JP4649883B2 - Thermosensitive liquid crystal-containing microcapsules, method for producing the same, and coating composition containing the microcapsules - Google Patents

Description

  The present invention relates to a microcapsule containing a thermosensitive liquid crystal and a coating composition containing the microcapsule.

  The thermosensitive liquid crystal can be changed from red to purple in accordance with a minute change in temperature in a specific temperature range. This thermosensitive liquid crystal loses its color development properties within a few months without durability against moisture in the air and ultraviolet rays such as sunlight.

In order to improve this, the encapsulation of a thermosensitive liquid crystal using an organic material such as a natural polymer or urethane has been studied (for example, see Patent Documents 1 to 4). However, these encapsulated thermosensitive liquid crystal particles still have a problem that the color development region is narrow, and the durability of color development is short due to poor weather resistance, chemical resistance, and water resistance. It is only put to practical use as a limited use such as decoration.
Japanese Examined Patent Publication No. 49-18351 Japanese Examined Patent Publication No. 52-1324 Japanese Patent Publication No. 56-15684 US Pat. No. 3,523,906

  The present invention provides a thermosensitive liquid crystal-containing microcapsule that is excellent in moisture resistance, weather resistance, water resistance, heat resistance, chemical resistance, etc., and that can maintain color development characteristics for a long time without impairing the color developability of the thermosensitive liquid crystal itself, and its production It aims to provide a method. It is another object of the present invention to provide a coating composition using the thermosensitive liquid crystal-containing microcapsules and a coating film formed from the coating composition.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention applied an organic coating (first capsule membrane) and an inorganic continuous coating (second capsule membrane) to the surface of the thermosensitive liquid crystal as a core material. It was found that a microcapsule containing thermosensitive liquid crystal having excellent durability (water resistance, chemical resistance, etc.) while maintaining the color development characteristics of the thermosensitive liquid crystal can be obtained. Based on this knowledge, further research has been developed to complete the present invention.

  That is, the present invention provides the following heat-sensitive liquid crystal-containing microcapsules, a method for producing the same, and a coating composition using the microcapsules.

  Item 1. A heat-sensitive liquid crystal-containing microcapsule obtained by encapsulating a heat-sensitive liquid crystal with a two-layer capsule film, wherein the two-layer capsule film comprises an organic coating (first capsule film) formed on the surface of the heat-sensitive liquid crystal and the first capsule film. A heat-sensitive liquid crystal-containing microcapsule comprising an inorganic coating film (second capsule film) formed on the capsule film surface.

  Item 2. The first capsule film is an organic film formed by coacervation by emulsifying and dispersing an organic polymer and a thermosensitive liquid crystal in an aqueous medium, and the second capsule film is an alkoxysilane or a hydrolysis condensate thereof. Item 2. The thermosensitive liquid crystal-containing microcapsule according to item 1, which is an inorganic coating formed using a reaction alignment agent and a curing catalyst.

  Item 3. Item 3. The heat-sensitive liquid crystal-containing microcapsule according to item 1 or 2, which is spherical and has an average particle diameter of about 3 to 90 μm.

  Item 4. Item 3. The heat-sensitive liquid crystal-containing microcapsule according to item 1 or 2, wherein the coating layer including the first capsule film and the second capsule film has a thickness of about 1 to 20 μm.

Item 5. A method for producing a thermosensitive liquid crystal-containing microcapsule obtained by encapsulating a thermosensitive liquid crystal with a two-layer capsule film,
(1) Producing an aqueous dispersion of first capsule particles in which an organic polymer and a thermal liquid crystal are emulsified and dispersed in an aqueous medium, and the thermal liquid crystal particles are coated with an organic coating (first capsule film) by coacervation. And the process of
(2) forming an inorganic coating (second capsule membrane) on the surface of the organic coating (first capsule membrane) of the first capsule particles produced in the step (1);
The manufacturing method of the thermosensitive liquid crystal containing microcapsule characterized by including.

  Item 6. Item 5 wherein, in the step (2), alkoxysilane or a hydrolysis condensate thereof, a reaction alignment agent and a curing catalyst are added to the aqueous dispersion of the first capsule particles produced in (1) to form an inorganic coating. The manufacturing method as described in.

