WO2021187412A1 - Method for producing potassium tantalate particles, method for producing film, potassium tantalate particles, film, antireflective film, optical element, and optical apparatus - Google Patents

Abstract

Provided is a method for producing potassium tantalate particles, the method including a heating step for heating a mixture containing (A) an oxide including tantalum, (B) a potassium compound which is potassium hydroxide and/or potassium chloride, (C) at least one alcohol selected from the group consisting of ethylene glycol, methanol, ethanol, 1-propanol, and 2-propanol, and (D) water.

Description

A method for producing potassium tantalate particles and a method for producing a film, and a method for producing potassium tantalate particles, a film, an antireflection film, an optical element, and an optical device.

The present invention relates to a method for producing potassium tantalate particles and a method for producing a film, and a method for producing potassium tantalate particles, a film, an antireflection film, an optical element, and an optical device. The present invention claims the priority of application number 2020-049969 of the Japanese patent filed on March 19, 2020, and for designated countries that are permitted to be incorporated by reference to the literature, the contents described in the application are as follows. Incorporated into this application by reference.

Potassium tantalate is expected to be used as an optical material, and examples thereof include those having a perovskite-type crystal structure (Patent Document 1 and the like).

Japanese Unexamined Patent Publication No. 2007-07626

The first aspect of the present invention is (A) an oxide containing tantalum, (B) a potassium compound which is at least one of potassium hydroxide or potassium chloride, and (C) ethylene glycol, methanol, ethanol, 1-. A method for producing potassium hydroxide particles, which comprises a heating step of heating a mixture containing at least one alcohol selected from the group consisting of propanol and 2-propanol and (D) water.

A second aspect of the present invention is a step of obtaining potassium tantalate particles by the above-mentioned production method, a mistification step of mistizing a dispersion containing potassium tantalate particles, and supplying the mistized dispersion to a substrate. A method for producing a film containing potassium tantalate particles, which comprises a feeding step and a drying step of drying the dispersion liquid existing on the substrate after the feeding step.

The third aspect of the present invention is potassium tantalate particles having an average particle size of 100 nm or less.

The fourth aspect of the present invention is a film containing the above-mentioned potassium tantalate particles.

A fifth aspect of the present invention is an antireflection film containing at least one layer of the above-mentioned film.

The sixth aspect of the present invention is an optical element provided with the antireflection film described above.

The seventh aspect of the present invention is an optical device including the above-mentioned optical element.

It is a conceptual diagram which shows an example of the film forming apparatus using the mist method in this embodiment.

Hereinafter, a mode for carrying out the present invention (hereinafter, simply referred to as “the present embodiment”) will be described in detail. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. In the drawings, the positional relationships such as up, down, left, and right shall be based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the ratios shown.

<Manufacturing method of potassium tantalate particles, potassium tantalate particles>

The method for producing potassium tantalate (KTaO ₃ ) particles (hereinafter, may be simply referred to as “particles”) according to the present embodiment is (A) an oxide containing tantalum and (B) potassium hydroxide or chloride. A potassium compound which is at least one of potassium, at least one alcohol selected from the group consisting of (C) ethylene glycol, methanol, ethanol, 1-propanol, and 2-propanol, and (D) water. It comprises a heating step of heating the containing mixture.

Conventionally, potassium tartrate having a small average particle size has been required for application to an optical thin film for the purpose of suppressing light scattering, a catalyst material requiring a large specific surface area, and the like. However, it has been difficult to obtain potassium tantalate having a small average particle size by the conventional production method.

According to the production method according to the present embodiment, nanoparticles of potassium tantalate having an average particle size of 100 nm or less can be efficiently produced. Such nanoparticles of potassium tartrate can be used not only in the film forming technique by the mist method described later, but also because the particles can be uniformly and densely arranged when the film is formed by the mist method. Light scattering can be suppressed, and a film having a high refractive index can be obtained. Therefore, the potassium tantalate particles according to the present embodiment can be suitably used as an optical thin film or the like that suppresses light scattering.

