JP2003113249A - Temperature-sensitive fine particle composition and sheet of temperature-sensitive fine particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display element having good contrast and a rapid thermoresponse rate, and further to provide a temperature-sensitive fine particle composition facilitating handling and production. SOLUTION: This temperature-sensitive fine particle composition is obtained by encapsulating an uncross-linked polymeric material having the lower limit critical eutectic temperature and changing the appearance between transparent and opaque states by sandwiching the boarder of the temperature, and a liquid in a microcapsule. A coloring matter can be mixed therewith, and microcapsules including different uncross-linked polymers having the different lower limit critical eutectic temperatures can be mixed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature-sensitive fine particle composition for use in display elements, light control elements, temperature-sensitive image display materials, etc., whose transparency is changed by thermal stimulation.

[0002]

2. Description of the Related Art Conventionally, stimuli-responsive gels that undergo repeated volume changes (swelling, contraction) upon application of stimuli such as heat, light, current, electric field, and pH have been generally known, and have been used as various functional materials. Attempts are being made to use it in the field. In particular, temperature-responsive gels such as cross-linked poly-N-isopropylacrylamide that responds to thermal stimuli have been actively studied for application to drug delivery, and many applications to display materials and light control materials have been attempted. As an example, a light control material using poly N-isopropylacrylamide gel (Japanese Patent Laid-Open No. 11-228850, 61-148423).
JP-A-61-148824, JP-A-61-1414
8425, JP-A-61-148426, JP-A-61
No. 149925 and JP-A No. 61-149926). In this case, the cross-linked poly-N-isopropylacrylamide has an LCST (lower critical solution temperature), so that the gel swells at a temperature of LCST or lower and contracts at a temperature of LCST or higher,
The optical properties were changed by the difference in particle diameter due to the contraction and expansion, and it was used as a light control material.

However, in this method, the crosslinked poly-N-isopropylacrylamide gel has a problem that it is difficult to shrink / expand when the heating rate is too high when the temperature rises. It is said that when the temperature rising rate is high, a temperature difference occurs between the outside and the inside of the crosslinked poly-N-isopropylacrylamide gel particles, and only the outside contracts first and the inside contracts. In order to shrink / expand, a slow temperature rising rate of about 1 ° C./min is required, which causes a problem of slow display response speed. Further, it is known that the cross-linked poly-N-isopropylacrylamide becomes insoluble in water and precipitates as fine particles and becomes cloudy when the temperature is raised to a temperature of LCST or higher. However, since the polymer is crosslinked, the polymer is actually insoluble in water even at a temperature of LCST or lower, and the difference in the degree of transparency / opacity at the temperature of LCST or lower / above is small and the contrast is low. .

Also, when uncrosslinked poly-N-isopropylacrylamide is used, it becomes insoluble in water above the LCST and fine particles appear, causing light scattering and clouding. This method gives higher contrast than cross-linked poly (N-isopropylacrylamide), but it was not enough yet. Further, if the light control element is made thick to obtain sufficient contrast, there is a problem that the response speed becomes slow.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems, an object of the present invention is to provide a display element having a good contrast and a high thermal response speed. Further, the temperature sensitivity is easy to handle and easy to manufacture. An object is to provide a fine particle composition.

[0006]

DISCLOSURE OF THE INVENTION As a result of investigations, the inventors of the present invention found that LCS was used as a material whose transparency is changed by thermal stimulation.
It was found that a temperature-sensitive fine particle composition capable of solving the above problems can be obtained by encapsulating an uncrosslinked polymer material having T (lower critical eutectic temperature) in microcapsules, and to complete the present invention. I arrived.

That is, the first feature of the present invention is that "an uncrosslinked polymer material having a lower critical eutectic temperature and changing to transparent or opaque at that temperature and a liquid are contained in microcapsules. The temperature-sensitive fine particle composition.

A second aspect of the present invention is based on the first aspect of the invention.
Further, the temperature-sensitive fine particle composition is characterized in that a colorant is encapsulated in microcapsules.

