阅读说明：本技术 刺激响应性复合粒子及其制造方法 (Stimulus-responsive composite particle and method for producing same ) 是由 八田政宏 川上浩 于 2018-04-23 设计创作，主要内容包括：本发明提供一种内含供电子性染料前体的微胶囊附着于使供电子性染料前体显色的电子接收性化合物的粒子的表面的至少一部分而成的刺激响应性复合粒子及其制造方法。(The present invention provides a stimulus-responsive composite particle in which a microcapsule containing an electron-donating dye precursor is attached to at least a part of the surface of a particle of an electron-accepting compound that develops the electron-donating dye precursor, and a method for producing the same.)

1. A stimulus-responsive composite particle comprising a microcapsule containing an electron-donating dye precursor and attached to at least a part of the surface of a particle of an electron-accepting compound that develops the electron-donating dye precursor.

2. The stimulus-responsive composite particle of claim 1, for use in any one of a pressure measurement and a thermal measurement.

3. The stimulus-responsive composite particle of claim 1 or 2,

The electron-accepting compound is at least one selected from the group consisting of activated clay, acid clay, kaolin, a phenol compound, a salicylic acid compound, and a hydroxybenzoate.

4. The stimulus-responsive composite particle of any one of claims 1 to 3,

The electron-accepting compound is at least one selected from the group consisting of activated clay, a bisphenol compound, and a salicylic acid compound.

5. The stimulus-responsive composite particle of any one of claims 1 to 4,

The electron accepting compound is activated clay and is used for pressure measurement.

6. The stimulus-responsive composite particle of any one of claims 1 to 4,

The electron-accepting compound is a compound represented by the following general formula (1) and is used for thermal measurement;

In the general formula (1), R¹、R²、R³And R⁴Each independently represents a hydrogen atom, a halogen atom, an amino group, a carboxyl group, a carbamoyl group, a hydroxyl group, an alkylsulfonyl group, an alkyl group or an aryl group; r¹、R²、R³And R⁴Wherein adjacent 2 are optionally bonded to each other to form a ring structure; m represents an n-valent metal atom, and n represents an integer of 1 to 3.

7. The stimulus-responsive composite particle of any one of claims 1 to 6,

The ratio of the mass of the electron-donating dye precursor to the mass of the particles of the electron-accepting compound is 0.02 to 20.

8. The stimulus-responsive composite particle according to any one of claims 1 to 7, having an average circle-equivalent diameter of 1 μm to 500 μm.

9. A method for producing a stimulus-responsive composite particle according to any one of claims 1 to 8,

The method comprises a step of applying a liquid containing microcapsules containing an electron-donating dye precursor to the surface of particles of an electron-accepting compound that develops the electron-donating dye precursor, and granulating the liquid.

10. A method for producing a stimulus-responsive composite particle according to any one of claims 1 to 8,

The method comprises a step of spraying and drying a liquid containing microcapsules containing an electron-donating dye precursor and particles of an electron-accepting compound for developing the electron-donating dye precursor.

Technical Field

The present invention relates to a stimulus-responsive composite particle and a method for producing the same.

Background

Materials that change color in response to stimuli such as pressure and heat have been known and used in various fields. For example, as a material used in the measurement of pressure, there is a pressure measuring film supplied by Fujifilm Corporation and represented by Prescale (trade name; registered trademark). In addition, as a material used in the measurement of the heat distribution, there is a heat distribution measuring film which is similarly supplied from Fujifilm Corporation and is represented by Thermoscale (trade name; registered trademark).

In recent years, the necessity of measuring pressure and heat has been increasing due to higher functionality and higher definition of products.

In view of such a tendency, for example, as a pressure measurement material capable of realizing the visibility and the reading of the concentration with a minute pressure, a pressure measurement material has been proposed in which a difference Δ D in color development concentration between before and after the pressurization at 0.05MPa is 0.02 or more and a color development reaction between an electron-donating leuco dye precursor and an electron-accepting compound is utilized (for example, refer to japanese patent application laid-open No. 2009-.

Further, as a heat distribution indicator capable of indicating a heat distribution having a large temperature difference (for example, 30 ℃ or higher) and having excellent raw material storability, a heat distribution indicator has been proposed, the heat distribution display body comprises a support, an organic polymer composite containing an electron donating dye precursor and a polymer, an electron accepting compound A which develops color of the electron donating dye precursor and has a predetermined structure, an electron accepting compound B having a predetermined structure, and a binder, wherein the content ratio (A: B) of the electron accepting compound A and the electron accepting compound B is 95:5 to 50:50 on a mass basis, and a heat distribution display layer having a content of the electron-accepting compound A in the total electron-accepting compound of 40 mass% or more (see, for example, Japanese patent laid-open No. 2010-181218).

Disclosure of Invention

Technical problem to be solved by the invention

In recent years, demands for measuring pressure, heat, and the like applied in various steps by visual observation have been increasing.

On the other hand, since conventional measuring materials (for example, the pressure measuring material described in japanese patent laid-open No. 2009-019949 and the heat distribution indicator described in japanese patent laid-open No. 2010-181218) have a form of a film, a sheet, or the like, for example, the balance, distribution, size, or the like of pressure or heat on the entire outer surface can be measured by visual observation, but it is difficult to measure the pressure, heat, or the like applied to the inside by visual observation.

An object to be solved by one embodiment of the present invention is to provide stimulus-responsive composite particles having excellent color rendering properties.

Another object of the present invention is to provide a method for producing stimulus-responsive composite particles having excellent color rendering properties.

Means for solving the technical problem

The means for solving the above problems include the following means.

< 1 > a stimulus-responsive composite particle comprising an electron donating dye precursor and, attached to at least a part of the surface of a particle of an electron accepting compound for developing the electron donating dye precursor, a microcapsule containing the electron donating dye precursor.

< 2 > the stimulus-responsive composite particle according to < 1 > for use in any one of pressure measurement and thermal measurement.

< 3 > the stimulus-responsive composite particle according to < 1 > or < 2 >, wherein the electron-accepting compound is at least one selected from the group consisting of activated clay, acid clay, kaolin, a phenolic compound, a salicylic acid compound and a hydroxybenzoate.

< 4 > the stimulus-responsive composite particle according to any one of < 1 > to < 3 >, wherein the electron-accepting compound is at least one selected from the group consisting of activated clay, a bisphenol-based compound and a salicylic acid-based compound.

< 5 > the stimulus-responsive composite particle according to any one of < 1 > to < 4 >, the above-mentioned electron-accepting compound being activated clay, and being used for pressure measurement.

< 6 > the stimulus-responsive composite particle according to any one of < 1 > to < 4 >, wherein the electron-accepting compound is a compound represented by the following general formula (1) and is used for thermal measurement.

[ chemical formula 1]

In the general formula (1), R¹、R²、R³And R⁴Each independently represents a hydrogen atom, a halogen atom, an amino group, a carboxyl group, a carbamoyl group, a hydroxyl group, an alkylsulfonyl group, an alkyl group or an aryl group. R¹、R²、R³And R⁴In (2), adjacent ones may be bonded to each other to form a ring structure. M represents an n-valent metal atom, and n represents an integer of 1 to 3.

< 7 > the stimulus-responsive composite particle according to any one of < 1 > to < 6 >, wherein the ratio of the mass of the electron-donating dye precursor to the mass of the particle of the electron-accepting compound (mass of the electron-donating dye precursor/mass of the particle of the electron-accepting compound) is 0.02 to 20.