  Item 7. In the step (1), the concentration of the thermosensitive liquid crystal in the aqueous medium is about 5 to 50% by weight, and the concentration of the organic polymer is about 2 to 50% by weight. In the step (2), in the aqueous dispersion The concentration of the first capsule particles is about 5 to 50% by weight, the amount of alkoxysilane or its hydrolyzed condensate is about 5 to 30 parts by weight with respect to 100 parts by weight of the aqueous dispersion, and the amount of the reactive alignment agent The production according to Item 6, wherein about 10 to 50 parts by weight with respect to 100 parts by weight of the aqueous dispersion and the amount of the curing catalyst is about 0.005 to 0.1 parts by weight with respect to 100 parts by weight of the aqueous dispersion. Method.

  Item 8. Item 8. A thermal liquid crystal-containing microcapsule produced by the production method according to Item 5, 6 or 7.

  Item 9. Item 10. A coating composition containing the thermal liquid crystal-containing microcapsules according to item 1, 2, 3, 4 or 8.

  Item 10. Item 10. The coating composition according to Item 9, wherein the thermosensitive liquid crystal-containing microcapsules are contained in the coating composition in an amount of about 5 to 70% by weight.

  Item 11. Item 11. A coating film formed by applying the coating composition according to Item 9 or 10 to a substrate.

  Hereinafter, the present invention will be described in detail.

  The heat-sensitive liquid crystal-containing microcapsules of the present invention are formed by coating the surface of a heat-sensitive liquid crystal, which is a core material (core substance), with an organic coating (first capsule film) and an inorganic continuous coating (second capsule film). .

Thermosensitive liquid crystal The thermosensitive liquid crystal used in the present invention refers to a liquid crystal having a characteristic of changing from red to purple in accordance with a minute change in temperature in a specific temperature range. Specific examples include liquid crystals having a cholesteric phase (cholesteric liquid crystals). This is because the molecular arrangement is oriented in a certain direction within one plane, but twists between the adjacent plane and a helical structure as a whole.

  In the cholesteric phase, the molecules are arranged in one direction with the long axis of the molecules in the layer as thin as about 3 mm in thickness. The direction of the molecules in the layers is twisted slightly for each layer, forming a “spiral” structure that rotates at an angle of 15 minutes per layer, and rotates about 2000 layers. Twist changes by applying temperature, and when the pitch width of the twist is wide, red is displayed, and as the pitch width becomes small, light is selectively reflected like yellow, green, blue, purple and prism. Applications include temperature displays such as thermometers and decorative items.

  The thermosensitive liquid crystal is used as a core material (core material) of a microcapsule, and is encapsulated in a particulate form using coacervation or the like described later to form particles (hereinafter also referred to as “first capsule particles”). To do.

Formation of First Capsule Film (Organic Coating) The first capsule film is composed of an organic coating that covers the surface of the heat-sensitive liquid crystal particles. This first capsule film protects the thermosensitive liquid crystal from the surrounding environment (for example, oxidation prevention), shields the color, taste, odor and toxicity, can be made into an apparent solid, and can change the apparent specific gravity. It is formed for the purpose of facilitating handling such as improving storage performance.

  The first capsule film can be formed using, for example, coacervation by emulsifying and dispersing an organic polymer and a thermosensitive liquid crystal in an aqueous medium. Coacervation is a method in which a thermal liquid crystal is emulsified and dispersed in fine particles of about 1 to 50 μm in an aqueous medium and suspended in a solution of an organic polymer, which is a hydrophilic polymer, on the surface of the thermal liquid crystal particles. In this method, an organic polymer is deposited and encapsulated. Thereby, particles (first capsule particles) obtained by coating (encapsulating) the thermosensitive liquid crystal particles with the organic coating (first capsule film) are produced. The organic coating contains an organic polymer as a main component.

  Here, the aqueous medium means a medium containing water as a main component, and may contain other components as long as the reaction is not adversely affected. The method of emulsifying and dispersing the thermosensitive liquid crystal can be performed by a known method such as stirring and homomixer emulsification.

  The concentration of the thermosensitive liquid crystal in the aqueous medium may be about 5 to 50% by weight, and preferably about 15 to 35% by weight. The above concentration range is recommended in order to suppress precipitation or aggregation of the thermosensitive liquid crystal.

  Organic polymers that are the main materials of the first capsule membrane include natural polymers such as gelatin, gum arabic, and sodium alginate; semisynthetic polymers such as carboxymethyl cellulose and ethyl cellulose; polyvinyl alcohol, nylon, polyurethane, polyester, Simple substances and composites (including mixtures) such as synthetic polymers such as epoxy and melamine can be used.

  Moreover, the density | concentration of the organic polymer in this aqueous medium should just be about 2 to 50 weight%, Preferably it is 5 to 20 weight%. The above-mentioned concentration range is recommended in order to make the film thickness of the first capsule film necessary for encapsulation and to maintain the color developability of the thermosensitive liquid crystal.