Further, the potassium tantalate particles obtained by the production method according to the present embodiment can be suitably used as a catalyst material or the like. Potassium tantalate is also expected to be used as a catalyst for various reactions such as organic synthesis reactions and photoreactions. Since potassium tantalate particles having an average particle size of 100 nm or less have a large specific surface area, they can be used as reactants in the system. High contact efficiency with substrates and the like. Therefore, the potassium tantalate particles according to the present embodiment can be suitably used as a catalyst having high catalytic ability.

Then, as one of the preferable aspects of the production method according to the present embodiment, there is a method by a solvothermal synthesis method. The potassium tantalate particles produced by such a production method have a certain degree of dispersibility in a dispersion medium such as water. Therefore, the potassium tantalate particles according to the present embodiment can be applied to a film forming technique or the like by the mist method.

Hereinafter, the components and manufacturing conditions that can be used in the manufacturing method according to this embodiment will be described.

The oxide containing (A) tantalum is not particularly limited, but tantalum pentoxide (tantalum pentoxide, Ta ₂ O ₅ ) is preferable from the viewpoint of availability, reaction efficiency, and the like.

The ratio of the component (A) in the mixed solution is not particularly limited, but is preferably 0.01 M or more and 1 M or less. Further, the lower limit thereof is more preferably 0.03 M, and further preferably 0.05 M. Further, the upper limit thereof is more preferably 0.5 M, and further preferably 0.3 M. In addition, "M" in this embodiment means a molar concentration (mol / L).

As the (B) potassium compound, at least one of potassium hydroxide and potassium chloride may be used. These may be used alone or in combination. Among these, potassium hydroxide is preferable from the viewpoint of basic strength.

The molar ratio (B / A) of the component (B) to the component (A) is not particularly limited, but is preferably 5 or more and 300 or less from the viewpoint of the reaction efficiency and the reaction cost of the potassium tantalate particles. Further, the lower limit thereof is more preferably 10, further preferably 20, and even more preferably 30. Further, the upper limit thereof is more preferably 280, further preferably 250, and even more preferably 220.

(C) As the alcohols, at least one selected from the group consisting of ethylene glycol, methanol, ethanol, 1-propanol, and 2-propanol may be used. These may be used alone or in combination of two or more. By using the component (C), the solubility of the component (B) is enhanced, and the reactants such as the cation component in the reaction system are captured, and the starting material is excessively grown (for example, the nucleation of potassium tantalate particles). It is possible to control the density, etc.) and suppress the increase in the particle size of potassium tantalate. From this point of view, ethylene glycol is preferable among the components (C).

From the above viewpoint, increasing the proportion of the component (C) in the mixed solution tends to reduce the particle size of potassium tantalum, and decreasing the proportion of the component (C) reduces the particle size of potassium tantalum. There is a tendency to increase (however, the action of this embodiment is not limited to this).

The ratio of the component (C) in the mixed solution is not particularly limited, but is preferably 0.1 M or more and 17 M or less. Further, the lower limit thereof is more preferably 1M. Further, the upper limit thereof is more preferably 8M. By setting the ratio of the component (C) in such a range, the average particle size of the above-mentioned potassium tantalate can be controlled more effectively.

In the production method according to this embodiment, at least (D) water is used as the solvent. That is, the heating step is performed in an aqueous solvent.

In the production method according to the present embodiment, in addition to the above-mentioned components (A) to (D), known components may be appropriately added as long as they do not inhibit the synthesis of potassium tantalate. For example, various catalysts for controlling the reaction rate, the basicity of the solution, and the like can be mentioned.

The heating temperature in the heating step is not particularly limited, but is preferably 150 ° C. or higher, more preferably 150 ° C. or higher and 300 ° C. or lower, from the viewpoint of the reaction rate and the yield of potassium tantalate. Further, the lower limit thereof is more preferably 160 ° C., further preferably 170 ° C., and even more preferably 200 ° C. Further, the upper limit thereof is more preferably 295 ° C., further preferably 270 ° C., and even more preferably 260 ° C.

