JP6520698B2 - Method for producing vanadium dioxide-containing particles and method for producing vanadium dioxide-containing particle dispersion - Google Patents

Description

  The present invention relates to a method of producing vanadium dioxide-containing particles and a method of producing vanadium dioxide-containing particle dispersions. In particular, the present invention relates to a method for producing vanadium dioxide-containing particles having a small average particle diameter and excellent thermochromic properties, and a method for producing a vanadium dioxide-containing particle dispersion using the production method.

  2. Description of the Related Art In recent years, in moving objects such as houses and buildings and vehicles such as vehicles, energy saving and comfort are achieved at locations (for example, window glass etc.) where large heat exchange occurs between the inside (indoors and vehicles) and the outside environment. It has been attempted to apply a thermochromic material to achieve both

  The “thermochromic material” is a material whose optical properties such as, for example, the transparent state / reflective state can be controlled by temperature. For example, when a thermochromic material is applied to a window glass of a building, it is possible to reflect sunlight in summer to block heat and transmit sunlight in winter to use heat.

At present, one of the most noted thermochromic materials is a material containing vanadium dioxide (VO ₂ ). It is known that vanadium dioxide exhibits thermochromic properties (properties in which optical properties are reversibly changed depending on temperature) by phase transition at a transition temperature around room temperature. Therefore, by utilizing this characteristic, it is possible to obtain an environmental temperature dependent thermochromic material.

  As a method for producing a thermochromic material, a thermochromic material is prepared by preparing microparticles containing vanadium dioxide or a dispersion thereof, and placing the particulates on a member to which thermochromic properties are desired to be exhibited, for example, via an adhesive or the like. The method to obtain is proposed (for example, refer patent document 1).

  Here, vanadium dioxide has some polymorphs of crystal phases such as A phase, B phase, C phase and R phase, but the crystal structure showing thermochromic properties as described above is a rutile type crystal. It is limited to the phase (hereinafter referred to as “R phase”). This R phase is also called M phase because it has a monoclinic structure below the transition temperature. In addition, in the vanadium dioxide-containing particles, in order to exhibit substantially excellent thermochromic properties, the particles are not aggregated, the particle size is in the nanometer order, and the particles have an isotropic shape. It is desirable to do.

  Although Patent Document 1 mentioned above describes a method for producing vanadium dioxide-containing particles of M phase by hydrothermal reaction, the finally obtained vanadium dioxide-containing particles contain coarse particles and have a large average particle diameter, There is a problem that sufficient thermochromic properties can not be obtained.

JP, 2011-178825, A

  The present invention has been made in view of the above problems and circumstances, and the problem to be solved is a method for producing vanadium dioxide-containing particles having a small average particle diameter and excellent thermochromic properties, and dioxide dioxide using the production method. It is an object of the present invention to provide a method of producing a vanadium-containing particle dispersion.

In order to solve the above-mentioned subject according to the present invention, as a result of examining the cause of the above problems etc., at least water and a raw material containing vanadium (V) are mixed to prepare a reaction liquid. After the temperature is raised to within the range of 200 to 250 ° C. and then cooled to 100 ° C. or less, the temperature is raised to the hydrothermal reaction temperature to cause a hydrothermal reaction, whereby the average particle diameter is small and thermochromic It has been found that excellent vanadium dioxide-containing particles can be produced.
That is, the subject concerning the present invention is solved by the following means.

1. A method for producing vanadium dioxide-containing particles containing vanadium dioxide having thermochromic properties, comprising:
Preparing a reaction solution by mixing at least water and a raw material containing vanadium (V);
Raising the temperature of the reaction solution to within the range of 200 to 250 ° C. from ambient temperature;
Cooling the reaction solution heated to a temperature of 200 to 250 ° C. to 100 ° C. or less;
And D. raising the temperature of the reaction solution cooled to 100 ° C. or less to the hydrothermal reaction temperature to cause a hydrothermal reaction.

  2. In the step of raising the temperature, the temperature of the reaction liquid is raised from normal temperature to within the range of 210 to 240 ° C. The method for producing vanadium dioxide-containing particles according to item 1 above.

  3. The method for producing vanadium dioxide-containing particles according to claim 1 or 2, wherein the reaction liquid is cooled to 25 ° C. or less in the cooling step.

  4. In the step of causing the hydrothermal reaction, the reaction liquid cooled to 100 ° C. or less is transferred to another apparatus, and then the temperature is raised to the hydrothermal reaction temperature to cause a hydrothermal reaction. The manufacturing method of the vanadium dioxide containing particle | grains as described in any one of to 3rd term.

  5. In the step of raising the temperature, the temperature of the reaction liquid is raised from normal temperature to within the range of 200 to 250 ° C. at a temperature rising rate within the range of 5.8 to 15.0 ° C./min. The manufacturing method of the vanadium dioxide containing particle | grains as described in any one of 1st term | claim to 4th term.

  6. The method for producing a vanadium dioxide-containing particle according to any one of Claims 1 to 5, wherein the hydrothermal reaction temperature is in the range of 250 to 300 ° C.

  7. The method for producing vanadium dioxide-containing particles according to any one of items 1 to 6, wherein the reaction liquid is subjected to a hydrothermal reaction for 12 to 72 hours in the step of causing the hydrothermal reaction.

  8. A method for producing a vanadium dioxide-containing particle dispersion, comprising the step of producing a vanadium dioxide-containing particle according to the method for producing a vanadium dioxide-containing particle according to any one of items 1 to 7.