  As a specific example of the coacervation method, first, a gum arabic solution and a heat-sensitive liquid crystal are stirred and emulsified and mixed, and an equal concentration gelatin solution is added thereto (here, the gum arabic solution and the gelatin solution may be interchanged). Good). When distilled water is added to this and the pH is adjusted with an acetic acid aqueous solution or the like (for example, about pH 4.0 to 4.3), gelatin and gum arabic react to produce a concentrated liquid polymer. Thereafter, when the temperature is lowered, coacervation begins, and a gelatin / gum arabic coating is deposited around the thermosensitive liquid crystal particles to form a capsule film. Furthermore, a hardener such as aldehyde is added to age the capsule film.

  As described above, an aqueous dispersion of the first capsule particles is produced. The film thickness of the first capsule film to be formed is about 0.5 to 10 μm, preferably about 0.5 to 5 μm. Moreover, the 1st capsule particle obtained is a spherical particle, The average particle diameter is about 2-70 micrometers, Preferably it is about 5-40 micrometers.

Formation of second capsule film (inorganic coating) The second capsule film is formed as an inorganic continuous coating on the surface of the first capsule film of the first capsule particle. That is, the second capsule film is composed of an inorganic film that covers the entire surface of the first capsule film. Unlike the first capsule membrane material, the second capsule membrane is characterized in that it is not easily decomposed and is formed as a continuous film with an inorganic material that is difficult to permeate moisture, organic solvents, and the like. is doing.

  The second capsule film is formed on the surface of the first capsule film using a wall material, that is, at least alkoxysilane or a hydrolysis condensate thereof, a reaction alignment agent, and a curing catalyst (for example, Example 1 (3)). , See FIG. Specifically, the second capsule film is formed by adding alkoxysilane or a hydrolysis condensate thereof, a reaction alignment agent, and a curing catalyst to the aqueous dispersion of the first capsule particles and stirring and mixing them.

  Alternatively, the reaction capsule may be added to the aqueous dispersion of the first capsule particles to treat the surface of the first capsule film, and then the alkoxysilane or its hydrolysis condensate and curing catalyst may be added and mixed with stirring.

  When the first capsule particle has a low solid content concentration, the first capsule particle aqueous dispersion is used by concentrating by distilling off the solvent so that the solid content concentration is about 5 to 50% by weight. It is preferable.

  In addition to the above components, an appropriate organic solvent (for example, toluene) or a surfactant may be added as necessary.

  Specific examples of each component are shown below.

The alkoxysilane and / or its hydrolytic condensate, for example, a silicone resin, silica sol Le及 beauty organosilica sol, curing or polymer water-soluble sodium silicate and the like.

The silicone resin is represented by the general formula (I):
R ¹ _n Si (OR ² ) _4-n (I)
(In the formula, R ¹ is an alkyl group having 1 to 8 carbon atoms or an aryl group, R ² is an alkyl group having 1 to 5 carbon atoms, and n is 1 or 2.)
And / or a liquid partial hydrolysis condensate thereof.

Examples of the alkyl group having 1 to 8 carbon atoms represented by R ¹ include a methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, s-butyl group, t- Examples thereof include linear or branched alkyl groups having 1 to 8 carbon atoms such as a butyl group, a pentyl group, and a hexyl group. Preferably, it is a C1-C4 alkyl group, and especially a methyl group and an ethyl group are preferably employed.

Examples of the aryl group represented by R ¹ include a phenyl group, a naphthyl group, and a toluyl group.

Examples of the alkyl group having 1 to 5 carbon atoms represented by R ² include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, s-butyl group, and t-butyl. And alkyl groups such as a group, a pentyl group, and a hexyl group. Preferred alkyl groups are those having 1 to 2 carbon atoms, that is, a methyl group or an ethyl group.

  The molecular weight of the silicone resin is a polystyrene-equivalent weight average molecular weight, for example, 400 to 10,000, preferably 500 to 7,000. Specific examples of such silicone resins include commercially available products such as SR2402, SR2405, SR2406, SR2410, SR2411 (Toray Dow Corning Co., Ltd.), KR-211, KR-214, KR-216, KR- 255 (Shin-Etsu Chemical Co., Ltd.), TSR-165, TSR170 (GE Toshiba Silicone Co., Ltd.) and the like.