A third aspect of the present invention is the microcapsule according to the first or second aspect of the invention, characterized in that microcapsules containing uncrosslinked polymer materials having different lower critical eutectic temperatures are mixed. It is a temperature-sensitive fine particle composition.

In a fourth aspect of the present invention, the temperature-sensitive fine particle composition described in any one of the first to third aspects of the invention is prepared by adding a water-based cross-linking polymer, a water-soluble polymer or water having no lower critical eutectic temperature. A temperature-sensitive fine particle composition characterized by being dispersed in a dispersible polymer.

A fifth aspect of the present invention is a temperature-sensitive fine particle sheet characterized in that the temperature-sensitive fine particle composition described in any of the first to fourth inventions is arranged on a substrate. is there.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The temperature-sensitive fine particle composition of the present invention is characterized by having a lower critical eutectic temperature, and encapsulating an uncrosslinked polymer material and a liquid which change to transparent or opaque at the temperature in microcapsules. .

Examples of the temperature-sensitive fine particle composition of the present invention are shown in FIGS.
Shown in. FIG. 1 is a view showing a microcapsule film 1 in which a liquid 2 and a polymer material 3 which changes to transparent or opaque according to temperature are enclosed. FIG. 2 is a view showing the composition of FIG. 1 in which the liquid 2, the polymeric material 3, and the colorant 4 are enclosed.

The display principle of the present invention will be described below. In the case of the particles of FIG. 1, at low temperature, the uncrosslinked polymer is dissolved in water, which is a liquid, and the particles of FIG. 1 are transparent. When the temperature is increased and the LCST temperature is exceeded, the uncrosslinked polymer becomes insoluble in water and becomes cloudy. By changing the state between transparent and opaque in this way, display becomes possible. According to this method, the concentration of the polymer having LCST can be increased in the microcapsule as compared with the case where the microcapsule is not provided. Therefore, there is an advantage that the opacity can be significantly increased at LCST or higher. In the case of the particles of FIG. 2, at low temperature, the uncrosslinked polymer is dissolved in water, which is a liquid, and therefore displays the color of the colorant. When the temperature is increased and the LCST is exceeded, the uncrosslinked polymer becomes insoluble in water and becomes cloudy. For this reason, the colorant inside the particles is hidden and white display is performed, and colorant color / white can be displayed.

Further, when two or more kinds of temperature-sensitive fine particle compositions having different LCSTs are prepared and each is colored with a different color, two or more kinds of colors can be displayed at the heating temperature. For example, by coloring the lower LCST polymer in blue, FIG.
A fine particle composition such as the above is prepared, and the other fine particle composition having a high LCST is colored red. Furthermore, when these two kinds of fine particle compositions were mixed and randomly arranged and observed, LCS
A purple color is observed at a temperature of T or lower. Where L of both
When heated to a temperature between CST, the blue particles with low LCST become cloudy and white, while the other red particles remain red because the temperature is still lower than LCST, and thus the two temperature-sensitive In the state where the fine particulate composition is lined up, it looks light red. Furthermore, when the temperature of the red temperature-sensitive fine particle composition is heated to a temperature equal to or higher than the LCST, the red temperature-sensitive fine particle composition also becomes cloudy and white, and thus appears white. This means that purple, red, and
It becomes possible to display three colors of white. The colors for coloring these temperature-sensitive fine particle compositions are not limited to blue and red. That is, various colors can be changed depending on the combination. When three or more colored fine particle compositions are combined, the types of colors that can be changed are further increased. With this method, multicolor display can be performed by a simple method as compared with the case where the microcapsules are not enclosed.

Next, constituent materials of the temperature-sensitive fine particle composition of the present invention and a method for producing the same will be described. In the present invention L
As the polymer material having CST (lower critical eutectic temperature), polyalkyl-substituted (meth) acrylamide such as poly-N-isopropyl (meth) acrylamide or a copolymer of alkyl-substituted (meth) acrylamide and (meth) acrylic acid , (Meth) acrylamide, copolymers with (meth) acrylic acid alkyl ester, and the like, and alkyl-substituted cellulose derivatives such as polyvinyl methyl ether, methyl cellulose, ethyl cellulose, and hydroxypropyl cellulose.