The heating time in the heating step is not particularly limited, but is preferably 30 minutes or more and 210 minutes or less from the viewpoint of the reaction rate and the yield of potassium tantalate. Further, the lower limit thereof is more preferably 40 minutes and further preferably 50 minutes. The upper limit is more preferably 180 minutes and even more preferably 150 minutes.

The pressure in the heating step is not particularly limited, but is preferably higher than the normal pressure from the viewpoint of the reaction rate and the yield of potassium tantalum. When heating is performed at a pressure higher than normal pressure, it is preferable to perform the heating step using an autoclave or the like. Specifically, for example, a high-temperature heated acid decomposition container or the like can be used.

Note that, in the production method according to the present embodiment, if necessary, a cooling step of cooling the mixed liquid may be performed after the heating step. The cooling means is not particularly limited, and known methods such as water cooling and air cooling can be adopted.

The average particle size of the potassium tantalate particles obtained by the production method according to the present embodiment can be 100 nm or less. The average particle size may be 80 nm or less, or 50 nm or less, depending on the intended use.

The "average particle size" as used in the present embodiment means particles existing in one field of measurement when observed by a TEM (transmission electron microscope) having a magnification of 120 k times (120,000 times), and each particle is measured. Let the arithmetic average of the major axis and the minor axis of be the particle size of the particle, and let the arithmetic average of the particle size of each particle be the "average particle size". The "major axis" means the longest axis of the particle, and the "minor axis" means the shortest axis of the particle. In addition, particles in which only a part of the particles are visible in one field of view are excluded from the target.

<Method of manufacturing a membrane containing potassium tantalate particles, membrane>

The method for producing a film containing potassium tantalate particles (hereinafter, may be simply referred to as “film”) according to the present embodiment is (A) an oxide containing tantalum and (B) potassium hydroxide or potassium chloride. (C) At least one alcohol selected from the group consisting of ethylene glycol, methanol, ethanol, 1-propanol, and 2-propanol, and (D) water. A heating step of heating the mixture to obtain potassium tantalate particles, a mistification step of mistizing a dispersion containing potassium tantalate particles, a supply step of supplying the mistized dispersion to a substrate, and a supply step after the supply step. , A drying step of drying the dispersion liquid existing on the substrate.

Since the potassium tantalate particles according to the present embodiment have high dispersibility in an aqueous solvent, it is possible to form a nanoparticle film by the method described above. The method for producing the nanoparticle film can be achieved, for example, by spraying a nanoparticle-containing mist obtained by mistizing (atomizing) a dispersion containing potassium tantalate particles by vibration of an ultrasonic pendulum in the MHz band. ..

Further, according to the above-mentioned method, since it is not necessary to heat-treat the substrate at a high temperature, restrictions on the material of the substrate can be relaxed. For example, a film can be formed on a flexible substrate made of a resin material having a low softening point.

Each process will be described below.

(1) For the heating step, the conditions described in the heating step performed in the above-mentioned method for producing potassium tantalate particles can be adopted.

As the (2) mistification step, any method may be used as long as it is a method of mistizing (atomizing) the dispersion liquid containing the potassium tantalate particles obtained in the (1) step. In this mist formation step, the operation of adding the potassium tantalate particles obtained in the step (1) to the dispersion medium to prepare the dispersion liquid may be performed.

As a mist generation method, a known method can be adopted, for example, a pressurized type, a rotating disc type, an ultrasonic type, an electrostatic type, an orifice vibration type, a steam type, or the like can be adopted. In the present embodiment, since it is a dispersion liquid of potassium tantalate particles, a method of physically mistizing (atomizing) is preferable. This facilitates liquid temperature control and droplet size control.

In the mist conversion process, by using a carrier gas, the mist of the dispersion liquid can be carried to the subsequent supply process. As the carrier gas, for example, an inert gas such as argon, helium, or nitrogen can be used.

Further, between the steps (2) and (3), a step of equalizing the mist by a mist trap or a retention step of providing a retention period (retention portion) of the mist may be performed.