Silica sol means a colloid in which fine particles of silicic acid (SiO ₂ · nH ₂ O) are dispersed in a dispersion medium such as water. For example, Snowtex AK, Snowtex C, Snowtex 40, Snowtex N, Snow Tex O, Snowtex LSS-45 (Nissan Chemical Industry Co., Ltd.), Cataloid S-30H, Cataloid SI-30, Cataloid SN, Cataloid SA (all trade names, manufactured by Catalytic Chemical Industry Co., Ltd.), Adelite AT- 30, Adelite AT-20N, Adelite AT-20A, Adelite AT-20Q (all trade names, manufactured by Asahi Denka Kogyo Co., Ltd.), Silica Doll 30, Silica Doll 20A, Silica Doll 20B (all trade names, Nippon Kagaku) Kogyo Co., Ltd.). In particular, the pH is 8.5 to 9. SNOWTEX C having an average particle diameter of 0 to 10 to 20 nm is preferably employed.

  Examples of the organosilica sol include methanol silica sol, IPA-ST, IPA-ST-UP, IPA-ST-ZL, EG-ST, NPC-ST-30, DMAC-ST, MEK-ST, MIBK-ST, and XBA-ST. PMA-ST (Nissan Chemical Industry Co., Ltd.) and the like.

The curing or polymer water-soluble sodium silicate, represented by the chemical formula _{Na 2 O · nSiO 2 · xH} 2 O, 1 No. _{(SiO 2: 35~38%, Na} 2 O: 17~19% ) No. 2 (SiO ₂ : 34 to 36%, Na ₂ O: 14 to 15%), No. 3 (SiO ₂ : 28 to 30%, Na ₂ O: 9 to 10%), 1 type of sodium metasilicate ( _{SiO 2: 27.5~29%, Na 2} O: 28.5~30%), sodium metasilicate two _{(SiO 2: 19~20%, Na} 2 O: 20~21%) , and the like.

  One of these silicone resins, silica sols and organosilica sols, water-soluble sodium silicate cured products or polymers may be used, or two or more of them may be used in combination.

  The reaction catalyst relates to the polycondensation reaction of the second capsule membrane. Lewis acids such as dibutyltin diacetate, dibutyltin dilaurate, tetraisopropoxytitanate, triisopropoxyaluminate, tetraisopropoxyzirconium; hydrochloric acid, sulfuric acid, nitric acid And organic acids such as p-toluenesulfonic acid; bases such as sodium hydroxide, ammonia and triethylamine. Of these, organic acids such as hydrochloric acid, sulfuric acid, nitric acid, and p-toluenesulfonic acid are preferably used from the viewpoint of the stability of the inorganic capsule that is the second capsule film, and particularly hydrochloric acid (concentration of about 0.05 to 2N). ) Is preferred.

  The reaction alignment agent is a reagent capable of firmly bonding the first capsule film and the second capsule film, and includes a so-called silane coupling agent. Specifically, an organic functional group (for example, an alkyl group, an alkoxyl group, a carboxyl group, a primary, a secondary, and a tertiary amino group having an affinity for an organic group (for example, a hydroxyl group) present on the surface of the first capsule membrane , A sulfonyl group, a mercapto group, an isocyanato group, an isothiocyanato group, a halogen atom), and an inorganic functional group that can react with the alkoxysilane and / or a hydrolysis-condensation product thereof, which is the main raw material of the second capsule membrane (for example, Si- OH).

  More specifically, as a reaction alignment agent, for example, methyltrimethoxysilane, methyltriethoxysilane, methyltri-n-propoxysilane, methyltriisopropoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltri-n- Propoxysilane, phenyltriisopropoxysilane, dimethyldimethoxysilane, dimethyltriethoxysilane, dimethyldi-n-propoxysilane, dimethyldiisopropoxysilane, vinyltrimethoxysilane, p-styritrimethoxysilane, γ-aminopropyltrimethoxysilane N-phenyl-γ-aminopropyltrimethoxysilane, γ-chloropropyltrimethosilane, γ-mercaptopropyltrimethoxysilane, γ-isocyanatopropyltrimethoxysilane, etc. Silicates such as run coupling agents, tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, tetraisobutoxysilane, tetra-sec-butoxysilane, tetra-tert-butoxysilane Among them, methyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-isocyanatopropyltrimethoxysilane are preferable.

  Since this reaction alignment agent plays a role of firmly bonding the inorganic coating (first capsule film) and the organic coating (second capsule film), a stronger capsule film is formed and excellent in durability. A thermosensitive liquid crystal-containing microcapsule is obtained.