According to the present invention, it is possible to provide a method of producing vanadium dioxide-containing particles having a small average particle diameter and excellent thermochromic properties, and a method of producing a vanadium dioxide-containing particle dispersion using the production method.
The mechanism for expressing the effects of the present invention or the mechanism of action is not clear but is presumed as follows.
In the production of vanadium dioxide-containing particles by a hydrothermal reaction, it is considered that nuclei of the vanadium dioxide-containing particles are generated during the hydrothermal reaction, and the nuclei grow to form vanadium dioxide-containing particles. On the other hand, in the method for producing vanadium dioxide-containing particles in the above-mentioned conventional technique, after the reaction liquid is prepared, the hydrothermal reaction is carried out without specifying the temperature condition etc. It is believed that nucleation and particle growth occur simultaneously. For this reason, the reaction proceeds in a state in which nuclei, primary particles in which nuclei have grown, and coarse particles generated by aggregation of primary particles and further particles are mixed in the reaction liquid, and the particle size is increased. It is believed that non-uniform and poorly thermochromic vanadium dioxide-containing particles are produced.
In the present invention, it is considered that vanadium dioxide-containing particles having a small average particle diameter and excellent thermochromic properties can be obtained by the following mechanism. That is, by raising the temperature of the prepared reaction solution to 200 to 250 ° C., only generation of nuclei is advanced without causing particle growth in the reaction solution. After that, the reaction is stopped by once cooling to 100 ° C. or lower, and only a nucleus is present in the reaction solution. After making this state, the reaction liquid is heated to the hydrothermal reaction temperature to carry out a hydrothermal reaction, whereby the nuclei in the reaction liquid are uniformly particle-grown and the average particle diameter is small, whereby the thermochromic It is believed that vanadium dioxide-containing particles with excellent properties can be obtained.

Schematic diagram showing temperature change of reaction liquid in the present invention and the prior art

The method for producing vanadium dioxide-containing particles of the present invention is a method for producing vanadium dioxide-containing particles containing vanadium dioxide having thermochromic properties, comprising mixing at least water and a raw material containing vanadium (V). Preparing the reaction solution, raising the temperature of the reaction solution from normal temperature to 200 to 250 ° C., and raising the temperature of the reaction solution heated to 200 to 250 ° C. to 100 ° C. or less And cooling the reaction liquid cooled to 100 ° C. or less to a hydrothermal reaction temperature to cause a hydrothermal reaction. This feature is a technical feature that is common to or corresponds to each claim.
In the present invention, in view of the effects of the present invention, in the step of raising the temperature, it is preferable to raise the temperature of the reaction solution from normal temperature to a range of 210 to 240 ° C.
In the present invention, it is preferable to cool the reaction solution to 25 ° C. or less in the cooling step. As a result, vanadium dioxide-containing particles having a smaller average particle size can be obtained.
In the present invention, after the reaction solution cooled to 100 ° C. or less is transferred to another device in the step of causing the hydrothermal reaction, the temperature is raised to the hydrothermal reaction temperature to cause the hydrothermal reaction. Is preferred. As a result, it is possible to perform the temperature raising step and the cooling step in parallel in a plurality of systems, mix the obtained plurality of reaction liquids, and carry out the hydrothermal reaction step in a batch with the same device, thus producing It is possible to improve the quality.
Further, in the present invention, in the step of raising the temperature, the temperature of the reaction solution is raised from normal temperature to a range of 200 to 250 ° C. at a temperature raising rate within a range of 5.8 to 15.0 ° C./min. It is preferable to This makes it possible to generate nuclei more reliably in the reaction solution, to suppress the formation of coarse particles, and to reduce the average particle diameter of the vanadium dioxide-containing particles.
In the present invention, the hydrothermal reaction temperature is preferably in the range of 250 to 300 ° C. Thereby, a sufficient reaction rate can be obtained, the average particle diameter of the vanadium dioxide-containing particles can be smaller, and the thermochromic properties can be further improved.
Moreover, in the present invention, in the step of causing the hydrothermal reaction, the reaction solution is preferably subjected to the hydrothermal reaction for 12 to 72 hours. Thereby, it is possible to easily control the average particle size of the vanadium dioxide-containing particles to be obtained, and to suppress an increase in energy consumption.

  Further, the method for producing a vanadium dioxide-containing particle dispersion liquid of the present invention is characterized by comprising a step of producing a vanadium dioxide-containing particle by the above-mentioned method for producing a vanadium dioxide-containing particle. This makes it possible to produce a vanadium dioxide-containing particle dispersion containing vanadium dioxide-containing particles having a small average particle diameter and excellent thermochromic properties.

  BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In the present application, “to” is used in the meaning including the numerical values described before and after that as the lower limit value and the upper limit value.

<< Outline of production method of vanadium dioxide-containing particles >>
The method for producing vanadium dioxide-containing particles of the present invention is a method for producing vanadium dioxide-containing particles containing vanadium dioxide having thermochromic properties, comprising mixing at least water and a raw material containing vanadium (V). Of preparing the reaction liquid (reaction liquid preparation step), the step of raising the temperature of the reaction liquid to within the range of 200 to 250.degree. C. from the normal temperature (temperature raising step), and raising the temperature to within the range of 200 to 250.degree. Cooling the reaction liquid to 100 ° C. or less (cooling step), and heating the reaction liquid cooled to 100 ° C. or less to the hydrothermal reaction temperature to cause a hydrothermal reaction (hydrothermal reaction step); It is characterized by having.

  The method for producing the vanadium dioxide-containing particles of the present invention will be described with reference to FIG. 1 (a) and 1 (b) are schematic diagrams showing the temperature change of the reaction solution in the method for producing vanadium dioxide-containing particles according to the prior art, and FIG. 1 (c) is a method for producing vanadium dioxide-containing particles according to the present invention. It is a schematic diagram which shows the temperature change of the reaction liquid.

As shown in FIGS. 1 (a) and 1 (b), in the prior art, once heating of the reaction liquid is started, it may be once held at a predetermined temperature (see FIG. 1 (b)). The temperature is raised without lowering the temperature of the reaction solution until it reaches the reaction temperature, and it is cooled after the hydrothermal reaction is completed. On the other hand, according to the present invention, after the temperature rise of the reaction solution is started to reach 200 to 250 ° C., the temperature is once cooled to 100 ° C. or less, then the temperature rise is started again to reach the hydrothermal reaction temperature. After the completion of the hydrothermal reaction, it is cooled again. As a result, vanadium dioxide-containing particles having a small average particle diameter and excellent thermochromic properties can be obtained.
Here, the hydrothermal reaction temperature is a temperature suitable for causing the reaction liquid to hydrothermally react, and the temperature rising of the reaction liquid after passing through the temperature raising step and the cooling step is completed, and finally reached It means the temperature. In the present invention, the hydrothermal reaction is started when the reaction liquid reaches the hydrothermal reaction temperature.