< 8 > the stimulus-responsive composite particle according to any one of < 1 > to < 7 > having an average circle equivalent diameter of 1 μm to 500 μm.

< 9 > A method for producing stimulus-responsive composite particles, which is the method for producing stimulus-responsive composite particles according to any one of < 1 > to < 8 >, the method comprising a step of applying a liquid containing microcapsules containing an electron-donating dye precursor to the surface of particles of an electron-receiving compound for developing the electron-donating dye precursor and granulating the liquid.

< 10 > a method for producing stimulus-responsive composite particles, which is a method for producing stimulus-responsive composite particles according to any one of < 1 > to < 8 >, comprising the step of spraying and drying a liquid containing microcapsules containing an electron-donating dye precursor and particles of an electron-accepting compound for developing the electron-donating dye precursor.

Effects of the invention

According to one embodiment of the present invention, a stimulus-responsive composite particle having excellent color rendering properties can be provided.

According to another embodiment of the present invention, a method for producing stimulus-responsive composite particles having excellent color rendering properties can be provided.

Drawings

Fig. 1 is a schematic view of a stimulus-responsive composite particle according to embodiment 1.

Fig. 2 is a schematic view of a stimulus-responsive composite particle according to embodiment 2.

Detailed Description

Hereinafter, an example of an embodiment to which the composite particle and the method for producing the same of the present invention are applied will be described. However, the present invention is not limited to the following embodiments, and can be carried out with appropriate modifications within the scope of the object of the present invention.

In the present invention, the numerical range represented by "to" includes ranges in which the numerical values recited before and after "to" are respectively the minimum value and the maximum value.

In the numerical ranges recited in the present invention, the upper limit or the lower limit recited in a certain numerical range may be replaced with the upper limit or the lower limit recited in another numerical range recited in a stepwise manner. In the numerical ranges recited in the present invention, the upper limit or the lower limit recited in a certain numerical range may be replaced with the values shown in the examples.

in the present invention, a combination of 2 or more preferred embodiments is a more preferred embodiment.

In the present invention, when there are a plurality of substances corresponding to each component, the content of each component is not particularly limited, but refers to the total content of the plurality of substances.

In the present invention, the term "step" includes not only an independent step but also a step that can achieve the intended purpose of the step if the step cannot be clearly distinguished from other steps.

In the present invention, "stimulus" in stimulus responsiveness refers to a physical stimulus given from the outside, such as pressure or heat.

[ stimulus-responsive composite particles ]

The stimulus-responsive composite particles (hereinafter, also simply referred to as "composite particles") of the present invention are formed by attaching microcapsules containing an electron-donating dye precursor to at least a part of the surface of particles of an electron-accepting compound that develops a color of the electron-donating dye precursor.

The composite particle of the present invention has excellent color developability.

Materials that change color in response to stimuli such as pressure and heat have been known and used in various fields. In recent years, the necessity of measuring pressure and heat has been increasing due to higher performance and higher definition of products, and for example, japanese patent laid-open No. 2009-019949 discloses a pressure measuring material capable of reading a density with a minute pressure. However, in the course of increasing demands for measuring pressure, heat, and the like applied in various steps by visual observation, the conventional pressure, heat, and the like measuring materials have a form of a film, a sheet, and the like, including the pressure measuring material described in japanese patent laid-open No. 2009-019949, and thus the pressure, heat, and the like applied to the outside can be measured by visual observation, but it is difficult to measure the pressure, heat, and the like applied to the inside by visual observation.

In contrast, since the composite particles of the present invention have a particle form, when they are mixed or kneaded with a material to be measured, pressure, heat, or the like applied to the inside except the outside can be measured by visual observation. That is, the composite particle of the present invention can be applied to a measurement object that is difficult to measure, in the form of a conventional film, sheet, or the like. Thus, it is very useful in various step studies.

In the composite particle of the present invention, the microcapsule containing the electron-donating dye precursor is attached to at least a part of the surface of the particle of the electron-receiving compound for developing the electron-donating dye precursor, and the position where the electron-donating dye precursor is present and the position where the electron-receiving compound is present are very close to each other, so that the color development reaction is easily caused and the composite particle has excellent color developability.

Further, for example, when pressure is applied to the composite particles of the present invention, the microcapsules are destroyed, and the electron donating dye precursor contained in the microcapsules is brought into contact with the electron accepting compound that develops the color of the electron donating dye precursor, thereby developing the color by a chemical reaction.

In addition, for example, when heat is applied to the composite particle of the present invention, color development is performed by bringing an electron donating dye precursor contained in a microcapsule into contact with an electron accepting compound that develops color of the electron donating dye precursor based on the occurrence of substance permeability in the microcapsule wall by heat or the occurrence of substance permeability in the microcapsule wall by heat, and based on the occurrence of substance permeability in the microcapsule wall by heat.

(Structure of composite particle)

Examples of the form of the composite particles of the present invention include the composite particles of embodiment 1 and the composite particles of embodiment 2, which will be described below.

Hereinafter, the form of the composite particle of the present invention will be described with reference to the drawings. Fig. 1 is a schematic view of a composite particle according to embodiment 1, and fig. 2 is a schematic view of a composite particle according to embodiment 2. In the drawings, the same reference numerals denote the same components.

As shown in fig. 1, the composite particle 1A of embodiment 1 is formed of a particle 10A of an electron-accepting compound and a plurality of microcapsules 20A containing an electron-donating dye precursor, and has a structure in which the plurality of microcapsules 20A containing an electron-donating dye precursor are attached to the surface of the particle 10A of the electron-accepting compound.

As shown in fig. 2, the composite particle 1B of embodiment 2 is formed of a plurality of particles 10B of the electron-accepting compound and a microcapsule 20B containing the electron-donating dye precursor, and has a structure in which the plurality of particles 10B of the electron-accepting compound are attached to the surface of the microcapsule 20B containing the electron-donating dye precursor.

In the composite particles 1A and 1B according to embodiments 1 and 2, since the microcapsules (20A and 20B) containing the electron donating dye precursor are present adjacent to the particles (10A and 10B) of the electron accepting compound that develops the color of the electron donating dye precursor, the electron donating dye precursor and the electron accepting compound are brought into contact with each other, and thus a color development reaction is easily caused, and the composite particles have excellent color developability.

In the composite particles of the present invention, the particles of the electron accepting compound may be present as single particles or may be present as aggregates (for example, aggregates) of a plurality of particles.

In the composite particles of the present invention, the particles of the electron accepting compound may be formed as composite particles with particles of other components than the electron accepting compound, as long as the microcapsules containing the electron donating dye precursor are attached to at least a part of the surface of the particles of the electron accepting compound.

Examples of the other component include, when the electron-accepting compound is an organic compound such as a phenol compound, a hydroxybenzoate, or a salicylic acid compound, a white pigment having an oil absorption property, a sensitizer, and the like.

In the composite particle of the present invention, the proportion of the microcapsule containing the electron donating dye precursor attached to the surface of the particle of the electron accepting compound is not particularly limited as long as the microcapsule is attached to at least a part of the surface of the particle of the electron accepting compound. The microcapsule containing the electron-donating dye precursor may be attached to the surface of the particle of the electron-receiving compound of 1/4 or more, to the surface of 1/2 or more, or to the whole.