The polymer material having these LCSTs can be produced by a general polymerization method such as precipitation polymerization, W / O emulsion polymerization method, reverse phase suspension polymerization method or solution polymerization method.

As the liquid used in the composition of the present invention, water, an aqueous electrolyte solution, alcohol, a water-soluble solvent or a mixture thereof can be used.

When coloring materials such as pigments and dyes are added to these fine particle compositions for coloring, the coloring method is as follows. Preferably. Examples of the coloring material used for coloring include various pigments and dyes, basic dyes, acid dyes, disperse dyes, reactive dyes, direct dyes,
Inorganic pigments such as fluorescent dyes, carbon black and titanium white, and organic pigments are preferable. Specific examples of these structures include azo-based, bisazo-based, triazo-based, anthraquinone-based, triphenylmethane-based, stilbene-based, ferrocyanine compounds, cobalt oxide compounds, phthalocyanine compounds, isoindolinone compounds, and molybten compounds. Examples include pigments and dyes.

The microcapsules, which are one of the constituent elements of the present invention, can be prepared by chemical methods (interfacial polymerization method, insolubilization reaction method),
It can be prepared by a physical method (spray drying method, fluidized bed method), a physicochemical method (phase separation method, interfacial precipitation method) or the like. The capsule film is preferably a polymer film, and is preferably a light transmissive film. Preferred materials for the microcapsule membrane are diamine, a reaction product of diol and acid dichloride, alginic acid, bectic acid, calcium salt of carboxymethyl cellulose, gelatin, gum arabic, polystyrene resin, polyvinyl acetate resin, cellulose acetate butyrate resin. , Cellulose resin, polymethylmethacrylate, polyester, polyamide, polyurethane, polyurea, polyether, polyvinyl alcohol, and the like. Among these, calcium alginate, polyamide, polyurethane and polyurea are preferable.

As a specific method for producing the microparticles of the present invention, a mixture of a preliminarily prepared polymer material having LCST and a liquid is added to a solution containing a material for microcapsules to form microcapsules. , L
A mixed liquid of a monomer, which is a precursor of a polymeric material having CST, and a liquid is added to a solution containing a material for forming a microcapsule to prepare a microcapsule containing the monomer, and the monomer is encapsulated in the microcapsule. And the like. In the encapsulation process, a stirring method using a stirrer, a method of ejecting the composition for capsules from a nozzle having a fine diameter to form capsules, or a method of spraying the composition for capsules to form capsules, etc. It is possible to form capsules having a desired particle size and shape.

The temperature-sensitive fine particle composition used in the present invention is preferably particles having an average particle size in a dry state of 0.01 μm to 5 mm, particularly 0.01 μm to 4 mm. If the average particle diameter is less than 0.01 μm, the problem of deterioration of contrast arises. On the other hand, if it exceeds 4 mm, there is a problem that the image quality becomes coarse and the composition becomes difficult.

The temperature-sensitive fine particle composition shown in FIGS. 1 and 2 is
It may be mixed with a water-based crosslinked polymer having no LCST and coated on the substrate, or may be mixed with a commonly used water-soluble or water-dispersible binder resin and coated. Further, it can be sandwiched between two base materials to form a temperature-sensitive fine particle sheet. FIG. 3 shows an example in which the temperature-sensitive fine particle composition 6 of the present invention is formed on the substrate 5. The protective layer 7 may be coated on the coated temperature-sensitive fine particle composition layer. Two
An example of sandwiching between the base materials is a method of laminating the film 8 on the coated temperature-sensitive fine particle composition layer. If necessary, the temperature-sensitive fine particle composition coating layer may contain a liquid 9 such as water.