  As the surfactant, nonionic surfactants are preferable. Specifically, for example, polyethylene glycol alkyl ethers such as polyethylene glycol stearyl ether and polyethylene glycol oleyl ether; polyethylene glycol such as polyethylene glycol polypropylene glycol decyl tetradecyl ether. Polypropylene glycol alkyl ethers; polyethylene glycol alkyl phenyl ethers such as polyethylene glycol octyl phenyl ether and polyethylene glycol nonyl phenyl ether; polyethylene glycol fatty acids such as ethylene glycol monostearate, ethylene glycol distearate, diethylene glycol stearate and polyethylene glycol distearate ester Glyceryl fatty acid esters such as glyceryl monomyristate, glyceryl monostearate, glyceryl monoisostearate; sorbitan fatty acids such as sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearate, sorbitan monooleate, sorbitan trioleate Esters: Polyethylene oxide adducts of glycerin fatty acid esters such as polyethylene oxide adduct of glyceryl monostearate, polyethylene oxide adduct of glyceryl monooleate; Polyethylene oxide adducts of sorbitan monopalmitate, polyethylene of sorbitan monostearate Polyesters of sorbitan fatty acid esters such as oxide adducts and polyethylene oxide adducts of sorbitan tristearate Polyethylene oxide adducts of sorbite fatty acid esters such as polyethylene oxide adducts of sorbite monolaurate, polyethylene oxide adduct of sorbite tetrastearate, polyethylene oxide adduct of sorbitol hexastearate; polyethylene of castor oil Examples thereof include oxide adducts.

  The concentration (solid content concentration) of the first capsule particles in the aqueous dispersion is about 5 to 50% by weight. If it is less than 5% by weight, thermal liquid crystal is precipitated, and if it exceeds 50% by weight, the thermal liquid crystal is aggregated. May happen. Preferably it is 15 to 35% by weight.

  The compounding quantity of alkoxysilane thru | or its hydrolysis-condensation product is about 5-30 weight part with respect to 100 weight part of said aqueous dispersions, Preferably what is necessary is just to use about 10-20 weight part. If it is less than 5 parts by weight, the film thickness of the second capsule film may be less than 1 μm, and encapsulation may be difficult. If it exceeds 30 parts by weight, the film thickness of the second capsule film exceeds 20 μm, resulting in poor color development. There is.

  The compounding amount of the reaction alignment agent is about 10 to 50 parts by weight, preferably about 20 to 30 parts by weight, based on 100 parts by weight of the aqueous dispersion. If it is less than 10 parts by weight, the first capsule particles and alkoxysilane or its hydrolysis condensate particles are produced separately, and if it exceeds 50 parts by weight, the alkoxysilane or its hydrolysis condensate reactant is sticky, The generated particles may agglomerate.

  The blending amount of the curing catalyst is about 0.005 to 0.1 part by weight, preferably about 0.01 to 0.05 part by weight, based on 100 parts by weight of the aqueous dispersion. If it is less than 0.005 parts by weight, it does not function sufficiently as a reaction catalyst, and curing failure tends to occur. If it exceeds 0.1 parts by weight, the reaction rate does not change.

  As a specific operation method for forming the second capsule film on the surface of the first capsule film, for example, using each of the above components, an aqueous dispersion of the first capsule particles is added to alkoxysilane or a hydrolysis condensate thereof, reaction orientation. An agent, a curing catalyst, and other components as necessary may be added, mixed and stirred at about 500 to 1500 rpm, and reacted at about 40 to 80 ° C. for about 12 to 36 hours. As a result, a thermal liquid crystal-containing microcapsule aqueous dispersion is produced. The microcapsules are dried under reduced pressure to produce the thermosensitive liquid crystal-containing microcapsules of the present invention.

  The heat-sensitive liquid crystal-containing microcapsules of the present invention are spherical and have an average particle size of about 3 to 90 μm (preferably about 10 to 60 μm).

  The film thickness of the coating layer (first capsule film + second capsule film) is about 1 to 20 μm (preferably about 2 to 10 μm). This is because, within a range where the film thickness of the coating layer is applied, a predetermined strength is imparted to the coating layer, and the color development characteristics of the encapsulated thermosensitive liquid crystal are suitably maintained without deterioration.