The ratio of the mass of the microcapsule containing the electron-donating dye precursor to the mass of the particle of the electron-accepting compound in the composite particle of the present invention (mass of the microcapsule containing the electron-donating dye precursor/mass of the particle of the electron-accepting compound) is not particularly limited, and is, for example, preferably 0.05 to 20, more preferably 0.1 to 10, and further preferably 0.2 to 5, from the viewpoint of the contact property between the particle of the electron-accepting compound and the microcapsule.

The ratio of the mass of the electron donating dye precursor to the mass of the particle of the electron accepting compound in the composite particle of the present invention (mass of the electron donating dye precursor/mass of the particle of the electron accepting compound) is, for example, preferably 0.02 to 20, more preferably 0.05 to 10, and still more preferably 0.1 to 5, from the viewpoint of color developability.

(physical Properties of composite particles)

The average circle-equivalent diameter of the composite particles of the present invention is not particularly limited, but is, for example, preferably 1 μm to 500. mu.m, more preferably 2 μm to 200. mu.m, and still more preferably 5 μm to 100. mu.m.

When the average circle-equivalent diameter of the composite particle of the present invention is 1 μm or more, the handling property is further improved.

When the average circle-equivalent diameter of the composite particle of the present invention is 500 μm or less, the resolution of the stimulus minute portion can be further improved.

The average circle equivalent diameter of the composite particle of the present invention is measured by the following method.

A TEM image of the composite particles, which was obtained by observation with a Transmission Electron Microscope (TEM) was read by an image processing software ImageJ (provided by National Institutes of Health), and subjected to image processing. More specifically, 5 composite particles arbitrarily selected from TEM images of several fields were subjected to image analysis, and the same-area equivalent circle diameter was calculated. The average circle equivalent diameter of the composite particles was obtained by simply averaging (so-called number average) the same area equivalent circle diameters of the 5 obtained composite particles.

(use of composite particles)

since the composite particles of the present invention have a particle form, when they are mixed or kneaded with a material to be measured, it is possible to measure pressure, heat, and the like applied to the inside, which have been difficult to measure by visual observation in the past, in addition to the above. In particular, the composite particles of the present invention have an advantage of being easily mixed or kneaded with a material that is difficult to dissolve in water, and thus can be applied even when the material to be measured is a resin, for example. Thus, the composite particles of the present invention are very useful in various step studies.

For example, in one embodiment of the composite particles of the present invention, since the composite particles have excellent color developability with respect to pressure, when used as a material for pressure measurement, the composite particles can develop color well by pressure and obtain good color developability (i.e., concentration gradient) corresponding to the difference in pressure. Accordingly, the composite particle of the present invention is suitable as a material for pressure measurement.

In one embodiment of the composite particles of the present invention, since the composite particles have excellent color developability with heat, when used as a material for thermal measurement, good color developability (i.e., concentration gradient) corresponding to a temperature difference can also be obtained. Accordingly, the composite particle of the present invention is suitable as a material for thermal measurement.

Specific uses include measurement of a tableting pressure at the time of producing a tablet, measurement of a temperature distribution at the time of drying treatment, and the like, measurement of a heat distribution at the time of heat molding of a resin material, measurement of a pressure distribution at the time of pressure molding of a resin material, and the like.

< microcapsules >

The microcapsule is composed of a capsule wall and a component contained in the capsule wall (hereinafter, also referred to as "capsule content").

The capsule wall and the capsule contents will be described in detail below.

(Capsule wall)

Examples of the capsule wall of the microcapsule include polyethylene, polystyrene, polyethylene, polyurethane, polyurea, polyurethane polyurea, and the like.

The capsule wall is preferably a polymer obtained by using an isocyanate compound and an organic solvent from the viewpoint of storage stability, more preferably a polymer having at least one of a urethane bond and a urea bond, and even more preferably polyurethane polyurea.

(Capsule contents)

Electron donating dye precursors

The microcapsules contain electron donating dye precursors.

The electron donating dye precursor may have a proton (hydrogen ion) such as an electron donating or acid accepting group；H⁺) On the other hand, the color developing property can be used without any particular limitation, and colorless is preferred.

In particular, the electron donating dye precursor has a partial skeleton such as a lactone, a lactam, a sultone, a spiropyran, an ester, or an amide, and when the electron donating dye precursor is brought into contact with an electron accepting compound described later, the partial skeleton is preferably a colorless compound which is opened or cleaved.

Examples of the electron donating dye precursor include compounds such as triphenylmethane phthalide compounds, fluorane compounds, phenothiazine compounds, indolylphthalide compounds, leucoauramine (leucoauramine) compounds, rhodamine lactam compounds, triphenylmethane compounds, diphenylmethane compounds, triazene compounds, spiropyran compounds, fluorene compounds, pyridine compounds, and pyrazine compounds.

As for details of these compounds, reference can be made to the description of Japanese patent application laid-open No. 5-257272.

The microcapsules may contain only one electron donating dye precursor, and may contain two or more kinds from the viewpoint of hue adjustment and the like.

The content of the electron donating dye precursor in the microcapsule is preferably 1 to 100% by mass, more preferably 5 to 99% by mass, and still more preferably 10 to 98% by mass, based on the total mass of the content of the microcapsule, from the viewpoint of color developability, for example.

-solvent-

The microcapsules may contain a solvent (so-called oil component).

In the application to thermal recording paper, pressure-sensitive copying paper, and the like, a known compound can be used as the oil component as the solvent.

Examples of the solvent include aromatic hydrocarbons such as an alkylnaphthalene compound such as diisopropylnaphthalene, a diarylalkane compound such as 1-phenyl-1-ditolylethane, an alkylbiphenyl compound such as isopropylbiphenyl, a triarylmethane compound, an alkylbenzene compound, a benzylnaphthalene compound, a diarylalkylene compound, and an arylindane compound; aliphatic hydrocarbons such as dibutyl phthalate and isoparaffin; natural animal and vegetable oils such as soybean oil, corn oil, cottonseed oil, rapeseed oil, olive oil, coconut oil, castor oil, fish oil, etc.; natural high-boiling fractions such as mineral oil.

When the microcapsule contains a solvent, only one kind of solvent may be contained, or two or more kinds of solvents may be contained.

The content of the solvent in the microcapsule is not particularly limited, and can be appropriately set according to the use of the composite particle.

For example, when the composite particles are used for pressure measurement, the content of the solvent in the microcapsule can be set to a range of 5% by mass to 90% by mass with respect to the total mass of the microcapsule content.

For example, when the composite particles are used for thermal measurement, the content of the solvent in the microcapsule can be set to a range of 0 mass% to 70 mass% with respect to the total mass of the microcapsule content.

Other ingredients-

The microcapsule may contain other components besides the electron-donating leuco dye and the solvent as an arbitrary component.

Examples of the other components include various additives such as an ultraviolet absorber, a light stabilizer, an antioxidant, paraffin wax, an odor inhibitor, and a complementary solvent. The auxiliary solvent will be described later.

The type and content of the additive in the microcapsule are not particularly limited, and can be appropriately set according to the use of the composite particle.

The average primary particle diameter of the microcapsules in the composite particles of the present invention is not particularly limited, and may be, for example, 0.1 μm or more and less than 1000 μm.

The average primary particle diameter of the microcapsules in the composite particles of the present invention can be measured specifically by the following method.