Specific examples of the water-based polymer having no LCST and the water-based cross-linked polymer include water-based polyester resins (anionic polyester, cationic polyester,
Nonionic polyester), water-based alkyd resin, water-based epoxy resin, water-based polyamide resin, water-based melamine resin (methyl etherified aupiloguanamine resin, acetoguanamine resin, etc.), water-based acrylic resin, PVA-based resin, gelatin resin, starch, etc. Examples include crosslinked resins. Alternatively, a method may be used in which the temperature-sensitive fine particle composition is dispersed in a UV / EB curable resin such as water-soluble polyethylene glycol diacrylate, coated on a sheet-shaped support, and cured by UV / EB irradiation or the like.

The main roles of the water-based crosslinked polymer are the following two. The first is to install the temperature-sensitive fine particle composition on a substrate. The second is to prevent evaporation of water in the temperature sensitive particulate composition. Here, when the capsule membrane of the temperature-sensitive fine particle composition is a hydrophilic and water-permeable material such as calcium alginate, the water-based cross-linked polymer swollen in water surrounds the temperature-sensitive fine particle composition. This makes it possible to prevent evaporation of water in the temperature-sensitive fine particle composition. That is, in such a case, it is essential to use the water-based crosslinked polymer. On the other hand, when the capsule film of the temperature-sensitive fine particle composition is a hydrophobic material such as polyamide, it is not necessary to consider the evaporation of water in the temperature-sensitive fine particle composition, so an aqueous cross-linked polymer is not necessarily used. You do n’t have to
A water-soluble or water-dispersible binder resin which is usually used can be substituted. Examples of the water-soluble or water-dispersible binder resin that is usually used include uncrosslinked PVA, acrylic resins, acrylic emulsions, and latexes such as SBR, but are not particularly limited.

The water-based crosslinked polymer should not have an LCST. If the water-based cross-linked polymer has LCST, the water-based cross-linked polymer itself shows white turbidity depending on the temperature, which obscures the white turbidity phenomenon of the temperature-sensitive fine particle composition.

There is no particular limitation on the kind of the sheet-like substrate used in the present invention, and paper (for example, pigment-coated paper, resin-coated paper), plastic film (for example, polyester, polyimide, polymethylmethacrylate, polystyrene, Glass such as polypropylene, polyethylene, nylon, polycarbonate, polyvinyl chloride, etc.), metal such as aluminum, etc. is used. It is preferable to use a transparent substrate. Further, the thickness of the sheet-shaped substrate is arbitrarily selected according to its application and is not particularly limited.

In the above-mentioned constitutional example of the temperature-sensitive fine particle sheet, the thickness of the layer containing the temperature-sensitive fine particle composition is preferably in the range of 1 μm to 5 mm, particularly 2 μm to 4 mm. If it is less than 1 μm, the dimming performance is deteriorated, and
When it exceeds mm, problems such as deterioration of response characteristics and resolution of display image quality may occur.

The image-recording method of the temperature-sensitive fine particle sheet using the temperature-sensitive fine particle composition of the present invention obtained as described above comprises a heating element such as a thermal head and the above-mentioned temperature-sensitive fine particle sheet. If it is brought close to the fine particle composition layer and heated above the LCST of the water-soluble polymer, or if a pen-like shape with a heating element incorporated at the tip is used,
Information such as characters and figures can be written on the recording sheet as if writing characters on paper. Of course, the image recording method is not limited to the above-mentioned method, and any method can be used as a means for transferring heat to the temperature-sensitive fine particle composition layer. The information recorded in this manner disappears when the temperature of the temperature-sensitive fine particle composition falls below LCST and the temperature-sensitive fine particle composition returns from the cloudy state to the transparent state. Therefore, it is possible to write the data over and over again.

When it is desired to retain the information once recorded, a method of arranging heating elements in a matrix can be considered as an example. This is because the heating elements that can be electrically controlled are installed side by side in a matrix on the sheet-shaped substrate, and a device that can electrically control each heating element is incorporated, and further, the above-mentioned It is obtained by laminating the temperature-sensitive fine particle composition layers. In this case, when the power is turned on, the information recorded once can be retained until the power is turned off. The heating element is not particularly limited, and any material capable of generating heat by passing an electric current can be used.