  Hereinafter, materials used in the method for producing vanadium dioxide-containing particles of the present invention, various conditions, measurement methods and the like will be described in detail.

[1: Reaction liquid preparation process]
In the reaction liquid preparation step, at least water and a raw material containing vanadium (V) are mixed to prepare a reaction liquid. The reaction solution may be an aqueous solution in which the raw material is dissolved in water, or may be a suspension in which the raw material is dispersed in water.

(Raw material containing vanadium (V))
In the present invention, the raw material containing vanadium (V) refers to a vanadium compound containing vanadium (V), or a mixture of the vanadium compound and another compound. As the said raw material, what was melt | dissolved in the solvent may be used, and what was disperse | distributed in the dispersion medium may be used.

The vanadium compound contained in the raw material is not particularly limited as long as it is a compound of pentavalent vanadium (V), for example, vanadium pentoxide (V ₂ O ₅ ), ammonium vanadate (NH ₄ VO ₃ ) Vanadium trichloride oxide (VOCl ₃ ), sodium metavanadate (NaVO ₃ ), etc. can be used. Among them, vanadium vanadium pentoxide, ammonium vanadate and vanadium trichloride oxide are preferred from the viewpoint of obtaining vanadium dioxide-containing particles of higher purity without preventing formation of vanadium dioxide-containing particles because they do not contain metal atoms other than vanadium atoms. Compounds selected from are preferred. Moreover, as a vanadium compound contained in a raw material, only 1 type may be sufficient and 2 or more types may be sufficient.

  The raw materials described above may be pretreated in the presence of hydrogen peroxide before the hydrothermal reaction step described later. By pre-treating in the presence of hydrogen peroxide before the hydrothermal reaction step, the reaction liquid becomes a sol, even if it contains a nonionic vanadium compound such as vanadium pentoxide in particular, The hydrothermal reaction can proceed uniformly. In this case, for example, 0.5 to 10 moles of hydrogen peroxide is added to the reaction solution with respect to 1 mole of the vanadium compound, and, for example, at about 20 to 40 ° C., for about 0.5 to 10 hours while stirring as necessary. You just have to make it react.

(water)
The water according to the present invention is not particularly limited, but high-purity water with few impurities is preferable, and specifically, purified water such as ion exchanged water, distilled water and the like can be used.

(Other compounds which the reaction liquid according to the present invention may contain)
The reaction solution according to the present invention preferably contains a reducing agent. The reducing agent may have the property of being easily soluble in water and may function as a reducing agent of the raw material containing vanadium (V), for example, hydrazine (N ₂ H ₄ ), hydrazine monohydrate Hydrate of hydrazine etc. (N ₂ H ₄ · n H ₂ O), oxalic acid ((COOH) ₂ ), hydrate of oxalic acid such as oxalic acid dihydrate (H ₂ C ₂ O ₄ · n H ₂ O) and the like. As the reducing agent, one type may be used alone, or two or more types may be used in combination.
The content of the reducing agent in the reaction solution is not particularly limited, and is, for example, 0.01 to 2 moles relative to 1 mole of the vanadium compound.

  When the reaction solution contains the above-mentioned reducing agent, it is possible to carry out an oxidation-reduction reaction before the hydrothermal reaction step described later. For example, the reaction solution containing a reducing agent may be reacted, for example, at 20 to 40 ° C. for about 0.5 to 10 hours while being stirred, if necessary, before the hydrothermal reaction step. When a plurality of reducing agents are employed, the plurality of reducing agents can be simultaneously or sequentially added to carry out the redox reaction. The redox reaction with the reducing agent may be performed simultaneously with the above-described pretreatment of the raw material with hydrogen peroxide (that is, pretreatment is performed using a reaction solution containing hydrogen peroxide and a reducing agent), or It may be sequentially performed separately from the pretreatment with hydrogen peroxide. By conducting the oxidation-reduction reaction before the hydrothermal reaction step, vanadium dioxide can be easily produced.

  The reaction liquid according to the present invention may be, for example, tungsten (W), molybdenum (Mo), niobium (Nb), tantalum (Ta), tin (Sn), rhenium (Re), iridium (Ir), osmium (Os) ), Ruthenium (Ru), germanium (Ge), chromium (Cr), iron (Fe), gallium (Ga), aluminum (Al), fluorine (F), phosphorus (P) and titanium (Ti) It may contain a selected compound containing at least one atom.

  By adding a compound containing these atoms as an additive to the reaction solution according to the present invention, it is possible to control the thermochromic property (particularly, transition temperature) of the finally obtained vanadium dioxide-containing particles.

In addition, the reaction liquid according to the present invention may further contain a substance having oxidative or reducibility. Such substances include, for example, hydrogen peroxide (H ₂ O ₂ ). By adding a substance having an oxidizing property or a reducing property, the pH of the reaction solution can be adjusted, or the above-mentioned raw material can be dissolved uniformly.

  In addition, the reaction liquid according to the present invention may contain, as a pH adjuster, an organic or inorganic acid or alkali such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, ammonium hydroxide or ammonia. The pH of the reaction solution is, for example, 4 to 7 from the viewpoint of the particle size of the vanadium dioxide-containing particles and the thermochromic property.

[2: heating process]
In the temperature raising step, the temperature of the reaction liquid prepared in the reaction liquid preparation step is raised from normal temperature to a range of 200 to 250 ° C.
Specifically, the prepared reaction solution is housed in a closed vessel such as an autoclave used for hydrothermal reaction treatment, and heated in a closed space to a temperature of 200 to 250 ° C. from normal temperature (eg 25 ° C.) Temperature rise to within the range of

  In the temperature raising step, it is preferable to raise the temperature from normal temperature to a range of 210 to 240 ° C. from the viewpoint of exhibiting the effects of the present invention.