Coating Composition The coating composition of the present invention contains the above-described heat-sensitive liquid crystal-containing microcapsules. Components other than the heat-sensitive liquid crystal-containing microcapsules can be appropriately selected according to the application and purpose of the paint, and known components are employed. For example, organic solvents (for example, alcohols such as methanol, ethanol, isopropanol, n-butanol, i-butanol, s-butanol, t-butanol, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether) , Ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, glycols such as propylene glycol monomethyl ether), water, pigments (for example, azo chelate pigments, insoluble azo pigments, condensed azo pigments, phthalocyanine pigments, indigo pigments, perinone pigments) Organic pigments such as pigments, perylene pigments, dioxane pigments, quinacridone pigments, diketopyrrolopyrrole pigments, isoindolinone pigments, metal complex pigments, yellow Iron oxide, red iron, carbon black, inorganic color pigments such as titanium dioxide) and the like. Binder resins (for example, natural polymers such as gelatin, polyvinyl alcohol, and cellulose, acrylic resin emulsion, acrylic silicone resin emulsion, polyurethane resin emulsion, etc.) may be included.

  The heat-sensitive liquid crystal-containing microcapsules are blended in the coating composition by about 5 to 70% by weight. When the blending amount is less than about 5% by weight, the coating film has a rough feeling. When the blending amount exceeds about 70% by weight, it becomes a matte coating film, and the gloss of the coating film may be lowered. Preferably it is 20 to 50 weight%.

  A coating film is formed by allowing the coating composition of the present invention to act on a substrate (to-be-coated object) and drying (for example, see Experimental Example 2 and FIG. 2). As a method of acting on the substrate (object to be coated), known methods such as coating, dipping, spraying, roll coater, bar coater, applicator, brush, and roller are employed. The substrate (object to be coated) is not particularly limited in material and shape as long as the coating composition can be applied, and examples thereof include materials such as metal, glass, plastic and ceramics. As a result, a coating film that is excellent in moisture resistance, weather resistance, water resistance, heat resistance, chemical resistance, etc., and that can maintain the color development characteristics for a long time without impairing the color development of the thermosensitive liquid crystal itself is formed.

  The liquid crystal particle-containing microcapsules of the present invention are coated with an organic coating (first capsule membrane) and an inorganic continuous coating (second capsule membrane), thereby providing moisture resistance, weather resistance, water resistance and heat resistance. Excellent in chemical properties, chemical resistance, etc., and can maintain the color development characteristics for a long time while taking advantage of the color developability of the thermosensitive liquid crystal itself. Such heat-sensitive liquid crystal-containing microcapsules having excellent durability can be widely incorporated into coating compositions.

  Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples without departing from the gist thereof.

Example 1 (Encapsulation of thermal liquid crystal)
(1) The matrix of the thermosensitive liquid crystal is cholesterol. A sterol is a crystalline alcoholic substance present in animal and plant oxides, and has a skeleton in which a 5-membered ring is condensed at the 1, 2-position of saturated phenanthrolene. Cholesterol, the main sterol of the animal body, has a structure having a C8-side chain and two methyl groups in this skeleton.

コレステロールは動物体の各組織中に存在するが、特に羊毛脂には多量に含まれており、感熱液晶の抽出原料としては羊毛を用いた。

Cholesterol is present in each tissue of the animal body, but it is particularly contained in a large amount in wool oil, and wool was used as a raw material for extracting heat-sensitive liquid crystal.

In a three-necked flask equipped with a stirrer, 38 parts by weight of cholesterol (0.1 mol), 12 parts by weight of pyridine (0.15 mol), 100 parts by weight of methylene chloride and 15 parts by weight of acetic anhydride (0.1 mol) were added, and the temperature was raised. Reflux for 2 hours. After standing at room temperature, 200 ml of ion-exchanged water is added, the ester content is separated into a methylene chloride layer, unreacted materials and the like into an aqueous layer, and extracted with a separatory funnel. After extraction with ion-exchanged water several times, the methylene chloride layer was distilled under reduced pressure to recover 34 parts by weight of cholesteryl acetate.
(2) Method for Encapsulating Gelatin-Acacia Gum as the First Capsule Membrane 9 parts by weight of the cholesteryl acetate and 30 parts by weight of a 10% by weight aqueous gelatin solution are added and emulsified in a three-necked flask equipped with a stirrer. Thereto, 30 parts by weight of a 10% by weight aqueous solution of gum arabic is dropped in a dropping funnel in about 20 minutes. Thereto, 200 parts by weight of warm water at 40 ° C. and then a 10% by weight acetic acid aqueous solution are added dropwise to adjust the pH to 4.0 to 4.3. This is lowered to 5 ° C. using an ice bath, 1 part by weight of 30% by weight formalin is added, and the pH is adjusted to 9.0 with a 10% by weight aqueous NaOH solution. Further, this solution was heated to 50 ° C. at a rate of 1 ° C./min to obtain spherical gelatin-gum arabic-capsulated thermosensitive liquid crystal-containing microcapsules having an average particle size of 25 μm.
(3) Method for Encapsulating Inorganic Coating as Second Capsule Membrane Into a three-necked flask equipped with a stirrer, the gelatin-arabic gum-encapsulated thermosensitive liquid crystal-containing microcapsule dispersion aqueous solution obtained in (2) was added at a solid content of 28% by weight. 100 parts by weight of the dispersion liquid concentrated to such an extent, 50 parts by weight of colloidal silica C (Snowtex C, manufactured by Nissan Chemical Co., Ltd., 30% by weight), 25 parts by weight of γ-isocyanatopropyltrimethoxysilane, and 0. 5 parts by weight of a 1N hydrochloric acid aqueous solution and 50 parts by weight of toluene were prepared.