(Function) According to the present invention, the region containing the uncrosslinked polymer material which is dissolved / precipitated by the application of the temperature stimulus and the liquid is held in a capsule form to improve the response speed of display. You can Compared with a conventional mixture of a crosslinked polymer gel and a liquid, this was uncrosslinked, and thus the slow response speed, which had been a problem in the past, was improved, and the contrast and repeatability were improved. In addition, as described above, multicolor display is possible by mixing capsules containing different LCST polymers. Furthermore, microcapsulation enables transport, storage, coating on a substrate, etc. It has the advantage of being easy.

(Fine Particle Production Example 1) A1 solution: N-isopropylacrylamide (NIPAM) 3.8
4 g, N, N, N ', N'-tetraethylenediamine 0.5 ml and sodium alginate 1.25 g are dissolved in 250 ml distilled water. A2 solution: Adjust 300 ml of distilled water to 3% and 0.5% of calcium chloride and ammonium persulfate, respectively.
Each of the A1 and A2 solutions is degassed with nitrogen gas. The A1 solution is added dropwise to the stirred A2 solution by a syringe. Particles with calcium alginate as a macrocapsule were generated at the same time as the dropping, and were encapsulated within 1 to 3 hours.
Polymerization of NIPAM ends. The obtained particles are 3 to 3 times with distilled water.
Washed 7 times. The fine particles obtained are transparent at 25 ° C, but 3
It became cloudy at temperatures above 2 ° C.

(Fine Particle Production Example 2) A1 solution: N-isopropylacrylamide (NIPAM) 3.8
4 g, N, N, N ', N'-tetraethylenediamine 0.5 ml, sodium alginate 1.25 g, blue pigment (trademark: TB-520Blue
0.0058 g of the dispersion liquid (manufactured by Dainichiseika) is dissolved in 250 ml of distilled water. A2 solution: Adjust 300 ml of distilled water to 3% and 0.5% of calcium chloride and ammonium persulfate, respectively.
Each of the A1 and A2 solutions is degassed with nitrogen gas. The A1 solution is added dropwise to the stirred A2 solution by a syringe. Particles with calcium alginate as a macrocapsule were generated at the same time as the dropping, and were encapsulated within 1 to 3 hours.
Polymerization of NIPAM ends. The obtained particles are 3 to 3 times with distilled water.
Washed 7 times. The fine particles obtained are blue at 25 ° C, but 3
It became cloudy at temperatures above 2 ° C.

(Fine Particle Production Example 3) A1 solution: N-isopropylacrylamide (NIPAM) 3.5
86 g, acrylic acid 0.254 g, N, N, N ', N'-tetraethylenediamine 0.5 ml, sodium alginate 1.25 g, red pigment (trademark: TB-1100Red dispersion, manufactured by Dainichiseika) 0.0042 g
Is dissolved in 250 ml of distilled water. A2 solution: Adjust 300 ml of distilled water to 3% and 0.5% of calcium chloride and ammonium persulfate, respectively.
Each of the A1 and A2 solutions is degassed with nitrogen gas. The A1 solution is added dropwise to the stirred A2 solution by a syringe. Particles with calcium alginate as a macrocapsule were generated at the same time as the dropping, and were encapsulated within 1 to 3 hours.
Polymerization of NIPAM ends. The obtained particles are 3 to 3 times with distilled water.
Washed 7 times. The fine particles obtained are red at 25 ° C, but 45
It became cloudy at temperatures above ℃.

(Fine Particle Production Example 4) A1 Solution: Commercial N-Isopropylacrylamide (NIPA
M) Polymer 3.84 g, sodium alginate 1.25 g 2
Dissolve in 50 ml distilled water. A2 solution: Adjust 300 ml of distilled water to 3% and 0.5% of calcium chloride and ammonium persulfate, respectively.
Each of the A1 and A2 solutions is degassed with nitrogen gas. The A1 solution is added dropwise to the stirred A2 solution by a syringe. At the same time as the dropping, particles having calcium alginate as a macrocapsule were generated. The obtained particles were washed with distilled water 3 to 7 times. The obtained fine particles were transparent at 25 ° C, but became cloudy at a temperature of 32 ° C or higher.