As the dispersion medium, in addition to water, an organic solvent such as ethanol, methanol, or propanol may be used. For example, the above-mentioned component (C) and component (D) can be used as the dispersion medium. The dispersion medium may be used alone or in combination of two or more. Further, the frequency band for atomization may be any one suitable for each dispersion medium, and is not limited to the above band. The material of the base material is not limited to glass, resin, metal, etc., and it is more desirable to provide a step capable of hydrophilizing the surface such as UV irradiation.

(3) The supply process is not particularly limited as long as it is a method of supplying mist to the substrate, and a known technique can be adopted. For example, a method of spraying the fine droplets obtained in the mistification step by the mist method onto the substrate can be mentioned. Examples of the mist method include ultrasonic spraying, mist CVD method, sonia source method, hot wall method and the like. These methods can be selected in consideration of the film thickness of the film formed on the substrate, the size of the droplets to be sprayed, and the like.

The supply step may be under atmospheric pressure, reduced pressure, or vacuum, but it is preferably under atmospheric pressure from the viewpoint of convenience.

Alternatively, the film containing the potassium tantalate particles may be patterned by spraying the mist-ized dispersion liquid onto the masked substrate corresponding to a predetermined pattern. As a result, dimensional control can be performed with high accuracy.

For example, as the masking material, a material that becomes relatively hydrophilic by light irradiation may be used. By irradiating the material with light corresponding to a predetermined pattern, a region having relatively hydrophilicity and a region having water repellency are formed, and in this state, a mist-ized dispersion liquid is sprayed to make the material liquid-friendly. The mist-ized dispersion can be arranged only in the region having the mixture.

Furthermore, since the material restrictions on the base material are relaxed, a thin film base material (sometimes called a "sheet base material") having high flexibility can be used as the base material. Furthermore, continuous production such as roll-to-roll (Roll to Roll) is also possible.

As the base material, for example, a known material can be used. For example, glass, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyether sulfone (PES), polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polyimide, polycarbonate (PC), cellulose triacetate (TAC). ), Cellulose acetate propionate (CAP) and the like.

(4) As a drying step, the dispersion medium of the dispersion liquid sprayed on the substrate is removed. For example, a film containing potassium tantalate particles is formed on the surface of the substrate by vaporizing the dispersion medium by irradiating light such as infrared rays or heating. The heating temperature can be set in consideration of the boiling point of the solvent, the softening point of the substrate, and other physical characteristics that affect the physical characteristics of the film. The softening point of the substrate referred to here means a temperature at which the substrate softens and begins to deform when the substrate is heated, and can be obtained by, for example, a test method according to JIS K7191-1.

After the step (4), if necessary, a UV irradiation step or the like may be performed for the purpose of modifying the base material such as imparting hydrophilicity.

Here, an example of a film forming apparatus that can be used in the manufacturing method according to the present embodiment will be described.

FIG. 1 is a conceptual diagram showing an example of a film forming apparatus using the mist method in the present embodiment.

The film forming apparatus 1 has a first tank for mistizing a dispersion liquid containing potassium tantalate particles, a second tank which is a mist trap for homogenizing the mist, and a third tank for spraying mist on the substrate 10.

The first tank contains the dispersion liquid S containing the above-mentioned potassium tantalate particles.

Air 20 for forming a mist flow path is flowing in the first tank.

The first tank is equipped with an ultrasonic vibrator 30. The ultrasonic transducer 30 mistizes the dispersion liquid containing the potassium tantalate particles. The particle size of the mist is not particularly limited, but is preferably 10 μm or less (for example, 1 to 10 μm). The mist generated in the first tank is conveyed to the second tank via a pipe provided in the first layer. In the second tank, excess mist collects in the lower part of the tank, and the mist having a more uniform particle size is conveyed to the third layer via a pipe provided in the second tank. It is preferable that the mist having a particle size of 5 μm or less (for example, 1 to 5 μm) is conveyed from the second tank to the third tank.

