was obtained.
Moreover, the vapor deposition film formed by the above-mentioned method was contacted (immersed) in an acidic solution at 50 ° C., and the contact (immersion) time with the acidic solution at which the refractive index of the thin film was 1.38 or less was measured.

(Example 5)
40 g of In ₂ O ₃ powder and 100 g of SiO powder (In ₂ O ₃ / SiO molar ratio was 0.06) were mixed, and a thin film forming material 5 was obtained in the same manner as in Example 1. A thin film having voids was produced in the same manner as in Example 1 except that this thin film forming material 5 was used. The contact time (immersion time) between the vapor-deposited film and the acidic solution was 1 minute, and the refractive index of the obtained thin film having voids was measured by the method described later. A thin film having voids with a contact time (immersion time) with an acidic solution of 1 minute and a refractive index of 1.47 was obtained.
Moreover, the vapor deposition film formed by the above-mentioned method was contacted (immersed) in an acidic solution at 50 ° C., and the contact (immersion) time with the acidic solution at which the refractive index of the thin film was 1.38 or less was measured.

(Example 6)
A thin film having voids was produced in the same manner as in Example 4 except that the temperature of the acidic solution was 75 ° C. The contact time (immersion time) between the vapor-deposited film and the acidic solution was 1 minute, and the refractive index of the obtained thin film having voids was measured by the method described later. A thin film having a void having a refractive index of 1.45 with a contact time (immersion time) of 1 minute with an acidic solution at 75 ° C. was obtained.
Moreover, the vapor deposition film formed by the above-mentioned method was contacted (immersed) in an acidic solution at 75 ° C., and the contact (immersion) time when the refractive index of the thin film was 1.38 or less was measured.

(Example 7)
A thin film having voids was produced in the same manner as in Example 5 except that the temperature of the acidic solution was 75 ° C. The contact time (immersion time) between the vapor-deposited film and the acidic solution was 1 minute, and the refractive index of the obtained thin film having voids was measured by the method described later. The contact time (immersion time) with the acidic solution at 75 ° C. was 1 minute, and a thin film having voids with a refractive index of 1.47 was obtained.
Moreover, the vapor deposition film formed by the above-mentioned method was contacted (immersed) in an acidic solution at 75 ° C., and the contact (immersion) time when the refractive index of the thin film was 1.38 or less was measured.

(Comparative Example 1)
190 g of In ₂ O ₃ powder and 100 g of SiO powder (In ₂ O ₃ / SiO molar ratio was 0.03) were mixed to obtain a thin film forming material 8 that was sintered in the same manner as in Example 1. A thin film having voids was produced in the same manner as in Example 1 except that this thin film forming material 8 was used. When the contact time (immersion time) between the vapor deposition film and the acidic solution was 1 minute, the vapor deposition film was peeled off from the film formation target, and a thin film having voids could not be formed.

<Evaluation of thin film (optical thin film) having voids>
The thin film (optical thin film) having voids in Examples and Comparative Examples was evaluated as follows. The results are shown in Table 1.

(Refractive index)
Using a spectrophotometer (Hitachi High-Technologies Corporation, product name: U-4100, incident angle 5 °), the reflection spectrum of the thin film (optical thin film) having voids in the examples was measured. The minimum value of the reflected light intensity when the incident light intensity was 100 was measured as the reflectance, and the refractive index was calculated from the measured reflectance using the Fresnel coefficient.
In the example, since double-sided polished glass is used as the film formation object for forming a thin film, the reflectance R ′ obtained from the measurement includes multiple repetitive reflections including back surface reflection. Since the measured reflectance R ′ includes multiple repeated reflections, the reflectance R of the thin film can be expressed by the following formula (1).

In the formula (1) in, R _o is the reflectance of the substrate (deposition material). The thin film reflectance R was calculated from the actually measured thin film reflectance R ′ based on the equation (1). The reflectance R of the thin film is a reflectance that does not consider reflection from the back surface.
Reflectance of the thin film R is the use of Fresnel coefficients may represent the refractive index n of the refractive index n _m and the thin film substrate (deposition material) using equation (2) below.

Here, by approximating the refractive index of the atmosphere is 1, the greater the refractive index n of the thin film than the square root of the refractive index n _m of the substrate, that the refractive index n of the thin film by the following formula (3) it can.

Also, the smaller the refractive index n of the thin film than the square root of the refractive index n _m of the substrate may represent a refractive index n of the thin film by the following equation (4).

  Based on the formulas (1) to (4), the refractive index n of the thin film (optical thin film) having voids was calculated. Regarding the refractive index n of the optical thin film, “Mitsunobu Koyama,“ Basic theory of optical thin film-Fresnel coefficient, characteristic matrix ””, Optronics Co., Ltd., February 25, 2011, first revised edition "

(Porosity (%))
The porosity (total porosity Vp) of the thin film (optical thin film) having voids in the examples was determined using the Lorenz-Lorenz equation shown in the following equation (5). In the following formula (5), n _f is the observed refractive index of the thin film, n _b is the refractive index of the backbone of the film. The refractive index n _{f of the} thin film is the refractive index of the thin film (optical thin film) having voids obtained based on the above formulas (1) to (4). Refractive index n _b of the backbone of the film was determined using the refractive index of the contact time after 1 minute of the composition and the acidic substance film materials.