(Fine Particle Production Example 5) A1 Solution: Commercial N-Isopropylacrylamide (NIP
AM) Polymer 1 g, 0.4 M 1,6 hexanediamine
30 ml of an aqueous solution in which 0.45 M sodium carbonate was dissolved and 30 ml of distilled water were mixed with stirring. A2 solution: Chloroform-cyclohexane mixed solution (1/4 by volume) containing 5% of surfactant SPAN85 150
Adjust ml. A3 solution: Chloroform-cyclohexane mixed solution of terephthaloyl dichloride 1.2 g (1/4 by volume) 1
Dissolve in 50 ml. The A1 and A2 solutions are mixed by stirring to emulsify. A3 was added to the stirred emulsion. The obtained particles were washed with distilled water 3 to 7 times. The fine particles obtained are at 25 ° C.
Was transparent, but became cloudy at a temperature of 32 ° C or higher.

(Fine Particle Production Example 6) A1 solution: N-isopropylacrylamide (NIPAM) 3.8
4 g, N, N'-methylenebisacrylamide 0.16 g, N, N,
0.5 ml of N ', N'-tetraethylenediamine and 1.25 g of sodium alginate are dissolved in 250 ml of distilled water. A2 solution: Adjust 300 ml of distilled water to 3% and 0.5% of calcium chloride and ammonium persulfate, respectively.
Each of the A1 and A2 solutions is degassed with nitrogen gas. The A1 solution is added dropwise to the stirred A2 solution by a syringe. Particles with calcium alginate as a macrocapsule were generated at the same time as the dropping, and were encapsulated within 1 to 3 hours.
Polymerization of NIPAM ends. 3 ~ with fresh water with fresh particles
Washed 7 times. The fine particles obtained are transparent at 25 ° C, but 3
Although it became cloudy at a temperature of 2 ° C or higher, the degree of cloudiness was weak.

(Fine Particle Production Example 7) A1 solution: N-isopropylacrylamide (NIPAM) 3.8
4 g, 0.5 ml of N, N, N ', N'-tetraethylenediamine and ammonium persulfate are dissolved in 250 ml of distilled water. The A1 solution is degassed with nitrogen gas and stirred. NIPA in 1-3 hours
The polymerization of M is completed. Fresh polymer aqueous solution at 25 ℃
Was colorless and transparent, but at a temperature of 32 ° C. or higher, the phenomenon of white turbidity was observed, but the degree of white turbidity was weak.

<Example 1> Fine particles The particle composition (aqueous dispersion liquid) of Production Example 1 was used in a transparent cylindrical bottle having a capacity of 1.5 ml (outer diameter: 11 mm,
Height 32mm). 35 prepared in advance
A transparent cylindrical bottle was placed in a water tank at ℃ and the color change at that moment was visually observed. Table 1 shows the evaluation results and other physical property values.

<Example 2> Fine particles (aqueous dispersion) of Fine Particle Production Example 2 and Fine Particle Production Example 3 were mixed in equal amounts and placed in a transparent cylindrical bottle (outer diameter 11 mm, height 32 mm) having a capacity of 1.5 ml. It was
A transparent cylindrical bottle was placed in a 35 ° C. water tank prepared in advance, and the color change at that moment was visually observed. Further, it was immersed in a 50 ° C. water tank prepared in advance, and the color change at that moment was silently observed. Table 1 shows the evaluation results and other physical property values.

Example 3 Fine Particles The particle composition (aqueous dispersion liquid) of Production Example 4 was added to a transparent cylindrical bottle (outer diameter: 11 mm, 1.5 ml capacity).
Height 32mm). 35 prepared in advance
A transparent cylindrical bottle was placed in a water tank at ℃ and the color change at that moment was visually observed. Table 1 shows the evaluation results and other physical property values.

Example 4 Fine Particles The particle composition (aqueous dispersion liquid) of Production Example 5 was added to a transparent cylindrical bottle of 1.5 ml capacity (outer diameter 11 mm,
Height 32mm). 35 prepared in advance
A transparent cylindrical bottle was placed in a water tank at ℃ and the color change at that moment was visually observed. Table 1 shows the evaluation results and other physical property values.