  This was stirred and mixed at 800 rpm and reacted at 50 ° C. for 24 hours (see, for example, FIG. 1). As a result, spherical thermosensitive liquid crystal-containing microcapsules having a particle size distribution of 1 to 70 μm and an average particle size of 30 μm were obtained.

Comparative Example 1
Microcapsules were produced in the same manner as in Example 1 except that γ-methacryloxypropyltrimethoxysilane was used instead of γ-isocyanatopropyltrimethoxysilane in Example 1.

  As a result, heat-sensitive liquid crystal microcapsules having a particle size distribution of 1 to 70 μm and an average particle size of 30 μm were obtained.

Comparative Example 2
Microcapsules were prepared in the same manner as in Example 1 except that γ-glycidoxypropyltrimethoxysilane was used instead of γ-isocyanatopropyltrimethoxysilane in Example 1.

  As a result, heat-sensitive liquid crystal microcapsules having a particle size distribution of 1 to 70 μm and an average particle size of 30 μm were obtained.

Comparative Example 3
Snowtex C of Example 1 (pH: 8.5-9.0, particle size 10 to 20 n m) in place of the SNOWTEX 20L (pH: 9.5 to 11.0, particle size 40 to 50 n m) Microcapsules were produced in the same manner as in Example 1 except that (colloidal silica; manufactured by Nissan Chemical Industries, Ltd.) was used.

  As a result, heat-sensitive liquid crystal microcapsules having a particle size distribution of 1 to 70 μm and an average particle size of 30 μm were obtained.

Comparative Example 4
Microcapsules were produced in the same manner as in Example 1 except that γ-isocyanatopropyltrimethoxysilane was not used in Example 1.

  As a result, heat-sensitive liquid crystal microcapsules having a particle size distribution of 1 to 70 μm and an average particle size of 28 μm were obtained.

Comparative Example 5
In Example 1, not all film material materials were used, and the heat-sensitive liquid crystal particles themselves were used as they were.

Experimental Example 1 (Solvent resistance test)
To 1 g of thermosensitive liquid crystal-containing microcapsules obtained in Example 1 and Comparative Examples 1 to 5, 2 ml of the same amount of solvent (xylene) is added and left at room temperature for 30 minutes after stirring. Thereafter, the dispersion is applied to black drawing paper and naturally dried. After drying, it was forcibly dried at 50 ° C. for 30 minutes to evaluate the color developability. The criteria for evaluation are as shown below.

10: Color development of thermal liquid crystal before encapsulation (based on this)
8:10 Color is slightly insensitive to temperature change, but there is no practical problem 6: First color is developed, but no color is developed after about 1 hour 4: Color is developed a little at first, but no color is developed after about 1 hour 2: Color develops only at the first edge but does not develop color after about 1 hour 1: Does not develop color

実験例２（塗膜の耐水性試験）
実施例１及び比較例１〜５で得られた感熱液晶含有マイクロカプセル５０重量部、ポリビニルアルコール（日本合成社製、ゴーセノール）２．５重量部、イオン交換水４７．５重量部混合したものを塗布液とし、バーコーダー＃４にて黒画用紙に塗布し、常温で１２時間放置して塗膜を形成した（例えば、図２を参照）。

Experimental Example 2 (Water resistance test of coating film)
50 parts by weight of thermosensitive liquid crystal-containing microcapsules obtained in Example 1 and Comparative Examples 1 to 5, 2.5 parts by weight of polyvinyl alcohol (manufactured by Nippon Gosei Co., Ltd., Gohsenol), and 47.5 parts by weight of ion-exchanged water were mixed. A coating solution was applied to black paper with Bar Coder # 4 and allowed to stand at room temperature for 12 hours to form a coating film (see, for example, FIG. 2).