First, the composite particles were observed with a Scanning Electron Microscope (SEM), and 100 microcapsules were arbitrarily selected. Each selected microcapsule was observed, and the particle size was measured to calculate an average value.

The number average wall thickness of the microcapsules in the composite particles of the present invention is not particularly limited, and can be appropriately set according to the application of the composite particles.

The number average wall thickness of the microcapsules in the composite particles of the present invention depends on various conditions such as the type of the wall material of the capsules, the content of the capsule contents, and the particle diameter of the capsules, but can be set in the range of, for example, 10nm to 1000 nm.

The "number average wall thickness of the microcapsules" in the present invention means the thickness (unit: nm) of a resin film (so-called capsule wall) forming the capsule particles of the microcapsules, and the "number average wall thickness" means a value obtained by obtaining and averaging the thicknesses (unit: nm) of the capsule walls of 5 microcapsules by a Scanning Electron Microscope (SEM).

The number average wall thickness of the microcapsules in the composite particle of the present invention can be measured specifically by the following method.

First, a dispersion of composite particles was obtained. The obtained dispersion liquid of the composite particles is applied to an arbitrary support and dried to form a coating film. A cross section of the resulting coating film was formed, the formed cross section was observed by SEM, and arbitrary 5 microcapsules were selected. The average value was calculated by observing the cross section of each selected microcapsule and measuring the thickness of the capsule wall.

As shown in the following formula, the wall thickness of the microcapsule (the thickness of the capsule wall) is governed by the relationship between the capsule wall and the content and the particle diameter of the microcapsule, and can be adjusted according to the particle diameter (average primary particle diameter) of the microcapsule, the density of the capsule wall (wall density), the amounts of the solute, solvent and auxiliary solvent contained in the microcapsule, the densities of the solute, solvent and auxiliary solvent contained in the microcapsule, the amount of the wall material (wall material amount), and the like.

Specifically, the thickness of the capsule wall can be adjusted, for example, by increasing the amounts of the solute, the solvent, and the auxiliary solvent (i.e., the content) contained in the microcapsule.

[ numerical formula 1]

δ＝D×10³/2×{[(S×ρ+W×γ×G)/(S×ρ)]^1/3-1}

δ: thickness of capsule wall [ nm ]

D: particle size of microcapsule [ mu m ]

S: the amounts of solute, solvent and auxiliary solvent contained in the capsule [ Kg ]

ρ: wall Density [ Kg/L ]

W: wall material [ Kg ]

Y: reaction Rate [ - ]

G: the densities (Kg/L) of the solute, solvent and auxiliary solvent contained in the capsule

The median diameter based on the volume standard of the microcapsules in the composite particles of the present invention is not particularly limited, and can be appropriately set according to the use of the composite particles.

For example, when the composite particles are used for pressure measurement, the median particle diameter in terms of volume standard of the microcapsules can be set to a range of 0.1 μm to 200 μm.

For example, when the composite particles are used for thermal measurement, the median particle diameter in terms of volume standard of the microcapsules can be set to a range of 0.1 μm to 10 μm.

In the present invention, the "median diameter of volume standard of microcapsules" means a diameter in which the total volume of particles on the major diameter side and the minor diameter side becomes equal when the particle diameter of the microcapsules whose volume accumulation is 50% is halved as a threshold value.

As for the volume-standard median particle diameter of the microcapsules in the composite particle of the present invention, specifically, it can be measured by the following method.

First, a dispersion of composite particles was obtained. The obtained dispersion liquid of the composite particles is applied to an arbitrary support and dried to form a coating film. The surface of the obtained coating film was photographed at 150 times magnification by an optical microscope, and the size of the microcapsule in all the composite particles in the range of 2cm × 2cm was measured and calculated.

< Electron accepting Compound >

Examples of the electron-accepting compound include clay materials such as activated clay, acid clay, attapulgite, zeolite, bentonite, and kaolin, phenolic compounds, and hydroxybenzoates.

Among these, the electron-accepting compound is preferably at least one selected from the group consisting of activated clay, acid clay, kaolin, a phenol compound (for example, a bisphenol compound), a salicylic acid compound, and a hydroxybenzoate, and more preferably at least one selected from the group consisting of activated clay, a bisphenol compound, and a salicylic acid compound.

Specific examples of the electron-accepting compound include 2, 2-bis (4-hydroxyphenyl) propane [ another name: bisphenol a), 2-bis (4-hydroxyphenyl) hexafluoropropane [ alternative name: bisphenol AF ], 2-bis (p-hydroxyphenyl) pentane, 2-bis (p-hydroxyphenyl) ethane, 2-bis (p-hydroxyphenyl) butane, 2 '-bis (4' -hydroxy-3 ', 5' -dichlorophenyl) propane, 1- (p-hydroxyphenyl) cyclohexane, 1- (p-hydroxyphenyl) propane, 1- (p-hydroxyphenyl) pentane, 1- (p-hydroxyphenyl) -2-ethylhexane, 3, 5-bis (alpha-methylbenzyl) salicylic acid and its polyvalent metal salt, 3, 5-di (tert-butyl) salicylic acid and its polyvalent metal salt, 3-alpha, alpha-dimethylbenzyl salicylic acid and its polyvalent metal salt, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, methyl p-hydroxybenzoate, ethyl p-hydroxyphenyl-1-hydroxyphenyl-propane, 1- (p-hydroxyphenyl) cyclohexane, 1- (p-hydroxyphenyl) propane, 1, 2-ethylhexyl p-hydroxybenzoate, p-phenylphenol, p-cumylphenol, and the like.

For example, when the composite particle of the present invention is used for pressure measurement, activated clay is more preferable as the electron-accepting compound from the viewpoint that the color developability of the composite particle is more excellent.

In addition, for example, when the composite particle of the present invention is used for thermal measurement, a compound represented by the following general formula (1) is more preferable as the electron-accepting compound from the viewpoint that the color developability of the composite particle is more excellent.

The compound represented by the general formula (1) has an advantage that, for example, the effect of lowering the glass transition temperature (Tg) of the capsule wall is small, and a small change in a small temperature difference can be found, and therefore, a difference in color development concentration corresponding to the small temperature difference can be expressed.

[ chemical formula 2]

In the general formula (1), R¹、R²、R³And R⁴Each independently represents a hydrogen atom, a halogen atom, an amino group, a carboxyl group, a carbamoyl group, a hydroxyl group, an alkylsulfonyl group, an alkyl group or an aryl group. R¹、R²、R³And R⁴in (2), adjacent ones may be bonded to each other to form a ring structure. M represents an n-valent metal atom, and n represents an integer of 1 to 3.

In the general formula (1), R¹、R²、R³Or R⁴The alkyl group may be unsubstituted or substituted. Preferably R¹、R²、R³Or R⁴The number of carbon atoms of the alkyl group is 1 to 8. R¹、R²、R³Or R⁴The alkyl group may be linear, branched or cyclic, and may have a substituent such as a phenyl group or a halogen atom.

As R¹、R²、R³Or R⁴Examples of the alkyl group include a methyl group, an ethyl group, a tert-butyl group, a cyclohexyl group, a benzyl group, and a 2-phenylethyl group.

More preferably R¹、R²、R³Or R⁴The alkyl group has a straight-chain or branched-chain structure and has 1 to 4 carbon atoms (wherein the number of carbon atoms does not include a substituent).