In the temperature raising step, the temperature of the reaction solution is preferably raised from normal temperature to within the range of 200 to 250 ° C. at a temperature rising rate within the range of 5.8 to 15.0 ° C./min. When the heating rate is 5.8 ° C./min or more, the variation in the average particle size and the particle size of the obtained vanadium dioxide-containing particles can be reduced. On the other hand, setting the temperature rising rate higher than 15.0 ° C./min is difficult in design of the apparatus and other temperature rising means.
In the temperature rising period from normal temperature to within the range of 200 to 250 ° C., the temperature rising rate is constant at any one value within the range of 5.8 to 15.0 ° C./min. The temperature rising rate may be varied with the passage of time within the range of 5.8 to 15.0 ° C./min.

Moreover, in the temperature raising step, it is preferable to stop the temperature raising once when the reaction liquid reaches a predetermined temperature before reaching 200 to 250 ° C., and hold the predetermined temperature for 0.5 to 5 hours. Thus, it is considered that by temporarily stopping the temperature rise, all the materials can be dissolved, and more uniform particles can be formed.
In this case, the reaction solution is maintained at a predetermined temperature for 0.5 to 5 hours, and then the temperature rise of the reaction solution is resumed to raise the temperature to 200 to 250 ° C. The heating rate may be the same or different after resumption. Further, in the process of raising the temperature from normal temperature to 200 to 250 ° C., the temperature rising stop and the temperature holding may be repeated a plurality of times.

[3: Cooling process]
In the cooling step, the reaction liquid heated to a temperature of 200 to 250 ° C. in the temperature raising step is cooled to 100 ° C. or less.
Specifically, the reaction solution contained in a closed vessel such as an autoclave used for hydrothermal reaction treatment is cooled to 100 ° C. or less by cooling in the closed space.

  The method of cooling is not particularly limited, and the closed container containing the reaction solution may be naturally air-cooled, or air may be blown to the outer wall surface of the closed container by a fan or the like. Further, for example, cooling may be performed by heat exchange in which a refrigerant or the like is brought into direct or indirect contact with the outer wall surface of the sealed container.

Further, in the cooling step, the reaction solution is preferably cooled to 25 ° C. or less. Thus, vanadium dioxide-containing particles having a smaller average particle size can be obtained.
In the cooling step, by cooling the reaction solution to a low temperature as much as possible, it is possible to more reliably stop the reaction proceeding in the reaction solution and obtain particles having a small average particle diameter, but energy consumption It is preferable to cool to about 25 ° C. from the viewpoint of the amount, the manufacturing cost, the productivity and the like.

[4: Hydrothermal reaction process]
In the hydrothermal reaction step, the reaction liquid cooled to 100 ° C. or less in the cooling step is heated to the hydrothermal reaction temperature to carry out the hydrothermal reaction treatment. Here, the hydrothermal reaction means a chemical reaction which occurs in a hot water (subcritical water) having a temperature and a pressure lower than the critical point of water (374 ° C., 22 MPa) and 100 ° C. or more.

The hydrothermal reaction step is carried out, for example, in a closed vessel such as an autoclave.
The conditions (amount of reactant, treatment temperature, treatment pressure, treatment time) of the hydrothermal reaction treatment are appropriately set, but the hydrothermal reaction temperature is, for example, in the range of 200 to 350 ° C., preferably 200 It is in the range of -300 ° C, more preferably in the range of 250-300 ° C. By setting the temperature to 350 ° C. or less, the average particle size of the vanadium dioxide-containing particles can be reduced. On the other hand, the higher the temperature, the faster the reaction rate, and at 200 ° C. or higher, a sufficient reaction rate is obtained, and the thermochromic properties of the vanadium dioxide-containing particles become more excellent.

In addition, the time of the hydrothermal reaction treatment is, for example, in the range of 0.1 hour to 7 days, and preferably in the range of 12 to 72 hours. By lengthening the time, the average particle size and the like of the obtained vanadium dioxide-containing particles can be controlled, and if it is within 7 days, it can be suppressed that the energy consumption amount is too large. In the present invention, the time of the hydrothermal reaction treatment does not include the time of the temperature raising step and the cooling step.
Further, the pressure of the hydrothermal reaction treatment is not particularly limited, but is, for example, a saturated water vapor pressure at the time of the hydrothermal reaction, and more specifically, for example, in the range of 5 to 7 MPa.

  In the hydrothermal reaction step, the reaction liquid cooled to 100 ° C. or lower in the cooling step is transferred to a device different from the device used in the temperature raising step and the cooling step, and then to the hydrothermal reaction temperature. It is preferable to raise the temperature to cause a hydrothermal reaction. By performing the hydrothermal reaction step with an apparatus different from the apparatus used in the temperature raising process and the cooling process, the temperature raising process and the cooling process are performed in parallel in a plurality of systems using a plurality of apparatuses. A plurality of reaction solutions can be mixed, and the hydrothermal reaction process can be performed collectively with the same apparatus. As described above, although the hydrothermal reaction step takes a long time, by adopting such a method, the productivity of the vanadium dioxide-containing particles can be improved.

  In addition, it is preferable that the hydrothermal reaction be performed while stirring, because the particle size of the vanadium dioxide-containing particles can be made more uniform.

  The hydrothermal reaction treatment may be carried out batchwise or continuously.

  After completion of the hydrothermal reaction treatment, it is preferable to rapidly cool the temperature of the reaction solution to 150 ° C. or less. More preferably, it cools to 150 degrees C or less within 30 minutes.

  By the above steps, a suspension containing vanadium dioxide-containing particles having thermochromic properties is obtained. The dispersion medium and the solvent may be substituted by filtration (for example, ultrafiltration) or centrifugation to the suspension to wash the vanadium dioxide-containing particles with water, alcohol or the like. The obtained vanadium dioxide-containing particles may be dried by any means. Thereby, the vanadium dioxide containing particle | grains which concern on this invention are obtained.

<< Vanadium dioxide-containing particles >>
The vanadium dioxide-containing particles produced by the method for producing vanadium dioxide-containing particles of the present invention at least contain vanadium dioxide (VO ₂ ) and have thermochromic properties.
The average particle size of the vanadium dioxide-containing particles is preferably in the range of 1 to 200 nm.

  With an optical film or the like containing such vanadium dioxide-containing particles, the generation of haze can be suppressed, and the visible light transmittance can be improved.

  An optical film can be produced by providing the vanadium dioxide-containing particles produced by the production method of the present invention, for example, on a substrate in a state of being dispersed in a binder resin.