The substrate 10 is arranged in the third tank, and the mist conveyed from the second tank is sprayed on the substrate. In the third tank, mist is sprayed on the substrate 10 for a predetermined time. Then, the dispersion medium of the mist adhering to the substrate 10 is vaporized to form a film containing potassium tantalate particles on the surface of the substrate 10. After a certain period of time has passed after spraying, new mist adheres to the substrate 10 before the mist evaporates, so that the dispersed dispersion liquid that has become droplets flows down and a uniform film is formed on the substrate 10. It disappears. The time for stopping the spraying of the mist on the substrate 10 may be the time when the mist containing the fine particles of potassium tantalate liquefies and flows down from the substrate 10, or a film having a desired film thickness is formed on the substrate 10. It may be at the time when it was done.

If the substrate 10 is heated excessively in the third tank, it may be deformed due to softening. Therefore, in the third tank, it is preferable that the mist is sprayed at a temperature lower than the softening point of the substrate to form a film. Further, when the substrate 10 is heated to a predetermined temperature or higher during mist spraying, the fine particles of potassium tantalate adhering to the substrate 10 aggregate and the uniformity of the film deteriorates. Therefore, more preferably, the mist is sprayed at a temperature of 40 ° C. or lower (for example, 10 to 40 ° C.) to form a film.

When the film is selectively formed on the substrate 10, the water-repellent film is selectively formed on the substrate 10 in advance so that the mist is arranged only in the region having relatively hydrophilicity. At this time, if the substrate 10 is arranged horizontally, the mist adhering to the relatively water-repellent region becomes difficult to repel water, and it may not be possible to selectively form a film. Therefore, in the third tank, it is preferable to spray the mist on the substrate 10 inclined with respect to the horizontal plane.

Similarly, in the third tank, it is preferable that the mist is sprayed on the substrate 10 that is inclined with respect to the plane orthogonal to the spraying direction of the mist. This is to remove excess fine particles adhering to the relatively water-repellent region by the force of mist spraying.

The film forming apparatus may omit the mist trap in the second tank.

As for the method of generating mist, in addition to generating it using the above-mentioned ultrasonic transducer 30, an electrostatic type that directly applies a voltage to a thin tube for spraying droplets to generate mist, and applying pressure to increase the flow velocity. Pressurized type that scatters the generated mist by colliding the generated gas with the liquid, rotating disc type that drops droplets on a disk rotating at high speed and disperses the generated mist by centrifugal force, micro-sized holes An orifice vibration type or the like that generates micro-sized droplets can be used by passing the liquid droplets through the orifice plate having the above, and cutting the droplets by applying vibration with a piezoelectric element or the like at that time. As for the mist generation method, these methods are appropriately selected according to the cost, performance, and the like. Further, a plurality of the above-mentioned methods may be combined to generate mist.

A preferable example of the film obtained by the above-mentioned production method is a film containing potassium tantalate particles having an average particle size of 100 nm or less. Such a film can be suitably used as an antireflection film or the like described later.

Further, the film according to the present embodiment may be a film in which potassium tantalate particles are dispersed in a resin material. As the component of the resin material, a suitable one can be selected according to the application of the film. Examples of the resin material include polymethylmethacrylate resin and the like.

<Anti-reflective coating>

Since a preferred example of the film according to the present embodiment is a film containing potassium tantalate particles, it can be suitably used as, for example, an optical thin film that suppresses light scattering. Therefore, the film according to the present embodiment can be suitably used as a layer constituting the antireflection film. Such an antireflection film may have a single-layer structure or a multi-layer structure having two or more layers. For example, it may be an antireflection film containing at least one layer of the film according to the present embodiment.

The antireflection film according to this embodiment can be provided on the surface of an optical element such as an optical lens of various optical devices such as a camera and a microscope. Since the surface reflection of an optical element such as an optical lens provided with such an antireflection film is suppressed, stray light can be removed.

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

<Measurement method>

・ XRD measurement:
A multipurpose X-ray diffractometer (“Ultima-IV” manufactured by Rigaku Co., Ltd.) was used as a measuring device, the radiation source was CuKα, the output was 40 kV, 40 mA, and the detector was “D / teX Ultra”.

・ ICP measurement:
An ICP emission spectroscopic analyzer (“Optima 3300” manufactured by PerkinElmer) was used as the measuring device.