R¹、R²、R³Or R⁴the aryl group may be unsubstituted or substituted. R¹、R²、R³Or R⁴The aryl group represented by (a) is preferably a 3-membered, 4-membered, 5-membered or 6-membered ring having 3 to 6 carbon atoms (wherein the number of carbon atoms is not a substituent), and may have a heteroatom.

As R¹、R²、R³Or R⁴Examples of the aryl group include a phenyl group, a tolyl group, a naphthyl group, a 2-furyl group, a 2-thienyl group, and a 2-pyridyl group.

R¹、R²、R³Or R⁴The aryl group represented by (a) is more preferably an aryl group of a 6-membered ring having 6 to 8 carbon atoms (wherein the number of carbon atoms is not a substituent).

As R¹、R²、R³Or R⁴Examples of the halogen atom include a chlorine atom, a bromine atom, and an iodine atom.

Examples of the substituent which the amino group, the carbamoyl group, the alkyl group and the aryl group may further have include a halogen atom, an amino group, a carboxyl group, a carbamoyl group, a hydroxyl group, an alkylsulfonyl group, an alkyl group and an aryl group. The number of carbon atoms of the substituent in the alkylsulfonyl group, the alkyl group, the aryl group, or the like is preferably 1 to 8.

More preferred mode is R¹、R²、R³And R⁴Each independently represents a hydrogen atom, an alkyl group or an aryl group.

As R¹、R²、R³And R⁴In a more preferred combination of (A), R¹Is a hydrogen atom, R²An alkyl group having 2 or 3 carbon atoms (the number of carbon atoms is 8 or 9 when the number of carbon atoms of the phenyl group is included) having a phenyl group, R³is a hydrogen atom, R⁴An alkyl group having 2 or 3 carbon atoms (the number of carbon atoms is 8 or 9 when the number of carbon atoms of the phenyl group is included) having a phenyl group.

In the general formula (1), M represents an n-valent metal atom, and n represents an integer of 1-3.

Examples of M include a sodium atom, a potassium atom, a copper atom, an aluminum atom, a calcium atom, a zinc atom, and the like.

Among them, M is preferably a polyvalent metal atom, i.e., a metal atom having a valence of 2 or more, more preferably an aluminum atom, a calcium atom or a zinc atom, and still more preferably a zinc atom.

Specific examples of the compound represented by the general formula (1) include salts of zinc, aluminum, calcium, copper, and the like such as 4-pentadecylsalicylic acid, 3, 5-bis (. alpha. -methylbenzyl) salicylic acid, 3, 5-di (. alpha. -octyl) salicylic acid, 5-. alpha. - (p-. alpha. -methylbenzylphenyl) ethylsalicylic acid, 3-. alpha. -methylbenzyl-5-tert-octylsalicylic acid, 5-tetradecylsalicylic acid, 4-hexyloxysalicylic acid, 4-cyclohexyloxysalicylic acid, 4-decyloxylsalicylic acid, 4-dodecyloxysalicylic acid, 4-pentadecyloxysalicylic acid, and 4-octadecyloxysalicylic acid.

The shape of the particles of the electron-receiving compound is not particularly limited, and may be any shape such as a sphere, an ellipse Yen, a cube, a needle, or an amorphous shape. The same applies to the case where the particle of the electron accepting compound is an aggregate of a plurality of particles.

The average circle-equivalent diameter of the particles of the electron-accepting compound in the composite particles of the present invention is not particularly limited, and can be appropriately set depending on the application of the composite particles.

For example, when the composite particles are used for pressure measurement, the average circle-equivalent diameter of the particles of the electron-accepting compound can be set to a range of 0.1 μm to 50 μm.

For example, when the composite particles are used for thermal measurement, the average circle-equivalent diameter of the particles of the electron-accepting compound can be set to a range of 0.1 μm to 10 μm.

The average circle-equivalent diameter of the particles of the electron-accepting compound is measured by the following method.

A Transmission Electron Microscope (TEM) image of the particles of the electron accepting compound obtained by observation with a TEM was read with an image processing software ImageJ (provided by national institutes of health, usa), and image processing was performed. More specifically, the same-area equivalent circle diameter was calculated by performing image analysis on 5 particles of the electron accepting compound arbitrarily selected from TEM images at several viewing angles. The equivalent circle diameters of the 5 particles of the electron-accepting compound obtained were simply averaged (so-called number average), and the equivalent circle diameter of the average circle of the particles of the electron-accepting compound was obtained.

The composite particle of the present invention may contain only one kind of electron-accepting compound, or may contain two or more kinds.

The content of the electron-accepting compound in the composite particle of the present invention is not particularly limited, and is, for example, preferably 30 to 3000 parts by mass, and more preferably 50 to 1500 parts by mass with respect to 100 parts by mass of the electron-donating dye precursor from the viewpoint of color development concentration.

[ method for producing stimulus-responsive composite particles ]

The method for producing stimulus-responsive composite particles of the present invention is not particularly limited as long as the stimulus-responsive composite particles described above can be produced.

As the method for producing stimulus-responsive composite particles of the present invention, the method for producing stimulus-responsive composite particles of embodiment 1 (hereinafter, simply referred to as "the method for producing embodiment 1") described below is preferred from the viewpoint that the stimulus-responsive composite particles described above are easily obtained and the obtained stimulus-responsive composite particles are more excellent in color developability.

Hereinafter, each step in the manufacturing method of embodiment 1 will be described in detail. The types and preferred embodiments of the components used in the respective steps are the same as those described in the section "stimulus-responsive composite particles", and therefore, the description thereof may be omitted here.

[ production method of embodiment 1]

The production method of embodiment 1 includes a step of applying a liquid containing microcapsules containing an electron-donating dye precursor to the surface of particles of an electron-accepting compound that develops an electron-donating dye precursor to granulate the particles (hereinafter also referred to as a "granulation step").

< granulation Process >

The granulation step is a step of applying a liquid containing microcapsules containing an electron donating dye precursor (hereinafter, also simply referred to as "microcapsule-containing liquid") to the surface of particles of an electron accepting compound for developing an electron donating dye precursor.

In the granulation step, the stimulus-responsive composite particles of the present invention in which microcapsules containing an electron-donating dye precursor are attached to at least a part of the surface of the particles of the electron-accepting compound are produced.

The amount of the microcapsule-containing liquid to be applied to the surface of the particle of the electron-accepting compound is not particularly limited as long as the amount is such that the particle in the form of a microcapsule containing the electron-donating dye precursor is attached to at least a part of the surface of the particle of the electron-accepting compound.

The amount of the microcapsule-containing liquid to be applied to the surface of the particle of the electron-accepting compound is not particularly limited, and for example, the mass of the electron-donating dye precursor contained in the microcapsule-containing liquid is preferably in the range of 0.03 to 3 times, and more preferably in the range of 0.05 to 2 times, the mass of the electron-donating dye precursor relative to the mass of the particle of the electron-accepting compound, from the viewpoint of color developability.

As long as the microcapsule-containing liquid can be applied to the surfaces of the particles of the electron-accepting compound, the object to which the microcapsule-containing liquid is applied may be a single particle composed of the electron-accepting compound, an aggregate in which a plurality of single particles composed of the electron-accepting compound are aggregated, or a composite particle composed of a single particle composed of the electron-accepting compound and a particle composed of a component other than the electron-accepting compound.