  The resulting coated coating film was confirmed to have color developability by visual evaluation after drying and after 48 hours with a moisture resistance tester (50 ° C., 95 RH%).

10: Color development of thermal liquid crystal before encapsulation (based on this)
8:10 Color is slightly insensitive to temperature change, but there is no practical problem 6: First color is developed, but no color is developed after about 1 hour 4: Color is developed a little at first, but no color is developed after about 1 hour 2: Color develops only at the first edge but does not develop color after about 1 hour 1: Does not develop color

It is the figure which showed typically the formation method of the 2nd capsule film | membrane (inorganic type coating film) of the thermosensitive liquid crystal containing microcapsule of this invention. It is a cross-sectional schematic diagram of the coating film which apply | coated the coating composition containing the thermosensitive liquid crystal containing microcapsule of this invention to a to-be-coated article.

Claims (11)

A heat-sensitive liquid crystal-containing microcapsule obtained by encapsulating a heat-sensitive liquid crystal with a two-layer capsule film, wherein the two-layer capsule film comprises an organic coating (first capsule film) formed on the surface of the heat-sensitive liquid crystal and the first capsule film. Ri Do from the inorganic film formed on the capsule membrane surface (second capsule membrane), the first capsule film was formed by coacervation of the organic polymer and heat-sensitive liquid crystal charged and emulsified in an aqueous medium An inorganic coating film which is an organic coating film, and the second capsule film is formed using a silica sol having a pH of 8.5 to 9.0 and a particle diameter of 10 to 20 nm, a silane coupling agent having an isocyanato group, and a curing catalyst. thermal liquid crystal-containing microcapsules, characterized in der Rukoto. The thermosensitive liquid crystal-containing microcapsule according to claim 1, wherein the silane coupling agent having an isocyanato group is γ-isocyanatopropyltrimethoxysilane. Thermal liquid crystal-containing microcapsules according to claim 1 or 2 average particle diameter are spherical is 3~90μ m. The first capsule layer and the heat-sensitive liquid crystal-containing microcapsules according to any one of claims 1 to 3 film thickness of the coating layer together second capsule membrane is 1~20μ m. A method for producing a thermosensitive liquid crystal-containing microcapsule obtained by encapsulating a thermosensitive liquid crystal with a two-layer capsule film,
(1) Producing an aqueous dispersion of first capsule particles in which an organic polymer and a thermal liquid crystal are emulsified and dispersed in an aqueous medium, and the thermal liquid crystal particles are coated with an organic coating (first capsule film) by coacervation. And the process of
(2) A silica sol having a pH of 8.5 to 9.0 and a particle diameter of 10 to 20 nm, a silane coupling agent having an isocyanato group, and a curing catalyst in the aqueous dispersion of the first capsule particles produced in the step (1). Adding and stirring and mixing to form an inorganic coating (second capsule membrane) on the surface of the organic coating (first capsule membrane),
The manufacturing method of the thermosensitive liquid crystal containing microcapsule characterized by including. The production method according to claim 5, wherein the silane coupling agent having an isocyanato group is γ-isocyanatopropyltrimethoxysilane. In the step (1), the concentration of the thermosensitive liquid crystal in the aqueous medium is 5 to 50 % by weight and the concentration of the organic polymer is 2 to 50 % by weight. In the step (2), the first in the aqueous dispersion The concentration of the capsule particles is 5 to 50 % by weight , the blending amount of silica sol having a pH of 8.5 to 9.0 and a particle diameter of 10 to 20 nm is 5 to 30 parts by weight with respect to 100 parts by weight of the aqueous dispersion , and isocyanato groups. The blending amount of the silane coupling agent is 10 to 50 parts by weight with respect to 100 parts by weight of the aqueous dispersion , and the blending amount of the curing catalyst is 0.005 to 0.1 parts by weight with respect to 100 parts by weight of the aqueous dispersion. The manufacturing method according to claim 5 . A microcapsule containing a thermosensitive liquid crystal produced by the production method according to claim 5, 6 or 7. A coating composition containing the thermosensitive liquid crystal-containing microcapsules according to claim 1, 2, 3, 4 or 8. The coating composition of claim 9, the heat-sensitive liquid crystal-containing microcapsules having containing 5 to 70 wt% in the coating composition. A coating film formed by applying the coating composition according to claim 9 or 10 to a substrate.

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