・ TEM measurement:
A transmission electron microscope (TEM; "JEM-2100" manufactured by Hitachi, Ltd.) was used as a measuring device, and measurement was performed under a magnification condition of 120 k (120,000) times.

・ Particle shape evaluation:
The TEM image of the particles was image-processed using the image processing software "imageJ 1.51j8". Specifically, the scale of 1 pixel was processed so as to correspond to the actual image, and the image was binarized.

Then, the average particle size was calculated according to the following method. First, the sample was centrifuged to extract particles. Then, when the particles are observed by TEM at a magnification of 120 k times (120,000 times), the particles existing in one field of view are targeted for measurement, and the arithmetic mean of the major axis and the minor axis of each particle is taken as the particle. The particle size was defined, and the arithmetic mean of the particle size of each particle was defined as the "average particle size". The "major axis" means the longest axis of the particle, and the "minor axis" means the shortest axis of the particle. In addition, particles in which only a part of the particles were visible in one field of view were excluded from the target.

<Examples 1 to 24>
To 5 mL of a 10 M potassium hydroxide aqueous solution _{, further add tantalum pentoxide (tantalum pentoxide, Ta 2} O ₅ ) and 5 mL of ethylene glycol to the concentrations shown in Table 1, and add a high-temperature pressurized acid decomposition vessel (manufactured by Parr). It was heated under the conditions shown in Table 1. After heating, it was confirmed by the above-mentioned measurement whether or not potassium tantalate (KTaO ₃ ) was obtained, and the average particle size was determined based on the above-mentioned method.

<Comparative example 1>
The production of particles was attempted under the same conditions as in Example 7 except that ethylene glycol was not added. As a result, the average particle size of the potassium tantalate particles was 101 nm.

From the above, it was at least confirmed that according to this example, potassium tantalate particles having a small average particle size can be efficiently produced.

1 ... film formation device, 10 ... substrate, 20 ... air, 30 ... ultrasonic vibrator, S ... raw material solution

Claims (15)

1. A group consisting of (A) an oxide containing tantalum, (B) a potassium compound which is at least one of potassium hydroxide or potassium chloride, and (C) ethylene glycol, methanol, ethanol, 1-propanol, and 2-propanol. A heating step of heating a mixture containing at least one alcohol selected from the above and (D) water is included.
   A method for producing potassium tantalate particles.
2. In the heating step, heating is performed at 150 ° C. or higher.
   The manufacturing method according to claim 1.
3. In the heating step, heating is performed in 30 minutes or more and 210 minutes or less.
   The manufacturing method according to claim 1 or 2.
4. The oxide containing (A) tantalum is tantalum oxide (Ta ₂ O ₅ ).
   The manufacturing method according to any one of claims 1 to 3.
5. The potassium compound (B) is potassium hydroxide.
   The manufacturing method according to any one of claims 1 to 4.
6. The (C) alcohols are ethylene glycol.
   The manufacturing method according to any one of claims 1 to 5.
7. The heating step is performed at a pressure higher than normal pressure.
   The manufacturing method according to any one of claims 1 to 6.
8. The molar ratio (B / A) of the potassium compound (B / A) to the oxide containing (A) tantalum is 5 or more and 300 or less.
   The manufacturing method according to any one of claims 1 to 7.
9. A step of obtaining potassium tantalate particles by the production method according to any one of claims 1 to 8.
   The mist-forming step of mist-forming the dispersion liquid containing the potassium tantalate particles, and
   A supply process for supplying the mist-ized dispersion liquid to the substrate, and
   After the supply step, a drying step of drying the dispersion liquid existing on the substrate is included.
   A method for producing a film containing potassium tantalate particles.
10. The average particle size is 100 nm or less.
    Potassium tantalate particles.
11. The potassium tantalate particles according to claim 10 are included.
    film.
12. The potassium tantalate particles are dispersed in the resin material.
    The film according to claim 11.
13. The film comprising at least one layer according to claim 11 or 12.
    Anti-reflection film.
14. An optical element comprising the antireflection film according to claim 13.
15. An optical device including the optical element according to claim 14.

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