When the particles of the electron-accepting compound are fine particles, it is preferable to use a granulator to granulate the particles of the electron-accepting compound in advance, that is, to use an aggregate of a plurality of particles as a target to be provided with the microcapsule-containing liquid.

When the electron-accepting compound is an organic compound such as a phenol compound, a hydroxybenzoate, or a salicylic acid compound, composite particles of the electron-accepting compound and particles of another component such as a white pigment having an oil absorption property or a sensitizer, which are obtained by granulating particles of the electron-accepting compound and particles of another component using a granulator, may be used as the target for applying the microcapsule-containing liquid.

The details of the components other than the electron-accepting compound are as described above.

Examples of a method for applying the microcapsule-containing liquid to the surface of the particles of the electron-accepting compound include a method using a granulator. The method of applying the microcapsule-containing liquid to the surface of the particles of the electron-accepting compound using the granulator is not particularly limited, and can be appropriately set depending on the amount of the electron-accepting compound, the physical strength of the electron-accepting compound, and the like.

Examples of the method for applying the microcapsule-containing liquid to the surface of the particles of the electron-accepting compound to granulate the particles include a fluidized bed granulation method, a spray drying method, and a stirring granulation method.

Among these, a fluidized bed granulation method is preferable as a method of applying a microcapsule-containing liquid to the surface of particles of the electron-receiving compound to granulate the particles.

According to the fluidized bed granulation method, the microcapsule-containing liquid can be uniformly applied to the particles of the electron-receiving compound from each direction by allowing the particles of the electron-receiving compound to flow in the air, and the removal of the volatile component such as the solvent and the application of the microcapsule-containing liquid to the particles of the electron-receiving compound can be performed together.

Examples of the fluidized bed granulation method include a rotary fluidized bed granulation method, a jet fluidized bed granulation method, a bottom-spray (Wurster) fluidized bed granulation method, a mechanical agitation combined type fluidized bed granulation method, and the like.

Examples of the granulator that can be used in the fluidized bed granulation method include a fluidized bed granulator, a rotary fluidized bed granulator, a jet fluidized bed granulator, and a mechanically-stirred composite fluidized bed granulator.

Specific examples of the pelletizer include a fluid bed pelletizer of powrex corp (model: FD-MP-01), a flow coater of free corp (model: FL-1), and the like.

The supply temperature of the gas to be supplied to the granulator is, for example, preferably 30 to 150 ℃, more preferably 40 to 120 ℃, and still more preferably 50 to 100 ℃.

The speed and time for applying the microcapsule-containing liquid to the surface of the particle of the electron-accepting compound are not particularly limited, and can be appropriately set according to the content of the microcapsule in the microcapsule-containing liquid, the viscosity of the microcapsule-containing liquid, and the like, for example.

The amount of the solvent such as water remaining in the stimulus-responsive composite particles obtained through the granulation step is not particularly limited, and can be appropriately set according to the application of the stimulus-responsive composite particles, for example.

< other working procedures >

In the production method according to embodiment 1, a step of forming microcapsules containing electron donating dye precursors (hereinafter, also referred to as a "microcapsule forming step") is preferably provided before the granulation step.

(microcapsule Forming Process)

In the microcapsule forming step, microcapsules containing an electron donating dye precursor are formed.

The microcapsule forming step preferably includes the following steps. Namely, a step of preparing an emulsion by dispersing an oil phase containing an electron donating dye precursor and a wall material in an aqueous phase containing an aqueous medium (hereinafter, also referred to as "emulsification step"), and a step of forming microcapsules containing an electron donating dye precursor by polymerizing the wall material forming the wall of the microcapsules (i.e., the capsule wall) at the interface between the oil phase and the aqueous phase to form the capsule wall (hereinafter, also referred to as "encapsulation step").

-an emulsification procedure-

In the emulsification step, an emulsion can be prepared by dispersing an oil phase containing the electron-donating dye precursor and the wall material in an aqueous phase containing an aqueous medium.

The oil phase at least comprises an electron-donating dye precursor and a wall material.

Details of the electron donating dye precursor are as described above.

Examples of the wall material forming the capsule wall include isocyanate compounds and silane coupling agents. Among them, the wall material is preferably an isocyanate compound, and more preferably an isocyanate compound having 2 or more isocyanate groups in 1 molecule.

Examples of the isocyanate compound include m-phenylene diisocyanate, p-phenylene diisocyanate, 2, 6-tolylene diisocyanate, 2, 4-tolylene diisocyanate, naphthalene-1, 4-diisocyanate, diphenylmethane-4, 4' -diisocyanate, 3' -dimethoxy-biphenyl diisocyanate, 3' -dimethyldiphenylmethane-4, 4' -diisocyanate, xylylene-1, 4-diisocyanate, xylylene-1, 3-diisocyanate, 4-chloroxylylene-1, 3-diisocyanate, 2-methylxylylene-1, 3-diisocyanate, 4' -diphenylpropane diisocyanate, 4,4 '-diphenylhexafluoropropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1, 2-diisocyanate, butene-1, 2-diisocyanate, cyclohexylene-1, 3-diisocyanate, cyclohexylene-1, 4-diisocyanate, dicyclohexylmethane-4, 4' -diisocyanate, 1, 4-bis (isocyanotomethyl) cyclohexane and 1, 3-bis (isocyanotomethyl) cyclohexane, isophorone diisocyanate, lysine diisocyanate, and the like.

The diisocyanate compound as the 2-functional isocyanate compound has been exemplified above, but triisocyanate compounds as the 3-functional isocyanate compound and tetraisocyanate compounds as the 4-functional isocyanate compound, which are analogized from these, may be used as the wall material.

The wall material may be an adduct of the isocyanate compound and a 2-functional alcohol such as an ethylene glycol compound or a bisphenol compound, or a phenol.

Examples of the condensate, polymer or adduct using an isocyanate compound include a 3-mer biuret or isocyanurate of the above 2-functional isocyanate compound, a compound which is polyfunctional as an adduct of a polyol such as trimethylolpropane and a 2-functional isocyanate compound, a formaldehyde condensate of phenyl isocyanate, a polymer of an isocyanate compound having a polymerizable group such as methacryloyloxyethyl isocyanate, lysine triisocyanate, and the like.

The isocyanate compound is described in "handbook of polyurethane resin" (published by Nissan GmbH, Japan Industrial News Co., Ltd. (1987)).

Among the above, the wall material forming the capsule wall preferably contains an isocyanate compound having 3 or more functions.

Examples of the 3-or more-functional isocyanate compound include 3-or more-functional aromatic isocyanate compounds, 3-or more-functional aliphatic isocyanate compounds, and the like.

The 3-or more-functional isocyanate compound is preferably an adduct (adduct) of a 2-functional isocyanate compound (a compound having 2 isocyanate groups in a molecule) and a compound having 3 or more active hydrogen groups in a molecule (a polyol, a polyamine, a polythiol, or the like having 3 or more functions), a 3-or more-functional isocyanate compound (an adduct-type 3-or more-functional isocyanate compound), a 3-mer of a 2-functional isocyanate compound (a biuret-type or isocyanurate-type 3-or more-functional isocyanate compound), or the like.

Examples of the 3-or more-functional isocyanate compound include xylylene-1, 4-diisocyanate, an adduct of xylylene-1, 3-diisocyanate and trimethylolpropane, a biuret compound, and an isocyanurate compound.