(Thermochromic property and transparency)
The vanadium dioxide containing particle | grains based on this invention have thermochromism and transparency.
The visible light transmittance of the vanadium dioxide-containing particles according to the present invention is preferably as high as possible, but is preferably 70% or more.

The thermochromic properties of the vanadium dioxide-containing particles are not particularly limited as long as optical characteristics such as light transmittance and light reflectance change reversibly due to temperature change. For example, the difference in light transmittance at 25 ° C./50% RH and 85 ° C./85% RH is preferably 30% or more.
The light transmittance of the vanadium dioxide-containing particles can be measured, for example, as a light transmittance at a wavelength of 2000 nm using a spectrophotometer V-670 (manufactured by Nippon Bunko Co., Ltd.).

Further, as described above, the vanadium dioxide-containing particle according to the present invention is, in addition to vanadium dioxide (VO ₂ ), tungsten (W), molybdenum (Mo), niobium (Nb), tantalum (Ta), tin (Sn), Rhenium (Re), iridium (Ir), osmium (Os), ruthenium (Ru), germanium (Ge), chromium (Cr), iron (Fe), gallium (Ga), aluminum (Al), fluorine (F), At least one atom selected from the group consisting of phosphorus (P) and titanium (Ti) may be contained. By containing such an atom, it becomes possible to control the phase transition characteristics (in particular, the dimming temperature) of the vanadium dioxide-containing particles. The total addition amount of these atoms to the finally obtained vanadium dioxide-containing particles is about 0.1 to 5.0 atomic% with respect to the vanadium (V) atom, and is, for example, 1.0 atom. %. Sufficient thermochromic property (for example, the difference of the light transmittance before and behind light control) can be ensured as the addition total amount is 5.0 atomic% or less.

<< Production Method of Vanadium Dioxide-Containing Particle Dispersion >>
The method for producing a vanadium dioxide-containing particle dispersion according to the present invention is characterized by comprising a step of producing vanadium dioxide-containing particles by the above-described method for producing vanadium dioxide-containing particles.

  As a method for producing the vanadium dioxide-containing particle dispersion liquid of the present invention, the reaction liquid after the hydrothermal reaction step may be used as it is as a vanadium dioxide-containing particle dispersion liquid, or vanadium dioxide obtained after the hydrothermal reaction step The method may further include the step of dispersing the containing particles in the dispersion medium.

  The dispersion medium is not particularly limited, and for example, an organic solvent such as alcohol or an inorganic solvent such as water can be used. When water is used as the dispersion medium, the dispersion medium may consist of water alone, or, for example, an organic solvent of about 0.1 to 10% by mass (in the dispersion liquid) in addition to water, such as methanol, It may also contain alcohols such as ethanol, isopropanol and butanol, and ketones such as acetone. Moreover, buffers, such as a phosphate buffer and an acetate buffer, can also be used as a dispersion medium.

  The vanadium dioxide-containing particle dispersion may contain, for example, an organic or inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, ammonium hydroxide or ammonia, or a pH adjusting agent such as alkali or the like. The pH may be adjusted to In addition, it is preferable that pH is 4-7 from a viewpoint that aggregation of the vanadium dioxide containing particle | grains in a vanadium dioxide containing particle dispersion liquid is suppressed.

  For example, it is possible to produce a film by applying the vanadium dioxide-containing particle dispersion produced as described above on a substrate.

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

<< Preparation of vanadium dioxide-containing particles 101 (comparative example) >>
To 30 mL of a 10 mass% aqueous solution of hydrogen peroxide solution (concentration 35 mass%, manufactured by Wako Pure Chemical Industries, Ltd.), 0.9 g of vanadium pentoxide (V ₂ O ₅ , manufactured by Wako Pure Chemical Industries, Ltd., special grade) is added. Stir for 4 hours at ° C to obtain a clear reddish brown sol. To the obtained sol, 2.5 g of a 5% by mass aqueous solution of hydrazine monohydrate (N ₂ H ₄ · H ₂ O, manufactured by Wako Pure Chemical Industries, Ltd., special grade) was slowly added dropwise to prepare a reaction liquid (reaction liquid Preparation process).

  The reaction solution stirred for 1 hour after dropping was added to a commercially available autoclave for hydrothermal reaction treatment (manufactured by Sanai Scientific Co., Ltd., HU-50 type) (provided with a 50 mL volume of a Teflon (registered trademark) inner cylinder in a SUS body). The temperature was raised from 25 ° C. (normal temperature) to a hydrothermal reaction temperature of 275 ° C. at a temperature rising rate of 1 ° C./min, and hydrothermal reaction was performed for 48 hours (hydrothermal reaction step). After the hydrothermal reaction, the resulting reaction product was cooled to room temperature, filtered, and the residue was washed with water and ethanol. Furthermore, this residue was dried at 60 ° C. for 10 hours using a constant temperature dryer. Thus, vanadium dioxide-containing particles 101 were obtained.

<< Preparation of vanadium dioxide-containing particles 102 (comparative example) >>
To 30 mL of a 10 mass% aqueous solution of hydrogen peroxide solution (concentration 35 mass%, manufactured by Wako Pure Chemical Industries, Ltd.), 0.9 g of vanadium pentoxide (V ₂ O ₅ , manufactured by Wako Pure Chemical Industries, Ltd., special grade) is added. Stir for 4 hours at ° C to obtain a clear reddish brown sol. To the obtained sol, 2.5 g of a 5% by mass aqueous solution of hydrazine monohydrate (N ₂ H ₄ · H ₂ O, manufactured by Wako Pure Chemical Industries, Ltd., special grade) was slowly added dropwise to prepare a reaction liquid (reaction liquid Preparation process).

  The reaction solution stirred for 1 hour after dropping was added to a commercially available autoclave for hydrothermal reaction treatment (manufactured by Sanai Scientific Co., Ltd., HU-50 type) (provided with a 50 mL volume of a Teflon (registered trademark) inner cylinder in a SUS body). The temperature was raised from 25 ° C. (normal temperature) to 190 ° C. at a temperature rising rate of 1 ° C./min (temperature rising step). After holding at 190 ° C. for 2 hours, the temperature was further raised from 190 ° C. to 275 ° C., which is a hydrothermal reaction, and hydrothermal reaction was performed at 275 ° C. for 48 hours (hydrothermal reaction step). After the hydrothermal reaction, the resulting reaction product was cooled to room temperature, filtered, and the residue was washed with water and ethanol. Furthermore, this residue was dried at 60 ° C. for 10 hours using a constant temperature dryer. Thus, vanadium dioxide-containing particles 102 were obtained.