(durability)
Silbon paper is layered on the thin film (optical thin film) having voids in the examples, and 500 g / cm ² using a pencil hardness tester (based on JIS K5600 scratch hardness (pencil method)) from above the Silbon paper. The sample was reciprocated 20 times while applying a load of. Remove the Sylbon paper, visually check the surface of the thin film (optical thin film) with voids, and B (Bad) is the one where the color change of scratches or reflected light is confirmed, and G is the one where the surface of the thin film does not change (Good).

(Relationship between contact time of acidic substance and In ₂ O ₃ / SiO molar ratio)
FIG. 3 shows the relationship between the contact time with an acidic substance for adjusting the refractive index of the thin film having voids in the examples to 1.38 or less and the In ₂ O ₃ / SiO molar ratio.

As shown in Table 1, the thin films of Examples 1 to 7 could have a refractive index of 1.38 or less. Even if the refractive index of the thin film cannot be reduced to 1.38 or less when the contact time with the acidic substance is within 1 minute, the refractive index of the thin film is increased by 1. by increasing the contact time with the acidic substance. It could be 38 or less. As for the thin films of Examples 1 to 7, when the absorptance was measured from the transmittance and the reflectance with a spectrophotometer, an increase in the absorptance could not be confirmed, and indium (I) oxide whose body color is black in the thin film ( In ₂ O) was not present, and it was confirmed that all of indium oxide (I) (In ₂ O) in the thin film was eluted by contact with the acidic substance.
As shown in Comparative Example 1, the deposited film formed by using a thin film forming material having an In ₂ O ₃ / SiO molar ratio exceeding 0.25 mole is peeled off by contact with an acidic substance, It was not possible to form a thin film having voids in the desired portions.

As shown in FIG. 1, from the SEM photograph of the surface of the thin film of Example 2, it was confirmed that fine groove-like voids were formed in the thin film.
As shown in FIG. 2, from the SEM photograph of the cross section of the thin film of Example 2, the thin film has many irregular columnar structures extending from the surface of the substrate to the surface of the thin film, and between the columns. Voids were confirmed. The columnar structure shown in the SEM photograph of FIG. 2 was presumed to be formed of silicon dioxide (SiO ₂ ) and partly indium oxide (III) (In ₂ O ₃ ).

As shown in FIG. 3, when the In ₂ O ₃ / SiO molar ratio of the thin film forming material is less than 0.05, even if the temperature at which the deposited film and the acidic substance are brought into contact is 75 ° C., the refractive index is 1 Since it has a thin film of .38 or less, the contact time between the deposited film and the acidic substance is expected to exceed 25 hours, so that the manufacturing time becomes longer and the productivity is lowered. On the other hand, as shown in Comparative Example 1 of Table 1, when the In ₂ O ₃ / SiO molar ratio of the thin film forming material exceeds 0.25 and is 0.30, the contact time between the deposited film and the acidic substance is 1 Even within a minute, the thin film was peeled off and the durability was lowered.

  According to the method for producing a thin film in one embodiment of the present invention, an optical thin film having excellent durability and low refractive index can be produced relatively easily, and not only a camera lens but also a high-definition liquid crystal panel or the like. In addition, an optical thin film that can also be used can be provided. An optical thin film according to an embodiment of the present invention includes an optical device such as a disk drive device including an optical pickup component such as an astronomical telescope, a spectacle lens, a camera, a band pass filter, and a beam splitter, and a display device including a high-definition liquid crystal panel. It can be used as a member.

Claims (9)

Depositing a thin film forming material on an object to be deposited by physical vapor deposition to form a deposited film;
Contacting the vapor deposition film with an acidic substance to obtain a thin film having voids,
A method for producing a thin film comprising using, as the thin film forming material, a mixture containing indium oxide and silicon oxide, wherein the indium oxide is 0.05 mol or more and 0.25 mol or less with respect to 1 mol of silicon oxide. .   The method for producing a thin film according to claim 1, wherein the silicon oxide contains silicon monoxide as a main component.   The manufacturing method of the thin film of Claim 1 or 2 whose refractive index of the said thin film is 1.38 or less.   The manufacturing method of the thin film as described in any one of Claim 1 to 3 whose porosity of the said thin film is 8% or more and 70% or less.   A thin film forming material comprising indium oxide and silicon oxide, wherein the indium oxide is a mixture containing 0.05 mol or more and 0.25 mol or less with respect to 1 mol of silicon oxide.   The thin film forming material according to claim 5, wherein the silicon oxide contains silicon monoxide as a main component.   An optical thin film comprising indium oxide and silicon oxide and having a refractive index of 1.38 or less.   The optical thin film according to claim 7, which has a porosity of 8% or more and 70% or less.   An optical member comprising the optical thin film according to claim 7 or 8 and a film formation target.