As the adduct type isocyanate compound having 3 or more functions, commercially available products can be used.

Examples of commercially available products of adduct type isocyanate compounds having 3 or more functional groups include Takenate (registered trademark) D-102, D-103H, D-103M2, P49-75S, D-110N, D-120N (isocyanate value: 3.5mmol/g) from Mitsui Chemicals, Inc., D-140N, D-160N, Sumika Bayer Urethane Co., Desmodur (registered trademark) L75, UL57SP, Nippon Polyurethane Industry Co., CORONATE (registered trademark) HL, HX, L, P301-75E from Asahi Kasei CORPORATION, BURNOCK (registered trademark) D-750 from DIC CORATION, and the like.

Among them, the adduct type 3-or higher-functional isocyanate compound is more preferably at least one selected from the group consisting of Takenate (registered trademark) D-110N, D-120N, D-140N and D-160N of Mitsui Chemicals, Inc.

As the isocyanurate type 3-or higher-functional isocyanate compound, commercially available products can be used.

Examples of commercially available isocyanurate type 3-or more-functional isocyanate compounds include Takenate (registered trademark) D-127N, D-170N, D-170HN, D-172N, D-177N, SUMIDUR N3300, Desmodur (registered trademark) N3600, N3900, Z4470BA, Nippon Polyurethane Industry Co., Ltd, CORONATE (registered trademark) HX, HK, DURANATE (registered trademark) TPA-100, TSA-100, TSS-100, TLA-100, TSE-100, and the like, which are available from Mitsui Chemicals, Inc.

As the biuret type 3-or higher-functional isocyanate compound, commercially available products can be used.

Examples of commercially available products of biuret type 3-or higher-functional isocyanate compounds include Takenate (registered trademark) D-165N, NP1100 from Mitsui Chemicals, Inc., Desmodur (registered trademark) N3200 from Covestro Japan Ltd., and DURANATE (registered trademark) 24A-100 from Asahi Kasei corporation.

The oil phase may contain a solvent, an additive, and the like as needed.

The details of the solvent and the additive are as described above.

In addition, the oil phase may contain a supplementary solvent from the viewpoint of improving solubility of the oil phase in the wall material. The auxiliary solvent does not contain the above-mentioned solvent (so-called oil component).

Examples of the auxiliary solvent include ketone compounds such as methyl ethyl ketone, ester compounds such as ethyl acetate, and alcohol compounds such as isopropyl alcohol. The boiling point of the auxiliary solvent is preferably 130 ℃ or lower.

The aqueous phase preferably comprises an aqueous medium and comprises an emulsifier.

Examples of the aqueous medium include water, alcohol, and a mixture of water and alcohol, and water is preferred.

The water is not particularly limited, and examples thereof include ion-exchanged water.

The emulsifier comprises a dispersant or a surfactant or a combination thereof.

Examples of the dispersant include polyvinyl alcohol and modified products thereof, polyacrylic acid amide and derivatives thereof, ethylene-vinyl acetate copolymers, styrene-maleic anhydride copolymers, ethylene-maleic anhydride copolymers, isobutylene-maleic anhydride copolymers, polyvinylpyrrolidone, ethylene-acrylic acid copolymers, vinyl acetate-acrylic acid copolymers, carboxymethyl cellulose, methyl cellulose, casein, gelatin, starch and derivatives thereof, gum arabic, and sodium alginate.

Among them, polyvinyl alcohol is preferable as the dispersant.

The dispersant is preferably not reacted with the wall material or extremely hardly reacted, and when a dispersant having a reactive amino group (for example, gelatin) is used in the molecular chain, it is preferable to perform a treatment for making the dispersant lose reactivity in advance.

The surfactant is not particularly limited, and conventionally known surfactants can be used.

Examples of the surfactant include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants.

When the aqueous phase contains an emulsifier, only one kind of emulsifier may be contained, or two or more kinds may be contained.

Further, the emulsifier is preferably contained in the aqueous phase, but may be contained in the oil phase.

The aqueous phase may contain other components such as ultraviolet absorbers, antioxidants, preservatives and the like as required.

In the production method of embodiment 1, the total amount of components (hereinafter, also referred to as "total solid content") obtained by removing the solvent, the auxiliary solvent, and the aqueous medium from the components contained in the oil phase (hereinafter, also referred to as "oil phase components") and the components contained in the aqueous phase (hereinafter, also referred to as "aqueous phase components") corresponds to the total solid content of the microcapsules to be produced.

The content of the electron-donating dye precursor in the oil phase is not particularly limited, and may be set to 5 to 95% by mass based on the total solid content, for example.

The content of the wall material in the oil phase is not particularly limited, and is appropriately set in consideration of the size, thickness, and the like of the microcapsule. The content of the wall material in the oil phase can be set to, for example, 5 to 80% by mass relative to the total solid content.

The content of the solvent in the oil phase is not particularly limited, and can be appropriately set according to the kind, amount, and the like of the components contained in the oil phase. The content of the solvent in the oil phase may be set to 0% by mass to 80% by mass, for example, with respect to the total solid content.

The content of the auxiliary solvent in the oil phase is not particularly limited, and can be appropriately set according to the type, amount, and the like of the wall material contained in the oil phase component. When the oil phase contains the auxiliary solvent, the content of the auxiliary solvent in the oil phase can be set to more than 0 part by mass and 500 parts by mass with respect to 100 parts by mass of the wall material, for example.

When the oil phase contains an additive, the content of the additive in the oil phase is not particularly limited and can be appropriately set according to the type of the additive and the like.

The content of the aqueous medium in the aqueous phase is not particularly limited, and may be appropriately set according to the kind, amount, and the like of the components contained in the aqueous phase.

The content of the emulsifier in the aqueous phase is not particularly limited, and can be appropriately set according to the use of the composite particles.

For example, when the composite particles are used for pressure measurement, the content of the emulsifier in the aqueous phase can be set to a range of 1% by mass to 40% by mass relative to the total mass of the oil phase component and the aqueous phase component.

For example, when the composite particles are used for thermal measurement, the content of the emulsifier in the aqueous phase can be set to a range of 2 to 50 mass% with respect to the total mass of the oil-phase component and the aqueous-phase component.

The method of preparing an emulsion by dispersing an oil phase in an aqueous phase is not particularly limited, and examples thereof include a method using a known emulsifying apparatus (e.g., a disperser) such as a homogenizer, Manton Gaulin (Manton Gaulin), an ultrasonic disperser, a dissolver (dispolver), and a Keddymill (Keddymill).

The amount of the oil phase component is preferably 0.1 to 1.5, more preferably 0.2 to 1.2, and further preferably 0.4 to 1.0 on a mass basis with respect to the amount of the water phase component (amount of the oil phase component/amount of the water phase component).

When the amount of the oil phase component is within the above range relative to the amount of the water phase component, the viscosity of the emulsion can be appropriately maintained, and the emulsion is excellent in the production suitability and the stability.

Encapsulation procedure

In the encapsulation step, a wall material forming a wall of the microcapsule (i.e., a capsule wall) is polymerized at an interface between the oil phase and the water phase to form a capsule wall, thereby forming a microcapsule containing the electron donating dye precursor. The microcapsules may be obtained in the form of a microcapsule-containing liquid (i.e., a microcapsule-containing liquid).