Example 5 The fine particle composition prepared in Example 1 was dispersed in an aqueous crosslinked polymer having no LCST by the following method. B1 solution: 10 g of acrylic acid and 30 mg of ammonium persulfate are added to 40 ml of distilled water. B2 solution: To 50 ml of distilled water, 0.1 g of N, N′-methylenebisacrylamide and 30 mg of iron (II) sulfate (FeSO ₄ 7H ₂ O) are added. The B1 solution, the B2 solution, and the fine particle composition of Fine Particle Production Example 1 were mixed, put in a vinyl bag, spread thinly, and allowed to stand for 2 hours to obtain a plate-like crosslinked product in which the fine particle composition was dispersed. It was lightly wiped of water, sandwiched between transparent PET having a thickness of 50 μm, and further wrapped with an OPP film. Four sides of the packaged OPP film were heat-sealed so that water did not seep out from the plate-like crosslinked product. The plate-like crosslinked product heat-sealed with OPP was immersed in a 35 ° C. water tank prepared in advance, and the color change at that moment was visually observed. Table 1 shows the evaluation results and other physical property values.

Comparative Example 1 Fine Particles The particle composition (aqueous dispersion liquid) of Production Example 6 was added to a transparent cylindrical bottle of 1.5 ml capacity (outer diameter 11 mm,
Height 32mm). 35 prepared in advance
A transparent cylindrical bottle was placed in a water tank at ℃ and the color change at that moment was visually observed. Table 1 shows the evaluation results and other physical property values.

Comparative Example 2 Fine Particles The particle composition (aqueous dispersion liquid) of Production Example 7 was added to a transparent cylindrical bottle of 1.5 ml capacity (outer diameter 11 mm,
Height 32mm). 35 prepared in advance
A transparent cylindrical bottle was placed in a water tank at ℃ and the color change at that moment was visually observed. Table 1 shows the evaluation results and other physical property values.

[0046]

[Table 1] Color change, response speed: Sensory evaluation of whether the color changes by heating instantly Contrast: Relative evaluation based on Example 1

[0047]

According to the present invention, it is possible to obtain a temperature-sensitive fine particle composition which is easy to handle and has a high thermal response speed, which is easy to handle, easy to manufacture and easy to sheet. , Seems to make a big contribution to industry.

[Brief description of drawings]

FIG. 1 is a schematic diagram of microcapsules containing an uncrosslinked polymer.

FIG. 2 is a schematic diagram of microcapsules containing an uncrosslinked polymer and a colorant.

FIG. 3 is a schematic view of a temperature-sensitive fine particle sheet (having a fine particle coating layer provided on a base material).

FIG. 4 is a schematic diagram of a temperature-sensitive fine particle sheet (two base materials provided with a fine particle coating layer).

[Explanation of symbols] 1: Microcapsule membrane 2: Liquid 3: Polymer material that changes with temperature 4: Coloring agent 5: Base material 6: Temperature-sensitive fine particle composition 7: Protective layer 8: Film 9: Liquid such as water

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Claims (5)

[Claims] 1. A temperature-sensitive fine particle composition comprising a microcapsule containing an uncrosslinked polymer material having a lower critical eutectic temperature and changing between transparent and opaque at the temperature. 2. The temperature-sensitive fine particle composition according to claim 1, which further contains a colorant in microcapsules. 3. The temperature-sensitive fine particle composition according to claim 1, wherein microcapsules containing uncrosslinked polymer materials having different lower critical eutectic temperatures are mixed. 4. The temperature-sensitive fine particle composition according to claim 1, which is dispersed in a water-based crosslinked polymer, a water-soluble polymer or a water-dispersible polymer having no lower critical eutectic temperature. A temperature-sensitive fine particle composition characterized by: 5. A temperature-sensitive fine particle sheet characterized by comprising the temperature-sensitive fine particle composition according to claim 1 arranged on a substrate.