<< Preparation of vanadium dioxide-containing particles 103 (comparative example) >>
To 30 mL of a 10 mass% aqueous solution of hydrogen peroxide solution (concentration 35 mass%, manufactured by Wako Pure Chemical Industries, Ltd.), 0.9 g of vanadium pentoxide (V ₂ O ₅ , manufactured by Wako Pure Chemical Industries, Ltd., special grade) is added. Stir for 4 hours at ° C to obtain a clear reddish brown sol. To the obtained sol, 2.5 g of a 5% by mass aqueous solution of hydrazine monohydrate (N ₂ H ₄ · H ₂ O, manufactured by Wako Pure Chemical Industries, Ltd., special grade) was slowly added dropwise to prepare a reaction liquid (reaction liquid Preparation process).

  The reaction solution stirred for 1 hour after dropping was added to a commercially available autoclave for hydrothermal reaction treatment (manufactured by Sanai Scientific Co., Ltd., HU-50 type) (provided with a 50 mL volume of a Teflon (registered trademark) inner cylinder in a SUS body). The temperature was raised from 25 ° C. (normal temperature) to 190 ° C. at a temperature rising rate of 1 ° C./min (temperature rising step). Next, the furnace was turned off, and the outer wall of the autoclave was cooled by air blowing from a fan to cool the reaction solution to 40 ° C. (cooling step). The cooled reaction solution was heated to a hydrothermal reaction temperature of 275 ° C., and hydrothermally reacted at 275 ° C. for 48 hours (hydrothermal reaction step). After the hydrothermal reaction, the resulting reaction product was cooled to room temperature, filtered, and the residue was washed with water and ethanol. Furthermore, this residue was dried at 60 ° C. for 10 hours using a constant temperature dryer. Thus, vanadium dioxide-containing particles 103 were obtained.

<< Preparation of Vanadium Dioxide-Containing Particles 104 >>
A vanadium dioxide-containing particle 104 was prepared in the same manner as in the preparation of the vanadium dioxide-containing particle 103 except that the temperature of the reaction liquid was raised to 200 ° C. in the temperature raising step.

<< Preparation of Vanadium Dioxide-Containing Particles 105 >>
A vanadium dioxide-containing particle 105 was prepared in the same manner as in the preparation of the vanadium dioxide-containing particle 103 except that the temperature of the reaction liquid was raised to 210 ° C. in the temperature raising step.

<< Preparation of Vanadium Dioxide-Containing Particles 106 >>
The vanadium dioxide-containing particles 106 were prepared in the same manner as in the preparation of the vanadium dioxide-containing particles 103 except that the temperature of the reaction liquid was raised to 240 ° C. in the temperature raising step.

<< Preparation of Vanadium Dioxide-Containing Particles 107 >>
A vanadium dioxide-containing particle 107 was prepared in the same manner as in the preparation of the vanadium dioxide-containing particle 103 except that the temperature of the reaction solution was raised to 250 ° C. in the temperature raising step.

<< Preparation of vanadium dioxide-containing particles 108 (comparative example) >>
A vanadium dioxide-containing particle 108 was prepared in the same manner as in the preparation of the vanadium dioxide-containing particle 103 except that the temperature of the reaction liquid was raised to 265 ° C. in the temperature raising step.

<< Preparation of vanadium dioxide-containing particles 109 >>
A vanadium dioxide-containing particle 109 was prepared in the same manner as in the preparation of the vanadium dioxide-containing particle 104 except that the reaction liquid was cooled to 25 ° C. in the cooling step.

<< Preparation of Vanadium Dioxide-Containing Particles 110 >>
A vanadium dioxide-containing particle 110 was prepared in the same manner as in the preparation of the vanadium dioxide-containing particle 104 except that the reaction liquid was cooled to 100 ° C. in the cooling step.

<< Preparation of vanadium dioxide-containing particles 111 (comparative example) >>
A vanadium dioxide-containing particle 111 was prepared in the same manner as in the preparation of the vanadium dioxide-containing particle 104 except that the reaction solution was cooled to 110 ° C. in the cooling step.

<< Preparation of Vanadium Dioxide-Containing Particles 112 >>
A vanadium dioxide-containing particle 112 was prepared in the same manner as in the preparation of the vanadium dioxide-containing particle 104 except that the temperature raising rate in the temperature raising step was changed to 10 ° C./min.

<< Preparation of vanadium dioxide-containing particles 113 >>
A vanadium dioxide-containing particle 113 was prepared in the same manner as in the preparation of the vanadium dioxide-containing particle 104 except that the hydrothermal reaction temperature was changed to 295 ° C.

<< Preparation of Vanadium Dioxide-Containing Particles 114 >>
The vanadium dioxide-containing particles 114 were prepared in the same manner as in the preparation of the vanadium dioxide-containing particles 104 except that the hydrothermal reaction temperature was changed to 250 ° C.

<< Preparation of Vanadium Dioxide-Containing Particles 115 >>
A vanadium dioxide-containing particle 115 was prepared in the same manner as in the preparation of the vanadium dioxide-containing particle 104 except that the hydrothermal reaction was carried out for hydrothermal reaction at 275 ° C., which is the hydrothermal reaction temperature, for 12 hours.

<< Preparation of Vanadium Dioxide-Containing Particles 116 >>
In the preparation of the vanadium dioxide-containing particles 104, vanadium dioxide-containing particles 116 were prepared in the same manner as the hydrothermal reaction step except that the hydrothermal reaction was performed at 275 ° C., which is the hydrothermal reaction temperature, for 72 hours.