The polymerization is carried out by polymerizing the wall material of the oil phase contained in the emulsion at the interface with the aqueous phase, preferably under heating.

The polymerization temperature varies depending on the kind of wall material, etc., but is usually preferably from 40 ℃ to 100 ℃ and from 50 ℃ to 80 ℃.

The polymerization time varies depending on the kind of the wall material, but is usually about 0.5 to 10 hours, preferably about 1 to 5 hours.

The higher the polymerization temperature, the more the polymerization time can be shortened, but when a content or wall material which is likely to decompose at a high temperature is used, it is preferable to select a polymerization initiator which functions at a low temperature and polymerize at a relatively low temperature.

for example, when a silane coupling agent is used as the wall material, the polymerization temperature is preferably 15 to 40 ℃, more preferably 20 to 30 ℃, and the polymerization time is preferably 1 to 40 hours, more preferably 5 to 30 hours.

In order to prevent the microcapsules from agglomerating with each other during polymerization, it is preferable to further add an aqueous medium (water, an aqueous acetic acid solution, or the like) to reduce the probability of collision between the microcapsules. In addition, sufficient stirring is also preferable. In addition, a dispersant for preventing coagulation may be added in advance during the polymerization. If necessary, a charge control agent such as nigrosine or other optional auxiliary agents may be added. The supplementary agent can be added at the time of capsule wall formation or at any point.

the average primary particle diameter of the microcapsules in the microcapsule-containing liquid is preferably 0.1 μm or more and less than 1000. mu.m.

The average primary particle size of the microcapsules can be further adjusted by changing the dispersion conditions in the emulsification step.

The particle size of the microcapsules in the microcapsule-containing liquid can be measured using any measuring machine, for example, micro track MT3300EXII from Nikkiso co.

The median particle diameter of the microcapsules in the microcapsule-containing liquid on a volume basis is not particularly limited, and can be appropriately set according to the use of the composite particles.

For example, when the composite particles are used for pressure measurement, the median particle diameter of the microcapsules in the microcapsule-containing liquid on a volume basis can be set in the range of 1 μm to 100 μm.

For example, when the composite particles are used for thermal measurement, the median particle diameter of the microcapsules in the microcapsule-containing liquid on a volume basis can be set to a range of 0.1 μm to 10 μm.

The median particle diameter of the microcapsules on a volume basis can be controlled by changing the dispersion conditions in the emulsification step.

The median particle diameter on a volume basis of the microcapsules in the microcapsule-containing liquid may be measured using a laser diffraction/scattering type particle size distribution measuring apparatus. As the laser diffraction/scattering type particle size distribution measuring apparatus, for example, microtrack MT3300EXII (Nikkiso co., Ltd.) can be used. However, the measuring device is not limited thereto.

The number average wall thickness of the microcapsules in the microcapsule-containing liquid is not particularly limited, and can be appropriately set according to the use of the composite particles.

For example, the number average wall thickness of the microcapsules in the microcapsule-containing liquid can be set to a range of 10nm to 1000 nm.

The number average wall thickness of the microcapsules can be adjusted by the particle diameter of the microcapsules, the density of the capsule wall (wall density), the amounts of the solvent and the auxiliary solvent in the microcapsules, the densities of the solvent and the auxiliary solvent in the microcapsules, the amount of the wall material in the microcapsules (wall material amount), and the like, as described above.

The number average wall thickness of the microcapsules in the microcapsule-containing liquid can be measured by the following method.

First, a microcapsule-containing liquid is coated on an arbitrary support and dried to form a coating film. A cross section of the resulting coating film was formed, the formed cross section was observed by SEM, and arbitrary 5 microcapsules were selected. The average value was calculated by observing the cross section of each selected microcapsule and measuring the thickness of the capsule wall.

[ production method of second embodiment ]

As a manufacturing method of another embodiment other than the manufacturing method of embodiment 1, for example, a manufacturing method of a second embodiment described below can be given.

Hereinafter, each step in the manufacturing method of the second embodiment will be described in detail. The types and preferred embodiments of the components used in the respective steps are as described in the section "stimulus-responsive composite particles", and therefore, the description thereof is omitted here.

The production method of the second embodiment is a production method of stimulus-responsive composite particles including a step of spraying and drying a liquid containing a microcapsule containing an electron donating dye precursor and particles of an electron accepting compound for developing the electron donating dye precursor (hereinafter also referred to as "spray drying step").

< spray drying Process >

The spray drying step is a step of spraying and drying a liquid containing at least microcapsules containing an electron donating dye precursor and particles of an electron accepting compound for developing the electron donating dye precursor (hereinafter, also referred to as "spray liquid").

In the spray drying step, the stimulus-responsive composite particles of the present invention in which microcapsules containing an electron-donating dye precursor are attached to at least a part of the surface of the particles of the electron-accepting compound are produced.

The spray liquid may contain other components such as a sensitizer, an oil-absorbing pigment, and an ultraviolet absorber, as needed, in addition to the microcapsules containing the electron-donating dye precursor and the electron-receiving compound.

The content of the microcapsules in the spray liquid is not particularly limited, and can be appropriately set according to the use of the composite particles.

For example, when the composite particles are used for pressure measurement, the content of the microcapsules in the spray liquid can be set to a range of 2 to 40 mass% with respect to the total mass of the spray liquid.

For example, when the composite particles are used for thermal measurement, the content of the microcapsules in the spray liquid can be set to a range of 1 mass% to 30 mass% with respect to the total mass of the spray liquid.

The content of the particles of the electron-accepting compound in the spray liquid is not particularly limited, and can be appropriately set according to the use of the composite particles.

For example, when the composite particles are used for pressure measurement, the content of the particles of the electron accepting compound in the spray liquid can be set to a range of 3 to 40 mass% with respect to the total mass of the spray liquid.

For example, when the composite particles are used for thermal measurement, the content of the particles of the electron accepting compound in the spray liquid can be set to a range of 2 mass% to 30 mass% with respect to the total mass of the spray liquid.

The solid content concentration of the spray liquid is not particularly limited, and is preferably 5 to 50 mass%, for example.

The temperature of the spray liquid is not particularly limited, and may be appropriately set according to the kind and amount of each component contained in the spray liquid, for example.

The method of spraying and drying the spray liquid is not particularly limited, and a known spray dryer (so-called spray dryer) may be used.

Specific examples of the spray dryer include a tray type spray dryer (type: L-8 i) of OKAWARA KAKOHKI CO.

The spraying speed of the spray liquid is not particularly limited, and may be appropriately set according to the viscosity of the spray liquid, for example.

The drying temperature is, for example, preferably 30 to 150 ℃ and more preferably 40 to 100 ℃.

< other working procedures >

The production method of the second embodiment preferably includes a step of forming microcapsules containing the electron-donating dye precursor (i.e., a microcapsule forming step) before the spray drying step.

The microcapsule forming step is as described in the section "production method of embodiment 1", and therefore, the description thereof is omitted here.

The microcapsule-containing liquid obtained in the microcapsule-forming step and the particles of the electron-accepting compound are mixed, and the resulting mixture can be used as a spray liquid in the spray-drying step.

In addition, the method of producing stimulus-responsive composite particles according to embodiment 1 is more preferable in that stimulus-responsive composite particles having higher responsiveness to a stimulus and exhibiting more excellent color rendering properties can be obtained.