<< Preparation of Vanadium Dioxide-Containing Particles 117 >>
In the preparation of the vanadium dioxide-containing particles 104, in the reaction liquid preparation step, 0.9 g of ammonium molybdate paratetrahydrate (special grade, manufactured by Wako Pure Chemical Industries, Ltd.) together with 0.9 g of vanadium pentoxide in an aqueous solution of hydrogen peroxide water The vanadium dioxide-containing particles 117 were similarly prepared except that

<< Preparation of Vanadium Dioxide-Containing Particles 118 >>
In the preparation of the vanadium dioxide-containing particles 104, in the reaction liquid preparation step, 0.02 g of magnesium nitrate hexahydrate (special grade, manufactured by Wako Pure Chemical Industries, Ltd.) is added to an aqueous solution of hydrogen peroxide solution together with 0.9 g of vanadium pentoxide. The vanadium dioxide-containing particles 118 were prepared in the same manner as described above.

<< Preparation of vanadium dioxide-containing particles 119 (comparative example) >>
In preparation of the above-mentioned vanadium dioxide-containing particle 101, oxalic acid dihydrate (special grade, manufactured by Wako Pure Chemical Industries, Ltd.) is used in place of dropping a 5 mass% aqueous solution of hydrazine monohydrate in the reaction liquid preparation step. A vanadium dioxide-containing particle 119 was prepared in the same manner except that 25 g was added.

<< Preparation of Vanadium Dioxide-Containing Particles 120 >>
In the preparation of the above-mentioned vanadium dioxide-containing particles 103, oxalic acid dihydrate (special grade, manufactured by Wako Pure Chemical Industries, Ltd.) is used in place of dropping a 5% by mass aqueous solution of hydrazine monohydrate in the reaction liquid preparation step. 25 g is added, and the reaction liquid is heated from 25 ° C. (normal temperature) to 220 ° C. in the temperature raising step, and further cooled in the cooling step until the reaction liquid reaches 50 ° C. Particles 120 were prepared.

<< Preparation of vanadium dioxide-containing particles 121 (comparative example) >>
To 30 mL of pure water, 1.2 g of ammonium vanadate (NH ₄ VO ₃ , manufactured by Wako Pure Chemical Industries, Ltd., special grade) was added, and this was stirred at 60 ° C. for 1 hour. To the resulting solution, 2.8 g of a 4.75 mass% aqueous solution of hydrazine monohydrate (N ₂ H ₄ · H ₂ O, manufactured by Wako Pure Chemical Industries, Ltd., special grade) was slowly added dropwise to prepare a reaction liquid ( Reaction liquid preparation process).

  The reaction solution stirred for 10 minutes after dropping is placed in a commercially available autoclave for hydrothermal reaction treatment (HU-50 type manufactured by Sanai Scientific Co., Ltd.) (provided with a 50 mL volume of a Teflon (registered trademark) inner cylinder in a SUS main body). The temperature was raised from 25 ° C. (normal temperature) to a hydrothermal reaction temperature of 285 ° C. at a heating rate of 1 ° C./min, and a hydrothermal reaction was performed for 24 hours (hydrothermal reaction step). After the hydrothermal reaction, the resulting reaction product was cooled to room temperature, filtered, and the residue was washed with water and ethanol. Furthermore, this residue was dried at 60 ° C. for 10 hours using a constant temperature dryer. Thus, vanadium dioxide-containing particles 121 were obtained.

<< Preparation of Vanadium Dioxide-Containing Particles 122 >>
To 30 mL of pure water, 1.2 g of ammonium vanadate (NH ₄ VO ₃ , manufactured by Wako Pure Chemical Industries, Ltd., special grade) was added, and this was stirred at 60 ° C. for 1 hour. To the resulting solution, 2.8 g of a 4.75 mass% aqueous solution of hydrazine monohydrate (N ₂ H ₄ · H ₂ O, manufactured by Wako Pure Chemical Industries, Ltd., special grade) was slowly added dropwise to prepare a reaction liquid ( Reaction liquid preparation process).

  The reaction solution stirred for 10 minutes after dropping is placed in a commercially available autoclave for hydrothermal reaction treatment (HU-50 type manufactured by Sanai Scientific Co., Ltd.) (provided with a 50 mL volume of a Teflon (registered trademark) inner cylinder in a SUS main body). Then, the temperature was raised from 25 ° C. (normal temperature) to 230 ° C. at a temperature rising rate of 1 ° C./min (temperature rising step). Next, the furnace was turned off, and the outer wall of the autoclave was cooled by air blowing from a fan to cool the reaction solution to 30 ° C. (cooling step). The cooled reaction solution was heated to a hydrothermal reaction temperature of 285 ° C., and was hydrothermally reacted at 285 ° C. for 24 hours. After the hydrothermal reaction, the resulting reaction product was cooled to room temperature, filtered, and the residue was washed with water and ethanol. Furthermore, this residue was dried at 60 ° C. for 10 hours using a constant temperature dryer. Thus, vanadium dioxide-containing particles 122 were obtained.

<< Preparation of vanadium dioxide-containing particles 123 >>
In the preparation of the vanadium dioxide-containing particles 122, in the reaction liquid preparation step, 0.029 g of ammonium tungstate parapentahydrate (special grade, manufactured by Wako Pure Chemical Industries, Ltd.) is added to pure water together with 1.2 g of ammonium vanadate Similarly, vanadium dioxide-containing particles 123 were prepared.

<< Evaluation of vanadium dioxide-containing particles 101 to 123 >>
The following evaluation was performed about the vanadium dioxide containing particles 101-123 prepared as mentioned above. The evaluation results are shown in Tables 1 and 2.

(1) Thermochromic evaluation In the preparation of each vanadium dioxide-containing particle, the reaction product obtained after the hydrothermal reaction is diluted 5000 times with pure water, and a commercially available stoppered quartz cell (two-sided light transmission type 45 mm × The transmission spectrum was measured with a heatable spectrophotometer (V-670 type, 190-2500 nm, manufactured by JASCO Corporation) in a size of 12.5 mm × 10 mm. The liquid temperature at the time of measurement was 25 ° C. and 80 ° C., and the measurement wavelength was 1300 nm. The difference in light transmittance between liquid temperatures 25 ° C. and 80 ° C. was calculated, and the thermochromic properties were evaluated according to the following criteria.

:: 20% or more ○: 15% or more and less than 20% Δ: 10% or more and less than 15% ×: less than 10%

(2) Average particle size evaluation The produced vanadium dioxide-containing particles are photographed with a scanning electron microscope (JSM-7401F manufactured by JEOL Ltd.), and the diameter of a circle having an area equal to the projected area of the particles is defined as the particle size. The arithmetic mean value of the individual particle sizes measured for 100 particles was determined, and this was taken as the average particle size. The average particle size obtained was evaluated according to the following criteria.

◎: less than 50 nm ○: 50 nm or more and less than 100 nm Δ: 100 nm or more and less than 200 nm ×: 200 nm or more

(3) Thermochromic evaluation of optical film First, the optical film was produced as follows using each vanadium dioxide containing particle | grains produced above.

  The following constituent materials were sequentially added, mixed and dissolved to prepare a coating solution for forming an optical functional layer of a water system.

3 mass% vanadium dioxide-containing particle dispersion 28 mass parts 3 mass% boric acid aqueous solution 10 mass parts 5 mass% polyvinyl alcohol aqueous solution (PVA-124; degree of polymerization: 2400, degree of saponification: 98 to 99 mol%; stock Made by Kuraray Co., Ltd. 60 parts by mass 5% by mass surfactant aqueous solution (softazoline LSB-R, manufactured by Kawaken Fine Chemical Co., Ltd.) 2 parts by mass

The above 3% by mass vanadium dioxide-containing particle dispersion is prepared by ultrafiltration of the reaction product obtained after the hydrothermal reaction and concentration to 3% by mass in the preparation of each of the above vanadium dioxide-containing particles. It is
Moreover, PVA-124 which is the said polyvinyl alcohol is a polymer whose ratio of the repeating unit containing a hydroxyl group is 50 mol% or more.

  The thickness of the coating solution for forming an optical functional layer prepared above is 1 on a transparent substrate of a 50 μm thick polyethylene terephthalate film (A4300 manufactured by Toyobo Co., Ltd., easy adhesion layer on both sides) using an extrusion coater. The wet coating was performed under the conditions of 0.5 μm. Subsequently, the coating film was blown with warm air of 110 ° C. for 2 minutes to be dried to form an optical functional layer. Thus, an optical film was produced.

Subsequently, the following evaluation was performed with respect to the produced optical film.
The produced optical film was attached to a fixing jig, and the transmission spectrum of the optical film was measured by a heatable spectrophotometer (V-670 type, 190-2500 nm, manufactured by JASCO Corporation). The temperature of the optical film at the time of measurement was 25 ° C. and 80 ° C., and the measurement wavelength was 2000 nm. The difference in light transmittance at temperatures of 20 ° C. and 80 ° C. was calculated, and the thermochromic properties were evaluated according to the following criteria. The larger the difference in light transmittance, the better.

:: 60% or more ○: 50% or more and less than 60% Δ: 40% or more and less than 50% ×: less than 40%

(4) Haze evaluation of optical film It carried out similarly to the thermochromic evaluation of the said optical film, produced the optical film, using each vanadium dioxide containing particle, respectively, and performed the following evaluation using the produced optical film.
The haze was measured according to JIS K7136 using a haze meter NDH2000 manufactured by Nippon Denshoku Kogyo Co., Ltd., and the value in terms of film thickness 100 μm was evaluated according to the following criteria. The smaller the haze, the better.

:: less than 5 ○: 5 or more and less than 10 Δ: 10 or more and less than 20 ×: 20 or more

(5) Summary As shown in Tables 1 and 2, the vanadium dioxide-containing particles according to the present invention have a smaller average particle size and excellent thermochromic properties than the vanadium dioxide-containing particles of the comparative example. I understand. Furthermore, the optical film produced using the vanadium dioxide containing particle | grains which concern on this invention is also excellent in thermochromic property, and a haze is small compared with the optical film of a comparative example.
Therefore, according to the method for producing vanadium dioxide-containing particles of the present invention, it can be said that vanadium dioxide-containing particles having a small average particle diameter and excellent thermochromic properties can be produced.

Claims (8)

A method for producing vanadium dioxide-containing particles containing vanadium dioxide having thermochromic properties, comprising:
Preparing a reaction solution by mixing at least water and a raw material containing vanadium (V);
Raising the temperature of the reaction solution to within the range of 200 to 250 ° C. from ambient temperature;
Cooling the reaction solution heated to a temperature of 200 to 250 ° C. to 100 ° C. or less;
And D. raising the temperature of the reaction solution cooled to 100 ° C. or less to the hydrothermal reaction temperature to cause a hydrothermal reaction.   The method for producing vanadium dioxide-containing particles according to claim 1, wherein the temperature of the reaction liquid is raised from normal temperature to within a range of 210 to 240 ° C in the step of raising the temperature.   The method for producing vanadium dioxide-containing particles according to claim 1 or 2, wherein the reaction liquid is cooled to 25 ° C or less in the cooling step.   In the step of the hydrothermal reaction, the reaction liquid cooled to 100 ° C. or less is transferred to another apparatus, and then the temperature is raised to the hydrothermal reaction temperature to cause a hydrothermal reaction. The manufacturing method of the vanadium dioxide containing particle | grains as described in any one of Claim 1 to 3.   In the step of raising the temperature, the temperature of the reaction solution is raised from normal temperature to within the range of 200 to 250 ° C. at a temperature rising rate within the range of 5.8 to 15.0 ° C./min. The manufacturing method of the vanadium dioxide containing particle | grains as described in any one of Claim 1- Claim 4.   The said hydrothermal reaction temperature exists in the range of 250-300 degreeC, The manufacturing method of the vanadium dioxide containing particle | grain as described in any one of Claim 1- Claim 5 characterized by the above-mentioned.   The method for producing vanadium dioxide-containing particles according to any one of claims 1 to 6, wherein the reaction liquid is subjected to a hydrothermal reaction for 12 to 72 hours in the step of causing the hydrothermal reaction.   A method for producing a vanadium dioxide-containing particle dispersion, comprising the step of producing vanadium dioxide-containing particles by the method for producing vanadium dioxide-containing particles according to any one of claims 1 to 7.

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